UNC 
 
 HEALTH SCIENCES LIBRARY 
 
 The Sheldon Peck Collection 
 on the History of Orthodontics 
 and Dental Medicine 
 
 Gift of 
 
 Sheldon Peck, DDS 1966 
 and 
 
 Leena Peck, DMD 
 
 Given in memory of 
 Harvey Peck, DDS 1962 
 
/ 
 
 
 
 
 
 
4 
 
 THE 
 
 NATURAL HISTORY 
 
 OF THE 
 
 HUMAN TEETH. 
 
The 
 
 NATURAL HISTORY 
 
 O F T H E 
 
 ' / 
 
 > i 
 
 . ' • * ' 
 
 HUMAN TEETH 
 
 EXPLAINING THEIR 
 
 STRUCTURE, USE, FORMATION, 
 GROWTH, AND DISEASES. 
 
 k « t 
 
 ILLUSTRATED WITH COPPER-PLATES. 
 
 By JOHN HUNTER, F. R. S. 
 
 And Surgeon to St. George’s Hofpital. 
 
 LONDON, 
 
 Printed for J. Johnson, N° 72. St. Paul’s Church-yard. 
 
 MDCCLXXI. 
 
 • • 
 
ADVERTISEMENT, 
 
 M OST of the Obfervations contained in the 
 following Treatife were made by the Author 
 
 before the Year 1755 ; and the Subftance of them 
 
 / • 
 
 conftantly demonftrated after that Period, in Dr, 
 Hunter’s Courfe of Anatomical Lectures, The Fi¬ 
 gures were drawn by Mr* Rymfdyk, under the 
 Author’s Direction, and engraved by Mefif. Strange, 
 Grignion, Ryland, and others* 
 

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T H E 
 
 CONTENTS. 
 
 /|F the Upper-Jaw page i 
 
 Of the Lower-Jaw 3 
 
 Of the Alveolar Proceffes 6 
 
 Of the Articulation of the Lower-Jaw 9 
 
 Of the Motion in the Joint of the Lower-Jaw 1 2 
 
 Of the Mufcles of the Lower-Jaw 1 5 
 
 Temporalis 1 9 
 
 Pterygoidaus Interims 2 2 
 
 Bterygoid/zus Ext emus 2 3 
 
 Digaftricus 2 5 
 
 Of the Structure of a Tooth 3 3 
 
 Of the Enamel ib. 
 
 Of the Bony Part of a Tooth 3 6 
 
 Of the Cavity of the Teeth 41 
 
 Of the Periofteum of the Teeth 4 3 
 
 Of the Situation of the Teeth 44 
 
 Of the Number of Teeth 46 
 
 Of the Incifores 4 9 
 
 Of the Cufpidatus 52 
 
 Of the Bicufpides 55 
 
 Of the Grinders 5 8 
 
 Of the Articulation of the Teeth 6 $ 
 
 Of the Gums 6 6 
 
 Of the Adion of the Teeth arifing from the Motion 
 of the Lower-Jaw 68 
 
 Gene- 
 
% 
 
 CONTENT S. 
 
 General Comparifons between the Motion of the Jaw 
 in young and in old People 7 2 
 
 Of the Formation of the Alveolar Procefs 7 4 
 
 Of the Formation of the Teeth in the Foetus 7 7 
 
 Of the Caufe of Pain in Dentition 80 
 
 Of the Formation and Progrefs of the Adult Teeth 82 
 Of the manner in which a Tooth is formed 8 6 
 
 Of the Oflification of a Tooth upon the Pulp 8 8 
 
 Of the Formation of the Enamel 94 
 
 Of the Manner of Shedding of Teeth 9 8 
 
 Of the Growth of the two Jaws 1 o 1 
 
 The Reafon for the Shedding of the Teeth 105 
 
 Of the Cavity filling up as the Teeth wear down 108 
 Of the continual Growth of the Teeth 1 1 o 
 
 Of the fenfibility of Teeth 1 1 4 
 
 Of Supernumerary Teeth 1 1 5 
 
 The Ufe of the Teeth fo far as they affect the Voice 1 1 7 
 Of the Clafs, among animals, of the human Teeth 1 1 9 
 Of the Difeafes of the Teeth 1 21 
 
 Of cleaning the Teeth 124 
 
 Of Tranfplanting the Teeth 126 
 
 Sixteen Plates and Explanations. 
 
 . - - . ----- — ■ - —— ■ '■■■■-—- ■■ -—— ■ ■■■■— . - * 
 
 E R R A T A. 
 
 Page 28. 1. 18. for Ther aide read Thyroids. 
 
 38. 1 . 2. for mol read Animal » 
 
 117. 1. 14. dele to. 
 
 V 
 
f 
 
 OF THE 
 
 « •. » f- •• « • r 7 * « 
 
 - ^ v • •' ' r v ' f - • * 
 
 U P P E R - J A W. 
 
 B EFORE vve enter into a defcription of the Teeth 
 themfelves, it will be necefTary to give an ac¬ 
 count of the Upper and Lower Jaw-bones, in which 
 they are inferted ; infilling minutely on thofe parts 
 which are connected with the Teeth, or ferve for their 
 motion and action, and palling over the others Rightly. 
 
 The Upper-Jaw is compofed of two bones, which 
 generally remain diitincl through life. They are very 
 irregular at their poRerior and upper parts, fending 
 upwards and backwards a great many procelfes, that 
 are conne&ed with the bones of the Face and Skull *. 
 The lower and anterior parts of the Upper-Jaw are 
 more uniform, making a kind of a circular fweep 
 from fide to fide, the convexity of which is turned for¬ 
 wards ; the lower part terminates in a thick edge, full 
 
 * Vide Plate III. Fig. iR and 2d. A A. 
 
 B 
 
 of 
 
2 
 
 OF THE UPPER-JAW. 
 
 of fockets for the Teeth. This edge is called in each 
 bone the Alveolar Procefs Behind the Alveolar Pro 
 cedes there are two horizontal lamellse, which uniting 
 together, form part of the roof of the Mouth, which 
 is the partition between the Mouth and the Nofe f. 
 
 This plate, or partition, is fituated about half an inch 
 higher than the lower edge of the Alveolar Procefs j 
 and this gives the roof of the Mouth a confiderable 
 hollownefs. 
 
 * 
 
 The ufe of the Upper-Jaw is to form part of the 
 Parietes of the Mouth, Nofe, and Orbits ; to give a balls, 
 or fupply the Alveolar Frocefs, for ilie fuperior row of 
 Teeth, and to counteract the Lower Jaw; but it has no 
 motion itfelf upon the bones of the Head and Face. 
 
 * Vide Plate I. Fig. i. a, b , c, d,. 
 
 ■f Vide Plate L Fig., i. e y 
 

 OF THE 
 
 i 
 
 L O W E R - J A W.’ 
 
 A S the Lower-Jaw is extremely moveable, and its 
 ^ ^ motion is indifpenfably necefifary in all the va¬ 
 rious operations of the Teeth, it requires to be more 
 particularly defcribed. It is much more fimple in its 
 form than the Upper, having fewer procefles, and thefe 
 not fo irregular. Its anterior circular part is placed di- 
 redlly under that of the Upper-Jaw; but its other parts 
 extend farther backwards *♦ 
 
 This Jaw is at firft compofed of two diltindl bones f ; 
 but thefe, foon after birth, unite into one, at the middle 
 of the chin. This union is called the Symphyfis of 
 the Jaw. Upon the upper edge of the body of the 
 bone is placed the Alveolar Procefs, a good deal fimilar 
 to that of the Upper-Jaw. The Alveolar Procefs ex¬ 
 tends all round the upper part of the bone, from the 
 Coronoide Procefs of one fide, to that of the other J. 
 In both Jaws they are every where relatively propor- 
 
 * Vide Plate III. Fig. i and 2. 
 
 f Vide Plate VIII. Fig. 1, 4, and 6. 
 
 J Vide Plate I. Fig. 2 . 
 
 B 2 
 
 tional 
 
4 
 
 OFT H E L O W ER-JA W. 
 
 donal to the Teeth 5 being thicker behind, where the 
 Teeth are larger, and more irregular, upon account of 
 the more numerous fangs inferted into them. The 
 Teeth that are fituated backwards, in the Upper-Jaw, 
 have more fangs than thofe that correfpond with them 
 
 ♦ ,1 
 
 in the lower, and the fockets are accordingly more ir¬ 
 regular. The Alveolar Procefs of the Upper-Jaw, is a 
 fection of a larger circle than that of the lower, efpe- 
 cialiy when the Teeth are in the fockets. This arifes 
 
 r V k 
 
 chiefly from the anterior Teeth in the Upper-Jaw be¬ 
 ing broader and flatter than thofe in the Lower *. The 
 pofterior part of the bone on each fide rifes aim oft 
 perpendicularly, and terminates above in two proceftes f; 
 the anterior of which is the higheft, is thin and point¬ 
 ed, and is called the Coronoide Procefs j;. The ante¬ 
 rior edge of this procefs forms a ridge, which goes 
 obliquely downward and forward on the jaw, upon 
 the outfide of the pofterior fockets §. To this procefs 
 the Temporal Mufcle is attached ; and as it rifes above 
 the center of motion, that Mufcle adls with nearly 
 equal advantage in all the different fituations of the 
 jaw. 
 
 The Pofterior Procefs, which is made for a move- 
 able articulation with the head, runs upward, and a 
 
 * Vide Plates I. and III. 
 
 f Vide Plate III. Fig. 2. e and Plate IV, Fig. 2. 
 
 $ Vide Plate IV. i i, 
 
 5 Vide Plate IV. Fig, 2. B c 
 
 6 little 
 
V 
 
 OF THE LOWER-JAW. 5 
 
 little backward ; is narrower, thicker, and fhorter, than 
 the anterior; and terminates in an oblong rounded head, 
 or Condyle *, whole longed axis is nearly tranfverfe. 
 The Condyle is bended a little forward ; is rounded, or 
 convex, from the fore to the back part; and likewife 
 a little rounded from one end to the other, or from 
 right to left. Its external end is turned a little for¬ 
 ward, and its internal a little backward ; fo that the 
 axis of the two Condyles are neither in the fame 
 Rraight line, nor parallel to each other; but the axis 
 of each Condyle, if continued backwards, would meet, 
 and form an angle of about one hundred and forty-fix 
 degrees ; and lines drawn from the Symphyfis of the 
 Chin, to the middle of the Condyle, would interfedl 
 their longed axis, at nearly right angles f. There 
 are, however, fome exceptions ; for in a Lower-Jaw, of 
 which I have a drawing, the angle formed by the fup- 
 poied continuation of the two axes, indead of being an 
 angle of one hundred and forty-fix degrees, is of one 
 hundred and ten only. The Lower-Jaw ferves for a bafe 
 to fupport the Teeth in the Alveolar Procefs, during 
 their adtion on thofe of the Upper-jaw in madication 
 and to give origin to fome mufcles that belong toother 
 
 parts. 
 
 -X- vide Plate IV. Fig. IP. E. 
 
 f Vide Plate I. Fig. 2. or Plate IV. Fig. 2; 
 
 OF 
 
 
4 
 
 OF THE 
 
 ALVEOLAR PROCESSES. 
 
 HE Alveolar Procefles are compofed of two thin 
 
 A bony plates, one external * * * § , and the other in¬ 
 ternal j*. Thefe two plates are at a greater diftance 
 from each other at their pofterior ends, than at the an¬ 
 terior, or middle part of the Jaw. They are united 
 together by thin bony partitions going a-crofs, which 
 divide the procefles at the anterior part, into juft as 
 many diftintft: fockets as there are Teeth J ; but at the 
 pofterior part, where the Teeth have more than one 
 root or fang, there are diftinft cells, or fockets, for 
 every root §. Thefe tranfverfe partitions are more pro¬ 
 tuberant than the Alveolar Plates ; and thus add late¬ 
 rally to the depth of the Cells, particularly at the an¬ 
 terior part of the Jaw. At each partition, the exter¬ 
 nal plate of the Alveolar Procefs is depreifed, and 
 forming furrows, or a fluting |] rounds the cells, or 
 
 * Vide Plate I. Fig. i. a, rt, a, a , a . 
 
 •f Vide Plate I. Fig. i. b , b , b. 
 
 } Vide Plate I. Fig. i. c , c , and Fig. 2, a . 
 
 § Vide Plate I. Fig. 1, d, d. and Fig. 2. b t c. 
 
 |j Vide Plate III. Fig. 2. F F F F. 
 
 4 
 
 cavi- 
 
OF THE ALVEOLAR PROCESSES. 7 
 
 cavities, for the roots of the Teeth. This is obferv- 
 able in the whole length of the Alveolar Proeefs of the 
 Upper-Jaw; and in the fore-part particularly of the 
 Lower-Jaw. The AlveQlar Procefles of each Jaw, form 
 about one half of a circular, or rather of an elliptical * 
 figure ; and at the fore-part in the Lower-Jaw they 
 are perpendicular, but project inwards at the poflerior 
 part, and deferibe a fmaller circle than the body of the 
 bone upon which they Rand f ; as we fhall obferve 
 more particularly hereafter, when we come to treat 
 of the Jaws of Old People. 
 
 The Alveolar Procefles of both Jaws fhould rather 
 be confidered as belonging to the Teeth, than as parts 
 of the Jaws ; for they begin to be formed with the 
 Teeth, keep pace with them in their growth, and de¬ 
 cay, and intirely difappear, when the Teeth fall ; fo 
 that, if we had no Teeth, it is likely we fhould not 
 only have no fockets, but not even thefe proceffes, in 
 which the fockets are formed * and the Jaws can per¬ 
 form their motions, and give origin to mufcles, with¬ 
 out either the Teeth, or Alveolar Proceffes. In fhort, 
 there is fuch a mutual dependence of the Teeth, and 
 Alveolar Proceffes on each other, that the definition of 
 the one feems to be always attended with that of the 
 other. 
 
 * Vide Plate I. Fig. 1. and 2 * 
 j- Vide Plate I. Fig. 2. 
 
 In 
 
 \ 
 
 1 
 
8 OF THE AL V CLEAR PROCESSES. 
 
 In the head of a young fubjeft which I examined, I 
 found that the two fnft Incifor Teeth in the Upper-Jaw 
 had not cut the Gum ; nor had they any root or fang, 
 excepting fo much as was necefTary to fallen them to 
 the Gum, on their upper furface ; and on examining 
 the Jaw, I found there was no Alveolar Procefs, nor 
 fockets, in that part. What had been the caufe of 
 this, I will not pretend to fay: whether it was owing 
 to the Teeth forming not in the Jaw, but in the Gum ; 
 or to the walling of the fangs. The appearance of 
 the Tooth favoured the flrft fuppofition ; for it was 
 not like thofe, whofe fangs are decayed in young fub- 
 jedls, in order to the fhedding of the Teeth ; and as it 
 did not cut the Gum, it is reafonable to think it never 
 had any fang. That end from which the fang 
 fhould have grown, was formed into two round and 
 fmooth points, having each a fmail hole leading into 
 the body of the Tooth, which was pretty well formed. 
 
 1 
 
 r 
 
 OF 
 
OF THE 
 
 t 
 
 ARTICULATION of the LOWER-JAW. 
 
 TUST under the beginning of the Zygomatic Procefs 
 ^ of each Temporal Bone, before the external Meatus 
 Auditorius, an oblong cavity may be obferved ; in di¬ 
 rection, length, and breadth, in fome meafure corre- 
 fponding with the Condyle of the Lower-Jaw *. Be¬ 
 fore, and adjoining to this cavity, there is an oblong 
 eminence, placed in the fame direction, convex upon 
 the top, in the direction of its fhorter axis, which 
 runs from behind forwards ; and a little concave in 
 the direction of its longer axis, which runs from 
 within outwards. It is a little broader at its outer ex 
 tremity ; as the outer correfponding end of the Con¬ 
 dyle deferibes a larger circle in its motion than the in¬ 
 ner f. The furface of the cavity, and eminence, is 
 covered with one continued fmooth cartilaginous cruft, 
 -which is fomewhat ligamentous, for by putrefaction 
 it peels off, like a membrane, with the common Perio- 
 fteuffi. Both the cavity and eminence ferve for the mo- 
 
 * Vide Plate II. L. and Plate IV. E E. 
 
 | Vide Plate II. K. and Plate XIV. F F. 
 
 C 
 
 tion 
 
OF THE ARTICULATION OF 
 
 10 
 
 cion of the Condyle of the Lower-Jaw. The furface 
 of the cavity is directed downward; that of the emi¬ 
 nence downward and backward, in fuch a manner that 
 a tranfverfe fecdion of both would reprefent the Italick 
 letter S *. Though the eminence may, on a fird view 
 of it, appear to project confiderably below the cavity, 
 yet a line drawn from the bottom of the cavity, to the 
 mod depending part of the eminence, is almod hori¬ 
 zontal, and therefore nearly parallel with the line 
 made by the grinding furfaces of the Teeth in the Up¬ 
 per-Jaw : and when we condder the Articulation far¬ 
 ther, we fhall find that thefe two lines are fo nearly 
 parallel, that the Condyle moves almod directly for¬ 
 wards, in paiTmg from the cavity to the eminence ; 
 and the parallelifm of the motion is alfo preferved by 
 the fliape of an intermediate cartilage. 
 
 In this joint there is a moveable cartilage, which, 
 though common to both Condyle and cavity, ought to be 
 confidered rather as an appendage of the former than of 
 the latter, being more clofely connected with it; fo as to 
 accompany it in its motion along the common furface of 
 both the cavity and eminence. This cartilage is nearly 
 of the fame dimenfions with the Condyle, which it 
 covers ; is hollowed on its inferior furface, to receive 
 the Condyle : on its upper furface it is more unequal, 
 being moulded to the cavity and eminence of the ar~ 
 
 * Yide Plate II. I* K. 
 
 tiers?- 
 
THE LOWER-JAW, n 
 
 ticulating furface of the Temporal Bone, though it is 
 confiderably lefs, and is therefore capable of being 
 moved with the Condyle, from one part of that furface 
 to another *. Its texture is ligamcnto-cartilagineous. 
 This moveable cartilage is connedled with both the 
 Condyle of the Jaw, and the articulating furface of 
 the Temporal Bone, by diilin< 5 t ligaments, arifing from 
 its edges all round. That by which it is attached to 
 the Temporal Bone, is the moil free and loofe ; though 
 both ligaments will allow an eafy motion, or Hiding 
 of the cartilage on the refpe&ive furfaces of the Con¬ 
 dyle, and Temporal Bone. Thefe attachments of the 
 cartilage are flrengthened, and the whole articulation 
 fecured, by an external ligament, which is common 
 to both, and which is fixed to the Temporal Bone, and 
 to the neck of the Condyle. On the inner furface of 
 the ligament, which attaches the cartilage to the Tem¬ 
 poral Bone, and backwards, in the cavity, is placed 
 what is commonly called the Gland of the Joint; at 
 lead, the ligament is there much more vafcular than at 
 any other part. 
 
 * Vide Plate II. L. 
 
 OF 
 
OF THE MOTION IN THE JOINT 
 
 I 2 
 
 OF THE 
 
 
 MOTION in the JOINT of the LOWER-JAW. 
 
 * * 
 
 f | A HE Lower-jaw, from the manner of its articula- 
 tion, is fufceptible of a great many motions. 
 The whole jaw may be brought horizontally forwards, 
 by the Condyles Aiding from the cavity towards the 
 eminences on each fide. This motion is performed 
 chiefly when the Teeth of the Lower-jaw are brought 
 diredtly under tliofe of the Upper, in order to bite, or 
 hold any thing very fall between them.. 
 
 i 
 
 Or, the Condyles only may be brought forwards, 
 while the reft of the jaw is tilted backwards, as in 
 the cafe when the Mouth is open ; for on that occafion 
 the anode of the Jaw is tilted backwards, and the chin 
 moves downwards, and a little backwards alfo. In 
 this lafl motion, the Condyle turns its face a little for¬ 
 wards ; and the center of motion lies a little below 
 the Condyle, in the line between it and the angle of 
 the Jaw. By fuch an advancement of the Condyles 
 forwards, together with the rotation mentioned, the 
 aperture of the Mouth may be confiderably enlarged ; 
 a circumflance neceflary on many obvious occafions. 
 
 The 
 
1 3 
 
 OF THE LOWER-JAW. 
 
 The Condyles may alfo flicle alternately backwards 
 and forwards, from the cavity to the eminence, and vice 
 verfa ; fo that while one Condyle advances, the other 
 moves backwards, turning the body of the Jaw from 
 fide to fide, and thus grinding, between the Teeth, the 
 morfel feparated from the larger mafs by the motion firfl 
 deferibed. In this cafe, the center of motion lies ex¬ 
 actly in the middle between the two Condyles. And it 
 is to be obferved, that in thefe hidings of the Condyles 
 forwards and backwards, the moveable cartilages do 
 not accompany the Condyles in the whole extent of 
 their motion ; but only fo far as to adapt their furfaces 
 to the different inequalities of the Temporal Bone : for 
 as thefe cartilages are hollow on their lower furfaces 
 where they receive the Condyle, and on their oppo- 
 fite upper furfaces are convex where they lie in the 
 cavity ; but forwards, at the root of the eminence, that 
 upper furface is a little hollowed ; if they accompa¬ 
 nied the Condyles through the whole extent of their 
 motion, the eminences would be applied to the emi¬ 
 nences, the caviries would not be filled up, and the 
 whole articulation would be rendered very infecure. 
 
 This account of the motion of the Lower-Jaw, and its 
 cartilages, clearly demonflrates the principal ufe of thefe 
 cartilages ; namely, the fecurity of the articulation ; 
 the furfaces of the cartilage accommodating them- 
 felves to the different inequalities, in the various and 
 
 free 
 
 * 
 

 OF THE MOTION, See. 
 
 free motions of this joint. This cartilage is alfo very 
 ferviceable for preventing the parts from being hurt 
 by the fri&ion ; a circumftance neceffary to be guarded 
 againft, where there is fo much motion. Accord¬ 
 ingly, I find, this cartilage in the different tribes of 
 Carnivorous Animals, where there is no eminence and 
 cavity, nor other apparatus for grinding; and where 
 the motion is of the true ginglimus kind only. 
 
