さ
​*

¦
{
THE
AMERICAN
SYSTEM OF DENTISTRY.
IN TREATISES BY VARIOUS AUTHORS.
EDITED BY
WILBUR F. LITCH, M. D., D. D. S.,
PROFESSOR OF PROSTHETIC DENTISTRY, THERAPEUTICS, AND MATERIA MEDICA IN THE
PENNSYLVANIA COLLEGE OF DENTAL SURGERY, PHILADELPHIA.
VOLUME I.
REGIONAL AND COMPARATIVE DENTAL ANATOMY,
DENTAL HISTOLOGY, AND DENTAL PATHOLOGY.
QUAE
WITH FIVE HUNDRED AND THIRTY-SEVEN ILLUSTRATIONS AND SIX PLATES.

PROSUNT
NIBUS
PHILADELPHIA :
LEA BROTHERS & CO.
1886.
Entered according to Act of Congress, in the year 1886, by
LEA BROTHERS & CO.,
in the Office of the Librarian of Congress at Washington. All rights reserved.
WESTCOTT & THOMSON,
Stereotypers and Electrotypers, Philada.
WILLIAM J. DORNAN,
Printer, Philada.
PREFACE.
No fact is now more fully recognized than that a clear, intelligent,
and comprehensive knowledge of any subject can best be communicated
by one who has a working acquaintance with it or has made it an
object of special research. To secure for the several departments of
this work writers thus informed, and willing to take from needed rest
and give to toil the time necessary for the systematic presentation of
their specialized knowledge, was not the least of the difficulties which
attended the inception of this undertaking. How well those who
assumed this labor have accomplished their several tasks these pages
must testify.
In judging of their work, the fact must be borne in mind that
those textual abridgments which are essential in a compend or man-
ual would fall far short of the obvious requirements of a systematic
treatise. Throughout the preparation of these volumes this distinction
has been recognized, and, while prolixity and useless verbiage have
been avoided, space has been given for the fullest possible exposition
of the subjects taught. Above all, it has been desired that each con-
tribution should be a teaching paper; hence no detail necessary to
make clear the meaning of the writer has been spared.
This particularity of method has been specially emphasized in the
sections devoted to technical processes and manipulative procedures;
and as a full comprehension of their intricate details can rarely be
attained through so imperfect an agency as a merely verbal descrip-
tion the text has been lavishly furnished with illustrations largely
made from original drawings and models prepared by the various
contributors.
Upon certain points in histology, pathology, and therapeutics some
divergence of views will be noted. The Editor has not sought to
enforce absolute harmony of doctrine, or assumed to commit this work
to a partisan advocacy of either side of questions which are still sub
judice. Recognizing the fact that the profession at large still differ
upon many questions of great although not vital importance, and that
3
4
PREFACE.
in practice the same end may often be attained by widely different
means, he has deemed it the wiser course to allow freedom of state-
ment to all, sure that at last the truer knowledge will prevail.
It has been found impossible in a work of this character to define
the limitations of each paper so sharply and rigidly as to avoid
all duplication of matter. It will, however, be found that if writers
traverse for short distances the same field, they do it from different
directions and survey it from varying standpoints, often to the reader's
profit; so that within reasonable limits this defect in the method of
literary collaboration is not an unmixed evil. It has, however, been
restricted to the narrowest possible bounds.
The Editor cannot close this preface without extending to the con-
tributors his heartfelt thanks for their generous co-operation. He
trusts and believes that they will find abundant reward for their
unselfish labors in that satisfaction which ever comes from a good
work well wrought, and in the approval of their professional brethren
everywhere.
His special thanks are due to Dr. JAMES W. WHITE, Editor of the
Dental Cosmos, and also to Professors C. N. PEIRCE, T. C. STELL-
WAGEN, HENRY LEFFMANN, and ALBERT P. BRUBAKER, for counsel
and help which have been of the highest value in the editorial super-
vision of this work.
June, 1886.
THE EDITOR.
*
CONTRIBUTORS TO VOLUME I.
BLACK, G. V., M. D., D. D. S.,
Professor of Pathology in the Chicago College of Dental Surgery, Chicago.
BRUBAKER, ALBERT P., A. M., M. D., D. D. S.,
Professor of Physiology and Pathology in the Pennsylvania College of Dental
Surgery; Demonstrator of Physiology in the Jefferson Medical College, Phila-
delphia.
CRYER, M. H., M. D., . D. D. S.,
Chief of Clinic of Oral Surgery, Medico-Chirurgical College of Philadelphia.
DALL, W. H.,
Curator of the Department of Mollusks, National Museum, Washington, D. C.
SUDDUTH, W. XAVIER, M. D., D. D. S., F. R. M. S.,
Demonstrator of Dental Histology in the Philadelphia Dental College, Phila-
Idelphia.
TRUMAN, JAMES, D. D. S.,
#
Professor of Dental Pathology, Therapeutics, and Materia Medica in the Dental
Department of the University of Pennsylvania.
WORTMAN, JACOB L., M. D.,
Anatomist to the U. S. Army Medical Museum, Washington, D. C.
•
5
CONTENTS OF VOLUME I.
PREFACE ..
PART I.
REGIONAL ANATOMY.
REGIONAL ANATOMY, ETC. By M. H. CRYER, M. D., D. D. S.
LYMPHATIC VESSELS OF THE HEAD AND NECK. By ALBERT P.
BRUBAKER, A. M., M. D., D. D. S.
PART II.
DENTAL ANATOMY.
"
PART III.
EMBRYOLOGY AND DENTAL HISTOLOGY.
EMBRYOLOGY AND DENTAL HISTOLOGY. By W. XAVIER SUDDUTH,
M.D., D. D. S..
INDEX..
THE TEETH OF THE INVERTEBRATES. By W. H. DALL.
337
}
THE TEETH OF THE VERTEBRATES. BY JACOB L. WORTMAN, M. D.. 351
•
PAGE
3
35
7
325
PART IV.
GENERAL AND DENTAL PATHOLOGY.
661
729
GENERAL PATHOLOGY. By G. V. BLACK, M. D., D. D. S.
DENTAL CARIES. By G. V. BLACK, M. D., D.D. S.
PATHOLOGY OF THE DENTAL PULP. By G. V. BLACK, M. D., D. D. S. 829
DISEASES OF THE DENTAL PULP, AND THEIR TREATMENT. By
JAMES TRUMAN, D. D. S. .
888
DISEASES OF THE PERIDENTAL MEMBRANE. By G. V. BLACK,
M. D., D. D. S.
ABRASION AND EROSION OF THE TEETH. By G. V. BLACK, M. D.,
D. D. S..
993
519
918
. 1011
ILLUSTRATIONS.
FIGURE
1. Section of a Sound Adult Femur.
2. Structure of the Neck of the
Femur
3. Fibula tied in a Knot after Mace-
ration in a Dilute Acid .
4. Transverse Section of Compact
Tissue of Humerus
5. Section Parallel to the Surface
from the Shaft of the Femur. .
6. Lamellæ torn off from a Decalci-
fied Human Parietal Bone
·
·
7. Transverse Section of Decalcified
Human Tibia
•
8. Lacunæ of Osseous Substance
9. The External Periosteum
10. Cells from the Marrow of Bone
during their Period of Develop-
ment
11. Three Multinuclear Giant-cells
•
(Osteoclasts).
•
12. Section of Part of One of the Limb-
bones of a Foetal Cat.
13. Imperfectly and
Upper Jaw
14. Occipital Bone, outer surface
15. Occipital Bone, inner surface
16. Development of Occipital Bone
17. Left Temporal Bone, outer surface
18. Left Temporal Bone, inner surface
19. Petrous Portion of Temporal Bone,
inferior surface.
•
Ill-developed
•
·
•
·
•
•
•
•
•
20. Development of the Temporal
Bone by Four Centres.
·
•
21. Sphenoid Bone, superior surface.
22. Sphenoid Bone, anterior surface.
23. Sphenoid Bone, posterior surface.
24. Foetal Sphenoid Bones
25. Left Parietal Bone, external sur-
face.
26. Left Parietal Bone, internal sur-
•
•
•
•
face.
27. Frontal Bone, outer surface
28. Frontal Bone, inner surface
29. Frontal Bone at Birth, developed
by two lateral halves
•
30. Ethmoid Bone, outer surface of
right lateral mass
31. Perpendicular Plate of Ethmoid
Bone
32. Ethmoid Bone, inner surface of
right lateral mass
33. The Vomer Bone
•
•
•
PAGE
FIGURE
36 34. Lèft Superior Maxillary Bone,
outer surface.
36
35. Left Superior Maxillary Bone,
inner surface.
38
38 36. The Anterior Palatine Fossa
37. Alveoli of Permanent Teeth
38. Development of the Superior
Maxillary Bone
39 39. Left Palate Bone, internal view
40. Left Palate Bone, posterior view.
40 41. Right Inferior Turbinated Bone,
internal surface
41
41 42. Right Inferior Turbinated Bone,
outer surface.
42 43. Left Lachrymal Bone, external
surface
•
44. Right Nasal Bone
4445. Left Nasal Bone
52.
53.
61
63 54.
64
·
46. Left Malar Bone, outer surface
44 47. Left Malar Bone, inner surface
48. Inferior Maxillary Bone, outer
surface
46
·
49. Inferior Maxillary Bone, inner
surface
49
50 50. Internal Face of the Right Maxilla
52 of Human Embryo of Three
54
Months
55 51. The Inferior Maxilla of a Fœtus
of Nine Months.
57
58
•
•
•
•
•
Appearance of Lower Jaw with
Deciduous Teeth.
Lower Jaw with Permanent Teeth
in position
Partial Absorption of Alveolar
Process
66 55.
•
Complete Absorption of Process
68 56. Absorption of Alveolar Process in
•
•
•
•
•
9
•
•
•
❤
•
•
·
•
Old Age
69 57. Hyoid Bone, anterior surface
(enlarged)
70 58. Temporo-maxillary Articulation,
72
internal view
74 59. Vertical Section of Temporo-
maxillary Articulation
76 60. Side View of Skull
61. Anterior and Posterior Fontanelles
at Birth.
76
119
62. The Lateral Fontanelles at Birth 119
77 63. Base of the Skull, inner or cerebral
surface
•
PAGE
•
•
82
83
885 BEN
86
87
89
91
92
94
94
95
96
96
98
98
100
102
105
105
106
106
121
78 64. Base of the Skull, external surface 125
80 65. Anterior Region of Skull .
131
106
106
107
108
113
114
116
•
10
ILLUSTRATIONS.
FIGURE
66. Roof of the Mouth
67. Vertical Section of Articular Car-
tilage
68. White Fibro-cartilage from an
Intervertebral Disc .
69. Fibro-cartilage of an Interverte-
bral Ligament
70. Multiplication of Cartilage-cells 141
71. Vertical Section of the Skin of
the Thumb.
72. Section of Skin
73. Tactile Corpuscle
74. Section of Hair-follicle
•
1
75. Lower portion of Hair-pouch,
from the lip of a kitten
·
·
•
76. Duct of the Sweat-gland.
77. Section of Coil of a Sweat-gland 152
78. Sebaceous Gland from the Alæ 115.
Nasi
79. Tendon of Mouse's Tail
80. Transverse Section from the
Sterno-mastoid
81. Muscular Fibre
82. Muscular Fibres (highly magni-
fied).
•
•
•
·
•
•
•
85. Magnified Human Muscular
Fibre
•
•
•
•
*
86. Nuclei of Muscular Fibre
•
87. Involuntary Muscular Fibre-cells
from Human Arteries
•
•
•
•
88. The Muscles of Expression
89. Muscles of the Head, Face, and
Neck
PAGE FIGURE
137 107. Anatomy of the Arteries of the
Neck, right side
139 108. The Arteries of the Face and
Scalp
139 109. The Internal Maxillary Artery
and its Branches
•
•
116. Ganglion-cell of a Frog
117. A Ganglion-cell within its Sheath
from the Human Sympathethic 264
118. Nerve-cell from Spinal Cord of
161
Ox
265
83. A Branched Muscular Fibre of 119. Section of the Saphenous Nerve 265
Frog's Tongue
162120. Diagram of Structure of Nerve-
fibre
•
266
84. Fragments of an Elementary
Fibre of the Skate .
90. Muscles of the Right Orbit .
91. Position and Attachment of the
•
•
•
•
•
•
•
•
Muscles of the Left Eyeball
92. The Temporal Muscle .
93. The Pterygoid Muscle.
94. Muscles of the Neck, anterior
184
•
view
95. Muscles of the Tongue, left side 187
96. Muscles of the Pharynx, external
view
•
•
•
101. Alveoli of a Serous Gland
102. The Salivary Glands
103. View of the Right Submaxillary
and Sublingual Glands, from
the inside
·
140110. The Internal Carotid and Verte-
bral Arteries, right side
Arteries of the Orbit, from the
outer side
•
·
104. The Meibomian Glands, etc. from
the inner surface of the eyelids
105. The Lachrymal Apparatus, right
side
106. The Arch of the Aorta and its
Branches
111.
143
146 112. Veins of the Head and Neck.
146 113. Vertical Section of the Skull,
147
showing the sinuses of the dura
mater
153
159
97. Muscles of the Soft Palate
98. Vertical Section through the
Mucous Membrane of the Large
Intestines of a Dog
99. Submaxillary Gland of the Dog. 204
100. Section of Human Submaxillary
Gland
161
161
148 114. The Sinuses of the Dura Mater,
151
seen in horizontal section of the
skull
164
167 125.
170 126.
175
127.
176
180 128.
181
163 122. Tubular Nerve-fibres
164 123. Nerve-fibres
•
192 131.
195
132.
202 133.
134.
>
210
211
212
215
•
162 121. Nerve-substance from the Eel,
magnified
205
206
207 135.
•
Veins of the Diploë, as displayed
by the removal of the outer table
of the skull .
•
•
·
•
·
•
124. Portions of Two Nerve-fibres
from a Young Rabbit
Nerve-fibre from the Sciatic
Nerve of the Rabbit.
Portion of the Network of Fibres
of Remak
•
•
•
•
•
•
•
PAGE
•
•
End-bulb from the Human Con-
junctiva
Termination of the Nerves in the
Salivary Glands .
Termination of Nerves in Non-
striped Muscular Tissue
Muscular Fibres of Lacerta viri-
dis, with the terminations of
269
•
Division of a Nerve-fibre, from
pulmonary membrane of frog. 269
Division of a Nervous Branch
into its Ultimate Fibres.
269
129. Plexus of Fine Non-medullated
Nerve-fibres of the Cornea . . 270
130. Intra-epithelial Nerve-termina-
tion in Cornea
•
217
223
231
236
238
250
257
·
260
262
264
•
266
267
267
268
268
nerves
Dissection of the Sinuses of the
Skull and Cranial Nerves
Base of the Brain .
136.
137. Semi-diagrammatic View of a
Deep Dissection of the Cranial
Nerves on left side of head. . 276
138. The Nervous Distribution of the
Head
139. Nerves of the Septum of the
Nose
277
278
270
271
272
272
273
274
275
ILLUSTRATIONS.
11
FIGURE
140: Diagram of the Optic Nerves and
Tracts in Man
141. Nerves of the Orbit, seen from
above
142. Nerves of the Orbit and Ophthal-
mic Ganglion
143. Distribution of the Second and
Third Divisions of the Fifth
Nerve and Submaxillary Gan-
glion
•
144. A Diagram of the Distribution of
the Fifth Nerve.
145. Pterygo-maxillary Region and
Fifth Nerve
•
146. The Spheno-palatine Ganglion
and its Branches
147. The Otic Ganglion and
Branches
158. The Deep Lymphatics
·
•
148. Diagram of the Facial Nerve and
its Distribution
149. Middle Fossa of the Base of the
Skull
•
150. Ganglia and Communications of
the Divisions of the Ninth,
Tenth, and Eleventh Pairs .
151. Tympanic Nerve
152. Distribution of the Ninth, Tenth,
and Eleventh Pairs of Nerves
on the left side
•
..
Rhiphidoglossate Teeth
•
its
•
•
·
Gland
156. Portion of the Medullary Sub-
stance of the Mesenteric Gland
of an Ox.
157. Superficial
Lymphatics and
Glands of the Head, Face, and
Neck
•
•
·
•
•
•
and
Glands of the Neck and Tho-
•
153. Origin and Connections of the
Glosso-pharyngeal, Pneumo-
gastric, and Spinal Accessory
Nerves
317
154. Dissection of the Side of the Neck 321 | 202.
155. Section of Small Lymphatic
- rax
•
159. Head of Nereis margaritacea .
160. Cephalic Region of the Leech
161. Oral Apparatus of Echinus
162. Dental System of Echinus .
163. Sectional Diagram of Molluscan
Radular Apparatus
164. Jaw of Tritonium .
165. Teeth of Bela
166. Teeth of Conus.
167.
168.Rhachiglossate Teeth
169.
170.
Tænioglossate Teeth
171.
172. Ptenoglossate Teeth
173.
174.
175.
176. Docoglossate Teeth
177.
•
PAGE
·
•
1
•
•
FIGURE
178.
279 179.
{
•
180.Jaws of Pulmonates
311
312
280 181.
182.
282 183.
184.
185.
186.
283 187. Section through the Skin of an
Embryonic Shark .
353
285 188. Third Lower Premolar of a Dog 355
189. Three Stages in the Develop-
ment of a Mammalian Tooth-
germ
296
300 190. Skull of the Codfish
191. Teeth of Notidanus.
303 192. Lower Jaw of Port Jackson
Shark
329
328 203.
204.
331
Teeth of Pulmonates. .
373
374
304193. Teeth of Rays
194. Ceratodus, and Teeth of Same. 376
306 195. Vertical View of the Upper Jaw
of a Dog.
397
196. Vertical View of the Lower Jaw
of a Dog.
398
197. Side View of the Skull of a Dog 402
198. Side View of the Skull of an
409
Armadillo
314 199. Side View of the Skull of Zeu-
glodon cetoides .
338 209.
339
340 210.
•·
212.
213.
347
347 214.
347
·
•
•
·
•
•
415
200. Mandible of Mesonyx ossifragus 418
201. Skull of Mesonyx ossifragus, an-
terior to post-glenoid process. 419
Right Mandibular Ramus of
Dissacus navajovius
420
Skull of Hyænodon horridus . 421
Skull and Part of the Posterior
Foot of two individuals of
Stypolophus whitia
. 349
4
•
205. Left Mandibular Ramus of Tri-
isodon quivirensis .
206. Skull of Leptictis haydeni
·
•
•
•
•
•
•
•
•
207. Parts of Upper and Lower Jaws
of Esthonyx burmeisteri.
425
332 208. Side View of a Portion of a
338
Skull of Blarina talpoides 426
Vertical View of Grinding Sur-
- face of Same
426
View of the Grinding Surface of
an Unworn Molar Tooth of
Dasyurus.
•
342
343 211. Two Incisors of the Lower Jaw
346
of Galeopithecus, external
view.
346
346
Vertical View of Upper and
Lower Jaws of European
Hedgehog.
•
•
•
PAGE
•
•
349
•
362
367
372
Fragment of the Lower Jaw of
a species of Miacis
Upper and Lower Jaw of two
species of Didymictis
430
348 215. Superior Maxillary Bone of Man 438
216. Inferior Maxillary
439
•
422
423
424
428
429
429
430
348 217. A. Left Upper Central Incisor. 440
218. A Lower Incisor
440
12
ILLUSTRATIONS.
FIGURE
PAGE
FIGURE
PAGE
482
219. Left Superior Human Canine. 441 262. Lower Molar of Same.
220. First Upper Bicuspid or Premolar 442 263. Skull of Hippotherium seversum 483
221. Second Lower Human Bicuspid 443 264. Molar Tooth of a species of
222. First Lower Human Molar. 443
223. First Superior Human Molar
224. Occlusion of the Teeth.
Horse
483
487
phant
490
267. Skull of Loxolophodon cornutus 492
449 268. Dentition of Virginia Opossum. 495
269. Dental Series of Kangaroo
497
532
•
225. Deciduous Teeth
226. Dentition in Childhood
227. Vertical View of the Upper Jaw
of a Seal (Phoca vitulina)
228. Vertical View of the Lower Jaw
of a Seal.
450 270. Human Blood-corpuscles
229. Skull of Amphicyon cuspigerus 452 271. Fibrin-filaments and Blood-tab-
230. Portions of Skull of Oligobunus
crassivultus.
·
•
•
·
•
•
•
·
lets
231. Part of Right Mandibular Ra-
454
Cells
453 272. Epithelial Cells in the Oral
Cavity of Man
mus of Temnocyon altigenis. 453 273. Columnar Ciliated Epithelium
232. Skull of Ailurodon sævus.
233. Superior Dental Series of Icti-
therium robustum .
234. Skull of Hyæna
235. Superior Sectorial and First Mo-
lar of Hyænictis græca .
236. Fragment of Lower Jaw of Hy-
ænictis græca
237. Skull of Proælurus julieni
238. Portions of Jaw of Proælurus
julieni
•
•
•
•
•
•
244. Upper and Lower Jaw of Amer-
ican Pine Marten
239. Skull of Archælurus debilis
460
•
240. Skull of Nimravus gomphodus. 459 280.
241. Skull of Dinictis cyclops
242. Skull of Pogonodon platycopis 461 281.
243. Cranium of Smilodon necator. 462
·
•
•
•
245. Cranium of Common Rat.
246. Grinding Surface of the First
Lower Molar of a Muskrat
247. Teeth of Fox Squirrel.
248. First Lower Premolar of Porcu-
•
261. A Superior Molar Tooth of spe-
cies of Hippotherium
•
•
•
•
•
•
•
pine.
249. Last Molar of Capybara
250. Dentition of Periptychus rhab-
dodon
251. Dentition of Ectoconus ditri-
•
•
·
•
·
•
•
·
•
445 265. Upper and Lower Jaw of Vir-
446
ginia Deer
446 266. Molar Teeth of Indian Ele-
447
455
455
468
469 289.
470 290.
474
475
·
480
481
285.
467 286.
467 287. Cross-section of Tadpole
S
481
482
274. Epithelium-cells of Salamander
Larva in Different Phases of
Division.
?
292.
293.
477 294.
479
295.
275. Connective-tissue Corpuscles.
537
456 276. Preparation of the Omentum of
Guinea-pig .
456 277. Bundles of the White Fibres of
458
Areolar Tissue
·
•
•
►
288. Three Stages in the Segmenta-
tion of the Rabbit's Ovum
Optical Section of Rabbit's Ovum
at the Close of Segmentation.
Rabbit's Ovum between Seventy
and Ninety Hours after Im-
pregnation
gonus
471
252. Skull of Phenacodus primævus. 473 291. Diagrammatic Views of the Blas-
253. Parts of Cranium of Meniscothe-
rium terrærubræ
474
547
254. Lower Jaw of Meniscotherium
terrærubræ.
todermic Vesicle of a Rabbit
on the Seventh Day.
Embryonic Area of a Rabbit's
Ovum on the Seventh Day 547
Rabbit Embryos of about the
Ninth Day, seen from the dor-
sal side
255. Molar Teeth of Dendrohyrax
arboreus
256. Skull of Hyracotherium augus-
tidens
257. Skull of Aphelops megalodus
258. Superior Molar Dentition of
Rhinoceros.
259. Upper and Lower Molar Teeth
of Lambdotherium
260. Upper and Lower Molars of
Right Side of a species of
Anchitherium
•
•
537
278. Elastic Fibres of Areolar Tissue 537
459 279. Articular Cartilage from Head
459
of Metatarsal Bone
Frog's Egg, Early Stage of De-
velopment.
Egg of Frog in Process of De-
velopment
•
•
282. Egg of Frog, farther advanced.
465 283. Tadpole, fully developed
466 284.
Cross-section of Frog's Egg
·
•
•
•
·
•
.
•
•
•
•
•
•
•
•
•
•
•
•
533
535
536
536
537
538
544
544
544
544
544
544
545
Rabbit Embryo of about the
Twelfth Day
Figures illustrating the Forma-
tion of a Face in the Human
Embryo
550
296. Face of an Embryo of Twenty-
five to Twenty-eight Days. 551
297. Embryo removed from the Ovum 551
298. Meckel's Cartilage from Human
Embryo of Forty to Forty-two
Days
545
546
548
549
552
ILLUSTRATIONS.
13
FIGURE
299. Embryo Pig an inch and a third
long; side view of Mandibular
and Hyoid Arches
•
300. Meckel's Cartilage, from jaw of
two-and-a-half months' human
•
•
foetus undergoing ossification. 553
301. Transverse Section through a
Blastoderm of Chick, about the
eighth hour after incubation
302. Porcine Embryo
303. Growth of Jaw from the Blasto-
derm
304. Embryotic Hairs and Hair-fol-
licle.
305. Longitudinal Section of Hair-
follicle
306. Commencing Replacement of
Old by New Hair
307. Sebaceous Gland and Hair .
308. Vertical Section of the Skin of
the Thumb.
309. Three Stages in Developing
Enamel-organ
•
Bone of a Human
thirteen weeks old
曹
​•
·
•
310. Porcine Embryo
311. Deposition of Fat in Connective-
tissue Cells.
•
•
312. Jelly of Wharton .
313. Porcine Embryo
314. Surface View, from below, of a
small portion of the posterior
end of the pellucid area of a
thirty-six hours' chick.
•
315. Osseous Lamellæ.
316. Transverse Section of Compact
•
•
j
•
•
320. Inferior Maxilla of Porcine Em-
bryo
•
321. Developing Lamella of Bone,
Porcine Embryo
322. Forming Bone in Human Foetus,
two months
•
Tissue (of Humerus)
317: Section of a Haversian Canal. 577
318. A Small Mass of Bone-substance
in the Periosteum of Lower
Jaw of a Human Foetus
319. Osteoblasts from the Parietal
Embryo
•
•
•
10
·
•
•
·
•
PAGE
552
562 341.
563 342.
564
568
572
FIGURE
331. Interglobular Spaces
332. Transverse Section of Shell of
Pinna
333. Membranous Basis of Shell of
Pinna
334. Longitudinal Section of Shell of
Pinna
335. Oblique Section of Prismatic
Shell-substance
343.
565 344.
566
567 345.
554
555 336. Enamel-prisms.
556
558
559 339.
559 340.
561
578
347.
576 348.
.589
•
•
349.
350.
·
337. Section of Hinge-tooth of Myo-
arenaria
•
338. Longitudinal Vertical Section of
the Upper Small Incisor of a
Rabbit
•
·
•
·
·
•
D
Diagrammatic Section of Enamel
and Dentine
Connective Tissue of Mesoblast;
Epiblast, formed of one layer
of cells.
612
Infant Layer of Epithelium and
Embryonal Connective Tissue . 613
Epithelium, infant layer; Em-
bryonal Connective Tissue
•
•
346. Epithelium with Infant Layer,
Connective Tissue, Band, and
Lamina
Longitudinal Transverse Section
of Inferior Maxilla
614
Mucous Membrane of Mouth. 615
Inferior Maxilla, first stage in the
formation of band .
•
Vertical Section of Band of Por-
cine Embryo
•
*
•
·
•
·
Longitudinal Transverse Section
of both sides of the Inferior
Maxilla
•
579 351. Vertical Section through Band
and Cord of 33 cm. Porcine Em-
bryo.
352. Vertical
580
•
•
•
•
Transverse Section
581
through Jaw of Porcine Em-
bryo.
582
•
353. Illustration of Invagination
354. Inner Tunic Enamel-organ of
Porcine Embryo
583
323. Developing Parietal Bone of a
Foetal Cat.
324. Transverse Section of a Bone. 584 355.
325. Section of Phalangeal Bone of
Vertical Transverse Section of
Jaw of Porcine Embryo
629
•
Human Foetus, five months. 585 356. Vertical Transverse Section of
326. Longitudinal Section through
Jaw of Porcine Embryo, show-
the Upper Half of the Decal-
ing differentiation of perios-
cified Humerus of a Foetal
Sheep
630
teum.
586 357. Vertical Transverse Section of
327. Section of Part of One of the
Jaw of Porcine Embryo
Limb-bones of a Foetal Cat. 588 358. Vertical Transverse Section of
328. Section of Femur of Human
Jaw of Porcine Embryo, in-
Foetus of five months
jected.
632
329. Section of Fang parallel to the
Dentinal Tubules.
359.
591
330. Section of Developing Tooth of 360.
Young Rat
592
·
•
•
•
Vertical Transverse Section of 9
cm. Bovine Embryo
Section of Jaw of Eight Months'
Human Foetus, showing ver-
PAGE
595
596
596
598
598
601
621
Vertical Section through Band
from Jaw of Porcine Embryo . 621
Same as 349, only more highly
magnified.
622
603
607
608
617
618
619
620
623
623
624
626
633
635
14
ILLUSTRATIONS.
FIGURE
tical transverse section of cen-
tral insisor
361. Temporary Molar (Rabbit), with
permanent molar developing
underneath.
··
•
362. Vertical Section of Jaw of Por-
cine Embryo.
640
363. Vertical Transverse Section Cen-
tral Incisor of Porcine Embryo 639
364. Stellate Reticulum, Inner Tunic,
and Odontoblastic Layer
365. Circle showing Dental Papilla,
Odontoblasts, Dentine, Amelo-
blasts, and Stellate Reticulum.
366. Vertical Section through Apex
of Central Incisor of 10 cm. Por-
cine Embryo
-
367. Calcification and Decalcification
of the Teeth
•
368. Comparative Stages of Calcifica-
tion of the Temporary and Per-
manent Teeth.
369. Vertical Section of a Tooth in situ
370. Sphygmographic Tracings illus-
trating Different Characters of
the Pulse.
371. Normal Capillary.
372. Capillaries after Passive Hyper-
æmia.
373. Natural Hæmostasis.
374. Ligatured End of the Crural Ar-
tery of a Dog.
375. Section of a Thrombus, after mod-
ified ligation
376. Diagram of the Conditions fol-
lowing Embolism of an End-
artery
377. Diagram of a Hemorrhagic In-
farct.
•
ature.
392. Pus-cells.
•
•
•
►
•
•
·
•
•
•
•
❤
•
•
•
PAGE
379. Crystals of Hæmatoidin
380. Crystals of Hæmin
381. Crystals of Hæmatoidin from a
Uterine Blood-clot.
382. Blood in Pernicious Anæmia .
383. From Red Medulla of Bone in
•
Pernicious Anæmia
•
•
•
•
•
•
Blood-corpuscles
386. Inflamed Human Omentum
387. Inflamed Iris.
388. Cornea of the Frog, excised three
hours after irritation.
•
•
389. Corpuscles of the Cornea, eight
hours after irritation.
390. Cornea, sixteen hours after irri-
tation
391. Cornea, about twenty-four hours
after the insertion of a fine lig-
•
FIGURE
393. Pus-corpuscles
636 394. Granulation-cells
#
637
638
641
378. Cells containing Blood-corpuscles
422.
from the neighborhood of a 423. Growths in Gelatin-tubes.
hemorrhage
686 424.
686 425.
687 426.
427.
687 428.
688429.
430.
689431.
384. Inflamed Capillary of the Mesen- 432. Fungus Growths.
tery of a Frog.
..691 433.
385. Amoeboid Movement of White
651
657
•
395. Section through the Border of a
Healing Surface of Granula-
tions.
642
403.
647 404.
405.
406.
682
"
705
396. New Formation of Blood-vessels
in a Granulating Wound. . . 706
397. Formation of the Ducts in the
Sprouting of a Grain of Corn. 707
Regeneration of Epithelium in
Cornea of a Rabbit
708
Sections showing Absorption of
Blood-clot.
Cross-section of Arterial Throm-
bus of Three Months
Carious Dentine
398.
399.
400.
401.
402.
684 419.
•
•
685 421.
668 410: Lactate-of-Zinc Crystals
679 411. Cocci and Diplococci
412. Fungus of Caries.
679 413. Tubules of Dentine united
681 414. Tubules from Natural Caries.
415. Outline of Epithelial Scale from
Human Mouth
Represent the number of cari-
ous cavities observed in one
hundred persons, and the po-
sition of these cavities on the
individual surfaces of the
teeth
. 782-785
407. Damp Chamber
792
408. Forms of Fungus from the Saliva 795
409.
.798
1 800
. 802
802
803
804
420. Fungus Growths.
434.
691 435.
692 436.
695 437.
438.
697 439.
698
698
•
•
·
·
PAGE
. 701
704
416. Fungus Growth in Starch
682 417. Fungus from Carious Dentine
418. Apparatus for Experiment with
Tobacco
•
1
•
•
•
•
•
•
•
804
804
. 804
809
814
709
•
710
766
440. Tissue of Dental Pulp.
441. Odontoblasts clinging to Imper-
fectly-developed Dentine .
442. Point of the Pulp of an Incisor
injected with Beale's Blue
831
443. Hyperæmia of the Dental Pulp 843
698 444. Dilated Blood-vessels from the
701
Dental. Pulp in Hyperæmia. 845
•
814
814
814
815
817
823
824
824
825
825
825
825
826
826
826
827
827
827
829
830
ILLUSTRATIONS.
15
"
· FIGURE
445. A Small Vein from a Hyper-
æmic Pulp...
446. Dilated Vessels from the Dental
Pulp.
447. Section of Hyperemic Pulp 847
448. Inflammation of Dental Pulp. 850
449. Section of Dental Pulp, showing
the invasion of the inflamma-
tory process.
450. Minute
•
L
Inflammatory Focus
within the Tissues of the
Pulp.
451. Lower Molar with Caries, and
microscopical section of the
•
·
same.
452. Progressive Suppuration of the
Pulp of an Incisor
453. Abscess within the Tissues of
the Pulp.
•
454. Carious Tooth and Microscopical
Section.
•
•
·
455. Chronic Inflammation of the
Pulp.
456. Deposit of Calcoglobulin within
the Tissues of an Inflamed
Pulp.
•
457. A Small Pulp-nodule
458. Section of a Pulp-nodule.
459. Pulp-nodules in the Canal Por-
tion of the Pulp.
460. Abrasion of a Cuspid Tooth and
461. Microscopical Section
462. Narrowing of the Pulp-chamber
in a Molar.
·
·
•
•
•
1
•
463. Deposit of Secondary Dentine
excited by Abrasion .
464. Deposit of Secondary Dentine,
resulting from caries of an in-
:: cisor
•
•
·
•
•
•
·
•
•
•
•
•
•
477. Representations of Osteo-den-
478. tine
PAGE
846 482.
FIGURE
481. Effect of Caries in Producing
Secondary Dentine
483.
914
846 484. Root and Membrane of Tooth. 919
485. Acute Alveolar Abscess of Supe-
rior Incisor pointing on the
Gum
930
850
851
858
860
465. Secondary Dentine, resulting
from irritation of the dentinal
fibrils by caries
466. Secondary Dentine in Pulp-.
chamber
468.
467. Carious Cavity in Molar Tooth,
469. and microscopical appearances 872
470. Dentinal Tumor within the
Pulp-chamber.
864
492.
861 493.
863
863 494.
867
868
486. Acute Alveolar Abscess of the
Lower Incisor pointing on the
Gum
·869
854
856
855 490. Upper Molar with Acute Abscess
at the Buccal Roots and Chronic
Abscess at the Palatine Root . 933
Upper Incisor with Acute Alveo-
lar Abscess the Pus from which
has raised the Periosteum from
the Hard Palate
491.
Blind Abscess at the Root of an
Upper Incisor
Chronic Alveolar Abscess at the
Root of a Lower Incisor
Chronic Alveolar Abscess at the
Root of an Upper Incisor, with
Fistula discharging on the
Gum
873
471. Proximal Decay in Incisor, and
microscopical appearances
875
877
503.
472. Calcification of the Dental Pulp 876 502.
473. Calcific Deposit in Incisor.
474. Lower Molar, with a large cari-
ous cavity, with cylindrical
calcifications
475. Cylindrical Calcification of the
Pulp.
476. Cylindrical Calcification, more
advanced stage
487. Acute Alveolar Abscess, with
Pocket of Pus between the
Periosteum and the Bone.
488. Necrosis of the Buccal Plate.
489. Acute Alveolar Abscess of
Lower Incisor
881
479) Atrophy of the Odontoblasts. 884
480.
496.
497.
501.
"
•
·
505. The Gingival Border.
879 506.
507.
•
•
•
•
•
·
•
a
866 495. Alveolar Abscess at the Buccal
Roots of an Upper Molar dis-
charging on the Face.
Scar caused by Alveolar Abscess
discharging on the Face
Alveolar Abscess at the Root of
a Superior Incisor discharging
into the Nose :
498.
941
Relations of the Roots of the
Teeth to the Antrum
870 499. Alveolar Abscess at the Root of
an Upper Molar discharging
into the Antrum of Highmore. 941
500. Abscess of Lower Incisor with
Fistula discharging under the
Chin
942
871
Abscess of Lower Incisor with
Cavity passing through the
Body of the Bone and dis-
charging beneath the Chin. 942
Fistula through the Lower Max-
942
·
illa
Loss of Bone and Teeth from
Subperiosteal Inflammation 944
878 504. Operation for the Remedy of
Scar caused by Alveolar Ab-
879
scess.
•
•
•
•
•
•
•
•
•
•
•
•
PAGE
931
932
932
932
933
936
938
938
939
939
•
Deposit of Serumal Calculus un-
der the Gingival Borders
Deposit of Serumal Calculus
within the Free Margin of
the Gum.
. 958
940
952
955
958
16
ILLUSTRATIONS.
FIGURE
508. Calculus and Destruction of the
Lower Border of the Alveolar
Wall and Peridental Mem-
brane
512.
513.
514.
}
522.
523.
524.
509. Absorption of the Septum of
Bone and Recession of Gum
510. Inflammation of the Gum from
Deposit of Salivary Calculus
511. Inflammation and Absorption of
the Gum and Lower Border of
the Peridental Membrane and
Alveolar Wall from Calculus. 960
Destruction of Tissues from
Salivary Calculus
PLATE I ..
PLATE II
PLATE III
PLATE IV
PLATE V.
PLATE VI
•
518.
519.
520. Destruction of Membrane and
Alveolus from Phagedenic
Pericementitis .
521.
•
961
515. Dr. George H. Cushing's Scalers 964
516. Farrar's Syringe
967
517. Alveoli irreparably Destroyed by
Calcic Inflammation
•
•
PAGE FIGURE
•
•
525. Acute Pericementitis with Ever-
sion of the Alveolar Wall . . 973
526. Phagedenic Pericementitis com-
plicated with Serumal Calcu-
lus .
.975
Incisions for Exposing the 981
Roots of the Teeth
981
Chronic Case of Phagedenic Peri-
cementitis
{
990
Amputation of the Affected Root
and Filling of the Pulp-cavity 991
Amputation of the Posterior Root
of the First Lower Molar
Erosion of the Lower Anterior
Teeth
. 991
999
1000
1004
534. Peculiar Case of Erosion of the
968
Superior Anterior Teeth. . . 1001
970 535. Artificial Erosion
970536. Section of the Crown of an
970
Incisor, showing effects of ero-
sion
971
971 537. Group of Odontoblasts with their
971
Processes
972
959
959 527.
528.
960 | 529.
530.
531.
532.
·
·
•
533. Erosion of both Upper and Lower
Dentures
LIST OF PLATES.
(
•
PAGE
•
1007
. 1009
•
. 505
507
509
511
513
515
PART I.
REGIONAL ANATOMY.
REGIONAL ANATOMY.
BY M. H. CRYER, M. D., D. D. S.
BONES.
BONES belong to one of the three groups of connective tissue, fibro-
connective, cartilage, and bone connective tissue. Each of these divis-
ions may be again subdivided into several minor divisions; but under
all circumstances the ground substance, or matrix, or intercellular sub-
stance of each is distinguished by the cells peculiar to it. The matrix
of fibro-connective tissue yields gluten or gelatin, that of cartilage
connective tissue yields chondrin, and that of bone connective tissue
yields the salts of calcium. With the single exception of the teeth,
bone is the hardest, heaviest, and most solid structure of the body:
it forms the framework of the body, keeps the parts in position, and
acts as lever and fulcrum; its grooves act as pulleys through which
glide the tendons of certain muscles; it protects vital parts, such as
the brain and spinal cord, from injury; it also, in great measure,
gives character and individuality of expression to the head and body
generally.
Bones are derived from the two great kingdoms of nature—the
organic and inorganic.
The principal portions of the several bones, such as the shafts of
long bones, are called the diaphyses; and the smaller parts, such as the
ends of long bones, their epiphyses, the term apophyses being applied
to those nodules on bones which are not formed from separate points of
ossification.
If a long bone be cut longitudinally (Fig. 1), it is seen to be made
up of an outer and an inner layer; the outer being called the compact,
the inner the spongy or cancellated, portion.
NOTE. The writer claims no originality for the purely descriptive matter herein
contained. In its preparation notes of the lectures of Professors Allen, Garretson,
Stellwagen, and Leidy have been of great value, and the following works have been
consulted and freely drawn from: Gray's, Allen's, Quain's, and Leidy's works on
Human Anatomy; Treves's Applied Anatomy; Bell's Anatomy of Expression; Allen's
Facial Region; Tomes's Dental Anatomy; Garretson's System of Oral Surgery; Parker
and Bessang's Morphology of the Skull; Klein's Elements of Histology; Flint's Physiology
and Diseases of the Nervous System; Cole's Studies in Microscopical Science; Prudden's.
Practical Histology; and Duhring on Diseases of the Skin.
35
36
ANATOMY.
The outer or compact portion is hard and ivory-like in texture, giving
rigidity and firmness to the shaft. In long bones the compact substance
is thickest in the centre of the diaphysis, gradually growing thinner
toward the ends, the fibres running longitudinally.
The inner, spongy, or cancellated portion is softer than the outer
covering, and is made up of slender bars and thin lamellæ, which cross
each other in various directions (see a a, b b, c c, Fig. 2), and produce
FIG. 1.

!!
Section of a Sound Adult Femur.
HEAD
NECK
-b
FIG. 2.

CREAT TROCHAN
SHAFT
Diagram showing the Structure of the Neck
of the Femur.
an open structure having a reticular appearance, so arranged as to form
an internal support to the outer portion of the bone. This formation
is specially marked in the upper end of the femur.
The cancellated portion is found in greatest quantity at the ends of
long bones, at which position the surfaces are enlarged for purposes of
articulation. It is the more vascular portion of bone; adds bulk with-
out greatly increasing weight; acts as a cushion to articulating surfaces;
and by its elastic properties modifies the force of concussion.
The flat bones, such as those found in the skull, furnish surfaces for
the more convenient attachment of ligaments, muscles, and tendons.
They are composed of two tables, an outer and an inner, with the
cancellated portion (diploë) between.
The cancellar substance of bones generally, but especially in those
of the cranium, is pervaded by irregular canals for the accommodation
of blood-vessels. The two plates or tables of flat bones are bound
together by the cancellated tissue, which not only helps to resist fracture,
but acts as a cushion, deadening the force of shock by distributing it
over larger surfaces, thus in great measure preventing injury to the
brain: it also combines great strength with lightness of weight.
If a close examination is made of a specimen, as shown in Fig. 1, by
the aid of a magnifying-glass, it will be found that the compact tissue
is porous in a greater or less degree, its density depending upon the
BONES.
37
amount of solid matter deposited in it. In other words, where the
spaces are small and contracted the solid matter is abundant; in the
spongy portions, the spaces being large, the solid matter is proportion-
ately less. It will also be observed that there is no line of demarcation
between the outer and inner structure, the compact gradually expanding
into the cancellated portion.
The color of bone depends upon the condition in which it is when
examined; if fresh, it will be of a yellowish hue, due to the contained
lymph and the fatty medulla. The blue shade so frequently seen is due
in a great measure to the mode of death. If the subject from which
the bone is taken died from drowning, suffocation, or any kindred cause,
a bluish tinge would be imparted to the bone. The redness of fresh
bone is dependent upon its vascularity; therefore some bones will be
redder than others, and the bones of young healthy persons more so than
those of the aged, whose osseous tissues contain a relatively greater
amount of inorganic matter.
Bones which have been cleaned, first by maceration in water, then in
ether, become white, the cartilaginous material, the blood, fat, and mem-
branes having been removed. By this process bones become extremely
porous by reason of the removal of the contents of the innumerable
small openings for blood-vessels which are found scattered over their
surface.
After exposure for a long time to the atmosphere, bones undergo
exfoliation and split into laminæ, thus demonstrating that osseous tissue
is heterogeneous and not homogeneous in its formation.
The weight of bones varies in direct proportion to their compactness
of structure. Their chemical analysis yields, on an average-
Calcium carbonate
Magnesium phosphate
Calcium phosphate.
Calcium fluoride.
Organic matter
•
•
•
•
7.05
2.08
58.39
2.25
30.23
100.00
It is seldom that the analytical chemists will produce exactly the
same results in their respective analyses of different bones, as it would
be difficult to find two bones identical in structure and composition.
There are many reasons for this, among which age may be mentioned
as a prominent factor. During youth bone is principally made up of
organic matter, but as life advances there is assimilated continually more.
inorganic material, part of the organic matter being lost. Disease may
also influence the proportional quantity of the inorganic constituents,
and, as might be expected, bones taken from different parts of the body
will be dissimilar in composition, as they are designed for different
functions.
If bone be placed in a solution consisting of one part of hydrochloric
acid to sixteen parts of water, the fluid being changed each day, the
inorganic matter will be dissolved out, leaving the organic material,
which is held together by its connective tissue, in its original shape,
these remaining parts being quite soft and flexible. Thus treated, a
38
ANATOMY.
FIG. 3.
vertebra will become like a sponge, and the long bones
may be tied into knots (see Fig. 3). In this way the
internal parts of bone may be prepared for study by
cutting away portions with a sharp knife or pair of
scissors.

A preferable manner of preparing bone for microscopi-
cal examination is to take a small piece, about half a
cubic inch in size, of the compact portion of a long bone,
either of man, dog, cat, or rabbit, and immerse it in an
aqueous solution of chromic or picric acid, either of
which hardens the organic tissue as well as dissolves
the inorganic matter, and renders the tissue capable of
being cut into thin sections, which are to be stained or
not according to methods in vogue by practical histol-
ogists. Hard sections can also be made by sawing a
small piece from a long bone and grinding it upon a
whetstone or plate of glass with emery-powder until
sufficiently thin.
When a bone is placed in a slow fire or a sufficiently
Fibula tied in a heated furnace, the organic material will be consumed,
Knot after Mace-
ration in a Dilute leaving only inorganic substance and the ash from the
Acid (from a spec-
men preserved in organic matter. The shape is still preserved, but the speci-
men is very brittle and will crumble almost at the touch.
spirit).
114024
………………
MINUTE STRUCTURE OF BONE.
A transverse and longitudinal section of the compact structure of
FIG. 4.
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Transverse Section of Compact Tissue of Humerus (magnified about 150 diameters). Three of the
Haversian canals are Seen, with their concentric rings; also the lacunæ, with the canaliculi
extending from them across the direction of the lamella. The Haversian apertures had become
filled with air and débris in grinding down the section, and therefore appear black in the figure,
which represents the object as viewed with transmitted light.
BONES.
39.
bone examined under a microscope will demonstrate the appearance, as
shown in Figs. 4 and 5.
FIG. 5.
The minute structure of bone is examined in five divisions-viz. (a)
the Haversian canals; (b) the bony
lamella; (c) the Sharpey or perforat-
ing fibres; (d) bone lacunæ; (e) can-
aliculi; and (f) bone-cells.
2
(a) THE HAVERSIAN CANALS
(Figs. 4 and 5) are named after their
discoverer, Clopton Havers. They
are from th toth of an inch
Too
in diameter, occasionally being found
as small as th of an inch. The
smallest canals are found near the
surface or outside of the bone, the
larger ones near the medullary canal.
Their general direction is longitudi-
nal with the axis of a long bone,
although they anastomose with each
other by short or oblique branches
at varying angles, while others pass
into the periosteum and the medul-
lary cavity, thus forming a reticu-
lated intercommunication by which
capillary blood- and lymph-vessels
pass, not only longitudinally, but from
the outer to the inner portion of the
bone. When the canals are not filled
by the above vessels the remaining the Femur (magnified 100 times): a, Haversian
space is occupied by delicate loose
connective tissue enclosing cellular
elements identical with the bone marrow, hereafter to be described.
(b) THE BONY LAMELLA is divided into three systems-viz. (1) the
Haversian, (2) interstitial, and general or (3) circumferential systems.
Section Parallel to the Surface from the Shaft of
canals; b, lacunæ from the side; c, others seen
from the surface in lamellæ which are cut hor-
izontally.
(1) The Haversian or Concentric System is a series of concentric rings
immediately surrounding each Haversian canal, varying in number from
four to twenty according to the age of the formation. All the lamina
do not form complete circles, some terminating between two others.
Frequently the rings are oval in shape, this form depending to some
extent on the cutting of the section. If cut obliquely to the canal, both
the rings and canal have an oval appearance, though the canal is not
always in the centre of its system.
(2) The Interstitial System.-The lamella of this system are com-
posed of bands of osseous tissue of varying thickness, running in dif-
ferent directions between the Haversian and the circumferential systems.

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(3) The Circumferential or Parietal System.-The lamella here are
principally found upon the surface of bone, although they are also seen
passing through the interstitial system, and even next to the medullary
cavity. They have a general direction parallel to the surface of the
bone.
40
ANATOMY.
(c) SHARPEY'S OR PERFORATING FIBRES.-Besides the three systems
of lamella which form for the most part all the intercellular substance
of bone, there is found in many instances a well-defined system of fibres
known as Sharpey's fibres (see Fig. 6). These pass through or pene-
trate the lamellae in a perpendicular or oblique direction, appearing to
dowel or bind the parts together. Many pass from the periosteum-
especially is this marked in the external table of the cranial bones-
while others seem to have their origin from some of the intermediate
FIG. 6.
b
Targe
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MA
Program Pag
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To
Man Ng

a
Lamella torn off from a Decalcified Human Parietal Bone at some depth from the surface: a, long
lamella; b, b, thicker part, where several lamellæ are superposed; c, c, perforating fibres: the fibrils
which compose them are not shown in the figure. Apertures through which perforating fibres had
passed are seen, especially in the lower part, a, a, of the figure (magnitude as seen under a power of
200, but not drawn to a scale).
lamellæ of the interstitial or circumferential systems, though it is more
probable they had their origin from the periosteum when that mem-
brane was in close contact with the lamella from which their fibres start.
These fibres are not found in the Haversian lamellæ. If a lamella is
torn away from a decalcified bone, these fibres can be seen attached to
the under surface of the removed portion, the apertures being visible in
the remaining bone from which the fibres have been drawn. They
are supposed to be ossified bundles of white fibrous tissue originally
belonging to the inner layer of the periosteum.¹
Occasionally these fibres do not ossify, and as they shrink or are
drawn out in removing the periosteum, perforations will be found lead-
ing into the bone. It is by means of these perforating fibres that tendons
and ligaments obtain such firm hold upon bones, their number being
increased at the points of such attachments.2
Bla
¹ Perforating fibres (e, e, Fig. 6) exist abundantly in the crusta petrosa or cementum
of the teeth (Sharpey). H. Müller has shown that some are of the nature of elastic
tissue (Quain's Anatomy).
2 The fibre-bundles of the tendon are continued into the bone as perforating fibres.
Some of the bundles of white fibres of the periosteum may also pass into the bone as
perforating fibres, and the same is the case with elastic fibres (Quain's Anatomy).
BONES.
41
e
S
ต
P
AD
MASS
"
1314
H
FIG. 7.

MUZIK
H
Transverse Section of Decalcified Human Tibia, from near the surface of the shaft: H, H, Haversian
canals, with their systems of concentric lamellæ; in all the rest of the figure the lamellæ are cir-
cumferential; S, ordinary perforating fibres of Sharpey; e, e, elastic perforating fibres (drawn
under a power of about 150 diameters).
FIG. 8.
(d) THE LACUNE OR LYMPH-SPACES (osseous corpuscles) are best
demonstrated in thin sections, prepared by grinding instead of softening
by acids and cutting with a knife or
microtome. When examined by trans-
mitted light the lacunæ have a dark
appearance, but when seen with a dark
background, the light being thrown
upon them, they will appear quite
white. They are very small cavities
situated between the lamellæ of the
bone, flattened ellipsoidal in shape,
and with many radiating elongations. Lacune of Osseous Substance (magnified 500
diameters): a, lacuna; b, canaliculi.
Ma
(e) THE CANALICULI are very fine
canals opening into the radiating elongations of the lacunæ. They ex-
tend between and through the different lamellæ, giving free communica-
tion to the lacunæ situated between the various lamella; they also pass
from the lacunæ to the Haversian canals, the surface of the bone, and
the medullary canals, and are intimately connected with the lymphatic
vessels situated in and around the bones, showing that the lacunæ and
canaliculi form the lymphatic system of the osseous structure.
(f) THE BONE-CELLS are flattened and nucleated, and are situated
within each lacuna, with prolongations extending into the canaliculi.
In structure they are analogous to the connective-tissue corpuscle.
"Rouget and Neumann have been able to detach the proper wall of the

ܝܢܕܐ
42.
ANATOMY.
""
66
lacuna and its appertaining canaliculi after decalcification, and to obtain
it separate with its included corpuscle. It can scarcely be doubted
that the protoplasm of the nucleated corpuscle takes an important share
in the nutritive process in bone, and very probably serves both to mod-
ify the nutritive fluid supplied from the blood and to further its distri-
bution through the lacunar and canalicular system of the bony tissue." ¹
In flat, thin, or irregular-shaped bones the Haversian canals, the
lamellæ, etc. are similar to those in the diaphyses of long bones, just
described, though the Haversian system is not so regular in formation.
B
THE PERIOSTEUM.
FIG. 9.
The periosteum is that membrane which covers the greater portion
of all surfaces of bone, and is composed in a great meas-
ure of fibrillated connective tissue. Between the inter-
lacing of the fibrous bundles lymph-spaces are formed
which contain elementary cellular matter. Although it
is made up of several closely-attached lamellæ, for con-
venience of description this structure is divided into two
principal layers, an outer and an inner.
The outer layer is the firmer of the two, being com-
posed mainly of one or more strata of dense white con-
nective tissue, with a few fine yellow clastic fibres inter-
spersed with several fat-cells. Blood- and lymph-channels
are found in abundance; the latter anastomose quite free-
ly with those of the inner layer.
The inner or osteogenic layer has its fibrous bundles
more loosely arranged than the outer, and is composed
chiefly of elastic fibres of connective tissue, generally ar-
ranged in several distinct strata. It is much more vas-
The External Peri- cular than the outer layer, the blood-vessels forming a
osteum laid open network of capillaries which anastomose with those of
and turned
from a
Young the outer layer and send numerous offshoots into the
Humerus. substance of the bone. In the lower strata of this layer,
or that one next to the bone, especially during the period of formation,
there is a large number of spheroidal or oblong granular cells or cor-
puscles, with oval nuclei, which are usually situated on the side of the
cell. These cells were named osteoblasts by Gegenbauer. The bone-
producing property of the inner layer of the periosteum is especially
well marked in the fully-developed inferior maxilla, clavicle, and bones
of the arm and forearm. If the surgeon when operating is careful to
first strip this membrane aside, he can excise or resect a large portion
of bone, the lost tissue being subsequently renewed to a great extent
through the agency of the osteoblasts.
If by disease or otherwise the periosteum be removed from any living
bone, the portion thus denuded generally suffers atrophy, and finally
necrosis. This is not usually the case, however, with the bones of the
cranial vault, as will be hereafter explained.
The periosteum serves as a support to the vessels which supply the
1 Quain's Anatomy.

Q
Indo
BONES.
43
bones with blood, these capillaries being assisted by the medullary
(nutritive) arteries, which pass directly into the bone and are distributed
throughout its system of Haversian canals, until they anastomose with
the branches coming from the periosteum. Thus the bones are per-
meated by the blood and absorbent vessels, a few nerves also entering
their structure. In the bones containing marrow there is an endosteum,
composed of a fine layer of areolar tissue, which lines the medullary
canals and other spaces. This lining membrane is very vascular, and
contains myeloplaxes or osteoclasts. Osteoclasts are also found at the
roots of deciduous teeth when their roots are being absorbed, and in the
lining membranes of bony sinuses. When the periosteum is stripped
from living bone, numerous bleeding spots appear, which indicate the
points where the vessels pass from the membrane into the bone. The
muscles, aponeuroses, tendons, and ligaments are attached to the bone
through the intervention of the periosteum, which is attached to the
bone by its perforating fibres. Tendons and ligaments obtain firm ad-
herence to bones by sending prolongations of their fibre-bundles through
the periosteum.
In inflammation of the bone the periosteum often becomes thickened,
and may be easily removed. At the point of attachment of a muscle
to a bone there is seen a roughening, a depression, or a protuberance
corresponding in size to the strength of the attached muscle.
THE MARROW OF BONE.
The marrow is a highly vascular, soft tissue situated within all bones.
It fills the medullary canals of long bones, the spaces within spongy
bones, and to a greater or lesser extent the Haversian canals of compact
bone tissue. As a matrix it has a small amount of fine delicate con-
nective tissue woven or interlacing in such a way as to form very thin
septa between the vesicles. Its color and composition vary according
age and the position it occupies within the bone; and this difference
has led to its generally being divided into two kinds-yellow and red.
The yellow receives its color from the large number of fat-vesicles it
contains, and is principally found in the medullary canals of long bones
and in small quantity in some of the cavities of spongy bone. Yellow
marrow is not found in young bones.
to
The red marrow is dependent for its color on its greater vascularity and
upon its containing red cell-elements independent of the blood; it lacks
adipose tissue in its substance, and is more fluid than the yellow. Red
marrow is situated in the spaces of spongy bones, especially the bodies
of the vertebræ, sternum, the ribs, and diploë of the cranial bones.
The vessels of the marrow, which are numerous, are imbedded within
its substance. Their walls are very thin, and they supply in part the
adjacent bone as well as the surrounding marrow. They anastomose
through the bone with those of the periosteum. Within the marrow
are found a variety of cell-elements (Fig. 10) which vary according to
position and age, and are described as the medullary or true mar-
row-cells; fat-vesicles or adipose-tissue cells; multinuclear giant-cells;
K
44
ANATOMY.
nucleated red blood-cells; osteoblasts; colored cells similar to the red
blood-corpuscles.
The Medullary or True Marrow-cells are round and nucleated. They
have amoeboid movements, and in general appearance may be com-
FIG. 10.

α
d
f
J
e
O
j
Cells from the Marrow of Bone during their Period of Development: a, b, multinuclear "giant-cells;"
é, f, g, lymph-cells from the marrow of the tibia of the guinea-pig, examined in the serum of the
blood; c, d, h, after the action of alcohol and water 33 per cent.; i, j, so-called osteoblasts from
the femur of a new-born dog, after the action of alcohol 33 per cent. (high power).
pared to lymph-cells or the white corpuscles of the blood, though some-
what larger and possessing a clearer protoplasm. This class is more
abundant in red than yellow marrow.
The Fat-vesicles are similar to those found in adipose tissue. As
previously stated, the color of yellow marrow is due to these vesicles,
of which it is in greater part made up. Fat-vesicles are found in very
small numbers in the red marrow.
FIG. 11.
The Multinuclear Giant-cells are large, soft, protoplasmic masses,
granular in appearance. They generally contain a large number
of nuclei; these are sometimes
grouped on one side, and have
a fine fibrillated network run-
ning through them. Some-
times they contain only one
nucleus, which is large and
shows indications of segmenta-
tion. These cells have been
called by Robin myeloplaxes,
and by Kölliker osteoclasts.
The latter authority considers
Three Multinuclear Giant-cells (Osteoclasts), from ab- them necessary to bone-absorp-
sorption-surfaces of growing bone (400 diameters-
Kölliker).
tion.
The Nucleated Red Blood-cells resemble the red corpuscles of the
blood, but are somewhat larger; they have a smooth, homogeneous
cell-body with a distinct nucleus. These cells are supposed by some to
lose their nuclei, become biconcave, and assume the character of the

BONES.
45
ordinary red blood-corpuscles. Those holding this view claim that
the marrow of the bones is one of the blood-producing tissues of the
body.
Osteoblasts (described p. 42) are found principally and in large
numbers in red marrow along the osseous trabeculi, especially during
the development of bone.
Red cells, having every appearance of red blood-corpuscles, are
numerous. Their presence has been explained by the fact that the
walls of the capillary blood-vessels are very thin and delicate, permit-
ting the escape of the corpuscles into the surrounding tissue.
Wapking
DEVELOPMENT OF BONE.
The central column of the body, consisting of the vertebræ and the
base of the skull, is seen in rudimentary outline at a very early period of
embryonal life. This outline, formed from the mesoblastic layer of the
blastoderm, and composed of tissue not unlike the primordial structure
by which it is surrounded, soon becomes cartilage; and in man, about
the fortieth day of embryonal life, bone-development commences in the
clavicle and inferior maxilla. This early ossification of the lower jaw,
before the upper, may be explained as due to the same law of develop-
ment that brings about the eruption of the inferior teeth before the
superior. Some of the lower animals, however, have more teeth in the
lower than the upper maxilla, the former being more important, as in
mastication it has active movement, while the upper jaw is passive.
Nearly all the bones of the body have their commencement in hyaline
cartilage. Those of the face, with the two exceptions of a portion of
the inferior maxilla and the inferior turbinated, and those covering the
brain, excepting a part of the occipital, are developed within membranes.
In addition to these two modes of formation, the cartilaginous and mem-
branous, bone seems to be principally developed from the osteogenetic
layer of the periosteum. From this it will be seen that it is best to con-
sider the development in three divisions--viz.: I. Intracartilaginous;
II. Subperiosteal; III. Intramembranous.
1
I. THE INTRACARTILAGINOUS (endochondral) BONES are those hav-
ing their origin or first formation in hyaline cartilage, which usually
presents, in minature, a general outline of the future bone. The trans-
formation from cartilage to bone is gradual, and commences at one or
more points, called centres of ossification. In the bones of the higher
animals, including man, the number of ossific centres varies, being
dependent on the degree of complexity in the formation of the bones
and the number of vessels and nerves which pass through them. If
there is but one point, it is usually situated near the middle and upon
the surface, else next to the perichondrium or future periosteum. For
convenience of description and facility of study the development of
endochondral bone may be divided into four stages:
1st. The first observable change is at one or more of the ossific points,
at which the cartilage-cells (for description see p. 138) immediately under
the perichondrium enlarge and multiply within their capsules, the matrix-
substance becoming partly absorbed.
46
ANATOMY.
2d. Into this area blood-vessels enter from the under layer of the
perichondrium (chondrogenetic layer), accompanied by osteoblasts (bone-
FIG. 12.
germs) and marrow-tissue.
As the vessels and osteo-
blasts advance into the
partly-absorbed cartilage, the
change of the cartilage is car-
ried on in front of them; thus
the cartilage becomes chan-
nelled, forming cavities ir-
regular in shape named me-
dullary spaces. These are
lined by osteoblasts and in-
vaded or permeated by blood-
vessels and marrow-tissue.
P

FRO
223
Cô Đơ
abouth 10³ p
liyo
in
A BID
Op
A
DO
80
On
pondr
C
bl
Section of Part of one of the Limb Bones of a Foetal Cat.
The calcification of the cartilage-matrix has advanced
from the centre, and is extending between the groups of
cartilage-cells, which are arranged in characteristic rows.
passu with the calcification of the cartilage-matrix. The
The subperiosteal bony deposit (im) has extended pari
cartilage-cells in the primary areolæ are mostly shrunken
and stellate; in some cases they have dropped out of the
space. At ir and in two other places an irruption of
the subperiosteal tissue, composed of ramified cells with
osteoblasts and growing blood-vessels, has penetrated the
secondary areola or medullary spaces; p, fibrous layer of
subperiosteal bony crust, and has begun to excavate the
the periosteum; o, layer of osteoblasts: some of them are
imbedded in the osseous layer as bone-corpuscles in at once removed.
lacunæ; bl, blood-vessels occupied by blood-corpuscles.
Galle
3d. That portion of the
cartilage basement-substance
which is not absorbed forms
irregular septa or trabeculæ,
and is infiltrated with fine
particles of calcic salts, caus-
ing opacity and a granular
appearance, which, when cut,
has a gritty feel: this process
im is called calcification, and is
an intermediate stage between
the absorption of the carti-
lage-matrix into medullary
spaces, and the ossification of
the bone by the influence of
in the osteoblasts.
Dim
4th. The last stage, fol-
lowing closely that of calci-
fication, is called ossification
through the influence of the
osteoblasts. Portions of the
walls of the medullary spaces
become absorbed, causing two
dullary spaces to
or more of the primary me-
to become
united and form secondary
spaces. In this way a great
calcified cartilage-matrix) is
part of the primary bone (or
"Turning our attention to
the exact way in which bone is formed under the influence of the osteo-
blasts, we find that just beneath these cells, lying along the walls of the
new-formed medullary spaces, the basement-substance of true bone begins
to be deposited, at first in the form of a narrow shell beneath each osteo-
BONES.
47
blast. These deposits, which on cross-section have a crescentic shape,
become thicker and thicker, rising up around the cell, which they finally
enclose the enclosed osteoblast becoming, as it would seem, a bone-cell.
This process occurring around each osteoblast, the walls of the medullary
cavities soon become covered with a layer of bone containing bone-cells.
New osteoblasts appear on the walls, and in turn become enclosed in a
layer of bone, and thus the lamellar arrangement of bone-tissue is pro-
duced. The remains of cartilage basement-substance between the
medullary space thus covered by bone finally disappear in a manner
unknown to us.' "" 1
•
II. THE SUBPERIOSTEAL BONE is the portion formed on the outer
surface of that which is developed within the cartilage, and by the
formation of which bones increase in thickness. It is deposited in a
manner similar to endochondral bone, through the influence of osteo-
blasts found on the inner portion of the osteogenetic layer of the peri-
chondrium, which has now become periosteum. The osteoblasts are
arranged along the line of blood-vessels and connective-tissue bundles.
of the osteogenetic layer of the periosteum, and as these structures are
not parallel to each other or to the surface of the bone, but cross at
various angles, forming an uneven network, they cause newly-formed
bone to have an uneven surface, with branching grooves and canals
passing in different directions. Upon the walls or sides of these grooves
and canals the osteoblasts, by means of which bone-tissue is deposited,
are distributed, spaces being left for blood-vessels and marrow-tissue:
these spaces subsequently become the Haversian canals. During
the time these canals and spaces are being encroached upon by ossific
deposit newer layers are commenced on the outer surface of the bone,
the fully-formed or ossified layer being continually overlaid by fresh
coatings in a manner similar to the lamella of the Haversian system:
by this process the bone grows in thickness. These lamellæ are held
or bound together by perforating fibres (Sharpey's fibres), which pass
through several layers at nearly right angles with the surface. These
fibres originate from the bundles of connective tissue of the subperios-
teal membrane, but do not all have connection with the periosteum
itself, though doubtless they had their origin from that membrane, the
same as the bone in which they are found. Perforating fibres are
usually ossified, but in some instances they are not, and in the drying
of the bone they become shrunken, leaving perforations.
In the long bones the cartilage grows and extends toward the
epiphyses, where, by gradually increasing in diameter, it causes the can-
cellated portion of the bone to present a somewhat similar shape to that
of an elongated hour-glass. Where deposition of bone first commenced
the cancellated part is the narrowest, and the cortical portion, which grows
from the periosteum, is the thickest. Toward the ends of the bones
the cortical substance gradually diminishes to a thin layer, thus main-
taining a nearly equal diameter for the bone from end to end. A little
before or about the time of the development of the periosteal bone the
central portion of the embryonal spongy or endochondral bone under-
goes a process of softening or absorption (osteoporosis, Schwalbe). In
1 ¹ Pruden's Practical Histology, 2d ed., p. 73.
(
Madagas
48
ANATOMY.
this way the central or marrow cavity is formed, and the partitions or
septa of the medullary spaces become absorbed, especially around the
medullary canal, thereby enlarging it. This absorption may be carried
on until the entire embryonal spongy bone is removed.
III. THE INTRAMEMBRANOUS OSSIFICATION takes place within
membranes of fibrillar connective tissue, independent of any carti-
laginous formation. It is found within the roof of the brain-case, as
in the parietal and frontal bones and portions of the occipital and tem-
poral, and within all the facial bones, except the inferior turbinated and
part of the inferior maxilla. (The base of the skull, the two inferior
turbinated, and part of the inferior maxillary bones are developed
within cartilage.) This development of bone is analogous to that of
periosteal formation, which takes place on or around endochondral
bones.
The parietal bone presents a good example of this development. At
first it is composed of a single fibrous membrane; next it divides near
its centre into two layers, these eventually becoming the external and
internal periosteums. Between these two layers are numerous inter-
lacing bundles of connective-tissue fibres, making an intervening network
between the two membranes and forming irregular medullary spaces
similar to the partially-absorbed cartilage in endochondral bone-forma-
tion. The bundles of connective-tissue fibres forming the walls of the
medullary spaces become infiltrated with calcic salts; the spaces them-
selves are occupied by blood-vessels and marrow-tissue, and their walls
lined by osteoblasts, which develop bone, as described p. 42.
As the centre thickens the cleavage of the membrane extends toward
the circumference, and bony spicula grow outward in radiating lines until
they meet neighboring bones, with which they unite by sutures.
While this process is going on, the two osteogenetic membranes deposit
successive layers of bone, causing an increase in thickness, each layer
becoming more dense, thus forming what are known as the external
and internal plates. Between the two tables of a fully-formed bone is
the cancellated structure or diploë. These irregularly-formed spaces
are made through absorption of portions of the bony tissue by osteo-
porosis. The diploë is a highly vascular tissue, in which the arteries
of the external and internal periosteum anastomose.
Stan
Bones are divided into four classes-viz. long bones, such as those of
the arm and leg; tabular or flat bones, as those forming the vault of the
cranium; irregular bones, such as the vertebræ; and short bones, as
those of the carpus and tarsus.
Many of the bones are arranged in symmetrical pairs, one on each
side, as illustrated in the ribs, arms, legs, parietal and temporal bones
while the vertebræ, commencing with the coccyx, and continuing upward
through the skull with the occipital, sphenoid, ethmoid, frontal, and
vomer, are single bones, developed from two symmetrical halves. The
inferior maxilla is usually described as a single bone, but in embryonal
life and in some of the lower animals there are two. In man the
bones on either side of the body are seldom of equal size, those of the
right side usually being slightly larger; their markings, such as processes
and foramina, are also dissimilar in size and shape.
BONES.
49
FIG. 13.
Disease of the soft parts often changes the shape of bones, particu-
larly in the young. Aggravated tonsillitis in childhood will, if chronic
and accompanied by hyper-
trophy, cause the roof of the
mouth to take an inverted
V-form (Fig. 13). If the
patient has suffered from the
disease on one side only, that
side will be pulled down.
This is due to the extra ten-
sion of the palato-glossus and
palato-pharyngeus muscles.
Thus the palatal processes of
the superior maxillæ and pal-
'ate bones are prevented from
forming the normal dome-
shape roof of the mouth, and
the vomer is directed or
pushed from its proper posi-
tion; becoming crooked or
lacking space to occupy its
normal position, it is de-
flected or pushed forward, thus forming an unduly large nose. By
proper treatment at an early period, many such deformities can be
avoided. Tumors of the maxillary sinus may change the shape of one
or more of the surfaces of the superior maxilla, and an aneurism or
other soft tumor constantly pressing against a bone will cause its
absorption.
Imperfectly and Ill-developed Upper Jaw.

In describing bones, the following terms will be used :
Proximal, the end or surface of a bone next to the centre of the body.
Distal, the end or surface that is farthest away from the centre.
Head. If the extremity forms a single rounded prominence, it is
called the head.
Condyles. If there are a pair of prominences, they are called con-
dyles, though this name is applied to the single articular eminence of
the occipital bone and of the lower jaw.
Neck is that portion which is constricted just below a head, condyle,
or other articular eminence.
Process is an elevation, projection, or prominence on a bone.
Spinous Process, a narrow and tapering prominence or elevation on
a bone.
Tubercle or a Tuberosity, an obtuse prominence.
Line, Ridge, or Crest, an elevation extending some distance along the
surface of a bone, a prominent border.
Foramen (plural Foramina), an aperture in a bone or between several
bones.
Canal or Meatus, a prolongation of a foramen for some distance in
the bone.
Fossa (plural Fossa), a broad, shallow depression.
Sinus, a cavity with a small external communication.
4
50
ANATOMY.
A line in measurement is one-twelfth part of an inch. In describing
the development of bones, weeks and months refer to embryonic and
foetal life.
An articulating surface is that portion of a bone where it joins
another.
A facet is a portion of an articular surface which is distinguished
from adjacent portions of the same surface by difference of its curva-
ture.
THE SKULL.
The skull is composed of twenty-two bones, exclusive of the six
otic (ear bones), the Wormian bones, and the teeth. These are united
by sutures and synchondroidal articulations, with the exception of the
FIG. 14.
Smooth Surface for Occip. Frontalis
Protube
LIC.
flor curved
rior
line.
Etui
curved
dyloia
FEUDE
14.09
יף .
F
Condyle for antic
Occip.
FINITY!
ine
ر ر ر و که وار
A
foremaid
NUCH
Cr
e s
tra
ROGE
Cercas
TRAPEZIUS
……………………………………..
Foramen
Magnum
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MINOR
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COMPLEXUS
..........
REGT.CAP
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Spine
OCCIPITO-FRONTALI
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silar Proc.
Occipital Bone, outer surface.
RECT.CAPIT.POSTIC.MAJOR
………………………………….
OBLIQUUS
SUPERIOR
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/CAPITIS
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…………………………
..
STERNO-MA
SPLENIUS CAPITIS
TOID
inferior maxilla, which is a diarthroidal joint. The skull approaches
the spheroidal shape, flattened at the sides, broader posteriorly than
anteriorly, and is supported upon the atlas, the first bone of the verte-
bral column. Anatomists divide the bones of the skull into two
groups-the cranial and the facial. The cranial bones, which encase
•

BONES.
51
the brain, are eight in number-one occipital, two temporal, one sphe-
noid, two parietal, one frontal, and one ethmoid. The remaining four-
teen bones form the oral cavity, nasal chamber, and portions of the
orbits. They are called the facial bones, and consist of the two superior
maxillary, two palatal, one vomer, two inferior turbinated, two lachry-
mal, two nasal, two malar, and the inferior maxilla, six being in pairs,
and two being single bones. The hyoid bone, though generally classed
as a bone of the neck, will be described with the bones of the head.
Occipital Bone. The occipital bone (Fig. 14) is situated at the base
of the cranium, at the top of the spinal column, and articulates with the
atlas. It is oval in form, resembling somewhat a saucer, and presents
for examination four angles, four borders, two condyles, two surfaces—
one concave or inner toward the brain, the other or outer convex. It is
also perforated on its under surface by a large oval foramen.
The Basilar Process forms the anterior (inferior) angle of the bone.
If a section of this process were made through the mesial line, the sur-
face would assume the appearance of a wedge about an inch in length,
widening from the anterior border of the foramen magnum, the base
of the wedge, about half an inch in thickness, being that portion of
the process which articulates with the sphenoid bone. In early life
a layer of cartilage intervenes between the basilar process of the
occipital and the sphenoid bones. This cartilage becomes ossified at
the age of puberty. The upper surface of the basilar process is grooved
for the accommodation of the medulla oblongata and basilar artery; the
under surface (laterally) is convex and forms the roof of the pharynx.
Near its centre is a rounded prominence called the pharyngeal spine, for
the attachment of the raphe and the superior constrictor of the pharynx.
On each side of this prominence is a rough depression for the attachment.
of the rectus capitis anticus major and minor muscles. Laterally, the
superior border of this process is roughened for articulation with the
petrous portion of the temporal bone, forming the petro-basilar suture.
During life, the under portion of this process is filled with a mass of
fibrous tissue.
}
G
The Superior Angle of the occipital bone articulates with the posterior
superior angles of the parietal bones at the position occupied in fœtal
life by the posterior fontanelle. The lateral angles articulate at the
posterior juncture of the parietals with the mastoid portions of the
temporal bones. The superior borders extend from the superior to the
lateral angles of the bone; they are deeply serrated for articulation with
the posterior borders of the parietal bones, and form the occipito-parietal
(lambdoid) suture. In this suture Wormian bones of different sizes are
most frequently met, the denticulations being distinctly marked. The
inferior borders extend from the lateral angles to the sphenoid bone.
Each border is divided into two portions by the jugular process. The
upper part is serrated for articulation with the mastoid portion of the
temporal bone, forming the occipito-mastoid suture; the lower portion:
is simply roughened.
The Jugular Processes, two in number, are sharp points of bone
extending laterally, and are analogous to the transverse processes of a
vertebra; they form the posterior boundary of the jugular notch.
52
ANATOMY.
The Jugular Notch is a smooth semicircular concavity, extending
half an inch outwardly and three-fourths of an inch anteriorly, forming by
its articulation with the temporal bone the jugular or posterior lacerated
foramen. This foramen is frequently divided by one or more septa, and
through it the ninth, tenth, and eleventh pairs of nerves pass out of the
brain-case. It is at this point also that the lateral sinuses terminate and
the internal jugular vein commences.
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FIG. 15.
Superior Border, artic. with

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60
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Inferior Angle
Occipital Bone, inner surface.
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with
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Lateral
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A
Mastoid portion
Inferior Border, artic. with Temporal bone
The External Surface.-On each side of the lateral borders of the
foramen magnum are the two condyloid processes (exoccipitales) which
articulate with the atlas (the first cervical vertebra).
The Condyles are elliptical in form and converge somewhat in front.
Their surfaces are convex, both transversely and longitudinally, being
divided into two articulating facets, which are occasionally separated by
a transverse groove. The inner side of each condyle is roughened for
BONES.
53
the attachment of the odontoid ligament of the axis (the second cervical
vertebra). Immediately above the anterior facet on either side are the
anterior condyloid foramina, situated at the side and above the foramen
magnum; they transmit the hypoglossal nerves. Occasionally these
foramina are found doubled, which allows the superior and inferior bun-
dles of the hypoglossal nerve to pass through separate foramina in their
exit. Behind the posterior facet is the condyloid fossa, which usually
contains the posterior condyloid foramen, for the transmission of the
occipital emissary vein to the lateral sinus. Two foramina are also
occasionally found in this situation. The outer surface of the tabular
portion of the occipital bone (supraoccipital) is divided transversely into
three sections by the superior and inferior curved lines. The superior
curved line runs inwardly from the lateral angles of the bone, at the
temporo-parietal suture, to the external occipital protuberance; it forms
the major portion of that line, which extends in the articulated skull
from the apex of the mastoid portion of the temporal bone on the one
side of the cranium to the same point on the opposite side. The inferior
curved line runs almost parallel with the superior. Its extremities are
situated at each jugular process, from which point it ascends to the
occipital crest. The lower two-thirds of the external surface is divided
longitudinally by the occipital crest. This crest is a slight ridge run-
ning from the external occipital protuberance to the foramen magnum.
The upper third, or that portion above the superior curved lines, is
comparatively smooth. The external occipital protuberance, which
gives attachment to the ligamentum nuchæ, is situated in the centre of
the superior curved line, and is analogous to the spinous process of a
vertebra. Its size varies in different individuals, being much larger in
some persons than in others. The upper margin of the superior curved
line gives attachment to the occipito-frontalis muscle, its inner extremity
to the trapezius, and just beneath the outer extremity are the points of
attachment of the splenius capitis muscle. On either side of the crest,
between the curved lines, are marked depressions for the attachment of
the complexus muscles, and just below and to the outer side of these is
a smooth surface for the insertion of the superior oblique muscles. The
space below the inferior curved line gives attachment to the rectus capitis
posticus major and minor muscles.
The Internal Surface of the bone is divided into four fosse by two
distinct ridges, transverse and longitudinal: the former runs from the
lateral angles to the internal occipital protuberance, the longitudinal
ridge extending from the superior angle of the bone to the foramen
magnum. The point where these ridges intersect is called the internal
occipital protuberance. The superior fosse afford lodgment to the lobes
of the cerebrum, while the inferior accommodate those of the cerebel-
lum. The superior part of the longitudinal and the transverse ridges
are generally grooved, to accommodate the longitudinal and the lateral
venous sinuses. Frequently the longitudinal sinus is found to the right
side of the superior longitudinal ridge,' particularly where it approaches
the intersection of the ridges.
S
The inferior portion of the longitudinal ridge is rounded, and is gen-
erally called the internal occipital crest.
K
54
ANATOMY.
The Foramen Magnum is the largest foramen of the brain-case.
It is situated on the inferior surface, between the jugular and basilar
processes and the tabular portion of the bone. It is oval in shape,
its long diameter being antero-posterior. It transmits the spinal cord
and its membranes, the spinal accessory nerves, and the vertebral
arteries.
STRUCTURE.-About one-third of the basilar process, commencing at
the foramen magnum, is made up of two plates of compact tissue.
These plates then divide and enclose between them cancellated tissue.
The jugular processes are principally made up of spongy substance,
the fosse being composed of compact tissue. The fosse for the lodg-
ment of the two lobes of the cerebellum are formed of compact bone,
the remainder of the tabular portion of the bone being made up in
a great part of two plates, with abundant diploë between them.
Especially is this the case near the occipital protuberance.
DEVELOPMENT.-The occipital bone is developed from osseous carti-
lage and osseous membrane. The condyloid (ex-occipital) and the basilar
(basi-occipital) portions commence to ossify in cartilage about the sev-
enth or eighth week of embryonic life, each having a separate nucleus
FIG. 16.
By 4 centres

at birth
the 4 pieces
separate
M
1 for occipital
portion
1 for each condylvid
portion
1 for basilar
po:tion
Join about 4 y?.
Join 5.6y...
Development of Occipital Bone.
or centre.
The osseous union of the basilar and condyloid portions
begins at the third or fourth year, and is completed by the end of the
fifth or sixth year. The basi-occipital and the basi-sphenoidal portions
of the respective bones are united by intervening cartilage until about
the fifteenth year, at which time ossification commences, and it is gen-
erally completed by the twentieth year.
The tabulated portion (supraoccipital) commences its process of ossi-
fication in membranous tissue a short time before the remainder of the
bone, from four centres, which at birth have been united and form one
bone. At this time three deep fissures are noticeable at the superior
and lateral angles. Occasionally the lateral fissures run into each other,
and the upper portion forms the interparietal bone of many animals.
The osseous union of the supra and the condyloid portions begins during
the second or third year, and is completed by the third or fourth year.
BONES.
55
REMARKS. The basilar and condyloid portions of this bone, being
so nearly connected with the mouth and associate parts, claim special
attention.
The basilar process forms the roof of the pharynx, and is situated on
a level with the posterior nares, and in surgical operations may be
reached through the nose or through the oral cavity.
Hydatid or exostosed cysts and other enlargements within the ante-
rior condyloid foramen, producing pressure upon the hypoglossal nerve,
would cause paralysis, atrophy, or deflection of the tongue.
The Temporal Bone (Fig. 17) is situated at the side and base of the
brain-case. It articulates in front with the great wing of the sphe-
noid bone, above with the parietal bone, behind with the lateral portion
of the occipital bone, and at the base of its petrous portion is wedged
FIG. 17.

Squam
Artic.with Malar.
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STYLO-HYOID
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STERNO-MASTO
Process
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eman dute sun sung
STOID
Mustoid
foramen.
Left Temporal Bone, outer surface.
in between the basilar process of the occipital and the great wing of the
sphenoid bone. By its outer surface it assists in the formation of the
temporal and the zygomatic fossæ and the zygomatic arch; by its under
surface it forms part of the roof of the parotid region; and by its inner
surface it forms part of the middle fosse of the brain-case. For con-
venience of description this bone is generally divided into three portions
-viz. the squamous (scale), the mastoid (nipple), and the petrous (rock).
G
56
ANATOMY.
The styloid process may also be added to this division, and studied sepa-
rately, as it has its own centre of ossification.
The Squamous Portion is divided into three parts-the ascending, the
horizontal, and the part forming the wall of the glenoid cavity. The
ascending portion is concavo-convex, the convexity, which is almost per-
pendicular, being smooth and giving origin to the temporal muscle. It
is marked by two grooves running upward, one near its anterior border,
the other at the posterior termination of the zygomatic arch. They in-
dicate the position of the deep temporal arteries at the upper border of
the squamous portion, where it articulates with the parietal bone, form-
ing the temporo-parietal suture (squamous); the outer table is extended
considerably beyond the inner, thus forming a scale or bevel at the
expense of the inner border. This scale overlaps the corresponding
surface of the parietal bone. That portion which forms the suture is
bevelled inwardly, the middle portion is serrated, and the lower portion
anteriorly is bevelled outwardly.
The zygomatic process (horizontal portion) has a triangular origin
from the squamous portion of the bone, where it bends abruptly inward
toward the base of the skull, and has three roots. Its large posterior
root passes backward, above the external auditory meatus, behind which
it forms the boundary between the squamous and the mastoid portions
of the bone, and is called the supramastoid ridge; this then curves
upward, and, uniting with the temporal ridge of the parietal bone,
forms the posterior boundary of the temporal fossa. The middle root
forms the outer boundary of the glenoid fossa; then bends inwardly
and terminates in the posterior glenoid process at the outer extremity
of the glenoid fissure. The anterior root runs directly inward in front
of the glenoid fossa, forming its anterior border, which is also known
as the eminentia articularis. At the juncture of this root with the
zygomatic process is a rounded eminence, called the tubercle, for the
attachment of the external lateral ligament of the inferior maxilla.
The zygomatic process projects outwardly from the skull about one-
fourth of an inch, and has an upper and a lower surface; it then turns
upon itself, and its posterior edge, which is thin, forms the superior
border. The inferior border is about half an inch in length, its
extremity being serrated and bevelled at the expense of the inferior
border, where it articulates with the zygomatic process of the malar
bone. The masseter muscle arises in part from the lower border of this
process, and each side of the upper border gives attachment to the two
layers of the temporal fascia.
The Glenoid Fossa is situated at the base of the squamous portion
of the bone. It is bounded in front by the anterior root of the zygoma,
behind by the tympanic plate of the petrous portion, externally by the
auditory process and middle root of the zygoma. It is divided into an
anterior and posterior portion by the glenoid fissure (fissure Glaserius,
the squamoso-tympanic suture). The anterior half is the articulating
portion of the fossa, and is occupied by the condyle of the inferior
maxilla. In man this is a complicated articulation, which will be
described subsequently. The posterior half accommodates the upper
portion of the parotid gland.
BONES.
57
The glenoid fissure communicates with the tympanum (middle car),
and lodges the processus gracilis of the malleus. It is at this point
that Meckel's cartilage is united to the bones of the ear in the early
stage of development. It also transmits the levator tympani muscles
and the tympanic branch of the internal maxillary artery. The chorda
tympani nerve passes through a separate canal parallel to the glenoid
fissure (canal of Hugier) on the outer side of the Eustachian tube and
between it and the carotid canal.
with
The Internal Surface of the temporal bone (Fig. 18) is concave
and marked by depressions for the middle lobe of the cerebrum. It is
FIG. 18.
Artiolates
Occipital
Petrous
Aqueductus Vestibuli
Depression for Dura-mater
Meatus Auditoruis internus
772
Bone
P
Posterior Surface
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Inner Surface
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Eminence for Superior Semicircular
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Opening for Smaller Petrosal Norve
Depression for Casserian ganglion
-Bristle passed through Carotid Canal
Left Temporal Bone, inner surface.
grooved for the meningeal arteries, which run almost parallel with the
deep temporal arteries on its outer surface. At the lower portion there
is an eminence corresponding partially to the glenoid fossa on the outer
surface. At this point the bone is so thin as to be almost transparent.
The Petrous Portion (Fig. 19), so named from its hardness, con-
tains the internal and middle ear. The facial nerve passes outward
through this part of the bone, and the internal cartoid artery inward;
it supports, in part, the cartilaginous portion of the Eustachian tube.
It forms a three-sided pyramid, with its base directed outward, its apex
forward, inward, and slightly downward, where it is wedged between
the basilar process of the occipital bone and the great wing of the
58
ANATOMY.
sphenoid, leaving a portion unoccupied by bone. This unoccupied
portion is called the middle lacerated foramen, and is filled up with
cartilage in the recent state. It has three surfaces: two (the anterior
and posterior) are situated within the brain-case; the other, the inferior,
on the outside.
The Anterior Surface looks forward and upward, marking in the base
FIG. 19.

Rough Quadrilateral Surface
Opening of carotid samal
Canal for Jacobson's nerve.
Aqueductus Cochle ce
Canal for Arnold's nerve
Jugular fossa
Vaginal process
Styloid process
Stylo-mastoid foramen
Jugular Surface
Auricular fissure
Canals for Eustachian tube
and Tensor tympani musele
LEVATOR PALATI
TENSOR
TYMPANI
file
Mu
Hi
Mastoid
proo.
STYLO-PHARYNGEUS
Petrous Portion of Temporal Bone, inferior surface.
of the brain-case the posterior border of its middle fossa, being divided
into a superior and an inferior portion.
The Superior Portion of the petrous portion of the temporal bone
is of hard consistency; near the centre is a rounded eminence mark-
ing the situation of the superior semicircular canal. A depression
near the apex defines the position of the Gasserian ganglion (semilunar
ganglion of the fifth pair of nerves; see p. 284). Below this depression
is the termination of the internal carotid canal. A narrow groove,
sometimes double, divides the superior from the inferior portions of the
surface. Along this groove are one or more minute openings, the prin-
cipal one being the hiatus Fallopii, for the transmission of the greater
superficial petrosal nerve; a smaller opening below is occupied by the
lesser petrosal nerve. The inferior portion, known as the tegmen
-
BONES.
59
tympani, is a thin layer of bone which forms the roof of the tympanum
and the bony portion of the Eustachian tube. It is bounded anteriorly
by the petro-squamous fissure, which commences internally at the angle
between the squamous and petrous portions of the bone, and extends
outwardly to the masto-parietal suture: internally it extends downward
and backward, forming the glenoid fissure (fissure of Glasserius).
The Posterior Surface looks backward and inward; it is less oblique
than the anterior, and forms, in great part, the anterior border of the
posterior fossa of the brain-case. Near its centre is a large orifice
leading into a short canal. The canal is directed outward, and is called
the internal auditory meatus. It transmits the seventh (facial) and
eighth (auditory) nerves and the auditory artery.
The meatus is about four lines in depth, and terminates in a thin
plate of bone, the lamina cribrosa, in the lower portion of which are
several small openings for the transmission of the divisions of the audi-
tory nerve; in the upper portion is the aqueduct of Fallopius, for the
passage of the facial nerve. This canal has a tortuous course through
the petrous portion of the temporal bone, passing at first outward for
a short distance between the cochlea and vestibule to the inner wall of
the tympanum; then backward over the fenestra ovalis, the ear, and then
downward, terminating at the stylo-mastoid foramen. External to the
internal auditory meatus, and between it and the posterior fossa, is a
slit-like opening, quite indistinct in some cases, which leads to a canal,
the aqueductus vestibuli. This canal transmits venous blood from the
internal ear. The superior border, which divides the anterior from the
posterior surface, is grooved for the superior petrosal sinus, but it never
extends to the apex of the bone. That portion of the border internal
to the meatus is depressed for the reception of a thick fold of dura mater,
under which the third, fourth, fifth, and sixth nerves pass.
The Inferior Surface of the petrous portion is rough and uneven.
From within outwardly, or from the apex to a large foramen situ-
ated about midway of this surface, is a rough triangular space which
gives attachment to the levator palati and tensor tympani muscles. The
large round foramen is the external opening to the canal for the internal
carotid artery. It first passes upward, then horizontally forward and
inward to the apex of the bone, from which point the vessel enters the
brain-case.
D
A plexus of the sympathetic nerve accompanies the artery in its
course through the canal. External to and a little above this foramen
is a smooth, deep depression, the jugular fossa, which varies in size in
different skulls, and when articulated with the jugular notch in the
occipital bone the two form the jugular foramen. Just back of the
jugular fossa, at the commencement of the border of the mastoid por-
tion of the bone, is an irregular, rough surface, the jugular facet, which
articulates by synchondrosis with the transverse process of the occipital
bone.
Several small foramina are situated in this portion of the bone. In
the ascending portion of the carotid canal is a small foramen for the
tympanic branch of the internal carotid artery, and between the jugular
fossa and the opening for the carotid canal will be found a foramen for
60
ANATOMY.
the tympanic branch of the glosso-pharyngeal (Jacobson's) nerve. On
the border between the posterior and the inferior surfaces, internal to
the jugular fossa, is the aqueductus cochlea, which transmits a vein from
the cochlea to join the internal jugular vein. In the internal portion
of the jugular fossa is a foramen for the auricular branch of the pneumo-
gastric nerve (Arnold's nerve).
The Tympanic Portion forms part of the roof of the external audi-
tory meatus, and is that part of the glenoid fossa which lies below
and posterior to the glenoid fissure. It is irregular in outline, and is
wholly made up of compact tissue. When examined externally, it
pre-
sents a U-shaped portion which bounds three-fourths of the external
auditory meatus; which opening leads direct to the tympanic mem-
brane. The remaining or upper boundary of the meatus is formed by
the squamous portion of the bone. The curve of the U is roughened
for the attachment of the cartilage of the ear. The tympanic division
extends inward and downward, encasing the base of the styloid process.
This division terminates anteriorly in the vaginal process and poste-
riorly in the glenoid fossa. It is concave in form, and receives the
upper portion of the parotid gland. It terminates in the point opposite
the spinous process of the sphenoid bone, at the commencement of the
opening for the cartilaginous portion of the Eustachian tube.
The Styloid Portion is of hard consistency, long and tapering, point-
ing downward, inward, and forward in the direction of the great cor-
nu of the hyoid bone; its average length is about one inch, though
sometimes it is greater, complicating surgical operations in the region
through which it passes. It is situated directly in front of the digastric
fossa and behind the vaginal process, which in great part surrounds it.
It gives origin to the stylo-pharyngeus, the stylo-glossus, and the stylo-
hyoideus muscles; also to it the stylo-hyoid and the stylo-maxillary
ligaments are attached. The mastoid portion is the enlarged roughened
portion situated at the posterior inferior extremity of the bone.
It
assists in forming the masto-occipital and the masto-parietal sutures,
the mastoid ridge separating it from the squamous portion of the bone.
It is divided into two portions, the mastoid and the posterior mastoid,
by the extension over it of the superior semicircular line from the occip-
ital bone, which line continues its curve, terminating at the extremity
of the mastoid process. The last is large, extending downward and
forward behind the external auditory meatus and the tympanic portion
of the glenoid fossa. It is small during infancy, but increases and
becomes of large size in the adult, especially in individuals with large
and powerful muscles. It serves for the attachment of the sterno-cleido-
mastoideus, the splenius capitis, and the trachelo-mastoid muscles, the
two former extending their attachment along the superior semicircular
line of the occipital bone. The internal portion of the mastoid process
is full of cells, which communicate with the middle ear. On the inner
portion and at the base of the process is a deep groove, the digastric
fossa, for the attachment of the digastric muscle; and on the inner side
of the groove and parallel with it is the occipital groove for the occipital
artery.
Between the mastoid and the styloid processes, and immediately in
BONES.
61
front of the digastric fossa, is the stylo-mastoid foramen, which is the
termination of the aqueductus Fallopii, and transmits the facial nerve
and the stylo-mastoid artery. Beneath the semicircular curved line are
one or more foramina of variable size which admit veins to the lateral
sinus. When these foramina are large, wounds in this region are dan-
gerous, as the blood would flow freely from the sinus. Sometimes these
veins enter the sinus through the suture.
FIG. 20.
The internal surface is marked by a deep groove, the sigmoid groove,
for the accommodation of the lateral sinus. Frequently these sinuses
vary greatly in depth in the same skull.
DEVELOPMENT.-The temporal bone is developed from four centres
of ossification. The squamous, the zygomatic, and the tympanic por-
tions are developed from
membrane, the petrous por-
tion and the styloid pro-
cess from cartilage. The
squamo-zygomatic portion
commences to ossify in the
lower part of the squamous
portion at the latter part of
the second or the beginning
of the third month of em-
bryonic life. Ossification
extends upward into the
squamous and outward into
the zygomatic portions.
Shortly afterward ˆ an OS-
sific centre appears in the
lower part of the membran-
ous tympanum, ossification
spreading upward and in-
ward until it joins the petro-
mastoid portion behind and 1 for Styloid proo.
the squamo-zygomatic in
front, forming the incom-
plete tympanic ring. Ossification of the petro-mastoid portion com-
mences much later, usually about the end of the fifth or the beginning
of the sixth month of fœtal life. The osseous deposits are made at
many points in the cartilage, being all united, however, at birth. The
styloid portion is the last to ossify, remaining cartilaginous until after birth.
The temporal bone is composed of four separate pieces at birth. The
mastoid process has not appeared, and does not commence to develop
until the second year; from this period it increases in size until adult
life, the air-cells appearing about the age of puberty. The external
auditory meatus at first is shallow, but increases in depth by the out-
growth of the united squamous and petro-mastoid portions above and
behind, and the tympanic portion in front and below.
The glenoid fossa is superficial, the articulating eminence being slight.
By the growth of the tympanic portion downward the depth of the
fossa is increased.
1 for Squamous
portion including
Zygoma
2nd mo.
1 for Auditory
provess
1 for Petrous
& Masturd
portions
q
W!!
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Portion.
Crocessus
Auditorius
Tym
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flemay birth
Petrous
fgom a
Ports
unite during 1 year
At Birth 3
piccos separate
Development of the Temporal Bone by Four Centres.
K

62
ANATOMY.
THE SPHENOID BONE.
The sphenoid bone is situated across the base of the skull, extending.
upward and anteriorly until it joins the frontal and parietal bones. It
is placed mostly in front of, but partially internal to, the temporal bones.
The posterior face of the body of the sphenoid bone articulates with the
basilar process of the occipital bone; anteriorly the articulation is with
the malar and palate bones, the ethmoid, and the vomer, and occasion-
ally, through the inferior angle of its anterior border, with the superior
maxilla. Acting as a key or wedge, the central location of this bone
causes it to enter into the formation of the anterior and middle fossa of
the brain-case by the inner, and of the temporal, zygomatic, and spheno-
maxillary fossa by the external, surface; also the orbital and nasal cav-
ities internally. It forms part of the roof of the pharynx, and the
hamular process of its internal pterygoid plate can be reached through
the mouth just posterior to the tuberosity of the superior maxillary
bone. It gives support to the superior dental arch and origin to three
of the four muscles of mastication. The great sensory nerve of the
teeth and face and the branch of this nerve governing the muscles of
mastication pass from the brain-case through three of the foramina of
this bone. It also gives passage to the optic, motor oculi, pathetic, and
abducens nerves, the ophthalmic artery and veins, and to two of the
meningeal arteries.
C
For convenience of study the sphenoid bone is divided into a body
and six processes, three on each side, a greater and lesser wing, and a
pterygoid process composed of two plates. The body of the bone is
cuboidal in shape, having six surfaces-a superior, inferior, anterior,
posterior, and two lateral.
The Superior Surface (Fig. 21), the most irregular of the six, is
situated within the brain-case. Its anterior border, known as the eth-
moidal spine, is thin, projects forward and slightly upward, and by its
centre articulates with the crista galli of the ethmoid bone. Just poste-
rior to this spine is a smooth, slightly concave surface extending back-
ward to the optic groove and laterally into the lesser wings. This
surface forms part of the floor of the anterior fossa of the brain-case.
The optic groove, slightly curved, passes nearly transversely across the
body of the bone, and terminates on either side in the optic foramina.
These foramina transmit the optic nerves and the ophthalmic arteries,
while the groove lodges the optic commissure. Just behind the optic
groove, and between it and the pituitary fossa (sella turcica), is a small
surface of bone, the olivary process, which assists in supporting the
optic commissure. Posterior to this process is a deep concavity, the
pituitary fossa (sella turcica) for the reception of the pituitary body..
All that portion of the bone situated behind this fossa, and between it
and the spheno-occipital articulation, is termed the dorsum sellæ. At
the superior lateral angles of this portion of the bone are the posterior
clinoid processes. The posterior border of the lesser wings terminates.
in rounded points, the anterior clinoid processes. At the superior
lateral angle of the anterior border of the pituitary fossa, on the poste-
rior margin of the olivary process, is sometimes seen a small tubercle
Gg.
BONES.
63
of bone, the middle clinoid process. Occasionally this process is con-
nected by a spiculum of bone with the anterior clinoid process, forming a
foramen; more rarely to both the anterior and posterior processes, form-
ing two foramina and a continuous and uninterrupted border from the
superior anterior angle of the lesser wing to the superior angle of the
dorsum sellæ.
The lateral surfaces of the body of the sphenoid bone are almost
entirely within the brain-case. A small portion, however, of this
surface runs forward and forms the proximal border of the foramen
rotundum, the base and proximal boundary of the sphenoidal fissure,
and continues forward until it meets the sphenoidal turbinated bones.
FIG. 21.
"L
Middle Clinoid process
Posterior Clinoid process
X
Foramen Opticum
Foramen Lacerum
anterius, or Sphe-
noidal Fissure
Foramen Rotundum:
14 Vesalii,
<<
Greater
Cerebral Surfa
Ovale
Spinosum
Spin. proc.
Etlimwidal Spine
Groove for
Olfactory nervo
Lesser Wing
Ant
Clinoid
attan
EH:moid,
with
Optic Groove
Olivary
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icas
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Supports
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720
of
portions
Bone
Squamous
Temporal
and
Sphenoid Bone, superior surface.
On that portion of the lateral surface within the brain-case is a marked
depression, the sigmoid groove, for the accommodation of the internal
carotid artery and the cavernous sinus.
The posterior surface is quadrilateral in shape. Until about the
fifteenth year this surface is separated from the occipital bone, with
which it articulates, by a layer of cartilage. At this time ossification
commences between the two bones, and is completed about the twentieth
Parietal
with
year.
In the middle of the anterior (nasal) surface is a thin vertical lamina
of bone which forms part of the septum of the nose and articulates with
the perpendicular plate of the ethmoid bone. On each side of this lam-
ina are irregular openings, varying in size in different bones, and often
in the same bone; they lead into the sphenoidal sinuses situated in the
body of the bone. The body of the bone is completely hollowed by
these sinuses, which accounts for the complete thinness of its walls.
The septum of bone between these cavities is generally deflected to
64
ANATOMY.
the one side or the other, making the sinuses of unequal size. Other
incomplete septa may be seen at the posterior portion of these cavities,
which divide them into several compartments. Sometimes they extend
back and penetrate the basilar process of the occipital bone. They are
lined by mucous membrane, which is continuous with that of the nasal
cavity. The larger part of the anterior surface of the body is formed
by the sphenoidal turbinated or spongy bones; they are triangular in
shape, their apices pointing downward and backward, their upper mar-
gins being somewhat deflected, which opens a passage or communication
between the sinuses and the nose. They are formed from separate
points of ossification, but soon unite with the sphenoid behind and the
ethmoid in front.
The Inferior Surface (Fig. 22) is apparently a continuation of the
anterior. It presents in the middle line a triangular spine, the ros-

Pterygoid
Ridge
Orbital
Surface of
Greater Wing
Rostrum
Pterygoid Note
one
Turbin
211
Vaginal
PIOC
FIG. 22.
Artie with Perpendicular
Plate of Ethmoid
Pterygo-
palatine
Canal
Groove for ala
of Vomer
Rostrum
Artic, with
Vomer
TERNAL
PTERYGO
*/}]}]}]
valits
mutilis
mih yuldu
TEMPORAL MUS
LAXATOR TYMPANI
Internal Pterygoid plate
Hamular process
Sphenoid Bone, anterior surface.
(In this figure both the anterior and inferior surfaces of the
body of the sphenoid bone are shown, the bone being held with the pterygoid processes almost
horizontal.)
trum, which is a continuation of the vertical lamina of the bone of the
anterior surface, and articulates with the fissure formed by the alæ of
the vomer. These ala, together with the vaginal process of the sphe-
noid, which are prolongations of the internal pterygoid plates, cover
the greater part of the inferior surface of the body of the bone, and
lock the parts together.
The Greater Wings are two irregular strong processes of bone
arising from the lateral surfaces of the body. They extend outward,
forward, upward, and backward, and present for examination three sur-
faces, the internal, external, and orbital; and five borders, the superior,
inferior, anterior, lateral, and posterior.
The Internal or Cerebral Surface is situated entirely within the
brain-case, and forms part of the middle fossa of the cranium. This
surface is deeply concave, and marked by eminences and depressions
Judg
BONES.
65
for the convolutions of the brain. At the point where the wing
joins the body of the bone anteriorly is a round opening, the foramen
rotundum, which transmits the second division of the fifth nerve.
About half an inch posterior to this may be seen an oval aperture
larger than the preceding. This is called the foramen ovale, and
transmits the third division of the fifth and the small petrosal nerves
from within outwardly, and the lesser meningeal artery from without
inwardly. Behind and a little external to the former, in the spinous
process of the bone, is a small aperture, the foramen spinosum, for the
transmission of the middle meningeal artery.
The External (Temporo-zygomatic) Surface is convex from above
downward, and is divided into two portions, a superior and an
inferior, by a ridge of bone, the infratemporal crest. The superior
portion is the larger of the two, averaging about half an inch in
width and an inch and a half in height. This is concave, forms part
of the temporal fossa, and gives attachment to part of the temporal
muscle. The inferior portion is also concave, enters into the formation
of the zygomatic fossa, and gives attachment to the outer part of the
external pterygoid muscle. The posterior border of this portion of the
bone extends downward and outward, and terminates externally in a
point of bone called the spinous process, which gives attachment to
the internal lateral ligament of the lower jaw and the laxator tympani
muscle.
The Orbital Surface, or that portion of the greater wing which
assists in forming the outer wall of the orbit, is smooth, and may be
divided for purposes of description into two portions, an outer and an
inner, by an imaginary line drawn from the notch found in its superior
border, for the accommodation of a branch of the lachrymal artery to
a point just external to the foramen rotundum. The outer portion is
quadrilateral in form, while the inner, or that immediately above the
pterygoid process, is triangular.
The Quadrilateral or Outer Portion is composed principally of
spongy tissue, though that which joins the malar bone is compact
and helps to form the orbito-temporal partition. This surface articu-
lates above with the frontal bone, externally with the malar bone, and
inferiorly it forms the posterior boundary of the spheno-maxillary fis-
sure. The inner portion is thin, being made up of compact tissue. The
superior border forms the posterior boundary of the sphenoidal fissure.
Just below this border, on the inner surface, near the imaginary line
dividing the orbital surface, there is generally found a small spine of
bone, for the origin of part of the lower head of the external rectus
muscle.
BORDERS.-The Superior Border is divided into two portions, an
outer and an inner; the outer is broad, triangular, and roughened, the
greater part being for articulation with the frontal, the remainder with
the parietal bone. The inner portion is thin, and forms the outer
boundary and anterior superior angle of the sphenoidal fissure or
anterior lacerated foramen.
The Inferior Border is smooth, rounded, and forms the posterior
boundary of the spheno-maxillary fissure.
VOL. I.—5
66
ANATOMY.
The Anterior or Malar Border is serrated for articulation with the
malar bone.
The Lateral Border is serrated, and bevelled above and below by the
projections of the outer plate and by the extension of the inner plate.
This border articulates with the squamous portion of the temporal
bone.
The Posterior Border (Fig. 23), somewhat concave in form, commences
at the body of the bone and terminates in the spinous process, the outer
FIG. 23.

Pterygo
fossa
APINANG
INTERNAL
PTERYGOID
Sphenoid Bone, posterior surface.
portion being rough for articulation with the apex of the petrous portion
of the temporal bone. The internal portion of this border is smooth,
and forms the anterior boundary of the middle lacerated foramen, and
is perforated by the posterior opening of the Vidian canal.
The Lesser Wings are two thin triangular plates of compact bone ris-
ing by two pedicles from the anterior superior portion of the body. They
extend outwardly in the direction of the superior border of the greater
wings, and terminate in short points. The superior surface of the
lesser wing is smooth, being a continuation of the body of the bone, and
helps to form the base of the anterior fossa of the brain-case. The infe-
rior surface is part of the roof of the orbit, and forms the superior and
part of the internal boundary of the sphenoidal fissure (lacerated
foramen).
The Sphenoidal Fissure is an opening approaching an isosceles triangle
in shape, the base of the triangle being the body of the bone, the apex
extending outward to the notch in the superior border of the greater
wing. When the sphenoid bone is articulated with the frontal, this
fissure becomes the anterior lacerated foramen, which transmits from
within outwardly the third, fourth, ophthalmic division of the fifth,
which breaks into three branches in this foramen, and the sixth nerve,
and from without inwardly the ophthalmic vein and a branch of the
lachrymal artery. The anterior border of the lesser wing is serrated for
articulation with the orbital plate of the frontal bone.
The Posterior Border of the lesser wing is short, and by its junction
BONES.
67
with the lateral border forms the anterior clinoid process. The inter-
nal aspect of this border at the point where it joins the body of the bone
is pierced by the optic foramen, which follows the line of junction of the
lesser wing with the body.
The Lateral Border is free, smooth, and rounded, and is received into
the fissure of Sylvius of the brain.
The Superior Pedicle is broad, thin, and forms the roof of the optic
foramen.
The Inferior Pedicle forms the base and external boundary of the
optic foramen. It is in shape a three-sided prism.
The Optic Foramen transmits the optic nerve and the ophthalmic
artery.
The Pterygoid Processes project downward from the junction of the
great wings with the body of the bone. Each process is composed of
two plates, which separate at their lower third, forming a triangular
notch for the reception of the pyramidal process of the palate bone, with
which it articulates by a serrated surface. Above the pterygoid notch,
anteriorly, is a smooth, triangular surface of bone which forms the pos-
terior wall of the spheno-maxillary fossa. At the upper border of this
triangular surface is seen the foramen rotundum, while at its superior
inner angle, or apex, will be found the anterior opening of the Vidian
canal. It is just at this point that the spheno-palatine or Meckel's gan-
glion is situated.
The external plate is broader than the internal. It is a continuation
of the great wing, passing downward and outward, forming a concavity
externally. Its anterior border articulates with the palate bone near to
the tuberosity of the superior maxilla. Its external surface gives origin
to the lower head of the external pterygoid muscle. The upper two-
thirds of these two plates of bone are joined anteriorly. Posteriorly
they diverge, forming the pterygoid fossa.
The Pterygoid Fossa.-The internal pterygoid muscle in this fossa
arises from the outer plate only.
The inner plate is vertical, longer, and thinner than the outer plate.
Its anterior border articulates with the palate bone. The posterior bor-
der is free, and forms the distal and lateral boundary of the posterior
naris.
The Scaphoid Fossa.-Above the pterygoid fossa, and between it and
the posterior opening of the Vidian canal, is situated the scaphoid fossa.
It gives origin to the tensor palati muscle, the tendon of which descends
the outer surface of the internal pterygoid plate to its inferior extremity,
winds around the hook-like projection, the hamular process, and is
inserted into the soft palate.
The hamular process can be felt at the posterior lateral portion of
the mouth, behind the tuberosity of the superior maxilla.
Vaginal Process.-The internal pterygoid plate at its upper internal
surface curves inwardly until it meets and partially leaves the body of
the bone. The extremity of this curve is called the vaginal process.
The internal surface of the external pterygoid plate forms part of the
external wall of the nasal chamber.
DEVELOPMENT.-The sphenoid bone is developed from fourteen cen-
--
68
ANATOMY.
tres of ossification. There is a natural division of these ossific points
into a posterior (postsphenoid) and an anterior (presphenoid) portion.
The Sella Turcica and the great wings belong to the former of these
divisions, while that portion of the body in front of the olivary process
and the lesser wings belong to the latter. This division is found com-
plete and persistent throughout life in many of the lower animals. At
about the eighth week of embryonal life ossification commences in the
postsphenoid division. There is one nucleus for each great wing (ali-
sphenoid), including the external pterygoid plates. About the same
time two nuclei appear for the posterior part of the body of the bone
(basisphenoid). These unite about the fourth month. After this union
FIG. 24.
1.
A.
B
2...
S
35.00
7.
D
Vo
-
A, the sphenoid bone of a fœtus, aged about three months, is seen from above. The great wings are
ossified; the body has two round granules of bone beneath the sella turcica, and the rest of it is
cartilaginous. In the small wings, which are formed from a single centre, the ossification has
encircled the optic foramen, and a small suture is distinguishable at its posterior and inner side.
The internal pterygoid processes are still separate (C4) in the preparation from which the draw-
ing was made.-B. This figure is copied from Meckel (Archiv, Bd. 1. Taf. vi. F. 23). It is stated to
be from a fœtus at the middle of the sixth month. The two granules for the body are united, and
a trace of their union is observable in the notch in front. The lateral projections of the body (5)
are separate pieces.-C is a sketch of the back part of the preparation shown in A. The internal
pterygoid process, which was united only by cartilage to the rest of the bone, has been drawn
aside.-D. This figure represents the sphenoid at the usual period of birth. The great wings are
separate. The anterior sphenoid is joined to the body.
1. The great wings; 2. The small wings; 2. Additional nuclei for the small wing; 3. The body: 4.
The internal pterygoid process; 5. The lateral processes of the body.
K



1.
two other centres appear, from which are formed the tongue of the bone
(basitemporal).
The Internal Pterygoid Plate arises from two separate points of
ossification, which appear about the fourth month. The internal plates
unite with the external pterygoid plates about the fifth or sixth month,
and are analogous to the pterygoid bones of some animals, in which
they remain separate throughout life. In the anterior (presphenoid)
division ossification commences about the eighth or ninth week by two
nuclei, which are deposited just outside the optic foramina. These form
the lesser wings (orbito-sphenoid). Two more centres appear on the
inside of the optic foramina, and form the presphenoidal portion of
the body of the bone. Some authors describe this portion of the bone
as developed from one centre of ossification, while others say that it is
formed from the same centres of deposit which build the lesser wings.
The sphenoidal turbinated bones arise from two centres of ossification,
generally after birth.
BONES.
69
At birth the sphenoid bone is in three separate parts, excluding the
sphenoidal turbinated bones. The great wings and external pterygoid
plates have joined the internal pterygoid plates on either side, and the
posterior portion of the body has joined the anterior portion, including
the lesser wings. The great wings join the body about the end of the
first year. The spheno-turbinated bones unite with the body, and the
posterior surface of the body with the basilar process of the occipital
bone about the age of puberty.
THE PARIETAL BONE.
The parietal bones form a large portion of the walls and the greater
part of the roof of the brain-case. They are two in number, quadri-
lateral in shape, and have two surfaces, an external and an internal; four
borders anterior, posterior, superior, and inferior; and four angles, ante-
rior superior, posterior superior, anterior inferior, and posterior inferior.
The External Surface (Fig. 25) is convex in form, the greatest con-
FIG. 25.
Articulates with Frontal B.
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Mastoid Port
Articulates with Occipital B.
Sphenoid Squamous
Left Parietal Bone, external surface.
vexity being in the centre of the bone, forming the parietal eminence
and indicating the point where ossification commences.
Below this
70
ANATOMY.
eminence is always one, and generally two, curved lines: the lower one
marks the superior boundary of the temporal fossa, and divides the
bone into two portions; the upper one limits the attachment of the tem-
poral aponeurosis. The superior portion of the external surface is rough,
porous, and covered by the aponeurosis of the occipito-frontalis muscle.
Close to the upper border, near the posterior superior angle, in one bone
or the other, is a small foramen, the parietal foramen, which transmits a
vein to the superior longitudinal sinus. This foramen is not constant;
it varies in size in different bones: sometimes it is situated between the
two bones. The inferior portion is flatter and smoother than the supe-
rior, and forms part of the temporal fossa.
The Internal Surface (Fig. 26) is deeply concave, and forms the pari-
etal fossa. It presents eminences and depressions corresponding to the
FIG. 26.
Post. Sup.
Angle
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Post. Infer.
Angle
Lateral
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Left Parietal Bone, internal surface.
convolutions of the cerebrum. Near the anterior inferior angle, at
a point posterior to the middle of the inferior border, will be seen
the commencement of grooves which extend upwardly and divide
into numerous branches. These grooves are for the accommodation
of the anterior and posterior branches of the middle meningeal arteries.
Sometimes the groove commencing at the anterior inferior angle has its
origin in a long canal. Along the inner aspect of the superior border
of this bone is a slight depression, which, together with its fellow on
BONES.
71
the opposite side, forms the groove for the longitudinal sinus. The
elevated edges of this groove give attachment to the falx cerebri. Below
this groove, especially in bones of old subjects, are seen several depres-
sions, which lodge the Pacchionian bodies. Extending across the poste-
rior inferior angle of the bone is a depression which forms part of the
groove for the lateral sinus.
BORDERS.-The Anterior Border is deeply serrated, and above is
slightly bevelled by the prolongation of the inner table, but toward the
lower angle it is bevelled by the extensions of the external table. This
anterior border articulates with the frontal bone, forming the parieto-
frontal part of the coronal suture.
The Posterior Border is irregular in outline, deeply serrated, and
articulates with the occipital bone, forming the parieto-occipital part of
the lambdoid suture. Numbers of what are known as Wormian bones
are often found attached to this border.
The Superior Border is the longest and thickest of the four. It is
deeply serrated, and articulates with its fellow on the opposite side,
forming the interparietal or posterior portion of the sagittal suture,
being all that remains after the ossific union of the two halves of the
frontal bone. Wormian bones are less frequently found in this border.
The Inferior Border is divided into three portions. The anterior
portion, about half an inch in extent, is thin and fluted, bevelled on its
outer surface for articulation with the great wing of the sphenoid bone,
which overlaps it and forms the spheno-parietal suture. The posterior
portion is thick, serrated, and articulates with the mastoid portion of
the temporal bone, forming the masto-parietal suture.
ANGLES.-The anterior superior angle is nearly a right angle. It
is completely ossified in adult life, but in infancy it is membranous,
and in conjunction with the membranous portions of the bone of the
opposite side and the adjoining portion of the frontal bone forms the
anterior or great fontanelle.
The posterior superior angle is an obtuse angle. In the articulated
skull it is situated at the junction of the interparietal (sagittal) and
parieto-occipital (lambdoid) sutures. In infancy this space is occupied
by the posterior superior fontanelle.
The Anterior Inferior Angle is the most prominent of the four.
It is thin and elongated, filling up the space between the frontal
bone and the squamous portion of the temporal bone. It articulates
with the great wing of the sphenoid bone. In infancy this space is
occupied by the anterior inferior fontanelle.
The Posterior Inferior Angle is thick, broader, and more rounded
than the others, and articulates with the mastoid portion of the tem-
poral and the lateral angle of the occipital bone; this is the location
of the posterior inferior fontanelle in infancy.
STRUCTURE. The parietal bone is made up of an outer plate of
compact tissue and an inner vitreous table, enclosing between them a
mass of cancellated fibrous bone.
DEVELOPMENT.-The parietal bone is developed within a membran-
ous matrix from one point of ossification, which appears about the
sixth week of embryonal life.
72
ANATOMY.
FRONTAL BONE.
The Frontal Bone (Fig. 27) is symmetrical in form-i. e. equal
on both sides of the median line of the head. It is situated in front
of the two parietal and a portion of the sphenoid bones, and above the
malar, lachrymal, nasal, part of the sphenoid, and ethmoid bones.
Though it is a true cranial bone, it forms that portion of the face called
the forehead, and is included in the "facial region." Its ascending
portion forms the anterior boundary and part of the roof of the brain-
FIG. 27.

TEMPORAL
ORBIC.PALFI
ATA, WA
CORRI
• SUPERCILII
Remains of Frontal Suture
Nasal
THE SEND THERE IS
悲しい
​Nasal
Eminence
Huiffimtas
-
Frontal
Eminence
Superciliary
Supra-orbital
Notch
or Foramen
Internal
Angular proc.
POLICIES IN THE
TotoTa
External
Angular proc.
Spine
Frontal Bone, outer surface.
case.
Its horizontal portion forms nearly the entire floor of the anterior
fossa of the skull and the roofs of the orbits. Laterally, the bone also
enters into the formation of the temporal fossa. It is composed prin-
cipally of compact tissue, and is divided into an ascending and a hori-
zontal portion.
The ascending portion commences at the supraorbital arch, and
extends upward and backward until it articulates with the parietal
bones. It has two surfaces, an external and an internal, and is divided
in the median line by a slight ridge. In young subjects before this
ridge is developed a suture occupies this line.
BONES.
73
The Supraorbital Arches are prominent curved borders of bone,
forming the superior boundaries of the orbits. They are most promi-
nent toward their outer extremities, and form the dividing-line between
the horizontal and ascending portions of the bone.
The Supraorbital Notch or Foramen.-At the inner third of the
supraorbital arch is a well-defined notch, the supraorbital notch;
sometimes this is converted into a foramen by a spiculum of bone
thrown out from its lower margin. When this spiculum is not present
the foramen is formed by fibrous tissue. It transmits the frontal
branches of the ophthalmic nerve, artery, and vein. There is generally
a small opening in the base of the notch for the passage of an emissary
vein from the diploë to join the ophthalmic vein.
The Frontal Notch is not constant: when it is, it is situated to the
median side of the supraorbital notch.
The External Angular Process.-The outer extremity of the supra-
orbital arch terminates in the external angular process. This is
strong, and projects to articulate with the frontal process of the malar
bone; the outer margin forms a sharp curved crest, which is the com-
mencement of the temporal ridge and affords attachment to the tem-
poral fascia. Just posterior to this crest is a slight concavity which
forms the anterior boundary of the temporal fossa.
The Internal Angular Process.-The inner extremity of the supra-
orbital arch terminates in the internal angular process, which is less
marked than the external, and articulates with the lachrymal bone. It
also gives origin to part of the orbicularis palpebrarum muscle.
The Nasal Eminence is between and slightly above the two internal
angular processes; it is a rounded elevation which forms a portion of
the anterior wall of the frontal sinuses.
The Frontal Sinuses are two irregular chambers situated above and
between the orbital plates, and separated by a thin lamina of bone.
They appear about the second year, and are formed by the dissolution
of tissue through the agency of osteoclasts. They continue to increase
in size until advanced age, at which time they often extend over the
orbits and occupy a larger or smaller portion of the bone above the
superciliary ridge: in the hollow-horned animals these cavities extend
into the bony base or cores of the horns. They are lined by mucous
membrane, and communicate with the nasal chambers through the
infundibulum of the ethmoid bone.
The Nasal Notch is situated below the nasal eminence: it is a
semilunar serrated border of bone for articulation with the ascending
process of the superior maxillæ, the vertical plate of the ethmoid, and
the nasal bones.
The Nasal Spine is a prominent process of bone in the centre of the
nasal notch it is firmly wedged between the nasal bones when they are
in position.
The Superciliary Ridges are above the supraorbital arches: they are
broad externally, where they are continuous with the nasal eminence.
They curve outwardly, becoming less prominent as they approach the
lateral surface of the bone. The internal portions of these ridges give
origin to the corrugator supercilii muscles.
74
ANATOMY.
The Frontal Eminences are about an inch above the superciliary
ridges, near the centre of each lateral half of the bone: they are two
rounded prominences, varying in size in different individuals, and are
seldom of equal size in the same bone.
The External or Upper Surface is smooth and rounded, and passing
over it is the aponeurosis of the occipito-frontalis muscles.
The Inner or Encranial Surface (Fig. 28) is marked by depressions
for the convolutions of the brain; by grooves running inwardly from
FIG. 28.

Articulates
Parietal Bone
Wedn
with
with
Great
VOORVITOO
wh
with Malar
Wing
Sphenoid
Posterior
and
Anterior
m m
Ethmoid
thmoidal for
ith
with
Lachrymal
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ser Wing
for Superior Longitudinal Sinus
with Nasal
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Meningeal Grooves.
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Fossan
Luchrymat
Frontal Sinus
Expanded base of Nasal Spine.
forming part of Roof of Nose
Frontal Bone, inner surface.
the lateral border for the accommodation of the anterior meningeal
arteries and their branches; and by several irregular hollows on either
side of the median line for the lodgment of the Pacchionian bodies.
The Internal Frontal Crest is the anterior termination of a groove
which occupies the median line of the internal surface of the bone.
The Foramen Cacum, anterior to the frontal crest, is a groove which,
when the frontal bone is articulated with the ethmoid, forms a blind
foramen. This foramen is continuous in childhood with the nasal
chambers, and transmits a small vein to the longitudinal sinus. In
adult life this so-called foramen is closed at its base.
BONES.
75
The Longitudinal Sinus commences at the foramen cæcum, passes
upward along the frontal crest to the groove, and thence backward over
the internal surface of the dome of the brain-case to the internal occip-
ital protuberance.
The Horizontal Surface is divided by the ethmoidal notch into two
portions, the orbital plates. The orbital plates are two concavo-
convex, triangular surfaces of bone separated by the ethmoidal notch.
They are each composed of two thin plates of compact tissue, the space
between them being largely occupied by the frontal sinuses.
The Inferior Surfaces of the orbital plates are concave and form the
roofs of the orbits.
The Lachrymal Fosse are slight depressions just internal to the
external angular process within the orbits; they lodge the lachrymal
glands.
The Trochlear Fossa are small concavities, sometimes tubercles, situ-
ated immediately behind the internal angular processes, within the
orbits; they afford attachments to the pulleys of the superior oblique
muscles.
The Superior or Encranial Surfaces of the orbital plates are convex
in form, deeply marked by eminences and depressions for the convolu-
tions of the brain: they form the greater portion of the floors of the
anterior fosse of the brain-case. The "digital depressions
called because of a fancied resemblance to markings made by pressing
the ends of the fingers upon some soft substance.
are so
The Ethmoidal Notch, between the two orbital plates, is a quadri-
lateral opening. In the articulated skull this notch is filled by the
cribriform plate of the ethmoid bone. On each side of the nasal spine,
running its entire length, is a grooved surface which enters into the
formation of the roofs of the nasal chambers..
The Fronto-ethmoidal Cells.-The borders of the ethmoidal notch
are marked by numerous depressions, which form half cells of irregular
shape. The ethmoid bone contains depressions of similar form in the
superior surface of its lateral masses, and when articulated with the
frontal bone forms the fronto-ethmoidal cells.
The Anterior and the Posterior Ethmoidal Foramina.-The borders
of the ethmoidal notch are each traversed at various angles by two
grooves. In the articulated skull these grooves, in connection with
similar ones in the ethmoid bone, form the anterior and posterior
ethmoidal foramina. The anterior foramina transmit the nasal nerves
and the anterior ethmoidal blood-vessels, while the posterior foramina
transmit the posterior ethmoidal blood-vessels.
The Borders of the Frontal Bone.-The upper half of the ascending
border is thick, serrated, and slightly bevelled by the prolongation of
the upper table. The lower half of this border is thinner than the
upper; it is serrated and bevelled by extension of the inner plate. The
upper seven-eighths of the border of the bone on either side articulate
with the parietal bones, forming the fronto-parietal (coronal) suture.
The lower eighth is rough and triangular, and articulates with the great
wing of the sphenoid bone, forming the spheno-frontal suture.
The inner border of the horizontal portion of the bone, just external
ANATOMY.
76
to the posterior margin of the ethmoidal notch, is thin and serrated,
and articulates with the lesser
wing of the sphenoid bone.
FIG. 29.

DEVELOPMENT.-The frontal
bone is an intra-membranous
bone, developing from two cen-
tres of ossification, which are
deposited, one on each side above
the orbital arches, about the
seventh week of embryonal life.
At birth the bone is in two por-
tions, which about the first year
unite by a vertical suture (saggi-
tal) in the median line. The
Frontal Bone at Birth, developed by two lateral halves. union commences from below
and extends upward; it is generally completed about the third year,
though occasionally the two halves remain separate much later in life.
ETHMOID BONE.
The ethmoid bone (Fig. 30), like the occipital, sphenoid, frontal,
vomer, inferior maxillary, and all bones in the median line of the
skeleton, is symmetrical. It is cuboid in form, and though a true
FIG. 30.
Cribriform Plate
with
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Fast, & Amt.,
Ethmoidal foramină
O s planum
STAFARMARA
with sup. Maxillary
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Uniciform
proc.
for Fuix
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Galli
ntal
Lachrymal
Slib. for
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with infturbinated b.
Ethmoid Bone, outer surface of right lateral mass (enlarged).
cranial bone it extends largely into the region of the face. It is
situated at the anterior part of the brain-case, between the orbits, and
forms part of the floor of the anterior cerebral fossa. When articulated
it closes the ethmoidal notch in the frontal bone and forms the greater
part of the internal walls of the orbital cavities. It also forms the
roof and part of the septum and external walls of the nasal chambers.
It is divided into a vertical plate and lateral masses, with a horizontal
BONES.
77
with Ethmoidal Spir
(cribriform) plate uniting the masses. The vertical plate (meso-ethmoid)
is again divided into the perpendicular plate and the crista galli.
The Perpendicular Plate (Fig. 31) is a thin lamina of compact bone
situated in the median line between the two lateral masses. It extends
FIG. 31.

prod
and
Perpendicular Plate
omer
with Triangulam
Frontal
with
culates
Nasal
with
ye of Septum
Perpendicular Plate of Ethmoid (enlarged), shown by removing the right lateral mass.
downward and forward in the direction of the intermaxillary suture,
though it is frequently deflected to the one side or the other. It forms
the upper third of the septum of the nose, and articulates posteriorly
with the crest of the sphenoid bone.
BORDERS.-The superior border of the perpendicular plate conjoins
the cribriform plate.
The Inferior Border is divided nearly in the centre into two portions.
The posterior inferior portion articulates with the vomer, while the
anterior inferior is roughened for the attachment of the nasal cartilage.
This cartilage is triangular in shape, and in the recent state forms part
of the septum of the nose.
The Anterior Border articulates with the under surface of the nasal
bones and also with the nasal spine of the frontal bone.
Grooves for Olfactory Nerves.-Immediately below the cribriform
plate, on the sides of the perpendicular plate, are fine grooves, running
downward, forward, and backward, in which are lodged the olfactory
nerves.
The Crista Galli (named from its resemblance to a cock's comb in
shape) is an extension of the perpendicular plate above the horizontal
portion of the bone between the anterior fosse of the brain-case. It is
ivory-like in appearance.
The anterior border of the crista galli is vertical in direction and
grooved at its base. In the articulated skull this groove, joining a
similar one in the frontal bone just anterior to the internal frontal
crest, forms the so-called foramen cæcum.
The Ethmoidal Wings.-Extending outwardly from the base of the
78
ANATOMY.
crista galli are two wing-like processes of bone, the ethmoidal wings or
alæ.
The posterior border of the crista galli is long, thin, and slightly
curved.
The longitudinal fold of the dura mater and the commencement of the
falx cerebri are both attached to the crista galli.
Lateral Masses (Fig. 32).—The lateral masses (ethmo-turbinated) are
cuboidal in form and present six surfaces-the superior and inferior,
external and internal, anterior
and posterior.
FIG. 32.

Sup Meatus
The Superior Surface.-
The anterior portion is com-
posed of irregular cell-like
openings, which are covered
in and completed by articu-
lation with the frontal bone.
The Ethmoidal Foramina
(Internal Orbital Canals).-
Crossing this border, about
half an inch apart, are two
slight grooves, which, when
conjoined to similar grooves
Ethmoid Bone, inner surface of right lateral mass (enlarged).
on the external border of the ethmoidal notch of the frontal bone, form
the anterior and posterior ethmoidal foramina: the first transmits the
internal nasal nerve, a branch of the ophthalmic and anterior ethmoidal
vessels, the posterior transmitting the posterior ethmoidal vessels and
spheno-ethmoidal nerve, a branch of the nasal.
The Inferior Surface extends from the inferior external border of the
lateral mass to the free margin of the middle turbinated bone in the
articulated skull, and from the anterior to the posterior surface of the
lateral mass. It is divided into three portions:
(a) The external portion lies between the inferior external border of
the lateral mass and the uncinate process anteriorly, the middle and pos-
terior line being formed by a curved plate of bone in the median line of
the inferior surface of the external mass. This portion articulates with
the superior border of the nasal surface of the superior maxilla, closing
in the cell-like cavities found on that border.
(b) Anteriorly, the middle portion is formed by the uncinate process
and posteriorly by the curved plate of bone forming the internal wall of
the anterior ethmoidal cells. The uncinate process arises from the mid-
dle of the anterior surface of the ethmoid bone, and extends downward,
outward, and backward, being somewhat hook-shaped in outline. It
articulates with the inner surface of the nasal process of the superior
maxilla, the ethmoidal process of the inner surface of the lachrymal
bone, and the inferior turbinated bone; it also assists in closing the
orifice leading to the maxillary sinus.
(e) The internal portion is free, and is formed by the curved border
of the middle turbinated bone in the articulated skull.
GRAS
The Internal or Nasal Surface is the most complex portion of the
bone. It forms part of the external wall of the nasal chamber, or all
BONES.
79
that portion of the wall which is devoted to olfaction. It commences at
the cribriform plate and descends downward and slightly forward. Its
posterior two-thirds is divided by a sulcus, which is directed backward
It
and inward. This groove forms the superior meatus of the nose.
extends backward to the posterior margin of the bone and terminates in
a deep notch. The anterior third of the internal surface is uninterrupted
from the cribriform plate to its lower border.
The Superior Meatus divides the internal surface of the lateral mass
into two portions—the superior and middle turbinated bones; it extends
antero-posteriorly upward, outward, and forward from the median line,
and communicates with the ethmoidal cells.
The Superior Turbinated Bone is all that portion between the sulcus
and the cribriform plate.
The Middle Turbinated Bone is that portion of the internal surface
lying below the sulcus and between it and the lower free border. The
middle turbinated bone is free, and extends downward into the nasal
chamber. Its lower border curves outward and upward toward the
superior maxilla, the outer surface of the curve appearing like a scroll.
This bone overhangs the middle meatus of the nose.
The Infundibulum.-At the anterior portion of the middle meatus
may be seen a passage known as the infundibulum, leading up through
the anterior ethmoidal cells into the frontal sinus.
The External or Orbital Surface of each lateral mass is a thin, smooth
lamina of bone, quadrilateral in form. Its length from the front to the
back is about double its width. This surface has also received the name
66
os planum," on account of its smoothness; it forms part of the inner
wall of the orbit. The two grooves which in the articulated bone assist
in forming the anterior and posterior ethmoidal foramina indent the
superior edge of this surface, which articulates with the frontal bone.
The inferior edge articulates with the superior maxilla.
The Anterior Surface extends inwardly from the os planum until it
reaches the nasal surface of the bone. It presents numerous cell-like
depressions. The inner portion of the anterior surface articulates with
the nasal process of the superior maxilla, the internal portion being
covered by the lachrymal bone; this, with the aid of the frontal bone,
already referred to, completes the anterior ethmoidal cells.
The Posterior Surface of the lateral masses is thin and penetrated by
numerous openings. It is divided into two portions, a superior and an
inferior. The superior portion articulates with the turbinated plates of
the sphenoid bone, and the inferior portion with the orbital process of
the palate bone. These bones conjointly complete the posterior ethmoid
cells.
The Cribriform Plate is symmetrical in outline, being divided into two
lateral halves by the crista galli. It forms part of the base of the ante-
rior fossa of the brain-case, and fits the ethmoidal notch of the frontal
bone. It unites the two lateral masses and vertical plate of the bone. The
olfactory sulcus, for the lodgment of the olfactory bulbs of the brain,
are depressions of the cribriform plate situated on each side of the crista
galli. This plate is pierced by numerous foramina for the transmission
of the filaments of the olfactory nerves: those next the crista galli pass
80
ANATOMY.
into the delicate perpendicular grooves and canals of the perpendicular
plate of the bone; next and external are those for the filaments distrib-
uted to the roof of the nasal chambers; and the outer ones pass into
fine canals which subdivide as they penetrate the lateral masses of the
bone. Some anatomists speak of these holes as forming three rows or
lines, but the irregular arrangement of them makes it an ideal rather
than a definite or distinct description.
The Cerebro-nasal Slit is immediately posterior to the ethmoidal
wings at the base of the crista galli. It is a narrow or strait opening
uniting the cranial cavity with the nasal chamber. External to this
above may be seen a groove extending posteriorly to the anterior eth-
moidal foramen. The passage, groove, and foramen are for the accom-
modation of the nasal nerve, a branch of the ophthalmic, and also a
branch of the ophthalmic artery.
DEVELOPMENT.-The ethmoid bone arises from three points of ossi-
fication-one for each lateral mass, the other for the perpendicular and
cribriform plates. They are deposited in the orbital plates of the late-
ral masses about the fourth or fifth month, and gradually extend into
the turbinated bones. During the first year it commences to ossify in
the perpendicular and cribriform lamellæ, the three parts uniting early
in the second year, ossification being completed during the fourth or
fifth year, at which time the ethmoidal cells commence formation.
VOMER.
The Vomer (Fig. 33) is a single bone, situated in the median line
of the nasal chamber, forming the principal portion of the bony sep-
FIG. 33.
}
with Triangular Cartilage.
ته ر
with Ethmoid.
Artic with Sphenoid.
Naso-palatine groove.
and
Palate.
G

Ala.
with Sup -Maxill. bones
Vomer.
tum. It usually is more or less deflected to one or the other side, and
is placed in front of and below the sphenoid bone, with the rostrum of
which it articulates, and below the ethmoid bone, articulating with the
perpendicular plate of the latter. It is a thin plate of bone, rhomboidal
in form, having four borders, superior, inferior, anterior, and posterior ;.
and two surfaces, a right and a left.
BONES.
81
The Superior Border is the thickest of the four, and is shaped like
the letter V. The upper portion of this V is described as two alæ or
wings, which extend on both sides of the rostrum of the sphenoid bone.
The lateral edge of each wing articulates with the superior margin of
the internal plate of the pterygoid process (vaginal process) of the sphe-
noid bone and the sphenoidal process of the palate bone.
The Inferior Border is long, thick, and uneven, for articulation with
the nasal crest of the superior maxillary and palate bones. It is thin-
ner posteriorly where it articulates with the latter bones.
The Anterior Border slopes downward and forward at an angle of
about forty-five degrees. The upper half of this border generally con-
sists of two thin lamina of bone, between which articulates the perpen-
dicular plate of the ethmoid. The inferior half is rough and uneven,
to give attachment in the recent state to the nasal cartilage.
The Posterior Border is free, and forms the septum of the posterior
nares. It is the shortest of the four borders-thin, smooth, and slightly
concave.
The Surfaces.-The right and left surfaces are smooth, but marked
by narrow grooves for the accommodation of blood-vessels. A larger
groove, sometimes formed into a canal (naso-palatine), traverses each
surface of this bone, running downward and forward, terminating in
the anterior palatine canal in the intermaxillary suture. These grooves
transmit the naso-palatine vessels and nerves.
DEVELOPMENT.-The vomer is an intracartilaginous bone formed
from one centre of ossification, which makes its appearance in the poste-
rior part of the bone at about the eighth week of embryonic life. From
this centre two lamina arise, and pass upward and forward on each side
of the median line until they meet the nasal cartilage. These two plates
of bone gradually unite from behind forward until about the age of
puberty, at which period they form a single plate of bone, marked on
its anterior and superior borders by a slight groove, indicating the
position where the two parts unite.
SUPERIOR MAXILLARY BONES.
The superior maxillary bones are of the utmost importance to the
dentist and to the surgeon. They give support to the upper teeth and
are subject to defects of development and to various pathological changes.
Chief among these may be mentioned cleft palate, congenital or acquired,
necrosis, caries, and odontocele. Either of these bones may be affected
by alveolar abscess, diseases of the antrum, which may give rise to such
symptoms as impaired respiration and discharge of offensive matter
through the nasal chamber. Tumors or abscesses of the antrum often
grow to such a size as to elevate the floor of the orbit, depress the roof
of the mouth, and bulge out the wall of the cavity, distorting the face
in the region of the canine fossa. Neuralgic trouble in the teeth may
be only symptomatic of disease of this bone, as neuralgia in the head
often may be traceable to the teeth. It is therefore highly necessary
that the bone should be carefully studied.
Together, the superior maxillæ are, of the bones of the face, second in
VOL. I.-6
82
ANATOMY.
importance and size only to the lower maxilla. When articulated they
form the bony base of the entire central portion of the face. Each one
assists in forming three cavities-first, part of the floor and the infra
and internal borders of the orbit; second, part of the sides and floor of
the nasal chamber; third, it contributes largely to form the roof or hard
palate of the mouth. It also assists in the formation of the zygomatic
and spheno-maxillary fosse and the spheno-maxillary and pterygo-
maxillary fissures.
Its body forms the walls of the maxillary sinus (antrum Highmori-
anum). It presents for examination a body, four surfaces, the orbital, the
proximal or nasal, the lateral or facial, and posterior or zygomatic; and
four processes, the nasal, the malar, the palatal, and the alveolar.
The Body (Fig. 34) may be compared to a very irregular triangular
FIG. 34.
Surface.
TENDO OOULT
Incisive fossa-
DEP
CALE NAST
ARIS
Cust
Outer

Nasal
proc.
Facial
Canine eminence
with Lachr
me..
Infra:
Surface.
Lachrymal tubercle.
zal.
Orbital Surface
drizz
with Ethmoid.
Incisors. Canine. Bicuspids.
Infra-orbital groove
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Molars
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Palate
with
Zygomatic Surface
Posterior Dental Canals
Maxillary Tuberosity.
Left Superior Maxillary Bone, outer surface.
pyramid, the base being the proximal surface and the apex under the
malar process.
The Orbital Surface is a triangular plate, smooth and slightly concave,
constituting the greater part of the floor of the orbit.
The Infraorbital Canal runs forward from the posterior border as a
groove, which at the centre dips or is covered by the orbital floor, and
makes its exit just above the centre of the facial surface, at the infra-
orbital foramen. It transmits the infraorbital vessels and nerve. A
branch of the infraorbital canal passes down the anterior wall of the
maxillary sinus and transmits the anterior dental nerve and vessels.
BONES.
83
Just external to the junction of this plate with the nasal process is a
small depression which gives origin to the inferior oblique muscle of
the eye.
The Mesial Border of the orbital surface at its anterior portion is
smooth, and in it is the commencement of the lachrymal groove, which
in the articulated skull becomes a canal and runs downward and slightly
backward to communicate with the inferior meatus of the nose. The
remainder of this border is roughened for articulation with the lachry-
mal bone anteriorly and the os planum of the ethmoid bone posteriorly.
The Anterior Border of the orbital plate and the orbital process of
the malar bone from the infraorbital ridge is sharp at its inner third,
but the remainder is rounded.
The Posterior Border of the above plate is frequently referred to as
the outer border: it extends from the centre of the malar process back-
ward and inward to the orbital process of the palate bone. The inar-
ticulated portion of this border, together with part of the orbital process
of the palate bone, forms the anterior boundary of the spheno-max-
illary fissure.
Bones partially closing Orifice of Antrum
marked in outline
Ethmoid
Inferior Turbinated
Palate
The Proximal or Nasal Surface (Fig. 35) presents a large irregular
opening into the maxillary sinus. This orifice is partially closed by
FIG. 35.
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Ant. Nasal Spine
Bristle
passed through
Ant. palat. Canal
Left Superior Maxillary Bone, inner surface.
articulation with the lachrymal, the uncinate process of the ethmoid,
the vertical plate of the palate, and the ethmoidal process of the inferior
turbinated bones of the same side. In the articulated skull one or two
small openings communicate from the antrum with the middle meatus
84
ANATOMY.
of the nose. Usually there is left but one small opening. Along the
superior border of this surface are a number of cellular openings, which
are closed in by articulation with the lachrymal and ethmoid bones.
The anterior two-thirds of the thin plate of bone below the aperture is
smooth and concave, forming most of the external wall of the inferior
meatus of the nose. The posterior third is slightly roughened for artic-
ulation with the vertical plate of the palate bone.
The Lachrymal Groove is at the anterior superior angle of the nasal
surface, behind the nasal process: it is converted into a canal by articu-
lation with the lachrymal bone, the uncinate process of the ethmoid,
and the lachrymal process of the inferior turbinated bone. The canal
extends downward and backward, terminating in the inferior meatus
of the nose.
In the recent state it is lined by a mucous membrane,
the lachrymal duct.
p
The Lachrymal Tubercle is a small prominence of bone at the junc-
tion of the infraorbital ridge with the external border of the nasal
process. This tubercle serves as a guide to the lachrymal sac, which is
the expanded portion of the lachrymal duct, situated posterior to the
tubercle.
The Posterior Palatine (Palato-maxillary) Canal, for the passage of
the posterior palatine vessels and anterior palatine nerves, commences
about the middle of the posterior border of the bone and runs downward
and forward as a groove, which in the articulated bone is closed by the
vertical plate of the palate bone to form a canal.
The Anterior Border of the nasal surface is thin and deeply indented
in its central portion, forming the lateral boundary of the anterior naris.
The portion of this border above the indentation is roughened and
articulates with the nasal bone; that below articulates with its fellow
of the opposite side, and forms half of the nasal spine.
The Lateral or Facial Surface is concave, and extends from the anterior
border to the root of the malar process. The outer portion of its supe-
rior border is roughened for articulation with the lower border of the
orbital process of the malar bone. Internally, this border is smooth,
and curves upward from the inner portion of the infraorbital ridge.
G
The Infraorbital Foramen.-Just below this ridge, about midway of
the border, is an oval aperture for the passage of the infraorbital nerve
and vessels. Between this foramen and the infraorbital ridge arises the
proper elevator muscle of the upper lip (levator labii superioris proprius).
The Canine Eminence is a vertical ridge that divides the lower portion
of this surface, and corresponds in position to the root of the canine tooth.
It gives origin to the depressor muscle of the wing of the nose and also to
the depressor of the upper lip. The Incisive or Myrtiform Fossa is a slight
depression between the canine eminence and the median border of the
bone. It gives origin to the depressor muscle of the wing of the nose
and to the depressor of the upper lip. Above, and a little external to
the incisive fossa, arises the compressor of the nose (compressor nasi).
The Canine Fossa is a larger depression on the outer side of the
canine eminence. The floor is very thin, and an into the
openin
antrum may be readily made through it. This fossa gives origin to
the elevator muscle of the angle of the mouth (levator anguli oris).
BONES.
85
The Posterior or Zygomatic Surface is convex, and extends from the
root of the malar process inward and backward to its articulation with
the vertical plate of the palate bone.
The Superior Border is well defined, and is the dividing-line between
this and the orbital surfaces. The central portion of the border is
marked by the infraorbital groove.
The Posterior Superior Angle is bevelled for articulation with the
orbital process of the palate bone.
The Tuberosity is a rounded eminence of bone just behind the posterior
inferior angle, back and above the wisdom tooth; it is often so fragile
as to be broken away in extracting this tooth, the roots of which curve
upward, outward, and backward in it. The inner surface of the tuber-
osity is frequently roughened for articulation with the pyramidal pro-
cess of the palate bone. The tuberosity in the living bone is penetrated
by numbers of nutrient vessels. Midway between it and the zygomatic
surface are several larger apertures which lead into canals in the sub-
stance of the bone; they are the posterior dental canals. One of them
passes into the substance of the bone, traverses the outer wall of the
maxillary sinus, and joins the anterior dental canal, which branches
from the infraorbital posterior to the infraorbital foramen. These
canals transmit the posterior dental vessels and nerves.
The Nasal Process is a thick irregular process of bone. Commencing
at the anterior superior angle of the facial surface of the bone, it extends
upward, inward, and backward, and forms part of the inner boundary
of the orbit and external surface of the nasal chambers. Its upper
extremity is serrated for articulation with the frontal bone in front
and the ethmoid bone behind, thus completing the anterior ethmoidal
cells. The anterior border is serrated for articulation with the nasal
bones.
The External Surface or Anterior Surface is marked by shallow
grooves, which are traces of the development and growth of the bone
downward. It is perforated by several foramina for the passage of
nutrient vessels to the substance of the bone. This surface gives origin
to the elevator muscle of the upper lip and of the wing of the nose
(levator labii superioris alæque nasi), the sphincter muscle of the orbit
(orbicularis palpebrarum), and the tendon of the eye (tendo oculi).
The Internal Surface of the Nasal Process is, for convenience of
description, all that portion of bone included between the superior
border and the floor of the anterior nares. This surface is marked by
two slightly concave portions of bone and two ridges. The lower ridge
articulates with the inferior turbinated bone, while the upper one articu-
lates with the middle turbinated bone.
The Inferior Meatus of the nose is bounded on the outside anteriorly
by the concave portion of bone below the inferior ridge. The Middle
Meatus is partly bounded externally by that concave portion between
these ridges. The Superior Meatus at its commencement is similarly
bounded by that portion of this surface above the superior ridge.
The Malar Process is rough and triangular, and projects outward and
upward from the external surface of the body of the bone. It forms a
strong abutment immediately above the first molar tooth, and articulates
86
ANATOMY.
with the malar bone. It gives origin to a portion of the masseter
muscle.
The Palate Process, with its fellow of the opposite side, forms about
three-fourths of the hard palate, the same process of the palate bones
making up the remaining fourth. This process has two surfaces. The
nasal or superior surface is smooth and concave from side to side; the
oral or inferior surface is vaulted and roughened to give attachment to
the muco-periosteum. It is also marked by numerous small depressions
for the lodgment of the mucous glands. Its anterior half is pierced by
minute foramina for the passage of nutrient vessels, and the antero-pos-
terior grooves on the posterior half are for the accommodation of the
posterior palatine nerves and vessels.
1
The Anterior Border of this process, where it fuses with the premax-
illa (see paragraph on development of superior maxilla, p. 88), is thick
and roughened, while its posterior border is thin, serrated, and articu-
lates with the palate bone.
The Mesial Border of this process and that of the premaxilla is
thicker before than behind, and is serrated for articulation with its fel-
low of the opposite side.
The Nasal Spine. The anterior border of the palate process is smooth
and concave; it terminates superiorly in a well-defined spine, which
gives attachment to the cartilage which forms the anterior portion of
the septum of the nose.
-
Samay
The Incisor Crest is a sharp projection just posterior and continuous
with the nasal spine, and between it and the incisor foramen.
The Nasal Crest is an elevation of the median border of this bone,
including the same border of the palate bone. These when joined form
the nasal crest for articulation with the vomer.
FIG. 36.
The Incisor Foramen (or foramen of Stenson) is situated immediately
behind the incisor crest, and leads downward and forward from the nasal
chamber toward the oral cavity, terminating just
back of the incisor teeth. As this foramen ex-
tends downward, it is soon converted into a
groove by the deficiency of its inner wall.
the articulated bones this groove forms the ante-
rior palatine meatus or canal, and opens on the
nasal surface of the palatal process through four
da

The Anterior Palatine Fossa. It foramina-the incisive foramina just described,
will be found to contain four
openings-two placed later- and the foramina of Scarpa or the naso-pala-
ally, 1, 2, and two in the mid- tine foramina. The meatus is seen as a single
dle, one (4) before the other
(3).
orifice back of the incisor teeth at the point of
union of the premaxillary bones with the palatal processes.
The Foramina of Scarpa, or Naso-palatine Foramina, are situated in
the plates of bone that separate the upper part of the incisor foramina,
and are anterior and posterior or directly in the mesial line, the posterior
opening transmitting the right and the anterior the left naso-palatine
nerves.
The Alveolar Process extends forward from the tuberosity, along the
inferior margins of the zygomatic and facial surfaces, to the median line
¹ Harrison Allen, Human Anatomy.
BONES.
87
of the bone, where it articulates with its fellow of the opposite side. It
is broader behind than in front, and composed principally of cancellous
or spongy tissue. It is curved in outline, corresponding to some extent
to the body of the bone above. This curve varies in different bones,
the extent of variation depending in great measure on the race and tem-
perament of the individual from which the bone is taken. With its
fellow in well-formed mouths its axis is parabolic. It is composed of
two plates of bone-an inner and an outer-with numerous septa of can-
cellous tissue uniting them and forming the alveoli for the accommoda-
tion or reception of the roots of the teeth.
The Outer Plate of the alveolar process is continuous with the facial
and zygomatic surfaces of the bone. It is the thinner and weaker of
the two, which accounts for the fact that a healthy tooth is more easily
pressed outward than inward. After a tooth has been extracted the
outer plate absorbs much more quickly and to a greater extent than the
inner.
43.1
The Inner Plate is well defined superiorly, where it forms an angle
with the palate process. It is thicker and stronger than the outer plate.
The Outer Surface is marked by eminences corresponding to the roots
of the teeth, and depressions marking the position of the interspaces.
The eminence over the canine tooth is more prominent than the others.
This surface at or near its superior margin, over the second bicuspid and
three molar teeth, gives origin to the buccinator muscle.
FIG. 37.
fire
Kat

0.
Mapstartimi
Alveoli of Permanent Teeth.
The Alveoli (Fig. 37) in the normal adult bone are eight in number,
and correspond in shape and size with the roots of the teeth which they
88
ANATOMY.
accommodate. The socket for the central incisor tooth is nearly conical
in shape. That for the lateral incisor is conical, but smaller and more
compressed meso-distally than the central socket, and often presents a
slight distal curve at its upper extremity. The socket for the cuspid
(canine) tooth is conical in form, deeper and larger than those for the
incisors, and somewhat compressed, especially at its inner aspect, form-
ing an oval in transverse section. The sockets for the bicuspidati
resemble flattened cones, that for the first bicuspid generally bifurcating
at the upper portion, as this tooth frequently has two roots.
The same
reason occasionally causes a bifurcation of the socket for the second
bicuspid. The sockets for the molar teeth are broad, and divided at
their upper three-fourths into three compartments. The socket for the
wisdom tooth is an exception to this formation, frequently not dividing
at all, and sometimes having more than three compartments.
The septa between the alveoli extend downward to a lower level
than the plates composing the alveolar processes, so that their free
margins are convex-a point to be remembered in practical dentistry
in fitting permanent bands and metal crowns on roots that are embraced
in the alveolar walls.
Each alveolar wall consists of a shell of thin, compact bony structure
surrounded by spongy tissue. This shell comes into contact with the
dense cortical plates composing the surfaces of the bone, mainly at the
margin near the neck of the tooth. At the apical portion of the sockets
are small openings for the entrance of vessels and nerves supplying the
teeth.
The teeth are held in their sockets by alveolo-dental connective tissue.
It is elastic, and allows a considerable motion of the teeth. In the
dried bone the loss of this tissue loosens the teeth and permits their
detachment from the sockets.
DEVELOPMENT.—The development of the superior maxillary bone
(Fig. 38) commences so early and increases with such rapidity that it is
difficult to mark out its line of growth. It arises in membrane from
many points of ossification, at least one each for the orbital plate, the
nasal process, and the alveolar border. These appear about the sixth
or seventh week of embryonal life, and soon coalesce. Hence these
parts are claimed by some to arise from one centre. They form the
lateral portion of the bone, which contains all the teeth except the two
incisors, and is called by comparative anatomists the true maxilla.
That portion of the bone which contains the central and lateral incisor
teeth arises from a separate point of ossification, and is known as the
premaxilla. In many of the lower animals it remains distinct from the
true maxilla throughout life.
When there is union between the two premaxillary bones in the
median line, but no lateral union between them and the true maxillæ,
they form the intermaxillary bone of the lower animals. In man the
premaxilla soon unites with the maxilla proper by a suture, which on the
facial surface may be seen until the sixth year, and on the hard palate
it generally remains until adult life. The suture on the hard palate
extends as far back as the posterior portion of the anterior palatal canal.
In single or unilateral complete cleft palate-i. e. the cleft extending
BONES.
89
1 for Naval &
Facial port
from the facial surface to the posterior portion of the palate process-
the premaxilla does not unite with the parts containing the other teeth,
neither do the true maxillæ and palatal processes of the palate bones
unite. In double cleft palate the incisorial divisions may have united
in the median line (forming an intermaxillary bone), but not laterally
FIG. 38.

1 for Orbital &
Malar ports
Malar
1 for Incisive port?
1 for Palatal port
cort
******
acial port
Anterior Surface.
An
comple
*[1]
Incisive
art
24611)
Start
Palatal
"port"
at
Birth

Inferior Surface.
Development of the Superior Maxillary Bone, by four centres.
with the true maxillæ. In some of these cases the vomer can be seen
protruding in the median line between the two halves of the hard palate.
The alveolar process is developed as a special support for the teeth.
At birth it is represented by the walls of a deep groove, in which
the deciduous and the germs of the permanent teeth are situated.
As the teeth grow the alveolar process advances, until it encases them.
Just prior to the shedding of the deciduous teeth their roots and their
bony processes are absorbed, and the latter are re-formed on the appear-
ance of the permanent teeth. This process again commences to disap-
pear on the loss of the second set of teeth, and in time may be wholly
removed. In certain diseased conditions of the bones this process dis-
appears to some extent before the permanent teeth are lost; and this
bone-absorption may go on until teeth otherwise healthy become loose
and drop out.
The Maxillary Sinus (antrum of Highmore) is the large air-cavity
situated in the body of the bone. It is irregularly pyramidal in shape,
the apex bearing toward the malar bone, into which it may extend, and
its base toward the nasal cavity. Its development is similar to the
sinuses in the frontal bone, and like them is not completed until after
the age of puberty, although it makes its appearance as early as the
fifth or sixth month of foetal life. Hence in early life the surrounding
90
ANATOMY.
1
walls are much thicker than in the adult. Its capacity varies in dif-
ferent subjects and in the opposite bones of the same subject, ranging
from one drachm to one ounce fluid measure, the average being about
three drachms. It is somewhat larger in the male than in the female.
The floor of the sinus is marked by irregular eminences correspond-
ing to the roots of the molar teeth. Sometimes it is punctured by the
roots of these teeth, which may extend into the sinus. The walls of
the sinus often support thin plates of bone which subdivide it into
small compartments. A knowledge of this fact is of importance in
operating on tumors and abscesses in this location, as the drill may
simply penetrate one of these distinct compartments, misleading the
operator as to the extent of the sinus or of the disease.
The sinus opens into the middle meatus of the nose by an orifice
of variable size situated at the base of the pyramid. This orifice
is partly closed by the uncinate process of the ethmoid, the vertical
plate of the palate, the inferior turbinated, and the lachrymal bones,
also by soft tissue, so that in the recent state it is about the size of an
ordinary lead-pencil. This small opening is situated near the upper
part of the sinus, and does not, when the head is perpendicular, afford
a ready outlet to fluids collected within the chamber.
The mucous membrane lining the sinus is ciliated, and is continuous
through this quill-like opening with the membrane lining the nasal
cavity. It is, however, less vascular than the nasal mucous membrane.
The sinus may be encroached upon by any of the teeth situated in
the superior maxilla, but those that most frequently protrude into it are
the roots of the first and second molars.
With the exception of the alveolar border the walls of the sinus are
quite thin. These walls are four in number-one extending toward the
orbit; another toward the nose and roof of the mouth, including a
portion of the palatal process; a third toward the facial and zygomatic
surfaces of the bone; and a fourth is formed by the alveolar border.
Morbid growths within the sinus will more readily cause either of the
first three walls to project or bulge than the alveolar process.
The posterior wall, or that toward the zygomatic surface of the bone,
is marked by the posterior dental canals, through which the posterior
dental vessels and nerves are conducted to the teeth. The anterior wall
is in like manner grooved by the anterior dental or incisor vessels
and nerves.
PALATE BONE.
The palate bones, two in number, are wedged between the superior
maxillary bones and the pterygoid plates of the sphenoid bone at the
back part of the nasal chambers. They assist in forming the bound-
aries of the orbital, nasal, and oral cavities, the spheno-maxillary, the
spheno-palatine, and the pterygoid fossa, the spheno-maxillary fissure,
the posterior ethmoidal cells, and the maxillary sinus.
The palate bone is composed of thin, delicate, and compact tissue.
Its general form is that of the letter L. It is composed of two plates,
a horizontal and vertical; and three processes, a pyramidal, orbital, and
sphenoid.
S
BONES.
91
The Horizontal or Palate Process.-This corresponds to the palate
process of the superior maxilla. It is thin, quadrilateral in form, and
presents for examination two surfaces and four borders.
The Superior Surface is smooth, concave from side to side, and forms
the posterior portion of the floor of the nasal chamber.
The Inferior Surface is smooth, excepting at its posterior portion,
where it is marked by a transverse ridge for the attachment of the
tensor palati muscle. This surface forms the posterior portion of the
hard palate.
Superior Meatus_
Sphono. Palatine Foramen
The Posterior Palatine (or Palato-maxillary) Canal is a groove,
sometimes a canal, situated at the outer portion of the ridge, for the
attachment of the tensor palati muscle. It is converted into a canal
by articulation with the superior maxilla. It transmits the posterior
palatine vessel and anterior palatine nerves.
VERTICAL
The Accessory Posterior Palatine Canal, or Canals, are between this
ridge and the pyramidal process.
The Anterior Border is serrated for articulation with the palatal pro-
cess of the superior maxilla.
The Posterior Border is free, smooth and concave, forming the pos-
terior boundary of the hard palate and floor of the nasal chamber.
FIG. 39.
PLATE
P
Process
77
Fds fo
biln
}
Orbital Process
Orbital Surface

tery guid
surf.
Artic.with Pter
rest
HORIZONTAL
bone.
Maxillary
Surface
V J J ? x V W
Artic
PLATE
e T.
Yarm
M
utures
Sup
Maxillary
Process
Left Palate Bone, internal view (enlarged).
This border gives origin to the soft palate, and terminates in the median
line in a sharp point. This point, when articulated with its fellow of
the opposite side, forms the posterior nasal or palatine spine and gives
origin to the azygos uvula muscle.
The External Border is situated just below the junction of the hori-
zontal and vertical plates. In it is the groove which assists in forming
a portion of the posterior palatine canal.
K
92
ANATOMY.
The Internal Border is much thicker than any of the others. It is
serrated and elevated into a ridge, which, when articulated with the
corresponding one of the opposite bone, forms a continuation of the
nasal crest of the superior maxilla, with which the vomer articulates.
The Vertical Plate is thin, and extends from the floor of the nasal
chamber to the upper extremity of the spheno-palatine notch. It has
two surfaces, an external and an internal; and four borders, an anterior,
posterior, superior, and inferior.
The Internal Surface is similar in structure to the same surface of
the superior maxilla. It is divided into three portions by two antero-
posterior ridges, the superior and inferior turbinated crests. The inferior
crest articulates with the inferior turbinated bone, and thus forms the
division between the inferior and middle meati of the nose. The
superior crest articulates with the middle turbinated bone (part of the
ethmoid), and forms the division between the middle and superior
meati of the nose. Between the superior turbinated crest and the
superior border of the bone is a groove which forms part of the superior
meatus.
The External Surface is generally rough and uneven. Its posterior
boundary is marked by a groove (occasionally a canal) which, in the
articulated skull, forms the posterior palatine canal, already described.
The Anterior Border is thin, its inferior turbinated crest projecting
anteriorly to form the maxillary process. This process assists in closing
the maxillary sinus.
The Posterior Border (Fig. 40) is
third is marked internally by a deep
FIG. 40.
Orbital
VERTICAL
PLATE
Noces
Orbital Surface,
Posterior
palatine
Canal
Sphenoid
fgamatic-Sa
FAL
AZYCOS UVULÆ
HORIZONTAL
PLATE
Sphenopalatine For.
Sphenoidal process. surface.
“Articular port. Ext. Surf
Non.articular port.
irregular and serrated. Its lower
groove, the edges of which articu-
late with the internal plate of the
pterygoid process of the sphenoid
bone, a portion of which fits into
the groove. Above the groove
this border articulates with the
outer edge of the internal ptery-
goid plate, the thin projecting
border overlapping its internal

Tuberosity
Left Palate Bone, posterior view (enlarged).
The Superior Border is divi-
ded by a deep notch, sometimes
a foramen, the spheno-palatine
notch or foramen, which divides
the orbital from the sphenoidal
process.
Post.
The Spheno-palatine Notch or
Foramen is converted into a fora-
Nasal Spins men by articulation with the sphe-
noid bone. It transmits the sphe-
no-palatine vessels and nerves
from the spheno-palatine fossa
into the nasal chambers.
The Inferior Border joins the external border of the horizontal plate.
The Pyramidal Process extends downward and backward from the
BONES.
93
inferior and posterior borders, and fits into the pterygoid notch between
the two pterygoid plates of the sphenoid. Posteriorly, this process has
a triangular surface which rounds out the lower portion of the ptery-
goid fossa. The borders of this process are serrated for articulation
with both pterygoid plates of the sphenoid bone.
The Orbital Process extends outwardly from the superior border of
the vertical plate, overhanging its outer surface. This process has five
surfaces, enclosing a cellular cavity, generally opening through its inter-
nal or ethmoidal surface. When it so opens it communicates with the
posterior ethmoidal cells. Sometimes, however, this cell-like cavity
opens through the posterior or sphenoidal surface and communicates
with the sphenoidal sinus, or it may open both ways. Three of these
surfaces—the anterior or maxillary, the posterior or sphenoidal, and the
internal or ethmoidal-are articulating surfaces, while the remaining two,
the superior or orbital and the external or zygomatic, are free.
The Anterior or Maxillary Surface is directed forward, outward, and
downward. It is oblong in form and articulates with the posterior
superior angle of the inner surface of the superior maxilla.
The Posterior or Sphenoidal Surface is directed backward, upward,
and inward, and articulates with the vertical portion of the sphenoidal
turbinated bone.
The Internal or Ethmoidal Surface is directed inward, upward,
and forward, and articulates with the vertical plate of the ethmoid
bone.
up-
The Superior or Orbital Surface is triangular in form, extends
ward and outward, and forms the posterior angle of the floor of the
orbit.
The External or Zygomatic Surface is smooth and oblong in form, is
directed outward, backward, and downward, and forms a portion of the
spheno-maxillary fossa.
The Sphenoidal Process curves upward, backward, and inward from
the posterior third of the superior border, and presents three surfaces,
the superior, external, and internal; and two borders, the anterior and
posterior.
The Superior Surface is the smallest of the three, and articulates with
the horizontal portion of the sphenoidal turbinated bone. It is marked
by a groove which assists in forming the pterygo-palatine canal.
The External Surface is divided into two portions, anterior and pos-
terior. The anterior portion is smooth, and helps to form the spheno-
maxillary fossa, while the posterior portion is rough, for articulation
with the inner surface of the pterygoid plate of the sphenoid bone.
The Internal Surface is smooth and concave, and forms part of the
outer wall of the posterior nares.
The Anterior Border forms the posterior margin of the spheno-pala-
tine notch.
The Posterior Border is serrated, and articulates with the inner sur-
face of the pterygoid process.
•
M
DEVELOPMENT.-The palate bone is developed from a single centre
of ossification, which is deposited in membrane, and appears at the
junction of the vertical with the horizontal plate about the seventh or
94
ANATOMY.
eighth week of embryonal life.
than the vertical plate.
THE INFERIOR TURBINATED BONE.
The inferior turbinated bones (maxillo-turbinal), two in number, are
situated at the lower third of each lateral wall of the nasal chamber.
Each bone forms the upper boundary of the inferior meatus of the
nose and the lower boundary of the middle meatus. It is thin and
frail, full of small foramina
and minute canals. It is
scroll-like in form, curving
outward and downward. It
presents a body with two
surfaces, an internal and an
external; two borders, supe-
rior and inferior; and two
extremities, anterior and pos-
terior.
with Lachrymal b.
with Sup. max. b.
Dep
FIG. 41.
Lac.proc.
Ethmoid
HA
Before birth the horizontal is longer

Maxill. proc.
with Ethmoid.
Ethmoid.proc
Right Inferior Turbinated Bone, internal surface.
The Internal Surface (Fig.
41) is convex from above
downward, and is marked by numerous foramina and longitudinal canals.
for the passage of blood-vessels and nerves.
FIG. 42.
The External Surface (Fig. 42) is concave, smoother than the inter-
nal, excepting at its lower margin,
where it is somewhat cellular in
structure and marked by numer-
ous foramina. It forms the roof
of the middle meatus of the nose.
The Superior Border is thin and
irregular, and is divided into three
portions, anterior, middle, and pos-
terior.
Lac
proo
with Palate.

Right Inferior Turbinated Bone, outer surface.
The Anterior Portion articulates
with the inferior turbinated crest
on the internal surface of the nasal process of the superior maxilla.
The Middle Portion has arising from it three processes-the lachry-
mal, the ethmoidal, and the maxillary.
The Lachrymal Process runs upward and forward, and articulates
with the anterior inferior angle of the lachrymal bone. The outer por-
tion of this process is grooved and assists in forming the lachrymal canal.
The Ethmoidal Process arises just anterior to the posterior third of
the superior border. It is broad, and extends upward to articulate with
the uncinate process of the ethmoid bone.
The Maxillary Process arises from the base of the ethmoidal process
externally, and curves outward and downward, forming a hook-like pro-
jection semicircular in shape. This process articulates with the inferior
border of the opening to the maxillary sinus.
The Posterior Portion of the superior border articulates with the
inferior turbinated crest of the palate bone.
BONES.
95
The Inferior Border is thickened, and marked by several indentations.
of a cell-like character.
The Extremities are narrowed and somewhat pointed, especially the
posterior.
DEVELOPMENT.-The inferior turbinated bone is developed from
cartilage from one point of ossification, which appears about the fifth
month of foetal life.
THE LACHRYMAL BONES.
The lachrymal bones, or os unguis, two in number, are situated at the
inner and anterior portion of the orbit, just posterior to the nasal pro-
cess of the superior maxilla. They pass downward into the nasal
chamber.
The lachrymal bone (Fig. 43) is the smallest and most delicate bone
of the face. It is quadrilateral in shape, and pre-
sents two surfaces, the external or orbital and the
internal or nasal; and four borders, anterior, pos-
terior, superior, and inferior.
The Orbital or External Surface is divided into
two portions, an anterior and posterior, by a verti-
cal ridge of bone, the lachrymal crest.
pre-
The Anterior Portion of the orbital surface
sents a smooth perpendicular groove, the lachrymal
groove, the upper part of which lodges the lachry-
mal sac.
In the articulated skull this groove as-
Articulates with Sup.Maxillary
FIG. 43.
with Frontal

ENSOR.T
\\……….
with
////
with Ethmoid
sists in forming the lachrymal canal.
Infer
ternal surface.
The Posterior Portion of the orbital surface is
smooth and concave, and forms part of the inner (Slightly enlarged)
wall of the orbit. The tensor tarsus muscle arises Left Lachrymal Bone, ex-
from the lachrymal crest and part of the orbital
surface just posterior to the crest. The hook-like process seen at the
lower portion of the lachrymal crest articulates with the lachrymal
tubercle of the superior maxilla, and completes the orbital orifice of
the lachrymal canal. Occasionally this hook-like process exists as a
separate bone known as the lesser lachrymal bone.
The Internal Surface forms part of the outer wall of the nasal cham-
ber. It is marked opposite the lachrymal crest on the external surface
by a longitudinal depression. That portion of the bone in front of this
depression enters into the formation of the outer surface of the middle
meatus of the nose; that behind it articulates with the ethmoid bone,
and in conjunction with the superior maxilla closes the anterior ethmoi-
dal cells.
Turbinated
The Anterior Border is the longest of the four, and articulates at the
inner margin of the lachrymal groove with the nasal process of the
superior maxilla.
The Posterior Border is thin and uneven; it articulates with the
anterior border of the os planum of the ethmoid bone.
The Superior Border is the thickest and shortest of the four.
articulates with the internal angular process of the frontal bone.
96
ANATOMY.
The Inferior Border is more complicated than any of the others. It
is thicker at the termination of the lachrymal crest than elsewhere,
which gives strength to the posterior wall of the lachrymal canal. It
is divided by the lower extremity of the lachrymal crest into two por-
tions, an anterior and a posterior.
The Anterior Portion, or that portion in front of the extremity of the
crest, extends downward, backward, and inward, and terminates in a
pointed process which articulates with the lachrymal process of the eth-
moid bone. As it extends downward it passes on the outer side of the
uncinate process of the ethmoid bone, and to the inner side of the orifice
to the maxillary sinus, and thus assists in closing the anterior portion
of the opening leading to the sinus. This portion also partly bounds
the lachrymal canal, and is supported by the uncinate process of the
ethmoid.
The Posterior Portion, or that situated behind the extremity of the
crest and below the orbital surface, articulates with the orbital plate
of the superior maxilla.
DEVELOPMENT.-The lachrymal bone arises from one point of ossi-
fication, which is deposited about the eighth week of fœtal life.
THE NASAL BONES.
The nasal bones, two in number, are situated at the upper portion of
the external nose, and form what is often termed the "bridge" of the
nose; also the anterior boundary of the nasal chambers.
The nasal bone is oblong in shape, has the lower extremity wider
than the upper, and presents two surfaces, anterior and posterior; with
four borders, superior, inferior, lateral, and median.
The Anterior or Outer Surface (Fig. 44) varies in shape, but may
be
said to be generally convex from side to side and concave from above
FIG. 44.
with Frontal B.
Artic with Sup. Maxill. b.
ad
with
-Opposite bone
Outer Surface.
Right Nasal Bone.
FIG. 45.

with
Frontal Spine

orest
with
Perpendicular
Plate of Ethmoid.
Froo
groove for nasal nerve
Inner Surface
Left Nasal Bone.
downward. The upper portion is punctured by numerous nutrient
foramina; the lower portion is smooth and rounded. Near the centre
of this surface will be seen a foramen which passes through to the
internal aspect of the bone, and transmits a small vein. This forament
BONES.
97
is not constant, and sometimes two foramina are found in this location.
Occasionally the foramen cæcum, the commencement of the longitudinal
sinus of the brain, opens on this surface.
The Posterior or Internal Surface (Fig. 45) is concave from side to side
and convex from above downward. Upon this surface is a longitudinal
groove (sometimes a canal) for the transmission of the internal branch
of the nasal nerve, which passes out between the bone and the lateral
cartilage of the nose.
The Superior Border is triangular in form, and serrated for articula-
tion in the nasal notch of the frontal bone.
·
VOL. I.-7
The Inferior Border is the broadest part of the bone. It is thin and
notched in the centre for the transmission of the anterior branch of the
nasal nerve; this border extends downward, outward, and backward,
terminating in a sharp point; it gives support to the lateral cartilage of
the nose.
In the articulated skull the inferior borders of the two nasal
bones form a triangular notch called the nasal angle, serving for partial
attachment of the lateral nasal cartilage.
The Lateral or External Border is the longest of the four; it is ser-
rated and bevelled at the expense of the anterior surface, and articulates
with the nasal process of the superior maxilla.
The Median or Internal Border at its upper portion is thick, gradu-
ally becoming thinner and tapering as it descends. When the bone
is articulated with its fellow of the opposite side the border produces
internally a vertical crest which forms part of the septum of the nose,
and articulates with the nasal spine of the frontal, the perpendicular
plate of the ethmoid bone, and affords attachment to the nasal carti-
laginous septum.
DEVELOPMENT.-The nasal bone is developed in membrane from
one point of ossification, which appears about the eighth week of
embryonal life.
THE MALAR BONES.
The malar (or cheek) bones are two in number, situated at the lateral
angles of the face, and support the most prominent portion of the
cheeks; they assist in forming the outer wall, lower border, and floor
of the orbit, the anterior portions of the temporal and zygomatic fossæ,
and the zygomatic arch. The bone is quadrangular in shape, and pre-
sents for examination a body with two surfaces, external and internal;
four processes, frontal, orbital, maxillary, and zygomatic; and five bor-
ders, superior, inferior, anterior, posterior, and sphenoidal.
The External or Facial Surface (Fig. 46) is convex in form; the
upper portion is smooth, and supports the sphincter muscle of the eye,
the orbicularis palpebrarum; the lower portion is roughened, and gives
origin to the major and minor zygomatic muscles. The upper portion
of this surface is pierced by one or two foramina, which pass into the
orbit and transmit the terminal ends of the lachrymal blood-vessels.
and nerves. The foramina or canals in the malar bone vary with
different subjects: sometimes they are double, and occasionally they are
wanting.
98
ANATOMY.
The Internal or Zygomatic Surface (Fig. 47) is directed backward
and outward toward the temporal fossa above and the zygomatic fossa
below; it is concave in form, and near the outer portion it is punctured
by one or two small foramina for the passage of blood-vessels and
FIG. 46.

Bristles passed through
Temporo-Malar Canuls
#x
LEV. LABII. SUP.
Maxillop
Frontal
with
TEMPO
with Temporal.
Left Malar Bone, outer surface.
nerves. At the anterior inferior angle of this surface is a rough tri-
angular plate of bone for articulation with the malar process of the
superior maxilla. The remainder of the internal surface is smooth,
and enters into the formation of the temporal and zygomatic fossæ; the
FIG. 47.
M
Fronta
pruc.
10
with Sphenoid
id
рос.
MASSETER
OMA
MAJOR
Zygomatic pro

M
with Super.
bone
Ell
illary
Left Malar Bone, inner surface.
lower third of this surface, extending as far as the lower border of the
bone, gives origin to the greater part of the masseter muscle.
The Frontal Process is the most prominent of the four: its upper
portion is thick and serrated, and articulates with the external angular
process of the frontal bone.
BONES.
99
The Orbital Process is situated at the outer wall and floor of the
orbit: it is divided into two surfaces, the orbital and the temporal; and
two borders, the external and the internal.
The Orbital or Anterior Surface is smooth and concave, generally
presenting two grooves, which extend to near its anterior border, and
terminate in two foramina or canals for the passage of vessels and
nerves -one to the facial surface of the bone, and the other into the
temporal fossa. This surface, together with the great wing of the
sphenoid bone, forms the external wall and part of the floor of the
orbit.
The Temporal or Posterior Surface, in connection with the external
angular process of the frontal bone, forms the anterior boundary of the
temporal fossa. This surface is smooth and convex: it is pierced by a
foramen leading to the orbit.
The Maxillary Process is the strongest and thickest of the four: it
extends along the entire anterior border of the bone, forming the articu-
lating portion of the zygomatic surface, and joining the malar process
of the superior maxilla.
The Zygomatic Process is situated at the posterior inferior portion of
the bone. It is broad and extends backward, its extremity being
bevelled at the extension of its lower part. It is rough and serrated,
and articulates with the zygomatic process of the temporal bone, com-
pleting the zygomatic arch.
The Superior or Orbital Border is smooth and rounded, and presents
in outline an inverted arch. It forms a large portion of the outer
boundary of the orbit.
The Inferior or Zygomatic Border extends horizontally backward to
the zygomatic process, which, together with the lower border of the
zygomatic process of the temporal bone, forms the inferior border of
the zygomatic arch. This border is roughened for the origin of the
masseter muscle.
The Anterior Border is continuous with the articulating surface of
the maxillary process. The elevator muscle of the upper lip (levator
labii superioris proprius) arises just above the suture marking this
articulation, its point of origin extending slightly on to the external
surface of the bone.
G
The Posterior or Temporal Border is thin and curved somewhat like.
an italic f. It faces backward, and is continuous above with the tem-
poral ridge, and below with the superior border of the zygomatic arch.
This border completes the circle enclosing the temporal region which
gives attachment to the temporal muscle.
The Sphenoidal Border extends downward and inward from the
frontal process to the non-articulating notch, when it exists, at the base
of the great wing of the sphenoid bone. This notch forms the anterior
boundary of the spheno-maxillary fissure. Occasionally the malar
bone does not enter into the formation of this fissure. When this
happens it is prevented from so doing by the articulation of the great
wing of the sphenoid with the superior maxilla, or by a small Wor-
mian bone. This border is serrated, and articulates with the great
wing of the sphenoid.
100
ANATOMY.
DEVELOPMENT.-The malar bone is developed in membrane from
two points of ossification, which appear about the eighth week of
embryonal life, uniting about the fourth month. Occasionally the two
portions of the bone remain separate throughout life. When this is
the case the bone is divided into an upper and a lower portion by a
horizontal interspace, the upper portion being the larger.
THE INFERIOR MAXILLARY BONE.
The importance of the inferior maxillary bone, mandible, or lower
jaw to the dentist and the surgeon cannot be over-estimated. Its posi-
tion, composition, and development, its nerve- and blood-supply, com-
bine to render it liable to various and grave diseases. In order that
these shall be thoroughly understood and properly treated, a detailed
knowledge of its anatomy is absolutely necessary.
The inferior maxilla is symmetrical in form, and is situated below
the alveolar border of the superior maxilla, beneath the zygomatic and
glenoid fossæ, articulating in the latter cavity. The lower border,
extending from side to side, forms the anterior inferior boundary of
the face. It assists in forming the lateral portions of the outer bound-
aries of the zygomatic fossa. It also forms the greater portion of the
superior boundary of the surgical squares of the neck and the digastric
triangles.
The inferior maxilla is the largest, heaviest, and strongest bone of the
head, and contains one-half the teeth. It presents for examination a
FIG. 48.
Symphysis
Mental ENT
process
COMUN
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for.
BUCCINATO
DER
LABII 'INFER
ANCULI ORIS.
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Body
Hi
VAN AAN and yet
ATYSMA MYOIDES
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Lot, oblique lina
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Coronar
TEM
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MEIDSS3231
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MASSETERI
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Inferior Maxillary Bone, outer surface, side view.
Condyle

Ramus
-Angle
body, which is horizontal in direction, and two rami, which extend
almost perpendicularly upward to the articulation with the temporal
bones.
BONES.
101
The Body or Horizontal Portion of the bone is parabolic in form,
the anterior portion presenting a slight vertical ridge, the symphysis.
This symphysis indicates the point of union between the primitive
halves of the bone, which unite shortly after birth. The body is
divided into two surfaces, external and internal; and two borders,
superior and inferior.
The External or Facial Surface (Fig. 48). The vertical ridge in the
median line of the external surface extends outward and forward about
halfway between the upper and lower borders of the bone. It divides
to the right and left and forms a triangular process, the mental process
or chin, a feature exclusively human.
The Incisor Fossa.-Above the mental process and below the incisor
teeth is a shallow depression, the incisor fossa. This fossa gives origin
to the elevator muscle of the lower lip (levator labii inferioris). At the
side, a little below the incisor fossa, beneath the cuspid (canine) tooth, is
a depression for the origin of the depressor muscle of the lower lip
(depressor labii inferioris).
The Mental or Anterior Dental Foramen is not constant in its position.
When the teeth are imbedded in the bone it is generally placed midway
between the superior and lower borders of the bone, below the root of
the second bicuspid tooth, though it may appear as far back as the first
molar or as far forward as the first bicuspid. This foramen transmits
the mental branches of the inferior dental nerve and vessels.
The External Oblique Line commences at the lateral portion of the men-
tal process, passes backward beneath the mental foramen, and extends
slightly upward and backward to the anterior margin of the ramus of
the jaw. That portion of this line below the mental foramen gives origin
to the depressor muscle of the angle of the mouth (depressor anguli oris).
Between the line of origin of this muscle and the inferior border of
the bone is a roughened surface for the attachment of the platysma
myoides muscle. This roughened surface divides the body of the bone
into two portions, a superior alveolar or mucous portion, and an inferior
basilar or non-mucous portion.
The Superior Alveolar or Mucous Portion is situated within the ves-
tibule of the mouth, and is covered by mucous membrane and muco-
periosteum. It gives origin to the buccinator muscle just below the
three molar teeth.
The Inferior Basilar or Non-Mucous Portion is outside and below
the vestibule of the mouth, and is covered with periosteum similar to
other bones.
The Internal Surface (Fig. 49) in the median line is marked by a
slight vertical depression corresponding to the symphysis externally.
The Mylo-hyoid or Internal Oblique Ridge commences at the base of
the coronoid process and extends downward and forward to a point
just below the genial tubercles, where it joins the ridge of the oppo-
site side. This ridge is but faintly marked as it reaches the median
line of the bone; it divides the internal surface into two portions, a
superior and inferior, and gives origin throughout its whole extent to
the mylo-hyoideus muscle. This muscle forms the floor of the mouth.
Between the posterior portion of this ridge and the wisdom tooth the
102
ANATOMY.
buccinator muscle of the cheek and the superior constrictor muscle of
the pharynx have slight attachments.
The Superior Portion is situated within the mouth, and is covered by
mucous membrane and muco-periosteum.
The Inferior Portion is all that surface of bone below the mylo-hyoid
ridge. It is situated below the floor of the mouth, and is covered by
periosteum.
The Genial Tubercles are situated at the lower portion of the median
line of the bone. They are four in number, two on each side. Occa-
sionally, these tubercles are indistinct, and sometimes they unite and form
one tubercle. The superior pair afford
origin to the genio-hyo-glossi mus-
cles, the lower pair to the genio-
hyoidei muscles.
FIG. 49.
Temporal
Artic. with
ERNAL
EXTER
¡PTERYGOID
Ramus
HONE
Trust fun
TEMPORAL
bo.kyoid
We
NTERNAL
PTERYGOID
101
FUCCIN
M
Mylo hyoid Ridge
215
The Sublingual Fossa is an oval
depression, posterior to the genial
tubercle, below the cuspid teeth and
above the mylo-hyoid ridge. This
Cen
sub lings
Fossu
HYQUD
Fossa for Submaxill. gland
for
DIGASTRIC
Body
Inferior Maxillary Bone, inner surface, side view.
kwar

-GENIO-HYO-GLOSSUS
GENIO HYOIDEUS
.
fossa supports the anterior border of the sublingual gland. It is wider
behind than in front.
The Digastric Fossa is a depression for the insertion of the digastric
muscle. It is situated at the anterior portion of the internal surface of
the bone, near the symphysis and the lower border of the inferior maxilla.
The Submaxillary Fossa is an oblong depression, wider behind than in
front, situated near the centre of the internal surface and between the
mylo-hyoid ridge and the lower border of the bone. In it rests the
external surface of the submaxillary muco-salivary gland.
The Mylo-hyoid Groove is situated beneath the mylo-hyoid ridge, com-
mencing at the posterior (inferior) dental canal. This groove accommo-
dates the mylo-hyoid nerve, artery, and vein as they pass to the floor of
the mouth.
The Superior Border of the bone extends from the ramus of one
side to the same point on the other. It is situated on that portion
of the bone analogous to the alveolar process of the superior maxilla.
BONES.
103
It is broader behind than in front, and is marked by sixteen pits of
various shapes for the accommodation of the teeth. The pits for the
central incisors are the smallest, conical in shape, and compressed later-
ally. Those for the lateral incisors are somewhat larger and not quite
so compressed. The cavities for the cuspids (canine or stomach) teeth
are situated at the angles of this border, are larger and deeper than
those for the incisors, but less compressed in proportion to their size.
The six anterior sockets just described are arranged in the form of an arc,
while those for the remainder of the teeth extend in almost a straight
line posteriorly, the straightness of the line varying with the tempera-
ment of the individual. The sockets for the bicuspid teeth are variably
compressed and occasionally bifurcated, though it is exceptional to find
a double-rooted inferior bicuspid. The sockets for the molar teeth are
round superiorly, but as they descend soon bifurcate into two flattened
cone-shaped depressions. Those for the third molar or wisdom tooth,
however, vary from this rule just as their roots vary.
The Alveolar Process is very similar to that of the superior maxilla
before described, the principal point of difference being in the external
plate. The external plate of the superior maxilla is thin throughout
The entire surface-so much so that the roots of the teeth are often bared
in macerating the bone. In the inferior maxilla the external plate is
thick and compact, thus rendering the lower teeth more difficult of
extraction than those in the upper jaw. After extraction the external plate
of the superior maxilla is absorbed much more rapidly and to a greater
extent than the internal plate, while with the external and internal plates
of the inferior maxilla the rate of absorption is more uniform.
I
-
The Inferior Border of the bone extends from a depression at the
union of the ramus with the body of the bone to the same point upon
the opposite side. It is thick, strong, rounding, and composed of com-
pact tissue. The depression or groove at the union of the ramus at the
base of the bone is sometimes called "the facial notch." It is at this
point that the facial artery passes from the neck to the face-an import-
ant fact to remember when the parts are wounded or in surgical opera-
tions on the face, for hemorrhage can generally be controlled by pressure
at this point.
MA
Ską
(
The Rami or Ascending Portions of the inferior maxilla are quad-
rilateral in shape and divided into two surfaces, external and internal ;
four borders, superior, inferior, anterior, and posterior; and two pro-
cesses, the condyloid and coronoid.
The External Surface is nearly flat. It is slightly roughened near
its posterior inferior angle for the insertion of the masseter muscle.
The Internal Surface. The central portion is marked by an oblique
opening, the posterior or inferior dental foramen. Running downward
and forward from the lower border of this foramen is a groove, the
mylo-hyoid, already described. Posterior to this groove, extending to
the angle of the bone, is a roughened surface for the insertion of the
internal pterygoid muscle.
The Posterior or Inferior Dental Foramen is oval in shape; a sharp
border of bone extends along its anterior margin, and terminates above in
a spine for the insertion of the internal lateral ligament of the lower jaw.
104
ANATOMY.
The Dental Canal extends through the body of the bone from the
posterior (inferior) dental foramen to the anterior (mental) foramen.
Its course is at first downward and forward, until it reaches the body
of the bone, through which it runs in a horizontal direction, finally
passing forward and opening through the mental foramen on the outer
surface of the bone. It lies beneath the alveolar process, and communi-
cates with the teeth and bony tissue through small canals. Opposite
the mental foramen in the substance of the bone there are small canals
passing forward to the cuspid and incisor teeth and the symphysis of the
chin. The posterior (inferior) dental canal and its branches transmit
the inferior dental nerve, artery, and vein.
S
The Superior Border of the Ramus.-Arising from this anteriorly is
an elevated process of bone, the coronoid process. From its posterior
portion there arises a rounded eminence of bone, the condyloid process,
which is continuous with the posterior border of the ramus.
The Coronoid Process is flat and pointed, being thinner at the apex
than at the base. The anterior border is a continuation of the external
oblique line. This border bends slightly outward as it ascends, and
terminates in the apex of the process. Extending downward and for-
ward from the apex of this process on its internal surface is a curved
ridge of bone which joins the internal oblique line just posterior to the
wisdom tooth. Between the anterior border and this rounded ridge of
bone, posterior to the third molar tooth, is a wide groove for the inser-
tion of a part of the temporal muscle above and the buccinator muscle
below. The posterior border of this process is thin, and forms the
anterior margin of the sigmoid notch. The outer surface of this process
is smooth, and affords attachment to a portion of the temporal and
masseter muscles. The inner surface is rough, and gives attachment to
the temporal muscle superiorly.
The Condyloid Process is shorter, thicker, and more massive than
the coronoid. It is continuous with the posterior or free border of the
ramus. As this border extends upward it widens, until it forms an
articulating surface convex in outline. The superior surface of the
condyloid process articulates with the anterior portion of the glenoid
fossa of the temporal bone. This surface is separated from the glenoid
fossa by interarticular fibro-cartilage.
The Neck is that constricted portion of bone immediately below the
articulating surface. Just internal to the posterior portion of the supe-
rior border of the ramus it presents a depression, the pterygoid fossa, for
the insertion of the greater part of the external pterygoid muscle. At
the junction of the neck with the articulating surface of the bone
externally is a tubercle for the insertion of the external lateral ligament.
Between the coronoid and condyloid processes is situated the sigmoid
notch. The border of this notch is thin and crossed by the masseteric
artery and nerve on their way to the masseter muscle.
The Inferior Border of the ramus is continuous with that of the body
of the bone. The point of junction between the inferior and posterior
borders is the angle. This angle extends outwardly, and is grooved
and roughened for the insertion of part of the superficial portion of the
masseter muscle.
G
BONES.
105
DOUGH
The Anterior Border.—(For description see Coronoid Process.)
The Posterior Border at its upper portion is smooth and rounding.
As it approaches the angle of the bone it is roughened for the insertion
of the stylo-maxillary ligament.
DEVELOPMENT.-The inferior maxilla is the second bone developed,
the clavicle being the first; it is developed from the first pair of what
are known as the visceral or branchial folds or arches of the embryo,
called the mandibular plates. These plates from the twenty-fifth to the
twenty-eighth day of embryonal life advance from the sides of the base
of the cranium and meet in the median line. Soon after this union
the cartilage of Meckel appears in the deeper portion of the mandibular
plate. In mammals the proximal end of this cartilage forms the mal-
leus (one of the small bones of the middle ear), and its distal portion
advances along the mandibular plate until it ineets its fellow of the
opposite side at the symphysis menti.
Meckel's cartilage (Fig. 50) forms in great measure what may be
termed a temporary framework for the support of the lower jaw. It
disappears at the latter part of the
fifth or beginning of the sixth month
of foetal life, and ossification proceeds.
FIG. 50.
Internal Face of the Right Maxilla of a
Human Embryo of about Three Months,
showing the natural size and the relative
About the fortieth day of embry-
onic life ossification commences from
several centres deposited on the out-
side, about midway between the prox-
imal and the distal extremities, in the
membrane which partially surrounds
the cartilage of Meckel. These cen-
tres speedily unite. Ossification then position of Meckel's cartilage.
proceeds in both directions along the
outer, under, and inner surface of the cartilage, but does not unite with
it. Ábout the sixtieth day a miniature jaw is formed, a small portion
of the body at the symphysis resulting from direct ossification of
Meckel's cartilage. The condyles and a portion of the rami are also
ossified from other cartilage. From the centre of the rami internally
Meckel's cartilage is prolonged backward to the glenoid fissure, and
thence to the middle ear. That portion which passes between the
temporal bone and the inferior maxilla
becomes surrounded by fibrous tissue and
forms the internal lateral ligament of the
jaw.
FIG. 51.

m
a
Prontas
CL
Limy
72

At birth osseous union between the lat-
eral halves of the bone has not taken place,
they being connected by fibro-cartilaginous
tissue. They unite, however, during the
first year, ossification commencing below
and extending upward, a trace only remain-
ing at the upper portion at the beginning
of the second year. The body of the bone
is shell-like, open at the top, and contains the germs of the teeth. The
coronoid processes are large proportionately to the remainder of the
2
T
The Inferior Maxilla of a Foetus at
about the Full Period of Intra-uter-
ine Life. The two sides (a, b) are
separate.
Z
106
UPOMNN
NAFA
ESTRUIRE
FIG. 54.
FIG. 52.

FIG. 53.
FIG. 55.
-3
JOANTHINIGAMIE JETHE A
FIG. 52. Appearance of Lower Jaw with Deciduous Teeth.
"L 53. Lower Jaw with Permanent Teeth in position.
แ 54. Partial Absorption of Alveolar Process.
66
55. Complete Absorption of Process.
$9729510
BONES.
107
bone, the condyloid processes being short and inclined slightly back-
ward. The rami are short, and but slightly deflected upward from the
axis of the body of the bone.
After birth the body of the bone becomes elongated (Fig. 52), increas-
ing backward behind the anterior (mental) foramen to a greater extent
than it does in front of it. This difference is to give greater space for
the accommodation of the permanent molar teeth.
The growth of the body of the bone above the oblique line is made
up principally of its alveolar process, which sustains the teeth. The
growth below the oblique line, both in extent and thickness, gives
strength to the bone and space for the attachment of muscles, lodg-
ment of glands, etc. The rami and condyles of the bone increase in
length, and the angles between the rami and the body of the bone
become less obtuse; finally, they are almost at right angles with the
body (Fig. 53), the difference in direction being due to the gradual sep-
aration of the jaws by the growth of the teeth. As the teeth wear
away, the jaws approach each other more closely again, and the angles
between the rami and the body of the bone begin to reassume their
FIG. 56.

1
Engraving showing Absorption of Alveolar Process in upper and lower jaw after loss of all the
teeth.
former shape (Fig. 54). When the teeth are lost by decay or otherwise,
the alveolar process is absorbed (Fig. 55), the depth of the bone thereby
diminishes, the mental foramen being nearly on a level with the supe-
rior border of the bone, the dental canal becoming superficial. The
buccinator, levator labii inferioris, and the genio-glossus muscles are
108
ANATOMY.
attached just below the superior border of the bone, sometimes extend-
ing well up on this border-a fact which, in such jaws, interferes in
a measure with the wearing of artificial teeth. The endeavor to bring
the jaws together after the teeth and alveolar process are lost causes the
angle between the ramus and body of the bone to assume almost the
same obtuse form as at birth (Fig. 56). The employment of artificial
teeth immediately after the loss of the natural ones delays to a certain
extent this change of form.
THE HYOID BONE.
The hyoid bone (Fig. 57), or os linguæ, is symmetrical in outline. It
FIG. 57.

Body.
Greater Cornu.
Middle Constrictor of Pharynx..
Hyo-glossus.
Lesser Cornu.
45.
Genio-hyo-glossus,
***
Thyro-hyoid.
Stylo-hyoid.
Omo-hyoid.
'Mylo-hyoid.
Sterno-hyoid.
Genio-hyoid.
Hyoid Bone, anterior surface (enlarged).
is situated in the median line of the upper part of the neck, at the
base of the tongue, and above the larynx. It is so superficially
placed that ordinarily the outlines of the bone can be traced beneath
the skin below the chin. It is a floating bone, having no osseous
articulation. In form it is U-shaped, the convexity of the U being
directed forward and its concavity backward. It is divided into a
body and four processes called horns or cornua, two on each side.
The Body or Central Portion (basihyal) of the bone is quadrilateral
in form. It is compressed from before backward, the anterior surface
being convex and marked in the median line by a vertical ridge. On
each side of this ridge are eminences and depressions for the attachment
of the genio-hyoid muscles. Below these the two mylo-hyoid, the two
stylo-hyoid, and the aponeuroses of the digastric muscles are inserted.
Between the surfaces for the attachment of these muscles are inserted
portions of the two hyo-glossus muscles.
The Posterior Surface is smooth and deeply concave. It is directed
backward and downward toward the epiglottis. The space between
this surface and the epiglottis is filled by loose areolar tissue.
The Superior Border is thin, rounding, and continuous with the
inner margin of the great cornua. It gives attachment to the thyro-
hyoid membrane.
BONES.
109
The Inferior Border is thicker than the superior, and gives attach-
ment to the sterno-hyoid muscles anteriorly and the thyro-hyoid muscles
posteriorly. The omo-hyoid muscles are attached at the junction of
the body with the great cornua.
The Great Cornua (thyrohyals) project backward from the body of
the bone on each side. They are compressed from above downward,
the ends being rounded for the attachment of the thyro-hyoid ligaments.
Their outer surfaces give attachment to the hyo-glossus muscles. The
superior borders of these horns give attachment to the superior con-
strictor of the pharynx, while on their inferior borders are inserted the
thyro-hyoid muscles.
J
The Lesser Cornua (ceratohyals) are short and conical; they accom-
pany the great cornua, and project upward and backward from the
body of the bone. Their extremities give attachment to the stylo-
hyoid ligaments.
DEVELOPMENT.-The hyoid bone is developed from the second pair
of visceral arches, and ossified from five centres of deposit-one for the
body and one for each of the cornua. The first centres for the body and
the great cornua are deposited during the last period of foetal life, those
for the lesser cornua not appearing until the first year. Ossific unions
between the greater cornua and the body of the bone take place during
middle life, while unions between the lesser cornua and the body do not
take place until advanced age. Occasionally the stylo-hyoid ligaments
are partially ossified.
THE SKULL AS A WHOLE.
The study of the skull as a whole includes a consideration of all the
bones of the head and face articulated, described under three heads:
I. General Development; II. Articulation; III. Regional Anatomy.
GENERAL DEVELOPMENT.
The entire bony structure of the head is developed from the meso-
blastic layer of the embryo. The axis around which the first parts of
the foetus are formed is called the notochord or chorda dorsalis. The
anterior or superior portion of this chord extends forward into the
mass of tissue which forms the principal matrix of the future bony
walls of the base of the brain-case, and terminates at the posterior
border of the pituitary fossa, its extreme anterior portion forming the
dorsum selle of the sphenoid bone.
From the anterior portion of the dorsum sellæ, in close proximity
to the posterior clinoid processes, two cartilaginous rudiments (known
as the trabeculæ cranii of Rothke) are thrown out and pass forward,
uniting in front of the olfactory depressions. As these rudiments pass
forward they unite and separate from each other at intervals, enclosing
small interspaces between them. The nasal cartilage is developed
directly from these trabeculæ at or near their union in front of the olfac-
tory fossa.
This axis, or line of origin, at the base of the brain-case is divided
into two portions, anterior and posterior.
110
ANATOMY.
:
The Anterior Portion, or spheno-ethmoid portion, forms in front of
the notochord, along the trabeculae cranii, and includes the matrix of
the presphenoid and the septal-ethmoid cartilage. It extends forward
to the anterior portion of the nasal cartilage and the aperture for the
external nose.
Behind the nasal cartilage the trabeculae cranii unite to form the
ethmo-vomerine cartilage, which forms part of the nasal septum. Later-
ally, the presphenoid cartilage, the matrix of the orbito-sphenoid, the
lesser wings of the sphenoid bone, and the optic foramen are developed.
The Posterior Portion, or occipito-sphenoid portion, is formed from
that part of the notochord situated behind the pituitary fossa, and, in
conjunction with the surrounding tissue, contains the matrix of the basi-
sphenoidal cartilages. This portion also extends laterally, and forms
the matrix of the exoccipital and periotic mass of cartilage which sur-
rounds the primary auditory vesicles.
The greater part of the occipito-sphenoid portion prolongs forward,
and extends below the posterior and middle primary encephalic vesicles,
and the matrix for the great wing of the sphenoid process derived from
the basisphenoid.
It will thus be seen that the base of the brain-case, extending to the
most anterior portion of the cartilage of the nose, is a foundation of
cartilaginous tissue, and all the bones-speaking of them as they are
divided by the comparative anatomist-arising immediately from this
foundation to form the base of the brain-case are cartilaginous bones.
The remainder of the bones of the brain-case, or those formed on each
side of the chorda dorsalis and trabeculæ cranii, such as the interpari-
etals and squamo-zygomatics, are developed in membrane. These mem-
branous bones are claimed by Kölliker to be of dermal origin and to
belong to the group of investing bones.
The facial bones, except the inferior turbinated, are developed in
membrane, similarly to the tabular bones of the head; and as the mem-
branous bones of the cranial vault articulate with the cartilaginous
bones which form the base of the brain-case, so all the membranous
bones of the face articulate from below with this same cartilaginous
foundation. The inferior maxilla would seem to be an exception to
this membro-cartilaginous articulation; but in the early stages of its
development it is connected, through the cartilage of Meckel, with the
periotic bones.
The Face.-The bones of the brain-case, formed from the notochord
and trabeculæ, are in an advanced state of development before the
facial bones commence to be built. To such an extent is this the fact
that the dermoid structure (the skin) lies almost in contact with all
that portion of the head below and anterior to the notochord, and
there is at this time no opening to the upper portion of the aliment-
any canal.
The facial bones arise from the under surface of the base of the
brain-case from certain processes, and push outward and downward,
leaving a layer of dermoid tissue on their inner as well as their outer
surfaces. This dermoid tissue becomes the mucous or epidermoid
(epiblastic) lining of the mouth, nasal cavities, and all the internal sur-
BONES.
111
faces of the face, excepting the tympanum and Eustachian tubes. These
tubes are lined with hypoblastic tissue similar to that which lines the
alimentary canal.¹
The processes in front which push downward and forward are called
the fronto-nasal; those on the side, the maxillary and mandibular.
Those which are situated deeply within the face are known as the
spheno-ethmo prolongations of the trabeculæ cranii.
The changes that occur during the formative process are complex:
they prodnce the external nose, the lips, and the cheeks; the mouth,
including the upper and lower jaws, the hard and soft palate; the nasal
chambers; the orbits; the labyrinths; the external auditory meatus and
tympano-Eustachian tubes; the different air-sinuses, such as the eth-
moidal, spheno-maxillary, and frontal cells. This explains how it is
that all the facial bones proper, excepting the malar, are lined by
mucous membrane. (The special development of each bone is described
under the head General Anatomy.)
ARTICULATIONS.
When two or more bones are united together, this union is called a
joint or articulation. There are three varieties of articulation in the
head-viz. sutura, synchondroses, and diarthroses.
THE SUTURA are those articulations which exist between the inter-
membranous bones and also between the intermembranous and inter-
cartilaginous bones of the head. This articulation permits of but slight
or no appreciable movement. The bones forming this variety of articu-
lation are separated from each other by a thin layer of membrane, that
on the outer surface of the joint being derived from the pericranium,
and that on the inside from the dura mater.
There are four kinds of sutures-viz. harmonic, squamosa, dentata,
and serrata..
The Harmonic sutures are those that have comparatively smooth
articulating surfaces or borders. Examples, the articulation between
the palate process of the superior maxilla and the palate bones, also
the internal surfaces of the articulations of the cranial vault.
The Squamosa (squama, a scale) are those in which the opposing
surfaces of bone are bevelled, overlapping each other like the scales of
a fish. Examples, the temporo-parietal and the temporo-sphenoidal
articulations.
The Dentata (dens, a tooth) are those in which the articulating bor-
ders of the bones are severally armed with numerous tooth-like pro-
jections fitting into corresponding indentations. Example, the suture
between the two parietal bones.
The Serrata (serra, a saw) are those in which the articulating borders
of the bones are marked like the teeth of a saw. Example, the suture
between the two halves of the frontal bone.
The dentation and serration of the borders of the bones of the brain-
case are not marked internally, the under surface of the dome of the
skull being smooth. On the internal surface, therefore, these sutures
1 Quain's Anatomy.
112
ANATOMY.
would be called harmonic, no matter under what head they might be
classed externally.
THE SYNCHONDROSES are almost immovable articulations. A thin
layer of cartilage intervenes between the intercartilaginous bones which
go to form this articulation, uniting them together. It is found between
the epiphyses and shafts of long bones. Examples, the occipito-sphe-
noidal articulation and the articulations of the hyoid bone at the cornua.
THE DIARTHROSES.-The greater number of the joints of the body
are of this variety. These articulations have extensive movement, such
as is seen in the elbow, knee, shoulder, hip, and temporo-maxillary
joints. The articulating surfaces of these bones are either convex or
concave, and covered by a thin layer of cartilage, forming a smooth
articulating extremity. Synovial cavities also exist between the ex-
tremities of the bones forming these joints, which are further lubricated
by a synovial fluid secreted by a delicate membrane lining all the inter-
nal portions of the joints excepting the cartilaginous, though it invests
the borders of the cartilages interposed between the joints and assists in
holding the bones in apposition. In some joints interarticular discs of
fibro-cartilage are placed between the articulating surfaces of bones
composing them, these discs dividing the space into two compartments
of dissimilar size. An example of this is seen in the temporo-maxil-
lary articulation.
Articulating surfaces are also often marked by irregular facets, so that
when the bones are at different degrees of flexion and extension in the
joint-cavity there is a special articulating point for that particular posi-
tion. The opposing surfaces of bones forming these joints are held in
apposition by fibrous tissue of various shapes as well as by synovial
membrane. This fibrous tissue receives its name according to its
relation with the joint. For example, the crucial ligaments of the
knee receive their name because they cross each other (obliquely), while
the capsular ligaments of joints are so named because they surround the
joints.
The diarthrodial articulation is variously subdivided. Gray speaks
of four divisions-viz. Arthrodia, Enarthrodia, Ginglymus, and Diar-
throdia Rotatoria; while Allen recognizes five divisions-the Arthro-
dial, Spherical, Cylindrical, Conical, and Composite. Here it will be
necessary only to describe the combination of these subdivisions which
covers the movements of the temporo-maxillary joint.
The Temporo-maxillary Articulations are formed by the union of the
condyloid processes of the inferior maxilla with the anterior portions of
the glenoid fosse of the temporal bones, the glenoid fissures being imme-
diately behind the condyles, while the eminentiæ articulariæ are in
front.
Gray describes the arthrodial as "that form of joint which admits of
a gliding movement, . . . . the amount of motion between them being
limited by the ligaments or osseous processes surrounding the articula-
tion, as in the articular processes of the vertebræ, the temporo-maxillary,
sterno-clavicular, and acromio-clavicular," etc. etc.
Allen describes the ginglymus or hinge-joint, which is a subdivision
of the cylindrical division of diarthrotic joints, as the "best expression.
BONES.
113
of a cylindroid joint. The axis of rotation is perpendicular to the axis
of the moving bone, or, as in the case of the elbow, the axis of two
bones, the radius and ulna, since both of these describe curvations
around the axis of rotation. The paths of movement of the hinge-
joint are free within certain limits. These degrees of freedom are of
necessity fixed by the direction of the greatest convexity. The co-opera-
tion of the surfaces is exact."
In man the temporo-maxillary articulation presents a combination
of these movements. In the Carnivora, however, this joint has no
gliding movement, as the condyle is a half cylinder working in a deep
glenoid fossa of corresponding form, which only allows an up-and-down
or hinge movement. In ruminants the condyles of the inferior maxillæ
are only slightly convex, and the glenoid fosse of the temporal bones
but slightly concave. This arrangement allows great latitude of motion,
and the joint is a combination of the arthrodial and of the hinge, as it
likewise is in man.
The gliding movement of this joint in man, characteristic of the
arthrodial articulation, has an important bearing in the adjustment of
artificial teeth. If the condyles of the inferior maxilla are carried
well up into the glenoid fosse when the mouth is closed, the jaws or
their teeth will be in proper apposition to each other.
The structures connected with the temporo-maxillary articulation are
generally described as five ligaments and two synovial sacs.
The liga-
FIG. 58.

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Temporo-maxillary Articulation, internal view.
ments are the capsular, external and internal lateral, stylo-maxillary,
and an interarticular fibro-cartilage. The capsular and external lateral
will be described as one ligament, while the internal lateral and stylo-
VOL. I.-8
114
ANATOMY.
maxillary, not being in direct connection with the joint, will be
described as accessory ligaments to the articulation (Fig. 58).
The Capsular Ligaments of the temporo-maxillary articulation is an
exceedingly loose fibrous bag. It is thin in front and on the inner side,
being thick and strong behind and on the outer side. It is attached
above to the articulating circumference of the glenoid fossa, and below
it encircles the neck of the condyle of the inferior maxilla. The most
superficial fibres of this ligament extend downward and backward from
the outer surface and tubercle at the anterior root of the zygoma to the
outer surface and posterior border of the neck of the inferior maxilla.
This portion is generally spoken of as the external lateral ligament of
the articulation.
The structures found within this joint (Fig. 59) are the interarticular
disc of cartilage and the synovial sacs.
FIG. 59.

///////
Glenvid
Feminential
Articuluris
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INTER-ARTIC.FIBRC_
AQROSTY
Vertical Section of Temporo-maxillary Articulation.
The Interarticular Disc of Fibro-cartilage is a thin plate of cartilag-
inous tissue situated between the articulating bones. It is elliptical in
form, its broadest diameter being transverse. Its lower surface is con-
cave for the accommodation of the condyle of the jaw, its upper surface
being concave in front, where it passes under the articular eminence,
and thick and convex behind, where it adapts itself to the deeper por-
tion of the glenoid fossa. Its circumference affords attachment to the
common capsular ligament, while its anterior portion gives insertion to
part of the tendon of the external pterygoid muscle. Its surfaces are
smooth and divide the articulating cavity into two unequal pockets.
Sometimes an opening will be found in the centre of this cartilage which
allows communication between the chambers. When this is the case
the synovial sacs are continuous with each other.
S
THE SYNOVIAL SACS are two pouches which secrete the fluid for
lubricating the joint. They are situated one above the other below the
interarticular disc of cartilage.
The Superior Synovial Sac is the larger and freer of the two. It
begins at the margin of the disc, and passes over the eminentia.
articularis, the roof of the glenoid fossa, and the upper surface of the
cartilage.
BONES.
115
The Inferior Synovial Sac is situated between the cartilage and the
condyle. It extends on the condyle posteriorly to a greater extent than
it does anteriorly.
The Internal Lateral Ligament is not directly connected with the
temporo-maxillary articulation, but acts as an accessory ligament to the
joint. It is a fascia-like band extending from the spinous process of
the sphenoid bone; becoming broader as it descends, it is inserted into a
triangular process of bone on the anterior border of the posterior dental
foramen. The external pterygoid muscle crosses the superior portion
of this ligament externally, the internal maxillary artery and the infe-
rior dental vessels and nerve passing lower down between the ligament
and the bone.
The Stylo-maxillary Ligament is the other accessory ligament of the
temporo-maxillary articulation. It is a strong fibrous band connected
with the deep cervical fascia, extending from a point in close proximity
to the apex of the styloid process of the temporal bone to the inferior
portion of the posterior border of the ramus of the jaw, where it is
inserted between the masseter muscle externally and the internal ptery-
goid muscle internally. The stylo-maxillary ligament divides the
parotid from the submaxillary region, and is connected by fasciculi
with the stylo-glossus muscle.
The movements permitted by the temporo-maxillary articulation are
more varied and of greater number than those of any joint in the body.
The jaw has the power of extension and retraction; it can be depressed
and elevated, moved from side to side, and combines all the movements
intermediate between these, thus allowing the gliding motion necessary
to mastication. The interarticular fibro-cartilage assists in these varied
movements and acts as a multiplier of them. The superior surface of
this cartilage glides forward on to the articular eminence of the anterior
root of the zygoma, while the condyle of the inferior maxilla rotates
on a transverse axis in the concavity of the inferior surface of this
cartilage. When the mouth is widely opened the cartilages of each
articulation move forward on to the articular eminence, the condyles
being carried upward on the lower surfaces of these cartilages. If the
inferior maxilla is drawn forward, so that the lower incisor teeth are in
advance of the upper ones, the action of this articulation is restricted
to a gliding of the superior surface of the interarticular cartilage over
the anterior root of the zygoma.
If the lower jaw is too much depressed, as is sometimes the case in
yawning, vomiting, the extraction of the teeth, or as the result of blows,
dislocation will follow. This luxation is caused by the interarticular
cartilage being carried forward to the eminence on one or both sides,
or by one of the condyles of the inferior maxilla breaking through the
anterior portions of the capsular ligament, its weakest point, and lodg-
ing in the zygomatic fossa.
SUTURES.
The bones of the skull, with the exception of the inferior maxilla and
temporal bones and the cartilaginous bones at the base of the skull, are
116
ANATOMY.
closely united through borders more or less uneven. This variety of
union is called a suture, and those occurring in the head may be sepa-
rated into four divisions-viz. those of the cranial vault, those of the
FIG. 60.

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lateral portions of the cranium, those of the face, and those of the occi-
put (Fig. 60).
In describing sutures the names of the bones forming them should
always be used.
SUTURES OF THE CRANIAL VAULT.-Those between the bones
forming the cranial vault are three in number.
I. The Interparietal or Sagittal Suture is between the two parietal bones,
extending from the frontal bone to the superior angle of the occipital
bone. In childhood, and occasionally in adult life, ossification between
the two halves of the frontal bone is not completed in the median line.
This causes the formation of a frontal suture, and a continuation of the
sagittal suture from the superior angle of the occipital bone posteriorly
to the nasal bones anteriorly. On either side of the suture posteriorly
BONES.
117
the parietal foramen or foramina are located, and Wormian bones of
large size are often found within the suture.
II. The Fronto-parietal or Coronal Suture is between the frontal and
parietal bones, extending across the anterior portion of the cranial vault
from the superior extremity of the great wing of the sphenoid bone on
one side to the same point on the other.
III. The Occipito-parietal or Lambdoid Suture is between the occipital
and parietal bones, extending from the mastoid portion of the temporal
bone on one side upward to the interparietal suture, and thence down-
ward to the mastoid portion of the temporal bone of the other.
Wor-
mian bones are more numerous within this than the other sutures.
KA
THE SUTURES OF THE LATERAL PORTIONS OF THE CRANIAL
VAULT are six in number, without referring to the parieto-frontal
and the parieto-occipital articulation where they come within these
regions.
The Fronto-malar Suture, describing this region from its anterior to
its posterior boundary, is between the external angular process of the
frontal bone and the frontal process of the malar bone.
The Fronto-sphenoidal Suture is within the temporal fossa, where the
frontal bone articulates with the great wing of the sphenoid bone. This
articulation forms the second suture.
The Spheno-malar Suture is the third; it also is within the temporal
fossa, and is formed by articulation of the malar bone with the anterior
border of the great wing of the sphenoid bone.
The Parieto-sphenoid is the fourth, and is found between the parietal
bone and the tip of the great wing of the sphenoid bone. In some rare
cases the parietal bone does not articulate with the sphenoid at this
point; the frontal bone then articulates directly with the squamous por-
tion of the temporal bone.
The Parieto-squamous Suture, the fifth, is formed by the articula-
tion of the parietal bone with the squamous portion of the temporal
bone.
The Parieto-mastoid Suture is the sixth, and is formed by the artic-
ulation of the parietal bone with the mastoid portion of the temporal
bone.
THE SUTURES OF THE FACE.-In the face the frontal bone assists
in forming several sutures. These likewise receive their names from
the bones that form them, as the fronto-sphenoid, fronto-ethmoid, fronto-
lachrymal, fronto-maxillary, and fronto-nasal. This rule for naming
sutures is carried out in describing the articulations between the other
bones of the face.
THE ARTICULATIONS OF THE OCCIPUT are those between the occipital
bone and the posterior inferior angle of the parietal bone, and of the
occipital bone and mastoid portion of the temporal bone.
The articulations between the bones at the base of the brain-case are
the occipito-sphenoid, occipito-temporal, and the temporo-sphenoid. In
early life a thin layer of cartilage is interposed between these bones,
which at adult age becomes ossified. These articulations, therefore, are
of the synchondroidal variety.
118
ANATOMY.
·
THE SKULL AND ITS ARTICULATIONS AT DIFFERENT PERIODS OF
LIFE.
About the second month of embryonal life the brain-case is divided
into two almost equal compartments by the tentorium cerebelli, which
at this period extends almost perpendicularly from its anterior attach-
ment within the skull. This division shows the posterior or cerebellar
portion of the encephalon at this period to be larger in proportion to
the anterior or cerebral than in the adult. Shortly after the second
month the rapid growth of the parietal bones causes the occipital por-
tion of the cranium to be pushed backward. By the final enlargement
of the frontal bones the anterior or cerebral fosse are completed.
J
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At birth the parietal bones are large in proportion to the other bones
of the head, and their centres of ossification are extremely prominent.
The frontal eminences and the occipital protuberance are also noticeably
convex.
During the first year, to accommodate the enlarging brain, the dome
of the case grows with greater rapidity than the base, the upper portion
of the frontal bone developing to a greater extent than the orbital por-
tion, which causes the prominence of the forehead peculiar to children
at this age. At this period the facial bones occupy but about one-eighth
of the entire skull, while at adult life they form almost one-half. The
external auditory meatus and the alveolar processes are but partially
developed, and only the anterior deciduous teeth are erupted. The
sutures are more or less open, while the different parts of the bones
formed by separate centres of ossification in many instances are not
united.
.
P
During the first year the sutures of the cranial vault are generally so
widely open that the border of one bone can be made to overlap that
adjoining without damage to either or to the brain of the child. Such
overlapping takes place during the birth of a child, and the head may
be subjected to considerable compression of various kinds during early
life with comparatively little or no injury.
The sutures according to their location, disappear at different periods;
the general ossific development of the individual likewise seems to influ-
ence their disappearance. Traces of them can be found in the skull as
late as the fiftieth or sixtieth year. When a suture is obliterated by
ossification such complete union is called synostosis.
Occasionally some pathological condition will cause a suture to close
prematurely. When this occurs the cranium will bulge on the opposite
side, in order to accommodate the brain as it develops.
Wormian Bones (ossa triquetra).-Wormian bones of various shapes
and sizes are found within the sutures uniting the membranous bones of
the cranial vault. They are rarely found in the face. Their form is
irregular, and their borders are adapted to the suture within which they
are situated. Generally they are small, but occasionally they exceed an
inch in diameter. They are most frequently found in the occipito-
parietal suture, where they are occasionally met with in considerable
numbers. Their function between membranous bones is similar to
that of cartilage between cartilaginous bones. They have their own
Gda
BONES.
119
centres of ossification, and act independently until synostosis takes
place.
Skull at Birth, showing the Anterior and
Posterior Fontanelles.
FONTANELLES.-The fontanelles of the head are six in number-two
situated in the median line, anterior and posterior, and four laterally.
They are membranous interspaces formed by the incomplete ossification
at the four angles of the parietal bones (Figs. 61 and 62).
The Anterior Median Fontanelle is situated at the anterior superior
angle of the parietal bones, and is formed by the incomplete ossific con-
FIG. 61.

ADID
FIG. 62.
The Lateral Fontanelles.
Mi
dition of these angles as well as the superior angles of the two halves of
the frontal bone. It is quadrilateral in form, its angles extending into
the four sutures belonging to the frontal and parietal bones. It is the
largest of the six fontanelles, and usually remains partially open until
the tenth or fifteenth month after birth, holding in this respect a close
relation with the rapidity of the development of the entire osseous system.
In quickly-closing fontanelles the teeth appear soon and the child walks
early. Sometimes this fontanelle remains open through years of early
life, and it has been known to exist in the adult.
The Posterior Median Fontanelle is situated at the posterior superior
angles of the parietal bones and the superior angle of the occipital bone.
It is triangular in outline, the angles extending into the sutures formed
by the parietal and occipital bones. This fontanelle is closed at birth
or shortly thereafter, the bones being united by membrane which per-
mits them to move freely upon each other.
The Lateral Fontanelles, four in number, are situated at the inferior
angles of the parietal bones and the bones in immediate juxtaposition
therewith. They are small in size and irregular in form, those situated
posteriorly being the larger. They are closed at birth or soon thereafter.
The fontanelles are gradually closed by the extension of the bones into
the membranes which fill the spaces. It is in this way that the angles
of the bones are completed and the sutures formed.
The posterior lateral and occasionally the anterior fontanelles are filled
1 Allen's Human Anatomy.
120
ANATOMY.
A
in by Wormian bones; usually all traces of the fontanelles disappear
about the fourth year.
THE WALLS OF THE BRAIN-CASE,'
The bones forming the walls of the brain-case are composed of two
plates of compact tissue, an outer and an inner, with intervening can-
cellated tissue, called diploë, between them.
The Outer or Fibrous Plate or Table is thick and tough, and rough-
ened in different places for the origin and insertion of muscles. It is
also covered by minute orifices for the attachment of the pericranium
(periosteum) and entrance of the nutrient vessels.
The Inner Plate or Vitreous Table is thinner, smoother, closer-grained,
and more brittle than the outer, and has a glossy appearance. The
minute orifices are not so numerous as they are externally, and they
give attachment to the dura mater, which acts as the internal peri-
M
S
osteum.
The Diploë (see Fig. 115, veins) is the cancellated tissue situated
between the external and the internal plates. It gives the bone light-
ness, and at the same time acts as a cushion to diffuse, and thus mod-
erate, shocks. It is extremely vascular, and gives passage to numerous
blood-vessels, which communicate with both the pericranium and the
dura mater in such manner that death of the pericranium is not always
followed by death of the bone. It is unevenly distributed throughout
the different parts of the skull, being thick in some places, as in the
region of the greater portion of the occipital bone and the mastoid por-
tion of the temporal bone, while it is entirely absent in others, as in
portions of the orbital plates of the frontal bone and the glenoid fossæ
of the temporal bones.
The Internal Surface of the Brain-case is smooth, glossy, and marked
by digitate depressions corresponding to the convolutions of the brain.
The interior of the skull is separated into two principal divisions-first,
the roof or dome; and second, the floor or base.
The Dome or Vertex of the brain-case is oval-shaped and vaulted,
generally wider behind than in front, and made up of the frontal, two
parietal, and a portion of the occipital bones. The sutures between
these internally belong to the variety known as harmonia. It is
marked by the superior longitudinal groove, which extends from its
anterior to its posterior portion. This groove is deeper in front and
behind than in its central portion. The surfaces of the bones are fur-
rowed for the accommodation of the meningeal vessels, and marked by
depressions of different depths for the lodgment of the Pacchionian
bodies.
Body
The Floor or Base of the internal portion of the brain-case is divided
into three pairs of fossæ, the anterior, middle, and posterior (Fig. 63).
The Anterior Fossa are formed by the cribriform plate of the ethmoid,
the orbital plates of the frontal, the lesser wings, and a portion of the
¹ For detailed particulars of the processes, surfaces, and foramina of the bones form-
ing the brain-case see description of individual bones. Foramina formed by the union
of two or more bones will be described under this heading.
FIG. 63.

Groove for Super. longitud. Sinus
Grooves for Anter. Moningeal A——
Foramen Cœcum:
Crista Galli-
Slit for Nasal nerve.
Groove for Nousal nerve.
Anterior Ethmaidol Foi.
Orifices for Olfactory nerves
Posterior Ethmoidul For-
Ethmoidal Spins--
Olfactory Grooves-
Optio Foramen.
Optic Groove
Olivary proo
Anterior Clinoid proc-
Middle Clinoid proc
proo..
Posterior Clinoid
Groove for
6th
For lacerum medium
Orifice of Carotid Canal
Norva
Depression for Casserian Ganglion
Meatus Auditor. Internus
Slit for Dura-Mater.
Sup. Petrosal groove
For. lacerum posterius
Auterior Condyloid Fon
Aqueduct. Vestibuli
Posterior Condyloid Fon.
Mastoid For.
Post Meningcal Grooves,
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122
ANATOMY.
body of the sphenoid bone. They are convex and digitated over the
orbits, concave over the ethmoid bone, the crista galli projecting upward
from the centre of its cribriform plate. Just anterior to the crista galli
is situated the foramen cæcum, the openings, including the cerebro-nasal
slit, for the olfactory and nasal nerves and vessels being found on either
side of the projection. At the union of the lesser wings with the body
of the sphenoid bone the optic foramina are found. These foramina
transmit the optic nerves and ophthalmic arteries. The lesser wings and
a portion of the body of the sphenoid bone form the posterior boundary
of these fossæ, the wings extending outwardly into the fissure of
Sylvius of the brain. The anterior fosse support the frontal lobes.
of the brain.
The Middle Fosse of the brain-case are formed by the great wings
and part of the body of the sphenoid bone, the squamous portion of
the temporal bone, and the anterior inferior portion of the parietal
bones. They are cup-shaped in form, and situated on a lower plane
than the anterior fossæ. They are bounded in front by the lesser and
a portion of the greater wings of the sphenoid bone, behind by the
anterior surface of the petrous portion of the temporal bone, externally
by the squamous portion of the temporal bone and the anterior inferior
angle of the parietal bones, and internally by the body of the sphenoid
bone.
The Pituitary Fossa separates these fosse in the median line.
The middle fossæ are digitated and their floors are pierced by numer-
ous openings. The anterior lacerated foramina, which are formed by the
approximation of the frontal bone and the body and two wings of the
sphenoid bone, open into these fossa anteriorly. Each of these foramina
transmits from within outwardly the third, fourth, and sixth, and the
ophthalmic division of the fifth cranial nerves. The ophthalmic vein and
a branch of the lachrymal artery pass through this foramen from with-
out inwardly. Just posterior to the anterior lacerated foramen, close to
the body of the bone, is the foramen rotundum. This transmits the
superior maxillary, the second division of the fifth nerve. Behind the
foramen rotundum, in the deepest portion of the fossa, is situated a
large oval foramen, the foramen ovale. It gives passage from within
outwardly to the inferior maxillary or the third division of the fifth
cranial nerves, and from without inwardly to the lesser meningeal
artery.
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External to the foramen ovale, and a little posterior to it, in the
spine of the great wing of the sphenoid bone, is situated the foramen
spinosum. This foramen gives passage from without inwardly to the
middle meningeal artery.
Between the round and the oval foramina is sometimes located a
small foramen, the foramen Vesali, for the transmission of a small vein
to the cavernous sinus.
Between the apex of the petrous portion of the temporal bone and
the body and posterior border of the great wing of the sphenoid bone
will be found the middle lacerated foramen (foramen lacerum medius).
In the recent state this foramen is filled up from below with fibrous
tissue. The carotid canal terminates at the apex of the petrous portion
BONES.
123
of the temporal bone at the external boundary of this foramen, while
the Vidian canal commences below at its anterior margin.
The hiatus Fallopii is a small canal, the opening of which is situated
on the anterior surface of the petrous portion of the temporal bone
just external to the termination of the carotid canal. This canal trans-
mits the Vidian nerve, which is a branch of the seventh or facial nerve,
and goes to the spheno-palatine ganglion. On the apex of the petrous
portion of the temporal bone is an irregular depression for the lodg-
ment of the ganglion of Gasser (semilunar ganglion). This is the
large ganglion of the fifth nerve.
Three divisions are thrown off from this ganglion within the middle
fossa, and pass outwardly through its walls or floor.
The middle cerebral lobes of the brain rest upon the floor of the
middle fosse of the skull.
The Posterior Fosse of the brain-case are in great part formed by
the occipital bone. This bone, in conjunction with a portion of the
body of the sphenoid bone, forms the floors; their anterior boundary
is formed by the posterior surface of the petrous portion of the tem-
poral bone, while the mastoid portion of the temporal bone and a small
portion of the parietal bones complete the sides.
These fosse are deeper and larger than the others. Their central
portions anteriorly are marked by the posterior clinoid processes.
The elongated concave surface of bone between the posterior clinoid
processes and the foramen magnum is composed of the dorsum selle of
the sphenoid bone anteriorly and the basilar process of the occipital
bone posteriorly. This surface lodges the medulla oblongata and the
basilar artery.
The posterior surface of the petrous portion of the temporal bone is
marked by a large opening, the internal auditory meatus. The seventh
and eighth nerves pass into this opening, the seventh going to the face,
while the eighth passes to the internal ear.
The posterior lacerated foramen (foramen lacerum posterius) is below
the internal auditory meatus, between the petrous portion of the_tem-
poral bone and the basilar process of the occipital bone. It is a large,
irregular, twisted, wedge- or pear-shaped aperture, the base rounded and
directed to the posterior and distal portion of the base of the skull, the
axis of its external opening being toward the mastoid process of the
temporal bone. This base is rounded, being formed by the jugular
fossa of the occipital and temporal bones. It is here, within this fora-
men, that the internal jugular vein is formed by the termination of the
lateral sinuses. The apex of the posterior lacerated foramen is gener-
ally separated into two divisions by the intrajugular processes of bone.
The posterior division transmits from the brain-case the ninth (glosso-
pharyngeal), the tenth (pneumogastric), and the eleventh (spinal acces-
sory) nerves, while the anterior division gives passage to the inferior
petrosal sinus.
1
The deep groove for the accommodation of the lateral sinus termi-
1 The sinuses of the brain-case are membranous for the passage of venous blood.
They resemble veins, differing from them in that they lack the fibrous and muscular
coats of these vessels.
124
ANATOMY.
nates at the posterior boundary of this foramen. From this point it
extends outwardly over the junction of the petrous with the mastoid
portion of the temporal bone, curves backward over the posterior infe-
rior angle of the parietal bone, and thence inward over the occipital
bone to the torcular Herophili, which is situated at the internal occipital
protuberance, and formed by the confluence of all the sinuses of the brain
excepting those transmitted through the petrosal sinuses. The posterior
condyloid and mastoid foramina open into this groove. In the region
of these sinuses the bones are generally extremely thick.
The central portion of the floor of the posterior fosse of the cranium
is pierced by the foramen magnum. This foramen transmits the spinal
cord and its membranes, the vertebral arteries, and the roots of the
spinal accessory nerves. The anterior condyloid foramen opens into
the anterior border of the foramen magnum. It transmits the twelfth
cranial nerve (hypoglossal).
The Cerebellar Fossce form that portion of the posterior fosse situated
between the lateral sinuses and the foramen magnum; they lodge the
lobes of the cerebellum.
THE EXTERNAL SURFACE OF THE BRAIN-CASE.
The external surface of the brain-case (Fig. 64) is divided into
five regions-a superior, inferior, anterior or facial, and two lateral
regions.
The Superior Region extends longitudinally from the supraorbital
arches anteriorly to the superior curved line on the occipital bone pos-
teriorly, and from the right to the left temporal ridges. It is in shape
an elongated dome, its length extending antero-posteriorly. It is flat-
tened in front to form the forehead, and projects behind. It is marked
by four eminences, two frontal and two parietal.
The greatest width of the superior region is generally from one pari-
etal eminence to that of another. No muscles arise or are attached in
this region, but it is well marked by fine pits for the attachment of the
pericranium, over which play the fibres and aponeuroses of the occipito-
frontalis muscle.
G-
BASE OF THE BRAIN-CASE.-When the facial bones are removed
from the anterior portion of the skull, the under surface of the brain-
case corresponds in great measure with the floor of its internal surface,
like which it is separated into three divisions-anterior or facial, middle
or cervical, and posterior or occipital; and these divisions are situated
directly under corresponding ones internally. This surface, however,
is rougher and the projections of bones are much more prominent than
on the internal surface.
The Anterior Portion is bounded anteriorly by the supraorbital arches,
with their notches or foramina, and the rough articulating surface for
the nasal bones and the nasal processes of the superior maxillary bones;
laterally by the external angular processes of the frontal bone and the
anterior border of the great wing of the sphenoid; and posteriorly by
the inferior border of the great wing of the sphenoid bone, and a line
drawn from the base of the anterior surface of the pterygoid process on
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LAXATOR TYMPANI.
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Auricular fissure.
125
126
ANATOMY.
one side, across the body of the sphenoid bone, to the same process on
the other side.
This region is symmetrically divided by the descending plate of the
ethmoid and the rostrum of the sphenoid bone.
The structures forming the anterior division on each side of this cen-
tral division, from within outwardly, are, first, the cribriform plate of
the ethmoid bone, which forms the roof to the nasal chamber; second,
the lateral masses of the ethmoid, which, through its os planum, forms
a portion of the inner wall of the orbital cavity; third, the orbital
plate of the frontal bone and a portion of the lesser wing of the sphe-
noid; and fourth, the great wing of the sphenoid, together with the
rough articulating surface of the external angular process of the frontal
bone.
Immediately in front of the ethmoid bone, and between the internal
angular processes of the frontal bone, will be found the articulating sur-
faces for the lachrymal, maxillary, and nasal bones.
The foramina of this region have already been described. They are
as follows: The perforations of the cribriform plate of the ethmoid
bone, the anterior and posterior ethmoidal foramina, the supraorbital,
anterior lacerated, and optic foramina within the orbital cavity, and the
foramen rotundum and Vidian canal.
The Median or Cervical Region is bounded anteriorly by the inferior
border of the great wing of the sphenoid bone, and by a line drawn from
the base of the anterior surface of the pterygoid process on one side,
across the body of the sphenoid bone, to the same point on the other.
The lateral boundary is formed by a line drawn along the pterygoid
ridge of the sphenoid bone, extending to the extreme outer point of the
glenoid fossa, and thence to the apex of the mastoid portion of the tem-
poral bone. The posterior boundary is formed by a line drawn from
the apex of the mastoid portion of the temporal bone on one side to the
same point on the other, crossing the centre of the condyloid processes
of the occipital bone and the foramen magnum.
A line drawn from the anterior portion of the rostrum of the sphenoid
bone to the centre of the anterior portion of the foramen magnum will
divide the middle region into two symmetrical halves.
The structures forming this division on each side of the central
line from its anterior to its posterior portion are as follows :
First: the Pterygoid Process, which extends downwardly.
Second: the Pterygoid Fossa, which is situated posteriorly between the
plates composing the pterygoid process. The outer plate of this process
gives origin within the fossa to the internal pterygoid muscle.
Third: the Scaphoid Fossa, at the base of the roots of the pterygoid
fossa posteriorly. This fossa gives origin to the tensor palati muscle.
Fourth the Vaginal Process, situated at the base of the internal
pterygoid plate, at its junction with the body of the bone.
:
Fifth the Inferior Surface of the Great Wing of the Sphenoid Bone.
-This surface is smooth, concave, and quadrilateral; it is situated just
external to the pterygoid process. It gives origin to the external head
of the external pterygoid muscle.
Sixth the Foramen Ovale, situated in the posterior portion of the
BONES.
127
inferior surface of the great wing of the sphenoid, back of, and a little
external to, the pterygoid process. This foramen transmits the inferior
maxillary nerve and the lesser meningeal artery.
Seventh the Foramen Spinosum, situated behind and externally to
the foramen ovale in the inferior surface of the great wing of the sphe-
noid bone. It transmits the middle meningeal artery.
:
Eighth the Spinous Process of the Sphenoid Bone, which is the pos-
terior external angle of the inferior surface. This process gives origin
to the laxator tympani muscle.
:
Ninth the Glenoid Fossa, situated external to the spinous process of
the sphenoid bone. This fossa is a large oval depression which receives
the condyle of the inferior maxillary bone in the articulated skull,
also the superior portion of the parotid gland.
and
:
Tenth the External Auditory Meatus, situated behind the posterior
external boundary of the glenoid fossa.
:
Eleventh the Glenoid Fissure, which passes inward and forward
through the centre of the glenoid fossa.
:
Twelfth the Eustachian Sulcus, which is between the inner extremity
of the glenoid fissure and the body of the sphenoid bone. The sides of
this sulcus are formed by part of the petrous portion of the temporal
and the great wing of the sphenoid bone, its internal portion being
frequently incomplete.
Thirteenth the Middle Lacerated Foramen, which is situated between
the apex of the petrous portion of the temporal and the body of the
sphenoid bone. In the recent state it is filled up by fibro-cartilage.
Its size varies in different skulls, and occasionally it is found filled with
bone.
:
Fourteenth the Petro-basilar Groove, between the petrous portion
of the temporal and the basilar process of the occipital bones. This
groove in the recent state is filled with fibrous tissue.
:
Fifteenth the Posterior Lacerated Foramen, which extends back-
ward and outward from the petro-basilar groove. This foramen is
formed by the union of the jugular fosse of the temporal and occip-
ital bones. It transmits the jugular vein and the ninth, tenth, and
eleventh nerves, a septum of bone often separating the vein from
the nerves.
:
Sixteenth the Opening for the Carotid Canal is situated on the under
surface of the petrous portion of the temporal bone, just anterior to the
posterior lacerated foramen.
:
Seventeenth the Digastric Groove, situated on the internal surface
of the mastoid portion of the temporal bone. It is long, deep, and
narrow, for the origin of the digastric muscle.
:
Eighteenth the Stylo-mastoid Foramen, situated at the anterior
extremity of the digastric groove at the base of the styloid process of
the temporal bone. This foramen gives exit to the seventh or facial
nerve.
:
Nineteenth the Styloid Process of the Temporal Bone extends down-
ward from a point just anterior to the stylo-mastoid foramen. The base
of this process is surrounded by what is termed the vaginal process.
Twentieth the Pharyngeal Spine is a small tubercle situated about
128
ANATOMY.
5
"
the centre of the basilar process of the occipital bone. This spine gives
attachment to what is known as the raphé of the pharynx.
cess.
Twenty-first: the Anterior Condyloid Foramen is just in front of the
condyles of the occipital bone, on the lateral surface of the basilar pro-
This foramen is the external orifice of the hypoglossal canal.
Twenty-second: the Condyloid Processes of the Occipital Bone are
situated on each side of the foramen magnum anteriorly. They are
double-convex articulating facets, upon which the head rocks within the
corresponding concavities of the atlas or first cervical vertebra.
POSTERIOR REGION.
1
The Posterior Division of the base of the brain-case is semicircular
in outline. Its anterior boundary extends from the apex of the mastoid
portion of the temporal bone on one side, across the articulating condyles
of the occipital bone, to the same point on the other side. Its posterior
or semicircular boundary extends from the apex of the mastoid portion
of the temporal bone on one side, upward and backward, joining the
superior curved line of the occipital bone, and passing along this ridge
to the occipital protuberance, from which point it runs forward and
downward on the ridge of the other side to the apex of the mastoid
portion of the temporal bone. The surface of bone included within this
semicircular outline, excluding the condyles, the posterior condyloid
foramina, and the foramen magnum, affords attachment to muscles.
The line forming the anterior boundary of the posterior region not
only separates it from the middle region, but is the axis between the
anterior muscles, which act as the motor power in bowing the head,
from those which antagonize these and raise and draw the head back-
ward this, therefore, is the axis upon which the head oscillates; its
centre is the point around which the head rotates.
On either side, immediately behind the condyles, are depressions
pierced by foramina leading to the lateral sinuses. These are known
respectively as the posterior condyloid fosse and foramina.
LATERAL REGIONS OF THE SKULL.
The points of interest on the lateral region (see Fig. 60) from the
posterior to the anterior boundary are the mastoid process, the external
auditory meatus, the auditory process, the glenoid fossa, all of which
are parts of the temporal bone; the zygomatic arch, formed by union
of the zygomatic processes of the temporal and the malar bones; the
condyloid and coronoid processes of the inferior maxilla.
Two deep fosse mark the lateral region of the skull-one above the
zygomatic arch, known as the temporal fossa, and the other below the
arch, known as the zygomatic fossa.
The Temporal Fossa occupies the greater portion of the lateral region
¹ In comparative anatomy this is the posterior half of the roof of the brain-case in
animals, it being above the spinal cord or neural cavity, and the only portion of the
roof formed from cartilage.
BONES.
129
of the skull. It is made up of parts of five bones-the temporal, the
sphenoid, and the malar below, the parietal and the frontal above-and
is crossed by seven sutures uniting these bones. It is also traversed by
grooves for the accommodation of the deep temporal arteries, and
marked by fan-like grooves for the origin of the deep fibres of the
temporal muscle.
The temporal fossa is bounded in front by the posterior surface of the
frontal process of the malar, the external angular process of the frontal,
and part of the great wing of the sphenoid bones. It is bounded above
and behind by the supratemporal ridge. This is formed by two slightly-
elevated borders that originate near the fronto-malar articulation from a
single point, from which it diverges into two nearly semicircular lines
that curve upward, backward, and downward across the fronto-parietal
suture at a distance of about a half inch or more from each other.
The Inferior Line extends backward and curves downward to join the
posterior root of the zygomatic process of the temporal bone. This
line is the uppermost limit of the deep attachment of the temporal
muscle.
The Superior Line, which is separated from the inferior, gradually
increasing the distance as it proceeds backward and downward, termi-
nates near the parieto-occipito-mastoid articulation. This upper line
and space between it and the lower afford attachment to the temporal
fascia. The inferior boundary of the temporal fossa internally is formed
by the infratemporal ridge. This ridge extends from the parieto-occip-
ito-mastoid articulation forward along the posterior root of the zygo-
matic process of the temporal bone, across the pterygoid ridge, which
separates the lateral from the inferior surface of the great wing of the
sphenoid bone, to the roughened prominence on the posterior border of
the malar bone. The external boundary of the temporal fossa is formed
by the zygomatic arch, and in the recent state by the temporal fascia.
This fossa accommodates the tendon and muscular fibres of the temporal
muscle.
T
The Zygomatic Fossa is below the zygomatic arch. It is an irregularly-
shaped cavity, bounded anteriorly by the posterior or zygomatic sur-
face of the superior maxilla; internally, by the external pterygoid
plate; superiorly, by the inferior surface of the great wing of the
sphenoid bone and a part of the squamous portion of the temporal
bone, the infratemporal ridge dividing the zygomatic from the tem-
poral fossa in this region; and laterally by the ramus of the inferior
maxilla.
The following openings will be found within the fossa: The orifices
of the Posterior Dental Canals, situated in the superior maxillary bone
for the transmission of the posterior dental vessels and nerves; the
Spheno-maxillary Fissure, between the sphenoid and the superior max-
illary bones, leading into the orbit; the Pterygo-maxillary Fissure,
between the pterygoid process of the sphenoid bone and the superior
maxilla, leading into the spheno-maxillary space or fossa; the Foramen
Ovale and Foramen Spinosum, situated in the great wing of the sphe-
noid bone in close proximity to each other. The foramen ovale trans-
mits the third division of the fifth nerve and a small meningeal artery,
VOL. I.-9
-
130
ANATOMY.
while the spinous foramen transmits the middle meningeal artery. The
Inferior Dental Foramen is situated in the inferior maxillary bone, and
transmits the inferior dental vessels and nerve, while between the zygo-
matic arch and the infratemporal ridge is the temporo-zygomatic strait,
joining it with the temporal fossa.
The zygomatic fossa accommodates the tendon and lower portion of
the temporal muscle, the external and internal pterygoid muscles, the
inferior maxillary nerve and its branches, and, finally, the internal max-
illary artery, passing through and giving off branches as it extends
inward and forward into the pterygo-maxillary fissure.
The Spheno-maxillary Fossa is a triangular space bounded behind by
the upper portion of the anterior surface of the pterygoid process; in
front by the internal portion of the zygomatic surface of the superior
maxilla and a portion of the palate bone; above by the under surface
of the body of the sphenoid bone and the orbital process of the palate
bone; and internally by the perpendicular plate of the palate bone,
which separates this fossa from the nasal chambers.
This fossa lodges the spheno-palatine (Meckel's) ganglion and the
terminal end of the inferior maxillary artery. Opening into it are the
pterygo-maxillary and spheno-maxillary fissures and five foramina-the
anterior lacerated, the rotund, the Vidian, the pterygo-palatine, and the
spheno-palatine.
The Pterygo-maxillary Fissure extends vertically between the superior
maxilla and the pterygoid process of the sphenoid bone. It is wider
above than below, and communicates with the zygomatic fossa, trans-
mitting the internal maxillary artery and vein.
The Spheno-maxillary Fissure extends nearly horizontally outward
and forward from the body of the sphenoid bone at an angle of about
forty-five degrees. Its posterior boundary is formed by the inferior
border of the orbital surface of the great wing of the sphenoid bone;
its anterior boundary is formed by the angle between the orbital and
zygomatic surfaces of the superior maxilla and a portion of the orbital
process of the palate bone. Externally it is bounded by a smooth notch
in the orbital process of the malar bone, and internally by the body of
the sphenoid bone.
This fissure extends between the orbit and the spheno-maxillary and
pterygo-maxillary fossa, and transmits the superior maxillary division
of the fifth nerve, the infraorbital artery and vein, and the ascending
branches of the spheno-palatine (Meckel's) ganglion.
The Pterygo-palatine Foramen is situated between the pterygoid
process of the sphenoid bone and the posterior border of the horizontal
plate of the palate bone. This foramen opens into a canal, the posterior
palatine, which passes directly downward, opening into the roof of the
mouth at the posterior lateral angle of the hard palate.
Occasionally there will be found in this locality two or more acces-
sory palatine canals, which give passage to branches of nerves from the
spheno-palatine ganglion to the hard and soft palate. These canals also
transmit vessels to the roof of the mouth.
The Spheno-palatine Foramen is situated between the superior bor-
der of the perpendicular plate of the palate bone and the under surface
BONES.
131
of the body of the sphenoid bone. This foramen opens into the pos-
terior portion of the superior meatus of the nose, and transmits the
naso-palatine nerve and vessels.
TENDO OCULI
FACIAL OR ANTERIOR REGION OF THE SKULL.
The facial region of the brain-case is bounded above by a curved
line extending from the extremity of the angular process of the
frontal bone on one side, upward across the frontal eminences, to the
Anterior
Nares
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Incisive fossa
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MASSETER.
S
ZYG.MAJ.
Temporal
bone
R
Groove for Facial as
angular process of the frontal bone on the other side; laterally by a
line drawn from the commencement of the superior boundary, down-
ward and slightly backward, across the malar bone to the angle of the
lower jaw, and below by the lower border of the inferior maxilla. It
132
ANATOMY.
is nearly oval in shape, being slightly broader above than below (see
Fig. 65).
The surface of the facial region is extremely irregular, presenting as
it does the orifices to several large cavities which protect three of the
organs of special sense-viz. that of sight, of smell, and of taste. This
region is divided into three portions-one central and two lateral.
The Central Portion commences a little above the nasal eminence,
situated between the internal angular processes of the frontal bone.
This eminence marks the position of the frontal sinuses.
Below the nasal eminence is a semicircular suture uniting the superior
maxilla and nasal bones with the frontal bone.
Directly under this suture is the bridge-roof or arch of the nose. It
is formed by the nasal bones and the nasal processes of the superior
maxillæ. It is convex from side to side, and concave from above down-
ward. The median line of this arch presents the internasal suture,
while its lateral surfaces are marked by the naso-maxillary sutures.
The nasal arch is generally pierced by a foramen on either side for
the passage of a vein.
Below the arch of the nose are situated the anterior openings to the
nasal chambers. Conjointly, they are pyriform in shape, bounded
above by the inferior border of the nasal bones, the lateral and inferior
boundaries being formed by the superior maxillæ. The borders of this
opening are sharp and give attachment to the lateral cartilage of the
nose.
Beneath the anterior opening to the nasal chambers are situated the
two incisive fossa, between which will be found the intermaxillary
suture.
Continuing downward, are next found the four incisor teeth, situated
in the alveolar border of the intermaxillary bone.
Below this, in the median line of the inferior maxilla, will be found
the four inferior incisor teeth and the symphysis menti, a slight vertical
ridge at its commencement, but as it passes outward and downward
diverging to form the mental process or chin, a feature characteristic of
man alone. On each side of the upper portion of the ridge are the
inferior incisive fossa.
The Lateral Portions of the face commence above in the frontal
eminences. These eminences are rarely of the same size on both sides
of the forehead. Below the frontal eminence is a depression situated
just above the superciliary ridge. Beneath this depression is the large
circular opening to the orbital cavity. This cavity is bounded above
by the Supraorbital Arch, which extends superiorly from the internal
to the external angular processes of the frontal bone.
The inner third of this boundary is marked by a notch or foramen,
the Supraorbital Notch or Foramen, for the passage of the frontal nerve
and vessels. The inferior boundary of the orbital cavity is formed
externally by the malar bone, below by the superior maxilla, and
internally by the nasal process of the superior maxilla and the lachrymal
bone.
The Infraorbital Foramen is below the infraorbital border, and affords
exit to the nerve and artery of the same name. It is internal to the
BONES.
133
maxillo-malar articulation, and below the foramen is situated the canine.
fossa.
The Canine Fossa is above the alveolar process of the superior max-
illa.
Anterior Dental or Mental Foramen is usually situated below a line
between the bicuspid teeth and above the external oblique line of the
inferior maxilla. This foramen transmits the mental nerve and vessels.
The Supraorbital Notch or Foramen, the Infraorbital Foramen, and
the Anterior Dental Foramen are situated in a vertical line, one beneath
the other. They give exit to the terminal branches forming the three
divisions of the fifth or trifacial nerve, which transmits sensation from
the face.
THE ORBITAL CAVITIES are two in number. They are situated
between the anterior portion of the brain-case and the superior portion
of the facial bones. They are irregular quadrilateral pyramids in shape,
their bases being directed forward and a little outward, and their apices
backward and a little inward. Their outer walls diverge from the median
line of the face at about an angle of forty-five degrees, while their inner
walls are nearly parallel with each other.
The roof of the orbit is concave, and formed by the horizontal or
orbital plate of the frontal bone and a portion of the lesser wing of the
sphenoid bone. The outer portion of the roof anteriorly is marked by
the lachrymal fossa for the lodgment of the lachrymal gland. There
is also a depression at the inner portion of the roof anteriorly for the
attachment of the pulley of the superior oblique muscle.
The floor of the orbit is formed by the orbital surface of the superior
maxilla and the orbital processes of the malar and palate bones, the lat-
ter being situated at the posterior median angle.
B
At the inner third of this surface anteriorly will be found the open-
ing to the Lachrymal Canal. The depression just external to the lach-
rymal canal is for the origin of the inferior oblique muscle of the eye.
The outer wall of the orbit is formed by the anterior or orbital surface
of the great wing of the sphenoid and part of the malar bone, its inter-
nal wall being formed by the nasal process of the superior maxilla, the
os planum or orbital plate of the ethmoid bone, and the lachrymal bone,
making, in all, seven bones involved in the formation of the orbital
cavity. Three of these bones, however, the frontal, ethmoid, and sphe-
noid, enter into the formation of each orbit, so that it takes but eleven
bones to form the two cavities.
The circumference of the orbit was described with the structures of
the face.
The apex of the orbit corresponds to the optic foramen.
There are ten openings into the orbit-viz. the optic, anterior lacerated,
supraorbital, malar, and the anterior and posterior ethmoidal foramina,
the lachrymal and infraorbital canals, the spheno-maxillary fissure, and
the facial opening.
The Optic Foramen opens into the apex of the orbital cavity,
between the body and lesser wing of the sphenoid bone. It trans-
mits the optic nerve and the ophthalmic artery from the brain into
the orbit.
134
ANATOMY.
The Anterior Lacerated Foramen is situated near the apex of the
orbital cavity, just external to the optic foramen, and extends upward
and outward between the greater and lesser wings of the sphenoid bone.
It transmits from the brain into the orbit the third, fourth, first division.
(ophthalmic) of the fifth and sixth nerves, and through the orbit into
the brain the ophthalmic vein and a small artery, a branch of the
lachrymal.
The Anterior and Posterior Ethmoidal Foramina are situated on the
inner wall of the orbital cavity in the ethmo-frontal suture, between the
ethmoid and frontal bones. The anterior foramen transmits from the
orbit into the brain-case the nasal branch of the ophthalmic nerve and
an artery and vein, branches of the ophthalmic, which accompany this
nerve.
The Posterior Foramen transmits from the orbit the posterior eth-
moidal artery and vein.
The Lachrymal Canal is situated at the anterior inferior angle of the
orbital cavity. Its superior orifice is between the nasal process of the
frontal bone and the lachrymal bone. From this point the canal extends
downward, inward, and backward, terminating in the inferior meatus
of the nose. It accommodates the lachrymal duct.
The Infraorbital Canal commences by a groove situated about the
centre of the posterior border of the floor of the orbital cavity. This
groove passes forward and downward into the body of the superior
maxilla, and makes its exit on the face in the infraorbital foramen
below the middle of the infraorbital ridge. It transmits the infra-
orbital nerve, which is a continuation of the second division of the
fifth or superior maxillary nerve, and infraorbital vessels.
The Spheno-maxillary Fissure is situated in the posterior portion of
the orbital cavity, extending from the body of the sphenoid bone for-
ward and outward to the sphenoidal border of the malar bone. It is
bounded in front by the posterior superior border of the superior max-
illa and orbital process of the palate bone, and behind by the inferior
border of the great wing of the sphenoid bone. It transmits from the
brain to the orbit the infraorbital nerve and vessels and branches of
nerves from the spheno-maxillary ganglion.
The Malar Foramina are situated within the orbital cavity on the
orbital surface of the malar bone. They transmit from the orbital
cavity to the cheek and temporal fossa terminal branches of nerves and
vessels. The facial opening is that opening formed by the anterior
borders of the orbit.
THE NASAL FOSSE.
The Nasal Fossa, two in number, forming the internal nose, are situ-
ated on either side of the median line of the face, and extend from the
under surface of the anterior portion of the brain-case superiorly to the
upper surface of the bones forming the hard palate inferiorly, and from
the facial border of the external aperture of the nose anteriorly to the
free border of the internal pterygoid plate posteriorly. They are sepa-
rated by a thin partition of bone, the nasal septum, open on the face by
T
BONES.
135
the anterior apertures, and posteriorly into the pharyngeal space by the
posterior nares. There are also several smaller openings leading from
the nasal fossæ in other directions.
For convenience of description the nasal fossæ are divided into a roof,
a floor, outer walls, and inner walls formed by the septum.
The Inner Walls or Nasal Septum.—These are composed of six bony
structures, named in the order of their importance viz. the perpendicular
plate of the ethmoid, the vomer, the crest of the superior maxillary and
palate bones, the rostrum of the sphenoid bone, and the nasal spine of
the frontal bone. These bones do not complete the septum, but have
a triangular notch in the anterior portion. In the recent state this is
filled by the nasal cartilage.
•
The nasal septum is rarely perpendicular, but is deflected either to
the one side or the other. In skulls with the flat or normal palate the
nasal septum is most apt to be perpendicular, but in those having the
inverted V-shaped (^) palate either the septum must be greatly deflected,
or pressure upward upon the vomer will push the perpendicular plate
of the ethmoid bone forward, thus causing that external protrusion
characteristic of the Roman nose.
The cause of this abnormal formation of one of these structures pari
passu with that of the other has been ascribed by Prof. Harrison Allen
to an inflammatory condition of the walls of the oro-naso-pharyngeal
space, frequent in some children, this producing tension of the muscles,
thus pressing the lateral portions inward, contracting this space, thereby
deforming the roof of the mouth,' and changing the natural dome shape
to the gable or Ʌ shape.
The septum of the nose is also occasionally incomplete, and this
imperfection is generally situated at the junction of the perpendicular
plate of the ethmoid bone with the vomer. It is also occasionally
marked by a groove or canal on each side for the passage of the naso-
palatine nerve.
The Roof of the nasal fossa is long, narrow, and irregular in outline.
It is divided into three portions-anterior, middle, and posterior.
The Anterior Portion is formed by the under surface of the nasal
bones and the nasal spine of the frontal bone. It is concave from side
to side, and extends inward and upward at an angle of about forty-
five degrees.
The Middle Portion is narrow, nearly horizontal in direction, and is
composed of the cribriform plate of the ethmoid bone.
The Posterior Portion is the longest of the three, and extends from
the posterior extremity of the cribriform plate, obliquely downward and
backward, to the free margin of the internal pterygoid plate. It is
composed of the body of the sphenoid bone and the ale of the vomer.
The Floor of the nasal fossa extends from the face anteriorly to the
pharyngeal space posteriorly. It is smooth, inclining slightly down-
ward and backward, being concave from side to side. It is composed
1 It is of great importance to recognize, and early in life guard against, the evil
results of the inflammation of the throat in children of a strumous diathesis, since it
is liable to produce deformity of these parts and irregularity of arrangement of the
teeth.
136
ANATOMY.
of that portion of the bony structure of this region which forms the
premaxilla and the palatal processes of the superior maxillæ and hori-
zontal plates of the palate bones.
The External or Lateral Wall is the most extended, uneven, and com-
plicated portion of the nasal fossa. Seven bones enter into the forma-
tion on each side-viz. the nasal, superior maxilla, lachrymal, ethmoid,
inferior turbinated, and palate bones, and the pterygoid process of the
sphenoid bone. To form the outer walls of both sides twelve bones are
required-two of the brain-case, the ethmoid and the sphenoid, and all
the bones of the face excepting four, the malar, the vomer, and the
inferior maxilla. These walls are divided by the projections of the tur-
binated processes of the ethmoid bone and the inferior turbinated bone
into three horizontal compartments, the superior, middle, and inferior.
The Superior Meatus is the shortest and shallowest of the three. It
is situated between the superior and inferior turbinated masses of the
ethmoid bone, and in the articulated skull between the superior and
inferior turbinated bones.
The Middle Meatus is situated between the middle and inferior tur-
binated bones, and forms two-thirds of the posterior portion of the outer
wall of the nasal fossa.
The Inferior Meatus is situated between the inferior turbinated bone
and the floor of the nose. It is the longest of the three meati.
The openings into the nasal fossa are numerous, and may be classified
as follows:
The Anterior Aperture is that pyriform opening leading from the
face into the fossa, and has been previously described.
The Posterior Aperture opens into the pharyngeal space.
It is
bounded above by the vaginal process of the sphenoid bone and the
alæ of the vomer; below by the palatal process of the palate bone;
internally by the vomer; and externally by the free border of the inter-
nal plate of the pterygoid process of the sphenoid bone.
The Lachrymal Canal opens into the superior portion of the inferior
mcatus, behind the nasal process of the superior maxilla and external
to the inferior turbinated bone. This canal is occupied by the nasal or
lachrymal duct, which conveys the lachrymal fluid from the eye into
the nose.
The Spheno-palatine Foramen is situated in a line just back of the
superior meatus. It is bounded below by the palate bone, above by
the sphenoid bone, and opens into the spheno-palatine space. It trans-
mits into the nasal fossa the naso-palatine nerves and vessels.
The Incisor Foramen, or Foramen of Stenson, is situated in the
anterior portion of the nasal fossa, near the septum and back of the
premaxilla. It opens into the anterior palatine canal on the oral aspect
of the hard palate, and transmits the anterior palatine vessels.
The Foramen of Scarpa is situated within the intermaxillary suture,
and opens into the anterior palatine canal on the oral aspect of the hard
palate. It transmits the naso-palatine nerve.
The Olfactory Apertures are those numerous small openings found in
the cribriform plate of the ethmoid bone. They communicate with the
brain-case, and transmit the filaments of the olfactory nerves.
BONES.
137
The slit-like openings in the anterior portion of the cribriform plate
communicate with the brain-case, and transmit the nasal nerve and the
vessels which accompany it.
The Openings into Air-cells.—In the dried skull there are generally
two openings into the maxillary sinus, but in the recent state there is
not often more than one. It is situated about the centre of the middle
meatus, and permits the passage of fluid from the antrum into the nasal
chambers.
The Infundibulum extends from the superior portion of the middle
meatus anteriorly to the outer side of the middle turbinated bone, unit-
ing this meatus with the frontal sinuses and the anterior ethmoidal
cells; it allows the fluid from these openings to descend into the nasal
chambers.
The other openings into the remaining air-cells have already been
fully described under the headings of the bones.
THE CAVITY OF THE MOUTH.
The Cavity of the Mouth is situated between the two superior maxil-
lary bones above and the inferior maxillary bone and their attached
muscles. When the jaws are closed this cavity is paraboloid in shape,
opening behind and below. In the recent state the inferior opening is
closed by the tongue and mylo-hyoid muscle.
The Roof of the Mouth (Fig. 66), which is formed by the hard palate,
is generally arched in front and flattened behind. It is composed of
the palatal processes of the
two superior maxillary and
palate bones.
FIG. 66.

The Posterior Border is
free, thin, and divided into
two portions by the posterior
nasal spine. On each side
of this spine the border is
concave, and terminates later-
ally in the pyramidal process
of the palate bone and the
hamular process of the sphe-
noid bone.
M
Roof of the Mouth.
Situated within the palato-
maxillary suture, just inter-
nal to the tuberosity of the
superior maxilla, are the pos-
terior and accessory palatine
canals for the transmission of the posterior palatine nerves and vessels.
The surface of the roof of the mouth is perforated by numerous
small foramina for the transmission of nutrient vessels to the body of
the bone, pitted for the lodgment of the mucous glands, and grooved
longitudinally for the accommodation of vessels.
The Floor of the Mouth.-The circumference of the floor of the
mouth is formed by the mylo-hyoid ridge. This ridge gives attach-
138
ANATOMY.
ment throughout its entire extent to the mylo-hyoid muscle, which,
together with the base of the tongue, forms the true floor.
The anterior and two lateral walls of the mouth are formed by the
alveolar processes and the teeth of both jaws.
Posteriorly the oral cavity opens into the pharyngeal space.
!
CARTILAGE.
CARTILAGE is one of the three groups of connective tissues of the
body. It is made up of cells imbedded in a matrix, which yields, on
boiling, chondrin, the basement-substance. That this differs from other
connective tissue has of late been questioned, and the view that it is a
distinct chemical substance now appears to be undergoing a change.
By some it is believed to be a mixture of gelatin, mucin, and salts.
(See Prudden's Normal Histology, p. 53.) Cartilage forms the entire
skeleton of many of the cold-blooded (or lower order of) animals, and
of others it constitutes a varying proportion. In the highest verte-
brates only a small portion of cartilage exists at puberty, though it is
found after this period in the covering of the articulating surfaces of
bones and connecting the ribs with the sternum; in the rings of the
trachea, walls of the bronchi, larynx, and other parts of the air-
passages; in the grooves through which muscular tendons glide; and
in interarticular discs situated between the articulating surfaces of bones,
where a decidedly firm though more yielding structure than bone is
required. The early embryonic life of the entire skeleton, with but
minor exceptions, is composed of cartilage, in which is gradually depos-
ited calciferous matter; it is then apparently absorbed and replaced by
bone-cells or osteoblasts, which first appear at the different points of
ossification and develop the entire bony structure. Temporary cartilage
is that which gradually develops into bone. Permanent cartilage is that
which remains cartilage throughout life, as the interarticular discs that
cover the articular extremities of bones, etc.
The principal function of cartilage in the higher vertebrates is its
physical property of elasticity. It yields to pressure or to muscular
force, but immediately resumes its normal position or shape when such
pressure or force is removed.
When placed between articulating extremities, as the proximate sur-
faces of the vertebræ, the temporo-maxillary articulation, etc. etc., it
acts as a cushion, diminishing the force of concussion. In positions
where shock would be particularly harmful there is interposed within
the joint, in addition to the cartilage covering the articular surfaces of
bones, a cartilaginous disc or extra cushion. Were it not for the car-
tilage placed within the joints situated between the feet and the head,
the shock communicated to the brain in the simple act of walking
would probably be so great as to absolutely prevent its practice in man.
The cartilages connecting the ribs with the sternum permit the
CARTILAGE.
139
expansion and contraction of the chest necessary to breathing, and
those within the walls of the air-passages prevent closure of the tubes
when they are flexed.
Histologists divide cartilage into two parts-the cartilage-cell and
the hyaline or intercellular substance or matrix.
Cartilage is also divided into three kinds, according to the character
of the matrix-hyaline cartilage, fibro-cartilage, and fibro-elastic carti-
lage.
Hyaline Cartilage is so named from its resemblance to glass. It
is firm, homogeneous, and more or less transparent according to thick-
FIG. 67.
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Vertical Section of Articular Cartilage covering the lower end of the Tibia, human (magnified about
30 diameters): a, cells and cell-groups flattened conformably with the surface; b, cell-groups
irregularly arranged; c, cell-groups disposed perpendicularly to the surface; d, layer of calcified
cartilage; e, bone.
ness. It is found at the articulating surfaces of all except intermem-
branous bones (articulating cartilage); at the anterior extremities of
the ribs (costo-cartilage); in the wings of the trachea, walls of the
FIG. 68.

Oo
White Fibro-cartilage from an Intervertebral Disc, human (highly magnified). The concentric lines
around the cells indicate the limits of deposit of successive capsules. One of the cells has a
forked process which extends beyond the hyaline area surrounding the cell, amongst the fibres
of the general matrix.
bronchi, and in the septum and lateral cartilages of the nose, etc. etc.
The articulating cartilage has cells and cell-groups, which near the sur-
face are flattened (Fig. 67). Late in life the costal cartilages become
finely fibrillated and occasionally completely ossified.
140
ANATOMY.
Fibro-Cartilage (white) (Fig. 68) receives its name because its matrix
is composed of bundles of fibrous connective tissue, the bundles being
arranged in layers. Between the lamella of these fibrous bundles are
rows of flattened, oval, nucleated cells, each cell being surrounded by a
delicate capsule. These cells are similar to those found in tendons, though
they are not so flat, and are distinguished by their surrounding capsule.
FIG. 69.
Where fibro-cartilage unites with tendinous tissue, as does the inter-
articulating fibro-cartilage of the temporo-maxillary articulation with
the tendon of the external pterygoid muscle, the two kinds of cells
merge imperceptibly into one another. The sesamoid cartilage, inter-
vertebral discs, interarticular cartilage, the interarticular fibro-cartilage
of the temporo-maxillary articulation, all are of the fibrous variety.
The Fibro-elastic Cartilage (yellow elastic) is spoken of by some
as reticular cartilage, by reason of the
arrangement of its fibres. In early
life this variety of cartilage is hyaline,
but in adult life it becomes permeated
with elastic fibres which proceed from
the perichondrium inward. It is the
most elastic of all cartilage. Its fibres
are fine, and so branch and anastomose
with each other as to form a dense net-
work, with spherical or oblong spaces.
or meshes, in which lie nucleated cells
of varying sizes surrounded by a zone
of hyaline cartilage. This cartilage is
found in the epiglottis, in the auditory
canals, the cartilage of Wrisberg and
Santorini, of the larynx, etc. etc.
Fibro-cartilage of an Intervertebral
Cartilage-cells have one characteristic which distinguishes them from
all others-viz. the power of casting around themselves a halo composed
of a substance similar to the matrix of hyaline cartilage; this halo or
capsule, however, possesses the property of absorbing certain stains
which do not affect true hyaline cartilage. It is therefore an independ-
ent structure, and forms what is known as the cartilage lacunae, which
are in reality lymph-spaces.
These lacunæ are not isolated cavities, but have minute capillary
tubes communicating with each other, and finally open into larger tubes.
which extend to the surface of the cartilage.

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NOW ANG PRES
02
Cartilage-cells are spherical or oval-shaped bodies, usually containing
one nucleus. Under certain circumstances, however, the shape of the
cell may be modified, as will be shown hereafter. They increase by
division (Fig. 70). At first the two new cells formed from the original
old one are arranged side by side, in close proximity to each other, and
are half-moon shape in outline. These cells gradually separate from
each other through the increase of the capsular substance between them.
Finally, a division takes place in the capsules or lacunæ and the new
cells are completed. But one cell usually occupies a lacuna, and during
the increase of cells by division each lacuna may contain two, four, six,
or eight cells, according to the rapidity of the proliferation.
THE SKIN.
141
Cells are often differently arranged in the same kind of cartilage, this
depending upon the depth of the cartilage and the connection it has
with other tissues. Where cartilage is joined to a synovial membrane
and an articulating capsule, the cartilage-cells are more or less branched,
and pass insensibly into the branched connective-tissue cells of the mem-
brane. In the hyaline cartilage of the foetus are many spindle or
FIG. 70.
с
A
B
D
E
M

Plan of the Multiplication of Cells of Cartilage: A, cell in its capsule: B, divided into two, cach with
a capsule; C, primary capsule disappeared, secondary capules coherent with matrix; D, tertiary
division; E, secondary capsules disappeared, tertiary coherent with matrix.
branched cells. The cells in the cartilage which separates an apophysis
from a diaphysis of long bones are arranged uniformly in vertical rows.
The Perichondrium covers cartilage as periosteum covers bone: it is
a vascular, fibro-connective tissue envelope containing a few elastic
fibres. It is furnished with blood-vessels, lymphatics, and nerves, and
is important, as it furnishes protection to the blood-vessels that supply
the cartilage. It covers all cartilage excepting that on the articulating
surfaces of bone and in the lines of ossification. Through the blood-
vessels of the perichondrium the adjacent cartilage receives nourishment
-not by the passage of the blood itself into the cartilage, but from the
plasma of the blood in the perichondrium, which permeates the cartilage
through numberless minute tubes that open into the lacunæ or capsules
of the cartilage by one end, while by the other they open into larger
tubes, freely communicating with the perichondrium.
The distance between the substance of the cartilage and its source
of pabulum or nourishment accounts for its slow repair after injury.
When cartilage has been injured the wound at first fills up with connee-
tive tissue. This connective tissue at times remains permanent, but is
occasionally transformed into hyaline cartilage. When the lesions are
deep the margins of the wound, being situated nearer to the perichon-
drium, are more likely to heal than the deeper portions.
Data
THE SKIN.
THE skin is the superficial covering of the body, extending over its
entire surface and into the openings of its mucous canals to varying
depths until it joins their mucous membrane. It is flexible, elastic,
and extensible. It is loosely attached to the parts directly beneath,
142
ANATOMY.
excepting at such places as the palmar surface of the hand, soles of the
feet, face, and the calvarium, where it is attached to the fascia beneath
by numerous stout fibrous trabeculae, the spaces between these bands
being filled with cushions of fat.
In the region of the face and neck, as is shown by the action of the
muscles of expression, the skin is movable and is under the control of
the striated or voluntary muscular structure.
The thickness of the skin varies in different regions of the body. On
the back, the palmar and plantar regions it is very thick, while in the
inguinal and axillary regions and on the eyelids it is extremely thin.
Hairs, either long or short, coarse or fine, are found protruding from
the skin throughout almost its entire extent, but they are much more
plentiful in some places than in others.
The Tactile Corpuscles are in the papille of the skin; they are the
principal organs of touch, and are capable of a high degree of cultiva-
tion, as is aptly illustrated in the marvellous sensitiveness of many blind
persons. By this sense can be detected degrees of heat and cold, hard-
ness and softness, and the direction of the air-current when but gentle.
The sensitiveness of the skin varies in different parts of the body, it
being most acute at the tips of the fingers and lips.
The skin is also an important excretory organ, and, under certain
circumstances, is capable of effecting absorption, its functions in this
respect varying in different parts of the body.
In some of the lowest orders of animals there is no integumentary
covering, while in others of a somewhat higher scale there is a distinct
outer layer of cells performing the functions of the integument. Others
are provided with special organs of secretion, as is illustrated in the shell
membrane of the mollusca, etc.
In the higher forms of animal life (the vertebrates) the integument
can be separated into two great divisions-the epiderm, or cuticle, or
scarf skin, and the derm, or corium, or cutis vera-synonymous names
for the skin layers that have much complicated its study.
The Blastoderm at a very early stage of its existence divides into two
layers, the epiblastic and the hypoblastic; a third, or mesoblastic layer,
derived from the contiguous portion of the epiblast and hypoblast, forms,
and is situated between them. From the epiblastic or upper layer
are formed the epiderm, or cuticle of the skin, and all its appendages,
such as the hair, the nails, the enamel of the teeth, the brain, and the
nerves. From the mesoblastic or middle layer are formed the true
skin, the cartilage, the bones, muscles, the dentine and cementum of the
teeth, etc. From the hypoblastic or lower layer are formed the epithe-
lium of the mucous membrane and the various glands of the alimentary
canal situated posterior to or below the palato-glossal fold of the mouth,
and in front or above the lower third of the rectum.
Fig. 71 is a diagram of the skin divided into different strata or layers.
The first natural or embryonic division is formed through its separation
into two layers, the upper one, the epiderm, being derived from the
epiblastic, and the lower one, the true skin, from the mesoblastic layer,
an apparent basement-membrane (hereafter explained) being situated
between them.
THE SKIN.
143
The Epidermis is that portion of the skin which is separated from the
deeper structure in the formation of a blister. It is clearly demonstrated,
as it constitutes the thin wall or covering of the blister. It comprises
FIG. 71.

バンブ
​ORDER
TOCCA
O
ROTEINAK
а
b
C
d
e
f
Vertical Section of the Skin of the Thumb, partly diagrammatic: a, stratum corneum, or epiblastic
portion, traversed by ducts of two glands; b, rete mucosum, with prolongations extending
between papilla beneath; between a and b is seen the stratum lucidum, also the basement-men-
brane; c, mesoblastic portion or papillary layer of corium. Near the centre of the figure is seen
a nervous papilla; d, reticular layer of corium with vascular plexus, nucleated connective tissue,
and interspaces; e, coils of four sweat-glands; f, fat-giobules in the meshes of connective tissue.
(From Hyde's Diseases of the Skin.)
all that portion of the first division above the basement-membrane. Its
under surface is uneven, being marked by depressions and elevations
corresponding to and fitting over the papilla of the true derm. Com-
144
ANATOMY.
mencing at its foundation or lower portion, it is subdivided as follows:
stratum Malpighii or rete mucosum, stratum granulosum, stratum
lucidum, and stratum corneum. The continued growth of the epidermis
as a whole, with its appendages, the hair, nails, and the enamel of
the teeth, depends upon this function of development of the stratum
Malpighii.
Stratum Malpighii.-Just above the papillary layer of the corium is
a layer of oval cells, each containing nuclei. These cells are constantly
undergoing proliferation, and are connected by numerous fine filaments
(imbricated cells). As the cells multiply, those which have been pre-
viously formed are pushed upward toward the surface, die, and are
cast off.
Stratum Granulosum.—Above the stratum Malpighii the cells change
their form become more flattened and possess large and distinct nuclei.
The protoplasmic contents of the cells also exhibit numerous granular
masses, and from this appearance the layer thus formed receives its
name.
Stratum Lucidum.-Above the stratum granulosum the cells flatten
out still more, become narrower and homogeneous, and sections of them
freely transmit light; hence the name.
Stratum Corneum.-Above the stratum lucidum another change in
the cells takes place. At first they appear to swell up, but soon assume
a more flattened appearance, the most superficial of them becoming
structurally horny scales are constantly undergoing desquamation.
The True Skin, Derm, Corium, or Cutis Vera is a tough, flexible,
elastic, highly vascular, and nervous tissue, containing lymphatic ves-
sels. It is developed from the mesoblastic or middle layer of the
blastoderm.
STRUCTURE. The true derm is principally composed of a reticulum
of white fibrous connective tissue largely interwoven with elastic fibres.
There are also found in it many independent lymphoid cells and a
complicated network formed by an intimate association of the processes
of the connective-tissue corpuscles. Unstriated or involuntary muscular
fibres are found in the vicinity of the nipples and their alveoli, etc., and
striated or voluntary muscular fibres are to be met with in the region of
the face, head, neck, and portions of the hand.
THE PAPILLÆ.
The true skin is divided into two portions, upper and lower, known
as the papillary and reticular (or vascular) layers. These receive their
name from their anatomical formations. The papillæ of these layers
are considered to be the organs of touch, as they are found more highly
developed at those points where the sense of touch is most delicate.
They act by extending the surface for the production of cuticular
tissue, and hence are found large and numerous under the nails. The
pulps of the teeth and the papille of the hairs are developed from
them. They are conical or finger-like in shape, and are either
simple or compound, sometimes dividing near their apices into two
or more projections. They vary both in shape and size in different
THE SKIN.
145
parts of the body, being largest on the palmar surfaces of the hands and
the soles of the feet. These papillæ of the true derm fit into correspond-
ing depressions of the epiderm. As the superior surface of the papillary
layer is approached the fibrous network of the connective and the elastic
tissue becomes finer and finer, the fibres approximating more closely until
they appear to form a homogeneous layer known as the basement mem-
brane of Todd and Bowman.
The fibres toward the inferior surface of the papillary layer are
coarser and more loosely interwoven than they are at the superior sur-
face, and finally pass into the subareolar tissue.
The Reticular Layer.-The line of demarcation between the upper
and the lower layers of the true skin is not clear and distinct, but one
part gradually merges into the other, the principal point of difference
being in the arrangement of the fibrous network. Descending from
above, the fibres become fewer and are situated farther apart, until a
coarse network is formed, which is finally lost in the subcutaneous con-
nective tissue. At this point these bands form a loose reticulum, the
meshes of which are generally filled with an abundance of fat.
G
Manda
The quantity of fat within the reticulum varies considerably in dif-
ferent regions of the body, being large about the mammary glands and
in the palms of the hands and the soles of the feet, while in the eye-
lids and about the ears but little if any is found.
The Blood-vessels of the Skin ascend through the subcutaneous con-
nective tissue, and divide as they pass through the true derm toward
the surface. They give off branches which pass to the fat-clusters,
sweat-glands, hair-follicles, and the corium. As they approach the
papillary layer they form a fine capillary network of anastomosing
vessels, the papillæ being supplied with capillary vessels which pass
through their central portion, furnishing an abundant supply of blood.
Veins accompany the arteries in their ramifications, but no blood-ves-
sels pass into the epiderm.
The Lymphatics are distributed throughout the entire surface of the
skin, except the epidermal layer, though not equally in all parts, being
larger and more abundant around the nipples and on the scrotum.
They are arranged in two strata, with anastomosing vessels between
them. The superior stratum is situated just below the network of
capillary blood-vessels, passing up into some of the papillæ in the
palms of the hands and soles of the feet. Valves are found in the
larger vessels of the corium, but not in the smaller ones or in those
of the superior layer. The hair-follicles and the glands of the skin have
special plexuses of lymphatics as well as of blood-vessels.
The lymphatics of the skin orginate in the spaces between the cells,
as they do in other kinds of connective tissue, and have a linear arrange-
ment between the bundles of fibres.
C
The Nerves. As the skin is the organ of the body possessing the
special function of touch-perception, it is but natural to expect many
nerves to be distributed over its surface; and as the degree of sensi-
bility varies, it is also to be supposed that the nerves are not equally
distributed. The principal branches pass through the subcutaneous
connective tissue, divide at the corium, and run in various directions,
VOL. I.--10
146
ANATOMY.
forming plexuses of fine nerve-fibres near the surface. From the
most superficial of these plexuses, or those situated immediately below
the epidermis,' fine non-medullated nerve-fibres pass upward between
the cylindrical cells of the stratum Malpighii of the cuticle, where they
terminate. The nerves are abundantly distributed to parts that are
covered with hair, especially where such hair is used as a sentient organ,
as is the case with the whiskers of the cat. The termination of many
of the nerves will be found in the tactile and Pacinian corpuscles.
The Tactile or Touch Corpuscles (Figs. 72, 73) are usually oval in
FIG. 72.

By
Section of Skin, showing two Papillæ and deeper layers of
Epidermis: a, vascular papilla with capillary loop passing
from subjacent vessel, c; b, nerve-papilla with tactile cor-
puscle, (the latter exhibits transverse fibrous markings);
d, nerve passing up to it; f, f, sections of spirally winding
nerve-fibres.
T
FIG. 73.
Ep

Tactile Corpuscle within a papil-
la of the skin of the hand,
stained with chloride of gold.
The convolutions of the nerve-
fibres within the corpuscle are
seen. Ep. epidermis.
shape they may be straight or slightly folded-and are situated within
certain of the papillæ of the corium; they are attached to medullary-
nerve-fibres. These papillæ contain no blood-vessels, and are called
tactile or sensory, in contradistinction to the vascular papillæ which
contain the blood-vessels. Their number varies according to location,
they being most numerous where the touch is most acute, as on the
inner or palmar side of the last phalanges of the fingers.
The Pacinian Corpuscles are oval or olive-shaped bodies, receiving
the terminal ends of cutaneous nerves. In the skin they are situated
in the subcutaneous connective tissue, and like the touch-corpuscles are
most abundant on the palms of the hands, soles of the feet, the fingers
and toes, and more especially on their distal phalanges.
Pigment. The color of the skin depends upon the deposit of pig-
ment-granules. This is generally found in the lowest stratum of the
1 The lymphatics do not pass into the epiderm, and that is the reason normal skin is
not an absorbing organ.
THE SKIN.
147
Malpighian layer, and appears to fade away gradually as it approaches
the surface. In the normal condition it is never found in the corium.
The color of the skin will depend upon the quantity of this pigmentary
deposit, varying from white to black according to race, and differing in
shade in the same race, as is illustrated in the blonde and brunette.
APPENDAGES OF THE SKIN.
In man these are the hair, teeth, nails, and sebaceous glands. The
teeth will be described elsewhere in this work.
THE HAIR, like the nails and the enamel of the teeth, is a peculiar
modification of the epidermis. It is developed from the epiblastic or
upper layer of the blastoderm, and consists necessarily of the same struc-
ture, and is governed by the same general laws of development, growth,
and sustenance, as the epidermis. It is found on nearly every part of
the surface of the body, the exceptional parts being the soles of the feet,
the palms of the hands, the eyelids, the inner surface of the prepuce,
glans penis, and the last phalanges of the fingers and toes.
Its color, length, and thickness vary according to the part of the
body on which it is found, and are influenced by race and tempera-
ment. The color, like that of the skin, depends upon the quantity of
pigment deposited within its structure, absolutely white hair having
Oftentimes the color varies, not alone in different individuals,
but in the same person, as the hair of the face
is seldom of the same shade as that on the
head.
none.
f.
e
The length of the hair varies from that
which does not extend beyond the opening of
the follicle to the longest grown upon the head.
Its thickness also varies considerably, that cov-
ering the head being finer than that found on
the face and on the borders of the eyelids, etc. d.
etc. Straight hair is coarser, and its trans- o
verse sections are more circular, than curly
hair, which is generally fine and oval in trans-
verse section.
a
p
፩
Anatomically, the hair is divided into a
root, shaft, and point.
The Follicle is formed by the dipping down
of the epiderm into the tissue below (Fig. 72).
The Root of the hair is that portion which
is in the hair-follicle of the skin.
The Bulb is the expansion of the extremity
of the root.
J.
FIG. 74.
2
-I 1
Z
Section of Hair-follicle: 1, dermic
coat of follicle; 2, epidermic coat
or root-sheath; a, outer layer of
dermic coat, with blood-vessels, b,
b, cut across; c, middle layer; d,
inner or hyaline layer; e, outer
root - sheath; f, g, inner root-
*
sheath; h, cuticle of root-sheath;,
The Shaft is that portion of the hair above
the mouth of the follicle. In straight hair its
transverse section is almost cylindrical; in
curly hair it is compressed or oval. It is composed of compact tissue,.
which gradually tapers as it approaches the end.
Histologically, the hair is also divided into three portions-the cuti-
►

148
ANATOMY.
cle, fibrous (cortical), and medullary portions, though the latter is not
always present.
The Cuticle is the outer or investing membrane of the hair, firmly
binding its bundles of fibres together. Under the microscope this mem-
brane is seen to be composed of fine imbricated scales. The upper edges
of these project and form fine transverse wave-like lines. They are
without nuclei, and are analogous to the upper cells of the corneous
layer of the epidermis, and perform a like function for the hair.
The Fibrous or Cortical Portion.-The bulk of the hair is made up
of this substance; it is translucent, and is arranged in longitudinal
FIG. 75.

R
с
IS-
OS
M-
LIGH
Oseboge
Oોને મેં બે મરે છે છે. GAOLA
આજે આપેો છે,
JESCIS
13:8746
991000
·H
F
P
Lower portion of Hair-pouch from the lip of a kitten: F, follicle; 7, transverse sections of connective-
tissue bundles of derma; M, arrector pili muscle; IS, inner root-sheath; OS, outer root-sheath;
P papilla; C, cuticle; R, root of hair; 77, hyaline or so-called structureless membrane (magnified
500 diameters).
bundles containing oblong patches of pigment-granules and other color-
ing matter of less intensity.
The fibres which make up the bundles composing this portion are
subdivided into flattened fusiform cells with slender elongated nuclei,
which are distinctly visible when certain reagents are used. There are
THE SKIN.
149
also spaces between these cells containing air which are called hair-
lacunæ; these are more abundant in white hair than in colored. Ex-
amined by transmitted light, these spaces are dark, but with reflected
light they are a brilliant white.
S
The Medulla or Pith is usually absent in the fine hairs covering the
surface of the body, and is not commonly met with in those covering the
scalp. It is also lacking in the hair of children under five years of age.
It is met with, however, in the short thick hairs. When present, it is
found in the centre of the shaft and is lost before reaching the point.
It is composed of soft cells, oblong or rectangular in shape, containing
minute particles, some of which appear like fat-granules. There are
also air-spaces between the cells.
Under the microscope, with transmitted light, the medulla appears to
be darker than the fibrous substance of the hair. When reflected light
is used, however, it appears white. This change in appearance is due to
the lacunæ found within its substance.
The Hair-follicles contain the hair, and are generally found in groups
of three or four, more rarely two; very rarely are they single. With
few excepted places they are found all over the entire integument. This
follicle is an elongated pear-shaped sac passing obliquely down through
the different strata of the skin into the subcutaneous tissue, in which fat
is found. The follicles of small hairs do not pass so deeply as those
of larger ones, and those which accommodate woolly hairs are curved
at the bottom, the ends often curving so far as to extend upward.
The mouth of the follicle is slightly funnel-shaped, the lower
portion being enlarged to accommodate the bulb or root of the hair.
The follicle is also invaginated over a pear-shaped papilla. It is
formed by the skin dipping down into the tissue below.
The coats of the follicle are separated into two divisions, dermic and
epidermic. These are again subdivided, the dermic into three layers—
external, middle, and internal; and the epidermic into an outer and an
inner root-sheath.
The External Layer is formed in a manner precisely similar to the
lower layer of the corium, with which it is continuous above. It, in a
measure, determines the form of the follicle, and in composition is highly
vascular and supplied with nerve-filaments. No elastic tissue enters
into its structure. The bundles composing this layer are laid longitu-
dinally with the axis of the follicle.
The Middle Layer is very similar in its structure and arrangement
of blood-vessels to the external layer of the corium. It is thinner, and
composed of transverse connective-tissue fibres with elongated nuclei.
Nerves have not been found in this layer.
The Internal Layer, or "glass membrane," corresponds in structure to
the basement-membrane of Todd and Bowman. It is a transparent,
homogeneous stratum, the inner surface of which is raised, the outer
surface being smooth.
The Epidermic or Cuticular Coat is that portion of the follicle derived
exclusively from the epidermis, and is continuous with it. It adheres
closely to the root of the hair, and is generally removed with the root
in extracting the hair. For this reason it is called the root-sheath,
150
ANATOMY.
ก
and is composed of two layers, called the external and the internal root-
sheaths.
The External Root-sheath is that portion of the hair-follicle which is
derived from the lowest or Malpighian stratum of the cuticle. It is
composed of several layers of polygonal cells with nuclei, as far as the
hair-bulb, where it is composed of but one row of cells, which become
continuous with the hair-bulb at its lowest portion.
The external root-sheath contains pigment-granules in the dark races,
and Langerhaus claims to have found in it nerve-filaments similar to
those found in the Malpighian layer of the skin.
The Internal Root-sheath is derived from the corneous layer of the
epidermis, but is not connected with it. It commences just below the
orifices of the sebaceous glands, passing downward to the bottom of
the follicle, where it joins the layer of columnar cells covering the hair-
bulb.
This sheath is composed of two layers an outermost, or layer of
Henle, and an innermost, or layer of Huxley. These two layers com-
mence as one just below the orifices of the sebaceous glands. As they
pass downward they again unite and form one layer of large polygonal
nucleated cells having no spaces between them, and finally become con-
tinuous with the hair-bulb.
The Outermost, or Layer of Henle, is composed of elongated, flat-
tened, non-nucleated cells, generally having spaces between them.
The Innermost, or Layer of Huxley, is composed of flattened, nucle-
ated scales two or three deep. The layer thus made forms the internal
lining of the follicle below the orifices of the sebaceous glands. The
innermost scales are imbricated, lapping over the superimposed layer of
cuticular imbricated scales of the hair, and thus serve to hold the hair
in position.
The Papilla of the Hair is a conical-shaped eminence in every respect
similar to the papilla of the skin-in fact, is a papilla of the skin car-
ried to a lower level than those entering into this structure, and being
continuous with the dermic layer of the follicle. It is highly vascular,
and is supplied with nerve-filaments. Its blood-vessels supply the
nourishment for its development and growth.
The bulbous expansion at the root of the hair is soft, and consists of
polyhedral epidermic cells united together by a cement-like substance.
These cells are continuous at the circumference of the bulb with the
outer root-sheath, from which they were originally derived. The base
of the bulb is attached to the bottom of the follicle, where the latter is
invaginated over the papilla, there being a depression in the base for
this purpose. The circumference of the base is attached to and contin-
uous with the lining membrane of the hair-follicle.
Extending over the surface of the papilla (above the basement-mem-
brane) is a special layer of short oval cells (hair-builders) which are
analogous to all similar building cells, such as those of the epidermis,
the nails, and the enamel of the teeth. The formation of these structures.
is governed by one general law: that is, the special layer of cells at the
base and on the circumference of the papilla are constantly in an active
state of proliferation. New cells are thus formed which push the older
Ga
THE SKIN.
151
ones upward into the bulb, where a special action takes place, some
going to form hair, others nails, etc. etc. They form the hair: the
great bulk of the cells become elongated and spindle-shaped, and
form what has been described as the fibrous substance of the shaft.
The Sudoriferous or Sweat Glands (Fig. 76) are distributed over
nearly the entire surface of the body. They are most numerous in parts
not supplied by hair, though they are plentiful in parts where the
growth of hair is abundant, their ducts occasionally emptying into the
hair-follicle. Krause has estimated the entire number distributed over
the body to be 2,381,248, or from 400 to 600 to the square inch on the
lower limbs, back of the neck, and trunk, where they are fewest, while
in the palms of the hands and on the soles of the feet they are found
in their greatest number, and reach 2800 to the square inch.
The length of the sudoriferous gland, together with its tube, has been
estimated to be about a quarter of an inch. This gives the human body,
containing as it does 2,381,248 such glands, about fifty thousand feet, or
over nine miles, of perspiratory tubing.
The size of the sudoriferous glands varies in different parts of the
body, those in the axilla being the largest. Here they have been
found about a sixth of an inch in diameter, though their average diam-
eter in this region is from one-thirty-sixth to one-twelfth of an inch, the
average over the entire body being one-seventieth of an inch.
E
r.
FIG. 76.
p

-PL
-BP
D
Duct of the Sweat-gland within the epithelial layers of the skin: BP, papilla with injected blood-ves-
sels; , valley between two papille; D, duct in the rete mucosum; E, E, epidermal layer; PL,
coarsely granulated epithelia, deeply stained with carmine; P, duct with corkscrew windings in
the epidermal layer (magnified 200 diameters).
These glands eliminate a large proportion of the aqueous and gaseous
matter from the body. Under ordinary temperatures, in the absence of
too severe physical exercise, perspiration goes on imperceptibly, but in
warmth and the stimulus of vigorous bodily exercise there is a percepti-
ble and more or less profuse flow.
These glands are situated in the lowest stratum of the corium, and
152
ANATOMY.
are found at various depths in the subcutaneous connective tissue, sur-
rounded by adipose tissue.
They are tubular, with a coiled, rounded, or flattened extremity, the
duct through the epiderm resembling a spiral screw. This duct ascends
vertically through the true skin and cuticle, terminating in an enlarged
pore or aperture (Fig. 76). Occasionally these glands are formed of two
tubes coiled around each other. When so formed the tubes unite at the
superior extremity of the gland and form one duct.
FIG. 77.
Both the duct and the gland proper are invested with connective
tissue similar to and continuous with the corium. Situated within this
tissue, which forms the outer
portion of the tube, is a
thin membrane which tra-
verses the gland and the
duct as far as the epidermis,
Dand is analogous to, and
continuous with, the base-
ment-membrane of the skin.
That portion of the tube
above this basement-mem-
brane is epidermic in struc-
ture, while the coiled por-
Ttion, or the true secreting
gland, is lined by a single
layer of cuboidal and poly-
s hedral epithelium (Fig. 77),
with nuclei, and often con-
taining pigment - granules.
Between these cells of the
basement-membrane is a
layer of non-striated mus-
cular fibres arranged longi-
tudinally. These fibres are
not found in the duct, which coils several times before leaving the
gland.
The duct proper is lined by an extremely fine cuticular membrane.
Between this lining and the basement-membrane are situated two or
three layers of epithelial cells. The epithelium within the tube forming
both the gland and the duct is continuous with the epidermis.

Gla
da a spot tangga
Section of Coil of a Sweat-gland: S, tubule lined by
cuboidal epithelia; 7, central calibre of the tubule; D,
the beginning of the duct; C, connective tissue with
injected blood-vessels (magnified 500 diameters).
S
Frida
The Ceruminous Glands found within the external auditory meatus
are so similar to the sudoriferous glands in structure and mode of
development that they have been classed as of that variety.
Sweat-glands are surrounded by numerous blood-vessels.
The Sebaceous Glands belong to the racemose variety. They are dis-
tributed over almost the entire surface of the body, with the exception
of the palms of the hands, soles of the feet, and the backs of the last
phalanges of the fingers and toes. They are situated within the corium
of the skin, and are usually connected with the hair-follicle by two
ducts which empty into it a little below its mouth. These glands do
not pass into the subcutaneous tissue.
THE SKIN.
153
M
The number and size of these glands connected with each follicle do
not depend upon the calibre of the hair, for some of the finest hairs
found upon the surface of the body have as many as six sebaceous
glands emptying into their follicles. Occasionally the gland has its
outlet upon the surface of the skin.
The largest of this variety of glands are found in connection with
the eyelashes, within the eyelid, and have received the name of Mei-
bomian glands. Sebaceous or cystic tumors, which sometimes appear on
the external surface of the head and in the eyelids, are caused by the
clogging of the orifices of these glands while active secretion goes on
within. The secretion of these glands on the face often becomes inspis-
sated, especially in the region of the alæ nasi.
Sebaceous glands differ in shape, though their general outline is pyri-
form, the duct of the gland corresponding to the stem of the pear.
In structure they are lobular (Fig. 78), each lobule consisting of a
FIG. 78.



