y '/ /7/jf ,/ V THE COMPARATIVE ANATOMY OF THE DOMESTICATED A:NIMALS THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS BY A. CHAUVEAU, M.D., LL.D. MEMBER OF THE INSTITUTE (ACADEMY OF SCIENCES); INSPECTOR-GENERAL OP VETERINARY SCHOOLS IN FRANCE ; PROFESSOR AT THE MUSEUM OF NATURAL HISTORY, PARIS 3£lebtset) nnXi lEnlarselJ, tDt'tt) tit ... 3. Masseteric or Temporo-maxillary Region . 4. Hyoideal Region ..... Comparison of the Musclea of the Human Head with those of the Domesticated Animals . ...... 1. Epicranial Muscles ..... 2. Musclea of the Face . . . . 3. Muscles of the Lower Jaw ..,<., 4. Hyoideal Musclea . . , . Axillary Region ... . . 1. Superficial Pectoral (Pectoralis Anticua and Transversos) . 2. Deep Pectoral (Pectoralia Magnus and Parvus) . Differential Characters ...... Costal Region .... , 1. Serratus Magnus ...,., 2. External Intercostala ... 3. Internal Intercostala » . » . . 4. Levatores Costarum . . . , , 5. Triangularis Stemi ..... Differential Characters ..„..,. Comparison of the Thoracic Musclea of Man with those of the Domesticated Animals ........ Inferior Abdominal Region ..... 1. Abdominal Tunic (Tunica Abdominalis, Tunica Elastica) 2. Wliite Line (Linea Alba) ..... 3. Great or External Oblique of the Abdomen (Obliquus Abdominis Externus) .... ... 4. Small or Internal Oblique of the Abdomen (Obliquua Abdominis Internus) ....... 5. Great Straight Muscle of the Abdomen (Rectus Abdominis) 6. Transverse Muscle of the Abdomen (Transversalis Abdominia) . Differential Characters . . ^ . . . c Comparison of the Abdominal Musclea of Man with those of Animals Diaphragmatic Region . ., . , ~ Diaphragm ...,..,, Differential Characters ....... Comparison of the Diaphragm of Man with that of Animals Article II. — Muscles of t-ue Anterior Limbs . ^ . o Muscles of the Shoulder ...... A. External Scapular Region ..... 1. P^xternal Scapular Aponeurosis ...... 2. Long Abductor of tiae Arm, or Scapular Portion of the Deltoid (Teres Externus) ....... 3. Short Abductor of the Arm (Postea Spinatus Minor), or Teres Minor 4. Supra-spinatus (Autea Spinatus) . . . . 5. Infra-spinatus (Postea Spinatus; ..... B. Internal Sea; ular Region ....... 1. SubscapuLiris ..... 2. Adductor of the Arm (Teres Internus, or Teres Major) 3. Coraco-humeralis, Coraco-brachialis, or Omo-brachialis 4. Small Scapulo-humeralis (Scapulo-Humeralis Gracilis, Soapulo-Hume- ralis Posticus) ....... Differential Characters ... .... Comparison ot the Muscle:* of the Shoulder of Man with those of Animals . Muscles of the Arm . . ..... A. Anterior Brachial Region ... . , 1. Long Flexor of the Forearm (Flexor Brachii), or Brachial Biceps 2. Short Flexor of the Forearm (Humeralis Obliquus, Brachialia Aaticus, or Humeralis Externus) ...... B, Posterior Brachial Region , .... .PACK 289 290 290 291 291 291 291 292 292 292 292 293 296 296 296 297 297 298 298 299 299 299 300 300 301 303 305 305 3u7 307 308 308 310 310 310 310 310 311 311 312 312 313 314 314 315 315 316 316 316 316 317 317 318 319 lABLE OF CONTENTS. 1. Large Extensor of the Forearm (Caput Magnum) 2. Sliort Extensor of the Forearm (Caput Medium) 3. Middle Extensor of the Forearm (Caput Parvum), Internal portion of the Triceps ...... 4. Small Extensor of the Forearm, or Ancouena Differential Characters ....... Comparison of the Muscles of the Arm of Man with those of Animals Muscles of the Forearm ....... Antibrachial Aponeurosis ....... A Anterior Antibmchial Ri^gion ..... 1. Anterior Extensor of the Metacarpus (Extensor Metacarpi Magnus) . 2. Oblique Extensor of the Metacarpus (Extensor Metacarpi Obliquus) 3. Anterior Extensor of the Plialatiges (Extensor Pedis) 4. Lateral Extensor of the Phalanges (Extensor Suffragiuis) B. Posterior Antibrachial Region ...... 1. Externiil Flexor of the Metacarpus (Flexor Metacarpi Externus, or Pos terior Ulnaris) . ...... 2. Oblique Flexor of the Metacarpus (Flexor Metacarpi Medius, or Anterior Ulnaris) .....••■ 5. Internal Flexor of the Metacarpus (Flexor Metacarpi Internus, or Pal maris Magnus) ...... 4 Superficial Flexor, Sublimis of the Phalanges (Flexor Pedis Perforatoa) 5. Detp Flexor of the Phalanges ( Flexor Pedis Perforans) . Differential Characters ...... Muscles proper to the Forearm in Camivora . . . 1. Proper Extensor of the Thumb and Index 2. Long Supinator ....... 3. Short Supinator ...... 4. Round Pronator ....... 5. Square Pronator ...... CJomparison ot the Muscles of the Forearm of Man with those of Animals 1. Anterior Region ....•• 2. External Region ....... 3. Posterior Region . . I , . . Muscles of the Anterior Foot or Hand ..... A. Muscles of tiie Anterior Foot in Camivora . 1 Short Abductor of the Thumb ..... 2. Opponeiis of the Thumb ..... 3. Short Flexor of tlie Thumb ..... 4. Adductor of the Index ..... 5. Cutaneous Palmar (Palmaris Brevis) .... 6. Adductor of the Small Diyit .... 7. Short Flexor of the Small Digit .... 8. Opponens of the Small Digit .... 9. Lnmbrici ....... 10. Metacarpal Interosseous Muscles .... B. Muscles of the Anterior Foot in the Pig .... C. Muscles of the Anterior Foot in Solipeds . . . D. Muscles of the Anterior Foot in Ruminants ... Comparison of the Hand of Man with that of Animals . A. Muscles of the Thenar Eminence ..... B. Muscks of the Hypothenar Eminence .... C. Interosseous Muscles ...... Article III.— Mi'scles of the Posterior Limbs . . . Muscles of the Gluteal Region, or Croup .... 1. Superficial Gluteus (Gluteus Externus) 2. Middle Gleuteus (Gluteus Medius, Gluteus Maximua) 3. Deep Gluteus (Gluteus Internus) .... Differential Characters ....... Comparison of the Gluteal Muscles of Man with those of Animals . Muscles of the Thigh ....... PAQIt 319 320 320 321 321 322 322 322 323 323 324 324 326 326 327 327 328 328 330 332 336 336 336 338 338 338 338 338 339 340 340 340 340 340 340 340 341 341 341 341 341 341 342 342 342 342 343 343 343 343 343 344 346 346 348 348 348 xn TABLE OF CONTENTS. A. Anterior Crural, or Femoral Kegion .... 1. Muscle of the Fascia Lata (Tensor Fascia Latse, Tensor Vagina Femoris) 2. Crural Triceps ....... 3. Crureus, Rectus Parvus, Anterior Gracilis B. Posterior Crural Region ...... 1. Biceps Femoris, Triceps Abductor Femoris 2. Semitendinorius Muscle (Biceps Rotator Tibialis) . 3. Semimembranosus (Adductor Magnus) .... C. Internal Crural Region ...... 1. Great Adductor of the Leg (Sartorius) .... 2. Short Adductor of the Leg (Gracilis) .... 3. Pectineus ....... 4. Small Adductor of the Thigh (Adductor Parvus, Adductor Brevls) . 5. Great Adductor of the Thigh (Adductor Magnus, Adductor Longus) 6. Quadrate Crural (Quadratus Femoris, Ischio-Femoralis) 7. External Obturator (Obturator Externus) 8. Internal Obturator (Obturator Internus) .... 9. Gemelli ....... Differential Characters . . . • . . . 1. Anterior Crural Region ...... 2. Posterior Crural Region . . . . • . 3. Internal Crural Region ...... Comparison of the Muscles of Man's Thigh with those of the Thigh of Animals 1. Anterior Muscles ....... 2. Muscles of the Posterior Region . ... 3. Muscles of the Internal Region ..... Muscles of the Leg .... . . Tibial Aponeurosis ........ A. Anterior Tibial Region ...... 1. Anterior Extensor of the Phalanges (Extensor Pedis) 2. Lateral Extensor of the Phalanges (Peroneus) . 3. Flexor of the Metatarsus (Flexor Metatarsi) B. Posterior Tibial Region ...... 1. Gastrocnemius, or Gemelli of the Tibia (Gastrocnemius Externus) . 2. Soleus (Plantaris) ...... 3. Superficial Flexor of the Phalanges (Flexor Perforatus, Gastrocnemius Internus) ........ 4. Popliteus ....... 5. Deep Flexor of the Phalanges (Perforans, Flexor Pedis) 6. Oblique Flexor of the Phalanges (Flexor Accessorius) . Differential Characters ....... 1. Anterior Tibial Region ...... 2. Posterior Tibial Region ...... Comparison of the Muscles of the Leg of Man with those of Animals . 1. Anterior Region ....... 2. External Region ....... 3. Posterior Region ....... Muscles of the Posterior Foot ...... Pedal Muscle (Extensor Pedis Brevis, Extensor Brevis Digitorum) . Differential Characters ....... Comparison of the Muscles of the Foot of Man with those of Animals 1. Dorsal Region ....... 2. Plantar Region ....... 3. Interosseous Muscles ...... Chapter III.— The Muscles in Birds ..... Chapter IV.— General Table of the Attachment of the Muscles in Solipeds ........ FAG1I 348 349 349 350 351 351 351 352 353 353 353 355 355 356 356 357 357 358 358 358 359 359 360 360 360 360 362 362 362 363 364 365 366 367 368 369 369 370 371 372 372 374 374 374 375 375 376 376 376 377 377 377 378 378 380 TABLE OF CONTENTS. xril BOOK II. THE DIGESTIVE APPARATUS. Chapter I. — General Considerations on the Digestive Apparatus Chapter II.— The Digestive Apparatus in Mammalia Article I. — Preparatout Organs of the Digestive Apparatus . The Mouth ....... 1. Lips ........ 2. Cheeks ....... 3. Palate ....... 4. Tongue ....... 5. Soft Palate ....... 6. Teetli ....... 7. The Moutli in General ..... Diflferciitial Characters in the Mouth of the other Animals Comparison of the Mouth of Man with that of Animals . Table of Dentitinu ...... The Salivary Glands ...... 1. Parotid Gland ...... 2. Maxillary or Submaxillary Gland .... 3. Sublingual Gland ...... 4. Molar Glands ....... 5. Labial, Lingual, and Staphyline Glands Differential Characters in the Salivary Glands of the other Animals Comparison of the Salivary Glands of Man witli those of Animals The Pharynx ....... Differential Characters in the Pharynx of the other Animals . Comparison of the Pharynx of Man with that of Animals . . The (Esophagus ...... Differential Characters in the (Esophagus of the other Animals . Comparison of the (Esophagus of Man with that of Animals Article II. — The Essential Organs of Digestion The Abdominal Cavity ..... Difterential Characters in the Abdominal Cavity of the other Animals Comparison of the Abdominal Cavity of Man with that of Animals The Stomach ....... 1. The Stomach of Solipeds .... Differential Characters in the Stomach of the other Animals 1. The Stomach of the Rabbit . . . . 2. The Stomach of the Pig .... . 3. The Stomach of Carnivora ..... 4. The Stomach of Ruminants ..... Comparison of the Stomach of Man with that of Animals The Intestines ....... 1. The Small Intestine ..... 2. The Large Intestine ...... A. Caecum ....... B. Colon ....... c. Rectum . . . . . . . Differential Characters in the Intestines of the other Animals 1. The Intestines of the Rabbit .... 2. The Intestines of Ruminants .... 3. The Intestines of the Pig .... 4. The Intestines of Carnivora . .... Comparison of the Intestines of Man with those of Animals General and Comparative Survey of the Abdominal or Essential Portion of the Digestive Canal ...... Organs Annexed to the Abdominal Portion of the Digestive Cftnal 1. Liver ....... 2. Pancreas ....... 3. Spleen .....•« 3 PAGK 391 396 396 396 397 398 399 400 408 411 423 424 430 431 433 434 436 437 438 438 439 440 441 446 446 447 450 450 450 450 455 455 455 455 463 463 463 463 463 471 471 471 471 477 479 484 484 485 486 488 490 492 493 494 494 502 503 TABLE OF CONTENTS. Differential Characters ia the Organs annexed to the Abdominal Portion of the Digestive Canal in the other Animals ..... 508 Comparison of the Organs annexed to the Abdominal Portion of the Digestive Canal uf Man with those of Animals ..... 510 Chapter III.— The Digestive Apparatus of Birds . . . ,511 BOOK III. RESPIRATORY APPARATUa Chapter I.— Respiratory Apparatus in Mammalia . , , 517 The Nasal Cavities ........ 517 1. The Nostrils .... .o. 518 2. The Nasal Fossae .... . . 519 3. The Sinases ..... . . 524 Differential Characters in the Nasal Cavities of the other Animala . . 526 Comparison of the Naisal Cavities of Man with those of Animals . 527 The Atr-tube succeeding the Nasal Cavities ..... 527 1. The Larynx ........ 527 2. The Trachea ....... 536 3. The Bronchi ........ 539 Differential Characters in the Air-tube succeeding the Nasal Cavities in the other Animals ........ 541 Comparison of the Larynx and Trachea of Man with these Organs in the Domesticated Animals ....... 542 The Thorax ......... 542 Differential Characters in the Thorax of the other Animals . . 545 The Lungs ......... 546 Differential Characters in the Lungs of the other Animals . . 552 Comparison of the Larynx, Trachea, and Lungs of Man with those of Animals . 553 The Glandiform Bodies connected with the Respiratory Apparatus . 554 1. The Thyroid Body or Gland . . . . . .554 2. The Thymus Gland ....... 555 Differential Characters in the Glandiform Bodies annexed to the Respiratory Apparatus in the other Animals ...... 556 Comparison of the Glandiform Botlics annexed to the Respiratory Apparatus in Man with those of Animals ..... 557 Chapter II.— The Respiratory Apparatus of Birds .... 557 • BOOK IV. URINARY APPARATUS. 1. The Kidneys ........ 568 2. The Ureters ........ 574 3. The Bladder ........ 575 4. The Urethra ........ 578 5. The Supra-renal Capsules ...... 578 Differential Characters of the Urinary Apparatus in the other Animals . 579 Comparison of the Urinary Apparatus uf Man witli that of Animals . 581 BOOK V. CIRCULATORY APPARATUS. riRST SECTION.— THE HEART . , .... 583 1. The Heart as a Whole ....... 583 2. External Conformation of tlie Heart ..... 584 8. Internal Conformation of the Heart ..... 587 TABLE OF CONTENTS. 4. Structure of the Heart .... 5. The Pericardium ...... 6. The Action of the Heart Differential Characters in the Heart of the other Animals Comparison of the Heart of Man with that of Animals . 8EC0ND SECTION.— THE ARTERIES Chapter I. — General Considerations . Chapter II.- Pulmonary Artery . Chapter III.— Aorta ..... Article I. — Common Aorta, or Aortic Trunk Cardiac, or Coronary Arteries . , . Article II. — Posterior Aorta .... Parietal Brandies of the Posterior Aorta , . 1. Intercostal Arteries .... 2. Lumbar Arteries .... 3. Dipliragmatic Arteries .... Middle Sacral Artery .... Visceral Branches of the Posterior Aorta . . 1. Broncho-CE.-iophageal Trunk 2. Coeliac Artery ..... 3. Antones of the head of a foetus at birth 34. Posterior bones of the head of a foetus at birth . 35. Head of the Rabbit (posterior face) . . . 36. Head of the Rabbit (antero-lateral face) . . 37. Ox's head (posterior face) .... 38. Posterior aspect of Horse's skull ... 39. Head of the Pig (posterior face). 40. Dog's htaA (posterior view) .... 41. Longitudinal and transverse section of the Horse's head . 42. Antero-posterior and vertical section of the Horse's head 43 Median and vertical section of the Ox's head 44. Inferior maxilla ..... 45. Head of the Camel ..... 46. Head of the Cat .... . 47. Hyoid bone •....• 18. Wormian bones of the Ox .... Chauveau 8 Chauveau . 8 Chauveau . 9 Chauveau . 9 Oriifinal 10 Original 10 Chauveau . 11 Chauveau . 12 Carpenter . 16 Carpenter . 17 Carpenter . 17 Carpenter . 20 After (hoeii . 25 Original 27 Original 28 Original 28 Chauveau . 29 Original . 32 Chauveau . 33 Chauveau . 34 Original 36 Chauveau . 37 Chauveau . 38 Chauveau . 39 Original 40 Original 46 Chauveau . 49 Chauveau . 50 Chauveau . 51 Chauveau . 52 Chauveau . 53 Chauveau . 53 Chauveau . 54 Chauveau . 57 Chauveau . 59 Chauveau . 62 Chauveau . 65 Original 66 Chauveau . 67 Chauveau . tJ8 Chauveau . 72 Chauveau . 72 Cluxuveau . 74 Chauveau . 7<; Chauveau . 77 Chauveau . 78 Chauveau . 78 Corrtevin 80 TABLE OF ILLUSTRATIONS. PIG. 49. Horse's head (anterior face) 50. Horse's head (posterior face) 51. Horse's head (lateral face 52. Ass's head (lateral face) 53. Crania of different breeds of Dogs 54. Front view of the human cranium 55. External or basilar surface of human skull 56. The sternum 57. Typical ribs of the Horse 58. Thorax of Man (anterior face) 59. Si-apula of the Horse (external face) 60. Scapula of the Horse (internal face) 61. Scapula of the Cat and Rabbit 62. Antero-external view of right humerus 63. Posterior view of right humerus 64. Humerus of the Cat and Rabbit 65. External face of the radius and ulna 66 Forearm bones of the Ass 67. Right fore foot of a Horse . 68. Carpus of the Horse (anterior face) 69. Carpus of the Horse (posterior face) 70. Posterior view of right metacarpus 71. Forearm and foot of the Ox (front view) 72. Lateral view of the digital region (outside of right limb) 73. Posterior view of anterior digital region 74. Plantar surface of third phalanx 75. Navicular bone 76. Anterior limb of the Pig 77. Forearm and foot of the Dog (anterior face) 78. Human scapula (external aspect) 79. Right human humeruti (anterior surface) 80. Human arm-bones (front view) . 81. Palmar surface of left human hand . 82. Hand of Man and the domestic Mammalia, normal and 83. The ossa innominata (seen from below) . 84. Pelvis (antero-lateral view) . 85. Pelvis (lateral view) . , 86. Pelvis of the Horse . . . 87. Pelvis of the Mare 88. Pelvic bones of the Cat and Rabbit . 89. Left femur (anterior view) . , 90. Left femur (posterior view) . 91. Section of left femur, showing its structure 92. Femur of the cat and rabbit 93. Posterior view of right tibia 94. Leg-bone of the Mule 95. Patella of the Horse (superior and posterior face) 96. Patella of the Horse (anterior face) . 97. Leg-bones of the Cat and Rabbit 98. Left liind foot (external aspect) 99. Tarsus of the Horse 100. Left hock (front view) 101. Left hock (internal aspect) 102. Posterior aspect of left metatarsus . 103. Human pelvis (female) . 104. Right human femur (anterior aspect) 105. Human tibia and fibula of right leg (anterior aspect) 106. Dorsal suifaee of left human foot 107. Anterior limb of the Horse (antero-external view) 108. Posterior limb of the Horse (aDtero-external view) 109. Skeleton of a Fowl .... PAGE Original 81 , Original 81 . . CJuiuveau . 84 , . Chauveau . 85 . . Chauveau . 89 , . Wilson 90 Wilson 91 , . Chauveau . 93 , . Chauveau . 94 . , Wilson 97 . . Chauveau . 99 Chauveau . 99 . Chauveau . 100 , . Original 101 . . Original 102 , Chauveau . 103 . . Original 104 . „ Chauveau 106 . Original 108 . Chauveau 109 . . Chauveau . 109 Original 111 „ Chauveau 113 \ . Original 114 , . Original 114 . Original 116 , Original 117 Chauveau 118 . Chauveau 118 Wilson 119 , , Wilson 120 Wilson 120 Wilson 121 teratological Chauveau 122 Chauveau . 127 Original . 129 Original . 129 Chauveau 132 . , Chauveau . 133 ■ . . Chauveau 136 . . Original 138 , . Original . 138 . . Original 139 . Chauveau . 140 . . Original . 141 , . Chauveau . 142 . . Chauveau . 143 . Chauveau . 143 Chauveau . 144 . . Original . 145 . Chauveau . 146 . . Original . 147 Original . 147 . . Original . 149 , Wilson . 151 Wilson . 152 , . Wilson . 152 . Wilson . 152 Chauveau . 155 , . Chauveau . 156 . Chauveau . 159 TABLE OF ILLUSTRATIONS. nr.. 110. Head of a Fowl (natural size: posterior view) 111. Sternum and bones of the wing . 112. Thoracic or pectoral vertebra of a Mammal 113. Caudal vertebra of the Turbot . 114. Cephalic vertebrae of the Dog ..... 115. Plans of the different classes of articulations . . Beaunis 116. Section of branchial cartilage of Tadpole . . . . 117. Fibro-cartilage .... 118. White or non-elastic fibrous tissue . 11!>. Yellow or elastic fibrous tissue . . 120. Cervical ligament and deep muscles of the Horse's neck 121. Intervertebral articulations 122. Cervical ligament of the Ox 123. Cervical ligament of the young Camel . 124. Atlu-axoid and occipito-atloid articulations . 12.5. Temporo-maxillary articulation . 126. Articulations of the ribs with the vertebrae (upper plane) 127. Articulations of the ribs with the vertebrae (inferior plane) 128. Scapulo-humeral and humeroradial articulations (external face) 129. Carpal articulations (front view) .... 130. Lateral view of the carpal articulations . . » . 131. Details of the metacarpo-phalangeal articulation of the Horse . 132. Carpal, metacarpal, and inter-phalungeal articulations of the Horse . 138. Section of inferior row of carpal bones, and metacarpal and suspensory ligament ..'..... 134. Posterior view of metacarpo-phalangeal and interphalangeal articu- lations ....... 135. Mctatarso-phalangeal and interphalangeal articulations of the Horse 136. Articulation of the foot (inferior face) .... 187. Longitudinal and vertical section of the digital region of the Horse 138. Tendnns and ligaments of the posterior face of the digital region of the Ox ...... . 189. Sacro-iliac and coxo-femoral articulations .... 140. Sacroiliac and coxo-femoral articulations 141. Feraoro-tibial articulation ...... 142. Ligaments attaching the three bones of the leg . 143. Tarsal articulations (front view) . . . . . 144. Articulations of the tarsus (lateral view) . 145. Ultimate fibril of muscle ...... 146. Striated muscular- tissue fibre ..... 147. Primitive fibre of red muscle . . . . . 148. Torn muscular fibre ...... 149. Primitive muscular fibre ...... 150. Relation of primitive.rauscular fibres with tendon 151. Transverse section of frozen muscle . . . • . 152. Arrangement of the fibres of a muscle . . . Beaunis 153. Distribution of capillaries in muscle . . . . . 154. Portion of elementary muscular fibre .... 155. Striated fibre of muscle during contraction .... 156. Horse fixed in first position ..... 157. Horse fixed in second position . . . . . 158. Lateral view of the neck (superficial muscles) . 159. Superficial muscles of the neck and spinal region of the back and loins 160. Lateral view of the neck (middle layer of muscles) . 161. Cervical ligament and deep muscles of the neck . 162. Muscles of the spinal region of the neck, back, and loins 163. Deep ditto ....... 164. Muscles of the back and cervix of Man . . . . 165. Muscles of the sublumbar, patellar, and internal crural regions . 166. Deep muscles of the sublumbar region .... 167. Sacro-iliac and coxo-femoral muscles .... PACh Chnuveau . 160 Chauveau . 164 Chduveau . 168 Chauveau . 168 Lavocat 168 and Bouchard 171 Carpenter . 172 Wilson 173 Carpfnter . 174 Carpenter . 174 Chuureau . 181 Chauveau . 182 Chauveau . 184 Chauveau . 185 Chauveau . 187 Chauveau . 188 Chauveau . 191 Chauveau . 191 Chauveau . 196 Chauveau . 201 Chauveau . 202 Chauveau . 204 Chauveau . 205 Chauveau . 207 Original 208 Chauveau . 210 Chauveau . 210 Chauveau . 211 Chauveau . 211 Chauveau . 213 Chauveau . 214 Chauveau . 217 Chauveau . 220 Chauveau . 222 Chauveau . 224 Bowman 232 Bowman 232 Renaut 233 Renaut 233 Renaut 234 Renaut 234 Kiihne 235 and Bouchard 236 Berres 236 Beale 237 Bowman 237 Chauveau . 240 Chauveau . 241 Original 245 Chauveau . 247 Original 248 Ch' niveau . 251 Chauveau . 261 Chauveau . 264 Wilson 267 Chauveau . 270 Cliauveau . 271 Chauveau . 273 XXX TABLE OF ILLUSTBATIONS. no. 168. Superficial musclee of the face and head . • . . 169. Muscles of external ear of Mule . 170. Muscles of the ear ....... 171. Hyoideal and pharyngeal regions .... 172. Superficial muscles of the Ox's head .... 173. Muscles of the human head .... 174. Muscles of the axillary and cervical regions . . « 175. Axillary and thoracic muscles ..... 176. Muscles of the inferior abdominal region (Ass) . . 177. Muscles of the anterior aspect of the body of Man . . 178. Diaphragm (posterior face) ...... 179. External muscles of the anterior limb .... 180. Muscles of anterior aspect of Man's upper arm . . 181. Internal aspect of left anterior limb .... 182. Deep muscles on external aspect of right anterior limb , . 1 83. Tendons and bursse of anterior limb of Horse 184. Flexor tendons of phalanges of Horse . . . . 1 85. Muscles of the forearm of the Ox ... . 186. Tendinous and ligamentous apparatus in the digital region of the Ox 187. Anterior antibrachial region of the Pig 188. Muscles of the forearm and paw of the Dog . . . 189. Superficial muscles of human forearm .... 190. Deep layer of superficial muscles of human forearm . 191. Muscles of human hand . . . . . 192. Dissecting- table ....... 193. Superficial muscles of the croup and thigh . . 194. Superficial muscles of the croup and thigh . . . 195. Muscles of the sublumbar, patellar, and internal crural regions 196. Deep muscles of the coxo-femonil region 197. Coccygeal and deep muscles surrounding the coxo-femoral articu- lation ..... 198. Superficial muscles of the croup and tliigli in the Cow 199. Muscles of the anterior femoral region in Man 200 Muscles of the posterior femoral and gluteal region in Man 201. External deep muscles of right posterior limb 202. Flexor muscle of metatarsus 203. Muscles on inner aspect of left posterior limb 204. Articular capsules and bursas in posterior limb . 205. External muscles of the leg of the Ox 206. Muscles of the human leg (anterior tibial region) 207. Superficial posterior muscles of the human leg 208. First layer of plantar muscles of human foot . . , 209. Third and part of second layer of plantar muscles of human foot 210. Squamous epithelium from the mouth . . . , 211. Columnar epithelium ...... 2 1 2. Columnar ciliated epithelium .... 213. Conical villi on mucous membrane of small intestine . 214. Fusiform cells of smooth muscular fibre . . , , 215. Hard and soft palate ..... 216. Composite papilla from tongue of Dog .... 217. Simple filiform papillae ..... 218. Foramen of Morgagni . ..... 219. Vertical section of a foramen cfiBCum ... 220. Muscles of the tongue, soft palate, and pharynx . . . 221. Lobe of racemose gland from the floor of the mouth . 222. Follicular gland ....... 223. Section of an amygdaloid follicle .... 224. Median longitudinal section of the head and upper part of neck 225. Magnified section of a canine tooth. . . . , 226. Section through the fang of a molar tooth . , 227. Transverse section of enamel . . . . c PAO« Original 275 Chauveau 280 Original 282 Original 287 Chauveau 290 Wihon 291 Chauveau 294 Original 295 Chauveau . 304 Wihon 306 Chauveau 309 Chauveau , 311 Wilson 317 Original 318 Original 321 Chauveau . 329 Chauveau 331 Chauveau . 333 Chauveau . 334 Chauveau . 335 Chauveau . 337 Wilson 339 Wilson 339 Wilson 342 Chauveau 344 Chauveau . 345 Original 347 Chauveau . 354 Chauveau , 356 Chauveau 358 Chauveau 359 Wihon 361 Wihon 361 Original 363 Chauveau 365 Original 367 Chauneau 370 Chauveau 372 Wilson 375 Wilson 375 Wilson 377 Wilson 377 Wihon 393 Kolliker 393 Carpenter 393 Wilson 394 Bowman 395 Chauveau 399 Chauveau 402 Chauveau 402 Chauveau 403 Chauveau 403 Chauveau 405 Kdlliker ■106 Kdlliker 406 Chauveau 407 Original 409 Wilson 412 Carpenter 413 Carpenter 414 TABLE OF ILLUSTRATIONS. xud no. 228. Theoretical section of dental eac of permanent incisor 229. Section of dentine and pulp of an incisor tooth . 230. Dentition of inferior jaw of Horse 231. Section of incisor tooth of Horse 232. Incisor teeth of Horse (details of structure) . 233. Profile of upper teeth of the Horse 234. Transverse section of Horse's upper molar . 235. The teeth of the Ox . 236. Ox's incisor tooth ..... 237. Incisor teeth of a Sheep two years old . 238. Teeth of the Pig . . . 239. General and lateral view of the Dog's teeth . . 240. Anterior view of the incisors and canine teeth of Dog 241. Ijateral and general view of the Cat's teeth 242. Dentition of the Rabbit .... 243. Section of the human face .... 244. Lobule of parotid gland .... 245. Capillary network of follicles of parotid gland . . 246. Termination of tlie nerves in the salivary glands 247. Inferior aspect of head and neck . . . 248. Maxillary and sublingual glands 249. Pharyngeal and laryngeal region 250. Median lengitudinal section of head and upper part of neck 251. Pharynx of the Horse (posterior view) . . . 252. Muscles of the pharyngeal and hyoideal regions 253. Human pharynx ..... 254. Transverse vertical section of head and neck . 255. Pectoral cavity and mediastinum 256. Theoretical transverse section of nbdominal cavity . 257. Theoretical, longitudinal, and median section of abdominal 258. The abdominal cavity, with the stomach and other organs 259.* Stomach of the Horse ..... 260. Interior of the Horse's stomach 261. Muscular fibres of stomach (external and middle layers) 262. Deep and middle muscular fibres of stomach . 263. Peptic gastric gland ..... 264 Portion of a peptic c«cum .... 265. Mucous gastric gland ... 266. Capillaries of mucous membrane of stomach 267. Stomacli of the Dog ... 268. Stomach of tiie Ox . 269. Interior of the stomacli of Ruminants 270. Section of the wall of the omasum of Sheep . . 271. Stomach of the Sheep .... 272. Section of the omasum of the Sheep 273. Section of a leaf of the omasum . . . 274. Longitudinal section of a large papilla from the omasTUU 275. Villi of human and Sheep's intestine 276. Portion of Brunner's gland .... 277. Section through Peyer's patch of Sheep . 278. Section through solitary follicle . . . 279. Injected villi of intestine . , 280. Blood-vessels in Peyerian glandula . 281. Diagram of origin of lacteals in villi 282. General view of the intestines of the Horse (right elde) 283. General view of the Horse's intestines (inferior aspect) 284. The colon of the Horse . . 285. Plan of the colon .... 286. Intestines of the Rabbit (general view) . 287. Stomach and intestines of the Sheep . . 288. General view of the intestines of the Ox . cavity Chauveau Carpenter Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Quain Wagner Berres Pfluger Original Chauveau Original Original Chauveau Original Wilson Original Chauveau Chauveau Chauveau Original Chauveau Chauveau Chauveau Chauveau KoUiker Kolliker KoUiker Carpenter Cliauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Chauveau Teichmann Thomson Teichmann Teichmann KoUiker Kolliker Funke Chauveau Chauveau Original Chauveau Qiauveau Chauveau Chauveau PAGE 415 416 418 418 419 421 422 425 425 427 428 429 429 429 430 432 434 434 435 436 437 441 442 443 445 447 448 449 452 453 456 457 458 460 460 461 461 462 462 463 464 465 467 468 469 470 470 474 474 475 476 476 477 477 479 480 481 482 486 487 488 TABLE OF ILLUSTRATIONS. FIG. 289. 290. 291. 292. 2:»3. 29i. 295. 29t). 297. 298. 299. 300. 3(Jl. 302. 303. 304. 305. 306. 307. 308. 309. 310. 311. 312 313. 314. 315. 316. 317. 3.8. 319. 320. 321. 322. 323. 324 325. 326. 327. 328. 329. 330. 331. 332. 3.33. 334. 335. 336. 337. 338. 339. 340. 341. 342. 343. 344. 345. 346. 347. 348. 349. General view of the intestines of the Pi" Intestines of the Dog . . " Digestive apparatus of the Cat . Human intestines . . Abdominal cavity, with the liver and other organs i^ortion of a hepatic column, with secreting cells Biliary capillaries and ducts Blood-vessels in lobules of liver Section of lobules of liver, with intra-lobular'veins iiiscretory apparatus of the Horse's liver Structure of the spleen (diagrammatic) . Malpighian corpuscles attached to splenic artery bplemc corpuscle from the spleen of Ox Liver of the Ox . Liver of the Dog, wiih its excretory Apparatus . * Under surface of the human liver General view of the digestive apparatus of a Fowl * Cartdages of the nostrils Transverse section of the head of a Horse c^eils ot the olfactory mucous membrane Fibres of olfactory nerve Cartilages of the larynx disarticulated Superior face of larynx . . . . Inferior lace of larynx Muscles of tlie Horse's larynx ' . * Postero-lateral view of larynx * • • . Entrance to the lar.vnx of the Horse 1 lie respiratory orgaus (inferior aspect) . * * ' Trachea, bronchi, and lungs of the Horse . ' Ciliated epithelium from the trachea Bronchial tube, with its bronchules Mucous membrane of a bronchial tube Iheoretical section of thoracic cavity, behind the heart * Theoretical section of thoracic cavity, at root of lungs inZXTuZ::' ''!"^*° ^^:^*-^' '^ ^^^^^ ^^ ^^^^ --^-^^ Lungs of the Horse . Cast of bronchiole Cast of bioncliial divisions Plan of a pulmonary lobule Infundibula of lung . Capillaries around the infundibula of lung Lung of the Sheep (inferior view) Human lungs and heart . Gland-vesicles of thyroid Portion of thymus of Calf Course and termination of ducts in thym^ gland of Calf General view of the air-sacs in the Duck General view of the genito-urinary apparatus in 'the Horse Horizontal longitudinal section of the Horse's kidnev Section of the cortical substance of the kidney Course of the uriniferous tubuli . Diagram of the circulation in the kidney Transvi'rse horizontal section of kidney The kidneys and bla.lder in the foetus of Solipeds Right kidney „f Ox (upper and external face) . Left kidney of Ox (internal and inferior face) Ihe cahces in left kidney of Ox Theoretical plan of the circulatory system The heart and principal vessels (left face) * . PACE Chauveau . 489 . Chauveau . 490 Chauveau . 491 Wils07i . 492 Original . 496 . Leidy . 493 . Irminger and Frey 498 . Kiernan . 499 Kiernan . 499 Chauveau . 500 Beaunis and Bouchard 504 . Kolliker . 505 Kolliher . 505 . Chauveau . 508 Chauveau . 509 Wilson , 510 • Chauveau . 513 Chauveau . 519 Chauveau . 520 Original . 521 Clarke and Schulfze 523 . Fcker . 524 . Chauveau . .^28 • Chauveau . 531 • Chauveau . 531 Chnuveati . 532 Original . 533 . Chauveau . 535 . Original , 537 Chauveau . 538 Kolliker . 539 . Heale , .540 Heale . 541 Chauveau . 545 Chauveau . 545 Chauveau . 545 Chauveau . ' 546 Chauveau . 548 Chauveau . 549 Chauveau . 550 Waters . 551 Kolliker . 551 Carpenter . 551 Chauveau . 553 Wilson . 553 Kolliker . 554 Kolliker . 556 Wilson . 556 Chauveau . 564 Chauveau , 569 Chauveau . 371 Ecker . 572 Hertz . 573 Bowman . 573 Original . 574 Chauveau . 577 Chauveau . 580 Chauveau . 580 Chauveau . 580 Colin . 582 Chauveau . 585 TABLE OF ILLUSTRATIONS. VIO. PAOR 350. The heart and principal vessele (right face) . . . Chauveau . 586 351. Rijjlit side of the heart laid open ..... Wilson . 587 352. Section of the heart at the level of the valves . . . Sibson . 589 353. Left cavities of the heart laid open ..... Wilson . 591 354. Auriculo-veutricular fibro-Ciirtiiaginous rings . . . Parchappe . 592 355. Anastomo.sing muscular fibres of heart .... Kolliker . 594 356. Mu3cular \vh~irl at point of iieart .... Bourgery . 594 357. Posterior unitive fibres of auricles ..... Bourgery . 595 358. E|)itlieliuni of the endocardium ..... Kolliker . 597 359 Human lungs and henrt (front view) .... Wilton . 599 360. Web of Frog's foot, showing blood-vessels and their anastomoses Wagner . 603 361. Epithelial cells of blood-vessels ..... Kdiliker . 604 362. Fenestrated membrane from the carotid artery of the Horse . Kolliker . 604 363. Coarse elastic tissue from pulmonary artery of the Horse . Kolliker . 604 364. Transition of a minute artery of the brain into capillary vessels . Kolliker , 605 365. Abdominal or posterior aorta and coeliac axis in the Horse . Chauveau . 614 366. Distribution of the small mesenteric artery .... Chauveau . 619 367. Arteries of the stomach of Ruminants .... Chauveau . 622 368. Lateral view of the genito-urinary organs in the male . . Chauveau . 627 369. Abdominal aorta, with its branches, in Man . . . Wilson . 628 370. The external and internal iliac arteries in the Mare . . Chauveau . 630 371. Principal arteries of posterior foot of Horse . . . Chauveau . 637 372. Anterior aspect of human leg and foot .... Wilson . 642 373. Posterior aspect of iiuman leg ..... Wilson . 642 374. Arteries of sole of human foot ..... Wilson , 643 375. Distribution of the anterior aorta .... Chauveau . 647 376. Terminations of the axillary artery in the Horse . . . Chauveau . 651 377. Arterits of the anterior foot (seen from behind) . . . Chauveau . 653 378. Arteries of the anterior foot of the Horse .... Chauveau , 655 379. Arteries of the human forearm and hand . . . Wilson . 660 380. Arteries of the brain ...... Chauveau . 666 381. Arteries of the head ...... Chauveau . 668 382. Rete mirabile of the Siieep (seen in profile) .... Chauveau 678 383. Rete mirabile of the Ox (post'-rior face) . . . . Chauveau . 680 384. Arteries of the face and head of Man .... Heath . 681 885. Radicles and collateral branches of the jugular vein in the Horse Chauveau . 691 386. Sinuses of the dura mater and radicles of the jugular vein of the Horse ........ Chauveau . 693 387. Subsphenoidal confluents in the Horse .... Chauveau . 695 388. Veins of the foot ...... . Bouley . 700 389. General view of the veins in the Horse .... Chauveau . 704 390. Vena portse and its roots ...... Chauveau . 707 *391. A lymphatic vessel with its valves .... Chauveau . 714 392. Section of a lymphatic rete mirabile .... Teichmann . 717 393. Section of lymphatic gland ..... Kolliker . 718 394. Section of simple lymphatic gland ..... Teichmann . 718 395. Section of the medullary substance of lymphatic gland of Ox . Kolliker . 719 396. Ordinary disposition of the thoracic duct .... Colin . 723 397. Double variety of the thoracic duct . . . .. Colin . 723 398. Triple variety of the thoracic duct ..... Colin . 723 399. Lymphatic system of tlie Horse ..... Colin . 725 400. Great lympliatic vein and entrance of the thoracic dnct . . Colin . 731 401. Great lymphatic duct (another variety) .... Colin . 731 402. Thoracic duct in the Ox . . . . . Colin . 732 403. A variety of the thoracic duct in tiie Ox . . . Colin . 733 404. Another variety of the tlioracic duct .... Colin . 733 405. A fourth variety of the thoracic duct .... Colin . 733 406. I'horacic duct of small Ruminants ..... Colin . 734 407. Diagram of structure of nerve-fibre .... Carpenter . 740 408. Nerve-tube ........ Ranvier . 740 *09. Multipolar or stellate nerve-cell . . • . ikker . 741 8 XXXIT TABLE OF ILLUSTBATI0N8. FIG. 410. Several multipolar nerve-cella .... 411. Pyrumidal cell of the grey substance . • 412. Ganglion from heart of Frog • - . . 413. Bipolar ganglionic cells and nerve-fibree 414. Stellate nerve-cell ..... 41.'^. Structure of ganglionic cells .... 416. General view of tlie spinal cord 417. Spinal cord at the cervical bulb or brachial plexus 418. Section of the spinal cord of the Horse at the lumbar region 419. Transverse section of spinal cord in the lumbar region . 420. Transverse section of spinal cord of Man in the middle of the lumbar region ...... 421. Ganglionic cell from the inferior coriiu of spinal cord . 422. Longitudinal section through cervical bulb of spinal cord of the Cat 423. Brain of the Horse (upper surface) . 424. General view of the brain (lower surface) . . 425. Superior view of the encephalic isthmus 426. Lateral view of the isthmus .... 427. Transverse section of the brain . . • 428. Dissection of the medulla oblongata . • 429. Median and vertical section of the brain 430. Layers and cells of grey mutter of cerebellum . 431. Section of the cortical substance of the cerebellum . 432. Antero-posterior and vertical section of the brain • 433. Brain of the Horse (lateral face) 434. Corpus Ciillosum ..... 435. Anterior portion of the lateral ventricles 436. Transverse section of human brain . . 437. Course of association nerve-fibres . . . 438. Course of association fibres in corpus callosum . • 439. (jourse of radiating fibres in the corona radiata 440. Layers and cells of a frontal convolution . . 441. Corticle substauc- of the cerebral hemispheres 442. Brain of the Ox . 443. Brain of the Sheep . . . . • 444. Brain of the Pig ..... 445. Lateral face of the Dog's brain 446. Br:iin of the Dog (upper face) ... 447. Brain of the Cat . 4^8. Base of the human brain .... 449. Muscular fibres, with teimination of motor nerve . 450. Nerves of the eye ..... 451. Section of the pons Varolii ... % 452. Lateral view of the medulla oblongata . 453. General view of the superior and inferior maxillary nerves 454. Section of medulla oblongata and pons Varolii . 455. Section of middle portion of medulla oblongata 456. Origin of the nerves arising from the medulla oblongata 457. Origin and distribution of the eighth pair of nerves in Man 458. Distribution of the nerves in the larynx of the Horse 459. Deep nerves of the head .... 460. Nerves of the guttural region in the Ox. 461. Innervation of submaxillary and sublingual glands . 462. Nerves of the face and scalp of Man 4(;3. Distribution of eighth pair of nerves on left side 461. Ganglion of a spinal nerve from the lumbar region . 465. Nerves of the brachial plexus . . . 466. External nerves of anterior limb . . . 467. Nerves of the digit of Horse . . . 468. Nerves of the digital region of Ruminants . 469. Nerves of the palmar face of Dog's foot . . PAG7 , Chauveau . 741 Chauveau . 741 , Ecker 742 . Ecker 742 , , Beale 742 . Beale and Arnold 742 , Colin 755 , Colin 755 , Chauveau . 757 , Deiters 758 e lumbar I. L Clarke 759 , KrauHe 760 the Cat I. L. Clarke 761 , Chauveau . 764 , Chauveau . 766 , , Chauveau . 770 ^ Chauveau . 773 , , CJiauveau . 775 Solly a7iJ Carpenter 776 Chauveau . 780 Duval 781 ^ ^ Kolliker 782 . CJiauveau . 783 , , CUiauveau . 787 , Chauveau . 789 , Chauveau . 789 , Ediiiger 793 , . Edinijer 794 . Edinger 795 . Edinger 795 , Cliauveau . 796 , Kolliker 796 . Chauveau . 797 , Cliauveau . 798 . Chauveau . 799 , , Chauveau . 800 , Chauveau . 801 , , Chauveau . 801 Hi/rachfeld and Leveill€ 802 , . Cohnheim . 806 , Chauveau . 812 , , Duval 814 , Erb 815 , , Chauveau . 818 , Duval 825 , Duval 833 , TouAGB 870 871 872 875 877 879 883 884 884 886 888 895 900 900 liOl 901 902 902 903 905 908 909 910 912 912 ,914 914 915 916 916 919 919 927 931 931 932 933 935 935 936 940 948 949 949 950 953 954 963 963 964 965 967 969 974 975 977 978 979 982 985 TABLE OF ILLUSTRATIONS. TIC. 530. Ovaries, oviducts, and uterus of a foetus (equine) 531. Ovarium of the Rabbit .... 532. Constituent parts of Mammalian ovum, entire . 533. Constituent parts of Mammalian ovum, ruptured . 534. Formation of the corpus luteum 535. Generative organs of the Mare, isolated 536. Generative organs of the Mare, in situ . 537. Termination of milk-duct in cluster of follicles 538. Ultimate follicles of mammary gland, with secreting cells 539. Microscopic appearance of milk 540. Human uterus, witii its appendages . . . 541. Ovary of the Bird ..... 542. Graafian vesicle . . . . » 543. Optical section of ovum of Rabbit . . . 544. Ovum of Rabbit . . . . • 545. Blastodermic vesicle of Rabbit . . . 546. Section of a Fowl's unhatched egg . . • 547. Area pellucida in early blastoderm . • 548. Transverse section of blastoderm . . • .549. Area pellucida of blastoderm . . • 550. Area pellucida in blastoderm . . . • 551. Transverse section of blastoderm . . . 