 In the Lower-Jaw, as in all the joints of the body, when 
 the motion is carried to its greateft extent, in any direc¬ 
 tion, the mufcles and ligaments are {trained, and the 
 perfon made uneafy. The ftate, therefore, into which 
 every joint molt naturally falls, efpecially when we are 
 alleep, is nearly in the middle, between the extremes 
 of motion ; by which means all the mufcles and liga¬ 
 ments are equally relaxed. Thence it is, that com¬ 
 monly, and naturally, the Teeth of the two Jaws are 
 not in contad ; nor are the Condyles of the Lower-Jaw 
 fo far back, in the Temporal Cavities as they can go. 
 
 O F 
 
\ 
 
 OF THE 
 
 MUSCLES of the LOWER-JAW. 
 
 TTAVING defcribed the figure, Articulation, Motion, 
 A A and ufe of the Lower-Jaw, it will be neceffary, 
 in the next place, to give fome account of the Mufcles 
 that are the caufes of its motion. 
 
 There are five pair of Mufcles, each of them capable 
 of producing various motions, according to the flirta¬ 
 tion of the Lower-Jaw, whether they act fingly, or in 
 conjunction with others ; and two or more of them 
 may be fo fituated, as to be capable of moving the Jaw 
 in the fame direction ; and every motion is produced by 
 the action of more than one Mufcle at a time. Thus, 
 if the Jaw is depreffed, and brought to one fide, either 
 the Maffeter, Temporal, or Pterigoidceus internus of 
 the oppofite fide will not only raife the Jaw, but bring 
 it to its middle fiate. It will be neceffary in the de- 
 fcription of each Mufcle, to give its ufe in the differ¬ 
 ent fituations of the Jaw ; by which means, after they 
 are all defcribed, their compound actions will be better 
 underflood. I fhall firft deferibe thofe which raife the 
 Jaw; then thofe which give it the lateral motion j and 
 
 laflhr 
 
 j 
 
 7 
 
OF T FI E MUSCLES 
 
 1 6 
 
 laflly, tliofe which deprefs it; proceeding in each clafs 
 as they rife in dilfedlion. 
 
 The mod fuperficial is the Mafleter : it is fituated 
 upon the poderior and lower part of the Face, between 
 the cheek-bone, and angle of the Lower-Jaw, diredtly 
 before the lower part of the Ear. It is a thick, fhort, 
 complex Mufcle, and a little flattened : it appears to 
 have two didindl origins, an anterior outer, and a pof- 
 terior inner ; but that is owing only to its outer edge 
 at its origin being flit, or double ; and the fibres of 
 thefe two edges having a different courfe, decuffating 
 each other a little. The anterior, and outer portion 
 of the Mufcle begin to rife from a fmall part of the 
 lower edge of the Malar Procefs of the Maxillary Bone, 
 adjoining to the Os Males ; and continues its origin 
 all along the lower horizontal edge of this lad bone, 
 to the angle where its Zygomatic Procefs turns up, to 
 join that of the Temporal Bone. The external layer of 
 fibres in this portion are tendinous at their beginnings, 
 while the internal are flefliy. 
 
 The poderior and inner portion of this Mufcle 
 begins to rife partly tendinous, and partly flefliy, from 
 the fame lower edge of the Os Malae ; not where the 
 origin of the other portion terminates, but a little 
 farther forwards ; and this origin is continued along 
 ,the lower edge of the Zygomatic Procefs of the Tem¬ 
 poral 
 
 / 
 
OF THE LOWER- JAW. 17 
 
 poral Bone, as far backwards as the eminence belong¬ 
 ing to the articulation of the Lower-Jaw. 
 
 From this extent of its origin, the Mufcle paffes 
 downwards to its infertion into the Lower-Jaw. The 
 anterior external portion is broader at its infertion 
 than at its origin ; for it occupies a triangular fpace of 
 the Lower-Jaw above the angle, and on the outfide, of 
 about an inch in lize, to about an inch and a half 
 from the angle towards the Chin. In confequence of 
 this extent of infertion, the fibres of this portion di¬ 
 varicate very confiderably. They are mofily flefhy at 
 their infertion, a few only being tendinous, particu¬ 
 larly thofe that are inferted backwards. The pofterior 
 and inner portion of the Mafieter is narrower at its in¬ 
 fertion than at its origin ; its pofterior fibres running for¬ 
 wards, as well as downwards, while its anterior run 
 almoft direCtly downwards. It occupies in its infer¬ 
 tion the remaining part of the fcabrous furface, above 
 the angle of the Lower-Jaw, which lies between the 
 anterior portion and the two upper proceftes, viz. the 
 Condyle and Coronoide. As the anterior fibres of this 
 portion rife on the infide of the pofterior fibres of the 
 other portion ; and as its pofterior fibres run forwards 
 as well as downwards, and its anterior run almoft: di¬ 
 rectly downwards, while the fibres of the other por¬ 
 tion radiate both forwards and backwards ; thefe two 
 portions in Lome meafure decuflate, or crofs one an- 
 
 D _ other. 
 
i8 
 
 OF THE MUSCLES, 8tc. 
 
 other. The anterior fibres, which run fartheft and 
 lowed down, are tendinous at their infertion, while 
 the pofterior and fhorted are flefhy. 
 
 The ufe of the whole Mufcle is to raife the Lower- 
 Jaw ; and when it is brought forwards, the pofierior 
 and inner portion will affiil in bringing it a little 
 back; fo that this Mufcle becomes a rotator, if the 
 Jaw happens to be turned to the oppofite fide. 
 
 We may obferve, that this Mufcle is intermixed 
 with a number of tendinous portions, both at its ori¬ 
 gin and its infertion ; which give rife to a greater 
 number of flefhy fibres, and thereby add to the 
 drength of the Mufcle.. 
 
 TEMPO- 
 
TEMPORALIS. 
 
 ¥ T is fitiiated on the fide of the Head, above, and 
 A fomewhat before the Ear. It is a pretty broad, flat, 
 . and radiated Mufcle ; broad and thin at its origin • 
 narrow and thick at its infertion ; and is covered with 
 a pretty ftrong Fafcia, above the Jugum, 
 
 This Fafcia is fixed to the bones round the whole cir¬ 
 cumference of the origin of the Mufcle. Above, it is 
 fixed to a fmooth white line, that is obfervable upon 
 the Skull, extending from a little ridge on the lateral 
 part of the Os Frontis, continued acrofs the Parietal 
 Bone, and making a turn towards the Mamillary Pro¬ 
 cefs. It is fixed below, to the ridge where the Zygo¬ 
 matic Procefs begins, juft above the Meatus Auditorius ; 
 then to the upper edge of the Zygomatic Procefs itfelf, 
 and anteriorly to the Os Malce. This adhefion, ante¬ 
 riorly, above, and pofteriorly, gives, as it were, the 
 circumference of the origin of the Temporal Mufcle. 
 
 This Mufcle arifes from all the bones of the fide of the 
 Head, that are within the line, for infertion of the ten¬ 
 dinous Fafcia, viz. from the lower and lateral part of 
 the Parietal Bone, from all the fquammous portion of 
 
 D 2 the 
 
20 
 
 T E M P 0 R A L r S. 
 
 the Temporal Bone, from the lower and lateral part 
 of the Os Frontis, from all the Temporal Procefs of 
 the Os Sphenoides, and often from a procefs at the 
 lower part of this furface, (which portion, however, is- 
 often common to this Mufcle, and the Pterygoidseus 
 externus) and from the pofterior furface of the Os 
 Malas. Outwardly* it rifes from the inner furface of the 
 Jugum, and from the whole inner furface of the Fafoia 
 above defcribed; At this origin, from the Jugum it is not 
 to be diltinguifhed from the MalTeter, being there, 
 in fa£t, one and the fame Mufcle ; and indeed the 
 Mafleter is no more than a continuation of the fame 
 origin, under the edge of the Jugum ; and might 
 properly enough be reckoned the fame, both as to its 
 origin and infertion, and in fome meafure in its, ufe 
 alfo* 
 
 The origin is principally fleftiy ; and the Mufcle 
 paffes from it, in general, downwards, and a little 
 forwards, converging, and forming a thin middle ten¬ 
 don. After which the Mufcle run,s downwards, on 
 the infide of the Jugum, and is inferted into the Co- 
 ronoid Procefs of the Lower-Jaw, on both tides tendi¬ 
 nous and flefhy, but principally tendinous. It reaches 
 farther down upon the intide of the Coronoid Procefs, 
 than upon the outer fide, where the infertion is conti¬ 
 nued as low as the body of the bone. 
 
 \ 
 
 The 
 
TEMPORALIS. 
 
 2 I 
 
 The posterior and inferior edge of this Mufcle 
 pafies over the root of the Zygomatic Procefs of 
 the Temporal Bone, as over a pulley, which con¬ 
 fines the action of the Mufcle to that of railing the 
 Lower-Jaw, more than if its fibres had pafled in a 
 direCt courfe from their origin to their infertion. 
 
 The ufe of the Temporal Mufcle,. in general, is to' 
 raife the Lower-Jaw ; and as it pafies a little forwards 
 to its infertion, it mull bring the Condyle at the fame 
 time backwards, and fo counteract the Pterygoidceus 
 externus of the oppolite fide ; and if both Mufcles 
 aCt, they counteract both the Pterygoidsei, by bringing 
 back the whole of the Jaw.. 
 
 FTERY- 
 
 / 
 
PTERYGOID-ffiUS INTERNUS. 
 
 ¥ T is fituated upon the infide of the Lower-Jaw, oppo- 
 
 fite to the MafTeter, which is upon the outfide. It 
 is a flrong fhort Mufcle, a little flattened, efpecially at 
 its infertion. It arifes tendinous and flefhy from the 
 whole internal furface of the external Ala of the 
 Sphenoid Bone ; from the external furface of the internal 
 Ala, near its bottom ; from that procefs of the Os Palati 
 that makes part of the Folia Pterygoidsea ; likewife from 
 the anterior rounded furface of that procefs, where it is 
 connected to the Os Maxillare fuperius. From thence 
 the Mufcle pafles downwards, a little outwards and 
 backwards, and is inferred tendinous and flefhy into 
 the infide of the Lower-Jaw, from the angle, up 
 almofl to the groove for the admifTion of the Maxil¬ 
 lary Nerve, where the furface of the bone is remark¬ 
 ably fcabrous. 
 
 The Ufe of this Mufcle is to raife the Lower-Jaw ; 
 and from its direction, one would fiifpedf that it would 
 bring the Condyle a little forwards ; but this motion 
 is contrary to that of the Lower-Jaw, for it is natu¬ 
 rally brought back when raifed. 
 
 P T E II Y- 
 
PTERYGOID^EUS EXTERNUS, 
 
 TS fttuated immediately between the external furface 
 of the external Ala of the Pterygoid Procefs, and 
 the Condyle of the Lower-Jaw; lying, as it were, ho¬ 
 rizontally along the bafis of the Skull. It is fome- 
 what radiated in fome bodies ; broad at the origin, and 
 fmallat the infertion; but the greater part of it forms a 
 round Prong flefhy belly; fo that the part that makes 
 it of the radiated kind is thin. 
 
 The thick and ordinary portion of it arifes tendinous 
 and ftefhy, from almoft the whole external furface of the 
 external Ala of the Pterygoid Procefs of the Sphenoid Bone, 
 excepting a little bit of the root at the pofterior edge ; 
 and towards the lower part, it arifes a little from the 
 inner furface of that Ala. The thin portion arifes 
 from a ridge of the Sphenoid, that is continued from 
 the procefs towards the Temple, juft behind the Fora¬ 
 men Lacerum inferius, which terminates in a little 
 protuberance. This origin is fometimes wanting ; 
 and in that cafe, the Temporal Mufcle arifes from that 
 protuberance ; and very often this origin is common 
 
 to both. Thefe two origins of this Mufcle are fome- 
 
 ♦ 
 
 times fo much feparated, as to make it a Biceps. 
 
 4. From 
 
24 
 
 PTERYGOID iEUS EXTERN US. 
 
 From thefc origins the Mufcle pafles outwards, and a 
 little backwards, converging ; that is, the fuperior fibres 
 palling outwards and backwards, and a little down¬ 
 wards ; while the inferior, or larger portion of it, palfes 
 a little upward. 
 
 'It is inferred tendinous and flefhy into a depreilion 
 on the anterior part of the Condyle and Neck of the 
 Lower-Jaw, upon the infide of that ridge, which is con- 
 tinued from the Coronoid Procefs. Likewife a little 
 portion into the anterior part of the moveable car¬ 
 tilage. A little portion is likewife inferred into the 
 anterior part of the moveable cartilage of the joint. 
 
 When this Mufcle ads fingly it is a rotator ; for it 
 brings the Condyle of the Jaw forwards, and likewife 
 the moveable cartilage, which throws the Chin to the 
 oppofite fide: but if it ads in conjunction with its 
 fellow of the oppofite fide, inflead of being turned to 
 one fide, the whole Jaw is brought forwards, and 
 thus thefe counterad the Temporal, &c. 
 
 Thefe two Mufcles generally ad alternately ; and 
 when they do fo, one ads at the time of depreilion, the 
 other at the time of elevation; fo that thefe Mufcles 
 ad, both when the Lower-Jaw is raifed, and when it is 
 tie p relied: yet they do not aflift either in railing or de- 
 preffing it. 
 
DIGASTRICUS. 
 
 YT is fituated immediately under, and a little upon 
 the infide of the Lower-Jaw, and outfide of the 
 Fauces, extending from the Mafloid Procefs to the 
 Chin, nearly along the angle made by the Neck and 
 Chin, or Face *. The name of this Mufcle exprefles 
 its general fhape, as it has two flefhy bellies, and 
 of courfe a middle tendon. Yet fome of its anterior 
 belly does not arife from the tendon of the pofterior, 
 but from the Fafcia, which binds it to the Os 
 Hyoides. Thefe two flefhy bellies do not run in the 
 fame line, but form an angle, juft where the tendon 
 runs into the anterior belly ; fo that this tendon feems 
 rather to belong to the pofterior, which is the thickeft 
 and longeft. 
 
 This Mufcle arifes from the Sulcus made by the in- 
 fide of the Mafloid Procefs, and a ridge upon the Tem¬ 
 poral Bone, where it is united with the Os Occipitis. 
 The extent of this origin is about an inch: it is flefhy 
 upon its outer part, viz. that from the Mafloid Procefs, 
 and tendinous on the infide from the ridge. From its 
 
 * Vide Plate II. E F. 
 
 ■f 
 
 origin 
 
DIGASTRIC US. 
 
 26 
 
 origin it pafTes forwards, downwards, and a little in¬ 
 wards, much in the direction of the polterior edge of 
 the Mammillary Procefs ; and forms a round tendon 
 firft in its center and upper furface. This tendon 
 pafTes on in the fame direction ; and when got near 
 the Os Hyoides, it commonly perforates the ante¬ 
 rior end of the Stylo Hyoideus Mufcle; and from the 
 lower edge of this tendon, fome fibres feem to go 
 off, which degenerate into a kind of Fafcia, that 
 binds it to the Os Hyoides ; and fome of it goes acrofs 
 the lower part of the Mylo-Hyoidceus, and joins its fellow 
 on the oppofite fide ; binding the Os Hyoides by a 
 kind of belt. At this part the tendon becomes a 
 little broader, makes a turn upwards, inwards, and 
 forwards, and gives origin to the anterior belly, which 
 pafTes on in the fame direHion, to the lower part of 
 the Chin, where it is inferted tendinous and flefliy, 
 into a flight depreflion on the under, and a little on 
 the pofterior part of the Lower-Jaw, almofl contiguous 
 to its fellow. Befides the attachment of the middle 
 tendon to the Os Hyoides, there is a ligamentous 
 binding, which ferves, in fome meafure, as a pulley. 
 This is more marked in fome fubj.edls than in others - 
 and this depends on the flrengtli of the tendinous ex- 
 panfion, which binds the tendon of the Digaflricus to 
 die Os Hyoides. 
 
 When we fay that thefe parts are attached to the 
 
 Os 
 
 7 
 
) 
 
 
 
 DIGASTRICUS. 27 
 
 Os Hyoides, we do not mean that they can be traced 
 quite into it, like fome other tendons in the body ; but 
 the Os Hyoides feems to be the moil fixt point of at- 
 tachment. Very often we find two anterior bellies to 
 eachMufcle; the uncommon one, which is the fmallefl, 
 does not pafs to the Chin, but joins with a fimilar 
 portion of the other fide, in a middle tendon, which 
 is often fixed to the Os Hyoides. At other times, we 
 find fuch a portion on one fide only; in which cafe it 
 is commonly fixed to the middle tendon of the Mylo. 
 Hyoidseus. 
 
 The ufe of thefe Mufcles with regard to the Lower- 
 Jaw, is principally to deprefs it; but according as one 
 adls a little more forcibly than the other, it thereby 
 gives the Jaw a fmall rotation ; and becomes, in that 
 refpedl, a kind of antagonifl to the Pterygoidseus Exter- 
 nus. Befides depreffing the Lower-Jaw, when we 
 examine the dead body, they would appear to raife 
 the Larynx. But although they have this effedt, a 
 proper attention to what happens in the living body, 
 will probably fhew, that their principal adtion is to 
 deprefs the Lower-Jaw, and that they arc the Mufcles 
 which are commonly employed for this purpofe. Let 
 a Finger be placed on the upper part of the Sterno- 
 Mafloidseus Mufcle, jud behind the pofterior edge of 
 die Mafloid Procefs, about its middle, touching that 
 edge a little with the finger; then deprefs the Lower- 
 
 E 2 Jaw 5 
 
 > 
 
DIGASTRICUS. 
 
 2 8 
 
 Jaw, and the pofterior head of the Digaftric will be felt 
 to fwell very confiderably, and fo as to point out the 
 direction of the Mufcle. In this there can be no de¬ 
 ception ; for there is no other Mufcle in this part that 
 has the fame direction ; and thofe who are of opinion 
 that the Digaftric does not deprefs the Lower-Jaw, will 
 more readily allow this, when they are told, that we 
 find the fame head of the Mufcle ad in deglutition *, 
 but not with a force equal to that which it exerts in 
 depreiling the Lower-Jaw. Further, if. the Sterno- 
 Hyoidei, Sterno-Thyroidei, and Cofto-Hyoidei, act¬ 
 ing at the fame time with the Mylo-Hyoidei, and 
 Genio-Hyoidei, affifted in depreffing the Jaw, the Os 
 Hyoides, and Thyroide Cartilage, would probably be de- 
 preiTed, as the bellies of the Srerno-LIyoidei, and of the 
 other lower mufcles, are by much the longed ; but on 
 the contrary, we find that the Os Hyoides, with the 
 Theroide Cartilage, is a little raifed in the deprelfion of 
 the Jaw, which we may fuppofe tobe done by the anterior 
 belly of the Digaftric : and fecondly, if thefe Mufcles 
 were to ad to bring about this motion of the Jaw, thefe 
 parts would be brought forwards, nearer to the ftraight 
 line between the Chin and Sternum, which is not the 
 cafe in this action; whereas we find it to be the cafe 
 in deglutition, in which thefe evidently ach By apply¬ 
 ing our Fingers upon the Genio-Hyoideus, and Mylo- 
 Hyoideus, near the Os Flyoides, between the two an¬ 
 terior bellies of the. Digaftric, (not near the Chin, 
 
 where 
 
D I G A S T R I C U S. 
 
 2 9 
 
 where the action of thefe two bellies may cccaficn a 
 miflake), we find thefe Mufcles quite flaccid ; which is 
 not the cafe in deglutition, nor in fpeaking, in which 
 they certainly do adt; nor do we find the Mufcles under 
 the Os Hyoides at all affedled, as they are in the motion 
 
 of the Larynx. 
 
 » 
 
 It has been obferved. that when we open the mouth, 
 while we keep the Lower-Jaw fixed, the forepart of the 
 Head or Face is neceflarily raifed. Authors have been 
 at a good deal of pains to explain this. Some of them 
 confidered the Condyles of the jaw, as the center of 
 motion ; but if this veere the cafe, that part of the 
 Head, where it articulates with the Spine, and of con- 
 fequence the whole body, mult be depreffed, in pro¬ 
 portion as the Upper-Jaw is raifed ; which is not true 
 in fadt. Others have confidered the Condyles of the 
 Occiput as the center of motion ; and they have con¬ 
 ceived the Extenfor Mufcles of the Head to be the 
 moving powers. The Mufcles which move the Head 
 in this cafe, are pointed out by two circumflances, 
 which attend all mufcular motion ; in the firfl place, 
 all actions of our body have Mufcles immediately 
 adapted to them ; and fecondly, when the mind wills 
 any particular adtion, its power is applied by inftindt 
 to thofe Mufcles only, which are naturally adapted to 
 that motion ; and further, the mind being accuflomed 
 to fee the part move which is naturally the molt 
 moveable, attends to its motion in the volition, al¬ 
 though 
 
30 DIGASTRICUS. 
 
 * # 
 
 though it be in that inftance fixed, and the other 
 parts of the body move towards it ; and although the 
 other parts of the body might be brought towards it 
 by other Mufcles, and would be fo, if the mind in¬ 
 tended that they fhould come towards it, yet thefe 
 Mufcles are not brought into adfion. Thus the Flex¬ 
 ors of the Arm commonly move the hand to the body ; 
 but if the hand be fixed, the body is moved by the 
 fame Mufcles to the hand. In this cafe, however, die 
 mind wills the motion of the hand towards the body, 
 and brings the Flexors into action ; whereas if it wiflied 
 to bring the body towards the hand, the Mufcles of the 
 
 t 
 
 forepart of the body would be put into action, and this 
 would produce the fame effect. 
 
 To apply this to the Lower-Jaw ; when we attempt 
 to open the Mouth, while the Lower-Jaw is immove¬ 
 able, we fix our attention upon the very fame Mufcles 
 (whatever they are) which we call into action, when 
 we deprefs the Lower-Jaw ; and we find that we a6t 
 with the very fame Mufcles ; for our mind attends to 
 the depreffing of the Jaw, and not the raifing of the 
 face ; and under fuch circumftanees the mouth is actu¬ 
 ally opened. We find then by thefe means the head is 
 raifed ; and the idea that we have of this motion, is 
 the fame that we have in the common deprefiion of the 
 Jaw ; and we fhould not know, except from circum- 
 fiances, that the Jaw was not really depreffed ; and 
 
 we 
 

 DIGASTR.ICUS. 31 
 
 we find at this time too, that the Extenfors of the head 
 are not in adtion. On the contrary, when the Jaw is 
 fixed in the fame fituation, if we have a mind to raife 
 the head, or Upper-Jaw, which of courfe mud open 
 the mouth, we fix our attention to the Mufcles that 
 move the head backwards, without having the idea of 
 opening our mouth ; and at this time the Extenfors of 
 the head aft. This plainly fliows, that the fame Muf¬ 
 cles which deprefs the Jaw, when moveable, muft raife 
 the head, when the Jaw is kept fixed. 
 