2
2
w
L
2

Sebaceous Gland of the Second Class, from the alæ nasi.
cluster of spherical secreting saccules. The secretion of each saccule is
collected into the principal duct of the lobule, and passes into the main
duct of the gland, which usually has its outlet a little below the mouth
of the hair-follicle.
154
ANATOMY.
1་
The outer surface of the saccules is formed by a basement-membrane
which is continuous with the basement-membrane of the skin. Next to
this membrane, within the gland, is situated a layer of polyhedral gran-
ular epithelial cells, each containing a spherical or an oval nucleus.
Resting upon this layer and filling the saccule is a layer of large poly-
hedral cells with spherical nuclei. The cells are largest near the centre
of the saccule, while toward its outlet they become atrophied.
The duct of the gland is a continuation of the outer root-sheath. The
cuboidal cells of the gland undergo active proliferation; as this process
continues the older cells are pushed toward the duct until they reach the
surface of the skin, where they form sebaceous matter.
K
AREOLAR TISSUE, TENDONS, AND MUSCLES.
THE AREOLAR TISSUE is the third variety of connective tissue, bone
and cartilage representing the other two. It is a soft filamentous sub-
stance, with considerable tenacity and elasticity. It is found immedi-
ately below the skin, extending between and forming the sheaths of the
muscles. It comprises the subcutaneous or superficial fascia and the
reflections into deeper planes known as deep fascia, and connects
mucous and scrous membranes with the parts which they line or
invest, in which position it is known as submucous or subserous areolar
tissue. It likewise both separates and encloses all muscles, forming
envelopes for them. It forms the sheaths around the blood-vessels and
deep-seated parts or organs, in which position it is designated interme-
diate areolar tissue, and if it comes in immediate contact with the part it
is called investing areolar tissue. In a word, it is found throughout the
various organs of the body, penetrating between the muscular bundles,
the lobes and lobules of the compound glands, following the vessels
and nerves to their finest divisions. It is continuous with itself, and
can be traced from one part of the body to another without interruption.
Hypodermic injections intended to enter the general circulation are
thrown within this tissue. It serves as the storehouse of fat. Drop-
sical fluids, by reason of the sieve-like arrangement of its meshes, may
be diffused through it from one part of the body to another. It allows
the skin to move freely over adjoining parts, and assists it in reassuming
the normal position after having been drawn in any one direction.
FASCIA.
Fascia, one of the divisions of areolar tissue, is composed of a multi-
tude of soft, fine, and somewhat elastic fibres, transparent in appearance,
but intermixed with numerous delicate colorless membranous laminæ.
These fibres and lamina are interwoven in every imaginable direction,
forming net-like meshes of different sizes. These interspaces communi-
cate freely with each other, many of them being filled with fat, which
AREOLAR TISSUE, TENDONS, AND MUSCLES.
155
is enclosed in its own vesicle. In health this tissue is moistened and
lubricated by a transparent fluid of the nature of lymph.
Fascia is divided into two varieties, superficial and deep.
Superficial or Subcutaneous Fascia connects the skin with the deeper
and firmer parts beneath by numerous delicate bands or trabecula; its
structure is more open than that of the deep fascia, and its bands run
more irregularly. It varies in thickness and density in different parts,
and is found distributed throughout nearly the entire surface of the
body. Within the meshes of this tissue is found the subcutaneous fat,
which forms a blanket of adipose tissue and serves to keep the body
warm, fat being a poor conductor of heat. No adipose tissue is found
upon the eyelids, the penis, and the scrotum. In animals, such as the
cow, the horse, and the dog, the superficial fascia contains within its
structure a muscle known as the panniculus carnosus, which extends
over almost the entire body. In man a muscle corresponding to this,
known as the platysma myoides, is found in the region of the head and
neck.
In some portions of the body the superficial fascia is separable into
several layers; this is especially true in the region of the groin. In
health the superficial fascia often becomes loaded with fat, this tissue in
corpulent people being much thicker. The opposite is the case with
emaciated people, the superficial fascia becoming extremely thin; its
fibrous bands are closely approximated, and the skin appears wrinkled
or in folds. Also on the soles of the feet and in the palms of the hands
it is very thin and closely attached to the skin. It is generally divided
into two or more layers, between which are the glands, and through
which pass the superficial blood-vessels, nerves, and lymphatics, these
structures having free communication with each other.
The Deep or Aponeurotic Fascia is immediately beneath the super-
ficial fascia. The course of its fibres is not so irregular as that of the
superficial fascia, inclining more to an arrangement in layers or bands,
with much less adipose tissue confined within its meshes; this forma-
tion makes it denser and stronger than the superficial fascia.
Like the superficial, the deep fascia extends over nearly the entire
surface of the body, forming an envelope which holds the muscles to
their shape and in their proper position. Numerous septa are given off
from it which dip down between the muscles, dividing and enclosing
their bands, subdividing and enclosing their fibres, and forming a sheath
which enwraps the vessels and nerves wherever met. It encloses the
tendinous structures in the same manner as the muscular. That portion
of the fascia which invests a tendon is called its theca or vagina.
This fascia also assists in forming intermuscular connections and
septa, as those between the two bellies of the digastric and the occipito-
frontalis muscle. When the fascia is broad and well defined it is
called an aponeurosis. The deep fascia, in different forms, serves to
attach muscles and tendons to osseous and other structures, and throws
off stout fibrous bands which form various ligaments, such as those sur-
rounding the joints, the annular and the bicipital, the palmar and the
plantar fascia, etc.
The deep fascia likewise forms pulley-like apertures through which
156
ANATOMY.
•
pass the tendons of muscles, good illustrations of these being found in
the trochlear of the superior oblique muscle of the eye and the pulley
for the passage of the intermuscular tendon of the digastric muscle.
A thorough knowledge of this fascia will materially assist in the diag-
nosis of deep tumors and in prognosticating the direction, course, or route
likely to be taken by morbid fluids and growths from one point to another.
Fascia of the Neck, Face, and Head.-The superficial fascia of the
face and anterior portion of the neck is so slightly developed, and so
intimately blended with the adjoining parts, that it is not recognized as
a separate tissue. Its thickness varies inversely to the development
of the platysma myoides and facial muscles, the one seeming to take
the place of the other. That portion of the fascia of the head situated
between the aponeurosis of the occipito-frontalis muscle and the integu-
ment is dense and firm, and by its fibres unites the skin, the fascia, and
the aponeurosis closely together. This union is so intimate that the
structures are difficult to separate in dissection. Between the layers of
the fascia as it extends over the temporal aponeurosis are situated the
muscles which move the external ear, as well as the superficial temporal
vessels and nerves. It is continuous behind with the superficial fascia
of the back part of the neck.
The Deep Cervical Fascia anteriorly is a dense structure, having a
somewhat complex arrangement, and is of great importance from a
surgical point of view: it limits to a certain degree the growth of cervical
tumors and abscesses and modifies their direction and their extent.
Deep-scated abscesses often follow the course of the fascia, though occa-
sionally these as well as tumors penetrate or stretch this membrane in
their growth and adopt a course of their own. The deep cervical fascia
is divided into two portions, superficial and deep, the superficial form-
ing a complete covering for the neck, enclosing every structure belonging
to it except the skin, the superficial fascia, the platysma myoides muscle,
and some superficial veins and nerves. In the anterior portion of the
neck it passes forward from the upper surface of the trapezius muscle
as it passes under the platysma to the posterior border of the sterno-
cleido-mastoid muscle, where it divides into two lamella-one, the super-
ficial, passing over, and the other, the deep, passing under, the muscle.
At the internal border of the sterno-cleido-mastoideus it again reunites,
thus forming a sheath for the entire muscle: from this point it passes
forward to the median line and joins its fellow of the opposite side.
Its attachment above anteriorly commences at the symphysis of the
lower jaw, passing backward along the base of the bone to the parotid
region, where it divides into two lamina, the deep layer passing beneath
the parotid gland to be inserted into the base of the skull. The stylo-
maxillary ligament is developed from this leaflet of fascia. The upper
layer passes over the parotid gland and masseter muscle, forming their
upper covering. Laterally, above, the fascia is attached to the zygo-
matic arch, from which it extends backward along the zygoma to the
posterior root, thence to the mastoid process of the temporal bone and
the superior curved line of the occipital bone, to which it is also
attached. The inferior attachment of this fascia is to the clavicle, near
which it is pierced for the passage of the external jugular vein on its
►
疲
​AREOLAR TISSUE, TENDONS, AND MUSCLES.
157
way from the neck to its deeper relations. In the median line in front
the fascia is also attached to the hyoid bone.
Below the thyroid body the deep fascia divides into two layers, the
upper and thinner going to the outer and upper portion of the sternum,
to which and the interclavicular ligament it is attached, while the lower
Both
layer is attached to the inner and upper portion of the sternum.
layers are superficial to the sterno-hyoid muscles. The space between the
layers of fascia extends laterally until it encloses the sternal heads of the
sterno-cleido-mastoid muscles. The anterior jugular vein passes through
this interfascial space, which contains loose connective tissue and fat,
also sometimes a small lymphatic gland. Thus the upper portion of
the deep fascia of the anterior part of the neck covers in all that por-
tion known as the surgical square of the neck, and externally offers a
barrier to the extension of abscesses and growths from the deeper
parts toward the surface, which causes them to burrow more deeply.
Abscesses forming exterior to this fascia rarely if ever burrow.
(a) The Deep Portion of the Cervical Fascia.-Near the anterior mar-
gin of the sterno-cleido-mastoid muscle a process is given off from the
superficial layer of the deep fascia which descends behind that muscle
and is associated with the depressors of the hyoid muscular system. It
invests the thyroid body and the front of the trachea, spreads out in
front of the large vessels of the neck, and passes into the thorax as far
as the pericardium. It is supposed to assist in suspending the heart.
(b) The Prevertebral Fascia is a layer of the deep fascia which,
being attached to the base of the skull, descends on the prevertebral
muscles into the thorax, separating them from the pharynx and
œsophagus. Laterally, it becomes continuous with, and forms the back
portion of, the carotid sheath, from which it extends outward and down-
ward over the scaleni muscles, the brachial plexus of nerves and sub-
clavian vessels, which it accompanies beneath the clavicle into the axilla,
where it forms the axillary sheath, and becomes connected with the
under surface of the costo-coracoid membrane.
-
Takag
(c) The Carotid Sheath. The upper portion of this sheath is formed
from the fascia described as a, while the under portion is derived from
that described as b. This sheath forms a complete covering to the caro-
tid artery, the internal jugular vein, and the pneumogastric nerve. A
thin fibrous septum is interposed between the artery and vein, thus form-
ing a separate sheath for each.
(d) The Omo-hyoid Fascia, which encloses the lower belly of the mus-
cle of the same name, is a strong fascia which passes over the muscle
extending down to the first rib. It is from this layer of fascia that the
band binding down the intermediate tendon of the omo-hyoid muscle is
obtained.
WA
(e) The Submaxillary Fascia consists of two triangular layers of the
deep fascia which enclose a space containing the submaxillary salivary
and lymphatic glands; the fascia is attached below to the intermediate
tendon of the digastric muscles; the outer layer passes upward to be
attached to the body of the lower jaw; the other layer passes inward
to be connected with the fascia covering the mylo-hyoid, the hyo-glossus,
and the stylo-glossus muscles; surgically speaking, it is attached to the
158
ANATOMY.
mylo-hyoid ridge of the lower jaw, the outer sheaths of these muscles
being a continuation of this fascia.
A study of the arrangement and attachments of the fascia described
above will show that abscesses forming in certain regions or between
certain fascia can burrow into other regions. For instance, an abscess
forming between a and b would be likely to burrow toward the media-
stinum, or an abscess immediately in front of the spine and beneath the
fascia b would probably pass downward to the posterior mediastinum,
or laterally toward the posterior triangle, or even into the axilla, etc.
The Deep Fascia of the head is divided into three well-defined por-
tions: (a) the occipito-frontalis aponeurosis, (b) the right, and (c) the
left temporal fascia. The first extends between the occipital and fron-
talis muscles, and is attached laterally to the temporal ridge. The tem-
poral fascia extend over the temporal muscles, being attached above to
the temporal ridges and below to the zygomas.
Abscesses forming under the occipito-frontalis aponeurosis generally
burrow backward to a V-shaped interspace near the external occipital
protuberance, while those beneath the temporal fascia will burrow down-
ward under the zygomas into the zygomatic fossæ.
The Deep Fascia of the Face, like the superficial, is indistinctly
developed. Its place, however, is supplied by an abundant quantity
of areolar connective tissue distributed through, and intricately asso-
ciated with, the muscular tissue, though it does not form a distinct
covering or fascia for the face, nor is it developed sufficiently to com-
pose sheaths to the muscles. It is lax, and readily allows the diffusion.
of infiltrations, thus accounting for the sudden and marked swelling of
the face during certain inflammatory affections..
This areolar tissue holds within itself a quantity of cushion-like
masses of connective tissue which are prominent in the following
localities: the hollow of the cheek; between the zygomatic and bucci-
nator muscles; at the lower margin of the orbit, particularly where the
orbicularis palpebrarum overlaps the elevators of the upper lip;
beneath the muscles elevating the upper lip above the oral angle; at
the groove where the facial artery passes over the inferior maxillary
bone;
and beneath the depressors of the lower lip.
As the skin of the face is thin and vascular, scars from plastic opera-
tions and other causes are comparatively inconspicuous. Prof. Allen in
his work on Human Anatomy observes that a very different result fol-
lows extensive cicatrization of the deeper parts: here the connective
tissue is abundantly present, and, as seen after ulceration from mercurial
sore mouth or after destructive stomatitis from any cause, serves to con-
vert the cheeks into false ligaments holding the jaws close together.
A very marked case of this kind presented itself at the Hospital of
Oral Surgery, Philadelphia, in 1883.¹
¡
TENDONS.
The tendons, with but few exceptions, are made up of bundles of
white fibrous connective tissue bound together by fasciculi from the
¹ See Garretson's Oral Surgery.
AREOLAR TISSUE, TENDONS, AND MUSCLES.
159
deep fascia, which form their sheaths. The sheaths not only enclose
the individual fibres composing the bundles, but the entire tendon.
This latter covering is called the theca.
The fibres which make up a tendon are arranged parallel with each
other, and have an undulating course. Occasionally the fibrous bun-
dles send off fasciculi, some running forward and others backward,
interlacing with each other. The bundles proper, however, do not
subdivide, but keep intact from one extremity to the other.
The connective-tissue cells of tendons, called tendon-cells, are arranged
in parallel rows (Fig. 79), and follow the line of the fibrous bundles
composing the tendon. They are so closely approximated that in a
longitudinal section they have a stellate appearance, due to compression.
of the cells and the elongated processes characteristic of all connective-
FIG. 79.

20 UURET
(SA) 17
Yemen Riessy on CASES
GOYAVAG
OD WAS
Tendon of Mouse's Tail, stained with logwood, showing chains of cells between the tendon-bundles
(175 diameters).
tissue cells, which protrude from them, uniting one cell to another. These
cells are minute protoplasmic bodies, thicker in the centre than at the cir-
cumference, and contain a round or oval nucleus with several nucleoli.
Tendons are found connected with muscles at either terminal extrem-
ity or between the two bellies of the same muscle. Their fibres usually
run continuously with those of the muscle, but they may join the mus-
cle at an angle. When the tendinous fibres unite with the muscular
fibres end to end, the tendon is subdivided into as many fibres as there
are fibres in the muscle to which it is united. Adherence to this law is
so uniform that the fibres of the tendon seem to be but a continuation
of those of the muscle. A close examination, however, of the muscular
extremity of the fibres of the tendon will show that they suddenly end
on coming in contact with the truncated extremity of the muscle-fibre.
The sheaths, formed by fasciculi from the deep fascia, which enclose
the bundles of fibres forming the tendon, pass from the tendon-bundles
to the muscular fasciculi, and are lost by overlapping the similar sheaths
which enclose the muscular fibres, they all being continuous.
Where the fibres of the tendon are obliquely united to those of the
muscle the small tendinous bundles are given off laterally just at their
point of union, and extend between or over the muscular fibres, but
their sheaths are lost in the muscle in a manner precisely similar to the
union of the parallel fibres.
MUSCULAR TISSUE.
Muscular tissue is made up of fibres collected into distinct and sepa-
rate masses. By means of this tissue all the active movements of the
160
ANATOMY.
body are produced. It is familiarly known as "flesh," and it is dis-
tributed over the entire framework of the body and in the coats of
blood-vessels and the viscera.
In the higher vertebrates the color of the muscular tissue is generally
red, varying in shade, however, according to the locality in which it is
found and to other circumstances. The voluntary muscles, called into
most constant action, are deeper in color than others of their class. A
marked illustration of this is shown in the pectoral muscles of the bird
and the common fowl. The former, being called into almost constant
use in the act of flying, are dark in color, while the latter, being almost
wholly inactive, are extremely light in shade.
Muscular tissue also constitutes a large proportion of the weight of
the human body. It has been estimated by Liebig that a man weighing
150 pounds is 27 pounds skeleton, 60 pounds viscera (with skin, fat,
blood, etc.), 63 pounds muscle.
Each muscle constitutes a separate organ, and either acts independ-
ently or in conjunction with other muscles as accessories. The great
vital property of muscular tissue is contractility, which power is
excited to activity by the influence of various stimuli.
The greater number of the muscles of the body, such as those of
locomotion, respiration, mastication, the first part of deglutition, expres-
sion, etc., are compelled by the will acting through the nerves with
which the parts are supplied. These are known as voluntary muscles.
Others, again, as those of the intestinal canal and the vascular system,
cannot be brought into action by the force of the will. These are called
involuntary muscles, and are controlled by the sympathetic nervous system.
These two classes of muscles differ also in their histological construc-
tion, and will therefore be considered separately.
The Voluntary Muscles are fibres appearing under the microscope trans-
versely striated, and generally oblong in shape. Usually, tendons are at-
tached to their extremities, by means of which they are united to bones, and
sometimes to other tissues; for instance, the sphincter muscle of the mouth.
The fleshy part of a muscle is called its belly, and its terminal pro-
longations are its tendons of origin and insertion. The term origin
of a muscle or tendon generally applies to that extremity which is
stationary, and the term insertion is applied to the more movable
point. Example: the origin of the temporal muscle is that portion
arising in the temporal fossa on the side of the head, while its insertion
is at the coronoid process of the inferior maxilla. The skull is the fixed
point of the muscle, while the lower jaw is the movable one. This
rule is not without exceptions, as in certain localities the fixed point of
a muscle may become the movable point. The origin of a muscle may
be large and its insertion small, and vice versâ; or the origin and inser-
tion may be of equal size.
A thorough knowledge of the origin and insertion of muscles is
absolutely necessary to a full understanding of the mechanical action
of the parts to which they are attached. It is essential in diagnostica-
ting fractures and dislocations. A knowledge, also, of the direction of
the fibres composing muscles, and of the relation of muscles to adjoining
parts, enables the surgeon to locate disease, and serves as a guide to the
AREOLAR TISSUE, TENDONS, AND MUSCLES.
161
position of blood-vessels and nerves. The power of a muscle depends
upon the number of its contractile fibres. When contracted, it increases
in thickness; its action, unless otherwise influenced by associate parts
or by its tendon passing through loops of fascia or over a pulley, is in
a direct line with the course of its fibres.
Fasciculi are the bundles of the fibres composing muscles. The
fibres which make up the fasciculi vary greatly in length in different
muscles. The fasciculi which form the bundles composing a muscle
run parallel with each other, never inter-
lacing, but extending from one terminal to
the other, except when interrupted by the
interposition of tendinous tissue, as in the
case of the digastric muscle.
R
FIG. 80.
a

Transverse Section from the Sterno-
mastoid in man (50 times magni-
fied): a, perimysium; b, endomys-
ium; c, fasciculi.
The Endomysium is the portion of the
above membrane partially surrounding the
fibres composing the fasciculi; the latter
are not continuously invested with it. The
chief uses of the perimysium and its parti-
tions are to connect the fibres and fasciculi
together, and to furnish spaces for the
accommodation of blood-vessels and nerves that supply the parts.
The fasciculi (Figs. 81 and 82) are prismatic in form, and the number
of fibres of which they are composed in different parts of the body
causes the variations in their thickness.
CATE
b
The Perimysium (Fig. 80) is the sheath
of areolar tissue that invests the muscles
and sends partitions inward between the
fasciculi, providing each with a special
sheath.
FIG. 82.
The texture of a muscle, whether coarse or fine, depends upon this
circumstance. The length of a fasciculus.
depends upon the length of the muscle, as
well as upon the arrangement of the tendons.
to which the extremities of the muscle are
attached. When the tendons are limited to
FIG. 81.


A
B
A, a small portion of Muscle, natural size;
B, same magnified 5 diameters, of larger
and smaller fasciculi, seen in a trans-
verse section.
¿
b
A few Muscular Fibres, being part of
a small fasciculus (highly magni-
fied).
the ends or extremities of long muscles, the fasciculi are of great length,
VOL. I.-11
1
162
ANATOMY.
having to pass from one extremity of the muscle to the other. But a
long muscle may be composed of a number of short fasciculi attached
obliquely to the sides of its tendon, which may advance upon its surface
or into its fleshy parts. Many short fasciculi, thus connected, produce
by their combined operation a more powerful effect than a few fasciculi
extending the entire length of a muscle. The latter arrangement, how-
ever, gives greater extent of motion.
The Fibres composing the Fasciculi are cylindrical or prismatic in
form. Their size is generally uniform, being in the muscles of the
trunk and limbs from th to th of an inch in diameter. It is
less in those of the head, especially in the face, where they range from
24th to 7th of an inch.
1
The general length of the fibres does not exceed an inch and a half.
In long fasciculi, therefore, they do not extend from the tendon of one
extremity to that of the other, but end in a rounded point invested by
sarcolemma adhering to approximate fibres.
Muscle-fibres generally neither divide nor anastomose. In the
tongue of the frog (Fig. 83), however, the muscular fibres as they
approach the surface divide into numerous branches, which are
attached to the under surface of the mucous
membrane. This is also true of man and vari-
ous animals.
FIG. 83.
C
Jo
1
400

GIBBIE
FIG. 84.
Muscular fibre is soft and contractile, and is
enclosed in a tubular envelope known as the sar-
colemma or myolemma. This envelope consists
of a transparent, apparently homogeneous mem-
brane, similar to
elastic tissue. It is
tough, and will oc-
casionally remain
entire when the
fibres which it en-
closes are ruptured
(Fig. 84). Nuclei
A Branched Muscular Fibre
are found on the
from the frog's tongue inner surface of the
(magnified 350 "diameters). sarcolemma, but
they belong to the contractile substance of the fibre, and not to the
sarcolemma.
Pa
The fibres of the facial muscles of mammals
and those of the panniculus carnosus follow the
same rule. The numerous attachments of the
latter muscle to the under surface of the skin
causes the peculiar external twitching movement
seen in these animals.

kunti
Fragments of an Elementary Fibre of
the Skate, held together by the un-
torn but twisted sarcolemma.
The Contractile Substance of voluntary muscular fibre, when examined
under a microscope of high power and with transmitted light, appears
marked with parallel bands (Fig 85), alternating dark and light; the
former are named the contractile discs, the latter the interstitial discs.
These bands pass across the fibre with great regularity. They are of
AREOLAR TISSUE, TENDONS, AND MUSCLES.
163
equal breadth, but when the fibre is considerably extended a dotted line
becomes visible in the centre of the light band. This characteristic
cross-striped appearance is found in all voluntary muscles, but is not
absolutely confined to them, as it is seen in the fibres of the heart, which
FIG. 85.

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A, portion of a medium-sized Human Muscular Fibre (magnified nearly 800 diameters): B, separated
bundles of fibrils, equally magnified; a, a, large, and b, b, smaller collections; c, still smaller; d, d,
the smallest which could be detached.
is considered an involuntary organ, though it is claimed that some per-
sons have partial control over it.
There is also a longitudinal striation seen in voluntary muscular
fibre, better marked where the transverse striation is somewhat indis-
tinct. After hardening in alcohol, voluntary muscular fibre may be
broken up longitudinally into so-called fibrils. The fibre is not, how-
ever, composed entirely of fibrils, but contains a considerable quantity
of an intermediate substance. After the action of dilute acids or of
gastric juice on muscle, the fibres display a disposition to break up trans-
versely in a direction parallel to the bands, and even into transverse
plates or discs formed by the lateral adhesion of the particles of approx-
imated fibrils. This separation of muscular fibre into discs is only pos-
sible after the coagulation of muscle-plasma or the action of reagents
upon it.
vintag
Muscular fibres also exhibit a number of clear oval nuclei (Fig. 86).
In the muscles of mammals these nuclei are situated upon the under
surface of the sarcolemma. Surrounding these nuclei there is sometimes
a certain amount of granular matter which is derived from the original
primitive embryonic protoplasm.
The nuclei of muscular fibre are not readily seen without the addi-
tion of acetic acid. One or two nucleoli may also be found within each
nucleus.
Mag
164
ANATOMY.
FIG. 86.
Blood-vessels in muscular tissue are extremely numerous. These carry
the material for the nourishment of the tissues and for the chemico-vital
changes which take place within them. When these vessels are filled
with coloring matter, the fleshy part of the muscles
supplied by them is in strong contrast with the tendons.
Arteries, accompanied by veins, enter the muscle at
various points, divide into branches, pass among the
fasciculi, and break up more and more as they extend
into the finer divisions of the muscle. Finally, they
penetrate the smallest fasciculi and terminate in capil-
lary vessels which run between the fibres. They are
supported by the subdivisions of the perimysium, and
supply it with capillaries. The diameter of these is
extremely small, and they form a fine network among
the fibres.

BOLLENUSHENKE
Lymphatics.—It is not known that there are any
lymphatic vessels in the voluntary muscular tissue, but
they are found in great abundance in the connective
tissue of its sheaths and tendons. They have their
commencement in connective tissue, and their office is
Muscular Fibre of a to collect and convey the lymph from the muscular
T48800315
substance and tendons.
fresh in sorum, high-
ly magnified, the sur-
face of the fibre be-
ing focus-
seen on the flat at
ed. The nuclei are
the surface of the
fibre, and in profile
at the edges.
a
The Nerves of the voluntary muscles are of large
size, and their branches pass between the fasciculi, often
uniting to form plexuses, from which smaller nerve-
filaments are given off and form finer plexuses, each
containing not more than two or three dark-bordered
nerve-fibres. Single nerve-fibres pass from these between the fibres of
the muscles, divide into branches, and finally terminate in motor end-
plates, which are situated upon the sarcolemma of the muscular fibres.
Small nerves also accompany the branches of
blood-vessels within the muscle.
FIG. 87.
2
-a
-0
Involuntary Muscular Fibre-
cells from Human Arteries.
Jadid



Involuntary Smooth or Unstriped Muscle.-
Excepting in the heart and a few other organs
of the body, involuntary muscular tissue is un-
2 striated, and its apparent fibres are made up of
elongated contractile cells bound together by a
homogeneous intercellular substance.
Unstriated muscular tissue is composed of con-
tractile fibre-cells (Fig. 87). These cells may
form fibrous bundles or they may be less regu-
larly arranged. They are elongated, and usual-
ly pointed at the ends. They vary greatly in
length in the different organs of the body, and
may bifurcate at one or both extremities. Each
cell has a nucleus, which is either oval or rod-
shaped, and situated, as a rule, centrally.
Involuntary muscle fibre-cells are spindle or
fusiform in shape. The wall or envelope, which
may wrinkle on the contraction of the fibre and produce an indistinct
dalių
AREOLAR TISSUE, TENDONS, AND MUSCLES.
165
appearance of striation, is very delicate and homogeneous. The cells
are united by an intercellular cementing substance. They are closely
packed into fasciculi, which in most cases cross and interlace one with
the other, the spindle-end of the cell fitting in between the bodies of
the other cells. The fasciculi are united at their ends by connective
tissue to the membranous parts, where such parts occur.
Unstriated muscular tissue is largely distributed in the coats of the
arteries, veins, and viscera. It is also found in the ducts of the sweat-
glands of the skin in the form of minute muscles attached to the hair-
follicles, and in the subcutaneous tissue of the scrotum. This tissue is
supplied by numerous nerves from the sympathetic system and abundant
blood-vessels, though these are fewer in proportion than in voluntary
muscular tissue. In the walls of the stomach and intestines numerous
lymphatic vessels are found.
The fibres of the muscular tissue of the heart, however, differ from
those of involuntary muscular organs generally, presenting as they do
transverse striæ. These striæ are, however, less distinct, and the mus-
cle-fibres are smaller in diameter, than those of voluntary muscles. The
fibres are also made up of quadrangular cells joined end to end, each cell
having a single oval nucleus situated near its centre; occasionally two
nuclei are found. The fibres composing this variety of muscle divide
and interlace, though they are not invested by sarcolemma.
VARIETIES OF MUSCLES.-General names have been given to mus-
cles significant of the arrangement of their fasciculi. Thus, when the
fasciculi of a muscle are attached to a central tendon obliquely, like the
feathers of a quill pen, the muscle is called penniform. If the fasciculi
of a muscle converge from a broad surface and are attached to a narrow
tendon, the muscle is called radiated. When the fasciculi of a muscle
are turned or twisted upon themselves the muscle is called a torsion
muscle. If the tendon of a muscle passes through a loop or around a
bony process, and its action is thereby diverted from a straight line with
the longitudinal axis of its body, it is called a pulley or trochlear muscle.
Those situated at the opening of tubes which separate one compartment
from another, and the fasciculi of which form circular bands, are called
sphincter muscles; they generally have no osseous attachment, and their
action is frequently antagonized by others.
Muscles also receive special names according to the regions which they
occupy, their situation in the region, and their origin and insertion.
Thus, the superficial muscles include the subcutaneous muscles, the
panniculus carnosus ; in man the rudiments of this muscle are the
muscles of expression, those moving the ears, and the platysma myoides.
These muscles contain a greater amount of contractile tissue than those
composing the deeper layers.
Muscles yield to pressure produced by tumors, aneurism or abscess,
and the products of inflammation pass with facility throughout their
tissue, generally taking the course of the areolar partitions.
These organs can be increased in size and firmness, by the enlarge-
ment of the individual fibres, through judicious exercise or training, but
they become smaller by an excess of physical activity or deteriorated by
inaction. The complete rest of the parts following fractures and other
166
ANATOMY.
local injuries reduces the size and tonicity of muscles, and this atrophied
condition often remains persistent. Modern surgery, to avoid this and
other pathological sequences, attempts the adjustment and fixation of
the ends of fractured bones with as little loss of muscular exercise as
possible.
THE NUMBER OF MUSCLES.-The whole number of muscles belong-
ing to the voluntary system is about 229: those of the head, 52;
of the neck, 24, exclusive of those belonging to the vertebral column.
The muscles of the head are divided into four groups-those of the
face, auricle, orbit, and of mastication.
The facial muscles (Fig. 88) are subdivided into three sets, named,
according to their location, the fronto-palpebral, the nasal, and the oral.
The fronto-palpebral muscles are the occipito-frontalis, the pyra-
midalis nasi, the orbicularis palpebrarum, and the corrugator supercilii.
The nasal muscles are the compressor nasi, the depressor alæ nasi, the
dilator naris anterior, and the compressor narium minor.
The oral muscles are the orbicularis oris, the levator labii superioris
alæque nasi, the levator labii superioris proprius, the depressor labii
superioris, the zygomaticus minor, the zygomaticus major, the levator
anguli oris, the risorius, the depressor anguli oris, the depressor labii
inferioris, the levator labii inferioris, and the buccinator.
The muscles of the auricle consist of the attolens aurem, the attrahens
aurem, and the retrahens aurem.
The muscles of the orbit are the levator palpebræ, the rectus supe-
rioris, the rectus inferioris, the rectus internus, the rectus externus, the
obliquus superioris, and the obliquus inferioris.
The muscles of mastication are the masseter, the temporalis, the
pterygoideus externus, and the pterygoideus internus.
The muscles of the neck are the platysma myoides, sterno-cleido-
mastoideus, the depressors of the hyoid bone, the muscles of the supra-
hyoid space, those of the pharynx and soft palate, the deep lateral, and
the prevertebrals.
THE FACIAL MUSCLES.
The facial differ markedly from all other voluntary muscles of the
body. In the first place, some of them have no bony origin; none
have bony insertions. That is to say, some of the facial muscles have
but one extremity attached to bone, the other being inserted into mus-
cles; while, again, several have no osseous attachment whatever. Their
fibres are more delicate, and, having no investing sheath of perimysium,
merge one into the other.
The voluntary muscles of the face are not as wholly under the power
of the will as are the voluntary muscles of the limbs, and are often
affected by mental impressions.
The Occipito-frontalis is in reality two muscles divided by an
aponeurosis. These are called the Occipitalis and the Frontalis:
The Occipitalis Muscle is thin and flat, arises from the outer two-
thirds of the superior semicircular line of the occipital bone and the
mastoid portion of the temporal bone above the attachment of the
AREOLAR TISSUE, TENDONS, AND MUSCLES.
167
sterno-cleido-mastoid, passes upward and forward, and terminates in
distinct tendinous fibres, which are continuous with the epicranial or
occipito-frontal aponeurosis.
The Frontalis Muscle is thinner and paler than the occipitalis, and is
more intimately connected with the skin. It arises from the aponeu-
rosis, on a transverse line, between the fronto-parietal suture and the
FIG. 88.

LEVATOR
ANGULI
SUPERIORIS
OBRICULARIS
(BWI
AT
FERIOR Sil
GUMATI
'MASSETER
The Muscles of Expression.
frontal eminences. It is larger than the occipitalis, and arises by two
heads slightly separated from the fibrous epicranial or occipito-frontal
aponeurosis, and passes downward over the forehead. The fibres con-
verge as they descend, the two portions of the muscle uniting just above
the nasal eminence to be inserted into the eyebrows. The central por-
tion of the muscle is continuous with the pyramidalis nasi, while a
large number of its fibres are interlaced with the corrugator supercilii
and orbicularis palpebrarum, and extend outward over the external
angular process of the frontal bone.
The Epicranial or Occipito-frontal Aponeurosis is a fibrous connec-
tive extension of the above muscles, covering the upper portion or
vertex of the skull from side to side, without division. Superiorly, it
is intimately connected with the scalp, though interspaces will be found
filled with granules of fat. So close is this connection that it is
difficult to separate the two by dissection. Between the epicranial
܀
168
ANATOMY.
aponeurosis and the pericranium there is a small amount of loose
connective tissue, which permits easy movement and readily admits of
dissection
Posteriorly, this aponeurosis is attached to the occipitalis muscle, a
portion of the superior semicircular line, and the occipital protuberance.
Anteriorly, it terminates in the frontalis muscle. Laterally, it presents
no distinct marginal termination, but is gradually blended into the
superficial temporal fascia, and affords attachment to the superior and
anterior aural muscles. Its outer surface is closely attached to the
skin by numerous bands of connective tissue.
Action.-By the contraction of the frontalis muscle the eyebrows are
elevated or arched, as in expressing surprise, delight, or doubt. This
elevation of the eyebrows causes the skin to wrinkle over the surface
of the forehead.
By the contraction of the occipitalis muscle the scalp is drawn back-
ward, and by an alternating action of the two muscles the scalp may
be moved forward and backward. Most people have not the power of
moving the scalp in both directions, the motion being limited to an
anterior direction only.
The Pyramidales Nasi are two in number. Their form, as their
name indicates, is pyramidal, and they are formed by the continuation
of the fasciculi from the frontalis muscle. They extend downward on
either side of the nose, widening as they descend, and, becoming ten-
dinous, join the tendinous insertion of the compressor nasi.
Relations. By its upper surface with the skin, and below with the
nasal bones.
The Orbicularis Palpebrarum is a thin sphincteric or elliptical muscle
having a bony attachment. It is closely adherent to the integument
covering the eyelids and surrounding the orbits. It is divided into
three portions-orbital, palpebral, and concentric.
The Orbital or Peripheral Portion arises from the internal angular
process of the frontal bone, the nasal process of the superior maxilla, and
the lachrymal groove. Its fasciculi diverge as they extend, the superior
passing upward and outward over the superior orbital arch toward the
temple, while the inferior pass downward and outward, inosculating with
the superior fibres at the outer portion of the orbit. The orbital por-
tion of the orbicularis palpebrarum is the strongest, while its fibres are
of deeper color than the other two portions. Internally, its fibres are
attached to the tarsal ligament, while next to the nose it has a bony
attachment such as described above. Its superior border is partially
held in position by descending fibres from the frontalis and by the
corrugator supercilii muscles. Its lower and outer margins are free.
The Palpebral Portion arises from the superior and inferior margins
of the tarsal ligament, passes outward over the eyelids, and is inserted
into the outer and lesser tarsal ligaments. This portion is much thinner
and its fibres are paler than the preceding.
The Concentric Ciliary or Inner Portion is somewhat stronger than
that covering the eyelids, and is confined to the margins of the vela.
The inner edges are free.
Relations. By its upper surface with the integument; by its under
AREOLAR TISSUE, TENDONS, AND MUSCLES.
169
surface the orbital portion is in relation with the frontalis and corrugator
supercilii muscles, their fibres interlacing, and with the supraorbital
vessels and nerves, the lachrymal sac, the origin of the levator labii
superioris, alæque nasi, and the levator labii superioris muscles; inter-
nally with the pyramidalis nasi, and externally with the temporal fascia.
The under surface of the palpebral portion of this muscle is connected
to the cartilage of the eyelid by fibrous connective tissue.
"
The Internal Tendo-palpebrarum (tendo-occuli) is a small white
fibrous band about two lines in length and one line in breadth. It is
attached to the nasal process of the superior maxilla in front of the
lachrymal groove, and runs outwardly across the lachrymal sac to the
inner commissure of the eyelids, where it divides into two portions, one
going to each lid. As the tendon crossess the lachrymal sac it gives
off from its under surface a strong aponeurotic lamina which covers the
sac and is attached to the lachrymal bone.
The External Tendo-palpebrarum is much weaker than the internal,
and is attached to the malar bone.
The Tensor Tarsi (Horner's muscle) is a thin layer of fibres arising
from the lachrymal crest behind the lachrymal sac.
It passes forward
and outward, and divides into two fasciculi, which are lost in the con-
centric portion of the orbicularis palpebrarum.
P
M
The Corrugator Supercilii is a small, deeply-colored muscle arising
from the inner extremity of the superciliary ridge, passing outward and
upward, its fibres diverging, some extending into the orbicularis and
frontalis muscles, terminating about the middle of the eyebrow. This
muscle is intimately adherent to the integument.
Relations. By the inner portion of its upper surface with the orbic-
ularis and frontalis muscles, the outer extremities of its fibres being
inserted into these muscles; by its under surface with the frontal bone,
the supratrochlear branches of the ophthalmic nerve and accompanying
vessels.
(The levatores palpebræ will be described with the motor muscles of
the eye.)
Actions.-The orbicular portion of the orbicularis palpebrarum is
wholly under the control of the will. Its upper fibres act by depressing
the eyebrow and drawing down the integument of the forehead, antag-
onizing the frontalis muscle. The lower portion elevates the integu-
ment of the cheek, and both combined wrinkle the skin at the outer and
inner angles of the orbital cavities. The office of this muscle is fully
exerted when the eye is closed with force.
The Palpebral Portion gives the peculiar movement to the eyelids
seen in winking or in sleep. It also draws forward the internal tarsal
ligament and the anterior wall of the lachrymal sac, causing it to open
for the reception of lachrymal fluid.
The Concentric or Ciliary Portion closes in the edges of the vela of
the eyes, and draws the cilia or lashes of the respective lids against each
other.
The Corrugator Supercilii muscle draws the skin over the forehead
downward and inward toward the upper part of the nose, causing the
vertical grooves made in frowning.
170
ANATOMY.
THE NASAL SET of muscles comprises the compressor nares, depres-
sor alæ nasi, and the dilatores nares. These are unimportant muscles,
composed of few fasciculi, and their actions are implied in their names.
FIG. 89.

CORRUGATOR SUPERCILI!
DATOR NARIS ANTER-
D TORNARIS POSTER-
COMERESSOR NARIUM MINOR-
DEPRESSOR ALÆ NASI
PYRAMIDENA
COMPRES
NARL
LEVATOR MENTI-
EYEABII SUP.etA
CORBETO UEL
SAB 9
RBICULARIS
EEV. LABII SUP
SORIS
Akkum
COMATIC MINOR
Portion
•F
CRISORIUS
COMATIC MAJO
ASSETER
C
Superficial
Portion
OCCIPITO
Its Tendinous Aponeurosis
Poral Fascia
ATTRAILENS
AUREM
AT TOLLENS AUF
RNO-CL
MASTON
NUTRA
HENS
UREM
FRONTALI
Watso
KOTELOT
Muscles of the Head, Face, and Neck.
The Compressor Nares is a small triangular muscle arising by its apex
from the inner portion of the canine fossa of the superior maxilla, its
fibres passing inward and upward, gradually expanding into a thin
AREOLAR TISSUE, TENDONS, AND MUSCLES.
171
aponeurosis, uniting with the corresponding muscle of the opposite side
and with the pyramidalis nasi.
The Depressor Ala Nasi are short radiated muscles arising from the
incisive fossæ of the superior maxilla, the fibres passing upward to be
inserted into the integument of the nasal septum and to the alæ of the
nose.
Besides those just described, there are several other muscles, with
irregular and indistinct fasciculi, which assist in enlarging the opening
of the nose. Among these are the compressor narium minor and the
dilatores naris anterior and posterior.
THE ORAL GROUP (Fig. 89) consists of the orbicularis and those
muscles having their insertion into it.
The Orbicularis Oris is a thin layer of muscular fibres, forming the
sphincter of the mouth. It is elliptical in form, its fibres being con-
tinued from one lip to the other around the angles of the oral opening.
It is divided into two portions, labial and facial, the labial or marginal
circle or rim forming the red portion of the lip. The facial or external
portion blends with the muscles which converge toward the mouth,
its fibres being inserted into them, and acting antagonistically to them.
The portion of this muscle corresponding to the upper lip is composed
of four slips of muscular fibres, two situated on each side of the cen-
tral portion. The outer slips are thin and weak, pass downward, and
are attached to the superior maxilla in the incisor fossa below the ori-
gin of the depressor alæ nasi. The inner two slips, thicker and stronger,
pass upward, and are inserted into the septum of the nose. At the
median line the space between these slips corresponds to the perpendic-
ular groove on the lip immediately below the nose. The two fasciculi
of the lower lip arise in the incisor fossa of the inferior maxilla exter-
nal to the levator labii inferioris. They pass upward and outward
toward the angles of the mouth, their fibres interlacing with the other
muscles of the lip.
Relations. By the inner margin of the superficial surface it is closely
connected with the integument, whilst superimposed between the outer
portion and the integument is a layer of fatty tissue; by its deep surface
with the mucous membrane, labial glands, and coronary arch of vessels
of each lip. Its internal circumference is immediately beneath the integu-
ment, and forms the free margins of the lips, whilst the outer circum-
ference is blended with the several muscles that converge from various
portions of the face to this point or muscle.
The Levator Labii Superioris Alaque Nasi is a thin triangular muscle
situated along the side of the nose, extending from the inner angle of
the orbital cavity to the upper lip. It arises by a pointed extension
from the upper and outer part of the nasal process of the superior
maxilla, passes downward and outward, and divides into two portions.
The smaller of these is inserted into the ala of the nose, the other being
prolonged downward and blending with the orbicularis oris and the
special elevator muscle of the upper lip.
Relations. By its superficial surface superiorly with the orbicularis
palpebrarum, and below with the integument.
The Levator Labii Superioris Proprius is the special elevator muscle
Ka
C
•
172
ANATOMY.
of the upper lip. It is thin and quadrilateral in outline, arising imme-
diately below the orbital cavity above the infraorbital foramen. Its
origin is chiefly confined to the superior maxilla, but a few of its fibres
extend from the malar bone. It passes downward and inward to be
inserted into the orbicularis oris and the integument of the superior lip.
It is situated on the same general plane as the levator labii superioris
alæque nasi, and is connected with it throughout its lower third.
Relations. By its superficial surface with the orbicularis palpebrarum
and the integument; by its inner surface with the infraorbital nerve
and its accompanying vessels as they emerge from the infraorbital fora-
men, a portion of the levator anguli oris, and the origin of the com-
pressor nasi muscle.
The Depressor Labii Superioris is a small muscle arising from the
lower portion of the incisive fossa of the superior maxilla and the
alveolar process immediately below the fossa. Its fibres pass npward
to the lower border of the nostrils and the partition of the nose. A
portion of the fibres of this muscle are attached to the integument cov-
ering the wing of the nose; the balance pass downward and are inoscu-
lated with the fibres of the muscles of the upper lip. It, with its fellow
and the mucous membrane, forms the frænum of the upper lip, and when
the alveolar process is absorbed after the loss of the teeth, it is often found
attached on the lower margin of the gum.
Relations. Within the vestibule of the mouth it is covered by mucous
membrane; above that portion it is covered with the muscles of the
upper lip; its deep surface rests upon the bone, and the median border
joins with its fellow of the opposite side.
The Zygomaticus Minor is an extremely slender muscle arising from
the anterior inferior portion of the malar bone, just behind the malo-
maxillary suture. It passes downward and forward, its fibres becom-
ing lost in those of the special elevator muscle of the upper lip near the
angle of the mouth.
Relations.-By its superficial surface with the orbicularis palpebrarum
and the integument; by its deep surface with the levator anguli oris.
The Zygomaticus Major is situated just external to the smaller muscle
of the same name. It arises from the malar bone in close proximity to
the zygomatic suture, and passes obliquely downward to the angle of the
mouth, where it is attached to the integument and becomes blended with
the fibres of the orbicularis oris and depressor anguli oris muscles.
Relations. By its superficial surface with the subcutaneous adipose
tissue; by its deep surface with the malar bone and the masseter and
buccinator muscles.
C
--
Variations. The zygomaticus minor is often absent, and occasionally
its fibres are lost in the integument before reaching the muscle of the lip.
At times also it arises in part or entirely from the orbicularis palpebra-
rum muscle, and is blended with the zygomaticus major and the levator
labii superioris. Occasionally it is separated into two muscles. The
zygomaticus major is also occasionally wanting, or it may be double,
and arises at times from the masseteric fascia.
The Levator Anguli Oris (canine muscle) arises from the canine fossa
immediately below the infraorbital foramen. It passes downward and
AREOLAR TISSUE, TENDONS, AND MUSCLES.
173
slightly outward to its insertion at the angle of the mouth. In this
position its fibres become blended with those of the orbicularis oris,
zygomaticus major and minor, and depressor anguli oris muscles.
Relations. Its upper surface is in relation with the special elevator
muscle of the upper lip, the infraorbital nerve, and vessels passing
between these two muscles. At the point of its insertion it is inti-
mately adherent to the integument; by its deep surface with the
superior maxillary bone, the buccinator muscle, and the mucous mem-
brane of the mouth.
The Risorius (smiling muscle), when present, consists of a few thin
fasciculi which arise from the deep fascia covering the masseter muscle
or the parotid gland, and occasionally as far back as the mastoid pro-
cess of the temporal bone. From this point it passes transversely for-
ward and inward, its fibres becoming blended with those of the depressor
anguli oris and the orbicularis oris at the angle of the mouth.
The Depressor Anguli Oris (triangularis menti) is a triangular mus-
cle arising by its base from the external oblique line of the inferior
maxilla, becoming narrow as it ascends to the angle of the mouth,
where its fibres become blended with the orbicularis oris and the
other muscles of this region.
Relations. By its superficial surface with the integument; by its
deep surface with the buccinator and depressor muscles of the lip.
The Depressor Labii Inferioris (quadratus menti) is quadrilateral in
shape, and arises from the inferior maxilla by a line of attachment extend-
ing from near the symphysis to a point a little posterior to the mental
foramen. Its fibres pass upward and inward, uniting with its fellow of
the opposite side and blending with the fibres of the orbicularis oris. It
is continuous below with the platysma myoides, and above it is inserted
into the integument. Between the fibres of this muscle will be found a
considerable quantity of adipose tissue.
Relations. By its superficial surface with a portion of the depressor
anguli oris and the integument, with which it is intimately connected;
by its deep surface with the mental nerve and vessels, the mucous mem-
brane lining the lower lip, the labial glands, and the elevator muscle of
the lower lip.
The Levator Labii Inferioris (levator menti) can be best exposed by
everting the lower lip and removing the mucous membrane.
It is a
small conical fasciculus arising from the upper portion of the incisor
fossa of the inferior maxilla, its fibres radiating as they pass downward
between the depressors of the lower lip to be inserted into the integu-
ment covering the chin.
Relations. By its superficial surface with the mucous membrane of
the vestibule of the mouth, with the lower margin of the orbicularis
oris and the integument covering the chin; by its deep surface with the
bone and the depressor muscle of the lower lip, and on its median bor-
der with its fellow of the opposite side.
The Buccinator is a thin and flat though powerful muscle situated
between the upper and lower jaws, and forming a considerable portion
of the wall of the vestibule of the mouth. Correctly speaking, it is not
a true facial muscle, belonging more properly to the pharyngeal con-
G
174
ANATOMY.
strictor muscles, being advanced forward into the face. It also differs
from the facial muscles by being enclosed in a sheath of thin fascia, and
is supplied by a different motor nerve. It arises from the lower margin
of the outer surface of the alveolar processes of the superior and inferior
maxillary bones opposite the molar teeth, from the anterior surface of
the pterygo-maxillary ligament, which is a narrow band of tendinous
fibres extending from the upper extremity of the hamular process
of the internal pterygoid plate of the sphenoid bone to the mylo-hyoid
ridge of the inferior maxillary bone, close to the position of the wisdom
tooth. From this extensive origin its fibres pass forward, converge,
and become thickened as they reach the lateral margin of the orbicularis
oris. At this point its central fibres decussate, those from the upper
portion becoming blended with the muscles of the lower lip, and those
from the lower portion blending with the muscles of the upper lip. The
superior and inferior fibres of the muscle continue forward without
decussation, inosculating with the superficial fibres of the orbicularis
oris, becoming lost on the opposite side of the mouth.
Relations. By its superficial surface with a considerable quantity
of soft adipose tissue, which separates it from behind forward from the
ramus of the jaw, a small part of the temporal muscle, the masseter
muscle, the muscles of expression connected with the angle of the
mouth, the parotid duct, which pierces the muscle opposite the second
molar tooth of the upper jaw, and the facial artery and vein; branches
of the facial and buccal nerves pass over it. By its deep surface it is in
relation with the buccal glands and mucous membrane of the vestibule
of the mouth.
ACTIONS OF THE ORAL MUSCLES.-When the whole of the orbicu-
laris oris muscle is brought into independent action, it closes the lips
both vertically and transversely, and when a forced action is brought
about, it projects the lips and wrinkles the integuments; when acting
jointly with the buccinator, the lips are closed and elongated trans-
versely. When the associated muscles which converge from nearly all
points act singly, they draw the orbicularis oris in the longitudinal direc-
tion of their fibres. When two or more muscles act together, the line of
traction will be between these muscles, the direction depending upon the
relative power of each muscle.
The common elevators of the lip and nose and the depressors of the
wing of the nose act upon these parts in opposition to each other, the
former elevating, the latter depressing. The muscles which are inserted
at the angles of the mouth not only elevate and draw the angle back-
ward, but in doing so they push the cheeks upward and thus elevate the
margin of the lower eyelid, as is shown by the expression of the mouth
and cheeks in merriment; while those which depress the angles also-
depress the cheeks, as illustrated by the face in grief.
THE MUSCLES OF THE EAR.
The auricular muscles are those that belong to the pinna of the ear.
There are several minute bundles of muscular fibres which extend from
one point to another in the pinna; also three larger muscles, two aris-
AREOLAR TISSUE, TENDONS, AND MUSCLES.
175
ing from the temporal aponeurosis, the other from the mastoid process
of the temporal bone and inserted in the pinna: they are named the
attolens aurem, the attrahens aurem, and the retrahens aurem. They
are only slightly developed in man.
The Attolens Aurem, or Auricularis Superior, is the largest of the three.
It is fan-shaped, arising by a broad head from the superficial fascia over
the temporal muscle, and is inserted into the anterior part of the helix
and the eminence upon the inner surface of the pinna. Its fibres are
extremely delicate; it is furnished with branches from the occipital
nerve.
The Attrahens Aurem, or Auricularis Anterior, is the smallest of the
three; it is thin, fan-shaped, and its fibres are pale and indistinct, aris-
ing from the superficial fascia over the temporal muscle, and are inserted
into the tragus. The nerve supplying it is derived from the facial and
the auriculo-temporal branch of the inferior maxillary.
The Retrahens Aurem, or Auricularis Posterior, is stouter than the
other two, and is composed of two or three fasciculi. The fibres are
deeper in color and distinctly marked. It arises from the mastoid por-
tion of the temporal bone; passing forward, it narrows slightly and is
inserted into the posterior aspect of the concha. The nerve-supply is
derived from the posterior auricular branch of the facial.
MUSCULAR ACTION.-With few exceptions man has no power to move
ears; therefore the muscular action is of little or no consequence.
the
MUSCLES OF THE ORBIT.
The muscles of the orbit (Figs 90 and 91) are seven in number-six
belonging to the movement of the eyeball: one is the elevator of the
FIG. 90.

Greater
Wing
Wesser
Wing
Sphenoid
no
Lear
Lower Head
TUMBUKA
ZATOR PALPEBRA SUPER.
»pond5.XXMKA NA KUKUKELET
ZAUPERIOR "OPLIODE
LINKAS MENANAMAMUJALITIJAT
QUART
OHJAUS
HELLY
INTERNAL7
FRECTUS
INFERIOR
Am
EXTERNAL RECTUS
CUS
erotic
"
2
O
tilag
Muscles of the Right Orbit.
upper lid.
With one exception, the seven muscles arise from the back
part of the orbit, passing forward to their insertions. The other, the
176
ANATOMY.
inferior oblique, arises from the floor of the anterior portion of the
orbit. They are named as follows:
The Levator Palpebræ,
The Superior Rectus,
The Inferior Rectus,
The External Rectus,
The Internal Rectus,
The Superior Oblique,
The Inferior Oblique.
The Levator Palpebra is thin, flat, and triangular in shape. It arises
by a narrow ribbon-like band from the under surface of the lesser wing
FIG. 91.
Rectus Superior
Levator
Palpebra Superior
Obliques Superior,
Lesser
Rectus
Internus
Wing
Straight muscles of the eye.
Relations.-Between the muscle and
the roof of the orbit are situated the
frontal nerve (branch of the ophthal-
mic or first division of the fifth), the
fourth nerve, and the supraorbital ves-
sels. Below it is the superior rectus
and the globe of the eye where it joins
the lid; it is situated behind the pal-
pebral ligament, and its deep surface rests on the conjunctiva. A small
branch of the third nerve controls its action and enters its under sur-
face.
Optic
foramen
of the sphenoid bone above and in
front of the optic foramen. It passes
forward over the eyeball, expanding
as it does so, and is inserted in the
fibrous tissue on the anterior surface
of the superior tarsal cartilage.

Its Upper Head
Lower Head
Rectus Inferior
The Relative Position and Attachment of the
Muscles of the Left Eyeball.
M
The Four Recti or Straight Muscles of the eye are straight, flattened
bands which arise from the borders of the optic foramen; they then
pass forward, as their names indicate, to be inserted into the sclerotic
coat three or four lines from the cornea. With the exception of the
superior rectus they may be said to have one common origin, which is
in the form of an oval ring, the ligament of Zinn, which commences
above, passing downward on the inner side to the lower margin of the
optic foramen, thence transversely across the anterior lacerated foramen,
where it is attached to the great wing of the sphenoid bone; from this
it passes again to the lesser wing on the outer side of the optic foramen.
The Superior Rectus is the weakest of the four straight muscles. It
has its origin between the levator palpebræ and the ring or ligament
of Zinn, some of its fibres having their origin in the ring.
The Inferior Rectus principally arises from the ligament of Zinn on
the inner margin of the anterior lacerated foramen.
The Internal Rectus arises from the ligament of Zinn on the inner
and lower margin of the optic foramen.
The External Rectus is the strongest muscle of its group. It usually
arises by two heads. The lower head is the stronger, and arises from the
ligament of Zinn and a spine on the lower margin of the anterior lace-
rated foramen, and also joins the inferior rectus muscle at its origin. The
upper head is the weaker, and arises between the anterior lacerated and
→
AREOLAR TISSUE, TENDONS, AND MUSCLES.
177
optic foramina. Fibres are given off from the two heads of the muscle,
forming a tendinous arch over the foramen, through which pass the
third, the nasal branch of the fifth, and the sixth nerves, also the
ophthalmic vein.
The Superior Oblique, or Trochlearis, is a narrow elongated muscle
situated at the upper and inner part of the orbit, internal to the levator
palpebræ. It arises close to and in front of the inner margin of the
optic foramen. It extends forward to the upper and inner angle of the
orbit, where it becomes tendinous as it passes through a fibro-cartilagi-
nous ring or pulley (trochlea) attached to the trochlear fossa or process,
near the internal angular process of the frontal bone. The contiguous
surface of the tendon and ring is lined by a delicate synovial membrane
enclosed in a thin fibrous sheath. After the tendon passes through the
ring it resumes its fleshy appearance; it is deflected backward, outward,
and downward, and passes between the eye and the superior rectus, to
be inserted into the sclerotic coat, a little beyond the outer margin of
that muscle and midway between the cornea and the entrance of the
optic nerve.
The Inferior Oblique is a thin, narrow muscle situated near the ante-
rior margin of the orbit and close to the outside of the orifice of the
lachrymal duct. It arises from a slight depression in the orbital plate
of the superior maxillary bone near the lachrymal canal, from which it
passes outward, backward, and upward between the inferior rectus and
the floor of the orbit, and between the external rectus and the eyeball,
terminating in a tendinous expansion which is inserted into the sclerotic
coat between the external and superior recti muscles near to the insertion
of the superior oblique.
ACTIONS OF THE ORBITAL MUSCLES.-The Levator Palpebræ Supe-
rioris is the elevator of the upper eyelid, being antagonized by the upper
palpebral part of the orbicularis muscle, which is the closer of the eye.
The eyeball is so suspended within the orbit that it is easily moved
upon a fixed axis, but does not apparently change its position as a whole,
nor do the actions of the muscles make any distinct alteration in its
form. The fixed axis upon which the eye moves is nearly in the centre
of the curvature of the posterior wall, and a little back of the middle
of the antero-posterior axis of the eyeball.
The movement of the eye is best classified in four actions: (a) lateral
movement (in and out): the inward motion is caused by the action of
the internal rectus, the outward by the action of the external rectus;
(b) perpendicular movement (up and down), the upward motion being
caused by the superior rectus, and the downward by the inferior rectus
muscles; (c) rotary movement, caused by the oblique muscles: the
superior oblique rotates the eye inward, and at the same time turns it
downward; the inferior oblique turns it outward and upward. The
rotary movement of the eyeball is required when looking at an object
with the head inclined to either side, in order that the vision may
fall equally upon the retina of each eye. (d) Is a movement in which
two or more muscles act together; for example, if the external and
superior rectus muscles are acting with equal power, the eyeball will be
directed in a line between the insertions of these muscles. It is by this
VOL. I.-12
178
ANATOMY.
12
co-ordination of movement that the muscles of the orbit cause the eye-
ball to move in the desired direction.
Fascia of the Orbit. The orbital space that is not occupied by the
eyeball, muscles, vessels, nerves, ganglia, and glands is filled up with
a soft cushion of fat and delicate yielding connective tissue. The
Capsule or Fascia of Tenon is formed from this connective tissue. It
is a thin membrane surrounding the greater part of the eyeball, and
forms a socket for the globe to turn in. It arises from the borders of
the orbit, passing behind the conjunctiva and giving it support, thence
backward over the eyeball to the entrance of the optic nerve. The
capsule is pierced behind by the optic nerve and the ciliary vessels and
nerves. The tendons of the muscles of the eyeball also perforate it
near their insertions, and it sends tubular prolongations over each
muscle, these extensions gradually taking the appearance of simple
areolar investment, except in the case of the superior oblique, to which
it forms a sheath as far as the pulley of that muscle.
The sheaths of the recti muscles send prolongations from their outer
surfaces to be attached to the outer margins of the orbits, which pre-
vent too great contractions of the muscles. The prolongations from
the inner and outer recti are stronger than those from the others, this
being especially so with the external recti, which are attached to the
malar bone and external tarsal ligament; the inner expansion is fixed
to the crest of the lachrymal bone, and the upper one connected with
the tendon of the levator palpebræ, thus enabling the superior rectus to
have an influence in the movement of the eyelid.
A
salamat
The inner surface of the capsule is connected with the eye by delicate
bundles of yielding connective tissue, allowing a large lymph-space to
exist between the capsule and the eye, which appears to act as a synovial
membrane in the movements of the globe.
The movements of the eye and its lids are to a certain extent governed
by the sympathetic nerves supplying the involuntary (non-striated)
muscular fibres which are found interspersed among the voluntary
muscles of this region.
Nerves. The levator palpebre, inferior oblique, and all the recti
muscles are supplied by the third nerve (motor oculi), the superior.
oblique by the fourth, and the external rectus by the sixth nerve.
MUSCLES OF MASTICATION.
The Masseter, the Temporal, the Internal Pterygoid, and the External
Pterygoid are generally classed as the muscles of mastication, leading
the student to infer that they are the only ones brought into action in
the process. This is not correct; the first three act in closing the jaws
together, while the fourth protrudes the lower jaw beyond the upper,
none of them having power to open the mouth, although with the head
erect the relaxation of the masseter, temporal, and internal pterygoid per-
mits the lower jaw to drop by gravitation. The muscles of the neck
open the mouth when the head is thrown backward. The mouth is
rigidly closed during the tonic spasm of the first-named muscles, as in
locked jaw or trismus.
AREOLAR TISSUE, TENDONS, AND MUSCLES.
179
The Masseter is a stout, thick, short, quadrilateral muscle extending
from the zygomatic arch to the inferior maxillary bone. It is composed
of two portions, superficial and deep, which differ in size and direction.
The Superficial Portion is the largest and strongest, and arises by a
thick tendinous aponeurosis (which passes downward into the muscular
fasciculi) from the lower border of the anterior two-thirds of the zygo-
matic arch and the lower margin of the malar bone: extending down-
ward and backward, it is inserted into the lower and outer half of the
angle of the jaw.
The Deep Portion is of triangular form; it is smaller and its muscu-
lar fibres are shorter than those of the superficial portion. It arises
from the posterior third of the lower border and from all the internal
surface of the zygomatic arch; passing downward and slightly forward,
it joins some of the superficial portion, and is inserted by a tendinous
aponeurosis into the upper half of the ramus and outer surface of the
coronoid process of the lower jaw; only the upper and back part of the
muscle is left uncovered by the superficial portion.
Relations.—It is principally covered by the skin and the fascia or
platysma myoides and its own fascia, which latter adheres intimately to
the tendon at its origin; at the back portion the parotid gland, the duct,
which lies across the muscle, and at the anterior border turns inward,
pierces the buccinator muscle and opens into the mouth through a little
teat-like projection of the mucous membrane: the upper portion of the
masseter muscle is overlaid by the orbicularis palpebrarum and zygo-
matic. A few branches of the facial nerve (seventh) and the transverse
facial vessels pass over it.
The muscle lies in contact below with the ramus of the jaw and the
buccinator muscle. Between the two muscles there is a large quantity of
delicate fat covering a nerve and vessels which enter the muscle through
the sigmoid notch.
Artery.-The Masseteric Artery, a branch from the second division of
the internal maxillary, conveys the blood-supply.
Nerve. The masseteric branch of the inferior maxillary (third divis-
ion of the fifth).
The Temporal Fascia is a dense glistening layer of fibres forming
an aponeurosis covering the temporal muscle above the zygoma, and
giving origin to its superficial portion. The fascia is attached supe-
riorly to the temporal crest of the frontal bone and to the upper of the
two curved lines on the parietal bone, extending as far back as the
parieto-occipito-temporal junction. It is thin and weak at its origin,
becoming thicker and stronger as it approaches the zygomatic arch,
near which it divides into two layers, these being separated by a quan-
tity of compact adipose tissue; these layers are attached respectively to
the inner and outer margins of the superior border of the zygomatic
arch. The fascia is separated from the skin by a thin membrane which
descends from the epicranial aponeurosis, and by the auricular muscles
also by some adipose tissue at the lower portion. If an abscess should
form beneath this fascia or within the muscle, the pus would be directed
to the coronoid process of the inferior maxilla, and thence into the mouth
along the adipose tissue of this region.
;
J
180
ANATOMY.
The Temporal Muscle (Fig. 92) is a radiating or fan-shaped muscle
situated in the temporal fossa and descending to the coronoid process of
the inferior maxillary bone. It is composed of a superficial and a deep
portion.
The Superficial Portion is thin and delicate, arising from the temporal
fossa or aponeurosis; its fibres are continuous above with those of the
FIG. 92.

Frontal
///////
Malar
HAR
Coronoid
proc.
ހހގހރހހހ
Lower Jo
M
**
P
Parietal
JA.
T
The Temporal Muscle, the zygoma and masseter having been removed.
deep portion, but are gradually lost below in the deep layer of the mas-
seter muscle.
The Deep Portion is thick and powerful; its anterior fibres are
almost vertical, while those behind pass obliquely forward. The mus-
cle arises by fleshy fibres from all the surface of the temporal fossa
The
except the anterior or that portion known as the orbital septum.
fibres gradually converge as they descend to form a central tendon,
which is inserted chiefly into the inner surface of the coronoid process
of the lower jaw.
Relations.-Its superficial surface is covered by the temporal fascia ;
the lower and anterior part is imbedded in fat which is a continuation
of that which lies between the masseter and buccinator muscles. The
upper part of its deep surface rests upon the bone; the deep temporal
arteries and nerves which supply the muscle pass between the muscle
and the bone; in its lower portion it is in relation with the external
pterygoid and part of the buccinator, the internal maxillary artery, and
temporal nerves.
Arteries. It is supplied by the superficial temporal branches of the
external carotid and the deep temporal arteries, branches of the internal
maxillary.
AREOLAR TISSUE, TENDONS, AND MUSCLES.
181
Nerves.—Its supply is from branches of the inferior maxillary nerve.
The Internal Pterygoid (Fig. 93) is a thick quadrilateral muscle of
coarse structure, interspersed with stout bands of fibrous tissue, extend-
ing from the pterygoid fossa to the inner angle of the jaw. It arises
principally in the pterygoid fossa from the inner surface of the external
pterygoid plate and from part of the tuberosity of the palate bone within
the fossa; it also has a smaller muscular strip from the external portion
of the tuberosity of the palate bone and the tuberosity of the superior
maxillary bone. It passes backward, downward, and outward, and is
inserted into the roughened portion on the inner side of the ramus of
the jaws between the angle and the posterior dental foramen.
"The internal pterygoid muscle is an important factor in maintain-
ing false ankylosis of the temporo-maxillary joint. After the division
FIG. 93.

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Lower
Great Wing
of
Sphenoid
////////////2
Ja w
Upper Head
Lower Head
Bon dy
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Angle
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The Pterygoid Muscle: the zygomatic arch and a portion of the ramus of the jaw have been removed.
of the anterior border of the masseter muscle this condition may persist,
but the ankylosis readily yields to the division of the internal pterygoid"
(Allen).
Relations.-The muscle is situated on the inside of the ramus of the
jaw, somewhat in the same manner as the masseter is on the outside.
Between its outer or lateral surface and the ramus of the jaws are the
accessory lateral ligament of the temporo-maxillary articulation, the
internal maxillary vessels, and the inferior dental artery and nerve; at
its upper part it is crossed by the external pterygoid muscle. Its inner
or median surface is related to the tensor palati and superior constrictor
of the pharynx, though there is a quantity of areolar tissue between the
constrictor and the internal pterygoid muscles.
Arteries.-The internal pterygoid is supplied by branches from the
second division of the internal maxillary artery.
182
ANATOMY.
Nerves.-Branches from the inferior maxillary division of the fifth.
The External Pterygoid is a short, thick, conical muscle, extending
almost horizontally from the under surface of the great wing and the
pterygoid process of the sphenoid bone to the condyle of the inferior
maxilla and the interfibro-articulating cartilage of the temporo-maxil-
lary articulation. It arises by two fleshy heads placed close together,
an inferior and a superior.
The Superior Head arises from the zygomatic surface of the great
wing of the sphenoid bone and the infratemporal ridge (pterygoid ridge)
which separates the temporal and zygomatic fossæ.
The Inferior Head is the larger of the two, and arises from the outer
surface of the external plate of the pterygoid process and the tuberosity
of the palate and the superior maxillary bones.
The two heads soon unite, forming a short, stout muscle passing back-
ward and outward almost horizontally to be inserted by two portions,
superior and inferior.
The Superior Portion is inserted into the anterior portion of the inter-
articular fibro-cartilage of the temporo-maxillary articulation.
The Lower or Inferior Portion is attached to the depression on the
anterior surface of the neck of the lower jaw.
Relations. On its outer surface the internal maxillary artery is
usually situated, passing between its two heads of origin: the buccal
nerves also come out between them. The ramus of the jaws and the
tendon of the temporal muscle are in relation with the outer surface.
The deep surface rests upon the upper part of the internal pterygoid
and the internal lateral ligament, the inferior maxillary nerve and mid-
dle meningeal artery. The superior border is crossed by the temporal
and masseteric branches of the inferior maxillary nerve.
Arteries. The muscle is supplied by a branch from the middle or
second division of the internal maxillary.
Nerve.-Branch of the inferior maxillary (third division of the fifth).
Variations. The external pterygoid sometimes receives a slip from
the temporal muscle.
The Pterygoideus Proprius (Henle), not constant, is a longitudinal
cleavage of the upper portion of the external pterygoid, forming a band
of muscular and tendinous fibres, sometimes entirely tendinous, extend-
ing from the infratemporal crest over the external pterygoid muscle to
the lower and outer portion of the external pterygoid plate, or to the
tuberosities of the palate and superior maxillary bones. Occasionally
it sends a slip to the pterygo-maxillary ligament or to the lower jaw.
The Pterygo-spinosus is a muscular strip occasionally found extend-
ing from the spine of the sphenoid bone to the posterior margin of the
external plate of the pterygoid process, between the two pterygoid mus-
cles. Sometimes this is replaced by a ligament, or even bone, leaving a
large foramen between the pterygoid and zygomatic fossa.
ACTION OF THE MUSCLES OF MASTICATION.-With the exception
of the external pterygoid, these muscles act as elevators of the inferior
maxillary bone, and bring the teeth of the lower jaw forcibly into con-
tact with the upper; the muscles which antagonize them (those which
open the mouth) are of much less strength.
-
AREOLAR TISSUE, TENDONS, AND MUSCLES.
183
The external pterygoid, having its fibres directed backward, and
nearly all of them horizontally, draws the condyle forward and brings
the interarticular fibro-cartilage upon the eminentia articularis; when
the muscles of both sides act in unison, they cause the lower jaw to pro-
ject. Their action is usually alternate, causing a sort of oscillating or
grinding motion of the molar teeth. The superficial portion of the mas-
seter acts in conjunction with the external pterygoid muscle in drawing
the jaw forward, while the posterior fibres of the temporal antagonize it,
drawing the jaw backward, thus acting for the trituration of the food.
THE MUSCLES OF THE NECK.
The Platysma Myoides lies immediately below the skin on the side
of the neck. It is a broad, thin, quadrangular, pale-colored sheet
of muscular fibres, superficial to the deep cervical fascia, extending
over the front and sides of the neck and the lower portion of the
face. It arises by thin bands from the subcutaneous connective tissue
over the deltoid, pectoral, and trapezius muscles: the fibres are directed
obliquely upward and forward over the clavicle and acromion process
to the side of the neck, gradually converging and approaching its fellow
of the opposite side, the most anterior fibres crossing over and inter-
lacing with each other in front of and below the chin. The greater
number of fibres are inserted in the outer surface of the lower jaw,
below the external oblique line anterior to the masseter muscle; others
pass upward to the lower lip and angle of the mouth; while others are
lost in the muscles of expression and the areolar connective tissue of
the face.
Variations.-The platysma myoides of man is the rudiment of the
panniculus carnosus, or great subcutaneous muscle, of quadrupeds; this
may explain its many variations in the human subject. Sometimes the
fibres extend upon the face and downward on the neck, shoulder, and
breast farther than usual, occasionally having attachment to the clavicle,
and also give off slips which pass from one muscle of expression to
another. The upper part of the muscle is occasionally joined by a slip
from the occipital bone or the mastoid process of the temporal; more
rarely it is absent on one or both sides.
Vessels.-The numerous superficial branchings of the region.
Nerves.-The platysma myoides receives its principal nerves of motion
from the descending branches of the facial; it is also influenced by
some of the spinal nerves.
Relations.—Above with the skin, to which it is closely united, espe-
cially in its lower portion; by its internal surface with the pectoralis
major, deltoid, trapezius, and the clavicle; in the neck with the deep
cervical fascia, between which and the muscle passes the superficial
cervical plexus of nerves, the external jugular vein and its tributaries,
and the anterior jugular vein. In the supra-hyoid region the facial
artery lies underneath it, separated by the deep cervical fascia; all
the superficial cervical lymphatics, sterno-cleido-mastoideus, omo-hyoid,
sterno-hyoid, and diagastric muscles are under it.
Actions. The platysma elevates the skin of the breast and shoulder,
M
184
ANATOMY.
and when these parts are fixed it draws the angle of the mouth down-
ward and outward. The muscle is brought into use in the act of
deglutition, and also acts during sudden fright.
The Sterno-cleido-mastoideus (Fig. 94) is a long, strong muscle, extend-
ing obliquely across the neck, from the mastoid process of the temporal
bone to the sternum and clavicle. It divides the surgical square of the
neck into two great triangles, anterior and posterior, and is ensheathed
FIG. 94.
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Cervical Fascia
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CLOSSUS
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STERNO - HYOID
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Muscles of the Neck, anterior view.
by two layers of the deep cervical fascia. It arises by two heads, the
sternal and the clavicular.
The Sternal Head is thick and rounded, tendinous in front, fleshy
behind, arising from the superior and outer part of the manubrium of
the sternum.
The Clavicular Head is flat, and is composed of fleshy and tendinous
fibres; arising from the inner third of the superior border of the clavicle,
it passes almost directly upward. The triangular space between the
two heads is filled up by areolar tissue. The two divisions gradually
unite midway in the neck, forming a thick round prominent muscle,
which extends upward and backward, and is inserted by short and
strong tendinous fibres into the external surface of the mastoid process,
commencing at its apex and extending upward and backward along the
superior curved line of the occipital bone, or semicircular line of the
AREOLAR TISSUE, TENDONS, AND MUSCLES.
185
base of the skull, terminating in a thin aponeurosis where it is attached
to the outer two-thirds of the line.
Relations.—Its middle three-fifths are covered superficially by the
platysma myoides, the remainder by the integument, and it is crossed
by the external jugular vein and the superficial branches of the cervical
plexus. Its deep surface passes over the sterno-hyoid, sterno-thyroid,
omo-hyoid, the posterior belly of the digastric, levator anguli scapulæ,
the splenius, and the scaleni muscles; also the cervical plexus, the
occipital artery, and a part of the parotid gland.
The common carotid artery, the internal jugular vein, and the pneu-
mogastric nerve enclosed in their sheath, descendens noni, and "com-
municaris noni nerves, pass under its anterior border, and the spinal
accessory nerve pierces its upper third.
Nerves.—The muscle is supplied by the deep cervical plexus and the
spinal accessory nerves.
Wha
May
Variations. The muscle is sometimes divided longitudinally into
two portions, called the sterno-mastoid and cleido-mastoid; they are
not infrequently described as separate muscles. Part of the muscle is
sometimes attached to the lower jaw; this condition is normal in the
bone. Besides this, it has many other varieties (see Quain and Allen).
Action.-When both muscles are acting together, the head is brought
forward, as in nodding; when extreme action is brought about, the
head is drawn upon the neck and the neck upon the chest. When
either muscle acts singly, especially when combined with the splenius,
the head is drawn toward the shoulder of the same side, the face being
rotated toward the opposite side. In the condition known as wry neck
or torticollis, the muscle on one side is rigidly contracted, or the opposite
muscle is paralyzed. When the head is fixed, these muscles become
accessory muscles of respiration by assisting in the elevation of the
thorax; it also serves to fix the clavicle, and in animals where the
clavicle is lacking the muscles assist in the elevation of the arms, as
their fibres are continued into the clavicular portion of the pectoralis
major and the deltoid.
The Infra-hyoid Muscles.-The depressors of the hyoid bone and the
larynx are the sterno-hyoid, the sterno-thyroid, the thyro-hyoid, and
the omo-hyoid.
The Sterno-hyoid is a thin, flat band of longitudinal fibres, arising
inconstantly from the upper and posterior portion of the sternum and
the posterior sterno-clavicular ligament; from that ligament and the
clavicle, or from the clavicle alone; and occasionally it partially arises
from the cartilage of the first rib. The fibres pass upward, and are
inserted into the body of the hyoid bone near the inner side of the omo-
hyoid muscle.
S
Relations. Its superficial surface below is covered by the sternum
and sternal end of the clavicle, and by the sterno-cleido-mastoid and
the platysma myoides muscles above. Its deep surface passes over the
sterno-thyroid, crico-thyroid, and thyro-hyoid muscles, and in part the
thyroid gland, the superior thyroid vessel, and the crico-thyroid and
thyro-hyoid membranes. The mesial borders of the two muscles vary
in
their proximity at the upper third there is a slight interval; in the middle
C
186
ANATOMY.
third they approach each other, and are again separated as they near the
clavicle. Close to the hyoid bone the outer margin is in contact with
the omo-hyoid muscle.
Action.-To depress the hyoid bone.
The Sterno-thyroid muscle is shorter and broader than the sterno-
hyoid, and is under that muscle. It arises near its fellow of the oppo-
site side from the posterior surface of the manubrium (first bone of the
sternum), below and nearer the median line than the origin of the
sterno-hyoid muscle, and inconstantly from the first and second costal
cartilages. It ascends, and, diverging from its fellow of the opposite
side, is inserted into the oblique line on the ala of the thyroid cartilage.
Relations.-Its superficial surface is in contact with the sternum,
sterno-cleido-mastoid, and the sterno-hyoid muscles. The deep surface
rests upon the innominate vein, the lower part of the common carotid
artery, the trachea, and the thyroid gland.
Action.-It depresses the thyroid cartilage and indirectly the floor of
the mouth.
The Thyro-hyoid is a small quadrilateral muscle, its fibres interlacing
with the sterno-thyroid, of which it is, to all appearance, a continuation.
It arises on the oblique line on the ala of the thyroid cartilage; it passes
upward and is inserted into the lower border of the body and great
cornu of the hyoid bone.
S
Relations.Its superficial surface is in contact with the sterno-hyoid
and omo-hyoid muscles. Its under surface rests upon the thyroid car-
tilage and thyro-hyoid membrane. The superior laryngeal nerve and
artery pass between the membrane and muscle before entering the
larynx.
Actions. The thyro-hyoid muscle raises the thyroid cartilage, or,
when that body is fixed, it lowers the hyoid bone.
Nerve. The muscle is supplied by a branch of the hypoglossal nerve.
The Omo-hyoid is a long, ribbon-shaped muscle, with two bellies
united by an intervening tendon; it extends from the shoulder to the
hyoid bone, crossing the neck diagonally and dividing the anterior and
posterior surgical triangles into four. The muscle arises from the upper
border of the scapula, near the suprascapular notch; it passes forward
and slightly upward, in a flattened narrow fasciculus, across the lower
portion of the neck to the point at which it lies beneath the sterno-
cleido-mastoid muscle, when it becomes tendinous, the tendon being held
down by a loop formed from the deep fascia, which has an attachment
to the cartilage of the first rib; it then passes nearly vertically close to
the outer border of the sterno-hyoid muscle, to be inserted into the
lover border of the body of the hyoid bone, in close proximity to, and
outside of, the sterno-hyoid muscle.
Relations. The superficial surface with the trapezius and sterno-
cleido-mastoid muscles, the deep cervical fascia, the platysma myoides,
and the integument. Its under surface passes over the scaleni, the
brachial plexus, the sheath containing the common carotid artery, the
internal jugular vein and pneumogastric nerve, the noni nerve, and
the sterno-hyoid and sterno-thyroid muscles.
Variations.-The muscle is sometimes divided throughout or in part;
AREOLAR TISSUE, TENDONS, AND MUSCLES.
187
occasionally only one belly is present, or the anterior belly is sometimes
fused with the sterno-hyoid muscle.
Action.-It depresses and carries the hyoid bone backward; it is also
a tensor of the cervical fascia.
THE MUSCLES OF THE SUPRA-HYOID SPACE.
The muscles of the supra-hyoid space (Fig. 95) are the digastric,
stylo-hyoid, mylo-hyoid, genio-hyoid, genio-glossus, lingualis, hyo-
glossus, and stylo-glossus.
The Digastric, as its name implies, is a double-bellied muscle, one
posterior and one anterior, extending from the mastoid portion of the
temporal bone to the anterior part of the lower jaw. The posterior belly
FIG. 95.

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Thyroid Cartilage
Muscles of the Tongue, left side.
is the longer and narrower of the two, and arises from the digastric
groove of the temporal bone, close to the stylo-mastoid foramen; pass-
ing downward, forward, and inward, it gradually diminishes as it
approaches the hyoid bone, and is lost in a tendon which usually
passes through the stylo-hyoid muscle near its insertion, and also
through its aponeurotic loop, which is lined by a synovial membrane,
M
188
ANATOMY.
and holds it in connection with the body and the great cornu of the
hyoid bone. The anterior belly is shorter and broader than the pos-
terior. It commences at the intermuscular tendon, passes upward and
forward, and is inserted into the rough depression on the internal lower
border of the inferior maxillary bone near the symphysis: its fibres
sometimes decussate with those of its fellow-muscle on the opposite side.
Stretching between the intermediate tendons and sheaths of the ante-
rior portions of these muscles of each side is a broad layer of fascia known
as the supra-hyoid aponeurosis, which is also attached to the great cornu
of the hyoid bone and the anterior bellies of each muscle; this gives a
firm support for the other muscles in the supra-hyoid space. This
aponeurosis corresponds to a layer of muscular fibres belonging to
the digastric muscle of some of the lower animals.
The digastric muscle subdivides the anterior superior surgical triangle
of the neck into the submaxillary and superior carotid triangles.
The Submaxillary Triangle is inverted, the base being above, and is
bounded by the lower border of the inferior maxillary bone and a line.
to the mastoid process; the other or lower sides are formed by the two
bellies of the digastric muscle, its tendon being held down by a loop of
fibrous tissue which forms the inferior angle. The outer or superficial
surface of this triangle is covered by a firm layer of the deep fascia
attached below to the tendon and to the bellies of the muscle, above to
the body of the inferior maxilla and to the fascia which extends over
the parotid gland. The inner surface is bounded by a deep layer of the
same fascia attached below to the tendon and muscle, while above it is
lost in the sheaths of the muscles of the floor of the mouth. Surgically
considered, it is continuous over these muscles, and is attached to the
lower border of the mylo-hyoid ridge of the lower jaw. In the tume-
faction of the submaxillary gland the enlargement exhibits a triangular
form on account of the shape of this envelope.
The Superior Carotid Triangle is bounded above by the posterior
belly of the digastric, below by the omo-hyoid, and behind by the
sterno-cleido-mastoid muscle, its apex presenting anteriorly at the loop
of the digastric and insertion of the stylo-hyoid muscle. The import-
ance of this triangle to the surgeon is due to the fact that in it are
found the points for ligation of many arteries.
Relations.-The anterior belly of the digastric muscle is more super-
ficial than the posterior; its outer surface being covered by the platysma
myoides and the deep cervical fascia, its deep surface rests upon the
mylo-hyoid muscle. Its posterior belly is deeply covered by the mas-
toid process of the temporal bone, the sterno-cleido-mastoid, and part of
the stylo-hyoid muscles, a lobule of the parotid gland, and part of the
submaxillary gland. Its deep surface is in relation with the transverse
process of the atlas, the internal jugular vein, the internal carotid artery,
and the origins of the facial and lingual arteries. The hypoglossal
nerve lies a little below the tendon.
Variations.—This muscle has many variations, and, like the omo-
hyoid, the entire muscle may be divided through one or both bellies.
The posterior belly may receive an accessory slip from the styloid
process, the angle of the jaw bone, or the splenius muscle; it has been
AREOLAR TISSUE, TENDONS, AND MUSCLES.
189
known to arise entirely from the styloid process. In rare instances the
muscle has been monogastric, in which case it is inserted into the mid-
dle of the lower jaw. Slips may pass from the anterior belly to the
hyoid bone. The tendon does not always pass through the stylo-
hyoid muscle.
The Mento-hyoid (Macalister) is an occasional slip found passing from
the body of the hyoid bone to the chin. It is sometimes composed of
parallel bands, and Macalister suggests that it may be a differentiated
portion of the platysma myoides.
Nerves. The posterior belly of the muscle is supplied by the facial
(seventh), and the anterior by the mylo-hyoid branch of the inferior
dental nerve.
K
Actions. The digastric muscles act in antagonism to the muscles of
mastication by assisting in depressing the inferior maxilla. When the
lower jaw is firmly fixed by the masticatory muscles, the digastric
assists in elevating the hyoid bone.
The Stylo-hyoid is a small slender muscle situated along the upper
border of the posterior belly of the digastric. It arises by a narrow
tendon from the upper half of the outer surface of the styloid process of
the temporal bone. It passes downward, forward, and inward, to be
inserted into the hyoid bone at the junction of the great cornu with the
body. It is usually divided into two portions near its insertion for the
transmission of the digastric muscle.
Relations. These are almost identical with those of the posterior belly
of the digastric muscle.
Variations.-The variations of the muscle are numerous amongst
them may be noted cleavage throughout its whole course, forming two
muscles, in some instances three. It is occasionally placed on the
inner side of the external carotid artery; the insertion is sometimes
partially or wholly in the tendon of the digastric muscle. It may be
fused with the omo-hyoid, thyro-hyoid, or mylo-hyoid muscles at the
hyoid bone. It may send slips to the lower jaw. Its place of origin
varies; sometimes there is an extra slip given off from the styloid pro-
cess and inserted into the small cornu, and accompanying or taking the
place of the stylo-hyoid ligament.
Nerves.-The muscle is supplied by the facial nerve.
Action.-To elevate and draw backward the hyoid bone.
Madde
The Stylo-hyoid Ligament. This being so intimately associated with
this group of muscles, it will receive next consideration. The ligament
is a thin fibrous cord developed from the deep fascia attached to the
lower portion of the styloid process, passing downward, forward, and
inward, to be inserted into the lesser cornu of the hyoid bone. Some-
times this ligament is of a cartilaginous nature, and even ossifies. In
many animals it is naturally osseous, and is named the epihyal bone.
The Mylo-hyoid is a triangular flat muscle placed between the inferior
maxillary and hyoid bones, and with its fellow of the opposite side
forms the muscular floor of the mouth (diaphragma oris, Meyer). It
arises from the mylo-hyoid (internal oblique) ridge of the lower jaw,
extending from about the third molar tooth to the symphysis. At its
insertion it is divided into two portions, a posterior and an anterior.
190
ANATOMY.
The Posterior Portion consists of those fibres which give the muscle
its name. They pass downward, inward, and backward, to be inserted
into the body of the hyoid bone.
The Anterior Portion passes in a more oblique direction, and is not
inserted into the hyoid bone, but into an indistinct intermuscular raphé
which extends from the symphysis of the jaw to the centre of the hyoid
bone; the muscular fibres are the longest near the hyoid bone, and
gradually grow shorter as the symphysis of the jaw is approached.
Relations. The mylo-hyoid muscle forms the floor of the mouth,
and at the same time part of the roof of the neck, thus giving it an
oral or superior and a cervical or inferior surface. The cervical surface
is in relation with the submaxillary muco-salivary gland, the anterior
belly of the digastric muscle, the facial artery and its submental branches,
and the mylo-hyoid vessels and nerves. The oral surface is in relation
with the genio-hyoid, genio-glossus, parts of the hyo-glossus and stylo-
glossus muscles; also the lingual branch of the fifth and twelfth nerves,
the sublingual gland, and the mucous membrane of the alveolo-lingual
groove. Its posterior border is free, a part of the submaxillary muco-
salivary gland curving around it to the upper surface, the duct of the
gland (duct of Wharton) passing along the upper surface of the muscle.
Variations. Sometimes the raphé is absent; in such cases the fibres
of each muscle interlace. It may be fused with the anterior belly of
the digastric muscle, or it may be entirely lacking and be substituted
by the digastric. Slips are sometimes received from some of the other
hyoid muscles. Occasionally the anterior portion of the muscle is defi-
cient, its origin extending no farther than the cuspid teeth: this muscle
is sometimes perforated and dissected by the lobules and duct of the
submaxillary muco-salivary gland.
Nerves. The mylo-hyoid nerve, a branch of the inferior maxillary.
Action.-The mylo-hyoid muscle draws the hyoid bone forward and
upward, and slightly assists in opening the mouth.
The Genio-hyoid is a narrow muscle extending from the symphysis
of the chin to the hyoid bone. It arises from the inferior genial
tubercle (mental spine) on the inner side of the inferior maxillary bone,
and passes downward and backward to be inserted into the anterior
portion of the hyoid bone.
Relations.—Below with the mylo-hyoid muscle, above with the genio-
glossus and with its fellow on the proximal border.
Variations.-The genio-hyoid may separate into two muscles, or it
may be united with the muscle of the opposite side. Slight variations
may be found between its origin and insertion.
Nerve. The genio-hyoid is supplied by a branch of the hypoglossal
nerve.
Action.-Same as the mylo-hyoid-to elevate and draw forward the
hyoid bone and to depress the lower jaw.
The Genio-glossus (often called genio-hyo-glossus, from its sup-
posed insertion on the body of the hyoid bone) is a thin, flat, radiat-
ing muscle, placed vertically on each side of the median line in front
of the tongue. It arises by a short tendon from the superior genial
tubercle (mental spine) on the inner aspect of the inferior maxillary
AREOLAR TISSUE, TENDONS, AND MUSCLES.
191
bone; from the tendon its fibres diverge from before backward, and are
inserted mainly into the under surface and body of the tongue, consti-
tuting the bulk of the structure of that organ. Some of its fibres pass
backward to the hyoid bone and to the side of the pharynx.
Relations.-On its median surface with its fellow of the opposite side,
from which it is separated within the tongue by the median raphé. Its
lateral surfaces are in contact with the lingualis, hyo-glossus, and stylo-
glossus muscles, the sublingual, the ranine vessel, the gustatory nerve,
and sublingual glands. The terminal portion of the hypoglossal nerve
penetrates its posterior part. The frænum linguæ is formed by the
union of the anterior upper borders of the two genio-glossus muscles,
which are covered by mucous membrane.
Variations. This muscle is sometimes united with the genio-hyoid
muscle, or it may give a few fine bundles to the epiglottis, to the stylo-
hyoid, or to the smaller cornu of the hyoid bone.
Nerve. This muscle is supplied by the hypoglossal nerve.
Action.-To draw forward and protrude the tongue.
The Lingualis muscle is a longitudinal fasciculus placed in the sub-
stance of the tongue, arising at the base and extending between the hyo-
glossus and genio-glossus muscles to the apex of the organ. Some of
its fibres intermingle with the stylo-glossus and hyo-glossus. The
ranine artery (the terminal portion of the lingual artery) passes along
its under surface.
The Hyo-glossus is a thin quadrate muscle, arising from the upper
border and the lateral portion of the great cornu of the hyoid bone,
also from the lesser cornu. Its fibres pass upward and slightly forward
to the posterior half and lateral portions of the tongue; they then
spread inward and forward over the dorsum, joining those of the stylo-
glossus toward the apex.
Relations. The hyo-glossus is related by its external surface with the
digastric, stylo-hyoid, stylo-glossus, and mylo-hyoid muscles, also the
deep part of the submaxillary muco-salivary gland, and is crossed from
below upward by the duct of Wharton and by the hypoglossal and
lingual nerves. Its internal surface rests upon the posterior portion of
the genio-glossus and the origin of the middle constrictor of the pharynx;
it is crossed by the lingual artery and the glosso-pharyngeal nerve.
Variations.-The lingual artery occasionally passes through the mus-
cle near the hyoid bone; it is at times composed of a number of sepa-
rate bundles. The muscles sometimes receive a slip, triticeo-glossus
(Bochdalek), from the thyro-hyoid ligament, which passes upward and
forward, lying on the inner side of the lingual artery and joining the
hyo-glossus.
Nerves. The muscle receives branches of the hypoglossal nerve.
Action.—To aid in depressing the tongue.
•
The Stylo-glossus is the shortest and smallest of the styloid muscles,
and passes from the styloid process to the tongue. It arises from the
outer and anterior portion of the apex of the process, and passes for-
ward and slightly downward and inward to the posterior part of the
tongue, where it divides into two portions, the longitudinal and the oblique.
The Longitudinal Portion passes forward, and is inserted along the
192
ANATOMY.
side of the tongue as far as the tip, blending with the fibres of the lin-
gualis in front of the hyo-glossus.
The Oblique Portion passes slightly downward over the hyo-glossus, its
fibres interlacing with those of that muscle and those of the palato-glossus.
Relations.-On its lateral surface the stylo-glossus is associated with
the parotid gland, the internal pterygoid muscle, sublingual gland, gus-
tatory nerve, and mucous membrane of the mouth; the internal sur-
face with the tonsils, the superior constrictor of the pharynx, and the
hyo-glossus muscle.
Variations.-The muscle has many variations, sometimes being absent;
at others it has been found to be double. It may receive slips or may
arise entirely from the angle of the jaw, the stylo-maxillary ligament,
the internal pterygoid muscle, or the tympanic portion of the temporal
bone. Slips may pass to the pharynx.
Nerves. Its nerve-supply is derived from the hypoglossal.
Action. To assist in retracting and elevating the tongue.
THE MUSCLES OF THE PHARYNX AND THE SOFT PALATE.
This group (Fig. 96) includes the superior constrictor, middle con-
strictor, inferior constrictor, stylo-pharyngeus, palato-pharyngeus, palato-
FIG. 96.
TYLO-PHARYN CEUS
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Muscles of the Pharynx, external view.
glossus, palato-Eustachian or
tensor palati, levator palati,
and azygos uvula.

The Superior Constrictor
muscle of the pharynx is a
thin quadrilateral muscle, sit-
uated, as its name implies, at
the upper portion of this mus-
cular pouch: its fibres are paler
than those of the middle and
inferior muscles. It arises,
commencing from above down-
ward, from the lower third of
the free margin of the internal
pterygoid plate and its hamu-
lar process, the tuberosity of
the palate bone, the reflected
tendon of the palato-Eusta-
chian or tensor palati muscle,
and the pterygo-maxillary liga-
ment-at which point some
of its fibres are continuous
from the buccinator; it also
arises from the posterior ex-
tremity of the mylo-hyoid
ridge, the mucous membrane
of the mouth, and the sides of
the tongue continuous with the
The
genio-glossus muscle.
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AREOLAR TISSUE, TENDONS, AND MUSCLES.
193
fibres from these various points of origin pass backward and curve inward
until they meet those of the opposite side, where many of the fibres inter-
lace. The remainder are inserted into the median line of the pharyngeal
raphé, in front of the cervical vertebræ, and a few of the fibres are inserted
in the pharyngeal spine and the aponeurosis attached to the basilar process
of the occipital bone.
The upper margin of the muscle is concave, being suspended at its
corners by the pterygoid process in front and the pharyngeal aponeurosis
behind. The surface between the border of the muscle and the base of
the brain-case is occupied by the pharyngeal aponeurosis, the lower
border of which becomes part of the wall of the pharynx, and is covered
by the middle constrictor muscle.
Variations.—The different heads of origin may be from various mus-
cles. The azygos pharyngis (Meckel) is a slip arising from the pharyn-
geal spine and inserted into the posterior pharyngeal wall.
Relations. To the outer surface of the muscle are the cervical verte-
bræ, the internal carotid artery, the pneumogastric, the glosso-pharyn-
geal, and spinal accessory nerves, the middle constrictor and the stylo-
pharyngeus muscles; related to its inner surface are the palato-pharyn-
geus muscle and the tonsils. The origin of the levator palati muscle
and the Eustachian fossa are also near to this surface.
Nerves-The nerve-supply is derived from the pharyngeal plexus.
Actions.-When it contracts, the pterygoid portion, being fixed at
both its origin and insertion, straightens the curvature of the superior
border and, at the same time, narrows the diameter of the naso-
pharynx. The pterygo-maxillary and inferior maxillary portions assist
in drawing the posterior wall of the pharynx forward.
The Middle Constrictor of the Pharynx is a flattened radiating muscle
situated on a plane below the superior constrictor. It arises from the
greater and lesser cornua of the hyoid bone and the stylo-hyoid ligament.
The fibres radiate as they pass backward, and, curving inward, are
inserted in the posterior median raphé, some of them interlacing with
those of the opposite muscle. The extent of their insertion is from
below the level of the hyoid bone to a position near the occipital bone.
The lower portions descend beneath the inferior constrictor as it passes
backward, while the upper fibres ascend and overlap those of the supe-
rior constrictor, the middle portion passing directly backward.
Variations. As in the previous muscle, the slips arising from differ-
ent points of origin, as those from the greater and lesser cornua, may
serve as separate and distinct muscles. Fibres may be received from the
body of the hyoid bone, and a slip (cyndesmo-pharyngeus, Douglas)
from the thyro-hyoid ligament is frequently present. Fibres may also
arise from the tongue and posterior part of the mylo-hyoid ridge of the
inferior maxilla, and interlace with the genio-glossus, as does the superior
constrictor. The upper fibres may reach the occipital bone.
Relations.-The external and posterior surface with the longus colli
and rectus anticus major; laterally, the carotid vessels, the pharyngeal
plexus, and some lymphatic glands. The inferior constrictor overlaps
its lower portion. The stylo-pharyngeus muscle passes between the
superior and middle constrictors, and the superior laryngeal nerve lies
VOL. I.-13
194
ANATOMY,
between the middle and inferior constrictors on its way to the thyro-
hyoid membrane. The internal surface where it does not overlap the
superior muscle is covered by mucous membrane and the stylo-pharyn-
geus and the palato-pharyngeus muscles.
Nerves.-The nerve-supply is from the pharyngeal plexus.
Actions. The upper fibres assist in elevating the hyoid bone and all
the structures connected with it; it also draws forward the posterior
pharyngeal wall.
The Inferior Constrictor muscle of the pharynx is the broadest, thick-
est, and shortest of the three, and lies the most superficially. As its
name implies, it is at the lower or inferior portion of the pharynx. It
arises from various points, commencing below at the lower and posterior
part of the cricoid cartilage, and from a tendinous arch between the cri-
coid and thyroid cartilages, from the inferior cornu and the oblique line
and upper border of the thyroid cartilage. From these points of origin the
fibres pass backward and upward, and, curving inward, join the raphé
and the fibres of its fellow from the opposite side. The fibres of the
lower portion are the shortest; their direction is horizontal, and they
combine with those of the oesophagus without a line of demarcation.
The balance of the fibres are about one-eighth of an inch below the
basilar process, and pass upward and backward, with an increase of
obliquity, to the posterior median line of the pharynx, covering more
than half its length.
Variations.-The muscle sometimes receives a fasciculus from the
thyro-hyoid, crico-thyroid, and sterno-thyroid muscles, or even from
the trachea.
Relations.-The external surface posteriorly is in apposition with the
cervical vertebræ and the muscles of this region; laterally with the
thyroid gland, the carotid arteries, and the sterno-hyoid muscles, the
internal surface of the middle constrictor, the stylo-pharyngeus, and the
palato-pharyngeus muscles, also the mucous membrane of the pharynx.
The superior laryngeal nerve and vessels pass over the upper border to
the larynx, and the inferior ascend beneath its lower border.
Nerves. The muscle is supplied by the pharyngeal plexus and the
external laryngeal nerve.
Actions. It assists in propelling the bolus of food into the oesophagus,
reduces the size of the lower part of the pharynx, and can act independ-
ently of the other muscles of the set.
The Stylo-pharyngeus muscle is slender, though the largest and longest
of the styloid set: above it is round; below it is broad and thin. It
arises from the inner side and near the base of the styloid process, passes
downward and inward between the superior and middle constrictors of
the pharynx, and gradually expands under the mucous membrane, some
of its fibres being inserted into the lateral walls of the pharynx and
united with the palato-pharyngeus: these are inserted into the posterior
border of the thyroid cartilage.
The glosso-pharyngeal nerve accompanies this muscle, commencing
on the outer side, and crosses over on its way to the tongue.
Variations.-Cleavage or doubling of the stylo-pharyngeus muscle
is frequent; occasionally it has been found divided into three. Super-
AREOLAR TISSUE, TENDONS, AND MUSCLES.
195
numerary elevators of the pharynx are frequently present; they arise
from the base of the skull in juxtaposition to the styloid process, or
from the petrous process of the temporal bone (anterior to the carotid
foramen) or the vaginal process of the same bone. These muscles are
named the petro-pharyngeus, which arises from the petrous portion;
spheno-pharyngeus, from the spine of the sphenoid; pterygo-pharyngeus
externus, from the hamular process; occipito-pharyngeus, from the bas-
ilar process; pharyngo-mastoideus, from the mastoid process: the last
named is very rare. The azygos pharyngis is frequently classed in
FIG. 97.
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Muscles of the Soft Palate, the Pharynx being laid open from behind.
this group: a description of it is given with that of the superior con-
strictor of the pharynx.
Nerves.-This muscle receives branches from the glosso-pharyngeal
Action.-To assist in elevating the pharynx.
The Palato-pharyngeus muscle (Fig. 97) is long and narrow, wider
at the extremities than in the middle, and extends from the soft pal-
ate to the pharynx ; it arises in the soft palate by an anterior and a pos-
Badg

196
ANATOMY.
terior portion, which embrace the levator palati and the azygos uvulæ
muscles.
The Anterior Head or Portion is the thickest; the fibres at the com-
mencement near the median line of the palate are associated with those
of the opposite side; they pass outward between the levator and tensor
palati muscles; fibres are also received from the free edge of the hard
palate and the aponeurosis of the velum.
The Posterior Head or Portion consists of scattered fibres, commen-
cing in the median line and associating with those of the opposite side.
At the edge of the soft palate the two portions unite, and receive two
slender bundles which arise from the inferior and anterior
part of the
Eustachian tube (salpingo-pharyngeus, Santorini); from this it passes
outward, downward, and backward posteriorly to the tonsils; it spreads
out, joining the fibres of the stylo-pharyngeus muscle, and is inserted
mainly into the superior and posterior border of the thyroid cartilage.
The remainder of its fibres are received into the fibrous layer of the
inferior part of the pharynx, passing as far as, or crossing, the median
line, and interlacing with those of the opposite side.
This muscle and the mucous membrane covering it form the palato-
pharyngeal fold, or "posterior half arch."
Relations.-At its origin the soft palate. Its anterior and posterior
surfaces are covered by mucous membrane, a layer of palatine glands
resting between the membrane and the muscle. Its superior surface is
related with the levator palati muscle. In the pharynx it passes between
the mucous membrane and the constrictor muscles.
Nerves.—Branches of nerves from Meckel's ganglion (spheno-pala-
S
tine).
Action. To elevate the pharynx in deglutition, the palate having
first been elevated by the levator palati. In its action it assumes a
nearly vertical position in the posterior part of the pharynx. Allen¹ and
Yule² conclude from observation that the palato-pharyngeus is the chief
factor in opening the Eustachian tube; it also keeps the soft palate in
position during respiration.
The Palato-glossus is a small muscle extending from the soft palate
to the posterior part of the tongue; it is narrower in the middle than
at its origin or insertion, and arises from the under surface of the soft
palate near the base of the uvula, the fibres of each side interlacing
at their origins. It passes downward, forward, and outward along
the lateral wall of the pharynx, anterior to the tonsils, and is inserted,
with the stylo-glossus, into the side and base of the tongue. This
muscle and the mucous membrane covering it form the palato-glossus
fold, or "anterior half arch."
Relations.—It passes downward along the outer wall of the pharynx,
between the constrictors and the mucous membrane.
Nerves.-Branches of the facial.

Action.-To depress and draw slightly forward the palate and assist
in elevating and drawing back the tongue. Allen³ observes:
“Both
muscles, acting together, depress the soft palate and draw it forward,
¹ Allen's "Memoir on Soft Palate," Trans. Amer. Med. Assoc., 1872, p. 537.
2 Journal of Anat. and Phys., viii., 1873. "Allen's Human Anatomy, p. 259.
AREOLAR TISSUE, TENDONS, AND MUSCLES.
197
and in the act of sucking constrict the nipple. Each muscle may be
looked upon as a sphincter on a deeper plane than the lips, but like it
in nature, and it is supplied by the same motor nerve-viz. the facial.
It is also a noteworthy fact that the plane of the two muscles limits
the region of involution of the epiblast, so that the palato-glossal mus-
cles are less splanchnic than the pharyngeal muscles proper.
""
The Palato-Eustachian, or Tensor Palati, is a broad thin muscle
extending from the orifice of the Eustachian tube to the palate, and
having a vertical and a horizontal portion.
The Vertical Portion arises from the scaphoid fossa at the root of the
pterygoid plates, the spinous process of the sphenoid bone, and the
lower and outer side of the Eustachian tube. Its flattened belly descends
perpendicularly between the inner side of the internal pterygoid muscle
and the outer side of the inner pterygoid plate, at the lower portion of
which it becomes a tendon and passes around the hamular process, and
continues thence to its insertion, forming the horizontal portion of the
muscle. There is a synovial bursa in connection with the tendon and the
process which allows the tendon to work backward and forward.
The Horizontal Portion passes inward, and is inserted into the apo-
neurosis of the soft palate and transverse ridge on the under surface
of the palate bone.
Relations.-Vertical portion, on its external surface, with the internal
pterygoid muscle; internal surface with the levator palati muscle.
Horizontal portion, at the point of its insertion into the soft palate;
the aponeurotic expansion is anterior to the levator palati muscle; the
under surface is covered by mucous membrane.
Nerves.-The muscle is supplied by branches from the otic ganglion.
Action. The palato-Eustachian, or tensor palati, has generally been
supposed to make the palate tense, and for this reason severance of the
tendon at the hamular process previous to performing the operation of
staphylorrhaphy was frequently favored. The principal function of the
muscle is now considered to be to open the orifice of the Eustachian
tube.
The Levator Palati is a long, thin, round muscle, extending from the
temporal bone to the palate at the lateral borders of the posterior nares.
It arises by a narrow tendon from the under surface of the petrous por-
tion of the temporal bone, anterior to the carotid canal, and from the
lower margin of the cartilage of the Eustachian tube, thence passing
downward, inward, and forward into the pharynx over the concave
margin of the superior constrictor, spreading out as it approaches the
soft palate, where the anterior and lesser part is inserted into the
aponeurosis of the palate; the posterior or larger part meets the fibres
from the opposite side underneath the azygos uvula muscle.
Relations. Its lateral surface with the tensor palati and superior
constrictor muscles; the internal surface is covered with mucous mem-
brane.
ww
J
Actions." With reference to the soft palate: the muscle elevates the
soft palate and makes it tense, since the right and left muscles act syn-
chronously. With reference to the Eustachian tube: the shortening of
the body of the muscle, together with the increase of its diameter, has a
198
ANATOMY.
tendency to close the orifice of the tube by elevating the lower border.
The action of the levator palati can readily be studied in the living sub-
ject by the rhinal mirror. By such aid the course of the muscle, even
when at rest, can be seen corresponding to an oblique fold of mucous
membrane, which may receive the name of the salpingo-palatal fold.
The levator palati receives much attention in the improved operation
of staphylorrhaphy. Fergusson, having noticed the influence of this
muscle in widening the cleft in the soft palate, essays its division before
uniting the freshened edges. This procedure is now an established
antecedent to the operation.
1
"The actions of the levator palati and tensor palati muscles have been
the subject of controversy. Valsalva as long ago as 1742 described
both the above muscles as dilators of the tube. Toynbee in 1853
revived Valsalva's account, and later Rüdinger and other German
writers have accepted this as the true action. Respecting the tensor
palati, Henle² is inclined to adopt the view that the muscle closes the
orifice; while, as seen in another part of the same volume (p. 117), he
doubts the ability of the muscle to close the tube. His views upon the
function of the levator palati agree with those expressed in the text.
"The author has long taught that the contraction of the levator palati
narrows the pharyngeal orifice of the tube. This action can be readily
seen in the living subject by the aid of reflected light. Cleland studied.
the action of the same muscles in a man who had lost the soft palate by
ulceration. He doubts the efficacy of the tensor palati in dilating the
tube, while he assigns to the levator palati its proper function, in assist-
ing to narrow the orifice. That the Eustachian tube (7. v.) is always
patulous in health, and that while certain muscles tend to narrow its
lumen none can obliterate it, seem to be fair deductions from its nature.'
274
The Azygos Uvula is not a single muscle, as its name implies, but
consists of a pair of narrow fasciculi, arising, one on each side, from the
posterior palatine spine of the palate bone and the aponeurosis of the
soft palate, the fibres passing backward to be inserted into the uvula.
Nerves.-The muscle is controlled by the facial nerve.
Action.-To contract the uvula.
MUCOUS MEMBRANE AND ITS GLANDS.
Mucous membrane forms the lining of all cavities and canals having
an external opening, such as the respiratory tracts, the passages trans-
mitting food in its various forms, and all outlets for excretive and secre-
tive fluids. The surface of the membrane is soft and yielding, and is
covered by a thick glistening, tenacious, transparent fluid called mucus,
which is secreted by numerous small glands hereafter to be described.
The mucus protects the membrane beneath from any deleterious matter
contained in foods, either in a solid state or in the form of solution.
The mucous membrane of the body can be divided into two great
systems-the genito-urinary and the gastro-pneumonic-each being
complete and continuous in itself.
1 Trans. Phil. Soc. Lond., 1853.
3 Journal of Anat. and Phys., iii., 1869, 97.
HARR
2 Anatomie, i. 755.
4 Allen's Human Anatomy, pp. 259, 260.
AREOLAR TISSUE, TENDONS, AND MUSCLES.
199
The Genito-urinary System is that which, commencing at the kidneys,
lines the urinary passages of both sexes, passing through the ureters,
bladder, and urethra, also the sexual organs, as the seminal ducts and
vesicles of the male, the vagina, uterus, and Fallopian tubes of the
female.
The Gastro-pneumonic System lines the alimentary canal and all ducts.
and glands which open into it; this system invests the air-passages
from the opening of the nostrils to the air-vesicles of the lungs. It
also lines the frontal sinuses and air-cells which communicate with them
or the air-passages. The membrane passes from the nasal chamber
through the Eustachian tube to the ear, also through the lachrymal
ducts to the eyes and lachrymal glands. The latter gland is developed
from a solid ingrowth of the conjunctiva.
The construction of the mucous membrane is very similar to that of
the skin, being developed from two layers of the blastoderm-the skin
from the epiblast and mesoblast, the mucous membrane (with certain
exceptions) from the hypo- and mesoblast: it is divided into two layers,
epithelium and corium, separated by an intermediate or basement-mem-
brane.
S
ÉPITHELIUM OF MUCOUS MEMBRANE.-The epithelial layer is
the most constant part of mucous membrane-i. c. it passes over and
into parts where the corium cannot be traced, as in the alveoli of the
lungs and upon the cornea of the eye; it is developed, with the excep-
tion hereafter given, from the lower layer (hypoblastic) of the blasto-
derm. This layer is variously classified, either according to its function
or to the shape and arrangement of the cells entering into its formation,
as simple, stratified, and transitional, the simple variety being again
subdivided into pavement, columnar, spheroidal or glandular, and cili-
ated.
When classified according to function, it is arranged as protective and
secretory, the first division being made up of stratified, transitional, cili-
ated, and pavement varieties; the latter is divided into columnar and
spheroidal (glandular).
THE EPITHELIUM OF THE ORAL CAVITY.-The epithelium within
the oral cavity is regarded as squamous stratified epithelium; the same
variety is also found in the lower part of the larynx, upon the edges of
the epiglottis, the true vocal cords, and in the oesophagus; also in the
anterior two-thirds of the nasal chamber.
The general arrangement of cells in the epithelium is very similar to
that of the epiderm; its deep or Malpighian layer contains very little
pigment, and is columnar in form, though this is not the case in embry-
onal life-the stratum granulosum and stratum lucidum of the epiderm
are not present; but with this exception the development, growth, main-
tenance, and desquamation are the same. It is analogous with the skin,
and is developed from the same layer of the blastoderm, which extends
internally as far as the palato-glossal fold, and sometimes farther.
Should any portion of the mucous membrane of the mouth become
constantly exposed to the action of the atmosphere as the result of surgi-
cal operations or other cause, it will assume the horny character of the
skin. In like manner, should any part of the skin become part of the
200
ANATOMY.
oral cavity, or be continuously subjected to the action of the fluids of the
mouth, it will take upon itself the functions and characteristics of mucous
membrane, assuming greater translucency, its cells becoming compara-
tively thin, some of them having small nuclei.
In the olfactory portion of the nasal chamber, the upper part of the
pharynx, also in the larynx, trachea, and bronchi, the cellular invest-
ment is made up of stratified cylindrical ciliated epithelium.
The epithelial cells of the mucous membrane are slightly separated,
but, like those of the skin, are held together by an intercellular cement
substance, and it is through this cement substance that absorption
(very slight) takes place when medicaments are placed either on the
skin or mucous membrane; as they pass through they enter the lymph-
spaces in the areolar connective tissue, and in this way get into the cir-
culation through the larger lymphatics.
The Corium of the mucous membrane lies immediately beneath the
basement-membrane, but is not always demonstrable. It is made up
very similarly to the corresponding layer of the skin-i. e. of areolar
connective tissue, sometimes containing a large intermixture of lymphoid
tissue. It also contains white and yellow fibrous connective tissue,
muscular tissue, vessels, lymphatics, and nerves. The corium varies in
thickness according to its locality. In the oesophagus, bladder, and
vagina the fibrous tissue is abundant, forming almost a compact web
and making the mucous membrane of these parts somewhat stout and
tough. In other parts, as in the stomach and intestines, the tissue is
retiform or lymphoid, lacking the white elastic tissue. Along the side
and beneath the tongue in the alveolo-lingual groove, also at the base
of the tongue and the epiglottis, and from that to the side of the pharynx,
the corium is exceedingly loose and pliable.
On the alveolar processes of the inferior and superior maxillary bones
this layer is made up of dense connective tissue, and is firmly attached
to the membrane immediately upon the bone which forms the gum tis-
sue or muco-periosteum (Allen). This muco-periosteum has both the
function of mucous membrane and periosteum, and it is through it
that the bone receives nourishment. When the membrane is lost or
destroyed, necrosis takes place the same as in bones which are supplied
with a true periosteum. Where cartilage is covered by mucous mem-
brane, as in the septum of the nose, Eustachian tubes, the larynx, etc.,
it is called muco-perichondrium (Allen), and acts as a nourisher and pro-
tector to the cartilage similarly to the perichondrium of cartilage.
Upon the hard palate the muco-periosteum is united by a fine
trabecula to the ridges of the bony surface. In the interspaces and
within the muco-periosteum there are small racemose glands. Upon
the soft palate it is more firmly adherent at the anterior surface than
the posterior, where it comes in contact with the gland tissue. It is
found on the roof of the pharynx attached to the aponeurotic membrane
of the base of the skull, and upon the tongue it is firmly attached and
forms the cortex.
Blood-vessels of the mucous membrane are generally very abundant.
The branches of the arteries and veins divide and subdivide in the sub-
mucous tissue as in the skin, and pass into the corium, where they again
AREOLAR TISSUE, TENDONS, AND MUSCLES.
201
divide and form a complete network of capillaries. This network,
when present, lies below the basement-membrane, projecting into the
papillæ of the papillary layer. The tubular and other glandular
apparatus are abundantly supplied with nourishment by this vascular
rete, which surrounds them for that purpose.
Lymphatics are found in the form of a network in the mucous mem-
brane, communicating with larger vessels in the submucous layer.
My
Nerves.-When muscular fibres exist in mucous membrane, the nerves
are chiefly distributed to them, also to the glandular apparatus; there
are also ganglionic plexuses in the submucous tissue. Some terminal
nerves have been found to pass through into the epithelium and ter-
minate between the epithelial cells: this appears to have been demon-
strated in the epithelium of the mucous membrane of the palate of a
rabbit.¹
J
Papilla and Villi are found upon some parts of the mucous mem-
brane: the former are conspicuous upon the tongue, as hereafter described,
and the latter are abundant and fully developed on the mucous membrane
of the small intestines.
THE SECRETORY GLANDS OF THE MUCOUS MEMBRANE.—The
secretory glands are organs which vary in structure and in their secre-
tion; part of them are situated within the mucous membrane, while
others are at various distances from it, though in all instances their
ducts open upon its surface. Although they differ considerably in their
function and locality, they have an embryonal derivation similar to that
of the epithelial tissue upon which their ducts empty their fluid; their
development usually begins during intra-uterine life. These glands are
essentially made up of one or more layers of secreting cells, usually
resting upon a basement-membrane. Immediately below the basement-
membrane there is an abundant supply of fine blood-vessels; when the
membrane is absent, the vessels are in close contact with the attached
ends of the cells.
Enlargement of secreting surfaces of any part is generally by reces-
sion or inversion (there are examples in nature where the increase of sur-
face is produced by protrusion or an elevation), which is carried from
very simple forms to various degrees of complexity. The first or most
rudimentary of these varieties is a recess, the result of the dipping down
of the Malpighian layer into the subepithelial tissue, and forming what
is sometimes called an epithelial sac, the shape of which is tubular or
saccular. This simple tube sometimes lengthens considerably and coils
upon itself, forming a ball, which is known as a coiled tube. The sweat-
glands of the skin are of this kind, and are formed by the dipping down
of the lower strata of the cells or the embryonal Malpighian strata.
These embryonal cells are not columnar in shape, as found in adult
tissue, and have been described by Zeigler 2 thus: "The cell by itself
appears originally as a microscopic mass of pale, finely-granular matter,
the so-called protoplasm. It usually contains within it a nucleus-that
is to say, a structure like a tiny vesicle-whose form may be round,
Odd
1 ¹ Quain's Anatomy.
2 From a paper read by Dr. W. X. Sudduth before the Odontographic Society,
Oct., 1884.
202
ANATOMY.
Kavaficaat
rod-like, or irregular, and in whose interior we can make out, by proper
handling, (1) small definite bodies, the nucleus corpuscles; (2) a net-like
framework of nucleus substances; and (3) a clear fluid, the nucleus
juice. The young cell is at first naked; only in its matured stages does
it develop on its surface an optically distinct membrane or other struc-
ture according to the special tissue of which it forms a part."
The cells of the embryonal Malpighian layer dip down into the
subepithelial connective tissue (the corium) and form epithelial buds,
which are the commencement of the mucous glands, although varying
in shape according to their locality and function. The glands, judging
from the nature of their epithelial lining, can be described under
three general modifications: I. Simple tubular mucous glands; II.
Compound tubular mucous glands; III. Compound tubular salivary
glands.
I. SIMPLE TUBULAR MUCOUS GLANDS (Fig. 98).-The crypts or
follicles of Lieberkühn that are found in the intestinal canal may be
taken as typical glands of this class. They
usually present the shape of a test-tube, form-
ed of the epithelium, the cæcal end pushing
the basement-membrane into the corium or
substance of the mucous membrane, the tube
opening on the surface. The cells lining the
tubes are of a single layer, and apparently of
the same character and continuous with the
columnar epithelial cells of the surface. They
are well distributed within the mucous mem-
brane, varying in number and kind accord-
ing to locality. They are generally placed
perpendicularly to the surface, and often close
together, in which position they constitute the
bulk of the mucous membrane, the thickness
of the membrane often depending upon the
length of the tubes, which differs in different.
localities. The cells are short, cubical, or
columnar, possessing a spherical or oval nu-
cleus. Although the gland-tubes are usually
single, some are bifurcated at the deep ex-
tremity, and the lower end may be somewhat
enlarged in its diameter.
W
་
From a vertical section through
the Mucous Membrane of the
Large Intestines of a Dog, show-
ing, m, the crypts of Lieberkühn
closely placed side by side, each
crypt lined with a layer of
These glands are found in large numbers in
columnar epithelium; mm, the stomach, large and small intestines, and
muscularis
mucosa; s, sub-
mucosa.
FIG. 98.

122
Mn2
the uterus.
Simple tubular glands occasionally have their secreting surfaces
increased by becoming pouched or loculated.
II. COMPOUND TUBULAR MUCOUS GLANDS.-The mucous glands
found in the mouth and the glands of Brunner in the intestines are
typical of this class, being small racemose glands. These glands open
upon the surface of the mucous membrane with a funnel-shaped mouth,
from which a duct passes in an oblique direction (the angle of obliquity
not always being the same) through the corium into the submucous
AREOLAR TISSUE, TENDONS, AND MUSCLES.
203
tissue, at which point the duct divides into several smaller ones, each
of which enlarges immediately after bifurcation and forms a separate
infundibulum; the tubes again narrow and make several irregular turns
or convolutions, and have a cæcal termination. It is these small twisted
tubes that form the secreting part of the gland. The epithelium lining
the glands varies in their different portions: the funnel-shaped mouth
has in man a stratified or pavement epithelium.
The duct proper is lined by a single layer of long, narrow, columnar
cells with intracellular and intranuclear network, giving a distinct long-
itudinal striation and slightly granular appearance to the cell. The
calibre of the duct is of considerable width.
The infundibular portion is lined with more or less flattened epithelial
cells, which gives comparatively a wide lumen to this portion of the
gland. The epithelial cells lining the convoluted portion of the small
tubes are columnar and very slightly granular, with a round or oval
nucleus situated near the outer end of the cell. The cell and nucleus
are made up of a network of fibrils, forming rather large meshes when
the gland is fully developed.
When the gland is active the cell contains drops of mucin; but when
it is inactive the cells are shorter, and become very granular and some-
what opaque; the lumen of this part of the gland is large.
The epithelium of these glands rests upon the basement-membrane,
and is made up of connective-tissue cells which are more branched, some
of the branches penetrating the septa between the intercellular cement
which holds them together.
Ka
Sometimes in the convoluted portion of the glands several embryonal
cells are found; these are located between the columnar epithelium and
the cells forming the basement-membrane or connective tissue of the
tubes.
These compound tubular glands sometimes assume a saccular form,
thus giving us the names of tubular, saccular, or racemose glands.
Sacculo-tubular glands are those which are intermediate in form
between saccular and tubular. The saccules or acini have a tubular
form.
The racemose glands, so called from their resemblance to bunches of
grapes, are modifications of the compound tubular glands, containing a
multitude of saccules having a rounded, pyriform, or thimble shape;
they are arranged in clusters, forming lobules and open into the extremi-
ties of the branched tubes; these tubes form ducts which join other sac-
cular ducts, forming larger branches of the clusters or lobules; the
lobular branches join together and form the main duct or ducts of the
whole gland, which empties its fluid upon the mucous membrane. The
size of the gland usually depends upon the number of lobules or clusters
and the number of saccules in a lobule; thus there are the small race-
mose glands, as those of the roof of the mouth, and others of large size,
like the parotid.
japan
Mucus.-The fluid that is secreted by these glands is viscid, lubric,
and transparent. Examined under the microscope, it is found to con-
tain epithelial cells, also round cells or mucous corpuscles. They so
closely resemble the white or pale blood-corpuscles that they are con-
204
ANATOMY.
sidered identical with them, having either migrated directly from the
blood-capillaries or from the lymphoid tissue surrounding the glands.
The number of mucous corpuscles depends on the glands which produce
the mucus; they vary according to locality.
III. COMPOUND TUBULAR SALIVARY GLANDS.-These, generally
speaking, are six in number, three on each side, named sublingual, sub-
maxillary, and parotid.
The minute anatomy and the physiological action of the salivary
glands prompted Lavdowsky to classify them into three groups: 1.
Mucous glands; 2. True salivary glands; 3. Muco-salivary glands.
FIG. 99.
Mucous Glands.-Examples: submaxillary and orbital glands of the
dog (Fig. 99) and cat and the sublingual glands of man. They are
similar to, though larger than,
the compound tubular glands of
the mucous membrane of the
mouth; their general construc-
tion is the same, with the excep-
tion of the epithelial lining of
the convoluted portion of the
tube, which is composed of mu-
cous cells the same kind of epi-
thelial cells as described in the
mucous membrane-and the pari-
a etal cells, or crescents of Gianuzzi.
These cells are somewhat similar
to the embryonal cell already de-
scribed; they stain deeper than
the surrounding tissue with ham-
otoxylin and eosin, thus showing
their protoplastic condition; they
are granular in appearance, and
form semilunar masses without
definite membrane, but with
pro-
jections that fit into the irregular-
shaped spaces between the epithelial mucous cells and the basement-
membrane with which they are in contact. The lumen of the convo-
luted portion is open and of considerable size.
When these glands are stimulated to secretion, either through the
natural source or by artificial means, the mucous cells at first increase
in size, and a viscous fluid is secreted which passes out by the ducts;
after the action has been continued a short time, the cell-nucleus changes
its shape and position, becoming smaller and granular, more rounded
and central, and the cell takes a deeper stain with carmine. If this
stimulation be prolonged until the glands become exhausted, the mucous
cells lose their identity, and are either lost by being carried off in the
mucus, or they become granular and look like the parietal cells found
next to the basement-membrane.

C
C
с
-d
Ja s
Submaxillary Gland of the Dog: a, mucous cells; b,
protoplasm cells; c, demilune of Gianuzzi; d,
transverse section of an excretory duct, with its
peculiar columnar epithelial cells.
K
"Heidenhain and Lavdowsky have asserted that they are destroyed,
and that their places are taken by a process of new cell-formation from
the parietal areas; but Ewald regards these smaller granular cells as the
AREOLAR TISSUE, TENDONS, AND MUSCLES.
205
shrunken remains of the mucous cells, consequent on exhaustion; and
Klein is of the opinion that such is in reality the case; for, arguing by
analogy, he finds that excessive stimulation results in structural changes
which have already been noted, and accompanied by watery secretion—
i. e. the cells have evidently discharged all their mucin, and have col-
lapsed and become both morphologically and physiologically like those
of the true salivary glands. He also states that in the submaxillary
gland of young animals all gradations are met with from small alveoli
with small lumen lined only with small granular cells, and alveoli some-
what larger and lined either partly with mucous cells, partly with gran-
ular cells, or altogether with mucous cells, to which are applied from
place to place groups of granular cells."¹
FIG. 100.
The True Salivary Glands.-Examples: the parotid gland of mam-
mals, parts of the submaxillary gland of man and the guinea-pig, the
orbital and submaxillary
glands of the rabbit. These
are also compound tubular
glands, and the general ana-
tomical form is the same.
The epithelial cells lining
the convoluted secreting
tubes or alveoli are different,
consequently their function
is not the same (Fig. 100).
Its epithelial cells are cubi-
cal, though the angles are
somewhat rounded; they are
placed in a simple layer, con-
tain a spherical nucleus placed
near the basement-membrane,
and are united with those of
the cell proper, forming to-
gether irregular and small
meshes. When the gland is
inactive these meshes contain a small quantity of fluid substance.
osmic preparations the cell appears to be packed full of distinct granules
of an albuminous nature which obscure the nuclei.
In

Kno
Section of part of the Human Submaxillary Gland. To the
right of the figure is a group of mucous alveoli, to the
left a group of serous alveoli.
Between the cells and basement-membrane there are quantities of
embryonal cells (crescents of Gianuzzi), though not so abundant as in
the glands last described.
The lumen in the convoluted portion of these glands is quite different
from that of the mucous glands; it is doubted by some whether it is
open at all. In the embryonal cell the protoplasm or intercellular
cement so completely fills the tube that it is not discernible.
"After a short period of activity the granules are found to have dis-
appeared in the outer part of the cell, the inner part being still distinctly
granular, and some granules, being apparently free within the lumen
of the alveolus [tube], now becoming distinct (Fig. 101). With more
prolonged activity the clear outer part increases in extent, and the
¹ Coles's Microscopical Science.
206
ANATOMY.
<
granules are found only in the part of the cells which is close to the
lumen, and in those parts which are contiguous to the adjacent cells
(corresponding, perhaps, to fine capillary clefts which pass from the
cavity of the alveolus between the cells). The nuclei have now become
FIG. 101.
Α
&A

B
୯


Alveoli of a Serous Gland: A, at rest; B, after a short period of activity; C, after a prolonged period
of activity. In A and B the nuclei are obscured by the granules of zymogen.
distinct and the cells are smaller; we may suppose, therefore, that the
granules, which no doubt contain the specific elements of secretion, are
formed by or from the protoplasm of the cells during rest, and are dis-
charged into the lumen and dissolved during activity. Probably, how-
ever, during activity, new granules are constantly being formed and
passed outward toward the lumen. According to Langley, the three
processes of growth of the clear protoplasm, conversion of this into
granules, and discharge of these into the lumen-are all proceeding
simultaneously in different parts of the cell during activity." 1
The Muco-salivary Glands.-Examples: the submaxillary glands of
man and of the guinea-pig. They are all compound glands with a
double function, which makes their anatomy complicated. Some of
the lobules composing the gland are constructed and their functions
are the same as those of the pure mucous glands (sublingual gland of
man), while other lobules are constructed and their functions are the
same as the pure salivary glands (the parotid of man); even some of
the convoluted tubes in the same lobule differ, some having the func-
tion of secreting mucus, while others secrete saliva.
"Besides these three forms, Bermann has observed that in connection.
with a large gland of Wharton's duct in many mammals he has discov-
ered a compound tubular mucous gland of unique structure." 2
The special mucous and salivary glands associated with the mouth,
nose, and pharynx are labial, buccal, molar, palatine, lingual, parotid,
submaxillary, sublingual, and lachrymal.
1
¹ Quain's Anatomy, 9th ed.
C
The Labial Glands are of two kinds-the mucous and sebaceous.
The mucous glands are small round racemose or compound tubular
glands about the size of small peas, situated between the mucous mem-
brane and the orbicularis oris muscle; their ducts open upon the mucous
membrane. The sebaceous glands are small, and situated on the outer
part of the red margin of the lip.
The Buccal Glands are small round racemose or compound tubular
glands (smaller than the labial), situated between the mucous membrane
and buccinator muscle; the ducts open upon the mucous membrane.
The Molar Glands are small round racemose or compound tubular
2 Coles's Microscopical Science.
AREOLAR TISSUE, TENDONS, AND MUSCLES.
207
glands (larger than the buccal glands), situated between the buccinator
and masseter muscles, and having separate ducts, which have their
orifices near the third molar tooth.
The Palatine Glands are situated in the deep portion of the muco-
periosteum of the hard palate and under the mucous membrane of the
oral and nasal surfaces of the soft palate and uvula; they are small,
round, racemose, or compound tubular glands, and form a continuous
layer upon each side of the roof of the mouth, but are absent in the
median line.
The Lingual Glands are of two kinds-the small racemose or com-
pound tubular and the simple tubular variety-situated under the
mucous membrane, principally on the posterior portion of the upper
surface of the tongue near the circumvallate papillæ and foramen
cæcum, several of the ducts of the glands opening into the foramen.
Those which open near the circumvallate papillæ, and where the taste-
buds are situated, secrete a watery fluid instead of mucus, as was for-
merly supposed. These glands are also found under the mucous mem-
FIG. 102.

Mastoid pro
Temporal A
DICASTRIC
ner
Socid Parotide
vno's duot
CustatoryM
"Sub-Maxillary
ht
CANYOLES
Ton
១
Il e
arton's duct
Chuck
Sub-Lingita
IN
The Salivary Glands.
brane on the borders of the tongue. On the under surface of the tongue,
near its apex, a number of these glands are grouped together, forming a
small oblong mass having several ducts in a line, which open upon the
mucous membrane.
The Parotid Gland (Fig. 102), so named from being situated near
208
ANATOMY.
'the ear, is the largest of the salivary glands. Its size varies consider-
ably in different people, the average weight being one ounce.
It is a
compound tubular racemose salivary gland.
Situation.-The Parotid Space is bounded in great part by a bony
framework, although the gland is not confined by the lines of the bony
structures. Anteriorly, it is bounded by the ramus of the inferior max-
illary bone; posteriorly, by the mastoid and styloid processes and the
tympanic portion of the temporal bone; its superior boundary is
formed by the convergence of the above structures; below, the boundary
is formed by an imaginary line drawn from the angle of the jaw to the
sterno-cleido-mastoid muscle. Between the mastoid and styloid pro-
cesses the gland comes in juxtaposition with the transverse processes
of the upper cervical vertebræ, especially the atlas. Upon examination
of an articulated skeleton it will be observed that by depressing the head
upon the chest this bony space will be decreased by the jaw coming
closer to the vertebrae, while in the movement of raising or extending
the head it is enlarged. By protruding the lower jaw until the inferior
teeth articulate outside the superior, the space also is enlarged. If the
jaw is depressed the space becomes compressed below, while above it is
increased by the slipping forward of the condyle.
The parotid gland has a very irregular shape; its superficial surface
is convex and lobulated and in close relation with its external fascia.
The anterior surface is divided by a perpendicular groove into an exter-
nal and an internal portion, the external of which extends forward to a
varied extent over the masseter muscle. It is from this anterior portion
that the parotid duct (duct of Steno) is given off; the internal portion
passes forward on the inside of the ramus between the pterygoid muscles.
The deep portion of the gland passes far inward toward the base of
the skull, vertebræ, and pharynx; the upper portion passes into and
occupies the posterior part of the glenoid fossa; the posterior and lower
portion rests upon the styloid process and its muscles, the sterno-cleido-
mastoid and digastric.
K
The Glandula Socia Parotidis, or Accessory Parotid, is a small sepa-
rate lobe, not always present, situated at the anterior external border,
below the zygomatic arch and upon the masseter muscle. The duct of
this lobe enters the parotid duct, where it crosses the masseter muscle.
The Parotid Duct, or Duct of Steno (or Steno's canal), is about two
and a half inches in length, its diameter varying at different portions,
its orifice being the narrowest part, only permitting the entrance of a
small probe. Where it pierces the buccinator muscle it is as large as
a crowquill, and at the position where it passes over the masseter mus-
cle it is from one-twelfth to one-eighth of an inch in diameter. The
duct commences at the anterior portion of the gland, leads over the
masseter muscle about one finger's breadth below the zygomatic arch, and
passes forward beneath an imaginary line drawn from the lower mar-
gin of the concha of the ear to a point midway between the ala of the
nose and the red margin of the upper lip, the transverse facial artery
lying above it. At the anterior border of the masseter muscle the duct
makes a short curve, almost at a right angle, inward; thence it passes
through the cushion of fat and the buccinator muscle; continuing
SADA
AREOLAR TISSUE, TENDONS, AND MUSCLES.
209
obliquely forward a short distance beneath the mucous membrane, it has
its outlet through a small papilla opposite the crown of the second supe-
rior molar tooth.
The Parotid Fascia.-The gland is closely encased in a covering derived
from the deep cervical fascia. The superficial layer of the parotid fascia
is dense and strong, arising posteriorly from the sheath covering the
sterno-cleido-mastoid muscle; after passing over the gland it is con-
tinuous anteriorly with the sheath of the masseter muscle. Above,
it is attached to the zygomatic arch; below, to its own deep leaflet.
The Deep Layer of the parotid fascia is neither so strong nor so dense
as its superficial; below, it is formed from a division of the deep cervi-
cal fascia where it passes beneath the gland to be inserted into the base
of the skull; it forms the stylo-maxillary ligament, and is connected
with the sheaths of the pterygoid muscles, leaving a space or gap
between the anterior edge of the styloid process and the posterior
border of the external pterygoid muscle. Thus it will be seen that the
gland is tightly bound down upon the outside by a close covering, while
within it is not so. The opening in the deep fascia spoken of above
gives communication between the parotid space and the connective tissue
above the pharynx.
The arteries of the gland are very numerous, consisting of a branch
direct from the external carotid, and branchlets from the divisions of
that trunk in its immediate vicinity, as the internal maxillary, tem-
poral, transversalis, facial, posterior auricular. The veins follow a sim-
ilar course.
The external carotid in passing behind the ramus of the
jaw enters the gland, not at the lowest portion, but at its inner and
anterior surface, and passes slightly backward and outward, becoming
more superficial as it ascends.
M
Jamaik
The lymphatic glands join those of the deep and superficial parts of
the neck, one or more being found in the substance of the parotid, and
others upon its surface. These glands are liable to become enlarged and
form a species of parotid tumor.
The nerves are derived from the facial, the auriculo-temporal, great
auricular, and the sympathetic plexus of the external carotid artery.
Experiments upon the dog and cat have shown that the cerebro-spinal
nerve-supply to this gland is from the glosso-pharyngeal. In addition
to the above are the lesser superficial petrosal nerve and the otic gan-
glion, the fibres finally being distributed to the gland through a branch
of the auriculo-temporal. The facial nerve passes through the gland,
though not so intimately bound up in its substance as is the carotid artery.
S
The Submaxillary Gland-so named from its position beneath the
maxillary bone-is smaller than the parotid, and weighs about two or
two and a half drachms. It is a muco-salivary gland, derived fromı
epiblastic structure. The lobules comprising the gland are not held so
tightly together as are those of the parotid, though they are more defined.
The gland is situated below the mylo-hyoid ridge of the inferior maxil-
lary bone in the submaxillary depression and in the submaxillary triangle
of the neck, which is bounded by the mylo-hyoid ridge of the bone and
a line drawn backward to the digastric groove of the temporal bone
above. The lower boundaries are composed of the posterior and ante-
VOL. I.-14
A
210
ANATOMY.
rior bellies of the digastric muscle. It is covered externally by the
superficial layer of the submaxillary fascia, the platysma myoides mus-
cle, and the skin; internally by its deep fascia, which separates it from
the mylo-hyoid, hyo-glossus, and stylo-glossus muscles.
The gland
extends backward to the posterior border of the mylo-hyoid muscle,
where it sometimes passes around its border to the upper surface, and
is separated, at the posterior part, from the parotid gland by the stylo-
hyoid ligament.
The Submaxillary Duct. (Wharton's), through which the secretion of
the above gland passes to the mouth, is about two inches in length,
and its coats are not so thick as those of the parotid duct. It com-
mences by the union of the ducts originating in the different lobules near
the posterior surface of the gland, and with some of the tissue of the
gland winds around the posterior border of the mylo-hyoid muscle. It
then passes forward and inward over the muscle and beneath the hyo-
glossus and the sublingual gland, terminating in a narrow opening
through a soft papilla at the side of the frænum linguæ, near the duct
on the opposite side. Occasionally isolated lobules of gland tissue are
found along the duct.
The arteries which supply the gland are branches of the facial and
lingual. The veins belong to the facial and lingual.
Its nerve-supply is derived from the submaxillary ganglion, which
obtains its motor filaments from the chorda tympani, and its sensory from
the lingual branch of the inferior
maxillary-sometimes, though sel-
dom, from the mylo-hyoid, a branch
of the inferior dental; the sympa-
thetic nerve branches from those
accompanying the arteries in this
vicinity.
The Sublingual or Gland of Bar-
tholin (Fig. 103) is so named from
its position under the tongue. It is
smaller than the submaxillary gland,
and secretes mucus only. The lobules
of this gland are not, as in the parotid
and submaxillary, united into one
with a single duct leading from it,
but are divided into several smaller
glands, each having an independent
duct.
They are arranged in a nar-
row, oblong form situated beneath
the mucous membrane of the mouth,
forming a ridge in the alveolo-lingual
groove. The ridge commences in
front of the tongue near the frænum,
and in close proximity to the gland
of the opposite side; it extends
backward and outward about one
and a half inches to near the first molar tooth. The inner surface of
FIG. 103.

712
Sin
-π
ď
sm
Th
Glands, from the inside. Part of the right
View of the Right Submaxillary and Sublingual
side of the jaw, divided from the left at the
symphysis, remains; the tongue and its mus-
membrane of the right side has been dis-
sected off and hooked upward, so as to expose
the mucous
the sublingual glands: sm, the larger super-
ficial part of the submaxillary gland;, the
facial artery passing through it; sm', deep
portion prolonged on the inner side of the
mylo-hyoid muscle, mh; st is placed below
the anterior large part of the sublingual
gland, with the duct of Bartholin partly
shown; s, placed above the hinder small
end of the gland, indicates one or two of
the ducts perforating the mucous membrane;
d, the papilla, at which the duct of Wharton
the commencement of the duct; h, the hyoid
opens behind the incisor teeth; d',
bone; n, the gustatory nerve; close to it is
the submaxillary ganglion.
AREOLAR TISSUE, TENDONS, AND MUSCLES.
211
the gland is in relation with the genio-glossus muscle, its lower surface
with the mylo-hyoid, and closely relates with the submaxillary duct
and the lingual branch of the fifth nerve.
The sublingual or ducts of Rivinus vary in number from eight to
twenty, corresponding generally to the lobules contained in the gland;
they open separately upon the surface of the mucous membrane over
the ridge formed by the gland, and a few may open into the submax-
illary duct.
The Duct of Bartholin is a single duct of the sublingual gland formed
by the confluence of small ducts arising from the posterior lobules,
which, at times, receive small branches from the submaxillary gland.
It passes in close proximity to the submaxillary duct, and either opens
into it or upon the mucous membrane near the orifice of the latter
duct.
Puncta,
Lachrymatin
The blood-vessels of the sublingual gland are from the submaxillary
and sublingual arteries and the veins.
The nerve-supply is derived from the submaxillary ganglion.
The Lachrymal Gland and its Ducts (Figs. 104, 105) leading to the
Nasal Chamber.—The lachrymal gland is situated principally within
FIG. 104.
Palm
Apertures of ducts &
Mon
<|)*
Glan
ta
SA
*** sub
Jad

Conjunctiva
The Meibomian Glands, etc., seen from the inner surface of the eyelids.
the lachrymal fossa of the frontal bone, at the superior lateral angle of
the orbit, behind the external angular process of the frontal bone, which
affords it protection. It is about half an inch wide by three-fourths of
an inch long. Its shape is somewhat that of a flattened almond. It is
concavo-convex, and has two surfaces, inferior and superior.
The Inferior or Concave Surface is in relation with the capsule of Tenon
or the fascia of the ball of the eye, and the superior and external recti
muscles.
The Superior or Convex Surface is closely applied to the periosteum
of the frontal bone, to which it is connected by a few tendinous fibres.
The lachrymal gland is racemose in structure, and is identical with
the true salivary glands, such as the parotid in man. It is enclosed in
212
ANATOMY.
a capsule and divided into two unequal portions, a superior or larger and
an inferior or smaller, with a thin layer of fascia between them.
The Superior Portion, which comprises the greater part of the gland,
is firmer in structure than the inferior-made so by the larger size of
its lobules and their greater
compactness of arrangement.
It is placed within the lach-
rymal fossa.
FIG. 105.

ch
Diffe
Glánd
X
Punola Lachrymalia
HE
Tuchy
מעייג
Sao
Nasul duct.
The Inferior Portion (glan-
dula lachrymalis inferior, Ro-
senmüller) is smaller than the
superior. Its lobules are mi-
nute in size and loosely col-
lected together, which gives it
a softer appearance than the
superior portion. It is situ-
ated in the subconjunctival
connective tissue, just back
of the lateral portion of the
upper eyelid.
Harder's Gland, found in
most mammals, is situated at
the inner angle of the eye.
In the ox, sheep, and pig,
The Lachrymal Apparatus, right side.
according to Wendt, it is similar in structure and function to the lach-
rymal gland, while in the musk-rat and guinea-pig it is like the seba-
ceous glands of the body. This gland is found in man and in the ape
in a rudimentary state (Gracomini).
T
The Caruncula Lachrymalis is a small pinkish-red body situated at
the inner angle of the eye-the rudiment of the nictitating membrane
of birds, which forms a kind of third eyelid for protection, without
obstructing the functions of the organ.
The Ducts of the Lachrymal Gland leading to the surface of the eye
are from ten to fourteen in number. They pass obliquely downward
beneath the mucous membrane, diverging slightly as they do so, and
finally open into the outer third of the superior palpebral sinus on a
line with each other. A few of the lobules composing the inferior
portion of the gland have independent ducts which open separately,
while others join the ducts coming from the superior or main portion
of the gland.
Arteries.-The lachrymal gland is supplied with blood through the
medium of the lachrymal artery, which is a branch of the ophthalmic.
Nerves. The lachrymal gland receives its nerve-supply from the
lachrymal nerve, which is a branch of the ophthalmic or first division
of the fifth cranial nerve.
The Lachrymal Canals, or Canaliculi, are four in number, a supe-
rior and an inferior for each eye. They have their origin in small
openings, the puncta lachrymalia, situated in the centre of a teat-like
elevation at the inner edge of each eyelid near the inner angle of the
eye, the lachrymal papilla. These canals terminate separately by open-
AREOLAR TISSUE, TENDONS, AND MUSCLES.
213
ing into the lachrymal sac, though they may open by one common duct.
They are lined by pavement epithelium. They pass to their termina-
tion imbedded in connective tissue and surrounded by longitudinal
fibres of the concentric or ciliary portion of the orbicularis palpebrarum
muscle, and empty by independent openings into the lachrymal sac.
Occasionally these canals merge into one another and terminate in one
common duct. They are lined by pavement epithelium.
The Superior Lachrymal Canal is smaller in calibre than the inferior,
though it is slightly longer, being nearly five lines in length and two
lines in width. It commences on the inner margin of the upper eyelid,
curves slightly upward, inward, and downward, and enters the orbital
aspect of the sac a little below its summit.
Ja
The Inferior Lachrymal Canal is somewhat thicker and shorter than
the superior. It commences at the inner margin of the lower eyelid,
passes slightly downward, inward, and upward, and enters the lachrymal
sac just below the superior canal.
The Lachrymo-nasal Passage is divided into two portions, the sac
and the duct, the latter being lined by a ciliated epithelium similar to
that of the nose.
The Lachrymal Sac is the upper enlarged portion of the lachrymo-
nasal passage, and is situated in the sulcus formed by the upper portion
of the lachrymal grooves in the lachrymal and superior maxillary bones.
It is retained in position by connective-tissue fibres which unite with the
periosteum of the bone, and by fibres with the internal tendo-palpe-
brarum and tensor tarsi. The sac is about half an inch long, being
a little wider than long at its broadest portion. It is flat on its inner
surface, which is that portion next the bone, but its external surface,
or that next the orbit, where the canaliculi find entrance, is rounded
and projects toward the eye. The superior portion of the sac is dome-
shaped, while the inferior portion is smaller and passes into the nasal
duct without any line of demarcation between them.
The Lachrymo-nasal Duct is formed by the lower portion of the
lachrymo-nasal passage. It is slightly over half an inch in length, and
extends from the lachrymal sac into the inferior meatus of the nose by
passing through the lachrymal canal. The duct is larger at its extrem-
ities than in the middle, and is adherent to the bony walls, through
which it passes, by connective-tissue fibres uniting it with the periosteum.
Valve-like folds of the lachrymo-nasal passage have been described
as existing at the openings, within the canaliculi of the sac, in the duct,
and at its termination in the nasal chamber.
THE TONSILS.
The Tonsils (tonsillæ amygdala) are two glandular bodies situated on
each side of the oro-pharyngeal space, which is in relation in front with
the palato-glossal fold (anterior palatine arch); behind, with the palato-
pharyngeal fold (posterior palatine arch); laterally, with the constrictor
muscles of the pharynx; and proximally or internally it is open, this
surface being covered by the mucous membrane of the oro-pharyngeal
space above referred to. The fact that the palato-glossal and palato-
214
ANATOMY.
pharyngeal muscles arise from closely-related portions of the palate,
and diverge as they descend to their insertions, causes the tonsillar space
to be narrow at the top and wider at the bottom; and the further fact
that the gland is about of equal width and thickness causes it to be
compressed above, while below it is comparatively free from pressure.
The tonsils are about three-fourths of an inch long, half an inch
wide, and about the same in thickness, their extremities being rounded.
They vary considerably in size in different individuals, the two often
being dissimilar in the same person. They are composed of masses of
connective-tissue fibres and diffused adenoid tissue embracing lymph-
follicles. On their free or proximal surface they are pitted with from
twelve to twenty indentations or foldings, in such a way that they pro-
duce small recesses or crypts situated within the substance of the gland.
These give the free surface of the gland a perforated appearance. The
crypts are lined by a continuation of the stratified epithelium covering
the mucous membrane of the mouth. The lymph-follicles above
referred to are arranged around the walls of the crypts, and outside
of the follicles are a number of small mucus-secreting glands. The
secretion from these mucous glands is thick and grayish in appearance;
it is discharged into the crypts. The retention of this fluid causes the
breath to become fetid. Sometimes this secretion becomes inspissated,
and is discharged in the shape of small balls of yellowish-gray matter
having a very offensive odor. The retention of this matter may cause
the tonsils to become highly inflamed.
When the tonsils are in normal condition, lymph-corpuscles migrate
from the body of the gland, through the mucous membrane on its free
surface, and enter the muco-salivary fluid of the mouth. These corpus-
cles, when detected in the saliva, are called by some writers mucous or
salivary corpuscles. These corpuscles absorb water, become spherical
in form, and finally disintegrate.
The Infratonsillar or Pharyngeal Tonsils are situated below the ton-
sils proper, in the upper part of the pharynx. As the mucous mem-
brane in parts of this region is covered by ciliated columnar epithelium,
it follows that some of the crypts of these glands are lined with the
same structure.
Arteries. The tonsils are extremely vascular bodies, being supplied
with blood through the medium of the tonsillar and palatine branches
of the facial artery, the descending palatine branch of the internal max-
illary, and the ascending pharyngeal. From these arteries a fine plexus
of capillaries is formed. These capillaries are distributed to the differ-
ent tissues within the gland. The extreme vascularity of the gland
causes its excision in whole or in part to be followed by considerable
hemorrhage. Although the internal carotid artery passes to the outside
of the superior constrictor of the pharynx, and is usually about three-
fourths of an inch back of the gland, it has been cut in performing
tonsillotomy, with very serious results. In operations upon the gland
the surgeon should direct his knife away from the artery.
magdat
w
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
215
BLOOD-VESSEL SYSTEM OF THE HEAD AND
ANTERIOR CERVICAL REGION.
THE head is supplied with blood by the two vertebral and the two
common carotid arteries, besides numerous anastomotic branches from
other trunks.
THE ARTERIES.
THE COMMON CAROTIDS (RIGHT AND LEFT).
The Common Carotids (Fig. 106) are very similar in position and in
their course through the neck on either side. They give off the same
FIG. 106.

BER, 2016 WE THE WASHE
Recurront Laryngeal
R? Vagus
1
•Ap
w of the poprawner of the
Right
Vena
Superior Vena Cava
Right
uricle
YAPAMAGATURDA
Right Com Care
الان
Coronary
Tufer
Appendix
Vend
Cava
1614
Ascending Portion
Thyroid Gland
Pinte
Left Vena Innominata
Rt Tuf. Thyroid
Linnut of Ponca
Pro
ight
Arts
Left P ATU
Pulmonary
Artery
Right Vent
'i
Thoraci
Aorta
hräthey
GAL AND
Left Fagus
Left Phrenic
Thoracic Duot
Pleura
R. Coronary
Coronary
Rf Subclavie
RF Com.Carotid Inavminute
BISE
Plan of the Branchus
The Arch of the Aorta, and its Branches.
Left Common Carotid
Subclar
Left
Ascending port ny
Arch
Appendix of Left Auricle
Transverst
of
Aorta
aanden.
!
Descending Ju
Lift Ceronary
216
ANATOMY.
number of branches, though these may vary in size. They are about
8 mm. (3 inch) in calibre. They differ both in their length and origin,
the left being the longer: it arises directly from the arch of the aorta,
and is more deeply situated than the right.
The Right Common Carotid Artery is the shorter of the two, and at
its origin is more superficially situated than the left. It is one of the
terminal branches of the brachio-cephalic (innominate) artery, the other
branch being the subclavian. The bifurcation of the brachio-cephalic
into the right common carotid and subclavian arteries takes place within
the thorax behind the sterno-clavicular articulation and above the level.
of the second dorsal vertebra. In front it is in relation with the right
brachio-cephalic (innominate) vein, and externally with the subclavian
vein and the pneumogastric and phrenic nerves.
The Left Common Carotid Artery arises from the left of the arch of
the aorta, and, with the exeption of the coronary arteries, which supply
the heart, is the second branch given off from that vessel. At its origin
it is situated within the thorax. It then passes upward and a little out-
ward to the left of the sterno-clavicular articulation, from which point
its course is similar to the artery of the right side. It is situated just
behind the upper portion of the sternum, and is covered by the sterno-
hyoid and sterno-thyroid muscles, and in early childhood by a portion
of the thymus gland. The left brachio-cephalic vein crosses it in front,
and behind it is in relation with the trachea, oesophagus, and thoracic
duct. Externally will be found the pleura, pneumogastric (tenth
cranial), and phrenic nerves.
In the neck the common carotids are generally similar in course and
situation, though they may differ slightly in size, and their termination
may be at a point slightly higher or lower on one side than the other.
They extend from the sterno-clavicular articulation on either side to
their termination opposite the upper border of the thyroid cartilage,
without giving off any branches. At the upper border of the thyroid
cartilage they divide into two large branches, the external and internal
carotids.
The Line of the Common Carotid Artery extends from the sterno-
clavicular articulation to a point midway between the angle of the jaw
and the mastoid process of the temporal bone. At the point where the
carotid arteries emerge from the thorax and enter the neck they are
closely approximated, being separated only by the anterior semicircum-
ference of the trachea. As they ascend the neck they diverge, and at
their termination are separated by the larynx and the pharynx, which
structures are pushed forward between them. They are deeply seated
at their origin, but become quite superficial in the region of the larynx.
The Sheath of the Common Carotid Artery is derived from the deep
cervical fascia, and encloses, together with the artery, the pneumogastric
nerve and internal jugular vein. The artery is situated to the median
side of the nerve, while the vein is external to both artery and nerve.
Each of these structures is separated from the others by a distinct
investment of connective tissue. The descendens noni nerve is occa-
sionally within the sheath of the common carotid, but more frequently
it passes down the neck upon the sheath.
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
217
Superficial Relations.-At the base of the neck the common carotid
artery is covered by the skin, platysma myoides, and deep fascia, and
by the sternocleido-mastoid, sterno-hyoid, and sterno-thyroid muscles.
FIG. 107.

mange guy Paint
Occipital
Posterior Aurion
790
اله
TUALIO
Posterior
Gilla
Belly
e
Plex u 3
-02
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Surgical Anatomy of the Arteries of the Neck, right side.
//////
CA
Crico-Thyroid AY,
It is crossed by the omo-hyoid muscle opposite the cricoid cartilage, and
below this by the anterior jugular vein. The upper portion of the com-
mon carotid, or that portion which extends from the omo-hyoid muscle
to its termination, is covered by the skin, platysma myoides, and deep
218
ANATOMY.
fascia, and by the anterior border of the sterno-cleido-mastoid muscle.
On dissection, however, because of the shrinkage which takes place in
the muscle after death, it is usually found that the anterior border
of the sterno-cleido-mastoid does not cover the artery in this position,
but it is found in the carotid triangle, which is bounded above by
the posterior belly of the digastric muscle, in front by the anterior
belly of the omo-hyoid muscle, and behind by the sterno-cleido-mas-
toid muscle, the sterno-mastoid branches of the superior thyroid artery,
and by the facial, lingual, and superior thyroid veins, crossing it in this
triangle. Occasionally it is partially covered by the thyroid gland.
Deep Relations.-The common carotid artery lies directly in front of
the cervical vertebræ, separated from them by the longus colli and the
rectus capitis anticus major muscles. The interval between the artery
and the transverse processes of the vertebræ being small, compression
backward in this situation to a great extent controls the flow of blood
through the vessels. In the median line the vessel is related, as it
passes from below upward, with the trachea, thyroid gland (the gland
at times overlapping the artery), larynx, oesophagus, and pharynx.
Variations. Normally, the common carotid artery gives off no
branches, and it is of the same calibre from its commencement to its
bifurcation. At other times either the superior or inferior thyroid
artery may arise from it, the artery being reduced in size above the
branches. The division of the common carotid into the external and
internal carotids may take place as high or higher than the hyoid bone,
or it may bifurcate lower down than its normal position; the common
carotid may be entirely absent, when the external and internal caro-
tids will generally arise directly from the aorta. At times, however,
the right common carotid may arise directly from the aorta alone or
in conjunction with the left-a condition common in some of the lower
animals.
The origin of the left common carotid is more varied than that of the
right. It may arise in either of the following ways: from or in con-
junction with the brachio-cephalic or subclavian, or by a common trunk
with the right common carotid, when the subclavian will arise directly
from the aorta.
Collateral Circulation.-If the common carotid artery be ligated, the
blood for the parts usually supplied by the internal carotid will be car-
ried by the vertebral arteries and the internal carotid of the opposite side.
These arteries, together with the other internal carotid, freely communi-
cate with each other through the circle of Willis at the base of the
brain. The blood for the parts supplied by the external carotid is car-
ried by the superior and inferior thyroids, which freely anastomose; by
the occipital and deep cervical, which also anastomose; and by the
external carotid of the opposite side through its communication with
the two superior thyroids, the lingual, facial, temporal, internal maxil-
lary, and occipital arteries.
S
QA
The External Carotid Artery is so called because it supplies the
external portion of the head with blood. It is about 6 mm. (1 inch)
in calibre, and arises from and is one of the terminal branches of the
common carotid. This origin is within the carotid triangle opposite
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
219
the upper border of the thyroid cartilage. From this point it passes up
the neck between the pharynx and the muscles resting upon the vertebra
in this region, to a point opposite the surgical neck of the lower jaw,
where it divides into two terminal branches, the internal maxillary and
the superficial temporal. As it ascends the neck it decreases in size, the
reduction in calibre being due to the number of large branches it gives
off. In early life it is smaller than the internal carotid, but it gradually
increases until adult life, when both arteries are of the same size.
Relations. At its origin the external carotid artery is situated at the
median side of the internal carotid, but soon becomes superficial to that
artery. It is covered by the skin, the platysma myoides and sterno-
cleido-mastoid muscles, and the deep fascia. The superior laryngeal
nerve passes behind the artery in this situation. Its deep relation at
its commencement is with the pharynx and hyoid bone. From this
position it passes up internally to the stylo-hyoid and posterior belly of
the digastric muscle and part of the parotid gland, which separates it
from the back part of the ramus of the jaw. The posterior belly of
the digastric muscle is a good guide in the ligation of the artery.
Throughout its upper portion it is separated from the internal carotid
by the stylo-glossus and stylo-pharyngeus muscles, the glosso-pharyn-
geal nerve, and part of the parotid gland.
The external carotid artery is usually unaccompanied by a vein,
although the temporo-maxillary vein crosses it within the parotid gland,
the anterior division of the temporo-maxillary vein passing downward
to the facial. The facial and lingual veins cross the artery below the
digastric muscle on their way to join the internal jugular. Higher up,
in the substance of the parotid gland, the artery is crossed by the facial
nerve, the hypoglossal nerve crossing it just below the posterior belly
of the digastric muscle.
Branches of the External Carotid Artery. The external carotid artery
in its ascent through the neck gives off eight branches. Their names,
in great measure, indicate their distribution. Three of the branches-
viz. the superior thyroid, lingual, and facial-pass anteriorly; two-viz.
the occipital and posterior auricular-pass posteriorly; one, the ascend-
ing pharyngeal, passes internally: it terminates in two branches, the
superficial temporal and the internal maxillary.
Variations. The general variations in the origin of the external
carotid artery have been mentioned under the head of the common
carotid. Other variations are caused by the manner in which its
branches are given off. The external carotid may at times be entirely
wanting. When this is the case the different branches which are usually
given off by it arise from a common trunk which represents the inter-
nal and external carotids. The superior thyroid and the lingual arteries
may arise from a single branch, instead of two separate branches, or
the lingual and facial or the superior thyroid, lingual, and facial may
originate in a similar manner. The superior thyroid may also arise
from the common carotid. The external carotid artery occasionally
divides at the angle of the jaw, reuniting again near the neck of the
inferior maxilla to form the temporal artery.
The Superior Thyroid Artery is the first anterior branch of the
M
220
ANATOMY.
external carotid. It is about 3 mm. († inch) in calibre, and arises
close to the bifurcation of the common carotid, on a level with or
slightly below the great cornu of the hyoid bone. It is very super-
ficially located within the carotid triangle. It passes slightly upward
and forward at first, after which it passes forward and downward, to
the upper margin of the thyroid cartilage, forming an arch. Here it
passes beneath the omo-hyoid, sterno-hyoid, and sterno-thyroid muscles,
supplying them with branches, and is finally distributed to the thyroid
gland, breaking up into numerous terminal branches, which anastomose
quite freely with the terminal branches of the inferior thyroid.
The Transverse Artery, which is not universal in its existence, is one
of the terminal branches that pass along the upper border of the isth-
mus of the thyroid body within its capsule. The transverse artery may
be of large size, and give off branches that overlie the isthmus.
The Superior Thyroid Artery gives off the following branches: the
hyoid, superficial descending or sterno-mastoid, superior laryngeal, and
crico-thyroid.
The Hyoid or Inferior Hyoid Artery is a small vessel that passes
inward from the superior thyroid along the under surface of the hyoid
bone beneath the thyro-hyoid muscle. It gives off branches that sup-
ply the muscles attached to the under surface of the hyoid bone, and
anastomoses with similar branches of the opposite side.
The Superficial Descending or Sterno-mastoid Artery passes downward
across the sheath of the common carotid artery. It is of importance to
remember this fact in operations for the ligation of the common carotid
in this region. This artery is distributed to the following muscles: the
omo-hyoid, sterno-hyoid, sterno-thyroid, sterno-cleido-mastoid, and infe-
rior constrictor of the pharynx.
The Superior Laryngeal Artery is the largest of the several branches
of the superior thyroid, being about 2 mm. (inch) in calibre. It
extends inward, accompanied by the superior laryngeal nerve; passes
under the thyro-hyoid muscle to the thyro-hyoid membrane; pierces
this membrane and enters the larynx, where it separates into two divis-
ions, superior and inferior.
JOIN
The Superior Division supplies the posterior surface of the epiglottis
and its mucous membrane.
The Inferior Division supplies the intrinsic muscles of the larynx and
its mucous membrane.
The Crico-thyroid Branch is a small artery about to 1 mm. ( to
inch) in calibre. It passes across the crico-thyroid membrane, and
anastomoses with the corresponding artery of the other side. The
position of this artery gives it importance, on account of the fact that
hemorrhage often occurs from its division in the operation of laryn-
gotomy.
Variations.-The superior thyroid artery may be larger or smaller
than usual. When this difference exists either way, one or more of the
other three thyroid arteries will be found to be increased or diminished
in size. Occasionally it is found to arise in common with the lingual
or facial, or both. It may also be a division of the common carotid.
The branch of this artery which supplies the sterno-cleido-mastoid mus-
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
221
cle is sometimes a separate and distinct branch of the common carotid.
It occasionally gives origin to the ascending pharyngeal artery, and its
hyoid branch is often very small or entirely absent. The superior
laryngeal branch also often arises from the external carotid, and occa-
sionally from the common carotid, and may pierce the crico-thyroid
space or pass through a foramen in the thyroid cartilage. The crico-
thyroid branch is sometimes of considerable size, and may interchange
with a branch to the thyroid body or a division of the inferior thyroid
artery.
THE LINGUAL ARTERY.
The lingual artery is about 3 mm. († inch) in calibre, and is the
second anterior branch of the external carotid. It arises within the
carotid triangle between the superior thyroid and facial arteries, and
nearly opposite the great cornu of the hyoid bone. It passes upward a
short distance, then turns downward, forming a concavity which is crossed
by the hypoglossal nerve. Thence it extends beneath the digastric and
stylo-hyoid muscles to reach the great cornu of the hyoid bone, running
parallel with it, under cover of the hyo-glossus muscle, to a point near
its anterior border, where it turns upward and passes to the under sur-
face of the tongue, through which it extends to the tip, where it termi-
nates in the ranine artery.
Relations.—This artery is divided into four portions, according to
the regions through which it passes. The first or superficial portion
is wholly within the carotid triangle, and is covered by the skin,
platysma myoides, and fascia of the neck, and rests upon the connective
tissue and middle constrictor muscle of the pharynx. The second or
horizontal portion is covered externally by the sterno-hyoid, digastric,
and the greater part of the hyo-glossus muscle, the hypoglossal nerve
passing to the outer side of the muscles: this portion of the artery
rests upon the middle constrictor muscle of the pharynx. The third or
ascending portion is that part which extends upward to the under sur-
face of the tongue: it passes between the hyo-glossus and genio-glossus
muscles. The fourth or ranine portion is generally in relation with the
intrinsic muscles of the anterior part of the tongue. Near its termina-
tion it becomes quite superficial and communicates with its fellow of the
opposite side.
B
The branches of the lingual artery are the hyoid, dorsalis lingual,
sublingual, and ranine arteries.
The Hyoid or Superior Hyoid Artery is the first branch of the lin-
gual, and arises within the carotid triangle. It passes to the upper
border of the hyoid bone, supplying the bone, the muscles attached
to its upper portion, and the fibro-adipose tissue between the bone
and the base of the epiglottis.
Tota
The Dorsalis Lingual Artery, which is occasionally replaced by sev-
eral smaller ones, arises from the second part of the lingual artery as it
passes beneath the hyo-glossus muscle. It extends to the upper surface
of the tongue, supplies the mucous membrane of this surface, as well as
the substance of the organ, and communicates with its fellow of the
222
ANATOMY.
4.
other side. Occasionally the artery will be found to be exceedingly
large. When this is the case, in addition to the structures already
mentioned it usually supplies the stylo-glossus muscle, the tonsils,
epiglottis, and soft palate.
The Sublingual Artery is, in reality, one of the terminal branches of
the lingual, the ranine artery being the other. It arises from the
lingual at a point opposite the anterior margin of the hyo-glossus
muscle. From this margin it passes forward between the genio-glossus
muscle and the sublingual gland, supplying the gland, the mucous
membrane of the floor of the mouth, the alveolo-lingual groove, and
gums; also extending to the mylo-hyoid and other muscles of this
region.
The Ranine Artery is one of the terminal branches of the lingual. It
arises opposite the anterior margin of the hyo-glossus muscle, and passes
in a tortuous course within the structure of the muscle to a point near
the tip of the tongue, where it is quite superficial. In its course it gives
off numerous branches and communicates with the corresponding artery
of the opposite side. This anastomosis is the most important between
the branches of the lingual artery, the others being capillary in cha-
racter.
The nutrition of the two halves of the tongue supplied by each lin-
gual artery and its branches is comparatively independent. The ranine
artery being so superficially situated, and so close to the frænum linguæ,
there is some danger of cutting it in the operation for so-called tongue-
tie.
Variations. The lingual artery may arise in conjunction with the facial
or superior thyroid, or the three arteries may arise as a common trunk
from the external carotid. Occasionally it arises from the internal max-
illary artery. Sometimes it accompanies the hypoglossal nerve along
the outer margin of the hyo-glossus muscle. The artery may be
entirely absent, and its place supplied by branches from the internal max-
illary, submental branches of the facial, or by the corresponding artery
of the other side. It occasionally gives origin to the ascending pha-
ryngeal artery, and the superior laryngeal, the submental, and the ascend-
ing palatine have been known to spring from it. Sometimes the supe-
rior hyoid branch of the lingual is entirely absent. When this is the
case its place is supplied by the inferior hyoid. The sublingual branch
of the lingual artery arises at times from the facial, and reaches its des-
tination by piercing the mylo-hyoid muscle.
Volg d
mat
THE FACIAL OR EXTERNAL MAXILLARY ARTERY.
The Facial or External Maxillary Artery (Fig. 108) is about 31 mm.
(inch) in calibre, and arises from the external carotid within the
carotid triangle a little above the lingual artery. It extends upward,
forward, and inward, passes beneath the posterior belly of the digas-
tric and the stylo-hyoid muscles, and enters the posterior part of
the submaxillary triangle. It then passes forward within the sub-
stance of the submaxillary muco-salivary gland, extending parallel
with the base of the lower jaw, close to the mylo-hyoid muscle. Leav-
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
223
ing the gland, it makes a sharp turn upward over the body of the
inferior maxillary bone, curving through a notch just in front of the
insertion of the masseter muscle. From its origin to this point, where
it curves over the body of the inferior maxilla, it constitutes the first
or cervical division of the artery. As it passes over the body of the
jaw the artery is quite superficial, being covered only by the skin and
platysma myoides muscle. In this situation the pulsation of the artery
FIG. 108.

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The Arteries of the Face and Scalp.
can be distinctly felt, and the flow of blood to parts above can be con-
trolled by direct pressure of the artery against the bone. This is like-
wise a favorable location for the ligation of the artery. From the base
of the jaw it passes obliquely upward and forward toward the inner
canthus of the eye, where it terminates in the angular artery and com-
municates with branches of the ophthalmic artery. From the body of
the jaw it passes between the masseter and depressor anguli oris muscles
to near the angle of the mouth. It then extends beneath the two zygo-
224
ANATOMY.
matici muscles and the levator labii superioris, passing over the buccina-
tor, the levator anguli oris, and occasionally over the levator labii supe-
rioris proprius. It terminates either upon the levator labii superioris,
alæque nasi, or within the substance of the muscle.
The facial artery is very tortuous both in the neck and in the face;
for if the course was a straight line from its origin to its termination
the artery by its inelasticity would bind the different structures through
or over which it passes, interfering with the free action of the jaws and
the mobility of the lips and muscles of expression. The same winding
of this vessel in the neck permits free movement of the larynx and its
associate parts, and prevents interference with deglutition.
The Facial Vein is superficial to and accompanies the facial artery
throughout its course; part of the submaxillary gland is interposed
between them in the neck. As they cross the jaw the artery and vein
are in close proximity, but in the face they are separated by the zygo-
maticus minor and the levator labii superioris. Branches of the facial
nerve pass over the artery as it crosses the infraorbital nerve; these
latter are usually separated by the elevator muscle of the upper lip.
Branches of the Facial Artery.-The branches of the facial artery
are divided into two sets, cervical and facial, according to the locality
through which they extend. They are as follows :
CERVICAL BRANCHES.
Inferior or ascending palatine,
Tonsillar,
Glandular,
Submental,
FACIAL BRANCHES.
Inferior labial,
Inferior coronary,
Superior coronary,
Lateralis nasi.
Angular.
The Inferior or Ascending Palatine Artery is the first branch of the
facial, though in some instances it arises from the external carotid. It
extends upward, and passes beneath the stylo-glossus and stylo-pharyn-
geus muscles, above which it will be found running between the internal
pterygoid and the walls of the pharynx to a level with the soft palate.
In its course it distributes branches to the surrounding muscles, the
tonsils, and the Eustachian tube. Near the levator palati muscle it
divides into two branches, superior and inferior. The superior supplies
the levator palati muscle, the soft palate, and the palatine glands. The
inferior supplies the tonsils and anastomoses with the tonsillar artery.
These two vessels also communicate with the posterior palatine branches
of the inferior maxillary artery.
The Tonsillar Artery, a branch of the facial, extends upward super-
ficially to the stylo-glossus muscles, passes through a perforation in the
superior constrictor of the pharynx, and gives off small branches to the
tonsils, side of the tongue, and mucous membrane of the surrounding
parts. When the tonsillar branch of the facial artery is absent, the
parts to which it is generally distributed are supplied by the descending
palatine or ascending pharyngeal branches, or both.
The Glandular Arteries (submaxillary) are several short branches
from the facial which are distributed to the muco-salivary submaxillary
gland. Some of these branches extend through the substance of the
T
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
225
gland, and are distributed to the stylo-hyoid, internal pterygoid, and
masseter muscles.
The Submental Artery is the largest and most important of the cervi-
cal branches of the facial artery. It arises at a point between the
submaxillary gland and the position of the facial artery as it turns
upward across the body of the jaw to reach the face. Occasionally it
arises from the sublingual artery; it extends in a continuous line from
the facial artery below the base of the jaw to its symphysis, where the
artery turns upward to the chin, supplying the muscles of this region
and anastomosing with the inferior labial and mental arteries and its
fellow of the opposite side. The mylo-hyoid muscle is situated on its
inner side, branches of the artery perforating the muscle and anastomos-
ing with the sublingual artery. In its course it distributes branches to
the neighboring tissues.
The Inferior Labial Artery is the first of the facial branches of the
facial artery. It arises soon after the artery reaches the face, and passes
forward beneath the depressor anguli oris muscle. Its branches are
distributed to the integument and muscles of the lower lip, and
anastomose with the inferior coronary, submental, and mental arteries.
The Inferior Coronary Artery supplies the lower lip. It arises at
the outer margin of the depressor anguli oris muscle, a little below the
level of the angle of the mouth, passes a short distance upward and
inward beneath the depressor anguli oris, depressor menti, and the
orbicularis oris muscles, and between the latter muscle and the mucous
membrane close to the free margin of the lip. Its branches supply the
muscles and mucous membrane of this region and the labial glands,
anastomosing with its fellow of the opposite side, with the inferior
labial, and the mental branch of the inferior dental artery.
The Superior Coronary Artery supplies the upper lip and arises
beneath the zygomaticus major muscle. It is larger and more tortuous
than the inferior coronary, and passes transversely between the mus-
cles and mucous membrane of the upper lip close to its free margin,
inosculating with the corresponding artery of the opposite side. It
supplies the muscles, mucous membrane, and labial glands of the upper
lip, and gives off two or three branches which pass to the nose. One,
the artery of the septum, passes along the columna nasi as far as the
tip of the nose, and supplies the septum. Another branch supplies the
alæ of the nose.
The inferior and superior coronary arteries occasionally arise as a
common trunk. If either or both are smaller than is generally the
case, the arteries of the opposite side are correspondingly increased in
size. It is by reason of their free anastomosis with each other that
they receive the name "coronary arteries," though this anastomosis is
not always present.
The Lateral Nasal Artery arises from the facial as it ascends along
the side of the nose. Occasionally this artery is replaced by two or
three smaller arteries. The branches of the lateral nasal supply the
wing and dorsum of the nose, and anastomose with the nasal branch of
the ophthalmic, infraorbital, artery of the septum, and corresponding
artery of the opposite side.
VOL. I.-15
226
ANATOMY.
The Angular Artery is properly the continuation of the facial. It
ascends between the inner canthus of the eye and the nose, and its
branches supply the tissues in this region, including the lachrymal
It anastomoses with the infraorbital and the nasal branch of the
ophthalmic.
sac.
Variations.—The facial artery may arise in conjunction with the
lingual and superior thyroid, and it may also have its origin above the
carotid triangle. When this is the case, it descends to its normal posi-
tion below the jaw. It may interchange with the internal maxillary
(deep facial) artery. It varies in size and distribution. Rare instances
are recorded where the artery has not passed upon the face, but has ter-
minated in the submental. At times it extends in the face only far
enough to supply the lower lip, and it frequently fails to give off the
lateral nasal and angular branches. When the facial artery is abnor-
mally short, and fails to extend to its usual termination upon the
face, the blood-supply is received through the enlargement of the nasal
branch of the ophthalmic and branches of the transverse facial (a divis-
ion of the temporal artery), or through one or more of the terminal
branches of the internal maxillary. In cases where any of these arteries
are small in size or entirely absent the facial artery may be increased
in size to supply the deficiency. Occasionally, while in the neck the
facial may give off a branch to supply the sublingual gland, the gland
in such case not receiving its usual supply from the lingual.
THE OCCIPITAL ARTERY.
The occipital artery is about 3 mm. (4 inch) in calibre, and arises
from the surface of the external carotid, opposite to, or slightly above,
the facial. From this origin, which is beneath the sterno-cleido-mas-
toid and the posterior belly of the digastric muscle, it passes upward
and backward, and is covered by the posterior belly of the digastric and
the stylo-hyoid muscle and a portion of the parotid gland. The hypo-
glossal nerve crosses it on its outer side. It then passes to the outside
of the internal jugular vein, the pneumogastric and spinal accessory
nerves, to an interspace between the transverse process of the atlas and
the mastoid process of the temporal bone. When it reaches the base of
the skull it is directed backward, following the occipital groove situated
to the inner side of the digastric fossa on the temporal bone. It lies
beneath the muscles attached to the mastoid process, and above the
superior oblique, complexus, and rectus posticus major muscles. When
it reaches the extremity of the groove it turns upward, passing through
the trapezius muscle, then over the occiput, being distributed to the
structures in this region, and anastomoses with the temporal artery and
corresponding artery of the opposite side.
The branches of the occipital artery are-
1. The muscular
;
4. Posterior meningeal ;
5. Mastoid;
6. Superficial or cranial.
The Muscular Arteries consist of several small branches which supply
the posterior belly of the digastric, the stylo-hyoid, splenius capitis, and
2. The auricular;
3. Descending cervical;
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
227
trachelo-mastoid; a branch somewhat larger than the rest supplies the
sterno-cleido-mastoid muscle. This branch usually arises a little above
the origin of the occipital artery, though it may arise from the external
carotid.
The Auricular Artery is a small branch which supplies the auricle and
the tissues near the mastoid process. This branch is not always present.
The Descending Cervical, or Ramus Cervicularis Princeps Artery, is
of large size, and arises beneath the splenius capitis muscle. Soon after
its origin it divides into two branches, superficial and deep. The super-
ficial branch perforates the splenius muscle, supplying it and the trape-
zius. The deep branch passes beneath the complexus and semi-spinalis
colli, and inosculates with the vertebral and the deep branch of the
superior intercostal. Through the anastomoses of these arteries a col-
lateral circulation is maintained after the ligation of either the common
carotid, external carotid, or subclavian arteries.
The Posterior or Meningeal Branch arises from the occipital, passes
up along the internal jugular vein, and enters the brain-case through
the jugular foramen; it supplies the posterior portion of the dura mater.
This artery is not always present.
The Mastoid Artery is a small branch from the occipital, which enters
the mastoid foramen of the temporal bone; it supplies the diploë, walls
of the mastoid cells and lateral sinus, and the dura mater in the occip-
ital fossa.
GRAND
The Superficial or Cranial Arteries are terminal branches of the
occipital, and pass between the integument and the occipital muscle,
supplying the structures in this region. They anastomose freely with
each other, with the corresponding artery of the opposite side, and the
posterior auricular and superficial temporal arteries.
Variations.-The occipital occasionally arises from the internal
carotid or in conjunction with the facial or from the cervical branch
of the inferior thyroid. Its direction also may vary: instead of pass-
ing to the median side of the trachelo-mastoid muscle, it may extend
laterally. It occasionally divides into a larger and smaller branch, the
smaller assuming the usual direction of the artery, while the larger
passes superficially to the sterno-cleido-mastoid muscle. The stylo-
mastoid artery occasionally arises from the occipital instead of the pos-
terior auricular artery.
THE POSTERIOR AURICULAR ARTERY.
The posterior auricular artery arises from the external carotid nearly
opposite the apex of the styloid process of the temporal bone, above the
digastric and stylo-hyoid muscles. It is about 2 mm. (inch) in cali-
bre; it extends obliquely upward and backward beneath the parotid
gland, and passes up the styloid process, where it is crossed by the
facial nerve. It then ascends between the cartilage of the ear and the
mastoid process of the temporal bone, becomes superficial, and divides
into two terminals, the auricular and the mastoid.
The branches of the posterior auricular artery are the stylo-mastoid
and the auricular.
228
ANATOMY.
The Stylo-mastoid Artery is long and slender, and enters the stylo-
mastoid foramen in the temporal bone, the facial nerve passing out by
the same opening. It gives off branches which supply the mastoid cells,
the stapedius muscle, the tympanum, and the semicircular canals of the
internal car. The continuation and termination of the stylo-mastoid
artery are very small; it extends forward within the aquæductus Fal-
lopii, anastomosing with the petrosal branch of the middle meningeal,
which is itself a branch of the internal maxillary. In young subjects
the artery that supplies the tympanum communicates with the tympanic
branch of the internal maxillary, thus forming a vascular circle around
the tympanic membrane, from which delicate vessels concentrate to
supply that structure.
The Auricular Artery, the other branch of the posterior auricular,
ascends behind the ear and distributes branches to the retrahens aurem
muscle, the posterior portion of the temporal region, and skin over the
mastoid process; two branches to the auricle supply both the inner and
outer surface of the pinna. Besides these, the posterior auricular artery
gives off small muscular twigs which supply the digastric, stylo-hyoid,
sterno-cleido-mastoid, and occipital muscles, the integument, and the
parotid gland.
Variations. The posterior auricular artery sometimes terminates in
the stylo-mastoid. It is occasionally quite small; sometimes it is abnor-
mally large, and takes the place of the occipital or superficial arteries.
At times it is given off by the occipital artery, and the transverse facial
may arise from the posterior auricular.
My
THE ASCENDING PHARYNGEAL ARTERY.
The ascending pharyngeal artery is the smallest of the eight branches
of the external carotid. It is long and slender, and extends in an almost
straight course from its origin to its termination. It usually arises from
the posterior part of the external carotid, from a half to one inch above
the origin of this artery, and passes upward between the external caro-
tid artery and the walls of the pharynx. The branches of the ascend-
ing pharyngeal artery are divided into three sets, as follows:
The prevertebral,
The pharyngeal,
The meningeal.
Gall
The Prevertebral Arteries are small and are distributed to the longus
colli and rectus capitis anticus muscles, the lymphatic glands of the
neck, sympathetic nerves and ganglia, and some of the nerves passing
out of the base of the brain-case; finally anastomosing with branches.
from the subclavian artery.
The Pharyngeal Arteries, in large measure, supply the muscles and
mucous membrane of the pharynx. The middle and inferior con-
strictor muscles are usually supplied by two branches, which anastomose
with branches of the inferior thyroid artery. A larger and more con-
stant branch is distributed to the superior constrictor muscle of the
pharynx, and furnishes small twigs which pass to the Eustachian tube,
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
229
soft palate, palato-Eustachian, and levator palati muscles, as well as to
the tonsils. The artery which supplies the tonsils and the soft palate is
occasionally quite large, and divides into two smaller ones, anterior and
posterior, which anastomose with the corresponding arteries of the oppo-
site side. These branches supply the place of the inferior palatine artery
when that is wanting or abnormally small.
The Meningeal Arteries are two or three in number, and pass into
the brain-case through the jugular and anterior condyloid and posterior
lacerated foramina to supply the dura mater of the brain.
THE SUPERFICIAL TEMPORAL ARTERY.
The Superficial Temporary Artery is about 34 mm. (4 inch) in calibre.
It is the smaller of the two terminal branches of the external carotid,
the internal maxillary being the other. It originates at the bifurcation
of the external carotid, which is situated a little below the level of the
head or condyle of the inferior maxilla, and opposite the upper por-
tion of the parotid gland. It here passes upward in a continuous line
with the external carotid, over the posterior root of the zygomatic pro-
cess. This is a favorite point to apply pressure to control hemorrhage
from this artery. From this point to its termination it lies between the
skin and the temporal fascia. It is usually about one inch in length,
and terminates in the anterior and posterior superficial temporal arteries,
which again divide into several branches.
The branches of the superficial temporal artery are-
The glandular,
The muscular,
The transverse facial,
The middle temporal,
The anterior temporal,
The posterior temporal.
The Glandular Arteries are several small branches which assist in
supplying the parotid gland.
The Muscular Arteries are one or two small branches which pass to
the masseter muscle.
GRAN
The articular,
The anterior auricular,
The Articulating Arteries are small twigs which supply the temporo-
maxillary articulation.
The Anterior Auricular Arteries are distributed to the anterior por-
tion of the auricle or pinna.
Ską
The Transverse Facial Artery arises from the temporal where that
artery is imbedded in the parotid gland. It passes horizontally or trans-
versely forward between the zygoma and the parotid duct, and rests upon
the masseteric fascia. It terminates upon the face by breaking up into
three or four branches, which are distributed to the orbicularis palpe-
brarum, zygomatici, levator anguli oris muscles and the integument,
anastomosing with the facial, buccal, and infraorbital branches of the
internal maxillary arteries. It also sends branches to the parotid
gland and masseter muscle.
The Middle Temporal Artery is a branch of the superficial temporal,
and is given off just above the zygoma. It passes inwardly through
the temporal fascia to reach a groove in the squamous portion of the
230
ANATOMY.
temporal bone, in which it rests. It gives off branches to the temporal
muscle, and communicates with the deep temporal branches of the
internal maxillary artery. Occasionally it gives off an orbital branch,
which passes along the superior border of the zygoma between the two
layers of the temporal fascia. This branch is distributed to the orbicu-
laris palpebrarum muscle, and inosculates with the lachrymal and pal-
pebral branches of the ophthalmic artery.
The Anterior Temporal Artery is the larger of the two terminal
branches of the superficial temporal. It passes obliquely forward and
slightly upward in a tortuous manner upon the temporal fascia, extend-
ing slightly above the orbicularis palpebrarum muscle, and terminates
in branches which anastomose with the corresponding artery of the
opposite side and the supraorbital and frontal branches of the ophthal-
mic artery. Branches are also given off which supply the skin, mus-
cles, and other structures in the anterior temporal region, the orbicularis
palpebrarum and frontal muscles.
The Posterior Temporal Artery is smaller, and its course is straighter,
than the anterior temporal. As it passes upward and slightly backward
toward the vertex of the skull, it rests upon the temporal fascia, and
anastomoses with ramifications of the corresponding artery of the oppo-
site side. It also gives off branches posteriorly which anastomose with
the occipital, and anteriorly which anastomose with the anterior tem-
poral. It supplies the skin and other tissues of the vertex of the
skull.
Variations.-Occasionally the anterior temporal artery passes verti-
cally over the vertex of the skull, giving off branches which anastomose
with the occipital artery. The transverse facial artery may arise
directly from the external carotid instead of from the superficial tem-
poral, and is sometimes very large, supplying the place of the facial
artery. Occasionally the transverse facial is double. The orbital
branch may be of large size and supply the eyelids and part of the
forehead, and communicate with the supraorbital. In aged people
the course of the temporal artery will be found to be more tortuous
than in early life.
THE INTERNAL MAXILLARY OR DEEP FACIAL ARTERY.
The Internal Maxillary (Fig. 109) supplies all the deep portions of
the face, including the teeth, part of the floor of the mouth, the
palate, the nasal chambers, the maxillary sinus, the greater portion
of the ethmoidal sinuses, part of the pharynx, and the dura mater
of the brain. It is the larger of the two terminal branches of the
external carotid, being about 5 mm. (inch) in calibre. It is given
off from the external carotid, within the parotid gland, a little below
and behind the condyle of the inferior maxilla, on a level with the
lower part of the lobe of the ear. In the first part of its course it
passes at right angles to the external carotid, and extends forward
in a tortuous manner between the inferior maxillary bone and the
internal lateral ligament, from which it passes obliquely upward
and forward upon the outer surface of the external pterygoid muscle
•
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
231
(occasionally it passes on the inner side), until opposite the space
between the two heads of this muscle. Here it turns inward between
these heads into the spheno-maxillary fossa, where it terminates in
various branches having close relation with the spheno-palatine
(Meckel's) ganglion.
For facility of studying, the branches of this artery are arranged
FIG. 109.

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The Internal Maxillary Artery and its Branches.
under three heads, according to their anatomical relation to the parts
which they supply:
The First or Maxillary Division extends from the external carotid to
the internal lateral ligament, and gives off five branches, which pass
into or through osseous foramina. These branches are the deep auric-
ular, tympanic, middle (or great meningeal), small meningeal, and the
inferior dental.
The Second or Pterygoid Division extends from the internal lateral
ligament to the point at which the artery passes through the space
232
ANATOMY
between the two heads of the external pterygoid muscle. This portion
has four branches, which supply the masticatory and buccinator muscles.
They are named, according to their distribution, the deep temporal,
pterygoid, masseteric, and buccal.
The Third or Spheno-maxillary Division extends from the inner sur-
face of the external pterygoid muscle to the termination of the artery
in the spheno-palatine fossa. It gives off six branches, each passing
into or through osseous foramina. They are likewise named, according
to their course or the parts supplied by them, the alveolar (or superior
maxillary), infraorbital, descending (superior) palatine, Vidian, pterygo-
palatine, and nasal or spheno-palatine.
ARTERIES OF THE FIRST DIVISION.
The Deep Auricular Branch is of small size, occasionally arising in
common with the tympanic branch, but usually it arises just external
to it, and perforates the anterior wall of the external auditory meatus.
It is distributed to the skin and the external portion of the tympanic
membrane.
The Tympanic Artery is the second and one of the smallest branches
of the internal maxillary. It passes to the tympanum through the gle-
noid fissure (fissure of Glaser), and is distributed to the structures of the
middle ear and the tympanic membrane. It anastomoses with the stylo-
mastoid and Vidian arteries.
ΤΣ
The Middle or Great Meningeal Artery is the third and largest
branch. It is also the largest artery supplying the dura mater. It has
a calibre of about 2 mm. ( inch) and arises from the upper side of the
internal maxillary, passing upward behind and close to the insertion of
the external pterygoid muscle through a loop of the auriculo-temporal
nerve, and reaches the brain-case through the foramen spinosum in the
spinous process of the great wing of the sphenoid bone. Within the
cranial cavity it passes in the direction of the anterior inferior angle of
the parietal bones along a groove anterior to and parallel with the
spheno-squamosal suture. When about midway of the suture it di-
vides into an anterior and a posterior branch. The anterior branch,
the larger of the two, passes across the outer and upper extremity of
the great wing of the sphenoid bone to the anterior inferior angle of the
parietal bone, terminating in numerous branches which extend upward
and backward toward the interparietal suture. Occasionally the
grooves
for the accommodation of this artery so deeply indent the bone as to be
eventually built over, thus forming canals. The posterior branch of the
great meningeal passes backward and upward along a groove, and crosses
the squamous portion of the temporal bone to the posterior half of the
parietal bone, where it usually divides into two, the anterior branch
ascending toward the vertex, while the other branch passes backward:
toward the occipital bone.
The great meningeal artery before passing into the brain-case supplies
through its branches a portion of the pterygoid muscle and the tissue in
proximity to the foramen spinosum. After entering the cranium it sup-
plies the dura mater, the bones, the diploë, the lachrymal gland, the
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
233
ganglion of Gasser of the fifth pair of nerves, and passes through the
hiatus Fallopii to anastomose with the stylo-mastoid branch of the pos-
terior auricular artery. It also anastomoses with branches of the
ophthalmic artery.
The Small Meningeal Artery is a branch often arising from the
great or middle meningeal artery before it enters the brain-case. In
some instances it arises from the upper part of the internal maxillary
artery, and passes into the brain-case through the oval foramen in the
great wing of the sphenoid bone. Before entering the brain-case its
branches supply the nasal fossa and soft palate. After passing into the
cavity of the skull it supplies the dura mater, bones and diploë of the
middle fossæ, and the ganglion of the fifth pair of nerves.
The Inferior Dental Artery arises from the under part of the
internal maxillary. It passes downward and forward between the
internal lateral ligament and the neck of the lower jaw to the posterior
or inferior dental foramen, through which it passes, accompanied by the
inferior dental nerve, into the inferior dental canal. Traversing this, it
terminates at the anterior or mental foramen in two divisions, known as
the incisor and mental branches. A small twig is given off close to its
origin (sometimes arising from the internal maxillary), and, with the
lingual nerve, is distributed to the mucous membrane of the mouth.
The Mylo-hyoid Branch is given off from the inferior dental artery
immediately before entering the posterior dental foramen. It descends
into the mylo-hyoid groove with the nerve and vessels of the same
name, and is distributed to the under surface of the mylo-hyoid muscle.
The portion of the inferior dental artery within the canal gives off
numerous small branches to supply the teeth and their surroundings.
The Incisor Branch is a continuation of the inferior dental artery,
and passes forward within the cancellated structure of the bone to sup-
ply the region of the chin and the anterior teeth.
The Mental Branch passes out through the anterior dental or men-
tal foramen, accompanied by the nerve of the same name, and supplies
the soft parts in the region of the chin, finally anastomosing with
branches of the facial artery.
W
ARTERIES OF THE SECOND DIVISION.
The Deep Temporal Branches of the internal maxillary are two in
number, anterior and posterior.
The Deep Anterior Temporal is situated in the anterior portion of the
temporal fossa, advancing upward and forward along the temporo-sphe-
noidal suture between the muscles and pericranium, its course being
indicated by the groove in the bone. In its ascent twigs are given off
to the temporal muscle, the bone, and occasionally to the diploë. Small
branchlets anastomose with the other temporal arteries. Offshoots also
pass forward through the small foramina in the malar bone to anasto-
mose with the lachrymal branch of the ophthalmic artery.
The Deep Posterior Temporal passes upward and slightly backward,
to be distributed to the deep portion of the temporal muscle, the peri-
cranium, and occasionally the diploë.
234
ANATOMY.
The Pterygoid Branches are not constant in number. They are small and
short; as their name indicates, they are distributed to the pterygoid muscles.
The Masseteric Branch is small and regular. It passes outward through
the sigmoid notch of the lower jaw, accompanied by the nerve of the
same name, and is distributed to the masseter muscle. It anastomoses
with the transverse facial artery, and may arise conjointly with the pos-
terior deep temporal. Velpeau is of the opinion that in dislocations of
the jaw this vessel is compressed, and may be ruptured.
The Buccal Branch is a small vessel which passes downward and for-
ward between the internal pterygoid muscle and the jaw to the outer
side of the buccinator muscle, to which it is distributed. It anasto-
moses with the transverse facial and branches of the facial artery.
ARTERIES OF THE THIRD DIVISION.
The Alveolar or Superior Maxillary Branch generally arises with the
infraorbital branch. It passes downward along the zygomatic surface
and tuberosity of the superior maxillary bone, and gives off small
branches, the posterior dental arteries, which enter the posterior den-
tal canals; twigs from these supply the superior molar and bicuspid
teeth, and anastomose with the anterior dental portion of the infra-
orbital branch. The mucous membrane of the maxillary sinus is
partly supplied by the posterior dental arteries, offshoots being also
distributed to the alveolar process and gums.
The Infraorbital Branch usually arises conjointly with the alveolar
branch. It passes forward, in company with the superior maxillary or
infraorbital nerve, along the infraorbital canal, from which it finds exit
upon the face through the infraorbital foramen. In the canal offshoots
are supplied to the inferior rectus and inferior oblique muscles of the
eye, the lachrymal gland, the connective tissue in the floor of the orbit,
and the mucous membrane of the maxillary sinus. It also gives off the
anterior dental artery, which descends through a canal in the bone to
supply the incisor, cuspid, and bicuspid teeth. This artery anastomoses
with the posterior dental of the alveolar branch, the union, however,
taking place in such a way as to make it difficult to say which artery
supplies the bicuspid teeth. On the face twigs from the infraorbital
supply the lachrymal sac and the surrounding tissue near its exit. They
also anastomose with branchlets of the facial, the nasal of the ophthal-
mic, and the transverse facial and buccal.
The Descending Palatine or Superior Palatine Branch passes down-
ward in the posterior palatine canal, accompanied by the anterior pala-
tine nerves (branches of the spheno-palatine (Meckel's) ganglion), and
emerges upon the posterior and lateral part of the hard palate. It passes
forward in a groove on the hard palate to the incisive foramen, at which
point it anastomoses with a branch of the naso-palatine artery. While
in the posterior palatine canal small twigs are given off to the mucous
membrane of the nose and tonsils. It also supplies the hard palate,
alveolar process, palatine mucous glands, mucous membrane, and the
gum tissue of the superior maxilla, and anastomoses with the ascending
palatine branch of the facial.
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
235
pot
The Vidian Branch passes backward in the Vidian canal in the oppo-
site direction to the Vidian nerve. Its branches are distributed to the
upper part of the pharynx, the opening of the Eustachian tube, the
levator palati muscle, and to the tympanum. It anastomoses with the
ascending pharyngeal and stylo-mastoid arteries.
The Pterygo-palatine Branch is a small artery which passes back-
ward and downward in the pterygo-palatine canal, accompanied by the
pharyngeal nerve. It is distributed to the sphenoidal cells, Eustachian
tube, and upper part of the pharynx.
K
The Nasal or Spheno-palatine Branch may be considered as the ter-
minal of the internal maxillary artery. It passes in a forward direction,
entering the nasal chamber through the spheno-palatine foramen, which
is situated at the back part of the superior meatus, dividing into inter-
nal and external branches. The internal division is the continuation
of the spheno-palatine, and holds the same name, though sometimes
it is called the artery of the septum, as it runs downward and forward
in the groove of the vomer, and terminates by anastomosing with the
descending palatine artery at the incisive foramen. It is distributed to
the bone, cartilage, and mucous membrane of the nasal septum. The
external branches, several in number, are distributed to the lateral part
of the nose, including the ethmoidal and sphenoidal cells, the maxillary
sinus, and the mucous membrane covering these parts.
Variations. The internal maxillary artery seldom varies in its origin,
though it has been known to arise from the facial (Quain). The num-
ber of branches given off may vary, there being two or more, which
arise by one common trunk. The branches may also convey blood to
parts which are generally supplied by the facial and lingual, and by the
branches of the ophthalmic and the temporal arteries. In the same
way the cranial branches may interchange with those of the internal
carotid.
THE INTERNAL CAROTID ARTERY.
The Internal Carotid Artery (Fig. 110) is about 6 mm. (4 inch) in
calibre, and, as its name indicates, is distributed in great part to the
internal, middle, and anterior structures of the brain-case.
It also sup-
plies the eye and the parts within the orbit, and partially the nasal
chamber, forehead, and nose. It is one of the terminal branches of
the common carotid, arising from that artery at its bifurcation opposite
the superior border of the thyroid cartilage, from which point it passes
upward, generally with a slight curve, to the carotid foramen in the
petrous portion of the temporal bone.
The internal carotid artery is divided anatomically into four portions
-cervical, petrous, cavernous, and intracranial.
The Cervical Portion is situated within the neck, extending from the
origin of the internal carotid in the superior carotid triangle to the caro-
tid foramen. Its line is usually slightly curved, though almost vertical,
but in some cases it will be found to be quite tortuous.
Relations. At first it is located more superficially than the external
carotid, and a little posterior to its outer side. It is covered by the
Sa pag
236
ANATOMY.
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The Internal Carotid and Vertebral Arteries, right side.
fascia, the internal border of the sterno-cleido-mastoid muscle, pla-
tysma myoides, and skin. Upon reaching the posterior belly of the
digastric muscle it passes beneath it and the stylo-hyoid, and continues
to the inner side of the external carotid. Above this point it is deeply
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
237
situated in the neck, the parotid gland, the styloid process, and stylo-
pharyngeus muscle being to its outer side. Its deep relations are with
the tonsils, the superior constrictor muscle separating them, the walls of
the pharynx, and transverse process of the upper three cervical vertebræ,
the rectus capitis anticus major muscle being posterior to it. The artery
is enclosed in a sheath in company with the internal jugular vein and
pneumogastric nerve, the vein lying upon the outer side posterior to the
artery. Upon reaching the skull the vein separates from the artery
and passes through the jugular or posterior lacerated foramen, the
artery passing through the carotid foramen. The glosso-pharyngeal,
pneumogastric, spinal accessory, and hypoglossal nerves are situated be-
tween the two vessels near these foramina. The occipital and posterior
auricular arteries cross it on the outside, the former below the digastric
muscle, the latter above. The pneumogastric nerve and the upper cer-
vical ganglion of the sympathetic are deeper than, and situated posterior
to, the vessel. The hypoglossal nerve crosses to its outer side, near the
lower margin of the digastric muscle; the glosso-pharyngeal nerve and
pharyngeal branch of the pneumogastric pass between the external and
internal carotids. The superior and external laryngeal nerves are inter-
nal to both arteries.
The cervical portion of the internal carotid seldom gives off any
branches, though occasionally its lower portion supplies the occipital or
ascending pharyngeal arteries. These, however, are rare variations.
The Petrous Portion of the internal carotid enters the carotid foramen
on the under surface of the temporal bone, and passes through a canal
to a point where it enters the cavernous sinus within the brain-case.
Its course within the bone is at first upward, passing immediately in
front of the tympanum or middle ear and the internal ear, being sepa-
rated from them by a thin lamina of bone. It then passes horizontally
forward and inward to the middle lacerated foramen, extending across
the tissues filling in this aperture.
This portion of the artery gives off a small branch to the tympanum
which anastomoses with tympanic branches from divisions of the exter-
nal carotid.
The Cavernous Portion of the internal carotid commences immedi-
ately above the middle lacerated foramen, and passes upward to and
along the sigmoid groove on the lateral surface of the body of the sphe-
noid bone. It terminates in the intracranial portion of the artery by
passing through the upper wall (which is membranous) of the cavernous
sinus close to the anterior clinoid process. The artery is situated on the
inner portion of the cavernous sinus. It is surrounded by filaments of
the sympathetic nerve, and is accompanied by the sixth nerve, which is
situated to its outer side. These structures are all covered by an envelope
derived from the lining membrane of the sinus. The third, fourth, and
ophthalmic nerves pass through the sinus external to the envelope.
Branches of this portion of the artery are distributed to the dura
mater, the pituitary body, Gasserian ganglion, and the walls of the
cavernous and inferior petrosal sinuses. It also gives off a branch
which anastomoses with the middle meningeal artery.
The Intracranial Portion of the internal carotid commences after the
238
ANATOMY.
artery passes through the upper wall of the cavernous sinus. Just
above this point the optic nerve passes to the inside of the artery, while
the third nerve passes externally. Near the anterior clinoid process this
portion of the artery gives off its first large branch, the ophthalmic,
while near the fissure of Sylvius it gives off the lateral (posterior) com-
municating artery of the circle of Willis. Above this point it finally
divides into the middle and anterior cerebral arteries.
The branches of this portion of the artery are the ophthalmic, the
anterior, and the middle cerebral.
The Ophthalmic Artery (Fig. 111) is about 2 mm. (inch) in cali-
bre. It is the first large branch of the internal carotid, arising from
that artery immediately after it passes through the dura mater, at the
last curve of the sigmoid flexure, just internal to the anterior clinoid
process. From this point it passes forward and a little outward over
the anterior portion of the cavernous sinus, through the optic foramen
into the cavity of the orbit, passing below and to the outer side of the
÷
7
FIG. 111.
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-13
15
14
8
10
Arteries of the Orbit, from the outer side: 1, internal carotid; 2, ophthalmic artery; 3, arteria cen-
tralis retina; 4, muscular branches; 5, lachrymal artery; 6, ciliary artery; 7, posterior eth-
moidal artery; 8, rectus inferior; 9, anterior ethmoidal artery; 10, obliquus inferior; 11, supra-
orbital artery; 12, facial artery; 13, frontal artery; 14, palpebral artery; 15, nasal artery.
optic nerve. The artery and nerve are enclosed within the same sheath,
which is derived from the dura mater. Within the cavity of the orbit
the artery leaves the sheath and passes obliquely over (occasionally
under) the nerve to the inner wall of the cavity, along which it travels.
in a horizontal direction between the superior oblique and internal rectus
muscles to the trochlear process or notch. Here it terminates by divid-
ing into frontal and external nasal branches.
The branches of the ophthalmic artery are the lachrymal, supraorbital,
central retinal, ciliary, posterior and anterior ethmoid, muscular, palpebral,
frontal, and external nasal.
Bakal
The Lachrymal Artery is the first branch given off by the ophthalmic.
It arises from its outer side immediately after it enters the cavity of the
orbit, and frequently while the artery is still within the optic foramen.
Together with the lachrymal nerve it passes along the outer wall of the
orbit below the external rectus muscle, and is distributed principally to
the lachrymal gland. The branches of the lachrymal artery are its
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
239
5
terminal ones, which pass to the upper eyelid and the conjunctiva, and
anastomose with branches of other arteries distributed to this region of
the face. One or two small twigs pass from the artery through for-
amina in the malar bone to the temporal fossa, anastomosing with the
deep temporal artery. Small branches also pass through the same
bone and anastomose with the deep and superficial arteries of the
check, which are branches of the transverse facial. A branch from the
lachrymal, which is given off soon after its origin, passes backward
through a notch in the margin of the anterior lacerated foramen, sup-
plies the dura mater, and anastomoses with the middle meningeal artery.
Other branches are distributed to the membrane covering the outer
wall of the orbit, the external and superior recti muscles, and the
levator palpebræ superioris muscles.
The Central Retinal Artery is a small branch arising from the oph-
thalmic soon after it passes out of the optic foramen. It passes
obliquely through the centre of the optic nerve, about a quarter of an
inch posterior to its point of entrance into the eyeball, and is distributed
to the retina and the hyaloid membrane. During embryonic life this
artery has a central branch which passes forward through the middle of
the vitreous humor of the eye to the posterior portion of the lens, upon
which it is lost.
The Ciliary Arteries are divided into a posterior and anterior set, the
former being subdivided into short and long ciliary arteries.
The Short Ciliary Arteries number four or five, and arise from the
ophthalmic as it crosses the optic nerve. They soon divide into twelve
or fifteen small branches, which pass forward in a tortuous or spiral
course through the adipose tissue surrounding the optic nerve to the
posterior part of the eyeball, where they pierce the sclerotic coat in close
proximity to the entrance of the optic nerve. Passing through the
sclerotic, they enter the choroid coat, and immediately break up into a
minute capillary plexus which forms the greater part of the internal
coat of the choroid. From the anterior portion of this plexus small
vessels are given off which pass to the ciliary processes.
The Long Ciliary Arteries are two in number, and but slightly larger
than the short ciliary vessels. They pass forward, one on each side
of the eyeball, and enter the sclerotic coat, passing between it and
the choroid to the ciliary ligaments, where they each divide into two
branches, superior and inferior. The four branches then diverge and
pass forward to the periphery of the iris (circulus major), where they
reunite and form an arterial circle. From this circle branches are dis-
tributed to the iris, some of the concentric extremities uniting to form
an inner circle (circulus minor) on the free or pupillary margin of
the iris.
The Anterior Ciliary Arteries number six or eight, and arise from
the muscular and lachrymal branches. They communicate freely with
each other, and form a vascular circle around the anterior portion of the
eyeball between the conjunctiva and the sclerotic coat of the eye. From
this circle small vessels pass through the sclerotic coat one or two lines
posterior to the margin of the cornea, and join the external vascular
circle of the iris.
240
ANATOMY.
The Posterior Ethmoid Artery arises from the inner side of the oph-
thalmic nearly opposite the posterior ethmoidal foramen. It passes
through this foramen, and is distributed, by a small meningeal branch,
to the portion of the dura mater situated in the anterior fossa of the
brain-case, as well as to the mucous membrane lining the posterior
ethmoidal cells and to the superior portion of the internal nose.
The Anterior Ethmoidal Artery is larger than the posterior. It arises
from the inner side of the ophthalmic close to the anterior ethmoidal
foramen. It passes through this foramen into the brain-case immedi-
ately above the cribriform plate of the ethmoid bone, and is accompanied
by the nasal nerve. The artery and nerve pass together through the
cerebro-nasal slit (anterior nasal foramen) of the ethmoid bone into
the nasal chamber, where the vessel receives the name of the anterior
nasal artery. The anterior ethmoidal artery is distributed through its
branches to the antero-ethmoidal cells, the dura mater of the ante-
rior fossa of the brain-case, the mucous membrane of the olfactory
portion of the nasal chamber, including the superior and inferior tur-
binated bones, and to the roof and septum of the nose, the branch
supplying the septum anastomosing with the naso-palatine artery. It is
also distributed to the frontal sinus, a branch passing between the nasal
bones and lateral cartilage in company with the nasal nerve, and anas-
tomoses on the face with branches from the facial artery.
The Muscular Arteries, branches of the ophthalmic, consist of two
principal ones, superior and inferior, and several smaller twigs.
The Superior Muscular Artery is the smaller of the two larger
branches of the ophthalmic, and is distributed to the levator palpebræ
superioris, superior rectus, and superior oblique muscles. The existence
of this artery is not constant.
The Inferior Muscular Artery passes anteriorly from the ophthalmic,
and is distributed to the external and inferior recti and inferior oblique
muscles. Its existence is more constant than the superior branch, and
it furnishes the principal number of the anterior ciliary arteries.
The Smaller Muscular Arteries arise from the ophthalmic at various
points along its course, as well as from its lachrymal and supraorbital
branches. They are distributed to the different muscles of the eye.
The Supraorbital Artery is the largest branch of the ophthalmic. It
arises in the posterior portion of the cavity of the orbit as the artery
crosses the optic nerve. It passes above the muscles of the eye,
accompanied by the frontal nerve, and extends anteriorly between the
periosteum covering the roof of the orbital cavity and the levator pal-
pebræ superioris muscle to the supraorbital foramen in the frontal bone.
It
passes through this foramen and divides into two branches, superficial
and deep. These branches anastomose with the temporal and angular
arteries, and with their fellows of the opposite side.
The Superficial Branch is distributed to the frontal muscle and to the
integument over this region.
The Deep Branch is distributed to the periosteum of the frontal bone.
The superficial and deep branches of the supraorbital artery also send
branches to the muscles within the orbit, and, as the supraorbital passes
out of the orbit, it supplies the diploë of the frontal bone by a branch
We
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
241
which enters a small foramen often seen within the supraorbital foramen
or notch.
The Palpebral Arteries are two in number, superior and inferior.
They usually arise together from the ophthalmic, nearly opposite the
pulley of the superior oblique muscle. From this point they diverge,
the superior branch passing above, the inferior below, the internal tarsal
ligament. They distribute small branches to the conjunctiva and the
lachrymal caruncle and sac. They then pass outward between the
orbicularis palpebrarum muscle and the trochlea, and encircle the eye-
lids near their free margins. They anastomose with branches of the
lachrymal as well as with the orbital branches of the temporal and
infraorbital arteries. A branch from the palpebral artery generally
accompanies the nasal duct into the nasal chamber.
The Frontal Artery is one of the terminal divisions of the ophthal-
mic, and arises in close proximity to the trochlear process or notch on
the frontal bone. It passes out of the orbital cavity, curves around
the internal angular process of the frontal bone or inner extremity of
the supraorbital arch, and is distributed to the superior lid of the eye,
integument, muscles, and pericranium of the forehead, as well as to the
nasal slip of the frontal muscle. It anastomoses with its fellow of the
opposite side and with the supraorbital artery.
The External Nasal Artery is the other terminal division of the
ophthalmic. It arises close to the trochlear process or notch on the
frontal bone, and passes forward over the internal tendo palpebrarum
and through the orbicularis palpebrarum muscle. It then extends down-
ward along the root of the nose, and communicates with the angular and
nasal arteries, branches of the facial. Occasionally it communicates by
a small branch with the artery of the opposite side, or it may pass down
the nose and anastomose with the anterior nasal artery, a branch of the
anterior ethmoidal. In its course it gives off branchlets to the lachrymal
sac, canal, and caruncle and the orbicularis palpebrarum muscle.
Variations. The lachrymal artery may arise directly from the middle
meningeal. When it so arises it passes out of the brain-case through
the notch in the border of the anterior lacerated foramen, and gives off
a small recurrent branch, which communicates with the lachrymal and
middle meningeal arteries, and again becomes part of the main trunk
of the lachrymal. Occasionally the major portion, or even all, of the
blood-supply of the lachrymal artery comes through this source. Where
the facial artery is small or altogether wanting the nasal artery is of
large size and supplies its place. The terminal branches of the oph-
thalmic artery have a large and varied communication with other
arteries in this region, such as its fellow of the opposite side, the facial,
infraorbital, transverse facial, temporal, middle meningeal, ethmoidal,
and the spheno-palatine.
THE CEREBRAL ARTERIES.
The Cerebral Arteries, branches of the internal carotid, are two in
number, anterior and posterior, the posterior cerebral artery being a
branch of the basilar.
VOL. I.-16
242
ANATOMY.
The Anterior Cerebral Artery is about 34 mm. (4 inch) in calibre.
It is one of the terminal divisions of the internal carotid, and arises at
the inner extremity of the fissure of Sylvius, close to the anterior clinoid
process. It passes inward and forward nearly at right angles with the
internal carotid, and at an obtuse angle with the middle cerebral, to a
point in close proximity to its junction with its fellow of the opposite
side, which occurs at the rostrum of the corpus callosum, anterior to the
lamina cinerea, where it gives off the anterior communicating artery
which forms a part of the circle of Willis. From this point it passes
forward a short distance from and nearly parallel with its fellow of the
opposite side until it reaches the anterior portion of the corpus callosum,
around which it curves, and breaks up into several branches to supply
the structures in the anterior portion of the brain-case.
The Middle Cerebral Artery is about 5 mm. (inch) in calibre, and
is one of the largest of the terminal divisions of the internal carotid.
It arises at the inner extremity of the fissure of Sylvius, and passes
obliquely upward and outward within the fissure to the superior surface
of the island of Reil. Here it subdivides into several branches, which
are distributed to the brain. It also, on the anterior portion, gives
off the lateral (posterior) communicating artery of the circle of Willis.
The Posterior Cerebral Artery is about 3 mm. (inch) in calibre,
and is one of the two terminal" branches of the basilar, hereafter to be
described. It arises with the corresponding artery of the opposite side
at a point just anterior to the pons varolii, close to the posterior clinoid
process of the sphenoid bone. It extends outward, and then curves back-
ward around the crus cerebri, and passes outward and upward between
the occipital lobe of the cerebrum and the cerebellum. It gives off
numerous branches which supply the different structures of the brain,
as well as the lateral (posterior) communicating artery of the circle of
Willis.
The Circle of Willis is a system composed of several short arteries
which communicate with each other and form a vascular circle which
surrounds the following structures at the base of the brain: the lamina
cinerea, optic commissure, infundibulum and tuber cinereum, corpora
albicantia, and posterior perforated space.
The circle of Willis is composed of the following arteries: the two
anterior cerebral, the anterior communicating, the upper portion of the
two internal carotids, the two lateral (posterior) communicating, and
the two posterior cerebrals.
The Two Anterior Cerebral Arteries form that portion of the circle of
Willis which extends forward and inward from their origin, which is
at the termination of the internal carotid, to the rostrum of the corpus
callosum just anterior to the lamina cinerea.
The Anterior Communicating Artery is about two lines in length, and
passes from one anterior cerebral artery to the other across the rostrum
of the corpus callosum anterior to the lamina cinerea. It forms the
anterior communicating branch of the circle of Willis between the two
anterior cerebral arteries. It also gives off branches which supply some
of the structures in close proximity to it.
Variations. This artery is occasionally represented by two branches,
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
243
and at times it is absent. When this is the case the two anterior cere-
brals are united into one in a similar manner to the two vertebrals
which form the basilar artery.
The upper portions of the two internal carotid arteries are situated
close to the anterior clinoid processes of the sphenoid bone, and in
calibre are much the largest of any of the arteries which form the circle
of Willis, though they constitute but a small part of its circumference.
Anteriorly they give off the anterior cerebral arteries, while posteriorly
they give origin to the posterior communicating arteries.
The Lateral (Posterior) Communicating Arteries are situated laterally
instead of posteriorly, as the generally-used name would imply. They
are seldom of equal size, the right being most frequently the larger.
They extend from the upper extremity of the internal carotid backward
and slightly inward, and pass beneath the optic tract and the crus cerebri
to the posterior cerebral arteries. At their most anterior portion in front
of the pons varolii they give off numerous branches to parts in close
proximity.
Variations.-The two lateral (posterior) communicating arteries occa-
sionally arise from the middle cerebral instead of the internal carotid.
The Two Posterior Cerebral Arteries form the posterior portion of the
circle of Willis. They are larger in calibre than any of the other ar-
teries which form the circle, except the terminal extremities of the inter-
nal carotids. They extend from the bifurcation of the basilar artery in
front of the pons varolii outward and slightly forward to the point of
junction of the lateral (posterior) communicating arteries.
Variations.—Occasionally this portion of the posterior cerebral artery
is quite small. When this is the case the corresponding artery of the
opposite side is proportionately large, thus equalizing the blood-supply.
The Basilar Artery is formed by the union of the right and left ver-
tebrals, which are branches of the subclavian arteries at the base of the
neck. This arrangement of vessels, together with the external carotids
and the circle of Willis, forms such a continuous communication that
if the common carotid be ligated or entirely obliterated on either side,
the blood may yet circulate to all parts of the brain, and also pass out
of the brain-case and supply the external parts of the head and face
through the anastomotic unions of the vessels of these parts.
SUBCLAVIAN ARTERIES.
The Subclavian Arteries are two in number, right and left, extending
from their origin, the right from the innominate, the left from the arch
of the aorta, to their terminations at the first ribs. Each forms an arch,
the concavity of which is directed downward, and the greater portion of
which is situated in the inferior posterior cervical triangle of the neck.
The proximal portion rests in the thoracic cavity. The artery passes
over the first rib and under the central portion of the clavicle into the
axilla. The summit of the arch is situated within the neck posterior to the
scalenus anticus muscle. The origin and relations of the proximal portion
of the arteries on either side are dissimilar, and will therefore be separately.
described. The subclavian arteries are divided into three portions.
244
ANATOMY.
The first or ascending portion of the right subclavian artery arises from
the innominate or brachio-cephalic artery at its point of bifurcation into the
right subclavian and right common carotid, which latter is situated close
to the trachea posterior to the sterno-clavicular articulation. From this
point it passes upward, outward, and a little backward until it reaches
the proximal border of the scalenus anticus muscle at the base of the
neck.
The second or transverse portion is the shortest, and is situated higher
in the neck than the remainder of the artery, thus forming the dome of
the arch. It commences at the termination of the first portion of the
artery, and passes outward behind the scalenus anticus muscle to its
distal border.
The third or descending portion of the artery passes downward, out-
ward, and forward from the distal border of the scalenus anticus muscle.
to a point where it passes from the neck over the first rib and under the
clavicle into the axilla, where it becomes the axillary artery. The third
portion of the subclavian artery is the most superficial. It passes
through a triangular space formed by the clavicle below, the omo-
hyoid muscle externally, and the anterior scalenus muscle internally.
Relations.-The first or ascending portion of the right subclavian
artery is covered by the skin, platysma myoides, deep fascia, outer
attachment of the sterno-cleido-mastoid muscle, the sterno-hyoid and
sterno-thyroid muscles, and the sternal end of the clavicle. The inter-
nal jugular and the vertebral veins cross it on their way to empty into
the right innominate vein. The pneumogastric nerve crosses to the inner
side of the internal jugular vein, while the cardiac branches of the sym-
pathetic and the phrenic nerves also pass over it. Its deep surface is
in close relation to the pleura, and behind it is separated by a cellular
interval from the longus colli muscle and the transverse process of the
seventh cervical vertebra. The right innominate vein is situated below
and slightly anterior to the artery, while the recurrent or inferior laryn-
geal nerve passes over it, returns upon itself, passes under the artery,
and extends upward to the larynx.
Ma
The second or transverse portion of the subclavian is wholly covered
by the scalenus anticus muscle, while more superficially it is crossed by
the sternocleidomastoid. The left phrenic nerve passes over the second
portion of the left subclavian artery, in this differing from the right
phrenic nerve, which crosses the first portion of the right subclavian.
It is also covered by the integument, platysma myoides, and the deep
fascia. The deep surface of the artery is in relation with the middle
scalenus muscle posteriorly, the brachial plexus of nerves above, and
below with the pleura. The scalenus anticus muscle is between the
subclavian artery and vein, the latter being anteriorly situated.
Relations.-The third or descending portion of the subclavian artery
is covered by the integument, platysma myoides, and deep fascia. The
subclavian vein lies superficial to, though slightly below, it, while the
external jugular and the veins of the shoulder pass over it to enter the
subclavian vein. It is also in close relation to the brachial plexus of
nerves, most of which pass over it, while one or two pass under it.
The first or ascending portion of the left subclavian artery is some-
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
245
what longer than the right, and is more deeply situated in the thoracic
cavity. It usually arises directly from the left extremity of the trans-
verse portion of the arch of the aorta, opposite the second dorsal verte-
bra. From this point it passes almost vertically upward, though slightly
outward, and emerges from the thorax into the neck, where it makes a
sharp curve outward over the apex of the left lung to reach the prox-
imal margin of the anterior scalenus muscle, from which point its direc-
tion and relations correspond to the artery of the right side, and there-
fore need no special description.
TRA
Relations.-The first or ascending portion of the left subclavian
artery is situated at its origin behind the pleura and upper portion of
the left lung. It is crossed by the left innominate vein, the internal
jugular, and vertebral veins. The pneumogastric nerve passes down
in front of it, and comes in contact with it near its origin. The phrenic
nerve crosses the artery close to the anterior scalenus muscle and exter-
nal to the thyroid axis. The cardiac nerves also pass in front of the
artery. Its deep surface is in close relation to the vertebræ, a portion
of the oesophagus, the thoracic duct, and longus colli muscle. The cord
of the sympathetic nerve passes up behind this surface. Internally are
the left common carotid artery, trachea, a portion of the œsophagus, and
thoracic duct. Externally is the pleura.
The Branches of the Subclavian Artery are four in number-vertebral,
internal mammary, thyroid axis, and superior intercostal. The first
three of these arise from the first portion of the subclavian before it
reaches the scalenus anticus muscle, while the last is derived from the
second portion. Occasionally a branch arises from the third portion
of the artery, and is known as the posterior scapular.
THE VERTEBRAL ARTERY.
The Vertebral Artery is about 5 mm. (3 inch) in calibre, and is usually
the first and largest branch of the subclavian. The artery on the right
side generally arises from the upper and posterior portion, about three-
fourths of an inch from the brachio-cephalic or innominate artery; that
on the left usually arises from the first portion of the subclavian as it
curves to the left at the base of the neck.
Variations. This artery may arise from any portion of the subcla-
vian or the common carotid, and even from the arch of the aorta, though
this latter abnormality is rare. Cases are reported where the vertebral
artery arises as two branches.
From its origin the vertebral artery passes upward and slightly
backward, and usually enters the foramen in the transverse process of
the sixth cervical vertebra. Occasionally, however, it enters the fora-
men in the fifth, fourth, third, or even as high as the second, cervical
vertebra. Sometimes it enters the foramen in the transverse pro-
cess of the seventh cervical vertebra. It then passes upward through
the remainder of the vertebral foramina, curves backward along the
upper surface of the atlas, and enters the skull through the foramen
magnum of the occipital bone. It passes along the side of the medulla
oblongata to its anterior portion, and joins the vertebral of the opposite
246
ANATOMY.
side at the posterior inferior extremity of the pons varolii to form the
basilar artery.
The Branches of the Vertebral Artery are divided into cervical and
encranial. The cervical branches are the lateral spinal and muscular;
the encranial branches are the posterior meningeal, posterior spinal,
anterior spinal, and the posterior cerebellar. The distribution of these
branches is generally implied in their names.
The Basilar Artery is formed by the union of the right and left ver-
tebral arteries, which takes place at the posterior inferior extremity of
the pons
varolii. From this point it passes forward and upward within
a groove along the middle of the superior surface of the basilar process
of the occipital bone to the anterior extremity of the pons, close to the
posterior clinoid processes. Here it divides into the posterior cerebral
arteries already described.
The Branches of the Basilar Artery are the transverse, six or eight in
number, which supply the under surface of the pons; the right and left
auditory, which pass through the internal auditory meatus of the tempo-
ral bone, together with the auditory nerve, and supply the labyrinths of
the ear; the anterior or inferior cerebellar, right and left, which supply
the anterior inferior portion of the cerebellum and other structures in
juxtaposition, and anastomose with the inferior cerebellar branches of
the vertebral; the superior cerebellar, right and left, which supply
through their numerous branches the cerebellum and other structures
in the vicinity; and the terminal or posterior cerebral arteries previously
described.
The Thyroid Axis is about 6 mm. (1 inch) in calibre and but a few
lines in length. It arises from the anterior superior surface of the first
part of the subclavian artery, and passes upward a very short distance
close to the proximal border of the anterior scalenus muscle. Here it
breaks up into three branches, inferior thyroid, suprascapular, and trans-
versalis colli.
It
The Inferior Thyroid Artery is about 34 mm. (4 inch) in calibre.
arises from the thyroid axis, and could be regarded as a continuation
of this artery. From its origin it passes directly upward in front
of the vertebral artery and under the central portion of the omo-hyoid
muscle. Slightly above the muscle, opposite the fifth cervical vertebra,
it curves inward in a tortuous manner, and passes beneath the sheath of
the large vessels of the neck and sympathetic nerve to the inferior part
of the thyroid body. Here it breaks up into fine branches which sup-
ply the gland and anastomose with branches of the superior thyroid
artery, as well as the corresponding artery of the opposite side. The
other branches of the inferior thyroid are the ascending cervical, inferior
laryngeal, and tracheal.
The Ascending Cervical Artery is about 2 mm. (inch) in calibre,
and arises from the inferior thyroid just as it curves inward behind the
sheath of the large vessels of the neck. It passes upward immediately
anterior to the phrenic nerve in the interspace between the anterior sca-
lenus and the rectus capitis anticus major muscles, and is distributed
through small branches to these muscles, a few branches extending
across the neck to anastomose with offshoots from the vertebral. Other
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
247
branches pass through the intervertebral foramina in close relation with
the cervical nerves, and supply the bodies of the vertebræ, the spinal
cord and its membranes, and anastomose at the upper portion of the
cord with the ascending pharyngeal artery.
The Inferior Laryngeal Artery is not uniform in size, and arises from
the inferior thyroid in close proximity to the thyroid body. It passes
upward, accompanied by the recurrent or inferior laryngeal nerve,
behind the inferior angle of the thyroid cartilage, and is distributed
to the muscles and mucous membrane of the larynx.
The Tracheal Artery is very constant in its existence. It arises from
the inferior thyroid opposite the transverse process of the seventh cervi-
cal vertebra, and passes downward behind the trachea to a point in close
relation to the bifurcation of the trachea. Here the artery divides into
branches which supply the trachea, bronchial tubes, lymphatic glands,
and lower portion of the longus colli muscle, and anastomoses with
the intercostal and bronchial arteries.
The Suprascapular Artery (transverse scapular or transverse humeral)
is about 34 mm. (4 inch) in calibre. It arises from the thyroid axis,
and passes outward and downward to the scapula. Its branches are the
thoracic, acromial, supraspinous, and infraspinous.
The Transversalis Colli, or Transverse Cervical Artery, arise from the
thyroid axis, and passes outward in a tortuous course to the superior
angle of the scapula, where it divides into the superficial cervical and
posterior scapular arteries.
The Internal Mammary and Superior Intercostal Arteries are import-
ant to the head and neck, as they by their relation with other arteries
complete the system of collateral circulation. The superior gives off
the deep cervical, which communicates with the arteria princeps cervicis
of the occipital artery.
THE VEINS.
The veins are those vessels of the body through which the blood is
returned to the heart. They originate at the termination of the capil-
laries (minute vessels between the arteries and veins) throughout the
body, and unite and anastomose to form larger vessels as they approach
the heart. They inosculate more freely than do the arteries, and, unlike
these, contain throughout their course numerous valves which open
toward the heart and prevent regurgitation of the blood. The veins
are divided into two groups-systemic and pulmonary.
The Systemic Veins are those which collect the blood from all portions.
of the body excepting the lungs. They are divided into two sets
those that collect the blood from the head, upper and lower extrem-
ities, and the greater portion of the body; and those that collect the
blood from the alimentary canal and its glandular apparatus below the
diaphragm, and terminate in the portal system. The systemic veins are
again divided into superficial and deep.
The Pulmonary Veins, four in number, two for each lung, collect the
blood, which is arterial, from the capillaries of the lungs and convey it
to the left auricle of the heart.
K
248
ANATOMY.
SUPERIOR VENA CAVA, INNOMINATE, AND THYROID VEINS.
THE SUPERIOR OR DESCENDING VENA CAVA (see Fig. 106) is the
large vessel that receives all the blood from the upper extremities, the
head, and the walls of the thoracic cavity. It is from
It is from 2 to 3 inches in
length, and commences at the junction of the right and left innominate
veins, internal to and just below the attachment of the first costal carti-
lage of the right side to the sternum. It passes almost directly down-
ward, curving slightly to the left, and enters the right auricle opposite
the third costal cartilage at its upper anterior portion, its orifice look-
ing downward and forward.
THE INNOMINATE OR BRACHIO-CEPHALIC VEINS are two in num-
ber, right and left. They each originate at the junction of the subclavian
and the internal jugular veins, which are situated posterior to the sternal
extremities of the clavicles, and extend downward to the origin of the
superior vena cava, which they form by their union. They are of
unequal length, and differ from most of the other veins of the body by
being destitute of valves.
THE RIGHT INNOMINATE VEIN is the shorter of the two, being but
slightly over 1 inch in length. It extends from its commencement
almost vertically downward external to the origin of the subclavian
and innominate arteries, the pleura being interposed between it and the
lung on the right side. The vessels which empty into it are the right
thoracic (lymphatic) duct, the right vertebral vein, right mammary,
right inferior thyroid, and the right superior intercostal veins.
THE LEFT INNOMINATE VEIN is larger and longer than the right,
being about 3 inches in length. It extends from its origin on the left
side of the sternum from left to right across the superior and anterior
portion of the chest, inclining slightly downward to its union with the
right innominate vein. It is in relation with the sterno-clavicular artic-
ulation, the upper portion of the manubrium, from which it is sepa-
rated only by the lower extremities of the sterno-hyoid and sterno-
thyroid muscles and the thymus gland, or its remains in the adult. The
three arteries arising from the arch of the aorta and the phrenic and
pneumogastric nerves pass down the neck in close proximity to it, the
transverse portion of the arch of the aorta being situated below it.
The Tributaries of the Left Innominate Vein are the thoracic (lym-
phatic) duct, the left vertebral, left inferior thyroid, and the left
rior intercostal veins.
supe-
Moder
THE INFERIOR THYROID VEINS are generally two in number, right
and left, though occasionally there are three or even four. They are
formed by the union of numerous small veins which originate in the
lower portion of the thyroid body, and which anastomose with similar
branches from the middle and superior thyroid veins. They pass down-
ward, and form a plexus in front of the trachea below the isthmus of
the thyroid gland. This plexus often causes trouble from hemorrhage
in the operation of tracheotomy. The inferior thyroid vein (or veins,
if there are more than one) of the right side are situated a little to
the right of the median line, while those of the left side are usually
directly in the median line. As they descend in front of the trachea
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
249
they are in close proximity to the sterno-thyroid muscles. The vein of
the left side empties into the left innominate vein, while that of the right
side varies in its termination. It may empty into the left innominate
vein in common with the vein of the left side or at the junction of the
right and left innominate veins, or into the right innominate vein.
Occasionally there exists a median vein which is independent of the
others, and which passes down along the central portion of the trachea
anteriorly. These veins are all supplied with valves, which are situated
at their terminal extremities.
The Tributaries of the Inferior Thyroid Veins are the tracheal and
inferior laryngeal.
VEINS OF THE HEAD AND NECK.
The blood of the head and the greater portion of the neck is returned
to the heart through the medium of two veins on either side, the exter-
nal and internal jugular (Fig. 112). Close to their termination these
large veins have valves. The other veins of the head and neck are
generally not supplied with valves. They are divided into external
and endocranial veins.
The External Veins are the temporo-maxillary, facial, temporal, inter-
nal maxillary, posterior auricular, occipital, lingual, and pharyngeal.
THE FACIAL OR ANTERIOR FACIAL VEIN commences near the inner
angle of the eye at the termination of the angular vein. It passes
downward and outward along the side of the nose, then extends
obliquely to the facial notch in front of the lower border of the
masseter muscle, where it passes inward and backward under the
platysma myoides and deep fascia, and crosses the digastric muscle,
below which it joins the anterior division of the temporo-maxillary
vein. This union forms the common facial vein, which is a short trunk
terminating in the internal jugular vein on a level with the hyoid bone.
The general course of the facial vein is similar to the facial artery,
though it is more superficially situated and less tortuous. Upon the
face it is imbedded in the subcutaneous fat, and passes above all the
facial muscles excepting the zygomaticus major, beneath which it ex-
tends.
K
The Tributaries of the Facial Vein are the
Angular,
Frontal,
Supraorbital,
Inferior palpebral (two or three),
Superior labial,
Buccal,
Masseter,
Parotid,
Submental,
Submaxillary,
Inferior palatine.
Deep facial, or
Anterior internal maxillary,
The Angular Vein is formed by the union of the frontal and supra-
orbital veins at a point near the articulation of the nasal and frontal
bones. It is quite superficially situated, and passes obliquely downward
and outward between the side of the nose and the inner margin of the
orbit.
The Tributaries of the Angular Vein are the nasal arch, which, when
250
ANATOMY.
present, spans the root of the nose and communicates with the angular
vein of the opposite side, the superior palpebral which is found on its
orbital side, the commencement of the ophthalmic vein with which pos-
FIG. 112.

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Veins of the Head and Neck.
teriorly it freely communicates, and anteriorly a few venules from the
nose.
The Frontal Vein is formed by the union of numerous small branches
situated over the greater part of the region of the frontal bone. It
communicates with small branches from the temporal and supraorbital
veins, as well as with branches from the corresponding vein of the
opposite side. It passes downward beneath the proximal extremity of
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
251
the eyebrow and terminates in the angular vein. The right and left
frontal veins occasionally communicate with each other, or they may
unite to form a single trunk, separating again into two branches.
The Supraorbital Vein is much smaller than the frontal. It is formed
by the union of small branches from the forehead, eyebrow, and eyelid,
and inosculates with the temporal and ophthalmic veins, uniting with
the frontal to form the angular vein.
The Inferior Palpebral Veins of either side originate in the lower
eyelid, being formed by branches from adjacent parts anastomosing with
the infraorbital veins. They terminate by emptying into the upper
portion of the facial vein.
The Superior Labial Vein commences in a plexus situated in the
upper lip, and anastomoses with the corresponding veins of the opposite
side. It passes outward and upward, and enters the facial vein on a
level with the ala of the nose.
The Deep Facial or Anterior Internal Maxillary Vein is of large
size, and originates in the pterygoid plexus formed by the internal
maxillary veins. It passes forward and downward in close apposition
to the zygomatic surface of the superior maxillary bone, and terminates
beneath the malar bone in the anterior facial vein.
The Buccal, Masseteric, and Parotid Veins are small branches that
originate in the structures indicated by their names. They terminate
by emptying into the lateral surface of the facial vein.
The Submental Vein is formed by branches which originate in the
submental region. It passes backward along the base of the inferior
maxillary bone, and terminates by emptying into the facial vein just as
that vessel curves under the jaw. Its anterior branch communicates
with the anterior jugular vein, and receives branches which come from
the region of the submaxillary gland and the mylo-hyoid muscle.
The Submaxillary Veins originate in the submaxillary muco-salivary
gland, and terminate either in the facial or submental vein.
The Inferior Palatine Vein originates in the structures in and about
the tonsils and soft palate. It passes downward in close proximity to
the pharynx, and generally terminates by emptying into the facial vein.
The following is from Allen's. Human Anatomy, p. 417:
"It will be seen that the venous supply of the face differs in some
important particulars from that of the trunk and limbs. In the last-
named localities both deep and superficial currents flow in the same
direction toward the heart. The facial trunk, however, is not formed
by primal venules, as is commonly the case, but by branches communi-
cating with the frontal and supraorbital veins, and by a transverse
branch found at the bridge of the nose. It is highly probable that
much of the blood of the interorbital space and of the locality about
the inner canthus of the eye flows through the orbital conduits to the
cavernous sinus. Farther down the face it is seen that the infraorbital
artery alone of all the vessels of the face possesses venæ comites. These
promptly join the orbital set of veins or aid in swelling the volume of
the internal maxillary vein. The veins corresponding to the deep parts
of the face, other than those mentioned, also seek an outlet in the same.
trunk, so that much of the superficial blood of the upper part and side
G
252
ANATOMY.
of the face passes inward to the brain-case and to the interior of the
facial region, while the remaining portion flows downward to join the
external and anterior jugular veins.
"It is of interest to note that in facial phlebitis the disease has a tend-
ency to extend upward, except when the exciting cause lies at a point
in or about the lower lip; in which case, as a rule, the inflammation
extends downward. In a case reported by M. Bechez,' illustrative of
of the fact just stated, a soldier, aged forty-two, was attacked with fever,
followed by redness and slight swelling of the forehead. This swelling
soon became more pronounced along the temporo-frontal veins, which
were hard, prominent, and of a violet color. The eyelids were œde-
matous and the conjunctiva chimosed. The patient died about the
seventh day. A somewhat similar case, recorded by Mr. T. H. Sylves-
ter, is interesting from the fact that the frontal veins determined the
extent of the inflamed tract. A puncture of the lip excited the phle-
bitis, which extended to a small vein at the outer side of the nose,
thence to the inner canthus, and from that point along the frontal
vein to the scalp, which became extensively infiltrated with pus. The
case terminated fatally at the end of five weeks.
"The relations existing between the venous blood of the face and that
of the brain-case are rendered evident by the fact that the state of the
circulation of the external nose is sometimes an index of the condition
of the vessels of the brain."
THE TEMPORO-MAXILLARY VEIN is a short trunk which commences
at the termination of the temporal and internal maxillary vein. It
extends downward within the parotid gland and along the outer sur-
face of the external carotid artery, between the sterno-cleido-mastoid
muscle and the ramus of the jaw, to a point near its angle, where it
divides into two branches. One branch passes downward and slightly
forward, uniting with the facial to form the common facial vein; the
other branch passes downward and backward, terminating in the
external jugular vein.
THE COMMON TEMPORAL VEIN is the medium through which, in
great measure, the blood is returned from the region of the distribution
of the temporal artery; the vein, however, does not accompany the
artery in its course. It originates above the base of the zygoma at the
termination of the superficial and middle temporal veins. It
It passes
downward and inward beneath the parotid gland, and unites with the
internal maxillary vein at the point of origin of the temporo-maxillary
vein.
C
The Tributaries of the Common Temporal Vein are the superficial and
middle temporals, the parotid, the articular, the anterior auricular, and
the transverse facial veins.
THE SUPERFICIAL TEMPORAL VEIN originates through the union
of numerous small branches in the form of a plexus which is situated
over the region of the vertex and side of the head. It anastomoses
with the corresponding artery of the opposite side, the frontal, supra-
orbital, occipital, and posterior auricular veins. These branches pass
downward, converge toward two central stems which finally unite, con-
¹ Gaz. héb., 1863, 716.
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
253
tinue downward and pass forward in front of the ear to a point just
above the zygoma, where it joins the middle temporal vein.
THE MIDDLE TEMPORAL VEIN originates in a plexus of veins situ-
ated in the temporal muscle. This plexus communicates with the deep
temporal veins as well as with the pterygoid plexus. The vein then
passes out of the muscle through the temporal fascia, and joins the
superficial temporal vein just above the base of the zygoma. Its orbital
branch originates from the union of a number of the external palpe-
bral veins; it inosculates with the supraorbital and facial veins, passes
backward, and terminates in the middle temporal vein.
THE PAROTID VEINS are small vessels which pass from the parotid
gland and empty into the common temporal vein.
THE ARTICULAR VEINS pass from the temporo-maxillary articula-
tion and terminate in the common temporal vein.
THE ANTERIOR AURICULAR VEIN passes from the external ear and
empties into the common temporal vein.
THE TRANSVERSE FACIAL VEIN returns the blood from the region
supplied by the transverse facial artery, and inosculates with the facial
and infraorbital veins.
THE INTERNAL MAXILLARY OR POSTERIOR FACIAL VEIN orig-
inates in a large plexus of veins which is situated between the temporal
and external pterygoid muscles, as well as partly between the two
pterygoid muscles. It passes backward and outward, accompanied by
the internal maxillary artery, enters the parotid gland, and terminates
by emptying into the temporo-maxillary vein about halfway between
the zygoma and the angle of the jaw. The plexus from which the
internal maxillary vein originates is formed by numerous tributaries
which arise from the region supplied by the internal maxillary artery.
These tributaries are the infraorbital, which commences on the face and
anastomoses with the veins below the eye, and passes backward through
the infraorbital canal and the spheno-maxillary fissure to join the ptery-
goid plexus; the posterior dental or alveolar, which commences on the
surface of the superior maxilla and the posterior superior teeth; the
superior palatine, spheno-palatine, and Vidian, which pass through
the foramina indicated by their names to join the plexus; the infe-
rior dental, which commences on the chin, receiving branches from
the lower incisor teeth, and passes backward along the inferior dental
canal, and emerges from the jaw at the posterior dental foramen, where
it is joined by the mylo-hyoid vein. It then passes directly upward to
the plexus; the deep temporal veins, three or four in number, descend
to the plexus. There are also other muscular branches, such as the
pterygoids, masseteric, and buccal, as well as a communicating branch
from the inferior ophthalmic vein, which join the plexus. The middle
meningeal veins are also tributaries. They are two in number, and are
the venæ comites of the middle meningeal artery. They originate
within the dura mater of the brain and inosculate with the cavernous
sinus.
THE POSTERIOR AURICULAR VEIN is much larger than the artery
of the same name. It originates in a plexus formed by small veins
situated at the posterior portion of the side of the head. This plexus
254
ANATOMY.
receives communicating branches from the temporal and occipital veins,
and occasionally a branch from the mastoid vein. It passes downward
behind the ear, crosses the mastoid process of the temporal bone and the
upper portion of the sterno-cleido-mastoid muscle, and terminates by
emptying into the external jugular vein.
THE OCCIPITAL VEIN commences on the back of the head, in the
region supplied by the occipital artery. It is formed from a plexus of
small veins and from the communicating branches of its fellow of the
opposite side, as well as from branches which enter the posterior auric-
ular and temporal veins. It generally communicates with the lateral
sinus of the venous system of the brain through the emissary vein, a
branch which traverses the mastoid foramen of the temporal bone. It
extends downward and forward, accompanied by the occipital artery,
and generally terminates by emptying into the internal jugular, though
occasionally it joins the external jugular.
THE LINGUAL VEIN arises from three sources—the ranine, the two
venæ comites, and the dorsal veins of the tongue.
The Ranine or Sublingual Vein is the largest of the branches which
go
to form the lingual. It commences by numerous superficial branches
situated on the under surface of the tip of the tongue, and anastomoses
with the corresponding vein of the opposite side. It extends backward,
covered by the mucous membrane of the tongue, and, accompanied by
the hypoglossal nerve, passes to the lateral surface of the hyo-glossus
muscle. Small veins empty into it from the mucous membrane of the
floor of the mouth, the substance of the tongue, and the sublingual
gland.
The Two Vence Comites are two small vessels which accompany the
lingual artery, and terminate by emptying into the lingual vein.
The Dorsal Vein originates in a plexus which is situated on the
under surface of the mucous membrane of the posterior part of the
tongue. These veins occasionally unite to form one common trunk, or
they may break up into several independent branches, which empty
either into the external jugular or the common facial vein. Cases are
reported in which they have emptied into the pharyngeal or internal
jugular vein.
THE PHARYNGEAL VEIN originates in the pharyngeal plexus, which
is formed by branches which pass from the lateral and posterior walls
of the pharynx. It also receives branches from the soft palate and
from the Vidian and meningeal veins, which pass through the oval
and spinous foramina in the sphenoid bone, and from the pterygoid
plexus. After receiving these branches it passes downward, and gener-
ally terminates by emptying into the internal jugular vein at the inferior
extremity of the parotid gland, though occasionally it passes into the
common facial vein or unites with the lingual or superior thyroid veins.
VEINS OF THE NECK.
The veins of the neck return the blood from the external and internal
portions of the head and face, the neck, and part of the region of the
shoulder. They are as follows:
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
255
External jugular,
Anterior jugular,
Internal jugular,
Vertebral.
THE EXTERNAL JUGULAR VEIN returns the principal portion of the
blood from the internal surface of the face and the external surface of
the head. It commences within the parotid gland near the angle of the
inferior maxillary bone. It is formed by the confluence of the posterior
auricular and the posterior division of the temporo-maxillary veins;
it passes almost perpendicularly downward. Its position is indicated
by a line drawn from the angle of the inferior maxilla to the middle
of the clavicle. It is quite superficially situated, being covered only by
the skin and the platysma myoides muscle. It is crossed about its centre
by the superficial cervical nerve. After leaving the angle of the jaw it
passes over the sterno-cleido-mastoid muscle, along its posterior margin,
to a point just above the clavicle, where it pierces the deep fascia of the
neck. It then extends slightly inward, and generally terminates by
emptying into the subclavian vein in close relation to the external bor-
der of the anterior scalenus muscle. Occasionally it terminates by
emptying into the internal jugular vein or at the point of junction of
the internal jugular and subclavian veins. The external jugular is
furnished with two sets of valves, one of which is imperfect and situ-
ated at its termination; the other set is perfect and located about an
inch and a half above the clavicle.
Tributaries.-The tributaries of the external jugular vein are the
posterior external jugular, transverse cervical, and suprascapular.
The Posterior External Jugular Vein commences by numerous
branches, which are situated in the muscles, skin, and fascia in the
region of the occiput and posterior portion of the neck. It terminates
by emptying into the external jugular vein midway between the clavicle
and the angle of the jaw.
The Transverse Cervical and Suprascapular Veins return the blood
from the region of the shoulder, and closely follow the course of the
suprascapular and transversalis colli arteries. These veins are sup-
plied with valves.
THE ANTERIOR JUGULAR VEIN varies considerably in size, and is
not constant in its existence. It commences below the chin, nearly in
the median line, by branches situated in the suprahyoid region, the
lower lip, and the chin. It also receives a communicating branch
from the submental vein. It passes downward, in close relation to the
middle of the neck, in a line with the sternal extremity of the clavicle.
Slightly above the clavicle it pierces the deep fascia of the neck, passes
outward and downward, behind the sterno-cleido-mastoid muscle, and
generally terminates by emptying into the lower extremity of the exter-
nal jugular vein, though occasionally it empties into the subclavian vein.
Just after this vein pierces the deep fascia it generally receives a com-
municating branch from the facial vein, and also small branches from
the larynx, and occasionally from the thyroid body. The transverse
cervical and suprascapular veins sometimes terminate in the anterior'
jugular vein. The anterior jugular veins of both sides occasionally com-
municate through small branches which extend from the lower extrem-
ities, one branch usually being of considerable size, and passing through
My
M
256
ANATOMY.
the interfascial space just above the sternum. This vein is not supplied
with valves.
THE INTERNAL JUGULAR VEIN is the largest and most import-
ant of the veins which descend the neck, and returns the blood from
the greater portion of the brain-case and superficial structures of the
face and neck. It commences at the termination of the lateral and
inferior petrosal sinuses in the enlarged and rounded portion of the
posterior lacerated (jugular) foramen, from which it passes downward
almost along a vertical line, and then slightly forward, and becomes
superficial at the lower portion of the neck. Its position is indicated
by a line drawn from the anterior portion of the mastoid process of the
temporal bone to the sterno-clavicular articulation, beneath which it ter-
minates by joining the subclavian vein to form the innominate vein.
This vein is not of uniform calibre throughout its course.
At its com-
mencement is the dilatation known as its bulb or sinus. Opposite the
hyoid bone it increases in size through its confluence with the common
facial and several deep veins. Near its termination it is slightly dimin-
ished in calibre, and furnished with a single or double valve which is
situated on its outer wall. This vein may be entirely absent on the
left side (Gruber).
Guad
Relations.-At its commencement the internal jugular vein is situ-
ated posterior to the internal carotid artery, the ninth, tenth, eleventh,
and twelfth nerves, and rests upon the rectus capitis lateralis muscle.
It then passes to the lateral side of the internal carotid artery, the
ninth (glosso-pharyngeal), and the twelfth (hypoglossal) nerves, pass-
ing between the vessels, while the tenth (pneumogastric) nerve passes
downward posteriorly between the vein and the artery, within the com-
mon sheath, the eleventh, (spinal accessory) nerve passing backward to
the inner side of the vein. After reaching the common carotid artery
the vein extends downward, somewhat overlapping this vessel. The
right internal jugular vein as it approaches its termination generally
diverges slightly from the artery, while the vein of the left side crosses
toward the median line.
K
Tributaries. In addition to the lateral and inferior petrosal sinuses,
the veins that empty into the internal jugular are as follows:
Superior thyroid,
Middle thyroid,
Occipital (occasionally).
The pharyngeal,
Lingual,
Common facial,
The pharyngeal, lingual, and common
described.
facial veins have already been
The Superior Thyroid Vein commences on the superficial surface
of the thyroid body by numerous small branches which extend from
its surface and the muscles in this region. It receives communicating
branches from the superior laryngeal and crico-thyroid veins, and passes
upward and backward to terminate in the internal jugular vein. Occa-
sionally it empties into the common facial vein.
Ma
The Middle Thyroid Vein commences by branches situated in the
lateral portion of the thyroid body, receiving tributaries from the
larynx and the trachea. It passes outward over the common carotid
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
257
artery, and terminates by emptying into the internal jugular vein
slightly above the level of the cricoid cartilage.
The Vertebral Vein commences by numerous branches situated in the
occipital region, these branches anastomosing with the occipital, the
deep cervical, and the posterior spinal veins. It passes downward
along the vertebral artery through the foramina in the transverse pro-
cesses of the first six cervical vertebræ, passes over the subclavian
artery, and terminates by emptying into the innominate vein near its
origin: it sometimes terminates in the subclavian. This vein is sup-
plied near its termination by either a single or a double valve. Occa-
sionally, as it passes down the body of the vertebræ, it receives two
branches, one opening into the vessel as it enters the foramen in the
transverse process of the atlas, while the other is received opposite the
seventh or vertebral prominence.
THE VENOUS SINUSES OF THE CRANIUM
are large canals (Fig. 113) analogous to veins, and into which the vari-
ous veins of the brain, the ophthalmic vein, and several emissary veins
FIG. 113.

Torcular
Horophili
Ins
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(Longitudinal
VenaGal oni
Superior longitudinal,
Inferior longitudinal,
Straight,
VOL. I.-17
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Vertical Section of the Skull, showing the sinuses of the dura mater.
empty. They are composed of two coats, internal and external. The
internal coat is a delicate serous membrane, being a continuation of the
lining membrane of the veins, while the outer coat is formed by the
dura mater. From this fact they are known as the sinuses of the dura
mater. They are fifteen in number, and are divided into two groups-
the supero-posterior and the infero-anterior.
THE SUPERO-POSTERIOR GROUP is composed of six sinuses :
Foramen Coccont
Occipital,
Right lateral,
Left lateral.
258
ANATOMY.
TORCULAR HEROPHILI.-Before passing to a description of the
sinuses it will be well to describe what is known as the torcular Hero-
phili. This is a dilatation formed by the confluence of the superior
longitudinal, the straight, the occipital, and the two lateral sinuses, and
is situated on the internal surface of the occipital bone at the internal
protuberance, where the superior longitudinal sinus terminates and the
lateral sinuses commence.
The Superior Longitudinal Sinus commences at the foramen cæcum
in the frontal bone, just anterior to the crista galli. In infancy, and
occasionally in adult life, this foramen is not a blind one, but opens
into the nasal chambers. When this is the case the sinus commences
within the nose. It passes upward, backward, and downward on the
under surface and in the median line of the dome of the brain-case, its
lower wall being formed by the upper border of the falx cerebri. It
terminates in the torcular Herophili. In shape it is triangular, and it
is crossed by numerous chords or trabecula (chorda Willisii). At its
commencement it is quite small, but increases gradually in size to its
termination. In its course it occasionally deviates from the median
line, especially as it passes along the occipital bone. It receives tribu-
taries from the veins of the brain, which enter the sinus in a forward
direction or opposite to the flow of blood along the sinus. Occasion-
ally a few of these veins which enter the sinus at its anterior portion.
do so in the direction of the blood-current. The tributary from the
external surface of the parietal bones which communicates with the
veins of the scalp passes through the parietal foramen to empty into
the sinus. It is small in calibre, and inconstant in existence on one or
both sides.
Tant
The Inferior Longitudinal Sinus is shorter and much smaller than
the superior. It is nearly cylindrical in form, and is often called the
inferior longitudinal vein. It commences at the anterior portion of the
free or inferior extremity of the falx cerebri, passes backward along its
inferior border to the tentorium cerebelli, and terminates in the straight
sinus. As it passes backward it receives several branches from the
falx.
The Straight Sinus (sinus tentorii) commences at the termination of
the inferior longitudinal sinus, which is situated at the anterior junction
of the falx cerebri and the tentorium cerebelli. It passes backward and
slightly downward in a straight line along the union of the falx cerebri
and tentorium. cerebelli, increasing in size as it extends, and terminates.
in the confluence of the sinuses. Its transverse section is triangular, a
few crossing cords being found in it. Besides the inferior longitudinal
sinus, its tributaries are the venæ Galeni magnæ, the inferior median
cerebri, the superior cerebellar, and small branches from the tentorium
cerebelli.
1
The Posterior Occipital Sinus is small and single, though occasionally
it is represented by two sinuses. It commences by branches situated
around the posterior border of the foramen magnum which communi-
cate with the posterior spinal plexus; it passes backward along the
inferior border of the falx cerebelli, and terminates in the confluence
of the sinuses. It receives small branches from the cerebellum.
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
259
The Lateral Sinuses in either side are large, though seldom of equal
size. This difference in calibre is caused to a certain extent by the
deflection of the straight sinus to one side or the other of the torcular
Herophili, and by its emptying into one or the other sinus. They
begin at the confluence of the sinuses, pass outward, forward, and
downward along the semicircular grooves to which the tentorium is
attached, and extend from the internal occipital protuberance outward
over the inferior posterior angle of the parietal bone, thence along
the sigmoid groove of the mastoid process of the temporal bone, over
the jugular process of the occipital bone, and terminate in the bulb of
the internal jugular veins situated within the rounded or enlarged por-
tion of the posterior lacerated (jugular) foramen. The tributaries of
these sinuses are veins from the posterior part of the cerebrum, from
the cerebellum, diploë, superior petrosal sinus, and emissary veins pass-
ing through the posterior condyloid and mastoid foramina, which are
communicating veins between the sinuses and the veins of the external
portion of the cranium.
THE INFERO-ANTERIOR GROUP is composed of seven sinuses :
Superior petrosal,
Transverse,
Anterior occipital.
Cavernous,
Spheno-parietal,
Circular,
Inferior petrosal,
The Cavernous Sinuses (Fig. 114), two in number, receive their name
from the fact of their being crossed or interlaced by numerous filaments
of connective tissue, which give them the appearance of cavernous tissue.
They are situated one on each lateral surface on the body of the sphe-
noid bone, and extend from the inner portion of the anterior lacerated
foramina backward to the apex of the petrous portion of the temporal
bones. They vary in width and shape, being narrow and pointed in
front and wide behind.
Their tributaries are, anteriorly, the terminations of the ophthalmic
veins. On their proximal surface they communicate with each other
through the circular sinus. A communicating branch from the ptery-
goid plexus of either side empties by passing through the oval foramina
in both wings of the sphenoid bone. They also receive branches from
the cerebral veins, and communicating branches from the spheno-parie-
tal sinuses. Posteriorly they terminate by emptying into the superior
and inferior petrosal sinuses. The third, fourth, and the ophthalmic
division of the fifth nerve on either side pass forward along the outer
walls to make their exit through the anterior lacerated foramina. The
internal carotid arteries, the sixth nerves, and the parotid sympathetic
plexuses pass forward to the inner margins of the floors of the sinuses,
the arteries and nerves passing through these cavernous sinuses; these
nerves and vessels are separated from the blood of the sinuses by their
thin lining membrane.
The Spheno-parietal Sinuses (two in number) are situated on the
under surfaces of the lesser wings of the sphenoid bone. They receive
communicating branches from the middle meningeal, anterior temporal,
and diploic veins, and occasionally a small vein, the ophthalmo-menin-
geal. They terminate by emptying into the cavernous sinuses.
260
ANATOMY.
The Circular Sinus is situated around the pituitary body within the
sella turcica. Its lateral portions communicate with the right and left
cavernous sinuses, while its anterior and posterior portions have received
the name of anterior and posterior intercavernous sinuses. They are
not constant in their existence, one or both being sometimes absent.
FIG. 114.

TAS
***
J-~,~~ "ADDIN 19
LONGITUDINAL SINUS
OPTIO NERVE
OPHTHALMIO VEIN
SPHENO-PARIETAL
SINUS
OIROULAR SINUS
OAVERNOUS SINUS
ANTERIOr ocoipiTAL
SINUS
SUPERIOR PETROSAL
SINUS
INFERIOR PETROSAL
SINUS
POSTERIOR 0001PITAL
SINUS
LATERAL SINUS
TOROULAR HEROPHILI
LONGITUDINAL SINUS
The Sinuses of the Dura Mater, seen in horizontal section of the skull.
Occasionally there is a third communicating sinus in this situation.
When this is the case it passes under the pituitary body.
The Superior Petrosal Sinus is a small canal which commences at the
posterior and lateral portion of the cavernous sinus, passes outward and
backward along a groove situated on the ridge between the anterior and
posterior surfaces of the petrous portion of the temporal bone, and
within the attached margin of the tentorium cerebelli, and terminates
by emptying into the lateral sinus as this large canal passes downward
in the sigmoid groove between the mastoid and petrous portions of the
BLOOD-VESSEL SYSTEM OF THE HEAD, ETC.
261
temporal bone. It receives tributaries from the cerebrum, cerebellum,
and tympanum, the last-named vessels passing through the petro-squa-
mous fissure.
The Inferior Petrosal Sinus is much shorter and wider than the
superior. It commences at the posterior extremity of the cavernous
sinus, passes downward and outward along a groove over the articula-
tion of the petrous portion of the temporal bone with the basilar process
of the occipital bone, extends through the anterior compartment of the
posterior lacerated foramen, and terminates by emptying into the ante-
rior portion of the bulb of the internal jugular vein.
The Anterior Occipital or Transverse Sinus (basilar plexus of Vir-
chow) is a communicating canal or plexus of vessels situated between
the right and left inferior petrosal sinuses in front of the foramen mag-
num. It receives branches from the anterior spinal veins.
VEINS OF THE ORBIT.
The veins of the orbit are two in number, superior and inferior
ophthalmic.
THE SUPERIOR OPHTHALMIC VEIN is considerably larger than the
inferior, and is by far the more important of the two. It commences
by the confluence of the frontal vein and a large communicating branch
from the angular vein, a tributary of the facial. It extends back-
ward through the orbit, in company with the ophthalmic artery, to a
point near the optic foramen, where it turns a little outward to enter the
proximal extremity of the anterior lacerated foramen. Here it passes
into the brain-case, and terminates by emptying into the cavernous
sinus.
Its tributaries are the veins which return the blood from the region
supplied by the ophthalmic artery as from the nasal chamber, the
anterior and posterior ethmoidal cells, the muscles of the eyeball, the
lachrymal gland, the eyeball, etc. These veins receive names corre-
sponding precisely to the arteries of the same region, and anastomose
freely with each other.
THE INFERIOR OPHTHALMIC VEIN is an accessory to the superior.
It commences at the terminations of the posterior ciliary and inferior
muscular veins, passes backward close to the floor of the orbit between
the inferior and external recti muscles, and usually leaves the orbit by
the spheno-maxillary fissure to terminate in the pterygoid plexus. It
occasionally terminates by emptying into the superior ophthalmic vein,
or it may pass through the anterior lacerated foramen to terminate inde-
pendently in the cavernous sinus. It receives tributaries from the
facial vein, from the temporal vein through the malar bone, and a
communicating branch from the superior ophthalmic vein.
THE DIPLOIC VEINS (Fig. 115) are those situated in the diploë of
the cranial bones. They can be seen to best advantage by stripping off
the pericranium, and then with a dental or surgical engine removing the
outer plate of bone. They will then be seen in great numbers, running
in various and tortuous directions, but with a general inclination down-
ward, and joining larger main branches in their course. They are
262
ANATOMY.
simply tubes grooved in the bone, their lining membrane being com-
posed of pavement epithelium, with some elastic tissue between the
epithelium and the tubes. As they pass downward and join other tubes
they increase in size and their lining tissue becomes more and more
FIG. 115.

teric
Dd.
Jing
a
O
Anterior.
。
impora
4.P
wlt.
..
All
Veins of the Diploë, as displayed by the removal of the outer table of the skull.
defined. There are usually four of these veins on each side of the
cranium-one frontal, two temporal, and one occipital.
The Frontal Diploic Vein is small, passes downward, makes its exit
through the small foramen in the supraorbital notch, and terminates in
the supraorbital vein.
The Anterior Temporal Diploic Vein commences in the frontal bone,
passes downward into the great wing of the sphenoid bone, where it
divides into two branches, one branch passing through to the outer side
of the head and emptying into the anterior deep temporal vein; the other
passing through the internal plate and emptying into the spheno-parietal
sinus.
The Posterior Temporal Diploic Vein commences by numerous
branches in the parietal bone, passes downward, and makes its exit
either through an opening in the posterior inferior angle of the bone
or through the mastoid foramen, to terminate in the lateral sinus.
The Occipital Diploic Vein is the largest of the four named. It com-
mences within the occipital bone solely, passes downward, and terminates
either externally in the occipital vein or internally by emptying into the
confluence of the sinuses or into the lateral sinus.
THE EMISSARY VEINS are those which form communicating branches
between the veins of the scalp and those at the base of the skull and the
various sinuses of the brain-case. They pass through various foramina,
THE NERVOUS SYSTEM.
263
i
and receive names to correspond with this fact. All the foramina are
not constant in their existence, and they vary in size. Named in the
order of their size and constancy, they are as follows:
The Mastoid, which empties into the lateral sinus by passing through
the mastoid foramen in the temporal bone.
The Parietal, which empties into the longitudinal sinus by passing
through the parietal foramen in the parietal bone.
The Condylar, which runs through the cervical plexus, and empties
into the lateral sinus by passing through the posterior condyloid foramen
in the occipital bone.
The Occipital, which is quite inconstant, extends from the structures
near the external occipital protuberance and empties into the torcular
Herophili by passing through a small foramen in this situation.
There are several other small emissary veins which pass through
different foramina, such as the ovale, middle lacerated, anterior con-
dyloid, and the carotid canal.
THE NERVOUS SYSTEM.
THE NERVOUS SYSTEM consists of all that portion of the body
engaged in the generation and transmission of nerve-force, through
which sensation, volition, and vital influence are conveyed to or from
the brain. It is made up of several organs known as nerve-centres,
nerves, and peripheral end-organs. These are arranged in two great
systems, the Cerebro-spinal and the Sympathetic; the former is frequently
described as the nervous system of animal life, the latter of organic or
vegetative life.
The Nerve-centres are found within the gray matter of the cerebro-
spinal centres, the ganglia of the roots of the spinal, and some of the cra-
nial nerves, also in the various ganglia of the sympathetic system. They
are composed of gray matter, white fibrous structure, and intercellular
substance known as neuroglia. Within the gray matter are found
numerous nerve- or ganglion-cells (Figs. 116, 117, 118). These cells.
are apolar, unipolar, bipolar, or multipolar in form; some investigators
claim those of the apolar variety to be undeveloped nerve-cells which
eventually become polar.
The function of the nerve-cells is to generate nerve-force in a manner
analogous to that of a galvanic cell or battery in the generation of
electricity.
The Nerves are white fibrous cords of various sizes extending between
nerve-centres and between nerve-centres and peripheral end-organs.
They do not generate nerve-force, but act as conductors, similarly to the
wires of a galvanic cell or battery in the transmission of electricity.
The nerves of the cerebro-spinal system are divided into three classes:
(1) those which conduct nerve-force from the nerve-centres outward to
the muscles, known as motor or centro-peripheral or centrifugal nerves;
1
264
ANATOMY.
(2) those conveying the impression received at the peripheral end-organs
to the nerve-centres, known as the sensory nerves and nerves of special
sense, or periphero-central or centripetal nerves; (3) those which unite
one nerve-centre to another, as the wires passing from one cell to
another in the same battery; these are known as intercentral nerves.
The Nerve-fibres are of two kinds, medullated and non-medullated.
The medullated or dark-border fibres are those which are found in the
cerebro-spinal nerves, with the exception of the olfactory. They vary
FIG. 116.

Ganglion-cell of a Frog (highly
magnified): a, a, straight fibre;
b, b, coiled fibro; c, smaller one
joining it.
•
FIG. 117.

A Ganglion-cell within its sheath from the Human
Sympathethic (highly magnified).
2000
in size from both to 12th inch, and are not always of equal size
in the same bundle. In fresh condition the fibre may be described as a
bright, glistening cylinder having a dark double contour, but after death
the outline of the fibre changes and is irregular, the result of decom-
position. The action of water, reagents, or mechanical disturbance pro-
duces the same appearance.
By viewing, with a moderate power, a cross-section of a nerve-fibre,
it is seen to be made up of a varying number of bundles or fasciculi
of fibres (nerve-fibres Fig. 119). The number of fibres in each fascic-
ulus, and of fasciculi in the nerve, increases or diminishes the size
of the trunk. These fibres and bundles usually run parallel to each
other in the same nerve, except at points where the nerve divides or
bifurcates. The whole is surrounded by connective tissue known as
THE NERVOUS SYSTEM.
265

ex
end
per
"
FIG. 118.
Nerve-cell from Spinal Cord of Ox, isolated after maceration in very dilute chromic acid (magnified
175 diameters). The cell has a well-defined, clear, round nucleus and a bright nucleolus. The
cell-processes are seen to be finely fibrillated, the fibrils passing from one process into another
through the body of the cell. a, axis-cylinder process, broken a short distance from the cell.
FIG. 119.
f
gorgeo
ep
A

50
Section of the Saphenous Nerve (human), made after being stained in osmic acid and subsequently
hardened in alcohol (drawn as seen under a very low magnifying power): ep, epineurium, or gen-
eral sheath of the nerve, consisting of connective-tissue bundles of variable size separated by
cleft-like areolæ, which appear as a network of clear lines, with here and there fat-cells and blood-
vessels; ƒ ƒ, funiculi enclosed in their lamellated connective-tissue sheaths (perineurium, p); enu,
interior of funiculus, showing the cut ends of the medullated nerve-fibres, which are inibedded
in the connective tissue within the funiculus (endoneurium). The fat-cells and the nerve-fibres
are darkly stained by the osmic acid, but the connective tissue of the nerve is only slightly
stained.
266
ANATOMY.
the common sheath or epineurium. Immediately beneath this sheath
are irregular lymph-spaces communicating with each other. A fibrous
layer, the perineurium, surrounds and forms a sheath for the different
bundles, giving room for the passage of blood-vessels supplying the
nerves. This layer is similar to the sheath of a muscle which forms a
covering to the bundles of muscular fibres. Within each bundle can
be seen the nerve-fibres, consisting of axis-cylinder, medullary sheath,
and neurilemma or sheath of Schwann, enveloped by a delicate tissue,
the endoneurium.
The Axis-cylinder (axial-band, axial-fibres) is the essential portion
of the nerve-fibre; it is nearly uniform in diameter, and undergoes no
interruption from the nerve-centre to near its peripheral distribution.
It is either cylindrical or flattened in shape, and passes nearly in the
central axis of the tube. When in a fresh condition it appears pale and
transparent, and when examined with a microscope, using a high power,
it is demonstrated to be composed of very fine homogeneous or more or
less beaded fibrilla.
These elementary or primitive fibrillee of Max Schultz are held together
by a faintly granular albuminous cement or interstitial substance. At
the termination of the axis-cylinder it is observed to divide up into
numerous fine filaments or fibrils. Some investigators claim that the
axis-cylinder has an independent or elastic sheath composed of neuro-
keratin.
The Medullary Sheath (white substance of Schwann) (Figs. 120 and
121) is composed of a glistening fatty
FIG. 120. substance enveloping the axis-cylinder,
3.
and produces the double or dark con-
tour associated with the nerve-fibres.
Situated between the axis-cylinder and
this sheath is a fine lymph-space con-
taining a small quantity of albuminous
fluid. This space is supposed to com-
of municate with the lymph-space which
Diagram
Structure of exists between the sheath and neuri-
Nerve-fibre. lemma (Fig. 122) through the bevelled
edges of the sections of the sheath. Histologists
hold a diversity of opinion regarding the minute
anatomy of the medullary sheath. It was formerly
considered to be a continious insulated tube, but is
now claimed by many to be made up of short seg-
ments, each fitting into the other by imbricated Nerve-substance (magni-
ends (incisions of Schmidt) (Fig. 123). It is also
divided into the internodal segments or constric-
tions of Ranvier. The sheath is not uniform in
thickness, which is the chief cause of the uneven
diameter of a medullated nerve-fibre. At certain
points in each internodal segment of Ranvier (here-
after described), upon the outer surface of the
sheath, are indentations or depressions for the lodg-
ment of nerve-corpuscles.
fied 200 diameters): a,
Nerve-tube of the com-
mon eel in water: the
delicate line on its exte-
rior indicates the tubular
membrane; the dark in-
ner one is the white sub-
stance of Schwann, slight-
ly wrinkled; b, the same
in ether. Several oil-glob-
ules have coalesced in the
interior, and others have
accumulated around the
exterior of the tube. The
white substance has in
part disappeared.
KAN
a
FIG. 121.
O


THE NERVOUS SYSTEM.
267
FBC d
FIG. 122.
7.......
23
^
00
01..
LAST
-07
A
1.
O
3
1.
2
A, tubular nerve-fibres, showing the sinuous outline and double
contours; B, diagram to show the parts of a tubular fibre-viz.
1, 1, membranous tube; 2, 2, white substance or medullary
sheath; 3, axis or primitive band; C, figure (imaginary) in-
tended to represent the appearances occasionally seen in the
tubular fibrês: 1, 1, membrane of the tube seen at parts where
the white substance has separated from it; 2, a part where the
white substance is interrupted; 3, axis projecting beyond the
broken end of the tube; 4, part of the contents of the tube
escaped.
3-
4
FIG. 123.




Nerve-fibres, fixed and stained
by perosmic acid, from the
posterior wall of dorsal
lymph-sac of frog: 1, 1,
medullary layer; 2, axis-cyl-
inder; 3, 3, constrictions of
Ranvier; 4, 4, incisions of
Schmidt.
The Neurilemma or Sheath of Schwann is the outer covering of a
nerve-fibre, and forms a continuous envelope; a narrow lymph-space
extends between it and the medullary sheath. It is the analogue of
the sarcolemma in a muscular fibre, and appears as a fine hyaline,
homogeneous, elastic membrane, with flattened or oval-shaped nucleated
corpuscles, known as nerve-corpuscles, situated between it and the
medullary sheath. The nucleus is generally seen in a depression of the
medullary membrane surrounded by a zone of granular protoplasm ;
this is especially the case in young subjects. The optic and auditory
nerves have no neurilemma.
The Nodes and Internodes of Ranvier (Fig. 124) are caused by the
annular constriction or breaks in the continuity of the medullary sheath
or white substance of Schwann. The axis-cylinder, the neurilemma, and
the lymph-spaces are not interrupted at these points, though the neuri-
lemma curves sharply inward and comes in close apposition to the axis-
cylinder. The point at which the constriction takes place is named the
node of Ranvier, and the portions between, the internodes of Ranvier or
interannular segments. Each internode or segment has usually one or
more nerve-corpuscles situated between the medullary sheath and the
neurilemma.
KATE
A fresh nerve treated with a solution of nitrate of silver or osmic
acid and exposed to the light demonstrates distinctly the nodes of
Ranvier (Fig. 125). After long exposure the silver salt penetrates
268
ANATOMY.
C
FIG. 124.
A
I
a
R
B
Portions of two Nerve-
Fibres stained with Os-
mic Acid, from a Young
Rabbit (425 diameters):
R, R, nodes of Ranvier,
with axis-cylinder pass-
ing through; «, primi-
tive sheath of the nerve;
c, opposite the middle of
the segment, indicates
the nucleus and proto-
plasm lying between the
primitive sheath and the
medullary sheath. In A
the nodes are wider, and
the intersegmental sub-
stance more apparent
than in B.
the structure of the nodes and passes along the axis-
cylinder, disclosing transverse markings named lines
of Frommann. The action of osmic acid will cause
the nodes to become almost colorless, while the me-
dullary or white substance, except close to the nodes,
will be stained a very dark color.

The Size of the Nerve-fibres varies, both in the
thickness of the medullated sheath and the diameter
of the axis-cylinder. This is dependent upon the
distance which it extends from the centre of its
origination the greater the distance covered, the
thicker will be the medullated sheath, though to
this there are numerous exceptions. As the fibre
approaches its termination the medullary sheath be-
comes gradually thinner, diminishing until lost
altogether, leaving only the covering of the neuri-
lemma with the nerve-corpuscles between the axis-
cylinder and the membrane, thus producing a non-
medullated nerve-fibre.
FIG. 125.
The Non-medullated or Pale Fibres (fibres of Rẻ-
mak) (Fig. 126) are made up of axis-cylinder, neu-
rilemma, and the nerve-corpuscles, which are situ-
ated at certain distances between the other two struc-
tures, the axis-cylinder being faintly striated. These
fibres are principally found in,
and compose the greater part of,
the sympathetic nerves, and are
the termination of the medullary
fibres. The olfactory nerve-fila-
ments are non-medullated, though
they cannot be classed as pale fi-
bres, as they have a distinct nu-
cleated sheath of their own. These
fibres (pale fibres) differ also from
the medullary fibres by branching
and joining offshoots from other
fibres, thus forming a fine net-
work. Triangular nuclei are
found at the nodal points, this
being the situation at which
these connections occur.
Before the final distribution
of the nerve-fibre it loses its
neurilemma, leaving nothing but
the axis-cylinder.
The Division of Nerves and
Nerve-fibres. As the nerve-
trunks extend from the centres
toward the periphery, they di-
vide and subdivide; some
branches unite with those of
p
600
a-
Wi...
cy
Ja ma se n
R
p

Nerve-fibre from
the
Sciatic Nerve of the
Rabbit, after the ac-
tion
of
of nitrate
silver:, ring form-
ed by thickened mem-
brane of Schwann; m,
white substance of
Schwann rendered
transparent by glyce-
rin; cy, cylinder-axis,
which just above and
below the level of the
annular constriction
presents the striæ of
Frommann.
THE NERVOUS SYSTEM.
269
other trunks, thus forming a single bundle arising from two or more
sources and possessing two or more functions; or they may break up
and unite in various ways, forming plexuses, as the brachial or cer-
vical.
The medullary fibres while in the nerve-cords or in the nerve-centres
do not branch or unite with each other; when near their termination
it is claimed they occasionally do so, in which case
the branches are always at one of the nodes of
Ranvier (Fig. 127). The new axis-cylinder thus
formed has its own medullary sheath and neuri-
lemma, being a continuation of the covering of the
nerve-fibre from which it originates.
FIG. 126.

_72
70
万
​Portion of the Network of
Fibres of Remak, from
the pneumogastric of
the dog: n, nucleus; p,
protoplasm surrounding
it; b, striation caused
by fibrils.
•
As the nerves approach their termination they
divide and subdivide into bundles, until they be-
come very minute, and consist of a single bundle
of a few fibres encased in a perineurium made of
FIG. 127.
C.
Division of a Nerve-
fibre, from pulmo-
FIG. 128.

a

d
nary membrane of Division of a Nervous Branch (a) into its
frog's lung.
ultimate fibres, b, c, d, e.
a delicate film of connective tissue (Fig. 128). Finally, the nerve
becomes a single medullated fibre, which soon loses its coat, exposing
the axis-cylinder; this ultimately breaks up into primitive nerve-fibrilla.
These become beaded, branching and uniting with each other, and form-
ing a very fine network, the density of which is dependent upon the
number of nerve-fibres distributed to the parts; thus, in some portions
270
ANATOMY.
a
FIG. 129.

C
d
Plexus of fine Non-medullated Nerve-fibres of the Cornea: a, a thick non-medullated nerve-fibre;
b, a fine one; c, d, elementary fibrils, anastomosing into a network.
of the body they have a closer woven network than others, as in the
cornea, skin, and mucous membrane (Figs. 129 and 130). In the two
latter tissues they are extremely abundant, forming two plexuses, a deep
and a superficial, the latter being the finer and closer woven.
FIG. 130.

PRO
•
Intra-epithelial Nerve-termination in the Anterior Epithelium of the Cornea, as seen in an oblique
section: a, an axis-cylinder; b, subepithelial nerve-fibrilla; c, intra-epithelial network; d,
epithelial cells.
If a nerve of sensation be traced from its network of distribution
toward its centre, it will be first found composed of primitive fibrils,
THE NERVOUS SYSTEM.
271
which form in themselves small axis-cylinders without any membranes.
These unite and form larger axis-cylinders, finally taking on the neu-
rilemma or white sheath of Schwann, then the medullary envelope, the
fibres uniting into bundles.
THE PERIPHERAL END-ORGANS.
The peripheral end-organs are divided into two classes, those of sen-
sation and those of motion.
B
The Peripheral End-organs of Sensory or Afferent Nerves.-Many
of these nerves terminate in fine plexuses or have free ends (as those
already described) under the final termination of the medullary nerve-
fibres, which are distributed to the mucous membrane, cornea, and skin.
Other terminations are found in various organs of special sense and
function: amongst the most important of these are the Pacinian and
tactile corpuscles (see Anatomy of the Skin for description), the spheroidal
end-bulbs of Krause, hair-bulbs, and nerves ending in gland-cells.
FIG. 131.
The small spheroidal end-bulbs of Krause, resembling to a certain
extent the Pacinian corpuscles, are found near the corneal margin of the
deeper layers of the conjunctiva (Fig. 131) of man and apes; in other
animals they are cylindrical. These
have also been found in various parts
of the skin and the mucous membrane
of the mouth. The spheroidal end-
bulbs are composed of polygonal cells
and slightly granular substance, sur-
rounded or invested externally by a
connective-tissue capsule, which is a
continuation of the sheath of Henle
of the nerve-fibre, and internally by a
nucleated membrane which is a con-
tinuation of the primitive nerve-enve-
lope. Usually the axis-cylinder enters
the bulb devoid of the medullary
C
C
G


CL
d
sheath, though occasionally it passes End- bulb from the Human Conjunctiva;
a, nucleated capsule; b, core-the outlines
of its cells are not seen; c, entering fibre,
branching, and its two divisions passing
to terminate in the core at d.
into the bulb with this covering. It
may enter undivided or in several
branches; if the latter, the branches
twist and intermingle with each other before entering, making a
number of turns, finally dividing into fibrilla within the bulb; these,
after making numerous convolutions, are ultimately lost within the
substance.
The Hair-bulbs contain terminations of fibres of the medullary nerves,
giving extreme sensitivity in cases where the hair is used as a sentinel, as
in the eyelashes and the whiskers of cats, dogs, and other animals.
NERVE-ENDINGS IN THE GLAND-CELLS.
As by mental influences some glands can be excited to secretion,
nerve-fibres must be directly connected with them. Plüger claims
272
ANATOMY.
3
FIG. 132.

2
Į
Modes of Termination of the Nerves in the Salivary Glands: 1 and 2, branching of the nerves between
the salivary cells; 3, termination of the nerve in the nucleus; 4, union of a ganglion-cell with a
salivary cell; 5, irregularly enlarged nerve-fibres entering the cylindrical cells of the excretory
ducts.
that both medullated and non-medullated fibres pass directly into the
secreting cells of the salivary glands of man (Fig. 132). Kupffer has
FIG. 133.
described the same connection
of nerves in some of the in-
sects.

Termination of Norves in Non-striped Muscular Tissue.
cher, in a slight bulbous expansion
ing cell.
The Peripheral End-organs
of Motor Nerves are of two
kinds-viz. those supplying
involuntary or non-striated
muscular tissue, and those sup-
plying voluntary or striated
muscular tissue.
The first class, those of the
involuntary or non-striated or
smooth muscular tissue (Fig.
133), belong to the sympathetic
nervous system or non-medul-
lary nerve-fibres. The fibres
of these nerves penetrate and
divide in the connective tissue
which surrounds the bundles
and muscular fibres. In this
position the axis-cylinder di-
vides into its ultimate fibrillæ,
these ending, according to Elis-
opposite the nucleus of a contract-
PA
The peripheral end-organs of voluntary or striated muscular tissue
belong to the medullary nerve-fibre, and are known as motorial end-
plates or end-plates of Kühne (Fig. 134). As the nerve-trunk advances
toward its distribution it divides and subdivides into its fibres, each
THE NERVOUS SYSTEM.
273
•
of which passes obliquely to a muscular fibre. Each muscular fibre
receives one or more nerve-terminals or end-plates. Most authorities
claim that at this point the medullary or white substance terminates,
and the neurilemma or primitive sheath (sheath of Schwann) becomes
continuous with the sarcolemma of the muscular fibre; others state that
it (the medullary sheath) terminates immediately after passing through
the sarcolemma. Ranvier says that it is the nucleated sheath of Henle,
and not the neurilemma, which is continuous with the sarcolemma.
After the axis-cylinder passes through the sheath of the muscular fibre,
it divides and subdivides into numerous fibrillæ, forming a network
FIG. 134.
S....
P...
P:.
So..
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Muscular Fibres of Lacerta viridis, with the terminations of nerves: a, seen in profile; P, P, the
nerve-end plates; S, S, the base of the plate, consisting of a granular mass with nuclei; b, the
same as seen in looking at a perfectly fresh fibre, the nervous ends being probably still excitable
(the forms of the variously-divided plate can hardly be represented in a woodcut by sufficiently
delicate and pale contours to reproduce correctly what is seen in nature); c, the same as seen two
hours after death from poisoning by curare.
which is imbedded in a more or less granular pale substance, usually
containing a number of oval nuclei having bright nucleoli. The sub-
division of the nerve-fibres, the granular substance, and the oval nuclei
forms the end-plates, which usually have only one fibre terminating in
them, though occasionally there are two.
THE CRANIAL NERVES.
The cranial nerves consist of one of the two divisions of the cerebro-
spinal system, receiving their name (cranial) from their origin within
the cranial cavity, with the exception of the spinal accessory, which
originates, in part, outside the brain-case, though this portion passes into
the cranium at the foramen magnum, and passes out in company with
its accessory portion through the posterior lacerated foramen.
A cranial nerve has two origins, superficial and deep: the first is
that portion of the nerve which can be traced to the circumference or
periphery of the brain; while the deep origin is in relation with the
deeper structure of that organ.
The cranial nerves (Fig. 135) pass out of the brain-case through the
foramina in the cranial bones at the base of the skull. Internally they
VOL. I.-18
274
ANATOMY.
are all situated near the median line, and as they pass out of the brain-
case there is reflected over them a prolongation of the dura mater, which
forms an enclosing sheath.
There are twelve pairs of cranial nerves.
Anatomists have desig-
FIG. 135.
Number.
First pair.
Second pair.
Third pair
Fourth pair
Fifth pair.
Sixth pair
Seventh pair
Eighth pair
Ninth pair
·
B-
·
•
Dissection of the Sinuses of the Skull and Cranial Nerves-the cavernous sinus dissected on the left
side; 1, third nerve; 2, optic nerve; 3, fourth nerve; 4, internal carotid artery; 5, Gasserian
ganglion of the fifth nerve, with its three divisions; 6, circular sinus; 7, superficial petrosal
nerve; 8, cavernous sinus; 9, sixth nerve; 10, transverse or basilar sinus; 11, seventh pair; 12,
superficial petrosal sinus: 13, eighth pair; 14, inferior petrosal sinus; 16, ninth nerve; 18, occip-
ital sinus; 20, lateral sinus; 21, torcular Herophili.
•
nated them by numbers corresponding with their superficial origin,
beginning at the anterior pair and passing backward on the under or
anterior surface of the brain (Figs. 136 and 137). These nerves are
known as motor nerves, sensory nerves, nerves of special sense, and
compound nerves. Their names and functions are as follows:
•
•
•
•
•
Name.
Olfactory
Optic.
Motor oculi
•
Pathetic
Trifacial
·
•
•
Abducens.
Facial
Auditory
•
•
21
Glosso-pharyngeal
Tenth pair
Pneumogastric
Eleventh pair Spinal accessory
Twelfth pair. Hypoglossal
•
•
•
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•
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Function.
Special sense, smell.
Special sense, sight.
Motion to five orbital muscles.
Motion to one orbital muscle.
Sensation and motion, possibly special
sense-taste.
Motion to one orbital muscle.
Motion to muscles of face.
Special sense, hearing.
Sensation, motion, and special sense-
taste.
Sensation and motion.
Motion.
Motion to muscles of tongue.
Nerves of Motion (or centrifugal nerves) are those which preside over
the action of the muscles of the body. They have their origin in the
THE NERVOUS SYSTEM.
275
deeper parts of the brain, extend outwardly, and terminate in the mus-
cular tissue; example, the facial (the nerve of motion to the muscles of
the face).
Nerves of Sensation (or centripetal nerves) are those which convey
the impression received at their peripheral ends to the substance of the
FIG. 136.
First Stda Rum
Middle Lobe
Whil
Lobe
16.
Olfactory N.
Longitudinal Fissure

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FRONTAL LOBE
PARIETAL LOBE
POSTR DIVISION OF
SYLVIAN FISSURE
TEMPORO-SPHEN
-OIDAL LOBE
OCCIPITAL LOBE
brain. (In the anatomical description of these and other nerves their
course is given from the brain outward.) Example, the first two divis-
ions of the fifth pair, which gives sensation to the upper two-thirds of
the face.
Nerves of Special Sense (centripetal) are those which convey the impres-
sion made upon their peripheral ends, conveying such impression to a
particular cell of the brain; example, the optic receiving impressions from
the retina and conveying them to certain centres within the brain.
276
ANATOMY.
13
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18
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FIG. 137.

IV
VI
13
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Semi-diagrammatic View of a Deep Dissection of the Cranial Nerves on the Left Side of the Head
(Quain). The Roman numerals from I to XII indicate the roots of the several cranial nerves as
they lie in or near their foramina of exit. V is upon the large root of the fifth, with the Gas-
serian ganglion in front; CI, the suboccipital or first cervical nerve; CVIII, the eighth. The
branches of the nerves are-1, supraorbital branch of the fifth; 2, lachrymal passing into the
gland; 3, nasal, passing toward the anterior internal orbital canal, and giving the long root to the
ciliary ganglion, 4'; 3', termination of the nasal nerve: 4, lower branch of the third nerve; 5,
superior maxillary division of the fifth passing into the infraorbital canal; 5', the same issuing
at the infraorbital foramen, and being distributed as inferior palpebral. lateral nasal, and supe-
rior labial nerves; 5", 6, ganglion of Meckel and Vidian nerve passing back from it; 6', palatine
and other nerves descending from it; 6", large superficial petrosal nerve: 7, posterior dental
nerves; 7', placed in the antrum, which has been opened, points to the anterior dental nerve; 8,
inferior maxillary division of the fifth; 8', muscular branches coming from it; 8x, the auriculo-
temporal branch cut short, and above it the small superficial petrosal nerve connected with the
facial; 9, buccal and external pterygoid; 10, lingual or gustatory; 10', its distribution to the side
and front of the tongue and sublingual gland; 10", submaxillary ganglion; below 10, the chorda
tympani passing forward from the facial to join the lingual; 11. inferior dental nerve; 11', the
same and part of its dental distribution exposed; 11", its termination as the mental nerve; 11",
its mylo-hyoid branch; 12, twigs of the facial nerve immediately after its exit from the stylo-
mastoid foramen, distributed to the posterior belly of the digastric and stylo-hyoid muscles; 12',
temporo-facial division of the facial; 12", cervico-facial division; 13, trunk of the glosso-pharyn-
geal; 13', its distribution on the side and back part of the tongue; 14, spinal accessory nerve; 14',
the same after having passed through the sterno-mastoid muscle, uniting with branches from the
cervical nerves; 15, hypoglossal nerve; 15', its twig to the thyro-hyoid muscle; 15", its distribu-
tion to the muscles of the tongue; 16, its descending branch, giving a branch to the anterior belly
of the omo-hyoid muscle, and receiving communicating branches at 16x from the cervical nerves;
17, pneumogastric nerve; 17', its superior laryngeal branch; 17", external laryngeal twig; 18,
superior cervical ganglion of the sympathetic nerve, uniting with the upper cervical nerves, and
giving at 18' the superficial cardiac nerve; 19, the trunk of the sympathetic; 19', the middle cer-
vical ganglion, uniting with some of the cervical nerves, and giving at 19" the large or middle
cardiac nerve; 20, continuation of the sympathetic nerve down the neck; 21, great occipital
nerve; 22, third occipital.
-
THE NERVOUS SYSTEM.
277
Compound Nerves are those composed of motor and sensory filaments,
and in some instances combining motion, sensation, and special sense;
example, the inferior maxillary or third divis-
ion of the fifth.
FIG. 138.

With the exception of the ninth, tenth, and
eleventh pairs, the cranial nerves are distrib-
uted to the head alone; those excepted have
also a distribution to the neck, the tenth pair
passing to the thorax and abdomen.
The regions supplied by the cranial nerves
are diagrammatically represented in Fig. 138,
from which it will be seen that nine of the
fourteen regions upon the head and neck are
supplied with sensation by some of the branches
of the fifth pair of nerves.
12
13
14
10
8
4
5
LA
7
7
2
6
OLFACTORY NERVES.
The Nervous Distribution of the
Head (Ranney): 1, region sup-
plied by the supraorbital branch
of the fifth nerve; 2, supplied by
the supratrochlear branch of the
fifth nerve; 3, supplied by the in-
fratrochlear branch of the fifth
nerve; 4, supplied by the infra-
orbital branch of the fifth nerve;
5, supplied by the buccal branch
of the fifth nerve; 6, supplied by
the mental branch of the fifth
nerve; 7, supplied by the super-
ficial cervical from the cervical
plexus; 8, supplied by the great
auricular from the cervical plex-
The olfactory or first pair of nerves (Fig. 139)
are those concerned in the special sense of smell.
They are about twenty in number, and derive
their superficial origin from the under surface
of the olfactory bulb of the brain, which is sit-
uated on the under, proximal, and forward
portion of the anterior lobe of the cerebrum.
These bulbs rest upon the olfactory sulcus of
the cribriform plate of the ethmoid bone, being us; 9, supplied by the temporo-
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malar fifth nerve;
10, supplied by the lachrymal
branch of the fifth nerve; 11,
supplied by the auriculo-tem-
poral branch of the fifth nerve;
12, supplied by the great occipi-
tal (a spinal nerve); 13, supplied
by the small occipital fronì the
cervical plexus; 14, supplied by
the supraclavicular from the
cervical plexus.
separated from each other by the crista galli.
The nerves pass downward through the nu-
merous foramina in the cribriform plate into
the superior nasal chamber. They are invested
by a covering derived from the membranes of
the brain, and are distributed to the mucous
lining of the superior meatus of the nose.
The nerves are divided into three sets-inner, outer, and middle. The
inner set is composed of the largest nerves: they are situated next to the
median line, and pass into delicate grooves or canals which descend on
either side of the perpendicular plate of the ethmoid bone. Some of
these canals run obliquely forward, and others obliquely backward.
Those that arise from the lateral portions of the olfactory lobes pass
into fine canals, which subdivide as they penetrate the lateral masses
of the ethmoid. A few of the more central of these nerves are dis-
tributed to the roof of the nasal chamber. No filaments extend to the
vomer or inferior turbinated bones. The olfactory nerves differ from
all other cranial nerves in being composed of non-medullated fibres.
Their terminal branches communicate freely with each other and form
a plexus beneath the nasal mucous membrane.
278
ANATOMY.
FIG. 139.

Nerves of the Septum of the Nose: 1, olfactory bulb and its ramifications in the septum; 2, nasal
nerve of the ophthalmic trunk; 3, naso-palatine nerve from Meckel's ganglion (too large in the
cut).
OPTIC NERVE.
The optic or second pair of nerves (Fig. 140) are the special nerves
of vision. Their encranial portion-viz. that which extends from the
superficial origin to where they pass out of the brain-case-is divided
into three parts, the optic tract, the optic chiasm, and the optic
nerve.
The Optic Tract is that portion which commences in the posterior
part of the optic thalamus, the anterior or superior lobes of the cor-
pora quadrigemina, and the corpora geniculata. The fibres from these
different sources unite and form a flattened or ribbon-like band (with-
out being invested by neurilemma), which passes obliquely forward and
inward, closely attached to the under surface of the superior portion of
the crus cerebri. Here it becomes more cord-like in appearance, and is
attached to the tuber cinereum and lamina cinerea. It receives addi-
tional fibres from these bodies, passes forward, and joins the optic chiasm
at its posterior lateral angle.
The Optic Chiasm or Commissure is an oblong body, nearly half an
inch in diameter, formed by the union of the optic tracts. It is lodged
in the optic groove, which is situated upon the olivary process on the
superior surface of the sphenoid bone. Its extremities are in close
apposition to the internal carotid artery of both sides. The fibres of
cach optic tract are divided into three sets-decussating, straight, and
intrageniculate.
The decussating set is composed of the greater number of the fibres of
cach optic tract. These fibres cross from one side to the other through
the chiasm, and thus the greater part of the optic nerve of the left side
is formed by fibres from the optic tract of the right side.
THE NERVOUS SYSTEM.
279
The straight set form the outer part of the optic tract. They pass
forward, and help to form the optic nerve of the same side.
The intergeniculate set (inferior commissure of Gudden) form the
inner part of the optic tract. They cross from one side to the other,
forming the posterior margin of the chiasm, and unite the fibres which
spring from the geniculate bodies. Many anatomists describe a set of
fibres which pass from one side to the other across the anterior margin
of the chiasm and form an inter-retinal set. The existence of this set of
fibres is still a matter of doubt, though Stilling has recently claimed
to have found them.
4
The optic nerve is a rounded cord which commences at the anterior
lateral angle of the optic chiasm. It extends outward and forward, and
FIG. 140.