552. Transverse section of dorsal region 553. Manner in which embryo and envelopes are formed 554. Diagram of foetal membranes .... 555. Exterior of the chorial sac (Mare) . 5.')ft Different parts of foetal Horse .... 557. Foetus of the Mare, with its envelopes 558. Portion of ultimate ramifications of umbilical vessels . 5,59. Vertical section of injected placenta 560. Portion of one of the foetal villi .561.. Equine foetus, opened on left side to show umbilical vessels 562. Blood-vessels in liver of an equine foetus at mid-term . 563. Liver of a Lamb at birth .... 564. Foetus of the Sheep ..... 565. Vertical section of a maternal cotyledon 566. Embryo of the Chick ..... 567. Section of embryo Duck .... 568. Embryo of the Chick ..... 569. Transverse section of embryo of Chick on third day 570. Plan of development of eye .... 571. Origin of encephalic centres in human embryo of fourth week 572. Plan of chorda dorsalis at period of formation of embryo 573. Plan of vertebra at an early period of development 574. Head of a foetal Lamb, showing Meckel's cartilage 575. Plan of first system of vessels (embryo) 576. Embryonic heart at an early period (anterior view) 577. Ditto, seen from behind .... 578. Heart of an equine foetus .... 579. Plan of tlie aorta and its arches at an early period . 580. Plan of the circulation in the human embryo (side view) 581. Section of embryo of Habbit 582. First appearance of the lungs .... 583. Embryo of Dog at twenty-five days 584. Origin of liver from intestinal wall of embryo Chick . 585. Urinary and genital apparatus in embryo Chick . Chauveau Pouchet Coste Coste Pouchet Chauveau Chauveau Sir A. Cooper Lehert Funke Wilson Chauveau Balhiani Van Beneden Van Beneden KoUiker Thomson Balfour Balfour Balfour Balfour Balfour Balfour Balfour Turner Chauveau Chauveau Chauveau Carpenter Turner Ecker Chauveau Colin Colin Chauveau Turner Balfour Balfour Balfour KoUiker KoUiker Wagner KoUiker KoUiker Huxley KoUiker KoUiker Kdlliker Chauveau Kdlliker Coste Balfour Wagner , Bischoff Miiller , Miiller THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS. GENERAL CONSIDERATIONS. DEFINITION AND DIVISIONS OP ANATOMY. Anatomy is the science of organization ; it studies the structure of animals when these are dead. It comprises two grand divisions — physiological anatomy^ which describes healthy organs, and pathological anatomy, the object of which is the description of diseased organs. Physiological anatomy, which alone is treated of in this book, in its turn embraces — 1. General anatomy, which is occupied with similar substances or tissues of the animal body, with regard to their texture, and their physical, chemical, and physiological properties, irrespective of the organs in which these tissues are found. The particular study of the anatomical elements entering into the composition of the tissues, is named histology. Histology necessarily requires the aid of the microscope. 2. Descriptive anatomy, which studies the situation, form, and relations of organs, as well as the relative arrangement of the various tissues composing them, with the exception of the structure and properties of these tissues. If this study be devoted to a single species, it is designated special anatomy. Example : human anatomy, or anthropotomy ; the anatomy of the Horse, or hippotomy. When descriptive anatomy embraces the study of the organization of the entire animal kingdom, and examines the differences which characterize the same organ or the same series of organs in each class, family, genus, or species, it is named comparative anatomy. Restricted to the domesticated animals, this study constitutes veterinary anatomy. Philosophical or transcendental anatomy differs from comparative anatomy, in that it indicates the analogies of organs or apparatus, rather than their differences, in order to exhibit as clearly as possible the general laws of organization. Finally, if descriptive anatomy be limited to denoting the relations existing between the various organs of a region, particularly with a view to the perform- ance of operations and the diagnosis of external diseases, it takes the names of topographical, regional, or surgical anatomy. 2 GENERAL CONSIDERATIONS. Enumeration and Classification of the Species of Domesticated Animals. The object of this book is the study of veterinary/ anatomy. The animals of which it treats belong to the Mammiferous class and to that of Birds. The domesticated Mammals of our climates have their representatives in a large number of orders. Thus, we find among them — 1. Of the Carnivora, the Dog and Cat; 2. A Kodent, the Rabbit ; 3. A Pachyderm, the Fig ; 4. Of Solipeds, the Horse and Ass ; the produce of the Male Ass with the mare, i.e. the Mule, and that of the Horse with the Female Ass, known by the name of Hinny ; 5. Of Ruminants, the Ox, Sheefp, and Goat. With regard to Poultry, they range themselves — 1. In the Gallinaceous or Columba order, the genera to which the Common Fowl, Guinea Fotvl, Turkey, and Figeon belong ; In the order of Palmipeds, the Goose and Duck. Girard has proposed a special classification for the domesticated Mammals, based upon the number of digits terminating each of their limbs, and has defined four categories : the first comprises the Horse, Ass, Mule, and Hinny, which take the name of monodactyles, because their digital region is composed of a single digit ; in the second, under the denomination of didadyles or hisulcate animals, those with two digits, such as the Ox, Sheep, and Goat ; in the third, or regular tetradactyles, is found the Pig, each of whose limbs has four digits ; lastly, the Dog and Cat, which most frequently have four digits on the posterior members and five on the anterior ones, and form the class of irregular tetradactyles. This nomenclature will not be followed here, as it is opposed to the general laws of organization. Philosophical anatomy has, in fact, demonstrated that there are really no true monodactyles, didactyles, etc. ; all are materially or virtually pentadactyles. It is therefore considered better to keep to the classification established by zoologists, because it prevents confusion in scientific language. The regimen and habits of the domesticated animals bring about differences in their organization ; these appear very great at first sight, though in reality they are not so marked as they seem. In order to study the descriptive anatomy of all these animals, we will not pass them in review, one after another, giving for each the description of every organ ; but shall take a type, which will most frequently be the Horse, implicitly compared with man, and briefly compare all the others with it. In this com- parison, the animals will be generally classed according to their domestic value ; though exceptions will be made to the rule which has been instituted by our predecessors, whenever any advantage in point of concision or perspicuity is likely to be obtained. General Ideas of the Organization of Animals. Order followed in studying the Various Apparatuses. The bodies of animals contain fluid and solid organic matters, as well as gases and some mineral substances. Organic Fluids. — The fluids are very abundant in the animal economy; GENERAL CONSIDERATIONS. 3 not only do they fill certain vessels constructed for them, but they also impregnate all the solid parts of the body. Their importance is very great, for without them the organic solids would perish ; an element deprived of humidity is ipso facto deprived of life. These fluids vary in their nature and composition. Apart from those that the solids imbibe, there is not one which is completely amorphous. In the midst of a liquid holding organized matter in solution, there are always formed elements which will be referred to hereafter. Examples : the blood and lymph. Organic Solids.— 4n studying the organic solids, we will proceed from the simple to the complex. Solid organized matter is amorphous — as in the hyaline substance of cartilage and the fundamental substance of bone tissue, or it assumes the form of more or less voluminous particles in every instance invisible to the naked eye, and to which the name of anatomical elements has been given. They may be reduced to three principal : the granule, the cell, and the fibre. Granules. — These are the smallest known elements. They may be held in suspension in animal fluids, remain free among the other elements, or be enclosed in the interior of cells. Their nature is not always the same : they are proteiCy fatty, or pigmentary. The piymentary granules are of a brown colour. Cells. — The cell is pre-eminently the anatomical element. Theoretically, the cell is a microscopic mass of a nitrogenous substance, viscid {protoplasm or sarcode), imiformly transparent, or slightly granular. Frequently in the midst of this protoplasm there is perceived a nucleus provided with a nucleolus, and at its periphery an enveloping membrane. The cell lives like an entire organism : it feeds, grows, multiplies, absorbs, secretes, moves, etc. It behaves like a complete animal, though it be a micro- scopic one. The form of the cell, as well as its volume and nature, vary. It has therefore received various names. There are round, polyhedral, fusiform, conical, stellate, and other shaped cells. Some have a diameter of 1-1 2000th part of an inch, while others are l-2000th part. Cells multiply in various ways : 1st, by the division of the nucleus and segmentation of the protoplasm in the interior of the enveloping membrane {endogenous multiplication) ; 2nd, by constriction, then division of the nucleus, protoplasm, and enveloping membrane {/issiparous multiplication) ; 3rd, by a kind of bulging or swelling of the enveloping membrane, and constriction and separation of the enlargement thus formed {gemmation). A large number of cells only temporarily remain in this condition. In con- sequence of modifications that cannot be referred to here^ they are converted into fibrillffi or other elements, in which it is difficult to recognize the primordial element. Others maintain the cellular form : then they develop, live, and die in several ways. Sometimes they are worn by the contact of foreign bodies, as on the sur- face of the skin ; sometimes they become liquefied, as in some glands ; and at other times they undergo fatty degeneration, which gradually brings about their complete destruction. The permanent cells are — 1. Rcematies or red corpuscles, which are found in a state of suspension in the blood ; they are round and discoid in Mammalia, with the exception of the Camel and Llama, in which they are elliptical, as well as in Birds, Reptiles, and 4 GENERAL CONSIDERATIONS. * the majority of Fishes. These cells have an envelope, but they do not have a nucleus in Mammalia ; 2. Leucocytes, white corpuscles, or lymph ceZZs, which float in the blood, lymph, chyle, and the connective tissue interspaces. These cells are susceptible of amse- boid movements, and their fundamental form is spherical ; though they are often irregular in shape, owing to the contractile prolongations they throw out, called pseupodes. They may have one or more irregular nuclei ; 3. Connective cells, which are flat, nucleated, and irregular ; they are applied to the fasciculi of connective fibres ; 4. Adipose cells, lying in the connective tissue and filled with fat, which has pushed the protoplasm and nucleus towards the envelope ; 5. Medullary cells, with a budding nucleus or multiple nuclei (myeloplaxes and medullo-cells), forming the principal elements of the marrow of bones ; 6. Ckirtilage cells, which have no envelope, and which, single or associated with a variable intermediate substance, form cartilages ; 7. Bone cells, lodged in a space remarkable for its elliptical shape and the numerous prolongations on its margin. The cells are nucleated, have no envelope, and secrete the fundamental sohd substance of the bony tissue ; 8. Contractile cells, which constitute the basis of muscular tissue. They are fusiform and nucleated ; 9. Nerve cells, met with in the cerebro-spinal centres and the ganglia of the cerebro-spinal and sympathetic systems. They are provided with one, two, or more prolongations called poles ; hence they are uni-, hi-, or multipolar. 10. Epithelial cells, found on the surface of tegumentary membranes, or laid over the interior of more or less divert iculated cavities (glandular cavities or glands). The epithelial element is lamellar or polyhedric, cylindrical, calcif orm, vibratile, etc, 11. Endothelial cells, always lamellar, and lining serous cavities and vascular canals. Fibres. — A fibre is an elongated element of variable dimensions and com- position. Thus, it may be very fine (connective fibre), or thick and limited by two borders more or less apart {muscular fibre) ; it is homogeneous throughout {elastic fibre), or has a contents and a distinct envelope {ne^'ve fibre). The vitality of fibres is not comparable with that of cells. Once formed, they are only nourished, for it is not yet definitely ascertained whether they can multiply. In the animal economy there are four kinds of fibres — 1. Connective fibre, an extremely fine element, but in which, nevertheless, two borders can be distinguished if it be examined by a power of from 800 to 1000 diameters. The fibres form fasciculi in the connective tissue, or are distri- buted in the midst of a fundamental substance — as in the fibro-cartilages. The connective fibre constitutes the most solid organs of the animal economy — the ligaments, tendons, etc. 2. Elastic fibre, found closely packed in certain organs, such as the cervical ligament and abdominal tunic, or forming a network in the midst of connective tissue ; it is even found in the framework of bones. 3. Muscular fibre, smooth or striped (striated), which has the property of contracting under the influence of stimuli. Smooth (or unstriped), is found in a large number of viscera ; striped is more especially in the domain of the locomotory apparatus. 4. Nerve fibre, very remarkable for its continuous axis-cylinder. It is foimd in the nerve centres, cerebro-spinal nerves, and great sympathetic system. GENERAL CONSIDERATIONS. 5 Inorganic Substances. — These substances {gaaes and mineral matters) are usually found in solution in the animal fluids. Their presence is indispensable in the constitution of the livina: body. Sometimes the mineral matters are solid, amorphous, or crystallized. In this condition they are rarely met with in healthy organs {internal ear) ; but they are frequently found in diseased ones. Tissues. — The anatomical elements, by being grouped in different manners, form tissues. Some tissues are constituted by one kind of element ; these are simple tissues— for example, epithelial tissue. But the larger number are formed by a combination of several different elements ; these are composite tissues — for example, nerve tissue. The anatomical, physico-chemical, and physiological characters of the tissues, are repeated, it need scarcely be remarked, in the anatomical, physico-chemical, and physiological properties of the elements which enter into their composition. Only four simple types of fundamental tissue are described, and which are based on the morphological, chemical, and physiological characters of the constituent elements — 1 . In the first place, there are to be noted the tissues of connective substance or framework, comprising the varieties of connective tissue, fibrous tissue, elastic tissue, cartilaginous tissue, and l)o?ie tissue. 2. Then there are the cellular tissues, formed entirely of persistent cells ; they are the epithelial tissue proper, and the glandular tissue. The cells of the epithelial tissue are differently arranged. If they are disposed in a single layer, they constitute a simple epithelium. ,- but if superposed so as to form two or more layers, then it is a stratified epithelium. According to the form of the superficial layer of cells, the epithelium is polyhedric, pavement, cylindrical, spherical, or caldform. In certain parts the superficial cells are furnished with vibratile cilia, and the epithelium is then called vihratile (or ciliated). 3. The third type is represented by the muscular tissue, the agent of move- ment, which is divided into striated and non-striated muscle. 4. Lastly, there is the nerve tissue, which is present under two aspects — white substance and grey substance. The first is formed entirely of nerve fibres and a supporting tissue or neuroglia ; the second by fibres and nerve cells united by neuroglia. The grey substance belongs to the most important portions of the nervous system — the brain, spinal cord, and ganglia, where it co-exists, with the white substance. The latter entirely constitutes the peripheral ramifications of the nervous system. Organs. — The term " organ " is given to any portion of the body having a determinate form and a function to fulfil. A bone, a muscle, the stomach, the liver, and the brain, are organs. General Arrangement of the Organs and Apparatus. — All animal organs are enclosed between two membranes named limitary or tegumentary membranes, which are continuous with one another at the margin of the natural openings. These are the sJcin and the mucous membranes, in the composition of which are included a layer of connective tissue and an epithelium Organs protected by these membranes are solid or hollow. Among the first, a certain number act as supports : such are the organs formed by the connective tissue, and particularly the cartilages and bones. Others are destmed to produce movements : these are the muscles. The action of the muscles is communicated directly to the organs that are to be « GENERAL CONSIDERATIONS moved, or it is transmitted through the medium of other orgaus, such as the tendons and the aponeuroses. The central nervous organs — the nerves properly so called — belong to this group of solid oro-ans. The activity of muscles and the sensibility of limitary membranes are due to them. With regard to the hollow organs, they are everywhere formed by an envelope of smooth (or unstriped) muscular tissue, lined by an internal tegumentary or mucous membrane. Examples : the bladder and stomach. There must also be included the vessels formed by elastic and contractile membranes arranged as canals, in which the blood and lymph circulate ; the glands, and, lastly, the serous membranes which line the interior of the splanchnic cavities, cover the surface of the organs contained in them, and the inner face of the articulations and synovial sheaths. It is remarkable that, in the trunk, the bones form two superposed cylinders,, one of which lodges the organs of circulation, digestion, and respiration, and the other the central nervous system {neural and hmmal ajHnder). Appaeatus. — Organs are very numerous in the animal economy, and in order to study them profitably it is necessary to classify them in a methodical manner^ according to their physiological affinities. Consequently, there have been col- lected into a single category all those organs which are destined to achieve the same physiological finality, and to such a group has been given the name of apparatus. Bichat has grouped the apparatuses according to the ultimate object of their functions, and has thus formed two great categories : one, comprising the apparatuses which maintain the individual {apparatuses of nutrition atid relation) ; the other, the apparatus destined for the preservation of the species {apparatus of generation). We will describe these apparatuses in the following order : — 1. Locomotor y Apparatus ; 2. Digestive Apparatus ; 3. Respiratory Apparatus ; 4. Urinary Depurative Apparatus ; 5. Circulatory Apparatus ; 6. Innervatory Apparatus ; 7. Sensory Apparatus ; 8. Generative Apparatus. This description will be terminated by a brief notice of the evolution of ths /obtus^ and its aj^endages. BOOK I. LocoMOTORY Apparatus. The locomotory apparatus is composed of all those organs which minister to the movements an animal may execute. It is certainly one of the most important in the economy, from the niunber and size of the pieces which enter into its formation, and by the necessary co-operation it affords the majority of the other apparatuses in the performance of the physiological acts allotted to them. It is constituted of two kinds of organs— the bones and muscles. The lones^ hard and resisting, stony in appearance, are really inert levers, joined by firm and movable articulations, which permit their playing upon each other with the greatest facihty, at the same time maintaining them in their relative positions. The muscles, grouped around the bones and attached to them, are soft organs which possess the property of contraction, under certain determinate conditions, and of involving in that movement the bones to which they are fixed by their extremities. The bones are altogether passive in their motion, while the muscles are really the active organs of locomotion — the power intended to move the bony levers. We will study, successively — 1. The bones, a particular branch of descriptive anatomy which has received the name of Osteology ; 2. The articulations, or Arthrology ; 8. The muscles, or Myology. FIRST SECTION. The Bones. CHAPTER I. THE BONES IN GENERAL. Bones, properly speaking, are only to be found in vertebrate animals, and constitute their principal zoological chara«ter. In the animal body they form an internal framework which consolidates the entire edifice, and gives it its general form and dimensions. It is advantageous, before commencing a particular description of each bone, to survey them in a general manner. This study comprises: 1. The description of the skeleton; 2. A summary indication of B THE BONES. the gen&ral principles which should be known, in order to comprehend the details of the special descriptions. Article I, — The Skeleton. The whole of the bones, considered in their natural relations to each other, constitute the skeleton. In order to prepare the skeleton of any animal, it is SKELETON OF THE DOG. sufficient to free it from the soft parts surrounding it. The skeleton should be designated natural^ if in this operation the hgaments that naturally join the SKELET^ OF THE CAT. various pieces together are allowed to remain ; and artificial if, after these liga- ments have been destroyed, it is necessary to replace them by materials foreign to the organization, such as iron or brass wire. TEE SKELETON. 9 The skeleton is divided into trunk and limbs. 1. The trunk offers for consideration, in the middle line, the spine or vertebral column — a flexible stalk measuring the entire length of the animal, and composed of a series of distinct pieces articulated one behind the other. An- teriorly, this stalk supports the head—a. pyramidal mass which results from the assemblage of a large number of bones. On each side of the middle portion of Fig. 3. SKELETON OF THE PIG. the spine, there are detached bony arches which have received the name of ribs, and which rest, directly or indirectly, by their inferior extremities, on a single bone called the sternum. These bony arches in this way circumscribe the thorax — a spacious cavity destined for the reception of the principal organs of respiration and circulation. 2. The limbs, four in number — two anterior and two posterior — are the ap- Fig. 4. SKEIiETON OF THE RABBIT. pendages which support the trunk of the domestic Mammals. They are usually distinguished as anterior and posterior (or fore and hiyid), but it will be more convenient to name them according to their relations, as thoracic (or pectoral) and abdominal limbs. Each represents a column divided into several rays resting upon one another, and generally forming more or less open angles. The anterior limbs 10 THE BONES. are each divisible into four principal regions : the shoulder, applied against the front part of the thorax ; the arm, which succeeds the shoulder ; and the fore- SKELETON OF THE HORSE. arm, and foot. The posfprior limbs also comprise four regions : the haunch or pelvis, which articulates with the posterior part of the spine : and the thigh, leg, and posterior foot. Fig. 6. SKELETON OF THE COW. In Birds, the posterior limbs alone assume the function of columns of support. The thoracic limbs, formed for flight, constitute the wings. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 11 The number of bones entering into the composition of the skeleton of the principal domesticated animals, arrived at the adult period of life, varies accord- Fig. 7. SKELETON OF THE SHEEP. ing to the species. They are apportioned to the regions of the trunk and limbs just mentioned, in the manner indicated in the following table : — Designatiok. SOLIPEDS.' Ruminants. Pig. Dog.' Vertebral Column' 48 45 50 46 Head* 28 37 28 27 29 29 28 27 Thorax SJioulder \ 1— 2 1— 2 . 1— 2 1— 2 Arm . I— 2 1— 2 1— 2 1— 2 Forearm 1 \ 2— 2 2— 4 2— 4 2— 4 Fore foot Pelvis ^ Double regions J 16-32 1— 2 20—40 1— 2 36—72 1— 2 36—72 1— 2 Thigh \ 1— 2 1— 2 1— 2 1— 2 Leg . 3— 6 3— 6 3— 6 3— 6 Hind foot ^ \ 15—30 19—38 36-72 32—64 Tc tals 191 196 270 255 Article II. — General Principles applicable to the Study of all THE Bones. The description of a bone comprises its name, situation, shape, internal con- formation, structure, and mode of development. ' One lumbar vertebra less is found in the Ass, and sometimes also in the Mule. * The 08 penis has not been included. * The sacrum is reckoned ns a single bone, and the number of coccygeal vertebrsB at an average of 16 for the Horse, 18 f r the Ox. 22 for the Pig, and 18 for the Dog. * The OS hyoides is reckoned as a single bone. 12 IDE BONES. Name. The nomenclature of osteology does not rest on any basis capable of confer- ring upon it a methodic form. Consequently, we find bones which derive their name from their shape (example : the fibula) ; others from their resemblance to known objects (the tibia and vomer). Some owe it to their position (the frontal bone), or their uses (the axis and parietal bones). Several attempts have been made to submit the nomenclature of the bones to more precise GENERAL FRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 13 and uniform rules, but the new designations proposed have not been sanctioned by custom. Situation. The situation of a bone should be viewed in two ways : 1st, Relative to the median plane of the body ; 2ud, Relative to the other portions of the skeleton. A. Situation relative to the median plane of the body. — The designation of median plane, improperly medimi line, is given to an imaginary vertical plane passing through the middle of the skeleton, which it divides from before to behind, into two equal portions. The bones may be situated on the median plane, in which case there is only one of each kind, and they are called single ; they are also named symmetrical hones, because the median plane divides them into equal lateral halves exactly alike. ^ The bones disposed in a double and regular manner on the sides of the median plane bear, for this reason, the name of pair bones ; they are also called asymmetrical bones, because their form does not admit of their being divided, in any sense, into two similar portions. On the contrary, a bone of this kind always offers the most perfect symmetry with its fellow on the opposite side.- B. Relative situation to the other parts of the skeleton. — To indicate the situation of a bone, considered from this point of view, is to make known the place it occupies in the region to which it belongs, and the connections it may have with adjoining regions. Thus, the radius is situated in front of the ulna, between the arm-bone and the carpus. Direction. This is absolute or relative. A. The absolute direction is related to the axes of the bones themselves. Thus it is that a bone may be rectilinear, curvilinear, or twisted. B. The relative direction is determined by the relation to the fictitious planes established around or in the interior of the skeleton, or with regard to the neighbouring bones. For example, a bone is vertical, horizontal, or oblique. In the latter case it may be downwards and backwards, or in the reverse direction. Example : the scapula is placed obliquely downwards and forwards. Shape of the Bones. FoKM. — This is also absolute or relative. A. Absolute Form. — The absolute form of a bone is that which it owes to the relations existing between its three dimensions — length, width, and thickness. a. A bone in which one of its dimensions much exceeds those of the other two is a long bone (example : the femur), provided it be hollowed out interaally by an elongated space — the medullary canal. Long bones belong exclusively to the limbs. In the animal economy there are found bones which resemble them in their dimensions, but they have no medullary canal (example :. the ribs). These differ essentially from the true long bones, and are also distinguished from them by the appellation of elongated bones, b. A bone that offers two dimensions much more developed than the third, is a flat or wide bone (example : the parietal bone). The bones of this category, destitute of a medullary cavity, are ' Instano's have been recorded of asymmetry in sfngle bones. Lesbre has seen the sixth cervical vertebra of the Horse tricuspid on one side and bicuspid on tlie other, and a last dorsal vertebra with one of its transverse processes having the characters of the lumbar vertebrae. ' But there might be slight differences in weight, torsion, etc. In Man there is nearly always a difference between the right and the left side. 4 14 TEE BONES. met with in the head and the upper regions of the limbs, c. A bone which offers nearly the same development in all its dimensions, is called a short bone (example : the astragalus). Destitute, like the preceding, of a medullary canal, the short bones are found in the spine and some regions of the limbs. B. Relative Form. —To make known the relative form of a bone, is to indicate the greater or less exact resemblance it may bear to geometrical figures, or to familiar objects. Thus, the scapula is a bone of a triangular shape. Regions of the Bones. — When describing the eminences and external cavities of bones, it is essential not to allude to them casually by passing indifferently from one to another. To avoid the difficulties resulting from the application of such an irrational system, it is necessary to divide the bone to be studied into several regions, in which external peculiarities can be examined successively, as they present themselves. The general course to be followed in order to learn the regions of a long, a flat, and a short bone, is as follows : — a. A long bone is always divided into three parts — a body and two extremities. The bodij or middle portion, or diaphijsis, is the narrowest part of the bone. In shape it is a geometrical solid, inclining somewhat to that of a very long prism. On the body of a bone, therefore, there are studied as many faces and planes, angles or borders, as on the prism it represents. The extremities, or epiphyses, are more or less considerable enlargements, formed primarily by a special bony nucleus, and offering articular surfaces, as well as surfaces for muscular or ligamentous insertion. h. A flat bone must necessarily have two faces, and borders and angles. c. A short bone has more or less faces, and plane or salient angles which are often ignored, because of their trifling importance. External Peculiarities of Bones. — These markedly attract the attention, because they modify the general shape of bones, and singularly assist in distinguishing one bone from another. These peculiarities, which are real distinctive features that permit their description to be precisely established, are always either eminences or cavities, according to their different uses. A. Eminences. — The eminences that stand out in relief from the surfaces of bones, are divided into two different categories. One class concurs in the formation of the articulations which join the bones to each other ; they are named articular eminences, in which, again, are distinguished diarthrodial and synarthrodial eminences, according as they belong to movable or immovable articulations. The others, usually destined for the insertion of ligaments and muscles, are called non-articular eminences or eminences of insertion. (The term imprint is also used in anatomy, and signifies a collection of small rugged eminences which make the surface of the bone uneven and rough. There are muscular, tendinous, ligamentous, and aponeurotic imprints, according as they give attachment to muscles, tendons, ligaments, or aponeuroses.) a. The synarthrodial eminences are always indentations more or less deep and finely cut, which stud the border of large bones. b. The diarthrodial eminences are volimainous, smooth, and in a fresh state covered with cartilage. They are named heads and condyles : heads, when they describe the segment of a sphere (head of the femur, head of the humerus) ; condyles, when they represent an ovoid segment cut parallel to its larger axis (condyles of the femur). c. The non-artwular eminences receive various names. If they are volumi- nous and much detached from the bone, they are called processes or apophyses. GEN Ell AL PBiNOIPLES APPLICABLE TO TUE STUDY OF ALL THE BONES. 15 Apopliyses receive (jualificatives derived from the aualoLfies perceived between them and knowu objects (examples : the styloid, clinoid, corouoid, and coracoid processes). The appellations of p-otubcra tires and tuhnoaities are given to non- articular eminences when they are large and round, and slightly detached. Lastly, they are named lines, crests, and ridges, when they are narrow and very long. The processes are sometimes epiphysary in early life, and formed by a special nucleus, B. Cavities. — The cavities of bones have also been divided into articular, diartJirodinl or syiiarthrodial, and non-articular cavities. a. The dinrtJiroditd ravities correspond to the eminences of the same name in the bony joints. They take the designation of glenoid cavities when they are oval and shallow, and cotyloid cavities when they are deeply excavated, like a basin or the cup of an acorn (examples : the glenoid cavity of the scapula, and the cotyloid cavity of the coxa). The synctrtJirodial cavities fit into the dentations opposed to them. b. The non-articular cavities serve either for ligamentous or muscular insertion, or for the passage of vessels, nerves, tendons, etc. They are termed channels or furrotrs, when they are wide, deep, and smooth ; grooves, when they are long, narrow, and smooth at the bottom ; and fissures, when they are narrow and rugged. Digital impressions is the name given to those excavations in bones which look as if produced by the pressure of the finger. The fossce, sinuses, cells, and notches are also non-articular cavities of bones. The sinuses and cells are formed by open spaces in the interior of bones ; notches, by cavities excavated on their margins. When a cavity passes quite through a bone, it is termed a foramen. If this foramen has a certain length, it is designated a conduit or canal. Fissures are long, narrow openings ; hiatus is the term appUed to a wide opening with an irregular outline. In order to aid the memory, the external peculiarities of bones are grouped in the following synoptical table : — Articulars . ^Non-Articulars I Synarthrodials \ Diarthrodials . Apophyses or processes . Protuberances. Tuberosities. Lines Crests. Dentations. Heads. Articulara • . .4 \Synarthrodia.8 .(^Sons. Condyles. Styloid-. « T>- .u A- , /Glenoids. jMartbrod.als -(cotyloids. Clin. .ids. U Channels. Coronoids. \- Furrows. Coracoids. Grooves. Mastoids. o Digital impressions. «• Fossae. Sinuses. Non-Articulars .. Cells. Notches. Foraminae. Canals. Ducts. Slits. Hiatuses. Internal Conformation of Bones, Sections made in various directions through the substance of bones, show that their internal conformation varies, according as they belong to the category of long, flat, or short bones. The diaphysis of long bones is hollowed out into a large fusiform cavity — the medullary canal. This' canal is absent in the flat and short bones, and is replaced by irregular cavities which communicate with each other, called medullary spaces. Its walls are formed by a very dense bony tissue. 16 THE BONES. the pores of which are scarcely visible to the naked eye, and which is called the compact substance. The extremities of long bones are surrounded by a thin layer of compact substance, while the remainder of their mass is constituted by the sponffi/ substance— honj tissue channeled into medullary spaces. {Reticulated bony tissue is but another form of spongy substance, the only difference between the two consisting in the cells or meshes of the first being formed of intercrossed osseous fibres, while those of the second are formed of lamellcB.) The medullary canal, and areolse of the spongy tissue, are filled by the marrow (or medulla). The flat bones are constituted by a layer of spongy tissue placed between two plates of compact substance. (In the flat bones of the cranium, the two layers of compact tissue are termed the vitreous tables, while the cells of the spongy tissue are designated diploe.) In certain points of their extent, the spongy substance disappears, and then the bone is composed of a single lamina of compact tissue. The short bones have a nucleus of spongy substance, enveloped in a layer, more or less thick, of compact tissue. The compact substance of the bones, being very resisting, is found in all those situations which have to sustain violent efforts. The spongy substance is very light when compared with its volume, and is met with in the wider portions of the bones, to which it affords increased size without adding sensibly to their weight. Structure of Bones. Bones are formed of a proper tissue, covered externally by a particular membrane — the periosteum, and occupied internally by the medulla, vessels, and nerves. A. Proper tissue. — The elements of the proper tissue of bone are always and everywhere the same ; the texture alone is modified in the compact and spongy substance. Everywhere the bone tissue is composed of a funda- mental substance, which is amorphous or slightly granular, white, and more or less opaque, according to the thickness it offers. This fundamental substance is penetrated by an infinite number of vascular canaliculi {bofie cavities), with prolongations (bone canaliculi), ^_^_^ which contain cells (bone cells). The cavities and their ipii^ %%~m\1 ( ■;'■ contents are named, osseous corpuscles or osteoplasts. In U^l I l\(-i ur~^nll\JfU a dried plate of bone, the corpuscles appear dark when viewed by reflected light, white and shining by direct light. In the spongy tissue, the bone corpuscles, anasto- mosing by the ends of their canaliculi, are distributed °^ throughout the lamellae of fundamental substance, which is intercrossed in such a way as to circumscribe the numerous medullary spaces. In the compact tissue, the corpuscles are regularly distributed in the substance of the bony lamellae, which are arranged in concentric layers. In a transverse section of the diaphysis of a long bone, it is noticed that the fundamental substance is excavated by an infinite number of vascular canaliculi, named Haversian canals (Figs. 9, 10). These canals measure from l-2500th to 1 -200th of an inch in diameter, and are parallel to each other and to the larger Fig. 9. VERTICAL SECTION OF BONE showing the network Haversian canals. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 17 axis of the bone ; they communicate frequently by transverse branches. While the most superficial open on the surface of the bone, beneath the periosteimi, and the deepest into the medullary canal, a certain number terminate in the areolae of the spongy substance at the ends of the bones. ^'^" ^^' The walls of these canals are con- stituted by several concentric lamella) of fundamental substance, in which are lodged the essential elements of the bony tissue. Each canal, with its vessels, its system of concentric lamellae, its osteoplasts, and its osseous canaliculi, forms a whole (the Haversian system) which represents the complete bone in miniature. All the Haversian systems preserve a certain independence ; the canaliculi of each, after reaching the mi^^te structure of bone, as shown in a thin • 1 1 11 n , 1 i section cut transversely to the direction of the periphery, are nearly all reflected to- Haversian canals. wards the centre (the recurrent canaliculi l, A Haversian canal surrounded by its concentric lamellae ; the lacunae are seen between the lamellae, but the radiating tubuli are omitted; 2, ibid., with its concentric laminae, lacunae, and radiating tubuli ; 3, the area of one of the canals ; 4, 4, intervening lamellae, and between them, at the upper part, several very long lacunae with their tubuli. Fig. 11. LACUN^ OR OSTEOPLASTS OF OSSEOUS SUBSTANCE, magnified 500 diameters. a, Central cavity ; 6, its ramifications. of Rcmvier) and rejoin the canaliculi of the same system, instead of anasto- mosing with those of the neighbouring system. Between the Haversian systems, there are the intermediate systems of lamellae which fill the spaces left through the imperfect contact of the former. In all the long bones there is a system of 2)eripher((l lamelhc, enveloping, ex- ternally, all the Haversian systems ; while a system of perimedullary lamellm, more or less perfect, also exists at the inner surface of the medullary canal. Sharpey observed that the peripheral bony lamellaj were traversed by fibres {Sharpei/s or peif orating fibres), and J. Renaut has remarked in the same lamellae the presence of elastic fibres. The proper tissue of bones is a framework of organic matter which has gelatine for its base, and in which are deposited the calcareous phosphates and carbonates which give to this tissue its characteristic hardness. This is easily rendered evident by immersing any bone in dilute nitric or hydro- chloric acid ; acid dissolve the calcareous salts, but do not act upon the organic framework. So it is, that after some days' maceration the bone becomes flexible, like cartilage, and loses part of its weight, although it preserves its volume and shape. The counterpart of this experiment may be made by submitting it to the action of fire. It is then rendered quite friable, because its organic skeleton has been destroyed, without the earthy salts it contained being affected. B. Periosteum. — This is a very vascular and nervous fibrous membrane which covers the entire bone, with the exception of the articular surfaces and the 18 THE BONES. insertions of tendons and ligaments. Its thickness and adherence are not the same everywhere ; it adheres most closely near the ends of bones. By its inner face it corresponds to the surface of the bone, into which it sends prolongations {arciform fibres) which ultimately become Sharpey's fibres : by its external face, it is continuous with the surrounding connective tissue and that of the muscular aponeuroses. The periosteum may be resolved into two layers, though these are not always very distinct. The superficial layer is essentially fibrous, and is formed by a network of elastic fibres containing bundles of longitudinal fibres and cells. The deep layer is a closer elastic network, with finer connective tissue fibres, and a larger quantity of cells and vessels. This is called the osteogenous layers because of its functions. C. Medulla. — The medulla, or marrow, is a pulpy, fatty substance, which fills the medullary canal and the areolae of the spongy tissue of the bones, and partly the Haversian canals. Somewhat consistent, and of a rosy tint in the bones of young animals, the marrow becomes diffluent and yellow in the bones • of those advanced in age, except in the vertebrae of the Horse, Ox, Dog, etc., and in the limbs of the Rabbit. In the first state, it is also mucous or fibrous in the cranial and facial bones undergoing development, and, rosy in colour, it only contains traces of fat ; while in the second, it has 96 per cent, of this substance. The medulla of bones is composed of : 1st, some trabeculae of delicate connective tissue and a network of stellate cells, to support the vessels and nerves ; 2nd, fat cells ; 3rd, particular cells, named by M. Robin medullo- cells and myeloplaxes. The medullo-cells, abundant in the red or foetal marrow, are small cells with a spherical or budding nucleus {Bizzozerd's cells), analogous to the lymph cells ; some are impregnated with haemoglobine. With regard to the myeloplaxes, these are enormous flat cells, irregular in outline, and containing a large number of nuclei. Rare in the yellow marrow, they are more particularly found adhering to the walls of the medullary canal, or the alveoli of the spongy tissue. D. Blood-vessels. — The arteries of bones belong to three orders — a distinction based on their volume and the extent of their distribution. The arteries of the first order penetrate to the interior of the medullary canal of long bones, by a particular orifice — the nutrient foramen. They soon divide into two branches, which break up into a network that lines the walls of the canal and enters the tissue of the medulla. This network communicates with the arteries of the second order, which go to the spongy tissue of the extremities of the long bones, penetrating them by the numerous nutritive foramina that surround the epiphyses. Lastly, the arteries of the third order are branches of the periostic network that enters the superficial Haversian canals. These canals may be considered, strictly speaking, as a third category of nutrient conduits. In the flat and short bones there are no arteries of the first order. Veins accompany the arteries, and are always more voluminous than these ; they frequently make their exit by special and very large openings at those points where the spongy tissue is abundant. The veins of bones sometimes exhibit saccular dilatations on their course. Certain veins in the cranial bones have their walls partly or entirely channeled in the bony tissue ; they are lined by a simple endothelium, E. Lymphatic vessels. — The existence of these cannot be affirmed. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 19 Nerves. — These belong to the cerebro-spinal and ganglionic system of nerves ; the latter are always vaso-motor nerves. Almost constantly, a somewhat voluminous nerve enters the medullary canal, by passing through the nutrient foramen, and is distributed to the medulla. The compact tissue receives few nerve filaments ; while, on the contrary, the spongy tissue at the extremities of the long bones, as well as the short bones,, contains many. Certain short bones, such as the vertebrte, are especially remarkable for the numerous nerves they receive. DEVELOPMENT OP BONES. The bones, before arriving at the condition in which we see them in the adult animal, pass through several successive phases, the study of which consti- tutes Osteogeny. Nearly all the bones were originally cartilaginous, those of the roof of the cranium and the face being only represented by fibrous tissue. We will examine the development of these cartilaginous and fibrous bones. A. Development of the Cartilaginous Bones. — In the embryo at an early period^ the bones are composed of a mucous material analogous to that which enters into the composition of all the other organs ; this matter is constituted by a mass of embryonic cells. Later, they become harder, white, and elastic — that is, cartila- ginous. Certain portions of the skeleton persist in this condition during the life of the animal. These permanent cartilages are found where the bony skeleton must have a certain amount of flexibility, and on the articular surfaces. The temporary cartilages, like the permanent, have a fundamental amorphous 01 hyaline substance, in which are embedded round cells containing one or several nuclei. But they soon undergo modifications, which result in giving to the pieces they form the hardness and structure of perfect osseous tissue. These modifications gradually cause the cartilage to disappear, and to be replaced by bony tissue, without the skeleton ceasing for an instant to preserve its form and functions. The process commences by calcification of the peri- chondrium and of the middle part of the diaphysis, which ensures the stability of the organ. Then the blood-vessels, which are constantly present in temporary cartilages, pass through the diaphysary nucleus, ramify, and are directed in a parallel manner towards the extremities. Simultaneously, the chondroplasts are arranged in parallel series in front of the vessels {rivulation of the cartilage), and finish by merging into large, irregular, elongated cavities, incompletely separated by bands of fundamental substance of the calcified cartilage, designated the directing lines of ossification. The blood-vessels enter these cavities, carrying to their surface cells which proliferate, and are differentiated into osteoblasts or productive cells of bone. The osteoblasts are deposited, layer upon layer, against the walls of the spaces limited by the lines of ossification, and form, by a kind of secretion, concentric strata of the osseous fundamental system which surrounds them ; then the osteoblasts become osteoplasts. The cavities made in the cartilage finish by becoming filled up, except at the centre, where a central cylindrical, space remains (Haversian canal), and a blood-vessel. In the extremities of the bones, where there are no Haversian canals, the preparatory modifications are the same as in the diaphysis, only the cartilaginous cells collect in small irregular masses, and not in parallel piles. Each of these 20 THE BONES. Fig. 12. masses forms layers of bone substance, that finish by constituting the lamellae of spongy tissue at the periphery and medullary tissue at the centre, to fill the areolae of the latter. In this way is accomplished the transformation of cartilage into bone. As will have been observed, it is not a mere calcification of the cartilaginous tissue, but a real substitution of bone tissue, presenting the following phases : 1. Peri- chondrial and endochondral calcification in places (nuclei or centres of ossifica- tion). 2. Invasion of the centres of ossification by vessels, rivulation of the cartilage. 3. Medullization of the cartilage, and formation of osteoblasts. 4. Development of the bone tissue, appearance of the osteoplasts. B. Development of the Fibrous Bones. — The bones originally fibrous are not merely charged with lime salts in order to acquire a bony appearance. They do not pass through a transitory cartilaginous state, but the phenomena of ossification take place in the fibrous tissue in the following manner : — The fasciculi of connective tissue become calcified, separate here and there from one another to form spaces, into which blood-vessels enter or osteoblasts appear. To this phase of medullization succeeds the phase of ossification, which is accomplished in the same manner as in the cartilaginous bones. Only the directing lines are represented by connective fasciculi, which later become Sharpey's fibres. C. Progress of Ossijication. — Ossification com- mences simultaneously in several parts of the skeleton, and in each of the bones in particular — though not throughout their entire extent at the same time. On CARTILAGE AT THE SEAT OF the coutrary, in certain determinate points of the carti- ossiFicATioN, showing at ifc laginous or fibrous mass, osseous tissue is developed ircells^"rirged*m column'! ^^^ich, gradually extending, ends by completely in- each of which is enclosed in a vadiug it. Thcsc poiuts are named nuclei (or centres) sheath of calcified intercellular ^f ossificatiou. The uuclci are primitive or comple- substance. , mi i i • , mentary. ihe latter, termed epiphyses, are in a fashion added to the bone, and wholly or partly form certain apophyses. Although these centres of ossificatiou increase from day to day, they never- theless remain for a long time independent of each other, and are united only by cartilage. When the skeleton is completely developed, the various centres of ossification become joined to each other, and the entire bone forms one piece ; there are no longer any apophyses. Up to the present time, attempts to discover the laws which govern the appearance of the centres of ossification have been futile ; the size of the bone counts for nothing ; and the influence of proximity to the centres of circulation, which has been sometimes brought forward (for the sternum, for example, which is never completely ossified), cannot be accepted. The law which presides over the union of the centres of ossification has also been sought for. A. Berard imagined he could formulate it in the following proposition .- Of the two extremities of a long bone, it is always that towards which the nutrient foramen is directed that is first united to the body of the bone. But to Berard's OENEBAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 21 law there are numerous exceptions ; and in order to demonstrate that it is not absolute, it is sufficient to indicate that the direction of the nutrient foramen varies much, not only in similar bones of different species of animals, but ako in similar bones of the same species ; and yet the progress of ossification is alwajs the same. The period when fusion of the epiphyses terminates in the domestic animals is still little known ; fusion is evidently complete when growth is achieved, but this period is markedly modified by hygiene and the vood animals receive. Renault and some breeders have observed, that in the pre-jocious breeds of cattle the evolution of the teeth is more rapid than in the common breeds. More recently, Sanson has affirmed that precocity, characterized by this prompt dental evolution, is marked by a more rapid fusion of the epiphyses, and he believes there is a direct relation between the evolution of the teeth and that of the bones. According to this principle, in the Horse the fusion of the epiphyses should commence and terminate between three and five years of age. Toussaint, however, did not share this opinion. In the Ox, Sheep, and Horse, he remarked that the first centres of ossification appeared in the body of the flat and the long bones, and in the centrum and arches of the vertebrae. When the first half of gestation had not been passed, no other points of ossifica- tion were seen. It is necessary to add, however, those of the second and third phalanges and the calcis, which comport themselves as long bones. In the last half of gestation, ossification invades the complementary nuclei, as well as the short bones ; the exceptions are the pisiform bone and the inner condyle of the humerus in the Calf and Foal, and the large and small sesamoid bones in the Calf only. Ossification of these bones of the skeleton is slow. It must also be mentioned that at birth the complementary nuclei of the coxoe are not yet visible, and they are not seen until ten months or a year afterwards. With regard to fusion of the epiphyses, it occurs at the following periods in the principal bones of the Horse ; at the twelfth to the fifteenth month in the second phalanx at first, then in the first phalanx ; at the fifteenth to the eighteenth month in the middle metacarpal, afterwards in the metatarsal. At this age fusion also occurs at the upper end of the radius and inferior ex- tremity of the humerus ; from twenty months to two years, at the lower end of the tibia ; from three to three and a half years, at the upper extremity of the humerus, at the two ends of the femur, and at the upper end of the tibia ; lastly, about five years, in the bodies of the vertebras and in the coxa?. In the Ox., ossification progresses at about the same rate as in the Horse, except that there is a little greater precocity in the fusion of the epiphyses of the humerus and radius, which are fused at the same time as those of the phalanges, and matacarpal and metatarsal bones. In this animal, the two lateral halves of the latter bones are united before union of the inferior epiphysis to the body of the bone. The Slieep offers an interesting peculiarity, in that the humero- radial epiphyses are consolidated before those of the phalanges, and towards the tenth month. If the results of these observations, made on our principal domestic animals, are compared with the evolution of the dental system, we are compelled to con- clude, with Toussaint, that fusion of the epiphyses does not commence at the same time as the eruption of the first permanent teeth. If a relationship exists between the evolution of the teeth and that of the bones, it has yet to be demonstrated in an exact manner. 22 THE BONES. Toussaint has also studied the course of ossification in the Dog, Pig, and Eabbit. In the Dog at birth, none of the complementary nuclei have been invaded by ossification. Consequently, bone tissue is only found in the dia- physis of the long and flat bones. In the three months after birth, the great majority of the epiphyses commence to ossify ; and after this period there only remain the pyramidal bone and the complementary nuclei of the coxag, in the cartilaginous condition ; the ossification of these latter commence at from five to six months. The skeleton of the Rabbit is, at birth, in a condition almost identical with that of the Dog ; nearly all the epiphysary nuclei of the humerus and that of the lower end of the femur, however, show osseous points. In the Fiij, at birth ossification is much more advanced than in the Dog ; but it is less so than in the larger Herbivora. The fusion of the epiphyses has been studied in the Dog. It commences at five months, in the phalanges and metacarpals, and continues in the humerus and radius, the corresponding epiphyses of which are consolidated at nine months ; at eighteen months there can be distinguished the nuclei at the upper "border of the scapula, the upper end of the humerus, inferior extremity of the radius and ulna, the epiphyses of the femur, and the bodies of the vertebrse. The latter facts support the preceding ones, and likewise demonstrate that the conclusions of Sanson are probably too absolute. Growth of the Bones. Bones increase by the superposition of new elements, while the soft parts of the organism grow by the interposition of new elements in the mass of pre- existing elements. The manner in which this apposition of new elements is accomplished is not the same in the long, the flat, or the short bones. 1. Long Bones. As a general rule, the long bones elongate by the growth and ossification of the temporary cartilage situated between the diaphysis and the osseous nuclei at the extremities. Consequently, elongation ceases when the primitive or complementary nuclei are fused with one another. The increase in length in the bones of the limbs does not take place everywhere in the same proportion. Duhamel, Flourens, and particularly Oilier and Humphry, have remarked that, in the thoracic limb, the extremity furthest removed from the humero-radial articulation grows fastest ; while in the abdominal limb, the extremity most distant from the femoro-tibial articulation grows the least. With regard to the increase in thickness of the bone, this occurs by ossifica- tion of the deeper layer of the periosteum — the osteogenous lager. The experiments of the authors just mentioned irrefutably demonstrate this, and those of Oilier have even proved that the periosteum may produce bone at a point where it has been transplanted. The periostic bone is developed according to the process of ossification in the fibrous tissue. In a transverse section of the diaphysis of a growing long bone, there is seen, as Laulaine has indicated, concentric circumferences united by radii of osseous substance. The diaphysary portion of the periostic bone is fused with the extremities, through the medium of the ossification notch of Ranvier — a prolongation of the periosteum into the articular enlargement around the cartilage of conjugation. The formation of bone tissue in the deeper layer of the periosteum is very active during the youth of animals, but it soon diminishes, and ceases completely in advanced age. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 23 If the phenomena of g^o^vth were not counterbalanced by those of absorption, long bones would acquire an enormous thickness and weight. But in the first period of life, in proportion as new layers are applied to the surface of bones, the deeper parts — those occupying the axis of the diaphysis — disappear by absorption. lu this way the medullary canal is formed, and a just proportion established between the volume and weight of the skeleton. When the bones are completely formed, during the entire adult period the process of destruction is equal to that of growth, so that their weight and com- position does not vary. At a later period, absorption is greater than the forma- tive force, which in old age is altogether in abeyance ; so that the organic matter of the bones is rarefied, and these lose their elasticity and gain in fragility. It has been remarked that the development of the bones is subordinate, in a certain measure, to the activity and resistance of the organs in their vicinity. Lesshoft and Popoff beheve that the development of a bone is in proportion to the activity of the neighbouring muscles, that the pressure of external organs — such as an aponeurosis — may produce torsion in a bone and retard its growth, so that its greatest thickness will correspond to the point where the surrounding resistances are at a minimum. Oilier, however, has noted that the long bones become more elongated when they do not sustain pressure on their extremities. 2. Flat Bones. — These bones have sometimes only one primary nucleus of ossification, placed in the centre. They grow by the increase of this nucleus, which gradually invades the mass of the bone in radiating from the centre towards the periphery. When they have several nuclei, some of these are at the margin, and in such a case the bones increase by ossification of the margmal epiphyses and growth of the central nucleus. Flat bones increase in thickness by the formation of sub-periosteal layers, and by the development of the spongy tissue between the two compact plates. 8. Short Bones. — These grow in thickness by the progressive ossification of the osteogenic layer of the periosteum ; and in length by ossification of the epiphysary cartilages, when they possess complementary nuclei. Nutrition of Bones. The experiments which consisted in feeding young animals with madder, and afterwards examining their osseous system, have for a long period demonstrated the nutrition of bones. When bones cease to grow, nutrition becomes less active ; but it is evident that it does go on, in order to maintain the organic matter of the osseous tissue in a proper condition. The abundance of vessels carrying blood to all parts of the bone tissue, alone suffices to prove the existence of a nutritive movement in these apparently stonj organs. 24 THE BONES. CHAPTER IL THE BONES OP MAMMALIA IN PARTICULAR. Akticle I. — Yertebeal Column. The vertebral column, or spine, is a solid and flexible stalk situated in the middle and upper part of the trunk, of which it forms the essential portion. It protects the spinal cord and sustains the thorax, as well as the principal organs of circu- lation, respiration, and digestion. Articulated anteriorly with the head, and terminating in a point at its posterior extremity, this stalk is formed by a some- what considerable assemblage of short, single, tuberous bones, to which has been given the name of vertehrce. These bones, though all constructed on a uniform type, yet do not offer the same configuration throughout the whole spine. The differences they present in this respect have permitted their being divided inta five principal groups ; whence the division of the vertebral column in five regions, which are, enumerating them from before to behind : 1. Cervical region. 2. Dorsal region. 3. Lumbar region. 4. Sacral region. 5. Coccygeal regioji. The first comprises seven vertebrae, which serve as a base for the animal's neck ; the second has eighteen, against which the ribs are placed ; the third has only six, which correspond to the loins ; in the fourth there are five, constantly fused into one mass in the adult, to constitute a single bone — the sacrum ; while the fifth possesses a variable number of small degenerate vertebrae, gradually decreasing in size to form the tail. The pieces constituting the first three regions are called true vertebrm ; those of the last two are designated /«7se vertebrce. The subjoined table indicates the number of vertebrae in each of the regions of the spine, in the horse and other domestic Mammalia. Animals. VeBTEBRjE. Cervical. Dorsal. Lumbar. Sacral. Coccygeal. Horse Ox Sheep Goat Camel Pig Dog Cat Rabbit 7 7 7 7 7 7 7 7 7 18 13 13 13 12 14 13 13 12 6 or 5 6 6—7 6 7 6—7 7 7 7 5 5 4 4 4 4 3 3 4 15-18 16—20 16—24 11—12 15—18 21—23 16—21 21 16—18 The characters belonging to all these vertebrae will be first studied ; then a particular description of those of each region will be given ; and, finally, an examination will be made of the spine as a whole. Characters common to all the Vertebrae. Each of these small bones is pierced from before to behind by a wide opening — the spinal foramen, or vertebral canal ; whence results, for the entire spine, a long canal traversing its whole length, and which lodges a very important portion of the nervous centres — the spinal cord. This canal, which traverses the vertebrae VERTEBRA. 25 from one end to the other, transforms it into a ring in which we recognize, for facility of description, two parts — the one inferior, the other superior. The first, or hodij, is very thick, and forma the base of the vertebrae ; the second, which is thin, has been designated spinous or spinal — from one of the pecuharities it presents, or annular — because it circumscribes the major portion of the spinal foramen. This division is not altogether an arbitrary one, for the body and the annular portion constitute, in the foetus, two distinct pieces, which do not become united for a long time after birth. Body {centrum). — The shape of the body of a vertebra is that of a prism Fig. 13. /'!■© ^^^mOW^p I f^. ELEMENTS OF A VERTEBRA. (AFTER OWEK.) A, Ideal typical vertebra; B, Actual thoracic vertebra of a bird; c, Centrum (or body), giving off, rf, d, the diapophyses, and p,p, the parapophyses {transverse and articular processes) ; the neural arch, enclosing the spinal cord, is formed by n, n, the neurapophyses (lamince), smd n, s, the neural spine (spinous process"); the hamal arch, enclosing the great centres of the circulation, is formed by h, h, the haemapophyses (costal cartilages) ; and h, s, the haemal spine (sternum). From both the neurapophyses and haemapophyses may be given off the zygapo- physes, z, z. The lateral arches, which may enclose the vertebral arteries, o, o, are completed by the pleurapophyses (ribs), pi. ; these in B are bent downwards, so as to form part of the ha;mal arch, and give off the diverging appendages, a, a. with four faces, of which two only — the superior and inferior — are free, and can be studied in the adult ; the two lateral faces are united and confounded with the annular portion. This prism also presents two extremities — an anterior and iposterior. Faces. — The superior face, limited in extent, forms part of the spinal foramen, constituting its floor. It exhibits : 1. On the middle hne, two roughened, prominent surfaces, representing two triangles, whose summits are opposed. 2, On the sides, two depressed smooth surfaces, perforated by one or more openings that lead to the interior of the bone. The inferior face is divided into two lateral portions by a median crest (the htemal spine). Extremities. — The anterior has a prominent convex head, more or less detached. The posterior offers a cavity for the reception of the head of the next vertebra. These two planes — the one convex, the other concave — do not come into immediate contact ; an elastic, flexible fibro-cartilage, firmly attached to each, is interposed between them. 26 THE BONES. Annular Portion (neural arch or neurop&physes). — This is formed by an osseous plate that curves suddenly downwards, in the shape of an arch, the two extremities of which approach each other, enclose the body, and become united to it. It offers for study: 1. An internal and an external surface. 2. An anterior and a posterior border. Surfaces. — The internal surface, concave and smooth, forms, with the superior face of the body, the spinal foramen. The external, convex and irregular, pre- sents : 1 . A single prominence, raised in the middle of the superior portion, and named the spinous process {neural spine). 2. The transverse jrrocesses (diapo- physes) are a double pair of eminences, one on each side, and projected trans- versely outwards. Borders. — The anterior border has two articular facets looking upwards : these are the anterior articular processes {prezygopophyses'), right and left. In each is a notch which, when placed in opposition to a similar excavation in the preceding vertebra, forms the intervertebral foramen. The posterior border pre- sents the same peculiarities, with this difference, that the articular faces of the posterior articular processes {postzyyopophyses) are inclined downwards, to corre- spond with the anterior facets of the succeeding vertebra.^ Structure of the vertebr(e,. — The compact substance, which is abundant in the spinous portion, forms in the body an extremely thin layer, inclosing a volumi- nous nucleus of spongy tissue. The latter is traversed by numerous venous canals, which open on the surface of the bone. Development. — It has been already shown that the body and spinous portion of a vertebra constitute, in young animals, two distinct pieces. Each was primarily formed from two lateral centres, which met on the median line. In the body, the fusion of these centres is so prompt, that it is generally believed, perhaps justly, that the development of this part of the vertebra proceeds from a single centre of ossification. The union of the two centres in the annular portion, usually designated the vertebral lamince {p)arapophyses), is slower. It commences in the most anterior vertebrfe, and is latest in the sacral and coccy- geal regions. To the three principal pieces of the vertebra in process of ossification, are added, at a subsequent period, complementary centres of ossifi- cation, variable in number according to the regions and species of animal ; there is always one for each of the anterior and posterior surfaces of the vertebral bodies ; while others, much less constant, concur to form the spinous and transverse processes. Characters proper to the Vertebrae of each Region. A casual inspection of a vertebra might suffice, strictly speaking, to dis- tinguish the region of the spine to which it belonged. For instance, a cervical vertebra is recognized by its volume, the absence of a spinous process, and the foramen which traverses the base of its transverse processes. The dorsal vertebra is conspicuous by its tubercular transverse processes, and by being furnished, outwardly, with an articular surface, as well as by the depressions on its body destined to receive the heads of the ribs. The lumbar vertebra has its long flattened transverse processes ; while the coccygeal vertebra offers rudi- (' Vertebrae which have centra concave at both ends, are designated amphiraslous. Those distinguished by a concavity in front and a convexity behind, are known as procxlous ; but if the cavity is behind and tlie convexity before, they are then named opisthocxlous. A vertebra of the above description belongs therefore, tu the opidhoceelous class.) VERTEBRM 27 mentary laminfe and processes. There is no necessity for noticinir the sacrum, the five pieces of which form one bone— a feature that markedly distinguishes it from the other regions of the vertebral column. But these few distinctive characteristics do not satisfy the requirements of descriptive anatomy ; so that it is necessary to undertake a more extensive study of each of these regions. 1. Cervical Vertebra. General Characters. — These vertebrae, the longest and thickest in the spine, present generally a cubical form. They are usually distinguished from the vertebrae of the other regions by the following characters : The inferior spine of the body is strongly marked, especially behind, where it terminates in a small tubercle. The head is well detached from the remainder of the bone, and describes a very short curve. The posterior cavity, wide and deep, represents a veritable cotyloid de- ^'g- ^^• pression, which is too large to fit the head exactly; the intermediate fibro-cartilage on these two sur- j faces is also of a great thickness. The spinous process forms a simple roughened, and but slightly prominent, ridge. The transverse processes, very developed, are elongated in an antero-posterior direction, and inclined downwards. In this region they are designated the trachelian processes, be- ^ cervical vertebra. cause of their relations with the trachea : a , « • o ' 1, bupenor spinous process; 2, an- foramen that traverses them from before to terior articular processes ; 3, pos- behind at their base has been, for the same ^^'■'°'" a'ti'^''-^'; I'l-cesses ; 5, an- , , , - tenor convex face of boily; b, 7, reason, named the tracfielian joramen {vertehral transverse processes, with their forctmen). The articular processes, large and tubercles or rudimentary ribs; 8, prominent, are inclined downwards and inwards. p"?terTor face. °' ''''"' ' ^' '""'''' The notches are wide and deep. Specific Characters. — The seven cervical vertebrse are reckoned from before to behind, and receive numerical names indicating their place in the region. First. — The first vertebra of the neck, which has been named the atJas,^ deserves a very careful description. At first sight there is recognized the great development of its transversal diameter, the considerable dimensions of the spinal foramen, and the thinness of its body. The intra-spinal face of the latter is divided into two portions by a transverse ridge : one anterior, furnished with hgamentous imprints, exhibits, laterally, two deep excavations, which lodge the venous sinuses ; the other, posterior, is smooth and concave from side to side, and forms an articular surface into which is received the odontoid process of the axis ; this surface takes the place of the cotyloid cavity. The inferior spine of the body appears as a large tubercle (Fig. 15, 6). The head is absent, and is replaced by two concave facets. The anterior articular processes have their ghding surfaces looking downwards ; they are joined to the two preceding facets to constitute two large diarthrodial cavities, which articulate with the occipital condyles (Fig. 15, 1). There is no spinous process, but a roughened surface instead. The transverse processes are large, flattened above and below, inclining forwards and downwards, and are provided with a thick ruT'ied lip. Posteriorly, ' Rudimentary ribs are sometimes attached by ligaments to the ends of the transverse processes (.LesbreX 28 THE BONES. ATLAS ; INFERIOR SDTIFACE. 1, Articular cavities for condyles of the occipital bone ; 2, articulai facet; 3, vertebral or antero-internal fora- men ; 4, posterior, or cervical fora- men ; 5, transverse process or wing ; quite at their base, and on each side of the spinal foramen, they show two large vertical facets which represent the posterior articular processes ; these facets are uneven, are confounded with the articular cavity of the upper face of the body, and correspond to the two analogous facets of the axis. Each trans- verse process is pierced at its base by two foramina, which traverse it from below upwards. The posterior represents the vertebral foramen of the other vertebrae ; while the anterior is continued to the external surface of the process by a wide, deep, but very short channel, running from with- out to within, and joins a third foramen, which enters the spinal canal. These last two openings, with the demi-canal which unites them, replace the anterior notch ; the posterior is altogether absent. Lastly, an inflected venous canal, the position of which varies, and it is also sometimes 6, tubercle representing the inferior absent, crosscs the laminae of the atlas, and opens, spinous process ; 7 superior arch, ^^ ^^q g^[^Q j^to ^J^g Spinal Canal, and OU the forming the roof of the spinal fora- , , ,i ,i , mi n men. Other, beneath the transverse process, ihe atlas contains much compact tissue, and is generally developed from six centres of ossification : two for the body, which at an early period becomes a solid piece, and two for the annular part ; the other two are complementary centres, each of which forms one of the two posterior undulated facets and lip of the corresponding transverse process. Second. — This is named the axis, or dentata (Fig. 16). It is the longest of all the cervical vertebrae ; those which succeed it gradually diminish in length and in thickness. The body of the axis has no increase anteriorly, but a conical process termed the odontoid, which is flattened above and below, concave and rough from one side to the other on its superior face ; convex in the same direc- tion and perfectly smooth on its inferior face. The latter represents an articular half-hinge, around which glides the con- cave articular surface on the superior face of the body of the atlas. The anterior articular processes are carried to the base and to each side of the odontoidian pivot, in the shape of two undulated facets, which are confounded with th .' gliding surface of the latter, the destination of which has been already noted. The spinous process, very large and elongated antero-posteriorly, is divided behind into two roughened lips. The transverse processes are slightly developed, and terminate posteriorly in a single tubercle, directed backwards. The anterior notches are very deep, and are most frequently converted into foramina. This vertebra, although voluminous, is light, in consequence of its containing much spongy substance. In the young animal, the odontoid process and the articular surfaces on each side, constitute Fig. 16. THE AXIS, OR DENTATA ; LATERAL VIEW. 1, Superior spinous process ; 2, odontoid pro- cess ; 3, intervertebral foramen, or hole of conjugation; 4, body; 5, inferior spinous process ; 6, 7, inferior and superior articu- lating processes. VERTEBRM 29 two centres, distinct from each other and from the body of the vertebra. After the axis, the cervical vertebnij diminish in length and increase in thickness ; while the obliquity of their articular processes becomes more pronounced the more distant they are from that vertebra. Third, fourth, and fifth. — Each of these has, at its transverse processes, two prolongations — one anterior, the other posterior. The inferior face of their bodies Fig. 17. AXIS AND SIXTH CERVICAL OF THE HORSE AND ASS. A. Axis of the Horse. 1, spinous process ; 2, tiaasverse process ; 3, odontoid process ; 4, lateral articular facet. B, Axis of the Ass. Same numbers and same signification. a', Sixth cervical vertebra of the Horse. 1, Articular hend ; 2, posterior articular process ; 3, articular cavity ; 4, posterior proloncration of the transverse process; 5, anterior ditto. b', Sixth cervical vertebra of the Ass. Same numbers and same signification. exhibits a median spine terminated posteriorly by a tubercle, which gradually increases in volume from the third to the fifth vertebra. The third presents, between its anterior and posterior articular processes, an almost complete gap ; if its anterior extremity be placed on a horizontal plane, it will touch that plane by its articular and transverse processes and its head. 30 TEE BONES. In the fourth, the articular processes are nnited by a thin, sharp osseous plate, notched only in front. Laid on a horizontal plane, the head remains some distance from that plane. The fifth is recognized by the continuous, thick, and rugged lamina which unites the articular processes, -and by the tubercle of the inferior spine on the body, which is in shape like the heart on a playing-card. Sixth. — This is distinguished by the slight prominence of the spinous process, but particularly by the almost total disappearance of the inferior spine, and the presence of a third prolongation, very strong and inclining downwards at its transverse process — a circumstance to which this vertebra owes its designation of tricuspid. Seventh. — This has received the name of promineas, because its spinous pro- cess, terminating in a point, is more distinct than in the preceding vertebra?, the axis excepted. It exhibits, besides : deep imprints, which replace the inferior spine ; a concave demi-facet on each side of the posterior cavity of the articulation of the head of the first rib ; a particular disposition of its transverse processes, which are unituberculous ; the complete absence of the vertebral foramen ; and, lastly, the depth and width of its notches. The spinal foramen, which has already assumed a somewhat considerable diameter in the sixth cervical vertebra, is still larger in the seventh. Ass. — The cervical vertebrae in this animal much resemble those in the Horse. Studying them more closely, however, it is possible to discover certain differences which distinguish them from those of the other Equidae. Thus, the rugosities on the arch of the atlas are much less marked than in the Horse, and form a kind of thick depressed tubercle. The vertebral foramen is very large in proportion to the size of the vertebra, and the canal uniting the two portions of the anterior foramen of the transverse process is deep and protected by a well-defined rim. The axis has a less elevated spinous process than that of the Horse ; its upper border, nearly parallel with the transverse process, is more deeply divided into two lips, and the summit of its transverse process extends backwards to the articular process, while in the Horse it does not go beyond the origin of the latter. In the third, the lamina uniting the two prolongations or points of the transverse processes, is notched behind the anterior prolongation, instead of being notchless as in the Horse. In the fourth and ffth this notch is still more marked. In every instance the anterior prolongation of the transverse process is always more detached and better circumscribed in the Ass than in the Horse. The same remark applies to the tricuspid ; the posterior prolongation is also better detached, and the middle prolongation extends nearly to the articular cavity of the vertebra — a prolongation which, in the Horse, does not exceed one- half the length of the posterior one. The seventh differs little from that of the Horse ; nevertheless, the uni-tubercular transverse process has, in front, a small ■ sharp projection which resembles somewhat the anterior prolongation of the bicuspid processes. In the Mule and Hinny, the cervical vertebrae hold the middle place between those of the Ass and the Horse. DlPPERENTIAL CHARACTERS OF THE CkBVICAL VEBTEBBiB IN THE OTHER DOMESTICATED Animals. A. Ox, Sheep, and Goat. — The cervical vertebrfe of these animale differ from those of Solipeds by their shortness, and the greater developraent of their insertion eminences. In the fe'Aeey and Goat they are relatively longer than in the Ox. The transverse processes of the VERTEBRA. 