 This is a proof too, that there are no other Mufcles 
 employed in deprefling the Lower-Jaw, than what will 
 raife the head under the circumflances mentioned. 
 This will further appear from the ftrudture of the 
 parts ; wherein four things are to be confidered, viz. 
 the articulation of the Jaw ; the articulation of the 
 Head with the Neck ; the origin, and the infertion of 
 Digaftric Mufcle. 
 
 * Suppofe A, the Upper-Jaw, to be fixed, and the 
 Lower-Jaw B, to be moveable on the Condyle C: if the 
 Digraftic contracts, its origin E, and infertion F will 
 approach towards one another ; in which cafe it is evi¬ 
 dent, that the Lower-Jaw will move downwards and 
 backwards. But if the Lower-Jaw be fixed, as in the 
 cafe fuppofed, and the Vertebral G G G be alfo fixed, 
 
 * Vide Plate II. 
 
 the 
 
32 I) I G A S T R I C U S, 
 
 the Condyle will move upwards and forwards upon 
 the eminence in the joint, the forepart of the head 
 will be puilied upwards and backwards by the Con¬ 
 dyle, and the hind part of the head will be drawn 
 downfo that the whole fliall make a kind of circu¬ 
 lar motion upon the upper Vertebra} ; and the Digadric 
 Mufcle pulling the hind part of the head towards the 
 Lower-Jaw, and at the fame time pufliing up the Con¬ 
 dyles againfl the fore-part of the head, acquires, 
 by this mechanifm, a very confiderable additional 
 power. 
 
 O F 
 

 OF THE 
 
 STRUCTURE of a TOOTH. 
 And, Firft, of the ENAMEL* 
 
 Tooth is compofed of two fubftances, viz. 
 
 Enamel and Bone. The Enamel, called like- 
 wife the vitreous, or cortical part, is found only 
 upon the body of the Tooth, and is there laid all 
 around, on the outfide of the bony, or internal fub- 
 flance *. It is by far the hardeft part of our body ; in- 
 fomuch that the hardeft and fharpeft faw will fcarce 
 make an imprefllon upon it, and we are obliged to ufe 
 a file in dividing or cutting it. When it is broken it 
 appears fibrous or ftriated ; and all the fibres or ftrice 
 are diredled from the circumference to the center of the 
 Tooth f. 
 
 This, in fome meafure, both prevents it from break¬ 
 ing in maftification, as the fibres are difpofed in arches, 
 and keeps the Tooth from wearing down, as the ends 
 of the fibres are always adling on the food. 
 
 * Vide Plate XIV. Fig. 14, 15, and 17. 
 
 f Vide Plate XIV. Fig. 21, 22, and 23. 
 
 F 
 
 The 
 
34 
 
 OF THE STRUCTURE 
 
 The Enamel is thickefl on the grinding fur face, and 
 on the cutting edges, or points, of the Teeth; and be¬ 
 comes gradually thinner on the Tides, as it approaches 
 the neck, where it terminates infenfibly, though not 
 equally low, on all fides of the Teeth*. On the bafe 
 or grinding furface it is of a pretty equal thicknefs, 
 and therefore is of the fame form with the bony fub- 
 flance which it covers f. 
 
 * * ' . " v r . - 0 r m > f t * 
 
 V ■ • ' ? . , ' J ). . ( , * V t ’ ' - * 
 
 It would feem to be an earth united with a portion of 
 
 ^ \ 
 
 animal fubftance, as it is not reducible to quick lime by 
 fire, till it has firft been diflblved in an acid. When a 
 Tooth is put into a weak acid, the Enamel, to appearance, 
 is not hurt; but on touching it with the fingers, it 
 crumbles down into a white pulp. The Enamel of Teeth, 
 expofed to any degree of heat, does not turn to lime: it 
 contains animal mucilaginous matter; for when expofed 
 to the fire, it becomes very brittle, cracks, grows black, 
 and feparates from the inclofed bony part of the Tooth. 
 It is capable, however, of bearing a greater degree of 
 
 heat than the bony part, without becoming brittle and 
 
 * ■ * - . . 
 
 black X 4 This fubftance has no marks of being vafcu- 
 
 * Vide Plate XIV. Fig. 21, 22, and 23, 
 f Vide Ditto. 
 
 J From this circumflance we can fhew the Enamel better by burning 
 a Tooth, as the bony part becomes black fooner than the Enamel. 
 The method of burning, and fhewing them after they are burnt, is as 
 
 follows.-Let one half of a Tooth be filed away, from one end to the 
 
 other, then burn it gently in the fire ; after this is done, wafh the filed 
 
 furface 
 
OF A TOOTH. 
 
 $S 
 
 lar, and of having a circulation of fluids : the moft fub- 
 tile injections we can make never reach it; it takes no 
 tinge from feeding with madder, even in the youngeft 
 animals ; and, as was obferved above, when foaked in 
 a gentle acid, there appears no grijily ovjiejloy part, with 
 which the earthy part had been incorporated 
 
 We fhall fpeak of the ufe and formation of the 
 Enamel hereafter, when they will be better underflood. 
 
 furface with an acid, or fcrape it with a knife. By this method you will 
 clean the edge of the Enamel, which will remain white, and the bony 
 part will be found black. 
 
 * In all thele experiments I never could obferve, that the Enamel 
 was in the leaft tinged, either in the growing or formed Tooth. This 
 looks as if the Enamel were the earth more fully depurated, or 
 ilrained off from the common juices in fuch a manner, as not to allow 
 the grofs particles of madder to pafs. Here it may not be amifs to re¬ 
 mark, that the names given to animal fubftance, fuch as Gluten, &o 
 are not in the leaft expreftive of the thing meant •, for there is no fuch 
 thing as glue in an animal, till it has either undergone a putrefactive pro- 
 cefs, or been changed by heat. And here too I would be underftood, 
 that I call earth no part of an animal j nor does it make up any part of an 
 animal fubftance. 
 
 > 
 
 F 2 
 
 O F 
 
OF THE BONY PART 
 
 OF THE 
 
 BONY PART of a TOOTH. 
 
 r T^ H E other fubftance of which a Tooth is com- 
 pofed, is bony ; but much harder than the mod 
 compact part of bones in general. This fubftance 
 makes the interior part of the body, the neck, and the 
 whole of the root of a Tooth. It is a mixture of two 
 fubltances, viz. calcarious earth and an animal fubftance, 
 which we might fuppofe to be organized and vafcular. 
 The earth is in very confiderable quantity ; it remains 
 of the fame fhape after calcination, fo that it is in fome 
 meafure kept together by cohefion; and it is capable of 
 being extracted by fteeping in the muriatic, and fome 
 other acids. The animal fubftance, when deprived of 
 the earthy part, by fteeping in an acid, is more com¬ 
 pact than the fame fubftance in other bones, but ftill is 
 foft and flexible. 
 
 That part of a Tooth which is bony, is nearly of the 
 fame form as a complete Tooth ; and thence, when the 
 Enamel is removed, it has the fame fort of edge, point, 
 or points, as when the Enamel remained. We cannot 
 by inje6tion prove that the bony part of a Tooth is vaf- 
 
 i cular: 
 
OF A TOOTH. 
 
 37 
 
 vafcular: but from fome circumftances it would appear 
 that it is fo ; for the Fangs of Teeth are liable to fwel- 
 lings, feemingly of the fpina ventofa kind, like other 
 bones ; and they fometimes anchylofe with the focket 
 by bony and inflexible continuity, as all other contigu¬ 
 ous bones are apt to do. But there may be a deception 
 here, for the fwelling may be an original formation, 
 and the anchylofis may be from the pulp that the Tooth 
 is formed upon being united with the focket. The fol¬ 
 lowing conflderations would feem to fhew that the 
 Teeth are not vafcular: firft, I never faw them injedled 
 in any preparation, nor could I ever fucceed in any at¬ 
 tempt to injedt them, either in young or old fubjedts ; 
 and therefore believe that there mud have been fome 
 fallacy in the cafes where they have been faid to be in¬ 
 jected. Secondly, we are not able to trace any veflels go¬ 
 ing from the pulp into the fubflance of the new-formed 
 Tooth ; and whatever part of a Tooth is formed, it is 
 always completely formed, which is not the cafe with 
 
 other bones. But what is a more convincing proof, is 
 ♦ 
 
 reafoning from the analogy between them and other 
 bones, when the animal has been fed with madder. 
 Take a young animal, viz. a pig, and feed it with mad¬ 
 der, for three or four weeks ; then kill the animal, and 
 upon examination you will find the following appear¬ 
 ance : firfl, if this animal had fome parts of its Teeth 
 formed before the feeding with madder, thofe parts will 
 be known by their remaining of this natural colour ; 
 
 but 
 
3 8 
 
 OF THE BONY PART 
 
 but fuch parts of the Teeth as were formed while the 
 mal was taking the madder, will be found to be of a 
 red colour. This fhews, that it is only thofe parts that 
 were forming while the animal was taking the madder 
 that are dyed ; for what were already formed will not 
 be found in the lead tinged. This is different in all other 
 bones; for we know that any part of a bone which is 
 already formed, is capable of being dyed with madder, 
 though not fo fad as the part that is forming ; there¬ 
 fore as we know that all other bones when formed are 
 vafcular, and are thence fufceptible of the dye, we may 
 readily fuppofe that the Teeth are not vafcular, becaufe 
 they are not fufceptible of it after being once formed. 
 But we fliall carry this dill farther ; if you feed a pig 
 with madder for fome time, and then leave it off for a 
 coniiderable time before you kill the animal, you will 
 find the above appearances dill fubfiding, with this ad¬ 
 dition, that all the parts of the Teeth which were formed 
 after leaving off feeding with the madder will be white. 
 Here then in fome Teeth we fliall have white, then red, 
 and then white again ; and fo we fliall have the red and 
 the white colour alternately through the whole Tooth. 
 
 This experiment fhews, that the Tooth once tinged, 
 does not lofe its colour; now as all other bones that 
 have been once tinged lofe their colour in time, when 
 the animal leaves off feeding with madder (though 
 -very flowly), and as that dye mud be taken into the 
 a ' condi- 
 
O F A TOOTH. 
 
 39 
 
 couffitution by the abforbents, it would feem that the * 
 Teeth are without abforbents, as well as other veffels. 
 
 This (hews that the growth of the Teeth is very 
 different from that of other bones. Bones begin at a 
 point, and fhoot out at their furface ; and the part that* 
 feems already formed, is not in reality fo, for it is^ 
 forming every day by having new matter thrown into* 
 it, till the whole fubftance is complete ; and even them 
 it is conftantly changing its matter. 
 
 Another circumftance in which Teeth feem different - 
 from bone, and a flrong circumftance in fupport of 
 their having no circulation in them, is that they never 
 change by age, and feem never to undergo any altera¬ 
 tion, when completely formed, but by abrafion; they 
 do not grow fofter, like the other bones, as we find in 
 fome cafes, where the whole earthy matter of the bones 
 has been taken into the conftitution. 
 
 From thefe experiments it would appear, that the 
 Teeth are to be confidered as extraneous bodies, with 
 refpedt to a circulation through their fubftance; but 
 they have moff certainly a living principle, by which 
 means they make part of the body, and are capable of 
 uniting with any part of a living body; as will be ex¬ 
 plained hereafter: and it is to be obferved, that affections 
 >■ 
 
 of the whole body have lefs influence upon the Teeth 
 
 than. 
 
/ 
 
 40 OF THE BONY PART, 8cc. 
 
 than any other part of the body. Thus in children 
 affe&ed with the rickets, the Teeth grow equally well 
 as in health, though all the other bones are much 
 affedled j and hence their Teeth being of a larger fize 
 in proportion to the other parts, their mouths are protu¬ 
 berant. 
 
 O F 
 
\ 
 
 OF THE 
 
 CAVITY of the T E E T H. 
 
 TT'VERY Tooth has an internal Cavity, which ex- 
 tends nearly the whole length of its bony part * 
 It opens, or begins at the point of the fang, where it is 
 fmall; but in its paflage becomes larger, and ends in 
 the body of the Tooth f. This end is exactly of the 
 lhape of the body of the Tooth to which it belongs* 
 In general it may be faid, that the whole of the Cavity 
 is nearly of the fhape of the Tooth itfelf, larger in the body 
 of the Tooth, and thence gradually fmaller to the extre¬ 
 mity of the fang ; fimple, where the Tooth has but one 
 root X > an d in the fame manner compounded, when 
 the Tooth has two or more fangs §. 
 
 This Cavity is not cellular, but fmooth in its furface: 
 it contains no marrow, but appears to be filled with 
 
 * Vide Plate XIV. Fig. i, 2, 3, &c. 
 
 •J* Vide Plate XIV. Fig. 1, 2. 3. &c, 
 
 J Vide Plate XIV. Fig. 3, 4,5, and 6. 
 
 $ Vide Plate XIV. Fig. 1, 2. 
 
 G 
 
 blood- 
 
42 OF THE CAVITY OF THE TEETH. 
 
 blood-veflels and, I fuppofe, nerves, united by a 
 pulpy or cellular fubdance. The velTels are branches 
 of the fuperior and inferior Maxillaries; and the 
 nerves mud come from the fecond and third branches 
 of the fifth pair. . , . 
 
 By injections we can trace the blood-veflels diflinctly 
 through the whole Cavity of the Tooth ; but I could 
 never trace the Nerves didinctly even to the beginning, 
 of the Cavity. 
 
 * Vide Plate XII. Fig. 7, 8, 
 
 r 
 
 O F 
 
OF THE 
 
 PERIOSTEUM of the TEETH, 
 
 Hr* H E Teeth, as we obferved, are covered by an 
 Enamel only at their bodies ; but at their fangs 
 they have a Periofteum, which, though very thin, is 
 vafcular, and appears to be common to the Tooth which 
 it inclofes, and the focket, which it lines as an invell- 
 ing internal membrane, It covers the Tooth a little be¬ 
 yond the bony focket, and is there attached to the Gum. 
 
 G % O F 
 
44 " 'OF THE SITUATION 
 
 OP THE 
 
 SITUATION of the TEETH. 
 
 » 
 
 9 1 A H E general fhape and fttuation of the Teeth are 
 obvious. The oppofttion of thofe of the two Jaws, 
 and the circle which each row defcribes, need not be 
 particularly explained, as they may be very well feen 
 in the living body, and may be fuppofed to be already 
 underftood, from what was faid of the Alveolar Pre¬ 
 cedes. 
 
 We may juft obferve, with regard to the fituation of 
 the two rows, that when they are in the moft natural 
 ftate of oontaeft, the Teeth of the Upper-Jaw project a 
 little beyond the lower Teeth, even at the fides of the 
 Jaws; but ftill more remarkably at the fore part, where 
 in moft people the upper Teeth lie before thofe of the 
 Lower-Jaw *: and at the lateral part of each row, the 
 line, or furface of contact, is hollow from behind 
 forwards, in the Lower-Jaw ; and in the fame propor¬ 
 tion it is convex in the Upper-Jaw j\ 
 
 ** Vide Plate III. Fig. i, a. 
 
 •+ Vide Plate III. Fig. j, 2. 
 
 6 The 
 
 1 
 
OF THE TEETH. A5 
 
 The edge of each row is Angle at the fore part of the 
 
 ■ 
 
 jaws; but as the Teeth grow thicker backwards, it 
 there fplits into an internal and external edge. The 
 canine Tooth, which we fhall call Cufpidatus , is the 
 point from which the two edges go off; fo that the 
 firft grinder, or what we fhall call the firft Bicufpis , is 
 the firft Tooth that has a double edge *. 
 
 ; * Vide Plate IV. Fig. i, 2. 
 
 / 
 
 O F 
 
OF THE 
 
 N U M B E R of T E E T H. 
 
 P H EI R Number in the whole, at full maturity, is 
 
 A from twenty-eight to thirty-two: I once faw 
 twenty-feven only, never more than thirty-two. Four¬ 
 teen of them are placed in each Jaw, when the whole 
 number is no more than twenty-eight; and fixteen, 
 when there are thirty-two. If the whole be twenty- 
 nine or thirty-one in number, the Upper-Jaw fome- 
 times, and fometimes the Lower, has one more than the 
 other ; and when the Number is thirty, I find them 
 fometimes divided equally between the two Jaws ; and 
 in other fubjeels fixteen of them are in one Jaw, and 
 fourteen in the other. In fpeaking of the Number of 
 Teeth, I am fuppofing that none of them have been 
 pulled out, or otherwife loft; but that there are from 
 eight to twelve of thofe large pofterior Teeth, which 
 I call Grinders, and that they are fo clofe planted as 
 to make a continuity in the circle: and in this .cafe, 
 when the number is lefs than thirty-two, the defici¬ 
 ency is in the laft grinder. 
 
 The Teeth differ very much in figure from one ano¬ 
 ther ; but thofe on the right fide in each Jaw referable 
 
 exactly 
 
 8 
 
OF THE NUMBER OF TEETH. 
 
 47 
 
 exactly thofe on the left, fo as to be in pairs; and the 
 pairs belonging to the Upper-Jaw nearly referable the 
 correfponding Teeth of the Lower-Jaw in fituation s 
 figure, and ufe *. 
 
 Each Tooth is divided into two parts, viz, firft, the 
 body, or that part of it which is the thickeft, and 
 Hands bare beyond the Alveoli and Gums ; fecondly, 
 the fang, or root, which is lodged within the Gum 
 and Alveolar Frocefs : and the boundary between 
 thefe two parts, which is grafped by the edge of the 
 Gum, is called the Neck of a Tooth. The bodies of the 
 different Teeth differ very much in fhape and fize, and 
 fo do their roots. The difference miift be confidered 
 
 hereafter. 
 
 The Teeth of each Jaw are commonly divided 
 into three claffes, viz. Incifors, Canine , and Grinders $ 
 but from confidering fome circumflances of their form, 
 growth and ufe, I chufe to divide them into the four 
 following claffes, viz. Incifores, commonly called Fore 
 Teeth *, Cufpidati, vulgarly called Canine ; Bicufpides , or 
 the two fir ft Grinders j and MoJares , or the three laft 
 Teeth. The number of each clafs, in each Jaw, for 
 the mod part, is four Incifores , two Cufpidati, four Bicuf¬ 
 pides, and four, five, or fix Molares . 
 
 * Vide Plate III. IV. V. 
 
 There 
 
4S OF THE NUMBER OF TEETH. 
 
 I 
 
 There is a regular gradation, both in growth and 
 form through thefe clafles, from the lncifores to the M>- 
 lares , in which refpedt the Cufpidati are of a middle na¬ 
 ture, between the lncifores and Bicufpides , as the lad are 
 between the Cufpidati and Molares ; and thence the lncifores 
 
 and Molares are the mod unlike in every circumdance * f. 
 
 » 
 
 * Vide Plate Ill. and V. 
 
 ■f It is here to be underftood, that the Teeth from which we take 
 onr defcription, are fuch as are juft completely formed, and therefore 
 not in the leaft worn down by maftication. Our defcription of each; 
 clals is taken /rom the Lower-Jaw ; and the difference between them,, 
 and their correfponding ciaffes in the Upper immediately follows that 
 defcription. 
 
 O F 
 
OF THE 
 
 I N C I S O R E S. 
 
 r T^ H E huifores are fituated in the anterior part of the 
 A Jaw; the others more backwards on each fide, in 
 the order in which we have named them. The bodies 
 of the Incifores are broad, having two flat furfaces, one 
 anterior, the other pofterior. Thefe furfaces meet in a 
 fharp cutting edge. The anterior furface is convex in 
 every direction, and placed almofl perpendicularly; 
 and the pofterior is concave and Hoping, fo that the 
 cutting edge is almoft diredlly over the anterior fur** 
 face *. 
 
 ✓ 
 
 Thefe furfaces are broadeft and the Tooth is thinneft 
 
 at the cutting edge, or end of the Tooth, and thence 
 
 ♦ 
 
 they become gradually narrower, and the Tooth thicker 
 towards the neck, where the furfaces are continued to 
 the narrowed: fide, or edge of the fang. The body of 
 an Incifory in a fide-view, grows gradually thicker, or 
 broader, from the edge or end of the Tooth to its neck; 
 and thefe coincide with the flat, or broad fide of the 
 fang ; fo that when we look on the fore part, or on the 
 
 * Vide Plate XIV. and Plate V. row 3, 4. 
 
 H 
 
 back 
 
OF THEINCISORES. 
 
 50 
 
 back part of an Incifor , we obferve it grows conftantly 
 narrower from its cutting edge to the extremity of its 
 fang. But in a fide-view it is thickeft or broadeft at its 
 neck, and thence becomes gradually more narrow, both 
 to its cutting edge, and to the point of its fang *. 
 
 The Enamel is continued farther down, and is thicker 
 on the anterior and back part of the. Incifor es than on their 
 fides, and is even a little thicker on the fore part than 
 upon the back part of the Tooth. If we view them late¬ 
 rally, either when intire, or when cut down through the 
 middle, but efpecially in the latter cafe, it would feem 
 as if the fang was driven like a wedge into, and had 
 fplit the body or Enamel of the Tooth f. They ftand 
 almoft perpendicularly, their bodies being turned a 
 little forwards. Their fangs are much fhorter than thofe 
 of the Cufpidati , but pretty much of the fame length with 
 all the other Teeth of this Jaw J. 
 
 r . 1 T x , > .Si r * * 
 
 In the Upper-Jaw they are broader and thicker, efpe¬ 
 cially the two firft : their length is nearly the fame 
 with thofe of the Lower-Jaw. They Rand a little ob¬ 
 liquely, with their bodies turned much more forwards 
 (the fir ft efpecially) and they generally fall over thofe 
 of the Under-Jaw. 
 
 " * . v . . • • ‘• - ■ * • * • * • 5 
 
 * t » 1 * ; . 
 
 * Vide Plate V. 
 
 | Vide Plate XIV. Fig. 17. 
 
 J Vide Plate Ill. Fig. 2. 
 
 The 
 
OF THE INCISORES. 
 