1
5
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2
6
Diagram of the Optic Nerves and Tracts in Man: 1, left eyeball; 2, right eyeball; 3, 3, corpora genic-
ulata interna; 4, 4, corpora geniculata externa; 5, tubercula quadrigemina; 6, 6, centres of vision.
in the cerebral hemispheres.
passes from the brain-case through the optic foramen in the sphenoid
bone, accompanied by the ophthalmic artery, which runs along its outer
and lower side. Before entering the optic foramen it is invested by a
slender sheath from the arachnoid membrane of the brain, but as it
passes into the foramen it is strongly enveloped by a prolongation
from the dura mater. Upon reaching the orbit this covering divides
into two, the outer blending with the periosteum, while the inner con-
tinues to invest the nerve until it pierces the sclerotic coat of the eye.
When the nerve enters the orbit it passes outward and downward
between the origins of the recti muscles to the posterior aspect of the
eyeball, being surrounded by the adipose tissue of the orbit. It enters
280
ANATOMY.
the eyeball about one-tenth of an inch to the inner side of its centre,
passes through the sclerotic and choroid coats, and terminates by
expanding into the retina. Within the orbit it is surrounded by adi-
pose tissue, ciliary vessels, and nerves, the central retinal artery enter-
ing the nerve about one-fourth of an inch from where it passes into the
sclerotic coat.
Variations.-The optic tracts occasionally pass through the optic
foramina without decussation. When this is the case the chiasm is
entirely absent.
Infra.Trochlear N
OCULO-MOTOR NERVE.
The oculo-motor or third nerve (Fig. 142) is a large, round, firm
cord which presides over the movements of the eye. It is the most
FIG. 141.
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Nerves of the Orbit, seen from above.
anterior motor nerve of the cerebro-spinal axis, and supplies all the
muscles of the orbit, including the sphincter muscles of the iris and the
ciliary muscle of the eyeball, with the exception of the superior oblique
THE NERVOUS SYSTEM.
281
and the external rectus. It arises superficially from the walls of the
interpeduncular space on the median surface of the crus cerebri, just
above the pons varolii. It extends forward and slightly outward to the
side of the posterior clinoid process, soon after passing which it enters
the superior lateral portion of the cavernous sinus, being invested by a
sheath from the dura mater. It runs through this portion of the sinus,
passes below the anterior clinoid process, and on to the proximal
extremity of the anterior lacerated foramen. Here it enters the orbit
by passing between the two heads of the external rectus muscle. As
it extends through the anterior lacerated foramen it divides into two
branches, superior and inferior.
The Superior Division of the Oculo-motor Nerve is the smaller of the
two. It passes inward over the optic nerve, and again divides into two
sets of branches, one being distributed to the superior rectus muscle,
while the other supplies the levator palpebræ superioris.
The Inferior Division of the Oculo-motor Nerve is the larger of the
two. It divides into three branches-the internal rectus, inferior
rectus, and inferior oblique.
The Internal Rectus Nerve passes beneath the optic nerve and supplies
the internal rectus muscle.
The Inferior Rectus Nerve supplies the inferior rectus muscle.
The Inferior Oblique Nerve is the longest of the three branches. It
passes forward between the inferior and external recti muscles to the
inferior and anterior portion of the orbit, and is mainly distributed to
the inferior oblique muscle. It also sends a few filaments to the inferior
rectus, and a short, thick communicating branch to the ophthalmic or
lenticular ganglion.
TROCHLEAR NERVE.
The trochlear, fourth, or patheticus nerve (Fig. 141) is the smallest
and the most slender of all the cranial nerves, though it has the longest
encranial course. It presides over the motion of the superior oblique
or trochlear muscle of the eye. It arises superficially from a point just
below the corpora quadrigemina and near the valve of Vieussens. From
this point it passes outward over the superior peduncle of the cerebel-
lum, then forward, curves around the lateral margin of the crus cerebri,
and penetrates the dura mater below the tentorium cerebelli. Near
the posterior clinoid process it enters the cavernous sinus, extends
along its outer and upper wall, and passes through the proximal por-
tion of the anterior lacerated foramen into the orbit. It then passes
forward and inward over the superior rectus and levator palpebræ
superioris muscles, and is distributed to the upper surface of the
superior oblique.
Branches.-Recurrent branches of this nerve are given off as it passes
through the tentorium cerebelli. They are distributed to the tentorium,
some of them extending backward to the lateral sinuses. In the cav-
ernous sinus it gives off branches which communicate with the carotid
plexus of the sympathetic nerve, and occasionally with the ophthalmic.
division of the fifth nerve. It sometimes sends a branch which anasto-
P
282
ANATOMY.
Sensory
Root
Motor
Root
Internal Carotid Ag.
& Carotid Plexus.
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INFERIOR
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Lower Division of 3 N.
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Lachrymal N
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Nerves of the Orbit and Ophthalmic Ganglion, side view.
moses with the lachrymal nerve. The trochlear nerve is supplied by a
small branch from the anterior cerebral artery.
ABDUCENT NERVE.
As the abducent, sixth, or external oculo-motor nerve is distributed
to a muscle of the orbit, it is here described with those that are asso-
ciated with it. This nerve presides over the motion of the external
rectus muscle, and arises superficially between the anterior pyramids
of the medulla oblongata and the pons varolii. Generally, a few
bundles of its fibres spring from the lower margin of the pons. · At
first it is flat, but as it extends it soon becomes rounded. It passes
forward, and penetrates the dura mater at the side of the dorsum sella
of the sphenoid bone. It enters the cavernous sinus, and passes along
its outer and inner portion, covered by a thin membrane. It enters the
orbit through the anterior lacerated foramen, between the two heads of
the external rectus muscle, and is distributed to this muscle, entering
its proximal or orbital surface.
Branches.-In the cavernous sinus it sends communicating filaments
to the carotid sympathetic plexus. On passing into the orbits it gives
off a branch which extends between it and the ophthalmic nerve. This
nerve is occasionally entirely absent. When this is the case the exter-
nal rectus muscle is supplied by a branch from the third nerve.
G
TRIFACIAL NERVE.
The trifacial, trigeminus, or fifth nerve is the largest of all the
cranial nerves. Through its wide distribution within the face and
THE NERVOUS SYSTEM.
283
over the head, its close relation to other nerves and to the plexuses
and ganglia of the sympathetic nerve, it becomes involved in nearly
all the diseases of the external portion of the head as well as the
superficial and deep parts of the face. "The intimate relations which
the nerve bears with the points of origin of the sixth, seventh, eighth,
ninth, tenth, eleventh, and twelfth cranial nerves in the floor of the
fourth ventricle possibly explain many of those phenomena which are
considered as reflex in character, and whose starting-point seems to
depend upon some irritation of the fifth nerve by means of various
branches" (Ranney). It resembles a spinal nerve, in that it arises by
two roots, anterior and posterior. The posterior root is sensory in
character, and has a ganglion upon it, while the anterior root has no
ganglion and is motor in character.
The large, sensory, or posterior root emerges from a point in close
proximity to the centre of the lateral surface of the pons varolii, but
nearer its superior than its inferior border (Fig. 136).
FIG. 143.

Sensory Root
Motor Root
Facial
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Distribution of the Second and Third Divisions of the Fifth Nerve and Submaxillary Ganglion.
The small, motor, or anterior root is made up of six or eight rounded
filaments (Vulpian), and emerges from the pons a little above the larger
posterior root, being separated from it by a few transverse fibres of
284
ANATOMY.
white substance. It is entirely distinct and separate from the larger
sensory root from its deep origin until it passes out of the cranial cavity
through the foramen ovale, when it becomes closely united with its third
or inferior maxillary division, hereafter to be described.
The deep origin of these two roots is widely separated from their
superficial origin. Following them backward from the anterior surface
of the pons varolii, they pass directly through the pons to the medulla
oblongata, without any connection whatever with its fibres. On reach-
ing the medulla they form three main divisions, one anterior and two
posterior.
The Anterior or Motor Division arises from the motor nucleus of
the fifth nerve, which is composed of large, ramified, and pigmented
cells situated below the lateral angle of the fourth ventricle, anterior to
the inferior facial nucleus, and on the proximal side of the large sensory
nucleus of the fifth nerve. It also arises from the gray matter at the
anterior portion of the iter beneath the corpora quadrigemina. As it
passes toward the pons it receives fibres which arise from the raphé.
The fibres have their origin in the nucleus of the opposite side or in
the pyramidal tract.
The Two Posterior or Sensory Divisions give general sensibility to the
face and head, extending as far back as its vertex. These divisions are
the superior and inferior.
The Superior or Larger Division arises from the superior sensory
nucleus of the fifth nerve. This nucleus is situated at the side of the
motor nucleus, and is composed of nerve-cells which are less compactly
arranged, but in greater numbers than the motor nucleus.
The Inferior or Smaller Division is a well-defined bundle of nerve-
fibres which arises from the inferior nucleus of the fifth nerve. This
is composed of cells situated in the gelatinous substance which consti-
tutes the tubercle of Rolando.
From their superficial origin these two roots extend obliquely upward
and forward across the summit of the petrous portion of the temporal
bone, and pass through an oval opening in the dura mater into the mid-
dle fossa of the brain-case. The larger posterior sensory root terminates
in the ganglion of Gasser,' which is situated in a depression on the supe-
rior part of the anterior surface near the apex of the petrous portion
of the temporal bone. This ganglion is broad, flattened, and somewhat
semilunar or crescent-shaped, and from this fact is often called the semi-
lunar ganglion of the fifth nerve. Its convexity is directed forward and
slightly upward. The cells of this ganglion are unipolar in shape. Its
surfaces are striated, and it receives on its inner side filaments of com-
munication from the carotid plexus of the sympathetic nervous system.
M
1 The structure of this ganglion was first recognized by Gasser, professor of anatomy
in Vienna. His observations, however, were published by Hirsch, a pupil of Gasser,
in 1765 (Hirsch, Paris Quinti Nervonum encephali, Vienne, 1765), in Ludwig (Scrip-
tores Nervologici minores selecti, Lipsia, 1791, tomus i. pp. 244 et seq.). Hirsch first gave
it the name of Gasserian ganglion.
Some authors call it Casserian ganglion, probably confounding Gasser with Casserius.
Casserius in his anatomical figures describes many parts of the brain and nerves, but
says nothing of the ganglion of the fifth (Casserius, Anatomische Tafeln, Franckfurt-am-
Mayn, 1756). (Flint's Physiology of the Nervous System, vol. i. p. 185.)
THE NERVOUS SYSTEM.
285
Flint claims "this anatomical point as of importance in view of some
of the remote effects which follow division of the fifth nerve through
the ganglion in living animals.' A few small branches emanate from
the ganglion, and are distributed to the dura mater and the tentorium.
""
From the anterior or concave margin of this ganglion the three large
divisions of the fifth nerve commence. It is from this that the nerve
receives the name of trifacial. These divisions again divide and sub-
divide as they pass forward to their terminations (Fig. 144).
FIG. 144.

34
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122
23
24
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16
MI
26
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28
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30
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17
20
A Diagram of the Distribution of the Fifth Nerve (Ranney): 1, the crus cerebri; 2, the sensory root
of the nerve; 3, the motor root of the nerve; 4, the Gasserian ganglion, upon the sensory root
only; 5, the ophthalmic nerve passing through the sphenoidal fissure; 6, the superior maxillary
nerve passing through the foramen rotundum to enter the spheno-maxillary fossa; 7, the inferior
maxillary nerve passing through the foramen ovale in company with the motor root; 8, a fila-
ment sent backward from the ophthalmic nerve to the tentorium cerebelli; 9, the frontal nerve;
10, the lachrymal nerve; 11, the nasal nerve; 12, the supraorbital nerve passing through the fora-
men of the same name; 13, the supratrochlear nerve; 14, the long ciliary nerves to the iris; 15,
the lenticular or ciliary ganglion; 16, the temporo-malar nerve, dividing into temporal-and malar
branches: 17, the spheno-palatine nerve, going to Meckel's ganglion; 18, the posterior dental
nerves; 19, the anterior dental nerves, given off in the antrum; 20, the naso-palatine nerve,
escaping at the anterior palatine foramen after passing through the antrum; 21, the anterior
palatine nerve after escaping from the posterior palatine foramen; 22, the deep temporal nerve;
23, the masseteric branch; 24, the buccal branch, which also often supplies the external pterygoid
muscle; 25, the pterygoid branch, going chiefly to the internal pterygoid muscle; 26, the poste-
rior palatine nerves after leaving the posterior palatine foramen, going to the muscles of soft
palate; 27, the auriculo-temporal nerve, splitting, and thus embracing the middle meningeal
artery; 28, the gustatory or lingual nerve, distributed to the anterior two-thirds of tongue; 29,
the inferior dental nerve, passing through the inferior dental canal beneath the teeth of the
lower jaw; 30, the mylo-hyoid nerve; 31, the chorda tympani nerve, joining the gustatory nerve,
and possibly bringing to it the perception of taste; 32, the middle meningeal artery; 33, the
fibres going to the cavernous plexuses of the sympathetic system; 34, the Vidian nerve, going
from Meckel's ganglion to the Vidian canal.-Ganglion of the Fifth Nerve; L, the lenticular
ganglion, sending fibres to the iris and ciliary muscle; C, the Gasserian ganglion; O, the otic
ganglion, lying on the inferior maxillary nerve below the foramen ovale; E, the submaxillary
ganglion, connected with the gustatory and chorda tympani nerves; M, Meckel's ganglion, lying
in the spheno-maxillary fossa.
"By tracing the various distributions of this nerve it will be seen that
it gives motor power to the muscles of mastication-viz. the temporal,
masseter, and pterygoids; also the anterior belly of the digastric and
mylo-hyoid muscles, and tensor palato " (palato-Eustachian)" and tensor
286
ANATOMY.
tympani, thus controlling the act of mastication and to some extent
deglutition and hearing. Fibres of the fifth nerve afford general sensa-
tion to the entire skin of the head and face, except in the occipital
region and the back and lower part of the ear, also to the mucous mem-
branes of the mouth, with the exception of the posterior pillar of the
fauces and the posterior third of the tongue, which derive their sensa-
tion by means of the glosso-pharyngeal nerves (Ranney).
The Ophthalmic, or first division of the fifth nerve, is the smallest
of the three cords, being but about an inch in length. The table on
page 287 will show that it is derived wholly from the sensory root. Its
function is to impart sensation to the eyeball, the lachrymal gland, the
mucous lining of the eye, and a portion of the nose and of the eye-
brow and forehead. It commences from the upper, inner, and anterior
portion of the margin of the Gasserian ganglion. It is a flattened cord,
and passes forward along the outer wall of the cavernous sinus, and
terminates before or just as it is about to pass through the anterior
lacerated foramen by dividing into three main branches, the frontal,
lachrymal, and nasal.
Branches of the Ophthalmic Nerve.-
Those within the cavernous sinus,
Frontal,
G
K
Lachrymal,
Nasal.
The ophthalmic nerve gives off two small branches within the cav-
ernous sinus.
The Frontal Nerve is the largest of the branches given off by the
ophthalmic, and is in reality its axial continuation. It enters the orbit
through the most superior portion of the anterior lacerated foramen,
and passes forward in the median line above the muscles and below the
periosteum. It terminates midway between the apex and base of the
orbital cavity, above the levator palpebræ superioris muscle, by dividing
into two branches of unequal size, the supratrochlear and the supra-
orbital.
The Supratrochlear Nerve is much the smaller of the two terminal
branches of the frontal. It extends obliquely inward and forward over
the trochlear muscle, passing out of the orbit, and curves around the
supraorbital arch between the supraorbital foramen and the trochlear fossa.
It then extends beneath the corrugator supercilii and frontalis muscles,
and divides into two terminal branches. These branches pierce the
orbicularis and frontalis muscles, supplying them as well as the integ-
ument; also the lower and median portion of the forehead, interlacing
with the corresponding nerve of the opposite side. This nerve also
gives off two distributing branches, one extending from the nerve near
the trochlear muscle, which passes downward and joins the infratrochlear
branch of the nasal nerve, and the other near its exit from the orbit,
which passes to the eyelid and bridge of the nose.
The Supraorbital Nerve is really a continuation of the frontal. It
passes forward, and emerges from the orbit through the supraorbital
notch or foramen. It then curves upward on the forehead, and divides
into a median and a lateral branch, which pierce the muscles and become
the cutaneous nerves. Its branches of distribution are several small
cords which descend to the structures of the upper eyelid, and one
THE NERVOUS SYSTEM.
287
The following table will serve to demonstrate the original trunks of
this nerve, with their different branches :
GANGLION OF GASSER (SENSORY ROOT).
MOTOR ROOT.
Ophthalmic.
•
Superior maxillary
Inferior maxillary.
[ Frontal. .
Lachrymal. .
Nasal
In the pterygo-maxillary fossa..
In the infraorbital canal . .
On the face or terminal.
Supra-trochlear.
Supra-orbital.
Superior branch.
Inferior branch.
Branch to dura mater.
Branch to ophthalmic ganglion.
Long ciliary branch.
Infratrochlear.
Motor branches from anterior
root
Internal nasal branch
External branches.
Orbital..
·
Spheno-palatine nerves (to Meckel's
ganglion).
Palpebral.
Nasal.
Labial.
{
Auriculo-temporal.
Sensory or posterior root through | Lingual or gustatory.
ganglion of Gasser.
Inferior dental
Buccal.
Posterior superior dental . . .
The middle superior dental.
Ascending.
The anterior superior dental ... { Descending.
{
Deep temporal
Masseteric.
Internal pterygoid.
External pterygoid.
Mylohyoid.
{
Internal or septal branch.
Lateral branch.
Anterior superficial branch.
Lachrymal.
Temporo-malar.
{
The superior set.
The inferior set.
Incisor.
Mental.
Anterior.
Posterior.
288
ANATOMY.
which passes outward under the orbicularis palpebrarum, interlacing
with the facial nerve. The muscular branches are distributed to the
corrugator supercilii, frontalis, and orbicularis palpebrarum. The
cutaneous branches are two in number, median and lateral. These
extend posteriorly as far as the occiput. The deep or pericranial
branches are distributed to the frontal and parietal bones. This nerve
also sends a filament which supplies the mucous membrane of the frontal
sinus. Occasionally the division of the supraorbital nerve takes place
within the orbit, the larger branch passing through the supraorbital
foramen, while the smaller branch extends internally around the supra-
orbital arch or through the frontal notch, which is occasionally present.
The Lachrymal Nerve is the smallest of the three divisions of the
ophthalmic. It passes along the outer side of the frontal nerve into
the orbit through the anterior lacerated foramen, encased in an indi-
vidual sheath derived from the dura mater. It passes forward and
outward near the periosteum of the orbit above the external rectus
to the lachrymal fossa of the frontal bone, accompanied by the lachry-
mal artery. It then penetrates the external tendo paipebrarum of the
eye and terminates in the upper eyelid.
Branches of Distribution.-On approaching the lachrymal fossa the
lachrymal nerve sends a communicating cord to the orbital branch of
the second or superior maxillary division of the fifth. This branch is
sometimes called the inferior division of the lachrymal nerve, and occa-
sionally passes backward through a canal in the outer wall of the orbit,
its divisions forming an arch from which branches are distributed to
the lachrymal gland and the conjunctiva. Within the lachrymal fossa
it sends branches to the lachrymal gland and the conjunctiva.
THE NASAL OR OCULO-NASAL NERVE is intermediate in size between
the other two divisions of the ophthalmic nerve. It commences from the
under surface of the ophthalmic nerve, and passes through the widest
portion of the anterior lacerated foramen into the orbit between the two
heads of the external rectus muscle, accompanied by the fourth nerve.
On either side of it are the two divisions of the third nerve. From the
anterior lacerated foramen it passes obliquely inward and forward over
the optic nerve below the superior muscles of the orbit to the anterior
ethmoidal foramen on the inner wall of the orbital cavity. It here
divides into the internal nasal and infratrochlear nerves.
Branches of the Nasal Nerve.-
Branch to the dura mater,
Communicating branches to
sympathetic nerve,
A
M
Long ciliary,
Spheno-ethmoidal,
Internal nasal,
Infratrochlear.
Ganglionic,
The Branch to the Dura Mater is a small filament which turns back-
ward and is distributed to the dura mater of the anterior cerebral fossa.
The Communicating Branches to the Sympathetic are a few distinct
filaments which communicate with the sympathetic network about the
ophthalmic artery (Allen).
The Ganglionic Branch is quite slender and about half an inch in
length. It usually commences from the nasal nerve as it extends
between the two heads. It passes along the outer side of the optic
THE NERVOUS SYSTEM.
289
nerve, and terminates at the posterior superior portion of the ophthalmic
(lenticular) ganglion, constituting its long or sensory root.
The Long Ciliary Nerves are two or three in number, and com-
mence from the nasal nerve as it extends across the optic nerve.
They pass along the inner margin of this nerve, and unite with
some of the short ciliary nerves from the ophthalmic ganglion.
They then pierce the sclerotic coat of the eye, pass forward between
it and the choroid coat, and are distributed to the ciliary muscles, the
cornea, and the iris.
The Spheno-ethmoidal (Luschka) or Posterior Ethmoidal (Krause)
Nerve passes from the nasal nerve to the posterior ethmoidal foramen
(posterior internal orbital canal), and is distributed to the mucous mem-
brane of the sphenoidal sinus and the posterior ethmoidal cells in front
of the body of the sphenoid bone.
The Internal Nasal or Ethmoidal Nerve is in the line of continuation
of, and generally described as, the nasal nerve. It passes through the
anterior ethmoidal foramen, situated between the frontal and ethmoidal
bones, into the brain-case, just external to the cribriform plate. It then
extends in a shallow groove along the outer wall of this plate to the
cerebro-nasal slit near the crista galli, passes through this slit, enters the
nasal chamber, and divides into three branches-the internal or septal
branch, the lateral, and the anterior superficial branch.
The Internal or Septal Branch of the internal nasal nerve passes
downward and forward, and supplies the anterior portion of the septum
of the nose.
The Lateral Branches of the Internal Nerve usually comprise two or
three filaments which are distributed to the anterior portions of the lat-
eral walls of the nasal chambers, including the extremities of the middle.
and inferior turbinated bones.
The Anterior or Superficial Branch passes downward in a longitu-
dinal groove or canal on the internal surface of the nasal bone until
it reaches the lateral cartilage of the nose. Here it extends between
the bone and the cartilage, runs beneath the compressor naris, and
becomes superficial, terminating in the spine, the wing, and the tip of
the nose.
G
The Infratrochlear Nerve is one of the terminal branches of the nasal
nerve, it being given off near the anterior ethmoidal foramen. It passes
forward along the inferior border of the superior oblique muscle and
parallel to the supratrochlear nerve, and receives a communicating branch
from it. As it approaches the trochlea it passes to the inner angle of
the eye and divides into two sets of branches. Those of the superior
set are distributed to the superficial structures of the superior eyelid ;
while those of the inferior set are distributed to the superficial struc-
tures at the root and side of the nose, the superficial portion of the
inferior eyelid, the caruncle, conjunctiva, the lachrymal sac, and the
lachrymal duct.
Variations." The nasal nerve occasionally (frequently, Krause)
gives filaments to the superior and internal recti. A branch to the
levator palpebræ superioris has been met with (Fäsebeck); offsets
from the nasal nerve as it traverses the anterior internal orbital canal to
VOL. I.-19.
290
ANATOMY.
the frontal sinus and ethmoidal cells are described by Meckel and
Langenbeck."1
SUPERIOR MAXILLARY NERVE.
The superior maxillary or second division of the fifth nerve is the
second in size of its three great divisions. It is composed entirely of
sensory fibres, and gives sensation to nearly all the structures of and
around the superior maxillary bone. It commences in the centre of the
convex or anterior margin of the Gasserian ganglion by a flattened and
plexiform band, passes horizontally and directly forward, and leaves the
cranium through the foramen rotundum in the great wing of the sphe-
noid bone. It then enters the pterygo-maxillary (spheno-maxillary)
fossa, and becomes more rounded and firmer in texture. It
this fossa surrounded by adipose tissue, and enters the infraorbital or
superior maxillary canal, and receives the name of infraorbital nerve. It
passes through this canal, and emerges upon the face through the infra-
orbital foramen. The branches of this nerve can be divided into four
groups, according to the locality of their origin.
passes across
The Orbital or Temporo-malar Branch (subcutaneous mala) is a
small nerve which arises from the upper portion of the superior max-
illary nerve just after it emerges from the foramen rotundum. It passes
forward into the orbital cavity through the spheno-maxillary fissure,
and immediately divides into two branches, temporal and malar.
The Temporal Branch passes forward in a groove on the outer wall
of the orbit until it reaches the temporal canal in the malar bone. It
passes through this canal into the anterior portion of the temporal fossa,
ascends between the bone and the temporal muscle a short distance,
pierces the muscle and its aponeurosis about an inch above the zygoma,
and terminates in filaments which supply the cutaneous structures of
the temporal region and the side of the forehead. It interlaces with
the facial and occasionally with the third division of the fifth nerve.
That portion of the nerve within the orbit sends one or two filaments
of communication to the lachrymal nerve, a branch of the ophthalmic
division of the fifth.
Ga
The Malar Branch at its commencement passes through the loose
adipose tissue at the lower angle of the orbit to the malar bone, through
which it extends in the malar canal in its lower portion, and emerges
upon the face usually by two branches. It is distributed to the cutaneous
tissues in this region of the cheek, and interlaces with the facial nerve.
The Spheno-palatine Branches are usually two in number, and are
given off from the middle of the lower surface of the pterygo-maxillary
portion of the second division of the fifth nerve. They pass downward
to the spheno-palatine or Meckel's ganglion.
The Posterior Superior Dental or Alveolo-dental Nerve usually arises
by one root, though occasionally it has two, from the second division of
the fifth nerve just before it passes into the infraorbital canal. When
it arises by one root it almost immediately divides into two, and forms
a superior and an inferior set of branches.
1 From Quain's Anatomy.
THE NERVOUS SYSTEM.
291
The Superior Set passes forward, and enters canals in the zygomatic
surface of the superior maxillary bone, traverses the base of the malar
process of this bone, and terminates in the canine fossa, interlacing with
the anterior dental nerves.
The Inferior Set is somewhat larger than the superior, and passes
downward, slightly outward and forward, to enter the posterior dental
canals. One of these canals traverses the outer wall of the maxillary
sinus, and joins the anterior dental canal extending from the infraorbital.
As the nerve passes forward in this canal it gives off branches which form
loops or plexuses, from which filaments are given off to enter the roots
of each of the molar teeth, and are distributed to their pulps, the outer
wall and mucous membrane of the maxillary sinus, the alveolar pro-
cess and the gums, and a few fibres to the bony structure of the antrum
of Highmore. Occasionally the posterior dental nerve is of large size,
and replaces an absent buccal nerve, a branch of the inferior maxillary.
The Middle Superior Dental Nerve is given off from the infraor-
bital soon after it enters the infraorbital canal. It passes outward,
downward, and forward in a special canal in the outer wall of
the maxillary sinus, interlacing with the posterior dental nerve, and
forms loops or plexuses from which filaments are given off to enter the
roots of the bicuspid teeth.
The Anterior Superior Dental Nerve is larger than either of the other
two divisions. It is given off from the infraorbital nerve a little before
it emerges from the infraorbital foramen. It passes in a special canal
of its own which begins in the anterior wall of the maxillary sinus,
extends at first inward, then downward, and is reflected upon the floor
of the nasal fossa. It then passes in a lateral direction, and communi-
cates with the canals of the middle and posterior dental nerves.
This
nerve gives off two sets of distributing branches, the ascending and the
descending.
The Ascending Nasal Set is distributed to the nasal spine of the supe-
rior maxillary bone, the mucous membrane of the anterior portion of
the inferior meatus, and to the floor of the nose.
The Descending or Dental Set is distributed through loops or plexuses
to the incisor and canine teeth, and interlaces with the middle and pos-
terior dental nerves.
The three superior dental nerves interlace or communicate with each
other in such a manner as to form loops or plexuses. These plexuses
(superior dental) are situated above the roots of the teeth, and it is
often, if not always, difficult to say where one begins and the other
ends. It is extremely probable that filaments from each of the three
nerves pass into the same tooth. This may account for the fact that
some of these nerves can be severed and the pulps of the teeth remain
vital.
The Facial or Terminal Set is composed of three nerves-the palpe-
bral, nasal, and labial. They arise from the infraorbital just as that.
nerve emerges from the infraorbital foramen.
The Inferior Palpebral or Ascending Set is generally made up of two
nerves. They ascend in a groove or canal, pass through the upper por-
tion of the proper elevator muscle of the upper lip, and are distributed
D
292
ANATOMY.
to the orbicularis palpebrarum, the skin, the conjunctiva of the lower
eyelid, and interlace at the outer angle of the orbit with the malar
branches of the orbital and facial nerves. A branch also
A branch also passes inward
and interlaces with the external nasal nerve, a division of the oph-
thalmic.
The Nasal or Internal Branches, two or three in number, pass inward
and outward between the fibres of the levator labii superioris alæque
nasi muscle, and are distributed to the skin of the nose and the lining
membrane of the nostril, and interlace with the nasal branches of the
ophthalmic nerve.
The Labial or Descending Branches are more numerous than the
branches of the other sets from the infraorbital nerve. They pass down-
ward beneath the levator labii superioris muscle, and are distributed to
the upper lip, its skin, mucous (labial) glands, and mucous membrane.
They also extend to the anterior portion of the gums.
The Infraorbital Plexus of nerves is situated below the orbit, and is
composed of branches from the infraorbital and facial nerves.
THE INFERIOR MAXILLARY NERVE.
The Inferior Maxillary, or Third Division of the Fifth Nerve, is the
largest of its three divisions. It differs from the other two divisions in
the fact that its function is mixed, being both sensory and motor; it
also probably supplies in a measure the special sense of taste. This
nerve is distributed to the inferior portion of the face, the inferior
maxillary bone, the inferior teeth, a portion of the tongue, and the mus-
cles of mastication. Its origin is composed of two portions, the sensory
and motor.
The Sensory (or larger) Portion arises from the inferior lateral and
anterior part of the margin of the Gasserian ganglion. It passes down-
ward through the foramen ovale in the sphenoid bone, accompanied by
the smaller anterior or motor root. Immediately after its exit from
this foramen the two portions unite, their fibres interlacing, to form one
nerve, the mixed function of the nerve being thus accounted for. It
then descends vertically internal to the external pterygoid muscle, and
divides into two sets of branches, anterior and posterior.
The Anterior Motor Branch or trunk of the inferior maxillary nerve
is the smaller of the two, and is composed almost entirely of motor fila-
ments, which are distributed to the muscles of mastication. It is divided
into four branches :
Deep temporal,
Masseteric,
The Deep Temporal Branches are usually two in number, though
occasionally there are three-anterior, middle, and posterior.
Pterygoid,
Buccal.
S
The Anterior Branch before piercing the external pterygoid muscle is
joined by a communicating filament from the buccal nerve. It ascends
across the infratemporal (pterygoid) ridge of the sphenoid bone, passes
to the anterior portion of the temporal fossa, and supplies that part of
the temporal muscle situated in this region.
The Middle Deep Temporal Branch passes outward above the exter-
THE NERVOUS SYSTEM.
293
nal pterygoid muscle, then curves upward, running close to the temporal
bone, and is distributed to the deep and internal portions of the temporal
muscle.
The Posterior Temporal Branch is made up entirely of motor fila-
ments. During the first portion of its course it is often associated with
the masseteric nerve. It passes in a tortuous manner upward and out-
ward, then upward through the proximal surface of the temporal mus-
cle; it passes out of this muscle and through its fascia from a half to
three-quarters of an inch above the zygoma, and then turns upward
beneath the skin and interlaces with the auriculo-temporal and facial
nerves.
The Masseteric Nerve is larger than the deep temporal, and arises in
close proximity to it. Occasionally these two nerves arise as a common
trunk from the third division of the fifth nerve. It passes backward
and outward between the upper portion of the zygomatic fossa and the
superior border of the external pterygoid muscle, curves slightly down-
ward and outward, and passes through the sigmoid notch in the inferior
maxillary bone. It then extends downward between the ramus of the
bone and the masseter muscle, to which muscle it is mainly distributed.
Its other branches of distribution are, first, a small communicating fila-
ment which interlaces with the deep temporal and independent deep
posterior temporal branch, and an articulating branch which passes to
the temporo-maxillary articulation.
The Internal Pterygoid Nerve is the shortest branch of the third
division of the fifth nerve. It is given off from its anterior and prox-
imal side on a level with the otic ganglion. It passes backward between
the ganglion and the lingual nerve, occasionally extending through the
ganglion to the inner side of the internal pterygoid muscle, to which
it is mainly distributed. Its other branches of communication are,
first, a motor root to the otic ganglion; second, a filament to the palato-
Eustachian (tensor palati) muscle; third, a branch to the tensor tym-
pani.
T
The External Pterygoid Nerve is not constant in its origin; it seldom
arises from the main trunk of the inferior maxillary, but generally in
conjunction with the buccal branch or from the internal pterygoid
nerve. It is distributed to the external pterygoid muscle.
The Buccal Nerve, though described under the head of the motor
branches of the inferior maxillary nerve, is almost entirely composed
of sensory fibres. It arises from the lateral margin of the main trunk
of the inferior maxillary by from one to three bundles, and is usually
joined at its origin by the anterior deep temporal and the external
pterygoid nerves. It passes outward, either between the two heads of
the external pterygoid or between the two pterygoid muscles; extends
downward to the inner surface of the coronoid process of the inferior
maxilla, thence forward between this process and the tuberosity of the
superior maxillary bone, occasionally passing between the fibres of the
temporal muscle close to its insertion. Midway between the lobe of the
ear and the angle of the mouth it becomes superficial, and terminates by
dividing into superior and inferior branches.
Branches of distribution are—
294
ANATOMY.
(a) Two or three external pterygoids, which are given off as the nerve
passes through the external pterygoid muscle.
(b) An anterior deep temporal branch, which usually joins the deep
temporal nerve. It passes upward to the thick portion of the tem-
poral muscle.
(c) A descending branch, which passes to the insertion of the tem-
poral muscle.
(d) Superior terminal branches, which supply the upper portion of
the buccinator muscle, the skin of the malar and buccal region. These
branches interlace with the facial nerve near the parotid duct.
(e) Inferior terminal branches, which pass forward to the angle of the
mouth, and are distributed to the skin, the lower portion of the buc-
cinator muscle, as well as the buccal mucous membrane and glands.
These branches, together with buccal branches of the facial nerve, form
a plexus around the facial vein.
Variations.—The buccal nerve occasionally arises from the superior
maxillary nerve. Turner reports a case in which it arose from the
inferior dental nerve and passed through a foramen in the alveolar
border near the ramus of the inferior maxillary bone. Gillette has
seen it arising in one case from the Gasserian ganglion, passing through
a special foramen situated between the round and oval foramen in the
great wing of the sphenoid bone.
The posterior or sensory branches of the third division of the fifth
nerve are--
Inferior dental.
Auriculo-temporal,
Gustatory or lingual,
The Auriculo-temporal Nerve usually arises by two roots, of unequal
size, situated close to the foramen ovale. At first they pass backward
and outward, one on either side of the middle meningeal artery. They
then unite and form a flattened trunk, which passes backward beneath
the external pterygoid muscle to the inner side of the neck of the condyle
of the inferior maxilla. It curves around the condyle of the lower jaw
in company with the superficial temporal artery, passes upward between
the ear and the temporo-maxillary articulation, thence over the zygoma
and beneath the superficial temporal artery, terminating in several fila-
ments which are distributed to the skin over the greater portion of the
temporal region, extending to its superior extremity. They interlace
anteriorly with the facial nerve.
Branches of the auriculo-temporal nerve are—
Communicating,
Articular,
Branches to external auditory meatus,
Parotid,
Anterior auricular.
The Communicating Branches are slender filaments which pass between
the otic ganglion and the third division of the fifth nerve near its origin.
One or two branches which are given off near the neck of the condyle
of the lower jaw pass forward beneath the facial nerve, unite with it
near the posterior border of the masseter muscle, and form one of the
principal communicating branches between the facial and trifacial nerves.
The Articular Branches are one or two fine filaments which
the temporo-maxillary articulation.
pass to
THE NERVOUS SYSTEM.
295
The Branches to the External Auditory Meatus are two in number,
superior and inferior. They pass between the bone and the cartilage to
enter the meatus, and are distributed to the lining of the ear.
superior branch gives off a filament to the membrana tympani.
The
The Parotid Branches supply the parotid gland. They are frequently
connected with the facial nerve.
The Anterior Auricular Branches are usually two in number. They
pass between the tragus and helix, and are distributed to the concave
surface of the auricle.
THE LINGUAL NERVE.
The lingual or gustatory nerve is second in size, and an important
branch of the third division of the fifth. From its origin it passes
down on the internal surface of the external pterygoid muscle, anterior
and a little to the inner side of the inferior dental nerve. These two
nerves have been observed arising from a common trunk and bifurcat-
ing near the posterior dental foramen. As the lingual nerve reaches
the lower border of the external pterygoid muscle it curves forward
between the internal pterygoid muscle and the ramus of the lower jaw,
inclines inward over the superior constrictor of the pharynx, under the
stylo-glossus muscle and above the deep portion of the submaxillary
muco-salivary gland. It then extends forward, crosses Wharton's duct,
passes below the mucous membrane of the alveolar lingual groove, and
terminates at the apex of the tongue.
Branches of Communication.-Near the origin of the lingual nerve a
communicating branch passes over the internal maxillary artery to the
inferior dental nerve. There is also a small branch which passes to
the hypoglossal nerve. This nerve also forms a plexus, from which
branches are distributed to the walls of the internal jugular vein, a
portion of the sinuses and the cancelli of the occipital bone, and inter-
lace with branches which pass through the anterior condyloid foramen.
The chorda tympani branch, which is a small nerve, arises from the
facial, and descends from the proximal extremity of the squamoso-
tympanic suture (fissure of Glasserius) to the acute angle of the lingual
nerve as it passes forward close to the lower border of the external
pterygoid muscle. At first there is only a mechanical union between
these two nerves, but subsequently they are intimately associated.
Branches pass directly to the submaxillary ganglion where it is in close
relation with the submaxillary muco-salivary gland. Anterior to the
last branch, one or two communicating filaments descend over the first
portion of the hypoglossal muscle to interlace with filaments from the
hypoglossal nerve.
The branches of distribution of the lingual nerve are-
$
A small branch to the palato-glossal fold (anterior palatine arch) and
the tonsils.
A sublingual branch, which is distributed to the mucous membrane
of the floor of the mouth, the gum tissue on the inner surface of the
inferior maxillary bone, and the sublingual mucous gland.
The lingual or terminal branches, which passs upward between the
296
ANATOMY.
fibres of the tongue, divide into finer filaments, which are distributed
to the mucous membrane of the anterior two-thirds of the tongue and
terminate in the conical and fungiform papillæ.
A few plexiform filaments, which pass beneath the tongue, some ter-
minating on the under surface of the tip and in the glands of Nühn.
THE INFERIOR DENTAL NERVE.
The Inferior Dental Nerve is the largest of the branches of the third
or inferior maxillary division of the fifth nerve (Fig. 145). From its
FIG. 145.
origin it passes downward,
accompanied by the inferior
dental artery, on the inter-
nal surface of the external
pterygoid muscle posterior
and a little to the side of
the lingual nerve. After
reaching the lower border
of the external pterygoid
muscle it passes between the
lateral ligament and the ra-
mus of the jaw, and enters
the inferior dental canal
through the posterior den-
tal foramen. It then passes
through this canal, and ter-
minates opposite the an-
terior or mental foramen
by dividing into incisor
and mental branches.
The branches of the in-
ferior dental nerve are-
A Communicating
Branch, which passes over
the internal maxillary ar-
tery to the lingual nerve.

S
3
7
9-
11
13
15
17
19
21-
20
-12
14
16
-8
18.
Pterygo-maxillary Region and Fifth Nerve: 1, temporal fas-
cia; 2, temporal muscle; 3, temporal branches of auriculo-
temporal nerve; 4, deep temporal branch of buccinator
nerve; 5, deep
6, externus;
7, deep temporal branch of masseteric nerve (inconstant);
8, buccinator (or long buccal) nerve (fifth); 9, masseteric
nerve; 10, buccal branch of seventh; 11, auriculo-temporal
nerve; 12, lingual nerve; 13, facial nerve (seventh) at stylo-
mastoid foramen; 14, buccinator muscle; 15, pterygoideus
internus; 16, supramaxillary branch of seventh; 17, infe-
rior dental nerve; 18, its mental branches; 19, its mylo-hyoid
branch; 20, inferior dental nerve in inferior dental canal
(opened); 21, masseter (turned down).
J
pap
A Mylo-hyoid Branch,
which is generally de-
scribed with the inferior
dental, which latter is a
sensory nerve, while the former is in reality motor in character. Its
fibres can be traced from its point of distribution backward to the ante-
rior or motor root of the fifth nerve. It is given off from the inferior
dental nerve just as it is about passing into the posterior dental foramen,
and passes downward and forward, accompanied by the mylo-hyoid
artery in the mylo-hyoid groove of the inferior maxillary bone. It is
distributed to the inferior surface of the mylo-hyoid and the anterior
belly of the digastric, also the tensor palati and tensor tympani mus-
cles. A few filaments from this branch pass through the mylo-hyoid
muscle and interlace with the lingual nerve. Branches are also de-
THE NERVOUS SYSTEM.
297
scribed as passing to the depressor anguli oris and platysma myoides
muscles (Henle), to the integument below the chin (Krause and
Schwalbe), and to the submaxillary gland (Meckel, Henle, Curnow).
The Inferior Dental Branches are numerous, and form loops or plex-
uses beneath the roots of the teeth similar to those found above the
superior teeth. From these loops fine filaments pass through the apical
foramina in the roots of the teeth of the lower jaw to supply the pulp
and tooth with sensation. There are also filaments which pass upward
and supply the alveolo-dental membranes and gum tissue.
The Incisor Branch is the continuation of the main trunk of the
inferior dental nerve. It passes forward under the inferior canine and
incisor teeth, and forms loops or plexuses similar to those formed by the
main branch, from which filaments are distributed to the teeth and sur-
rounding tissues in like manner.
The Mental or Labial Nerve is the larger of the two terminal divis-
ions of the inferior dental nerve. It passes outward from the canal
through the anterior dental (mental) foramen, and immediately breaks
up into three branches beneath the depressor anguli oris muscle. The
inferior branch descends, and is distributed to the chin. The two supe-
rior branches ascend to supply the lip, its mucous membrane, and the
labial glands. These three branches freely interlace with the supra-
maxillary branch of the facial nerve.
Kdy
The inferior dental nerve occasionally receives one or two communi-
cating filaments from other branches of the inferior maxillary nerve.
The Lesser Inferior Dental Nerve (Sapolini) is frequently present.
It arises from the Gasserian ganglion, and unites with the inferior
dental nerve after entering the inferior dental canal.
SYMPATHETIC GANGLIA CONNECTED WITH THE
FIFTH NERVE.
<
The sympathetic ganglia (ganglia of the fifth nerve) found in con-
nection with the trifacial nerve belong to the general sympathetic sys-
tem found throughout the body. This sympathetic system is composed
of a large number of ganglia, cords, and plexuses.
The Ganglia are separate centres for the conveyance and distribution
of various cords and filaments, consisting of motor, sensory, and sym-
pathetic fibres. They contain nerve-cells very similar to those found in
the encephalon and spinal cord. These ganglia are arranged in two
chains situated on each side of the body near the central line. They
commence with the ophthalmic ganglion in the orbit, and extend
downward along each side of the vertebral column, and terminate below
in the ganglion impar in the coccygeal region.
The ganglionic or sympathetic system is independent and separate
from the general nervous system, but is intimately connected with it by
communicating branches which pass from the motor and sensory roots
of the cerebro-spinal nerves, as well as by direct filaments which extend
between it and the cerebro-spinal centres. The sympathetic nervous
system is distributed to the mucous membranes, the viscera, the coats of
blood-vessels, and to the non-striated or involuntary muscular fibres.
298
ANATOMY.
The nerves of this system form plexuses in various parts of the body,
especially around the arteries. They are not found in connection with
striated voluntary muscular fibres. The cardiac muscle, being partially
striated, yet involuntary, is an exception. Numerous ganglionic cells are
found situated at the terminal ends of sympathetic nerve-fibres.
THE CRANIAL GANGLIA, OR GANGLIA OF THE FIFTH PAIR OF
NERVES.¹
CEREBRAL GANGLIA.
NAME.
OPHTHALMIC Between the op-Fifth
OR CILIARY. tic nerve and
external rec-
tus.
TINE
MECKEL'S.
SITUATION.
OTIC.
SPHENO-PAL-Spheno - maxil-Fifth
OR lary fossa.
SUBMAXIL-
LARY.
SENSORY Root. MOTOR ROOT.
nerve, Third nerve.
nasal branch.
spheno-p a la-
tine branches.
Above the sub- Fifth nerve, lin-
maxillary gual or gusta-
gland.
tory branch.
nerve, Seventh nerve, Carotid plexus,
through Vid- by means of
ian and large Vidian nerve.
petrosal
branches.
Ophthalmic,
Spheno-palatine,
SYMPATHETIO BRANCHES or
ROOT.
DISTRIBUTION.
amen ovale.
auriculo-tom-
poral branch.
Below the for-Fifth nerve, Seventh nerve, Plexus on the To tensor tym-
through small middle men-
petrosal.
ingeal artery.
Fifth nerve,
through in-
ternal ptery-
goid branch.
pani and ten-
sor palati
muscles.
Nag va
Cavernous
plexus.
1
To ciliary mus-
cle and iris.
Orbital, nasal,
naso-palatine,
anterior or
large palatine,
middle or ex-
ternal
pala-
tine.
Seventh nerve, Plexus on the To
through chor- facial artery.
da tympani
branch.
The cranial ganglia, or ganglia of the fifth pair of nerves tabulated
above, are four pairs-viz.:
After Ranney.
submaxil-
lary gland and
Otic,
Submaxillary.
The Ophthalmic, Lenticular, or Ciliary Ganglion is situated in the
posterior portion of the orbital cavity, between the external rectus mus-
cle and the optic nerve, in close apposition to the ophthalmic artery. It
is a small, flattened, and reddish body, surrounded by adipose tissue, its
flattened surfaces being the proximal and the distal. It measures about
one line in length from before backward.
Its branches or roots of communication are-
mucous mem-
brane of the
mouth.
1. The Sensory or Long Root, which is a slender filament arising
within the cavernous sinus from the nasal branch of the ophthalmic
division of the fifth nerve. It enters the posterior superior angle of the
ganglion. Occasionally a filament is found which extends from the
lachrymal nerve to the ganglion.
2. The Motor or Short Root, which is shorter and thicker than the
sensory root, and occasionally divides into two branches. It is derived
from the inferior oblique branch of the motor oculi or third nerve, and
joins the ganglion at its posterior inferior angle.
3. The Sympathetic or Middle Root, which is derived from the system
to which the ganglion belongs. This root is smaller than either of the
others, and originates in the cavernous sinus, being derived from the
THE NERVOUS SYSTEM.
299
carotid plexus. Through this plexus it communicates with the cervi-
cal ganglion. As it extends forward to the posterior border of the
ganglion, it occasionally unites with the long or sensory root, forming a
common trunk.
Variations in the Roots.-The ophthalmic ganglion may receive
accessory roots from the superior division of the motor oculi, the
lachrymal, abducens, or spheno-palatine ganglion (Henle, Tiedemann).
"According to Reichart, the ophthalmic ganglion does not receive its
sympathetic fibres by a single root, but by several fine filaments, the
majority of which accompany the third nerve.
"It appears from the mode of development and arrangement in many
of the lower vertebrates that the ophthalmic ganglion is morphologically
associated more intimately with the third nerve, having, in fact, the sig-
nificance of a spinal ganglion of that nerve (M. Marshall, Schwalbe).
"1
Its branches of distribution are to the iris and ciliary muscles. The
short ciliary nerves, ten to fifteen in number, arise in two sets, superior
and inferior.
The Superior Set arises from the anterior superior angle, and passes
forward, in a wave-like manner, between the optic nerve and the supe-
rior rectus muscle to the posterior part of the eyeball.
The Inferior Set is more numerous than the superior, and arises
from the anterior inferior angle of the ganglion. It passes in a wave-
like manner below the optic nerve and above the inferior rectus muscle
to the posterior part of the eyeball. It is accompanied by the long cil-
iary nerves which are derived from the nasal branch of the ophthalmic
division of the fifth. One or more of its fibres join the short ciliary nerves.
Both the superior and the inferior sets pass forward through the
sclerotic coat of the eye in delicate grooves on its inner surface, next to
the choroid coat, and are distributed to the ciliary muscle, the iris, and
the cornea. A small filament penetrates the optic nerve to the arteria
centralis retina (Tiedemann).
Many
SPHENO-PALATINE GANGLION.
The spheno-palatine ganglion (ganglion of Meckel) (Fig. 146) is the
largest of the cranial ganglia. It is situated in the pterygo-maxillary
fossa in front of the anterior opening of the Vidian canal, close to the
spheno-palatine foramen. It is triangular in form, with its apex point-
ing backward in the direction of the Vidian canal, and is surrounded
by adipose tissue. Its outer surface is convex, and averages about one-
fifth of an inch in diameter. It is reddish-gray in color, excepting at
its broadest part, where it is composed entirely of gray matter.
The branches or roots of communication of the spheno-palatine
ganglion are-
1. The Sensory Roots, two in number, which arise from the superior
maxillary nerve as it passes through the pterygo-maxillary fossa. They
enter the ganglion separately, one at the anterior and the other at the
posterior corner of the upper surface. Many of the fibres of these
roots pass through the ganglion without becoming incorporated with
1 Quain's Anatomy.
300
ANATOMY.
it, and receive no influence from it. These fibres form the palatine
nerves.
2. The Motor Root, which is quite long, and arises from the facial
nerve or the large superficial petrosal nerve at the geniculate ganglion
(intumescentia gangliaformis) within the aqueduct of Fallopius. From
this point it passes forward through the hiatus Fallopii on the anterior
surface of the petrous portion of the temporal bone, then inward beneath
the Gasserian ganglion, being separated from it by a thin layer of dura
mater. It then pierces the fibro-cartilage occupying the middle lace-
rated foramen, and passes to the outer side of the internal carotid artery.
FIG. 146.

of
Term
Vaso Palatine Nervo-
Spillea
EBURT
ONELIGROTY
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Hard
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Div.
2nd
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Palatine N.J,
Est. Tube
Eust
5th N.
interior Palatine N.
Pharyngeal
T
ང་ ང་
Tonsil
Soft Palate
Mullal
The Spheno-palatine Ganglion and its Branches.
At this point it is joined by the sympathetic root or the large deep
petrosal nerve of the spheno-palatine ganglion, and the two conjointly
receive the name of the Vidian nerve. They pass into the Vidian canal
in the sphenoid bone, extend through this canal, and at the exit enter
the posterior or apicial extremity of the ganglion. The gray matter of
the ganglion extends along the nerve as far as the origin of the sympa-
thetic at the carotid plexus.
3. The Sympathetic Root, or the large deep petrosal nerve, commences
from the carotid plexus which surrounds the internal carotid artery.
These filaments unite and form a short branch of reddish color and soft
texture, which passes forward and joins the motor root of the ganglion
to form the Vidian nerve, above described. Occasionally these two
roots remain separate throughout their course, and enter the ganglion
ununited.
THE NERVOUS SYSTEM.
301
The branches of distribution of the spheno-palatine ganglion are
1. Ascending or Orbital Branches, consisting of three or four fine
filaments which pass into the orbit through the spheno-maxillary
fissure, and are distributed to the periosteum and mucous membrane of
the posterior ethmoidal and sphenoidal sinuses by passing between the
sphenoid and ethmoid bones.
K
Some of the branches which pass upward are distributed to the neu-
rilemma of the optic nerve (Arnold and Longet).
A branch from the ganglion ascends to the sixth nerve (Bock and
Valentin).
Also a branch to the ophthalmic ganglion (Tiedemann).
Two or three branches, spheno-ethmoidal, ascend to the superior por-
tion of the internal orbital wall, pass through the posterior ethmoidal
foramen, and enter the brain-case (Luschka).
2. The Descending or Palatine Branches, three in number-anterior,
posterior, and external. These three branches pass from the superior
maxillary nerve through that portion of the ganglion in which there
is little ganglionic or gray matter. They thus pass to their distribution
without becoming involved or influenced by the ganglion, except it be
to a very slight extent.
G
The Anterior or Large Palatine Nerve passes downward in the poste-
rior palatine or palato-maxillary canal, and enters the oral cavity at
the posterior palatine foramen. It then passes forward in a groove on
the side of the hard palate to its anterior portion, where it joins the
naso-palatine nerve. It is distributed to the gums, mucous glands, and
membrane of the hard palate. This nerve gives off a separate branch
(middle palatine), which passes downward to the soft palate in a separate
canal. It also gives off branches (inferior nasal) while in the canal,
which are distributed to the middle and inferior turbinated bones.
The Posterior or Small Palatine Nerve passes downward, accompanied
by a small artery in the small palatine canal, to the soft palate, and
divides into two sets of branches. One set is distributed to the levator
palati and azygos uvula muscles, and may be composed entirely of
motor filaments coming from the great superficial petrosal branch of the
motor, facial, and the Vidian nerves. The other set, which is sensory,
is distributed to the mucous membrane of the superior surface of the
soft palate, the glands of the soft palate, as well as to the tonsils.
The External Palatine Nerve is the smallest of the three descending
branches, and is not always constant in its existence. It passes down-
ward through the external palatine canal, which is situated between the
tuberosity of the superior maxilla and palate bones, and is distributed
to the tonsils, uvula, and outer portion of the soft palate.
The Internal or Nasal Branches consist of two divisions, upper nasal
and naso-palatine.
The Upper Nasal Branches, four or five in number, are small, and
pass horizontally inward through the spheno-palatine foramen into the
posterior superior portion of the nasal chamber. They are distributed
to the posterior superior portion of the nasal septum, to the mucous
membrane covering the superior and middle turbinated bones, and to
the posterior ethmoidal cells.
'}
302
ANATOMY.
The Naso-palatine Branch (nerve of Cotumnius, Scarpa) is larger
than the upper nasal branches, and is an important division of the nasal
nerves. It is long and slender, and arises from the proximal surface
of the spheno-palatine ganglion. It passes through the spheno-palatine
foramen across the roof of the nasal chamber to the septum, where it
turns downward and forward, and extends in a groove or canal on the
vomer to the foramina of Scarpa or naso-palatine foramina. These are
two in number, anterior and posterior, and are situated in the inter-
maxillary suture. The nerve of the right side usually passes through
the posterior foramen, while the nerve of the left side passes through
the anterior. These two nerves (right and left naso-palatine), meeting
in the common or anterior palatine meatus or canal, form a fine plexus,
from which minute filaments are distributed to the palate posterior to
the incisor teeth and interlace with the anterior or great palatine nerve.
"In its course along the septum small filaments are furnished from the
naso-palatine to the pituitary membrane."
22 1
The Posterior Branches generally assume the name of the Vidian
nerve (already described) and the pharyngeal nerve.
The Pharyngeal or Pterygo-palatine Nerve consists of several fine
filaments which frequently arise from the Vidian nerve, instead of from
the posterior portion of the ganglion. It passes downward through
the pterygo-palatine canal, accompanied by an artery of the same name,
and is distributed to the mucous membrane of the upper portion of the
pharynx and neighborhood of the Eustachian tube.
OTIC GANGLION.
The otic ganglion (ganglion of Arnold) (Fig. 147) is a reddish-gray
body situated just below the foramen ovale, and in close apposition to
the proximal surface of the inferior maxillary nerve at the point of
union of its motor root with the third sensory division arising from the
Gasserian ganglion, the cartilaginous portion of the Eustachian tube
to its inner surface, while the middle meningeal artery passes up into the
brain-case just posterior to it. It is a flattened oval body, its widest
diameter, which is about one-sixth of an inch, being antero-posterior.
Its branches or roots of communication are
Sp
1. The Long or Sensory Root of Arnold is composed of the lesser super-
ficial petrosal nerve, which is a continuation of the tympanic branch of
the glosso-pharyngeal, and a branch from the geniculate ganglion of the
seventh. The ganglion also receives an important sensory branch from
the auriculo-temporal nerve of the fifth.
2. The Motor or Short Root of Arnold is derived from the internal
pterygoid branch of the inferior maxillary division of the fifth. It also
receives motor filaments through the lesser superficial petrosal derived
from the geniculate ganglion of the seventh nerve.
3. The Sympathetic Root, which is derived from the plexus around
the middle meningeal artery.
The branches of distribution of the otic ganglion supply in part the
1 Quain's Anatomy.
THE NERVOUS SYSTEM.
303
parotid gland, the chorda tympani, tensor tympani, palato-Eustachian
muscles, and the mucous membrane of the middle ear.
Vo
THE SUBMAXILLARY GANGLION.
The submaxillary or lingual ganglion is situated above the deep
portion of the submaxillary muco-salivary gland, close to the outer
portion of the hyo-glossus muscle. It varies in shape and size, usually
FIG. 147.

11110
***
1st Div.
TENGOR
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chlo-Temporal N.
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The Otic Ganglion and its Branches.
being triangular, but occasionally it is fusiform or plexiform, or absent
altogether.
Its branches or roots of communication are
1. The Sensory Root, which arises from the lingual branch of the
inferior maxillary nerve and enters the posterior portion of the gan-
glion.
2. The Motor or Long Root, which is formed from the motor fila-
ments of the lingual nerve received from the chorda tympani branch of
the facial.
3. The Sympathetic Root, which arises from the sympathetic plexus
around the facial artery.
The branches of distribution of the submaxillary ganglion are prin-
cipally those that supply the submaxillary muco-salivary gland and its
duct (duct of Wharton). Other branches pass upward, and interlace
with the lingual nerve, forming a plexus on the side of the tongue, from
which filaments are given off which supply the mucous membrane of the
mouth. Baldwin and other anatomists describe a sublingual ganglion
which is situated on the branch of the submaxillary ganglion which
+
304
ANATOMY.
passes to the lingual nerve. Occasionally one or two small branches.
are found which communicate with the hypoglossal nerve (Meckel and
Bose). None of the branches of the submaxillary ganglion are dis-
tributed to muscles, which is in marked contrast with the branches
from the otic ganglion.
5
THE FACIAL NERVE.
The facial, seventh, or nerve of expression (the portio dura of the
seventh pair of nerves, according to the arrangement of Willis) (Fig.
148) controls the muscles of expression. This fact alone would make
it a nerve of vast importance to all those who study the face either from
a surgical or an artistic standpoint. It not only transmits the motor
stimulus to all the superficial muscles of the face, except the levator
FIG. 148.
3-
1
2
;

6
4
2
Diagram of the Facial Nerve and its Distribution: 1, Facial nerve at its entrance into the internal
auditory meatus; 2, its exit at the stylo-mastoid foramen; 3, 4, temporal and posterior auricular
branches, distributed to the muscles of the external ear and to the occipitalis; 5, branches to the
frontalis muscle; 6, branches to the stylo-hyoid and digastric muscles; 7, branches to the upper
part of the platysma myoides; 8, brauch of communication with the superficial cervical nerve of
the cervical plexus.
palpebræ superioris, but likewise to the scalp, the external ear, platysma
myoides, buccinator, posterior belly of the digastric, and stylo-hyoid
muscles. Through communicating branches it unites the anterior and
THE NERVOUS SYSTEM.
305
posterior cranial nerves, and by so doing increases the functional power
of some of these nerves.
The following are some of its communicating branches :
It communicates with the three divisions of the fifth nerve;
With the spheno-palatine, submaxillary, and otic sympathetic ganglia;
A branch to the auditory nerve;
A branch to the glosso-pharyngeal nerve ;
Through its auricular branch it also communicates with the
pneumo-
gastric nerve. It will be seen that through this large communication it
supplies other structures, which will be described hereafter.
The superficial or apparent origin of the facial nerve is from the
uppermost lateral portion of the medulla oblongata in a groove between
the olivary and restiform bodies, just below the pons varolii. The eighth
or auditory nerve is in close apposition to its outer side, the two being
separated only by a couple of filaments which are known as the inter-
mediary nerve of Wrisberg (portio inter duram et mollem).
This intermediary nerve is more or less connected with the facial and
auditory nerves, but from the fact of its greater connection with the
facial it has been classed as one of its roots (accessory root of Sappey).
It passes between the two nerves into the internal auditory meatus, and
terminates in the geniculate ganglion.
The facial nerve passes from its origin, in company with the eighth
or auditory nerve, forward and outward between the pons varolii and
the middle peduncle of the cerebrum, around which it curves to enter
the internal auditory meatus, situated in the posterior surface of the
petrous portion of the temporal bone. It rests in a groove on the
upper part of the meatus, the auditory nerve being below, while the
nerve of Wrisberg still retains its position between the two. On reach-
ing the upper extremity of the meatus, the seventh nerve passes into and
through the aqueduct of Fallopius. This aqueduct runs an extremely
tortuous course through the petrous portion of the temporal bone. It is
at first directed outward for a short distance between the cochlea and the
vestibule to the wall of the middle ear; then it bends backward over
the fenestra ovalis, then downward behind the pyramid and the middle
ear, and terminates at the stylo-mastoid foramen, at which point the
nerve makes its exit on the face. It passes from this point downward
and forward in the substance of the parotid gland, and breaks up into
numerous branches to supply the muscles of expression.
The branches of the facial nerve are tabulated as follows by Prof.
Allen:¹ 1
Branches of the geniculate ganglion,
six in number,
Before escaping at the stylo-mastoid
foramen,
VOL. I.-20
The great superficial petrosal nerve.
"C
(C
(C
The lesser
Branches to the sympathetic system.
(C
(+
((
(C
(<
((
tympanic plexus.
pneumogastric nerve.
glosso-pharyngeal nerve.
Stapedius.
Chorda tympani.
1
¹ Allen's Anatomy, p. 529.
Connecting branches with pneumogastric.
((
(C
<<
glosso-pharyngeal.
-
1
306
ANATOMY.
After escaping from the stylo-mastoid
foramen,
Comma
ތ
MWA
A for
ބ
Supramaxillary.
Cervical.
The Geniculate Ganglion (intumescentia ganglioformis) is a reddish
enlargement on the foremost part of the facial nerve, which contains
FIG. 149.
numerous nerve-cells. It is situ-
ated on the curve as the nerve
turns from the horizontal to the per-
pendicular direction in the aqueduct
of Fallopius. It does not receive
all the fibres of the facial nerve, but
receives the terminal ends of the nerve
of Wrisberg. The nerves arising
from this ganglion are six in num-
ber, the names of which will be found
in the preceding table.
The Great Superficial Petrosal Nerve
(Fig. 149) arises from the geniculate
ganglion of the seventh nerve, and is
the largest of the ganglionic branches.
It passes forward through the hiatus
Fallopii on the superior portion of
the anterior surface of the petrous
portion of the temporal bone, from
which it passes inward beneath the
Gasserian ganglion, being separated
from it by a thin layer of the dura
mater. It then pierces the fibro-car-
tilage occupying the middle lacerated
foramen, and passes to the outer side
of the internal carotid artery. At
ufii
b
dll',, a small
C
Posterior auricular, {Auricular.
Occipital.
Stylo-hyoid.
Digastric.
Stylo-glossal.
This drawing represents the Middle Fossa of
of the temporal bone cut through so as to
the Base of the Skull, with the petrous part
expose the nerves joining the facial (from
the skull, with the middle meningeal artery
branching on it; 1, facial nerve by the side
Bidder): a, external ear; b, middle fossa of
the 2, large superficial petrosal
nerve; small superficial petrosal nerve
over the
the external superficial petrosal nerve;
5, chorda tympani; 8, eighth nerve.
Temporal.
Temporo-facial, Malar.
Cervico-facial,
Infraorbital.
Buccal.

this point it is joined by the sympathetic root or the large deep petrosal
nerve of the spheno-palatine ganglion, and passes into the Vidian canal
in the sphenoid bone under the name of the Vidian nerve. It extends
through this canal, and enters the apex of the spheno-palatine ganglion.
The Lesser Superficial Petrosal Nerve extends from the geniculate
ganglion of the seventh nerve and unites with a branch from the nerve
of Jacobson. It then passes through a small foramen and joins the
otic sympathetic ganglion.
The Branch of Communication with the Sympathetic System, or the
External Superficial Petrosal Nerve (Bidder), is not always present
(Ruber). It forms a communicating filament between the geniculate
ganglion and the sympathetic plexus around the middle meningeal
artery.
THE NERVOUS SYSTEM.
307
The Branch of Communication with the Tympanic Plexus is a small
nerve which connects the geniculate ganglion with the sympathetic tym-
panic plexus.
The Communicating Branch with the Pneumogastric Nerve passes out
of the stylo-mastoid foramen, and communicates with the pneumogastric
nerve through its articular branch.
The Communicating Branch with the Glosso-pharyngeal Nerve arises
from the facial as it leaves the stylo-mastoid foramen. It communicates
with the glosso-pharyngeal nerve below its petrosal ganglion.
The branches of the facial nerve before it escapes from the stylo-
mastoid foramen are-
1. Stapedius;
2. Chorda tympani ;
3. Connecting branches with pneumogastric nerve;
4. Connecting branches with glosso-pharyngeal nerve.
The Stapedius or Tympanic Nerve is the most slender branch given
off by the facial nerve. It arises opposite the pyramid of the internal
ear, passes through a fine canal, and is distributed to the stapedius muscle.
The Chorda Tympani Nerve arises from the facial nerve on the proxi-
mal side of the geniculate ganglion, though apparently it arises back of
the tympanum close to the outer extremity of the aqueduct of Fal-
lopius. From its origin it passes upward in a special curved canal
nearly parallel to the aqueduct of Fallopius, and enters the posterior
wall of the tympanic cavity close to the tympanic membrane. It here
becomes invested by mucous membrane, arches upward between the
long handle of the malleus and the vertical process of the incus to its
anterior angle. It then passes out of the tympanum through a for-
amen (canal of Hugui) at the side of the glenoid (Glasserian) fissure,
extends downward on the proximal side of the internal lateral ligament
of the inferior maxillary bone, and forms a union with the lingual
branch of the fifth nerve at a point where the nerve forms an acute
angle by bending forward under the inferior border of the external
pterygoid muscle. It is then distributed to the submaxillary muco-
salivary gland and to the tongue. The chorda tympani nerve receives
a communicating branch from the otic ganglion just before joining the
lingual nerve. There is considerable discussion among anatomists and
physiologists as to the origin and functions of this nerve. Some claim.
that it is a continuation of the nerve of Wrisberg, while J. Sapolini
claims it as an independent cranial nerve, entitled to be classed as
the thirteenth cranial nerve. Its function is also still in doubt, some
claiming it to be a motor nerve, others a nerve of sensation, while
others regard it as a special nerve of taste.
The Communicating Branch with the Pneumogastric Nerve arises from
the facial nerve a little before its exit from its canal to join the upper
ganglion of the pneumogastric. This branch is not constant.
The Communicating Branch with the Glosso-pharyngeal Nerve arises
from the facial just as that nerve makes its exit from the stylo-mastoid
foramen. It passes to the petrosal ganglion of the glosso-pharyngeal.
The branches that arise from the facial nerve after it has passed out
of the stylo-mastoid foramen are six in number—viz. :
308
ANATOMY.
Stylo-glossal,
Temporo-facial,
Cervico-facial.
Posterior auricular,
Stylo-hyoid,
Digastric,
The Posterior Auricular Nerve arises from the facial near the stylo-
mastoid foramen. It passes backward in close apposition to the lateral
border of the posterior belly of the digastric muscle, and then curves
outward and upward between the ear and the mastoid process of the
temporal bone, where it divides into two branches, auricular and oc-
cipital.
Gadg
The Auricular Branch passes upward behind the ear, and is distrib-
uted to the retrahens aurem, the small muscles, and the skin on the
back part of the pinna. Occasionally it sends a filament to the atollens
aurem muscle.
The Occipital Branch passes upward in a curved direction along the
superior semicircular line, the posterior boundary of the base of the
skull. It is distributed to the occipital muscle.
The branches of communication of the posterior auricular nerve are
with the great auricular and the small occipital nerve of the cervical
plexus, and with the auricular branch of the pneumogastric nerve.
The Stylo-hyoid Nerve is a long slender branch which is distributed
to the stylo-hyoid muscle, and interlaces with the sympathetic plexus
of the external carotid artery.
The Digastric Nerve frequently arises in common with the stylo-hyoid.
It soon divides into two or three small filaments which are distributed
to the posterior belly of the digastric muscle and interlace with the
glosso-pharyngeal nerve near the base of the skull, and occasionally
with the spinal accessory and pneumogastric nerves.
The Stylo-glossal Nerve (lingual nerve of Hirschfeld) is a long and
exceedingly delicate branch which arises from the facial nerve near the
base of the styloid process of the temporal bone. It passes downward
and forward behind the stylo-pharyngeus muscle to the side of the
pharynx and the base of the tongue. It receives several branches of
communication from the glosso-pharyngeal nerve, and is distributed to
the stylo-glossus and palato-glossus muscles, being lost in the mucous
membrane at the base of the tongue.
The Temporo-facial Division of the seventh nerve is the larger of its
two terminals. It passes forward and upward in the substance of the
parotid gland on a level with the neck of the lower jaw. The exter-
nal carotid artery and the temporo-maxillary vein are situated to its
inner side. At the neck of the lower jaw the nerve breaks up into
three branches, temporal, malar, and infraorbital. Before it branches,
however, it receives filaments of communication from the auriculo-
temporal nerve. After its division it receives communicating branches
from the fifth nerve. The temporo-facial nerve and its communicat-
ing branches, together with numerous small branches from its three
main divisions, form an irregular network of nerves known as the pes
anserinus.
The Temporal Branch passes upward over the zygoma nearly at right
angles to it, and soon breaks up into numerous branches which are dis-
tributed to the region of the temple and side of the forehead, including
THE NERVOUS SYSTEM.
309
the following muscles: attrahens and attolens aurem, frontalis, part of
the orbicularis palpebrarum, and the corrugator supercilii. It commu-
nicates with the three divisions of the fifth nerve, the auriculo-temporal,
a branch of the inferior dental, the temporal branch of the superior
maxillary, and the supraorbital and lachrymal branches of the oph-
thalmic nerve.
The Malar or Ocular Branch passes forward, inward, and slightly
upward to reach the external portion of the orbital cavity, and is dis-
tributed to the orbicularis palpebrarum and the corrugator supercilii.
On the upper eyelid communicating filaments of this nerve inter-
lace with the lachrymal and supraorbital branches of the ophthalmic,
while on the lower eyelid they communicate with branches of the
infraorbital.
M
The Infraorbital or Transverse Branch is larger than the other two
divisions. It passes nearly horizontally forward and inward over the
masseter muscle to the space between the orbit and the mouth, and
divides into a superficial and deep set of branches.
The Superficial set passes between the integument and the muscles of
the face; its filaments are distributed to the zygomatic, levator labii
superioris alæquæ nasi, and the small nasal muscles.
The Deep Set passes beneath the levator labii superioris, and is dis-
tributed to the levator anguli oris and buccinator muscles. The termi-
nal filaments of this set of nerves interlace with the filaments of the
infraorbital and superior maxillary and infratrochlear nerves to form
the infraorbital plexus, which is situated beneath the levator labii supe-
rioris proprius.
The Cervico-facial Branch is smaller than the temporo-facial, and
passes obliquely downward and forward through the substance of the
parotid gland to the angle of the inferior maxillary bone. It then
extends on to the face below the other divisions of the facial nerve, and
passes to the superior portion of the neck. At the angle of the jaw it
terminates by dividing into three branches, buccal, supramaxillary, and
cervical. When this nerve is within the parotid gland it receives a
communicating filament from the great auricular nerve of the cervical
plexus.
The Buccal Nerve in the first portion of its course passes between the
parotid gland and the masseter muscle, then extends over the muscle in
the direction of the angle of the mouth. It is distributed to the bucci-
nator, palato-glossus and orbicularis oris, and receives communicating
branches from the buccal and temporo-facial divisions of the inferior
maxillary nerve.
The Supramaxillary Nerve is often double-that is, it is represented
by two distinct nerves. It passes forward along the deep surface of
the depressor anguli oris, and is distributed to the muscles of the
lower lip and chin. A branch from this nerve extends forward along
the margin of the lower jaw to the symphysis menti. It communicates
with the mental branches of the inferior dental nerve and a branch from
the inferior maxillary division of the fifth nerve.
The Cervical Nerve (inframaxillary) passes downward and forward,
pierces the deep cervical fascia, and breaks up into slender branches
310
ANATOMY.
which form a series of arches beneath the platysma myoides muscle,
extending inward to the suprahyoid region. It supplies the platysma
myoides and the skin in this region, and communicates with the super-
ficial cervical plexus.
AUDITORY NERVE.
The Auditory or Eighth Nerve (portio mollis of the seventh nerve,
according to Willis) is the special nerve of hearing, and is distributed to
the ear alone. It arises superficially or apparently by two roots, which
are situated between the olivary and restiform bodies just posterior,
though closely in apposition, to the facial or seventh nerve. On leav-
ing the medulla oblongata the two roots unite, and the nerve then
passes, together with the facial, to the bottom of the internal auditory
meatus. Here it terminates by separating into superior and inferior
divisions.
The Superior Division breaks up into three branches, which pass to
the utricle, and ampullæ of the superior and external semicircular
canals of the ear.
The Inferior Division is chiefly distributed to the cochlea, though it
also supplies the saccule and posterior semicircular canal.
The Nerve of Wrisberg is situated between the auditory and facial
nerves from their origin to the termination of the auditory nerve.
Some of its fibres unite with those of the auditory nerve, while the
nerve itself is connected with the geniculate ganglion of the facial nerve.
GLOSSO-PHARYNGEAL NERVE.
The Glosso-pharyngeal or Ninth Nerve (the first and smallest trunk
of the eighth pair, according to Willis) (Fig. 150) is the sensory nerve
of the mucous membrane of the pharynx, the posterior third of the
tongue, and the middle ear. It is also the nerve which controls the
motions of the stylo-pharyngeal muscle. It communicates through
the otic ganglion with the inferior maxillary division of the fifth
nerve, the facial and pneumogastric nerves, and the sympathetic sys-
tem. Its superficial or apparent origin is from the upper or anterior
surface of the medulla oblongata, in the groove between the olivary and
restiform bodies, and between the pneumogastric and auditory nerves.
It arises by four or five filaments, which are collected into two bundles,
the anterior being the larger. It passes from its origin outward and
forward beneath the anterior portion of the flocculus, and makes its
exit from the brain-case through the middle compartment of the pos-
terior lacerated foramen in company with the pneumogastric and spinal
accessory nerves. It has a separate sheath of its own, however, formed
from the dura mater. Within the foramen the nerve assumes the form of
a slender rounded cord, and passes through in a groove which is occasion-
ally transformed into a canal, the most anterior of the three nerves. While
in this groove or canal the nerve is characterized by two enlargements, the
superficial being the jugular, and the inferior the petrous ganglion. From
the posterior lacerated foramen the nerve passes forward between the inter-
THE NERVOUS SYSTEM.
311
FIG. 150.
nal jugular vein and internal carotid artery, crosses over the artery to its
anterior aspect, and descends behind the styloid process and the stylo-
pharyngeus muscle. It then curves
gradually forward over the lower
portion of this muscle and beneath
the hyo-glossus, and reaches the base
of the tongue.
The Superficial or Jugular Gang-
lion (ganglion of Ehrenritter) is sit-
uated in the upper portion of the
posterior lacerated foramen to the
outer side of the nerve, only the por-
tion of the nerve in juxtaposition
being involved in the ganglion,
the other portions passing down to
join below with the fibres that have
emerged from the ganglion. It is
from a half to one line in length,
and sends a filament of communi-
cation to the superior cervical gang-
lion.
}

GLOSSO-PHARYN-
(NINTH
CRANIAL)
NERVE.
GEAL
74
13
1. Tympanic branch,
or Jacobson's
nerve,
14
8
10
615) 4. 3.
Voo
The Inferior or Petrous Gang-
16
lion (ganglion of Andersch) is larger Diagram (from Bendz) of the Ganglia and Commu-
and more important than the jug-
ular ganglion, and is constant in its
existence. It is about three lines in
length, and involves all the fibres
of the nerve.
It is situated in a
depression near the lower margin
of the petrous portion of the tem-
poral bone, and communicates by
branches with the auricular branch of the pneumogastric nerve, with the
ganglion at the root of the pneumogastric, though this branch is not con-
stant, and frequently the nerve below the ganglion sends communicating
branches to the facial nerve.
Tenth,
and Eleventh Pairs: 4, cerebellum; B, medulla
oblongata; C, spinal cord; 1, root of glosso-
pharyngeal nerve; 2, roots of vagus; 3, roots of
spinal accessory; 4, jugular ganglion; 5, petrous
ganglion 6, tympanic arch; 7, ganglion of the
root of the vagus; 8, auricular branch; 9, gan-
glion of the trunk of vagus; 10, branch from the
last to the petrous ganglion; 11, inner portion of
spinal accessory; 12, outer portion of the same: 13,
pharyngeal branch of vagus; 14, upper laryngeal
branch; 15, branches to the sympathetic: 16, fas-
ciculus of spinal accessory prolonged with vagus.
Communnicating
filaments to
15
A TABLE OF THE BRANCHES OF THE GLOSSO-PHARYNGEAL
NERVE, AND THEIR DISTRIBUTION.
Branches of dis-
tribution to
VETE
↑ SERBERO DU IN mant
11111
(Large petrosal nerve.
Carotid plexus.
Small petrosal nerve.
(Fenestra ovalis.
Fenestra rotunda.
Eustachian tube.
2. Carotid.
3. Pharyngeal branches (help to form the pharyngeal plexus).
4. Muscular branches (to muscles of the pharynx).
5. Tonsillar branches (help to form the tonsillar plexus).
6. Lingual branches.
The Tympanic Nerve (nerve of Jacobson) (Fig. 151) is a long, slender
filament which arises from the petrous ganglion of the glosso-pharyn-
geal, and passes into a canal, the opening to which is situated on the ridge
312
ANATOMY.
FIG. 151.
between the posterior lacerated foramen and the entrance to the carotid
canal. From this point it ascends through the canal to the inner wall of
the tympanum, thence along a groove on the surface of the promontory,
and leaves the middle ear at its
superior and anterior portion. It
then becomes the superficial pe-
trosal nerve, and passes through
a small canal under the tensor
tympani muscle. This canal ter-
minates in one of the small open-
ings external to the hiatus Fal-
lopii. The nerve from this point
extends downward through the
petro-sphenoidal fissure or a
small foramen in the great wing
of the sphenoid bone, and termi-
nates in the otic ganglion.

$115
Ca
"////
BOX
Th
Cour
/////
B
A
(proje"
13
D
A drawing of the Tympanic Nerve (from Breschet's
bone; B, petrous portion of same; C, lower maxil-
work on the ear): A, squamous part of temporal
lary D, internal carotid tensor
nerve;
tympani muscle; 1, carotid plexus; 2, otic ganglion;
3, glosso-pharyngeal nerve; 4, tympanic nerve; 5,
branches to carotid plexus; 6, branch to fenestra
rotunda; 7, branch to fenestra ovalis; 8, branch to
join the large superficial petrosal nerve; 9, small
superficial petrosal nerve; 10, nerve to tensor tym-
pani muscle; 11, facial nerve; 12, chorda tympani;
13, petrous ganglion of the glosso-pharyngeal; 14,
branch to the membrane lining the Eustachian
tube.
Its branches of communica-
cation are two in number-one
with the carotid sympathetic
plexus, and the other with the
tympanic plexus. After the
nerve assumes the name of the
small superficial petrosal it is
joined by a filament either from
the geniculate ganglion of the fa-
cial nerve or by the large super-
ficial petrosal nerve from the fa-
cial.
Its branches of distribution are
to the tympanic plexus, the fenes-
tra rotunda, fenestra ovalis, the
promontory, and the mucous membrane of the tympanum and Eusta-
chian tube.
The pharyngeal branches (carotid branches, Henle) are three or four
in number, the largest of which passes along the internal carotid artery
to communicate with the pharyngeal branch of the pneumogastric nerve
and the sympathetic system, and form the pharyngeal plexus. This
plexus supplies the superior and middle constrictor muscles and mucous
membrane of the pharynx.
The Muscular Branches supply principally the stylo-pharyngeus
muscle, though filaments pass to the mucous membrane of the pharynx,
and occasionally to the borders of the base of the tongue. They may
communicate with the facial nerve (Rudinger).
The Tonsillar Branches are slender filaments which pass to the mucous
membrane of the lower portion of the tonsillar space, where they form
a plexus (circulus tonsillaris). From this plexus branches extend to
supply the mucous membrane covering the tonsils, the palatal folds, soft
palate, and the palato-glossus muscle.
The Lingual or Terminal Branches are two in number. The larger
THE NERVOUS SYSTEM.
313
one passes to the upper portion of the posterior third of the tongue, and
breaks up into numerous branches which supply the circumvallate pa-
pillæ and mucous membrane over this region, extending back as far as
the anterior surface of the epiglottis. The smaller branch extends for-
ward to the posterior half of the side of the tongue and interlaces with
the lingual nerve. It supplies the mucous membrane of this portion.
of the tongue.
PNEUMOGASTRIC NERVE.
The pneumogastric or tenth nerve (nervus vagus, par vagum, or sec-
ond trunk of eighth nerve, according to Willis) (Fig. 152) at its origin
is purely a sensory nerve, but through its communication with at least
five motor nerves it takes on motor functions, and distributes both sen-
sory and motor filaments to different organs and tissues. It is the most
widely distributed of all the cranial nerves, having more communicat-
ing branches. Its general distribution is to the pharynx, œsophagus,
stomach, and alimentary canal, the larynx, trachea, heart, and blood-
vessels. It is thus intimately connected with the digestive, respiratory,
and circulatory systems.
Its superficial or apparent origin is from the anterior surface of the
upper portion of the medulla oblongata, between the olivary and resti-
form bodies, and also immediately between the glosso-pharyngeal and
the spinal accessory nerves. It is made up of from fifteen to twenty
filaments, which unite and form a flattened band. It passes transversely
outward across the flocculus to the middle compartment of the posterior
lacerated foramen, through which it makes its exit from the brain-case.
It is enclosed with the spinal accessory nerve in a single sheath made up
of dura mater and arachnoid membrane, and is separated from the glosso-
pharyngeal nerve by fibrous and occasionally by osseous tissue.
The ganglia of the pneumogastric nerve are two in number, jugular
and cervical.
The Jugular or Superior Ganglion (ganglion of the root) is situated
within the posterior lacerated foramen. It is grayish in color, oval or
nearly spherical in shape, about two lines in diameter, and embraces all
the fibres of the nerve. It has branches communicating with the facial
nerve while the latter is in the aqueductus Fallopii, and with filaments
from the glosso-pharyngeal nerve and from the nerve of Arnold—with
the petrous ganglion of the glosso-pharyngeal, the spinal accessory
nerve, and the sympathetic system.
The Cervical or Inferior Ganglion (ganglion of the trunk or plexiform
ganglion) is situated upon the pneumogastric nerve a little below the
base of the skull, a half inch beneath the superior ganglion. It is of a
reddish-gray color, loose or plexiform in texture, and contains gray
fibres and nerve-cells interspersed between its white fibres. It is flat-
tened and cylindrical in shape, and measures from six to ten lines in
length and two lines in width. Its communication with other nerves is
complicated, all of its fibres not passing through to become involved in
their functions. Its branches of communication are-
1. The Accessory Portion of the Spinal Accessory-This is the most
314
ANATOMY.
33
7
9-
1)
355
33-
31-
29..
21-2
13-
15
S
17-
19-
21
27z
25-
23-
Syadz
FIG. 152.

24 6 8
-18
-20
-16
$22
Minim
-10
12
-24
-26
TARI
-28
30
-32
-34
36
Distribution of the Ninth, Tenth, and Eleventh Pairs of Nerves on the Left Side: 1, Gasserian gan-
glion of fifth nerve; 2, internal carotid artery; 3, pharyngeal branch of pneumogastric; 4, glosso-
pharyngeal nerve; 5, lingual nerve (fifth); 6, spinal accessory nerve; 7, middle constrictor of
pharynx; 8, internal jugular vein (cut); 9, superior laryngeal nerve; 10, ganglion of trunk of
pneumogastric nerve; 11, hypoglossal nerve (cut) on hyo-glossus muscle; 12, ditto (cut), commu-
nicating with eighth and first cervical nerve; 13, external laryngeal nerve: 14, second cervical
nerve, looping with first; 15, pharyngeal plexus on inferior constrictor; 16, superior cervical gan-
glion of sympathetic; 17, superior cardiac nerve of pneumogastric; 18, third cervical nerve; 19,
thyroid body; 20, fourth cervical nerve; 21, 21, left recurrent laryngeal nerve; 22, spinal accessory
communicating with cervical nerves; 23, trachea; 24, middle cervical ganglion of sympathetic;
25, middle cardiac nerve of pneumogastric; 26, phrenic nerve (cut); 27, left carotid artery (cut);
28, brachial plexus; 29, phrenic nerve (cut); 30, inferior cervical ganglion of sympathetic; 31, pul-
monary plexus of pneumogastric; 32, [arch of the] thoracic aorta: 33, esophageal plexus; 34,
vena azygos superior; 35, vena azygos minor; 36, gangliated cord of sympathetic.
important branch, and passes over the surface of the ganglion, many of
its fibres becoming involved in the pharyngeal and laryngeal branches
of the pneumogastric nerve, the remainder uniting with the main trunk
and passing to the cardiac and inferior laryngeal nerves.
THE NERVOUS SYSTEM.
315
2. With the hypoglossal nerve, by two or three filaments.
3. Generally with the arcade formed by the anterior branches of the
first and second cervical nerves.
4. With the sympathetic system through branches from the superior
cervical ganglion. (Fibres from this ganglion extend to join the main
trunk as it passes downward.)
The pneumogastric nerve passes from its inferior ganglion vertically
down the neck upon the outer wall of the pharynx, behind the internal
jugular vein and internal carotid artery above and the common carotid
below, the nerve, vein, and artery being enclosed in a common sheath.
On passing from the neck into the thorax the right and left nerves do
not follow a similar course or bear the same relations with the tissue
with which they come in contact.
Encranial,
The Right Pneumogastric Nerve enters the thorax between the subcla-
vian vein and the first portion of the subclavian artery. It then passes
between the right innominate vein and the innominate artery, then
behind the arch of the aorta in a groove between the trachea and the
œsophagus to the root of the lung, where it becomes somewhat flattened
and gives off numerous branches, which are joined by similar branches
from its fellow of the opposite side. These branches together form the
right posterior pulmonary plexus. The nerve is then continued down-
ward by two cords to the posterior surface of the oesophagus, where it
subdivides and communicates with similar subdivisions from the corre-
sponding nerve of the left side forming the oesophageal plexus. From
this plexus the nerve, after receiving fibres from the left pneumogastric,
is formed into a single cord, and passes down the neck in close apposi-
tion with the posterior surface of the oesophagus, through the diaphragm,
and reaches the posterior surface of the stomach, where it spreads out
and distributes branches to the liver and the solar plexus.
The Left Pneumogastric Nerve enters the thorax between the left
common carotid and subclavian arteries, crosses the inner surface of
the innominate vein, and passes down in front of the descending portion
of the arch of the aorta. It will thus be seen that it holds a more ante-
rior position in the thorax than the nerve of the right side. From the
arch of the aorta it passes behind the root of the left lung, spreads out
to receive branches from the right nerve, and forms the left posterior
pulmonary plexus. From this plexus it descends in close apposition to
the anterior surface of the oesophagus, giving off branches to form the
œsophageal plexus. It then passes as a single trunk in front of the
œsophagus, through the diaphragm to the anterior surface of the stomach,
to which it is distributed. It sends branches to the spleen, pancreas,
liver, and small intestines.
The following tabulated arrangement of the branches of the pnemo-
gastric nerve is taken from Prof. Allen's Anatomy:
Excranial,
Auricular.
Meningeal.
Anastomotic,
With the spinal accessory nerve.
With the glosso-pharyngeal nerve.
With the hypoglossal nerve.
With the sympathetic nerve.
316
ANATOMY.
Excranial
(cont.)
Pharyngeal and
laryngeal,
Thoracic,
Abdominal,
Pharyngeal.
Superior laryngeal.
Inferior laryngeal.
Thoracico-cardiac.
Pulmonary
Esophageal.
Hepatic.
Gastric.
Intestinal.
·
The Auricular Branch (auricularis vagi nerve of Arnold) arises from
the superior ganglion, or ganglion of the root of the pneumogastric
nerve, situated within the posterior lacerated foramen, and immediately
receives a communicating filament from the petrous ganglion of the
glosso-pharyngeal nerve. It then passes backward behind the bulb of
the internal jugular vein, and enters a foramen near the base of the
styloid process of the temporal bone, which is situated to the inner side
of the aqueduct of Fallopius. Within the canal it forms a communi-
cation with the facial nerve, after which it passes through a canal situ-
ated close to the internal auditory meatus between the tympanic and
mastoid processes of the temporal bone. At that point it emerges from
the bone, divides into two branches, the posterior division joining the
posterior auricular branch of the facial nerve, while the anterior division
is distributed to the integument and cartilage of the back of the car
and the posterior and inferior portion of the auditory canal.
Variations. In rare instances the auricular branch of the pneumo-
gastric nerve is entirely absent, or it may have no communication with
the facial nerve. Occasionally its individuality is lost by uniting with
the facial nerve, in which case its fibres are distributed with the poste-
rior auricular branch of the facial.
The Meningeal Branch is quite small, and arises from the anterior
border of the superior ganglion of the pneumogastric.
It passes
upward, and is distributed to the dura mater in the vicinity of the
posterior lacerated foramen.
Anastomotic Branches. The larger number of anastomosing branches
of the pneumogastric nerve are distributed to the circulatory, respira-
tory, and digestive systems. In the jugular foramen small branches
are given off to the dura mater and to the ear; in the neck branches
are distributed to the pharynx, larynx, and heart; in the thorax
branches are supplied to the heart as well as the lungs and oesophagus;
in the abdomen its terminal branches are distributed to the stomach,
liver, and other organs.
The Pharyngeal Branches (Fig. 153) are the principal motor nerves
of the pharynx. They are usually two in number, but there may be more
than two; occasionally there is but one. They arise from the superior
and inner portion of the inferior or cervical ganglion of the pneumo-
gastric nerve, or, more properly, they are composed of fibres which come
from the accessory portion of the spinal accessory nerve, which passes
over this portion of the ganglion. They pass downward and inward,
generally behind the internal carotid artery, but occasionally in front
of it, to the superior border of the middle constrictor muscle of the
pharynx, where they divide into numerous branches which interlace

THE NERVOUS SYSTEM.
317
FIG. 153.
with branches from the glosso-pharyngeal, superior laryngeal, and the
sympathetic system, through the superior cervical ganglion, to form
the pharyngeal plexus. This plexus is extremely important, and
is situated on the lateral surface of the
middle constrictor muscle. It usually
contains one or more ganglia. Branches
are distributed from this plexus to the
muscles and mucous membrane of the
pharynx. It also gives off the lingual
branch of the vagus nerve (Luschka).
They receive branches from the glosso-
pharyngeal and pneumogastric nerves,
pass downward, and join the hypoglossal
nerve where that nerve curves around
the occipital artery.
The Superior Laryngeal Branch arises
as a rounded cord from the middle and
inner side of the inferior ganglion or
ganglion of the trunk of the pneumo-
gastric nerve, or "from the side opposite
to the point of junction of the pneumo-
gastric with communicating branches of
the spinal accessory, so that probably the
superior laryngeal nerve contains few if
any motor fibres from this nerve" (Flint).
Quain, in describing the lower ganglion,
says: "The accessory part of the spinal
accessory nerve runs over the surface of
the ganglion, and is in a great measure
continued directly into the pharyngeal
and superior laryngeal nerves.'
7
8.
9..
10
3
6
3
..4
Origin and Connections of the Glosso-
pharyngeal, Pneumogastric, and Spi-
nal Accessory Nerves: 1, facial nerve;
2, glosso-pharyngeal; 3, pneumogas-
tric; 4, spinal accessory; 5, hypo-
glossal; 6, external (muscular) branch
The superior pharyngeal nerve is the
important sensory nerve of the larynx,
especially in the region of the glottis.
It acts as the sentinel to the opening of
the air-passage to guard against foreign
matter, such as food, solid or liquid, from
entering during deglutition. It is also
motor in its function, and distributes
motor filaments to the crico-thyroid mus- of the spinal accessory; 7, superior
cle, as well as small filaments to the in-
ferior constrictor and arytenoid muscles.
It passes downward and inward behind
both the internal and external carotid
arteries, thence along the superior margin of the inferior constrictor
muscle of the pharynx, where it divides into two branches, external and
internal. Previous to its division it receives filaments from the upper
cervical sympathetic ganglion and from the pharyngeal plexus.
laryngeal branch of the pneumogas-
tric; 8, pharyngeal plexus; 9, laryn-
geal plexus and upper cardiac branches
of the pneumogastric; 10, tympanic
plexus, from a branch of the glosso-
pharyngeal.
The External Laryngeal Branch is smaller but longer than the supe-
rior laryngeal. It passes downward and forward under the depressor
318
ANATOMY.
of the hyoid bone, and is distributed to the crico-thyroid muscle. It
also sends branches to the inferior constrictor of the pharynx and the
arytenoid muscles. It receives communicating filaments from the
upper cervical sympathetic ganglion, and interlaces with branches from
the inferior laryngeal nerve.. It also sends communicating or cardiac
branches to the cardiac plexus. Occasionally communicating branches
from this nerve pass to the pharyngeal plexus, distributing branches to
the thyroid body, the mucous membrane of the true vocal cords, and
the depressor muscles of the hyoid bone.
The Internal Laryngeal Branch is shorter though thicker than the
external laryngeal. It passes forward along the thyro-hyoid membrane
to the median line of the neck, pierces that membrane in company with
the superior thyroid artery, and enters the internal portion of the larynx,
being situated beneath the mucous membrane. Here it divides into
numerous branches, which are distributed as follows:
1. A branch which passes upward in the aryteno-epiglottic fold to
the posterior surface of the epiglottis. Some writers claim that a few
filaments of this nerve pass through the epiglottis to its anterior surface.
2. A branch which passes to the base of the tongue as far as the cir-
cumvallate papillæ.
·
3. Several small branches which pass downward and supply the
mucous membrane of the aryteno-epiglottic fold in the region of the
glottis, and as far downward as the false vocal cords and the back of
the larynx.
4. There is also a long branch which passes beneath the ala of the
thyroid cartilage, and unites with a branch from the recurrent or infe-
rior laryngeal nerve at the lower portion of the larynx.
The Inferior or Recurrent Largngeal Nerve is the principal motor
nerve of the larynx, and supplies all its intrinsic muscles excepting the
crico-thyroid. The right and left inferior laryngeal nerves differ in
their origin and in their relation to the tissues of the neck.
The Right Inferior Laryngeal Nerve arises from the main trunk of
the pneumogastric, close to the point where this nerve crosses the right
subclavian artery. It curves around the under and posterior surface
of this artery, passes obliquely upward and inward behind the common
carotid and inferior thyroid arteries, and reaches a groove between the
trachea and the oesophagus, ascending in this groove to the level of the
crico-thyroid articulation.
The Left Inferior Laryngeal Nerve arises from the main trunk of the
pneumogastric as that nerve passes over the left extremity of the trans-
verse portion of the arch of the aorta. It curves around the lower sur-
face of the arch just external to the ductus arteriosus or its remains after
birth, when it becomes a ligament. It then passes upward on its pos-
terior surface, and similarly to the nerve of the right side; extends
behind the common carotid and inferior thyroid arteries to the groove
between the trachea and the oesophagus, terminating on a level with the
crico-thyroid articulation, where both nerves break up into branches.
Their terminal branches are distributed to all the intrinsic muscles of
the larynx excepting the crico-thyroids, these muscles being supplied
by the superior laryngeal. It also distributes a few filaments to the
THE NERVOUS SYSTEM.
319
mucous membrane below the rima glottidis. In their passage upward
these nerves distribute small branches to the structure and mucous mem-
brane of the trachea and oesophagus and to the inferior constrictor mus-
cle of the pharynx. As the nerves pass beneath the large arteries of
the neck they send communicating branches to the inferior cervical sym-
pathetic ganglion and to the cardiac plexus, which is formed by the
interlacing of branches from the pneumogastric nerve and sympathetic
system. The right inferior laryngeal nerve occasionally sends a fila-
ment to the pericardium.
The Cardiac Branches arise as two sets, and receive the name of cer-
vical and thoracic branches.
(
The Cervical Cardiac Branches are two or three in number (usually
three), two of which arise from the main trunk of the pneumogastric
in the upper region of the neck, and unite with the cardiac branches of
the sympathetic system as they descend. The third branch arises from
the pneumogastric nerve just before it enters the thorax. On the right
side the nerve passes in front of the brachio-cephalic artery, and unites
with the superior cardiac nerve in its passage to the deep cardiac plexus,
a few filaments passing to the coats of the aorta. On the left side the
nerve passes in front of the arch of the aorta, and unites with the supe-
rior cardiac nerve or passes directly to the superficial cardiac plexus.
The Thoracic Cardiac Branches of the right side arise partially from
the trunk of the pneumogastric nerve below the origin of the right
recurrent laryngeal as the nerve lies close to the trachea, and partially
from the recurrent branch of the pneumogastric. They terminate in
the deep cardiac plexus. The branches of the left side usually arise
from the recurrent or inferior laryngeal nerve and terminate in the
superficial cardiac plexus.
The Pulmonary Branches are separated into two sets, anterior and
posterior.
The Anterior Pulmonary Branches are the smaller of the two sets,
and consist of two or three slender filaments which arise from the pneu-
mogastric nerve below its cardiac branches. A few of these filaments
pass to the trachea before they form, together with the sympathetic
system of the pulmonary artery, the anterior pulmonary plexus.
Fibres from this plexus encircle and pass along the bronchial tubes
to their terminations in the air-cells of the lungs.
The Posterior Pulmonary Branches are larger and more numerous
than the anterior. They arise from the flattened portion of the pneu-
mogastric nerve behind the root of the lung. They unite with filaments
from the second, third, and fourth thoracic sympathetic ganglia to form
the posterior pulmonary plexus. From this plexus a few filaments are
distributed to the inferior and posterior portion of the trachea, to the
muscular tissue and mucous membrane of the central region of the
œsophagus, and a few to the posterior superior portion of the pericar-
dium. The principal portions of these branches, however, surround the
bronchial tubes, and pass along them to the air-cells of the lungs in the
same manner as the branches from the anterior pulmonary plexus. The
anterior and posterior pulmonary plexuses of each side give off a large
number of communicating branches which pass between each other, so
320
ANATOMY.
that filaments from both the right and the left pneumogastric nerve pass
to the right and left lungs.
The Esophageal Branches arise from the pneumogastric nerve, both
above and below its pulmonary branches. Those which arise below are
the larger and spring from the oesophageal plexus. The nerves from
the right and left side interlace quite freely, and are distributed to the
muscular tissue and mucous membrane of the lower third of the
œsophagus.
The Abdominal or Terminal Branches of the right and left sides.
differ in their distribution. Those of the left side enter the abdominal
cavity upon the anterior surface of the oesophagus, and when opposite
the cardiac orifice of the stomach divide into numerous branches.
These branches are distributed to the muscular tissue of the walls of
the stomach and to the mucous membrane of its anterior portion, lesser
curvature, and great cul-de-sac, interlacing with branches of the right
nerve and the sympathetic system. There are also branches (hepatic)
which pass from the lesser curvature of the stomach, between the folds
of the gastro-hepatic omentum, reach the transverse fissure of the liver,
to be distributed to the hepatic substance.
The abdominal branches of the right side enter the abdomen on the
posterior surface of the oesophagus. On reaching the stomach they
break up into branches, some of which are distributed to the muscular
tissue and mucous membrane of its posterior portion, interlacing with
branches from the left nerves; while others pass to the liver, spleen, kid-
neys, suprarenal capsules, and to the whole of the small intestine, and
communicate with the solar plexus.
SPINAL ACCESSORY NERVE.
The spinal accessory or eleventh nerve (the third trunk of the eighth
nerve according to the arrangement of Willis) (Fig. 154) is a motor
nerve, which is separated into two divisions. The first division controls
the action of the sterno-cleido-mastoid and part of the trapezius muscle;
the second division, after uniting with the pneumogastric nerve, supplies
motor filaments to muscles, and, as was demonstrated by Bischoff in
1832, presides over phonation. This fact was also proved by Bernard.
A TABLE OF THE BRANCHES OF THE SPINAL ACCESSORY NERVE.
Branches to the pharyngeal plexus.
(C
(C
((
superior laryngeal nerve.
recurrent laryngeal nerve
(thus supplying the muscles of phona-
tion).
(C
(6
Branch to the sterno-mastoid muscle.
trapezius muscle.
Branch to the sterno-mastoid muscle.
trapezius muscle.
((
..
THE SPINAL ACCES-
SORY OR ELEV-
CRANIAL
ENTH
NERVE.
Accessory portion,
Spinal portion,
(C
Communicating
branches to
First cervical nerve.
Second cervical nerve.
Third cervical nerve.
Fourth cervical nerve.
nerve by reason of
The name "spinal accessory" was given to this
its relations with the pneumogastric nerve, and also because of its origin,
THE NERVOUS SYSTEM.
321
One
which is quite extensive and divided into two portions or roots.
root arises from the lower portion of the medulla oblongata, and the
other from the cervical portion of the spinal cord.
FIG. 154.

-8
13--
5-
7k
J.
15
18
-16
-20
-10
~12
-14
.4
17 19 21
The Side of the Neck: 1, occipital artery; 2, facial vein; 3, spinal accessory nerve; 4, facial artery; 5,
internal jugular vein; 6, hypoglossal nerve; 7, communicans noni nerve; 8, lingual artery; 9,
pneumogastric nerve; 10, superior laryngeal nerve; 11, phrenic nerve; 12, superior thyroid
artery; 13, sterno-cleido-mastoideus (reflected); 14, common carotid artery with descendens noni
nerve; 15, inner end of clavicle reflected; 16, sterno-hyoid; 17, subclavian vein (cut); 18, omo-
hyoid; 19, subclavian artery giving off the thyroid axis and the internal mammary artery; 20,
inferior cervical ganglion of sympathetic; 21, apex of pleura.
The Medullary or Accessory Portion or Root.-The superficial or ap-
parent origin is by four or five delicate filaments situated in the groove
between the olivary and restiform bodies on the side next the medulla
oblongata, just below the superficial origin of the pneumogastric nerve.
The Cervical Portion or Root arises by six or eight filaments from
the lateral tract of the entire length of the cervical portion of the spinal
cord, though its superficial origin is not generally distinguishable below
the fourth or fifth cervical nerve. The lowest filament is generally
single; the others, however, emerge from the cord in pairs. These
filaments ascend along the cord, increasing in size as each additional
filament is added, and extending between the ligamentum denticulatum
and the posterior roots of the spinal nerves. The first and second spinal
nerves are often connected to these filaments. After reaching the for-
amen magnum, through which it enters the brain-case, it curves outward
to the middle compartment of the posterior lacerated foramen, in which
it joins the medullary root. The two roots then interchange fibres with
VOL. I.-21
322
ANATOMY.
each other, and occasionally form a single trunk. In this region the
two roots are contained in a single sheath of the dura mater with the
pneumogastric nerve. A branch of communication extends between the
accessory and medullary portions of the superior ganglion of the pneu-
mogastric nerve.
The encranial portion of the spinal accessory is separated into two
divisions, internal and external, which are almost identical in origin
with the two roots of the main nerve.
The Internal Medullary or Accessory Portion, which contains nearly
all the fibres arising from the medulla, passes over the inferior ganglion
of the pneumogastric nerve (ganglion plexiformis), and becomes inti-
mately associated with it. It is distributed through the pneumogastric
nerve to the larynx, pharynx, and other structures. (See Pneumo-
gastric Nerve.)
The External or Spinal Portion (muscular branch) is the longer of
the two branches, and contains nearly all the filaments which arise from
the spinal cord, and may receive all the fibres of the posterior root of
the first cervical nerve. It passes from the posterior lacerated foramen
downward, backward, and outward in front of the internal jugular vein,
but occasionally behind the vein, over the transverse process of the atlas,
to the superior third of the sterno-cleido-mastoid muscle. It generally
pierces this muscle, though it may pass beneath it and appear in the pos-
terior cervical triangular space beneath the trapezius muscle. It com-
municates by branches with the medullary portion in the posterior lace-
rated foramen, with the first cervical nerve, and the superior ganglion of
the pneumogastric nerve, while beneath the trapezius muscle it gives off
branches which unite with branches from the third, fourth, and fifth
cervical nerves which assist in forming the cervical plexus. It also
distributes branches to part of the sterno-cleido-mastoid muscle and
to the clavicular portion of the trapezius muscle.
Jame
HYPOGLOSSAL NERVE.
The hypoglossal, twelfth, or sublingual nerve (the ninth nerve accord-
ing to the arrangement of Willis) (Fig. 152) is the last of the cranial
nerves. Its chief function is in connection with the movements of the
tongue in deglutition and articulation. It is also distributed to all the
muscles which are attached to the hyoid bone. It arises superficially
or apparently by twelve or fourteen filaments, which pass from the
groove situated between the olivary body and the anterior pyramid of
the medulla oblongata. The filaments are collected into two separate
bundles, superior and inferior, which are directed outward, pass behind
the vertebral artery, and extend toward the anterior condyloid foramen;
and as they enter this foramen or foramina¹ they receive a separate
sheath from the dura mater, and unite into a single trunk as they
emerge from the brain-case and pass into the deep portions of the neck.
From this point it extends to the median side of the internal jugular
vein and the pneumogastric nerve. It then descends the neck nearly
Occasionally there are two foramina in the occipital bone. When this is the case
the bundles pass through separate openings.
盘
​THE NERVOUS SYSTEM.
323
in a vertical (slightly forward) direction on the median side of the
internal jugular vein, and between it and the internal carotid artery,
to a level with the lower margin of the digastric muscle. It here, in
the superior carotid triangle of the neck, becomes superficial, and curves
around and under the occipital artery near its origin. It then passes
forward over the external carotid artery, above the hyoid bone, beneath
the tendon of the digastric and the lower portion of the stylo-hyoid,
and between the mylo-hyoid and the hyo-glossus muscles, terminating
by dividing into branches in the genio-glossus muscle.
TABLE OF THE BRANCHES OF THE HYPOGLOSSAL NERVE.
To the ganglion of the trunk of the
pneumogastric nerve.
THE HYPOGLOSSAL OR
TWELFTH CRANIAL
NERVE.
Branches of com-
munication.
Branches of dis-
tribution.
:
To the superior cervical ganglion of
the sympathetic.
To the loop between the first and second
cervical nerves.
To the gustatory nerves.
Descendens noni nerve.
To thyro-hyoid nerve.
To genio-hyoid nerve.
To stylo-glossus muscle.
To hyo-glossus muscle.
To genio-hyo-glossus muscle.
To the intrinsic muscles of the tongue.
The branches of communication of this nerve as tabulated above are-
1. With the pneumogastric nerve, which passes between the inferior
ganglion of that nerve and the hypoglossal nerve immediately after it
leaves the skull. There is also a communicating branch which passes
between these two nerves near to the point where they cross the occipital
artery.
2. With the sympathetic system by a filament of considerable size,
which passes between the superior cervical ganglion of that system and
the hypoglossal nerve.
P
3. With the first and second cervical nerves, which pass between the
loop connecting these two nerves, the spinal nerves, and the hypoglossal
nerve together.
4. Two or three branches of communication with the gustatory
nerve, which pass between the hypoglossal nerve and the gustatory or
lingual branch of the fifth nerve in the region of the anterior border
of the hyo-glossus muscle.
The branches of distribution of the hypoglossal nerve are the—
Branches to the tongue,
Genio-hyoid.
Recurrent,
Descending thyro-hyoid,
The Recurrent Branch arises from the hypoglossal nerve within the
anterior condyloid foramen. It passes into the brain-case, and is dis-
tributed to the dura mater and walls of the vascular sinus close to the
foramen magnum. It is also distributed to the diploë of the occipital
bone (Luschka).
Cap
The Descending or Descendens Noni Branch is a long, slender fila-
ment which arises from the hypoglossal nerve as it curves under the
occipital artery. From this point it descends the neck, at first in front
of the internal carotid artery, either within the common sheath with
M
324
ANATOMY.
the vessel, or upon its outer surface, to a point just above the tendon of
the omo-hyoid muscle. In its descent it distributes a small branch to
the anterior belly of this muscle. It then divides into two or three
branches, and receives one or two communicating branches from the
second and third cervical nerves (communicans noni). By this union a
plexiform loop is formed, with its concavity upward. This loop occa-
From
sionally receives another small branch from the cervical nerves.
this plexiform loop branches are distributed to the sterno-hyoid, sterno-
thyroid, and omo-hyoid muscles, and sometimes to the cardiac and phrenic
nerves within the thorax.
The Thyro-hyoid Branch arises from the hypoglossal nerve in front
of the external carotid artery, from which point it descends, and is dis-
tributed to the thyro-hyoid muscle.
The Branches to the Tongue are the stylo-glossus, hyo-glossus, and
genio-glossus, which are given off from the hypoglossal nerve while it
is located between the mylo-hyoid and the hyo-glossus muscles. They
are distributed to the muscles indicated by their names, and send
branches to other muscles in the substance of the tongue, as well as to
the genio-hyoid muscle.
Variations.-Occasionally the right and left hypoglossal nerves com-
municate by a branch which passes between them in the neighborhood
of the genio-hyoid muscle. In rare cases filaments are distributed to
the mylo-hyoid muscle (Krause). According to Luschka, E. Bischoff,
Holl, and others, the descendens noni nerve does not in reality arise
from the hypoglossal nerve, but is derived from the upper cervical
nerves, which are temporarily associated with the hypoglossal. Holl
states that the branches going to the thyro-hyoid and genio-hyoid
muscles are composed of fibres which arise from the spinal nerves.
LYMPHATIC VESSELS OF THE HEAD AND
NECK.
BY ALBERT P. BRUBAKER, A. M., M.D., D.D.S.
THE LYMPHATICS.
THE LYMPHATICS, and the glands in connection with them, consti-
tute a system of vessels most important to the nutrition of the body.
In all the vertebrate animals this system is superadded to the circula-
tory, and is designed to carry back into the general blood-current the
excess of nutritious fluid which has been exuded from the capillary
blood-vessels for the purposes of nutrition. The fluid which the lym-
phatic vessels contain is known as lymph, and resembles in its physical
and chemical constitution the liquor sanguinis or blood-plasma.
The lymphatic vessels have a very extensive distribution, being found
in nearly all the tissues and organs of the body which receive blood.
They are absent, or at least have not yet been discovered, in the hair,
nails, epidermis, and other structures usually regarded as non-vascular.
Lymphatics are widely distributed throughout the body, but are more
abundant in some situations than in others. The inner surfaces of the
limbs are more abundantly supplied than the outer surfaces, while the
lines of junction of the limbs with the trunk are especially rich in both
vessels and glands. In the thoracic and abdominal cavities they are
very numerous. In the majority of situations in which the lymphatics
are found they are arranged into a superficial and a deep set, the former
being very fine and situated in and beneath the skin and mucous mem-
branes, while the latter are much larger and follow the course of the
large blood-vessels.
bu
The lymph, when examined microscopically, is seen to consist of a
clear colorless plasma, in which are imbedded an immense number of
corpuscular elements. The lymph which has been obtained from man
and inferior animals is usually colorless and transparent, although at
times it presents a faintly yellowish hue. It is odorless, slightly saline
in taste, alkaline in reaction, and possesses in the dog a specific gravity
of 1022. Like the blood, lymph undergoes a spontaneous coagulation
when withdrawn from the body, although the coagulum is never so firm
as in the case of the blood. In its chemical composition lymph also
resembles the blood. Analyses made by Lassaigne of the lymph obtained
from a cow demonstrated that it contains, in 1000 parts, water, 964;
fibrin, 0.9; albumen, 28.0; fatty matter, 0.4; inorganic salts, 6.7.
The corpuscular elements of the lymph, known as lymph-corpuscles
or leucocytes, are found floating in the lymph-plasma. When examined
325
326
ANATOMY.
1
microscopically they resemble in many respects the white corpuscles of
the blood, but they are smaller and less uniform in size, varying from
2006 to 5000 inch in diameter. In addition to the lymph-corpus-
cles there are present in almost every specimen of lymph small gran-
ules, regarded by some as free nuclei, which have a gray color and
exhibit the Brownian movement. Red corpuscles are also found, par-
ticularly in the large lymphatic trunks and in the thoracic duct.
The lymph-corpuscles vary much in size, shape, and general appear-
ance. Some are quite small, spheroidal in shape, and consist of a single
nucleus surrounded by a small quantity of protoplasmic matter. Others
are larger, and frequently contain several vesicular or spheroidal nuclei
which are surrounded by a limiting membrane, while the enveloping
mass of protoplasm is quite abundant. Many leucocytes contain "col-
lections of granules which are highly refractive and impart to the cor-
puscle a distinctly granular character. The lymph-corpuscles are made
up of a fine network of an albuminous material, in the meshes of which
is found a colorless semifluid substance apparently of an albuminous
character. There is no cell-wall present in any of the true lymph-cor-
puscles. They originate either by subdivision of pre-existing cells or
are developed within the lymphatic glands.
K
ORIGIN OF LYMPHATICS. The mode of origin of the lymphatics
has until recent years been involved in the greatest obscurity. But the
investigations of Von Recklinghausen, Klein, Ludwig, and many others
have gone far toward demonstrating the true origin of these vessels.
The following modes of origin are now well known:
1. Origin in Lymph-spaces or Juice-canals.-Throughout the con-
nective-tissue system of the body are located numbers of small, irregu-
lar, stellate spaces which communicate very freely with each other.
These are the so-called juice-canals of Von Recklinghausen, and are
supposed to represent the ultimate radicles of the lymphatic vessels.
They vary considerably in size, and their shapes are determined by the
nature of the tissues in which they are placed. They do not possess an
endothelial lining, but contain one or more connective-tissue corpuscles
which exhibit characteristic amoeboid movements.
As these spaces
communicate very freely with each other, the movement of the lymph
through them and around the islets of tissue readily takes place.
The lymph-spaces communicate directly with the lymph-capillaries,
as was also demonstrated by Von Recklinghausen. The lymph-capil-
laries constitute a plexus of fine vessels which give rise to the smallest
lymphatic trunks; they vary in shape according to the tissue in which
they are found, and also in size, but are always larger than the capil-
lary blood-vessels. Their walls are formed by a lining of simple endo-
thelial cells with characteristic sinuous margins.
Chapt
TRAN
k
2. Origin in Openings on the Surface of Serous Membranes.-The
large scrous cavities, such as the peritoneal, pleural, pericardial, sub-
arachnoid, etc., have been shown by Klein, Von Recklinghausen, and
many others to communicate with the lymphatic vessels. Their mode
of origin can best be studied upon the peritoneal surface of the central
tendon of the diaphragm. This surface is covered with a layer of
endothelial cells, whose sinuous margins can be readily exhibited by
LYMPHATIC VESSELS OF THE HEAD AND NECK.
327
+
•
staining the surface with a solution of nitrate of silver. At intervals
between these cells are found large free openings which have received
the name of stomata. These openings communicate by means of short
canals with the lymph-capillaries that are found among the fibrous
tissue of which the diaphragm is composed. Upon the pleural surface
similar openings have also been demonstrated. The serous cavities.
of the body may therefore be regarded as true lymph-spaces, which
communicate primarily with the lymph-capillaries, and secondarily with
the lymphatic trunks. Stomata in all respects similar to those found
on serous membranes have been shown to be present on the surfaces of
mucous membranes, which in all probability are directly connected with
the lymph-capillaries.
3. Origin in Perivascular Lymph-spaces. Within the substance of
the brain, spinal cord, bone, and other tissues His and Robin have
shown that the capillary blood-vessels are surrounded by a lymph-space
bounded and limited by a cylindrical sheath formed of endothelial cells,
which is in frequent communication with the lymph-capillaries. The
blood-vessel thus floats in the lymph-stream. In addition, the tunics
of the large blood-vessels, both the intima and adventitia, are traversed
by lymph-channels which open very freely into each other. This
arrangement of the blood-vessels permits of a free interchange by
osmosis of the fluid portion of both blood and lymph.
STRUCTURE OF LYMPHATIC VESSELS.-The lymphatic trunks have
their origin in the fine plexus of lymph-capillaries previously described.
In their course toward the centre of the body they pursue generally a
direct route. They anastomose by bifurcation very freely with neigh-
boring vessels, pass through the lymphatic glands, and vary but little
in size from origin to termination. Their walls are so exceedingly trans-
parent and delicate that when empty it is with difficulty they can be
Their diameter varies from to inch. After the lymphatic
trunks have emerged from the lymph-capillaries they acquire three dis-
tinct coats, which resemble in their structure and arrangement the coats
of the veins.
seen.
25
Sp
The internal coat is delicate and elastic, and is composed of a layer
of longitudinal elastic fibres covered with a layer of flattened nucleated
endothelial cells with wavy or sinuous margins. The middle coat con-
sists of white fibrous tissue, which is arranged longitudinally, and of
unstriped muscular and elastic fibres, which are disposed transversely.
The external coat is composed of identically the same structures, but
the muscular fibres pursue rather a longitudinal than a transverse direc-
tion. These three coats are known respectively as the tunica intima,
tunica media, and tunica adventitia. The walls of the lymphatic
trunks are abundantly supplied with blood-vessels (vasa vasorum), and
it is highly probable that they are also supplied with nerves (nerva
vasorum), though the latter have not been indisputably demonstrated.
On physiological grounds their existence might be inferred.
Valves.-The lymphatics generally are provided with valves, which
have the same structure and fulfil the same function as the valves with
which the veins are furnished. These valves are very numerous, and
are located at such short intervals along the course of the vessel as to give
·
328
ANATOMY.
j
rise to a beaded appearance. They are not farther apart than
to
inch. The superficial vessels are most abundantly supplied with
valves, those of the arm containing from sixty to eighty between the
fingers and axillary glands, while the corresponding vessels of the
lower limbs contain from eighty to one hundred. The valves are
generally arranged in pairs, and consist of two semilunar folds, with
their concavities directed toward the larger vessels. They are formed
by a reduplication of the lining membrane, the two folds being strength-
ened by fibrous tissue from the middle coat.
Lymphatic Glands. The lymphatic glands are small lenticular bodies
placed along the course of the lymphatic vessels as they pass from their
points of origin toward the thoracic duct. They are exceedingly numer-
ous, the total number being estimated at from five to seven hundred.
They vary considerably in size, some not being larger than a pin's
head, while others attain a size equal to that of a kidney bean. As the
lymphatic glands are in connection with the vessels, they may,
like them,
be divided into a superficial and a deep set; the former are most
abundant around the head and neck and at the lines of union of the
limbs with the body; the latter are found most abundantly in the
thorax and abdomen along the course of the deep-seated vessels. The
glands situated between the folds of the mesentery are known as the
mesenteric glands. The lymphatic vessels as they approach a gland
break up, before entering it, into a number of small branches-the
vasa afferentia, which penetrate its investing membrane. From the
opposite side of the gland the lymphatics again emerge, as the vasa
efferentia, and a short distance beyond it unite to form trunks larger,
but fewer in number.
The lymphatic glands present at one point a depression which is
termed the hilum, through which the blood-vessels pass into and out
of the gland, and through which
also emerge the efferent vessels.
Except at the hilum the gland
is entirely covered externally by
a membrane composed of dense
connective tissue. The interior
of the gland is soft and pulpy,
e of a dark color, and mottled in
appearance. The superficial part
of the gland is termed the corti-
cal, the deeper part the medullary
portion (Fig. 155).
From the inner surface of the
investing membrane there pass
inward partitions or septa of
lamellated connective tissue
which divide the outer zone of
the gland into small compart-
ments, which are conical in
shape in consequence of the
convergence of the partitions toward the centre of the gland. These
b
g/c
д
FIG. 155.
a d

{{{C
f
d
a
d
h
Section of Small Lymphatic Gland, half diagram
matically given, with the course of the lymph:
a, the envelope; b, septa between the follicles or
alveoli of the cortical part; c, system of septa of
the medullary portion down to the hilum; d, the
follicles; e, lymph-cords of the medullary mass;
afferent lymph-vessels, the different lymphatic
streams from which surround the follicles and
flow through the interstices of the medullary por-
tion; 9, confluence of these to pass through the
efferent vessel (h) at the hilum.
LYMPHATIC VESSELS OF THE HEAD AND NECK.
329
6
FIG. 156.
spaces or alveoli are from to inch in diameter, and are con-
24
nected with each other through openings in the septa. When the
septa reach the medullary portion they subdivide and form bands or
cords which interlace in every direction and constitute a loose mesh-
work, the spaces of which communicate with each other and with the
alveoli. Within the meshes of the gland is contained the proper gland-
substance. In the conical compartments it is moulded into a pear-shaped
mass, while in the medullary part it assumes the form of rounded cords,
which, like the trabecular meshes, are connected with each other. In
both the cortical and medullary regions, however, there is a clear space
between the gland-pulp and the trabeculæ, which is termed the lymph-
sinus, through which the lymph flows as it passes through the gland.
This lymph-sinus is crossed by a
fine network of retiform connective
tissue in which the nuclei of the
endothelial plates covering it are
distinctly seen (Fig. 156). This
reticulation offers considerable re-
sistance to the flow of lymph
through it. The glandular sub-
stance itself consists of essentially
the same elements. It is support-
ed by a framework of retiform tis-
sue, in the meshes of which are
found immense numbers of lymph-
corpuscles. The glandular sub-
stance is separated from the lymph-
sinus by a denser layer of reticu-
lum, although it is not so compact
as to prevent the lymph, and even
the corpuscles, from passing out
into the lymph-sinus. The lym-
phatic glands are abundantly sup-
plied with blood-vessels. Arteries
enter the gland at the hilum, pene-
trate into the medullary substance,
and terminate in a fine capillary
plexus, which is surrounded and
supported by the retiform tissue.
The veins arising from this plexus
leave the gland also at the hilum.
a
God
The lymphatic vessels which
enter a gland ramify in the in-
vesting membrane, and then open
directly into the lymph-sinus. The efferent vessels begin by fine
branches, which also communicate directly with the lymph-sinus.
When the lymphatic vessels enter a gland they lose their external and
middle coats, and retain only the endothelial, which lines the inner sur-
face of the lymph-sinus. The current of lymph, therefore, can pass
directly from the afferent vessel through the lymph-sinus into the effer-
A
ROUTES
d
SOUS
b
d
6
G

Portion of the Medullary Substance of the Mes-
enteric Gland of an Ox, the artery injected
with chromate of lead (highly magnified); a,
medullary cylinder with capillary network, fine
reticulum of connective tissue, and a few lymph-
corpuscles; b, b, superficial lymph-path or me-
dullary sinus traversed everywhere by a retic-
ulum of nucleated cells; this reticulum has
been represented only at e, with numerous
anastomosing prolongations; the lymph-cor-
puscles have for the most part been removed
with a camel's hair brush; d, d, trabeculæ com-
posed almost exclusively of unstriped muscu-
lar tissue. A small medullary cord or bridge,
containing a blood-vessel and numerous lymph-
corpuscles, is shown at the left of the figure as
springing from the medullary cylinder.
BO
330
ANATOMY.
ent vessel. In addition to this primary current there is a secondary
current always flowing from the capillary blood-vessels outward into
the lymph-sinus which carries with it immense numbers of lymph-cor-
puscles, which enter the efferent lymphatic vessels.
The thoracic duct is the general trunk of the lymphatic system, into
which most of the lymphatic vessels of the body empty. It is from
eighteen to twenty inches in length, extending from the root of the neck
downward to the second lumbar vertebra. It measures in diameter about
one-eighth of an inch, though at its inferior extremity, where it expands
into the receptaculum chyli, it is somewhat wider. Its walls have the
same general structure as the walls of the lymphatic vessels, consisting
of three coats-an internal, or endothelial; a middle, elastic and mus-
cular; and an external, or fibrous. The inner surface of the duct is
abundantly supplied with valves. This general duct empties into the
venous circulation at the junction of the left internal jugular and sub-
clavian veins.
DONA
LYMPHATIC VESSELS OF THE HEAD AND NECK.
The lymphatic glands and vessels of the head and neck may be
divided into a superficial and a deep set. The superficial set may again
be subdivided, according to their location, into-
1. A Facial Group, consisting of two or three small glands situated
in front of the ear at the root of the zygoma and upon the outer aspect
of the parotid gland. A small gland is occasionally found near the side
of the root of the nose, though the rest of the facial region is singularly
free of glands, none being found above the line of the mouth (Fig. 157).
2. A Post-aural Group, consisting of three or four glands situated
slightly above the insertion of the sterno-cleido-mastoid muscle, and one
other at the base of the occipital bone.
3. A Submaxillary Group, from eight to ten in number, situated
beneath the base of the inferior maxillary bone. The largest of this
group is in close relationship with the outer surface of the submaxillary
salivary gland. This group lies quite superficially, being only covered
in by the skin and superficial fascia.
4. A Cervical Group, more numerous than the preceding, which is
arranged along the course of the external jugular vein. At the inferior
boundary of the neck these glands are found in greatest number, espe-
cially in the space behind the insertion of the clavicular portion of the
sterno-cleido-mastoid muscle. At this point they penetrate the deeper
region of the chest and become connected with the axillary glands.
The deep glands may also be divided, according to their location,
into-
1. A Facial Group, from six to eight in number, situated in the
spheno-maxillary space and alongside of the pharyngeal wall.
2. A Cervical Group, located along the course of the carotid artery
and jugular vein, and extending from the upper limit of the neck down-
ward as far as the thorax.
The lymphatic vessels of the head and neck may be divided into a
LYMPHATIC VESSELS OF THE HEAD AND NECK.
331
superficial and a deep set. The superficial may be subdivided, accord-
ing to their location, into-
ita
1. A Facial Group, which arises from the central part of the forehead
and descends obliquely along the course of the facial vein, and enters the
submaxillary glands.
Doorpita
•
FIG. 157.
མ ས འབར ་ བ་ ་ ་
Temporal
ถนนย
ul,
Parotid
ال ۲۰۱۰
1M
vi)
STERNO
W
Nevy
The Superficial Lymphatics and Glands of the Head, Face, and Neck.
711!!
m

set.
2. A Cranial Group, which consists of a temporal and an occipital
The former, arising from the superior portion of the cranium,
descends in front of the auricle, passes through the facial glands, and
finally terminates in the glands of the neck; the latter, receiving the
lymph from the occipital region of the cranium, converges and descends
along the course of the occipital artery, and enters the post-aural glands
on the mastoid process, and subsequently joins the lymphatics of the
neck (Fig. 158).
332
ANATOMY.
The deep facial group of lymphatics has its origin in the temporal
fossa, the orbital and nasal cavities, and the mouth. Some of the lym-
phatic vessels of the brain-case emerge through the oval and spinous
foramina in the sphenoid bone and join this series of lymphatics. All
of the vessels constituting this series then pass outward along the course
of the internal maxillary vein, and enter the glands in the neighborhood
of the angle of the inferior maxillary bone.
FIG. 158.

//////}}
Gilan
Eterna
Fem
MCQUE
LEATMENTTIAN.
Sun
Party turns west in the g
Anterior Med
WAL
The Deep Lymphatics and Glands of the Neck and Thorax.
The deep cranial group of lymphatics contains those vessels which
come from the brain-case, the pia mater, and the arachnoid through the
foramen lacerum posterius.
The superficial and deep lymphatics of the neck, formed by the union
of the facial and cranial vessels, also receive branches from the tongue,
pharynx, larynx, thyroid body, and other regions of the neck. They
LYMPHATIC VESSELS OF THE HEAD /
AND NECK. 333
descend the neck and follow the course of the veins and carotid artery.
At the same time they progressively decrease in numbers. Those on the
right side empty by a short trunk into the right lymphatic duct, which
enters the venous circulation at the junction of the right internal jugu-
lar and subclavian veins. Those on the left side enter the main tho-
racic duct.
PART II.
DENTAL ANATOMY.
TEETH OF THE INVERTEBRATES.
TEETH OF THE VERTEBRATES.
THE TEETH OF INVERTEBRATES.
By W. H. DALL.
ALMOST every large group of organisms below the vertebrates, until
we reach the Molluscoidea and lower radiated animals, exhibits in some
of its members one form or another of prehensile or masticatory appa-
ratus connected with the alimentary canal. None of these exhibit true
homologies with vertebrate teeth, though sometimes presenting remark-
able similarity to the latter in external form. Before considering these
organs in detail it is desirable to formulate some appropriate definition
which shall distinguish between mandibular and dental appendages in
the sense in which the latter may be said to exist in the invertebrates.
For our purposes we shall consider as teeth only such appendages as
spring from the interior of the oral orifice; are differentiated by their
chemical constitution and mechanical attachments from the surrounding
tissues; perform their functions in a vertical plane as distinguished
from a lateral or horizontal one; and are opposed either to similar
teeth, to a superior mandible, or to the roof of the oral cavity.
This excludes the modified limbs which form the paired and laterally
opposed oral appendages of insects and crustacea, and a great variety of
other appendages which are more naturally classed as jaws, mandibles,
fangs, or stomacholiths. While not homologous, many of these present
such striking similarity of form with vertebrate oral appendages that
the same vernacular name seems more appropriate than a new desig-
nation. No one would hesitate to call the mandibles of a parrot or
hawk and those of the cuttlefish by the same name, even if they were
not aware that they are put to an identical use.
Throughout the invertebrates teeth are dermal structures, however
much special modifications may mask their relations. They may con-
sist of calcified connective tissue, of horny matter, or of chitin or an
allied substance. Chitin and substances with very similar qualities are
almost characteristic products of invertebrate organization. Of them
are formed the wing-cases of beetles and most of the hard elastic tissues
of the exterior of insects. A chitinoid substance is insoluble in boiling
liquor potassæ, and hardly affected by immersion in the strongest acids.
Its lightness, elasticity, and strength fit it remarkably for the work
required of the insect exoskeleton and similar uses. The teeth and
jaws of mollusks, the nippers, mandibles, and setæ of worms, and
many similar invertebrate organs, are composed to a greater or less
extent of chitinoid material. This aids materially in the preparation
of these structures for microscopical examination and study. By heat-
VOL. I.-22
+
A
G
Magn
337
338
DENTAL ANATOMY.
ing in potash solution they can be freed with little trouble from adhe-
rent muscles or other organic material. Chitinous substances are, how-
ever, rather difficult to stain, and in time, unless naturally colored, become
in Canada balsam almost transparent. The student who may wish to
preserve an interesting specimen in a permanent mount for the micro-
scope should bear this in mind, and, if necessary, use some other medium.
Part of the difficulty about staining may be met by mounting in a tinted
medium, which will then contrast with the object itself. With regard
to the teeth and jaws of mollusks, special details will be mentioned far-
ther on. Many of these appendages are so thick or of such contorted
form as to require a deep cell and low powers in order to bring the
whole in focus at once. The beauty and multitudinous variety of these
organs, and the fact that they are within easy reach of anybody, make
them very attractive objects for the microscopist, who has a wide field
for investigation in their study.
In the annelids, so-called teeth occur in many groups, but, on the
whole, partake rather of the nature of jaws than teeth, though fre-
quently double on each side, or even more numerous. This group com-
prises most of the creatures commonly called worms, as well as the
leeches, etc. Their bodies, as well shown in the common earth-worm,
are divided into more or less well-defined rings of muscular tissue,
which correspond internally to segments, often more or less partitioned
off from each other. These rings or annulæ for the most part contain
successive groups of similar organs, but the anterior segments are usually
modified to bear special organs.
In general the jaws are developed on the second or buccal segment,
or on a proboscis which is itself an appendage of this segment, and may
be protruded from the mouth to a con-
siderable distance. They are chitinous,
most commonly paired, lateral and oppo-
FIG. 159.
Fc
F
k
Nereis
margaritacea, head
with protruded jaw-appa-
ratus of the pharynx, from
the dorsal surface (after M.
Edwards): k, jaws; A ten-
tacles; P, palpi; Fe, tenta-
cular cirri (from Claus's
Zoology).
FIG. 160.
k
10
a
b
a, cephalic region of the medicinal
leech (the three jaws are visible); b,
one of the jaws isolated, with the
finely-serrated free edge.
P


site, of almost infinitely varied form, resembling in a general way the
maxillæ of insects, and mimicking, in miniature, combs, saws, rasps,
claws, etc. etc.
In the leeches (Hirudina) the mouth is provided with three lenticu-
lar jaws, with the projecting edges finely serrate, and having a partly
rotatory motion about a point central to the three. The medicinal
THE TEETH OF INVERTEBRATES.
339
leech has two rows of serrations on each jaw; other species doubtless
vary in the buccal armature.
These animals have
In all the annelids reparation of amputated parts, including the
buccal organs, is common and apparently easy.
existed from very early geological time, and small bodies, supposed to
be the fossilized jaws or "teeth" of annelids, have been found in the
Paleozoic rocks of both Europe and America.
In insects no true teeth exist. Mandibles and jaws occur in infinite
variety, usually essentially lateral in position and motion, and easily
observed, especially in such forms as the larger grasshoppers and beetles.
Among the spiders teeth are equally absent, the poisonous fangs being
merely modifications of limbs or segmental appendages, as, indeed, are
nearly all the buccal appendages of the annulated or articulated inver-
tebrates.
Among the Crustacea, lobsters, shrimps, crabs, etc., the maxillary
organs are but modifications of entire limbs translated from the locomo-
tive series and set apart as special mouth-organs. Most of the Crustacea
have a suitable masticatory apparatus of this sort, but in certain para-
sitic forms become organs of attachment or are altogether wanting. If
we examine the digestive organs of one of the higher Crustacea, such as
the crab or lobster, we find the stomach divided into two regions, the
anterior or cardiac and the posterior or pyloric region. These are sepa-
FIG. 161.
f
f
C

(From T. Rymer Jones's Outline of the Animal Kingdom.) Oral Apparatus of Echinus : a a a a a,
pyramidal pieces forming the lantern of Aristotle; bb, internal projections from shell; ccccc,
teeth enclosed in their sockets; dd, interposed osseous pieces; e e, curved processes; ƒƒ, gg, hh,
i i, kk, muscular fasciculi for the movements of the jaw.
rated more by their functions than by their form. The anterior part is
provided with certain masticatory appendages or stomacholiths, often
termed teeth, though more analogous to a sort of calcareous gizzard.
These consist of several calcareous pieces, moved by appropriate mus-
cles, inserted in the membranous wall of the stomach, armed with a
340
DENTAL ANATOMY.
smooth median plate and lateral molar-like organs, whose mimetic
resemblance to the molar teeth of some forms of Mammalia affords a
beautiful illustration of the way in which, through the selective influ-
ence of similar functions, analogous structures may be built up in organs
which have no homology whatever. Two smaller points, bicuspid in
the lobster, tricuspid in the crab, complete the calcareous apparatus; in
the pylorus a series of fine hairs is placed, which doubtless act as a
strainer, preventing the escape of coarser particles of food until they
have been sufficiently comminuted by these grinding organs.
The
(6
lady" in the lobster, with which children amuse themselves, is part
of this apparatus, which of course differs in detail in different genera
and species.
2
The denticulations on the claws of Crustacea have of course no claim
to be considered as teeth, though they assist in breaking up the food.
Among the echinoderms, sea-urchins, starfish, crinoids, etc. certain
forms possess an apparatus commonly known as Aristotle's lantern,
which contains what may fairly be regarded as true teeth (Fig. 161).
Among the sea-urchins the Echinidae and Clypeastrida possess such an
apparatus, the mouth being central; in the Spatangide the mouth is
at one side, and there are no teeth. Among the other echinoderms,
the starfishes (Asterida) have no teeth; the brittle stars (Ophurida)
have short, flat, calcareous processes which are moved by muscles
and have the name of palæ
angulares. They are attached
to the mouth-skeleton, and
are supposed to be used for
mastication.
FIG. 162.
Among the recent crinoids
or sea-lilies the mouth is
closed by lobes of the peri-
d some, which
which may contain
calcareous plates hardly to
be called teeth. The other
groups are edentulous.
1
The singular and remark-
able mouth-apparatus (Fig.
162) in our common sea-urchin
or sea-chestnut (Echinus) has
been observed by every one
who has passed any time at
the seaside. It is frequently
detached from the test of the
2
e
d d
α
1
S

a
a
"(
(From the same Author.) Dental system of Echinus: 1.
represents three of the pyramidal pieces forming the
lantern of Aristotle," in situ: a a, cutting extremities
of the incisor teeth, which are of enamel-like hardness;
faces of the jaws; d d, arched processes. 2, an isolated
a', a', a', fibrous roots of the same; b b, opposed flat sur-
pyramid: e, its external surface; a, same as in 1.
animal, and retains its form for some time, even while washed about by
the waves on the beach. It is very complicated in its arrangement,
but in essentials consists of five hard, calcareous, wedge-shaped sockets
or alveoli (Fig. 162, b, b), each containing one porcelainous chisel-
shaped tooth. The teeth (Fig. 162, a, a) are, like those of rodents,
softer on the inner than on the outer side, and therefore in wearing
always preserve a sharp edge. The union of the alveoli produces a
pentagonal cone with its apex pointing downward, and formed by the
P
THE TEETH OF INVERTEBRATES.
341
coming together of the points of the five teeth. Each alveolus consists
of two halves united in the middle line, and each half of an upper and
lower portion. In life the alveolus is concealed within the tissues, only
the point of the tooth projecting. The socket is interradial in position
with relation to the test of the echinus, or opposite the interambulacra
or spaces between the rows of walking suckers. Above and between
the upper ends of the alveolar pieces are certain rather thick radial
pieces called rotulce or falces, each of which in the Echinidae bears a
bifurcated piece known as the radius (Fig. 162, d, d). In this group,
at the oral end of the ambulacra (of the interambulacra in Cidaris), are
calcified internal arched processes called auricula, each formed of two
pieces (Fig. 161, b, b). The auriculæ are supposed to be homologous
with the internal ambulacral ossicles of the starfishes and ophiurans or
brittle stars. Retractor muscles pass to the outer edge of the alveoli
from the auricula; the former are also connected with transverse mus-
cular fibres. The oral framework is also provided with protractor
muscles proceeding from the alveoli to the lower edge of the corona,
besides special muscles connected with the radii.
The food of the Echinida consists of seaweed or small shellfish and
crustaceans, or, in the case of those forms which are edentulous, of sea-
mud and coral sand, which contains much nutritive material. While
the teeth are useful in breaking up the harder parts of the food, no
grinding or true mastication is possible, as they only meet near their
sharp and slender points.
The study of this complicated and wonderful oral apparatus, which
may be easily indulged in at any watering-place by the sea, will afford
many hours of amusement and instruction to the curious student of
nature.
Among all the invertebrate animals a parallel to the variety in form
and importance in systematic classification of the teeth of vertebrates is
alone to be found with the Mollusca, and among them only with certain
groups.
The Mollusca have been divided into two principal groups by later
writers-the Cephalophora or Glossophora on the one hand, and the
Acephala or Lipocephala on the other. These have a general corre-
spondence with the possession or non-possession of a "head" or its con-
comitant, a muzzle and dental apparatus. Not every species of the
many thousands which comprise the Cephalophora (whelks, snails, peri-
winkles, coat-of-mail shells, limpets, tooth-shells, sea-butterflies, nauti-
lus, squid, or cuttle- and devil-fishes) are provided with teeth, but these
special instances are the exceptions to the rule. On the other hand, no
single member of the Acephala (clams, oysters, mussels, cockles, fresh-
water clams, scallops, etc.) has either a head or a dental apparatus.
The apparatus, reduced to its simplest terms (Fig. 163), consists of a
tube entering the floor of the gullet in the median line behind the mouth,
called the radular sac. The odontophore, or chitinous band upon which
the teeth are set, pointing upward and backward like the papilla on a cat's
tongue, grows out of the radular sac like a finger-nail from its sheath.
The odontophore and teeth collectively form the radula. The floor of
the sac is carried forward by natural growth in that direction, bearing
G
342
DENTAL ANATOMY.
•
FIG. 163.
d
the radula upon it, generally over an arched, cartilaginous mass known
as the buccal cartilage, and down to the front edge of the buccal carti-
lage immediately behind the mouth. This serves as an elastic pad by
which the denticulate surface of the radula may be pressed against any
object to be drilled or torn with the teeth. It is controlled by retractor
and protractor muscles, by which it can be pulled forward into the
oral opening or even be somewhat protruded a fact which can easily
be observed by giving a common wood-snail or large slug a bit of bread
or lettuce to eat. The tissues
about the cartilage are so loose
and flexible as to offer no ob-
stacle to the transfer. Beyond
this, in certain groups (as the
common whelk), the radular
floor, to which the odontophore
adheres closely, and with which
it moves, may be so loosely
attached to the buccal cartilage
as to slide over it like a towel
over a roller, and, controlled by
a complicated set of muscles,
may be made to move back and
forth, or even go through with
a semi-rotary motion upon the
buccal cushion. The radula in
this way may be made to act
the part of the strip of emery
or pumice cloth sometimes used
on the convex and not on the
in dentistry, only the rasping effect is
concave side. The annexed schematic diagram will indicate the rela-
tions of the parts.
In addition to the radula, the mouth of the cephalophorous mollusks
is often provided with a chitinous' armature of another sort. In many
mollusks a jaw or jaws are present, which may be a strong black pair,
recalling the jaws of a parrot, opposed to one another in the vertical
line and largely composed of a substance allied to chitin, as in the
squids and cuttles (reinforced with calcareous matter in the case of the
pearly nautilus); or merely an arch of delicate chitinous matter without
a lower jaw, as in some pulmonates; or a number of pieces composing
an arch, as in other land-snails; or a central upper piece of horny mat-
ter with a lateral accessory piece on each side, as in the pond-snails
(Limnæa, etc.). There are large groups, however, without a jaw.
Be

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miryally st
In
Sectional Diagram of Molluscan Radular Apparatus,
vertically divided: o, mouth; m, jaw or mandible;
7, lower lip; d, d', upper and lower epidermis of the
muzzle;, gullet;, teeth set on the odontophore,
which rests on the muscular radular floor, sup-
ported by the muscular buccal mass, from which
extend backward retractor muscles (k, le,), and in
which is (c) imbedded the buccal cartilage; s, the
opening of the radular sac; p, papilla which secretes
the teeth and odontophore.
¹Investigations by Troschel show that the teeth of most gastropods consist almost
wholly of chitinous matter. The radular floor or ribbon upon which they are inserted
contains about 94 per cent. of chitin and 6 per cent. phosphate of lime. The jaws of
Dolium and Helix pomatia show a 1 or 2 per cent. greater proportion of lime; other
helices would show hardly a trace. The references of previous naturalists to the pres-
ence of iron and silicon in the radula is supposed by Troschel to have been due to the
presence of a few sand-grains among the teeth analyzed. Slight differences doubtless
exist between different kinds of mollusks, which would explain the differing results of
various analyses.
THE TEETH OF INVERTEBRATES.
343
FIG. 164.
Some of the nudibranchs, or naked sea-snails, and cuttlefish have a sort
of spiny internal collar in the form of an oval ring, as well as a well-
marked mandible. The trumpet-conch
(Tritonium) has two heavy black spi-
nous pieces hinged above with cartilage.
The forms of the jaw are numerous and
afford good characters for classification,
but they all differ from the jaws of
other invertebrates, in that the motion
and action of the jaws are essentially
vertical, and not from the sides toward
the middle, as in insects and annelids,
though the accessory pieces may have a lateral motion. In some of the
Glossophora there is also a gizzard, which may be supplied with small
calcareous plates or stomacholiths, recalling the "gastric teeth" of
Crustacea.
difficul
Q

Jaw of Tritonium, showing one of the two
pieces of which the arch is composed.
Returning to the radula, we find in the innermost extreme of the
of the radular sac a papilla which forms the matrix of the teeth
and odontophore. This latter organ, whose situation has already been
described generally, consists of a ribbon of chitin longitudinally divided
into three areas. The central area or rhachis is bordered on each side
by a margin or pleura, which in many cases is bent up on each side so
as to form a gutter, with the rhachis at the bottom. In front of the
buccal cartilage the pleure are much widened laterally, so as to cover
and defend the front of the cartilage. In the Toxoglossa the teeth are
few in number, and appear to be inserted directly on the muscular
radular floor without an odontophore. The teeth are cemented to or
spring from the odontophore, in most cases having their points directed
upward and backward. They are arranged in longitudinal and trans-
verse rows, the former in straight lines; the transverse rows being gen-
erally curved or angulated symmetrically on each side of the median
line or tooth. Any of the longitudinal rows may be absent. In a very
few genera the radula is absent or the odontophore is edentulous.
The teeth are composed of a base, a shank or stem, and a cutting edge
or point, the latter simple or variously denticulated. The base is con-
spicuous in some forms, hardly evident in others; in some the surface
of the odontophore is elevated into a sort of boss beneath each tooth,
and among the limpets, etc., such bosses sometimes exist without a tooth
upon them. The shank may be short or long, simple or curiously orna-
mented, or perforated. The form of the cutting points is very varied,
and they are sometimes furnished with a minute brush-like appendage.
As a rule, the carnivorous forms have simpler and more claw-shaped
teeth.
The central tooth of each transverse row is normally symmetrical,
and the succession of them forms the median longitudinal row. These
teeth are called median or rhachidian teeth. They are generally pres-
ent, but are absent in a number of genera. On each side of the median
tooth are the lateral or pleural teeth. These are asymmetrical, being
rights and lefts, and having a tendency to bend toward the median line.
The number of longitudinal rows of laterals varies a good deal. They
344
DENTAL ANATOMY.
are most numerous in the land-snails, and may be wholly absent or
reach into the hundreds. Outside of the lateral teeth on each side are
frequently several series of flat, plate-like, or slender spiny teeth, which
are called uncini. They too may be very numerous, especially in the
vegetable-feeding sea-snails, or may be wholly absent. But in normal
cases, when one series is absent on one side of the median line it is also
absent on the other, so that the radula with respect to the teeth is bilat-
erally symmetrical. Abnormal radulæ are met with where the teeth
will be deformed or asymmetrical; in normal radulæ the anterior teeth
are usually broken and worn with use, and those in the posterior extreme
are soft, light-colored, and half formed, each longitudinal row of
teeth being secreted by the same pair of the radular papilla; if it is
abnormal at all, the abnormality extends through the whole row during
the life of the mollusk. The adult perfect teeth vary from nearly trans-
parent to an amber-yellow or reddish-brown, and sometimes the cutting
points are black. In any large whelk they are easily visible to the
naked eye; in large cuttlefish the radula may be an inch wide. On
the other hand, in some minute land-shells (Vertigo, etc.), where the
whole shell is hardly bigger than a pinhead, high powers are needed to
observe them. The radula may be quite short, reduced even to a single
pair of teeth in a few cases, while in the limpets it is very long, and in
one periwinkle (Tectarius pagoda) it has been found to be seven times
as long as the length of the animal's body. Such radulæ are of course
always coiled up, and only the anterior portion comes into use at any
one time.
Car
The form and arrangement of the teeth are of great use in classifica-
tion—a fact discovered by Prof. S. Loven of Stockholm in 1846. Since
this time many authors have studied them, and great advances have
thus been made in the systematic arrangement of mollusks; but the
number of species is so great and the workers are so few that a vast
amount remains to be done before we can consider the classification of
our American species to be placed on a sound foundation. The great
development of the groups of fluviatile and land snails (Helix, Limnæa,
Physa, Vivipara, Amnicola, etc. etc.) in the woods and fresh waters of
the United States puts it in the power of any one possessed of a toler-
able microscope to add solid facts to the treasury of science. Trusting
that this brief survey of the subject may lead some reader to interest
himself in it, I add the following instructions for examining the
radula of mollusks:
In large snails the radula and buccal mass may be easily dissected
out; in small ones the anterior part of the body, and in minute ones the
whole body (after breaking the shell), may be taken. With a pair of
forceps, a test-tube, an alcohol lamp, some watch-glasses, and some
needles fastened in little wooden handles, a little caustic potash, and a
microscope, the student is prepared for work.
The radula, or the part of the snail containing it, should be dropped
into about a teaspoonful of half-saturated solution of caustic potash in
water in the test-tube. This may then be gently boiled over the lamp;
too violent boiling may spill the contents of the tube. Held in the
forceps, the tube may be moved in and out of the flame as experience
THE TEETH OF INVERTEBRATES.
345
will soon indicate. In a few moments the soft parts disappear, leaving
the jaw and radula in the solution, which may be poured into a watch-
glass and the radula taken out on the point of a needle, washed in pure
water, and then put under the microscope. It will be found so curved,
except in very small mollusks, as to need the presence of a cover-glass
to bring it into focus: an ordinary live-box answers well. It may be
best examined in water as a medium. To get at the form and number
of the separate teeth, it will generally be necessary to tease the radula
to pieces with the points of two needles. When the radula is micro-
scopic and cannot be seen in the liquor potassæ, the watch-glass may
put on the stage and twirled round a little, when all the solid particles
will be impelled toward the centre and the radula found and picked out
under the microscope.
be
Tag
After drawing the various parts, so as be able to construct a diagram
of the teeth, the object should be preserved in a little tube or vial with
some weak alcohol and a tight stopper (rubber is the best), and suitably
labelled; or it may be mounted on a slide in the usual way, avoiding
Canada balsam, which will soon make it invisible unless stained.
The number of transverse rows of the teeth is of slight importance
compared with the exact representation diagrammatically of a single
transverse row or of the median tooth and one side of the
row, which
is in most cases all that is required.
The jaw is often too horny to bear much treatment with potash; the
teeth (except in some marine forms) are much more refractory; experi-
ence will soon guide the student, who may practise on common species
until he gains proficiency. The character of the jaw, especially of the
land-snails, is also important for classification, and it should be care-
fully delineated.
As the number of transverse rows may be large, and the number of
teeth in each row sometimes great, the total number of teeth is occa-
sionally surprising, and has been computed for some species at from
twelve thousand to forty thousand.
To describe the teeth of mollusks in detail would require several vol-
umes,¹ even in the present imperfect state of our knowledge. The
annexed illustrations will give a general idea of their character in some
of the chief groups of mollusks.2
It is a remarkable fact that if we divide the crawling mollusks, or
Gastropoda, into two great groups, one containing the hermaphrodite
and the other the unisexual forms, we shall find that in the former
(Monaca) the auditory sacs contain numerous small otoconia, and the
form of the radula is short and broad, the pleura imperfectly distin-
guished from the rhachis, and the teeth usually numerous and possess-
¹ Much assistance may be gained from Troschel's Gebiss der Schnecken, Berlin, 1856-
80, and in the works of Binney, Bland, Stimpson, and others on the land- and fresh-
water shells of the United States, published by the Smithsonian Institution at Wash-
ington. Woodward's Manual of Recent and Fossil Shells may also be advantageously
consulted. These are all cheap works. References to other literature of the subject
may be found in the annual volumes of the Zoological Record, published by Macmil-
lan, London.
S
2 The figures are placed in the text as if fronting the observer, with their cutting
points upward as in life (except Fig. 166); the right side of the radula is the left side
of the figure in each case.
346
DENTAL ANATOMY.
ing a general similarity to one another on either side of the rhachidian
row. In the mollusks where the sexes are divided (Diaca) we find
single otoliths in the auditory sac, and the radula tending to a more
long and narrow form, with the lateral teeth, in general, less numerous
and showing much more diversity of form among themselves. To these
generalizations there are a few exceptions, as in most laws of wide appli-
cation, but which may be accounted for on other grounds. The former
type of dentition has been termed "pavemental," as recalling the uni-
form blocks of a granite pavement, and the other "ribbon-" or "strap-
like."
The highest type of dentition is that which has been called toxoglos-
sate (or arrow-toothed), and which consists of two longitudinal rows of
slender hollow or grooved teeth, each row set on a slender, flexible chit-
inous thread, apparently representing the pleurae of the odontophore.
Each tooth is usually provided with a duct, which conveys a poisonous
fluid to near the point, and the latter is frequently barbed or arrow-
shaped, from which the name is derived. Examples of this group are
Conus and Bela, both marine forms, the former tropical, the latter
FIG. 166.
FIG. 165.
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Teeth of Bela.
Teeth of Conus, showing barbs and poison-duct.
northern, in distribution. The animal of Conus aulicus of the Moluc-
cas can give a severe bite. Admiral Sir Edward Belcher of the British
navy was bitten by one of them as he picked it out of the water, and
compared the acute pain which followed to the burning of phosphorus
under the skin. The bite, which was soon followed by a kind of blister,
was small, triangular, and deep. Troschel¹ has described the apparatus
of the gland and duct.
St



The Toxoglossa have no rhachis or rhachidian tooth, and no jaws; in
some of them the series is reduced to a single pair of teeth, and for a
time these were supposed to be edentulous.
Next to these come the Rhachiglossa, of which the typical forms
(Voluta) have only a rhachidian tooth, but the larger number, such as
FIG. 167.
AM
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Rhachiglossate Teeth: 2 Fig. 167. Single rhachidian tooth of Voluta.-Fig. 168. Transverse series in
Cynodonta. Fig. 169. Transverse series in Pusus antiquus.

FIG. 168.
Мамастан
FIG. 169.

¹ Geb. der Schnecken, ii., 1866, p. 15 et seq.
2 All the figures of teeth show single transverse rows, unless otherwise stated.
THE TEETH OF INVERTEBRATES.
347
the common whelk (Buccinum; Fusus, and Cynodonta are also examples)
have one lateral tooth on each side of the rhachidian. These teeth are
straight, are usually prettily denticulated on the cutting edge, and the
radula is long and strap-like. The jaw is represented by two lateral
rudiments, as in the next group. There are a few exceptional cases
where the tooth on the rhachis is reduced to an edentulous flat plate.
The bases of the teeth point forward in this group.
The Taenioglossa (bent-toothed) are a very extensive assembly, which,
amongst others, contains the largest part of our gill-breathing fresh-
FIG. 170.

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FIG. 171.

Tænioglossate Teeth. Fig. 170. Teeth of Rissoa.-Fig. 171. Teeth of Vivipara.
water snails. The teeth are bent so that their cutting edges turn toward
the base of the tooth, which is consequently set on the odontophore with
the base as well as the point turning backward, as otherwise the crea-
tures would bite out of, instead of into, their own throats. They have
a rhachidian and three lateral teeth on each side of it, and in a few
cases a few uncini, but these are very exceptional. Rissoa and Vivipara
are good examples of this sort of dentition.
A small group which has been called Ptenoglossa (feather-toothed)
is generally supposed to lie between the Rhachi- and Taenioglossa. Sca-
FIG. 172.
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Ptenoglossate Teeth: teeth of Scularia.
laria, or the wentle-trap, is an example of this kind. The animals are
marine, carnivorous, and have numerous slender similar lateral teeth
with a bare rhachis and no uncini.

Rhiphidoglossate Teeth: Teeth of Gibbula.
the immense number of needle-like uncini which
species. The rhachidian is usually present; the
variable; the uncini always numerous and similar.
M
The Rhiphidoglossa (needle-toothed) comprise an immense variety of
marine snails and a few operculated land- and fresh-water snails, such
as Helicina, Neritina, Gibbula and Haliotis. The name is derived from
FIG. 173.

exist in many of the
number of laterals is
They are set on the
348
DENTAL ANATOMY.
odontophore as in the Taenioglossa. In this group most of the species
have a well-developed mandible or jaw, usually hinged in the middle
line with a softer cartilaginous portion.
FIG. 174.

FIG. 175.
Rhiphidoglossate Teeth: Teeth of Haliotis.
The last of the great groups among the diœcious mollusks is that of
the Docoglossa (plate- or chevron-toothed), which includes the limpets,
and is divided into three principal subdivisions-one (Acmaa, etc.)
without a rachidian tooth, and rarely with uncini; another (Patella,
etc.), with well-developed uncini and laterals, and generally no rachid-
FIG. 177,
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FIG. 176.


Docoglossate Teeth: Fig. 175.-Teeth of Lepeta fulva-Fig. 176. Teeth of Acmaa virginea.-Fig. 177.
Teeth of Patella vulgata.
ian; the third (Lepeta), with a large rhachidian, without laterals, but
having uncini. All these forms have a well-developed jaw, and all are
marine. They are very archaic in their characters.
It merely remains to indicate the types of dentition among the her-
maphrodite mollusks, the majority of which are air-breathers, but which
have also many marine representatives, and a few which, like Limnoa,
the common pond-snail, breathe air, but live in the water, or, like
Siphonaria, live by the borders of the sea, and are prepared with gill
and lung to breathe whatever comes handiest.
The Helices (which are found under rotten logs, etc. in almost any
wooded place, and are recognizable by their depressed spiral shell and slug-
like body) have a typically pavement-like dentition. This resemblance is
common to many allied groups, such as Achatina, Siphonaria, Succinea,
etc., and the pond-snails, Limnæa, Planorbis, and others. The most
interesting and little known are the Physas, a group of beautifully pol-
ished pond-snails with a sinistrally wound shell.
The annexed figures indicate the character of the jaw and teeth in
several of the air-breathing mollusks. In some others the jaw is formed
THE TEETH OF INVERTEBRATES.
349
of several pieces, more or less overlapping and making the arch flexible,
thus facilitating the protrusion of the buccal mass in feeding. The
FIG. 178.
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FIG. 181.
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Jaws of Pulmonates: Fig. 178. Jaw of Tebennophorus.--Fig. 179. Jaw of Arion.-Fig. 180. Jaw of Glyp-
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teeth; C, outer laterals.
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FIG. 183.
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Teeth of Pulmonates: Fig. 183. Teeth of Achatina.—Fig. 184. Teeth of Siphonaria.—Fig. 185. Teeth
of Succinea. Fig. 186. Teeth of Limnaa; c, rachidian; 1, lateral teeth. In these figures the teeth
are represented as if seen from above and behind.
tilage, doubtless for the same purpose. In the pond-snails (Limnæa)
the arch has two small, delicately-hinged lateral pieces, which have a
1
350
DENTAL ANATOMY.
lateral movement in connection with the vertical movement of the true
mandible.
Having indicated the character of the teeth in divers forms of mol-
luscan animals, it remains only to refer to their functions. As already
stated, they are used for masticating vegetable or tearing animal matter
on which the creatures feed, and, in some cases, as weapons of offence
and defence. They have still another use-that of drilling through hard
substances, such as the shells of other mollusks for the purpose of
devouring the inhabitant. This causes the small round holes so com-
monly seen in dead shells on the beach. This process has been
watched, and is very slow in most cases, two or three days being
required by a Purpura to drill through a small clam-shell. Many
young oysters are annually destroyed in this way by a mollusk known
to the oyster-men as the "drill." Some of the tropical forms secrete
an acid which must hasten the process a good deal, but in most cases
the work is done by pure friction with the radula in a rotary manner.
After the hole is drilled the destroyer inserts his proboscis and sucks
the fluids of his victim. The traces of the teeth are perfectly visible
on the sides of the perforation. Their action may be watched by put-
ting a pond-snail on the glass walls of an aquarium where it has become
overgrown with green confervoid slime. A few of these snails are fre-
quently placed in aquaria for the purpose of keeping the walls clean.
St.
THE COMPARATIVE ANATOMY OF THE
TEETH OF THE VERTEBRATA.
BY JACOB L. WORTMAN, A. M., M. D.
A STUDY of the dental organs of the Vertebrata is one replete with
much interest when viewed from the standpoint of the naturalist. The
circumstance that their modification is so intimately associated with the
food-habits of the animal, being principally concerned in the prehension
and comminution of the food, and that to these same habits we must
look for the most powerful influences and incentives to modification in
general, causes them to assume more than ordinary importance in the
estimation of the philosophic anatomist who earnestly addresses himself
to the problem of vertebrate evolution.
The fact, too, that the perfect condition in which they have been so often
preserved in the fossiliferous strata of the earth's crust has frequently
furnished the only evidence which we possess of the existence of forms
long since extinct, causes them to be regarded as objects of still greater
interest. When we reflect that with nothing more to guide his judg-
ment than the dental series of an animal the expert paleontologist can,
generally, not only indicate with great certainty the character of the
food upon which the animal subsisted, but its general characteristics
and relationships as well, even though the date of its existence be
removed to a remote period in geologic history, but little surprise
can be felt that so much thoughtful attention has been bestowed
upon this set of organs.
No series of anatomical structures has proved of greater utility to the
systematist who has endeavored to indicate the exact relationship or
philogenetic history of mammalian forms than the teeth. Generally,
the student who attempts to master the subject is discouraged almost at
the very threshold of his undertaking by the apparently great diversity
of tooth-forms to be met with in the mammalian class; but if looked
at from a developmental point of view, and if a little careful attention
is bestowed upon the plan of organization of the teeth of certain groups,
it is not difficult to discover that there are certain central or primitive
types from which it is easy to derive other related forms of dentition.
by simple addition, subtraction, or modification of parts already pos-
sessed.
Careful attention to this subject for several years past, with the assist-
ance of the light which American paleontology is now able to throw
upon the question, has convinced me more and more of the truth of
this assertion; and I feel well assured that we are now in a position to
351
352
DENTAL ANATOMY.
lay down some broad principles in regard to dental evolution, at least
among certain groups of the Mammalia, where they have been subjected
to the greatest amount of modification.
Although there are many questions concerning the origin and details
of tooth-evolution of many aberrant forms which remain to be solved,
yet the discoveries which have been made in palaeontology within the
last twenty-five years leave scarcely a living group of animals, the
development of whose teeth has progressed beyond the primitive stages,
from which we have not gained some important information relative to
the phases through which they have passed to reach their present con-
dition. The possibility of reducing our knowledge of the dental struc-
tures of the Mammalia to a broad and comprehensive basis was long
since recognized by Prof. Cope, to whom probably more than any one
else we are indebted for a genuine philosophic insight into the forms
and structure of these teeth. Scarcely less important are the contribu-
tions of John A. Ryder and Dr. Harrison Allen, whose learned researches
into the probable causes of tooth-modification have marked notable
stages in the progress of the subject and have opened new and inter-
esting fields for investigation. Nor should we omit a mention of the
researches of Flower, nor those of Tomes, Waldeyer, Frey, Hertwig,
Magitot, and Legros, into the histology and development in later
times.
•
Commonly, teeth are defined as hard bodies attached to the parietes
of the mouth or oral extremity of the alimentary canal, whose chief
function is the seizure and comminution of the food. Morphologically
considered, however, they are specialized dermal appendages situated in
the buccal cavity, and characterized by the presence of certain calcified
tissue developed from the true derm or corium of the integument,
known as dentine. It will be seen from this definition that the term
"tooth," strictly speaking, is limited to those structures of the oral
cavity which alone possess such tissue, although it is a recognized fact
that to other epithelial or cuticular structures, found in many inverte-
brate and some few vertebrate forms, the term "tooth" has likewise
been applied.
While they all subserve the same purpose, and are therefore analo-
gous, their chief distinction consists in this-viz. in the latter, so far
as they have been investigated, these organs consist of a corneous or
horny substance, which is invariably derived from the more superficial
epidermal layer, and is therefore ecderonic in origin. In the former
a papilla arises from the corium, being sunk into a fold or pit, and
eventually undergoes more or less calcification from its summit down-
ward by a deposition in its substance of lime salts, forming dentine.
The dentine thus formed is a hard, elastic substance, consisting of
closely-set parallel tubuli, branching as they go, and whose crown may
or may not be invested with an exceedingly hard and unyielding sub-
stance derived from the deeper layers of the epidermis, known as enamel.
These are, then, enderonic in origin.
...
JA
Those of ecderonic source include the so-called teeth of Annulosa,
Mollusca, Insectæ, etc. among the invertebrates, as well as the horny
teeth of Ornithorhynchus, palatal plates of the Sirenia, and the horny
TEETH OF THE VERTEBRATA.
353
i
If the term "tooth "
teeth of the lampreys among vertebrates.
is applicable to these structures, then we must likewise include the
"baleen" of the Cetacea and the beaks of birds and reptiles, which by
common consent are far removed from true teeth. For all such I think
the term oral armature is preferable, from the fact that their produc-
tion not infrequently depends upon the modification of organs widely
different in origin.
On the other hand, those of enderonic source are found only within
the limits of the Vertebrata, and range in form from the simple cone
usual among fishes to the higher complex grinding organs of certain
herbivorous mammals. They all agree in being developed from the
corium of the lining membrane of the mouth, which is continuous with,
and really a part of, the integument, invaginated at an early period.
There is a possible exception in the pharyngeal teeth of fishes, which
Ryder considers to be of hypoblastic origin or developed from the base-
ment-layer of the mucous membrane of the alimentary canal, and which
are practically the same as those of epiblastic origin, as far as their
relation to the surface is concerned.
E
When we speak of teeth being modified dermal appendages, it will
not be amiss to cite the evidence upon which such a generalization rests.
This is best afforded by a study of the relationship and development of
the dermal armature of certain elasmobranch fishes, of which the shark
is a good example and furnishes us with one of the earliest, and there-
fore one of the most primitive, conditions of the Vertebrata.
In these fishes the defensive power of the integument is augmented
by the production of numerous hard bodies in its substance, which have
been termed "dermal denticles" by Gegenbaur. These structures,
which are likewise known as "placoid scales," are distributed over
the whole of the integument in shark-like fishes, and are ordinarily
FIG. 187.
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d
C
Vertical Section through the Skin of an Embryonic Shark: c, corium; c, c, c, layers of corium; d,
uppermost layer; 2, papilla; E, epidermis; e, its layer of columnar cells; ó, enamel layer (from
Gegenbaur, after Hertwig).
rhomboidal in form, with their apices directed obliquely backward.
They consist of a solid body, which is inserted by its base into the
VOL. I.-23
354
DENTAL ANATOMY.
corium, with an exposed part, which is covered with a substance indis-
tinguishable from the enamel of the teeth. The structure of the body
is likewise coincident with true dentine, and becomes fused with a basal
plate of osseous material. Their development is as follows: First, a
papilla arises from the uppermost layer of the corium, being covered in
by the epidermis (see Fig. 187). From the deepest layer of the epi-
dermis, or that which corresponds with the Malpighian layer, a special
epithelial covering is furnished, which eventually becomes, by a process
of histological differentiation, the enamel of the exposed part. The
papilla, before the conversion of its substance into dentine, exhibits a
central cavity, from which fine branched canals radiate to the surface.
Eventually, calcification takes place, beginning at the summit, and the
salts of lime are deposited in the substance of the papilla, giving rise to
the dentine. Gegenbaur observes: "The placoid scale has therefore the
structure of dentine, is covered by enamel, and is continued at its base
into a plate formed of osseous tissue; as they agree with the teeth in
structure, they may be spoken of as dermal denticles."
Now, in the early embryonic stages the integument bearing these
dermal denticles is pushed into the oral cavity, where they become
somewhat enlarged, and appear in the adult form as teeth. Tomes
says:2
2 "No one can doubt, whether from the comparison of the adult
forms or from the study of the development of the parts, that the teeth
of the shark correspond to the teeth of other fish, and these again to
those of reptiles and mammals; it may be clearly demonstrated that
the teeth of the shark are nothing more than highly-developed spines of
the skin, and therefore we infer that all teeth bear a similar relation to
the skin." Thus the generalization is reached that teeth are but spe-
cialized dermal appendages.
With this statement of the nature of teeth in general, we are now pre-
pared to begin a more special inquiry into the organization of a single
tooth. For this purpose I have selected the third lower premolar of
the dog as an average and easily-procurable example of a generalized
type among the higher forms, which will serve to illustrate the compo-
sition and nomenclature of the several parts of which all teeth, with few
exceptions, are made up.
For convenience of description, the several parts of most teeth can be
divided into crown, fang, and neck, although there are many in which
no true fangs are formed, owing to the persistent and continuous growth
of the tooth; in all such no distinctions of this kind can be recognized.
In the particular tooth under consideration, however, we can distinguish
without difficulty an enamel-covered crown, which corresponds with the
exposed part of the tooth in the recent state; two more or less cylindrical
fangs or roots, by which the tooth is implanted in the aveoli and attached
to the jaw bone; and a slight constriction at the point where the fangs.
join the crown, known as the neck (see Fig. 188). The crown in form
resembles a laterally compressed cone, with an anterior and posterior
cutting edge. It is covered by a dense shiny white substance of great
hardness, the enamel, which ceases at the point where the fangs com-
¹ Elements of Comparative Anatomy.
2 A Manual of Dental Anatomy.
>
TEETH OF THE VERTEBRATA.
355
FIG. 188.
mence. At the base of the crown the enamel is thrown into a conspic-
uous fold or ridge, which completely encircles the tooth at this point, and
is called the cingulum. Of the two cutting edges, the posterior is the
more extensive, and is interrupted in its descent from the summit of the
crown by a deep transverse notch, which constricts off
a prominent cusp known as the posterior basal tuber-
cle. A slight indication of a second cusp of this kind
is seen immediately behind it as an elevation of cingu-
lum. The anterior is the shorter, and descends from
the apex of the crown to the cingulum without inter-
ruption. It is placed nearer the inner than the outer
border of the tooth, and curves somewhat inward at
its lower extremity.

The fangs are two in number, occupying an antero-
posterior position, and give firm support to the crown.
They are covered by a softer substance, resembling bone-
tissue, known as cementum or crusta petrosa of human
odontography. This material is continued over the
entire surface of the crown as an excessively thin stratum in the unworn
teeth of the Carnivora and several other orders, but can be demonstrated
only by the most delicate manipulation and the use of the microscope. It
assumes a more important relationship with the crown, as we shall pres-
ently see, in the herbivorous species of mammals.
Of the two fangs, the posterior is the larger, but the shorter, and takes
the greater share in the support of the crown, although the cleft which
separates them at their summits is placed directly beneath the summit
of the crown. It is broad at its base, and tapers somewhat abruptly to
an obtuse point. It is traversed by a vertical groove upon its anterior
moiety, which fits into a corresponding ridge on the side of its socket.
The anterior root is the more slender and the longer of the two. It
tapers more gradually, and is likewise traversed by a broad, shallow
groove upon its posterior aspect. At the point of each fang will be seen
a small aperture, the apical foramen, through which the nerves and
nutrient vessels pass to the pulp.
So far, we have spoken only of the external appearance of the tooth
and of those substances which make up its outer coverings; but if both
the cementum and enamel were removed, it would still preserve its
original form, so great is the preponderance of the dentine as a constit-
uent element. This can best be seen in a longitudinal vertical section,
since at no part in an unworn tooth is the dentine exposed in these ani-
mals. Although the dentine is quite thick, and constitutes by far the
greatest part of the tooth, it nevertheless does not form a solid body;
on the contrary, a considerable cavity is hollowed out in its centre, this
being largest in the part which makes up the body of the crown, and
extending down each fang. This cavity lodges the dentinal pulp, the
formative and nutrient organ of the tooth, and is in communication
with the exterior by means of the apical foramina of the fangs.
While this structure, in common examples of enamel-covered teeth, is
observable with the unassisted eye, a more minute study of the organiza-
tion of the various tissues must be conducted with the aid of the micro-
Third Lower Premolar
of a Dog (Canis ja-
miliaris), enlarged.
-
356
DENTAL ANATOMY.
scope. This necessarily requires a considerable amount of experience
and skill in the manipulation and preparation of material, so that to
the unpractised observer a proper determination of the things which one
may see is not always an easy matter. On this account I have chosen
to follow the conclusions of the recognized authorities, especially the
excellent treatise on dental anatomy by Charles S. Tomes, in this brief
statement of the histology, rather than trust the accuracy of my own
observations on the same. Since the histology of human teeth has been
more fully made out than perhaps the histology of those of any other
animal, it is here taken for illustration, although I am fully aware that
important deviations from the structure here described are to be met
with among the Vertebrata.
Dentine. As we have already seen, the tooth consists of a dentine
body with a central cavity lodging the pulp, an enamel-capped crown,
and cementum-covered roots. The dentine is a hard, highly elastic,
translucent substance of a yellowish-white tinge, having a silky lustre
upon fracture. It is composed of an organic matrix highly impreg-
nated with calcareous salts; through this matrix closely-set parallel
tubuli radiate from the pulp-cavity toward the periphery in a direction
at right angles to the surface of the tooth.
▸
Of perfectly dry dentine the following chemical analysis is given by
Von Bibra :
Organic matter (tooth-cartilage)
Fat
Calcium phosphate and fluoride
Calcium carbonate
Magnesium phosphate.
Other salts
•
·
27.61
0.40
66.72
3.36
1.18
.83
The organic basis of the matrix, although closely related to that of
bone, is said not to be identical with it, and is hence called "dentine" or
"tooth-cartilage;" it is perfectly structureless and transparent. After the
tooth has been decalcified by submitting it to the action of dilute acid
for a few days, the matrix will still preserve the characteristic shape of
the tooth, and can readily be studied.
As already stated, the tubuli, which are likewise known as dental
tubes, permeate the matrix in all directions, opening freely upon the
walls of the pulp-cavity, by which arrangement all parts of the dentine
are brought into direct communication with the central nutrient organ,
the pulp. They are most nearly approximated and their diameters
greatest at their commencement on the walls of the pulp-cavity, but,
pursuing a somewhat wavy course, gradually diminish in size, owing
to the numerous branches which they give off. These branches, although
not uniform in size, anastomose freely with those of the neighboring
tubuli, and frequently show varicosities in their course. They termi-
nate either by gradually fading out, by anastomosing with other
branches, by ending in loops, or by entering the enamel and cement-
um layers.
Kome
While the dental tubes may be said to be channelled out in the sub-
stance of the dentine cartilage, the walls of the tubuli are not formed
by this cartilage, but each tubuli is furnished with a structure known as
TEETH OF THE VERTEBRATA.
357
the dentinal sheath, which accompanies it throughout all its plexiform
radiations. The structure of these dentinal sheaths is not certainly
known, owing to the impossibility of isolating them without decalcifica-
tion of the dentine. Some histologists believe that they are calcified,
while others express doubt as to the correctness of this conclusion. One
very marked peculiarity which they possess is their great indestructibil-
ity. Dentine when submitted to the action of strong acid for a suf-
ficient length of time to completely destroy the intervening cartilage,
or when boiled in caustic alkali, will still exhibit these dentinal sheaths,
for it is indeed only in this way that their presence can be demonstrated
satisfactorily. One writer (Magitot) denies their existence altogether.
Enclosed within each dentinal sheath is a soft fibril, the dentinal
fibrils, which take their origin from the cells of the odontoblastic layer
of the pulp, presently to be noticed, and of which there are sufficient
reasons for believing them to be nothing more than processes or pro-
longations. There is, however, considerable discussion upon the exact
nature and relationship of these fibrils. Magitot maintains that they
are continuous with a layer of reticulate cells which lie beneath the
odontoblasts; these freely communicate with processes of the odonto-
blasts, so that there is a very direct communication between the den-
tinal fibrils and the nerves of the pulp. He would therefore ascribe to
them a sensory function. Klein, on the other hand, holds that the
odontoblasts are concerned only in the formation of the dentine matrix,
and that the dentinal fibrils are long processes of deeper cells extended
between the odontoblasts. Whichever of the various views now held
may ultimately prevail, this much appears to be settled-viz. that the
dentine is extensively invaded, so to speak, by soft plasmic material
derived from the pulp, by which it is not only nourished, but also ren-
dered highly sensitive.
G
J
In the outermost layer of the dentine, which underlies the cementum,
numerous globular spaces are found, in which many of the dentinal
tubes end; these are filled with soft living plasma. These spaces,
if such indeed they may be properly termed, give to this layer a dis-
tinctly granular appearance, whence it was called by Tomes the "gran-
ular layer." Other structures, known as the interglobular spaces, pos-
sessing a ragged outline and short pointed processes, may frequently
be seen in dried sections of dentine. They are said by Tomes to be
most abundant at a little distance below the surface, and he believes.
them to pertain rather to a pathological than to a normal condition.
Add
The Tooth-pulp.-It appears best to describe in connection with the
dentine the pulp or formative organ, in consequence of the intimate
relation which exists between them. As has already been stated, it is
lodged in the pulp-cavity, and is the principal, if not the only, source
of blood- and nerve-supply to the dentine. In the young and growing
tooth, especially about the time calcification begins, it is largest and
assumes its greatest functional activity and importance, from the fact
that it is through its mediation that the dentine is formed; in fact, in
the early stages of dental development, as we shall hereafter see, it is
coincident with the dentine organ itself, of which in the adult tooth it
is the inconsiderable remnant. As senile changes supervene it gradually
4.
358
DENTAL ANATOMY.
loses its formative energy, and may become entirely obliterated. Taken
at the adult stage of the tooth, it is seen to consist of indistinct finely
fibrous connective tissue containing numerous cells. The outermost
layer of the pulp is known as the membrana eboris, and is made up of
a single layer of highly specialized cells of a dark granular appearance,
somewhat elongated, termed odontoblasts. These odontoblasts possess
large oval nuclei, and are provided with three sets of processes, as fol-
lows: the dentinal processes, which are identical with the dentinal fibrils,
and, as we have already seen, enter the dental tubes; the lateral pro-
cesses, by which they are connected with each other; and, lastly, the
pulp processes, extending down to a deeper layer of cells. This latter
layer of cells is somewhat intermediate in size between those more deeply
seated and the odontoblasts. Three or more arteries enter at the apical
foramen, and form a rich capillary plexus a short distance beneath the
membrana eboris. The nerves enter by several trunks along with the
arteries, and soon break up into a fine network in the substance of the
pulp. According to Boll, nerve-fibres penetrate the dentinal tubuli in
company with the dentinal fibrils, but this view is not fully accepted.
Cementum.—The cementum in human and many other teeth of similar
structure may be said to be confined to the roots, investing them exter-
nally, unless the enamel cuticle or membrane of Nasmyth, mentioned
above, pertains to it, which C. S. Tomes and others believe to be the
case. It, like ordinary bone, consists of a gelatinous base combined
with calcareous salts, and is permeated by vascular canals. Its histo-
logical structure presents so many characters common to bone that it is
difficult to consider it anything more than a slight modification of that
tissue. Just as in bone, large irregular spaces (lacunae), filled with pro-
toplasmic substance and presenting numerous minute radiating canals
(canaliculi), which anastomose with those of neighboring lacunæ, are
found in ordinarily thick cementum ; certain differences are, however,
seen to exist.
G
-
The lacunae of cementum, for example, are more variable in size
and are noted for the great length of their canaliculi. The direction,
too, of the canaliculi is generally parallel with that of the dentinal
tubuli, radiating from two sides only, whereas in bone-tissue they
radiate in all directions. It has been already stated that the dentinal
tubuli sometimes enter the cementum layer. When this is the case
they become continuous with the canaliculi of the most deeply dis-
tributed lacunæ. The outermost or granular layer of the dentine goes
so far toward establishing a complete transition in structure between the
cementum and the dentine that it is generally impossible to draw a
dividing-line and say where the one ends and the other begins. As to
limit of distribution of the cementum on the surface of the teeth in man,
monkeys, carnivores, and insectivores, different views have been expressed,
owing to the various constructions that have been placed upon the nature
and relationship of the enamel cuticle or Nasmyth's membrane, already
mentioned. Waldeyer, Huxley, and Kölliker hold that it is no way
connected with the cementum, but that it is a product derived from the
enamel, and is therefore epithelial in origin. C. S. Tomes, Magitot,
and Wedl, on the other hand, maintain that it is a part of the cementum
TEETH OF THE VERTEBRATA.
359
1
extended over the entire crown of the tooth, and becomes continuous
with its outermost layer in the vicinity of the neck. It is one of those
excessively thin membranes (not over 20 inch in thickness, accord-
ing to Kölliker) which are peculiarly indestructible and resist the ac-
tion of the strongest acids and alkalies. When stained with the nitrate
of silver, it shows a peculiarly reticulated structure resembling epithe-
lium, which is believed by Tomes to be due to the pitted surface on its
interior, by which it is applied to the enamel-prisms. Encapsuled
lacunæ are likewise found in its substance, which would be difficult to
explain if it were not a part of the cementum layer. Tomes has like-
wise traced its connection with the outer layer of the cementum on sev-
eral occasions, and is therefore firmly of the opinion that it is a continua-
tion of this tissue.
J
Enamel. The excessively hard, shiny substance investing the crown
of the tooth is the enamel. It is by far the hardest tissue to be met
with in the animal body, being at the same time the poorest in organic
constituents. Where it exists at all, it generally forms a cap of varying
thickness over the exposed part of the tooth, except in those instances
where there is an excessive development of cementum in this situation,
which causes it to occupy a position between the cementum and dentine,
as seen in the most exclusively herbivorous feeders, of which the horse,
cow, and elephant are good examples. Even here paleontological evi-
dence is quite conclusive in support of the proposition that their earlier
representatives possessed teeth with naked enamel-covered crowns. This
condition of nudity of the enamel is coincident with shorter cusps and
less elevated ridges of the crown, and, as we have good reasons to infer
from analogy, with more omnivorous habits of feeding. It can thus be
shown that this anomalous arrangement of the tissues is one acquired
comparatively late in the development of these forms for the exclusive
purpose of giving greater strength to the lengthened cusps, thereby
affording immunity from fracture during the act of mastication.
Von Bibra gives the following chemical analysis of the enamel of an
adult human tooth:
Calcium phosphate and fluoride
Calcium carbonate
Magnesium phosphate
Other salts .
Cartilage
Fat.
•
•
•
·
J
89.82
4.37
1.34
.88
3.39
.20
The proportion of the organic to the inorganic material is therefore 3.59
to 96.41, while in dentine it is 28.01 to 71.99. Its structure consists.
of minute hexagonal prisms, known as enamel-fibres or enamel-prisms,
whose long axes, broadly speaking, have a direction at right angles to the
surface of the tooth. It is a comparatively rare occurrence to find the
fibres pursuing a perfectly straight course from the dentine to the sur-
face, but such is found to be the case in the enamel of the manatee or
sea-cow and several other forms. Usually, they are tortuous, and fre-
quently decussate, as in the human subject, which renders it difficult to
trace the course of an individual fibre. A variety of patterns is pre-
360
DENTAL ANATOMY.
sented by the arrangement of these prisms in the enamel of different
animals, especially of the "gnawing quadrupeds," or rodents.
The prisms, when decalcified and isolated, exhibit slight varicosities
or enlargements, giving them a distinct transversely striated appearance,
not unlike that of voluntary muscular fibres. They are otherwise
structureless. It is maintained by Bödecker that the prisms are not
absolutely in contact, but that minute spaces exist between them which
are filled with active protoplasmic material, which becomes continuous
with that of the dentinal tubuli, thereby furnishing a means of nutrition.
Some investigators admit this interstitial substance, but attribute to it
no greater function than that of simple cementing material, while others,
again, claim that the prisms are in absolute contact, and that no inter-
vening substance is demonstrable. Owing to the disparity in extent
between the outer and inner surface of the enamel, as well as the fact
that the individual prisms do not decrease in size nor branch in their
course outward to the surface, considerable spaces would be left if it were
not that they are occupied by numerous prisms which do not penetrate
to the dentine. The prisms end in sharp-pointed extremities which are
received into corresponding pits in the enamel cuticle or membrane of
Nasmyth.
MANA
DEVELOPMENT.-Next in order will be briefly noticed the develop-
ment, so as to complete in this connection an entire statement of the
anatomy of a single tooth. It may be said that although teeth of dif-
ferent types differ to a wonderful degree in their forms, which would
scem to indicate differences quite as great in other respects, yet, in
fact, the plan of their development is substantially the same wherever
found. So far is this true that the description of the embryology of
one tooth will, with little modification, answer fairly well for all teeth.
The more important of these modifications in the details of development
will be discussed in connection with the teeth of the various subdivis-
ions of the Vertebrata.
We have already stated that the teeth are derived from the lining
membrane of the oral cavity, which blends with the integument at the
lips. The principal differences between the integument which covers
the surface of the body and the mucous membrane which lines the ali-
mentary canal are those of function and origin, the structure being
essentially the same. In the one the individual cells of the epidermal
layer become devitalized and scale off, while in the other they are
actively engaged in the secretion of mucous, gastric, intestinal, and
other juices during alimentation. The devitalization and consequent
"shedding of the skin" is greater in some forms than in others. In
the frogs and salamanders, for example, the skin is kept constantly
moist by an abundant mucoid secretion, and the epithelium of the integ-
ument may be said to be more "alive" in these animals than in birds,
reptiles, or mammals. The difference in origin consists in the import-
ant fact that the integument is formed from the epiblastic or outermost
layer of primitive embryonic growth, while the mucous membrane of
the alimentary canal is derived from the hypoblastic or innermost layer
of the same. In the early stages of the development of the embryo the
skin is more or less invaginated into the mouth-cavity, and partakes
TEETH OF THE VERTEBRATA.
361
The real point
somewhat of the nature of mucous membrane proper.
of blending is, in the embryo at least, not at the lips, but lies inside the
borders of the jaws. If, therefore, we limit the term "mucous mem-
brane" in this situation to that tissue which is of hypoblastic origin,
then the teeth of the jaws cannot be said to be developed from the
mucous membrane of the mouth, as is commonly stated, but from the
invaginated integument.
In many fishes teeth are found far back in the pharynx, and are
attached to the gill-arches and pharyngeal bones. I am informed by
Mr. J. A. Ryder, whose extensive knowledge of the embryology of
fishes renders his statements highly authoritative, that these teeth lie
beyond the limits of the invaginated integument, and are truly of hypo-
blastic derivation. If this be true, the generalization that all teeth are
modified dermal spines is certainly incorrect. It affords us, however,
an example in which identical structures have been produced from tissue
of vastly different origin in a similar manner, and in all probability
attributable to the same causes-viz. repeated stimulation of a particu-
lar point, which eventually gave rise to a calcified papilla.
The point at which a tooth is about to be developed is marked by a
proliferation of the cellular elements of the tissue in which it will ulti-
mately appear. These eventually arrange themselves into three organs,
which have been denominated the dentine organ, the enamel organ, and
the dental sacculus. This latter organ becomes so modified in some ani-
mals, in which coronal cement is extensively developed, as to merit the
distinction of cementum organ. Taken collectively, they represent the
tooth-germ. C. S. Tomes very justly remarks that "the tooth is not
secreted or excreted by the tooth-germ, but an actual metamorphosis of
the latter takes place." The three principal tissues, dentine, enamel,
and cementum, thus produced, are formed from their respective organs,
and consequently separate parts of the tooth-germ. Although many
adult teeth do not possess enamel upon their crowns (e. g. edentates or
sloths, armadillos, etc.), yet the presence of an enamel organ in the early
stages of growth is believed to be a universal feature of the development
of all teeth, and is one of the strongest arguments for their community
of origin, however much they may have been subsequently modified.
The Enamel and Dentine Organs.-In the earliest stages of the
development of a mammalian tooth, which is here taken for descrip-
tion, a slight longitudinal depression in the epithelium covering the bor-
ders of the jaws is noticeable; this is somewhat augmented in depth by
the addition of a ridge upon either side of it. At the bottom of this
groove the deepest or Malpighian layer of the epithelium grows down
into the corium as a continuous fold or lamina, being directed down-
ward and a little inward. In cross-section this fold resembles a tubu-
lar gland and extends throughout the entire length of the jaw. In the
positions where teeth are to be formed the lower extremity of this
lamina is considerably enlarged by the rapid multiplication of its con-
stituent cells. The continuity of the fold is now broken up, and the
structure which is destined to become the enamel organ appears as a pro-
cess of epithelium comparable in shape to a Florence flask (Fig. 189).
The outermost layer of the organ at this stage is made up of cells of
(*
362
DENTAL ANATOMY.
the columnar variety which still retain their connection with the Mal-
pighian layer above, from which they were orignally derived, while the
interior of the enlarged ex-
tremity is composed of polyg-
onal cells.
FIG. 189.
bc
d
a
J
As development proceeds, the
edges of the enlarged extremity
grow more rapidly downward
than the centre, which causes it
to assume a bell-shaped form,
with the concavity directed
downward. Synchronous with
this growth, a papilla arises
from the corium beneath and
is closely invested by the enamel
organ. The appearance of this
papilla marks the earliest stage
in the development of the den-
tine organ, but it will be well
to examine more closely at this
stage the structure of the enamel
organ. While it retained the
shape of the Florence flask its
periphery consisted of colum-
nar epithelium, the interior be-
ing made up of polygonal cells.
Coincidentally with its assump-
tion of the bell shape those cells
of the peripheral layer which are
brought into juxtaposition with
the dentine bulb or organ un-
i
<
dergo great elongation and en-
largement, forming very regular
six-sided prismatic bodies, and
are known as the enamel-cells.
transformed into a stellate retic-
The polygonal cells of the interior are
ulum composed of cells with remarkably elongated processes; these pass
through a series of unaltered cells known as the stratum intermedium into
the enamel-cells. Lastly, we have the outer layer, which is little changed,
and still remains connected with the Malpighian layer by a slender cord
of epithelium. This layer is called the external epithelium of the
enamel organ.
Before the dentine papilla makes its appearance "a dark halo," more
vascular than the surrounding parts and corresponding to the epithelial
lamina or fold which gives rise to the enamel organ, is to be seen in the
submucous tissue or corium. Immediately beneath the enlarged ex-
tremity of the enamel organ the dentine papilla is developed at about the
time this stage is reached by the enamel organ. In its peripheral layer
highly specialized cells with several sets of processes, odontoblasts-
already described in connection with the tooth-pulp-make their appear-
a
b.
с
d-
h
e
1
k.
C
J
h
3
2

a
AEM120
FEELERS WAS
C
-ƒ
h
-9
Three Stages in the Development of a Mammalian
Tooth-germ: a, oral epithelium heaped up over germ;
b, younger epithelial cells; c, deep layer of cells or
rete Malpighii; d, inflection of epithelium for enam-
el germe, stellate reticulum; 7, dentine germ; g
inner portion of future tooth-sac; h, outer portion
of future tooth-sac; i, vessels cut across; k, bone of
jaw (from Tomes, after Frey).
,
TEETH OF THE VERTEBRATA.
363
ance, while in the remainder of the bulb numerous other cells, identical
with those of the tooth-pulp, are developed. It also becomes highly
vascular. Very soon the odontoblasts nearest the surface undergo
metamorphosis into a gelatinous matrix, and their nuclei disappear;
they are next calcified from the summit downward, and we soon recognize
a thin dentine cap over the entire bulb, which gradually increases as
development proceeds. The central portions of the odontoblasts remain
uncalcified and form the dentinal fibrils, while the lateral processes occa-
sion the numerous anastomoses of the dentinal tubuli and fibrils seen in
the adult tooth. The dentine mass is gradually thickened by successive
increments from within by a repetition of the process above described,
so that it will thus be readily seen that the configuration of the dentine
body, and consequently the entire tooth, is established as soon as calcifi-
cation has fairly set in.
K
Returning to the enamel organ, we can now briefly follow its devel-
opment to completion. We have already seen that it consists of an
outer layer of columnar epithelium covering the convex portion, and is
connected by a slender cord with the Malpighian layer above. It con-
sists also in part of an internal stellate reticulum which passes by means
of a layer of rounded cells (stratum intermedium) into the enlarged,
greatly-elongated prismatic cells lining the concave lower surface, which
invests the dentine organ like a cap. Before the enamel is completed
the external epithelium, the stellate reticulum, and stratum interme-
dium disappear altogether, but before this atrophy takes place the neck
or epithelial cord of the enamel organ gives rise to the tooth-germ of the
permanent tooth as a diverticulum which is developed in the same way
as the germ of the first or deciduous tooth just described.
The essential part of the enamel organ, or rather that which ulti-
mately results in the formation of enamel, consists of enamel-cells.
These, as we have said, become greatly elongated and assume the form
of regular hexagonal prisms, which agree in shape with the calcified
enamel-prisms of the complete tooth. Just as in the odontoblasts of the
dentine, they are transformed into a gelatinous matrix, the nucleus dis-
appears, and calcification begins from above, the only difference being
that the enamel-prisms calcify completely, and are therefore not tubular,
while in the corresponding structures of the dentine dentinal tubuli are
left. Different views have been advanced in regard to the exact desti-
nation as well as the function of the several parts of the enamel organ
spoken of above as disappearing by atrophy. As to the fate of the
external epithelium, Waldeyer holds that after the disappearance of
the stellate pulp it becomes applied to the outer surface of the enamel
as the membrane of Nasmyth, which would certainly seem to be its
most natural fate; but Kölliker, Magitot, and Legros claim, on the
other hand, that it disappears altogether. Most authors believe that
the enamel organ is devoid of vascularity, but Beal asserts that there is
a vascular network in the stratum intermedium. If it be non-vascular,
then it is more than probable that the pulp represents stored-up pabulum
from which the requisite formative energy is derived. If vascular, it
then probably subserves a mechanical purpose only, as some authorities
believe.
364
DENTAL ANATOMY.
The Dental Sacculus and Cement Organ.-So far, no mention has
been made of the development of the dental sacculus. At an early
period in the growth of the dentine papilla a process of the submucous
tissue arises from its base and seems to grow upward on the outside of
both dentine and enamel organs, finally coalescing on top, so as to enclose
the growing tooth-germ in a shut sac, the dental sacculus. Whether
there is an actual growth of processes from the base of the dentine bulb,
or whether the adjacent connective tissue is transformed into it, appears
not to have been very accurately determined; at all events, the con-
nective tissue immediately in contact with the germ soon becomes
distinguishable from that external to it by becoming richer in cells,
vessels, and fibrillar elements. When the sacculus is fully formed, it
is made up of an outer and an inner wall, both richly vascular. The
outer wall becomes the dental periosteum, while in the inner wall,
especially in the vicinity of the roots, osteoblasts appear and are calci-
fied into cementum, as in the formation of ordinary bone-tissue. Its
close application to the surface of the enamel, and partial or imperfect
calcification in most teeth, give rise to the membrane of Nasmyth. In
those animals, however, in which coronal cement is formed, such as the
Herbivora, there is developed in connection with the inner wall, between
it and the enamel, a fibro-cartilaginous structure containing character-
istic cartilage-cells. These undergo calcification in a manner not dif-
ferent from that seen in the formation of cartilage bone, and produce the
cementum in the teeth of these animals. It is then known as the
cementum organ.
We have now made clear, we trust, as complete a statement of the
anatomy of a single tooth as is consistent with brevity, but which will
serve as a basis for the comprehension of the more special part of our
subject-viz. the morphology of the teeth in the various subdivisions of
the Vertebrata.
THE ACCESSORY ORGANS-THE TEETH, THEIR STRUCTURE, DEVEL-
OPMENT, REPLACEMENT, AND ATTACHMENT, IN FISHES.
It will be impossible to gain anything like a concise understanding
of the dental organs of this extensive assemblage of vertebrate forms
until we have first briefly outlined their classification. In this I have
followed Prof. Gill, believing that his interpretations more nearly coin-
cide with a natural arrangement.
It is a common practice of naturalists to consider the Vertebrata as
divisible into five classes, as follows: Pisces, or fishes; Batrachia, or
frogs, salamanders, etc.; Reptilia, or snakes, turtles, lizards, etc.; Aves,
or birds; and Mammalia, or mammals; but according to Prof. Gill
there are differences quite as great, if not greater, between certain mem-
bers of the old class Pisces as there are, for example, between some fishes.
and frogs. For this reason he divides the permanently gill-bearing ver-
tebrates, or those which aërate the blood throughout the entire life of the
individual by means of specially adapted organs known as "gills," into
four classes, which he defines as follows:
TEETH OF THE VERTEBRATA.
365
I. Skull undeveloped, with the notochord persistent and extending to the anterior
end of the head. Brain not distinctly differentiated. Heart none.
LEPTOCARDII.
II. Skull more or less developed, with the notochord not continued forward beyond
Heart
the pituitary body. Brain differentiated and distinctly developed.
developed and divided at least into auricle and ventricle.
A. Skull imperfectly developed, with no lower jaw. Paired fins undeveloped,
with no shoulder-girdle nor pelvic elements. Gills purse-shaped.
MARSIPOBRANCHII.
B. Skull well developed, with a lower jaw. Paired fins developed (sometimes
absent through atrophy), and with shoulder-girdle (lyriform or furcula-
shaped, curved forward, and with its respective sides connected below), and
with pelvic elements. Gills not purse-shaped
LYRIFERA.
ɑ. Skull without membrane bones ("a rudimental opercular bone" in Chimara)
gills not free, the branchial openings slit-like, usually several in number;
exoskeleton placoid, sometimes obsolete; eggs few and large.
•
•
ELASMOBRANCHII.
b. Skull with membrane bones; gills free; branchial openings a single slit on each
side, sometimes confluent; exoskeleton various, not placoid; eggs compara-
tively small and numerous
PISCES.
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The first of these classes, Leptocardii, includes a few small fish-like
animals, such as the well-known amphioxus or lancelet occurring on our
coast, in which no skull exists. They are in many ways most remark-
able forms, being the most primitive of all vertebrates, but as they are
devoid of teeth, this class can be dismissed without further consideration.
The next, Marsipobranchii, embraces the lampreys, whose "horny teeth"
have already been alluded to. The relationship as well as examples of
each order of the remaining two classes is expressed in the subjoined
table (p. 366), which is compiled from Dr. Gill's papers on the
classification of fishes.
C
The Accessory Organs.-A consideration of these organs necessarily
involves not only a study of the bones and cartilages taking share in
the boundary of the oral cavity, but of all bones and cartilages in connec-
tion with which teeth are developed. It would likewise properly include
a mention of the muscles which move these parts, together with the vas-
cular and nervous supply; but owing to their great range of variation,
as well as the limited space at my disposal, these latter will not be con-
sidered. This, in my judgment, is best accomplished by describing the
normal arrangement in some typical fish and comparing all others with
it. For this purpose a gadoid fish, or one of the cod tribe, is most suit-
able, since it exhibits the structure which obtains in a large majority of
ichthyic forms.
If a well-cleaned skull be examined, it will be seen to consist, in the
first place, of a cranium or brain-box, or that part which remains intact
after the skull has been boiled or macerated a sufficient length of time
to cause the soft parts to disappear and the arches and appendages to
become disarticulated. This contains the brain, and becomes continuous
at its lower back part with the vertebræ or axial pieces of the body skele-
ton into which the spinal cord passes. Suspended from either side of its
posterior portion there is a chain of bones which extends down beneath
the throat and bears the pectoral fins; this is known as the shoulder-gir-
dle or scapular arch (see Fig. 190).
SALE
A short distance in front of this, or at a point about midway between
the root of the scapular arch and the eye-socket, another arch springs
366
DENTAL ANATOMY.
Class, LEPTOCARDII: example, lancelet.
Class, MARSIPOBRANCHII: ex. lampreys.
Class, ELASMOBRANCHII
Class, PISCES
Sub-class, HOLOCEPHALI: ex. chimera.
Sub-class, PLAGIOSTOMI
[ Sub-class, GANOIDEI
Sub-class, TELEOSTEI
Orders,
Super-orders,
Orders,
Raiœ: ex. rays, sawfishes, and torpedos.
Squali: ex. sharks.
Hyoganoidei
Brachioganvidei
Dipnoi
Chondroganoidei
Order, Order, Order, Order,
Cycloganoidei: ex. bowfin.
Rhomboganoidei: ex. bony gars.
Crossopterygia: ex. polypterus.
ghli
Bo
Sirenoidei: ex. mudfishes.
Selachostomi: shovel-nose sturgeon.
Chondrostei: sturgeons.
Opisthomi: spiny eels,
Apodes: ex. eels.
Scyphophori.
Nematognathi: ex. catfishes.
Telecocephali: ex. carp, herring, salmon, pike, perch, etc.
Pediculati: ex. batfishes, anglers, etc.
Lophobranchii: ex. sea-horses.
Plectognathi: puffers, foolfishes, etc.
TEETH OF THE VERTEBRATA.
367
known as the hyo-mandibular arch (see Fig. 204). Attached to the
the proximal portion of the lower jaw, which is attached to it; this is
from the side-wall of the cranium and passes downward and forward to
pos-
Fata
FAC
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FILTE
ENER
INDIA
cl
TIRETE
Фр
sop
sc
V
scl
act
ptm
со
sb
FIG. 190.
eo hy
stm
br
br
sy
fr ept pf
sor ps
mpt
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a. mik
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ecpt
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bh
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TILX
d
pmx
fr
top pop
Skull of the Codfish (Gadus morrhun): pmx, premaxillary; n, nasal; 7, lachrymal; pf, prefontal; ept, ecto-pterygoid; fr, frontal; sy, symplectic; hy, hyo-mandib-
ular; eo, epiotic stm, supratemporals; so, supraoccipital; ptm, post-temporal, first vertebra: see, supraclavicle: c/, clavicle; op, operculum; sop, suboper-
culum; sc, scapula: fr, fin rays: ac, actinosts; co. coracoid; br, branchiostegal rays; top, interoperculum; pop, preoperculum; ch, cerato-hyal; uh, uro-hyal;
sphenoid.
bh, basi-hyal; art, articular; d, dentary; mx, maxillary; pl, palatine; qu, quadrate; ecpl, ecto-pterygoid; mpt, meso-pterygoid; so suborbital; ps, para-

368
DENTAL ANATOMY.
terior portion of this arch are several broad, flat, scale-like bones which
cover the gills and are called opercular bones. The upper posterior one
is the operculum. The one in front of this, presenting a curved outline
anteriorly and a posterior serrate border, is the preoperculum, while the
two beneath are the interoperculum and suboperculum respectively. The
arch itself is composed, first, of the hyo-mandibular bone (Fig. 190,
hy), which by its proximal extremity is attached to the side-wall of the
cranium, being lodged in a distinct oblong socket; secondly, of the
quadrate (qu, Fig. 190), which articulates with it by suture at its lower
extremity; thirdly, the symplectic, a small splint occupying a groove
in the inner side of the quadrate; and, lastly, the lower jaw, which is
movably articulated with the quadrate and which normally supports
teeth. Each half is made up of the dentary or tooth-bearing piece,
meeting its fellow of the opposite side in the median line or symphysis,
and an articular piece which connects the dentary with the quadrate.
To this may be added the coronoid, a small bone superimposed above
the junction of the articular and dentary, and an angular which lies
just beneath the articulation of the quadrate and articular.
From the region of the quadrate another chain of bones extends
upward, forward, and inward to the anterior part of the roof of the
mouth, where it is attached by ligament to the side of the vomer, or
that bone which forms the prominent rostrum of the cranium after the
removal of the arches. This chain is known as the palato-quadrate
arch, and the bones entering into its composition are the ento-, meso,
ecto-pterygoids and the palatine. The ento-pterygoid is applied to the
hyo-mandibular and quadrate upon their anterior margins; the meso-
pterygoid starts out from the quadrate and ento-pterygoid, and extends.
toward the vomer, where it meets the palatine, which completes the
arch. The ecto-pterygoid lies above the junction of the meso-pterygoid
and the palatine (Fig. 190).
Immediately in front of the vomer, and attached to it and to the pala-
tines, are two considerable bones which project downward and backward,
bounding the upper posterior portion of the canthus of the mouth-the
superior maxillaries. In front of these, again, are the pre- or intermax-
illaries, limiting the anterior boundary of the oral cavity above.
Another bone, which in some forms (ex. catfishes) reaches the roof of
the mouth, needs to be noticed in this connection. The suborbital
ring, or those bones which encircle the orbit below, articulates by its
most anterior piece (lachrymal) with a bone suturally united to the
cranium and taking part in the boundary of the orbit in front and
above. This is the prefrontal, and, as already remarked in the cat-
fishes, owing to the width of the mouth takes part in the formation of
its bony roof, and in some species bears teeth. This bone is frequently
mistaken for the vomer, but, as I have recently ascertained, is certainly
the prefrontal, which must likewise be added to the category of tooth-
supporting bones in fishes.
The several arches and bones so far enumerated, with the exception
of the scapular arch-which never, to my knowledge, is dentigerous-are
in direct relation with the mouth, and are exclusively concerned in pre-
hensile and crushing functions; but those which are to follow, especially
S
TEETH OF THE VERTEBRATA.
369
the branchial arches, were primarily used in connection with respira-
tion, so that any relations with the teeth which they may have subse-
quently acquired must be looked upon as a secondary modification.
This peculiarity, moreover, is of such wide application in the class
Pisces that a description of these parts cannot well be omitted in a con-
sideration of the accessory organs.
The hyo-branchial skeleton lies beneath the base of the cranium, and
is pretty well concealed in a side view by the opercular, hyo-mandibular,
and quadrate bones. It is connected with the rest of the skull at two
points-viz. by the articulation of the stylo-hyal bone with the hyo-
mandibular, and the other by means of loose connective tissue which
binds the upper portion of the branchial arches to the base of the cra-
nium. Its general structure will be best understood by describing it as
composed of a series of transverse bony arches placed one in front of the
other, rising up from the floor of the mouth and meeting in the median
line above.
Gall
The most anterior of these is the hyoid arch, which is formed by two
median basilar pieces upon either side, the basi-hyals. Passing from
within outward, we have first the cerato-hyals, to which are appended
the branchiostegal rays. The next piece in the arch is the epi-hyal, fol-
lowing which is the stylo-hyal. This latter bone is a slender rod, and
serves to complete the connection of the hyoid arch with the hyo-man-
dibular bone. From the interval between the two most anterior basi-
hyals there projects a small bone forward which supports the tongue, and
is hence called the ento- or hyo-glossal. Projecting backward from the
inferior surface of these same basi-hyals is another piece, the uro-hyal.
Behind the hyoid, and similarly composed, are the five branchial
arches, of which the last two are somewhat modified. The three ante-
rior ones are made up of median basilar bones, the basi-branchihyals.
With these are articulated the hypo-branchials upon the outside, after
which follow the cerato-branchial and epi-branchial pieces. In the
fourth branchial arch, counting from before backward, the hypo-
branchials are absent, and the uppermost segments are considerably
dilated and support teeth; they are then known as the superior pharyn-
geal bones. The fifth arch is quite rudimentary, containing only the
cerato-branchial elements, which are generally much enlarged and bear
teeth; these are the inferior pharyngeal bones.
The arrangement here described is found without substantial modi-
fication except as regards relative size and the degree of ossification of
the several parts in nearly all the sub-class Teleostei. In the Elasmo-
branchii, however, the skull remains largely cartilaginous, and the hyo-
mandibular arch is always more or less imperfectly represented. The
maxillæ and premaxillæ are likewise absent. In the chimeroid division.
(Holocephali) neither the hyo-mandibular nor quadrate elements can be
made out, the mandible being attached directly to a broad triangular
cartilaginous lamella which stretches out from the sides of the base of
the skull, and whose anterior part bears the teeth of the upper jaw. It
will thus be readily understood that this cartilaginous plate, continuous
with the chondro-cranium, represents both the undifferentiated upper
portion of the hyo-mandibular and all of the palato-quadrate arches.
VOL. I.-24
370
DENTAL ANATOMY.
M
In the Plagiostomi (sharks and rays), on the other hand, a separate car-
tilaginous element representing the hyo-mandibular bone is always pres-
ent, and affords an articular surface to the lower jaw or mandible, which,
moreover, in all the elasmobranchiates consists of a single cartilaginous
bar, the primitive Meckelian cartilage. The palato-quadrate arch is
likewise present and forms the dentigerous border of the upper jaw (see
Fig. 204). Since the hyo-branchial skeleton in these forms is not con-
cerned in the support of teeth, it can be dismissed without further
mention.
The principal deviations in the structure and relationship of the den-
tigerous apparatus from the typical teleostean one to be met with in the
sub-class Ganoidei are furnished by the Dipnoi and Chondroganoidei.
The former of these orders includes the three living genera Ceratodus,
Protopterus, and Lepidosiren of Australia, Africa, and South America
respectively. They are most remarkable and interesting representatives
of types in some respects low down in the scale of ichthyic organization,
while in others high, in that they furnish many transitional characters
between true fishes and the Batrachia (frogs and salamanders). It is
highly probable that from some as yet undiscovered relative of this
group the Batrachia have been derived by descent.
In this order the skull is devoid of both maxillæ and premaxillæ,
and, as in the chimeroid elasmobranchiates, the hyo-mandibular arch is
not completely differentiated, the lower jaw being articulated directly to
the cranium. There is, however, a well-defined palato-quadrate arch
supporting teeth. The hyo-branchial skeleton, although resembling the
teleostean type of structure considerably, is edentulous. In the Chon-
droganoidei (sturgeons) the skull as well as the arches remain largely
cartilaginous. The suspensorium (proximal part of the hyo-mandibular
arch) presents two elements, usually homologized with the hyo-mandib-
ular and quadrate pieces of the teleostean skull; the latter of these
pieces affords attachment to the mandible. There is also a palato-quad-
rate arch. Only one species of this group, the shovel-nose sturgeon,
possesses teeth, and these, according to Owen, appear only in the young.
The remainder of the Ganoidei agree with the Teleostei in the structure
and arrangement of the accessory organs. The latter sub-class, how-
ever, exhibits numerous minor variations, which are confined principally
to modifications of the hyo-branchial skeleton, such as the loss or atrophy
of certain of its component elements; these are so numerous and varied
in their nature that it would be impossible, and quite foreign to the
object of the present article, to enumerate them.
Teeth of the Elasmobranchii.-As already observed, this class is divis-
ible, not only by the differences which obtain in the arrangement of the
several arches, but by the disposition, structure, and manner of replace-
ment of the teeth, into two primary groups, of which the sharks
and rays constitute one, and the Chimære the other. Of these, the
former is the more primitive, and in all probability gave origin to the
typical fishes, while the latter resembles more closely the dipnoans, and
may indeed prove to have been their ancestors.
The teeth of the sharks are always numerous, and are pre-eminently
adapted to the predaceous habits of their possessor. They are borne
Making
TEETH OF THE VERTEBRATA.
371
upon the cartilaginous mandibuli and palato-quadrate arches, being
attached not to the cartilages themselves, but to a thick, dense fibrous
membrane which forms an external investment. They are arranged in
concentric rows on the summit and inner surface of the jaws, being
developed from the bottom of a longitudinal fold of the lining membrane
in this situation, known as the thecal fold. The teeth of the upper-
most row, or those occupying the margins of the jaws, stand upright
and do service as the functional ones until discarded; those of the next
row, as well as all the succeeding ones, usually occupy a recumbent
position, with their apices directed downward or upward according as
they belong to the upper or lower series; but it not unfrequently hap-
pens in some species that the second, and even the third, rows may
exhibit different degrees of erection. As a general rule, but a single
row of teeth are in use at one time. The individual teeth composing
the longitudinal rows may be disposed with reference to those of the
succeeding ones so as to be parallel vertically, as is well exemplified
in the genus Lamna, or they may be placed in such a manner as to
alternate with each other, a condition seen in the blue shark (Car-
charias). As would naturally be surmised from this arrangement, the
way in which succession takes place is for the row beneath to rise up
and take the place of those in use. This is accomplished by the fibrous
gum in which their bases are imbedded sliding bodily over the curved
surface of the jaws from within outward, continuously bringing fresh
rows into position, as was long since demonstrated by Prof. Owen.
It thus happens, on account of this peculiar and, in my judgment,
remarkably primitive manner of succession, that large numbers of teeth
little worn are cast off during the life of each individual, and that
replacement goes on far in excess of the actual requirements of the ani-
mal, and quite independently of their temporary use as organs
of pre-
hension and mastication-a fact which in itself demonstrates their der-
mal relationship. The only assignable cause for this extravagant devel-
opment of teeth, it appears to me, is due to inequalities in the rapidity
of growth in different parts of the body, which causes the integument
invaginated during embryonic development to be restored or evaginated
during adult growth. If this hypothesis be correct, then the whole
question of the force concerned in the succession of the teeth is reduced
to the simple explanation of inequalities of growth primarily, however
much it may have been subsequently complicated and obscured in the
higher forms. Looked at from this standpoint, it is not such an
inscrutable mystery as C. S. Tomes and others would have us believe.
M
Considerable variety of form exists in the teeth of the different species;
they may be heterodont (that is, different in various parts of the jaws);
isodont (alike throughout); or hemihomodont (in which the individual
teeth of the lower jaw are alike, but different from those of the upper
jaw, and reciprocally). In all, the teeth nearest the back part of the
mouth are smaller than those in front. The simplest form to be met.
with is the unmodified cone with a sharp point and a broad base. Such
is found in the large Rhinodon and some "dog-fishes;" to this may be
added basal denticles, as in the genus Lamna; or it may have a com-
pressed triangular outline with serrate edges, as in the upper teeth of
God.
372
DENTAL ANATOMY.
the blue shark (Carcharias). These lateral serratures may become so
strongly developed as to give to the tooth a distinct comb-like appear-
ance-e. g. lower teeth of Notidanus (Fig. 191).
FIG. 191.

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Teeth of Notidanus (after Gunther).
The most remarkable modification in the dental organs of sharks is
exemplified by the Port Jackson shark (Cestracion), in which the poste-
rior teeth gradually become broad and form a regular pavement on the
surface of the jaws similar to that seen in many rays. This structure
exists in consonance with the shellfish-feeding habits of the animal, in
the exercise of which great crushing and comminuting power is required
to be exerted. These fishes are of especial interest, inasmuch as they are
the only living representatives of an extensive and widely-distributed
group which appeared on the earth far back in the Devonian Epoch,
and whose remains, as Owen justly remarks, "would have been scarcely
intelligible to us unless the key to their nature had been afforded by the
teeth and spines of the living cestracionts."
The teeth of the anterior part of the jaw (Fig. 192) are the smallest,
and present a compressed conical form with the apex produced into a
sharp point. Proceeding backward, they gradually assume an oblong
oval outline, progressively increasing in size, their sides becoming
applied to each other in such a manner as to form a regular pavement.
The maximum size is attained at about the fourth tooth from the poste-
rior end of the series, after which they decrease rapidly, although still
preserving their modified crushing form.
The progressive changes in size and form, as well as the disposition,
of the most highly modified teeth in this animal, are seen to be in direct.
accord with the uses to which they are put, and serve to illustrate, as so
TEETH OF THE VERTEBRATA.
373
inany other dentitions do, the reasonableness of the view originally pro-
posed by J. A. Ryder, to the effect that mechanical causes have been
largely instrumental in bringing about the modifications of the teeth.
It will be readily understood that the greatest mechanical advantage
would be gained and the greatest pressure exerted by passing the mor-
sel to be crushed to the posterior part of the mouth. The teeth in this
situation or in its vicinity have sustained the greatest amount of strain,
and are consequently most modified, while those of the anterior part of
the mouth have been largely exempt from such influences, and are there-
fore little modified. I will have occasion to recur to this hypothesis on
a future page.
The teeth of the rays present quite as great, if not a greater, range of
variety than do the sharks. In general, they are more numerous, more
closely crowded together, and possess forms better adapted for crushing
than for seizing and lacerating. They are developed in the same way as
in sharks, rising up from the bottom of a thecal fold on the inner sur-
face of the jaw and being carried upward by a rotation outward of the
FIG. 192.

←~?»«~~
Lower Jaw of Port Jackson Shark (Cestracion phillippsi).
membrane in which they are imbedded. In Raia stelluata, from the
California coast, the teeth succeed one another vertically, as in Lamna
among the sharks, and do not form a close pavement on the biting sur-
face of the jaws, they being separated from each other by slight intervals.
In form the base of the crown represents an equilateral triangle, with
the apex directed forward; from this a prominent ridge passes back-
ward across the middle line of the base, and is produced into a sharp
conical point. The teeth of the anterior part of the mouth are the
largest, and gradually decrease in size as the canthus or angle of the
mouth is reached. In the "barndoor skate" (Raia lavis) the teeth
374
DENTAL ANATOMY.
are more closely set, but are not in absolute contact; as in Raja stelluata,
those of the several rows are arranged vertically, but their bases are
more rounded, with only a faint indication of the backwardly project-
ing cusp, which is confined to the teeth of the anterior part of the jaws.
In the common "stingray" (Trygon centrurus) the teeth are some-
what quadrangular, and have their sides directly applied to each other,
forming a dental sheath of continuous pavement over the working sur-
face of the jaws; those of the successive rows are disposed diagonally.
Their crowns are of an oval form, well adapted for crushing and grind-
ing hard substances. The "eagle rays" or "sea-devils" present a series
of modifications of the teeth which diverges from that of the stingrays,
and terminates in the most unique of all dentitions to be found amongst
the Vertebrata-viz. that of Aetobatis. Of this group the genus Rhi-
noptera possesses tessellated teeth with flat hexagonal crowns, of which
FIG. 193.
a
d
Ma




h
C
Teeth of Rays: a, b, Rhinoptera; c, Myliobatis; d, Aëtobatis.
the median or anterior ones may be elongated transversely. The fossil
species, R. Woodwardi, has the three median vertical rows enlarged.
In Myliobatis there is only one large median row, with three smaller
ones upon either side, while in Aëtobatis the teeth of the median row
alone remain, and are articulated to each other by a finely serrate border.
These modifications are well shown in the accompanying figures. The
anomalous sawfish (Pristis), although in no way peculiar as far as the
teeth of the mouth are concerned, nevertheless possesses a remarkably
elongated snout, armed upon either side by a row of hard, conical bodies
usually referred to as teeth. In their histological structure they agree
with true teeth, but exhibit the peculiarity of being lodged in separate
sockets and growing from persistent pulps-a condition unusual among
fishes. It is more than probable that they are dermal spines specially
developed in this situation for some important purpose which is not at
present fully determined.
TEETH OF THE VERTEBRATA.
375
I proceed next to consider the teeth of the Chimæræ (Holocephali),
which group some authors make equal in rank with the Elasmobranchii,
which then include the sharks and rays only. The peculiarities of the
dental succession alone of this latter group, it appears to me, is quite
sufficient to separate them widely from all others, and it seems some-
what remarkable that this character has never been utilized by the
systematists in their schemes of classification.
▼
The teeth of the "ratfish" (Chimera plumbea) are six in number, of
which two belong to the lower and four to the upper jaw. The two
inferior ones may be described as broad, slightly-curved plates of mod-
erate thickness in the form of a right-angled triangle. That border
which corresponds to the perpendicular is almost straight, and is lodged
in a shallow groove which runs lengthwise along the inner surface of
the jaw; that which represents the base is applied to the corresponding
surface of the opposite tooth; while the border representing the hypoth-
enuse forms the free cutting edge of the tooth. This border is some-
what devious, being interrupted by three prominences. The inner
surface is also slightly ribbed. The two posterior upper teeth are
similar plates of a quadrilateral form with their free edges roughly
serrate. The two anterior teeth above somewhat resemble ordinary
mammalian incisors, and are large and scalpriform. This peculiarity
has given them the name "rabbit-fish" or "ratfish." Each tooth
has a cavity in the edge by which it is attached and in which the pulp
is lodged. But a single set of teeth are developed during the life of the
individual, and these are of persistent growth. Another living allied
genus, Callorhynchus, is found in Australian seas, in which the teeth are
similar to those of Chimera, but in the two fossil genera, Edaphadon
and Passalodon, supposed to belong to this group, the teeth are anky-
losed to the jaw, which is more or less bony. On this account it is
more than probable that they are to be referred to the dipnoans rather
than to the chimæroids.
The Teeth in True Fishes.-The teeth of the class Pisces, although
apparently presenting an extensive range of modification, have not,
debarring the dipnoan ganoids and the plectognath teleosts, as a general
rule, departed very widely from the simple conical pattern. There are
some forms, however, in which the structure and arrangement are quite.
anomalous. It is in this group that the maximum development, as far
as numbers is concerned, is reached. The salmon, pike, and some per-
coids may be cited in which teeth are developed in almost every con-
ceivable part of the mouth and number many thousands; while in
others, as the carps and suckers, they are few and confined to the
pharyngeal bones. In others, again, as the pipefishes and sea-horses,
teeth are entirely absent.
In
The teeth of the dipnoans are unique among fishes, and, like those of
the chimæroids, are limited in number and grow from persistent pulps.
The teeth of the dipnoans, the dental plates of the chimæroids, and the .
so-called “rostral teeth" of the sawfish are the only examples so far
known of permanent teeth to be met with among piscine forms.
The dental armature of Ceratodus Fosteri (Fig. 194), which may be
taken as illustrative of this peculiar group, has six teeth, of which four
376
DENTAL ANATOMY.
FIG. 194.
belong to the upper and two to the lower jaws.
Those of the upper series are supported upon the
palato-quadrate arches and upon a cartilaginous
plate which corresponds in position with the
Those of the lower series are set upon
the inner piece of each dentary bone, and be-
come firmly attached thereto by ankylosis.
vomer.
The two most anterior, and by far the smallest
of the upper pairs of teeth, form cutting plates
which resemble somewhat the crown of a broad
incisor with the posterior border well rounded
off. They are arranged in the form of a V, with
the point directed forward, having their greatest
extent in an anterio-posterior direction. After
a considerable interval the two large peculiarly
constructed upper back teeth appear, similarly
placed in the form of a V, and co-ossified
with the bony arches. Their greatest length is
quite equal to one-third the entire length of the
skull, the breadth being much less. Each of
these dental plates-for such they may be prop-
erly called-has a slightly curved internal bor-
der, with the convexity directed inward. The

Ceratodus: a, a, teeth of same.
(
!
a
TEETH OF THE VERTEBRATA.
377
lower or working face presents internally a considerable flat pitted surface
reaching the entire length of the tooth, whose plane is directed outward
and a little upward. It is slightly broader in front than behind. The
outer border is indented by five wide vertical grooves, forming six verti-
cally convex lamelliform projections, which encroach somewhat upon the
flat surface internal to them as well-defined parallel ridges; the anterior
one passes entirely across the face of the tooth, or, rather, skirts its anterior
margin, and becomes continuous with the slightly elevated internal bor-
der in this situation. The grooves are deeper in front than behind, leav-
ing the anterior projections the most pronounced, while the last one is
scarcely perceptible. The points of the projections describe a gentle
curve from before backward, the convexity being outward.
J
The two teeth of the lower jaw are very similar to those of the
upper, but are somewhat narrower, owing to a decrease in width of the
flat pitted surface. As already stated, they are ankylosed to two plates
of bone which cover the inner and half of the lower surface of Meckel's
cartilage or the central axis of the lower jaw. It will thus be seen that
each ramus of the mandible consists of an inner and an outer bony plate
enclosing the central cartilaginous axis, which meet in the median line
below. To these is added a third piece at the symphysis on its lower
surface, so that the bony part of the jaw-which in all probability corre-
sponds with the single dentary piece in other fishes-is made up of
three, one of which bears teeth. This fact is of great morphological
significance, and will be referred to again when we come to discuss the
attachment of the teeth.
In the two allied genera Protopterus and Lepidosiren the teeth are
very similar to those of Ceratodus, but in numerous extinct forms refer-
red to the dipnoans a considerable amount of variety exists. As regards
the development of the teeth in this group, very little is known, and
until this has been studied it will be impossible to say whether the den-
tal plates are moulded upon a single papilla or represent the combined
calcification of several. Judging from their complexity, the latter
would seem to be the case.
The teeth of the remaining ganoids are of the ordinary conical form
which prevails to so great an extent in the Teleostei. In number, posi-
tion, replacement, etc. they likewise agree so closely with the average
teleost dentition that it is unnecessary to make any further mention of
them.
""
Among teleosts, however, there are several well-marked modifications
in the dental armature which deserve to be noticed. One of these is
presented by the Plectognathi (plaited jaw), of which the "trigger-fish
Balistes vetulus) and the "swell toad" (Diodon geometricus) represent
the extremes in dentition. The teeth of the mouth of Balistes are
twenty-two in number, of which fourteen belong to the upper and
eight to the lower jaw. Those of the superior series are disposed in
two rows, one placed immediately behind the other, and both are lodged
in the premaxillary bones. The most anterior of these rows contains
eight teeth, while in the posterior one there are only six. In the front
row the mesial pair are the largest, of a subtrihedral form, tapering
gradually to an obtuse point. Those upon either side decrease regu-
-
378
DENTAL ANATOMY.
larly in size toward the back part of the jaw, and have notched cutting
extremities.
The teeth of the posterior row are applied closely to those of the
front row, and are completely concealed when the mouth is closed.
They have a broader, more incisiform pattern. The teeth of the lower
series are like the corresponding ones of the upper front row, and are
lodged in the dentary bone. They are attached by slight ankyloses to
the respective bones upon which they are supported by having their
bases placed in a shallow alveolar depression, in the middle of which
a conical process of bone rises up and is received into the hollow basal
portion of the tooth. The successors of those in use are developed deep
down in the substance of the jaws, in bony crypts which communicate
with the exterior by means of foramina in the side of the jaws in the
vicinity of the bases of those in use. All the teeth in this species are
said by Owen to be covered with enamel. There are likewise small
conical hooked teeth developed upon the pharyngeals.
While the teeth of Balistes are more nearly affiliated with the normal
teleost condition, those of Diodon, on the other hand, show a much
wider departure. When the mouth is closed the biting surface of the
jaws seems to be invested with a continuous covering of tooth-sub-
stance; upon close inspection this is found to consist of a number of
dentine plates closely incorporated with the bone of the jaws and more
or less fused together at the base. Each one, however, develops sepa-
rately, and takes its place when its predecessor has disappeared through
wear. Just inside the margin of each jaw, in the middle line, is to be
seen a broad rounded mass consisting of transverse plates of dentine
intimately blended and ankylosed to the jaw bones. A faint median
longitudinal suture divides each into two parts; when this becomes
more distinct and extends to the edge of the jaw, as it does in some
species, it constitutes the mark of generic distinction of the genus Tetro-
don. The plates composing this mass, which is peculiar to these fishes,
are developed in the same manner as the teeth, and are strictly homol-
ogous with them.
S
Many other examples quite as peculiar as the last one could be cited
among the dental organs of fishes, but more time and space would be
required than is afforded the present paper.
The mode of development is essentially the same as that described
for the mammal, with the exception that the dental sacculus is generally
simple; the dentine papilla arises from the corium, and the oral epithe-
lium dips down to form a cap-like investment, in both of which calci-
fication takes place in the manner already described. With regard to
the succession and attachment of the teeth in this group, as well as in
the Batrachia and Reptilia, some preliminary points in the development
of the jaw bones must first be noticed.
Jan
In the early stages of embryonic development each jaw is primarily
made up of two cartilaginous bars which meet in the median line in
front. In the upper jaw these bars are known as the palato-pterygoid
bars, and in the lower jaw as Meckel's cartilage. In the elasmobranchs
these bars persist, and the teeth are supported by them. As a conse-
quence of this condition, as we have already seen, succession in them
TEETH OF THE VERTEBRATA.
379
takes place by a movement of the fibrous gum, in which the bases of
the teeth are imbedded, outward over the curved surface of the jaw.
Coincidently, however, with the ossification of the skeletal axis the
osseous bases of the dermal denticles coalesce to form the dentary bones,
as has been shown by Hertwig. By reason of the development of this
bony envelope of the primitive axis of the jaw, any further movement
of these denticles is prohibited, being firmly co-ossified with it.
During the coalescence of the denticles a portion of the primitive
tooth-bearing membrane is enclosed beneath the fused osseous plates,
and retains its original formative energy, thereby furnishing a source
of supply quite equal to that of the sharks. The denticles whose basal
plates form the sides and under portions of the dentary bones disappear,
while those on the summit of the jaw are retained as teeth. A confor-
mation of this position by evidence other than that afforded by embry-
ology is seen in the dentary bones of Ceratodus, in which each one is
made up of three or four pieces which have failed to coalesce.
The attachment of the teeth, therefore, in this group, as we would be
led to anticipate, is by ankylosis to the dentary and other bones which
support them. Still, there are many brush-like structures which are
identical with true teeth to be found in the mouths of many fishes,
which remain imbedded in the lining membrane and do not develop
any connection with the underlying bones. There are several ways by
which the teeth become fixed to the jaw bones in ankylosis, but the most
common is for the central axis of the tooth to be occupied by a cone of
osteo-dentine, which blends with the bone of the jaw. Several families
of fishes have some of the teeth attached by an elastic hinge, by which
they can be bent down in one direction and resume an erect attitude.¹
TEETH OF BATRACHIA AND REPTILIA.
As we pass from the dental organs of the more typical fishes to those
of frogs, salamanders, newts, etc., constituting the batrachian subdivis-
ion, a marked diminution in the number of individual teeth is to be
observed. With the appearance of perfected air-breathing organs the
complex hyo-branchial skeleton, typical of the fishes, becomes greatly
reduced and simplified as the higher forms are approached; conse-
quently, the branchial and pharyngeal teeth disappear in all the
Vertebrata above fishes.
In all those Batrachia in which teeth exist they are usually disposed
in a single row on the borders of the jaws, and are supported by the
maxillary, premaxillary, and dentary bones respectively. In addition
to these, each vomer (for there are two) bears a single row of teeth,
between which and the maxillary row the lower jaw bites. As a rule,
the Reptilia, on the other hand, lack the vomerine set, but in some of
them (serpents, for example) teeth are developed upon the pterygoids
and palatines, as well as upon the maxillary and dentary bones.
The teeth of the Batrachia present so limited a range of variation that
the description of one will serve to give a general idea of the dentition
of the whole group.
This fact was first noticed by Prof. Gill.
380
DENTAL ANATOMY.
It should be stated here that some of the tailless species (toads) are
quite edentulous, while in others (the frogs) teeth are absent in the lower
jaw. All the existing tailed batrachians, however, are provided with
teeth which present practically the same pattern and disposition which
obtains throughout the entire sub-class.
An excellent and easily-obtained example of this latter subdivision is
found in the Alleghany Menopoma, popularly known as the "hell-
bender." In this animal the skull is remarkable for its flatness and
breadth, as well as the almost perfect semicircular outline which the
dentigerous surface of the jaws presents. The mandible, as in the fishes,
is composed of angular, articular, and dentary pieces, and is suspended
to the cranium by means of two bones known as the squamosals through
the intervention of the quadrates.
CAR
The palato-quadrate or palato-pterygoid arch is not so well defined,
although the principal elements are present. The vomers are two in
number, and occupy their usual position behind the maxillaries, sharing
in the formation of the bony roof of the mouth. The maxillaries and
premaxillaries also have the same position as in the fishes, but are less
mobile, on account of sutural connections with the surrounding bones.
The biting surface of each jaw is produced into a sharp ridge by rea-
son of the existence of a well-marked ledge extending the full length of
its internal face. This ledge is converted into a groove in the recent
state by a fold or flap of the gum, which forms its internal wall, and is
in all probability homologous with a similar structure (the thecal fold)
found in the sharks. At the bottom of this groove the tooth-germs of
the successive sets of teeth are developed. It will be seen, therefore,
that the general arrangement is not different from that of the sharks;
but this important difference is to be observed in the sharks the bases
of the teeth are at first directed upward, and it is only when they are
about ready to take position on the working surface of the jaw that they
assume the erect attitude; this, as we have already seen, is due to the
movement of the entire gum outward. This manner of replacement
gives weight to the conclusion that the teeth in the sharks are invagi-
nated dermal spines, the position of which we would expect to find
reversed upon the inside of the jaws.
In the batrachians, on the contrary, the teeth are said to have an erect
position from the earliest stages of development, and it is less easy to
see how they represent dermal spines or how the position came to be
reversed. Believing, however, that all the maxillary and mandibular
teeth were originally of tegumentary origin, as is clearly demonstrable
in the sharks, it is more than probable that the arrest of the outward
movement of the gum in the batrachian by the appearance of ossifi-
cations around Meckel's cartilage to form the dentary bones is responsi-
ble for this change. It is quite possible that the tooth-germs of the
batrachian do at first have the same position as those of sharks—that is
to say, with the points directed downward-and that the formative
energy of the tissues beneath causes them to become erect at a compara-
tively early period.
S
WOR
We have already stated, in connection with the account of the dental
of the elasmobranchs, that tooth-succession is primarily due to
organs
TEETH OF THE VERTEBRATA.
381
the evagination of the lining membrane of the oral cavity. Whether
this is caused by unequal rate of growth of the surrounding parts,
whereby this lining membrane is forcibly pulled outward and replaced
from within, or whether the formative energy inherent in the membrane
itself causes it, is difficult to determine. This primary cause of succes-
sion is profoundly affected by the development of an osseous sheath
from this same membrane around the central cartilaginous axis of the
jaws. It seems plausible that secondarily the cause of tooth-succession
is to be sought for in the proliferation of the cellular elements beneath
the young and growing germ.
To the inner side of the external osseous wall of this groove in Meno-
poma the functional teeth are attached; their bases are slightly enlarged
and extend quite to the bottom of the groove, while the tapering crowns
reach considerably above the level of the jaw. Attachment takes place
by the ankylosis of that part of the base which is in contact with the
outer wall to the bone of the jaw through the intermediation of osteo-
dentine. This manner of implantation is known as "pleurodont," on
account of the fancied resemblance of the teeth so attached to ribs.
·
The teeth in use at any given time are from thirty to forty in num-
ber upon either side in each jaw; they are subequal in size, and are
placed with great regularity, being separated by spaces about equal to
the width of a single tooth. Their crowns are sharp-pointed and
slightly recurved; they are said in some species to be tipped with
enamel, which is probably true of all. The vomerine teeth are fewer
in number than the maxillary, there being not more than twelve or
fifteen upon either side. Their line of direction and manner of implan-
tation coincide with the maxillary row external to them, agreeing with
those also as to size and form.
In some of the extinct batrachians, notably the labyrinthodonts, there
were several teeth of the maxillary and premaxillary set considerably
enlarged and of a caniniform pattern. The species of this section were
mostly of large size and presented a formidable dental armature. They
likewise differ from all other of the Batrachia in that the teeth were
implanted in distinct sockets, and were rarely if ever attached to the
body of the jaw by ankylosis. The structure of the teeth is a curiously
complex one, and finds no parallel throughout the entire Vertebrata,
save in one extinct saurian (Ichthyosaurus) and several fishes, which
exhibit a similar condition in a less perfected degree.
The external surface of the crowns of the teeth in the labyrintho-
donts is marked by a number of longitudinal ridges, separated by what
at first sight would appear to be comparatively shallow grooves extend-
ing from the base to the apex of the crown. Upon cross-section, how-
ever, these fissures are seen to penetrate into the body of the tooth to a
remarkable depth-to a point, in fact, quite near the pulp-cavity or cen-
tral axis of the tooth, where they are separated from it by a thin wall
of dentine. The entire outer surface is covered by a thin layer of
cement, which is reflected inward to the bottoms or internal termina-
tions of the fissures just mentioned. The cut edges of this reflected
layer of cement, which is of uniform thickness throughout, are almost
straight for a short distance beneath the surface, but soon become very
382
DENTAL ANATOMY.
tortuous. The arrangement of the dentine is as follows: The axial
portion of the tooth consists of a central cone of dentine hollowed out
in the centre to receive the pulp. In cross-section this cone appears as
a ring surrounding the pulp-cavity; from it plates of dentine, which are
cleft by the fissures from without, radiate to the periphery, pursuing the
same tortuous course as that of the fissures. These dentinal plates are
separated from each other by fissures which radiate from the axial cav-
ity, but do not reach the exterior of the crown.
Some of the dentinal
plates do not arise from the central ring, but appear on transverse sec-
tion as processes from the periphery of the crown directed toward the
central axis, thus causing the fissures which radiate from the pulp-cavity
to become bifurcated at their outer or peripheral terminations. Some
of these accessory processes reach but a short distance toward the inte-
rior, while others penetrate halfway or more to the centre.
This complexity in the arrangement of the tooth-substances has sug-
gested the name of the typical genus, Labyrinthodon, which was orig-
inally described by the great anatomist Prof. Owen. Just how it has.
been produced is difficult to understand.
C
TEETH OF THE REPTILIA.-This class of vertebrated animals in-
cludes snakes, lizards, crocodiles, turtles, etc., and, considering the
extinct as well as the recent forms, is divisible into eleven distinct
orders, according to Prof. Cope's classification. Of these, but five are
represented in the existing fauna, the others having become extinct in
the different epochs of the earth's history.
;
The batrachians make the nearest approach to the permanent gill-
breathing vertebrates in all the essential features of their structure; the
Reptilia, on the other hand, furnish us with the transitional forms lead-
ing to the avian and mammalian stems. It is a very significant fact-
and one upon which the doctrine of evolution is primarily based, so far
at least as the Vertebrata are concerned-that the lowest forms appeared
first in the order of time, and were followed by those higher in the
organic scale; thus we have the cartilaginous fishes as the earliest rep-
resentatives of vertebrated animals; after them come the batrachians
next the reptiles and birds, and finally mammals. It must be borne
in mind, however, that the highest of one group is not always most
nearly related to the group next above it; for example, if we compare
the structure of a bony fish with that of a salamander, a great interval
will be found to exist, but if we institute a comparison between the latter
and a dipnoan fish, which is comparatively little removed from the car-
tilaginous forms, this interval will be found to be materially diminished.
Thus, the conclusion is obvious that the Batrachia sprang not from the
higher bony fish, but from some generalized representative of the pis-
cine type. The same reasoning can be applied to other divisions.
As regards the Reptilia, the chief distinction between them and the
Batrachia consists in the circumstance that the latter during the larval
stages of their existence breathe by means of gills like the fishes, whère-
as the Reptilia breathe by means of true lungs from the time of birth.
Important osteological differences are found in the bones of the skull.
14
-
The earliest appearance of the Reptilia dates back to the Permian
Epoch, where they are represented by a group of peculiar batrachian--
TEETH OF THE VERTEBRATA.
383
like reptiles which has been designated the Theromorpha by Prof. Cope.
This group includes two important divisions, one of which, the Anomo-
dontia, was first described by Prof. Owen from the Triassic (?) deposits
of South Africa; the other is the Pelycosauria, which is so far known
only from the American Permian.
The osteological structure of this order furnishes us many transitional
characters between the Batrachia and more typical Reptilia, on the one-
hand, while on the other they seem to stand in ancestral relationship to
the prototherian Mammalia. Their batrachian affinities are manifested
in the structure of the pectoral and pelvic arches, in the structure of the
limbs, and the possession of teeth on the vomer. In the absence of a
parasphenoid bone in the base of the cranium and the unicondylian
condition of the skull they are markedly reptilian. The structure
of the pelvic and pectoral arches and limbs, together with the intercen-
tral articulation of the ribs, allies them with the lower Mammalia.
Their dental organs present a considerable variety of structure-in
some instances departing widely from the simple conical form usual
among the other orders of this class of the Vertebrata. In one genus
(Dimetrodon) there were two large caniniform teeth in each premaxil-
lary, implanted in distinct sockets; these were followed by a single row
of maxillary teeth, whose crowns resemble somewhat the premolars
of the dog in general pattern. They were lodged in distinct alveoli,
and exhibit the remarkable peculiarity of being implanted by double
fangs, or rather single ones deeply grooved upon either side, otherwise
unknown among the Reptilia. The first tooth behind the maxillo-pre-
maxillary suture is enlarged into a canine, and the entire maxillary
series does not exceed fifteen in number. The palato-pterygoid arch is
present, and one of its elements, probably the pterygoid, is thickly
studded with small conical teeth irregularly disposed. Another element
which lies internal to this last-mentioned bone is described by Prof.
Cope as bearing a single row of teeth. Other genera related to this
one are Theropleura, Clepsydrops, etc. of Cope, which present minor
differences in the form and size of the corresponding teeth.
A nearly-allied family of this group is the Diadectida, likewise
described by Cope. A typical example of the dentition of this family
is seen in Empedocles molaris, wherein the pattern of the crowns of the
molars is thoroughly unique. The teeth are disposed on the borders of
the premaxillary, maxillary, and dentary bones, as well as upon the
vomer, which forms a median keel in the roof of the mouth. The max-
illo-premaxillary set in the upper jaw describe a sigmoid curve in their
line of implantation, and form an uninterrupted series from the front
to the back of the mouth. There are fourteen teeth belonging to this
series, of which the first two are larger than those immediately succeed-
ing them. They have obtuse subconic crowns, and are lodged in dis-
tinct alveoli. From this point the teeth gradually decrease in size up
to the sixth, when they again become larger and more complex in pat-
tern. The crowns of the typical molars have a much greater transverse
than longitudinal extent; the grinding surface is somewhat elliptical in
outline, and is provided with a submedian cusp which stands nearer the
outer than the inner border. The portion of the crown external and
Model
J
384
DENTAL ANATOMY.
internal to the median cusp is horizontal, and has its surface thrown
into conspicuous folds or wrinkles. The teeth of the lower jaw are
essentially like those of the upper. The vomerine teeth are small and
conical, and are disposed in two longitudinal rows.
In the typical genus (Diadectes) there is a well-developed canine,
while in another member of the family (Helodectes) there are canines
and a double row of maxillary teeth upon either side in the dentigerous
surface of these bones.
·
In the other subdivision of this order-viz. Anomodontia-the den-
tition is reduced to large pointed, recurved tusks, which are lodged by
distinct sockets in the maxillary bones. The rest of the jaw is edentu-
lous, and was in all probability ensheathed in a corneous substance, as
in the existing turtles. Other extinct members of this subdivision,
notably Rhynchosaurus and Oudenodon, were entirely edentulous, and
in all probability were the ancestors of the turtles.
That division known as the Crocodilia includes the alligators, croco-
diles, gavials, etc., which are separated from the other Reptilia by a
number of important osteological characters, prominent among which is
the complete development of the bony roof of the mouth. Teeth are
supported by the premaxillary, maxillary, and dentary bones only, the
palatines and pterygoids having approximately the same relations and
edentulous condition as in the mammalian skull. In no crocodilian so
far known are the teeth ever ankylosed to the body of the bones upon
which they are borne, but, on the contrary, they are set in distinct
sockets disposed in a single row along the margins of the tooth-bearing
bones. In young specimens the alveoli are apt to be ill defined, more
especially toward the back part of the jaws, but as age advances the
bony partitions become more distinct. On account of each tooth having
a distinct alveolus, this division of the Reptilia was formerly known as
the thecodonts, in contradistinction to the pleurodonts-a condition
already mentioned in connection with Menopoma—and acrodonts, pres-
ently to be described.
A good example of the dentition of a crocodilian reptile is afforded
by the Mississippi alligator (Alligator Mississippiensis), which can be
found in almost any osteological collection in this country. In the
upper jaw there are from eighteen to twenty-two teeth upon either side,
of which five are usually set in each premaxillary and the remainder in
the maxillary bones. The most anterior of the premaxillary series is
the smallest, from which they gradually increase in size to the fourth,
which is nearly twice as large as any of the others; the fifth is about
equal to the third. The first of the maxillary series is likewise the
smallest; the three succeeding teeth gradually increase in size until the
third is reached (the ninth counting from the first tooth in the premax-
illary), which is known as the canine of the upper jaw. The eighth and
tenth are frequently as large as the canine. Behind, the teeth become
smaller, and are again enlarged in the vicinity of the sixteenth or sev-
enteenth from the first premaxillary tooth; from this point they rapidly
diminish toward the posterior end of the tooth-line.
In the lower jaw the teeth are likewise of unequal proportion, but
those which are largest in the one series are opposed by the smallest of
TEETH OF THE VERTEBRATA.
385
the opposite set; thus that tooth which is caniniform in the lower jaw
is the fourth, and bites in front of the corresponding tooth above. It is
received into a deep fossa in the upper jaw just internal to the alveolar
border at the point of junction of the maxillary with the premaxillary
bone, or between the fifth and sixth teeth above. It not unfrequently
happens in old specimens that this fossa is converted into a foramen
leading to the external surface of the skull by the perforation of its
base. In such cases the point of the lower canine passes through the
upper jaw and appears upon the upper surface.
The only important distinction between the alligators and the croco-
diles consists in the fact that in the latter this fossa is open externally,
causing the tooth-line to be interrupted by a deep notch, whereas in the
latter it is intact.
Both the alligators and the more typical crocodilians are remarkable
for the breadth of the palate and the flatness of the muzzle, as well as
the alternate increase and decrease in the size of the teeth from before
backward; but in the gavials the snout is very long, narrow, and almost
cylindrical; the teeth, too, are more nearly equal and of more regular
proportions.
In the alligator the anterior teeth have conical crowns terminating in
sharp points, which are slightly recurved. The posterior ones have
more obtuse crowns, which terminate below by a moderately well-defined
neck. In some species the anterior and posterior surfaces of the crowns
are produced into trenchant edges, which may be more or less serrated
in the alligator this is but faintly marked.
;
The manner of succession is not different from that of the other lower
vertebrates. If the root of a tooth in place be exposed, the successional
sets in various stages of development will be seen below and to the inside
of it, arranged in the form of a nest of crucibles. This arrangement
results by reason of the absorption of the inner wall of the root of the
tooth in place which the immediate successor causes. By this means the
point of its crown comes to occupy the pulp-cavity of the functional tooth.
In the order Lacertilia, which includes the lizards proper, a more
varied development of the dental organs is met with. As a general
rule, teeth are borne upon the pterygoid and palatine as well as upon
the maxillary, premaxillary, and mandibular bones. There are, how-
ever, some exceptions, one of which is afforded by our little "horned
toads" (Phrynosoma), in which the palatines and pterygoids are eden-
tulous. The teeth may be either "pleurodont" or "acrodont" in their
manner of implantation, but in certain extinct forms (e. g. Mososaurus)
both conditions are to be observed. In the case of acrodontism the
bases of the teeth are soldered to the summits of slight elevations which
arise from the alveolar border of the jaws. Pleurodontism, as has
already been mentioned, consists in the ankylosis of the base and outer
sides of the teeth to the outer wall and bottom of the dental groove.
Another variety of implantation, known as coelodontism, has been
described, in which the tooth has a permanent pulp-cavity, and is
attached to the outer wall, leaving the base free; it should be men-
tioned that in pleurodonts the pulp-cavity is not permanent; it
soon becomes obliterated, leaving the tooth solid.
་་
VOL. I.-25
Grand
386
DENTAL ANATOMY.
A fair example of a pleurodont lacertilian is afforded by the majority
of the numerous species of the Iguanida, although some of the members
of the iguanian family, such as Isturus, Lophyrus, Calotes, and others,
are acrodont. In the horned iguana (Metopocerus cornutus) the max-
illary and premaxillary teeth are from twenty-two to twenty-three in
number upon either side. The central ones of the premaxillary set,
of which there are four, are smallest, the outer ones slightly enlarged.
These, together with the first five or six maxillary teeth, have sub-
conic recurved crowns, while the crowns of the posterior maxillary
series are laterally compressed into anterior and posterior cutting
edges and terminated by a principal cusp. Of the two edges, the
anterior is the longer and is interrupted by three minor cusps, the
posterior being shorter and bearing only a single accessory cusp. The
presence of these cusps gives the crown a serrated appearance when
viewed from the side.
The teeth of the lower jaw are from twenty to twenty-two in number
upon either side, and are similar in form to those above, with the excep-
tion that there are generally two accessory cusps upon either trenchant
edge of the crown. There is in addition to these a single row of small
conical teeth supported by each pterygoid bone; the number of these
varies from five to seven.
The only lacertilian which is known to be poisonous is the "Gila
monster" (Heloderma suspectum) of our American fauna. Recent
experiments of Drs. Mitchell and Reichart of Philadelphia have
demonstrated beyond doubt the poisonous qualities of its salivary
secretion. Considerable interest therefore attaches to its dental organs,
as well as to the anatomy of the poison-glands; this latter subject I
am, unfortunately, not in a position to describe, and will therefore
limit what I have to say here to a consideration of the teeth only.
This animal, of which there are two species, is confined to the desert
wastes of the South-western United States, where it is not of rare occur-
rence. In life it has a rather repugnant appearance, which is no doubt
increased by our knowledge of its poisonous qualities. It attains a
length of eighteen inches or two feet, and is covered with bright yellow
spots, a circumstance which gives the name Heloderma to the genus,
meaning "sun skin." Its venomous nature was not known until the
experiments above mentioned were made, although Prof. Cope had
reason to suspect as much, and gave the name "suspectum" to the
species, which he described several years before.
G
The teeth are supported by the premaxillary, maxillary, and dentary
bones, the palatine and pterygoids being edentulous. Those of the pre-
maxillary, of which there are three upon each side, are the smallest of
the upper teeth. They increase regularly in size from before backward,
and form a continuous series, with the maxillary teeth behind, which
continue to augment their dimensions up to the eighth tooth from the
median premaxillary pair or the fifth of the maxillary set. From this
point backward the two remaining teeth become slightly smaller. The
teeth of the lower jaw are nine in number, and are disposed very much
in the same manner as those above-the smallest in front and the
largest toward the back part of the mouth. A considerable disparity
TEETH OF THE VERTEBRATA.
387
in size exists between the inferior series and the corresponding teeth
above, those below being much the longer and more robust.
In their manner of implantation they cannot be said to be either
acrodont or pleurodont, but rather intermediate between the two. The
internal aspect of each jaw, which is remarkable for its breadth, is slightly
bevelled internally, causing the outer edge to rise a little above the inner.
Nearer the outer than the inner edge of this bevelled surface are a num-
ber of low bony elevations, corresponding to the number of the teeth in
functional use, to the summits of which they are attached by ankylosis.
In some instances these elevations are so faintly indicated that the teeth
appear to be soldered to the bevelled surface of the jaw directly. Just
internal to the basis of the functional teeth may be seen the successive
sets in different stages of development. In the recent state they are
covered by a fold of the gum, which likewise covers up the bases
of the functional teeth.
The form of the crown is that of a long, slender, sharp-pointed cone
curved inward and backward. The anterior surface of each tooth is
marked by a well-defined groove extending from the base to the apex.
It is somewhat deeper at the base than the summit, and is most distinct
in the teeth of the lower jaw. The intervals between the bases of the
teeth allow abundant room for the accommodation of poison-glands, the
secretion of which is conveyed down these grooves and thus injected
into the wound which the teeth inflict upon a prey.
Another group of curious and interesting reptiles is the Dinosauria,
which became extinct at the close of the Cretaceous Epoch. They are
of especial interest on account of their remarkable bird-like affinities,
and, according to the views of many authors, were the direct progenitors
of the struthious birds, or ostriches, emus, etc. They were mostly of
gigantic size, and some of them are remarkable for the great number
of teeth contained in the upper and lower jaws; others, again, were
almost edentulous.
In the iguanodonts and hadrosaurs, which are typical representatives
of the herbivorous division of this order, the crowns of the teeth are
somewhat expanded and are marked externally by vertical ridges, while
the internal portion is smooth and rounded. In Iguanodon the external
surface, to which the enamel is confined, is traversed by three vertical
ridges, separated by vertical grooves; the anterior and posterior edges
were serrated, as in Iguana, before the crown was abraded by wear.
In the hadrosaurs there is but one vertical ridge, which is external in the
upper and internal in the lower teeth. The part which bears this ridge
is known as the enamel or cementum plate. Prof. Cope has recently
had the opportunity of satisfactorily determining the dental peculiarities
of this group of gigantic saurians, as exemplified by the genus Diclonius,
through the fortunate discovery of an almost complete skeleton by Dr.
Russel Hill and the author in the Bad Lands of Dakota during the
summer of 1882.
According to Prof. Cope's description, there are in all two thousand
and seventy-two teeth. Of these, there were not more than two or three
hundred in use at one time, the others being arranged in successive rows
beneath, ready to take the place of the functional ones when they were
388
DENTAL ANATOMY.
worn out. One striking peculiarity which this reptile presents is in the
dentigerous character of the splenial and the edentulous condition of
the dentary bones of the mandible. The teeth are relatively small, and
are placed at some distance from the anterior part of the mouth. This
part of the jaws is believed to have been occupied by a kind of horny
sheath similar to that found in birds and turtles.
The proportions of the limbs were those of the kangaroo, the posterior
greatly exceeding the anterior in size. The general shape of the skull
is very much like that of a bird with a large spatulate beak; it was
supported upon a long, flexible neck, which was doubtless useful to the
animal in gathering the soft aquatic vegetation upon which, from the
character of its teeth, it is supposed to have subsisted. It likewise
had a powerful tail, much deeper than thick, which probably served
not only as a fifth limb in balancing the weight of the animal, but
could also have been useful as a swimming organ. The feet were pro-
vided with true hoofs.
The carnivorous dinosaurs were scarcely inferior in size to the her-
bivorous species, but were of a more slender and active build. Their
jaws were provided with large, powerful conical teeth, better adapted
for the capture of living animal prey. The terminal phalanges were
ensheathed in distinct claws.
Another order of the Reptilia, and one which is probably best known,
is the Ophidia, or snakes. Especial interest attaches itself to the dental
organs of many of this group, inasmuch as their poisonous bite consti-
tutes one of their most conspicuous features and renders them particu-
larly obnoxious as well as dangerous to life.
According to most systematists, the order is divisible into five sub-
orders, which have been defined as follows:
I. "The palatine bones widely separated, and their long axes longitudinal; a trans-
verse (ecto-pterygoid) bone; the pterygoids unite with the quadrate bones.”
"None of the maxillary teeth grooved or canaliculated "
Cl.
Asinea.
Tortricina.
b. Some of the posterior maxillary teeth grooved"
•
Ital
·
•
•
C.
"Grooved anterior maxillary teeth succeeded by solid teeth"
(6
d. Maxillary teeth few, canaliculated, and fang-like"
II. "The palatine bones meet or nearly meet in the base of the skull, and their long
axes are transverse. No ecto-pterygoid bone; the pterygoids are not con-
nected with the quadrate bones" (Huxley)
Scalecophidia.
The first of these sub-orders includes nearly all of the harmless or non-
venomous species, of which the black snake, garter snake, boa, etc. are
familiar examples. The second includes a single family with few species,
said to be harmless; they are confined to Africa. The third sub-order
embraces such forms as the deadly cobra, the coral snake, harlequin
snake, and others. The fourth includes the vipers, rattlesnakes, adders,
etc. The last is represented by few species which are non-venomous.
Proteroglyphia.
Solenoglyphia.
کر
In general, the dentigerous elements of the ophidian skull may be said
to consist of maxillary, palatine, and pterygoid bones of the upper and
the dentary bones of the lower jaw, although in the pythons and tor-
trices teeth exist upon the premaxillaries as well. In Rachiodon, a
singular African species of the Asinea, the teeth of the jaws are
extremely small and soon disappear. This loss is compensated for by
an excessive development of the hypopophyses of several of the anterior
TEETH OF THE VERTEBRATA.
389
vertebræ, which pierce the superior wall of the oesophagus and are
tipped with a layer of hard cementum. The food of this species con-
sists of the eggs of small birds, which it swallows whole. During the
act of deglutition the calcareous shell is brought into contact with and
crushed by these œsophageal teeth, thus preventing the escape of any of
the nutritious substances.
In the non-venomous species the maxillary bone is long, and bears a
row of teeth which are of variable size in the different parts of the jaw
in different genera. In some the teeth are largest in front and smallest
behind; in others it is the reverse of this; while many have the teeth
of equal size throughout; then, again, certain teeth of either jaw may
be specially enlarged and separated from the others by a diastema. All
these conditions have received distinct names.
All serpents are acrodont, and the crowns of the teeth consist of long,
sharp-pointed, recurved cones which are designed more to prevent the
escape of a struggling prey than as instruments of mastication. The
two rami of the lower jaw are bound together at the symphysis by
elastic ligaments, which, together with the great distensibility of the
throat, due to the mobility of the suspensory bones, allows them to
swallow objects many times larger than the usual diameter of the body.
During the act of swallowing the recurved and pointed teeth act as so
many hooks to prevent a backward movement of the object.
In the sub-order known as the Proteroglyphia the maxillary bone is
shortened somewhat, and the anterior teeth are enlarged and grooved on
their anterior faces. One of these teeth (the anterior) is the largest, and
is denominated the fang. It is permanently erect in these serpents, being
ankylosed to the maxillary bone, which is capable of comparatively little
movement.
1
In the solenoglyphs, on the other hand, of which the rattlesnake is an
excellent example, the maxillary bone attains its maximum of abbrevia-
tion and supports a single tooth, the fang. It is movably articulated
with the lachrymal above by means of a ginglymoid joint. The fang is
canaliculated or perforated in the direction of its long axis by a canal
which opens near its point. This canal results from the fusion of the
free edges of the anterior groove, which remains open in the fangs of the
proteroglyphs. When the mouth is closed, the maxillary bones are
retracted and the fangs lie parallel with the roof of the mouth; when
the animal “strikes," the maxillary bones are extended by special mus-
cles and the fangs become erect.
The canal of the fang receives at its proximal termination the duct
of the large poison-gland, which lies above it, so that when the punc-
tured wound is inflicted the poisonous secretion is injected into it. This
is facilitated by a coincident contraction of the muscles which surround
the gland. It has been suggested by Owen that as the quantity of saliva
and lachrymal secretion is increased during particular emotions, so the
rage which stimulates the venom-serpent to use its deadly weapon must
S
¹ Usually, a number of teeth are found just behind the fang in this bone, some of
which are nearly or quite as large as the fang itself. These are the teeth which are
destined to succeed the functional fang whenever it shall have been shed or lost by
accident.
390
DENTAL ANATOMY.
be accompanied with an increased secretion and great distension of the
poison-glands.
In reference to the poisonous character of this secretion, it is a well-
known fact that the normal saliva of many animals is more or less
dangerous when injected directly into the blood, and that in a state of
rage it is rendered more so. Prof. Cope has recently called my atten-
tion to the possible explanation of the poisonous character of this anal-
ogous secretion of the venomous serpents: that since their peculiar
method of locomotion would expose them most frequently to injuries
and inconveniences calculated to excite this state, the normal salivary
secretions have become accordingly modified.
The remaining orders of the Reptilia do not exhibit any important
modifications of the dental system worthy of special notice.
1
Cat
STA
THE TEETH OF THE MAMMALIA.
WITH a consideration of the teeth of the Mammalia we enter upon a
study of a series of dental organs whose complexity, variety, and spe-
cialization surpass those of any other group of the Vertebrata. The
wide diversity of conditions under which the different members of this
great group exist would of itself lead one to anticipate a corresponding
diversity in dietetic habits, as well as organs suitable for the prehension
and assimilation of the substances by which they are nourished. The
broad grinding surface afforded by the molar tooth of the elephant, the
sharp, trenchant, sectorial dentition of the lion, the great scalpriform
incisors of the beaver, the small cylindrical teeth of the armadillo, are
a few examples of the great range of variety which mammals exhibit
in the form of their dental organs.
As already remarked in the introductory pages, this study is greatly
facilitated by considering it from the standpoint of evolution, or rather
in the light of the paleontological history of the group. If we look
upon the fossil remains of any given period of geologic time as the
representatives in part of the animals which at that time inhabited the
earth, it then becomes of the utmost importance to ascertain the exact
relationship which the animals of each period bear to those which have
preceded and succeeded them in time. It is needless to say that the
conclusions which we are compelled to draw from studies of this cha-
racter are important and significant, and serve to bring into the closest
connection many isolated facts which if considered by themselves would
be wholly unintelligible.
B
Some objection to this method of treatment will doubtless be raised
by those who do not accept evolution as a demonstrated fact, or those,
again, who consider our information concerning extinct forms too meagre
for purposes of generalization. In answer to these objections it must be
urged that paleontological law compels us to recognize the important fact
that in every department of life the generalized has preceded the spe-
TEETH OF THE VERTEBRATA.
391
cialized in time; we pass from the simple to the complex, whether an
individual organ or the entire organism be considered; and the teeth
form no exception to this rule. So conclusive is the testimony which
it is now possible to adduce in support of this general proposition, and
so pregnant are the minds of modern biologists with this belief, that it
seems utterly impossible to escape the conviction that life from its earli-
est inception has been continuously, and in many instances progressively,
modified. As to the nature of the causes which have induced this modi-
fication, there is much less unanimity of opinion. It is a question
regarding which the most exhaustive philosophic discussion is now in
progress.
Ma
When we speak of the origin of mammalian teeth, it is necessary to
have some definite knowledge of the origin of this class of animals before
we can be absolutely certain of just what constitutes a primitive mamma-
lian dentition. Unfortunately, the evidence which would enable us to
determine the ancestry of the mammal beyond dispute has not as yet
been found, but it appears sufficiently evident that we are limited in our
choice to the Batrachia and Reptilia of the Permian Period. Huxley,
who has devoted considerable attention to this subject, concludes that
we must go backward past the Reptilia directly to the Batrachia. This
conclusion is primarily based upon a comparison of the pelvic arch of
the monotremes with that of the batrachians. In addition to the evi-
dence drawn from this source, upon which his argument is principally
founded, the following reasons are given for this view: "The Batrachia
are the only air-breathing Vertebrata which, like the Mammalia, have a
dicondylian skull. It is only in them that the articular elements of the
mandibular arch remain cartilaginous, while the quadrate articulation
remains small, and the squamosal extends down over the osseous ele-
ments of the mandible, thus affording an easy transition to the mam-
malian condition of those parts. The pectoral arch of the monotremes
is as much batrachian as it is reptilian or avian. The carpus and tarsus
of all Reptilia and Aves, except the turtles, are modified away from the
batrachian type, while those of the mammal are directly reducible to it.
Finally, the fact that in all Reptilia and Aves it is a right aortic arch
which is the main conduit of arterial blood leaving the heart, while in
the Mammalia it is the left which performs this office, is a great stum-
bling-block in the way of the derivation of the Mammalia from any of
the Reptilia or Aves. But if we suppose the earliest forms of both
Reptilia and Mammalia to have had a common batrachian origin,
then there is no difficulty in the supposition that from the first it was
the left aortic arch in the one series, and the right aortic arch in the
other, which became the predominant feeder of the arterial system.'
""
If we had only the recent forms to consider, the argument advanced
by this learned anatomist would be specially potent; but when we study
carefully the osteology of the Reptilia of the Permian Period, many of
the arguments here advanced are invalidated. The structure of the
pectoral and pelvic arches of the theromorph Reptilia, as has been ascer-
tained by Cope, resembles that of the monotremes far more than does
that of any known batrachian. The carpus and tarsus of these forms
are almost identical with those of the monotremes, while comparatively
M
pr
392
DENTAL ANATOMY.
little importance can be attached to the dicondylian character of the
skull, from the fact that there is in certain members of this group a
double articular surface on the occipital bone for the atlas vertebra.
The only osteological character left in which the Batrachia resemble
the Mammalia most is that of the quadrate articulation; which resem-
blance is somewhat counterbalanced by the approaches to the distinctive
peculiarities of the mammalian dentition found only in the Theromorpha.
The condition of the arterial system must remain inferential for this
group, since it became extinct, so far as we now know, at the close
of the Permian Period. Upon the whole, I am disposed to think that
there are quite as many reasons to regard the theromorph Reptilia
as the ancestors of the mammal as there are to regard in the same
light any of the Batrachia so far discovered.
www
Accepting the "placoid scale" or the "dermal denticle" as the struc-
ture from which all teeth were primarily derived, we have, as charac-
ters of a primitive dentition, the following: (1) the conical form; (2)
increased number; (3) frequent and almost endless succession. These
conditions we have fulfilled in many of the sharks. The next step in
specialization consists in the fusion of the basal osseous plates of the
❝dermal denticles" to form the maxillary and dentary bones, to which
the teeth become attached by ankylosis. This, we have already seen,
obtains in a majority of the fishes, and is associated largely with the
simple conical form. In the Batrachia the conical form, this mode of
attachment, as well as the succession, are closely adhered to, but the
individual teeth are reduced in number. In certain of the Reptilia―e. g.
Theromorpha-another advance is made in the implantation of the teeth
in distinct sockets, with a disposition to form more than one root or
fang. There are still, however, many successive sets of teeth developed.
Lastly, in the Mammalia the teeth are generally greatly reduced in
number; they are always implanted by one or more roots in a distinct
socket, and there are never more than two sets developed, the second
of which is only partially complete; they are also, as a general rule,
of a complex nature and show a wide departure from the primitive
cone.
In searching, therefore, for a primitive or generalized mammalian den-
tition, the most important point to be taken into consideration is the
following numerous single-rooted teeth, confined to the maxillary and
mandibular bones, implanted in distinct sockets, with a complete devel-
opment of one or more successive sets. It is possible, even probable,
that this stage in tooth-development was reached in the ancestors of the
Mammalia before they assumed their distinctive characteristics as such;
but the nearer any approach is made to this condition on the part of the
mammal, in that proportion it may be regarded as primitive in its den-
tal organization.
Having already spoken of the probable origin of the Mammalia, it
now remains to give a brief synopsis of their classification before pro-
ceeding to a detailed description of their teeth. The arrangement here
adopted is, with some modification, the one which has been proposed by
Prof. E. D. Cope, and is based upon a study of both fossil and recent
forms:
TEETH OF THE VERTEBRATA.
393
MAMMALIA.
TABLE OF CLASSIFICATION OF MAMMALIA.
PROTOTHERIA. { Monotremata (duckbill).
EUTHERIA.
Didelphia.
Monodelphia
Polyprotodontia (opossum).
Diprodontia (kangaroo).
Plagiaulacida (extinct).
Mutilate Series
Unguiculate Series .
Ungulate Series .
{
Sirenia (sea-cow)
Cetacea.
Bunotheria.
Rodentia.
Cheiroptera (bats).
Carnivora
{
Primates (monkeys, man, etc.).
Taxeopoda
Amblypoda (extinct).
Proboscidea (elephants).
Diplarthra .
•
Zeuglodontia (extinct).
Denticete (toothed whales).
Mysticete (whalebone whales).
Insectivora (shrew, etc.).
Tillodonta (extinct).
Toxodontia (extinct).
Prosimia (lemurs).
Sciuromorpha (squirrels).
Myomorpha (rats).
Hystricomorpha (porcupines).
Lagomorpha (rabbits).
Fissipedia (dogs, cats, etc.).
Pinnipedia (seals).
Condylarthra (extinct).
Hyracoidea (hyrax).
{
Artiodactyla (hog, cow, deer, etc.).
Perissodactyla (horse, tapir, etc.).
394
DENTAL ANATOMY.
It will be seen, from the foregoing table, that the Mammalia
are divisible into two primary groups, which hold the rank of sub-
classes. The first of these, Prototheria, has but two living repre-
sentatives, both of which are confined to the continent of Australia.
These are the Echidna, or spiny ant-eater, and the duck-billed platypus.
The principal characters by which they are separated from all other
Mammalia may be conveniently contrasted with those of the second
sub-class, Eutheria, as follows: in the former there are (1) "large and
distinct coracoid bones, which articulate with the sternum. (2) The
ureters and the genital ducts open into a cloaca into which the urinary
bladder has a separate opening. (3) The penis is traversed by a ure-
thral canal which opens into the cloaca posteriorly, and is not continuous
with the cystic urethra. (4) There is no vagina. (5) The mammary
glands have no teats." In the Eutheria, on the other hand, (1) "the
coracoid bones are mere processes on the scapula in the adult, and do
not articulate with the sternum. (2) The ureters open into the bladder,
the genital ducts into a urethra or vagina. (3) The cystic urethra is
continuous with the urethral canal of the penis. (4) There is a single
or double vagina. (5) The mammary glands have teats" (Huxley).
In their anatomical structure the Prototheria resemble the reptiles and
birds more than does any other mammal. This is particularly conspic-
uous in the pectoral arch and the reproductive system. On this account,
De Blainville applied the name Ornithodelphia (bird womb) to them,
by which they are sometimes known. Strange as it may seem, no fossil
remains of great antiquity of this most primitive group of all Mammalia
are with certainty known to exist, but it may yet be found that the
earliest mammalian representatives, which date as far back as the
Triassic Period, and which are known from teeth and jaw bones
only, really belong to the Prototheria rather than to the Didelphia, or
pouched series of the Eutheria, as is frequently maintained. Both
the living forms are devoid of true teeth.
We
The second sub-class, Eutheria, has two principal divisions: Didelphia
(double womb), including those animals popularly known as the
"pouched quadrupeds," of which the opossum, kangaroo, wombat,
etc. are familiar examples; and the Monodelphia (single womb),
which embraces all the remaining mammals. The name of the first
subdivision, Didelphia, was applied by its author, De Blainville, with
reference to the peculiar habit which these animals possess of sheltering
their helpless young in an abdominal integumentary fold. This is corre-
lated with the only important character in which they differ from the
monodelph division-viz. the complete absence of an allantoic placenta
or any uterine connection between mother and foetus. In consequence
of this peculiarity of gestation the young are born in an exceedingly
helpless and imperfect condition, and are nourished for a considerable
period in the marsupium or pouch of the mother. This character is
1 The classification of the Mammalia proposed recently by Prof. Huxley includes
three principal subdivisions-viz.: Prototheria, Metatheria, and Eutheria. The terms
Prototheria and Eutheria were employed by Prof. Gill a number of years previously to
designate the two principal groups of this class, and appear to have been appropriated
by Huxley without credit.
TEETH OF THE VERTEBRATA.
395
:
considered of sufficient value by some to give the Didelphia a rank equal
to that of the Prototheria, and they consequently make three primary
divisions of the class-Ornithodelphia, Didelphia, and Monodelphia, after
De Blainville. If this were associated with any other characters of
structural importance it would be quite sufficient, but since it is not,
and in view of its unreliability and inconstancy in the lower Vertebrata,
I am not disposed to regard it as equal in value to the strong structural
characters by which the Prototheria are defined.
The subdivision of the Monodelphia is not an easy matter, if indeed
any important divisions further than the separation of the mutilate
series can be made. It is convenient, however, to adopt the classifica-
tion of Lamarck, and divide them into three series, as follows: the
mutilate series, the ungulate series, and the unguiculate series. The
first of these includes the Cetacea, or whales, and the Sirenia, or sea-
COWS. The only character by means of which they are associated
is the absence of hind limbs and the loss of the articular processes of
the bones of the manus. The Cetacea form a perfectly natural and
homogeneous group, and are entitled to a wide separation from all
other Mammalia. We at present know very little concerning their
development or ancestry, further than that their Eocene representative,
Zeuglodon, resembled the ordinary monodelphous type more than does
any other member of the order. They are undoubtedly a very old and
distinct group, and it would not be at all surprising if they are ultimately
found to have descended directly and independently from the Prototheria.
The Sirenia, or sea-cows, on the other hand, appear to be simply
modified ungulates that have gradually assumed their present structure
in accordance with their aquatic environment. The Miocene genus
(Halitherium) of this order had distinct hind limbs, and in many ways
resembled the primitive hoofed Mammalia. For this reason it is
probably best to associate them with the ungulate rather than with
the mutilate series, since they differ in almost every essential feature
from the Cetacea, except in the loss of the posterior members.
The separation of the two remaining series, ungulate and unguicu-
late, depends entirely upon the distinctions to be drawn between "hoof"
and "claw." If we contrast, for example, two such structures as the
claw of the lion and the hoof of the horse, the distinctions are perfectly
obvious, and we will experience no difficulty in recognizing the differ-
ences; but if we carefully trace the respective lines of ancestry of these
two forms backward to the Eocene Period, we will find them converging
to such an extent as to involve the hoof-and-claw question in almost
hopeless confusion.
--
S
There are, however, two principal lines or stems which have terminated
in the distinctly hoof-bearing mammals on the one hand and the claw-
and nail-bearing on the other. The exact point at which these two lines
converge has not as yet been satisfactorily determined, but it is undoubt-
edly true that they approached one another to a remarkable extent in
the early Eocene. The ancestry of the entire ungulate series is indi-
cated by the Taxcopoda of Cope, to whose persistent efforts and schol-
arly researches we are alone indebted for their discovery and description.
The primitive or central stem of this order is the Condylarthra, from
J
Add
396
DENTAL ANATOMY.
which we pass by easy stages through the extinct genus Meniscotherium
to the little hyrax or "coney," whose classification has long remained
a puzzle to zoologists. From this group the extinct amblypods and
elephantoid animals likewise came, while the Perissodactyla and the
Artiodactyla are traceable directly to it.
The unguiculate series also has a generalized order, from which all
the others radiate in different directions. This order has been called the
Bunotheria by Cope, and exhibits a central axis in the sub-order Insect-
ivora, the representatives of which are among the oldest of monodelph
mammals. From the Insectivora we derive the Creodonta, a group of
extinct insectivoro-carnivorous animals which terminates in the Car-
nivora. In another line come the lemuroids, monkeys, and man, while
in still another are the Cheiroptera or bats, which are simply insectivores
modified for flight.
One other order, the Edentata, or sloths, armadillos, ant-eaters, etc.,
remains to be accounted for. Some authors believe them to be affiliated
with the unguiculate series, and to have sprung from the central insect-
ivorous group. Paleontology has so far given us very few if any hints
concerning the origin of this order, and it is probable that it will not
be until the Eocene and Miocene Tertiaries of South America are more
fully explored that any important information will be had upon this
subject. At present I consider the evidence too meagre to hazard an
opinion.
G
DIVISIONS OF THE MAMMALIAN DENTITION.-Many years ago
Prof. Owen called attention to the fact that in many of the Eutheria
there are two sets of teeth developed during the life of the individual—
a deciduous or milk set and a permanent set-while in others but a single
set appears. The former of these two conditions he designated by the
term diphyodont, and to the latter he gave the name monophyodont den-
tition. It likewise so happens that generally, in those that have two
sets (diphyodonts), the teeth in the various parts of the mouth are dif-
ferent in form and complexity, while in those that have but a single set
(monophyodonts) the teeth are alike throughout. The diphyodont den-
tition is therefore, as a general rule, heterodont, that is, there are many
kinds of teeth, and the monophyodont dentition is homodont, or all
the teeth are alike. It was therefore originally supposed by Owen that
diphyodont and heterodont and monophyodont and homodont were cor-
relative and interchangeable terms, but it has since been discovered that
there are many exceptions to this rule.
M
It must be borne in mind that the terms diphyodont and monophyo-
dont are simply conveniences by which we are enabled to express briefly
the conditions of replacement, and are not in any way to be looked upon
as definitive of a natural group. The degree to which the second den-
tition is developed in the various sections of the Mammalia is subject to
extreme variation, and it is not always an easy matter, if not frequently
an utter impossibility, to determine whether certain teeth belong to the
deciduous or permanent set, or in the monophyodonts to say whether
it is the permanent or deciduous set which has been lost. There are,
however, as will appear later, several important series in which the
replacement and position are sufficiently constant to enable us to divide
J
--
TEETH OF THE VERTEBRATA.
397
the teeth into several categories, the convenience of which, to say the
least, if not the real importance, is undeniable. The question of the
nature and relationship of the milk dentition to the permanent one
will be discussed after the teeth of the several groups have been
considered.
THE TEETH AND THEIR ACCESSORY ORGANS IN THE DOG.—I have
thought best to next present a detailed description of the adult structure
of an average diphyodont dentition, together with the accessory organs,
in order that the student may become familiar with the technicalities
before proceeding to consider the teeth of the various sections of the
Mammalia, The dog has been selected as an example of this kind,
partially on account of the generalized condition of the teeth, but
principally on account of the readiness with which the student will
be enabled to provide himself with the necessary material.
The teeth of the dog (Figs. 195 and 196) are forty-two in number,
of which twenty belong to the upper and twenty-two to the lower
jaw. The most anterior teeth of the upper series are relatively small,
and are implanted in the free edge of the premaxillary bones in such a
manner as to describe the arc of a circle. These are known as the
incisors (ic, Figs. 195, 196). Behind these, after a slight interval, are
FIG. 195.

ELLEDER:
m
tiny
...mum.com.
pm
1
pmx
PPf
pl
apf
Vertical View of the Upper Jaw of a Dog (Canis familiaris): ic, incisors; c, canine; pm, premolars;
m, molars; s, sectorial; pmx, premaxillary bone; mx, maxillary bone; pl, palatine; af, anterior
palatine foramen; ppf, posterior palatine foramen. The position of the third premolar is slightly
abnormal.
mx
ic
a pair of strong, laterally compressed curved teeth, the canines, which are
lodged deeply in the substance of the maxillary bone, immediately behind
the maxillo-premaxillary suture. Behind the canines, again, are six
teeth on each side, which progressively increase in size and complexity
as we proceed backward until the penultimate tooth is reached, the last
one being somewhat smaller. These are termed molars and premolars.
The tooth-line of each moiety of the upper jaw presents three curves,
the most anterior of which is formed by the three incisors and canine,
with a strong convexity outward; the line of the next four describes a
gentle curve whose convex surface is inward; while that of the last two
curves boldly inward toward the median line.
The number of teeth in the lower jaw is one in excess of that of the
upper, which is caused by the addition of a small single-rooted tooth at
398
DENTAL ANATOMY.
the posterior end of the series. They describe the same curves, so as to
oppose those of the upper series. The incisors of the upper jaw, as has
already been stated, are lodged in the pre- or intermaxillary bones,
which limit the anterior part of the oral cavity above. The definition,
therefore, of an incisor tooth of this series is one which has a pre- or inter-
maxillary implantation irrespective of its size or form. The incisor teeth
of the lower jaw are the corresponding ones which are brought into opposi-
tion with those of the upper jaw when the mouth is closed. The teeth thus
defined are three in number upon each side above and below in this animal,
and are implanted by single slightly recurved fangs in distinct sockets or
alveoli. In the upper series the median pair is the smallest, the outer
ones gradually increasing in size. The base of the crowns of the four
middle teeth is somewhat trihedral in form, with the apex flattened from
before backward and produced into three cusps, of which the central
one is the largest. The entire apex of the crown is slightly recurved.
Upon its inner aspect the crown presents a basal ledge or cingulum,
which sends out a low ridge to each of the lateral cusps. The lateral
incisors are the largest and are somewhat caniniform. Like the median
ones, their crowns have a strong basal cingulum posteriorly, but the
lateral cusps are absent; the apex terminates in a strong hooked point.
The incisors of the lower jaw are similar to those of the upper, with
the exception of the median pair, which is much the smallest and occu-
pies a more anterior position than the others. The internal lateral cusps
of these teeth are very faintly indicated, if indeed they can be at all
made out, while the external lateral cusp is present and situated high
up in the two median pairs. In the lateral ones it has a position nearer
the base of the crown, and is separated from the median cusp by a deep
fissure.
Between the lateral incisors and canines of the upper series there is a
space or diastema about equal to the width of the lateral incisor. This
space serves to receive the lower canine when the mouth is closed. At
the back part of it upon the outside may be seen the suture by which,
FIG. 196.
S
DE
pm
M

Sic
m
Vertical View of the Lower Jaw of a Dog (C. familiaris); ic, incisors; c, canine; pm, premolars;
m, molars; s, sectorial.
the premaxillary bone joins the maxillary in the dentigerous border
of the jaw. Just behind this suture the superior canine is lodged.
The definition, then, of a superior canine tooth is one which is situated
in the maxillary bone immediately behind the maxillo-premaxillarg suture,
provided it be not too far back, whatever may be its form, size, or func-
TEETH OF THE VERTEBRATA.
399
tion, while the canine of the lower jaw is the tooth which closes just in front
of it.
The canines of the dog are large, recurved, pointed teeth, projecting
far above the level of the others, with slightly trenchant anterior and
posterior edges. They are almost equal in size and very similar in
shape. A very useful means by which they can be distinguished from each
other, if at all worn and isolated from the rest of the teeth, is to note
the point at which the worn surface exhibits itself. It must be remem-
bered that the lower canine closes in front of the upper, in consequence
of which the posterior face of the lower impinges against and abrades
the anterior face of the upper; the anterior face of the lower canine also
comes in contact with the lateral incisor, and an abrasion takes place at
this point; but the posterior face of the upper canine is seldom worn
except by long-continued use, so that ordinarily these points of wear
serve as a useful guide in distinguishing between them. There is a
slight difference in form, which can be ascertained only by close and
careful comparison.
Behind the canines are four teeth which have been designated premo-
lars. The reason for this distinction is founded upon the circumstance
that these are the teeth situated behind the canine which vertically suc-
ceed the corresponding ones of the deciduous or milk set. The defini-
tion, therefore, of a premolar tooth is one which, being situated behind
the canine, displaces in a vertical direction a deciduous or milk tooth; all
others behind these are true molars. This is the definition which was
originally proposed by Owen, to whom we are greatly indebted for this
nomenclature: it would appear to be entirely satisfactory and sufficient,
were it not for the fact that the first tooth counting from before back-
ward, which is generally enumerated in the premolar series, does not
have any deciduous predecessor. If we adhere strictly to this definition,
it cannot be justly considered a premolar, but common usage has so
long given it a place in this category that it appears advisable to
still call it such. It should be remembered, however, that this is by
no means an isolated case, but that other animals exhibit similar
peculiarities.
J
The first premolar, so called, of the superior series is the smallest of
the four, and is implanted rather obliquely in the maxillary bone; its
single fang is slightly compressed laterally, and joins the crown at a
moderately well-defined neck. The crown has an elongated oval form,
terminated by a prominent obtuse cusp and surrounded by a well-
marked ledge or cingulum, which is most conspicuous upon its inner
face. From the summit of the main cusp two well-defined ridges
descend to the cingulum, one on the posterior and the other upon the
anterior border, giving to the tooth a slightly trenchant appearance.
The hindmost of these two ridges divides the posterior half of the
crown into two equal parts, and terminates with a very slight enlarge-
ment in the cingulum, while the anterior one has a more internal direc-
tion, and terminates in a distinct tubercle which occupies a position at
the base of the antero-internal portion of the crown. The two ridges
and the cingulum below enclose a shallow triangular depression inter-
nally, the outer face being convex.
400
DENTAL ANATOMY.
The second and third premolars are considerably larger than the first,
and are implanted by two roots, of which the posterior is the larger.
These two teeth resemble one another very closely, the only appreciable
difference being their slight disparity in size. Their crowns, like that of
the first, are of greater longitudinal than transverse extent, and are pro-
duced into a prominent cusp situated a little anterior to the centre. The
posterior ridge is interrupted shortly before it joins the cingulum by a
deep transverse notch which gives rise to a distinct cusp, the posterior
basal tubercle, situated over the hinder root. A faint indication of a
second cusp is seen just behind this as an elevation of the cingulum.
The antero-internal tubercle is present, and occupies relatively the same
position as it does in the first premolar. The cingulum is more promi-
nent on the inner than on the outer side of the crown, and with the two
ridges encloses a triangular space.
The fourth premolar is by far the largest and strongest tooth of the
premolar series. It is commonly known as the "flesh tooth," or supe-
rior sectorial, for reasons presently to be given. It is implanted by
three roots, two external and one internal. The crown is composed of
two principal lobes supported by the two external roots, and a small
antero-internal one supported by the internal fang The two prin-
cipal lobes have an antero-posterior position, and are separated from
each other by a deep, narrow fissure. Of these, the anterior is the
larger and higher of the two; when viewed externally it resembles a
cone with the anterior contour produced. Internally it is flattened
somewhat, so as to correspond with the flattened inner surface of the
posterior lobe. Posteriorly it is produced into a strong blade-like ridge,
which is terminated by the vertical fissure, while its anterior surface is
marked by a moderate vertical ridge. The posterior lobe is essentially
chisel-shaped in form, with the bevelled edge external; its apex forms.
a blade-like crest which extends the entire length of the lobe. The
internal lobe is small, and occupies a position at the antero-internal
angle of the crown, being connected with a faintly-marked cingulum
which surrounds the base of the crown. When we attempt to homol-
ogize the component lobes of this tooth with those of the premolars in
advance of it, it is not difficult to see that the anterior lobe is the prin-
cipal cone, that the posterior one is merely an exaggerated posterior
basal tubercle, while the internal lobe is strictly homologous with the
structure which has a similar position in the others. The three anterior
premolars are not in as close contact as the teeth in the back part
of the jaw, but are separated from each other by slight intervals, which
are most conspicuous between the first and second.
The premolars of the lower jaw are similar in form to those of the
upper, with the important exception of the fourth or last, wherein
there is to be found a wide difference both in size and structure.
The first of the lower series is smaller than the corresponding tooth
above, and has a simpler, more conical crown. It is separated by a
considerable diastema from the canine in front of it, but is almost in
contact with the second behind. The second and third resemble those
which are in a like position in the upper jaw, while the fourth is also
similar to the corresponding tooth above, with the exception of a
TEETH OF THE VERTEBRATA.
401
slightly increased size and the possession of a well-defined second
posterior basal lobe. It slightly overlaps the great first true molar
behind it.
The true molars of the superior series are two in number upon each
side, and are placed directly behind the premolars. The definition of a
true molar tooth is one which, being situated behind the premolars, does
not displace a deciduous or milk predecessor. The two molars above
are three-rooted, with broad tuberculated crowns imperfectly quadran-
gular in outline. The first, which is more than twice the size of the
second, has two strong obtuse conical tubercles on the external portion
of the crown, situated directly over the anterior and posterior external
roots; they are subequal and separated from each other by a transverse
notch. Internal to these there is a broad ledge, well rounded off inter-
nally, bearing three cusps. The one most internal is lunate in form, and.
is closely connected with the cingulum, which surrounds the base of the
tooth. The cusp situated near the antero-internal angle is the largest,
and has a subtrihedral form. A distinct ridge passes outward and for-
ward from it to join the cingulum. Posterior to this last-mentioned
cusp, and separated from it by a wide open notch, is the third tubercle,
less distinctly marked than either of the others. An analysis of the
various cusps of which the crown is composed leaves little room to
doubt that the two external cusps are strictly homologous with the two
external ones of the sectorial in advance of it-that the internal ledge
which bears the three tubercles represents the greatly enlarged internal
lobe of the sectorial, which has been removed to a more posterior
position, and has acquired an important addition from the cingulum.
That part of it which is exactly homologous with the internal lobe
is the principal cusp at the antero-internal angle, which in some car-
nivorous animals is continued outward and backward as a prominent
ridge, and does not develop the third tubercle. If the lunate cingular
cusp be subtracted, the crown will be seen to resemble that of the
sectorial in its general features.
The second true molar is like the first, except that the internal ledge
exhibits, instead of three tubercles, two crescentiform ridges.
The first true molar of the lower jaw is the largest tooth in the entire
dentition of the dog, and is the sectorial of the inferior series. It is
implanted by two powerful roots at a point about midway between the
anterior extremity and the condyle of the lower jaw, and occupies a
position near the canthus or angle of the mouth. Its crown may be
described as composed of two anterior blade-like cusps, a small inter-
nal tubercle, and a low tubercular heel. Of the two anterior cusps, the
posterior is the larger, and rises gradually above the level of the one
anterior to it; both are convex internally, but somewhat flattened exter-
nally to correspond with the internal flattened surface of the two blades.
of the superior sectorial. They are separated from each other by a deep,
narrow fissure. The heel is low, and occupied by two cusps disposed
transversely, of which the outer one is the larger. A faint ridge con-
nects them, enclosing a shallow basin in front; on this account the heel
is said to be basin-shaped. The internal tubercle is small, and is placed
at the inner posterior part of the median lobe. In many carnivores it
VOL. I.-26
402
DENTAL ANATOMY.
completely disappears, as does also the heel, as we shall presently see.
The fourth superior premolar and the first inferior true molar are called
sectorial, on account of their scissor-blade structure and the manner in
which they oppose each other. If the macerated skull of a dog be care-
fully examined, it will be seen that the incisors of each series oppose
each other almost exactly, while the lower canines close in front of the
upper. As a consequence of this, the first premolar below closes in
advance of the first premolar above; the second below in the interval
between the first and second above, etc., but always upon the inside, on
account of the unequal width of the two jaws. Now, the inferior sec-
torial bites against the superior in such a manner that its blades exactly
oppose those of the tooth above after the manner of a pair of shears, so
that when the mouth is closed the inferior sectorial is completely hidden
from view; the heel opposes the first true molar above. Those who
have ever studied the habits of dogs or wolves must have noticed that
when they wish to divide a tough animal membrane or ligament they
pass it back to the canthus of the mouth on one side and make several
short quick strokes of the jaw; this is the shearing movement of the
sectorials.
The remaining two true molars are much smaller, the last being one
of the smallest of all the teeth, and is implanted by a single root. It is
said to be permanently absent in some races of the domestic dog, espe-
cially the "pugs" and "Japanese sleeve dogs." The second molar is
two-rooted, with a tuberculate crown of a more or less quadrate form.
Two transverse cusps occupy the anterior part, while a third is placed
at the postero-external angle of the crown on the edge of a broad flat
heel. A basal cingulum is also present. The last tooth has an obtusely
FIG. 197.

Na p
V
Side View of the Skull of a Dog (C. familiaris).
conical crown. The homologies of the cusps of the inferior true molars
are not evident in the dog, but when we come to examine allied forms
it will be found that the two blades of the sectorial represent the primi-
tive cone, and the anterior basal lobe of the ordinary premolar greatly
enlarged and specialized, while the heel represents the two posterior
•
TEETH OF THE VERTEBRATA.
403
basal tubercles arranged transversely; the internal tubercle is an extra
outgrowth from the cingulum.
In the case of many extinct animals the succession, and consequently
the discrimination, of the molars and premolars would be attended with
considerable difficulty were it not for the fact that in a majority of the
Mammalia the first true molar is the first of the permanent set of the
molar and premolar series which comes into place. By the time the
last or fourth premolar is cut, which is usually one of the last, the first
true molar immediately behind it is considerably worn down by use, so
that this disparity of wear will of itself frequently serve to locate the
exact limits of each series. It is a rule which is often employed by
paleontologists to determine the dental formula of an animal the suc-
cession of whose teeth is unknown. When the anatomist wishes to
indicate briefly the number of the various teeth of any particular ani-
mal, he employs what is called a dental formula. By this method the
permanent dentition of the dog would be expressed as follows: I., C.
1, Pm. 4, M. ; which means that there are three incisors upon each
side above and below, that there is one canine upon each side above and
below, that there are four premolars, and that there are two true molars.
above and three below. This manner of abbreviation is convenient and
easily understood, and saves both time and space in descriptions.
w'd
The division of the teeth into incisors, canines, premolars, and molars,
although open to some objection, is nevertheless useful, since it serves to
locate, in the case of addition or subtraction of a tooth to or from the nor-
mal diphyodont number, the exact position in which the change has
taken place. In the marmoset monkeys of South America, for exam-
ple, the total number of teeth is thirty-two, the same as in man.
An
inspection of their formula, however, which is I. 2, C. †, Pm. 3, M.
3. M. 3/
32, will show that there is an important difference between the num-
ber of molars and premolars, the formula in man being I. 4, C. †, Pm.
, M. 3. In the former it is a molar which is lost; in the latter it is a
premolar. Another example of this kind is seen in the upper and lower
teeth of the otter, in which they are equal in total number, but unequal
as far as the respective kinds are concerned. The dental formula in this
animal is I. §, Č. 4, Pm. 4, M. 36.
2
1
1
The Accessory Organs.-This subject properly embraces a considera-
tion of the bones by which the teeth are supported, the muscles con-
cerned in their movement, the blood-vessels by which they are supplied
with nutriment, and the nerves distributed to them. The bones in
which the upper teeth are implanted are the maxilla and premaxillæ,
which are usually enumerated as bones of the face. The maxillary bone
(Fig. 195, mx) is by far the largest one belonging to this category, and
forms the greater part of each moiety of the upper jaw. It likewise
contributes to the formation of the cheek, orbit, and palate, and also
takes the principal share in forming the boundary of the nasal cham-
ber. The maxillary bones do not meet in the median line above, on
account of the interposition of the nasals and premaxillaries, but
below they send inward two thin horizontal plates which meet in
the middle of the roof of the mouth.
For descriptive purposes it is convenient to divide each bone into
B
404
DENTAL ANATOMY.
three external surfaces, the facial, palatine, and orbital. The facial sur-
face, which is the largest of the three, is directed outward, and is irregu-
larly triangular in form, with the apex directed forward. The superior
border of this surface is considerably curved, and joins the premaxillary
in front and the nasal behind. The posterior border is irregular, and is
in contact from within outward with the frontal, lachrymal, and malar
bones respectively, being excluded by these bones from the rim of the
orbit. The inferior border is known as the dental or alveolar border,
on account of its affording support to the canine, premolar, and molar
teeth of the upper jaw. It is in contact with the premaxillary in front,
and terminates behind in a free extremity beneath the orbital fossa.
The surface thus bounded is uneven, being interrupted by elevations
and depressions. At the anterior angle the superior canine is implanted,
and the course of its powerful curved root is indicated by a well-marked
ridge or swelling of the external surface. Behind and above the pos-
terior termination of this is a broad, shallow depression, while behind
and below is another depression, the canine fossa, ending posteriorly in
a large foramen, the infraorbital foramen, situated above the interval
between the third and fourth premolars. Behind the infraorbital for-
amen a strong process is thrown up to meet the malar; this is known
as the malar process of the maxillary. The posterior superior angle is
produced into a considerable rounded process, which passes as far back-
ward as the centre of the orbit to articulate with the frontal. This is
the nasal process of the maxillary, and is the homologue of a corre-
sponding process in the human skull bearing this name.
The posterior or orbital surface is relatively small, convex from before
backward, and concave from side to side. It is somewhat triangular in
shape, and forms the greater part of the floor of the orbit, being directed
upward and backward. It is bounded above and externally by the
malar, directly above by the lachrymal, and internally by the palatine
bones respectively, terminating in a free rounded border behind. The
internal portion of this last-mentioned border is separated from the
palatine by a notch, and forms a conspicuous eminence known as the
maxillary tuberosity. At the anterior extremity of this surface is seen
the posterior opening of the infraorbital canal, which traverses the max-
illary bone and serves for the transmission of the second division of the
trigeminal or fifth nerve, as well as a part of the external carotid artery,
which terminates in this situation as the infraorbital. This surface is
perforated by small foramina for the entrance of the superior dental
nerves and arteries.