31 atlafi arc leee inclined than in the Horse, and have no vertebral foramina ; the poeterior facets for articulation with the axis, are nearly flat and join each other. The axis has a semi-cylindri- cal, not a conical, odontoid process, which is so concave on its upper surface that it looks like a groove. Its spinous process is not so thick as in the Horse, and is nut bitid posteriorly. In tlie fict succeeding vertebrse, a rugged continuous lamina unites the anterior articular processes to the posterior. The spinou.s process inclines forward, and is flattened 1 transversely at its summit, which is sometimes bifid ; it progressively increases in height from the third to tlie fifth vertebra. In the sixth, the transverse processes have only two prolongations — a superior and inferior; the latter, large and flattened on both sides, is bent abruptly downwards. The spinous process has already attained the height of 1^ to 2 inches in this vertebra, and is flattened laterally. The seventh well deserves the name of prominens, its spinous process being no less than from 4 to 4f inches (see Figs. 6 and 1). B. Camel.— in the Cumtl, the cervical vertebrae are longer and thinner than in the other large domestic animals. Altogether, they form one-third of the total length of the spine. Their vertebral laminae are deeply notched before and behind, which allows thetn to easily enter the spinal canal. Their articular processes are convex, and from the second to tlie sixth inclusively, the vertebral foramen is small and deeply placed in the laminae. The atlas is distinguished from that of the Horse and Ox by the absence of the tubercle on the inferior face of the body, and the shortness of the transverse processes, of which the border is thin and sharp. The vertebral foramen makes a somewhat long course in the transverse process of this vertebra, and opens at the bottom of the excavation in which the anterior inter- vertebral foramina meet — the latter being double. The axis is very long and constricted in its middle ; the inferior crest is only slightly salient ; there are double invertebral foramina, the largest of which is divided by a bony septum ; the odontoid process is as in the Ox. The other cervical vertebrae gradually diminish in size and increase in thickness from before to behind. In the third, fourth, a.nii fifth, the transverse processes are bi-tuberculated. In the sixth, the transverse process is a wide and thick plate, inclining downwards. The seventh is recognized by its long spinous process and the smallness of its transverse process, which has a larger and more obvious vertebral foramen than the other vertebrae (see Fig. 8). C. Pig. — Of all the domesticated animals, this has the shortest, the widest, the most tuberous, and consequently the strongest cervical vertebrae. The body of these bones has no crest on the inferior face ; the head, but little detached, is scarcely round, and looks as if driven back on itself; consequently, the posterior cavity is not deep. The vertebral himinae are very narrow, and scarcely extend from one part of the vertebra to the other in the superior portion, so that the spinal canal appears at this point to be incomplete. In the atlas, the transverse processes are less inclined than in Ruminants ; the vertebral foramen is not constant, and when it exists, opens on one side, under the transverse process, and on the other, on iis posterior margin, after pursuing a certain tiack in the substance of the bone. The odontoid process of the axis is constricted at its base. This vertebra is distinguished by its high and thin spinous process inclining slightly back, by its transverse processes being but slightly prominent, and perforated by an enormous vertebral foramen. In the four succeeding vertebras, the spinous process terminates in a blunt point, and inclines forward ; slightly salient in the first, it gradually rises in the others. The transverse processes form two prolongations: fine, the superior, is tuberous, and is joined to the anterior articular process by a plate of bone, which is pierced by a foramen ; the other, the inferior, flattened on both sides, bent downwards, and large, as it belongs to a posterior vertebra, transforms the inferior face of these vertebral bodies into a large groove. The seventh has a spinous process as long as those of the dorsal region. A perforated bony plate, as in the preceding vertebrae, unites the anterior articular process to the single tubercle composing the transverse process : the latter is continued back nearly to the posterior notch by a second plate, also perforated with a foramen (see Fig. 3). D. Dog and Cat. — In these animal.*, the cervical vertebrae are long and thick, and much resemble those of Solipeds. Nevertheless, besides their smaller volume, they are distinguished : 1. By the disposition of their corresponding articular surfaces : the anterior, or head, is nearly flat, and is even slightly excavated in its centre : the posterior, or cavity, is but little hollowed to receive the head of the next vertebra ; 2. By the width of the vertebral laminae, which overlap one another; 3. By the height of their spinous processes, which increases as the ▼ertebrae extend back : 4. By the great extent of the anterior and posterior articular procesaeSr 82 THE BONES. which are united by means of a continuous and very salient bony plate, that considerably augments the transversal diameter of each vertebra. In the atlas, the articular surface for the odontoid pivot is confounded in front with the cavities which correspond to the occipital condyles. The two facets wliicli are annexed posteriorly to this artipular surface, instead of being plane or gently undulated, as in tbe other domesticated animals, are transformed into real glenoid cavities. The transverse pro- cesses are carried directly outwards and a little backwai and gives rise on each side to the superior curved lines. The styloid processes are short and much bent inwards. The basilar process, wide, short, and thick, has a groove in the middle of its external face ; this groove is sometimes absent in the Sheep and Goat. The condyloid foramina are double, sometimes triple ; the superior foramen does not pass directly into the cranium, but goes to a vast conduit tliat opens behind on the lateral margin of the occipital foramen, and wliich terminates in front by twi) orifices, one entering the parieto- temporal canal, the other opening on the external surfiice of the bone. The foramen lacerum is divided into an anterior and posterior forameu, by the mastoid portion of the temporal bone. B. Sheep and Goat. — The inner tuberosity is only marked by a slight prominence of the internal plate of the bone. In the occipital bone of these animals are found the peculiarities noted in that of the Ox ; the groove on the basilar process is sometimes absent, and in the Sheep the superior curved lines are very salient and occupy the summit of the head. Tnis feature is still more marked in the Goat, and also more in the Cervine species, in which this bone Somewhat re.'^embles that of the Horse. C. Camel. — The bone shows a double angle as in Solipeds. In its anterior and .-uperior portions it resembles that of the Horse, and in its posterior portion that of the Ox. The crest, which constitutes the origin of the parietal crests, as well as the superior curved lines, are thin, sharp, and very high. The styloid processes are short, wide, thick, and articulated by harmonic suture with the tuberosity of the temporal bone. The superior curved lines are scarcely marked in young animals. D. Pig. — The occipitnl bone in this animal is not bent anteriorly; but the transverse protuberance representing the curved lines forms, nevertheless, as in the Horse, the summit of the Head. This eminence, which is excavated on both s-ide-s on the posterior face, unites in front with the parietal bone, which abuts on the occipital at an acute angle. There is no external occipital protuberance, properly speaking, and the styloid processes are very long and directed downwards. E. Carnivora. — The external occipitnl tuberosity is very strong and high. The external occipital crest is absent or little marked ; the styloid procc sscs are short. The furamen lacerum is divided into two portions by the mastoid process, and the basilar prociss is wide, long, and thick, and hollowed on the side by a cliannel tliat joins a similar one in the temporal bone to form a large venous canal. This last communicates, behind, with the posterior foramen lacerum, and opens, in front, in the cranium, where it is continuous with the cavernous groove of the sphenoid. The anterior angle forms a very marked prominence, which is deeply fixed into the parietal bone, and partly constitutes the internal occipit .1 process of that bone. The latter does not show the lateral excavations at its base; they are found lower, towards tiie summit of the petrous bone, on the sides of the occipital. The parieto-temporal canals are, nevertheless, continued to the base of the process, which they traverse to open into its interior. In the most intelligent breeds, the occipital foramen is deeply notched above (Faure). THE HEAD. 49 Fig. 27. 2. The Parietal Bone (Fig. 26). The parietal is a wide and thin bone, very much arched to form the roof of the cranial cavity. It is bounded above by the occipital bone, below by the frontal, and laterally by the two temporal bones. It offers for study an external and internal fare, and a circumference divided into four regions or borders. Faces. — The external fare is convex. It exhibits two curved ridges with concavity directed outwards ; these two crests, which are termed the parietal ridges, approach each other and unite superiorly, to be continued with the antero- posterior ridge of the occipital bone ; below they diverge and proceed, one on each side, to join the supra-orbital process. They divide the surface of the bone into three portions : two lateral, which are rough and traversed by vascular channels, forming part of the temporal fossae ; the third, or middle, is plane, smooth, and of a triangu- lar form, and covered by the skin. The internal face is concave, covered by digital impressions, and grooved by small vascular canals ; it offers, on the middle line, and altogether above, the parietal protuberance. This trifacial and very salient projection presents at its base, on each side, an excavation elongated transversely, into which opens the parieto-temporal canal, and which lodges a venous sinus. It is continued, in front, by a median crest, which is often replaced by a slight groove — the saggital furrow, bordered by linear imprints. Two other ridges, resulting from the abutment of the lateral border of the bone against the anterior face of the petrous bone, rise from the sides of this eminence and descend to the sphenoid bone ; they separate the cerebral from the cerebellar cavity. Borders. — The superior border is notched, thick, and slightly dentated ; it articulates with the occipital bone. The inferior border, slightly concave, and deeply dentated. offers an external bevel in its middle portion, and an internal bevel on its sides ; it corresponds with the frontal bone. The lateral borders are very thin, and are cut, at the expense of the external plate, into a wide, sloping edge, which shows a groove destined to form the parieto-temporal canal. A very prominent angle separates each into two portions — an inferior, that articulates by suture with the squamous portion of the temporal bone ; and a superior, curved inwards towards the centre of the cranial cavity. The latter portion of the lateral border is in contact with the anterior face of the petrous portion of the temporal bone, with which it concurs to form the lateral crest that descends to the parietal protuberance. Structure. — This bone contains much compact tissue, the spongy substance existing only in its middle. Dei^elopment. — It is developed from two large lateral centres of ossification, to which is added a single centre to form the parietal protuberance. In early life the parietal ridges are absent. head of the cat (posterior aspect). 1, Occipital bone ; 2, zygomatic process of the tempoml bone ; 3, t_vmpanic bulb; 4, condyle of the temporal buue ; 5, malar bone ; 6, orbital process of the malar; 7, liitto of frontal bone; 8, 8, palatine bones; 9. 9, m;ixil- lary bone; 10, premaxillary bone; 11, pterygoid bone; 12, sphenoid bone ; 13, vomer. 50 THE BONES. Differential Characters of the Parietal Bone in other Animals. A. Ox.^Tlie parietal bone in the Ox does not of^cupy the anterior aspect of the head, but concurs with the occipital to form the base of the neck. It represents a very narrow osseous plate, elongated transversely, and curved at its two e.xtremities, wliicli descends into the temporal fossae to rest upon the sphenoid bone. There are no parietal ridges. Tlie internal protuberance is only marked by a slight elevation of the internal plate ; for the most part it belongs to the occipital bone. The parietal bone of the Ox is developed from three centres of ossiti cation, and the middle nucleus is even primarily divided into lateral halves; but these centres are consolidated ^¥ith each other at an early period, as well as with the anterior portion of the occipital. It does not aid in the formation of the parieto-temporal canal, and is excavated internally tiy cavities which communicat* with the frontal sinuses. B. Sheep, Goat. — The parietal bone of the Sheep and Goat is relatively much larger than that of the Ox. It participates in the formation of the parieto-temporal canal, and has no sinuses. C. Camel. — This bone occupies the anterior face of the cranium ; but it is long, narrow, and deeply lodged between the squamous portion of the temporal bone and tlie frontal bone, to rest on tlie sphenoid. The parietal crests, thin and elevated, lie against each otiier for nearly their entire length, and are not pro- longed to the frontal bone (Fig. 45). These crests do not exist at an early age. D. Pig. — The parietal bone is very thick ; it has two very marked crests, which do not meet at their upper part (Fig. 28). E. Dog, Cat. — In the -Doli(lated with the nasal bone for about the upper two-thirds of its length. There is no incisive foramen or cavity for the tusk, The incisive openings are oval. D. Dog, Cat. — Of small size, the premaxilla of Carnivora has no incisive foramen or alveolar cavity for the canine tooth. The incisive open- ings are the same as in the Pig. Fig. 39. E. Rabbit.— Proportionately voluminous, the pre- r ^ maxilla of the Rabbit is remarkable for the great de- *^ " velopnient of its ascending processes, which reach the f'JL^^ ^^^j^^^^ f frontal bone, and the width of the incisive slits, which are confounded above the internal processes. It carries two incisors, placeil one before the other. 3. Palatine Bones (Fig. 38). The folate or palatine, bones are situated be- tween the supermaxillaries, at the margin of the guttural opening of the nasal cavities, and are articulated with the sphenoid, ethmoid, vomer, frontal, and pterygoid bones. Elongated from above to below, flattened laterally, and curved towards each other at their inferior extremity, which is flattened from before to behind, these bones, though irregular in shape, offer for study tivo faces, two borders, and two extremities. Faces. — The external face of the palate bone is divided into three fractions — a superior, or orbital, an inferior, or palatine, and a middle, or articular. The first is smooth and slightly ex- cavated, and participates in the formation of the maxillary hiatus : it shows a small groove, the staphi/loid, which reaches the palatine fraction in passing between the posterior border of the bone and the alveolar tuberosity. The second is not extensive, and looks backwards in conse- quence of the antero-posterior flattening which the bone presents at its inferior extremity ; it forms part of the roof of the palate. The third presents a lamellar and denticulated surface which corresponds to a similar face on the supermaxillary bone, and is channeled from above to below by the internal groove of the palatine canal. The internal face, smooth and concave, forms part of the external wall and the floor of the HEAD OF THE PIG (POSTERIOR FACE). 1, Occipital tuberosity ; 2, occipi- tal foramen ; 3, occipital con- dyle ; 4, condyloiil foramen; 5, basilar process ; 6, 6, mastoid crest; 7, styloid process of the occipital bone ; 8, articular surface of the temporal bone ; 9, mastoid protu- berance ; 10, foramen laoerum; 11, subsphenoidal })rocess — external wing of pterygoid process ; 12, palatine crest ; 13, pterygoid bone (internal wing of the i)terygoid process) ; 14, inferior orifice of the palatine canal ; 15, 15, incisive openings. nasal fossa. Borders. — The anterior is indented, near its superior third, by a deep notch, which is often converted into a foramen, the nasal. Below this notch the bone is thin and denticulated for union with the supermaxillary bone ; above, its two plates separate widely from one another, giving rise to a very spacious cavity €8 THE BONES. which forms part of the sphenoid sinus. The posterior border presents, above, a rugged crest called the palatine, flattened from side to side, bent outwards, and bordered at its base and inwards by a very narrow synarthrodia! surface, which responds to the pterygoid bone. It is smooth and concave in its inferior half, and forms, with that of the opposite side, a parabolic arch (palatine arch) which circumscribes, below and at the side, the double guttural orifice of the nasal cavities. Extremities. — The superior, flattened on both sides, is bevelled on the external side to articulate with the subspheuoidal process. The inferior, flattened from before to behind, is curved inwards and united by simple suture with that of the opposite bone. Structure and development. — This is a very com- pact bone, developed from a single centre of ossifi- cation. Differential Characters in the Palatine Bone in OTHER Animals. The principal distinctive feature of this bone in the different domestic animals is due to the part it takes in forming the arch of the palate. In tliis respect there are very great differ- ences in vaiious species, but in none of tliem is this part so redufcd as in Solipeds, in which the bone is scarcely equal to one-fifth of the palatine surface. A. Ox, Sheep, Goat. — 'I'l.e palatine bone in these animals is very developed, and noticeable for the considerable extent of the palatine portion of its external surface. The palatine canal is entirely channeled uut in its substance. The palatine cri 8t, very thin an I elevated, is formed altogether by the posterior border of the palate bone, the pterygoid, and the subsphenoidal process. There is no excavation for the sphenoidal sinuses ; but, instead, all that part of the bone which enters into the roof of tlie palate is hollowed, but in the Ox only, by irregular cavities which communicate with the maxillary sinus of the same side. The nasal foramen is very wide. B. Camel. — The btaphyline fissure is wide and deep; the palatine crest is very developed, and has two rugged depressions at its base. The palatine canal is not included in the palate bone ; it opens at the second molar. C. Pig. — The palatine portion is less developed than in Ruminants, for it forms less tlan one-fourth of the palatine arch ; on the other hand, the orbital portion is very limited. Tiie palatine crest is n placed by a tuberosity, against which rests, outwardly, the subsphenoidal process, and inwardly the pterygoid bone. Tlie union of these three parts constitutes, on the posterior surface of tlie head, a thick and very remarkalde trifid projection or mamelon. D. Dog, Cat.— It is in the C;rnivora that tlie palatine bones are of greatest extent in their proper palatine jiortion, as they constitute nearly one-half of tlie palatine arcli. They have no share in the formation of the sphenoidal sinuses, but furnish a small excavation to the maxillary sinuses. E. Rabbit. — The palatine bones lesemble those of the Horse, dog's head (posterior face). 1, Occipital tuberosity ; 2, occipital foramen ; 3, occi- pital condyle ; 4, condyloid foramen ; 5, styloid process of the occipit;il ; 6, mastoid protuberance ; 7, concave temporo-maxillary articular surface ; 8, supra-condy- loid eminence; 9, inferior orifice of the parietu-tem- poral canal ; 10, posteridr foramen lacerum ; 11, ditto, anterior. On the op- posite side at a is shown the orifice communicating with the Eustachian tube and the tympanum ; at b the passage for the carotid loop. 12, Body of the sphenoid ; 13, oval fora- men ; 14-, inferior orifice of the subsphenoidal canal ; 15, pterygoid bone ; 16, nasal surface of the palate bone; 17, palatine surface of the same; 18, vomer; 19, supermaxillary bone ; 20, incisive opening. with regard to the part they play in forming the palatine arch. The palatine canal opens also between the palatine and superior maxillary bones, but the palatine crests are proportionately more developed than in Solipeds (Fig. 35). TEE HEAD. 69 4. Pterygoid Boxe (Figs. 34, 38).^ A small and very short bone, elongated from above to below, flattened on both sides, and situated on the inner aspect of the subsphenoidal process, but external to the vomer. Its external face is in contact with the palate and sphenoid bones ; the internal is smooth, and covered by the pharyngeal mucous membrane. Its superior extremity is tapering, and concurs in forming the Vidian canal ; the inferior is thickened into a small pointed process (the hamular process), the apex of which, directed backwards, offers outwardly a groove which serves as a pulley to the tendon of the tensor palati muscle. This bone is composed entirely of compact tissue, and is developed from a single centre of ossification. Differential Characters in the Pterygoid Bone of other Animals. A. Ox, Sheep, Goat. — The pterygoid of the Ox, Sheep, and Goat is very wide, and closes an aperture left between the sphenoid and palatine bones. B. Camel.— In the Camel the pterygoid is short, broad, and applied to tiie internal face of the subsphenoidal process and palatine crest. It does not concur in tlie formation of the Vidian canal. Its inferior extremity has a narrow and deep fissure. C. Pig. — (See the description of the palatine bone.) D. Camivora. — This bone is very strong in Carnivora, and quadrilateral in shape. 5. Malar or Zygomatic Bone (Figs. 26, 34). This bone, also designated the ju^cd bone, is elongated from above to below, flattened on both sides, and irregularly triangular in shape ; it is situated on the side of the face, and articulates with the supermaxillary, lachrymal, and temporal boues. It is described as having two faces, two borders, a base, and a summit. Faces. — The external face comprises two portions separated from each other by a semicircular ridge that extends from the summit to the middle of the anterior border of the bone, and concurs to form the outer margin of the orbit. The anterior portion, smooth and concave, belongs to the orbital cavity. The posterior, more extensive, is also smooth and slightly convex. The internal face is excavated in its central part, which corresponds to the maxillary sinus. On its margin it shows denticulations and lamellte for articulation with the super- maxillary bone. Borders. — The anterior, thin and denticulated, is joined to the lachrymal bone. The posterior, or masseteric border, is thicker, and constitutes a roughened crest, the zygomatic ridge, which is continued above with the posterior border of the process of the same name, and below with the maxillary spine. Base and summit. — The base, very thin, is united to the supermaxillary bone. The sunomit, flattened from before to behind and bevelled on its anterior face, joins the zygomatic process, and forms with it the jagal bridge, or zygomatic arch. Structure and deveJofmeni. — This bone is rather spongy in its upper part, and is developed from a single nucleus of ossification. Differential Characters in the Malar Bone of otheu Animals. A. Ox, Sheep, Goat. — The malar bone of Ruminants is very developed. The zygomatic crest is no longer formed by the posterior border of the bone, but is carried to the posterior part of the external face, and runs parallel with the eyebrow. The summit is bifurcated, the This bone is the representative of the internal icing of the pterygoid process in Man. 70 THE BONES. anterior branch forming a buttress against the summit of the orbital process of the frontal bone, while the posteiior articulates with the temporal. In these animals, the huiie ofifers several centres of ossification. B. Camel. — This bone is very little developed, and is compressed from before to behind. Its anterior face is very concave, and circumscribes the orbit posteriorly. Its posterim face considerably overhangs the maxillary bone, and forms a very salient zygomatic crest. The Bummit is bifurcated, as in the Ox. C. Pig. — The summit of this bone in the Pig is flattened on each side, and divideil into two brandies, between which is wedged the summit of the zygomatic process ; the anterior branch is very short, and does not join the frontal bone. D. Camivora.— The malar of the Dog and Cat only articulates with the supermaxillary bone, and by its base alone. The crest describes a curve, the concavity backwards, and the summit comports itself as in the Pig. F. Rabbit. — The bone is flattened on both sides ; the summit, united with the zygomatic process of the temporal bone, is single ; while the base is confounded entirely with the malar tuberosity (Fig. 36). 6. Lachrymal Bone (Figs. 26, 51). A small, thin, and very light bone, bent on itself at a right angle, it is situated beneath the orbit, which it aids in forming, and is wedged between the frontal, nasal, supermaxillary, and malar bones. It is studied on its external and internal faces and circumference. Faces. — The external is divided into two regions, superior and inferior, by a curved crest which forms part of the orbital margin, and is provided with notches, which are variable in their form and number. The superior region, named the orbital, because of its situation in the orbit, is slightly concave and smooth. It presents, near the orbital margin, the orifice of the lachrtjmal dud, which traverses the maxillary sinus and opens on the internal face of the super- maxillary bone, where it is continued by a fissure ; behind this is the lachrijmnl fossa. The inferior ox facial region is shghtly bulging, and provided sometimes with a tubercle for insertion, — the lachrymal tubercle. The internal face is employed, for the whole of its extent, in the formation of the walls of the maxillary and frontal sinuses ; it exhibits a cylindrical prominence produced by the bony tube of the lachrymal duct. Circumference. — This is very irregular, and denticulated for articulation with the neighbouring bones. Structure and development. — This bone is entirely compact, and is developed from a single nucleus of ossification. In the Ass, the lachrymal tubercle is placed towards the anterior border of the bone ; usually, it partly belongs to the nasal bone, and is consequently found on the suture uniting the lachrymal bone to the proper bones of the nose. Differential Characters in the Lachrymal Bone of other Animals. A. Ox, Sheep, Goat. — The lachrymal bone, much more extensive than that of the Horse, forms in the 1 ottom of the orbit an enormous protuberance, hollowed internally by the maxillary sinus, and the walls of whicii are so thin and fragile that the slightest jar is sufficient to cause their fracture (in tlie skeleton). It would be convenient to designate it the lachrymal protuberance.^ In the smaller Ruminants, the inferior region of the internal face shows a depression — the lachrymal fossa. B. Camel. — This bone is much smaller than in the Horse ; its facial portion especially Is almoirt rudimentary. There is no lachrymal protuberance nor tubercle, the latter being carried to the superior maxilla. C. Pig. — In the Pig there are observed a lachrymal fossa and two lachrymal canals, which ' Girard, who named this eminence the orbital protuberance, wrongly described it as belonging to the supermaxillary bone. THE BEAD. 71 are pierced outside the orbibil cavity, and soon coalesce in the eubetance of the bone to constitute a sinfjle canal. Tlie fussa is very deep. D. Camivora.— This bone in Carnivora is extremely small. Its extorual face entirely belongs U^ the orbit, and does not descend beneath the margin of tliat cavity: it has no lachrymal fossa. The reduced dinunsions it prosentB in these animals well justifies the name, 08 unguis, given to it in pnthropotomy. 7. Nasal Bones (Fig. 26). Situated on the anterior aspect of the head, these bones articulate with each other in the median line, and are fixed between the frontal, lachrymal, and super- maxillary bones ; they are trian,i,ailar in shape, eloni,'ated from above to below, flattened from before to behind, and otfer for study two faces, two borders, a base, and a sununit. Faces. — The external or anterior face, wider above than below, is convex from side to side, and almost smooth. The posterior, internal, or nasal face exhibits a vertical crest passing along the external border of the bone, which gives attach- ment to the turbinated portion of the ethmoid ; at its superior extremity this crest bifurcates, and between its two branches shows a concave surface which forms part of the frontal sinus. For the remainder of its extent the internal face is smooth, and covered by the mucous membrane of the nasal fossa ; it is also excavated into a channel to form the superior meatus of this cavity. Borders. — The external border is very thin in its upper two-thirds, and articu- lates with the lachrymal bone, the anterior border of the supermaxillary, and the extremity of the external process of the premaxilla. In its lower third it becomes isolated from the latter bone, in forming with the anterior border of its large pro- cess a very acute re-entering angle, the opening of which looks downwards. The internal border is denticulated fox contact with the opposite bone. Base and Summit. — The base occupies the superior extremity of the bone ; it describes a curved line with the convexity above, and, in uniting on the median line with that of the opposite bone, forms a notch similar to that of the heart figured on playing-cards ; it is bevelled, at the expense of the internal plate, to articulate with the frontal bone. The summit of the two nasal bones, which is pointed, constitutes the nasal prolongation — the name given to a single triangular process which comprises all that portion of the nasal bones separated from the premaxillaries by the re-entering angle before mentioned. Structure and development. — Almost entirely compact in structure, it is developed from a single centre. Differential Characters in the Nasal Bones of other Animals. A. Ox, Sheep, Goat. — The nasal bones of the Ox are never "consolidated with each other, nor yet v?ith the neiglibouring bon( s. The external border only comes in contact to a small extent with the supermaxillary bone ; the superior extremity is tixed in the notch of the inferior border of the frontal bone. At their inferior extremity, they each present a notch which divides them into two points. In the Sheep and Goat the nasal spine is unifid, as in the Horse (see Figs. 30, 32). B. Camel. — In the Camel, the proper bones of the nose are short and narrow; their external border is in contact only with the superior maxilla ; the upper extremity is rounded. At the inferior extremity, they show a well-marked notcli, whicli divides them into two points, but the inner point is very small. C. Pig. — These bones are long and narrow, and traversed on their external face by the fissure that descends from tlie supra-orbital foramen. The nasal prolongation is short. D Carnivora. — The two bones ot the nose are little developed, and are wider below than above; they have no nasal prolongation, but offer, instead, a semicircular notch. 72 THE BONES. E Rabbit.-Proportion..tely long and wide, the uasal bone of the RabbU articulates by the whole of its external border, with the ascending process of the premaxillury bone. The anterior extremity of the nasal bone is very slightly salient. Fig. 41. LONGITUDINAL AND TRANSVERSE SECTION OP THE horse's head, SHOWING THE FLOOR OF THE CRANIAL AND NASAL CAVITIES, WITH THE MAXILLARY SINUSES. 1, Condyloid foramen. 2, Section of the parieto temporal canal. 3, Foramen lacerum basis cranii. 4, Carotid notch. 4', Maxillary notch: a, supermaxillary fissure ; 6, cavern- ous fissure. 5, Origin of the supra-sphe- noidal canals : c, sella Turcica. 6, Optic fossa. 7, Portion of the crista-galli process. 8, Cribriform plate of the ethmoid bone. 9, Perpendicular plate of the i^ame bone. 10, 10, Its lateral masses. 11, Interior of the great ethmoidal cell. 12, 12, Bottom of the maxillary sinuses communicating with the sphenoidal sinuses. 13, Superior maxillary sinus. 14,Inferior maxillary sinus. 14', Superior compartment of the maxillary turbinated bone, forming part of the latter sinus. 15, Section of the supermaxillo- dental canal. 16, Channel of the vomer. 17, Internal process, or point of the pre- maxillary bone. ANTERO- POSTERIOR AND VERTICAL SECTION OF THE HORSE'S HEAD. 1, Condyloid foramen ; 2, parietal protulierance ; 3, internal audi- tory hiatus ; 4, cerebral cavity ; 5, cerebellar cavity ; 6, supe- rior border of the perpendicular plate of the ethmoid bone (crista- galli process) ; 7, ethmoidal volutes — nasal face ; 8, vestiges of the right frontal sinus; 9, ditto of the sphenoidal sinus ; 10, ptervgoid process; 11, eth- moidal turbinated bone ; 12, maxillary turbinated bone ; 13, crest of the supermaxillary bone to which the latter is fixed ; 14, vomer. A, Orifice of communication between the nasal cavity and the sinus. THE HEAD. 73 8. Turbinated Bones (Fig. 42). The turUnated (or tnrbinal) bones, two on each side, repref5ent two irregular bony columns, wider above than below, compressed laterally, hollowed internally, and lying vertically side by side on the external wall of the nasal fossa, which they divide into three meatuses or passages. They are distinguished into anterior and posterior turbinated bones. The anterior or superior, also named the ethmoidal, is formed by a very thin plate of compact tissue — fragile and like papyrus, fixed by its anterior border to the internal crest of the nasal bone, and rolled on itself, from before to behind, in the same manner as the cells of the ethmoid bone. Above, it is confounded with the last-named bone, of which it is only, properly speaking, the most anterior volute. At its inferior extremity, it is prolonged by a fibro-cartilaginous frame- work to the external orifice of the nose. Its internal cavity is partitioned by a transverse plate into two portions : the superior compartment forms part of the frontal sinus ; the inferior is subdivided by other small lamellae into a variable number of cells which communicate with the nasal cavity. This bone, developed from a single nucleus, is ossified at the same time, and in the same manner, as the ethmoidal cells. Before birth, it is already intimately consolidated with the nasal bone. The posterior, inferior, or maxiUarij turbinated bone resembles the first, except in some particulars. Thus, its bony or proper portion is not so long or volu- minous, while its cartilaginous part is, on the contrary, more developed. It is attached, by its posterior border, to the vertical and sinuous crest of the super- maxillary bone, and is rolled from behind to before, or in an inverse direction to the other. It has no connection with the ethmoid, and its superior cavity forms part of the inferior maxillary sinus. It is late in becoming ossified, and is scarcely united in a definite manner to the maxillary bone until the horse is about a year old. The meatuses are distinguished into anterior or superior, middle, and posterior or inferior. The first passes along the front of the ethmoidal turbinated bone ; the second separates the two turbinated bones, and presents, near its superior extremity, the opening communicating between the sinuses and the nasal cavities.' The third is situated behind the maxillary turbinated bone, and is confoimded with the floor of the nasal fossa. The turbinated bones are essentially disposed to furnish the membrane of the nose with a vast surface of development. This membrane, indeed, covers their entire superficies, and even penetrates the anfractuous cells of their lower compartment. Differential Characters in the Turbinated Bones of other Animals. A. Ox, Sheep, Goat. — In the Ox (Fig. 43), the ethtuoidal tiirbiiiated bone is very small, and is united to tlie nasal bone by the two borders of its osseous plate ; its internal cavity entirely belongs to the frontal sinus. The maxillary turbinated bone is very deveUjped, and is joined to the bone which sustains it at a later period than in the Horse. Tlie bony lamina of which it is composed, is curved un itself in two different direc'ti(ms — from before to behind by its posterior border, and behind to before by its anterior border. It is fixed to the supermaxillary bone by its middle part, through the medium of a particular bony lamina, and it very incom- ' The two turbinated bones, in being applied against the excavation on the inner face of the supermaxillary, almost entirely close it, only leaving between them a vertical slit which con- stitutes the opening mentioned above. 74 THE BONES. pletely closes the excavation which concurs to form the maxillary siuus. In the skeleton there is also found behind, and at the base of this turbinated boue, a vast opening which is totally closed in the fresh condition by the pituitary membrane. Tlie maxillary siuus is not prolonged in its interior. In the smaller Ruminants, the cavity of the sinus is closed by the maxillary turbinated bone in a more complete manner than in the Ox. B. Camel. — The ethmoidal turbinated bone is very .small. Otherwise it is as in the other Ruminants. C Pig. — The same arrangement as in the Sheep and Goat, except that the bones are much longer and less fmgile. D. Carnivora. — These bones in the Dog and Cat are particularly distinguished for their numerous con- volutions. Neither participate in the formation of the frontal or niaxillary sinuses; the latter is not in any way closed by the maxillary turbinated bone, but opens into the nasal cavity by a large gaping aperture. E. Rabbit. — The bones are arranged as in the Dog, but the folds are less numerous. 9. Vomer (Figs. 34, 38). This, a single bone, elongated from above to below, flattened on both sides, and extending on the median line from the body of the sphenoid to the premaxillary bone, offers for study two lateral faces, two borders, and tivo extremities. The fares are smooth, plane, and covered by the nasal membrane. The anterior border is channeled for the whole of its length by a deep groove, which receives the posterior border of the cartilaginous septum of the nose. The posterior border is sharp and smooth in its upper half, which separates the two guttural openings of the nasal cavities : it is thick and slightly denticulated for the remainder of its extent, and rests on the median suture resulting from the union of the two supermaxillary bones. The superior extremity is provided, in its middle, with a notch which divides it into two lateral prolongations shaped like a cat's ears {wings of the vomer) ; it articulates with the inferior sphenoid, ethmoid, palatine, and pterygoid bones. The inferior extremity rests on the prolongations of the premaxilh'e. This bone is entirely compact, and is developed from one centre of ossification. MEDIAN AND VERTICAL SECTION OF THE ox's HEAD. 1, Cimdyloid foramen ; 1', posterior ori- fice of the occipital lateral canal joining the parieto-temporal canal in front j 2, internal auditory hiatus ; 3, anterior foramen lacerum ; 4, pos- terior ditto ; 5, iutra-cranial orifice of the parieto-temporal canal ; 6, 6, median bony plate separating the frontal sinuses ; 7, lamina which iso- lates the sphenoidal sinus; 8, lamina partitioning the palatine portion of the maxilliary siniise-- ; 9. oval fora- men; 10, optic fossa; 11, vomer; 12, pterygoid bone ; 1.3. large open- ing leading into the ma.xillary sinus, and which, in the fresh state, is closed by the pituitary membrane ; 14, max- illary turbinated bone; 15, eihmoidal turbinated bone ; 16, great ethmoidal cell. B. Camel. Differential Characters in the Vomer of OTHER Animals. A Ox, Sheep, Goat. — This is a very wide and thin bone, resting only on the lower half of the median suture of the premaxdlaries (Fig. 43). Wider in its upper part than in the Ox, the vomer reaches, outwardly, the THE HEAD. 75 orbital cavity. By its it\ferior bonier, it rests on thu entire length of the median suture of the palatine ami supermaxilLiry bones. C. Pig. — The vomer in this animal adheres to tlie bones of the palatine arch for a great extent. The free porticm of the inferior border is short and but little prominent. D. Carnivora. — In the Dog and Cat, the vomer is short, but its wings are very large. 