 S 1 
 
 The two firf Incifores cover the two fir ft, and half of 
 the fecond of the Lower-Jaw, fo that the fecond Incifor 
 in the Upper-Jaw covers more than half of the fecond* 
 and more than the half of the Cufpidatus of the Under- 
 Jaw *. 
 
 The edges of the Incifores by ufe and fridlion, in fome 
 people, become blunt and thicker ; and in others they 
 fharpen one another, and become thinner. 
 
 v _» . *- • » r . • .«* 
 
 * Vide Plate III. Fig. i. 
 
 • » % r 
 
 i 
 
OF THE 
 
 CUSPIDATUS. 
 
 < * 
 
 HP H E Cufpidatus is the next after the Incifores in each 
 Jaw; fo that there are four of them in all. They 
 are in general thicker than the Incifores , and confider- 
 ably the longefl of all the Teeth *. 
 
 The fhape of the body of the Cufpidatus may be 
 very well conceived, by fuppofing an Incifor , with its 
 corners rubbed off, fo as to end in a narrow point, in- 
 ftead of a thin edge f; and the fang differs from that 
 of an Incifor , only in being much larger if. 
 
 The outfide of the body of a Cufpidatus projects moft at 
 the fide next the Incifores , being there more angular than 
 any where elfe. 
 
 * Vide Plate VI. Fig. i. Plate V. Row I, 3 d Fig, bb. 
 Vide Plate IV. Fig. i, at bb» 
 j Vide Plate VI. Fig, i. 
 
 The 
 
OF THE CUSPIDATUS. 
 
 55 
 
 The Enamel covers more of the lateral parts of thefe 
 Teeth than of the Incifores ; they ftand perpendicularly, 
 or nearly fo, projecting farther out in the circle than 
 the others, fo that the two Cufpldati and the four Incifores 
 often (land almofl in a ftraight line, efpecially in the 
 Lower-Jaw. 
 
 This takes place only in adults, and in them only 
 when the fecond Teeth are rather too large for the arch 
 of the Jaw *, for we never find this when the Teeth are 
 at any diftance from one another, or in young fubjedts. 
 Their points commonly projedt beyond the horizontal 
 line formed by the row of Teeth, and their fangs run 
 deeper into the Jaws, and are oftener a little bent. 
 
 In the Upper-Jaw they are rather longer, and do not 
 projedt much beyond the circle of the adjacent Teeth ; 
 and in this Jaw they are not placed vertically, their 
 bodies being turned a little forwards and outwards. 
 
 When the Jaws are clofed, the Cufpidatus of the Upper- 
 jaw falls between, and projedts a little over the Cufpi¬ 
 datus and firft Bicufpis of the Lower-Jaw. When they are 
 a little worn down by ufe, they commonly firft take an 
 edge fomewhat like a worn Incifor , and afterwards be¬ 
 come rounder. 
 
 The 
 
54 
 
 OF THE CUSPID AT US. 
 
 The ufe of the Ciifpiclati would feem to be, to lay hold 
 of fubdances, perhaps even living animals ; they are 
 not formed for dividing as the Incifores are ; nor are they 
 fit for grinding. We may trace in thefe Teeth a fimi- 
 larity in ftiape, iituation, and ufe, from the mod im¬ 
 perfectly carnivorous animal, which we believe to be 
 the human fpecies, to the mod perfectly carnivorous, 
 viz. the lion. 
 
 j ] 'i . ' ■ l .. • . ,. : ■ I : ■ : .. 
 
 O F 
 
r\ 
 
 OF THE 
 
 C».l ' / i 111 O > * , i' . •*’ i!)' • ‘i r j\ >/’ j (i .V , I 
 
 y - lM. :_rJ' Cl : ' ■ ‘ «' . . ■ ■ t: ■ • * / 
 
 BICUSPIDES. 
 
 1 . . ■ ‘ ' l * ‘ * ,x t ~ • " • - t 1 1 • u ■ ’ -j 
 
 T Immediately behind the Cufpidati , in each Jaw, Hand 
 JL two Teeth, commonly called the firft and fecond 
 Grinders, but which, for reafons hinted at above, I fhall 
 fuppofe to conflitute a particular clafs, and call them 
 
 »__ * •' i * i'■ • . * /1 f • > - 
 
 Bicufpides . 
 
 T . . ■ on ’■ . ' :• '-Mr, ’ .'• ?' ' 
 
 Thefe (viz. the fourth and fifth Tooth from the fym- 
 phyfis of the Jaw) refemble each other fo nearly, that 
 
 a defcription of the firil will ferve for both. The firft 
 
 ^ • ' * 
 
 indeed is frequently the fmalleft, and has rather the 
 
 longefl fang, having fomewhat more of the fhape of 
 the Cufpidatus than the fecond. 
 
 r • . .;. V, '' ii ' } 
 
 The body of this Tooth is flattened laterally, an- 
 fwering to the flat fide of the fang. It terminates in two 
 points, viz. one external and one internal. The external 
 is the longefl and thickeft ; fo that on looking into the 
 mouth from without, this point only can be fedn, and 
 the Tooth has very much the appearance of a Cufpidatus; 
 efpecially the firfl of thefe Teeth. I he internal point 
 
 i 
 
OF THE BICUSPIDES. 
 
 is the lead, and indeed fometimes f© very fmall, that 
 the Tooth has the greateft refemblance to a Cufpidatus 
 in any view *, At the union of the points the Tooth is 
 thickeft, and thence it lofes in thicknefs, from fide to 
 fide, to the extremity of the fang ; fo that the fang 
 continues pretty broad to the point, and is often forked 
 there. All the Teeth hitherto defcribed often have their 
 
 points bent, and more particularly the CufpldatL 
 
 \ 
 
 ' * . V ' J 
 
 The Enamel paffes fomewhat farther down exter¬ 
 nally and upon the infide, than laterally ; but this dif¬ 
 ference is notfo confiderable as in the Incifores , and Cufpi- 
 dati \ in fome indeed it terminates equally all round 
 the Tooth. They {land almolt perpendicularly, but 
 feem to be a little turned inwards, efpecially the laft 
 of them. 
 
 t) 
 
 In the Upper-Jaw they are rather thicker than in 
 the Lower, and are turned a very little forwards and 
 outwards. Thefirfi: in the Upper-Jaw falls between the 
 two in the Lower. The fecond falls between the fecond 
 and the firfi: Grinder : and both project over thofe of 
 the Lower-Jaw, but lefs than the Incifores and Cufpidati . 
 
 The Bicufpides , and efpecially the fecond of them, 
 in both Jaws, are oftener naturally wanting than any of 
 
 * Vide Plate IV. Fig. i, 2, cu 
 
 Sfc 
 
 « 
 
OF THE BICUSPIDES. 
 
 S 7 
 
 the Teeth, except the Dentes Sapientia ; thence we might 
 conjecture that they are lefs ufeful ; and this con¬ 
 jecture appears lefs improbable, when we confider, that 
 in their ufe they are of a middle nature between Cutters 
 and Grinders ; and that in molt animals, fo far as I have 
 obferved, there is a vacant fpace between the Cutters 
 and Grinders. I have alfo feen a Jaw in which the 
 firlt Bicufpis was of the fame lhape and fize as a 
 Grinder, and projected, for want of room, between the 
 Cufpidatus and fecond Bicufpis. Thefe and the Grind¬ 
 ers alter very little in lhape on their grinding furfaces 
 by ufe; their points only wear down, and become 
 obtufe. 
 
 O F 
 
 N 
 
G F T H 2 
 
 ? " ~ / 
 
 ' 9 
 
 G R I N D E R S. 
 
 1 N defcribing the Grinders we fhall fir ft confider the- 
 * fir ft and fecond conjundtly, becaufe they are nearly 
 the fame in every particular ; and then give an account 
 of the third or laft Grinder,, which differs from them in. 
 fome circumftances. 
 
 The two firft Grinders differ from the BicufpideSj 
 principally in being much larger, and in having more 
 points upon their body, and more fangs 
 
 The body forms almoft afquare, with rounded angles.. 
 The grinding furface has commonly five points, or pro¬ 
 tuberances, two of which are on the inner, and three 
 on the outer part of the Tooth ; and generally fome 
 fmaller points at the roots of thefe larger protube¬ 
 rances. Thefe protuberances make an irregular cavity 
 in the middle of the Tooth. The three outer points do 
 not fland fo near the outer edge of the Tooth, as the 
 inner do on the infide ; fa that the body of the Tooth 
 
 * Vide Plate IV. Fig. 1, 2, d d. 
 
 fwells 
 
OF THE GRINDERS. 
 
 5 9 
 
 iwells out more from the points, or is more convex, on 
 the outfide. The body towards its neck becomes but very 
 little fmaller, and there divides into two flat fangs, one 
 forwards, the other backwards, with their edges turned 
 outwards and inwards, and their fides consequently 
 forwards and backwards : the fangs are but very little 
 narrower at their ends, which are pretty broad, and 
 often bifurcated. There are two cavities in each fang, 
 one towards each edge, leading to the general cavity 
 in the body of the Tooth. Thefe two cavities are 
 formed by the meeting of the fides of the fang in the 
 middle, thereby dividing the broad and flat cavity into 
 two * j and all along the outfide of thefe (and all the 
 other fiat fangs) there is a correfponding longitudinal 
 groove. Thefe fangs at their middle, are generally 
 bent a little backwards f. 
 
 The Enamel covers the bodies of thefe Teeth pretty 
 equally all round. 
 
 The fir ft Grinder is fomewhat larger and flronger 
 than the fecond ; it is turned a little more inwards than 
 the adjacent Bicufpides , but not fo much as the fe¬ 
 cond Grinder. Both of them have generally Shorter 
 fangs than the Bicufpides. 
 
 * Vide Plate XIV. Fig. 7, where four dark fpots are obferved. 
 
 -f- Vide Plate VI. Fig. 1. 
 
 I 2 
 
 There 
 
60 OF THE GRINDERS. 
 
 There is a greater difference between thefe Grinders 
 in the Upper and Lower-Jaw, than any of the other 
 Teeth. In the Upper-Jaw they are rather rhomboidal, 
 than fquare in their body, with one fharp angle turned 
 forwards and outwards, the other backwards and in¬ 
 wards j befides they have three fangs, which diverge, 
 and terminate each in a point ; thefe are almoft round, 
 and have but one cavity. Two of them are placed near 
 each other perpendicularly, over the outfide of the 
 Tooth ; and the other, which generally is the largefl, 
 {lands at a greater diflance on the infide of the Tooth, 
 Ranting inwards. In this Jaw thefe two Grinders are 
 inclined outwards, and a little forwards ; they project 
 a little over the correfponding Teeth of the Lower-Jaw, 
 and they are placed further back in the mouth, fo that 
 each is partly oppofed to two of the Lower-Jaw.. The 
 fecond in the Upper-Jaw is fmaller than the others, 
 and the firft and fecond are placed directly under the 
 - Maxillary Sinus. I once faw the fecond Grinder naturally 
 wanting on one fide of the Lower-Jaw. 
 
 The third Grinder is commonly called Dens Sapientiee } 
 it is a little fhorter and fmaller than the others, and in¬ 
 clined a little more inwards and forwards. Its body is 
 nearly of the fame figure, but rather rounder, and its 
 
 fangs are generally not fo regular and diflincT, for they 
 
 \ 
 
 often appear fqueezed together; and fometimes there is 
 only one fang, which makes the Tooth conical: it is 
 
 much 
 
OF THE GRINDERS. 61 
 
 much fmaller than the reft of the Grinders. In the 
 Upper-Jaw this Tooth has more variety than in the 
 Lower, and is even fmaller than the correfponding 
 Tooth of the Lower, and thence Hands directly oppofed 
 to it; but for this circumftance the Grinders would 
 reach farther back in the Upper-Jaw than in the Lower, 
 which is not commonly the cafe. 
 
 In the Upper-Jaw this third Grinder is turned but a 
 very little outwards ; is frequently inclined fomewhat 
 backwards ; and it projects over that of the Under-Jaw. 
 It oftener becomes loofe than any of the other Teeth. 
 
 They are placed under the poflerior part of the Max¬ 
 illary Sinus, and there the parts which compofe the 
 Sinus are thicker than in the middle. The variations 
 as to the natural number of the Teeth, depend com¬ 
 monly upon thefe Dentes Sapient 'uz. 
 
 to 
 
 Thus from the Incifores to the firft Grinder, the Teeth 
 become gradually thicker at the extremity of their bo¬ 
 dies, and fmaller from the firft Grinder to the Dens Sa - 
 pent'uz. From the Cufpidatus to the Dens Sapientia the fangs 
 become much fhorter ; the Incifores are nearly of the 
 fame length with the Bicufpides. From the firft Incifor 
 to the laft Grinder, the Teeth Hand lefs out from the 
 fockets and Gums,- 
 
 4 
 
 The 
 
6.2 
 
 O F T HE G R I N D E R S. 
 
 The bodies of the Teeth in the Lower-Jaw are turned 
 a little outwards at the anterior part of the Jaw, and 
 thence, to the third Grinder, they are inclined gradu¬ 
 ally more inwards. The Teeth in the Upper-Jaw pro¬ 
 ject: over thofe of the Under, efpecially at the fore-part, 
 which is owing to the greater obliquity of the Teeth 
 in the Upper-Jaw; for the circle of the fockets is nearly 
 the fame in both Jaws. This oblique fituation, however, 
 becomes gradually lefs, from the Incifores backwards, to 
 the lafl Grinder, which makes them gradually project 
 lefs in the fame proportion. 
 
 The Teeth in the Upper-Jaw are placed farther back 
 in the circle than the correfponding Teeth of the Lower; 
 this is owing to the two firft Incifores above being broader 
 than the correfponding Incifores below. All the Teeth 
 have only one fang, except the Grinders, each of which 
 has two in the Lower-Jaw, and three in the Upper *. 
 
 The fangs bear a proportion to the bodies of the 
 Teeth ; and the reafon is evident, for otherwife they 
 would have been eafily broken, or pufhed out of their 
 fockets. The force commonly applied to them is oblique, 
 not perpendicular ; and they are not fo firmly fixed in 
 
 * Thofe Anatomifts who allow the Teeth to have more fangs, have 
 been led into a miftake, I fuppofe, by often obferving two canals in 
 one fang •, and thence concluded, that fuch a fang was originally two, 
 nnd that tliefe were now grown together. 
 
 the 
 
OF THE GRINDERS. 
 
 6 $ 
 
 tlie Upper-Taw, that is, the Alveolar Procefs in that is 
 not fo ftrong as in the Under-jaw : it is perhaps on 
 this account, that the Grinders in that Jaw have three 
 fangs. 
 
 This particular firutfture in the Alveolar Procefs of 
 the Upper-Jaw, is perhaps to give more room for the 
 Antrum Highmorianum \ on this fuppodtion the fangs mil ft 
 be made accordingly, i. e. fo that they fhall not be pufli- 
 ed into that cavity ; now, by their diverging, they in- 
 clofe as it were the bottom of the Antrum, and do not 
 pufh againft its middle, which is the weakeft part; 
 and the points of three diverging fangs will make a 
 greater refinance (or not be fo eafily pufhed in) than if 
 they were placed parallel. If there had been only two, 
 as in the Lower-Jaw, they muft have been placed 
 oppof te to the thinned: part of the Antrum ; and three 
 points placed in any direction but a diverging one, 
 would have had here much the fame effect as two; 
 and as the force applied is endeavouring to deprefs the 
 Tooth, and pufh it inwards, the innermoft fang di¬ 
 verges mod, and is fupported by the inner wall of the 
 Antrum . That all this weaknefs in the Upper-Jaw is for 
 the increafe of the Antrum is probable, becaufe all the 
 Teeth in the. Upper-Jaw are a good deal fimilar to 
 thofe in the Lower, excepting thofe that are oppofite to 
 the Maxillary Sinus ; and here they differ principally in 
 the fangs, without any other apparent reafon; and 
 
 what - 
 
6 4 OF THE GRINDERS, 
 
 what confirms this, is, that the Dentes Sapientia in both 
 Jaws are more alike than the other Grinders ; for this 
 reafon, as I apprehend, becaufe the Dens Sapientia in 
 the Upper-Jaw, does not interfere fo much with the 
 Maxillary Sinus„ 
 
 What makes it Hill more probable that the two firfl 
 fuperior Grinders have three fangs on account of the 
 Maxillary Sinus, is, that the two Grinders on each fide 
 of the Upper-Jaw, in the child, have three fangs, and 
 we find them underneath the Antrum ; but thofe that 
 fucceed them have only one fang, as in the Lower-Jaw; 
 but by that time the Antrum has paffed further back, 
 or rather the arch of the Jaw has projected, or fhot 
 forwards, as it were, from under the Antra, fo that the 
 Alveolar Proceffes that were under the Antrum at one 
 age, are got before it in another. ' 
 
 That the edge of every fang is turned towards the 
 circumference of the Jaw, in order to counteradl the 
 adting power, we fhall fee when we confider the Mo¬ 
 tion of the Jaw, and the Ufe of the Teeth. 
 
0 F T H E 
 
 ARTICULATION of the TEETH. 
 
 HT' H E fangs of the Teeth are fixed in the Gum and 
 Alveolar Procelfes, by that fpecies of Articulation 
 called Gomphofis, which, in fome meafure, refembles 
 a nail driven into a piece of wood *. 
 
 They are not, however, firmly united with the Pro- 
 cefles, for every Tooth has fome degree of motion ; and 
 in heads which have been boiled or macerated in water, 
 fo as to deftroy the Periolteum and adhefion of the 
 Teeth, we find the Teeth fo loofely connected with their 
 fockets, that all of them are ready to drop out, except 
 the Grinders, which remain as it were hooked from 
 the number and fhape of their fangs. 
 
 * Vide Plate I. for the fockets; and Plate VI. for the Teeth them- 
 felves in their fockets. 
 
 K 
 
 O F 
 
O F 
 
 THE GUMS. 
 
 f I ^ HE Alveolar Procedfes are covered by a red vaf- 
 cular fubdance, called the Gums, which has 
 as many perforations as there are Teeth ; and the 
 neck of a Tooth is covered by, and fixed to this Gum. 
 Thence there are flefhy partitions between the Teeth, 
 paffing between the external and internal Gum, and, 
 as it were, uniting them j thefe partitions are higher 
 than the other parts of the Gum, and thence form 
 an arch between every two adjacent Teeth. The 
 thicknefs of that part of the Gum which proje<5ls 
 beyond the fockets is confiderable ; fo that when the 
 Gum is corroded by difeafe, by boiling, or other- 
 wife, the Teeth appear longer, or lefs funk into the 
 Jaw. The Gum adheres very firmly in a healthful 
 date both to the Alveolar Procefs and to the Teeth, but 
 its extreme border is naturally loofe all around the 
 Teeth. The Gum, in fubdance, has fomething of a 
 cartilaginous hardnefs and eladicity, and is very vafcu- 
 lar, but feems not to have any great degree of fendbi- 
 lity ; for though we often wound it in eating, and in 
 picking our Teeth, yet we do not feel much pain upon 
 thefe occafions j and both in infants and old people, 
 8 where 
 
OF THE GUM S, 6.7 
 
 where there are no Teeth, the Gums bear a very conli- 
 derable prelTure, without pain. 
 
 The advantage arifing from this degree of infalli¬ 
 bility in the Gums is obvious, for till the child cuts its 
 
 ' '"'l ' T " ’ i *; t’ *'» # \ 
 
 Teeth, the Gums are to do the bulinefs of Teeth, and 
 are therefore formed for this purpofe, having a hard 
 ridge running through their whole length. Old peo¬ 
 ple, who have loll their Teeth, have not this ridge. 
 When in a found Hate, the Gums are not eafily irritated 
 by being wounded, and therefore are not fo liable to 
 inflammation as other parts, and foon heal. 
 
 - • • . t 1 l - \ 7 * f , < -; 1 
 
 * < ; I -• f r r ; , - - . . 1 • , f . r* r , - »• 
 
 The Teeth being united to the Jaw by the Periofleum 
 and Gum, have fome degree of an yielding motion in 
 the living body. This circumllance renders them more 
 fecure ; it breaks the jar of bony contadl, and prevents 
 fractures both of the fockets and of the Teeth thcm- 
 felves. 
 
 K 2 
 
 O F 
 
OF THE ACTION 
 
 O F T H E 
 
 ACTION of the T EETH, arifing from the 
 Motion of the Lower-Jaw. 
 
 r | n HE Lower-Jaw may be faid to be the only one 
 A that has any motion in maftication ; for the Upper-* 
 Jaw can only move with the other parts of the head. 
 That the Upper-Jaw and head fhould be raifed in the 
 common act of opening the mouth, or chewing, would 
 feem, at firft fight, improbable; and from an attentive 
 view of the mechanifm of the joints and mufcles of 
 thofe parts, from experiment and observation, we find 
 that they do not fenfibly move. We Shall only mention 
 one experiment in proof of this, which feems conclufive : 
 let a man place himfelf near fome fixed point, and look 
 over it, to another diftant and immoveable object, when 
 he is eating. If his head fhould rife in the leafl degree, 
 he would fee more of the diftant object over the neared 
 fixed point, whichin fadt he does not. The nearer the fixed 
 point is, and the more diftant the objecT, the experi¬ 
 ment will b£ more accurate and convincing. The refult 
 of the experiment will be the fame, if the neared point 
 has the fame motion with the head; as, when he looks 
 
 4 
 
 from under the edge of a hat, or any thing elfe put 
 
 upon 
 
OF THE TEETH. 
 
 69 
 
 upon his head, at fome diftant fixed objedh We may 
 conclude then that the motion is entirely in the Lower- 
 Jaw : and, as we have already defcribed both the 
 articulation and the motion of the bone, we fhall now 
 explain the action of maftication, and, at the fame time, 
 confider the ufe of each clafs of Teeth. 
 
 With regard to the adtion of the Teeth of both Jaws, 
 in mafiication, we may obferve, once for all, that their 
 action and re-adtion rauft be always equal, and that the 
 Teeth of the Upper and Lower-Jaws are complete, and 
 equal antagonifts both in cutting and grinding. 
 
 / 
 
 When the Lower-Jaw is deprefled, the Condyles Hide 
 forwards on the eminences 5 and they return back again 
 into the cavities, when the Jaw is completely raifed. 
 