T
The inferior or palatal surface forms a considerable part of the bony
roof of the mouth as well as the floor of the nasal chamber. It is limited
in front by the premaxillary bone, externally by the free alveolar border,
posteriorly in part by the palatine and in part by a free edge, and inter-
nally by the suture with which it joins its fellow of the opposite side. It
is slightly concave from side to side, the alveolar border being consider-
ably elevated. Posteriorly it sends backward a narrow strip which ter-
minates in a free edge behind; anterior to this, at a point opposite to the
anterior part of the sectorial, it widens rapidly. From this point
to its anterior termination it gradually narrows again. Just internal
Ka
G
TEETH OF THE VERTEBRATA.
405
to the sectorial is seen a deep depression, the sectorial fossa, which
serves to accommodate the blades of the inferior sectorial when the
mouth is closed. Internal to this, again, are usually two, sometimes
three, foramina, the posterior palatine foramina, which transmit the pos-
terior palatine vessels and nerve. From the largest, most anterior of
these a shallow groove is continued forward in which the palatine ar-
tery is lodged. This is the palatine groove.
The line of junction of the two palatal plates of the maxillaries is
marked by a longitudinal ridge, the sutural ridge, which gives support
to the vomer above. The maxilla articulates with the premaxilla and
nasal in front, with the frontal above, and with the lachrymal, malar,
and palatine behind.
The premaxillæ are small bones placed in front of the maxillæ, the
two together forming the anterior termination of the upper jaw. Each
consists of a thickened anterior portion meeting in the median line,
together with an ascending or vertical process and a horizontal process.
The thickened body forms the lower boundary of the anterior nares,
and by its free alveolar border lodges the incisor teeth. The ascending
or vertical process is a long, sharp spicule of bone which springs from
the outer side of the body and furnishes the external wall for the narial
opening. It is directed upward and backward, and insinuates itself
between the nasal above and the maxilla below. This is known as the
nasal process of the premaxilla. Upon either side of the median line
the horizontal or palatine processes pass backward to the maxillæ, form-
ing the anterior portion of the bony palate. These processes are in con-
tact with each other in the middle line, but each is separated from its
body by a wide hiatus, which is converted into a foramen by the inter-
position of the palatal plate of the maxillary behind. These large oval
foramina are conspicuous features in the macerated skull, and are known
as the incisive or anterior palatine foramina. They transmit the ante-
rior palatine vessels and nerve.
The next and last bony structure to be noticed in connection with the
teeth is the mandible or lower jaw. This part of the skeleton in human
anatomy is known as the inferior maxilla, and consists, in the adult state
at least, of a single bone (the two halves co-ossified), as is also the case
in the monkeys and several other mammals. In the majority of them,
however, it is made up of two more or less persistent pieces, which may
unite in extreme old age to form a single bone. The mandible of the
dog consists of two symmetrical elongated halves, the rami, diverging
behind and coming in contact in front in the median line by two rough-
ened surfaces, the symphysis. They are bound together by the inter-
position of fibro-cartilage at this point, and are movably articulated to the
skull behind by two transversely elongated processes, the mandibular con-
dyles, placed near the middle of the posterior border. Each ramus is
laterally flattened, with the inferior border considerably curved in an
antero-posterior direction. In front this border slopes gradually upward
to meet the alveolar or dentary border, while behind it is terminated by
a prominent, slightly-inflected process, the angle. The dentary border is
nearly straight, and is prevented from reaching the posterior border by
the intervention of a broad flat recurved plate of bone, the coronoid pro-
·
S
-
406
DENTAL ANATOMY.
cess, which rises high above the level of the surrounding parts. The
posterior border is interrupted by two notches, between which is situ-
ated the condyle. Immediately in front of the condyle is a wide and
deep depression, the masseteric fossa, for the insertion of the powerful
masseter muscle. In front of and below the condyle, on the inner side,
is a conspicuous opening, the inferior dental canal, which gives passage
to the inferior dental artery and nerve. On the external surface, behind
and below the root of the canine, is another opening, the mental foramen,
through which a part of the nerve makes its exit to be distributed to the
lower lip.
The Muscles.-The principal muscles concerned in the movement of
the lower jaw are the temporal, masseter, external, and internal ptery-
goids, the digastric, genio-hyoid, and mylo-hyoid.
The Temporal is a broad, thick, fleshy muscle which covers the side
wall of the brain-case from the post-orbital process in front to the lamb-
doidal or occipital crest behind, reaching as high up as the sagittal crest
above, and completely filling up the temporal fossa, to which it gives its
name. Its fibres converge fan-wise to be inserted into the summit of
the coronoid process of the ramus of the mandible. Its principal action
is to elevate the lower jaw. By its leverage and great strength the ani-
mal is enabled to take a firm grip upon its prey.
G
The Masseter is a short, thick muscle arising from the under and a
part of the outer surface of the malar bone, as well as the posterior part
of the maxillary, and, passing downward and backward, is inserted into
the masseteric fossa of the ramus. Its action is similar to that of the
preceding muscle.
The Internal Pterygoid muscle consists of a strong bundle of muscu-
lar fibres which takes its origin from the pterygoid fossa in the base of
the skull, and passes downward and outward to its insertion in the lower
part of the angular process. By its contraction the lower jaw is drawn
upward and inward, but owing to the manner in which the teeth inter-
lock no extensive lateral movement is possible. The most reasonable
view of the action of this muscle, as well as the succeeding one, is,
that by the contraction of those of one side the sectorial apparatus of the
side opposite is enabled to perform a more perfect shearing movement,
just as the blades of a pair of scissors must be pressed closely together
in order to make them cut. From the direction of its fibres it likewise
assists in elevating the jaw.
The External Pterygoid arises from the pterygoid plate of the sphe-
noid bone, and is inserted into the base of the condyle, and as far
forward as the inferior dental canal. Its action has already been
alluded to.
The Digastric is a large muscle which arises from the skull behind
the auditory bulla in a strong bony prominence, the paramastoid pro-
cess, and passes forward to its attachment on the inferior margin of the
ramus in front of the angular process. Its action is to depress the jaw
and open the mouth.
The Genio- and Mylo-hyoid muscles are broad muscular sheets which
lie between the rami forming the floor of the mouth in the recent state,
being attached to the hyoid bones and the "fork" of the jaw. They
<+
TEETH OF THE VERTEBRATA.
407
assist in depressing the mandible, and consequently in opening the
mouth.
Vessels and Nerves.-The blood-vessels by which the teeth and the
muscles described above are supplied are derived from the external
carotid artery, which passes forward along the side of the neck, giving
off branches to the various structures in this situation. This artery does
not terminate, as in man, in the temporal and internal maxillary arteries
-at least it is so generally considered by anatomists. Both the right
and left common carotids spring from the innominate, as in the Carniv-
ora generally. After giving off the thyro-laryngeal branch, remarkable
for its large size, to the thyroid gland and larynx, it passes forward in
front of the transverse process of the atlas vertebra, where it gives off
the occipital artery, which goes to the back of the head and the deep
muscles of the neck. Upon the base of the skull in the vicinity of the
carotid canal it bifurcates into two principal branches, the external and
internal carotids, the latter entering the skull through this canal to be
distributed to the brain, the latter continuing forward through the ali-
sphenoid canal, giving off in its course the laryngeal, lingual, facial,
posterior auricular, and superficial temporal branches. Near the con-
dyle of the lower jaw it describes a remarkable sigmoid curvature be-
tween this structure and the internal pterygoid muscle, thence passing
forward to the infraorbital canal, where it receives the name of the
infraorbital artery. Between the condyle and the infraorbital canal the
following principal branches are emitted by this arterial trunk: the
inferior dental artery, which enters the inferior dental canal and sup-
plies the teeth of the lower jaw; the deep posterior temporal, which
furnishes a masseteric branch passing through the sigmoid notch, or that
between the condyle and coronoid process of the ramus, to enter the
masseter muscle; several pterygoid arteries, which go to the pterygoid
muscles; the ophthalmic artery, distributed to the eye; the deep ante-
rior temporal; the palatine, buccal, and alveolar arteries; lastly, the
superior dental artery, which supplies the teeth of the upper jaw.
The nerves supplying the teeth and accessory organs are derived
principally from the trigeminal or fifth pair of cranial nerves. This
is essentially a mixed nerve in function, arising by two roots, a large
sensory and a small motor root. At a short distance from its origin the
sensory root swells out into ganglionic enlargement, the Gasserian gan-
glion, after which it divides into three branches the ophthalmic or first
division, the superior maxillary or second division, and the inferior max-
illary or third division.
The first of these makes its exit from the cranial cavity through the
sphenoidal fissure, and supplies by its subdivisions the eyeball, mucous
membrane of the eyelids, the skin of the nose and forehead, dividing into
frontal, lachrymal, and nasal branches.
The second of these branches, the superior maxillary, issues from the
skull through the foramen rotundum, and supplies the side of the nose,
upper teeth, and the upper part of the mouth and pharynx. It crosses
from the foramen rotundum directly to the infraorbital canal, in the
vicinity of which it gives off the anterior and posterior dental nerves
which supply the teeth.
408
DENTAL ANATOMY.
The third division, inferior maxillary, passes out of the skull through
the foramen ovale, just outside of which it is joined by the motor root.
It then divides into two branches, a small anterior one distributed to
the muscles of mastication, and a large posterior branch, which supplies
the ear, side of the head, lower lips, gums, teeth, salivary glands, and
inside of the mouth. The posterior branch divides into the auriculo-tem-
poral, which passes backward to the temporal region; the inferior dental,
which supplies the teeth of the lower jaw; and the gustatory, or the nerve
of taste, which goes to the mucous membrane of the tongue.
The lips, tongue, and salivary glands should also be mentioned in
connection with the accessory organs, since they serve an important
purpose in preventing small particles of the food from escaping during
mastication, as well as supply the requisite moistening fluid whereby
comminution is more readily accomplished and the food rendered more
digestible.
TEETH OF THE EDENTATA, OR BRUTA.
Although this group is by no means the most primitive of the Mam-
malia, as will be seen by reference to the table of classification, yet the cha-
racters which we have assigned to the ideal primitive mammalian dentition
are most nearly approached in certain members of this order. Whether
the comparatively simple form and absence of enamel in the adult tooth,
which is characteristic of all the animals of this order, pertain to a prim-
itive state, or whether this condition has been reached by a process of
retrogression or degradation, as many believe, we are not at present pre-
pared to say, in the absence of any knowledge of their paleontological
history beyond the latest Tertiary epoch. There is one character, how-
ever, in which one at least is more decidedly primitive than any other
known Eutherian mammal, and that is the succession of all the teeth but
one (the last) by a second set. I refer to the nine-banded armadillo
(Tatusia peba). It is not certainly known whether this condition exists
in any other of the edentates or not, with the exception of the sloths,
which are truly monophyodont.
The term Edentata is inappropriate, inasmuch as one would be led to
suppose from the name that they have no teeth. The original term,
Bruta, was applied to this order by Linnæus, which he defined by the
absence of incisor teeth. It was afterward changed to Edentata by
Cuvier-a name which has been extensively adopted by subsequent
authors. It was formerly supposed that no incisor teeth are ever pres-
ent in this group, but the discovery of new forms proved this to be
erroneous. The median incisors, however, are wanting in all cases so
far known. The definition of the order now most commonly given
is "absence of enamel on the teeth." This peculiarity appears at first
sight striking and quite sufficient to separate them from all other mono-
delphous mammals, but C. S. Tomes has shown' that the tooth-germs
of the nine-banded armadillo have distinct enamel organs, which are
subsequently aborted as the tooth comes to maturity. This discovery is
important, since it indicates pretty clearly that the loss of enamel is a
¹ Philos. Trans., 1876,
TEETH OF THE VERTEBRATA.
409
•
mark of degeneracy, and leads indirectly to the conclusion that the
armadillos at least are descended from ancestors with enamel-covered
teeth, who in all probability were the possessors of a completely devel-
oped second set.
The only assignable cause for this degenerate condition of the dental
organs is the peculiarity of their food-getting habits. Many of them
feed upon insects, which they capture by means of a long whip-like
tongue covered with the viscid secretion of the submaxillary glands, and
swallow whole. This manner of feeding would occasion little demand
for masticatory organs, which from disuse would gradually fall into a
rudimentary condition and eventually disappear. Those in which the
entomophagous habit is exhibited in its greatest perfection are edentu-
lous, and have small mouths with extremely long tongues. All the
Edentata in which this structure exists at all show a tendency toward
such a habit—even the arboreal sloths, which are said to be exclusively
vegetable feeders.
•
Flower has recently shown that the sloths are intimately connected
with the ant-eaters and armadillos of South America through the extinct
megatheroids, and that all the American forms have probably descended
from a common ancestor, while the Old World forms are likewise closely
related and descended in another line. It is probably true that the arma-
dillos are most nearly related to the ancestral form, and that the sloths
represent an offshoot which was derived from them after they had lost
the enamel of the teeth in the manner indicated.
The teeth of the armadillos are, with one exception, relatively small
cylindrical bodies implanted in the dentigerous borders of the lower jaw,
maxillary, and sometimes premaxillary bones. They are entirely devoid
of enamel, and grow continuously throughout the life of the animal, in
consequence of which no roots are formed.
FIG. 198.

WWWWN
zazz
Side View of the Skull of a Seven-banded Armadillo (Tatusia hybridus ?)
In the seven-banded armadillo (Tatusia hybridus, Fig. 198¹) there are
seven teeth above and eight below upon each side. So little is known
¹ The specimen here figured is in the U.S. Army Medical Museum, and is labelled
Tatusia septemcinctus. It exhibits the peculiarity of having eight teeth upon one side
and seven upon the other in the upper jaw. There is, however, a considerable space
between the first and second tooth of the right side, which would indicate that a tooth
is missing. The number ascribed to this species by Owen is seven above and eight
below upon each side. Its exact identification is therefore difficult.
410
DENTAL ANATOMY.
about their succession that it is impossible to say whether there are
molars and premolars represented or not. The teeth of the upper series
are lodged in the maxillary bones, and begin at a considerable distance
behind the maxillo-premaxillary suture. They progressively increase
in size up to the fifth or sixth tooth, the last being quite small. They
are not in contact with each other, but are separated by slight spaces
about equal to the width of a tooth. The teeth of the lower jaw are
similar to those of the upper jaw in size and shape, with the exception
of the last, which is much larger than the corresponding tooth above.
The teeth of the inferior series close in the intervals between those of
the upper and conversely, causing the summits of the crowns to wear,
as Prof. Owen puts it, "into two facets divided by a median transverse
ridge." The form of the working surface of the tooth is therefore
wedge-shaped. The first two teeth of the lower jaw shut in front of
the first tooth above, and the last three teeth above behind the last one
of the lower series, leaving them with little or no opposition. Each
tooth continues its cylindriform shape to the bottom of the alveolus in
which it is implanted, having its base excavated into a large pulp-
cavity. It consists of dentine and cementum only.
In another species, the nine-banded armadillo, the number and form
of the teeth are the same. The teeth of this animal, as has already been
stated, have a successional set. According to the definition laid down
for premolar and molar teeth in the diphyodont Mammalia generally,
there would be one molar and six premolars in the dentition of this
animal. The rooted appearance of the deciduous teeth, according to
Tomes, is not due to the possession of true roots, but to the absorp-
tion set up by the approach of the successors.
The genus Priodon of this group has as many as one hundred teeth,
the greatest number exhibited by any land mammal. They are rela-
tively small and simple in form, and are confined to the maxillary and
mandibular bones. They vary in number from twenty-four to twenty-
six upon each side in the upper, and from twenty-two to twenty-four
upon each side in the lower jaw. In the living genus Dasypus there is
one tooth upon each side implanted in the premaxillary bone, which,
according to the definition, becomes an incisor, while in still another
extinct genus, Chlamydotherium, almost equalling in size the rhinoceros,
there were two incisors above and three which opposed them below. In
Glyptodon the teeth are more complex in pattern, being laterally com-
pressed and divided by two vertical grooves upon each side, which are
opposite to each other. The resulting structure from this arrangement
is three transverse vertical plates connected in the centre by an isthmus.
There were teeth in the premaxillaries in this genus.
The megatheroids afford another example of moderate complexity in
the enamelless teeth of the Bruta. In the gigantic extinct Megatherium
there are five molars above and four below upon each side. They are
very deeply implanted in the substance of the jaw bones, and have
remarkably elongated pulp-cavities, which communicate with the grind-
ing surface by means of a narrow fissure. The pulp-cavity is imme-
diately surrounded by soft, more or less vascular dentine-the vaso-
dentine of Owen--which is covered by a thin layer of unvascular, much
TEETH OF THE VERTEBRATA.
411
harder dentine. Upon the outside of this comes the cementum, which
has a great thickness upon the anterior and posterior face of the tooth.
Owing to the unequal powers of resistance which these substances offer,
the teeth wear in such a manner as to present two transverse crests each,
and are therefore spoken of as lophodont. They are confined to the
maxillary and mandibular bones and grow from persistent pulps.
In another extinct allied genus, Megalonyx, the teeth are oval in sec-
tion, and did not wear into transverse crests as in Megatherium, but have
slightly concave grinding faces. The first tooth of the upper series also
is considerably enlarged and caniniform in shape, as in one of the liv-
ing sloths. Another nearly-related form is Mylodon, likewise extinct,
which exceeded the rhinoceros in size. The first tooth above, instead
of being enlarged and caniniform, is smaller than the succeeding ones,
and otherwise like them in pattern.
The dental formula of the three-toed sloth (Bradypus tridactylus) is
I. 8, C. 8, M. 4-18. It has been observed, however, that there is
in some young examples of this species a small extra tooth in the lower
jaw just in front of the first permanent one, which is shed before the
animal attains to the adult state. The teeth are relatively small, of a
columnar form, and implanted to a moderate depth in the substance of
the jaws by a deeply-excavated base for the accommodation of the per-
sistent pulp. The grinding surface presents a central depression in the
vaso-dentine, surrounded by a raised rim on its outer margin composed
of the harder dentine, which usually wears unequally into one or two
prominent points. The teeth of the upper and lower jaws do not
oppose each other exactly, but alternate when the mouth is closed.
In the two-toed sloth (Cholopus didactylus) the dental formula is the
same. The first tooth in each series, which in the edentates generally
is the smallest, is here greatly increased in size, of a subtrihedral form,
and of a caniniform pattern. They are separated by a considerable
diastema from the rest of the teeth, and are implanted above in the
maxillary bones a short distance behind the maxillo-premaxillary
suture. It will be seen, therefore, that as far as the definition of a
canine tooth is concerned, all the conditions are fulfilled; but the
tooth in the lower series, which has undergone a similar modification,
violates the definition of a canine, inasmuch as it closes behind the
upper caniniform tooth instead of in front of it. It is therefore a
matter of uncertainty whether these teeth are strictly homologous with
the canines of the diphyodont Mammalia or not. From the manner in
which they oppose each other the posterior surface of the upper and the
anterior surface of the lower are extensively abraded, and their summits
worn into sharp points, which would render them efficient weapons of
offence or defence should the animal choose to use them as such.
The next tooth of the upper series is relatively small, and is implanted
rather obliquely, with the summit inclined backward and inward. The
two following teeth are larger, with a central depression upon the grind-
ing face, and having the external and internal portions of the rim pro-
duced into sharp points. The last tooth is about equal to the second in
size, which it also resembles in form.
The teeth of the lower series resemble those of the upper, with the
412
DENTAL ANATOMY.
exception that the three posterior ones are more robust and gradually
decrease in size from the second to the last. Viewing the teeth and
accessory bony structures of this animal as a whole, the premaxillæ are
remarkable for their small size, little extension anteriorly beyond the
maxillæ, and the complete absence of the ascending or nasal process, as
well as their edentulous condition. The palatal plates of the maxillæ
are widest in front and gradually narrow posteriorly, causing the dental
series of opposite sides to converge behind. In the lower jaw the two
halves are completely co-ossified, as in monkeys and man; the anterior
part of the symphysis is produced into a peculiar spout-like termination,
at the base of which the jaw widens rapidly; and the rami are little
divaricated posteriorly. The posterior teeth are implanted in a strong
inwardly projecting ledge, in consequence of which the dentigerous
border gradually approaches the median line as it proceeds backward.
The mental foramen is placed below the interval between the third and
fourth teeth near the middle of the ramus.
T
5
With respect to the teeth themselves, Owen gives the following com-
mon and constant characters of both recent and extinct sloth-like ani-
mals, which would include the megatheroids: "Teeth implanted in the
maxillary, never in the intermaxillary bones; few in number, not ex-
ceeding -4; composed of a large central axis of vascular dentine,
with a thin investment of hard or unvascular dentine, and a thick_outer
coating of cement. To these, of course, may be added the dental cha-
racters common to the order Bruta-viz. uninterrupted growth of the
teeth, and their concomitant implantation by a simple deeply-seated exca-
vated base, not separated by a cervix from the exposed summit or crown."
Of the two Old World genera now living, but one has teeth. This
is the aard-vark (Orycteropus), or, as it is sometimes called, the Cape
ant-eater. Its dental formula is M. 7-7=26, of which the anterior
ones of each series are not unfrequently wanting or concealed by the
gum. The teeth of the superior set progressively increase in size from
before backward up to the last tooth, which is smaller. They are oval
in section, with the exception of the fourth and fifth, and have wedge-
shaped triturating surfaces, like the armadillos. The fourth and fifth
above and the last two below have two vertical grooves, one upon each
side, which give to them an hour-glass shape upon section.
The teeth of this animal do not exhibit the customary excavated base
of the Edentata generally, but are continued solid to the bottom of the
sockets. Their minute structure is peculiar, and resembles that found in
Myliobates among the elasmobranch fishes; the dentine is of the variety
known as plici-dentine. This consists of a series of small vertical par-
allel tubuli which pass up from, and are virtually prolongations of the
pulp-cavity. From these the dentinal tubuli radiate toward the per-
iphery, just as they do from the single pulp-cavity of the human tooth
already described. Owing to this peculiarity, Prof. Owen regarded the
tooth of Orycteropus as an aggregate of many denticles, each with its
proper_pulp-cavity and dentinal tubes.
In Europe fossil remains of edentates are known from the Middle
Miocene of Sansan in France and the upper Miocene deposits of Piker-
mi in Greece. Two genera, Macrotherium and Ancylotherium, have been
M
VO
TEETH OF THE VERTEBRATA.
413
described by Lartet and Gaudry, from feet and limb bones principally,
nothing being known of the skull or teeth. In South America fossil
remains of this order are very abundant in the Pampean or Pliocene
deposits. Older deposits on the Parana River have furnished M.
Ameghino with numerous forms which stand in ancestral relation to
those of the Pampean beds, and which, it is interesting to observe,
have more or less enamel on the teeth. In North America, Prof.
Marsh has described a genus under the name of Morotherium, from
the Loup Fork or Upper Miocene strata, from feet bones only. The
teeth are not known.
TEETH OF THE CETACEA.
According to Dr. Theo. Gill's arrangement, the cetaceans are divisible
into three groups or sub-orders, as follows: Mysticete, including the
"whalebone whales ;" Denticete, or the "toothed whales," and Zeuglo-
dontia, a division which includes Zeuglodon and several other extinct
genera. In the Mysticete, teeth are present in a foetal state only, being
absorbed before birth. This loss of the teeth is compensated for by the
development of large corneous plates, the "baleen plates," which depend
from the roof of the mouth. The more important of these are of a tri-
angular form, and are arranged along each side of the palate in such
a manner as to be transverse to the axis of the skull, the centre being
occupied by smaller ones, also placed transversely. Altogether, they
form by their extremities a vaulted surface into which the large tongue
fits accurately, their edges being broken up into numerous stiff hairs
which project into the mouth. The animal feeds by taking large quan-
tities of water into the mouth and expelling it again through the nos-
trils ("spouting "); any small aquatic animals which may have been
contained in it are entangled in the fringes of the baleen plates, and
subsequently collected by the tongue and swallowed. It will thus be
seen that the baleen acts as a sort of sieve or strainer, and is pre-
eminently adapted to the capture of the small aquatic forms with which
the sea in certain places literally swarms. Each baleen plate possesses
a pulp situated in a cavity at its base, from which it is developed, and
through which it is regenerated as fast as worn away. According to
Tomes, each hair-like fibre has within its base a vascular filament or
papilla; "in fact, each fibre is nothing more than an accumulation of
epidermic cells concentrically arranged around a vascular papilla, the
latter being enormously elongated. The baleen plate is composed
mainly of these fibres, which constitute its frayed-out edges; and in
addition to this there are layers of flat cells binding the whole together
and constituting the outer or lamellar portion."
•
Ind

All the whalebone whales possess rudimentary teeth, or rather dentine
and enamel organs, which undergo very little calcification before absorp-
tion sets in. In the fin-backs (Balaenoptera) these dentine organs are
simple in the front part of the mouth, bifid in the middle, and trifid in
the back part of the jaw. They are placed in an open groove along the
jaw, as in all other Mammalia at this stage of embryonic growth, and
do not differ from them in any important particular.
414
DENTAL ANATOMY.
In the second sub-order (Denticete) no baleen plates are developed;
teeth are always present, and are more or less persistent. They are
implanted by single roots, and are in some instances very numerous.
No second dentition has ever been observed in any member of this
group, and they are, so far as known, truly monophyodont. In the
common porpoise of our coast (Delphinus chymene), which is an average
example of this sub-order, the teeth are about ninety-four in number,
and are lodged in the premaxillary, maxillary, and mandibular bones.
They are implanted by single slightly enlarged fangs in ill-defined
sockets incompletely partitioned off from each other, and in what at
first sight seems to be a wide-open groove. Their crowns taper grad-
ually to a sharp point, which is strongly incurved. The first two teeth
in the upper jaw are small and implanted in the premaxillary bone,
which furnishes a very small part of the dentigerous border of the upper
jaw. Behind these the maxillary teeth rapidly increase in size up to the
seventh or eighth tooth, after which they continue to the fifteenth or six-
teenth almost equal in size, and then gradually diminish in size toward
the posterior part of the jaw. The teeth of the inferior series are like
those of the upper, except that the posterior ones are more robust.
The jaws are remarkable for their great length and narrowness, and the
arrangement of the bones of the face when compared with other mam-
mals is also peculiar. The coronoid process of the lower jaw is obsolete.
In other members of the Delphinida-the dolphin, for example-the
teeth are often as many two hundred, the greatest number exhibited by
any mammal, or they may be reduced to a single functional tooth, as in
the narwhal (Monodon). In this latter species four teeth are found in a
foetal state, but the two lateral ones are lost or absorbed before birth.
In the male narwhal the left of the two anterior ones, which is placed
in the premaxillary bone, grows from a persistent pulp and attains a
length of ten or twelve feet. This formidable tusk is almost straight,
and is marked by spiral ridges which wind forward from left to right.
The corresponding tooth of the opposite side sometimes reaches a devel-
opment equal to that of the left, but more frequently its growth is
arrested and it remains buried beneath the gum, as do both in the
female. Owing to this circumstance, it has been thought that it
serves as a sexual weapon similar to the antlers of the deer, but until
the habits of the animal are better known this explanation of its use
must remain conjectural.
K
The great bottle-nosed whale (Hyperoödon bidens) is, to all outward
appearances, edentulous, but careful examination reveals the presence of
two, sometimes four, well-calcified conical teeth in the front part of the
jaw, which remain more or less completely hidden by the gum. In
addition to these, there are usually twelve or thirteen small rudimentary
teeth imbedded in the gums of both jaws, which soon disappear.
In the sperm whale (Physeter macrocephalus) the exposed and func-.
tional teeth are confined to the lower jaw. These are about twenty-
seven in number in each ramus, loosely implanted in a wide-open gutter,
with the alveoli or sockets scarcely perceptible. They are at first
sharply conical, but by attrition wear down into obtuse cones, biting
into pits or cavities in the gums of the upper jaw. In this jaw there
TEETH OF THE VERTEBRATA.
415
are a number of persistent rudimentary teeth concealed in the thick
gums, one pair of which is exposed in the small pug-nosed sperm whale
(P. simus).
In the dolphin of the Ganges (Platynista gangetica) the total number
of teeth is one hundred and twenty-four, of which there are thirty upon
each side above and thirty-two upon each side below. In the young
animal their crowns are produced into sharp cones, but by attrition the
posterior teeth are worn down to such an extent as to become molari-
form in shape. The last tooth in this species not unfrequently develops
a double root or fang, and is the only example of the kind to be met
with in living cetaceans.
The teeth of the dolphins of the Amazon are surrounded at the bases
of their crowns by a well-marked ledge or cingulum, which throws up
a strong internal cusp. On this account Dr. Gill elevates the genus
Inia to the rank of a family.
The sub-order Zeuglodontia is extinct, and includes a number of fossil
cetaceans, some of which are estimated to have attained a length of
seventy feet. They differ from living representatives of the order in
many important osteological characters, but not more prominently than
in their dental organization. Besides being heterodont and having the
posterior teeth implanted by two or three roots, some, if not all, were
diphyodont as well. The exact extent of the replacement, however, is
not fully known, but it is certainly true that two sets of teeth were
developed. In Zeuglodon cetoides (Fig. 199), from the Claiborne
FIG. 199.

Side View of the Skull of Zeuglodon cetoides (after Gaudry).
Eocene deposits of Louisiana, Alabama, and Mississippi, the teeth
are divisible by their form and position into incisors, canines, and
molars. Three teeth with conical recurved crowns are implanted by
single roots in each premaxillary bone, which in this animal contributes
a considerable part of the tooth-bearing border of the upper jaw. Of
these the anterior is the smallest and placed at some distance behind the
extreme anterior border, the posterior ones gradually increasing in size.
Behind these, near the maxillo-premaxillary suture, is a strong recurved
single-fanged tooth of a caniniform pattern, and one which both by
position and form becomes the homologue of the canine in the ordinary
heterodont dentition. The rest of the alveolar border is occupied by
four rather large more or less trenchant teeth, referable to the molar
and premolar series. Each of these is implanted by two roots, and has
a laterally compressed crown of a triangular form with the apex of the
triangle at the summit. Each of the anterior and posterior edges are
416
DENTAL ANATOMY.
interrupted by three well-marked cusps, which give to the tooth a
strongly-serrated appearance.
The heterodont and diphyodont character of the teeth of this cetacean
serves to bring the anomalous, and in many respects degenerate, dental
organs of this order into the closest relationship with the teeth of the
ordinary diphyodont Mammalia, and, being the oldest member of
the group so far known, goes far toward filling the wide gap between
these aquatic and the terrestrial mammals.
TEETH OF THE UNGUICULATE SERIES.
In considering the dental organization of this vast assemblage of
mammiferous animals it is necessary to have at the very outset a correct
conception of the primitive or ancestral stock from which all of them
have been derived, if such can be found to exist. This can be learned
only by a careful study of the successional history of the various orders
composing it. In searching, then, for this original stem we can by this
method exclude many of the groups from this position by fixing the
date of their appearance, and thereby establishing their exact limit in
time. We know, for example, that the Primates could not be the
ancestral group, for the obvious reason that they do not extend beyond
Miocene time; nor the Carnivora, which appeared about the same time;
nor the Rodentia, which date from the Middle Eocene; nor the Cheir-
optera, which can be traced back no further than the Upper Eocene.
We are therefore restricted in our choice to the insectivores, lemuroids,
creodonts, or tillodonts, which alone of the entire series continue back-
ward to the base of the Eocene Period. With reference to the creodonts,
I do not believe that any important distinctions exist between them and
the insectivores, while the line between this latter group and the lem-
uroids and tillodonts becomes extremely shadowy at this point.
B
Prof. Cope unites the insectivores, lemuroids, tillodonts, creodonts,
and tæniodonts into one order, which he calls Bunotheria, and defines
the several sub-orders as follows:1
I. Incisor teeth growing from persistent pulps:
(a) Canines also growing from less persistent pulps, agreeing with external
incisors in having molariform crowns
•
(b) Canines rudimental or wanting; hallux not opposable
Canines none; hallux opposable .
Taniodonta.
Tillodonta.
Daubentonioidea.
·
II. Incisor teeth not growing from persistent pulps:
(a) Superior true molars quadritubercular; hallux opposable
Prosimia.
(b) Superior true molars quadritubercular; hallux not opposable. Insectivora.
(c) Superior true molars tritubercular or bitubercular; hallux not opposable.
Creodonta.
8
I believe, with this author, in classifying those forms in which the
incisors grow from persistent pulps as a distinct group from those in
which the incisors are normal, as far at least as their growth is con-
cerned. In the first division there are three well-defined sub-orders. In
the second division it is extremely questionable whether more than two
sub-orders should be made. If we use the opposable and non-opposable
condition of the hallux as a character, we will have two perfectly natural
1 Proceedings Academy Natural Sciences Philada., 1883.
TEETH OF THE VERTEBRATA.
417
series-the prosimian or lemuroid and the insectivorous; but if we go
further, and establish another sub-order upon the tritubercular or quad-
ritubercular character of the superior molar teeth, it will necessitate the
wide separation of forms closely related to each other by every import-
ant feature of their anatomical structure-a course which I do not deem
advisable nor in keeping with our present knowledge of the subject.
According to Prof. Cope's definition, the only character in which the
Creodonta differ from the Insectivora is the tritubercular superior molars
as distinguished from the quadritubercular; and in order to make the
Creodonta homogeneous he is compelled to take out of the old group
Insectivora the Taupaiada, Centetida, Chrysiochloride, and Talpida, and
place them in the Creodonta. Aside from the inadvisability of such a
course, these teeth in many of the above-named families are altogether
intermediate between the tritubercular and quadritubercular pattern, the
postero-internal tubercle being represented often by a rudimentary cingu-
lum, which may be entirely absent or produced into a strong cusp.
Then, again, the snperior molar teeth of the prosimian division are
indifferently tritubercular or quadritubercular; and if we adhere to
this practice in the one, why not in the other? In consequence of
these facts, I propose to unite the Creodonta with the Insectivora into
a single division, for which the old name Insectivora may be retained.
Thus constituted, paleontological history, in my judgment, points
strongly to the fact that this group stands in the important relationship
of ancestors to a large part, if not the whole, of the unguiculate Mam-
malia. Working upon this hypothesis, it will be desirable to describe
the more important types of dental structure to be met with in this sub-
order, after which they can be followed out to their respective termina-
tions in the various orders and sub-orders which make up the series.
Malaga
INSECTIVORA.-The simplest form of dental structure in this sub-order
is exhibited by the extinct genera Mesonyx and Dissacus of Cope, from
the American Eocene strata. The teeth of Mesonyx (Figs. 200, 201)
are forty-four in number, disposed as follows: I. 3, C., Pm. 4, M.
42. The incisors are relatively small, with subconic crowns, which
are closely approximated. The superior canines are large, recurved, and
pointed, being placed at a considerable distance from the incisors to
accommodate the crown of the inferior canine. The three anterior pre-
molars of the upper jaw are two-rooted, with the exception of the first,
which is probably single-rooted. They have comparatively simple com-
pressed crowns, with a principal cusp and a posterior basal lobe, sur-
rounded by a basal cingulum. The fourth is more complex, and resem-
bles the true molars posterior to it. Like them, it has three principal
cusps, of which two are external and one internal, giving to the crown
a triangular shape. In the first true molar the postero-external angle
of the crown is produced into a strong blade-like process, a develop-
ment of the cingulum which is conspicuous in all. The last molar of
this series is bicuspid, the posterior of the two external cusps being
absent.
Pagal
In the lower jaw both the premolars and molars are remarkable for
their simplicity. The first premolar is single-rooted, and has a sub-
conic crown, as in the dog. The teeth behind it are two-rooted, and
VOL. I.-27
418
DENTAL ANATOMY.
have a general premolariform appearance, the true molars exhibiting but
little departure from the conical pattern of the lower Vertebrata. As in
the premolars of the dog, their crowns are laterally compressed, of a
FIG. 200.

Futs
b
a
Mandible of Mesonyx ossifragus, Cope, from the Wasatch Epoch of the Big Horn River, Wyoming, one-
third natural size (after Cope).
triangular form when viewed from the side, having a principal median
cusp, to which are added an anterior and posterior smaller one from the
cingulum.
It is a matter of considerable interest to find in this ancient represen-
tative of the unguiculate series so simple and generalized a dentition,
inasmuch as it furnishes a key to an interpretation of the lobes and
cusps of the teeth of many of the succeeding forms. It is more than
probable that this particular species is not the original ancestral form
from which the others have been derived, on account of certain charac-
ters presented by the skeleton, but, as far as the teeth of the lower jaw
are concerned, they exhibit just such a transitional condition between
the primitive cone of the theromorph Reptilia and the lowest forms
of mammalian teeth as we would most reasonably expect to find in
the primitive ancestor.
The various steps in this process of dental evolution I conceive to
have been as follows: (1) additions to the anterior and posterior edges
of the cone and the formation of a cingulum; (2) division of the single
TEETH OF THE VERTEBRATA.
419
root into two; (3) addition of basal cusps from the cingulum. It is a
fact worthy of notice that in the conical dentition the teeth of one series
do not exactly oppose those of the other, but close in the intervals be-
tween them. This in animals that attempted to crush a morsel of food
would cause stimulation of the anterior and posterior edges of the tooth,
thereby determining the point of the greatest nutritive activity and con-
sequent growth. Long-continued vertical pressure I believe to be an
adequate cause for the appearance of the wrinkle or fold of the enamel
covering at the base of the tooth which is designated as the cingulum.
FIG. 201.

Skull of Mesonyx ossifragus, anterior to post-glenoid process, one-third natural size, from the Wasatch
beds of Wyoming (after Cope).
The formation of two roots I believe to have been the result of the in-
equality of pressure exerted upon each tooth during the act of mastication,
whereby there was an effort to displace the tooth in an antero-posterior
direction, or, in other words, to give it a forward and backward rocking
420
DENTAL ANATOMY.
movement, as the greatest pressure was in front of or behind it. This
would cause the stimulation of the anterior and posterior faces of the root,
and as a consequence of this a vertical groove was first formed upon each
side, which eventually coalesced, dividing the root into two.
As we
have already seen, this condition is found in a theromorph reptile,
and is likewise to be found in the premolars of many existing animals.
The development of basal cusps would naturally follow at those points
where the crown sustained the greatest amount of resistance, which
would be at the base of the triangle.
It is a rule of pretty general application in heterodont teeth that the
molars are more modified than the premolars. This, in all probability,
results from the greater mechanical advantage which is gained by bring-
ing the morsel to be crushed or divided to the posterior part of the
mouth; that is to say, the resistance as near to the power as possible.
The power in this case is the muscles which close the mouth, which,
being attached to the posterior part of the jaw, exert the greatest
influence upon those teeth in the vicinity of their attachment.
The next step in dental complication is seen in the genus Dissacus,
from the lowest Eocene, the lower teeth of which are represented in
Fig. 202. They are very similar in general appearance to those of
FIG. 202.

α

b
Dissacus navajovius, Cope. Right Mandibular Ramus, three-fourths natural size: a, external; b, supe-
rior view, from the Puerco Beds of New Mexico (after Cope).
“Dajemo vam
Mesonyx, with which they also agree in number. There is, however, an
additional cusp developed upon the inner side of the median cone near
its summit, which is the homologue of the internal tubercle of the infe-
rior sectorial of the dog, as well as that of many other animals of the
unguiculate series. The upper teeth are not known. The genera in
which the mandibular teeth present this premolariform structure are
associated by Cope into a family which he calls the Mesonychida.
As a probable derivative of this family we have the extinct family
Hyaenodontida, of which the teeth of the single genus Hyaenodon are
represented in Fig. 203. This animal is known, so far, from the Mio-
cene deposits of this country and Europe only, and has been shown by
Prof. W. B. Scott of Princeton College to be a near relative of Mesonya.
The dental formula is, according to Gaudry, I. §, C. †, Pm. 4, M. 3
3/
42. The incisors resemble those of the dog, the median pair being
TEETH OF THE VERTEBRATA.
421
the smallest, the outer pair the largest. The canines are large, pointed,
and recurved. The anterior premolars above are two-rooted and have
premolariform crowns. The third and fourth are three-rooted, with
FIG. 203.

Will
Hyænodon horridus, Leidy. Skull, one-half natural size (from Cope, after Leidy).
three external and one internal cusp, which in the third premolar is
small and placed far back; in the fourth it is large and has a position
nearer the middle of the tooth; while in the first and second molars it
is anterior and more or less rudimental. The anterior cusp and median
422
DENTAL ANATOMY.
cone in these latter teeth form cutting blades and are truly sectorial in
their nature.
In the lower jaw the first premolar is two-rooted, with a compressed
crown without basal lobes. The second, third, and fourth have well-
developed posterior basal lobes, with the anterior absent. The first true
molar has three lobes, which form an imperfect trilobed sectorial blade.
The second is also trilobed, having the anterior cusp and median cone
developed into a true sectorial, while the posterior lobe forms a cutting
heel. In the third the heel is rudimental or absent, and the anterior
lobe and median cone are modified into a perfect trenchant blade.
From the Mesonychidae we pass, through Dissacus and Triisodon, to
another extinct family, which Prof. Cope calls the Leptictide. In an
FIG. 204.

с
OLGA
PR
zzzzzul
man
701070
44
7
a
PILLALU
ངས་
d
Skull and Part of the Posterior Foot of two individuals of Stypolophus whitic, Cope, two-thirds nat-
ural size: a, b, side and under views of the skull; c, portion of lower jaw; d, ankle-joint (after
Cope).
Eocene genus of this family, Stypolophus, Cope (Fig. 204), the dental
formula is I. 3, C., Pm. 4, M. 44. The incisors, canines, and
}
premolars are very like the corresponding teeth in Mesonyx. The last
superior premolar is, like the true molars, tritubercular, with the pos-
TEETH OF THE VERTEBRATA.
423
terior external angle produced into a prominent process, which is con-
nected with the postero-external cusp by a sharp cutting ridge. The
cingulum also furnishes a broad ledge upon the outside of the two
external cusps.
In the three inferior true molars the median cone, the anterior basal
lobe, and the internal tubercle are all well developed, and are disposed
in such a manner as to form an equilateral triangle, with the apex
directed forward and the base backward. Of these, the anterior basal
lobe occupies a position at the apex of the triangle, the median cone
and internal lobe being placed at the external and internal angles of
the base respectively. The posterior basal lobe is also present in the
form of a low heel, which may in some genera retain a simple cutting
form or may be broken up into several and become "basin-shaped.
This form of tooth Prof. Cope proposed some years ago to designate by
the name of "tuberculo-sectorial." There can be little doubt that it
furnishes the point of departure for the sectorial teeth of the lower jaw
FIG. 205.
a
C
מענייןן
b
d
Str
""

Left Mandibular Ramus of Triisodon quivirensis, three-fourths natural size, from the Puerco of New
Mexico; a, external view, displaying last temporary molar in place; b, the same from above; c, the
same, internal side, the temporary molar removed and the permanent fourth premolar displayed
in the jaw; d, the fourth premolar seen from above (after Cope).
of the modern Carnivora on the one hand, and the quadritubercular
lower molar of the entire unguiculate series on the other.
As will be seen, it displays the same elements that are found in the
inferior sectorial of the dog, the only difference being in the relatively
424
DENTAL ANATOMY.
smaller size of the internal tubercle and the modification of the primi-
tive cone and anterior basal lobe into a more perfect sectorial form in
the dog. The quadritubercular tooth has been derived from this by the
suppression of the anterior basal lobe, the reduction in size of the median
cone and internal tubercle, and the division of the heel into two cusps,
whereby the median cone becomes the antero-external tubercle, the
internal tubercle the antero-internal, and the heel the two posterior
ones.
The genus Triisodon of Cope (Fig. 205) affords a perfect transition
between Stypolophus and Dissacus, as far as the pattern of the infe-
rior teeth is concerned. In another genus, Chriacus, Cope, from
the Lower Eocene, which is provisionally referred to this family, the
upper molars are tritubercular with a strong internal cingulum, which
develops a rudimental fourth cusp behind. This forms one of the
examples referred to in which it is difficult to say whether the teeth
in question are tritubercular or quadritubercular, and goes far toward
invalidating the definition of the Creodonta as given by Cope.
This author says in reference to this family, and more especially to
this genus: "Two groups are easily recognized among the Leptictida.
In the first of these the last or fourth inferior premolar is a simple pre-
molariform tooth, different from the inferior true molars and without
FIG. 206.
any internal cusp. In the second
division the fourth inferior premo-
lar is either like the first true mo-
lars or approximates their form by
the presence of an internal tubercle.
To the latter group belongs the ge-
nus Chriacus, which, from the slight
development of the fourth inferior
premolar, approximates the first di-
vision. This genus may, however,
be improperly referred to the Creo-
donta." 1

M

Still another genus of this family,
Mioclonus, also from the Eocene,
presents truly quadritubercular
lower molars. The premolars are
simple and conical, and differ widely
in their structure from the molars.
The superior true molars are sim-
ilar to those of the preceding genus,
with the exception that the fourth
tubercle is better defined and fur-
nishes another example of the tran-
sition between the tritubercular and
quadritubercular condition.
In the typical genus Leptictis of
Leidy (Fig. 206) the dental formula is probably the same as that of
Stypolophus, the lower jaw being imperfectly known. The upper teeth
1 "The Creodonta," American Naturalist, April, 1884, p. 348.

Leplictis haydeni, Leidy. Skull, natural size, from
the White River beds of Nebraska (from Cope,
after Leidy).
TEETH OF THE VERTEBRATA.
425
are like those of Stypolophus in having the fourth premolar and all the
true molars tritubercular. There is no broad ledge external to the outer
cusps, however, as in that genus, and the posterior external angle of the
crown is not produced. It is from the White River Miocene of this
country, as is also a nearly-related genus, Ictops of Cope. The only
difference between these two genera is the more complex form of the
fourth superior premolar in the latter.
The living genus Centetes, or tenrec of Madagascar, is closely related
to this family, and differs only in the incomplete condition of the zygo-
matic arch. The number and form of the teeth are very like those of
Leptictis, and it is highly probable, as Cope suggests, that Centetes is
the living descendant of this genus.
FIG. 207.
Another quite remarkable genus which Cope places in this family is
from the Eocene, and was
described by him under the
name of Esthonyx. Its
dental formula (Fig. 207)
is I., C., Pm. &, M. 3
=34. The single superior
incisor of each side is great-
ly enlarged, and exceeds the
canine in size. The first pre-
molar is small and has a
simple crown. The next is
larger, and is tritubercular.
The third is like the true
molars, with the exception.
that it lacks the internal
cingulum. The true molars
have two external cusps,
bordered upon the outside
by a broad ledge which is
produced anteriorly into a
marginal cusp. There is
a large internal cusp, from
which is developed at its Esthonyx burmeisteri, Cope: a, b, c, parts of upper and lower
inner posterior extremity
jaws, natural size (after Cope).

a
b

10
WOOD MA
a strong cingulum, the representative of the fourth cusp, which is con-
tinued thence around the base of the crown behind to join its broad
external portion. This is another case wherein the tritubercular and
quadritubercular question is involved in uncertainty.
In the lower jaw the median incisors are small, the outer pair
enlarged, almost equalling the canines. The first two premolars are
small, the third larger, resembling the true molars somewhat in form.
The molars support two Vs, of which the anterior is most elevated.
An analysis of the crown shows it to be of a modified tuberculo-secto-
rial nature, wherein the three anterior cusps are connected by ridges
that extend quite to their summit and form the anterior V. The broad
heel displays two cusps connected by a strong ridge; from the outer of
these, again, another ridge passes obliquely forward to join the internal
426
DENTAL ANATOMY.
cusp, thereby completing the second V. The last molar has a fifth cusp
behind, in this respect resembling many of the lemuroids.
The family most nearly approximated to this genus is that including
the shrews (Soricidae), which always have two incisors both above and
below, greatly enlarged. In Blarina talpoides, a living species of this
country, the teeth (Figs. 208, 209) are thirty-two in number, of which
FIG. 208.

Side View of a Portion of a Skull of Blarina talpoides (much enlarged).
The sixth tooth of the upper series is placed somewhat internal to
the others, and is not represented in the drawing.
FIG. 209.
S
α
i
b
Vertical View of Grinding
Surface of a, a lower mo-
lar, and b, an upper mo-
lar (enlarged.)
twenty belong to the upper and twelve to the lower jaw. Owing to the
very early co-ossification of the premaxilla with the maxilla and the
paucity of suitable material, I am at present unable to give the proper
dental formula of this animal. Neither can I find any statement upon
the subject further than that of Owen, in which he refers to the European
species, Sorex araneus, with only eight teeth upon each side in the upper
jaw, and says: "The determination of the small teeth between the large
anterior incisors and the multicuspid molars depends upon the extent of
the early ankylosed intermaxillaries; the incisors being defined by their
implantation in these bones, the succeeding small and simple crowned
molars must be regarded as premolars, not any of them having the
development or office of a canine tooth their analogues in the lower
If he confines his statement to this
jaw are implanted by two roots."
species, it is probably correct to refer all those teeth between the large
incisors and the anterior one of the last three to the premolar series; but
in Blarina there are six teeth to be disposed of. Allowing the normal
number of premolars (four), we have either three incisors and no canine,
or, as is most probable, two incisors and a canine, which would give the
following formula: I. 4, C., Pm. †, M. g. This determination of
course may prove to be incorrect.
¹ Odontography, p. 418.
TEETH OF THE VERTEBRATA.
427
ť
The two large incisors above are hook-shaped, with a prominent pos-
terior ledge at the base, which in some species of this family is produced
into a strong basal cusp. The next two teeth are much smaller and sub-
equal, while the three following, rapidly decrease in size, the last becom-
ing very small. Exclusive of the large hook-shaped incisor, the above-
mentioned teeth display a principal cone with an internal lobe and
an external cingulum, which is most distinct in the fourth, fifth, and
sixth. The next tooth, which I take to be the last premolar, marks an
abrupt change both in the character and size of the teeth of the upper
series. It is almost equal in size to the first true molar, which it resem-
bles very closely in structure.
The crowns of the molars may be described as consisting of four
principal cusps or tubercles, of which two are external and two internal,
and are therefore quadritubercular. The two external cusps stand at the
apex of two Vs, which open externally, giving to this part of the tooth a
distinct W pattern. At the extreme antero-external angle of the crown
there is a considerable cingular cusp, which is connected with the main
antero-external tubercle by a prominent ridge, thereby forming the first
downward stroke of the W. From this main tubercle another well-
marked ridge passes outward and backward to another small cusp of
the cingulum, situated at a point midway between the two main exter-
nal tubercles on the outer edge of the crown, forming the first upward
stroke of the W and completing the first V. The second downward
stroke of the W is furnished by a ridge connecting the small median
marginal cusp with the postero-external tubercle, while the second upward
stroke of the W is formed by a ridge continued outward and backward
to the postero-external angle of the crown, where it terminates in as light
enlargement.
From the apex of each of the Vs a high ridge passes inward, meeting
at the antero-internal angle of the crown, forming a distinct U. The
inner part of this crest is the antero-internal tubercle. The postero-
internal tubercle stands just behind it, and exhibits a somewhat cres-
centiform pattern. It will be seen that the tooth just described does
not differ materially from those of some other insectivores already
noticed, especially Esthonyx. The principal differences are to be found
in the greater development of the marginal cingular cusps and connect-
ing ridges upon the external part of the crown, which we have, in a
measure, foreshadowed in Esthonyx and others.
In the lower jaw the single pair of incisors are large, scalpriform, and
procumbent. The two succeeding premolars are small, single-fanged,
and have simple crowns. The first two true molars are the largest of
the molar and premolar series, and exhibit a structure identical with
that of Esthonyx. The last is very small, and corresponds with the last
tooth of the upper jaw, which frequently disappears. The crowns of
all the teeth are stained a deep wine-color by a pigment which pene-
trates the substance of the enamel, this tissue being remarkable for its
thickness in all the Insectivores.
-
Considerable discussion has taken place in regard to the nature of the
external Vs and the exact homology of the two external tubercles. Since
this W-structure is common to the superior true molars of all the moles,
428
DENTAL ANATOMY.
shrews, and insectivorous bats, as well as some others of the unguiculate
series, it is desirable to have a thorough understanding of it. Cope
maintains¹ that the median and anterior marginal cusps are the homo-
logues of the two external tubercles of the teeth of such a form as Sty-
polophus (Fig. 204), and that the two cusps, which are here homolo-
gized as the representatives of the two external tubercles of this genus,
he proposes to call intermediate tubercles. Mivart, on the other hand,
holds that all the marginal cusps are developed from the cingulum, and
that the true external tubercles have come to occupy a more and more
internal position on the crown-a view which I believe to be correct.
2
The evidence upon which I base my opinion is to be found by exam-
ining the teeth of such genera as Stypolophus, Esthonyx, and Scapanus
of the unguiculate series, and Thylacinus, Didelphys, Phascogale, and
Dasyurus among the marsupials. In the genera Stypolophus and Estho-
nyx, as we have already seen, the way is paved, so to speak, for the
formation of the two Vs by the appearance of a broad ledge external to
the two main outer cusps and the elevation of the cingulum into a small.
cusp at the antero-external angle of the crown, as well as the backward
prolongation of the postero-external angle and its connection with the
postero-external tubercle by a strong ridge. This latter ridge I
regard as the strict homologue of the last upward stroke of the W. In
these two genera the only modifications necessary to produce the W
would be greater separation of the two external tubercles and the pres-
ence of a median marginal cusp connected with them by ridges.
In the genus Scapanus, or hairy-tailed moles, of this country the fourth
superior premolar does not exhibit the W-shaped arrangement in the
same perfection that the true molars do, the anterior
V being rudimental or absent. The cusp at the an-
tero-external angle, however, is present, and can be
clearly shown to be of a cingular origin. It cannot
therefore, as Cope supposes, represent the true antero-
external tubercle, in this tooth at least. In the sec-
ond unworn true molar of Dasyurus (Fig. 210) all
the marginal cusps are present, but the median one
is not connected with the two main external tuber-
cles by ridges, leaving the W imperfect. In this
tooth nothing is more apparent than the cingular
origin of all the marginal cusps; and no one can
doubt, it appears to me, that they are strictly homol-
ogous with the cusps in a like position in the molars
of those animals in which the W is perfectly formed..
A careful consideration of the teeth of the genera above mentioned in
my judgment effectually disposes of the whole question, and demon-
strates beyond doubt the correctness of the position here maintained,
notwithstanding the conclusions of so high an authority as Prof. Cope
to the contrary.
Galeopithecus, or the so-called flying lemur, constituting another
C
FIG. 210.
b
a
View of the Grinding
Surface of an Un-
worn Molar Tooth of
Dasyurus (enlarged):
a, internal; b, exter-
nal; ‹, anterior aspect
of the crown.
Big
Magd

"Mutual Relations of the Bunotherian Mammalia," Proceed. Acad. Nat. Sciences
Philadelphia, 1883, pp. 81-83.
2 Journal of Anatomy and Physiology, ii. 138, figures, 1868.
TEETH OF THE VERTEBRATA.
429
family (Galeopithecida), is quite aberrant in the form of its incisors
and some of the premolars. The incisors are two in number upon
each side in the upper jaw, and those of the opposite sides are separated
by a wide edentulous space; the first is minute and comparatively
simple; the second is relatively large, two-rooted, and in every way
similar to the tooth behind it, which is lodged in the maxillary bone.
The form of the crown is that of a greatly flattened cone with anterior
and posterior cutting edges. The anterior edge is interrupted by one
minor denticle, the posterior by four, making it dis-
tinctly serrated. The next tooth behind this one is
sometimes called a canine, but it is more probably
a premolar; if this be the case the premolars are
three in the upper jaw. The last premolar is like
the molars, with three principal cusps and two small
intermediate ones.
FIG. 211.

Biod
In the lower jaw the incisors (Fig. 211) form a
continuous arch around the alveolar margin, and
are of a most remarkable pattern. They are four in Two Incisors of the Lower
Jaw of Galeopithecus, ex-
ternal view (enlarged).
all, of which the outer pair is somewhat the larger ;
they have broad incisive crowns, which are cleft to
the base by deep vertical fissures like the teeth of a comb. In the
middle pair there are seven such fissures, dividing off eight slender col-
umns, whereas in the lateral pair there are ten.
S
The next tooth has a somewhat similar shape, but there are only four
fissures, which do not penetrate so deeply; its crown cannot therefore be
said to be more than serrate. The true molars are quintitubercular,
with very elevated cusps.
70
In the European mole (Talpa europea), which may be taken as a fair
representative of the family Talpida, the dental formula is I. §, C. †,
Pm. 4, M. &=44. The incisors of the upper series are normal both in
size and structure. The upper canine is large, recurved, and pointed,
and exhibits the remarkable peculiarity of being implanted by two
fangs. The premolars are simple compressed
teeth, increasing progressively in size from the
first to the fourth. The true molars are tritu-
bercular, with the W-shaped structure externally.
FIG. 212.
In the lower jaw the first four teeth are
small and incisiform; the next is large, two-
rooted, and caniniform, performing the func-
tion of the inferior canine. It is, however,
really a premolar, since it closes behind the
superior canine, and not in front of it. The
tooth immediately in front of it is the true
canine, notwithstanding its small size and in-
cisive office. The three succeeding premolars
are similar to the corresponding teeth above.
The true molars are quadritubercular, or rather
intermediate between the tuberculo-sectorial and
the quadritubercular patterns.
In the hedge-hogs (Erinacida) (Fig. 212) and the elephant shrews


b
a
Vertical View of a, the upper
jaw, and b, the lower jaw, of
European hedge-hog (Erina-
ceus).
430
DENTAL ANATOMY.
(Macroscelida) the molars are quadritubercular both above and below,
and exhibit no traces whatever of the complex W-structure. If it is
imperative to make any division of the Insectivora upon the characters
of the teeth, I would suggest that the W-arrangement of the cusps
of the superior true molars be considered as available for the purpose,
although I would be seriously disposed to question this character alone
as indicative of community of descent.
с
FIG. 213.
Another family of the Insectivora which in all probability stands in
ancestral relationship to the Carnivora is the one which Cope calls the
Miacida. It is represented by two genera, Didymictis and Miacis, both
from the Eocene of North America. In this family we have, as Cope
remarks, "the point of nearest approximation of the Creodonta and
Carnivora. This is indicated by the fact that
the sectorials are sectorials both by position.
and form, such as are not elsewhere met with
in the Creodonta. The genera might readily
be taken for members of the Canidæ and Vi-
verrida (dogs and civets) but for the struc-
ture of the astragalus, which is thoroughly
creodont."
b

A
The genus Didymictis may be certainly re-
garded as the ancestor of the civets, while it is
more than probable that Miacis (Fig. 213) was
the immediate progenitor of the dogs. In the
teeth of Didymictis (Fig. 214) the dental formula is not completely
FIG. 214.
Fragment of the Lower Jaw of a
species of Miacis : a, external, b,
internal, and c, vertical views.


AAN
b
с
a
е
f
21321
18
d


Two Species of Didymictis: a, b, c, internal, vertical, and external views of lower jaw of D. dawkin-
sianus, from Big Horn Beds; d, e, f, D. haydenianus; d, upper-jaw fragment, vertical view; e, frag-
ment of left ramus, inner side; ƒ, vertical view of same,—all natural size (after Cope).
known, but most probably it is I. §, C. †, Pm. 4, M. = 40. The
3
fourth premolar above is sectorial in form, the two true molars tuber-
cular.
In the lower jaw the first true molar has lost much of its typical
tuberculo-sectorial structure, which is best seen in the decreased size of
the internal tubercle and the tendency of the anterior basal lobe and the
1 "The Creodonta," American Naturalist, May, 1884, p. 483.
TEETH OF THE VERTEBRATA.
431
primitive cone to fuse into a cutting blade. A single tubercular molar
follows the sectorial, which exhibits, as does the second lower true molar
in the dog, a reduced or degraded condition of the tuberculo-sectorial
pattern.
Miacis has three true molars in the lower jaw, of which the first
is sectorial, in this respect resembling very closely the lower jaw of the
dog; its complete dental formula is not known.
TEETH OF THE PROSIMLE.-With this group we enter that division
of the Bunotheria which leads out to the monkeys and man. Its palæon-
tological history reveals an antiquity quite equal to that of any other
of the Monodelphia, continuing backward to the lowest Eocene. It
is customary with most naturalists to regard the Prosimice as widely
separated from the Insectivora on account of the higher order of brain-
structure which the living representatives of the lemurs display, and
they are accordingly placed near the Primates. Owing to the perish-
able condition and non-preservation of the soft parts in the extinct
forms generally, we will never be able to know the exact structure
of their brains, but must be content to judge of its generalized or
specialized character by the mould of the cranial cavity, which in
many respects is unsatisfactory.
It can be shown in the ungulate series that the lowest Eocene repre-
sentatives possessed brains, judging from the cranial casts, almost as low
in the scale of organization as that of the lowest known mammals, and
it is likewise true that the brains of the Eocene prosimians were more
generalized than those now living. I do not think there can be any
radical differences shown to exist between the structure of the brain
of such forms as the squirrel shrews (Taupaiada), the elephant shrews
(Macroscelida), and the Galeopithecide of the insectivores, and the
true lemurs (Lemurida), the fossil Adapis, and others of the Pro-
simia. The very fact of their remote antiquity and appearance in an
age when the brain-development of all the Mammalia was small would
of itself lead to the supposition that they too at first possessed brains of
lowly organization. It should be here stated that very few skulls of
the Eocene prosimians are known.
The dental formula of the spectrum lemur (Tarsius spectrum) is
I. 4, C. †, Pm., M. Of the two pairs of incisors in the upper jaw,
§.
the median is much the larger; they are closely approximated, long,
pointed, and conical, and are surrounded at the base by a prominent
cingulum, which is well defined upon the anterior face of the crown.
The next pair are much smaller, and also have pointed crowns and
basal cingula. The upper canines are about equal in size to the
median incisors, which they resemble both in the form of their
crowns and the cingulum at the base.
The first premolar is the smallest of the three, and is placed just
behind the canine; its crown is simple and pointed. The next two are
larger and imperfectly two-lobed, the internal lobe being represented by
a strongly-developed cingulum which continues around upon the outer
face of the tooth. The true molars are subequal in size and tritubercu-
lar. The two external cusps are well developed, and placed at the
external border of the crown. The internal lobe is relatively large,
432
DENTAL ANATOMY.
and occupies a position opposite the interval of the two external. A
moderate cingulum is developed on its internal aspect, and continues
around to the outside of the tooth.
In the lower jaw the single pair of incisors come close together above
the symphysis, and completely fill the space between canines; they have
conic crowns and are smaller than the median pair above. The canines
are larger than those above, and like them have pointed, slightly re-
curved apices. The premolars resemble those above, with the exception
that the internal lobe is absent. The true molars are quadritubercular,
with the two anterior slightly elevated. A trace of the anterior basal
lobe is visible, and is best marked in the first, which brings the struc-
ture of the tooth into close correspondence with the tuberculo-sectorial
of the Insectivores, and strongly suggests its derivation from it, as so
many other examples of a similar kind do. The last molar displays a
fifth lobe behind the two posterior ones, and is therefore quintituber-
cular. This species is the sole representative of the family Tarsiida.
In the typical lemurs of the family Lemurida the two pairs of upper
incisors are separated from each other by a wide space in the centre, both
being small and subequal. The superior canines are large; the pre-
molars, with the exception of the first, have a small internal cusp.
The molars are quadritubercular by reason of the internal cingulum
rising up into a cusp at the postero-external angle of the crown.
Various intermediate conditions between the perfect development of
this cusp and its almost complete absence are to be seen. The fourth
premolar, too, is in some genera like the true molars, in which case the
last molar is small.
The incisors of the lower jaw are two in number upon each side, and
are long, slender, laterally compressed teeth, having a procumbent
implantation. The canines resemble them very much both in shape
and position, being a little larger. The first premolar is large and
caniniform, and would be readily taken for the canine at the first
glance. The two following are smaller, and usually have simple
crowns. The molars are truly quadritubercular, the anterior basal
lobe being entirely absent. The last molar may or may not have
a fifth posterior tubercle.
TEETH OF THE TILLODONTA, TÆNIODONTA, AND DAUBENTONI-
OIDEA. The aye-aye (Chiromys) of Madagascar is generally associated
with the lemurs in the sub-order Prosimice, but naturalists-notably
Profs. Cope and Gill-have seen fit to give it a rank equal to that of
the lemuroids and place it in a distinct sub-order, Daubentonioidea, on
account of the aberrant character of its teeth as compared with the lemurs.
There are two other Eocene groups which go with it and constitute the
first division of the order Bunotheria, according to Cope.
Ma
The dental formula of the adult aye-aye is, according to Owen, I. },
C. f, P. 4, M. 318. The upper incisors are curved as in the Roden-
tia, and deeply implanted in the jaw. Their exposed portions are con-
tiguous, their widely-excavated fangs diverging as they proceed back-
ward. The incisors of the lower jaw are similar in shape to the upper
ones, and are implanted as far back as the coronoid process. They
are all covered with enamel, both in front and behind, and grow from
F
TEETH OF THE VERTEBRATA.
433
persistent pulps. In the entire investment of enamel they offer an
important difference from the incisors of the rodents, which they other-
wise closely resemble. The enamel being thicker upon the anterior than
upon the posterior face of the tooth causes them to wear into chisel-
shaped extremities, whereby the same effective gnawing instruments
are produced as in the typical gnawing quadrupeds. The molar and
premolar teeth are four in number upon each side in the upper, and
three upon each side in the lower, jaw. They are implanted after a
considerable interval behind the incisors, leaving a wide space or
diastema, as in the Rodentia. The first and last molars of the upper
series are the smallest, and have single roots; the second and third
larger, and implanted by three fangs each. Their crowns have simple
subelliptical grinding surfaces. The molars of the lower jaw are similar,
the first being implanted by two roots, the second and third by one each.
The deciduous or milk dentition is I. 4, C. f, Pm. 12. In the
milk set a small incisor appears upon each side of the median pair, and
is not replaced by a permanent one. Two teeth in this set occupy the
spaces between the premolars and incisors above, and have been con-
sidered canines, they having no permanent successors. The single decid-
uous molar in each jaw is succeeded by the permanent premolar.
2
The Tillodonta is a group which was discovered and described by
Prof. O. C. Marsh from the Upper Eocene deposits of Wyoming Ter-
ritory. In the typical genus, Tillotherium, the dental formula, as given
by this author is, I. 2, C. †, Pm. , M. = 34. The median pair of
§, §
incisors in each jaw are large and scalpriform, being faced with enamel,
as in the rodents. They grew from persistent pulps, as is indicated by
the large pulp-cavities at the base. The outer pair are small and did
not grow persistently. The canines are much reduced, and placed well
back in the alveolar border. The first of the three premolars of the
upper jaw is small and simple, the other two being larger and of a more
complex pattern.
The structure of the crowns of the superior molars is not very differ-
ent from that of Esthonyx. Two external cusps are present, which are
not well separated from each other; external to them is a broad cingu-
lar portion which is produced anteriorly into a process more marked
than in Esthonyx. Internally two cusps are present, the posterior being
lunate and consisting of a highly-developed cingulum. In the anterior,
or that which corresponds with the antero-internal cusp of the quadri-
tubercular molar, two well-developed ridges pass outward from its sum-
mit, one toward the anterior, and the other toward the posterior external
angle of the crown, giving it a rounded U-shaped appearance. The
pattern of the lower molars is identical with that of Esthonyx.¹
In a general survey of the dentition of this genus I am compelled to
dissent from the views expressed by Mr. Tomes, wherein he says that
the molar teeth are of the ungulate type, and that the order combines.
characters of the Carnivora, Ungulata, and Rodentia. While it is true
that the scalpriform incisors faced with enamel is a condition exhibited
by the rodents, a condition also found in the Toxodontia, I fail to
1
B
HANS
¹See Professor Marsh's monograph of this group, American Journal of Science and
Arts, vol. xi., 1876, p. 249.
VOL. I.-28
434
DENTAL ANATOMY.
discover the faintest trace of either carnivorous or ungulate relation-
ship. On the other hand, it seems to me that the evidence points
strongly to the fact that this group is the direct descendant of Esthonyx,
which preceded it in time. This is especially seen in the increased size
of the mesial pair of incisors, the reduction of the canines, loss of one
premolar in the upper jaw, and the remarkable similarity in the pattern
of the molar teeth. That Esthonyx is an insectivore allied to the shrews
there is scarcely any doubt. It is also probable that this group gave
origin to the toxodonts, but the exact connections between them are
not now apparent.
Another family, Stylinodontidae of Prof. Marsh, makes approaches in
this direction in the growth of the molars as well as the incisors from
persistent pulps.
In the Taeniodontia the incisors are large and scalpriform, and were
of persistent growth; the molar and premolar series are not separated
from them by any diastema, in the lower jaw at least, and the canines,
or those teeth regarded as such, in the inferior set also grew from per-
sistent pulps, and have grinding crowns.¹
TEETH OF THE PRIMATES OR QUADRUMANA.-The teeth of this
order are closely affiliated with those of the typical lemuroids in the
structure of the molars, and when compared with that of the other
groups the amount of dental variation is comparatively insignificant.
The order is naturally divisible into five families, of which the mar-
mosets and platyrrhines of South America and the catarrhines and
anthropoids of the Old World, as well as man, constitute the respective
divisions. Of these families, the marmosets (Hapalida) are the most
generalized and approach nearest to the lemurs in several important
characters, prominent among which are the relatively smooth cerebral
hemispheres, want of opposability of the thumb and its termination by
a distinct claw instead of a nail,2 and the possession of tritubercular
instead of quadritubercular molars. Since they are found only in the
New World, and as lemuroids were very abundant in this country in
the Eocene Period, it seems probable that they are the derivatives of
some member of this group. It is a fact worthy of notice that in the
curious Eocene genus Anaptomorphus we have a near approach to the
anthropoid condition of the teeth. In the shortness of the jaw and cer-
tain cranial peculiarities it also resembles the higher monkeys. For this
reason Cope believes that the simians have descended directly from this
lemur.
The dental formula of the genus Midas is I. 4, C., Pm. 3, M. =
12244
32, which obtains in the one other living genus. The upper incisors
have longitudinally flattened incisive crowns, with a prominent inter-
nal ledge at the base. The median pair is the larger, as is gener-
¹ Prof. Cope has established this sub-order upon the peculiar condition of the canine
teeth of the lower jaw, or at least those which he supposes to be such; the only know-
ledge we have of the teeth of the upper jaw is confined to the large scalpriform incisors.
This sub-order must be regarded as provisional until we know more of the upper teeth,
as well as the relationship of some genera apparently intermediate between it and the
Tillodonta.
2 Many of the lemurs are provided with an opposable thumb, which is terminated by
a distinct nail. In this respect the marmosets are even below the lemurs.
TEETH OF THE VERTEBRATA.
435
ally the case in all the Primates, and are in contact in the median
line. The smaller outer incisors follow closely in the dentigerous
border of the premaxillaries, after which there is a wide space, almost
equal to the width of the two incisors, for the passage of the lower
canine. The canines of the upper jaw are comparatively strong for the
monkeys, and have pointed, slightly recurved crowns which project far
above the level of the other teeth; there is a deep groove upon their
anterior faces.
The premolars or bicuspids are three in number, and completely fill
the interval between the canines and molars. The first is the smallest,
and has a prominent pointed external cusp on the grinding surface, to
which the cingulum adds a low U-shaped internal portion; the second
and third are similar, except that the internal lobe is no longer cingular,
the cingulum furnishing a second internal ledge. The true molars are
two in number upon each side, in this respect differing from all known
Primates. The only approach to this condition to be met with else-
where in the order is in the dentition of man, in whom it appears, as
we will hereafter see, that the last molar, or the "wisdom tooth," is
gradually becoming rudimentary or defective in the higher races. Vari-
ous causes have been assigned in explanation of this fact, one of which
is that the greater development of the brain necessitates the expenditure
of smaller amount of growth-force upon the maxillary bones, whereby
insufficient room is allowed and the tooth stunted. If this be the real
cause, it is difficult to understand why in the lowest representatives of
the order—and those, too, in which the cerebral hemispheres are pro-
portionally the smallest the complete suppression of the last molar
should have occurred.
The two pairs of lower incisors are small and of the usual incisiform
pattern, being considerably smaller than the canines. The lower incisors
of the allied genus, Hapale, are proclivous, the canines being relatively
small and approximated to them, as in the lemurs, although not to so
great an extent. The canines are almost equal to the upper ones in size,
and follow the outer incisors without interruption. The three lower
premolars are subequal, the summit of the first being elevated above
the level of the succeeding teeth. In the first the anterior basal lobe, the
principal cone, and an imperfect heel can be indistinctly made out, while
in the second and third the internal tubercle is present. In the true
molars there are four indistinct cusps; the anterior basal lobe has almost
completely disappeared, and all the cusps are of equal height. A care-
ful study of unworn teeth will show them to be a still further modifica-
tion of the tuberculo-sectorial type, whereby the perfect quadrituber-
cular has been produced.
3
The next division, Platyrrhines, or flat-nosed monkeys, constitute the
family Cebidae, in which the dental formula is I., C., Pm. , M. &
=36. They belong to the continent of South America, and have pre-
hensile tails and generally rudimentary thumbs. The canines are usually
strong and prominent, and the superior molars have a well-defined ridge
connecting the antero-internal with the postero-external cusps, a rem-
nant of the tritubercular condition. This ridge is found with varying
constancy in the superior molars of all the Primates, and marks the
T
436
DENTAL ANATOMY.
connection between the internal cusp and the postero-external tubercle,
which generally exists in the tritubercular tooth. The postero-internal
cusp, which lies inside and behind this ridge, is the last one which has
been added to complete the quadritubercular tooth in the upper jaw. In
the squirrel monkeys of this family the lower incisors have a tendency
to be proclivous, as in Hapale of the marmosets, thus retaining the
lemurine character of these parts. No fossil remains of this family are
known except from very late geological time, and these do not differ
materially from those now living.
The teeth of the Catarrhines (Semnopithecida) show a reduction in
the number of premolars, whereby the formula I., C. †, Pm. 2, M.
3
=32, the same as that of man, is reached. The incisors are of the
same shape as in man, the central pair being considerably larger than
the outer pair. The canines are always strong and powerful teeth, and
their apices are always elevated above the other teeth. They reach their
maximum of development in the baboons, more especially in the dog-
headed baboon, Cynocephalus, in which they are deeply grooved ante-
riorly. In this group the first premolar below is implanted by a double
fang, with its apex directed upward and backward. The anterior root
is naked for some distance, and presents in front a blunt edge which
bites against the posterior edge of the powerful superior canine, giving
to this part of the jaw a peculiar and characteristic appearance. The
second lower premolar of Cynocephalus is quadritubercular, with all the
cusps well developed, but in the macaques the posterior tubercles are
not well defined. Both the upper and lower true molars increase in size
from the first to the last, the last lower one being distinctly five-lobed.
In the semnopithiques the incisors are more nearly equal in size; the
canines are smaller and less deeply grooved than in the baboons; the first
and second molars are subequal, while the last lower molar is propor-
tionally narrower, but still retains the fifth lobe. The typical cerco-
pithiques have the last lower molar quadritubercular and all the molars
subequal. Fossil remains of this family are known from the Miocene
and Pliocene deposits of Europe and Asia, but no characters of unusual
importance occur in their dentition.
G
The next family of this order includes the anthropoid or tailless apes,
which are also confined to the tropics of the Old World. They consti-
tute the family Simiida, and are distinguished from the preceding fam-
ily, Cercopithecida, principally by the absence of the tail; from the suc-
ceeding family, Hominida, by the circumstance that the hallux is oppos-
able, whereas in the latter it is in a line with the other digits and is not
opposable. Other characters of considerable anatomical importance are
also found which distinguish them from man.
The orang
The teeth of this family are the same in number as those of man,
but considerable differences are found in the relative size of the canines
and the last molar when compared with that which obtains in the
human subject. Although they are organized substantially upon the
same plan, the teeth are larger and stronger than in man.
(Simia satyrus) is probably the most human-like in its dentition, although
in other respects the gorilla and chimpanzee most resemble man. The
molar teeth in this animal are remarkable for the straight line in which
"
TEETH OF THE VERTEBRATA.
437
they are implanted in both jaws, and contrast with the graceful curve
they pursue in the normal human mouth.
The median pair of incisors are larger both above and below; in the
upper jaw they are more than twice the size of the lateral pair, while in
the lower jaw they are more nearly equal. Between the lateral pair
and the canine above there is a considerable space, into which the lower
canine bites. The canines are relatively large, and their apices rise far
above the level of the surrounding teeth. They are imperfectly trihe-
dral in form, with a trenchant edge behind. These teeth are larger in
the male than in the female.
Jugada
The premolars or bicuspids differ from those of man in the upper
jaw in being implanted by three roots like the molars; their crowns
are very similar to those of man, presenting essentially the same ele-
ments. The pattern of the crowns of the molars is like that of the
human subject both above and below, but the last molar is as large as
the others; it is implanted by three roots, and is always perfectly formed.
In the lower jaw the two posterior molars slightly exceed the first in
size, and the last is distinctly five-lobed. The first lower premolar is
two-rooted, and has a faint resemblance to the corresponding tooth in
the baboons. The second is also implanted by two roots, and its crown
agrees with that of man.
In the other genera minor differences only are to be met with in the
form, pattern, and arrangement of these organs.
THE HUMAN DENTITION.
In this connection we come next to consider the teeth of man; and
before so doing I am constrained to make some general remarks in
regard to the position he occupies in the zoological scale. While it is
undeniable that by virtue of his superior brain-capacity and intellectual
development man is to be accorded a place at the head of the animal
kingdom, it is nevertheless true that much of his anatomical structure
has not been specialized beyond that of many of the lower forms. The
fact that different members of the mammalian sub-class have been mod-
ified in different directions, some to fit one environment and some
another, has led to the specialization of different sets of organs, and
that, moreover, in different ways as the surrounding conditions and
particular exigencies of the case have required.
It is these differences which enable the naturalist to construct zoologi-
cal definitions of the major or minor groups, such as orders, sub-orders,
families, genera, etc. The impracticability of determining which ani-
mal is highest or lowest in the scale of organization is thus rendered
apparent from the fact that a comparison of different sets of organs is
involved. Thus, in their dental, digestive, and limb structure the
ungulates surpass all other Mammalia in complexity and specialization,
and in these respects may be said to be highest, while in the matter of
brain-development they are much inferior to others. The monkey line
or Primates, on the other hand, of which man is at the head, retain a
comparatively generalized structure of the limbs, teeth, and digestive
GAR
438
DENTAL ANATOMY.
organs, but have outstripped all others in the development of the cere-
bral nervous system.
C
It is only upon an evolutionary basis that we are enabled to compre-
hend the significance and import of the manifold modifications with
which the morphologist is called upon to deal, and it is not at all un-
natural that in the consideration of the human or any other dentition
the student should first of all bend his energies to the discovery of the
relative position which his subject holds in the system. All the evi-
dence which anatomical and paleontological science can now bring to
bear on the question tends to show that man is the legitimate product
and highest expression of the evolutionary forces in that line of devel-
opment which began with the Eocene lemuroids, however objectionable
this conclusion may be to many. No adequate conception of his place
in nature or the structure of any set of his organs can be had without
a comparison with the other members of the stem to which he naturally
belongs. This reason alone has induced me, somewhat contrary to cus-
tom, to give an account of the human dentition in this situation, rather
than at the latter part of the present article.
Looked at from the point of view of the comparative odontologist,
these organs present little of general morphological interest beyond that
displayed by other Primates; but from the practical standpoint of the
operative dentist they are of the greatest importance. In the course
of this account many questions in connection with this latter phase of
the subject will doubtless suggest themselves to the reader which are not
within the scope of the present part of the work to discuss, its object
being merely to outline the anatomy.
The dental formula of the human subject is, normally, I., C. †,
2
Pm. ½, M. }=18=32, the same as that found in the Old World
16
16
FIG. 215.
monkeys. Much variation from this num-
ber exists, however, by reason of the failure
of development of the superior lateral inci-
sors and of the third molars, the wisdom
teeth or dentes sapientiæ; these molars may be
present in the upper or lower jaw only, or they
may fail to develop on one side in one or
both jaws, or, again, they may be completely
aborted. These variations are most fre-
quently met with in the higher races of man-
kind, and are said to be of rare occurrence in
the inferior races. The teeth are implanted
in the alveolar process in such a manner in
both jaws as to describe a regular parabolic
curve, being uninterrupted at any point by
the intervention of diastemata or spaces.
The summits of the crowns have, when
normally developed, approximately the same level, the canines not
excepted, thereby affording a marked contrast with the apes and mon-
keys, in which the crowns of the canines are always more elevated than
the other teeth.
The incisors are four in number in each jaw, those of the upper being
MOQL
Superior Maxillary Bone of Man.
VERS
Going

TEETH OF THE VERTEBRATA.
439
implanted in the premaxillary bones, which at an early period coalesce
with the maxillaries. Of these, the central pair is the larger and has a
slightly more anterior position than the lateral ones, on account of the
curve of the alveolar border. Their incisive nature is manifested by
the possession of a crown, which is bevelled on its palatine or lingual
surface¹ to a cutting edge, being broader at the extremity than at the
FIG. 216.

Inferior Maxillary Bone of Man.
base. The adjacent teeth are in contact at their coronal extremities, but
on account of the narrower base a slight interval appears between them
at the margin of the gum. The root joins the crown without any
marked constriction, so that a neck can scarcely be said to exist; from
this point it tapers gradually to an obtuse termination, being imperfectly
trihedral in form and slightly recurved.
In newly-erupted teeth the cutting edge of the crown is divided into
three inconspicuous cusps, which soon disappear through wear, leaving
it smooth. The basal termination of the crown is indicated by the limit
of the enamel covering, which is of greater vertical depth on the labial
and palatine or lingual than on the lateral faces, so that if a line be
drawn around the tooth at the most extreme basal portion of the
enamel, it will touch only the labial and palatine prolongations, and
not mark its exact limit on the mesial and distal surfaces. These
1
The nomenclature of the various surfaces of a tooth as it stands in position in the
jaw, it seems to me, is simplified by employing terms with the following signification :
If the tooth-line were straightened out upon each side, the surface which looks away
from the condyle would be anterior, and that which is directed toward it would be pos-
terior; the surface directed toward the median line of the mouth would be internal, and
that directed away from it external. In this system some confusion may arise with
respect to the incisors and canines, in which the anterior surface is internal and con-
versely, owing to the curvature of the tooth-line; but while it has appeared to me best
to speak of the surfaces as if the tooth-line were straight, I have in this paper adopted
terms now most familiar to the dental profession, which are represented by the follow-
ing: The surface looking toward the anterior part of the mouth and median line is
called the mesial surface; its opposite, looking toward the condyle, the distal surface.
In the superior row the surface which has been designated the internal I shall term
the palatal, and in the inferior row the lingual, while the external surface is the buccal
for the molars and bicuspids, and labial for the incisors and cuspids or canines.
The triturating surfaces of the molars and bicuspids are termed the masticating surfaces,
while the incisive surfaces of the incisors and cuspids or canines are denominated the
cutting edges.
440
DENTAL ANATOMY.
projections of the enamel present convex outlines basally, and are
separated from each other by two wide V-shaped notches occupying
the mesial and distal faces.
а
b
A Left Upper Central In-
or labial aspect; b, inter-
cisor of Man: Cl, external
nal or aspect.
FIG. 217.
77
The labial aspect of the crown is convex from side to side, as well
as from above downward, and is of greater vertical than transverse
extent. Upon either side the crown is triangular
in form, with the apex of the triangle terminating
at each free angle of the cutting extremity, and the
base directed toward the root; the basal part of the
triangle is interrupted by the V-shaped notch already
alluded to. That lateral surface which is directed
toward the median line (mesial) is comparatively
flat and most produced at the extremity, while the
one which looks away from the median line (distal)
is more rounded, having its terminal angle less pro-
duced. The interior or palatine surface is also tri-
angular, but the base is formed by the free cutting
edge and the apex turned toward the root. Usually, this surface is
nearly flat, but in some examples it presents a broad central concavity
whose depth may be considerably augmented by the presence of two
marginal ridges meeting at the radicular extremity or apex of the tri-
angle. These ridges, which are homologous with the cingulum of other
teeth, sometimes develop a small cusp at their point of junction, in front
of which there is usually a deep pit in the enamel-"a favorite site for
caries." As a general rule, the cingulum is but faintly marked, and the
posterior or palatine face is slightly concave.
wing
The lateral incisors of the upper jaw are smaller than the median pair,
but have approximately the same form. The labial face is more convex
from side to side, and the outer or distal angle of the cutting edge is
much more rounded off than in the median. The lingual surface may
be slightly concave from above downward, and convex in the opposite
direction, without any trace of the cingulum, or, as is most generally
the case, it is concave, with the cingulum present, and elevated into a
small cusp at the point of junction of the two lateral ridges. The
basilar contour of the enamel covering is the same as in the preced-
ing tooth. The root is more compressed laterally, of relatively greater
length, and tapers more gradually to its termi-
nation, giving to the tooth a more slender and
less robust appearance.
FIG. 218.
10
Kar
The pulp-cavities of these two teeth have sub-
bstantially the same shape, and the description of
one will answer for that of both. Its form is
that of an elongated tube, gradually increasing
in diameter from the apical foramen in the apex
A Lower Incisor of Man: a, of the root to a point which nearly coincides
anterior, and b, lateral view.
with the summit of the V-shaped notch in the
enamel on the lateral surface of the crown, where it becomes contracted
in an antero-posterior direction, but enlarged in its transverse diameter.
It is prolonged upon either side into a slight cornua, which reaches but a
short distance beyond the level of the general cavity; the one which cor-
TEETH OF THE VERTEBRATA.
441
responds to the internal or mesial angle of the cutting edge of the crown
is a little the longer of the two.
The two pairs of lower incisors reverse the condition of the superior
set, in that the central ones are the smallest. Their crowns have sub-
stantially the same pattern as those in the upper jaw, with the exception
that an internal or lingual cingulum is never developed. They are readily
distinguished from those above by their smaller size and greater lateral
flattening of the roots. The pulp-cavity and basal enamel contour are
like the corresponding teeth above.
FIG. 219.
The cuspids, canines, or "eye teeth," are the next in order behind the
incisors; in both jaws they completely fill the gap between these latter
teeth and the bicuspids, being in contact with
them at the mesial and distal extremity of the
crown. They are in every way stronger and
more robust than the incisors, and are im-
planted by roots whose length, proportionate
to that of the crown, is much greater. In the a
upper jaw these are indicated on the external
surface of the maxillary bone by a vertical
ridge or swelling which in many skulls extends
quite as high as the lower border of the ante-
rior nares.
b
A Left Superior Human Canine:
a, external, and b, internal
view.
The crown is terminated by an obtuse point,
which has a position in a line with the longitudinal axis of the root.
Upon either side of this cusp the terminal extremity slopes away, but
still retains a blunt cutting edge. When the median cusp is reduced by
wear the crown does not look very much unlike that of an incisor; its
labial or external face is broader above than below,¹ and convex in both a
transverse and a longitudinal direction, as in the incisors; the palatal or
internal surface is also bevelled, and the lateral surfaces (mesial and
distal), or those which lie adjacent to the contiguous teeth, are likewise
somewhat triangular in form, but more rounded. In the superior
canines a slight ridge descends upon the external or labial face from
the summit of the terminal cusp to the neck, but is absent in the
corresponding teeth below.
The internal or palatine aspect is slightly convex from side to side,
but concave from above downward. The palatine convexity is occa-
sioned by a well-marked vertical ridge which extends from the summit
of the terminal cusp to the cingulum below; this latter structure is
usually well defined, being stronger in the upper than in the lower teeth.
There is, as a general rule, a prominent basal cusp at the junction of
the two lateral ridges which connects with the vertical ridge, leaving a
deep pit upon either side-a spot where caries very frequently occurs.
As already stated, the extremity of the crown slopes away upon either
¹ When the terms above, below, superior, and inferior are used in connection with a
single tooth, they refer to the free as opposed to the implanted extremities: in the
upper jaw the part of the crown which is really above is that which joins the root, but
in the lower jaw it is the reverse of this. It is convenient to use these terms for all
teeth, as they correctly apply to the lower teeth, so that when we speak of the superior
extremity of the crown, the free or terminal part is meant, whether it belong to the
upper or lower jaw.
442
DENTAL ANATOMY.
side of the median cusp; that side which lies next to the premolars or
bicuspids is longer than that which is directed toward the incisors, so
that the distal or posterior moiety is greater than the mesial or anterior.
This inequality of the two sides exists in both pairs of the canines, being
less marked in the lower than in the upper; it furnishes a very useful
rule by which a canine can be referred without difficulty to its proper
side of the mouth.
The inferior cuspids or canines differ principally from those above in
the shorter root, blunter median cusp, and less-marked posterior or lin-
gual cingulum and basal cusp. The roots of both are thicker labially
than lingually, and are generally traversed by a vertical groove upon
either side.
G
b
The bicuspids or premolars are four in number in each jaw, and afford
a further complication of the pattern of the crown by reason of the ele-
vation of the basal cingulum into a strong in-
ternal cusp.
In proportion as this part of the
crown is well marked and complicated, there is
a corresponding disposition to increase in the
number of roots or fangs. These teeth, as their
name implies, are provided with two cusps to the
crown; those of the superior set are of subequal
dimensions and considerably exceed the lower
ones in size. The crown of the bicuspid, when
viewed vertically, presents an imperfectly quad-
rate outline, which is most distinct in the second,
and are broader than long. Two strong cusps, of which one is exter-
nal and the other internal, occupy the grinding face, and are separated
by a deep notch or valley, deepest in the centre. The anterior and pos-
terior margins of this valley are bordered by slight ridges which con-
nect the anterior and posterior extremities of the cusps; the anterior of
these is a little more elevated than the posterior, and forms a useful
guide in determining the mesial and distal surfaces of the tooth, and
consequently the side of the jaw to which it belongs. In some instances
the enamel forming the floor of the valley and adjacent sides of the
cusps and ridges is quite smooth, but most frequently it is considerably
wrinkled and thrown into a number of minor cusps and ridges, with
intermediate indentations which offer receptacles for the lodgment of
food.
a
C
FIG. 220.
First Upper Bicuspid or Pre-
molar of Man: a, vertical
view of the crown; b, lateral
view.
GARAN
J
Of the two cusps, the external is slightly the larger and more ele-
vated; it likewise has a greater antero-posterior extent. Its form is
very much like the entire crown of the cuspid, terminating superiorly
in a median cusp, from which the cutting edge gradually slopes away
upon either side. The internal vertical rib is also present, but the
external is absent. The internal or palatine cusp is thicker transversely
than the buccal, and is more rounded. On account of the connecting
ridges it has somewhat of a crescentic pattern.
Commonly, there is, to all appearance, but a single root, which is
traversed upon the mesial and distal faces by vertical grooves which
may unite near the apex, causing it to become divided. These vertical
grooves are the external indication of two pulp-cavities in the implanted
TEETH OF THE VERTEBRATA.
443
extremity, which unite about midway of the root, and are thence con-
tinued upward into the crown as a common cavity. The cavity thus
formed is of greater transverse than antero-posterior¹ extent; in the
vicinity of the neck it is little more than a narrow transverse fissure,
which widens somewhat above, and is prolonged into two cornua corre-
sponding to the two cusps. The external of these is the larger and most
elevated.
While this condition of the roots and pulp-cavity is the one usually
to be met with, nevertheless two roots are frequently found in the
first bicuspid, and three roots are occasionally
developed, two of which support the outer cusp;
the pulp-cavity has then, of course, three divis-
ions.
FIG. 221.
The principal differences between the upper
and lower bicuspids or premolars are seen in the a
size of the internal cusp as compared with the
external, the more cylindrical form of the root,
and the almost complete absence of the vertical
grooves, on account of which the pulp-cavity
is, as a general rule, single. The crown con-
sists of a large, somewhat conical external cusp, very convex without,
to which is added a low lunate internal cingular ridge. The internal
vertical ridge of the external cusp joins this cingulum near its central
portion, leaving a deep pit upon either side where the destructive agen-
cies of decay on the crowns of these teeth exhibit themselves most fre-
quently. The degree to which this vertical rib is developed is subjected
to great variation; it may be almost entirely absent in some individuals
or strongly developed in others. The crown of the second or posterior
bicuspid or premolar is more quadrate in outline than the anterior or
first; the internal cusp is better developed, and frequently shows a tend-
ency to form two.
Second Lower Human Bicus-
pid: a, b, vertical and lat-
eral views.
FIG. 222.
The normal number of true molars is twelve, three on either side in
each jaw, but, as already remarked, the last in both series may be absent.
In a series of adult skulls of various civilized races which I have
examined, twelve out of forty had one or both of these teeth wanting
from the upper series, and in the lower jaw
the proportion was ten to thirty. It is highly
probable that in many of these cases these
teeth had been present, but had disappeared
early in life. Many examples could be cited
in which the last or third molars wholly fail
to be erupted, and it is established upon good
authority that in many families one, two, or
all of these teeth are habitually absent from
generation to generation.
In the lower jaw the three molars in the
more typical lower races are equal in size and substantially alike in pat-
tern; their crowns are quadrangular in section, with the angles consider-
b
b
a
1
2
First Lower Human Molar: a, verti-
cal view of the crown; 1, anterior;
2, posterior aspect; b, side view.
1
By antero-posterior in this connection is meant the diameter which corresponds with
the long axis of the jaw.
444
DENTAL ANATOMY.
ably rounded off. They support four principal cusps, as in the quadri-
tubercular molar generally, together with a fifth one behind, which is
strictly homologous with the heel of these teeth in the more generalized
members of the Primate section. These are separated by four distinct
fissures arranged in the form of a cross; where the two limbs cross each
other they widen out into a median valley deepest in the centre. The
longitudinal of these, or the one which separates the external from the
internal principal cusps, terminates in a posterior bifurcation which con-
stricts off the fifth cusp or heel. The enamel lining this valley is, in
perfectly unworn teeth, much corrugated, so that it is sometimes difficult
to distinguish the principal cusps.
They are, with the exception of the last or third molar, implanted by
two antero-posteriorly flattened roots, which join the crown at the mod-
erately well-defined neck. These may be connate, having the two roots
indicated only by a vertical groove upon either side. Each root is hol-
lowed out in the centre to receive the radicular portion of the pulp, the
cavity corresponding with the external form of the root. These unite
into a common cavity above, which at about the time the tooth is erupted
is relatively very large, but which becomes smaller with age, and is final-
ly in old age obliterated through progressive calcification. The body
of the cavity is terminated superiorly by cornua corresponding to the
five cusps of the crown; of these the two anterior are most prolonged,
and reach slightly above the inferior limit of the outer enamel covering.
In the higher races the last or third molar is usually smaller than the
first and second, and does not have the cusp so well defined; but in
many of the negro skulls I have examined it is nearly as large, and
quite as well formed, as the two anterior to it. This tooth is more
constant, both as regards presence and form, than the corresponding
tooth above. It is, as a rule, two-rooted, but these roots may be
confluent, in which case two vertical grooves mark a tendency in this
direction.
The superior molars, like those in the lower jaw, are three in num-
ber, and have quadritubercular crowns normally, but many examples
can be found in which the postero-internal cusp, the last one added in
the quadritubercular molar, is little more than a cingulum,¹ and is
scarcely entitled to the appellation of a cusp. In such cases it fre-
quently has a position internal to the antero-internal cusp, and all
stages between that and its normal position are to be met with.
The grinding face of the crown is of a squarish form, bearing a
It is probable that this condition, of which I have seen a number of examples in
the higher races, is a degenerate one, and is an effort to return to the tritubercular
stage. Dr. Harrison Allen, in a communication to the Academy of Natural Sciences
of Philadelphia, has recently called attention to the fact that in senile changes those
structures which have been added last in the course of evolutionary growth are the
first to disappear. Although this condition cannot be said to be in any way depend-
ent upon individual senility, it is in all probability the result of senility of the race,
wherein retrogressive modifications of any set of organs are first apparent in those
parts which were the last to appear. It should be stated here that to Dr. Allen is due
the credit of having prepared the way for all the more important generalizations that
have been made in regard to the evolution of the quadritubercular tooth from the more
primitive types. He demonstrated that the postero-internal cusp of the human molar
is an outgrowth from the cingulum.
TEETH OF THE VERTEBRATA.
445
cusp at each angle. Of the two external, the anterior is slightly the
larger, and is usually connected with the antero-internal by a strong
ridge which skirts the anterior margins of the crown. The posterior
is separated from it by a fissure which terminates internally in the
median valley; it is also connected with the antero-internal cusp by a
ridge, the oblique ridge. From its posterior
margin a well-developed cingulum passes in-
ward on the posterior border of the crown to
join the postero-internal cusp, of which, as
already remarked, this latter is a part.
G
a
FIG. 223.
b
b, vertical view.
The antero-internal cusp is the largest of
the four, and by reason of its union with
the cross-ridges above mentioned has a some-
what crescentic appearance. It is placed at First Superior Human Molar: «,lat-
the apex of a V which opens externally and
encloses the median valley. The postero-internal cusp in the specimen
figured stands a little posterior and internal to the last mentioned, being
separated from it by a deep groove; it is little more than an enlargement
of the strong posterior cingulum.
The roots are three in number, of which two are external or buccal,
and support the two outer cusps, and one internal or lingual, supporting
the two internal cusps. The two outer are not unfrequently connate,
in which case the line of separation of the radicular portions of the
pulp-cavities is indicated by a vertical groove. The palatine is the
largest and longest root of the three.
While the structure here described usually obtains in the first and
second molars, the last is more simple and variable. In the more civil-
ized races it is exceptional for these teeth to be regular either in form or
position, so great is their variability. The crown resembles in a gen-
eral way those of the first and second molars, except that the oblique
ridge is generally absent and the two internal cusps are blended together.
The roots are connate and somewhat curved at their implanted extrem-
ity, and the pulp-cavity is single.
Occlusion of the Teeth.-The diagram (Fig. 224) on p. 446 represents
the occlusion of the teeth. It has been previously stated that in a well-
formed denture no one tooth rises higher than its fellows; that is, if
the crowns of the teeth in position be turned, cusps and cutting edges,
upon a plain or even surface, each tooth rests upon this surface. From
this arrangement there is nothing to interfere with a perfect occlusion.
Still, the fact must be recognized that while the above-described arrange-
ment is true of a perfectly-developed jaw and teeth, yet so rarely is it
found that it may be considered an ideal denture.
MAVÉ
It has also been stated that the superior arch or row of teeth describes
the segment of a larger circle than does the inferior row; this being the
case, when the two are brought in contact, as in normally closing the
mouth, the anterior superior teeth are thrown slightly over and anterior
to the corresponding inferior teeth. Also with the bicuspids and molars,
the external cusps of the superior ones are in closing slightly external to
the corresponding cusps of the inferior. Another serviceable peculiarity
is the noticeable absence of an exact opposition of tooth to tooth in clos-
446
DENTAL ANATOMY.
ing, as will be seen by the diagram: the greater width of the superior
central covers the width of the inferior central and a small portion of
the inferior lateral; this brings the superior lateral over the remainder
of the inferior one and the mesial fourth of the inferior cuspid, while
the cusp of the superior cuspid fits into the concave space between the
cusp of the inferior cuspid and the first bicuspid. In like manner, this
FIG. 224.

10
irregularity of opposition is maintained in all the teeth, so as to give
each tooth a bearing on two teeth, except the superior third molar,
which has but the corresponding tooth in the lower jaw for an antag-
onizer. This irregularity of opposition contributes to the efficiency of
the teeth in mastication, and is a valuable feature when a tooth is lost
from the arch in either jaw, for by this arrangement the tooth in partial
antagonism with the one lost still maintains a portion of its usefulness
by its occlusion with yet another tooth.
The Deciduous or Temporary Teeth (Fig. 225), twenty in number, are
FIG. 225.
Valbom

797
MACA
smaller than the permanent set, though they resemble them in their
eral conformation of crown and root, the bicuspids of the permanent set
gen-
TEETH OF THE VERTEBRATA.
447
2
not being represented in the deciduous dentine. The formula, when they
are normally developed, is I. 4, C., M. &=18-20, the premolars or
bicuspids being confined to the permanent set. A marked point of dis-
similarity, as compared with their successors, is in the termination of the
enamel on the neck of the tooth. In the permanent teeth the gradual
completion of the enamel on the border of the cement marks but indis-
tinctly the point of union of these two structures, while at the base of
the deciduous crown the terminating enamel on the buccal and labial
surfaces is recognized by a ridge or well-defined border which unmis-
takably marks its limitation and develops a well-constricted neck. This
difference is often of importance in deciding as to whether a tooth in
question belongs to the deciduous or permanent series. These teeth,
from the fact that their crowns are largely calcified before birth, are
much less liable to vices in conformation than their successors, but from
deficient nutrition, want of use, and neglect not unfrequently become an
easy prey to the ravages of dental caries. In common with a large class
of the order to which man is closely allied, the difference in number
between the deciduous and permanent set is twelve, the additional
teeth being without predecessors.
The accompanying figure (226) represents the denture of a child about
FIG. 226.

2
seven years of age. Twenty deciduous teeth, ten in each jaw, and the
four first permanent molars, are erupted. The second permanent molar
is seen in the crypt in the posterior part of each maxilla. Commencing
with the median line, to the right of it and just above the erupted decid-
uous central incisor, we observe the permanent central with its crown
fully calcified and the root partially so. In this case the crown of the
permanent tooth stands in front of or on the labial side of the partially
absorbed root of the deciduous central. This is not its constant relative
position; not unfrequently the deciduous root is in front of the crown,
as is seen in the adjoining lateral incisor. In this case the crown of
448
DENTAL ANATOMY.
.
the permanent lateral has the position which it invariably maintains.
The crown of the permanent cuspid is here normally located quite above
the root of its predecessor, and at the side of and in close proximity to
the wing of the external nares. Next in position, a little below and
slightly posterior to this cuspid crown, is that of the first bicuspid, this
and its fellow, the second bicuspid, are located between the roots of
their respective predecessors, the first and second deciduous molars.
The same is true of those on the other side of the jaw, and, with slight
variation, the same relative positions of the deciduous roots and perma-
nent crowns are observed in the inferior maxilla. It is above stated
that the figure represents the teeth of a child about seven years of age.
The first permanent molars, it should be noted, are at this age erupted
and in position, though their roots are not quite completed. The per-
manent central incisors will be the next to take their position at about
the age of eight, followed by the laterals at nine, the first bicuspids at
ten, the second bicuspids at eleven, the cuspids from twelve to thirteen,
and the second molars from twelve to fourteen, which completes the
eruption of the permanent teeth, with the exception of the third molars
or wisdom teeth, these may take their position at eighteen or some years
later. The anatomy of human dentition is further illustrated in plates
placed at the end of this paper (see p. 505).
Maan
TEETH OF THE CARNIVORA.
Our knowledge of the philogenetic history of the unguiculate series
has so increased within the last few years that it is now a matter of great
difficulty to say just what forms should be included in the order Carniv-
ora, as at present defined. If we take into account the living forms only,
no one will hesitate in fixing its limit and giving to it a moderately good
definition; but when the fossil representatives are considered, the interval
between it and some of the contiguous orders, especially the Insectivora,
is brought down to extremely small limits. We have already seen that
the Miacida approach the dogs and civets in the Carnivora on the one
hand, and the Leptictide of the Insectivora on the other. If a dog,
bear, cat, and seal, all of which are admitted to belong to the Carnivora,
be selected, and a careful comparison of their anatomical structure insti-
tuted, the differences between them will be found to be much greater
than between such forms as Stypolophus, Centetes, Miacis, and the dogs
and civets.
Every increment to our knowledge of the more exact relationship
of the various groups seems to bring us nearer to the conclusion that our
present classification is largely a matter of convenience, and often fails
utterly to express the deeper and more important facts of origin and
ancestry. Such reflections bring us abreast of the question, What is an
order, a family, or a genus, etc.? And just here we approach a prob-
lem as to the solution of which no two naturalists agree.
It appears to me that the only way out of these difficulties is to con-
sider the test of ancestry the only true basis of affinity. If it can be
shown, for example, that any given assemblage of organic forms have
descended from a common ancestor, however much they may differ
TEETH OF THE VERTEBRATA.
449
among themselves, such a line or branch constitutes a natural division.
Viewed from this standpoint, there can be little doubt that the order
Carnivora represents the terminal extremities of several distinct branches,
which arose not from one, but from two or perhaps three points in the
Insectivora. The same reasoning holds good for many other orders.
The order Carnivora, as at present understood, is divisible into two
sub-orders-Fissipedia, or the land carnivores, and the Pinnipedia, or
aquatic flesh-eaters. The latter division includes the seals, sea-lions,
and walruses, and is distinguished by the flipper-like modification of
the feet for progression in the water, as well as by several important
cranial characters. They are all known to be diphyodont, but the milk
teeth disappear early; in some cases this occurs before birth, and in
others a few weeks after. The teeth always possess comparatively
simple crowns, which are either simple cones, as in the majority of
the Cetacea, or laterally compressed, like the premolars of the dog,
with smaller cusps along the edge, giving a well-defined serrated
structure.
There are three families of this group, viz. the Phocida or seals, the
Otarida or sea-lions and sea-bears, and the Trichecida, or walruses.
In the common seal (Phoca vitulina), which is a good example of the
first, the dental formula is I., C. 1, Pm. 4, M. 34. The central
pair of incisors above (Fig. 227) are the smallest, with sharp-pointed,
1
FIG. 227.

Jet-
Vertical View of the Upper Jaw of a Harbor Seal (Phoca vitulina).
slightly hooked crowns; the next are similar in shape, but a little
larger, while the outer pair are abruptly increased in size.
These are
separated from the canine by a diastema to admit the lower canine.
The canine is a powerful tooth, with a conical recurved crown, and is
deeply implanted in the maxillary bone. In the specimen figured, which
is a young individual, it is remarkable for the very large size of the
pulp-cavity, which extends nearly to the apex of the crown. The first
premolar follows just inside and behind the canine, giving a crowded
appearance to the first two premolars, the longitudinal axes of which
are directed very obliquely to that of the succeeding teeth: it has no
deciduous predecessor, as the corresponding tooth in the dog, and is one
of the many examples in which it is difficult to say whether it should
be relegated to the milk dentition as a persistent milk molar or whether
it should be referred to the permanent set. It is implanted by a single
root, also remarkable for the size of the pulp-cavity, and has a crown
VOL. I.-29
450
DENTAL ANATOMY.
with a principal hook-shaped cusp, a small posterior basal cusp, and a
strong internal cingulum.
The next three premolars are similar, except that they are larger,
implanted by two roots, and have two posterior accessory cusps, the
hindermost of which is very small. The single molar differs from the
rest of the teeth in advance of it in having an anterior basal cusp, being
relatively thicker at the base of the crown, and with a moderately well-
defined internal cingulum, which displays a tendency to develop inter-
nal cusps.
FIG. 228.
The incisors and canines of the lower jaw are like those above, but
the two incisors of each side are separated at the median line. The first
premolar is single-rooted and
somewhat larger than its fellow
above. The crown displays a
median cone with three poste-
rior accessory cusps, and one
very minute anterior one. The
following teeth, including the
molar, are all similarly con-
structed, but have the anterior
basal cusp better defined.
In the hooded seals (Cystophora) the incisors are two upon each side
above, and one upon each side below. The canines are comparatively
large and powerful, while the molars and premolars are small and reduced
to simple conical bodies, similar to the teeth of the cetaceans. In another
genus (Stenorhynchus) the teeth are remarkable for the great length of
the cusps, and in one species, Leptonyx, for the curvature of the acces-
sory cusps toward the principal one, thereby resembling the trident
of a fishing-spear.
Vertical View of the Lower Jaw of a Harbor Seal.

Be
2
A good example of the dentition of the Otarida is furnished by the
fur seal (Callorhynus ursinus), which can usually be found in museums.
The dental formula is I. 3, C. 4, Pm. 4, M. 36. The two median
pairs of incisors above are subequal and laterally compressed. They
each present a deep transverse notch in the summit of the crown, into
which the incisiform extremities of the lower incisors bite; the outer
pair are larger and sharp-pointed. The canines are relatively longer
and more slender than in the seals, and have a well-defined posterior
trenchant edge. The succeeding teeth are all alike in form and size,
being implanted by single fangs. Their crowns are of a triangular
shape when viewed from the side, and present a single cusp. It fre-
quently happens that the bases of these teeth just where they emerge
from the gums are very much eroded, the cause of which is not at
present well understood.
k
Both the Phocida and Otarida are remarkable for their comparatively
weak and slender jaws, the backward direction of the coronoid process,
and the great distance intervening between its base and the last tooth.
In the seals the palate is very broad posteriorly, and the last tooth does
not extend behind the anterior root of the zygoma, whereas in the sea-
lions the palate is long and narrow, and the last tooth is placed consid-
erably behind the anterior termination of the zygomatic arch.
TEETH OF THE VERTEBRATA.
451
The Trichechida or walruses exhibit the most anomalous condition
of the dental organs of any pinniped carnivore so far known, in that
two enormous tusks are developed in the upper jaw, which occupy the
position and fulfil the functions of canines. Owing to the transitory
character of some of the other teeth, it is difficult to assign a definite
dental formula to this animal. Prof. Flower makes it out to be I.,
C. 1, Pm. 3, M. f. Besides these there are, according to Tomes, sev-
eral other small teeth to be found frequently in the position of the inci-
sors, and he is disposed to regard them as the rudimentary representatives
of the permanent normal ones in other animals; there can be little doubt
that he is correct. Rudiments of true molars are also not unfrequently
present in the back part of the jaws. The incisors and molars are small
and simple, and are soon worn down even with the gums into obtuse oval
grinding surfaces. The canines of the upper jaw protrude far below the
level of the symphysis, and grow from persistent pulps. They are com-
posed of dentine with a thin investment of cementum.
Tomes says of
them: "These great tusks are employed to tear up marine plants and
turn over obstacles, the walrus feeding upon crustacea and also upon sea-
weed, etc.; they are also used to assist the animal in clambering over
the ice; as they are of almost equal size in the female, they cannot be
regarded as weapons of sexual offence, but they are undoubtedly used
in the combats of the males."
WARN
The walruses and sea-lions agree with respect to the use of the hind
limbs for progression on land, being able to walk on all fours fairly
well; in the seals, on the other hand, the posterior members are rotated
backward, and permanently fixed in this position, so as to be of little
or no use in walking. In this respect they approach nearer to the
cetacean condition.
Viewing the Pinnipedia as a whole, I am inclined to think that the
relationship existing between them and the Fissipedia is more apparent
than real; and although paleontology does not at present permit us to
judge, I am of the opinion that they will ultimately be found to have
been derived from an entirely different ancestry. Fossil remains are
known as far back as the Miocene, but all that have so far been found
are typically pinniped. The simple structure of the teeth finds a par-
allel in the Insectivora in the teeth of the lower jaw of the genus
Mesonyx, already described, which Cope believes to have been more or
less aquatic from the evidence afforded by some of the limb bones. This
genus or an allied one may have been the progenitor of the pinnipeds,
but too little is known of the skull-structure to say anything about the
affinities between them.
The fissiped Carnivora are more extensive, both in number and
variety, than the pinnipeds, and enjoy a wider range of distribution.
Some of them are almost exclusively aquatic in habit, while others are
arboreal, fossorial, or terrestrial. It is in this group that we meet with
the highest specialization of the dental organs for the purpose of seiz-
ing, lacerating, and devouring living prey. In many the claws are
extremely sharp and hook-shaped, and are provided with a special
apparatus by which they are made retractile, thereby rendering them
efficient organs of destruction and prehension as well. The feet are
452
DENTAL ANATOMY.
not modified into flippers, as in the pinnipeds, but constitute distinct
The canines
61
paws," which in the aquatic forms have webbed toes.
are always present and generally of formidable proportions, while the
sectorial or shearing apparatus is present only in those that subsist
exclusively on an animal diet.
They have been divided by Prof. Flower into three groups, which he
has called the Cynoidea, Ailuroidea, and Arctoidea, defining them by the
characters of the otic bullæ and the base of the skull. The first of
these includes the dogs, wolves, and jackals, etc., and in all probability
represents the central group. From it the civets, cats, etc., consti-
tuting the Ailuroidea, branch off on the one hand, while the bears,
weasels, raccoons, etc. are closely connected on the other. The Cynoidea
comprises two families-according to most authors only one; these are
the Canida, or dogs, wolves, foxes, etc., and the Megalotidæ, including
the single genius Megalotis, or the fennec of Africa, which, for reasons
which will appear hereafter, I am strongly disposed to regard as an
entirely distinct family.
FIG. 229.
A typical dentition of the Canida has already been described in that
of the dog. About the only dental variations of importance to be seen
in this family consists in the re-
duction of the number of premo-
lars, addition or subtraction to the
number of upper true molars to or
from that of the dog, subtraction
from the lower molar series, and
slight modification in form of the
sectorials. Upon these variations
principally some thirteen or fifteen
genera have been defined. The
dental formula for many of the
genera is the same as that of the
dog, I., C., Pm. 4, M. =
/
42, but the extinct Miocene genus
Amphicyon (Fig. 229), found both
in this country and Europe, had
three true molars in the upper jaw.
In another extinct genus (Enhy-
drocyon), described by Cope from
the Miocene of the John Day beds
of Oregon, the premolars are re-
duced to three in each jaw. Oligo-
bunus is the name given by this
author to another extinct genus
from the same locality, in which

Skull of Amphicyon cuspigerus, Cope, with last
superior molar lost, one-half natural size, from
the John Day beds of Oregon (after Cope).
the molar formula is Pm. 4, M. . The principal part of the skull is
represented in Fig. 230. Still another genus of this family has been
described by the same author from the rich fossiliferous deposits of that
region under the name of Hyanocyon, which has three premolars above
and below, with only a single true molar above.
The sectorials of the more typical Canidæ are like those described in
TEETH OF THE VERTEBRATA.
453
the dog, but in some genera-notably Temnocyon of Cope-the heel of
the lower sectorial, instead of being basin-shaped, retains the more primi-
tive structure, and consists of a single trenchant cusp (see Fig. 231).
In the extinct genus Ailurodon of Leidy the dental formula is the
same as in the dog, but it approaches the cats, and especially the hyænas,
FIG. 230.


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Portion of Skull of Oligobunus crassivultus, Cope, one-half natural size: 1a, right maxillary bone from
below; 2, right mandibular ramus from above (after Cope).
FIG. 231.
in having three cusps to the blade of the superior sectorial, whereas the dog
has only two. The premolars too are more robust than in the dog, consti-
tuting another approach to the
condition of the Hycenidae. The
skull is represented in Fig. 232.
The genus Ichtitherium of Gau-
dry (Fig. 233), from the Miocene
of Pikermi, Greece, is an allied
genus, but the third molar of the
lower jaw is absent, leaving a for-
mula, I., C. †, Pm. 4, M.2-40.
In one species (I. robustum) the
last superior molars have nearly
the same proportions as in the
dog, while in another (I. hippa-
rionum) the last molar is consid-
erably reduced in size. It will
thus be seen that these two genera
depart from the central or typical
Canida, and establish close con-
nections with the Hyaenidae, which
are closely affiliated with the cats



Ramus, one-half natural size, viewed from without,
within, and above (after Cope).
and belong to the Ailuroidea. Temnocyon alligenis, Cope: part of Right Mandibular
Cope has suggested that Ailu-
rodon is the ancestor of the hyænas; and there is undoubtedly much
evidence to support this opinion.
The second family of the Cynoidea is the Megalotida, which is dis-
454
DENTAL ANATOMY.
49
tinguished from the Canidae-and, for that matter, from all other
diphyodont monodelphous mammals-by the possession of four true
molars in the lower jaw, thereby giving the formula I. 3, C., Pm.
4 M. 3/
46. The only other cases in which there are more than
three true molars normally are found in the marsupials, edentates, and
cetaceans; and in these two latter orders we have already seen that the
teeth are not generally divisible into incisors, canines, premolars, and
molars, on account of the development of only a single set. In the
marsupials, however, as we shall presently see, the normal number of
FIG. 232.

16.9.9.1
FESTA
6
Skull of Ailurodon sævus, Leidy, three-eighths natural size (after Cope).
true molars is four, just as the number three is most common to dip-
hyodont monodelphs. Reduction of the normal number is to be fre-
quently observed in the monodelphs, and, as we have just seen in the
Canida, occurs in genera otherwise nearly related; it cannot therefore
be regarded as of more than generic importance, but there are no cases
known to me in which teeth have been added. On the contrary, I am
firmly of the opinion that not so much as a single tooth has ever been
added to the diphyodont mammalian dentition in the course of develop-
ment, but that specialization has invariably gone in the opposite direc-
TEETH OF THE VERTEBRATA.
455
tion, as almost all evidence of paleontology goes to show. The teeth
are not otherwise remarkable, resembling distantly those of the dog in
general pattern. The sectorials are not well defined, and the crowns
generally have a tendency to the tubercular structure.
The second division of the Fissipedia (Ailuroidea) includes five fam-
ilies, the exact definitions of which the increasing knowledge of the
extinct forms is tending every
day to break down into hopeless
confusion. The definitions are
already very unsatisfactory and
in many cases fail to define.
The families which approach
nearest to the Canidae are the
Hyonida or hyænas, and the
Viverrida or civets. The evi- Superior Dental Series of Ictitherium robustum, two-
thirds natural size (from Cope, after Gaudry).
dence already cited brings the
former of these families into the closest relationship with the central
cynoid group. The dental formula of the existing hyenas (Fig. 234)
is, I., C. 1, Pm. 4, M. = 34. The incisors and canines have very
much the same pattern as the corresponding teeth in the dog, as do
also the premolars, with the exception of their more robust proportions
1
FIG. 234.
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FIG. 233.

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Skull of Striped Hyæna, Hyæna striata.
and the addition of an anterior cutting lobe to the superior sectorial.
In the lower sectorial the heel is very rudimental and the internal
tubercle is wanting. The single superior true molar is small and
456
DENTAL ANATOMY.
situated just internal to the posterior part of the great superior sec-
torial, so as to be completely hidden in an external view of the jaw.
FIG. 235.
In an extinct species (Hyaena eximia) there were four premolars in the
lower jaw, giving the formula I. 3, C., Pm. 4, M. 136. The infe-
rior sectorial also has a well-defined heel.
In the more ancient or Miocene represent-
ative of this family (Hycnictis græca,
Fig. 235) the superior molar is much
larger and has a more posterior position;
the inferior sectorial (Fig. 236) has a rela-
tively large basin-shaped heel, and there is
a small second true molar behind it. It is
through this genus that the transition is
effected from the Hyanide to the Canide
by way of Ictitherium and Ailurodon.

Superior Sectorial and First Molar of
Hyænictis græca (after Gaudry).
214 BUUSTOM
ESTA ANYS **
14.
The dental formula of the Viverida
varies somewhat by reason of decrease in number of the premolars.
and molars. The more important of these will be noticed after we have
first described the dentition of a typical example of the family, which is
found in the genus Herpestes, or the mongoose. The dental formula is
FIG. 236.
S
I. §, C. 1, Pm. 4, M. = 40. The in-
cisors of the upper series have flattened
oval crowns without lateral lobes, in-
creasing in size from first to third; the
canines are long, pointed, and recurved;
the first three premolars have the usual
pattern, but are devoid of accessory
cusps. In the fourth premolar or su-
perior sectorial the blade is composed
of the usual two posterior cusps, sepa-
rated by a fissure remarkable for its
depth. There is also a rudimental an-
terior basal lobe, which arises from the
cingulum. The internal lobe is unusually strong, and sends a trenchant
ridge backward and outward to join the principal cone. The next
tooth, or first true molar, is tritubercular, with two external and one
internal cusp; the crown is remarkable for its transverse extent. The
last molar is relatively small, and has a more internal position, possess-
ing a bicuspid crown. The decrease in size of the true molars from that
of the great sectorial, and the strongly inward curvature of the tooth-line
behind, are more pronounced than in the dog, and altogether interme-
diate between that of the latter animal and the cats.
Cal
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Fragment of Lower Jaw of H. græca, show
ing sectorial and second molar (after
Gaudry).
http

The incisors of the lower jaw are smaller than the corresponding
teeth above, and the summits of their crowns are distinctly notched;
the canines are like those of the upper jaw, while the premolars have
basal cusps which are largest behind. The first true molar or inferior
sectorial furnishes a pattern intermediate between the tuberculo-sectorial
and the well-defined sectorial. The primitive cone and anterior basal
lobes are connected into a blade, the internal tubercle being large and
furnishing the characteristic triangular appearance of this portion of the
TEETH OF THE VERTEBRATA.
457
crown. The heel consists of a raised margin bearing several small tuber-
cles. The last molar is quadritubercular, and seems to have retained
the anterior triangle of the preceding tooth, together with one cusp of
the heel. If this be so, it is an exception to the general rule, according
to which the anterior cusp becomes obsolete.
In the two-spotted paradoxure (Nandinia) of West Africa the molar
series is frequently reduced to M., while in the bintourong (Arctictis)
the last molar above and the first premolar below are often absent. The
premolar formula of the genus Galidea is normally, which likewise
obtains in the kusimanse (Crossarchus) from the West Coast of Africa.
The form of the inferior sectorial of the genus Cynogale, a Bornean
representative of this family, is nearer that of a tubercular than a sec-
torial tooth. The three anterior cusps which go to make up the tri-
angular portion are very much reduced, and have altogether lost their
sectorial character; the superior sectorial, however, is much better de-
fined as such. In another genus (Eupleres) the teeth are very small
and the incisors stand far apart, on account of which, together with
several cranial peculiarities, Dr. Gill gives it a distinct family rank.
It will thus be seen in a survey of the dental organs of this family
that they are almost identical with the genus Didymictis of our American
Eocene, which has already been described, and I think there can be little
doubt that they are the derivatives of this or some nearly related genus.
Another family, which stands intermediate between the civets and
cats, is represented by the single living genus Cryptoprocta, which is
limited in its distribution to the island of Madagascar. Some authors
classify it as a sub-family of the cats, others as a sub-family of the
civets, while others again make it a distinct family. No better argu-
ment, it seems to me, could be advanced in support of its intermediate
nature. It undoubtedly has strong affinities with both families, and
goes far toward bridging over the interval between them. The recent
discoveries of Cope and Filhol have shown it to be the surviving rem-
nant of an extensive group which lived in this country and Europe, and
which were the ancestors of the cats, and in all probability the deriva-
tives of the more generalized civets. In distinguishing between the
Felida, Viverride, and Cryptoproctida the foramina at the base of the
cranium afford the best, if not the only, grounds for separation. Pre-
vious to our knowledge of the extinct forms the number of the molar
teeth was also used for this purpose, but owing to the intermediate
condition of this latter character in many of the fossils it must be aban-
doned as altogether worthless. In the Cryptoproctide the alisphenoid
bone is perforated by a canal-the alisphenoid canal-for the passage
of the external carotid artery in its course forward. The foramen for
the entrance of the internal carotid in its passage to the brain is also well
defined, and of a considerable size. In the Felidae there is no alisphe-
noid canal, and the carotid canal is minute or absent. In the Viverrida
the alisphenoid canal is generally present, but not invariably so; the for-
amen for the entrance of the internal carotid is of moderate proportions,
as in the Cryptoproctidae, from which I can see no very good reasons for
distinguishing them as a family. Cope associates a number of extinct genera
together under the name of Nimravida, and defines them from the Felida
Audr

458
DENTAL ANATOMY.
by a number of characters in which they agree with the Cryptoproctidæ ;
the distinctions between them and this latter family are not so apparent.
The dental formula of Cryptoprocta is I. §, C. †, Pm. †, M. †=34.
The incisors and canines resemble those of the cats generally; the first
premolar in the upper jaw is caducous, and does not usually appear in
the adult skull. The superior sectorial has a rudimental anterior basal
lobe, an internal tubercle, and a well-defined blade. The molar is a
much smaller tooth, and has an internal position, as in the hyænas. In
the lower jaw the sectorial has a faint heel and lacks the internal tuber-
cle, and is altogether feline in its appearance.
The following extinct genera are enumerated and defined by Cope as
belonging to the family Nimravidæ :¹
I. Lateral and anterior faces of mandible continuous; no inferior flange.
a. No anterior lobe of superior sectorial; inferior sectorial with a heel;
canines smooth.
Proælurus.
Pseudælurus.
Cryptoprocta.2
T
Pm. 4, M.; inferior sectorial without internal tubercle
II. Lateral and anterior faces of mandible separated by a vertical angle; no infe-
Pm. 4, M.; inferior sectorial with internal tubercle.
Pm., M. inferior sectorial without internal tubercle
rior flange; incisors obspatulate.
a. No anterior lobe of superior sectorial; inferior sectorial with a heel (and
no internal tubercle); incisiors truncate.
Pm. 4, M.; canine smooth
Pm. 3. M. 1 ; canines denticulate
37
2
Pm., M.; canines denticulate
III. Lateral and anterior faces of mandible separated by vertical angle; an inferior
2
?
Pm. 1, M.
?
Τ
flange; canines denticulate.
a. No or a small anterior basal lobe of superior sectorial; inferior sectorial
with a heel. No posterior lobes on crown of premolars.
Pm., M. 1
Pm. 3, M.
T
Pm. M. †
31
2 or 3
·
Archælurus.
Alurogale.
Nimravus.
•
Dinictis.
Pogonodon.
Hoplophoneus.
Eusmilus.
·
Prolaurus is known to have possessed five digits in each foot, as
Cryptoprocta, and it is probable that two sub-families should be made,
FIG. 237.
since others had only four in the
pes. The dentition of Proælurus
(Fig. 237) is more primitive than
Cryptoprocta in the following cha-
racters: there are four premolars in
the lower jaw; the superior sectorial
has no anterior basal lobe; the in-
ferior sectorial has a strong heel and
an internal tubercle; and there are
two true molars below.

Pseudælurus agrees more nearly
with Cryptoprocta, but lacks one
premolar in the upper series. As
already observed, the first premolar
is caducous in this latter genus, and
In the sec-
they may be the same.
Proælurus julieni, Filh., two-thirds natural size.
1 "On the Extinct Cats of America," American Naturalist, Dec., 1880.
2 I have combined the Nimravida and the Cryptoproctida, and have inserted this
genus where it seems to most appropriately belong.
TEETH OF THE VERTEBRATA.
459
ond section the anterior and lateral faces of the mandible are separated
by an angle or vertical ridge, which gives to the jaw the appearance of
having a square chin.
FIG. 238.
The genera of this section, with the exception of Elurogale, are from
the Miocene beds of the John
Day Valley, Oregon, and were
described by Cope; the pre-
molar series shows a gradual re-
duction in number, but they all
retain the heel to the inferior
a gallery
b
sectorial and the generalized Proœlurus julieni, Filh., two-thirds natural size: a, inner
view of mandible; b, superior view of inferior teeth;
c, inferior sectorial, natural size (from Cope after
Filhol).
character of two true molars in
the lower jaw. Archælurus and
Nimravus are represented in the accompanying figures, 239 and 240.
FIG. 239.
Archaelurus debilis, Cope, Skull, one-half natural size (after Cope).
FIG. 240.
3
a
4
2
C



Skull of Nimravus gomphodus, Cope, two-fifths natural size (after Cope): 1, 2, first and second true
molars; 3, 4, third and fourth premolars of lower jaw.
460
DENTAL ANATOMY.
In the third section the mandible possesses a strong inferior flange
upon each side to protect the powerful canines of the upper jaw, which
in some forms project far below the level of the symphysis. They are
therefore known as the "sabre-tooth division." In the first of these
genera, Dinictis (Fig. 241), the true molars are, the inferior sectorial
FIG. 241.

Skull of Dincitis cyclops, one-half natural size (after Cope).
has a heel, and the true molar above is a moderately well-developed
tooth, as in the preceding genera. The genera Hoplophoncus and Pogon-
odon carry dental specialization several steps further, while in Eusmilus
we have the highest point reached by any of this group, which is in
many respects superior to the living cats.
Cope, in commenting upon the dentition of this group, says:
"It is
readily perceived that the genera above enumerated form an unusually
simple series, representing stages in the following modifications of parts:
(1) In the reduced number of molar teeth; (2) in the enlarged size of
the superior canine teeth; (3) in the diminished size of the inferior
canine teeth; (4) in the conic form of the crowns of the incisors; (5)
in the addition of a cutting lobe to the anterior base of the superior
sectorial tooth; (6) in the obliteration of the inner tubercle of the lower
sectorial, and (7) in the extinction of the heel of the same; (8) in the
development of an inferior flange at the latero-anterior angle of the
front of the ramus of the lower jaw; (9) in the development of cutting
lobes upon the posterior border of the large premolar teeth. .
The succession of the genera above pointed out coincides with the order
of geologic time very nearly.
The relations of these genera are
very close, as they differ in many cases by the addition or subtraction
of a single tooth from each dental series. These characters are not
even always constant in the same species, so that the evidence of
descent, so far as the genera are concerned, is conclusive. No fuller
genealogical series exists than that which I have discovered among the
extinct cats."
The last family of the Ailuroidea is the Felidae, in which we meet
with the highest point in specialization that has been reached in the flesh-
TEETH OF THE VERTEBRATA.
461
"
PP
eating Mammalia. It includes two divisions—one in which the superior
canines are normal and without the vertical angles and inferior flanges
to the mandible; and another, "sabre-tooth division," wherein the
superior canines are enormously enlarged, denticulate, and protected
by inferior flanges of the rami.
The first of these groups or sub-families is the more generalized, and
embraces all the existing cats or those animals popularly known as lions,
FIG. 242.

PG
4 3
2
Pogonodon platycopis, Skull, less than two-fifths natural size (after Cope): 2, 3, 4, second, third, and
fourth premolars, and 1, first molar of lower jaw; PG, post-glenoid foramen; PP, post-parietal
foramen.
1
tigers, leopards, panthers, etc. Five genera have been established in this
division on characters of the teeth and orbit. It is here that the domestic
cat belongs, and its dentition may be taken as a good average represen-
tation of that of the sub-family.
I
The dental formula in this animal is I., C., Pm., M. 30.
The incisors are relatively small, and are disposed almost transversely
across the front of the jaw. The first premolar above is a small, single-
rooted tooth, and is situated at a considerable distance from the canine,
which has the usual form and proportions of that tooth in the Carnivora
generally. The second is larger and two-rooted, while the fourth
or upper sectorial is decidedly the largest tooth of the superior series
it has three external cusps united into a blade, and a small internal
tubercle. The single molar is very small and functionless, being
placed internal to the posterior part of the large sectorial. In the
lower jaw the premolars are proportionately large, having two fangs
and posterior accessory cusps. The sectorial is specialized, and con-
sists simply of two cusps forming a trenchant blade; both the heel
and internal tubercle are absent.
The lynxes have one less premolar upon each side above than the cat,
and for this reason are placed in a distinct genus. In the flat-headed
cat and the fishing cat the orbit is completely encircled by bone—an
unusual occurrence in this family. In both, the number of teeth is the
462
DENTAL ANATOMY.
same as in the domestic cat, but in the former the first premolar in the
upper jaw has a single fang, whereas in the latter this tooth is two-
rooted. Upon these characters two genera have been established. The
clouded tiger of India has a dental formula like that of the lynxes, and
approaches the "sabre-tooth division" in the enlargement of the supe-
rior canines, by reason of which it has also been given a generic rank.
The hunting leopard, or cheetah, forms another genus, and is distin-
FIG. 243.
Tur
Gille
BANG

Cranium of Smilodon necator, Gervais, one-third natural size (after Cope).
guished by the absence of the internal tubercle of the superior sectorial.
All the other cats are very much alike, and can be distinguished from
one another only specifically, being classified, therefore, under the genus
Felis.
;
TEETH OF THE VERTEBRATA.
463
2
2 or 1
The second division is extinct, despite the fact that they reveal to us
the most perfect laniary dental apparatus yet known within the limits.
of the Carnivora, and were of the most formidable size. Two genera
are known, of which the cranium of one (Smilodon) is represented in
Fig. 243. In this animal the dental formula is I. 3, C. †, Pm.
M. † = 24 or 26, and marks the extreme point in dental specialization in
f
this order, as far as reduction is concerned. The canines of the upper jaw
are of prodigious size in comparison with those of the lower series, having
compressed crowns with serrulate edges. The superior molar has disap-
peared, and the first premolar in the lower jaw in some species is
wanting. The exact use of the great superior canines is not very
clearly understood. The possession of retractile claws, the reduction of
the molar and premolar series, together with the general perfection of
the sectorial apparatus, are strictly in keeping with a most carnivorous
habit; but with all this it must have been impossible for the animal to
open its mouth wide enough to take a firm grip upon a living prey, on
account of the great length of the upper canines.
Seeing that in the existing cats their chief destructive powers reside
in their biting qualifications, it is difficult to understand how these
animals inflicted wounds sufficient to destroy their prey, unless they
did so with that part of the tusk which projected below the level of the
symphysis when the mouth was closed, just as the walrus uses his tusks
to clamber over the ice. They may also have been used to assist the
animal in climbing, and in this way attained their great size.
The animals composing the last group, Arctoidea, are the least car-
nivorous, and do not as a general rule display as trenchant and sectorial
dental organs as the two preceding; in two families the almost exclu-
sively carnivorous habits are manifested by sectorials of moderate per-
fection; this condition is associated with a reduction of molars and
premolars from the number possessed by the dog. In the others the
molars are more or less tubercular-a structure better fitted for the
mastication of the mixed diet upon which they subsist-and usually
exceed the premolars in size and strength. The extremes of dental
variation in this group are exhibited by the bears and weasels, of
which the former are the farthest and the latter the least removed
from the more typical carnivores in the structure of the teeth.
In the bears the dental formula is the same as in the dog, but in
most of the living species the three anterior premolars are very small,
and frequently disappear in old age, leaving a wide space between the
fourth and the canine. In the upper jaw the teeth progressively
increase in size from the fourth premolar to the last molar, which,
besides being quadritubercular, is provided with a large posterior
heel rounded off behind; by the addition of this heel the crown is
rendered elliptical in transverse section, the antero-posterior diameter
being twice that of the transverse. The first true molar has four
cusps on its triturating face, and is subquadrate in outline; the fourth
premolar is tricuspid, as in the dog, but the two outer cusps are not
united into a perfect blade, and the internal lobe is large and has a
median position. This tooth is relatively small, and is situated consid-
erably in advance of the canthus or angle of the mouth; it is doubtful
464
DENTAL ANATOMY.
whether its possessor ever makes use of it as a sectorial organ, but
rather prefers to tear the tough animal membranes than to divide them
with the sectorials, as the dogs and cats do.
G
In the lower jaw the first true molar betrays the same lack of car-
nivorous specialization as the upper teeth, being essentially tubercular
in structure, although the proper elements of the sectorial of the dog
can be easily made out; the crown is much elongated, and is narrower
in front than behind, the heel composing at least half of the crown.
The next tooth behind it is the largest of this series, and is perfectly
quadritubercular; the last molar is smaller, with a subcircular grinding
face, upon which the tubercles are poorly defined.
While the structure here described is found in all the northern more
carnivorous bears, the tropical frugivorous species retain to a greater
extent the integrity and more normal condition of the anterior premo-
lars. This is especially apparent in a genus recently discovered in the
mountains of oriental Thibet and described under the name of Eluro-
pus. In this animal the first premolar only is small, while the others
gradually increase in size to the last molar, which has a comparatively
small heel.
The paleontological evidence is as yet too meagre to demonstrate
with any considerable degree of certainty the evolution of this group of
the Carnivora, but some suggestive hints of their former connection with
the Cynoidea are afforded by the extinct genus Hyaenarctos, which was
originally described by Dr. Falconer from the Sewalik Hills in India.
This genus displays three premolars of normal proportions and a large
sectorial, together with a last superior molar in which the heel is absent.
In one species in particular, H. hemicyon, from the Miocene of Sansan
in France, which is provisionally referred to this genus, the two true
molars in the upper jaw have about the same proportions as in the dog,
and otherwise resemble them very much. The sectorial, as is indicated
by the roots, was large, with the internal tubercle placed opposite the
middle part of the crown. If it were not for this latter fact, the frag-
ment of the upper jaw upon which the species was established would
readily pass for that of a member of the Canide.
In the weasels, which constitute the family Mustelidae, the sectorials
are well defined as such, and some of them, notably the typical weasels,
possess retractile claws. In none does the molar formula exceed 1,
except a fossil genus, Lutrictis, a near ally of the otters, in which the
molars are two in the upper jaw; it may, however, be reduced to †, as
in the case of the Cape ratel (Mellivora capensis). The premolars vary
in number, as do also the sectorial in structure.
The dentition of the American pine marten (Fig. 244) will serve
as an illustration of this family, although it is somewhat more
specialized in a carnivorous direction than most of them. Its dental
formula is I., C. 4, Pm. 4, M. 1 38. The incisors, canines, and
premolars have approximately the same structure as those of the dog,
except that the fourth premolar or superior sectorial has the two outer
cusps blended together, with the vertical notch absent. The true molar
is tubercular, and has a greater transverse than longitudinal extent.
In the lower jaw the sectorial is very much like that of the dog,
TEETH OF THE VERTEBRATA.
465
while the second molar is small, single-rooted, having a crown with
one cusp.
The teeth of the raccoons and allied forms are intermediate between
those of the bears and weasels in many respects, with a stronger tend-
ency to the tubercular than to the sectorial pattern.
FIG. 244.
TEETH OF THE CHEIROPTERA.-The modification of the anterior
members for flight distinguishes this order from all other unguiculates
at once.
Excluding this peculiarity, which is universal among them,
they are closely related to the Insectivora,
and without doubt have been derived
from some arboreal representative of
this order. It is conceivable that in
jumping from branch to branch they
have first developed a lateral fold of
integument, similar to that seen in the
flying squirrels, which later involved
the fore limbs and extended to the neck.
The flying lemur (Galeopithecus) fur-
nishes such a transitional condition, both
in the possession of the membrane and
the elongated and slender fore limbs, al-
though it is highly improbable that the
bats have descended through this genus.


The incisors are never more than two
upon each side above, while the lower
jaw is usually provided with the same
number, but may be increased to three.
Canines are always present in both jaws,
but are of variable proportions. In the insect-eating forms (Animalivora),
which includes the great bulk of the species, the upper molar teeth invari-
ably display the peculiar W-pattern of the moles, shrews, etc. of the Insec-
tivora, already noticed. The premaxillary bones are always small, and
seldom meet in the median line so as to leave the tooth-border inter-
rupted in front. In the W-pattern of the superior molars, the absence
of the median pair of upper incisors, and the small premaxillaries it is
interesting to note the resemblances they bear to the squirrel shrews
(Taupaiada), the only other insectivores besides the flying lemur which
are known to be arboreal in habit. Ignorance of the rest of the anat-
omy of this genus does not permit me to state whether it strengthens
this resemblance or otherwise, but upon the whole I am inclined to
believe that some such arboreal insectivore was the ancestor of the bats.
Vertical View of the Upper and Lower
Jaw of American Pine Marten (Mustela
americana).
(Ga
The dentition of the blood-sucking vampires is modified in accord-
ance with their habits, as is also the entire alimentary canal, and devi-
ates quite extensively from the normal condition of that of the insect-
eaters. The alimentary tract consists of little more than a straight tube
from mouth to anus, and is thus adapted to the assimilation of the
blood of living animals, upon which it feeds.
The large incisors of the upper jaw are two in number, one upon each
side, whose roots extend into the maxillary bone, and whose compressed,
sharp-pointed, hook-shaped crowns are specially fitted to puncture the
VOL. I.-30
466
DENTAL ANATOMY.
skin of an animal sufficiently to cause the blood to flow freely. The
canines are almost equal in size and similar in shape, while the lower
incisors and canines are small. The molars are reduced to two in the
upper and three upon each side in the lower jaw; the upper molars are
implanted by single fangs and have simple conical crowns; in the lower
jaw the first two are like those above, but the third has two fangs and
a bilobed crown, and is considered by Owen to be homologous with the
last premolars of insectivorous bats. The dental formula is thus re-
duced to I., C. †, Pm. } = 20.
2
The frugivorous bats, which are popularly known as "flying foxes,"
offer another deviation from the usual structure in the pattern of the
molar teeth; those in the upper jaw have crowns of a subcircular form
in outline with a central longitudinal depression, upon each side of
which the edge is elevated into a cusp. Those of the lower series are
similar but smaller, with the cusps more pronounced and the median
groove narrower.
TEETH OF THE RODENTIA.-The amount of minor variation in the
dental organs of this order is so extensive that their complete elucida-
tion is hardly within the scope of the present work; a description of
the leading types must suffice. That which most conspicuously distin-
guishes the rodents from all other mammals is the possession of two
powerful curved incisors in each jaw, which grow from persistent pulps
and are faced with enamel. The roots are implanted deeply in the sub-
stance of the jaw bones in the lower jaw, often reaching as far back as
the coronoid process. In consequence of the distribution of the enamel
upon the front face of the tooth, leaving the dentine naked behind, the
inequality of wear between the two surfaces is always marked, and con-
stantly preserves a chisel point to the crown-a structure pre-eminently
adapted to the gnawing habits of its possessor. Concomitant with this
modification the canines are always absent, the premaxillary bones are
large to support the roots of the incisors, and there is a wide space
between the first molar or premolar and the incisor, in which no teeth
appear. The mandibular condyle, moreover, is globular in form and
never transverse, thereby allowing excursion only in an antero-poste-
rior direction.
The order thus distinguished is divisble into four sub-orders, of
which the rat, squirrel, porcupine, and rabbit are typical representatives
of each.
Cranium of Common Rat, Mus
decumanus.
S
FIG. 245.
The dental formula of the common rat (Fig. 245) is I. †, C. f, Pm. f,
M. } = 16. Deciduous teeth are entirely
wanting, and it is therefore monophyodont
-a condition which we would be led to
anticipate, as far as the molar and premolar
series is concerned, in view of the subtrac-
tion of the latter. The absence of any de-
ciduous predecessors of the two pairs of in-
cisors is said to be a constant feature of all
that monophyodontism of this highly heter-

rodents except the hares, so
odont animal need not occasion surprise.
The incisors are of the usual pattern displayed by the order-large,
TEETH OF THE VERTEBRATA.
467
curved, compressed teeth, with chisel-shaped crowns, which are stained
a deep orange color on the anterior face; the pigment which produces
this color is intimately incorporated with the enamel itself, as in the
shrews, and serves to sharply define the limits of the enamel covering.
In both the upper and lower jaws the first molar is the largest and
the third the smallest. They are implanted by distinct roots, the oppo-
site rows of teeth being nearly-parallel. The crowns are made up of
three curved transverse ridges, with the convexity in front and the con-
cavity behind; the two anterior of these, in the upper teeth, are termi-
nated internally by well-marked cusps, which rise above the summits
of the ridges. In the last tooth the anterior and posterior of these
ridges are less distinctly marked, and are reduced to little more than
internal tubercles. The second molar of the lower jaw has the last
crest rudimental, and in the third it is entirely wanting.
FIG. 246.
While this structure prevails in the teeth of the more typical murines,
others possess molars with crowns of much greater complexity and
without roots. Such is exemplified by the arvicoline
section of the Muridae, in which the crown is cleft to
the median line by vertical fissures upon each side
placed alternately. The structure of the grinding sur-
face which results from this arrangement is a system
of alternate triangular prisms connected in the middle
of the crown by a narrow band of dentine. This is
well shown in the accompanying figure.
www
Vertical View of the
Grinding Surface of
the First Lower
Molar of a Muşkrat
(Fiber zibethicus).
T
d
SHOW
In the squirrel division premolars are always pres-
ent, in consequence of which there are deciduous teeth. With the excep-
tion of the beaver family, the teeth are very similar in the different spe-
cies, the only important variation occurring in the number of premolars.
In the common fox squirrel the dental formula is I. 1, C. 8, Pm. †,
M. = 20. The incisors (Fig. 247) are not so robust as in the rat,
and, like them, are colored upon the anterior face.
3/
FIG. 247.


Vertical View of the Teeth of Fox Squirrel (Sciurus carolinensis).
The first and only premolar is smaller, implanted by three roots, and
has a triangular tricuspid crown.
The three true molars in the upper
468
DENTAL ANATOMY.
jaw are larger and subequal in size. Their crowns are imperfectly quad-
rate in outline, and provided with two transverse crests which join a
large marginal cusp on the internal border. There is in addition an
anterior and posterior cingulum, which becomes continuous with the
large marginal cusp. The inferior molars have the same quadrate out-
line as those above, but the crowns present a central depression sur-
rounded by a slightly elevated margin bearing a cusp at each angle.
In this sub-order is to be found the nearest approach to the quadri-
tubercular condition of the molar teeth in any of the Rodentia, in con-
sequence of which there is little difficulty in comprehending their organ-
ization; but when we come to analyze the highly complex form of
molar which some of the porcupines exhibit, we naturally seek for a
key to a solution of their structure on the basis of the quadritubercular;
this is all the more natural when we remember that the squirrels present
the oldest known representatives of the order in the genus Plesiarctomys
of Middle Eocene Age, which scarcely differs generically from the living
forms. The teeth of the American porcupine (Erethizon), while possess-
ing in general the molar pattern of the squirrel, nevertheless differs from
it sufficiently in the direction of the more specialized hystricine teeth to
let us into the secret of how these complex forms have arisen from that
of the squirrel.
ww
In the description of the molars of the squirrel we have already seen
that the face of the crown is marked by three transverse ridges, enclos-
ing two valleys, which open externally and are bound-
ed internally by a thick marginal cusp. Now, in the
first premolar of the porcupine (Fig. 248) which is un-
usually instructive, the three transverse ridges are pres-
ent, but considerably augmented in height, together
b with a fourth ridge behind added from the cingulum.
The valleys separating the three anterior crests open
externally, while the fourth coalesces externally with
the third, so as to enclose a deep pit or fossette; the
strong internal marginal cusp is likewise present, but
is interrupted on its inner side by a deep wide valley
which opens internally. The succeeding molars are
like it in structure, except that the first and second
transverse ridges unite at their extremities to form
a second fossette in front.
a
FIG. 248.
d

с
of Porcupine
First Lower Premolar
zon dorsalis), vertical
posterior; e, internal
view: a, anterior; b,
;
and d, external sur-
faces of the crown.
In other genera of this group the valleys are still further deepened by
the elevation of the ridges, and other indentations are added from within.
As a protection against fracture of the now laminar crests, cementum ist
added, which completely fills up the valleys, leaving the grinding surface
approximately smooth. This is the condition attained by the beaver
among the sciuromorph or squirrel sub-order, as well as a majority of the
hystricomorphs or porcupines. As a further complication in this series,
the external and internal valleys unite across the face of the crown, leaving
transverse laminae connected only at the base and bound together above
by cementum; of which the guinea-pig is an example. Finally, the
extreme of specialization is reached in the capybara, wherein these trans-
verse laminæ are as many as thirteen or fourteen in a single tooth.
TEETH OF THE VERTEBRATA.
469
This point of perfection rivals that of the elephant, and is undoubtedly
a long way removed from the quadritubercular structure. On account
of this highly complex molar dentition and certain cranial peculiarities
Dr. Gill has proposed to give this genus a distinct family rank.
The last sub-order of the Rodentia is the Lagomorpha, which includes
the hares and rabbits. The dental formula in this group is constantly
I. 4, C., Pm. 3, M. 28, in addition to which in very young spe-
cimens there is another or third pair of inci-
sors in the upper jaw to be added to the per-
manent set. Huxley has recently shown that
the deciduous dentition is D. I. 3, D. M. 3,
which brings this group of the Rodentia into
strict accord with other Mammalia in the re-
placement of the teeth.
FIG. 249.

insan mer..
**** 10 ks •**
Last Molar of Capybara (Hydro-
chœrus cupybara), vertical view.
The median pair of superior incisors depart
from the usual pattern, inasmuch as they are indented upon their anterior
faces by a vertical groove near the middle of the tooth; they are other-
wise as in the genera already noticed, except that they lack the orange
color of the enamel. Immediately behind each of these incisors, and
applied closely to them, is to be seen a small cylindrical tooth, the second
pair of incisors. In the very young state a third pair can usually be
found imbedded in the gum external to the two median ones, which fall
out soon after birth. The single pair of the lower jaw are not grooved
and have the usual form common to the order.
The molars are remarkable for their great length in a vertical direc-
tion, as well as their antero-posterior compression; they grow contin-
uously and do not form roots. With the exception of the first premolar
and the last molar, the molars and premolars of the upper jaw are alike,
and consist of two vertical transverse laminæ closely united in the middle
line, the division of which is indicated both on the inner and outer sides.
of the tooth by a vertical groove. The first premolar and last molar are
made up of a single lamina, the enamel being thrown into two vertical
folds upon the anterior part of the first premolar. In other respects the
rabbits are remarkable for the entire absence of the coronoid process.
and the very small bony palate, which forms little more than a bridge
across the roof of the mouth.
TEETH OF THE UNGULATE SERIES.
So far, excluding the rodents, our attention has been confined to those
dental organs in which the molars have not, with few exceptions, passed
beyond the quadritubercular stage of development; this condition, we
have the best of reasons to conclude, was preceded by the tritubercular
in the upper and the tuberculo-sectorial, or at least a tooth possessing
its elements, in the lower jaw. When one compares these short-crowned
rooted tubercular molars with the complex rootless molars of a horse,
cow, or elephant, he might spend hours and days in thoughtful contem-
plation without discovering the faintest relationship existing between
their respective patterns; nor would we be any nearer a solution of
the difficulty had not the researches of paleontologists brought to our
470
DENTAL ANATOMY.
understanding a knowledge of these organs before they had assumed those
distinctive characteristics and specialized patterns which they now display.
There are few students of odontography who are acquainted with the
facts of mammalian paleontology as they now stand who have not had
repeatedly forced upon their attention the gradual decrease in complexity
of the molar teeth of the ungulates as we go backward in time. Cope
has recently shown that the earliest ungulates had, as a general rule,
tritubercular molars-a condition which is as primitive as that of many
insectivores; and in no instance do we meet with highly specialized teeth
until the latest geological periods are reached.
The ungulate series is divisible into four orders, which have been
characterized and defined by Cope upon the structure of the limbs. The
oldest of these orders, Taxeopoda, is remarkable for the generalized cha-
racter of the limbs as compared with the later ungulates; they possess five
toes upon each foot, and in one family, the Periptychida, the superior
true molars are tritubercular—a fact which brings the ungulate stem to
a point not far removed from the Insectivora of the unguiculates. This
order includes three sub-orders, two of which are extinct, and one, the
Hyracoidea, being represented by two living genera, popularly known
as the coneys.
The most ancient of these three sub-orders is the Con-
dylarthra, a group thus far known only from the American Eocene. A
careful study of their osteology leads to the conclusion that they are the
ancestors of all succeeding ungulates, furnishing just such a generalized
type in the proper geological position as is necessary to satisfy the
demands of the development hypothesis; they likewise enable us to
comprehend more clearly the mutual relationship and evolution of the
entire series.
TEETH OF THE TAXEOPODA.-As the Condylarthra are the oldest
of this order and the most primitive in their organization, it will be best
FIG. 250.

α
037006
68
wo
b
Dentition of Periptychus rhabdodon, Cope, two-thirds natural size: a, superior molars from below;
b, inférior molars from above-from the New Mexican Puerco (after Cope).
to commence with a consideration of their teeth. Three families are
referred to it, one of which, the Periptychidae, is confined to the lowest
Eocene deposits.' In the typical genus, Periptychus (Fig. 250), the
1
When the lowest Eocene is mentioned, reference is made to the Puerco beds, which
were formerly considered to belong to the Tertiary; Prof. Cope now considers that they
are of Cretaceous age.
TEETH OF THE VERTEBRATA.
471
dental formula is I. 3, C. 4, Pm. 4, M. 3=44, the normal diphyodont
number. The incisors are relatively small and of the usual pattern; the
canines are large, powerful teeth, and resemble those of many carniv-
orous and insectivorous animals. The premolars gradually increase in
size from the first to the fourth, which considerably exceeds the true
molars in size; the crowns of the last three premolars in the upper jaw
have a large external conical cusp and a strong internal ledge; those of
the lower jaw have a strong outer cusp, with a small accessory one at
the antero-internal, and two at the postero-internal, angle of the crown.
The true molars of the upper series appear at first sight to be com-
plex and multicuspid, but upon analysis it is found that they are essen-
tially tritubercular, with minor cusps added. The two usual external
cusps are present, together with one large internal tubercle somewhat
crescentic in horizontal transverse section. The three principal cusps
are homologous with the three cusps of the molar teeth of many of the
Insectivora already mentioned, and like them are placed in the form of
a triangle, but the two horns of the crescent are interrupted by the
development of two intermediate cusps; to these are added two small
interior cingular marginal cusps, making seven in all. The lower
molars are quadritubercular, with a faint representation of the anterior
basal cusp of the tuberculo-sectorial still remaining. The postero-
external cusp is connected with the antero-internal by a ridge which
crosses the face of the crown obliquely; this ridge is found in some of
the insectivores, notably Esthonyx, and is what remains of the former
connection of the heel with the anterior or triangular part of the tuber-
culo-sectorial. The enamel of both the molars and premolars of this
genus is curiously sculptured, owing to the presence of a number of
FIG. 251.

α
0
с
009
b
Ectoconus ditrigonus, Cope, two-thirds natural size: a, maxillary and premaxillary bones from below,
retaining a good deal of the matrix; b, last two inferior molars, worn by use; c, three deciduous
with first permanent molar of a young animal (after Cope).
vertical grooves and ridges, it being the only case of the kind known in
the Mammalia. In an allied genus, Ectoganus (Fig. 251), the molars
are larger than the premolars, and their crowns are further complicated
by the addition of an outer cingular cusp, giving a total of eight of the
472
DENTAL ANATOMY.
most complex tritubercular teeth yet known. This figure displays
more clearly than that of Periptychus the relationship of the component
cusps.
Other genera of this family, of which there are seven in all, display
simple tritubercular molars, which resemble the corresponding teeth of
the insectivores to a remarkable extent.
The second family of this sub-order is the Phenacodontida, which
continues to the Upper Eocene Period. Fragmentary remains of the
typical genus Phenacodus were known as long ago as 1873, but very
little was known of its true nature until, some nine years later, the
writer was fortunate enough to discover two almost complete skeletons,
representing two distinct species, in a fine state of preservation while
exploring the Wasatch deposits of the Big Horn Basin, Wyoming Ter-
ritory. This material has afforded Prof. Cope, at whose instance the
exploration was undertaken, the opportunity of not only determining
the position and affinities of this remarkable genus, but a key to a cor-
rect interpretation of many of his later discoveries, as well as a basis for
one of the most important generalizations yet introduced in relation to
the hoofed Mammalia.¹
&
The dentition of this genus (Fig. 252) approaches nearer to that of
the higher ungulates than the preceding family, although the interval
between them is comparatively small. Its formula is I. §, C. †, Pm. 4,
M. 44. The premolars are of a simpler pattern than the molars,
the posterior ones becoming tritubercular. The superior molars have
quadrate crowns bearing four principal cusps, placed at each angle, to
which are added several minor cusps, the rudiments of structures which
assume considerable importance in the later and more specialized gen-
era. The four principal cusps are the usual ones of the quadritubercular
molar, two external and two internal, and are low, more or less conic,
obtuse structures. Between the outer and inner ones are two isolated
tubercles, which are later developed into cross-ridges connecting the
outer and inner cusps, thereby producing the lophodont molar which
is so characteristic of some groups of the ungulates. At a point mid-
way between the two outer cusps, on the external margin of the crown,
the cingulum is produced into a small tubercle, which in most of the
specialized ungulates becomes connected with and unites the two Vs
formed by the crescentic structure of the two external cusps, just as in
some of the insectivorous genera already described.
In the lower molars four tubercles are present, of which the postero-
external is connected with the antero-internal by a well-marked ridge.
The anterior basal lobe is reduced, but still present in the form of a low
cingular ridge.
The molar teeth of this animal display a typical bunodont dentition,
and upon a correct understanding of their organization depends a proper
comprehension of all the succeeding specialized molars of this series.
It is by simple additions to, and modifications of, the component lobes
and crests of this pattern that all the complex ungulate molars have been
produced; if the advocate of the evolution hypothesis had no other evi-
¹ See Prof. Cope's valuable memoir of this group, American Naturalist for August.
and September, 1884.
TEETH OF THE VERTEBRATA.
473

$
Son
HOUSIN
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AVRUL
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b
α


FIG. 252.-Skull of Phenacodus primævus, Cope, one-half natural size (after Cope).
474
DENTAL ANATOMY.
dence upon which to base his belief than that afforded by the gradual
complication of the molar teeth from this point upward in the hoofed
FIG. 253.

a
* meet the
Meniscotherium terrærubræ, Parts of Cranium, three-fourths natural size-from Wasatch Beds of New
Mexico: a, cranium from above; b, from below; c, portion of upper jaw, displaying deciduous
molars (after Cope).
Mammalia, this alone, it appears to me, would be sufficient to gain for
it a respectful consideration at the hands of its opponents.
FIG. 254.
Leatmi
D
C

α
αι
ODEDOVER
Lower Jaw of M. terrærubræ, three views (after Cope).
The last family of this sub-order is the Meniscotheriida, whose den-
tition is represented in Figs. 253, 254. The dental formula of the
TEETH OF THE VERTEBRATA.
475
&
single genus Meniscotherium is given by Cope as follows: I., C. 1,
Pm. 4, M. =44. As compared with Phenacodus, the canines are
relatively smaller and the molars more complex; the same elements are
readily recognized as in the molars of that genus, but the two exter-
nal cusps are crescentic and elevated, the two contiguous horns being
connected with the median external cusp, which now forms a vertical
ridge or rib on the external part of the crown. The intermediate tuber-
cles are also present, and are greatly enlarged; the anterior is crescentic
and the posterior oblique and elongate. Of the two internal cusps, the
anterior is conic, while the posterior is crescentic.
The lower molars exhibit two Vs, by reason of the development of
cross-ridges connecting the external with the internal cusps and the
increase in height of the oblique ridge. The tooth-line is uninterrupted
by a diastema, and the incisors did not grow from persistent pulps.
The second sub-order, Hyracoidea, has long remained a puzzle to
zoologists, and has been associated at different times near the rodents,
at others with the perissodactyle ungulates, and latterly has been made
the type of a distinct order. The discovery of the Condylarthra leaves
no doubt of its relationship with these forms, and the propriety of
making it a sub-order of the Taxeopoda is at once apparent. The
dental formula of the two living genera, Hyrax and Dendrohyrax, is
given, I., C. f, Pm. 4, M. § = 36, although DeBlainville in his figures
of the different species represents some of them with only two incisors
in the upper jaw instead of four.
FIG. 255.
The incisors grow from persistent pulps and have large pointed
the canines are entirely absent from both jaws; the molars
and premolars have complex crowns-in one genus, Hyrax, being
almost identical with those of the rhinoceros; on account of this com-
plexity Cuvier placed it in the same group with that animal. In the
other genus, Dendrohyrax, the molar teeth are quite different, and upon
careful comparison with those of Meniscotherium betray unmistakable evi-
dence of near relationship. This resemblance is
not confined to the molar teeth alone, but is strik-
ingly shown in the general form of the skull,
and especially in the great enlargement of the
angular portion of the mandible. The upper
molars of this genus (Fig. 255),¹ like Menisco-
therium, have two crescentic external cusps con-
nected by a vertical rib, and two intermediate
tubercles, which are more or less blended with
the two internal cusps, while the lower molars
have essentially the same pattern as those of
this genus.
The whole structure of the molars
represents just such an advance over that of the
as we should be led to anticipate on a priori grounds.
extinct Eocene genus
It is true that the canines are absent in Dendrohyrax, and incisors
grow from persistent pulps; but this is not at all remarkable when we
consider the great interval of time between them and an approach to
this condition, as far as the canines are concerned, in their reduced size,
¹This figure does not represent the structure of the grinding face very clearly.
1.
4
Vera, taki
2
$
3
a
Molar Teeth of Dendrohyrax
arboreus, vertical view: a,
superior molar; 1, external,
2, anterior, 3, internal, and
4, posterior surfaces of
crown; b, inferior molar;
1, external, 2, internal sur-
faces (after De Blainville).
b
476
DENTAL ANATOMY.
in the extinct genus. Altogether, I am disposed to regard Menisco-
therium as the direct ancestor of the Hyracoidea, notwithstanding their
wide separation in both time and space.
As a further complication in the molar pattern of this line, we have
the complete fusion of the intermediate tubercles with the internal cusps
in Hyrax, which, as already stated, gives the pattern of the molars of
the rhinoceros.
It is believed by Cope, from evidence afforded by the structure of the
limbs, that the Toxodontia, a group of curious extinct ungulate forms
found in the later geological horizons of South America, belong to this
order. I am unable to find any confirmation of this position from a
study of the teeth, but it may be that they have been derived from a
condylarthrous source.¹
The dentition of the typical genus Toxodon contains incisors, pre-
molars, and molars only, the canines being absent, and all were of per-
sistent growth. The two pairs of incisors above are large and scalpri-
form, as in the rodents, of which the outer greatly exceed the mesial
pair in size. In the lower jaw these teeth are three in number upon
each side, and were also of persistent growth. They are subequal in
size, and have imperfectly prismatic crowns similar in shape to the tusks
of the boar in transverse section, being covered with enamel only upon
the anterior convex surface.
The molars, of which there are seven upon each side above, gradually
increase in size from the first to the last. It is highly probable that
the first four of these teeth are premolars, but in the absence of any
knowledge of the milk dentition and the manner of its replacement,
this, of course, is inferential. They have remarkably long crowns,
with an altogether unique pattern, and did not develop roots. In
section they are triangular, with the apex of the triangle directed forward
and outward. Upon the inner side there is a deep indentation or fold
reaching to a point near the centre of the crown, which may be the
valley separating the two internal cusps. The only arrangement sim-
ilar to this is seen in the last upper molars of many of the Ungulata,
of which Meniscotherium furnishes an average example. Here the pos-
tero-internal cusp is absent, and the two outer cusps are intimately
blended. In the rhinoceros (Fig. 257) the last molar goes even further.
in this direction by reason of the fusion of the elements and the obliter-
ation of the external rib. It is conceivable that some such structure as
this preceded the present one in Toxodon, but until the paleontological
evidence of the philogeny of this group is more fully known this is the
only explanation which can now be offered to account for their aberrant
pattern. The pattern of the lower molars is very like that of Menis-
cotherium-a fact which lends countenance to the above hypothesis.
TEETH OF THE TRUE UNGULATA. This order includes nearly all
the modern and many extinct ungulate animals, and is conspicuously dis-
tinguished from all other hoofed forms by the interlocking character of
the proximal and distal rows of the carpal and tarsal bones. Cope has
called it the Diplarthra, in allusion to the double articular surface af-
forded by the ankle-bone (astragalus) to the cuboid and navicular below.
1
¹ I have elsewhere spoken of their relationship to the Tillodontia.
Cl
TEETH OF THE VERTEBRATA.
477
whereas in the Condylarthra the astragalus articulates distally with the
navicular or scaphoid only-a condition which obtains in nearly all
Mammalia. Two prominent divisions of this order can be recognized
-the Artiodactyla, or "split hoofs," of which the hog, cow, and deer,
etc. are familiar examples, and the Perissodactyla, whose only living
representatives are the horse, tapir, and rhinoceros.
The latter sub-order is divisible into a number of sections, which,
when we consider the extinct forms constituting at least nine-tenths of
the species, we are not able to separate by any characters of very great
anatomical importance, notwithstanding the fact that the extremes of
the several stems are different enough. That family which stands
nearest to the Condylarthra is the Lophiodontidae, a group of extinct
generalized perissodactyls from the Middle and Lower Eocene beds.
The digital formula is not so great as in the Condylarthra, being only
4-3, and in one instance 3-3; that is to say, four toes on the anterior
and three on the posterior limbs.'
Hyracotherium (Fig. 256) is a typical example of this family, or at
FIG. 256.

}
UNI (MIS

Skull of Hyracotherium augustidens, Cope, from the Wind River Beds of Wyoming (after Cope).
least that section of it whose dentition approaches nearest to Phenacodus;
and if it were not known that the carpal and tarsal articulations were
different, they might easily be mistaken for the same family, so great is
the resemblance of their teeth. The dental formula of this animal is
I. §, C. †, Pm. 4, M. 3 = 44, the same as Phenacodus. The premolars
are different from the molars, being simpler in form, and the first in
both jaws is separated from the others by a diastema. The molar pat-
¹ Prof. Marsh has described several genera of this group, which he has called Eohip-
pus, Orohippus, etc., but the descriptions are so brief that it is impossible to form any
correct estimate of their true relationship. Eohippus, he says, has five toes, but further
than this its osteology has not been described. It would be interesting to know in what
respects it differs from the phenacodonts, Hyracotherium, Pliolophus, etc.
478
DENTAL ANATOMY.
tern is substantially the same as in Phenacodus, with the slight excep-
tion that the cusps are more elevated and laterally flattened, and the
external rib is very small or absent in Hyracotherium. In the nearly
allied genus Pliolophus, which I suspect to be the same as Orohippus of
Marsh, the last or fourth premolar below is like the true molars in form,
and is quadritubercular, while the genus Lophiotherium has the third
and fourth premolars below, like the true molars.
In the second section of this family the external lobes of the superior
molars are laterally flattened and intimately blended together, so as not
to be well distinguished. Of these the anterior is much the smaller, and
is convex externally, whereas the posterior is large and concave without.
The intermediate tubercles no longer exist as such, but form prominent
crests which connect the external with the internal cusps, crossing the
crown somewhat obliquely. In the lower molars the external and inter-
nal cusps are also connected by crests, giving the typical lophodont pat-
tern. As a rule, the premolars are trilobed, and the molar formula is
Pm. 4, M. 3, but in one genus (Dilophodon), recently described by Prof.
Scott, there are only three premolars in the lower jaw. In another
genus, lately described by the same author under the name of Desma-
totherium, the third and fourth upper premolars are like the molars,
and are four-lobed.
K
The tapirs form another nearly related family (Tapiridae), which no
doubt sprang from some member of the preceding group. The incisors
and canines are like those of the Lophiodontidae, but the canines in the
lower jaw of the living forms are somewhat procumbent. The third and
fourth premolars in the upper jaw are like the true molars, which dis-
play the four cusps connected by cross-ridges remarkable for their trans-
verse direction in contrast with the oblique crests of some of the preced-
ing family. The two external lobes are likewise different in their
subequal proportions, both being convex externally and well separated
from each other.
The lower premolars except the first are like the molars. The exter-
nal and internal lobes are connected by strong cross-crests, which are
as much elevated as the cusps themselves, and there is no ridge crossing
from the postero-external to the antero-internal lobe, as in Hyracothe
rium and Phenacodus.
From this family we pass to the rhinoceros section of the sub-order.
In accordance with what the philosophic student of the living forms
would be led to anticipate, this section pertains to a later geologic period
than the preceding, and not unnaturally would he seek for the connect-
ing links between them and that section of the Lophiodontidae, in which
the external lobes are flattened. Through the researches of American
paleontologists we are now in a position to fully comprehend all the
more important steps in the evolution of this group, and I fail to recall
in the whole range of vertebrate paleontology an instance in which the
demands of the evolution hypothesis are more completely satisfied than
in the present one.
The molar formula of the rhinoceros is Pm. 4, M. 3, the usual num-
ber in perissodactyles; but, as regards the incisors and canines, the great-
est variability is to be observed. In the two-horned African species
TEETH OF THE VERTEBRATA.
479
neither canines nor incisors exist in the adult animal, they having
completely disappeared in the course of development. On the other
hand, in the remarkable and interesting Eocene genus Orthocynodon
of Scott and Osborn,¹ the canines are of normal size and erect in posi-
tion, as the name implies. The number of incisors has not been defi-
nitely determined, owing to the imperfect condition of the single specimen
FIG. 257.

WH
JONI
CREPE
ZARADA
Skull of Aphelops megalodus, Cope, an extinct American rhinoceros.
known, but it certainly had two, and probably three, in the lower jaw,
as there is abundance of room between the canine and the second incisor
for another tooth. If the number is three in the lower jaw, it would
imply a like number in the upper, which would bring it very near to
the Lophiodontidae. From this condition of the dentition, which is very
nearly that of the Lophiodontidae, we pass to the genus Amynodon of Prof.
Marsh, in which the lower canine is much smaller and procumbent,
with the incisors reduced to two pairs in each jaw. Following this
1
See Bulletin No. 3 Contributions from E. M. Museum of Geology and Archæology
of Princeton College, May, 1883.
+
480
DENTAL ANATOMY.
genus in time comes the Lower Miocene representative Aceratherium, in
which the incisors are two upon each side in the upper and one in the
lower jaw, with the upper canine absent. The Middle Miocene fur-
nishes a genus, Ceratorhinus, in which the incisors are one upon each
side above and below, and a canine in the lower jaw only. Finally,
we have a complete disappearance of both incisors and canines in 'some
species now living. The reduction of the incisors and canines from
Orthocynodon to Colodonta, a living species, can be summarized as
follows: I., C., Orthocynodon; I., C., Amynodon; I. 4, C. f,
Aceratherium; I., C., Ceratorhinus; I. f, C. f, Calodonta.
FIG. 258.
1
b
3
2
3
2

1
a
Superior Molar Dentition of Rhinoceros: a, anterior; b, posterior end of series. The figures 1, 2, 3
indicate molars and premolars.
In the earliest forms the molars are more complex than the pre-
molars, but in the later and living species the premolars are as highly
organized as the molars, and like them in form; this is well shown in
the accompanying figure.
About twelve genera have been described, seven of which come from
the fossil beds of North America. Through Orthocynodon, as was
pointed out by Profs. Scott and Osborn, they inosculate with the Lo-
phiodontida, after which they branch into several distinct lines. While
the rhinoceroses have perpetuated the type of molar which began with
the last section of the lophiodonts, other forms inherited the pattern of
the hyracotheroids, and from this point the dentition was gradually spe-
cialized, not so much through subtraction of the number of teeth as
addition and complication of the different lobes and crests of the
crowns of both molars and premolars. The culminating point of
this line is found in the living horses.
The first step beyond Hyracotherium in this series is seen in the
Eocene genus Ectocium of Cope, in which the external rib is better
defined, the external cusps more crescentic, and the cusps and oblique
ridge of the lower molars are more prominent. In the next geological
stage (Upper Eocene) we meet with the family Chalicotheriida, abun-
dantly represented in the Wind River deposits by the genus Lambdothe-
rium, likewise described by Cope. In this form (Fig. 259) the external
cusps of the upper molars are considerably elevated, of a crescentic form,
and connected with an external median rib. The anterior cross-crest
still has a tubercular form, while the posterior is crest-like and blended
with the postero-internal lobe. The four cusps of the inferior molars
are connected by cross-ridges and the oblique crest, so as to form two Vs,
opening internally. The tooth here represented is the last one, which in
many of the perissodactyls has a prominent heel (h). In this animal
TEETH OF THE VERTEBRATA.
481
the antero-internal cusp (ai) becomes bifid at its summit, and the ante-
rior basal lobe (k) again assumes considerable importance.
Following the chalicotherioids, and as a probable derivative of then,
we meet with the palæotherioids, in which the molar pattern makes a
considerable advance in complexity
over that of the preceding family,
and the premolars are now like the kai ai pi
molars. ~ Anchitherium is a good
representative of this group, and
is here taken for illustration. This
genus is of especial interest, in view
of its ancestral relation with the
horses; it is here that we get the
first distinctive traces of equine
peculiarities, although several gen-
era intervene between it and the
modern Equidæ or horses. The
species were numerous, most of them
equalling the sheep in size, and had
three subequal toes on each foot. The incisors, as in all the preceding
genera, are plain incisiform teeth, without the pits or "mark" found in
the corresponding teeth of the horses. Well-developed canines are like-
wise present.
FIG. 259.
y.


pe
a
10 at 100 dan ge
1 2 0 0
b
X
..ae
de dat on
pee..
pi pe
b
a
pi
Upper and Lower Molar Teeth of Lambdotherium,
vertical view, natural size: a, superior; b, last
inferior molar. In the upper molar, ae, antero-
external; pe, postero-external; ai, antero-in-
ternal; pi, postero-internal or principal cusps
respectively; y, external vertical rib; a, an an-
terior cingular cusp; acc-pcc, anterior and pos-
terior cross-crests. In the lower molar the
principal cusps are lettered the same: k, ante-
rior basal lobe; ai', accessory cusp; h, heel.
ace
FIG. 260.
The superior molars (Fig. 260) display the same elements as those of
Lambdotherium; the external cusps are very much flattened and cres-
centic, having their vertical dimensions considerably augmented. The
cross-crests form laminar ridges connected with the two internal cusps at
the base, and separated from them above by open notches; they reach
quite across the face of the crown. The
two internal cusps almost equal the
external ones in height, but have a
more conical form; they are sepa- b
rated from each other by a deep
fissure or valley opening internally.
On the posterior border of the crown.
the cingulum develops an accessory
cusp, which has a tendency to form
a cross-crest in this situation and enclose a valley between it and the
posterior cross-crest.
ai

α
1
2
Upper and Lower Molars of Right Side of a
species of Anchitherium : 1, upper; 2, lower
tooth; a, anterior; b, posterior border.
In the molars of the lower jaw the same elevation of the lobes and crests
is to be observed; their pattern is substantially that of Lambdotherium.

In a later geological epoch the genus Hippotherium carries dental
modification a step farther toward that of the existing horses. The
outer toes are much reduced, the incisors possess the peculiar pits of
the horse, the molars are more complicated, and the entire appearance
is decidedly equine. A strict comparison of the elements of the molars
with those of Anchitherium is generally difficult, on account of the thick
deposit of cement which fills up the valleys and spaces between them.
To obviate this difficulty and bring out more clearly the relationship
between them, I have represented in Fig. 261 an unworn molar in
VOL. I.-31
482
DENTAL ANATOMY.
which the cementum has been removed. Although the respective pat-
terns are very much alike in their general structure, the differences con-
sist in this: the external cusps of the superior molars are relatively
larger, more perfectly crescentic, and strongly inclined inward in Hip-
potherium. The anterior cross-crest is better developed and joins the
posterior cross-crest, so as to enclose a deep pit or valley between it and
the antero-external cusp, which is filled with cement in the natural
α
FIG. 261.
d
66
b
с
A Superior Molar Tooth of a species of Hip-
potherium, with cementum removed: a, añ-
terior; b, posterior; c, internal; d, external
borders. Vertical view, natural size.
K
aé
FIG. 262.
ai ať pi
---h
| Apoi, siis kong
po
Lower Molar of same. Letters as in Fig. 259.
Grati
D


state; this is called the anterior lake in the worn tooth. The posterior
cross-crest bends around to join the posterior cingular cusp, which, with
the postero-external cusp, furnishes the boundary of the posterior lake.
To these cross-crests are added a greater or lesser number of vertical
folds, which give the borders of the lakes a crenate appearance when
the crown is much worn. The internal cusps are relatively small, the
posterior being connected with the corresponding cross-crest, the ante-
rior isolated. To all these must be added the increased height and the
presence of cementum.
The lower molars (Fig. 262) do not exhibit such marked difference
from the Anchitherium type as do those above, but they are neverthe-
less more complex in their increased depth, complete isolation of the
accessory antero-internal cusp, and the addition of cementum. The grind-
ing surface of the teeth resulting from this arrangement of the enamel,
dentine, and cement is kept constantly rough by reason of the inequalities
in the rate of wear which these substances sustain during mastication.
Coincident with this structure of the crown the roots disappear and the
tooth grows continuously-a condition necessary to compensate for the
great waste of the tooth-substance.
Lastly, we come to the modern horse, in which digital reduction has
reached the extreme point in this series, or that furthest removed from
the pentedactyle Condylarthra. As is well known, the digital formula
in this family is 11 in functional use, with the second and fourth
represented by the rudimentary metapodials commonly known as the
splint bones."
The incisors are peculiar and characteristic, inasmuch as the working
face is interrupted by a deep pit caused by the upward growth of the
posterior cingulum. Previous to extrusion, the posterior wall of this
cavity is incomplete and does not rise so high as the anterior.¹ After
1
Ryder, "On the Origin and Homologies of the Incisors of the Horse," Proc. Acad.
Nat. Sci., Philada., 1877.
TEETH OF THE VERTEBRATA.
483
the tooth has been in use for a little while, however, the face is worn
down smooth, and the central depression appears bounded by a layer
of enamel, between which and the enamel covering the outer surface of
FIG. 263.

l

Skull of Hippotherium seversum, Cope (after Cope).
the tooth, may be seen the dentine. The incisors are not all cut at the
same time, the last appearing at the age of five years, on account of
which the central pit disappears through wear sooner in those teeth
which are first extruded than those which
are cut last. By observing carefully the
date of appearance of the various inci-
sors, and the consequent difference in time
at which the pits are obliterated in the
different teeth, veterinarians have estab-
lished some very useful rules by which
the age of a horse can be approximately
told with considerable certainty up to ten
or twelve years.
ai
pi
Canines, or the "bridle teeth," are pre-
sent, but they are of smaller size, and some-
times disappear in the female. The first
premolars in both jaws are normally ab-
sent, but there are many cases on record in which they are present.
Hippotherium they are normally present and functional.
Molar Tooth of a species of Horse. Let-
ters as in the preceding figures.
In
The molars present essentially the same pattern as those of the pre-
ceding genus, the only difference of importance being found in the
acc...
a---.
FIG. 264.
ae y
pe

pec
484
DENTAL ANATOMY.
enlargement of the antero-internal lobe and its connection by a ridge
with its corresponding cross-crest. Some species of Hippotherium show
a gradual advance from the conic isolated condition of this element to
its enlarged and sub-connected form.
Thus it is that paleontology has enabled us to fully comprehend
the different steps in the production of these complex and specialized
organs from the simple bunodont pattern. To say that such evidence
is without its special bearing on the great problem of biology, or that
evolution or development has not taken place, is to deny the truth of
the assertions herein made. Many intermediate steps between those
given could be cited, but time and space have compelled me to limit
the examples to the most salient.
The remaining perissodactyles exhibit different degrees of modification
of the bunodont type, none having reached the same stage of perfection
as the horse.
The second sub-order of the ungulates, Artiodactyla, attained its
greatest development at a later geological period, and it is probably in
the present epoch that the genera and species are the most numerous.
A few genera are found in the Lower Eocene, but they are of rare
occurrence as compared with the perissodactyles. It is probable that
they two came off the condylarthrous stem, but the direct evidence to
substantiate this supposition is wanting. They are primarily divisible
into two groups, Bunodontia and Selenodontia, characterized by the
pattern of the molar teeth and the consequent condition of the posterior
termination of the maxillary bones. In the former division, of which
the hog is an excellent example, the molars have approximately the
same pattern as Phenacodus; the tooth-line is little curved, and the
posterior extremity of the maxillary is applied closely to the pala-
tine and pterygoid bones, whereas in the Selenodontia the molar teeth
have crescentic cusps, and the posterior borders of the maxillaries are
separated by a wide sinus from the palatines and pterygoids. These
characters at first appear insignificant and inadequate to establish and
define two such great groups as the foregoing; but when we remember
that they express a very important structural modification, and that the
two are correlated, we cease to express surprise.
Of these two divisions, the Bunodontia is the older, and as a conse-
quence the more generalized. Their generalized characters are most
conspicuously displayed in the increased number of digits, bunodont
teeth, absence of horns, non-complexity of the stomach, and separate
condition of all the limb bones. In fact, the suilline artiodactyles are as
primitive in many respects as the Condylarthra, but in the arrangement
of the carpal and tarsal elements they are specialized and far removed
from their primitive ancestry.
In the hog the dental formnla is I. 3, C. †, Pm. 4, M. 344. The
outer pair of incisors are small, and sometimes fall out in old age. The
canines are relatively large-disproportionally so in the male-and in
the upper jaw curve round in such a manner that the point of the crown
is directed upward. The enamel of these teeth does not uniformly
invest the crown, but is disposed in three bands corresponding with its
trihedral form. The canines of the lower jaw are more slender and
TEETH OF THE VERTEBRATA.
485
have a normal direction. It is said that castration arrests the excessive
development of the tusks of the boar, just as this operation profoundly
affects the growth of the antlers of the deer-a circumstance which at
once relegates the cause of this condition to sexual influences.
The first premolar has no deciduous predecessor, and disappears soon
after the adult stage is reached. The rest of the premolars increase in
complexity and size from front to rear, but none of them are quadri-
tubercular. The first and second molars are quadrate in section, with
four-lobed crowns. The last molar is greatly elongated in an antero-
posterior direction, which is occasioned by the possession of an enormous
heel, much as in the bears, and its crown, as in the others, besides pre-
senting the normal four cusps, has an immense number of subsidiary
tubercles, giving to it a decidedly wrinkled appearance.
In the wart-hogs (Phacochorus) a very peculiar modification of the
molar pattern is to be seen in the last tooth. In the unworn state the
crown of this tooth presents about thirty small tubercles, arranged in
three rows in a direction longitudinal to the axis of the body, the inter-
mediate spaces between them being occupied by cementum. When wear
takes place, the summits of these cusps are abraded, leaving as many
little dentine islands bordered by enamel; they are strengthened by the
addition of cement.
Wakat
The canines are of enormous size, devoid of enamel, and grow from
persistent pulps; the superior ones are directed upward at first, piercing
the upper lip, and then curve backward toward the eye; their length is
sometimes as much as eight or ten inches. All the molar teeth are gen-
erally shed in old age, with the exception of the fourth premolar and
the last true molar, so that the molar dentition is practically reduced at
this time to four upon each side in both jaws, and is the only case of
the kind known in the Mammalia.
The peccaries constitute another family of this division, and are
known from the lowest Miocene, if not from the Upper Eocene depos-
its. Their molar dentition is more nearly like that of the Condylarthra
and primitive perissodactyles than other suillines, lacking, as a rule, the
great development of the minor tubercles of the molars of the hog as
well as the elongated heel of the tooth. The canines, moreover, are nor-
mal in direction, and the great disparity in size between these teeth does
not exist in the sexes. The incisors are of the usual pattern, although
the outer pair is absent from both jaws in some genera.
From this family the transition is easy to the earlier forms of the
selenodonts, in which the feet were multidactyle; in one genus, Oreodon,
as has been recently shown by Prof. W. B. Scott, the anterior limb was
provided with the normal number of toes, five. That family, which
almost completely bridges the chasm between these divisions, is the
extinct Anthracotherida, whose remains are abundant in the Miocene
strata of Europe, but less so in this country.
It is somewhat uncertain how many genera should be referred to
this family, and by what character or characters it should be defined.
Palæochorus, which by common consent is a suilline, has four lobes upon
the crowns of the superior molars, which are conic and not connected
with an external rib, together with two small intermediate cusps, repre-
486
DENTAL ANATOMY.
senting the cross-crests very much as in Phenacodus. Charopotamus,
another genus from the Eocene of France, is altogether intermediate
between Palæochoerus and Anthracotherium, the typical representative
of this family, in the pattern of the superior molars; the external
cusps are somewhat crescentic, but the external rib is rudimentary or
absent. In the first molar the anterior of the two intermediate tuber-
cles only is present, while in the other two molars it is very small
and insignificant; the two internal lobes are conic.
Following this genus in time come Anthracotherium, Hyopotamus,¹
Ancodus, and others in which the anterior of the two intermediate
tubercles is the only one which is present in the upper molars. This
character, I am therefore disposed to believe, defines a natural group,
and should, in connection with the external rib and crescentic form of
the external cusps, be the test of limitation of this family.
Two derivatives of the Eocene Hyopotami, Xiphodon, and Anoplo-
therium soon became specialized in their limb structure, but, strangely
enough, disappeared in the Early Miocene. Another line was com-
menced contemporaneously with that of the anthracotheroid in the
genus Dichobune, wherein the posterior intermediate tubercle only was
retained. It continues forward through the genus Cainotherium into
the Upper Miocene deposits of Sansan, where it gradually faded from
existence, leaving no modified descendants. This, it appears to me,
constitutes another family, definable by the above character.
From the Anthracotherida have sprung all the modern artiodactyles,
with the possible exception of the cameloids and the existing suillines,
together with other stems which are extinct. Many extinct genera
complete the connections with the living forms in all the osteological
and dental details, which it is scarcely within the scope of the present
article to discuss.
In the production of a perfected double crescentic pattern of the
superior molars in this sub-order from the short-crowned semi-buno-
dont anthracotheroids, the anterior intermediate tubercle has gradually
usurped the function of the true antero-internal cusp, it having been
reduced to a small cusp situated internal to the mesial horns of the
inner crescents on the inner basal portion of the crown (see Fig. 265).²
Specialization of the dental organs of the Selenodontia is seen in the
following characters: (1) Formation of double crescents in the superior
and inferior molars; (2) great elevation of the cusps and deposit of a
thick layer of cementum, filling up the valleys; (3) loss of the roots of
the molars and premolars, and their growth from persistent pulps; (4)
reduction of the premolars to three in each jaw; (5) subtraction of the
canines and incisors from the upper jaw; (6) the reduction in size and
approximation of the lower canine to the incisors; and finally (7), the
Gaudry places the appearance of this genus in the sands of Beauchamp, which
probably corresponds with our Bridger Beds or Upper Eocene. He also fixes the date
of appearance of Paleochorus in Europe in the deposits of Saint-Geraud-le-Puy, Middle
Miocene. In this country Hyopotamus does not appear until the Lower Miocene,
whereas Palaeochoerus probably extends into the Bridger epoch.
2 For a further knowledge of the fossil forms of these families the reader is referred
to the important work of Prof. Albert Gaudry, "Les Enchainements du Monde animal
dans les Temps géologiques," in which the more important genera are figured.
TEETH OF THE VERTEBRATA.
487


FIG. 265.
SIDERE
а
b
Vertical View of an Upper and a Lower Jaw of Virginia Deer (Cariacus virginianus): a upper, b, lower jaw.
488
DENTAL ANATOMY.
development of a long diastema in front of the premolars. While
the complete assumption of these characters is reached only in the
bovine ruminants, others exhibit all the intermediate stages of modi-
fication tending in that direction.
The common Virginia deer (Cariacus virginianus) has been selected
as an average example of the higher selenodont dentition; although
in its family (Cervidae) canines are sometimes found in the upper
jaw, there is little or no cementum on the crowns of the molars, and
they have well-defined roots. It will therefore be observed that it does
not fulfil all the requirements of the most highly specialized selenodonts
in its dental organization. The dental formula of this species (Fig.
265) is I. &, C. f, Pm. &, M. =32. The incisors have long
spatulate crowns, the median pair being the larger, the outer ones
decreasing gradually in size. The canines are smaller than the outer
pair of incisors, which they resemble very much in shape, being applied
closely to them. After an immense interval follow the premolars, the
first two in the lower jaw being comparatively simple, the third four-
lobed like the succeeding molars. The molars display two perfect
double crescents, of which the outer are convex externally. The last
molar has a fifth lobe. In the upper jaw the premolars are bilobed,
the internal being convex internally and enclosing a deep valley between
it and the external cusp. The true molars have double crescents enclos-
ing two valleys. The antero-internal of these crescents is made up of
the anterior intermediate tubercle, which has become greatly enlarged
and developed into a crescentic form, the true antero-internal cusp being
situated internal to and behind it. The proper evidence to support this
determination is to be found by examining the superior molars of Hyopot-
amus, Anoplotherium, and Xiphodon, it which it will be seen that the
antero-internal cusp becomes gradually smaller.
TEETH OF THE PROBOSCIDEA.
The last order of the ungulate series whose dental organs remain to
be noticed is that including the elephants, mastodons, etc. The animals
composing this group are the largest of terrestrial mammals, and display
many curious modifications of the primitive ungulate type. Probably
no part of their organization has been more profoundly affected in their
gradual evolutionary growth than the teeth, and were it not for the fact
that abundant evidence is at hand to demonstrate the successive steps in
the progressive modification from a more simple type, we would be at
a loss to comprehend the manner of production of these most complex
of all teeth.
Two genera of proboscideans are found in the existing fauna of Asia
and Africa, but these are only the inconsiderable remnant of a once
greater and much more widely distributed representation, as is indicated
by their fossil remains. During the later Tertiaries proboscideans were
not unknown in both the northern and southern hemispheres in all the
extensive land-areas; in some parts of the northern hemisphere, where
they are now extinct, judging from their fossil remains immense herds
and droves must have at one time existed.
TEETH OF THE VERTEBRATA.
489
M
In the African elephant (Loxodon africanus) the dental formula is
I., C. 8, Pm. and M. . The two incisors are greatly enlarged,
implanted in deep sockets, and grow from persistent pulps. They are
preceded by small deciduous teeth, and when first protruded are tipped
with enamel, which soon wears off. The tooth then consists mainly
of dentine covered by a thin layer of cement, the dentine presenting
a slightly modified form known as "ivory." This substance, as is well
known, is extensively used in the arts and has a fixed commercial value.
Although not exclusively confined to the tusks of the elephant, never-
theless the chief source of supply of this material is derived from them.
Tomes cites an example in which a pair of tusks of this species were
exhibited in England that weighed three hundred and twenty-five
pounds and measured eight feet six inches in length and twenty-two
inches in circumference; the average weight, however, does not exceed
from twenty to fifty pounds. The female of this species has tusks quite
as large as the male, but in the Indian species the tusks of the male
exceed those of the female in size.
The molar teeth of the living elephants are very much alike in gen-
eral pattern and mode of replacement, which is unique; the description
of one will therefore suffice to convey an intelligent understanding of
the entire subject.
S
Both existing species have a molar formula of §, which are divided
into milk molars, true molars. There is sometimes, in addition to
these, a small rudimentary milk molar in front, which increases the
total number to seven upon either side in each jaw.
Although the total number of molars is normal or nearly so, they are
not all in place nor in existence at the same time. Barring the occa-
sional rudimentary one, the first molar in the Indian species cuts the
gum at a considerable distance from the front of the jaw about the
second week after birth. It is implanted by two fangs, and displays
a subcompressed crown bearing four cross-ridges, and is therefore lopho-
dont in pattern. The upper tooth corresponding to this one cuts the
gum a little earlier, and possesses five cross-crests. These teeth are shed
at about the age of two years.
Before the disappearance of the first two teeth the second molars
come into place from behind. They are considerably larger than the
first, being on an average two and a half inches in length by one inch
in breadth. Their crowns are of similar form, but have the number of
cross-ridges increased to eight or nine. They are implanted by two
fangs, and are shed before the beginning of the sixth year.
By the time the second molar has been worn out the third molar,
averaging four inches in length by two in breadth, makes its appear-
ance. Its crown has from eleven to thirteen cross-plates on its working
face, and is also supported by two fangs, of which the posterior is much
the larger.
It is said to be worn out and shed about the ninth year.
The teeth so far enumerated are taken to be homologous with the
second, third, and fourth milk molars of the ordinary diphyodont den-
tition, which have in this case failed to develop permanent successors.
This conclusion is rendered reasonably certain, as we shall presently see,
by the fact that their ancestors had a more or less complete permanent
TOMA
490
DENTAL ANATOMY.
premolar system, which underwent progressive subtraction as they
approached the modern proboscideans.
Three teeth which are homologous with the permanent true molars
are developed behind these in a similar manner. They increase in size
and complexity from before backward: the first, or fourth of the entire
series, bears fifteen or sixteen plates; the second has from seventeen to
twenty plates; while the last supports from twenty to twenty-five. The
first true molar disappears between the twentieth and twenty-fifth years
of the animal's life, the second somewhere about the sixtieth, while the
last is retained until the termination of the animal's natural existence,
which is said to be more than one hundred years.
The structure of these teeth is complex, and, as we have said on a
former page, resembles that of some of the hystricine rodents, such as the
capybara, for example. The cross-ridges near their summits are broken
up into a number of conical projections, which, when abrasion first takes
place, present so many dentine islands surrounded by a rim of enamel :
these are arranged in rows across the face of the crown in the position
of the future plate (see Fig. 266). As wear goes on these islands unite
FIG. 266.
a

KO
KOS
00
HOOF
00390
Vie
b
Molar Teeth of Indian Elephant (Elephas indicus), after Tomes: a, anterior; b, posterior border.
below, and form transverse lamella composed of a narrow strip of den-
tine surrounded by enamel. Between these much-elongated lamellæ,
which are all blended together at the base of the crown, a thick deposit
of cementum is found; it also invests the lateral surfaces of the crown
and prevents fracture of the cross-plates.
In the growth of the tooth the anterior plates or crests are first
formed, and come into position and use long before the posterior. As
a consequence of this, the most anterior plates wear out and disappear
while the posterior ones are still being formed. This is well shown in
the accompanying figure. As new plates are added from behind, the
whole tooth moves forward, which probably exerts some influence in
the removal of the tooth in front of it. Finally, before the tooth dis-
appears altogether, it presents an oval area of smooth dentine sur-
rounded by enamel and cementum. It is then no longer efficient as a
grinding organ, and is consequently discarded.
It will be seen by this arrangement of the three tooth-substances on
the working surface of the crown, and by reason of the varying rate of
their wear, the teeth of the two jaws when brought into opposition
afford most perfect machinery for the grinding up of the coarse herba-
ceous substances upon which the elephant feeds.
The two genera of existing proboscideans may be readily distinguished
A
TEETH OF THE VERTEBRATA.
491
by the character of the plates of the molar teeth. In the African species
they are fewer in number on the corresponding teeth than in the Indian,
and they have a distinct lozenge-shaped pattern upon cross-section,
whereas in the Indian species they present an oval outline upon cross-
section and the enamel border is crenate. In the number and succes-
sion of the teeth the two genera are alike.
The genus Deinotherium includes a few species whose remains have
been found in the Miocene deposits of Europe, and which were but
little if any inferior to the living proboscideans in bodily proportions.
They are the oldest representatives of this order so far discovered, and
especial interest attaches to their teeth, inasmuch as their structure fur-
nishes a clue to a more perfect understanding of the later and more
complex types.
The premaxillary bones were edentulous, but the front part of the
lower jaw was provided with two large decurved tusks. What particu-
lar use the animal made of these teeth is difficult to imagine. The
molar formula is Pm. 3, M. 3. The structure of these teeth is not very
different from that of the tapir, consisting of a moderately short crown
bearing two or three cross-crests. Both the premolars had deciduous
predecessors, just as in the diphyodonts generally. These animals,
however, were very elephantine in every other feature of their anatomy,
and were in all probability provided with a trunk.
From this condition of the dental organs we pass to the mastodons,
in which there is a marked approach to the elephants. In some species
there were two tusks in each jaw, but the lower ones were small, and in
many cases disappeared early in life. The molars increase in complex-
ity and size from before backward, the posterior ones bearing in some
species as many as ten cross-crests, which were unsupported by a
cementum deposit; in others the cross-ridges are much fewer in num-
ber. Many species are known, and when all are considered a complete
transition between the comparatively simple lophodont and the extreme
lamellate patterns is afforded. Many of them had deciduous teeth,
which were vertically succeeded by two, and probably three, permanent
premolars. As the elephantine molar pattern was acquired, however,
these were gradually lost.
Altogether, it is impossible for a student of odontography to study
carefully the teeth of this order, and not be thoroughly convinced in the
end that the complex pattern has gradually, but none the less certainly,
arisen from the simpler one. If this, therefore, is true of one series, it
must be of all.
THE AMBLYPODA.
Another order of hoofed mammals which became extinct at the close
of the Eocene Period has been described from the fossil-bearing deposits
of this country. They were mostly of gigantic proportions, and exhibit
affinities with both the proboscideans and the Perissodactyla. They are
most nearly related, however, to the Toxeopoda, with which they were
contemporary in the Eocene.
Nearly all of them have the full complement of incisors, canines, pre-
:
492
DENTAL ANATOMY.
1.
FIG. 267.

Mwanamkent
no
····
to de un apmetner
Skull of Loxolophodon cornutus, Cope, a species of amblypod from the American Eocene (after Cope).
molars, and molars, and in some the canines were greatly enlarged. The
molar pattern is of moderate complexity, and shows a considerable
;
1
TEETH OF THE VERTEBRATA.
493
departure from the primitive tritubercular ancestry. In the lower jaw
the molars are lophodont, while in the upper they have a single cres-
cent of moderate perfection. Owing to their near relationship with the
Toxeopoda, it is highly probable that their teeth represent an extreme
modification of the tritubercular pattern, but of the different steps in
their production lack of space prevents me from speaking here. I must
refer the reader to the papers of Profs. Cope and Marsh for a more
complete description of the dentition of this order.
TEETH OF THE MARSUPIALS.
I have indicated on a preceding page that this division of the Mam-
malia is sharply defined from the monodelphs by the circumstance that
no connections are formed between the foetal envelopes and the walls of
the uterine cavity during gestation, so that no placenta is developed.
They are therefore known as the implacental division of the Eutheria;
they are likewise known as the Didelphia and Marsupialia. The young
are born in an exceedingly helpless and imperfect condition, and are
transferred to the pouch or marsupium of the mother, where, by a special
arrangement, the nourishment is forced into their months until such time
as they are enabled to help themselves.
In the majority of the lower Vertebrata very little development of
the young takes place in the body-cavity of the mother; the ovum is
relatively large, by reason of the addition of an abundant supply of pab-
ulum sufficient to nourish the embryo until the later stages of develop-
ment are reached. It has been recently ascertained that the monotremes
reproduce in the same way; that is, they lay eggs like birds and rep-
tiles, which are hatched in a similar manner. The whole plan of devel-
opment moreover, is like that of the bird (mesoblastic)—a condition
which would be reasonably suggested by a study of their reproductive
system.
As the monotremes furnish the connecting link between the higher
mammal and the reptile, so do the marsupials, as far as reproduction is
concerned, afford a transitional stage between the monotremes and the
monodelphs. For this reason we would naturally be led to look for
primitive and transitional characters in their teeth. Unfortunately,
these organs do not in many particulars go beyond the lowest forms of
the monodelphs sufficiently to give us any clear insight into the inter-
mediate structures and patterns which must have preceded the diphyo-
dont monodelph dentition; still, some of the earliest representatives of
mammalian existence which have been referred to in this group possess
a greater number of heterodont molar and premolar teeth than any
known mammal.
In the small living marsupial genus Myrmecobius the dental formula
is I. 4, C. 1, Pm. 3, M. &=54. The incisors are small, subconic teeth,
implanted in the premaxillary bones above, and followed by the canines,
which have the usual laniary form. The premolars have laterally-com-
pressed, unicuspid crowns, and are implanted by two roots. The molars
exceed in number those of any other marsupial, reaching the unusual
number of six in each jaw. Owing to the imperfect descriptions of
494
DENTAL ANATOMY.
the crowns of these teeth, and never having seen a specimen myself, I
am at present unable to say just what the pattern of the crown is. From
the best information at my command I suppose it to be somewhat after
the style of a modified tuberculo-sectorial. I further do not know
whether the succession has been observed, and whether a proper distri-
bution of the molars and premolars expressed in the above formula has
been made; but, judging from the condition in marsupials generally, I
am induced to believe it to be correct. It is so given by Owen and
Waterhouse.
Some fragmentary remains, consisting principally of jaws and isolated
teeth, of a number of small mammals have been discovered from time
to time in the Jurassic and Triassic deposits of this country, Europe,
and South Africa, in which the teeth behind the canines reach as high
a number as twelve in each lower jaw in some species. These are some-
what arbitrarily divided into an equal number of molars and premolars,
but whether any or all of them had deciduous predecessors is not
known. The reason for this division is that the first six behind the
canine are premolariform in shape, while the others possess a number of
sharp cusps. They have been referred to the marsupials and assigned a
position near to Myrmecobius, but until their osteology is better known
this is doubtful. Inasmuch as they are the oldest known mammals, we
should anticipate on a priori grounds that they really belong to the
monotremes instead of the marsupials. The great number of teeth cer-
tainly constitutes an approach to the Reptilia, and if they possessed a
complete development of a second set, which is not at all improbable,
the transition between reptile and mammal would be in a measure com-
plete as regards the teeth.
Another strange and remarkable genus, Plagiaulax, together with a
number of allies, comes from these ancient horizons. In this animal
the molar pattern is complex for so early a representative of the Mam-
malia, and is difficult to understand. In the lower jaw of Plagiaulax
there are seven teeth, of which the first is large, curved, and pointed,
and is probably an incisor. This is followed after a considerable space
by four teeth, all of which, except the first, are implanted by two roots
and increase gradually in size. Their crowns are terminated superiorly
by a wedge-shaped crest directed antero-posteriorly, which is rendered
subserrate by the presence of a number of oblique vertical grooves.
Behind these are two smaller teeth with tubercular crowns, which
have been supposed to represent true molars.
Godd
The remaining marsupials which are really known to be such are
divisible into the Polyprotodontia, or those of predaceous habits, having
many incisors, and the Diprotodontia, vegetable feeders, having only
two incisors, in the lower jaw. As far as dental characters go, they all
agree in the possession of four true molars; there are never more than
three premolars, and the deciduous molars, which are succeeded at a
comparatively late period by the last premolars, are reduced to one in
each jaw. This, therefore, furnishes another example wherein the defi-
nition of a premolar is violated.
C
Three families are included in the polyprotodont division, one of
which, the opossums, is confined to North and South America, and the
}
TEETH OF THE VERTEBRATA.
495
other two to the continent of Australia. As the common Virginia
opossum is a good representative of this division, it is here taken for
illustration and description. The dental formula is I. 4, C. †, Pm. 3,
M. 4 = 50. The incisors (Fig. 268) have a truncate cylindroid pattern,
FIG. 268.

α

b
Dentition of Virginia Opossum (Didelphis virginianus): a, upper: b, lower jaw.
implated by single fangs, and differ considerably from the correspond-
ing teeth of the carnivores, which they exceed in number by two upon
each side in the upper, and by one upon each side in the lower, jaw. The
canines have relatively the same size and form as in the dog, and indi-
cate clearly the carnivorous habits of their possessor. The premolars
are simple premolariform teeth implanted by two roots, the first being
smallest and separated from the other two by a diastema.
The molars of the lower jaw are essentially tuberculo-sectorial in pat-
tern, with the external cusp of the anterior triangle largest. The heel is
tritubercular and of large size. The molars of the upper jaw are inter-
esting, inasmuch as they furnish a transitional stage in the formation of
the W pattern described in the moles, shrews, etc. The first molar has
the following structure: The crown is triangular in transverse section,
with the apex directed inward, at which is situated the antero-internaĺ
cusp or the one corresponding with the single internal tubercle of the
tritubercular molar. At the antero-external angle is situated a cusp of
moderate dimensions, which in perfectly unworn specimens is more or
less blended with the cingulum; just internal to this, upon close inspec-
tion, can usually be seen the rudiment of another cusp, which becomes
better defined in the second molar. The exact homologies of these two
cusps are not clear, but it seems very probable that the external is of
cingular origin, and that the one internal to it is the true homologue of
the antero-external cusp of the tritubercular tooth. On the outer edge
of the crown, posterior to the two just described, is another cusp, which
disappears in the last two molars, but which is well defined in the first.
and second. This cusp is homologous with the one which terminates
the median external part of the W in the molars of the shrew and mole.
A little posterior to a line drawn between this last-mentioned cusp and
the one most internal is another large well-defined tubercle, from which
496
DENTAL ANATOMY.
a conspicuous ridge passes outward and backward to the produced pos-
tero-external angle of the crown.
It will thus be seen that all the requisite cusps are present in the first
and second molars for the production of the W-structure, and that it
would only require the presence of connecting ridges to complete it.
A distinctive characteristic of this, as well as most other marsupials,
is seen in the strong inflection of the angle of the jaw and the vacuities
caused by failure of ossification in the posterior part of the palatine bones.
Another family of this group includes the Phascogales, Tasmanian
devil, the dog-headed opossum, etc. of the Australian continent and
neighboring islands. This family is known to naturalists as the
Dasyurida, and is distinguished from the opossums proper (Didelphi-
du) by having the incisor formula. In the genus Phascogale there
are three premolars in the upper jaw and two in the lower; in Dasyurus,
or the Tasmanian devil, there are only two premolars in each jaw, which
number also obtains in the dog-headed opossum (Thylacinus).
The pattern of the molar teeth of this latter animal is very much like
that of Mesonyx, consisting in the lower series of a principal cone, to
which are added anterior and posterior basal cusps.
The upper
molars are tritubercular, as in that genus, but there is a consider-
able cingular ledge external to the two outer cusps.
The lower molars of the other two genera are very similar to those
of the opossum, already described. The pattern of the upper molars
of Dasyurus have been alluded to in connection with those of the shrew,
and need no further description; those of Phascogale are essentially the
same.
The bandicoots, constituting the family Peramelidae, are distinguished
by an incisor formula g. The canines are reduced, and placed relatively
far back in the dentigerous border of the jaws. The molar and
pre-
molar formula is the same as in the opossum, and there is a similar-
ity of pattern in the corresponding teeth of the two families.
In the second division, Diprotodontia, the incisors are reduced to two
in the lower jaw; the canines are always small, and in many cases alto-
gether wanting, while the molars are more complex, being better adapted
to the mastication of a vegetable diet, upon which they principally feed.
The kangaroo furnishes a typical example of this group, and is here
described. The dental formula of Bennett's wallaby (Halmaturus
bennetti) is I., C. &, Pm. 4, M. 428. The three pairs of incisors
in the upper jaw (Fig. 269) are subequal and closely approximated,
except in the middle line, where those of the opposite side are separated
from each other by a considerable space. They have incisiform crowns,
and are implanted by enlarged roots caused by an unusually thick coat
of cement. These are opposed by a single tooth on each side below,
whose direction is almost a continuation of the long axis of the jaw,
so procumbent is its implantation. They are long teeth with enamel-
covered crowns, slightly compressed from side to side, so as to present
cutting edges on the surfaces which would correspond to the anterior
and posterior faces if the tooth were erect, but which in its present
position are superior and inferior. The superior edge bites against
the three upper incisors, opposing them exactly.
TEETH OF THE VERTEBRATA.
497
After a long interval come the premolars, which have approximately
the same structure in the two jaws as do the molars behind them. The
premolars are implanted by two roots, and have crowns whose longitu-
dinal diameter greatly exceeds the transverse. The summit of the crown
terminates in an antero-posterior ridge, which is bordered at the base
FIG. 269.

019707
a
b
Dental Series of Kangaroo (Halmaturus bennetti): a, upper, b, lower jaw.
internally in the upper ones by a well-marked cingulum bearing several
small cusps; this cingulum is absent from the inferior teeth.
The crowns of the molars are highly lophodont, consisting of two
strong transverse crests connected in the median line by an antero-pos-
terior ridge. They are all nearly equal in size and alike in both jaws.
In the phalangers, which constitute another family of this division,
the incisors are the same as in the kangaroo. Small canines are usually
present, and the premolars may be increased to three in the upper jaw.
The third premolar has substantially the same structure as that of the
kangaroos, but the molar pattern is selenodont, resembling in this respect
the artiodactyle ungulates. They are quadritubercular, the four cusps
being crescentic in section, with the crescents reversed in the lower jaw,
just as in the artiodactyles.
Still another family is represented by the wombat, whose dentition.
exhibits a modification in the same direction as the rodent monodelphs.
in the reduction of the incisors to a single pair in each jaw and their
growth from persistent pulps. The canines are absent, the premolars
are, and the molars, as well as incisors and premolars, grow contin-
uously during the life of the animal. The molar pattern consists of
transverse laminæ, greatly elongated and united by cement, much as in
capybara, one of the rodents.
A gigantic extinct marsupial animal (Thylocoleo) has been described
from the late Tertiary deposits of Australia, whose affinities and prob-
able habits have provoked a good deal of discussion among English
paleontologists. In each jaw there is a pair of enlarged, hooked, and
pointed teeth in the position of the median incisors; these are followed
in the upper jaw by three small teeth, the posterior of which probably
VOL. I.-32
498
DENTAL ANATOMY.
represents a canine; in the lower jaw but a single tooth of this kind
exists. Next follows a relatively enormous tooth, corresponding in
pattern with the single premolar of the kangaroo, and is therefore tren-
chant. Behind these are one small tooth in the upper and two of like
nature in the lower jaw.
From the trenchant nature of the large premolariform teeth, Prof.
Owen, its describer, has considered it to have been carnivorous in habit,
while Prof. Flower concludes, from the enlarged incisors and general
resemblance of the enlarged teeth to that of the premolars of the kanga-
roos, that it is really affiliated with this group and was a vegetable feeder.
Other marsupials might be mentioned, but the principal modifications
of the dental organs of this group have already been set forth in the
types selected.
THE MILK DENTITION.
In the preceding pages we have spoken of the deciduous or milk den-
tition of the diphyodont Mammalia so far only as they relate to the
permanent set in matters of definition. It now remains to discuss the
more important question of their true nature and relationship to the
permanent teeth in a philosophic sense. Are they superadded embry-
onic structures similar to the amnion and allantois, which subserve a
temporary purpose and disappear with approaching maturity, or are
they to be homologized with the first set of teeth of the lower Verte-
brata?
S
Before proceeding to a discussion of these questions, it will first be
necessary to give a general statement of the more important features of
their anatomy, as well as the principal characters in which they differ
from the permanent teeth.
As regards their development, it must be borne in mind that their
enamel organs are originally derived from the lining membrane of the
oral cavity, or at least that part of it which immediately covers the axes
of the jaws, by a dipping down of the epithelium, while the dentine
organ is developed from the underlying embryonic tissue. The enamel
organs in this case are said therefore to arise de novo. After a time the
enamel organs of the permanent incisors, canines, and premolars appear
by a process of budding from the necks of the enamel organs of the
deciduous teeth, but that of the first molar in the human subject arises
de novo, just as those of the temporary teeth do from the primitive
epithelial layer of the mouth.
From the neck of the enamel organ of this tooth the enamel organ
of the second true molar buds out, while the third is derived from the
second in a like manner. Whether this order of development is true
of all diphyodont mammals is not known, and is a subject which very
much needs further investigation.
The form of the milk teeth resembles that of the permanent ones
which succeed them, as a general rule; an important exception to this,
however, is to be observed in the last milk molar, which in the majority
of cases is more complex than the permanent tooth which succeeds it. In
the ungulates the last milk molar in the lower jaw resembles the last
TEETH OF THE VERTEBRATA.
499
true molar in having three lobes, while in the upper jaw the last two
milk molars have the complex pattern of the permanent molars. It is
a rule of pretty general application that the last milk molar, and in many
instances the last two, are succeeded by teeth of a simpler pattern.
They may be well developed and retained in the jaw for a consider-
able period, as in the dog, or they may be extremely small, and shed, or
rather absorbed, before birth, as in some of the seals. There may be as
many as six in each jaw, as in the case of the nine-banded armadillo, or
they may be reduced to a single one in each jaw, as in the marsupials.
The usual number of milk molars is four in what may be called the
typical diphyodont dentition, in which there are forty-four permanent
teeth in all. Subtractions from this number are of common occurrence
by reason of the first milk molar failing to develop a permanent succes-
sor or its complete disappearance. This, as we have seen, occurs in the
dog and many other animals in which the number of premolars is nor-
mal. That this tooth is a persistent milk tooth is suggested by the fact
that its enamel organ arises de novo, like those of the milk teeth generally.
In the monophyodonts one set has been lost, and the question nat-
urally suggests itself, Which one is it? The very rudimentary con-
dition of the milk teeth in the seals, which reaches an extreme point in
the elephant seal, has led Prof. Flower to conclude that the single set
of the monophyodonts is homologous with the permanent set of the
diphyodonts, the first set having become rudimental and finally disap-
peared. He further concludes that the milk dentition generally is some-
thing superadded, and cannot therefore be homologized with the first
set of the lower vertebrates. These conclusions are adopted by many
authors.
G
In the first place, as regards the homology of the single set of teeth
of the monophyodonts, there is much plausibility in Prof. Flower's
position; but, upon the whole, our information respecting the exact
limits of monophyodontism is too meagre to reach any satisfactory results
in a solution of this question. It may yet turn out that many of the
Cetacea, in which it is thought to be universal, really have rudimentary
deciduous teeth in the early stages of growth, as has been suggested by
Tomes. Among the edentates the nine-banded armadillo has already
been cited as having two sets of teeth, and it does not seem at all improba-
ble that all armadillos will ultimately be found to be diphyodont.
It should also be remembered that an approach to monophyodontism
is made in many diphyodonts; and in all cases in which there is a par-
tial loss of one set there can be little doubt that it is the second which
has been subtracted. An example of this is afforded by the probos-
cidean series. In Deinotherium there were two and probably three per-
manent premolars; in some species of mastodons they are reduced in
number to two or three; while in the existing elephants they have com-
pletely disappeared. The teeth which remain in the position of the pre-
molars in these animals are certainly persistent milk molars. The first
premolar of the dog, hippopotamus, and others is a case of the same
kind. If monophyodontism has been produced in this way, then the
single set which remains is not homologous with the permanent set of
the diphyodonts, but combines the two, the molar dentition being made
500
DENTAL ANATOMY.
up of the true molars and persistent milk molars, with the permanent
premolars subtracted.
1
With reference to the second conclusion, that the milk dentition is
something superadded, Dr. Tomes very justly raises objection on the
ground that the history of the development of the permanent teeth
interposes a difficulty. He says: "The tooth-germ of the milk tooth
is first formed, and the tooth-germ of the permanent is derived from a
portion (the neck of the enamel germ) of the formative organ of the
milk tooth. Again, in most of those animals in which there is an end-
less succession of teeth, such as the snake, the newt, or the shark, each
successive tooth-germ is derived from a similar part of its predecessor;
the natural inference from which would be that the permanent set, being
derived from the other, was the thing added in the diphyodonts.'
""
Aside from the inherent improbability of this hypothesis of super-
addition of the milk teeth, if the mammal has been derived from the
reptile or batrachian-which is true if evolution is true-it is not at
all remarkable, but, on the contrary, quite in keeping with the nature of
the case, that the descendants should have retained some of their ancestral
features. In the Batrachia and Reptilia there are many sets of teeth
developed during the life of the individual, of which the first arises de
novo, and all the succeeding ones are derived from that which precedes
it. Altogether, I am disposed to regard the diphyodont mammalian
dentition in the same light: those teeth which take their origin pri-
marily from the epithelial lining of the mouth are strictly homologous
with the first set of the lower vertebrates. This would include in the
first set the deciduous incisors, canines, molars, and the first true or
permanent molars. The second set of the batrachian and reptile would
be represented by the permanent incisors, canines, premolars, and sec-
ond true molar. The third succession would be represented by the last
molar of the diphyodont dentition.
This view, of course, is based upon the presumption that the devel-
opment of the true molars is the same in all diphyodonts as it is in
the human subject-viz. that the enamel germ of the first is derived
from the epithelial lining of the mouth; that that of the second is
derived from the neck of the first; and that of the third from the
second.
If it shall be found, however, on further investigation, that in any
diphyodont the enamel germs of all the molars arise de novo, then they
must in all such cases be added to the first set. This objection may be
urged against the view that there are three, or even two, successions
represented in the molars of the diphyodont-viz. that they do not suc-
ceed each other vertically, as in the case of the reptile and batrachian ;
but this I do not consider of vital importance. There is one thing upon
which I would strongly insist, and that is that the first true molar in
the human dentition is a persistent milk tooth.
¹ Manual of Dental Anatomy, p. 302.
TEETH OF THE VERTEBRATA.
501
CONCLUSIONS, ACKNOWLEDGMENTS, ETC.
THROUGHOUT the foregoing pages I have endeavored not only to
give the leading characteristics of the principal modifications of the
dental organs of the Vertebrata, but have in many cases, so far as our
knowledge of the extinct forms would permit, endeavored to trace the
leading steps in the production of the complex from the simple form.
In so doing I have been made aware of the difficulties which beset such
an undertaking: the principal burden of these difficulties lies in the com-
paratively imperfect knowledge we possess of the palaeontological history
of certain groups. In others the ancestry is more clearly indicated, and in
my judgment the evidence is sufficient to demonstrate with a reasonable
degree of certainty the more important steps in their dental evolution.
The modification of an organ from a simple to a complex structure
necessarily implies a cause or force adequate to the production of such
result. What, then, is the nature of the force or forces involved, and
what is their method of operation? To simply say that this or that is
so, that this tooth is simple and that is complex, without giving any
reason why it is so, conveys little information. If one tooth is sim-
ple and another complex, there are reasons for it, and it is not only
within the province, but is clearly the duty, of the odontologist to dis-
cover and point out these reasons if they can be found to exist.
Two explanations for all such phenomena have been offered. One
of these presumes that they were created so by supernatural forces, but
as to the nature of these forces we are not informed; much less do we
know about the manner in which it was done. The other assumes that
the natural or physical forces, operating through distinct and well-known
physiological laws, are alone responsible for the resulting modifications.
Between these two explanations the naturalist experiences little diffi-
culty in deciding which is most in accordance with the observed facts
at his command. While the one rests solely upon the vaguest assump-
tion, unsupported by so much as a single fact, the other rests upon
observed scientific truth, which any one can verify who will take the
pains to investigate. When we ascribe these modifications to the physi-
cal forces, the conclusion seems inevitable that those of a mechanical
nature have been most largely concerned in the modification of form.
G
The change in form or size of any organ is principally due to addi-
tion, subtraction, or transposition of the histological elements of which
it is composed; these, as is well known, are directly dependent on the
amount of physiological waste and repair which the organ sustains, or,
in other words, the extent of use and disuse. In proportion as an organ
or a part of an organ is used, in that proportion will there be increased
destruction of its substance and a corresponding determination of the
nutritive fluids to supply the loss. The reverse is true of disuse.
In the harder tissues of the animal body strain and pressure have
likewise been potent factors in the determination of form. Recognizing
the importance of these influences, Mr. J. A. Ryder has constructed a
most ingenious and far-reaching hypothesis in regard to the teeth, which
he terms "the mechanical genesis of tooth-forms." In this he satis-
1 Proceedings Acad. Nat. Sciences, Philada., 1878.
502
DENTAL ANATOMY.
factorily accounts for the forms and patterns of the molar teeth of the
ungulates by the manner in which they have used their jaws. He has
shown that in the bunodonts the mouth is simply opened and closed
during mastication-a movement which is associated with a short-
crowned tubercular molar-while in the selenodonts the lower jaw
makes an extensive lateral sweep, and is associated with long-crowned
crescentic molars. The conclusion is therefore obvious that as the buno-
donts were compelled, through force of circumstances, to live upon a
diet which required more extensive comminution before it could be
properly assimilated, they gradualy develop greater mobility of the
lower jaw; as a consequence of this, the patterns of the molar teeth were
modified through pressure in accordance with this movement. If this
proposition be true of the teeth of the ungulates, it must likewise be true
of all other animals.¹
Dr. Tomes in his Manual of Dental Anatomy criticises Mr. Ryder's
conclusions, as follows: "The simple mechanical explanation that the
teeth are drawn out into these forms hardly conveys much information,
seeing that the tooth, before it is subjected to these influences, is quite
finished, and its form, such as it is, is unalterable; while to effect an alter-
ation in the form of a masticating surface an influence must be brought
to bear upon the tooth-germs at an exceedingly early period. It might
with equal justice be said that the crown of the tooth, being formed
thus, had influenced the excursions of the jaw, and so modified the
condyle."
It is evident that Dr. Tomes has either failed to grasp the mean-
ing of Ryder's reasoning, or else denies one of the most important
principles of the evolution doctrine. I am not aware that Ryder has
anywhere asserted that the production of the selenodont pattern of
the ungulate molar took place in a single generation, as Dr. Tomes's
criticism would seem to imply. As a matter of course, the tooth of a
modern ungulate when it comes into position is "quite finished," but
were the teeth of the ancestors of the modern ungulates quite finished
when they came into position? Ryder has attempted to show that this
finishing process was a gradual one, which took many generations to
accomplish, and the facts of paleontology bear out this view. The
bold assertion of Dr. Tomes, to the effect that the masticating surface
of a tooth when it comes into position is unalterable, is open to very
grave and serious doubts. If the form of a bone or any other organ
of the animal body can be influenced by impact and strain, as all evolu-
tionists believe, then I can see no reason why a tooth is not amenable
to the same influences.
Gem
The suggestion which Dr. Tomes offers, to the effect that the crowns
of the teeth have determined the direction of the jaw movements,
and so modified the condyle, is somewhat absurd. It is equal to
assuming that structure has determined habit-a most remarkable
conclusion for an evolutionist of the pronounced type of Dr. Tomes.
The fact of the matter is, the evolution hypothesis assumes the very
opposite of this.
I have always believed it to be one of the cardinal
¹ Dr. C. N. Pierce has elaborated the views of Ryder and made important additions
to this mechanical hypothesis.
TEETH OF THE VERTEBRATA.
503
។
principles of that great doctrine to consider that structure is largely the
result of habit. Upon the whole, I find it quite impossible to harmonize
such a suggestion with what this author holds on page 268 of the same
work, in which he says: "It would be impossible in these pages to go
through the arguments by which Mr. Darwin has established his main
propositions; it must suffice to say here that he has fully convinced all
those who are not in the habit, from the fixity of early impressions, of
putting many matters upon another footing than that established by the
exercise of reason, that any modification in the structure of a plant or
animal which is of benefit to its possessor is capable-nay, is sure-of
being transmitted and intensified in successive generations until great
and material differences have more or less masked the resemblances to
the parent form."
As a result of paleontological investigation we know that the form
of the mandibular condyles has been very little, if any, modified, while
the teeth have. We know, moreover, that it was a gradual process, and
that all complex patterns had their origin in simple ones.
I feel well satisfied that there is not a single dentition of a complex
nature that has not been profoundly modified by these same mechanical
influences. If evolution has taken place as a result of the physical
forces, it is impossible to discover any forces sufficient to produce such
results other than those of strain, impact, and pressure. These have in
some instances probably been exerted upon the young and growing tooth-
germs; in others they have operated upon the adult tooth, thereby fur-
nishing the causes for individual variation and determining the direction
of the hereditary energies.
T
In the preparation of the present article my grateful acknowledgments
are due to the following gentlemen: to Prof. E. D. Cope of Philadelphia,
who has kindly accorded me free access to his large and valuable collec-
tion of fossil vertebrates, without which it would have been impossible
to include the extinct forms. He has likewise placed at my disposal all
the illustrations in his possession which relate to his labors in this field.
To Mr. J. A. Ryder for many wise and valuable suggestions in the
developmental history of the teeth and other kindred subjects. To
Dr. Theo. Gill for the loan of illustrations and much important infor-
mation; and, finally, to Prof. C. N. Pierce, at whose instance I was
led to undertake the present work. I also wish to express my obliga-
tions to this gentleman for much kindly advice and assistance.
Of the works consulted I have made free use of C. S. Tomes's Manual
of Dental Anatomy, a most useful and important work; also, of the pub-
lished writings of Profs. Owen, Huxley, Gegenbaur, Flower, Cope, Leidy,
Allen, Ryder, Marsh, and others.
t
504
DENTAL ANATOMY.
27
DESCRIPTIONS OF PLATES.¹
PLATE I-Figs. 1 and 2 represent the deciduous incisors and cuspids, with their labial surfaces,
and the molars with their buccal surfaces facing. Also the normal number of roots for these teeth
in situ.
Figs. 3 and 4 represent the superior incisors, cuspids, and molars with their palatine surfaces, and
the full inferior set with their lingual surfaces facing.
Figs. 5 and 6 represent the mesial surfaces of the full deciduous set, and both mesial and distal
surfaces of the molars.
PLATE II.-Figs. 1 and 3 represent the full permanent set of thirty-two teeth, sixteen in each jaw,
with the labial surfaces of the incisors and buccal surfaces of bicuspids and molars exposed: a a, the
central incisors, right and left; b, the laterals; cc, the cuspids or canines; dd, the first bicuspids;
e e, the second bicuspids; ff, the first molars; gg, the second molars; hh, the third molars.
Figs. 2 and 4 represent the anterior teeth, incisors, and cuspids, with their cutting edges notched,
as they are usually seen in the newly-erupted teeth, this uneven or notched appearance usually dis-
appearing in a few months, or at most in a year, after eruption.
PLATE III-Figs. 1 and 2 represent the deciduous or temporary teeth divided longitudinally
through their lateral diameter.
Figs. 3 and 4 represent the same teeth divided through their antero-posterior diameters. These
cuts give a very accurate idea of the relative size of the crown and roots, and of the position occupied
by the pulp-chamber in the same.
PLATE IV. Fig. 3 gives in contrast a sectional view of deciduous and permanent upper teeth
divided through their lateral diameters.
Fig. 4, a sectional view of the corresponding lower teeth divided through their antero-posterior
diameters. a, b, c, represent, respectively, the deciduous and permanent front incisors in contrast;
d, e, f, the lateral incisors; g, h, i, the cuspids; k, deciduous molars, upper and lower; and l, m, the suc-
cessors to the deciduous molars, the bicuspids; n, o represent permanent molars. c, f, i, m, o have
dotted lines, indicating the thickness of enamel removed by wear, atrophy of the cementum, and reduc-
tion in the size of the pulp due to progressive calcification, these changes being incident to old age.
PLATE V. represents in Fig. 1, letters a to h and a to h, the longitudinal or vertical sections of the
sixteen superior teeth, showing the labio-palatine diameter of the pulp-chamber and canal in crown
and roots, the section of the molars being through the anterior buccal and palatine roots, while the
bicuspids d e and d e illustrate the result of such a compression of the fang or root as to divide the
pulp-chamber into two canals-a condition which so frequently exists in these flattened roots.
The double-lettered series, d d to h h and d d to hh, represent in the molars a section through the pos-
terior buccal and the palatine roots, from which is quite readily recognized the slightly greater lateral
diameter of the pulp-chamber in the crown and the larger canal in the posterior buccal root over that
in the anterior buccal root, while the bicuspids lettered e e d d and d d e e illustrate a modified pulp-
chamber and canal, with bifurcation of the root in one, these being cut through a different axis or plane
from the single-lettered series.
A
Fig. 2, letters a to hand a to h, represents the sixteen inferior teeth with the section through their
long diameters, as in the superior series. These incisors illustrate the compressed or flattened con-
dition of their roots in contrast with the cylindrical character of the roots of the superior incisors,
while the bicuspids d e and d e illustrate the singleness of their pulp-chamber and the cylindrical con-
dition of their roots as in contrast with the flattened or compressed condition of the roots of the supe-
rior bicuspids. The molars f, g, h, and f, g, h represent sections through the anterior root, illustrating
its compressed condition and divided pulp-chamber in the first and second molar, and a somewhat
flattened one in the anterior root of the third molar; ƒƒ, 9 g, kh, and ƒ‚f, g g, h h represent the single
and cylindrical pulp-chamber in the posterior root of the inferior molars, while b b, c c and a a, b b
represent the incisors and cuspids of the same series, with modified pulp-chambers arising from modi-
fied development.
-
PLATE VI. —Fig. 1, from a to h and a to h, represents the superior teeth, with transverse or horizon-
tal section through the base of the pulp-chamber in the crown, viewing the entrance to the canals of
the several roots, while the same letters in Fig. 2 represent the inferior series in the same manner.
Fig. 3 represents the superior teeth, with the transverse or horizontal section made below the
largest diameter of the pulp-chamber and through the canals after they have diverged from the cen-
tral chamber, but before the roots into which they run have in the molars bifurcated.
Fig. 4 in like manner represents the inferior series, well illustrating the flattened or compressed
condition of the canal in anterior roots of the molars and the division of the chamber, as is frequently
found in the roots of the inferior incisors.
S
The letters a a, b b, c c, d d, ƒ ƒ, d d and e e (Fig. 3) represent the relative shapes, whether circular,
oval, or flattened, of the pulp-canal in the roots of the superior central and lateral incisors, the cuspids,
the first and second bicuspids, and the first, second, and third molars, while the same letters in Fig.
4 represent the relative shapes of the pulp-canal in similar teeth in the inferior series.
1 These plates are taken from v. Carabelli's Anatomie des Mundes.
PLATE I.
Fig. 1.
Fig. 2
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44

PART III.
EMBRYOLOGY AND DENTAL HISTOLOGY.
DENTAL EMBRYOLOGY AND HISTOLOGY.
BY W. XAVIER SUDDUTH, M. D., D. D. S.
PHYSIOLOGICAL CONSIDERATION OF LIFE-FORCE.
WHAT is the nature of life? is a question which man is ever asking
of the universe of which he is so wondrous yet so infinitely small a
part. From the earliest times the ultimate purpose of all scientific
research has been to elicit a sufficing reply to this inquiry. The deepest
thinkers and most devoted searchers after truth have speculated and
investigated in the hope of making up something like a satisfactory
answer. But, though knowledge has been augmented and phenomena
explained, the great life-mystery remains unrevealed. The question
still is asked, What is that vital or living principle which we call life?
Scientists and philosophers have ventured various and widely diver-
gent theories in explanation of the nature and powers of vital phenom-
ena. Setting aside opinions that are so manifestly based upon fallacies
as to carry with them no inkling even of definite signification, the great
variety of theories advanced in our own day may be for the most part
reduced to two or three classes.
In the early part of the present century Lorenz Oken, a devotee of the
physical school, proclaimed "primordial slime" to be the original source
of life and the material basis of all living bodies. This "primordial
slime" possessed in all essentials the same qualities and the same import-
ance now ascribed to the substance known as protoplasm. The proto-
plasm theory-varied in many ways as to the first vitality on earth-
has occupied the attention of the most earnest scientists and profoundest
thinkers of the age.
It is not my intention to notice to any extent the different phases
which this theory has assumed, but I wish to be understood as antag-
onizing that interpretation of it which aims to make the beginning of
life in the individual solve the great mystery of the beginning of life
in the world. I desire, at the outset, to forestall any misapprehension
of facts I may state hereafter, and to impress upon my readers the wide
difference between accepting protoplasm as the first formative substance
and ascribing to it the power of spontaneous generation, since it by no
means follows that because it is the essential and active agent in the
formation of every tissue, in the construction of every organ and of
every form of mechanism existing in a living being, it is in any sense
self-originating.
Perhaps the most plausible theory advanced by speculators concerning
J
519
520
DENTAL EMBRYOLOGY AND HISTOLOGY.
life-formation is that of evolution, but evolutionists themselves assign
several meanings to the term. One class maintains that the develop-
ment hypothesis is restricted to the living world-that it simply teaches
that all grades of life have arisen from the simplest beginnings, the
higher being derived from the lower by a long course of organic devel-
opment solely through the operation of such forces and laws as belong
to matter. Another class holds that the hypothesis includes not only
the evolution of living forms from pre-existing living forms, but the
spontaneous production of living from non-living material. A vast
majority of the practical, working scientists in Europe and America—
those who report not what they wish nor hope nor imagine, but only
what they see, who are seeking, not the mere support of cherished
hypotheses, but the uncolored truth from Nature, refuse to accept the
doctrine of evolution, while at the same time they fully allow the value
of many of the facts gathered by its followers.
In regard to the "transmutation of species," that part of the theory
of evolution which undertakes to show how the higher grades of life
came by a series of natural changes from the lower, Agassiz has written
thus:
WA
"I wish to enter my earnest protest against the transmutation theory.
It is my belief that naturalists are chasing a phantom in their search
after some material gradation among created beings by which the whole
animal kingdom may have been derived by successive development from
a single germ or from a few germs. I confess that there seems to me a
repulsive poverty in this material explanation that is contradicted by
the intellectual grandeur of the universe. I insist that this theory is
opposed to the processes of Nature as we have been able to apprehend
them; that it is contradicted by the facts of embryology and palæon-
tology, the former showing us forms of development as distinct and
persistent for each group as are the fossil types of each period revealed
to us by the latter; and that the experiments on domesticated animals
and cultivated plants, on which its adherents base their views, are
entirely foreign to the matter in hand."
From the side of geology-on which evolutionists very largely de-
pend for the support of their scheme-we have many an earnest pro-
test, of which the following may serve as an illustration:
"Were all the anatomists of the earth against us, we should not one
jot abate our confidence. For we have examined the old records, but
not in cabinets, where things of a different age are put side by side, and
so viewed might suggest some glimmering notions of a false historical
connection. We have seen them in spots where Nature placed them,
and we know their true historical meaning. We have visited in suc-
cession the tombs and charnel-houses of these old times, and we took
with us the clue spun in the fabric of development; but we found this
clue no guide through these ancient labyrinths, and, sorely against our
will, we were compelled to snap its thread, and now dare to affirm,
with all the confidence of assured truth, that geology-not seen through
the mists of any theory, but taken as a plain succession of monuments
and facts-offers one firm cumulative argument against the hypothesis
of development" (Sedgwick).
"
PHYSIOLOGICAL CONSIDERATION OF LIFE-FORCE.
521
1
Still stronger words than these have been spoken against the doctrine
of spontaneous generation. It is even admitted by nearly all the fore-
most evolutionists themselves that as yet not an instance of life-forma-
tion without seed has been made out. "It is true," say they, "that
the knowledge of man has not yet enabled him to make a vegetable or
animal germ, but the time may come when it will be done."
299
66
"To-morrow, and to-morrow, and to-morrow, says Dr. Beale,
'has always been the refuge of the philosophers who have faith in the
dogma that matter alone is competent to develop every form of life.
But the 'to-morrow' of Lucretius has not yet dawned; and how many
thousand years, I would ask, may be expected to pass away before the
prophecies of those who would now go along with Lucretius shall be
fulfilled?" Again, speaking directly of the theory of spontaneous
generation, he says: "I cannot but remark that the more minutely
investigation is carried out, the more thoroughly and intently facts
bearing upon the matter are examined, the more improbable, in my
judgment, does it appear that any living form should be derived directly
from the non-living. Notwithstanding all that has been recently written
upon this subject, I cannot but feel surprised that at this time many
good reasoners should decide in favor of the de-novo origin even of
bacteria. Whether we consider the matter from the experimental side
only, or study the evidence obtained in a general survey of Nature, or
carefully reflect upon the facts learned from investigations concerning the
properties of living and non-living matter with the aid of the most
perfect instruments of minute research now at command or from other
standpoints, the conclusion seems to me irresistible that the verdict of a
jury of well-educated men would be against the direct origin of any
form of living from any form of non-living."
" 1
Pasteur asserts decisively, "There is no circumstance now known
that permits us to affirm that microscopic beings have come into the
world without germs, without parents like themselves. Those who
affirm it have been victims of illusions, of experiments badly made,
and infected with errors which they have not been able to perceive or
avoid. Spontaneous generation is a chimera."
Did our limits allow we might multiply quotations almost indef-
initely to show that the most thoughtful among working scientists, both
at home and abroad, deny that there have been proved cases either of
transmuted species or of spontaneous generation. On the contrary,
experimental investigation is constantly furnishing positive proof of the
permanence of species, and so intensifying the vast dissimilarities be-
tween the living and the non-living as to preclude the possibility of
drawing even an analogy between the properties peculiar to living mat-
ter and any properties known in connection with the non-living.
K
The distinctive characteristic of non-living matter is rest; the dis-
tinctive trait of living matter is motion, life. The non-living, once
formed, never changes from internal causes; its parts invariably pre-
serve the position which they have once taken in respect to each other,
unless endowed with the properties of life by the aid of organisms
already living. Living bodies, on the contrary, from the very lowest in
1 On Life and on Vital Action in Health and Disease.
¿
Gam
!
522
DENTAL EMBRYOLOGY AND HISTOLOGY.
the vegetable kingdom to those concerned in the development of man,
are continually in action. This capacity of movement is the broad essen-
tial character which distinguishes living matter absolutely from all other
matter, and makes a clear-cut boundary between it and the non-living.
It has been claimed that the phenomena of the minute organisms which
lie on the very verge of the vast area of what we know as the living
are not essentially different from those of the highest points in the area
of the non-living which they touch. The wonderful revelations of the
lowest forms of life made by the modern microscope have shown that
not only is the assertion entirely groundless, but the highest form of
living matter is not more unlike non-living than is the lowest-that
one is, in fact, just as near and just as far from inorganic matter as
the other."
66
With all our study, we must admit that at best we have only been
able to demonstrate life in its concrete form. It is a correlation of
forces that our present knowledge does not enable us to separate into
ultimate principles. We know the elements that compose the vital stuff;
we know their physical properties. But how these elements can be so
combined as to acquire the wonderful properties of life is as great a
mystery now as when God first "breathed into man the breath of life,
and he became a living soul.' Humanity stands to-day, as in the
remotest past, with the same question on its lips: What is life? What
is it to be?
""
But whatever may be the essential nature of the central force which
determines the form and action of living bodies, it cannot be denied.
that some power does exist and act in every organism independent of
the physical and chemical forces of Nature. "Besides the material sub-
stance of which a living body is constructed, there is also an immaterial
principle, which, though it eludes detection, is none the less real, and to
which we are constantly obliged to recur in considering the phenomena
of life. It originates with the body, and is developed with it, while yet
it is totally apart from it." We are as certain that this inscrutable prin-
ciple does exist as we are of the constancy of species-a phenomenon
depending on its operation. Every living thing tells of some wonder-
ful power which is capable of controlling matter and its forces-"a
power which we cannot isolate and physically examine, but the effects
of the actions of which we may study."
Let us use a familiar illustration: If one grain of copper be dissolved
in three pints of water, a distinctly blue tint is imparted to the volume
of water. We cannot see the finely-triturated particles which by their
minute subdivisions have given the blue tint to the water-they do not
reveal themselves even to the microscope-but we know that they exist,
and that by the process of evaporation we may receive back our one
grain of copper. But you ask, How can this illustration be applied to
the question of ultimate life-force? We answer: In all our study of
life we see the "blue tint," as it were. Especially is this the case in
the microscopic study of the formative material which we designate pro-
toplasm. Beyond the protoplasm we see the manifestations of a uni-
versal power by virtue of which all formation, whether vegetable or
animal, takes place. We see how protoplasmic atoms act under the
STRUCTURE OF CELLS.
523
direction of this indwelling principle just as plainly as we see the blue
tint of the water; and we feel as sure that there is a force outside the
properties of matter, which pervades and vivifies every living particle,
as we do of the grain of copper left after the evaporation of its men-
struum. It is only as man contemplates, at the same time, matter and
mind that he is able to master the first data of life-science or form even
a dim conception of that Infinite Spirit "whom none by searching can
find out."
Update
But we must now leave the question of how life begins, and consider
life as it presents itself to our eyes when seen in its minutest forms and
at its earliest known stage of existence-i. e. as an aggregation of trans-
parent cells.
The unit of life, as we are able to demonstrate, is expressed in small
bodies denominated cells, and "the life-history of the individual cell is
the first important and indispensable basis whereon to found the true
physiology of the life-history of all the orders of creation." We shall
therefore take our starting-point from the simple cell, which is the same,
in respect to its chief characters, in animal and vegetable life.
STRUCTURE OF CELLS.
A mature cell is composed of a nucleus, a cell-body, and a cell-limit,
or wall. The nucleus is that part of the cell which is first formed from
the germinal matter, and is the first to be affected when a change in form
occurs. The nucleus may assume various shapes, as round, oval, rod-
like, or irregular. It generally encloses central dots, termed nucleoli,
of
which are thought by some histologists to be the enlargements por-
tions of an irregular network of fibres which can be seen inside the
nucleus. The cell-body is the formed material which surrounds the
nucleus. The cell-wall is the limit of this formed material. When we
speak of a cell-wall, we do not mean that there is any abrupt demarca-
tion between the cell-body and its outer edge; the one passes gradually
into the other. Cells draw their nourishment from a protoplasmic sub-
stance which circulates in the intercellular spaces. This supply of cell-
pabulum is inert until acted upon by the living principle resident in the
cell. Such are the visible parts of a cell when seen in its early stage of
existence.
K
mah
C
Kwa
Ziegler, speaking of the youngest embryonal cells, says: "The cell
by itself appears originally as a microscopic mass of pale, slimy, finely-
granular matter the so-called protoplasm. It usually contains within
it a nucleus-that is to say, a structure like a tiny vesicle, whose
form may be round, oval, rod-like, or irregular, and in whose interior
we can make out, by proper handling-1, small definite bodies, the
nucleus-corpuscles; 2, a net-like framework of nucleus substance; and,
3, a clear fluid, the nucleus juice. The young cell is at first naked.
Only in its maturer stages does it develop on its surface an optically
distinct membrane or other structure according to the special tissue
of which it forms a part." This accords with my own observation.
For example, in studying sections from the mucous membrane of the
mouth it is found that the deepest part of the epithelial layer of the
W
524
DENTAL EMBRYOLOGY AND HISTOLOGY.
mucous membrane of the mouth in the embryo is formed of a layer of
protoplasm, which is conspicuous in preparations stained with hama-
toxylon and eosin in that it stains more darkly than the surrounding
tissue. In this protoplasmic basis-substance are found small spheroidal
cells (nuclei), sometimes arranged in regular layers; in other cases the
dark-stained layer of protoplasm is wider, and several layers of sphe-
roidal cells exist-not arranged in strata, but presenting an irregular
appearance, and in some instances being four or five cells deep. These
spheroidal cells have no distinct cell-body or membrane, and the sur-
rounding protoplasm presents no characteristic feature. The youngest
cells of the Malpighian layer take the stains similarly to the embryonal
connective-tissue cells lying immediately beneath in the submucous
layer, and at this stage present the same shape, and can be seen in the
pig embryo 1- centimeter in length, and in the human embryo at the
thirty-fifth day.
As the nuclei are crowded up from this bed of protoplasm, they carry
with them a certain portion of protoplasm which surrounds the nucleus
as a cell-body, and as they approach the surface of the epithelium they
apparently develop a cell-wall; in this state they present an imbricated
border which unites them to their fellows. (For further description and
figures see section on Mucous Membrane of the Mouth, p. 611.)
The shape of cells depends to a great extent upon the reciprocal
pressure of fellow-cells. This is specially noticeable in cells developed
from the epiblast and hypoblast: these may be round, oval, cylindrical,
columnar, prismatic, hexagonal, or tessellated in form. The cells devel-
oped from the mesoblast-viz. the connective-tissue group-vary from
round or oval to fusiform with numerous fibrillæ. The size of a cell
may be th part of an inch in diameter; some are larger, some
smaller; the nucleus may be th of an inch in diameter; the nucle-
olus 100th of an inch in diameter, more or less.
1
0
shagga
PHYSIOLOGICAL CONSIDERATION OF CELLS.
Dependent upon an inherent principle, the nature of which we have
never been able to divine, cells have a threefold character: the power
of self-preservation, of multiplication, and of functional activity.
In the first place, out of the common stock of cell-pabulum each cell
has the power to assimilate such constituents as are needed to prolong
its existence. That different cells require different kinds of food, and
are able to convert the same into matter like themselves, is evidenced
by the fact that chemical reagents give manifestly different results on
the various cells. A simple demonstration is found in the action of
staining agents upon different tissues. Cells have, within a certain
limit, the power of overcoming deleterious agents or conditions. This
limit is not great as regards the cell itself, but for the tissue of which
it is a component part the range is much more extended.
Recovery after the loss of a portion of the cellular elements that com-
pose a tissue is generally very rapid, and depends upon that attribute
of cells we term multiplication. Increase of cells is accomplished by
segmentation, which, beginning in the nucleus, results in the division
PHYSIOLOGICAL CONSIDERATION OF CELLS.
525
of the parent into two equal parts, each of which when detached absorbs
nutrient matter, and, soon attaining the same size as the mother-cell,
multiplies in turn. The principle enunciated by Virchow twenty years
ago, Omnis cellula e cellulâ, is as much in force now as then. Discov-
eries regarding the methods of cell-multiplication have been made, but
no instance of metaplasia between members of different groups or fam-
ilies has been demonstrated. That the repair of tissues depends upon
the multiplication of cells of like families is the accepted belief of his-
tologists to-day. A surface denuded of its epithelium does not recover
itself from the connective tissue beneath, but from the edges of the
wound by the extension of the borders toward the centre, thus gradu-
ally forming a complete skin. It is true that the regeneration of con-
nective tissue is through granulation-tissue, but granulation-tissue is
developed from the escaped white blood-cells; and I think we can
place white blood-cells in the list of connective tissues developed from
the mesoblast. The change from white blood-cells to plasma-cells and
fixed connective-tissue cells is simply a matter of adaptation to environ-
ment.
A
We come now to the consideration of the third attribute of cells
that of functional activity. The life of the individual rests in the life
of the individual elements that compose it. The human body is made
up of millions of individualities which are dependent upon a special
localized principle for their functional activity. These units of life not
only have the power of individual cellular activity, but, united, they
form organs which are but the expressions of their aggregation. A
tissue is what it is by reason of the elements that constitute it, and the
function it performs is only the united expression of its component
parts. Cellular activity, then, is the basal principle that underlies all
visible life-functions.
The limit of duration as regards the life of an organism is in adverse
ratio to the scale it occupies in the order of being. A perversion of
physiological action in the individual organism gives rise to a patho-
logical condition known as disease. Total and permanent cessation of
functional activity is that state of being which we recognize as death.
Death may result from outside influences or by reason of the cells hav-
ing performed their life-office.
SARA
Cells are developed to perform well-known physiological actions,
and when a pathological result is produced it has its origin in some
outside influence. Cells have not the power to produce pathological
results unless stimulated by some agent which lies without the bounds
of physiological action; and when so stimulated they act through their
original channels. Thus, we see that pathological conditions are only
perverted physiological conditions. Many physiological processes pre-
sent pathological appearances, but when we study their deeper expres-
sions we find that they are purely physiological. For instance: in the
development of bone, giant-cells or osteoclasts are always present taking
down the first-formed bone from the inner side, while the osteoblasts
are adding to its circumference. In the resorption of the roots of tem-
porary teeth we find another excellent example of physiological action
which bears upon its face the stamp of a pathological process. In this
526
DENTAL EMBRYOLOGY AND HISTOLOGY.
case giant-cells are Nature's physiological agents, by whose aid she
removes tissues that have performed their life-office.
There can be no doubt that cellular activity can be induced by dif-
ferent agents, but the action of a given tissue is always the same-pro-
vided the other conditions remain unchanged-whatever may be the
nature of the outside irritant. Too little stress is laid upon the character
of the irritant, and too much on the visible expression of Nature's effort
to remove it.
The close intimacy existing between physiological and pathological
processes is very clearly seen in the action of giant-cells. In one
instance they are the expressions of normal action; in another they are
actively engaged in producing pathological results. Let us study them
in their several conditions.
Giant-cells are found in connection with a perversion of the equili-
brium of the circulation which results in increased nutrition. In most
instances where such disturbance is found it can be directly traced to
some local irritant. We see a hyperemic condition of some organ or
part of the body, which state is quickly followed by congestion and
the exudation of white blood-corpuscles. These tend to form granula-
tion-tissue. The increased nutrition does not sufficiently account for
increased cellular activity, either as regards multiplication or function-
congestion not always resulting in cell-multiplication. There is back.
of all that can be observed some force inherent in the cell itself that
leads to these special attributes-an ego which has the power to turn
the local irritant into a cellular stimulant.
Ziegler, writing on this subject, says: "The proposition, often enun-
ciated as if it were self-evident, the stronger the external stimulus
the greater the proliferation,' cannot be accepted as true. We can, at
most, admit that slight stimuli, sufficient merely to excite the cell with-
out injuring it, may perhaps call into play its powers of multiplication;
but nothing has been experimentally established concerning the nature,
the action, or the mode of application of such stimuli. If, then, it be
true that external injurious agencies are not competent to induce multi-
plication of cells, we must have recourse to the normal vital stimuli if
we are to explain the process of pathological cell-growth. For the
due growth and multiplication of a cell certain external conditions must
be fulfilled. Above all, it is necessary to provide for a certain degree
of warmth and a certain modicum of proper nutritive material. In
addition to this there must be no obstacle in the way of multiplication.
These are the external requirements. The internal condition is the
inherent faculty of the cell to assimilate the nutriment offered to it. In
a tissue not undergoing transformation the factors favoring proliferation
and those which inhibit it must be in a state of balance. If this bal-
ance be disturbed toward the side of the proliferous forces, the cells
proceed to grow and to multiply. The factors in question resolve them-
selves on analysis into three. In the first place, it is conceivable that
the capacity of the cell to assimilate nutriment may be increased. Such
increase can only be conditioned by an increase in the normal stimuli
required for the preservation of the cell. Such stimuli are warmth;
for many cells, light; for the muscles, motor impulses; for glands,
G
Kadan
PHYSIOLOGICAL CONSIDERATION OF CELLS.
527
Increased stimula-
special excitations from the nervous system, etc.
tion of this kind may, as a fact, lead not only to intensified functional
metabolism in the tissue concerned, but even to hypertrophy of its
elements. Such hypertrophies, which we may call functional hyper-
trophies or hypertrophies of action, are specially common and remark-
able in muscles and glands (heart-muscles, bladder-muscles, kidneys,
etc.). As we have said, they are referable, in part at least, to increased
vital activity in the cells, consequently upon increased physiological
stimulation. A second possible factor is increase in the supply of nutri-
ment. This plays a chief part in hyperplastic processes, at any rate.
A third is the removal of the normal checks to growth. Its effect is
most evident in the processes described as regenerative. If we attempt
in particular cases to make out to which of these factors cell-multipli-
cation is due, we are led to see that it is rare for any one factor alone to
be the efficient cause.
"The remarkable regulating mechanism of the vessels is so adjusted
that when the function of a tissue is increased, its blood-supply is
increased to correspond. In like manner, when the smallest fragment
of tissue is removed, the slight loosening of the surrounding texture is
enough to augment the stream of transudation from the vessels. In
consequence of these adjustments increased supply of nutriment plays
a great part in all the formative disturbances of nutrition.
"Cohnheim, in his Allgemeine Pathologie, has insisted on the import-
ance of increased supply of nutriment even more strongly than we have
done. According to his view, it is the sole influential factor, compared
with which the intrinsic activity of the cell is quite secondary. We are
unwilling to condemn the cell to play so passive a part, but rather agree
with Virchow,' who affirms that the cell is not nourished, but nour-
ishes itself." Functional hypertrophy is therefore not to be looked
upon as the mere consequence of the increased blood-supply to the
active organ.
"If the assimilative activity of the cells were not augmented, the
mere presence of a greater supply of nutriment would be valueless.2
"We shall more readily comprehend the activity of the tissue-cells——
i. e. their behavior under various conditions and the changes they pass
through, now at rest and now manifesting intense formative energy-
if we consider first the vital manifestation of an organism that is uni-
cellular, micro-organisms of bacteria and yeast-plants, and their mode
of life. If we reflect on the conditions essential for the multiplication
of such organisms, we note that the nature of the nutrient fluid is (next
after the adjustment of the temperature) the factor of higher import-
ance. In suitably composed fluids the fungi develop much more luxu-
riantly than in those that are ill-suited. But we are not thereby justi-
fied in assuming that the cell plays a merely passive part-that all it
has to do is to take up the nutriment offered to it. The cell is, on the
contrary, active, and its activity has a special influence on the liquid
itself. It has the power to induce certain chemical changes in the
liquid, to decompose certain substances contained in it, and to change
1 Cellular Pathology.
2 See Samuel's Allg. Path., 1879; Paget's Surgical Pathology, Lect. 3.
J
528
DENTAL EMBRYOLOGY AND HISTOLOGY.
ย
6
this condition so as to adapt them for assimilation by itself. The cell
does not merely take in and give out material; it acts catalytically'
on its environment. This is proof at least that the cell possesses a high
degree of spontaneity—that it has the power of making more available
for its own sustenance the various forms of nutriment that come in its way.
"It is also of great interest to note that the cell is ultimately limited in
its formative activity by its own products. When the amount of nutri-
ment present is abundant, the activity of the cell comes to an end, not
through the exhaustion of the supply, but through its contamination
with certain products of cell-metabolism.
66
Many of the substances engendered in fermenting liquids by the
action of fungi tend to check the growth and multiplication of the
fungi themselves; when present in quantity they may put a stop to
multiplication altogether.
Sal
"The alcoholic fermentation, and the multiplication of the yeast-plant
which produces it, come to an end when a certain proportion of alcohol
has been generated in the fermenting liquid. In septic putrefaction the
bacteria generate compounds, such as carbolic acid, which are destructive
to themselves. If we may apply these facts of fungus physiology to
the cell physiology of higher organisms, we find that they illustrate,
first of all, this principle: that the quantity and quality of the nutritive
material at the disposal of the cell have a profound influence upon its
behavior; and, secondly, this other that the cell has nevertheless an
intrinsic power of utilizing this material, and of appropriating what is
suitable to itself out of various combinations. Lastly, the limits im-
posed on the multiplication of fungi by the products of their own
activity may help us to understand how the formative activity of the
cells of complex organism may be temporarily checked.
"We cannot, indeed, regard the intercellular substance of the connec-
tive tissues as equivalent in significance to the products of the chemical
changes induced by the bacteria. Yet the comparison may at least
enable us to conceive how cell-growth may tend to limit and to check
itself without the interposition of extensive resistance. In the connec-
tive tissues the formation of the intercellular substance is the limiting
factor; in the epithelia it is the cohesion or cementation of the individ-
ual cells into a firm and single whole, just as in yeast fermentation it
is the formation of alcohol. When the alcohol is withdrawn in the
latter case, the multiplication of the yeast-fungus goes on again. So,
likewise, if the intercellular substance be dissolved away from a connec-
tive tissue, or if the continuity of the epithelial mosaic be loosened or
interrupted, the faculty of multiplication is again awakened in the con-
stituent cells; or if (as in the epithelia) it has never been dormant, it is
at once intensified.”
Cellular activity, as found in normal development, depends upon some
force which cannot be explained by chemistry and physics or without
calling in the aid of the hypothesis of vital functions. Cells stimulated
by the indwelling vital power proliferate until the typal demands of the
tissues are reached. In many tissues this growth is so adjusted as to be
self-limiting, as in the Haversian system of bones, in which the devel-
opment is centripetally arranged, thus lessening the calibre of the enclosed
PHYSIOLOGICAL CONSIDERATION OF CELLS.
529
capillary vessels, and so diminishing the supply of cell-food. The
innate governing principle in normal development decides that cellular
activity shall set in at one point and not at another. This is beautifully
illustrated in the development of the hair, glands, and the enamel organ
of the teeth. These organs are formed by an infolding of the super-
imposed epithelium. This process begins in localized cellular activity;
rapid cell-multiplication follows, and the new-formed cells sink into the
subepithelial tissue. The point of greatest activity is always found in
the deepest portions of the ingrowing tissue; and this activity continues
until the typal demands of the special organ are met, when it ceases.
No other satisfactory explanation of the action of cells can be given
than that an independent life-principle resides in them which directs
their growth and function. As we investigate more minutely we find
that insuperable difficulties present themselves to any physical interpre-
tation of the facts connected with living cells.
Fleming has established beyond dispute that cell division is depend-
ent upon nucleus division. In some instances, however, the nucleus
divides and a subsequent division of the cell does not follow. In this
case multinuclear cells are formed. We do not know positively why
cellular activity results, but it is probable that the cells are stimu-
lated to an increased assimilation of cell-pabulum, as an increased sup-
ply of nutrition does not always produce giant-cells. Some authors
hold that giant-cells or osteoclasts found in connection with resorption
of bone are produced by the liberated bone-cells; but the fact that
giant-cells appear in connection with the resorption of other hard tis-
sues which do not contain bone-cells seems to establish for them an
independent identity. When speaking of erosion of bone, Ziegler uses
the terms osteoclasts, giant-cells, and resorption-cells as synonymous,
and asserts that they arise from multiplication of exuded white blood-
cells. Resorptive-cells in some cases contain but one nucleus. They
are, however, considerably larger than ordinary cells, so we will use the
term giant-cells in the sense of larger cells having a specialized func-
tion, whether they be multinuclear or not.
Giant-cells are found in diseases where great cellular activity exists,
as, for example, in miliary tuberculosis, syphilis, myeloid sarcoma, and
hyperplastic granulation-tissue; they are also found in connection with
the resorption of bone in normal development, and in the roots of
temporary teeth and other bodies that Nature desires to remove. They
are developed in all the above-named cases unless the exuded cells are
destroyed and a purulent condition produced.
Ziegler, writing of the resorption of tissue, says:
"The first stage is the formation of a zone of inflammatory infiltra-
tion around the foreign body. This is followed by the development of
granulation-tissue, and at length of fibrous tissue. If the foreign body
is not meanwhile absorbed, it thus becomes encapsuled. Only insoluble
and compact bodies can remain quite unaltered, for resorption is, as it
were, attempted, even though it be in vain. Bodies which are at all
assailable are sure sooner or later to undergo changes. These ensue as
follows: The migratory leucocytes, transformed into uninuclear or mul-
tinuclear formative cells, attach themselves to the surface of the object.
VOL. I.-34
<
kateg
+
530
DENTAL EMBRYOLOGY AND HISTOLOGY.
If this be made up of smaller parts, or if particles of necrosed tissue be
mingled with it (such as decomposed blood in hemorrhagic patches),
these are taken up by the cells and carried off by the white blood-cells
which migrate from the blood-vessels. These migratory cells appro-
priate the foreign substances lying in the tissue. They let their proto-
plasm flow round them, and so take them up into their interior. By
frequent repetition of this process granule-carrying cells are produced.
According to their contents these have been variously described as fat-
granule carriers, blood-cell carriers, pigment-granule cells, cinnabar-
carrying cells, etc. If the foreign body be compact and not to be
broken up, the cells cling to its surface. If there be accessible cavities
or clefts in it, they penetrate into these. If the cells be insufficiently
nourished, they become fatty and die. If new vessels are formed to
supply them, they develop as granulations. Very often, indeed, multi-
nuclear or giant-cells are found in such circumstances.'
""
"A dead piece of bone inserted under the skin of an animal and
examined a few weeks after will be found interpenetrated with vascular
granulations, and the trabecula will be beset in many places with giant-
cells. The whole process is very similar to that of physiological bone
resorption."
"This process is peculiarly modified when the foreign substance is
firmly connected with the surrounding tissue-when it is, in fact, a
necrosed fragment of the tissue itself, such as bone or kidney. In this
case the first step is the separation of the living from the dead."
"Langhans was the first to describe minutely the process by which
larger foreign bodies are absorbed. He pursued the subject experimen-
tally by producing extravasations of blood in various animals. He
thus discovered the giant-cells. Heidenhain also found them in pieces
of elder-pith which he had inserted in the abdominal cavity of animals.
Ziegler always met them in connection with his experiments in placing
cover-glasses, slightly separated, under the skin of a dog. Later exper-
iments with sponge-grafting have demonstrated their presence and active
agency in the absorption of the pieces of sponge."
Resorption of tissues or foreign substances is a purely physiological
process. The pathological phase is found, not in the removal of the
offending substance, but in the irritant which brought about the resorp-
tive process. Hitherto, too much stress has been laid upon the visible
expression of Nature's effort to remove the irritant, and too little on the
character of the irritant itself. Pathological results may attain to the
resorptive process through the action of giant-cells by reason of the jux-
taposition of healthy tissue, but such conditions are incidental, and not
the direct point of attack. Cells have not the power to produce path-
ological results, except they be pathologically stimulated, and when so
stimulated they act through their own peculiar channels. I look upon
giant- or resorption-cells as Nature's physiological agents, by whose
aid she removes tissues which have performed their life-office, and
substances which by their presence are hurtful to the animal economy.
The action of giant-cells in this process belongs to the third attribute
ascribed to cells-viz. that of function. They secrete a fluid which has
the power of digesting the tissues in their immediate neighborhood. In
ky
M
MORPHOLOGICAL APPEARANCE OF CELLS.
531
claiming this attribute for them we do not go beyond the physiological
action of cells. The process of digestion is well known to every student
of physiology. In the stomach glands secrete certain fluids, by whose
action that which we call food is so changed that it can be taken into
the blood and assimilated by different parts of the body. A failure on
the part of these glands to produce their normal fluid results in what
we term indigestion. Food-stuffs, unless prepared and dissolved by
the fluid secreted by the glands of which we have been speaking, cannot
be assimilated. We find that what is true of the digestion of food-
stuffs is also true of the resorption of tissues. In order that a tissue
may be removed it must first be digested by the cell-fluid, after which
it can be taken up by the lymphatic system. It is true that very small
particles, by reason of their minute subdivision, do enter the lymph-
channels, but they are not assimilated into the general system; they are
deposited in the first gland into which the lymphatic empties. In-
stances of this kind are found in cases of respired particles of coal- and
stone-dust, and as a consequence we have the pathological condition
known as the "coal-miner's" and the "stone-hewer's" lung.
K
As I have already said, in order that any tissue may be assimilated
it must first be digested. In the cases above mentioned the soluble
ferment is secreted by the giant-cells at the point of irritation. The
juxtaposition of the secreting cells and the tissue to be resorbed is a
matter of essential import. The ferment or fluid in question is not an
exuded fluid of the blood; it is as truly a specialized fluid as are the
secretions of the peptic glands of the stomach. The nature of the body
to be resorbed has no more influence in the production of the secretions
than have various food-stuffs which are taken into the stomach over
the secretions of the stomachic glands. Then, again, resorbed and
resorber must be in actual contact, as is seen in every instance where
tissues are removed. The secretion acts upon the tissues found in its
immediate neighborhood, whether they be living or dead. This fact is
well illustrated in the resorption of the roots of temporary teeth. It
matters not whether the pulp, the life of the root, be alive or dead, so
long as the surrounding parts do not become purulent.
Resorption, then, is the result of the physiological action of cells
stimulated by irritation to increased cellular activity; but in order that
they may so act the irritation must not be too severe. If, when the
pulp of a temporary tooth dies, a chronic abscess results, physiological
resorption of the root cannot occur. Its removal is then accomplished
by necrosis, and giant-cells are not found. Resorption by giant-cells, as
we have seen, can only occur when the cells are stimulated to an increased
assimilation of the over-supply of nutrition which is produced by the
local irritant.
MORPHOLOGICAL APPEARANCE OF CELLS.
Under this head we will briefly consider blood-corpuscles, epithelial
and connective-tissue cells.
The physical appearance of blood is that of a red fluid somewhat
thicker than water. When examined under the microscope we find
532
DENTAL EMBRYOLOGY AND HISTOLOGY.
suspended in the fluid (serum) of the blood small spheroidal and disc-
shaped bodies known as blood-corpuscles. These blood-corpuscles or
cells vary not only in form, but also in color and action. One of the
disc-shaped corpuscles, seen by itself, looks slightly yellow in color, but
when seen in a mass the mass is clearly red; and it is to the presence
of these cells that the blood owes all its color, the other blood-cells
and the serum being alike colorless. Upon the warm stage or when
subjected to the action of a strong salt solution they become crenated
in form (see Fig. 270, c, c); if the salt solution be displaced by distilled
water, they assume their original shape for a short time, but soon
bcome swollen and decolorized, the hæmoglobin which gives them their
color being freely soluble in water.
In different animals the corpuscles vary both in size and form. In
Mammalia they exist in general, like those of man, as circular discs,
larger or smaller, but without nuclei. In birds and cold-blooded
animals nuclei are found, but the cells, instead of being circular, are
oval and larger. "The size of the corpuscles," says Foster, "seems to
bear no relation to the size of the body, but, as has been pointed out
by Milne-Edwards, there occasionally exists a relation between the size
and the muscular activity of the animal. Thus it was found that in
deer and other fleet-footed animals the corpuscles were relatively small;
in Amphibia, which are comparatively sluggish, the corpuscles were
relatively larger. The relation,
then, that the diameter of the
corpuscle would bear to the
muscular activity would be in
an inverse ratio. It has also
been found that the higher the
scale of life is advanced the
smaller the diameter of these
bodies becomes."
FIG. 270.
pl

p
с
gol
Besides the red blood-cells,
there are others slightly larger,
not colored at all, and not cir-
cular and flat, like those above
described, but round like a ball;
these are termed colorless or white
corpuscles. When watched un-
der the microscope-care being
taken to keep the temperature
the same as that of the body-
<<
p
с
Human Blood as seen on the Warm Stage (magni- they are seen to have a peculiar
fied about 1200 diameters): r, r, single red corpus-
cles seen lying flat; "", "", red corpuscles on their
edge and viewed in profile; ", red corpuscles
arranged in rouleaux; c, c, crénaté red corpuscles;
p, a finely granular pale corpuscle;, a coarsely
granular pale corpuscle. Both have two or three
of shape at the moment of observation; in ga
amoeboid movement, by means
of which they are able to trans-
port themselves from place to
place; it is owing to this ca-
pacity of movement that they
have received the name of wan-
were undergoing changes.
nucleus also is visible.
g
こと
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go's
p
K
dering leucocytes. Their activity varies with the rise and fall of the
temperature and the amount of oxygen present in the tissue. Under
MORPHOLOGICAL APPEARANCE OF CELLS.
533
•
favorable circumstances they may be seen migrating from the sides of
blood-clots. When at rest the white corpuscles are spheroidal, but in
a state of activity they are continually changing in shape. Sometimes
they assume an irregular form, throwing out pseudopodia or prolonga-
tions (Fig. 270, p), such as are found in the amoeba; in fact, so strong
is their resemblance to that minute animal that they have been called
the human amœbæ.
The white blood-cells are lighter than the red, and traverse the
vascular channels upon the periphery of the vessels. They also pass
through the walls of the capillaries, and are found normally in the
various tissues of the body; in pathological conditions they migrate
in vast numbers. Each pale corpuscle has one or more nuclei, which
are surrounded by a mass of protoplasm unconfined by a cell-wall (g).
By certain methods of staining, the nuclei are demonstrable.
32
In size the white corpuscles are somewhat larger than the red, aver-
aging about go of an inch in diameter, and they always retain about
the same measurement in different species of animals. They bear to
the red the proportion of 1 to 500.
Besides these red and white cells or corpuscles there may also be seen
in the blood free granules and fine filaments (Fig. 271). Some of the
granules are round (B), others angular. In
some instances the angular granules are con-
nected with the fine filaments (A), as if they
formed the nucleus from which the filaments
radiate.
FIG. 271.

A
The blood-corpuscles and granules can be
washed out from a small quantity of blood
that has been allowed to clot upon a slide,
and there will be nothing left but an opaque,
stringy substance. This white stringy sub- B
stance is fibrin, which may now be stained
and examined.

The physiology of the blood is perhaps Fibrin-filaments and Blood-tablets:
less understood than any other part of the
animal organism. Many theories have been
advanced as to its origin. It seems most
rational to believe that one which teaches
that the lymph-corpuscles become altered by
contact with pre-existing white blood-cor-
puscles, and that these in turn are changed into red corpuscles, which in
time disintegrate, their pigment being taken up by their successors.
A, network of fibrin, shown after
washing away the corpuscles from
a preparation of blood that has
been allowed to clot; many of
the filaments radiate from small
clumps of blood-tablets. B (from
Osler), blood-corpuscles and ele-
mentary particles or blood-tablets
within a small vein.
Prudden, speaking of the origin of blood-cells, says: "Direct observa-
tion has shown that, in some animals at least, the white blood-cells can
multiply by division. Whether the cells which supply the place of
those which seem to be used up in the process of growth and reparation
are produced in this way, and, if so, whether the division occurs in the
blood- or lymph-vessels, or in the cell-spaces of the connective tissue,
or in certain special organs, or whether they are produced in a manner
entirely unknown to us, these are questions not only of theoretical but
of practical interest; but in spite of much research and the accumula-
534
DENTAL EMBRYOLOGY AND HISTOLOGY.
tion of many observations bearing on the matter, we are still unable to
give them a definite answer. Still more obscure, if possible, is the
origin of the red blood-cells. Although in the adult man they seem to
possess no nucleus, yet in embryonic life they certainly are furnished with
that structure; we find nucleated red blood-cells. Now, it has been
recently shown that in certain parts of the body in adult life cells occur
which in many respects resemble the nucleated red blood-cells of the
embryo; such cells are found, for example, in the spleen, in the red
marrow of bones, etc. The most plausible theory in regard to the
matter is that in certain parts of the body-spleen, marrow, lymph-
glands, and liver-white blood-cells are produced, a part of which are
changed into the red blood-cells. The so-called nucleated red blood-
cells are supposed to be intermediate forms. It must be remembered,
however, that this view is not established as yet, and many observers.
do not ascribe to the so-called nucleated red blood-cells the significance
upon which the advocates of this theory insist.”
K
Klein says that "at an early stage of embryonic life, when blood
makes its appearance it is a colorless fluid, containing only white cor-
puscles (each with a nucleus), which are derived from certain cells of
the mesoblast. These white corpuscles change into red ones, which
become flattened, and their protoplasm becomes homogeneous and of a
yellowish color. All through embryonic life new white corpuscles are
transformed into red ones. In the embryos of man and mammals these
red corpuscles retain their nuclei for some time, but ultimately lose them.
New nucleated red blood-corpuscles are, however, formed by division of
old red corpuscles. Such division has been observed even in the adult
blood of certain lower vertebrates (Peremeschko), as well as in the red
marrow of mammals (Bizzozero and Torre). An important source for
the new formation of red corpuscles in the embryo and adult is the red
marrow of bones (Neumann, Bizzozero, Rindfleisch), in which numerous
nucleated protoplasmic cells (marrow-cells) are converted into nucleated
red blood-corpuscles. The protoplasm of the corpuscles becomes homo-
geneous and tinged with yellow, the nucleus being ultimately lost. The
spleen is also assumed to be a place for the formation of red blood-cor-
puscles.
HO
W
"Again, it is assumed that ordinary white blood-corpuscles are trans-
formed into red ones, but of this there is no conclusive evidence. In
all these instances the protoplasm becomes homogeneous and filled with
hæmoglobin, while the cell grows flattened, discoid, and the nucleus in
the end disappears. Schäffer described intracellular (endogenous) forma-
tion of red blood-corpuscles at first as small hæmoglobin particles, but
soon growing into red blood-corpuscles in certain cells of the subcu-
taneous tissue of young animals. Malassez describes the red blood-
corpuscles originating by a process of continued budding from the
marrow-cells. The white corpuscles appear to be derived from the
lymphatic organs, whence they are carried by the lymph into the cir-
culating blood."
AND
det
Notwithstanding these differences of opinion regarding the origin of
blood-cells, there is almost universal agreement as to the function per-
formed by the blood; and it is to be hoped that with improved means
EPITHELIAL CELLS.
535
for observation we shall soon be able to solve the enigma of its deriva-
tion. That there must of necessity be some means for renewing aged
cells or supplying lost ones is admitted by all, but as to the special
mode of their origin there seems to be considerable doubt. The white
blood-corpuscles are probably the main source of supply for the regen-
eration of lost tissues, osteoblasts, and the other members of the connec-
tive-tissue group. This part of the subject will be considered in detail
later on.
G
EPITHELIAL CELLS.
A very delicate membrane forms the outer covering of the derma or
true skin of animals, and enters also into the structure of glandular
organs; to it the name epithelium is given.
The microscope has shown this tissue to be an aggregation of epithelial
cells, differing in different situations in form and function.
Epithelial cells are derived from both epiblast and hypoblast. We
will dismiss the consideration of those which have their origin in the
hypoblast, and confine ourselves to the epithelium of the mucous mem-
brane of the mouth, premising that it is derived from the same source
as the skin. It is certainly analogous in form, being only slightly
modified by constant immersion in the fluids of the mouth, which
does not permit the oldest or
outer layer to assume the cor-
neous nature found in the most
superficial layer of the skin.
FIG. 272.
The epithelium of the mouth
belongs to the stratified epithelial
group: it may be considered as
transitional epithelium, and is
composed of several layers of
cells which are constantly un-
dergoing the process of desqua-
mation. These layers of cells
are held together by an inter-
cellular cement-substance, which
exists in small quantities.
:
We divide the layers into
three kinds the infant, older,
and oldest. The oldest layer
can readily be studied by exam-
ining microscopically the saliva
or scrapings from the tongue.
Under examination this layer
very plainly appears to be made
up of flattened discs containing
nuclei. The cells of the corne-
ous layer of the skin, however,
as a rule, do not contain nuclei. The cells vary so much in size that no
definite measurement can be given.
O
of

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0 0
י.
C
0
gon
0
0
a
00.0
Q
Epithelial Cells in the Oral Cavity of Man: a, large;
b, middle-sized; c, the same with two nuclei (high
power).
536
DENTAL EMBRYOLOGY AND HISTOLOGY.
alie
FIG. 273.
Columnar Ciliated Epi-
thelium Cells.
a
D
g
In some of the cold-blooded animals the palate
is covered with ciliated cells. These are for the
most part spheroidal in form, and do not differ
greatly from the cells above described. The most
remarkable circumstance in connection with them
is the movements of their cilia, which arise from
the broad side of the cell. These hair-like append-
ages are supposed to be prolongations of the cell-
protoplasm. They can be seen in the frog, and ex-
amined while yet in motion by scraping the surface
Th

T
0
Z
FIG. 274.

石
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X
This
m
d
X
Z
PMAN
2013
ישט
20
L
N
RADARE
SAKUS
Epithelium-cells of Salamander Larva in Different Phases of Division: a, normal cell, by compari-
son with which the following changes may be noted: I. The network of filaments of the resting
nucleus becomes formed into a sort of skein, formed apparently of one long convoluted filament;
the nuclear membrane and the nucleoli disappear or are merged into the skein (b, c, d). II. The
skein becomes arranged in the form of a roselle, the filaments looping in and out, to and from the
centre (e). III. The outer loops of the rosette separate so that the filament breaks into a num-
ber of V-shaped fibres arranged like a star (aster, f, g, h). IV. The V-shaped fibres separate into
two groups, the ends of which are for a time interlocked (i,j, k). V. The two groups pass to the
opposite poles of the now elongated nucleus and form a star-shaped figure (1) at each pole (dyaster).
Each of the stars represents a daughter-nucleus. VI. Each star of the dyaster goes through the
same changes as the original nucleus, but in the reverse order-viz. rosette (m), skein (n), and net-
work (o, p, q)-passing finally into the condition of a typal resting nucleus. The protoplasm of
the cell divides soon after the formation of the dyaster (m). Sometimes fine lines may be seen in
the protoplasm, during the process of division, radiating from the poles cf the nucleus, and others
uniting the two daughter-nuclei.
P
EPITHELIAL CELLS.
537
A
Two Flattened and Branched Connective-tissue Corpuscles from the subcutaneous areolar tissue.
Opposite la secondary lamella, projecting toward the observer, is seen in optical section as a
dark line.
FIG. 276.
dt
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FIG. 275.
2



FIG. 277.
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200°
From a Preparation of the Omentum of Guinea-pig: a, artery; v, vein; c, young capillary blood-
vessel; d, fat-cells formed by infiltration of ordinary connective cells with fat-globules.
FIG. 278.
ZA V
Bundles of the White Fibres of Areolar Tissue, partly
unravelled.
P
A
C
d
α
V


A, Elastic Fibres of Areolar
Tissue, from the subcutane-
ous tissue of the rabbit.
of the mucous membrane and transferring the substance thus obtained
to a slide, adding tepid water.
538
DENTAL EMBRYOLOGY AND HISTOLOGY.
Ciliated cells are also found in the nasal passages of man, an illustra-
tion of which may be seen in Fig. 273.
The middle or older layer of cells of the buccal epithelia are more or
less polyhedral in shape, and have an imbricated border: they are some-
times called "prickle cells," and generally extend beyond the oral cavity
into the pharynx.
The deepest or infant layer of the epithelium of the mouth is com-
posed of spheroidal or slightly cylindrical cells placed vertically upon
the dividing-line between the epithelium and the dermal layers. It is
in this layer of the rete Malpighii that cell-multiplication occurs; the
FIG. 279.

Articular Cartilage from Head of Metatarsal Bone of Man (osmic-acid preparation); the cell-bodies
entirely fill the spaces in the matrix (310 diameters): a, group of two cells; b, group of four cells;
h, protoplasm of cell, with g, fatty granules; n, nucleus.
changes whereby the cells undergo division appear first in the nucleus
(see Fig. 274, after Fleming, from Schaefer's Histology), afterward
extending to the cell-body in adult tissues.
The method of cell-growth in embryonal tissues will be considered
later on, in the section on the development of the mucous membrane of
the mouth.
Connective-tissue cells of the dermal layer of the mouth are of two
kinds, fixed and wandering cells. The first are fibrillated, and have a
definite relationship to the basement-substance, although varying in
form and number in different positions. The second are spheroidal,
and have been considered in our study of the white blood-corpuscles.
The fixed cells may have one or more processes, and when infiltrated
with fat, constitute fat-tissue.
EMBRYOLOGY.
539
The intercellular substance is broken up into fibres, both yellow and
white. The yellow fibres are elastic (Fig. 278), and are more or less
abundant in areolar tissue. The white fibres form the interlacing net-
work which binds the tissues together throughout the body. They are
joined in bundles, as may be seen by referring to Fig. 277.
There yet remains to be considered hyaline cartilage, which belongs
to the connective-tissue group. In this tissue spheroidal flattened or
angular cells, containing one or more nuclei, are seen lying in a homo-
geneous basement-substance (see Fig. 279), which is said to yield chon-
drin upon being boiled. The cells are sometimes finely, at other times
coarsely, granular. Both the capsule which surrounds the cell and the
hyaline intercellular substance possess higher refractive power than does
the cell itself.
Having thus brought our brief examination of a few of the more
important characteristics of cell-action and morphology to a close, it
only remains to express the hope that it will stimulate the student to
a better and more careful survey of the whole subject. The import-
ance of such a survey cannot be too strongly urged upon his attention,
for without definite knowledge of cellular structure it is impossible to
prosecute histological inquiries with any degree of success.
We are now better able to enter upon the subject of Embryology, a
subject in regard to which what we know at present is so little in com-
parison to what we do not know that there remains an illimitable field
for our inquiries and discoveries.
EMBRYOLOGY.
Down to our own century, though many important truths bearing
upon embryology were known to anatomists and physiologists, nothing
could have been farther from their conception than the fact now uni-
versally admitted that all animals, without exception, arise from eggs.
Aristotle and his followers recognized three modes of generation-
viz. oviparous, viviparous, and spontaneous generation. By the prog-
ress of investigation the last mode of generation was shown to be a
thing unknown in Nature, and in 1651, Dr. William Harvey announced
that there is no essential difference in the mode of generation between
oviparous and viviparous animals, but that "all animals whatsoever,
even the viviparous, and man himself not excepted, are produced
from ova." A little later Linnæus expressed this great truth in the
sentence so often quoted, "Omne vivum ex ovo;" but neither he nor
Harvey appreciated the full significance of these statements, for the exist-
ence of the mammalian egg was not then dreamed of. Since then the
discoveries of Von Baer, Négrier, Pouchet, and others have shown not
only that "the egg is common to all living beings without exception,
from the lowest radiate to the highest vertebrate, but that its structure
is at first identical in all, composed of the same primitive elements and
undergoing exactly the same process of growth up to the time when it
assumes the special character peculiar to its kind;" and the only real
difference between oviparous and viviparous animals is that in the Ovip-
ara the fecundated egg is discharged from the body of the female and
3
540
DENTAL EMBRYOLOGY AND HISTOLOGY.
deposited in some suitable receptacle, in which it is afterward hatched,
while in the Vivipara it is retained in the body of the female and there
nourished till it develops into a perfect organism.
In common parlance, we understand by an egg a spheroidal body
composed of a mass of yolk, surrounded by what is known as the
white of the egg, and an outer covering or shell. But to the embryolo-
gist the envelopes of the egg are mere accessories, while the true egg-
or, as it is called, the ovarian egg-with which the life of every organ-
ism begins, is a minute globule of protoplasm. The undeveloped ova-
rian egg immediately after its fertilization is uniform in appearance
throughout the animal kingdom, the human ovum at this stage corre-
sponding in structure to those which stand at the very foot of the zoo-
logical scale.
P
The ovarian egg is at first a mere speck of living protoplasm, but
through the processes of nutrition development proceeds, and presently
there appears a bright, transparent spot on the upper side of the egg
near the wall or outer membrane-the nucleus, as it is called. When
this albuminous spot becomes a little larger there arises in its centre a
minute speck of matter slightly more opaque than the surrounding
matter: this is called the germinal spot. At this stage of its existence,
when the egg consists of a protoplasmic body containing in its interior
a nucleus which in turn envelops a nucleolus, its resemblance to a cell
is unmistakable; and, in fact, an egg when forming is a perfect cell-
structure. But while closely resembling the cell in structure there is,
nevertheless, in this ovarian mass of protoplasm a wonderful power
which separates it from the cell by differences too great to be bridged
over-an inherent force by which its destiny as a distinct individual
is assured. Agassiz has described this difference better than most
embryologists:
"While we recognize the identity of cell-structure and egg-structure
at this point in the history of the egg, we must not forget the great dis-
tinction between them—namely, that while the cells remain component
parts of the whole body, the egg separates itself and assumes a distinct
individual existence. Even now, while still microscopically small, its
individuality begins; other substances collect around it, are absorbed.
into it, nourish it, serve it. Every being is a centre about which many
other things cluster and converge, and which has the power to assimi-
late to itself the necessary elements of its life. Every egg is already
such a centre, differing from the cells around it but by the principle of
life in which its individuality consists, which is to make it a new being,
instead of a fellow-cell with those that build up the body of the parent
animal and remain component parts of it. This intangible something
is the subtle element that eludes our closest analysis; it is the germ of
the immaterial principle according to which the new being is to develop.
The physical germ we see; the spiritual germ we cannot see, though
we may trace its action on the material elements through which it is
expressed."
At this period of its growth the microscopic cell is as truly an inde-
pendent organism as it ever becomes; it is itself the young animal, and
the action of the vital principle is manifest in it from the earliest moment
EMBRYOLOGY.
541
of its career, guiding and directing a series of changes which result at
last in the complete development of an individual perfect in its adapta-
tions and wonderful in its mechanism. The physicist and chemist are
utterly unable to explain the energy and power which throb with
unceasing pulse in every atom of living matter which enters into the
formation of the several parts that make up the complete organism, or
tell us in what way the multitudes of cells which exist in connection
with its various tissues live, grow, and form, so that at length are pro-
duced the many textures of the living thing, each perfectly fulfilling the
object of its formation.
""
In all our study of the phenomena of embryonic development from
the tiny cell we shall see how this vital power, "unlike any physical
agency yet discovered, manifests a remarkable capacity, so to say, of
prevision. The changes effected by living matter at one time are carried
out, as it were, in anticipation of future change, as if the conception of
what was to be had been acted upon even while the early changes were
proceeding. We shall see how this vital force, though it imprints
upon the protoplasmic germ no trace by which it can be distinguished
from a fellow-germ, unfailingly clears the way for its onward devel-
opment according to prearranged forms, controlling and directing its
growth into the perfect structure having the capacities and powers of
the parent germ. It is impossible to express in any force-terms the
inherent principle by which one germ develops into an oak, and
another into the bird which seeks shelter amid its foliage, or explain
how typal forms and peculiarities are handed down from generation to
generation, so that each plant and animal reproduces its own kind.
Consider for a moment the immense number, the perfect separation, of
the different kinds of animals and plants, their power of life and repro-
duction, and their wonderful fruitfulness.
Consider first their number. In the animal kingdom the number of
living species which have been satisfactorily made out and described is
more than one hundred thousand, and botanists reckon about as many
different kinds of plants. Not one of this great multitude of plants
and animals has ever produced a structure unlike its kind. No
seed of wheat has ever yielded barley, or seed of alder grown up into
an oak. The egg of the hen has never been made to produce any
other animal than the chick, and the egg of the frog produces only the
frog. It is true that the young frog or tadpole when first hatched
from the egg is unlike its parent in external appearance and habits of
life. But in this and other instances the process of development goes
on after the young embryo has left the egg, till at last the perfect like-
ness to the parent is established. Here, again, we see how the vital
power transcends physical forces, for it controls the successive forma-
tion and disappearance of different organs adapted to the different
modes of infant life, but which would be useless when the adult state
is reached. For my own part, the more I look into the phenomena of
embryonic development the more am I convinced that they determine
"the unity of the authorship of a wonderfully complicated design, exe-
1 It is true that hybrids have been produced from the mixture of two species, but they
have never been known to perpetuate themselves.
542
DENTAL EMBRYOLOGY AND HISTOLOGY.
cuted on a groundwork broad as time and whose scope and bearing are
deep as eternity." In them we find, "not a material connection by
which blind laws of matter have evolved the whole creation out of a
single germ, but the clue to that intellectual conception which spans
the whole series of the geological ages and is perfectly consistent in all
its parts.
""
GENERAL ACCOUNT OF EMBRYONIC DEVELOPMENT.
In our investigations into the first stages of embryology we are of
necessity confined to the lower animals. It is not possible to secure
well-preserved human embryos in sufficient numbers to enable us to
formulate even a theory of development, except as we arrive at our
conclusions by reason of such knowledge of the processes of develop-
ment as we are able to glean from the field of comparative embryology.
I have found the rabbit and pig more easily obtainable than other ani-
mals, and have therefore devoted most of my time to the study of their
embryos.
The human embryos of which I have had the fortune to become pos-
sessed have been two months or more old; a great many have not been
in a good state of preservation; consequently, I have been obliged to
seek other sources for my supply of microscopical material. Judging
from the paucity of illustrations drawn from human embryos under
two months, I conclude that other observers have found the same diffi-
culty. Very valuable specimens are being constantly lost through neg-
lect or lack of knowledge as to the methods necessary to preserve them.
Noticeable as this is regarding embryos, it is much more so in the case
of the ova.
No studies--at least so far as I am conversant with the
literature upon the subject-have been made upon the segmenting
human ova or the first stages in the development of the blastoderm.
There is a vast field yet open for study in this direction. The exact
nature of impregnation has not been definitely settled, and even the
processes of segmentation have not been sufficiently studied.
The most convenient and easily-obtained mammalian eggs are from
the rabbit. The variations between them and human ova are no doubt
considerable, but by reason of the impossibility of obtaining human.ova,
and the difficulty attending the study of those more closely allied to
them, we are obliged to accept those of the rabbit as a compromise.
Many observers have noted the changes occurring in the egg of the
fowl in its early stages; these very closely resemble those which occur
in the mammalian egg. The former eggs are oviparous that is, the
ova are produced and developed by incubation outside the body;
while the latter are viviparous, brought forth alive, the period of
incubation being within the body.
W
Budge
Mammalian eggs come from two ovaries, which are said to produce
ova alternately. In the development of the ovaries the cylindrical epi-
thelium which covers their surface is by a process of involution enclosed
in the connective-tissue substance of the ovary at many points in the
form of solid buds or cords. These soon become detached from the
surface epithelium, and set up a rapid process of cell-proliferation, in a
GENERAL ACCOUNT OF EMBRYONIC DEVELOPMENT.
543
short time breaking up into small oval or irregularly-formed masses of
cuboidal or polyhedral-shaped cells. These are surrounded by the con-
nective tissue of the ovary, which by condensation forms one of the coats
of the Graafian follicles, as the points in which the ova are developed are
called.
Rapid differentiation now occurs inside the connective-tissue envelope,
until the ovum which occupies the central portion is surrounded by
several distinct layers of cells. As development progresses the Graafian
follicles approach the surface and rupture at regular periods. The ripe
ovum, when set free by the rupture of the mature Graafian follicle, is
taken up by the fimbricated ends of the Fallopian tube. Impregnation
generally occurs in the upper third of the Fallopian tube: unimpreg-
nated eggs soon perish.
Before proceeding to a study of the more complicated development
of the embryo of the rabbit, human, and pig, we will consider that of the
tadpole. The ovum-by a process of segmentation-consists of a vast
number of cells which form a double membrane within the vitelline mem-
brane. This is called the blastoderm. In the fresh-laid egg the blasto-
derm consists of two layers of cells, an internal and an external. Shortly
after incubation in the region of the primitive trace there appears a thick-
ening of the blastoderm, which results in the formation of a middle layer.
The blastoderm now consists of three layers: the external, or epiblast;
the internal, or hypoblast; and the middle, or mesoblast.
If at this stage of development we examine a longitudinal section of
the egg of a frog, the blastoderm will be seen in profile (see Fig. 280).
The anterior portion (2), which occupies the position of the head, is
thicker than the posterior part, or tail (3). As development progresses
the ovum more nearly approximates the shape of the tadpole, and the tail
assumes the more prominent part (Figs. 281, 282, and 283). Concomitant
with the changes seen in profile, other changes are occurring. These
can be demonstrated by making cross-sections of the body (Fig. 284).
Arising at A, A are two processes which extend longitudinally the
entire length of the tadpole, occupying a dorsal position. Between
these two plates or ridges (B) a groove is seen, which, as the plates
develop, naturally deepens (Fig. 285, B). The plates grow rapidly,
and, folding together, form a canal in which is developed the spinal
cord and nerve-centres (Fig. 286, B). Around this canal are developed
the vertebræ, which appear first as cartilaginous matrices, but which
afterward become ossified (c, c).
About the time the dorsal plates are seen the abdominal plates arise
from the under side of the blastoderm, and, growing rapidly, com-
pletely enclose the hypoblastic layer within the abdominal cavity (Fig.
287). Within the latter cavity the remains of the vitellus are enclosed.
The hypoblast gives rise to the lining membrane of the alimentary
canal. At first this is a closed sac or pouch, without either anterior
or posterior outlet. As development progresses, an involution of the
epiblastic layer, which finally unites with the hypoblastic layer of the
intestinal canal, gives rise to the mouth at the anterior part, while a
similar indipping at the posterior end forms the rectum (Fig. 283).
Having thus briefly considered the stages of development in the tad-
•
544
DENTAL EMBRYOLOGY AND HISTOLOGY.
2.
4-
FIG. 280.
Diagram of Frog's Egg, in an Early Stage
of Development, longitudinal section: 1,
thickened portion of external blastodermic
layer; 2, anterior extremity of the embryo;
3, posterior extremity; 4, internal blasto-
dermic layer; 5, cavity of vitellus.
M
FIG. 281.
Egg of Frog in Process of Development.
·3
FIG. 282.
Egg of Frog, farther advanced.
FIG. 283.
Tadpole, fully developed.
A
FIG. 284.


Cross-section of Frog's Egg,
showing blastoderm same age
as Fig. 280: A, A, lateral folds
situated upon either side of
groove B.
FIG. 285.
A

B
C
Cross-section of Frog's Egg, same
stage of development as seen
in Fig. 281: A, A, lateral pro-
cesses; B, neural groove.
FIG. 286.
B
A


Cross-section of Tadpole, showing
same stage of development as
seen in Fig. 282: B, neural
canal; c, c, lateral processes of
spinal column.
FIG. 287.
B.
C



Cross-section of Fully-developed
Tadpole: letters same as seen
in Fig. 286.
GENERAL ACCOUNT OF EMBRYONIC DEVELOPMENT.
545
pole, we are better prepared to take up the study of the more compli-
cated processes as seen in the evolution of the ovum of the rabbit as it
develops into the embryo.
After leaving the ovaries the ovum of the rabbit passes slowly down
FIG. 288.
A
ер
Op A
www
wang
hy
Three Stages in the Segmentation of the Rabbit's Ovum (from Quain's Anatomy, after Bischoff):
A shows the division of the ovum into two nearly equal masses; B, the formation of four spheres
by division of the two of the preceding stage; C, the stage with eight segmentation-spheres.
FIG. 289.
ер
B
B




10 @
Optical Section of Rabbit's Ovum at the Close of Segmentation (from Balfour, after Ed. van Beneden):
ep, epiblast; hy, primitive hypoblast; bp, spot where the epiblast has not yet grown over the
hypoblast.
the Fallopian tube, where it meets the spermatozoa, impregnation taking
place in the upper third of that tube, and the ovum reaching the uterus
VOL. I.-35
546
DENTAL EMBRYOLOGY AND HISTOLOGY.
about the fourth day. In their course through the Fallopian tube
nearly all ova become coated with albumen, this covering attaining its
greatest thickness in the egg of the fowl, where it is commonly known
as the white of the egg.
Segmentation in the ovum of the rabbit occurs throughout the whole
structure, but in the egg of the fowl it is less complete, being confined
to one point on the surface. In the mammalian egg the process of seg-
mentation is in all probability by segmentation of the nucleus first,
division following in the cell-body, as in the division of cells in gen-
eral. (See Fig. 274, p. 536.)
The ovum of the rabbit first divides into two parts, these again into
four, then into eight, and so on until the ovum has become infinitely
subdivided into hundreds of minute cells. These myriad cells are
in fact the component parts of the young rabbit that is to be. They
will undergo certain modifications to become muscle-cells, bone-cells,
blood-cells, and so on, adapting themselves to the very different tissues
and organs they are to build up. All these cells have descended from
a common protoplasmic mass, yet they have as much "their definite
and appointed share in the formation of the body now as at any later
stage of its existence."

After segmentation the larger cells arrange themselves upon the per-
iphery, enclosing the smaller ones in the central portion. The outer
layer of cells is called the epiblast, and the inner the hypoblast.
The ovum has by this time reached the uterus, and consists of a
spherical-shaped vesicle (Figs. 290, 291). Development now proceeds
FIG. 290.
br
Ty
Zp
ep
Want

Rabbit's Ovum between Seventy and Ninety Hours after Impregnation: br, cavity of blastodermic
vessels; ep, epiblast; hy, primitive hypoblast; zp, zona pellucida.
very rapidly. The hypoblastic layer of cells, which occupied only a
small spot upon the inner side of the epiblastic layer, gradually spreads
in such a manner as to form an inner layer to the epiblast, which in
turn encloses the former as a blind sac or pouch, within which is found
the remains of the vitellus.
V

GENERAL ACCOUNT OF EMBRYONIC DEVELOPMENT. 547
Outside these two layers the zona pellucida forms another coating.
It, however, does not play any essential part in the further develop-
FIG. 291.
Diagrammatic views of the Blastodermic Vesicle of a Rabbit on the Seventh Day (from Balfour, after
Ed. v. Beneden): In the left-hand figure the vesicle is seen from above; in the right-hand figure,
from the side. The white patch (ag) is the germinal area; and the slight constriction (ge) marks
the limit to which the hypoblast has extended.
"y
ment of the embryo, at least in so far as we are to consider the subject;
and henceforth we will not mention it.
This embryonic area is the result of the thickening of the hypoblast
at the point where the development of the primitive streak will pres-
FIG. 292.
ag-
0
Embryonic area of a Rabbit's Ovum on the Seventh Day (from Kölliker): The shaded part (ag) is the
embryonic area; 00 is the region of the blastodermic vesicle immediately surrounding the embry-
onic area, into which the mesoblast has already spread, and in which blood-vessels will shortly
appear; pr, primitive streak; rf, medullary groove.
548
DENTAL EMBRYOLOGY AND HISTOLOGY.
ently appear. Previous to the formation of the latter, however, there
is formed a third layer, which locates itself between those already
developed, and is known as the mesoblast. It is mainly produced by
the proliferation of the cells of the epiblast (Fig. 292).
The cellular activity of the epiblast proceeds rapidly, and results in
the formation of two medullary plates which arise in parallel rows,
between which lie the medullary groove or primitive streak. At the
anterior portion, in the very first differentiation of the groove, a dark
spot is seen, known as the "nodal point of Hensen," which subse-
quently marks the front part of the groove. Its signification is not
exactly known.
The medullary plates develop rapidly, expanding at their anterior
portion into a spatula-shaped crescent (Fig. 293). This gives rise to
FIG. 293.
ao
ap
str
pz
rf
UP
vd
ph.
1
1'0
artu
afr
ap-
wh
ав
af
mh
hh
-pr
HOME


štuka
Rabbit Embryos of about the Ninth Day, seen from the dorsal side (from Kölliker): ab, optic vesicle;
af, amnion; ap, area pellucida; h and he, heart; h', medullary plate in region of future fore-brain;
, medullary plate in region of future mid-brain; hh and "", hind-brain; mh, mid-brain; ph,
pericardial section of body-cavity; pz, lateral zone; pr, primitive streak; rf, medullary groove;
str, vertebral zone; m, protovertebræ; vh, fore-brain, vo, vitelline vein.
the cephalic end of the embryo. The first indication of the vertebral
column is seen about the eighth day, in the formation of the first pair of
somites. They are located in the region of the neck, and mark the line
of union of head and trunk. The latter gradually elongates by the
addition of other pairs of somites, the growth in length being from the
first-formed somites caudal-ward. The medullary groove deepens as
GENERAL ACCOUNT OF EMBRYONIC DEVELOPMENT.
549
the embryo grows older; the medullary folds become higher, and finally
unite over the medullary groove, which they have made by their growth.
The union of the sides begins at the anterior part. The canal thus
formed is called the neural canal, and locates the spinal cord. The
caudal end grows rapidly, pair after pair of somites being added, until
at the twelfth day the embryo presents the appearance seen in Fig. 294.
FIG. 294.
um
ht
ce
th
mb

ор
mx
ivy
md
hy
S!
Rabbit Embryo of about the Twelfth Day (from Balfour, after Weldon): ce, cerebral hemisphere; f,
fore limb;, hind limb; hy, hyoid arch; in, v, fourth ventricle; mb, mid-brain; ma, maxillary
arch; md, mandibular arch; op, eye; th, thalamencephalou; um, umbilical stalk.
The embryo rabbit of twelve days has reached about the stage of
the human embryo of four weeks and the pig 1 cm. in length.
In describing the rabbit embryo of twelve days Foster and Balfour
say: "The latter stages in the development proceed, in the main, in the
same manner as in the bird. The cranial flexure soon becomes very
marked, the mid-brain forming the end of the long axis of the embryo
(Fig. 294, mb). The sense-organs have the usual development. Under the
fore-brain appears an epiblastic involution giving rise both to the mouth
and to the pituitary body. Behind the mouth are three well-marked
pairs of visceral arches. The first of these is the mandibular arch
(Fig. 294, md), which meets its fellows in the middle line and forms
the posterior boundary of the mouth. It sends forward on each side
a superior maxillary process (mx), which partially forms the anterior
margin of the mouth.
As the embryo increases in length, the convexity of the spine be-
comes greater, and the head and tail ends approximate each other. The
chin rests hard upon the breast, and the caudal convexity comes in con-
tact with the forehead. The limbs are seen as buds springing off from
the sides of the body (fl and hl). The umbilical stalk (um) arises from
the concave surface of the embryo and extends posteriorly.
As we have before said, a sufficient number of human embryos under
four weeks of age have not been obtained to establish any definite
description of development prior to that age. The earliest authenticated
observations were made by Allen Thomson (see Fig. 297, human embryo
550
DENTAL EMBRYOLOGY AND HISTOLOGY.
of four weeks, somewhat enlarged). The mandibular arch (c) and the
maxillary arch (d) are quite plainly shown.
The proportion of the cephalic as compared with the caudal end of
the human embryo is not as great as that seen in the rabbit. Our next
illustrations (Fig. 295) show the human embryo in various stages of
FIG. 295.