10. Inferior Maxillary Bone (Fig. 44). The inferior maxillar// bone is not consolidated with any of the preceding bones, and is only united to two of them — the temporals — by diarthrodial articulation. It is a consideralile bone, situated behind the upper jaw, and composed of two symmetrical branches, which are flattened on both sides, wider above than below, curved forwards in their upper third, joined at their lower extremities, and separated superiorly so as to leave a wide gap between them, like the letter Y in shape, called the intra-maxiUary space. Each offers for study tiro faces, two borders, and two extremities. Faces. — The external face of the maxillary branches is smooth and rounded in its inferior two-thirds, and transformed superiorly into a rugged surface, in which is implanted the fibres of the masseter muscle. The internal face presents, in the corresponding point, an excavated surface on which is remarked the superior orifice of the maxillo-dental canal, a long channel which descends between the two plates of the branch, passing under the roots of the molar teeth, and insensibly disappearing in the body of the bone after being widely opened externally by the mental (or anterior maxillar//) foramen. In its inferior two-thirds, the internal face is smooth, nearly plane, and shows nothing very remarkable. Near the alveolar border there is a slightly projecting line — the myloid ridije ; and quite below, or rather at the very summit of the re-entering angle formed by the separation of the branches, there is a slight rugged excavation confounded with that of the opposite branch, and named the genial surface. Borders. — The anterior, also named the alveolar border, exhibits for study a straight or inferior, and a curved or superior portion. The first is hollowed by six alveoh to receive the inferior molar teeth. The second, thinner, concave, and rugged, serves for muscular insertion. The posterior border is also divided into straight and curved portions. The latter is convex, thick, rugged, and margined on each side by an uneven hp ; the first is regularly rectilinear, so that all its points rest at the same time on a horizontal plane ; it is thick and rounded in the young animal, but becomes sharp with age ; an oblique and transverse fissure — the maxiUary — separates it from the curved part. The union of these two portions forms the anylc of the jaw. Extremities. — The superior extremity has two eminences : a condyle, and a long non-articular process named the coronoid process. The condyle is elongated transversely, and convex in its two diameters ; it responds, through the medium of a fibro-cartilaginous disc, to the articular surface of the zygomatic process. The coronoid process is situated in front of the condyle, from which it is sepa- rated liy a division called the sigmoid or corono-condgloid notch ; it is flattened on both sides, and curved backwards and slightly inwards. From the union of the branches of the maxillary bone at their inferior extremity, results a single piece, flattened before and l)ehind, and widened like a spatula, which has been designated the body of the bone. This merits a special description. Its form allows us to divide it into an anterior or buccal face, a posterior or 76 THE BONES. labial face, and a circumference. The anterior face is smooth and concave, is lined by the buccal mucous membrane, and supports the free extremity of the tongue. The posterior face is convex, more extensive than the preceding, and continuous with the external face of the branches. It presents : 1. On the median line, a slight crest or small groove — traces of its being originally separated into two pieces. 2. On the sides and above, the mental foramen — the inferior orifice of the maxillo-dental canal. On a level with this foramen, the bone very markedly contracts to form the neck. The circumference describes a parabolic curve, the concavity being uppermost, and joins, by its extremities, the anterior border of each branch. It is excavated in its middle part by the six alveoli for the lodgment of the inferior incisors, and behind these — in male animals only — there is an additional alveolus for the tusk. The portion included on each side Fig. 44 INFERIOR MAXILLA. 1, Mental foramen ; 1', superior orifice of the maxillo-dental canal ; 2, surface of implantation for the raasseter muscle ; 3, myloid ridge ; 4, coronoid process ; 5, condyle. between the last incisor and first molar, forms a more or less sharp ridge, which constitutes the inferior interdental space or l)ar (diastema). Structure and development. — Formed, like all the flat bones, by two compact plates separated by spongy tissue, the inferior maxilla is developed from two centres of ossification, which correspond to each branch, and which coalesce some time after birth. But in the human foetus, there can oe seen five pieces developed around the dental canal — the coronary, articular, angular, opercular, and premaxillary — which proves.that the maxilla of Mammalia is formed on the same type as that of oviparous Vertebrata (Lavocat). Differential Characters in the Inferior Maxilla op other Animals. A. Ox, Sheep, Goat. — In these animals, the part of the posterior border of the inferior maxilla below the molars is convex, and cannot rest on a horizontal plane by all its points at the same time. The condyle is convex in its small diameter, and sliy;htly concave laterally The coronoid process is bent backwards and outwards. The body does not show any alveolus for the tusk, because this tooth is not present in these animals ; but it is hollowed by eight alveoli for the incisor teeth. The two branches of the bone are never consolidated, but remain movable on each other during life. THE HEAD. 77 B. Camel.— The brandies are short and tliick, the body very long, and the interdental space considerable. The strnight border of the branches has a poaterior rectilinear border, aa in the Horse ; the anterior margin of tlie curved portion is tliin and sharp. On its internal face is seen a plate in front of the superior opening of the inferior dental foramen, and a mylo- hyoid fissure. Tlie condyle is convex in front, flat and oblique behind. The coronoid process is very strong. Below the condyle is a process separated from the latter by a deep notch. The circumference of the body is excavatid by eight alveoli — six for the incisors, and two for the canines. C. Pig. — A straight line leading from the greater axis of the alveoli of the molar would Fig. 45. HKAn OF THE CAMEL. 1, Occipital bone; 2', parietal crest; 3, squamous temporal; 4, fi-ontal bone ; 4', supra-orbital foramen; 5, malar bone; 6, nasal bones; 7, superma.xillary bone; 7', infra-orbital foramen; 8, premaxillary bone; 9, inferior maxilla; 10, 11, openings of the inferior dental foramen. not traverse the posterior border of the maxillary branches, the bottom of these alveoli corre- sponds to the relief on the inner face. The condyle is compressed on both sides, and elongated from before to behind: while the coronoid process is short and wide. Tlicie is no neck; the interdental spaces iire very short; and the maxillo-dental canal opens inferiorly by multiple orifices. D. Camivora. — In Carnivora, this is hollowed at the point corresponding to the insertion of the masseter muscle into a somewhat deep fcssa. The posterior border is disposed as in Ruminants, and below the condyle lias a very marked tuberosity. The condyle represents an ovoid segment, and fits exactly into the temporal cavity. The coronoid process is very strong, elevated, and wide. The mental foramina are double or treble. There are no interdental spaces, nor excavated surface on the inner face of the branches ; and the latter are never consolidated. E. Rabbit. — In the maxilla of the Babbit, the coronoid process is very short, and the condyle narrow and elongated from before to behind. The posterior border is deeply notched 78 THE BONES. HEAD OF THE CAT. 1, Parieto-occipital suture; 2, parietal bone; 3, frontal bone ; 4, orbital process of the frontal bone ; 5, malar bone ; 6, supermaxil- lary bone ; 7, 7, premaxilla ; 8, nasal bone ; 9, tympanic bulb ; 10, inferior maxilla. in its curved portion ; the interdental space is very long ; and the body has only two alveoli for the incisors. 11.— The Hyoid Bone (Fig. 47). The hi/oid bone constitutes a small and special bony apparatus which serves to support the tongue, as well as the Fig- ■*^- larynx and pharynx ; its description is placed immediately after that of the bones of the head because of its con- nection with that region, it being situ- ated between the two branches of the supermaxillary bone, and suspended from the base of the cranium in an oblique direction from above to below, and from before to behind. This apparatus is composed of seven distinct pieces, arranged in three series : a middle, constituted by a single bone, and named the bod?/ ; two lateral, form- ing two quasi-parallel branches, to the extremities of which the body is articu- lated. Body or basihyal. — The body of the hyoid resembles a fork with two prongs. It presents : 1. A middle part flattened above and below, and consequently provided with a superior and an inferior face. 2. A single and long pro- ^'^' ^^" longation flattened on both sides, which is de- tached from the middle part, and directed forward and downward to plunge into the muscular tissue of the tongue : this is the anterior a/Ypendu of the hyoideal body, or lingual proJongation. 3. Two late- ral corniia, thyroid cornua, grpat rornaa, or arnhyah, projecting backwards and upwards, articulating by their extremities with the thyroid cartilage of the larynx, and offering, at their point of union with the middle part, two con- vex diarthrodial facets looking upwards, and corresponding with the styloid cornua. The body of the hyoid bone is developed by three centres of ossification — a middle, and two lateral for the cornua. Branches. — The three pieces composing these are articulated end to end, by HYOID BONE OF THE HORSE. 1, Body or ba^ihyal ; 2, lingual prolongation ; 3. 3, thvroid cornua, great cornua, or urohyals ; 4, 4, styloid coriu.a, small cornua, or apohyals ; 5, 5, styloid nuclei or ceratohyals ; 6, 6, styloids, great hyoideal branches, or stylohyals ; 7, 7, arthrohyals, or cartilaginous nuclei attaching the hyoid to the temporal bone. TUE HEAD. 79 means of a cartilaginous substance that joins them together ; they are of very unequal dimensions. The first, which is in relation with the body, is of medium size, and is named the st//loid conn/, smaU corny, or small hranrh. The second, termed the styloid nuchus, is the smallest. The third, the largest, constitutes the styloid process or lone, or yreat branch. 1. The styloid corniia {ajwhyaJ) is a small cylindrical piece bearing a concave diarthrodial surface on its inferior extremity to unite it to the body ; it is very spongy, and is developed from two ossifying centres, one of which, the epiphysary, is for the inferior extremity. 2. The styloid nucleus {cerafohyaJ), which is often absent, is embedded in the uniting cartilaginous substance. 3. The styloid bone, or yreat hyoideal branch (stylohyal), is long, thin, flattened on both sides, and directed obliquely from above to below, and before to behind ; it presents two faces, two borders, and two extremities. The faces — an external and internal — are marked by some few imprints. The anterior border is sharp and slightly concave in its upper third. The posterior border is thicker, and is divided into two portions — a superior or horizontal, which is very short, and an inferior or vertical, much more extensive. The angle they form at their point of junction presents a salient, and more or less roughened, tuberosity. The superior extremity is united to the hyoideal prolongation of the temporal bone by means of a cylindrical fibro-cartilage. By its inferior extremity, the styloid bone is united either to the styloid nucleus or the styloid cornu, forming a sharp elbow directed forwards. The styloid bone, developed from a single centre of ossification, is almost entirely formed of compact tissue. Differential Characters of the Hyoid Bone in other Animals. A. Ox, Sheep, Goat. — The hyoid bone of Ruminants is always composed of seven jiiecea . the styloid nucleus, the presence of which is not constant in Solipeds, is never absent in these, and has the proportions of the second small branch. The anterior appendix is very short, and only rejjresents a large mamelon. B. Camel. — The byoid is in this animal as in the Ox. C. Pig. — The body is voluminous and deprived of an appendix; the small branches are sliort and consolidated with the body ; wliile the large branches, curved like an S, are very thin, and are not united to the small brandies au'l the temporal bone by fibro-cartilage, but bj veritable yellow elastic ligaments. D. Carnivora. — The three pieces composing the bo ly of the hyoid in early life are never consolidated in tlie adult animal, but always remain isolated, as in Man. The middle piece has no anterior appendix; the fibro-cartilages uniting tiie styloid portions to each other and to the temporal bone are very long and flexible. 12. Wormian Bones (Fig. 48). This name has been given to small irregular bones which Worms observed between some of the sutures of the cranial bones. They are developed after birth, in the cranial, cranio-facial. and facial sutures. Their number and position varies with the species of animals, and even the breeds of the same species. Vaguely described by Rigot, they have been recently studied by Cornevin, who observes that the cranial Wormian bones are rare. In more than sixty crania, they were found only once or twice in the Ox and Horse at the junction of the petrous with the occipital bone. The Wormian bones of the cranio-facial and the facial suture are more frequent ; nevertheless, they have been met with almost exclusively in the heads of common-bred animals, particularly in the bovine species. Cornevin has described a fontanelle lachrymo-nasal bone (Fig. 80 THE BONES. 48, 2), and Wormiau fronto-nasal (Fig. 48, 1), as well as an internasal, orbital, zygomato-maxillary, maxillo-nasal-incisive bone, (Sometimes two Wormian bones are found in the same head.) OP THE HEAD IN GENERAL. 1. Geneeal Configuration. From the union of all the bones which constitute the cranium and face, there results a quadrangular pyramid, with summit inverted, which it is necessary to study as a whole. We will pass in '^'S' ■*^- review, successively, its four faces, its base, and its summit. A. Anterior Face. — This is subdivided into four regions (Fig. 49) : 1. Parietal region. — This has for base the anterior portion of the occipital bone and the parietal bones. Limited, above, by the external occi- pital tuherositij, it presents on the middle line a spur which soon bifur- cates to form the parietal or temporal crests ; the latter join the posterior border of the zygomatic process. 2. Frontal region. — Larger than the preceding, it is usually plane and lozenge-shaped. Boimded iuferiorly by the fronto-nasal suture, this region projects, laterally, the orbital pro- cesses, the base of which is pierced by the supra-orbital foramen, and the anterior border — somewhat sharp — is frequently made irregular by small notches, one of which is often converted into a foramen. 3. Nasal region. — This region has for its base the proper bones of the nose. It is narrow, convex on each side, and plane, concave, or convex in its length, according to the animals. It advances above the entrance to the nasal cavities, where it forms the nasal prolongation, the summit of which, in the Horse, ceases at nearly two fingers' breadth from the intermaxillary symphysis. 4. Incisive region. — Principally formed by the incisive bones, this region presents : the inferior opening of the nasal cavities, divided in the fresh state by the median cartilaginous septum of the nose ; the incisive slits on the floor of the nasal fossae ; the intermaxillarg sgmphgsis, channeled above by a more or less deep groove in nearly all Horses, but raised, on the contrary, into a conical tubercle in the Ass and Hinuy, and perforated in the middle by the incisive canal. Right and left of the intermaxillary symphysis this region is convex, and elevated by the prominence which the roots of the incisor teeth form. B. Posterior Pace. — In this are recognized four distinct regions (Fig. 50) : 1. Sub-occipital region. — This presents : in the middle, the basilar process^ WORMIAN BONES OF THE OX. (AFTER CORNEVIN.) 1, Fronto-nasal Wormian bones ; 2, 2, lachrymo- nasal fontanellar bones. THE HEAD. 81 a strong piece more or less deeply channeled, according to the animals, and provided at its inferior extremity with rugosities for the attachment of the anterior straight muscles of the head ; on the sides, the lacerated foramina— large irreo-ular Fig. 49. horse's head (anterior face). 1, Occipital tuberositv ; 2, origin of the mastoid crest ; 3, parietal bone; 4, saggital suture ; 5, junc- tion of the parietal and temporal bones ; 6, zygomatic arch ; 7, frontal bone ; 8, frontal suture ; 9, temporal fossa ; 10, supra-orbital foramen ; 11, 12, lachrymal bone ; 13, malar bone ; 14, nasal border of frontal bone ; 15, nasal bone ; 16, suture of nasal bones; 17, super- maxillary bone ; 18, infra-orbital foramen; 19, anterior, or pre- maxillary bone ; 20. foramen in- cisivum ; 21, incisor teeth (young mouth). horse's head (posterior face). 1, Occipital tuberosity ; 2, foramen magnum ; 3, 3, occipital condyles; 4, 4, styloid processes; 5, 5, petrous bone ; 6, basilar process ; 7, ptery- goid fijsure of the sphenoid bone ; 8, foramen lacerum ; 9, 9, supra-condylnid. or anterior mas- toid process; 10, In, articular eminence, or temporal condyle; 11, body of sjihenoid bone; 12, pterygoid process; 13, ethmoid bone; 14, temporal bone and sphenoidal suture; 16, lachrymal bone; 16, vomer; 17, malar l)one ; 18, maxillary tuberosity; 19, posterior, or guttural opening of the nose ; 20, palate bone ; 21, palatine styloid process; 22, palato-maxil- lary foramen; 23, jialatine process of superior maxillary bone, with suture ; 24, ditto of pre- maxillary bone; 25, premaxillary bone; 26, upper incisor teeth ; 27, point of junction of the premaxillary with the superior maxillary bone ; 28, upper molar teeth (young mouth). openings divided, in the fresh state, into two portions {anterior and posterior lacerated foramina). To the outside of these openings is the base of the tuberous portion of the temporal bones, especially the tympanic bulb or petrous bone ; above 82 THE BONES. are the condyloid fossce with their condyloid foramen, and the styloid processes of the occipital bone or jugular eminences. 2. Suh sphenoidal region. — This region is notably constricted in its middle part, where it has for base the body of the posterior sphenoid bone ; it is enlarged above by the temporal articular surfaces. It is limited by the inferior border of the foramen lacerum, on which are three notches transformed into foramina by the tissue that partitions the foramen lacerum basis cranii in the fresh state. These openings are, passing from within to without, the carotid or cavernous foramen, the foramen ovale or foramen rotundum ; they are all preceded by a groove on the surface of the bone. On each side of the body of the sphenoid is the narrow Vidian fissure, prolonged by the Vidian canal, and margined outwardly by the origin of the suhsphenoidal process. Laterally, is the sabsphenoidal canal for the passage of the internal maxillary artery, which is continued forward by two branches, one of which opens into the orbital hiatus, the other into the temporal fossa. 3. Spheno-pcdatine region. — This extends from the superior sphenoid to the palatine arch. In the median plane it shows a vast elliptical opening — the gutturcd opening of the nascd cavities, divided at the bottom into two portions by the vomer, and bordered laterally by two elevated crests (pterygo-pcdatines) resulting from the junction of the pterygoids with the palatine crests ; and limited in front by the posterior border of the palatine bones, which is raised in its middle by a blimt point directed backwai-ds — the nasal spine. Beyond the pterygo-palatine crests is a slightly depressed surface, on which run the branches of the internal maxillary artery and the superior maxillary nerve. This surface extends, above, to the orbited or sphenoidal hiatus, below to the maxillary hiatus. In the maxillary hiatus are : the upper opening of the superior dental canal, the palcdine canal, and the nasal foramen. In passing from the maxillary hiatus on the margin of the guttural opening of the nasal cavities, we meet with the staphyline fissure, which is limited above by the alveolar tuberosity. 4. Pcdcdine region. — This is a wide elongated surface, limited laterally by the molar teeth and interdental spaces, and in front by the incisors. It shows : in the middle, the pcdcdine and superior maxillary suture, which terminates at the incisive canal ; on the sides and above, the inferior opening of t\iQ palatine grooves, prolonged by i\iQ pcdcdine fissures ; in front, the incisive slits. C. Lateral Face. — This is a pair face, and comprises three regions (Fig. 51) : 1. Maxillary region. — This is very extensive. Its shape is triangular, base superior — the supermaxilla being joined to the premaxilla. Proceeding backward, there are observed : a fossa, in which opens the infra-orbital foramen ; the lower orifice of the superior dental canal, pierced above the third molar tooth ; the mcdar or zygomatic spine — a long vertical crest for the insertion of the masseter muscle, commencing above the fourth molar teeth, and continuing upwards with the malar bone and zygomatic process. Lastly, the maxillary region is limited, above, by the orbit and the maxillary tuberosity. 2. Orbital region. — This includes the orbit or orbited cavity, for the reception of the essential and some of the accessory organs of vision. In Man and the Quadrumana this cavity has complete bony walls, but in the domestic animals it always largely communicates with the temporal fossa, and it is not always even circmnscribed at its opening by a solid ring. A fibrous lining {ocular sheath) converts it into a distinct cavity. In the Horse, the outUne of the orbit is constituted : below, by the lachrymal THE HEAD. 83 bone ; above and in front, by the frontal bone and its process ; externally, by the malar bone. If its two lart^^est diameters are measured, it is remarked that this opening is scarcely ever regularly circular, its width varying from above to below or from without to within. With nine Horses' heads of various ages and breeds, equal diameters were found in only one, the other eight being unequal ; of these, the vertical diameter of the orbit predominated in tive. and was least in three. In the .4.S.S, as a general rule the vertical diameter is smallest, the relation between the two diameters varying from 1-09 to ri5. Otherwise, the entrance to the orbit is irregularly square, and the orbital process which covers it is much wider and more salient than in the Horse — as Lecoq asserted, and as the observations of Goubaus and Sanson have confirmed. We have also noticed these differences, and they are not the only ones which permit the skeleton of the Ass to be recognized ; for there have been already cited those of the spine and bones of the head — such as the articular depression surrounding the basilar process, the vascular furrow on the styloid process, the position of the lachrymal tubercle, and the conical eminence surmounting the premaxillary symphysis, above the incisive foramen ; others will be noted hereafter (Figs. 51, 52). With regard to the cavity of the orbit, it is separated from the maxillary hiatus and the temporal fossa by two linear imprints, diverging forwards, to which the ocular sheath is attached. It presents, on its floor, the upper orifice of the lachrymal canal, the lachr//mal fossa, where the small oblique muscle of the eye has its fixed insertion ; and within this, but higher, the little depression for the bend of the great oblique muscle of the eye. 3. Temporal region. — This region is more extensive than the preceding, and is composed of three principal parts — the temporal fossa, zygomatic arch, and petrous portion of the temporal bone. The temporal fossa surmoimts the orbit, from which it "is incompletely separated in Solipeds and Ruminants by the orbital arch ; in the other domestic animals, this arch is incomplete in such a way, that in the skull the temporal fossa is confounded for the greater part with the orbit. Situated obliquely down- wards and outwards on the sides of the cranium, the temporal fossa is oval in shape, and bounded inwardly by the occipital or temporal crest, outwardly by the anterior border and longitudinal root of the zygomatic process. It lodges the temporalis muscle ; consequently, its width in our animals is proportionate to the power of that muscle. It is studded with muscular imprints, and has several vascular foramina which enter the parieto-temporal canal. The zijfiomcdic arch is formed as if by a loop thrown from the cranium on to the face, outside the temporal fossa and the orbit. It is constituted by the zygomatic process of the temporal bone and the malar bone, which latter prolongs it to the maxillary region. The tuberosity of the temporal hone shows, outwardly, the external auditory canal, usually larger in the Ass than the Horse. Between this orifice and the supra-condyloid eminence is the opening of the parieto-temporal canal ; and behind the latter are several irregular ridges, one of them being the hyoid process. The external face of the tympanic case is also studded with some styloid prolongations, one of which, more developed than the others, serves for the insertion of the peristaphyline muscles. Above the hyoid process is the mastoid process, and between these two parts is the external orifice of the aqueduct of Fallopius. From the mastoid process extends the mastoid crest, the summit of 84 THE BONES. which meets the external occipital protul)erance ; it is crossed by the mastoid groove, which gives the mastoid artery passage to the parieto-temporal canal. All of the petrous portion is surrounded by deep clefts, resulting from the simple union of this bone with its neighbouring pieces. D. Base. — The base or superior extremity of the head, formed by the occipital bone, represents a trapezoid surface, incurvated from before to behind. It is separated from the anterior face by the external ocnpitaJ tuberosity, the projection of which is always greater in the Ass and Mule than in the Horse, with the exception of the English Horse, in which it has been found very developed (Figs. 51, 52). It is separated from the lateral faces by two crests — Fig. 51. M 19 15 12 17 22 horse's head (lateral face). 1, Occipital condyle; 2, styloid process of the occipital boue ; 3, external occipital tuberosity, 4, parietal crest; 5. external auditory hiatus; 6, zygomatic process of the temporal bone; 7, frontal bone; 8, orbit; 9. lachrymal bone and its tubercle; 10, zygomatic or malar bone ; 11, nasal bone; 12, superni ixillary bone ; 13, zygomatic spine; 14, infi a-orbital foramen; 15, pre- maxillary or intermaxillary bone; 16, incisor teeth; 17, molar teeth; 18, inferior maxilla; 19, maxillary fissure; 20, maxillary condyle; 21, coronoid process of the maxilla; 22, mental foramen ; 23, supra-orbital foramen ; 24, basilar process of the occipital bone. the superior curved lines — which are prolonged backwards on the styloid processes of the occipital bone. In the middle plane is the orripitnl crest, behind the tuberosity ; it terminates, in becoming gradually effaced, at the orripitnl foramen, which is bordered on each side by the condyles of the occiput. The condyles are separated from the styloid processes by two deep notches — the sti/lo-condyloid notches. Between the middle line and the superior curved lines, are muscular imprints irregularly arranged in a half-circle — these are the inferior curved lines. The base of the skull joins the anterior and posterior faces in forming angles ; these possess some interest, as they may afford an important differential character between the Ass and Horse. THE HEAD. 85 If one of the branches of a goniometer be placed tangentially to the surface of the basilar process, and the other to the summit of the external occipital tuberosity, the basilo-occipital angle will be obtained. In the measurements we have taken of eight heads of Horses of diverse ages and breeds, this angle has varied from 70° to 91°. We except the head of a young English Stallion, the basilo-occipital angle of which was from *J2° to 100°. Measurement of the heads of Asses showed the angle to be 103°. The average basilo-occipital angle was 85'8G° for the Horse, and 95° for the Ass. If, instead of taking the basilo-occipital angle, the goniometer be applied to the origin of the temporal crests and the superior outhne of the occipital Fig. 52. 20 e 18 19 IS 12 17 ass's head (lateral face). 1, Occipital condyle; 2, styloid process of the occipital bone, with a very marked furrow on its external face; 3, e-Tternal occipital tuberosity, more developed than in the horse; 4, parietal crest; 5, external auditory hiatus; 6, zygomatic process of the temporal bone; 7, frontal bone; 8, orbit, with its external outline more angular thm in the hoise ; 9, lachrymal bone, with its tubercle partly implanted on the nasal bone; 10, zygomatic or malar bone; 11, nasal bone; 12, supermaxilla ; 13, zygomatic spine ; 14. infra-orbital foramen ; 15, premaxillary bone, with its inner border raised by a salient tubercle above the incisive canal ; 16, incisor teeth ; 17, molar teeth; 18. inferior maxilla; 19, maxiliarv fissure; 20, maxillary condyle; 21, coronoid process ; 22, mental foramen ; 23, supra-orbital toramen, carried more to the middle of the orbital process than in the horse ; 24, basilar process of the occipital bone. foramen, the parieto-occipifal angle is obtained. In the Horse, this angle is between 81° and 104° : in the Ass between 77° and 87° — the average being 91-12° for the Horse, and 84° for the Ass. It was foreseen that the value of these angles would be in inverse relation. In all cases when, on a head, the basilo-occipital angle was found very open and the parieto-occipital more closed, combined with a great development of the external occipital tuberosity and the differential characters already described, it was certain to be the head of an J.s.s. In the English Horse, the external 86 TIJE BONES. occipital tuberosity of which is very developed, the two angles in question are nearly equal. In the Mule and Hinn//, the value of the angles is intermediate between the Horse and Ass. In the Mule, the mean value has been 86 '12° for the basilo-occipital angle, and 88° for the parieto-occipital angle. In the Hinny, it was 87° for the first, and 81° for the second. E. Summit. — This results from the union of the four faces ; but, instead of being acute, it is flattened from behind to before, curved from side to side, and furnished with the incisor teeth.^ 2. Conformation of the Cranium in Particular. Retzius was the first to start the idea of considering the cranium of Man independently of the face. He distinguished the races of mankind as brachy- mphalir (short-headed), and dolichocqihaUc (long-headed) — that is, crania long from before to behind, and crania relatively short. Broca more recently compared the transverse diameter of the cranium with the antero-posterior diameter taken as a unit, and has expressed this relation in hundredths by the term cepludk index. For some years, Sanson has endeavoured to introduce into the classifica- tion of animals the calculations of Retzius and Broca. Taking the dimensions of the cranium as a basis, he has divided Horses into two groups — the brachy- cephalic and the dolichocephalic kinds. If the cerebral cranial cavity — the only important one for this purpose — be enclosed in a parallelogram, two sides of which shall be at a tangent to the most salient points of the parietal bones, and the other two pass in front of the external auditory canals and across the supra-orbital foramina, the dimensions of the base and height of this parallelogram, measured in a straight line, will correspond to the longitudmal and transverse diameters of the cranium. In proceeding thus, Sanson has found that in certain crania the transverse diameter is greater than the longitudinal (brachy cephalic crania), while in certain others the transverse is shorter than the longitudinal diameter {dolichocephalic crania).^ Toussaint took direct measurements of the interior of the cranium, and, no matter what the breeds of horses were which he examined, he always observed that the longitudinal diameter exceeded the transverse. We have made cranio- metrical investigations on a number of Horses, and are able to confirm Toussaint's statements. In eight skulls from different sources, the longitudinal diameter varied between 113 and 133 millimetres, the transverse between 88 and 104 millimetres. Consequently, in none of these animals was the transverse diameter equal to the longitudinal. In the number examined were the skulls of a Syrian and an English stallion — types which Sanson would have selected as the most brachycephalic ; the relations between the length and width were I'll for the first, and 1'31 for the second. The average for the eight heads was r24. We are of opinion that there are no brachycephalic Horses, in the rigorous sense of the word, such as Sanson admits ; so that, if it is attempted to establish brachycephalic and dolichocephalic types, it will be necessary to previously fix what shall be the limit between these two types, and this has not yet been done. The crania of Asses from the south of France are longer than that of the ' For tlie regions of the head, see Lavocat's Nouvelle Osteologie rompar^e de la tete des Animaux Domestiques. * Sanson, " Me'moire sur la Nouvelle determination d'un type specific de race Chevaline," Journal de VAnaiomie et de la Physiologie, de Ch. Robin, 1867; also the later works of M. Sanson. THE HEAD. 87 Horse ; for in eight the average relation between the length and width was r25, instead of 1"24 — a difference not very great, certainly. The difference becomes more marked, however, between the Ass and Horse, if the length of the cerebral be compared with that of the cerebellar cavity. This comparison has yielded an average of r962 in the Horse, and r927 in the Ass — which proves that the cerebellar cranium is longer in the Ass than the Horse. The cranium is, as it were, strangled behind the orbital processes of the frontal bones. In glancing at the cranium of the Horse and Ass, it would at first appear that that of the Ass is relatively naiTOwer than the cranium of the Horse. We have measured six heads of each species for the width of the cranium at its greatest diameter, behind the orbital processes, and, in comparing these two diameters, have obtained the following results : in the Horse, the relation varied between ri8 and l"21 ; in the Ass, between r20 and r47. The average has been, for the Horse, r226, and r335 for the Ass. From these figures, it might be concluded that the cranium of the Ass is relatively more constricted at its inferior extremity than that of the Horse. In the hybrids of the Horse and Ass, the cranial cavity is more elongated, and in this respect the Hinny more resembles the Ass than the Horse. With regard to narrowness of the cranium behind the orbital processes, the 3hih holds the middle place between its parents, while the Hinny comes nearest to the Ass — the reverse of what is noticed in the development of the cerebellar cranium. In Ruminants, the shape of the cranium is more or less masked by the frontal or parietal sinuses ; consequently, it is difficult to study satisfactorily this part of the head, particularly in the bovine species. The cranium of the domestic Dog offers great varieties ; for the creation of numerous breeds has brought about important differences in the form and dimensions of this part, which it is impossible to deal with here. 3. Relations between the Cranium and Face. Instead of studying the cranium alone, we may compare it with the face in regard to width, length, and the area that each of these two regions occupies in a vertical and median section. We may also, in measuring the facial angle, form an idea of the manner in which these two regions unite to form the head. 1. The forehead, properly speaking, measured from the union of the parietal crests to the fronto-nasal suture, is always, in the Horse, longer than the cerebral cranium, the second to the first being as 1 : 1-425. The forehead of the Ass is proportionately less developed, for we have found that the cranium is to the forehead as 1 : r265. 2. This shortness of the Ass's forehead, which renders the head heavy, is corrected by its narrowness ; the head enlarges at the orbital processes. In com- paring the distance between the supra-orbital foramina and the transverse diameter of the cerebral cavity, it has been noted that the width of the cranium is to the space between these foramina as 1 : 1*454 in the Horse, and 1 : 1 '2 65 in the Ass. The forehead of the Ass is, therefore, in proportion to the cranium, shorter and narrower than in the horse. From this point of view, the heads of the Mule and Hinny are intermediate to those of their parents ; but the first of these hybrids is nearer the Horse, and the second approaches the Ass. 3. Cuvier imagined that one of the means of judging of the intelligence ot animals, would be to compare the area of the craniiun with that of the face, measured on a median section of the head, deprived of the lower jaw. This 88 . THE BONES. great naturalist remarked that the area of the cranium diminishes as the animals are further removed from the human type, while the area of the face increases in the same sense. Colin has studied the heads of the domesticated animals from this point of view. Putting to one side the surface occupied by the einuses, he found that the area of the cranium to the face was as — 1 : 2-69 in the Horse. 1 : 2 09 in the Ass. 1 : 3-43 in the Ox. 1 : 2-20 in the Ram. 1 : 1-95 in the Goat. 3 24 in the Pig. 117 in the Dog. 0-68 in the Cat. 1-47 in the Rabbit. 054 in the Lamb. From this table it will be seen that, if the domesticated animals are classified according to the area of the cranium, they will stand in the following order : Cat, Dog, Rabbit, Goat, Ass, Ram, Horse, Pig, and Ox. 4. Camper measured the facial angle by drawing two lines, starting from the entrance to the nasal cavities, and passing towards the middle of the external auditory canal and towards the most prominent part of the forehead. The facial angle gives an idea as to the relative volume of the face and cranium, and the dimensions of the latter ; but with animals it furnishes very imperfect information, because of the form of the face and the development of the sinuses around the cranial cavity. Colin has measured the facial angle of the domestic animals, by drawing two lines from the upper incisors towards the external auditory canal and the fore- head, in the point corresponding to the lower end of the brain ; and he obtained the following average values : from 12° to 15° for the Horse ; 16° for the Ass ; 20° for the Bull ; from 20° to 25° for the Ram ; from 34° to 41° for Dogs ; and 41° for the Cat. On the other hand, we have measured this angle in Equines, and find that it varies : in the Horse, between 11° and 13" ; in the Ass, between 12° and 16° ; and in the Mule, between 13° and 15°. In the Hinny, it measures 14°. It is somewhat remarkable that, in the Equid«, the Ass should have a greater facial angle than the Horse. 4. Modifications due to Age. Age brings modifications bearing upon the form of some regions of the head, the development of external peculiarities of the bones, the shape of the cranium, and its relations with the surface. 1. It has been remarked that the development of the occipital tuberosity, the temporal crests, and the lachrymal tubercle, increases with age in the Equine species ; the infra-orbital foramen, which is frequently only a notch in youth, becomes a true foramen when the animal is advanced in age. In the Foal, the forehead is convex ; that bone and the nasal bones become flat as the creature grows, and sometimes even the line of the nasal bones is concave in old age. The maxillary region, which is at first convex, becomes gradually hollow as the molar teeth are pushed out of the alveoli ; while the straight part of the posterior border of the inferior maxilla becomes thin and sharp in very old Horses. The entrance to the orbit is also notably modified, though its shape is not identical in all the animals. In every instance, it has been remarked that the direction of the larger axis of the orbital cavity, comprised at first in the plaue which passes by the auditory canal and the implantation of the upper incisors, is depressed in THE HEAD. front, and at an advanced age is found in a plane passing by the inferior extremity of the zygomatic crest and the summit of the external occipital tuberosity. 2. If the cranium be examined by itself, it will l)e noted that, in proportion, it is less narrowed behind the orbital processes in the young animal than in the adult. "With regard to the cerebellar cranium, it is elongated when the animal is aged — a consequence of the natural development of the external occipital tuberosity. 