 This fimple adtion produces a grinding motion of the 
 Lower-Jaw, backwards on the Upper, and is ufed 
 when we divide any thing with our fore Teeth, or 
 Incifores, For this purpofe, the Incifores are well formed ; 
 as they are higher than the others, their edges mull 
 come in contadt fooner and as the Upper projedt over 
 the Under, we find in dividing any fubftance with them, 
 that we full bring them oppofite to one another, and as 
 they pafs through the part to be divided, the Lower- 
 Jaw is brought back, while the Incifors of that Jaw 
 Aide up behind thofe of the Upper-Jaw, and of courfe 
 
 pafs 
 
70 
 
 OF THE ACTION 
 
 pafs by one another. In this way they complete the di- 
 vifion, like a pair of fcifiars ; and at the fame time they 
 fliarpen one another. There are exceptions to this ; for 
 thefeTeeth in fome people meet equally,viz. in thofe people 
 whofe Fore-Teeth do not project further from the Gum, 
 or focket, than the back Teeth; and fuch Teeth are not 
 fo fit for dividing ; and in fome people the Teeth of the 
 Lower-Jaw are fo placed, as to come before thofe of the 
 Upper-Jaw; this fituation is as favourable for cutting 
 as when the over-lapping of the Teeth is the reverfe, 
 except for this circumftance, that the Lower-Jaw muft 
 be longer, and therefore its adlion weaker. 
 
 The other motion of the Lower-Jaw, viz. when the 
 lateral Teeth are ufed, is fomewhat different from the 
 former. In opening the mouth, one Condyle Aides a 
 little forwards, and the other Aides a little further 
 back into its cavity ; this throws the Jaw a little to 
 that fide, juA enough to bring the lower Teeth direflly 
 under their correlponding Teeth in the Upper-Jaw : this, 
 is done, either in dividing, or holding of fubfiances; 
 and thefe are the Teeth that are generally ufed in the 
 laft mentioned action. When the true grinding motion 
 is to be performed, a greater degree of this lafi 
 motion takes place ; that is, the Condyle of the oppo- 
 fite fide is brought farther forwards, and the Condyle 
 of the fame fide is drawn farther back into the cavity 
 of the Temporal Bone, and the Jaw is a little deprefif- 
 
 ed. 
 
 i 
 
OF THE TEETH. 
 
 7 i 
 
 ed. This is only preparatory for the effetd to be pro¬ 
 duced ; for the moving back of the firft mentioned 
 Condyle into the focket, is what produces the effect in 
 maftication. 
 
 The lateral Teeth in both Jaws are adapted to this 
 oblique motion ; in the Lower they are turned a little 
 inwards, that they may a<d more in the direction of 
 their axis ; and here the Alveolar Procefs is Pronged 
 upon the outfide, being there fupported by the ridge at 
 the root of the Coronoid Procefs. In the Upper-Jaw the 
 obliquity of the Teeth is the reverfe, that is, they are 
 turned outwards, for the fame reafon ; and the longed 
 fang of the Grinders is upon the infide, where the 
 focket is drengthened by the bony partition between * 
 the antrum and nofe. Hence it is, that the Teeth of 
 the Lower-Jaw have their outer edges worn down fird ; 
 and, vice verfa, in the Upper-Jaw. 
 
 GENE- 
 
72 GENERAL COMPARISONS.; 
 
 Jy * # 
 
 i 
 
 GENERAL COMPARISONS 
 
 BETWEEN THE 
 
 MOTION of the JAW in young and in old People. 
 
 I N children who have not yet Teeth, there does not 
 feem to be a Aiding motion in the Lower-Jaw. The 
 articular eminence of the Temporal Bone is not yet 
 formed, and the cavity is not larger than the Condyle ; 
 therefore the center of motion in fuch, mud be in the 
 Condyle. In old people, who have loft their Teeth, the 
 centre of motion appears to be in the Condyles, and 
 the motion of their Jaw to be only depreftion and ele¬ 
 vation. They never deprefs the Jaw fufficiently to bring 
 the Condyle forwards on the eminence, becaufe in 
 them the mouth is fufficiently opened when the Jaw is 
 in its natural pofition. 
 
 % 
 
 Hence it is that in old people, the gums of the two 
 Jaws do not meet in the fore part of the mouth *, and 
 they cannot bite at that part fo well, as at the fide 
 of the Jaw ; and,inftead of the grinding motion, which 
 
 * Vide Plate VII. where the Symphyfis of the Lower-Jaw, when 
 the mouth is fhut, projects iconfiderably farther forwards than that of 
 the Upper. 
 
 would 
 
ON THE MOTION OF THE J At, 73* 
 
 would be ufelefs, where there are no Grinders j they 
 bruife their food rather by a fimple motion of the Jaw 
 upwards and downwards. 
 
 It is from the want of Teeth in both thofe ages, that 
 the face is fhorter in proportion to its breadth. In an 
 old perfon, after the Teeth are gone, the face is fhorter, 
 while the mouth is fliut, by almod the whole lengths 
 of the Teeth in both Jaws j that is, about an inch and 
 an half. . 
 
 From the want of Teeth too, at both thofe ages, the ca¬ 
 vity of the mouth is then fmaller j and the tongue fecms 
 too large and unmanageable, more efpccially in old 
 people. In thefe lad we obferved alfo, that the chin 
 projects forwards, in proportion as the mouth is fliut ; 
 becaufe the balls of the Lower-Jaw (which is all that now 
 remains) defcribes a wider circle than the Alveolar Pro- 
 cefs in younger people. The Jaws do not project fo 
 much forwards in a child, as in an adult ; hence the 
 face is flatter, efpecially at the lower part. In propor¬ 
 tion as the lad Grinders are produced, the Tides of the 
 curve formed by the Jaws become longer, and pufli for¬ 
 ward the fore-part, none of the additional part palling 
 backwards. The fore-part alfo continues nearly of the 
 fame fize, fo that the whole Jaw is longer in proportion 
 to its breadth, and projects farther forwards. 
 
/ 
 
 74 OF THE FORMATION 
 
 OF THE 
 
 « 
 
 FORMATION of the ALVEOLAR PROCESS. 
 
 TYAVING confidered the Alveolar Procefles in their 
 •** adult, or perfedl {late, we {hall next examine and 
 trace them from their beginning. 
 
 We obferve the beginning of the Alveolar Procefs at a 
 very early period. In a foetus of three or four months 
 it is only a longitudinal groove, deeper and narrower 
 forwards, and becoming gradually more fhallow and 
 wider backwards: inftead of bony partitions, divid¬ 
 ing that groove into a number of fockets, there are only 
 {light ridges acrofs the bottom and fides, with interme¬ 
 diate depreifions, which mark the future Alveoli 
 
 In the Lower-Jaw the veffels and nerves run along 
 the bottom of this Alveolar cavity, in a flight groove, 
 which afterwards becomes a complete anddiflindl bony, 
 canal. 
 
 * Vide Plate VIII. Fig. i, 2. 
 
 7 
 
 1 
 
 The 
 
OF THE ALVEOLAR PROCESS. 
 
 7S 
 
 The Alveolar Procefs grows with the Teeth, and 
 for fome time keeps the hart of them. The ridges 
 which are to make the partitions fhoot from the fides 
 acrofs the canal, at the mouth of the cell, forming hol¬ 
 low arches : this change happens firfl at the anterior 
 parts of the Jaws *. As each cell becomes deeper, 
 its mouth alfo grows narrower, and at length is almoE, 
 but not quite, clofed over the contained Tooth. 
 
 The difpofition for contracting the mouth of the 
 cell, is chiefly in the outer plate of the bone, which 
 occafions the contracted orifices of the cells to be nearer 
 the inner edge of the Jaw. The reafon, perhaps, why 
 the bone {hoots over, and almoft covers the Tooth, is 
 that the Gum may be firmly fupported before the 
 Teeth have come through. 
 
 The Alveoli which belong-to the adult Grinders, are 
 formed in another manner; in theLower-Jaw they would 
 feem to be the remains of the root of the Coronoid Pro¬ 
 cefs for the cells are formed for thofeTeethin the root of 
 that Procefs; and in proportion as the body of the bone, 
 and the cells already formed, pufh forwards from under 
 that Procefs, the fucceeding cells and their Teeth are 
 formed, and pufhed forward in the fame manner. 
 
 * Vide Plate VIII. Fig. i, 2, 3, 4, 5, and 6 . 
 
 f Vide Plate VIII. Fig. 7, which is moft remarkable in thole of the 
 Grinders *, as thefe Alveoli are not opened for the exit of the Teeth. 
 
 I Vide Plate X. Fig 1. 
 
 L 2 
 
 In 
 
76 OF THE ALVEOLAR PROCESS. 
 
 In the Upper-Jaw there are cells formed in the tu¬ 
 bercles for the young Grinders, which at firfl are very 
 fhallow, and become deeper and deeper as the Teeth 
 grow ; and they grow fomewhat fafter, fo as almofl to 
 inclofe the whole Tooth before it is ready to pufh its 
 way through that inclofure and Gum *. There is a 
 fucceflion of thefe, till the whole three Grinders are 
 formed. 
 
 / N # ~ 
 
 * Vide Plate I. Fig. 10. 
 
OF THE 
 
 FORMATION of the TEETH in the FOETUS. 
 
 H E depreflion, or firfi rudiments of the Alveoli ob- 
 A fervable in a Foetus of three or four months, is 
 filled with four or five little pulpy fubfiances, which arc 
 not very difiimft at this age. About the fifth month 
 both the procefies themfelves and ti e pulpy fubfiances 
 become more diftindt; the anterior of which are the rnoft 
 complete. About this age too the ofiifications begin on 
 the edge of the firfi Incifores . The Cufpidati are not in 
 the fame circular line with the refi, but fomewhat on 
 the outfide, making a projection there at this age, there 
 not being fufficient room for them. 
 
 In the fixth, or feventh month, the edges, or 
 tips, of all thefe five fubfiances are begun to ofiify, 
 and the firfi of them is a little advanced * ; and befides 
 thefe, the pulp of the fixth Tooth has begun to be 
 formed; it is fituated in the tubercle of the Upper- 
 
 * Vide Plate X. Fig. 4, 5, where thefe edifications are reprefented. 
 
 6 Jaw, 
 
yB OF THE FORMATION OF THE TEETH 
 
 Jaw, and under and on the infide of the Coronoid Pro- 
 cefs in the Lower-Jaw: fo that at this age, in both Jaws, 
 there are in all twenty Teeth begun to ofiify, and the 
 ftamlna of twenty-four. They may be divided into the 
 Incifores , Cifpidati , and Molares ; for at this age there are 
 no Bicufpides , the two lad teeth in each fide of both Jaws 
 having all the charadteridics, and anfwering all the 
 purpofes of the true Molares in the adult, though when 
 thefe fird Molares fall out, their places are taken by the 
 Bicufpides, 
 
 » i 
 
 The Teeth gradually advance in their edification, 
 and about the feventh, eighth, or ninth month after 
 birth, the Incifores begin to cut or pafs through the 
 Gums ; fil'd, generally, in the Lower-Jaw. Before this 
 time the ofiificationsin the third Grinder, or that which 
 makes the fil'd in the adult, are begun K 
 
 The Cufpidatus and Molares of the Foetus are not formed 
 fo fad as the Incifores ; they generally all appear nearly 
 about the fame time, viz. about the twentieth, or 
 twenty-fourth month ; however, the fil'd Grinder is 
 often more advanced within the focket than the Cufpi - 
 datns, and mod commonly appears before it. 
 
 * Vide Plate X. Fig. 6, where the firft Incifors had cut the Gum, 
 and where the third Grinder in the child, or firft in the adult, was begun 
 to offify. 
 
 Thefe 
 
IN THE FOETUS. 
 
 79 
 
 Thefe twenty are the only Teeth that are of ufe to 
 the child from the feventh, eighth, or ninth month, 
 till the twelfth or fourteenth year. Thefe are called 
 the Temporary, or Milk Teeth, becaufe they are all 
 fhed between the years of feven and fourteeen, and are 
 fupplied by others. 
 
 O P 
 
 
So OF THE CAUSE OF PAIN 
 
 O F T H E 
 
 * f • jf 
 
 CAUSE of PAIN in DENTITION. 
 
 ^T^HESE twenty Teeth, in cutting the Gum, give 
 pain, and produce many other fymproms which 
 often prove fatal to children in Dentition. It has been ge- 
 rally fuppofed that thefe fymptoms arife from the 
 Tooth’s prefling upon the infide of the Gum, and 
 working its way mechanically ; but the following ob- 
 fervations feem to be nearer the truth. 
 
 ^ i 
 
 The Teeth, when they begin to prefs againfl the 
 Gum, irritate it, and commonly give pain. The Gums 
 are then affedted with heat, fwelling, rednefs, and 
 the other fymptoms of inflammation. The Gum is not 
 cut through by fimple or mechanical preflure, but the 
 irritation and confequent inflammation produces a 
 thinning, or wafting of the Gum at this part: for it 
 often happens that when an extraneous, or a dead fub- 
 ffance, is contained in the body, that it produces a de- 
 ftrudtion of the part between it, and that part of the 
 fkin which is nearefl it, and feldom of the other parts, 
 excepting thofe between it and the furface of a cavity 
 opening externally, and that by no means fo fre¬ 
 quently ; 
 
IN CUTTING OF TEETH. 
 
 8 i 
 
 quently. And in thofe cafes there is an abforption of 
 the folids, or of the part deftroyed, not a melting down, 
 or folution of them into Pus. The Teeth are to be 
 looked upon as extraneous bodies, with refpeft to the 
 Gum, and as fuch they irritate the infide of that part 
 in the fame manner as the Pus of an abfcefs, an exfo¬ 
 liation of a bone, or any other extraneous body; and 
 therefore produce the fame fymptoms, excepting only 
 the formation of matter. If, therefore, tliefe fymptoms 
 attend the cutting of the Teeth, there can be no doubt 
 of the propriety of opening the way for them; nor 
 is it ever, as far as I have obferved, attended with any 
 dangerous confequence. 
 
 O F 
 
 M 
 
Sz 
 
 OF THE FORMATION AND PROGRESS 
 
 OF THE 
 
 FORMATION and PR OGRES S of the 
 ADULT TEETH. 
 
 • I 
 
 T T AVING now confidered the firfl formation, and 
 ^ ^ the progrefs of the Temporary Teeth, we fhall next 
 defcribe the formation of thofe Teeth which are to 
 ferve through life. 
 
 In this enquiry, to avoid confufion, I fhall confine 
 the defcription to the Teeth in the Lower-Jaw ; for the 
 only difference between thofe in the two Jaws, is in the 
 time of their appearance, and generally it is later in 
 the Upper-Jaw. Their formation and appearance pro¬ 
 ceeds not regularly from the firfl Incifor backwards to 
 the Dens Sapientia , but it begins at two points on each 
 fide of both Jaws, viz. at the firfl Incifor , and at the firfl 
 Molaris. The Teeth between thefe two points make a 
 quicker progrefs than thofe behind. 
 
 The Pulp of the firfl adult Incifor, and of the firfl adult 
 
 Molaris begin to appear in a Fcetus of feven or eight 
 
 # 
 
 months, and five or fix months after birth the oflifi- 
 
 eation 
 
OF THE ADULT TEETH. 83 
 
 cation begins in them; foon after birth the Pulp of the 
 fecond Incifor and Cufpidatus begin to be formed, and 
 about eight or nine months afterwards they begin to 
 oilify ; about the fifth or fixth year the firft Bicufpis 
 appears ; about the fixth or feventh the fecond Bicufpis , 
 and the fecond MoJaris; and about the twelfth, the 
 third Molar is, or Dens Sapi entice. 
 
 The firfi five may be called the permanent Teeth : 
 they differ from the temporary in having larger fangs. 
 The permanent Incifores and Cufpidati are much thicker 
 and broader, and the Mo/ares are fucceeded by Bicufpides % 
 which are fmaller, and have but one fang. 
 
 All thefe permanent or fucceeding Teeth are formed 
 in difiintfi Alveoli of their own; fo that they do not fill 
 up the old fockets of the temporary Teeth, but have 
 their new Alveoli formed as the old ones decay *. 
 
 * 
 
 The firfi Incifor is placed on the infide of the root of 
 the correfponding temporary Tooth, and deeper in the 
 jaw. The fecond Incifor and the Cufpidatus begin to be 
 formed on the infide, and fomewhat under the tem¬ 
 porary fecond Incifor and Cufpidatus . Thefe three are all 
 fituated much in the fame manner, with refpeft to the 
 firfi fet; but as they are larger, they are placed fome¬ 
 what farther back in the circle of the Jaw. 
 
 * Vide Plate X. Fig. 1, 2, and 3. 
 
 » \ 
 
 / 
 
 M 2 
 
 The 
 
84 OF THE FORMATION AND PROGRESS 
 
 The firft Bicufpis is placed under, and fomewhat 
 farther back than the firft temporary Grinder, or fourth 
 Tooth of the child. 
 
 The fecond Bicufpis is placed immediately under the 
 fecond temporary Grinder. 
 
 The fecond Molaris is ft mated in the lengthening 
 tubercle in the Upper-Jaw, and direCtly under the Coro- 
 noid Procefs in the Lower. 
 
 • * * 
 
 The third Molaris , or Dens Sapientia, begins to form 
 immediately under the Coronoid Procefs. 
 
 The firft Adult Molaris comes to perfection, and cuts 
 the Gum about the twelfth year of age, the fecond about 
 the eighteenth, and the third, or Dens Sapientia , from 
 the twentieth to the thirtieth: fo that the Incifores and 
 Cufpidati require about fix or feven years, from their 
 firft appearance, to come to perfection; the Bicufpides 
 about feven or eight; and the Molar es about twelve. 
 
 1 
 
 It fometimes happens that a third fet of Teeth ap¬ 
 pears in very old people ; when this does happen, it is 
 in a very irregular manner, fometimes only one, at 
 other times more, and now and then a complete fet 
 comes in both Jaws. I never faw an inftance of this 
 
 kind 
 
OF THE ADULT TEETH. 85 
 
 kind but once, and there two fore Teeth fhot up in the 
 Lower-Jaw. 
 
 < 
 
 I fhould fuppofe that a new Alveolar Procefs mull 
 be alfo formed in fuch cafes, in the fame manner as in 
 the production of the firfl and fecond fets of Teeth. 
 From what I can learn, the age at which this happens 
 is generally about feventy. From this circumftance, 
 and another that fometimes happens to women at this 
 age, it would appear that there is fome effort in na^ 
 ture to renew the body at that period. 
 
 When this fet of Teeth which happens fo late in 
 life, is not complete, efpecially where they come in 
 one Jaw, and not in the other, they are rather hurtful 
 than ufeful; for in that cafe we are obliged to pull 
 them out, as they only wound the oppofite Gum. 
 
 T FI E 
 
86 THE MANNER IN WHICH 
 
 THE 
 
 MANNER in which a TOOTH is formed. 
 
 T p H E body of the Tooth is formed firft, afterwards 
 -*■ the Enamel and Fangs are added to it. All the 
 Teeth are produced from a kind of pulpy fubftance, 
 which is pretty firm in its texture, tranfparent, ex¬ 
 cepting at the furface, where it adheres to the Jaw, 
 and has at firft the fliape of the bodies of the Teeth 
 which are to be formed from it *. Thefe pulpy fub- 
 flances are very vafcular, they adhere only at one part 
 to the Jaw, viz. at the bottom of the cavity which is 
 to form the focket ; and at that place their veffels en¬ 
 ter ; fo that they are prominent, and fomeyvhat loofe in 
 the bony cavity which lodges them. 
 
 They grow nearly as large as the body of the 
 Tooth before the offification begins, and increafe a little 
 for fome time after the offification is begun. They are 
 furrounded by a membrane, which is not connected 
 with them, excepting at their root or furface of adhefion. 
 
 # Vide Plate XII. Fig. 4, 5, 6. 
 
 6 
 
 This 
 
A TOOTH IS FORMED. 87 
 
 This membrane adheres by its outer furface all around 
 the bony cavity in the Jaw, and alfo to the gum where 
 it covers the Alveoli. 
 
 When the pulp is very young, as in the Foetus of 
 fix or feven months, this membrane itfelf is pretty 
 thick and gelatinous *. We can examine it bed in 
 a new-born child, and we find it made up of two la- 
 mellrt) an external and internal: the external is foft and 
 fpongy, without any veflels ; the other is much firmer, 
 and extremely vafcular, its veffels coming from thofe 
 that are going to the pulp of the Tooth: it makes a 
 kind of Capfula for the pulp and body of the Tooth. 
 While the Tooth is within the gum, there is always a 
 mucilaginous fluid, like the Sinovia in the joints, be¬ 
 tween this membrane and the pulp of the Tooth. 
 
 When the Tooth cuts the gum, this membrane like- 
 wife is perforated; after which it begins to wafle, *and 
 entirely gone by the time the Tooth is fully formed, 
 for the lower part of the membrane continues to ad¬ 
 here to the neck of the Tooth, which has now rifen as- 
 high as the edge of the gum. 
 
 * Vide Plate XII. Fig. 1, 2 i 
 
 a f 
 
88 OF THE OSSIFICATION OF A TOOTH 
 
 OF THE 
 
 OSSIFICATION of a TOOTH upon the PULP. 
 
 r | ^ H E beginning of the offification upon the pulp 
 
 A is by one point, or more, according to the kind 
 of Tooth. In the Incifores it is generally by three 
 points, the middle one being the higheft, and the fir ft 
 that begins to oflify. The Cufpldatus begins by one point 
 only the Bicufpis by two, one external, which is 
 the firft and the higheft, and the other internal. The 
 Molares , either in a child, or an adult, begin by four 
 or five oftifications, one on each point, the external al¬ 
 ways the firft *. Where the Teeth began to oflify at one 
 point only, that offification gradually advances till the 
 Tooth is entirely completed but if there are more 
 than one point of offification, each offification in- 
 creafes till their bafis come in contact with one ano¬ 
 ther, and there all unite into one J ; after which they 
 advance in growth as one offification. 
 
 * Vide Plate X. Fig. 4, where fome of the diflind oftifications 
 may be obferved. 
 
 | Vide Plate XIII. Fig. 1, 2, 3, &c. 
 
 I Vide Plate X. Fig. 5. 
 
 4 
 
 The 
 
UPON THE PULP. 
 
 8 ? 
 
 The oflifications in their progrefs become thicker 
 and thicker where they firil began, but increafe fader 
 on the edges of the Teeth; fo as thence to become 
 more and more hollow, and the cavity becomes deeper 
 As the oflification advances, it gradually furrounds the 
 Pulp till the whole is covered by bone, excepting the 
 under furface: and while the oflifications advance, 
 that part of the Pulp which is covered by bone is al¬ 
 ways more vafcular than the part which is not yet co¬ 
 vered f. 
 