A
·α
2
R
с


E
Figures illustrating the Formation of the Face in the Human Embryo (from Quain's Anatomy): A,
head of an embryo of about four weeks (after Allen Thomson): 1, mandibular arch; a, ear. B,
head of an embryo of about six weeks (after Ecker): 1, mandibular arch; 1', hyomandibular
cleft. C head of an embryo of about nine weeks (after Ecker).
development: A, four weeks, corresponding to pig embryo 1 centimeter
in length; B, six weeks, shows the same progress in development as
seen in foetal pigs 1 centimeters; while the last, C, equals in length a
pig embryo 2 centimeters.
2
Having thus shown the comparative ages and stages of development
in foetal life, we will confine ourselves in our further study largely to
pig embryos, the supply of which in a good state of preservation is
unlimited.
Development of the Jaws and Buccal Cavity.-The first indication of
the formation of the oral cavity is seen very early in the life-history of
the embryo. Considerable difference of opinion is recorded regarding
the exact time of its formation in the human embryo. In Fig. 296,
representing the twenty-fifth or twenty-eighth day of foetal life, the wide
cavity seen at (6) represents the posterior portion of the buccal cavity.
The growth of the maxillary arches closes this cavity anteriorly. Its
floor is formed by the inferior maxillary arches (4). These arise from
the first pharyngeal arches. The superior maxilla arises from three
separate points. On either side of the face a process springs off from
the first pharyngeal arch (one side of which is shown at d in Fig. 297).
The processes pass downward and forward, and unite with the sides of
the nasal process.
From the frontal prominence (1) the third process, the incisive, grows
downward, and fills in the space between the ends of the two preceding
processes. By the union of these three processes the superior maxilla is
completed. Failure of union between the middle and two lateral pro-
cesses gives rise to the deformity known as hare-lip. This may be
simple, and occur on either side at the juncture of the intermaxillary
bones with the lateral processes, or in the median line at the point of
GENERAL ACCOUNT OF EMBRYONIC DEVELOPMENT.
551
union of the two intermaxillary bones themselves; or it may be double,
by reason of the non-union on both sides.
FIG. 296.
Development of the Palate.-The plates which form the hard palate
arise from the lateral processes of the superior maxilla and grow toward
each other, uniting in the median
line. Previous to their develop-
ment and union the buccal cavity
and nose are as one cavity. The
separation is usually completed by
the end of the second month.

10
5
4
7
"
8
O
5
4-
Face of an Embryo of Twenty-five to Twenty-
eight Days (magnified fifteen times): 1, frontal
prominence; 2, 3, right and left olfactory fosse;
4, inferior maxillary tubercles, united in the
middle line; 5, superior maxillary tubercles;
6, mouth or fauces: 7, second pharyngeal arch;
8, third; 9, fourth; 10, primitive ocular ves-
icle; 11, primitive auditory vesicle.
When for any reason union does
not occur between the two plates,
there results what is known as cleft
palate. This is very apt to accom-
FIG. 297.

Embryo removed from the Ovum, and magni-
fied: a, amnion; b, yolk-sac; e, mandibular
arch; d, maxillary arch; e, hyoidean arch
behind this are the first and second branchial
arches; f, rudiment of fore limb; g, auditory
vesicle; h, eye; i, heart (X 5).
pany hare-lip, the same causes which give rise to the latter operating to
prevent the normal development of the palate bones, which, as we have
seen; follow the development of the intermaxillary bones.
Turning our attention now to the inferior maxilla, we see, by refer-
ring to Fig. 294, that the inferior or mandibular arch also arises from
the first pharyngeal arch (md). In the human embryo these processes
are said to have been seen as early as the fifteenth to the eighteenth day
of foetal life. They arise in pairs, as do the lateral processes of the
superior maxilla, and grow very rapidly, union occurring in the median
line at about the twenty-eighth day. (See Fig. 296.)
The maxillæ arise as solid buds from the mesoblastic layer, and are
covered externally by the epiblast. The maxillary bones belong to the
class of splint bones, and are not preformed in cartilage, but ossify by
what I term interstitial ossification."
1
""
With the development of the maxillæ the anterior boundaries of the
oral cavity are formed. Posteriorly, there is seen a "foetal septum
between the forming cavity and the upper end of the intestinal canal
as the buccal cavity and the upper end of the intestinal canal near each
other the septum diminishes in width, and finally disappears entirely.
;
1 ¹ My own classification. See section on Calcification.
552
DENTAL EMBRYOLOGY AND HISTOLOGY.
In the viviparous family the perforation of the fœtal septum occurs,
in most cases, before birth; when, however, it does not occur, there
arises a pathological condition known as impervious oesophagus.
Of necessity, the lining membrane of the mouth is formed from the
involution of the epiblast. The point of union between the epiblastic
and hypoblastic layers is located at variable distances from the upper
end of the oesophagus, even to the union of the latter with the cardiac
end of the stomach.
FIG. 298.
Meckel's Cartilage. The central portion of the inferior maxilla, very
soon after the union of the two lateral processes, becomes differentiated
into a cartilaginous cord which serves to strengthen the jaw. To this
band or cord the name of the
discoverer, Meckel, has been
given. It is formed in two
parts arising from the mallei
of either side, which unite, as
do the lateral processes of the
jaw, at the symphysis mentis.
The cartilaginous matrices of
the bones of the ear become
directly ossified, as does the
Meckelian cartilage of the jaw.
The former undergo ossification
about the third month.
D
C
Meckel's Cartilage from Human Embryo of Forty to
Forty-two days, and before the appearance of the
maxillary bone (magnified ten diameters): A, en-
largement of cartilage near its union with the neck
of malleus; D, union with cartilage of opposite side;
M, head of malleus; N, handle of malleus; E, carti-
lage of the incus; í, cartilage of the stapes; O, car-
tilage of the os lenticulare. The outlines of a jaw
have been added to the figure to show the relative
position occupied by the cartilage in the jaw. (After
Magitot and Robin, Dean's translation.)
tg.
Regarding Meckel's cartilage
very little has been written, and
I deem the reason to lie in the
fact that very little study has
been given to the subject of maxillary ossification. Foster and Balfour,
speaking of the development of the mandibular arch of the chick, say:
"In the inferior maxillary process two developments of cartilage take
place-a proximal and a distal. The proximal cartilage is situated at
the side of the periotic capsule, but is not united with it. It is known as
the quadrate, and in the early stage is
merely a small knob of cartilage. The
quadrate cartilage ossifies as the quad-
rate bone, and supplies the permanent
articulation for the lower jaw. The
distal rod is called Meckel's cartilage;
it soon becomes covered by investing
(membranes) bones, which form the
mandible, and its proximal end ossi-
fies as the articulare.”
mk.
S M
M
E
A
BR
N

FIG. 299.
ml

mb
tty ż
rhy
st
7a
st.h.
th.h.
hh.
blu
Embryo Pig an inch and a third long; side
view of Mandibular and Hyoid Arches
(Parker): tg, tongue; mk, Meckelian carti-
lage; ml, body of malleus; mb, manubri-
um or handle of the malleus; thy, tegmen
tympani;, incus; s, stapes. The rest of
the letters refer to the hyoid arch.
Regarding its development, Foster
and Balfour simply quote from Par-
ker's account of the pig: "In a some-
what later stage (Fig. 299) the upper
end of the mandibular bar, without be-
coming segmented from the ventral part, becomes distinctly swollen, and
clearly corresponds to the quadrate region of other types. The ventral
GENERAL ACCOUNT OF EMBRYONIC DEVELOPMENT.
553
part of the bar constitutes Meckel's cartilage (mk). In the course of
further development the Meckelian part of the mandibular arch becomes
enveloped in a superficial ossification forming the dentary. Its upper
end, adjoining the quadrate region, becomes calcified, and then absorbed,
and its lower, with the exception of the extreme, is ossified and subse-
quently incorporated in the dentary." Tomes says: "About the fortieth
day a centre of ossification appears in the mandibular process, which,
spreading rapidly, soon forms a slight osseous jaw outside Meckel's car-
tilage, which is not, however, in any way implicated in it, and very soon
begins to waste away; so that by the end of the sixth month it has dis-
appeared. That end of it alone which extends up to the tympanum
does not waste away, but becomes ossified into the malleus. There are,
however, observers who hold that in some animals, at all events, Meckel's
cartilage plays a more active part in the ossification of the jaws." Dean
agrees with the authors above quoted on all essential points.
The disappearance of Meckel's cartilage is accomplished by calcifica-
tion, and afterward by ossification. The development of bone in the
jaw begins in the embryonic connective tissue surrounding Meckel's
cartilage; the latter, occupying the central portion of the jaw, is sur-
FIG. 300.
с

db
a
d.b
c.t
_m.c.
Meckel's Cartilage, from jaw of two-and-a-half months' human foetus undergoing ossification: a, nor-
mal cartilage-cells; c, enlarged cells containing calcific material; db, db, developing bone; ct, con-
nective tissue (X 250).
rounded by the connective tissue of the mesoblastic layer, which in turn
is covered externally by that of the epiblast.
Development of bone in the inferior maxilla begins in the mesoblastic
layer prior to the differentiation of the periosteum, about the fortieth
day. As the forming bands of bone thicken they encroach upon
Meckel's cartilage, which is also undergoing calcification. Under the
554
DENTAL EMBRYOLOGY AND HISTOLOGY.
influence of the osteoblasts the cartilage is broken down and becomes
ossified and incorporated into the substance of the maxilla. These
changes are very plainly shown in the accompanying cut, from a photo-
micrograph (Fig. 300).
Ossification of Meckel's cartilage differs from that known as intercar-
tilaginous; in the latter case there is rapid proliferation of the cartilage-
cells, the cartilaginous head (femur) increasing in size in proportion to
the encroachment of the ossification zone. This does not occur in ossi-
fication of Meckel's cartilage. There is no increase of cartilage-cells,
except at the points of articulation, where true intercartilaginous ossi-
fication occurs. In the body of the jaw the cartilage simply becomes
calcified, and afterward ossified and incorporated into the substance of
the maxilla, as before stated. It entirely disappears before the fifth
month-not by wasting away, but by ossification. This change begins,
as we have seen, at two and a half months; at three months it is almost
complete, and at four months, in nearly every case which I have exam-
ined, no trace of the cartilage remains. In the pig it persists much
longer, and is unaffected by ossific processes in embryos ten centimeters
in length.
Tolah/010
KOR
DEVELOPMENT OF THE BLASTODERM.
In the unincubated chicken egg the blastoderm is composed of two
layers-the epiblast and the hypoblast. There is little or no change
observable until after the eighth hour of incubation, but between this
and the twelfth hour marked changes occur. Cross-sections of the
chick at this time will show a decided proliferation of the epiblastic
FIG. 301.
pvs.
ho!
TOMA
Jalolos
jola]
0 0 0 0 0 0 0 0
g og oo oog on a O O O O Co Loooo!
layer in the region of the primitive streak.
this time, is formed of a single layer of cells
due to the lateral pressure of fellow-cells.
0000
$800
60005005070000000
yk
Sk
ep
Con
Stand

ky
;
Transverse Section through a Blastoderm of Chick, about the eighth hour after incubation (after Bal-
four); the section passes through the middle of the primitive streak: pvs, primitive streak
ep, epiblast; hy, hypoblast; yk, yolk of the germinal wall.
The epiblast, previous to
somewhat oval in shape,
The hypoblast consists of a single layer of cells, which lie parallel
with the surface of the blastoderm, while the epiblastic layer stands,
palisade-like, upon the surface. Between the flat layer of the hypoblast
and the proliferated cells of the epiblast, are seen a few scattering cells
which appear to have arisen from the hypoblast, but the greater part
of the thickening is from the epiblast.
There is little or no change appreciable in the histological appearance
of the blastoderm until about the eighteenth or twentieth hour, when the
DEVELOPMENT OF THE BLASTODERM.
555
epiblast-now composed of one or more layers of cells-is seen to have
separated from the mass of proliferated cells which lie beneath it. It
is at this juncture that the mesoblast may be said to have assumed a
separate entity.
The mesoblast is composed, as we have seen, of cells derived from
both hypoblast and epiblast, but chiefly from the latter. About the
twentieth hour, if the cells of the mesoblast are examined with a high
power (Zeiss, oil im.), it will be seen that they are stellate in form.
They take the stain similarly to the cells of the epiblast, and it is only
in carefully-prepared specimens studied with high powers-that we are
able to detect any difference. They lie in a bed of protoplasm, and it
is from this fluid-with which they are constantly bathed that they
derive their nourishment. They are simply nucleated structures, each
containing numerous granular particles. They are the bioplasts of Beale,
the nuclei of the future cells of the connective-tissue group. They have
no cell-body, and consequently no cell-limit or wall. As they advance
in age they gradually accumulate around themselves formed material,
probably the undigested or unassimilated portion of the surrounding
protoplasm. They thus assume distinctive and characteristic forms.
Their processes gradually become thicker and more pronounced, so as
to be visible even with low powers. The changes in the cells can now
FIG. 302.
1
ΙΣ

-ct
Porcine Embryo (24 cm. X 250): ct, embryonic connective tissue of mesoblast.
be seen in the lower jaw of a foetal pig two and a half centimeters in
length (Fig. 302).
In the development of the oral cavity and associate parts we do not
have to do with the hypoblastic layer of the blastoderm, so we will
hereafter confine ourselves to the head of the embryo.
The epiblast in an embryo pig 1 cm. in length is composed of one or
more layers of nuclei or bioplasts lying in a bed of protoplasm. With
low powers they appear in no manner different from the underlying
mesoblastic cells, except that the nuclei are closer together; and in
sections stained with hæmotoxylon and eosin assume a darker hue than
those of the mesoblast. The epiblast now constitutes the "infant"
layer of the epithelium, being the deepest layer of the rete Malpighii.
556
DENTAL EMBRYOLOGY AND HISTOLOGY.
It surrounds the lower jaw, forming a lining for the mouth and an outer
coat for the jaw.
The jaw is a process which has budded off from the main body of
the blastoderm, and is composed of a layer of mesodermic tissue sur-
FIG. 303.

ct.
sep.
ct, connective tissue of mesoblast; ep, epiblast (single layer of cells). The epiblast is separated from
the mesoblast mechanically.
rounded by a vesicle or sheath of the epiblast (Fig. 303). Here, then,
we have an excellent opportunity to study the several tissues which arise
from these two layers of the blastoderm, as far as the microscopical ap-
pearances are concerned. A 1 cm. pig embryo presents about the same
stage of development macroscopically as found in a human embryo of
four weeks. Histologically, it may be compared with a chick of from
twenty-four to thirty-six hours or a rabbit embryo of twelve days.
PRODUCTS OF THE EPIBLAST AND MESOBLAST.
Let us first consider some of the products of the epiblastic layer, or,
as we shall hereafter call it, the epithelial layer. These are nails, hairs,
glands, and the enamel organ.
Development of Nails.-The nails are appendages of the epidermis,
and are developed by an accretion and hornification of the cells which
constitute the epithelial layer. Desquamation does not occur, but the
cells coalesce, and, becoming glued together, form the nails. The nails
can be resolved into their cellular elements by the use of dilute nitric
acid.
In nails we distinguish three portions-the body, nail-groove, and
nail-bed. The nail arises from the nail-bed by a hornification of the
epithelium of that portion; it increases in thickness by the addition of
cells from the under side, the nail being thickest at its free border. It
PRODUCTS OF THE EPIBLAST AND MESOBLAST.
557
is attached along its lateral borders to the nail-grooves, which consist
of folds in the skin. The nail merges by almost insensible gradations
from the corneous layer of the skin in its posterior portion into the
hornified nail. The sides of the nail are not soft, and do not pass
gradually from the corneous layer of the skin, but are completely
hornified down to their attachment to the skin in the lateral grooves.
The nail is developed in the lunula-as the nail-bed is sometimes
called-from a matrix of the epithelial cells constituting the rete Mal-
pighii, which, thickening, prevents the blood-vessels of the corium from
showing so plainly as in the body, and accounts for the lighter color of
that portion of the nail. Between the nail and the corium are seen the
infant cells of the Malpighian layer, constituting only a single layer
near the free margin, but gradually becoming thicker toward the poste-
rior part of the nail-body. The corium, which underlies the nail, and
is situated between it and the bone, does not differ essentially from
the corium of other portions of the skin. The papillæ are somewhat
longer, and are inclined slightly forward by the outward growth of the
nail, which is firmly attached to the corium, and through it to the peri-
osteum of the bone. The vascular system differs in no manner from
that of the other parts of the corium; the capillary vessels end in capil-
lary loops which "supply nourishment to the Malpighian layer. This
layer gradually becomes considerably thickened, and, folding upon itself,
forms a shallow pocket or groove which will in time be occupied by the
nail-root. This infolding is not unlike that formed for the glands, hair,
and enamel organ.
daddy
The cells which have been pushed up from the nail-bed have assumed
a peculiar translucent appearance, and do not take the stain freely.
They are becoming hornified by desiccation and deposition into the cell-
body of a greater proportion of carbon and sulphur, both of which are
generally found in the epidermis. As a consequence of desiccation, the
cells which constitute the body of the nail lose their nuclei and become
condensed into a compact tissue or structure, for the examination of
which it is necessary to resort to the use of strong alkalies, which resolve
the nail into its cellular elements.
M
In the developing nail the line of division between the epiderm
covering the end of the finger and the free border of the nail is
plainly marked by a condensed layer of cells, which does not partake
of the nature of either tissue, but which lies, as it were, on the border-
land between the two. This layer will form the attachment of the nail
at its free margin.
The lengthening of the nail corresponds with the growth of the fin-
ger, being from the posterior portion outward. The nail is somewhat
thicker at the free border than it is nearer its origin.
No sweat or sebaceous glands are found underneath the nail, which
perhaps accounts for the change of the epidermis at that point into the
nail by the process of desiccation.
Hairs, glands, and the enamel organ are formed by an ingrowth of
the Malpighian layer into the mesodermic portion underneath. Just
why the rapid multiplication of epithelial cells should result in one
place in the formation of nails or horns, while in another part their
558
DENTAL EMBRYOLOGY AND HISTOLOGY.
increase results in an ingrowth which forms hairs, glands, etc., is a
question which has puzzled the brains of thoughtful men since anything
has been known of the histology of tissues. The only answer that can
be made is that in so doing the cells are obeying a vital power which
cannot be explained from a knowledge of their microscopical character
or chemical composition, or from a knowledge of the ultimate sub-
stances into which they may be resolved, but which endows each cell
with a distinct individuality. That such is the case no one can doubt
who has for himself studied the development of tissues. If such is not
the case, why is it that the cells of the mesoblast-which in the first
instance arise almost altogether from the epiblast-form one line of
tissues, while the parent epiblast forms another entirely different? So
far as we can make out in the early stage of the differentiation of the
mesoblast from the epiblast, there is no histological difference between
the two; but they have each separate offices to perform, and unless
interfered with by lack of material (cell-pabulum) they go on growing
and forming until they have produced very different tissues. From the
time of the separation of the mesoblast from the epiblast, histological
differences are presented which become more and more marked at each
succeeding stage, until at last the products of their life-work show the
widest divergence.
Development of Hairs.-The process of the development of hairs is
somewhat more complex than that of nails, but is of a similar nature.
FIG. 304.

Amman
B
B
a..
6-
J.--..
ՂՆ..
TIT
C.....
d.....
e...
h..
A
a
C


d....
C......
C...
h....
f
A, Hair-rudiment from an Embryo of Six Weeks: a, horny, and b, mucous or Malpighian layer of
cuticle, basement-membrane; m, cells, some of which are assuming an oblong figure, which
chiefly form the future hair.
B, Hair-rudiment, with the Young Hair formed, but not yet risen through the cuticle: a, horny,
b, Malpighian, layer of epidermis; c, outer, d, inner, root-sheath; e, hair-knob; f, stem, and g,
point, of the hair; , hair-papilla; m, n, commencing sebaceous follicles.
C, Hair-follicle, with hair just protruded.
Instead of being developed, like the nails, upon the surface, they are
developed inside a pouch or sac, through the mouths of which they
push their way to the surface. The first appearance of the development
PRODUCTS OF THE EPIBLAST AND MESOBLAST.
559
of hairs is seen in the pig 3 cm. in length or in human foetuses between
the third and fourth months. The infant cells of the rete Malpighii
FIG. 305.

71
h
k
g
op
e
M
d.
p
a
m
Hair-follicle in Longitudinal Section: a, mouth
of follicle; b, neck; c, bulb; d, e, dermic coat;
f, outer root-sheath: g, inner root-sheath; h,
hair; k, its medulla; 7, hair-knob; m, adipose
tissue; n, hair-muscle; o, papilla of skin; p,
papilla of hair; s, reté mucosum, continuous
with outer root-sheath; ep, horny layer; 1, seba-
ceous gland.
a
j
b
a-
fi
FIG. 306.
B

قالات
Commencing Replacement of Old
by New Hair (Toldt): a, outer
root-sheath; b, dermic coat of fol-
licle f, downgrowth of epithe-
lium to form new hair-follicle; p,
papilla of new hair commencing;
j, root of old hair; t, duct of seba-
ceous gland.
-
appear to thicken at many points; this thickening proceeds until they
dip into the underlying corium. The cellular activity does not lessen
B
560
DENTAL EMBRYOLOGY AND HISTOLOGY.
until the sac has reached the typal limit of its growth. The sac is filled
with cells which have been pushed off from the infant layer. The sur-
rounding connective tissue has now become somewhat condensed, and
constitutes the outer root-sheath. The continued development of the
cells at the deepest portion of the sac causes it to expand and become
bulbous; this appearance gives rise to the term hair-bulb.
From this time onward the effort of Nature, as expressed in ingrowth,
ceases, and her energy is directed toward the surface. The cells which
are pushed off from the infant layer become condensed in the central
portion of the sac-not into a solid shaft, but into the cortical portion
of the hair surrounding the medullary cavity. The hair-bulb rests upon
a papilla, which is developed from the corium, and which invaginates
the deepest portion of the hair-bulb, so that the latter covers the sides
of the papilla in much the same manner as though a bell had been let
down over it; this union serves to form the attachment of the base of
the hair.
The connective-tissue papillæ have no special signification, but come
and go as the hairs are destroyed and new hairs develop. They are not
a special product of foetal life, but are developed all through life as new
hairs are formed, for hairs are short-lived, and are constantly being cast
off, and new ones formed in their places. When the hair-bulb atrophies,
a new bulb is sent down from the remaining portion of the hair-follicle
(Fig. 306); this in turn becomes invaginated by a new papilla; a new
hair is formed, which by its upward growth pushes the old hair out.
When the entire epithelial portion of the follicle atrophies, there cannot
arise a new bulb, and consequently the process of future development
ceases. The hair papillæ contain loops of capillary vessels. The depth
to which the follicle penetrates into the subcutaneous tissue is in propor-
tion to the size and length of the hair, as is also the thickness of the
root-sheath. Larger hairs are set more deeply and firmly in the under-
lying tissue than smaller ones. Whether the size of the hair governs
the depth and firmness of its attachment, or the depth and firmness the
size of the hair, I leave to the reader to settle for himself. Probably
Nature knew from the beginning just how to build each part so as to
have it best subserve the purpose for which she intended it. Questions
of this kind are continually arising in the mind of the student in
Embryology, and especially is this true in our study of the products
of the epiblastic layer.
Development of Glands-Sebaceous Glands.-These are a differentia-
tion from the same infolding of the epithelial layer as the hair-follicle,
and develop simultaneously with it. In early foetal life the sebaceous
gland is much larger and more prominent than the hair-follicle-so much
so that the hair-follicle is apparently situated in the mouth of the gland.
Sebaceous glands belong to the racemous type (like a bunch of grapes).
They are developed by an infolding of the epithelial layer, which
becomes involuted, forming several pockets which open into one com-
mon duct. This duct finds outlet into the sheath of the hair-follicle or
the surface of the skin. The outer wall of the gland is composed
upon
of a connective-tissue envelope formed from the slightly condensed sur-
rounding connective tissue of the corium. Inside this is situated a layer
Gall
PRODUCTS OF THE EPIBLAST AND MESOBLAST.
561
of small polyhedral granular cells containing oval nuclei; this is the
continuation of the infant layer of rete Malpighii. Very frequently
these cells are seen to contain droplets of oil. Their office is to secrete
the oil which serves to lubricate the hair and skin. Inside this layer,
FIG. 307.



3
2
ها
1
2

Sebaceous Gland and Hair: 1, hair-follicle; 2, simple gland; 3, 4, 5, compound glands.
and occupying the cavity of the gland, are seen cells which have been
pushed off from the outer layer, and which become larger as they near
the central portion of the gland. The older cells pass through varying
stages of fatty degeneration until they are forced from the mouth of
the gland as sebum, a substance holding in suspension minute oil-glob-
ules. The sebaceous glands rest upon the erector papillæ muscles,
and are moved as the hairs move. No doubt the action of these
muscles materially aids the ejection of the contents of the glands;
vigorous brushing of the hair tends to increase the flow of this oily
secretion.
Sweat-Glands.-The other glands developed from the epithelium are
the tubular sweat-glands. Their development does not differ materially
from that of the sebaceous glands, except that instead of assuming a race-
mous form they curl or coil upon themselves at their deepest extremity,
in a very peculiar manner, presenting the appearance of a ball (Fig. 308).
VOL. I.-36
562
DENTAL EMBRYOLOGY AND HISTOLOGY.
The epithelial cells found in sweat-glands are polyhedral or cuboidal in
form. Their office, implied in their name, is too well known to need
further explanation.
180
માગ
DRI
FIG. 308.

NOUDA
15% 15-20
ng on the
a
b
d
@
f
Vertical Section of the Skin of the Thumb, partly diagrammatic: a, stratum corneum, traversed by
ducts of two glands; b, rete mucosum, with prolongations extending between papillæ beneath;
between a and is seen the stratum lucidum; c, papillary layer of corium. Near the centre of
the figure is seen a tactile corpuscle; d, reticular layer of corium with vascular plexus, nucleated
connective tissue, and interspaces; e, coils of four sweat-glands; f, fat-globules in the meshes of
the connective tissue.
Development of the Enamel Organ.-The development of this organ
differs but very little from that of the hair-follicle. This is especially
true of the enamel organ of the permanent molars, the cords for which
arise directly from the epithelial layer of the mucous membrane of the
PRODUCTS OF THE EPIBLAST AND MESOBLAST.
563
mouth. A detailed account of the development of the enamel organ
does not fall within the province of this section; we will therefore con-
fine ourselves to its simplest form of development as seen in the sixth-
year molar. The cord for this molar is said by some to arise from the
distal face of the second-year temporary molar, but I doubt the accuracy
of the statement.
bc
FIG. 309.
At the point where the cord for the tooth is to arise, be it from the
band or directly from the surface epithelium, active cell-multiplication
is seen. The layer of infant
cells, by reason of this cellu-
lar activity, becomes depressed
into the substance of the sub-
epithelial tissue in the form
of a blind pouch. Fig. 309-
which has been so extensively
copied from Frey's Histology-
was evidently taken from the
posterior portion of the jaw,
and it shows quite correctly the
changes in the form of the cord
in the development of one of
the permanent molars. I will
use it here for the illustration
of the point in hand.
d
The cells of the infant layer
are not columnar, as shown in
the cut, but oval or spheroidal
(as I will take occasion to
show when we come to the
development of the teeth prop-
er). This cut is introduced for
the purpose of calling attention k
to the errors of many who have
written upon this subject.
Three Stages in Developing Enamel-Organ (Mamma-
lian).
1. a, dental ridge; c, infant layer of cells, here wrongly
figured as columnar; d, cord for permanent molar
(probably) as it arises directly from the epithelium
of mouth.
tunic.
The ingrowing sac elongates
into a cord, thus sinking more
deeply into the submucosa.
(See Fig. 309, 1, d.) The great-
est cellular activity is found in
the deepest portion of the in- 2. e, stellate reticulum; f, dentinal papilla; ø, inner
growing sac, as we have seen
in the development of hairs
and glands. The cord under the pressure of rapid cell-multiplication
becomes bulbous. In turn, this bulbous part becomes invaginated by
the upward growth of the dentinal papilla (2, f)—at first slightly (Fig.
309, 2), afterward completely (Fig. 309, 3). Presently it is severed
from the epithelium of the mouth by the breaking up of the neck of
the cord at the same time there springs up from around the sides
of the enamel organ a connective-tissue envelope (3, h) which is con-
nected at its base with the dentinal papilla. This grows up and around
:
b.
J
a
a
C
d
е
h
1.
e
J
3
2

CL
с
h
-J
3., outer tunic; i, transverse section of vessel; k,
forming bone.
564
DENTAL EMBRYOLOGY AND HISTOLOGY.
the enamel organ, enveloping it in very much the same way as the
hair-bulb enwraps the papillæ, by forming a bell-shaped cover. We
have now a fully-developed dental follicle, the connective-tissue envelope
corresponding to the outer root-sheath of the hair-follicle. The layer
of epithelial cells which lies just inside the connective-tissue envelope
is a continuation of the infant layer of the rete Malpighii, and the cells
have not, as yet, changed their shape, being more or less oval, tending
somewhat to a cylindrical form. They are most emphatically not
columnar or prismatic, as has been so often stated and represented in
cuts by previous authors. That they do become so later no one can
doubt, but not until they are differentiated into a special cell for a
special office; and that is the secretion of the enamel.
Between the walls of the invaginated enamel organ the older cells,
which have been pushed up from the infant layer of the rete Malpighii,
are assuming a stellate shape (Fig. 309, 2, e), and we find the spaces
between the fibrils filled with a fluid which is probably rich in proteids.
Let us now turn our attention to the connective-tissue group, the
product of the mesodermic layer of the blastoderm.
DEVELOPMENT OF THE CONNECTIVE-TISSUE GROUP.
As before stated, connective tissues arise from the mesoblastic layer
of the blastoderm. For convenience of study we will consider-1,
embryonic connective cells in their earliest stages of development; 2,
fibrillar connective tissue; 3, plasma-cells; 4, areolar tissue; 5, mucous
tissue; 6, blood-corpuscles and vessels; 7, dentinal papillæ and odonto-
blasts; 8, osteoblasts; 9, cement organ.
Embryonic Connective Tissue.-The mesoblastic layer of the blasto-
derm in a foetal pig 1 cm. in length is composed of nucleated bioplasmic
FIG. 310.

-ct
Porcine Embryo (23 cm. X 250): ct, embryonic connective tissue of mesoblast.
bodies, oval or round in form. They soon begin to assume a fibrillated
appearance, sending out short processes, which may be seen in the chick
at thirty hours and in the pig 1 cm. in length; in a pig 21 cm. the
fibrillated nature of the bioplasmic bodies is more marked (Fig. 310).
DEVELOPMENT OF THE CONNECTIVE-TISSUE GROUP. 565
The processes are so fine that it requires very high amplification to
demonstrate them. The intercellular spaces, filled with protoplasm, are
large in proportion to the number and size of the cells. As devel-
opment progresses this order is reversed, and the cells with their pro-
cesses constitute an almost solid mass of tissue. The intercellular fibrillar
connective tissue is formed by the separation of the protoplasm into very
fine fibres. At first these fibrils are few in number, but gradually
increase in thickness by becoming joined together into bundles, which
anastomose with other similar bundles, thus forming a dense network
of connecting fibres. The longitudinal striations seen upon the bundles
of fibres are due to the fact before stated, that these bundles are made
up of primary elementary fibrils, which by special methods of technique
or staining may be demonstrated. Variations in the size of the bun-
dles are dependent upon the number of fibrils contained in them. They
are held together by a semifluid cement substance, which, according to
Klein, partakes of the character of globulin.
Fibrous connective tissue forms the sheaths of muscles, which it
binds into bands, and is continuous at their termini as tendons, by
which they are attached to the osseous system. It also forms the tissue
of the periosteum, pericementum, and the perichondrium; it spreads
out into membranes and lines all the serous cavities; forms the tissue
of the dermal and subdermal layers; and is, indeed, an important factor
in the formation of nearly all the organs of the body. Very generally
c.t.
FIG. 311.
f."
ポー
​g
Deposition of Fat in Connective-tissue Cells: f, a cell with a few isolated fat-droplets in its proto-
plasm; f', a cell with a single large and several minute drops; f", fusion of two large drops; I,
granular or plasma cell, not yet exhibiting any fat-deposition; ct, flat connective-tissue corpus-
cle; c, c, network of capillaries.
distributed through the connective tissue are round cells, called plasma-
cells. These are, in all probability, migrated white blood-corpuscles,
and have been previously considered.
Development of Fat or Areolar Tissue.-This is formed by a process
of infiltration into the substance of the plasma-cells. At first these
droplets are very small, but as they accumulate they gradually coalesce
and unite to form larger drops. By the aggregation and fusion of the
fat droplets the cell-body is entirely filled, and the nucleus is crowded
to one side of the cell; a thin cell-wall encloses the cell-contents, and
Gand

566
DENTAL EMBRYOLOGY AND HISTOLOGY.
thus we have ordinary connective tissue developed into areolar tissue.
This, as we have seen in the article on Anatomy, forms the principal
tissue of the derm and many other portions of the body.
Mucous tissue is most typically shown in the jelly of Wharton. It
belongs normally to embryonal life, and when found in adult tissues is
pathological in character, and is then called myxomatous tissue. It
belongs to the connective-tissue group, and is composed of branching
stellate cells lying in an undifferentiated protoplasmic basis-substance.
FIG. 312.

Z
Jelly of Wharton: 7, ramified cells intercommunicating by their branches; l, a row of lymph-cells;
f, fibres developing in the ground-substance.
I introduce mucous tissue here in order to show the distinction
between it and the stellate reticulum of the enamel organ, which we are
soon to discuss. Some have called the latter myxomatous tissue.
Development of Blood-corpuscles and Vessels.-If we stain a section
through the mesodermic layer of a foetal pig 1 cm. in length very deeply
with hæmotoxylon, and afterward with eosin, it will be seen that some of
the cells are dark purple and others bright red. In form they are simi-
lar, and it is only by the differentiating action of the stain that we are
able to demonstrate any difference between them. In parts of the section
these red cells are indiscriminately distributed; in other portions, how-
ever, they will be seen to have arranged themselves in rouleaux; these are
the newly-developed blood-corpuscles. The embryonic connective-tissue
cells of the mesoblast arrange themselves around the rows of blood-cor-
puscles, and, becoming fibrillated, form the walls of the capillary vessels.
In an older embryo, 2 cm. in length, the formation of capillary
vessels by a process of budding may be distinctly seen (Fig. 313).
These arise in solid bands of protoplasm which appear red in sections
The bands extend and form a
stained with hæmotoxylon and eosin.
network of granular protoplasm. The same process of development of
new vessels may be seen in granulation-tissue. The solid buds or pro-
cesses become hollowed out by vacuolation, and into the tubes thus
formed the circulation extends. The surrounding protoplasm becomes
liquefied, and forms the plasma in which the corpuscles float. The walls
are formed, as before described, by the embryonal connective-tissue cells.
KAN
DEVELOPMENT OF THE CONNECTIVE-TISSUE GROUP. 567
At first they are quite thin, but as the tissues grow older muscular tissue
is developed and the walls of the vessels are thickened.
FIG. 313.
From the above description it will be seen that I hold that the blood
is developed in its first formation from the embryonic connective cells
of the mesoderm. This theory
is also advanced by Klein and
many others who have written
upon the subject; all very
generally agree in classifying
blood-corpuscles in the connec-
tive group. Balfour holds es-
sentially the same views in re-
gard to them, and locates their
origin in the mesoblastic layer.
He considers that the formation
of the protoplasmic network or
bands precedes the formation of
true blood-corpuscles, and says:
"In the pellucid area, where
the formation of the blood-ves-
sels may be most easily observed,
a number of mesoblastic cells are
seen to send out processes (Fig.
314). These processes unite,
and by their union a protoplas-
mic network is formed contain-
ing nuclei at the points from
which the processes started.
The nuclei which, as a rule, are much elongated and contain large oval
nucleoli―increase very rapidly by division, and thus form groups of
nuclei at the, so to speak, nodal points of the network. Several nuclei
may also be seen here and there in the processes themselves. The net-
work being completed, these groups by continued division of the nuclei
increase rapidly in size; the protoplasm around them acquires a red color,
and the whole mass breaks up into blood-corpuscles (Fig. 314, b. c.). The
protoplasm on the outside of each group, as well as that of the uniting
processes, remains granular, and together with the nuclei in it forms the
walls of the blood-vessels. A plasma is secreted by the walls, and in
this the blood-corpuscles float freely. Each nodal point is thus trans-
formed into a more or less rounded mass of blood-corpuscles floating in
plasma, but enveloped by a layer of nucleated protoplasm, the several
groups being united by strands of nucleated protoplasm. These uniting
strands rapidly increase in thickness; new processes are also continually
being formed; and thus the network is kept close and thickset, while
the area is increasing in size. By changes similar to those which took
place in the nodal points blood-corpuscles make their appearance in the
processes also, the central portions of which become at the same time
liquefied. By the continued widening of the connecting processes and
solution of their central portions, accompanied by a corresponding
increase in the enveloping nucleated cells, the original protoplasmic

G
Many
_bl.r
ct
Porcine Embryo (2½ cm. X 250); bl. v., developing
blood-vessel, breaking up of solid band into blood-
corpuscles; ct, embryonal connective tissue.
568
DENTAL EMBRYOLOGY AND HISTOLOGY.
network is converted into a system of communicating tubes, the canals
of which contain blood-corpuscles and plasma, and the walls of which
are formed of flattened nucleated cells.
Fig. 314.
"The blood-corpuscles pass freely from the nodal points into the hollow
processes, and thus the network of protoplasm becomes a network of
blood-vessels, the nuclei of the
corpuscles and of the walls of
which have been, by separate
paths of development, derived
from the nuclei of the original
protoplasm. The formation of
the corpuscles does not proceed
with equal rapidity or to the
same extent in all parts of the
ppr blastoderm. By far the greater
part are formed in the vascular
area, but some arise in the pel-
lucid area, especially in the hin-
der part. In the front of the
pellucid area the processes are
longer and the network accord-
ingly more open; the corpuscles
also are both later in appear-
ing and less numerous when
formed."

b.c
JOO
a p.pr
b.c
-n.
n
αν
Surface View, from below, of a small portion of the
posterior end of the pellucid area of a thirty-six
hours' chick (to illustrate the formation of the
blood-capillaries and blood-vessels, magnified 400
diameters): b. c., blood-corpuscles at a nodal point,
already beginning to acquire a red color: they are
enclosed in a layer of protoplasm, in the outermost
part of which are found nuclei, a. These nuclei
subsequently become the nuclei of the cells form-
ing the walls of the vessels. The nodal points are
united by protoplasmic processes p. p., also contain-
ing nuclei with large nucleoli (n).
Assuming the truth of the
above account, it is evident that
the blood-vessels of the yolk-sac
of the chick do not arise as spaces
or channels between the adjacent
cells of the mesoblast, but are
hollowed out in the communi-
cating protoplasmic substance of the cells themselves. The larger ves-
sels of the trunk, however, are probably formed as spaces between the
cells, much as in the case of the heart.
There yet remain to be considered in this connection the dentinal
papillæ, cement organ, odontoblasts, osteoblasts, and cementoblasts.
Dentinal Papilla.-This important organ is developed from the
embryonic connective tissue of the mesoblast under the influence of the
ingrowing enamel organ. We have seen in our study of developing
hair that papillæ are developed wherever and whenever a hair-bulb is
found growing into the connective tissue, whether in embryonic or
adult life, and that upon this process depends the reproduction of hair
that has fallen out. Now, I consider the dentinal papillæ to be a sim-
ilar differentiation of the ordinary connective tissue. They originate at
any period in life, from the development of the first-formed temporary
teeth to that of the wisdom tooth or third molar of the permanent set.
In the light of our study of the analogous formation of the hair-papillæ,
I do not think it rational to believe that there is a papillary layer, sheet
of dentinal tissue, or semilunar area.
DEVELOPMENT OF THE CONNECTIVE-TISSUE GROUP. 569
No difference can be demonstrated histologically between the cells of
the papillæ and the surrounding embryonic connective-tissue cells of the
jaw. Again, it is not to be presumed that this dentinal sheet persists
until all the dentinal papillæ for the permanent teeth are formed; on
the contrary, when the time for the development of such papillæ arrives,
they are formed from the ordinary connective tissue found in contact with
the cord of the enamel organ, and at any point or depth to which it
reaches.
The cord does not penetrate the mesoblastic layer searching for a
papilla already formed or for a dentinal sheet, but, like the solid
ingrowth which forms the hair, it has the power to superintend the
differentiation of a papilla for itself. The enamel organ is a specialized
tissue which superintends the formation of the papilla and shapes the
pulp, and consequently the tooth; in a word, it is the first essential
element in tooth-formation, the papilla occupying a secondary position.
The first indication of the development of the papillæ varies so much
in the several teeth, even in the same jaw, that no set rule can be laid
down. It is safe to say, however, that when the ingrowing cords
become bulbous the time is ripe for their appearance.
The papilla is first seen as a condensation of the connective tissue
outside and in juxtaposition with the deepest point of the bulbous cord.
By its growth in a direction opposite to the enamel organ of the tooth
it causes this organ to invaginate itself, after which there is differen-
tiated from the surrounding connective tissue, on all sides of the bell-
shaped enamel organ, a follicular wall which is connected with the
papilla at its base. This is the cement organ, in connection with which
cementoblasts are found underlying this fibrous connective-tissue layer,
the future pericementum.
Cementoblasts are analogous to osteoblasts; in fact, they are osteo-
blasts which have received the additional name of cementoblasts. Per-
sonally, I would prefer to call them by their original name but for the
fact that we have adopted the name cement for the osseous covering of
the roots of teeth.
d
Osteoblasts are specialized cells belonging to the connective-tissue
group, and the probable nature of their origin will be discussed in the
section on Ossification.
Upon the surface of the dentinal papilla, at a period which precedes
the formation of dentine, a layer of cells may be seen; these are termed
odontoblasts. They are developed from the ordinary connective-tissue
cells of the papilla. Their differentiation can be studied by following
the side of the papilla from its base to its apex in a specimen which
shows the beginning of the process of dentinification.
At the base they are generally spheroidal or oval in form, but higher
up on the sides of the papilla they are somewhat cylindrical, while at
the apex they are columnar. They are sometimes connected with the
tissue of the papilla by slender processes.
On the side of the forming dentine they have one or more processes
called dentinal fibrils, which penetrate the forming dentine and superin-
tend its arrangement into tubules, the centre of which they occupy as
the organic part of the dentine. In some instances these fibrils pene-
570
DENTAL EMBRYOLOGY AND HISTOLOGY.
ر
trate the intercellular spaces of the cementoblastic layer, and dentine is
formed around the terminal fibrils, causing an interdigitation of the
dentinal tubules and the enamel-prisms. This interpenetration precedes
the process of calcification of the enamel.
This now brings us to the consideration of the subject of calcification,
which rightly precedes the study of both amelification and ossification.
CALCIFICATION.
"Calcification is the process of change into a stony substance contain-
ing much lime, as in the formation of the teeth" (R. Owen). In the
light of the present status of scientific investigation I would change the
above definition as follows: Calcification is that process by which (organic)
tissues become hardened by deposition of salts of calcium in their inter-
cellular substance, as exemplified in the formation of bones and teeth.
The intercellular substance found in organic tissues is fluid, and into
this fluid minute particles of lime salts, in such fine subdivision as not
to be demonstrated by even the highest powers of the microscope, are
deposited in regular systems after the several forms of calcified tissues.
This arrangement is superintended by specialized cells for each particular
structure-osteoblasts for bone, odontoblasts for dentine, etc. These cells
secrete lime salts and deposit them in the intercellular substance.
All cells lie embedded in, or are bathed by, a fluid which is more or
less gelatinous in consistency. It is from this surrounding medium that
the cells derive the supply of nourishment necessary for the performance
of their functions. Cells are capable of cellular activity in proportion
to the amount of cell-pabulum this fluid contains. I do not say that
cells are active according to the amount of food-supply present, but that
they are capable of putting on cellular activity just in proportion to the
amount of cell-food at hand, and in this way are stimulated to increased
functional activity. Bricks cannot be made without straw, neither can
tissues present increased functional powers without plenty of food with
which to nourish themselves. The presence of an intercellular substance.
is of essential importance in the development of tissues. In embryonic
life the quantity of cell-pabulum is very marked. It is at this period
that calcification begins in two forms-ossification and amelification;
the first under the superintendency of the connective-tissue group of cells,
and the second a product of the epithelium.
Connective tissue is developed from the mesoblast, while the epithe-
lium is produced from the epiblast. In our former studies we found a
wide difference between the tissues of the two layers, and we shall find
a yet wider difference between their products.
Under the calcified products of the connective-tissue group we will
consider bone, cement, and dentine; under the calcified products of
epithelial tissues, enamel, shells, etc.
The essential difference between the two depends upon the matrix,
and the manner in which the lime salts are deposited, rather than upon
the character of the cells which govern the deposition. The general
appearance of cells is dependent, to a very considerable extent, on the
matrix in which they lie, yet an epithelial cell, while presenting varia-
Giga
CALCIFICATION.
571
tions, is nevertheless always epithelial in its nature, and so are its prod-
ucts. The same is true in regard to the connective-tissue group: an
interchange between the two tissues is not known in all the domain of
normal or pathological histology, neither can this interchange occur
between the products of the two tissues. Those who hold that the
enamel is a differentiation of a dentinal basis-substance have not com-
prehended the subject in all its bearings. Enamel is no more modified
bone than is the shell of the mollusk.
Ty
Enamel and shells are analogous structures, and are secreted by the
epithelium upon, and not in, the substance of tissues. The shell of the
snail is secreted upon its surface, and the lime salts form a semi-crystal-
lized mass.
Enamel is secreted by the ameloblasts upon the already
formed layer of dentine, there being no basis-substance between the
layer of ameloblasts and the formed layer of dentine, and, as in the
case of the shell, the lime salts crystallize-not, however, into true
crystals. Shells and enamel are identical except in their mineral con-
stituents. Enamel is nothing more or less than a coat of mail, and as
such best serves the processes of nature.
As we have seen in our study of developing epithelium, there is little
or no intercellular substance above the infant layer of cells. In the
development of nails the hornification occurs, not in the infant layer,
but in the older layer, or "stratum granulosum" of other writers. So
in the deposit of enamel the lime salts are secreted (shed out) by the
cells of the infant layer-not in the infant layer, where the greatest
amount of intercellular substance is found, but upon the under sur-
face of the infant layer-upon an already formed layer of dentine.
These cells have become altered in form and specially endowed with
functional power. This point will be considered in presenting the
subject of the development of the ameloblasts.
We have seen, when treating of the development of connective tissue,
that the proportion of intercellular substance largely preponderates over
the cells themselves. Into this intercellular substance the calcified
products of the connective-tissue group are deposited.
Connective tissues are divided into three great classes: (1) fibrous
connective tissue; (2) cartilage; and (3) bone, in which class dentine is
included. Each of these is subdivided into several varieties, as will
appear farther on, but in all instances the ground substance, matrix, or
intercellular substance is to be distinguished from the cells themselves.
In the fibrous connective tissue the matrix yields gelatin, and the cells
are called connective-tissue corpuscles. In cartilage the ground substance
yields chondrin, and the cells are called cartilage-cells. In the third
group the ground substance contains inorganic lime salts, and the
cells are termed bone-cells.
"The matrix of osseous substance is a dense fibrous connective tissue
-i. e. a substance yielding gelatin on boiling. The cement substance
between the fibrils is petrified, owing to a deposit of insoluble lime salts,
chiefly carbonates and phosphates. These can be dissolved out by strong
acids (as hydrochloric), and thereby converted into soluble salts. Thus
the organic matrix (Fig. 315) of osseous substance, called ossein, may be
obtained as a soft, flexible material easily cut" (Klein).
572
DENTAL EMBRYOLOGY AND HISTOLOGY.
The ossein mentioned above is the calco-globulin of Mr. Rainey. It
is evident that the basis-substance left after decalcifying bone has changed
its nature, and no longer presents the
characteristics of the intercellular sub-
stance in which the lime salts were de-
posited.
FIG. 315.
The intercellular substance is com-
posed of protoplasm. In life this con-
tains, besides the albuminoids, a living
principle which permits it to modify its
form and perform functions. Just what
this principle is we have never, by chem-
istry, been able to determine, for by the
use of the reagent which we employ to
Appearance of Matrix left after Decalcifi-
cation by HCl. Osseous Lamellæ, oblong-
branched bone-lacunæ and canaliculi demonstrate its molecular constituency
between them.

K
we destroy the living principle, and
have left only the material substance which held the active principle in
bounds. Chemical analysis shows protoplasm to be composed of pro-
teids, in which are held in suspension carbohydrates and fats. These
substances are undoubtedly formed from protoplasm by the action of
the living matter of the cell. We also find in different parts of the
body several varieties of substances derived from the above-mentioned
constituents of protoplasm-gelatin, mucin, etc.
Under the direction of the vital principle found in living protoplasm
-viz. cells—the lime salts are deposited in forms peculiar to each
tissue. Lime salts, however, may crystallize without the body, but the
form of the structure in the body depends upon the superintendency of
specialized cells. Tubular bone or dentine is deposited by odontoblasts,
and calcospherules of bone by osteoblasts. These cells do not exert
any other influence upon the depositing structure than that of shaping
it according to certain prescribed and prearranged forms. They are, in
fact, but the moulds which shape the accumulating mass. Where lime
salts are deposited in albumen or any other gelatinous material there
appears no definite form other than that naturally assumed by the
particular lime salt when undergoing crystallization.
Renal calculi are in all probability formed by the deposition of lime
salt in a matrix of mucus, for similar calculi can be formed artificially
outside the body. "The chemical substances to be employed in the pro-
duction of the artificial calculi," says Mr. Rainey, "are a soluble com-
pound of lime and carbonate of potash or soda dissolved in separate
portions of water, and some viscid vegetable or animal substance, such
as gum or albumen, mixed with each of these solutions. The mechani-
cal conditions required to act in conjunction with the chemical means are
the presence of such a quantity of the viscid material in each solution as
will be sufficient to make two solutions, when mixed together, of about
the same density as that of the nascent carbonate of lime, and a state of
perfect rest in the fluid in which the decomposition is going on, so that
the newly-formed compound may be interfered with as little as possible
in its subsidence to the sides and bottom of the vessel. This will
require two or three weeks or longer, according to the size and com-
DEC
CALCIFICATION.
573
pleteness of the calculi. But I have not found that they increase at
all after six weeks."
Mr. Rainey has by many and thoroughly scientific tests proven the
analogy between his artificial calculi and those formed in the body.
The lime salts are deposited in both cases in a gelatinous matrix, but
without the forming influence of the specialized cells which we find in
true calcification. The difference between crystallization outside of the
body and crystallization within it is due to the action of the specially-
endowed cells which superintend the deposition of the lime salts.
The lime salts which are deposited in the intercellular substance enter
into some chemical combination with the protoplasm which composes
this intercellular substance, the nature of which is not known; but it
is not due to any special action of the living protoplasm, as such, for
we find the same apparent characteristics shown where lime salts are
thrown down in albumen or mucilage. The product thus obtained is
insoluble in acids: a portion or all of the lime salts will be given up,
but the matrix will remain.
On this subject Mr. Tomes has written as follows: "The insoluble
salts of lime are altered in their behavior by association with organic
compounds a fact which was first pointed out by Rainey and has
been more recently worked out by Professor Hasting and Dr. Ord.
If a soluble salt of lime be slowly mixed with another solution
capable of precipitating the lime, the resultant lime salt will go down
as an amorphous powder, or, under some circumstances, in minute
crystals. But in the presence of gelatin, albumen, and many other
organic compounds the form and physical character of the lime salts
are materially altered, and in the place of an amorphous powder there
are found various curious but definite forms quite unlike the character
of crystals produced without the intervention of the organic substance.
Mr. Rainey found that if calcium carbonate be slowly formed in a thick
solution of mucilage of albumen, the resultant salt is in the form of
globules, laminated in structure, so that the globules may be likened to
tiny onions, these globules, when in contact, becoming agglomerated
into a single laminated mass, it appearing as if the lamina in immediate
apposition blended with one another. Globular masses, at one time of
mulberry-like form, lose the individuality of their constituent smaller
globules, and become smoothed down into a single mass; and Mr.
Rainey suggests as an explanation of the laminated structure that the
smaller masses have accumulated in concentric layers which have sub-
sequently coalesced; and in the substitution of the globular for the
amorphous or crystalline form in the salt of lime when in contact with
various organic substances Mr. Rainey claimed to find the clue for the
explanation of the development of shells, teeth, and bone. At this
point Professor Hasting took up the investigation, and found that other
salts of lime would behave in a similar manner, and that by modifying
the condition of the experiment very various forms might be produced.
But the most important addition to our knowledge made by Professor
Hasting lay in the very peculiar constitution of the 'calcospherites,' by
which name he designated the globular forms seen and described by
Rainey. That these are built up of concentric laminæ like an onion
574
DENTAL EMBRYOLOGY AND HISTOLOGY.
،
เ
has already been mentioned, and Mr. Rainey was aware that albumen
actually entered into the composition of the globule, since it retained
its form even after the application of acid. But Professor Hasting has
shown that the albumen left behind after treatment of a calcospherite
with acid is no longer ordinary albumen: it is profoundly modified,
and has become exceedingly resistant to the action of acids, alkalies,
and boiling water, and in fact resembles chitine, the substance of which
the hard skin of insects consists, rather than any other body. For this
modified albumen he proposes the name of calcoglobulin,' as it appears
that the lime is held in some sort of chemical combination, for the last
traces of lime are retained very obstinately when calcoglobulin is sub-
mitted to the action of acids. The calcospherite,' then, has a true
matrix of calcoglobulin, which is capable of retaining its form and
structure after the removal of the great bulk of the lime. Now, it is
a very suggestive fact that in the investigation of calcification we con-
stantly meet with structures remarkable for this indestructibility; for
example, if we destroy the dentine by the action of very strong acids or
by variously-contrived processes of decalcification, putrefaction, etc.,
there remains behind a tangled mass of tubes, the dentinal sheaths' of
Neumann, which are really the immediate walls of the dentinal tubes.
Or if bone be disintegrated by certain methods, there remain behind
large tubes found to be the linings of the Haversian canals (Kölliker),
and small rounded bodies recognizable as isolated lacunæ; and in the
culicula dentis we have another excellent example of this peculiarly
indestructible tissue. In point of fact, as will be better seen after devel-
opment of the dental tissue has been more fully described, on the border-
land of calcification, between the completed, fully-calcified tissue and the
formative matrix, as yet unimpregnated with lime, there very constantly
exists a stratum of tissue which in its physical and chemical properties
very much resembles calcoglobulin.”
6
It should also be noted that globular, spherical forms are constantly
to be seen at the edges of the thin cap of forming dentine, and may
be also traced in and around the interglobular spaces. Moreover,
isolated spherules of lime salt have been described by Messrs. Robin
and Magitot as occurring abundantly in young pulps of human teeth,
as well as those in Herbivora, where their presence was noted by Henle.
This brings us to the consideration of the first division of calcified
products-viz. bone.
T
G
Pa
OSSIFICATION.
By ossification we mean the deposition, under the superintendency
of the osteoblasts, of the salts of calcium into the intercellular proto-
plasmic basis-substance.
Bone is simply an aggregation of calcospherules. These are at first
thrown out or secreted as a thin covering around the osteoblasts. The
specialized cell, at the time when it assumes the office of bone-builder,
is at its highest state of development as regards functional activity, and
has also attained its greatest magnitude. From the formation of the
first layer of bone the cells begin to decrease in size, and they continue
:
OSSIFICATION.
575
to lessen until the typal demands of each spherule are reached, when the
process ceases. The wall of the calcospherule is thickened at the expense
of the size of the osteoblast itself; so that the bone-cell--which is really
the encased osteoblast-is perceptibly smaller than the original osteoblast.
Osteoblasts are round or oval bodies varying considerably in diameter.
They are not fibrillated, and in this respect correspond to plasma-cells.
They lie in actual contact with one another, and as ossification proceeds
the points of contact draw out into fine fibres. Salts of calcium are
deposited in the protoplasm which bathes the osteoblasts and have their
location in the meshes of these fibres.
In intermembranous ossification of the skull-cap and subperiosteal
development of bone the osteoblasts are arranged in layers in the sub-
stance of the fibrous membranes or underneath them, and the deposit
of lime is along the fibres, giving them an opaque, granular appearance.
The deposition begins on one side of the line of osteoblasts, and pre-
sents as many indentations as there are osteoblasts in line.
The crescentic nature of the first part of the layer secreted by the
osteoblasts is plainly shown when they (the osteoblasts) are displaced or
where they are considerably shrunken. As the process of secretion
proceeds the osteoblast becomes enclosed in a thin spherule of formed
material, designated by Mr. Rainey as calcoglobulin. This shell of
bone is pierced here and there by the fibres of the osteoblast which are
left as the osteoblast shrinks. The deposition of bone is really in the
meshes of these fibres.
The body of the cell is spheroidal, hence the deposition assumes a
spheroidal form; accordingly, we denominate it a calcospherule.
As the process of secretion goes on depositing from the circumfer-
ence toward the centre the fine processes before mentioned continue to
be united with the osteoblasts. Their terminal fibrilla anastomose with
those of other osteoblasts, and these again with others; those which lie
nearest the capillary vessels connect with them, thereby receiving nour-
ishment, which they in turn give to the outer layer of bone-cells.
The office of these processes, then, is to supply the nutrient matter
needed to support life in the bone-cells.
Bone-cells are nothing more or less than encapsuled osteoblasts which
are occupying the homes which they have builded themselves. The
cavities which they occupy are the lacuna of the old writers; the canals
in which their processes lie are the canaliculi, and the capillary vessels
the Haversian system. These lacunæ and their canaliculi, together with
the Haversian canals, are occupied in living bone by the above-described
organic element.
If we dry a portion of the shaft of a long bone-by which process
we destroy the organic element-and afterward saw off small sections
and grind them quite thin, then mount them in hard balsam so that
the spaces will not become penetrated by the balsam, but remain filled
with air, we may observe the following arrangement: larger or
smaller canals (Haversian), around which are arranged, concentrically,
oval spaces (lacunæ), from which radiate numerous fine canals (canal-
iculi), which connect with other similar canals, and these in turn with
the Haversian canals.
da
576
DENTAL EMBRYOLOGY AND HISTOLOGY.
Now, if we had taken a portion of the same bone, when fresh, and
placed it in dilute picric acid and decalcified it, afterward cutting thin
sections and staining them with picrocarmine, we should not have seen
the cavities which we observed in the section of dried bone; for while
by the process of drying we destroyed the contents of the cavities, by
the use of the picric acid we preserved their contents.
In lacunæ we find bone-cells; in canaliculi, processes of bone-cells;
in Haversian canals, capillary vessels.
By studying sections prepared according to the methods above de-
scribed, we are able to understand the real formation of bone. It is
needless to remark that our present knowledge of bone-formation is the
result of the accumulated research and careful observation of scientists
for many generations.
The general misuse of the terms lacunæ, canaliculi, and Haversian
canals attests the need of a more thorough understanding of the pro-
cess of bone-formation. A brief recapitulation of the more important
points may make the subject clearer to the reader.
The osteoblasts do not become calcified, but remain as the life-occu-
pants of the calcospherules, and by reason of such occupancy make it
possible for us to produce, by drying, the cavities known as lacunæ.
Calcification is a process of secretion around, and not in, the cell. The
mollusk secretes upon, and not in, its body, and the secreted portion of
its shell does not contain organic tissue. The only living matter
found therein is the body of the mollusk, which we can extract and yet
FIG. 316.

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Transverse Section of Compact Tissue (of Humerus). (Magnified about 150 diameters.) Three of
the Haversian canals are seen, with their concentric rings; also the lacunæ, with the canaliculi
extending from them across the direction of the lamella. The Haversian apertures had become
filled with air and débris in grinding down the section, and therefore appear black in the figure,
which represents the object as viewed with transmitted light.
leave the shell as perfect a shell as before the death of its occupant.
We do not think of attributing to the shell the possibility even of such
a thing as an inflammatory process, for the reason that the shell is
OSSIFICATION.
577
composed of material unsusceptible of any change except that of disin-
tegration. The mollusk may add to its shell internally, but it must
necessarily be at the expense of the size of its own body. And so it is
with the osteoblasts: they are arranged in close proximity-so close
that the first secreted calcospherule joins that of a neighboring sphe-
rule, and by this juxtaposition and coalescence solid bone is formed.
Fracture of the shell may also be repaired by the same cells which
in the first place secreted the shell.
FIG. 317.
The area of tissue supplied by a capillary vessel at the beginning of
the process of calcification marks the limit of the Haversian system.
The osteoblasts are arranged around the
outer portion of this area, and the first-
formed layer of calcospherules consti-
tutes the periphery of the Haversian
system; the next-formed layer of sphe-
rules lies inside the first-formed layer,
thereby lessening the space occupied by
the capillary vessels; the third layer is
still inside the second; and so on centrip-
etally, until the several layers almost
The
entirely fill the space (Fig. 316).
remaining space is occupied by the vas-
cular and lymphatic system, and no less
an authority than Schaefer claims the
presence of nerves (Fig. 317).
In the centripetal manner of develop-
ment I see a wise design on the part of
Nature to limit the space occupied by the
calcospherules and mark the outline of
the Haversian system. This centripetal
arrangement lessens the calibre of the
vessels, but yet allows them abundant
capacity to carry sufficient cell-pabulum to keep alive the enclosed
organic tissue.

Valen
S
V.
#pang 371
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to winter
Z
Section of a Haversian Canal, showing
its contents (highly magnified): a, small
arterial capillary vessel; v, large ven-
ous capillary; ", pale nerve-fibres cut
across cleft-like lymphatic vessel:
one of the cells forming its wall com-
municates by fine branches with the
branches of à bone-corpuscle. The sub-
stance in which the vessels run is con-
nective tissue with ramified cells; its
finely granular appearance is probably
due to the cross-section of fine fibrils.
The canal is surrounded by several con-
centric lamellæ.
sym-
Thus is cellular activity made self-limiting and a beautiful and
metrical object conformed to its purpose brought into being. Were the
process of bone-formation centrifugal, we should be more likely to find
abnormalities and distortions.
This brings us to the consideration of the several forms in which
bone is developed. We have seen how the calcospherules are built and
by their aggregation made into compact bony tissues, and it now remains
to discuss the several different forms they assume under the government
of pre-existing tissues which modify their arrangement.
Nearly every author gives a different interpretation of the existing
classifications. Upon those known as intracartilaginous and subperi-
osteal they generally agree, but there seems to be considerable difficulty
in harmonizing their views upon the third class-viz. intramembranous.
This, as I shall try to show, grows out of the fact that this classification
is made to cover too much ground.
Dr. T. Mitchel Prudden describes this form of ossification as occur-
VOL. I.-37

578
DENTAL EMBRYOLOGY AND HISTOLOGY.
ring "in the substance of pre-existing fibrillar connective-tissue mem-
branes," and cites the skull-cap as a typical example. He classifies
subperiosteal development separately.
Dr. Carpenter says: "The intermembranous form of ossification prin-
cipally occurs in the flat bones of the head, and is also the mode by
which long bones increase in girth." It will be seen from the above
that Dr. Carpenter considers intermembranous and subperiosteal forma-
tions of bone under one head.
FIG. 318.
Klein recognizes two classes-enchondral and periosteal, or inter-
membranous—and says: "All the bones of the limbs and of the verte-
bral column, the sternum and the ribs, and the bones forming the base
of the skull, are preformed in the early embryo as solid hyaline carti-
lage covered with a membrane identical in structure and function with
the periosteum, which at a later period it becomes. The tegmental
bones of the skull, the bones
of the face, with the lower jaw,
except the angle, are not pre-
formed at all. Only a mem-
brane identical with the future
periosteum is present, and un-
derneath and from this bone is
gradually deposited." Under
the division intermembranous
he further says: "All bones not
preformed in the embryo as
cartilage are developed directly
from the periosteum in the
manner of periosteal bone just
described."

а
b
M
:
The accompanying cut is
here reproduced as the only
one published—at least, so far
as I am aware-that has any
reference to maxillary ossifica-
tion. It is evidently taken
from a quite mature foetus, as
osteoclasts are figured, and they
do not make their appearance in the jaws until very near birth, at which
time a periosteum has been differentiated and subperiosteal bone-forma-
tion is in active progress; this is also the case in all the bones of the
body, the maxillæ being no exception to the rule.
а
A Small Mass of Bone-substance in the Periosteum of
Lower Jaw of a Human Fœtus: «, osteogenetic lay-
er of periosteum; b, multinucleated giant-cells, my-
eloplexes. The one in the middle of the upper mar-
gin is an osteoclast, whereas the smaller one to the
left upper corner appears concerned in the forma-
tion of bone. Above (c) the osteoblast-cells become
surrounded by osseous substance, and thus become
converted into bone-cells.
Dr. Shakespeare,¹ in speaking of intramembranous development of
bone, says: "The intermembranous formation of bone is analogous to
the development of bone from the periosteum. For instance, the bones
of the cranium have their origin in a fibrous membrane which soon pre-
sents a division into two layers similar both in structure and function to
the outer and inner layers of the periosteum."
Schaefer² makes only two divisions-intercartilaginous and intermem-
branous. He says: "Sometimes the bone is preceded by cartilage,
2 See Schaefer's Histology.
1 Allen's Anatomy.
OSSIFICATION.
579
FIG. 319.
which first of all becomes calcified, and this is invaded, and for the
most part removed, by an embryonic tissue which deposits bony matter
in the interior of the cartilage, whilst at the same time layers of bone
are being formed outside, under-
neath the periosteum. This is in-
tercartilaginous or enchondral ossi-
fication. Sometimes the bone is
not preceded by cartilage, and then
the only process which occurs is one
corresponding to subperiosteal ossi-
fication of the former variety. The
ossification is then known as intra-
membranous.” From the above it
is seen that this author makes in-
tramembranous and subperiosteal
bone-formation analogous except
as regards position.
Z
G

Q
O
&
C-
&
Osteoblasts from the Parietal Bone of a Human
Embryo thirteen weeks old: a, bony septa, with
the cells of the lacunæ, or bone-corpuscles; b,
layers of osteoblasts; c, the latter in transition
to bone-corpuscles (very high power).
Gray makes two main divis-
ions-intracartilaginous and in-
tramembranous-and places sub-
periosteal as a subdivision of the second. As an example of the
first, he cites the "long bones;" of the second, the "cranial bones"-
viz. the occipital as far as it enters into the formation of the vault
of the skull, the parietal and frontal bones, the squamous portion of
the temporal with the tympanic ring, the Wormian bones, the nasal,
lachrymal, malar, palate, upper and lower maxillary, and vomer; also,
apparently, the internal pterygoid and the sphenoidal turbinated
bones. The intramembranous ossification," he further says when
discussing that division, "is that by which the bones of the vortex
of the skull are entirely formed. In the bones which are so devel-
oped no cartilaginous mould precedes the appearance of the bone-tissue.
The process, though pointed out originally by Dr. Nesbitt in the year
1736, was first accurately described by Dr. Sharpey, and it does not
appear that subsequent observers have been able to add anything essen-
tial to his description. This is substantially as follows: In the mem-
brane which occupies the place of the future bone a little network of
bony spicule is at first noticed, radiating from the point of ossification.
When these rays of growing bone are examined by the microscope,
there is found a network of fine clean fibres (osteogenetic fibres), which
become dark and granular from calcification, and as they calcify they
are found to enclose in their interior large granular corpuscles, or osteo-
blasts. These corpuscles at first lie upon the osteogenetic fibres, so that
the corpuscles must be removed by brushing the specimen with a hair
pencil in order to render the fibres clear, but they gradually sink into
the areola developed among the fibres. The areolae appear to be the
rudiments of the lacunæ, the passages between the fibres form the
canaliculi, and the osteoblasts are the rudiments of the bone-cells."
This, with slight modification, is a very good description of intramem-
branous ossification as seen in the parietal bones of the skull-cap, but
does not answer for the maxillæ, as we will see later on.
Th
htt
580
DENTAL EMBRYOLOGY AND HISTOLOGY.
From the above quotations I think I am justified in saying that
all agree regarding the manner and method of intracartilaginous and
subperiosteal bone-formation, and intramembranous also, in so far as
it refers to the parietal bones; but, judging from the paucity of illus-
trations and literature treating directly upon the formation of the
remainder of the group not preformed in cartilage, I conclude that
there has been less investigation of this than of kindred subjects.
From my own studies in bone-formation, I am convinced that we
need all the classifications made by previous writers, and that still
another is essential to a clear understanding of ossified products. I
shall therefore make a fourth class, which I term interstitial. In our
future study of bone, then, we shall have to consider four ways in which
it may be developed: I. In the substance of the embryonal connective
tissue of such bones as are not preformed in cartilage; found in maxil-
lary ossification: interstitial (my own classification). II. In pre-existing
membranes, as in the skull-cap: intramembranous. III. Underneath
the periosteum, as in the cortical portion of long bones: subperiosteal.
IV. In pre-existing cartilage, as in the head of the femur: intracarti-
laginous.
FIG. 320.
I. Interstitial Formation of Bone.-I introduce this term for the ear-
liest development of bone, believing that it is needed. The term intra-
membranous, while applying to the manner of development in the
parietal and some others of the flat bones, does not apply to the
maxillæ and bones of that class.
I am more convinced of the ne-
cessity of such a division of the
intramembranous group than of
the need of making a distinction.
between the latter and subperios-
teal bone-formation. At best, in-
tramembranous ossification occu-
pies only a transitory stage, and
gradually passes into subperiosteal
by the differentiation of the peri-
osteum; and I think a careful con-
sideration of the subject will so
convince the reader.

ct.
In the microscopic investigation
of early embryonic life (pig 24 cm.,
and human 2 mo. ; see cut) cells are
seen grouped together here and
there in the central portions of
both the inferior and the superior
maxillæ, which have taken the
stain in such a manner as to call
attention to their appearance; in
other words, they have been differ-
Under low powers they do not differ
in form from the surrounding cells, but under high amplification they
show no processes as do the ordinary connective-tissue cells even at
entiated by the staining process.
Inferior Maxilla Porcine Embryo (2½ cm. X
240): 0, osteoblasts grouped together, surround-
ed by embryonal connective tissue, ct.
OSSIFICATION.
581
this age. They differ in more than mere appearance, however, as is
evidenced by their different chemical action when subjected to the stain-
ing process, when they take on a darker shade than other cells.
Staining is not tingeing; it is a chemical reaction exerted by the
separate tissues upon certain dyes, by reason of which we obtain differ-
ent colors in sections which contain one or more tissues or cells which
have different chemical reactions, as in the case in hand. The darker-
stained cells are osteoblasts (bone-builders) (Fig. 321). They are found
FIG. 321.
Ꮕ
Ser
ARGE
ct.
2-24
ct.
Porcine Embryo (5 cm. long X 250): a, osteoblasts situated at the ends of the lamelle of bone; db,
developing lamella of bone containing bone-cells; ct, ct, embryonal connective tissue.
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near the central portion of the jaw, which, though composed of the
mesoblast, is surrounded by the epiblastic layer. There is as yet no
indication of a condensation of the connective tissue into a membrane
such as we find when ossification first commences in the skull-cap. A
few osteoblasts-independent of the influence of either membrane or
periosteum-arrange themselves in groups here and there. These
groups are the points of ossification (Fig. 320, o), and from them the
process extends as the jaw develops.
At first these specialized cells are grouped together in a double layer,
but later they may be seen at the termini of the trabecula-which are
already in a somewhat advanced stage of calcification-where they
appear to be a continuation of the process of bone-formation (Fig. 321,
o); or, to use a simple illustration, they are the fully-equipped work-
men (the osteoblasts) waiting for material (lime salts) with which to
begin the work of bone-building.
Under the superintendency of the osteoblasts, a crescentic layer of true
bone is deposited upon the side of the osteoblast in apposition with a
similar crescentic layer formed by an osteoblast located on the opposite
side of the line. The sides of each crescent join similar crescents
582
DENTAL EMBRYOLOGY AND HISTOLOGY,
formed by fellow-workmen on either side. As deposition progresses
the osteoblast becomes encircled by a shell of lime. As the trabecula
widens by enclosing the osteoblasts which lie upon its sides new layers
of osteoblasts are found arranging themselves on the walls, which in
turn become enclosed in a layer of bone. Thus, by the accumulation
of successive layers of calcospherules, the broadening of the bands of
bone-tissue is accomplished. As the osteoblasts build themselves into
the wall their places are taken by fresh recruits. When each osteoblast,
by secreting its calcospherule, completes its life-work as a bone-
builder, it becomes a bone-cell, and from that time on occupies the
house it has builded. (See Fig. 322.)
FIG. 322.
b
The maxillary bones, including the alveolar processes, are thus pre-
formed in provisional bone. The foetal jaw is as truly the antetype of
the mature jaw as the foetal
head of the femur, which is
preformed in cartilage, is the
pattern or matrix-former of
the mature femur. This is
so even in the very early
stages of its development.
The alveolar walls surround
the microscopic follicle and
present the same ragged ap-
pearance when the overly-
ing mucous membrane is re-
moved that we see later in
mature tissue. The maxil-
lary bones cannot be said to
have any special points of
as do other
ossification,
bones: development is gen-
eral. The fact that the al-
veolar processes have not their analogue in form in any other portion
of the body, strongly points to the correctness of my views regarding
their special manner of development.
kay
The first-formed bone is removed by internal resorption, which is
concomitant with the external growth by regular methods, which we
shall now describe.
c.sp.-
ct
Human Foetus, 2 months (X 250): o, osteoblasts (the dark
lines which come to the edge of the figure at b represent
bands of forming bone); c. sp., calcospherule surrounding
an osteoblast; c, embryonal connective tissue.
dadd

Stand
After the formation of the periosteum two other classes of bone-
development occur-viz. intramembranous and subperiosteal. The essen-
tial point of difference between the two is found in the location of the
embryonal plates of bone. Intramembranous development, as such per
se, belongs entirely to fœtal life, and is found in its most typical form in
the development of the skull-cap; here it has reference only to the first-
formed bone, which we have before said is provisional in character, the
growth which takes place after birth being subperiosteal in its nature.
And so it is in regard to interstitial development: the cortical substance
of the mature jaw is developed underneath the periosteum. Indeed, we
may say that all bone-formation is provisional until such time as the
bones have nearly reached the typal demands of nature, for of those
OSSIFICATION.
583
first developed not a trace will remain in the fully-formed bone. The
space occupied by bone in the foetal jaw will be nerve-canal in the
mature jaw; of the later products of calcification-say after birth-at
least some will be found in the fully-formed jaw.
In placing the division-line between provisional and permanent bone-
formation at birth I do not wish to lay down any arbitrary rule. I
simply desire to illustrate as clearly as I am able to do so my meaning,
and impart to the mind of the reader some tangible point from which
to reason. Regarding bone developed prior to birth, I think it is per-
fectly safe to say that not a trace will be found in mature bone. `In
making this statement I do not lose sight of the fact that adult tissues
are continually being reproduced. I speak only of the form, not of the
integral constituents of the formed material. Nevertheless, if there is
any stability in tissues, it surely will be found in the inorganic formed
material of bones.
II. Intramembranous Formation of Bone.-We will now consider the
second division of our classification-viz. intramembranous development
of bone. Prior to the appearance of the first layers of bone (pig 4 cm.)
there is seen a condensation of the connective tissue immediately under-
neath the epithelial layer. There has not as yet been any attempt on
the part of nature to differentiate what may properly be termed skin.
The epiblast is composed of only one or two layers of epithelial cells.
The condensed layer underneath is the first trace of the future peri-
FIG. 323.

ost
a
b
of
sp
sp
Part of the Growing Edge of the Developing Parietal Bone of a Foetal Cat (13 inch long): sp, bony
spicules, with some of the osteoblasts embedded in them, producing the lacunæ; of, osteogenic
fibres prolonging the spicules, with osteoblasts (ost) between them and applied to them.
osteum. There is as yet no indication of periosteum in the jaws.
Nature hastens ossification in the skull-cap in order to protect the
584
DENTAL EMBRYOLOGY AND HISTOLOGY.
delicate tissues of the brain-substance, which is being differentiated
even at this early period.
If a piece of the skull-cap of a foetal cat (Fig. 323), one and a half
inches in length, which has been hardened, be cut out and divided into
its several layers, and examined with the microscope, thin plates of bone
will be seen; these can be rubbed with a stiff brush until they are thin
enough to be examined by high powers. If the plates have been pre-
viously stained, a very nice specimen can thus be obtained. But for the
best understanding of the manner of development we take the parietal
bone-say of a five months old human foetus--and decalcify it and cut
sections; upon examination, lamellæ, or plates of bone, will appear in
the now well-defined fibrous periosteum. These embryonal plates are
situated in the substance of the periosteum in such a manner as to
FIG. 324.

a
Transverse Section of a Bone (ulna). (Magnified 20 diameters.) The openings of the Haversian
canals are seen encircled by concentric lamellæ. Other lamella run parallel with the surface,
forming the cortical layer.
form connecting cavities which locate blood-vessels and marrow-tissue.
The deposition of lime salts is controlled by the osteoblasts, as in inter-
stitial bone-formation. These lamellæ of provisional bone are so
located as to divide the fibrous layer into two separate layers: from the
outer, periosteum is formed; and from the inner, the dura mater probably
arises. That these plates of bone are only temporary is evidenced even
at this time, for side by side with the osteoblasts are found osteoclasts
(bone-destroyers), the two processes going hand in hand. The wall is
being taken down as fast as it is built and carried farther out, so as to
give more space for the rapidly-growing brain.
OSSIFICATION.
585
III. Sub-periosteal Bone-formation.-As the name implies, this form
of development takes place underneath the periosteum, and is, of neces-
sity, a later product than interstitial development. We have seen that
repair of bone after caries is generally due to this mode of growth.
The vascular supply for the nourishment of bones is largely located
in the periosteum. Small branches of the larger trunks of vessels,
which are found in the periosteum, penetrate the cortical portion and
form anastomosing loops with other branches which are found in the
marrow-cavity. It is thus that Haversian canals are formed at right
angles to the surface of the bone, and are seen to radiate toward the
FIG. 325.

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een
&
Cantor.'
02
A.
Section of Phalangeal Bone of Human Foetus, 5 months (magnified about 75 diameters): oz, the cartilage-
cells in the centre, midway between the epiphyses, are enlarged and separated from one another
by a dark-looking calcified matrix; im, layer of bone deposited underneath the periosteum; 0,
layer of osteoblasts by which the layer has been formed. Some of the osteoblasts are already
embedded in the new bone as bone-cells in the lacunæ. The cartilage-cells are becoming enlarged
and flattened, and are arranged in rows above and below the calcified centre. At the ends of the
cartilage the cells are small, and the groups are irregularly arranged; the cartilaginous heads are
surrounded by perichondrium.
centre like the spokes of a wheel, following no regular course, but
winding here and there, sometimes crossing and recrossing one another.
In the shaft of a long bone the Haversian systems follow the line of
586
DENTAL EMBRYOLOGY AND HISTOLOGY.
the axis of the bone, the irregular arrangement being most generally
found near the ends of the bone.
Subperiosteal bone-formation does not begin evenly along the surface
FIG. 326.

bv
p
X
ic
do
i m
C
X
Lof
pf
Longitudinal Section through the Upper
Half of the Decalcified Humerus of a
Foetal Sheep, as seen under a magnify-
ing power of about 30 diameters: ic, the
part of the shaft which was primarily
ossified in cartilage; what remains of
the primary bone is represented as
dark, enveloped by the clear secondary
deposit. The areolæ of the bone are
occupied by embryonic marrow with
osteoblasts, and blood-vessels variously
cut, represented as dark lines. One
long straight vessel (bv) passes in ad-
vance of the line of ossification far
into the cartilaginous head; most of
the others loop round close to the car-
tilage. At one or two places in the
older parts of the bone elongated groups
of cartilage-cells (c) may still be seen,
which have escaped absorption. im,
the part of the bone that has been
ossified in membrane-that is to say, in
the osteoblastic tissue under the peri-
osteum. It is well marked off from
the central portion, and is bounded,
peripherally, by a jagged edge, the pro-
jections of which are indistinctly seen
to be prolonged by bunches of osteo-
genic fibres. A row of osteoblasts
covers the superficial layer of the bone.
The subperiosteal layer is prolonged
above into the thickening (p), which
encroaches upon the cartilage of the
head of the bone, and in which are
seen, amongst numerous osteoblasts
and a few blood-vessels, the straight
longitudinal osteogenic fibres (/), and
some other fibres (p) crossing them,
and perhaps representing fibres of
Sharpey. The calcareous salts having
been removed by an acid, the granular
ossific deposit passing up between the
rows of cartilage-cells is not seen in
this specimen; it would have extended
as far as a line joining the marks X X.
Observe the general tendency of the
osseous trabeculæ and the vascular
channels between them to radiate from
the original centre of ossification. This
is found to prevail more or less in all
bones when they are first formed,
although the direction of the trabecula
may afterward become modified in re-
lation with varying physiological con-
ditions, and especially as the result of
pressure in different directions.
underneath the periosteum, but at certain points which are governed by
the location of a capillary blood-vessel. At first lamellæ are developed
at right angles to the periosteum; the first-formed layer is pitted and
uneven, but as the process extends the bone becomes more compact,
OSSIFICATION.
587
until a smooth surface is formed. From this time on, even through
the process of resorption and rebuilding, the surface is nearly always
found to be smooth. The Haversian systems themselves almost entirely
disappear in the cortical portion of long bones, the final deposition
being from layers of osteoblasts which are found directly under-
neath the periosteum. Thus a dense cortical bone is formed which
gives strength to the bony columns (Fig. 324, a).
In some instances the penetrating fibres of the periosteum are found
in this cortical portion. These may persist for a longer or shorter time
as such, and are known as Sharpey's fibres (Fig. 7, p. 41, Sec. on
Anatomy). A similar arrangement is seen at the point of tendinous
attachment for muscles.
IV. Intercartilaginous Development of Bone. As early as the fifth
day in the chick and in 1 cm. foetal pigs certain bones are found preformed
in cartilage-viz. the bones of the skeleton, occipital, sphenoid, ethmoid,
nasal, etc. It will be found that these cartilaginous formations bear a
very close resemblance to the bones which will replace them; they are
the matrix-formers which serve as the antetypes of the mature tissues.
This is shown very nicely in Fig. 325; here the epiphyses are similar
in form to the mature articulating heads of the phalangeal bone. The
cartilaginous heads are only separated by the zone of ossification. If
the section had been made through the same phalanx, before develop-
ment had progressed quite so far, the heads would have been seen to be
in apposition.
The increase in length of the bone is by the development of the shaft,
the heads being pushed lengthwise in either direction. The first percep-
tible change is seen about the middle of the phalanx. The cartilage-
cells are enlarged at the expense of the intercellular hyaline basement-
substance, which latter is becoming finely granular in appearance, due
to infiltration of minute granules of lime salts. This change in the
character of the cartilage-cells can be seen extending a considerable dis-
tance from the borderland of calcification. The cells have arranged
themselves into rows on a line with the axis of the shaft, gradually
diminishing in size from the enlarged cells in the ossification zone, to
their normal size as found in the unchanged heads.. The capillary
blood-vessels push their way into the calcifying cartilage, or, what is
more probable, the penetration of the capillaries antedates the change
in the cartilage. This arrangement is very nicely shown at bv in Fig.
326, where a blood-vessel has burrowed its way into the very centre
of the cartilaginous head.
The zone of calcification which has been figured so extensively as
occurring in the central portion of the head, and which some authors
claim is independent of the action of the blood-vessels, I have proven
-to my satisfaction, at least-to be none other than a zone of calcifica-
tion located around the terminal loop of one of these vessels.
Sometimes vessels may be seen to enter the head of the cartilage from
the sides as well as from the marrow-cavity, and wherever they penetrate
we find alterations in the character of the cartilage-cells. These changes
are chiefly confined to the arrangement and deposition of lime salts in
the basement substance.
588
DENTAL EMBRYOLOGY AND HISTOLOGY.
1
Prudden says: "If we examine the cartilage at a considerable distance
from the line of ossification, we find the ordinary appearance of
hyaline cartilage with more or less flattened cells. Approaching
now the zone of ossification, we find that the cells are larger, are
le
De
Vie
FIG. 327.

Mo 10%
00
O
@APM
Db
BADE
00
1 D T X ) A VAD
UM
Bouth wp4 WA
AUX
05°
↓
39
@
76
b l
Naim
ir
Section of Part of one of the Limb-
bones of a Foetal Cat, at a more ad-
vanced Stage of Ossification than is
represented in Fig. 325, and somewhat
more highly magnified. The calcifi-
cation of the cartilage matrix has
advanced from the centre, and is ex-
tending between the groups of car-
tilage-cells, which are arranged in
characteristic rows. The subperiosteal
bony deposit (im) has extended pari
passu with the calcification of the
cartilage matrix. The cartilage-cells
in the primary areolæ are mostly
shrunken and stellate; în some cases
they have dropped out of the space.
At ir and in two other places an ir-
ruption of the subperiosteal tissue,
composed of ramified cells with osteo-
blasts and growing blood-vessels, has
penetrated the subperiosteal bony
crust, and has begun to excavate the
secondary areolæ or medullary spaces;
p, fibrous layer of the periosteum; 0,
layer of osteoblasts: some of them are
embedded in the osseous layer as
bone-corpuscles in lacunæ; bl,"blood-
vessels occupied by blood-corpuscles.
Beyond the line of ossific advance the
periosteum may be noticed to be dis-
tinctly incurved. This incurvation
is gradually moved on, the cartilage
expanding behind it until the head
of the bone is reached, when it forms
the periosteal notch or groove repre-
sented in the preceding figure.
br
arranged in rows or groups of frequently four, eight, or sixteen, etc.,
the intercellular substance being less in amount, corresponding to the
increase in size and number of the cells. Farther inward we find the
cells still more plainly arranged in rows, very large, sometimes globular
or flattened against one another, and the basement-substance reduced to
quite thin septa, enclosing spaces in which the rows of large cartilage-
cells lie. Then comes a narrow zone, in which the septa of the base-
ment-substance are filled with fine granules of lime salts: calcification
Here the cartilage-cells have assumed a peculiar granular cha-
racter. Finally, still nearer we find that the lime salts have disap-
zone.
¹ T. M. Prudden, Normal Histology.
OSSIFICATION.
589
2
FIG. 328.
peared from the septa, and that the spaces which contained the large
granular cartilage-cells have become continuous with the advancing vas-
cular, bone-walled marrow-cavities, above described. It is to be dis-
tinctly understood that the calcifi-
cation zone is not bone, but only
calcified cartilage, the true bone
being first formed after this lime
has disappeared, on the surface of
the septa in which it was tempo-
rarily deposited-for what purpose
we do not know." (See accom-
panying figure, 328.)
The lengthening of the shaft pro-
ceeds until the cartilaginous head
itself becomes ossified, when all
further extension ceases and the
bones are said to be fully devel-
oped. This time varies in different
bones and also in the same class of
bones.

FROM
.n.c.
.cc.
db.
nt.
As regards the origin of the oste-
oblasts in the first instance I am
pretty fully convinced that they are
the ordinary embryonic connective-
tissue cells. That this is so in the very early stages such as we have
described in interstitial development (p. 580) there seems to be no room
for doubt. The close intimacy between the vascular supply and ossifi-
cation tends to confirm the opinion held by some, that they are modified
white blood-corpuscles. For my part, I see no antagonism between the
two theories above mentioned. I think it can be quite clearly demon-
strated that even fixed connective-tissue cells are only modified white
blood-corpuscles which have passed through several gradations governed
by location and environment, appearing (I.) as white blood-corpuscles
in the vessels; (II.) as escaped white blood-corpuscles; (III.) plasma-
cells; (IV.) fixed connective-tissue cells. Ziegler has made extensive
studies in regard to the changes of the migrated white blood-corpuscles
into fixed connective-tissue cells in pathological conditions where there
is set up a process of progressive metamorphosis, and says that without
doubt such is the process of change.
From Femur of Human Foetus of 5 months (X
250): mc, normal cartilage; cc, calcified carti-
lage; db, the dark line representing developing
bone; mt, marrow tissue.
C
Osteoblasts are a constant concomitant of bone-formation. Ossifica-
tion is a process which is under the superintendency of the osteoblasts.
We have seen that there exists an intimate relationship between the
vascular supply and calcification which precedes ossification. The
breaking down of the cartilaginous matrix is, without doubt, due to the
modifying influence of the capillary vessels. The hyaline basement-
substance is dissolved and the cartilage-cells are liberated. These carti-
lage-cells pass into the form of fibrillated connective-tissue cells from
which cartilage is originally developed.
The point I desire to make is this that the white blood-cells are the
common basis from which the several members of the connective-tissue
S
590
DENTAL EMBRYOLOGY AND HISTOLOGY.
group spring. In some instances osteoblasts are produced from con-
nective-tissue cells; sometimes they have their origin in cartilage-cells;
but their most frequent and persistent source is found in the white
blood-corpuscles.
Magg
Nature always uses the material at hand, in so far as it is available.
If the bone is being deposited by intercartilaginous ossification, there is
no necessity that the cartilage-cells should be destroyed or materially
altered. They are, no doubt, modified and endowed with special func-
tional powers; in a word, they become osteoblasts. And such use of
pre-existing cells may occur in intramembranous and subperiosteal bone-
formation. The fixed connective-tissue cells in all probability act as cen-
tres of calcification. In interstitial ossification true fibrous connective
tissue has not as yet been found; it is embryonic connective tissue, and
the cells are consequently embryonic connective-tissue cells.
There is very little difference, except as regards size, between the
osteoblast and the surrounding connective-tissue cells. Thus we find
that bone is developed in truly embryonic tissue as well as in older
tissues; it is developed in cartilage and in membranes; it is developed
in normal and in pathological conditions; and yet the process of ossifi-
cation is ever the same, although the location or arrangement of the
deposition may vary according to the essential differences in the tissues
in which bone is formed. The only unvarying element that is found
in intimate relation with all these tissues is the migrated white blood-
corpuscle; and, by reason of its close relationship with the process of
ossification, it seems to me to be more reasonable to infer that the white
blood-corpuscle becomes modified in form and endowed with such spe-
cialized functional power as to be able to superintend the development
of bone.
Kdy
CEMENTIFICATION.
This is only a slightly-modified form of subperiosteal development of
bone. In mature tissues the pulp, covered by a layer of dentine vary-
ing in thickness, acts as a large Haversian canal, around which the
cement is deposited in concentric layers, the whole forming a large
Haversian system. Sometimes this arrangement is modified, and
Haversian canals are seen running at right angles to the surface.
When this does occur, cementification differs in no respect from sub-
periosteal bone-formation.
I have cut sections from the roots of teeth in which well-defined
Haversian canals were seen to enter the sides of the roots, and I have
no doubt that if we were to search for them more carefully we could
often find them. Quite a number are recorded in dental literature
under the name of multiple foramina.
Cementification is the analogue of subperiosteal formation of the
cortical substance of long bones. The first deposited layer of cement
is permanent, there being no provisional cement to be afterward broken
down. The circumference of the root at the beginning of the process
of the deposition of cement is as great as it ever attains. The increase
in thickness of the dentine is from the periphery toward the centre, at
DENTINIFICATION.
591
the expense of the size of the pulp, just as the Haversian systems develop
by successive layers of calcospherules which are situated inside the cir
cumferential layer. The thickening of the cement is from the first layer
deposited upon the dentine externally, thus enlarging the circumference
of the root. The limit to this accretion
is found in the fully-formed alveolar wall
which surrounds the root.
FIG. 329.
When, at certain points, the process
extends beyond typal limitations, we have
a pathological condition, and malforma-
tion results; in later years the cement
may become thickened (exostosis) as the
result of constant irritation.

2.
We find that the process differs in no
degree from the first-formed cement. The
pericementum is analogous and continuous
with the periosteum. It is a cement organ
only in the same degree that the periosteum
is a bone organ. We know that both have
the special function of superintending
the deposition of their several products
after injury or loss, and that, stimulated
by irritation, they produce pathological
conditions by secondary deposits. They
are the persistent organs under the direc-
tion of which nature repairs injuries.
The individual elements which form
cement are the osteoblasts, or-if it is de-
sirable to increase the number of terms in
connection with tooth-development-the
cementoblasts. Calcospherules of lime are
formed in a manner similar to those de-
scribed in connection with our study of
ossification.
Vill
DENTINIFICATION.
:
3
Section of Fang parallel to the Dentinal
Tubules (magnified 300 diameters): 1,
cement, with large bone-lacunæ and
indications of lamella; 2, granular lay-
er of Purkinje (interglobular spaces);
3, dentinal tubules.
A single layer of osteoblasts, or cemen-
toblasts, is first formed around the per-
iphery of the dentine of the root. By a process identical with that
of subperiosteal bone-formation, the cementoblasts become enclosed in
spherules of lime; successive layers appear, each in turn assuming the
characteristics of the first-formed layer, till finally, by their aggregation,
the cement is thickened to the typal point. A section of cement show-
ing the similarity existing between it and bone is seen in the accom-
panying figure (329, 1). The union of the cement and the dentine
is also shown very nicely, and will be referred to farther on, when
treating of that subject.
M
Dentine is a specialized product developed by specialized cells. In
form dentine is very different from the several varieties of bone hereto-
592
DENTAL EMBRYOLOGY AND HISTOLOGY.
fore considered. We have already studied-under the head of the con-
nective-tissue group-the development of the special cells which super-
intend its formation-viz. odontoblasts.
Dentine is only a still more modified form of bone than cement. If
we so desired, we could make a fifth class of ossified products and call
it tubular ossification; but I prefer to hold to the existing nomenclature,
and will speak of the process as dentinification.
Like cement, the first layer of dentine formed is a permanent product.
I use the term in contradistinction to provisional deposition as found in
the study of ossification.
Odontoblasts are a modified form of connective-tissue cells. They
are situated upon the periphery of the pulp, and send out rod-like pro-
cesses to the inner side of the enamel organ in the crown.
Under the superintendency of the odontoblasts lime salts are deposited
around these rod-like fibrils, and thus form tubular dentine.
In our study of the development of bone we found that canaliculi
were formed by the deposition of lime salts around the fibrils of the
osteoblasts and within the calcospherules. Each calcospherule is a
separate entity composed of an organic bone-cell with radiating pro-
cesses around which inorganic lime salts have been deposited in such a
manner as to form a perfect spherule. The dental pulp may be com-
pared to a gigantic osteoblast, the fibrils of the odontoblasts represent-
ing the fibrils of the osteoblast. The dentine covering the pulp
corresponds to the wall of the calcospherules, and the canals of the
dentinal tubuli to the canaliculi.
The deposit of dentine is the work of mature cells which lie upon the
surface of the dentinal pulp, being arranged in a single row. Dentine
FIG. 330.
is a secretion of lime salts under the
superintendency of the odontoblasts
-not around themselves, as in the
case of the encapsuled osteoblast,
but around their fibrils. These
being rod-shaped, the deposition
naturally assumes a tubular form.
The fibrils remain as the persistent
organic contents of the dentinal
tubuli, just as the fibres of the
bone-cells are found to occupy the
canaliculi. The thickening of the
dentine is by accretion of lime
salts in such a manner as to
lengthen the tubuli. The fibrils
lengthen as the dentine thickens,
and the odontoblasts recede before
Mongolia
by
d
:

b
Part of Section of developing Tooth of young
Rat, showing the Mode of Deposition of the
Dentine (highly magnified): a, outer layer of
fully-calcified dentine; b, uncalcified matrix
with a few nodules of calcareous matter; c,
odontoblasts with processes extending into
the dentine; d, pulp. The section is stained lengthen the tubuli.
with carmine, which colors the uncalcified
matrix, but not the calcified part.
the forming dentine, leaving a process behind.
Each individual odontoblast does not become encapsuled, as do the
osteoblasts, but remains free upon the surface of the pulp all through
the life of that organ. They do, however, become encapsuled, in the
aggregate, by the dentine of the entire tooth.
As we have before said, the pulp, with the odontoblasts, represents a
DENTINIFICATION.
593
bone-cell; the pulp-cavity, a lacuna; while the dentinal fibrils are
The canals of the
analogous to the processes of the bone-cells.
dentinal tubuli represent the canaliculi in which the processes or fibrils
are situated.
We have seen that the thickening of the wall of the calcospherule is
at the expense of the size of the osteoblast, and to a certain extent this
is true of the tooth. But it must be remembered, however, that
deposition of dentine is from one side of the odontoblast, and not
circumferentially, as is the case in ossification (Fig. 330).
Additions to the thickness of bands of bone are produced by the
addition of successive layers of osteoblasts, which one after another
become enclosed by the deposition of lime salts. The thickening of the
dentinal wall is accomplished by a single layer of odontoblasts which
begin the process, and these cells persist throughout the life of the
pulp, and when stimulated by the irritation of invading decay have the
power to throw out a secondary layer of dentine, which acts as a barrier
against the enemy. This thickening is at the expense of the cavity of
the pulp, and consequently of that of the size of the organ itself.
The formation of the dentine of the root is also somewhat similar.
The circumference of the outer layer of the dentine of the root is as
great when first formed as it ever will be. The thickening of the wall
is by a process similar to that seen in the Haversian systems, which, as
we know, is at the expense of the contents of the Haversian canals.
The dentine of the root of a tooth is a hollow column which increases
in length by extension and in thickness by internal deposition of lime
salts. Under the superintendency of the odontoblasts new layers are
being continually added to the end of the tube until the necessary
length is completed. The apical foramen is the open end of the column.
As the root reaches the required length this open end is constricted
by internal deposition, and finally almost closes, until we see it as it
appears in the ordinary apical foramen. The dentine reaches its re-
quired thickness in the crown first. Sometimes more than one apical
foramen is found in a single root. This is due to a division of the
pulp in this special case, and the phenomenon is governed by the
same law that regulates the development of the separate roots of the
molar teeth. The papilla divides into several parts, which indicate
the position of the future roots, and dentine is developed around
each part in a manner exactly similar to that which we have above
described.
In the development of the dentine of the crown the process is some-
what modified. În shape the dentine of a tooth has the outward appear-
ance of a double cone, the bases uniting at the cervical portion. The
papilla, beginning as a microscopic object lying in what is afterward
the very apex of the pulp at the cutting edge of the tooth, commences
the deposition of the dentine directly under the enamel organ, and the
tubules are developed in a line corresponding to the axis of the tooth.
The papilla rapidly widens at its base, throwing out odontoblasts from
its side, and as it does so the direction of the tubules gradually changes,
tending more and more to a position at right angles to the axis; which
position they assume at the neck of the tooth. The pulp has its great-
VOL. I.-38
594
DENTAL EMBRYOLOGY AND HISTOLOGY.
est diameter at the cervical portion at the time when the first developed
layer of dentine is formed at that line. From this time forward the
thickening of the wall of the dentine of the crown can be truly said to
be at the expense of the size of the pulp.
Many persons have been deceived by mistaking the microscopic organ
for the fully-developed, or macroscopic, tooth. At eight months the
crown is not yet fully formed. The infolding of the lower portion of
the enamel organ is due partly to the shrinkage of the very delicate
pulp-tissue at its deepest extremity and partly to the fact that the deep-
est edge of the enamel organ always precedes the specialization and full
development of the pulp. These contracted edges will in time be
straightened by the expansion and growth of the pulp at that point.
In order to become convinced that this appearance is not the exten-
sion of the enamel organ below the cervical portion of the tooth, as
has been claimed by some (thus making the cement organ a continua-
tion of the enamel organ), it is only necessary to measure the length
of the enamel organ in its different stages of development and com-
pare these with the length of a fully-developed enamel cap.
It is difficult for the mind to picture the whole of an object from a
part, and it is still harder for it to grasp the wide distinction existing
between microscopic and macroscopic objects. But the interpretation
of the location of the cervical margin of a developing tooth, which at
six or eight months has become a macroscopic object, is accomplished
easily enough. This can be done with an ordinary pocket-rule, and
does not require any of the refinements of microscopic measurement.
The deposition of dentine is around the fibrils of the odontoblasts,
which latter stand nearly at right angles to the surface of the dentine.
Kandand
Mature dentine is a solid mass of calcified tissue. It is held by some
that it is composed of individual tubes; however true this may be of
forming dentine, it cannot be said of mature dentine. In the process
of development the salts of calcium are deposited around the fibrils of
the odontoblasts, and in a certain sense dentinal tubuli may be said to
exist at that time. We may say that dentine is an aggregation of tubes
containing fibrils, but in the process of aggregation they lose their iden-
tity as such, becoming cemented together into a solid tissue.
I think, however, it is more in keeping with the facts in the case to
say that dentine is a secretion thrown out by the odontoblasts in the
meshes of the dentinal fibrils. The deposition is in the protoplasm which
fills the interspaces between the fibres. By the deposition of lime salts
into the protoplasmic basis-substance calcoglobulin is formed, and the
dentine tissue becomes a homogeneous mass penetrated by many par-
allel canals filled with the persistent dentinal fibrils.
Besides the parallel canals filled with the dentinal processes, many
lateral canals are seen branching off from the main tubes and forming
anastomoses with neighboring canals. It must not be lost sight of for
a moment that the appearances seen in ground sections of dentine are
produced by the destruction of the contents of the dentinal canals. If
we hold that distinct and separate dentinal tubes exist in mature den-
tine, then we must consider them as having many fine branches, in-
creasing in numbers as we proceed toward the periphery of the dentine.
Kan
N
AMELIFICATION.
595
No;
FIG. 331.
This is not consistent with our ideas of the character of a tube.
the nature of dentine is very like that of mature bone: though it
assumes a different form, yet it is developed in a similar manner, and
by the aggregation and agglomeration of its individual elements a
tissue is formed which we class
among ossified products. Then,
again, the occurrence of interglob-
ular spaces in dentine militates
against the tubular theory. These
can only be explained by admitting
that dentine is secreted into a pro-
toplasmic basis-substance. "Inter-
globular spaces," so called, are
composed of masses of calcoglobu-
lin, which masses have not become
fully calcified. The dentinal fibrils
pierce them and are continuous upon
either side (Fig. 331, c); while they
make breaks in the continuity of
the dentine tissue, yet they do not
in any way interfere with the cha-
racter or form of the dentinal processes.
of calcoglobulin, see p. 574.)
In conclusion, the fact that dentine is not capable of being broken up
into tubes is in my mind conclusive evidence against the theory of the
existence of a dentinal sheath per se as the wall of a dentinal tube.
Dentine is an osseous tissue permeated by numerous anastomosing
canals which in life locate the fibrils of the odontoblasts.

C
111
BITO
A small Portion of the Dentine with Interglob-
ular Spaces (350 diameters): c, portion of in-
cremental line formed by the interglobular
spaces, which are here filled up by a trans-
parent material.
(For a discussion of the nature
AMELIFICATION.
The late Dr. Carpenter, who gave the greater part of his life to the
study of conchology, and who has perhaps done more than any other
man to lighten the dark places of this subject, says: "The structure of
the outer layer of the common Pinna projects beyond the inner, and
there often forms laminae sufficiently thin and transparent to exhibit its
general character without any artificial reduction. If a small portion
of such a lamina be examined with a low magnifying-power by trans-
mitted light, each of its surfaces will present very much the appearance
of a honeycomb; whilst its broken edge exhibits an aspect which is
evidently fibrous to the eye, but which, when examined under the
microscope with reflected light, resembles that of an assemblage of
segments of basaltic columns. This outer layer is thus seen to be
composed of a vast number of prisms having a tolerably uniform size
and usually presenting an approach to the hexagonal shape. These
are arranged perpendicularly (or nearly so) to the surface of the
lamina of the shell; so that its thickness is formed by their length
and its two surfaces by their extremities. A more satisfactory view
of these prisms is obtained by grinding down a lamina until it pos-
sesses a high degree of transparence, the prisms being then seen (Fig.
W
596
DENTAL EMBRYOLOGY AND HISTOLOGY.
332) to be themselves composed of a very homogeneous substance, but
to be separated by definite and strongly-marked lines of division. When
such a lamina is submitted to the action of dilute acid, so as to dissolve.
away the carbonate of lime, a tolerably firm and consistent membrane
FIG. 332.

O
ANAL
Section of Shell of Pinna, taken transversely
to the direction of its prisms.
è cards à
FIG. 333.

Membranous Basis of Shell of Pinna.
is left, which exhibits the prismatic structure just as perfectly as did the
original shell (Fig. 333), its hexagonal division bearing a strong resem-
blance to the walls of the cells of the pith or bark of a plant." The
shell of the Pinna and other species of the mollusk family is a
structure analogous to enamel. Both are calcified products of the epi-
blast. We see variations in the form of the products of the connective-
tissue group-as, for instance, in bone-and we also find variations in
calcified epithelial structures. We have seen, in the calcification of
bone, that cells do not become calcified, but simply superintend calcifica-
tion; and I think we shall be able to show that the same rule holds
good for the calcified products of the epiblast.
A
As we have already said, salts of calcium enter into chemical com-
bination with proteids, and thus form a new group of products called by
Mr. Rainey calcoglobulin. This modified form of albumen is insoluble
in acids; therefore we have an organic matrix left behind after decalci-
fying the several varieties of bone. The form of the bone is seen in the
decalcified material. This same matrix is found in the prismatic layers
of shells, but not in enamel. There must, then, be some reason for its
existence in the one case, and not in the other.
I hold, with Drs. Carpenter and Huxley, that all calcified products
are excreted, and that there is not an actual conversion of living cells
into calcified tissues. In some instances the cells become encapsuled,
but lime salts are not deposited in the body of the cell; in other words,
calcification by conversion cannot be demonstrated. In the formation
of bone variations occur due to the position and matrix in which the
deposition takes place; this is also the case with the products of the
epiblast. The shell of the Pinna is excreted, or shed out, upon the sur-
AMELIFICATION.
597
face; the calcified product occupies the position of the stratum granulo-
sum, or what I term the older layer of cells. Upon the surface of the
prismatic layer we find a layer of hornified or corneous cells, and, under-
neath the calcified tissue, the formative layer-viz. the rete Malpighii, or
infant layer of cells.
It is well known that this infant layer, or rete Malpighii, consists
of nucleated structures which lie in a bed of protoplasm. This layer
of protoplasm surrounds and bathes the cells of the older layer to a
certain extent, growing less and less in quantity as we approach the
surface. This protoplasmic substance does not differ in character
from that which surrounds the cells of the connective-tissue group.
So far as we know, the two fluids are identical: salts of calcium
enter into chemical combination with protoplasm in the latter case,
and why not in the former?
The first-formed layer of the shell of the mollusk lies in the proto-
plasm which bathes the formative, or infant, layer of cells of the rete
Malpighii. These cells are the active agents in its deposit; they have
become specialized and endowed with new functional power that they
may superintend the deposition of the salts of calcium which enter into
the composition of the shell. Their office is identical with that of the
osteoblast.
The calcium salts are shed out from the ends of the cell as from the
surface of a membrane-which, indeed, they form. They do not
become individually encapsuled, as do the osteoblasts, but the body
of the Pinna, covered externally with epithelium which remains as
the lining membrane of the shell, becomes enclosed by the shell, and
thus the infant layer may be said to be encapsuled.
The thickening of the shell is at the expense of the size of the body
of the Pinna, just as the thickening of the wall of the calcospherule is
at the expense of the size of the osteoblast. If we decalcify a shell and
make sections, we find a matrix which differs only in form from that
found in bone. The prismatic layer of the rete Malpighii has laid
down the calcified products in the form of prisms, and cross-sections
of the decalcified product will reveal their form just as well as ground-
sections. Cross-sections will present the appearance of a honeycomb
from which the honey has been extracted: the extracted honey com-
pares to the salts of calcium, which before decalcification existed as
prisms, and occupied, as did the fluid honey, the cells of the comb.
In the development of the shell the protoplasm shed out between the
prismatic cells of the infant layer is limited in quantity. The secreted
salts of calcium which are thrown out by the cells enter into chemi-
cal combination with the peripheral layer of protoplasm and form
calcoglobulin, which, as we have before shown, is insoluble in acids.
The sheath which surrounds the prism, as the protoplasm does the
prismatic cell, may be compared to the wax in the cell of the honey-
comb. Regarding the sheath, and the material which enters into its
structure, Dr. Carpenter says:
"It sometimes happens in recent, but still more commonly in fossil,
shells that the decay of the animal membrane leaves the contained prisms
without any connecting medium. As they are then quite isolated, they
598
DENTAL EMBRYOLOGY AND HISTOLOGY.
can be readily detached one from another, and each may be seen to be
marked by striations. By making ground-sections of the shell per-
pendicularly to its surface we obtain a view of the prisms cut in the
direction of their length (Fig. 334), and they are frequently seen to be
marked by delicate transverse striæ closely resembling those observ-
able on the prisms of the enamel of teeth, to which this kind of shell-
structure may be considered as bearing a very close resemblance except
as regards the mineralizing ingredients. If a similar section be decalci-
fied by dilute acids, the membranous residuum" (the interprismatic
cement-substance, which by its insolubility in acids shows it to be per-
haps identical with Mr. Rainey's calcoglobulin) "will exhibit the same
resemblance to the walls of the prismatic cells viewed longitudinally,
and will be seen to be more or less regularly marked by the transverse
striæ just alluded to." (See Fig. 335.)
FIG. 334.
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"These appearances seem best accounted for by supposing that each
(prism) is lengthened by successive additions at its base.
"This 'prismatic' arrangement of the carbonate of lime in the shells
of Pinna and its allies has been long familiar to conchologists and
regarded by them as the result of crystallization. When it was first
more minutely invested by Mr. Bowesbank and the author, and was
shown to be connected with a similar arrangement in the membranous
residuum left after the decalcification of the shell-substance by acid,
microscopists generally agreed to regard it as a calcified epidermis, the
long prismatic cells being supposed to be formed by the coalescence of
the epidermic cells in files and giving their shape to the deposit of car-
bonate of lime formed within them. The progress of inquiry, however,
has led to an important modification of this interpretation, the author
being now disposed to agree with Prof. Huxley in the belief that the
entire thickness of the shell is formed as an excretion from the surface
AMELIFICATION.
599
of the epidermis, and that the horny layer which in ordinary shells
forms this external envelope, or 'periostracum,' being here thrown out
at the same time with the calcifying material, is converted into the like-
ness of cellular membrane by the pressure of the prisms that are formed
by crystallization at regular distances in the midst of it.
"The internal layer of the shells of the Margaritaceæ and some other
families has a 'nacreous,' or iridescent, lustre which depends (as Sir D.
Brewster has shown) upon the striation of its surface with a series of
grooved lines, which usually run. nearly parallel to each other.
6
"As these lines are not obliterated by any amount of polishing, it is
obvious that their presence depends upon something peculiar in the
texture of this substance, and not upon any mere superficial arrange-
ment. But when the nacre is treated with dilute acid, so as to dissolve
its calcareous portion, no such repetition of membranous layers is to be
found; on the contrary, if the piece of nacre be the product of one act
of shell-formation, there is but a single layer of membrane. This
layer, however, is found to present a more or less folded or plaited
arrangement, and the lineation of the nacreous surface may perhaps
be thus accounted for. A similar arrangement is found in pearls,
which are rounded concretions projecting from the inner surface of
the shells of Avicula and possessing a nacreous structure correspond-
ing to that of mother-of-pearl.' Such concretions are found in
many other shells, especially the fresh-water mussels, Unio and Ano-
don, but these are usually less remarkable for their pearly lustre ;
and when formed at the edge of the valve, they may be partly, or
even entirely, made up of the prismatic substance of the external
layer, and may be, consequently, altogether destitute of the pearly
character. In all the genera of the Margaritace we find the exter-
nal layer of the shell prismatic and of considerable thickness, the
internal layer being nacreous. But it is only in the shells of a few fam-
ilies of bivalves that the combination of organic with mineral compo-
nents is seen in the same distinct form, and these families are for the
most part nearly allied to Pinna. In the Unionidae (or fresh-water
mussels) nearly the whole thickness of the shell is made up of the inter-
nal, or nacreous,' layer; but a uniform stratum of prismatic substance
is always found between the nacre and the periostracum, really consti-
tuting the inner layer of the latter, the outer being simply horny."
The nacreous layer of the shell is found upon the inner side, next to
the formative layer, and, being polished, protects the shell against the
action of any pathological condition which may occur in the body of
the mollusk. The cortical, or nacreous, layer of enamel is also found
next to the formative layer. They are both the last-formed products
of the formative organ. The polished surface of enamel also protects
it against pathological conditions which may arise in the surroundings
of the tooth.
delig
As we have seen, the shell is secreted above the infant layer of the
rete Malpighii. By referring to the section on the development of the
ameloblasts it will be seen that the bulbous cord invaginates itself, and
thus forms a double cap for the dentinal papilla. By this invagination
the ends of the cells, which were external in the bulbous cord, come in
600
DENTAL EMBRYOLOGY AND HISTOLOGY.
contact with the outer surface of the papilla. Now, the enamel is
deposited, or secreted, from these lower, or deeper, ends of the amelo-
blasts; the prismatic layer found in shells, on the other hand, is secreted
from the upper ends of the cells. If enamel were secreted in a similar
manner, the ameloblasts would be situated between the forming enamel
and the dentine; which is not the case.
The mineralizing constituents of enamel vary considerably from those
of shells. The amount of organic material found in shells is also far
greater than that of enamel.
Whether there is less protoplasm shed out from the under side of the
cells than from the upper, and whether the mineral ingredients which
go to form enamel-prisms do not enter into combination with the pro-
toplasm as readily as do those of shells and bone, are points which
I am not able to prove. It is certain, however, that there is found
in enamel only a very small per cent. of fixed material.
I use the term fixed material to designate protoplasm which has passed
into a state where it requires to be digested by and through the action
of the living principle which is found in the non-fixed material. It is
the "formed material" of Beale, and in this particular instance it is also
the "calcoglobulin" of Mr. Rainey.
According to different chemical analyses, the amount of fixed material
found in enamel varies from 1 to 3 per cent.; it is only demonstrable
by chemical analysis. There is not a sufficient quantity of this mate-
rial to be demonstrated by the microscope, as no trace of a matrix can
be seen after decalcification. I doubt if there enters into the formation
of enamel, as a necessary constituent part, the least trace of protoplasm
or organic material. It would be very difficult indeed to obtain a por-
tion of enamel for chemical analysis which would not contain some
"organic material," using the term as in contradistinction to inorganic.
I much prefer the use of fixed or formed material, for I think it has
been pretty conclusively shown that organic, or living, matter cannot
enter into chemical combination with inorganic matter, as such, except
the living lose its living principle and become non-living (fixed or
formed material). When we consider the fact that enamel is devel-
oped in and surrounded by organic matter, that it frequently encapsules
a greater or less amount, and that the fibres of the dentine interdigitate
with the enamel-prisms, it does not seem at all strange that analysis
should show from 1 to 3 per cent. of "organic" material which has
passed into formed material: a contrary result would be the more
surprising.
If dilute acids are allowed to act upon shells, the salts of calcium
which form the prisms are dissolved, leaving a matrix of fixed mate-
rial (calcoglobulin). The interprismatic or fixed material is insoluble
in acids; the latter only serve to harden and preserve the former.
This interprismatic cement-substance surrounds the prisms as a sheath,
and cross-sections of decalcified shells plainly demonstrate its existence.
(See Fig. 333.)
When enamel is acted upon by dilute chromic acid for a short time,
the interprismatic cement-substance is dissolved out and the prisms fall
apart and remain unchanged, thus demonstrating that the material
AMELIFICATION.
601
which holds the prisms together is more freely soluble in this acid than
are the prisms themselves, being just the reverse of what we have seen
in decalcification of shells by dilute acids. Then, again, when, through
disintegration, the organic material of shells is destroyed, the prisms are
released and fall apart. Such an occurrence in connection with enamel
is not known.
Regarding the striations found upon the enamel-prisms, I am fully
satisfied that they are caused by inequalities upon the surface of the
prisms. I submitted this question to Mr. Christian Febiger of Wil-
mington, Delaware, who is perhaps the best authority in this country
upon Diatomaceae. It is well known that in the study of diatoms the
very greatest nicety of judgment is necessary in order to differentiate
between such points as the one in hand, and the opinion of an expert
microscopist like Mr. Febiger should have a very considerable weight.
He said, without hesitancy, after studying a ground-section of enamel in
which the markings showed quite plainly, that they were wave-lines,
due, not to striations or interlacing fibres, but to inequalities upon the
surface of the section. The section examined had been placed for a
very short time in a dilute solution of muriatic acid and then washed
and mounted in glycerin. By this method the markings show better
than by any other I have used. The accompanying figure shows this
FIG. 336.
213
Marble
AMER
WILTIRAND
A
B
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153
HEADER LE
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ENERS
B
22
J


Enamel-Prisms (350 diameters): A, fragments and single fibres of the enamel isolated by the action
of hydrochloric acid; B, surface of a small fragment of enamel, showing the hexagonal ends of
the fibres.
appearance very accurately. Mr. Tomes has advanced substantially the
same opinion; he says:
"In perfectly healthy human enamel the fibrillar arrangement is not
so very strongly marked; the prisms are solid, are apparently in abso-
lute contact with one another, without intervening substance.
"But Bödecker, basing his conclusions upon the examination of thin
sections stained with chloride of gold, holds that enamel is built up of
columns of calcified substance between which minute spaces exist.
These are filled by a material which takes stain deeply and is probably
analogous to the cement-substance of epithelial formations. As seen in
602
DENTAL EMBRYOLOGY AND HISTOLOGY.
sections it gives off exceeding fine thorns, which apparently pierce the
prisms at right angles to their length; so that it forms a close network
very intimately mixed up with the calcified portion of the enamel.
،
"It is not of uniform thickness, but is beaded, and Bödecker attributes.
to it a rôle of far greater importance than that of a mere cementing sub-
stance, for he regards it as being an active protoplasmic network which
renders the enamel much more alive' than it has hitherto been con-
sidered to be. He believes it to become continuous with the soft con-
tents of the dentinal tubes through the medium of large masses of
protoplasmic matter found at the margins of the enamel and dentine.
6
"But although there are various reasons for suspecting that enamel is
not completely out of the pale of nutrition from the moment that a
tooth is cut, yet further observations are needed before the activity and
importance of the cement-substance demonstrated by Bödecker can be
held to be fully established. Klein remarks that the enamel-cells,
like all epithelial cells, being separated from one another by a homo-
geneous interstitial substance, it is clear that the remains of this sub-
stance must occur also between the enamel-prisms; in the enamel of a
developing tooth the interstitial substance is larger in amount than in
the fully-formed organ. It is improbable that nucleated protoplasmic
masses are contained in the interstitial substance of the enamel of a
fully-formed tooth, as is maintained quite recently by Bödecker.""
The first-formed layer of enamel is deposited in more or less proto-
plasm. This is proven by the fact that we can decalcify immature or
developing enamel up to a certain thickness, and yet have a matrix left.
This layer becomes more fully impregnated with lime salts, and the
later deposition, which adds to the length of the enamel-prisms, seems
to be laid down without any matricial substance.
This first-formed layer constitutes the zone in which the dentinal
fibres interdigitate with the enamel-prisms.
That points or spaces occur in enamel-the analogue of the inter-
globular spaces found in dentine-I fully believe; but such spaces are
filled with calcoglobulin, and not with living protoplasm. Any such
deviation is pathological, as it is in dentine.
Where these spaces occur upon the surface of the enamel, or so near
the surface that the thin layer can be easily broken through, they give
rise to the pitted or grooved points found in erupted teeth. The fixed
material is dissolved out by soluble ferments produced by the organic
tissue surrounding the erupting tooth. This fixed material is not solu-
ble in the ordinary acids of the mouth, and only disintegrates through
the action of soluble ferments and putrefactive processes. Regarding
the character of these fluids I refer to Dr. Black's article upon the
Pathology of Caries.
-
Variations in the hardness of enamel are due to several conditions,
some normal, others pathological. Normal variations are found in dif-
ferent temperaments and in different species. The enamel on the teeth
of rodents is much harder than that found upon the teeth of carnivorous
animals. Such variations are illustrations of the law of "adaptation to
environment," upon which so much stress is laid by some writers. This
I admit, but claim that the adaptative power existed from the beginning.
AMELIFICATION.
603
These variations are seen in shells, and from the analogy found in
their development I have no hesitancy in saying that variations in den-
sity of enamel are dependent upon the same conditions. Dr. Carpenter,
speaking of the varying degrees of density found in shells, says:
FIG. 337.
"This [increased] hardness appears to depend upon the mineral
arrangement of carbonate of lime; for, whilst in the prismatic and
ordinary nacreous layers this has the crys-
talline condition of calcite, it can be shown
in the hard shell of the Pholas to have the
arrangement of arragonite, the difference
between the two being evidenced by polar-
ized light. A very curious appearance is
presented by a section of a large hinge-
tooth of Myo-arenaria (Fig. 337), on
which the carbonate of lime seems to be
deposited in nodules that possess a crys-
talline structure resembling that of the
mineral termed wavelight. Approaches to
this curious arrangement are seen in many
other shells."

Variations in hardness of enamel may Section of Hinge-tooth of Myo-arenaria.
arise, as we have already indicated, by
reason of pathological conditions resulting from interglobular spaces,
which sometimes occur in enamel. The points are, without doubt,
analogous to such spaces found in dentine. I am even willing to
acknowledge that a condition corresponding to that found in shells.
may also be found in enamel-that is, an interprismatic matrix can be
formed; but if it should occur, it would be pathological in character.
I have ground many sections of teeth and examined many ground by
others, but have yet to see the first specimen of an interprismatic
matrix. That there is the least trace of organic interprismatic sub-
stance to be demonstrated in normal enamel I have very serious doubts,
and think the action of dilute acids upon fully-calcified enamel substan-
tiates the doubt.
Let us study such action.
A ground-section of mature enamel should be placed upon a slide
and a cover-glass cemented on, leaving a small opening on two sides.
If a 4th of 1 per cent. solution of chromic acid be allowed to run under
the cover by capillary attraction and then removed from the other side
by blotting-paper, we can study the action of the acid upon the stage
of the microscope with high powers.
But before we begin the study of the action of chromic acid on enamel
let us see how it acts upon organic tissues. It is considered one of the best
preservative fluids we have, and enters into the famous Müller's fluid,
which is noted for its quality of preserving nerve-tissue. Now, if there
is any organic substance in enamel, we shall be able to preserve it in good
form and note the result. The interprismatic substance is first attacked
by the acid and the prisms are liberated; chromate of calcium crystals
are formed in great numbers. If there existed an organic interpris-
matic cement-substance, the action of this dilute solution of chromic acid
604
DENTAL EMBRYOLOGY AND HISTOLOGY.
would tend to preserve it, and the prisms would be held together more
firmly than before. After the acid has been allowed to act fifteen min-
utes it is displaced by distilled water and pressure made upon the cover-
glass, when the prisms fall apart. They may now be easily examined
even with very high powers.
S
If we substitute a solution of HCl (muriatic acid) for the chromic-
acid solution, and of similar strength, we know that the organic tissues
will be destroyed by its action. If there is any organic tissue cementing
the prisms together, we should certainly be able to demonstrate it here;
for the organic substance would be dissolved out and the prisms lib-
erated. But is such the case? Far from it. The acid acts upon the
enamel evenly as regards its penetration from the free margin; it dis-
solves the peripheral portion a little faster than it does the body of the
prism, so that they present a somewhat dentated border along the exter-
nal, or outer, surface of the enamel; but the whole mass gradually melts
away before the action of the acid, not leaving the least trace of organic,
or fixed, material behind, as in the decalcification of bone where the
same acid is used. The fixed material, or calcoglobulin, as we have
seen, is insoluble in acids; hence, if enamel were calcified-as is bone-
by deposition in the albuminous intercellular substance, we should by
both of the above methods have the matrix remaining after decalcifica-
tion.
S
midag
In my experiments I have taken every precaution against failure. I
have embedded ground-sections of teeth fresh from the mouth in cel-
loidin and fixed them upon a slide, taking care to cut the outlines of the
teeth upon the reverse side of the slide with a diamond. After observ-
ing these precautions, I allowed a of 1 per cent. solution to flow under
the cover-glass, and noted the result by placing the slide upon the stage
of the microscope; but I have never been able to see any reticular sub-
stance after decalcification. I have also stained sections without being
able to demonstrate any matrix. Such a basis-substance could not by
any means have been lost or destroyed; the celloidin served as a perfect
embedding mass, and was not acted upon by the acids in the least
degree, neither did it hinder the process of staining; for it is well
known to be more permeable to stains than tissue itself.
I took all these precautions because my observations regarding the
action of acids upon enamel are not in accord with those held by C.
Tomes and others, and I consider this a very essential point to estab-
lish accurately. Mr. Tomes does not state whether his experiments
were made upon mature or developing enamel, but from the cuts he
furnishes one would infer that his studies were made upon mature
tissues, as it is not possible to demonstrate isolated prisms-especially
striated prisms—until calcification is completed, or nearly so.
1
Then, again, Mr. Tomes speaks of the above-mentioned cut as fol-
lows: "The accompanying figure, taken from enamel softened by
prolonged maceration in a 1 per cent. solution of chromic acid, shows
this well," etc. There is a mistake somewhere. Either Mr. Tomes's
1 per cent. solution of chromic acid is a great deal weaker than the one
I use, or else English teeth decalcify, more slowly than American teeth;
¹ Tomes's Dental Anatomy, p. 51.
AMELIFICATION.
605
"
for I have found that the action of a 1-per-cent. solution of chromic
acid, even when not prolonged, results in complete decalcification and
removal of the entire enamel-covering of a tooth. Again, Mr. Tomes
says: "If dilute hydrochloric acid be applied to a section of enamel,
the axial parts of the fibres (prisms) are first attacked, and are dissolved
away; so that if the section be transverse a fenestrated mass remains."
I think this phenomenon is capable of an opposite interpretation. If
we carefully study sections of enamel ground in the direction of the axis
of the prisms which have been exposed to the action of a very dilute
solution (of HCl), we find that the edge is dentated, and that the light
lines which mark the sides of the prisms end in the bottom of the inden-
tations, thus clearly demonstrating that the action of the acid is slightly
more rapid upon the peripheral than upon the axial portion of the
prism.
The next statement made by Mr. Tomes I can fully substantiate. It
is as follows: "During the formation of enamel the hardening salts are
deposited first in (around) the periphery of the enamel-cells; so that the
youngest layer of enamel is full of holes, each one of which corresponds
to the centre of a fibre (prism)." This I have observed as a constantly-
occurring phenomenon, and consider it as thoroughly substantiating my
position that the enamel-cell, or ameloblast, superintends the deposition
of the enamel-prism, and does not become directly calcified, as is held
by Mr. Tomes.
.
G
I look upon enamel as nothing more or less than a coat of mail sup-
plied by Nature to protect the dentine and subserve the processes of
mastication. The presence of any considerable organic material in the
enamel would be directly against the proper fulfilment of its office.
Nature, when left to herself, develops a beautiful and symmetrical
object perfectly capable of subserving its purpose, and any deviation
from this standard is classed under the head of pathological conditions.
The fluids of the mouth are normally alkaline or neutral, and against the
action of such conditions of the saliva the constituent parts of enamel
are proof. The enamel is not proof, however, against the action of
acids; neither, indeed, was it intended to be.
The cross-striations found upon enamel-prisms as well as upon the
prisms of shells indicate the manner of their development-i. e. by
addition in length. This also accounts for the layers of pigment some-
times seen in these structures. They follow the course of the striated
lines, and are undoubtedly laid down at varying times in the course of
the formation of the prisms. The pigment seen in enamel is deposited by
the ameloblasts. Experiments have been made of feeding young guinea-
pigs upon madder, then allowing some time to elapse, after which the
madder diet is resumed. When killed and the tissues studied, the mad-
der dye was found to be deposited in bands or layers in the bone which
was developed while the experiment was being carried on. The bands
of unstained bone lying between the layers which had been colored by
the dye represented the period which had elapsed between the different
experiments. It was found that the width of the bands was entirely
under the control of the experimenter, thus conclusively proving that
the pigmentation was from within, and that it was secreted by the bone-
PAN
Ma
606
DENTAL EMBRYOLOGY AND HISTOLOGY.
cells. I have no doubt that if the enamel had been examined it would
have shown a similar arrangement.
The amount of pigment found in enamel varies very considerably in
different animals, and generally bears a close relation to the density of
the enamel; but whether it has any influence upon the hardness or not
I am unable to say. Those teeth which have the greatest amount of
pigment have the most compact formation, and vice versa. Pigmenta-
tion after eruption comes from without and may be due to various
causes the use of tobacco is the most probable source of external pig-
mentation. The interprismatic cement-substance becomes dissolved by
the acids of the mouth to a greater or less depth, and the pigment
lodges in the spaces so formed, also coating the surface.
This pigmentation must not be confounded with the change in the
color of the enamel which results from death of the pulp. In a vast
majority of cases the enamel in human teeth, by reason of its translucency,
transmits the varying changes in the color of the dentine. That there
is no pigmentation of enamel itself in these cases may be proved by cut-
ting out the underlying dentine and filling with chloride of zinc or some
other white filling. Indeed, this mode of "mechanical bleaching" has
come into almost general practice.
na
This naturally brings us to the consideration of the dense polished
outer coat of enamel.
This layer shows a distinct characteristic variation from the prismatic
layer underneath. It is the outer capping of the prisms, and furnishes
a polished surface for the coat of mail which is best adapted for its
office. Smooth, polished surfaces are known to resist the eroding action
of acids longer than rough surfaces. The character and shape of the
ameloblasts change before this layer is formed. From a membrane
composed of prismatic cells, they now assume a horizontal direction.
I have studied these changes in the form and direction of the axis of
the ameloblasts in sections of incisor teeth of rodents, where it was
very plainly shown. Enamel is here being continuously formed on the
labial side, at the base of the tooth, to supply loss by attrition. All
the stages of calcification, as well as the changes which occur in the
ameloblasts, are plainly demonstrated in one tooth. Below a certain
point the enamel-prisms are yet unfinished, and here the ameloblasts
are seen to be prismatic in form; toward the surface they gradually
shorten and widen until near the margin of the gum, when they change
from a position at right angles with the axis of the tooth to a longitu-
dinal direction. Mrs. Emily Whitman also noted these changes in
studying the development of the teeth in the ray and rabbit. Mrs.
Whitman says:
.
"The cuticula of the mammalian tooth has several times been found
to have the same structure, and it has been possible, in transverse and
longitudinal sections, to trace the gradual transition of the enamel-cells
into a perfectly homogeneous membrane (Fig. 338), the cylindrical cells
growing shorter as they approach the crown of the tooth, until, instead
of being columnar, they are almost square, and finally flattened, and
at last the outlines of the cells quite disappear, and there is left a
perfectly homogeneous membrane.
Kateg
AMELIFICATION.
607
ег
"These changes are not easy to follow; in many preparations it is
impossible to make anything out, and the drawings have been made
from most fortunate preparations selected from some thousands of
sections prepared in various ways.
"The cuticula dentis, then, is formed by the metamorphosis of more
or less of the enamel-cells, and this metamorphosis may begin before
FIG. 338.
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A portion of a Longitudinal Vertical Section of the Upper Small Incisor of a Rabbit: em, 1, 2, 3, 4, 5,
are cells of the enamel-membrane drawn at intervals, showing their gradual change as they
approach the crown of the tooth, until, on its exposed portion, they form a homogeneous mem-
brane. Obj. F. Zeiss.
،
any calcification of the underlying dental tissues. In this stage it has
been frequently taken for the 'newly-formed layer of enamel,' for the
'basement-membrane,' and for the first-formed layer of dentine.""
It is evident that if the prisms depend upon the shape of the amelo-
blasts for their form the lime salts laid down from this altered mem-
brane would differ materially from the secretion from the ends of the
prismatic ameloblasts, and so we find it.
The analogy between the internal layer of the Pinna, which we have
before studied, and the outer layer of enamel, is complete. Each
individual prism of enamel is the work of a single ameloblast; the
ama
608
DENTAL EMBRYOLOGY AND HISTOLOGY.
outer layer of enamel, however, is secreted by the cuticula dentis
before the tooth erupts.
The origin and office of Nasmyth's membrane, or cuticula dentis,
has been a matter of very considerable speculation. I am fully con-
vinced, from a study of the teeth of rodents, that this membrane arises.
by a metamorphosis of the ameloblastic layer as described by Mrs. Whit-
man, and I further believe that the change in the character of this mem-
brane is of prime importance in the development of enamel. We have
seen that the enamel-prisms derive their form from the prismatic amelo-
blasts. This being the case, the ameloblastic layer, as such, could not
complete the calcification of the cortical layer of enamel. This layer is
deposited underneath the cuticula dentis, and in its deposition the life-
work of this membrane is completed; for it cannot be shown to have
any other essential signification. In a newly-erupted tooth the enamel
may be divided into three layers-the internal, or prismatic; the corti-
cal, or nacreous; and the organic layer, or cuticula dentis.
FIG. 339.
d.
Diagrammatic Section of Enamel and Dentine: d, dentine; em, enamel prisms; nl, nacreous layer;
ct, cuticula dentis.
Calcium phosphate and fluoride
Calcium carbonate
Magnesium phosphate
Other salts
Cartilage
Fat..
In the nacreous, or cortical, layer we have a structure analogous in
formation and character to the internal, or nacreous, layer found in
shells. The latter has been conclusively demonstrated by Dr. Car-
penter to be secreted by the altered layer of cells which produced the
older prismatic layer. The cuticula dentis corresponds to the mem-
brane described by Dr. Carpenter as found in connection with the
nacreous layer of shells.
Organic .
Inorganic
URME
Variations in density in the enamel of the teeth of different individ-
uals are due to several causes. The first essential difference lies in the
proportionate amounts of phosphate and carbonate of calcium. Enamel
in which there is more than a minimum amount of calcium carbonate
will be softer than enamel which contains less-the deficiency being
supplied by phosphate of calcium-and vice versa, as will be seen from
the following table, made by Von Bibra:
·
em.
•
nl. ct.

•
•
•
ป
Adult
man.
89.82
4.37
1.34
.88
3.39
.20
3.59
96.41
Adult
woman.
81.83
8.88
2.55
.97
5.97
a trace.
5.97
94.03
It will be seen by the above table that the essential point of difference
between the enamel of man and woman lies in the contained amount
AMELIFICATION.
609
of carbonate and phosphate of calcium. It is a well-known fact that,
as a rule, the teeth of women are softer than those of men; this, I think,
is accounted for by the greater per cent. of carbonate salts of calcium,
being 4.37 in man and 8.88 in woman.
There is also found more
organic," or fixed, material in the teeth of woman than in man—5.97
in the former, as against 3.59 in the latter. We have already seen that
in that degree in which enamel contains fixed, or organic, material is it
incapable of performing its office and resisting the action of the fluids
of the mouth.
46
Dr. Miller of Berlin has very conclusively shown that the products
of fermentation have the power of digesting the fixed material found in
dentine; they therefore would act upon any similar material found in
enamel. But, as I have said before, any considerable amount of fixed,
or organic, material in enamel is pathological, and enamel that contains
such material will be found to decay very early in life.
The newly-erupted tooth hardens by desiccation after it makes its
appearance. The saliva found in a child's mouth is neutral or, more
generally, alkaline. The latter condition probably extracts water from
the enamel. The teeth are constantly exposed to currents of air, which
certainly extract water. This is fully demonstrated by the checking of
the enamel in the mouths of persons who habitually breathe through the
mouth. The fact that the enamel of teeth which have been extracted
for some time becomes so hard that it will turn the edges of our best
burrs proves the correctness of my assertion, that enamel hardens by
desiccation.
A crystallized substance of the character which we are studying
cannot become denser than it is except by giving up a portion of its
water of crystallization. Crystallized bodies vary in density, but the
variation is due to the different forms of crystallization of the several
ingredients which go to make up the body. When crystals give up a
part of their water of crystalization they become exceedingly brittle.
Now, enamel is not a pure crystallized product, but, nevertheless,
evinces this same property to a considerable extent; you can chip the
thin edge of the enamel in the artificially dried tooth very easily by
slight pressure of the thumb-nail. I know of no law by which a
crystal once formed can become denser except by the one already
named-viz. that of desiccation. I know it is a popular idea among
dentists that enamel varies in hardness at different times, but I have
never seen a case where I was fully convinced that enamel once softened
by the acids of the mouth ever became harder, except, it might be, by
desiccation. I have seen children's teeth which were quite soft when
erupted become harder in time, and by the use of tooth-powders; but
whether it was the powder or the time-which latter allowed of desic-
cation-is an open question. I am in favor of crediting the latter
with accomplishing the benefit. I have been in the habit of using
powder dry, and so advising my patients. I have no doubt that, so
used, it will extract water from the enamel and hasten the hardening
process.
The enamel of teeth which have given up a portion of their water
of crystallization do not resorb it and return to their former condition.
VOL. I.-39.
610
DENTAL EMBRYOLOGY AND HISTOLOGY.
When it has become checked by constant breathing through the mouth,
it always remains checked. Then, again, I have no doubt that teeth
the enamel of which has softened during pregnancy, for instance
-may appear to harden; but in such cases the softening has been
superficial, and this thin layer, by the processes of attrition, becomes
worn away, and the underlying layer of enamel, which has not been
affected, becomes polished and cannot be told from the outer layer by
ordinary observation.
Finally, then, enamel is the product of an organ which in the erup-
tion of the tooth ceases to exist, and which, if it does remain, is lifted
by the eruption beyond the source of nutrient supply and cannot there-
after exercise any influence over the physical condition of the enamel.
The many varieties of calcified tissues are due to the variations in the
form and nature of the matrices and the conditions and positions in
which the lime salts are laid down. They are not dependent upon any
variation or special vital function exerted upon the crystallizing prod-
ucts, but are due to the form of crystallization and the special salts of
calcium which enter into their formation. I do not think that the
theory advanced that secondary changes do occur in enamel by recrys-
tallization can be demonstrated.
DEVELOPMENT OF THE TEETH.
It is with the feeling that no easy task lies before me that I enter
upon this section. Frey has well said that tooth-development is the
most difficult subject that embryologists are called upon to demonstrate.
The study of developing hair and glands is comparatively simple, and
calcified products alone do not seem intricate; but when we approach
the consideration of both these conditions in one structure, we seem to
stand before an unfathomable mystery. It is only as we approach the
problem from the standpoint of general histology that we get anything
like a full and true interpretation of the phenomena of tooth-devel-
opment. A microscopic examination of the intimate tissue concerned
in tooth-development led to the discovery that the teeth are developed
in the mucous membrane; that, instead of standing in close relation to
the bony skeleton of the body, they are a part of its outer, or dermal,
system; that they are developed in a similar manner to hair, nails, glands,
etc., by a process of involution. Besides conducting us to new truths
concerning the nature and constitution of the teeth, the microscope has
shown us how to apply this knowledge in a better system of hygienic
rules which aim at rendering their decay less rapid, their life more
vigorous, and their loss less frequent.
All who wish successfully to prosecute pathological inquiries regard-
ing decay of the teeth will do well to acquaint themselves not only with
the histological character of the teeth of the human subject, but with
that of some of the lower animals.
I have compared tooth-development in the human with that found
in embryo pigs, calves, and lambs, and find that the porcine embryo
varies very little from the human. Pig embryos are so easily obtained,
and in any size desired. that I am confident that they will come to be
THE EMBRYONAL MUCOUS MEMBRANE OF THE MOUTH. 611
almost universally used to demonstrate the subject under consideration.
I furnish them to my classes, and allow them to harden and cut them
at will.
The very early stages of development have been the ones over which
so much misunderstanding has arisen, and these differences of opinion
have largely resulted from a study of poor specimens. By obtaining
good specimens from porcine embryos these difficulties can be obviated.
The late advance in our knowledge of this subject is due to new
technique in methods of staining and section-cutting, especially the
introduction of celloidin, by means of which we have been able to obtain
sections of human teeth that had progressed even as far as the eighth
month, and teeth of other animals of corresponding age, without disturb-
ing the relationship of the parts.
Before the introduction of celloidin into our technique it was not
possible to obtain sections of jaws with teeth in situ without more or
less mutilation, especially if calcification had proceeded to any consid-
erable extent; by its aid I have been able to preserve a serial line
of slides without break or tear in the sections employed. And,
further, the illustrations made by the new process of photolithograph-
ing have enabled me to eliminate the much-tabooed "personal equa-
tion" which accompanies wood-cuts. Whatever may be said against
photomicrography in its delineation of cell-structure, surely no excep-
tion can be taken to it as a delineator of the outlines of organs or
structures like the developing tooth. It gives an accurate picture,
upon whose exact amplification we can rely.
I have taken my illustrations from serial lines of porcine embryos,
referring to the corresponding ages in the human foetus as I proceed,
believing that it is better to describe those specimens which are best pre-
served and of which I have been able to make good photomicrographs
than to use human foetuses less perfectly preserved.
T
THE EMBRYONAL MUCOUS MEMBRANE OF THE MOUTH.
There exists a great lack of agreement among writers on dental
embryology regarding terms and descriptions of the mucous mem-
brane of the mouth during the evolution of the teeth. It must be
remembered at the outset that the membrane itself is in a formative
state and presents different aspects in the several stages. The most
marked changes are seen in the epithelial layer. This is analogous
and continuous with the skin covering the body, as I have taken
occasion to show in presenting the development of the oral cavity.
There is, however, one point of difference between the two, due to the
widely different conditions in which they are located. The external
covering of the body is constantly subject to the drying action of the
atmosphere, which produces the corneous layer. The sweat-glands, to
a greater or less extent, keep the skin moist, but not sufficiently so
to prevent desiccation. The oral mucous membrane is at all times
bathed by the saliva, which prevents it from assuming the corneous
appearance seen in the outer covering of the body. The same may
be said of the rectum and vagina: were the conditions of the mem-
612
DENTAL EMBRYOLOGY AND HISTOLOGY.
branes the same as those of the skin, we would find an analogous
condition in the oldest layer of cells. As proof of the latter state-
ment I cite the following case, to which my attention was called some
time ago—a chronic case of procidentia of over two years' standing;


Mucous membrane.
Embryonal Mucous Membrane.
Epidermis.
Dermis.
Older layer.
Infant layer.
Mature Mucous Mombrane.
Embryonal connective
tissue.
Oldest layer.
Older layer.
MAJ
Infant layer.
LOT ARE A The go ba
Basement-membrane.
La Vang
Corneous layer.
Skin.
- ma cha
dana geleden » PREZATAI
Older layer.
Infant layer.
April
Callagha
Papillary layer of mem- Papillary layer of
brana mucosa.
dermis.
Sub-mucosa.
Subdermis.
pighii.
Rete Mal-
The above diagram shows a comparison between the developing mucous membrane, mature mucous
membrane, and skin. Between the epidermis and dermis lies the division-line commonly called
the "basement-membrane."
the mucous membrane of the vagina was turned completely inside out,
and for that length of time had been exposed to the external atmosphere.
The most careful examination, except for the absence of hairs, could
not elicit any difference between that which was formerly the lining
FIG. 340.

Ot.
ep.
Porcine Embryo (1— cm. in length, × 250): ct, connective tissue of mesoblast; ep, epiblast, formed of
one layer of cells.
membrane of the vagina and the skin covering any other portion of
the body. Here we have a positive demonstration that the difference
between the mucous membrane of the vagina and the skin is one of
environment, and not a physiological difference, and does not neces-
sitate a different classification. If the terms which appeared first in
THE EMBRYONAL MUCOUS MEMBRANE OF THE MOUTH. 613
Dean's translation of Legro's and Magitot's Dental Follicle-viz.
infant, older, and oldest layers-come to be adopted, it will very con-
siderably simplify our terminology and materially assist the student
to a comprehension of the subject. The table on p. 612 will
help to disabuse these terms of their intricacies, and to show a com-
parison between the developing mucous membrane as seen at the com-
mencement of the formation of the band, the mature mucous membrane,
and the skin.
The developing mucous membrane, as shown by the following serial
studies from photomicrographs, will exhibit very plainly the changes
which it undergoes. The first one (Fig. 340), taken from a porcine
embryo 1-cm. in length, shows the epithelial layer to consist of a
single layer of cells. Considerable space is seen between the cells,
which consist simply of nuclei lying in a bed of protoplasm; they
are oval, with their longest axis placed longitudinally and parallel
with the basement-membrane.
FIG. 341.
The next one in the series (pig 1 cm.) indicates that rapid cell-
multiplication is proceeding. The mucous membrane has thickened,
and is now formed of several
layers of spheroidal cells-not
arranged in strata, but pre-
senting an irregular adjust-
ment, in some instances several
cells deep. These cells have
not differentiated any cell-body
or wall, but, like those before
seen, are still located in a bed of
protoplasm. This constitutes
the infant, or deepest, layer of
the rete Malpighii.

ep.
In the next specimen (porcine
embryo 21 cm. in length) in the
region of the band the epithelial
layer is perceptibly thickened,
and in such a manner as to
depress the underlying tissue
and fill the groove thus made.
This figure is presented here to show that at the very inception of the
formative process there is no appearance of columnar cells in the deep-
est layer of the rete Malpighii, as has been so extensively stated by
other authors. The character of the cells of the infant layer has not
changed; there has simply been an aggregation of nuclei along the line
of the forming band, which is the result of such accumulation.
In the next of our series (pig 3 cm.) a noticeable change is seen: cell-
multiplication is rapidly progressing and the mucous membrane is con-
siderably thickened. The infant layer is as well marked as before; the
cells are of a similar character, nuclei lying in a bed of protoplasm, per-
haps a little more closely packed, thus giving the infant layer a darker
appearance. This is now made more noticeable by the fact that above
the infant layer a second layer of cells is seen, forming an older layer,
Lot.
Porcine Embryo (13 cm. X 250): ep, epithelium, in-
fant layer; et, embryonal connective tissue with
large intercellular interspaces.
K
614
DENTAL EMBRYOLOGY AND HISTOLOGY.
the cells of which, in being pushed up from the infant layer, have car-
ried a certain amount of protoplasm with them, surrounding each cell.
A marked difference is seen between this protoplasm, which surrounds
the nuclei of the older layer, and that surrounding the nuclei of the
infant layer. In the latter case, with hæmotoxylon and eosin, it stains
very readily and darkly, while in the former it appears as an un-
stained mass surrounding the nucleus. The nucleus is the germinal
matter, while the unstained mass surrounding it is the formed material
(Beale). The nucleus and the formed material constitute what is com-
monly known as a cell.
ер
These cells are surrounded by a certain quantity of protoplasm, which
stains darkly, as does the intercellular protoplasm in the infant layer,
and forms the lines which appear in the older layer in Fig. 343. The
quantity of intercellular material decreases as we proceed toward the
FIG. 342.
f
ep
bcot
ww
ct.
g

Porcine Embryo (21 cm. X 250): b, region of band; ep, epithelium, infant layer; c, embryonal con-
nective tissue. The space between the two layers was produced by tearing the specimen
intentionally.
surface, and the quantity of formed material increases; so that the cells
grow larger. This surrounding formed material of the cell-body is, in
all probability, the undigested or unassimilated protoplasm from which
the germinal matter, or nucleus, draws its nourishment.
As we proceed in our examination of older embryos we find the cells
losing their well-defined outlines, until they assume the appearance
seen in Fig. 272, taken from a scraping of the tongue in an adult
human mouth. They constitute the oldest layer, are farthest removed
from the source of nutrition, and correspond to the corneous layer of
the skin.
For a description of the epithelium of the skin I cannot do better
than make several quotations:
"The epithelium constitutes the superficial layer of the skin. In
the adult tissue the epithelium is composed of two layers of cells-a
THE EMBRYONAL MUCOUS MEMBRANE OF THE MOUTH. 615
،
younger, which lies at the deepest portion, and an older, at the surface
-the outer or horny layer, consisting of very thin, transparent, tough,
scale-like cells, which present, for the most part, no nuclei and are
packed closely together; and the inner layer, the so-called mucous or
Malpighian layer, consisting of larger and smaller nucleated cells of
varying shape and character. In the deeper portion, adjoining the
corium, the cells are more or less cylindrical; above this they are sphe-
roidal or polyhedral or elongated; still nearer the surface they become
flattened, and finally merge into the thin cells of the horny layer.
the middle zone the cells present a peculiar jagged outline, looking as
if they were bordered by short, delicate spines, by which the cells.
appear dovetailed together. These spined cells-called prickle cells—
are very characteristic of this part of the epidermis, and are also found
In
FIG. 343.

-CD
9.
&
®
a)
D.)
ot.
il.
ct.
Vertical Section Mucous Membrane of Mouth (7 cm. porcine embryo X 250): ol, older layer of
cells; i, infant layer of cells; ct, connective tissue of mesoblast.
in certain other parts of the body where stratified epithelium occurs, as
in the vagina, mucous membrane of the mouth, etc."" (Prudden).
Then again:
"The mucous membrane [of the mouth] and the skin are ana-
tomically analogous and continuous structures. The first clothes the
internal and the other the external surface, and the description of the
one will, with slight modifications, apply to the other. In a general
sense, they are composed of two strata, or layers-the dermis and the
epidermis; yet, for convenience of description rather than for any other
reason, they have been variously subdivided. The external stratum, the
epidermis, composed entirely of epithelial cells, has been described as
consisting of two layers, the external being termed the corneous and the
616
DENTAL EMBRYOLOGY AND HISTOLOGY.
13
internal the Malpighian. The 'scarf-skin' raised on the external sur-
face of the skin by a blister and the pellicle detached from the palate
by hot drinks represent the corneous layer of the epidermis. By some
authors this is called the 'true epidermis,' and by some the 'cuticle.'
This layer is composed of the old epithelial cells which have ceased to
perform any of the vital functions. The subjacent layer, formed of
living epithelial cells which vary in form and size, is denominated
(among many terms) the stratum Malpighii'" (Dean's Dental Follicle).
These descriptions apply to adult tissues. Let us turn now to the
consideration of embryonal tissues, for it is with the latter that we have
to deal in the study of the development of the teeth.
DENTAL RIDGE.
I will first consider a section from the jaw of a porcine embryo 1
cm. (Fig. 341) in length; this compares in age with a human foetus of
four weeks. In the epiblastic layer which covers the gums is seen the
first indication of that cellular activity which later will result in the
evolution of the teeth. By comparing the epithelial covering of the
gums we shall see that it is composed of two or more layers of oval
cells which present evidences of active cell-multiplication, while the
same membrane upon the outer portion of the body is yet composed
of only one layer of cells. The thickening of the epithelial cov-
ering of the gums is at first general, and results in the formation of
a thick layer. The next change is not so much evidenced upon the
surface as it is in vertical sections of the jaws. The same cellular
activity which resulted in a general thickening of the epithelial cover-
ing of the gums now becomes centred along a line which marks the
crest of the gums and locates the line to be occupied by the future arch
of teeth. The multiplication of cells is found to be in the infant layer
of the rete Malpighii, or that layer which lies nearest the supply of
cell-pabulum that is furnished by the vessels located in the subepithe-
lial tissue. No vascular supply has ever been demonstrated in the
epithelia proper.
S
DA
Rapid cell-multiplication along the line just described results in a
thickening of the older layer of cells, giving rise to a slight ridge
higher in some embryos than in others. This ridge has been des-
ignated by Kölliker, Waldeyer, and Kallman as the Kieferwall, or
maxillary rampart.
Concomitant with the formation of the ridge, the proliferation of the
cells of the infant layer causes a depression of the subepithelial layer
lying immediately underneath. Were we to lift up this thickened
epithelial layer, it would leave behind a groove in the underlying
tissue; but let it be remembered that in lifting the ridge or rampart of
epithelial cells we have made the groove. It is never a ditch or groove
per se, but, when found, is always an artificial product which can be
made at will. As cell-multiplication advances this groove deepens,
taking a direction toward the centre of the arch.
1
To this groove filled with epithelial cells ¹ "Legro and Magitot have
¹ Dean's translation, Legro and Magitot.
DENTAL RIDGE.
617
given the name bourrelet, which means a rounded pad or cushion.
This structure was for a long time supposed to be cartilaginous in its
nature, and hence called cartilago dentalis, until Raschkow discovered
its epithelial character. M. Guillot (1859) named it the odontogenic
part, or the generating part, of the teeth."
The term band, which has been so universally adopted, while not
expressing the exact nature of the thickened layer of cells, yet when
modified by the adjective epithelial as nearly expresses the principal
characteristics as any other; and for lack of a better term we will use
it hereafter.
From the condition seen in a vertical section through the jaw of a 21
cm. porcine embryo, which compares with the human at from the forty-
fifth to the sixtieth day, as seen
in the accompanying photomi-
crograph (Fig. 344), the epithe-
lial band rapidly deepens by
cell-proliferation at the deepest
point. The centre of the lower
jaw is occupied by Meckel's
cartilage, and the axis of the
band assumes a direction which
would cause it to pass between
the cartilage and the inner side
of the jaw. Were such lines
continued in the same direction
from several points of the band,
they would converge to a given
FIG. 344.
B

1
ep
c.t
centre.
In vertical transverse sections
the band assumes a plough- Porcine Embryo (21 cm. X 60), inferior maxilla:
B, first stage in the formation of band; ep, epithe-
lium; ct, embryonal connective tissue.
share shape with the mould-
board side directed toward the
inner side of the jaw. This is shown very nicely in Fig. 345, taken
from a porcine embryo 2 cm. in length, which compares with a human
foetus of two and one-half months. The convex surface of the band is
toward the outer side of the jaw. This peculiar curve is almost univer-
sally seen, and constitutes one of the most characteristic and persistent
features of the band. The walls of the band are composed of the infant
layer of cells, while its centre is filled with the older cells, which have
been pushed off from the sides as new cells have been developed in the
infant layer. Note the fact-so plainly shown-that the deepest layer of
the rete Malpighii (infant layer) is not composed of columnar cells, but
of oval nuclei surrounded by a mass of protoplasm, which does not as
yet present any indication of separating into cell-body for each individ-
ual cell. When the nuclei are pushed up from this bed of protoplasm,
a certain amount of it accumulates around each nucleus and becomes the
cell-body, on the surface of which a cell-membrane soon becomes visible.
We have then a ditch or groove in the subepithelial tissue filled to over-
flowing with epithelial cells which by reason of their growth have formed
the groove in which they lie.
W
618
DENTAL EMBRYOLOGY AND HİSTOLOGY.
The band as seen in its inception is broad (Fig. 344), but as devel-
opment progresses and it sinks deeper into the jaw it becomes narrower,
as seen in Fig. 345. The band is deepest at the anterior portion of the
FIG. 345.
h
ep.
il
ct.
Vertical Section Band Porcine Embryo (23 cm. X 250): ep, epithelium with infant layer (il); b, band;
ct, connective tissue.
jaw, gradually growing shallower until it flattens out into the epithelial
covering of the gums. The sections here shown are taken from the
region of the premolars in the pig-first or second molars in the human
embryo. The band in the region of the incisors is considerably deeper
than at the point where the section from which this figure was made was
cut. Posteriorly it grows shallower, until it finally disappears.
Cellular activity increases rather than diminishes as age advances;
this activity evinces itself in that part of the band which is located
deepest in the tissues. The rapid multiplication of cells at this point.
causes the deepest edge of the band to become expanded, and as this
band sinks farther into the substance of the jaw this expanded por-
tion becomes indented its entire length through the resistance offered
by the underlying tissues. Thus a sheet, or lamina, is given off from
the inner side of the band.
There are two ways of demonstrating the formation of the lamina-
one by vertical transverse sections of the jaw, when at this age every
section cut will show the band as a W-shaped infolding of the infant
layer; whereas the previous figure (345), representing an earlier
stage in development, will show it to be V-shaped. Imagine a V-
shaped process by reason of multiplication of its contents becoming U-
shaped, and afterward, by indentation of the base of the process, becom-
ing W-shaped, and you have a fair illustration of the change which the
infolding epithelium assumes. (See Fig. 346, showing the W-shaped
band; b represents the outer base of the W, and is situated on the outer
side of the jaw and corresponds to the original V-shaped band-process;
!

DENTAL RIDGE.
619
7 is located on the inner side of the jaw, and is the internal sheet or
lamina which has arisen from b, as if a second V had been added to the
side of the first, thus forming the W-shaped process. These two pro-
cesses are termed the band and lamina. The latter is only a process of
the former.)
If we cut longitudinal transverse sections of both sides of the infe-
rior maxilla, we first obtain sections of the mucous membrane; later
we get sections horseshoe-shaped in form, the outer and inner edges of
which will show a layer of epithelium, the bulk of the section being
made up of embryonal connective tisue. Located equidistant from
either side we will see a band of epithelial cells which extends entirely
around the arch of the horseshoe-shaped section. Now, if such a sec-
ep.-
il-
ct
FIG. 346.

tare
c.t
b
7.
Porcine Embryo (3 cm. X 250): ep, epithelium with infant layer at il; ct, connective tissue; b, band;
l, lamina.
tion be made of the jaw of a 3 cm. pig, we will find that for a certain
distance from the surface our sections will appear as above described;
but as soon as we reach the deepest part of the ingrowing epithelial
processes we will find two (2) bands of epithelial cells instead of one,
thus showing that we have cut across the W-shaped processes known as
the band and lamina. Between the two bands the space is occupied by
embryonal connective tissue similar to that formed upon either side of
the bands, and forming the boundary of the section. We will find, as
before, on both outer and inner side, epithelium. (See Fig. 347, repre-
senting a section from one-half of such a horseshoe-shaped section.)
As we have seen, cellular activity is evidenced in the deepest portion
of the ingrowing processes. The lamina forms no exception. While
cell-proliferation apparently seems to come to a stand in the band, rapid
620
DENTAL EMBRYOLOGY AND HISTOLOGY.
cell-multiplication still proceeds in the lamina, which extends deeper
into the substance of the jaw.
Ha
FIG. 347.

@.t
b
c.t.
Longitudinal Transverse Section Inferior Maxilla (3 cm. porcine embryo X 40): b, band, solid at
anterior portion, but divided posteriorly into band and lamina.
As this change is being accomplished the band becomes somewhat
shallower and in some instances disappears, the more rapid growth of
the lamina apparently causing the straightening of the outer base of the
W, known as the band proper. When we consider that the lamina is
only an offshoot from the side of the band, it is very easy to understand
how the transferrence of development from one side of the band to the
other would give rise to the disappearance of the original process.
Development so far has been general in character. The band and
lamina have a common office, and that is to give origin and direction to
the cords for the temporary teeth. Individualization now begins. The
internal development of cells continues with unabated energy, express-
ing itself, not in the extension of the sheet, or lamina, but at regular
intervals which correspond to the positions to be occupied by the tem-
porary teeth. Here small buds make their appearance, and soon extend
into slender cords, each cord developing in time into the enamel organ
of a temporary tooth (Fig. 348).
The length of the cord varies in different mammals, those in
human and porcine embryos being quite short, while in the fœtal
calf and lamb it attains considerable length. The cords for the per-
manent teeth are of necessity longer than those for the temporary set,
DENTAL RIDGE.
621
having to descend beyond and beneath the latter. The cord is com-
posed of a solid ingrowth of the cells which constitute the lamina from
c.t
FIG. 348.

c.t.
c.t
Ct
Longitudinal Transverse Section of both sides of the Inferior Maxilla (3 cm. porcine embryo × 25):
b, band; c, cords for temporary central incisors; c, connective tissue, surrounded on its outer
circumference by a thick epiblastic layer.
which the cords arise. The lamina, as we have
band, and this in turn from the oral epithelium.
the latter, the infant layer, consti-
tutes the outer layer of the cord.
It is composed of oval or spherical
cells similar to those described in
studying the development of hair
and glands. These cells have been
very extensively spoken of as col-
umnar. They sometimes assume a
cylindrical shape when the layer is
only one cell deep; but if more
than one layer exist, then they are
universally oval or spherical. The
formation of the cord is very nicely
shown in Fig. 349.
b
seen, arose from the
The deepest layer of
FIG. 349.

e.p.
C
c.t.
The cells seen at c are the older
cells which have been pushed off
from the infant layer (d), which
forms the outer tunic of the cord.
The cords at first stood at right
angles to the inner side of the band,
having an axis similar to the direction of the plane of the lamina of which
Vertical Section through Band from Jaw of Por-
cine Embryo (31 cm. X 60): ep, epithelium; b,
band; c, cord; ct, connective tissue.
622
DENTAL EMBRYOLOGY AND HISTOLOGY.
they are an extension. They radiate to a common centre, and lines drawn
through their several axes would intersect each other in the centre of
FIG. 350.

il
c.t
PR
Du
L
201
Qwm
MAR
V
C
dr
2
01.
← (
ఇ)
3
*KÉ
:à
Ct.
شه
*3
ер.
Same as 349, only more highly magnified: b, band; c, cord; dr, dental ridge; ep, epithelium: et, con-
nective tissue.
base of the tongue, and are the lines referred to when speaking of the
direction assumed by the plane of the band in the first instance.
The cord soon turns sharply upon itself and dips more or less deeply
downward into the substance of the jaw. Internal proliferation of
cells results in the formation of a bulbous extremity, which I have
designated the bulbous cord. With these changes the cord is seen to be
becoming more deeply embedded in the substance of the jaw and curves.
in more and more toward the plane of the band, thus assuming a sickle
shape. (See Fig. 351.) The cord now very much resembles a Mattson
syringe with a short nozzle. The neck of the cord, which forms the
connecting-link between the bulbous part and the band, does not keep
pace with the deepest extremity in growth, assuming more and more the
character of a neck, and is very rightly named the neck of the enamel
organ.
A horizontal transverse section made of the jaw at this stage of devel-
opment will show a vertical transverse section of the cord lying beside
a longitudinal section of the band.
Studying sections from the jaw of a 34 cm. pig, we notice that the cord
has become pear-shaped, and the section presents the appearance of a stir-
rup. The flattening at the deepest portion is caused by contact with a new
element-viz. the dentinal papilla, which now presents a new feature
for our consideration.
The papilla which will constitute the future pulp of the tooth is, as
DENTAL RIDGE.
623
ep
il
ер
il
dp:
Z
ct
ct.
Vertical Section through Band and Cord of 34 cm. Porcine Embryo X 60: ep, epithelium with infant
layer (il); b, band; c, pear-shaped cord; d, dental papilla; c, connective tissue. In this cut the
walls of the cord are shown very plainly to be a continuation of the infant layer of the epithelium.
c.ct
FIG. 351.

FIG. 352.
NofC S.P
Any
ct

ep.
!!!
ot
it.
c.t.
oct.
d.p
Vertical Transverse Section through Jaw of Porcine Embryo (5 cm. X 60): N. of c., neck of cord for
enamel organ; ep, epithelium; il, infant layer; b, band; ot, outer tunic; i, inner tunic; ct, con-
nective tissue; dp, dental papilla; c. ct., condensed connective tissue forming follicular wall and
continuous with the periosteum.
we have before said, developed from the subepithelial connective tissue
of the jaw.
Its growth is upward, or gumward, while the growth of
the cord has been downward into the substance of the jaw. The com-
624
DENTAL EMBRYOLOGY AND HISTOLOGY.
bination of these two elements into one organ seems to fulfil the same
office as does fructification in the egg. New life is at once infused into
the tissue, and very rapid and material changes now occur. The process
of invagination sets in, by which the two tunics are formed.
FIG. 353.
A ready illustration of the process of invagination of the bulbous cord
is made by taking in one hand a syringe with an egg-shaped bulb, the
tube being attached to the small end.
Hold the tube between the first and
second fingers, the bulb lying in the
hand; with the end of the thumb of
the same hand press the large end of
the bulb until it comes in contact
with the small end. By this process
the larger end of the bulb is invagi-
nated in the upper, and that is what is
meant when we speak of the invagi-
nated cord. The cord invaginates
itself in a manner similar to intes-
tinal invagination. In this perfect
illustration of the manner in which
the two tunics are formed, your thumb
represents the dentinal papilla filling
the concave space in the enamel organ,
and the tube represents the neck of
enamel organ to the epithelial layer of
A

B

the cord which still connects the
the mouth.
G
Similar invaginative processes occur in the formation of the hair-bulb
and the glomeruli of the kidney.
As invagination progresses the older layer of cells, which occupy the
interspace between the walls of the invaginating canal, are seen to be
undergoing a marked change. The account given by Legro and Magitot
is so complete, and so conforms to my views upon the subject, that I can-
not do better than incorporate it into my manuscript. They say:
Jag
"If we now examine the composition of the enamel organ [at the
period of development represented in Fig. 354], say about the fifteenth
week of the human embryo, we find that the primitive elements (polyg-
onal cells, which occupy its central portion, and the [prismatic?] cor-
tical layer) have undergone notable modifications. We discover, in
fact, that the middle region of this organ is occupied by some elements
of a new form essentially differing in appearance from that of the orig-
inal cells. These are stellate bodies, composed of a central nucleus sur-
rounded by a transparent or finely-granulated mass, which ramifies and
inosculates with the neighboring elements. These star-shaped bodies
occupy at first only the centre of the enamel organ, those near the per-
iphery preserving their original polygonal form, but becoming stellate
in proportion as the dimensions of the organ increase. It will be
noticed, however, that the anastomosing processes are always much
longer and more ramified as the cells are situated nearer to the central
portion, while in the vicinity of the periphery it is somewhat difficult
to distinguish these processes, as they are here only rudimentary. The
And
Cand
DENTAL RIDGE.
625
elements thus described are immersed in a translucid amorphous mass
coagulable in acids and having the consistence and appearance of the
white of an egg.
These starred bodies or stellate cells, as they are
usually termed are formed directly at the expense of the polygonal
elements composing the internal mass of the enamel organ. The pro-
cess is as follows: The substance mentioned above interposes itself
little by little between these originally small polyhedral cells, and thus
their walls lose their mutual contact except at certain points where they
still cohere. As a direct result of this phenomenon the primitive polyg-
onal cells exhibit a number of depressions extending from their exterior
surface toward the centre, giving them their stellate appearance. From
this transformation the primitive cells would become entirely insulated
by the intervention of this new mucous formation were it not for these
connecting processes, which give to this organ, as a whole, its peculiar
reticulated appearance and to each cell its stellate form. It is a remark-
able fact that no line of juncture can be discovered where these cells
are connected with each other, the various reagents failing to disclose
the least trace of it, so effectually have these parts been cemented
together. According to this theory, the stellate arrangement of the
'pulp' of the enamel organ (the intimate composition of which we do
not propose to describe in this memoir) results from a simple modifica-
tion of the form of the primitive polygonal cells-a change which they
have undergone passively, as it were. These elements of the enamel
organ, notwithstanding their stellate form, must be regarded, therefore,
as absolutely epithelial in their nature. The mechanism of this trans-
formation, however, differs materially from that given by Kölliker, and
after him by several other anatomists, who contend that these prim-
itive cells might take this stellate form spontaneously. Our opinion,
however, is in conformity with that of Waldeyer, who was the first to
properly examine and describe this phenomenon, though Huxley at a
much earlier day had advanced the idea (hypothetically, it is true) that
the enamel organ had an epithelial origin; but he did not indicate
the mode whereby the transformation of its elements was affected."
The stratum intermedium of Hanover consists of those cells which
lie nearest the infant layer of the inner tunic. They have not become
stellate, as have the cells found nearer the central portion of the enamel
organ. They are younger than are the stellate cells. They have no
particular signification other than that which we assigned to them when
discussing the formation of the cuticula dentis. Nearer the central por-
tion of the enamel organ a more marked reticulation is seen in most
specimens.
MAD M
Satel
The vacuoled appearance of the interior of the enamel organs begins
in the central portion in the oldest layer of cells; the cells which lie
nearest the infant layer are the last to become affected. The change
does not occur uniformly, but in places here and there. This is shown
very nicely in the accompanying figure (354). The part from which
the cut was taken comprises that portion, including the inner tunic and
the overlying cells, situated immediately above the apex of the dentinal
papilla. The infant cells of the inner tunic are of the character before
described, no attempt having as yet been made upon the part of Nature
VOL. I.-40.
626
DENTAL EMBRYOLOGY AND HISTOLOGY.
to differentiate the ameloblastic layer. Although these cells occupy the
position where the first formation of enamel will make its appearance,
the older layer (ol), in the central part of the figure, remains unchanged,
the process of infiltration having not as yet begun. But on either side
of these unaltered cells, at sr, sr, the stellate cells are very plainly
shown. Between the stellate cells larger and smaller spaces occur.
This stellate appearance is largely due to post-mortem changes. The
actual spaces which occur between the stellate cells are chiefly the result
of shrinkage. If an osmic-acid solution (1 per cent.) and alcohol, equal
parts, be injected underneath the mucous membrane covering the jaws
of an 8 or 10 cm. pig while the embryo is yet warm, and then immersed
in a similar solution to harden, the post-mortem changes in the cells
will be to a greater or less extent arrested. If we lift the mucous
membrane from its bed after the tissue is sufficiently hardened, the
enamel organs will adhere and bring up with them their papillæ. The
•
Sr
FIG. 354.
ol
Sr
Lit.
Inner Tunic Enamel Organ Porcine Embryo (6 cm. × 250); it, inner tunic; ol, older layer; sr, sr,
stellate reticulum.
enamel organ is thus isolated from all surrounding calcified tissue, and
we are able, after embedding, to make sections without waiting for the
bone of the jaw to be decalcified, decalcification necessitating the use of
acids which will cause more or less change in the soft cells in the interior
of the enamel organ. The fibrillated condition of the stellate cells seen
in specimens hardened in Müller's fluid, chromic acid, etc. is demon-
strated, by the osmic-acid method, to be in reality a broad mesh. The
reticular appearance seen in the chromic-acid preparations results from
post-mortem shrinkage in the older cells which fill the interior of the
enamel organ. I fully believe that if we could examine these cells at
once, before any shrinkage occurs, we should be able to prove the fact
that in life they are not stellate, but large polygonal cells. I am led to
this inference by the above-noted experiments, the better methods of
technique showing a less fibrillated appearance than do other methods
which allow more shrinkage.
Sections of isolated enamel organs might be obtained by the freezing
method were it not for their minute size; if this could be done without
the use of any hardening fluids, better studies could be made. It is to
1

DENTAL RIDGE.
627
be remembered that the cells which occupy the central portion of the
enamel organ are the older cells which have been pushed off from the
sides by the development of the infant layer, which constitutes the
walls of the organ. The central mass of cells are thus enclosed in
a sac as are the cells of sebaceous glands. The latter, under this con-
dition, pass through a retrograde process and become, through fatty
degeneration, the oily material secreted by the glands. The cells of the
enamel organ become infiltrated by fluid instead of fat; this fluid is
freely soluble in the fluids which are used to harden the tissues. The
cells undergo a sort of retrograde process due to the abnormal confine-
ment between the tunics of the enamel organ, but not the same as that
found in the glands above referred to. The shrinkage due to the giv-
ing up of this water results in the stellate form they assume after death.
In the meshes of the stellate cells prepared by the osmic-acid method are
seen numerous minute granular bodies which have a high refractive
power; if a few drops of dilute nitric acid be put on the slide near the
edge of the cover-glass and allowed to run under by capillary attraction,
these granular bodies will disappear, and at the same time large numbers
of bubbles will accumulate and force themselves out from under the cover-
glass. In this experiment we have a positive demonstration of the pres-
ence of carbonate of lime in the meshes of the stellate cells of the fully-
developed enamel organ previous to the beginning of the process of
calcification of the enamel. These granules of lime do not appear in
sufficient quantity to result in completely-calcified tissue, but are held
in a state of suspension; as the meshes of the stellate reticulum shrink
the granules of lime are brought nearer together, and by approximation
stiffen the tissue. The presence of a non-shrinkable material in the
meshes of the stellate cells of the enamel organ accounts for the different
results, as regards shrinkage, in the preparation of tissues.
Previous to the beginning of development of the enamel we find little
or no shrinkage of the enamel organ during the hardening and decalci-
fying processes, provided the hardening is accomplished first. It is only
after the stellate cells have given up a portion of their lime salts, either
by forming enamel or by being decalcified before hardening, that any
considerable shrinkage occurs. The shrinkage in the first instance is
localized in that portion nearest the forming enamel; in the latter it is
general. The shrinkage on the part of the enamel organ, in any case,
is more apparent than real, the space formed by the separation of the
enamel from the ameloblasts being largely due to the greater shrinkage
of the dental pulp, which draws the formed dentine and enamel down
from the sides of the cone-shaped enamel organ. If the stellate reticu-
lum is, as has been stated, very rich in albumen, and does not contain
calcific material in large quantities, there would be a very great shrink-
age in preparation, due to the rapid taking up of its water by the acids
used in decalcifying, which is not the case previous to the commencement
of the formation of the enamel. But after calcification has begun and
the stellate reticulum has given up a portion of its lime salts, then more
or less shrinkage is noticed; or if decalcification is first accomplished
by hydrochloric acid, which has no hardening property, and the tissue
is afterward hardened in alcohol, we notice the same phenomenon,
•
628
DENTAL EMBRYOLOGY AND HISTOLOGY.
<
which is due to the same cause-viz. the giving up of its lime salts
previous to the coagulation of the albumen in the substance of the
tissue. Thus, I see in the stellate reticulum an essential agent in the
process of the formation of the enamel, and not a mere occupier of the
space to be taken by the formed enamel, as some would have us believe.
It is more. In the first place, it is the storehouse, so to speak, of the
calcific material from which the first-formed layer of enamel is derived.
Then, again, there is a very great difference in form between the enamel
organs of the centrals, cuspids, and molars in the same mouth; and
that this difference exists among the several classes of teeth, none will
dispute. From this I hold that the enamel organ is the matrix-former:
as the foetal femur is to the mature femur, so is the enamel organ to the
fully-developed tooth. They are the matrices that govern the form of
the fully-developed tissue-at least, in a general way in each can be
seen the type of the resulting product. The concave face of the enamel
organ gives form to the future tooth in the Carnivora by the dentine
forming against the inner ends of the ameloblasts. Sometimes the fibrils
of the odontoblasts penetrate between the ameloblasts, and we have as a
result an interlacing of the dentinal fibrils and the enamel-prisms. This
interlacing of the fibrils of the odontoblasts with the ameloblasts mil-
itates against the theory of a limiting membrane existing between them.
That this occurs before the process of calcification begins I have no
doubt, although I have not been able to demonstrate it. The forcing
of the soft fibrils of the odontoblasts between the calcified enamel-prisms
is impossible. I have a pathological section from a human incisor,
taken from the superior maxilla of a man who when he was four years
of age was kicked in the mouth by a horse and seriously injured.
When his permanent incisors erupted, they had furrows on their labial
and lingual faces, showing faulty development; into these furrows
horns of dentine projected fully one-half the thickness of the enamel.
The fissure in the enamel probably resulted from a displacement of the
ameloblasts at the time of the accident. Into the fissure thus formed
the fibrils of the odontoblasts projected, thus showing the tendency of
the odontoblasts to send out their fibrils until they meet an obstruction.
In normal development this obstruction is formed by the inner layer of
the enamel organ.
Much discussion has arisen regarding the nature of the union occur-
ring between the papilla and the enamel organ; there exists no intimate.
connection between the two surfaces other than that of perfect adapta-
tion to each other. Vessels or nerves have never been demonstrated
to pass from one to the other. The relation is analogous to that sus-
tained by the epithelium and dermal layers of the mucous membrane
of the oral cavity, from which they have their origin. As there is no
direct union between the two organs, enamel and dentine, so is there no
such union between their products. The enamel cap can be very easily
lifted from off the dentine cone, especially from an extracted tooth
which has been allowed to dry. The enamel and dentine separate very
readily at their line of union in teeth in situ when it becomes necessary
to remove the enamel cap for the application of bands for crowning
roots, thus demonstrating the lack of positive union between the two.
DENTAL RIDGE.
629
c.c.t..
Sections from the jaw of a 6 cm. pig show the process of invagination
farther advanced. The papilla, which originated as a microscopical
point, rapidly increases in size. It is made up of embryonal connective-
ct:
p
0,t
aru-
aw
FIG. 355.
n of C.

L
VIV
ep
il.
sr
sp
Jp
i. t. d.b
Vertical Transverse Section of Jaw of Porcine Embryo (6 cm. X 60): ep, epithelium, with. infant
layer (i); b, band; n of e, neck of cord; d, connective tissue; c. ct., follicular wall; p, periosteum;
au, alveolar wall; of, outer tunic; dp dental papilla, with (sp) space between it and inner tunić
(it); db, developing bone of jaw.
tissue cells similar to those found in other parts of the body. It is
richly supplied with capillary vessels, but I have never been able to
demonstrate any nerve fibres in the formative stages of the dentinal
organ
Many changes are now seen to be occurring in the jaw; here appears
the first attempt upon the part of Nature to differentiate a periosteum.
The boundary of the jaws is very clearly marked by the condensation
of the fibrous connective tissue at pp (Fig. 356). Outside of this mem-
branous layer the muscular plates are seen in a formative state, and
external to the muscular layer is seen the dermal tissue, covered
by the epidermis. Inside the periosteum is seen the forming bone
of the jaw (db, db). It is independent of the periosteum and Meck-
el's cartilage. It is Y-shaped, with the top of the Y toward the
mucous membrane of the mouth. In the open, or upper, part of the
forming bone the forming enamel organs are located at eo, eo. The posi-
tion occupied by Meckel's cartilage is peculiar in the pig, and differs
materially from that in the human embryo. This is owing to the dif-
ferent form of the two arches. The human is horseshoe in shape, and
Jamai
630
DENTAL EMBRYOLOGY AND HISTOLOGY.
ерт
the cartilage occupies the central portion of the arch; the arch in the
porcine embryo is V-shaped, the base of the V corresponding to the
anterior portion of the mouth. The two sides of the inferior maxilla
come in contact at a considerable distance from the front of the mouth
and at the point of union of the two sides of the jaw. Meckel's car-
tilage, which in the posterior portion occupies the central part of the
jaw, as it does in the human throughout, is seen to converge toward
the inner side of the jaw and locate in apposition with its fellow of the
opposite side. At the anterior portion of the jaw this union is complete,
but as we proceed posteriorly the sides gradually separate, until, in the re-
gion of the molars, they are entirely separated. Where a section is made
across both sides of the inferior maxilla this divergence between the
two sides of Meckel's cartilage forms an accurate guide to the location
cct.
P
ろ
​Co:
db
FIG. 356.
ер

****
袁文
​FREE
eo.
d.b.
p
ер.
mc.
Vertical Transverse Section of Jaw of Porcine Embryo, showing differentiation of Periosteum (5 cm.
X25): pp, periosteum of either jaw; c. c., follicular wall, appearing as a continuation of the peri-
osteum; b, band; eo, enamel organs for premolars; ep, epithelium; db, developing bone; mc,
Meckel's cartilage.
of the section, whether it is a central, cuspid, premolar, or molar. After
the development of the papilla this determination can be made by the
form of the papilla, whether it be uni- or multicuspid.
The direction assumed by the papilla is somewhat across the axis of
the enamel organ; and if it be a cuspid, the form of the papilla is more
conical than that of a central incisor, which is more or less wedge-shaped.
Springing from the base of the papilla is seen, in the section, two
processes which are connected with the papilla. These are sections of a
circular process which arises all around the base of the papilla, and,
extending up and around the outer part of the enamel organ, envelops
it as an outer tunic. This connective-tissue envelope does not in reality
arise from the base of the pulp, but is formed by a condensation of the
fibrous connective tissue in which the enamel organ lies. Its connec-
CC.
DENTAL RIDGE.
631
tion with the papilla is accounted for in that the papilla itself arises
from the same connective tissue. This differentiation of the connective-
tissue envelope is accomplished contemporaneously with the formation
of the periosteum, and is seen at c. ct. (Fig. 357).
The exact office of this connective-tissue envelope is not known. I
hold that it eventually forms the pericementum, and as such becomes
the cement organ. pp marks the periosteum for the jaw; c. ct., the peri-
cementum for the root of the tooth, developed at the same time from
the same embryoplastic elements, and later analogous and contin-
uous structures. The products of the two membranes are very
similar, cement being only a slightly modified form of cortical bone;
which latter, as we have seen, is formed by subperiosteal develop-
ment, and the former by subpericemental ossification. I consider the
effort to differentiate between the two membranes as too fine a dis-
tinction to be substantiated. That some slight difference can be found
no one doubts, but it arises from the fact that the pericementum lies
between two bony walls, while the periosteum has bone only on one
side and soft tissues on the other. I consider it a case of adaptation
to environment.
Sections from jaw of a 7 cm. pig show the process of condensation of
the follicular wall more markedly. The developing germ now has the
appearance of being surrounded by an outer envelope, excepting at the
upper portion, where it yet remains connected with the mucous mem-
brane by the neck of the enamel organ. The stellate arrangement of
the internal, or older, cells of the enamel organ is quite well marked.
The alveolar wall is well developed and extends far up the sides of
the follicle. The body of the bone of the jaw is becoming denser, and
the developing enamel organ more nearly fills the temporary alveolus.
The position occupied by the dentinal papilla is still markedly on one
side of the axis of the enamel organ.
Sections from the jaw of an 8 cm. porcine embryo show the process
of invagination almost complete. The concave surface of the cup-
shaped enamel organ is filled with the dentinal papilla, or pulp. The
development of the alveolar wall has progressed considerably. The size
of the follicle has materially augmented. The mucous membrane of the
mouth has increased in thickness. The neck of the enamel organ is
shortened and evidences of cellular activity are seen in the inner tunic,
over the apex of the papilla. The stellate reticulum is well developed
all through the central portion of the enamel organ. The sides of the
alveolus now come in close contact with the sides of the follicle, the
fibrous connective tissue of the follicular wall uniting and blending
with the periosteum of the alveolar wall. The cells of the inner tunic
are oval, there having as yet been no attempt upon the part of Nature
to differentiate ameloblasts. Between this and the next size (10 cm.)
this change occurs, but, as their development can be demonstrated upon
the sides of the specimen even after the process of amelification has pro-
gressed to a considerable extent, we will proceed at once to the study of
a section from a 10 cm. porcine embryo which has been injected.
I think this is by far the finest specimen I have prepared; it shows
the beginning of the process of calcification at the apex of the papilla.
632
DENTAL EMBRYOLOGY AND HISTOLOGY.
3
But before proceeding to discuss that phase of tooth-development let us
take into consideration the other changes which the follicle and sur-
roundings have undergone. In the first place, note the very consider-
able increase in size. The lens with which the photomicrograph from
FIG. 357.
..
A
mens
ep.
-il.
-n-of-c.
ct
P
-on
Apple D
ot.
it.
-db.
cct.
dp.
db.
Vertical Transverse Section of Jaw of Porcine Embryo (8 cm. X 60): ep, epithelium, with (i) infant
layer; n of c, neck of cord; c, connective tissue; c. c., follicular wall; p, periosteum; dp, dental
papilla; ol, outer tunic; it, inner tunic; sr, stellate reticulum; db, developing bone.
which this illustration was made was the same used for photographing
all the others of the series; I purposely used the same amplification for
this serial line, so as to show the comparative increase in size as well as
the histological changes which occur.
It will be noticed that the alveolar wall has noticeably increased in
height, presenting itself a little above the apex of the follicle. This
appearance is, however, somewhat deceptive, for we must take into con-
sideration another point, and that is the disappearance of the stellate
reticulum over the apex of the developing tooth, which markedly
decreases the height of the enamel organ at that point; it also
gives the follicle the appearance of having settled deeper into the sub-
stance of the jaw. The breaking up of the enamel organ, as such, over
the apex of the forming tooth is a constant accompaniment of the
beginning of calcification. The enamel organ now presents, in section,
the appearance of a pair of saddle-bags hanging over either side of the
dental papilla, or pulp. The inner and outer tunics are separated by a
..

DENTAL RIDGE.
633
well-developed stellate reticulum. This specimen was well injected,
and the vascular supply is nicely shown, both in the pulp and in the
follicular wall. At the apex of the tooth the capillaries come in direct
contact with the outer ends of the ameloblasts; this is made possible
FIG. 358.

THAT
ер.
-il.
-c.p.
wh⋅ep.
ct.
-P
-0.
-SP₁l
Odp
ot.
-Sr
it.
V
c.ct.
Vertical Transverse Section of Jaw of Porcine Embryo, injected (10 cm. × 60): ep, epithelium, with
(i) infant layer; a, layer of ameloblasts; o, layer of odontoblasts; cp, cord for permanent tooth;
of, outer tunic, inner tunic; sr, stellate reticulum; wh. ep., whorls of epithelium formed from
outer tunic and stellate reticulum; d, dentine; dp, dentinal pulp; v, blood-vessels of pulp; ct, con-
nective tissue; c. ct., follicular wall; p, periosteum; sp, space.
by the breaking up of the outer tunic and the disappearance of the
stellate reticulum. The entire thickness of the mucous membrane is
not shown in this figure, the field of the lens not being large enough to
include it all. Over the apex of the developing tooth masses of epithe-
634
DENTAL EMBRYOLOGY AND HISTOLOGY.
lial cells remnants of the outer tunic and the stellate reticulum—are
seen, and are marked wh. ep. They have been called whorls of epithe-
lium because of their tendency to gather into nests resembling somewhat
the nests seen in epithelioma. The space between the apex of the devel-
oping tooth and the overlying epithelium is more or less filled with
these whorls of epithelial cells and the buddings which have arisen from
the sides of the temporary cord. The space (sp) seen between the layer
of ameloblasts and the forming tooth-structure is the result of shrink-
age, which occurred as a post-mortem change. The intimate relationship
between the follicular wall and the periosteum is well exhibited in this
figure.
Mag'
We have now shown the three organs which will superintend the
calcification of the tooth: the layer of ameloblasts-that is, a portion
of the ameloblastic layer, as seen at a; the odontoblastic layer, situated
over the apex of the pulp, at o; and the follicular wall, at c. ct., which
will form the osteogenetic layer for the development of the cement.
With this brief summary, we will now take up the consideration of
the manner in which the cords for the permanent teeth arise, and after-
ward return to the study of the special manner in which calcification
occurs.
DEVELOPMENT OF THE CORD FOR THE PERMANENT TEETH.
What I have thus far said has reference to the twenty temporary
teeth. The permanent teeth which will displace these arise from an
epithelial cord which has its origin from the cord of a corresponding
temporary tooth. This statement holds good for the centrals, laterals,
bicuspids, and-in some instances-for the sixth-year molars. When
the sixth-year molar does not derive its cord directly from the mucous
membrane of the mouth, it arises from the distal face of the second-year
temporary molars. As a rule, however, the cords for the permanent mo-
lars arise directly from the epithelium of the mouth. It is held by some
that the cords for the twelve permanent molars arise from the lamina.
at the same time as the cords for the temporary teeth, but lie dormant
until the time comes for their special development; others hold that
the cords spring from the débris of the temporary cords. I do not
think that either position can be substantiated, for, as I have previously
shown, the band flattens out posteriorly into the mucous membrane of
the jaw at about the position to be occupied by the sixth-year molars.
I do not look upon the band as an essential element in tooth-develop-
ment except as it serves to direct the line of the dental arch. It is to
be remembered that at the time when the formative process for the tem-
porary teeth begins there has been no effort upon the part of Nature to
establish the boundary of the jaws. The muscular plates have not as
yet been differentiated, and the jaws are simply solid buds from the
body of the mesoblast, and are surrounded by the epiblastic layer.
Such being the case, the band acts as the guide to the proper location
of the temporary teeth. But, the jaws having been formed, the twelve.
permanent teeth naturally take a proper location.
Concomitant with the origin of the cords for the permanent teeth,
DEVELOPMENT OF CORD FOR PERMANENT TEETH.
635
the temporary cords present certain buddings which gather themselves
into whorls of epithelial cells; to these have been attributed the origin
of supernumerary teeth. I have no opinion to advance in the matter,
never having seen any developing enamel organs in such position as to
connect this supposed source with these abnormalities. The cord for the
permanent teeth arises, as a rule, from the lingual aspect of the tempo-
rary follicle or the cord for the same. With the severance of the tempo-
rary enamel organ from its cord, the cord for the permanent enamel organ
appears as a continuation of the former, and passes down upon the
lingual aspect of the temporary tooth. This is shown in the preced-
ing figure (358). The direct continuation of the temporary cord into
FIG. 359.
ST.
d:
dp-
02-
Jep.
-il.
fot.
i tu
C
ct
cp.
mamagi

Vertical Transverse Section 9 cm. Bovine Embryo (X 250): ep, epithelium; 2, infant layer; cp, cord of
permanent tooth, still united at c with outer tunic (0%) of temporary tooth; 2, inner tunic; ol,
older layer of cells, known as stratum intermedium; dp, dental papilla; d, dentine; sr, stellate
reticulum.
the permanent is nicely shown in the accompanying cut from a 9 cm.
bovine embryo, where the connection is not yet entirely severed between
the cord and the temporary tooth-follicle.
The time for the origin of the cord for the permanent teeth varies
considerably. In the human embryo the cord for the permanent cen-
tral incisor first makes its appearance about the fifth month. In the
porcine and bovine embryos the cords for the permanent central incisors
arise when the foetus has attained about 8 cm. in length. Those of the
premolars in porcine embryos arise as we have seen in the 10 cm. fœtus
(Fig. 358). The length of the cords for the permanent teeth varies
noticeably in different species and in different teeth of the same species.
The course of the cords for the permanent teeth also assumes a more
spiral direction than do the cords for the temporary teeth. I have
never been able to satisfy myself as to the special signification, if any,
636
DENTAL EMBRYOLOGY AND HISTOLOGY.
that these convolutions may have. They may arise from unequal cellu-
lar activity at different points; at any rate, they are well-known charac-
teristics of the cords for the permanent which distinguish them from
the cords for the temporary teeth. The cord passes down upon the lin-
gual aspect of the temporary tooth and follows the same changes which
FIG. 360.

dp
aw
e.7-
&
c.p
асли
e.v.
N
Section of Jaw Eight Months Human Foetus, showing Vertical Transverse Section of Central Incisor,
(injected; X 40): el, enamel; d, dentine; dp, dental papilla or pulp; aw, alveolar wall; ep, enamel
organ permanent tooth; er, entrance to vessels; n, nerve.
we have noted in the cord for the temporary tooth. It becomes bulbous
at its deepest extremity; then it becomes invaginated by contact with
the dental papilla, after which it settles deeper into the substance of the
jaw, and is finally separated from the mucous membrane of the mouth.
(See Fig. 360, cp.) It gradually becomes deeper seated, until it comes
DEVELOPMENT OF CORD FOR PERMANENT TEETH.
637
to occupy a position directly underneath the temporary tooth, and is
very nicely shown in Fig. 361, representing a temporary molar from
jaw of rabbit. The multicuspid nature of the enamel organ for the
molar teeth is here plainly shown.
cp
dp-
dpp
aw
d
FIG. 361.

SHO
d.
-g₁
α
aw.
cct
Temporary Molar (Rabbit), with permanent developing underneath; the enamel has been removed
by acid in decalcifying process: d, dentine; o, odontoblasts; aw, alveolar wall; dp, dental pulp;
cp, enamel organ for permanent molar; dpp, dental papilla from permanent molar; g, margin
of gum (40).
The changes which occur in the enamel organ have been considered
under the head of the formation of the stellate reticulum and develop-
ment of the ameloblasts. The latter we noticed briefly under the prod-
ucts of the epiblastic layer. We will now enter into the study with
more detail. The accompanying figure is the same as that presented
638
DENTAL EMBRYOLOGY AND HISTOLOGY,
on p. 633, and is here introduced to serve as a guide to the higher-
power studies which are to follow. The circles drawn at a, b, c, d rep-
aut
C
SY
d.p
N-
FIG. 362.
a

·c.p
d.
m.c.
-ar
b
T
Vertical Section Jaw Porcine Embryo (10 cm. X 25); circles a, b, c, d, indicate positions from which
figures are taken: op, cord, permanent; aw, alveolar wall; dp, dental papilla, or stellate reticulum;
n, nerve; v, vessels; me, Meckel's cartilage.
resent the positions from which Figs. 343, 363, 365, 366, were taken.
The first of these we presented when considering the development of the
mucous membrane of the mouth, on p. 615.
The line il marks the infant layer of cells. This line also consti-
tutes the outer and inner tunic of the enamel organ. The cells which
fill the interspace correspond to those in this cut marked ol. Now, thor-
oughly to appreciate the relative positions of the two tunics it is neces-
sary to remember that the enamel organ is formed by an infolding and
involution of the infant layer of the epithelium, and as such it is com-
posed up to a certain time of elements of a like nature with the infant
layer of the mouth, from which it arises. After a time, however, the
character of the cells undergoes certain changes, which we will describe
later on.
We took occasion to say, when considering a section from a por-
cine embryo 8 cm. (see Fig. 357) in length, that the two tunics, both
outer and inner, gave no indication of the appearance of the amelo-
blasts, but that they still presented the same features seen in the infant
layer of the mucous membrane of the mouth. Up to this time the outer
and inner tunics have presented the same features. They have both
been composed of oval nuclei lying in beds or sheets of protoplasm
which constituted the walls, inner and outer, of the enamel organ.
The first change noted is seen over the apex of the papilla. The pro-
toplasm begins to break up into columns, which stand at right angles
to the sides of the papilla; each column contains a nucleus.
The
DEVELOPMENT OF CORD FOR PERMANENT TEETH.
639
shapes of the cells are not unlike those previously described in study-
ing the sweat-glands. They are columnar or basaltic in character, and
are, as may be inferred, specialized cells for a special purpose.
The several stages through which the infant layer which composes
the inner tunic passes may be studied in the one specimen in hand. We
have seen the character of the cells which form the infant layer of the
mucous membrane of the mouth, also the inner tunic of the enamel
organ of the 8 cm. pig. By referring to Fig. 362, taken from the side of
FIG. 363.
dp.
it-
SX
***
sp
-ot.
-c.ct.
Devi

Vertical Transverse Section Central Incisor Porcine Embryo 10 cm.; free border enamel organ seen
in circle b, Fig. 360 (× 250); dp, dental papilla; sr, stellate reticulum; of, outer tunic; it, inuer
tunic; sp, space; c. cl., condensed connective tissue of follicular wall.
the enamel organ (circle b), it will be seen that no change has occurred.
There has been no effort upon the part of Nature to develop amelo-
blasts, but as we proceed higher up the sides of the papilla we see at
circle c that the formation of columnar cells has begun; and when we
reach the apex circle d, well-marked columnar cells are seen. Now, thor-
oughly to understand the reason why we do not find columnar cells at
b, we must remember that calcification begins at the apex, and not upon
the sides, of the papilla. The lower borders of the enamel organ are
growing and extending deeper and deeper into the substance of the
jaw. This rapid development of cells continues until the sides of the
enamel organ have attained their typal length, when growth ceases and
the cells of the inner tunic become converted into true columnar cells,
the development of which has proceeded from the apex of the papilla
along the sides toward the free border of the enamel organ. So, if we
reverse the order of our study, we shall be able to follow the several
stages of developing ameloblasts. But, as it will be more convenient to
study the formation of ameloblasts and odontoblasts together, we will do
so, first premising that the ameloblasts are a product of the epiblastic
640
DENTAL EMBRYOLOGY AND HISTOLOGY.
&
layer and arise from the inner tunic, and that the odontoblasts belong
to the connective-tissue group and are derived from the dentinal papilla,
or pulp. By referring to Fig. 364, taken from the position marked
Sr.
$1,
FIG. 364.
it
Fi
stellate reticulum; i, inner tunic; o, odontoblastic layer.
by a point opposite the line sr (Fig. 362), and magnified 500 diameters,
it will be seen that the ameloblasts and odontoblasts have not as yet
made their appearance. This is below the point where calcification has
reached. Proceeding up the sides to the lowest point where the for-
mation of dentine appears-marked by circle e, and more highly mag-
nified in Fig. 365-we see the first appearance of odontoblasts (o); they
present themselves as elongated cells with fine processes extending into
the homogeneous, calcareous mass. On the outer side of this line of
forming dentine the layer of ameloblasts is plainly seen; the amelo-
blasts are columnar in form, with the nucleus of each situated at its
outer end. Still outside of the ameloblastic layer is plainly seen the
flattened layer of older cells which are always observed lying upon the
layer of ameloblasts; they are the cells which have not become stellate
-the stratum intermedium. Outside of these, and situated between
the two tunics, is the stellate reticulum, which, with the outer tunic,
is rapidly passing through a retrograde process by which it loses its
identity.
The development of dentine always precedes the formation of enamel.
The disappearance of the outer tunic occurs about the same time as the
beginning of the calcification of the first layer of enamel, the salts of
calcium which are stored up in the meshes of the stellate reticulum
only sufficing to furnish material for the very first formed layer of
enamel. With the disappearance of the outer tunic and the stellate
reticulum, as such, the ameloblasts come in direct communication with
ܚ
•

DEVELOPMENT OF CORD FOR PERMANENT TEETH. 641
the rich plexus of capillary vessels, the latter furnishing the lime salts
for the completion of the calcification of the enamel. By referring
to Fig. 366, taken from circle d, it will be seen that a slight layer of
enamel has been formed which has the appearance of a honeycombed
layer. Between this layer of enamel and the layer of ameloblasts a
space is noticed which was caused by shrinkage in the process of
FIG. 365.

dp.
-SP.
0.
d.
sp
·A.
Circle c, Fig. 360 (X250): dp, dental papilla; o, odontoblasts; d, dentine; sp, space; a, ameloblasts;
sr, stellate reticulum.
hardening. Into this space projects a fibrillated margin of the amelo-
blastic layer known as Tomes's processes, of which we will speak later.
There exists considerable confusion regarding the outer tunic of the
enamel organ.
The most erroneous statement concerning it was pub-
lished by Waldeyer, who says: "As far as the external epithelium
reaches, the adjoining connective tissue exhibits its tolerably regularly-
formed vascular papillæ, which project into the epithelium and cor-
respond to the papillæ found in the remaining portion of the oral
mucous membrane." He also presents a cut which does not represent
the true condition of the enamel organ at this stage of development,
either in the human or porcine foetus. He neglects, however, to state
the age or length of the foetus-two essential points to be considered in
presenting illustrations. This cut has been extensively copied, and
those who have used it have also neglected to locate it. Now, the
outer tunic does not present indentations in its surface until it begins to
break up; it is smooth and even, like the inner tunic, until the time
comes for its disappearance. The history of its retrogression can be
followed as carefully as can the progression of the inner tunic. If we
examine Fig. 363, taken from circle b of Fig. 362, we shall be able to
VOL. I.-41
!
642
DENTAL EMBRYOLOGY AND HISTOLOGY.
note the difference in the two tunics at the free margin of the enamel
organ. In younger specimens there is no apparent difference between
the two, but it must now be remembered that calcification has com-
menced at the apex of the tooth, and that material changes will now
occur in the inner tunic; these have been noticed. The character of the
enamel organ as such is rapidly changing; it has served its purpose,
and from now on, upon the apex of the papillæ, it will disappear, and
this change will gradually proceed down the sides of the papillæ until
the typal demands of the enamel cap are reached.
FIG. 366.
There is, however, a marked difference between the inner and the
outer tunic at this stage. The inner tunic gives evidences of rapid cell-
proliferation and consists of many
nuclei, forming a thick layer; on
the other hand, the outer tunic con-
c.ct sists of a single layer of cells. This
is very happily shown in the figure
by the shrinkage which has occurred
just above the free margin, allow-
ing the outer tunic to stand out in
relief. This same character of the
outer tunic, as compared with the
inner tunic, is seen at circle c. At
circle d (Fig. 366) the outer tunic
and the cells of the stellate reticu-
lum have settled down upon the layer
of ameloblasts, sometimes arranging
themselves in whorls, seen at wh. ep.
(Fig. 358). Just what their signifi-
cation is I am unable to state pos-
itively, but from my studies in com-
parative embryology I am led to
believe that they supply the places
made by the increase in the circum-
ference of the enamel, and account
for the short prisms seen in ground-
sections of enamel.
dp

Fl.
-α.
Tp
él.
d
0.
Vertical Section through Apex of Central In-
cisor 10 cm. Porcine Embryo (X 500) : c. ct., con-
nective tissue of follicular wall; F, flat layer
of stratum intermedium; a, ameloblasts; Tp,
Tomes processes into space; el, enamel; d,
dentine; o, odontoblasts; dp, dental papilla.
Gr
In the development of teeth, where
the enamel is to form a coat of mail
on the crown of the tooth-viz. the
Carnivora-the line of ameloblasts
that is first formed does not repre-
sent the same number of ameloblasts
that will finally complete the process of calcification. The outer cir-
cumference of the developed enamel is many times larger than that
of the first calcified layer. If this represented a straight line, as the
enamel on the rodent's tooth does, then the space would be made at one
end of the line; but here it is in the form of the greater part of a circle.
The expansion occurs at all parts, and the cell-supply from which the
ameloblasts are developed is found lying in close proximity to the
ameloblasts. Along the side of the enamel organ which forms the
DEVELOPMENT OF CORD FOR PERMANENT TEETH. 643
straightest line fewer cells are found than on the upper arc of the cir-
cle, where the expansion is greatest.
In the rodents we do not see the same thickness of cells outside the
ameloblastic layer as we find in the Carnivora. Previous to the forma-
tion of the ameloblasts in the rodent's tooth the inner tunic is made up
of three or four cells, arranged as before described, on the outer boun-
dary of which an equally thick layer of spheroidal cells appears, being
also densely packed. Outside of these is the fibrous connective-tissue
envelope.
This dense layer of spheroidal cells grows thinner toward the cut-
ting edge, until at the point where the prismatic ameloblasts are fully
formed it disappears, and we find the fibrous connective-tissue layer
with its numerous capillaries in apposition with the ends of the amelo-
blasts. The office of the spheroidal cells in this instance is to develop
ameloblasts to supply the places of those which were carried up with the
growing tooth, enamel being developed only on the labial face, which
represents almost a straight line. The extension of the line of amelo-
blasts is from the first-formed enamel-prism nearest the base of the
tooth, and here we find located the supply which replaces such exten-
sion.
G
The persistence of the enamel organ at the base of the continuously-
growing rodent's tooth has to my mind a peculiar signification: it is the
forerunner of calcification. The same thing is seen upon the sides of the
developing tooth in the Carnivora and Herbivora, after the commence-
ment of the calcification of the enamel, but it disappears with the com-
pletion of the enamel cap in length. The final calcification in thickness
is accomplished after the atrophy of the enamel organ has occurred. It
is absolutely essential that the capillary vessels should come in contact
with the enamel-cells before the process of calcification can be completed.
In the human foetus this atrophy occurs at the apex about the fifth
month, when only a very thin layer of enamel has been formed.
In the injected specimens which I have made and studied I have
never been able to demonstrate any vessels in the internal portion of
the enamel organ. I consider, from the experiments with the osmic-
acid preparations of enamel organs, that the lime salts which go to
form the first layer of enamel are supplied by the enamel organ itself.
The quantity, however, as I have before stated, is not sufficient to
complete the process of calcification; but that a certain proportion is fur-
nished by the enamel organ I have no doubt. I have never been able
to demonstrate any capillary vessels in the stratum intermedium. The
nourishment of the inner tunic comes from the vessels of the pulp until
such time as it is cut off from them by the development of the layer of
dentine which separates them most effectually from that source of
supply.
The enamel organ is not a secreting organ except in so far as it
furnishes the lime salts for the calcification of the first-formed layer of
enamel, because its disappearance as an enamel organ quickly follows
the formation of this first layer. This being the case, the supply of
salts of calcium must of necessity be derived from another source.
As regards the development of the enamel, there are many theories.
Madd
644
DENTAL EMBRYOLOGY AND HISTOLOGY.
Some hold that the enamel is a differentiation of a dentinal basis, but
the fact that calcification of both dentine and enamel, beginning at the
same line, progresses in opposite directions, makes that ground unten-
able. Others hold that the enamel results from the calcification of the
enamel-cells themselves. From a casual examination this does appear
to be so; but if such were the case, then at the beginning of calcification
the enamel-cells would correspond in length to the length of the devel-
oped enamel-prisms, and the decrease in the length of the enamel-cells
would be commensurate with the increase in the thickness of the enamel,
or the enamel-cells would extend on themselves as calcifiation progresses;
which phenomenon has not been established. It is asserted that the
multiplication of the ameloblasts in the direction of their length is
from the cells of the stratum intermedium as rapidly as calcification
occurs at their free ends—that is, the calcification of the cell-body at
one end and the building up at the other are made a consequent
necessity. If the ameloblasts are directly calcified, it is the only place
in normal development of tissue where calcification of cell-body does
occur. In the development of bone the osteoblasts do not become cal-
cified, but the lime salts are deposited around the spherical osteoblasts
in the form of spherules, increasing in thickness from within outward;
and, thus approaching one another, they coalesce. The osteoblasts per-
sist as the organic contents of the lacunæ. The connection of one
lacuna with neighboring lacunæ forms the canaliculi, and the capillary
blood-vessels around which the osteoblasts are arranged become the
Haversian canals.
In the calcification of dentine, as we have seen, the odontoblasts do
not become directly calcified, but send out rod-shaped fibrils, around
which tubular dentine is formed; so also in the enamel we have the
prismatic ameloblasts superintending the deposit of prismatic enamel.
If a newly-formed layer of enamel which lies on the dentine in a thin
plate be torn off from a thick section of tooth and mounted, the outer
surface will be seen to be pitted—that is, provided you have succeeded
in getting the enamel in just the right stage of calcification. The
periphery of the pits corresponds to that of the ameloblasts. The
ameloblasts, during the formation of enamel, seem to be impregnated
with lime salts and break with a clean fracture at almost any point
-sometimes near the newly-formed enamel, and sometimes at a point
just inside the nucleus.
Ad
C. S. Tomes noticed the fact of the probable impregnation at the end
nearest the forming enamel, and cited it as proof of the actual conver-
sion of the ameloblasts into enamel-prisms. The impregnation of both
ends of the cells is accounted for in the fact that they are carrying lime
salts to the forming enamel. The pits in the newly-formed enamel are
the central portion of the prisms, from which the still uncalcified exu-
dation has been drawn by the ameloblasts when they were separated
from it.
This semi-calcified material, which adheres to the ameloblasts, gives
the appearance of a fibril or prolongation of the cells themselves. These
fibrils which have been called Tomes's processes-I consider as thust
being mechanically made; for they do not always appear, but depend
K
.:
DEVELOPMENT OF CORD FOR PERMANENT TEETH. 645
upon a certain condition of the calcific material. They do not occur
persistently, as do the fibrilla of the odontoblasts. I have, under favor-
able circumstances, succeeded in demonstrating them in sections of pigs'
teeth, where they showed very plainly indeed, being nearly or quite as
long as the ameloblasts themselves and several times longer than the
enamel was thick. As a rule, however, the ameloblasts separate from
the forming enamel so as to leave a comparatively smooth line or plate
—that is, provided the sections have been sufficiently thin, so as not to
show a ragged edge from the overlapping of the cells themselves.
have never been able to demonstrate processes that would lead me to
infer the least analogy between them and the fibrilla of the odonto-
blasts. That the enamel organ exists in the commencement of the
development of the teeth is now generally admitted. There are certain
classes of teeth, however, that do not possess enamel, and in which,
although there is an enamel organ developed, the stellate reticulum
fails to appear. In all cases where there is to be a deposit of enamel
we find a stellate reticulum fully developed, and my observation leads
me to believe that the calcification of the enamel-matrix is due to the cal-
cific material stored in the meshes of the stellate cells of the enamel organ.
The subject of calcification has already been considered, and will be
referred to here only in a general manner. After the temporary teeth
are developed and have served their purpose, they are then removed by
resorption of their roots and their places taken by the permanent set.
The process of resorption is physiological, and is accomplished through
the agency of giant-cells. This part of the subject has been considered
quite fully under the head of Physiological Action of Cells, in the open-
ing chapter. The comparative stages of decalcification of the temporary
and calcification of the permanent teeth have been so well delineated by
Prof. Pierce in his chart in the Dental Cosmos (August, 1884) that I
cannot do better than reproduce it here (see p. 647), together with the
explanatory text accompanying the same:
"In the microscopical examination of dense animal tissues, or such
tissues as are impregnated with the salts of lime, it becomes evident.
that they, like vegetable structures, have periods of growth and of rest,
which are illustrated by concentric layers or zonal shades, and that,
while these conditions are normal, they are both modified and intensified
by the genius presiding over the function of nutrition. Unfortunately,
however, in dating the progressive solidification of tissues, we can with
a degree of certainty mark the beginning and the end only, the inter-
mediate lines merely approximating the conditions which we attempt to
illustrate; yet they are near enough to exactness to give a comprehen-
sive idea of the condition of the average tooth at a certain age, and in so
doing they serve as an important guide in the performance of many
necessary dental operations (Fig. 1).
"From the tabular statement or chart to which we have alluded
above we see that by the seventh week of intrauterine life, and when
the embryo is less than one and a quarter inches in length, preparation
is made for the development of the enamel-germ or matrix, followed in
the ninth week by the dentine-germ, these germs continuing in or
through their progressive stages until the seventeenth week, when we
G
CONS
Ja
646
DENTAL EMBRYOLOGY AND HISTOLOGY.
find in the incisors and cuspids the border-line between the enamel-
and dentine-germs receiving depositions of the salts of lime; or, to
speak more correctly, we see the formation of the odontoblast-cells
and their conversion into dentine and the ends of the enamel-cells
into enamel by the formation and calcification of the ameloblasts. By
the end of the nineteenth week the same developmental process has
reached the molars, and from this period until the fortieth week, or
time of birth, the growth of the tooth-germs and their calcification pro-
gress simultaneously. At birth the calcification of the crowns of the
eight incisors is quite complete; the four cuspids and four first molars
are fully two-thirds calcified, and the four temporary second molars
have their crowns for half their length solidified by the same process.
At the end of the following three months the infant enters into the
critical period of its life, and from a glance at the condition of the
twenty deciduous teeth and their progressive developmental changes it
is fair to assume that this condition has not a little to do with the vari-
ous abnormal systemic lesions or disturbances to which the child is
liable at this age. In close proximity to the sharp and irregular edges
of the calcifying extremity of each partial or complete tooth-crown lies
the vascular papilla-the primitive tooth-pulp-and any want of corre-
spondence between the absorption of the overlying gum at the coronal
extremity and the deposition of solid matter at the calcifying or papil-
lary extremity must produce, by this retarding influence, an irritation
limited in its extent by the number of teeth advancing, the duration
of the cause, and the ramifications of the trifacial or fifth pair of nerves
and the extent of the sympathetic disturbances to which they are liable.
The necessity for operation when the irritation becomes pathological is
so unmistakable that it seems hardly necessary to remind you of the
great advantage to be gained from the free use of the lance as soon as
this condition becomes apparent.
G
M
"Another point worthy of recognition is the period at which the cal-
cification of the apical ends of the roots of all the teeth is completed.
Not infrequently these deciduous teeth, before eruption is complete,
have become a prey to rapid molecular decomposition through the
agency of dental caries. Pulps are sometimes exposed while yet the
root is not completed in its growth. The impropriety of resorting to
the ordinary method of pulp-devitalization is, under such circumstances,
very apparent. When we consider the time of calcification, it is not a
matter of surprise that the crowns of the deciduous teeth are much less
frequently subject to malformations and defects arising from deficiency
in the quantity and quality of enamel and dentine than those of the
permanent set. The crowns of these teeth are largely provided for in
embryonic life, and unless the mother during gestation is in markedly
poor health, so that the function of nutrition is but imperfectly per-
formed, the foetus invariably escapes the necessary consequences of im-
perfect nutrition, which is so common after birth; yet if during this
important period to the embryo there should be a prolonged attack of
ill-health and systemic depression, the crowns of the deciduous teeth
would give its history by deficiency in the quantity and quality of
enamel and dentine.
DEVELOPMENT OF CORD FOR PERMANENT TEETH.
647

22 months after birth
18 months after birth
12 months after birth
6 months after birth
40th week (birth)
30th week embryo
18th week embryo
17th week embryo
FIG. 367.
CALCIFICATION AND DECALCIFICATION OF THE TEETH.
FIG. 1.
FIG. 3.
12 years
10 years
9 years
8 years
7 years
6 years
5 years
4 years
3 years
2 years
1 year
At birth
BIG.
Pannell
Calcification of the Deciduous Teeth.
ali
D
AA
FIG. 2.
4.
5-
6
ה
5-
6.
dail
8
M
9-
É mai
10
2
11
12
0
A
9.
Decalcification of the Deciduous Teeth.
The numbers on Fig. 3 indicate years.
TA
Calcification of the Permanent Teeth.
From a Paper by DR. C. N. PEIRCE, in the DENTAL COSMOs for August, 1884.
10
BAB
:7
6
5
9.
10-
11.
ག་ i
བ་་་
20 years.
18 years.
16 years.
14 years.
12 years.
10 years.
9 years.
8 years.
25th week
embryo.



648
DENTAL EMBRYOLOGY AND HISTOLOGY.
"We come now to the permanent teeth, the calcification of which is
illustrated by Fig. 2. By again referring to the tabular statement above
mentioned we see that as early as the fifteenth week of embryonic life
preparation is made for the development of the four first permanent
molars, and following close upon these, in the sixteenth week, is the
inflection giving rise to the enamel organ for the twenty anterior per-
manent-the successors to the twenty deciduous-teeth, and from this
period until the birth of the infant the germs for twenty-four of the
permanent teeth are passing through their several progressive stages
preparatory to receiving the salts of lime. At birth, then, the child
has not only the twenty deciduous teeth largely advanced toward calci-
fication, but has germs of twenty-four permanent teeth, in twelve of
which calcification commences the first year. The germ of the second
permanent molar makes its appearance the third month, and that of the
third molar the third year, after birth.
JO
"The permanent teeth, unlike the deciduous, are during the periods
of calcification constantly subjected to the influence of morbid systemic
conditions, and any abnormal nutritional condition, of but a few days'
duration, if occurring during the period of coronal calcification, is sure
to make an impression upon the crowns of the teeth, which are at the
time undergoing this process, markings or defects being located at the
point of calcification and limited in extent or modified by the severity
and duration of the abnormality or lesions. The principal object or
advantage of Fig. 2 will be to determine the age of the child when
the systemic conditions existed which caused the faults or imperfec-
tions in the development of the teeth. If serious nutritional disturb-
ances have occurred prior to the termination of the tenth year, some
one or more of the permanent teeth must in all probability have recorded
it. Another service which this illustration will render will be in deter-
mining the condition of the apical end of the root or roots in any given
tooth, when beginning treatment, from pulp-exposure arising either
from caries or fracture, and also from partial or complete dislodgment
by accident. This knowledge will in many instances aid the operator
in forming his judgment as to the best methods to be pursued for the
relief of his patient.
"As represented by the first and second lines in the diagram, we see
that the four first permanent molars and the eight incisors have prior to
the termination of the first year all received a portion of their lime salts,
and before the termination of the third year twenty-four of the thirty-
two teeth are in this process of development. The fifth year the second
permanent molars and the eighth year the third molars or wisdom teeth
commence calcification. With the permanent set it is rarely that the
patient suffers from the effects of interrupted dentition, as is so fre-
quently prominent in first dentition; yet at times both the cuspids and
bicuspids are so retarded in their eruption by the persistence of their
deciduous predecessors, or by a small and contracted condition of the
maxillary bones, that serious trouble results; also, from induration of
the gums or non-absorption of the anterior portion of the ramus or
tuberosity, either the first, second, or third molar may be the cause of
much local inflammation and a febrile systemic condition, and especially
DEVELOPMENT OF CORD FOR PERMANENT TEETH. 649
is this invariably the result of an impacted third molar. The fact that
the third molars are developed during the period of childhood and
youth and while the system is liable to frequent conditions which impair
nutrition is probably one potent reason for their frequent lack of useful-
ness and durability.
"The decalcification or absorption of the roots of the deciduous teeth
is illustrated as far as practicable by Fig. 3, and in this effort your
essayist has found it extremely difficult to do more than approximate
the time at which this interesting and somewhat obscure physiological
process is carried on.
The average period at which it commences will
be sufficient to indicate the time when much care will be necessary in
the application of the arsenical paste for the devitalization of the pulp,
and in the subsequent treatment of the pulp-chamber and root-canal.
This process, usually commencing in the incisors before the close of the
fourth year, progresses gradually, when normally accomplished, from
the extreme end of the root toward the crown for about three years,
and usually releases this deciduous crown between the seventh and
eighth years, the central incisor being some months in advance of the
lateral. The absorption of the roots of the first deciduous molars may
be placed a year later than that of the lateral incisors, commencing
about the middle or close of the sixth year and terminating with the
removal of the first deciduous molars, about the tenth year, the second
molars following usually some months or a year later. The cuspids-
invariably the last of the deciduous teeth to be shed-have their period
of absorption from the eighth to the twelfth year. While these periods.
would correspond with the absorption and removal of the teeth in the
average mouth, so variable are they in different families that many
would be widely different from the above figures.
"I have just spoken of this absorptive process as being physiological
and somewhat obscure. It certainly is both, and, in contradistinction
to the evolution of the tooth, may be termed its dissolution. .
What induces this molecular dissolution it is difficult to state, though
the several conditions which are always present are readily recognized;
but the part they play is so obscure that it is not readily ascertained.
The manner of its commencement when successful-always at the end
of the root-and the presence of a vascular papilla in close proximity
to the absorbing surface are, with the retention of pulp-vitality, three
essential accompaniments, and the absence of any one of them would
militate against the completion of the process.
"The statement that the presence and pressure of the permanent
tooth are essential cannot be sustained, for frequently the decalcification
of the deciduous tooth is successfully accomplished in the absence of its
successor; and again, how often do we find the permanent tooth im-
pacted against or within the bifurcated roots of the deciduous molar, or
pressing down by the side of its single-rooted predecessor, both being
more or less displaced by the persistence of the deciduous tooth without
absorption! That the organ has served its purpose, and that the nour-
ishment which had previously been appropriated by it is diverted or
relegated to its successor, is probably the most plausible explanation we
can give of this interesting physiological process.
650
DENTAL EMBRYOLOGY AND HISTOLOGY.
"This demonstration of dissolution and evolution is not alone con-
fined to the teeth. The ramus of the inferior maxillary gives evidence
of a similar phenomenon by absorption from its anterior border, with
corresponding growth of its interstitial tissue, giving development and
prominence to its posterior line. There are also bone-cased cavities and
canals, increasing in diameter and capacity by absorption from within
and addition to the surrounding walls. These, we conclude, are the
results of similar physiological efforts. Roots which have long been
bathed in pus from the establishment of chronic alveolar abscesses fre-
quently display a worm-eaten appearance. This, though representing
dissolution, is a chemical and pathological process depending, we sur-
mise, entirely upon the acrid condition of the pus, and is not in any
case to be mistaken for the physiological process which we have above
described.
"In recording the periods of calcification of the deciduous and perma-
nent teeth it should be noted that in many instances a want of corre-
spondence between their calcification and eruption exists. By prema-
ture removal of the gum the crown is frequently exposed while yet
there is no root-calcification, as instanced in deciduous incisors when
erupted at birth, their crowns only being calcified, which is the normal
condition of these teeth at this age. Again, not infrequently the persis-
tence of the deciduous cuspids and molars as well as of the indurated
gum over an advancing permanent molar causes delay in the eruption
of the permanent teeth until after the calcification of their roots is com-
pleted. These instances illustrate that in one case eruption takes place
without the development of the root, and in the other we have complete
development of both crown and root without eruption.
-
"In presenting to you to-day the periods of calcification as repre-
sented by Fig. 2, I am not unmindful that Dr. G. V. Black, of Jack-
sonville, Ill., had previously published in the Proceedings of the
Illinois State Dental Society a series of diagrams representing the
same physiological process. The results of his researches so nearly
correspond with those of mine that I have been encouraged to present
them with others representing the calcification and decalcification of
the deciduous teeth.'
""
Taks
The comparative stages of calcification of the temporary and perma-
nent teeth are also nicely shown in Fig. 368, taken from a jaw of child
seven years of age. (This specimen is one of a series belonging to Prof.
T. C. Stellwagen.) The eruption of the permanent incisors and sixth-
year molars has been accomplished. The lateral incisor crown and a
portion of the root are formed. The root of the temporary lateral is
partially resorbed. The crowns of the cuspids, first and second bicus-
pids, and the twelve-year molars are well advanced in the process of
calcification. The roots of the central incisors are not, however, fully
formed, but the apical foramen still remain largely open. The roots
are exposed by removing the bony covering; sufficient is left at mf to
mark the mental foramen. The cancellated nature of the alveolar wall
is such that the greatest mobility is afforded the erupting tooth. The
pressure of the lips externally prevents the arch protruding; this is
opposed by the outward pressure of the tongue, so that no uneasiness
COMPARATIVE CHRONOLOGY OF DENTAL FOLLICLE.
651
should be felt by the practitioner, provided the teeth under his care were
erupting the upper external to the lower.
MOX
1m.
FIG. 368.

2m.
Chist
2nd.bc.
6thy.m.
12th.y.th.
Drawing from Prepared Specimen from Prof. Stellwagen's Cabinet: a, permanent central incisor;
b, erupting permanent lateral incisor; c, developing permanent cuspid; 1m, first temporary
molar; 2m, second temporary molar; mf, mental foramen. The other letters plainly indicate
their adaptation.
m.f. 1st.bo.
COMPARATIVE CHRONOLOGY OF THE DENTAL FOLLICLE.
In sections from the jaws of the common snake which are supplied
with successional teeth, all the stages of tooth-development may be
observed in the same section, from the first infolding of the mucous
membrane through the invaginative process to complete calcification.
The same may be seen in sections from the jaw of the dogfish. In the
human foetus the first indication of tooth-formation is seen about the
forty-fifth day, and consists in the formation of the epithelial band.
There is as yet no indication of points of ossification; Meckel's car-
tilage marks the central portion of the inferior maxilla. Between this
age
and two months the evolution of the lamina and cords for the tem-
porary is accomplished. The cords for the central incisors are bulbous,
while those for the other teeth show varying stages of development,
those for the molars being less fully developed than are those for the
incisors. Ossification is seen in both jaws alike. This is also true in
regard to the development of the dental follicles for the temporary
teeth, which occurs simultaneously in both jaws for the same teeth. At
three months the enamel for the incisor teeth is nearly developed, the
process of invagination having attained considerable progress. The cen-
tral portion of the enamel organ gives indication of formation of the
stellate reticulum. The forming bone has become a distinctive feature
of the jaws and stands out in bold relief in sections stained with hæmo-
data
652
DENTAL EMBRYOLOGY AND HISTOLOGY.
toxylon and cosin. There is no noticeable difference between the two
tunics. The follicular wall is plainly seen.
At the fourth month the inner tunic at the apex of the papilla gives
evidence of the development of the ameloblasts. The surface of the
papilla at the apex also is covered by columnar cells, the odontoblastic
layer. The central portion of the enamel organ is distinctly stellate.
The stratum intermedium, lying upon the outer surface of the amelo--
blasts, is also well marked. The follicular wall is well developed and
almost surrounds the enamel organ, which is still connected to the
mucous membrane of the mouth by its neck. The cord for the perma-
nent tooth may be seen in some instances coming off from the side of
the enamel organ or from the neck of the enamel organ. In other cases
the cords for the permanent do not make their appearance until a later
period. I have not been able either by measurement or by other signs.
to establish any definite time for the origin of the cords of the perma-
nent teeth.
Between the fourth and fifth month for the central incisors is accom-
plished the separation of the enamel organ from the mucous membrane
of the mouth by the severance of the cord and the complete encapsula-
tion of the enamel organ by the follicular wall.
At the fifth month the process of calcification of both enamel and
dentine has considerably advanced for the incisors. The cuspids also
show a thin enamel cap. The first and second molars give evidence of
the multicuspid arrangement. The cord for the sixth-year molar is
also seen.
The bone of the jaw is largely developed, Meckel's cartilage
has disappeared by ossification, and the alveolar walls are well formed
and extend high up on the sides of the dental follicles.
At the eighth month, as seen in Fig. 360, calcification has progressed
to a considerable extent. The enamel organ for the permanent central
incisor is well developed and somewhat invaginated, and occupies a
position upon the lingual face of the temporary tooth.
"On examining sections taken from the jaws of subjects two or three
months after birth we discover in the region occupied by the follicle of
the first permanent molar a process or prolongation, cylindrical in form,
emanating from the epithelial cord of the latter follicle, and which
takes a horizontal and backward direction, terminating in a bulbous
extremity. This prolongation is the commencement of the follicle of
the second permanent molar. Thus we fix the date of the origin of
this follicle at the third month after birth. At about the third year of
infancy the epithelial bourgeon that represents the enamel organ of the
third molar originates from the cord of the preceding tooth-that is, the
second permanent molar. According to the numerous observations we
have made, this date may be regarded as very nearly accurate, though
the difficulties of which we have already spoken have prevented us
from following out the successive phases of evolution in a very rigid
manner. Yet that a little cap of dentine is visible in this follicle about
the twelfth year is true beyond a doubt."1
Bovine and porcine embryos show the same development for the same
lengths, although there is a very considerable difference in the sizes of
¹ Dean's trans. Legro and Magitot.
COMPARATIVE CHRONOLOGY OF DENTAL FOLLICLE.
653
the foetuses at birth.
about the same time.
Evolution of their dental follicles seems to begin
At 1½ cm. in the porcine embryo there is no indication of the forma-
tion of the band. The same holds good for the bovine embryos. The
mucous membrane of the mouth of each is thicker than the external
epithelium.
At 23 cm. the band is distinctly marked and the cells are heaped up
over the line of the infolding epithelium.
At 3 cm. the lamina has made its appearance, and shortly afterward
the buds for the cords of the temporary teeth are seen.
At 4 cm. the process of invagination begins, which marks the appear-
ance of the dentinal papilla; these arise from the embryonal connective-
tissue elements into which the enamel organ by its growth is projected.
At 5 cm. the differentiation of the follicular wall has begun from the
surrounding embryonal connective tissue. In its origin and character
it is analogous with the tissue of the papilla, but seems to be condensed
into a membrane, and in this differs from the pulp-tissue.
At 6, 7, and 8 cm. invagination is seen to be progressing, until at the
last-named measurement it is complete. The formation of the stellate
reticulum has also been accomplished. The bone of the jaw, which first
made its appearance at 3 cm., has now well-defined alveoli, and the
bodies of the maxillæ are well developed.
At 9 cm. the dentine cap is plainly visible, and the cords for the per-
manent teeth are seen springing off from the lingual face of either the
enamel organ of the temporary tooth or from the cord of the same.
At 10 cm. the enamel organ over the apex of the papilla has disap-
peared. The enamel presents itself as a thin layer lying upon a cap of
dentine of considerable thickness. The cord for the permanent tooth
extends down upon the side of the follicle, having separated from the
temporary follicle, which is now fully enclosed by the fibrous con-
nective-tissue follicular wall, the future cement organ.
We might multiply words in further description; suffice it to say
that at birth the crowns of the central incisors are fully formed, and
very soon after erupt. My studies in ovine embryos have been confined
to some half dozen at birth; the crowns in these cases were fully calci-
fied and offered excellent examples for the study of Nasmyth's mem-
brane, which has the character of a structureless membrane covering
the enamel, and which is easily made discernible by the use of dilute
acids.
S
Sections through the face of a fatal puppy, the facial bones of which
very nearly compare with those of the human foetus, make good studies.
I have never had the pleasure of examining equine fœtuses, and shall
take the liberty of quoting from Legro and Magitot, taken from Dean's
translation:
“Our observations have been made upon equine embryos of different
ages. From these we have determined certain facts in relation to the
various phases of follicular evolution. For the first three embryos we
are indebted to the courtesy of M. Raynal, of the veterinary school at
Alfort. In the youngest of these (14 weeks) the enamel organs of the
central nippers (incisors) are already formed and the bulb has made its
654
DENTAL EMBRYOLOGY AND HISTOLOGY.
appearance. For the lateral nippers the enamel organ is just beginning
to show itself. These facts indicate that the evolution of the follicles
of these teeth in man and other mammals appears to be synchronous.
For the molars it is found that at this same epoch the bulb has appeared.
for all the follicles of the first dentition, as have also the first traces of
the follicular wall. In a second embryo (of 27 weeks) the follicles of
the central incisors are closed, while those of the first lateral incisors.
are just beginning to exhibit the bulbs, and those of the second lateral
incisors only the enamel organ. These facts, as we see, additionally
confirm the unequal development of the different incisors in this animal..
In the molars the facts are analogous; the follicle of the first temporary
molar is closed at this date, while the enamel organ of the second has
only just made its appearance, and no trace of that of the third molar is
yet visible. It is at this period, also, that the first indication of the
enamel organ appears for the first permanent molar. In a third
embryo, measuring 255 millimeters [10 inches], corresponding to about
28 weeks, the follicles of the permanent incisors are closed and com-
plete; the enamel organ is well developed. The ameloblasts of the
interior bed are very large, and the external epithelial layer has already
disappeared, but no trace of dentine yet appears.
"The follicles of the permanent incisors have arrived at the period
when the enamel organ already caps the bulb, which is just appearing,
but is not yet constricted at its base. For the temporary molars the
follicles are about equally developed. They are closed and well formed,
but without any appearance of the dentine cap. The organ of coronal
cement is already beginning to manifest itself. From the fragments of
the ruptured epithelial cord numerous buddings have been produced.
"From the fourth (an equine foetus of 31 weeks), owing to a very
prolonged maceration in alcohol, we were prevented from deriving much
advantage. We were only able to determine that the temporary follicles
were fully developed and provided with caps of dentine of considerable
thickness. Some fragments of the epithelial cord (long since broken,
without doubt) were still remaining. The organ of coronal cement was
fully developed.
"We will conclude these chronological considerations with a few
notes relative to the rodents. In an embryonal guinea-pig of 2 cm.
[ inch] in total length, which appeared to correspond to about the
middle period of gestation, the follicle was at the stage when the enamel
organ, in form of a hood, covers the bulb; there was no follicular wall
or dentine cap apparent.
"In another embryo of the same species of 4 cm. [1 inches] in
length, the temporary follicles were formed, and their stages of devel-
opment were nearly the same. They were provided with a dentine cap
covered with a thin layer of enamel. In the rabbit we discover that at
birth the incisors have effected their eruption, the molars still enclosed,
but already capped with thick layers of dentine and enamel. Beneath
the temporary molars we observe the presence of the permanent follicles,
already provided with a thin but distinctly manifest layer of dentine."
SN =
Jabatan
The Dental Papilla, or Pulp.-The dental pulp first makes its
appearance as a slightly condensed area of tissue in juxtaposition
NERVES OF THE PULP.
655
to the lowest portion of the developing enamel organ. Its differentia-
tion seems to be controlled by the enamel organ. It is composed at
this early stage of embryoplastic connective-tissue cells, and differs in no
manner, as regards its constituent elements, from the surrounding tissue.
In stained specimens it presents a somewhat darker color, due to the
condensation of the cells which compose it. As we consider it in the
further stages of development there is presented no characteristic which
may not be seen in the surrounding embryonal connective tissue. Blood-
vessels early show themselves and form numerous anastomosing loops,
which give the papilla a highly vascular nature. The first indication
of the office of the papilla, or pulp, as the formative organ of the den-
tine of the tooth, is seen in the human foetus of four months and the
porcine embryo 8 or 9 cm. in length. There is developed a layer of
cells upon the apical surface of the papilla; these cells are termed odon-
toblasts. At first they are oval in form and differ very little from the
ordinary connective-tissue cells which make up the principal portion of
the papilla. The cells of this outer layer-membrana eboris, as it has
been termed-gradually become elongated and send out processes which
connect them with each other and with the cells of the pulp, and also
extend outward toward the inner tunic of the enamel organ. These
latter processes are called the dentinal fibrils. The odontoblasts become
columnar in shape as the time nears for the commencement of their
work as dentine-builders. As calcification progresses from the apex of
the papilla new odontoblasts are developed on the sides of the papilla,
until the membrana eboris forms an outer covering to the papilla, and
finally the fully-developed pulp. After the dentine is completely cal-
cified the odontoblasts again change their form into oval cells, and con-
tinue to exist as such throughout the life of the pulp. When stimulated
by irritation, whether from caries or by thermal changes brought about
by loss of tooth-structure, by attrition, or abrasion, the odontoblasts
again assume their old functional activity and develop secondary
dentine.
While these changes have been going on in the formative outer layer
of the pulp the embryonal connective-tissue cells are developed into
ordinary connective-tissue cells.
Between these fixed connective-tissue cells may be seen the ordinary
plasma-cells noticed throughout the connective-tissue system, the pulp
being no exception to the rule.
NERVES OF THE PULP.
The nerves of the pulp are many and consist of medullated and non-
medullated fibres, which enter the pulp through the apical foramen in
various-sized bundles. Passing forward, they break up into smaller
branches and form a rich plexus underneath the odontoblastic layer.
Regarding their termination many speculative theories have been ad-
vanced, but little or no definite knowledge has been presented. Some
assert that the finer fibres pass between the odontoblasts and either unite
with the dentinal fibrils or pass with them into the dentinal tubuli.
Others assert that the non-medullated fibres become united with the
656
DENTAL EMBRYOLOGY AND HISTOLOGY.
stellate layer of cells, which may be seen lying underneath and con-
nected with the odontoblastic layers.
I am unable to make any statement regarding the termination of the
nerves of the pulp. I am very skeptical regarding their having any
direct connection with the fibrils of the odontoblasts, and have never
been able to demonstrate any such relationship. Then, again, as no
nerves can be demonstrated until after calcification has progressed to
a very considerable extent, the proof is conclusive that they are not an
essential element to the process. I am more inclined to the view held
by Magitot-that the terminal fibrils unite with the odontoblasts, and
that sensation is thus transmitted by the dentinal fibrils to the terminal
branches of the nerves. As there exists a very considerable degree of
ignorance regarding the termination of nerves in other parts of the
body where the conditions are favorable for their demonstration, I do
not think it strange that we should be unable to state authoritatively
just how they terminate in the pulp, seeing that the technique for their
demonstration in that organ is so difficult.
The calcification of the crown being completed and the time for erup-
tion having arrived, the process of eruption begins as the tooth makes
its appearance above the gum. The root is gradually developed; the
jaw is also growing rapidly and gives a firmer setting for the erupting
tooth. The attachment of the tooth to the jaw is fibrous in character
and surrounds the root as a membrane, being united to the root on one
side by many fine prolongations, which penetrate and anastomose with
the processes of the bone-cells which occupy the lacunae of the cemen-
tum. A similar attachment exists with the alveolar wall upon the
outer periphery. The development of the cement, as we have seen
when discussing that subject, is accomplished in a manner identical with
subperiosteal formation of bone. The formative membrane remains as
the pericementum and persistent cement organ. The deposits of sec-
ondary cement known as exostoses are due to this membrane. The pro-
cess of calcification is not always a continuous, harmonious effort upon
the part of Nature, but is subject to many interruptions; these leave
their indications upon the cement, enamel, and dentine. Interglobular
spaces are seen in both dentine and enamel. These we have discussed
to a considerable extent. The pits seen upon the surface of the enamel
are no doubt, in some instances, caused by these spaces. The serrations
seen upon the edges of newly-erupted teeth-so long known as "Hutch-
inson teeth"-have now pretty generally come to be attributed not alto-
gether to congenital syphilis, but to lack of nourishment or inherited
conditions which may be other than syphilitic.
Besides the markings seen upon the individual prisms, there are other
lines which run transversely across the prisms. These have been called
the "broken striæ of Retzius." The lines of stratification have a more
or less decided brownish tint, but just what gives rise to the appearance
I am unable to conjecture. It is held by some to be the result of an
arrest in the process of calcification, each line marking such a period;
others hold that it is due to the varying character of food taken by the
mother during gestation, some being rich in lime salts of one kind,
while another salt predominates in another kind of food. If this is the
A
NERVES OF THE PULP.
657
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case, then the same statement will hold true regarding the action of
food-stuff's upon the teeth of the second dentition. The lines of strati-
fication that lie nearest the dentine are longest and form a complete
arch. Those that lie nearer the surface do not form an arch, but “ run
out" on the sides of the tooth, growing shorter as the surface near the
neck of the tooth is reached. Those nearest the dentine conform more
FIG. 369.

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Vertical Section of a Tooth in situ (15 diameters): c is placed in the pulp-cavity, opposite the cervix
or neck of the tooth; the part above is the crown, that below is the root (fang). 1, enamel with
radial and concentric markings; 2, dentine with tubules and incremental lines; 3, cement or
crusta petrosa, with bone-corpuscles; 4, dental periosteum; 5, bone of lower jaw.
or less in direction to the surface of the dentine, but the lines seen near
the neck stand at an acute angle to the surface of the dentine.
These lines are also seen in the dentine and bear an almost parallel
relation to the surface, although, as a rule, the brownish color is very
generally absent.
The pigmentation of enamel of many of the rodent family, as we have
VOL. I.-42
658
DENTAL EMBRYOLOGY AND HISTOLOGY.
observed, is normally so, and may be said to bear a close relationship to
the density of the teeth, those hardest being most deeply pigmented, and
vice versa. This rule holds good in human teeth as well. I am inclined
to the opinion that chemical constituents of the enamel have much to do
with its color. The darker teeth are much more resistive to caries than
are the softer varieties.
In the accompanying figure we have combined in one section all the
products of calcification we have been considering-viz. bone of jaw,
cementum, dentine, and enamel.
PART IV.
Data warga qarqe ka ng deme
GENERAL AND DENTAL PATHOLOGY.
GENERAL PATHOLOGY.
DENTAL CARIES.
PATHOLOGY OF THE DENTAL PULP.
DISEASES OF THE DENTAL PULP, AND THEIR
TREATMENT.
DISEASES OF THE PERIDENTAL MEMBRANE.
ABRASION AND EROSION OF THE TEETH.
GENERAL PATHOLOGY.
By G. V. BLACK, M. D., D. D. S.
Karl 1, 19 Matter, we had Allah
W past and a rapid piger Va
INTRODUCTION.
HEALTH is a standard condition of the body in which all of its
functions are regularly and normally performed. Any marked devi-
ation from this is disease, no matter what the deviation may be. It is
impossible to frame a strict definition of this standard of health, for the
reason that it may vary within certain but rather wide limits. It is not
the same in all individuals, nor always the same even in the same
person. The various functions may, at different times or in different
individuals, vary quite perceptibly in their degree of activity consid-
ered as a whole, so that some persons are habitually more robust than
others. Again, among the individual functions some may be relatively
less active than others without an impairment of health that can prop-
erly be considered a diseased condition. Some functions may be more
active, others less so, and yet the departure from the normal equilibrium
of functional activity may not be such as to impair so seriously the
equable relation and mutual dependence of the various functions as to
justify us in considering the individual unsound in health. A person
may be fairly healthy and not be in the highest degree of health.
În disease there is a deviation in the performance of some one of
the functions of the economy so marked that the individual is readily
conscious of discomfort, or such morbid processes are in operation as
will bring about a condition of disability by their continued action.
In the great majority of diseased conditions the patient is at once made
conscious by his sensations that something is wrong. He becomes
aware of a departure from the normal state by a feeling of discomfort
either general or local. There are, however, some forms of disease so
insidious in their approach that the patient may not become conscious.
of their presence until very serious mischief has been done. There-
fore the feelings of the person, while they are usually a safe guide
as to the condition of the health, are not to be regarded as infallible.
A disease is an assemblage of morbid phenomena that have so often
been noticed to occur contemporaneously or to follow each other in a
certain order as to enable those skilled in their study to recognize them
as marking a special form of deviation from health. In the study
of these assemblages of symptoms, the groupings of which mark the
different diseases known to us, it has long been noted that certain patho-
logical states are common to various individual diseases. Of these the
most constant are changes in the circulation of the blood and in the
661
662
GENERAL PATHOLOGY.
blood itself, or in the relation of the blood to the tissues. Some of these
changes may occur without other morbid symptoms preceding them-
i. e. may be primary; or they may be dependent on changes that have
preceded them-i. e. may be secondary; others are always secondary.
In the study of individual diseases it is found to be cumbersome to
enter into a detailed description of all these accompanying phenomena.
A separate description of them is most convenient, and at the same
time far more satisfactory, for in this manner we may save much repe-
tition and avoid confusion. If the processes of inflammation be under-
stood, it is much easier to describe the formation of an alveolar abscess,
for in that case the description will not necessarily include a detailed
account of the inflammatory process, but may be confined to the causes,
peculiar characteristics, and results of the process in that particular situa-
tion. As this is true here, it is also true in the various other situations
in which local inflammations may occur; and what is true of inflamma-
tion applies also to many other morbid phenomena. For these reasons
I purpose describing under the above caption various morbid conditions
that are common to many diseases, especially those of the blood and of
its circulation.
THE PULSE.
The pulse is produced by the action of the heart. This organ acts as
a pump, taking the blood from the great veins and driving it into the
arteries. With each contraction of the heart a considerable quantity of
blood is projected forcibly into the aorta, and through this it is distrib-
uted to the entire arterial system. The arteries are so many elastic
tubes, and the volume of blood in passing causes a sudden expansion
of their walls at each impulse, which may be distinctly felt on placing
the finger over any artery that lies near the surface. In the very super-
ficial arteries the impulse may, in many instances, be seen. This
movement is known as "the pulse." As the pulse is caused by the
action of the heart, it becomes an index to the condition of that organ.
If the heart be strong and vigorous, we will find a strong pulse; if
weak, the pulse will be correspondingly so. This result is modified by
the condition of the arteries. The arteries are not simply elastic tubes,
but contain within their walls a circular coat of smooth muscular fibres
by which their calibre may be diminished or increased, this action being
governed by the vaso-motor system of nerves; which influence is con-
tinually modifying the pulse in various ways.
The importance of an accurate knowledge of the pulse becomes mani-
fest when we consider that most diseases kill by arresting the action of
the heart. In all cases of accident the condition of the pulse will give
a more certain indication as to the immediate danger of the sufferer
than an examination of the local injury sustained, for the reason that
it affords an index to the condition of the nervous system, and tells the
surgeon at once whether or not the patient has suffered any considerable
depression of vital power in consequence of the injury. In disease the
pulse is sure to give the signal of danger promptly and afford an early
indication for treatment. It is true that in many instances the nervous
THE PULSE.
663
system gives way first, as is shown by muttering delirium and sleepless-
ness; but in these cases the anxiety of the physician arises more from
the effect these conditions will ultimately have on the circulation than
from danger as manifested directly through the nervous system. This
delirium and inability to rest exhaust the patient, and at last the heart
by its feeble pulsations signals the approach of fatal debility. In case
of typhoid fever the delirium may be marked and long continued, yet
so long as the action of the heart remains good, as indicated by the cha-
racter of the pulse, fair hopes may be entertained that the patient will
recover. It is the final effect of disease on the heart that destroys life;
therefore it is hardly possible to overestimate the importance of an inti-
mate knowledge of the varying qualities of the pulse and the indica-
tions they give of the effects of disease on the powers of life.
In the study of the varying phases of the pulse we should recognize
three principal divisions of the subject-namely, 1st, frequency; 2d,
quality; 3d, intermittence.
Frequency of the pulse relates solely to the succession of the pulsa-
tions. These may succeed each other with varying rapidity, giving a
frequent or infrequent pulse.
Under the term quality we consider the character of the individual
pulsations. This division of the subject is at once the most important
and the most difficult. Quality is rarely dependent upon frequency or
infrequency, but these conditions are usually dependent upon quality.
We may express the principal qualities of the pulse as follows: The
individual pulsations may be strong or weak, hard or soft, large or small,
quick or slow (or short or long), compressible or incompressible, regular
or irregular, dicrotous.
Intermittence is the failure of an occasional pulsation. This may
occur very regularly, or it may be irregular in its occurrence. More
frequently it is the failure of every third or fourth beat or pulsation.
EXAMINATION OF THE PULSE.-The pulse may be examined in any
artery that lies near enough the surface to be easily felt by the finger. The
radial artery at the wrist is, however, the one generally used, because
it is the most convenient. Any other artery may be selected if from
any cause the use of this one should be inconvenient. If the examina-
tion is only for the determination of the frequency of the pulse, any
position in which the pulsations can be distinctly felt will answer the
purpose; but for determining the qualities of the pulse much more care
is required. In making this examination the wrist of the patient should
usually be taken between the thumb and fingers in such a way that the
ends of three fingers may be placed easily on the artery. The position
should never be strained or uncomfortable either to the patient or the
physician. The wrist of the patient should be straight or a little
extended, but it should not be flexed, for in that case the artery is
placed in a bad position for examination. In simply counting the pulse
one finger is all that is required. In determining the qualities of the
pulse one finger should first be pressed very lightly on the artery, and
afterward more firmly, and the pressure varied from time to time
until all of the finer qualities are ascertained. In determining the
compressibility of the pulse all three fingers should be used, bringing
664
GENERAL PATHOLOGY.
them to bear one after the other until the degree of compressibility
is ascertained. Of this I will presently speak more definitely. The
matter of the examination of the pulse demands much careful and patient
study from those who would become proficient in the determination of
its qualities and in the interpretation of its meanings. There are vari-
ous circumstances that modify the normal pulse, some of which will be
mentioned hereafter. It must always be remembered that the pulse at
the wrist varies very much in volume in different individuals, on account
of differences in the size of the artery, so that mere volume has not so
much significance at a first examination. Also, the radial arteries of
the two sides often differ in size very materially, so that one may serve
to correct the other. In any case in which the examination of the radial
pulse leaves the condition of the circulation in doubt, other arteries
should be consulted for the more perfect correction of the readings.
In the administration of anaesthetics it is very convenient to take the
pulse from the temporal artery.
FREQUENCY OF THE PULSE.-In health the frequency of the pulse
presents wide variations. Some persons in seemingly good health have
habitually a pulse of 100 beats in the minute, while in others it may
fall as low as 50. These extremes of variation are, however, very rare.
The greater number of persons will be found to have a pulse-rate of
from 60 to 85 beats in the minute. Anything above 85 may be
regarded as an abnormally frequent pulse in the adult. On the other
hand, anything below 60 may be regarded as abnormally infrequent.
In children the pulse is more frequent than in adults. The following
statement will give a sufficiently clear idea of this:
The infant at birth
The child at five years
The child at ten years
•
Pulse-rate 140
(6 100
90
((
G
The pulse of children is, of course, subject to variations similar to those
of the adult. In women the pulse is a little more frequent than in men,
the excess averaging about nine beats in the minute. Position also
affects the pulse-rate; it is a little more frequent in the standing than
in the recumbent posture. In sleep the pulse usually falls about ten
beats in the minute.
There are many causes of frequency of the pulse, such as severe
exercise, emotional or mental excitement, hysteria, diseases of the heart,
debility, fever, reflex irritation, etc.
Usually, it is not difficult to determine the cause of frequency of the
pulse. Frequency produced by violent exercise, emotion, or mental
excitement passes away very soon after the cessation of the cause.
Therefore, examinations made at intervals will, if the patient be kept
under observation, soon clear up this point. Nervous patients usually
present an acceleration of the pulse when first approached by the phy-
sician, especially if he be a stranger; and for this reason the pulse
should be again taken after some time has elapsed.
In hysteria there is sometimes a pulse very frequent and continuous ;
the rate may be as high as 150 beats in the minute. In patients that
present themselves for dental operations this cause of frequency will
THE PULSE.
665
sometimes give rise to some difficulty in diagnosis. A little observa-
tion of these cases will, however, almost always set the operator right.
When grave illness occurs the hysteria usually disappears spontane-
ously.
Gleda
In fevers the pulse is generally accelerated in proportion to the rise
of the temperature. This is not uniform, however. In a few instances
I have noted a very high temperature associated with an infrequent
pulse, but this is evidently rare. From what has been said in regard
to the variations of the pulse in health, it will be seen that there is no
absolute pulse-temperature ratio. Any rule that may be given is sub-
ject to considerable variations. In general it may be stated that there
will be an increased frequency of eight beats of the pulse to each degree
of rise in the temperature. The same causes accelerate the pulse more
in children than in adults, and the ratio also varies somewhat in differ-
ent fevers. Thus, with a given temperature the pulse is more frequent
in scarlet than in typhoid fever. A pulse which has a greater rapidity
than the temperature explains indicates debility of the heart, unless it
be dependent upon mental excitement, hysteria, or organic cardiac dis-
ease. It may be stated as a law of the action of the heart that what it
lacks in power it endeavors to make up in frequency. A pulse that
day by day becomes more frequent, the temperature remaining the same,
shows progressive prostration. A pulse of 130 occurring in fever is
serious, a pulse of 140 to 150 shows great danger, and a patient with a
pulse-rate of 160 will almost certainly die.
Inflammations of the heart and its membranes are exceptions to this
rule, for in these a very frequent pulse is of less serious import. In such
cases we may find a pretty severe pericarditis with extensive effusion
into the pericardial sac, with perhaps but little rise of the temper-
ature, and a pulse of 140 to 150 per minute, and very bad in quality,
without very great danger to life. Here the state of the pulse is the
direct result of the condition of the heart itself, and does not reflect the
condition of the vital powers, as it does when it is secondarily affected
through the general prostration of the nervous system. In these forms
of heart lesion, especially in endocarditis, the muscular substance of the
organ is also inflamed, which disturbs its action, or its motions may be
interfered with by the exuded fluid in the cavity of the pericardium.
With this embarrassment the circulation becomes very poor, and from
the want of oxygenation of the blood the patient may show consider-
able blueness of the skin; the breathing too may be proportionately
hurried; yet clinical observation shows that very few die directly from
this cause, it being rather a remote cause of death through injury to
the valves of the heart or through a resultant fatty degeneration. Of
valvular lesions I will speak again.
QUALITIES OF THE PULSE.-Under this head it is my purpose to
inquire especially into the character of the individual pulsations. These
depend upon the condition of the heart and arteries jointly. If the heart
is weak, it cannot give strong pulsations, and, other things being equal,
the pulsations will be lacking in volume and tone. The condition of
the arteries, however, may modify this in several ways, so that various
characters will be produced. As has been said, the calibres of the arte-
666
GENERAL PATHOLOGY.
This pro-
ries are directly affected by the vaso-motor system of nerves.
duces what is known as variations in "arterial tension." In the condi-
tion of health the blood may be said to be grasped by the muscular coats
of the arteries with a certain degree of force. Therefore the blood is
constantly subjected to a considerable degree of pressure, which is
plainly indicated by the "spirting" when an artery is severed. Bleed-
ing lessens the volume of the blood directly, yet it requires a consider-
able reduction in the volume to very materially reduce the arterial pres-
sure. So too, conversely, the volume of the blood may be doubled by
the process of transfusion before the arterial tension is materially
increased. This equality of the arterial tension is maintained directly
by the nervous system acting upon the muscular coats of the arteries,
through which these vessels are contracted or expanded to accommodate
the changing volume of the blood. This tension in disease is subject to
very wide alterations, and, in the main, these alterations reflect the con-
dition of the nervous system. It is this coincidence of conditions that
gives to the qualities of the pulse their importance. In disease strength
of the heart and tension of the arterial system do not always coincide.
The source of their enervation is different. The heart receives its
supply from the great sympathetic and from ganglia situated within
itself, but principally from the pneumogastric, while the vaso-motor
nerves seem to arise from the spinal cord. Hence, while in many
respects the condition of the heart and arteries may coincide, they do
not do so of necessity.
·
A compressible pulse is produced by relaxation of arterial tension.
This condition permits the blood to flow through the arterial system
and into the capillaries with less restraint, and, if the heart is strong,
produces a large soft pulse that may be readily compressed. In this con-
dition of the arteries a weak heart will produce a correspondingly small
and quick pulse. The compressibility of the pulse is ascertained by
placing two or more fingers on the artery and exerting more or less
firm pressure until the pulsation is no longer felt under the finger near-
est the distal (or terminal) end of the vessel. The degree of pres-
sure required to do this determines the compressibility. If this is not
accomplished with a reasonable pressure, the pulse is said to be incom-
pressible and marks a strong heart with a fairly high arterial tension,
and indicates a good condition of the system. If this incompressibility
is extreme, as is often the case in the beginning of fevers, sedatives are
called for, and especially so if the pulse is very frequent. In the reverse
case, if the pulse be easily compressible, quick, and very frequent, it
marks a condition of general prostration, and calls for stimulants, espe-
cially cardiac stimulants, such as digitalis. It will be noted here that
these differences are based on the qualities of the pulse independent of
its frequency. Yet it is a clinical fact that a full strong pulse never
becomes so frequent as the small quick pulse, which is the indication of
dangerous prostration.
A relaxed condition of the arterioles with a heart of only moderate
strength will give a full round pulse that, if not closely observed, might
readily be mistaken for a strong heart-beat. The ease with which it
may be compressed will at once correct the error and set the physician
THE PULSE.
667
right as to the actual condition of his patient. In the relaxed condition
of the arteries their walls present but little resistance to expansion by
the blood-wave, and a very feeble contraction of the heart is sufficient
to produce a tolerable dilatation of the artery, and the blood passes into
the capillaries-which are probably also dilated-so easily that it pro-
duces very little resistance to compression. On the other hand, in high
tension of the arterial system the artery is sometimes found to be so
tense and hard that it is easily felt by the finger even in diastole of the
heart, and may be traced for a considerable distance up the arm, feeling
In
much like another tendon lying among the tendons of the wrist.
such cases, even though the heart may have a fair degree of strength, the
pulse-beat is small, hard, and long-small, because the heart, though of
good strength, is unable to produce much expansion of the tense, hard
walls of the artery; it is hard for the same reason; and it is long be-
cause the blood cannot pass otherwise than slowly into the capillaries
on account of the diminished calibre of the arterioles. This marks a
condition of nervous irritation, and usually, when it is extreme, an exalt-
ation of sensibility. When these conditions are present in connection
with a weakened condition of the heart, we will find a small, frequent,
and shot-like pulse, and as the decline of the patient progresses and
the tension begins to give way the pulse becomes quick and thready.
The sphygmograph is an instrument for recording the pulse-waves,
and much aid is obtained from it in the study of the varieties presented
by them. This instrument will, however, only give us the form of
the pulse-wave. It is not to be depended upon for information as to
the strength of the pulsations, for this is not always shown by the
height of the pulse-wave, as has already been sufficiently indicated;
and even if this were not the case, it is so difficult to apply the instru-
ment to the artery with equal regularity that there is much uncertainty
in its use. The pictures of the pulse made by this instrument are, how-
ever, of the greatest benefit in gaining an accurate knowledge of the con-
ditions of the circulation; they point out at once the differences between
high and low arterial tension, and the study of them leads the observer
to a better judgment of these conditions by the use of the finger. For
this reason I introduce some tracings representing some of the prin-
cipal varieties of pulsations. (See Fig. 370.)
In most diseases, both acute and chronic, failure of the circulation is
very generally accompanied by evident signs of general prostration and
failure of the powers of life. Yet by watchfulness this may be first
discovered in the pulse; and it is not infrequently the case that this
sign is present for some time before others manifest themselves. A
patient with fever may not show any special evidences of weakness;
the temperature may not be very high; he may take food fairly well;
turn in bed with seeming ease, and the voice may be strong; but if the
pulse is frequent and easily compressible, the patient is liable to sink at
any time, and, in fact, is in a dangerous condition. It must always be
remembered that there are occasional individual peculiarities which
render the pulse especially sensitive, so that a little fever may accelerate
it greatly without indicating danger. Such peculiarities can be learned
only by acquaintance with the individual patients.
668
GENERAL PATHOLOGY.
The following conditions usually give rise to high arterial tension:
Affections of the nervous system; the rigor of fevers; Bright's disease
of the kidneys; lead-poisoning; gout; degeneration of the vessels.
It may be useful to add here some account of the changes that may
be expected in the pulse during the progress of an ordinary acute ill-
FIG. 370.

J
(a) Normal.

(b) Full and bounding.
(c) Low arterial tension.
(d) High arterial tension.
s



(e) Intermittent.
wwww
мммммммм
(ƒ) Irregular.
(g) Dicrotous.
Sphygmographic Tracings illustrating Different Characters of the Pulse.


ness.
These present, of course, great variations in different cases, yet
there are certain changes that follow in succession so often that they
may be said to form a sort of general rule. In case a person of robust
constitution be attacked with acute fever, the pulse will differ in the
separate stages of the progress of the affection. During the chill the
arteries contract-i. e. high arterial tension occurs-and the pulse is
frequent, small, hard, long, and incompressible (Fig. 370, d). During
the continuance of this condition the temperature of the patient rises
rapidly. With the disappearance of the chill it will be found that the
pulse has changed in character in one particular: the arterial tension
has relaxed. The pulse now becomes large, and is much softer, but it
is still strong and incompressible, for the heart is yet vigorous, and is
perhaps excited to unusual activity, giving a "full bounding pulse"
(Fig. 370, 6). This is a condition in which sedatives are of advantage,
especially if this character of pulse be very marked. As the fever con-
•
A
THE PULSE.
669
tinues for days, and perhaps for weeks, oscillations will occur in the
qualities of the pulse, especially if there is a disposition to recurring
chill. But without this there will be oscillations both in the strength
of the contractions of the heart and the tension of the arteries; but in
the long run both these will be found to be gradually losing ground;
the pulse becomes both smaller and softer, and the individual beats are
comparatively short (Fig. 370, c). Gradually the pulse becomes very
compressible, indicating extreme exhaustion of the nervous mechanism.
In case there is a disappearance of the fever, an enlargement of the
pulse-beat indicates safety for the patient; provided always that this
enlargement is from increased strength of the heart, and not from
increased relaxation of the arteries. This is determined by the com-
parative compressibility of the pulse. Increased arterial relaxation is
usual at the time of the subsidence of a protracted fever, but if the pulse
shows a fair increase in volume at the same time, all is well. If, how-
ever, the volume of the pulse fails to increase with the arterial relaxation,
fatal prostration is indicated and arterial stimulants are urgently called
for. If the case approaches a fatal termination, the pulse becomes very
small, quick, frequent, and generally thready. In case of recovery the
pulse gradually reassumes its former vigor with the returning strength
of the patient.
IRREGULARITIES OF THE PULSE.-The normal pulse is perfectly
regular in its rhythm; that is to say, the contractions of the heart fol-
low each other in very exact time, one beat occupying just as much
time in its performance as another. In disease this regular rhythm is
sometimes disturbed, in such a way that some contractions of the heart
occupy more time in their performance than others, so that a long pul-
sation may be followed by a short one. In this way the normal rhythm
is lost and the beating of the heart becomes irregular. In all such cases
the force of the heart-beats is as irregular as the time. A strong pul-
sation will follow a weak one. These variations from the normal are
known as the irregular pulse (Fig. 370, f). This must be sharply dis-
tinguished from the intermittent pulse. In this the regularity of the
heart-beat is maintained, but occasionally a beat fails. The irregular
pulse is of far more significance than the intermittent. It is most fre-
quently seen associated with disease of the mitral valve, though it occurs
sometimes in great prostration of the heart in the later stages of fevers
that terminate fatally. This pulse is said to be diagnostic of mitral
disease, but it must be remembered that it is not always present in this
affection, there being many cases of extensive mitral lesion accompanied
with a perfectly regular pulse; yet when irregularity occurs without
other symptoms being present to account for it, this disorder is at least
suggested. Irregularity is also frequently present in fatty degeneration
of the heart. This pulse is occasionally seen, too, in connection with
disorders of the nervous system, and is often a valuable diagnostic sign
in meningitis, both in the acute and tubercular forms. Except in
affections of the membranes of the brain, an irregular pulse is very
rare in children, even in the same disorders in which it is seen in
adults. Irregularity is usually cured, or at least greatly benefited, by
the use of heart-stimulants.
670
GENERAL PATHOLOGY.
DICROTISM.-Dicrotism results from diminished arterial tension, and
is the exaggeration of the normal impulse or shock seemingly given to
the blood-wave by the closure of the aortic valves. Viewing the heart
as a pump, and following its motions, we will easily gain an under-
standing of this secondary wave which the sphygmograph shows us is
present in all forms of the pulse, and which may be seen in all the
charts on page 668. When the ventricle is filled the heart contracts
forcibly and the blood is driven into the aorta. Then there comes the
expansion of the ventricle from which the blood has just been expelled,
and the tendency is for the blood to return into the heart. As a matter
of fact, a portion of the blood now contained in the elastic artery does,
with the cessation of the impulse, return toward the heart; and in this
act the aortic valves are caught and forcibly closed, causing a sudden
arrest of the returning volume of blood at a time when the artery is in
active contraction upon it. These two forces, acting together at a time
when there is a marked relaxation of the arterial system, cause a second
expansion of the principal blood-wave, which necessarily occurs during
its subsidence, as is seen in the charts. It is probably only in great
arterial relaxation that marked dicrotism can occur, and it is usually.
associated with weakness of the heart as well. In some instances this
second blood-wave is almost as high as that of the true pulsation, and
may be plainly recognized with the finger, so that one not accustomed
to pulse-examinations might mistake its significance and count the beats
as double their real frequency. This form of pulse, however, is very
rare, although it is occasionally met with in fevers.
1
INTERMITTENT PULSE.-When the rhythm of the pulse is regular,
with the exception that an occasional beat fails, it is said to be an inter-
mittent pulse. The omissions of the beat may take place frequently or a
considerable interval may occur between them (Fig. 370, e). They may
happen regularly after every second or third beat, or even after longer
periods; sometimes they are entirely irregular in their occurrence.
Intermittence differs entirely from irregularity of pulse, and is of much
less serious import. In some persons intermittence of the pulse is a
constitutional peculiarity, lifelong in duration and unattended by evil
consequences; more frequently it does not appear until middle life; in
other cases its occurrence is only occasional, the attacks being induced
by the use of certain articles of food or by certain extraneous conditions.
Many persons who have a pulse occasionally intermittent are made very
uncomfortable by it, but perhaps the greater number are unconscious of
the condition. It seems in no way to endanger life, and the sphygmo-
graph shows that in many cases the apparently omitted beat is really a
very feeble pulsation not sufficiently pronounced to be felt by the finger.
THE PULSE IN LESIONS OF THE HEART.-The importance which the
subject of lesions of the heart has for the specialist, and particularly for
those who administer anæsthetics, is such that I do not like to pass the
subject without notice, although anything like a sufficient treatment of the
variations of the pulse in these conditions would be beyond the scope of
this article. There is not much doubt that the failure on the part of
dentists to detect these conditions contributes to the number of fatalities.
that are continually occurring in that special field of practice. A close
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
671
study of the pulse is one of the best safeguards against these calamitous
results. But a short time since a person presented herself to me asking
that an anesthetic be administered for the extraction of a tooth. Exam-
ination of the pulse at once revealed insufficiency of the aortic valves,
and on inquiry it was learned that the patient had gone outside of her
personal acquaintance for the express purpose of obtaining an anesthetic.
which had been denied her at home. A few weeks later she suddenly
died.
In aortic regurgitation from any considerable insufficiency of the
valves the pulse is quite characteristic. The blood flows back into the
heart during diastole, instead of being caught and held by the aortic
valves, and the arteries become quickly collapsed or much more empty
of blood than in other conditions. This gives a pulse of great arterial
relaxation with a marked exaggeration in certain directions. The rise
of the blood-wave may be the same as in the ordinary pulse, but when
the height is reached it falls suddenly, almost as if the artery had col-
lapsed. This characteristic presents various degrees as the aortic insuf-
ficiency is more or less extensive. In extreme cases the pulse seems to
give the fingers a quick, sharp, shot-like blow, and disappears as sud-
denly as it came. These phenomena are intensified by raising the wrist
high above the patient's head, so that gravitation will assist in empty-
ing the artery.
Magda
In aortic regurgitation the pulse is often visible in certain of the
superficial arteries, but this also occurs in arterial degeneration and
in very high arterial tension, especially if persistent for some time.
Markedly visible pulsations in the neck should always lead to further
examination for the cause. In high tension the artery remains com-
paratively hard and firm during diastole of the heart, while in aortic
regurgitation it collapses suddenly. In the former condition the pulse-
beat is long, and in the latter it is short or quick. In degeneration of
the arteries the vessels become tortuous, and remain distinctly hard after
all the blood has been pressed out of them; and if degeneration is
extensive, calcareous plates are frequently found in the arterial walls.
The pulse-beats in aortic obstruction, so long as the heart is otherwise
perfect, are long, small, and infrequent. The reasons for this are
explained by the fact of the increased difficulty of the transit of the
blood through the narrowed orifice. This makes the rise of the blood-
wave peculiarly slow. Hence the peculiar characters of the pulse. If
this condition is accompanied by other lesions, the pulse will, of course,
be modified.
Mitral disease has already been noticed.
Ma
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
Before entering upon the study of the variations that occur in the
amount, quality, and distribution of the blood, it seems well to refresh
the mind of the reader as to certain points in the physiology of the cir-
culation. While studying the pulse we learned that the arterial system
is under the control of the vaso-motor system of nerves in such a way
as to give high and low arterial tension. This system of nerves is capa-
Tabl
Madd
672
GENERAL PATHOLOGY.
ble of changing the condition of the circulation of the blood in various
other ways, and of accommodating a greater or less amount of blood in
the vessels, either as a whole or in individual parts of the circulatory
system; that is to say, the vaso-motor system does not necessarily act
as a unit, operating at once on the whole vascular system, expanding
or dilating it as a whole, but it may and does act locally as well, pro-
ducing variations in the supply of blood to the different parts of the
organism. Many of these local variations are of a purely physiological
nature, such as occur in the glands during their quiescent and their
active states. As an instance of this action I may refer to the well-
demonstrated fact that the supply of blood to the salivary glands may
be greatly increased, even by the sight of desirable food: the glands
become turgid, and the outpouring of the saliva is at once begun or
greatly increased. Every dentist is also well acquainted with the
marked excitement of the salivary glands during the performance of
painful operations within the mouth. These are examples of reflex
actions of the nervous system by which impressions received by sensory
nerves produce local variations in the circulation by being reflected
through the vaso-motors, and may be regarded as the type of the reflex
phenomena of the vaso-motor system wherever they occur. Dilatations
and contractions of the vascular system occur in response to irritation of, or
impressions made upon, sensory nerves. The impression received by the
sensory nerve passes along the course of the afferent nerve to the cen-
tral ganglion, and from thence is reflected back through the efferent
nerve as a motor impulse. This statement holds good in both normal
and abnormal conditions. In the mechanism of the nutritive functions.
impressions are probably received by nerves not sensory in the ordinary
sense or in the sense that the impresssions they convey are perceived
by the mind in any way. The result, however, is precisely the same in
the one case as in the other. My meaning here may be illustrated by
the results of the ligation of the arteries. When an artery conveying
the blood to a certain part is ligated the immediate result is to lessen
the blood-supply to that part, even though it is supplied by several
other arteries. Within a very short time there is a dilatation of the
other vessels leading to the part, so that the blood-supply becomes
normal. This will always occur if the necessary quantity of blood
can be supplied by a reasonable expansion of these vessels. How does
this occur? It is not from the injury sustained and by reflection through
the sensory nerves, for an injury otherwise similar, but not diminishing
the blood-supply, would not produce a similar effect. Then the effect
must be produced by other nerves that take cognizance of the nutritive
processes and reflect the needs of the tissues for the nutritive fluid. In
this manner the blood-supply to the several parts of the body is regu-
lated in accordance with the needs of each, and is continually under-
going change, especially in the glandular organs that are periodical
in their activity. These changes may be seen also in any of the tis-
sues that may be subjected to microscopic examination in the living
state. The small arteries do not remain uniformly of the same diam-
eter, but are seen to contract and expand more or less continuously, now
admitting more, now less, blood to the part. It would seem, then, that
-
12
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
673
the needs of each individual tissue are thus reflected through the vaso-
motor nerves in such a manner that there is a corresponding movement
of the muscular fibres of the arteries regulating the blood-supply in
every part of the body, and that the nerves thus acting play the part
of sensory nerves in the reflex phenomena in the fact that they convey
afferent impulses that are in turn converted into efferent motor impulses.
This is in accord with the general physiological law that sensory impres-
sions or impulses travel from the distal to the central (afferent), and all
motor impulses travel from the central to the distal (efferent). In the
normal healthy organism the harmony of these relations is preserved.
In disease this harmony is often seriously disturbed, and it is my pur-
pose to notice some of these disturbances presently.
Pursuing the study of this system of nerves, it is definitely ascertained
that paralysis of the vaso-motor nerves produces arterial relaxation.
If the nerves distributed to any part are severed-as, for instance,
those supplying the hinder leg of an animal-all of the arteries of
that member dilate and the leg becomes surcharged with blood. This
seems to show that it is the office of this system of nerves to hold, by
means of the circular muscular fibres of the blood-vessels, a certain
grasp or pressure on the blood they contain, and that the maintenance
of this pressure—or tone, as it is sometimes called-is necessary to the
proper performance of the functions of the circulation. The greatest
proportionate amount of muscular fibre is in the smallest arteries, and
it is these that undergo the greatest change in calibre. In this way the
blood is not only more firmly grasped, but its outflow from the arteries
into the capillaries is regulated.
Experiment shows that after the vaso-motor nerves of a part have
been severed and the vessels have lost their tone, this will in time be
recovered, the nerves in the mean time remaining asunder. From
this experimental fact it is inferred that there are ganglia in the walls
of the blood-vessels themselves that are capable of maintaining the tone
of the circulation in the absence of the central force or influence, but
that under all ordinary conditions these minor ganglia are dominated
and controlled by the one central power which unifies the whole system
and renders it complete. This is, in brief, a recital of the mechanism
of the vaso-motor influence, and its office in the control of the circula-
tion as at present understood. A more detailed discussion of it, while
very desirable, is beyond the limit of this article.
PLETHORA.—The term plethora is used to designate a condition in
which the total quantity of the blood is too great. The term general
hyperomia is also used in the same sense. This condition will occur
when from any cause the blood-forming organs are unduly active, and
is indicated by habitual over-fulness of the capillaries as shown in
undue redness of the skin and turgescence of the venous circulation,
especially that of the abdominal region known as the portal system.
We may also have another condition closely akin to this, in which the
bulk of the blood is not notably increased, but in which the propor-
tion of the red corpuscles is greater than normal. The fluid portions
of the blood are probably subject to greater fluctuations than are its
solid constituents; and within reasonable bounds this is of compara-
VOL. I.-43

674
GENERAL PATHOLOGY.
tively little importance. The energies of the body, and especially its
nutritive powers, upon which these energies depend, are closely con-
nected with the corpuscular elements of the blood, especially the red
corpuscles. Their importance is shown by the fact that animals bled
nearly to death may be resuscitated by the injection of these corpuscles
in serum. From what is known of their physiological relations, it
might be inferred that the effect of an excessive quantity of blood with
the full proportion of red corpuscles, or of a superabundance of the red
corpuscles without an excess of fluid, would produce over-activity of the
circulation and a disposition to undue excitation of the organs of the
body. Such effects, in fact, constitute the phenomena of the condition of
plethora. The power of the heart's action is increased; sensibility and
muscular irritability are augmented; some rise in the temperature may
be noted; the brain is more prone to excitement; and the whole body
takes on a full and rotund outline. Pain in the head is liable to be
produced by excitement or by stimulants, on account of the unusual
power of the circulation; and this condition is thought to involve a
liability to cerebral congestion. Febrile attacks are rendered more
intense, and acute inflammations are more readily excited. It is
important to discriminate between plethora and other morbid con-
ditions. In pregnancy the fluid elements of the blood are often much
increased without a true plethora. In this case there is not an abnor-
mal increase of the red blood-globules, and other signs of the state of
plethora are wanting. Abnormal fulness of the blood-vessels from
some impediment to the returning veins might sometimes be mistaken
for this condition.
A tendency to plethora may be inherited, or it may be acquired by
over-feeding on rich foods, wines, etc., connected with diminished
expenditure of blood-constituents in the nutrition of the body. This
is directly favored by sedentary habits, the digestive and assimilative
functions remaining active.
Experiments in the transfusion of blood in animals give us some idea
of the extent to which the volume of the blood may be increased. Worm
Mueller injected the defibrinated blood of dogs into other dogs, and by
careful experiment found that the normal amount of blood might be
increased one-half or three-fourths without materially endangering the
health of the animal, and double the normal quantity would be borne
without much apparent inconvenience. If, however, the quantity was
increased much beyond this, perturbations of the circulation occurred,
and the animal died within a day or two. It appears from these
experiments that the excess of blood injected is quickly disposed of—
that within three or four days there is only an excess of the globules,
and at the end of two weeks these also have disappeared. From the
results of these experiments it may be concluded that there is some
mechanism in the body having the power of regulating the amount
of the blood, but as to what this mechanism may be there is as yet
no definite knowledge.
LOCAL HYPERÆMIA, OR CONGESTION.-Local hyperæmia consists in
the presence of an undue amount of blood in a particular part. Two vari-
eties, differing in mode of origin and in character, are recognized: these are
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION. 675
known as active and passive, or arterial and venous hyperemia or con-
gestion. It is essential that the distinction between these forms be well
understood, for they arise under different circumstances and are of widely
different significance. Local hyperæmia, when active, is dependent on the
condition of the arteries, and when passive on the condition of the veins.
In the active variety the arterioles of the affected region are actively
dilated, admitting to the part an unusual amount of blood; this flows
unobstructed through the capillaries to the veins, and there is, conse-
quently, an increased amount of blood passing through the affected area,
the blood being therefore more highly arterial than normal. In the
passive or venous variety these conditions are exactly reversed. There
is some obstruction to the passage of the blood by the veins away from
the part; and the actual amount of blood passing through it is dimin-
ished, the blood itself being more highly venous than normal. In
active hyperæmia there is not an unusual retention of the blood in the
part, but rather the reverse; while in the passive variety there is an
unusual retention of the blood in the part. These are the essential
points of difference in the two forms of hyperæmia.
Active local hyperaemia is constantly occurring in the organism as a
physiological process in all those glandular organs that have normal
periods of activity and quiescence. This happens with most of the
secretory organs. The salivary glands are hyperemic while actively
secreting during the process of eating. The glands of the stomach con-
tain more blood, and much more is passing through their vessels, dur-
ing the process of digestion than in the periods of rest. This is called
for by the increased amount of work to be accomplished at these times,
and serves as an illustration of the perfect and delicate working of the
mechanism of the nutritive processes. This is not confined to the glan-
dular structures, but extends to the other tissues as well. A muscle
receives more blood in its periods of active work than in its periods of
rest. Any perversion or undue and hurtful activity of any of these
processes constitutes a pathological hyperæmia, and the natural inference
would be that an organism so adjusted, and seemingly so liable to over-
strain upon its individual parts, would be very prone to this kind of
perversion of functional activity. Clinical experience shows, however,
that this kind of difficulty is not so common as might be expected; yet
its occurrence is of sufficient frequency to afford numerous examples.
The pulp of a tooth in the normal condition transmits but one sensa-
tion, that of pain, excited by heat or cold; at each such excitation there
is a transient dilatation of its arterioles. If this form of excitation
be frequently repeated for a considerable period, a condition of patho-
logical hyperemia will be induced, during the continuance of which
the least possible thermal change will produce excruciating pain.
This may be considered an exaltation of a perfectly normal function
to such a degree that it becomes a pathological condition. Some-
thing of the same nature is seen in the glandular system. The
stomach is often teased into a state of physiological hyperemia by
the ingestion of improper food, and the brain may take on a similar
condition from repeated mental excitement. These are types of hyper-
æmia that are liable to be followed by the inflammatory process, and
G
Jedn
trada
676
GENERAL PATHOLOGY.
their further discussion will be taken up in connection with that
subject.
It is to direct experimentation through vivisection that we are in-
debted for our knowledge of the phenomena of hyperemia in its simple
and uncomplicated forms, and indeed for what knowledge we possess of
the vaso-motor system of nerves. There are no anatomical differences
existing in the nervous system by which we can know a motor from a
sensory nerve. By means of vivisection, then, the vaso-motor nerves
are found to emanate from the spinal cord with the posterior or sensory
roots of the spinal nerves, and pass to the sympathetic system by way
of the rami communicantes. After passing some distance, up or down
as the case may be, with this system, they again join the spinal nerves
in communicating branches, and pass to the extremities in company
with the motor and sensory nerves of these parts. When hyperemia
is produced directly by severing the vaso-motor nerves, it presents the
following phenomena: The parts become somewhat swollen and red-
dened by the entrance of a greater amount of blood into them, and at
the same time the temperature is markedly elevated. The elevation of
temperature, however, in the most intense hyperemia that can be pro-
duced never quite reaches that of the central portions of the body;
indeed, it may be accounted for in all cases by the increased amount of
warm blood passing through the circulatory apparatus. This process,
when excited in this way-i. e. by interference with the vaso-motor
nerves-never leads to inflammation. It seems to have relation solely
to the state of the blood-vessels, which are simply widely dilated, ad-
mitting a larger quantity of blood. If the induced hyperemia be of
large extent the immediate effect is to reduce the general blood-pressure;
but this is quickly regained, unless there are other reasons for depres-
sion. The blood-pressure seems to have little to do with the state of
hyperæmia, for it is no greater in the hyperamic part than elsewhere.
Indeed, it may be actually less, for the reason that the blood is less
hindered in its passage to the venous system, there seeming to be an
expansion of the capillaries as well. Owing to the increased diffused
redness this is well seen in any parts that are sufficiently transparent.
We can now understand why we have a collateral hyperemia after
the ligation of an artery. If the carotid artery be tied, the corre-
sponding vessel of the opposite side becomes expanded. This is not to
be explained by increase of the blood-pressure caused by the stoppage
of the flow through the artery ligated, for such increase of pressure
would be either general or in the arteries most directly connected with
the ligated branch. This is not the case. The expanded artery is the
one that can most directly supply the territory deprived of blood by
the ligation. This is a reflex phenomenon, taking place through the
action of the vaso-motor nerves in response to the needs of certain tis-
sues for blood. This is the type of the reflex phenomena of the vaso-
motor nerves in all cases of this character. Increased quantities of
blood are, through these reflex actions, called to special parts or terri-
tories of the circulation under a great variety of circumstances of which
some have already been indicated. If the hands are smartly struck
together a few times, a reponse in the form of increased redness will be
J
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
677
received, a local hyperemia having been called forth. This simple
experiment will serve to illustrate a principle which seems of import-
ance in the study of the subject, and constitutes the basis of a division
of the local hyperemias into two classes. It has already been suffi-
ciently explained that simple hyperæmia, or local dilatation of the vas-
cular system through reflex action, never gives rise to inflammation. It
is evident, however, that in the experiment just related a continuance or
increased severity of the cause might beget the inflammatory process.
This is true of very many of the causes of local hyperæmia, and many
of them are actually followed by inflammation; therefore they may be
designated as hyperaemias of irritation. In this case the inflammation
is not in consequence of the hyperemia, for we have seen that inflam-
mation does not necessarily follow the most extended dilatation of the
vessels in complete paralysis of the vaso-motor nerves: the inflamma-
tion is the result of tissue injury.
Increase of blood-pressure is not often local, and even if it were it
could not ordinarily produce hyperæmia. The vessels of the general
system cannot be dilated to any considerable degree by this cause. In
the lungs, however, the case is different. Here the object is the aëration
of the blood, and the vessels are so arranged in the walls of the air-
vesicles that the blood is spread out in very thin sheets. These capil-
lary sheets are not composed of simple round anastomosing capillary
twigs, as in the other parts of the body, but in the normal condition of
expansion of the lung they are distinctly flattened. This renders them
easily distensible by increase of pressure.¹ Therefore we are liable to
active congestion of these organs in consequence of sudden increase of
the blood-pressure from any cause.
Passive hyperemia occurs whenever there is obstruction to the
flow of blood away from the part by the veins. In this case the cap-
illary system of the region becomes overfilled with blood, which, on
account of retention or unusually slow movement, becomes highly
venous in character. This is also called passive congestion, venous
hyperemia, or congestion. This state is seen in connection with debil-
ity or enfeeblement of the heart. In the normal state of the circula-
tion the blood is urged forward with sufficient power to cause it to
ascend from dependent parts against gravity without perceptible hin-
drance; but if the heart, which is the principal motive-power of the
circulation, becomes weakened or disabled in its valves, the blood fails
to return promptly by the veins, and stagnation is the result. The
effect is the same if the veins be so obstructed that there is only a
partial return of the blood from a part, the circulation being otherwise
good. The congestion, except in the lungs, is probably in no case
materially increased by arterial pressure, as was formerly supposed.
The dilatation of the capillaries is a reflex phenomenon occurring in
response to the needs of the tissues for arterial blood. Every individual
living cell in the organism must have access to free oxygen, must absorb
oxygen and exhale carbonic acid-must breathe in order to maintain its
C
Wang
1 See monograph, "The Circulation of the Blood in the Air-vesicles of the Lungs,"
by G. V. Black, D. D. S., St. Louis Med, and Surg. Journal, and Missouri Dental Journal
1878.
678
GENERAL PATHOLOGY.
vitality. This is just as true of the individual elements of the organ-
ism as of the organism as a whole. We have already seen that it is the
office of the vaso-motor system of nerves to regulate the supply of blood
to the individual parts of the organism, and with this, of course, the
supply of oxygen which the blood conveys. The dilatation of the
vessels is, under these circumstances, a gasp for breath. In this thought
we have the key to the otherwise singular phenomena of the so-called
passive congestions. These congestions occur on interference with the
circulation, whether the arterial pressure is high or low, whether the
power that drives the blood be great or small. It occurs if the veins
be obstructed before a powerful current of blood driven by a vigorous
heart, or in the presence of a feeble current driven by a heart too weak
to compel the return of the blood against the attraction of gravitation.
This kind of hyperemia may occur under a great variety of circum-
stances, and is common to a great variety of diseases. It is seen first in
the dependent portions of the body in all the forms of valvular disease
of the heart when they have made such progress as to interfere mate-
rially with the propulsion of the blood. It is prone to occur in diseases
of the kidneys, and is an element in all dropsical disorders. It is lia-
ble to occur in the later periods of any of the continued fevers that
cause great enfeeblement. It is seen in anæmia and great nervous
exhaustion; indeed, in any condition of great reduction of the vital
powers. It occurs also from pressure on the veins preventing the return
of the blood. This is often seen in the pregnant female from the pres-
sure of the uterus on the veins. In persons not very strong it may occur
in the feet from long standing, as is not unfrequently noted among den-
tists who stand much at the chair. It may be produced by tumors that
compress or otherwise obstruct the veins-in short, by anything what-
ever that obstructs the free passage of the blood back to the heart.
The results of passive hyperemia are somewhat complex. In case of
the obstruction of a vein the amount of hyperemia will obviously
depend on the number of anastomosing branches in the neighborhood.
If these be sufficient, the blood will be conveyed by these channels, and
no hyperemia will result. But in case these are not present in sufficient
number to convey the blood, then the retained blood becomes more than
usually venous in character; and in proportion as this takes place the
vessels of the part are dilated, relaxed, admitting more and more blood
to the part. The degree of this engorgement will depend directly on
the amount of obstruction, and may vary from a slight fulness of the
vessels to complete stagnation and the complete filling of the tissue with
blood. In case there is only a moderate slowing of the blood-current,
the tissue will contain more blood than the normal quantity, but the
most obvious sign will be the escape of an undue proportion of the
blood-serum from the vessels into the tissues, especially the cellular,
areolar, or connective tissues of the part, forming what is known as
ædema. When this escape of the fluid parts of the blood is not consid-
erable, it is taken up by the lymphatic vessels of the part and conveyed
back into the blood; but if there is more than these vessels can dispose
of in this way, then the part becomes swollen and oedematous. This
swelling is characteristic in that it has a doughy feel under the finger,
M
wd
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
679
sure.
and remains deeply pitted for some time after the removal of the pres-
If now the obstruction is removed, the blood-current is soon
re-established and the oedema disappears. The occurrence of these
phenomena is the same when the obstruction is the result of any
other cause, as great debility.
Diapedesis of the red blood-globules occurs when the stagnation is
more considerable. This is the passage of the red blood-globules
through the walls of the
blood-vessels into the tis-
sues. This occurs mainly,
if not entirely, in the capil-
laries without the rupture
of their walls. There seems
to be some difference of
opinion as to whether the
blood-globules pass through
the endothelial plates of
which these walls are
formed, or pass out between
them at points, called sto-
mata, where several of these
plates join, as shown in the
diagram (Fig. 372). The
fact of the escape of the
red globules is well shown
in passive hyperæmia arti-
ficially produced by ligating
the veins in the tongue of
the frog. After a consider-
able amount of red blood Normal Capillary, with Capillaries after Passive Hyper-
endothelium mapped
out by treatment with
nitrate of silver.
æmia apertures between the
cells greatly enlarged-the so-
called stomata (Arnold).
has escaped into the tissues
by this process, if the cause
is removed complete recovery takes place and the arteries seem to have ¬
suffered no injury; the hemorrhage ceases at once. Arnold supposed
that the so-called stomata at the corners of the endothelial plates were
enlarged, as shown in the figure; but this idea seems now to have been
given up in favor of the doctrine that the globules pass through the
tissue without leaving any sign.
The nutritive power of the tissues becomes much weakened in passive
hyperemia if long continued. This gives rise to the sloughing of parts
that bear the pressure of the body, and the formation of what are called
bed-sores, these being prone to occur in great debility caused by long-
continued fever or by other protracted illnesses that notably weaken
the circulation.
FIG. 371.
FIG. 372.


Gangrene may occur in case of extreme passive hyperemia with
intense oedema. In this case the aëration of the tissues fails so com-
pletely that they die en masse. In this way in a case of Bright's
disease of the kidneys I have seen a whole limb become gangre-
nous.
THROMBOSIS.-A thrombus is a blood-clot that forms, under a vari-
680
GENERAL PATHOLOGY.
C
ety of circumstances, in the vessels while the blood is actively circulat-
ing. The clot which closes the divided end of an artery and that which
forms after the ligation of an artery are also called thrombi. These
varieties of thrombi differ quite remarkably in character. In order
that we may appreciate these differences it is necessary that we study
their mode of formation. The coagulation of the blood has been very
closely studied (Zahn), both theoretically and in its clinical aspect. And
the conditions under which the blood will coagulate seem to have been
pretty clearly made out. In order that a clot may form three agents
are essential-fibrin ferment, fibrinogen, and paraglobulin (Schmidt).
In the presence of the fibrin ferment the two latter substances unite to
form fibrin, which is the essential factor in the formation of the clot.
The paraglobulin and the ferment substance are found to reside in the
white blood-globules, and the fibrinogen exists in a state of solution in
the blood-plasma. In order that a blood-clot may form, it is necessary
that white blood-globules be disintegrated and the ferment substance
and paraglobulin set free. Therefore as long as the white corpuscles
are circulating and remain alive the blood will continue fluid. In order
to maintain the life of the white blood-corpuscles it is necessary that
they should not be exposed to contact with dead matter nor with in-
flamed or injured tissue. It has been demonstrated by experiment
(Lister) that the blood may be kept fluid in the still condition for a long
time if it is in contact with living tissue. If within the living body an
artery is carefully ligated (so as not to injure its internal coat) at two
points in such a manner as to include a portion filled with blood, this
will remain fluid for twelve or fifteen days. If the section thus ligated
be cut out, the blood will, under favorable circumstances, remain fluid
for several days. These experiments show clearly that the coagulation
of blood is not on account of the arrest of motion, as was once sup-
posed. When we examine critically all the conditions under which the
coagulation of the blood takes place, it will be found that the cardinal
points are these: Contact with dead matter, such as the walls of the
vessel in which it is drawn or any inanimate object-(the more rough
and uneven the surface of contact the quicker will be the coagulation),
contact with changed living tissue, whether this change be the result of
inflammation or injury, such as cutting, bruising, or tearing the flesh.
Under any of these circumstances some of the white globules of the
blood become so far disintegrated as to give up the paraglobulin and
fibrin ferment, and in the presence of the latter the former at once unites
with the fibrinogen of the blood-plasma for the formation of the semi-
solid fibres of fibrin by which the blood is held together in a gelatinous
kong
K
mass.
In hemorrhage occurring from the division of an artery the closure
of the severed extremity by thrombus is favored by the flow of the
blood over the injured tissue, and the greater the amount of injured
tissue with which the blood may come in contact in proportion to the
calibre of the vessel, the quicker it will be closed. Therefore, an artery
severed by a blunt instrument that causes much bruising of the tissues
is much more readily closed by the clotting of the blood than if severed
by a very sharp instrument. Nature has also provided means of increas-
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
681
FIG. 373.
ing the contact of the escaping blood with the injured tissue. When an
artery is severed, the inner coat contracts
within the outer walls-i. e. becomes the
shorter-and is pulled backward into the outer
wall of the vessel, and at the same time the
cut end is narrowed (Fig. 373). In this way
the flowing blood is brought into contact with
the greatest possible surface of injured tissue.
The formation of the thrombus is begun by
the adhesion of the white blood-globules to
the injured surface. These adhere one after
another, and are held fast by the formation
of a little fibrin; others adhere, and more
fibrin is formed until the end of the vessel is
completely filled. In this process the red
globules take no part, and if the thrombus Natural Hemostasis. The divided
ends of the artery (d) retract
within the sheath (a), and by
contracting diminish the calibre
of the canal. Blood coagulates in
the sheath (a) around the orifice
of the divided vessel, and in the
artery itself (b) up to the first ·
branch (e); and lastly, plastic
lymph is poured out from the
divided coats of the vessel, and
by its organization the perma-
nent closure takes place (Jones).
is very slowly formed, very few of them
will be included in the clot, and it will be
white or gray in color. In this position,
however, a thrombus is usually red from the
entanglement of red globules. After the ar-
tery is closed the coagulation of the blood in
the artery proceeds until the first lateral
branch is reached. This in time becomes organized, or rather is
absorbed, and its place filled with new tissue, and the vessel is per-
manently closed (Figs. 374 and 375).
K
In the ligation of arteries the blood is caused to clot by injury to the
internal coat. In this case the thrombus is always red, for it contains
all the blood-constituents. If the clot should not, before the ligature
comes away, become sufficiently firm to resist the blood-pressure, sec-
ondary hemorrhage will occur.
J
Thrombi form in the blood-vessels under various circumstances. This
may be well studied in the mesentery of the frog. When this is ex-
posed for microscopic study, a vessel of some size may be in some way
injured-by pricking with a needle or placing some irritant in contact
with it-and the progress of the building of the thrombus watched.
As the blood passes over the injured point a few white globules adhere
to it. Upon these others are slowly deposited in successive layers, and
the little lump is seen to grow larger and larger as the successive layers
are deposited. This may continue steadily until the vessel is completely
occluded and the passage of the blood stopped; or after a little clump
is formed it may be detached by some movement or by the force of the
passing blood-current and float away. A second clump will then be
deposited in the same manner as the first. During the growth of these
the outline of the white blood-globules is usually lost. They seem, as
the rule, to become fused with the forming fibrin into one mass, though
sometimes a few continue to show their outlines. It does not seem that
the destruction of very many white blood-globules is necessary to pro-
duce a considerable clot. The liberated material acts as a ferment, and
according to the law of the action of ferments a very little may produce

d--
Ľ
682
GENERAL PATHOLOGY.
繡
​a great result by causing changes in other substances without itself
entering into the combination.
Thrombi formed in the manner just stated are always white or nearly
So. This is always the case when they are formed slowly in the blood-
stream, from the fact that very few red blood-globules or none become
entangled in the forming mass. This circumstance enables the pathol-
ogist to determine whether or not a given blood-clot has been formed
FIG. 375.