3. The relation of the areas of the cranium and face change with age. If the measurements obtained by Colin on the Lamb and Ram are compared, it will be perceived that the face grows as the creature ages. This change is very evident if the development of the young Hare is watched. At birth the face is very short — like that of a common dog, it is said ; but when development is completed, we know how much the face has become lengthened. -1-. Finally, in consulting the table of angles drawn up by Colin, we might believe that the facial angle widens as the animal advances in age. Thus, in the young Hinny, Colin estimated the facial angle at 15° ; this angle was 16° on an Fig. 53. A, B, C, D. 1, P'ronto-parietal crests; 2, external occipital tuberosity; 3, 3, superior root of the zygomatic process of the temporal bone. old Hinny, and 17° on another very old one. In every instance, however, according to the same table, this angle will be equal in a four-years-old Horse and in an adult Horse ; and even in the Calf it diminishes one degree when it becomes an adult animal. The measurements we have taken in domestic Solipeds, have demonstrated that the facial angle diminishes in a constant manner as the animal grows old. Thus, this angle is 16° in an Ass three years old ; it is 15° in the adult, and 12° in the very old Ass. We have found it 13° in a Foal of two years, and 11° in an old Horse ; 15° in a Mule of eighteen months, and 12';30° in a very aged Mule. This question has, therefore, to be again examined ; and, however it may be decided, it will be seen, by what has been stated, that age induces very interesting changes in the form and proportions of various parts of the head. If the crania of different breeds of Dogs are compared, there will be found very marked diversities in the prominence of the parietal convexity, and the development and distance apart of the fronto-parietal crests. A mere glance at the figures above (Fig. 53), will afford evidence of this. 90 THE BONES. On the cranium of the Mastiff (a), the parietal bulgings are httle marked ; the parietal crests are very elevated, and join each other early, so that the temporal muscles are in contact throughout the greater part of their inner margin. In the little Lap-dog (d), the parietal crests are widely separated from one another, and the cranium is so very convex as to resemble that of a Monkey. Between these extremes are many intermediates (b, c) ; and it would appear that the development of intelligence in the Dog results in rendering the parietal bones more convex, and the temporal fossEe narrower. Comparison of the Head of Man with that op the Domesticated Animals. Fig. 5+. 1. Occipital bone. — The occipital of Man is large, flat, incurvated like a shell, and the ex- ternal tuberosity is slightly developed, aud united by a ridge to the occipital t'oramen, which is relatively very wide. Two series of ridges arise from the external tuberosity and pass towards the circum- ference of the bone ; these are the superior and inferior curved or semicircular lines. There is an anterior and a [losterior condyloid fossa pierced by a foramen at tlie bottom; and the jugular eminences, wide and slightly prominent, replace the styloid processes of the domesti- cated animals. The internal face of the occipital of Man corresponds with the cerebrum and cerebellum ; and for this purpose it shows four fossae, distinguisiied into superior or cerebral, and inferior or cerebellar. TJiese fossfe are separated by a crucial projection wiioise most developed portion forma the internal occipital protuberance. The union of the occipital with the parietal bones, con- stitutes the liimhdoidal suture. At the point where this bone meets the parietal and the squamous portinn of the temporal, is found, in the infant, the lateral posterior fontanel. 2. Parietal bones. — The parietals are always isolated in early life, aud sometimes consolidated with each other at the adult age. They are very large, quadrilateral, and occupy the summit and sides of the cranium. The parietal crests are absent, but are replaced, in certain individuals, by two faintly marked curved lines situated a little above the inferior border of the bone. The middle portion of the external face is very convex. On the internal face there is no i)arietal protuberance, but in its stead the internal occipital tuberosity. It also exhibits ramous channels, which in disposition are analogous to the ribs of a fig-leaf ; as well as the parietal fossa, which corresponds to the parietal eminence. 3. Frontal bone. — The frontal bone of Man forms the upper part of the face and the anterior portion of the cranium. Convex from behind forward, then vertical in its upper three-fourths, the bone suddenly bends at the orbit.s, so as to become horizontal in its lower fourth. The external face offers, above tlie forehead, two Literal frontal eminences, and above the nose, a middle frontal boss. To the right and left of the latter are two salient arches — the supra-orbital ridges. The internal face entirely belongs to the cranial cavity. It offers, on the median line, the saggital groove terminated by a frontnl crest; and on each side of this line the frontal fossae, corresponding to the eminences of that name, and orbital bosses to match the orbital roofs. There is no mortise for the articulation of the sphenoid bone. On the middle portion of the superior frontal border, in young persons, is the anterior angle of the anterior fontanel. The anterior border exhibits three supra-orbital foramina and the orbital archei. front view of the human cranium. 1, Frontal bone ; 2, nasal tuberosity ; 3, supra-orbital ridge ; 4, optic foramen ; 5, sphenoidal fissure ; 6, spheno-maxillary fissure ; 7, lachrvmal fossa ; 8, opening of the nose divided by the vomer; 9, infra-orbital foramen ; 10, malar bone ; 11, symphysis of the lower jaw; 12, mental foramen; 13, ramus of the lower jaw ; 14, parie- tal bone; 15, coronal suture; 16, temporal bone ; 17, squamous suture ; 18, upper part of the great ala of the sphenoid bone; 19, com- mencement of the temporal ridge ; 20, zygoma of the temporal bone concurring to form the temporal arch ; 21, mastoid process. TEE HEAD. 91 Fig. 55. 4. Ethmoid bone. — In Man, the externnl face of the lateral masses — formed by a very thin lamina, termed the os planum or lamina papyracae — belongs to the internal wall of the orbit. 5. Sphenoid hone. — Tliis is distinguished, in Man, into a body and four wings — two large and two small. The inferior surface of the body offers nothing remarkable, except the presence of a conical prolongation named the beak (rostrum) of the sphenoid. The external face of the greater wings forms part of the temporal fossa, as also tlie external wall of the orbit. At the union of the wings with the body, are detached two bifid pterygoid proci-^scs; their internal branch represents the pterygoid bones of animals. There is no sub- sphenoidal canal. The two lesser wings are very thin and triangular, and .visible only on the superior surface of the bone ; they constitute the processes of Ingrassias. On the internal face of tlie bone are found: (1) a deep pituitary fossa, limited by four clinoid pro- cessi's; (2) an optic fossa, shallow, showing very short optic canals transformed into foramina ; (:->) f lie sphenoidal fissure, whicii replaces the great super- eplienoidal canal in the Horse; (4) the great fciranien rotundum ; (5) the internal face of the wings, much excavated ; (6) the foramen ovale, which transmits the inferior maxillary nerve ; (7) the small foramen rotundum that lodges the spheuo-spinous artery. 6. Temporal bone. — In the squamous portion of the temporal bone of Man, the zygomatic process only rests on the malar bone, as in Ruminants. The glenoid cavity is concave in every sense, and divided into two parts by an opening named the Ji^sura Glaseri ; the anterior portion oidy is articular— tlie posterior, lying against the external auditory canal, does not belong to the articulation ; it corresponds to the supra-con- dyloid eminence of the Horse. The tuberous portion is consolidated with the squamous. It is divided into a mastoid and a pyramidal portion ; the latter com- prises, in its turn, the petrous and tympanic portions. The mastoid portions correspond to the mastoid pro- cess, mastoid protuberance, and superior border of the petrous bone in the Horse. It presents a rugged mastoid process. Above this is the mastoid canal ; and aliove and behind it, the digastric gmove — the pyramid forming a considerable projection in the interior of the cranium. The styloid process or bone is altogether separate from the other pieces of the hyoid, and in the adult is consolidated with the tem- poral bone. 7. SupermaxilJa. — In Man the premaxilla is no longer found independent, the centre which forms it coalescing with the supermaxillary bone. The supermaxilla of man cuueurs, for the greater part of its extent, to form tlie floor of the orbit ; it is also divided into three faces : an external or facial, a superior or orbital, and an internal or naso-palatine. The external face presents, from before to behind: (1) a. small fo.ssa, into which is inserted the inyrtilorm muscle ; (2) the infra-orbital, or canine fossa, showing the inferior orifice of the infra-orbital canal; (3) a crest corresponding to the maxillary spine of Solipeds : (4) the alveolar tuberosity. This face carries, in front, a prolongation that forms the ascending process, also named, because of its relation, the tionto-nasal process. The superior or orbital face offers a fissure which precedes the infra-orbital canal, and, outwards, the malar process. The internal face is divided by the palatine process. It shows, in front, the half of the anterior nasal spine and a groove which participates in the formation of the incisive canal. 8. Palatine bone. — The palatine bone of Man is formed of two osseous laminae —one horizontal, the other vertical— which are joined at a right angle. The first part presents : one-half of the EXTERNAL OR r.ASILAR SFRFACE OF THE BASE OF THE HUMAN SKULL. 1, 1, The bony palate; 2, incisive, or anterior palatine foramen; .3, pala- tine process of palate bone, with the posterior palatine foramen ; 4, palate spine with transver.se ridge ; 5, vomer ; 6, internal pterygoid palate ; 7, hca- phoid fossa; 3, external pterygoid plate, with fossa ; 9, zygomatic fossa ; 10, basilar process of occipital bone ; 11, foramen magnum; 14, glenoid fossa; 15, meatus auilitorius exter- nus ; 16, fiirainen lacerum anteriiis ; 17, carotid foramen of left side; 18, foramen lacerum posterius, or jugular foramen; 19, styloid process; 20, stylo-mastoid foramen, with jugular tubercle and digastric fossa ; 21, mas- toid process; 22, occipital bone ; 23, posterior condyloid fossa. 92 THE BONES. posterior nasal spinej whicli is altogether rudimentary, or even null in animals; the orifice of the posterior palatine canal, which belongs entirely to the palate bone; the pterygo-palatine foramen ; lastly, the pterygoid process, which represents tlie pterygoid bone of animals. The vertical portion forms tlie external wall of the nasal cavities by its internal face, and by its external face concurs in the formation of the zygomatic or temporal fossa. 9. Malar bone. — Tliis otfeis tiiree faces. The external, or cutaneous, serves as a base for the most salient part of the cheek. The superior, or orbital, forms part of the external wall and floor of the orbit ; it belongs to a long apophysis — the orbital process — which rests on the sphenoid and frontal bones. The posterior face is smooth and concave behind, where it aids to form the temporal fossa; in front it is uneven, and articulates with the supermaxilla. The posterior, or masseteric border, unites with the zygomatic process of the temporal bone. 10. Lachrymal tone. — This bone is also called the os unguis in Man, because of its likeness to the nail in shape and tenuity. It is entirely lodged in the orbit, and its external face is divided into two portions by a vertical crest ; the portion situated in front of this crest forms part of the lachrymal groove. By its internal face, the lachrymal bone limits, outwardly, the bottom of the nasal cavities, and covers the anterior cells of the ethmoid ; by its posterior border, within the orbit, it articulates with the os planum of the ethmoid. 11. Nasal bone.— The proper bones of the nose of Man exhibit a great analogy to those of the Dog. They do not possess a nasal prolongation, and they articulate with the lateral cartilage of the nose. 12. Vomer. — The same general form and relations as in Solipeds. 13. Inferior maxillary ^one.— This bone in Man is in shape somewhat like a horse-shoe. It is nearly of the same width throughout its whole extent. The symphysis is vertical — a character peculiar to Man. Below this symphysis is a triangular projection — the mental eminence. The genial surface of the Horse is replaced by four little tubercles, termed the genial processes. The alveoli of the molar teeth form a great projection on the inner face of the bone. The mylo-hyoid ridge is very developed. The superior orifice of the dental canal is covered by a little sharp lamina. From this orifice begins the mylo-hyoidean groove. The coronoid process is short ; the condyle is bent towards the median line, and the sigmoid notch is wide and shallow. The superior border contains fourteen or sixteen alveoli. Article III. — The Thorax. The thorax represents a coinoid cage, elongated from before to behind, suspended under the vertebrae of the dorsal region, and contains the principal organs of respiration and circulation. It is composed of bony arches named ribs, thirty-six in number — eighteen on each side — and a single piece — the sternum, which selves for the direct or indirect support of the inferior extremi- ties of the ribs. The Bones of the Thorax in particular. 1. Sternum of the Horse (H^mal Spine) (Fig. 56). This is an osteo-cartilaginous body, elongated from before backwards, flattened on each side in two-thirds of its anterior extent, and above and below in its posterior third ; it is slightly curved on itself, and situated beneath the thorax in an oblique direction downwards and backwards. It offers for study, a superior face, two lateral faces, three borders, and tu>o extremities. Faces. — The superior face, slightly concave longitudinally, represents an isoscelated lengthened triangle, the summit of which is directed forwards ; it constitutes the floor of the thoracic cavity. The inferior face is shaped like the keel of a ship, having in its middle a longitudinal ridge, which decreases in height from before to behind. It has two inclined planes placed towards each other, each of which has two parts — a superior and an inferior. The first shows eight diarthrodial cavities, which receive the inferior extremity of the cartilages of the true ribs. These cavities are elongated vertically, and draw closer to each other THE THORAX. 93 as they extend backwards. The inferior part, which is more extensive before than behind, offers to the powerful pectoral muscles a large surface for insertion. Borders. — The fico infnior borders separate the superior from the inferior faces ; they are situated above the diarthrodial cavities, are united anteriorly, and each gives attachment to a fibrous band. Extremities. — The anterior, flattened on each side and curved upwards, exceeds to some extent the first articular cavity of the lateral faces, and in this way con- stitutes the rerrind prolonnd'ioa {pr(rstenium) of the sternimi. The posterior extremity is flattened superiorly and inferiorly, and forms a large cartilaginous plate, very thin, concave above, convex below, which has received the name of the abdominal prolongation {ensiform cartilage), or xiphoid appendage. Structure and development. — The sternum is One of the parts of the skeleton Fig. 56. THE STERNUM. 1, The cervical prolongation (prcBstemum, or cariniform cartilage) ; 2, the xiphoid appendage (or ensiform cartilage); 3, 3, cavities for the articulation of the sternal cartilages ; 4, inferior border. which do not undergo complete osseous transformation. It is developed, in Solipeds, from six single nuclei of spongy substance, ranged one behind the other, like beads on a string. These nuclei never coalesce to form a solid piece, but remain separated during the life of the animal, by the primary cartilaginous mass. The latter constitutes the entire anterior prolongation of the bone and its carina, as well as the xiphoid appendage. When these parts of the sternum become ossified — which is rare — they are only partially so. Differential Characters in the Sternum of other Animals. In all the domtsticateii animals except Solipeds, the sternum is flattened above and below instead of on both sides. A. Ruininants. — In Ruminants, each piece is developed from two lateral centres of ossifi- cation. The bones which compose it are seven in number; they are much more compact than those in the sternum of the horse, and at an early period ate united to each other, with the exception of the fir.st, which is joined to the second by a diarthrodial articulation that permits it to execute lateral movements. There is no cervical prolongation, and the xiphoid cartilage is feebly developed and well detached from the body of the bone. In the sternum of the Goat and Sheep, the two first pieces have no diartlirodial joint, but are simply united by a layer of cartilage, which, in old animals, becomes completely ossified. The sternum of the Camel has a very oblique direction downwards and backwards, and is formed by seven pieces ; the first is somewhat rudimentary, while the two are very strong, and serve as a base for the sternal callosity ur pad. B. Pig. — The sternum of this animal presents in its general conformation the essential features of that of large Ruminants. It is provided with a well-defined cervical prolonp-ation, and is composed of six pieces, which, at least in the four or five last, are each divided into two lateral nuclei. C. Camivora. — The sternum of the Dog and Cat is formed of eight pieces, elongated from before to behind, hollowed in their middle part, and thick at their ends— formed, indeed, like the last coccygeal vertebrae of the Horse. They are never ossified to each other. 9 94 TEE BONES. 2. The Ribs (Pleuropophyses) (Fig. 57). As has been already remarked, on each side of the thorax there are eighteen ribs. These are nearly parallel to each other, and separated by the intervals termed the intercostal spaces. Attached by their superior extremity to the vertebrae of the dorsal region, these bones terminate at their inferior extremity by an elastic and flexible prolongation, named the cosfcd cartilage, by means of which they are brought into direct or indirect relations with the sternum. The characters common to all the ^'g- ^'^- ribs will be first noticed, then the special features which serve to distinguish them from each other, and, lastly, the differences they exhibit in other than Soli- ped animals. A. Chaeacters common to ALL THE Ribs. — These will be studied from a typical point of view, first in the rib itself, and then in its cartilage. 1. Description of a typical rih. — A rib is an elongated asymmetrical bone, oblique from above to below, and from before to behind, flattened on both sides, curved hke a bow, and twisted on itself in such a fashion that its two extremities cannot rest on the same horizontal plane. It is divided into a middle portion or body, and two extremities. MiddJe portion. — This offers two faces and two borders. The external face is convex, and hollowed by a wide groove in its anterior half ; it shows superiorly, towards the point corresponding to the angle of the rib in Man, some tubercles and muscular imprints. The internal face is concave and smooth, and covered by the pleura, which separates it from the lungs. The anterior border is concave, thin, and sharp ; the posterior— convex, thick, and covered with rugged eminences — is channeled inwardly by a vasculo-nervous groove, which disappears near the middle of the rib. Extremities. — The superior has two eminences — a head (capituhim) and a tuberosity (tuberculum) — which serve for the support of the rib against the spine. TYPICAL RIBS OF THE HORSE. A, Inner face of the fifth sternal rib. B, External face of the first asternal rib. 1, Head of the rib; 2, its fissure ; 3, neck ; 4, tuberosity ; 5, articular facet ; 6, scabrous fossa for the insertion of the interosseous costo-transverse ligament ; 7, groove on the external face ; 8, vasculo-nervous groove on the posterior border ; 9, prolonging cartilage ; 10, A, articular tuberosity for union with the sternum. TEE THORAX. 95 The first is formed by two articular demi-facets, placed one before the other, and separated by a groove for ligamentous insertion ; it is isolated from the tuberosity by a narrow part, named the acrk, which exhibits a rugged fossa for the implantation of a ligament. The second — situated behind the head, and smaller than it — is provided with imprints on its margin, and presents an almost flat diarthrodial facet at the summit. Each rib articulates by its head and tuberosity with two dorsal vertebrie : the head is received into the intervertebral articular cavity ; the tube- rosity corresponds, by its facet, to the transverse process of the posterior vertebra. The inferior extremity is tuberous and excavated by a shallow cavity, irregular at the bottom, for the reception of the upper end of the costal cartilage. Slnictnre ami derelopment. — The ribs are very spongy bones, especially in their inferior moiety, and are developed at a very early period from three centres of ossification — a principal for the middle portion and inferior extremity, and two complementary for the head and tuberosity, 2. Descriptio/i of a typiraJ costal ritrtiUnje. — The costal cartilage (JuBmapophysis) very evidently represents the inferior rib in Birds ; it is a cylindrical piece, slightly compressed at the sides, and round and smooth on its faces and borders. By its superior extremity, it is united to the rib it serves to lengthen, and forms with it an angle more or less obtuse, opening in front. At its inferior extremity, it is terminated by an articular enlargement, or by a blunt point. In youth, the costal prolongations are entirely composed of cartilaginous matter, but they are soon invaded by ossification : so that in the adult animal they are already trans- formed into a spongy substance, with large areola3 which remain during life surrounded by a thin layer of cartilage. B. Specific Chaeacters of the Ribs. — The ribs, like the vertebrae of each region of the spine, have received numerical designations of first, second, third, etc., computing them from before to behind (Fig. 5). Owing to the presence of an altogether essential characteristic, they are naturally divided into two great categories — the sternal or true ribs, and the asternal or false ribs. The sternal ribs, numbering eight — the first eight — have their cartilages terminated inferiorly by an articular enlargement, which corresponds to one of the lateral cavities of the sternum, and brings the true ribs into direct contact with this portion of the skeleton. The asternal ribs, ten in number, rest on each other — the last on the seventeenth, that on the sixteenth, and so on — by the inferior extremity of their cartilage, which ends in a blunt point. The cartilage of the first false rib is united somewhat closely to the last sternal rib, and it is through the medium of this that all the asternal ribs lie indirectly on the sternum. If, however, the ribs are considered altogether, with regard to the differential characters presented by them in their length, width, and degree of incurvation, it will be noted : 1. That their length increases from the first to the ninth, and from this diminishes progressively to the last. 2. That the same progressive increase and decrease exists in the cartilages. 3. That they become gradually wider from the first to the sixth inclusive, and then contract by degrees until the eighteenth is reached : 4. That the curve described by each is shorter and more marked as the rib is situated more behind. It may be added, that the channel on the external face is less conspicuous in proportion as the rib is narrow. The first rib, considered individually, is always distinguished by the absence of the groove on its outer surface, by the vasculo-nervous groove on its posterior border, and the groove or notch intermediate to the two facets of its articular head. It is also recognized by the deep muscular imprints on its external face, 96 THE BONES. the shortness and thickness of its cartilage, and particularly by the articular facet which this cartilage exhibits inwardly, to correspond to that of the opposite rib. The last rib has no channel on its external surface, and the facet of its tuberosity is confounded with the posterior facet of the head. This last character is also nearly always remarked in the seventeenth rib, and sometimes even in the sixteenth. In the Ass, the ribs in general, but particularly those most posterior, are less curved than in the Horse. They differ more particularly in the curve of the neck being much shorter — a difference which is most obvious when the goniometer is applied to the angle of the rib, and the most salient part of the head and tube- rosity. By this means we have obtained an angle the value of which was greater in the Ass than in the Horse : from 78° to 180° for the external ribs, and from 100° to 132° for the asternal ribs, of the first ; from 60° to 12r>° for the sternal, and from 140° to 150° for the asternals, of the second. The upper extremity of the sternal ribs in the Ass is less twisted outwards than the same part in the Horse ; and in the latter, the plane which passes by the head of the rib is more distant than the plane which, in the Ass, passes across the tubercle. The ribs of the Mule are intermediate between those of the Ass and Horse, with regard to the value of the angle just indicated ; they approach those of the Ass by the twist in their superior extremity. Differential Characters in the Ribs of other Animals. The number of riba varies like that of the dorsal vertebrae. The following table indicate the number of these bones in the diflferent domesticated animals : — Pig 14 Ox ; 13 Sheep 13 Goat 13 Dog 13 Camel 12 Rabbit 12 A. Rmninants. — These animals, with the exception of tlie Camel, have eight sternal and five asternal ribs. In the Ox, they are longer, wider, and less arched than in Solipeds. The articular eminences of the superior extremity are voluminous and well detached; the neck especially is very long. The sternal ribs are joined to their cartilage of prolongraent by a real diarthrodial articulation. In the last rib, and sometimes in the one before it, the tuberosity is scari'cly perceptible, and has no articular facet. In the Sheep and Goat, the sternal ribs are consolidated with the cartilages (Figs. 6. 7). The Camel has eight sternal and four asternal ribs. The ribs increase in length to the tenth, and in width to the sixtli only. They are less curved and are shorter, proportionately, than those of the Ox, the shortness being very marked in the first three. The tubercle is less defachefl than in the Ox, but the neck is longer and stronger (Fig. 8). B. Pig. — In this animal there are fourteen pairs of ribs, seven of which are sternal and seven asternal. The first are provided with cartilages of prolongnicTit flattened on both sides, extremely wifle and shar}), and convex on their superior bor.ler. In the four last asternal ribs, the fncet of their tuberosity is confounded with the posterior facet of the head (Fig. 3). C. Carnivora. — They possess thirteen ribs on each side — nine sternal and four asternal. These are very much arched, U'lrrow, and thick, and their cartilages rarely ossify. In the Dog, the articular facet of the tuberosity remains isolated from the posterior facet of the head in all the ribs. It is absent in the three last ribs of the Cat (Fig. 2). The Thorax in General. The description of the interior of the thoracic cavity will be referred to when treating of the respiratory apparatus. It is only necessary here to examine the TEE THORAX. 97 external surface of this bony cas^e. For this purpose it is divided into six regions — a superwr plane, an inferior phme, two lateral planes, a base, and a summit. Planes. — The snperior plane is separated into two portions by the spinous processes of the dorsal vertebrse ; each forms, with these spinous processes, the costo-vertebral furrow, intended to lodge the majority of the muscles belonging to the spinal region of the back and loins. The inferior plane, less extensive than the preceding, offers : 1. On the median line, the cariniform and xiphoid cartilages of the sternum ; 2. On the sides, the chondro-sternal articulations, and the cartilages of prolongment of the true ribs. The lateral planes are con- vex and wider at their middle part than in front or behind, and exhibit the intercostal spaces. They serve to give support, anteriorly, to the superior segments of the two anterior limbs. Base. — This is circumscribed by the posterior border of the last rib, and by the cartilages of all the asternal ribs ; it is cut obliquely downwards and for- wards, and gives attachment, by its internal circumference, to the diaphragm — a muscle tig. 58. which separates the thoracic from the ab- dominal cavity. Summit. — It occupies the anterior por- tion of the thorax, and presents an oval opening, elongated vertically, situated be- tween the two first ribs. This opening constitutes the entrance to the chest, and gives admission to the trachea, the oeso- phagus, and important vessels and nerves. Comparison of the Thorax of Man with THAT op the Domesticated Animals. 1. Sternum. The sternum of Man is flatteneil before and behind, and diminishes in width from above to be- low. The xiphoid appendage is narrow, and single or bifid. Be8iital groove. The head is better detached and the trochlea deeper than in the Horse. The medul- lary eanal of the humerus of the Ox is sometimes cros-sed by an osseous band. B. Camel. — Humerus cylindrical and nearly straight. Torsion furrow shallow ; nutrient foramen on its anterior face. Bicipital groove doulde, the inner cavity being larger than the external. The inferior articular surface is relatively very narrow, and tlie external trochlea deep. C. Pig. — The humerus of this animal is com- pressed on both sides; the head is much bent back- wards, which increases its 8 inflection. A single bicipital groove placed within the superior extremity ; the external trochanter voluminous, and the summit turned over the bicipital groove. Deltoid imprint and internal tuberosity of the body replaced by simple muscular imprints. D. Dog and Cat. — The humerus is very elon- gated and more S-curved than in all the other animals, and the internal tuberosity is replaced by some imprints ; while the bicipital groove is single, and the nutrient foramen, on the posterior face, is as in the Ox, Sheep, and Pig. Tlie coronoid fossa com- municates with that of the olecranon by a foramen. E. Rabbit. — The humerus of this animal greatly resembles that of the Dog, except that it is much more flattened on each side, and the deltoid imprint is on the anterior face and nutrient foramen on the inner face of the bone. Forearm. This region has for its base two bones — the radius and cubitus (or i/luc), united into a single piece {os antihrarhii) at an early period in most of the domesticated animals. 1. Radius (Figs. 65, 66). This is a long bone, placed in a vertical direction between the humerus and the first row of carpal bones, and divided into a body and two extremities. HUMERUS OF THE CAT AND RABBIT. , Humerus of tlie Kabbit. B, Humerus of the Cat. 1, Condyle ; 2, trochlea ; 3, diaphvsis ; 4, external trochanter ; 5, internal trochanter ; 6, bicipital groove. lOi THE B0NE8. Fig. 65. Body. — Slightly arched and flattened before and behind, it presents for study two faces and hvo borders. The anterior face is convex and perfectly smooth. The posterior, a little concave from one extremity to the other, offers : 1. Near the external border, a triangular surface, covered with asperities, elongated vertically, very narrow, commencing near the upper fourth of the bone, and terminating in a fine point towards the lower fourth ; this surface is brought into contact with the anterior face of the ulna by an interosseous liga- ment, which is completely ossified before the animal reaches adult age. 2. Above, there is a wide, trans- verse, but shallow groove, which aids in forming the radio-ulnar arch, and shows, near the point where it touches the preceding surface, the nutrient foramen of the bone. ;3. Near the internal border, and towards the inferior third, there is a vertically elongated and slightly salient eminence for insertion. The two borders — external and internal — are thick and rounded ; they establish an insensible transition between the faces. Extremities. — The superior is larger thau the inferior. It has : 1. An articular surface elongated from one side to the other, concave from before to behind, wider within than without, and moulded to the articular sur- face of the inferior extremity of the humerus ; there is also seen, outwardly, a double depression {glenoid cavities), which receives the two lips of the external trochlea ; in the middle, an antero-posterior ridge, which is received into the internal trochlea ; within, an oval cavity corresponding to the internal border of the former. 2. The external tuberosity, placed at the extremity of the great diameter of the articular surface ; it is prominent and well detached. 3. The internal or bicipital tuberosity — a large, very rugged, and depressed process, situated within and in front of the glenoid cavity. 4. A little lower, and on the same side, there is a strong muscular and ligamentous imprint, separated from the preceding tuberosity by a transverse groove intended for the passage of a tendon. 5. The coronoid process,^ a small conical eminence, at the summit of which terminates, anteriorly, the median ridge of the articular surface. 6. Two diathrodial facets elongated transversely, cut on the posterior outline of the large articular surface, with which they are con- founded by their superior border ; they correspond with similar facets on the ulna. 7. Below these, a roughened surface which extends to the radio-ulnar arch, and is in contact with an analogous surface of the same bone through the medium of an interosseous ligament. In the Horse, this ligament rarely becomes ossified. The inferior extremity, flattened before and behind, presents : 1 . Inferiorly, an articular surface elongated transversely and somewhat irregular, responding to the four bones in the upper row of the carpus. 2. On the sides, two tuberosities > In Mun this btjlongs to the ulna. EXTERNAL FACE OF THE RADIUS AND ULNA. 1, Ulna; 2, point of the ulna; 3, beak of ulna or olecianon ; 4, rndio-ulnar arch ; 5, supero external tuberosity ; 6, radio-ulnar articular surfaces for the humerus; 7, bicipital tu- b rosity ; 8, shaft or body of the radius ; 9, grooves for tendons. THE ANTERIOR LIMBS. 105 for ligamentous insertion — the internal salient and well circumscribed, the other external, and excavated by a vertical fissure — in which passes a tendon. i'>. In front, three i^rooves for the glidini^ of tendons ; the external is the largest, and vertical like the median ; the internal, the narrowest, is oblique downwards and inwards. 4. Posteriorly, a strong transverse ridge which surmounts the articular surface, and serves for the insertion of ligaments. Structure and development.— "Yho. radius is a very compact bone, and is developed from three centres of ossification — one for the body, and two for the extremities. 2. Ulna (Figs. 65, 66). This is an elongated, asymmetrical bone, in the form of an inverted triangular pyramid, applied against the posterior face of the radius, to which it is united in adult Solipeds. It offers for description a middle portion and two extremities. Middle portion. — This has three fiues wider above than below, and three iorders which become joined at the inferior extremity of the bone. The external fare is smooth and nearly plane. The internal is also smooth and slightly hollowed. The anterior is formed to correspond with the radius, and presents pecuharities analogous to those of the posterior face of that bone. Thus, there is found, in proceeding from above to below : 1 . Two small diarthrodial facets.^ 2. A roughened surface. 3. A transverse groove for the formation of the radio- ulnar arch. 4. A triangular surface, studded with rugosities, which occupies the remainder of the bone to its lower extremity. The lateral borders — external and internal — are sharp, and, like the anterior face, are in contact with the radius. The posterior border is concave, rounded, and thicker than the other two. Extremitief<. — The superior extremiti/ comprises all that portion which exceeds the articular surface of the radius. It constitutes an enormous process — the olecranon — flattened on both sides, and presenting : 1. An external face, slightly convex. 2. An internal excavated face. 3. An anterior border, thin and sharp superiorly, notched below to form the sigmoid cavity^ — an articular surface concave from above downwards, rounded from one side to the other, which corresponds with the humeral cavity, and is surmounted by a sahent prolongation named the beak of the olecranon. 4. A concave and smooth posterior border. 5. The summit — a kind of thick roughened tuberosity which terminates the ulna above, and into which are inserted the extensor muscles of the forearm. At its inferior extremity, the ulna ends, towards the lower fourth of the principal portion of the forearm, in an acute point, and sometimes by a small knob {capitulum ulnce). It is not rare to see it prolonged, especially in the Ass and Mule, to the inferior external tuberosity of the radius. This tuberosity then appears to belong to it, at least in part ; and all that portion which is situated behind its vertical groove might be justly considered as a dependency of the ulna. Structure and development. — The ulna contains much compact tissue, even in the region of the olecranon ; it is also very solid. It is an imperfect bone, developed from two centres of ossification only, one of these being for the apex of the olecranon. In the Ass (Fig. 66), the radius is more curved than in the Horse, and when its anterior face is placed on a horizontal plane, the bone only rests on its upper The smaller sigmoid cavity of Man. The greater siymoid cavity of Man. 106 THE BONES. end and the middle of the body. It is also distinsjuished from that of the Horse by the depth of a narrow groove, which passes through the rough lip above and behind the inferior surface, superior to the small fossa F'g« 66. that receives the third bone of the upper row of the carpus during flexion and extension movements. The ulna of this animal is more developed than that of the Horse, and its olecranon is proportionately shorter, broader, and more hollowed on its internal face. The inferior extremity (Fig. 06, !)) is nearly always formed by a particular nucleus, which is also sometimes the case in the Horse. In the Hinny, the bone of the forearm resembles that of the Ass, with the exception of the smallness of the lower end of the ulna. Differential Characters in the Forearm Bones of OTHER Animals. Tlie principal differential characters that they present are con- nected with the relative dimensions of the two bones and their mode of union. Regarding these, and as generally applicable, the follow- ing principles may be laid down : — ■ 1. The development of the ulna is in direct relation to the division of the foot. — Monodactylous animals — such as the Horse, Ass, and Mule — have, in fact, only a rudimentary ulna. In the pentadacty- lous animals, ou the contrary — aa Man, the Cat, Elephant, etc.,^ this is a veritable long bone which equals, or even exceeds, the radius in volume. 2. TJie closeness of union between the radius and ulna is in increased proportion as the animal exclusively employs its inferior extremity for standing and walking. — Thus, in Solipeds and Rumi- nants, and Pachyderms in general, the two bones are consolidated, or at least united by an interosseous ligament, and in so firm a manner that they can only execute very obscure movements on each other. The anterior limb of these animals is, indeed, only used to support the body on the ground. In those, on the contrary, which may employ it to dig up the soil, climb on trees, etc., or as an organ of prehension, the radius and ulna are merely joined at their extremities by an articulation, which permits them to move upon one another with the greatest facility. Rodents, the majority of the Carnivora, and the Quadrumana, are so provided ; but it is in Man that the relative independence of the two bonea is carried to the highest degree. No animal can so easily execute the movements of pronation and supination of the hand, which are determined by the play of tiie two bones of I he forearm on each other. To the indication of these fundamental characters, may be added some details on a few particular and important points. A. Ox, Sheep, Goat. — The forearm of the Ox is short; that of the Sheep and Goat is longer ; but in the three species, the ulna— thicker than in the Horse— is a long bone developed from three primary nuclei. It extends the whole length of tlie radius, and concurs in forming the articular surface corresponding with the carpal liones. The inferior articular suifnco is cut obliquely downwards and inwards. There are two radio-ulnar arches — a superior and in- ferior — united externally by a deep fissure. The union of the two bones is more intimate than in the Horse; for ossification alw.iys ends by invading that portion uf the interosseous ligament placed above the superior vascular arch (Fig. 71). FOREARM BONES OF THE ASS. 1, Diaphysis of the radius ; 2, bicipital tuberosity ; 3, external and superior tuberosity of the radius ; 4, groove for the passage ot the anterior extensor of the phalanges ; 5, surface for insertion of branch of the perforans tendon ; 6, body of the ulna interrupted at its lower third, but more complete than usual ; 7, summit of the olecranon ; 8, beak of ditto; 9, in- ferior extremity of ditto; 10, radio-ulnar arch ; 11, cre.st above the inferior articular surface of the radius, behind. THE ANTERIOR LIMBS. 