 The adheflon of the Pulp to the new-formed Tooth, or 
 bone, is very flight, for it can always be feparated from it 
 without any apparent violence, nor are there any veflels 
 going from the one to the other; the place, however, 
 where it is mod drongly attached is round the edge of 
 the bony part, which is the lad part formed. When the 
 bone has covered all the Pulp, it begins to contract a 
 little, and becomes fomewhat rounded, making that 
 part of the Tooth which is called the neck ; and from 
 this place the fangs begin f. When the fangs form, they 
 pufh up the bodies of the Teeth through the fockets, 
 which wade, and afterwards through the Gum, which 
 
 * Vide Plate XIII. Fig. <7, b, c , d t two rows of Incifors fawed 
 down the middle, the higheft of the child, the other of the adult » 
 c, /» g> two rows °f Grinders fhewing the fame circumftances. 
 
 *f* Vide Plate XII. Fig. 5, 6 . 
 
 J Vide Plate XIII. Fig 1. 2, 3, See. 
 
 N 
 
 alfo 
 
po OF THE OSSIFICATION OF A TOOTH 
 
 alio waftes, as has been explained upon the cutting of 
 the Teeth ; for before this time the riling of the Teeth 
 is fcarce ohfervable, as the Pulp was at firft nearly of 
 the ftze of the body of the Tooth itfelf, and wafted 
 nearly in proportion to the increafe of the whole oftifi- 
 cation. 
 
 The Pulp has originally no procefs anfwering to the 
 fang *; but as the cavity in the body of the Tooth is 
 filled up by the oftification, the pulp is lengthened into 
 a fang. The fang grows in length, and rifes higher and 
 higher in the focket, till the whole body of the Tooth 
 is pufhed out. The focket, at the fame time, contracts 
 at its bottom, and grafps the neck, or beginning fang, 
 adheres to it, and rifes with it, which contraction is 
 continued through the whole length of the focket as 
 the fang rifes; or the focket which contained the 
 body of the Tooth, being too large for the fang, is 
 wafted or abforbed into the conftitution, and a new Al¬ 
 veolar portion is raifed with the fang ; whence in reality 
 the fang does not fink, or defcend into the Jaw. Both in 
 the body, and in the fang of a growing Tooth, the ex¬ 
 treme edge of the oftification is fo thin, tranfparent, 
 and flexible, that it would appear rather to be horny 
 than bony, very much like the mouth or edge of the 
 fhell of a fnail when it is growing: and indeed it would 
 
 x Vide Plate XII. Fig, i, 4, 5, and 6 . 
 
 feena 
 
feem to grow much in the fame manner*, and the 
 offified part of a Tooth would feem to have much the 
 fame connexion with the pulp as a fnail has with its 
 fhell. 
 
 As the Tooth grows, its cavity becomes gradually 
 fmaller, efpecially towards the point of the fang. In 
 tracing the formation of the fang of a Tooth, we 
 hitherto have been fuppofing it to be fingle, but where 
 there are two, or more, it is fomcwhat different, and 
 more complicated. 
 
 When the body of a Molares is formed, there is but 
 one general cavity in the body of the Tooth, from the 
 brim of which the offification is to flioot, fo as to form 
 two or three fangs f. If two only, then the oppofite 
 parts of the brim of the cavity of the Tooth flioot acrofs 
 where the Pulp adheres to the Jaw, meet in the mid¬ 
 dle, and thereby divide the mouth of the cavity into 
 two openings J ; and from the edges of thefe two 
 openings the two fangs grow §. 
 
 We often find that a diflimfl offification begins in 
 the middle of the general cavity upon the root of the 
 
 * Vide PlateXIII. Fig. i, 2, 3, or Fig. 
 
 | Vide Plate XIII. Fig. 1, a a . 
 
 J Vide Plate XIII. Fig. b. 
 
 % Vide Plate XIII. Fig. c d e. 
 
 N 
 
 Pulp, 
 
92 OF THE OSSIFICATION OF A TOOTH 
 
 Pulp, and two proceffcs coming from the oppofite 
 edges of the bony fhell join it; which anfwers the 
 
 fame purpofe. 
 
 When there are three fangs, we fee three proceffes 
 coming from fo many points of the brim of the cavity, 
 which meet in the center, and divide the whole into 
 three openings *; and from thefe are formed the three 
 fangs f. We often find the fangs forked at their 
 points, efpecially in the Bicnfpides. In this cafe, the 
 fides of the fang as it grows, come clofe together in 
 the middle, making a longitudinal groove on the out- 
 fide; and this union of the oppofite fides divides the 
 mouth of the growing fang into two orifices, from 
 which the two points are formed. 
 
 By the obfervations which I have made in unravelling 
 the texture of the Teeth, when foftened by an acid, 
 and from obferving the difpofition of the red parts in 
 the Tooth of growing animals, interruptedly fed with 
 madder, I find that the bony part of a Tooth is formed 
 of Lamella, placed one within another. The outer 
 Lamellae is the firft formed, and is the fhorteft: the 
 more internal Lamella lengthen gradually towards the 
 fang, by which means, in proportion as the Tooth 
 
 * Vide Plate XIII. Fig. A- g> 
 
 f- Vide Plate XIII. Fig. h, /, k. 
 
 grows 
 
UPON THE PULP. 
 
 93 
 
 \ v *' r i ' - • * 
 
 grows longer, its cavity grows fmaller, and its fides 
 grow thicker *. 
 
 How the earthy and animal fubftance of the Tooth 
 is depofited on the furface of the pulp is not perhaps 
 to be explained. 
 
 * Vide Plate XII. Fig. 7, 8. 
 
 O I 
 
 / 
 
94 - 
 
 OF THE FORMATION 
 
 OF THE 
 
 FOR M ATION of the ENAME L. 
 
 1 N fpeaking of the Enamel we poftponcd treating of 
 
 its Formation, till it could be more clearly under- 
 Hood; and now we fhall previoufly defcribe fome parts 
 which we apprehend to be fubfervient to its formation, 
 much in the fame manner as the Pulp is to the body 
 of the Tooth. 
 
 From its fituation, and from the manner in which 
 the Teeth grow, one would imagine that the Enamel is 
 firft formed ; but the bony part begins firft, and very 
 loon after the Enamel is formed upon it. There is 
 another pulpy fubftance oppolite to that which we have 
 defcribed; it adheres to the infide of the Capfula, where 
 the Gum is joined to it, and its oppolite furface lies in 
 contacft with the bafis of the above defcribed Pulp, and 
 afterwards with the new formed balls of the Tooth : 
 whatever eminences or cavities the one has, the other 
 has the fame, but reveifed, fo that they are moulded 
 exadtly to each other. 
 
 In 
 
/ 
 
 OF THE ENAMEL./ 95 
 
 In the Inciforei it lies in contact not with the (harper 
 cutting edge of the Pulp, or Tooth, but againft the 
 hollowed infide of the Tooth ; and in the Molares it is 
 placed directly againd their bafe, like a Tooth of the 
 oppofite Jaw. It is thinner than the other Pulp, and 
 decreafes in proportion as the Teeth advance. It does 
 not feem to be very vafcular. The bed time for exa¬ 
 mining it is in a Foetus of feven or eight months old. 
 
 In the granivorous animal, fuch as the horfe, 
 cow, 8cc. whofe Teeth have the Enamel intermixed with 
 the bony part *, and whofe Teeth, when forming, have 
 as many interdices as there are continuations of the 
 Enamel, we find procedes from the Pulp palling down 
 into thofe interdices as far as the Pulp which the Tooth 
 is formed from, and there coming into contact with it. 
 
 After the points of the fil'd deferibed Pulp are begun 
 to ofiify, a thin covering of enamel is fpread over them, 
 which increafes in f thicknels till fome time before the 
 Tooth begins to cut the Gum. 
 
 The Enamel appears to be fecreted from the Pulp 
 above deferibed, and perhaps from the Capfula which 
 inclofes the body of the Tooth. That it is from the 
 Pulp and Capfula feems evident in the horfe, afs, ox, 
 dieep, &c. therefore we have little reafon to doubt of 
 
 ♦ Vide Plate XIV. Fig, 19, 20, 
 
 6 
 
 it 
 
(;6 O F THE FORMATION 
 
 it in the human fpecies. It is a calcareous earth, pro¬ 
 bably diiTolved in the juices of our body, and thrown 
 out from thcfe parts which a6t here as a gland. After 
 it is fccrcted, the earth is attracted by the bony part 
 of the Tooth, which is already formed ; and upon 
 that furface it crydallizcs. 
 
 The operation is fimilar to the formation of the fliell 
 of the egg, the done in the kidneys and bladder, and 
 the gall done. This accounts for the Undated crydal- 
 lized appearance which the Enamel has when broken, 
 and alfo for the direction of thefe Stria *. 
 
 The Enamel is thicker at the points and bads than at 
 the neck of the Teeth, which may be eadly accounted 
 for from its manner of formation ; for if we fuppofe it 
 to be always fecreting, and laid equally over the whole 
 furface, as the Tooth grows, the fird formed will 
 be the thicked.; and the neck of the Tooth, which is 
 the lad formed part inclofed in this Capfula, mud have 
 the thinned coat ; and the fang, where the Veriojleum 
 adheres, and leaves no vacant fpace, will have none of 
 the Enamel. 
 
 * The Author has made many experiments on the formation of 
 different Calculi , and finds they are formed by cryftallization, which 
 were communicated to his brother, and taught by him to his pupils in 
 1761, and which he propofes to give to the Public as foon as his time 
 will permit. 
 
 At 
 
OF THE ENAMEL. 
 
 97 
 
 At its firft formation it is not very hard ; for by ex- 
 pofing a very young Tooth to the air, the Enamel cracks, 
 and looks rough : but by the time that the Teeth cut 
 the Gum, the Enamel feems to be as hard as ever it is 
 afterward ; fo that the air feems to have no effect in 
 hardening it. 
 
 / 
 
 O F 
 
 » 
 
9 * 
 
 OF THE MANNER 
 
 OF THE 
 
 MANNER of SHEDDING of TEETH. 
 
 N opinion has commonly prevailed, that the firfh 
 
 fet of Teeth are puflied out by the fecond ; this, 
 however, is very far from being the cafe : and were it 
 fo, it would be attended with a very obvious inconve¬ 
 nience ; for, were a Tooth puflied out by one under¬ 
 neath, that Tooth mull rife in proportion to the growth 
 of the fucceeding one, and ftand in the fame propor¬ 
 tion above the reft. But this circumftance never hap¬ 
 pens : neither can it; for, the fucceeding Teeth are formed 
 in new and diftimft fockets, and generally the Incifores 
 and the O/fpidati of the fecond fet are fituated on the 
 infide of the correfponding teeth of the firft fet *; and 
 we find, that in proportion to the’ growth of the fuc¬ 
 ceeding Teeth, the fangs of the firft fet decay, till the 
 whole of the fang is fo far deftroyed, that nothing re¬ 
 mains but the neck, or that part of the fang to which 
 the Gum adheres f, and then the leaft force pufhes the 
 Tooth out. It would be very natural to fuppofe, that this 
 
 * Vide Plate X. Fig. 2, 3. 
 
 * Vide Plate XV. which (hews the gradual decay in the Angle and 
 double Teeth, and alfo in one Grinder of a horfe. 
 
 was 
 
OF SHEDDING OF TEETH. 
 
 99 
 
 was owing to a conflant p refill re fromthe rifing Teeth 
 againfl the fangs or fockets of the firfl fet: but it is 
 not fo; for, the new Alveoli rife with the new Teeth, 
 and the old Alveoli decay in proportion as the fangs of 
 the old Teeth decay, and when the firfl fet falls out, 
 the fucceeding Teeth are fo far from having deftroyed, 
 by their preffure, the parts againfl which they might 
 be fuppofed to pufh, that they are Hill inclofed, and 
 covered by a complete bony focket. From this we fee, 
 that the change is not produced by a mechanical pref¬ 
 fure, but is a particular procefs in the animal ceco- 
 nomv. 
 
 I have feen two or three Jaws where the fecond tem¬ 
 porary Grinders were fhedding in the common way, 
 without any Tooth underneath ; and in one Jaw, where 
 both the Grinders were fhedding, I met with the fame 
 eircum fiance. 
 
 A remarkable infiance of this fort occurred to me in 
 a lady who defired me to look at a loofe Tooth/ which 
 I found was the laft temporary Tooth not yet fhed. I 
 
 defired that it might be drawn our, and told her it was 
 of no ufe, and could not by any art be fixed, as it was 
 one of the Teeth that is naturally fired, and that 
 another might come in its place: however fhe was dif- 
 nppointed. 
 
 0 2 
 
 Thefe 
 
100 OF THE MANNER, See. 
 
 Thefe cafes prove evidently, that in fhedding, the firft 
 Teeth are not pufhed out by the fecond fet, but that they 
 grow loofe, and fall out of their own accord. That the 
 fucceeding Teeth have fome influence on the fhedding 
 of the temporary fet is proved by thofe very cafes; fincc 
 in one of the fir ft mentioned the perfon was above twenty 
 years of age, and in the other the lady was thirty ; and 
 it is reafonable to believe, that the fhedding of thefe 
 Teeth was fo late in thofe inflances, from the want of 
 the influence, whatever it is, of the new Teeth. When 
 the Incifores and Cufpidati of the new fet are a little ad¬ 
 vanced, but long before they appear through their bony 
 fockets, there are fmall holes leading to them on the 
 infide, or behind the temporary fockets and Teeth ; and 
 thefe holes grow larger and larger, till at laft the body 
 of the Tooth pafTes quite through them. 
 
 A 
 
 O F 
 
OF THE GROWTH OF THE TWO JAWS. 
 
 i o i 
 
 OF THE 
 
 GROWTH of the TWO JAWS. 
 
 S a knowledge of the manner in which the two 
 
 M ^ Jaws grow, will lead to the better underftanding 
 the {bedding of the Teeth ; and as the Jaws feem to 
 differ in their manner of growing, from other bones, 
 and alfo vary according to the age, it will be here pro¬ 
 per to give fome account of their growth. 
 
 In a Foetus three or four months old, we have de- 
 fcribcd the marks of four or five Teeth, which occupy 
 the whole length of the Upper-Jaw, and all that part 
 
 of the Lower which lies before the Coronoid Procefs, 
 
 for the fifth Tooth is fomewhat under that procefs *. 
 
 Thefe five marks become larger, and the Jaw bones 
 of courfe increafe in all directions, but more confider- 
 ably backwards ; for in a Foetus of feven or eight 
 months, the marks of fix Teeth in each fide of both 
 Taws are to be obferved, and the fixth feems to be in 
 the place where the fifth was ; fo that in thefe lafl four 
 
 * Vide Plate VIII. Fig. i, 2. 
 
 4 
 
 months 
 
\ 
 
 10 2 OF THE GROWTH OF THE TWO JAWS. 
 
 months the jaw has grown in all directions in propor¬ 
 tion to the incrcafed fize of the Teeth, and befides has 
 lengthened itfelf at its poftcrior end as much as the 
 whole breadth of the focket of that fixth Tooth*. 
 
 The Jaw Rill increafes in all points till twelve months 
 after birth, when the bodies of all the fix Teeth 
 are pretty well formed but it never after increafes in 
 length between the fymphyfls and the fixth Tooth ; and 
 from this time too, the Alveolar Procefs, which makes the 
 anterior part of the arches of both Jaws, never becomes 
 a feCtion of a larger circle, whence the lower part of 
 a child’s face is flatter, or not fo projecting forwards as 
 in the adult f .. 
 
 After this time the Jaws lengthen only at their pofle- 
 rior ends j fo that the fixth Tooth, which was under the 
 Coronoid Procefs in the Lower-Jaw, and in the tuber¬ 
 cles of the Upper-Jaw of the Foetus, is at lafl, viz. in the 
 eighth or ninth year, placed before thefe parts ; and then 
 the feventh Tooth appears in the place which the fixth 
 occupied, with refpeCt to the Coronoid Procefs, and tu¬ 
 bercle ; and about the twelfth or fourteenth year, the 
 eighth Tooth is fituaied where the feventh was placed. 
 
 * Vide Plate Will. Fig. ^ 4, 5, 6 , for the general increafe of the 
 Jaws, but more particularly backwards. 
 
 -J- Vide Plate VIII. Fig, 7, for thefe faCts,. 
 
 At 
 
OF THE GROWTH OF THE TWO JAWS, i o 3 
 
 m 
 
 At the age of eighteen, or twenty, the eighth Tooth is 
 found before the Coronoid Procefs in the Lower*Jaw» 
 and under, or fomewhat before the tubercle in the 
 Upper-Jaw, which tubercle is no more than a fuc- 
 ceflion of fockets for the Teeth till they are completely 
 formed. 
 
 In a young child the cavity in the temporal bone for 
 the articulation of the Jaw is nearly in a line with the 
 Gums of the Upper-Jaw ; and for this reafon the Con¬ 
 dyle of the Lower-Jaw is nearly in the fame line *; but 
 afterwards, by the addition of the Alveolar Procefs and 
 Teeth, the line of the Gums in the Upper-Jaw defeends 
 confiderably below the articular cavity ; and for that 
 reafon the Condyloid Procefs is then lengthened in the 
 fame proportion. 
 
 In old people who have loft all their Teeth, the 
 articulation comes again into the fame line with the 
 Gums of the Upper-Jaw J; but in the Lower-Jaw, the 
 Condyles cannot be diminifhed again for accommo¬ 
 dating it to the Upper, fo that it necefTarily projects be¬ 
 yond the Gums of the Upper-Jaw at the fore part. 
 When the mouth is Unit, the projection of the Jaw at 
 the chin, fits the two Jaws to each other at that place 
 
 * Vide Plate VIII. Fig. ? r. 
 
 -]- Vide Plate VII. 
 
 where 
 
i o 4 OF THE GROWTH OF THE TWO JAWS. 
 
 where the Grinders were fituated, and where the ftrength 
 of maftication lies ; for if the chin was not further from 
 the center of motion than the Gums of the Upper-Jaw, 
 at the fore part, the Jaws, in fuch people as have loft 
 all their Teeth, would meet in a point at the fore 
 part, like a pair of pinchers, and be at a conftderable 
 diftance behind 
 
 * Vide Plate VII. 
 
 THE 
 
THE 
 
 
 i REASON for the SHEDDING of the TEETH. 
 
 S the {hedding of the Teeth is a very lingular 
 
 x ^ procefs in the animal ceconomy, many rea- 
 fons have been afligned for it ; but thefe rea- 
 fons have not carried along with them that con¬ 
 viction which is defired. Authors have not fully 
 confidered the appearances which naturally explain 
 fhemfelves; nor have they confidered the advan¬ 
 tages neceffarily arifing from the fize and conflruc- 
 tion of only fucli a number as the firft fet ; nor 
 have they confidered fully the difadvantages that fuch 
 fize and conftruction would have, if continued when 
 it is neceffary to have a greater number, which is the 
 cafe with the adult. 
 
 We {hall confider thefe advantages in a child where 
 the fhedding Teeth are all completely formed, which 
 will be fetting them in the cleareft point of light; 
 and alfo, the difadvantages that would occur, if in the 
 adult thefe were not changed for another fet fomewhat 
 different. 
 
 
 P 
 
 If 
 
1 06 THE REASON FOR THE SHEDDING 
 
 If the child had been fo contrived, as not to have 
 required Teeth till the time of the fecond fet’s appear¬ 
 ing, there would have been no occalion for a new fet: 
 but the Jaw-bones being confiderably fmaller in children 
 than in adults, and it being neceffary that they (hould 
 have two Grinders, there is not room for Incifores and 
 Cufpidati of fufhcient (Ize to ferve through life ; and 
 the firft formed Grinders having neceffarily too fmall 
 fangs, and the Jaw increaling at the back part only, 
 thefe two Grinders would have been protruded too far 
 forwards, and at too great a diftance from the center of 
 motion* This variation in the fize of the Teeth is like- 
 wife a reafon why the fecond fet are not formed in 
 the fockets of the hr ft ; and why the old fockets are 
 deftroyed. 
 
 Thefe circumftances with regard to the (bedding of 
 the Teeth, contradicft the notion of the fecond fet being 
 made broader and thicker, by the refinance they meet 
 with in pufhing out the firft. For were we on a partial 
 view of the fubjecft, to admit the fuppoftcion, the Bicuf 
 pides would effectually overturn our hypothecs ; be- 
 caufe here the fecond fet are much fmaller than the 
 firft, and yet the refiftance would be greater to them 
 than to the Incifores . 
 
 From the manner in which the Teeth are (lied, it is 
 evident that drawing a temporary Tooth, for the eafier 
 
 pro- 
 
i o 7 
 
 OF THE TEETH. 
 
 * 1 
 
 protrafion of the one underneath, will be of no great 
 fervice ; for in general it falls out before the other can 
 touch it. But it is often of much more fervice to 
 pull out the neighbouring, or adjacent temporary Tooth; 
 for we mull be convinced by what has been advanced 
 with regard to the changes in fize, that excepting the 
 whole were to Hied at the fame time, or the order of 
 fhedding, viz. from before backwards, were to be in¬ 
 verted, that the fecond fet of Incifores and Cnfpidati mull be 
 pinched in room, till the Grinders are alfo died : and 
 therefore we find it often of ufe to draw a temporary 
 Tooth, that is placed further back; and it would, per¬ 
 haps, be right upon the whole, always to draw, at 
 lead the firft Grinder ; and, perhaps, fome time after, 
 the fecond Grinder alfo. » 
 
 P 2 
 
 O F 
 
OF THE CAVITY FILLING UF 
 
 1 08 
 
 Q F THE. 
 
 CAVITY filling up as the TEETH wear 
 
 down. 
 
 A TOOTH very often wears down fo low, that its 
 cavity would be expofed, if no other alteration 
 were produced in it. To prevent this, nature has taken 
 care that the bottom part of the cavity fhould be filled 
 up by new matter, in proportion as the furface of the 
 Teeth is worn down. This new matter may be eafily 
 known from the old j for when a Tooth has been worn 
 down almofi to the neck, a fpot may always be feen in 
 the middle, which is more tranfparent, and at the fame 
 time of a darker colour, (occafioned, in fome meafurc, 
 by the dark cavity under it) and is generally fofter 
 than the other*. Any perfon may be convinced of the 
 truth of thefe obfervations, by taking two Teeth of the 
 fame clafs, but of very different ages, one juft com¬ 
 pletely formed, the other worn down almoft to its 
 neck. In the laft he will obferve the dark fpot in the 
 center; and if as much is cut off from the complete 
 
 * Vide Plate XIV. Fig. 24, 25. 
 