2
2 M
FIG. 374.
Dovely com
MZ
Longitudinal Section of the Ligatured End
of the Crural Artery of a Dog, fifty days
after the application of the ligature, show-
ing the newly-formed vessels in the throm-
bus and their communications with the
vasa vasorum: 7%, thrombus; M, muscular
coat; Z, external coat (× 20, O. Weber).
B p"
に
​1
M
ré
B
2

A Thrombus, ten days old, after
modified ligation. Longitudinal
cut. Low power. After ligature
at 4, the artery was seized and
compressed at B between the
arms of a pair of forceps. a, ad-
ventitia; m, media; e, cellular
tissue; p, cellular formation at
bottom of clot, non-organized,
and apparently not larger than
such an accumulation usually is
at five days; it consists mainly of
cells similar to white blood-cor-
puscles; only a few epithelioid
cells are scattered though it,
and no granulations springing
from it penetrate the crevices
of the laminated clot (d) imme-
diately above; at p', there is
","
an ingrowth of the intima and
inner layers of the media. At L,
above the point of compression,
a blood-clot like that at rested,
but handling caused its displace-
ment,
by gradual growth on account of some injury, inflammatory or other-
wise, to the vessels, or from stagnation of the blood. This character of
clot can be closely imitated artificially by rapidly whipping freshly-
drawn blood with a bundle of small twigs, to which the forming fibrin
will adhere, leaving the red globules in the blood-serum. By working
quickly and carefully the clot adhering to the twigs will be nearly
white, and all the fibrin can in this way be taken from the blood. This
is the mode of preparing defibrinated blood for transfusion.
But one cause is known for the formation of thrombi in the living
vessels, and this is some actual injury to their walls. This injury may
be effected in a multitude of ways. On account of pressure or extreme
weakness of the heart the blood may stagnate in the vessels until the
endothelium becomes seriously impaired. Arteritis may affect them, or,
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
683
in fact, any of the diseases to which the arteries are liable. It may
result directly from injury in wounds, pricking with sharp instruments
as the result of accident or in using the hypodermic needle, etc.
Thrombi often form in the debilitated heart. This is supposed to
occur when the cavities of the heart are not completely emptied of blood
at each contraction. Under such circumstances a portion of blood will
remain in the apex of the ventricle and stagnate, or it may lodge
behind the valves or in other nooks. The clotting, once begun, may
continue until the motions of the heart are so interfered with as to cause
death. A diseased and roughened condition of the valves of the heart
is another cause of thrombus.
The organization of thrombi will be considered under the head of
Processes of Repair.
EMBOLISM.-Embolism is usually a result of thrombosis. A part or
the whole of a thrombus becomes detached from its place of formation
and floats away with the blood-stream. If this be in the arteries, it
must pass into a smaller artery, and finally it will come to a point
where the calibre of the vessel is too narrow to allow it to pass, and the
plugging of the artery and the stoppage of the flow of blood through it
are the result. An embolus is, however, not necessarily a detached
thrombus. It may be any conceivable thing that can gain entrance to
the vessels and travel with the blood, as detached bits of tumor, chalky
deposits from the valves, oil-globules, or air that may have gained
entrance to the vessels, or other foreign substance. If we know where
an embolus starts, we can have some idea where it will lodge. If it be
in an artery, it is likely to follow the most direct line until a point is
found too small for it to pass; if it is in the portal system, it must
lodge in the liver; if it is in the veins, it must lodge in the lungs after
passing the heart; if it is in the heart, it may go to any part of the
general system, but the manner in which the carotids are given off from
the arch of the aorta frequently causes emboli to be sent to the brain.
The results of embolism vary greatly with the position of the lodg-
ment of the embolus. In case there are many arteries with free anasto-
moses, the circulation is restored almost at once, and no harm results,
for it is only the capillary circulation that is important to the tissues.
The most that can occur in this case will be the formation of an abscess,
and this is not likely to result unless the embolus contains septic mate-
rial. Generally the embolic clot becomes organized, or, more strictly,
is partially absorbed, and this part of the artery is reduced to a solid
cord.
Hemorrhagic infarction results from embolism of arteries that have
no anastomosing connections. These are sometimes called end-arteries.
This arrangement of the arteries occurs in several of the organs of the
body, as the brain, the kidneys, the lungs, the spleen, the pulps of the
single-rooted teeth, and in various other positions. Infarction is very
important on account of the serious, and often fatal, damage done to
important organs. Such arteries supply blood to a definite piece of
tissue, and when this supply is cut off by an embolus death of that tis-
sue is the inevitable consequence. The lateral branches of the principal
arteries of the tongue of the frog are without anastomosing branches,
684
GENERAL PATHOLOGY.
and Cohnheim has employed them to study this subject experimentally
(Fig. 376). He introduced little pellets of blackened wax into the
FIG. 376.


k b
Diagram of the conditions following Embolism of an End-artery. In the figure to the left the state
of anæmia after the embolism is shown; in the other figure the regurgitant current from the vein
is indicated (after Cohnheim).
division of the aorta that communicates with the tongue, and succeeded
in obstructing these particular arteries. When thus obstructed the effect
was to stop the movement of the blood in the area supplied by the
branch in arteries, capillaries, and veins. This state did not remain.
long, for soon there was observed a backward movement of the blood
through the vein into the capillaries of the district, which went on
slowly until these were distended with blood. But the movement did
not cease with the wide distension of the vessels, for soon a remarkable
phenomenon became apparent-the rapid diapedesis of the red globules
of the blood into the tissues. This went on until the whole area was
completely engorged with blood. How can this be explained? It
is said that the diapedesis is occasioned by the impairment of the
capillary walls from deprivation of arterial blood, but we have already
seen, while studying active hyperæmia, that diapedesis also occurs from
the obstruction of the veins, and that if the obstruction be removed.
within a reasonable time, the capillary walls prove not to be impaired.
It seems to me clear that this is not the true explanation of this phe-
nomenon. Neither are the vessels expanded by the pressure of the
blood, for, as we have seen, the blood-pressure is reduced to the lowest
possible standard by the closure of the artery. The expansion of the
vessels in this, as in other instances that I have heretofore noticed, is to
be explained from the standpoint of physiology rather than from that
of dynamics. These tissues are deprived of aërated blood, and the
expansion of the vessels is a reflex phenomenon denoting an effort to
supply this need. The needs of the tissues are supplied, normally, by
the absorption of certain constituents of the blood; and here we find
this so exaggerated that the whole blood is absorbed in the effort to obtain
aëration. Therefore, the tissues of the region become completely
engorged with blood, which, as the impairment of tissue proceeds,
coagulates, and the coagulum encloses the tissue in its meshes. That
there occurs final deterioration of the endothelium of the vessels is a
matter of course, but this is not the cause of the diapedesis, but a result
of deprivation of aërated blood.
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
685
·
FIG. 377.
An infarct will have the form of the bit of tissue supplied by the
artery plugged by the embolus, and is usually cone-shaped, with the
apex at the point where the embolus has lodged
and the base at the surface of the organ in
which it has occurred (Fig. 377). In recent
infarcts the appearance is that of a blood-clot
in the tissues. In time this shrinks and the
fluid portions disappear by absorption. Sur-
rounding it there is a zone of hyperemic tissue,
and usually some projection of young granula-
tion-cells into its mass. Under favorable cir-
cumstances the whole infarct will be absorbed
and its place supplied by fibrous tissue, as is
generally the case in the spleen. But very
often the infarct becomes of a pale-yellow or
whitish color, from the loss of the coloring
matter of the blood, and finally undergoes fatty Diagram of a Hemorrhagic In-
degeneration, and is absorbed or remains as a
kind of cyst. The position of the infarction
has to do with the evils connected with it. In
the brain the infarct is more prone to softening
than in other regions, apparently on account of
the very small amount of the connective-tissue element, and its presence
there is of much graver moment, owing to the importance of the tissue
destroyed. In other positions the injury is less serious, the degree
depending on the amount of tissue included. In the retina it may
cause the loss of sight; in the kidney, the loss of the gland-tissue
involved. If the embolus lodge in the artery of a tooth-pulp at the
apical foramen, the pulp will be lost; and, as in this position the fluids
are not readily absorbed, alveolar abscess is sooner or later likely to
occur. It must be remembered that the plugging of such minute
arteries as this may be by oil-globules.
a
ひ
​farct: a, artery obliterated by
an embolus (e); v,vein filled with
a secondary thrombus (th); 1,
centre of infarct which is be-
coming disintegrated; 2, area
of extravasation; 3, area of col-
lateral hyperæmia (O. Weber).
HEMORRHAGE.-Hemorrhage may occur in two distinct forms-by
rupture of the vessels and by diapedesis. The blood may pass outside
of the body, may escape into the cavities of the body, or it may make
place for itself in the tissues by forcing them asunder, or it may infil-
trate the tissues. Hemorrhage by rupture may occur from any of the
vessels, great or small; that by diapedesis occurs only in the capillaries.
The latter has already been considered in some of its phases. Hemor-
rhage from rupture is generally traumatic in origin, as in wounds made
by cutting or tearing the flesh. It may also occur from sloughing or
by the perforation of the vessels by ulceration. Disease of the vessel
may so weaken the walls that they give way to the blood-pressure, as in
aneurism, atheroma, etc. There are some persons whose blood-vessels
are so constituted that they are unusually easy of rupture. This is
called the hemorrhagic diathesis. It is sometimes inherited. Aside
from these causes there are some diseases, as scurvy, the anæmias, and
the septic fevers, in which a disposition to hemorrhage is induced either
by alterations of the constitution of the blood or of the tissues. In some
of the diseases named, and also in purpura hæmorrhagica, blood is

1
e....
th
3
-
686
GENERAL PATHOLOGY.
extravasated in small spots of tissue-ecchymoses-often freely distrib-
uted over the body. It is probable that in some of these cases the bleed-
ing is by diapedesis.
Hemorrhage is stopped naturally by the coagulation of the blood.
This was described under the head of Thrombosis (p. 679). In some
conditions of the blood there seems to be a partial failure of coagulation,,
and in this case the stoppage of the bleeding becomes more difficult.
This is often noticed in the hemorrhagic diathesis, and occurs in persons
who little by little have lost a large amount of blood, until they have
become anæmic. It is also seen in the spontaneous anæmias and in
exhaustion from fevers. Under ordinary circumstances the loss of
blood, by reducing the power of the circulation, assists in the arrest of
hemorrhage, but this occurs only before the blood has become changed
by the loss of a large proportion of its red blood-globules; these are
always lost in greater proportion than the other constituents of the
blood, and are not replaced with the same facility. This accounts for
the change in the constitution of the blood in repeated hemorrhages. In
all of these cases the effort should be to restore the normal condition of
the blood by appropriate treatment. This applies to bleeding by dia-
pedesis as well.
The absorption of blood that has escaped into the tissues is a matter
of much interest, and presents some singular phenomena. When the
fluid portions of the blood alone escape, forming oedema, the serum is,
if not in too great quantity, disposed of by the lymphatic vessels.
Some of the corpuscular elements may also be carried off in the same
way; but where a considerable number of the red globules are distrib-
uted in the tissues they cannot be so removed, and are disposed of,
many of them at least, by the wandering cells. These cells accomplish
this by taking them into themselves as the amoeba takes its food. Once
within the wandering cells, they soon disappear (Fig. 378). It is not
FIG. 378.
a
b
Cells containing Blood-corpuscles from
the neighborhood of a Hemorrhage:
a, with fresh corpuscles; b, with dark
granules from disintegration of red
corpuscles.
FIG. 379.
Crystals of Hæmatoidin from an Old Hemorrhage in
the Brain: their color is reddish-brown (× 350).
unusual to see several red globules within one wandering cell, as shown
in the figure. It is of course impossible that the multitude of red globules
in large extravasations should be disposed of in this way. These lose their
fluid portions by absorption, and the globules remain. Their coloring
matter is slowly dissolved out, and often stains the tissues of the neigh-
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
687
FIG. 380.
borhood. This staining is of various colors, according to the concen-
tration of the coloring matter, from a blue-black to a light-yellow tinge.
The dissolved coloring matter is finally all absorbed, and the tissues
present their usual appearance.
In case of considerable extrav-
asations forming clots the col-
oring matter is often deposited
in the crystalline form (Figs.
379 and 380). I have obtained
some beautiful crystallizations
by the section of clots occurring
a short time before death, and
also from uterine clots. (See
Fig. 381.)
OPING

ANEMIA.-The term anaemia
in its strict sense means without
blood, but it is used to designate
those conditions in which the
blood is deficient in quantity
or in quality. Deficiency in
quantity may result directly
from hemorrhage, and is then
called acute traumatic anæmia. Otherwise than in this way a true
deficiency in the quantity of the blood, without other deviations from
the normal standard, is rarely seen. By active hemorrhage the arte-
FIG. 381.
** >>#<%==} }
AARON

Crystals of Hamin, prepared artificially by adding
glacial acetic acid to a drop of blood, heating and
evaporating to dryness (X 350).

•
Crystals of Hæmatoidin from a Uterine Blood-clot. The crystals have been somewhat broken in the
cutting of the section (Black, × 40).
rial tension is rapidly reduced, and general debility is induced in
proportion to the loss of blood. The bulk of the blood, however, is
quickly made up by the absorption of the fluids from the alimentary
688
GENERAL PATHOLOGY.
canal and the tissues into the circulation, and the normal tension is
thus restored. Besides this, a notable loss of blood may occur, and
the tension be kept up by the contraction of the arterial walls under
the influence of the vaso-motor nerves. In these two ways the arte-
rial system accommodates itself to a considerable loss of blood with-
out the occurrence of notable anæmia; and it is only by the loss of
large quantities of blood that serious damage to the vital powers re-
sults. In case the loss of blood occurs repeatedly, a qualitative dam-
age to that fluid results without notably diminishing its bulk, for the
plasma is replaced much more readily than the corpuscular elements.
The white blood-globules move slowly along the walls of the vessels,
and are much inclined to cling to them, and are not lost in hemorrhage
in the same proportion as the red globules, which usually occupy the
central portion of the blood-stream. Now, the red globules when lost
are regenerated very slowly; therefore, when hemorrhages occur fre-
quently the effect on the quality of the blood, if the loss is considerable
in the aggregate, may become serious. This constitutes what is known
as hydræmia, or watery blood. The nutritive value of the blood
depends on the proportion of its red globules, and if these are deficient
a condition of debility results, no matter what the bulk of the circulat-
ing fluid.
Spontaneous anæmia is a term used to designate a condition of defi-
ciency of the red corpuscles occurring without any direct loss of blood.
The normal proportion of the red globules to the whole blood is esti-
mated at about 13 per cent. In spontaneous anæmia it may sink as
low as 6 or even 4 per cent. In this condition there is always a
notable reduction of the vital powers, and such patients usually exhibit
marked debility. This condition may be induced by a great variety
of circumstances, such as exhaustion from overwork of any kind, and
especially by continuous mental application. It is also induced by a
variety of forms of chronic illness and by protracted fevers.
·
Essential or pernicious anæmia may come on without any perceivable
connection with other ailment of any kind, and is prone to a fatal ter-
-
FIG. 382.
mination. Its characteristic is a marked
reduction in the number of red cor-
puscles. Some authorities describe a
red globule inferior in size to the nor-
mal red one as characteristic of this
disease (Fig. 382). So far as I am
able to determine, it seems probable
that this is not an abnormal form of
red globule, but a white globule that
has become stained with the coloring
matter of the red. Cornil and Ran-
vier state that they have not been able
to find these abnormal corpuscles, but
find that " many white corpuscles,
especially the largest, contain very
small amber-colored spherical granules grouped around the nuclei.
This can be explained by the destruction of the red corpuscles, particles

海
​bodies are the normal red corpuscles; the
Blood in Pernicious Anemia: the larger
smaller are the round, more deeply colored
ones usually found-so-called microcytes
(Eichhorst).
Konta
VARIATIONS IN THE BLOOD, AND IN ITS DISTRIBUTION.
689
of which have been absorbed by the white corpuscles." It is known
that in health there is a continuous consumption of the red corpus-
cles of the blood, and it is probable that the essential phenomenon
of this disease is an exaggeration of this function, and that the con-
sumption exceeds the powers of regeneration. This consumption is
supposed to take place in the liver, but it is also known that under
certain circumstances the red globules are destroyed by the white, and
that these may become temporarily stained. This leads to the supposi-
tion that these corpuscles may be of that character. The place of the
formation of the red blood-corpuscles is not certainly known. This
function has been attributed to the spleen, to the lymphatic glands, and
to the marrow of the bones. The bone-
marrow seems to have been found in a
diseased state in many cases of anæmia,
and under these circumstances cells very
like the red blood-globules have been dis-
covered (Fig. 383).
FIG. 383.
Chlorosis is a form of anæmia seen in
females at or about the age of puberty.
It is supposed to be due to a deficiency
in the formation of the red blood-corpus-
cles, and is very amenable to treatment.
with the preparation of iron. With this
condition there is often associated some
deficiency in the vascular system, such as
narrowness of the aorta or some of the important blood-vessels. Con-
trary to what is usually seen in the other forms of anæmia, the body
seems well nourished in chlorosis, but there is the same defect in the
proportion of the red blood-globules. The flesh, however, is usually
soft and flabby, and a disposition to oedema is manifest in the extrem-
ities. Chlorotic patients are more than usually liable to nervous
disorders.
b
u
一幕
​177
pa
From Red Medulla of Bone in Per-
nicious Anæmia: «, nucleated red
corpuscles; c, a red corpuscle with
granular nucleus; b, large nucleated
cells, forming the bulk of the altered
marrow (× 350).
In all these forms of anæmia the diminution of the coloring matter
of the blood appears to be the prime factor, and cases of marked cha-
racter now and then occur in which this deficiency is very marked,
while the number of the corpuscles remains normal or nearly so. The
bulk of the blood is not necessarily diminished, but may be more watery
than normal, and may not clot so readily. This often gives rise to
difficulty in controlling hemorrhage. Secondary changes in the tissues,
especially in the form of fatty degenerations, may occur in any of the
forms of anæmia from the imperfect nutrition of the tissues. Inflam-
matory processes are languidly performed, and are more prone to run a
chronic course. The treatment of alveolar abscess, diseased pulps of
teeth, or any of the inflammatory diseases of the mouth or other parts
is rendered more uncertain and difficult.
Local anæmia is the diminution of the blood of a part. It is prob-
able that this occurs in various organs as a feature of the neuroses or
as perversions of innervation. There seems to be such a thing as a
tonic spasm of the arteries of a part or organ, during the continuance
of which the amount of blood admitted to it is materially lessened.
VOL. I.-44
690
GENERAL PATHOLOGY.
Some neuralgic affections are thought to be of this character. Anæmia
in all of its forms is especially liable to give rise to, and, seemingly,
not unfrequently constitutes the basis of, the more obstinate forms of
neuralgic affections.
INFLAMMATION.
The classic signs of inflammation are redness, heat, pain, and swelling.
These describe with sufficient accuracy the more obvious superficial
characteristics ordinarily presented by the inflammatory process, but
convey very little idea of the changes that are in progress. These
processes have for the most part been learned in comparatively recent
times by direct microscopic observation of inflammations artificially
produced for this special purpose. In the study of this process sharply
divergent views have been developed by certain prominent pathologists,
each of whom has his followers; so that the student in his first attempts
to follow the explanations given in the different works that have recently
appeared is very liable to find himself in a confused labyrinth of con-
flicting detail, from which he will emerge with anything but clearly-
formed views of the phenomena. For this reason I think it best occa-
sionally, in the course of my descriptions of these processes, to make
brief citations of these differences as I understand them, with the view
of assisting younger readers in clearing up this seeming confusion.
Otherwise than this I shall adhere to the plan I have thus far followed-
of making but few references to the opinions of others.
For the microscopic study of the phenomena of inflammation any of
the membranes that are sufficiently thin and transparent to be readily
observed during the life of the animal may be employed, as the web of
the frog's foot, the frog's tongue, the omentum, or the mesentery.
When such a membrane is prepared for examination and placed on
the stage of the microscope, an irritant is applied and the subsequent
changes observed. The changes induced in this process may also be
studied by the more ordinary plans of microscopic research.
When the tongue, mesentery, or web of the foot of the frog is brought
under observation, the blood in the vessels is seen to be circulating in
the normal manner. Upon the application of an irritant the first nota-
ble change is a contraction of the vessels. This is so slight, and endures
for so short a time, that some observers have even denied its occurrence.
Very soon the vessels begin to dilate, and the flow of the blood through
the part is notably increased. The streams are larger and the blood
flows more swiftly. This is now, to all appearance, a simple hyper-
æmia, the hyperemia of irritation, that invariably precedes the appear-
ance of inflammation. After this has persisted for a time it will be
noticed that the blood-streams are slowing their movement. Where
before the individual corpuscles could with difficulty be made out on
account of their rapid movement, they are now readily distinguishable.
The red globules for the most part occupy the centre of the current,
while the white are seen to be creeping along the margins, stopping and
clinging to the vessel's wall, then letting go and moving on, to stop and
cling fast again. This is repeated continuously by the white globules
A
1
INFLAMMATION.
691
that are seen passing the field of view. Finally, some are seen to
become more decidedly adherent to the wall, as if fused with it, and
others to be likewise adherent in the neighborhood. As this progresses
they begin to be piled the one on the other; and all this time the blood-
current is becoming slower and slower. Some of the white globules
that have seemed to hold fast are seen to loosen, and after swaying for
a time float away with the current. In all this movement it will be
noticed that the globules appear to be developing an adhesiveness that
they did not manifest at the beginning of the observation. Those that
gradually break away and move off from the focus of the irritation-
which now can only be seen in this disposition to stickiness-seem to
lose this property as they recede from the field. This will give the
impression that it is the vessel's wall in which this stickiness is devel-
oped, and not in the blood-globule. In the focus of this action the adhe-
sion of the white globules will go on until the entire inner wall of the
vessel is completely covered as with a pavement, and they may be piled
one upon the other. This adhesion of the globules is the first step in
the process that can be considered as significant of inflammation. It
may indeed be inferred that the hyperemia is that of irritation, and will
lead to inflammation; but there is nothing in the microscopic appear-
ance of the tissues or of the blood in the vessels by which the difference
can be noted until the adhesion of the white globules has become man-
ifest. With the adhesion of the white globules, as it advances, there is
also seen a disposition to the adhesion of the red. These at first occu-
pied the centre of the blood-streams, but as the adhesion of the white
globules progresses the channels become narrowed, the motion of the
FIG. 384.
1
-
f
C
FIG. 385.
We


❤
FIG. 384.-A Capillary of the Mesentery of a Frog nine hours inflamed, showing detachment of an
endothelial cell, which is finally carried off by the blood-current (high-power): e, capillary walls;
1, white blood-corpuscles or leucocytes external to the walls; f, capillary endothelia, granular and
swollen with projecting bellies; 9, cells of adventitia, also swollen and granular; a, d, i, colorless
corpuscles adherent to the walls; d is rather firmly bound to the wall by means of a bud pene-
trating the latter; i, a corpuscle adherent to the point of union of two adjacent endothelial cells;
a, a white corpuscle adhering tightly to the upper end of an endothelial cell, b, which is partly
pried out from its bed by the action of the red discs. The arrow indicates the direction of the
current (Shakespeare).
FIG. 385.-A White Blood-corpuscle, or Leucocyte, from human blood, showing amoeboid movement
(Klein).
blood is slow, and the red globules turn aside also and begin to adhere
to the walls with the white. In this way the channels are progressively
692
GENERAL PATHOLOGY.
:
1
filled up with the mass of globules, and the motion of the blood is finally
stopped altogether. This is the condition of stasis (Fig. 384).
Before this point has been reached another phenomenon will have
become manifest-the diapedesis of the white blood-globules from the
vessels into the surrounding tissues. Under favorable circumstances
some of the adherent globules will be seen to have sent a prolongation
through the wall of the vessel (Fig. 384, d), and gradually the whole
of the globule follows it, and is on the other side among the tissues.
Here its amoeboid movements become more apparent, and it is seen to
move among the tissues surrounding it (Fig. 385). This diapedesis
now goes on rapidly, a few red globules mingling with the white, until
the whole of the tissue is thickly studded with them, especially in the
neighborhood of the vessels. In the mean time, the fluid constituents
of the blood have also escaped from the vessels to so great an extent
that the tissue has become swollen and clouded to such a degree that
the further following of the phenomena is seriously interfered with, so
that the changes that finally occur in the tissue itself cannot be followed
FIG. 386.

f
fi
u
O
b
WP
ANDREATHEN THE REASON THAN
20000
WE
J
300
Inflamed Human Omentum. The phenomena of inflammation are seen in the veins and capillaries,
the condition being normal at the artery (c), where b represents endothelium covering the tra-
becula (a). In the vein (d) there are many white corpuscles along the wall: some of these are emi-
grating (e); f, desquamated endothelium; g, extravasated red corpuscles (Ziegler).
with the accuracy that scientific precision demands. Fig. 386 gives an
idea of the appearances presented in inflammation of the omentum.
We may now review the processes we have thus far observed, with
¹ On account of the variety of positions in which this cell is seen, and its peculiar
In the blood it is
changes of form, it has been designated by a variety of names.
called the white blood-corpuscle or leucocyte; in the tissues outside of the blood-
vessels it is variously designated as the leucocyte, amœboid cell, or wandering cell.
These terms therefore apply to the same cell-forms.
INFLAMMATION.
693
the view of a better understanding of their meaning. The hyperemia
is undoubtedly of the same nature as hyperemia in general, and in
itself presents no phenomenon other than that of the most simple dilata-
tion of the blood-vessels. As we have seen (p. 692), this process does
not lead to inflammation, yet here we find it forming a part of the
inflammatory condition. This happens from the fact that in this case
there is an additional element not present in simple local hyperæmia.
This additional element is tissue injury. The hyperæmia can be in no
way the cause of the inflammation, but the same causes that produce
inflammation induce hyperemia as one of its phenomena. This hyper-
æmia may be induced by a tissue injury so slight that no characteristic
inflammation results; for it must be understood that this process may
begin to decline and go on to the resumption of the normal condition at
any stage whatsoever. Therefore this is called the hyperemia of irrita-
tion. In severe inflammation this hyperemia is much diffused in the
neighborhood, as seen in the diffusion of the redness and heat. It gives
rise to oedema and swelling in the neighboring parts, without the accom-
panying inflammatory process, which in all of the phlegmonous varieties
is confined to a certain area called the focus.
K
G
The elevation of the temperature, so far as this is capable of being
determined by experiment, is due to the hyperæmia. The increase of
heat is carried to the part by the greater influx of warm blood; there-
fore it never rises higher than that of the internal parts, no matter how
intense the inflammation. Cohnheim caused an intense inflammation in
one fore leg of a dog by scalding, and hyperemia in the other by divid-
ing the vaso-motor nerves, and examined the blood returning from each.
That from the hyperamic limb was found to be slightly the warmer.
The mass of experimentation in this direction confirms this observation.
This seems to completely refute the doctrine that the increase of heat in
inflammation is caused by the more active metamorphosis of tissue
through increased oxidation. It is now certain that if increased heat
is thus developed, it is to so slight an extent as not to be appreciable by
the ordinary means of experimentation.
The swelling is caused by three separate factors: the dilatation of the
arteries, capillaries, and veins; the hyperemic exudation; and the in-
flammatory exudation. The blood-vessels, especially the capillaries,
become widely expanded; and in most of the tissues these are so
numerous that this dilatation in itself must cause a considerable increase
in the dimensions of the part. The swelling is, however, manifestly
produced chiefly by the exudates, and will be great or small as these
are abundant or scanty. If the hyperemia is intense and widely dif-
fused, it will produce a corresponding amount of oedema in the neigh-
borhood. This, in many of the varieties of inflammation, is sharply
differentiated from the inflammatory focus, showing itself in the readi-
ness with which it is pitted by pressure of the finger. The swell-
ing in the part inflamed, on the contrary, becomes hard and resistant.
This difference is owing to the different character of the exudates in
these localities. The qualities of these will be considered under the
head of Exudates.
The pain in inflammation is supposed to be caused partly by the
C
Sty
694
GENERAL PATHOLOGY.
injury to the tissues and nerves of the part which has produced the in-
flammation, and partly by the compression and stretching of the nerves
by the swelling. The fact that inflammations occurring in the same parts
under different circumstances differ very remarkably in this respect
seems to show that the cause has much to do with the production of
pain. This is illustrated by comparison of the pain produced by a plas-
ter of mustard-seed with that caused by a plaster of cantharides. In
many cases the amount of pain is not in proportion to the intensity of
the inflammation; in others it is excessive. As a rule, inflammations
occurring in the firmer tissues are more painful than those occur-
ring in parts that are less dense. The individual tissues vary much
as to the intensity of the pain induced. Our knowledge of the modus
operandi of the production of pain is so limited that not much can be
gained by the consideration of the subject.
The exudates are derived mostly from the blood. These are the ser-
ous, the fibrinous, and the corpuscular. The serous exudate is poured
out from the dilated blood-vessels in the neighborhood of the inflam-
matory focus-in the region of hyperæmia. It is not peculiar to inflam-
mation, but occurs in all the forms of hyperemia. It is a thin, watery
fluid, differing slightly from the plasma of the blood. It is but slightly
coagulable, and does not coagulute in the tissues. It, however, seems
always to contain some fibrinogenous matter in addition to dissolved
albumen.
The fibrinous exudate is peculiar to inflammation. It contains in
solution a large amount of fibrinogen. This amount seems not to be
constant, but varies widely in different cases. It is always exuded from
the blood-vessels in the fluid state and coagulates in the tissues. It is
this that causes the first clinical differences between hyperemia and
inflammation; the exudate of hyperemia remains fluid in the tissues,
and is therefore easily displaced by pressure of the finger, while the
exudate of inflammation coagulates in the tissues, and is not easily dis-
placed by the finger, but forms a firm and resistant swelling. This
exudate seems also to have more of the properties of glue than is found
in the blood-clot, and it serves to bind the lips of a wound together with
considerable firmness. Most pathologists seem to regard the coagula-
tion of this exudate as taking place in the same manner as that I have
described for coagulation of the blood. (p. 680); but there is reason to
suppose that the origin of the fibrin ferment is different. Instead of this
being furnished entirely by the destruction of the white blood-globules,
it may, and probably is, furnished principally by the inflamed tissue.
It has been suggested by Denys de Commercy and Alexander Schmidt
that this coagulation is effected by a substance furnished by the tissues
in a state of inflammation, called by the latter fibrino-plastin. It is
stated by Cornil and Ranvier that "under the influence of an intense
inflammatory congestion the fibrinous matter escapes from the vessels
and coagulates by uniting with the fibrino-plastic substance derived
from the cells. The coagulation takes place suddenly and in successive
layers, the exudate in contact with the tissues alone coagulating." The
amount of this exudate is in many instances very large, and very thick
layers are sometimes found lining the serous cavities when their walls
INFLAMMATION.
695
are inflamed (Fig. 387). Within the tissues this exudate has but a
limited duration. It soon disintegrates and disappears. It first breaks
up into fine granules, and finally be-
comes completely liquefied.
FIG. 387.
The white blood-corpuscles are ex-
uded (by diapedesis) with the fibrin-
ous exudate, and they alway's accom-
pany it in the tissues. Their mo-
tions are probably not interfered d
with to any considerable extent by
the coagulation. I have remarked
that the movements of the white
blood-globules increased greatly
after their exit from the vessels.
This seems to be kept up so far
as they have been traced. They are
not always confined to the tissues
that are living, but wander into al-
most anything that comes in their
way. Blood-clot is invaded by
them, and they become filled with
the red globules. (See Fig. 387.) If milk is injected, they take up the
milk-globules and become filled with them. If an insoluble coloring
matter in fine powder be injected, the particles of this also are taken
up; and much use has been made of this by pathologists in tracing
the wanderings of these little bodies. If a frog be injected with finely
granular vermilion, and then the cornea of another animal, as the rab-
bit, is removed and buried in the tissues of the frog, and left for two or
three days, it will be found on examination that the leucocytes of the
frog have wandered into the fragment of cornea in great numbers,
carrying with them the vermilion as a mark of their identity. If the
swimming-bladder of a fish be filled with water which has been so
impregnated with common salt as to be of the same density as the
blood, and then buried in the tissues of an animal until inflammation
is established about it, these bodies will be found in the water, they
having penetrated the bladder membrane. Nothing but actual solids
seems to hinder their wanderings, and wherever they go they are con-
tinually picking up any little particles they may meet in their way
which do not belong in the tissues or have become useless there.
•
Tissue-changes in inflammation have been the subject of the most per-
sistent inquiry on the part of experimental pathologists within the last
decade, and have given rise to much controversy. It will be remem-
bered that when we terminated the study of inflammation by aid of the
microscope (p. 692) the tissue had become so clouded by the inflamma-
tory exudates that further observation of the changes going on was
impracticable. This fact has confined this mode of the study of the
subject to the onset of the inflammatory process. No plan has as yet
been devised by which the further changes which may occur in the
tissue-cells of the part can be accurately observed during the life of the
animal; thus efforts for the further accurate following of these processes

C
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a
GUL
Iris
inflamed after injury by a piece of iron
thrust into the eyeball: a, pigment; b, circu-
lar fibres; c, radiating fibres; d, inflammatory
exudate composed of coagulated lymph and
leucocytes. Leucocytes are seen also in the
tissue (X 350, Black).
Body
Radi
696
GENERAL PATHOLOGY.
are subject to the greatest disadvantage. There have been many and
various attempts to overcome this difficulty, and after following out
with some care all of the more feasible of these, success has been but
partial. This is also illustrated by the differences of opinion that exist
as to the actual occurrences. Difference of opinion as to the explana-
tion of the meaning of phenomena does not argue faulty observation, but
when our best observers differ diametrically in regard to what actually
occurs, the morphological changes, we must suppose that the observa-
tions are either so difficult that they are liable to be inaccurate, or that
the morphological changes are inconstant, or at least differ under cir-
cumstances so nearly the same that observers have failed to note the
divergence. However this may be, the part the tissues play in the
process of inflammation is not yet so accurately known that the best
observers are able to harmonize their findings. In some cases the differ-
ences of opinion seem to result from modes of expression and in the
explanation of phenomena rather than in differences of observed phe-
nomena. Other disagreements occur from the use of different modes
of observation. I will note the principal points of divergence as I
proceed.
Song
T
My
In the prosecution of this inquiry the effort has been to follow up the
tissue-changes in those non-vascular structures deriving their nutriment
from blood-vessels that lay at a considerable distance. This is done
with the view of separating as perfectly as possible the phenomena due
to tissue-change from those that are due to infiltration from the vascular
system. For this purpose the cornea and the cartilages have usually
been selected. The healthy eye of the frog or other animal may be
used. A puncture is made, and the serum from the anterior chamber
is collected in a suitable receptacle. A piece of the cornea is now
excised and immersed in the liquid with the membrane of Descemet
uppermost, and the little chamber so closed as to prevent evaporation,
with the view of preventing changes in the density of the liquid. Pre-
pared in this way, the tissue will retain its vitality for a considerable
time, and give the best opportunity possible for the study of the normal
structure. So long as the life of the tissue remains perfect, no structure
whatever can be made out; every part is perfectly transparent; but as
the tissue begins to die its form-elements come into view one after
another-first, the epithelium, then usually some leucocytes just
beneath, and finally the cornea-corpuscles with their branching pro-
cesses. This observation is first made to familiarize the observer with
the normal appearances. Then the observations on the inflamed cornea
are made in precisely the same manner for the study of the changes
that may have occurred. This is Professor von Recklinghausen's
method, and with slight variations has been adopted by nearly all
who have made this class of observations. Now the cornea of the
living animal is irritated in some definite way, and after the lapse of
a certain time, which varies in duration in different observations, it is
treated in the same way and the tissue-changes studied. In these
studies improvements have been made from time to time, the most
notable of which is that by Prof. Stricker, of the continuous irriga-
tion of the tissues under examination, with the serum of the animal
INFLAMMATION.
697
from which they were taken, this keeping them for a longer time-
alive.
For a description of the changes which occur in the tissues of the
cornea when studied in this way I cannot do better than to make some
quotations from the admirable article of J. Burdon Sanderson in Holmes's
System of Surgery:
FIG. 388.
"If a cornea which has been irritated a quarter of an hour before by
the application of a point of caustic to its surface is examined in the
same way (as described above), the conjunctival epithelial layer can at
once be distinguished, along with a few leucocytes, underneath and
among the epithelial elements. If an hour or two has elapsed, the
proper cornea-corpuscles are visible as dark stellate or spindle-shaped
spots on a transparent ground. Of these, some are homogeneous, and
can be distinguished from the surrounding substance by a slight differ-
ence of shade. In others, which are finely granular, the processes or
rays are subject to slight variations of contour. These amoeboid move-
ments of the rays, although very sluggish as compared with young pro-
toplasm in general, are rendered much more active by subjecting the
preparation to a stream of blood-serum." . . . "In the cornea excised
three hours after irritation some of the corpuscles exhibit no change,
excepting that their outlines are more strongly marked; in others there
seem to be, in addition to the irregular nucleus above referred to, one or
more spheroidal bodies which are, im-
bedded in some other part of the cor-
puscle (Fig. 388). This appearance
affords the earliest sign that the pro-
cess which has hitherto been called
'proliferation' is beginning; that is to
say, that the mode of life of the proto-
plasmic mass is changing from the nor-
mal quiescent state which fits it to take
part in a permanent tissue to the state-
of reproductive or germinating activity
-that new bodies are being formed in
the body of the parent mass, to which
such terms as germs' or 'offspring
are applicable. A part of the original
living substance of the element begins.
a new life, much more active than it
before possessed, and a new organic
development. Since the introduction
of the method of observing structural changes in living tissues, pathol-
ogists have learned that it is a constant characteristic of the change we
are considering that the rejuvenescent part or substance acquires the
property of contractility; in other words, that all protoplasm when
assuming new life and beginning new organic development is endowed
with the faculty of amoeboid movement.
(
(6 Between the fifth and twelfth hours after irritation the cornea-
corpuscles become more distinct and granular, while their processes
become thicker and shorter, until at length many of them lose altogether
Cornen of the Frog, excised three hours
after (Sanderson).
J
Gam

698
GENERAL PATHOLOGY.
FIG. 389.
their characteristic stellate or caudate outline and are converted into irreg-
ular clumps. If the cornea is exam-
ined in this stage after treatment with
chloride of gold, it is seen that in
those parts in which the structural
changes are most advanced the nor-
mal character of the tissue is entirely
lost (Fig. 389). The beautiful net-
work produced by the interlacing of
the normal corpuscles is no longer
visible; in place of it the field is scat-
tered over with clumps of irregular
form, in some of which the caudæ are
represented by rounded knobs, while
in others the outlines are almost sphe-
roidal. Most of these bodies are so
granular that their contents cannot be Altered Corpuscles of the Cornea, excised
eight hours after irritation (Sanderson).
distinguished, but in others the newly-
formed germs are plainly visible. The number of these germs varies
according to the stage of irritation, so that in the same cornea clumps
containing a numerous offspring may be seen in one part, while in others
the germination is only beginning (Figs. 390, 391).
"That the interpretation suggested by these appearances is the true
one, that the clumps containing numerous round corpuscles are nearly
FIG. 390.
FIG. 391.

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Cornea, sixteen hours after irritation: amœ-
boid masses containing numerous newly-
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Cornea, about twenty-four hours after the inser-
tion of a fine ligature: masses containing
young elements in the neighborhood of the
thread (Sanderson).
of the nature of mother-cells, the observer can best assure himself by
returning to the method of examination first described; that is to say,
by placing the inflamed tissue under the microscope alive, at the same
time stimulating the elements in question to increased amoeboid move-
ment by irrigation with serum. It is then seen that the germs change
their relative position with the movements of the mass of protoplasm in
which they are enclosed, just in the same way as the granules and
INFLAMMATION.
699
ingesta do in the body of an amoeba, rolling one over another in such
a manner as would not be possible if they were not really contained in
the mass.'
22
It is on observations of the same nature as those so well described
in these paragraphs that Prof. Stricker has founded his doctrine of
inflammation, which he expresses in these words (I quote from his
article in the International Encyclopædia of Surgery). He considers
the essential phenomena to consist of "metamorphosis of tissue; return
to the embryonic condition; division into amoeboid cells of the masses
which have become movable; hence the destruction and the suppuration."
This constitutes the basis of the doctrine of inflammation as taught by
Stricker and others who have confirmed his observations. Cornil and
Ranvier (Manual of Pathological Histology, 1880) express the same
idea in the following words: "The process evolves in the following
order hypertrophy of the nucleus; increase, then division, of the proto-
plasm; destruction of the enveloping membrane of the cell; destruction
of the fibrous or of the fundamental substance; production of fundamen-
tal tissue; formation of new vessels." According to this doctrine, the
tissues in inflammation are stimulated to greater activity in that amoe-
boid cells are formed by the division of the original cells of the part,
and the cells thus formed may, in the height of the inflammatory pro-
cess, become pus-corpuscles through a lowering of their vitality, as in
the formation of abscess on pus-yielding surfaces or mingled in the
tissues (purulent infiltration); and in that when the height of the pro-
cess has passed such cells as have not been too much reduced in vitality
enter into the process of repair. The diapedesis and wandering of the
leucocytes are noted, but they are assigned a subordinate place in the
formation of pus and the building of tissue in the reparative process.
The leucocytes are intermingled, but the principal part, both in the
formation of pus and the rebuilding, is done by the cells newly formed
by the breaking up of the old protoplasmic masses.
This doctrine is directly controverted by Cohnheim and his colaborers,
who contend that all pus is formed directly from the diapedesis and
collection of the leucocytes from the blood, and that all tissue repair is
accomplished by the development of these cells. These pathologists
regard the tissues as taking no part whatever in the process-that they
are passive, or if they undergo any change it is always retrograde,
which if continued results in the death of the cells; in which condition
they mingle with the pus without forming a characteristic element, but
in form of minute bits or shreds of dead tissue if not completely dis-
solved. Cohnheim particularly has repeated Stricker's observations in
the most painstaking way without being able to discover the tissue-
changes described, and upon this negative evidence reaffirms his doc-
trine that the tissues remain passive. On the contrary, it is claimed
that Cohnheim has, in repeating Stricker's experiments, so varied them
that they have been rendered ineffective. However this may be, there
still remains a disagreement on this point, Stricker asserting the activity
of the tissues in the inflammatory process, and Cohnheim as positively
asserting that they are passive.
Touching the theory of inflammation held by Cohnheim, it seems
700
GENERAL PATHOLOGY.
that his attention has been arrested principally by the changes that
occur in the vessel's wall. These changes become obvious in various
ways, and constitute, in the microscopic study of the subject, the most
prominent factors. As we have seen in the microscopic study, the first
sign which is characteristic is the development of an adhesive quality
by the vessel's wall, which causes the passing blood-globules to linger,
and finally to adhere. This change increases until the passage of the
globules is arrested and stasis induced. Then we have an increased
permeability of the wall of the vessel; its fluid contents pass through
in greater quantity than normal, and in addition to this the white glob-
ules pass through the wall in abnormal numbers. These processes have
been studied in the most painstaking way by the best experimental
pathologists, and I think most observers will agree with Ziegler when
he says that "the alterations in the vessel which take place in inflam-
mation cannot be histologically demonstrated." These changes are
not of a morphological character, at least until very great progress has
been made, but relate solely to the physiological condition of the tissue
composing the vessel's wall. This condition Cohnheim supposes to be
that of paralysis produced directly or indirectly by the exciting cause
of the inflammation. The vessels are widely expanded, and remain so
during the continuance of the process. The adjacent tissues are also
regarded as paralyzed; and in this condition take no part whatever in
the processes that are going forward. This narrows the inflammatory
process to a very few factors: injury to the tissues, and especially to the
vessel's wall, by any form of irritation; paralysis of the tissues, and
especially of the vessel's wall, as a result of this injury; increased per-
meability of the vessel's wall to both the fluid and the globular elements
of the blood, which permits their escape into or among the elements of
the tissue; the tissues while in the state of paralysis become crowded
with these elements to an abnormal degree; under these adverse con-
ditions the tissue-changes that occur are in the direction of their death
and destruction; pus is formed by the aggregation of leucocytes, which
come originally from the blood by diapedesis through the walls of the
vessels, mingled with the results of the disintegration and liquefaction
of tissue that may be destroyed. Briefly stated, these constitute the
phenomena of inflammation, as held by Cohnheim and his followers.
The changes in the tissue-cells, a description of which I have quoted
from the admirable article of Burdon-Sanderson, are denied; and it is
claimed that all pus-corpuscles originate from the white blood-corpus-
cles, and that all the tissue of repair is also derived from the same
source through the development of these same white blood-cells.
The exciting cause of inflammation is tissue injury. It is obvious that
this may occur in a multitude of forms. It may result directly from a
wound, and this may vary from the slightest prick of a thorn to the
crushing of a limb. It may occur from a chemical irritant, such as the
caustics, or irritating medicaments, either animal or vegetable, as the
Spanish fly or mustard. It may occur from the action of irritants
that are carried to the spot by the blood itself, as is seen in in-
flammation of the gingivæ by mercury or the inflammation of the
neck of the bladder by cantharides. It may also be caused by the
K
INFLAMMATION.
701
presence of micro-organisms that may gain access to, and are able to
develop in, the tissues, as in the case of the Bacillus anthracis and many
other microscopic forms that have been made known by recent experi-
mental study. These varying causes of inflammation give rise to various
outward expressions of the phenomena. Some inflammations are con-
centrated within a very small area, while others are diffuse or are spread
over a comparatively large area. Some affect a certain tissue only, while
others may affect several varieties of tissue at the same time. Some
inflammations are prone to pass on to the production of pus, as is the
apical pericementitis,' while others are prone to terminate in resolution
without the formation of pus, as in erysipelas. If the cause acts con-
tinuously the inflammation will become chronic; in case the action of
the cause is but momentary, the induced inflammation will generally
terminate after an acute stage of short duration. These variations as to
cause, coupled with individual idiosyncrasies and various conditions of
body, give rise to the different forms of the affection.
Abscess is the result of a severe but circumscribed inflammation which
causes the destruction of a certain area of tissue; or leucocytes may col-
lect in large numbers at the centre of the focus of the inflammatory
process, and, being reduced to a very low state of vitality, become aggre-
gated together and cause a separation of the tissues, thus forming a pus-
cavity. The differences of opinion as to the origin of these cells has
been mentioned, and need not be further discussed at present; for,
whether they arise in the one way or the other, they become pus-cor-
puscles when reduced to a certain state of vitality or when they com-
mingle with the contents of a pus-chamber (Figs. 392, 393). Tissue is
FIG. 392.
FIG. 393.
(893)
G
יג
с
BRUSS
ď
Pus-cells: a, from a granulating wound; b,
from an abscess of cellular tissue; c, the
same treated with dilute acetic acid; d, from
a bone fistula (necrosis); e, migrating cells
(Rindfleisch).
α.
d
石
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&
00
1
C
888
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700
3
((?)
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Pus-corpuscles: 1, a, b, in water; c, d, e, after the
action of acetic acid; 2, division of nuclei (Vir-
chow).
usually destroyed in the focus of an intense inflammation, and, becoming
dissolved or forming small gangrenous masses, mingles with the fluid
and corpuscular exudates to swell the volume of pus. While this is in
progress in the focus of the inflammation the exudation of coagulable
lymph is filling the surrounding tissues, and in this way the abscess
is, as it were, walled in. The abscess may continue to enlarge by a
continuous destruction of its immediate walls. This destruction is,
however, usually greatest in the direction of the least resistance, which
brings the pus nearer the surface, favoring its discharge. In this
event, if there is no continuous cause of tissue injury keeping up the
¹ Inflammation at the apex of the root of a tooth after the death of the pulp.
702
GENERAL PATHOLOGY.
inflammatory process, the walls of the abscess-cavity begin to be built
up by granulations, and healing is accomplished in the same manner as
in any other breach of continuity.
An ulcer¹ is a condition attended by a progressive destruction of
tissue, accompanied with the formation of pus or ichor in some of its
forms, and which is confined to the surface of the body or to natural
cavities, as the mucous surfaces. In this condition there is often a
cause that continues to act and keeps up the discharge indefinitely;
otherwise the ulcer heals after the first destruction of tissue and the
formation of pus. The process is in no wise different in its modus
operandi from that taking place in abscess, except that of location, the
one being within the tissues, the other on the surface. The word ulcer
carries with it, however, the idea of chronicity connected with progres-
sive waste or destruction of tissue.
In case of abscess or ulceration Stricker accounts for the destruction
of tissue at the focus of the inflammation on the theory of the conver-
sion of the fixed cells into amoeboid cells, which finally are converted
into pus-cells. Hence the disappearance of tissue and the formation
of the cavity. After the intensity of the inflammatory process has
passed the same amoeboid cells which have been converted into pus-cells
begin to develop, and finally form the tissue of repair. According to
Cohnheim, all this is the work of the exuded white blood-corpuscles.
An inflammation may begin to abate at any stage of the process.
"The repair of the damaged vessel-wall is brought about by the vis
medicatrix of the blood itself" (Ziegler). If, when the injurious influ-
ence has ceased, the blood brings to the injured vessel the material
required for restoring it to its normal state, the inflammatory disturb-
ance comes to an end, the exudation ceases, and the process of healing
is begun. In the earlier stages of the process this consists in the
restoration of the walls of the vessels to their normal state of
compara-
tive impenetrability, and the removal of the exudates by the lymphatics
and blood-vessels. If a small amount of tissue has been injured, it is
reproduced, the muscle-cell producing new muscle, periosteum produ-
cing new bone, and so on (Ziegler).
This manner of reproduction is, however, confined to very small
Ge
1 There seems to be considerable confusion in the use of this word. Many make no
difference between the processes of ulceration and suppuration, while others distinguish
sharply between them. Loomis (Principles and Practice of Medicine) regards suppu-
ration and ulceration as the same processes, except that that which forms a cavity, a
pocket within the tissues, is an abscess, and that which is limited to the surface is an
ulcer.
Sir James Paget says: Ulceration is that part or effect of an inflammatory process.
in which the materials or inflamed tissues, liquefied or degenerate, are cast off in solu-
tion or very minute particles from the free surfaces, or, more rarely, are absorbed from
the surface of the body" (Holmes's System of Surgery). In this article he holds 'dis-
tinctly the doctrine (if I understand him aright) that laudable pus is not formed in
ulceration. It must be ichor or something lower than laudable pus; and as "the ulcer
tends to heal its discharge becomes more like laudable pus."
W. H. Van Buren (International Encyclopædia of Surgery) regards that process of
destruction of tissue by which the contents of an abscess make their way to the surface
as ulceration, and says: "Under all possible circumstances this molecular death is the
essential feature of the process which we call ulceration."
Billroth (Surgical Pathology) says: "An ulcer is a wounded surface which shows no
tendency to heal."
INFLAMMATION.
703
amounts of tissue. If any considerable masses are to be re-formed, it is
accomplished by a process entirely different. In the explanation of this
process there is again encountered a divergence of views among pathol-
ogists, which, however, has its foundation in the differences of opinion
already explained. It amounts to simply this: Is the regeneration of
the lost parts accomplished by the return of the normal fixed cells to
the embryonal form, the amoeboid state, and the redevelopment of these,
or is it accomplished by the development of the leucocytes into con-
nective-tissue cells? I need not again enter this field of controversy,
as all agree that the new tissue formed in the healing of wounds is by
the development of the amoeboid cells, which according to the one
theory are produced from the fixed cells, and according to the other
from the leucocytes. The new tissue formed is called granulation-
tissue, inflammatory new formation, scar-tissue, tissue of repair, etc.
The formation of this tissue takes place in this wise: If the surfaces
of a wound be examined twenty-four hours after it is inflicted, they
will be found intensely red and more or less swollen. The tissue-
elements are still distinguishable, but have become somewhat blurred.
On the second or third day the original tissue is hidden from view,
being covered with a more or less copious secretion, which at first is
inclined to dry, if not too abundant, into a semi-gelatinous film, which,
as the secretion becomes better established, changes to a creamy con-
sistence and assumes a yellowish hue. This is composed of coagulable
albuminous matter mixed with numerous corpuscular elements. The
latter are amoeboid cells that have sunk so low in the scale of vitality
as to be incapable of further development, and have become pus-corpus-
cles. Here and there over the surface of the wound, if it is doing well,
will be seen little red prominences. These are granulations, which are
composed almost entirely of the same amoeboid cells, which have taken
on a redevelopment and are destined to form the new tissue for the
filling of the wound. Thus the pus and the newly-formed tissue are
developed from the same class of cell-forms; the one sinks so low in
the scale of life that it cannot recuperate, and the other, being more
favorably placed, lives and grows. These cells result from the inflam-
mation set in action by the injury to the tissues in the production of
the wound, through which the adjacent tissue becomes infiltrated with
leucocytes, and probably others are developed by changes in the fixed
cells as well, and both go to the formation of either pus or granulations
as they may be more or less favorably placed. It would seem that the
so-called leucocyte is the proper reparative cell of the connective tissues
belonging to them and having its home among them. The name of
white blood-corpuscle is a misnomer. The wandering of the cell by
way of the blood-streams is perfectly natural and normal. These cells
wander through the tissues at will, and are found everywhere, in all of
the tissues and in the blood. They are most probably a product of the
connective-tissue group, and in their development always form connective
tissue. I therefore regard each of the views, although they seem to stand
over against each other, as substantially correct, but only representing a
part of the phenomena of the inflammatory process. The combination of
the two is necessary to the complete explanation of the cycle of events.
704
GENERAL PATHOLOGY.
Wherever there is trouble in the tissue the leucocytes are congregated,
they being attracted by the changes that take place in the fluids of the
part. Thus the stickiness of the vessel's wall brought about by changes
in the cells under the influence of an irritant arrests those that are in
the circulation, and others are promptly formed by the changes in the
cells of the injured tissue.
We may now pursue the development of these cells in the forma-
tion of the granulations and subsequently of the tissue of repair. The
whole life-history of these cells has not yet been made out, but
much in regard to their growth is known. The brilliant experiments
of Ziegler will illustrate the subject best. This experimenter placed
together bits of glass, one of which was a cover-glass used in micro-
scopic observations, so as to leave a space of a very small fraction of a
line between them, and these he buried in the flesh of a living animal.
The presence of this, together with the injury caused in placing it,
produced sufficient inflammatory action to bring a number of wan-
dering cells to the spot. These crept in between the bits of glass,
and developed there. And as these were so close together, the cells
were necessarily in a single layer, which placed them well for micro-
scopic study. These bits of glass were removed from day to day
and the development of the cells studied. Fig. 394 is an illustration
FIG. 394.
d
CL
α
1
d
d
b
с
b
1
C
K


Granulation-cells: a and a₁, leucocytes; b, b, various formative cells; c, formative cell with two
nuclei; c, with many nuclei; d, d, d, formative cells developing connective tissue; e, complete
connective tissue (X 500, picrocarmine preparation, Ziegler).
of these, showing the progressive changes of form of the individual
cells in the formation of tissue. a is the form of the cell when it first
takes its place as a granulation-cell; a₁ shows the same cell as degener-
ated into a pus-cell; b shows various forms assumed by the cells in the
course of their development into tissue. In watching these from day to
day it is found that certain of the cells, presumably the weaker, disap-
pear; and Ziegler supposes that they are devoured by the stronger or
!
Vide
INFLAMMATION.
705
4
that their substance goes to feed them. In other instances several cells
seem to flow together and form one with many nuclei, as seen at c, c1, the
so-called giant-cells. Within my personal observation this form of cell
has occurred mostly in connection with secondary neoplasms. They
would probably occur in connection with Ziegler's glass slips, but I
doubt their general presence in healthy granulations. It will be seen by
studying the illustration how the cells increase in volume and put out
long slender processes. By the interlacing of these with similar pro-
cesses from the neighboring cells they become very firmly united into
tissue. But this is not all. At d the cells are shown still further
developed, and in the forms to the right in connection with this letter
it will be noticed that the granular area of the cell has diminished and
is connected with a finely fibrous substance, which is also seen at e, which
represents the developed tissue. This fibrous material is a connecting
substance which finally forms the bulk of the reparative tissue, the
original cell remaining as a delicate spindle-cell.
If a wound be watched from day to day, it will be seen how it is pro-
7
C.
C
20.05
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FIG. 395.
9

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Section through the border of a Healing Surface of Granulations: a, secretion of pus; b, granulation-
tissue, with capillary loops, whose walls consist of a longitudinal layer of cells decreasing in thick-
ness from within outward; c, beginning of the cicatricial formation in the deep layers (spindle-
cell tissue); d, cicatricial tissue; e, complete epithelial covering; the central layer of cells consists
of serrated cells; f, young epithelial cells; g, zone of differentiation (X 300, Rindfleisch).
gressively filled up by the growth of the granulations. The cells are
piled the one on the other in the form of little clumps which may be
seen with the naked eye, and it is these that have given the name of
VOL. I.-45
706
GENERAL PATHOLOGY.
"granulations." This seems to require that new cells be continually
approaching the surface and taking their place at the very outer surface.
of the granulations. In the microscopic study of granulation-tissue it
is found that the cells actually do this; that is, the young cells are on
the surface (Fig. 395); but what portion of them wander to this posi-
tion from the tissues beneath or by way of the blood-vessels, and what
portion are developed in situ by multiplication, is still an open question.
Great multitudes of the cells are separated from the surface as pus-cells,
and in this way are lost.
When, in the growth of the granulations, two opposite sides approxi-
mate, and finally touch each other, the cells coalesce in the same man-
ner as the cells that are piled the one on the other, and thus union is
established and the opposing walls of the wound are united. It there-
fore follows that if the opposing surfaces of a wound are placed in per-
fect approximation, the first cells that take their places at the surface
unite the wound, and the time required and the expenditure of vital
energy are reduced to the minimum. In what is known as healing by
first intention the wound is sealed by the plastic exudate which I have
described as first covering the surface of the open wound as a semi-gelat-
inous film. This holds the adjacent walls together, and the cells that
perform the true reparative process find within this gelatinous substance-
the best possible conditions for their development, so that in this posi-
tion none are lost in the form of pus-cells.
The development of blood-vessels keeps even pace with the formation
of the granulations, so that every little granule or clump of cells has its
vascular loop which carries the nutritive fluid directly to it. The vas-
cular network of vessels that forms in granulation-tissue is exceedingly
rich and intricate. Some idea of this is shown in Fig. 396. The man-
Hom
Sokirat
CNET
FIG. 396.
AKER
A
New Formation of Blood-vessels in a Granulating Wound (after Arnold).
ner of the formation of these vessels is probably the same in all tissue
that is in the process of development, whether it be in the original
growth or in the tissue of repair. This is by a process of budding from
the blood-vessels already formed. It always takes its rise from the
capillary loops, the bud from one always joining with one from a neigh-
M

INFLAMMATION.
707
FIG. 397.
a
boring loop, as shown in Fig. 395. These loops are formed as solid
processes, and hollowed out afterward by the removal of the central
substance of the cells. This process of the formation of ducts takes
place in the same manner in the vegetable kingdom, and is easily
observed, especially in the sprouting of seeds. If a number of grains
of corn be planted in damp earth under suitable conditions for germi-
nation, and every twelve hours sections for microscopic examination be
made of two of these (one cut lengthwise and the other crosswise of the
germ), the process of the formation of the ducts, which are hollowed out
in the same manner as the
blood-vessels in animals, may
be followed with the greatest
accuracy. In Fig. 397, at a,
I have represented a row of
large cells as they appear in
the germ of the grain twelve
hours after planting, and at
b the cross-section is shown.
These grow in length, and
their number is increased by
fission. After a certain time
their growth seems to cease;
they begin to lose the central
part of their substance and
are rapidly converted into
tubes, the walls of the cells
alone remaining, which are
joined together end to end.
At c and d of the figure these
are shown as they appear on
the fifth day. This seems to
conform very perfectly to the
manner of formation of the
first blood-vessels in the de-
velopment of the foetus, and is much easier of accurate study.
с
In the animal, after the formation of vessels is once begun, all
new vessels are formed from buds given off from cells of the existing
vessels. These, though they unite with similar buds, seem to be per-
fectly fused together as a single cell. After the hollowing out is accom-
plished, however, the formed vessel presents the usual appearance of
epithelial plates joined together for the formation of its walls.

b
d

Formation of the Ducts in the Sprouting of a Grain of
Corn, in sections cut twelve hours after planting. A
series of large solid cells are seen placed end to end, as
at a.
b is a cross-section of the same, showing the cell
to be finely granular, and staining brings the nucleus
into view. It is shown surrounded by the neighboring
cells. c shows the same cell converted into a tube by
hollowing out. Fifth day: d, the duct on the fifth day,
showing the elongated cells hollowed out, forming
a tube, the walls of which show "duct-markings
(Black).
Gly
Granulation-tissue during its formation is very soft and friable. The
capillary loops come so near the surface, and their walls are so thin,
that the slightest touch is likely to cause hemorrhage, and the tissue
contains much fluid. As it grows older and the cells begin to assume
the spindle shape and form the fibrous connecting substance, it becomes
much drier and firmer. Many of the capillary loops that were formed
during the growth of the granulations are obliterated and the tissue
shrinks, drawing the surfaces of the wounds together, usually in such a
way as to diminish its surfaces and lessen the remaining scar. This
708
GENERAL PATHOLOGY.
tendency to shrinkage, while in the main beneficial, sometimes produces
disastrous results. This is seen most prominently in case of burns or
other injuries involving a large extent of surface, in which the shrink-
age of the cicatrix often produces distortion. This shrinkage continues
for a considerable time after the complete cicatrization of the wound.
The reproduction of epithelium is always by proliferation from the
existing epithelial cells at the margin of the wound or by division of
young cells. In normal conditions the epithelial cells are continually
being shed, and are as constantly being regenerated by the multiplica-
tion and growth of cells from beneath. These cells are never produced
from connective-tissue cells, but always from the epithelial cell; hence
in the healing of wounds the epidermis that finally covers in the gran-
ulations is projected from the margins. This is seen in the form of a
very delicate film at first extending a little way inward all around the
wound. Fig. 398 gives the microscopic characters of such a film from
FIG. 398.
a
ME
WATOS
万
​
d
Regeneration of Epithelium in Cornea of a Rabbit: a, fibrous transformation of nucleus; b, partial
separation of the fibres and hour-glass change of nucleus in the process of division; c, complete
division of nucleus; d, complete division of cell (Eberth).
the cornea of the rabbit, and illustrates the process of division of the
young cells. This increases from day to day in width until all of the
granulations are covered in, the secretions cease, and the wound is
healed. For some time, however, the layer of epithelium remains very
thin and soft. By degrees this becomes thicker and denser, until in
most small wounds it approaches closely the characters of the normal
parts, but in large wounds it usually remains permanently much thin-
ner than normal.
Transplantation of epithelium to the surface of granulations is prac-
tised for the purpose of bringing about a more speedy cicatrization of
the wound. This little operation illustrates an important point in the
physiology of these cells which determines their behavior in pathological
conditions. When the epithelium is completely destroyed over a con-
INFLAMMATION.
709
a
siderable surface, as by a burn, no epithelium is produced on that sur-
face except as it is projected from the margins where the epithelium is
intact. Now, if the smallest bits of the epidermis from any portion of
the body of the same individual or of another be clipped off and laid
on the granulations, it will be observed that within a few days a film
of epithelium will spread from this point. By placing many of these
it is possible to cause a large wound to cicatrize much sooner than it
would otherwise do. In this way the peculiar epidermis of the white
man may be transplanted to the negro, producing a patch of white skin,
or vice versa. This shows that these cells have, independent of the
organism to which they belong, a life and individuality of their own
which they are capable of carrying into strange places and of asserting
among strangers.
The organization of blood-clot, so called, is a process of great import-
ance, not only as a matter of scientific inquiry, but also in its clinical
bearings. The blood-clot meets the surgeon at every turn, and its clin-
ical importance cannot well be over-estimated. If he ties an artery, he
depends on the so-called organization of the blood-clot that forms in
its interior to hold against the blood-pressure after the ligature has
sloughed out or has been absorbed. If a blood-clot forms in a wound.
FIG. 399.
C
eye:
Œ
d
C
FIG. 400.
W
K

вс
FIG. 399.-Absorption of Blood-clot. Section through the margin of a clot formed among the tissues by
extravasation, showing the growth of granulations by which it is removed: a, a, portions of clot;
b, b, original tissue; c, c, granulations springing from the original tissue and projecting into the
clot; d, d, wandering cells or leucocytes that seem to have taken red blood-discs into their inte-
rior. (Section cut in gum arabic and stained with hematoxylin; X 350, Black.)
FIG. 400.-Absorption of Blood-clot. Section through the margin of a blood-clot formed by extravasation
in the tissues, showing the growth of the granulations by which it is removed: a, portion of clot,
showing fibrinous reticulum enclosing the blood-discs, which are much shrunken, and occasional
wandering cells interspersed; b, newly-formed tissue projecting into the mass in the form of pro-
cesses, which are covered with young granulation-cells, e, c. The granulations are in intimate
relation with the clot. (Section cut in gum arabic and stained with hæmatoxylin; × 350, Black.)
after it has been closed, what is its significance? how is it disposed of?
and what is its effect on the healing of the wound? These questions
710
GENERAL PATHOLOGY.
will now admit of answer, thanks to the experimental study of recent
years.
When a blood-clot has formed from any cause in the midst of tissues
of fair functional activity, away from contact with the air, and there-
fore safe from contamination from without, it causes a slight inflamma-
tory process to be developed in its immediate neighborhood. This
brings to the spot numbers of the amoeboid cells, which actively attack
the clot in all its parts, but especially its margins. In addition to the
cells that wander free into the clot, granulations spring out into it from
all sides, and as they grow the clot disappears to give them room (Figs.
399 and 400). The clot is digested, dissolved, and removed. Thus the
connective-tissue forming cells grow into the substance of the clot as they
grow into the meshes of the sponge in the sponge graft, and the clot is
removed by solution in the same manner as the sponge. In this manner
very large clots are many times removed, leaving in their stead a quan-
tity of newly-formed tissue that is of no value. In time this also shrinks
away partly and is partly absorbed, so that in the end but little remains
to show that there has been a clot in the locality. The clot itself has no
power of organization any more than the sponge in the sponge graft,
but as the sponge it acts as a stimulant to the growth of the granula-
tions by which it is removed. It is possible also that in some positions
the blood-clot may, as the sponge graft, act as a ladder on which granu-
lations may climb, and in this manner assist in the formation of tissue
for the filling out of lost parts; but in this respect it is much inferior
even to the sponge in the character of the new tissue produced, which
is usually of a very loose texture and shrinks together to an extreme
degree (Fig. 401).
FIG. 401..
KA


From the Cross-section of an Arterial Thrombus of Three Months: f, lumina of vessels in the throm-
bus, x, x, x (× 300, Rindfleisch).
In order that the granulations shall grow in blood-clot it must remain
aseptic. Therefore it usually happens that clots which are exposed to
the air are decomposed, and constitute a much greater hindrance to the
healing process than in subcutaneous wounds. It has been shown by
Lister that blood-clots do not decompose as readily as most other sub-
stances; yet clinical experience demonstrates that in very many cases
their decomposition seriously interferes with the process of granulation
by becoming the foci of septic processes. If the clot remains aseptic,
it retards the process of healing by the time required to fill it with
granulations. I think a close comparative study will show that granu-
www.h
FEVER.
711
lations form less rapidly in a blood-clot than in the filling of an open
wound, and certainly the tissue formed is usually much less perfect.
Formerly it was held that the substance of the clot became itself tis-
sue. This was the conclusion arrived at by O. Weber, Budnoff, and
others, but recent studies have shown so plainly that the organization
takes place in the manner I have just stated that it is accepted by
pathologists generally.
FEVER.
Fever is a condition of the general system characterized by elevation
of the temperature and attended with increased frequency of the pulse.
This condition has no known anatomical characters; at least, none that
seem really essential to the condition of fever. It seems to consist of a
disturbance of the function of heat-production, or of the relations that
normally exist between the functions of heat-production and heat-dissi-
pation. Fever occurs as an accompaniment of many and various lesions;
and so common is this that it is expected to follow any lesion of con-
siderable gravity, and in such cases may be considered as symptomatic.
Fever occurs also as the forerunner and accompaniment of most of the
grave inflammations, such as pneumonitis or lung fever, inflammation
of Peyer's patches in typhoid fever, and various other forms of disease
known as the essential fevers, so called from the fact that the condition
of fever seems to be the prominent factor in the disease. It also pre-
cedes and accompanies the inflammation of the skin or eruption in the
exanthems, as in smallpox, scarlet fever, measles, etc. Fever usually
occurs after the infliction of wounds or surgical procedures which pro-
duce tissue injury of any conceivable kind in which much tissue is
involved. This is the more certain of occurrence if the wound is open
to the surface. This form of the disorder is known as wound fever or
surgical fever. Fever is also liable to occur without any appreciable
lesion of any known kind whatever that we are able to determine by
our physical senses, either as a forerunner, accompaniment, or sequel.
A person may be attacked with a feeling of languor, perhaps have some
headache, abnormal dryness of the mucous membranes, some thirst, etc.,
and a thermometer placed under the tongue may show a rise in the
bodily temperature of from three to five degrees. At the same time the
pulse may rise in frequency from 75 beats in the minute to 100 or even
120. These symptoms may continue from six to twenty-four hours,
and then subside with complete restoration to health, leaving no sign
whatever of any disease connected with or explaining this disturbance
of function.
From what has been said it would seem evident that fever does not
arise from any one specific morbific cause: it may, and evidently does,
arise from a variety of causes. As throwing light on this point, it
might be useful to inquire into the particular tissue prominently
affected, but as there are no anatomical lesions yet discovered that
are essential to this condition, the inquiry must be directed by the dis-
turbance of function. This leads to the questioning of the particular
systems that make up the community of systems that combine to form
712
GENERAL PATHOLOGY.
the sum of the functional activities. In this inquiry we will be more
or less troubled by uncertainties. The older pathologists seem to have
regarded the nervous system as the one specially affected, but recent
investigations point to the blood as being primarily at fault, or at least
indicate that fever results from some form of poison that has gained
access to the blood and is circulating in it. Recent experiments demon-
strate that the injection of pure healthy pus into the veins of the dog
produces fever with certainty and promptness, and that the fever thus
induced runs a very regular course, passing away in two days, more or
less, according to the amount of pus injected (Senator). In this case it
would seem that fever has a material cause, in that a substance is in the
blood that in some way interferes with the proper and normal func-
tions so as to increase its temperature. This increase in the tempera-
ture is the one essential factor. Increased frequency of the pulse is a
usual accompaniment of fever, but is not invariably present, and may
be induced by various causes independent of fever. We may and do
have fever without increased frequency of the pulse, and we may reduce
the frequency of the pulse during the existence of fever without mate-
rially altering the temperature. It is well known that during the exist-
ence of fever the pulse-rate may, by the administration of veratrum
viride, be reduced without lowering the temperature as expressed by
the thermometer. I recall a case of typhoid fever in a boy of twelve
years, who when I first saw him had a pulse-rate of 70 to the minute,
and at the same time a body-temperature of 107° F., as registered by a
thermometer in the axilla.. In this case veratrum viride had been given.
Occasionally, even where no heart sedative has been administered, fever
may be seen without a frequent pulse, though this is evidently rare. It
is not very uncommon, however, to see the temperature out of propor-
tion to the frequency of the pulse, or the reverse. A high pulse-rate,
therefore, while an accompaniment that is almost universal, is not abso-
lutely essential to the condition of fever. As it is with this, so it is with
the other symptoms, as thirst, loss of appetite, the sensation of heat felt
by the patient, etc. Any of these may be wanting, and in some rare
cases all of them, and still the continued elevation of the temperature
marks the condition of fever as being present notwithstanding. Fever,
then, is shown to be present by the existence of this one fact of high
temperature, and the other conditions that usually accompany it are
due to this increase of the temperature-are caused by the fever-are
products and not essential factors.
The increase of heat in fever is not in any sense local. Even though
the febrile movement may have resulted from a purely local inflamma-
tion, the rise of temperature is always general and affects all parts of
the body alike. Increased local heat accompanying local inflammations
must not be confounded with fever. In fever the whole blood is
warmer than normal, and this increase may stop at five or eight degrees.
above the normal, or in severe cases it may pass on to ten, but rarely
above this limit. The organism in its normal condition possesses a self-
regulating power as regards its temperature which under the varying
circumstances of climate and seasons preserves the blood at about the
same degree of heat-viz. 98° to 99° F. Therefore when it is observed
A
CA
Bal
FEVER.
713
that this equable temperature is disturbed, and that an elevation is
steadily progressing or is maintained above the normal, some factor has
entered into the economy from without, or has been produced by faulty
chemico-vital processes within, that has the effect of unbalancing the
combined functions of heat-production and heat-dissipation. This may
occur shortly after the receipt of an injury or the rise of an inflamma-
tion or of a complaint of languor, or seemingly as the result of the most
varied physical disturbances.
All of the features of the affection are arranged around this one cen-
tral phenomenon. The patient may or may not be conscious of the
increased heat. At the beginning of the rise of his temperature he
generally complains of chilly sensations. What is known as a chill or
rigor is coincident with a rise of temperature that is more or less sudden
or rapid, as is indicated by a thermometer under the tongue or in the
axilla. The sensations of the patient are not to be trusted, for while he
is shivering with cold his temperature may rise several degrees. After-
ward flashes of heat begin to alternate with the sensation of cold, and as
the case progresses the patient becomes unpleasantly conscious of the
increased heat of his body. In the onset of certain forms of fever the
occurrence of chill is a prominent manifestation. This is especially
the case in what is known as chills and fever; and indeed in all of the
types of malarial fever the duration and severity of the chill are espe-
cially marked, and the patient may be shivering with cold for an hour
or more, during which time he is unable to recognize the fact that he is
really unusually warm. The chill seems to mark a sudden rise of tem-
perature, but the gravity of the chill is not always in proportion to the
rapidity of the increase of heat. It has been suggested that the chill is
an illusory sensation brought about by the change in the temperature
relation of the body and the surrounding air; but there is evidently
some other factor in the production of chill that is not yet certainly
made out.
In other than the malarial fevers there is much difference as to the
production of chill. Thus, in most of the grave inflammations of the
internal organs, such as occur in pneumonitis and other of the continued
fevers that are accompanied with distinct and severe inflammations, the
occurrence of chill at the onset is the rule, and the severity of the chill
usually bears some proportion to the severity of the attack. In inflam-
mations not primarily accompanied with fever a chill is very likely to
mark the beginning of the formation of pus or the development of an
abscess. It is generally not very severe, and the fever which results.
usually passes away with the more complete formation of the abscess.
This seems to have some relation to the particular conditions at the seat
of the inflammatory process, in that the fever is called forth in the early
period of the inflammation or of the formation of pus, and ceases after
the effusion of plastic lymph has, so to speak, walled in the inflamma-
tory products by the closure of the lymphatics, by which absorption into
the general circulation is prevented or rendered less in amount. I will
speak of this again.
In surgical fever (fever following shock or accompanying the devel-
opment of inflammation in a wound) the chill is usually absent or but
--
714
GENERAL PATHOLOGY.
slightly developed. The fever in this case comes on more gradually,
and the temperature does not attain so high a degree. If, however, the
chill should be pronounced, the fever which follows is likely to be
accompanied with graver symptoms than the fever that is ushered in
without marked chill.
In connection with the increase in the temperature of the blood in
fever other evidences are presented, showing derangement of the func-
tions of heat-production. Tissues are being destroyed by combustion
or oxidation to an abnormal degree in consequence of the necessity for
material sufficient to keep up the increased heat-production. It appears
from the recent experimental studies of Senator, H. C. Wood, and others
that the excretion of urea is doubled or tripled as a result of the
increased destruction of albuminous material-blood-plasma, blood-
corpuscles, the sarcose elements of muscular tissue, etc. Hence the
increase in the salts of the urine and the increased excretion of carbonic
acid which are also noted. At the same time, digestion and assimilation
are disordered, appetite is wanting or is seriously impaired, and in this
way the usual food-supply for renewing the waste of the tissues is
greatly diminished or cut off entirely. Hence the absorption of adipose
tissue, waste of the muscles, and impairment of the blood follow as
results of, or it may be said form a part of the phenomena of, fever. It
thus becomes evident that the abnormal production of heat during fever
is maintained by the consumption of valuable material not used for this
purpose in a state of health, or the regeneration of which is prevented
by the accompanying conditions of impairment of the functions of diges-
tion and assimilation. With this view fever might be said to consist of
a disorder of nutrition made manifest in increased heat-production and
increased tissue-waste.
be pres-
It appears from the exhaustive experimental research of Prof. H. C.
Wood that the temperature of the body is no certain guide to the extent
of the abnormal heat-production that may be in progress in a given case
of fever, for another factor enters into the disorder-namely, disordered
heat-dissipation. It therefore follows that if the dissipation of heat be
interfered with, a rise of the temperature of the body may occur without
over-heat-production, and, vice versa, over-heat-production may
ent without rise of bodily temperature. It thus appears that the heat
of the body is controlled in a large degree by the orderly play that nor-
mally exists between the combined functions of heat-production and
heat-dissipation, and that the occurrence of a rise of temperature may be
due to either increased heat-production or diminished heat-dissipation.
Touching this point Prof. Wood formulates the following proposition:
"Fever is a complex nutritive disturbance, in which there is excessive
production of such portion of the bodily heat as is derived from chem-
ical movements in the accumulated material of the organism, the over-
plus being sometimes less, sometimes more, than the loss of heat-pro-
duction resulting from abstinence from food. The degree of bodily
temperature in fever depends, in greater or less measure, upon a dis-
turbance in the natural play between the functions of heat-production
and heat-dissipation, and is not an accurate measure of the intensity of
increased chemical movements of the tissues."
San
G
FEVER.
715
The cause of fever is in some degree elucidated by the experimental
research of Senator, already alluded to. This experimenter injected fresh
healthy pulse into the subcutaneous tissue of dogs, and found that it reg-
ularly produced a state of fever. Two or three hours after the pus was
injected the temperature began to rise, and a state of fever was inaugurated
that continued two or three days, and subsided unless the injection was
repeated. This and similar experiments have established a connection
between inflammation and fever that was inferred previous to the
experimentation, but which is now placed on a more certain basis.
The relation between these processes has been observed clinically since
the inception of surgical knowledge. When a wound of considerable
magnitude is inflicted, clinical experience has led men to expect the rise
of fever to coincide very closely with the rise of inflammation in the
wound; and it has been noticed especially that if the progress of the
wound was favorable, this fever would begin to subside when the
inflammatory process had reached a certain point-i. e. when the secre-
tions were established, as the process has been denominated. This cor-
responds very closely with the time when the wound is, so to speak,
walled in by the inflammatory exudates in such a manner as to prevent
absorption of the materials elaborated by the inflammatory process.
If the fever recurs after this period or if it persists, the surgeon is led
to seek some other cause for its recurrence or persistence. This is gen-
erally found to be some change in the condition of the wound or in the
development of an abscess in connection with some foreign substance
overlooked-a pocket in an unexplored nook in which retained pus has
begun burrowing, or something of this general nature that has caused a
fresh inflammatory movement; or it may be that the wound as a whole
has taken on a septic condition. When no such causes as these can be
found in connection with the case, the surgeon of to-day will regard the
fever as arising from conditions foreign to the wound itself.
3
In this view of the matter we must suppose that some material has
been elaborated in connection with the process of inflammation which,
when taken into the blood, has the effect of disturbing the existing nor-
mal relations between heat-production and heat-dissipation in such a
way as to give rise to fever, or which increases heat-production. This,
as we have seen, has been the direct result of the injection of the fresh
products of inflammation into healthy animals; therefore in the light
of the clinical history of wound surgery, and the connection of fever
therewith as related above, we cannot escape the conviction that the
fever in each instance has a material cause in the absorption of the prod-
ucts of inflammation directly from the wound into the circulation.
G
In pursuing the clinical history of this subject farther we shall find
that fever is also produced by inflammations independently of the
formation of pus, though not so generally perhaps; yet the number of
cases in which the fever is developed before the beginning of pus-forma-
tion is really very large. Then the cause of fever, in these cases at least,
is not necessarily the absorption of the pus itself, but of the products
of perverted cell-action which precede the development of pus. Some
reference to these products have been made in the study of the process.
of inflammation as relating to the activity of the tissues. In this per-
716
GENERAL PATHOLOGY.
version of cell-activity under the influence of, or as a result of, irrita-
tion or tissue injury, products of an abnormal character seem to be
formed which, when carried into the circulation in sufficient quantity,
serve to inaugurate the condition of fever. On the basis of observations.
similar to those cited above Dr. Sanderson speaks of the "infective "
power of the products of ordinary inflammation, and arrives at the con-
clusion that "fever is the product of a fever-producing cause contained
in the blood or tissue-juices, the morbific action of which on the organ-
ism is antecedent to all functional disturbance whatever;" and speaks
of fever as "from first to last a disorder of protoplasm."
It is not necessary to suppose that all fevers result from the products
of inflammation; indeed, such an hypothesis could not be maintained
upon the facts at present in our possession, for many cases of fever
occur which are in no way related to inflammation, so far as physical
examination has thus far developed. This seems to be but one cause
out of many. It seems probable that there are other forms of perverted
cell-action, not yet known to us, which take place in the economy
and are capable of giving rise to products which may act as a cause.
Putridity is regarded as a cause, and the soluble sepsin of Bergman,
which is undoubtedly the waste product of certain micro-organisms,
and which holds a close relationship to the alkaloids of the higher
plants, has been demonstrated experimentally to be capable of produ-
cing fever when introduced into the system. Besides this, a number
of micro-organisms have been proved to stand in a causative relation to
fever, and other causes will in all probability be identified in the near
future.
J
The supposition so widely held that fever has its origin in irritation,
which has given rise to the terms "irritative fever," "sympathetic
fever," "fever from constitutional irritation," seems not to be main-
tained. The most persistent experimentation with that end in view has
failed (in dogs) to produce fever by the irritation of peripheral nerves.
Dr. Billroth has made these experiments in various ways, as by forcible
injections of air into the subcutaneous tissue, by exposing nerve-trunks
and irritating them with ammonia, by suspending weights to nerve-
trunks, by tearing the inner coats of the vessels, by injecting powders
into the blood so as to form emboli, by rubbing the ears with croton
oil, etc., and in no case did he succeed in producing immediate fever.
On this and similar experimentation he arrived at the conclusion that
fever always has a material cause. Various other experiments have
been made with this end in view, and after a close review of them it
seems that the conclusions of Billroth are maintained. This idea of
irritative fever has been so widely held, and has seemed so well sus-
tained by clinical observation, that it is displaced with difficulty; but,
as Prof. Wood so aptly says, "as our knowlege grows, fevers supposed
to be due to peripheral irritations are shown, one by one, to have their
origin in toxæmia."
Still, it seems hardly possible that all of the fugitive fevers that we
see, many of them enduring only for a few hours and then passing away
with complete restoration of health, or those mild febrile reactions of
childhood that arise seemingly from slight intestinal irritations, the
FEVER.
717
fever so common during the cutting of the teeth of children, and the
like, all come from an actual poisoning of the blood. However this
may be, it is now very certain that all of the graver forms of fever
which were formerly supposed to arise from irritation are due to a
material cause circulating in the blood.
How the fever-producing poisons act in the production of fever, or
upon what tissue, cannot now be certainly affirmed. It does not seem
probable that their action is on the general protoplasm of the body. If
this were the case, fever would often be expressed locally, for it is
hardly conceivable that in all cases the poison could be so perfectly dis-
tributed that no local expressions of its action should be noticed. Then
it must act on the blood directly or on the nervous system. These two
form systems that are more general and widereaching in their bonds of
union with the system at large than any other. The nervous phenom-
ena of fever are so prominent that in the absence of exact experimental
evidence we would naturally look to it as the system most prominently
affected. It is well known that certain poisons affect certain portions
of the brain or nervous system prominently when they gain access to
the circulation and are carried to the particular part by the blood. This
is seen in the action of alcohol, of opium, of strychnia, and many other
drugs. All of these in a certain sense act as blood-poisons; that is to
say, they reach the tissue upon which their impression is made through
the medium of the blood. It seems most probable that the fever-pro-
ducing poisons act in the same way. Of ordinary malarial fever Prof.
Wood says: "The chill, the fever, and the sweating in their regular
sequence and their periodical occurrences most plainly bear evidence to
a neurotic origin." The same author calls attention also to the well-
known fact that the paroxysm of fever may be replaced with a par-
oxysm of neuralgia "and various local vaso-motor and secretory dis-
turbances" which can with difficulty be conceived as being induced
otherwise than through the nervous system.
C
The discussion of our present knowledge of a probable heat-centre,
or several centres acting in unison in a state of health for the control
of the temperature of the body, in its relations to fever-production
would lead me beyond the space alloted to this article. The experi-
mentation that has been had, especially that by Prof. Wood, amounts
almost to a demonstration, although the centre is not precisely located.
The complete demonstration of such a centre, and of its powers and
capabilities, will add greatly to our knowledge of this important sub-
ject. So far, it has been definitely determined that irritation of cer-
tain portions of the brain affect heat-production and heat-dissipation
in a very marked degree; and this knowledge seems entirely suf-
ficient to serve as the basis of the doctrine set forth above. On this
basis Prof. Wood formulates the following: "Irritative fever, if it
exist, is produced by an action on the nervous system. Fever occur-
ring in case of blood-poisoning is often, and probably always, the
result of a direct or indirect action of the poison on the central ner-
vous system, and hence is a neurosis."
RESULTS OF FEVER.-The usual tendency of fever is toward self-
limitation. In other words, the tendency is toward a spontaneous
718
GENERAL PATHOLOGY.
·
return to health after some days-more or less according to the nature
of the cause.
For instance, in the case of a common boil of moderate
severity we should expect a rather mild form of fever, lasting one
or two days and then passing away. In inflammations of greater
extent a greater rise of temperature and continuing for a longer time
would be expected. In cases of acute alveolar abscess there may
be a temperature of 104° F., running for two or three days. This,
however, may be regarded as rather unusual, and when it occurs marks
the case as a somewhat grave one, with the probability that some necrosis
of bone about the root of the affected tooth will occur. This necrosis
is not caused by the fever, but results from the severity of the inflam-
mation causing the fever. Therefore the severity of the fever is some
indication as to the severity of inflammations. It may be stated that
all of the symptomatic fevers which accompany the slighter forms of
inflammation, such as I have mentioned, pass away spontaneously within
a few days. In the continued fevers the cause is more persistent, and
evidently remains in action for a much longer time, this differing much
with the various forms of these affections.
J
If fever exceeds a certain degree, it becomes in itself dangerous to
life. It rarely exceeds 107° or 108° F.; that is to say, this intensity
of fever, or a rise of the temperature of the blood to this degree, is
usually fatal if it continues many hours. Some time since there came
under my observation the case of a young woman from whom the
ovaries had been removed for the cure of violent and persistent hys-
teria: the temperature began to rise a short time after the operation, the
increase continuing rapidly and steadily in spite of all efforts to coun-
teract it. Within ten hours it had passed 108° F., and in another hour
the patient died, with the thermometer indicating the extreme tempera-
ture of 110°. After death the temperature continued to rise until 112°
was reached. It is usual for cases having a temperature of 108° or over
to prove rapidly fatal, although some instances of recovery after a much
higher temperature had occurred have been reported. Therefore, the
upward limit of fever is controlled only by the endurance of the par-
ticular patient. There is usually no great danger from fever until 106°
is passed, unless the high temperature be long maintained; but this
temperature is not to be endured very long without remission. In the
continued fevers, in which the temperature reaches this height, there are
regular remissions, usually corresponding with the diurnal fall of tem-
perature in health, which seem to relieve the patient and enable him to
endure the very high temperature of the evening.
Persons sometimes succumb to a much lower temperature, though this
is rather unusual unless there is some other cause of death co-operating.
A few years ago I had under observation a case of seemingly mild type-
of typhoid fever in which the patient became comatose, and died on the
tenth day, the fever not having risen above 103° at any time. Post-
mortem examination revealed the usual lesion of this stage of the dis-
ease, but this was mild in degree. No cause of death was found other
than the fever.
From the nature of fever there must be much injury to the tissues,
especially if the febrile movement is intense and long continued. The
SHOCK.
719
injury to the nervous structures is manifest in the delirium and other
perturbations of the mental faculties that so generally accompany severe
fevers. In severe and long-continued attacks the muscles are especially
In this
affected by the destruction of the sarcose element of the fibres.
way portions of the fibres of certain muscles are occasionally injured to
such an extent as to cause lameness for some time after recovery. The
general emaciation has been spoken of: this is the usual result of fever;
all of the tissues suffer waste, but the fatty tissues are perhaps destroyed
to a greater extent than any others.
SHOCK.
Shock is a sudden and notable depression of the vital powers result-
ing from an injury more or less grave, or from an impression made on
the nervous system through the medium of the sensorium, as by fright,
sudden and overpowering mental emotion, etc. In its phenomena it
seems to consist of a sudden check of the circulation brought about
through the agency of the nervous system: this may be so grave as to
cause instant death, or may result in prostration more or less prolonged,
with or without a successful reaction following it. It was long ago
noted that death sometimes resulted suddenly after injuries that left no
trace of their destructive effects on the vital organs, and that many
instances in which death was less immediate could not be explained by
the visible effects of the injury sustained. It frequently occurs that
persons who have sustained some injury sink into a state of prostration
not to be accounted for by the severity of the hurt, such persons, even
though apparently moribund, being sometimes within a day or two
restored to their usual health and vigor. These cases can be explained
in no way other than upon the supposition that the nervous system had
been suddenly overpowered. Hence the term shock. Collapse is also
used in the same sense.
It is not to be.inferred that there is actually no tissue-change in these
cases, but there certainly is none that can be recognized by our physical
senses through either macroscopic or microscopic examination. It can-
not be supposed, however, that such grave symptoms can occur without
some molecular disturbance in the nerve-cells which for the time renders
them incapable of the proper performance of their functions.
The cause of shock has been a subject of much inquiry, especially
among surgeons, who are continually brought in contact with the
graver forms of this condition. The general nature of shock remains
the same, no matter whether it result from bodily injury or mental
impressions. Diminished energy of the nervous system, resulting in
enfeeblement of the circulation, is prominent in every symptom, and
the general reduction of the vital powers seems to depend on this for
its inauguration and continuance. The injury to the nervous system is
especially manifest in the demeanor of the sufferer, and this is expressed
in a variety of ways. In one case a person who has received a serious
injury may for a time apparently disregard it; he seems not to suffer
pain, and is possessed of a calmness that under the circumstances is
entirely unnatural, while at the same moment the surgeon will perhaps
720
GENERAL PATHOLOGY.
discover a marked pallor, soon followed by coldness of the skin. The
pulse becomes weak, small in volume, and passes under the finger with
a peculiarly short and quick stroke, denoting an extreme relaxation of
the vascular system. The failure of the nervous system is seen in other
directions as well. Questions are answered slowly and hesitatingly, as
though not fairly understood; the tone of the voice is changed, and
perhaps markedly enfeebled. The motions of the patient may show
extreme weakness; sentences give place to monosyllables; and the
patient may sink into a state bordering upon unconsciousness, in
which he takes no notice of what is going on around him. He may
recover from this condition speedily, with full restoration of the normal
tone and vigor of the nervous system, or recovery may be delayed
indefinitely. There is, however, generally a reaction within one or
two days.
In other cases all of the more profound symptoms of shock may
occur suddenly. Coma, or even death, may almost immediately follow
the receipt of a comparatively trifling injury or from mental impressions
that in other persons, and perhaps in the same person at another time,
would scarcely be noticed.
Shock differs materially from syncope. Emotion, the sight of a wound,
and various trifling circumstances may cause a momentary stoppage of
the action of the heart, with a temporary loss of consciousness, and not
be productive of shock. The production of shock evidently involves
some other factor, for instead of a temporary arrest of function there
appears to be a real injury to the structure upon which the functioning
power depends that renders immediate recovery impossible. Time must
be had for recovery from this tissue injury, and during this period these
functions are imperfectly performed, apparently from lack of power.
The symptoms seem to point to the failure of those nerve-centres that
maintain the proper tension of the vascular system. Normally, the
walls of the arteries are contracted upon the blood they contain, so as
to keep up a certain degree of arterial pressure, this being to a lesser
extent complemented by the veins. In shock there is a sudden letting
go
of this tension, of this grasp on the blood. The vascular system is
relaxed abnormally, and in such a manner as to interfere with the cir-
culation. At the same time there is a relaxation of the energies of the
heart, but not a stoppage as in syncope, except it be in some of those
grave forms that result in almost instant death, in which this point can-
not well be studied and distinguished from other symptoms. The rule
is that the heart maintains its action, but in a very feeble way; and it
appears to have been shown by experiment on the frog that even when
the heart is stopped it may be induced to resume its action by supplying
it with blood. Prof. Goltz of Strasbourg performed the experiment in
this way: A frog was suspended in a vertical position with the legs
hanging down and the heart exposed. After a few moments' delay, to
see that the circulation was going forward normally, the animal was
struck a smart blow on the surface of the abdomen. The heart stopped
its contractions at once, and after a few moments began again feebly,
but it was clear that it was propelling no blood into the aorta, for the
upper part of the vena cava was empty and no blood was supplied to
d
SHOCK.
721
"
the heart. The effect of the blow seemed to have paralyzed those
nerve-centres which control the tension of the vascular system, causing
such a dilatation of the vessels of the abdomen particularly that the
blood did not fill them, and the heart was unable to proceed normally
for want of the usual stimulus of a proper blood-supply. When the
animal was laid down, so that gravitation would bring the blood to the
heart, the normal pulsations were resumed. It is clear that the animal
could not have recovered had it remained suspended, for without the
circulation, which under the circumstances could not be resumed, the
nerve-centres could not recover their vigor. But with this the tension
was soon restored. This experiment shows that an animal-and prob-
ably a man as well-may bleed to death without the loss of a drop of
blood, simply by the dilatation of the vessels to such an extent that they
shall not be filled with blood. It is probable that the great vessels of
the abdomen when utterly relaxed will contain the whole blood of the
vascular system, and in this condition it will for the time be as com-
pletely lost to the system as though it had been poured out. This seems
to indicate the exact manner of death in some of the cases of shock
already alluded to. Savory states that instant death may occur from
a blow on the epigastrium which, though severe, leaves no detectable
lesion; and Mansel-Moullin relates a case of sudden death from shock
caused by the introduction of a trocar into a cyst of the liver, in which
the tissue injury was so trifling that death could not be explained except
on a supposition of a paralysis of the vaso-motor centres.
These facts seem to show plainly the nature of the condition which is
known as shock or collapse. The vaso-motor nerves are for the time
rendered inoperative, and in this way the circulation is so enfeebled,
when not cut off entirely, that its functions are imperfectly performed,
and the whole system suffers in consequence. There seems to be a pos-
itive enfeeblement of the heart as well, probably from the same cause,
for in those cases of the lesser degrees of shock the effect on the heart
seems to be the prominent factor, at least the most marked symptom. Yet
in all cases the character of the pulse, which is very short and compres-
sible, speaks plainly of lack of arterial tension. The heart is so far
independent of other innervation than that contained within its own
walls that it is capable of continuing its regular rhythmical actions when
all other sources of nerve-supply are cut off. The great nerve-centres
may be removed one after another until the last one is severed, and yet
the nerves contained in its own walls will serve the purpose of continuing
its motions. At the same time, it is so connected with these great nerve-
centres that the irritation of one of its connecting branches may bring it
to an immediate stop. Not only this, but irritation applied to a per-
ipheral nerve may produce the same effect through reflex action. We
have also learned through direct experiment, some of which was detailed
while treating of hyperæmia, that the blood-vessels, veins as well as
arteries, are under a control of the same nature and are affected in
the same way by similar causes. While all of this is true, and the
heart may be stopped by these reflex impulses, and the tone of the
arteries may be relaxed, the local nerves of the heart will, after a time,
set up these actions anew independently of other nerve-influence.
J
It is
VOL. I.-46
722
GENERAL PATHOLOGY.
not shown that the blood-vessels will recover their tone so readily as
the heart, but, on the contrary, experiment and clinical observation
combine in the illustration of the fact that their enfeeblement is recov-
ered from with much greater difficulty.
C
The molecular disturbances in shock should not be passed over without
notice. All function is directly dependent upon remolecularizations of
matter, or at least molecular motion or chemico-vital changes in some
form. This is the opinion of the scientific world at the present time.
In the performance of labor by the muscles the sarcose material of the
fibres undergoes molecular changes with every contraction, and these
changes result in the formation of waste products which are eliminated.
Therefore if these changes occur with such rapidity that this cannot be
resupplied by the nutrient functions in the necessary proportion, the
muscle becomes exhausted; rest is then necessary that nutritive repair
may bring the muscle up to the normal standard again. That which
is true of the muscles is true also of other tissues. If in any case a
functioning tissue is called upon for an extraordinary expenditure of
energy, exhaustion occurs very quickly. In the case of shock the ner-
vous system is overcome, and fails either partially or altogether in the
performance of certain of its normal functions, such as that of main-
taining the usual tension of the circulating system, and to a lesser
degree, perhaps, that of cerebration and the voluntary motions. This,
however, is not the only injury that occurs in shock. Under some cir-
cumstances the life-force as it exists in the individual cell is unable to
carry forward in the normal manner its remolecularizations of matter
in the processes of nutrition and denutrition, and the changes become
abnormal, resulting in the formation of substances unhealthful in quality
or quantity. This is seen in fatty degeneration. The tone of the life-
force as it exists in the individual cells is lowered to such a degree that
the matter of which the cell is composed, instead of passing regularly
on to the formation of waste products in the normal manner, falls into
the molecular groupings of oil. This oil gathers in the form of minute
globules in the midst of the cell, instead of passing away with the
normal waste products; which circumstance permits of its discovery
by means of microscopic examination-a thing that would be impossi-
ble if the abnormal substance were more soluble. Changes of a similar
nature undoubtedly occur in shock, though they differ in the character
of the products. Just what these changes are is unknown, but the
evidence that they occur is to my mind conclusive. It has long been
known that fright, or any other form of mental impression productive
of a slight degree of shock, is liable so to change the milk of the
nursing woman that it will act as a poison to the child. This can be
explained only on the supposition that the chemico-vital' changes-the
remolecularizations of matter-which take place in the formation of the
waste products, and in the elaboration of the secretions as well, have
been imperfectly, or at least improperly, carried on, and have resulted
in the formation of abnormal molecular groupings, thus giving rise to
chemical substances that prove injurious.
In the discussion of the subject of fever it was explained that it
was always the effect of a material cause. One of the most common
Kanga
SHOCK.
723
of these is always produced in the peculiar tissue-changes that are
taking place in the process of inflammation, and we find fever to
result in case the inflammatory movement is considerable. All forms
of shock are followed during the stage of reaction by fever. The regu-
larity of the occurrence of this fever leaves us no room to doubt that it
has resulted from some injury to the tissues which has rendered the
performance of the chemico-vital remolecularizations both difficult and
imperfect in their results, so that molecular groupings are formed that
give a chemical substance capable of producing fever. There is, then,
in addition to the paralysis of the vaso-motor nerve-centres, or as a
result of this, an injury to some portion of the tissues; and this may
be the nerve-tissue through which the chemico-vital changes are ren-
dered imperfect or abnormal.
-
The symptoms of shock vary indefinitely in its different manifesta-
tions, but these differences are more of degree than of kind. In its
extreme forms its features are plainly marked. The appearance of
the patient is that of the most extreme prostration. There is pallor
of the face and of the whole surface of the body; this is also very
apparent in the mucous membranes where they are exposed to view, as
in the lips and mouth. The surface is abnormally cold, and is covered
with moisture, sometimes like great drops of sweat, cold and clammy
in character. The features appear pinched and dull, the eyelids are
drooped, and the eye itself seems to have lost its wonted expression.
The debility of the muscular system is apparent in every motion if the
patient attempts to move at all, and even in his position when he is
motionless. The respiratory movements are usually feeble and short;
they may be panting and irregular or gasping, and in the most grave
conditions may be scarcely perceptible. The pulse is generally frequent,
though it may be rather infrequent, and occasionally quite irregular.
It is always very weak, and passes under the finger with a short quick
stroke, leaving the artery soft and limp between the heart-beats, and is
very compressible, indicating the extreme relaxation of the arteries.
The temperature is always more or less reduced, and it seems that the
amount of the reduction is some indication of the gravity of the case,
though some of the cases with very low temperature recover even after
a temperature of 93° F., and Wagstaffe reports a case that recovered
after the extreme depression of 91.5° F. had been reached. The mind
is generally clear, but the person may be drowsy and bewildered when
aroused. In a minority of cases the senses are unusually acute—so
much so that the patient seems continually on the alert and bordering
on a condition of excitement. In this latter condition questions may
be answered in a quick, jerky manner, but more generally they are
answered hesitatingly, as though very slowly comprehended.
These symptoms may vary in degree from a condition in which death
occurs within a few moments or a few hours to that of an impairment
of the functions to so slight a degree as to amount to nothing more
than an expression of weariness. Every conceivable condition between
these extremes may be noticed. In the medium or lighter forms of
shock there is often seen that which Travers has aptly termed "prostra-
tion with excitement." This may be present from the first, or it may
Chil
Karda
724
GENERAL PATHOLOGY.
become apparent during the following reaction. The patient may seem
perfectly frantic and tortured with the most terrible forebodings, in
which condition no question will be answered or apparently noticed. I
once witnessed a case of this kind in a man who had had both legs crushed
under a railway-car, and who screamed the same words almost contin-
uously until stopped by the administration of an anesthetic preparatory
to amputation. In this condition nothing in the way of encouragement
is heeded, no form of advice or counsel is of any use, though there
seems no lack of consciousness. The mind is too completely occupied
with the terrors of the situation to admit any other mental impression.
In all of this the condition of the circulation and of the skin, and all
of the other symptoms except those relating to the condition of the
mental faculties, are the same, only perhaps less in degree, as in cases
of profound shock with stupor. This, like all of the other conditions
of shock, may be manifested in all degrees from a mere watchfulness to
the most complete delirium.
The liability of individuals to shock seems not to be regulated by any
known laws. One person dies from shock under apparently the same
circumstances under which another escapes it entirely. Nothing definite
can be stated as to the liability of this or that individual to shock under
given circumstances; yet it may be affirmed that as a general rule those
whose constitutions have been broken down by debauchery are more
liable to shock than others. Individual idiosyncrasy that cannot be
determined in advance seems to have much to do with the difference of
liability. Taken all in all, it may be said that the liability to shock is
in proportion to the extent of the injury. Hence grave forms of shock
are oftenest seen in connection with serious injuries and extensive sur-
gical operations. Extensive burns, scalds, and contusions, crushing
wounds and capital surgical operations, are most often attended with
grave forms of shock. The danger seems to be greatest in case of
wounds of the trunk, especially of the abdomen, and decreases as the
seat of injury is extended along the extremities. A comparatively large
proportion of cases of shock have been observed in connection with
railway accidents, resulting in part, perhaps, from sudden suspension
of motion or from being thrown violently against objects, and in part
from fright. Mansel-Moullin states that "instances of severe and last-
ing shock, often assuming most insidious forms, are met with from time
to time in cases of this kind, without there being any definite bodily
lesion, and, indeed, are often the more severe when this is quite absent
and there is no other explanation than the general mental cause.' Some
years ago I observed a case illustrative of this. A car, when at full
speed, was thrown violently down an embankment, and fell on its side.
One of the passengers fell with his hands through a window, where
they were caught between the car and the ground in such a way as to
hold him fast. The car immediately took fire and was burning rapidly
when he was rescued. When I saw him, four hours after, he was in a
state of profound shock, in which he took no notice whatever of what
was going on around him. No bodily injury was found except a slight
cut on one cheek made by glass. Reaction began in about twenty-four
hours, and he made a good recovery.
GRA
SHOCK.
725
Sometimes
Reaction from shock varies extremely in different cases.
it is prompt, and the usual health is resumed rapidly and perfectly. In
other cases it is tardy, and the patient lingers along for days and weeks
without marked improvement; and it is noteworthy that this is as
apt to be the result in the lighter as in the graver forms of shock.
As a rule, reaction may be expected to begin within one or two days.
During the reaction the temperature, which is below the normal, usu-
ally rises several degrees; and the rule is that there is marked though
not very intense fever. The occurrence of this in a mild degree is
regarded as favorable, and when it occurs promptly the patient will
usually go rapidly on to complete recovery. If it is delayed and not
well marked, recovery is generally slow and often very imperfect. The
principal thing to be done is to give the patient quiet and as perfect rest
as possible. The large majority of surgeons recommend the judicious
use of stimulants, especially brandy, for the purpose of favoring reac-
tion; but a few-notably the late Dr. J. T. Hodgen of St. Louis―
reject this treatment as bad practice, and prefer to depend on complete
rest. The mental condition is of importance. The mind should be as
much at rest as possible, and especially should sleep be had. Most
surgeons agree in the use of opium, when necessary, to procure this.
Among other stimulants, strychnia, belladonna, and digitalis have been
used with advantage.
Shock resulting from dental operations seems not to have received due
consideration in past years, for the reason, perhaps, that it is seldom
seen in its graver forms. It should not be forgotten, however, that it
is liable to occur at any time with all of its attendant dangers. But it is
the lesser and more insidious forms of shock that are most to be feared
as a result of dental operations. The following passage from Mr.
Savory's article on this subject in Holmes's System of Surgery is appli-
cable here:
"Hitherto, the influence of shock has been considered only in its
extreme effects when directly producing a state of collapse, but it must
be a very narrow view of the subject which would overlook its less
severe though much more frequent results. It may operate in any
degree, and produce in one case, as has already been seen, instant death,
or a state not to be distinguished from it for a time even by the most
anxious scrutiny; in another case effects so trivial that the symptoms
pass unnoticed or unheeded by a superficial observer.
"There are many cases on record, and many more known to every
surgeon, of death from this cause, less sudden, but in many instances
scarcely less inevitable. In some cases injuries or operations compara-
tively trivial in their nature induce a condition of otherwise unaccount-
able debility, and terminate in death by asthenia. A careful inquiry
into the history of such cases will often elicit facts which enable us to
reconcile the apparent disproportion of cause and effect.
"After injuries or operations sufficiently severe to produce a serious
impression on the system, yet by no means amounting to a condition of
collapse, reaction is sometimes defective and unduly delayed. The
patient remains depressed; there is no heat of surface; the pulse is
weak and perhaps unsteady; he does not sleep soundly, though he may
726
GENERAL PATHOLOGY.
be constantly dozing; and the stomach is often irritable. In a word,
there is an absence of sympathetic fever.'
"""
In these paragraphs we find an expression of conditions that not
unfrequently follow as a result of dental operations. They are closely
akin to what is known as nervous exhaustion, but approach closer still
to the condition of true shock in its lighter manifestations. These
two conditions grade into each other in such a way that no exact
line can be drawn. The major forms of shock occur suddenly from
some impression that overpowers the nervous system at a single stroke,
producing a marked dilatation of the whole vascular system, so as to
leave the heart without a due supply of blood. Nervous exhaustion
comes on very slowly from some cause that continues to act, and is often
very insidious in its approach. It occurs oftenest, perhaps, from too
continuous employment, mental strain, or any continuous condition that
overtaxes the nervous energies for a considerable time. In many cases
the minor forms of shock do not occur so suddenly as is usually the
case in the major forms, nor so slowly as in nervous exhaustion, but are
usually the result of more or less prolonged pain, nervous irritation,
mental excitement, or some form of extraordinary effort. On this
point Mr. Savory, after describing the more immediate results of
shock, says: "But the effects of a shock to the system are not always
thus limited in their nature and duration. Those which have been
described may be termed primary or direct, but sometimes these are
succeeded by those that are more remote and secondary, including per-·
haps, after a shorter or longer interval, grave mischief, or it may be
even death. It is not uncommon to have various forms of local disease
or disturbance of the general health referred to some previous shock
which the system has sustained. 'He has never been the man he was
since-' is a familiar allusion to a case of this kind; and after making
every allowance for exaggeration and misinterpretation, the relation of
cause and effect between some previous shock and present mischief may
often be clearly and unequivocally established."
Such results as these are liable to happen occasionally in dental prac-
tice, and the lighter manifestations of shock are of frequent occurrence.
A patient, perhaps a lady, presents herself at the time of her appoint-
ment to have several fillings inserted. There may be some special
reason on her part or on the part of the operator for a long sitting. As
the operations progress it is found that they are very painful, yet the
patient is anxious to have them done with, and makes an heroic effort to
bear the pain so that their accomplishment may not be delayed. Thus
the operations go forward for one, two, three, and it may be four hours
continuously. The operator may even be encouraged to persist by the
not unusual fact that the patient flinches less in the third hour than in
the first; but if he would follow up the pulse from hour to hour, he
would find certain changes taking place. It will have lost markedly
in tone and volume, and as it passes under the finger may perhaps
present a peculiar thrill that was not present at the beginning of the
operations. Sometimes it will be more frequent, sometimes less. There
is also a perceptible change in the character of the motions of the
patient. They may be quick, with a slight inclination to jerkiness, or
SHOCK.
727
be languid and unusually slow. The face is pale, and the thermometer
shows a slight reduction of the temperature. The patient is finally dis-
charged, and goes her way without any very decisive sign that there is
anything wrong; but she has a restless night, and the next day there is
slight fever. This is of a mild type perhaps, and occasions no great
uneasiness, or it may be more severe and accompanied with a feeling of
great weariness. In the more ordinary cases this passes away in from
three to five days with complete restoration to health, but occasionally
the patient falls into a state of nervous exhaustion from which she
rallies very slowly.
I might give a number of cases coming under my observation illustra-
tive of this, but one or two must suffice. One of the most notable of
these was observed some ten years ago. A young lady of eighteen came
from a distance by appointment to have carious teeth filled. Upon exam-
ination it was found that there were two exposed pulps, besides other
smaller cavities. Both the young lady and her parents insisted that all
should be done that day if it was possible, it being necessary that they
should return on account of important engagements: the lady said that
she had no fears as to bearing any necessary operation, even the direct
removal of the exposed pulps. The operations were proceeded with,
and everything was borne without a murmur. My patient was a fine
specimen of physical development, and I soon found that she prided
herself on her powers of endurance. The pulps were, at her urgent re-
quest that there should be no delay, removed directly with the broach,
and the filling proceeded with. After three hours of continuous ope-
rating the patient was discharged for two hours' rest. She returned
promptly, but something in her appearance arrested my attention as not
being just right, yet in answer to questions she said she felt perfectly
well, only a little tired. The operations were resumed, and all went
well at first, but after an hour, the latter part of which had been occu-
pied in the excavation of a very sensitive cavity, I found that the pulse
had become very easily compressible and other evidences of shock were
becoming very apparent. Gutta-percha fillings were placed in the cav-
ities excavated and operations suspended. I found it necessary to assist
her to a couch, as it was evident that she was unable to walk steadily.
After two hours in the recumbent posture she seemed better, and was
taken to the train by her parents, and went home, some fifty miles by
rail, and I saw her no more. I afterward learned from her mother that
her condition became much worse en route home, and that for four or
five days she was in "a stupid condition," and after this she passed into
a nervous fever which continued for several months. Up to the time I
last heard from her, four years after the incident, she had been more or
less an invalid.
M
In dental practice the temptation to overtax patients who are so situ-
ated that it is very inconvenient for them to make frequent visits is very
great, and great care should be exercised to avoid evil results. The
case I have given is an extreme one, it is true, but many cases of a less
grave character occur, and from much more trivial operations. Only
a short time ago I placed fillings in two lower molars for a lady of
about twenty-three, at the time in rather delicate health, though she
M
728
GENERAL PATHOLOGY.
considered herself fairly well. The teeth were quite sensitive, but there
was no unusual difficulty. The operation was followed by very decided
shock, sufficient to confine her to the bed for several days. After six
weeks the operations on other teeth were undertaken, special care being
exercised; yet after an operation of an hour's duration there was decided
prostration, followed the next day by fever and restlessness. This patient
was evidently extraordinarily susceptible to shock, but the case serves to
illustrate the necessity for due care in the performance of dental opera-
tions, and especially the necessity for a close study of this subject by
dentists as well as by other specialists in medicine.
V
DENTAL CARIES.
By G. V. BLACK, M. D., D. D. S.
INTRODUCTION.
CARIES OF THE TEETH consists of a chemical disintegration of
the elements of the tooth, molecule by molecule. This disintegration
always begins on the surface of the tooth, usually in some pit, groove,
or other irregularity, at the point of contact of the proximal surfaces
and about the necks of the teeth. Such places are protected from the
friction of mastication and the movements of the lips and tongue, thus
favoring the lodgment of particles of food until fermentation takes
place, this resulting in the formation of products which decompose the
constituents of the tooth. When a beginning has been made, the
destructive process spreads toward the interior of the organ; and, as
the dentine is more readily affected than the enamel, a cavity is formed
whose interior is larger than its orifice. This cavity enlarges very grad-
ually—so slowly, indeed, that usually, if examined at an interval of a
week or a month, no progress is appreciable. But if the examination be
instituted after an interval of two or three months, it will generally
be found that progress is very decided. Thus, the area of the decay
increases steadily until the crown of the affected tooth is destroyed.
There are, however, in different cases great variations in the rapidity
with which the disease advances. As caries progresses, the enamel, on
account of its greater resistance to disintegration, is undermined by the
solution of the dentine and is left unsupported; the enamel itself, how-
ever, also slowly disintegrates on its inner surface, and finally breaks
away, leaving an irregular jagged opening. This effect is extremely
variable. Sometimes the breaking away is such that the cavity is
widely open before there is very much destruction of tooth-substance;
in other cases a larger portion of the dentine may be destroyed, while
the enamel remains almost perfect.
The color of caries varies from an ashy gray or white to a bluish or
deep black. Every shade between these may be found. Many of the
intermediate colors have something of a yellowish hue. It is common
for the decayed mass to present different shades of color in different
parts. The rule is that the outer parts are darkest, while the inner
approach more nearly the color of the tooth, or may even be lighter
in shade. Occasionally other colors may be seen, but I am persuaded
that these are accidental and dependent on some unusual extraneous
deposit. Those decays that present in the greater part of the mass the
nearest approach to the color of the tooth, or are lighter in shade, rep-
729
730
DENTAL CARIES.
resent those that are rapidly progressive; while, on the other hand, those
that present a deep-black appearance throughout their mass are making
very slow progress or have ceased to progress at all. These latter have
been termed stationary decays.
It is not necessary that all the elements of the tooth-substance be
disintegrated to constitute caries. In most cases of rapidly progressive
caries there is remaining in the softened mass a sufficient amount of the
original elements to preserve the histological forms of the dentine. This
serves to separate caries sharply from certain other accidents and diseases
to which the teeth are liable, among which I may mention mechanical
abrasion, spontaneous or chemical abrasion, and the absorptive pro-
cesses. In these the constituents of the dentine are removed entire, and
in the first two the surface is left hard and firm, while in the latter the
softening is very slight indeed. These must not be confounded with
caries. They will not be considered in this article except as they stand
related to true caries. In caries the elements of the dentine are always
removed piecemeal, producing first a softened mass, which afterward
suffers further disintegration, and finally falls to pieces, forming a
cavity. Therefore, it is a constant condition of progressive caries that
those portions of the decaying mass that are nearest the sound dentine
are comparatively little softened, and upon microscopic section present
the histological forms of the dentine with but little change. As we
recede farther from the junction of the diseased part with that which
remains normal, we find that the disintegration is progressive until
all trace of the original form-elements are lost, and we have noth-
ing remaining but débris or an open cavity.
Caries of the teeth has been known in all historic ages of the world,
and wherever prehistoric human remains have been discovered traces
of this disease have been found. It seems to be, and to have been,
universal in the sense of affecting all nations and tribes of the human
race. All have not been equally affected, but no race of men seems to
have escaped its ravages. It has been thought that the savage races
were not so much afflicted as the civilized, but my own study of the
remains of ancient peoples will not bear out this opinion. This research
has, however, been limited within comparatively narrow bounds-too
narrow, perhaps, to serve as the basis of conclusions. Unfortunately,
the literature of the subject furnishes no data that are of much value
in this direction, but what there are strongly support the statements
made above. Some hasty examinations recently made of the condition.
of prehistoric skulls found in a number of the principal museums show
that those peoples were subject to decay of the teeth to as great an ex-
tent as the civilized races of to-day. It is possible that future research
upon this point will show that certain races which have lived in a certain
way or upon certain kinds of food may have suffered less than others
which have lived differently. The studies I have been able to make
in this direction indicate that the races of men who have eaten largely
of acid fruits have had less decay of the teeth than those who have
been debarred by their position or climate from the use of such articles
of food. Generally, those tribes that have subsisted largely on flesh
and grain have suffered more from caries than those that have had a
ETIOLOGY OF CARIES.
731
}
more exclusively vegetable and fruit diet. Our knowledge upon this
point is, however, too meagre to warrant any lengthy discussion of it.
Among the individuals of the same tribe or nation there are observed
the greatest differences in the liability to caries of the teeth. Some per-
sons in almost every community escape it entirely, while others, their
neighbors, subjected seemingly to the same influences, suffer from its
ravages. The reasons for this are wholly unknown. The persons who
escape this disease are, however, comparatively few. There is no dis-
ease that is so common or so widespread or that so generally afflicts
the human family.
ETIOLOGY OF CARIES.
In the study of the causes of disease it is common to divide them
into predisposing and exciting. The predisposing causes are such as
render the individual more liable to attack, but are not in themselves
sufficient to usher in the disease. The exciting causes are such as are
actually responsible for its inauguration. It is the custom of writers
on pathology to consider the predisposing causes of the particular dis-
ease under consideration first, and this is usually the most natural
order of presentation; but in the present case there seems to be suf-
cient reason for reversing this order. It does not appear that the pre-
vious consideration of the predisposing causes will materially contribute
to an understanding of the exciting causes, but these will be much easier
understood after the exciting causes have been studied, and the presenta-
tion will thus be simplified.
Kat
It seems well, however, that in the beginning of this study we notice
the views that within a century past have from time to time been pre-
sented, and which illustrate the growth of thought as observation and
experience have added fact after fact to our knowledge of the subject.
It has been treated of by very ancient writers, but the works of Boudett
and Jourdain, which appeared within the interval from 1754 to 1766,
seem to have been the foundation of the scientific investigations that
were undertaken in after-years, and mark an era of awakening thought
and of experimental study. Before this time many had written, and in
a sense had written well, but they seem to have recorded such thoughts
as came to them from what, as compared with the authors mentioned
and those that came after them, may be considered casual observation.
The common thought of the medical men of those days was that decay
of the teeth resulted from inflammation, and the effort was to account.
for its phenomena on that hypothesis. John Hunter, who was a very close
observer and a careful writer, while regarding caries of the teeth as result-
ing from inflammation, much in the same manner as necrosis of the
bones or mortification of the soft parts, expresses dissatisfaction with
this idea, deeming it insufficient for the explanation of the phenomena
of gradual decomposition with the formation of the carious cavities.
He does not, however, offer any theory on this point.¹
panda
1 This is fairly shown in the following extract from the work of John Hunter
(Practical Treatise on the Diseases of the Teeth, and the Consequences of them, 1778):
"The most common disease to which the teeth are exposed is such a decay as would
732
DENTAL CARIES.
Mr. Fox in 1806, and others of about this period, were much more
exact in their descriptions of the processes of caries. It was regarded
as resulting from inflammation of the lining membrane of the pulp-
chamber (membrana eboris). This, in case it was severe, was regarded
as depriving the dentine of its nutrition, and, it was supposed, would
occur at isolated points within the pulp-chamber, as in inflammation of
the periosteum of the bones, causing the death of certain portions of
the dentine, which would then decompose with the formation of the
carious cavities.
Mr. Bell as late as 1829 still regarded caries as a result of inflam-
mation, but gives a different explanation of the process. He assumes
as a cause an inflammation of the dentine beginning immediately beneath
the enamel, or, in other words, in the superficial portions of the dentine,
resulting in the death of the part inflamed. This dead part then acts
as an irritant, causing the continuance of the inflammation, and thus
the process is progressive until the destruction of the crown of the tooth
is accomplished. He says:
"It (caries) may be defined, mortification of any part of a tooth, producing
gradual decomposition of its substance. The latter clause of the definition
is not, perhaps, essential, but it expresses the invariable condition of the
disease.
"The true proximate cause of dental gangrene (caries) is inflammation,
and the following appears to be the manner in which it takes place: When,
from cold or any other cause, a tooth becomes inflamed, the part which suf-
fers the most severely is unable, from its possessing comparatively but a
small degree of vital power, to recover from the effects of inflammation,
and mortification of the part is the consequence.
"The situation in which gangrene (caries) invariably makes its first
appearance, immediately under the enamel, upon the surface of the bone,
is, I think, explicable only with the view I have taken of the structure of
the teeth and the nature of this disease. As the vessels and nerves which
supply the bone of the teeth are principally derived from the internal
membrane, it is natural to conclude that in so dense a structure the organ-
ization would be less perfect in those parts which are farthest removed
from its source, and that, in the same proportion, they would be less cap-
able of resisting the progress of mortification.
"The continued and invariable progress of dental gangrene is only to be
accounted for by following up the same reasoning. When a portion of
any of the other bones loses its vitality, it acts as an extraneous body, pro-
ducing irritation in the surrounding parts, and a process of absorption is
set up in a line of living bone in contact with it in order to effect its sepa-
ration. A similar effort appears to me to be made in gangrene of the teeth,
but with a very different result, in accordance with the difference in the
·
appear to deserve the name of mortification. But there is something more; for the
simple death of the part would produce but little effect, as we find that teeth are not
subject to putrefaction after death, and therefore I am apt to suspect that during life
there is some operation going on that produces a change in the diseased part. It almost
always begins externally in the small part of the body of the tooth, and commonly
appears first as an opaque white spot. This is owing to the enamel losing its regular
crystalline texture and being reduced to a state of powder, from the attraction of cohe-
sion being destroyed, which produces similar effects to those of powdered crystal.
When this has crumbled away, the bony part of the tooth is exposed (the dentine);
and when the disease has attacked this part, it generally appears as a brown speck."
ETIOLOGY OF CARIES.
733
structure of the two seats of the disease. When a portion of the tooth is
killed by inflammation, it excites, as in the other case, an increased action in
the vessels of the surrounding portion of bone; but that very action, which
in such bones as possess greater vital power becomes remedial by promot-
ing the removal of the cause of irritation, produces in the present case the
continued extension of the disease, for the irritation thus excited, instead
of effecting the removal of the part by absorption, as in other necrosed
bones, at once destroys its vitality and renders it only an additional por-
tion of dead matter to that which had already existed. This, in its turn,
becomes an extraneous and irritating body to the surrounding bone, in
which the same action is set up and the same mortification produced; and
thus portion after portion is successively irritated and killed, until the
whole crown of the tooth is destroyed.”
Dr. Fitch of Philadelphia, who wrote in 1829, also expresses very
similar views, and in the second edition of his work, published in 1835,
I find this view maintained and supported by citations of the works of
Hunter, Fox, Koecker, and others.
:
Koecker, while holding opinions almost identical with those of Bell
as to the part taken by inflammation in the initiation and progress of
caries, adds a new thought. After a full and careful reading of his
work, I should interpret his meaning to be about this: Decay is a two-
fold process the first of these is inflammation of the dentine, resulting
in the death of a portion of the inflamed area; the second is the disin-
tegration of this dead or mortified part by chemical agencies or putre-
faction. While thus recognizing the agency of chemical processes in the
production of the cavity, he supposes that they act only on parts which
have been rendered inert by a preceding inflammatory process. He
says:
1
"One great cause of confusion and contradiction pre-eminently discover-
able in every essay treating either theoretically or practically of this fatal
malady (caries) of the teeth is the surprising manner in which the disease
itself has been confounded with its effects, viz. putrefaction, or the living
tooth under the influence of the disease, and the dead tooth which has been
destroyed by it—an error by which authors have been led away from the
subject in their inquiries and observations, and have been induced to adopt
and to advance theories and practices false and unnatural in their facts
and principles, as well as dangerous and destructive in their application.
"Caries of the teeth must be considered as similar to gangrene in other
parts of the system. And where we speak of caries as a disease we mean
that diseased action in the bony structure of the living tooth produced by
the chemical irritation of its dead and rotten parts.
"Hence it is indispensable that we should make a due distinction
between caries considered as a disease in the tooth and the effect of that
disease-viz. mortification and putrefaction of its whole structure.
66
Caries, in fact, is that state of the tooth in which mortification has
taken place in one part and inflammation in the part contiguous to it, the
former originally produced by the latter, and the latter continually kept
up by the former.'
""
Nevertheless, this author, in common with his contemporaries, de-
scribes two forms of caries-one beginning on the surface of the tooth,
1 Principles of Dental Surgery, by Leonard Koecker, M. D., p. 111.
734
DENTAL CARIES.
and the other beginning in the interior of the tooth-structure, internal
caries. This latter he seems to have regarded as analogous to abscess
occurring in the bone, and says:
As the disease is more actively resisted by the greater vascularity, and
consequent activity, of the internal structure than by the harder and less
vital external parts of the tooth, it never proceeds so far toward the cavity.
containing the nerves as to render this membrane altogether unprotected
by the bony structure, before it has penetrated through the external osseous
parts, including the enamel, and has thus formed a natural outlet for the
bony abscess.'
""
It is curious how long and how continuously this old error of regard-
ing caries as having its beginnings within the structure of the dentine
was maintained-an error that, seemingly, should have been corrected
by any reasonably close observer. Yet, with the then prevailing sup-
position that caries was the result of inflammation, there seemed to be
no reason why it should not as readily have its beginning in the depths
of the dentine as on its surface. Koecker makes a sharp advance, how-
ever, upon the observations of his predecessors, in that he affirms
decisively that caries never extends inwardly so far as the pulp of the
tooth without having first appeared on the surface of the organ.
It will be noticed that these views coincide with the theories of the
causes of diseases of the bones in general, but especially those resulting
in caries or necrosis. Decay of the teeth was regarded as a sim-
ilar affection, but it was assumed, that, on account of their inability to
repair the damages to their structure, the dead portion decomposed and
a cavity was formed. The causes which were then generally regarded
as leading to this inflammation were changes of temperature and other
injurious impressions upon the surface of the teeth. It was, however,
held by some that the causes might be wholly internal, and that decay
might begin in the internal parts of the tooth (Fox) and work its way
outward, not appearing on the surface until great damage had already
been sustained. This opinion followed naturally from the supposition
that decay resulted from inflammation beginning in the membrana
eboris. In the bones inflammation of the periosteum may deprive
the part beneath of nourishment and cause its necrosis; after this
manner, inflammation of the membrana eboris was regarded as depriv-
ing the superimposed dentine of its nourishment, causing caries. But
the supposition most generally advocated was that the inflammation
began in the dentine, just beneath the enamel.
About 1830 the inflammatory theory was attacked by a very large
number of intelligent dentists, and it was shown that, without great
modification, it was untenable. Harris in America, Robertson in Eng-
land, Regnard in France, and very many others, presented arguments
against it. Among the most potent of these was that based on the fact
that human teeth that had been removed, and afterward prepared and
mounted as substitutes, artificial teeth made from ivory, etc., were as
liable to decay as the natural organs. As such materials were then
much used for these purposes, this fact was very generally noted. This
decay, which was in all respects like that in the natural organs and ran
ETIOLOGY OF CARIES.
735
a similar course, could not have been caused by inflammation or by any
vital process pertaining to the tooth itself. Hence the cause of decay must
be regarded as extraneous to the teeth and acting upon them from without.
Harris, especially, has given emphasis to another form of argument that
deserves mention from its intrinsic importance in educating the mind to
the appreciation of the fitness of any proposed remedy for a given dis-
ease. At the time the inflammatory theory was in vogue as explaining
the nature of caries, the best authorities, although recommending the
operation of filling the carious cavities, expected only temporary relief
from it. But it was rapidly becoming the custom to fill the cavities
for the purpose of curing the affection, also to remove superficial decay
with the file for a similar purpose. In the hands of skilled persons
these operations were becoming very effective. It is evident that if
the decay of the tooth was the result of vital forces resident within its
substance, these remedies would tend to increase the mischief they
were designed to cure.
In 1835, Robertson of Birmingham, England, published his remark-
able work,¹ in which he advanced the theory that caries resulted from
chemical disintegration of the tooth-substance, and denied the agency
of inflammation. This destruction was accomplished, he contended,
by the action of an acid which was generated by decomposition of ali-
mentary particles or of fluids of the mouth suffered to lodge about the
teeth. These points of lodgment were shown to be the same as those
in which caries made its beginnings, as in pits, grooves, and crevices,
also between the teeth or about the margins of the gums.
Regnard of Paris also published a work in 1838 in which he defined
caries as "destruction of the teeth by decomposition." This, he contended,
was accomplished by an acid generated by decompositions taking place
in the very spot where its effects were shown.
As supporting this opinion, Regnard has formulated the following :2
-
"1st. Artificial teeth were fastened by threads of silk. These threads,
which surrounded the neighboring teeth, became impregnated with saliva
and covered with alimentary particles, and soon corrupted them; they
became then a cause of caries to the teeth. This is so true that the limits
of the caries proceeding from this cause are traced by the limits of the
thread itself.
"2d. For sustaining the artificial teeth metallic caps are made to envelop
one or more of the natural teeth. These constantly served to remove the
pain produced by the wearing away of the teeth. These caps were not
made with so much precision that there did not exist any space between
them (and the teeth). The fluids of the mouth, the alimentary particles,
soon lodged in these spaces; and if the persons who wore these caps were
not very careful, these fluids of the mouth, these alimentary particles,
decomposed and became the active cause of caries to the teeth. I have
seen molars whose crowns were entirely destroyed by this cause in the
space of six, five, and even four, months.
"3d. Human teeth and the teeth of the hippopotamus were used for
artificial teeth. These teeth, being of an organic nature, are capable of
¹ A Practical Treatise on the Human Teeth, showing the Causes of their Destruction and
the Means of their Preservation, by William Robertson, Old Square, Birmingham.
2 Quoted from Desirabode, Part 1st, p. 169.
736
DENTAL CARIES.
decomposing in the mouth. Then, if by a badly-arranged economy the
persons who wore them still preserved them when they were in a state of
decomposition, they decayed the neighboring teeth which are in immediate.
contact with them."
Regnard further enforces his doctrine by the following considerations :
"If, now, I devote my attention to the different parts of the teeth in
which decay commences, I see that they are precisely those where the ali-
ments and fluids of the mouth stop and remain sufficiently long to decom-
pose themselves. It is in the necks of the teeth, in the interstices of these
organs, in the anfractuosities of the large molars, in these pointed holes
that we observe sometimes upon the external face of the first and second
large inferior molars or upon atrophied teeth. If we reflect precisely upon
the mode of action of caries, we see that they act in the same manner as an
acid, that they deprive the tooth of its phosphate of lime, and upon the
point where it exerts itself reduces it to a cartilaginous substance. Let
us see if we can find in the decomposition of the alimentary particles or
buccal humors an explanation of these phenomena. Now, chemistry teaches
us that all vegetable or animal substances in a state of decomposition give
birth to acidiferous products, to nitric acid, sulphuric acid, etc.-all acids
which produce the same effect on the teeth."
Regnard advanced arguments that were, in effect, identical with those
of Robertson. These views were immediately antagonized in France by
M. Desirabode. While this author did not deny that the teeth might
be injured by acids, he says: "To take the action of acids upon the
teeth as the cause of decay in as absolute a sense as Regnard, is, accord-
ing to our opinion, an error a great error.'
""
p
In opposition to the theory advanced by Regnard, M. Desirabode
formulates the following propositions :'
1
"1st. A great number of caries commence in the ivory, which is often
deeply affected, whilst the enamel is entire...
"2d. Many teeth, principally the last large molars, come from their
alveoli deeply decayed, without, consequently, having been submitted to the
action of any kind of an acid.
(C
'3d. If it was always and solely an acid which affects the teeth, this
action would be general; it would have but one point of decay; the whole
of the dental system would certainly be decayed.
*
*
*
*
*
"5th. Finally, the saliva and buccal humors are not as frequently acid
as Regnard thought; we have often found alkalies among persons who had
their teeth badly decayed. Our researches in this respect accord perfectly
with the opinion of Dr. Donni, who expresses himself thus:
C
The alkalinity of the saliva has been avowed long since, but it has
been proven only-in these latter years particularly-by the experiments
of Tiedman and Gmelin.""
In regard to the first of these propositions he says:
"Caries, according to our knowledge, as we have already said, proceeds
frequently from the interior to the exterior. Smote in its vitality either
by an act of nature which cannot be explained, and to which the pulp is
1
Complete Elemenis of the Science and Art of Dentistry, by M. Desirabode, Surgeon
Dentist to the King, Part 1st, p. 160.
ETIOLOGY OF CARIES.
737
not always a stranger, or because the delicateness of its tissue was not able
to resist the agents with which teeth are constantly brought in contact, the
ivory becomes the seat of a change which affects at the same time its color
and the force of cohesion which unites its particles. A yellow or brown
spot manifests itself near the enamel, which it invades by degrees until it
extends upon the surface of the crown. This envelope loses in this respect.
its transparency, a natural consequence of the separation of the elements
which constitute it. Whilst the interval layer of ivory which unites the
enamel with the subjacent layers is not destroyed, the spot preserves the
color, and even shining aspect, which belongs to the teeth; but it loses this
brilliancy as soon as the connection is severed which binds the ivory and
enamel together."
He then proceeds with the presentation of the usual arguments in
favor of the old hypothesis, which are fairly represented in the above.
It is easy for us of the present generation to see that these arguments
were based upon erroneous observations, but we must remember that
very many facts that are thoroughly established to-day were then either
unknown or the observations leading to their establishment were
accredited by comparatively few persons. And in this instance the
great majority of dental operators asserted that decay did begin in
the interior of the dentine. This illustrates some of the difficulties in
the way of advance of thought.
It must be remembered that at the time these works were written the
views expressed by Robertson and Regnard were in the most direct
opposition to the theory generally held-namely, that caries resulted in
some way from inflammation of the dentine; and, as might be expected,
they were not very readily accepted. These authors denied in toto the
influence of inflammation in the production of caries, and advanced
what has since been known as the chemical theory-that all caries of
the teeth is the result of chemical action or is caused by the operation
of a corrosive agent acting from without. This entirely precluded the
idea that decay ever, in any case, had its beginning in the internal parts
of a tooth, and the accuracy of the observations that led to that belief
was boldly questioned and denied. Further, the origin of the corrosive
agent was accounted for on the hypothesis (for it could not at that time
have been said to be proven) that it was produced at the very spot
where decay began by the lodgment and fermentation of particles of
food. Each of these authors proceeds to examine most attentively the
particular spots at which each of the several teeth are most liable to the
beginnings of decay, and finds that it never occurs on clean and smooth
surfaces, but, on the contrary, the attack is in all instances made at such
points as collect and retain alimentary particles, as in the interstices
between the teeth, in pits and grooves in the enamel, or at such points
as, from any cause whatever, retain particles until fermentation takes
place; consequently, they claim that decay is caused by an acid produced
by the fermentation of particles of food at the spot where the decay com-
mences. So far as it is here expressed, I believe this view of the etiology
of caries to be strictly correct, and that the facts developed during the
succeeding years tend to confirm it.
When we consider the fact that at the time these authors wrote the
VOL. I.-47
738
DENTAL CARIES.
1
best of human thought and intelligence, and the deductions from all
observations except their own, were diametrically opposed to their the-
ory (a theory which all of the labor of the years intervening up to
the present time has hardly been sufficient to demonstrate), that the laws
of fermentation were very little understood, and that they had not the
means of confirming their suppositions by direct experiments made
either by themselves or by others, their writings seem very remark-
able.
While their knowledge was limited within a comparatively narrow
range, and their work as a whole exhibits less of learning than that of
many of their contemporaries, yet they perfectly agree on this point,
and evidently arrived at the true conclusions regarding it from a close
analytical study of the phenomena of decay as they observed them.
The generally erroneous nature of the thought and observation of
that period is well expressed in the arguments against these views by
Desirabode.
The bold denial by these men that caries ever had its beginning
within the dentine, as its truth was gradually established, had, however,
great weight in confirming the chemical hypothesis.
It is exceedingly curious to note that in accepting the chemical
theory a large part of the profession either misunderstood or lost
sight of its main facts as related by the authors I have mentioned.
Perhaps the most prevalent error, and one that has been most persist-
ently prominent, is that contained in the objection that was imme-
diately expressed by M. Desirabode-namely, that if acids caused
decay, they would, from their necessary general distribution in the
mouth, act upon all parts of the teeth, instead of spending their force
on particular points. It will be seen at once that the idea of the local-
ized development of an acid by fermentation is lost sight of in the
expression of this objection. If the acid enters the mouth with the
fluids as they are secreted by the glands, or with the food, or in any
manner by which they would be generally distributed, there is no reason
why they should act at particular points only.
Ön the other hand, much confusion has arisen through the supposi-
tion that caries might be caused by acids commingled with the fluids
of the mouth or introduced from without. This is the form of error
that has been most persistently present in the writings on this subject
up to the present time. I may say that the acidity or alkalinity of the
general fluids of the mouth or of the food plays but a small part in the
case, provided these reactions be not in such degree as materially to
modify the act of fermentation taking place in the out-of-the-way points
about the teeth. The teeth may decay when the fluids of the mouth
are habitually acid or when they are habitually alkaline. The condition
governing the beginning and progress of caries is neither of these, but is
dependent directly on the lodgment of substances at particular points
and their fermentation with the production of an acid. It is in this
manner that caries has its beginnings, and its progress is maintained by
the continuance of this act of fermentation.
W
The failure to grasp this thought in its full meaning was perhaps
quite natural. This subject of fermentation has been one of the most
ETIOLOGY OF CARIES.
739
difficult with which the intelligence of man has had to grapple, and was
evidently not understood by those who conceived the fermentation
hypothesis for the origin of caries. It was, indeed, known that many
substances give rise to acids of various kinds during the process of
decomposition by fermentation or putrefaction, but what was the modus
operandi was an open question that was debated at that day only by
the most astute chemists. The molecular-motion theory of fermenta-
tion and putrefaction cannot be said to have been fully developed until
1840, when Justus Liebig wrote his Chemistry in its Application to
Agriculture and Physiology as a report to the British Association for
the Advancement of Science. The subject had, indeed, been under dis-
cussion for several centuries without the development of any theory for
the rational explanation of the observed phenomena upon which the
learned men of the world could agree. This theory had been imper-
fectly shadowed forth for many years, but it seemed to require the
genius of Liebig to systematize and place it before the world of thought
in tangible form. Yet even before the work was completed an antag-
onist had arisen in the germ theory of these processes, growing out of
the discovery of the yeast-plant by Schwann in 1838; and these two
rival theories have struggled with each other for the mastery almost up
to the present time, and there are perhaps many who will assume that
the struggle is still going on. During this time it is but fair to say
that there has been no theory of fermentation that has been fully
accepted. The full explanation of caries of the teeth required an
acceptable explanation of the processes of fermentation, and the learn-
ing of the period failed to afford this. For this reason the subject has
always been enveloped in a degree of obscurity that has rendered all
attempts at explanation unsatisfactory.
In this condition of the minds of men it is quite natural that other
modes of explanation should be sought. And in the last half century
almost every source of knowledge has been questioned with the hope
of obtaining an answer, but none has been vouchsafed; for after
threading the labyrinth of the theories propounded-and these have
been many-the questioner has again turned back to the theory of fer-
mentation with all its mystery and uncertainty. When we review the
literature of the subject we find that since the time of Robertson
and Regnard this explanation of the subject has never been entirely
lost sight of. It must be confessed, however, that it has often been
presented in so confused a manner, and so mixed with other theories,
that its best friends could with difficulty recognize that a vestige of it
remained.
Now, after the work of so many years has been added in the effort
to explain the nature of fermentation, and when the labors of such men
as Schwann, Schroeder, Lister, Koch, Klein, and Miller have made us
acquainted with the agency of micro-organisms in the processes of fer-
mentation and putrefaction, this seems to be regarded as another of the
new theories which have sprung to the front demanding a hearing. If
any have this thought, I wish to say that it is a misconception. It is
but a further explanation of the old theory as propounded by Robertson
and Regnard—an explanation of the processes of the fermentation by
1
740
DENTAL CARIES.
which the acid spoken of by them is produced-and as such is not a
theory that in any wise supplants or displaces that hypothesis.
Among the writings that have appeared since the works of Robert-
son and Reguard there are perhaps none that have deservedly attracted
more attention than those of John Tomes. As a microscopist and his-
tologist this author probably did more to give the profession correct views
of the structure of the teeth and the phenomena presented by caries
than any other writer.
As a contemporary of Robertson, Mr. Tomes was well acquainted
with his views; but we do not find in his work any discussion of the
theory of fermentation as applied to this subject. Mr. Tomes was a
microscopist, and as such depended very largely on the teaching of that
instrument for the views he entertained, and his writings seem to indi-
cate that he began with a strong bias in favor of the theory of inflam-
mation. Mr. Robertson, on the other hand, was not a microscopist,
and seems not to have had any confidence that studies made by the aid
of that instrument would be of any assistance in the explanation of the
nature of caries. Under these circumstances it is not surprising that
the views of the two men should be divergent.
In the earlier writings of Mr. Tomes we find views expressed that
coincide in the main with those of Koecker, but with a more decided
leaning to the theory of the action of acids as the active agents in the
disintegration of parts rendered susceptible to their operation by a dis-
eased action going on within the dentine. While this disease of the
dentine was regarded as being of the nature of inflammation, Mr.
Tomes finds by his microscopic inquiries that the phenomena of this
process, as we understand them in its occurrence elsewhere in the tissues,
cannot take place in the dentine. Yet he concludes by saying, in effect,
that these phenomena are only the observed result of disturbance of the
vital processes which are beyond the reach of investigation. The den-
tine is evidently endowed with vitality, though this vitality is invested
in a different histological form from that of other tissues of the body,
rendering it impossible that the same phenomena should appear on
account of or in response to a given disturbance of this vitality. The
dentine cannot become hyperemic, because there is no provision for the
circulation of the blood-globules within its structure; the entrance of
leucocytes is prevented by the smallness of its tubules; and so on with
all of the usual phenomena of the process known as inflammation; yet
we cannot, on account of these differences in histological form, assert
that the vitality existing in the dentine may not be disturbed in such a
manner as to produce phenomena which will be peculiar to its histologi-
cal forms. Mr. Tomes has critically examined the phenomena of caries,
evidently with the intent to discover whether there were presented any
conditions indicating a disturbance of the vitality of the dentine. In
this search it must be admitted that he is in a degree successful, for he has
shown what every experienced dental surgeon must recognize as true-
namely, that in the beginnings of caries the dentine at the point of incip-
ient disintegration becomes hypersensitive, and not a few patients com-
plain when the parts are disturbed by the contact of foreign bodies.
This phenomenon seems to be a sufficient evidence of a disturbance of
*
mga
ETIOLOGY OF CARIES.
741
vitality, for how else can we account for the hyperesthesia? As the
caries advances and the point of exposure of the dentine is removed
from the surface, this manifestation of pain is diminished or relieved,
this agreeing precisely with similar phenomena manifested in injuries.
to the surface of the body; for it is well known that the skin is more
sensitive to painful impressions than the parts beneath.
Again, Mr. Tomes describes what he terms "the transparent zone"
as existing between the dentine affected by caries and that which has
remained perfectly normal. In his earlier works this was regarded as
being caused by the calcification of the dentinal fibrils, and as such was
regarded as a vital act of resistance to the advance of the carious pro-
cess -an act by which the fibrils shut themselves in from an external
irritant, and attempted to build a barrier against further disintegration.
There is no doubt as to the microscopic appearances described, but in
his earlier works, or those that were written soon after the discovery of
the dental fibrils, this author seems to have been unfortunate in his
interpretation of them; for it has been since determined that instead of
being an act of vitality, by which a barrier is placed against the further
progress of disintegration, it is, in fact, only the earliest stage of that
process, and there is really no calcification of the fibrils. Mr. Tomes
corrects this error in the recent editions of his work.
From these studies Mr. Tomes concluded that the life-force resident
in the dentine possesses a certain power of resistance to injurious im-
pressions, and that this resisting power must be overcome by some
force or cause before disintegration can occur. In other words, the
phenomena of caries must be preceded by something having the power
of destroying the life of the part. This something may be a diseased
state of the dentine similar in its nature to inflammation of the other
tissues; but for this idea he does not strenuously contend, for he sup-
poses that the life of the part may be destroyed by the same agent that
effects the disintegration. Mr. Tomes says:1
"In speaking of the predisposing and exciting causes of caries, allusion
has yet to be made to those agents which may be regarded as acting in the
double capacity of depriving the dentine of its normal powers of resistance
and of producing its immediate decomposition.
"In considering the subject from this point of view, we must be prepared
to admit that the dentine is possessed of vitality, and that vitality must
have been lost before the tissues undergo decomposition. If we take, for
example, the effect produced on the skin by the application of caustic pot-
ash, the immediate result is the destruction of vitality in the part with
which it comes in contact, and its secondary effect will be the disorganiza-
tion of the part destroyed. But had the power exerted by the potash been
incapable of depriving the skin of vitality, the secondary effect, that of pro-
ducing decomposition, would have been successfully resisted. In the case
of a tooth the application of potash would not produce conclusive results,
but the use of a mineral acid would be followed by consequences similar to
those mentioned with respect to the skin. The vitality of the part would
be destroyed, and decomposition would succeed the loss of life.
"It may be said that agents of this character are not applied to the
teeth, but such as have sufficient power to destroy are applied; and it is
1 System of Dental Surgery, p. 372, 3d ed., 1859.
742
DENTAL CARIES.
by taking an extreme case that we are best able to examine the mode of
action and the ensuing results.
(C
Litmus-paper applied within the cavity of a carious tooth almost inva-
riably gives strongly-marked acid reaction, and thus furnishes evidence of
the existence of an agent capable, if unresisted by the vitality of the den-
tine, of depriving that tissue of its earthy constituents, leaving the gelatin
to undergo gradual decomposition, favored by the heat and moisture of the
mouth."
Mr. Tomes, therefore, while insisting on the presence of vital phe-
nomena in the production of caries, finally admits a process that is
almost purely chemical. From this point he proceeds to examine into
the condition of the oral fluids with the view of finding the acids that
do the mischief. He says:
4
"In examining the circumstances under which the decomposition of the
dentine takes place and under which it is resisted, apart from the influence
of vitality, any one must be struck with the power that is exerted by the
mere form of the surface involved. Supposing the disease to be situated
in a deep fissure or upon the side of a tooth against which another tooth is
placed, the decomposition will go on with more or less rapidity, the rate
being varied in accordance with the condition of the oral fluids. But if
the cavity be superficial, and so placed that it is subject to friction during
mastication, the progress is relatively slow; and if the low walls of such a
cavity be removed, the part will become polished by the act of mastication
and by the motions of the tongue, and decomposition will be completely
arrested quite independently of any power of resistance exercised by vital
action. Again, let a tooth be placed under circumstances the opposite of
the preceding. For example, take a bicuspid of the upper jaw the distal
surface of which is decayed, and remove the softened dentine; then let dry
and
cotton wool be forced between the defective tooth and its neighbor,
renewed only once in three or four days; at the end of a fortnight or three
weeks it will be found that the surface of the cavity, which was left hard
and dense after the first operation, has become soft, and that the softening
extends to a considerable depth. Had the cotton, prior to its introduction
between the teeth, been dipped into a solution of resinous gum, such as
mastic, the surface of the cavity would have remained unaltered, owing to
the exclusion of moisture. But where the wool only is used, the secretions
of the mouth are not only not excluded, but are held in constant apposition
with the exposed dentine by the saturated wool.
(C
Experiments of this character lead to the conclusion that within the
mouth are agents present which, under favoring circumstances, are capable
of decomposing the dental tissues, and the source of these agents becomes
the next question which naturally suggests itself."
This astute writer has left the subject of the influence of fermentation
in the production of acids untouched. He attentively examined the
fluids of the mouth in varying conditions of the system, and found in
them acids, which he concluded must be sufficient to account for the phe-
nomena of the disintegration of the dentine in the form of caries. That
these acids are found there is no doubt. Under various circumstances
the saliva itself becomes acid, and from my own examinations, which
have been somewhat extended, it appears that it is usually acid (the
mixed fluid) in the state of fasting; and the mucus is slightly acid in
ETIOLOGY OF CARIES.
743
the greater number of persons I have examined; especially is this so if
the gums about the necks of the teeth are slightly irritated. Indeed,
I may say that from my own observations I have conclusively con-
firmed Mr. Tomes's findings as to the frequency of acidity of the fluids
of the mouth. But this does not constitute a satisfactory explanation
of the occurrence of caries. Against such a supposition the argument
of Desirabode, quoted in a note elsewhere, applies with its full force.
If we succeed in accounting for the production of decay on the chemical
hypothesis at all, we must account for the application of the acid to the
particular point where that decay manifests itself, to the exclusion of
other parts of the denture; otherwise we must fail. Therefore, acidity
of the fluids of the mouth cannot be the active exciting cause of caries,
though it is possible that this condition may be indirectly instrumental
as a predisposing cause. This feature of the subject will be discussed
on another page.
There is no doubt that the writings of Mr. Tomes had a powerful
effect in drawing the thought of the profession away from the fermen-
tation hypothesis as an explanation of the active cause of caries of the
teeth. This, however, can hardly have delayed the full explanation of
the phenomena, for before the processes of fermentation and putrefac-
tion could become explainable a vast deal of labor in other directions
was necessary; and this, from the very nature of the case, could best
be done by others than those actively engaged in dental practice.
This search in the fluids of the mouth for the active factor in the
production of caries did not begin, however, with Mr. Tomes. Amos
Westcot, for the purpose of ascertaining what effect the acids supposed
to be present in the oral fluids would exert on the teeth, had already
made a series of experiments, in which he found that they were decal-
cified by very high dilutions.
Subs
These experiments were published in the third volume of the Ameri-
can Journal of Dental Science, and have been referred to by many
writers since that time. They led to a vast number of analyses of
the oral fluids in all conditions of health and disease, and almost
unlimited experimentation in decalcification of the teeth in varied
dilutions and compounds of the various known acids, an intimate
acquaintance with the varying conditions of the oral secretions and
the effects of acids on dentine being thus developed, but little or noth-
ing being accomplished explaining the processes of caries of the teeth,
except to demonstrate that in simple solution by acids certain of the
phenomena of caries are absent.
KÉ
In the progress of this study the most diverse views have from time
to time appeared, and the formation in the fluids of the mouth of almost
every known acid, by some possible changes of molecular groupings, has
been assumed.
1
Some few have been satisfied with the theory of fermentation, as was
Goddard, who supposed acetic fermentation to be the prime factor;
but the great majority of writers have invoked the aid of vital processes
resident in the tooth itself for the production of caries or for limiting its
effects, or for both; and, altogether, the agency of vitality in this process
¹ Goddard on the Teeth, 1854.
744
DENTAL CARIES.
has been most thoroughly studied, seemingly in all possible aspects,
but without results. At the present time the only influence that we
can attribute to vitality is that it has some power to limit the rapidity
of decay in the otherwise normal tooth. Teeth that have lost their
pulps, and as a result the vitality of the dentine, decay more rapidly.
The great number of pulpless teeth now retained in the mouth
give abundant opportunity for observation upon this point; but it is
uncertain whether this slower progress of caries in the living tooth is
on account of its vitality or because the tubules are occupied with the
dentinal fibrils in such a way as to prevent by their bulk that more rapid
ingress of the agent of solution which would occur were the tubules
laid open by the loss of the fibrils. This latter thought seems to be
more in harmony with the phenomena, and yet it must be admitted that
it is difficult to conceive that the living contents of the tubules, the den-
tinal fibrils, should be powerless and incapable of exerting any influence
when their vitality is directly disturbed. Yet, after all the study that
has been expended on this point, there have been developed no evidences
of vital resistance on the part of the dentine itself, other than hyperæs-
thesia, capable of withstanding adverse criticism.
The principal evidence of vitality of the dentine, however, is exhib
ited in changes that occur in the tissues of the pulp itself on account of
irritation of the distal ends of the dentinal fibrils in the processes of
caries and of the abrasions. These are fully considered in the article
on Pathology of the Dental Pulp, and need not be referred to here,
especially as they do not relate to caries further than that they are one
of its remote consequences. The fact that these morbid effects are trans-
ferred to the pulp through a considerable portion of dentine, without
visible change in the dentine itself, denotes its incapacity for the exhibi-
tion of morbific changes through vital activity or the agency of vital
forces resident within itself.
A few observers seem to have abandoned both the chemical and the
vital theory, and have sought to explain the results by other means.
Bridgeman, in an essay on this subject,' attributes caries to peculiar
electrical conditions in which the crown of the tooth becomes the pos-
itive electrode, and the tissues in which the tooth is invested the nega-
tive. When these conditions are intensified by abnormal qualities of
the fluids of the mouth, the crown portion of the tooth yields up
its
lime salts, setting free the acids with which they were combined; ~and
this leads to molecular disintegration of the substance of the dentine in
the form of caries. This is certainly a very ingenious theory, but is at
variance with so many facts that any effort to maintain it must be futile.
It can be readily understood, however, that by placing different metals
in the teeth as fillings the saliva may act as an excitant and a battery
be produced. From these artificial conditions I have seen effects that
seemed to be the product of electrical currents.
Another thought has been advanced to account for caries on the
hypothesis of vital action. In this it is supposed that on account of a
disturbance of vitality, such as might produce inflammation in other
parts of the system, the nutrition-or, more properly, the vital action-
1 Transactions Odontological Soc., vol. iii. p. 369.
Code
ETIOLOGY OF CARIES.
745
of the particular part is disturbed in such a manner that an additional
molecule of acid is formed, giving rise to the acid superphosphate of
lime or the withdrawal of a molecule of lime, which is replaced by
basic water, thus changing the insoluble neutral phosphate into a solu-
ble acid phosphate. This idea seems to have arisen from a suggestion
by Mr. Coleman that the acidity of caries was probably due to the
formation of the acid phosphate of lime.
P
Among the many theories that have appeared from time to time to
account for caries by the introduction or development of particular acids
in the mouth, there are several that deserve mention either because of
the high estimation in which they have been held by large numbers of
intelligent practitioners, or for their intrinsic importance, or for the
ingenuity with which they have been presented. One of these, espe-
cially urged by Dr. George Watt, and which may be termed the min-
eral-acid theory, has in America exercised considerable influence. I
should, however, say that, while Dr. Watt claims that these acids espe-
cially are the cause of decay, he does not exclude the action of the
organic acids. According to this theory, the particular acids produc-
tive of the great mass of caries are nitric, sulphuric, and chloro-
hydric. These give rise to three distinct varieties of decay, differing
the one from the other in accordance with what is supposed to be the
peculiar action of each of the acids in question. Nitric acid is said to
produce white decay; sulphuric, black decay; and the chlorohydric, the
intermediate colors. It is held that any of these acids may be formed
in the mouth or may be introduced into that cavity, but for the produc-
tion of caries they must be formed at the exact spot at which they act
upon the tooth by some form of decomposition which takes place in
substances that may find lodgment about the teeth. This, then, is in
strict accord with the theory of Robertson, and amounts to an effort to
explain the mode of procedure by which the acid is produced and to
define the particular acids.
With regard to nitric acid, Dr. Watt says:'
•
Att
Jed
"It is a singular fact that though oxygen and nitrogen manifest but
little affinity for each other, yet they unite in various proportions, forming
at least five well-known distinct compounds. It appears, however, from a
variety of circumstances, that their tendency is to unite in the proportions.
which form nitric acid. The protoxyd is readily decomposed, and yields
nitrogen, oxygen, and nitrous acid. The binoxide, if brought in contact
with the atmosphere, takes from it two equivalents of oxygen, and also
becomes nitrous acid, or NO, (the old chemical formule are used here).
Hyponitrous acid, NO, on admixture with water is converted into nitric
acid and binoxide of nitrogen; thus, 3NO, NO, + 2NO₂, in which case
the latter will be converted into nitric acid. It follows from this that if
oxygen and nitrogen unite at all in the mouth, let the proportions be, at
the first, what they will, nitric acid must be the ultimate result, as air and
moisture, the only agents necessary in the transformation, are here always
present.
(C
Nitrogen is emphatically a conservative element, and manifests but
little tendency to unite with anything, and especially with oxygen. It is
1 Chemical Essays, p. 62.
746
DENTAL CARIES.
probable, therefore, that these two elements unite indirectly. It should be
borne in mind that organic nitrogenous bodies contain hydrogen and
oxygen as well as nitrogen. Consequently, by their decomposition, these
elements are liberated. The mutual affinities of the hydrogen and nitro-
gen take precedence, and the result is the formation of ammonia, NH.
But ammonia exposed to the action of oxygen is always decomposed, an
oxide of nitrogen being formed, and of course nitric acid is the result.
((
With this view of the case, and from the fact that many persons per-
mit the buccal mucus as well as particles of nitrogenous food to remain
around, upon, and between the teeth till decomposition is effected, it is not
surprising that the white variety of dental caries is so frequently found."
The formation of other acids in the mouth is followed out by a sim-
ilar mode of procedure. For instance, this author says:
(C
Albumen is a constituent of mucus, and is contained in many articles
of food. Sulphur, if not a constituent of, is always united with, albumen.
Its ordinary presence in the mouth is therefore easily explained. Sulphur
and oxygen unite directly under various circumstances, as in the combus-
tion of sulphur, but it is probable that the union here is effected by indirect
means. Hydrosulphuric acid, or sulphuretted hydrogen, is one of the results
of putrefactive decomposition of albuminous substances. The breaths of
our patients often bear ample testimony to its presence in the mouth. Now,
the oxygen of the atmosphere rapidly decomposes this acid by taking its
hydrogen to form water. The sulphur is therefore set free, and, being in
the nascent state, its affinities are increased in energy, and it also unites
with oxygen, forming the sulphurous acid, SO₁₂, which in the presence of
the water of the saliva is rapidly converted into sulphuric acid, or SO,"
2,
This acid is regarded as acting on the constituents of the tooth but
very feebly, so that the texture of the dentine is not entirely broken up,
but by its tendency to the removal of the elements necessary to the for-
mation of water, for which it has a very powerful affinity, the tooth-
substance is carbonized, giving rise to very black, slowly progressive
decays.
In respect to the formation of chlorohydric acid the following quota-
tion will be sufficient:
"Though in its normal state the saliva is alkaline, yet in a great variety
of abnormal conditions it contains one or more free acids, and the chloro-
hydric is one of those most frequently present. It often originates, no
doubt, in the decomposition of the soluble chlorides contained in the saliva
and mucus.
When the chlorine of these is liberated, it takes hydrogen.
from the water of the saliva, and this acid is the result of the union."
This acid, in the degree of concentration in which it would be likely
to be produced in the mouth, is not regarded as capable of dissolving
the animal portions of the tooth. It is therefore supposed to remove
the lime salts, giving rise to those soft, pulpy forms of caries in which
there is a large mass that still retains its histological forms.
In his essays on this subject this author has endeavored to keep before
his readers the idea that the acid must be formed at the very spot where
its effects are manifested in the production of the phenomena of caries,
for he has taken pains to state in connection with the consideration of
ETIOLOGY OF CARIES.
747
each of these acids that it may be taken into the mouth with the food
or in the form of medicine, and that, while if used in this fashion care-
lessly it might injure the teeth, it could not thus produce the phenomena
of caries, evidently for the reason that its action would not be spent on
the particular parts of the teeth, to the exclusion of other parts.
The views entertained of the formation of these acids in the mouth
seem not to rest on any basis of experimental study of which we have
record, but rather upon a supposed likeness of the varieties of caries to
the observed action of these particular acids. Later developments show
that the results are dependent upon other agents.
The views just given have been much more prominent in America
than in Europe. It seems that in the Old World the tendency has been
to regard the organic acids as those more likely to be concerned in the
production of caries. Their action has been investigated in this coun-
try as well, but the most elaborate treatise on this phase of the subject
has been written by Dr. Magitot of Paris.
After a very elaborate study of the etiology of dental caries Dr.
Magitot says:
1
"The preceding considerations tend to establish that dental caries results
from a purely chemical alteration of the enamel and ivory of the teeth,
either by the products of acid fermentation developed in the saliva or by
active agents introduced directly into the mouth. Now, if this theory be
correct, we should be able to obtain the same effects by subjecting sound
human teeth out of the body and deprived of life to the direct action of
the same agents which produce this affection in the economy. This is in
fact possible, and we shall relate and develop a series of experiments by
which, sometimes in the mouth and under the ordinary conditions of devel-
opment of natural caries, sometimes in liquids artificially prepared, we have
produced changes identical with that of this malady.
Thus will be demonstrated, as it seems, without doubt, the true nature
of dental caries, which it will be impossible to regard henceforward as an
affection of internal and organic origin or a vital lesion of nutrition, as has
been generally believed up to this time.
""
Some of the experiments related by Dr. Magitot consist in a syste-
matic observation of human teeth prepared and mounted on natural roots
as pivot teeth. After some years of wear in mouths in which caries
was actively progressive in the remaining natural teeth, the substituted
teeth were affected with caries in the same manner as the natural organs.
The cavities were of the same form, in the same positions in which caries
is seen to attack the natural organs, and the whole appearance of the
cavities produced showed the affection to be precisely similar. There
was the same kind of progressive softening of the dentine, and the con-
tents of the cavities had the same acid reaction that is always found
to exist in progressive caries of natural teeth.
These experiments are related at length, and are considered as settling
beyond all doubt the fact that caries is caused by an agent acting from
without, and is independent of the vitality of the tooth attacked. Dr.
Magitot, however, says: "A fundamental distinction must be observed.
¹ Treatise on Dental Caries, Experimental and Therapeutical Investigations, by Dr. E.
Magitot, translated by Thomas Chandler, D. M. D., p. 121.
748
DENTAL CARIES.
It consists in the absence of all phenomena of reaction on the part of
the tooth and the absent dental pulp, whilst in pathological caries the
injured organ reacts and struggles against the invasion of the disease.'
This resistance is regarded as sufficient to render the progress of the
disease slower, and even, in some favorable cases, to arrest it altogether.
Another series of experiments was undertaken to determine the effect
on the teeth out of the mouth of solutions of different substances. Some
of these were fermentable, others not.
Several experiments were made with solutions of sugar. Solutions
were made with one part of sugar to three parts of water, and in this
perfectly sound teeth were placed under two conditions: 1st. They were
simply laid in the liquid without any kind of protection; 2d. The teeth
were completely protected with a coating of wax except at a single point
on the enamel. The vessel was then set away loosely corked and
allowed to remain two years, in which time the solutions were, of course,
allowed to undergo the process of fermentation. At the end of the two
years the fluid was found markedly acid, of a deep reddish color, and
covered with a deep mould. The teeth not protected by the coating of
wax were completely decalcified. The teeth protected with wax at all
but one point were also decalcified, but at the point of exposure there
was a localized cavity having all the characteristics of caries. In
another experiment identical with this, except that a little animal mat-
ter was added to hasten the process of fermentation, the result was
almost exactly similar. In the third experiment a few drops of crea-
sote were added, to prevent fermentation. This seems to have failed.
The fermentation proceeded with results similar to those just described.
In the fourth experiment glucose was added and a few drops of creasote,
to prevent fermentation, and the teeth were placed in solution as before.
In this instance fermentation was successfully prevented. The solution.
at the end of two years remained clear. There was no mould and
none of the teeth showed any alteration whatever. In the fifth experi-
ment teeth arranged in the same way were placed in a cold saturated
solution of sugar of milk. No fermentation took place, and there was
no effect produced on the teeth. In the sixth experiment a one-to-
three solution of cane-sugar in distilled water was brought to the
boiling-point and hermetically sealed while hot. A group of sound
teeth had been weighed with great care and placed in the flask before
heating the solution. At the end of two years no fermentation had
taken place. The teeth appeared unchanged. They were dried and
again weighed, and it was found that they had undergone no loss what-
ever. A seventh experiment with glucose under identical conditions
with the last showed similar results.
The experiments with sugar seem to show conclusively that as sugar
it has no hurtful influence on the teeth, but when fermentation takes
place the teeth are profoundly affected. In each of the cases the fermen-
tation was of the acid character, not vinous, and the acid first produced
was generally acetic or lactic, which latter acid usually passes into the
butyric fermentation, and finally is liable to change into other forms as
the different fermentative processes succeed each other. In this series of
experiments, therefore, the teeth were in turn subjected to various acids
ETIOLOGY OF CARIES.
749
without any knowledge as to their strength or the duration of the expos-
ure to any particular one; but the results show conclusively what we
may expect from the fermentation of sugar in contact with the teeth.
In another series of experiments the white of an egg was mixed
with water, the conditions being otherwise the same as in the experi-
ments with sugar. At the end of two years the results were very sim-
ilar. In the solutions that underwent the process of fermentation the
teeth were decalcified, but in those in which fermentation did not take
place the teeth remained perfect.
Experiments with the organic acids produced the following results;
in each case the teeth remained in the solution two years:
Lactic acid, 1 to 1000, but slight effect.
Lactic acid, 1 to 100, teeth decalcified.
Butyric acid, 1 to 1000, teeth partially decalcified.
Butyric acid, 1 to 100, teeth completely decalcified.
Citric acid, 1 to 1000, teeth partially decalcified.
Citric acid, 1 to 100, teeth wholly decalcified.
Malic acid, 1 to 1000, enamel chalky, dentine partially decalcified.
Malic acid, 1 to 100, teeth decalcified.
Cider, teeth decalcified.
G
Acetic acid, 1 to 1000, teeth not affected.
Acetic acid, 1 to 100, enamel not affected, dentine decalcified, and the
roots of the teeth shrivelled.
This gives a fairly good idea of the power possessed by the organic
acids to decalcify the teeth. It must be remembered, however, that in
the solution of 1 to 100 the decalcification, though complete in two
years, progresses very slowly, so that a momentary exposure of a tooth
to even a much stronger solution would be productive of no appreciable
injury.
Dr. Magitot has experimented also with many other substances whose
action seems to me to have little or no relation to the etiology of caries.
The views entertained by him, however, doubtless led him to attach to
them an importance greater than I can give them. He says:'
"It is perfectly established that dental caries results from the direct
alteration of the organ by means of substances which originate in the saliva
or are accidentally introduced an alteration usually preceded and favored
by certain congenital or acquired predispositions of structure or anatomical
conformation. .
"Caries, regarded from this point of view, consists, then, precisely in a
simple solution of the calcareous salts of the dental tissues by an acid
element developed or brought in contact with them. Such is the rigor-
ously logical conclusion which seems to us to result from all the considera-
tions and experiments just stated."
It would seem that this author places substances introduced into the
oral cavity upon the same plane as those developed in contact with the
teeth. This being the case, he has experimented with the acids and
substances contained in food or condiments. It is also curious to note
that while he has been careful as to the fermentation of the fluids with
1 ¹ Pp. 158-164.
750
DENTAL CARIES.
which he has experimented—and in a large number of them fermenta-
tion has produced the acid which has decalcified the teeth experimented
upon, which fact he particularly notes-yet he nowhere puts prominently
forward the thought that these agents are formed in contact with the
identical points at which caries is manifested. It is true that fermenta-
tion taking place within the mouth is many times alluded to, and the
agency of micro-organisms in the process is also admitted; still, but
slight importance is attached to them.
1
Continuing, Magitot says:"
M
"Other secondary phenomena are sometimes produced concurrently
about the altered parts, and have by various observers been held to a cer-
tain degree responsible. It is thus that putrid decompositions, which have
especially for their source débris of animal or vegetable substances of ali-
mentation, have been invoked; in like manner the cryptogams and vibrios,
whose formation we have regarded as an epiphenomenon of the malady,
have been considered as agents of the alteration by Facinus, thus taking.
precedence of the theories of Pasteur."
It seems to have been Dr. Magitot's thought that the agents that
produce caries are either developed in the fluids of the mouth, and
evolved with them as they are secreted, or else are introduced from
without, rather than formed in isolated points of fermentation. In his
search for these agencies all the varying conditions of the fluids of the
mouth in health and disease have been questioned. That in such
agencies are to be found some of the predisposing causes of the malady
there seems no reasonable doubt; but certainly, after all the fruitless
search of the last half century, it is time to turn our attention else-
where. I would here reiterate the proposition that if the cause of
caries of the teeth is to be found in the disintegration of their structure
by an acid or by acids, we must find that these agents are produced or
applied at the very spot where the caries has its beginnings or is making
its advances. Otherwise we must fail. Caries of the teeth is, as a mal-
ady, strictly localized, and is not the product of any agent distributed
generally in the oral fluids.
There are many other authors, such as Weld, Salter, Coleman, Taft,
and others, who have written well on this subject, and from whom we
might quote; but in doing so only slight shades of difference in the
views presented would be obtained, without in any wise affecting the
trend of thought already given; it is, therefore, unnecessary to our
present purpose.
AGENCY OF MICRO-ORGANISMS IN CARIES.
In the previous pages considerations have been presented which lead
to the conclusion that caries of the teeth is a result of the corrosive action
of acids developed in contact with them. Certain observations of the
utmost importance in the further explanation of these processes are now
to be noticed. They relate to the agency of those micro-organisms con-
cerned in the various fermentative processes by which acids are produced.
I P. 164.
AGENCY OF MICRO-ORGANISMS IN CARIES.
751
From time to time during the discussion of the relations of micro-
organisms to the process of fermentation there have appeared suggestions
that decay of the teeth might be a result of the action of microbes. But
the first extended study of fungi in connection with this process was
undertaken by Leber and Rottenstein, who published an account of
their observations in 1867. At the time their studies were made plans
for the separation and individual study of those micro-organisms which
appear in connection with the carious process had not been systematized.
Hence these observers seem to have confounded all other micro-organ-
isms with Leptothrix buccalis. By treating decayed dentine with iodine
and acids a violet color of the granular masses filling the widened
tubules was obtained, and the conclusion that these were composed,
in part at least, of micro-organisms was announced-an observation
since confirmed by the use of the improved methods of staining intro-
duced by Dr. Koch. So complete has this demonstration been that in
any case of erosive softening of tooth-structure within which micro-
organisms cannot be demonstrated by well-known processes we are
justified in saying that such a softening is not true caries, or is not of
the nature of caries as it is found in the human mouth. Leber and Rot-
tenstein do not regard the fungus as capable of penetrating the normal
enamel or dentine, but suppose that, a beginning being made by an acid,
it enters, and by its growth assists in the destructive process.
The following extracts define the views of these authors upon this
point (pp. 68-97):
Kdy
"From what has been said, it results that two principal phenomena man-
ifest themselves in the formation of dental caries-viz. the action of acids,
and the rapid development of a parasitic plant, the Leptothrix buccalis.”
"It seems that the fungi are not able to penetrate an enamel of normal con-
sistency. The dentine itself, in its normal condition of density, offers great
difficulties to their entrance, and we are not yet sure that the leptothrix
could triumph over this resistance." "We cannot decide at present if
the leptothrix is able to penetrate sound dentine when from any circum-
stance it happens to be denuded." "But if the enamel or dentine
become less resistant at any point through the action of acids, or if at the
surface of the dentine a loss of substance has occurred, then the elements
of the fungus can pass into the interior of the dental tissues, and produce
by their distension, especially of the dentine, effects of softening and destruc-
tion much more rapid than the action of acids alone is able to accomplish."
"The participation of the fungus is constant in the production of
caries which has reached this stage. As soon as a loss of substance can be
shown there is found the presence of fungus, so that the question whether
or no acids alone could produce ravages more considerable is without
importance."
The modus operandi by which Leptothrix buccalis (or other micro-
organisms) may produce softening of the dentine is left without expla-
nation. It may here be mentioned that in the very beginning of this
line of investigation a mistaken idea was entertained, which has been
perpetuated in nearly all subsequent writings upon the subject—that if
micro-organisms are instrumental in the production of decay they must
¹An English translation appeared in 1868.
752
DENTAL CARIES.
K
first enter the structure of the tooth. This error seems dependent upon
a failure (which is very apparent) fully to comprehend the theory of fer-
mentation with the production of an acid, which acid, being formed in
contact with a particular part of the tooth, acts chemically upon its sub-
stance and decomposes it. It should be remembered that if microbes act
at all in this process it is through their agency in setting up fermentative
changes, during the progress of which substances are chemically altered
in such a way as to create an acid or other chemical agent capable of act-
ing on the constituents of the tooth and decomposing them. Therefore
contact with the tooth, provided this contact be sufficiently prolonged,
is all that is required. The chemical substance provided goes before
and prepares the way for the entrance of fermentative agents. This
fact being kept in mind, much of the confusion of ideas apparent in the
earlier discussions of this question will be prevented.
The work of Leber and Rottenstein made a profound impression on
the dental profession, notwithstanding the fact that most of their propo-
sitions fell from lack of evidence. The subject has since then been
taken up by others, improved methods have been devised, and our
knowledge has been greatly increased. In this work Messrs. Milles
and Underwood of London have taken an important part. Their results
were communicated at the meeting of the World's Medical Congress held
in London in 1881. These gentlemen had the use of the improved stain-
ing methods introduced by Dr. Koch, and fully verified the findings of
Leber and Rottenstein as to the presence of micro-organisms in the tubules
of carious dentine. After an extended series of flask experiments, they
announce the conclusion that the decalcification of the teeth in decay is
accomplished by an acid secreted by the organisms, and that there are
other phenomena present, such as the widening of the tubules and the
discoloration of the decayed mass, which are not to be explained by the
action of acids. The widening of the tubules is regarded as being the
direct work of the micro-organisms, which consume the dentinal fibrils
and the decalcified walls of the tubules (they use the term channels), and
in this way finally break down the entire mass.
After passing over the vital theory of caries as being already com-
pletely disproved, Milles and Underwood say:
"With regard to the purely chemical theory, we cannot accept it as
wholly satisfactory, for the following reasons:
"1. Because the destruction of dentine effected by the action of acids
alone under aseptic conditions does not resemble caries either in color or in
consistency, it being colorless and gelatinous, the process uniformly
attacking all parts of the surface.
"2. Because sections of dentine so destroyed show uniform destruction
of the matrix, but not enlargement of the channels occupied by the fibrils;
whereas the true caries first attacks the soft tissues-i. e. the fibrils-and
encroaches from that point d'appui upon the surrounding calcified structure,
thereby producing the characteristic enlargement of the channels, until two
channels break into one, the intervening matrix being wholly destroyed.
"3. That, although artificial caries has been produced exactly resembling
true caries, we have failed to discover any record of experiments in which
this has been the case when septic influences were excluded. Two experi-
AGENCY OF MICRO-ORGANISMS IN CARIES.
753
ments have indeed been recorded in which the teeth were protected from
septic agencies, in one by the addition of creasote, in the other by hermetic
sealing of the flask (see Magitot's experiments), and in neither of these did
caries occur.
We assume, therefore, that two factors have always been in
operation: (1) the action of acids, and (2) the action of germs. Further,
our own flasks show that malic and butyric acid, with saliva in a meat
infusion, have not, under aseptic conditions, produced caries.
"It may be asked, If a tooth can be decalcified by acids out of the mouth,
and these acids are constantly in action in the mouth, then if they produce
caries why can they not produce simple decalcification? To this it may be
replied that acids alone do not destroy a living tissue-that the stomach is
not digested by its own acids until it has been removed from the body.
"4. Lastly, we would urge that when caries occurs in the mouth it is
always under circumstances more favorable to the action of germs than to
that of acids. There is always, first of all, a minute pit or haven where
germs can rest undisturbed and attack the tissue. We cannot, upon the
purely acid hypothesis, explain why the same acids that originally caused the
decay, gaining access through some minute imperfection of the armor of
enamel, do not in the same mouth or under the same conditions attack the
wounded enamel at the edges of a filling. The germs cannot rest there:
they are constantly washed away if the surface is fairly smooth; but the
acids literally bathe the part (during the intervals between the acts of mas-
tication, when the alkaline parotid and submaxillary saliva neutralizes
their action).
This theory-which, for the sake of distinction, may be called 'septic'
-is rather an amplification of the chemical theory than a contradiction of
it. Most probably the work of decalcification is entirely performed by the
action of acids, but these acids are, we think, secreted by the germs them-
selves, and the organic fibrils upon which the organisms feed, and in which
they multiply, are the scene of the manufacture of their characteristic
acids, which, in turn, decalcify the matrix and discolor the whole mass.
"From our observations on cementum to which caries has extended we
conclude that the process is very similar: the bioplasmic contents of the
lacunæ and canaliculi afford board and lodging for the organisms, which
multiply, and, when sufficiently numerous, decalcify the surrounding bone,
so that each lacuna loses its outline and extends in all directions."
In regard to the order of the occurrence of the phenomena of caries,
and the relation of micro-organisms thereto, the conclusions of these
observers were an advance upon anything before developed, and, con-
sidering the fact that they had not been able to make out the life-history
of the fungus, its physiological processes, by any manner of demon-
stration, it seems quite remarkable that they should have approached
so nearly to accuracy of judgment. They did not make the neces-
sary separation of the organisms found, nor cultivations for the study of
their individual characters and the molecular changes or remoleculariza-
tions of matter they induce when in contact with different substances.
GO
This, thanks to Dr. Miller, has been done in case of some of the
micro-organisms of the mouth, and it only requires a continuance of
the work to make us familiar with them all. It must be remembered,
however, that this requires a vast amount of labor of the most pains-
taking character as well as a thorough training in this kind of work.
I have had enough experience in it myself to form some judgment in
VOL. I.-48
754
DENTAL CARIES.
the matter, and it seems to me impossible for one burdened with the
cares of a full, or even a light, practice successfully to carry out any
considerable series of these observations with that care and accuracy
which the subject demands. The chances for contaminations and mis-
takes in various directions are so great as to require one's whole thought
for their successful avoidance. For these reasons I shall not, in what
I have to say on this particular subject, put forward my own observa-
tions where I can avail myself of those of persons whom I know to
have been better situated and better prepared for the work, and whose
skill is known and recognized. I would say, however, that it is by
no
means certain that one who has busied himself principally with
original research of this character is best calculated to construct theories
from the facts derived from even his own experiments.
This work is as yet in its infancy, and, though enough has been
accomplished to furnish an ample basis of fact for the formation of
well-grounded theories not only as to the agency of micro-organisms,
but also as to the modes of their action, the development of many addi-
tional facts may be expected in the near future. It seems unnecessary
to follow all who have written on this point. Nearly all who have
attempted to investigate in this field have added something to our know-
ledge of it. Even in those cases in which no facts of enduring value have
been added difficulties have been illustrated for the benefit of those who
followed. But, after all, the most important part of the work has been
done by those in no wise connected with the dental profession, and it is
to them we must go for a knowledge of the agency of micro-organisms
in the decompositions in general, and the work in our particular field
must be guided and directed by the information thus gained.
Ever since the discovery of the yeast-plant by Schwann, and the
establishment of the fact of its necessary participation in the act of
alcoholic fermentation, it has been assumed by a considerable portion
of the best students of natural phenomena that this was the type of
all fermentations and decompositions. Indeed, it was soon shown by
Schwann and his colaborers that sterilized solutions would not undergo
decomposition, fermentation, or putrefaction when hermetically sealed,
nor even after the admission of air purified by heat. This, however,
was not considered conclusive. It was claimed that the disposition to
decomposition is communicated by the contact of substances in a state
of molecular motion, by which their elements are being rearranged in
new forms, and that heat will stop this molecular movement and destroy
the tendency until it is again communicated by the contact of this kind
of influence. This, it was asserted, might exist in the gaseous form
and be freely communicated by means of the air. In 1854, however,
Schroeder sterilized fermentable solutions and soups, to which he ad-
mitted air after having filtered it through sterilized cotton, with the
idea that if organic germs caused decomposition these would be caught
in the meshes of the filter. This experiment was eminently successful.
Solutions did not decompose, though the air was admitted without heat
or other change than removal of the particles floating therein. These
particles were supposed to be-in part, at least-organic germs which
See Liebig's Organic Chemistry in its Application to Physiology and Agriculture.
1
AGENCY OF MICRO-ORGANISMS IN CARIES.
755
would undergo development when brought in contact with a favor-
able soil.
After this came the brilliant experiments of Pasteur and his colabor-
ers, in which it was conclusively proven that none of the fermentations
or putrefactions could progress without the presence of organic germs,
and that each one of these is dependent on the presence of a special
form of organism peculiar to it, and to none other. Following close on
these discoveries came their application in surgery by Lister, who by
the use of appropriate means for arresting the ingress of micro-organ-
isms succeeded in preventing decomposition in wounds. These results,
most of which have been accomplished within my own lifetime and
memory, have had the effect of almost completely banishing the old
molecular-motion theory of Liebig and substituting the germ theory in
its stead.
The brilliant results of this series of observations are of the greatest
importance in the explanation of the phenomena under consideration.
For this reason the close study of these fermentative processes is of the
utmost importance to those who would gain the most accurate under-
standing of caries of the teeth.
As briefly representing the results of these investigations we may form-
ulate the following propositions:
The act of fermentation comprises the physiological processes of life
-namely,
1st. The formation of a solvent (which is usually an unorganized fer-
ment, peptonizing agent, or diastase) for the performance of the act of
digestion, or the preparation of food-material for absorption and assimi-
lation.
Ag
M
2d. Assimilation or nutrition, or the act of tissue-building.
3d. The formation of waste products, the act of denutrition, or the
shedding out of material that has once been formed into protoplasm or
used in connection with the process of tissue-building.
4th. The capability of reproduction in a definite line of forms.
The performance of these acts is the condition of the physical existence
of life, and they must be performed by every form of life, no matter
how high or how low in the scale.
1
As illustrating the physiological processes of fermentation, it is well
to study the higher plants (not disregarding the physiological processes
of the higher animals), for the reason that in them certain processes can
be better made out than in the microscopic organisms. For this pur-
pose I have made diligent study of some particular plants that seemed
to give better facilities than others. Among these studies the sprouting
of the grain of corn presents especial facilities for observation in micro-
scopic section. It, as most others, is composed of three natural divis-
ions-the germ, the perigerm, and the starch envelope. The germ is
the embryo plant; the perigerm (the scutellum of botanists) is the organ
of digestion destined to serve the needs of the germ during its embry-
onic development; the starch envelope is a store of food to serve the
young plant until such time as it shall have developed the organs with
which it will be enabled to gather its own food.
Under the influence of warmth and moisture the germ is quickened
756
DENTAL CARIES.
into activity, and at the same time the perigerm elaborates a substance
which is known as a soluble or unorganized ferment, the office of which
is the digestion of the store of starch with which it is surrounded. This
soluble ferment, diastase, or digestive fluid, comes in contact with the
starch-granules and converts this substance into glucose and levulose.
This is exactly similar, physiologically, to the formation of the pep-
tones by the gastric juice of the animal, and is the digestion which fits
the food, the starch, for the needs of the developing germ of the corn.
When this remolecularization of the starch is thus accomplished, it is
taken up by a set of ducts that convey it to the germ. This set of
ducts ramify plentifully through the mass of the perigerm and form a
plexus immediately beneath its epithelium, a layer of columnar cells
separating the perigerm from the starch envelope. By the careful ·
use of sugar tests it is possible to follow this sugar along these ducts to
the germ, and, after the growth of the germ has advanced somewhat,
into the ducts of the growing plant. But here it is lost; another kind
of remolecularization has taken place, by which it is converted into the
tissues of the growing plant. This change is nutrition. As these pro-
cesses go forward, and are followed by the preparation of sections at the
expiration of each twelve hours after the planting of the grain, it will
be seen that the starch-grains that lie nearest the perigerm have disap-
peared, and that the meshes in which they lie are empty, and afterward
those that lie next, and so they continue to disappear as the germ grows,
until its rootlet has struck down into the soil and the leaflet is spread to
the air. The organs for the gathering of the food for the plant have
found the elements from which that food is to be obtained, and the
store of starch, not yet quite exhausted, is no longer needed.
But this is not all. If the grains of corn are planted in a soil the
constituents of which have been chemically examined, it will be found
that during the process of germination this soil has received acetic acid.
This is in accord with the laws of life as we find them everywhere
expressed wherever they have been sufficiently examined, for in con-
junction with all growth we find the formation of waste products. In
this case the waste products are acetic acid, which is left in the soil, and
carbon dioxide, that is given off to the air. This, as we shall see pres-
ently, is the type of the process of fermentation.
Suppose we have planted the seed in two inches of damp sand placed
upon a piece of polished marble. Growth takes place, and the roots
strike down through the loose sand and soon come in contact with the
solid stone. They are unable to penetrate this, and, instead, they spread
out upon its surface. After this growth has continued for a time, if the
plants and sand be carefully removed from the polished stone, it will
be found that wherever a rootlet has come in contact with it, it has
left its trace in the form of a removal of the polish; and a close exam-
ination of this shows that a portion of the solid rock has been dissolved
and removed, leaving the imprint of every rootlet (Sachs). The roots
have been doing the same toward the stone that the perigerm did toward
the store of starch. They have been preparing the food for the nutri-
tion of the growing plant, and the hardness, the apparent insolubility,
of the stone has not been a sufficient barrier against them. They have
LA
AGENCY OF MICRO-ORGANISMS IN CARIES.
757
furnished the means of dissolving it (Sachs supposes this solvent to be
carbon dioxide), and have appropriated such of its elements as were
demanded by the needs of the plant. This is an illustration of the
universal law that all living things, both plant and animal, must digest
and prepare food-material for assimilation. In the physiological sense
it is not essentially different from the digestion which takes place in all
the higher animals, including man. In the higher animals this is a
very complex process performed by an elaborate physical mechanism.
In the walls of the stomach a special tissue is developed, the office
of which is to prepare the unorganized ferment, pepsin, which, with
the aid of other substances elaborated by similarly specialized organs,
performs the office of digestion for the whole group of cellular forms
that constitute the animal.
In the seed there is still a division of labor. Here we find, indeed,
in the perigerm an organ set apart for the accomplishment of the act of
digestion as in the higher animals, but its mechanism is so different and
so simplified that nothing but the closest study of its functions will
remind the student of the analogy that exists between it and the stomach
of the animal. In the plant there is no specialized group of cells for
this office, but the performance of the act is distributed among the root-
lets. Now, when we follow this process down through the lowly organ-
isms, we find a continuous simplification of the mechanism for the per-
formance of this function until all trace of a specialized organ is lost.
Shall we conclude from this that the function is lost? Is it not more
probable that as we descend to those very lowly organisms we will find all
of these functions combined in the single cell? If, now, we turn our atten-
tion to the plant known as the torula, which is the active agent in alco-
holic fermentation, and study its physiology, we find the following facts:
"When pure vinous yeast is washed with distilled water, a peculiar
substance is found dissolved in the water. This is yielded continually
during the life of the plant. Examinations have proven this substance
to be an unorganized ferment having a peculiar effect upon sugar. This
has been examined by Berthelot, Becamp, and others. It has been pre-
cipitated and obtained in the form of a powder somewhat similar to pep-
sin, and when redissolved has been found to retain its original power
over cane-sugar. This action is to split up the sugar into two sub-
stances, called glucose and levulose.
-
"This reaction always takes place as the primary step in alcoholic
fermentation, and is the primary digestion which permits the appropri-
ation of the food-material by the yeast-plant. This is entirely analogous
to the digestion of food in the stomach of an animal, by which such food
is received in the blood, to be conveyed to the tissues for their nutrition,
and is the same as the digestion of starch in the seed; but it is accom-
plished in the surrounding media instead of a receptacle provided for
the purpose.
"This is one instance of a type of digestion which I believe to be
universal in case of all unicellular animals and plants. The formation of
a stomach is a provision for the conservation of force, but it in no way
changes the modus operandi of the digestive function." ¹
Formation of Poisons by Micro-organisms, p. 84, Black.
758
DENTAL CARIES.
+
Here, as in all other forms of life, we are unable to follow by any
form of experimentation known to us the further changes that take
place. In the seed we have followed the digested material into the
ducts of the growing germ, and they are lost in what we suppose to be
the changes of nutrition. In the animal we may follow the digested
material into the blood, and again it is lost in the changes of the nutri-
tive process. But in both of these we find the material returned again
in the form of waste products. Now, in the yeast-plant we have also
followed the changes consequent upon the digestive process.
We may
also watch the growth of the plant by the aid of the microscope, and see
the young buds spring forth, and follow their development into full-
grown cells. We have no reason for the supposition that this growth is
different in the main points of its physiology from the other forms of
life that we see around us. Then the further changes in the digested
material must be those of the nutrition of the plant through which its
growth is maintained, and in harmony with all other forms of life the
material must be returned in the form of waste products. This we find
in the form of alcohol and carbon dioxide. This, then, is fermentation,
and forms the recognized type of all of the fermentations known to us.
In all that have yet been sufficiently made out, in which the life-pro-
cesses have been successfully followed, the essential phenomena have
been found to agree substantially with those here detailed. Among the
animal forms the principal waste products are urca and carbon dioxide.
Among the vegetable forms the waste products are the alkaloids, the
organic acids, and carbon dioxide. In the torula, which is the agent
of alcoholic fermentation, the waste products are alcohol and carbon
dioxide. In acetic fermentation the waste products are acetic acid and
carbon dioxide. This proves to be the law of fermentation and putre-
faction so far as they have yet been accurately followed.¹
It will be seen that these propositions cover the essential factors of
all life-processes, and link together the proposed three kingdoms (the
microbe, the vegetable, the animal) in one chain of functional activities
that are common to all and necessary to all. That fermentation is the
result of the life-processes of certain forms of micro-organisms may now
be accepted as a truism, and will not be argued.
There are certain chemical processes which in their results closely
imitate the fermentations. These are still called fermentation, but they
are essentially different in their mode. A number of substances which
are formed naturally by true processes of fermentation can be formed
artificially by chemical processes.
What is called fermentation by an unorganized ferment is but the first
step in a true fermentation. In digestion this is seen in the conversion
of starch into sugar by the ptyalin of the saliva, in the conversion of
flesh into peptone by pepsin, in the conversion of cane-sugar into glucose
and levulose by the unorganized ferment of the torula or vinous yeast-
plant. All of these are agents formed in the life-processes of living
organisms, and the fact that they may be separated from that organism,
precipitated, and dried, and will perform their function afterward on
Pat
¹ I have developed these laws more at length in the little work Formation of Poisons
by Micro-organisms.
AGENCY OF MICRO-ORGANISMS IN CARIES.
759
being dissolved in water, only shows their wonderful power. They
are only the agents of digestion separated from the organisms by
which they were formed. The boiling temperature renders them
inert.
The essential physiological processes of the life of agents of fermenta-
tion must harmonize with those which characterize life in general, for
while, in the study of biology, we find the most endless variety of form,
there is presented only one plan of relation to the material world. The
physical instruments for the performance of these acts may vary indefi-
nitely without vitiating the act itself. Thus a description of a process
of fermentation of any particular character involves the physiological
processes of the organism which is the agent of that fermentative change.
This is very much more important than the morphology of that particu-
lar form of life. As the agent of fermentative changes, we are princi-
pally interested in its behavior toward the material world in respect to
its physiological acts; or, in other words, we should inquire into the
nature of its digestive agent and its waste products. What is its food,
and in what chemical form is it delivered back after having served the
purposes of the organism? These are its essential characteristics. As
a micro-organism, its form may be confounded with others even by the
skilled observer.
It is this feature of the experimentation and observations of Dr.
Miller of Berlin that gives them their peculiar value. In the studies of
this subject in its relations to caries of the teeth antecedent to his, many
had perhaps seen the same micro-organisms, which act as the agents of
that fermentation by which the acids are formed, through which the
dissolution of the substance of the tooth in caries is effected; but no
one had made sufficient study of their physiology to know anything of
their remolecularizations of matter, and they therefore failed to learn
their essential characteristics. While these previous studies were very
important in that they served to show the difficulties with which the
observer had to contend, and were essential to the formation of appro-
priate plans of experiment, they are now of little use in the further
elucidation of the process of caries.'
Dr. Miller began his observations with a series of experiments with
saliva, with a view to ascertaining whether, organic germs being excluded,
it contains anything capable of setting in motion such a process of change
as would produce an acid at isolated spots where it or food might be
detained about the teeth. In this search the ordinary phenomena of
the conversion of starch by ptyalin was observed, but with this conver-
sion the process terminated. Sugar was formed, but no acid of any
kind. This agrees perfectly with all that was known of the fermenta-
tive powers of this fluid; and from many sources we have learned that
the further decomposition of food-particles lodging about the teeth must
be in accord with the decompositions in general-that is to say, it must be
-
1 The experiments of Dr. Miller of Berlin, Germany, to which I shall have frequent
occasion to allude in what follows, were published in the Independent Practitioner of Feb-
ruary, March, and May, 1884, and May and June, 1885; and I deem them so important
that, with the consent of Dr. Miller, and through the courtesy of Dr. Barrett, editor of
the above-named journal, they are reproduced as an appendix to this paper.
760
DENTAL CARIES.
accomplished by the life-processes of an organic ferment. In the decom-
position of these particles as they from time to time are presented in the
mouth, a considerable variety of fungi are to be found. The separation
of each of these the one from the other, and the study of their physio-
logical processes separately by individual cultivations, would be a great
task, and was not at first undertaken. In the previous studies of this
subject it had been sufficiently determined that the micro-organisms
appearing in the deeper parts of the mass of progressive caries were
much more constant in their characters and apparently presented fewer
varieties. This being the case, it seemed best to study the organisms
found there. With this in view, culture-mediums¹ were infected by
fragments of softened dentine taken from the deeper portions of the
carious mass, with precautions to prevent the ingress of any germis
from other sources. These were kept in an incubating apparatus at the
temperature of the blood. The usual controls (culture-mediums pre-
pared, but not infected) were placed with them. Fermentation took
place promptly in the infected tubes. This occurred with sufficient
uniformity to demonstrate conclusively that the ferment was derived
from the carious dentine. The fermentation was constantly accompanied
by acidification of the culture-medium, as shown by the use of litmus-
paper. Other mediums were then infected by transferring to them a
minute portion from one of those that had undergone the fermentative
process. These new cultures promptly underwent the same process.
This was continued for a sufficient number of generations to show con-
clusively that there was present an organic ferment capable of the con-
tinuous propagation of its kind-a point of great importance in this
investigation. This much being determined, the question of the capa-
bility of the acid generated to decompose the elements of the tooth with-
out other concentration than that attained in the culture was tried. For
this purpose fragments of fresh and sound dentine were introduced into
the cultures. These were promptly softened by the solution of the
lime salts.
Thus was found a ferment within the carious dentine showing itself
capable of continuous propagation in a certain line; hence, a living fer-
ment. It was also demonstrated that this living ferment is capable of
forming an acid of sufficient concentration to decalcify dentine. In
connection with these cultures there constantly appeared a micro-organ-
ism in appearance the same as that so constantly present within the cari-
ous dentine. As this remains the same in all of the cultures, it is per-
fectly evident that it is the organic ferment which by its life-processes
produces the results stated.
Gh
By methods which seem to have been carried out with due care,
Dr.
Miller has found, isolated, and tested the unorganized ferment (soluble
ferment) or digestive fluid of this organism. This he found to have an
effect upon cane-sugar identical with that of the unorganized ferment
of the yeast-plant-i. e. it converts cane-sugar into levulose and glucose
(dextrose). This action is similar to that of most of the organisms
subsisting upon the sugars.
The acid produced has also been subjected to analysis by the same
¹ See appendix to this paper.
AGENCY OF MICRO-ORGANISMS IN CARIES.
761
experimenter, and found to be lactic acid, the waste product of the
organism.¹
Thus the four essentials in the physiology of this organism have been
made out―viz. a digestive body, assimilation as shown by growth, a
definite waste product (lactic acid), and the capacity for reproduction in
a definite line of forms. These findings sufficiently demonstrate the
existence of a living ferment; and as this ferment was in all instances
obtained directly from the deeper parts of carious dentine, and the
acid produced is proven to be sufficiently active, without further con-
centration, to decompose the elements of a tooth, the evidence seems
sufficient to connect it with this process as the cause.
There are, however, some other points in the physiology of this
organism, some of which have been determined, very important in rela-
tion to the process of decay. In the depths of a carious mass the
access of the oxygen of the air is, to say the least, very precarious, and
it becomes important to know whether the organism is capable of devel-
opment when excluded from free oxygen. It would seem, from a review
of Dr. Miller's experiments, that it is practically anaerobic, as its devel-
opment is not hindered by any exclusion from the air that he was able
to devise. It is also certain that the presence of oxygen is not espe-
cially detrimental to its growth or its acid-generating power, as it pro-
duced sufficient acid to decalcify dentine when enclosed in a tube corked
with cotton. Therefore the organism is capable of development and
the production of its characteristic acid on the surface of a tooth upon
which it may find a lodgment, or in the innermost depths to which it
may penetrate the dentine. In its relation to caries this is a very
important consideration; for if there is no other hindrance to its devel-
opment and the performance of the functions detailed, caries would be
practically incurable without the complete removal and exclusion of the
organism from the carious cavity. As it might proliferate anew and
renew the fermentative process, the leaving of a single germ on any
part of the walls of a cavity would effectually destroy the usefulness
of an otherwise most perfect stopping. After making many examina-
tions of decayed dentine and the organisms found in it, I cannot con-
ceive that in all of the carious cavities successfully treated by the
stopping process a perfect removal can have been effected; some explana-
tion of their failure to proliferate becomes necessary.
It is possible that this explanation will be found in a failure of the
food-supply of the organism. It is well known that micro-organisms
are often confined to certain qualities of food, as is the case with other
K
¹ In the earlier controversies it was pointed out by Justus Liebig that if alcohol was
formed as an effect of the life and growth of the yeast-plant, as claimed by Schwann,
it must be regarded as the waste product of that organism. In the discussions of recent
years this point has not had the prominence given it that it deserves. Indeed, most
writers have left it without explanation. At the same time, they have recognized cer-
tain facts going to show that this is the true explanation of the phenomena. One of
the most prominent of these is that this product, when it exceeds a certain amount, is
always poisonous to the organism which produces it, and thus checks its development.
This effect is in all respects similar to that of urea upon the animal in case of failure
of excretion, and in harmony with well-known physiological laws. Dr. Miller in his
experiments has found also that when a certain amount of lactic acid has been formed
the growth of the organism is retarded.
762
DENTAL CARIES.
organized beings, and Dr. Miller's findings seem to demonstrate with
sufficient clearness that the different forms of sugar constitute the nat-
ural food of the plant, those not directly fermentable being promptly
converted by the unorganized ferment of the organism. It seems also
that the organism is capable of growing in beef-extracts without the
presence of sugar, but with such a complete change in its physiological.
operations that no acid is produced. This singular phenomenon is
vouched for by Dr. Miller. In my own experiments on this point the
fungus did not seem to grow well, but there was generally, after some
days, a slight acidification, though nothing comparable to that in the
sugar cultures. The great difficulty I experienced in the prevention of
contaminations leads me to place more confidence in Dr. Miller's exper-
iments than in my own, yet after what I have seen I cannot regard the
organism as being at home in a pure beef-extract. Then, if by the opera-
tion of filling it is enclosed in such a manner that sugar cannot be obtained,
its power in the production of caries is at an end as soon as the sugar
enclosed with it is consumed.
So far as the growth of the organism in the mouth is concerned, the
question of its power to digest starch is of but little consequence, for
the reason that this substance is always converted into a fermentable.
sugar by the ptyalin of the saliva. Therefore, if any of the forms of
sugar or starch are present in solution, they will be readily absorbed to
almost any depth by carious dentine. Thus the organism is supplied
with the proper food for the production of lactic acid, and can act in
the production of caries. There are, perhaps, very few mouths in
which this form of food is not supplied in sufficient amount for its needs,
and it is well demonstrated by experiment that in case of temporary
deficiency there will be no destruction of the organism, for it may sub-
sist—for a time, at least-without this aliment.
This series of facts developed by direct experiment seems sufficient to
demonstrate the correctness of the suppositions of Robertson and Reg-
nard. They fill the gap left by them-viz. the demonstration of the
process of fermentation and the production of the acid by which the
constituents of the teeth are decomposed. This demonstration, however,
does more than explain the development of the acid and the solution
of the lime salts of the tooth. Caries presents phenomena other than
these, and which all previous theories failed to account for-notably the
widening of the tubules and the constant appearance of micro-organisms
within them; for in the solution of teeth by acids this characteristic
widening of the tubuli is not present. In natural caries the tubuli are
constantly found packed full of micro-organisms, and in the series of
experiments alluded to it has been demonstrated that these organisms
are capable of liquefying several varieties of semisolid culture-mediums,
and my own experiments show that some liquefaction of gelatin occurs in
the presence of a very small amount of sugar. In addition to this, it is
fairly well shown that the organism is capable of living on pure beef-
extracts. To do this it must digest them. With these facts in view,
the widening of the tubules is easily accounted for. A portion of the
glue-giving basis-substance, after having been robbed of its lime salts,
is dissolved. It is probable that this is done by the unorganized fer-
AGENCY OF MICRO-ORGANISMS IN CARIES.
763
ment of the organism, and that the results of this digestion are appro-
priated. Indeed, the known facts detailed render this the most obvious
explanation of the phenomenon. It accounts not only for the widening
of the tubules, but for the final complete breaking down of the struc-
ture of the dentine with the formation of a cavity. It is not necessary,
however, to refer the final disintegration of tooth-structure to the action.
of this organism alone; for after a considerable degree of softening has
occurred it is probable that other organisms, so plentiful in the mouth,
may assist in the process.
Another point in the physiological processes of living beings deserves
notice here. It is an established law that the waste products of an
organism become poisonous to that organism when they have collected
in a certain quantity. This is true of urea in the animal, it is true of
alcohol in the vinous fermentation, and Dr. Miller found it to be true
of the organism causing caries. When lactic acid has accumulated in
certain amount (this amount being not yet definitely determined), the
further development of the organisms is interfered with. Their power
to go on producing lactic acid in the depths of the dentine is accounted
for by the formation from the lime salts of the tooth of the lactate of
lime, which does not interfere with the further development, and, in
fact, is equivalent to a removal of the waste product. Long before the
existence of a special organism in lactic fermentation was known, it had
been found that by adding chalk or other form of lime the fermentation
could be continued and much more lactic acid produced. Following up
these facts, Dr. Miller has analyzed carious dentine and found it to
contain calcium lactate.
With these facts before us, the localization of caries is no longer an
enigma. It is clear that with the motions of mastication and of the
lips and tongue these organisms will not be allowed to grow on any
parts of the teeth that are exposed to friction. Hence caries never
occurs at such points. But they may grow in the form of little col-
onies in any places where they are secluded from direct washings by the
saliva, and in which they are protected from displacement. Such pro-
tected points are found between adjacent teeth, in pits, fissures, or any
irregularities of form that will give them lodgment. These points give
the opportunity for fungi. Direct experiment shows that they will pro-
duce acid abundantly within twenty-four hours after their implanta-
tion. If in any such place this acid is developed in contact with the
tooth, and the development is allowed to progress without interruption,
the effect of the acid will be to decompose the enamel, and finally to
penetrate it and form a place of lodgment in which the fungus can con-
tinue its development without being subject to frequent displacements.
Many have said that this fungus is incapable of attacking enamel.
That is evidently true. The fungus has no power of attacking any-
thing or growing into anything, except it be a thing that offers spaces
filled with soft tissue, or openings into which it may grow as the vine
grows through the spaces in a lattice-work. It is not the organism that
makes the attack, but the products of the organism, the lactic acid.
When the dentinal tubules are once exposed, they form a protection to
those filaments of the fungus which strike into them in the process of
K
764
DENTAL CARIES.
growth, and development occurs in that direction. Hence the continu-
ous progress of caries when it has once fairly begun in the dentine. Then
the growth will continue in any direction in which space is offered for
the development of filaments. In this way the tubules become packed
full of the organisms, and the surrounding dentine is always decalcified
in advance of the growth of the fungus by the lactic acid produced.
That this is the true explanation of the etiology of dental caries there is
no longer a reasonable doubt. There is nothing presented in the phe-
nomena of the affection of which this does not afford a rational explana
tion. That there are difficulties still surrounding some phases of the
occurrence or non-occurrence of the affection in special cases and under
special conditions there is no question. These will be discussed on
another page.
I take the following extract, written by the American editor, from
Coleman's Dental Surgery and Pathology:
Q
"A theory has been advanced that these parasites, which may be found
in mouths where the teeth are perfectly sound and without any unfilled
cavities of decay, have lodged in the carious places simply as locations
where they are partially protected from dislodgment by the breath, drink,
or food, as fissured rocks will support vegetable or animal life in the crev-
ices, while the smooth surfaces, exposed to the winds and rains, are bare of
vegetation."
So far as plant-life is concerned this is about correct. The rootlets
of plants can no more obtain a hold upon the rocks in such positions than
the fungus of caries can grow on the exposed parts of a tooth. But where
a crevice furnishes a place for the lodgment of a seed, and moisture
retains a little dust, plants are found to grow, and their rootlets emit a
solvent that causes the solid stones to yield them nourishment. In this
way the hard rocks are caused to crumble. I have already explained
how it is that the rootlets of the growing plant leave their imprint on
polished stone. It is well known that old tombstones that have been
allowed to become moss-grown first lose their polish, then their surface
is softened and crumbles away. The lichens leave their imprint upon
the rocks by dissolving and appropriating a part of their substance.
So it is with plant-life wherever found. The relation of life to the
material world is such that many of its forms will wrest their food
from even the solid stones by aid of the juices formed for this purpose.
The fungus of caries destroys the teeth in a similar manner.
PHENOMENA OF CARIES.
The phenomena presented by caries have been well described by
Tomes and others who have followed him. In this study there has
not been much disagreement as to what has been seen.
There have,
however, been sharp disagreements as to the interpretation of the phe-
nomena observed. The more important of these points of difference
have now been for the most part harmonized, and the controversy need
not here be revived. For these reasons I do not deem it desirable that
the progressive development of the views now entertained be followed
PHENOMENA OF CARIES.
765
out. It will be sufficient to describe these changes as we now under-
stand them, with but occasional references to the views of those who
have previously written upon the subject.
Caries is not known to begin on a smooth, clean surface of a tooth.
It may, as already stated, begin in any position in which lodgments occur,
whether the surface be even or not, but it is seen much oftener to occur
upon uneven surfaces, or those that lie in contact with an adjoining tooth
or in such relation to it as to protect a portion of the surface from fric-
tion, and thus favor the lodgment of particles of food. Fissures that occur
in the enamel are also often affected with caries. In case caries begins in
a fissure of the enamel of a tooth after it has fully risen above the gum
(in the eruption of the tooth), the first obvious sign is the dark color of
the fissure. This change of color may be very decided or very slight.
The amount of change of color in the fissure itself gives no indication
of the amount of caries. Indeed, we may often find these fissures dis-
colored when there is no caries whatever. Usually, however, trial with
an instrument will show an exposure of the dentine, with softening
immediately beneath the fissure. Probably, in a large proportion of
these cases, the enamel in the deeper parts of the fissure was never per-
fect. Often there may be reasonable doubt as to whether the imper-
fections seen are the result of the agent productive of caries or of
faulty development. I will therefore describe the effects seen in caries
of the enamel in connection with the appearances presented by the affec-
tion in other positions.
When the enamel of a fissure has been penetrated, a softening of the
dentine occurs immediately beneath. If the tooth is very nearly normal
in its structure, this softening is in the form of a cone with its apex
toward the pulp of the tooth and its base against the enamel imme-
diately surrounding the fissure. If the fissure is of some considerable
length, it may modify this form slightly. It is readily seen from the
form of the cavity that there is a tendency to follow the dentinal tubes,
for the greatest penetration is almost uniformly along the length of
those tubes terminating immediately beneath the fissure. There is also
seen a marked disposition to extension laterally. When I analyze my
observations closely in regard to this lateral extension, I find it to be
very much confined to the immediate region of the junction of the den-
tine and the enamel. If now the structure of the dentine at this point
is closely studied, it is found to be a region in which there are a great
number of anastomosing loops connecting the dentinal tubes, and as new
tubes become involved penetration takes place in the direction of their
length. These facts show that there is a strong tendency to penetration
in the direction of the natural openings in the dentinal structure-a
fact that has been remarked by most of those who have studied the
subject, especially by Tomes, Leber, and Rottenstein. The penetration,
however, does not in all cases seem to be confined to these directions,
for carious cavities are found of the most various shapes; and the
instances in which penetration has been transverse to the direction of
the tubules are not few. These differences have been especially noted
by the older authors, and have given rise to the terms "penetrating
caries," "spreading caries," etc. These deviations from the direction
J
M
766
DENTAL CARIES.
of the tubules are often, if not always, due to faulty formation of the
dentine. This is most distinctly demonstrable in the case of what is
called spreading caries. It is seen oftener in the first molars than any
other teeth, and in the carious points having their beginnings in the
fissures of the grinding surface. In these cases, if the carious process
has not already progressed so far as to have destroyed much of the
crown, it will at once be seen that the development of the first-formed
portion of the crown was distinctly faulty. If the decay has proceeded
so far as to destroy the evidence of this in the particular tooth, it may
generally be demonstrated by the examination of those portions of the
other teeth which were in process of formation at the same time. Thus,
when the first molars are affected, the surface at or near the cutting
edges of the central incisors should be scrutinized. In these cases the
decay often spreads over the crown of the tooth superficially, destroying
the entire grinding surface without penetrating to a considerable depth.
Not unfrequently this is so very marked that the caries is seen to extend
under the enamel over the margins of the grinding surface in such a
way that when the enamel breaks away the remaining part of the crown
is nearly flat. At this point the decay may cease, as the parts are
smoothed down by the friction of mastication.
FIG. 402.
a
If in a case of this kind not too much affected by the destructive
process sections are prepared for microscopic examination, it will be
found that in the dentine there
are numerous imperfections in
the form of interglobular spaces,
or there may be very imperfect.
depositions of lime salts, pre-
senting various forms, but espe-
cially are they often seen in the
form of a granular layer, more
or less thick, just beneath the
enamel. Every case of caries
I have examined presenting
marked deviations from the
direction of penetration which I
first described has been explain-
able on the basis of faulty forma-
tion. Therefore the proposition
seems to be maintained that
caries penetrates dentine mostly
in the direction of its natural
The fact that in
openings.
many cases the openings are
abnormal and due to faults

REMAST
The section shows the the
Carious Dentine, stained with fuchsin to show micro-
tubules as filled with micro-organisms along the junc
are very much enlarged. ( immersion objective.
tion of the dentine with the enamel at a. The tubules
of development does not affect this statement.
The penetration transversely to the dentinal tubules of the crown
portion of the tooth in normally-formed dentine is usually very slight
indeed, and that which does occur is probably due to penetration through
the very fine connecting tubuli which pass from the one to the other.
The reasons for this become very obvious when considered in connection
PHENOMENA OF CARIES.
767
with the cause of caries as detailed in the former pages of this paper.
The fungi which effect the dissolution of the elements of the tooth by
the formation of their special products grow into the natural openings,
and are confined to them until such time as the structure falls to pieces.
This falling to pieces does not occur suddenly, but there is ordinarily a
more or less considerable thickness of affected dentine covering that
which is yet normal. In this, in which the histological elements still
retain their forms nearly perfect, the natural openings are found to be
crowded with the fungus up to within a short distance from the normal
tissue. There is, I believe, always a zone of partially softened dentine,
free from the fungus, lying next to that which remains normal. In all
the lateral branches large enough to admit them, the fungus granules will
be found in single file, while very many tubuli are seen to be too small
to permit their entrance. Thus a reason for this peculiarity in the direc-
tion of penetration is furnished.
If, beginning at other points on the surface of the tooth, the direction
in which caries penetrates is examined, we find the same general rule
observed; and if the structure of the tissue involved is known, the
direction that the softening will take may be readily foreseen. The
deviations from the normal direction of the natural openings of the tissue
will be in consequence of some one of the forms of abnormal develop-
ment; and an acquaintance with these will be, in the main, a sufficient
guide in determining the direction probably followed by the carious
pro-
cess in those instances of deviation from the usual course which are occa-
sionally met with. All who have made extensive studies of faulty devel-
opment have noted the frequency of a granular zone just beneath the
enamel, especially in the sides of the crown toward the neck of the
tooth. In other cases there is a distinct enlargement of the anastomos-
ing loops of the tubules at the juncture of the dentine and enamel.
Again, rings of interglobular spaces more or less perfectly encircling
the crown occur quite often. Many of these are, however, broken up
into irregular clumps or isolated patches. It will readily be seen that
these conditions will give the direction of penetration great variations
and result in cavities of irregular forms. Some will spread widely just
beneath the enamel and produce a broad shallow cavity; possibly this
spreading may be in a particular direction, which, if the point of begin-
ning is on the side of the crown, is likely to be in a direction leading
around the tooth.
The penetration of the structure in the line of the tubules leads to
the exposure of the pulp, usually before great spreading has occurred.
Extended examinations show that in any considerable number of cases
in teeth of the best development exposure of the pulp will occur with
the least destruction of tissue; that is to say, that the more perfect the
development, the more completely the penetration is confined to the
direction of the tubules.
The effects of the softening of dentine by caries are different from
those observed in softening obtained by simple solution in an acid. If
a section of dentine is subjected to the action of a mineral acid, the
decalcification of its whole substance occurs; but there is a marked dis-
position to the isolation of the individual tubes by the more rapid solu-
768
DENTAL CARIES.
tion of the intertubular substance. In this way, by careful work, the
tubules may be isolated without any apparent enlargement of their inter-
nal calibre. The appearances are distinctly different in caries. It is
true that there is seen some disposition to the isolation of the tubules,
but at the same time the internal calibre is distinctly and markedly
enlarged; and this enlargement of the internal diameter is often, if not
most generally, such as to destroy the walls of the tubes before the dis-
solution of the intertubular substance, thus merging two into one, three
into one, etc., until the histological structure is lost. In many instances
this enlargement is seen to be quite regular, but in the greater number
of cases I have examined there has been a disposition to irregular swell-
ings or a more or less nodulated appearance of the individual tubes.
Among the different tubules there are also very great differences noted.
Some are very much enlarged, while others are but slightly changed.
In all of these a proper staining with an aniline dye will show that all
available space within the swollen tubules is occupied by micro-organ-
isms. This condition of enlargement does not occur until the tubules
are occupied by this fungus. As has been before remarked, the soften-
ing precedes the growth of the fungus, but the enlargement of the
tubules does not.
J
Gang
(gig
!
Very early in the progress of the softening the tubules present a
very peculiar appearance, in that the intertubular substance becomes
more clearly defined, and in such a way as to outline the tubular walls.
This appearance has been described by Tomes as similar to a multitude
of tobacco-pipe stems in cross-section. The effect will not be produced
by the solution of dentine in an acid, but is peculiar to caries as it
occurs naturally in the human mouth. In stainings made with chloride
of gold of sections of fresh dentine softened to a certain degree with
acids this appearance may be greatly exaggerated by the staining of
the walls of the tubules a bright red, while the intertubular substance
remains clear. It may also be shown in other ways that the inter-
tubular substance is different in some degree from the walls of the
tubules; but no satisfactory explanation of this peculiar appearance
in caries has yet come to my notice.
The penetration of enamel is distinctly different from the penetration
of dentine. This substance has not the natural openings that are cha-
racteristic of the dentine, and therefore does not present the same oppor-
tunities for growth of the fungus within its structure. It has been
held by most of those who have written on this subject that the fungus
is incapable of attacking enamel. If by the term "attack" is meant an
invasion or growth of the fungus into the substance of the enamel, this
view is correct. No signs of the fungus are to be found in the enamel
until after it has become so far disorganized that its crystals are loosened
and begin to fall apart. Except that of localization, and in some in-
stances discoloration, the softening of the enamel in the first stages of
caries presents no other phenomena than those produced on that. sub-
stance by acid action out of the mouth. In case this effect is rapid, the
enamel is seen to lose its transparency, and soon its crystals or prisms
show a disposition to fall apart in such a way as to give the impression
-
PHENOMENA OF CARIES.
769
that they have been separated the one from the other. This disinte-
grated material is easily removed from the surface in the form of a fine
dust, and upon microscopic examination is found to be composed of
short lengths of the enamel-prisms or rods. It seems that the acid has
the effect of dissolving the connecting substance which unites these
prisms or rods into a compact mass, and that the rods themselves are
dissolved more slowly. Thus the enamel first becomes porous, and
finally some of the rods fall away, leaving minute openings through its
substance by way of which the fungi of caries are admitted to the den-
tine beneath. On the proximal surfaces of the teeth, near the point of
contact, a portion thus softened may frequently be found; this may be
brushed away and the surface again polished, and show no opening
exposing the dentine. Other such cases may on careful investigation
show one or several openings of minute size through which the dentine
is exposed. After such exposure the enamel is undermined by the more
rapid softening of the dentine, which extends laterally under it. In this
condition the enamel is more or less disintegrated from its internal sur-
face. This disintegration presents precisely the same characteristics as
that occurring on the outer surface.2 In this way the enamel is grad-
ually destroyed through its entire thickness, or more often, by the more
rapid disintegration of the dentine beneath, is weakened and left unsup-
ported, and breaks away, leaving the opening into the cavity jagged
and irregular. In many instances of very rapid decay, however, espe-
cially if the enamel be very thick and strong, the carious process will
extend to a considerable distance under it laterally before breakage
occurs; and in this case the opening may be so small that the cavity
might escape detection but for a slight discoloration which is seen
through the enamel.
Discoloration in caries presents a wide range of variation. When it
occurs in the fissures, as in the grinding or buccal surfaces of the molars,
it is generally accompanied from its commencement by a dark color of the
enamel along the walls of the fissure. The carious dentine beneath may
be very dark; it may also be white, slightly yellowish, or of any shade
between this and a jet black. In caries commencing in the proximal
surfaces of the teeth, if the progress in the enamel be very slow or if
the process of softening has been only slight and then has ceased, the
surface of the enamel becomes very dark to a point as deep as the injury
to its structure extends. In many cases, however, particularly those in
which the progress is rapid, the surface of the enamel affected loses its
transparency, but remains white, or it may be even whiter than normal.
The rule, both in caries of enamel and in that of dentine, is that the more
rapid the progress of the disease the lighter the resultant color. But even
¹ As representing the histological elements of the enamel, the words prisms, crystals,
and rods have been used in a like sense by writers.
2 J. Tomes has described the solution of the enamel-rods as occurring first in the cen-
tral part of the rod. This appearance is often given in artificially-prepared specimens
in which a section has been momentarily exposed to the action of an acid. But in all
of my experiments in which sections have been exposed to the action of dilute acids
until the enamel-rods have fallen apart, it has seemed clear that the connecting sub-
stances were primarily dissolved, thus separating the rods. I have uniformly found
this true of carious softening.
VOL. I.-49
770
DENTAL CARIES.
where the mass of the carious contents of a cavity are light colored
there is often some discoloration about its margins. When the opening
into the cavity is hidden on the proximate sides of the teeth or under
cover of a deep fissure, the location of many carious areas is shown by
their color appearing through the enamel.
The discoloration of the carious parts does not seem to depend in any
degree on the carious process. It appears to be determined by the set-
tling of coloring matters into the partly-decomposed tissue. These
seem to be derived chiefly from the dark sulphurets formed in the
mouth by the action of sulphuretted hydrogen upon such metallic ele-
ments as may be present. This discoloration is easily and perfectly
imitated out of the mouth upon teeth that have been acted upon to
any considerable extent by acids. To accomplish this, place them in
water holding a small quantity of sulphuretted hydrogen in solution,
fill the vessel full, and place in the dark to prevent decomposition of
the solution; and the tissues of the teeth, to a point as deep as that
affected by the acid, will gradually assume a dark color. This fact,
taken together with the other fact that all rapidly-progressive cases of
caries are in color white or nearly so, especially in their inner parts-
leads to the supposition that the discoloration is in no wise dependent
on the agent that produces caries, but is borrowed from without. It
should be mentioned also that when caries has ceased or become station-
ary all of the injured tissue usually assumes a dark color within a short
time. The color of caries, therefore, affords some index to the rate of
progress. The lighter colors pertain to the more rapidly progressive
cases, and the very dark colors, those that are dark through the sub-
stance of the dentine, to cases that are stationary. The fungus is dead.
PREDISPOSING CAUSES OF CARIES.
The study of the predisposing causes of caries presents a wide range
for observation and speculation. Certain conditions manifestly predis-
pose the teeth to caries, and the manner of their effect is easy of explana-
tion. Other conditions seem to predispose to caries, while the manner
in which they act to that end is, with our present knowledge, not
demonstrable. Many conditions heretofore regarded as active causes
of caries must now be viewed as predisposing causes only, or as having
no relation to the affection.
ease.
Faulty formation of the teeth is probably one of the most effective pre-
disposing causes of caries. Yet in a more strict sense it cannot be
regarded otherwise than as a condition giving opportunity for the dis-
These faulty formations may be divided into two varieties of
deviation from the normal-those relating to form, and those relating to
structure, the latter of which, so far as they relate to the dentine, have
been considered in connection with the phenomena of caries. It seems
clear that an acid which will dissolve the lime salts of the teeth will do
so whether the formation be good or indifferent; for this faulty forma-
tion has relation not to the molecular or chemical composition of these
salts, but to the physical structure of the part. Density makes a
great difference in the rapidity of the solution, on the same principle
PREDISPOSING CAUSES OF CARIES.
771
舁
​that an acid capable of dissolving or decomposing very soft and porous
chalk will also decompose chalk of the most solid form. The latter
will, however be decomposed much more slowly than the former, for
the reason that the acid can act only on the surface, while if the acid
permeates the structure it will act much more rapidly. This is the
principle upon which the more rapid decay of the teeth of faulty struc-
ture must be explained. We may add to this the fact that in many
cases of faulty formation there is not so much of the lime salts to be
dissolved as in the denser structures.
On this principle it is clear that if in any case the structure of the
enamel is imperfect it will be more susceptible to injury by the agents
productive of caries than if it were perfect, and will be penetrated
where, under otherwise similar conditions, a perfect enamel would not;
at least, the time required to effect the penetration would be very differ-
ent in the two cases. The cause that acts on the one, however, will act
on the other only in less degree.
Imperfections of the enamel of the teeth are liable to occur in any
position. It has generally been claimed that they are especially liable
to occur on the proximal surfaces. My own examinations do not bear
out this idea. It is true that in the majority of cases the enamel is
somewhat thinner on these surfaces, but its structure seems to be just as
good as elsewhere, and its power to resist the corrosive action of acids
is the same, except that its thinness allows it to be penetrated more
quickly.
The faults in enamel which chiefly predispose to decay of the teeth
are those which occur in the form of pits and fissures. These combine
faults of structure with faults of form. They occur in the grinding
surfaces, and less frequently in the buccal surfaces of the molars, in the
grinding surfaces of the bicuspids, and in the palatine surfaces of the
incisors. Teeth of the best form and structure otherwise seem to be
most liable to this class of faults; especially those that are large and
the cusps of which are very prominent. In most of these cases it
seems that the growth of the enamel organ has not quite kept pace with
the growth of the dentine, or that there has been a want of correspond-
ence between the two in such a way that the last of the ameloblasts to
be calcified are pulled slightly apart, a fissure resulting as a consequence.'
¹I have carefully followed the formation of this class of faults in microscopic sec-
tions of growing human teeth during their entire period of development, and noted
especially the relations of the formation of the dentine and enamel from the beginning
to the end of the calcification of the crown. There seems to be an impression that the
entire crown of the tooth is formed before the calcification begins. This is an error.
The formation and calcification are in progress at the same moment, but as soon as a
part is calcified it ceases to change its form. This calcification begins on the summit
of the cusps, and at this time all of the form of the tooth that is unchangeable is rep-
resented in those points. The remaining parts of the tooth are not yet formed. Take,
for example, a bicuspid. The first hard tissue is the points of the cusps, and these lie
very close together, but do not touch. As growth proceeds they move farther apart
continuously until the form of the grinding surface of the tooth is completed. Now,
if there has been a strong growth of dentine, and the enamel is built thick and high
on the cusps, the breadth of the enamel-membrane is not sufficient to dip down perfectly
into the centre of the depression, and its cells are separated at the central point in such
a way as to leave a gap which is finally represented by a fissure. The principle of the
formation of the fissure is the same in all positions, and applies to the formation of pits
772
DENTAL CARIES.
This is occasionally so complete that a portion of the dentine is left
uncovered or with but a slight thickness of very imperfect enamel.
This is not always enamel in the true sense, in that it is devoid of
enamel-rods. It is probably composed of the same matter as the con-
necting substance between the enamel-rods, which, as we have found, is
easier of solution than the substance of the rods themselves.
This ease
of solution, however, is not the principal condition predisposing to
caries. The predisposition is found principally in the form-a pit or
groove, giving opportunity for caries by serving as a point for the
retention of particles of food, etc., until the process of fermentation has
created an acid which will act on the tissue. When it is once implanted
in them, these pits protect the fungus from dislodgment, thus favoring
its development, and little by little the enamel is dissolved out and
admission to the dentine gained.
The manner of contact of the proximal surfaces has much significance
in predisposing the teeth to decay. Those in which there is the great-
est amount of surface not self-cleansing are, other things being equal,
most liable to caries. Hence, teeth so formed that the proximal surfaces
are at all points very nearly in contact, yet without actually touching, are
rendered more liable to caries, provided the festoon of the gum does not
fill the space. When I analyze the conditions under which caries is
most liable to occur, I am convinced that this is of great importance,
and that caries generally does not occur while this space is filled by the
gum to the point of contact of the adjacent teeth. Two reasons may
be given for this: First, the festoon of the gum fills the space and
tends to prevent lodgments from occurring; second, the secretion given
out by the healthy gum, especially that coming from the gingival space,
is antiseptic to a sufficient degree to prevent fermentation of very slight
amounts of matter in immediate contact with it. Therefore, so long as
the gum remains healthy, decay does not begin in immediate contact
with its border. The breaking down of this septum of the gum by
the repeated forcing of food between the teeth or from other causes
becomes a predisposing cause of decay. I may add also that, without
becoming distinctly unhealthy, the gum sometimes recedes slightly from
between the teeth, and in this way predisposes the teeth to caries by
giving opportunity for its beginnings, in that a receptacle is formed for
the lodgment of particles which undergo fermentation in contact with
the teeth. Malpositions of the teeth, when of such character as to favor
such lodgments, also predispose to the beginning of caries; and in these
cases it is often shown that what is supposed to be the strongest enamel
will be penetrated if placed in such position that lodgments occur
against it.
Hereditary influences are very powerful predisposing causes of decay
of the teeth. This has been recognized by all who have examined the
subject. Indeed, this influence is too manifest to be overlooked by any
one who has given the subject close attention. It seems to me, however,
that it has in the past been by many much overrated, though it must
as well. It seems evident that the ameloblasts will allow of some spreading without
division one from the other, but this tolerance is limited, and in the later stages of cal-
cification the power of proliferation is reduced to the lowest point.
PREDISPOSING CAUSES OF CARIES.
773
be acknowledged as an important factor. Two separate factors enter
into the law of heredity in its relation to caries: one of these is capable
of demonstration; the other must for the present be regarded as an
hypothesis. The first is all told in the transmission of form. That
peculiarities of form are transmissible from parent to child is of course
generally held to be a truism, and requires only simple mention. As
has been seen in the previous pages, deviations from the best forms of
teeth are powerful in predisposing to caries. This element of heredity,
great as it is, is probably not the greatest. This does not furnish a
reason why one person may go through a long life without caries, while
much the greater number of his neighbors suffer from its effects. There
is undoubtedly something in the constitution of the fluids of the mouth
of different persons rendering them favorable or unfavorable to the
propagation of fermentation. Differences in the constitution of the
saliva of different individuals are sufficiently manifest. Some persons
have saliva which is exceedingly viscid or emits a peculiar odor, and
one or the other of these peculiarities is likely to be present in other
members of the family. This is also true of other fluids, as the per-
spiration. It is also true that the lower animals are subject to diseases
having their basis in the growth of micro-organisms to which men
are not liable, and vice versa. Men are but slightly susceptible to
anthrax, which makes such havoc among sheep and cattle in some
parts of Europe, while the lower animals are not subject to measles,
whooping cough, etc. Again, adults are usually insusceptible to
many diseases which prevail among children. In the present state of
our knowledge we can account for these differences only on the sup-
position that there are variations in the constitution of the cellular ele-
ments or fluids which render them in the one case unfavorable, and in
the other favorable, to the action of the cause of disease. It is only on
this supposition that a rational explanation can at present be founded.
There has been great endeavor to explain the tendency to caries upon
the basis of changes in the nutrition and structure of the teeth them-
selves. Certainly, there has been sufficient study of this point to
demonstrate that the predisposition is not explainable on this basis.
We must assume that in some cases the cause of caries is not present in
the mouth, or, if present, that it is too feeble to produce active results.
There is not a sufficient difference in the structure of the teeth them-
selves to account for the manifest differences seen in practice. Indeed,
the strongest and best-formed teeth often fall a prey to caries and are
rapidly destroyed, while in other cases teeth not nearly so good either
in form or structure are unaffected. When we examine the cause of
caries and the conditions of its activity, we are forced to the supposition
that the basis of these differences is in the environment of that cause,
affecting its activity, not in the power of the teeth to resist.
This holds a close relation to heredity as manifested in other diseases.
Of all diseases that are to-day regarded as hereditary, there is probably
not more than one (syphilis) directly transmissible from parent to child.
In all others the element of heredity must be in the constitution of the
cellular elements or the peculiar character of the fluids that in some way
renders the subject susceptible to the particular form of disease. If the
1
•
774
DENTAL CARIES.
special disease has as its basis a change in the physiological qualities of
activities of the cellular elements, as in the cancers, there is something in
the physiological constitution of the individual rendering the cellular
elements peculiarly liable to this form of excitement. If the particular
disease has a fermentation as its basis, the fluids of the individual must
furnish a favorable soil for the growth of the fungus of that fermenta-
tion. Again, persons acquire a temporary susceptibility to certain dis-
eases, not from a condition of ill-health that is in any way manifest,
but apparently through some minor changes, as yet impossible of anal-
ysis, in the action of the vital forces of the organism or constitution of
the fluids. If we can trust the combined observations of the profession,
changes that are of the same order certainly occur in the predisposition
to caries. Why is it that pregnant women become temporarily more
susceptible to caries? Certainly not from any change in the structure
of the teeth themselves, rendering their lime salts more easy of solution
by an acid. Of all the tissues of the body, the teeth are least prone to
structural changes consequent upon variations in nutrition, and there-
fore are least liable to temporary susceptibility to disease on that
account.
The saliva is certainly in a large degree antiseptic in its qualities, and
opposes the process of fermentation, notwithstanding the fact that fer-
mentation, in some of its forms, is continually in progress in the mouth.
It is practically impossible to protect wounds of the mouth from micro-
organisms, yet these wounds are less liable to sepsis than any others in
the organism that are exposed to external influences.
It is possible that what have been noted as the antiseptic qualities of
the saliva as seen in its relation to wounds in the mouth may be due
to the continued irrigation of the surfaces by the flow of fresh saliva,
which washes away septic organisms or their products. This in a large
degree explains the occurrence of decay in protected points only, and fur-
nishes a reason for the rare occurrence of caries in the lower incisors.
When all of the facts known to us are considered, the most plausible
supposition is that there are differences in the saliva that in some cases
render it an unfavorable soil for the propagation of the peculiar fermen-
tation found to be the cause of caries. In other cases it becomes a very
favorable soil for the growth of this peculiar fungus, and caries is cor-
respondingly active. When we look around us and gather together the
facts at our command in regard to the susceptibilities of those forms of
life which we know, and see how they affect each other in ways that seem
inscrutable, these suppositions, while losing none of their mystery, are
seen to be in harmony with those forced upon us in other fields of
observation.
MORBID CONDITIONS OF THE FLUIDS OF THE MOUTH.
By most authors who in the past have examined the subject morbid
conditions of the saliva and of the mucus of the mouth have been con-
sidered as among the active causes of caries. In view of the expla-
nation given in the previous pages, this becomes impossible. If the
causes of caries have been correctly detailed, the influences favorable to
MORBID CONDITIONS OF THE FLUIDS OF THE MOUTH. 775
caries exerted by the morbid conditions of the saliva must be subordi-
nate or secondary, in that they furnish a better soil for the promotion
of fermentation or assist in decomposition by virtue of the acid they
may contain. The first of these influences has been considered under
the head of Heredity. That the fluids of the mouth often contain acids
in a very dilute form, but sufficient in amount to be readily detected by
litmus-paper, is well known to all who have given attention to the sub-
ject. This acid, whatever its origin, is distributed generally in the
fluids. There is no localization demonstrable by our present modes of
research, except it be that the mucus exuded from the gum in a state
of irritation is more markedly acid than the other fluids. This latter
point, as it affects only special cases, will be examined later.
Some years ago very extended examinations of the fluids of the
mouth were made with reference to acidity and its possible connec-
tion with caries. I made personal tests in several thousand cases.
These gave rather complex results, but in the main seemed to demon-
strate that the two conditions were in no wise connected as cause
and effect. So decided was this that, while I went into the series of
observations with a conviction that Tomes, Magitot, and others were
right in attributing caries to this cause, I retired with the belief that,
whatever be the cause of caries, it has little or no connection with
acid saliva. In many the tendency to caries was not in any degree
related to the degree of acidity of the fluids of the mouth. In an article
which I wrote in 1880, after this series of experiments, these sentences
Decay of the teeth is certainly a specific disease, running a
specific course, and evidently arising from a specific cause, but this
cause is not as yet certainly known."
"While there is no decay
without the presence of an acid, there is not necessarily decay because
of the presence of an acid." "While an acid is not only always
present, but is probably a necessity to the inception and progress of
decay, there may be an agent acting in conjunction with the acid that
is not yet known or recognized."
66
occur :
991
Now, after the demonstration of the cause of caries by Dr. Miller,
which represents the unknown in these sentences, we are able to analyze
the probable effects of morbid conditions of the fluids of the mouth more
closely than before, especially after studying the microscopic phenomena
in the light thrown upon them by the demonstration of the cause. It
is now perfectly clear that acids alone, while they may decalcify the
teeth, cannot produce the phenomena of caries. Dr. Mayr has well
said: "The decay under consideration is so specific that the mere action
of acids is not sufficient to produce it.' The occurrence of micro-
organisms in, and the widening of the calibre of, the tubules is a prom-
inent manifestation without which the presence of caries, no matter
what the amount of softening, may confidently be denied. This has
now been confirmed by so many observers that it has become a truism
and after the studies of the physiology of this fungus cited in the pre-
vious pages we have no need to go to the fluids of the mouth to find
the acid. It is developed in situ. Acids that are commingled with the
fluids of the mouth, whether developed therein or introduced from with-
1 Independent Practitioner, 1884, p. 195.
;
·
776
DENTAL CARIES.
out, cannot produce caries. There is no reason why an acid commin-
gled with the fluids of the mouth should exert a localized action on the
teeth. Their action would be general, and greatest on the exposed sur-
faces. It is not impossible that some such effect is produced—indeed,
I have seen evidence that such is the case-but this does not seem to
have any relation to the localized action which represents the inception
of caries.
Acid mucus occurs under circumstances that seem in certain cases to
connect it with the inception of caries. These are those forms of the disease
which occur near the margin of the gum in connection with points of
irritation. In irritations of the gum-tissue there often arises a markedly
acid condition of the mucus exuded at that spot. This has been espe-
cially noted by Tomes and Magitot, and is regarded by them as a direct
cause of decay of the teeth. I cannot, in the light of recent develop-
ments, regard it as a cause of caries proper, but it may be productive
of a softening of the tissue at that point or an actual solution of the
lime salts, which will give the opportunity for the implantation of the
agents productive of fermentation and caries. Certainly, observation.
seems to connect local irritations of the gingiva with a certain propor-
tion of that form of caries beginning about the necks of the teeth; and
it is sufficiently demonstrated that under these circumstances the mucus
is markedly acid. It should be noted, however, that in these cases the
irritation is not of such a character as to be productive of pus. All
observation shows that pus, wherever it occurs, is directly preventive
of caries. If under any circumstances pus is continuously discharged
into a cavity of decay, the decay ceases. This furnishes a reason
why roots of teeth protruded through the gum, and thus exposed,
so seldom decay. There is generally an irritation of tissue in their
neighborhood sufficient to keep them more or less bathed in pus. This
is also noted in case of roots which have lost their crowns, and the gum
of which is in such a condition as to keep its broken end bathed in pus;
also in some cases in which chronic alveolar abscess discharges into a
cavity through the pulp-canal. This affords a condition of environ-
ment that is markedly opposed to caries; and, though pus is dis-
tinctly different from saliva, it is still an evidence of the possibility
-we may say the probability-that changes in the constitution of the
saliva may occur that will render it unfavorable to the propagation of
}
caries.
G
There is another form of acid mucus that seems to be distinctly differ-
ent from that produced by irritation of the gums, in that no irritation is
apparent and the condition is more or less permanent. In some cases it
seems to be hereditary. It may, however, be acquired. In this condi-
tion the mucus seems much indisposed to mix with the other fluids of
the mouth. It is more viscid than normal, and may be drawn out in
long threads by touching the finger to the gums and withdrawing it. I
have seen cases in which these threads could be extended to the arm's
length before they would break. This character of the mucus has been
noted by a considerable number of writers, and seems to have been
regarded as an active cause of caries. It certainly appears to furnish a
condition favorable to the propagation of the disease, for in most of the
MORBID CONDITIONS OF THE FLUIDS OF THE MOUTH. 777
cases that have come under my observation caries has existed, and has
been severe and usually difficult of successful treatment.
Absorptive processes stand in such close relation, clinically, to the
production of acid mucus from points of irritation, and the results,
when slight, are so similar, that it is difficult to discriminate between
them. I have reference here to absorptions just beneath the margin of
the gum or at the point of union of the soft tissue with the tooth, con-
sequent upon some slight irritation. This is a factor in the predispos-
ing causes of caries that has not until recently had recognition.' This
absorption is in all respects similar to that which occurs at the roots of
teeth which have been transplanted, and, like that, is dependent on a
slight irritation of tissue, through which irritation it is caused to tempo-
rarily take on a new function-that of the production of a substance
which dissolves the hard structures with which it is in contact, making
room for the growth of its own granulations.
The phenomena of absorption may be studied in a variety of positions
and circumstances. Wherever observed, we find very much the same
conditions in the tissue involved. This is true whether it be in the
removal of the root of a temporary tooth, removal of bone in change of
form (physiological), removal of the roots of replanted teeth, burrowing
into pieces of ivory that have been thrust into the flesh for the purpose
of experiment (Krause, Koelliker, Tomes), removal of sponge in the
sponge-graft, or the absorption of the surgeon's animal-membrane liga-
tures (pathological). In all cases granulation-cells or leucocytes are
brought in contact with the substance to be removed, under the influ-
ence of which it gradually disappears. (In the physiological absorption
of bone the osteoblasts have been regarded as performing this function.)
Just what the cellular action is in these cases is not at the present time
positively demonstrable. But that the substance which effects the solu-
tion is of the nature of an unorganized ferment seems almost certain.
Krause suggests that it contains lactic acid. At any rate, the granula-
tions invade the tissue gradually, and room is made for them by its dis-
appearance. In this way the part is burrowed out, whether it be bone,
tooth-substance, catgut, or sponge, and the granulations fill the space.
In all cases of pathological absorption it is fairly demonstrable that the
action is in response to an irritation or excitement of a mild character
of the cells of the part in which leucocytes are formed or called and pro-
ceed to the building of granulations. If in any case the irritation is of
such intensity that pus is formed, the process of absorption fails. As
the part of the tooth acted upon rises above the soft tissues, this in time
becomes dark colored; and if it be on a smooth, self-cleaning surface
not too deep, no decay results. If, however, the process of absorption
has produced excavations sufficiently deep to afford lodgments and thus
give the opportunity for fermentation, the result is the formation of a
cavity by true caries. Then these absorptions are not a direct cause of
decay, nor are they caries in themselves; but they give the opportunity
for the implantation of true caries, and are therefore a predisposing
cause.
C
Prof. W. H. Eames of St. Louis has described certain effects upon
¹ Formation of Poisons by Micro-organisms, 1884, Black.
778
DENTAL CARIES.
the crowns of teeth as the product of absorption brought about by the
absorbent organ, so called, which removes the root of the temporary
tooth or effects the liberation of the permanent tooth in the process of
its eruption through the gums.¹
1
Cervical absorptions (absorptions at the necks of the teeth) are gener-
ally very small affairs which before caries results are liable to be over-
looked; indeed, heretofore they have been altogether unnoticed. They
occur about the necks of the teeth after the age of maturity or late in
life. As the irritation proceeds there is often a tendency to the short-
ening of the gingival margin, in such a way as to expose more of the
neck of the tooth. In this manner the injury becomes exposed, and caries
is implanted. In many cases the irritation causes a thickening and
eversion of the gum in the form of a little pocket; caries is induced,
and proceeds to the formation of a cavity. This is oftenest seen on
the buccal surfaces.
G
ever,
I have said that cervical absorptions are generally slight. This, how-
is not always the case. I have in my possession several specimens
in which they are very large, having destroyed a large part of the crown
of the tooth. In one of these, a lower molar, the pulp-cavity was laid
open. The granulation-tissue which filled the space was still in the
cavity formed, and came away with it when it was extracted, giving
me the opportunity for a close inspection. This, however, shows no
differences from the absorptions in general. In another lower molar
the larger part of the crown was destroyed, and the posterior root
separated from it by granulations that seemed to have grown in
from the gum at the posterior border. Cavities formed in this way
differ from those formed by caries, in that there is very little softened
tissue; and this does not present the phenomena of caries, but those
of absorptions of the roots of the permanent teeth.
+
Clinically, it is almost impracticable to divide these effects when slight
from those supposed to be produced by acid mucus. There is a similar
irritation of the gum, and the general appearances are very closely allied
as to the effects upon the tooth-structure. They occur at very nearly the
same points on the surfaces of the teeth, so that after the occurrence
of caries the one cannot with certainty be told from the other. The
results of acid mucus, however, are always distinctly below (toward the
crown) the margin of the gum, while cervical absorption is always at
a point in contact with the gum and covered by it.
Diseases of various sorts have been regarded as predisposing to caries
of the teeth, and many observations tend to confirm this supposition.
In some of the continued fevers there is an acid condition of the scanty
saliva continuing for days and weeks together; and it is not uncommon
to find a number of carious cavities making their appearance a short
time after convalescence, as has already been explained. The distribu-
tion of the acid saliva is general, and its effects should be seen, if at
all, on the teeth generally, not localized. A more probable explana-
tion of these phenomena is to be found in the fact that through neglect
for so long a period to remove lodgments fermentation in the interstices.
about the teeth has been allowed to go on unobstructed. This applies
¹ Transactions of the Illinois State Dental Society, 1884.
Grad
CLINICAL HISTORY OF CARIES.
779
to all forms of disease that interfere with the usual motions of the
mouth or with the usual care of the teeth. There is no sufficient evi-
dence that diseased conditions give rise to changes in the teeth them-
selves that render them more susceptible to caries.
There is, however, sufficient proof that a predisposition to caries is
often acquired in cases where it did not exist in early life or is not
transmitted as a hereditary predisposition. As explained in connection
with the subject of heredity, the supposition that some change in the
constitution of the saliva renders it a more favorable soil for the prop-
agation of fermentation is the only hypothesis which, with our present
knowledge, seems tenable. This explanation applies to variations in the
constitution of the fluids brought about by temporary deviations from
health, as well as more lasting changes.
CLINICAL HISTORY OF CARIES.
Under this caption it is intended to study caries of the teeth as it
appears clinically, laying aside the consideration of its etiology and
microscopic features except as incidental references.
Caries has pretty definitely fixed habits as to its points of beginning,
and one of its most notable characteristics is that it never attacks a
tooth on a surface that is smooth and is constantly kept worn and
clean by the attrition of mastication or the friction of the tongue,
lips, or cheeks. All such points are absolutely exempt from attack.
The points on the surface of the teeth at which caries has its begin-
nings may conveniently be divided into four classes, according to the
character of the surface:
Class 1st. Pits and grooves in the enamel;
Class 2d. Proximal surfaces;
Class 3d. Smooth surfaces which from any cause are habitually
unclean;
Class 4th. Necks of the teeth, at or near the junction of the cemen-
tum and enamel.
These classes of caries have different characters peculiar to these posi-
tions, and which are of considerable importance in a clinical sense.
The first class is, in a large majority of patients presenting_themselves
for dental operations, the earliest to make its appearance. It occurs in
the pits and grooves in the enamel wherever found-in the molars, in
the corrugations of the grinding surface, and in the groove or pit which
is often present in the buccal surface; in the bicuspids, in the groove in
the grinding surface or pits that often occur at either end of this groove;
in the upper incisors, in a pit or groove often present in the lingual sur-
face; in any pits, grooves, or imperfections resulting from faulty forma-
tions or arrest of development in any position in the surface of any of
the teeth.
C
The occurrence of this class of decays is dependent principally on the
opportunity given for fermentation at these points by the depth of the
pits and grooves in the several teeth. This is modified by the individ-
ual predisposition to caries. In the child this latter may be inferred
after having learned the condition of the teeth of the parents. If caries
780
DENTAL CARIES.
begins early in these positions, it may or may not be marked by a dark
color of the pit or groove. If, however, a beginning is delayed for from
five to ten years after the eruption of the tooth, a dark color is usually
present. The enamel in this position is very thick and heavy, and the
pit or groove often penetrates it more or less completely; so that caries
apparently does not begin on the outside, but in the depths, of the pit,
from which it spreads under the strong enamel to a considerable extent,
and often penetrates the dentine deeply before giving any sign, especially
in children where the dark color is not present as a warning.
This is
often shown by an ashy-gray color seen through the enamel. In older
patients this color is more generally dark.
This type of caries often appears very soon after the eruption of the
tooth; the first to appear in the permanent teeth are usually in the first
molars. These cavities occur in about 25 per cent. of first molars, or
an average of one to every patient who applies for dental operations.
(My charts, which are presented on pp. 782-785, are constructed from
my records of fillings, and teeth extracted are not taken into account.
This in some degree vitiates the result. First molars are extracted in
larger proportions than other teeth; therefore the numbers given in the
text are probably too low.)
In the main, there is a considerable degree of correspondence as to
time in the beginnings of caries in the pits of the several teeth, pro-
vided these pits are about equal in depth and form; so that in the reten-
tion of foreign matter they will be about equal. For instance, if decay
occurs in the first molar at eight years, or two years after its eruption,
decay may be expected in the pits of the second molar about fourteen,
the corresponding period in the age of the tooth or time after its erup-
tion. It will be seen that if the conditions are the same the same time
will be required to produce a cavity, and observation shows that in the
majority of cases this is true clinically. The second molars, however,
show only about 15 per cent. of decays in the pits, or only a little more
than half as many as the first molars. This is probably due to the fact
that the pits are generally not so deep. This is also true of the bicus-
pids and incisors; and in these teeth (the pits are very often absent) the
decays are much fewer in number. The time of their occurrence may
generally be reckoned by the rule given above; but it will be noted
that in those teeth in which decay is more rare the age at which it
occurs is somewhat greater. This, however, is probably not true of the
pits of the incisors. These occur only in a small proportion of cases;
but if very pronounced, they decay at about the same time as, or a little
later than, those in the first molars. The wisdom teeth often decay
much sooner after their eruption than the other teeth. This is ex-
plained by the fact that there is often a long period of irritation of the
tissues by which they are surrounded during their eruption, and that
they are injured by absorptive processes or by acid mucus.
If they
escape this that is, if they come through the gum readily-they decay
relatively later than any other teeth. The reasons for this will appear
subsequently.
The second class, or proximal decays, in cases in which the predisposi-
tion is marked, are as a general rule a year or two later in their appear-
CLINICAL HISTORY OF CARIES.
781
ance than the first class, and also follow pretty closely the order of the
eruption of the teeth. But if in the individual case the predisposition
to caries is but slight, they will usually be several years later in their
appearance. In this class there is often an exception in the mesial sur-
faces of the first molars, which frequently very soon after their erup-
tion are infected from a close contact with a carious surface on the
second milk molar. The importance of this class of carious cavities ist
evident from the fact that they outnumber all others combined in the
ratio of about 3.38 to 1. (This is the result given in Charts Nos. 1 and
2. In these it is probable that the number of cavities indicated in the
proximal surfaces of the bicuspids is too large, on account of the number
of adults who require refilling of these cavities. Refillings in cavities
previously filled by myself have been carefully eliminated, but cavities
previously filled by others have not been designated in my records.)
Occurring on smooth surfaces of the teeth, where the enamel is gener-
ally fairly good and free from pits, they are somewhat slower in their
beginnings than those of the first class, probably because the penetration
of this enamel is more difficult. But the position offers the best advan-
tages for lodgments and fermentation, and the conditions for this are
more constantly present than in any of the other positions in which
caries has its beginnings. In some examinations of the skulls of the
older Indian races made a few years ago I found that they presented a
very much larger proportion, comparatively, of this class of caries than
our own people. Where the predisposition to caries is less, this class
will be found in greater relative proportion, and the cavities will appear
later in life. The ratio in which they occur on the individual surfaces
of the several teeth is displayed in the charts.
The beginnings of this class of cavities are very much hidden. The
special point at which a great majority of them occur is just above
(toward the root of the tooth) the point of contact of the teeth, where
the cavity cannot be seen. If observed closely at the right time, a very
minute opening, or it may be several openings not far apart, will be
found, the enamel about these being softened through the greater part
of its thickness, and generally injured for a space on either side. There-
fore, in preparing small proximal cavities for filling, very wide cutting
is required to remove all of this injured enamel. Very often-gener-
ally, I may say, unless revealed by a delicate exploring instrument-
the first discoverable trace of these cavities is a discoloration which
shows through the enamel of the crown. In young persons this has
usually an ashy opacity, but in older persons it is likely to be dark.
When this appears, caries has made considerable progress in the dentine.
It is not very unusual for the pulp to become exposed before the patient
is aware of the existence of a cavity, the evidence of which, in molars
and bicuspids, is often first made known to the patient by the sudden
breaking down of the undermined enamel of the crown, toothache fre-
quently following, from compression of the exposed pulp. Of the four
classes of caries this is by far the most destructive.
The third class comprises but comparatively few cases.
These are,
for the most part, seen on the labial surface of the incisors and buccal
surfaces of the bicuspids and molars. (This and the fourth class are
782
DENTAL CARIES.
3RD.
MOLAR
0.7
0.0
7.0
1.4
DHE
DISTAL
PALATINE
GRINDING
BUCCAL
MESIAL
DISTAL
11.2
2.1
22.
2ND.
MOLAR
PALATINE
GRINDING
4.5
0.0
14.5
1.2
2.2
6.2
OCOC
47.5
1ST.
MOLAR
BUCCAL
MESIAL
DISTAL
PALATINE
GRINDING
BUCCAL
MESIAL
ΤΟ
FIG. 403.

44.0
24.0
7.2
16.0
17.0
2ND.
BICUSPID
0.2
6.7
4.0
40.6
* * * Trade -
Number of decays in all Surfaces
> ** ** ****, and our ma vaan ve da
1ST.
BICUSPID
16.1
20.0
O.I.
31.0
**** ***
A
CUSPID
DISTAL
PALATINE
GRINDING
BUCCAL
MESIAL
DISTAL
PALATINE
GRINDING
BUCCAL
MESIAL
DISTAL
PALATINE
INCISIVE
BUCCAL
MESIAL
DISTAL
PALATINE
INCISIVE
BUCCAL
MESIAL
6.6
1:3
12.6
II.0
0.6
1.8
47.0
1.6
LATERAL
INCISOR
UPPER JAW.
CHART No.'l,
16.0
15.5
0.6
1.3
1.6
28.0
26.3
65.2
CENTRAL
INCISOR
DISTAL
PALATINE
INCISIVE
BUCCAL
MESIAL
Surface
2.6
1.5
3.2
31.6
^^
to
15
20
25
DESCRIPTION OF CHARTS.
These charts
represent
the
persons,
and
the
posi-
number of carious cavities observed in one hundred
tion of these cavities on the individual surfaces of the teeth. There are five columns of squares
devoted to each tooth of one side of the mouth, representing the five surfaces as shown on the left
hand. The number of cavities in the surface represented is shown by the number of squares dark-
ened, so that the effect of the diagram as a whole gives a striking picture of the frequency of decay
in the individual surfaces of the several teeth. On the right the percentage, or the number per hun-
dred persons, is given in figures calculated to the first decimal point. On the left the percentage of
cavities in the individual teeth for all surfaces is given in the same way. The cavities occurring on
30
35
CLINICAL HISTORY OF CARIES.
783
3RD.
MOLAR
DISTAL
LINGUAL
4 de ❤
18.0
GRINDING
BUCCAL
MESIAL
43.0
2ND.
MOLAR
1
3,900
43.3
1ST.
MOLAR
FIG. 404.

23.3
2ND.
BICUSPID
13.5
1ST.
BICUSPID
DISTAL
LINGUAL
GRINDING
BUCCAL
MESIAL
DISTAL
LINGUAL
GRINDING
BUCCAL
MESIAL
DISTAL
LINGUAL
GRINDING
BUCCAL
MESIAL
DISTAL
LINGUAL
GRINDING
Number of decays in all Surfaces
6.5
CUSPID
7.0
LATERAL
INCISOR
BUCCAL
MESIAL
DISTAL
LINGUAL
INCISIVE
BUCCAL
MESIAL
DISTAL
LINGUAL
INCISIVE
BUCCAL
MESIAL
0.0
0.8
1.7
LOWER JAW.
CHART NO. 2.
2.0
3.7
0.0
6.0
CENTRAL
INCISOR
DISTAL
LINGUAL
INCISIVE
BUCCAL
MESIAL
Surface
Ст
2.8
0.0
0.5
0.7
2.0
5
10
15
20
25
RROTAARE TOGOftÈreateDoNTER
surface is counted;
one side of the mouth only are represented. And only one decay in an individual
that is, if two or more pits are found decayed in the grinding surface of a molar, but one is counted;
and the same rule is followed with all of the other surfaces.
30
35
Charts No. 1 and 2 (upper and lower jaw) are made up from my records of fillings for 628 persons of
all ages, and therefore represent what is seen in practice rather than the actual number that may
occur.
Charts No. 3 and 4 (upper and lower jaw) are made from 100 of my own patients between the ages
of ten and twenty-five years, for whom I have filled all cavities and know the condition at present.
They represent the actual number of cases in which the individual surfaces have decayed in these
100 persons.
}
784
DENTAL CARIES.
FIG. 405.

I
umber of decays in all Surfaces 57.5
CHART NO. 3.
UPPER JAW.
niên làm vào tình hình tà THIÊN HÀ
-
•
2000!
43.5
****
11.0
24.0
•
25.0
38.0
17.5
6.0
CENTRAL
INCISOR
LATERAL
INCISOR
CUSPID
1ST
BICUSPID
2nd.
BICUSPID
1ST.
MOLAR
2ND.
MOLAR
3RD.
MOLAR
Surface
MESIAL
BUCCAL
INCISIVE
PALATINE
DISTAL
MESIAL
BUCCAL
INCISIVE
PALATINE
DISTAL
MESIAL
BUCCAL
INCISIVE
PALATINE
DISTAL
MESIAL
BUCCAL
GRINDING
PALATINE
DISTAL
MESIAL
BUCCAL
GRINDING
PALATINE
DISTAL
MESIAL
BUCCAL
GRINDING
PALATINE
DISTAL
MESIAL
BUCCAL
GRINDING
PALATINE
DISTAL
MESIAL
BUCCAL
GRINDING
PALATINE
DISTAL
5
ΤΟ
15
20
25
30
33
33.0
3.5
.5
5.0
17.5
28.5
2.5
.5
3.0
9.0
7.5
.0
.0
.0
3.5
6.5
.0
3.5
.0
14:0
8.5
.5
7.0
.0
9.0
6.0
1.5
24.5
.0
6.0
5.0
.5
10.5
.0
1.5
.0
1.5
4.5
.0
.0
CLINICAL HISTORY OF CARIES.
785
FIG. 406.

CHART NO. 4.
LOWER JAW.
Number of decays in all Surfaces
الاناء
#
********❤❤❤⇓⇓⇓⇓⇓ we the du m«
•
6+
it
+
5.0
5.
3.0
4.5
15.0
45.0
22.0
4.5
·******
CENTRAL
INCISOR
LATERAL
INCISOR
CUSPID
1 ST.
BICUSPID
2ND.
BICUSPID
1ST.
MOLAR
2nd.
MOLAR
3RD.
MOLAR
Surface
MESIAL
BUCCAL
INCISIVE
LINGUAL
DISTAL
MESIAL
BUCCAL
INCISIVE
LINGUAL
DISTAL
MESIAL
BUCCAL
INCISIVE
LINGUAL
DISTAL
MESIAL
BUCCAL
GRINDING
LINGUAL
DISTAL
MESIAL
BUCCAL
GRINDING
LINGUAL
DISTAL
MESIAL
BUCCAL
GRINDING
LINGUAL
DISTAL
MESIAL
BUCCAL
GRINDING
LINGUAL
DISTAL
MESIAL
BUCCAL
GRINDING
LINGUAL
DISTAL
5
10
15
20
25
30
35
3.0
.0
.0
.0
1.0
1.5
.0
Gööö ü ü öööû
3-5
.5
1.5
1.0
1.0
.0
1.0
4.0
.5
5.0
.0
5.5
8.0
6.0
27.5
.0
3.5
2.5
2.0
15.0
.0
2.5
.5
1.0
3.0
.0
.0
VOL. I.-50
786
DENTAL CARIES.
not distinguished on the charts, being mixed with others that appear on
the same surfaces.) In the incisors their beginning is usually marked
by the dark color of the enamel near the gum. This face of the tooth
is habitually gummed over with half-dried mucus and débris, thus giv-
ing opportunity for fermentation and caries. Inquiry will generally dis-
close the fact that the person habitually sleeps with the mouth open,
this often being traceable to some obstruction in the nasal passages.
These cavities occur chiefly in persons under eighteen years of age,
and not unfrequently before the twelfth year. In the bicuspids and
molars this form of decay also occurs, and apparently from habitual
uncleanliness, which, however, does not seem to be traceable to the
same causes.
The fourth class is always accompanied by a diseased condition of
the gums. They have their beginnings very close to the margin of the
gum, or even beneath it, just at the junction of the enamel and cement.
The gum, however, is usually everted or shrunken from the neck of the
tooth before caries proper is demonstrable. The manner of the begin-
ning of these cavities has been described in the consideration of acid
mucus and absorptions in their relations to caries. They do not often
occur in children, but are generally seen in middle life or old age. In-
deed, this form of caries may almost be said to be the only type that
attacks elderly persons. Occasionally it wrecks a denture after danger
from the other classes of caries has long since passed.
The characteristics presented by caries of the teeth in individual cases
are of great importance in the clinical sense. The rule is that if, after
beginning in a tooth, the caries advances rapidly, it will do so in all
other cases occurring in that individual. If it is seen to proceed slowly
in the teeth first attacked, its progress will be slow in those that are
attacked later. This may be denominated a characteristic observed in
individual cases. It must be noted, however, that the number of
beginnings of caries hold but little correspondence to the progress after
a beginning has been made. In some cases decay commences early in
a few teeth only, and they are very quickly destroyed; in other cases
the individual teeth are attacked at intervals of considerable duration,
and in each case are quickly destroyed. It is not uncommon in the
examination of cases in which there have been no dental operations to
find that several teeth have been destroyed by caries, while all the
others have entirely escaped, or that in a very few others decay has
begun and is running the same rapid course. In another series of indi-
viduals an opposite condition will be found. Several carious cavities.
may have formed, while very few of them have progressed so far as to
do serious injury, continued observation showing that they are still
making comparatively slow progress. In other cases very few cavities
will be found, these few remaining almost stationary.
Thus it will be seen that caries in individual cases presents special
characteristics in reference to the liability to the beginning of decay, and
also as to the progress of that decay after the beginning has been made.
As these characteristics are combined in each individual case, they may
be formulated as follows:
First Characteristic: Many decays start and progress rapidly.
Andy
CLINICAL HISTORY OF CARIES.
787
Second Characteristic: A few decays start and progress rapidly.
Third Characteristic: Many decays start and progress slowly.
Fourth Characteristic: A few decays start and progress slowly.
These characteristics seem to be dependent on two conditions and
their opposites-namely, the activity of the cause of caries in the indi-
vidual case, and the opportunity presented for attack by the condition
of the surfaces of the individual teeth. If the cause of caries be active,
if the condition of the fluids of the mouth be such as to favor it, caries
that has gained a start will progress rapidly to the destruction of the
tooth. After the causative agent is once implanted in the dentine,
the circumstances giving or withholding opportunity no longer affect
its progress.
This progress may be modified by one of two influ-
ences or by both-namely, by the condition of the fluids penetrating
the cavity, and by the condition of the tissue being destroyed. The
latter modifying influence occurs only in individual cases in which the
dentine is of faulty formation, which abnormality has been sufficiently
described in connection with the phenomena of caries. The principal
condition modifying the general rate of progress of caries is the state of
the fluids entering the cavity. It will be seen, from the studies con-
tained in the preceding pages, that the food-material upon which the
fungus must depend for its acid-producing power, and without which
caries cannot progress, is not found within the dentine, but must be
absorbed from without. This circumstance is of much importance in
this connection-not from the probability that this food-material is
likely to be scarce in the buccal fluids, but as showing the dependence
of the active agents in the production of caries upon the fluids external
to the cavity.
G
J
The beginnings of caries are dependent largely on those predisposing
causes that give opportunity. Without the presence and activity of the
cause there can be no caries; and the degree of that activity will tend
to modify the number of cavities, because a certain degree of action will
be sufficient to make a breach under conditions in which a less degree
of activity would fail. This is not the principal circumstance modify-
ing the beginnings of caries; for if it were, we would not see those
cases in which one or two teeth have been quickly destroyed, while
the others have escaped altogether. The principal circumstances giving
opportunity for the beginnings of caries are unfavorable forms of the
teeth and habits of uncleanliness. This is illustrated by the tendency
of carious cavities to occur in pairs on certain surfaces of similar teeth
on opposite sides of the mouth, where the form is presumably the same.
The predisposing conditions due to faults of form giving opportunity
for the beginnings of caries have, however, been sufficiently discussed
on a previous page, to which the reader is referred.
These characteristics are seen in every possible degree of intermixture
and affect all classes of caries. I have seen some cases in which the
teeth seemed to have been attacked in every possible position, and rap-
idly destroyed, very soon after emerging from the gun. In these cases.
the condition of the fluids of the mouth is certainly such as to favor
that process of fermentation which is the basis of caries, and the forms.
of the teeth are of a kind to favor the beginnings at numerous points. It
788
DENTAL CARIES.
!
is doubtful, however, if any formation or structure of the teeth, be they
ever so perfect, could withstand the conditions present in such cases.
The activity of the processes calculated to decompose them is so ener-
getic that the strongest teeth would be destroyed in a short time. The
worst cases I have seen were those of two Swedish girls, twin-sisters,
eighteen years old, who came to me for advice a few years ago. In
these most of the teeth, including the lower incisors, which are SO
generally exempt from caries, were already decayed to the gums, and
those that still retained a portion of the crown were attacked at from
one to four points. Fortunately, such cases are rare. With this as the
worst representative of the beginnings and the destructiveness of caries,
we might give cases illustrating all forms of gradation, down to a case
in which an individual tooth shows a dark spot indicating that at some
time in the past the products of fermentation had injured the enamel.¹
Caries of the teeth is essentially a disease of youth (compare charts).
This is especially the case with the first and second classes of caries,
which comprise the great mass of cases. It is a notable fact that the
predisposition to caries diminishes as age advances. It is usually
strongest in childhood or youth, and the greater number of cavities
have begun at the age of eighteen. Very nearly all of the first and
second classes have begun before the age of twenty-five. Perhaps
there is more than one reason for this. If we suppose that the dis-
position to caries remains the same, it is presumable that at the age of
twenty-five years all points favorable to the beginnings of decay have
been attacked. All except the wisdom teeth have for a dozen years or
more been exposed to the agents productive of caries; and if beginnings
have not been made within this time, it is presumable that they will not
be made unless there is some change in the conditions. This is prob-
ably the principal condition of the cessation of the beginning of new
¹ Some years ago I proposed the terms vis inita (beginning power), from vis, power,
force, and ineo, to begin; and vis deleta (destroying power), from deleo, to blot out, to
destroy, to represent these characteristics. These terms may readily be used for the
purpose of expressing the conditions in any given case, and for this purpose I asso-
ciate with them numbers to show the degree of the special characteristic. The follow-
ing gives the extremes of the possible combinations:
Vis inita 1, combined with vis deleta 1 to 100.
Vis deleta 1, combined with vis inita 1 to 100.
These may be used in the description of cases for the purpose of the more ready and
accurate representation of the facts that may exist or of the conditions observed, without
reference to the causes which may be supposed to underlie these effects. For instance,
in describing the conditions found in case of the two Swedish girls spoken of in the text,
I should say there was present vis inita 100 and vis deleta 100. This expresses my
conception of caries of the worst characteristics or the most violent form in which it
is manifested. In a case in which a medium number of decays made their appear-
ance, and each of these was running a very rapid course to the destruction of the teeth
attacked, I would represent it as vis inita 50, vis deleta 100. In another case, in which
a medium number of beginnings of decay was apparent, and these presented rather a
dark color and showed other characteristics indicating that the progress was rather
slow and yet decided, I would state it as vis inita 50, vis deleta 25. In this way all
gradations of the characteristics of caries as manifested in the individual case may
be readily presented without unnecessary circumlocution. The use of this plan is
also of great advantage in teaching.
In this use the term vis inita represents the actual exercise of the opportunities pre-
sented for the beginnings of caries in the individual case, and vis delete the activity
of the progress after the beginnings are made. The terms themselves are purely
arbitrary.
CLINICAL HISTORY OF CARIES.
789
cavities. There is much reason, however, to believe that the environ-
ment of the causative agent becomes with advancing age less favorable
to progress. The first of the permanent teeth to take their places in
the arch are those most frequently affected by caries (see charts). Caries
already begun advances less rapidly in older persons, and in some cases
cavities cease to progress. The cases of general spontaneous cessation
of progress in carious cavities are few, no matter what the age, yet a
number of such cases have occurred under my observation. The dis-
position to caries is not steady, however, but presents fluctuations more
or less marked. These are sometimes seen following an illness. In
women it is often noted in pregnancy, especially in first and second preg-
nancies. Other conditions have from time to time been noted which
seemed temporarily to dispose the individual to an exacerbation of the
tendency to caries. Yet in the great majority of cases this disposition
is gradually diminished with increasing age to such an extent that if
the cavities are well treated but few decays will begin after the patient.
is thirty or thirty-five years old, and the beginning of these will gener-
ally be found to depend upon some change in the conditions giving
opportunity.
Gledal
V
dav
This leads to the consideration of the infectious nature of caries,
which is best shown by the results of treatment in cases which mani-
fest a strong predisposition to the disease. Many times I have
undertaken cases in which there seemed to be but little hope of
success; yet I have found that if caries could be eradicated from the
mouth, and its exclusion maintained for a time, the tendency to the
disease rapidly diminished, and to such an extent as to make its con-
trol a matter of but little difficulty. Infection is always a strong
element in the beginning of caries. I have had, in numbers of cases,
opportunity to study this feature in the children of the same family,
where some would be careless and others fairly careful in attendance for
operations. Those who were careless, and in this way allowed the con-
tinuance of the conditions favoring infection-namely, a number of
cavities continuing in progress and adding to the amount of the fungus
growing in the mouth-have almost uniformly had much the larger
number of cavities at the age of twenty or twenty-five. It is doubtful
if this fungus grows well in the mouth where it is fully exposed to the
saliva. Partial seclusion seems more favorable to it. Certainly it does
not produce results unless it is fairly well secluded and sheltered from
the fluids of the mouth. Possibly, as already explained, this may be
due to the washing away of its products.
In a considerable number of cases there is a spontaneous cessation
of caries in cavities that have made considerable progress. This is, in
most instances, connected with some change in the form of the cavity,
usually the breakage of one or more of its walls in such a manner as
to give to all of its parts free access of the fluids of the mouth. This,
if the individual is approaching middle life and the predisposition to
caries has not been very considerable, will be sufficient to stop the prog-
ress of the decay. In case the predisposition to caries is strong, it is
necessary that the whole surface decayed be exposed to the friction of
mastication to bring about a cessation of the decay. In this case the
790
DENTAL CARIES.
whole of the injured tissue will become intensely black. In a number
of instances I have seen the spontaneous cessation of a considerable
number of decays under conditions that showed plainly that the cause
had ceased to act. The fungus was dead.
The fourth class of caries is occasionally seen to become very trou-
blesome after the other classes have ceased altogether. It is the class of
decay that is most likely to give trouble in old age. Its beginnings are
determined almost entirely by irritations of the gingivæ, giving rise to
absorptions about the necks of the teeth, which, becoming exposed
through the recession of the gums, become the seat of caries. They are
usually broad cavities that are shielded partially from the free entrance
of the fluids of the mouth, either by débris or by adjoining teeth or by
an overhanging gum. The teeth are attacked one or two at a time,
probably at considerable intervals or very irregularly as to time.
Occasionally the teeth in a certain part of the mouth may be attacked
together. Caries of this character is sometimes very destructive-more
for the reason that the position is such that the pulp of the tooth
is exposed with but little destruction of tissue than on account of
the decay. The beginnings are usually in the cementum near its
junction with the enamel, and in the molars, especially, the pulp-
canals are often in close proximity. Decays very much resembling
these are often seen in younger persons who wear partial plates abut-
ting against the remaining teeth.
:
APPENDIX.
zarad amateurs did, tegl 15%
FERMENTATION IN THE HUMAN MOUTH:
ITS RELATION TO CARIES OF THE TEETH
THE INFLUENCE OF ANTISEPTICS, FILLING MATERIALS, ETC.,
UPON THE FUNGI OF DENTAL CARIES.
.
THE FUNGI OF DENTAL CARIES; THEIR PURE CULTIVATION AND
EFFECT UPON LOWER ANIMALS.
BIOLOGICAL STUDIES ON THE FUNGI OF THE HUMAN MOUTH.
BY DR. W. D. MILLER, BERLIN, GERMANY.¹
DURING the last two years I have stated at different times and places,
as the result of many experiments, that "the first stage of dental caries
consists in a decalcification of the tissue of the teeth by acids which are
for the greater part generated in the mouth by fermentation." The
object of the investigations described in this and the following papers is
to determine this ferment and the conditions essential to its action. I
shall seek in what follows to present no views which are not the legiti-
mate and necessary results of rigid and exact experiment, and I shall
give in detail a description of each series of experiments, in order that
every one may have an opportunity to judge of the accuracy of the
work and the justice of the conclusions drawn from it.
It is, nevertheless, with some hesitancy that I venture to present
before the dental profession the results of my last six months' labor,
having learned by experience the almost endless number of agents.
which combine to vitiate such a series of experiments as that which
I am about to offer, and the exceeding great care which is necessary
in excluding or eliminating all irrelevant factors. If, therefore, I have
been guilty of any oversight or failed to take all possible precautions to
guard against error, I hope that some one will kindly show me where
I have gone astray and put me in the right course again.
The larger apparatus necessary for these experiments are:
Reprinted from the Independent Practitioner, February, March, and May, 1884, and
May and June, 1885.
791
792
DENTAL CARIES.
1. A large double-walled incubator, with gas-regulator for maintain-
ing any desired constant temperature.
2. A Koch sterilizer.
FIG. 407.

GUILLIE
HHH
It is not necessary to mention the smaller
instruments, glass vessels, etc., etc., nor the
apparatus necessary for making a chemical
analysis of the products of the fermentation;
these are sufficiently familiar to every one.
To avoid repetition, I will say here that
all vessels and instruments used in the cul-
ture experiments were purified in the flame
of a Bunsen burner when practicable, otherwise by exposing for fifteen
minutes in the drying-oven to a temperature of 150° to 160° C. (302°
to 320° F.), and that all substances used as culture substrata were ster-
ilized four times by exposure, at intervals of twelve hours, for half an
hour, to steam at 100° C., in a Koch sterilizer. Furthermore, all infec-
tions from carious dentine were made as follows: The cavity of a
freshly-extracted carious tooth is cleared of food and carefully brushed
over with a pledget of cotton dipped in carbolic acid (90 per cent.).
The acid is then thoroughly absorbed by means of bibulous paper, and
layer after layer of the soft dentine removed with a repeatedly purified
instrument until the deeper parts are reached; then a portion of the
clean soft dentine scarcely as large as a pin-head is removed and quickly
brought into or upon the culture medium.
Infections from the mouth were made by scratching upon the surface
of the mucous membrane of the cheek or the margin of the gum with
the end of a clean platinum wire, and then dipping it into the culture
medium. The materials used for culture were:
P
A B
W
YAMA
NA D
Wedd
Ska K
d
3. A damp chamber. (See Fig. 407.)
4. A drying-oven for sterilizing instru-
ments, glass vessels, etc., at a temperature
of 150° C.
5. A good microscope with either water or
oil immersion.
Damp Chamber: a, shallow glass
vessel partially filled with water;
b, glass globe lined with wet bib-
ulous paper; c, metallic stand for
culture-tubes.
No. 1. Sterilized saliva.
Sugar
Starch
•
No. 2. Sterilized milk.
No. 3. Decoction of malt
Sugar
No. 4. Sterilized saliva
Water
Starch
Sugar
50.0
1.0
0.5
50.0
1.0
M
The malt decoction is made by boiling, with slight evaporation, 20.0
dry malt with 120.0 water for ten minutes, and filtering.
50.0
50.0
. 20.0
2.0
po
FERMENTATION IN THE HUMAN MOUTH.
793
:
The starch is added to the cold solution of water and saliva and
stirred until it becomes evenly divided throughout the solution; it is
then poured into shallow glass vessels with glass covers and put into
the sterilizer for complete sterilization; it there congeals and forms a
It
solid mass, upon the surface of which the infections may be made.
possesses all the advantages of gelatin, with one great additional one,
in that it does not liquify at blood-temperature.
No. 5.
Decoction of malt
Sugar
Starch.
•
Prepared in the same way as No. 4.
No. 6. Beef-extract
Water.
No. 7. Water.
Beef-extract
Sugar
•
•
•
100.0
2.0
20.0
2.0
100.0
100.0
2.0
2.0
No. 8. Fresh-baked potato cut into slices one-half inch
thick with a clean knife.
Other substances were used, but need not be considered here. Ad-
ditional sugar is not absolutely necessary where malt is used, though
I have so far obtained better results by adding a small quantity. The
kind of sugar is immaterial, provided it be fermentable; even cane-
sugar, though not directly fermentable, is converted into a fermentable
variety in the culture. Where small quantities of any culture material
were used the cultures were kept in the damp chamber, to prevent their
drying up or becoming too concentrated by evaporation. All cultures
were made under a temperature of 36° to 38° C.
We will begin with the fundamental experiments.
Exp. 1. Fresh saliva is mixed with sugar or starch, 1-40, and kept
at blood-temperature. It invariably becomes acid in four to five hours.
But some one, no doubt, will say that this is a result of no consequence,
because the experiment was not made within the oral cavity; for his
personal benefit we give the following:
Exp. 2. A glass tube 2 cm. long and 3 mm. wide is filled with starch,
sterilized, and fastened to a molar tooth in the mouth on going to bed;
next morning the contents of the tube will have a strong acid reaction.
A cavity in a tooth or a piece of linen which may be saturated with a
solution of starch will answer the purpose as well as the glass tube.
That the acid is the same in each case will be further established below.
Exp. 3. The mixture of saliva with starch or sugar is kept for a half
hour in the sterilizer at 100° C., and then placed in the incubator; it
does not become sour in four, nor in twenty-four, hours-in fact, not at
all. We conclude that the ferment is rendered inactive by a tempera-
ture of 100° C.
Exp. 4. The starch is heated to 150° C. before mixing with the
794
DENTAL CARIES.
saliva; the solution still becomes sour. Conclusion: The ferment
exists, not in the starch, but in the saliva.
We have now to determine the question, Is it an organized ferment
(fungi), or is it an unorganized ferment (ptyalin)?
This question is determined by the following experiments :
Exp. 5. From 6 to 8 grams of saliva are agitated in a test-tube with
as much sulphuric ether as it will take up, starch added, and the whole
put in the incubator. On examination after a few hours we will find
sugar in the solution, but no acid; in other words, the acid-forming
ferment has been rendered inactive, but the unorganized sugar-forming
ferment not.
Exp. 6. Instead of ether, enough carbolic acid is added to make the
solution one-half per cent. strong; the result is the same. These two
experiments show that the ptyalin of the saliva (which was not injured
by the presence of the ether or the carbolic acid, as proved by the fact
that it retained its diastatic action) is not the cause of the acid reaction.
Exp. 7. According to Paschutin, ptyalin is devitalized by exposure
twenty minutes to a temperature of 67° C. Organized ferments could
not be killed by the same means. We accordingly subject a mixture of
saliva and grape-sugar to the given temperature for twenty minutes.
We thereby destroy the ptyalin; the mixture, nevertheless, becomes
sour if allowed to stand in the incubator for twenty hours. This
experiment confirms the result of experiments 5 and 6, and we begin
to suspect that we have to deal with an organized ferment. This sup-
position is confirmed by the following experiment.
Exp. 8. Six to eight drops of a perfectly sterilized solution of sugar in
saliva (1-40) in a miniature test-tube with cotton cork are infected from
the mouth or with carious dentine, as described above; in twenty-four
hours the solution will be acid. With a fraction of a drop of this solu-
tion a second tube is infected; it will likewise become acid. From this
a third, etc., etc.; each becomes acid in turn, while the control tube
(containing the same solution not infected) remains neutral.
B
The conclusion is plain that we have to do with a ferment which is
capable of reproducing itself; in other words, an organized ferment.
It therefore becomes evident that not only free in the mouth, but in the
deeper parts of carious dentine, we have a fungus which is capable of
producing an acid reaction in characteristic substrata.
Exp. 9. Each of thirty small tubes was furnished with eight drops
of solution No. 1, and each of thirty other tubes with as many drops
of solution No. 3, and all were sterilized. Twenty-four were then
infected from the mouth, twenty-four with carious dentine, and
twelve were left as controls. In twenty-four hours all forty-eight
of the infected solutions were acid, while the twelve controls remained
neutral.
Exp. 10. Make a solution of 40.0 of saliva and 1.0 of starch; put
equal portions in two flasks, a and b, and cover the surface of the solu-
tion in a with a layer of pure oil, to prevent the free access of air; or,
Exp. 11. Place flask a in an air-tight bottle containing a fresh alka-
line solution of pyrogallic acid (which abstracts the oxygen from the
air); or,
FERMENTATION IN THE HUMAN MOUTH.
795
Exp. 12. Exhaust flask a by means of the air-pump, so as to produce
a tolerably complete vacuum. The quantity of acid produced in a will
be, on an average, the same as that produced in b.
We conclude from experiments 8, 9, and 10 that the fungus in ques-
tion is independent of the free access of air or oxygen for its develop-
ment and characteristic action—a conclusion which would exclude the
fungus of vinegar (Mycoderma aceti), and which is of the utmost prac-
tical importance, since it signifies that this fungus can develop and per-
form its work deep in the dentinal tubules or under fillings, provided
the necessary materials are furnished it.
Exp. 13. Place a piece of carious dentine upon the surface of the
culture material described in number 4, 5, or 6; in twelve hours the
dentine will be surrounded by a white ring from 4 to 8 mm. in diam-
eter; the material within this ring will be partially liquefied and have
an acid reaction. The same result follows when the infection is made
from the mouth.
FIG. 408.
Exp. 14. Produce 10.0 of saliva by chewing a sterilized quill tooth-
pick, add 0.5 starch or sugar, and place in the incubator. Then give
the oral cavity a most thorough cleansing with pure water, using tooth-
pick, brush, and floss, the object being to free the mouth from micro-
organisms as completely as possible. Then produce again 10.0 saliva,
add 0.5 starch or sugar, and put in the incubator; the amount of acid
produced in a given time will in the latter case be often as low as one-
fourth of that in the former. Conclusion: By thoroughly cleansing the
mouth we no doubt remove the greater portion of the fungi; hence the
small amount of acid produced. By using strong antiseptics or by repeat-
edly filtering the saliva we may reduce the amount of acid produced in
twenty-four hours almost to 0. An experiment yet to be made is to take
the saliva direct from the gland before it becomes infected with the organ-
isms of the mouth; it should not then become sour when mixed with starch
and allowed to stand at blood-temperature. In every case a careful
microscopic examination of the cultures was made, revealing the constant
presence of a fungus, chiefly in the
form of diplococci, either single or
in chains, less often in the form of
bacteria, bacilli, or even threads.
(See Fig. 408.) Sometimes all these
forms are found on a single thread,
thus proving what I have already
demonstrated for Leptothrix buccalis
and Leptothrix gigantea (Miller), the
genetic connection of these different
forms. The particular form in which
the fungus occurs depends somewhat
upon the culture medium, as well as
upon the age of the culture. By
using a glass tube as culture vessel
NO NO NO NO
O OBUTI ENG STOR
mastegika
Page

we may demonstrate that, whether Some of the forms in which the fungus treated
of in this article occurs.
the culture is made in the mouth or
out of it, under similar conditions the fungus is the same.
The fungus
796
DENTAL CARIES
is not capable of producing an acid reaction of all substances in which
it may vegetate. A luxuriant growth may be obtained in beef-extract,
but no acid is produced unless sugar is present. It is only from carbo-
hydrates (especially sugar) that it appears to be able to produce acid in
any considerable quantity or at all. This question, however, as well as
the morphology, physiology, development, and life-conditions of the
fungus, will receive subsequent consideration.
We have, then, a micro-organism which agrees morphologically with
the Bacterium acidi lactici, and which, without the presence of oxygen,
produces acid from sugar; so that we would probably not be far from
right if we were to say that the organism in question is simply the fun-
gus of lactic acid. We will, however, reserve our decision for another
page, where the analysis of the product of the fermentation will be
given, that being the one sure method for determining the species
of any ferment bacterium.
Calend
In all cultures it is, of course, essential that the culture substratum
be neutral when the inoculation is made; should it be acid, it must
be neutralized. This is best accomplished by very carefully adding the
carbonate of sodium. Without this precaution it would be somewhat
difficult to determine whether acid had been produced by the action of
the fungus or not.
In the light of these experiments, the thorough decalcification of the
tooth-substance in caries is easily accounted for. The saliva is, no doubt,
always, particularly in mouths of uncleanly persons, impregnated with
sugar, either taken directly into the mouth or formed there by the action
of the ptyalin of the saliva upon starch. The question of the presum-
able diastatic action, as well as of a presumable inverting power on the
part of the organisms themselves, will be considered in the section on
Physiology.
Wherever this stagnates between the teeth in fissures, etc., etc., espe-
cially during sleep, it must become acid. When a portion of the dentine
has become decalcified, it, as is well known, takes up the liquids of the
mouth, and the fungi with them, like a sponge, and the fungi, being
independent of the free access of air, go on producing acid within the
dentinal tubules. As each layer of dentine becomes softened in turn
the micro-organisms follow after, continually producing new acid.
Hereby the zone of softened, non-infected dentine is readily under-
stood. The production of acid is entirely independent of the reaction
of the saliva as it enters the mouth; hence the uselessness of "testing
the saliva" for acid. That the liquid squeezed out of the tubules of
decaying dentine has an acid reaction every dentist in America who has
a piece of blue litmus-paper and is not color-blind can easily prove for
himself.
S
The result of experiment 6 plainly shows one cause of the good effects
which the profession has seen from the use of carbolic acid.
The fact that a pure culture was obtained in most cases by the first
inoculation seems to indicate that the fungus exists in a state of tolerable
purity in the deeper parts of the carious dentine. This question will,
however, receive consideration later. The action of the fungus upon
FERMENTATION IN THE HUMAN MOUTH.
797
substances which contain no carbohydrates will also be considered
under Physiology.
1
In addition to these experiments, I add the following: A sound
bicuspid tooth was sawed into sections, varying from 3 to 1 mm. in
thickness, and an equal number of these sections placed in each of two
test-tubes. Into one of these test-tubes were then brought 5 c.c. of a
perfectly neutralized 2-per-cent. aqueous solution of beef-extract; into
Both
the other the same solution, with the addition of 0.2 cane-sugar.
tubes, with their contents, were then sterilized, and upon cooling infected
from a pure culture of the fungus under consideration.
The solution in the second tube became acid in a few hours; not so,
however, with that in the first tube, it being non-fermentable. At the
end of one week the thinner sections in the second tube were so far soft-
ened that one of them, removed for examination, could be easily bent
between the fingers. At the end of the second week all but the thicker
One of these sections was now
sections were completely decalcified.
placed upon the freezing microtome and made into cuts, which were
stained in fuchsin and mounted in Canada balsam. A microscopic
examination showed that the fungi had penetrated many of the tubules
to a considerable depth, the invaded tubules being at the same time
slightly extended. At the close of the third week the invasion was
found to have become much more extensive, the tubules much dilated,
and in some places the walls were broken through, leading to the forma-
tion of oval spaces or caverns in the dentine. In short, we had a typi-
cal case of caries.
It is hardly necessary to state that the thinnest sections in the first
tube, where the development of the fungus was not accompanied by an
acid fermentation, did not show even the traces of softening, to say
nothing of caries.
I had, then, produced caries by inoculating sound dentine from a
pure culture of a fungus found in carious dentine in the presence of the
same fermentable substances that occur in the mouth. It seems that a
clearer solution of the problem can at present scarcely be expected. Of
course the thought at once suggests itself to every one that this decay is
quite independent of putrefaction; all evidence points to the conclusion
that putrefaction at most does nothing more than dispose of the already
devitalized and much riddled remains of tissue, and we are in danger of
overrating its influence even at this stage.
Pieces of dentine in a solution kept constantly pure and sour by fer-
mentation not only become softened and show the microscopic changes
characteristic of carious dentine, but finally, after some months, disap-
pear altogether, as has repeatedly been the case in my cultures. From
this we must infer that the process commonly known as putrefaction is
absolutely essential at no stage of caries; especially is this the case in
caries of enamel.
It has been intimated that the active agent in this process is nearly
related to, if not identical with, the fungus of sour milk, Bacterium
acidi lactici. The analysis of the product of fermentation will show
the truth or falsity of this supposition.
The method of carrying out such an analysis will now be given: 200
798
DENTAL CARIES.
c.c. fresh saliva are mixed with 2.0 starch and allowed to stand forty-
eight hours at blood-temperature; the mixture is then filtered and
heated to 100° C., to stop the fermentation. This process is repeated
until about a litre of the solution has accumulated. It is then placed
in a retort and reduced to a volume of about 75 c.c.
It will be very
strongly acid. A few drops of this liquid are added to a thin solution
of methyl-violet, and leave it unchanged; from this we conclude that
we have to deal with an organic acid, as an inorganic acid would turn
it first blue, and then green. Since the acid did not distill during the
prolonged boiling, we may set it down as non-volatile; hence a non-
volatile, organic acid. The distillate was very slightly acid; we will
call it distillate No. 1, as we wish to refer to it again.
The solution was further reduced in volume to about 40 c.c. over the
water-bath, and then transferred to a large glass vessel, briskly shaken
with 1 to 2 litres of sulphuric ether, and allowed to stand until the ether
became perfectly transparent. This was then filtered into a large retort
and distilled, proper precautions being observed to prevent accidents.
When the volume had been reduced to about 50 c.c., the solution was
filtered into a porcelain vessel and still further reduced over the water-
bath. A portion of the solution tested in the short tube of a Mitscher-
lich double-shadow polaristrobometer gave as a mean of nine readings a
rotation of the plane of polarization equal to 0.015°, or 0° 0.9′. In
other words, the solution was optically inactive, the 0° 0.9' being far
within the range of the error of experiment, especially as the solution:
was not absolutely transparent.
FIG. 409.
An excess of freshly-prepared oxide of zinc was then added to the
solution and the whole slowly and carefully boiled, water being added
as it was found necessary, till the reaction
became neutral, or nearly so, filtered into a
large glass evaporating dish, and put away at
the temperature of the room for the salt to
crystallize. A drop of this solution placed
upon a glass slide gave upon crystallization
the forms seen in Fig. 409, which are at
once recognized as crystals of lactate of zinc.
In a few days a quantity of a whitish crystal-
line powder had formed. This was placed
upon a filter, the mother-liquid squeezed out,
washed in absolute alcohol, dissolved in hot
water, recrystallized, and dried over sulphuric
acid;
it then weighed 0.343. After exposing to a temperature of 100°
C., or a little more, till the weight became constant, it weighed 0.2816;:
it lost, accordingly, 17.9 per cent.¹ of water of crystallization, corre-
sponding to 3 molecules of water. The salt was then dissolved in
water, the zinc precipitated as carbonate and burned. The burned
mass (zinc oxide) weighed 0.0970. We have, consequently,

AX
Substance analyzed (a zinc salt) = 0.343
Oxide of zinc
= 0.097
1 Theoretically, 18.2, or 0.3 per cent. more.
FERMENTATION IN THE HUMAN MOUTH.
799
The zinc oxide is seen to be equivalent to 28.2 per cent. of the
substance analyzed.
The formula for the inactive ethylidene lactate of zinc is
CH₂O3} Zn +3H,O=243 + 54.
Dried at ordinary temperature, it contains 27.3 per cent. zinc oxide.
The result obtained from the analysis differs, therefore, from that
deduced from the formula by less than 1 per cent., and settles beyond
doubt the fact that the substance analyzed was the lactate of zinc, or
that the acid generated by the fermentation is lactic acid—or, more
exactly, inactive ethylidene lactic acid, since, as shown above, the acid
solution was optically inactive and the zinc salt contained 3 molecules
of water of crystallization. The salt was furthermore soluble in 62
parts water at 14° C.
I repeated the analysis with the following solution :
Water, 1000 c.c.
Saliva, 300 c.c.
:
Bouillon, 200 c.c., made by boiling 125.0 beef ten
minutes in 300 c.c. of water.
Sugar, 10.0.
This solution, being slightly acid, was neutralized with the carbonates
of lime and sodium, sterilized, and infected from a pure culture of the
fungus in question. It was treated throughout exactly in the manner
above described, except that the zinc salt was converted into the sul-
phide instead of the carbonate, and burned with powdered sulphur in a
stream of hydrogen. The result was as follows:
Substance analyzed
Zinc sulphide
Zinc
Wing
instead of 26.74 per cent., as deduced from the formula-a difference
of only of 1 per cent.
In this case the substance was dried at 100° C. before weighing, and
the formula becomes
C,H,O, Zn
C₂H₂O
3
5 3
1.0540
0.415
26.38 per cent.
podgladan
One more analysis was made, using—
Water,
Liquid beef extract,
Sugar,
243.
Toda
1000 c.c.
20 c.c.
10.0
The result was the same, and need not be given, the two analyses
above described being abundantly sufficient to show that the acid gen-
erated by the fungus in question is the common ferment, lactic acid.
Distillate No. I, referred to above, owed its slight acidity, we now
know-in part, at least-to lactic acid, since, when an aqueous solution
800
DENTAL CARIES.
of lactic acid is boiled, a small fraction of the acid goes over with the
water. To ascertain, however, whether any other acid, especially vola-
tile, was present, the distillate was boiled with carbonate of lime,
filtered, evaporated to dryness, a small amount of dilute sulphuric
acid added, and heated in a retort over the water-bath. A few drops
of an oily acid came over, which when taken upon the fingers smelled
like butyric acid; the amount, however, was so small that no attempt
could be made to analyze it.
XX
$
C
I have been able with some degree of certainty to establish the pres-
ence of lactic acid in carious dentine by a method theoretically so
simple that it seems strange it has never been made use of before, but
which, however, in practice, is carried out only with great difficulty.
My first and second attempts were only partially successful; the third
succeeded sufficiently well to justify its description here.
In this experiment I made use of fifteen teeth, all containing consid-
erable quantities of carious dentine, and all extracted on the day of use.
The remains of food were first removed from the cavities, but none of
the softened dentine; then all the softened dentine was taken out and
placed in a porcelain vessel, cut or picked into fine pieces, placed in a
test-tube with 1 c. c. of water and two drops of a 10-per-cent. solution
of hydrochloric acid added. Any free lactic acid in the carious den-
tine would remain free, and any existing in combination with lime
would be set free by the hydrochloric acid. It was then gently shaken
with about 25 c.c. sulphuric ether, and the latter, holding the lactic acid
in solution, was after some minutes poured off into a second test-tube;
here it must be allowed to stand from twenty-four to forty-eight hours,
till it becomes perfectly clear. It was then filtered into a porcelain
dish, evaporated, a few drops of distilled water and a small quantity of
freshly-prepared zinc oxide added, gently boiled (water being added as
necessary) for ten minutes, the three or four drops of liquid remaining
filtered on to a glass slide and allowed to crystallize. I obtained the
forms seen in Fig. 410. Their close resemblance to
the crystals of the lactate of zinc (Fig. 409) will be
seen at once. There can, in fact, scarcely be a doubt
that they are lactate-of-zine crystals. The lactic acid
concerned in their formation must, of course, have
existed in the carious dentine.
FIG. 410.

I have noticed in the dental journals a tendency on
the part of some writers on this subject to derive a
large amount of satisfaction from the statement that,
after all, what I have done to clear up the subject of dental caries was
done and known long ago. One writer even states that he might
almost have said two years ago something that I said but a few months
since. Let me say, once for all, that I have too little spare time to
devote any of it to the discussion of the question who said this or that
first, or even who might almost have said something two years ago.
There is perhaps no human disease about which more has been said
than about caries of the teeth; and when the subject shall have received.
its final settlement, there will be hundreds who may say, "I told you
so." Malassez and Vignal very justly say of Baumgarten, who claims
FERMENTATION IN THE HUMAN MOUTH.
801
priority over Koch in the discovery of the tubercle bacillus, “Il ne suffit
pas de trouver, il faut prouver ;" and I do not hesitate to say, with
reference to some of the discussions which for years have been carried
on concerning the cause of dental caries, "Il ne suffit pas de deviner, il
faut trouver et prouver."
It is not enough to guess the cause, or guess at it: we must find the
cause, and, having found it, prove that it is the cause sought for.
If we infect a beef-extract-sugar solution with carious dentine, as
already described in this paper, using every possible precaution to
obtain perfectly pure material and to prevent the access of germs
from without, and keep the solution at 37° C., we may observe the
following phenomena: In from eight to ten hours the solution will
show a slight cloudiness, which at no time, however, amounts to com-
plete opacity. Tested with sensitive litmus-paper, it will be seen that
the acid reaction has already appeared. In fifteen to twenty hours the
fermentation will generally have reached the most active state, and
soon afterward a colorless, flocky precipitate will begin to form on the
bottom of the vessel, accompanied by a corresponding clarifying of the
solution and a diminution of the fermentative activity. After the lapse
of forty-eight hours the sediment will have completely formed, and the
solution will be almost as transparent as when the experiment began.
The time required for the completion of this series of phenomena will,
however, naturally depend somewhat upon the amount of dentine taken
for the infection and the amount of the solution used.
Impurities in the culture manifest themselves in various ways—it
may be by an excessive cloudiness of the liquid, or by the formation of
a skin upon the surface of the solution, or the failure of the latter to
become clear after the regular lapse of time, etc., etc.
Dentine is an excellent medium for separating the different fungi
found in the mouth, the most of them not being able to exist in the
deeper parts, partly on account of the acidity of the medium, partly on
account of the lack of free oxygen. We may, therefore, with the
proper amount of care, obtain material of such purity as to produce
a pure culture in the first generation.
If we microscopically examine the sediment which has formed on the
bottom of the vessel, we shall find it to consist of cocci and diplococci,
either single or in chains-in either case, without motion. Under a low
power they appear round and regular; with oil immersion they are
seen to be round or oval, regular or irregular, involuted, etc., present-
ing the most various shapes and sizes. I have never been able to detect
the existence of spores, and reproduction takes place only after the scheme
presented in Fig. 411, Nos. 1, 2, 3, 4, 5, 6, 7. A coccus which may be
round in the beginning by extension in one axis becomes oval or elon-
gated; soon after, it shows a contraction in the middle, resulting in the
production of a diplococcus or two cocci, each of which may produce
two cocci in the same manner.
We find, consequently, in a chain taken from a growing culture, some
of the cocci round, others oval; some of the diplococci but slightly con-
tracted, while in others the contraction amounts almost to a complete
division. (See Fig. 411, d, e, f.) Frequently the cells acquire a pro-
VOL. I.-51
R
802
DENTAL CARIES.
nounced bacterium form; so that if they did not occur in the same chain
with the ordinary forms, one would be in doubt as to whether they
belonged to the same species.
The growing cells in a chain sometimes turn upon their shorter axis,
and then, growing out in the new direction, produce very peculiar fig-
a
"ISOCONS; ✪
FIG. 411.
1 2 3 4 6 07
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ures (Fig. 411, f, g). In stagnant cultures the cells under high power
are mostly very irregular, having in groups the appearance of the bones
of the wrist. (See Fig. 411, a, b.)
Very characteristic are the involution forms produced both in stag-
nant cultures and in media which are not well adapted to the needs of
the fungus. Here the forms and sizes are so various that it sometimes
becomes exceedingly difficult, if not impossible, to tell if certain ones
are normal or abnormal. (See Fig. 411, h, i, j, k.) In exceptional
cases the threads surround themselves with a thick gelatinous sheath,
(See Fig. 411, c.) The protoplasm of the
involuted cells generally presents a gran-
ular appearance (Fig. 411, h,k).
FIG. 412.
If we make a large number of cultures
at once, we will in about one case out of
five to ten (and if the cultures are made
in a decoction of malt much more fre-
quently) meet with a second fungus,
essentially different from the one just
described. It occurs chiefly in form of
bacilli, but also as leptothrix, bacteria,
diplococci, and cocci singly, or, as is
mostly the case, in long zig-zag threads
(Fig. 412).
The discovery of this fungus, with its
different forms of development, affords a
very ready explanation of the fact that in a single dentinal tubule we
sometimes find a transition from leptothrix to bacilli, from bacilli to
bacteria, and from bacteria to cocci-an occurrence which I demon-
FERMENTATION IN THE HUMAN MOUTH.
803
strated nearly two years ago before the American Dental Society of
Europe, before the Gesellschaft fuer Heilkunde in Berlin, and to vari-
ous private persons, including some of the most celebrated mycologists
in Germany. Those who maintain, as was done in the British Dental
Association, that such cases may not be found, are responsible for their
own mistake.
Macroscopically, cultures of this fungus in beef-extract-sugar solution
are not easily to be distinguished from cultures of that described above.
The fungus collects as a sediment on the bottom of the vessel; it never
forms a skin on the surface of the liquid, and produces but a moderate
cloudiness of the same. In most decoctions, however, they present
some peculiarities. Sometimes the fungus floats about in the solution.
in semi-transparent balls, or rises up from the bottom of the vessel like
a miniature cloud of smoke, or collects in small patches on the sides of
the vessel, while the solution itself remains almost perfectly clear. The
cells are motionless and do not form spores.
FIG. 413.
In order to discriminate between these two fungi, I will designate
for the present the one first described by the
prefix A (alpha), and the one under considera-
tion by the prefix ẞ (beta). In all probability,
the B-fungus also produces lactic acid from
sugar. I say "in all probability," because,
though I have always been able to detect lactic
acid in cultures of this fungus, I could not say
with absolute certainty that cocci and diplococci
of the species A were not present.
We have, then, in carious dentine two dis-
tinct fungi-one always, the other often, pres-
ent; the former surely, the latter probably,
producing lactic acid from sugar. If these
fungi are the direct cause of dental caries, we
should be able to produce caries by subjecting.
sound dentine to their action. This I have
accomplished, as already described.