107 B. Camel. — The radius of this animal lias a narrow, superior, articulating surface of two glenoid cavities, separated by a median salient crest terminating in front by a very marked corouoid process; the bicipital tul)orosity is large, and on the anterior face. The ulna is very concave in its middle part, and tiie olecrauou is broad and low. C. Pig. — Tlie radius is short, its inferior surfait- cut rather obliquely as in Ruminants, and partly formed by the inferior extremity oF tlie ulna, whicii is a volnininous bone provided with a medullary canal, and soii(]ly united to the radius by an interosseous ligament, the complete ossitication of wliich is rare. It is flattened before ami behind, and is spread over the posterior face of the radius, so as nearly to completely cover it. The olecranon is very prominent (Fig. 7t>). U. Dog, Cat. — The two bones of tlie forearm are nearly equal in volume, and are in contact only by their extremities, where they show for this purpose : 1. Above, on the ulna, a concave articular surface — the small sigmoid cavity ; and on the radius, a rounded hinge-like facet. 2. Below, two facets analogous to the preceding, but much smaller; that on the radius is concave, and that on the ulna convex. Tliese two bones slightly cross each other, so that the upper end of the ulua touches the radius behind and inwards, while the interior terminates altogether outwards. In the Pig and Ruminants, the lower end is in contact with the upper row of carpal bones (Fig. 77). E. Rabbit. — The ulna is still more developed than in the Cat, and more curved length- ways. The posterior border of the olecranon ia almost vertical, instead of being oblique from before to behind, and the sigmoid notch is deeper and shorter curved than in the Camivora. ANTERIOR (OR FORE) FOOT, OR HAND. The anterior foot, or hand, is the region which presents the greatest diffe- rences when it is examined in the various individuals of the animal series. Nevertheless, notwithstanding these varieties, its constitution is fundamentally the same, and may be divided into three sections — the carpus, metacarpus, and phalangeal region. In vertebrate animals, the hand is composed of a certain number of parallel or quasi-parallel segments, which constitute the digits. Each complete digit is subdivided into three sections, placed one above the other ; these are, reckoned from above to below — carpus, metacarpus, and phalanges. The number of apparent digits varies from one to five ; and, however it may otherwise appear, philosophical anatomy has shown that the hand of all the domesticated animals may be considered as belonging to the pentadactylous type. When it does not appear to be so, this is due to more or less numerous or extensive atrophies or abortions always occurring according to fixed laws. (See remarks hereafter on the Hand in General.) 1. Carpal Bones (Figs. 67, 68, 69). The carpus (or knee) forms the base of the hand. Situated between the inferior extremity of the radius and the superior extremity of the metacarpal bones, it is composed of several small bones joined to each other, in the fresh state, by extremely solid articular bands. Collectively, they form an almost quadrilateral mass, in which may be distinguished two faces and four borders. The anterior face is slightly convex from side to side, and irregular ; it is in contact with the tendons of the extensor muscles of the metacarpus and phalanges. The posterior face is very unequal, and converted — especially outwardly — into a groove, in which the tendons of the flexor muscles of the phalanges glide. 108 THE BONES. Fig. 67. The superior horder articulates with the radius ; the inferior border with the metacarpal bones. The lateral borders are nearly flat ; above and behind the external border is remarked a considerable eminence, formed by the bone which will be hereafter studied as the super- carpal bone (pisiform or trapezium). In the carpus of the Horse are seven or eight bones, which are disposed in two superposed rows. The superior row comprises four bones placed side by side, and designated by the numerical names of first, second, third, and fourtli, viewing them from without to within. The inferior row has only three, which are named in the same manner. In applying to them the names proposed by Liser, we have, in the upper row — 1. The pisiform, or supercarpal bone. 2. The cuneiform bone. 3. The lunar bone. 4. The scaphoid bone. In the inferior row — 1. The unciform bone. 2. The magnum bone. 3. The trapezoid bone. 4. The trapeziiun (not constant). The description of these bones is most simple, and may be made in a general manner for all. Thus, with the exception of the supercarpal bone, they are solid, nearly cubical in form, and exhibit on their periphery : 1. Articular surfaces. 2. Surfaces for insertion. The articular surfaces are small, flat, or slightly undulating facets, distributed on the superior, in- ferior, and lateral faces ; none are found in front or behind. The superior and inferior faces are entirely occupied by a single facet, which responds either to the radius, the metacarpals, or to the bones of the other row. The lateral facets are always multiple, and in contact with the bones of the same tier ; they do not exist, of course, on the outside of the bones at the ends of each row. The surfaces for insertion are absent on the superior and inferior faces ; they separate, in the form of roughened depressions, the lateral articular facets. Before and behind, they are covered by more or less marked rugosities. Bones of the Upper or Antibrachial Row (Figs. 68, 69). — The first, or os pisiforme, is outside the row ; it is situated above and behind the carpus, whence its name of super- carpal bone, by which it is usually known in veterinary anatomy. This bone, which merits a special description, represents a disc flattened on both sides. RIGHT ANTERIOR FOOT OR HAND OF A HORSE. 1, Radius; 2, grooves for the ex- tensor of the phalanges; 3, scaphoid; 4, lunar; 6, cunei- form ; 6, pisiform ; 7, mag- num ; 8, unciform ; 9, great metacarpal; 10, small meta- carpal ; 11, sesamoid bone ; 12, suffraginis ; 13, coronary; 14, navicular; 15, pedal ; 16, basi- lar process. THE ANTERIOR LIMBS. 109 offering for study two faces and a circumference. The external face is convex, roughened, and channeled anteriorly by a groove that traverses it from above to below, in which glides the inferior tendon of the external flexor of the CARPUS OF THE HORSE (ANTERIOR FACE). ', Pisil'orm or su|)ercar))al bone (first of the upper row) ; 2, cuneiform (second ditto) ; 3, lunar (third ditto); 4, scaphoid (fourth ditto); 5, unciform (first of lower row); 6, OS magnum (second ditto) ; 7, trape- zoid (third ditto); 9, inferior articular face of the radius; 10, groove for the oblique extensor tendon of the meta- carpus; 11, groove for the anterior ex- tensor of the metacarpus ; 1'^, groove for the anterior extensor of the phalanges ; 13, superior extremity of the laige meta- carpal bone; 14, tubeicle for the inser- tion of the anterior extensor of the meta- carpus ; 15, superior extremity of the external small metacarpal bone. CARPUS OF THE HORSE (POSTERIOR FACE> 1, 2, 3, 4, 5, 6, 7, Same bones as in preced- ing figure ; 8, trapezium (fourth bone of the lower row); 9, 9, inferior articular surface of the radius ; 10, transverse crest for insertion of common posterior liga- ment of the carpus; 11, superior extremity of large metacarpal bone; 12, rugosities in which are fixed the deep layer of the suspensoiy ligament of the fetlock or superior sesamoid ligament ; 13, external Bmall metacarpal ; 14, internal ditto. metacarpus. Its internal face — smooth and concave — concurs in forming the external wall of the carpal sheath. The circumference presents, in front, two 10 110 THE BONES. articular facets : the superior, concave, corresponds to the radius ; the inferior, convex, is in contact with the second bone of the upper row. The other three bones of this row increase in volume from without to within. The second bom, os pyramidaUs, or cuneiform, articulates with the radius, the first bone of the lower row, the third of the upper, and the supercarpal bone ; it has, in all, five articular facets. The third, or os lunare, has six facets, and is united below to the first and second bones of the second row. The fourth, or os scaphoides — the most voluminous of the row — has only four facets, and articulates by its inferior face with the os magnum and trapezoides. Collectively, the second, third, and fourth bones of the upper row form two articular surfaces. The superior, or radial articular surface, is very irregular ; but in examining it from without to within, there may be observed : 1. A glenoid cavity on the cuneiform bone. 2. In front, a transversely elongated condyle on the lunar and scaphoid bones. 3. A groove placed behind the preceding condyle. The inferior articulating surface, which corresponds to the second row, is constituted by several undulated facets ; it is convex outwardly and in front, concave posteriorly and inwardly. Bones of the Inferior or Metacarpal Row (Figs. G8, 69). — The thick- ness of these bones decreases from without to within. The first, wiciform, or hookbom (os hamatum), has four diarthrodial facets, and responds, above, to the two first bones of the superior row ; below, to the first and second metacarpals. The second, os magnum, or os capitatum, — the largest — has seven articular facets, three of which are on the interno-lateral face. It articulates, above, with the lunar and scaphoides ; below, with the principal metacarpal and the internal rudimentary metacarpal. The third, or trapezoides — the smallest — is provided with five facets, and is in contact with the scaphoides above, and the middle and internal metacarpals below. Collectively, these bones of the lower row form two large diarthrodial surfaces. The upper surface responds to the bones of the upper row, and is constituted in front, and from without to within, by a small condyle and two glenoid cavities ; behind, by two isolated condyles, formed by the os magnum and the trapezoides. The inferior articular surface is only formed by more or less long and plane facets, which incline towards each other. It articulates with the three portions of the metacarpus. Structure and development. — Each carpal bone is formed by a nucleus of close spongy substance, enveloped in a very thick layer of compact tissue. Each is developed from a single centre of ossification. The carpal bones of the Ass much resemble those of the Horse, but the upper face of the lunar is more concave ; the facet of the cuneiform., for the pisiform, is less concave, but larger and triangular, and is always separated from the superior articular surface by a rough, wide, and deep groove. The pisifoy m is more circular than that of the Horse, and is modified in shape to correspond with the cuneiform ; while the inferior surface of the os magnum is almost plane in the Ass, but in the Horse it is cut into a condyle in front and a glenoid cavity behind. Lesbre states that the trapezium is more frequent in the carpus of the Ass than the Horse. J THE ANTERIOR LIMBS. Ill The carpal bones of the Hinny are like those of the Ass, but those of the Mule resemble the Horse. Fig. 70. Differential Characters in the Carpal Bones of other Animals. A. Ox, Sheep, Goat. — In these aiiimala the carpus is composed of only six bones — four in the upper and two in the lower row, where the os magnum and trapezoid are fused together. The pisiform bone is in shape as its name implies, has no groove, and has no relation with the radius. Tiie cuneiform bone articulates with the radius and ulna. The bones of the lower' row only articulate with the large metacarpal bone (Fig. 71). B. Camel. — Among the seven carpal bones of tiie Camel are seen : a pisiform b;)ne, having on its external face a large smooth groove; a lunar, flattened on each side, and deeply notched laterally ; an unciform having a pyramidal prolongation behind; an os magnum, smaller than the latter ; and a trapezoid, little developed, and entirely removed to the posterior part of the carpus. C. Pig. — Tlie carpus of the Pig, like that of Man, contains eight bones — four in each of the rows. The second bone of the upper row articulates with the ulna, and to a very small extent with the radius. In the bones of the lower row, it is observed that the first articulates witli the two external metacarpals, the second with the great internal metacarpal, tlie third with the preceding and the small internal meta- carpal. The fourth, or trapezium, terminates inferiorly by a blunt point, and lias no relations with the metacarpal bones, because the thumb is entirely undeveloped in this animal (Fig. 76). D. Dog, Cat. — In the Cut and Dog there are also eight bones. Lesbre says, however, that the scaphoid and lunar are sometimes one bone, and that often a lenticular bone is found in tiie upper row. The cuneiform bone is very developed, and occupies all the external border of the carpus, articulating witli the ulna, first bone of the second row, and the first metacarpal. 1 he pisiform bone is elongated, prismatic, tliick at both ends, and lias in front two contiguous articular facets — one for articulation with the ulna, the other for union with the cuneiform bone. The bones of the lower row diminish in size from the first to the fourth, and articultte— the first, with the first and second metacarpals; the second, with the metacarpal of the third digit; the third, with the fourth digit : and the fourth with the metacarpus of the thumb. E. Rabbit. — This animal possesses nine carpal bones; for it is stated that lietween the two rows there is a piece which Blainville has named the intermediate bone. It really belongs to the upper row, and represents the scaphoid. There are, therefore, five bones in the first carpal row of the Rabbit, and in this respect the hand of this species more nearly approaches the typical hand than that of the other domestic animals (see the Hand in General). 2. Metacaepal Bones (Figs. 67, 70). In Solipeds, the metacarpus is composed of three bones, named the " metacarpals," standing parallel to each other. These are the principal metacarpal and the two rudimentary metacarpals — an external and internal. Principal Metacarpal Bone {os metacarpi magnum). — This is a long cylindrical bone, situated vertically between the carpus and the digital region. Body. — The body is a little depressed before and behind, which permits it to be described as having two faces and tico borders. The uyiterior face is perfectly smooth and rounded from side to side. The posterior face is flat, and exhibits : 1. Towards the upper third, the nutrient foramen of the bone. 2. On the sides, POSTERIOR VIEW OP RIGHT METACARPUS. 1, Head of large meta- carpal bone for ar- ticulatioa with the trapezoiii , magnum, and unciform ; 2, inner splint, rudi- mentary, or small metacarpal bone,for articulation with the trapezoid ; 4, scabrous surface for the attachment of the suspensory liga- ment ; 5, nutrient foramen ; 6, median ridgeseparating the two inferior con- dyles. 112 THE BONES. two narrow, roughened surfaces, parallel and elongated vertically, commencing near the superior extremity, to disappear a little below the middle of the bone ; these surfaces are held in apposition to the rudimentary metacarpals, by an interosseous ligament which is often ossified in old Horses. The borders — external and internal — are very thick, round, and smooth, like the anterior face. Extremities. — The superior is flattened before and behind, and presents. 1. Above, an undulating articular surface, formed by the union of several flat facets more or less inclined towards each other ; they articulate with all the lower row of carpal bones. 2. Anteriorly and inwardly, a tuberosity for muscular insertion. 3. Posteriorly — and directly above the roughened surfaces of the posterior face — four small diarthrodial facets in pairs, and running into the larger articular surface by their superior border ; they are adapted to similar facets on the rudimentary metacarpals. The inferior extremity, elongated transversely, articulates with the first phalanx and the sesamoid bones by an articular surface— convex from before to behind — which is composed of two lateral condijks separated by a median spine. The two condyles would be exactly alike, if the autero-posterior diameter of the external condyle were not less extensive than that of the opposite condyle. Both are hollowed on the sides by an excavation for the attachment of ligamentous fasciculi. Structure and development. — The principal metacarpal is one of the most compact bones in the body. It is developed from two centres of ossification, one of which is for the inferior extremity. Rudimentary Metacarpals {ossa metacarpi parva). — The two rudimentary {small) metacarpal (or splint) bones are elongated, and placed against the posterior face of the principal bone, one without, the other within. Each is in the form of an inverted pyramid, and exhibits a middle part and two extremities. Middle portion. — Prismatic and triangular, this offers : 1. Three faces — an external, smooth and rounded from one border to the other ; an internal, plane, and equally smooth : an anterior, covered with asperities to give attachment to the interosseous ligament uniting the lateral metacarpal bone to the median. 2. Three salient borders which markedly separate the faces from each other. Extremities. — The supei'ior, the largest, is named the head, and shows : above, a diarthrodial facet which articulates with one or two bones of the inferior row of the carpus ; in front, other two small facets continuous with the preceding, and in contact with similar facets on the large metacarpal bone ; on the other points of its periphery are rugosities for the attachment of ligamentous and tendinous fibres. The inferior extremity only reaches to about the lower fourth of the large metacarpal bone, and terminates in a small button-shaped enlarge- ment, which is never fused with the latter. The two small metacarpals, although very much alike, may yet be easily distinguished from each other. For instance, the internal bone is always the thickest, and often the longest ; besides, the superior articular surface of its head results from the union of the two facets articulating with the two last carpal bones of the lower tier. Structure and development. — Of a somewhat compact texture, like all the long bones, these have no medullary canal, and are developed from only one ossifying centre. Not unfrequently, however, the tubercle is formed from a special centre. The metacarpus of the Ass is recognized by : 1. The great inequality of the small metacarpals. 2. The thickness of the large metacarpal (the width is to the thickness as 1"35 : 1 in the Ass, and as I'b'd : 1 in the Horse). 3. The depth of THE ASTERIOR LIMBS. 113 the depressions above the inferior articular surface, poste- riorly. 4. The level form of the facet articulating with the OS magnum of the second row. 5. The presence of a small, flat, vertical facet on the posterior contour of the upper articular surface of the large metacarpal. In the Mule and Hinny, the small metacarpals are nearly alike, as in the Horse ; the large metacarpal is flattened, as in that animal, with marked depressions posteriorly. Fig. 71. Differential Characteks in the Metacarpus of other Animals. The number of metacarpal bones naturally varies with tbat of the digits : — In the Carnivora there are 5 In tlie Pif? there are 4 In Ruminants there are 2 or 3 With rt-grard to their shape and form, they oflfer interesting differences, whicli will now bo studied A. Ox, Sheep, Goat. — In these animals the metacarpal bones are two in numl>er — a principal, which itself results from the consolidatioa of the second and third metacarpals; another, altogether rudimentary, situati d outwardly ; and a thinl — not constant — embedded in a fibroua cord passing along the i-mer border of the principal metacarpal. The principal metacarpal is channeled ou its anterior face, and for its wliole Itngtli, by a deep vascular fissure — a trace of the primitive separation of the bone into two pieces. Tliis fi.ssure presents, inferiorly, the anterior onfice of a canal that completely traverses the bone. The posterior face is also marked by a very slight longitulinal groove. The superior extremity exhibits, externally and pusteriorly, a single diar- throflial facet for articulation with the rudimentary metacarpal. The inferior extremity is divided by a deep notch into two articular surfaces, which together resemble the single surface in the Horse; each articulates with one of the digits ; the external is always smaller than the internal. In the foetus, the two long bones that form the great metacarpal are simply laid together, and their medullary canals are separated from each otlver by tiie double partition which results from this apposition; after their coalescence, however, the partitions are completely destroyed by absorption, and in a short time there is only a single medullary canal for the entire bone. The rndimentary metacarpal is only a small osseous stylet, articu- lating, by a dial throdial facet, behind and to the outside of the superior extremity of the principal metacarpal ; it is sometimes absent in the Sheep and Goat. B. Camel. — The metacarpus of the Camel is very long, quadran- gular in its up[>er two-thirds, and flattened behind and before in its inferior third. Its posterior face is converted into a kind of concave furrow, by the considerably raised borders of the bone. The superior articular .surface is divided into two parts by a large roughened depres- sion ; the inner part is on a higher level than the outer. The inferior extremity is also divided into two articular surfaces by a very deep notch ; each surface is condyloid in its anterior moiety, and is like that of the Horse in its posterior moiety. C. Dog, Cat, Rabbit.— The five metacarpals of the Dog and Cat articulate with each other, at their superior extremities, by lateral facets; they offer, at their inferior extremity, a condyle prolonged back- wards by an articular surface resembling that of the Horse. The 4, 5, 6, first, second, and tbii'd booes of the upper row of the carpus; 7, 8, of the lower row ; 9, rudimentary metacarpals; 10, principal metacarpal 12, internal digit. FOREARM and FOOT OF the ox (front view). 1, Olecranon ; 2, body /of the ulna; 3. body of the radius; first and second bones 11, external digit; 114 TEE BONES. middle two are always longer than the two lateral. The smallest belongs to the fifth digit, or thumb, and is terminated interiorly by a trochlea. D. Pig. — The four metacarpals of the Pig articulate with each other, as in the Carnivora. The second and third are larger tliau the first and fourth. The fifth metacarpal is not developed (Fig. 76). 3. Bones of the Phalangeal or Digital Eegion (Figs. 72, 73). Solipeds have apparently only one digit, supported by the principal metacarpal bone, and composed of three pieces placed end to end, one upon another. The first comprises three bones — a principal, the Jirst phalanx — and two complemen- Fig. 72. Fig. 73. LATERAL VIEW OF THE DIGITAL REGION (OUTSIDE OF RIGHT LIMB). 1, Large metacarpal bone ; 2, .3. outer and inner sesamoids; 4, first, ])roximal, os suf- fraginis, or metacarpal phalanx ; 5, its posterior surface ; 6, tuberosity for liga- mentous insertion ; 7, inner condyle of ditto ; 8, eminences on second phalanx for attachment of lateral ligament; 9, smooth surface for passage of deep flexor tendon on second phalanx ; 10, median or second phalanx, os corona, or small pastern bone ; 11, navicular bone; 12, third phalanx, pedal, or coffin bone ; 13, its basilar process. POSTERIOR VIEW OF THE DIGITAL REGION. 1, Large metacarpal bone ; 2, 3, outer and inner splint bones ; 4, b, sesamoid bones ; 6, suffragiuis ; 7, 8, tuberosities for inser- tion of crucial ligaments ; 9, triangular space for insertion uf short sesamoid liga- ment ; 10, anterior face of suffraginis ; 11, 12, tuberosities for ligamentous inser- tion ; 13, articular depression separating condyles; 14, 15, second phalanx; 16, scabrous surface for ligamentous attach- ment; 17, smooth surface for gliding of deep flexor tendon ; 1 8. navicular bone ; 19. }iedal bone; 20, basilar process; 21, plantar foramen. tary ones, the sesamoids. The second is formed by the second phalanx, and the last, which terminates the limb, is constituted by the third phalanx, and an accessory bone which has received the name of the small sesamoid {navicular bone). First (proximal) or Metacarpal Phalanx (Large Pastern Bone, or Os Suffraginis). — The first phalanx (Figs. 72, 73), the smallest of all the long bones, is situated in an oblique direction from above downwards, and behind to before, between the principal metacarpal and the second phalanx. THE ANTERIOR LIMBS. 115 Body. — Flattened before and behind, this bone exhibits : an anterior face, round from one side to the other, and slightly roughened above and below ; a posterior face, flat, covered with ligamentous imprints in the form of a triangle with the base reversed ; two lateral borders, thick, rounded, and provided with some imprints. Extremities. — The superior, the largest, presents : Above, an articular surface adapted to the inferior metacarpal surface, and consequently composed of two glenoid cavities separated by a groove running from front to back ; laterally, and a little posteriorly, a well-defined tubercle of insertion. The inferior extremity has a transversely elongated articular surface, to articulate with the second phalanx ; this surface is formed by two condyles separated by a middle groove, and surmounted laterally by a small tuberosity for ligamentous insertions. The external condyle is smaller than the internal, and when the bone is placed upon a horizontal plane, the anterior face turned upwards, it only touches by thi-ee points — the two tubercles of the upper extremity and the internal condyle ; by pressing on the external condyle, it is easy to make the bone oscillate. The first phalanx is a very compact bone, and is developed from two points of ossification, one of which is for the superior extremity alone. Professors Vachetta and Fogliata. of Pisa, assert that this bone, as well as the second phalanx, has three centres of ossification during uterine life. Sesamoids (Figs. 72, 73). — These are two small, short bones placed side by side behind the superior extremity of the first phalanx, the articular sur- face of which it completes, as it has not extent enough to be exactly adapted to the metacarpal surface. Each of these bones represents a small, irregularly shaped polyhedron, or, rather, a short trifacial pyramid. It offers : an anterior face, which is articular, and corresponding to the inferior extremity of the principal metacarpal bone, moulded, as it were, on one of the condyles and one of the sides of the median ridge ; a posterior face, covered with cartilage in the fresh state, and forming, with that of the opposite bone, a gliding concave surface for the flexor tendons of the phalanges ; a lateral face, studded with ligamentous imprints ; a summit, directed upwards : and a base, turned downwards, and serving for the attachment of several ligaments. Second (or Median j Phalanx (Os Coron.e, Small Pastern Bone (Figs. 72, 73). — This is a short bone, situated in the same oblique direction as the first phalanx, and between it and the third. Its general form is that of a cube flattened before and behind, and offering the following features : an a)>terior face, covered with some slight imprints ; a posterior face, provided, above, with a transversely elongated gliding surface : a superior face, channeled by two glenoid cavities, to match the inferior articulating surface of the first phalanx ; an inferior face, formed on the same plan as the last — being occupied by two unequal condyles, which articulate with the third phalanx and the navicular bone ; two lateral faces exhibiting a very marked imprint. In the interior of this bone is found a nucleus of very condensed spongy substance, enveloped in a layer of compact tissue. It is usually developed from a single centre of ossification, though in many objects there is a complementary nucleus for the superior articular and the posterior gliding surface. Third (Distal or Ungual) Phalanx, Os Pedis (Pedal or (Joffin Bone) (Figs. 72, 73, 74). — This is a short bone which terminates the digit, and sustains the hoof that incloses it and the navicular bone. When completed by a special ^iro-cartilaginous apparatus, it represents the segment of a very short cone. 116 TBE BONES. obliquely truncated behind, from the summit to the base. It offers for study : three faces, three borders, and two lateral angles. Faces. — The anterior, convex from side to side, and cribbled by porosities and vascular openings, shows on each side : 1. The preplantar fissvre — a horizontal groove more or less ramified, which commences behind, between the retrossal and basilar processes, terminating in front in one of the foramina that penetrate the bone. 2. The patilohe eminence — a roughened projecting surface, situated between the preceding fissure and the inferior border of the bone. The superior face is occupied by an articular surface formed by two glenoid cavities and a slight median ridge ; it comes in apposition with the inferior face of the second phalanx. The inferior (or solar) face, hollowed out like an arch, is divided into two regions by the semilunar crest, a salient line which describes a curve forwards. The anterior region is perforated with very fine porosities, and corresponds to that part of the hoof named the sole. The posterior region shows, immediately behind the semilunar crest, a median imprint, and two lateral channels designated the plantar fissures. These originate at the root of the basilar process, are directed obliquely downwards and inwards, and open into th.Q plantar foramina, the external orifices of two large canals which enter the bone and unite in its interior to form the semilunar Y\z. 74. PLA.NrAR SURF.\CE OF THIRD PHALANX. 1, Lower face, or sole ; 2, 3, wings, or retrossal pro- cesses ; 4, internal border ; 5, plantar foramina. Sinus. Borders. — The superior describes a curve, with the convexity forward, and presents : 1. In its middle, the pyramidal eminence of the os pedis— a single tri- angular process, flat before and behind, roughened on its anterior aspect, and concurring, by its posterior surface, to form the articular surface which responds to that of the second phalanx. 2. Laterally, two facets of insertion which encroach on the anterior surface, and even advance, posteriorly, nearly to the preplantar fissure. The inferior border is thin, dentated, convex, and semicir- cular ; it is perforated by from five to ten large foramina, which pass into the bone. The posterior border is slightly concave ; on it is observed a very narrow, transversely elongated, diarthrodial facet, which becomes confounded with the superior large articular surface, and is adapted to a similar facet on the navicular bone. Lateral angles. — These are two projections directed backwards, on the summit of which the three borders of the bone unite, and which gives attachment to the lateral fibro-cartilages. A deep notch — the origin of the preplantar fissures — separates each into two particular eminences : one, the superior, named by Bouley the basilar jrrocess ; the other, the inferior, prolonged behind, and desig- nated by Bracy Clark the retrossal process (from retro, behind, and ossa, bone). Structure. — The os pedis exhibits in its interior the semilunar sinus — a cylin- drical, transversely elongated, and semicircular cavity resulting from the arching anastomoses of the two plantar canals. From this cavity pass off numerous channels, which anastomose frequently with each other, and open externally by the foramina on the anterior face of the bone, or by those on its inferior border. The OS pedis has for its base a nucleus of spongy substance, surrounded by a layer of compact tissue. The latter is thicker towards the pyramidal eminence than elsewhere, and sends into the interior numerous prolongations which form TEE ANTERIOR LIMBS. 117 the walls of the semilunar sinus, as well as the bony channels which spring from it. Development. — The third phalanx, formed from a sin^^le nucleus of ossifica- tion, undergoes numerous changes in its configuration during life. Thus, in the young animal the lateral angles are thick, obtuse, and but little prolonged posteriorly ; but as it grows older, they increase in length and become salient. The development they then assume, is due to the progressive ossification of the lateral cartilages implanted on their surface. It often happens, in \ery old horses, that this ossifying process is carried to an extreme degree, and nearly the whole substance of these complementary organs is invaded. From the commencement, its inevitable result is to convert the notch which separates the basilar from the retrossal process into a foramen. T/i£ complfmcntarij Jibro-cartilat/iuoifs apparatus of the os pedis. — To under- stand properly the disposition of this portion of the foot, it is necessary that a previous knowledge of the ligaments and tendons attached to the os pedis Fig. 75. should have been accpiired ; therefore • a. 3, a detailed description will be given when the Horse's foot is studied as a whole, in the article on the Sense of Touch. It will be sufficient here to state that this apparatus consists of two lateral pieces — the fihro-cartiIa//es of the OS pedis, united behind and below by the plantar rushion — a fibrous and elastic mass on which rests the navicular bone, through the medium of the perforans tendon. The Small Sesamoid or Navicular Bone (Figs. 72, TSV — This short bone is annexed to the third phalanx, behind which it is situated ; it is elongated transversely, flattened above and below, and narrow at its extremities. It offers : 1. A superior face, on which are pro- longed the glenoid cavities and the median ridge of the articular surface of the OS pedis ; it articulates with the second phalanx. 2. An inferior face, divided by a slight ridge into two undulated facets, and covered with cartilage to form a gliding surface. An anterior border, channeled lengthways by a groove of insertion, above which is remarked a diar- throdial facet that brings the small sesamoid into contact with the posterior border of the third phalanx. 4. A posterior border and two extremities, for ligamentous insertion. This bone, as well as the sesamoids, originates from a single centre of ossification. It is formed of a layer of compact tissue enveloping /a nucleus of very condensed spongy substance. (For differences in the Ass, see Posterior Limb.) NAVICDLAR BONE OF THE HORSE. Anterior Border and Inferior Face. 1, articu- lar facet for the facet on the posterior border of the OS pedis; 2, roughened groove on the anterior border ; 3, inferior face, smooth and undulated. B, Posterior Border and Superior Face. 1, Articular face for the lower end of the second ]ihalanx; 2, posterior border, with many foramina. US THE BONES. DiPrERENTIAL CHARACTERS IN THE DIGITAL REGION OF OTHER AnIMALS. In the other domesticated animals, the number of complete digits ia as follows:— Carnivora 5 Pig * Ruminants 2 A. Ox, Sheep, Goat. — These animals certainly possess four digits, but only two are per. feet— the midius and annularis — and these articulate with the inferior extremity of the principal metacarpal (Fig. 71). The two others — the index and auricularis — are in a rudimentary con- dition, and are represented by two small bones situated above and behind the metacarpo- phalangeal articulation. In the Ox, Sheep, and Goat, each of the perfect digits comprises (like the single digit of the Horse) three phalanges and three sesamoids. The first phalanx fairly represents the moiety of this phalanx in the Horse. It has no Fig. 77. Fig. 76. «?/ ANTERIOR LIMB OF THE PIO. FOREARM AND FOOT OF THE DOG (AN- TERIOR face). 1, First digit ; 2, second digit ; 3, third digit; 4, fourth digit ; 5, thumb; 6, 7, 8, 9, first, second, third, and fourth boues of the lower row of carpal bones ; 10, 11, fii'st and second bones of the upper row; 12, supercarpal bone; 13, body of the ulna ; 14, apex of the olecranon; 15, beak of the olecranon; 16, body of the radius. posterior imprints, but shows them on its inner surface for the attachment of several ligaments. This internal face is plane, and the external convex ; these characters are repeated in the other two phalanges. It is also remarked in all the phalangeal bdues, that the external articular facet of the extremities is always larger than the internal. Of the two sesamoids, the t- xternal THE ANTERIOB LIMBS. 119 Fig. 78. is wilier and less elongated than tlie internal. They articulate with each other and with the first phalanx, by small diarthrodial facets. The second phalanx is hollowed internally by a small medullary cavity. The ungual phalanx, as a whole, resembles one of tlie lateral moieties of the os pedis of Solipeds. This phalanx has no complementary fibro-cartilage, basilar process, or retrossal eminence, nor yet a cavity for insertion on the sides of the pyramidal eminence. The semilunar crest is replaced by an obtuse, thick, and rugged ridge, which occupies quite the posterior limit of the inferior face of the bone. Three large canals penetrate the third phalanx— two to the base of the pyramidal eminence, and one towards tho origin of the preplantar fissure. They form, in the interior of the bone, a vast sinus, giving rise to several vascular canals which open on the surface. There is only one foramen at the base of the pyramiilal eminence in the smaller Buminants. B. Camel, — In this animal, there are in each digit only three phalanges and two large sesamoids. The direction and form of these phalanges differ notably from what is seen in Ruminants. The first phalanx is long, very oblique, constricted in the middle, and very thick at both ends. On the superior articulating surface is a single glenoid cavity, divided posteriorly by a median groove. The inferior surface is prolonged on tlie posterior face of the bone, wliich is converted into a kind of pulh y. The second phalanx is nearly horizontal, and much flattened above and below. The ungual phalanx is somewhat like an irregular trifacial pyramid with a blunt summit; neurits base, on its upper face, it has a roughened tubercle. C. Pig. — The Pig has four complete digits articu- lating from the mefacarpals ; the thumb is absent. The index and auricularis — or fourth and fifth digits — are short, and do not usually rest on the ground (Fig. 76). D. Dog, Cat, Rabbit.— The five digits of the 7 og aii.haft (^f the ilium, with the ilio-pectineal crest; 4, cotyloid cavit)' ; 5, symphysis pubis ; 6, inferior ischiatic spine and tuberosity. loid angle by a fissure which runs obliquely inwards and downwards. The internal is united with that of the opposite bone, to form the pubic portion of the pelvic symphysis. Angles. — The ex- F'Sj ^^• ternal, also named the cotyloid angle, is the thickest of the three. To it chiefly belongs the rugged depressed surface that constitutes the bottom of the coty- loid cavity. The in- ternal unites with the analogous angle of the opposite bone. The postni&r is consolidated at an early period with the antero - internal angle of the ischium, to enclose, inwardly, the oval foramen. Ischium (Figs. 84, 85). — This is the mean, in volume, of the three pieces of the coxa. Situated behind the pubis and ilium, it is flattened above PELVIS (LATERAL VIEW). 1, External angle of the ilium, or anterior iliac spine; 2, internal angle, or posterior iliac spine; 3, shaft of the ilium and ilio- pectineal line; 4, cotyloid cavity, or acetabulum; 6, inferior ischiatic spine, with tuberosity behind. 130 THE BONES. and below, and of a quadrilateral form. It offers for study : two /aces, four borders, smd/our angles. Faces. — The superior is smooth and nearly plane, and forms part of the floor of the pelvic cavity. It has a small nutrient foramen directed outwards. The inferior presents some rugosities, clustered particularly about the symphysis. Borders. — The anterior, thick and concave, circumscribes the oval foramen posteriorly. The posterior, straight and directed obliquely forwards and inwards, forms, with the analogous border of the opposite bone, a large notch named tjie ischial arch. It exhibits, throughout its extent, a rugged depressed lip (the spine), arising from the side of the inferior face. The external, thick and concave, constitutes the lesser ischiatic notch. The internal is joined to the ischium of the other side, to constitute a portion of the pelvic symphysis. Angles. — The antero-external, or cotyloidean, is the most voluminous of the four, and affords for study : 1. An excavated diarthrodial facet, making part of the cotyloid cavity. 