 Tooth 
 
AS THE TEETH WEAR DOWN. 
 
 109 
 
 Tooth as hath been worn off the old one, the cavity of 
 the young Tooth will be found cut through ; and on 
 examining the other, its cavity will be found filled up 
 below that furface. Now this obfervation contradicts 
 the idea of the hole leading into the cavity of the Tooth 
 being clofed up; and what is ft ill a further proof of it, 
 I have been able to injeff veffels in the cavities of the 
 Teeth in very old people when the Alveolar Procefs 
 has been gone, and the Teeth very loofe in the Gum- 
 
 Old people are often found to have very good fets of 
 Teeth, only pretty much worn down. The reafon of 
 this is, that fuch people never had any diforder in their 
 Teeth, or Alveolar Proceffes, fufficient to occafion the 
 falling of one Tooth. For if by accident one Tooth is 
 loft, the reft will neceffarily fail in fome degree, even, 
 though they are found, and likely to remain fo, had 
 not this accident happened ; and this weakening caufe 
 ia greater, in proportion to the number that are loft- 
 From this obfervation, we fee that the Teeth fupport 
 one another. 
 
 1 
 
 O F 
 
no OF THE CONTINUAL GROWTH 
 
 OF THE 
 
 CONTINUAL GROWTH of the TEETH. 
 
 T T has been aflerted that the Teeth are continually 
 growing, and that the abrafion is fufficient to keep 
 them always of the fame length ; but we find that they 
 grow at once to their full length, and that they gra¬ 
 dually wear down afterwards; and that there is not 
 even the appearance of their continuing to grow. The 
 Teeth would probably projedt a little farther out of the 
 Gum, if they were not oppofed by thofe in the oppofite 
 Jaw; for in young people, who had loft a Tooth be- 
 fore the reft had come to their full length, I have feen 
 the oppofite Tooth projedt a little beyond the reft, be¬ 
 fore they were at all worn down. It may be further 
 obferved, that when a Tooth is loft, the oppofite one 
 may project from the difpofition of the Alveolar 
 Procefs to rife higher, and fill up at the bottom 
 of the fockets ; and the want of that natural pref- 
 fure feems to give that difpofition to thefe precedes, 
 which is beft illuftrated in thofe Teeth which are formed 
 deeper in their fockets than ufual. As a proof that the 
 Teeth continue growing, it has been faid that the fpace 
 
 of 
 
OF THE TEETH. 
 
 11 i 
 
 \ " 
 
 of a fallen Tooth is almofl filled up by the increafed 
 thicknefs of the two adjacent Teeth, and the lengthening 
 of that which is oppofitc. There is an evident fallacy 
 in the cafe ; either the obfervations have been made 
 upon fuch Jaws as above deferibed, or the appearances 
 have not been examined with fufficient accuracy ; for 
 when the fpace appears to have become narrow by the 
 approximation of the two adjacent Teeth, it is not 
 owing to any increafe of their breadth, but to their 
 moving from that fide where they are well fupported, 
 to the other fide, where they are not. For this reafon 
 they get an inclined direction; and I obferve it extends 
 to the feveral adjacent Teeth in a proportional lefs de¬ 
 gree, and affedfs thofe which are behind *, more than, 
 thofe which are before the vacant fpace. 
 
 In the Lower-jaw the back Teeth are not fixed per¬ 
 pendicularly, but all inclined forward ; and the de- 
 preffion of the Jaw increafes this pofition : the afition 
 of the Teeth, when thrown out of the perpendicular, 
 has aifo a tendency to increafe that oblique direction, 
 as a pair of feiffars, in cutting, puflies every thing for¬ 
 ward, or from the center of motion : therefore this 
 alteration, I think, is moll commonly obfervable in the 
 Lower-Jaw. 
 
 * Vide Plate XVI. Fig. i, h c. 
 
 7 
 
 And 
 
I I 2 
 
 OF THE CONTINUAL GROWTH 
 
 And that Teeth are not actually always growing in 
 breadth, mull be obvious to every perfon who confiders, 
 that in many people, through life, the Teeth Hand fo 
 wide from each other, that there are confiderable fpace-s 
 between them ; which could not be the cafe if they were 
 always growing in thicknefs. 
 
 We might add too, that according to the hypothecs, 
 the Dens Sapientia fhould grow to an enormous fize 
 backward, becaufe there it has no check from preffure; 
 and in people where the Dens Sapientia is wanting in 
 one Jaw, which is very common, it fhould grow to an 
 uncommon length in the oppofite Jaw, for the fame 
 reafon. But neither of thefe things happens, 
 
 I need hardly take notice, that when a Tooth has loft 
 its oppofite, it will in time become really fo much longer 
 than the reft, as the others grow fliorter by abrafion ; 
 and I obferve that the Tooth which is oppofite to the 
 empty fpace, becomes in time not only longer for the 
 above-mentioned reafon, but more pointed. The apex 
 falls into the void fpace, and the two fides are rubbed 
 away againft the fides of the two approaching Teeth 
 next to that fpace. 
 
 The manner of their formation likewife fhews that 
 Teeth cannot grow beyond a certain limited fize. To 
 illuftrate this I may obferve, that I have often, in 
 
 the 
 
OF THE TEETH. 
 
 11 3 
 
 the dead body of adults, found the left Cufpidatus 
 of the Upper-Jaw, with its points fcarcely protrud¬ 
 ing out of the Alveolar Procefs, though the Tooth 
 was completely formed, and longer than the other 
 by the whole point, which in that other was worn 
 away *. This Tooth, at its firft formation, had been 
 deeper in the Jaw than what is common ; and after it had 
 grown to the ordinary flze, it grew no longer, though 
 it had not the refill an ce of the oppofite Teeth to let 
 bounds to its increafe : yet commonly in thefe cafes 
 the Tooth continues to project further and further 
 through the Gum ; though this is not owing to its 
 growing longer, but to the focket filling up behind it, 
 and thereby continuing to pulh it out by flow degrees. 
 
 * Vide Plate VIII. Fig. 8. 
 
 Q 
 
 O F 
 

 OF THE 
 
 SENSIBILITY of TEETH. 
 
 T HE Teeth would feem to be very fenfible; for 
 they appear to be fubjedt to great pain, and are 
 eafily and quickly affedted by either heat or cold. 
 
 We may prefume that the bony fubftance itfelf, is 
 not capable of conveying fenfations to the mind, be- 
 caufe it is worn down in maftication, and occafionally 
 worked upon by operators in living bodies, without 
 giving any fenfation of pain in the part itfelf. 
 
 In the cavity of a Tooth it is well known that there 
 is exquifite fenfibility *, and it is likewife believed, that? 
 
 this is owing to the nerve in that cavity. This nerve 
 
 \ 
 
 would feem to be more fenfible than nerves are in* 
 common j as we do not obferve the fame violent effedts 
 from any other nerve in the body being expofed either 
 by wound, or fore, as we do from the expofure of the 
 nerve of a Tooth. Perhaps the reafon of the intenfenefs, 
 as well as the quicknefs of the fenfe of heat and cold in 
 the Teeth, may be owing to their communicating thefe 
 to the nerve fooner than any other part of the body. 
 
 O F 
 
O F 
 
 \ 
 
 SUPERNUMERARY TEET H. 
 
 E often meet with Supernumerary Teeth ; and 
 
 * * this, as well as fome other variations, happens 
 oftener in the Upper than in the Lower-Jaw, and, I 
 believe, always in the Incifores and Cufpidatu I have 
 only met with one inltance of this fort, and it was in 
 the Upper-Jaw of a child about nine months old : there 
 were the bodies of two Teeth, in (hape like the Cufpidati , 
 placed dire6tly behind the bodies of the two firft per¬ 
 manent Incifores ; fo that there were three Teeth in a 
 row, placed behind one another, viz, the temporary In - 
 fifor, the body of the permanent Incifor , and that fuper- 
 numerary Tooth. The molt remarkable circumftance 
 was, that thefe Supernumerary Teeth were inverted, 
 their points being turned upwards, and bended by the 
 bone which was above them not giving way to their 
 growth, as the Alveolar Procefs does. 
 
 It often happens that the Incifores and Cufpidati , in the 
 Upper-Jaw efpecially, are fo irregularly placed, as to 
 give the appearance of a double row. I once faw a 
 remarkable inltance of this in a boy ; the fecond In - 
 
 \ 
 
 Q ~ 2 
 
ii 6 OF SUPERNUMERARY TEETH. 
 
 clfor in each iide was placed farther back than what is 
 common, and the Cufpidatus and firft Jncifor clofer toge¬ 
 ther, than if the fecond Incifor had been dire&ly be¬ 
 tween them 5 fo that the appearance gave an idea of 
 a fecond row of Teeth. 
 
 This happens only in the adult fet of Teeth, and is 
 owing to there not being room in the Jaw for this 
 fecond fet, the Jaw-Bone being formed with the firft fet 
 of Teeth, and never increafing afterwards *, fo that if 
 the adult fet does not pafs further back, they muft 
 over lap each other, and give the appearance of a fe¬ 
 cond row. 
 
U S E of the TEETH fo far as they affed the 
 
 VOICE. 
 
 'T' H E Teeth ferve principally for maftication ; and 
 that ufe need not be farther explained. 
 
 They ferve likewife a fecondary, or fubordinate pur- 
 pofe 5 giving ftrength and clearnefs to the found of the 
 voice, as is evident from the alteration produced in 
 fpeaking, when the Teeth are loft. 
 
 This alteration, however, may not depend entirely 
 upon the Teeth, but, in fome meafure, on the other or¬ 
 gans of the voice having been accuftomed to them ; and 
 therefore when they are gone, thofe other organs may 
 be put out of their common play, and may not be able to 
 adapt themfelves fo well to this new inftrument. Yet 
 I believe that habit in this cafe-has no great effed ; 
 for thofe people feldom or never m get the better 
 of the defed ; and young children, who are fhedding 
 their Teeth, and are, perhaps, without any Fore Teeth 
 for half a year or more, always have that defed in their 
 
 voice i 
 
i i 8 OF THE USE OF TEETH, &c. 
 
 voice, till the new Teeth come ; and as thefe grow the 
 voice becomes clear again. 
 
 This ufe feems to be entirely in the Fore Teeth ; for 
 the lofs of one of thefe makes a great alteration, and 
 the lofs of two or three Grinders feems to have no fal¬ 
 lible effect. As an argument for the ufe of the Teeth in 
 modifying the found of the voice, we may obferve, 
 that the Fore Teeth come at a time when the child be¬ 
 gins to articulate founds, and at that time they are fo 
 loofe in the gums, that they can be of very little fervice 
 in maftication. 
 
 Every defeat in fpeech, ariling from this defedl in 
 the organ, is generally attended with what we call a 
 lifp. People who have loll all their Teeth, and moll old 
 people for that reafon, lofe, in a great meafure, their 
 voice. This arifes partly from the lofs of the Fore Teeth, 
 but principally from the lofs of all the Teeth, and of the 
 Alveolar ProcelTes of both Jaws, by which means the 
 mouth becomes too fmall for the tongue, and the lips 
 and cheeks become flaccid ; infomuch that the nicer 
 movements of thefe parts, in the articulation of founds, 
 are obllru&ed ; and thence the words and fyllables are 
 indiftindlly pronounced, and llurred, or run into one 
 another. 
 
 6 
 
 Under 
 
Under what CLASS do the HUMAN TEETH 
 
 come, 
 
 TVTATURAL Hiftorians have been at great pains 
 ^ to prove from the Teeth, that man is not a car¬ 
 nivorous animal; but in this, as in many other things, 
 they have not been accurate in their definitions ; nor 
 have they determined what a carnivorous animal is. 
 
 • 
 
 If they mean an animal that catches and kills his 
 prey with his Teeth, and eats thatflefh of the prey juft 
 as it is killed, they are in the right; man is not in this 
 fenfe a carnivorous animal, and therefore he has not 
 Teeth like thofe of a Lion ; and this, I prefume, is 
 what they mean. 
 
 But if their meaning were that the Human Teeth 
 are not fitted for eating meat that has been catched, 
 killed, and drefied by art, in all the various ways that 
 the fuperiority of the human mind can invent, they 
 are in the wrong. Indeed, from this confined way of 
 thinking it would be hard to fay what the human 
 Teeth are fitted for ; becaufe, by the fame reafoning 
 man is not a graminivorous animal, as his Teeth are 
 not fitted for pulling vegetable food, &c. They are 
 
 not made like thofe of cows or horfes, for example. 
 
 The 
 
 \ 
 
120 CLASS OL THE HUMAN TEETH. 
 
 The light in which we ought to view this fubjeft is, 
 that man is a more perfect or complicated animal than 
 any other ; and is not made like others, to come at 
 his food by his Teeth, but by his hands, directed by his 
 fuperior ingenuity ; the Teeth being given only for the 
 purpofe of chewing the food, in order to its more eafy 
 digeftion: and they, as well as his other organs of di- 
 geflion, are fitted for the convention of both animal 
 and vegetable fubftances into blood ; and thence he is 
 able to live in a much greater variety of circumftances 
 than any other animal, and has more opportunities of 
 exercifing the faculties of his mind. He ought, there¬ 
 fore, to be confidered as a compound, fitted equally to 
 live upon fleih and upon vegetables. 
 
 O F 
 
O F T H E 
 
 DISEASES of the TEETH. 
 
 npH E Teeth are fubjedt to difeafes as well as other 
 parts of the body. Whatever the diforder is that 
 affedts them, it is generally attended with pain ; and 
 from this indeed we commonly firft know that they 
 are affedted. 
 
 Pain in the Teeth proceeds, I believe, in a great mea- 
 fure, from the air coming into contadt with the nerve 
 in the cavity of the Tooth ; for we feldom fee people 
 affedled with the Tooth-ach, but when the cavity is 
 expofed to the air. 
 
 It is not eafy to fay by what means the cavity comes 
 to be expofed. 
 
 The moft common difeafe to which the Teeth are 
 fubjedl, begins with a fmall, dark coloured fpeck, ge¬ 
 nerally on the fide of the Tooth where it is not expofed 
 to preffure ; from what caufe this arifes is hitherto 
 unknown. The fubftance of the Tooth thusdifcoloured^ 
 
 R gradually 
 
122 
 
 OF THE DISEASES OF THE TEETH. 
 
 gradually decays, and an opening is -made into the 
 cavity. As foon as the air is thereby admitted, 
 a confiderable degree of pain arifes, which is pro¬ 
 bably owing to the admiftion of the air, as it may be 
 prevented by filling the cavity with lead, wax, 8tc. This 
 pain is not always prefent ; the food, and other fub- 
 ftances, perhaps fill up the hole occafionally, and prevent 
 the accefs of the air, and of confequence the pain, 
 during the time they remain in it. When an 
 opening is made into the cavity of the Tooth, the in- 
 fide begins to decay, the cavity becomes larger, the 
 breath at the fame time often acquires a putrid Factor, 
 the bone continues to decay till it is no longer able to 
 fupport the preflure of the oppofite Tooth, it breaks 
 and lays the cavity open. We have not as yet found 
 any means of preventing this difeafe, or of curing it; 
 all that can be done, is to fill the hole with lead, which 
 prevents the pain, and retards the decay ; but after 
 the Tooth is broken, this is not practicable ; and for 
 that reafon it is then beft to extract it. 
 
 It would be beft of all to attempt the extraction of 
 a Tooth by drawing it in the direction of its axis: but 
 that not being practicable by the inftruments at pre¬ 
 fent in ufe, which pull laterally, it is the next beft to 
 
 - * « 
 
 draw a Tooth to that fide where the Alveolar Procefs 
 is weakeft ; which is the infide, in the two laft grinders 
 on each fide of the Lower-Jaw, and the outfide in all 
 the others. 
 
 It 
 
OF THE DISEASES OF THE TEETH. 123 
 
 It generally happens in drawing a Tooth, that the 
 Alveolar Procefs is broken, particularly when the Grind¬ 
 ers are extracted; but this is attended with no bad 
 
 1 
 
 confequences, as that part of the Alveolar Procefs from 
 which the Tooth was extracted always decays. 
 
 In drawing a Tooth, the patient complains of a 
 difagreeable jarring noife, which always happens when 
 any thing grates againft the bones of the head. 
 
 R 2 
 
 O F 
 
 1 
 
O F 
 
 CLEANING the TEETH. 
 
 ROM what was faid of the nature and ufe of the 
 •*“ Enamel, it is evident, that whatever is capable of 
 deflroying it, mull be hurtful; therefore all acids, 
 gritty powders, and injudicious methods of fcaling the 
 Teeth are prejudicial : but limply fcaling the Teeth, that 
 is, clearing them of the ftony concretions which fre¬ 
 quently colleft about their necks, while nothing is 
 fcraped off but that adventitious fubftance, is proper and 
 ufeful. If not removed by art, the quantity of the 
 ftony matter is apt to increafe, and to affedt the gum. 
 This matter firft begins to form on the Tooth near to 
 the Gum; but not in the very angle, becaufe the mo¬ 
 tion of the Gum commonly prevents the accumu¬ 
 lation of it at this part. I have feen it cover not only 
 the whole Tooth, but a great part of the Gum: in this 
 cafe there is always an accumulation of a very putrid 
 matter, frequently confiderable tendernefs and ulcera- 
 6 tion 
 
OF CLEANING THE THETH. 125 
 
 tion of the Gum, and fcaling becomes abfolutely ne- 
 ceflary *. 
 
 * The animal fluids, when out of the courfe of the general circulation, 
 efpecially when they ftagnate in cavities, are apt to depofit an abfor- 
 bent earth, and form concretions. This earth is fometimes contained 
 in the fluids; and is only depofited ; as in the formation of the ftone in 
 the urinary pafiages: in fome Cafes, perhaps, the fluids undergo a 
 change, by which the earth is Brit formed, and afterwards depofited. 
 This depofition takes place particularly in weakened parts, or where 
 the circulation is languid, or where there are few arteries, fuch as about 
 joints and tendons * as if it were intended to flrengthen thde parts, 
 if they fhould at any time give way •, for if an artery, for inftance, is' 
 overcome by the adtion of the heart, and unnaturally dilated, its coats have 
 commonly thefeconcretions formed every wherein their interflices. The 
 fame thing happens alio in the coats of incyfled tumors, which are con- 
 ftantly diftended; in cafes of diftentions of the Tunica Vaginalis Teftis, ' 
 &c. It is alfo apt to take place in parts which have loft their natural 
 functions j as in the coats of the eye in cafes of blindnefs, and in 
 difeafed lymphatic glands, &c. and where the living power is diminilh- 
 ed in the fyftern, as in the arteries, membranes, &c. of old people; 
 and in fome particular habits, as in thofe who are afredted by the gout. 
 
 The fame fort of depofition takes place likewife where there is any 
 fubftance with fuch properties as render it a faBafis for cryftallization ; 
 as when extraneous bodies are lodged in the bladder: whence fuch 
 bodies are fo often found to form the Nucleus of a ftone. The fame 
 thing happens in the bowels of many animals; whence the Nucleus of 
 inteftinal concretions, or bezoars, is commonly a nail, or fome indigef* 
 tible fubftance which had been fvvallowed. The cruft, which .collects 
 upon the Teeth, Teems to be a cryftallization of the fame nature. 
 
 V. 
 
 1 4 
 
 • ’ ... . . ■ 7.-7 * . _ r \ : i 71. • j 
 
 * 
 
 - * * /* * e f r • • t s 
 
 « • > C - ./I . ’ ' < 
 
 O.F 
 

 0 F 
 
 I 
 
 / 
 
 TRANSPLANTING the TEETH. 
 
 XT' ROM confidering the alrnoft conftant variety of 
 > the fize and fhape of the fame clafs of Teeth in 
 
 v 4 
 
 different people, it would appear almoft impoflible to> 
 find the Tooth of one perfon that fhould fit, with any 
 degree of exa&nefs, the focket of another; and this ob- 
 fervation is fupported, and indeed would feem to be 
 proved by obferving the Teeth in fkeletons. Yet we can 
 adlually tranfplant a Tooth from one perfon to another^ 
 without great difficulty, nature affifting the operation, 
 if it is done in fuch a way that fhe can affifl; and the 
 only way in which nature can affifl, with refpeft either 
 to fize or fhape, is by having the fang of the tranfplanted 
 Tooth rather fmaller than the focket. The focket, in 
 this cafe grows to the Tooth. If the fang is too 
 large, it is impoflible indeed to infert it at all in that 
 flate; however, if the fang fhould be originally too 
 large, it may be made lefs ; and this feems to anfwer 
 the purpofe as well* 
 
 \ 
 
 The fuccefs of this operation is founded on a difpo- 
 fition in all living fubftances, to unite when brought in¬ 
 to 
 
OF TRANSPLANTING THE- TEETH 
 
 127 
 
 contact with one another; although they are of a diffe¬ 
 rent ftrudture ; and even although the circulation is 
 only carried on in one of them. 
 
 This difpoAtion is not fo conAderable in the more per¬ 
 fect or complex animals, fuch as quadrupeds, as it is in 
 the more Ample or imperfect; nor in old animals, as in 
 young : for the living principle in young animals, and 
 thofe of Ample conftrudtion, is not fo much conAned 
 to, or derived from one part of the body ; fo that it con¬ 
 tinues longer in a part feparated from their bodies, and 
 even would appear to be generated in it forfome time; 
 while a part, feparated from an older, or more perfetff 
 animal, dies fooner, and would appear to have its 
 life entirely dependent on the body from which it 
 was taken. 
 
 Taking off the young fpur of a cock, and Axing it 
 to his comb, is an old and well known experiment. 
 
 I have alfo frequently taken out the Tejlh of a cock 
 arfci replaced it in his belly, where it has adhered, and 
 has been nourifhed ; nay, I have put the Teftis of a cock 
 into the belly of a hen with the fame effetff. 
 
 In like'manner a freffi Tooth, when tranfplanted 
 from one focket to another, becomes to all appearance 
 a part of that body to which it is now attached, as 
 a much 
 
128 OF TRANSPLANTING THE TEETH. 
 
 much as it was of the one from which it was takenj 
 while a Tooth which has been extracted for fome time, 
 fo as to lofe the whole of its life, will never become 
 firm or fixed ; the fockets will alfo in this cafe acquire 
 the difpofition to fill up, which they do not in the cafe 
 of the infertion of a frefh Tooth. 
 