CL
ს
In Fig. 413, a, are scen in outline two
tubules of dentine melted together by natural
caries, and in Fig. 413, b, two tubules melted
together by artificial caries.
In Fig. 414, a, are likewise two tubules
from natural caries, and in Fig. 414, b, two
from artificial caries. It is a fact of consider-
able interest that, though the fungi themselves.
are perfectly colorless, pieces of dentine sub-
jected to their action become yellowish, light
brown, or dark brown, etc., depending upon
the medium in which the culture is made,
while different pieces of dentine in the same.
culture do not by any means necessarily acquire the same color.
The carrying out of this experiment is attended with difficulties, and
some may try it and fail; I have failed many times. The necessity of
804
DENTAL CARIES.
a
repeatedly changing the solution very much increases the danger from
impurities; especially must the saccharomycetes be guarded against.
The acidity of the medium caused by the caries fungi renders it very
favorable for their development; and when
they have once found their way into a culture,
it might as well be thrown away at once.
Again, notwithstanding the presence of the
pieces of dentine, the solution sometimes be-
comes sufficiently acid to impair, if not to
destroy, the vitality of the fungus. In this
case the dentine becomes softened, but only a
slight invasion of the tubules takes place.
Then, of course, in the very last stage of
caries, other fungi, especially Leptothrix buc-
calis, are present in the decomposing dentine,
and sometimes produce an appearance in its
superficial layers which I have not attempted
to reproduce artificially. It is not difficult
by a simple microscopic examination of the
fluids of the mouth, as well as of carious dentine, to find forms mor-
phologically identical with those described above.
!!
In Fig. 415 is seen in outline a portion of an epithelial scale from the
FIG. 415.
FIG. 414.
B
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མྨ མི
zbzzzzzk
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FIG. 416.
human mouth, highly magnified, with the fungi lying upon the surface.
Theforms seen in Fig. 416 were obtained from a glass
tube filled with starch and kept in the mouth over-
night, while Fig. 417 is from carious dentine. The
A caries fungus agrees morpho-
logically with the fungus of sour
milk as delineated by Pasteur.
Later experiments, however, ren-
der it probable that the souring
of milk is produced by an alto-
gether different fungus, a short, thick bacterium,
FIG. 417.
|||-
FERMENTATION IN THE HUMAN MOUTH.
805
occurring in twos, seldom fours, which may also be found in the human
mouth (though probably not deep in carious dentine), and will be con-
sidered at another time.
In the case of both fungi the fermentation goes on independently of
the presence of free oxygen. I have already shown that where only a
trace of oxygen is present in no way comparable with the amount of
acid produced, the degree of acidity was as great as where there was
free access of air. Whether, however, this trace of oxygen is essential
to the life of these fungi-i. e. whether without it they would perish
from asphyxia-is a question which we will not discuss here.
It has been generally supposed that the production of lactic acid by
fermentation from sugar is accompanied by the evolution of carbonic
acid; in fact, Fluegge says that no fermentation can go on without the
production of carbonic acid. This statement will hardly be borne out
by a study of the fermentation produced by the fungi of tooth caries.
A glass vessel of 500 c.c. capacity was filled with beef-extract-sugar
solution infected with a pure culture of caries fungi and made air-tight
with a rubber stopper carrying an efflux-tube for collecting the gas over
mercury. After twenty-four hours, during which time 1.75 c.c. acid
had been produced, one single gas-bubble was collected, which may
have been due to a slight change of temperature, as well as to a veritable
gas-evolution. The splitting appears, therefore, to be perfectly smooth,
and to take place in accordance with the simple formula,
C₂H₁₂O6=2C3H6O3.
It presents a marked contrast to the stormy character of the butyric
and alcoholic fermentations, in case of which the pressure of the gas
evolved is often sufficient to burst the vessels containing the cultures.
12
There is perhaps at nearly all times a sufficient amount of sugar in
the oral cavity to enable the fungi of caries to carry out their charac-
teristic ferment action. It remains, nevertheless, an interesting question
whether they have the power to form sugar out of starch-i. e. whether
they have any diastatic action. About thirty cultures in an aqueous
solution of beef-extract and starch and in a solution of starch in steril-
ized saliva gave, for the most part, negative results; in exceptional
cases a slight diastatic action appeared to take place, which I am in-
clined to regard as the result of some impurity in the culture or an
error in the experiment.
C
On the other hand, the fungi appear without doubt to possess the
power to invert or to render non-fermentable sugars fermentable, since
cane-sugar, which is not fermentable and does not reduce alkaline solu-
tions of sulphate of copper, acquires both these properties when sub-
jected to their action. That this result is caused by the action of a
ferment produced by the organisms, and which may be separated from
them, is, I think, demonstrated by the following experiment: By mak-
ing
number of cultures at one time in vessels of 200 to 500 c.c. capa-
city and collecting the sediment which was deposited on the bottom of
the vessels, I succeeded in bringing together a considerable quantity of
the fungi; this was then treated with 90-per-cent. alcohol filtered and
dried in a porcelain vessel, thoroughly rubbed with sand, digested with
Ma
806
DENTAL CARIES.
water at 23° C., and again filtered; the filtrate (which must be clear
and should contain the ferment in solution) was added to a solution of
cane-sugar, which then showed in the long tube of a Mitscherlich polar-
iscope a rotation equal to 5.19°. The solution was now allowed to
stand four hours at a temperature of 38° C., after which time it pro-
duced a rotation of only 4.54°, indicating a decrease of about two-
thirds of a degree. The solution also produced a slight reduction of
an alkaline solution of sulphate of copper-i. e. a certain portion of the
cane-sugar had been converted into invert sugar.
In the presence of the fungi the non-fermentable sugar, by the action
of the invertine produced by the fungi, takes up one molecule of water
and is converted into invert sugar, a mixture of levulose and dextrose,
both of which are fermentable:
C₁₂H22O11 + H2O = CH₁₂O + CH₁₂O
6 12 6
Levulose.
6 12
Dextrose.
Cane sugar.
6*
We may say, therefore, that the micro-organisms require sugar to
produce fermentation, but that it is immaterial which kind of sugar is
furnished them. The fermentation is most active between the tempera-
tures 35° and 40° C. Above 50° and below 15° C., little or no pro-
duction of acid takes place.
In addition to these two species of fungi, others of minor importance
are occasionally met with in the mouth, and will receive attention
later on.
Balan
I would not have any one think that I look upon the above as a
thorough consideration of the fungi of tooth caries; to me it appears
very imperfect. Nevertheless, I have thought it well to present the
matter before the profession in the hope that others might be induced
to take it up and help to complete the work thus begun. I will now
present the results of experiments relating to the action of various
antiseptics, filling materials, etc. upon the fungi under consideration.
THE INFLUENCE OF ANTISEPTICS, FILLING MATERIALS, ETC. UPON
THE FUNGI OF DENTAL CARIES.
Having established upon an experimental and scientific basis the fact
that caries of the teeth is to a certain extent the direct result of the action
of ferment acid or acids¹ upon the tissue of the tooth, followed, particu-
larly in the case of the dentine, by the action of the ferment organisms
themselves upon the decalcified tissue, it becomes a matter of the first
importance to determine, first, by what means we may counteract the
action of the acids or prevent their production; second, by what means
we may save the already decalcified dentine from complete destruction.
Evidently, there are three methods by which the desired end may be
partially obtained:
1. By repeated, thorough, systematic cleansing of the oral cavity and
the teeth we may so far reduce the amount of fermentable substances in
the mouth and the number of ferment organisms as to materially dimin-
1 The chief work in the production of caries is performed by lactic acid; other acids
are only auxiliary factors.
FERMENTATION IN THE HUMAN MOUTH.
807
ish the production of acid. This is so self-evident that it needs no
further comment.
2. By the repeated application of alkaline substances we may to a
certain extent neutralize the acids before they have acted upon the teeth
to any considerable degree.
3. By a proper and intelligent use of antiseptics we may destroy the
organisms themselves, or at least render them inactive. It is this method
which is especially applicable in the second stage of dental caries—i. e.
the stage which follows the decalcification-and to which we will here
give exclusive attention. We must, however, constantly bear in mind
that, by whatever method we proceed, a previous thorough cleansing of
the teeth is absolutely indispensable. There is no known solution, alka-
line or antiseptic, applicable in the human mouth which will penetrate
between the teeth or to the bottom of fissures and cavities when these
are filled with food in sufficient quantity to have any appreciable effect.
Therefore before all antiseptics or alkaline washes come the toothbrush,
toothpick, and floss silk.
In my experiments for determining the action of various antiseptics
upon the fungi of tooth caries it appeared to me that by allowing the
antiseptic to act upon the fungi in their natural medium, saliva, I could
obtain results of more practical value than by experimenting upon them
in artificial solutions and in pure cultures, neither of which ever occurs
in the human mouth. Furthermore, since the fungi can attack the
teeth only after a partial decalcification, we have, in the first place, to
demand of an antiseptic not so much that it destroys the fungi as that
it prevents the production of acid by them.¹ Consequently, if an acid
reaction failed to appear in a solution of saliva and sugar to which a
certain antiseptic had been added as soon as in a like solution to which
no antiseptic had been added (control), it was taken as evidence of the
activity and value of the antiseptic used. This method could, of course,
be used only with substances having a neutral reaction. The solutions
were also subjected to a microscopic examination, to render the evidence
doubly sure.
In the following table I have indicated the percentage of each anti-
septic experimented upon which must be present in a sweetened-saliva
solution to prevent the appearance of an acid reaction in twenty-four
hours, or, in case of alkaline or acid antiseptics, to prevent the develop-
ment of the characteristic fungi in the same time.
For example, if to 100,000 parts of sweetened saliva we add one
part of bichloride of mercury, the solution will not be found acid after
the lapse of twenty-four hours even though the control become sour in
four or five hours. If we add only one part to 500,000, the acid reac-
tion will appear somewhat later than in the control.
This table is designed to show the comparative strength of the anti-
septics most commonly used. The action of the antiseptics having an
acid or alkaline reaction upon the fungi was determined by the use of
the microscope alone:
Mat
1 The production of acid may be taken as synonymous with the development of the
fungi, though the failure of the acid reaction to appear after a certain length of time
does not necessarily indicate that the fungi have been devitalized.
808
DENTAL CARIES.
Bichloride of mercury
Nitrate of silver
Iodoform
Naphthaline
Iodine
Oil of mustard
•
Permanganate of potas.
Eucalyptus oil
Carbolic acid.
Hydrochloric acid
Phenylic acid
•
Liquid of Agate Cement.
Liquid of Excelsior Cement
Lactic acid
.
•
•
Carbonate of sodium
Salicylic acid (Conc. alcohol sol.)
Alcohol
•
·
1
•
•
PRODUCTION OF ACID
(Development of Fungi).
Prevented.
Retarded.
1-500,000
1-100,000
1-50,000
1-100,000
1-10,000
1-5,000
1-4,000 (?)
1-6,000
1-2,000
1-1,000
1-600
1-500
1-500
1-200
1-250
1-225
1-125
1--100
1-75
1-10
1-9,000
1-15,000
1-5,000
1-2,000
1-1,000
1-1,000
1-500
1-250
1-200
1-125
1-20
The experiments show that bichloride of mercury is about two hun-
dred times as powerful as carbolic acid, and demonstrate very clearly
the mistake of substituting weak solutions of this antiseptic (1-1000, as
I have seen recommended) for concentrated carbolic acid. One one-
thousandth is only one-fifth as powerful as pure carbolic acid, which in
many cases may be used with impunity. It is consequently useless to
attempt to introduce the sublimate solution for the purpose of sterilizing
root-canals, cavities before filling, etc., unless we may use at least a
-per-cent., if not a 1-per-cent., solution. I see no reason, however,
why this may not be done. In a few cases I have used a 1-per-cent.
solution for treating root-canals, and do not hesitate, particularly with
the rubber dam adjusted, to wipe out cavities before filling with a 2-per-
cent. solution, and see no possible evil which could result from it. A
well-known physiologist in Berlin has told me that he uses a 1-per-cent.
solution in his own mouth for aphthæ, and with excellent results. We
should not, however, overlook the fact that a 1-per-cent. sublimate solu-
tion is only one-fifth as powerful as pure iodoform.
As a mouth-wash I have frequently used a-per-cent. (1-1000)
solution myself, and have seen no bad results from it; I would not,
however, recommend it to my patients in this strength. It has, besides,
for me, an exceedingly disagreeable and lasting taste which it is difficult
to disguise, and produces an immediate increased secretion of saliva and
mucus which is very annoying. A-per-cent. solution (1-5000) may
eventually be brought into use; in this concentration it is four times as
powerful as a 1-per-cent. solution of carbolic acid. The very high
antiseptic power of nitrate of silver is particularly noteworthy. Why
may it not be employed in place of the much more dangerous mercuric
chloride?
ma
The action of tobacco upon the fungi is worthy of notice. Five
grammes of old Virginia plug were boiled fifteen minutes in 50 c.c. of
water, the loss by evaporation being constantly replaced; the decoction
was then filtered and a portion added to an equal volume of saliva with
sugar. This produced a mixture scarcely stronger than that which
many veteran chewers carry around in their mouths all day, and in it
FERMENTATION IN THE HUMAN MOUTH.
809
the fungi led only a miserable existence. Much more remarkable, how-
ever, was the action of tobacco-smoke upon the fungi, the smoke from
the first, third, or last quarter of a Colorado Claro cigar being found
amply sufficient to sterilize 10 c.c. of a beef-extract-sugar solution pre-
viously richly infected with caries fungi.
FIG. 418..
The apparatus used for this experiment
(see Fig. 418) explains itself. A current
of water passing through the part B in the
direction indicated by the double-headed
arrow produces a current of air through the
part A in the direction shown by the single-
headed arrow which draws the smoke from
a lighted cigar through the solution. The
rate at which the cigar smokes may be regu-
lated at will by the cock of the hydrant.
In consideration of the strong antiseptic
power of tobacco-smoke, we might be
inclined to infer that tobacco-smokers
should never suffer from caries of the
teeth; it is evident, however, that there
are very many points in the dental arch to
which the smoke never penetrates.
In the preparation of cavities for in-
serting fillings it is naturally often next
to impossible to remove all the carious
dentine, and in all such cases it is espe-
cially desirable that the filling material
itself should possess antiseptic properties,
since we, in using such a material, not only
destroy those organisms existing in the
carious tissue, but the material, if it re-
mains permanently antiseptic, retards the
working of the ferment organisms from
without and the appearance of secondary
decay. We need, therefore, a material for
filling which is not only antiseptic at the time of insertion, but which
remains permanently so after being inserted. I have endeavored to
determine the relative antiseptic power of different filling materials
(cements, amalgams, etc.) not only at the moment of mixing, but after
they were thoroughly dry, after they had lain some hours in sweetened
saliva, and after they had been an indefinite time in the human mouth.
A large number of miniature test-tubes (homeopathic pill-tubes) were
provided with cotton stoppers and sterilized. Into each was brought
c.c. of beef-extract-sugar solution previously infected with carious
fungi (pure culture). To the first tube was added a small drop of a
1-per-cent. sublimate solution, the second tube was left untouched, and
into the third, fourth, fifth, etc. were brought the filling materials whose
antiseptic virtues were to be tested; these were in the form of cylinders
2 mm. in diameter and 3 mm. long; if old fillings from the mouth were
used, pieces were taken having approximately the same size.
1
2
1
d"
B
d'
V
PANEVIENS
•*****
e
а
a
G

A
a, glass cylinder with infected solu-
tion; b, c, glass tubes; d, d', d", rub-
ber tubing; e, cigar (Colorado Cla-
ro); B, water air-pump. A current
of water passing through B in the
direction indicated by the double-
headed arrow produces a partial
vacuum in the bulb, and conse-
quently a current of air in the di-
rection shown by the single-headed
arrow, or through the cigar, which
if lighted will smoke at a rate deter-
mined by the pressure under which
the water is flowing.
810
DENTAL CARIES.
These tubes now being placed in the incubator, their contents became
clondy one after the other. In those tubes which contained fillings of
but slight antiseptic power the development of the fungi proceeded
rapidly and the cloudiness soon appeared; if, on the other hand, the
filling was strongly antiseptic, the development of the fungi was hin-
dered and the cloudiness appeared later. The first tube to which the
sublimate solution had been added of course remained clear, and by
comparing the others with this it was easy to see just when the turbidity
began to show itself; the second tube, containing no antiseptic and no
filling, served as control, and the space that intervened after the control
became turbid till any one of the other tubes became turbid was a meas-
ure of the antiseptic power of the material in that tube.
As the result of a great number of experiments, I have been able to
get together the following table.
When the control tube becomes turbid in five hours, then-
A tube containing an old oxyphosphate filling becomes turbid in.
((
<<
an old oxychloride filling becomes turbid in
a gold cylinder becomes turbid in .
(4
((
((
((
<<
(6
(6
((
(C
(C
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((
((
(C
(C
((
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(C
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a Hill's stopping cylinder becomes turbid in
an amalgam cylinder (kept twelve hours in saliva) becomes
turbid in.
·
•
an agate cylinder (kept twelve hours in saliva) becomes
turbid in.
an old amalgam filling becomes turbid in.
·
an amalgam cylinder (mixed dry) becomes turbid in
an amalgam cylinder (mixed wet) becomes turbid in
•
an oxyphosphate cylinder (twelve hours in saliva) becomes
turbid in.
•
an iodoform cement cylinder (fresh) becomes turbid in.
a globule of mercury becomes turbid in .
a cylinder of black oxide of mercury becomes turbid in
a cylinder of any copper amalgam becomes turbid in
any old copper amalgam filling becomes turbid in .
a cylinder of oxychloride (fresh) becomes turbid in
The (—) signifies that the solution remained permanently clear.
CC
.
·
•
an amalgam cylinder (twelve hours old) becomes turbid
in .
an old filling of tin and gold becomes turbid in
an oxyphosphate cylinder (twelve hours old) becomes
turbid in
·
D
•
•
bid in.
a piece of dentine from a tooth impregnated by a copper
amalgam filling becomes turbid in.
an iodoform cement cylinder (twelve hours old) becomes
turbid in
•
1
•
5 hours.
..
5
5
5
5
6
an agate cylinder (twelve hours old) becomes turbid in. 64
an iodoform cement cylinder (twelve hours in saliva)
becomes turbid in.
51%
58
6/
a pyrophosphate cylinder (mixed dry) becomes turbid in 71
a pyrophosphate cylinder (mixed wet) becomes turbid in 78
an oxychloride cylinder (twelve hours old) becomes tur-
9
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5/1/
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12
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it
We see from these results that the only filling at present in use which
exerts a continual antiferment' action upon the walls of the tooth and
its immediate surroundings is the old copper amalgam; not only that,
but the very substance of the tooth containing such a filling itself
¹ I use the terms antiferment and antiseptic interchangeably, though the former is
perhaps preferable, since we are treating of ferment, and not septic organisms.
FERMENTATION IN THE HUMAN MOUTH.
811
becomes antiseptic, a piece of bluish or bluish-green dentine from such
a tooth very powerfully retarding the development of the fungi, and,
indeed, in two cases completely destroying them. Secondary decay in
such a case would be next to impossible where anything like cleanliness
was observed.
This result is well supported by observations which I have had
abundant opportunity to make for the last five years here where this
material is so extensively used, and I do not hesitate to say that if our
only object is to check the destruction of tissue by caries there is no
material at present in use with which this object may be so surely
accomplished as with a good copper amalgam. It is a material, how-
ever, which I have never used, though I am not aware of any bad
effect produced by it beyond the discoloration of the tooth. Skogs-
berg's iodoform cement came into my hands too late to complete the
experiments with it. It has undoubtedly strong antiseptic properties,
which it does not completely lose even when exposed to the saliva, and
might, no doubt, be used to great advantage as a foundation for perma-
nent fillings. Old fillings of tin and gold possess slight antiseptic power,
still less (almost zero) old amalgam fillings (not copper). The very
inconsiderable power of amalgams to prevent the development of fer-
ment fungi is a source of some surprise, since we have been accustomed
to look upon them as very active in this respect. It is probably a mis-
take to attribute the hardening of dentine under amalgam fillings to the
antiseptic action of the amalgam, since in the first place it possesses this
power to but a slight degree, and in the second place the hardening
may take place under fillings of gutta-percha equally well. If we dry
the cavity but indifferently well and then choose a piece of gutta-percha
which we think will about fit the cavity, warm it, and stuff it into the
cavity, we, of course, can expect only bad results. If we proceed as
follows, we will obtain excellent results, as I have seen time and again :
Adjust the dam, excavate carefully, especially the margins, wash with a
strong antiseptic, dry thoroughly with bibulous paper, and then with
the hot-air syringe, till the surface of the dentine becomes whitish,
paint with a thin solution of copal varnish, dry again with warm air,
then put in the gutta-percha in small pieces, one after the other, being
sure that each piece sticks to its place, especially along the margin, just
as if you were making a filling of gold. A piece which has once moved
in its place must not be allowed to remain, as a leak will be the result.
Remove such a filling after two years, and the cavity will often be found
in an excellent condition for a gold filling.
The oxychlorides, when first mixed, are powerfully antiseptic, but
soon lose their energy when exposed to the action of saliva.
The oxyphosphates are very much inferior to the oxychlorides in
antiseptic power, and should never be used in cavities where there is
much soft dentine. This conclusion is borne out by my own experience
in practice, and by that of others with whom I have conversed on the
subject. Dr. Paetsch first called my attention to the disastrous results
of such a practice, and his testimony was confirmed by that of Dr.
F. P. Abbott and others.
It must not be expected that the results given in the above table are
812
DENTAL CARIES.
absolutely free from error. The experiment is attended with more diffi-
culties than are at first sight apparent; especially does the sterilization
of the filling materials themselves involve much time and labor, and the
results are not always constant; this was especially the case with iodo-
form cement. Amalgams and phosphates gave quite constant results.
The tests with some of the materials were made over twenty-five
times; with others, such as copper amalgams, where there was no
doubt as to the result, only a few experiments were made.
Caries of the teeth, except in the later or last stage, is the result of a
ferment process, and the organisms found in the deeper parts of decay-
ing dentine, which I have isolated and obtained in pure culture, are fer-
ment organisms. The decomposition of the pulp and contents of the
root-canal, attended by bad-smelling products, is, on the other hand, a
putrefactive process in which entirely different species of fungi are con-
cerned. Whether or not the results which I have obtained for the fungi
of caries would apply equally well to those putrefactive fungi is a ques-
tion which can be settled only by experiment upon pure cultures of the
same.
Although I have now, as I think will be granted, established upon a
sure basis the fact that caries of the teeth may result directly from the
action of acid-producing fungi in the presence of fermentable carbo-
hydrates, the conclusion would hardly be justifiable that by keeping
the mouth constantly and perfectly free from all fermentable substances,
or by repeated application of antacids or antiseptics to all parts of the
teeth, or by all these means together, we could ever banish dental caries
from the oral cavity. A most powerful influence which we do not well
understand is exerted by the nutritive processes in the teeth themselves.
I am assured by men who have grown old in the practice of dentistry
that mouths which have long been under their observation, and which
practically have been completely free from caries for years, at once, on
account of some sudden change of health, show a general breaking down
or crumbling of the teeth en masse in the space of a few weeks. It has
also been my experience that patients who have been dismissed by their
dentists in America with the assurance that, according to previous expe-
rience, their dentures would require no treatment for one or two years,
have come to me a few weeks later with teeth looking as though they
had not been under the hands of a dentist for years. Some say the
ocean-voyage spoiled their teeth; others attribute it to a change in
the climate, food, health, etc.
Subj
At any rate, we have here a cause which lies without the domain of
both bacteria and acids (either ferment or otherwise). The lime salts of
the teeth are supposed to form with the organic matter of the tooth a
definite chemical compound, and it is probably due to this fact that sim-
ple salts of lime are so much more readily soluble in weak acids than
pulverized tooth-bone, or that the tartar upon the teeth is so much more
easily soluble than the teeth themselves; so that when any one rinses
his mouth with vinegar, and afterward finds lime in the vinegar, we
know that the lime in by far the greater part-if, indeed, we may not
say altogether-came from the tartar. Now, though there is no posi-
tive evidence for the supposition, it is certainly not altogether improb-
FERMENTATION IN THE HUMAN MOUTH.
813
able that, as a consequence of certain derangements in the nutritive
functions of the teeth resulting from a change of health, etc., etc., a dis-
solution of the affinity between the lime salts and the organic matter
may take place, thus setting free the easily soluble lime salts, which are
then carried away in solution or washed out mechanically. This is a
supposition only, which I bring forward because facts in this case are
absolutely wanting. If it should, perchance, contain a trace of truth,
then adult and pulpless teeth should be less subject to these sudden
attacks of caries than young teeth with living pulps.
There still remains much hard work to be done before the subject of
dental caries may be dismissed as having received a final solution in all
its different phases. There are men enough in the profession, however,
who are willing to work, and who do not shrink from the tasks yet to
be performed.
THE FUNGI OF DENTAL CARIES: THEIR PURE CULTIVATION AND
EFFECT UPON LOWER ANIMALS.
In the preceding pages will be found the description and illustrations
of two species of micro-organisms obtained from carious dentine. These
species I isolated by inoculating culture liquids with very small pieces.
of carious dentine taken from near the border of the normal tissue. If
the fungus was not at once obtained in the pure state, a second culture
tube was inoculated, after the method of fractional culture, with a min-
imum portion of the first, and so on. It soon, however, became appar-
ent that the capture of these two species by no means ended the work;
on the other hand, new forms continually presented themselves, and, in
order to be able to determine definite characteristics for each species,
resort was had to the culture on plates of gelatin prepared with beef
extract, calf's broth, malt decoction, etc.
The beef-extract gelatin, for example, I prepare as follows: 200 c.c.
water + 3.0 beef extract + 3.0 sugar are first neutralized, then slowly
boiled for five minutes and filtered (filter and all other vessels, of course,
sterilized). After cooling, 8.0 of the finest gelatin is added and grad-
ually heated till the gelatin is dissolved; it is then cleared with the
white of an egg, and all together kept at the boiling-point for about five
minutes, stirring constantly to prevent burning; it is then passed through
a filter surrounded by a bath of boiling water into glass tubes with cot-
ton stoppers (both sterilized), and kept in a refrigerator. When to be
used, it is melted in warm water and poured upon sterilized cold glass
plates, which may be 0.15 m. long by 0.07 m. wide, and placed in the
moist chamber. The layer of gelatin should be about 2 mm. thick.
-
Suppose, now, we have a culture containing different species of fungi
and we wish to separate them. A thin platinum wire with one end
melted into a glass rod is sterilized in the flame of a Bunsen burner,
and on cooling dipped into the impure culture and lightly drawn across
the surface of the gelatin; the fungi which adhered to the platinum
wire are thereby scattered in a row upon the surface of the gelatin, and
in a short time we will find that at certain points in the row one form
of fungus has developed and at other points other forms. Now, if we
814
DENTAL CARIES.
take upon the end of our platinum wire a small quantity of fungi from
one of these points and draw it across the surface of a second plate, we
will in parts of this line invariably obtain a pure culture of one of the
species in the original impure culture, nearly every species being dis-
tinguished by some characteristic in the form which it takes in growing
and in its action upon the gelatin. Having obtained a pure culture in
this manner, test-tubes containing gelatin are inoculated with it. In
these it may be kept in a pure state for weeks or months, while the
plates are always short-lived.
The gelatin method of pure culture has one great disadvantage in
the low melting-point of the gelatin : 24° to 25° C. is the highest tem-
perature to which they can be exposed without danger
of melting, and this, to fungi which are accustomed to
a temperature of 37° C., is not always a matter of
indifference. I have succeeded in isolating three spe-
cies besides the ones previously described (see p.
802), and-only for the purpose of distinguishing
them-I will designate them by the Greek letters y, d,
and ε.
These fungi are shown in Figs. 420, 421,
and 425. In Fig. 419 I have reproduced the fungus
described on page 802 as a caries fungus, for the sake of comparison.
When the species a, y, and d are isolated, it is not difficult to tell one
from the other; when, however,
they are mixed together, it is next
to impossible to determine which
is which, and especially is this
the case with a and y. Their
modes of development on gelatin
arc, however, so different that we
possess therein a ready means of
distinguishing between them. The
a-fungus, sparingly inoculated
few days the appearance which I
It may be compared to a
bunch of grapes which pre-
sents all gradations from the
fully-developed berry to the
little green one; the masses
of fungi are globular or
ovoid, exceedingly fine, and
semi-transparent, presenting
altogether a strikingly beau-
tiful culture which it is im-
possible to even approx-
imately represent by draw-
ing. It furthermore forms.
a button upon the surface
of the gelatin; the latter
becomes softened, but not
liquefied. On the plates it
FIG. 419.
AY
FIG. 420.
1
CO
FIG. 423.
into gelatin tubes, presents in a
have attempted to represent in Fig. 422.
FIG. 422.
2
FIG. 421.
FIG. 424.
MENTIONELE MEMBELA PERDS (200
?
J



FERMENTATION IN THE HUMAN MOUTH.
815
*
mm.
presents soft, milky ridges or knots raised sometimes a millimeter above
the surface of the gelatin and obtaining a width at the base of 3 to 6
The y-fungus differs from all other fungi that I have yet found
in decaying dentine in that it completely liquefies the gelatin. The cul-
ture tubes present, therefore, a funnel-shaped area of liquefied gelatin,
while the fungi themselves fall to the bottom of the funnel. (See Fig.
423.)
This fungus forms furrows in the plates; and if the plate is turned
on its edge, the whole mass of fungus flows from one end of the furrow
toward the other or slides quite off the plate.
The d-fungus (Fig. 421) forms completely opaque masses which may
have a slight yellowish tinge, provided the gelatin itself is yellowish.
It has a small surface-growth and liquefies the gelatin only to a slight
extent. In cultures on plates which are two or three days old, the row
of fungus appears to lie in a trough or depression in the gelatin. It
does not move, however, when the plate is turned on edge. (See Fig.
424.)
For the fungus of Fig. 425 I have not yet been able to establish
definite peculiarities of growth. As far as my observations have at
present extended, it differs from that of Fig.
421 in that it is almost entirely wanting in
surface-growth and forms colorless masses
even in colored media. It does not liquefy
the gelatin. Viewed by transmitted light, it
appears to have a bluish tinge and a slight
opalescence. It grows, however, very slowly,
and I have consequently as yet been unable to
establish certain and definite characteristics for
FIG. 425.
བ་་
MY
13!!
·
30
it. The fungus described on page 802 grows still more slowly at gel-
atin temperature, and I cannot at present give any microscopical feat-
ures by which cultures on gelatin may be distinguished.
The most important feature connected with all these fungi, especially
the coccus-forms, is that they possess a ferment activity-in other words,
they are capable of producing acid out of sugar, or, in the human mouth,
out of starch, by the aid of the diastatic action of the saliva. They may
consequently all be looked upon as factors in the decay of the teeth. I
would not venture to say that the a-fungus is more concerned in the
process of caries than all the rest together; nevertheless, such is the
constancy with which I have found it that if any one else should make
the assertion I would have no reason for contradicting him. Cultivated
in liquid substrata, none of them form films or skins upon the surface
of the liquid, but powdery or fleecy precipitates upon the bottom and
sides of the vessel. None, so far as I have observed, produce an evolu-
tion of carbonic acid in solutions containing sugar, nor do they appear
to suffer when the access of oxygen is restricted.
A question of great importance not only for dentists, but for general
physicians-and, in fact, for everybody—is that relating to the possible
pathogenic nature of these fungi. We find in the works of Leyden and
Jaffé, Haussman, Bollinger, James Israel, etc., sufficient ground for the
statement that "these fungi, in all parts of the human body which they
816
DENTAL CARIES.
reach, can play the same malignant rôle as upon the teeth." Gangrene
of the lungs, abscesses of the mouth and throat, chronic pyæmia, etc., etc.
have by various authors been ascribed to the action of the fungi of the
human mouth. Raynaud, Lannelongue, and Pasteur produced what
they called maladie nouvelle by inoculating rabbits with the saliva of a
child bitten by a mad dog, and A. Fraenkel has in a number of cases
produced sputum-septicemia by inoculating rabbits with his own saliva.
We ask ourselves, then, the question, May not many of our obscure
cases of infectious disease which now and then appear after extraction
or other dental operations, and which are without further examination
attributed to the unclean instruments or hands of the dentist, be the
result of an infection produced by micro-organisms in the patient's own
mouth? If a man's saliva contains organisms which when brought into
the blood of a rabbit occasion death in twenty-four hours, would it be
a matter of no consequence to produce so large a wound in his mouth
as that caused by the extraction of a tooth? For the purpose, if pos-
sible, of throwing some light upon this question, I have undertaken a
series of experiments for determining whether the organisms which are
most commonly found in the human mouth possess the power of pro-
ducing death (by septicemia or otherwise) by inoculation. These exper-
iments, as well as the others recorded in this article, I have, in fact, only
begun. My absence from home, however, prevents my carrying them
on during the summer months, and I have determined, therefore, to pre-
sent the results which I have already obtained, few and imperfect as they
are.
Co
The inoculations have thus far been performed on three rabbits, one
rat, and six white mice. They were made partly with a mixture of the
two fungi ɑ and y, and partly with saliva which had been kept in ster-
ilized calf's broth for fifteen hours at blood-temperature.
Each rabbit received 1 c.c. of the infected liquid, injected directly into
the lung or abdominal cavity; the rat 0.2 c.c., and the mice 0.1 c.c.
Exp. 1. Small rabbit inoculated with 1 c.c. in the abdominal cavity:
In the course of a few hours the rabbit appeared evidently ill, refused
to eat, and remained quiet in the corner of the cage. In twenty-four
hours diarrhoea appeared, with a slight elevation of temperature. These
symptoms increased during the next day, till fifty hours after the time
of inoculation it was found at the point of death. The examination
showed the blood to be almost entirely free from organisms and no
indication of septicemia. Living fungi were found, however, in the
abdominal cavity, and a large part of the right lobe of the liver was
completely riddled with masses of fungi; also in the faces were found
enormous numbers, which morphologically were identical with those in
the liver, their entrance into the alimentary canal from the liver being
easily accomplished. I unfortunately neglected, however, to establish
their identity by the proper cultures.
Exp. 2. Rabbit inoculated as in Exp. 1: The animal manifested a
slight indisposition on the second day, from which it soon recovered.
Exp. 3. Rabbit inoculated in the right lung with saliva which had
been kept in sterilized calf's broth for fifteen hours at 37° C.: No
effect apparent.
FERMENTATION IN THE HUMAN MOUTH.
817
Exp. 4. White rat, injection in abdominal cavity: The animal
remained well.
FIG. 426.
Exps. 5-11. Seven white mice; five inoculated in abdominal cavity
with a- and y-fungi; two in the lungs with saliva in calf's broth: Of
the former two died at about the fortieth hour under the same symp-
toms as in Exp. 1. Great numbers of fungi were found in the abdom-
inal cavity, which by culture on gelatin proved to be the y-fungus. A
number of colonies were likewise found in the liver. Microtome sec-
tions of the liver of the rabbit stained in fuchsin show, when examined
under the microscope with sufficient
light to drown the tissue, a distribution
of the fungi very similar to that often
seen in the outermost layers of carious
dentine. (See Fig. 426.) Of course no
definite conclusion can be drawn from
a few experiments. They are, however,
sufficient to show that these fungi cer-
tainly do possess a pathogenic character,
and when brought into other parts of
the human body may be able, under
predisposing conditions, to produce dis-
astrous results. Especially the contin-
ual swallowing of these fungi in great numbers may by their ferment
activity alone in the course of time produce very serious derangements
of the stomach and alimentary canal, since the small percentage of
hydrochloric acid in the stomach, even in the presence of the normal
quantity of pepsin, is not sufficient to devitalize them. It was with a
certain degree of satisfaction that I have failed thus far to find the
coccus of sputum-septicemia in my own saliva. It is, however, very
desirable that experiments should be made with the saliva of many per-
sons, for the purpose, if possible, of determining in what proportion of
cases this fungus is present.

ات
..
EX
Messrs. Underwood and Milles have endeavored to repeat some of
my earliest experiments in the production of artificial caries, but, under
those very abnormal conditions against which I entered warning in the
Independent Practitioner, failure was the necessary result. They per-
formed, further, a very elaborate experiment, lasting six months, in
which the baths became so putrid and offensive that "they quit the
experiment with relief." They naturally produced no caries, thereby
furnishing an admirable confirmation of the fact to which I have so
often called attention that it is impossible to produce even a trace of
caries by putrefaction alone. They tried a third experiment, putting
the fungi under such abnormal conditions that they could not produce
acid, and of course failed again, once more confirming the fact that I
have long since established-that we can have no caries without acid.
With these experiments they risk the statement that artificial caries is
probably an impossibility. The production of artificial caries is a fait
accompli, and to deny its possibility is only to endanger the reputation
of him who denies. They state further that they can find no softened
dentine which does not contain micro-organisms. This, however, is con-
VOL. I.--52
818
DENTAL CARIES.
trary to the experience of a great many American microscopists, and,
moreover, as I have elsewhere stated, I shall take with me to the next
meeting of the American Dental Society of Europe several hundreds of
specimens of carious dentine, and be ready to show the areas of softened,
non-infected dentine on any one or on all of them.
Messrs. Underwood and Milles understand me, in the third place, as
being of the opinion that all the micro-organisms connected with caries
of the teeth are only different forms of one fungus. The readers of the
Independent Practitioner know better. I have stated simply that one
of the many fungi found in the human mouth in connection with caries
of the teeth may produce different forms of development. This is the
fungus which I have designated by the prefix ẞ. It is scarcely neces-
sary to add that I am always prepared to prove its existence micro-
scopically, as well as on the authority of many of the best mycologists
of Germany.
f
No one, I think, will deny that within the last few years I have done
a large amount of work and contributed some evidence toward the solu-
tion of the problem of dental caries. The amount of material dealt with
and the ground gone over have been so extensive that it has been abso-
lutely impossible, with the greatest efforts, to remain as long by each
step as would have been desirable. It may be, therefore, that at some
points the subject has not been presented with sufficient clearness or
decisiveness; it may be, too, that at some points the conclusions have
been faulty, since I make no pretension to infallibility. Time will show
whether this is the case. At present I know of no important change
which I could make if I were to rewrite all my contributions of the last
three years.
I desire to give, in closing, a very short résumé of the work which I
have accomplished:
1. I convinced myself by the examination of some thousands of slides
of carious dentine that micro-organisms were always present, and that
they, without any doubt, were the cause of various anatomical changes
which were found to take place in the structure of the dentine during
caries. (Here, of course, the question of priority does not suggest itself:
Leber and Rottenstein, as is well known, were the first to give definite
expression to this fact.)
2. I proved, at the same time, that the invasion of the micro-organ-
isms was not, in the majority of cases, simultaneous with the softening
of the dentine, but that large areas of softened dentine could be found
that contained no fungi. Of all those who examined my preparations
in America, no one, whatever his theory, ever once denied this fact. I
concluded from this that the softening of the dentine went in advance
of the invasion of the organisms.
3. I determined by analyses of masses of carious dentine sufficiently
large to give reliable results that the softening of the dentine is of the
nature of a true decalcification; that the decalcification of the outer
layers is almost complete and diminishes in degree as we advance
toward the normal dentine; furthermore, that the same relations
maintain in dentine softened in a mixture of saliva and bread or in
weak organic acids; also, that in a mass of carious dentine the lime
BIOLOGICAL STUDIES ON FUNGI OF HUMAN MOUTH. 819
salts had been removed to a much greater extent than the organic
matter.
4. I maintained from the first that the softening of the dentine was
produced by acids for the most part generated in the mouth by fer-
mentation. I had, however, no direct proof of this.
5. I proved that fungi exist in great numbers in the human saliva
and in carious dentine which have the power to produce acid under
conditions which are constantly present in the human mouth. I deter-
mined this acid-for one of the fungi, at least-to be the ordinary
ferment, lactic acid.
6. I produced caries artificially which under the microscope cannot
be distinguished from natural caries by subjecting sound dentine to the
action of these fungi in fermentable solutions.
7. I determined the influence of various antiseptics and filling mate-
rials upon the fungi of caries.
8. I isolated various forms of these fungi and determined, in part, the
conditions most favorable to their development, their characteristic reac-
tion upon gelatin, their physiological action, their effect when inoculated
into the system of lower animals, and their possible connection with cer-
tain obscure diseases generally attributed to the carelessness of the dentist.
My continual search has been after facts, and such facts as I have
obtained I have presented before the profession, never putting before
them either theory or speculation, nor anything which was not the result
of severe and continued labor; and in this spirit I propose to prosecute
this work, as well as any other that I may undertake in the interest of
the profession.
BERLIN, May 21, 1884.
NOTE. Since writing the above I have succeeded in producing death by septicemia
of both mice and rabbits by injecting into the lung saliva from the mouth of a per-
fectly healthy person.
BIOLOGICAL STUDIES ON THE FUNGI OF THE HUMAN
MOUTH."
MO
IN order to be able to determine upon the proper course to be taken
in the attempt to remove or check the progress of any disease, it is
necessary that our ideas of the cause and course of that affection be
established upon the most certain, exact, and scientific data which we
are capable of attaining. Unfortunately for the dental profession, the
attempt to furnish a scientific solution of the problems of dental caries
has until recently been confined to a very few, and even now a majority
¹ German mycologists use the term Pilz indiscriminately to designate either schizo-
mycetes, blastomycetes, hyphomycetes or myxomycetes. When it is desirable to refer
to any one of these groups in particular, they use the prefixes Spalt, Spross, Schimmel
or Faden, and Schleim, giving Spaltpilz, Sprosspilz, Schimmel- or Fadenpilz, and Schleim-
pilz. Following their example, I have in previous papers used the term "fungus" for
all of the four groups of mycetes mentioned above, and shall also use the term in this
paper, in which only schizomycetes are treated of.
820
DENTAL CARIES.
of the investigators in dental pathology are content to restrict their
observations to the clinical aspect of the question-a course which
could never produce a satisfactory solution-while others even openly
advocate a speculative course and do not hesitate to ascribe to every new
factor discovered in nature a role in the production of caries of the teeth.
Consequently, we have had presented to us, in turn, worms, acids, inflam-
mation, electricity, infusoria, bacteria, putrefaction, toxic agents, etc., etc.,
as causes or conditions of caries dentinum, some of these theories con-
taining some truth and some a surprising amount of absurdity. In the
last two or three years, however, a great advance has been made in the
methods of study and a number of important points have been firmly
established:
kendal
1. The observation of Leber and Rottenstein that micro-organisms
are constantly present in decaying dentine has been confirmed (Weil,
Milles, Underwood, Miller).
2. The softening of dentine in caries has been shown to be chemically
identical with that produced by certain weak organic acids (Miller, Jese-
rich, Bennefeld).
3. It has been established that various organisms found in the human
mouth produce the decalcifying acid by first converting non-fermentable
sugars into fermentable varieties, and secondly by splitting fermentable
sugars into lactic acid (Miller, Hueppe).
4. The same organisms have been found capable of dissolving decal-
cified dentine, while they have no apparent effect, even after two or three
years, on sound dentine (Miller).
5. Caries of dentine chemically and morphologically identical with
natural caries has been produced outside of the mouth (Miller).
6. It has been furthermore shown that certain of the organisms of
the human mouth are capable of developing under exclusion of air,
thus making it possible for them to propagate within the substance of
the dentine (Miller, Hueppe).
I propose to describe in the following pages a series of experi-
ments made for the purpose of obtaining more definite information
respecting the number and morphology of the fungi of the human
mouth, and their physiology, as far as is necessary to an understanding
of the part which they may perform in the production of caries of the
human teeth.
At the meeting of the American Dental Association at Saratoga a
number of tubes containing pure cultures of fungi were passed around;
with regard to these a reporter remarked that "they were evidently
beyond the information of the majority." It is not very flattering to
American dentistry if its representative association allows a question of
so great importance to remain beyond its comprehension, nor is there
any excuse for such a condition of things now, so widespread have the
methods of pure culture become. I rather incline to the opinion that
the reporter misinterpreted the apathy of the members of the society.
I shall, at any rate, here describe in a few words the methods now uni-
versally employed in isolating any given fungus, and then more in detail
give the means which I have used to ascertain the physiological charac-
teristics of the different fungi when obtained in pure culture.
BIOLOGICAL STUDIES ON FUNGI OF HUMAN MOUTH.
821
We will start with a solution densely impregnated with micro-organ-
isms and a number of tubes of culture gelatin perfectly sterilized. The
gelatin being melted, we add to the first tube one bead (on a loop of
sterilized platinum wire) of the solution; this is called the first dilution.
From this tube we add two or three beads to a second tube (second dilu-
tion), and from the second five or six beads to a third tube (third dilu-
tion). The gelatin is then poured upon horizontally placed sterilized
cold glass plates. It congeals in a few seconds, and the three plates are
placed in a pile (on glass benches) in a moist cell. The plates are exam-
ined after twenty-four to thirty-six hours under a magnification of 100
diameters. By this means the fungi are so separated that on the third
plate there will generally not be more than two to ten (on the second
there may be one hundred or two hundred, while on the first, of course,
there are very many more). As each micro-organism develops, being
fixed in the gelatin, we will have at that point a pure culture of that
particular kind; at another point we obtain a colony of a second kind;
and so on.
In general, colonies of different fungi may be distinguished
with the greatest ease by their microscopic appearance. With a steril-
ized platinum wire bent at right angles at the end we now pick up a
number of the colonies of each kind under the microscope (100 diam-
eters), and transfer them directly to tubes of culture gelatin, only one
colony to each tube. We have then (except in case of a possible acci-
dental air-infection) pure cultures. Some experience is necessary to
enable one to pick up the colonies under the microscope. Beginners
should not attempt it with plates where more than one colony is in the
field at once.
May
6. Does it cause putrefaction?
7. Does it have a diastatic, inverting, or peptonizing action?
8. Has it a pathogenic character?
Gy
The method described on page 813 may also sometimes be used to
great advantage. For fungi which do not grow on gelatin, agar-agar or
congealed blood-serum should be used. The former, 1 to 14 per cent.,
has a higher melting-point than gelatin, 10 per cent., and remains solid
at the temperature of the human blood. When it is used for plate-cul-
tures, it must be melted in hot water and the infection made at a tem-
perature of 40° to 42° C. Below this temperature it becomes solid and
cannot be poured; above it the germs would be liable to suffer. In
other respects the agar-agar media are treated as the gelatin. Congealed
blood-serum cannot, of course, be poured upon plates. It is prepared
in test-tubes so inclined as to give the greatest possible surface, and a
minimum quantity of the substance containing the fungus or fungi
spread over the surface. Having obtained a pure culture of any
fungus, the points to be determined regarding it are the following:
1. Its morphology (bacillus, spirillum, micrococcus).
2. Is it movable? Does it produce spores?
3. What are its growth-characteristics on various media, microscopi-
cally and to the naked eye?
4. What are its relations to oxygen ?
5. Does it produce fermentation? If so, what fermentation, under
what conditions, and with or without development of gas?
822
DENTAL CARIES.
9. Does it produce coloring-matter?
10. What is its susceptibility to the action of the various antiseptics?
The first and second of these questions are, of course, determined by
the microscope alone; the third, by the microscope and the naked eye
combined; the fourth, by the methods described on page 814, or by
placing a thin strip of mica upon one half of the culture-plate before
the gelatin solidifies. The mica then adapts itself closely to the surface
of the gelatin, excluding the air; and if the fungus requires oxygen for
its development, the colonies beneath the mica either will not develop at
all or they will be very small compared with those on the other half of
the plate, their growth ceasing as soon as the oxygen in the gelatin has
been consumed (Koch). The fifth point is answered by infecting fer-
mentable solutions with the fungus in question, placing it under various
conditions of temperature, etc., and determining the products of fermen-
tation (if any); the sixth, by analogous methods; the seventh question
is determined by the action of the fungi upon starch, cane-sugar, and
albumen (boiled white of egg); the eighth, by experiments on animals;
the ninth, by the appearance or non-appearance of color in the vegeta-
tion itself or in the surrounding medium; the tenth, by experiments
that will readily suggest themselves. Other points to be investigated
will be mentioned farther on.
Boiled potato is a medium of great value in the determination of
schizomycetes. No medium, however, requires greater care in prepara-
tion and after-treatment than this in order to obtain satisfactory results.
Any sound potato which does not become mealy or crack open on boiling
will do for the purpose. It is first thoroughly washed and brushed,
and, all defective spots and deep eyes being removed, it is placed for
one hour in a corrosive sublimate solution, 5 to 1000, then in the steam
sterilizer for one-half to one hour. In the mean time, the moist cell is
sterilized and the bottom lined with filter-paper wet with sublimate
solution, 5 to 1000. The potatoes are while hot removed from the
sterilizer with sterilized forceps, cut into halves with a cold sterilized
knife, and placed directly upon the sublimate paper (the cut surface up)
and the cell closed. Potato-sections prepared in this way should remain
unchanged indefinitely. When the potato has become cool, the cover
of the cell is carefully removed and the fungus which is to be cultivated
is spread upon a space about as large as a dime in the centre of the sec-
tion. Fungi which, morphologically as well as in their reaction upon
gelatin, agar-agar, and blood-serum, show no appreciable differences,
may sometimes be easily distinguished by aid of the potato culture.
The potato can seldom be used to separate fungi-i. e. to prepare pure
culture. It is chiefly used as a reagent in distinguishing between fungi
already in pure culture. For example, all comma bacilli yet discovered
grow on potato except the one found by Dencke in old cheese, which
does not develop at all on potato, and is thereby at once distinguished
as an entirely different fungus.
Eggs may often be used to great advantage. They are prepared as
follows: The fresh egg is placed in sublimate, 5 to 1000, for ten min-
utes, then in the steam sterilizer for one hour. The cell for eggs is
prepared as for potatoes, except that a sterilized glass plate resting on a
BIOLOGICAL STUDIES ON FUNGI OF HUMAN MOUTH.
823
glass bench is placed in the bottom to support the egg-sections. As the
eggs must be handled with the fingers, the hands must be thoroughly
washed, then soaked in sublimate, 5 to 1000, and then washed again in
alcohol absolutus, to remove the sublimate. The eggs are shelled while
still hot and cut into two, three, or four sections. They are vaccinated
in points upon the white; the yellow is not so well adapted to culture
experiments, since it cannot be cut with a smooth surface.
I always keep on hand sections of potato and egg, also tubes of gela-
tin, agar-agar, and blood-serum; and when in my practice particularly
good material or anything uncommon presents itself, a portion of it is
at once transferred to these different culture media; so that it is pretty
sure to develop in one of them, at least. For example, I have several
times met with a fungus in the human mouth which produces a yellow-
ish coloring-matter, and which absolutely refuses to grow on anything
which I have tried except potato.
By use of the methods described I have isolated twenty-two different
fungi from the secretions or deposits of the human mouth, and have
endeavored to determine, as far as possible, their separate peculiarities
of growth, physiological action, etc. It will, however, at once suggest
itself to every one that a thorough study of twenty-two different fungi
involves an enormous amount of labor and might constitute almost a
life-task for one experimenter. The task is, moreover, rendered still
more difficult by reason of the fact that many of these fungi show dif-
ferences of action when cultivated in different media, rendering the
number of experiments necessary to come to a definite conclusion doubly
great. I shall, therefore, not attempt to present an exhaustive treatment
of the subject, but rather an introduction, hoping, at the same time, to
establish some points which may be of use in bringing about a clearer
understanding of the factors involved in the production of dental
caries.
Regarding the first point to be considered—the morphology of the
fungi-it is not at all necessary to enter into a minute description of all
the different forms here presented; the figures will give a sufficiently
clear idea of their diversity and the appearance of their colonies under
a low power.
For the rest, suffice it to say that ten of them are micro-
or diplococci, five are bacteria, and six bacilli. Some show more than
one form of development. It would, however, lead us too far from
our subject to discuss this fact here.
In liquid media three grow out into long leptothrix, forming bundles
or meshes of intertwining uni- or multicellular threads, while one
develops into spirilli; eight are motile, fourteen are non-motile, while
three only have been seen to form spores. The others multiply by
division alone.
With reference to the latter point, however, I have not made exam-
inations sufficiently careful or extensive to be able to speak decidedly.
Eight liquefy nutritive gelatin, one converts it into a paste,
thirteen leave it unchanged. On agar-agar the differences
of growth are not sufficiently pronounced to deserve par-
ticular mention. In gelatin the microscopic appearance
of the colonies of a sufficient number of these fungi is
FIG. 427.
a
C
B
824
DENTAL CARIES.
shown in the figures (b). It will be seen that the appearance of the
colonies forms a much safer means of differentiation than the morpho-
logical characteristics of the fungi, it being very seldom that in growing
two fungi present exactly the same appearance. An exception is, how-
ever, presented by 6 and 7, which to the naked eye and under the
microscope grow on gelatin exactly alike; moreover, on potato, white
of egg, blood-serum, agar-agar, and milk their effect is identical. One,
however, produces a yellow coloring-matter, the other not; and thereby
they are easily distinguished. The others may all be readily distin-
guished by their growth on potato.
FIG. 428.
In relation to oxygen they show great differences. Ten are strictly
aërobian—i. e. they grow only where the air has free access; four are
not strictly aërobian-i. e. they propagate also when the atmospheric
air is excluded, though not so rapidly; eight grow equally
well with or without access of air; sixteen produce an acid
reaction in a solution of beef-extract, peptone, and sugar;
four produce an alkaline reaction without the appearance
of bad-smelling products and appear to leave the solution
neutral. With regard to the six, however, the results were not satis-
factory, sometimes the reaction being acid, at other times neutral or
alkaline, depending somewhat upon the material used for the cultures.
1
Some which produce an acid reaction in fermentable solutions give
rise to an alkaline reaction in non-fermentable solutions. The acid pro-
duced is probably in all, or in nearly all, these cases, lactic acid. This
fact I established for No. 1 by chemical analysis, for No. 2 by forming
the zinc salt and crystallizing, for No. 5 by the color test. In the
other cases the acid was not determined. Thirteen were repeatedly cul-
tivated on potato. Of these, five grew rapidly, one in particular cov-
ering the whole surface of the section in forty-eight hours and completely
liquefying it to a depth of 1 to 2 mm., the liquefied mass flowing off at
the sides; the others develop very slowly and attain only a limited
growth. I am not able to say whether any of them
possesses a diastatic action. It is, however, highly prob-
able. Fifteen were cultivated on boiled white of egg.
Four grew very rapidly, No. 19 (see Fig. 439) in par-
ticular in from two to four days, converting the egg into
a semi-transparent pasty mass which gradually disap-
peared. In the first two days large quantities of sulphuretted hydrogen
are developed; later, ammonia. Seven grew slowly on the white of
egg, and four scarcely at all. The nourishment of the fungi naturally
takes place at the expense of the albumen of the egg, which is converted
into a soluble variety by the peptonizing action of the fungus. In two
cases the presence of peptone could be detected in the dissolved mass
·
L
FIG. 429.
a
›
D
Two drops carbolic acid, 1 drop chloride of iron, 20 c.cm. water, produce a violet color
which becomes yellow on the addition of lactic acid, even in very dilute form. I am
not prepared to say that this is an absolutely sure test for lactic acid. It is the test
used by Prof. Ewald and others for detecting lactic acid in the stomach, and is con-
sidered by them to be decisive. Of course the culture material itself must not give
this reaction. Beef-extract, for example, cannot be used, as it already contains lactic
acid. A few other substances also give this reaction, but none, I believe, which are
likely to be produced in these cultures.
BIOLOGICAL STUDIES ON FUNGI OF HUMAN MOUTH.
825
after separation from the albumen by the biuret reaction,
the organisms producing more peptone than they needed
for their own consumption.
Some of them produce in fermentable solutions con-
siderable quantities of gas. If a glass bulb with a fine
stem drawn out to a point be filled with milk inoculated with No. 3
(see Fig. 428), otherwise sterile, and kept at blood-temperature, in
twenty-four hours so much gas will be generated that on breaking off
the point the whole contents of the bulb will be ejected with consider-
able force. The same effect may sometimes be produced,
though not so markedly, when non-fermentable solu-
tions are used. We may expect a similar action to take
place when we seal up a dead pulp in a tooth, the gas
itself not only escaping through the apical foramen, but,
if its exit is hindered, ultimately forcing particles of the decomposing
pulp through with it. The question suggests itself whether certain
configurations seen in carious dentine may not owe their origin in
part to the pressure of gas.
FIG. 430.
"
✩
FIG. 431.
a
Qita
Four produce coloring-matter, Nos. 5 and 7 (Figs. 430 and 431) in
gelatin cultures some days old, forming brick-yellow masses such as
may be seen occasionally on the buccal surface of teeth which are not
kept well cleaned.
FIG. 432.
On potato they appear bright yellow. Nos. 10 and 13 give
the gelatin for a space 1 cm. in diameter around the colony a grass-
green tinge. I doubt very much whether either of these
organisms has anything to do with the production of green
stain, all my attempts to isolate a chromogenic fungus directly
from green stain having thus far failed. Cultures of some of
these fungi were made on dentine and enamel. Sections of
dentine, when decalcified, neutralized, and soaked in saliva
and sugar, formed, when kept in a perfectly damp cell, a
medium on which a considerable development took place, microtome
sections of the dentine after two weeks showing a destruction of sub-
stance at the point of inoculation.
On sections of normal dentine the fungi in some cases appeared to
maintain an existence until the organic matter exposed upon the surface
of the section was consumed, after which the development ceased, while
normal enamel, as might have been expected, formed about as good a
culture substratum as glass or porcelain.
A description of the cultures in milk, blood-serum, etc. is not neces-
sary for our present purpose; also, experiments on animals have been
made in too limited a number to lead to accurate results.
It is very plain, however, that a study of the pathogenic
character of twenty-two fungi is out of the question. No.
19, which possesses peculiar interest on account of its
similarity to the cholera-bacillus, was tested on mice,
guinea-pigs, and rabbits. A small quantity from a pure
culture injected into the abdominal cavity of mice almost
invariably caused death in a few hours. Guinea-pigs and rabbits have
a
6).
~~~
FIG. 433.
a
Diff
826
DENTAL CARIES.
FIG. 434.
thus far shown themselves proof against it even when large quantities
were injected into the duodenum (the ductus choledochus not being
ligated). Experiments were made with a number of antiseptics in
addition to those given on page 810. Arsenious acid,
contrary to the repeated statements of one of our
journals, possesses an antiseptic power at least half as
great as that of carbolic acid, and about twenty-five
times greater than absolute alcohol. Chlorate of potas-
sium, on the other hand, possesses scarcely any available
power whatever. Peroxide of hydrogen proved to be particularly active.
The following practical conclusions appear to follow from the experi-
ments above recorded:
??
1. A great majority of the fungi found in the human mouth are
capable of producing acid from cane- or grape-sugar, and it is proba-
ble that, with very few exceptions, all can when the proper conditions are
presented to them. In nearly all cases which have been examined with
special reference to this question the acid has appeared to be lactic. The
acetic-acid fermentation, which cannot go on at temperatures above 35°
C. (Fluegge), is out of the question in the human mouth, nor is there
as yet any proof of the presence of more than minute traces of butyric
acid.
2. In non-fermentable substances the reaction will be found either
neutral or alkaline, in some cases considerable quantities of ammonia
and sulphuretted hydrogen being produced. If, therefore, a decom-
posing pulp is sealed up in a tooth, its reaction cannot be acid, and
caries cannot take place in either the pulp-chamber or the root-
canals.
A
3. Of considerable interest is the fact that the same fungus may produce
an acid reaction in one substratum and an alkaline in another. If, for
example, No. 19 (Fig. 439) be
cultivated in certain neutral non-
fermentable substances, an alkaline
reaction will appear; if then sugar
be added, the reaction will in a few
hours change to acid. In such a
case we undoubtedly have two dis-
tinct processes going on-first, the nutrition of
the organism, accompanied by the appearance of
alkaline products; and secondly, its fermentative
S
action, accompanied by acid products. Ordinarily, the latter so out-
weigh the former that the resultant reaction will be acid. This is,
however, by no means necessarily the case. On the other hand, condi-
tions may readily be produced under which the resultant reaction will
be neutral or alkaline, especially in the human mouth, where so many
different fungi and so various conditions are present. In such a case
the result would be to put a temporary check upon the advance of the
decalcifying process-in other words, upon the caries itself. In the case
of particularly foul-mouthed persons the foulness itself may become a
preventive of caries.
FIG. 435.
،
V
VALERO (22-
G
FIG. 436.
a
Cl

BIOLOGICAL STUDIES ON FUNGI OF HUMAN MOUTH.
827
4. The possession of a peptonizing action by a large number of these
fungi readily accounts for the solution of the decalcified dentine.¹
5. Any one of these fungi which can produce acid by fermentation of
carbohydrates or can dissolve the decalcified dentine may aid in the pro-
duction of caries, while any one which combines both
these properties-as many of them do-may alone
bring about the phenomenon of dental caries. A solu-
tion of the dentine or enamel without previous decalci-
fication cannot take place. The fact which I have so
often affirmed, and which was denied by Milles and
Underwood-that one continually meets with large
tracts of softened, non-infected dentine-has been com-
pletely confirmed by Arkovy and Matrai. They say: "The invasion.
extends, however, only to a certain depth, and only isolated tubules
show a deeper invasion, sometimes to twice the depth, and reach the
border of the normal dentine," the whole territory between the isolated
tubules being free from invasion.
6. The comparative or complete independence of many of these
organisms of the free access of air renders their propagation within
the dentine or under fillings where softened, non-
sterilized dentine has been left an easy matter.
FIG. 438.
FIG. 439.
7. The fact that dentine and enamel form so
exceedingly poor culture substrata for schizomy-
cetes is an additional proof of the position that
their attack upon the teeth is only secondary—
i. e. they owe their rapid devel-
opment to the secretions, deposits,
etc. of the oral cavity; and not
until the tissue of the tooth has
undergone a certain change-first
decalcification, second peptoniza-
tion-can they adapt it to their
nourishment. The decalcification
باہر
∞
S
"
FIG. 437.
a
2


b
is produced chiefly by acid resulting from the action of the organisms
upon certain carbohydrates in the human mouth, while the peptoniza-
tion is produced either by the direct action of the protoplasm of the
organisms upon the decalcified dentine or by the action of a ferment
which they produce.
1
A knowledge of the properties of the fungi of the human mouth, as
¹Not a little confusion has been introduced by attempted artificial definitions of
putrefaction and fermentation. The idea that every change in nitrogenous organic
substances must be of the nature of putrefaction is particularly misleading. A ferment
of the nature of pepsin which dissolves coagulated albumen is widely distributed among
the fungi of fermentation as well as putrefaction, and the schizomycetes in general
require nitrogenous substances in some shape for their nutrition. The dissolution of
the organic portion of dentine is by no means dependent upon the presence of
putrefactive organism, but may be accomplished equally well by fermentation. As
previously stated, I never found a putrefactive organism in the deeper portions of carious
dentine. Moreover, the acid reaction of carious dentine is highly unfavorable to the
development of such organisms. I intend to repeat and extend my experiments on
this point. The presence of putrefactive organisms, while it would accelerate the sec-
ond stage of caries, could only retard the first.
828
DENTAL CARIES.
given above, combined with a microscopic and chemical examination of
carious tissue and comparative studies of caries of living and dead teeth,
appear to me to furnish a fair solution of the phenomena of dental
caries. That other agents than those of a parasitic nature are also
often concerned there can be no doubt. To say nothing of predispos-
ing causes, an acid reaction of the oral secretions, acid medicines, acid
foods, etc. may give rise to caries at points which otherwise probably
would have escaped.
PATHOLOGY OF THE DENTAL PULP.
By G. V. BLACK, M. D., D. D. S.
THE dental pulp comprises the soft tissue that occupies the central
cavity of the crown of the tooth and the canals in the roots to the
apical foramen. It is thus divided into two portions-the coronal
portion or bulb, which occupies the crown-cavity, and the canal por-
tion, which occupies the roots or root-canals. Aside from this, the
coronal portion has a projection of its tissue under each of the of
cusps
the tooth, as in the molars, which are called the horns of the pulp.
These horns are often quite long and slender, especially in young
teeth with long cusps. Generally, the form of the pulp corresponds
pretty closely to that of the tooth, except that it is every way more
slender.
The Tissue of the dental pulp is of the connective-tissue group, and
supports an abundant supply of blood-vessels and nerves. Its mass is
a
CAS
FIG. 440.
d

FJ-53
"
SE
f
Git
C
ď
e
Margin of Dental Pulp: a, a, dentinal fibrils, pulled out of the dentine; b, b, membrana eboris
or layer of odontoblasts; e, c, transparent zone between the odontoblasts and the cells of the pulp
proper; d, d, layer of cells closely packed together; e, e, blood-vessels; ff, cells less closely
placed toward the central portions of the pulp (Wales' immersion in. objective).
made up of a semi-gelatinous matrix, which is quite thickly studded
with cells, but these cells do not in themselves form a complete tissue,
in that they are not placed in contact with each other. They are
829
830
PATHOLOGY OF THE DENTAL PULP.
imbedded in the gelatinous matrix, always a little apart from each
other, even where most thickly set. The accompanying illustration (Fig.
440) gives a good idea of the pulp-tissue as seen with a high power in
thin sections stained with hæmatoxylin. This is from the crown portion
of the pulp, and in this the cells are set in no particular position rela-
tively to each other, but seem to be placed as if by accident in every
conceivable position. In the root portion this is different: the cells
are there placed with their long axis parallel with the long axis of the
canal; which arrangement gives the tissue quite a different appearance.
The Cells are generally spindle-shaped, with a delicate filament or
process extending from either end. The form, however, varies con-
siderably, especially in the coronal portion of the pulp. Some may
be seen so delicate and slender that they seem but little else than a
filament, while others are nearly round and much larger in their
central part. Again, we meet with many cells, especially in the
coronal portion, that have three and four filaments extending in as
many directions. In the normal pulp these filaments are very slender
and are lost in the gelatinous matrix. These, in all well-prepared sec-
tions, appear as minute threads in all parts of the tissue (as shown in
the illustration).
A
FIG. 441.
The Distribution of the Cells varies considerably in different portions
of the pulp. They are fewest in number in the central parts of the
coronal portion. All around the periphery of the pulp, just a little
inside the layer of odontoblasts, we find a zone that is much more
thickly studded with cells (d). This is seen
in all parts of the pulp periphery. Between
this and the layer of odontoblasts there is a
narrow zone that is usually almost or quite
destitute of cells. In sections so prepared
as to show them this is found to be occupied
by a very fine plexus of nerves.
The Odontoblasts form the periphery of
the pulp, and lie in contact with the dentine
(Fig. 440, b). As seen with hematoxylin
staining, they seem to be flask-shaped cells
with a process extending into the dentine,
the fibrils of Tomes, or the dentinal fibrils.
There is also a process extending from
the pulpal end of the cell which does not
take the stain and cannot be seen by this
mode of preparation. In Fig. 441, I have
shown these cells as they appear in plain
unstained section, mounted in glycerin,
with the one-sixteenth inch immersion
objective. The cells are shown just as
are drawn just as they lay distorted they happened to lie, without correcting
Odontoblasts clinging to a Fragment
of Imperfectly-developed Dentine.
The tissue was pulled away in
mounting the section. The cells
in the mounting, but a good idea is
given of their true form (glycerin
mounting, th inch obj.).
any of the distortion caused by the mount-
ing. In this section the odontoblasts seem
to have been pulled off from the tisssue of the pulp in pressing down
the cover-glass, and the fibrils are evidently somewhat stretched out of
6
S

Grad
STRUCTURE OF THE DENTAL PULP.
831
1
the dentine; otherwise the drawing may be regarded as representing
very closely the true form and relations of these cells to each other and
to the dentine.
FIG. 442.
The Blood-vessels of the pulp are very numerous. In young teeth, the
roots of which are not yet fully formed, there are usually a number of small
arteries entering the pulp; but as the apical foramen becomes narrower
these diminish in number, until finally there are not more than two or
three, and in a very large number of cases only one. This divides and
subdivides until the entire tissue of the
pulp is filled with a network of capil-
laries, which is especially rich in the per-
iphery of the organ immediately beneath
the odontoblasts. Fig. 442 gives a good
idea of this. The veins are usually a
little larger than the arteries, and anasto-
mose with each other very freely. The
blood-vessels of the pulp are remarkable
for the thinness of their walls-a fact that
becomes very important in the study of
its pathological conditions. The smaller
veins are generally nothing more than the
endothelial cells placed edge to edge or
margin to margin. The arteries have a
circular and a longitudinal layer of mus-
cular fibres, but these are very thinly
distributed.

Kadang
The Nerves of the Pulp enter the apical
foramen usually in a single bundle, which
breaks up but little in the canal portion
of the pulp, but in the coronal subdivides
in every direction to send filaments to the
periphery. Immediately beneath the layer of odontoblasts there is a
very delicate plexus of fine naked nerve-filaments. These are not well
seen in sections stained with hematoxylin, but with chloride of gold or
by treating with caustic potash, as recommended by Boll, they come into
view.
Point of the Pulp of an Incisor. in-
jected with Beale's blue to show the
blood-vessels (X 25).
This makes up, in brief, the sum of the pulp-tissue. The only ele-
ment really peculiar to it is the odontoblast or dentine-forming cell.
The tissue may be regarded as semi-foetal in type; that is to say, it is
a true connective tissue which seems not to have reached mature devel-
opment. It is only occasionally in the root portion that we see the cells
so placed in relation to each other as to form a tissue by their conjunc-
tion during the health of the organ. They seem to be simply imbedded
in the gelatinous matrix, as is seen so markedly in the tissues of the
foetus. The gelatinous matrix contains no areola during the health of
the organ, but, as we shall see, often becomes areolar in chronic hyper-
æmia and chronic inflammation of the pulp. The dental pulp seems to
be destitute of lymphatics-a fact of considerable moment, as will be
seen in the study of its pathology and symptomatology. With these
points well in mind we are prepared to study the changes that occur in
-
832
PATHOLOGY OF THE DENTAL PULP.
the diseases of the pulp. But before proceeding to this it may be well
to examine the sensory functions of the pulp, with the view of a better
understanding of its symptomatology.
THE SENSORY FUNCTIONS AND SYMPTOMATOLOGY OF THE
DENTAL PULP.
A proper understanding of the sensory functions of the dental pulp
is so important to the correct interpretation of its symptomatology that
it seems to me necessary to introduce here its consideration. It is gen-
erally and correctly considered that the physical function of the pulp is
the formation of the dentine and the maintenance of its vitality. But
aside from this the pulp has a special sensory function which is limited
in the most remarkable manner, and which, so far as I am able at pres-
ent to determine, has no parallel among the organs and tissues of the
body. This function consists in a peculiar resentment to thermal changes.¹
1
It requires both the pulp and peridental membrane to make up the
sum of the sensory functions of the tooth. The sense of touch resides
wholly in the peridental membrane, which receives the impression of
even the slightest touch upon any part of the surface of the tooth. The
pulp, on the other hand, has not the sense of touch. If it had, it is
clear that it would not be able to exercise it in the normal condition of
complete encasement within its dentinal chamber. It is completely
shielded from contact with the outer world, and in this condition has
no need for the sense of touch or the tactile sense. This is true also of
the dentine. Indeed, the dentine derives its sensory function directly
from the pulp through the fibrils of Tomes or dentinal fibrils, and,
except that it is more limited, agrees in all respects with the pulp. The
dental pulp responds very promptly to injury-not by means of a sense
of touch, but by means of the sense of pain. There is a sharp distinc-
tion to be made between these two functions-a distinction having a spe-
cial bearing upon the symptomatology of the organ. The tactile sense
is a localizing sense. The sense of pain when standing alone is not a
localizing sense. It may be said that the mind takes no cognizance of
organs that have not the tactile sense. It does not follow that these
organs fail to respond to injurious impressions through the sense of
pain, though some organs, as the retina, have not even this property.
Pain, however, is not accurately located by the mind without other aid
than the mere sense of suffering. For instance, a patient can form no
conception as to whether a painful sensation proceeds from the stomach,
the transverse colon, or other organ in the neighborhood, for the simple
reason that these organs are destitute of the tactile sense. Patients, in-
deed, learn to associate certain pains with certain affections-as much,
perhaps, by the qualities of the pains as by any sense of localization.
This quality of localization is purely a matter of education and not a
matter of special endowment. On the other hand, an injury to the sur-
face of the body involving the skin is accurately located by the associa-
1 This is spoken of in the introduction to the article on Diseases of the Peridental
Membrane; but on account of its intrinsic importance, and a desire to make each arti-
cle complete in itself, it will be treated here as if not mentioned elsewhere.
SYMPTOMATOLOGY.
833
tion of the sense of pain with the tactile sense; and the more pronounced
and acute the tactile sense of the part, the more precisely will a minute
injury be located. Hence we find in practice that pain from injuries to
the surface is correctly located by the patient whether he has the oppor-
tunity of individual inspection of the parts or not. This, as I have
indicated, is not the case with internal parts that have not the tactile
sense; and it is in disease of these parts that we have what is known
as reflected pain. Reflected pain is a pain located by the mind of the
patient at a distance, more or less great, from the seat of injury or dis-
ease by which it is caused. This is probably divisible into two quali-
ties or kinds of reflection. In the one variety the pain is simply
wrongly located by the mind; in the other the pain is actually induced
in another place through a perversion of nervous function. Our meagre
knowledge of the modus operandi of the production of pain renders the
very accurate following of this subject extremely difficult; but when we
see muscular contractions occurring in different parts of the body, the
effect of disturbance of nervous function by local disease, it is reason-
able to suppose that pain also may be thus produced. Indeed, these
muscular contractions may be the source of reflected pains which are
accurately located through what is known as the sixth or muscular sense.
Much of the pain in the muscles of the back occurring in women in con-
nection with disorders of the uterus is of this character. Pleurodynia
may occur as an expression of disturbed nervous function, the result
probably of intense tonic contraction of a few fibres of some one of the
intercostal muscles, or it may be of isolated fibres of several of them.
Much of what we know as reflected pain is, however, generally of a
different character from these latter examples, and its mode of produc-
tion is different. A patient complains of a persistent pain in the knee,
and the surgeon recognizes it as a symptom of disease of the hip-joint.
The cause of the pain is in the hip-joint, but the diseased tissue, being
destitute of the tactile sense-indeed, in this case of any nerves of sense-
the pain is wrongly referred by the mind of the patient. A patient has
pain in and retraction of a testicle, and the surgeon will probably be
suspicious of stone in the urinary bladder, and look for the other symp-
toms with which the presence of a calculus is usually associated. An-
other complains of a pain in the region of the scapula (shoulder-tip
pain), from which the physician diagnoses disease of the liver. In
inflammation of the iris the principal seat of pain is in the brow. In
this manner we might go on indefinitely enumerating examples of re-
flected pain, and in every instance it will be found that the diseased
organ is one that has not the tactile sense. The instances given are
among the best known, and most constantly associated with the organs
named, that occur in symptomatology, and serve to illustrate the general
principles of the subject. But in very many instances there is no well-
defined point at which pain is felt in diseases of a given internal organ.
Pain may be felt at various points, and may be shifting from one point
to another; may be in close proximity to the diseased organ or remote
from it; may be slight or severe. For instance, in case of stone in the
urinary bladder, besides radiating pains and the symptoms that have
their seat in the neck of the bladder and urethra, "spasmodic con-
VOL. I.-53
Ca
P
834
PATHOLOGY OF THE DENTAL PULP
54
tractions in the rectum, vagina, testes, neighborhood of the kidneys,
perineum, or thighs, burning sensations in the soles of the feet, in the
heels, or in the elbows, may be present, occurring mostly in paroxysms'
(Ziemssen).
I have spoken of reflected pain as the product of muscular contractions
through perversion of nerve-function. There is another mode of the
production of pain closely akin to this, which occurs through disturb-
ance of the vaso-motor nerves, producing contractions or dilatations of
the muscular coats of the arteries, thereby causing variations in the
blood-supply to local parts or organs. In the following pages I give
experimental proof of the association of intense pain with hyperæmia;
and it seems to be conceded that local deprivation of blood (anæmia) is
also a cause of pain, and to which form of disturbance are referred many
of the types of so-called neuralgia.
The true office of symptomatology is the accurate observation, record-
ing, and grouping of these reflected pains, so that the combined results
of investigators will be of use to the practitioner in the determination
of the ailments of his patients. It is to the general principles of this
subject, as established in the field of general practice, that we must go
for the basis on which to found our study of the symptomatology of the
dental pulp. In order that this shall be of most service to us, we should
first understand as accurately as possible the actual sensory functions of
the organ in health. I have explained above that the dental pulp has
not the tactile sense. In this respect it is a true internal organ, and as
such its symptomatology must be studied.
The dental pulp manifests a very decided sensibility to thermal
changes; not that it readily determines degrees of temperature or dis-
tinguishes heat from cold; in fact, the pulp, unaided by the nerves
of other parts, as the lips, gums, and peridental membrane, seems
incapable of so discriminating.
Experiment.-Select a normal tooth; one standing alone is to be
pre-
ferred; adjust the rubber dam; then pack cotton or other non-conduct-
ing material around the neck of the tooth. When this is done apply
another piece of rubber dam to the tooth over the cotton. About one-
half of the crown may be left exposed after the second piece of rubber
dam has been applied. Both pieces of rubber should be sufficiently
large to allow water to be used with a syringe without danger of com-
ing in contact with the patient's face or clothing, and between them
napkins and cotton should be so placed that a very perfect non-con-
ductor shall be formed. Any tooth may be used by placing the first
piece of dam over three teeth, one on either side. When all is satis-
factorily arranged and the patient's eyes are shielded, throw alternately
a jet of ice-water and a jet of hot water on the exposed crown of the
tooth. It will be found that the patient feels a sharp twinge of pain
from the contact of each jet, but does not experience the sensation of
heat or cold at all.
The teaching of this curious little experiment is of great importance
in the study of the symptomatology of the dental pulp; normally, this
sense of pain upon sudden changes of temperature is the only sensation
conveyed to the sensorium from this organ. That sense by which we
!
SYMPTOMATOLOGY.
835
recognize heat and cold is contributed by the lips and gums, but the
pulp itself resents thermal change by the sense of pain. This general
fact we see exemplified almost every day: a person taking a drink of
ice-water, if not accustomed to it-and generally if he is-experiences a
twinge of pain in the teeth: this resentment to heat and cold is the special
sense of the dental pulp; under normal conditions it has none other what-
.ever.
In diseases of organs having a special function the expressions of
disease are exaggerated during the exercise of that function, and the
case is generally made worse for the time. In affections of the uterus
seen during the performance of the function of menstruation, and
so on with other organs. With many organs of the body the perform-
ance of their peculiar function is necessary to the continued existence of
the individual, and cannot be suspended; but in all cases where rest
can be had without endangering the patient it seems to be the plain duty
of the physician to secure it. The oculist should shield from the light
an inflamed retina or iris, accompanied with photophobia, in order that
the diseased tissue may have rest from the performance of its peculiar
function. On the same principle, a diseased dental pulp should be
shielded rigorously from thermal change. Indeed, it may be stated
that a very large proportion of the difficulty that arises in the pulps
of teeth under treatment is due to inattention to this one point. The
careless handling of the burr or sand-paper dise may, simply from
over-heat, instantly precipitate a condition of disease from which, as
we shall see farther on, the pulp of the tooth will never recover.
In the symptomatology of the pulp of a tooth there are certain points,
based on its structure and sensory functions, that are peculiar to it, as
distinguished from the diseases of the peridental membrane and neigh-
boring tissues, and are constant for all of its diseases. This being the
case, it may be well to consider these peculiarities separately. We have
already seen that the pulp is, in its symptomatology, an internal organ,
and as such fails to locate its ailments. This is so marked a peculiarity,
and has come to the notice of the observant specialist so frequently, that
it need only be mentioned to be understood. Yet the full force of this
proposition seems not to be appreciated. It may be stated that no one
can locate with reasonable certainty a single diseased pulp among the
teeth by the sensation of pain alone. When it is properly located it is
done by other means. By the sensation alone the patient is generally
able with certainty to refer the pain to a given side of the face, but
nothing more. The more definite location of the pain is left to the
chance notion of the patient, or is determined by some accompanying
circumstance, as the existence of a cavity: a sudden pain is felt, and the
tongue finds a crumb crowded into the cavity in a certain tooth; this
occurring repeatedly, the location of the ailment becomes in this manner
definitely and correctly fixed in the mind. In some such way as this
most of the cases that present themselves for treatment are correctly
located by the patient. But in any case in which the patient is left
without some such guide the pain is more likely to be located wrongly
than rightly; and especially if there exist circumstances calculated to
lead the patient astray, he is very sure to err.
836
PATHOLOGY OF THE DENTAL PULP.
Recently I was called on by a lady who had for some days been
suffering severely with a pulpitis. I found that before calling on me
she had been to three practitioners, but failed to obtain relief, owing to
the fact that she had located the pain in one tooth, while each of the
dentists whom she had consulted had located it in another. The patient
was certain she was right, and her advisers were equally sure that their
diagnosis was correct, and in the disagreement nothing could be done
for her relief. Upon examination I found that she referred the pain to
a second molar that had recently been filled, and that the cause of
trouble was in the first bicuspid, as shown by the temperature test. The
patient imperatively demanded the removal of the offending molar.
After trying in vain to explain to her her mistake, and finding that in
her disturbed mental state the sacrifice of a tooth was the only possible
way out of the difficulty, I seized a pair of forceps and removed the
offending bicuspid before she was aware that I had "fastened on the
wrong tooth," as she expressed it. The relief from pain which followed
had the effect to bring her to her senses and to the admission that she
"must have been mistaken as to the tooth;" but this required some
days.
Cases of such absolute insanity as this are not very common, but
cases of pain wrongly located are of very frequent occurrence. Some
months ago I had a patient who for several weeks had suffered with
recurring pain in the superior bicuspids of the right side. She had
forced cotton saturated with some harmless nostrum between them for
the relief of the pain until they stood apart one-eighth of an inch. The
teeth were perfectly sound, and responded normally to the temperature
test. The cause of pain was found in an exposed and hyperæmic pulp
in the second lower molar of the same side, which had a carious cavity
under the margin of the gum that had escaped the observation of the
patient.
The pain in these cases is not always referred to the teeth. One of
the most constant localities of reference is in the ear of the same side.
It may, however, be referred to the temple, the infraorbital foramen,
the malar prominence, the angle of the lower jaw, the side of the neck,
and other localities more remote.
The teeth in these cases are never sore to the touch. Pressure, or
even the stroke of an instrument, calls out nothing abnormal, but a
dash of cold water upon the offending member will usually excite a
vigorous paroxysm of pain.
In acute diseases of the dental pulp its sensitiveness to thermal
changes is augmented, usually, to a very marked degree. In most
cases this is the first symptom that attracts the attention of the patient,
and is often present for some time before other symptoms are noticed;
and even after the suffering becomes severe the paroxysms may occur
only after exposure to thermal change. As a rule, any pain in the
region of the face or ear that is markedly increased by filling the mouth
with cold or warm water has its origin in disease of the pulp of a tooth.
The most notable exceptions to this rule are to be found in some of the
rarer types of neuralgia of the branches of the fifth pair of nerves in the
form of painful tic, and in the earlier stages of apical pericementitis
DENTAL NEURALGIA.
837
caused by the expansion in the pulp-cavity of gas arising from decom-
position of pulp-tissue, in which case warm water causes an increase of
pain by increasing the expansion. In the later stages of acute disease
as the pulp approaches a moribund condition its sensibility is lessened,
and is finally lost.
The DIFFERENTIAL DIAGNOSIS between diseases of the dental pulp
and the different forms of pericementitis is usually easily made out, if it is
remembered that the peridental membrane is the organ of the tactile
sense for the tooth. If the peridental membrane is inflamed, the tooth is
sensitive to the touch, and is not sensitive to reasonable thermal changes;
while in acute and painful diseases of the pulp the tooth is not sensitive
to the touch, but is very sensitive to changes of temperature. Reflected
or radiating pains do not occur in diseases of the peridental membrane
without the presence of a tooth that is sore to the touch. In case of
reflected pain from disease of the pulp the tooth is not sore to the touch.
In Degenerations of the dental pulp its sensibility to thermal change
is generally markedly diminished. In some cases I have noticed that
painful sensations came on some minutes after excitation by thermal
change, as though the pulp was incapable of the usual quick response.
This may be true even though the pulp is in a condition to cause very
severe pain, and under these conditions I have thought that there was
a greater tendency to reflected pain. In such cases unusual difficulty
is encountered in the differential symptomatology between neuralgia and
reflected pain from the dental pulp. The greater tendency to reflected
pain in these cases is probably on account of the comparative insensi-
bility of the pulp to local disturbances.
Dental Neuralgia is a form of the affection which has its immediate
exciting cause in some disease of the dental pulp. This should not be
confounded with the reflected pains spoken of above. In many cases,
however, a differential diagnosis is difficult to arrive at, on account of
the close similarity of the symptoms. Dental neuralgia very rarely, if
ever, occurs in other than persons who are of what may be called a neur-
algic diathesis; that is to say, disease of the dental pulp alone is not
a sufficient cause of neuralgia, but in persons who, by virtue of their
nervous constitution, are subjects of neuralgic affections, or in persons
who, on account of malaria, anæmia, or other form of nervous depres-
sion or exhaustion, have temporarily come into a neuralgic condition,
the irritation of a diseased pulp may be the exciting cause determining
an attack in the branches of the fifth pair of nerves, or even in more
remote parts. In making this statement the reflected pains of which I
have spoken above are excluded. They do not properly come under the
denomination of neuralgic affections, though they seem to have been
widely recognized as such by members of the profession. It is rather
to the credit of the scientific following of the symptomatology of disease,
that many of the painful maladies heretofore regarded as neuralgic have
been assigned names in accord with their true character. Still, after the
exclusion of these forms of reflected pain cases occur now and then that
undoubtedly present the characteristics of neuralgia. It seems that
irritation of terminal nerves will slowly bring about an unusual excita-
bility of the region supplied by the nerve-trunk from which the branch
838
PATHOLOGY OF THE DENTAL PULP.
involved in the irritation proceeds, and often of others in close sym-
pathetic relation therewith. This is especially noted in the hyperæs-
thetic condition of the first branch of the fifth pair during painful dis-
eases of the eye, and equally so in the second and third in diseases of
the pulps of the teeth. This hyperesthesia of the second and third is
to be explained by the fact that both contribute to the nerve-supply of
the teeth, and are thus brought into close relations with each other.
Therefore in neuralgic conditions of the general system a peripheral
irritation may inaugurate a true neuralgia. But while this is true, it
must be remembered that the fifth pair of nerves is a frequent seat of
neuralgia from causes entirely occult or remote from the teeth; and
these may even affect the teeth themselves prominently. It will be seen,
therefore, that I cannot go into the details of this subject without treat-
ing of the general subject of neuralgia, which would be out of place in
this article.
Gab
However, those forms of the affection that arise in anæmic individ-
uals from the irritation caused by a diseased tooth-pulp have usually
certain peculiarities that serve in some degree to distinguish them from
those that arise from causes more occult. These I will try to point out
as they have appeared to me in practice.
Neuralgias of the fifth pair of nerves arising from occult causes or from
irritation which is probably central or in the course of the nerve-trunk,
usually affects one or the other of its three principal branches. This
may be the first, second, or third, but the second or third is more fre-
quently the seat of the affection than the first. The pain may apparently
be located in the trunk of the nerve or in its terminal branches, and
therefore may appear prominently on the skin. It is somewhat rarely
that it is found affecting two of the branches of the fifth at the same
time. In the forms of neuralgia that have as their exciting cause a dis-
eased dental pulp, the pain is first felt in the second or third branch of
the fifth pair, but very soon affects both, the pain alternating between
the two, or there may be painful points referable to both at the same
moment. The pain does not appear in the terminal branches or in the
skin. After some time the pain manifests a peculiar tendency to pass
down the side of the neck, and finally into the chest or arm of the
affected side; and there is pain in the ear in a very large number of
cases; which is not the case in neuralgia from other causes. Paroxysms
of pain are liable to be excited by trifling circumstances, as in other
forms of neuralgic affections, but more particularly by changes of tem-
perature affecting the teeth, or they come on during eating or after
meals. In some cases the recumbent position has seemed to increase
the pain. But the most reliable symptom of this form of neuralgia is
the fact that the disturbance of a particular tooth is sufficient to induce
a paroxysm; not the rapping of the tooth with an instrument or any
form of violence applied to the surface of the tooth, but the touching
of the pulp with an instrument or sudden changes of temperature.
I have usually found this form of disease to be connected with the
legenerations of the pulp described hereafter. Sometimes several cases
have occurred that seemed to indicate a particular pathological condition
of the organ, attended with a tendency to neuralgia, but further investi-
SWELLING OF THE DENTAL PULP.
839
gation has again dispelled this idea, and now it seems to me fairly well
settled that it is the condition of the patient that determines this form
of pain, rather than the particular form of disease of the dental pulp
by which it is excited. It appears, however, that neuralgia rarely
results from acute affections of the pulp.
Swelling (that is apparent) is uniformly absent in the diseases of the
dental pulp. In diseases of the peridental membrane swelling occurs
uniformly, either in slight degree or extensively. Especially is there
apt to be some swelling and tenderness of the lymphatics of the angles
of the neck. This does not occur in any of the diseases of the dental
pulp. The only instances in which I have noted exceptions to this rule
have been in inflammations of the pulp in children, in teeth of which
the roots were not yet fully developed, and consequently were still wide
open at the apex. But even in these cases it is of rare occurrence. This
fact is to be explained by the consideration of the anatomy of the parts,
together with the theory of oedema and the cause of the swelling of the
lymphatics in inflammatory diseases. In regard to the latter, it seems
that in inflammations the tissue-changes are imperfectly performed,
resulting in the formation of abnormal waste products which are taken
up by the lymphatics. These cause swelling and tenderness of the first
lymphatic glands at which they arrive in their course toward the central
parts of the body. This being the case, it is clear that different inflam-
mations will differ as to the amount of swelling they will cause in these
glands, those of a septic character usually causing the most, for the
reason, perhaps, that the poisonous products of micro-organisms are
added to that produced by the abnormal tissue-changes. Thus a com-
canker sore" on the mucous membrane will often cause more
trouble to the glands in the angles of the neck, than an alveolar abscess.
The principal reason why we have no lymphatic swellings in connection
with inflammations of the dental pulp is probably to be found in the
fact that the pulp has no lymphatics; therefore the altered products of
inflammation are not removed by that system of vessels.
mon
The absence of oedema in inflammations of the dental pulp is evi-
dently owing to the confinement of the organ in its dentinal chamber,
together with the absence of areolæ in its tissue. These two causes com-
bine primarily to prevent the escape of the serum of the blood from
the vessels, and secondarily to prevent its infiltrating the surrounding
tissues. It cannot pass through the dentine, and in the normal condi-
tion the apical foramen is too narrow to allow of much escape by that
route, especially as inflammation is for the most part confined to the
bulb of the pulp at some distance from the apical foramen. For these
reasons, any effusions that occur in the pulp are necessarily removed by
the veins, if removed at all, and therefore do not cause swelling of con-
tiguous parts. Ordinarily, the effusions must be very slight, for the
simple reason that there is no space for their accommodation. That
swelling of the pulp occurs, however, must be plain to every one who has
noticed its protrusion into a cavity of decay through an orifice exposing
its tissue.
In widespread diffusive inflammation or hyperæmia of the pulp there
may be some effusion into the apical space, causing the tooth to be
840
PATHOLOGY OF THE DENTAL PULP.
lifted slightly in its socket, and giving symptoms resembling apical
pericementitis. I have noted symptoms of this kind a few times in
intense hyperæmia induced primarily by thermal changes; but it seems
most likely, when all of the facts are considered, that these symptoms,
when occurring in teeth with living pulps, are the result of some slight
traumatic injury to the peridental membrane, such as would occur from
inadvertently catching a hard substance between the teeth in mastica-
tion. At any rate, in the preparation of sections of the pulp I have as
yet been unable in any instance to connect this class of symptoms with
either inflammation or hyperæmia of the organ; and I have made a
number of selections with this special end in view, but in each instance
have found the pulp healthy. These results are contrary to my pre-
vious convictions. The only class of cases in which I have been able
to demonstrate the existence of inflammatory products at the apical
foramen have been those in which the pulp was almost wholly disor-
ganized.
S
Makedon
HYPERÆMIA OF THE DENTAL PULP.
Hyperæmia of the dental pulp is probably the most important of its
pathological conditions, for the reason that it is among the most com-
mon that the dentist has to combat, and for the fact that it so often
terminates in the destruction of the organ. By the term hyperemia is
meant the over-filling of the vessels of the pulp with blood. This sub-
ject seems to have been in the past very generally overlooked by writers
on dental pathology, probably on account of the difficulties of examina-
tion and discovery of the exact conditions at the moment of extraction.
Heretofore, this condition has been studied subjectively for the most
part; that is, symptoms have been depended upon to reflect the condi-
tion of the organ, and while hyperemia has had recognition, it has
usually been regarded as an accompaniment of the inflammatory pro-
cess. This is a grave mistake: there is probably no organ or tissue in
the body in which hyperemia unaccompanied by other morbid process
is so common or so dangerous to the tissue involved. For these rea-
sons, together with the intrinsic importance of the subject, I have fol-
lowed its study as closely as the limited time of a busy practitioner
would allow, and since determining to write this treatise have taken
pains to make a practical reinvestigation of the whole subject, for the
purpose of the correction of any possible error of previous studies.
Before proceeding farther it may be well to give in some detail the
modes of study that I have found best calculated to give correct infor-
mation on this subject; and it may as well be said now that these plans
of research apply to the study of all of the morbid processes of the
organ, but more especially to hyperæmia. For the purposes of micro-
scopic section the dental pulp furnishes but a small amount of tissue,
and it will be seen at once that it cannot be handled for the purpose of
preparation as can tissues that may be had in larger amounts. The
efforts that have been made at decalcifying the tooth and afterward
hardening, and then making sections of the pulp in situ, have not given
satisfactory results-partly on account of the action of the acid upon the
banata 4
HYPEREMIA OF THE DENTAL PULP.
841
pulp-tissue, and partly on account of the distortion of the tissues by
shrinkage. Then, too, the blood in the vessels at the time of extraction
has generally been lost. The question of retaining and displaying in
microscopic section the natural injection occurred to me a number of
years ago; and after some experiment I found it possible to do this in
such a manner as to display the difference between the healthy and the
hyperemic pulp in very striking contrast. The first object to be accom-
plished in this study is to capture the condition, or, in other words, to
be able finally to place the pulp in section under the lens with the ves-
sels containing the blood just as they did at the moment the tooth was
removed from the alveolus, at least without their having lost the red
blood-globules. This process I will give very briefly.
When a suitable case is presented, first examine the condition of the
tooth itself as seen in the mouth. Then obtain its history, the symp-
toms it has presented from the first painful impressions until the pres-
ent. If the pain has been paroxysmal, find if possible what has been
the disturbing cause that has ushered in the paroxysms, the duration of
the paroxysms, the occurrence of soreness on closing the mouth, and, in
short, a full history of the case. The condition of the tooth at the mo-
ment of extraction, especially as to pain, is a matter of prime importance
in this study.
M
Now extract the tooth and drop it at once into Müller's fluid. It
should not be handled nor disturbed in any way. It should lie in this
fluid for at least one week, at the expiration of which time it will be
found that the blood in the vessels has become so hard that it will not
be displaced if carefully handled, and that the red globules have pre-
served their form perfectly, and will do so during the subsequent hand-
ling. After the expiration of this period the tooth should be cracked
in the vise, as recommended by Salter. This is done by wrapping it in
muslin and placing it in the jaws of a powerful vise (this should be so
strong that there will be no springing together of the jaws on cracking
the tooth, as that would be liable to crush the pulp), and bringing them
together steadily until the tooth cracks open. If it is skilfully placed,
the line of fracture will generally follow the long axis. Then place the
tooth in clear, freshly-filtered Müller's fluid and carefully remove the
pulp from its bed. In some instances the layer of odontoblasts will
remain adherent to the walls of the pulp-chamber, in others they will
remain with the pulp, and often the dentinal fibrils will be pulled
out of the dentine to a considerable length. The pulp is now to be
placed in a thin solution of gum arabic to which some gum camphor
has been added to prevent mould. The strength of this solution is very
important; it should in no case be strong enough to float the pulp. This
should be the test of its strength. If the fluid be of greater specific
gravity than the pulp, its tissue will shrink, otherwise not. The gum-
arabic solution should now be slowly evaporated in any convenient way,
so that it is not done too rapidly, to the consistence of very thick jelly.
This should require three or four days, and it will be found that the
impregnation of the pulp-tissue with the gum will keep even pace with
the thickening of the solution, and that the tissue will remain at the
bottom of the vessel. When the solution has become as thick as is con-
842
PATHOLOGY OF THE DENTAL PULP.
sistent with handling, the pulp should be taken up with as much muci-
lage as will conveniently adhere to it, and placed, in such a position as
may be desirable for cutting, on a bit of fine cork, which is then floated
on alcohol with the side on which the pulp is placed down. In from
twelve to thirty-six hours, according to the amount and consistence of
the mucilage, the surface will become hard from the abstraction of the
water by the alcohol. It should not be allowed to become too hard or
the tissue will be injured. A little experience and judgment will enable
one to control this. When the drying has reached the right point, the
tissue, cork, and all should be invested in the microtome in the proper
position for cutting, using paraffin or other suitable substance for imbed-
ding, and allowed to stand for twelve or twenty-four hours. The moist-
ure remaining in the mass will by this time have become evenly dis-
tributed, so that it will be of equal consistence throughout. It should
now be just hard enough to cut smoothly when kept wet with alcohol.
If all has been properly done, it will be found that very fine sections
can be made. Every particle of the tissue can be cut, and if desirable
the sections can be numbered and examined in their order, and every
part of the tissue brought under the lens. The sections may be mounted
directly in glycerin without dissolving out the mucilage, and every cell
retained in position, or the mucilage may be dissolved out in tepid
water, and afterward the section may be stained or prepared in any way
desirable, just as can those obtained by any other process; and it will
be found that the blood will remain in all but the largest vessels.
C
-
A
.
For the illustration of this subject I have chosen sections stained with
hæmatoxylin, except in a few cases which will be noted. This is done,
not for the reason that this staining is thought better than any other,
but rather for the sake of uniformity of illustration. In the study of
any such subject the various modes of preparation should be employed.
Hyperæmia may occur in any degree, from a slight distension of the
vessels of the pulp to an expansion that seems enormous, and, consider-
ing the close encasement of the organ in its dentinal envelope, almost
inexplicable. The distension of the vessels is usually seen in the great-
est degree in the bulb or coronal portion of the pulp, and is apt to be
very unevenly distributed; but it is not uncommon to find the vessels of
the whole of the bulb of the pulp greatly expanded and overfilled with
blood. Fig. 443 represents a field from the margin of a section of the
pulp of a tooth extracted during a severe paroxysm of pain, the vessels
containing the natural injection except at some points, as at c, c, c, c,
from which the coagulum has fallen in the handling of the section.
This was a case of extreme sensitiveness to thermal changes, in which
severe paroxysms of pain, lasting for an hour or more, were occasionally
occurring, seemingly excited by very trivial changes of temperature.
This condition had continued for several weeks. The tooth was much
decayed, but the pulp was not actually exposed, though but a thin cov-
ering of dentine remained. The examination reveals no signs of inflam-
matory changes whatever. This I find common in those cases in which
a pulp has become abnormally sensitive to thermal changes without
exposure or irritation from external sources other than changes of tem-
perature. This forms an important feature of the pathology of the
HYPERÆMIA OF THE DENTAL PULP.
843
dental pulp, for the reason that its causes are so constantly present and
their action augmented in every case of filling with metal. It is liable
to occur in the pulp of any tooth, however sound and otherwise
healthy.
Sensitiveness to thermal changes in a certain degree is, as has been
explained above, the normal sensory function of the pulp. In each
instance of the exercise of this function there is an unusual amount of
α
FIG. 443.
E

Hellboy
·b
b
Hyperæmia of the Dental Pulp, showing the natural injection of the vessels: a, a, membrana eboris,
or layer of odonoblasts; b, b, b, b, vessels distended with blood; c, c, c, c, points from which the
blood has fallen in handling the section.
blood sent to the organ. This, when in a reasonable degree, is purely
physiological—a temporary physiological hyperæmia which calls out a
simple warning in the form of an unpleasant sensation, and immediately
passes away. It is evident in this case that no injury results; but when
this is repeated frequently with a degree of thermal change that is inor-
dinate, the vessels finally fail to contract in a normal manner and remain
overfilled with blood, and at the same time acquire an unusual degree
of susceptibility to thermal influences, so that very slight changes pro-
duce great results. This is evidently in a large degree a nervous phenom-
The tension of the blood-vessels, the degree of their contraction
upon their contents, is under the control of the nerves of the vaso-motor
system, and in the dental pulp these are prominently affected by ther-
mal change in such a way that the vessels in some degree let go their
grasp on the blood and expand passively before the pressure of the cir-
culation. This condition becomes pathological when the part has become
inordinately excitable by over-stimulation or the vessels fail to resume
their normal tonicity after the momentary excitement has passed.
enon.
844
PATHOLOGY OF THE DENTAL PULP.
Irritation of the distal ends of the dentinal fibrils augments the sus-
ceptibility of the pulp to thermal changes, and in this way. contrib-
utes to the development of the condition of hyperæmia. This is a
matter of observation, or is based on the fact that very much the larger
number of observed cases of hyperemia are to be found in teeth in which
the dentine is largely exposed by decay or some of the forms of abra-
sion. This can in part be explained by the fact that the covering
of dentine is reduced in thickness, thereby contributing to the ease with
which thermal changes may penetrate to the interior; but we are con-
tinually witnessing the rise of this condition in case of cavities that are
so hidden away between the teeth that this cause cannot operate. In
many of these cases there is actual exposure of the pulp with inflamma-
tion, but hyperemia occurs repeatedly without exposure of the organ.
It is evident, however, that this cause only renders the pulp more sus-
ceptible by increasing the excitability of its nerves. That this condi-
tion is by no means dependent on any lesion of the tooth for its origin
is exemplified by its frequent occurrence in perfectly sound teeth.
The Pain in hyperemia is sharp and lancinating, and paroxysmal in
its character, especially in the earlier stages. It is usually referred to
the teeth, though it very often happens that the patient is unable to
refer it to a particular tooth or designates the wrong one. In case the
pain has been slowly developed in a particular tooth without a cavity
that has attracted the patient's attention, or in case there are many cav-
ities in the teeth, it is very liable to be referred to any part of the dis-
tribution of the fifth pair of nerves, and may exhibit the peculiar
changes of position so characteristic of some of the forms of facial neur-
algia. The reference of the pain to the ear is very common. A close
study of the symptoms will connect the beginning of the paroxysms.
with some form of thermal change. This sometimes requires more care-
in the inquiry than, from the nature of the case, would be expected. It
often happens that a patient has insensibly learned so perfectly to shield
the tooth from direct contact with cold water that he may drink ice-water
with impunity even when a tooth is so sensitive to thermal change that
a breath of cold air is sufficient to precipitate a severe paroxysm of pain,
or the pain may come on shortly after drinking from the cooling of the
contiguous parts. Patients have often told me that ice-water taken in
the mouth did not cause pain, when on examination I have found that
water twenty degrees lower in temperature than the blood thrown
directly on the tooth would cause the most excruciating suffering. It
is quite remarkable how perfectly some persons learn to shield their
teeth from the effects of ice-water. Recently in conversation with a
physician on this point he contended that thermal change did not affect
his teeth any more than other tissues of his body; he could drink ice-
water without any disagreeable sensation whatever, and had done so for
years. I asked him to fill his mouth with ice-water and distend his
cheeks with it; which he did at once. The result was a paroxysm of
pain (described by him as "awful") which continued for some minutes..
He had, as most people do who use ice-water, learned unconsciously to
shield his teeth from contact with the water while in the act of drink-
ing. This is the reason so many people come to us with hyperæmia of
C
J
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+
Batign
HYPEREMIA OF THE DENTAL PULP.
845
the pulp and give a history in which pain from changes of temperature
has no place. The painful tooth is actually shielded from contact with
cold water unwittingly, but every breath of cold air affects it. This is
markedly exemplified by the comfort afforded by completely covering
in the affected tooth with a closely-fitting gutta-percha cap; which, I
may add, is almost the sole treatment that I have employed in this con-
dition for some years past. The point is simply to obtain absolute rest
from thermal change until there is complete recovery of the normal tone
of the vessels.
Tissue-change in hyperemia unaccompanied by inflammation is con-
fined to the walls of the vessels, and, so far as is yet determined, con-
sists of a passive distension resulting from a semi-paralysis of the local
action of the vaso-motor nerves of the part. This may be more or less
complete, and the distension slight, or it may be very great. This dis-
tension may be recovered from very quickly, as is usually the case in
the early stages of the affection, or as the case progresses recovery of the
normal calibre of the vessels does not occur for days together, or possi-
bly not at all. There is no change in the coats of the vessels that can
be determined by microscopic investigation except the one of distension.
This distension, as most commonly seen in well-prepared sections, is
fairly represented in Fig. 444. This is from a case that had been sub-
ject to paroxysms of pain for some weeks, and was extracted during
one of these. During the greater part of this time, however, it had
remained free from pain. In some cases of a similar character—i. e.
presenting similar symptoms, but extracted during the interval of quiet
-nothing remarkable is presented; the veins in the bulb of the pulp
may be abnormally large and contain more blood than usual, while the
arteries will be almost or quite empty and the injection of the capillary
system wanting. This difference is very striking when the sections of
FIG. 444.

Х
Dilated Blood-vessels from the Dental Pulp in Hyperæmia, from tooth extracted during a paroxysm
of intense pain.
a number of pulps of known history are carefully compared, and shows
the wonderful degree of recuperation from this condition of engorge-
ment.
As the case progresses, the cause continuing to act at frequent inter-
vals-i. e. in cases that present a history of frequent and very severe
846
PATHOLOGY OF THE DENTAL PULP.
pain, usually attributable to thermal changes-the blood-vessels lose
their regular outline and become more or less varicose. In Fig. 444
I have represented quite a remarkable group of these varicosities as
they appeared in the pulp of a tooth extracted during a paroxysm_of
pain. In my studies of this subject I have met with so large a number
of cases presenting this varicose enlargement of the vessels that I must
think it quite common. They occur in every possible form of contor-
tion. Occasionally a vein will be seen presenting a peculiar nodulated
appearance and seemingly crowded with blood-globules to the point of
bursting, as shown in Fig. 445. In some instances single protuber-
FIG. 445.
A Small Vein from a Hyperæmic Pulp, greatly distended and nodulated.
ances will be seen upon the side of a vessel, as though it had been a
weak point distended by force from within. Salter has noticed these
aneurismal enlargements, but seems to have connected them with the
sloughing or ulceration of the pulp; in which he is quite right, for I
have also seen them in the position named by him. It seems to me
quite curious that he had not also noticed this condition of the vessels.
separate from ulceration. In Fig. 446, I have copied his illustration.
FIG. 446.
а
Gr



b
Dilated Vessels from the Dental Pulp (Salter's Dental Pathology, p. 154): a, from the root portion;
b, from the coronal portion.
This is also an enlargement of paralyzed vessels, and certainly belongs.
to the condition of hyperemia as associated with the inflammatory
process, which will be presently considered.
This enlargement of the vessels is only the beginning of the story of
hyperæmia. When the enlargement becomes excessive, and in some
instances in which it does not seem so very great, another phenomenon
presents itself. This is the migration of the red blood-corpuscles from
the vessels, as in infarction, described in the article of this work on Gen-
eral Pathology, to which the reader is referred for the general principles
involved in the subject. In the dental pulp, however, this is not by any
means always a complete infarction, but the escape of blood-globules
HYPERÆMIA OF THE DENTAL PULP.
847
Fre. 447.
here and there through the pulp-tissue, where the distension of vessels
seems to be the greatest. This is often interspersed with what seem to
be slight extravasations of blood. In Fig. 447 is presented an illus-
tration of this taken from the
pulp of a tooth which I ex-
tracted during a most intense
paroxysm of pain that had
been continuous for several
hours nearly the whole of
the tissue of the bulb of the
pulp contained red blood-cor-
puscles scattered through its
substance. A large proportion
of the veins were enormously
enlarged, as shown at a, a, and
splotches of red blood were seen
at many points in the tissue, as
shown at b, b, b. I have noted b
this condition in a considerable
number of cases, and also have
evidence in the remains of
partly-absorbed clots in my
sections that even this may
be recovered from; at least,
the condition of occasional ex-
travasations. This lesion evi-
dently leads, in many cases, to
J
the complete infarction of the Section of Hyperemic Pulp, showing aneurismal dilata-
tions of the vessels, extravasations of blood, and red
blood-discs escaped apparently by diapedesis: a, a, di-
lated vessels; b,b, b, extravasated blood. Besides this,
red blood-discs are plentifully distributed everywhere
in the neighborhood of the veins. The tooth was ex-
tracted during a paroxysm of pain.
pulp, in which its tissue is en-
tirely filled with red blood-
globules, resulting in its de-
struction. It has not been my
fortune to prepare sections of a pulp in a state of complete infarction,
but I have no doubt that many of the sudden deaths of the pulp en
masse occur in this way.
Hyperemia leads to diffuse inflammation of the pulp whenever any
considerable amount of red blood has escaped into the tissues; it is
doubtful if it will occur before this. My own observations have not
decided the point, but the experiments of Cohnheim seem conclusive in
showing that inflammation does not result from the most extreme
hyperemia that can be induced by the paralysis of the vaso-motor
nerves. In his experiments there was probably no extravasation of
red blood to act as a nidus of the inflammatory movement. My obser-
vations seem to show conclusively that in almost every extravasation
a mild form of inflammatory action is set up, by which new elements.
are thrown out which act the part of absorbents in the removal of the
extravasated blood, and that in this way a general diffusive inflamma-
tion of the pulp may be brought about as a result of hyperæmia. In
this way also diffusive inflammation of the pulp very often occurs with-
out the exposure of the organ to any external irritation whatever.

C
SB
@
poo
848
PATHOLOGY OF THE DENTAL PULP.
The causes of hyperemia have probably been sufficiently indicated by
what has been said above. It should be added, however, that heat
operates as powerfully in its production as cold, and that the dentist,
by the careless use of the burr in the engine, but especially by the heat-
ing of the sand-paper disk in the finishing of fillings, is constantly liable
to precipitate a condition of hyperemia from which recovery is very
difficult or impossible. Inordinate heating in this way operates power-
fully to dilate the vessels of the pulp; and from the observations I have
made I am confident that extravasations occasionally occur from this
cause, resulting finally in the death of a pulp which at the time of the
filling of the tooth was in good condition. I have noted these unto-
ward results in my own practice and in that of others.
Sag
INFLAMMATION OF THE DENTAL PULP.
There is probably no tissue in the body in which inflammation, with
its characteristic tissue-changes, can be studied in prepared sections to
better advantage than in the dental pulp. This is owing chiefly to the
fact that its cells are, comparatively, sparsely distributed in its matrix,
and for this reason are not so much in the way of the observation of the
inflammatory elements; then, too, the normal cells have so nearly the same
general form and character that changes in them are easily noted. I think
I may say that I have studied the characteristics of this process as it
occurs in the dental pulp with more pleasure than in any other tissue.
But, however interesting this phase of the subject may be, I must refer
the reader to the article on General Pathology, where he will find it dis-
cussed in detail; here I will consider the subject only as it relates to the
dental pulp.
Inflammation of the dental pulp has been discussed in some degree
by almost every writer who has taken up the subject of dental pathol-
ogy. It is therefore well known to the profession. There are, how-
ever, some conditions surrounding the pulp of a tooth which render
inflammation of this organ peculiar in some of its phases, and which I
wish especially to notice. One of these is the peculiar relation of the
pulp to thermal changes, and the consequent augmentation of the
inflammatory movement by the frequent exacerbations of the hyper-
æmia accompanying it. Most inflammations are accompanied by
hyperæmia, and I know of no difference between the hyperæmia
occurring as an accompaniment of inflammation and that occurring
from other causes. It must be plain to every one that in an organ so
prone to hyperæmia as is the dental pulp, and in which the blood-ves-
sels are so liable to injury from this cause, inflammation will be more
likely to assume a serious form than under other conditions. To this
is added the fact that it is encased in solid walls of dentine, and is thus
prevented from obtaining relief, as do other organs of the body, by
swelling. For these reasons the dental pulp is more liable to destruc-
tion of tissue from the inflammatory process than other structures.
The rise of inflammation of the pulp of the tooth as a result of hyper-
æmia has already been sufficiently discussed, and need not occupy our
attention now.
Stat
•
INFLAMMATION OF THE DENTAL PULP.
849
The chief causes of inflammation of the pulp of the teeth are, either
exposure of the organ by decay, some one of the forms of abrasion,
mechanical violence in the form of accident, or the operations of the
dentist in the preparation of cavities and the insertion of fillings. Sim-
ple exposure of the pulp to the fluids of the mouth is usually sufficient
to set up an inflammatory action. at the point exposed; at least in my
cuttings of the pulp I have found no case of complete exposure of the
organ in which, on microscopic examination, the usual signs of inflam-
matory action were not present at the point of exposure This inflam-
mation is, in many cases, limited to a very small amount of tissue; often
to a very small portion at the immediate point of exposure. Inflam-
mations that are strictly localized are very common. Occasionally, how-
ever, widespread inflammations are found which involve large portions
of the pulp-tissue, but this is an exception to the general rule. Even
in cases where the pulp is destroyed by the inflammatory process, it is
usually accomplished little by little by the process of suppuration or
ulceration, the invasion of the tissue showing a decided tendency to fol-
low the course of the veins as they take their way toward its central
parts and thence into the root portion, in such a way that the pulp is
hollowed out, leaving its periphery intact until its blood-supply is cut
off by the destruction of the vessels supplying it. In many of my sec-
tions this manner of invasion is very marked. If a tooth is extracted
during a paroxysm of pain, inflammation of the pulp is almost uni-
formly accompanied by the signs of hyperæmia, they being present in
a marked degree in the immediate neighborhood of the seat of inflam-
mation; but if the tooth is removed during a period of quiet, the
hyperemia is limited to the vessels within the inflamed area. This is
so constant that I am forced to the conclusion that the condition of
pain depends very largely on the hyperæmia.
—
Wedl, Tomes, Salter, and Harris all speak of the very frequent occur-
rence of inflammation of the pulp before exposure of the organ. Much
as I regret to differ with these gentlemen, to whom we owe so much
of our present knowledge of dental pathology, my examinations have
forced me to a different opinion. That inflammations do occur without
exposure of the organ is no doubt true, as I have already indicated; but
certainly the great mass of the cases occur coincidently with the expo-
sure or afterward. If the pulp be examined by breaking open the tooth
directly after extraction, and the existence of abnormal redness of its
tissues or fulness of its vessels be regarded as evidence of inflammation,
and this judgment be not corrected by careful preparation of the tissue
for examination with reasonably high powers of the microscope, the
cases of hyperemia that I have described would all be regarded as cases
of inflammation. From the fact of the general absence of any consid-
eration of the subject of hyperemia in the works mentioned, I suspect
that this is the true explanation of the difference of opinion.
The tissue-changes due to inflammation are very easily followed in
the dental pulp, especially in fine sections stained with hematoxylin or
fuchsin. Other modes of preparation may be better for the determina-
tion of difficult points in the morbid process, but for the simple deter-
mination of its presence I know of no method superior to this. In
VOL. I.-54
GR
C
850
PATHOLOGY OF THE DENTAL PULP.
Fig. 448 I give an illustration, with a high power, taken from the
margin of a field of inflammation, showing the inflammatory elements
distributed among the normal tissue-cells. a, a point out the normal
cells of the part; these are all more or less swollen, especially their pro-
FIG. 448.

а
Z
Inflammation of Dental Pulp: a, a, normal cells; b, b, b, b, inflammatory elements; c, cells in process
of division (in.).
cesses.
At b, b, b, b I have pointed out the inflammatory elements; these
are leucocytes in the process of development and self-division, derived
from the blood (white corpuscles) or from the rejuvenation of the original
cells of the part. I have drawn the outline of each individual cell and
its relation to its neighbors as perfectly as possible by aid of the camera
lucida, and it will serve to show of what the inflammatory change con-
sists, and how clearly it is seen by this mode of preparation.
G
FIG. 449.
As the inflammatory process proceeds, the normal cells of the part
disappear and are replaced by the inflammatory elements, which are in
fact young cells destined to develop and re-form the tissue, or degener-
ate and form pus, as they are
more or less favorably placed.
The mode of origin of these ele-
ments is discussed at length in the
article on General Pathology. In
some instances we may see in our
sections, if not the actual diape-
desis of the white globules from
the veins, the results of this dia-
pedesis in the most unmistakable
manner. In Fig. 449 I give
an illustration of this as it ap-
pears in a section of a pulp that
seems to have been caught with

Section of Dental Pulp, showing the invasion of the the inflammatory process rapidly
inflammatory process along the course of the veins
-the diapedesis of the white blood-corpuscles.
invading its substance. The illus-
tration shows a group of distended
veins at a point just before they enter the root portion of the pulp;
and the tissue immediately around each of the veins is thickly studded
INFLAMMATION OF THE DENTAL PULP.
851
with leucocytes that have evidently escaped from the veins within a very
short time before the extraction of the tooth. This part of the section
resembles very much, except that the staining renders the cellular elements
far more apparent, what is seen in the early stages of inflammation in the
mesentery or web of the foot of the frog. In searching over sections of
inflamed pulps I often see little islands of inflammation in the midst
of apparently healthy tissue, as though a new nidus had been formed
at a little distance from the point of irritation or exposure of the organ.
It seems evident that these are occasionally the central points for the
formation of those minute abscesses that are so often formed in the midst
of the pulp-tissue. In Fig. 450 is given an illustration of one of these
FIG. 450.
a

Zuo
-
a
Minute Inflammatory Focus within the Tissues of the Pulp: a, a, arterial twigs; b, a nerve-bundle;
c, collection of leucocytes.
a very small one indeed, but one that cannot be mistaken. In this
the inflammatory elements are very closely grouped together, with but
few leucocytes scattered in the neighborhood. This is seen only occa-
sionally in my sections. More frequently such islands of inflammation
are seen in the diffusive inflammation that results from the condition of
hyperemia and slight extravasations of red blood. In these cases the
tissue is apt to be stained with the coloring matter of the red blood-cor-
puscles that have been broken up in the process of absorption. I have
made sections of a few pulps the tissues of which were thickly studded
with these; and occasionally appearances indicate very certainly that
extravasations have occurred at different times, some being advanced in
the process of absorption, and others being comparatively fresh.
•
This breaking up of the red blood-corpuscles-or, rather the effect
of it has been noticed by several writers. When it occurs in large
amount the coloring matter is absorbed into the dentinal fibrils, occa-
sionally in such quantities as to give the dentine a red color, making it
appear as though it were hyperemic or as if the blood had really entered
the dentine. This is most likely to be noticed about the junction of the
enamel and cementum, where there is the least thickness covering the
dentine from view. I think, however, that this redness of the dentine.
occurs oftenest after death of the pulp from infarction. In this case
N
852
PATHOLOGY OF THE DENTAL PULP.
there is a breaking up of the red blood-discs in the process of disinte-
gration, and a large amount of coloring matter is set free in solution,
and frequently will be found in the crystalline form in blood-clots.
While in the state of solution this may enter the tubules in large
amounts, and cause the discoloration of the entire dentine. In this
case it is apt to be much blackened by the formation of the dark sul-
phurets, giving to the tooth a blue-black or even a black color, instead
of a dark red.
I have seen but few cases in which there was a clear and unmistak-
able deposit of inflammatory lymph making space for itself within the
pulp-chamber. One quite notable case occurred in the pulp of a second
molar removed from a robust girl of fourteen years. This presented a
history of a severe toothache, lasting for two days, two weeks previous to
the time of extraction. The pulp was very slightly exposed from decay,
and the deposit of lymph was in the neighborhood of this exposure,
spreading over perhaps one-eighth of the surface of the pulp, and seemed
to have been beneath the layer of odontoblasts. At least, it lay on the
periphery of the pulp, and the odontoblasts were wanting; and it is fair
to presume that they had adhered to the wall of the pulp-chamber when
the pulp was removed from its bed-a thing that occurs in fully one-
third of the cases in pulps that are fairly healthy. I cannot, therefore,
assume that the odontoblasts had been destroyed, though they were cer-
tainly placed in a very unfavorable position. This pulp presented also
evidences of previous extravasations of blood from hyperæmia. These
deposits are occasionally seen within the tissues of the pulp in the form
of islands, and usually seem remarkably free from cellular elements.
G
It seems to me that these facts show that the dental pulp has consid-
erable power of recuperation from the inflammatory state. It is certain
that moderate extravasations of blood are disposed of successfully, and
that a considerable bulk, considering the size of the organ, of inflam-
matory lymph is tolerated without destroying it, and would undoubtedly
be disposed of by the tissues if the case were placed under favorable
conditions.
The symptoms of inflammation of the pulp cannot be very certainly
differentiated from those of hyperæmia. It seems to me evident that in
both cases the pain is for the most part dependent on the hyperæmia,
and therefore very nearly the same line of symptoms are present. The
pain in inflammation, however, is less paroxysmal or is more inclined to
be continuous. The paroxysms continue for a longer time, and, instead
of the pain ceasing, it is dull, heavy, and persists with more or less
pertinacity. The pain, too, is much more liable to come on at night
after retiring. It seems that in some instances the difference in the
blood-pressure in the upright and the recumbent posture is sufficient to
determine a state of pain by the greater expansion of the injured vessels
in the inflamed tissue. It is probable that this may happen also when
the vessels have been repeatedly injured by hyperæmic distension; but
it is, I think, less liable to occur under such conditions. At all events,
the differential diagnosis is in many cases very difficult to make out
satisfactorily. I may say that in the cases that I have selected for
making sections I have tried this very carefully for the purpose of
INFLAMMATION OF THE DENTAL PULP.
853
determining the differential symptomatology; but my success has not
been such that I can speak very positively of any especial symptoms
that are diagnostic. The general rule has been that I have found ex-
posed pulps inflamed, whether there have been symptoms of any kind
or not. (I do not mean here pulps covered by softened dentine that
would be exposed in excavating, but pulps that are actually exposed to
the fluids of the mouth.) I am satisfied that there are a great many
cases in which exposed pulps become inflamed and go on to suppura-
tion and the final destruction of the organ without presenting any symp-
toms whatever; indeed, it is by no means uncommon to find the pulp in
a state of suppuration or ulceration in such cases. I am inclined to the
opinion that inflammation without decided hyperæmia is not a painful
affection. Certainly, it may destroy the pulp of the tooth without pro-
ducing pain.
The causes of inflammation of the dental pulp seem to be, in most
cases, external violence and the contact of the saliva. I have uniformly
found the pulp inflamed if it had been so exposed that the saliva had
had free access to it, whether it had presented any symptoms or not.
It
must be admitted, however, that the number of pulps obtained for exam-
ination, exposed but presenting no symptoms, have been comparatively
limited. The part that micro-organisms play in the production of in-
flammation of the pulp is uncertain, but, all things considered, I have
been inclined to the opinion that it is a very important one. Still, in
my microscopic examinations I have not yet been able to find the tissues
of the pulp invaded by them; possibly this may be the result of faulty
manipulation, yet the same processes that I have used successfully in
other situations have failed to reveal them here. They are plentiful,
however, in the pus from suppurating pulps, and undoubtedly their
waste products have much to do with the initiation of the inflammatory
process.
Of the ability of the dental pulp, when placed in good hygienic con-
ditions, to recover from inflammation, there can be no doubt whatever.
The observed facts given in the previous pages fully warrant this state-
ment, and it is also justified by clinical experience, judged in the light
of microscopic investigation.
SUPPURATION OF THE PULP
is of very frequent occurrence; indeed, it seems that the dental pulp is
especially prone to suppuration when fully exposed to the fluids of the
mouth. In the greater number of cases in which I have made careful
examination superficial suppuration has been present; yet I have found
a considerable number of cases in which the organ had evidently been
widely exposed for a considerable time, and in which inflammation had
made considerable progress, without any evidence of suppuration, and
in which the layer of odontoblasts was still in position. Again, cases
are found, and are by no means rare, in which suppuration has begun
in the form of abscess within the substance of the pulp at a little dis-
tance from the exposed point. In the great majority of cases, however,
the suppuration begins superficially, and the layer of odontoblasts at
854
PATHOLOGY OF THE DENTAL PULP.
the point of exposure is destroyed. In Fig. 451, A, I have repre-
sented in diagram a first molar with a proximal decay exposing the pulp.
The darkened portion of the pulp at 6 shows the extent of the invasion
of the pulp-tissue by the inflammatory process. In B is given an illus-
tration of the tissue which I have taken from a central section, and
which includes the most of the inflamed area. In this I have left the
FIG. 451.
A
-O
gove
b
B

Go
?
A, Diagram of Lower Molar, with caries at a which exposes the pulp. The darkened portion at b
shows the extent of the inflammation. The rest of the organ was free from inflammatory change.
B, Illustration of the Inflamed Tissue, showing a part destroyed by suppuration at a. The odonto-
blasts are undermined at b. The blood-vessels which were filled with blood-clot in the section
are left blank here, that they may be more apparent.
blood-vessels blank, that they may be more apparent, though in the
section they are filled with clotted blood. It will be noted that in the
greater part of the field the normal cells of the part have disappeared
and given place to inflammatory elements, and that at the immediate
point of exposure the odontoblasts are wanting, and the tissue has been
invaded by the suppurative process forming a deep pocket.in its sub-
stance. The undermining of the layer of odontoblasts at the point b is
worthy of especial note (See Fig. 452 also.). This undermining of the
odontoblasts occurs so often that I may say that it is the general rule in
what may be called progressive suppuration of the pulp, which is the
form that I have most generally found. Occasionally I have found
suppuration or more properly, perhaps, ulceration-following a very
superficial inflammation, in which the tissue was apparently melting
In
down into a sanious pus thickly inhabited by micro-organisms.
these instances there is a very superficial area of the tissue in which the
blood seems to be clotted in the vessels, whether the tooth be extracted
during a paroxysm of pain or not, and the melting down of the tissue
is evidently on account of the deprivation of blood by this clotting pro-
SUPPURATION OF THE DENTAL PULP.
855
FIG. 452.
cess, as has been suggested by Salter. It is probable that the micro-organ-
isms, by the molecular changes which
they produce in their life-processes,
yield a material that determines this
persistent clotting in the superficial
capillaries, and in this way keep up
the ulcerative process.

Q-
b
In most cases, however, as has
been said, the invasion of the inflam-
mation precedes the breaking down
of the tissue in a much wider zone;
and it is often seen to penetrate
deeply into the substance of the
pulp, following the direction of the
veins. This tendency is well seen
in Fig. 452, taken from a section of
the pulp of a superior lateral incisor
in which about one-fourth of the
pulp at the coronal portion had been
destroyed. This section also gives
an excellent showing of the tendency
to the undermining of the layer of
odontoblasts. In this way the pulp
is progressively destroyed from the d
point of exposure toward the apex
of the root. In many cases this pro-
cess is evidently in progress for many
weeks together, during which time
the suppuration alternates with ef-
forts, always unsuccessful, at repair. e
In this way the pulp is destroyed,
little by little, until only a small por-
tion remains in the root-canal toward
the apical portion. In other cases,
however, the entire organ is destroy-
ed at once by gangrene or infarction.
That the pulp ever becomes cica- Progressive Suppuration of the Pulp of an In-
cisor: «, healthy tissue; b, odontoblast layer,
or membrana eboris; c, inflamed tissue, in
which the veins are seen to be dilated; «, line
of demarcation of the suppurative process; e,
pus.
trized and capable of performing its
functions after suppuration has been
established I have no direct proof
that is entirely satisfactory. In some
clinical cases I have thought that this
had been accomplished, but there is so
much liability to error in these obser-
vations that this judgment must be taken with à considerable degree of
allowance.
A part of the crown portion of the pulp had
been destroyed by suppuration, and in the
remaining portion it will be noted how the
pulp is hollowed out, the process pursuing the
course of the veins and converging to the
centre ( 100, reduced).
"
100%
B
ABSCESS OF THE DENTAL PULP
is of frequent occurrence; and it seems to me probable that the suppu-
rative process very often makes its beginnings in the form of a minute
856
PATHOLOGY OF THE DENTAL PULP.
abscess just within the layer of odontoblasts. These cells exhibit less
disposition to change under the influence of inflammation than the other
cells of the pulp, and I have often found them retaining their form and
position when the tissue in immediate juxtaposition with them had been
destroyed. Therefore, it seems probable that the first formations of
pus would be retained behind them for a time in the form of a tiny
abscess; at least, this is suggested by the facts observed.
FIG. 453.
B
Abscesses lying deeper in the tissue of the organ are seen to form by
the aggregation of the inflammatory elements into a compact mass or
little masses that lie near each other and run together in the process of
increase. These cells, on account of the unfavorable conditions of their
environment, degenerate in-
to pus-cells, and the result
is the formation of an ab-
scess. Fig. 450 represents
very fairly a beginning of
the collection of inflamma-
tory elements that might well
serve as the nidus of an ab-
scess if the conditions were
unfavorable to their contin-
ued vitality. In Fig. 453
is given an illustration in-
cluding about the half of a
minute abscess that I dis-
covered in the sections of
the pulp of a central incisor
about midway of its length.
The coronal portion was sup-
purating, and the inflamma-
tion was rather more ex-
tended in its tissue than is

Matthe
Vo
W
WO
Abscess within the Tissues of the Pulp. The field includes
about one-half of the little pocket of pus (× 250).
common. I have seen abscess in the pulps of the molars much oftener
than in the single-rooted teeth. Here it is not very uncommon to find
several minute pockets of pus at a little distance from the point of
exposure in cases in which the pulp has been exposed for a consider-
able period. When we note the swelling that usually accompanies the
formation of an abscess in the soft parts, we can gain some idea of the
destructive effect produced by the formation of an abscess in the tissue
of the dental pulp, encased as it is in the dentine without the opportunity
of obtaining the increased space necessary for the accommodation of the
forming pus. This applies with the same force to the formation of
pus on the surface of the organ when there is not a complete exposure
that will allow of its escape, the formation of pus after a filling has
been inserted, or under a capping. In any of these conditions, if the
amount of pus formed is more than can find room, the compression and
strangulation of the organ are inevitable; and I have every reason for
believing that this form of strangulation and destruction of the pulp is
not infrequent. This conclusion is based on the frequent finding of
minute abscesses in the living pulp as prepared for microscopic exami-
CHRONIC INFLAMMATION OF THE DENTAL PULP.
857
nation, the occasional discharge of minute quantities of pus from such
abscesses by puncture, and also from the surface of the pulp after the
removal of cappings, which I have noticed in practice, as well as the
speedy relief from pain afforded by these operations.
The pain in abscess of the pulp is often very violent. It seems to
arise differently from that occasioned by hyperæmia, in that the onset
of the attack is not sudden and violent, but begins with a slight gnawing
pain that persistently increases in severity, often until it becomes very
intense. If relief is not obtained by the discharge of the pus in some
direction, strangulation will sooner or later occur, the pain then ceasing.
This, within from six to twenty-four hours, will probably be replaced
by symptoms of apical pericementitis. Hyperæmia may of course be
coincident with the formation of abscess and may mask its symptoms.
Small amounts of pus may be retained in the pulp-chamber indef-
initely, and in this position may possibly undergo absorption. I have
noted some instances in which it had undergone fatty degeneration, and
seemed to be partially converted into an emulsion, as described by Salter.
Under these circumstances gas is occasionally formed by a process of
decomposition. Only a few days ago I was removing the pulp from a
central incisor after it had lain in Müller's fluid for a week, and imme-
diately on cracking the tooth I discovered in its tissue a cavity that
contained a bubble of gas. Possibly this may have formed after pla-
cing it in the fluid, but the conditions for its formation must have been
present before the extraction of the tooth, for they could not have arisen
after it was placed in the fluid. Upon section of the pulp I found
unmistakably that the gas-bubble was in an abscess-cavity. This is the
only instance in which I have found evidence of the formation of gas
within the living organ; and even in this I cannot say that the for-
mation was not post-mortem. The generation of gas within the closed
pulp-chamber, in which suppuration of the pulp is going on, undoubtedly
takes place in some instances. In such cases warm liquids should
increase the pain by expanding the gas, while cold would relieve it
by the opposite effect.
C
CHRONIC INFLAMMATON OF THE DENTAL PULP
may take any one of three forms. The more common forms are chronic
inflammation with the continuous shedding of pus, which has been suffi-
ciently described; chronic inflammation with the addition of new ele-
ments, or inflammatory hypertrophy; and chronic inflammation accom-
panied with degeneration of structure, or inflammatory degeneration.
No considerable hypertrophy of the pulp can occur while it is
enclosed in a normal pulp-chamber, for the simple reason that there is
no room for its expansion. In cases of exposure of the organ, however,
a very considerable hypertrophy occasionally occurs, the new growth
pushing out into the cavity of decay which has caused the exposure.
This is seen as a fleshy mass in the carious cavity, and is often much
greater in bulk than the pulp from which it has sprung. This growth
does not all take place outside of the cavity, for there is often evidence
in the arrangement of the tissue that shows us plainly that much of the
858
PATHOLOGY OF THE DENTAL PULP.
growth has taken place within the cavity, and has gradually been
squeezed out through the opening. In other instances the growth
seems to have occurred mostly at or without the orifice, exposing the
pulp. In the greater number of the cases I have examined the
growth seems to have been determined by the continual irritation of
the tissue of the pulp by the sharp corners of the opening into the pulp-
chamber. The growth itself is almost uniformly composed of granula-
tion-tissue of rather a low type, which remains in a very primitive state.
The accompanying illustration will give a good idea of this (Fig. 454).
FIG. 454.
B

O
b
Of
00
20
900
EXO
NGC42
30

Pool
A, A Diagram of a First Lower Molar, with a cavity at a completely filled by a hypertrophy of the
pulp, which has grown out through the orifice, exposing the pulp at b.
B, A Field illustrating the Tissue of the Growth, which is composed almost entirely of granulation-
tissue of a very primitive type: a, a covering of epithelium presenting papillæ; b, epithelium
apparently without papillæ.
Occasionally I have seen the tissue much more developed, approaching
fibrous tissue in its structure. Many of these growths are covered on
the exposed surface with the usual squamous epithelium of the mucous
membrane of the mouth. This, evidently, has not developed from the
tissues of the pulp, but is a transplantation from the epithelium of the
adjacent gum, which has occurred after the fashion of skin-grafting.
With the frequent abrasions that occur in the act of mastication I can
readily understand how the epithelium could be transplanted, but I can-
not understand how this form of epithelium could be developed from the
tissues of the pulp. In a few instances such a growth has been known
to become calcified. John Tomes figures a case in which the pulp
seems to have become somewhat hypertrophied after breakage of the
crown of the tooth, and afterward to have become calcified. Heider
1
¹ Dental Surgery, p. 540.
SEA
DEGENERATION OF THE DENTAL PULP.
859
The
There was a
and Wedl, in their eighth plate,' also give a figure of a similar case
which occurred in an incisor tooth of the antelope. I have seen a very
curious case of this kind occurring under a metallic capping. Some of
the older members of the profession will remember that before the intro-
duction of the cements there was a considerable effort to preserve the
pulps of teeth by bridging over with thin plates of metal. Owing to
a threatened alveolar abscess, it became necessary for me to remove a
filling made by Dr. Isaiah Forbes of St. Louis, which the patient told
me had had a capping of this kind in position for twelve years.
case was a lower wisdom tooth standing alone, with a very large amal-
gam filling occupying the anterior part of the crown.
little caries about its margin that enabled me to insert a point and
pry the filling out en masse. This disclosed a large piece of gold plate
which had been laid over an exposure of the pulp, leaving a consider-
able space between it and the bottom of the cavity. I was surprised to
find this filled completely with what was evidently a calcification of the
hypertrophied pulp, which had grown out and filled the space left under
the capping. The mass was slightly movable, showing that it was not
attached to the original dentine, but extended into the pulp-chamber in
such a way that it was necessary to cut it to pieces to remove it. This
form of calcification is evidently very rare.
Another result of inflammatory hypertrophy of the pulp-one that
is very rarely seen, however—is the absorption of dentine from the
inner walls of the pulp-chamber, causing its enlargement. I have never
met with a case in which I had the opportunity of a systematic exam-
ination of this process, but in practice have seen several well-marked
cases, and just now have under observation a first lower molar in which,
on removal of the pulp, I found the whole of the floor of the pulp-
chamber missing. Ten years ago, as my record shows, I capped a very
ugly exposure in this tooth and made a large gold filling. For two or
three years the pulp has been irritable, and I finally determined to
remove it; and upon doing so found the pulp-chamber enormously
enlarged, and that an opening to the peridental membrane between the
roots had been formed. Another case was that of a central incisor in
which the enlargement of the pulp-chamber was not so great, but was
unmistakable.
G
DEGENERATION OF THE STRUCTURE OF THE PULP
may occur from long-continued inflammation of a low grade. From
my personal observations I should think that the tissue does not at any
time become the seat of a high grade of inflammatory action; if so, the
inflammatory elements must be removed by some process of degener-
ation and absorption. The original cells of the part also, for the most
part, disappear or lose their nucleus, and become converted into very
fine fibres. Areola develop in the matrix, and all the histological cha-
racters of the tissue are profoundly changed. Fig. 455 is given as an
illustration of this, from a pulp thus affected in an extreme degree. These
areola were evidently filled with fluid; hence a kind of oedema of the
¹ Atlas of the Pathology of the Teeth.
860
PATHOLOGY OF THE DENTAL PULP.
FIG. 455.
organ must have existed which in the enclosed pulp-chamber has prob-
ably gradually destroyed the cellular elements, and new elements thrown
out in the inflammatory process have suffered the same fate. At any
rate, those that are seen are all more or less shrivelled in appearance.
This particular case was taken from
the mouth of a young lady seven-
teen years old, and presented a his-
tory of rather severe pain at several
different times during four or five
months; it was "often uneasy." It
had not given severe pain for two
months before extraction. Cases
are met with that present every
possible grade of change, from the
occasional appearance of areola to
portions of the pulp, as shown in
the complete areolation of large
the illustration. But in the most

O
Chronic Inflammation of the Pulp, areolation,
and degeneration.
extreme cases I have seen the areolation has not extended to the whole
tissue. All grades will be found in the same pulp. The bulb suffers
most, and often that part of the bulb nearest an exposure, while the rest
of the organ seems to retain its tone more or less perfectly. How much
hyperemia may have to do in the production of this condition I cannot
say. The evidence of oedema presented by the abnormal areola would
indicate that the effusion was hyperemic rather than inflammatory, but
in all of these cases I have found the evidences of inflammatory action
unmistakable.
My observations of this condition of the pulp lead me to the opinion
that the sensibility of the organ is markedly diminished as this con-
dition is developed. I have not, however, found a sufficient number of
well-marked cases in the cuttings I have made to feel very certain of
the symptomatology. From what I have seen I would suggest that
this is probably the manner of the death of those pulps that we some-
times find dried up (mummified) in their chambers.
DEPOSITS OF CALCOGLOBULIN
are found associated with inflammation in a considerable number of
cases. I have not seen this deposit mentioned in any writings on this
subject, yet it is so prominent that I fail to understand how it could
have been overlooked. To my mind, this formation is associated with
the formation of what are known as pulp-nodules. It possesses the
same form of elements common to the pulp-nodule, including the forms
of the calcospherite, but is soft enough to be readily cut with the knife
in the preparation of sections, while the pulp-nodule is very hard. It
has been present in a number of the pulps that I have cut, always in
the inflamed portion, and usually near the point of exposure, often
lying immediately beneath the layer of odontoblasts, but occasionally
much deeper within the tissues of the pulp. It usually occurs in
irregular masses, occasionally of considerable size; and scattered about
DEPOSITS OF CALCOGLOBULIN.
861
these there are generally a number of small globular forms, many of which
have the onion-like layers of the calcospherite quite distinctly marked.
In Fig. 456 I give an illustration of one of these masses as it occurred
FIG. 456.
in the pulp of a second molar
from the mouth of a girl of
fifteen years. About one-half
of the coronal portion of the
pulp was involved in inflam-
mation, which, from the his-
tory of the case, must have
been present for as much as
two months, the tooth re-
maining quiet most of the
time, but subject to par-
oxysms of pain lasting from
a few moments to two or
three hours. There were sev-
eral such masses as the one
represented in the pulp-tissue, all lying a little inside of the odontoblast
layer and having globular forms in their mass or attached to their mar-
gins. In one part of the pulp there were a number of detached globules
similar to those attached to the specimen shown. When mounted in
glycerin, without staining, these masses are very transparent and show
no color whatever. They stain an intense red with fuchsin, and are not
bleached by immersion in alcohol for five or six hours. With hama-
toxylin they are stained blue or purple. Judging from the forms pre-
sented by these bodies, I suppose them to be calcoglobulin: I have not
made the chemical examination that would be required to demonstrate
this. They are entirely different from lymph-deposits, and do not
show the reactions peculiar to amyloid deposits.
The idea that calcoglobulin is deposited in the pulps of teeth in the
soft state has been arrived at with some difficulty, from the fact that it
was known only as the basis of the pulp-nodule, the calcospherite, and
perhaps of the dentine and bones, which remained after the solution of
the lime salts with which it was originally combined. It thus forms
the matrix of these bodies, and the assumption that this is calcoglobulin
necessarily embraces the idea that the basis substance may be formed in
the absence of sufficient lime salts for the complete calcification of the
matrix. I know of no record of the accomplishment of this by arti-
ficial means, and certainly the subject needs further investigation.
The only situations of the natural-or, I might say, the pathological—
formation of the calcospherite is in the dental pulp and in varicose veins.
The formation of these bodies artificially seems to require the presence.
in solution of albumen, the salts of lime, and carbonic acid (carbon
dioxide). When these materials are brought together in a tightly-stop-
pered bottle, calcospherites closely resembling those found in the dental
pulp and in varicose veins are slowly deposited at the bottom. This
subject has been very closely investigated by Rainie, Ord, Harting, and
others, and the identity of the artificial forms with those found in the
situations named seems well established. Now, the fact that these

MEECE
Deposit of Calcoglobulin within the Tissues of an
Inflamed Pulp.
862
PATHOLOGY OF THE DENTAL PULP.
2
bodies, called in this situation phlebolites or phleboliths, are found only
in varicose veins where there is a condition of congestion or venous
hyperæmia-in which cases, as is well known, there is a supersaturation
of the blood with carbonic acid-seems to have an important bearing on
the conditions of their formation wherever found. When there is venous
congestion, as in the varicosities of the veins, the blood often becomes
intensely venous, or, in other words, an unusual amount of carbonic
acid has accumulated in it, and the blood may at the same time hold a
sufficient quantity of the salts of lime. In this case we have the con-
ditions found necessary for the formation of these bodies by the arti-
ficial process, and in the blood-vessels such locations are the only ones.
in which these bodies are found. This suggests the inference that in
the dental pulp the formation of these bodies is dependent on a con-
dition of congestion; which inference is strengthened by the finding
of these soft forms only under the conditions of inflammation.
In this connection the question arises as to whether this soft form is the
usual mode of origin of these bodies, they becoming more heavily im-
pregnated with lime salts afterward. In favor of this idea is the state-
ment made by most authors-and with which I concur-that in the
growth of enamel and dentine there is a stratum constantly presented
that has not acquired its full amount of lime salts, and is still compara-
tively soft. In the preparation of developing teeth I have often cut
quite a little thickness of this without difficulty. Yet in all of my
examinations I have never found a pulp-nodule in a soft shell or with
a softer portion on the outside; and it seems to me that if the above
were the true mode of their origin, I should have found this. This
question has an important bearing on the subject of pathology as con-
nected with the pulp-nodule. If these bodies are formed in the tissues
of the pulp only under the conditions of venous congestion or inflam-
mation, their presence has a signification that I had not attached to
them. There can be no doubt but their presence in the pulps of teeth
has some relation to irritation of the dentinal fibrils, for I have cer-
tainly found an increased number in the teeth of those who had suffered
much from decay or abrasion, each of which exposes the fibrils to irri-
tation.
Kateg
QUA
The facts given above as to the mode of the formation of these bodies
suggest the idea that calcoglobulin and the pulp-nodule originate in the
veins of the pulp as a result of venous congestion or hyperæmia, and
that the vessel is obliterated thereby; and it must be admitted that
those conditions that are known to be favorable to the promotion of
such congestions are the conditions under which we find the greatest
number of pulp-nodules. I have, however, looked for evidences of
their formation within the veins without success. Certainly, we find
the congestions and the varicose veins, and most of these bodies have
about them a condensation of tissue resembling in some degree a mem-
brane; which fact has been noted by Wedl and a number of other
writers. But I have not been able to make out in this any resemblance
to the structure of the walls of the veins. Again, the forms of these
bodies as seen in the dental pulp give no indication of their formation
in the veins.
PULP-NODULES.
863
FIG. 457.
The Pulp-nodule may be found in any part of the pulp-tissue, but
occurs mostly in the coronal portion or near the junction of this with
the root portion. It is of irreg-
ular form, and in most specimens
it is irregularly nodulated, as if
made up of an aggregation of
smaller nodules. In Fig. 457 is
given a representation of one of
these magnified (the true size be-
ing represented at a), which gives
a good idea of the surface appear-
ance of the mass. In respect to
the nodulation there is the great-
est variety, some specimens pre-
senting a very smooth outline.
These are usually the large ones,
but even with these the nodulated
surface is the rule. They are very
hard, and are composed of the
FIG. 458.
same material as the dentine, but A Small Pulp-nodule, as seen with a low power,
have not the same structure. In
showing its nodulation: a represents the nat-
ural size (X 15).
Fig. 458 I have represented this
as seen in section. The bodies made up of concentric rings are the cal-
cospherites. These rarely make up any very considerable portion of the
bulk of the nodule; indeed,
I think they are as plenti-
fully distributed in this sec-
tion as in any that I have cut.
The balance of the mass is
made up of calcific material
that shows no structure what-
ever, or may have some irreg-
ular lines or faults running
through it without any def- a
inite arrangement. Usually,
this is very clear and trans-
parent, but a considerable
number of specimens are ir-
regularly clouded. These are
not calcifications of the tissue
of the pulp, but are formed in
the midst of the tissue, mak-
ing room for themselves by
pushing the tissue aside, or,
possibly, they may be formed in varicose veins, as suggested above.
This distinction is important as dividing calcific degenerations of the
pulp-tissue, in which the tissue itself is impregnated with lime salts,
from the pulp-nodule. Both forms are found in the form of irregular
bodies, and are not unfrequently associated in the same calcific deposit.
The nodules found in the root portion of the pulp are usually smoother

-

Section of a Pulp-nodule, showing many calcospherites,
as pointed out by a, a.
864
PATHOLOGY OF THE DENTAL PULP.
in their outline, and are much more likely to contain calcified tissues, than
those found in the coronal portion. These are often associated with
calcific degeneration of the pulp-tissue, which will be considered pres-
ently. In Fig. 459, I give an illustration of a group of these nodules.
FIG. 459.

1.
Pulp-nodules in the Canal Portion of the Pulp (× 50).
There has been a disposition on the part of the profession to attach
considerable importance to pulp-nodules in the pathological sense.
After a very close investigation of the subject I cannot share this feel-
ing. Whatever may be the circumstances attending their formation,
they seem to do no injury after they are once formed; at least, that is
the inference to which I am driven after a very large number of exami-
nations of these bodies in teeth of known history. Carefully-conducted
examinations show that they are more abundant in the teeth of the mid-
dle-aged and the old than in those of the young. They are also more
plentiful in the teeth that have been worn by mastication or have suf
fered from any of the forms of abrasion than in others. In these cases
the individual teeth that may have escaped the abrasion are about as
liable to contain the nodules as the worn ones. I also find an increased
number in teeth from mouths of persons that have suffered much from
caries. Indeed, any circumstances that may expose the dentinal fibrils
and subject them to irritation seem to contribute to the formation of
pulp-nodules, not only in the teeth directly affected, but also in those
that are not affected. Only a short time ago I selected four sound
teeth, the enamel of which seemed very perfect (removed from the
mouth of a woman twenty-five years old, the greater part of whose
teeth had been destroyed by caries), and endeavored to make sections
of them. Every part of the tissue was studded with these nodules to
such an extent that I obtained but few sections good enough to display
the condition of the tissue. These showed the tissue to be perfectly nor-
mal. In studying the pulps of teeth of known history I have been
unable to find that those with pulp-nodules have given any peculiar
symptoms or have given more pain than those without these bodies.
It is, however, quite possible that these may occur of such size near
the conjunction of the coronal and root portion of the pulp, or in the
root portion, as to interfere with the circulation, and in this way con-
tribute to the degeneration of the organ; or they may by their volume
interfere with its functions.
C
HARD FORMATIONS WITHIN THE PULP-CHAMBER.
CLASSIFICATION.-A classification of the hard formations within the
pulp-chamber seems desirable, yet it is doubtful if this can be done in a
SECONDARY DENTINE.
865
perfectly satisfactory way at the present time; and, besides, it does not
seem best to attempt to consider these entirely apart from the diseases
of the soft parts, for the reason that the one seems in many cases to be
directly dependent on the other. Some attempt at classification will,
however, serve the purpose of simplifying description; I therefore give
the following:
1st. Secondary Dentine.-A new growth of dentine more or less
regular in formation, excited by abrasion, decay, or other injury, by
which the dentinal fibrils are subjected to irritation at their distal ends.
2d. Dentinal Tumor within the Pulp-chamber.-An erratic growth of
dentine into the pulp-chamber united to the wall by a pedicle. The
structure is usually very irregular.
3d. Nodular Calcifications among, but not of, the Tissues of the Pulp.
These are the irregular nodulated masses so frequently seen either as
very small stones or irregular masses. They contain many calcospher-
ites. These were considered with the soft parts for the sake of con-
venience.
4th. Interstitial Calcifications of the Tissues of the Pulp.-This is the
counterpart of calcifications elsewhere in the body, as in the arteries, etc.
5th. Cylindrical Calcifications of the Pulp, the tissues of which are
probably in a state of fibrous degeneration. Usually seen in the pulp-
canals.
6th. Osteo-dentine.-Erratic formations showing both the lacunæ of
bone and dentinal tubes.
Calcospherites may be seen in connection with any of these. Many
irregular formations are found that are scarcely assignable to any of
these forms, and it is not unusual to find them intermixed with each
other.
Secondary Dentine is the result of a new growth excited by some
abnormal condition of, or injury to, the tooth. It is always deposited
upon the walls of the pulp-chamber, and results in the reduction of its
size. This must be distinguished from the normal growth of the dentine.
In the young the pulp-chamber is comparatively very large, and dimin-
ishes in size for some time (which cannot be definitely stated) after the
tooth has otherwise completed its growth or has attained the full form
of its root and crown. This growth is continuous with the general
structure of the dentine, without break or demarcation of any kind so
long as it continues normal; but in case a new growth is excited by
abnormal conditions there is generally a departure from the normal
structure that distinguishes it sharply from the original dentine, and
enables us to make out the original form of the pulp-chamber. This
departure from the normal structure varies greatly in different cases.
It is occasionally marked by a sharp curve or change in the direction
of the tubules only, or there may be, and generally there is, a marked
diminution of their numbers. Occasionally the sudden diminishing of
the number of the tubules will be the only distinguishing mark, and in a
very few instances I have seen what seemed to be a great reduction in
the size of the chamber, that had occurred with such perfect regularity
of structure as to leave no line of demarcation whatever; but this is rare.
Generally there is a marked difference in the color of the new structure
VOL. I.-55
866
PATHOLOGY OF THE DENTAL PULP.
as compared with the primary dentine, by which it is readily distin-
guished with the naked eye. This is seen in teeth that have been so
worn by abrasion as to expose the new structure in the form of a yel-
lowish spot which marks out the original form of the pulp-chamber.
The extent to which secondary dentine may be formed is a question of
much importance. There seems to be a widespread opinion that the pulp-
chamber may be obliterated by the formation of secondary dentine. This
is an error. At least I know of no well-authenticated case of this kind.
The secondary deposit seems to be limited within certain but not very
definite bounds, which always stop short of the complete filling of the
chamber. This deposit, as compared with the size of the pulp-cavity, is
more extensive in the single-rooted teeth, as the incisors and cuspids,
than in the molars. In the former it is not unusual to see considerable of
the crown portion completely filled, so that the secondary formation will
do good service in the protection of the pulp from exposure. In Fig. 460
is given an illustration of this as it is usually seen in the anterior teeth
affected by abrasion. It will be noticed that the pulp-cavity is per-
FIG. 461.

FIG. 460.
-ď
f
e
ď
C
S
a
P
2%
KORTER
***..
b

d
Fig. 460.-Secondary Dentine, filling the pulp-chamber in case of abrasion of a cuspid tooth: a, por-
tion lost by abrasion; e, abraded surface; d, secondary dentine, filling a portion of the pulp-
chamber, and acting as a protection to the pulp; e, slender point of the pulp; irregular deposits
are seen on the walls of the pulp-chamber, as atƒ; g, cylindrical calcifications in the root portion
of the pulp-chamber.
Fig. 461.-Secondary Dentine, from the same specimen as Fig. 460, magnified sufficiently to show the
difference in primary and secondary tissue: a, abraded surface of crown; b, secondary dentine;
c, primary dentine; d, junction of primary with secondary dentine; e, remains of pulp-tissue;
f, small oval masses of calcific material.
fectly filled for only a very short distance in advance of the abrasion.
This is more definitely shown in Fig. 461, from the same specimen,
magnified sufficiently to show the structure as compared with the pri-
mary dentine. In this case it will be seen that the secondary formation
SECONDARY DENTINE.
867
is fairly regular, but that the number of dentinal tubes is much dimin-
ished. This is quite the common form of secondary formations in the
incisors and cuspids when they are slowly worn by attrition. This
kind of formation is always limited, though some cases present much
more of the secondary formation than others before the final degener-
ation and death of the pulp; which seems very certain to follow sooner
or later, probably from exhaustion. In the root portion of this speci-
men (Fig. 460) there is an extensive deposit of cylindrical calcifications
(to be described presently), which very surely mark the last perform-
ances of the organ.
FIG. 462.
1
In the pulps of the molar teeth affected by abrasion we find similar
deposits of secondary dentine; but in this case there are certain pecu-
liarities that deserve mention, especially as they are of importance in
the clinical sense. In all of the double- or triple-rooted teeth there is
a very distinct enlargement of the pulp in the coronal portion, from
which the several root portions diverge into their canals. This forms
the bulb of the pulp, which is absent in the single-rooted teeth. Now,
in this case the formation of secondary dentine is confined almost ex-
clusively to the bulb of the pulp, extending into the root portion very
little, if at all, or, we may say, it is confined to the very orifice of these
canals. Otherwise than this the deposit is very nearly uniform on all
parts of the walls of the chamber, or if differ-
ences exist the deposit is least on the anterior
and posterior walls and greatest on the floor
and roof. In Fig. 462 I have accurately drawn
the outline of a section of the crown of a supe-
rior molar abraded but slightly (though its as-
sociates were badly worn), for the purpose of
illustrating the position of the secondary de-
posits as they are most generally seen in cases
of extreme reduction of the size of the pulp.
The lightly-shaded portion represents the orig-
inal form and size of the chamber, and the dark mustration of the Narrowing of
shading that portion not filled by the second-
ary deposit. It will be noted in this case that
the deposit is as great, or nearly so, rootwise
from the remaining portion of the pulp, as
that deposited next the crown; and in the one
root which appears in the drawing the narrow-
ing of the canal is confined to the portion orig- abrasion; c, c, remaining pulp-
inally within the pulp-chamber. So far as
deposits of secondary dentine are concerned,
this remains quite constant in all of my sec-
tions. In some cases the rootwise deposit is
the greatest, but the difference is never very great. The narrowing of
the root-canals within the original pulp-chamber is occasionally so ex-
treme that it is difficult to get a broach through them; but the root-
canal is usually about the normal size, provided always that there are not
other hard formations except the secondary dentine. There are, how-
ever, occasional exceptions to this rule in which there is considerable
Cl
the Pulp-chamber in a Molar
(superior) by the deposit of sec-
ondary dentine resulting from
abrasion, showing the portions
of the chamber in which the
deposit usually occurs. The
light-shaded portion (b) shows
the original dimensions of the
chamber, which in this in-
stance seems to have been pret-
ty large; a, a point of deep
chamber, which is mostly
with irregular masses; d, one
of the root-canals. It will be
observed that the narrowing of
the root-canal is within the
original pulp-chamber,
mad.
w
$
d
с
da

868
PATHOLOGY OF THE DENTAL PULP.
narrowing of the canals, but I have seen very few. In those cases in
which the root-canal is obstructed I have generally found it to be with
pulp-nodules, cylindrical calcifications, or general calcification of the
tissues of the pulp. In Fig. 463, at c, c, there is a blocking of the
A
b-
a
•
*
WEETEST OF T
FIG. 463.
B

α
noddidden.
Tw
S
Bath
▸
A
****
-
a
a
Reduction of the Size of the Pulp-chamber by deposit of secondary dentine excited by abrasion.
A, Diagram of a Lower Molar badly worn, showing narrowing of the pulp-chamber.
B, Illustration of the Tissue of the Secondary Deposit: a, a, a, a, outline of the original pulp-cham-
ber, from which the secondary growth has begun; in the rootwise portion there appears à second
line of beginning; b, globular dentine, in which a few dentinal tubes may be seen traversing the
the globules; c, irregular crystalline deposits.
entrance to the root-canals by calcific deposits in the form of irregular
crystalline masses. In this figure, at A, is represented a lower molar
with the crown very much abraded by mastication, the pulp-cavity of
which is very much reduced by the growth of secondary dentine. The
lines a, a, a, a point out the original outlines of the pulp-chamber, and
The
the new tissue formed is seen to be quite regular in its structure.
rootwise portion of the new formation shows two lines of the beginning
of new growth, showing that there had been a cessation and rebeginning
of the process.
In passing I will call attention to the peculiar structure
at b, in which a series of globules are seen to have a few dentinal tubes
passing through them. Here the secondary growth has become mark-
edly abnormal; and this abnormality is expressed in some form in
almost every case in which the pulp has died from exhaustion follow-
ing large deposits of secondary dentine.
It is found that these growths of secondary dentine caused by abra-
sion are not confined to the particular teeth worn, but if there is con-
siderable wear of the teeth generally, those that may have escaped
abrasion will have the growth of secondary dentine in very nearly the
same degree as those that have actually suffered from the wear.
Growths of Secondary Dentine excited by Caries present some features
that differ markedly from those excited by abrasion. As has been seen,
deposits of secondary dentine excited by abrasions are very generally
equally distributed on the inner walls of the pulp-chamber. In their
structure and in the direction of their tubules they resemble very closely
the normal dentine. In the study of secondary dentine the growth of
which has been excited by the irritation of caries this is quite different
in a large proportion of cases. The irritation is confined to a smaller
SECONDARY DENTINE.
869
number of fibrils, and the new growth is very generally confined to a
small part of the pulp-chamber immediately opposite the fibrils irritated
-not generally, indeed, to the exact fibrils that are involved in the
decay, but to that portion of the pulp-cavity. In Fig. 464 I give an
FIG. 464.
a
A
C
B

b
Calcification, or Deposit of Secondary Dentine, resulting from caries of an incisor.
A, Diagram of Section of Incisor, showing caries at a, and secondary dentine at b.
B, Illustration, magnified 200 diameters, to show the tissue of the secondary dentine: a, pulp-cham-
ber; b, b, secondary dentine; e, primary dentine. It will be noticed that the dentinal tubes in
the secondary dentine gradually disappear, giving place to a clear calcification.
illustration of this. At A is represented a section of a central incisor with
a small dark decay in the proximal surface at a, and a growth of sec-
ondary dentine at b, which is confined to the side of the pulp-chamber
toward the decayed point. At B, I give an illustration of the tissue of
the new growth, in which it will be seen that there is a marked diver-
sion of the tubules from the normal direction at the beginning of the
new growth, and also that the tubules soon become irregular, and finally
disappear, leaving the portion next to the pulp simply a clear calcifica-
tion, showing that the pulp has degenerated and become incapable of the
proper performance of its physiological functions-a sure precursor of
its complete destruction. This tooth was from the mouth of a negro
woman who came to me with an acute apical pericementitis. She was
sure the tooth had not given her pain before the present attack. The
pulp was not exposed, and no cause could be assigned for its death. I
should say that in grinding the section I found that the pulp-chamber
contained numerous calcific masses, which were lost, unfortunately, with-
out their character having been ascertained. As there were many decayed
teeth in the mouth, much of this may have been excited by sympathy.
Yet the case illustrates very well the general nature of secondary dentine
excited by decay. It is of medium type as to the regularity of structure,
and the result is that which we may expect to follow in cases of consid-
K.
870
PATHOLOGY OF THE DENTAL PULP.
erable secondary deposit-deatli of the pulp from degeneration of its
structure.
In Fig. 465 is presented another case in which the exciting cause of
the new growth was apparently about the same as that in Fig. 464.
This case presented a history of hyperemia from thermal changes. At
A is given a diagram of the tooth considerably enlarged, showing the
FIG. 465.
O
A
d
250SRAMA.;
B

***********
а
Secondary Dentine, resulting from irritation of the dentinal fibrils by caries.
4, Diagram of an Incisor having a decay in the labial surface, a, and a deposit of secondary dentine at
b. The point from which the illustration B is taken is shown by c.
B, Illustration of the Tissue of the Secondary Deposit in A: a, primary dentine; b, secondary dentine;
c seems to be a blood-vessel that has become calcified; d, an irregular fault having some resem-
blance to the lacunæ of bone; e, pulp-chamber. It will be noted that there are irregular deposits
of granular matter in the substance of the secondary dentine, and that the tubules wind about
them.
с
relative position of the decay and the growth of secondary dentine.
indicates the point from which the field B was taken. In this case the
secondary formation was very irregular, and presented many fields of
granular calcific material interspersed among the dentinal tubules. At
c a blood-vessel seems to have been caught in the new growth, and has
become calcified. At d there is a curious form resembling in some
degree the lacunæ of bone, but I am inclined to the opinion that it is
simply a fault. This case presents a curious specimen of irregular
formation. If space permitted a great variety of these might be
presented.
Fig. 466 is an illustration of a case in which the seondary formation
has been excited by a very small decay on the labial surface of an incisor,
and is confined almost entirely to the fibrils, the distal ends of which
are irritated by the carious process. Such cases have been spoken of
by a number of writers, but within my personal observation secondary
dentine so strictly limited as this has been rare. It serves well to illus-
trate the fact recognized by most of those who have critically examined
this subject, of the effect that is occasionally produced within the pulp-
chamber by the irritation of the distal ends of the dentinal fibrils by the
processes of caries. It must not be supposed, however, that such effects
as those illustrated here or in other writings on this subject are uniformly
SECONDARY DENTINE.
871
present in the pulp-chamber in cases of caries of the dentine. The facts
are quite the reverse; and it is well that it is so, for, unless my observa-
tion is at fault, any very considerable deposits of secondary dentine mean
exhaustion and degeneration of the pulp, followed finally by its complete
destruction. In the search among decayed teeth for secondary dentine
we may indeed find many examples and an indefinite variety of forms,
FIG. 466. B

a
A
a

~~
а
4, Section of an Incisor having a small dark decay in the buccal (or labial) surface: a, the tubules
leading from this to the pulp-chamber are pointed out at b. At e a small deposit of irregular
secondary dentine has occurred, which is seeu magnified in B. The shading at e shows some
secondary deposit along the wall of the pulp-chamber. The turning of the tubules away from
the principal deposit, as shown at a, a in B, is very singular.
but the great majority of decayed teeth present no secondary formations.
The circumstances that determine the formation of secondary dentine in
the one case or fail to bring it about in another are by no means well
known. My personal observations on this point seem to show that the
greater number of these formations are found in connection with decays
that have progressed very slowly, or, in other words, cases in which the
dentinal fibrils have for a long time been continuously exposed to irri-
tation. I have found them mostly in persons of middle age, though
occasionally in those not yet past their teens. They are not, there-
fore, confined to any time of life, nor, so far as I am able to determine,
to any peculiar condition of the teeth or the patient. I think they will
be found oftener in cases in which the teeth have many cavities than in
those in which the cavities are few. The teeth seem bound together by
a bond of sympathy that is very marked, and any cause that produces a
considerable effect upon one tooth has its effect upon all, often in a very
great degree. This is seen most prominently, perhaps, in the second-
ary deposits excited by abrasions, in which all the pulps of the teeth
suffer from the wear of a part of the number. But it is seen also in all
of the diseases to which the teeth are subject. Decay that causes irrita-
tion with deposits of pulp-nodules in one tooth is certainly liable to
Ga
872
PATHOLOGY OF THE DENTAL PULP.
bring about similar results in the pulps of those otherwise unaffected.
Inflammation of the pulp of a single tooth will induce hyperesthesia
of the pulps of the whole denture, etc. This is seen in other organs of
the body as well. If one eye is seriously diseased, the other suffers from
sympathy, and in certain pathological conditions oculists often extirpate
one eye in order to save the other. The effect of one diseased tooth
others is in every respect similar, though not so great in degree.
Dentinal Tumors within the Pulp-chamber are rare forms of the growth
upon
FIG. 467.

MO
O
A
FIG. 468.
じろっ
​-α.
!?".
Joh
×350
B

FIG. 469.

x350
Unr
A, Section of an Upper Molar Tooth: a, a carious cavity; b, fairly regular secondary dentine; c, a
dentinal tumor which has grown into the pulp-chamber, occupying the greater part of it. This
was attached to the wall of the chamber by a rather narrow pedicle. The structure is extremely
irregular, and varies much in its different parts. The section was saturated with balsam and
ground thin and polished; afterward the balsam was dissolved out in turpentine, and it was then
soaked in chloroform to remove the turpentine, and finally mounted dry.
B (Fig. 467) represents one field of view, and Figs. 468 and 469 two others. The tubules are quite
remarkable for the large number of their branches and the irregularity of their direction.
of secondary dentine, in which a more or less considerable calcific mass
is attached to the wall of the pulp-chamber by a pedicle. These growths
are occasionally notable for the singular irregularity of their structure.
DENTINAL TUMORS.
873
1
I have met with some very remarkable examples. One of these is rep-
resented in Figs. 467, 468, and 469. In Fig. 467, at A, is given a
diagrammatic representation of a molar which had a small cavity in
the anterior proximal surface. Opposite this there appears an ordinary
growth of secondary dentine, pointed out by b; c is a large pediculated
tumor arising from the growth of secondary dentine, and composed of
the most extravagantly irregular dentine that has been my fortune to
see. At B is given an illustration representing a field from this, and
in Figs. 468 and 469 two more, which, taken together, illustrate the
characteristics of the tissue very fairly. The illustrations will do more
to convey a correct idea of the structure of this tumor than any verbal
description that I am able to give. It is very transparent, except in
some points where it is shaded by extremely fine tufts of tubules, as in
some parts of each of the figures. These tufts form one of the prom-
inent characteristics of the tissue, and appear here and there throughout
its mass.
These seem to unite in many places to form unusually large
dentinal tubes, which, after pursuing a straight course for a short dis-
tance, are apt to be abruptly curved and lost, generally by passing out
of the section, but sometimes seeming to end in blind extremities. There
are also many very curious groupings of these tufts, as though odonto-
FIG. 470.
A
B
f
g
d
C

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a
Dentinal Tumor within the Pulp-chamber: A, diagram of the tooth, with dotted line showing the posi-
tion of the section B. In B'the pulp-chamber is shown in section, nearly natural size, showing the
tumor within. Cis an illustration of the tissue of the tumor; a, a, the primary dentine; b, irreg
ular tubules connecting the new growth with the primary dentine-most of these are very dark
and irregular; c, a calcospherite included in the mass: d, apparently a blood-vessel calcified; e,
calcified tissue; f, a finely granular mass; g, a spur of very transparent dentine. Dentinal
tubules appear at h, h.
blasts, or at least dentinal fibrils, had originated at these localities. In
some fields, of which Fig. 468 is an example, the tubules are very
874
PATHOLOGY OF THE DENTAL PULP.
sparsely distributed. In others they are quite thickly placed, or even
crowded, as in Fig. 469. But the more general character is that of
irregular grouping of the tubules with intervening clear spaces, as seen
in B, Fig. 467. Now and then there are seeming faults filled in with
very fine granular matter, one of which occurs in Fig. 468.
In Fig. 470 another case is illustrated, in which the new growth
seems to consist partly of secondary dentine, which is intermixed with
granular calcific material, calcified tissue, and calcospherite. These two
specimens represent the extremes of tissue-formation occurring in these
tumors. They are universally connected with the walls of the pulp-
chamber by a pedicle, either narrow or broad, by which the dentinal
tubes have passed into the tumor. It happens many times in the prep-
aration of sections of these pathological growths that the pedicle is lost,
giving the impression that the dentinal fibrils are developed within the
tissues of the pulp. I cannot but regard this as an error.
In every
case in which I have had the proper opportunity for the examination
of these masses presenting dentinal tubes they have sprung from the
walls of the pulp-chamber, and some portion of the tubes are con-
tinuous with those of the primary dentine. And now I should regard
the appearance of undoubted dentinal tubes in any mass within the
pulp-chamber as a sufficient proof of that fact.
This form of tumor is confined exclusively to the pulp-chamber. I
have never seen such a growth in the root portion. The causes which
lead to the growth are evidently the same as those leading to forma-
tions of secondary dentine generally. What circumstances determine
the erratic tumor-like form of the growth is entirely unknown. So far
as the symptomatology is concerned, I know of no observations that
throw any light whatever on the subject. The existence of the growth
cannot be known until after the destruction of the organ, and its occur-
rence is so rare that we are not likely to obtain much light by having
known the history of the chance cases discovered.
Calcifications of the Tissues of the Pulp are probably the most difficult
of the problems presented in the consideration of the pathological forma-
tions within the pulp-chamber. Many specimens are presented which
it is impossible to assign to any specific class, no matter how skilfully
we may arrange our classification; yet in most of these cases we will
find, if we have the proper opportunity of examination, that some part
of the tissue is incorporated in the calcific mass, or so attached to it as
to show that it is also undergoing the process of infiltration with lime
salts. There are very few cases presented that show the form-elements of
the tissue calcified in such a manner that it can be certainly identified;
but after a large number of examinations with the object of determining
this point, it is found that there are certain characteristic differences
between these calcifications and the pulp-nodules that distinguish them
with a considerable degree of certainty. They do not present the nod-
ulated appearance of the pulp-nodules, but, on the other hand, have
rather a regular outline with generally a smooth surface. When
prominences are present, they are in the direction of the trend, as
it
may be called, of the tissue being calcified or the direction pursued
by the blood-vessels of the part. The characteristics of the tissue,
t
CALCIFICATIONS OF THE DENTAL PULP.
875
}
I
if it may be so termed, will be discussed in connection with the
illustrations.
Heretofore there seems to have been no effort to distinguish between
these formations and the pulp-nodule. To my mind, the distinction is
important in the pathological sense. The presence of a few pulp-nod-
ules in a tooth is of very little significance so far as the future health
of the pulp is concerned. We find no degeneration of the tissues of
the pulp associated with them, unless, indeed, there are other causes
of ill health of the organ. But tissue-calcification is uniformly asso-
ciated with degeneration of the uncalcified tissues of the pulp. It is true
that pulp-nodules may be seen in pulps that are rapidly undergoing the
processes of degeneration, and may also be included within these calcifi-
cations. When once formed they do not disappear, and they will be
connected with any diseased condition which may afterward overtake
the organ. On the other hand, tissue-calcifications are never met with
in healthy tissue.
In Fig. 471, I have illustrated a case of calcification which seems to
include within it the form-elements of an inflamed pulp. At A, I have
FIG. 471.
A
a
C
B

6
7
A, Diagram of a Section of a Central Incisor, with a proximal decay at a which seems to have pene-
c marks the
trated the original pulp-chamber, but the opening is closed by a calcification at b.
position of a detached mass of calcific material that was lost in mounting the section.
B, Illustration showing the Appearance of the Calcific Deposit. This seems to be a calcification of
inflamed or cicatricial tissue. At a there is the appearance of a blood-vessel; b, pulp.
represented, diagrammatically, a central incisor with a proximal decay
at a which opens the original pulp-cavity. This opening is closed by
a calcific mass at b. At c there was a large elongated mass unattached
to the walls of the pulp-chamber which was lost in mounting the sec-
tion after it was ground At B, I give an illustration of a field of the
mass b in A, in which the form-elements appear quite distinctly. At a
there is the appearance of a blood-vessel with its branches. My suppo-
sition is that this calcification occurred after the exposure of the pulp by
decay and inflammation of the pulp-tissue, and that for the time, ro
doubt, the pulp was protected. But in the formation of this protective
876
PATHOLOGY OF THE DENTAL PULP.
covering-or, we may say, primarily by the inflammation-processes of
degeneration were inaugurated that resulted finally in the destruction of
the organ.
Many calcifications of this order are found from time to time that are
very large-as large, indeed, as the capacity of the pulp-chamber will
allow. But the attachment of the mass to the walls of the pulp-cham-
ber, as was the case in Fig. 471, is rather an exception to the rule. I
have often seen these so perfectly fitting to the walls of the chamber in
such cases that they appeared to be attached until I had ground a sec-
tion. Fig. 472 is an illustration of a case of this character. At A, I
A.
OL
α
B
e
FIG. 472.
B
****
d
b
Wat


•
Calcification of the Dental Pulp. At 4 is shown the outline of a lower molar with a cavity at b. The
pulp-chamber is much reduced in size and filled with calcific material, as shown in B. a, a large
granular mass of calcific material, which is very transparent, but finely granular. A few very
irregular lines are seen in the centre, which slightly resemble dentinal tubes; b, an erratic growth
of irregularly formed and unusually transparent dentine; c, line of the growth of dentine from
the floor of the pulp-chamber: the growth from other directions is so perfectly regular as to leave
no markings; d, margin of the cavity of decay; e, a bundle of cylindrical forms of calcific mate-
rial extending down into the root-canal. These extended to the apex of the root.
give an illustration showing a lower molar with a proximal decay at the
junction of the enamel and cementum, exposing the pulp. In this case
there has been a marked reduction in the size of the pulp-chamber by a
secondary growth of dentine that is remarkable for its regularity, as will
be seen by the inspection of the illustration of the tissue as shown in B.
The line of the new growth is clearly marked in the rootwise portion at
c, but in other directions there exists no demarcation whatever. At b
there is a distinct dentinal tumor in the form of a spur having its base
at c, where it springs from the rootwise portion of the original wall of
the pulp-chamber, and its point turns in under the calcific deposit a. At
a is a calcification that fills nearly the entire pulp-chamber. The mass is
very clear and transparent, and presents a finely granular appearance,
without any sign of structure except some irregular lines in its centre.
With the low power with which the drawing was made these resemble
CALCIFICATIONS OF THE DENTAL PULP.
877
dentinal tubes, but with higher powers they are found to present cha-
racters which show them to be faults. At either extremity of the mass
the degenerated tissue is apparent in the form of minute irregular
threads which give these parts a clouded appearance. At the root-
wise extremity it is connected with some cylindrical calcifications (e)
which extend down into the root-canal.
These two illustrations may be regarded as exhibiting the extremes
that appear in the study of this subject-the first showing most clearly
the form-elements of the tissue calcified, and the last exhibiting the few-
est traces. Generally, nothing can be clearly made out except some fine
lines that seem to represent fibres that have persisted or the perverted
forms of cells which seem to have escaped impregnation with lime salts.
This may occur in groups, as I suppose, resulting in faults of irregular
form, or single cells may remain, distorted perhaps beyond recognition.
In some such way most of the tissue-calcifications possess a great diver-
sity of markings of which nothing definite can be made by microscopic
examination. In Fig. 473 is represented a field from a calcification
FIG. 473.
B
A
-a
A, Outline of Incisor, with crown destroyed by decay. There is a calcific deposit in the root portion
of the pulp-chamber & inches long, pointed out by a.
B, Illustration showing the characters of the calcification. Some of the forms resemble somewhat
the lacunæ of bone (X 350).
a.
occurring detached from the dentinal walls in the root of a carious inci-
sor. A is a diagram of the tooth, and the calcific mass was about half
an inch in length, nearly filling the canal in the position pointed out by
In B the peculiar markings are shown. The mass is very trans-
parent, so that these forms are seen as clearly as if mounted alone.
They have some resemblance to the lacunæ occurring in the cementum,
and, while there might be a reasonable ground for difference of opinion,
I suppose them to be faults formed by the persistence of tissue-cells that
resisted calcification. A large portion of this mass presented no mark-
ings of any kind. Something of this class of fault occurs in almost
every tissue-calcification, and the forms of them are as various as can
be imagined.
KÖNY
.


878
PATHOLOGY OF THE DENTAL PULP.
1
The size and form of these masses vary indefinitely. They may be
large enough to fill the pulp-chamber or they may be very minute.
They are evidently formed very slowly, and may have their beginnings
at several or many centres; and these separate pieces will coalesce as
they enlarge in the same manner as is seen in the calcific plates that
occasionally occur in the walls of the arteries. It would be interesting
to know if there is any connection between this calcification in the
dental pulp and in the arteries. I know of no observations in this
direction.
Cylindrical Calcification is a peculiar form of interstitial calcification
of the pulp occurring only in the root-canal, and is connected with the
most marked degeneration of the tissues of the whole organ. At least
I have not met with this form of calcification passing considerably into
the coronal portion of the pulp in any case that I have examined. I
present illustrations of this form in its varying degrees in Figs. 474,
A
FIG. 474.

B
A, Outline of a Lower Molar, with a large carious cavity at a; b, pulp-chamber. The shaded portion,
c, was occupied by cylindrical calcifications.
B, Illustration of the Cylindrical Calcifications (X 100).
✔
475, 476. It occurs in patients of all ages, but perhaps is seen most
frequently in middle-aged people who have suffered much from decay
of the teeth or from abrasions. In the earlier stages of the process
the calcific points are found within the tissues in very small cylinders
or spindle-shaped masses too small to be seen with the naked eye.
In this condition the pulp, when rolled in the fingers, will have a dis-
tinct gritty feeling, as if it contained particles of sand. It is difficult
to make fine sections of such a pulp, for the reason that these hard
grains will destroy the edge of the section knife. But when a section
is had, it will be found that the cellular elements have mostly disap-
peared, or have lengthened out into slender spindle-cells to such an
extent as to give the tissue a very distinct fibrous appearance; and
lying parallel with these are found the little cylinders of calcific mate-
rial, as seen in B, Fig. 474. At A, in the same figure, I give a diagram
of the tooth, a lower molar with a large crown decay, from which the
specimen was taken, in which the shaded portions of the pulp show the
parts in which this form of calcification was found. This, I will say,
agrees well with other cases that I have examined. In Fig. 475 the
preparation was picked to pieces and spread out with needles, and it
gives a better exhibition of the fibres seen in the tissue: it will be noticed
in the fibres lying across the main trend of the tissue in the field how
A
CALCIFICATIONS OF THE DENTAL PULP.
879
FIG. 475.
the cylinders are attached to them by their ends. In picking these apart
in the field of the microscope this is still more observable, and then it
is found that each cylinder is firmly attached at either end to a little
bundle of fibrous material;
and it is hard to escape the
conviction that these fibres
are being infiltrated with
lime salts. A pulp containing
these calcifications will be dis-
tinctly stiffened, and may be
bent about and will retain the
curve given it like lead wire.
Indeed, this is uniformly the
condition of those pulps that
seem stiff when removed by
the broach.

Fig. 476 represents an
extreme degree of this form
of calcification. Here is a
more curious phenomenon
still. The cylinders have
grown and run together, but Cylindrical Calcification of the Pulp.
instead of coalescing end to
end, forming rods, as might
have been expected, they are
irregularly jointed, and in the effort to pick these apart with needles it is
found that these joints are held together quite firmly by fibres passing
from the one to the other. In this condition the root portion of the pulp
becomes very stiff; yet it may still be bent, and will retain its bent posi-
tion like annealed wire. I do not think that this form of calcification
ever runs together into a solid mass. It is evidently a distinct form, and
dependent on a peculiar condition of the tissue of the pulp. I have seen
FIG. 476.
This has beer
spread with needles, and the fibres that lay across the
general trend show how the calcifications are attached
at the end to the fibres. It will also be noticed that the
tissue has lost its normal forms and degenerated into
an irregular fibrous mass (X 100).

3
Cylindrical Calcification, more advanced than in Figs. 474 and 475. Instead of running together and
forming a solid mass, they are irregularly jointed (X 100).
nothing in other parts of the body with which to compare it. We indeed
find long, flattened calcifications in the arteries, but I have seen none with
the distinctly jointed appearance shown in Fig. 476. What forces are in
operation to produce these peculiar forms I am unable to say.
I am
880
PATHOLOGY OF THE DENTAL PULP.
I
equally at a loss as to the symptomatology of this class of cases.
think there is no doubt that the death of the pulp follows closely in
the wake of the calcification. Mr. Salter has also examined this form
of calcification and described it in some detail. I agree with him in
saying that "the whole of the tissues, cells, nuclei, connective tissue,
blood-vessels, and multitudes of nerves, are swallowed up and obliter-
ated in the calcific process.'
"The calcification is clearly not in-
terstitial in the sense of being between the fibres," but the whole tissues
are impregnated with the calcific material. They are not pushed aside,
as in the formation of pulp-nodules, but are involved in the calcific pro-
cess in the sense of being infiltrated, and thus converted into the hard
substance and completely destroyed as tissue. But the calcific process
is not the primary change, for before the calcification has begun the
tissue is already profoundly changed, as has been indicated already, so
that the cells have mostly disappeared.
""
This form of calcification does not as a rule stand alone, but is asso-
ciated with other forms. Generally, there is more or less calcification
of the tissues of the coronal portion of the pulp at the same time. This
may be of any of the varieties, but with the exception of deposits of
secondary dentine it is more commonly associated with interstitial
calcifications in the form of smooth, round boulders, such as is shown
in Fig. 472, or there may be several smaller stones of this variety.
Osteo-dentine is the rather inappropriate name that has been applied
to osseous formations within the pulp-chamber. In the human teeth
these formations are very rare, but in the teeth of animals they are seen
quite often, especially in the very large animals. I have seen a number
of these from the tusks of the elephant in which there seemed to be a
mixture of dentinal tubes and bone-corpuscles. But to enter into a
discussion of these peculiar formations in the animal kingdom generally
would lead us too far for the purposes of this article.
It has been my
intention to adhere strictly to the human teeth both in description and
illustration, notwithstanding the very great interest presented in the
comparative study afforded in the diseases and accidents of the teeth
of the animals.
The undoubted osseous formations met with in the pulp-chamber of
the human teeth are very rare. In making this statement I exclude all
hard formations in which bone-corpuscles are not present. This seems
not to have been done by many who have written on this subject; but,
on the other hand, some writers seem to have called almost all irregular
formations osteo-dentine. The great bulk of these have not the slightest
resemblance to bone.
The cases of osseous formation within the pulp-chamber that I have
met with have all presented the general characters of cementum, and
have been found in the root-canal attached to the dentinal wall or resting
upon some irregular formation which separates them slightly from the
dentine. This is different from the reflection of the cementum slightly
into the pulp-chamber from the apical foramen, which occasionally occurs
in such a way that I should not consider it in any sense pathological. It
seems to me evident that bone will not form in these positions until after
the atrophy of the layer of odontoblasts; at least, the specimens that I have
OSTEO-DENTINE.
881
examined all indicate this. I present two illustrations of this in Figs.
477 and 478, both taken from incisor teeth that have been considerably
abraded and the pulp-chamber partially filled by secondary deposits.
.FIG. 477.
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A
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Osteo-dentine.
A, Outline of Abraded Incisor, with point of pulp-chamber (a) closed by secondary dentine; b points
out a narrowing of the root-canal by a deposit of osteo-dentine.
B, Illustration of the Tissue of the Deposit: a, pulp-chamber; b, ossific material; c, layer of very
small calcospherites; d, primary dentine (× 350).
FIG. 478.
OPOL
-a
B
b

-h
d


c
-d
e
f
Osteo-dentine.
A, Outline of Incisor, showing a narrowing of the root-canal at b by a deposit of osteo-dentine.
B, Illustration of the Tissue: a, primary dentine; b, line of the beginning of a growth of secondary
dentine; c, secondary dentine; d, layer of granular matter; e, osteo-dentine. This has the
lacunae at g and dentinal tubes at . f seems to be the surface of the osseous deposit; i, irregu-
lar crystalline deposits; h, the pulp-chamber (× 350).
They are enough alike in every respect to have been taken from the
same mouth, though, as a fact, they were not. In each I present a dia-
gram of the tooth at A, with the position of the osseous deposit pointed
VOL. I.-56
882
PATHOLOGY OF THE DENTAL PULP.
out by b. It will be noticed that in each case the pulp-chamber is very
much narrowed at the point of the bony deposit, and is wider again
toward the apex of the root. The only other position in which I have
seen a similar deposit was in the palatine root of an upper molar, and
in this the same narrowing occurred. In B of each of these figures the
tissue is illustrated, and affords a better description than I can give in
words. I will call attention to the fact that in Fig. 477 the bone is
deposited upon a layer of small calcospherites, at which the dentinal tubes
stop suddenly and completely. This growth seems to be in all respects
a true cementum, presenting quite perceptibly the peculiar stratified
appearance so generally seen in that structure. In Fig. 478 this is
entirely different. There is a secondary dentine of very imperfect
structure in which the dentinal tubes gradually disappear, and then the
osseous formation is deposited upon a layer of granular matter. At k
there seems to be a return of dentinal tubes. This particular section
more nearly merits the name "osteo-dentine" than anything else that I
have seen from the human mouth. It is possible that osteo-dentine may
occur in other portions of the pulp of human teeth, or even in isolated
nodules, as is undoubtedly the case in the teeth of animals, but as I
have not met with them in all my cuttings, I think they must be very
rare.
The Condition of the Layer of Odontoblasts in the varying states of
the dental pulp is a point of the greatest interest, and I have delayed
the consideration of it until this time, for the reason that I wished to
present the other tissue-changes first, in order, as far as possible, to sim-
plify description and prevent repetition. It will be seen that in all of
the deposits of secondary dentine, except it be some of the more rare
forms of dentinal tumor, the dentinal tubes, if not markedly dimin-
ished at the very beginning, soon begin to disappear; and if the case
has met with no mishap in the way of exposure or hyperæmia of suf-
ficient severity to cause death of the pulp, the dentinal tubes disappear
entirely, giving place to clear calcification, deposits of granular matter,
calcospherites, or other irregular structures. I believe this conclusion
of the deposits of secondary dentine is universal if it is not brought to
a stop by the premature death of the pulp. This means exhaustion of
the organ to such an extent that it is no longer capable of physiologi-
cal function; for, no matter by what cause it may be excited, we must
regard the formation of true dentine in normal form as a physiologi-
cal product of the organ, and whatever may be the differences of view
in regard to the matter, all must regard the layer of odontoblasts as
very nearly related to the formation of the dentine. The processes
emanating directly from these cells are the occupants of the dentinal
tubes are the dentinal fibrils; and without these there is no dentine,
for it is the presence of these that gives the structure the characteristics
by which it is known to the histologist. Hence without the odonto-
blasts we cannot have the formation of dentine. There may be calcific
material, but it will not have the form of dentine. This is exempli-
fied in most of the illustrations that I have presented of the secondary
formations within the pulp-chamber. These considerations, together
with the ever-present fact that the characters of the secondary deposits
CHANGES IN THE ODONTOBLASTS.
883
of dentine soon begin to show a failure as to the normal number of the
tubes, has led me into the study of the condition of these cells in the
varying conditions of the pulp as regards secondary deposits. I have,
however, found this an exceedingly difficult study. In cases of calci-
fication it is very difficult to get good sections without decalcifying the
hard tissues, and in so doing the tissue is so deranged and otherwise
injured as to be of little use. Again, in removing the pulp from its
chamber the layer of odontoblasts so often remains clinging to the den-
tinal walls, either as a whole or in part, as to cause much vexation.
With all of these troubles in the way it is not surprising that the study
of this layer of cells in its diseases has made so little progress.
I have already alluded to the fact that this layer of cells seems to
persist unchanged in acute inflammations of the pulp until it is under-
mined by the processes of suppuration. This, however, does not argue
the greater vitality of these cells, but rather the reverse, for it shows
that they are less susceptible to changes of form than the other cells
of the organ. The facts already given speak plainly of the atrophy of
the odontoblasts before the death of the pulp as a whole. Indeed, some
of my observations seem to indicate that the pulp may remain alive for
a considerable time after the atrophy of a large proportion of the odon-
toblasts. In many of my sections of pulps that had been long in a
state of disease the peculiar structure of the margin of the pulp in which
the odontoblasts lie has been present, but without the odontoblasts, or
with one here and there only, or with patches from which they were
missing, very much the same as we often see in secondary dentine where
the tubes fail in patches or become fewer in number and finally disap-
pear. Again, I have found in some sections that all signs of the nor-
mal periphery of the pulp were missing, and yet along the margin
there was an occasional odontoblast which took the stain in a very
unusual manner, as though profoundly changed in its chemical con-
dition.
In Figs. 479 and 480 are given illustrations of these changes. These
can be better appreciated by comparison with Fig. 440, in which the
full number of odontoblasts that occupy the periphery of the pulp are
present. This form of failure of these cells seems to accompany the
degenerative changes of the tissues of the pulp that have been described,
and, taken together with the evident persistence of these cells during
the changes due to acute inflammations, show us plainly that it is in the
chronic diseases that we must expect the atrophy of this layer. This
agrees also with what is seen in secondary dentine. It seems that these
cells are profoundly affected by irritation of the distal ends of the
fibrils, for we often find them depositing secondary dentine in cases of
abrasion, as has been indicated, and in connection with this perform-
ance the cells disappear. Not only this, but they disappear in many
cases in which there has been no deposit of secondary dentine whatever.
This has appeared prominently in two cases in which there had been
long-continued inflammation, accompanied with hypertrophy of the
pulp which was projected into the cavity of decay, as shown in Fig. 454.
In neither of these cases were there any secondary deposits except a few
pulp-nodules and a few masses of calcoglobulin; but over a consider-

884
PATHOLOGY OF THE DENTAL PULP.
able part of the coronal portion of the pulp there were patches from
which the odontoblasts had disappeared from their matrix. The pos-
sibility that these had been pulled out of their matrix in the removal
of the pulp from its chamber has been fully considered. This pulling
out occurs in a considerable number of cases, so that I have become
acquainted with its indications; and in the cases mentioned these indi-
cations are entirely wanting. Fig. 479 was taken from the coronal
portion of the pulp of a tooth that had a considerable hypertrophic
growth extending into a carious cavity, and from the history given by
the patient it had evidently for five or six months been subject at inter-
vals to severe attacks of inflammation; and, though there had been a
large increase of its tissue, showing a tenacious vitality and a strong
tendency toward reconstruction, the odontoblasts had disappeared from
many parts of its surface, and in other parts there were but few left in
the matrix of the membrana eboris, as is shown in the figure. In this
pulp there was another abnormal condition of this membrane that
deserves mention, though it is but an accidental disturbance: Along
the dentinal wall, extending from the point of exposure through which
the hypertrophic growth was extruded, the dentinal fibrils had been
drawn considerably out of the dentine, and the layer of odontoblasts
turned so that their long axis was almost parallel with the dentinal
wall, with their pulpal ends inclined toward the opening: this was evi-
FIG. 479.
FIG. 480.
WZ
Atrophy of the Odontoblasts (compare with
Fig. 440) (7th inch immersion).
a
A


Atrophy of the Odontoblasts: a, odontoblasts
that have taken the stain in an irregular
manner. There is also a peculiar variation
in their size. Some areolations appear in
the tissue (th inch immersion).
dently done by the swelling of the pulp and the protrusion of its mass
through the opening.
Fig. 480 is an illustration of the condition of the membrana eboris in
a pulp that had been somewhat reduced in size by the deposit of sec-
CHANGES IN THE ODONTOBLASTS.
885
ondary dentine excited by abrasion. It had also suffered from hyperæmia
and extravasations, as was shown by both the history and the appearance
of old clots in its tissue, and finally was found to be in a state of chronic
inflammation at the time of extraction. The odontoblasts had disap-
peared from a great portion of the periphery, and in many places all
indication of the membrana eboris was lost. The illustration was taken
It will
from a point at which a few scattering odontoblasts remained.
be seen that the usual demarcation of the membrana eboris is wanting,
and the odontoblasts that remain are sticking in among the other cells
and the inflammatory elements. They also present a singular variation
in size, and the staining is different from the healthy cells. The general
structure of the pulp was also much changed, areolations appearing in
its matrix at a number of points.
In cases of much less degenerative change in the general structure of
the pulp there are often observed changes of a more or less marked cha-
racter in the odontoblasts; and my observations, taken as a whole, seem
to indicate that these changes are quite common to the chronic affections
of the organ, and especially so where there have been considerable sec-
ondary deposits of any kind except the pulp-nodules. It is probable
that it accompanies them also if the pulp-nodules are very consider-
able in bulk.
g
The influence of the destruction of the membrana eboris with its
odontoblasts in cases of exposure of the pulp is a question of great
interest. It is to be regretted that there is no direct observation on
this point that will assist us in arriving at conclusions. I have many
times seen a hard formation that closed the breach, and for the time
seemed to shield the pulp from external injury in cases which I had
capped at a time when the pulp was fully exposed, and in such con-
dition that I think there could be no doubt of the destruction of the
odontoblast layer. But I have never had the opportunity of micro-
scopic examination of such a case. A number of times I have drilled
through these deposits to remove a dead pulp; and, so far as I was able
to judge of the condition by such a mode of examination, it is not dif
ferent from that found in death of the pulp following secondary deposits
excited in other ways.
A sufficient number of examinations of the sec-
ondary deposits in cases of exposure and known destruction of a portion
of the surface of the pulp would settle the question as to whether these
cells may be re-formed after they have once been destroyed. Until such
observations have been carefully conducted in sufficient number, or until
direct evidence of their re-formation has been had, the question must
remain an open one. At the present time what evidence we possess on
this point is certainly against such re-formation with the restoration of
physiological function. In some cases of dentinal tumor-such, for
instance, as that presented in Fig. 467-there seem to have been new
dentinal tubes originated, and with these there must have been odonto-
blasts. The number of the tubes, and the peculiar tufts uniting to form
tubes, seem to me to be evidence that odontoblasts have come into
existence, but the tissue formed is in no sense physiological. Still,
in these, in every instance, some portion of the dentinal tubes comes
directly from the primary dentine.
886
PATHOLOGY OF THE DENTAL PULP.
GENERAL CONSIDERATIONS.
In the foregoing pages I have frequently alluded to the fact-which
is apparent in a very large proportion of my microscopic preparations
-that any of the secondary calcific formations within the pulp of the
tooth result in exhaustion and the final death of the pulp. This fact
is so prominent that it seems to me that it cannot well be overlooked,
and yet in the capping of exposed pulps it seems to have been the
thought of the profession that to be able to obtain a secondary deposit
under such circumstances was to ensure the permanence of the health
of the pulp. This was my own thought some years ago, but further
clinical experience, combined with the closer microscopic study of the
subject, has convinced me that this is a mistake. Secondary deposits
may, and do, ensure temporary quiet, but so far from ensuring health
are they that, as a matter of fact, they bring about the very state of
matters that we most wish to avoid the degeneration and final destruc-
tion of the pulp. In a large majority of cases, however, this result is
brought about very slowly, and thus has escaped the notice of most
observers. For if an exposed pulp is capped and the cavity filled, and
the case seems to do well for a year or two, it is regarded as a success,
and is lost sight of. When this returns some years later with a dead
pulp, it is treated as one of the great mass of such cases that are con-
stantly presenting themselves, and probably no note is made of the fact
that it was capped at a certain time and was one of the many successful
cases. And precisely the same thing is true of a large number of teeth
in which very large fillings are made in cases in which there is no ex-
posure of the pulp, as well as in many in which the fillings were not so
very large. The fact seems to be that any condition of abnormal irri-
tation is liable to produce these results whether it be from a capping, a
large filling that increases the thermal changes by the greater conduct-
ing power of the metal of which the filling is composed, the exposure
of the fibrils by abrasion, or other deleterious influence. And, taking
my own records as a guide, I should be compelled to say that very large
fillings without non-conductors in teeth with pulp not exposed are more
destructive than well-made cappings with non-conducting material
where pulps are fully exposed; provided that the capping material be
at the same time non-irritating. It will be seen that in all of these
cases the cause of difficulty lies in the fact of continuous irritation, and
it makes but little difference from whence that irritation comes; it will
in time do its work of destruction.
S
The time that pulps may live after the beginning of secondary de-
posits is a question of great importance. At present we are almost
without exact observation on this point. Undoubtedly, the time varies
widely in different cases, and may be said to extend from a year or two
to half a lifetime or even more. A very large proportion of these pulps,
however, are lost within ten years. Some of these cases will result in
abscess, but very many pass on for years in a state of perfect tran-
quillity, giving no indication of the death of the organ. The only
cases in which I have had the opportunity of making microscopic
examination have been those of death of the pulp from causes other
CAPPING OF THE DENTAL PULP.
887
than exposures capped by myself, and have not included cases in which
I have had certain knowledge of the state of the pulp at the time of
capping by others; but from the gross examination of clinical cases I
have no doubt that, with the exception of the nature of the deposit, the
general pathological changes are the same as those seen in very slow or
stationary caries; that is, function becomes more and more irregular or
abnormal until the pulp fails entirely.
Very many cases of capping pass on for years without any deposit
whatever, and seem to remain in a perfectly healthy condition. This
we must regard as the most desirable result that can be obtained.
Enough of these cases have been noted to demonstrate the possibility
of rendering the conditions so nearly normal that no disturbance of the
functions of the organ occurs.
In relation to the symptomatology of the dental pulp more exact
information is to be desired, especially as to the differential diagnosis
of its different states. This will require that cases of known history
be prepared in large number for microscopic examination and the
results classified. The old plan of judging of the condition of the pulp
by the symptoms presented is of but little scientific value until we shall
have more direct knowledge of the conditions by which the symptoms
are produced; and this can be gained only by the methods of study
indicated.
DISEASES OF THE DENTAL PULP, AND
THEIR TREATMENT.
BY JAMES TRUMAN, D. D. S.
THE diseases of the dental pulp, while not numerous, are an import-
ant part of the pathological conditions coming under the care of the
dentist. It has been the aim of the writer to present the subject in the
clearest manner possible, without undue overloading with quotations.
As the minute anatomy of the dental pulp is fully treated elsewhere in
this volume, no allusion has been made to it. Considerable space has
been given to the consideration of thermal influence, as that important
factor in pulp-irritation has measurably been neglected and its influence
underrated in the production of pulpitis, etc.
The subjects treated are embraced under the following headings:
THERMAL INFLUENCES.
Changes from Normal.
NODULAR DEPOSITS.
POLYPUS OF THE PULP.
1st. Simple Exposure.
2d. Superficial Pulpitis.
3d. Deep-seated Pulpitis.
4th. Devitalization.
5th. Gangrene.
6th. (So-called) Dry Gangrene.
THERMAL INFLUENCES.
The pathological condition of the pulp cannot be properly understood
without devoting some consideration to the primary causes of inflamma-
tion in that organ, originating in external influences which bear more
or less directly upon the diseases subsequently manifested.
The prolongations of the odontoblastic layer through the tubuli
practically extend the pulp to the remotest ramifications of these passages,
and, as they occupy the largest proportion of the dentine, it follows that
the pulp cannot be considered simply as a central organ of the tooth-
body, but must hold important relations to all parts of the tooth, and
in return must receive all impressions made at the peripheral ter-
minations; and in proportion to the extent of these will the effect be
temporary or destructive. When it is understood, therefore, that in all
exposed dentine surfaces we are dealing directly with the central organ
—
S
888
THERMAL INFLUENCES.
889
through its vital extensions, the importance of carefully considering the
causes of irritation will be properly appreciated.
The pulp proper, while it undoubtedly receives impressions through
the enamel, is never seriously affected by these unless disturbed by some
sudden concussion or movement of the tooth or by deposits of calcific
matter, but remains in the quiet performance of its function as one
of the sources of nutrition to the entire structure. When, however, the
dentine becomes exposed by the progress of caries, the contents of the
tubes are kept in a continuous state of irritation. While the tube-con-
tents have not as yet been demonstrated as consisting of a nerve-fibre or
fibres, it is demonstrably true that sensation is carried from periphery
to centre through this channel; and where sensation is, a certain amount
of inflammation is always possible. While this is true in theory, it is
practically demonstrated by the fact that the exposed tubes are a source
of inflammation in the pulp, oftentimes through quite thick layers of
dentine; and this is only possible under the supposition that the irrita-
tion of the surface layer has extended, by the general law governing
inflammations, to the central tissue.
Pulpitis may, therefore, be said to have its origin in quite remote
irritation; and this irritation may be produced by any of the many
sources of disturbance present in the oral cavity, or it may originate
from the action of the varying temperatures to which all teeth are
exposed. The direct and most positive cause is in the progress of caries.
The extent and rapidity of inflammation will depend on the density of
the tooth affected. In soft-structured teeth with great deficiency of
inorganic material the chemical action leaves exposed a greater propor-
tion of organic matter, and necessarily opens up a larger surface of inner
tubular tissue to the irritating action of the acid fluids, débris of decay,
fungi, etc. The result is not only a more rapid destruction of the tooth,
but, at the same time, a more speedy increase of the inflammation along
the inner tubular contents. In very dense teeth the irritation is reduced
to a minimum, and it is therefore rare to find the pulp affected. This
is to be attributed to the contracted calibre of the tubes and the ex-
tremely slow progress of the disease. Between these two extremes there
exist all grades of structure dependent on age and systemic conditions.
The causes already described rarely result in inflammation of the pulp
prior to actual exposure, and may be regarded as simply placing the
tube-contents in a condition suitable for the more positive action of
atmospheric influence. This, from its continuous and more decided
impression, becomes a serious factor in the preliminary irritations, with
results more frequently injurious to the pulp than all the other causes
combined. As before stated, the density of the tooth contributes a pro-
portionate degree to its effect, and it therefore follows that the age must
be considered in any treatment given teeth. Young or imperfectly-
developed dentine, for reasons already enumerated, is more liable to
these impressions, while old age is scarcely affected at all; hence the
treatment adapted to the latter is clearly inadmissible in the former.
Cold and heat, whether communicated through fluids or by draughts of
air, have a similar effect, producing a violent shock and acute pain, which,
if long continued, will result, as before stated, in pulp-irritation and
Go
890
DISEASES OF THE DENTAL PULP, AND TREATMENT.
final devitalization. In moderately or very dense teeth this may produce
but slight irritation, and, following the general law, may result in extra
development of secondary dentine, an effectual barrier being thus inter-
posed against further irritation. The operation of this law is beautifully
illustrated in the formation of secondary dentine by occlusion in teeth
worn down on the cutting edges and in the development of extra-cemen-
tal tissue in exostosis, and also in the calcification of the tubuli in caries.
in dense teeth. This is, however, only possible under favorable condi-
tions-conditions rarely or never present in young teeth. Hence the
filling of all such teeth with good conductors, without some intervening
media to prevent the irritating influence, must be regarded as an ob-
jectionable practice. In exact ratio to the sensitiveness of the tissue
will be the danger of thermal action, and this hyperesthetic state will
be in proportion to the conditions already described.
It is important to bear in mind the possible pathological contingencies
in the treatment of so-called sensitive dentine. Over-stimulation from
an irritant will have a very deleterious effect if too long continued or if
applied over a too thin layer of dentine. The peculiar and quite differ-
ent action of various obtundents must be carefully studied in their pos-
sible relations to the pulp, those being the best to use-if used at all—
that confine their action to the superficial layer; and those of great
penetrating power, of violent action, or that continue their devitalizing
power through absorption should be used sparingly or be abandoned
altogether. Among those of great penetrating power may be classed
chloride of zinc, and of devitalizing power, arsenic.
The possible changes that may arise through thermal action necessi-
tate care in the treatment of all teeth, no matter what may be the struc-
ture. While it does not come within the province of this paper to dis-
cuss the question, it will not be out of place to suggest that as a general
rule no very sensitive teeth should be filled with as good a conductor as
gold without a preparatory layer of gutta-percha, tin, or some equally
reliable non-conducting material. Especially is this applicable to im-
mature teeth or the teeth of children between the ages of twelve and
fifteen. Indeed, so liable is the pulp to be affected during this period
that it is very questionable whether gold should ever be used in that
class of teeth.
1st. Simple exposure.
2d. Superficial pulpitis.
3d.
Deep-seated pulpitis.
The destructive action through conditions heretofore alluded to result
eventually, if not checked by remedial agents, in direct irritation of the
central organ. This opens up a long chain of tissue-disturbance that
may end in the total destruction of the tooth, and possibly to more
remote and serious lesions. These changes from the normal to abnor-
mal may be classified as follows:
4th. Devitalization.
T
5th. Gangrene.
6th. (So-called) Dry gangrene.
St

Simple Exposure. The progress of the destructive forces eventually
removes all intervening layers of dentine, and the pulp lies directly
CHANGES FROM NORMAL.
891
exposed to their influence. While this organ, from its large supply of
nerve-fibres, is very sensitive and easily disturbed by impingement of
foreign matter, it very frequently bears this exposure without indications
of pain; indeed, it not unfrequently happens that it passes through all
the stages enumerated without any sign more than an occasional uncom-
fortable sensation. This is not, however, always the case. Fresh expos-
ures always, when visible, present a rich red appearance, from the fact
that the red blood-corpuscles have not been given time to take on the
condition of stasis, or stagnation, in the progress of inflammation. The
bright-red spot so familiar to all practitioners has, therefore, only a lim-
ited duration, and gives place to the secondary, or dark, stage peculiar
to areas of inflammation, whether limited to minute or covering large
surfaces. The red spot is therefore the indication of a pulp in a nor-
mal condition, or as near that as it is possible to have it and still
require treatment. The exposure may not be visible to sight, as it
may have occurred through the cracks always possible in dentine in
defects of structure or by accident. It will, therefore, in such cases, be
manifestly impossible to diagnose its condition or judge the length of
time of exposure or the extent of the inflammation. The red presenta-
tion is the indication for a favorable judgment as to the propriety of the
so-called process of capping. In proportion as the pulp has degenerated
toward pulpitis will the possibility of success be decreased. This has
been the experience of the writer, and is fully in accord with the gen-
eral professional sentiment on this subject.
Cond
The difficulty in diagnosing a slight exposure is oftentimes very great,
and, as it is of vital importance that this should be correctly done, the
examination should be thorough. The simulation of exposure of the
pulp by sensitive inner tubular fibres is always a source of difficulty.
If it has been exposed to irritation for some days, the excavator may
fail to find it; resort must be had then to some agent that will penetrate
minute openings and act as a searcher. For this purpose nothing is
superior to finely-carded cotton. The fibres of this insinuate themselves
into minute orifices, and the opening must be very small indeed that
will not be entered by them. The result is momentary pain, more or
less acute, depending on the size of the aperture.
While this simple
test is not wholly to be relied on, it is the best at present at command,
as it certainly is a very delicate one. Sensitive dentine is not affected
by it, for the reason that the test is only available after excavation of
all débris of decay; and this process cuts off all fibres level with the
orifices of the tubes, into which, on account of their microscopical
minuteness, the fibres of cotton cannot penetrate.
Superficial Pulpitis.—Inflammation of the pulp proceeds by the usual
stages accompanying other inflammations-first, the irritation caused by
the foreign matter; then the period of excitement or increased flow of
blood, followed by the static period; then gradual loss of vitality in the
part most affected; eventual death, followed by a putrescent condition.
The first stage is that comprised under this heading, which may be
described as superficial pulpitis from the fact that it frequently retains
that character for a long time, and may therefore be properly considered
as a distinct variety. When it assumes a chronic character, it is evi-
892
DISEASES OF THE DENTAL PULP, AND TREATMENT.
dently due to a large amount of vitality in the individual, giving a
resisting power to the encroachment of disease. This peculiarity is
often manifested in the power of resistance some pulps possess against
the action of arsenic. Ordinarily, however, superficial pulpitis is of but
short duration, and, following the general law, continues to the destruc-
tion of the whole organ. The possible error in diagnosis will be found
in the difficulty of determining the extent of the lesion and whether it
may not possibly have reached the condition of deep-seated pulpitis, the
latter condition being generally accompanied by more or less periosteal
disturbance, which will at times furnish a guide to judgment, though
the violence of the inflammation will have to be the general diagnostic
sign. If there is but little activity, if pain is not excessive and is not
coupled with periostitis, the pulpitis may be regarded as superficial;
but, on the other hand, if acute with the other accompaniments, it has
reached a point where devitalization is certain to result, and any effort
to abort the inflammatory state must result in failure. The usual
attempt to quiet such pulps and then cap with some foreign material
has but little to recommend it, and the final result is almost invari-
ably devitalization.
The destruction of the life of the pulp is by no means dependent on
exposure by caries. The organ holds its vitality by the slight connec-
tions with the main vessels and nerves through the oftentimes very con-
tracted canal, the apical foramen of the tooth. It requires but a very
slight disturbance at this point to cut off all sources of nutrition in this
direction, and the pulp's life is sacrificed. This is much more easily
accomplished than is generally supposed, judging by the very rough
appliances, and the still rougher modes of using them, that have been
adopted from time to time for the purpose of moving teeth. The sepa-
ration of teeth by the wedge and hammer and powerful screws is but
one sample of the wrong application of force upon a delicate tissue.
The elasticity of the pericementum admits of a limited movement, and
any force used beyond that must be cautiously applied, to prevent
strangulation of the vessels of the pulp at the apex. The pulp may
be devitalized and give no immediate sign, or it may result in sudden
congestion or rapid discoloration. A sudden blow has the same effect,
and, as this is peculiarly liable to occur to children, the largest percent-
age of loss from this cause occurs in the earlier years of life and very
frequently fails of recognition until a later period, when discoloration
gives the usual indication. Devitalization occurring under these cir-
cumstances is not necessarily a source of discomfort to the individual.
The pulp-tissue is gradually decomposed or mummified, and the matter
is gradually absorbed into the body of the tooth, and, in connection
with the dead material already there, produces the dark appearance
before alluded to. Such a tooth may remain comparatively comfortable
for years.
It requires the ingress of atmospheric germs to produce
the products of decomposition which render the treatment the most
troublesome and uncertain of any of the pathological conditions of
which the dentist is called to take charge. This can be more properly
considered under-
M
Gangrene. This term is applied to the pulp in the last stages of
GANGRENE.
893
decomposition, for it is death preceded by inflammation. This may
have been superinduced by the exposure of the organ, or, as previously
described, by a too suddenly applied force. The destruction of the
vitality leaves a mass of dead matter confined within narrow limits.
This, even when exposed to the air, may remain quiescent for a long
time, provided there is free egress for the products of decomposition.
One of these-sulphuretted hydrogen-is formed rapidly. If by any
means the aperture becomes closed, the excessive irritation from pres-
sure that this produces rouses the pericementum into activity; the result
is periostitis. This will give rise to symptoms more or less aggravated,
depending largely on temporary or permanent systemic conditions. The
state of the pulp at this pathological period is of far more importance
than has generally been conceded. Unless great care is exercised, com-
plications of a serious character are certain to result. The septic poison
so infiltrates the surrounding tissue by long continuance that the treat-
ment very often becomes exceedingly tedious, and in some cases ineffect-
ual, especially in cachectic individuals. Atmospheric air as a factor in
decomposition is in no case more clearly demonstrated than in pulps of
this character. When confined in a sealed cavity, as in teeth without
caries, they may remain, as previously stated, for years without any dis-
turbance; but a free opening brings in a new element, and the destruc-
tive process immediately begins. In the exposed pulp this is always
present; hence pulps of this character are loaded with germs. This is
not the place to discuss the influence of bacteria on inflammatory con-
ditions, but the observations of the writer point unerringly to the fact
that their presence is quite necessary to the progress of such conditions,
and their destruction is absolutely essential before any good result can
be effected. Careful microscopic examinations in pyrorrhea alveolaris
have demonstrated that very positively. Treatment of gangrene, there-
fore, must be based on this fact first, and, secondly, must be directed to
an elimination of the gaseous products. This part of the subject will be
more thoroughly treated hereafter.
Dry Gangrene. This peculiar state of the pulp, subsequent to de-
struction of its vitality, is not easy of explanation, but there are cases
which are undoubtedly produced by the development of secondary den-
tine, and a consequent stagnation in the circulation, as in gangrena
senilis. This is often observed in teeth of old persons, but is more
rarely seen where death of the pulp has taken place in a closed cavity.
It has been termed the "mummified condition of the pulp." It is a
frequent result of capping with oxychloride of zinc, and in such cases it
is evidently due to its great penetrating property, dependent, probably,
upon its affinity for the water and power of combining with the albu-
men of the tissues. It is for this reason, to a large degree, that oxy-
chloride of zinc is the most valuable capping material, as it produces
this very desirable state-a state in which the tooth is generally effect-
ually preserved from the results described under the head of Gangrene.
TREATMENT.—The treatment of simple exposure, as well as the other
more complicated pathological changes, has assumed increased import-
ance with the development of dentistry; indeed, it may be said to base
its progress and right to be deemed worthy to be called a profession
Ja
Moder
K
894
DISEASES OF THE DENTAL PULP, AND TREATMENT.
upon the intelligent conception of the management of this organ. The
feeble and generally futile efforts to treat it made by the older dentists
were necessarily failures, as they were of a purely empirical character
and a continual violation of what are now well-understood principles.
The old method of destruction by the actual cautery, while theoretically
correct, was impossible of application with the then imperfect appli-
ances, and the knowledge of the proper subsequent treatment was
wholly wanting. There was little or no progress until after the in-
troduction of arsenic as a devitalizer by Spooner, in 1836. It came
into use very slowly, and Dr. Harris, the ablest of the pioneer dentists,
for several years failed to perceive any advantage in its use, and he
passed from his laborious and useful life before the pulp and its entire
pathological relations were understood. It is very doubtful whether the
half century that has been given to its study has clearly solved all the
problems connected with it.
The two modes of treatment that have been adopted are-the one
being conservative, and the other destructive-diametrically opposed,
yet both lead directly to the same end, the preservation of the tooth.
The former is effected by what is known now as capping, and the other
by devitalization and removal.
GA
Capping was very early adopted, in accordance with the theory that
if the pulp could be protected from pressure it would maintain its
vitality and perform its proper function for an indefinite period. This
was based on erroneous conceptions of the character of the central
organ, and also on defective knowledge of the powerful influence of
other sources of irritation. It was not then clearly understood that
the surface of the pulp from the period of first exposure is in a patho-
logical condition, and that this must progress unless measures be taken to
abort it, and that the mere interposing of some media, though nearly
allied to dentine in character, would not avail to prevent this gangrenous
destruction. The germ theory of disease was then unknown, and it is
not, therefore, remarkable that the efforts at pulp-preservation usually .
ended in pulp-destruction. The earliest attempts were simply to protect
the pulp from contact with the filling. The first cappings were made
of gold and lead cut in circular form of a size sufficient to rest on the
adjacent solid tissue. These were stamped to form a concave surface
over the pulp. For this purpose gold was generally used, though lead,
owing to its poorer conducting property, was regarded by many as pref-
erable. Harris advocated the forming of the filling by so packing the
gold that the caps would be formed out of the filling a very difficult,
and always an uncertain, operation. The results were not satisfactory.
In subjects of great recuperative power the pulp would be preserved in
spite of the defective process, but the number was so limited and the cases
of failure were so numerous that the process was abandoned by all good
operators. Attempts were made to modify the supposed injurious effect
of the metals by the substitution of a material nearly allied to dentine,
under the supposition that irritation would be thus reduced to a min-
imum; ivory, quill, and gutta-percha were therefore substituted, with
but little better results. These were followed by asbestos, plaster of
Paris, goldbeater's skin, collodion, court-plaster, tissue-paper saturated
CAPPING.
895
with solution of Canada balsam, lactophosphate of lime, and finally
oxychloride of zinc, oxyphosphate of zinc, and oxysulphate of zinc.
While these have been introduced nearly in the order named, there
was an interregnum of years after the use of the metals before much
reliance was placed on any form of capping, and the operation regarded
as most satisfactory was the destruction and removal of the pulp and
the filling of the canals. This, however, involved tedious operations,
with a constant percentage of failures in inaccessible roots. So frequent
were these that the active minds of the profession continued experi-
menting with various agents, but no good results were attained until
the introduction of oxychloride of zinc as a filling material. It is
uncertain who was the first to suggest this as a covering, but its use
developed such surprising results that its almost universal adoption is
one of the remarkable revolutions in the history of dentistry. This
was owing partially to the general desire to make dental operations
shorter if equally good results could be attained, and also to the general
feeling that the destruction of the pulp cut off the principal, if not the
only, source of nutrition to the dentine, practically rendering it a dead
tooth with a partial vitality maintained through the cementum.
The theory of the action of the oxychloride was not well understood
at this period, but the results were manifested in pulps retaining their
full vitality for quite long periods of time and remaining perfectly com-
fortable. The number of years that have elapsed since its introduction
for this purpose have given ample time to arrive at intelligent conclusions
regarding it and other similar materials, and, while the writer does not
propose to dogmatize, it would seem appropriate to the subject to give
his views in connection with a description of the different modes of
capping at present in use and a statement as to the direction in which
failure or success may be looked for.
That capping can be made an invariable success must ever remain an
impossibility. The delicate nature of the organ upon which we are
called to operate-endowed, as it is, with sensory nerves inviting the
inflammatory condition upon the slightest irritation-makes any treat-
ment at once difficult and uncertain. Systemic peculiarities, the anæmic,
the scrofulous, the syphilitic diatheses,-all operate against a satisfactory
prognosis; and so common are these antagonistic forces that it is some-
what remarkable that there has been any degree of success.
The pulp from the moment of exposure being irritated by atmo-
spheric germs, etc., it becomes necessary that the treatment attempted
should first aim to overcome this condition. If the inflammation has
not advanced too far, the action of some sedative combined with an anti-
septic may be all that is requisite as a preliminary treatment. Oil of
cloves, oil of cajeput, iodoform, or a 10-per-cent. solution of carbolic
acid may be used at this period with markedly good results. It must
be remembered, however, that capping over freshly-exposed pulps is
alone under consideration.
The theory of the action of the oxychloride of zinc has been that its
escharotic action is limited—that it preserves not only all the superficial
tissue destroyed, but in case of devitalization of the balance of the pulp
will preserve it also in the before-mentioned dry-gangrenous state; so
896
DISEASES OF THE DENTAL PULP, AND TREATMENT.
that even if death supervenes the disastrous results usually following
the death of the pulp are averted. That this is true experience has
amply demonstrated. Its porous character makes it a good absorbent,
and its poor conducting quality is an additional element in its favor.
In discussing the merits of an agent the requirements to be met
must be taken into consideration; they are-1st. Close contact, to
exclude air; 2d. Porosity; 3d. Non-conduction; 4th. Property of pre-
serving tissue in case of death. With our present knowledge, these seem
to be necessary; and an agent failing to meet all of these requirements
will be a failure except under most favorable conditions-conditions of
extraordinary vitality and resisting power. There is at present but one
agent known that meets all these demands-the oxychloride of zinc.
This is regarded by some as too powerfully escharotic, but this effect
can be modified by an intermediate capping. Gutta-percha has no
superiority over horn, quill, etc.; for, while it may be applied in solution
and be perfectly adapted, it is still a foreign element without any of the
peculiar therapeutic properties of some of the other substances. The same
may be said of collodion, the resins, etc. The deep-penetrating property
of oxychloride of zinc gives it decided therapeutical advantage over
any other agent. This is very marked in the treatment by it of other
pathological states, as in chronic pericementitis, alveolar abscess, etc. It
is this penetrating power which ensures the pulp from decomposition in
case of death, as the effect has been transmitted to the farthest extrem-
ity of the tissue. As oxyphosphate of zinc does not possess this quality,
it is quite valueless in comparison with the first named, and will neces-
sarily fail of good results. Hence, while each of the agents named has
one or more of the required properties, success can be attained in the
largest number of cases only by the use of that material possessing
these in the fullest degree; and in the judgment of the writer, until
some other material can be demonstrated as superior, reliance must still
be placed on oxychloride of zinc. It must be said, however, that this
opinion is widely at variance with some very good authorities.
Coleman' gives the preference to nitric-acid treatment. He says:
"The softened dentine having been cleared away and the cavity other-
wise prepared, the sensitiveness of the exposed pulp is lessened by a free
application of carbolic acid; and then a small disc of card but little
larger than the exposed surface, and well saturated with the strongest
nitric acid, is laid gently upon it, and so retained for about half a min-
ute. At times a sensation like toothache, but never severe, is felt for a
few moments afterward. After removal of the nitric acid a cap of thick
paper moistened with carbolic acid is placed over the pulp, and, if the
tooth is to be filled with foil, over the paper cap one of metal, concave
on the pulp-surface, to guard the pulp from all pressure. The filling
is then completed." In amalgam fillings he recommends "to give a
coating of oxychloride over the first paper cap, in place of the metal
This is done to prevent change of temperature.
one."
In considering the action of any agent in its effect on the pulp the
possibility of the development of osteo-dentine must enter as a factor.
If this were possible under all conditions, nothing more could be hoped
¹ Dental Surgery and Pathology.
CAPPING.
897
for or desired; but that such is not the result, except in the fewest num-
ber of cases, must be clear to every observer, and the reasons for this
must be apparent. If it occurs at all, it must be where the pulp is the
nearest possible to a normal condition, the full normal state being very
seldom met with. The vitality of the subject must be above the aver-
age, and-of equal importance-the agent used must have a limited
power of stimulation. It is, therefore, if this position be correct, use-
less to expect new formations, except in limited degree, from the direct
action of any of the usual agents. Oxychloride is too powerful an
escharotic; oxyphosphate is preferable; and so on through the list.
But little dependence can be placed upon this result, and until we have
some gauge to determine the actual amount of excitation necessary to
produce new tissue a favorable result may be regarded only in the light
of an accident.
The introduction of oxychloride of zinc as a filling and capping mate-
rial was naturally followed by investigation in other directions; efforts
were made to avoid the direct injurious escharotic effect of this and
other valuable agents. Dr. J. S. King in 1871 suggested covering the
pulp, prior to the insertion of the oxychloride, with a paste made of
carbolic acid and oxide of zinc. The anaesthetic and antiseptic proper-
ties of the former were supposed to meet the necessary requirements,
while the latter furnished a convenient means of retaining it in a soft
magma, and effectually excluding the air and giving a cushion on which
to rest the denser filling, and thus avoid the effect of pressure. This
theoretical view was sustained in practice. It was found that by pla-
cing a very small quantity directly over the pulp no pain followed the
introduction of the oxychloride, and the results were apparently more
satisfactory. Carbolic acid of full strength should not be used, a 20-
per-cent. solution being quite strong enough. This mixture can be
prepared at the time needed and gently pressed in position by a piece
of spunk or bibulous paper, which at the same time absorbs any excess
of fluid. Then cover this with the oxychloride, either as a cap or as a
filling of the entire cavity.
Dr. J. E. Cravens in 1873 suggested the following practice as hasten-
ing the formation of secondary dentine. After careful drying of the
cavity the pulp is covered with a paste prepared as follows: "Upon a
warm slab of ground glass put a drop of Merck's lactic acid and twice
that volume of magma or freshly-precipitated phosphate of lime; then
rub until a complete solution is effected. This is lactophosphate of lime.
To this solution add dry phosphate of lime until the paste is of proper
consistence for application. Place the paste directly on the exposed
pulp so as to occupy all the space and yet make no pressure upon it;
then remove the moisture from the surface of the paste with spunk or
some absorbent; then cover it with two or three pieces of bibulous
paper cut to fit the cavity and moistened with sweet oil. Press this
carefully upon the paste, especially upon the border; then cover this,
and fill with oxychloride. No preparative treatment is required."
This dressing should remain for from two to six weeks, and must not be
disturbed during that time.
For the purpose of protecting the pulp a film of collodion has been
VOL. I.-57
898
DISEASES OF THE DENTAL PULP, AND TREATMENT.
used, a drop being placed over the exposed portion and the ether allowed
to evaporate before covering it with the capping. Dr. Francis of New
York suggested the saturation of tissue or Japanese paper with Canada
balsam and laying this gently over the pulp. This plan has been quite
extensively adopted by some prominent operators, who regard it as
superior to other modes. Various other processes have been suggested,
all looking to the same end, each and all having the same percentage
of success and failure. One of the most satisfactory in the writer's
hands has been a modification of Dr. King's method, which he has
used almost exclusively since it was first mentioned; and that is the
addition of a small amount of iodoform to the paste of carbolic acid
and oxide of zinc. The value of this agent as an antiseptic can hardly
be overestimated, and as an obtunder of pain it is second only to chlo-
roform. Its non-irritant quality renders it peculiarly adapted for this
purpose. The two objectionable features are the odor and the tendency
to nauseate; hence it must be used only in minute quantities for this
purpose, as it is presumed that this will remain on the pulp for an
indefinite period.
The practice in regard to subsequent treatment varies, and its discus-
sion does not fall to the province of the writer. Suffice it to say that
some make use of the material adopted—whether it be gutta-percha,
oxychloride, oxyphosphate, or oxysulphate-simply as a cap, filling the
balance of the cavity with the permanent material. The safest plan,
however, is to prepare the capping of sufficient thickness to support a
metal filling, if that is decided upon, doing this while the capping
material is in a semiplastic condition; then fill temporarily with gutta-
percha, to test results. At a future sitting the filling can be finished
without risk of disturbing the capping first placed-a consideration of
very great importance.
In closing this portion of the subject it may be said that no plan has
as yet been proposed that gives a satisfactory solution of the problem
under discussion; and, while it remains true that the pulp ought to be
saved, no treatment has as yet been devised and no specific been intro-
duced to accomplish this in all cases, and, as before stated, it would
seem impossible that this can ever be done while conditions are as we
find them. From the great discrepancy in reports from different sec-
tions, it is very evident that localities have much to do with success.
This ought to be expected. Healthy locations, giving vigorous organi-
zations, would result more favorably than the opposite, and the treat-
ment that would give a large percentage of success in the one would
result in almost total failure in the other.
The discussion of treatment has been wholly confined to freshly-
exposed pulps or those but slightly affected by long exposure. Those
in the first or secondary stages of pulpitis have not been mentioned, but
will be more fully considered in the proper place. It may be stated as
a rule that in proportion to the extent of the inflammation in the pulp
will be the probability of failure.
Before entering into the treatment of inflamed pulps it will be con-
sistent with the plan marked out to consider the subject of entire devital-
ization and removal. This mode of procedure antedated that of capping,
}
DEVITALIZATION.
899
and was for many years the only mode of overcoming the difficulties
arising from exposures; but the treatment-if it may be dignified by
this title was confined to the anterior teeth. This was necessarily so,
as no appliances were then in use adapted to the posterior teeth. The
plan then adopted was that before described-destroying the pulp by
the actual cautery, or, by what was in more general use, hooked or barbed
instruments, to tear it out by force. It is needless to say that either of
these operations was so barbarous in its infliction of pain that it is
scarcely presumable that many submitted to it. The removal at the
present time may be performed with a minimum amount of pain by
the use of local anaesthetics and the galvano-cautery, but at the period
referred to neither of these agents was known. Up to the time when
Spooner introduced arsenic as a means of devitalization the canals from
which pulps had been removed were allowed to remain unfilled; the
result was decomposition of the remaining organic matter, followed
by pericementitis, alveolar abscess, etc. The reasons for this were not
then understood, and the untoward results were ascribed to the operation,
and not to the true cause--the leaving unclosed canals to become recep-
tacles for effete matter with its train of evils. It was not until long
after the introduction of arsenic that this imperfect mode of operating
was in part remedied. The credit of this is due to Dr. Maynard of
Washington, D. C., who perfected the process now known as filling the
canals. Until this was demonstrated as an effectual remedy when per-
fectly performed, the filling of teeth was of very little service. Atten-
tion was immediately turned to improving the mode of introducing
arsenic and of limiting its action. Since that period the experience
derived has more clearly demonstrated its value, and it remains the only
agent that will effect the destruction of the pulp with certainty and with
comparatively little pain to the individual. To accomplish this, how-
ever, certain things are to be considered.
J
T
Arsenic acts by first exciting the sensory nerves and then paralyzing
them, arousing inflammation violent in proportion to the amount used.
This first stage of excitement passes off, and the arsenic is gradually
absorbed. Death of the organ does not immediately follow; indeed,
cases have been noticed where sensation returned after apparent death.
As the irritation is violent at the earlier stages, and is, as before stated,
in proportion to the quantity used, it follows that an overdose will pro-
duce an amount of excitation that will defeat the object of its use; or,
in other words, the inflammation suddenly aroused will resist the ab-
sorption, probably through the action of the well-known law that pres-
sure of fluids on one side of a membrane tends to prevent the passage
of fluids or substances in solution upon the other side, and thus arsenic
will fail to do more than increase the congestion. The same result is
manifest in the use of large quantities in the stomach, the sudden
inflammation frequently producing a similar effect on a larger scale.
The recognition of this well-known fact renders the application of
arsenic to inflamed pulps of doubtful value; indeed, it is very well
understood that the irritated tissue will resist its action, and the
application must be delayed until the inflammation has been reduced
by treatment. It therefore follows that the destruction by arsenic will
A
رد.
900
DISEASES OF THE DENTAL PULP, AND TREATMENT.
*
1
be more satisfactorily performed, as in the case of capping, upon pulps
the least irritated or nearly freshly exposed. The fact also having been
demonstrated that quantity increases inflammation, and proportionately
so to the amount used, it follows as a necessary sequence that it is better
and safer to use minute quantities; and it has been further found by
experience that this amount, when properly applied, may be reduced to
ther of a grain and be effectual to the extent of destruction desired.
It has been further demonstrated that an amount sufficient to devitalize
the entire pulp at one application is too large, as the destructive effect
may be continued through the tissue in the apical foramen to the
periosteum, and that the limitations of amount should be confined
to the quantity that will carry destruction to the upper third of the
tissue in the canal without comprising all of it. Keeping, then,
this general statement in mind, its preparation and use may be
described.
The preparation of arsenious acid for use in devitalizing the pulp was
in the earlier days of its introduction regarded as of more importance
than at present. Various agents were from time to time suggested
either to reduce the pain or to limit the action of the arsenic to the part
For the
for which it was intended, or else to give bulk to the mass.
first purpose morphia was recommended, and for the second charcoal
and other materials. Why charcoal should have been used is not very
clear, nor did it come into general use. Morphia, however, still retains
its place with many, but the majority, probably, of operators use at
present arsenic without any other combination than creasote or carbolic
acid. One of the first to recommend morphia in connection with arse-
nious acid and creasote was Dr. J. D. White of Philadelphia. His for-
mula was:
R. Acidi arseniosi, gr. j;
Morphine sulphatis, gr. ij;
Creasoti,
q. s.
S. To be made into a thick paste by several hours' trituration.
M.
The proportional amounts of arsenic and morphia varied with differ-
ent operators, and Dr. Foster Flagg suggested the use of acetate of
morphia in place of the sulphate. His formula was:
R.
Acidi arseniosi, gr. J;
j
Morphine acetatis, gr. ij
Acidi carbolici, gtt. iij.
Capta
M.
Garretson makes it equal quantities of arsenious acid and acetate of
morphia. Dr. J. D. White regarded thorough trituration as of great
importance, to the end that the arsenic and morphia might be com-
pletely combined, but, the specific gravity of the former being greater
than that of the latter, the arsenic would mainly sink to the bottom of
the receptacle, thus introducing an element of uncertainty in its applica-
tion; so that the preparation of small amounts and the spreading the
mass over a considerable surface became a necessity if the operator would
make the application with a reasonable degree of certainty of having
received sufficient arsenic to accomplish the end desired. Owing to the
DEVITALIZATION.
901
separation produced by the greater specific gravity of the arsenic even
after the long trituration, the simple mixing of these ingredients in the
glass or porcelain vessel in which it was to remain came to be the usual
mode adopted; for this purpose the ordinary glass or porcelain tooth-
powder boxes are all that is required. Very little creasote or carbolic
acid should be used; for the thicker the paste is, the more convenient
will be its application.
It is very questionable whether the addition of morphia is any im-
provement, as it has never been satisfactorily demonstrated that it
diminishes the pain of the process. Adding bulky foreign substances
is a decided detriment, as this prevents any approach to exactness of
measurement—a matter which is of great importance.
The amount of pain following the application of arsenic is dependent
on two conditions: first, the state of the pulp at the time; and sec-
ondly, the amount of pressure given to it by the covering used. Pulps
will always give a painful response to pressure, but this will be aggra-
vated in proportion to the inflammation already present in the tissue.
In a highly-inflamed pulp the pain will be severe and continuous, and
the arsenic, as already stated, will fail to act upon it. The patient will
have hours of suffering with negative results. On the other hand, if
there has been little or no irritation of this organ, the application causes
pain which lasts for an hour and then ceases. The remarkable uni-
formity of this period leads to the conclusion that direct pressure must
have something to do with the pain, but this does not entirely explain
it. It would seem as though this amount of time was required to par-
alyze the nerves of sensation, while a longer period is necessary for the
entire devitalizing process. This would appear to be the only reason-
able explanation, as the pain is present when the utmost care has been
taken to avoid pressure, and this will continue to the time specified. So
certain is this that in non-irritated pulps the operator can safely prom-
ise his patient relief at the expiration of the hour. Continuation of
pain over this period is a certain indication that the pulp was in an
inflamed condition prior to the application. The patient should in
all cases be instructed to return if the pain continues after the period
named.
K
T
Exactness in administration is of great importance, for the rapidity
of absorption of arsenic in non-inflamed tissue renders any excess of the
agent a possible danger-a danger proportionate to the density of the
tooth and the age of the patient. The destruction of the life of the
entire pulp is not required, nor is it desirable. The upper third should,
if possible, be kept in a nearly normal condition; its removal does not
produce much pain and the parts in and around the foramen are left in
a much better state. The danger of an excess of arsenic passing through
to the pericementum is always imminent and should be carefully guarded
against; the smallest quantity, therefore, of the paste should be taken :
if applied directly to the pulp, a very minute amount will answer.
is difficult to give any clear idea of this in fractions of a grain, espe-
cially when paste is used, but an approximation may be arrived at by
stating that an amount sufficient to lie on the point of a small hatchet-
shaped excavator will be sufficient. From the to, or even 10,
It
25
902
DISEASES OF THE DENTAL PULP, AND TREATMENT.
of a grain of the powder may be used, depending on the position and
character of the exposure. The most feasible mode of arriving at this
is to divide a grain on a slab into the number of parts desired; this
will familiarize the mind with the required amount.
It must be remembered that arsenic is rapidly absorbed by any
organic matter with which it is brought in contact, so that foreign
matter will prevent its action on the pulp-tissue just in proportion to
the amount present; hence, the débris from decay should all be removed
before making the arsenical application, and in the use of covering mate-
rials those of a nature to absorb should be discarded or their contact
with the arsenic be prevented by an intermediate layer of metal.
The preparation of the cavity having been completed, the tooth should
be carefully invested with the rubber dam, especial care being taken to
have it bind closely at the gum-margin. Dry out the cavity, and then
make the application direct to the pulp. Cover this with a lead cap,
and then fill the balance of the cavity with gutta-percha. This part
of the operation should be carefully performed, to avoid the possibility
of the arsenic reaching the gum-tissue. Care must also be exercised
that no arsenic adheres to the shank of the instrument, as this may
accidentally lodge where it is not desirable to have it. For this reason
wide-mouthed vessels as receptacles are the only ones fit to use, and the
narrow-necked bottles so universally sold, containing arsenic and car-
bolic acid, should be condemned for this purpose.
Jo
Where the tooth is so badly broken that it is difficult to secure proper
support for the retaining filling, recourse may be had, on proximal
surfaces, to the adjoining tooth; where this fails, the filling should be
ligatured in place. The difficulty of treating fractured teeth with
arsenic has been very great, as these, in the case of anterior teeth, are
frequently broken in such a manner that no supporting walls are left.
An application of very minute amount should be made; cover this with
a thin layer of gutta-percha and ligature it in position. This may
destroy only a portion of the pulp, but still sufficient to enable the
operator to secure a place for a second application, which generally is
required. A very neat mode of accomplishing this is suggested by Dr.
Kirk of Philadelphia: he uses the surgeon's rubber plaster where but
a portion of the tooth is left, carrying it round the tooth. It will adhere
satisfactorily for several days, or long enough to accomplish the object.
The destructive character of arsenic is so well understood that any care-
lessness in its use in this operation amounts to malpractice, and should
be condemned as such. When properly applied and carefully guarded,
no agent is more thoroughly under control or more safely used; but in
careless hands nothing can be more dangerous to the life of the tooth
and surrounding tissues. Extensive sloughings have been produced by
a lack of caution. While this is true, the very remarkable stories of
the supposed bad results in its use have, generally, no foundation in
fact.
The application should remain about twenty-four hours before exam-
ination. If the operation has been performed with judgment, the pulp
will be partially destroyed-sufficiently so to be removed.
This operation, though apparently simple, is attended with consider-
DEVITALIZATION.
903
able difficulty if attempted immediately after the devitalization by
arsenic. In the single-rooted tooth the instrument is readily passed to
the farthest extremity of the canal. The canals of the superior bicus-
pids and the molars, superior and inferior, are far more difficult of
access. The extreme minuteness of the canals in the buccal roots of the
superior first and second molars and the anterior root or roots of the
inferior molars increases the difficulty. The operation is also rendered
more uncertain by the bent form of the roots. Enlargement of the
canal by drilling is possible to a portion of its extent, though great
care is required to avoid passing the drill through the root. Cavities on
the distal surfaces of molars require special treatment. Entrance to the
canals through this surface is accomplished only by a sacrifice of a large
portion of the tooth. Entrance to the pulp can be effected more satis-
factorily by drilling through the buccal surface in the direction of the
roots, or, what is preferable, to enter through the masticating surface,
provided a cavity has previously existed on that surface; otherwise, the
amount of labor required hardly justifies the operation.
The instrument generally used to remove the pulp is made from a
watchmaker's broach, temper drawn and the steel barbed. This would
be a very satisfactory instrument had it any lasting property, but the
barbs naturally flatten or the steel breaks after one or two operations.
The best instrument for this purpose is probably one made from steel
wire, filed down to the proper size, then flattened at the extremity, bent
in the form of a delicate hook, and tempered at this portion.
To remove the pulp the instrument must be passed carefully up the
canal as far as possible and then rotated, in order to cut off the pulp-
connections. When the barbed instrument is used, the danger of break-
ing is always present; and when this occurs, the fractured end is removed
with difficulty. It may be accomplished by passing a second instrument,
wrapped with cotton, up by the side of the first. The barbs become
entangled in the cotton, and the broken piece is thus removed. A mag-
netized instrument has been recommended for this purpose, but the
attractive force is, as a rule, insufficient to accomplish the removal.
The operation will be found at all times difficult and tedious, and some-
times impossible. When this proves to be the case, the piece should be
carefully located and the filling material carried directly to the most
constricted portion of the canal and the balance carefully and very
solidly filled. Where this has been well done, the writer has never
known any unpleasant results to follow the leaving of the fragment
of steel in the canal.
The pulp on removal will show the dividing-line between the part
affected by the agent and that still in the normal state, provided
that the amount of arsenic used has been small.
The proper time for filling the roots after the removal of the pulp has
been a subject of much controversy. The safest plan is to place a mild
antiseptic, as eucalyptus oil or oil of cloves or eugenol, in the canal and
let it rest. The objection to immediate filling lies in the fact that there
must be a collection of fluid and lymph in the canal from the apical
foramen, and possibly from the canaliculi of the dentine, inviting putre-
factive processes. It is necessary, therefore, to place the canal or canals
904
DISEASES OF THE DENTAL PULP, AND TREATMENT.
under
proper treatment before inserting the filling. Those who advo-
cate immediate filling contend that delay in closing the canal increases
this collection of fluid, while the filling arrests it. Whatever force there
may be in this reasoning, it is certainly the safest plan to wait for a
restoration to normal conditions. Dr. Litch recommends, before filling,
repeatedly to pass up each canal a probe heated to white heat, thus not
only desiccating, but superficially carbonizing, the walls of the canals.
A second application of arsenic should not be made upon a pulp par-
tially destroyed by this agent. If a portion of the pulp has been devi-
talized, except in the case of fractured teeth, it is better, and altogether
more prudent, to let the pulp rest a day or two before attempting its
removal. Some pulps are affected very slowly and require more than
the usual twenty-four hours. In some cases repeated applications of
arsenic fail to have any immediate effect, and in one case coming under
the observation of the writer this was repeated several times, when, fail-
ing to get any results, the tooth was capped, and at the expiration of
a year was examined, under the supposition that possibly a small
amount of arsenic might have been absorbed and death followed ;
but the pulp still retained its full vitality, and was recapped.
The resisting power of the tissue of the pulp after devitalization by
arsenic is very clearly demonstrated in the tenacity with which the
organ resists the attempt to remove it. Even with the best-arranged
barbed instruments this is by no means an easy matter, and frequently
ends in its coming out in torn portions. This demonstrates—if demon-
stration be needed-that arsenic has no effect upon the tissue itself.
The force of the retention is very easily understood when it is remem-
bered that the pulp, with its microscopic connections, has intimate rela-
tions with almost the entire dentine, exclusive of its attachments
through the foramen.
Arsenic, to a limited extent, is a preserver of tissue, but this does not
prevent ultimate decomposition, which at the expiration of ten days will
have progressed so far as to make the removal of the pulp or pulps a
very easy matter; indeed, they may be drawn out by a pair of small
surgical forceps. A delay, however, in removal to this period of change
is wrong, as any approach to putrescence endangers the success of the
subsequent treatment necessary to restore to healthy conditions.
That the pulp is very easily removed is true, but, from what has been
already said, it will be understood that waiting for putrescence is a very
reprehensible practice. The effect is precisely the same as in other forms
of devitalization; indeed, pericementitis is seemingly more certain to
follow than where death has occurred from causes enumerated. The
best plan is to remove at once.
TREATMENT OF SUPERFICIAL PULPITIS.-Inflammation of the pulp
may, as already stated, be limited in its area of action, not spreading to
any extent beyond the crown portion; this slight irritation may or may
not be accompanied by acute pain. The tooth, however, is never wholly
comfortable. Attempts have constantly been made to save these pulps
by capping, but it must be acknowledged with only a moderate degree
of success. The reasons for this have already been fully stated, and it
therefore only remains to give the general treatment.
TREATMENT OF SUPERFICIAL PULPITIS.
905
If pain is an accompaniment, the inflammation must be reduced by
mechanical and antiphlogistic measures. These consist in the removal
of all decayed matter pressing upon and continuing the irritation of the
pulp; local depletion of the congested vessels by bleeding and then
thoroughly syringing with lukewarm water, to remove all particles
of loose matter. The pulp may be temporarily capped by an agent or
combination of agents. These should, first, destroy all bacterial germs;
second, obtund pain; and, third, destroy septic emanations. To effect the
first result, the agents that may be used are numerous. Of these, car-
bolic acid justly holds a high place; but this, while superior as a germ-
destroyer, is a powerful escharotic, and in practice its use in full strength
has been found not altogether satisfactory. Its valuable properties are,
however, manifested when reduced to about 20-per-cent. solution. Car-
bolic acid is a local anesthetic of considerable importance and can usually
be depended upon to relieve the pain of pulpitis, but is more effective when
combined with iodoform. The fact that this has the dual properties of an
antiseptic and an anesthetic of nearly equal value to chloroform renders
it superior to all other agents for this purpose. As these two agents cover
the three desired qualities, they are recommended as fulfilling the require-
ments of an excellent and very effective application. The medium to
retain these in position may be the oxide of zine; they should be com-
bined at the moment of using and placed gently over the pulp. If it is
found necessary to dismiss the patient for the time, a temporary filling
of gutta-percha should be placed over this, care being taken not to press
upon the temporary covering. To avoid the possible disturbance from
the products of decomposition-always a possible factor of disturbance
in these pathological states-it is safer to leave a passage through the
temporary filling for the escape of an excess of gas. This is readily
made by building the material round a canal-plugger and upon comple-
tion withdrawing it. Treatment of these teeth should never be attempted
without this precautionary measure. Ordinarily, one or two applica-
tions will give satisfactory results; but if systemic conditions are unfa-
vorable, the inflammation will not easily yield to palliative treatment,
and resort must be had to the destruction of the pulp either by the
arsenical application or by the removal of the portion of the pulp most
diseased and the capping of the balance. This latter treatment is pref-
erable in both cases, for, as already stated, arsenic does not act readily
on inflamed surfaces, and a removal of a section before applying it is
a matter of necessity. The plan of cutting out a portion of the pulp
was probably first suggested by Dr. Allport of Chicago. It consists in
the excision of a portion of the pulp at the orifice of exposure, drawing
the edges of the incised part together and inducing their union, and in
this manner closing the wound. From the "extreme delicacy of the
operation," Dr. Allport regards it as "rarely a practical one." Witzel
of Germany suggested in 1879 a modification of this. His plan was to
treat with arsenious acid, and then after a limited time to cut out the
crown portion and preserve the balance, or stump, of the pulp by cap-
ping. As the use of arsenic must necessarily sooner or later destroy the
entire pulp, this mode cannot be recommended. Cases very frequently
occur in chronic pulpitis where this operation of partial extirpation is
godin
p
906 DİSEASES OF THE DENTAL PULP, AND TREATMENT.
necessary; this is readily performed with a minimum amount of pain
by the use of local anaesthetics. The pulp may be placed under the
influence of chloroform, a drop or two being sufficient; or it may be
benumbed by rhigolene, ether-spray, or cocaine; or an application may
be made of iodoform paste-iodoform, carbolic acid, and oxide of zinc.
If either the first or the last be used, time-from five to ten minutes
-must be given for the action of the agents. Then with a sharp burr
revolved rapidly by a dental engine the most highly-inflamed portion
can quickly be removed. This accomplished, the pulp may be placed
under a non-irritant antiseptic dressing, as oil of cajeput, and event-
ually be capped or destroyed by arsenic, as may be desired.
The treatment of deep-seated pulpitis is substantially the same as
for that just described, except that any attempt at amputation must,
from the nature of the case, be futile. The indications here are acute
pain, generally complicated with slight persistent irritation, which will
be manifested by pain upon striking the teeth. The aim must be to
reduce the inflammation as much as possible by the means proposed in
superficial pulpitis. Avoid any attempt at destruction by arsenic, as
the effect of this would simply be to increase the irritation. It is better
and safer to keep the pulp under the dressing until the acute inflamma-
tion destroys the vitality, and then remove before the period of putres-
The point to be enforced is to avoid over-treatment. Removal
of the pulp is the only effectual course to pursue, for anything less than
this is almost sure to end in disappointment.
ence.
The management of gangrenous or putrescent pulps is probably one
of the most difficult and unsatisfactory of any of the operations the
dentist is called upon to perform. These may be classed under two
forms the one where death has occurred from extrinsic, and the other
from intrinsic, influences. The liability of the anterior teeth in early
life to receive blows makes the presentation of teeth having dead pulps,
and yet being at the same time free from decay, not unusual. Again,
regulating teeth frequently produces a similar result. Thermal action
in young teeth too early filled with metal, exposures, etc. may produce
devitalization. Blows or any sudden movement may result in strangu-
lating the sources of nutrition at the apical foramen, or they may cut
off the delicate connections entirely; but in the writer's judgment the
effect is doubtless produced by strangulation. The reason for this con-
clusion is found in the fact that in regulating teeth where the movement
is comparatively regular and without sudden jar the same result is some-
times apparent. The fact that this occurs at all should relegate to the
obscurity of the past the practice of the rapid separation of teeth by the
wedge, mallet, screws, and other barbaric instruments of the earlier
professional life, for they certainly now have no place in the proper
treatment of teeth.
From whatever cause death occurs, the fact must be remembered that
the appearance of quiescence and comfort in the organ is wholly decep-
tive, and that it is ready to arouse to violent inflammation the connect-
ing and surrounding tissues on apparently very slight disturbance. A dead
pulp may remain for years-and, it may be, for life-very quiet if not
exposed by caries, but may in a few hours produce violent pericementitis
TREATMENT OF GANGRENOUS PULPS.
907
•
if exposed to the action of the atmosphere. It is, therefore, oftentimes
a question in the diagnosis of such a tooth whether the great risk war-
rants meddling with it at all. The prognosis must take in the possible
results from systemic conditions. If these are unfavorable, it would be
much better to allow the tooth to remain quiet rather than risk the
more serious evil of acute pericementitis, alveolar abscess, and possibly,
in a depraved habit of body, necrosis. All teeth with dead pulps are
subject to this, but those sealed in a cavity are peculiarly liable to take
on extreme manifestations. The preliminary treatment must first be, if
devitalization has occurred in a tooth without pulp-exposure, to make an
opening through the enamel and dentine into the pulp-chamber. This is
best accomplished in the anterior teeth by the use of the engine, to pene-
trate the enamel at the basilar ridge. Then take up the hand-drill, care
being taken to point the drill in the direction of the long axis of the
root. The entrance of the drill in the pulp-chamber will be manifested
by a sudden dropping into a cavity. This accomplished, drilling should
cease and an application of an antiseptic be made-eucalyptus oil, per-
manganate of potash, or iodoform-and scaled up, care being taken to
leave the before-described vent through the filling; the object of this
care is to avoid any undue irritation and to prevent the development
of germs. On the second visit the devitalized pulp may be removed.
Whether the odor of decomposition be present or not, the treatment
should always be based on the supposition that putrescence has com-
menced. Ordinarily, there is no difficulty in the removal of the
decomposed pulp: a slight twist of the barbed broach will bring away
all that may remain.
pada kada
S
The odor of putrescence is ordinarily present. The product of this
decomposition principally sulphuretted hydrogen-is undoubtedly the
prime factor in pericemental disturbance, and the importance of elim-
inating this cannot be overestimated. The amount of pressure from
this rapidly-developing gas is very great, and until this is overcome
filling of the roots must be regarded as a very dangerous operation.
It is difficult, owing to the contracted space in the canal, to make any
application that will reach all parts of the tooth and chemically change
the gaseous products; hence à vent must be left, as described. The
philosophy of the treatment must be based on the conditions present,
the rapid development of bacteria, the generation of gas, and septic
poison requiring an agent or agents that will meet these distinct
conditions. While it is true that an ordinary antiseptic, such as car-
bolic acid, boracic acid, salicylic acid, etc., may destroy the bacteria
present and prevent further decomposition, it is equally true that the
conditions are not fully met; besides, the former in full strength is
too irritating, and is not very effective in reduced form. It does
not act chemically on the products of decomposition before mentioned,
nor do any of the ordinary antiseptics. The subject was first clearly
stated by Dr. Litch of Philadelphia,' and it is to his work that we
are really indebted for the only intelligent answer to the query,
What shall be done with putrescent pulps? After discussing the
character of antiseptic agents, he says:
¹ Cosmos, February, 1882.
908
DISEASES OF THE DENTAL PULP, AND TREATMENT.
"A careful discrimination must be made between the powers, respect-
ively, of such antiseptics as carbolic acid, creasote, oil of cloves, oil of
thyme, oil of cajeput, etc., and such other antiseptics as chlorine, bro-
mine, and iodine, which, in addition to their antizymotic power, are
true chemical antagonists of those sulphuretted-hydrogen compounds
of which putrefactive gases are constituted, such gases being immedi-
ately decomposed by them, their hydrogen element going either to the
chlorine, bromine, or iodine, to form, respectively, hydrochloric, hydro-
bromic, or hydriodic acids, the sulphur being in each case precipitated.
"This can readily be demonstrated by acting upon a small portion
of ferrous sulphide with dilute sulphuric acid and passing the sulphur-
etted-hydrogen gas which will result from the reaction through tincture
of iodine. A milky precipitate of sulphur will at once appear, and at
the same time the characteristic color of the iodine will disappear in
consequence of the conversion of the iodine into hydriodic acid, a
heavy, colorless gas which remains in solution in the water present in
the alcohol of which the tincture is made.
"If the sulphuretted hydrogen is passed through the strongest possi-
ble solution of carbolic acid, no such precipitation of sulphur occurs;
no change either in the appearance or chemical constitution of the car-
bolic acid is manifest.
No matter how thoroughly the odor of
putrefaction in a room or in a tooth may be masked or disguised by the
characteristic odor of carbolic acid, creasote, oil of cloves, or, indeed,
any antiseptic oil, the gases are none the less present, although their
odor is neutralized; the disinfection is only apparent, not real. The
further formation of putrefactive gases may be prevented, but the
decomposition of those already formed must be accomplished by those
chemical agents bromine, chlorine, or iodine."
It is questionable whether the position of Prof. Litch can be sucess-
fully refuted. Practice demonstrates fully the correctness of the theory,
and since the adoption of this mode of treatment the writer has had
more satisfaction and far less anxiety in the management of these cases
than at any former period. The mode he adopts is to syringe out the
canal thoroughly with warm water to which a small amount of listerine
has been added. Then take about the twentieth part of a grain of iodo-
form¹ and moisten it with a 20-per-cent. solution of carbolic acid; carry
this on a few fibres of cotton to the extremity of the canal and then seal
up the crown with gutta-percha, leaving the vent through the filling.
It may require repeated applications to remove the odor of putrefaction.
The same effect has been said to be produced rapidly by the perman-
ganate of potash, but it is questionable whether its low germ-destroying
power makes it as valuable as some other agents. Dr. Miller2 has very
satisfactorily demonstrated the comparative value of various antiseptics,
the bichloride of mercury standing at the head of the list as a germ-
destroyer. While this is true of a very minute quantity of this agent,
But in-
it
may be equally true of a larger quantity of a weaker one.
1 The writer does not wish to be understood as asserting that iodoform stands in the
same chemical relation to H2S as iodine, but that in its clinical presentations it seems
to be equally as effectual.
2 Dental Practitioner, June, 1884.
TREATMENT OF GANGRENOUS PULPS.
909
crease in quantity is not always possible, as a very strong solution of
permanganate of potash would probably result in discoloration of the
tooth. Other antiseptics can, however, be used in large quantities with-
out risk, and with results equally good as with the bichloride of mer-
cury. In illustration of this, sulphate of quinia is one of the very best
germicides in and around inflamed gums. The writer has had better
results from this than from any other remedy. The theory of its action
is that, in addition to its germ-destroying power, it inhibits the migra-
tory movements of the white blood-corpuscle, and thus retards inflam-
matory processes.
The removal of all odor from the pulp-canals is supposed to be the
guide to determine the time for filling them. It must be borne in mind
that the pulp practically extends throughout the dentine, and that there
must be a vast amount of microscopic tissue necessarily left in the
canaliculi for future decomposition or discoloration; this is undoubt-
edly the cause of the change of color, more or less pronounced, in all
these teeth. Care should be taken to have the antiseptic fluids pass
well into the tubes, and to accomplish this by imbibition time must be
given. A tooth should, therefore, be kept under an antiseptic for sev-
eral weeks before filling.'
cla
The next consideration is as to the filling material to use for this pur-
pose. This is of far more importance than is generally conceded. The old
plan was to fill always with metal, gold, or tin, and the results, while
excellent, were not equal to those effected by other modes, for reasons
now well understood. Wood, and even cotton saturated with carbolic
acid, have been used. Gutta-percha, the oxyphosphates, and the oxy-
chlorides have each found earnest advocates.
The necessity of having a thoroughly compact and solid filling would
seem to require no argument, yet there are many who appear to think
facility of removal a prime requisite. The writer's judgment, based on
a long experience in filling canals, is that no canal can with safety be
left loosely filled even with the best germicide present. That a gold
filling will give better results, provided it is packed solidly, than a
cotton, felt, or any other loose substance, has been demonstrated too
often to be now successfully controverted. It is certainly settled that
a canal must be impervious to fluids and the entrance of atmospheric
air made impossible. If a material that combines solidity with anti-
septic properties can be used, that should take precedence. Of the plas-
tics, the oxychlorides alone meet this requirement; the peculiar property
of these and their deep-penetrating power should bring them into more
general use. The writer's attention was early called to this by the
remarkable results attained by the use of oxychloride in the treatment
of alveolar abscess, in which teeth have repeatedly been rendered com-
fortable, loose teeth tightened, the production of pus stopped, and the
fistula closed by simply filling the canal with oxychloride of zinc. The
constant repetition of these results led to the abandonment of gold or
tin and the substitution of this material, and years of practice have
¹ Dr. Kirk (Cosmos) suggests the use of sodium carbonate in pulps of this character.
He dries out the cavity and introduces a small particle of this agent, leaving it there a
short time. It can be used in crystals or in solution.
910
DISEASES OF THE DENTAL PULP, AND TREATMENT.
served only to confirm this judgment. Chronic pericementitis, or even
chronic alveolar abscess, is oftentimes best treated by simply filling the
canals.
The mode of insertion is quite a simple one. A few fibres of cotton
dipped in a thin batter of the oxychloride are passed into and packed
solidly in the canal or canals. This becomes a solid mass in a short
time, and if properly placed will be impenetrable to any of the fluids
permeating the tooth. A method proposed by Dr. Hullihen of Wheel-
ing, Va., in these cases was to leave the canal unfilled and make a vent
at the free margin of the gum by drilling a hole through the root to the
canal. This makes it a drainage-conduit, and, while the tooth may be
comparatively comfortable, it is always malodorous and liable at any
time to take on more complicated pathological conditions. This opera-
tion should be used only as a means of temporary relief. A mode of
filling roots adopted by many good operators is to pass cedar saturated
with carbolic acid into the canal; the swelling of the wood is supposed
to perfectly fill the canal. Theoretically, this seems a very faulty ope-
ration. There is no certainty as to the length of time carbolic acid will
retain its power, and wood is always a good absorbent. Reference need
only be made to the condition of old wooden pivots and the adjacent
tissue to furnish argument against the practice.
The dry gangrene so called in contradistinction to the previously-
described moist gangrene-is not of much pathological significance.
The pulp is shrivelled and the canal is entirely free from the results of
decomposition. The tooth retains its color. The reason for this state
of the pulp is not very clear. It, however, according to the observation
of the writer, occurs principally in very dense teeth, especially in the
teeth of old age. This leads directly to the supposition that there has
been a gradual filling up of the tubuli with secondary dentine, preventing
the free circulation of fluids, if not stopping them entirely; this is evi-
dently the case in senile dentine. While the possibility of this process
is doubted by Wedl, who regards the translucency described by Tomes
as dependent on the continuation of the "process of the dentine cells
existing in the translucent portions of senile dentine, and that, as they
still retain the property of imbibition, it may be assumed-with a certain
degree of plausibility, at least that these processes as well as other tis-
sues in the decay of advanced age have lost more or less their distensi-
bility, that their central vitreous substance has disappeared, and that,
together with the investing walls of the dentinal tubules, they have
become closed in such a manner that the entrance of atmospheric air
is no longer possible." The writer's observations on senile teeth, and
also on teeth lost at an early period of life through extreme density,
are fully in accord with the conclusion of the elder Tomes. If these
conclusions be accepted, the dryness observable in senile dentine, result-
ing in dry gangrene of the pulp, can be readily understood and the
latter condition accounted for.
karlandı
Teeth with mummified pulps (dry gangrene) require no attention on
the part of the operator further than to remove the remains and fill.
They never, so far as observed, are a source of irritation, and it is rare
that they come into the hands of the dentist for treatment.
NODULAR DENTINE.
911
NODULAR DENTINE.
Under this name are classified the secondary deposits found in pulps.
They may be purely physiological in character, and are not necessarily
pathological. Indeed, it is difficult to draw the dividing-line between
these two conditions, for the one may run into the other through the
ordinary processes of development.
The formation of secondary tissue is dependent on so many and such
diverse conditions that it is impossible to class it as belonging to any
particular period or state. It may be found at all ages, in all teeth,
and it has been observed even in deciduous teeth. There is one law,
however, that seems universal in its application, and that is that the
structure must average a superior grade. In other words, teeth of
strong, dense character, yellowish color, are peculiarly liable not only
to new formations, but to have this extra development assume the nod-
ular or granulated form.
The relations sustained by the pulp to dentine and the part the
former takes in the development of the latter are better understood
to-day than at any former period, but no satisfactory explanation has been
attempted throwing light on the peculiar form dentine assumes or show-
ing why at a certain period in development it changes its character. It
is, however, well known that the new formation differs from the normal,
or regular dentine, in the irregularity of the tubuli, there being a dis-
tinctive line of demarcation between the new and the old. All that is
really understood in regard to it is that up to an uncertain period nor-
mal tissue is developed, and after that the formation assumes the cha-
racter of secondary, or osteo, dentine.
Before considering the character of these formations it may be well to
examine into the probable causes that lead to their origin. They may
be classified under two heads:
1st. Increase of density.
2d. Irritation.
The increase of density may occur at any age, and the familiar exam-
ple of senile dentine, with its superabundance of secondary tissue, is a
common presentation. Between these two extremes may be found all
degrees of formation, ending frequently in loss of the teeth, they being
thrown out as foreign bodies. Increase of density necessarily means an
increased deposition of the inorganic material in the organized body.
If it be accepted that the pulp is capable of forming dentine, either nor-
mal or abnormal in character, at all periods-and this is not disputed—
it follows as a natural sequence that the cellular formative elements
must possess unlimited power of development which is not confined to
the peripheral cell-layer, but is equally distributed throughout the pulp;
that every portion must be so endowed and be equally amenable to the
universal law of formation. Secondary dentine is, therefore, not con-
fined to the pulp proper in the form of minute grains or larger nodular
calcifications, but is manifested in the translucent dentine of Tomes,
which is but another state of the same development. Wedl does not
regard this as proved, as by the use of "heated dilute hydrochloric
acid" he was able to demonstrate that the "processes of the dentinal
912
DISEASES OF THE DENTAL PULP, AND TREATMENT.
cells" were brought into view. "In these experiments no essential
differences could be discovered between the translucent and less diapha-
nous portions of the dentine." These experiments would seem con-
clusive, especially those subsequently made to demonstrate the power of
imbibition remaining in the fibrils or odontoblastic prolongations; but
the means resorted to seem fatal to the conclusions. Secondary dentine
is "not as dense as normal dentine and has less carbonate and more
phosphate of lime" (Schlenker), and consequently would be less able to
resist the action of powerful reagents. The result would necessarily be
a reopening of the canals in the dried specimens, and because coloring-
matter could be injected into the tubuli it does not necessarily follow
that the fibrilla, while retaining the form, also retained normal vital
powers. The inference drawn by Wedl does not seem justified by
the results. The importance of determining this must be apparent
when it is considered that if the transparent zone is not recognized as
a consolidation into secondary dentine it will be difficult to understand
the law of its formation anywhere, and the nodular deposits must
remain an enigma. Experiments with reagents are not always satis-
factory, for the reasons stated, and the matter must be determined prin-
cipally by inference, by analogy, and by results. The secondary forma-
tions in the tubuli occur in exceptionally dense teeth; the color simulates
that of normal tissue, and its power to resist the encroachment of caries
proves its comparative density. The well-known fact is that so-called
eburnated dentine is but a form of arrested decay, and that in all very
dense teeth caries progresses with extreme slowness-and in these the
transparent zone is marked-indeed, is never seen in soft-structured
teeth. In exceptional cases of extreme density there appears to be a
total cessation of nutrition; the power of imbibition by natural pro-
cesses is in a great measure lost and the connection with the perice-
mentum broken up. This is remarkably illustrated in the loss of single
and entire sets of otherwise perfectly-formed teeth, and that through no
pathological changes, as in pyrorrhoea alveolaris. A patient of the
writer, aged thirty-five, with a remarkably beautiful and dense set of
teeth, gradually lost them all, until, edentulous, he was forced to resort
to artificial substitutes. Microscopic examination of thin sections by
high powers failed to show the slightest trace of tubular formation ex-
cept in the inner third nearest the original pulp-canal. The whole tissue
was diaphanous and apparently homogeneous. It was clearly a case of non-
nutrition. Dr. Kirk² in a paper on the care of the children of the Insti-
tution of the Deaf and Dumb of Philadelphia illustrates the possibility
of increasing the density as well as producing nodular deposits at a very
early age. He says: "The majority of pupils are admitted between the
ages of ten and twelve years. After a year's residence in the institution
-during which time they are given excellent care in all that relates to
their physical welfare-a marked improvement will be observed in the
character of their teeth: they will be found exceedingly hard and dense,
making the wear and tear on cutting instruments very great.
... But
the most conclusive evidence which I have met with of the value of the
¹ Wedl, Pathology of the Teeth.
2 "Relation of Food to Teeth," Dental Office and Laboratory.
·
G
NODULAR DENTINE.
913
J
diet-table, so far as the nutrition of their teeth is concerned, is the un-
usual number of cases of arrested caries and the formation of so-called
secondary dentine. . . As showing still further the abundance of
bone-forming material with which the blood is supplied, I have re-
moved in two cases large pulp-nodules from the sixth-year molars of
children not over eleven years of age."
Without extending the argument farther, it may be assumed that the
facts warrant the opinion that the new formation in the tubuli is in
direct ratio to the density.
The effect of irritation is well known to be a cause of new formations.
The increased development of the cementum at the apex of roots—
familiarly known as exostosis-is produced by a slight irritation, as the
wearing of a plate over a root, the jar of clasps attached to a plate, the
malocclusion of teeth, etc., etc. On the other hand, an excessive irrita-
tion produces absorption or destructive pathological conditions. Rea-
soning from this well-understood fact, it would be expected that the law
of hypertrophy, as applied to bone, would give equal results with den-
tine, so nearly allied to it in character. The very familiar example of
the wearing away of the anterior teeth furnishes us with an answer to
this proposition. New formations proceed equally in proportion to
wear, provided that wear is not too rapid. If the process is very slow,
secondary dentine will develop gradually until the entire coronal pulp
is obliterated and the tooth worn down to the gum-border. On the
other hand, if too rapid, the pulp is quickly exposed. This is exactly
a repetition of the before-mentioned result in slow caries. The progress
of the disease produces an amount of irritation to develop new forma-
tion. In medium- or soft-structured teeth this is not possible; hence
rapid destruction.
P
When we extend this familiar process of formation and destruction to
the growth of new formations of the pulp, we are led at once to the
conclusion that irritation is the principal-though possibly not the only
-cause of secondary deposits. It is very probable that the process of
mastication has very much to do with nutrition and increased inorganic
deposits. It has long been observed that those teeth in constant use are
more perfectly formed and resist caries better than those rarely brought
under the forces of mastication. This can be accounted for only by the
constant jar and slight irritation producing the before-mentioned result.
It has yet to be demonstrated by actual observation whether these teeth
are more liable to nodular calcifications than others, but theoretically this
should be the case.
The effect of caries in producing new formations in direct line with
the disease is beautifully shown in an illustration from Schlenker. In
this case the new formation is clearly the result of irritation carried
through the tissue and proceeding in proportion to the caries. The
same result is seen in Fig. 482, from the same author, in which the new
formation extends over a still greater surface. By the wear from a
clasp, a metal filling, especially gold, may produce a similar result by
the constant, though slight, irritation through changes of temperature.
A similar effect is usually expected from capping pulps; but this expec-
1 Untersuchungen über die Verknöcherung der Zahnnerven. Vierteljahrsschrift. f. Z.
VOL. I.-58
914
DISEASES OF THE DENTAL PULP, AND TREATMENT.
:
tation is rarely realized, as here the irritation is excessive and becomes
a destructive force. In absolute inflammation of the pulp new forma-
FIG. 482.

WATTS
FIG. 481.

b
a.
a, caries; b, adhering dentine forma-
tion; e, a free nodule with the con-
nection dissolved.
·7
Longitudinal Section through Ca-
nine. Secondary dentine the
result of a clasp (Schlenker).
tion is impossible. Schlenker says of inflammation of the periosteum
followed by abscess that "if in such teeth secondary dentine is found it
must not be accepted as positive that this is the result of inflammation
of the pulp. If the pulp is inflamed, all new for-
mations cease in hard tooth-structures."
FIG. 483.

The same author divides the new formations into
six distinctive sections: 1. Enameloid; 2. Enamel-
dentoid; 3. Dentoid; 4. Dentine-osteoid; 5. Oste-
oid; 6. Calcoid. In regard to the former, the
enamel nodule, he says: "At the yearly meeting
of the Central Society of German Dentists held at
Freiburg, 1875, I exhibited two free enamel nod-
ules found in the pulp-tissue, since which time I
have added three others free and two specimens
of adhering enamel formations."
From the enamel-dentoid, or combination of
enamel and dentine, he has two examples. In the
dentine-osteoid the combination of cement and den-
tine takes place. The osteoid, as its name implies,
consists wholly of cement, and the calcoid the cal-
cification, in the connective tissue of the pulp, and
felt as grains of sand.
Section through Canine,
with the Pulp: a, entire
pulp; b, partial calcifica-
tion; c, part of the pulp
ker).
The calcification of the tissue of the pulp into
without nodules (Schlen- nodules is finely represented by an illustration from
the same author. The symptoms of calcification
are not sufficiently marked to render the diagnosis an easy one; indeed,
the decision must rest largely on the character of the teeth and the
exclusion of other sources for the neuralgic pains present. The usual
G
POLYPUS OF THE PULP.
915
mode of diagnosing pericementitis fails here, for, as before stated, vio-
lent inflammation renders new formations an impossibility. The pain
is in paroxysms, worse during the night and accompanied with a boring
sensation.
Ordinarily, the new development is not a cause of neuralgia; indeed,
it may be considered quite exceptional that this occurs, for in some one
of its forms secondary tissue may be said to exist in every mature tooth.
When, however, it assumes the granulated form, producing unequal pres-
sure on the sensory nerves of the pulp, the result is pain-oftentimes of
the most aggravated character. This may be confined to one tooth, but
frequently will be repeated in one tooth after another until the entire
denture is involved. Dr. Garretson mentions a case of this character
where each tooth in turn was extracted, and all presented nodular calcifi-
cation. Schlenker also gives a large number of cases.
The TREATMENT must be either to destroy the pulp or to extract the
tooth; in most cases the former course will give relief. The suspected
tooth must be carefully drilled through to the pulp and the usual appli-
cation of arsenic made. If devitalization fails, nothing remains but to
extract. Efforts have been made to reimplant these teeth, after remov-
ing all calcific deposits, and with some degree of success.
POLYPUS OF THE PULP.
In teeth much broken down by caries there is necessarily a constant
irritation of the exposed pulp. This does not always result in a slow
destruction of the organ, but eventuates in a hypertrophied condition
that in time fills up the cavity of decay. In the experience of the
writer these polypi are more frequently found in the inferior molar teeth
where the crown has been hollowed out to a thin external wall. The
increased development may be of small size or it may fill the entire
cavity. Its character is readily determined by pressing it to one side,
when it will be found to be a bulbous formation attached by a con-
stricted neck to the coronal pulp. This will distinguish it from an
epulis, which is attached to the alveolar walls. It is not ordinarily
very sensitive.
It has a dark-red color and is of a 66 spongy or
fleshy consistence." "It contains an abundance of roundish and
spindle-shaped cells, the bodies of the cells varying slightly in
extent, which, together with a small amount of fibrous intercellular
substance, comprise the principal portion of the tumor.
The groups
of cells are in long rows and have a radiated arrangement. The cells,
which are provided with processes, unite here and there to form a net-
work; rows of spindle-shaped cells also are met with; the blood-vessels
pursue a tortuous course from the interior toward the periphery, are
numerous, comparatively large, and invested with thick fibrous sheaths.
The type presented by the capillary ramifications is different from that
found in the pulp. Nerves or the remains of the parenchyma of the
pulp are not to be seen. . . The parenchymatous connective tissue
is the seat of the proliferation described as sarcoma of the pulp, in which
the parenchyma gradually is destroyed, as is indicated by the absence of
nerves and the altered character of the blood-vessels. As the sarcoma
916
DISEASES OF THE DENTAL PULP, AND TREATMENT.
is located upon the outside of the remains of the pulp, it serves in a
measure to protect the latter" (Wedl).
The tumor may be purulent in character, though the amount of pus
is limited. A number of such cases in the experience of the writer gave
no evidence of pus-formation.
This proliferation of the pulp is principally confined to comparatively
young teeth and teeth imperfectly calcified. They bleed readily at the
slightest touch, but the ordinary result of inflammation of the pulp is
not present. They do not end in pulp-devitalization, pericementitis, alve-
olar abscess, nor are they usually very uncomfortable. They seem to
be, as Wedl expresses it, secondary formations, and furnish a protection
to the central organ.
In cases of fracture where the pulp has been suddenly and violently
irritated there may be an enlargement of the pulp of a somewhat differ-
ent character. This will be extremely sensitive. In other respects it is
similar to the ordinary polypus. "In microscopic structure this sprout-
ing of the pulp differs little from the insensitive polypus, but its vitality
implies a more abundant nerve-supply" (Salter).
1
TREATMENT. The difficulty of giving any treatment to cases of
fungous growth has long been understood. The polypus can readily
be cut away, but it will return, and for the reason laid down; under
the destruction of the pulp by arsenic it resists that agent, and hence
success has not warranted prolonged effort in this direction. Coleman
gives a mode of treatment that in his hands has been satisfactory. He
says: "We first dose the growth with carbolic acid, to deaden its sensi-
tiveness, and then with a scythe-shaped lancet cut away as much as pos-
sible. After the bleeding has ceased we carry out the nitric-acid process.
This was described at length in considering the subject of capping. It
consists of applying the strongest nitric acid on a disk of cardboard to
the pulp and retaining it there for about thirty seconds. It is then
removed and the pulp capped.
""
PROR
Dr. B. G. Marcklein recommends the continued use of iodine upon
and around the fungous growth. He says: "After removing all for-
eign substances, dry the cavity as carefully and thoroughly as possible,
and then apply the tincture of iodine with a pledget of absorbent cotton
or bibulous paper until the entire growth has been covered with the
iodine; after which, seal the cavity in the usual manner. This should
be repeated every twenty-four hours until it has been entirely destroyed.
If any portion of the pulp in the canals resists this treatment, it should
after the expiration of ten days be devitalized by arsenic and the root or
roots filled in the usual manner. For this purpose I prefer the oxy-
chloride of zinc to any other material. If the fungous growth should
fill the entire cavity, as is sometimes the case, it is necessary to modify
the first part of the treatment. In such cases proceed as follows: Take
small pledgets of bibulous paper or absorbent cotton saturated with tinc-
ture of iodine and place them between the fungoid and the walls of the cav-
ity until as much pressure has been made as is consistent with the comfort
of the patient, but in no case should it be carried to the extent of giving
pain. This dressing is to be repeated daily until sufficient room has
¹ Dental Surgery and Pathology.
Pa
MORE
POLYPUS OF THE PULP.
917
been obtained to proceed as in the first case. Some of the last class
of fungoid growths are very persistent in resisting treatment, but I have
never seen a case that did not yield where treatment was kept up for
any length of time."
The writer's experience in various modes of treatment does not justify
a hopeful prognosis in these cases, and the final result has been a resort
to extraction as the only effectual remedy.
DISEASES OF THE PERIDENTAL MEM-
BRANE.
By G. V. BLACK, M.D., D.D.S.
The peridental membrane covers the root of the tooth and serves to
unite it with its alveolus. In its structure it is very different from a
periosteum, and its functions are different. The connection of the tooth
with the wall of the alveolus is more that of an immovable joint, and
yet a joint that permits a certain passive motion by which the tooth is
cushioned, so to speak, against the hardships of severe blows and con-
cussions that it is liable to receive in the performance of its peculiar
functions of tearing and grinding food. This joint has, however, none
of the elements of the joints that are movable by the muscles. There
is no cartilage and none of the other elements of the movable joints
intervening between the root of the tooth and the bony walls of its
alveolus: the joint is effected by the interposition of fibrous tissue, with
a sparse intermixture of cellular elements. In the formation of this
joint the fibrous tissue is disposed in a definite form relative to the root
of the tooth and the alveolar process. This is found to be, for the
greater part of the root, in the form of a set of fibres running down-
ward (toward the crown of the tooth) and outward (toward the alveolus),
connecting with the alveolus. These fibres serve to swing the tooth in
such a way that, while it is permitted a very slight motion in its socket
in any direction in response to a strain that may be brought against it,
its position is regained at once when the strain is removed. This par-
ticular disposition of the fibres is found all over the body of the root
of the tooth, but on the apex of the root and near the neck of the tooth
the disposition of the fibres is different. At the apex the space between
the end of the root and the alveolar wall is a little greater than else-
where. This I shall call the apical space (Fig. 484). In this space the
fibres radiate from the apex of the root to the alveolar wall in various
directions without much regularity; yet it can generally be seen that
there is a disposition to radiate fanlike from the apex of the root to the
alveolus. Toward the rim of the alveolus the downward trend of the
fibres is rapidly lost, and as the rim of the alveolus is passed this trend
is reversed. In this way the fibres are gathered, as they pass from the
1
+
¹ In the descriptions given throughout this article I shall regard the tooth as a cone,
with the crown as the base and the end of the root as the apex. Therefore, toward the
crown, or base, is downward, and toward the apex of the root is upward, no matter
whether the tooth be in the upper or lower jaw.
918
BLOOD-SUPPLY..
919
tooth, into rather a thick mass just over the rim of the alveolus, where
they are continuous with, or merge into, the periosteum, which covers
the outer surface of the alveolar process. This forms what has been
termed the dental ligament. I will describe the gingivæ in connection
with the diseases which have their beginnings in them.
FIG. 484.
The blood-supply of the pulp of the tooth and its peridental mem-
brane is admitted to the api-
cal space, usually, by a single
arterial twig for each root.
When within this space, it
breaks up into a number of
branches, and one of these
enters the apical foramen,
while the others pass down
toward the crown of the
tooth within the structure
of the peridental membrane.
These are generally found
about midway between the
root of the tooth and the
alveolar wall, and in unin-
jected sections cut lengthwise
will often give the impression
that the membrane is com-
posed of two layers, as we
find it described in some of
the older works. As these al
arteries proceed down the
sides of the root they send
out branches into the walls
of the alveolus that anasto-
mose freely with the arteries
that supply the gums. And
just at the rim of the alveo-
lus there is a pretty rich
And L
plexus formed by union with Root and Membrane of Tooth: p, p, peridental mem-
brane; ap, apical space; a, artery; al, al, alveolar pro-
cess; 1,, dental ligament.
the arteries of the periosteum
and of the gum—the gingival
plexus. This being the case, it is evident that the peridental mem-
brane may receive its blood-supply from either of these two opposite
In alveolar abscess the blood-vessels of the apical space are
often completely destroyed, but, as the anastomosis with the vessels of
the gum over the alveolar rim and through the alveolar wall is so rich,
the membrane does not suffer from lack of blood.
sources.

p
HITZZZZ
- BARE THE THREE and go the
S
a
ap
P
Hal
I
The nerve-supply of the peridental membrane is also derived from
two sources. These correspond perfectly with the sources of the blood-
supply, and need no further description except to say that in this instance
the principal supply seems to be from the direction of the gum and
through the alveolar wall. This may not so plainly appear from ana-
tomical examination, but experimental observation demonstrates that the
920
DISEASES OF THE PERIDENTAL MEMBRANE.
sensibility of the peridental membrane is not appreciably impaired by
the destruction of the nerves in the apical space.
The peridental membrane is the organ of touch of the tooth; the
enamel has no sense of touch. And the pulp is so encased within the
hard structures of the tooth that it could not exercise the sense of touch
if it possessed it; which, as a matter of fact, it does not. The pulp of
a tooth conveys painful impressions only, and under normal conditions
these impressions are aroused only by thermal changes. By means of
the nerves of the peridental membrane, however, every touch upon the
tooth is reported to the sensorium. These nerves are the proper nerves
of touch for the tooth-as much so as are the nerves distributed to the
finger-ends for the fingers. No other nerves of the tooth are so situated
as to receive impressions made upon the tooth, and these must receive
the impressions in a secondary way (which, by the way, is the case with
all nerves of touch. In the fingers' ends these nerves are covered by
the epithelium). When a tooth is touched, as by the tongue, by articles
of food taken into the mouth, or by the finger, the peridental membrane
receives the pressure, and through its nerves a sensation of touch is con-
veyed to the brain. Such a touch cannot affect the pulp of the tooth,
because it cannot reach it; therefore the peridental membrane is the only
organ of touch possessed by the tooth. This sense of touch is in normal
conditions rather feeble, yet sufficiently pronounced to respond readily
to very slight pressure on any tooth. That these nerves of touch are not
distributed principally by way of the apical space I have satisfied my-
self by examination of the sensibility of this membrane after removing
everything from the apical space. One of the most noteworthy observa-
tions I have made on this point was in the case of a young lady who had
lost the pulp of the first bicuspid at a time when the apical foramen was
still widely open, and through which another operator had inadvertently
passed quite a large pellet of cotton. I found it necessary to cut through
the alveolar wall in order to remove it, and I took particular care to
remove everything in the apical space. The space was much enlarged
by absorption, and was in a septic condition. In this case the pulp of
the tooth was gone; the nerves entering the peridental membrane by
way of the apical space were gone; and yet this tooth, at the earliest
date at which the sense of touch could be differentiated from the sense
of pain, was found to possess the sense of touch in a high degree. As
progress toward recovery was made the sense of touch in this tooth
became the same as in the others—or, in other words, it became nor-
mal. This and similar cases in which the same results were observed,
establish the fact that the nerves of touch of the tooth are to be found
in the peridental membrane, and that they are received-for the most
part, at least by way of the nerves distributed to the gum through the
wall of the alveolus.
Therefore we find that the teeth are normally well supplied with
nerves and blood from at least two different sources, and that, though
one of these sources of supply may be cut off, they seem not to suffer
materially on that account-at least, this is the case with the peridental
membrane. Now, the cementum of the tooth is supplied with nutrient
material from the peridental membrane. It follows that the loss of
CLASSIFICATION.
921
some of the avenues by which this nutrient material may reach it will
not materially impede its continued nutrition, and therefore will not
materially lower its standard of health. This agrees substantially with
what is seen in daily clinical experience. Teeth that have lost their
pulps go on decade after decade continuing in the most perfect health.
The sense of touch remains perfect; the connection of the tooth with
the neighboring parts shows no signs of disturbance.
DISEASES OF THE PERIDENTAL MEMBRANE.
One of the first things that the student should recognize in the study
of the pathology of the peridental membrane is the fact that it is sub-
ject to various forms of disease. Among these there are several dis-
tinct varieties of inflammation, which arise from distinct causes and
require different treatment for their cure. No classification can at pres-
ent be made that will be free from objections; yet a classification, even
if not perfect, will assist in the comprehension of the details of the
subject.
Classification.-1st. Traumatic pericementitis, or inflammation of the
peridental membrane resulting from injuries.
2d. Absorption of the roots of the permanent teeth: (a) In diseased
conditions of the peridental membrane; (b) After injuries and trans-
plantations, replantations, etc.
3d. Pericementitis, or inflammation of the peridental membrane, hav-
ing its seat in the apical space and following the death of the pulp of
the tooth. This is the only inflammation of this membrane to which
this term should be applied without the use of a descriptive adjective,
and even here I think it is better to use the term apical pericementitis.
4th. Alveolar abscess. This abscess always has its seat in the apical
space, and is a result of apical pericementitis following the death of the
pulp of the tooth.
5th. Gingivitis, inflammation of the gingival border of the gum and
lower border of the peridental membrane, occurring mostly from con-
stitutional causes, including salivation from mercury, iodide of potassi-
um, etc.
6th. Calcic inflammation of the gums and peridental membrane, a
diseased condition dependent upon deposits of calculus, salivary or
serumal, on the necks of the teeth.
7th. Phagedenic pericementitis, a specific, infectious inflammation
having its beginnings in the gingivæ and accompanied with destruc-
tion of the peridental membranes and alveolar walls.
It will be noted that in this classification we have two distinct
groups
of pathological manifestations, the one having its beginnings in the apical
space, and the other having its beginnings in the gingivæ.
Those conditions resulting from injuries to the roots of the teeth, and
from replantations, transplantations, etc., will be treated in another
article, to which the reader is referred. I will only treat of the pathol-
ogy of absorption of the roots of the permanent teeth in those cases in
which no previous injury has been observed.
On this point it may be stated as an axiom that such absorption never
922
DISEASES OF THE PERIDENTAL MEMBRANE.
occurs during the maintenance of the health of the peridental membrane.
As to the conditions of this absorption we have very positive informa-
tion; I cannot speak so certainly as to the nature of the causes which
bring about these conditions. Absorption of the roots of the temporary
teeth is in all respects a physiological process; the absorption of the
roots of the permanent teeth cannot be so regarded; and yet an exam-
ination of the process in the two instances reveals the fact that they are
identical in their nature, although the causes by which the process is set
in action in the two instances are entirely different. Resorption of the
roots of the temporary teeth is effected by certain cells known as odon-
toclasts; resorption of bone in the physiological processes of change of
form is effected by cells known as osteoclasts. Each of these processes
is physiological, and the cell or tissue that performs this function in
each instance, is the same, the only difference being one of position.
each instance, as the calcific material is removed, the space is filled with
newly-formed cells that crowd into the breach; so that newly-formed
cells are always presented to the surface being absorbed. It is certain
that these cells form a solvent that effects the solution of the calcific
material, though it is not yet known precisely what this solvent is. It
has been suggested by Rustizky and Krause that it contains lactic acid.
This suggestion seems to have arisen from noting the behavior of these
cells toward staining agents, and cannot be regarded as conclusive.
In
These cells not only effect the solution of the living bone, but they
burrow into necrosed bone or pieces of ivory that are thrust into the
tissues for the purpose of experiment (Billroth, DeMorgan, Tomes,
Krause, Koelliker), and in this case the peculiar cells are to be found
in the burrowings, the same as in the ordinary resorption of the bones
or the roots of the temporary teeth. This shows us that the process of
absorption is in no wise dependent upon the life of the tissue being
absorbed. Further, other substances than bone may be absorbed.
It has become quite customary among surgeons to use ligatures of
animal membrane, such as catgut, silkworm-gut, etc., for deep su-
tures ; these are left in, and are absorbed. In the microscopic
study of this process it has been found that the leucocytes aggre-
gate themselves about the ligature, and that in their presence its
substance disappears in such a way as to form irregular pockets, the
same as is seen in the absorption of bone. The cells crowd into the
space gained, keeping it completely filled, until, finally, when the last
particle of the ligature is removed, it is accurately represented by a
solid cord of newly-formed living tissue. In case of the sponge-graft
the sponge is removed in precisely the same manner, and is replaced by
newly-formed tissue. In modus operandi these several processes are
identical. In each instance an excitation of the tissue in the neighbor-
hood of the substance to be absorbed is necessary, and it is also neces-
sary that this excitation be not so great as to cause the formation of pus,
as this, among other causes, will prevent the cells from performing their
physiological function. In cases where a ligature has been used any
considerable pus-formation in the immediate neighborhood is known to
defeat the absorptive process. The presence of pus similarly arrests the
absorption of other substances or tissues.
·
B
P
CONDITIONS OF ABSORPTION.
923
Now, by the application of the facts here presented we can know the
conditions under which the roots of the permanent teeth are absorbed.
There must in each instance be a mild form of irritation that will
keep up local excitement of a particular kind. In the physiological
processes this excitation is probably furnished by the nervous system.
In the pathological processes of absorption the excitation is undoubtedly
furnished by some local irritant which acts more or less continuously.
What this irritant may be must be determined for each case inde-
pendently. In many of the cases of absorption it will be found
extremely difficult to determine the exact cause of the excitation, but in
all cases that have come under my observation the tissues in the imme-
diate neighborhood of the destructive process have been found hyperemic
and presenting the macroscopic appearance of granulation-tissue.
In many cases that present themselves to the practitioner it will be
very difficult to assign a cause for this chronic irritation. One of the
most frequent causes in my experience has been the protrusion of
root-fillings beyond the apical foramen into the tissues of the apical
space, where they keep up a very low degree of irritation. I have
seen many cases in which this was the only cause that I was able to
assign for the difficulty. These cases have nearly all been those in
which I have myself filled the roots with gold. But since the filling
of root-canals with gutta-percha has come in vogue I have met with
a few cases in which the protrusion of that substance seemed to have
acted as a cause. It is plain, however, that these materials will not
invariably produce this result; for I have seen cases where the root-
filling had extended into the tissues, and so remained for years without
evil consequences.
Some of the cases that have come before me have seemed to arise from
some cause entirely hidden. In one very remarkable case eight teeth of
the upper jaw had lost their roots by absorption. Three of the eight had
root-fillings that I had introduced fourteen years before; in the other
five the pulps were alive. The process seemed to have been about the
same in those with living pulps as in those in which the pulps were
dead. The woman had become very intemperate and excessively fat.
A number of cases have come to my notice in which this absorption
has occurred on the roots of teeth otherwise healthy.'
The absorptive process in these cases is usually very irregular. It
may attack the root at any point and remove its substance in the most
irregular manner, or the root may be removed almost as are the roots
of the temporary teeth. Irregularity of absorption is, however, the
rule. This affection presents no symptoms by which it can be recog-
nized before it becomes manifest by the loosening of the crown of the
tooth. It is not amenable to treatment.
Apical Pericementitis, or Pericementitis following the Death of the
Dental Pulp.-This, together with its resultant, alveolar abscess, is
!
¹ Since writing the above I have met with a case in which all of the posterior root
and the floor of the pulp-chamber of a lower molar has disappeared by absorption.
The tooth had a large contour-filling occupying the posterior half of the crown, which
I placed there ten years ago, after capping the pulp. The pulp was alive, as I found by
drilling into the pulp-chamber.
924
DISEASES OF THE PERIDENTAL MEMBRANE.
the most painful affection to which the teeth are liable. It consists of
an inflammation of the peridental membrane, always beginning in the
apical space, in the immediate neighborhood of the apical foramen. It
never occurs during the life of the pulp of the tooth, or, if so, not until
the pulp is irreparably inflamed. The tissue involved in the inflamma-
tory process is encased between the walls of the alveolus and the root of
the tooth in such a way as to hinder its expansion when engorged by
the influx of blood. The tissue, although in normal conditions not
unusually sensitive, is richly supplied with nerves, and in the inflam-
matory state soon becomes exquisitely painful. This inflammation is
very prone to terminate in suppuration, with the formation of alveolar
abscess. The affection may be ushered in immediately upon the death.
of the pulp of the tooth, or it may be indefinitely delayed. In some
instances this inflammation may precede the death of the pulp, the
inflammation of the latter seeming to be projected through the apical
foramen. This, however, very rarely occurs, the rule being that the
death of the pulp precedes the beginning of the inflammation in the
apical space, usually some days, or until putrescence of the pulp has
proceeded so far as to give rise to poisonous material, which escapes
into the tissues by way of the apical foramen. In very many cases
this is delayed for weeks or months, or may not occur even during
a lifetime. The rule, however, is that it does occur sooner or later.
It may be very positively stated that no tooth with an empty pulp-
chamber is safe from apical pericementitis.
W
The SYMPTOMS of acute apical pericementitis vary much in different
cases, but this variation is more as to the severity of the pain than as to
the character of it. It is usually ushered in by a dull pain referred to
the affected tooth. Usually this is at first somewhat relieved by pres-
sure, but as the inflammation increases in severity pressure of the oppos-
ing teeth causes extreme pain; and, as the swelling of the tissues in the
apical space causes a slight elevation of the tooth in its socket, thus
bringing the whole force of the occlusion upon this tooth, this becomes
the source of extreme suffering. Now the mucous membrane over the
affected root begins to present signs of inflammation; it becomes a
deeper red than the other parts of the mucous membrane, and the pres-
sure of the finger causes pain. As the case progresses still farther the
gum is liable to assume a purplish hue. The pain is continuous and
becomes throbbing, each pulsation causing an exacerbation of the pain.
Pus is usually formed in the apical space very quickly-within twenty-
four hours-but sometimes is delayed for several days. With the
formation of pus the case becomes one of acute alveolar abscess, which
will be described presently.
The DIAGNOSIS of acute apical pericementitis usually presents very
little difficulty. Pain caused by pressure on the affected tooth is a con-
stant symptom that distinguishes it sharply from hyperæmia, or inflam-
mation of the pulp of the tooth. In diseases of the dental pulp the
affected organ does not become tender to the touch-at least, not until
the inflammation has passed through the apical foramen, thus ushering
in apical inflammation. In apical pericementitis the pain is always re-
ferred definitely to the particular tooth. In pulpitis the patient is often
A
CHRONIC APICAL PERICEMENTITIS.
925
uncertain as to the exact location of the pain; such an uncertainty on
the part of the patient is in all cases sufficient to exclude acute apical
pericementitis. Pain referred to different parts of the face, the ear, or
other remote points, in the absence of a tooth sore to pressure, also
excludes this disease as the cause, while it is characteristic of the
affections of the pulp of the tooth. If the practitioner will keep well
in mind the functions of the two organs, there cannot be much difficulty.
The peridental membrane is the organ of touch of the tooth, and there-
fore definitely locates its ailments. The pulp of the tooth is not an
organ of touch, and therefore does not definitely locate its ailments,
but is especially prone to cause reflected pain, or pain referred to asso-
ciate or distant parts. This is characteristic of the diseases of those
organs that have no nerves of touch, as is seen in pain referred to the
knee in hip-joint disease, pain referred to the region of the scapula in
disease of the liver, pain referred to the brow in inflammation of the
iris, etc. This peculiarity occurs so frequently in diseases of organs
having no sense of touch as to make it a general law of symptomatol-
ogy. Another point of prime importance is the fact that the dental
pulp is especially sensitive to thermal changes, and that this sensibility
is markedly increased in its diseases. The peridental membrane, on the
other hand, has no special sensitiveness to thermal changes, and such
sensitiveness is not developed to any considerable degree in its diseases.
Therefore the existence of special sensitiveness to thermal changes in
connection with a given case marks it at once as an affection of the
pulp. There seems to be but one condition in which thermal change
causes marked pain in acute or chronic apical pericementitis, and this is
in cases when the pulp-chamber of the tooth is filled with gas in such a
way as to cause pressure on the tissues of the apical space. In this case
heat will give rise to an expansion of the gas, increasing the pressure
and the pain, while the application of cold will relieve it. This, then,
is diagnostic; for in affections of the pulp both heat and cold cause pain
when suddenly applied.
Chronic apical pericementitis has all of the characters of the acute
variety in a modified form. The patient usually complains of sore-
ness of a particular tooth. This may be considerable, or it may be so
slight as to occasion annoyance only. This condition may remain sta-
tionary for an indefinite time, or it may come and go, lasting a day, or
two or three days, at a time. In some cases there will be marked con-
gestion of the gum about the affected tooth; others will present no
signs whatever to the eye. In most cases there will be some sensitive-
ness to pressure made with the finger over the root of the affected tooth;
in these cases the tooth is not sensitive to thermal changes. The pres-
ence of such sensitiveness is sufficient for the exclusion of this affection
from the diagnosis.
This form of disease is more likely to be confounded with phagedenic
pericementitis than any other. They agree in many of their manifesta-
tions, but an examination of the peridental membrane as directed in
treating of that affection cannot fail to render the diagnosis clear.
The CAUSE of apical pericementitis, acute or chronic, is always some
irritating agent that finds its way into the tissues of the apical space by
A
926
DISEASES OF THE PERIDENTAL MEMBRANE.
way of the apical foramen. This agent is usually furnished by products
of the decomposition of the pulp of the tooth. The tooth will in most
instances be found with a cavity of sufficient depth to expose the pulp-
chamber, the pulp being in a state of active decomposition, or, the pulp
having been long dead, its chamber is found crowded with decomposing
filth. The instances are not few, however, in which the affected tooth
is found to be perfectly sound. In these cases the pulp has previously
died from some of the diseases or accidents to which it is liable, and
decomposition of the contents of the pulp-chamber has taken place. A
large number of the cases seen in practice are those in which the pulp,
after the insertion of a filling, has died from thermal changes or from
pressure on the pulp. In those cases in which there is no external
opening into the pulp-chamber it is not uncommon for the case to go
on for a long time after the death of the pulp before painful symptoms
manifest themselves-probably from the fact, so repeatedly noticed, that
the pulp dries up, or becomes mummified, instead of undergoing decom-
position. Sooner or later, however, serum will percolate into the cham-
ber and decompose, furnishing the necessary poisonous material for
lighting up inflammation in the apical space. According to recent
observations in regard to the influence of micro-organisms-their neces-
sity to the process of putrefaction-it is difficult to understand how
decomposition can take place in the closed pulp-chamber, it having
never been open; but, however this may be, the fact remains that such
decompositions do occur. In very many instances this is postponed,
as stated above, and during this time the peridental membrane retains
its health.
Aside from this, there are many instances in which the pulp-chamber
is filled with decomposing filth for indefinite periods and no inflamma-
tion results. It is probable that in these instances the apical foramen
has become so closed with débris as effectually to prevent the passage
of poisonous material.
→
In the TREATMENT of apical pericementitis the first thing that should
receive attention is the pulp-chamber of the affected tooth. If there is
a cavity opening into it, this should be enlarged, so as to gain free access
to the root-canals; the decomposing pulp, or anything else that may be
in the chamber or root-canals, should be removed in the most perfect
manner possible, and the interior subjected to the most thorough cleans-
ing. The best instruments for the purpose are the barbed broaches well
known in the shops of dealers in dental instruments; these are usually
put up in assorted sizes very suitable for this operation. Each broach
should be examined before using, to see that none of the cuts for form-
ing the barbs are so deep as to weaken the shaft at that point, rendering
it liable to break. The use of the broach requires considerable practice
to obtain the best results. It should usually be passed up beside the
pulp with the barbs turned toward the wall of the chamber; and when
the point has gone far enough, the barbs should be turned against the
soft tissue and the broach withdrawn. Usually, the entire pulp will
come out with it if the motion is skilfully executed; but sometimes the
tissue will simply be torn up and the broach will come away without
the pulp, especially when it is in a state of partial decomposition. Then
CHRONIC APICAL PERICEMENTITIS.
927
it will be necessary to twist the tissue around the broach. In doing this
the greatest care should be exercised not to break the instrument and
leave a part of its shaft in the root-canal. I have usually found it well
to pass a fine broach carefully through the apical foramen, to make sure
that it is open, so that if any pus has already formed it may be dis-
charged through the root-canals. After this is done the interior of the
pulp-chamber and root-canals should be bathed with some good disin-
fecting agent. In practice I have found that it matters little what this
is, so that it is not an irritant and accomplishes the office for which it
is intended—the thorough disinfection of the parts. For this purpose
I have used carbolic acid more than any other agent, and I think
this is most used by the profession. Other substances seem to act just
as well, such as iodoform, sanitas, eucalyptus, iodine, salicylic acid, and
a number of others. An objection to the use of carbolic acid has been
raised by some operators on the ground that it is liable to close the api-
cal foramen prematurely by the coagulation of albuminous material.
Theoretically, the objection would seem to be well taken, but in prac-
tice I have not experienced any difficulty from this cause.
After disinfecting, the pulp-chamber should be loosely filled with cot-
ton which has been dipped in some antiseptic lotion, and the cavity tem-
porarily sealed. In a large majority of cases this treatment will be
sufficient to terminate the difficulty. Within a few hours the pain
will subside and the soreness disappear. In all cases the cavity
should be sealed moisture-tight, and, if pus is forming, should be
changed with sufficient frequency to prevent pressure from accumu-
lation.
K
Cases are now and then met with in which this treatment is insuf-
ficient—that is, the pain persists. In such cases various means have
been resorted to for the arrest of the inflammatory process. Counter-
irritation is one of the simplest, and is often a very effective remedy. The
form of counter-irritation that I most resort to is this: Cut a piece of
soft blotting-paper the size desired and stick it on a small bit of rub-
ber dam. Moisten the paper with chloroform, and place it over the
root of the tooth in such a way that the rubber will protect the lips or
cheeks from the action of the agent. This will, if the mucous mem-
brane is dried before it is applied, make a blister within three or four
minutes. I have thought it more effective, however, not to carry it to
that extent, but to apply it until there is sharp burning, then remove,
then reapply in the same way after an interval; and keep repeating this
as long as seems necessary. Any means by which the chloroform can
be applied to the parts and its evaporation prevented will be effective.
I not unfrequently use it on a bit of punk, under my finger. Many
plans for the application of counter-irritation in these cases have been
devised from time to time, such as pepper-bags, plasters into the com-
position of which some one or more of the vesicants or irritants are
incorporated. These, if well made, are effective and convenient.
•
Local blood-letting will often be effective, and is to be recommended
in those cases in which local congestion is a prominent factor. This is
best done by a cut encircling the tooth at its neck or by a cut in the
mucous membrane immediately over the affected root. This, to be
928
DISEASES OF THE PERIDENTAL MEMBRANE.
most effective, should be carried to the bone. In persistent cases it is
better to penetrate the bone and lacerate the tissues of the apical space.
This is quickly done by means of a well-directed drill driven by the
engine. It is needless to say that this is an instrument that should be
used with great care.
A still better result is usually obtained by the use of carbolic acid for
the painless penetration of the apical space. It is best done in this wise:
The mucous membrane is first dried at the point at which it is desired
to make the opening, and napkins are so placed as to keep it dry. Then
a plugging-instrument with fairly sharp serrations and of convenient
shape is selected. The point of this is dipped into a 95-per-cent. solu-
tion of carbolic acid, and a drop conveyed to the mucous membrane;
this will at once produce a white eschar. Then a slight scratching
motion with the serrated point is begun, with the view of removing the
tissue that is whitened. This is continued until the carbolic acid is
thick with the débris of the tissue torn up, then it is dried out and
another drop added, as before, and the process continued. This is
repeated as often as may be necessary, going deeper and deeper into the
tissue in the desired direction until the bone is laid bare. Then a fresh
drop of the acid is placed on the bone and the periosteum carefully
raised over a sufficient space; then with a sharp chisel cut through to
the peridental membrane. This will generally cause some pain and
some bleeding, but after giving a little time for this to cease, and add-
ing more of the acid, the apical space can usually be reached without
difficulty. No blood should be drawn at any time during the opera-
tion except in penetrating the wall of the alveolus. In doing this no
tissue is removed until it is anaesthetized by the carbolic acid. This is
a little tedious, but it is almost painless, and the general effect is usu-
ally better than by other modes of penetrating the apical space. The
carbolic acid has the effect of modifying the pain, and the opening left
does not close so readily. I have frequent occasion to use this process
with very sensitive patients, and have found it to be quite satisfactory.
These means of relief may with advantage be supplemented by con-
stitutional treatment, especially in the more severe acute forms. Hot
foot-baths at bedtime are usually found effective in combating the
inflammation, if made use of before pus has formed. A brisk saline
cathartic is still better, and it is well to follow it with quinine on the
following day. This treatment is especially recommended in those
obstinate chronic forms occasionally met with. In these it is well to
repeat this several times within a few days.'
4
Thing
¹ Exclusive reliance upon local medication, so common in dental practice, is an evil
which should be amended. At the request of Dr. Black the writer presents the follow-
ing summary of a line of constitutional treatment which in a large percentage of cases
has in his hands proved effective in preventing suppuration. It will be observed that
it varies in detail, but not in principle, from that recommended in the text.
1st. After the evacuation of purulent matter or pent-up gases from the pulp-cham-
ber, apply to the gums, over the implicated tooth, one or two good Swedish leeches.
American leeches are unruly and difficult to manage in the mouth or upon any circum-
scribed surface. Each leech will draw about a fluidrachm of blood. After their removal
the hemorrhage can be almost indefinitely prolonged by wiping away the clot as fast as
it forms in the wound made by the leech and directing the patient to rinse the mouth
with warm water as long as it may be desirable to continue the bleeding. In this way
ALVEOLAR ABSCESS.
929
Alveolar Abscess.-Alveolar abscess results from inflammation having
its seat in the apical space proceeding to the formation of pus; there-
fore the location of alveolar abscess is always in its inception the apical
space, no matter where it may afterward extend. If this be not the
case, it is not alveolar abscess even though it be an abscess within the
alveolus of a tooth. This term has been employed from time immemo-
rial to designate this special form of abscess, and it should be strictly
confined to this one form, so that all may know exactly what is meant.
If an abscess occurs on the side of a root of a tooth as the result of
injury, and be not the effect of the death of the pulp of the tooth, it is
properly a traumatic alveolar abscess. If such an abscess occurs from
any of the diseases that attack the sides of the root of the tooth and it
is thought well to designate it as alveolar, the word should in all cases
be accompanied by an adjective expressing the fact. This is necessary
to accuracy.
Alveolar abscess, then, is in all cases a result of apical pericementitis.
If the case is not seen until the formation of pus has begun, or if the
means employed for subduing the inflammation have proved ineffectual,
all the symptoms will show an aggravation. The gums over the
affected tooth will become deeply congested, and perhaps actually
from a fluidounce to a fluidounce and a half of blood may readily be abstracted from
each leech-bite, in addition to the amount originally drawn. When leeches are not
obtainable, the method of scarification of the gum recommended in the text should be
followed. Leeching not only possesses the great advantage of being an entirely pain-
less method of abstracting blood, but secures a greater outflow than that obtainable
from a simple incision. It should always be practised before any local medication is
attempted, as the presence of any foreign substance upon the gum interferes with the
biting of the leech, if it does not entirely prevent it.
2d. After the removal of the leeches give a full dose-from 6 to 10 grains-of
quinine. This somewhat reduces the temperature and the force of the circulation, and
possibly tends to retard the inflammatory process by arresting the migration of the
leucocytes through the walls of the congested capillaries, although in the ordinary
medicinal dose this may be considered doubtful.
3d. Following the quinine, give one drop of tincture of aconite-root every hour until
bedtime. For safety, place the required number of drops (and no more) in a small bottle,
carefully instructing the patient as to dosage. Ten or twelve drops are usually sufficient
for the required number of hours, and this amount, even if taken at once by an adult,
would not prove fatal. From such small doses no very marked effect upon the force or
frequency of the circulation can be expected, but they will at least hold the inflamma-
tion in check and prevent an increased pulse-rate. Larger doses of aconite should not be
given unless the patient can be kept constantly under observation and the effect of each
dose noted-a precaution which the exigences of dental practice usually make imprac-
ticable. Under proper safeguards a reduction below the normal of from five to ten beats
per minute in the pulse-rate is desirable and safely attainable.
4th. At bedtime give a full dose (10 grains) of Dover's powder. This is to be taken
in conjunction with a liberal amount of hot lemonade, the feet to be previously well
soaked in hot water, and the patient, when in bed, well covered, to promote sweating.
This treatment is a most effective feature in general medication in this class of cases.
The opium eases pain, quiets nervous irritation, lowers the circulation, and in conjunc-
tion with ipecacuanha promotes diaphoresis, thus diverting to the cutaneous surface
perverted blood-currents, draining the congested vessels of their contents, and dimin-
ishing the force and frequency of the circulatory impact upon the inflamed area.
5th. The following morning give a brisk saline cathartic. If given during the previous
day, its operation is likely to take the patient out of bed at night, and thus to interfere
with the action of the Dover powder.
6th. Quinine, aconite, and opium to be continued (according to indications) until
inflammation subsides, on the one hand, or the abscess has formed and discharged,
on the other. (See Treatment of Alveolar Abscess.)-ED.
VOL. I.-59
930
DISEASES OF THE PERIDENTAL MEMBRANE.
inflamed. The pain becomes in many instances intolerable, and there
may be a rigor followed by fever. In a number of instances I have
seen fever of 103° and 104° F. in severe cases of acute alveolar
abscess.
The first pus formed is pent up in the apical space by bony walls on
all sides, and the pressure becomes very great; this results in rapid
absorption of the surrounding bone. The rule in such cases is that the
pus
will burrow in the direction of the least
resistance, and, as the bone about and enclos-
ing the apical space is softer than the exter-
nal lamina, it usually happens that notable
destruction of bone occurs before the surface
is reached, thus forming a considerable pus-
cavity (Fig. 485). Even in this case, how-
ever, the tissues of the peridental membrane
occupying the apical space are not, as a rule,
destroyed. The fibres are swollen and great-
ly elongated, and the pus usually occupies
spaces between them. This swollen tissue
forms the mass so often seen attached to the
end of the root of a tooth extracted while in
this condition, or later, after the abscess has
become chronic. The explanation of this
seems to be that the fibres are loosened from
the alveolus by absorption of the bone, but,
the root of the tooth not being absorbed, the attachment of the fibres
to the cementum is not broken up. This is the usual condition of the
tissues in alveolar abscess, but in some cases it happens that this tissue
is destroyed and the end of the root denuded of its membrane, which
complicates the healing process. It seems from my own observation,
however, that this occurs but rarely in the acute forms; in the chronic
form it is more frequently met with.
During the time that the pus is burrowing in the bone the pain con-
tinues to be very severe and is of that throbbing character so peculiar
to abscess-formation. The gums over the affected root become deeply
congested and often much thickened by engorgement with blood, and
the lymphatics about the angle of the jaw are liable to become very
sore and swollen. There is not often during this time much swelling
of the tissues of the face. Finally, the pus will find an exit from the
bone. This usually occurs on the buccal side of the arch (the mouth is
regarded as consisting of two cavities-the lingual cavity, inside the
dental arch; the buccal cavity, outside the dental arch and inside the
cheeks and lips), as shown in Figs. 485, 486, but may occur in any
direction, the rule being that it will burrow in the direction of the least
resistance. It is in obedience to this law that the large cavity is formed
in the bone about the apical space. This portion of the bone is of a
cancellated structure, and is much more rapidly absorbed than the denser
portions near the surface; therefore there is usually a very considerable
cavity formed in this portion of the bone in the first stage of the pro-
cess, but after the penetration of the outer lamina of the bone the pus
C
FIG. 485.
b

a
dl
Acute Alveolar Abscess of Supe-
rior Incisor pointing on the
Gum: a, abscess-cavity in the
bone; b, floor of the nostril; c,
lip; d, tooth.
ACUTE ALVEOLAR ABSCESS.
931
FIG. 486.
finds its way into the soft tissues, where the resistance is less and
the destruction of the bone ceases or progresses less rapidly. With
the escape of the pus from its imprisonment within the bone comes
a modification of all the symptoms. There is usually a marked
abatement of the intense pain. This, however, is only an abatement,
not a cessation: the pain continues in a less intense form. The feat-
ures, which up to this time had shown but little of the effects of the
malady except the expression of suffering, now become swollen, often
with great rapidity. Frequently all the tissues of the side of the face
affected become intensely oedematous and distorted, the eye closed, and
the jaws so stiffened that the mouth can
be but slightly opened. In this condition
an examination will show a large tumor
of the gum over the affected root. This
may be in either the lingual or the buccal
cavity, but in a great majority of cases it
is found in the buccal. The tumor will
be found fluctuating, and if left to itself
will very generally open on the gum, just
over the root of the tooth. This result
should, however, be anticipated by opening
with the bistoury, for it not very unfre-
quently happens that the tissues of the
gum are raised from the bone and the pus
finally gains an exit at the gingival mar-
gin; which complicates the process of re-

C
Anasa
CL
covery.
After the discharge of pus the inflam-
matory symptoms usually abate very rap-
idly. The pain generally subsides within
a few hours, and the swelling within a day
or two, though pus may continue to be dis-
charged indefinitely. The amount of
pus
formed in these cases is often very consid-
erable, the discharge being profuse and con-
tinuing for a number of days. The quan-
tity, however, gradually lessens, and after four or five days it is usually
reduced to a comparatively small amount. The abscess, if left to itself,
usually assumes the chronic form, the pus continuing to be discharged,
but in lessened volume. With the exception of the fistula and the
slight discharge of pus, the parts now assume, so far as the eye can
detect, their normal condition. This is the chronic form of alveolar
abscess.
d
Acute Alveolar Abscess of the Lower
Incisor pointing on the Gum: a, ab-
scess-cavity in the bone; c, lip; d,
tooth.
•
Acute alveolar abscess presents three forms in respect to the manner in
which the pus leaves its bony enclosure. It may at once penetrate into
the soft tissues, as described above (Figs. 485, 486); it may separate the
periosteum from the bone and form a cavity for itself between the two,
as shown in Fig. 487; or it may follow the peridental membrane down
the side of the root and be discharged at the margin of the gum. The
second is the form of abscess that is most likely to be attended with
932
DISEASES OF THE PERIDENTAL MEMBRANE.
necrosis of portions of bone, and for this reason should receive prompt
attention for the purpose of preventing or limiting this very unfavorable
result. This seems to occur mostly in those cases in which the inflamma-
tion has run very high, and in which there
has been, or exists at the time of the escape
of the pus from the bone, a very considerable
inflammation of its substance and of its peri-
osteum, by which the layer of osteoblasts have
become so softened that they are readily sepa-
rated from the bone beneath. In this condi-
tion of things the pus, in making its escape
from the bone, instead of penetrating the over-
lying tissues, raises the periosteum in the same
manner as in subperiosteal inflammations. In
this way separation of the periosteum from the
bone over a considerable surface occasionally
occurs; and if the parts are suffered to re-
main in this condition for a considerable time,
necrosis more or less extensive will result. If,
on the other hand, the pus be promptly dis-
charged, so that the periosteum may be again
brought in contact with the parts from which it was separated, not much
harm will follow; it will readily be-
come reattached, and the parts will
heal without difficulty. Separation of
the periosteum is to be suspected when
the tumor of the gum is broad and com-
paratively soft. After discharge of the
pus by means of the bistoury an exami-
nation with a probe will reveal the fact
that the bone is more or less extensively
stripped of its periosteal covering. This
form of abscess, when left to itself, is
prone to discharge at the gingival mar-
FIG. 489.
с
FIG. 487.
b

a
d
Acute Alveolar Abscess with Pocket
of Pus between the Periosteum
and the Bone: a, abscess-cavity in
lip; d, tooth; e, pus-cavity beneath
the periosteum.
the bone; b, floor of the c,
FIG. 488.
D
1004
Necrosis of the Buccal Plate of the Alveolar Pro-
cess from Alveolar Abscess.
C
b
CL
d
e
*****
Categ
S


Acute Alveolar Abscess of a Lower Incisor with
Pus-cavity between the Bone and the Perios-
teum: a, pus-cavity in the bone; b, pus be-
tween the periosteum and bone; c, lip; d,
tooth; e, tongue.
gin after having separated the periosteum from the outer wall of the alveo-
ACUTE ALVEOLAR ABSCESS.
933
lar process. In this condition the only blood-supply that this portion of
the process can obtain is that which may come from the other side of the
tooth through the anastomosis of the arterial branches in the peridental
membrane, already in a more or less inflamed condition, or through the
Haversian canals of the septum of the alveolar process between the teeth.
This, it will at once be seen, will, in the inflamed condition of the parts,
be a very precarious supply; and, as a result of this condition, necrosis
of the alveolar plates overlying the root affected and those immediately
adjacent is very liable to occur. Loss of these plates by necrosis occur-
ring in this manner is shown in Fig. 488.
This form of abscess, occurring in the lower jaw (Fig. 489), is per-
haps more likely to point on the face than any other of the acute forms,
on account of the fact that gravitation carries the pus in that direction.
This may drop gradually down and the pus be discharged under the chin,
forming a chronic abscess such as is shown in Fig. 500; or if it be an
anterior tooth, it may open in front, under the lip; or if it be a posterior
tooth, on the lower border of the cheek. Less frequently this may happen
from alveolar abscess in the upper jaw, the abscess pointing almost any-
where on the face, but more especially just under the prominence of the
malar bone, in front of the attachment of the masseter muscle (Figs.
490 and 495).
The opening of an alveolar abscess on the face is always a grave mis-
fortune because of the scar that is almost inevitable, and for this reason
such a result should be guarded against with the utmost care. When it
is apprehended, the pus should without delay be discharged into the
mouth by use of the bistoury.
Occasionally this form of abscess is seen to raise the periosteum and
soft tissues from the hard palate, the pus having discharged from its
bony enclosure in that direction (Fig. 491). My observation leads me
FIG. 490.
FIG. 491.
e


i
f
e
b
g
***
*****.
с
d
Upper Molar with Acute Abscess at the Buccal
Roots and Chronic Abscess at the Palatine Root:
a, cavity of acute abscess in the bone; b, pus-
cavity between the bone and periosteum, ex-
tending out under the prominence of the malar
process; c, tissues of cheek; d, tooth; e, maxillary
sinus;, nostril; g, malar process; h, cavity of
chronic abscess discharging at i. (Compare with
Figs. 495, 496, and 504.)
с
CL
d
Upper Incisor with Acute Alveolar Abscess
the Pus from which has raised the Perios-
teum from the Hard Palate: a, very large
abscess-cavity in the bone; b, pus-cavity be-
tween the periosteum and bone; c, lip; d,
tooth; e, floor of nostril.
to the conclusion that in this case there is not the same tendency to dis-
charge at the gingival margin as in cases in which the tumor is situated
934
DISEASES OF THE PERIDENTAL MEMBRANE.
in the buccal cavity. When the abscess points in the hard palate, there
is about the same liability to necrosis of the alveolar process, yet it
usually seems to be limited more to the margins. Occasionally I have
seen the periosteum stripped from the bone over the entire roof of the
mouth, but retaining its attachment at the gingivæ and along the line
of the posterior border of the hard palate, forming in this way a pus-
cavity filling the entire palatine arch. In these cases, extensive as is
the separation of the periosteum, necrosis of the bone but rarely occurs;
indeed, I have never witnessed a perforation of the hard palate from
this cause.
This is probably due to the fact that the bones are thin and
their blood-supply from the mucous membrane of the opposite surface
is not interfered with. This accounts for the fact that in the palate.
necrosis of bone is usually limited to the immediate neighborhood of
the teeth, where the blood-supply may be cut off by the tissue injury.
In these cases we recognize two causes of necrosis of bone. One is
the intensity of the inflammatory process, which destroys by producing
stasis over a considerable territory. This may cause necrosis in any
locality whatever. The other occurs in such localities as may be de-
prived of their blood-supply by the injury of tissues in their immediate
neighborhood upon which they are dependent. This is confined, for the
most part, to the alveolar process, which receives its blood from two
sources through the vessels of the gum and periosteum of the outer
surface of the process, and through the vessels that enter the apical
space and supply the alveolar dental membrane. The latter vessels are
cut off-temporarily, at least-by the formation of abscess in the apical
space. Now, if the periosteum also is separated by the burrowing of
pus beneath it, the death of this portion of bone seems inevitable, and
clinical observation shows that this result does take place if this con-
dition of things remains for a considerable time; yet it does not neces-
sarily occur at once, and even here necrosis of the process may be pre-
vented by prompt action in discharging the pus and keeping the parts
in apposition.
The third form is that in which the pus, instead of penetrating the
surface of the bone, finds its way along the side of the root, following
the peridental membrane to the gingival margin, and is discharged at
that point. This form is more rare than either of the others. When it
occurs, it destroys a considerable part of the peridental membrane, and
the alveolar process overlying this quickly disappears. This condition
is readily recognized by passing a thin, flat, pointed instrument up by
the side of the root and finding the peridental membrane wanting;
whereas, if the pus has penetrated to the surface of the bone above and
been discharged at this point, the peridental membrane, on raising the
periosteum, will be found intact. The third form is perhaps more liable
to be mistaken for phagedenic pericementitis than any other type of
alveolar abscess.
Occasionally there occurs a case of alveolar abscess accompanied by ex-
tensive necrosis of the bones of the face. I have seen one extreme case
in which all of the lower border of the right superior maxilla, including
the whole floor of the antrum of Highmore, and all of the teeth from
the central incisor to the wisdom tooth, were carried away. I did not
CHRONIC ALVEOLAR ABSCESS.
935
see the case until the necrosed parts were loosened, but, from the history
given by the patient, there seemed to be no doubt that the trouble arose
from acute alveolar abscess at the roots of the first molar. That tooth
had for some time been decayed, and the patient had had severe tooth-
ache several times; in one of these attacks the face began to swell, and
it was in this inflammation that the necrosis occurred. The patient was
a young man about twenty years old, and when I saw him was quite
anemic. He made a good recovery after the removal of the necrosed
portions of bone. Another extensive case was that of a boy of nine
years, in which all of the teeth from the cuspid to and including the
twelve-year
molar—which had not erupted-came away. This seemed
to have arisen from alveolar abscess at the root of the first molar, which
had been allowed to run its course without attention. Cases so exten-
sive as these are, fortunately, very rare. In a few cases I have seen
extensive necrosis of the alveolar processes that seemed to arise from
abscesses occurring independently at the roots of various teeth, all of
which had been neglected. In such cases the general health of the
patients has usually suffered greatly, and they generally present an
anæmic appearance.
Chronic alveolar abscess usually follows the acute form if the case is
left to itself. The causes of this abscess are such that they are not self-
limiting, as is the rule with a large proportion of the abscesses to which
the human frame is liable. A common boil, or phlegmon, is cured
spontaneously by the discharge of its contents; this is the general result
in abscesses of the soft tissues. In subperiosteal abscess the discharge
of the contents results in a spontaneous cure in those cases in which no
necrosis of bone has occurred; but if there is necrosis, the presence
of the dead bone may cause the abscess to assume the chronic form
by its continuous irritation of the tissues with which it is in contact.
In alveolar abscess we may, and generally do, have the case continu-
ing in the chronic form without the presence of necrosed bone. In
this case the irritant that is responsible for the continuance of the
abscess is derived from the pulp-chamber of the affected tooth; that
is, the same cause that brought about the acute form remains to
keep up the chronic-namely, the discharge of septic matter from the
pulp-chamber of the tooth into the apical space.
The presence of this abscess is known, except in that form called
blind abscess, by a fistulous opening in the neighborhood. The position
of this opening and the direction of the burrowing of the pus in chronic
abscess furnish a great variety of forms, presently to be considered;
just now the conditions peculiar to the apical space will engage our
attention. When the pus is discharged from the acute abscess, the
inflammation subsides and the parts, so far as the eye can detect, return
to their normal condition, except that a fistulous opening remains.
Even this may close, and, though rarely, the abscess may be cured
spontaneously. The rule, however, is that the fistulous opening con-
tinues, and that pus may be found at the orifice at any time. The flow
of pus is often profuse for the first few weeks, but, as a rule, it is gradu-
ally reduced until it is quite small in amount, and often the orifice heals
over and opens again every few days; sometimes it closes permanently.
<
p
936
DISEASES OF THE PERIDENTAL MEMBRANE.
FIG. 492.
Then we have the condition of blind abscess (Fig. 492), in which there
remains a mass of tissue in the enlarged apical space with which more or
less pus is constantly intermingled. This
condition of things may continue almost
without change for any length of time,
or the pus may be burrowing through
the tissues without the patient's knowl-
edge. A tooth in this condition is lia-
ble to periodic fits of soreness which will
from time to time attract to it the atten-
tion of the patient. In such a case the
symptoms differ but little from chronic
pericementitis. The contents of the pulp-
chamber are in a state of constant putre-
faction, and the resulting products are
as constantly being discharged into the
apical tissues in a quantity sufficient to
prevent healing. In this chronic form
changes in the enlarged apical space take place very slowly, and usu-
ally are not very marked in their character. It seems evident from the
comparisons I have made from time to time that the absorption of
bone about the apical space is greater in the chronic than in the acute
forms; therefore I conclude that in the majority of chronic alveo-
lar abscesses the absorption of the bone is slowly progressing, though
this is not necessarily true in all cases. I have seen some chronic
abscesses of long standing in which the absorption of bone was very
slight. In the majority of cases, judging from clinical experience
gained in the treatment of these forms, the tissues of the apical space
do not seem to be very much impaired in their vitality; for such ab-
scesses heal with the greatest facility when the cause by which they are
maintained-septic matter from the pulp-chamber-is removed. Still,
there is a considerable number in which this is not the case.
In some
of these cases the difficulty seems to consist solely in the low state of the
vitality of the tissues; so that time is required for them to recover tone.
In others there is an actual destruction of the tissues of the apical space,
this proceeding to such an extent that a portion of the apex of the root
is denuded of its tissue. This is always a very grave condition as re-
gards the prospect of recovery. Another complication also is liable to
occur the deposit of serumal calculus on that portion of the root which
has lost its covering of tissue. This calculus is evidently derived from
the exuded serum, and not unfrequently is deposited in the form of
crystalline or crystal-like points; so that when the finger is passed over
it one is strongly impressed with the similarity of the sensation to that
produced by a burr. This calculus is an irritant, and is especially so
when in this form, and of course it is impossible that the case can heal
while it remains.

a
b
Blind Abscess at the Root of an Upper
Incisor: a, abscess-cavity in bone; b,
drill-hole exposing the pulp-chamber
for
Cases are now and then met with that have taken on a septic condi-
tion and assumed a more aggravated type. In all of the cases before
mentioned the pus is of the character known as laudable, but in the
septic condition it becomes sanious, or very thin and watery. Now the
Ch
THE BURROWING OF PUS.
937
destruction of tissue becomes more apparent. Not only the bone, but
the neighboring soft tissues, are found to be wasting away, and several
openings for the discharge of sanious pus are likely to be formed; and
the case, if left to itself, is likely to terminate in the spontaneous loss of
the tooth. This condition has been described by Dr. Ingersol as alveo-
lar ulceration. It seems to be caused by micro-organisms different from
those usually found in the pus of ordinary alveolar abscess; but our
knowledge of it is as yet too indefinite for positive statements to be made.
Chronic alveolar abscess may result directly from chronic apical peri-
cementitis without acute inflammation having been present at any time;
indeed, it may take place so quietly and with so little disturbance that
the patient will not remember that the tooth has ever been sore or that
anything has been wrong with it. The tooth affected is not necessarily
decayed. Its pulp may have died from any of the diseases to which it
is liable, and the tooth may present the appearance of the most per-
fect health. An abscess formed in this quiet way subsequently pre-
sents no symptoms different from those that follow the acute form.
K
The condition of the tooth in chronic abscess is not necessarily very
characteristic. Of course the pulp is always dead, and in a certain pro-
portion of the cases the tooth will be discolored by the absorption of
the coloring-matter from the decomposing pulp, or after this by the
formation of the dark sulphurets. This discoloration may exist in any
degree, from the slightest perceptible tinge to a deep black. The rule
is that there is some change of color by which the fact can be recog-
nized that the tooth has lost its pulp. In many cases this is only a
slight loss of translucency. Such a tooth is never sensitive to cold, and
by this test the right tooth can usually be selected in case of doubt as
to which of a number of teeth may have an abscess supplying the pus
discharged from a fistulous opening in the neighborhood.
The burrowing of pus in the chronic forms of alveolar abscess forms
a very important element in their history. This presents the widest
variations, and is occasionally the source of much perplexity to the
physician and the surgeon. The general rule is that the discharge is
continued at the point at which the acute abscess at first opened—i. e.
upon the gum over the affected root (Figs. 493, 494). This is, how-
ever, a general rule to which there are many exceptions. The point of
discharge is frequently changed during the continuance of the chronic
form; the fistulous opening heals over, and after a time the pus appears
at another point, which may be at a distance from the original opening.
This change may be, and generally is, made with so little disturbance
that the patient is not cognizant that it is taking place until the new
point of discharge is noticed. Exceptionally, considerable disturbance
occurs; in fact, the abscess may again assume the acute form and force a
new opening in a different direction or at a more remote point. The
cases in which there is a certain soreness and stiffening of the tissues
through which the abscess is burrowing are more common.
This is
especially the case if the parts be freely movable or if the pus is finding
its way through muscular tissue, and yet it is singular how far pus may
burrow among muscles without serious inconvenience. It often happens
that the stiffening of the muscles is all that is complained of.
938
DISEASES OF THE PERIDENTAL MEMBRANE.
Among these burrowings of pus in this class of abscesses some gen-
eral rules may be pointed out, and some particular forms that occur
oftener than others may be mentioned. It is a general law of the bur-
rowing of pus that it will go in the direction of the least resistance;
FIG. 493.
b
с
CL
LUMES OFTEN
d
Chronic Alveolar Abscess at the Root of a
Lower Incisor: «, abscess-cavity in the
bone; b, fistula discharging on the gum;
c, lip; d, tooth.
b-
с
FIG. 494.
d
CL
C


Chronic Alveolar Abscess at the Root of an Upper
Incisor with Fistula discharging on the Gum:
a, abscess-cavity in the bone; b, mouth of
fistula; c, lip; d, tooth.
this law pertains more especially to the acute forms of abscess. In the
chronic forms, in which the movement of the pus is very gradual, it is
guided largely by gravitation, and therefore sinks to a lower point.
Now, these two forces, acting together, will explain most of the move-
ments of pus in the burrowings of chronic abscess. If, in the down-
ward wanderings of the pus, it comes in contact with a more dense
tissue, it will usually be deflected from its course toward that of less
resistance; or if it be entangled in the fibres of such a tissue as the
muscular and these run at an angle with the perpendicular, there will
be seen a tendency to follow instead of to cross the fibres. Again, if
the pus is burrowing in a softer tissue and in its course comes in con-
tact with a muscle, it will usually be deflected and pass around the more
dense tissue in the direction most favored by gravitation. In the same
way, it will be turned from its course by dense fascia and burrow
beneath it. This is the general law observed in studying the burrow-
ings of pus in cases of chronic abscess, but it is by no means univer-
sal, for cases are occasionally presented in which it seems to be
directly disobeyed. In the mass of cases, however, these will be found
.to be exceptional.
Now, by the application of these laws we will be assisted in tracing
a discharge to its source, though in some exceptional cases it may mis-
THE BURROWING OF PUS
939
{
lead. The rule is that we will find the point of discharge below the
source of the pus; hence chronic abscesses of this class that burrow to
a considerable distance are likely to discharge on the lower portion of
the face or on the neck, and occasionally as low as the clavicle. Dr. E.
D. Swain of Chicago has given me the details of a case coming under his
care which illustrates this tendency. The pus from a chronic abscess at
the root of a second superior molar became entangled in the fibres of
the masseter muscle and followed them down through their length.
At the lower border it emerged from this muscle beneath the border of
the platysma myoides, and, having become entangled in the fibres of
this, followed their direction downward and backward to the border
of the trapezius, where it discharged on the skin. The masseter muscle
was so disabled that the mouth could not be opened to the usual width,
and the line of the sinus was readily traceable under the surface as it
followed the platysma.
It is rather unusual for the pus from abscesses in the upper jaw to
follow such a course. When such a discharge comes to the surface, the
FIG. 496.

d
e
FIG. 495.

с
a
...
180 1
• 1997 - 19
Crying
f
*******
Alveolar Abscess at the Buccal Roots of an Upper Molar
discharging on the Face: a, abscess-cavity in the
bone; b, fistula opening on the face; c, maxillary
sinus; d, nostril: e, tooth; f, tissues of cheek. (Com-
pare with Figs. 490, 496, and 504.)
LA S
|||
Scar caused by Alveolar Abscess dis-
charging on the Face. (Compare with
Figs. 495, 504, and 490.)
usual point is just beneath the prominence of the malar bone and in
front of the anterior border of the masseter muscle (Fig. 495)—at least,
of the abscesses of the upper jaw discharging on the face which have
come under my observation more have presented at this point than at
all others together. All those that I have seen in the act of pointing
in this position have been of the acute form, but the history given me
in some cases indicates that the chronic forms may occasionally point in
this direction after the closure of the fistula opening on the gum over
the affected root. The particular point of discharge seen in Fig. 496
forms a very characteristic scar, and on that account is of special inter-
940
DISEASES OF THE PERIDENTAL MEMBRANE.
est. My observation leads me to the conclusion that such fistulæ are
usually the result of acute abscess of the form shown in Fig. 489, in
which the periosteum is separated from the bone far out under the malar
prominence. When the new tissue formed by the healing of the sinus
has contracted, the skin is drawn inward under the malar prominence
in such a way as materially to disfigure the face. The healing of the
fistula forms a strong cord of new tissue, which in this instance has one
of its ends attached to the skin and the other to the periosteum. This
binds the skin down to the bone permanently unless it be relieved by an
operation. (See p. 952.)
This class of abscess may discharge, also, anywhere in the region below
the eye. As a general rule, the muscles are avoided, the pus burrowing
around them when they happen to lie in the way. For this reason,
perhaps, there is a tendency, when an abscess at the root of an anterior
tooth discharges on the face, for the discharge to appear in the triangle
between the levator labii superioris alæque nasi and the levator labii
superioris. In two cases I have seen the discharge from an abscess of
a central incisor appear close to the wing of the nose.
Occasionally we find an alveolar abscess discharging on mucous
membranes other than those of the mouth; such cases are usually
from abscesses situated in the upper jaw.
I have three times seen abscesses at the
root of the incisors discharging into the
nasal cavity (Fig. 497). In these instances
the pus passed through the bone, and in
each instance the abscess-cavity was very
large. I have also met with one instance
in which the pus from an anterior tooth
passed back beneath the mucous mem-
brane and discharged at the junction of
the hard and soft palate. Several cases
of this kind have been reported in dental
literature. Such cases are liable to cause
the patient much trouble before a correct
diagnosis is made unless he falls under
the care of one who has given them some
special study.
The relation of the antrum of High-
more to the roots of the teeth (Fig. 498) is such that alveolar abscess
is liable to discharge into that cavity. This sinus presents great vari-
ations in individual cases. In some there is a heavy lamina of bone
between the roots of the teeth and the cavity, but occasionally a case is
met with in which the roots of the teeth actually project into it, being
covered, however, by a very thin lamina of bone in addition to the
mucous membrane; in this case an abscess occurring at the end of the
root will inevitably discharge into that cavity. This will sometimes
produce serious complications, especially if the pus is not freely dis-
charged by way of the nostril. The pus may also find its way into this
cavity when there is considerable bone between it and the root of the
tooth (Fig. 499).
с
FIG. 497.
b

a
d
Alveolar Abscess at the Root of a Su-
perior Incisor discharging into the
Nose: a, large abscess-cavity in the
bone; b, mouth of fistula on the floor
of the nostril; c, lip; d, tooth.
Juded
Tamp
ABSCESS OF THE ANTRUM.
941
By far the larger number of alveolar abscesses discharging on the
face are situated in the lower jaw; this is undoubtedly for the reason
that in this position the tendency is for the pus to be carried downward
FIG. 498.

***ng •
·ORMATI**
my get m
0.340.
Skull with the Malar Process cut away, exposing the Antrum of Highmore, and with the Buccal
Plate of the Alveolar Process removed, exposing the Roots of the Teeth, thus showing the rela-
tions of the Roots of the Teeth to the Antrum.
in
anmi
O
by gravitation. The greater number of these cases occur after the abscess
has at one time opened on the gum, but finally has discharged so little pus
that the fistula has closed. Then the pus that remains burrows little by
little in the direction in which it is carried by gravitation, until it finally
finds its way to the surface-usually,
somewhere along the lower border
of the inferior maxilla. As show-
ing how insidious this creeping of
pus may be, I recall a case in which
FIG. 499.
b
was treating an abscess at the root
of a lower incisor for a patient in my
own house; the case did not progress
very favorably, but after a few weeks
the discharge ceased and the fistula
closed. Some time after this, when
I was congratulating myself that the
cure would be permanent, the patient
one day called my attention to a "lit-
tle pimple" under the chin. On ex- Alveolar Abscess at the Root of an Upper Mo-
lar discharging into the
amination, I found, to my astonish-
ment, that the abscess, which I had
thought well, had found a new out-
let in that position, the pus having followed along the periosteum as
shown in Fig. 500. This had occurred so quietly that the patient
had discovered no unpleasant symptoms, though I had now and then
inquired after his conditon. This is a form seen quite frequently,
as compared with other abscesses opening on the face. These may,
however, present anywhere on the face below the lip, though just under

C
d
a
· · *******
Part.
SIN» $ 4¹ #
--- **4
0014
· PARENT
f
more: a, abscess-cavity in the bone; b, mouth
of fistula on the floor of the antrum; c, pus
in the antral cavity.
942
DISEASES OF THE PERIDENTAL MEMBRANE.
the chin seems to be a favorite point for them to open. Another form
that opens at the same place I have illustrated in Fig. 501; in this the
FIG. 500.
FIG. 501.


b
b
с
lj.
d
b
Chronic Alveolar Abscess at the Root of
a Lower Incisor with Fistula discharg-
ing on the Face under the Chin: a, ab-
scess-cavity in the bone; b, b, b, fistula
following the periosteum down to the
lower margin of the body of the bone
and discharging on the skin.
**
FIG. 502.
tiffa.
Butt!
700274
Fistula passing down through the Body of the Lower
Maxilla. (See page 943.)
··
M
* + % 0%
**** plane
*******
с
pus has burrowed directly through
as this must, I think, usually occur from abscesses that were chronic
the
body of the bone. Such cases
from the first-blind abscesses,
the pus from which has never
penetrated the outer lamina of
bone over the affected root. In
such a case the pus may very
readily make its way through
the body of the bone, in obe-
dience to gravitation.
a
d
b
Chronic Alveolar Abscess of the
Root of the Lower Incisor with
Abscess-cavity passing through
the Body of the Bone and dis-
charging on the Skin beneath
the Chin: «, very large abscess-
cavity; b, mouth of the fistula.

This class of cases is not ne-
cessarily confined to the anterior
part of the lower jaw, but may
occur at any point from angle
to angle. Fig. 502 illustrates
rather an unusual case that
was presented to me some
years ago. There was a fis-
my
tulous opening just beneath the body of the lower maxilla, about the point
where the facial artery crosses over the bone in ascending to the face; this,
DIAGNOSIS OF ALVEOLAR ABSCESS.
943
•
the patient stated, had been discharging for more than eight years. Early
in the history of the case he had had a tooth extracted, with the view
of effecting a cure; but the operation failed of its purpose. Following
up the sinus with a small probe, I found that it came from the body of
the bone, and finally detected a loose substance. On carefully taking
the direction and length of my probe, I found that this must be in
the position formerly occupied by the roots of the tooth that had been
extracted. Examination of the gums at the point revealed nothing
unusual; the parts seemed healthy, but the space formerly occupied by
the now missing molar seemed to be as wide as when it was removed.
I dissected off the soft tissue, and found what seemed to be very solid
bone; but with the first stroke with the chisel and mallet the chisel
passed into a cavity. In this cavity I found a piece of necrosed bone
that from its form seemed to be the septum that had been between the
roots of the extracted molar; this bit of necrosed bone was the irritant
that had kept up this discharge for so many years.
Alveolar abscesses opening on the skin are not confined to the face,
but they may point still lower down, as on the side of the neck as far
as the clavicle. I have myself seen quite a number that had opened at
one-third and one-half the distance between the os hyoides and the clav-
icle. A route often taken in these cases is for the pus to follow the
fibres of the platysma until the anterior border of the sterno-cleido-
mastoid is reached, and there come to the surface. It is only occasion-
ally that this point is passed, and then the pus may continue its bur-
rowing as far as the clavicle. This is apt to carry it well out toward
the shoulder.
The DIAGNOSIS of alveolar abscess, especially the acute form, does
not often present much difficulty, for there is nearly always a very sore
tooth to which the patient's attention has been strongly directed. The
great dread of having a tooth extracted will, however, often cause a
patient to keep that important fact from the physician. I have seen
a number of patients who would say they had had no toothache, when
a tooth was so sore that they dared not close the teeth together. This
fact, however, hardly furnishes an excuse for treating a case of acute
alveolar abscess as one of erysipelas-an error in diagnosis which more
than once I have known made; the tumor of the gum is usually
present and the general appearance of the swelling is quite character-
istic after the case has reached a stage in which it could be mistaken
for that disease. In some cases it might be confounded with subperios-
teal inflammations, but these are more liable to be mistaken for alveolar
abscess when they occur on the maxillary bones. Indeed, I have seen
some cases in which it was very difficult to determine whether the be-
ginning of the trouble was with the periosteum covering the bones or
in the sockets of the teeth. The case from which Fig. 503 was made
occurred under my own observation. I saw it early, and it was clearly
a case of subperiosteal inflammation having its beginning just below the
infraorbital foramen. Pus had evidently formed there, but the patient
very positively refused to have anything done; and when I saw him
again, a few days later, there was extensive necrosis that carried away
four teeth with a considerable piece of the superior maxilla, laying open
·
944
DISEASES OF THE PERIDENTAL MEMBRANE.
the antrum of Highmore. The discharge of pus was at the free margin
of the gum; and if I had not seen the case early, I should certainly have
taken it to be one of alveolar abscess. Except as a matter of accuracy,
this error would then have been of no importance; for it could have
made no difference in the treatment.
Subperiosteal inflammation occurring
under the temporal muscle,
especially if it be in the temporal
fossa, will usually discharge its
pus into the mouth near the last
molar tooth of the upper jaw, or
it will appear on the face from
under the zygomatic arch; and
if the case be somewhat chronic,
it may be mistaken for alveolar
abscess. The temporal muscle is
covered by a very dense fascia
which prevents the pus from com-
ing to the surface, and the fibres
of the muscle will carry it in the
direction indicated. In two cases
I have met with there was very
lit-
tle pain complained of in the tem-
poral region; both were fatal from
the resulting necrosis of the skull.
In chronic abscess discharging at any distance from the teeth, as on
the lower margin of the lower jaw or on the side of the neck, the
chances that the pus may come from some small point of necrosis
should always receive consideration. I have twice seen such cases, in
which the discharge was in the same region in which we usually find it
when, starting from alveolar abscess, the pus has burrowed into the
tissues of the neck; in both of these cases the discharge was found to
be caused by necrosis of the ramus of the lower jaw. In the search for
the source of the discharge the condition of the teeth will often materi-
ally aid us. It must always be remembered that it is not necessary
that a tooth be decayed or in any wise painful in order that it may be
the subject of chronic abscess; but it must have lost its pulp, and there-
fore will not respond to the tests for vitality in that organ. Such a
tooth, also, will very generally show a change of color-will be a shade
or several shades darker than the teeth that are healthy. These points,
in those cases in which the teeth are all seemingly good, will generally
serve to indicate the affected tooth and aid materially in tracing the pus
to its source. It must be remembered, also, that almost precisely the
same symptoms may arise from impacted teeth; discharges from these
very generally occur on the face if they lie deep in the bone. I have
seen quite a number of these cases, in which the only way of distin-
guishing them from the more common form of alveolar abscess was
the tracing of the sinus and finding in this way the impacted teeth.
The TREATMENT of alveolar abscess in the vast majority of cases pre-
sents but little difficulty. It consists in the simple cases in the removal
of the irritant that has acted as the cause-i. e. septic matter from the
FIG. 503.

DUD
Loss of Bone and Teeth from Subperiosteal Inflam-
mation.
TREATMENT OF ALVEOLAR ABSCESS.
945
pulp-chamber of the affected tooth. If the case has occurred at the apex
of a worthless crownless root, or if, from any cause, the tooth cannot be
rendered useful if retained, the proper course is to extract at once, which
ends the case. This is true though the abscess be of long standing and
though the pus may have burrowed to a great distance. Even in those
cases in which the pus is discharging on the side of the neck no other
treatment is necessary, provided, always, that there are no spicule of
necrosed bone to keep up the irritation. Except in rare cases, extrac-
tion is not necessary to a cure; and if the tooth is otherwise in a con-
dition to be useful to the patient, extraction would be very improper
M
treatment.
In acute cases it is generally best to evacuate the pus as early as pos-
sible and then allow the parts rest until the extreme soreness of the tooth
has somewhat abated before undertaking further treatment. I have
already detailed the treatment of apical pericementitis. Alveolar
abscess is merely such a case gone on to the formation of pus; there-
fore the treatment must be varied to suit the different conditions that
have arisen. If no tumor has as yet formed on the gum over the root
of the affected tooth, and the condition as to soreness will allow of its
being done, the pulp-chamber should at once be opened and the canals
of the root cleared of their contents, in order to allow the pus to escape
through the tooth. This course is generally better than to make an
opening through the outer lamina of bone with instruments; for, as a
rule, the pus will escape by way of the pulp-canal sufficiently well for
all practical purposes. If the pus does not escape at once on opening
the pulp-chamber and root-canals, a delicate instrument should be passed
through the apical foramen, in order to remove any hindrance that may
be lodged there. In a minority of cases the pus will not escape by
this route, although the apical orifice may be open-for the reason,
probably, that some part of the tissue of the apical space covers the
foramen as a valve, preventing outflow. In case the pus escapes read-
ily in this way, it should be allowed some time-from half an hour to
two hours to discharge, and then some disinfectant should be placed in
the pulp-canal on a pledget of cotton and the cavity sealed so tightly as
to exclude saliva. After this, if found necessary, the tooth may be
opened from time to time for the discharge of pus that may accumulate;
but in the majority of cases this will not be required. Such cases will
usually heal at once or within a short time without other treatment. So
general is this that it has become my habit to dismiss these cases for a
week or ten days, advising the patients, however, to consult me imme-
diately if they have a return of pain; and I find that it is only occa-
sionally that anything further is required, the case being well at the
next visit of the patient. If pain should recur, it is because more pus
has collected, and all that is necessary is to open the tooth, discharge it,
and again treat as before.
In case the pus cannot be discharged in this manner, an opening to
the apical space should be made as directed in the treatment of apical
pericementitis and the pus discharged in this way. It is best in this
class of cases to place in the opening made in the gum a pledget of
cotton, which should be moistened in a 95-per-cent. solution of car-
VOL. I.-60
Kad
946
DISEASES OF THE PERIDENTAL MEMBRANE.
bolic acid. This will prevent the wound from closing and save the
necessity for another operation should the abscess not heal at once.
In those cases in which the external lamina of the bone has already
been penetrated by the burrowing of the pus and a tumor is present on
the gum over the affected root, it is best to discharge it at once with the
bistoury, and if the tooth is very sore-which is almost always the
case-not to open the pulp-chamber until the soreness has somewhat
abated. In this case it is especially necessary to place something in the
opening in the gum to keep it patulous, for the fistula should not be
allowed to close until the pulp-chamber has been opened and the root-
canals cleared of offensive material. Usually, after two or three days
the soreness will have so moderated that the pulp-chamber may be
entered without very much pain. This should be done as early as
practicable and the root-canals properly disinfected, after which the
opening in the gum should be allowed to heal. This class of cases,
when they occur in patients of reasonably good health, heal with great
facility. It is not unusual for cases in which the intense swelling of the
parts has caused the utmost distortion of the features, accompanied with
the most intense pain and fever, to be to all appearance perfectly well
in a week or ten days, while some of the milder forms are, so far as
pain and soreness are concerned, well within a day or two.
Constitutional treatment in the graver forms of acute alveolar abscess
should not be overlooked nor neglected. The nature of the affection is
not such that it can be cured by the internal administration of remedies,
and that is in no wise the object of medication, but rather to limit the
intensity of the inflammatory action on the one hand and to promote the
healing process on the other. It may also have for its object the mitiga-
tion of the pain. In very many of the cases that present themselves for
treatment the inflammatory process will have reached its height-that
is, it will begin to abate at once-on the discharge of the accumulation
of pus; and in this case nothing can be done by the use of internal
remedies to limit the extent of the inflammation. This has been an
argument against the use of internal medication. But even in the cases
stated internal medication may still save portions of bone from necrosis
by the more ready reduction of the oedematous swelling and the quicker
restoration of the normal circulation of the parts.
The duration of the inflammation is almost as important a factor in
the production of necrosis as its intensity; therefore in all cases of con-
siderable severity of the inflammatory process the local treatment should
be supplemented with an active saline cathartic as an aid in the speedy
reduction of the oedema and induration of the parts, with the view of
the quicker restoration of the normal circulation to the alveolar borders
and such other tissues as may be endangered. This treatment will also
contribute much to the comfort of the patient by reducing the duration
and intensity of the suffering. I do not insist that the cathartic should
be saline, but it should be such as will produce large watery stools and
be prompt in its action. If thought necessary, an opiate may also be
given for the mitigation of the pain. In many cases the pain continues
very severe for several hours after the discharge of the pus unless coun-
teracted by this form of medication. After the cathartic has acted it
htt
TREATMENT OF CHRONIC ALVEOLAR ABSCESS.
947
J
should usually be followed by a stimulant tonic; this should be pre-
scribed on general principles, and will vary with the individual con-
ditions of the patient. If his general health is fairly good, 10 or 15
grains of quinine in divided doses will suffice. If the patient be
anæmic, one of the salts of iron should be added; and in cases in
which, from the nature of the case, extensive necrosis is thought prob-
able, the treatment should be especially vigorous.
Áll fomentations or poultices applied to the face should be strictly for-
bidden in acute alveolar abscess, for the reason that they invite an opening
on the face; and if any softening in this direction is discoverable, the
freest opening and drainage into the mouth should at once be estab-
lished over the affected root, with the view of preventing such a result.
In this matter special care is required in cases of the second form occur-
ring in the lower jaw (Fig. 488).
If the treatment of the acute form fails of its object—the cure of the
abscess-the case soon passes into the chronic form, which will now be
considered.
The TREATMENT of chronic alveolar abscess presents, in some of its
phases, characteristic differences from the treatment of the acute forms.
There is generally no soreness or any considerable inflammation to con-
tend with. The treatment is therefore more purely local and relates
more especially to the removal of the cause perpetuating the discharge
of pus-indeed, I may say wholly to this; for if the cause be removed,
the tendency is to a spontaneous cure. Cases are sometimes presented
to the practitioner in which the systemic conditions are so depraved
and recuperative power is so low that an abscess will not heal without,
in addition to local treatment, the use of remedies directed to the im-
provement of the general health.
With reference to local treatment, chronic alveolar abscess is best
divided into five forms, according to the conditions present in the apical
space:
1st. The simple form. In this the tissue of the apical space has not
been so injured as to prevent a ready and spontaneous cure upon the
removal of the fetid contents of the pulp-chamber.
2d. Cases in which injury to the tissue of the apical space has been
so great as to prevent its taking on a healthy action readily, or in which
it has been actually destroyed over a portion of the apical end of the
root.
3d. Cases in which the tissue at the apical end of the root has been
destroyed and serumal calculus has been deposited on the denuded
portion.
4th. Septic abscess.
5th. Cases complicated with necrosis of bone.
The diagnosis of these different forms is not always easily made, for
the reason that the apical space is not accessible for this purpose without
either considerably enlarging existing openings or making a sufficient
opening artificially; and if the abscess be of either the first or the second
form-as may be expected in a great majority of cases-this is entirely
unnecessary and may do harm. All that can be gained by an exam-
ination of the apical end of the root is to ascertain if serumal calculus
948
DISEASES OF THE PERIDENTAL MEMBRANE.
is deposited upon it or to learn whether or not the walls of the alveolus
are necrosed. In case the apical opening is sufficiently large to do this
readily without very material disturbance of the parts, it may be done
at once; otherwise, the treatment should be begun with the idea that
the case is of the simple form.
The treatment of the simple form of alveolar abscess consists merely
in removing the débris from the pulp-chamber and root-canals of the
affected tooth and thoroughly disinfecting them. For this purpose the
pulp-chamber should be well opened with the drill and burr, no matter
whether the tooth be much or little decayed or whether it be decayed at
all, so that free access shall be obtained to the canals; and then these
must be well cleaned with the broach. The enlargement of the canals
in the roots of teeth with any sort of drill is not to be recommended; the
chances are that it will do more harm than good. Indeed, in those
cases in which it can be done safely it is not needed, and where it is
needed it cannot be done safely. I have seen so much harm from
this procedure that I feel that I cannot too strongly condemn it.
When the root-canals are well cleaned with the broach, they should
be bathed with a good antiseptic and a pledget of cotton moistened
with an antiseptic lotion placed in the root-canals and then the cavity
in the tooth temporarily filled, but in such a way that the entrance of
the fluids of the mouth will be thoroughly prevented. With this the
patient should be discharged for a week or ten days, to give time for
the spontaneous cure of the case. The rule is that at the next visit of
the patient the abscess will be healed. As to the medicament used to
disinfect the root-canals in these cases, I have found that it makes but
little difference what is used, so that it accomplishes that one purpose
well. Carbolic acid, eucalyptus, iodine, salicylic acid, creasote, iodoform,
and various other antiseptics, seem to answer equally well. In some
cases in which there is a large quantity of pus, and especially if it
be rather offensive in character, it is well to wash out the whole
tract of the abscess thoroughly at the first sitting. This is best done
by means of Farrar's syringe, but any other syringe with a suitable
nozzle may be used. This having been charged with the fluid, its noz-
zle is introduced as far into the canal as may be necessary, and, having
all dry, is sealed in place with a piece of warmed gutta-percha and the
contents of the syringe forced through the apical foramen and out at
the fistulous opening. The fluids best suited to this purpose are sul-
phuric ether and peroxide of hydrogen. I have used sulphuric ether
for many years, and have always been pleased with it; it cleans the
parts well and seems to have a very valuable stimulating effect on
the tissues. Since the introduction of the peroxide of hydrogen to the
profession by Dr. A. W. Harlan of Chicago I have made considerable
use of it for the purpose of thoroughly cleaning abscesses, and find it
to take a place not filled by any other drug at our command. When
introduced into an abscess-cavity, oxygen is liberated, producing an
expansion of twelve times the volume of the liquid; thus a small
amount of the drug will with its effervescence expel the contents of a
large abscess. It is for this reason especially fitted for cleaning blind
abscesses, into which a little of the drug may be forced through the
(A)
TREATMENT OF ALVEOLAR ABSCESS.
949
root-canal. After the washing is completed the pulp-canals should be
filled with cotton saturated with a disinfectant, and the cavity temporarily
filled as directed above.
In any of the forms of alveolar abscess cases will occur in which it
will be impossible to open the apical foramen and gain access to the
abscess by that route. This is always to be regretted, as the treatment
succeeds best when directed through the canals; but in such cases the
medicaments may with a fair degree of success be applied through the
fistulous opening by injection with Farrar's or other suitable syringe.
The nozzle of the syringe should, if practicable, be carried through the
fistula directly to the apex of the root.
For some years I have quite largely used the following :
1 part;
Carbolic acid (crystals), 2 parts;
Oil of gaultheria, 3 parts. Mix.
Take of Oil of cinnamon,
This I use in those cases that require a stimulant disinfectant. The
compound seems to possess properties quite different from carbolic acid.
It may be used freely on the mucous membranes of most persons with-
out the least danger of producing an eschar. Its antiseptic properties
are sufficient for use in the pulp-chamber and root-canals. But its
principal use is as a stimulant antiseptic to tissues that have lost their
tone from long-continued inflammation; hence it is especially useful in
the second form of chronic abscess. It may be injected into the apical
space without danger of destroying tissue. It may be diluted with oil
of lemon or oil of anise.
M
If after a week's time the fistulous opening should still be maintained,
or in case of blind abscess pus should appear on opening the root, the
treatment should be repeated. If the abscess does not heal in the course
of another week or ten days, it may be regarded as belonging to the
second class, or possibly to the third; and an examination may now be
made, to ascertain whether or not there is a deposit of serumal calculus.
on the end of the root. Whether this should be done or not, however,
will depend on conditions that must be decided in each case for itself.
If there is no such deposit, the case will generally heal after time is given
for the recuperation of the tissues of the apical space. A stimulating
treatment is indicated. Caustics can do no good, but, on the con-
trary, may destroy what tissue remains. It is true that such cases
will often get well after the use of caustics, but my experience is
that they will require more time than if the caustics were not
used. My observation is that too much is done for these cases by
many operators. The main thing is to keep them clean and give
them a chance to get well.
If the case does not heal within a reasonable time, the examination.
for deposits of serumal calculus should be made. An opening should
be effected or the existing fistula should be sufficiently enlarged for an
examination of the root; and if calculus be found, it should be thor-
oughly removed with suitable instruments. There is positively no
chance for the case to heal as long as any of this deposit remains. It
is better to cut away the end of the root than to leave the least trace of
翼
​950
DISEASES OF THE PERIDENTAL MEMBRANE.
the deposit. After the calculus has been removed in a satisfactory
manner the case should again be left to itself to heal, simply keeping
the parts clean. The prognosis in such cases is always doubtful; the
greater number of them will recover, but some will be found in which,
no matter what the treatment, there will be no reattachment of the
tissue to the root. This, however, is rare. When we remember that
Hunter boiled teeth for replantation, and yet obtained a union of the
pericementum to the root of the tooth, we should expect such cases to
reform the lost membrane and get well.
In the fourth class of abscesses, in which there is a discharge of a
thin, watery, and offensive pus occasionally tinged with blood, con-
nected with a more or less rapid, but marked, destruction of tissue, a
more heroic treatment is required. In these cases there is a condition
not ordinarily found in alveolar abscess. It is not kept up simply by the
escape of septic matter from the pulp-chamber of the tooth, but is a true
septic abscess, in which the poisonous material is being produced among
the tissues themselves. For a remedial effect on this the strongest anti-
septics are needed. The whole abscess should be injected with either a
95-per-cent. solution of carbolic acid, strong tincture of iodine, or
ethereal solution of iodoform. The injection should be repeated per-
haps twice within four days. The object in this treatment is to destroy
this septic condition, and thus to convert the abscess into the simpler
form; and as soon as that is accomplished the severe measures should
be suspended and milder treatment substituted. This class of abscesses
will give the most unsatisfactory results of any that are met with in
practice. There is generally a comparatively great destruction of tis-
sue, and a correspondingly long time is required for the healing pro-
In the mean time, the case will require constant care to keep the
parts in good condition.
cess.
Abscesses that are complicated with necrosis of the alveolar process
require special care in their treatment. If this lesion is discovered
early in the case, the parts should be well cared for until by the nat-
ural process of the absorption the necrosed portions are loosened; they
should then be carefully removed. I have learned by clinical experi-
ence that much of an alveolar process may be destroyed by necrosis
from inflammation without necessarily destroying the hope of saving
the tooth. Many of those cases that present a very bad appearance
heal with surprising facility with a little care. In Fig. 488 I have
represented a case in which the outer, or buccal, plates of the alveolar
process were destroyed from an alveolar abscess, with more than half
of the septum between two of the teeth; and yet those teeth are in very
good condition to-day, eight years after the occurrence. The sketch was
made at the time the necrosed portions of the bone were removed, and
as nearly as possible represents the actual condition of the case. The
treatment may be very briefly related. Before the pieces of necrosed
bone, were loose enough to be removed the teeth were found to be so
loose that it was thought best to wire them together and to their neigh-
bors, to prevent motion. The parts were kept well cleaned by use of
the syringe. As soon as it was practicable the necrosed portions were
removed. Between two of the teeth the septum of necrosed bone passed
TREATMENT OF ALVEOLAR ABSCESS.
951
so far toward the lingual side that I had some trouble in removing it
without disturbing the teeth, and in all the teeth the necrosed portion
extended over the apices of the roots. The removal being accomplished,
the soft tissues were laid in place over the roots, and maintained by a
stitch passed around the central tooth of the series. Mild, stimulating
antiseptic washes were used with the syringe daily until the discharge
of pus ceased: this was in about a week, and the case was then gradu-
ally left to itself. A short time ago this patient allowed me to pass a
small exploring-instrument in various directions through the tissues
over the site of the former necrosis, and I found the alveolar process
completely restored.
In most cases of necrosis of the alveolus where I have seen the patient
daily I have succeeded in obtaining a restoration of the part, but it
requires constant care. If the management of dressings, etc. is left to
the patient, failure will generally result, for the reason that the parts
become more or less septic, and instead of healthy granulations there
is destruction of tissue. Where, however, the necrosis is less extensive,
recovery is brought about with much more facility. In all these cases
the condition of the pulp-chambers of such teeth as have lost their
pulps should receive prompt attention, to prevent the discharge of
poisonous matter by way of the apical foramen.
In those cases discharging on the face there is not necessarily any
difference in the treatment of the abscess itself, but in the very begin-
ning of the treatment the sinus should, if its situation is such as to
make this possible, be cut off as near as practicable to the root of the
tooth and the pus directed into the mouth. The sinus will then heal
without further treatment, and the abscess is to be treated as usual. In
some rare cases there may be a spicula of necrosed bone in the course
of the sinus; this may have floated into it from the alveolus and lodged
in a narrower part, or it may have come from a slight necrosis of bone
that the pus has uncovered in its burrowings. Any such source of
irritation as this will, until it is removed, prevent the healing of the
sinus.
In the treatment of these cases many complications will arise that
will tax the ingenuity of the operator. Some time ago I found, in
a case of abscess at the root of a lower incisor, that the pus had bur-
rowed down the anterior surface of the lower jaw to the point of the
chin, though the fistulous opening was still maintained on the
gum in
the usual position. The abscess was of the second class, and did not
heal readily. I found great difficulty in preventing the pus from drop-
ping into the pocket, and, fearing that it would come through the skin,
I, after unsuccessfully trying several expedients, finally passed a bis-
toury carefully down the length of the pocket and made a considerable
cut as close to the bone as possible, laterally, on both sides of the sinus.
I then put a compress on it for two days, so arranging it as not to hin-
der the escape of the pus on the gum. This produced enough adhesive
inflammation in the parts to close the sinus at once. Afterward the
abscess healed by the slow process usual in such cases. In all cases of
this kind the ingenuity of the operator must be depended upon to over-
come the difficulties that may present themselves. No set rules to accom-
952
DISEASES OF OF
THE PERIDENTAL MEMBRANE.
plish this can be given for them, for the reason that all the conditions
cannot be foreseen; and if rules were given, the intelligent dental sur-
geon would be likely to follow methods of his own devising in each
case as presented.
The general rule is that the sinus will need no attention after the
abscess has healed. It often makes a very ugly scar; but if this is
under the chin, it will not be much exposed to view, and if on the neck.
may be covered by the clothing. If on the face, however, there will be
disfigurement; each case must be studied with the view of lessening
this as much as possible. The cord formed by the healing and contrac-
tion of the sinus is always somewhere attached to the bone, and it will
often draw in the tissues in such a way as to be very unsightly. This
is especially the case when the abscess has pointed just under the prom-
inence of the malar bone in front of the attachment of the masseter
muscle. In this case, if the finger is thrust into the mouth and a pull
made outward against the scar, the round cord by which it is held down
to the bone will be plainly felt. Now a tenotomy-knife may be passed
in through the tissues of the cheek, and while a strong pull is being
made on the cord it may be cut off where it is attached to the bone;
this will allow the cheek to come out to its proper fulness at once.
Then a pin may be passed through the central part of the scar and left
lying against the face, to keep it
in that position until the wound
heals. This little procedure will
greatly diminish the deformity,
but will not entirely eradicate the
scar (Fig. 504). In some such
way most of the cases where the
scar is badly drawn inward may
be improved.
FIG. 504.

Finally, the case must be put in
condition to prevent the recurrence
of abscess. To do this, the con-
tamination of the tissues of the
apical space with poisonous mate-
rial from the pulp-chamber of the
affected tooth must be rendered
impossible; this is effected by fill-
ing the root-canals and pulp-chamber with some enduring material.
The requirements of a material for this purpose are threefold-first,
that it shall be enduring, that it shall neither absorb moisture nor be
subject to solution in any of the fluids of the body; second, that it shall
be unirritating to tissues with which it may be brought in contact;
third, that it shall be capable of such manipulation that the root-canals
can be perfectly and solidly filled with it. Many materials have been
proposed from time to time for this purpose, but of them all only two
seem to me to possess these qualities in a sufficient degree to recommend
them for the purpose; these are gold and gutta-percha. The gold meets
the first two requirements most perfectly, while the gutta-percha—
which was first recommended for this purpose by Dr. O. A. Glidden at
Illustration of Operation for the Remedy of Scar
on the Face caused by Alveolar Abscess. (See
p. 940. Compare with Figs. 490, 495, and 496.)
DISEASES OF THE PERIDENTAL MEMBRANE, ETC. 953
the meeting of the Illinois State Dental Society of 1873—is superior to
it in the last. It seems well demonstrated that either of these materials
can be so manipulated as to make a thoroughly solid root-filling, but in
very delicate and tortuous canals the gutta-percha can be more easily
forced to the apex than the gold. When the pulp-chamber and root-
canals are solidly filled with either of these, the possibility of the forma-
tion of septic matter within them is at an end. The methods of
manipulation by which the filling is accomplished belong rather to the
operative department, and their consideration in detail here would occupy
too much space.
The time at which a permanent root-filling should be made is an
important consideration which must depend on the judgment of the
operator in each individual case. Except in some peculiar cases, the
healing of the abscess should be assured before the filling is undertaken :
it is best that the abscess be actually well. When the operator is as-
sured of this, the sooner the root is filled, the better. In those cases in
which the apex of the root is cut away in order to remove from its dis-
tal side the last traces of a deposit of serumal calculus, it is probably
best to fill the root at once, for the reason that the foramen may be cut
to a point where it is rather large; if the root is at once filled, any
material that is forced through into the apical space can readily be
removed and the end of the root made smooth. Otherwise than in
some such case as this the filling of the root before the abscess is well
is not to be recommended. The principal reason for delay is the fact
that the best means of treatment is through the open root-canals; there-
fore this avenue should not be closed until the operator is assured that
it will no longer be needed.
DISEASES OF THE PERIDENTAL MEMBRANE HAVING THEIR BEGIN-
NING AT THE MARGIN OF THE GUM.
This group of diseases has generally been passed over without very
accurate description by authors who have written on the subject in past
years. They have universally been grouped together under one name
without differentiation. This name has varied with the different writers.
to such an extent that in looking over the literature of the subject we
find almost as many names as authors. Spongy gums, inflammation of
the gums, scurvy of the gums, false scurvy, diseased gums, gingivitis,
pericementitis, suppurative inflammation of the gums, pyorrhoea alveo-
laris, odontolithus, etc., are among the terms most commonly used. The
descriptions of this class of affections as given in works on dental sub-
jects have generally been very short and imperfect, and even to-day I
know of no book or writing that can be said to give a complete treat-
ment of this branch of pathology. There have, however, appeared in
the journals during recent years a number of very important papers
treating of special phases of the subject which have had the effect of
calling general attention to and of awakening interest in it. In this
work Dr. J. M. Riggs of Hartford, Conn., has very justly the credit of
having taken the initiative. Others had treated of the subject before
Dr. Riggs, but this gentleman, by repeatedly calling attention to it in
954
DISEASES OF THE PERIDENTAL MEMBRANE.
society meetings, at the same time illustrating it by clinical operations,
succeeded in awakening the general interest of the profession. What-
ever we may now think of Dr. Riggs's explanation of the pathology
of this class of lesions or of his method of treating them, he deserves
the profound gratitude of the profession for what he has done. Unfor-
tunately, Dr. Riggs has not left much in our literature on the subject,
his communications having been oral, not written. And there is but
little in the works of previous writers that will be available to me in
the preparation of this portion of the paper; but of what I find I
shall make free use, especially of what I have from time to time written
myself. The classification I have given at the beginning of this paper
may be imperfect and the growing knowledge of the profession may in
time suggest improvement, but for the present it seems to be the best
that presents itself, and I give it with the hope that it will be useful in
the future study of this very important subject-a subject that has
hitherto been neglected to an extent hardly creditable to the dental pro-
fession.
-
It has seemed to me that the time has come when the old names
should be dropped and others introduced that are more in harmony
with what is now known of the pathological conditions present in each
case. This I acknowledge to be a difficult task, but it is absolutely
necessary to accuracy. It cannot be expected that the profession at
large will have definite ideas of these diseases until we have definite
descriptions under definite names. In other words, so long as the
nomenclature and writings on a given subject are vague and indefinite,
so long will men's ideas of that subject be indefinite. The term gingi-
vitis I limit to those inflammations of the gingivæ that occur from con-
stitutional causes or the lighter forms of inflammation from soft deposits
on the teeth. It may be argued and justly—that all of the diseases
of this class begin with an inflammation of the gingivæ; but when
another factor has entered into the case, probably in its inception, it is
proper that that factor should be expressed; hence the term calcic in-
flammation, expressive directly of the nature of the cause that perpet-
uates the disease. This is seen in two forms-serumal calculus and
salivary calculus; but as these relate to the origin of the calculus
that induces the inflammation rather than to the character of the
inflammation itself, and as the two are very often blended together
in the same case, it has hardly seemed to call for a separate name.
K
In the term phagedenic pericementitis I have again expressed the
most prominent factor of the affection that is at the present time defi-
nitely determined-its destructive character. It is true that the calcic.
form is destructive, but not to the same extent. This disease is, in my
opinion, caused by a specific form of micro-organism, but this has not
been determined with sufficient accuracy to justify a name expressive
of that conception. If in the future this should be determined with
that definiteness demanded by science, a nomenclature should be
adopted expressive of the fact.
3
Gadg
The names heretofore in use have been applied to the entire group of
diseases, and among them no distinctions have been made; the most of
them are now no longer used. The term pyorrhoea alveolaris expresses
GINGIVITIS.
one fact common to all of these forms after they have made consider-
able progress, including alveolar abscess as well-a flow of pus from the
alveolus. It must be seen by all that when we come to a classification
of these affections this term loses all distinctiveness and cannot be of
use. Possibly this name might be retained as expressive of the whole
group of diseases in which there is a flow of pus from the alveolus, but
this could not be of much value; especially is it objectionable after the
use that has been made of it in the past. I therefore think it best to
drop it altogether.
FIG. 505.
Gingivitis. Before entering upon the study of gingivitis and that
group of diseases having their beginnings at the gingival margin of the
gums it may be well to call attention to the
structure and functions of the parts. What
are known as the gingivæ, or gingival margins
of the gums, are those parts of the soft tissues
that immediately surround the necks of the
teeth and are in conjunction with them—the
free margin of the gum (Fig. 505).
h
9-
The exposed surface of the free margin of
the gum is covered with a very dense squa-
mous epithelium which fits it well to withstand
the severe abrading contact with food necessary
in the act of mastication. This rests upon a i
layer of softer epithelial cells, which cover a
series of papillæ projected from the fibrous
tissue beneath as a glove covers the fingers;
the whole, when in the normal condition, rests
on the rim of the alveolus and is drawn snugly
around the neck of the tooth, forming a strong,
resistant, yet flexible, cushion to the tissues
which it protects. It is also strongly at-
tached to the neck of the tooth and periosteum
of the wall of the alveolus by radiating bun-
dles of fibrous tissue that have become known
as the dental ligament. In health this attach-
ment to the tooth is from one-eighth to three-
eighths of an inch from the extreme edge of
the free margin, varying somewhat in different
persons and about the different teeth of the
same person and the different surfaces of the
individual teeth. That part of the gingival
margin that lies in against the neck of the
tooth is of a different structure from its other
parts. Here it is clothed with a very soft,
round, or polygonal gland-like epithelium that
suggest the formation of a gland, but fails to assume the glandular
structure, though it seems to have been regarded as such by Serres.
This-which I shall call the gingival organ-emits a profusion of small
rounded cells which are always found in the saliva (Salter) and are
usually called mucus-corpuscles. It is not probable that all of these
7
Adaptat
!
e-
a
pa mga ka-
• →→→→
***********
955

*******
***********
с
cl
-b
The Gingival Border: a, enamel
of the tooth; b, dentine: e,
cementum ; d, peridental
membrane; e, epithelial
covering of the gingival bor-
der; gingival organ;
dental ligament; h, subepi-
thelial tissue; i, bony wall
of the alveolus.
!!,
956
DISEASES OF THE PERIDENTAL MEMBRANE.
are derived from this source, but many of them certainly are, for they
can be had for examination any time by passing a thin, flat-pointed
instrument under a healthy free margin of gum and transferring that
which adheres to a slide for microscopic examination. These often
accumulate in considerable numbers under the free margin of the gum,
and, mixed with micro-organisms, form the bulk of those soft cheesy
masses that to the naked eye so nearly resemble pus that they are often
mistaken for it. Indeed, Koelliker seems to have considered these cor-
puscles as a modified form of pus. They are, however, always found
in this position, and therefore must be considered normal. Still, it is a
question whether these little masses of cells or rings of cells that sur-
round the necks of the teeth should be considered glands. If so, what
is their function? At the present time this question cannot be answered
satisfactorily, the subject not having been sufficiently studied. We have,
however, some facts bearing on the question in the direction most im-
portant to the subject in hand. It is well known that certain glands
have the power of the selection and excretion of certain poisons, and in
this way of eliminating them from the system, and that in the passage,
if the substance be in large amount, hyperemia, or even inflammation,
may result. It is also known that mercury and iodide of potassium
will produce inflammation of the free margins of the gums, and Salter
has found that these cells are in greater abundance under these circum-
stances; also that the cells taken from the gingival border and submit-
ted to chemical tests after the person has taken iodide of potassium are
found to yield and are tinged with iodine. We have here, then, a suf-
ficient proof that gingivitis may occur from constitutional causes, or, in
other words, from poisons that circulate in the blood and have an elect-
ive affinity for this gingival organ. Certain medicinal agents are known
to possess this property; what other substances there may be having
similar affinities is as yet only a subject for conjecture. We can now
speak positively of mercurial gingivitis and gingivitis from iodide of
potassium. Each of these is a form of true constitutional gingivitis,
usually termed salivation because the salivary glands are excited at the
same time. Either of these forms of the disease may so extend that
it might be termed a pericementitis, and that from mercury in some
cases might take the name of any of the tissues of the mouth or face;
but this is in all cases an extension of the inflammation from the gingi-
væ, which are uniformly the point of attack. It is not my intention to
discuss these diseases further, as they are sufficiently treated in works
on general medicine, and, thanks to a wiser use of remedies, they are
now very rarely seen.
In the influences that produce scurvy we find another cause of con-
stitutional gingivitis that is unmistakable, and the course of the affec-
tion, taken apart from the other manifestations of the disease, has much
in common with the simpler forms.
S
Aside from these three well-known forms of gingivitis, a form occurs
quite often-mostly in young persons-that is of much less note and
requires only a passing notice. This is an inflammation usually con-
fined to the gingivæ, but extending to most of the teeth. The margins
of the gums become red and swollen and bleed from trifling causes.
CALCIC INFLAMMATION OF MEMBRANE AND GUMS.
957
There is often some eversion of the gum, and the pockets thus formed
are filled with the peculiar mucus-corpuscles, pus-corpuscles, and the
usual micro-organisms of the mouth. This inflammation seems not to
assume a destructive character. There is little or no separation of the
tissues from the necks of the teeth, and the difficulty is usually tran-
sient, lasting but a few weeks. In those cases, however, where there is
a disposition to accumulations of calculus or other irritating substances,
it may serve as the starting-point of a more permanent local irritation ;
it therefore requires the attention of the dentist. It will always be
favorably modified by habits of cleanliness, and will soon pass away
without other treatment; therefore the removal of the accumulations is
usually all that is indicated. Of course the patient should be instructed.
in regard to the matter of keeping the parts well cared for. Some cases
will be met with in which a brisk saline cathartic as an eliminant will
be advisable, and this may be followed by the vegetable acids with
advantage. For this purpose I have found nothing better than oranges
or lemons; indeed, in all of this group of diseases these fruits seem to
exert a very salutary effect.
There is but little doubt that simple gingivitis is often the starting-
point of the more grave diseases of the peridental membranes pres-
ently to be described. The inflamed and swollen state of the gingivæ
favors the lodgment of calculus by interfering with the natural tendency
to cleanliness which results from the unrestrained use of the teeth in
the mastication of food. This tendency is readily seen in most mouths
when from any cause one portion of the mouth is not freely used, as in
the case of a sensitive carious tooth. In such cases the effect of disuse is
generally quickly seen in accumulations of débris, if not actual deposits
of calculus, about the necks of the teeth in the region disused, with the
consequent tendency to calcic inflammation. Now, in case of simple
gingivitis, continuing for some weeks, the patient will become cautious
about the use of the teeth and will avoid those things that hurt the
gums, and therefore will not make that free use of the teeth best calcu-
lated to keep them freed from such accumulations in the natural way.
In this manner Nature's plan for cleanliness is thwarted, and the condi-
tion is prone to pass into one of calcic inflammation.
Calcic¹ Inflammation of the Peridental Membrane and Gums.-I use
the term calcic inflammation of the peridental membrane and
gums to
express that condition in which inflammation of these parts is caused
and perpetuated by deposits of calculus on the necks of the teeth. As
deposits on the teeth will be the subject of a special paper, I will not
enter into a discussion of the causes that lead to them, further than these
may depend on the local conditions. I recognize that a tendency to
calcific deposits may be a constitutional vice which is probably hered-
itary in many cases, but may be acquired. This constitutional vice may
be favored by conditions of the teeth themselves, by their form, by
irregularities in their arrangement, by the condition of the gums, as in
the swollen state found in simple gingivitis, by vicious personal habits,
A
M
In the use of the term "calcic" denoting the cause of inflammation I follow an
established usage, as seen in the terms traumatic inflammation, traumatic fever, septic
fever, etc., all of which denote the cause, not the result, of the conditions named.
958
DISEASES OF THE PERIDENTAL MEMBRANE.
such as want of cleanliness, and by the use of soft foods which require
but little use of the teeth, etc. Calcic inflammation is really one of the
most grave of the diseases of the teeth-not that it is so very difficult
of management when rightly understood, but from the great number of
cases that occur and its insidious character, by which it so often destroys
the denture before the patient is aware of the danger. Within my
observation it is causing the loss of more teeth than is caries.
subject, therefore, merits the closest possible attention.
The
This variety of inflammation is dependent directly upon the accu-
mulation of calculus upon the necks of the teeth, and presents two forms
that may appear distinct from each other or may be blended together in
the most intimate way. This relates to the source of the calculus and
the position of the deposit. One form is derived from the serum that
exudes from the tissues in a state of disease, and is uniformly deposited
under the free margin of the gum; the other is derived from the saliva,
and is deposited on the necks of the teeth close up against the free mar-
gin of the gum, but not beneath it. Any of the conditions that favor
deposits favor thus far the development of the affection. Simple gin-
givitis will in this way contribute to its development. Indeed, one
form of calculus seems to be dependent for its production upon previous
conditions of disease; this is not properly salivary calculus, but the
calcareous deposit from the serum. This I shall call serumal calculus.
So far as I know, this form of calculus was first noticed by Dr. Brown
of Georgia in an article in the American Journal (October, 1870). It
was also described by Dr. Ingersol (Ohio Journal, August, 1881) some-
what at length under the title of "Sanguinary Calculus." I have not
been able to determine that this form of calculus is characteristic of any
one form of disease; it seems to be a result of any pathological state of
the gingivæ causing them to weep a serous fluid. It is not, however,
confined to the gingivæ, but may occur on any part of the root of the
tooth, and not unfrequently is found on the apex of the root in old
FIG. 506.
FIG. 507.


a
a
Section of an Upper Molar with its Alveolus,
etc., showing Deposit of Serumal Calculus
under the Gingival Borders: a, a, serumal
calculus.
a-
a
Section of an Upper Incisor showing
at a, a a Deposit of Serumal Calculus
within the Free Margin of the Gum.
cases of alveolar abscess. Yet it occurs much more frequently than
elsewhere on the necks of the teeth immediately beneath the gingival
border (Figs. 506, 507). There seems to be in the location and circum-
Ad
SERUMAL CALCULUS.
959
stances of the deposit of this calculus on the necks of the teeth a sug-
gestion that this particular deposit may be from the secretion of the
gingival organ; there is not enough known of the matter, however, at
the present time to warrant any definite statements. It is possible that
it may be formed without previous local disease, but my personal obser-
vations do not favor this idea.
As seen in this position, the deposit is generally in the form of a very
hard brownish crust, but it is often deposited in little nodules adhering
very firmly to the neck of the tooth, and usually extending to a large
number, if not to all, of the teeth. It is in no wise limited, even in its
beginnings or in its greatest accumulations, to the neighborhood of the
ducts of the salivary glands, as is seen so prominently in the deposits
of salivary calculus. My observation leads me to the conclusion that
this deposit is determined by irritation of the gingivæ. This may be
caused by neighboring deposits of the ordinary salivary calculus, by
accumulation of micro-organisms or of food, or it may be from local
irritation arising from constitutional causes. When a slight deposit has
once taken place, it becomes an irritant which will in itself perpetuate
the disease. It seems to possess peculiar irritating qualities, keeping
the adjacent gum and lower border of the peridental membrane in a
state of chronic inflammation resulting in the continued, though very
slow, increase of the deposit. This deposit, when it is the sole apparent
cause of trouble, may be many years in accumulation before it will be
productive of serious conditions; finally, however, some ulceration of
the lower border of the peridental membrane will occur, and it will be
FIG. 508.

a
Section of an Upper Incisor showing at a a
Deposit of Serumal Calculus and Destruc-
tion of the Lower Border of the Alveolar
Wall and Peridental Membrane, with a
slight Recession of the Gum, exposing the
Calculus.
FIG. 509.
a

DAD
Absorption of the Septum of Bone and Re-
cession of the Gum between the Central
and Lateral Incisors caused by Deposits
of Serumal Calculus under the Gingivæ.
very gradually destroyed, exposing the neck of the tooth. As fast as
the membrane is detached from the root of the tooth the rim of the
alveolar wall or socket of the tooth is absorbed, and the gum recedes
with it, often exposing the brownish girdle of serumal calculus encir-
cling the neck of the tooth (Fig. 508). Sometimes this condition of
shrinkage is manifested by the subsidence of the septum of gum-tissue
that drops down between the necks of the teeth, this forming a very
960
DISEASES OF THE PERIDENTAL MEMBRANE.
characteristic mark of the progress of the affection (Fig. 509). In
these cases, as already explained, the lower border of the peridental
membrane is destroyed and the septum of the alveolus absorbed, this
allowing the gingival border to recede. It is not the gum that suffers,
so much as the peridental membrane and alveolar wall. This condition
is also frequently seen in connection with phagedenic pericementitis, but
is not so characteristic, as in this disease there is less tendency to shrink-
age of the gums. This does not occur in the same way from deposits
of salivary calculus, on account of the greater tendency to active inflam-
mation of the adjacent parts. More rarely, however, even with none
but serumal deposits, the gum will be markedly inflamed, reddened,
and spongy, and will bleed at the slightest touch. In either case pus
will be found beneath the inflamed gum and usually be seen exuding
on pressing the parts with the finger. If now the incrustations be
removed, the peridental membrane will be found intact, though in an
inflamed condition, just above the attachment of the crust, making a
strong contrast to the conditions found in phagedenic pericementitis
(presently to be described), in which the peridental membrane is de-
stroyed and deep pockets are formed extending far beyond the cal-
careous deposits that may be present. (Compare Figs. 506, 507, and
508 with Figs. 518, 519, and 520.)
As these conditions continue the peridental membrane becomes more
and more diseased; the formation of pus is more and more profuse;
ordinary salivary calculus is now deposited on the root above the rim
of brown serumal calculus, or this form may also extend along toward
the apex of the root.
Section of a Lower Incisor with a large De-
posit of Salivary Calculus impinging upon,
and causing Inflammation of, the Gum.
At this stage of the disease all the symptoms are likely to become
aggravated and there is a continual flow of pus from the sockets of the
FIG. 510.
FIG. 511.
REPA
G
Section of an Upper Molar with Deposit of
Calculus on its Buccal Surface causing In-
flammation and Absorption of the Gum
and Lower Border of the Peridental Mem-
brane and Alveolar Wall.
S


diseased teeth, these gradually becoming loosened. In this condition
that portion of the peridental membrane remaining about the end of
the tooth becomes much thickened; so that, while the tooth shakes
CALCIC INFLAMMATION OF MEMBRANE AND GUMS. 961
about in every direction, it is still held in position with considerable
tenacity. This condition of things is quite characteristic of the disease,
and even at this late period serves to distinguish it from phagedenic
pericementitis, in which the membrane around the end of the root is
usually destroyed, while remaining still intact on some portions of the
side. In this condition the teeth are irretrievably lost.
FIG. 512.
The conditions resulting from the deposit of salivary calculus are in
all of their manifestations much the same as those just described. In
this class of cases, however, the deposit is generally much more pro-
nounced in the neighborhood of the openings of the ducts of the sali-
vary glands—that is, on the lingual surfaces of the lower incisors (Fig.
510) and on the buccal surfaces of the upper molars (Fig. 511). It is
not, however, confined to these localities. The beginnings of the
deposits are almost always at these points, and as the deposit increases
it spreads to either side, finally, in many
cases, going the whole round of the den-
tal arch. Thus the deposit, beginning
on the lingual surface of the lower in-
cisors, will gradually creep in between
the teeth, and finally encircle them, and,
passing from tooth to tooth, ultimately
involve the entire set. This also may
occur in the upper jaw, beginning with
the molars of either side (Figs. 512,
513, and 514). Again, it is not un-
common to see mixtures of the two
kinds of calculus, the salivary occupy-
ing the necks of the teeth near the ducts of the glands, and the ser-
FIG. 514.

FIG. 513.
| ► ap
****-
Sectional Illustration of a heavy Deposit
of Salivary Calculus on a Lower In-
cisor, with partial Destruction of the
Alveolus of the Tooth.
umal occupying those more remote.
VOL. I.-61
Heavy Deposits of Salivary Calculus caus-
ing general Calcic Inflammation.


►
Sectional Illustration of Inferior
Incisor with Deposit of Salivary
Calculus less heavy than that
shown in Fig. 512, but with
greater Destruction of the Alve-
olus.
The salivary calculus is usually
962
DISEASES OF THE PERIDENTAL MEMBRANE.
of a light-yellow color, but is sometimes quite dark; it is much softer,
is deposited in very much larger quantity than the serumal variety, and
is much more rapid in its destructive effects. It seems to be more irri-
tating to the surrounding tissues than the serumal. No tissue retains its
health if in contact with salivary calculus; wherever it accumulates it
carries destruction. Not only this, but it is very prone to follow up its
destructive effects by fresh deposits in the space gained, and in this way
is continually on the aggressive. Yet, if the deposit be cleared away
from the teeth, the peridental membrane, just above, will be found
intact; it may be inflamed and changed in texture, but it is not de-
stroyed for any considerable distance in advance of the forming calcu-
lus. In this way the teeth are often loosened very rapidly. The lower
incisors are usually the first to suffer and the first to be lost, after which
the others, one after the other, are liable to suffer the same fate, until
the entire denture is lost.
Instances are now and then met with of very large deposits of this
calculus; I have often seen several molar teeth hidden from view by
being covered completely in by them. The lower incisors sometimes
bear a deposit greater in bulk than themselves. The destructive effects
of this calculus do not seem to depend so much on the amount of the
deposit as upon its distribution. For instance, the lingual surfaces of
the lower incisors may carry a load of calculus equal to their own bulk
and not suffer very much harm so long as their proximal and labial
surfaces are free, while a much less amount of deposit, when extending
entirely around the neck of the tooth, will cause a much greater destruc-
tion of the peridental membrane. It would appear, also, that when the
deposit takes place very rapidly in a certain position there is less tend-
ency to encroachment upon the tissues; the deposit in such cases seems
to override the tissues instead of insinuating itself beneath them and
around the root of the tooth.
C
In any case, it is not so much the deposit of calculus that is to be
feared as the continuance of that deposit in contact with the tissues; for
this it is that brings about the evil results. The gums and peridental
membrane naturally heal kindly and quickly even after very consider-
able mutilation, and will do the same after an active inflammation has
been developed by the presence of calculus; but when this continues for
month after month and year after year, a time comes when they lose the
power of recuperation: the tone of the tissue is lost and they become
incapable of returning to health. This is seen in every degree. Some
cases that look very badly will heal readily; others, only after much
careful nursing has given them time and opportunity for recuperation.
Still other cases refuse to heal so long as the teeth remain in their sock-
ets-a clear indication that the tone of the peridental membrane has
been irretrievably lost. I wish to emphasize this statement. It is not
the tooth that is at fault, as many seem to suppose, but the peculiar tis-
sue of the peridental membrane, the recuperative capacity of which has
been worn out. John Hunter boiled teeth for replantation, and yet the
tissues of the peridental membrane were found equal to the task of
uniting with their roots. Teeth have been replanted successfully after
having been knocked out and carried about in the pocket for hours.
TREATMENT OF CALCIC INFLAMMATION.
963
Can we imagine that the teeth in the mouth could be in a much worse
condition? Certainly it is not the condition of the teeth themselves
(provided, always, that they are properly cleaned), but the very low
state of the vitality of the remaining portions of the peridental mem-
brane, that renders the process of repair impossible.
TREATMENT.—The most important measure in the treatment of cal-
cic inflammation of the peridental membrane and gums is the removal
of the concretions from the teeth, and next the arousing in the mind of
the patient an active determination to keep them clean in the future.
These two measures are absolutely necessary to success; nothing can be
accomplished unless they are scrupulously carried out. But with these
two points attained success is assured in all cases during the early or
middle of the course of the disease. It should always be kept in mind
that this is purely a local affection dependent solely upon the irritation
of accumulations of calculus, and that these accumulations form the
only bar to a restoration of the health of the parts. Especially should
these facts be impressed on the mind of the patient, and he should be
made to understand that the result will depend largely upon his own
efforts. The removal of these concretions in such a manner as to assure
success is, however, one of the most difficult operations in dental sur-
gery. Another very serious difficulty standing in the way of success is
the very slack and inefficient notions that have been held in regard to
it by the profession at large. When dentists learn to regard this opera-
tion as equal in importance to, and requiring as much thoroughness as,
the filling of teeth, and when they apply themselves with the same dil-
igence to acquiring the necessary dexterity in its performance, they will
be rewarded with success; without this, success in the treatment of this
disease cannot be attained. Either of the forms of calculus is an irri-
tant, and this remains true no matter how small the quantity. The
leaving of a small portion—be it ever so small-of calculus on the side
of the root of a tooth is just as fatal to the result of this operation as is
the leaving of a small portion of carious dentine on the margin of a
cavity in which a filling is to be inserted. Absolute thoroughness is
the requirement. (For more detailed description of the operative pro-
cedures in the removal of calculus the reader is referred to the article
on Calcareous Deposits on the Teeth.)
The instruments for this operation should be formed with the greatest
care and delicacy. They should for the most part be fashioned to work
with a pushing motion—that is, they should work from the hand in the
act of removing the concretions. Curved and hooked or hoe-shaped
instruments formed to work toward the hand with a pulling motion may
be of service in the removal of the bulk of the larger concretions of
salivary calculus, but they are of inferior value in the removal of the
last portions of the deposits or for serumal calculus that is deposited.
high up under the gum. For this purpose all the hooked instruments,
no matter how delicately formed, should be discarded and slender points.
made to work with the pushing motion substituted. These should be
made of the finest steel. The points should be from one-sixteenth to
one-eighth of an inch in width, very thin-not thicker than ordinary
writing-paper-and very gradually thicken up toward the shank, so as
964
DISEASES OF THE PERIDENTAL MEMBRANE.
FIG. 515.
to form a good spring. This part of the instrument should be of a fine
spring temper to within three-sixteenths of an inch of the point, and
the remainder should be hard. The point itself should be ground.
square, and kept sharp with the hone. These should be made in a suf-
ficient number of forms, as regards curve of the spring part of the
instrument, to enable the operator easily to reach any portion of the
root of any tooth. Six or eight of these will be found sufficient for
any operation that may present itself, and the instruments have the
advantage of being easy of manage-
ment if well formed. Those known
as Dr. George H. Cushing's scalers
seem to be the best yet in the
market (Fig. 515). These instru-
ments may be passed freely in be-
tween the most crowded teeth and
reach every point where deposits
adhere, and if judiciously used
are capable of removing all in-
crustations with the least possible
inconvenience to both patient and
operator. They may be used with
both the pushing and the lateral
should be especially relied upon
motion, but the pushing motion
for the bulk of the work. At
present no rules for this can be
given that seem to me to be espe-
cially useful. The particular plans
of manipulation will depend large-
Dr. George H. Cushing's Scalers.
these scalers are well shown. All the
The forms and general character of
instruments except No. 6 are intended
to be used with the push stroke. Nos.
1 and 2 are specially intended for ap-
to the
fower incisors; they are also admirably
adapted for removing calculous depos
its below the gum between molars and
bicuspids, and from the posterior sur-
faces of the last molars. No. 2 can be
passed quite to the extremity of most
roots with less disturbance to the soft ly on the manipulative habits of
the operator.
tissues than a thicker or more rigid
instrument would cause. Nos. 3 and 4
are for removing deposits at and below
the gum between the teeth, particularly
the lower front teeth. They can also be
easily used upon the sides of the roots
At first sight the operations
seem very simple. The principal
of many teeth, being passed toward difficulty is in the finding and
the apex of the root in a line nearly or
quite parallel with that of the axis.
No. 5 is intended to be passed between
the lower front teeth at or near the
gum and then directly upward, to re-
move the deposits on the proximal
surfaces. No. 6 is a hoe, and is in-
tended to be passed quite to the apex
of the roots where a hoe is desired.
removal of the last particles of
calculus. The bulk of the incrus-
tations may be removed in a few
moments by the merest tyro, but
the removal of the last traces re-
quire a measure of skill and pa-
tience that can be developed only by the most determined effort
aided by considerable practice. But, after all, one of the most
difficult points is the obtaining of the conception of the require-
ments in its full force and completeness. The expression of
this in words is a simple impossibility; it must be learned at
the chair; by the watchful scrutiny of cases in practice; by
carefully searching out the causes of failure in individual cases;
by the finding of small scales that have prevented healing where
it was thought all had been removed; by the finding of a little
pus here and the cause of its continuance in a small particle


2
3
4.
5 6
Govt
TREATMENT OF CALCIC INFLAMMATION.
965
overlooked high up under the gum; by the finding of an inflamed point
there, and the discovery of its cause in an unremoved scale. In a word,
the proper conception of the absolute perfection required in this operation
must be learned by a careful scrutiny of one's own failures, with the deter-
mination to correct them.
In many cases there will be found small incrustations of very slight
thickness that lie so closely and smoothly to the root of the tooth that
an instrument may slide over without removing, or even detecting them
except by the most cultivated touch. These, when they occur in out-
of-the-way places hidden by the gum, will tax the patience and skill of
the most experienced operator, and it will require repeated efforts to
find and remove them. The presence of all such points will after some
days be manifested by a failure of the healing process, and they must
be searched out before the case is discharged. Generally, such scales are
dark-colored, and are readily seen if they can be so uncovered as to make
visual search available. This may be much aided and extended by the
plan proposed by Dr. Gilmer of Quincy, Ill., which consists in packing
salicylized cotton¹ under the free margin of the gum and allowing it to
remain for twenty-four hours, its expansion causing the gum to stand
off from the tooth, so that small scales may be seen. This must be
done with care and no more than the necessary pressure used, or the
tissue of the gum will be injured. If judiciously done, the neck of the
tooth may be exposed to view up to the attachment of the peridental
membrane and without causing a slough. In positions where these
plans of search cannot be made available the touch alone must be de-
pended upon. The cutting away of the gum for the purpose of finding
the last traces of calcareous deposits is in all cases to be deprecated;
such deposits should be found and removed without this, for unless the
gum tissue be in over-abundance any removal of it is detrimental to the
future usefulness of the teeth and is entirely unnecessary to the curative
process. Where there is hypertrophy of the gum, removal is judicious
treatment and will expedite a cure. It is true that cases in which no
hypertrophy exists are more easily managed by cutting away the gum
as far as it is diseased than by the more conservative method of treat-
ment, but in the calcic forms of inflammation there seems to me to be
but little excuse for this procedure, as it is destructive of tissues that
can be restored to health and usefulness, and which, when once de-
stroyed, are not readily reproduced, the result being an undue and per-
manent exposure of the root of the tooth. The plan-so much practised
of late—of removing the lower border of the peridental membrane and
alveolar wall, but retaining the tissue of the gum, while not so destruc-
tive, is entirely unnecessary in the calcic forms of inflammation, unless
the case be complicated with such a thickening of the alveolar border
as will prevent the gum tissue from approximating closely to the root
of the tooth. This is occasionally seen in old cases of serumal deposits.
Then it is only necessary to break down the prominences of the wall of
the alveolus in such a way that the tissue may assume the normal osi-
G
1 Salicylized cotton is prepared by soaking common cotton in an ethereal solution of
salicylic acid (40 grains to the ounce) and then drying it. This will irritate the gum
much less than cotton alone-or, indeed, than any other substance that I have tried.
966
DISEASES OF THE PERIDENTAL MEMBRANE.
tion. Especial care should be had in all cases to preserve as much of
the gum as possible, for upon that depends, for the most part, the
renewal of the lost tissue. The rule is that the destruction of
the gum is in any chronic case fatal to such restoration, the root
of the tooth remaining denuded as far as the gum has been de-
stroyed.
In all inflammations of the peridental membranes and gums originat-
ing in irritation from calculus, of whatever variety, or kept up by these
causes, the tendency is to speedy recovery after their removal, provided,
as has already been remarked, this is done before a certain stage of the
destructive process has been reached. This stage of the affection is
marked by a very distinct enlargement of what remains of the alveoli
of the teeth-the rim of the alveolus having already been lost by ab-
sorption-and the thickening of the peridental membrane. In this case
the teeth loosen in their sockets and the peridental membrane becomes
profoundly changed in its character and qualities. But before this time
there is little else to do than to keep the teeth clean after once removing
all the crusts. There is usually seen an increased tendency to the
growth of the fungi of the mouth about the necks of the teeth during
the healing process, and this cause alone is very often sufficient mate-
rially to retard the cure. These should be carefully removed at least
twice a day for a time, using for the purpose a soft brush and some dis-
infectant lotion; water strongly acidulated with lemon or orange, or
even water alone, will answer. The motion of the brush should always
be lengthwise of the teeth instead of across them, as is the manner of most
persons in cleaning the teeth; this point is important, and the patient
should be very carefully instructed in regard to it. The brush, used in
this way, will clean the teeth better, and at the same time injure the
inflamed gum less, than in any other way. In the greater number of
cases this is all that is required to complete the cure.
But the operator
should keep every case under his care until it is quite well, for it will
often happen that some points will need attention that have seemed to
be doing well for a week or two, and examination will show additional
calculus requiring removal.
In cases of long standing in which there has been considerable wast-
ing of the alveolus and general enlargement of the sockets of the teeth,
with thickening of the peridental membrane, still more care should be
taken with the after-treatment. Much more time will be required for
the return of the tissues of the peridental membrane and gum to the
normal condition. Indeed, the normal condition of the parts will never
be completely restored. The case will usually recover, if at all, with
more or less of the root of the tooth denuded of peridental membrane
and gum, which tooth will ever after be more liable to deposits of cal-
culus; it will, therefore, require more vigilance on the part of the
patient to keep it well after health is attained.
In many cases of calcic inflammation the tissues will be found in a
state of active inflammation, turgid, and much thickened. In this con-
dition I have found a from 20-to-30-per-cent. solution of chloride
of zinc, applied carefully about the teeth, very effective in con-
stringing the gum and removing from the tissue the condition of
TREATMENT OF CALCIC INFLAMMATION.
967
FIG. 516.
extreme congestion. This is applied to the best advantage by
what is known as Farrar's syringe (Fig.
516), by the use of which the remedy is
placed in the exact position, and in the
amount desired. This instrument, or some
instrument that possesses its advantages,
should be used for the application of any
of the remedies for this disease, except, it
may be, the milder washes with which the
patient may be entrusted. Without such an
appliance it is simply impossible to place
the remedies in the position required. The
only point at which the application of rem-
edies is especially effective is under the free
margin of the gum, and instruments must be
used by which this can be accomplished. In
these cases escharotics should not be used in
the after-treatment, except within the first
few days. Remedies of this class reduce the
vitality of the tissues to which they are ap-
plied; indeed, unless they are used for the
purpose of destroying something that serves
to keep up the irritation, such as micro-
organisms in the outer strata of partially
dead tissue, or for the complete destruction
of tissue so low in the scale of vitality as to
make this advisable, they should not be ap-
plied at all. With this end in view, it is
occasionally well to use carbolic acid full
95 per cent. in the beginning of the treat-
ment. Magitot has advised the use of
chromic acid; other cauterants also may be
used. But after one or two applications any
of these substances should be discarded in
favor of those remedies that tend more to
the stimulation of the tissues. For this
purpose there is perhaps nothing better than
the oil of cinnamon. The ordinary cinna- Farrar's Syringe for the Application
mon water makes a very agreeable wash,
but is not of sufficient strength to be very
effective. Where there is great tissue-injury, I have found the fol-
lowing an excellent remedy:
of Remedies in Diseases of the
Peridental Membrane.

[ [ [ [ ] } } } } } } } } }) } } })})})})})})
羊羊
​TINTONNELLARTAREST
Take of Oil of cinnamon,
dr. iv.
dr. iv.
Oil of gaultheria,
Carbolic acid (crystals), dr. i. Mix.
Kañu
This may be freely used on the brush, or may be made into an emul-
sion in water at the time of using, and in that way used as a wash.
This is at once a fairly good antiseptic and stimulant, and is a very
efficient remedy. The principal indication is to keep the parts clean,
968
DISEASES OF THE PERIDENTAL MEMBRANE.
and to stimulate mildly those tissues that have been in a state of inflam-
mation for so long as to have lost their tone, until they have recovered
their vigor. Any plan of treatment that will effect this will answer all
the requirements. Our materia medica contains a large number of
appropriate remedies.
In those cases of long standing in which the alveolus is so much
destroyed that the teeth have already become very loose not much can
be done (Fig. 517); the rule is that the patient will do better with arti-
FIG. 517.
*
IN LO S
+
P
w
roy the port made of the fa
K
The Alveoli irreparably destroyed by Calcic Inflammation.
ficial teeth. If, however, it is only the four lower incisors that have
become very loose-as often happens-and the remaining teeth can be
readily cured, these incisors may be secured to the others by wiring or
by slender clasps, thus keeping them moderately firm, and so fitting
them to do fairly good service, often for a long time, if sufficient care
is taken to keep them clean. They will often serve better than artificial
teeth in this position.
The general law as regards PROGNOSIS is this: If the gum covers
the root sufficiently to form an alveolus of sufficient depth to hold the
tooth with the necessary firmness, it may be expected that care and time
will restore the membrane to health and the bony parts will be suf-
ficiently rebuilt to serve the purpose of holding the tooth in its posi-
tion;
but if the gum-tissue is gone as shown in Fig. 517, there is prac-
tically no hope for a restoration. Then the continual looseness of the
teeth will in itself serve as an irritant to perpetuate the inflammation.
Phagedenic Pericementitis, or Destructive Inflammation of the Peri-
dental Membrane.-Phagedenic pericementitis is a disease distinct from
those previously described, yet it has many features in common with
them. It may have its beginning in a gingivitis that in its inception
cannot be distinguished from the simple form, or its character may be
masked by deposits of either serumal or salivary calculus. On some-
accounts it would seem to merit the name of infectious pericementitis,
but I do not regard the infectious character of the affection as suf-
ficiently well established to warrant such an appellation, and for this
reason must therefore regard the term "infectious alveolitis "-used
by Dr. Adolph Witzel of Essen, Germany-as premature. Further-
more, it seems to me that the disease is essentially one of the peridental
membrane rather than of the walls of the alveolus, as would be indi-
cated by the use of Dr. Witzel's terminology. If the disease were of
Atlan
!

PHAGEDENIC PERICEMENTITIS.
969
:
;
the bony walls instead of the contents of the alveolus, I see no reason
why the ailment should be cured simply by the removal of the teeth
certainly, if the disease were essentially of the bone, this result would
not so invariably follow. But, on the other hand, it can be readily
understood how, the disease being essentially of the peridental mem-
brane, the removal-the destruction-of this would terminate the
case. This agrees also with my observations as to the starting-point
and the order of progress of this pathological condition.
The disease under consideration consists, then, in an inflammation of
a peculiar character which results in the destruction of the peridental
membrane. This destruction, also, is closely followed by the absorption
of the walls of the alveolus; so that in the end both are destroyed. The
disappearance of the two is so nearly synchronous that it is often diffi-
cult to say which has gone first; indeed, they seem to go together. In
its least complicated form the disease is not accompanied with salivary
calculus, or calculus of any kind. It seems to consist essentially in an
inflammation-which may be acute or chronic-by which the peridental
membrane is separated from the root of the tooth and destroyed fibre
by fibre, cell by cell, very much as bone is destroyed molecule by mole-
cule in the disease known as caries. In the progress of this destruction
the membrane first becomes swollen; its individual fibres are very
much enlarged and lengthened and intermixed with an abundance of
inflammatory elements. The fibres seem first to separate from the root
of the tooth and then to melt down, but still to retain their hold on
the alveolar wall until completely destroyed. There is not necessarily
any considerable inflammation of the gums; they are generally but
slightly affected. In the chronic forms the disease is often limited very
strictly to the peridental membranes. So far as I have had opportunity
to observe its beginnings, it seems to take the form of a simple gingi-
vitis, presenting a reddening of the gingival margins about the teeth
attacked, this soon disappearing as the disease advances, or possibly
becoming less apparent on account of the more general reddening
of the neighboring gum tissue. At first there will be seen only an
irritation of the gingivæ, but after this has persisted for some time
close examination will show that the lower margin of the membrane
is destroyed here and there in such a way that a thin, flat, but dull,
blade will pass up along the side of the root farther than it should.
A destruction of the tissue of the peridental membrane has begun,
and already there is a slight pocket that contains a very little pus. This
destructive process extends gradually toward the apex of the root—i. e.
follows the length of the fibres of the membrane-and in most cases
narrow, deep pockets are formed beside the root of the tooth (Figs. 518
and 519). This may occur only at one side of the root or at two or
three points, which may be on the lingual or buccal sides of any of
the teeth, or it may attack the proximal sides-indeed, any part of the
membrane. As the destructive process extends lengthwise of the root
it also more slowly widens, often quite irregularly, extending around the
root; so that the tendency is to the destruction of the entire root-mem-
brane. It is usually very irregular in its attacks; cases are seen in
which the disease is for some time confined to one side of the root of a
wendy
Ską
970
DISEASES OF THE PERIDENTAL MEMBRANE.
1
single tooth or of two or three teeth. But the infectious character of
the affection is shown by the tendency to attack the neighboring teeth,
for in this way they are liable to fall one by one. This liability is not
FIG. 518.
FIG. 519.


C.
b
b
a-
Section of an Upper Molar showing De-
struction of its Membrane and Alveolar
Wall by Phagedenic Pericementitis: a,
deposit of serumal calculus; b, b, gum
covering pus-cavity (c, c) formed by the
destruction of the peridéntal membrane
and alveolar wall. (Compare with Figs.
506 and 507.)
a
C
·b
a
a
Illustration of a Case of Phagedenic
Pericementitis: a, a, dotted lines rep-
resenting the outlines of the roots of
the teeth; b, b, irregular lines repre-
senting the extent of the destruction
membrane and walls
of the alveolus. It will be noted that
the gums appear nearly perfect. (Com-
pare
confined to particular groups of teeth, as is the case with inflammation
from salivary calculus attacking the lower incisors or upper molars, but
seems to attack any of the teeth indifferently, no particular one being
more liable to it than others. When the disease is confined to one side
of the root, as the lingual sides of the upper incisors, the teeth are very
liable to be gradually displaced, moving in a direction from the diseased
surface; so that the teeth mentioned will slowly protrude forward. This
is probably to be accounted for by the swelling of the membrane. In
this manner the teeth may be gradually distorted as to their relative
positions. This is frequently seen in the separation of particular teeth
when the proximal sides of the roots are the points of attack.
FIG. 520.
b
More rarely the entire gingival margin of the peridental membrane
is attacked at once and all destroyed together. I have seen this, how-
ever, in but few instances, the formation
of pockets being the rule. These pock-
ets deepen and widen, and finally encir-
cle the root of the tooth, but much
oftener pass up the length of the root
to its apex before it has completely en-
circled it. When the disease is not
complicated with deposits of calculus,
it often happens that the entire apex
of the root is stripped of its membrane,
while the tooth is still held in place by
the membrane of one side of the root,
which has as yet been but little affected
(Figs. 521, 522). Even in
Even in this con-
dition the gums may have a fairly good
appearance; they will show more red-
b
a
Section of Upper Incisor showing
Destruction of its Peridental
Membrane and Alveolus by
Phagedenic Pericementitis: a,
gum-tissues covering pus-cavity
(b) formed by the destruction of
the peridental membrane and
alveolar wall.

G
PHAGEDENIC PERICEMENTITIS.
971
ness than normal and will occasionally be deeply injected, especially if
the tooth has periods of soreness. Usually there is little or no recession
of the gum, and casual observation might not detect the presence of the
FIG. 521.

The same case shown in Fig. 519 denuded of the soft
tissues to show more plainly the loss of the walls
of the alveolus. This drawing was made after
raising a semicircular flap of the soft tissues over
each root for the purpose of thorough exploration.
(See Fig. 527.)
Loss of Bone and thickening of the Borders
of the Lost Portion from Phagedenic Peri-
cementitis. Shown denuded of the soft
tissues.
FIG. 522.

disease. In respect to the outward appearance of disease, however, there
may be observed the greatest variety.
FIG. 523.
The margins of the alveolar processes usually disappear as the de-
struction of the peridental membrane advances. Whether this precedes
or follows the destruction of the membrane is often difficult to deter-
minę, but I have seen enough cases in which it was clearly demonstra-
ble that the destruction of the peridental membrane preceded the wast-
ing of the process to convince me that such wasting is simply a
result of the loss of the membrane, as is the case when a tooth is.
extracted. There is, however, something more than this; for effects
of disease of the process other than absorption are found. In a consid-
erable number of cases, especially those of the more chronic forms of
the disease, we may discover a definite thick-
ening of the alveolar wall at or near its mar-
gin which is clearly the result of exostosis
brought about by the irritation in the imme-
diate neighborhood. In most if not all of
these cases the peridental membrane will be
found destroyed between this thickened rim
and the root of the tooth. Furthermore, if
the gum be slit up and turned back, giving
time for the blood to be sufficiently cleared
away to get a good view of the parts, it is
readily determined that the portion of the
alveolus lying next the tooth has been ab-
sorbed. We have, therefore, an absorption
of the inner portion of the alveolar wall and
at the same time a deposit of bone on the
outer portion; so that finally the margin of
the alveolar wall is decidedly thickened in
such a way that the gum-tissue is held away
from the root of the tooth. This usually occurs on the buccal or pala-
tine wall; this, as it causes the gum to project, can be seen, and may be
b
C
GA
ROUN
-

Section of an Upper Incisor show-
ing Destruction of the Peridental
Membrane and Eversion of the
Alveolar Wall with thickening
of its Border: a, serumal calcu-
lus; o, thickened border of the
alveolar wall; e, pus-cavity.
972
DISEASES OF THE PERIDENTAL MEMBRANE.
readily felt with the finger. In these cases the absorption of the inner
wall of the alveolus is readily determined by thrusting a delicate point
through the tissues inside of this rim and exploring the widened alveo-
lus (Fig. 523). Even in slowly-progressive cases this thickening of
the rim of the alveolus is by no means constant, and then the rim
of the alveolus is simply destroyed; in this case there is often a cha-
racteristic falling away of the gum if the destructive process has eaten
away the whole septum between two teeth. The appearance is much
the same as that often seen in calcic inflammation, already described.
But many cases will be found where there is a deep pocket on the
proximal side of the root of one tooth, while the membrane of its
neighbor is uninjured; and in this case the gum will usually be sup-
ported in its position by a lamina of bone that will remain next to the
sound membrane and may appear complete
(Fig. 524). The thickening of the rim of
the alveolus is usually very irregular and
but rarely fully encircles the tooth. It may
border the destructive process in any posi-
tion, and may sometimes be seen bordering
a deep pocket over which the whole thick-
ness of the alveolus is destroyed (Figs. 521
and 524); in this way oddly-shaped prom-
inences of the alveolus are occasionally seen.
FIG. 524.
Loss of the Bony Wall of the Alve-
olus and thickening of the Bor-
ders of the Lost Portion from And, as the destructive process is going on
It
Phagedenic Pericementitis.
will be observed that only half
of the septum between the two
bicuspids is destroyed; the peri-
dental membrane of only one of
the teeth having been attacked,
the bone immediately adjacent
to the sound membrane is main-
beneath this thickening of the bone, there
will often be found jagged prominences that
will in themselves interfere with the healing
process if they are not removed at the be-
tained. Also note the separation ginning of the treatment. This thickening
of the teeth. (Compare with Fig.
528.)
of the alveolus is not seen in the cases that
progress very rapidly. The destruction of
bone in these cases seems to be a process of absorption rather than
molecular necrosis, and is in part the result of the pressure caused by
the swelling of the membrane in its inflamed state and partly from the
condition of irritation of the membrane causing it to take on an absorp-
tive action. I have seen but few cases in which actual necrosis of the
alveolar border could be determined-so few that I must regard this
condition as resulting from some accidental condition not necessarily
pertaining to the disease.

<<
A
M. Magitot has spoken of absorption of the roots of the teeth in
connection with this disease; I had not seen this until recently. Within
the past year I have met with two marked cases, in which, so far as I
am able to determine, the absorption was due to the irritation of the
membrane. It seems evident from the nature of the affection that
this would occur but rarely. The membrane is first separated from
the root, and absorption of that part of the root could not take
place afterward, for the reason that the pus would prevent the contact
of the living tissue. I have expected trouble from the absorption
of the roots after healing, but as yet have met with no cases. The
absorption of the alveolar wall is easily understood, for the living tis-
PHAGEDENIC PERICEMENTITIS.
973
FIG. 525.
sue usually remains in contact with it—at least, for a considerable time
-and even when it is entirely denuded it contains within its bony
structure the elements necessary to bring about its absorption. How
much of the eversion of the wall of the alveolus may be due to the
pressure caused by the swelling of the membrane is hard to determine.
In some cases that I have recently studied very closely I cannot account
for the eversion in any other way, impossible as this seems at first
In one I made a
glance. All of these seemed to be acute cases.
very critical examination after slitting the gum and laying it off from
the bone. I found the width of the space between the root of the tooth
and the bone to be three-sixteenths of an inch. The shape of the space
is shown in the drawing (Fig. 525). In
this case there had been no complaint of
trouble in this locality dating back more
than two weeks, and I had carefully exam-
ined the mouth six weeks before without
discovering anything of this nature. Two
years before, I had treated this patient for
phagedenic pericementitis affecting a num-
ber of the upper teeth, and ever since had
kept watch of it to note the progress of the
reformation of the alveolar walls lost at that
time, some of which are as yet represented
only by soft tissue. My own observation,
together with the statements of the patient,
would indicate that this eversion had oc-
curred within the space of two or three
weeks. There had been considerable pain
for about a week; and when I first saw it,
the gum was inflamed and swollen and pus
was discharging freely from under the free
margin. I cut out the everted portion of
the bone, and after washing thoroughly with peroxide of hydrogen in
which 1 grain of bichloride of mercury to the ounce was dissolved I
stitched the gum back snugly about the neck of the tooth, and it healed
almost as readily as an incised wound. This case seems quite novel
and if it had not occurred in a mouth that had previously been infected
with phagedenic pericementitis, I might have passed it by for the time
as an abscess occurring from some accidental cause.
The other cases
of similar character that I have seen have not run so rapid a course.
;;
The following case may be regarded as representative of the most
acute form of this disease. About one year ago Miss D., a teacher,
called on me for advice, saying that for three months she had had pain
in the teeth of the right side of her mouth which came on every week
or two, would last two or three days, and then subside. The pain was
not very severe at any time, but radiated more or less to the check, malar
process, and temple. At these times the teeth on the affected side were
sore to the touch and she was not able to chew on that side of her mouth,
and latterly some of the molars were sore almost continuously. An
examination of the teeth revealed no decay. The eye detected a pro-

a
-b
Acute Pericementitis with Eversion
of the Alveolar Wall: a, swollen
gum, which is raised above its
normal position on the crown of
the tooth; b, everted alveolar
wall; ; c, pus-cavity, which also
appears to contain fibres of the
peridental membrane clinging to
the wall of the alveolus.
974
DISEASES OF THE PERIDENTAL MEMBRANE.
nounced hyperæmia of the gums about the molars of the affected side,
especially of the upper jaw-not particularly of the margins of the
gums, but extending over their entire buccal surface. The gums, how-
ever, fitted properly to the teeth without any sign of shrinkage. The
teeth showed signs of good care; there was no calculus or other accu-
mulation to be seen about them anywhere. The second upper molar
had too much motion in its socket, but would not be called very loose.
Taking a thin, flat scaling-instrument, I passed it up under the free
margin of the gum of this tooth, and found the peridental membrane
completely destroyed over the entire surface of the buccal roots. By
passing a small needle-like exploring-instrument through the tissues in
various directions I found that the entire buccal wall of the alveolus
was gone, and also much of that part of the bone between the buccal
and palatine roots. The third molar had a narrow, deep pocket at the
posterior part of the buccal surface. About the first molar there were
two pockets, which, taken together, almost encircled the tooth, but were
not very deep. The first bicuspid had a deep, narrow pocket extending
up two-thirds of the length of the root. On the buccal side, extending
around to the proximal side of the anterior root of the lower first
molar, there was a pocket extending almost the length of the root, with
a corresponding loss of bone. There were a few other points of attack
of less note in other parts of the mouth. By reference to my records
I found that I had not examined the lady's mouth for fourteen months.
I had made a large number of fillings for her in the years past, and had
known her as a very careful patient. I feel very certain that there
could have been no beginning of this disease prior to my last examina-
tion of the mouth, therefore all of this destruction had occurred since
that time. The patient had noticed it only three months before. I
extracted the upper second molar, and then found that the only part of
the peridental membrane that was perfect was that of the palatine side
of the palatine root; all of the membrane was destroyed but this. No
salivary or serumal deposits whatever were found upon the tooth or its
root. The remaining teeth were at once put under treatment, and
by the use of antiseptic stimulants a cure was readily effected, with
complete restoration of the membranes.
In another instance a lady came to me with one of her bicuspids in
her hand. She said that on account of its apparent looseness she had
called the attention of her dentist to it only a month before, and had
been informed that no disease could be found. Two days before calling
on me she had picked it out with the thumb and finger. An examina-
tion revealed the fact that there was very serious destruction going on
about the roots of a number of the remaining teeth. Usually, the gums
do not show much inflammation unless the case is complicated with de-
posits of calculus, and in this case there was so little appearance of any
serious disease that a dentist of good repute had failed to discover it,
though his attention had been directly called to it by the patient.
These I regard as the most typical cases of the acute form of the dis-
ease when not complicated with deposits of calculus. The rule is that
the progress is slower and there is more appearance of disease to be seen
in the neighboring parts than in the cases just cited. I have one case
but
PHAGEDENIC PERICEMENTITIS.
975
now under observation that for five years I have been watching without
using anything more than a little palliative treatment. When I first
observed it, it was in its inception, and I have had the opportunity of
frequent examination; and, fortunately, there has been only very little
salivary calculus to complicate the case, and this is confined to the lower
incisors. In this time eight teeth have been lost, and some others are in
a very precarious condition. Soreness of the affected teeth comes on at
irregular intervals, lasting a few days at a time and then passing away.
This is common to the most of these cases, though I have seen a number
that had made considerable progress without any complaint of pain at
any time.
FIG. 526.
A class of cases occur on the lingual sides of the superior incisors that
seem rather different from the usual types, and yet are evidently of the
same nature. They are generally compli-
cated with serumal deposits on the necks
of the teeth, and I think occur oftenest
in those persons that breathe mostly
through the mouth. They have generally
been rather persistent. Fig. 527 is a sec-
tional illustration from one of these. The
gum is usually thickened from the inflam-
mation of its tissue and on account of the
loss of the alveolar wall recedes, exposing
more or less of the roots of the teeth. The
teeth are often protruded to such an extent
as to render them unsightly. They are
usually very slow in their progress, and
are apt to have serumal deposits extending
high up toward the apex of the root.
Thus far I have spoken mostly of that
class of cases that have not been complicat-
ed with deposits of salivary or serumal cal-
ulus. This may be said to be the simplest
form, but it is not the least destructive.
one, for I have seen the peridental membrane destroyed as rapidly
without deposits of calculus as with them. Indeed, so far as the results
are concerned, the presence of calculus seems to make but little differ-
ence. The great majority of the cases are complicated with these deposits.
The rule is that we find nodules of serumal calculus under the margin
of the gum even though the mouth has been well cared for; and if there
has not been good care as to cleanliness, there will usually be deposits
of salivary calculus also. When this occurs in considerable quantity,
the appearance of disease becomes much more apparent because of the
greater inflammation of the gum-tissue caused by the calculus. Here
we have, in fact, the two diseases existing together-calcic inflammation
from the deposits of calculus, and phagedenic inflammation farther up
toward the apex of the root of the tooth. It is evidently this dual form
so often presented by these affections that has so long delayed the recog-
nition of the phagedenic variety as an independent disease. Every one
who has had any considerable experience in the treatment of this class

HHAB
P
a
-b
Phagedenic Pericementitis compli
cated with Serumal Calculus on
the Lingual Surface of the Upper
Incisors (sectional view): a, ser-
umal calculus; b, inflamed and
thickened gum that has fallen
into the space made by the loss
of bone, exposing a part of the
serumal calculus; c, pus-cavity.
976
DISEASES OF THE PERIDENTAL MEMBRANE.
of cases must have noticed the great differences they manifest in regard
to healing after the removal of the calculus. This is not to be explained
in all cases by imperfections in the performance of the operation. A
certain minority of the cases will not heal, no matter how perfectly this
is done; but the turgescence of the gum will diminish while the dis-
charge of pus continues and the destructive process is still in unabated
progress. This is the one fact that has so discouraged the profession
with the treatment of these cases. It often has happened that the cases
that promised the best results have proved the most rapidly destructive;
it thus becomes a matter of the greatest importance that we be able to
determine whether we have in a given case only an inflammation of
the gums from deposits of calculus-calcic inflammation-or whether
there is in addition a phagedenic inflammation of the peridental mem-
brane. Our prognosis will be far more favorable if we determine that
we have only a calcic inflammation to deal with. The absence of pock-
ets extending up beside the roots of the teeth above the deposits of cal-
culus (toward the apex of the root) is the surest indication of the absence
of the phagedenic form of the disease. If this disease is not present, it
will be found, when the last of the salivary calculus is removed, that the
peridental membrane is intact just above-that is, it is attached to the
root of the tooth. There are no points where the peridental membrane
is destroyed much farther than the calculus has extended. The calcu-
lus may, however, have extended so far as to cause the loosening of the
teeth, and thus bring about their loss. In this case there is usually far
more wasting of the tissue of the gum than in phagedenic pericementi-
tis, and there is usually, perhaps generally, a peculiar thickening of the
tissue of the peridental membrane at the apex of the root-the tissue of
the apical space-which holds the tooth quite firmly and yet allows it
to shake about in the remains of the socket. This condition is quite.
uniformly absent in phagedenic pericementitis; so that the tooth drops
from its socket, often almost without effort, though it has not seemed
very loose-that is, did not shake about much in the remains of the
socket. This difference is quite characteristic.
Mag
If the disease is phagedenic pericementitis, we will, on the other hand,
when the calculus is cleared away, find that the peridental membrane is
destroyed at particular points much farther than the calculus has extended
on the root of the tooth, forming the pockets I have described, and the
wall of the alveolus, instead of being destroyed as a whole, is destroyed
somewhat in the form of fissures extending toward the apex of the root;
or it is only over a portion of one of the surfaces of the root, leaving
angular prominences of the bone that are often unduly thickened, as
though the margin of the bone was everted. In the final loosening of
the tooth it will usually be found that it is at last held by a portion of
the membrane of one of its sides, the membrane over the apex of the
root having been destroyed. These differences, as they are closely
studied from day to day in the examination of the cases that present
themselves for treatment, become quite characteristic and afford a pretty
reliable ground of diagnosis. I have given these points at some length
for the reason that they have been so generally overlooked by the
profession.
ETIOLOGY OF PHAGEDENIC PERICEMENTITIS.
977
It may here be said that cases occur in which the usual types are
variously combined, and which cannot very certainly be assigned to
either one or the other class. These will generally be old chronic
cases of calcic inflammation which have been in progress for many
years, and in which the gum tissues have been brought to so low a
state of vitality that they no longer resist the encroachments of the
ordinary micro-organisms of the mouth and are continually invaded
by them. In these cases some wide pockets may be seen by the side
of the roots of the teeth, but there is a more general wasting of the
tissues and a more dilapidated appearance of the whole apparatus of
mastication. In this class of cases it is common to see nearly all of the
teeth loose--perhaps very loose-at one time, none, or very few, having
been lost, all being held by the thickening of the tissues of the apical
space. This state of things is characteristic of the last stages of general
calcic inflammation of the peridental membrane and gums, and is sel-
dom or never seen in the phagedenic variety.
K
Another point should not be overlooked. It sometimes happens that
a case of alveolar abscess simulates the form of phagedenic pericemen-
titis so closely as to cause a mistake in diagnosis. In this case an
abscess occurs at the root of a tooth from the previous death of the
pulp and consequent apical pericementitis, and the pus, instead of being
discharged by any of the more usual routes, eats its way along the side
of the root and is discharged at the margin of the gum. In this
In this process
the peridental membrane is destroyed over one side, or a portion of the
side, of the root, forming a narrow pocket in some cases very much
resembling the very deep pockets of phagedenic pericementitis. If in
such cases it is remembered that when pockets of such magnitude are
formed by the disease in question there are very sure to be other points
of attack in the neighborhood, it will do much to clear up the diagnosis.
The absence of these should always rouse a suspicion that the case may
be one of alveolar abscess and lead the inquiry in that direction.
Of the ETIOLOGY of phagedenic pericementitis we have no very defi-
nite information. It seems most probable that the disease is caused and
maintained by the presence of some peculiar fungus or form of micro-
organism and that it is infectious. Some years ago I thought I had
detected a form of fungus that stood in a causative relation to it, but
further study has placed the matter in such doubt that I prefer to con-
sider it as not proven. Others have also pointed out a seeming causa-
tive connection of certain forms of micro-organisms with the disease.
W
¹ International Medical Congress, London.
VOL. I.-62
God
1
Dr. Arkoevy of Buda-Pesth says: "There constantly occurs a cer-
tain fungus-formation which I find in close connection with the wasting
of the alveoli and gingival margin, as well as the subsequent loosening
of the teeth; it is quite different from leptothrix buccalis, although it is
in developmental relation with it." Dr. Arkoevy seems to think that
the fungus stands in causative relation to the disease. Dr. Joseph Islai,
of the same place, has also studied this fungus, and expressed a similar
conviction. Dr. Adolf Witzel of Essen, Germany, describes the disease
as infectious alveolitis" and considers it to be primarily of the alveolar
borders. He says: "We have, in fact, to deal neither with an ulceration
(6
2
2 British Journal, 1882.
We
978
DISEASES OF THE PERIDENTAL MEMBRANE.
of the gum nor with a primary inflammation of the periosteum, but with
a molecular necrosis of the alveoli, or caries of the dental sockets, pro-
duced by septic irritation of the medulla of the bone." Again, Dr.
Witzel says:
"Should you ever chance to extract a tooth at the early
stage of the disease, you will find the soft disorganization of the dental
periostcum confined to the neck of the tooth. The remaining portions
of it are velvet-like and loosened, and present a brilliant vascular
injection increasing toward the root and associated with small nodules
and lobular granulations. I have not yet examined these growths for
nests of micrococci, but I have no doubt that they are to be found not
only in the granulations, but also in the infected medullary tissue of the
interalveolar partition. In the pus which may be obtained from the
affected alveoli by pressing the gum we observe under the microscope a
countless number of micrococci and bacteria, which doubtless find in the
pockets of the gum tissue the most favorable condition for their contin-
uous development."
I have with some care repeated the observations here alluded to and
made many others of a like nature, and there can be no doubt as to the
facts of the presence of micro-organisms in these situations. All these
observations are very suggestive and show conclusively that these par-
ticular tissues are invaded by micro-organisms. My own observa-
tions, however, are not explicit in determining a single variety in these
positions, and are therefore not sufficiently definite. There is such a pro-
fusion of micro-organisms constantly found in the mouth, especially in
conditions of disease, that it is a work of the utmost difficulty to sepa-
rate them and single out that particular form which produces the mis-
chief and obtain experimental evidence of the fact that will bear the
test of adverse criticism. Until this is done in a way to satisfy the
critical demands of science it cannot be positively affirmed that this is
a disease that owes its origin to the life and growth of micro-organisms.
There are, however, other forms of evidence, which, while not so posi-
tive in their nature, may be of use in the absence of better testimony;
these also point to micro-organisms as the cause of the disease. They
may briefly be stated as follows: Those remedies that are known to
destroy micro-organisms influence the disease most favorably; indeed,
no other form of medication has been known to produce decidedly
favorable results. The complete removal of the diseased tissue will
often be sufficient to produce a cure. The presence of the disease in
one part of the mouth is generally followed by its appearance in the
neighborhood. It is observed that the disease will not flourish except
in situations in which a fungus-growth would have some form of pro-
tection against the free flow of the buccal fluids such as the pockets
formed by rather deep free margins of the gum will give; hence the
cure of the disease by the removal of all free margins of the gums.
Besides this, I have observations which, though they are not of such a
nature that I can make a scientific use of them, fully convince me that
the disease may be transplanted from person to person-that it is inocu-
lable; hence it may be transplanted to the cleanest mouths, and the
greatest care should be given to the instruments used in the treatment
of these cases, to prevent its being conveyed to others. This point is
-
FA
Cat
ETIOLOGY OF PHAGEDENIC PERICEMENTITIS.
979
The facts
certainly true whether the disease is due to a fungus or not.
I have given show conclusively that it is purely a local disease, and not
dependent upon any poison circulating in the blood of the patient or
upon any systemic disorder. I have also become satisfied that it is
in no wise hereditary, as is the disposition to the deposit of calculus ;
yet it seems likely that deposits of calculus do predispose the patient
to this disease by placing the free margins of the gums in a more
favorable condition for its propagation. Farther than this I do not
think the deposits of calculus favor its development.
In making these statements I have not overlooked the fact that many
who have written on this subject have regarded the disease as due to
constitutional causes, and that in our journal literature we have reports
of many cases in which such causes have been assigned. Among these
may be found in turn nearly all those diatheses that are obnoxious. In
these reports it is seldom that we find descriptions that will enable us to
identify with certainty a specific form of disease of the peridental mem-
brane; indeed, in most of the cases reported, the descriptions are so
vague that we are unable to say whether the particular case was a gin-
givitis from constitutional causes, a simple calcic inflammation, or an
inflammation of the phagedenic variety. For this reason the value of
most of the reports that have been made is essentially limited.
That cases of inflamed gingivæ with extension to the peridental
membrane occur from constitutional causes I have conclusively shown.
Such disease may be produced at will by the use of mercury and other
known substances, and we have every reason to conclude that such dis-
ease may be produced by agents that are entirely unknown to us circu-
lating in the blood. Until we can differentiate these forms from the
calcic and phagedenic varieties in the reports given us it is difficult,
however, to estimate the true value of the observations.
Sp
The gouty and rheumatic diatheses have been regarded as contribut-
ing to inflammations of the peridental membrane; this opinion seems
to be quite generally entertained by English practitioners whose oppor-
tunities for the observation of such cases, especially of the gouty dia-
thesis, are very abundant. In my locality this disease is rare, but
among the few families subject to it who have come under my obser-
vation disease of the peridental membrane has not appeared except in
a few cases which were clearly calcic, and which promptly returned to
a state of health without other treatment than the removal of the local
cause. As to the rheumatic diathesis, my opportunities seem to have
been sufficient; but an analysis of my cases of disease of the peridental
membrane of all sorts fails to connect this diathesis with them as a
cause.
The scrofulous diathesis seems to favor the development of any of
this group of diseases. From my personal observations I should say that
this influence is to be regarded purely as a predisposing cause-a con-
dition in which the tissues of the individual have less power of resist-
ance, and therefore more readily succumb. Anaemia and various other
disorders or conditions serve much in the same way as predisposing
causes.
The TREATMENT of phagedenic pericementitis calls for certain opera-
980
DISEASES OF THE PERIDENTAL MEMBRANE.
tions in common with the treatment of calcic inflammations. In all
cases the first thing to be done is to discover and remove any and all
deposits that may be on or about the necks of the teeth or their roots.
In the phagedenic form of inflammation this presents greater difficulties
than in the calcic form, for the reason that the deposits are often situ-
ated farther up on the roots and are more covered in by the soft tissues.
It also happens more frequently that lying close against the sides of the
roots of the teeth there will be found very thin scales, these being so
smooth that their outlines are with the greatest difficulty detected by the
touch; for this reason much care and patience is required for their com-
plete removal. This operation, however, must be absolutely complete in
order to effect a cure. This calculus, which is usually of the serumal
variety, is an irritant, no matter how small the amount, and any parts
left will serve to keep up the irritation.
As I have described the process and the instruments for the removal
of the scales in treating of calcic inflammations, repetition is unneces-
sary. I would only urge the necessity for absolute perfection in this
operation. With the removal of all deposits from the teeth the simi-
larity in the treatment in the two diseases ends, for in calcic inflamma-
tion the tendency is to spontaneous cure when all calcic deposits are
removed, but in the phagedenic forms there is no such tendency.
The further treatment is best considered under two heads-Surgical
and Medicinal. In a large proportion of the cases the surgical treatment
may end with the removal of the deposits from the necks of the teeth.
This applies to all those cases in which there has as yet been but little
destruction of the pericementum and alveolar walls and not much
thickening or eversion of the alveolar margins, and will presently
be considered.
In the graver cases surgical operations sometimes seem necessary-not
but that we may effect a cure without them, but the cure will be accom-
plished much more readily with them. When there is rapid destruction
of the tissue and a considerable portion of the alveolar wall has been
destroyed and much of the peridental membrane detached from the root
of the tooth, it is found better to cut away some parts of this with
instruments. The pericementum is in a state of molecular disintegra-
tion and the alveolar wall is undergoing active absorption. Experience
seems to demonstrate that the direct removal of a portion of these
with instruments will expedite the cure. The means of doing this
will vary greatly with the case. In cases in which the destructive
process has not been very great and the diseased parts can be readily
reached with an instrument passed up between the tooth and the
gingival margin, a hoe-shaped excavator with a broad cutting edge
or a chisel bent at an angle of twenty-five to fifty degrees may be
introduced and the margin of the alveolar wall cut away as far as
the judgment of the operator may dictate. This should usually be
carried to such an extent that the bone may be felt to become firm and
resistant to the cutting edge of the instrument. In this operation the
greatest care should be taken not to wound or injure the gingival mar-
gin. This remark applies, however, only to that margin. The soft
tissue farther up toward the apex of the root may be lacerated con-
Wi
TREATMENT OF PHAGEDENIC PERICEMENTITIS.
981
siderably without evil result; but if the gingival margin be broken
down or so injured as to cause a slough, this margin will be lost, and
will defeat our efforts to obtain a reformation of the peridental mem-
brane in its completeness. The stretching of the gingival margin by
an instrument passed through for cutting away the process or the
removal of the calculus is sometimes a serious evil. After the opera-
tion is completed the gingivæ should close around the neck of the tooth
as well as, or better than, before it was begun. The closing of the
gingival aperture in such a manner that irritating substances, and even
the saliva, may-in the main, at least-be kept out will diminish the
growth of micro-organisms to the minimum and expedite the cure. In
cases still more grave, in which the cutting away of the diseased bor-
ders of the bone cannot, without injury, be well done through the gingi-
val aperture, other modes of operating should take its place. The gums
should be cut through directly over those portions of the alveolar wall
to be removed or in such position that they will be readily reached with
the instrument. This may be in the form of a puncture through which
an instrument may be passed in several directions, or a flap of the soft
tissue may be raised as represented in Figs. 527, 528, and the tissues
FIG. 527.
FIG. 528.
**
300
Illustration of the Position and Form of Incision
through the Gum for exposing the Root of the
Tooth and injured Alveolar Process: a, incis-
ions. (Compare with Figs. 520 and 521.)
a
DOU
WADA
Incision for the Treatment of the Root
and Alveolar Process in a Case of Phage-
denic Pericementitis. (Compare with
Fig. 524.)
Ang


beneath exposed to view. In this way the gingival margin may be
saved from injury, and the denuded root of the tooth may be closely
examined for any traces of calculus or other deposits and most thor-
oughly cleaned, while the trimming of the alveolar wall may be more
perfectly done. After all is satisfactory and the wound properly
washed as presently, described the flaps should be replaced and
stitched down. In all cases the cutting of the alveolar walls should
be done in such a way that the soft tissues will lie closely against the
roots of the tooth. No spaces should be left intervening, for all such
become pockets for the growth of micro-organisms and the formation.
of pus, which invariably retards the cure; therefore it is especially
necessary that all jagged points of the bone be removed, all thick edges
be trimmed down or broken away. All eversions of the alveolar wall
should be cut off or their form so modified that no intervening space
shall be left between them and the root of the tooth. In cases of ever-
sion of the alveolar wall or thickening of its borders without consider-
able destruction of the peridental membrane, this may be cut away by a
few well-directed blows of a chisel passed directly through the gum, and
the bone so broken down that it will lie close in against the root of the
982
DISEASES OF THE PERIDENTAL MEMBRANE.
tooth. The pieces may be left in this position rather than mutilate the
gingival margin in the effort to remove them. If they become necrosed,
they will be thrown out within a few days, or will, if they retain their
vitality, become united with, and assist in the rebuilding of, the alveolar
wall. In those cases in which very deep pockets have formed extend-
ing lengthwise of the root of the tooth, with thickened borders of the
alveolar wall on either side, I have found it best to raise a semicircular
flap of the gum in order that I may reach both sides with the chisel and
pare them down in such a way that the soft tissues may lie in smoothly
against the root of the tooth. I regard the chisel as much better for
this purpose than the burr. The burr driven by the engine produces
unnecessary injury of the soft tissues in very many instances, and the
trimming of the alveolar process is usually not so evenly and per-
fectly done as with the excavator or the chisel and the injured tissues
are left in a much worse condition. Besides, there is more danger of
injury to the gingival border. The object of this operation is twofold:
first, the removal of tissues sunk so low in the scale of vitality as to be
unable to recuperate, and with them the removal of the micro-organisms
by which they are invaded; in this way the operation acts as a power-
ful antiseptic. A reasonable degree of mutilation of the subjacent tis-
sues acts as a stimulant and invites the formation of granulations for the
restoration of the lost parts; if, however, the mutilation of the tissues
be carried too far, the injury will overbalance the good results. Second,
the placing of the tissues in such position as to obliterate all interspaces,
so that granulations may be the more effective in forming reattachments
and repairing the injured parts.
SO
M
It is important that all blood-clots be removed. This is true of all
surgical wounds, and here it is doubly so, for the reason that the clot
will so generally become septic. A bloot-clot, as such, is perhaps not
an irritant, yet it is always a hindrance to the process of repair. It
never becomes organized, as was held by the older pathologists, but is
removed by a process of absorption. Granulations grow out into its
mass, and the clot disappears as they advance; therefore, even when the
clot does not decompose, considerable vital energy is expended in its
removal and the granulations are diverted from the immediate work of
connecting the different parts of the lesion. In this particular instance
the clot is almost always decomposed by the micro-organisms present
in the tissues or entering from without; therefore the parts should be
washed with a peroxide-of-hydrogen solution of bichloride of mercury
(1 grain to the ounce) in order to remove all blood-clots, and for the
further purpose of rendering the parts as nearly aseptic as possible.
Then, if a flap has been raised, it should be stitched in place. It is only
in a few of the more acute cases that we may expect the parts to unite
with the root of the tooth by first intention, but it is often desirable that
the wound through the gum tissue should unite at once; this it will very
generally do if the parts are placed well in apposition. If they are not
so placed, the fluids of the mouth are liable to wash away the granula-
tions and considerably delay the union. In order to prevent this, I am
in the habit of first, after thoroughly drying the parts, covering the
immediate wound with a bit of tissue-paper and then coating the whole
TREATMENT OF PHAGEDENIC PERICEMENTITIS.
983
1
surface with a solution of gutta-percha in chloroform; this completely
seals up the wound and prevents it from becoming septic, in addition to
the protection to the granulations. This, if desired, may also be used to
seal up the gingival margins after operations through the gingival aper-
ture, by first drying the parts thoroughly and packing the gutta-percha
around the necks of the teeth. In order to render it more secure in its
position, a wire or thread may be used to first secure to the teeth a
small piece of undissolved gutta-percha, to which the solution may be
added. This means of sealing the gingival margins would be very val-
uable if the gutta-percha would cling to the gums with more tenacity,
but it will generally hold for two days if well applied. Some effort in
this direction has been made in the way of the construction of plates to
fit over the parts, but such an apparatus is likely to do more harm by
the collection of irritating agents under it than good by preventing fric-
tion. The requirement of such an appliance is that it shall hermetically
seal the parts. After these operative procedures the further treatment
is to be conducted as recommended for the simpler cases that are treated
without other surgical interference than the thorough cleaning of the
necks and roots of the affected teeth.
-
Many cases of this disease will be met with in which operative
procedures further than the thorough cleaning of the necks and de-
nuded portions of the roots of the teeth are entirely unnecessary. If
there are no thickened or roughened margins to interfere with the con-
tact of the parts, in many cases the medicinal treatment may be begun
at once, even when considerable portions of the alveolar wall have been
lost.
Padd
Some of the cases will present no calculus whatever to be removed,
but even in these the roots should be well cleaned, for a close examina-
tion will show them to be coated with an apparent gummy material which
clings quite closely and tenaciously to the root and should generally be
loosened with an instrument. This is usually composed of micro-organ-
isms and a kind of inspissated mucus or pus. The cavity or pocket
should now be thoroughly washed with peroxide of hydrogen, for the
removal of all débris. This and all subsequent washings may be done
with peroxide of hydrogen in which a grain of the bichloride of mercury
to the ounce has been dissolved. This combination has become quite a
favorite in my hands for the beginning of the treatment, on account of
its very fine antiseptic qualities. This washing should be done with the
Farrar's syringe, or other instrument possessing its advantages.
In most cases we may go directly forward with antiseptic stimulant
remedies presently to be described, but in some of the more acute forms
the gums and soft tissues will occasionally be found much congested
and turgid with blood. In such cases, after thoroughly cleaning the
parts and washing with the peroxide of hydrogen and bichloride of
mercury, it is well to begin the treatment with the application of a 30-
per-cent. solution of chloride of zinc; this should be applied deep down
in the pockets. After one or two applications of this remedy others of
a different character should take its place, for its principal use is that of
an astringent for the reduction of the calibre of the blood-vessels, which
have become abnormally large. This remedy, however, possesses another
Walang
984
DISEASES OF THE PERIDENTAL MEMBRANE.
advantage in its antiseptic quality, which in this disease is very import-
ant. In phagedenic inflammation, whether acute or chronic, the inflamed
tissue is usually very slow in the formation of granulations for the reat-
tachment of the peridental membrane and restoration of the lost parts.
The tissue seems to have lost tone; the character of the irritant or cause
seems to be such that the tissues are lowered in their vitality, and for
this reason they require a stimulating course of treatment in order to
induce them to form granulations. For this purpose there is perhaps
nothing yet discovered that acts better than the oil of cinnamon, but,
as the destruction of the micro-organisms found growing in the tissues
is an important desideratum, carbolic acid may be added, in the propor-
tion of 1 part of carbolic acid in crystals to 2 parts of oil of cinnamon,
or the mixture recommended for the treatment of alveolar abscesses may
be used. This should be applied within the pockets regularly once in
four days.
The object of this treatment is twofold: first, the destruction of the
micro-organisms or the removal of the septic character of the disease ;
second, the stimulation of the tissues, whose vitality is low. In pursu-
ing this treatment it is especially important that the application be made
with regularity. I have pursued this plan of treatment, closely study-
ing the cases day after day by aid of the microscope, and have found
that the next day after the application of the remedy no micro-organ-
isms could be found in a mobile state, and all efforts in staining and
searching in this way for micro-organisms among the tissues have failed,
but on the fourth day they will usually be found. This plan of treat-
ment is very much like the weeding of a foul garden: we may go over
it to-day with a hoe and destroy all the growing weeds, but within a
few days young weeds will be found springing up again, and it is neces-
sary to repeat the operation. We may destroy the growing weeds with
the hoe, but we cannot destroy the seeds that are in the ground; there-
fore the hoeing must be repeated time after time for success. The seeds.
that are in the ground must sprout and the sprouts be destroyed. Just
so with our treatment in this disease: we can destroy the growing
micro-organisms with our remedy, but we cannot destroy the spores
that are in the tissues; therefore the treatment must be followed
up
week after week until the spores have been eradicated from the tissues.
Then we may expect the healing process to go on undisturbed and the
tissue to recover its normal tone. This is the theory of the treatment,
and is found to succeed. I mention the particular remedies that are
favorites in my hands, but it is not necessary that these special
ones be used. Any other remedies that may answer a similar pur-
pose-and of these our materia medica furnishes many-may be used
instead.
If the operator understands the principles upon which the treatinent
should be conducted, he should have but little difficulty in the selection
of suitable preparations. In addition to those which I have mentioned,
¹ 1-2-3 Mixture.
1 part.
Carbolic acid (crystals), 2 parts.
Oil of gaultheria,
3
(6
Take of Oil of cinnamon,
Mix.
TREATMENT OF PHAGEDENIC PERICEMENTITIS.
985
Dr. A. W. Harlan of Chicago has been instrumental in the introduction
of a number of agents that are very valuable. Among these I will men-
tion the iodide of zinc in solutions of various strength as an astringent
and stimulant, combinations of iodoform and eucalyptus, iodoform and
eugenol, iodoform and oil of cinnamon, weak solutions of chloride of
aluminum in water, 1 to 3 grains to the ounce, sanitas and eugenol, 3
parts of the former to 1 of the latter, as a germicide and tissue stimu-
lant, resorcin in solution, from 8 to 24 grains to the ounce of water, as
an antiseptic and tissue stimulant. All of these except the iodoform
combinations are to be injected with Farrar's syringe into the pockets
once in four days. The iodoform mixture may be packed into the
pockets.
Dr. T. L. Gilmer of Quincy, Ill., has used phenol camphor¹ success-
fully in the treatment of this affection. He regards it as especially use-
ful in obstinate chronic cases, and has found it succeed where other
remedies seemed incapable of preventing the continuous discharge of pus.
It is certainly a good parasiticide and its stimulant qualities seem very
excellent. Its taste will be very objectionable to some persons. It is
to be injected into the pockets in the same manner as the other remedies
named.
The washing with the peroxide of hydrogen, either with or without
the addition of the bichloride of mercury, should generally be repeated
at each sitting, for the purpose of freeing the pockets from all débris
before the application of the other remedies. Lately I have successfully
treated some cases with this alone.
In the after-treatment of all cases the greatest care should be taken to
prevent injury to the granulations in process of growth. Usually, after
a decided disposition to heal is shown, the treatment should be limited
to keeping the parts well cleaned. As a wash for the patient to use
with the brush during the treatment the ordinary cinnamon-water of
the United States Pharmacopoeia is very excellent and agreeable. Most
of my patients, however, have used the 1-2-3 mixture (page 984)
diluted to about one-half with oil of anise or oil of lemon, or without
dilution, by placing half a dozen drops on the brush once per day.
This mixture seems to be in general use among physicians of my
acquaintance for the treatment of catarrhal affections of the mucous.
membranes, especially the chronic forms, and its results are especially
good. Any disinfectant stimulant wash will be beneficial, though not
much reliance can be placed on anything of this kind, for the reason
that it cannot be applied to the diseased parts (within the pockets) by
the patient.
Just here a word in regard to the action of antiseptics may be import-
ant. A great majority of the antiseptics which are safe for use in con-
nection with living tissues are depressant of the living forces and act
directly to impair the functional activity of the living cells. For this
¹ Phenol camphor is prepared as follows:
Take of Carbolic acid, in crystals, each 3 ss.
Gum
?
Mix and heat on a sand-bath until both are melted; they combine to form an oily
liquid.
986
DISEASES OF THE PERIDENTAL MEMBRANE.
reason the use of a strong disinfectant agent in this disease cannot be
recommended, for, instead of building up, they tend to further depress
the tissues already lowered in tone; therefore in their use it is especially
necessary that some agent be combined with them to counteract this
influence. Yet this can be only partially done, because any agent
which will depress life in the form of micro-organisms will also depress
life as it exists in the individual cell in the tissues; yet experimental
study of the action of remedies shows us plainly that the different anti-
septics depress the life-force of the animal cells and that of the micro-
organisms in a different ratio. Hence there should be discrimination in
their selection. Carbolic acid possesses this depressant power in a very
marked degree. In the combination of carbolic acid with the oil of
cinnamon and the oil of wintergreen the depressant effect of the car-
bolic acid is reduced to the least degree as to its action on the animal
cells, while retaining its power over the vegetable cells. In this way
we retain that quality of the carbolic acid desired, while we remove its
undesirable properties. In eugenol we have also an antiseptic possess-
ing a minimum depressing power over the animal cells; hence it is
valuable in the treatment of this affection. In the bichloride of mer-
cury we have an agent seemingly possessing very peculiar power over
the life of micro-organisms-an agent which in solutions of 1 to 300 or
1 to 1000 parts seems to destroy the life of these low organisms without
especially influencing the animal cells with which it may come in con-
In studying the effect of these solutions I have been unable to
discover that they produce any marked local depression; this would
indicate that their depressing power is rather feeble. Carbolic acid used
in the same way would cause marked local depression. This quality of
carbolic acid renders it inapplicable, in its unmodified form, for use in
this disease.
tact.
In regard to the reparation of the peridental membrane and the
alveolar wall in this disease it may be said that repair rarely or never
takes place after the manner of healing by first intention, but is always
by granulation. Granulation may begin in the tissues overlying the
parts of the root, but the reattachment creeps in from the margin of the
injury where the peridental membrane is intact, or from the extremity
of the pocket above, and slowly covers over the denuded portion of the
root of the tooth. This is usually a slow process, but varies greatly in
different cases. In explanation of this three theories may be entertained:
First, in those cases in which the destruction of the membrane is trau-
matic or very recent it may be supposed that the cementum covering
the root has not lost its vitality, and that its cells may grow, subdivide,
and throw out processes beyond the surface of the cementum which may
join with the granulations from the soft parts. In this way we can sup-
pose the peridental membrane to be reformed, or rather reattached to
the root of the tooth by first intention. As a fact, we see this occur in
case of incision. Observation shows that this does not occur in the
healing process following this disease. Second, we may suppose that,
the cells of the cementum having lost their vitality, the granulations
from the soft tissues grow into the old canaliculi or lacunæ of the
cementum and reinhabit them, and in this way the reattachment is
MA
SPONGE-GRAFTING.
987
formed with the root of the tooth. Third, we may suppose that the
cells or granulations from the soft parts grow into the root of the tooth
and remove a portion of the old tissue of the cementum by absorption
and reform so much of it as may be necessary, and in this way reattach-
ment occurs. However it may be, it is certain that the peridental
membrane will attach itself to the root of a dead tooth, for otherwise
Hunter would not have succeeded in any case in obtaining the attach-
ment of the peridental membrane to the root after boiling the tooth,
and yet this mode of preparing teeth for the purpose of replanting was
recommended by him in 1778. In this case we must assume the reat-
tachment of the peridental membrane to be that of the second or third
of the supposititious forms above mentioned. In a large proportion of
the chronic cases, at least, of this disease, the reattachment must be in
the same way.
-
In the treatment of phagedenic pericementitis the complete reforma-
tion of the peridental membrane should be expected in all cases if the
gingival margin has remained intact. Just so far as the margin of the
gum may have receded from its normal position, just so far will we fail
of regaining the reformation of the peridental membrane-that is to
say, if a portion of the root of the tooth is uncovered, we cannot expect
a reformation of its peridental membrane at that point.
The renewal or reformation of the alveolar wall is far more uncer-
tain, yet in most cases this will also be reformed. I have examined my
cases very carefully on this point, and have found that in most of them
the alveolar wall has been slowly reproduced, yet in some in which the
reformation of the peridental membrane has been complete the alveolar
wall has not reformed during the two or three years the cases have been
under observation.
These, so far as I have yet observed, are all cases in which there was
much eversion of the alveolar wall, which was not cut away at the time
of the treatment. These observations have determined me hereafter to
cut away much more freely.
ease.
Sponge-grafting suggests itself as a means of renewing the gingivæ
and lower border of the peridental membrane when lost from this dis-
Soon after the introduction of this operation in general surgery,
a few years ago,
I made trials of it in the mouth with the view of test-
ing its efficiency in the restoration of lost parts. For this purpose very
fine sponge thoroughly freed of sand is prepared by macerating it in
dilute hydrochloric acid, to remove any calcareous material it may con-
tain. It should then be rendered aseptic by maceration in some one of
the antiseptic solutions-preferably, one that will be the most nearly
non-irritant to the granulations to which it may be applied. Thus pre-
pared, the sponge is cut to a suitable size and applied to the granulating
sore in such position, form, and quantity that it will represent the lost
part, due allowance being made for after-shrinkage of the newly-formed
tissue. The granulations will quickly grow into all of the meshes of the
sponge and completely fill every space. The growth of the granulations
seems to be stimulated and greatly accelerated by the presence of the
sponge, while its meshes seem to act as a ladder on which they climb,
so that the form of the sponge directs the form of the growth. The
MAKE
988
DISEASES OF THE PERIDENTAL MEMBRANE.
sponge, when enclosed by the granulations, is absorbed; in other words,
it is digested or dissolved in a material elaborated by the granulations
in contact with it, and in this form taken into the circulation. It is
thus removed completely, leaving newly-formed tissue in its place.
This new tissue is, of course, scar or cicatricial tissue, and shrinks very
much after the absorption of the sponge; it is therefore necessary that
the sponge should be abundantly large when first applied.
Under favorable conditions the granulations grow into the sponge
with such facility and so rapidly that it seems to offer a wonderful
opportunity for the restoration of lost parts. The sponge can be
trimmed to any form desired, so that the space left by the sloughing
of the part or tissue destroyed by accident can be very perfectly refilled.
In practice, however, some serious objections to its use have been de-
veloped, which, as they have come to be understood, have very much
modified the opinion of surgeons as to its general usefulness. In the
first place, in those cases in which the sponge-graft seems to have done
well, the new tissue that has grown is often very poor in quality and
liable to excessive shrinkage. The second, and worst, objection to its
use is that the sponge-graft is especially liable to become septic. It
seems to offer a remarkably favorable harbor for septic micro-organ-
isms, and not unfrequently non-pathogenic forms will fill the sponge
in such numbers as to do great mischief. When these pests have once
gained a foothold in the sponge, it is next to impossible to dislodge
them with any antiseptics that can be applied with safety to the granu-
lations. All this is true in any case in which the sponge-graft can be
applied, and has caused its abandonment by the careful surgeon in all
but the most necessary, and at the same time most promising, cases.
These are cases of loss of tissue on exposed parts where antiseptics can
readily be applied, and where the wound is not subject to irrigation by
any of the secretions but its own. Wounds of the hands or feet in
which the parts, wound, sponge-graft, and all, can be frequently im-
mersed in an antiseptic lotion or can be perfectly sealed by dressings
impervious to micro-organisms, offer the most favorable conditions for
the sponge-graft, while, on the other hand, the natural cavities of the
body, in which these precautions are impossible, are the most unfavor-
able positions for this procedure.
4.
S
G
In my efforts at sponge-grafting for the renewal of the peridental
membrane and gingival margin I have proceeded in this wise: After
determining by examination the size and form of the space, a suit-
able piece of prepared sponge is cut as near the required form as
practicable and placed well up into the pocket, between the remaining
portion of the gum and the root of the tooth. It should be of such
form and size that when thus placed it will cover the exposed portion
of the cementum and extend farther down on the crown of the tooth
than the gum should do, so that it may be secured in position by a liga-
ture passed about the tooth. The space for the reception of the graft
can often be improved and its form more accurately determined by tent-
ing with antiseptic cotton for a few hours before the application of the
sponge. If the case progresses favorably, the granulations will within
twenty-four hours have grown into the meshes of the sponge to such an
SPONGE-GRAFTING.
989
extent as to secure it in its position, and the ligature is no longer needed
except to retain the sponge in immovable contact with the cementum
of the root of the tooth, and thus favor the attachment of the tissue. In
a few cases this has been accomplished, but even in these but little good
has resulted, seemingly because of the poor quality of the new tissue,
while a large proportion of the cases failed utterly on account of inflam-
mation and suppuration, induced, apparently, by the foul condition of
the sponge.
In the mouth antiseptic precautions are next to impossible on account
of the flow of saliva and its constant contamination with micro-organ-
isms. Indeed, in this position the sponge cannot be kept in good con-
I have
dition for a day by any precautions thus far known to us.
thought to accomplish this by applying antiseptics very frequently, but
have uniformly failed. In many instances the contamination is only
with non-pathogenic organisms, and the constant ingrowth of the gran-
ulations will succeed in expelling the intruders even from a foul, stink-
ing sponge, but in my own hands the contamination has so often been
with septic organisms, as evinced by the occurrence of fever, that I
must regard it as in some degree an unsafe, as well as a very uncertain,
procedure. The more extended the grafts, the more care is required in
their management, especially as the danger from sepsis is in some
degree in proportion to the surface from which absorption may take
place.
mat
Gatlin
In one case a woman of about fifty-a sponge-graft was applied
for the purpose of filling in the upper jaw a gap about as large as the
last joint of the finger, the opening having been caused by exfoliation
of bone. For the first two days it seemed to do well, and the granula-
tions were rapidly filling the sponge. On the third day the patient had
some fever, and on the fourth day it was found necessary to her safety
to remove the sponge and adjacent tissues with the knife. Septicemia
was very pronounced, but after the removal of the cause the effect read-
ily passed away, and no great harm was done farther than a slight in-
crease of the gap which it was intended to fill.
Fa
C
The application of the sponge-graft for the rebuilding of the peri-
dental membrane and gum about one or two teeth cannot be regarded
as especially dangerous to the patient, but the occurrence of fever in
several cases under my observation shows plainly that it is not entirely
devoid of danger, and that the extended application of these grafts in
the mouth would not be justifiable even if the results were more uni-
formly successful than they have proved in my hands.
prog
Before closing this paper I wish to say a word in regard to the
habit of the profession in the management of this group of diseases.
It seems as yet to be the universal custom to consider them as constitut-
ing one disease, and therefore there has been no division of treatment.
The treatment which has been most strongly urged is in its surgical
aspects similar to that which I have here recommended for the phage-
denic variety, and it has been applied to all of the forms, the calcic as
well as the phagedenic. This treatment, especially in the calcic forms
of the disease, is entirely unnecessary, and even hurtful; for if the peri-
dental membrane and the alveolar wall are largely cut away, the injury
K
990
DISEASES OF THE PERIDENTAL MEMBRANE.
is unnecessarily increased. Clinical experience demonstrates that in the
calcic variety of the disease the tendency is toward a return to health,
and that the mutilation of the parts is not only unnecessary to that
end, but results in a much greater shrinkage of the gum-tissue and
increased exposure of the root of the tooth, the great evil which we
should labor to avoid; therefore I urge a close discrimination between
these two forms of disease.
AMPUTATION OF THE ROOTS OF TEETH.
In practice a considerable number of cases occur in which a valuable
tooth can be retained by the amputation and removal of one of its roots.
These are cases in which one root of a molar has lost its socket from
any cause, such as alveolar abscess neglected until the membrane is
destroyed and the gum shrunken away, or from localized calcic inflam-
mation, but perhaps oftenest from phagedenic pericementitis. In any
of these cases, if the tooth be a first molar, or a second molar with the
roots well separated and the other roots in a fairly good condition or
capable of being rendered so by appropriate treatment, the root which
has lost its socket may be cut away and the tooth will be fairly well
supported on the root or roots that remain. The greater number of my
amputations have been of the palatine root of the upper first molar,
although I have frequently renioved one or the other of the roots of
the first molar of the lower jaw. The amputation of the palatine root
of the first molar of the upper jaw is the easiest of performance, and
leaves the tooth on its remaining roots in a better condition than any
other tooth after a similar operation. The amputation is usually easily
performed with the fissure-burr driven by the engine, or a common drill
may be used to drill a row of holes through the root very close together,
after which they may be connected by cutting out the interspaces with
the fissure-burr. It is a work of but
a few moments by either plan. The
root should be cut as close to its bifur-
cation as possible; and if, after its
removal, it is found not to be cut low
enough, the remaining part should be
burred away, so that no point shall
be left. Finally, the whole surface
should be made thoroughly smooth.
Figs. 529 and 530 will give a good
idea of this. The operation involves, of
course, the filling of the pulp-canals
of the healthy roots, as is usual in
pulp-cases, and it is usually best to fill
the root to be amputated solidly with
gold before the operation of removal,
as it is then more easily done. If from
any cause this is inconvenient, with a fissure-burr a fissure may be cut
which will include the pulp-canal as it emerges from the pulp-chamber,
FIG. 529.
MA
Chronic Case of Phagedenic Pericementitis
in which the whole of the Palatine Root
of an Upper Molar is denuded of its Mem-
brane. (Compare with Fig. 530.)
W

AMPUTATION OF THE ROOTS OF TEETH.
991
and which may be filled at any convenient time after the removal of the
root.
The amputation of one of the roots of the first molar of the lower
jaw is perhaps called for oftenest from neglected alveolar abscess of the
posterior root—at least, this has been the case in my practice. The ope-
ration is performed by the same means as that described for the removal
of the palatine root of the upper molar. The operation, however, is rather
more difficult, for the reason that it is not so easy of approach in the
process of cutting, nor is the root so readily removed after it has been
severed from the crown. Generally, the root should be cut as close to
the bifurcation of the roots as possible and sloped down toward the prox-
imal surface in such a manner that when the gum is well and shrunken
as wide a space as practicable shall be left between the cut surface and
the gum, so that it may the more easily be kept clean. (See Fig. 531.)
FIG. 530.

***
$
Case represented in Fig. 529 after Treatment by
Amputation of the affected Root and filling
of the Pulp-cavity and Canals. (Compare with
Fig. 529.)
FIG. 531.
a

نلود
b
Amputation of the Posterior Root of the
first Lower Molar (the roots of the teeth
are shown by dotted lines): «, root re-
moved; b, line of gum after shrinkage
has occurred.
Usually this is most readily accomplished by passing a long fissure-
burr through between the roots and cutting backward, or, if it is the
anterior root that is being severed, forward. In most cases the lips.
can be held sufficiently out of the way to permit of this without diffi-
culty. In some cases the incision will open into the pulp-chamber; but
if this has been solidly filled before the operation, it will occasion no
difficulty.
The removal of the root after it is severed from the crown is occa-
sionally a little perplexing, yet in most cases in which this operation is
advisable the alveolus of the root is so much destroyed that it comes
away easily and may be pushed through to the lingual side with any
appropriate instrument. Occasionally it will be found necessary to
burr away some of the buccal side of the root to allow it to clear the
crown as it is turned toward the inside of the mouth. These two posi-
tions are those in which the amputation of an entire root will oftenest
be found available, but occasionally other teeth will be found on which
the operation may be performed with advantage. These operations
have uniformly been very satisfactory. A tooth that has long been a
source of continuous annoyance is rendered comfortable and serviceable.
add
The amputation of the apex of the root of any of the teeth is occa-
sionally required in case of long-neglected abscess. This is generally
992
DISEASES OF THE PERIDENTAL MEMBRANE.
made necessary by the collection of serumal calculus on the apex of the
root or by the cementum of the apex becoming so infiltrated with the
products of putrefactive processes that it becomes an irritant. In the
first case it is generally best to remove the serumal calculus if this can
be done without too much mutilation of the parts, but I have sometimes
felt that to cut off the end of the root was the least objectionable of the
two. In the second case the amputation of the apex of the root seems
to be the only remedy. The operation is usually easy of performance
with the fissure-burr. In any case in which this is justifiable there is
usually no difficulty in reaching the root, for the bone covering it is
generally destroyed by disease, so that only the soft tissues are in the
way; but any margins of bone may readily be removed with the burr
or chisel.
This operation has been recommended by various persons within the
last two decades, but in my hands the percentage of cures of old chronic
abscesses by this means has not been sufficiently great for me to recom-
mend it with much confidence or to affirm that it will be found service-
able in any considerable number of cases; it should be used as a last
resort only. The operation is usually not very painful and can be
done in a few moments, and is worthy of a trial before giving up
an otherwise valuable tooth.
ABRASION AND EROSION OF THE TEETH.
BY G. V. BLACK, M. D., D. D. S.
ABRASION.
ABRASION of the teeth is a gradual loss of their substance from
mechanical causes. It is seen almost entirely on the grinding sur-
faces of the molars and bicuspids, the cusps of the cuspids, and the cut-
ting edges of the incisors. From the time that the teeth come through
the gums they are subjected to wear through the exercise of their pecu-
liar function in masticating food. Unlike other organs of the body,
they are incapable of repairing losses which they may sustain by attri-
tion, and portions of their substance removed in this way are perma-
nently lost. If the epithelium of the sole of the foot is worn thin by
attrition in walking over a sandy way, it is soon replaced by a growth
of
young cells from beneath and restored to its usual thickness. Except
the teeth, this is true of any other portion of the body subject to attri-
tion. Even the harder structures, such as the nails, are subject to a
continuous growth through which the losses by wear are replaced. This
growth always takes place at what may be termed the root of the organ
-not upon the surface worn away-and the nail as a whole is pushed
forward to supply the portions lost by the processes of attrition. In the
case of certain animals-notably the rodents-we find the teeth con-
structed on this plan; that is to say, they are continuously-growing
organs in which the loss sustained by attrition upon the working end is
continually counterbalanced by normal additions at the growing end,
and in this way the whole tooth is continuously moved forward to com-
pensate for the loss.
Salad
This plan of compensating for loss by attrition is not present in the
Herbivora, Carnivora, or Omnivora. In these the teeth have a definite
period of formation and growth; and when this is completed, the size
and form of the tooth are no longer subject to change through vital
processes. Any loss by the process of attrition is, therefore, permanent.
A certain amount of wear is normal, and present in each individual
as age increases. When the incisors first present themselves through
the gums, they are distinctly tuberculated on their cutting edges. These
tubercles usually disappear by the processes of abrasion at periods vary-
ing from the twelfth to the eighteenth year, and the cutting edge of the
tooth assumes a straight or slightly-curved line, which it afterward
maintains. At the same time facets produced by wear appear on the
sides of the cusps of the molars and bicuspids. These facets are deter-
mined by the peculiarities of the antagonism of the particular denture
VOL. I.-63
993
994
ABRASION AND EROSION OF THE TEETH.
examined, and are, therefore, inconstant as to position. They always
occur at such points as come in contact when the jaws are closed nor-
mally. In cases of fracture and disturbance of the relative positions of
the two jaws the line of normal closure may as early as the fourteenth
year be found in reasonably good casts of the teeth by noting these facets
and bringing them together. In several instances at an earlier age I
have succeeded in doing this by making use of the facets on the milk-
teeth. In some cases the occlusion of the teeth is very imperfect, so that
but few teeth touch when the jaws are closed, and in this case there will
be correspondingly few facets.
The rapidity of wear seems to depend more on the manner of the
antagonism than upon any other circumstance. Other conditions may
modify it, such as the hardness of the teeth, which may hinder, or their
softness, which may hasten, the process. The habitual use of rough,
coarse food requiring much trituration will naturally produce more
wear than the habitual use of very soft foods, etc. These are only
modifying conditions, and not principal elements, in the predisposition
to great waste by wear. I am persuaded that the chief causative agency
consists in the rubbing of the teeth one upon another, as is plainly shown
in the disposition to the formation of facets on the teeth of young per-
sons. This wear is normal so long as these facets remain distinct and
clear; when these are lost, it becomes abnormal.
Two elements seem to enter into abnormal wear, or abrasion. The
principal of these is a fault in the antagonism of the teeth which per-
mits sliding movements when the jaws are closed. In the perfectly
normal antagonism of the human teeth sliding movements of the teeth
of the one jaw upon those of the other without parting them slightly
are impossible, for the reason that the cusps of the upper teeth fit into
the sulci of the lower, and vice versa, in such a way as to prevent it.
In the normal use of the teeth this adaptation is made more perfect by
the formation of the facets above alluded to, which are in this case
always on the slopes of the cusps; for by this process the points which
tend to hold the teeth asunder are worn down, allowing the cusps to
become more firmly seated in the sulci opposite. In this way an antag-
onism naturally good becomes perfected. If, on the other hand, the
antagonism is from the beginning very imperfect, so that the cusps of
the teeth of the opposing jaws rest the one upon the other, the case is
altogether different. This involves the formation of facets on the points.
of the cusps instead of on their sides, and in this way the cusps are short-
ened and a flat surface is established. If at first there are but few points
preventing a sliding motion of the jaws, such points are usually early
worn down by lateral or backward-and-forward motions, and all hin-
drance to these, and even to rotary motions, is removed. These move-
ments are then liable to become habitual with the person and the teeth
are worn flat, and in this condition ground down with abnormal rapidity.
This is especially liable to occur if at the same time the incisors are in
such a position that their cutting edges come the one upon the other.
In this case all restraint upon lateral, and even rotary, movement is
speedily removed; and such movements are often adopted by the indi-
vidual, with the effect of rapidly wearing away the teeth.
·
ABRASION.
995
!
In a considerable number of cases I have noted an habitual disposi-
tion to rub the teeth together-to gritting, as it is called, of the teeth-
and this seemed to be connected with abnormal abrasion. It will read-
ily be seen that a habit of this kind, once formed, may be maintained
for years, and by the abnormal wear which it occasions may tend to
remove the cusps of the teeth quite rapidly, and as these are removed
the lateral and back-and-forward movements take a wider range, until
the cusps disappear. Then the abrasion will proceed as if the antag-
onism had been faulty from the beginning. In this class of cases it is
not unusual to see the upper incisors worn from their palatine surfaces
until they become very thin, and finally only the enamel of the labial
surface is left, this breaking away, leaving a jagged edge. As the jagged
portions are gradually removed a wider range is given to the forward
motions of the lower jaw, and the wear proceeds more rapidly than
before. It thus appears that as the abrasion progresses it becomes
more rapid, and it is not infrequent to find the teeth worn down to the
gum within a very few years after they become distinctly flat, so as to
permit of rotary movement upon a given plane.
K
In these cases, if a few teeth have been lost in one jaw, the teeth in
the opposite jaw, having no antagonists, are not worn down; and if the
loss has occurred early, they will be found to have retained their cusps,
serving to show the original form of the denture. In addition to this,
they will have risen in their sockets also; so that their crowns will pro-
ject much beyond the plane of the other teeth. Occasionally irregular-
ities formed in this way become very prominent.
When flat surfaces have been formed and wear has proceeded so far
as to expose the dentine, this, being softer than the enamel, is hollowed
out in the form of a cup by the trituration of food. These cup-shaped
cavities are often of considerable depth, especially in case the enamel is
very thick and strong. They are apt to be deepest when the teeth are
about one-third or one-half worn, for the reason that on this part of the
crown the enamel is thicker than it is farther toward the neck of the
tooth. Where this cupping out is considerable, the enamel is liable to
be broken away as the wear approaches those portions about the neck
of the tooth, where it is thinner. In these cases it is very liable at such
points to split away from the dentine up to its junction with the cemen-
tum. Then the dentine wears in such a way that food slides away from
between the teeth during the process of trituration, a deep groove being
abraded; or if the loss of enamel has extended over the greater part of
one side, while it remains intact on the other, the tooth may be worn to
a wedge-shape. By such mechanism as this teeth occasionally become
very much worn and misshapen.
It is therefore characteristic of simple abrasion of the teeth that a
flat surface is formed as the leading abnormality. This results from
the rubbing away of the cusps by lateral and back-and-forward move-
ments of the jaws, either from a habit acquired or from an original
imperfection in the antagonism. As yet no way of checking this, when
it has once made sufficient progress to be noticeable, has been put into
practice. It seems probable that the judicious building of cusps at suit-
able points, so that they would interlock in such a way as to prevent the
996
ABRASION AND EROSION OF THE TEETH.
I
sliding movements, would in a large measure prevent the disastrous
results. While, in some cases that have been presented, I have thought
of doing this, I have not had quite sufficient confidence to subject my
patient to the amount of disagreeable manipulation required. Still, if
it were proven to be effectual, it would be well worth doing. One great
difficulty in the way of such an operation is the uncertainty of diag-
nosis.
Another procedure that might be utilized in many cases is the early
correction of slight irregularities in such a way as to seat the cusps in
the sulci of opposing teeth. This has the same objection as that men-
tioned above. Yet my own observations in the correction of irregular-
ities show conclusively that if the diagnosis were made sufficiently early
and the corrections effected it would save the teeth from untimely destruc-
tion. As I write I have before me the cast from the mouth of a boy
thirteen years old, the cast being made for the purpose of correcting an
apparently slight irregularity of the anterior teeth, in which the cusps
of the first molars are so much flattened by the antagonism being on
their points as to render them practically useless for the prevention of
sliding movements. This early wear will illustrate the extreme diffi-
culties of this subject.
It does not seem to have entered the minds of writers in the past that
abrasion abnormal in degree is a thing calling for early diagnosis and
operative procedures for the prevention of its ultimate results; there-
fore a sufficient mass of well-digested facts bearing on the subject have
not been collected to enable even the well-informed operator to confi-
dently recommend a tedious operation, of the utility of which his
patient can have no conception, and concerning which the operator
himself is in doubt.
in doubt. Yet if the cause of this abnormal wear is such
as I have represented it to be, it is capable of correction by the early
adjustment of irregularities, or by the timely and judicious building of
cusps with gold or gold and platinum foil that will prevent free slid-
ing movements and save the denture from untimely abrasion. Of
course all dentists are acquainted with the capping, or building down,
of abraded teeth, but I now allude to operations that will prevent abra-
sion in its inception and preserve the form of the teeth.
Abrasion also occurs in portions of the denture after the loss of a
considerable number of the teeth, owing to the fact that all the force
of the muscles closing the jaws and all the work of mastication have
been thrown on a few teeth. In these instances, if much sliding motion.
is allowed, abrasion will be very rapid. This I have been in the habit
of correcting, and the results have been such as to give me assurance
that by the aid of the judicious registering and discussion of observa-
tions we should, in full dentures, be able to make timely diagnosis of
danger in this direction and apply the remedy in time to prevent abnor-
mal abrasion.
In abrasion of the teeth there are no changes in the adjacent dentine
except it be a slight yellowing of the superficial portions of the exposed
surface. Formerly it was supposed that consolidation of the dentinal
fibrils occurred as an effort of vitality to erect a barrier to farther prog-
In those cases in
ress (J. Tomes). This view is no longer tenable.
EROSION.
997
which the progress of wear has been exceedingly slow, as well as in the
more rapid ones, the dentinal tubules are found to be open at the abraded
surface. There is also a popular notion that the surface of the abraded
dentine is harder than normal. This is an error. The assumption that
the dentinal fibrils undergo calcification probably has had something to
do with this opinion, but the principal circumstance leading to it is
doubtless the difficulty experienced in penetrating abraded surfaces with
instruments. This difficulty exists, and has been noted by many; but
it is, however, not on account of a greater density of the dentine, but
is the superior resistance of a polished surface over one that is not
polished. Precisely the same differences are noted in the penetration
of polished and unpolished surfaces of marble, or any other kind
of stone.
Abraded dentine is often exquisitely sensitive, and certain changes
are found to take place in the dental pulp as a consequence. These
will be discussed after the consideration of erosion.
EROSION.
Erosion of the teeth is an affection characterized by a loss of substance
of the organ occurring without apparent cause. It always has its begin-
ning on the surface of the tooth over a limited space, and very gradually
a pit or groove is formed which steadily widens and deepens, until in
many cases a large part of the tooth is destroyed. This happens most
frequently on the labial surface of the crown, and is often confined to
the anterior teeth. It has been noted by a number who have written
on kindred subjects, and much variety of opinion has been expressed in
regard to it. In addition to the term erosion, it has been termed chem-
ical abrasion, decay by denudation, etc., while others, as Salter, have
regarded it as being essentially a result of friction applied by the tooth-
brush or in some manner not very easy to comprehend.
As 'most usually seen on its first appearance, erosion consists of a
slight cup- or dish-shaped excavation in the enamel of some one of the
anterior teeth, generally situated from a half line to a line below the
free margin of the gum. It is, however, not confined to this position,
and may occur at any point on the crowns of any of the teeth; but
perhaps four-fifths of the cases that have come under my observation
have begun as far forward as the first bicuspid, and one-half or more
have been on the labial surfaces of the incisors. Next to the incisors,
the cuspids are much the more frequent points of attack. This applies
to both the upper and the lower jaw. When this little excavation is
discovered on one tooth, if it be closely watched it will be seen in the
course of a few months-possibly a few weeks-that it is gradually
broadening and deepening, and as this process goes on it will be noticed
that little cups are appearing in a similar position in the teeth next
adjacent. The erosion is rarely solitary, though such cases are known
to occur. It very generally extends from tooth to tooth at either side
of the one first attacked, but in nearly every case there is a preference
that is quite noticeable for one or the other side. Although I have seen
a number of cases that seemed to have begun on the central incisors and
998
ABRASION AND EROSION OF THE TEETH.
in which the invasion of these continued to be about equal, I have never
yet seen a case that maintained a symmetrical progress in respect to the
the other teeth. The illustrations on another page will give a good idea
of this. In many cases there is a marked tendency to the formation
of a sharp angle with the surface of the enamel on the lower (toward
the crown) margin of the erosion. This is particularly noticeable in
Fig. 532. Occasionally this is seen to be next the gum (Fig. 534), but
much more rarely, and in some instances both the upper and the lower
margins are very square incuts. A few days ago I was consulted in
regard to a case in which both of the superior central incisors were cut
as if done with a No. 4 separating file, the cut extending considerably
into the dentine. This case is remarkable as being the deepest cut, in
proportion to its width, that I have ever seen. Generally the incuts
are of considerable width; and if one margin is squarely cut in, or
nearly so, the other slopes much more gradually to the surface, as will
be seen in all the illustrations presented. More rarely cases may be
seen in which the excavations are nearly circular, with the sides equally
sloping. It will thus be observed that there is nothing definite as
relates to form. I have seen a few cases in which there was a groove
excavated lengthwise of the crown of the tooth, but these are very rare.
Dr. Cushing of Chicago has related to me a curious case that came
under his care, in which a groove was excavated in the labial surface
of an incisor close to the proximal border, extending from near the
gum to the cutting edge, from which point it passed backward across
the cutting edge and then down, in the form of a groove in the palatine
surface, nearly to the gum. Such a form as this is certainly remarkable.
Another variety, of which two cases have come under my observation,
is the wasting of the proximal surfaces of the teeth. In each of these
round holes were formed, passing through between the teeth (each
tooth being about equally eroded), as if filed out with a rat-tail file,
the surfaces remaining hard and finely polished. When one of these
first came under my observation, the crowns of the central incisors
were almost severed from their roots, and similar openings were in pro-
cess of formation between the other teeth on one side as far back as the
space between the first and second bicuspids, while on the other it
extended to the lateral incisor and cuspid only. This effect was con-
fined to the upper jaw. In the other case the teeth of both jaws were
similarly affected.
www
In all these cases the erosion makes the greatest progress in the teeth
first attacked, and, in whatever stage of progress the case is seen, the
extent of the loss of substance gradually diminishes as it recedes from
this point in either direction. The difference in the extent of the loss
of substance generally has a close relation to the time of beginning.
Exceptions to this rule now and then occur, but it holds good in so
large a majority of cases that after seeing the position and form of the
erosion in two or three teeth we may prognosticate pretty certainly the
form it will take in the adjacent teeth if the case progresses without
interruption. This progress is well marked in illustrations 532 and 533.
So far as my observation extends, the form and direction of the erosion
are not materially changed-but rarely, at any rate-after it has once
EROSION.
999
begun. If the teeth are regular in the arch, the second tooth attacked
will be eroded in almost precisely the same form as the first, and so on
with third and fourth. But it is rare to see two teeth which are
alike in the extent of erosion at the same date, except it be the cen-
tral incisors. Those on which the process begins later will pass
through the same forms and stages which the first has gone through
before them.
Fig. 532 represents a cast made from an impression of a case in the
practice of Dr. E. D. Swain of Chicago; its principal peculiarity is the
FIG. 532.
1
a.
2
d.......
3
a....
4
a.
5
a.
B


J
97%
Case of Erosion of the Lower Anterior Teeth (drawn from a cast prepared by
Dr. E. D. Swain of Chicago): B, silhouettes representing the loss of substance
in five of the affected teeth: 1, right lateral incisor; 2, right central; 3, left
central; 4, left lateral; 5, left cuspid. The lines aadaa show the position of
the margin of the guni. A line is drawn also to show the original form of the
tooth.
uniform sharpness of the angles made by the erosive pro-
cess. Usually, when a groove is formed in this position,
the margins are more rounded. It will be seen that at the
time this impression was taken the erosion had extended
from the right lateral incisor to the left first bicuspid of
the lower jaw, with the deepest point of erosion in the left
central incisor. In this case the left central was doubtless
the point of beginning, from which it gradually extended
to the other teeth. In all of these the surface of the teeth
is cut into as if done with a square file, and the particular
angles are maintained in all of the teeth affected. I have
shown these angles in the silhouettes of the incisors and
cuspid.¹
The surface of the exposed dentine was firm and hard and had a per-
fect polish everywhere, and there was no jutting of the enamel above
the eroded dentine at any point. These tissues, differing so much in
¹ These silhouettes were made as follows: An impression was taken from the cast in
modelling compound, care being taken to get it as sharp as possible. When this was
thoroughly cold, it was oiled lightly and a cast made, also of modelling compound, by
pressing the softened material quickly and firmly into the impression. When cold,
they parted very readily. The cast was then cut away from before backward, perpen-
dicularly, from its right-hand end until the right lateral incisor was reached. Then
the cut surface was dressed down carefully on a piece of emery-paper laid flat until the
centre of the tooth was reached, producing a perpendicular section from before back-
ward of this tooth. The surface was then smoothly finished on fine emery-paper, and
the back part of the cast was cut away to something near the shape of the tooth. (This
cast was only of the labial surfaces; therefore the lingual surfaces as shown are
only an approximation to correctness.) This was then inked on an ordinary rubber-
stamp inking-pad and the silhouette of this tooth printed. The cast was then trimmed
to the centre of the next tooth and its silhouette printed in the same way, and so on
from tooth to tooth. These accurately represent the angles.
1000
ABRASION AND EROSION OF THE TEETH.
density, were finished as evenly and smoothly, the one with the other,
as if done on the lapidary's wheel.
Fig. 533 was made from the cast of a case in my own practice, and
represents the teeth as I first saw them. The patient was sufficiently
intelligent to give what seemed to be a very reliable account of its prog-
FIG. 533.

100000
00000
B
A Case of Erosion (drawn from the cast): B, silhouette from a perpendicular line through the left
centrals, upper and lower, showing the loss of substance.
ress. A little more than three years before, she had noticed slight cups,
which caused her some solicitude, appearing on the labial surfaces of
the upper central incisors, near the gums. These were observed to
widen very slowly, but seemingly very steadily, toward the cutting edge
and laterally. About six months later the same condition was seen on
the lower centrals, and the lesion seemed to progress more rapidly than
the erosion of the upper teeth; so that at the end of the first year the
loss of substance appeared to be about equal in depth. At about this
time the erosive process was seen to be making its appearance on other
teeth. Her dentist was then consulted, and she was told that the
trouble resulted from the use of a stiff toothbrush which she employed.
Very much against her will, she abandoned the brush for a year.
During this time the erosion made more rapid progress than before,
and the sensitiveness of the eroded surfaces, already quite considerable,
increased greatly; so that, in addition to the marred appearance of the
teeth, the hyperesthesia became a source of great annoyance, occasional
exacerbations occurring, during which exquisite suffering resulted when-
ever the eroded surfaces were touched. Finding that the abandonment
of the use of the brush did not retard the erosion, she again resumed it;
but, on account of the great sensitiveness of the eroded surfaces, she was
ever after compelled to avoid them in cleaning her teeth. The erosion
continued steadily, and at the end of the third year was as represented
in the illustration. At this time intense hyperesthesia of the pulps had
occurred in the central incisors above and below. The sensitiveness
was so extreme that the patient could not be induced to submit to any
manipulation whatever. I therefore gave an anesthetic and removed
the pulps of the four centrals, which had the effect of rendering the
patient fairly comfortable. Before cutting into the teeth the outline of
the former pulp-chamber was distinctly seen in what seemed to be the
'
EROSION.
1001
exposure of a secondary deposit, and in the removal of the pulps it was
found that the chambers were abnormally small, on account of secon-
dary deposits. After proper treatment of the root-canals the contour
of the four incisors was restored with gold and platinum foil, and has
stood perfectly to this date (two years). In the mean time, the erosion
of the other teeth has been progressing, but much more slowly than for-
merly, and the sensitiveness has abated to such a degree that they are
fairly comfortable. The indications now are that the process has come
to a spontaneous standstill. I have in several instances observed this.
spontaneous cessation of erosion after it had made considerable progress,
and in this case I do not think that the treatment of the central incisors
had any influence in bringing about this result. The cessation did not
occur at once, for very decided advance was made during the six months
following the operation.
FIG. 534.
Fig. 534 was made from a cast of a case occurring under the obser-
vation of Dr. George H. Cushing of Chicago, and is here introduced
because of its marked peculiarities.
The case had not progressed very
far when this cast was made, but
I learn from Dr. Cushing that it
is steadily advancing without any
disposition to change in the form
of the eroded surfaces. In this
case the incut is sharply down
from the surface of the enamel-
slightly undercut, indeed-in a
circular line following the free
margin of the gum and about
half a line from it, until the proximal borders of the tooth are reached,
and then these borders are followed toward the cutting edge. The
superficial portions of the tooth are smoothly removed in the included
area, being deepest in that portion nearest the gum, and thinning out
toward the cutting edge in such a way as to leave a perfectly flat sur-
face. The surface thus eroded is perfectly hard and smooth in all its
parts. This is the left lateral and central. In the tooth next adjacent.
on either side the erosion has begun in the same way, only that it has
not extended over the crown of those teeth lying next those first attacked
at the time the cast was taken. It will be observed that the right cen-
tral is a little rotated in its socket-a circumstance that will have the
effect of modifying the form of the erosion occurring in it. I have
noted this in enough cases to be sure that it is the position of the tooth
that produces the modification—a fact that is of importance in consid-
ering the etiology of the affection.

10000
Peculiar Case of Erosion of the Superior Anterior
Teeth (drawn from a cast prepared by Dr. Geo.
H. Cushing of Chicago).
The forms shown in these illustrations serve to give an idea of the
variations that occur in this process. Each case examined presents
characteristics peculiar to it, and to no other. There are however, not-
withstanding their sharp differences, certain similarities of form run-
ning through all the cases, which, after one has become accustomed to
observing this affection, at the first glance mark them as cases of ero-
sion. There are some cases in which the effect is seen over a large part
1002
ABRASION AND EROSION OF THE TEETH.
of the labial surfaces of the teeth without any sharp incuts at any point;
others in which a simple groove well rounded at its bottom occurs across
the crown of the teeth, near the gum, and at the margins of the enamel.
I think it a fact that those cases which are thus indefinite as to their
boundaries are not as rapidly destructive as those that show sharp
outlines.
Erosion sometimes exists in association with mechanical abrasion.
Where this occurs I think it is simply intercurrent, and not because the
two processes have anything in common in their etiology. The only
cases that I have seen in practice or in the literature of the subject
seeming to offer a suggestion of interdependence of the one upon the
other are those which affect the cutting ends of the incisors in some rare
cases of mechanical abrasion. In a few cases that came under
my obser-
vation several years ago all the crowns of the teeth, except the usual
cupping out of the dentine, were worn flat and smooth, and the antag-
onism was perfect in the bicuspids and molars; but the incisors failed,
in the worst case, to come together, by about three-sixteenths of an inch.
It does not seem to me possible that this shortening of the incisors
could have been the effect of simple abrasion. They cannot possibly
be brought in contact, and they have become almost useless in the pre-
hension of food; so that, as a matter of fact, they are scarcely used at
all. Yet they continue to lose substance much faster than those teeth
that bear the burden of mastication and the friction of the one upon
the other. I have sought to find some explanation of this in the struc-
ture of the dentine, but without result; the structure of the teeth that
were rapidly losing substance seemed as good as that of the others."
The effect is certainly that of erosion, and is identical with that process
as seen on the labial surfaces of the teeth and occurring independently
of mechanical abrasion. This has been noted by most writers since
the time of Hunter.
ETIOLOGY.
The etiology of mechanical abrasion has been sufficiently explained in
connection with its description.
The etiology of erosion is probably one of the most obscure subjects
in pathology; with our present knowledge, it is practically unexplain-
able. This being the case, it seems incumbent upon every writer
who treats of the subject to give any facts in his possession that may
seem to have significance, in the hope that from the accumulation of
data something tangible may be derived in the future. In the past
various suggestions have been made, most of which seem untenable.
The chemical theory, notwithstanding the many valid objections to it,
is perhaps the one more generally held. Some, with J. Tomes and
¹ One of these cases was treated by restoring in gold the contour of the lost tissue, so
as to perfect the antagonism. For this purpose pits were drilled, into which screws
were driven, and, without otherwise cutting the surface, the gold built about these for
retention. The surface was simply carefully washed with sulphuric ether, to cleanse it
of any possible adherent animal matter. I had opportunity occasionally to see the case
up to the time of the patient's death, ten years after the operation; the treatment was
successful in every respect. This seems to argue that the cause was not in the tooth
itself.
ETIOLOGY.
1003
Salter, seem to regard it as the effect of the vigorous use of the tooth-
brush, or some other form of friction—indeed, as a species of abrasion.
It is, however, difficult to believe that simple friction of any kind can
produce the effect seen in the cases I have illustrated, and many other
forms occur equally difficult of explanation by that hypothesis. A
causative agency has been sought for in the structure of the teeth them-
selves, but microscopical examination of the tissue undergoing erosion
gives no results except to demonstrate that the fault does not lie in this
direction, such teeth being generally found perfect in their organization
and development. Again, faulty development has certain characteristics
that are well known. If many teeth are faulty in a part of their struc-
ture, the faults are present in those parts of each of the teeth in process
of development at the same time; therefore, if what I have called
erosion were the washing out or brushing away of such portions of the
tooth as were soft from faulty development, the erosion should follow
the developmental lines, which it does not do in any case that I have
seen.
The erodent, whatever it may be, acts from without. Neither the
dentine nor the enamel immediately adjacent to the portions being re-
moved, even up to the immediate surface, shows any changes whatever
except it be a slight discoloration which is present in only a portion of
the cases.
There is, indeed, in most of the cases a very marked sen-
sitiveness of the surface eroded, and finally of the pulp itself-which
condition I shall discuss presently-but this does not seem to influence
the hard tissues in any degree. Sensitive dentine is just as hard as den-
tine that is not sensitive.
As already stated, the more generally accepted theory is that erosion
is in some way effected by acids, and, all things considered, this supposi-
tion is perhaps more tenable than any other that has been advanced;
still, there are great difficulties in the way of its adoption. It is gen-
erally admitted that if it be an acid that acts as the agent the action.
must be different from anything now known to us. On this point I
can throw some light, though I will fall far short of clearing up the
mystery. Teeth may, by the action of acids, be eroded artificially so
nearly like some of the forms seen in the human mouth that the dif-
ference cannot well be demonstrated. It is difficult to conceive, how-
ever, that the same conditions should occur in the mouth. But the
experiment shows that it is not impossible that erosion may be the action
of acids.
-
In 1870, while studying experimentally the condensation of gases on
the metals (surface attraction) and the corrosion of metals with weak
solutions of acids in the still condition as compared with the effects
when the solutions were kept in motion, it occurred to me to try the
effects on the teeth. From the results of my experiments on metals I
supposed that the parts of a tooth exposed to a brisk current would not
be softened in a given solution so rapidly as in the still condition. The
apparatus I was using at the time was a train of wheels like those of a
common clock, only heavier, run by a weight and made to revolve a
glass paddle in a glass jar. This apparatus when in motion caused the
liquid to spin around in the vessel continuously. It was capable of
1004
ABRASION AND EROSION OF THE TEETH.
regulation, so that it would give a current of any number of feet per
minute up to one hundred or more. The jar was filled with a solution
of hydrochloric acid of the strength of 1 part of acid to 400 parts of
water, and the apparatus was arranged to run at about forty revolutions.
per minute.
FIG. 535.
a
Two bicuspids fresh from the mouth and perfect, with fairly long
cusps (removed to obtain room for the correction of iregularity), were
placed with their proximal surfaces together, to repre-
sent a natural position, and their roots were enveloped
in gutta-percha, to represent the gum and alveolus,
leaving the crowns exposed. These were fixed in the
current in such a way that it would strike against
their buccal surfaces not quite squarely, but at an
angle that would cause the current that passed between
the teeth to be deflected slightly from its course. The
effect on these teeth was quite remarkable and entire-
ly at variance with anything that I had expected.
Metals corrode much less in a current than in the
still condition in a given solution of acid, and the
difference is quite marked on any surfaces that are
Artificial Erosion.
The original form of
the tooth is repre-
sented at . At b
the same tooth is
represented after
having been subject-
ed to a current of a
solution of hydro- well sheltered from the current, and I naturally ex-
chloric acid for five
days. Strength of
solution, 1 to 400.
pected that something similar would occur in case of
the teeth. The result, however, was the removal of
the cusps and the formation of a round opening between the two teeth.
The effect on the cusps was noted on the second day, and the opening
between the teeth on the third. On the fifth day the condition of the
teeth was such as shown in the illustration (Fig. 535), in which a shows
the condition of the tooth at the beginning as well as I could do it after
witnessing the results, and b represents the condition on the fifth day
of the experiment.'
b
The effect of the acid was to cut away the teeth at the points where
the current broke around the sharper angles, especially over the points
of the cusps. At the point where the solution ran between the teeth,
that tooth against which the current bore while being deflected from its
course was cut in the form of a deep groove, which corresponded in
width with the space between the contact of the two teeth and the gutta-
percha that represented the gum. The other tooth was grooved also,
but not so deeply. At these points the eroded surface was left fairly
hard and smooth, as in erosion as it occurs naturally in the mouth.
The groove between the teeth reminded me strongly of a case I had
seen some time before, in which round openings were cut between
several teeth, while the effect on the grinding surface was more like
abrasion.
These experiments were repeated a number of times with results that
were somewhat variable. Three months' trial with a solution of 1 of
acid to 1500 of water gave no appreciable result. Very strong solu-
tions produced general softening.
These experiments show that an acid may possess an action under a
¹These figures are made from the drawings that accompany my notes of the experi-
ments made at the time. I have represented only the tooth most eroded.
ETIOLOGY.
1005
change of circumstances very different from that seen when the action
takes place in the ordinary still condition, and leads us to suspect that
there may be circumstances modifying its erosive power which are not
yet known or recognized. When we come to analyze the results of
these experiments, this is all that can be said of it, so far as the expla-
nation of erosion is concerned; for if an acid were present in the mouth
in the strength of solution that is required to produce this peculiar effect
out of the mouth, the teeth would be quickly destroyed. Were this not
the case, it is difficult to conceive of a current being maintained in the
mouth sufficient to effect the erosions met with in practice. Indeed,
some of the forms of erosion are such that a current could not possibly
be the cause-such forms, for instance, as are given in Fig. 534, where
there is a perpendicular incut in a half circle, or in Fig. 535, where the
teeth were eroded in the form of cups, or in many other cases that might
be given.
The possibility that erosion might be effected by something like the
absorptive processes occurred to me some years ago. Certainly a num-
ber of cases that have come under my observation have shown a peculiar
congested condition of the lip that came against the portion of the labial
surface being eroded, and it seemed probable that an acid secretion
abnormal in character was being produced at this immediate point,
which, together with the motions occasioned by the lip, might effect
the solution of the substance of the tooth. In a few instances I have
seen clearly the impression of the eroded surface in the lip, showing
that it fitted into it very exactly. At the same time, litmus-paper
applied to the lip showed that the secretions at that point were decidedly
acid. This seems very near a demonstration of the cause, but I have met
with cases in which no such agency could be proven-cases in which
there is no tissue in habitual contact with the surface.
Dr. E. D. Swain of Chicago, who has taken much interest in this
subject, has made a close study of the theory of electrolysis, especially
of the ideas advanced by Mr. Bridgeman, whose experiments he has
repeated and varied, using a large number of acids, different strengths
of solution, etc., becoming finally convinced, however, that the explana-
tion is not to be found in this direction.¹
While pursuing these experiments Dr. S. has made some important
discoveries in the diffusibility of acids, a table of which I have the priv-
ilege of giving. This table represents the percentage of each of the acids
named (dissolved in distilled water) that can clearly be detected as giv-
ing an acid reaction with litmus-paper :
Oxalic acid .
Citric acid
Phosphoric acid
•
Acetic acid
Butyric acid
Tannic acid
Tartaric acid
Sulphuric acid
Nitric acid
Hydrochloric acid
•
•
•
•
•
•
•
•
•
•
·
Per cent.
1-260 of 1
1-160 of 1
1-130 of 1
1-65 of 1
1-30 of 1
1-30 of 1
1-260 of 1
1-130 of 1
1-130 of 1
1-140 of 1
¹ I am indebted to Dr. Swain for the privilege of the perusal of several unpublished
manuscripts on this subject.
1006
ABRASION AND EROSION OF THE TEETH.
Dr. Swain's results agree with my own conviction as to the possible
influence of electrolysis in the causation of this affection. Even if it
were shown that the teeth could be eroded successfully by this method,
the matter of the peculiar localization would present to its adoption as
a theory (as it does to every other yet advanced) an obstacle that seems
insurmountable.
The theory that it is caused by acid mucus is supported by several
who have written on the subject, and our present knowledge affords no
alternative but the acceptance of the general idea that it is the action of
an acid under some peculiar modifying influences as yet unknown to us.
While this is unsatisfactory in the extreme, there seems to be nothing
better to offer. The influence of micro-organisms appears to be out of
the question. These enemies are accustomed to seek foul places, and
eroded surfaces are habitually clean surfaces. If by a change of con-
ditions the surface eroded becomes habitually foul, caries takes the place
of erosion. This occurrence is very rare, but is not unknown.
SENSITIVENESS OF THE DENTINE.
The extreme sensitiveness of the eroded surfaces, not unfrequently
occurring, has been alluded to. In a number of cases I have seen this
so extreme that only the destruction of the pulp of the tooth afforded
relief. Indeed, experience has taught me that this result is sooner or
later likely to follow spontaneously, notwithstanding the large amount
of secondary dentine usually found over the pulp in this disease. I
have seen the death of the pulp occur when there was seemingly an
abundance of dentine between it and the eroded surface for its protec-
tion. On the other hand, while I have seen the pulp-chamber cut
through either after being closed with a secondary deposit or after the
death of the pulp, I have never seen a case in which the living pulp
became exposed. There seems to be something in the cause of this
affection peculiarly irritating to the dentinal fibrils, and the results of
that irritation are shown by pathological changes in the pulp of the
tooth. This naturally leads to an examination of the anatomical and
physiological conditions that produce these peculiar results.
The dentine has no demonstrable nerves, and with our present facil-
ities for microscopic examination it is reasonable to suppose that if they
were present we would be able to demonstrate them. It seems to have
been the thought of pathologists that in the production of the sensation
which we call pain some nerve or nerve-ending has received the initial
lesion which has produced this effect. It has long been recognized that
in the strict adherence to this doctrine we would be unable to account
for even the normal sensitiveness of dentine, much less the occurrence
of hyperesthesia. Yet the hyperesthesia does occur, and in the most
excruciating forms, and especially in the disease we are considering. It
seems, therefore, fitting that we should study this condition in connec-
tion with this disease, especially as there is here absolutely no discover-
¹ Dr. E. D. Swain of Chicago gives a case in which the pulp was fully exposed from
erosion.
t
SENSITIVENESS OF THE DENTINE.
1007
able pathological change in the dentine itself which presents this hyper-
æsthesia, except a waste of its surface.
FIG. 536.
Fig. 536 is a sectional view of a central incisor with an erosion at a
which exposes the dentinal fibrils. At b the layer of odontoblasts are
shown-these line the pulp-cham-
ber-and at c a nerve-branch the
finer filaments of which are found
ramifying in close conjunction with
the odontoblasts. The processes
from these odontoblasts form the
dentinal fibrils which pass by way
of the dentinal tubules to the per-
iphery of the dentine. The odon-
toblast and its process, the denti-
nal fibril, constitute one cell; the
protoplasm is united in one life;
and whatever markedly affects
the protoplasm of the fibril affects
the protoplasm of the whole cell. d
For this reason any pathological
changes that may be set in mo-
tion in consequence of irritation
of the dentinal fibrils are found
in the odontoblasts and the tissues
in intimate association with them
-in that portion of the pulp
marked e in the figure. Along
the course of the fibril itself no
pathological changes whatever can be discovered, seemingly for the
reason that the hard substance of the dentine-the basis-substance and
the lime salts—is incapable of manifesting vital phenomena, is not liv-
ing protoplasm. This portion of the dentine is essentially fixed mate-
rial. It may be acted upon, but does not in itself act. It is passive.
The changes which occur in the tissues of the pulp in consequence
of distal irritation of the dentinal fibrils are sufficiently discussed in the
paper on Pathology of the Dental Pulp, and will not be repeated here
except for the purpose of illustration. The effect of slight but continu-
ous irritation of the ends of the fibrils is seen in the production of sec-
ondary deposits of dentine, which in those cases in which the area of
irritation is small are not unfrequently confined to the area represented
by the pulpal ends of the fibrils irritated. If the area of irritation is
large, as in most cases of mechanical abrasion, the area of secondary
deposits includes the whole internal surface of the pulp-chamber. If the
intensity of the irritation of the fibrils be more considerable, the result
will be irritation of the pulp, instead of secondary deposits, or possibly
both, the secondary dentine proper giving place to irregular deposits.
In case the irritation becomes excessive, well-marked hyperæmia of the
pulp will occur, which occasionally results in the destruction of that
organ before it is exposed to external influences other than through
the medium of the fibrils.

-
***
C2
d
Section of the Crown of an Incisor: a, an erosion
exposing the dentine; b, the layer of odonto-
blasts lining the pulp-chamber; c, a
branch the delicate filaments of which are dis-
tributed about the layer of odontoblasts; d, d,
gingival margin; E, point at which pathological
changes first occur as the result of irritation of
the dentinal fibrils at a.
Let
1008
ABRASION AND EROSION OF THE TEETH.
Here we find that the pathological changes pass from the external to
the internal structures by way of the protoplasmic lines, the dentinal
fibrils. Having injured the process of a cell, the cell itself is injured.
Protoplasm is sensitive; this is exhibited in the amoeba, the leuco-
cyte, and the young connective-tissue cells generally. All of these
respond to stimulants, both mechanical and chemical, and exhibit their
sensitive properties by certain motions, by ceasing from the perform-
ance of motions, and by various forms of contraction. They exhibit
sensitiveness to thermal changes. Cold tends to slow their motions,
and if its degree is increased will stop them entirely. Heat renders
their motions more active for a time; but if the increase of the temper-
ature is continued, it causes them to take on a state of tetanic con-
traction and assume the spherical form. If the heat is discontinued,
the movements will be resumed. Among the chemical irritants many
affect them in a marked degree. Common salt in very small quantity
(a drop of a 1-per-cent. solution added very slowly) first quickens
their motions, and then causes sudden tetanic contractions, and in
amoeba the expulsion of any food they may contain at the moment
(Brunton). The acids and alkalies affect them prominently. Hydro-
chloric acid causes the amoeba to contract and form a ball with a sharp
double contour. In it occur twitching motions which expel any food it
may contain in its substance.
Matt
These are a few of the many well-known examples of the effects of
reagents upon protoplasm by which its sensitiveness is shown. The
leucocyte exhibits the same phenomena, with some variations, as do also
the young connective-tissue cells. Leucocytes from different animals
show some differences in their response to different stimulants.
These cells contain no nerves, and we cannot say that they exhibit
pain; but when protoplasmic bodies-cells-come to be built into tis-
sue and enter into physiological relations with nerves, may not this sen-
sitiveness-which in the simple cell, when standing alone, is exhibited
in motion, or tetanic contraction-be communicated to the sensorium
and translated into the sensation which we know as pain? There
seems to be no reasonable objection to this view, while there are some
difficulties that are more readily explained by this than by the hypothe-
sis that in the production of pain the initial lesion must be of some
nerve or nerve-ending.
Fig. 537 represents diagramatically a group of odontoblasts with
their processes, the dentinal fibrils, with a nerve-branch in close con-
junction with the odontoblasts. In case of the irritation of the distal
ends of the processes of these cells pain is produced, yet no nerve or
nerve-ending is touched, there being no nerves in the dentine. Every-
where in the periphery of the pulp fine nerve-filaments may be demon-
strated in close conjunction with the odontoblasts, and it seems evident
that they communicate to the sensorium the impression made on the
protoplasm of these cells through the injury to the fibrils. In this as
in most other cases sensation follows the lines of pathological changes.
According to present theories, hyperemia is induced through the agency
of the nervous system by a reflex action, and must be induced by the
same manner of reflex action as pain itself.
SENSITIVENESS OF THE DENTINE.
1009
Pathologists have generally regarded the nerve-endings as receiving
the initial impression or injury in the production of pain on touch. It
is a subject, however, that has always been very obscure-in fact, unde-
monstrable. Nerve-tissue is certainly itself sensitive, for pain may be
produced by the injury of sensory nerves; but pain so induced is referred
to the tissue to which the nerve is distributed, not to the nerve itself.
Indeed, so far as consciousness goes, we would never know that we had
nerves. In most positions in the body nerve-endings and the cellular
elements are in such close relation that it is impossible to injure one
а
FIG. 537.
6

d
Group of Odontoblasts with their Processes (deutinal fibrils): a, odontoblasts; b, fibrils; c, nerve-
supply. Irritation at the point d produces pain.
without injuring the other. The experimental isolation of a tissue-
injury from injury to the nerves (these being intact) for the purpose of
determining which receives the initial lesion causing pain does not seem
to have been thought of or to have been possible to other positions than
the one under discussion, and the general fact that without nerves there
is no pain seems to have led physiologists to adopt the supposition that.
the nerves or their endings received the initial lesion giving the sensa-
tion of pain.
A close study of the literature of the subject of sensory nerve-endings
and their relation to the various sensations will serve to demonstrate the
obscurity of the subject and show how inaccurate is our knowledge of it.
In practice the cases in which pain is developed—that is, demonstrably
due to the direct wounding of nerves or nerve-endings-are very few
indeed. In this statement I have not reference to pain or perturbations.
of functions that may result from disease of the nerve-centres; in this
case we would deal with the nerve-cells (ganglion-cells) individually,
and their processes. These are protoplasmic bodies in which specialized
function is developed to such a wonderful degree that their injury pro-
duces exceedingly complex results.
The striped or voluntary muscles furnish an example of the propaga-
tion of impulse along protoplasmic bodies which is like that I have sug-
gested in case of dentinal fibrils, except that it is an efferent instead of
an afferent impulse. There is but one motor nerve-ending in conjunc-
tion with a single muscular fibre, no matter what its length (Krause,
Koelliker); this is sufficient to communicate the impulse to contraction
to the whole fibre, though it may be much longer than the dentinal
fibril. Here it will be seen that the passage of an impulse along a
VOL. I.-64
1010
ABRASION AND EROSION OF THE TEETH.
protoplasmic body from a nerve-ending seems demonstrated. In the
explanation offered of the sensitiveness of dentine the impulse passes
along a protoplasmic body to a nerve-ending. The conduction in the
two instances is the same, but the impulse travels in the opposite
direction.
By this consideration of the facts at hand it seems clear that this is
the mode of transmission of sensation from the dentine. The dentine
has no nerves, and, with the peculiar arrangement of the odontoblasts
and their processes, nerves are not needed. The dentinal fibrils being
processes of the odontoblasts, and these cells being in physiological rela-
tion to the sensory nerve-éndings, the conditions for the translation of
injury to protoplasm into the sensation of pain are complete.
These considerations also render sufficiently clear the reasons for
hyperesthesia of dentine and injury to the dental pulp by irritation of
the dentinal fibrils.
:
INDEX TO VOLUME I.
A.
Abdominal plates of embryo, 543
Abducent nerve, 282
septum, destruction of, 972
wall, destruction of, 971
development of, 107, 632
eversion of, 971
Alveoli of inferior maxilla, 103
of superior maxillary bone, 87
Alveolitis, infectious, 968
Alveolo-dental nerve, 290
of dental pulp, 855-857
septic, treatment of, 950
Absorption of bone, 47
of ligatures, 922
anterior superior, 291
branches of, 291
Amalgam in caries, 811
of roots in phagedenic pericementitis, Amblypoda, teeth of, 492
973
Amelification, 595
Ameloblasts, 641
Abrasion and erosion of teeth, 993
of teeth, prevention of, 996
secondary dentine resulting from, 867
Abscess, 701
alveolar, 929
blind, 936
of roots of teeth, 921
Absorptive processes in caries, 777
Accessory palatine canals, 91
parotid gland, 208
Achatina, teeth of, 349
Acid causing caries, analysis of, 798, 799
mucus in caries, 776
produced by fungi of human mouth, 824-
826
Action of muscles of mastication, 182
Acute apical pericementitis, diagnosis of,
924
symptoms of, 924
Eluropus, teeth of, 464
African elephant, teeth of, 489
tusks of, 489
Ailurodon, teeth of, 453
Air-cells, openings of, 137
Alligator, dentition of, 385
Alveolar abscess, 929
chronic, 935
constitutional treatment in, 946
diagnosis of, 943
discharge of, at gingival margin, 934
on face, 933
discharging into antrum, 941
into nose, 940
on neck, 943
evacuation of pus in, 945
opening pulp-chamber in, 948
pointing in hard palate, 934
treatment of, 944
margin, thickening of, 971
or superior maxillary artery,
process, necrosis of, 951
of inferior maxilla, 103
Alveolar process of superior maxilla, 86
maxillary bone, 86
removal of, 980
234
contact of capillaries with, 633
Amphicyon, teeth of, 452
Amoeboid cells, 692
Amputation of dental pulp, 905
of roots of teeth, 990
Amynodon, teeth of, 479
Anæmnia, 687
Analysis of acid causing caries, 798, 799
Anatomy, Dental, 351
Regional, 35
Anchitherium, teeth of, 481
Angular artery, 226
vein, 249
Annelids, teeth of, 338
Anomodontia, teeth of, 384
Anterior auricular arteries, 229
vein, 253
cerebral artery, 242
condyloid foramina, 53, 124, 128
communicating artery, 242
dental foramen, 101, 133
ethmoid artery, 240
ethmoidal foramina, 75, 134
fossa of brain-case, 120
jugular vein, 255
lacerated foramen, 66, 122
median fontanelle, 119
nasal openings, 132
occipital or transverse sinus, 261
palatine canal, 86
meatus, 86
superior dental nerve, 291
temporal artery, 230
Anthracotheridæ, genera of, 485
molars of, 486
1011
1012
INDEX TO VOLUME I.
Anthroidial articulation of Gray, 112
Anthropoid apes, teeth of, 436
Antiseptic filling materials, influence of, on
fungi of dental caries, 806
power of filling materials, 810
wash in calcic inflammation, 967
Antiseptics in alveolar abscess, 948
in plagedenic pericementitis, 984
power of, 808
uses of, on gangrenous pulps, 907
Antrum of Highmore, 89
Aortic obstruction, pulse in, 671
regurgitation, 671
Apical foramen, 355
pericementitis, 923
cause of, 925
chronic, 925
constitutional treatment of, 928
treatment of, 926
space, 918
painless penetration of, 928
Aponeurosis, occipito-frontalis, 167
supra-hyoid, 188
Aponeurotic fascia, 155
Apophyses of bones, 35
Appendages of skin, 147
Appendix to paper on dental caries (Mil-
ler), 791
Aqueduct of Fallopius, 59, 305
Aqueductus cochlea, 60
vestibuli, 59
Archælurus, teeth of, 459
Arctoidea, teeth of, 463
Areolar tissue, 154
Arion, jaw of, 349
Aristotle, lantern of, 339
Arrow-tooth (Toxoglossate) dentition, 346
Arsenious acid, action of, on dental pulp,
901
and morphia pastes, 900
method of application to dental pulp,
902
use of, on dental pulp, 899
Arteries, 215
alveolar or superior maxillary, 234
angular, 226
anterior cerebral, 242
communicating, 242
ethmoid, 240
temporal, 230
ascending cervical, 246
pharyngeal, 228
meningeal branches of, 229
auricular, 228
basilar, 243, 246
buccal, 234
central retinal, 239
cerebral, 241
ciliary, 239
circle of Willis, 242
crico-thyroid, 220
deep auricular, 232
temporal, 233
descending cervical, 227
palatine, 234
dorsalis lingual, 221
Arteries, external nasal, 241
facial or external maxillary, 222
frontal, 241
glandular, 224
incisive, 233
inferior coronary, 225
dental, 233
labial, 225
laryngeal, 247
palatine, 224
thyroid, 246
infraorbital, 234
internal carotid, 235
maxillary, or deep facial, 230
lachrymal, 238
lateral communicating, 243
nasal, 225
left common carotid, 216
lingual, 221
masseteric, 234
mental, 233
middle cerebral, 242
or great meningeal, 232
temporal, 229
muscular, of the orbit, 240
mylo-hyoid, 233
nasal or spheno-palatine, 235
occipital, 226
ophthalmic, 238
palpebral, 241
posterior auricular, 227
cerebral, 242
communicating, 243
ethmoid, 240
temporal, 230
pterygoid, 234
pterygo-palatine, 235
ramus cervicularis princeps, 227
ranine, 222
right common carotid, 216
small meningeal, 233
stylo-mastoid, 228
subclavian, 243
sublingual, 222
submental, 225
superficial temporal, 229
superior coronary, 225
laryngeal, 220
suprascapular, 247
thyroid axis, 246
tonsillar, 224
tracheal, 247
transversalis colli, 247
transverse facial, 229
tympanic, 232
vertebral, 245
Vidian, 235
Articular veins, 253
Articulating arteries, 229
Articulation, diarthroses, 112
temporo-maxillary, 112
Articulations, 111
of base of brain-case, 117
of occiput, 117
of skull at different periods, 118
synchondroses, 112
INDEX TO VOLUME I.
1013
Artiodactyla, divisions of, 484
Atrophy of odontoblasts, 884
Attolens aurem muscle, 175
Attrahens aurem muscle, 175
Ascending cervical artery, 246
nasal nerve, 291
or orbital nerve, 301
pharyngeal artery, 228
meningeal branches of, 229
Auditory nerve, 310
Auricular artery, 228
Auriculo-temporal nerve, 294
Axis-cylinder, 266
Aye-aye, teeth of, 432
Azygos uvula muscle, 198
B.
Balistes vetulus, teeth of, 377
Baleen plates of cetacea, 413
Band of embryo, 618
Bartholin, duct of, 211
gland of, 210
Base of brain-case, 124
Basement-membrane, 145
Basilar artery, 243, 246
branches of, 246
process of occipital bone, 51, 54.
Batrachia, teeth of, 379
Bats, classification of, 465
dentition of, 465
probable derivation of, 465
Bears, evolution of, 464
teeth of, 463
Beginnings of caries, 779
Bela, teeth of, 346
Bell on caries, 732
Bichloride of mercury in phagedenic peri-
cementitis, 986
Bicuspids, human, 442
Biological studies, cultures for, 822
methods in, 821
on fungi of human mouth, 819
Black on formation of poisons by micro-
organisms, 757
Blarina, teeth of, 426
Blastoderm, 142, 543
development of, 554
Blind abscess, 936
Blood, absorption of, 686
-clot, granulations in, 710
how formed, 680
organization of, 709
-corpuscles, 531
development of, 566
physiology of, 533
-pressure, increase of, 677
-supply of peridental membrane, 919
variations in, and in its distribution, 671
-vessels, development of, 566, 706
of dental pulp, 831
of muscles, 164
of skin, 145
system of, 215
thrombi in, 681
Bloodletting, local, 927
Bodies, stellate, 624
Body of inferior maxillary bone, 101
Bone-cells, 41, 575
canaliculi of, 41
formation, subperiosteal, 47, 585
Bones, 35
apophyses of, 35
arrangement of, 48
articulations of, 118
cancellated, 36
chemical analysis of, 37
cranial, 50
dentigerous, of dog, 403
development of, 45
diaphyses of, 35
epiphyses of, 35
ethmoid, 76
facial, 131
frontal, 72
Haversian canals of, 39
hyoid, 108
inferior maxillary, 100
turbinated, 94
inflammation of, 43
intracartilaginous, 45
lachrymal, 95
lacunæ of, 41
lamellæ of, 39
malar, 97
maxillary, inferior, 100
superior, 81
minute structure of, 38
nasal, 96
occipital, 52
palate, 90
parietal, 69
perforating fibres of, 40
periosteum of, 42
softening of, 37
sphenoid, 62
spongy, 36
subperiosteal, 47
temporal, 55
turbinated, inferior, 79
superior, 79
vomer, 80
weight of, 37
Wormian, 118
Bourrelet, 617
Brachio-cephalic veins, 248
Bradypus tridactylus, teeth of, 411
Brain-case, anterior fossa of, 120
articulations of base of, 117
floor of, 120
middle fossa of, 122
posterior fossa. of, 123
walls of, 120
Bridgeman on caries, 744
Broken striæ of Retzius, 656
Buccal and labial surfaces, caries in, 781
artery, 234
cavity, development of, 550
glands, 206
nerve, 293, 309
Buccinator muscle, 173
Bulbous cord, invagination of, 624
1014
INDEX TO VOLUME I.
Bunodontia, teeth of, 484
Bunotheria, classification of, 416
C.
Calcic inflammation of the peridental mem-
brane and gums, 957
prognosis in, 968
treatment of, 963
Calcification, 570
and decalcification of teeth, chart of, 647
cylindrical, 878
of bone, 46
of dental pulp, 914
of dentine, 644
of permanent teeth, Pierce on, 645
of pulp, symptoms of, 914
treatment of, 915
of teeth, 363
of tissues of dental pulp, 874
Tomes on, 573
Calcoglobulin, 575
deposits of, in inflamed pulp, 860
Calcospherules, 575
Calculus, removal of, 963
Camphor phenol, 985
Canal, anterior palatine, 86
Haversian, 39, 576
inferior dental, 104
infraorbital, 82, 134
lachrymal, 134, 136, 212
naso-palatine, 81
posterior palatine, 84, 91
Vidian, 65
Canaliculi of bone, 41, 576
Canals, accessory palatine, 130
dentinal, 594
Cancellated portion of bone, 36
Canine eminence, 84
fossa, 84, 133
Canines, definition of, 399
human, 441
Cape anteater, teeth of, 412
Capillaries, lymph, 326
Capping materials, 894
of exposed dental pulp, 886, 894
Capsular ligament, 114
Capsule of Tenon, 178
Capybara, teeth of, 469
Carbolic acid in capping, 897
in superficial pulpitis, 905
Carbonate of sodium as an antiseptic, 909
Cariacus, teeth of, 488
Caries, absorptive processes in, 777
acid mucus in, 776
action of tobacco on, 808
agency of micro-organisms in, 750
beginnings of, 779
characteristics of, 786
clinical history of, 779
commencement of, in enamel, 765
dental, 729
producing secondary formations, 913
discoloration in, 769
diseases causative of, 778
etiology of, 731
Caries, experiments on, 797
fungi causing, 801, 802
fungi of, 814, 815
growths in, 767
hereditary influences causing, 772
infectious nature of, 789
inflammatory, theory of, 734
in necks of teeth, 786
in pits and grooves of the enamel, 779
in proximal surfaces, 779
lactic acid in, 798
penetration of dentine in, 765
of enamel in, 768
phenomena of, 764
predisposing causes of, 770
pulp-exposure in, 767
Carious dentine, lactic acid in, 800
surfaces, classes of, 779
Carnivora, classification of, 448
teeth of, 448
Carotid artery, external, 218
internal, 235
canal, 59, 122, 127
sheath, 157, 216
superior triangle, 188
Cartilage, 138
-cells, 140
connective tissue, 35
elasticity of, 138
fibre, 140
fibro-elastic, 140
hyaline, 139
interarticulating disc of, 114
lacuna, 140
Meckel's, 105
nasal, 77
Cartilago dentalis, 617
Caruncula lachrymalis, 212
Cats, dental evolution of, 460
Cause of apical pericementitis, 925
of fever, 715
of shock, 719
Cavernous sinus, 259
Cavity of the mouth, 137
Cebidae, teeth of, 435
Cell-movements in inflammation of dental
pulp, 850
-proliferation, Ziegler on, 526
Cells, amoeboid, 692
bone-, 41
cartilage-, 140
embryonal, of mucous membrane, 201
epithelial, 535
granulation-, 704
44
medullary or true marrow,
morphological appearance of, 531
multipolar giant-, 44
nucleated red blood-, 44
physiological consideration of, 524
stellate, 624
structure of, 523
wandering, 214, 692
Cementification, 590
Cementoblasts, 569, 591
Cement organ, 364
development of, 364
INDEX TO VOLUME I.
1015
Cementum, 358
canaliculi of, 358
lacunæ of, 358
Central retinal artery, 239
Centrifugal nerves, 274
Centripetal nerves, 275
Ceratodus, dentition of, 375
Cerebral arteries, 241
fossa, 124
nasal slit, 80
Ceruminous glands, 152
Cervical fascia, 156
ganglion, 313
nerve, 309
Cervico-facial nerve, 309
Cervicularis princeps artery, 227
Cetacea, baleen of, 353
teeth of, 413
Characteristics of caries, 786
Chart of calcification and decalcification
of teeth, 647
Charts, 782-785
Chlorosis, 689
Cholapus didactylus, teeth of, 411
Chorda tympani nerve, 307
Chronic alveolar abscess, 935
discharging on face, 940
pus burrowing in, 937
apical pericementitis, 925
Ciliary arteries, 239
ganglion, 298
nerves, 299
long, 289
Cingulum of premolar of dog, 355
Circle of Willis, 242
Circular sinus, 260
Civets, teeth of, 457
Classes of carious surfaces, 779
Classification of bone, 48
of fishes, 365
of Mammalia, 393
Clinical history of caries, 779
Clinoid processes, anterior, 62
middle, 62, 63
posterior, 62
Change in the maxillary bones after birth, Connective tissue, 135
107
Cocci in caries, 801
Collateral circulation of carotid arteries,
218
Collodion in capping, 897
Coloring matter produced by fungi, 825
Color of bones, 37
of muscle, 160
Common carotid arteries, 215
artery, left, 216
line of, 216
Common carotid artery, right, 216
sheath of, 216
variations of, 218
temporal vein, 252
Compact portion of bone, 36
Comparative chronology of dental follicle,
651
Composition of enamel, 608
Compound tubular salivary glands, 204
mucous glands, 202
nerves, 277
Compressible pulse, 666
Compressor nasi muscle, 170
Condyle of bones, 49
Condyles of occipital bone, 52, 128
Condyloid fossa, 53
Cheiroptera, teeth of, 465
Chemical analysis of bone, 37
Chill in fever, 713
Chimera plumbea, dentition of, 375
Chiromys, teeth of, 432
634
Chitin, 337, 342
of enamel organ, 620
Chloride of zinc in calcic inflammation, Cornea, irritation of, 697, 698
966
Cornua of hyoid bone, 109
Coronal suture, 112
Coronary artery, inferior, 225
superior, 225
Coronoid process, 104
Corpuscles, lymph, 325
osseous, 41
Pacinian, 146
tactile, 142, 146
white, 325, 532
Cortical layer of enamel, 608
Corrugator supercilii muscle, 169
Counter-irritation, 927
Cranial bones, 50
nerves, 223
processes of inferior maxilla, 104
Congestion, local, 674
embryonic, 564
envelope, 630
fibrillar, 565
Constitutional treatment in alveolar ab-
scess, 946
of apical pericementitis, 928
Contractile substance, 162
Conus, teeth of, 346
Cord for permanent teeth, development of,
region supplied by, 277
Crest, infratemporal, 65
of nasal bones, 97
Cribriform plate, 79
Crico-thyroid artery, 220
Crista galli, 77
Crocodilia, teeth of, 385
Crustacea, masticatory apparatus of, 339
Crusta petrosa, 355
Cryptoproctidæ, classification of, 458
teeth of, 457
Culture materials, 792, 793
Cultures for biological studies, 822
gelatin, 814
Cup-shaped abrasions, 995
Cusps of teeth, facets on, 993
Cushing's scalers, 964
Cuticula dentis, 606
Cylindrical calcification, 878
1016
INDEX TO VOLUME I.
D.
Death of dental pulp, 852
Decalcification of temporary teeth, Pierce
on, 645
Deciduous dentition of man, 446
Decomposition of the dental pulp, 892
Deep auricular branch of internal maxil-
lary artery, 232
cervical fascia, 156
facial or anterior internal maxillary
vein, 251
artery, 230
vein, tributaries of, 251
fascia, 155
of face, 158
of head, 158
temporal artery, 233
Deep-seated pulpitis, treatment of, 906
Degeneration of structure of dental pulp,
859
Deinotherium, dentition of, 491
Delphinidæ, teeth of, 414
Dendrohyrax, teeth of, 475
Density of dentine, causes increasing, 912
Dental anatomy, 351
caries, 729
growths of secondary dentine excited
by, 868
erosion, hyperæsthesia in, 1006
follicle, comparative chronology of, 651
formula, 403
groove, 616
ligament, 919, 955
nerves, middle superior set, 291
neuralgia, 837
operations, shock from, 725
papilla, 641
pulp, 592-636
abscess of, 855-857
blood-vessels of, 831
calcification of, 914
of tissues of, 874
causes of inflammation in, 849
producing devitalization of, 892
cells of, 830
chronic inflammation of, 857-859
death of, 852
decomposition of, 892
degeneration of structure of, 859
differential diagnosis between diseases
of, 837
dilated vessels of, 846
diseases and treatment of, 888
exposure of, 853
function of, 832
gangrene of, 892
hyperemia of, 840-843
inflammation of, 848-853
irritation of, 844, 889
microscopic study of, 840-842
nerves of, 831
pathology of, 829
removal of, 903, 926
sensitiveness to thermal changes in,
848
Dental pulp, sensory functions and symp-
tomatology of, 832
simple exposure of, 890
suppuration of, 853-855
swelling of, 839
symptoms of inflammation of, 852
fissure of, 829
ridge, 616
sacculus, 361, 364
tissues, 356
tubes, 356
Dentary bone of fishes, development of,
378
Dentate sutures, 111
Dentinal canals, 594
fibrils, 357
secondary dentine resulting from irri-
tation of, 870
papilla, 568, 622
processes, 357, 594
sheath, 357
tubules, softening of, 768
Dentine, 356
analysis of, 356
calcification of, 644
deposit of, 592
development of, 593
discoloration of, 852
granular layer of, 357
increase of density of, 911
nodular, 911
organ, 361
development of, 361
secondary, 911
resulting from irritation of dentinal
fibrils, 870
sensitiveness of, 1006
structure of, 356
Dentinification, 591
Dentition of alligator, 385
Deposition of fat, 565
Deposit of dentine, 592
Deposits of calcoglobulin in inflamed pulp,
860
secondary causes of, 913
Depressor alæ nasi muscle, 171
anguli oris muscle, 173
labii superioris muscle, 172
Dermal denticles, 353
development of, 354
structure of, 353
spines, 354
Descendens noni nerve, 323
Descending cervical artery, 227
or dental nerve, 291
palatine artery, 234
nerves, 301
Desiccation of enamel, 609
Desirabode on caries, 736
Desmatotherium, teeth of, 478
Development, embryonic, 542
of alveolar wall, 632
of blood-corpuscles, 566
of blood-vessels, 566, 706
of bone, 45
intercartilaginous, 587
INDEX TO VOLUME I.
1017
Development of bone, intramembranous, | Diploic veins, 261
48
subperiosteal, 47
of bones of the face, 110
of buccal cavity, 550
of cord for permanent teeth, 634
of dentine, 593
of dermal denticles, 354
of enamel, 643
of enamel organ, 562
of epiblast, 555
of ethmoid bone, 80
of fat, 565
of frontal bone, 76
of glands, 560
of hair, 558
of head, 109
of hyoid bone, 109
of inferior maxilla, 105
of interior turbinated bone, 95
of jaws, 110, 550
of lachrymal bone, 96
of malar bones, 100
of maxillæ, 551 ·
of mesoblast, 555
of nails, 556
of nasal bone, 97
of occipital bone, 54
of parietal bone, 71
of palate, 551
of palate bone, 93
of pharyngeal teeth of fishes, 361
of sphenoid bone, 67
of superior maxillary bone, 88
of the teeth, 360, 609
of teeth of fishes, 378
of temporal bone, 61
of vomer, 81
Devitalization and removal of dental pulp,
898
of dental pulp, causes producing, 892
Devitalized pulps, removal of, 907
Diadectes, teeth of, 384
Diagnosis of alveolar abscess, 943
of exposed dental pulp, 891
Diapedesis of red blood-globules, 679
of white blood-globules, 692
Diaphyses of bones, 35
Diarthrosis, articulation, 112
Diclonius, teeth of, 387
Dicrotous pulse, 670
Didelphis Virginianus, teeth of, 495
Didymictis, teeth of, 430
Differential diagnosis between diseases of
the dental pulp, 837
Digastric fossa, 60, 102
groove, 60, 127
muscle, 187
nerve, 308
Dilated vessels of dental pulp, 846
Dilophodon, teeth of, 478
Dimetrodon, teeth of, 383
Dinictis, teeth of, 460
Diodon, teeth of, 378
Diphyodont dentition, 396
Diplöe, 120
Diprotodontia, teeth of, 496
Discoloration in caries, 769
of dentine following death of dental
pulp, 852
Disease, definition of, 661
Diseases causative of caries, 778
of dental pulp and their treatment, 888
of peridental membrane, 918, 921
having their beginning at margin
of gum, 953
Dissacus, teeth of, 420
Distal end of bones, 49
Division of nerve fibres, 268
Divisions of mammalian dentition, 396
Dicoglossata, 348
Dog, teeth of, 397
Dolphin, teeth of, 414
Dome or vertex of the skull, 120
Domestic cat, teeth of, 461
Dorsal plates of embryo, 543
Dorsalis lingual artery, 221
Dorsum sella, 62
Dry gangrene, 893, 910
Duct, lachrymal, 212
lachrymo-nasal, 213
of Bartholini, 211
of Steno, 208
of Wharton, 210
parotid, 208
submaxillary, 210
thoracic, 330
Ducts of Rivinus, 211
sublingual, 211
E.
Ear, muscles of the, 174
Echinidæ, food of, 341
Echinus (sea-urchin), dental system of, 340
oral apparatus of, 339
Ectocium, molars of, 480
Ectoconus, teeth of, 471
Edentata, teeth of, 408
Egg, ovarian, 540
Eggs, mammalian, 542
Eighth nerve, 310
Elasmobranchii, definition of, 365
teeth of, 370
Elasticity of cartilage, 138
Elephants, teeth of, 488
Eleventh nerve, 320
Embryo, dorsal, plates of, 543
neural, groove of, 543
plates of abdominal, 543
Embryology, 539
and histology, dental, 519
Embryonal cells of mucous membrane, 201
mucous membrane of the mouth, 611
Embryonic connective tissue, 564
development, 542
Embolism, 683
Eminence of parietal bone, 69
Emissary veins, 262
Emenentia articularis, 56
Empedocles molaris, teeth of, 383
1018
INDEX TO VOLUME I.
Enamel, 359
analysis of, 359
cells, 362
composition of, 608
cortical layer of, 608
cuticle, 358
desiccation of, 609
development of, 643
fixed material in, 600
formed material in, 600
membrane, 606
nacreous layer of, 608
organ and papilla, connection between,
628
cord of, 620
inner tunic of, 626
development of, 361, 562
organic, layer of, 608
prisms, 359, 601
structure of, 359
variations in hardness of, 602
Endochondral bone, 45
Endomysium of muscles, 161
Endosteum of bone, 43
Envelope, connective tissue of, 630
Epiblast, 142, 543
Epithelium of mucous membrane, 199
of oral cavity, 199
reproduction of, 708
of the skin, 614
transplantation of, 708
Erosion and abrasion of teeth, 993
etiology, 1002
Erosions of teeth, position and form of,
997-1002
Esthonyx, teeth of, 425
Ethmoid bone, 76
process of turbinated bone, 94
Ethmoidal cells, posterior, 79
foramina, 75, 78, 134
development of, 555
products of, 556
Epicranial or occipito-frontal aponeurosis, Facial artery, 222
branches of, 224
167
Epidermis, 143
Epiphyses of bones, 35
Epithelial cells, 535
notch, 75
spine, 62
wings, 77
Etiology of caries, 731
of erosion, 1002
of mechanical abrasion, 994
of phagedenic pericementitis, 977
Eustachian sulcus, 127
Evacuation of pus in alveolar abscess, 945
Evolution, theory of, 520
Examination of pulse, 663
Exciting cause of inflammation, 700
Exostosis, causes producing, 913
Experiments on caries, 797
Exposure of dental pulp, secondary de-
posit in, 886
External auditory meatus, 60, 127
angular process, 73
carotid artery, 218
with acids on teeth, 1003-1006
Exposed dental pulp, capping of, 886
diagnosis of, 891
Exposure of dental pulp, 853
treatment of, 893
branches of, 219
jugular vein, 255
and tributaries, 255
lateral ligament, 114
maxillary artery, 222
nasal artery, 241
oblique line of inferior maxilla, 101
occipital protuberance, 53
palatine nerve, 301
pterygoid muscle, 182
nerve, 293
plate, 67
rectus muscle, 176
surface of brain-case, 124
tendo-palpebrarum muscle, 169
Exudate, fibrinous, 694
Exudates in inflammation, 694
F.
Face, swelling of, in acute alveolar abscess,
931
Facets in cusps of teeth, 993
bones, 131
muscles, 166
nerve, 304
communicating branches, 305-307
origin of, 305
table of its branches, 305
notch of inferior maxilla, 103
or anterior region of skull, 131
or terminal nerves of superior maxil-
lary, 291
region of skull, 131
vein, 224, 249
Farrar's syringe, 967
Fascia, 154
aponeurotic, 155
deep, 155
cervical, 156
of face, 156
of head, 156
of neck, 156
of orbit, 178
of Tenon, 178
omo-hyoid, 157
parotid, 209
prevertebral, 157
subcutaneous, 155
submaxillary, 157
superficial, 155
temporal, 179
Fasciculi of muscles, 161
Fat, deposition of, 565
development of, 565
-vesicles or adipose tissue, 44
Faulty antagonism of teeth producing
wear, 994
formation of the teeth, 770
INDEX TO VOLUME I.
1019
Fermentation a cause of caries, 738
in human mouth, experiments on, 793-
795
its relation to caries of teeth, 791
in mouth, apparatus for experiments on,
792
Fever, 711
cause of, 715
chill in, 713
heat-production in, 714
results of, 717
surgical, 713
temperature in, 711
Fibres, muscular, 162
Fibrillar connective tissue, 563
Fibrils, dental, 357
Fibrinous exudate, 694
Fibro-cartilage, 140
-connective tissue, 35
-elastic cartilage, 140
Fifth nerve, 282
origin of, 284
pair of nerves, sympathetic ganglia of,
297
teeth of, 364
Fissure, pterygo-maxillary, 130
glenoid, 56, 57, 127
sphenoid, 66
malar, 97, 134
mastoid, 124
naso-palatine, 86
of Scarpa, 86
optic, 62, 67
parietal, 117
table showing distribution of, 287
posterior condyloid, 53, 124
ethmoidal, 75, 78, 134
Filling materials, antiseptic power of, 810 Formation of bone, interstitial, 580
for pulp-canals, 909
intramembranous, 48, 583
pulp-canals, 899
of ducts in grain, 707
time for, 903
used in capping, 898
Fishes, classification of, 365
of poisons by micro-organisms, Black
on, 757
spheno-maxillary, 65, 99, 130, 134
Fistula discharging under the chin, 942
passing through lower maxilla, 942
Fixed material in enamel, 600
Flagg, Foster, formula for nerve-paste, 900
Flat bones, 36
Floor of nasal fossa, 135
of the mouth, 137
Fluids of the mouth, morbid conditions of,
774
Flying foxes, teeth of, 465
Foetal septum, 551
Fomentations in alveolar abscess, 947
Fontanelle, anterior median, 119
posterior median, 119
Fontanelles, 119
lateral, 119
Foramen, anterior condyloid, 124
dental, 101, 133
lacerated, 66, 134
cæcum, 74
incisive, 86, 136
infraorbital, 84, 132
jugular or posterior lacerated, 52
lacerum medius, 122
posterius, 123
magnum, 54, 124
malar, 97, 134
mental, 101
middle lacerated, 58, 127
of Scarpa, 136
Foramen of Stetson, 86, 136
optic, 133
ovale, 65, 122, 126
parietal, 70
posterior dental, 103
lacerated, 127
pterygo-palatine, 130
rotundum, 65, 122
spheno-palatine, 92, 130, 136, 127
spinosum, 65, 122
stylo-mastoid, 60, 122
supraorbital, 73, 132
Vesali, 122
Foramina, anterior condyloid, 53
ethmoidal, 75, 78, 134
lacerated, 122, 134
infraorbital, 132
Formed materials in enamel, 600
Formula, dental, 403
Fossa, anterior, of the brain-case, 120
canine, 84, 133
cerebral, 124
condyloid, 53
digastric, of inferior maxilla, 102, 127
incisive, 101
lachrymal, 75, 133
middle, of the brain-case, 122
nasal, 134
parietal, 70
pituitary, 62
posterior, of brain-case, 123
pterygoid, 67, 104
scaphoid, 67
spheno-maxillary, 130
sublingual, 102
temporal, 128
trochlear, 75
zygomatic, 129
Fox squirrel, teeth of, 467
Frænum of lower lip, 173
of upper lip, 172
Frontal artery, 241
bone, 72
eminence, 74
nerve, 286
notch, 73
processes of malar bones, 98
sinuses, 73
vein, 250
Fronto-ethmoidal cells, 75
-malar suture, 117
-parietal suture, 117
-sphenoidal suture, 117
1020
INDEX TO VOLUME I.
Function of peridental membrane, 920
Fungi causing caries, 801, 802
coloring matter produced by, 825
of caries, 814, 815
action of sugar, 805
evolution of carbonic acid by, 805
of dental caries, their pure cultivation
and effect upon lower animals, 813
of human mouth, acid produced by, 824-
826
biological studies on, 819
morphology of, 823
relation to oxygen, 824
peptonizing action of, 824
oxygen in relation to, 805
production of gas by, 825
Fungus growths in caries, 767
G.
Galeopithecus, teeth of, 428
Ganglion, cervical, 313
-cells of nerves, 264
ciliary, 298
Gasserian, 284
geniculate, 306
jugular, 313
inferior or petrous, 311
lenticular, 798
of Andersch, 311
of Ehrenritter, 311
of Meckel, 299, 301
ophthalmic, 598
optic, 302
otic, 302
semilunar, 284
spheno-palatine, 299, 301
submaxillary, 303
of dental pulp, 892
Gangrenous pulps, causes of, 906
treatment of, 907
Gasserian ganglion, 284
Gastro-pneumonic system of mucous mem-
branes, 199
superficial jugular, 311
sympathetic, of fifth pair of nerves, 297 Granulation-cells, 704
Gangrene, dry, 893, 910
Gelatin cultures, 814
General development of the head, 109
pathology, 661
Generation, spontaneous, 521
Genial tubercles, 102
Geniculate ganglion, 306
Genio-glossus muscle, 190
hyoid muscle, 190
Genito-urinary system of mucous mem-
brane, 199
Geomalacus, jaw of, 349
Gila monster, teeth of, 386
Glands, submaxillary, 209
buccal, 206
ceruminous, 152
compound tubular mucus, 202
saliva, 204
development of, 560
labial, 206
lingual, 207
lymphatic, 328
Meibomian, 153
molar, 206
muco-salivary, 206
mucus, 198, 204
of mucous membrane, 198
palatine, 207
racemose, 203
sebaceous, 152, 560
secretory, of mucous membrane, 201
simple mucous, tubular, 202
sudoriferous, 151
Gingival organ, 955
Gingivitis, 955
Ginglymus, or hinge-joint of Allen, 112
Glands, lachrymal, 211
of Bartholin, 210
parotid, 207
sublingual, 210
sweat, 151
true salivary, 205
Glandular arteries, 224
Glandula socia parotidis, 208
Glasserian fissure, 56
Glenoid fissure, 56, 57, 127
fossa, 56, 127
Glosso-pharyngeal nerve, 310
communicating branches of, 312
lingual branches of, 312
muscular branches of, 312
pharyngeal branches of, 312
table of branches, 311
Glyptodon, teeth of, 410
Glyptostoma, jaw of, 349
Gold in caries, 811
Gouty inflammations of the peridental
membrane, 979
Grain, formation of ducts in, 707
Granulations in blood-clot, 710
Great superficial petrosal nerve, 306
wings of sphenoid bone, 64
Groove, dental, 616
digastric, 127
medullary, 548
mylo-hyoid, 102
Grooves for olfactory nerves, 77
Growth of bone, 47
Gum, structure of, 955
Gutta-percha for filling pulp-canals, 909
H.
Hair, 147
bulb of, 147
cuticle of, 148
development of, 558
fibrous or cortical portion of, 148
follicles of, 147-149
medulla of, 149
papilla of, 150
root of, 147
health of, 149
shaft of, 147
Halmaturus, teeth of, 496
INDEX TO VOLUME I.
1021
Hamular process, 67
Hanover, stratum, intermedium of, 625
Hapale, teeth of, 435
Harmonic sutures, 111
Haversian canal, 576
canals of bone, 39
Heads of bones, 49
Health, definition of, 661
Heart lesions, pulse in, 670
Heat-production in fever, 714
Hedgehog, teeth of, 429
Heloderma suspectum, teeth of, 386
Hemorrhage, 685
Hemorrhagic infarction, 683
Hereditary influences causing caries, 772
Herpestes, teeth of, 456
Heterodont dentition, 396
Hiatus Fallopii, 58, 123
Highmore, antrum of, 89
Hippotherium, teeth of, 481
Hirudina (leeches), teeth of, 338
Histology, dental, 519
of teeth, 356
Hog, teeth of, 484
Homodont dentition, 396
Horse, canines of, 483
digits of, 482
incisors of, 482
molars of, 483
Human dentition, 437
Hunter on caries, 731
Hyæna, teeth of, 455
Hyænidæ, evolution of, 453
Hyænarctos, teeth of, 464
Hyænictis, teeth of, 456
Hyænodontidæ, teeth of, 420
Hyaline cartilage, 139
Hyo-branchial skeleton, 369
bones of, 369
Hyo-glossus muscle, 191
Hyoid artery, 220
bone, 108
development of, 109
Hyo-mandibular arch of codfish, 367
Hyperæmia, 676
local, 674
of dental pulp, 840, 843, 847, 848
pain in, 844
passive, 677
results of, 678
tissue, change in, 845
Hyperesthesia in dental erosion, 1006
Hypoblast, 142, 543
Hyracoidea, ancestry of, 476
Hyracotherium, teeth of, 477
Hyrax, teeth of, 475
Hypoglossal nerve, 322
communicating branches of, 323
lingual branches of, 324
table of, 323
I.
Ictitherium, teeth of, 453
Iguanidæ, teeth of, 386
Iguanodon, teeth of, 387
Incisive artery, 233
crest, 86
foramen, 86, 136
fossa of inferior maxilla, 101
of superior maxilla, 84
Incisors, definition of, 398
human, 438
lower, human, 440
upper central, human, 440
lateral, human, 440
Indian elephant, molars of, 490
tusks of, 489
Infant layer of epithelium, 618
Infarction, hemorrhagic, 683
Infection by micro-organisms of the mouth,
816
Infectious alveolitis, 968
nature of caries, 789
Inferior constrictor muscle, 194
coronary artery, 225
curved lines of occipital bone, 53
dental artery, 233
canal, 104
foramen, 103
nerve, 296
branches of, 296, 297
communicating branch, 296
incisive, branches of, 297
lesser, 297
mental or labial branch, 297
labial artery, 225
laryngeal artery, 247
longitudinal sinus, 258
maxilla, at birth, 105
development of, 105
movement of, 105
maxillary bone, 100
nerve, 292
deep temporal branches of, 292
posterior temporal branch of, 293
meatus, 85, 136
oblique muscle, 177
ophthalmic vein, 261
or palatine artery, 224
or recurrent laryngeal nerve, 318
palatine vein, 251
palpebral veins, 251
pedicle of sphenoid bone, 67
petrosal sinus, 261
petrous ganglion, 311
rectus muscle, 176
thyroid artery, 246
veins, 248
turbinated hone, 94
crest, 92
Inflammation, 690
chronic, of dental pulp, 857-859
exciting cause of, 700
exudates in, 694
in dental pulp, causes of, 949
of bone, 43
of dental pulp, 848-853
cell, movements in, 850
lymph-deposits in, 852
recovery from, 853
symptoms of, 852
1022
INDEX TO VOLUME I.
Inflammation of dental pulp, tissue-changes | Irregularities of pulse, 669
in, 849
944
of peridental membrane, cause of, 893
pain in, 693
subperiosteal,
swelling in, 693
temperature in, 693
tissue-changes in, 695
white blood-corpuscles in, 695
Influence of disease on bones, 49, 135
Infraorbital artery, 234
canal, 82, 134
foramen, 84
foramina, 132
nerve, 290
plexus, 292
ridge, 84
Infratonsillar or pharyngeal tonsils, 214
Infratemporal crest, 65, 129
Infratrochlear nerve, 289
Infundibulum of ethmoid bone, 79
of nasal chamber, 137
Inner tunic, 640
of enamel organ, 626
Innominate veins, 248
right and left, 248
Insectivora, teeth of, 417
Inter-articulating disc or fibro-cartilage,
114
-cartilaginous development of bone, 587
-globular spaces, 357, 595, 766
-maxillary bone, 88
-parietal bone, 54
suture, 116
Intermittent pulse, 670
Internal angular process, 73
auditory meatus, 59, 123
carotid artery, 235
frontal crest, 74
jugular vein and tributaries, 256
laryngeal nerve, 318
lateral ligament, 115
mammary artery, 247
maxillary artery, 230
deep temporal, branches of, 233
vein, 253
nasal nerves, 289
oblique ridge, 101
occipital crest, 53
protuberance, 53
pterygoid muscle, 181
nerve, 293
plate, 67, 68
rectus muscle, 176
tendo-palpebrarum muscle, 169
Interstitial formation of bone, 580
Intra-cartilaginous bone, 45
Intra-membranous bone, 48
formation of bone, 48, 583
Invagination of bulbous cord, 624
Invertebrates, teeth of, 337
Involuntary, smooth, or unstriated mus-
cles, 164
Iodine, uses of, on gangrenous pulps, 908
Iodoform in capping, 898
in superficial pulpitis, 905
of teeth caused by inflammation of the
throat, 135
Irritation causing secondary dentine, 913
of cornea, 697, 698
of dental pulp, 844, 889
Ivory, nature of, 489
J.
Jaw, development of, 550, 629
Jelly of Wharton, 566
Jugular foramen, 52
ganglion, 313
notch, 52
process of occipital bone, 51
K.
Kangaroo, teeth of, 496
Koecker on caries, 733
L.
Labial and buccal surfaces, caries in, 781
glands, 206
or descending nerves, 292
Labyrinthodonts, teeth of, 381
Lachrymal artery, 238
bone, 95
canal, 134, 136, 212
crest, 95
duct, 212
fossa, 75, 133
gland, 211
groove, 84
nasal duct, 213
passage, 213
nerve, 288
process, 94
sac, 213
tubercle, 84
Lactic acid in caries, 798
in carious dentine, 800
Lacto-phosphate of lime in capping, 897
Lacuna-cartilage, 140
Lacunæ of bone, 41, 576
Lagomorpha, teeth of, 469
Lambdoid suture, 117
Lambdotherium, molars of, 480
Lamella of bone, 39
Lamina cribrosa, 59
of embryo, 618
Lantern of Aristotle, 339
Laryngeal artery, 220
Lateral communicating arteries, 243
fontanelles, 119
masses of ethmoid bone, 78
nasal artery, 225
processes of pulp, 358
region of the skull, 128
sinuses, 259
Layer, odontoblastic, 640
Leber and Rottenstein on caries, 751
Leeching in apical pericementitis, 928
Leeches (Hirudine), teeth of, 338
INDEX TO VOLUME I.
1023
Left common carotid artery, 216
Lemurs, teeth of, 431
Lenticular ganglion, 298
Leptictis, teeth of, 424
Leptocardii, definition of, 365
Leptothrix buccalis, 751, 795
gigantea, 795
Lesser superficial petrosal nerve, 306
wings of sphenoid bone, 66
Leucocytes, 325, 692
Levator anguli oris muscle, 172
labii inferioris muscle, 173
superioris alæque nasi muscle, 171
proprius muscle, 171
palati muscle, 197
palpebral muscle, 176
Life, nature of, 519
Ligament, capsular, 114
dental, 919, 955
internal lateral, 115
stylo-hyoid, 189
-maxillary, 115
Ligaments of the temporo-maxillary artic-
ulation, 113
Ligatures, absorption of, 922
Limnæa, teeth of, 349
Line ridge or crest, 49
Lingual artery, 221
glands, 207
nerve, 295
branches of communication, 295
vein and tributaries, 254
Lingualis muscle, 191
Lister, method of, 755
Lizard, teeth of, 386
Local congestion, 674
hyperæmia, 674
Longitudinal sinus, 75
Lophiodontidae, digital formula of, 477
teeth of, 477
Loxodon Africanus, dentition of, 489
Lutrictis, teeth of, 464
Lymph-capillaries, 326
Lymph, composition of, 325
-corpuscles, 325
deposits in inflammation of dental pulp,
852
-sinus, 329
-spaces, 326
of bone, 41
Lymphatic duct, 330
glands, 328
vessels, 325
of head and neck, 330
structure of, 327
valves of, 327
Lymphatics, deep, 330
of muscles, 164
of skin, 145
origin of, 326
superficial, 330
Lyrifera, definition of, 365
M.
Magitot on caries, 747
Magnum foramen, 124
Malar bones, 97
foramina, 97, 134
process, 85
Malpighi stratum, 144
Malpighian layer of the skin, 615
Mammalia, classification of, 393
origin of, 391
teeth of, 390
Mammalian dentition, divisions of, 396
eggs, 542
Marmosets, dentition of, 434
Marrow-fat, vesicles of, 44
of bone, 43
red, 43
red cells of, 45
yellow, 43
Marsipobranchii, definition of, 365
Marsupials, distinctions of, 493
teeth of, 493
Masseter muscle, 179
Masseteric artery, 234
nerve, 293
Mastication, action of muscles of, 182
muscles of, 178, 406
Mastodon, teeth of, 491
Mastoid artery, 227
foramen, 124
portion of temporal bone, 60
Materials for capping, 894
Matrix of osseous substance, 571
Maxillæ, development of, 551
Maxillary bone, inferior, 100
superior, 81
bones of codfish, 368
process of turbinated bone, 94
of malar bones, 99
sinus, 89
Meatus, anterior palatine, 86
external auditory, 60, 127
inferior, 85, 136
internal auditory, 59, 123
middle, 136
of superior maxillary bone, 85
superior, 136
of ethmoid bone, 79
of superior maxillary bone, 85
Mechanical abrasion, etiology of, 994
Meckel's cartilage, 57, 105
development of, 552
ossification of, 105, 554
ganglion, 299
Medullary groove, 548
or true marrow-cells, 44
plates, 548
sheath, 266
Megalonyx, teeth of, 411
Megalotidæ, teeth of, 453
Megatherium, teeth of, 410
Meibomian glands, 153
Membrana eboris, 358
destruction of, 885
Membrane, basement, 145
corium of mucous, 200
epithelium of mucous, 199
mucous, 198
1024
INDEX TO VOLUME I.
Membrane of enamel, 606
of Nasmyth, 358
Meningeal arteries, 229
Meniscotherium, teeth of, 474
Menopomea, dentition of, 381
Mental artery, 233
foramen, 101, 133
process, 101
Mento-hyoid muscle, 189
Mesoblast, 142, 543
development of, 555
products of, 556
Mesonyx, teeth of, 418
Miacis, teeth of, 430
Micro-organisms in phagedenic perice-
mentitis, 977
of the mouth, infection by, 816
Microscopic study of dental pulp, 840-842
Microscopical examination, preparation of
bone for, 38
Midas, teeth of, 434
Middle cerebral artery, 242
clinoid process, 63
constrictor muscle, 193
deep temporal nerve, 293
fossæ of brain-case, 122
lacerated foramen, 58, 122, 127
meatus, 85, 136
or great meningeal artery, 232
superior dental nerve, 291
temporal artery, 229
vein, 253
turbinated bone, 79
Migrating lymph-corpuscles of tonsils, 214
Milk dentition, 498
Miller, experiments of, 759
on fermentation in the human mouth,
its relation to caries of the teeth,
791
Mills and Underwood on caries, 752
Minute structure of bone, 38
Molar glands, 206
Molars, definition of, 401
human, 443
of elephant, shedding of, 490
wear of, 490
Molecular disturbances in shock, 722
Mollusca, dental apparatus of, 341, 349
Molluscan animals, functions of teeth, 350
radular apparatus, 342
Mollusks, chitinous armature of, 342
radular of, instructions for examining,
344, 345
Monkeys, teeth of, 434
Monodon, teeth of, 414
Monophyodont dentition, 396
Morbid conditions of fluids of the mouth,
774
Morphia and arsenious-acid pastes, 900
Morphological appearance of cells, 531
Morphology of fungi of the human mouth,
823
Motion, nerves of, 274
Motor nerves, peripheral end-organs of,
272
Mouth, cavity of, 137
Mouth, embryonal mucous membrane of,
201, 611
floor of, 137
roof of, 137
Movements of inferior maxilla, 115
Muco-periosteum, 200
salivary glands, 206
Mucous glands, 198, 204
membrane, 198
embryonal cells of, 201
epithelium of, 199
gastro-pneumonic system of, 199
genito-urinary system of, 199
glands of, 198
secretory glands of, 201
Multipolar giant-cells, 44
Mummified condition of the pulp, 893
pulps, 910
Muscles, action of orbital, 177
attolens aurem, 175
attrahens aurem, 175
azygos uvulæ, 198
blood-vessels of, 164
buccinator, 173
contractile substance of, 162
corrugator supercilii, 169
depressor anguli oris, 173
labii inferioris, 173
labii superioris, 172
endomysium of, 161
external pterygoid, 182
facial, 166
fasciculi of, 161
size of, 162
fibres of, 164
genio-glossus, 190
-hyoid, 190
Honer's, 169
hyo-glossus, 191
inferior oblique, 177
constrictor, 194
internal pterygoid, 181
involuntary, 164
levator anguli oris, 172
labii superioris alæque.nasi, 171
proprius, 171
palati, 197
palpebræ, 176
lingualis, 191
lymphatics of, 164
of mastication, action of, 182
mento-hyoid (Macalister), 189
of ear, 174
of mastication, 406
oral group, 171
middle constrictor, 193
mylo-hyoid, 189
nasal set, 170
neck, 183
action of, 183, 185
nerves of, 164
number of, 166
occipito-frontalis, 166
of orbit, 175
of the pharynx, 192
omo-hyoid, 186
:
INDEX TO VOLUME I.
1025
Muscles, oral, action of, 174
orbicularis oris, 171
palpebrarum, 168
orbital, action of, 177
palato-Eustachian, 197.
-glossus, 196
194
superior constrictor, 192
oblique, 177
supra-hyoid space, 187
temporal, 180
tensor palati, 197
tarsi, 169
thyro-hyoid, 186
trochlearis, 177
unstriped, 164
varieties, 165
voluntary, fibres of, 160
zygomaticus major, 172
minor, 172
-pharyngeus, 195
perimysium of, 161
pterygoideus proprius (Henle), 182
pyramidales nasi, 168
recti or straight of the orbit, 176
retrahens aurem, 175
risorus, 173
soft palate, 192
sterno-cleido-mastoideus, 184
-hyoid, 185
-thyroid, 186
stylo-glossus, 191
-hyoid, 189
-pharyngeus,
Muscular arteries of the orbit, 240
fibres, 162
tissue, 159
Muskrat, teeth of, 467
Mustilidæ, teeth of, 464
Myeloplaxes of bone, 43
Mylo-hyoid artery, 233
groove, 102
muscle, 189
nerve, 296
ridge, 101
Myolemma, 162
Myrmecobius, dentition of, 493
Myrtiform fossa, 84
.
N.
Nacreous layer of enamel, 608
Nails, development of, 556
Narwhal, teeth of, 414
Nasal angle, 97
aperture, posterior, 136
arch, 132, 136
artery, lateral, 225
bones, 96
cartilage, 77
chamber, infundibulum of, 137
crest, 86
eminence, 73
fossa, 134
muscles, 170
nerve, branches of, 288
notch, 73
VOL. I.-65
Nasal openings, anterior, 132, 136
or internal set of nerves, 292
or spheno-palatine artery, 235
process of superior maxillary bone, 85
septum, 135
abnormality of, 135
spine of frontal bone, 73
of superior maxilla, 86
of superior maxillary bone, 86
Nasmyth's membrane, office of, 608
origin of, 608
Naso- or oculo-nasal nerve, 288
-palatine canal, 81, 136
foramina, 86
nerve, 302
Neck, muscles of, 183
of bones, 49
veins of, 254
Necks of the teeth, caries in, 786
Necrosis of alveolar process, 951
of bone, cause of, in alveolar abscess, 934
Nervæ vasorum, 327
Nerve, axis-cylinder of, 266
-centres, 263
eighth, 310
eleventh, 320
endings in gland-cells, 271
fibres, 264, 268
fifth, 282
table showing distribution of, 287
medullary, sheath of, 266
ninth, 310
non-medullary or pale fibres, 268
posterior superior dental, 290
seventh, 304
sixth, 282
supply of the peridental membrane, 919
tenth, 313
trifacial, 282
trigeminus, 282
twelfth, 322
Nerves, abdominal or terminal, branches
of pneumogastric, 320
abducens, 282
alveolar dental, 290
anterior palatine, 301
superior dental, 291
articular, 294
ascending or orbital, 301
auditory, 310
auriculo-temporal, 294
buccal, 293, 309
cardiac branches of the pneumogastric,
319
centrifugal, 274
centripetal, 275
cervical or intramaxillary, 309
cervico-facial, 309
chorda tympani, 301
communicating branches of the facial,
306
compound, 277
cranial, 273
descending or descendens noni, 323
palatine, 301
digastric, 308
1026
INDEX TO VOLUME I.
1
Nerves, division of fibres, 268
end-plates of Kühne, 272
external pterygoid, 293
facial, 304
first pair of, 277
fourth pair of, 281
frontal, 286
ganglion-cells of, 264
glosso-pharyngeal, 310
hypoglossal, 322
incisor, 297
inferior dental, 296, 297
maxillary, 292
or recurrent laryngeal, 318
infraorbital, 290
intratrochlear, 289
internal laryngeal, 318
nasal, 289
pterygoid, 293
lachrymal, 288
left pneumogastric, 315
lesser inferior dental (Sapolini), 297
superficial petrosal, 306
lingual, 295
long ciliary, 289
masseteric, 293
mental or labial, 297
middle deep temporal, 292
superior dental, 291
motor oculi, 280
peripheral end-organs, 272
mylo-hyoid, 290
nasal or oculo-nasal, 288
naso-palatine, 302
neurilemma of, 267
nodes and internodes of Ranvier, 267
occipital, 308
œsophageal, 320
branch of the pneumogastric, 320
of external auditory meatus, 295
of motion, 274
of pulp, 655
of muscles, 164
of sensation, 275
of skin, 145
of special sense, 275
olfactory, 277
ophthalmic, 286
optic, 278
orbital or temporal malar, 290
parotid, 295
pathetic, 281
pharyngeal or pterygo-palatine, 302
pneumogastric, 313
accessory portion of, 313
cervical or inferior ganglion of, 313
communicating of, 312
jugular or superior ganglion, 313
lingual or terminal branches of, 312
posterior auricular, 308
superior dental, 290
temporal, 293
pulmonary branches of the pneumogas-
tric, 319
recurrent branch, hypoglossus, 323
right pneumogastric, 315
Nerves, second pair of, 278
sensory peripheral end-organs, 271
spheno-ethmoidal, 289
palatine, 290
spheroidal end-bulbs of Krouse, 272
spinal accessory, 320
stylo-glossal, 308
-hyoid, 308
superior maxillary, 290
supramaxillary, 309
supraorbital, 286
supratrochlear, 286
table of the branches of the fifth, 287
320
of the hypoglossal, 323
of the spinal accessory,
temporal, 308
third pair of, 280
thyro-hyoid, 324
tonsillar, 312
branches of, 312
trochlear, 281
tympanic, branches of, 312
of Wrisberg, 305, 310
Nervous system, 263
nerve-endings in gland-cells, 271
peripheral end- organs of
nerves, 272
of sensory nerves, 271
Neural groove of embryo, 543
Neuralgia, dental, 837
Neurilemma, or sheath of Schwann, 267
Ninth nerve, 310
Nitric-acid treatment in capping, 896
Nodes of Ranvier, 267
Nodular dentine, 911
deposits in pulp, 862
Nodules in pulp-tissue, 914
Non-medullary or pale nerve-fibres, 268
Notidanus, teeth of, 372
Notochord or chorda dorsalis, 109
Nucleated red blood-cells, 44
Number of muscles, 166
O.
Obtundents, use of, 890
Occipital artery, 226
branches of, 226
motor
posterior meningeal, branches of, 227
bone, 51
basilar process, 51, 54
pharyngeal, spine of, 51
crest, 53
groove, 60
nerve, 308
vein, 254
Occipito-frontalis aponeurosis, 167
muscle, 166, 167
mastoid suture, 51
parietal suture, 117
Oculo-motor nerve, 280
Odontoblastic layer, 640
Odontoblasts, 357, 569, 592, 641
atrophy of, 884
of dental pulp, pathological condition
of, 882
INDEX TO VOLUME I.
1027
Odontoclasts, 922
Olfactory apertures, 136
nerves, 277
Olivary process, 62
Omo-hyoid fascia, 157
muscle, 186
Ornithorhynchus, horny teeth of, 352
Operation for diseased alveolar process, 980
for scar on the face, 952
Opercular bones of codfish, 368
Ophidia, classification of, 388
Ophthalmic artery, 238
muscular branches of, 240
ganglion, 298
nerve, 286
Optic chiasm or commissure, 278
foramen, 133
foramina, 62, 67, 133
groove of sphenoid bone, 62
nerve, 278
tract, 278
Oral armature, 353
cavity, epithelium of, 199
muscles, 171
actions of, 174
Orbicularis oris muscle, 171
palpebrarum muscle, 168
Orbit, fascia of the, 178
muscles of the, 175
veins of, 261
Orbital cavity, 132, 133
plates, 75
process of malar bones, 99
of palate bone, 93
Organic layer of enamel, 608
Organization of blood-clot, 709
Origin of osteoblasts, 589
Orthocynodon, teeth of, 479
Orycteropus capensis, teeth of, 412
Ossa triquetra, 118
Osseous corpuscles, 41
Os lingua, 108
planum, 79
Ossein, 571
Osseous substance of matrix, 571
Ossification, 574
classification of, 577
of bone, 46
Osteoblasts, 42, 45, 575
origin of, 589
Osteoclasts, 43, 44, 922
Osteo-dentine, 880
Osteo-porosis, 47
Os unguis, 95
Otic ganglion, 302
Ovale, foramen, 65, 122
Ovarian egg, 540
Ovum, segmentation of, 543
Oxychloride of zinc for filling pulp-canals,
909
use of, in capping, 895
Oxychlorides in caries, 811
Oxygen in relation to fungi, 805
relation of fungi to, 824
Oxyphosphates in caries, 811
of zinc for filling pulp-canals, 909
P.
Pacchionian fossæ, 71
Pacinian corpuscles, 146
Pain in hyperæmia of dental pulp, 844
in inflammation, 693
Painless penetration of apical space, 928
Palatal process, 86
Palate, development of, 88, 551
bone, 90
Palatine glands, 207
spine, 91
vein, inferior, 251
Palato-Eustachian muscle, 197
-glossus muscle, 196
-pharyngeus muscle, 195
-quadrate arch of codfish, 368
Palpebral arteries, 241
Panniculus carnosum, 183
Papilla and enamel organ, connection
between, 628
dental, 641
dentinal, 568, 622
of skin, 144
Parietal bone, 69
eminence, 69
foramen, 70
foramina, 70, 117
fossa, 70
Parieto-mastoid suture, 117
-sphenoid suture, 117
-squamous suture, 119
Parotid arteries, 229
duct, 208
fascia, 209
gland, 207
glandula socia, 208
space, 208
veins, 253
&
Par vagus nerve, 313
Passive hyperæmia, 677
Pasteur, experiments of, 755
Pathological condition of odontoblasts of
dental pulp, 882
Pathology, general, 661
of the dental pulp, 829
Peccary, teeth of, 485
Penetration of enamel in caries, 768
Pepper bags, 927
Peptonizing action of fungi, 824
Perforating fibres, 40
Pericementitis, apical, 923
diseases of, 918, 921
function of, 920
phagedenic, 954, 968
Pericementum, formation of, 631
Perichondrium, 141
Peridental membrane, blood-supply of, 919
nerve-supply of, 919
structure of, 918
Perimysium of muscles, 161
Periosteum, 42
Peripheral end-organs of nerves, 271
of jaw, development of, 629
separation of, in alveolar abscess, 932
Periptychus, teeth of, 470
1028
INDEX TO VOLUME I.
Peroxide of hydrogen in alveolar abscess, | Posterior communicating arteries, 243
condyloid foramina, 53
dental foramen, 103
ethmoid artery, 240
ethmoidal cells, 79
foramina, 75, 134
facial vein, 253
fossa of brain-case, 123
lacerated foramen, 52, 123, 127
median fontanelle, 119
nasal aperture, 131
occipital sinus, 258
palatine canal, 84, 91
region of the skull, 128
superior dental nerve, 290
temporal artery, 230
nerve, 293
948
Perpendicular plate of ethmoid bone, 77
Petro-basilar groove, 127
suture, 51
Petrous portion of temporal bone, 55, 57
Phacochorus, teeth of, 485
Phagedenic pericementitis, 954, 968
complicated with serumal calculus,
975
treatment of, 979
Pharyngeal arteries, 228
or pterygo-palatine nerve, 302
spine of occipital bone, 51, 127
teeth of fishes, development of, 361
vein, 254
Pharynx, muscles of the, 192
Phlebitis, 252
Poultices in alveolar abscess, 947
Predisposing causes of caries, 770
Prefrontal bone of catfishes, 368
of codfish, 368
Premaxillary, 88
bones of codfish, 368
cingulum of, 355
Pierce on calcification and decalcification Premolar of dog, 354
of teeth, 645
Pigment of skin, 146
Pine marten, teeth of, 464
Pinna, shell of, 596
Pisces, definition of, 365
Pituitary fossa, 62
Placoid scales, 354
Plagiaulax, teeth of, 494
Plates, medullary, 548
Plethora, 673
Pleurodont dentition, 381
Plexus, infraorbital, 292
Pliolophus, teeth of, 477
Pneumogastric nerve, 313
Physiological consideration of cells, 524
Physiology of the blood, 533
Phenacodus, teeth of, 472
Phenol camphor, 985
Phenomena of caries, 764
abdominal branches, 320
anastomotic branches, 316
auricular branch, 316
cardiac branches, 319
communicating branches, 313
inferior laryngeal branch, 318
left, 315
meningeal branch, 316
œsophageal branches, 319
pharyngeal branches, 316
pulmonary branches, 319
right, 315
superior laryngeal branch, 316
table of, 315
Porcupine, teeth of, 468
Polyprotodontia, teeth of, 494
Polypus of pulp, 915
structure of, 915
treatment of, 916
Port Jackson shark, teeth of, 372
Portio dura, 304
mollis, 310
Posterior auricular artery, 227
nerve, 308
vein, 253
basal tubercle, 355
cerebral artery, 242
clinoid foramen, 124
crown of, 354
fangs of, 354
neck of, 354
parts of, 354
Premolars, definition of, 399
Prevention of abrasion of teeth, 996
Prevertebral arteries, 228
fascia, 157
Primates, teeth of, 434
Primitive dentition, characters of, 392
streak, 547
trace, 543
Priodon, teeth of, 410
Prisms, enamel, 601
Proælurus, teeth of, 458
Proboscidea, teeth of, 488
Process, alveolar, of inferior maxilla, 103
of superior maxillary bone, 86
anterior clinoid, 62
condyloid, 104
coronoid, 104
ethmoid, 94
external angular, 73
frontal, 98
hamular, 67
internal angular, 73
jugular, of occipital bone, 51
lachrymal, 94
malar, 85
maxillary, 94
of malar bones, 99
mental, 101
middle clinoid, 63
nasal, of superior maxillary bone, 85
of bones, 49
olivary, 62
orbital, 93
of malar bones, 99
palatal, 86, 91
posterior clinoid, 62
pyramidal, 92
INDEX TO VOLUME I.
1029
Process, sphenoidal, 93
spinous, 49
styloid, 60
uncinate, 78
vaginal, 67
zygomatic, 99
Processes, condyloid, 128
dentinal, 594
pterygoid, 67
Products of the epiblast and mesoblast,
556
Prognosis in calcic inflammation, 968
Prosimiæ, teeth of, 431
Protopterus, teeth of, 377
Proximal end of bones, 49
surfaces, caries in, 779
manner of contact of, 772
Pseudælurus, teeth of, 458
Ptenoglossate teeth, 347
Pterygoid artery, 234
bones of codfish, 368
fossa, 67, 104
notch, 67
processes, 67
spinosus muscle, 182
Pterygoideus proprius muscle, 182
Pterygo-maxillary fissure, 130
-palatine artery, 235
foramen, 130
Pulmonary veins, 247
Pulmonates, jaws of, 349
teeth of, 349
Pulp calcification, symptoms of, 914
treatment of, 915
-canals, method of filling, 910
-chamber, dentinal tumors within, 872
hard formations within, 864
dental, 592, 636
exposure in caries, 767
irritation in dental erosion, 1007
mummified condition of, 893
nerves of, 655
-nodules, 862
polypus of, 915
-tissue, nodules in, 914
Pulpitis, origin of, 889
superficial, 891
Pulps, mummified, 910
Pulse, compressible, 666
dicrotous, 670
different characters of, 668
examination of, 663
frequency of, 664
how produced, 662
in aortic obstruction, 671
in lesions of the heart, 670
intermittent, 670
irregularities of, 669
qualities of, 665
Pus, burrowing of, 930
of chronic alveolar abscess, 937
through lower maxilla, 942
formation of, in apical space, 930
Putrefactive gases, generation of, 907
Putrescent pulp, causes of, 906
treatment of, 907
Pyramidal process, 92
Pyramidales nasi muscle, 168
Pyorrhoea alveolaris, 954
Q.
Quadratus menti, 173
Quinia as a germicide, 909
R.
Rabbit, deciduous teeth of, 469
teeth of, 469
Racemose glands, 203
Rachiglossate teeth, 346
Rachiodon, teeth of, 388
Radular apparatus, molluscan, 342
of mollusks, instructions for examining,
344
Rami of inferior maxilla, 103
Ramus cervicularis princeps, 227
Ranvier, nodes of, 267
Ranine artery, 222
Rat, teeth of, 466
Ratfish, teeth of, 375
Rattlesnake, fangs of, 389
Rays, teeth of, 373
Red blood-globules, diapedesis of, 679
cells of marrow,
marrow, 43
Region supplied by cranial nerves, 277
Regional Anatomy, 35
Regnard on caries, 735
Regurgitation, aortic, 671
Removal of calculus, 963
of dental pulp, 926
Reproduction of epithelium, 708
45
of tissue, 702
Reptilia, teeth of, 382
Resorption of the roots of temporary teeth,
922
of tissue, Ziegler on, 529
of tissues, 530
Results of fever, 717
Rete Malpighii, 617
Reticular layer of skin, 145
Reticulum stellate, 626, 640, 641
Retrahens aurem muscle, 175
Retzius, broken striæ of, 656
Rheumatic diathesis, 979
Rhinoceros, dental evolution of, 478
teeth of, 478
Rhiphidoglossate teeth, 347
Ridge, dental, 616
infraorbital, 84
Riggs's disease, 954
Right common carotid artery, 216
Risorus muscle, 173
Rivinus, duct of, 211
Robertson on caries, 735
Rodentia, teeth of, 466
Roof of mouth, 137
of nasal fossa, 135
Root-fillings after alveolar abscess, 952
obtrusion of, into apical space, 923
Roots of teeth, absorption of, 921
1030
INDEX TO VOLUME I.
Roots of temporary teeth, resorption of, | Shoulder-girdle of codfish, 365
922
Rostrum of sphenoid bone, 64
Round foramen, 65, 122
S.
Sacculus, dental, 361
Sagittal suture, 116
Salicylized cotton, 965
Salivary calculus, 960, 961
glands, compound tubular, 204
increased supply to, 672
muco-, 206
true, 205
Sanguinary calculus, 958
Sarcolemma, 162
Scalers, Cushing's, 964
Scaphoid fossa, 67, 126
Scar on the face, operation for, 952
Scarpa, foramina of, 86, 136
Schlenker on new formations, 914
Schroeder, experiments of, 754
Scrofulous diathesis, 979
Sea-urchin (Echinus), dental system of, 340
oral apparatus of, 339
Seal, teeth of, 449
Sealing gingival margins, 983
Sebaceous glands, 152, 560
Secondary dentine, 865-872, 911
causes producing, 912
formation of, 890
deposit in exposure of dental pulp, 886
deposits in dental erosion, 1007
formations resulting from metallic fill-
ings, 913
resulting from wear of clasps, 913
Secretory glands of mucous membrane, 201
Sectorials, characters of, 402
Segmentation of ovum, 543
Sella turcica, 62, 68
Selenodontia, teeth of, 486
Semilunar ganglion, 284
Semnopithecida, teeth of, 436
Sensation, nerves of, 275
Sensitive dentine, treatment of, 890
Sensitiveness of the dentine, 1006
to thermal changes in dental pulp, 843
Sensory functions of dental pulp, 832
nerves, peripheral end-organs of, 271
tract in teeth, 1009
Septic abscess, treatment of, 950
Septum, fœtal, 551
..
nasal, 135
Serrated sutures, 111
Serumal calculus, 958
Seventh nerve, 304
Sharks, teeth of, 370
Sharpey's fibre, 40, 47
Sheath of common carotid artery, 216
of Schwann, or neurolemma, 267
Shock, cause of, 719
from dental operations, 725-728
liability to, 724
molecular disturbances in, 722
symptoms of, 723
Sigmoid groove, 61
of sphenoid bone, 63
notch, 104
Simiida, teeth of, 436
Simple exposure of dental pulp, 890
mucous tubular glands, 202
Sinus, anterior, occipital or transverse, 261
cavernous, 259
circular, 260
inferior longitudinal, 258
petrosal, 261
longitudinal, 75
lymph, 329
maxillary, 89
posterior occipital, 258
superior longitudinal, 258
sphenoidal, 63
spheno-palatal, 259
straight, 258
superior petrosal, 260
Sinuses, frontal, 73
lateral, 259
of brain-case, 123, 257, 259
venous, of the cranium, 257
Siphonaria, teeth of, 349
Sirenia, palatal plates of, 352
Sixth nerve, 282
Skin, 141
appendages of, 147
blood-vessels of, 145
derm, corium, or cutis vera of, 144
epidermis of, 143
epithelium of, 614
lymphatics of, 145
nerves of, 145
reticular layer of, 145
papilla of, 144
pigment of, 146
stratum corneum of, 144
granulosum of, 144
lucidum of, 144
Malpighii of, 144
tactile corpuscles of, 142, 146
true, 144
Skull, 50
and its articulations at different periods,
118
as a whole, 109
facial or anterior region of, 131
general development of, 109
Ïateral region of, 128
posterior region of, 128
Sloth, three-toed, teeth of, 411
Small meningeal artery, 233
Smilodon, teeth of, 463
Snakes, poison-glands of, 389
teeth of, 388
Sodium carbonate as an antiseptic, 909
Soft palate, muscles of the, 192
Softening of bone, 37
Space, apical, 918
Spaces, interglobular, 595, 766
Special sense, nerves of, 275
Species, transmutation of, 520
Sperm whale, teeth of; 414
INDEX TO VOLUME I.
1031
ካ
Spheno-ethmoidal nerves, 289
-malar suture, 117
-maxillary fissure, 65, 99, 130, 134
fossa, 130
-palatal sinus, 259
-palatine foramen, 130, 136
ganglion, 299
nerve, 290
notch, 92
Sphenoid bone, 62
ethmoidal spine, 62
bone, optic groove of, 62
spinous process, 65
Sphenoidal fissures, 66
process of palate bone, 93
sinuses, 63
turbinated bones, 64
Sphygmographic tracings, 667, 668
Spinal accessory nerve, 320
table of, 320
Spinosum, foramen, 122
Spinous process of sphenoid bone, 65, 127
Sponge-grafting, 987
Spongy portion of bone, 35
Spontaneous generation, 521
Squamo-tympanic suture, 56
Squamous portion of temporal bone, 56
sutures, 111
Stellate bodies, 624
cells, 624
reticulum, 626, 640, 641
Stapedius or tympanic nerve, 307
Stellwagen on caries, 764
Steno's duct, 208
Sterno-cleido-mastoid muscle, 184
-hyoid muscle, 185
-mastoid artery, 220
-thyroid muscle, 186
Stetson, foramen of, 86, 136
Stoppings used in capping, 898
Straight sinus, 258
Stratum corneum, 144
granulosum, 144
intermedium, 362, 642
of Hanover, 625
lucidum, 144
Malpighii, 144
Stricker on inflammation, 699
Structure of cells, 523
of dermal denticles, 353
of enamel, 359
of gum, 955
of occipital bone, 54
of parietal bone, 71
of peridental membrane, 918
Styloid process of temporal bone, 60, 127
Stylo-glossus muscle, 191
nerve, 308
-hyoid ligament, 189
muscle, 189
nerve, 308
-mastoid artery, 228
foramen, 60, 127
-maxillary ligament, 115
-pharyngeus muscle, 194
Stypolophus, teeth of, 422
Subclavian arteries, 243
Sublingual artery, 222
fossa, 102
gland, 210
Submaxillary duct, 210
fascia, 157
fossa, 102
ganglion, 304
gland, 209
triangle, 188
Submental artery, 225
vein, 251
Subperiosteal bone formation, 47, 585
inflammation, 944
Succinea, teeth of, 349
Sudoriferous glands, 151
Sulphuretted hydrogen, generation of, in
pulp, 907
in pulp-chamber, 893
Superciliary ridges, 73
Superficial fascia, 155
jugular ganglion, 311
or cranial arteries, 227
pulpitis, 891
treatment of, 904
temporal artery, 229
branches of, 229
muscular branches of, 229
vein, 252
Superior carotid triangle, 188
constrictor muscle, 192
coronary artery, 225
curved lines of occipital bone, 53
hyoid artery, 221
labial veins, 251
laryngeal artery, 220
longitudinal groove, 120
sinus, 258
maxillary bone, 81
bone, alveoli of, 87
nerve, 290
malar, branch of, 290
orbital or temporo-malar branch of,
290
spheno-palatine branch of, 290
temporal branch of, 290
meatus of nasal chamber, 79, 85, 136
oblique muscle, 177
ophthalmic vein, 261
pedicle of sphenoid bone, 67
petrosal sinus, 260
rectus muscle, 176
thyroid artery, 219
turbinated bone, 79
crest, 92
vena cava, 248
Suppuration of dental pulp, 853-855
Suprahyoid aponeurosis, 188
space, muscles of, 187
Supramastoid ridge, 56
Supramaxillary nerve, 309
Supraorbital arches, 73
artery, 240
nerve, 286
notch or foramen, 73
vein, 251
1032
INDEX TO VOLUME I.
Suprascapular artery, 247
Supratrochlear nerve, 286
Surgical anatomy of the basilar process,
55
fever, 713
Sutura, 111-115
Suture, coronal, 117
fronto-malar, 117
-parietal, 117;
-sphenoidal, 117
inter-parietal, 116
lambdoid, 117
occipito-mastoid, 51
-parietal, 117
parieto-mastoid, 117
-sphenoid, 117
-squamous, 117
petro-basilar, 51
sagittal, 116
spheno-malar, 117
squamo-tympanic, 56
temporo-parietal, 56
Sutures dentata, 111
harmonic, 111
of cranial vault, 116
of face, 117
of skull, 111, 115
serrata, 111
squamosa, 111
Sweat-glands, 151
Swelling in inflammation, 693
of dental pulp, 839
Symphysis menti, 132
Symptomatology of dental pulp, 832
Symptoms of shock, 723
Synchondrosis articulation, 112
Synostosis, 118
Synovial sac, 114
Systemic veins, 247
Teeth, hypoblastic derivation of, 353
occlusion of, in man, 445
origin of, in invertebrata, 352
of, in vertebrata, 352
Temnocyon, teeth of, 453
Temperature in fever, 711
in inflammation, 693
Temporo-facial nerve, 308
-maxillary articulation, 112
interarticulating disc of, 114
ligaments of, 113
synovial sac of, 114
vein, 252
T.
Table of the branches of the facial nerve,
305
of the glosso-pharyngeal nerve, 311
of the pneumogastric nerve, 315
of the cranial sympathetic ganglia, 297
showing distribution of fifth nerve, 287
Tactile corpuscles, 142, 146
Tæniodonta, teeth of, 434
Tænioglossate teeth, 347
Tapirida, teeth of, 478
Tarsius spectrum, teeth of, 431
Tatusia hybridus, teeth of, 409
Taxeopoda, teeth of, 470
Tebennophorus, jaw of, 349
Teeth, calcification of, 363
development of, 360, 609
ecderonic, origin of, 352
enderonic, origin of, 353
epiblastic, derivation of, 353
faulty formation of, 770
general definition of, 352
histology of, 356
Temporal bone, 55
fascia, 179
fossa, 128
muscle, 180
Tendo-oculi muscle, 169
Tendons, 158
Tenon, capsule of, 178
fascia of, 178
Tensor-palati muscle, 197
-tarsi muscle, 169
Tenth nerve, 313
Terms used in describing bones, 49
Thermal changes, sensibility of dental
pulp to, 832-834
Thrombus, formation of, 681
Sympathetic ganglia of fifth pair of nerves, Thylocoleo, teeth of, 497
297
Thyro-hyoid muscle, 186
nerve, 324
Thyroid artery, superior, 219
axis, 246
Tillodonta, teeth of, 433
Tin in caries, 811
Tissue, areolar, 154
cartilage, 35
changes in hyperæmia, 845
in inflammation, 695
of dental pulp, 849
connective, 35
fibre, connective, 35
granulations, 704
muscular, 159
reproduction of, 702
resorption of, 530
Tobacco, action of, on caries, 808
smoke, action of, on caries fungi, 809
Tomes on calcification, 573
influences affecting the dental pulp, 888
Thoracic duct, 330
Three-toed sloth, teeth of, 411
Thrombosis, 679
on caries, 741
processes, 642
Tonsillar artery, 224
nerves, 312
space, 213
Tonsils, 213
infra- or pharyngeal, 214
Toothbrush, mode of using, 966
Tooth-cartilage, 356
·
-germ, 361
-pulp, 357, 592, 636
arteries of, 358
lateral processes of, 358
INDEX TO VOLUME I.
1033
Torcular Herophili, 124, 258
Toxodontia, teeth of, 476
Toxoglossa, teeth of, 343
Toxoglossate (arrow-toothed) dentition, 346
Trabeculæ cranii, 109
Tracheal artery, 247
Tracings, sphygmographic, 667, 668
Transplantation of epithelium, 708
Transverse artery, 220
facial artery, 229
vein, 253
Transversalis colli artery, 247
Treatment of alveolar abscess, 944
of apical pericementitis, 926
of calcic inflammation, 963
of chronic alveolar abscess, 947
of phagedenic pericementitis, 979
Triangle, submaxillary, 188
supra-carotid, 188
Trifacial nerve, 282
Trigeminus nerve, 282
Triisodon, teeth of, 424
Tritonium (trumpet conch), jaw of, 334
Trochlear nerve, 281
fossa or tubercles, 75
Trochlearis muscle, 177
True salivary glands, 205
skin, 144
Trumpet conch (Tritonium), jaw of, 343
Tubercle of temporal bone, 56
posterior basal, 355
Tubercle or tuberosity, 49
Tubercles, genial, 102
Tuberosity of superior maxillary bone, 85
Tubes, dental, 356
Tumors, dentinal, within pulp-chamber,
872
Tunic, inner, 640
Turbinated bone, inferior, 79
middle, 79
superior, 79
crest, inferior, 92
superior, 92
Twelfth nerve, 322
Tympanic artery, 232
nerve, 311
portion of temporal bone, 60
U.
Ulceration, 702
Uncinate process, 78
Unguiculate series, teeth of, 416
Ungulata, teeth of, 476
Ungulate series, classification of, 470
teeth of, 469
V.
Vaginal process of sphenoid bone, 67
of temporal bone, 60
Vampires, teeth of, 465
Variations in hardness of enamel, 602
of common carotid artery, 218
Variety of muscles, 165
Vasa afferentia, 328
Vasa efferentia, 328
vasorum, 327
Vaso-motor nerves, influence on the circu-
lation, 673
Veins, 247
angular, 249
anterior jugular, 255
common temporal, 252
deep facial, 251
diploic, 261
emissary, 262
external jugular, 255
facial or anterior facial, 249
frontal, 250
inferior ophthalmic, 261
palpebral, 251
thyroid, 248
innominate or brachio-cephalic, 248
internal jugular, 256
maxillary, 253
left innominate, 248
lingual, 254
middle temporal, 253
occipital, 254
of head and neck, 281
of neck, 254
of orbit, 261
pharyngeal, 254
posterior auricular, 253
facial, 253
pulmonary, 247
right innominate, 248
submaxillary, 251
submental, 251
superficial temporal, 252
superior labial, 251
ophthalmic, 261
or descending vena cava, 248
supraorbital, 251
systemic, 247
temporo-maxillary, 252
transverse facial, 253
Vena cava superior, 248
Venous sinuses of cranium, 257
Vents for putrefied pulp-canals, 910
Vertebral artery, 245
Vertebrata, teeth of, 351
Vertical crest of nasal bones, 97
plate of palate bone, 92
Vesali, foramen of, 122
Vessels, lymphatic, 325
Vidian artery, 235
canal, 65, 123
Virginia deer, teeth of, 488
opossum, teeth of, 495
Voluntary muscles, 160
Vomer, 80
development of, 81
W.
Walls of the brain-case, 120
Walrus, teeth of, 451
Wandering cells, 692
Wart-hog, teeth of, 485
Watt on caries, 745
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1034
INDEX TO VOLUME I.
Weasels, teeth of, 464
Wedl, on polypus of the pulp, 916
Weight of bone, 37
Westcot, experiments
Wharton, jelly of, 566
Wharton's duct, 210
of, 743
White blood-corpuscles in inflammation,
695
globules, diapedesis of, 692
corpuscles, 532
White, J. D., formula for nerve-paste,
900
Willis, circle of, 242
Wormian bones, 118
Wrisberg, nerve of, 310
Yellow marrow, 43
Y.
Z.
Zeuglodon, teeth of, 415
Ziegler on cell-proliferation, 526
on resorption of tissue, 529
Zona pellucida, 547
Zonites, jaw of, 349
Zygomatic fossa, 129
process of malar bone, 99
of temporal bone, 56
Zygomaticus major muscle, 172
minor muscle, 172
END OF VOLUME I.

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