 Thefe appearances fhew that the living principle 
 exifts in the feveral parts of the body, independent of the 
 influence of the brain, or circulation, and that it fubfifts 
 by thefe, or is indebted to them for its continuance; and in 
 proportion as animals have lefs of brain and circulation, 
 the living power has lefs dependence on them, and be¬ 
 comes a more active principle in itfelf; and in many 
 animals there is no brain nor circulation, fo that this 
 power is capable of being continued equally by all the 
 parts themfelves, fuch animals being nearly fimilar in 
 this refped to vegetables. 
 
 n.: 
 
1* LA TE I 
 
 Pui'/uAH cuwrdAyr fc Act of /JJt. ty rj„/tn.,ott 
 
EXPLANATION 
 
 » * 
 
 OF THE 
 
 PLATES. 
 
 PLATE I. 
 
 FIG. I. 
 
 A Rcprefentation of the under-fide of the Upper-Jaw, without the 
 Teeth. 
 
 aaaaa The outer line of the circle, or what is commonly called 
 the outer plate of the Alveolar procefs. 
 
 b b b The inner line of the circle, commonly called the inner plate. 
 cc The io fingle Sockets, viz. for the Incifores, Cufpidati, and 
 Bicufpides. 
 
 dd The 3 double Sockets for the Molary, or triple-fanged Teeth. 
 The two firft have three fockets, and the laft only two. 
 
 Fig. II. A reprefentation of the upper part of the Lower-Jaw, View¬ 
 ing particularly the Sockets of the Teeth. 
 
 a The Sockets of the ten fingle-fanged Teeth. 
 b The fockets of the 3 double-fanged Teeth. 
 
 S 
 
 PLATE 
 
A 
 
 PLATE II. 
 
 A Sketch of the Head to explain v/hat was faid of the motions cf 
 the Lower-Jaw. 
 
 A The Section of the Head which was made to bring the Articu¬ 
 lation of the Lower-Jaw into view. 
 
 B Lower-Jaw. 
 
 C The condyle of the Lower-Jaw. 
 
 D The occipital condyle of the Head. 
 
 E F The Digaftric Mufcle. 
 
 E Its origin. 
 
 E Its infertion. 
 
 GGG The Vertebra of the Neck. 
 
 H The Meatus Auditorius ext emus. 
 
 I The hollow, or cavity in the temporal bone for the articulation of 
 the Lower-Jaw. 
 
 K The eminence before that cavity, likewifefor articulation,, 
 
 L The moveable cartilage of the Joint. 
 
 ' . D I i 
 
//V///.</✓/ nct'-ertfa-tuf to Act of I‘cr /t/cr tj/c/t! ' J/o // At. Iff A- bt/ IJo/twn . 
 
I 3 LATE 111 
 
PLATE III. 
 
 \ 
 
 Fig. I. A front view of the Upper and Lower-Jaws of an adult* 
 with a full fet of Teeth. 
 aa&aa The Upper-Jaw. 
 
 bb Its attachment to the check-bones below the orbits, 
 cc The Lower-Jaw. 
 
 Fig. II. A fide view of both Jaws in the fame Hate. 
 
 A AAA The Upper-Jaw. 
 
 B B The body of the Lower-Jaw. 
 
 C Its afcending procefs. 
 
 D The Root of the Coronoid Procefs. 
 
 E The Condyle. 
 
 F F F F The fluted Alveolar Procefles* 
 
 4 ’ f 
 
 S 2 
 
PLATE "IV, 
 
 Fig. T. The bafis of the fkull, and of the Upper Jaw, with a full 
 fet of Teeth ; fhewing the cutting edges and grinding fur faces of the 
 Teeth of the Upper-Jaw, and the cavity and eminence of the tempo¬ 
 ral bane for the articulation of the Lower-Jaw. 
 a a a a The four Incifores. 
 
 b b The two Cujpidati. _ 
 
 ( c T he four Buufpides. 
 dd The fix Grinders. 
 
 e e The two cavities in the temporal bones for the articulation of 
 the condyles of the Lower-Jaw. 
 
 //The two eminences upon which the condyles move, in many 
 actions of that bone. 
 
 Fig. II. A view, from above and behind, of the Lower-Jaw, with a 
 full fet of Teeth-, fhewing the cutting edges and grinding furfaces of 
 the Teeth in that Jaw, with the Coronoid ProcefTes, and condyles for 
 articulation. 
 
 a a a a The four Incifores. 
 b b The two Cufpidati. 
 c c 'The four Bicufpides. 
 dd The fix Grinders. 
 e e The Coronoid ProcefTes. 
 
 // The Condyles. 
 
 Fig III. The moveable cartilage of the joint of the Lower-Jaw. 
 a The cut furface of a longitudinal fedlion of it. The lower and con¬ 
 cave furface is what is articulated with the Condyle-, the upper and 
 convex furface is what is in contact with the Temporal Bone. 
 

 
 2 J u Mbt/i/ trecort/vriyr lc dot of Par/unne'nt Meet/ 45 - IJ'jf /■ /•/ JJt>/nr.n>H . 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 s 
 
 
 
 t 
 
 
 *. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 I 
 
 
 
 
 
 
 
 
 - 
 
 
 
 
 

 
 
 ; 
 
 * - y 
 
 
 
 
 
 V 
 
 
 ' 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
PLATE V. 
 
 PuMAiiLmr<'/•<////// to Art <rf ParLiamc nf 3Pa// So. /jy/. t// /Jo/ia.ton. 
 

 
 P L A T E ' V. 
 
 Two views of the fixteen Teeth of one fide of both Jaws, taken 
 out of their fockets to expofe the whole of each Tooth. 
 
 Row i. The Teeth of the Upper Jaw, feen from the outfide. 
 
 Row 2. The fame view of the Teeth of the Lower-Jaw : the five 
 fingle are fimilar to thofe in the Upper-Jaw, but the Grinders in this 
 have only two fangs. 
 
 a a The two Incifors. 
 
 b T\\t-Cufpidatus , fhewing in the fame view how much it is longer 
 than the others. 
 
 cc The Bicufpides. 
 
 d d The two firft Grinders, having three fangs. 
 
 e The third Grinder, or Dens Sapientia having alio three fangs. 
 
 Row 3 and 4. A fide view of the fame Teeth, fhewing that the 
 Incifores and Cufpidati in this view differ from the former view more 
 than the Bicufpides or Grinders. 
 
 Row 3, a a The two Incifores of the Upper-Jaw, fhewing the hol¬ 
 lowed inner furface of the body of thofe Teeth. 
 
 b The Cufpidatus , fhewing the fame. 
 
 c c The Bicufpides , fhewing the two points on the bafis of each. 
 The firfl of them has a forked fang. 
 
i 
 
 PLATE ' VI. 
 
 / 
 
 Fig. T. A fide view of the Upper and Lower-Jaw, in which the 
 outer plate of the Alveolar Procefs was taken off to expofe the Fangs 
 of the Teeth in their lockets. The length of each fang is at once 
 feen with refped to its neighbour, and this kind of articulation pointed 
 out at one view. 
 
 Fig. II. A view of the infide of the Teeth of both Jaws in their 
 natural fituation when the mouth is (hut. In this view the fpedator’s 
 eye is fuppofed to be placed behind and below the two Jaws, 
 
 5 l-i 
 
P/MtMt, d txooa? ‘At a// to .Act of Parliament Mat/ 46. ////• fa/IJoUn.um 
 
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 4 / - * 
 
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PL ATETU 
 
PLATE 
 
 VII. 
 
 The bones of the head of a very old woman, who had loft her 
 Teeth a confiderable time before death. The whole Alveolar Pro- 
 ceftes arc gone in both Jaws, which allows of the Lower-Jaw being 
 railed about two Inches higher than v/hat is common in (hutting the 
 mouth, before the gums of both Jaws can come into con tad ; by 
 this increafed motion of the Lower-Jaw, the chin is brought more 
 upon a line with the articulation, therefore projects beyond the Upper- 
 Jaw confiderably. 
 
P. L ATE VIII. 
 
 This plate fhews the gradual growth of the two Jaws, efpecially of 
 the Alveolar Proceffes. 
 
 Fig. I. and II. One fide of the Lower and of the Upper-Jaw of 
 a Foetus about three or four months old. 
 
 a a The groove which is afterwards formed into Sockets. 
 
 Fig. III. and IV. One fide of the Lower and of the Upper-Jaw of 
 a Foetus about fix months old, at which age (a a) iome of the partitions 
 have fhot acrofs near the anterior part, forming diftindt cells. 
 
 Fig. V. and VI. The Upper and Lower-Jaw of a new born child, 
 fhewing the laft mentioned circu-m fiance in a more advanced (late. 
 
 Fig. VII. The Lower-Jaw of a child feven or eight months old, 
 in which the two firfl Incifores had cut the gum, fhewing the fockets 
 of fix Teeth. 
 
 a a The mouths of the Alveoli contracted over the Teeth, efpecially 
 thofe of the Grinders, where they have not yet begun to open for the 
 paffage of the Teeth. 
 
 Fig. VIII. A fketch of an Upper-Jaw where the Cufpidatus of that 
 fide had been formed high up in the Jaw, and therefore never could 
 appear through the Gum. a The fang of the Cufpidatus. b Its body 
 contained in the Upper-Jaw and Alveolar Procefs. 
 
 Fig. IX. A fketch of the Upper-Jaw of a child, where the Cuf¬ 
 pidatus was inverted, fo that its point was turned up againfl the Jaw, 
 and the growing mouth of its cavity towards the Gum. a The point 
 of the Cufpidatus turned up againfl the Jaw. b The open and growing 
 part of the Tooth which fhould be formed into a fang. 
 
 Fig. X. The out-line of the Lower Jaw of a child, to fhew that 
 the Condyle is then nearly on a line with the Gums. 
 
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PLATE 
 
 IX. 
 
 Fig. I. One fide of the Upper and Lower-Jaw of a fubjecft about 
 eight or nine years of age, where the Incifores and Cufpidati of the Foetus 
 were fhed, and their fuccefiors rifing in new fockets; (hewing like- 
 wife the two Grinders of the child, with the Bicufpides forming under¬ 
 neath. The firft adult Grinder was ready to cut the Gum; and the 
 fecond Grinder in the Lower-Jaw is lodged in the root of the Choronoid 
 Procefs, and in the Upper-Jaw it is in the tubercle. 
 
 Fig. II. Part of the Lower-Jaw cut through at the fymphyfis. The 
 Incifor of the child is (landing in its focket, and the adult Incifor form¬ 
 ing in a diftinft focket underneath. > 
 
 Fig. III. Another view of the fame piece of the Jaw, to (hew that 
 the Bicufpides are formed in diftind fockets of their own, and not in 
 the focket of the Grinder which (lands above. 
 
 Fig. IV. The five Teeth in the half of each Jaw of a Foetus of 
 feven or eight months, (hewing the progrefs of ofiification from the firft 
 Incifor to the fecond Grinder. 
 
 Fig. V. The fame teeth fomewhat farther advanced. 
 
 Fig. VI. The Teeth of a child of eight or nine years of age, (hew¬ 
 ing the five temporary Teeth in a more advanced (late, with the firft 
 adult Grinder. The adult Incifores and one Cufpidatus are alfo begun to 
 be formed. 
 
 T 
 
PLATE 
 
 X. 
 
 Fig. I. The Teeth of one fide of both Jaws, from a child of five 
 or fix years of age. B B,C C The temporary Teeth almoft completely , 
 formed. AD, Seven, viz. four above and three below, of the fuc- 
 ceeding Teeth feen at the roots of the firft fet. E E, The body of the 
 firft adult Grinder nearly formed. 
 
 Fig. II. The Teeth of one fide of both Jaws, from a child of feven 
 years of age. This is an age in which there are more Teeth formed 
 and forming than at any other time of life. B B, C C, The ten tem¬ 
 porary Teeth complete. A D, Ten incomplete to fucceed them. 
 EE, Two adult Grindersj making twenty-two in this fide, and cf 
 courfe forty-four in the whole. aaaa y the Fangs of the temporary 
 Incifors beginning to decay at their points. 
 
PLATEX 
 
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PLAT 
 
 E 
 
 XI. 
 
 Fig. I. The Teeth of a child eight or nine years old; principally to 
 fhevv the progrefs of the fecond Set, and the beginning and decay of the 
 firft Set. 
 
 A A, The firft Incifores of the fccond or permanent Set. B. The 
 fecond Incifcr. C. The Cufpdatus. D E, The Bicufpides. F G, The 
 two firft Molares. 
 
 ab , The temporary Incifores , the firft of which in the lower Jaw is ■ 
 wanting, having been fhed. c , The Cufpidati. d e. The temporary 
 'Mo lares. 
 
 Fig. II. The Teeth of a youth about eleven or twelve years old, 
 fhewing the farther progrefs of the one Set towards perfection, and of 
 the other in their decay. 
 
 aaaa , The Incifores of the fecond Set, which had all cut the Gum. 
 bb , The Bafis of the third Molaris or Bens Sapentioe. c c, The re¬ 
 maining Molares of the firft Set, with decayed Fangs, dd , The two 
 firft Molares of the fecond Set, fo much advanced that they had cut 
 the Gums. 
 
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 P LATE 
 
PLATE XI r. 
 
 Fig. I. The Lower-Jaw of a Foetus, from which part of the Gum 
 and bony focket is taken off, to expofe the membrane which inclofes the 
 Teeth, rf, The upper edge of the gum. b b b , The membrane which 
 covers the Teeth. 
 
 Fig. II. The Upper-Jaw of the fame Foetus* fhewing the fame 
 membrane in that Jaw. 
 
 Fig. III. The Lower Jaw of a new-born child, where this inclofing 
 membrane is opened, to fhew the bodies of the Teeth that were co¬ 
 vered by. it. The blood veffels which.run in its fubftance are alfo ex- 
 poled. 
 
 <3, The body, of the Tooth, b , The membrane. 
 
 Fig. IV. That part of the Jaw and Gum which contains the O/- 
 pidatus . The whole is a little magnified. The membrane is opened 
 and turned off on each fide, and the fore part is turned down. The 
 upper part of the pulp is covered with its bony (hell, which is feen by 
 its want of veffels. 
 
 tf, The olfified part of the. Tooth. £, The pulp, c c , The membrane 
 opened and turned back. 
 
 Fig. V. and VI. Two pulps magnified. Fig. V. The pulp of the 
 Cufpidatus , Fig. VI. That of the Grinder. The ofiifications are remov¬ 
 ed, to fhew that the pulp is of the fame fhape with the Tooth which is 
 formed upon it. As far down on the pulp as the veffels are feen, the 
 offification had advanced ; which fhews that it is more vafcular where 
 the operation of offification is going on. The lower ragged edge, a, is 
 part of the capfula turned down. 
 
 Fig. 7. One of the Grinders of the Lower-Jaw, fawed down to 
 expofe the two cavities or canals leading to the body of the Tooth., 
 where they unite, and form a. fquare. cavity. In thefe two canals are 
 feen two arteries, which run on to the common cavity, and there ra¬ 
 mify. The veins are not injedted. The whole is magnified. 
 
 In the body of the Tooth may be oblerved a number of ftrata, each 
 of which is loft in the circumference of the Tooth. 
 
 a a. The Jaw-bone and Gum cut through. b y The body of the 
 Tooth, c c , The two fangs, d d , The arteries running into the cavities 
 of the fangs. 
 
 Fig. VIII. An Incifor prepared and magnified in the fame manner, 
 fkewing the lame circumftances in that Tooth. 
 
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PLATEXIII 
 
PLATE 
 
 XIII. 
 
 Fig. I. Shews the formation of the cavity and fangs of the Mo- 
 lares. The upper row are thofe of the Lower-Jaw, and the lower 
 thofe of the Upper. A A, a is the common cavity in the body of 
 the Tooth, which in the 2d, a a , is deeper than in the firft. B fhews 
 the bony arch thrown over the mouth of the cavity, and dividing that 
 into two openings which give origin to the two fangs. CD E, The 
 progrefs of thefe fangs. F, a Molaris of the Upper-Jaw, where the 
 mouth of the cavity is a little tucked in, at three different points, from 
 which three offifications fhoot. G fhews thefe offifications, and the 
 beginning of three fangs. H LK, fhews the gradual growth of thefe 
 fangs. 
 
 Fig. IF. Is a comparative view of the Incifors and Grinders of the 
 child and adult; for the better underftanding of which they are fawed 
 down the middle, fhewing in a fide view the gradual increafe of thefe 
 Teeth. The uppermoft row is of the child, and the lower of the 
 adult, ab c d. Shew the gradual growth of the body, fangs, and cavity 
 of the of Incifors both ages, efg , Shew thefe circumftances in the 
 Grinders. 
 
 Fig. III. i, 2, 3, 4, 5 , 6, 7, fhewing the gradual growth of a fingle 
 Tooth, from its firft formation nearly, to its being almoft complete. 
 
PLATE • XIV. 
 
 Fig. I. II. III. IV. V. and VI. Shew the cavities of tiie Teeth in 
 
 the Infciores , Cufpidatus , Bi cufpidatus , and Molares. 
 
 Fig. VII. A Molaris of the Lower-Jaw, with part of its fangs 
 fawed off, to fhew that the fides of the cavity or canal have grown to¬ 
 gether, and divided it into two final! canals, which are reprefented by 
 the two dark points. 
 
 Fig. VIII. and IX. The cavity in the body of the Teeth feen in 
 tranfverfe fedtions. 
 
 Fig. X. and XL Longitudinal fedtions of the Molares to expofe the 
 cavities. 
 
 Fig. XII. The bafis of a Molaris whofe points were worn down, 
 and the bony part which projected into thofe points expofed. 
 
 Fig. XIII. A Molaris , whofe bony part is wholly expofed, and only 
 a circle of Enamel left covering the fides all round. 
 
 Fig. XIV. and XV. A lateral view of the Enamel of a Molaris 
 and a Bicufpis cut longitudinally. 
 
 Fig. XVI. A Cufpidatus worn fo much down, as to expofe the 
 whole end of the bony part, a circle only of Enamel remaining. 
 
 - Fig. XVII. An Incifor flit down its axis, to fhew the Enamel upon 
 the body of the Tooth, covering much more of the convex than of the 
 concave part. 
 
 Fig. XV 111 . An Incifor , fhewing the fame as Fig. XVI. 
 
 Fig. XIX. A horfe’s Tooth flit down its whole length, to fhew 
 how the Enamel is intermixed with the bony part, and that it pafles 
 through the whole length of the Tooth. The Enamel is reprefented 
 by the white lines, which are peniform, fhewing the If riated texture of 
 the Enamel. 
 
 Fig. XX. The grinding furface of a horfe’s Molaris , to fhew the 
 irregular courfe of the Enamel. 
 
 Fig. XXI. An Incifor a little magnified, flit down its middle, to 
 fhew that the Enamel is flriated, and that the Strips are all turned to¬ 
 wards the centre. 
 
 Fig. XXII. A Grinder in the fame ftate, to fhew the fame circum- 
 flances. 
 
 Ficr. XXIII. The bafis of a Molaris broken through, fhewing that 
 the Enamel is flriated in this view alfo, and that all the Stria point to 
 the centre. N. B. The Teeth muft be broken to fhew thefe fads. 
 
 Fig. XXIV. An old Tooth, whofe bafis has been worn down be- 
 fow the original termination of the cavity in the body of the Tooth, 
 and that end has been filled up, in the fame proportion, with new matter, 
 to prevent the cavity being expofed. This matter is of a darker co¬ 
 lour, as reprefented in the figure. 
 
 Fig. XXV. Another Tooth in the fame ftate. 
 
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PLATE XV. 
 
 Fig. I. A horfe’s Tooth that was juft ready to be (lied. The 
 three parts of the Tooth which ftand up a a a inclofed the rifing end of 
 the young Tooth. This is all that was left of a long Tooth. 
 
 Fig. II. A feries of Grinders of the child, from their being com¬ 
 plete to their utmoft decay, a is a Grinder of the Upper-Jaw nearly 
 complete, in which the three fangs are almoft formed, b has fome of 
 its fang abforbed, c more, d ftill more, e nearly all gone, and / the 
 whole of the fangs gone, only the neck and body remaining. 
 
 Fig. III. A feries of In afore s in the fame ftate. No. i. A complete 
 formed Tooth. 2. The fang fomewhat decayed. 3. More fo. 4. Still 
 more. 5. The fang almoft gone: and, 6. the whole fang gone, the 
 neck and body only remaining. 
 
Fig. I. The outlines of a Lower-Jaw, in which one or two Grin¬ 
 ders have been loft out of the fpace a , and where the bodies of the two 
 adjacent Teeth, b c, have approached one another, by the prefiure 
 which has been applied to their bafts in maftication, from the want 
 of their fupport on that fide: we fee alfc the wafte of the Alveoli which 
 belonged tO'the loft Teeth. 
 
 Fig. II. Four Lower-Jaws at different periods of life, from the age 
 when the five fhedding Teeth are completely formed, to that of a com. 
 plete fet. This figure fnews four things: i. The lengthening of the 
 Jaw backwards, which is feen by the oblique line made by the four 
 condyles: 2. The gradual rife of the two proceffes above the line of the 
 Teeth : 3. The gradual increale of the Teeth in proportion as the Jaw 
 lengthens: And fourthly, the part formed, always keeping of the fame 
 ftze. aaa a The Condyles, b bbb The Coronoide Proceffes. c The 
 Alveolus , in which the Grinder of the Adult is forming, ddd The firft 
 Grinders formed, ee The Alveoli for the formation of the fecond 
 Grinder. //Thefe completely formed, gg The Alveoli for the third 
 Grinder, h That Grinder formed. 
 
 The two lines i k and i m mark the diftance between the fymphyfis 
 of the chin and fixth Tooth ; they are parallel, or nearly fo : it is im- 
 poffible that there fhould be a mathematical exa&nefs in four different 
 Jaws. The line il feparates the Incifores and Cufpidatus from the Mo- 
 lares in the child, and th z.Bicufpidates in the adult. This line is ob¬ 
 lique, and the diftances between the two ends of the two lines, i k and 
 i l, at i i, is nearly the fame with the diftance between the ends of the 
 two lines i /, and; m , at / m. 
 
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