2. The posterior extremity of the supra-cotyloidean crest, limited by a small transverse fissure which separates from the external border of the bone. The antero-internal angle is consolidated with the posterior angle of the pubis. The jwstero-external angle forms the ischial tuberositg. This is a large prismatic process which looks upwards, and is prolonged by a salient ridge, elongated from before to behind, with its sharp border turned outwards and downwards. The postero-internal angle forms, with that of the other ischium, the summit of the triangular space which constitutes the ischial arch, or pubic arch of some species. The Coxa in General. — This bone, the three constituent parts of which we have just been studying, presents for consideration, as a whole, a middle portion and two extremities. The middle, very much contracted, offers, outwards and downwards, the cotyloid cavity (or acetabulum), which has not yet been described, because its study does not properly pertain to either of the three regions of the coxa. This cavity is intended to receive the articulating head of the femur, and represents the segment of a hollow sphere ; it is circimiscribed by a very salient rim, which is thin at its free margin, and widely notched on the inner side. The deeper portion is occupied by the roughened and depressed surface already designated as the bottom of the cotyloid cavity {fandus acetabuli), which communicates, by the internal notch of the rim, with the inferior groove of the pubis. The anterior extremity, flattened on both sides, and formed by the ilium, rests, as has been shown, on the sacrum. The posterior extremity, flattened in an inverse sense to the preceding, is constituted by the pubis and the ischium, and is traversed, from above to below, by the sub-pubic (or obturator) foramen — the large oval aperture which separates these two bones from one another, and perforates the floor of the pelvis ; this opening is closed in the fresh state by muscles. The two coxae, by uniting in their posterior part, form the articulation to which has been given the name of ischio-pubic or pelvic symphysis ; thus united, the two bones represent something like a V with the opening in front — a circumstance which makes the lateral diameter of the pelvis greater in front than behind. Structure and Development of the Coxa.— To the three centres of ossification which constitute the coxa, are added two complementary centres : one for the anterior spinous process and spine of the ihum, another for the ischial tuberosity. THE POSTERIOR LIMBS. 131 It must be added that there is, within aud iu front of the cotyloid cavity, a cotyloid nucleus analogous to the g-lenoid nucleus of the scapula. This nucleus, comprised between the three bones of the coxa, has been named by Serres the Y-shaped bone. In youth, the diiferent parts of the coxa are very thick, and the spongy tissue is abundant, while the compact is rare. The pubis is always convex on its two faces, and the middle part of the coxa — that adjoining the cotyloid cavity — is of considerable thickness, a feature which much diminishes the extent of the pelvic cavity. As the animal advances iu age, however, the layers of compact tissue increase in thickness, approaching each other as the spongy substance is lessened. The pubis becomes thinnest, aud at an advanced period of life is sometimes even translucid. The compact tissue is always abundant in the neighbourhood of the cotyloid cavity, as this is the centre on which converge all the impulsive efforts com- mimicated to the trunk by the posterior limbs. It is also in this cavity that ossification commences. B. The Pelvis in Geneeal. 1. External and Internal Conformation of the Pelvis. — The pelvis is a kind of rear cavity iu the form of a cone, which prolongs the abdominal ca\ity between the sacrum and coccygeal vertebra?. It occupies the posterior part of the trunk, aud, with regard to its conforma- tion, presents for study an external and internal surface. Extermil surface. — This may be resolved into four planes or faces. The superior plane is slightly oblique from above to below, and before to behind ; its degree of obliquity varies. It is contracted from before to behind, and shows : 1. On the median line, the spinous processes of the sacral and the first coccygeal vertebrae. 2. On each side the sacral grooves, at the bottom of which open the supra-sacral canals. The inferior plane is nearly horizontal. Formed by the pubes and ischial bones, it presents from before to behind : 1. In the middle, the ischio-pubic symphysis. 2. On each side the subpubic groove, the oval foramina, and the inferior face of the ischial bones. 3. Quite externally, the cotyloid cavities, by which the pelvis rests upon the posterior limbs. The latei-al faces are oblique downwards and outwards, and are wider in front than behind. They exhibit : 1, The spine of the iliimi and the two anterior spinous processes. 2. The external iliac fossa. 3. The ischial arch. 4. The supra-cotyloid crest or ischiatic spine, which presents, outwardly, the surface of insertion for the internal or deep gluteus muscles. 5. The lesser ischiatic notch. 6. The ischial tuberosity. Internal surface. — The internal surface of the Horse's pelvis cannot be divided into two portions as in Man, because the inner surface of the iliac bones is not hollowed out to form an anterior cavity. The pelvis of Sohpeds is, therefore, a simple conoid cavity, in which are distinguished four planes or faces, and two apertures called the inlet and outlet. The anterior openincj, or inlet, is nearly circular, especially in the Mare, and a little obUque downwards and backwards. It is limited above by the inferior face of the first vertebra of the sacrum ; inferiorly, by the anterior border of the 132 TEE BONES. pubis ; and on the sides by a part of the inner face of the ihac bones, and alsc the internal aspect of the pectineal crests. The inlet presents four diameters, a knowledge of which is important iu obstetrics — a vertical, horizontal, and two oblique. The first, the sacro-pubk, extends from the inferior face of the sacrum to the anterior border of the pubic symphysis ; its mean length is 8:|^ inches. The second, the bis-iliac, is measured from one pectineal crest or eminence to another ; the mean of this is Hj&^ inches. The two last diameters, the ileo-sacral, are estimated from the inferior face of the sacro-iliac articulation of one side to the ilio-pectineal eminence of the other ; this is, on an average, 8^^ inches. These measurements irrefutably Fig. 86. FKLVIS OK THK HORSE. demonstrate that the inlet is not elliptical in the vertical direction ; but it may happen that the transverse diameter is the greatest. The posterior aperture or outlet, situated at the posterior end of the pelvic cavity, gives exit to the rectum and genital organs. It is limited by the inferior face of the summit of the sacrum, the superior face of the ischial bones, the supra-cotyloid crest or ischiatic spine, and the internal face of the sacro-sciatic ligaments. At the outlet only two diameters are recognized — a vertical and a horizontal. The vertical, extending from the inferior face of the sacrum to the superior face of the ischial symphysis, measures on an average 6^^ inches. The horizontal diameter, comprised between the two supra-cotyloid crests, is 7yV inches. The superior face of the pelvic cavity is a little concave from before to THE POSTERIOR LIMBS. 133 behind ; it has for base the sacrum, which presents on each side of the mediau line the subsacral foraniina. This part is also culled the sacral plane, or roof of the pelvis. The inffrior region^ or ischio-pubic plane, is formed by the pubes and the ischial bones. It is concave from side to side ; its anterior border is nearly straight, and its posterior border is scooped out by a wide notch to form the arch of the Ischium. It has been remarked by Goubaux, that the portion of this plane correspond- inuf to the pubis presents numerous varieties. The superior face of the pubis may be convex in its anterior moiety, and concave in its posterior ; or it may be Fig. 87. PELVIS OF THB MARE. concave before and convex behind, the concavity being separated from the convexity by a transverse ridge. This ridge is sometimes represented by a series of small conical eminences ; at other times this upper face is disposed as a smooth inclined plate, directed backwards and upwards, and a kind of rim surmounts the anterior contour of the oval foramen.^ With regard to the lateral faces, they are formed by a small portion of the inner face of the iliac bones, and in great part by the sacro-sciatic ligaments. The foetus must pass through the pelvic canal during parturition ; it is, therefore, important to know at any time if the female pelvis is of sufficient dimensions to allow the fcBtus to leave it. Pelvimetry is the name given to ' It is neoeesary to be aware of the frequency of these aaperities on the floor of the pelvic oarity, in order not to arrive at false inductions when exploring the bladder per rectum. 134 THE BONES. that section of obstetrics dealing with the diameters of the pelvis. These may be determined in several ways, which, in veterinary surgery, daily receive the sanction of experience. Some years ago we indicated one,^ which consists in measuring the horizontal distances between the two haunches and the two ischiatic tuberosities, and the vertical distance extending from the coxo-femoral articulation to the most salient part of the croup ; then to take a fourth of the total of the two first measurements, in order to obtain the transverse diameter of the inlet, and three-fourths of the third, to have the vertical diameter of this opening. Saint-Cyr and Violet have investigated the relation existing between the height of the Mare and the vertical diameter of the pelvis, then that of the width of the croup to the bis-iliac diameter ; and they have found that the first was equal to 0-1515 centimetres ; the second to 0-4654, in a well-bred Mare, to 0-3945 in common-bred Mares. Consequently, according to the pelvimetric procedure of these authorities, it is sufficient to multiply the height of the Mare by 0-1515 to have the vertical diameter of the inlet, and the width of the croup by 0-4654 or 0-3945, according to circumstances, to find the transverse diameter. But this question rather appertains to obstetrics.'^ 2. Differences in the Pelvis of tijje Sexes. — The pelvis of the Mare exceeds that of the Horse in all its dimensions, but the difference is most marked in the transverse diameters (Figs. 86, 87). The inlet forms a vast circumference, when compared with that of the male ; the pectineal crests are wide apart, and the distance separating the anterior border of the pubis from the lower face of the sacrum is considerable. If the pelvis be viewed in its superior plane, it is found that in the Mare the ischiatic notches are very deep ; that the internal border of the ilium forms a regularly curved and very concave line ; and that the supra-cotyloid crests, or ischiatic spines, are widely separated from each other. It is also noticed that the floor of the pelvis is wide, and that the bones composing it tend towards the same horizontal line. In the male, the ischiatic border is only represented by a very curved line ; this line is composed of two almost straight portions, which join at an obtuse angle at the origin of the neck of the ilium ; the supra-cotyloid crests are relatively near each other, and bent towards the longitudinal axis ; while the two moieties of the pelvic floor are directed very obhquely downwards and inwards. In the Mare, the ischial arch is larger than in the male, and forms a regular curve uniting the two tuberosities of the same name. In the Horse, the two ischial tuberosities are but little apart, and the ischial arch forms a somewhat acute angle, with its borders nearly straight. Lastly, when the pelvis is examined in its inferior plane, in addition to the features already indicated in the ischial arch, it is found that in the Mare the obturator foramina are large and nearly circular, while in the Horse they are elliptical ; the cotyloid cavities are also further removed from the ischio-pubic symphysis in the female than in the male. The sacrum of the Mare has appeared to us, in some individuals to be a little more arched from before to behind than that of the Horse ; but this character is not constant. ' Arloing, Journal Vet€rinaire de Lyon. 1868. * Saint Cyr and "Violet, Traits d'Obstetrique Vet^inaire. Paris: 1888. THE POSTERIOR LIMBS. 135 The following figures, relating to the capacity of the pelvis of the Mare and Horse, confirm what has just been enunciated : — Make. Borizontal Diameters. Horse. Horizontal Diameters. Between the Pectineal Crests. Between the Supra-cotyloid Greets. Between the Pectineal Crests. Between the Supra-cotyloid Crests. Inches. Inches. Inches. 8A Inches. 6i1, Mare. Vertical Diameters. Horse. Vertical Diameters. Between the Sacrum and Pubis. Between the Sacrum and Ischium. Between the Sacrum and Pubis. Between the .Sacrum ani Ischium. Inches. 8^ Inches. Inches. 8 Inches. To recapitulate, there is observed in the pelvis of the Mare : — 1. A great increase in the transverse diameters. 2. A deep and regularly concave ischiatic notch. 3. A wide and concave ischial arch. 4. Circular obturator foramina. 5. The cotyloid cavities distant from the pubic symphysis. In the Ass, the inlet of the pelvis is a longer oval than in the Horse. The coxae are distinguished by : 1. The less curvature of the anterior border of the ilium. 2. A slightly excavated external iliac fossa. 3. The triangular shape of the obturator foramina. 4. A short and deep notch separating the external border of the ilium from the angle of the haunch. .5. The direction of the tuberosities of this angle ; they approach more nearly the parallelism with the median plane of the trunk than in the Horse. 6. The disposition of the rugo- sities in tubercles for the insertion of the suspensory ligaments of the corpus cavemosiun on the inferior face of the ischium. In the Ass, also, a line which would unite the inferior contour of the auricular facet to the most salient point of the angle of the haunch, would be parallel to the anterior border of the ilium, while it would be oblique on this border in the Horse. The inlet of the pelvis in the Hinny resembles that of the Ass ; in that of the Mule, it holds a middle place between the Ass and Horse. The pelvis of the Hinny resem})les that of the Ass, also, by the form of the obturator foramina, the direction of the anterior border of the ilium, and the position of the auricu- lar facet ; while that of the Mule, on the contrary, resembles the pelvis of the Horse in these features. The reverse is noted with regard to the disposition of the angle of the haunch. Differential Characters in the Pelvis of other Animals. It is remarked : 1. That in all the domesticated animals, with the exception of Solipeds and the Camel, the direction of the coxse is nearly horizontal. 2. That in all, the ilium is more oblique than in Solipeds. 3. Tliat in all, the transverse diameters of the pelvis are relatively less extensive. A. Ruminants. — In the Ox, the space between the two coxse is scarcely so great in front 136 THE BONES. as behind; the ilium is not voluminous, and has only three processes on the anterior and superior ilinc spines. There is no furrow on the lower face of the pubes, and its upper face, like that of the ischium, is very concave. Three eniiueiicea are seen on the posteio-external angle of the ischium. In early life, the ischio-pubic symphysis shows an epiphysary nucleus in the middle of its inferior face. (The epiphysis on the inner border of the ischium has been considtreil by some anatomists as an independent bone, and described by them aa the inter-iscMdl hone). The ischio-pubic symphysis has, in the middle of its inferior face, a thick protuberance, flattened on each side and very pointed ; in early life this is an epiphysis, and the epipliysary nucleus, bifurcated posteriorly, is continued along the posterior border of the ischial bones aa far as the ischial tuberosity, in the form of two marginal bands. The rim of the cotyloid Fig. 88. cavity has also three notches, and the supra-cotyloid crest, or ischiatic spine, is very ele- vated and sharp, and but little roughened outwarily. In the Sheep and Goaty the coxae aie yet more horizontal and proportionately longer than in the Ox, but tlie upper face of the ischium and pubis i.s less concave ; tiie external iliac fossa is separated into two portions by a small longi- tudinal crest. The pelvis of the Camel is remarkable for its great ob- liquity, its shortness, and its narrowness. The anterior border of the ilium is convex ; the pubis and ischium are very tliiek; the rim of the cotyloid cavity is elevated and regular; tlie ischio-pubic sym- physis forms a rugged crest outside the pelvis; and the ischial tuberosity is disposed in the same manner as in the Horse. B. Pig.— The pelvis of the Fig closely resembles that of the smaller Ruminants ; though the crest of the ilium is convex, and there is no pro- tuberance outside the ischio- pubic symphysi.-i. The pelvic cavity is vast, in proportion to the animal's height, and the ischio-pubic symphysis is late in becoming ossified. C. Dog. — In the Dog, the transverse diameter of the pelvis is greater behind than in front ; it is smallest between the cotyloid cavities. The ilium is nearly vertical, and its external face is much depressed. The notch forming tlie ischial arch occupies no more than the internal moiety of the posterior border of the ischium ; between this arch and the ischial tuberosity, is a rugged lip directed downwards. There is no furrow on the lower face of the pubis. Ossification of the symphysis is even later than in the Pig. D. Cat. — In the Cat, the ilium is proportionately narrow, and the supra-cotyloid crest higher, than in the Dog. The posterior border of the ischium is regularly convex from without to within, and the pubic symphy.sis has, inferiorly. a somewhat salient crest (Fig. 88). E. Rabbit. — Pelvis horizontal ; ischium nearly as long as the ilium ; external ilac fossa divided by a blunt longitudinal crest ; supra-cotyloid crest little elevated, straight, and ending abruptly behind by a kind of notch ; rim of the cotyloid cavity complete, or having a slight posterior notch ; ischial tuberosities parallel and not divergent, as in the Dog : and posterior border of the ischium concave, and very obliquely directed forwards and inwards (Fig. 88). PELVIC BONES OF THE CAT AND RABBIT. A, Pelvis of the Cat. B, Pelvis of the Rabbit. 1, Sacrum ; 2, external iliac fossa; 3, great ischiatic notch ; 4, external border of the ilium ; 5, supra-cotyloid crest ; 6, cotyloid cavity ; 7, crest above the shaft or neck of the ilium; 8, small sciatic notch ; 9, anterior extremity of the symphysis pubis ; 10, ischium; 11, ischial tuberosity; 12, pubis; 13, obturator foramen. TEE POSTERIOR LIMBS, 137 Thigh. This has for its base one bone — the femur. Femur (Figs. 89, 90). The femur (os femon's) is a long, pair bone situated in an oblique direction downwards and forwards, between the coxa and the principal bone of the leg ; it is divided into a bod/j (or shaft) and t/ro extremities. Body. — It is irregularly cylindrical, and presents for study four faces. The e^.rtnrial, internal, and anterior., confounded with one another, are regularly rounded and almost sniooth, showing only some slight imprints and vascular grooves. The posterior, nearly plane, and wider above than below, oifers : 1. Outwardly and towards the superior third, an uneven circular surface. 2. On the same level, and inwardly, a slight crest, oblique downward.** and outwards. ?K In the middle, a very extensive roughened surface, having the form of an obliquely angular parallelogram, for the attachment of the great adductor muscle of the thigh. 4. Below this surface, a large vascular groove running obliquely outwards and downwards. On the limit of the posterior and external faces are found, towards the upper third, a large rugged, flattened eminence, curved in front, and termed the suhtrochanterian crest (or external smidl trochanter ^), because of its position under the trochanter ; below, a deep fossa, named the subcondyloid, garnished at its bottom with asperities, and bordered in front by an uneven lip. On the limit of the posterior and internal face, there are ol)served from above to below : 1. The smcdl trochanter — a large scabrous tuberosity, elongated in conformity with the bone, and situated near its upper fourth. 2. A marked longitudinal imprint for the attachment of the pectineus ; behind, it is confounded with the surface for the insertion of the great adductor muscle of the thigh, and presents, in front, the nutrient foramen of the bone. :^). The origin of the great posterior fissure. 4. Quite below, a collection of large tubercles which form the supra- condyloid crest. Extremities. — The superior extremity is sensibly flattened before and behind, and shows : 1. Inwardly, an articular head which is received into the cavity of the acetabulum. This head is separated from the other portion of the body by a neck, which is, however, not well marked in the Horse, and forms two-thirds of a sphere, excavated in its internal part by a very deep cavity for ligamentous insertion. 2. Outwardly, a very large eminence — the trochanter major, or great {external) trochanter, in which is recognized, as in the trochlea of the humerus : a summit, much more elevated than the articular head, and slightly bent inwards ; a convexity, encrusted with cartilage, and anterior to the summit, from which it is separated by a narrow and deep notch ; a crest situated under the convexity, and formed by a tuberculated surface, on which one of the tendons of the middle gluteus muscle becomes inserted, after gliding over the convexity. 8. Posteriorly, the trochanteric ox digital fossa — a deep cavity studded with imprints, and circum- scribed, outwardly, by a salient lip {trochanteric ridge), which descends vertically ' Thi8 is tlie third trochanter of Cuvier, and takes the place of the external and superior branch of the linea a^pera of Man. (It is the external small trochanter of Percivall, and the middle trochanter of Leyh ) 138 THE BONES. from the summit of the trochanter to the posterior face of the bone, where it gradually subsides. The inferior extremity is flattened before and behind ; consequently, its larger axis crosses at a right angle that of the upper extremity. It is distinguished by the presence of two condyles and a trochlea. The two condyles, placed behind, one beside the other, articulate with the superior extremity of the tibia. They are separated by a deep depression designated the infercondyloid fossa, whica lodges the spine of the tibia and the interosseous ligaments of the femoro-tibial Fig. 89. Fig. 90. LEFT FEMUR (ANTERIOR VIEW). 1, Head ; 2, 2, trochautei* major, with ita crest ; 3, trochanter minor, subtrochaa- terian crest, or third trochanter; 4, in- ternal trochanter ; 5, notch for insertion of ligamentum teres ; 7, 8, tuberosities for tendinous and ligamentous insertion; 9, trochlea. LEFT FEMUR (POSTERIOR VIEW). Head ; 2, trochanter major ; 3, trochanter minor; 4, internal trochanter; 5, fossa for insertion of ligamentum teres; 6, trochanteric fossa; 7, 8, tuberosities; 9, fossa for the insertion of the external meniscus; 10, supra-condyloid fossa ; 11, condyles. articulation. The external condyle bears, outwardly, two fossae — one superior, for ligamentous insertion ; the other, inferior, for muscular attachment. The internal condyle presents, posteriorly and inwardly, near the posterior extremity of the intercondyloid notch, a roughened depression for the insertion of the Jibro-cartilaginous meniscus interposed between the external condyle and the corresponding articular plane of the tibia. It is surmounted outwardly — on the side opposite to the intercondyloid notch — by a large tubercle for insertion. The trochlea^ a wide pulley on which the patella glides, is situated in front of THE POSTERIOR LIMBS. 139 Fig. 91. the condyles. It is slightly oblique downwards and inwards, and appears to continue in front the intercondyloid notch. Of the two lips which border its cavity laterally, the internal is the thickest and the most prominent. Between the external and the corresponding condyle, is seen a digital fossa for muscular insertion. Structure and development. — The femur, very spongy at its extremities, is developed from four principal centres of ossification : one for the body, another for the articular head, the third for the trochanter, and the last for the inferior extremity alone. The femur of the Ass offers several differential characters, the principal of which have reference to the length of the neck, the development of the third trochanter (trochanter minor), and the curvatures of the diaphysis. The greater length of the neck causes the internal trochanter to be some distance from the hori- zontal plane on which the inner face of the bone lies ; in the Horse this trochanter is always in contact with the plane. The small trochanter is less developed than in the Horse, as may be seen on laying the bone on its external border ; for the femur of the Ass rests by the trochanter major and external condyle, while in the Horse, it lies on the latter and the subtrochanteric crest. With regard to the curvatures, there is remarked a slight diminution in that which carries the head of the bone backwards, and a shght increase in the twist of the diaphysis around its longitudinal axis, which alters the equilibrium of the bone ; so that it is impossible to have it in stable equilibrium when it rests on the trochanter major, head, and inner lip of the trochlea ; this is easily accomplished with the femur of the Horse. By the dimensions of the neck and internal trochanter, the femur of the Hinny and Mule holds a middle place between their progenitors ; while in the development of the trochanter major, and the degree of torsion around its longitudinal axis, the femur of the Hinny much resembles that of the Ass, and the Mule that of the Horse, though the conditions of equilibrium always remain the same as in the latter. SECTION OF LEFT FEMUR, SHOWING ITS STRUCTURE. Differential Characters in the Thigh-bone of the other Animals. In all the domesticated animals except Solipeds, the femur tends to become curved longi- tudinally, prismatic, and triangular ; the posterior face contracts, and the surfaces for insertion that it presents gradually approach each other, until tliey become confounded, and form a linea nspera in certain species. The head is more distinct; the internal trochanter is a rough tubercle, ami is joined to the large trochanter by an oblique ridge ; the large trochanter sub- sides, and forms a single mass, the summit and convexity of which are confounded ; the third trochanter, the fossa, and the supra-condyloid crest are more or less effaced. In addition to these modifications, there are others special to each species. A. Ruminants.- In the Ox, there is no subtrochanteric crest; the supra-condyloid fossa is shallow, and the crest little noticeable. The head is well detached, and has its centre excavated by a shallow fossa of insertion. The trochlea is narrow, and its inner border ascends much higher on the anterior face of the bone than the external. Ill the Sheep and Goat, the general form of the femur resembles that of the Ox. It is observed, however, that the body is slightly curved backwards ; that the Bupra-condyloid fossa 140 TEE BONES. is nearly obliterated ; that the trochanter has subsided nearly to a level with the articulat head ; and that the trochlea is circumscribed by two equal-sized lips. The femur of the Camel more nearly resembles that of Man. It is long, slender, and curved backwards. The body is prismatic in its middle portion, and the two br;)nches of the linea aspera meet in the middle and diverge towards the ends. Tlie articular head is very much separated from the trochanter major, which is below the level of the most prominent part of the head. The internal condyle is smaller than the external, and the trochlea is narrow, while its lips are equal. B. Pig. — In the femur of the Pig, there is also noticed a supra-condyloid fossa, but it is wide and shallow ; the rugosities of the posterior face are replaced by some salient lines ; the trochanter major is on a level with the head; the latter is supported by a somewhat constricted neck, and is situated within, and in front of, the trochanter major. This latter disposition changes the direction of the great axis of the superior extremity, which obliquely crosses tliat of the inferior extremity. C. Carnivora. — In the Dog and Cat, the femur is long and curved like a bow. The rugged surfaces of the posterior face are confounded, and furm two crests repre- senting the linea aspera of the human femur. These crests do not lie against eacli otiier in the middle portion of the bone — they are merely parallel ; then they diverge above and below, to terminate beneath the great and small trochanters, and above the two condyles. The trochanter major is not so high as the particular head. Thft femur of Carnivora is also distinguished: 1. By the complete absence of the third trochanter and the supra-condyloid fossa — this last being replaced by a small tubercle, which terminates below the external branch of the linea aspera. 2. By the marked constriction and length of the neck supporting the articular head. 3. By the depth of the digital fossa. In the Cat and Rabbit are found small bony nodules, embedded like sesamoids in the substance of the lateral ligaments of the femoro-tibial articulation. After mace- ration, they often adhere to the condyles of the femur. D. Rodents. — The femur of the Rabbit reseinblea that of the Dog. It is flat before and behind, and more bent inwards at its upper end. The internal trochunter appears as a crest, and not a tubercle ; and the sub- trochanteric crest is very developed, and placed im- mediately below the trochanter major. A. - B FEMTJR OF THE OAT AND RABBIT. I, Femur of the Rabbit. B, Femur of the Cat. 1, Diaphysis ; 2, head ; 3, internal trochanter; 4, trochauter major ; 5, subtrochanteric crest ; 6, trochlea; 7, internal condyle; 8, sesamoid imbedded in the internal ligament of the femoro-tibial articu- lation. Leg. This has for its base three bones : the tibia, peroneus {gv fibula), and the rotula {or patdla). 1. Tibia (Fig. 93). The tibia is a long prismatic bone, thicker at the superior than the opposite extremity, and situated between the femur and the astragalus, in an oblique direction downwards and backwards, constituting the principal portion of the leg. It has a bodt/ or shaft, and ttvo extremitips. Bodf/.—Thk offers for study thref faces and thrpp borders. The faces are wider above than below. The external is almost smooth, and is concave in its superior part and convex below, where it deviates to become the anterior. The internal, slightly convex on both sides, presents, superiorly, deep imprmts for the attachment of the adductor muscles of the thigh and the semitendinosus. The posterior, nearly plane, is divided into two triangular surfaces : one, superior THE rOSTERIOR LIMBS. 141 Fig. 93. slightly roughened, serves for the attachment of the popliteus muscle ; the other inferior, much more extensive, is farrowed into numerous longitudinal crests, which give attachment to the perforaus muscle. On the limit of these two surfaces is remarked the nutrient foramen of the bone. The bordf^rs are distinguished as antnior, cxtfrnnJ., and internal. The ///-.s/ is rounded, and not very salient in its inferior two-thirds ; it forms, in its superior third, a curved crest, with the concavity external, which joins the anterior and superior tuberosity of the bone ; this has received tlie name of the tibi((l crest. The exteiiud border is very thick and concave above, where it constitutes, in common with the fibula, the tibial arch. The internal is also very thick, straight, and provided superiorly with some salient tubercles to which the popliteus is attached. Extremities. — The superior extremiti/., the most volumi- noiLS, is formed by three tuberosities — an anterior and two lateral, which are external and internal. The first., the smallest, is a rugged process continuous with the tibial crest, and separated from the external tuberosity by a wide and deep groove, into which passes a tendinous cord ; it is excavated, in front, by a vertically elongated fossa, which lodges the middle ligament of the patella. The external tuberosity, medium in size and the most detached, has outwardly an articular facet for the head of the fibula. The internal tuherositij, the largest and least detached, presents : on the sides, ligamentous imprints ; behind, a small tubercle which gives attachment to the posterior crucial ligament of the femoro-tibial articulation. The superior face of the two lateral tuberosities is occupied by two large, irregular, and undulated articular surfaces, which respond to the condyles of the femur, through the medium of the two meniscus-shaped fibro-cartilages interposed between the two bones. Of these two surfaces, the ex- ternal is always the widest, because it serves, by its posterior part, for the gliding movements of the popliteal tendon. They are separated from each other by the tibial spine — a conical articular eminence, divided into two lateral parts by a groove for insertion excavated at its base ; and in front by two lateral facets for the insertion, anteriorly, of the two inter-articular cartilages ; it is bordered behind by another fossa, which receives the posterior insertion of the internal meniscus. The inferior extremiti/, flattened behind and before, ex- hibits an articular surface moulded on the pulley of the astragalus, and two lateral tuberosities. The articular surface is formed by two deep cavities, oblique forwards and outwards, and separated by a median tenon which terminates posteriorly by a very prominent projection, on which the bone rests when it is made to stand vertically on a hori- zontal plane. The external tuberosity ^ projects but little, and is traversed in its ' The external malleolus of Man 12 POSTERIOR VIF.W OF RIGHT TIBIA. Tibial spine ; 2, fossa for the insertion of the internal meniscus ; 3, eitei-n;il tuberosity with articulation for the fibula : 4, fos^a for the insertion of exter- nal meniscus ; 5, fibula, forming with the tibia the tibial arch ; 6, shaft, or body of the tibia; 7, 8, exteinal and in- ternal malleoli, inferior tuberosities, or lateral processes of the tibia; 9, articular trochleae with a median ndge, for articulation with the astragalus. 142 THE BONES. LEO-BONES OP THE MTTLE, WITH THE FIBULA COMPLETELY DETACHED. i. Nutrient foramen ; 2, insertion sur- face for the perforans ; 3, insertion surface for the popliteus; 4, tibial ridge ; 5, fossa for the insertion of the anterior crucial ligament ; 6, in- ternal articular surface ; 7, external articular surface ; 8, tubercle for the insertion of the posterior crucial liga- ment ; 9, fossa for the insertion of the internal meniscus; 10, tibial crest ; 11, internal and inferior tu- berosity ; 12, external and inferior fissure of the tuberosity ; 13, pos- terior prominence formed behind by the median spur of the inferior articu- lar surface;' 14, superior extremity of the fibula articulating with the tibia; 15, the body of the fibula — com- pletely developed in this specimen. middle by a vertical fissure. The internal tubfrosifij,^ better defined, is margined pos- teriorly by an oblique channel. Structure and development. — The tibia is very compact in its inferior portion, and is developed from five chief centres of ossifica- tion. The body is formed, by one and the superior extremity by two, the anterior tuber- osity having one of these ; the last develops the whole of the inferior extremity of the bone, except the external tuberosity, which is de- veloped from a separate nucleus, that at ap early period becomes fused with the principal one of the epiphysis. The tibia of the Ass is remarkable for the more or less perfect equality of the promin- ences around the inferior articular surface, so that this bone can sometimes lie in stable equilibrium on its inferior extremity. It is also distinguished from that of the Horse by : 1. The more or less marked obliquity of the grooves which articulate with the astragalus. 2. The disposition of the oblique prominence coursing the surface, for the insertion of the popliteus muscle. 3. The great development of the imprint for the semitendinosus muscle, and the crest above the groove for the oblique flexor tendon of the phalanges. The tibia of the Mule and Hinny more particularly resembles that of the Horse. 2. Fibula, or Peroneus (Fig. 94). A small, undeveloped bone, elongated and styloid in shape, situated outside the tibia, and extending from the superior extremity of that bone to the middle or lower third of its body. The middle fortion of the fibula is thin and cylindrical, and forms above, in common with the external border of the larger bone, the tibial arch. Its superior e^ttremitij ., wide and flattened on both sides, has received the name of head. It offers, on its internal face, a diarthrodial facet to articulate with the external and superior tuberosity of the tibia ; on its external face it shows ligamentous im- prints. The inferior extremity of the fibula ' The internal malleolus. I THE POSTERIOR LIMBS. 143 terminates in a blunt point, and gives attaeliment to the ligamentous fibres that unite it to the tibia. The fibula is sometimes continued to the external inferior tuberosity of the latter bone, with which it is confounded ; and as this tuberosity always forms a special nucleus, particularly in the young Foal, it seems natural, having regard to the disposition observed in Pachyderms and the Caruivora, to consider it as the inferior extremity of the fil)ula fused to the tibia. In these animals, indeed, the tnlxTOsity or external maleoliis is formed by the inferior extremity of the fibula. Structure and development. — This bone is very compact, and apparently developed by a single nucleus of ossification ; though, in reality, there are two, one of which is for the head of the bone. 3. Patella (Figs. 95, 96). A small, short, and very compact bone, situated in front of the femoral trochlea, and annexed to the tibia, to which it is attached by three extremely solid ligamentous bands. The small polyhedron which it represents only offers for study three faces : Fig. 95. A Fig. 96. PATELLA OF THE HORSE (SUPERIOR AND POSTERIOR faces). 1, Superior face ; 2, posterior articular face ; 3, external border. PATELLA OF THE HORSE (ANTERIOR FACE). 1, Aaterior face ; 2, external border ; 3, iaternal border. the superior, roughened, and serving for the insertion of the triceps cruralis an(3 rectus muscles ; the anterior, convex and irregular ; and the third, the posterior, moulded on the femoral trochlea, to which it is but imperfectly adapted. In the fresh state, however, the articular surface formed by the latter face is completed by a fibro-cartilaginous apparatus, which will be noticed when describing the femoro-tibial articulation. This articular surface is composed : 1, Of a median ridge, which occupies the bottom of the trochlear cavity. 2. Of two depressed, gliding, lateral facets on the sides of this cavity ; the internal facet is always larger than the external — a disposition which permits the patella of one limb to be distinguished from that of the other. The Patella of the Ass is usually narrower than that of the Horse, but this feature would scarcely permit of its being distinguished from that of the other domestic Equidae. 144 THE BONES. Fig. 97. Differential Characters in the Leg-bones of the other Animals. In the leg-bones there is observed, in the various domesticated iinin)als, differences analo- gous to those mentioned as existing in the forearm of the pectoral limb. More particularly is this the case with regard to the development of the^^twZa. Tlie relations existing between the development of that bone and the number of digits, is less mark( d than tliat which exists between the development of the ulna and the division of the digital region. Thus, in Rumi- nants the fibula is only represented by its inferior nucleus of ossification, although there are two apparent and free digits. In these animals the patella is also very narrow ; and in hU the domesticated species except Solipeds, the articular grooves in the lower end of the tibia are directed im- mediately from before to behind. A. Ox, Sheep, Goat.— In the Ox, the tibia is short ; it is longer in the Goat and the Sheep. The tibia of these animals is remarkable for : 1. The absence of the lateral facet on the supero-external tuberosity. 2. The absence of a vertical fossa on the anterior tuber- osity. 3. The absence of roughened lines on the pos- terior face. 4. The obliquity downwards and inwards of the inferior articular surface. The most salient point of this surface is the anterior extremity of the middle tenon. The body of the fibula and its upper extremity are replaced by a fibrous cord, which is sometimes ossified wliolly or in part, and may then resemble the fibula of Solijieds. The inferior extremity forms a small isolated bone (the tarsal coronoid bone of some authorities), articulating in one direction with the tibia, and in another with the calcis and astragalus. B. Camel. — The tibia of the Camel is very long, slightly bent outwards at its upper end, and inwards at the lower end. The tibial crest is high and sharp. The posterior face shows only one roughened line limiting the popliteal surface. C. Pig.— In the Pig,tlie fibula is flattened on both sides, extends the whole length of the leg, and is united to the tibia by its two extremities: above, by a diar- throdial facet ; below, by an inteross^eous ligament. It is developed from three ossifying centres; the in- ferior articulates with the calcis and astragalus. D. Dog, Cat. — In Carnivora, the tibia, is long and slender, and presents a salient anterior crest. The fibula is also as long as the tibia, and is united to that bone at three points : at the two extremities by articular surfaces, in the inferior third and middle by an interosseous ligament. E. Rabbit. The leg-bones of this animal much resemble those of Carnivora, differing only in: 1. More pronounced flattening of the tibia on each side at its upper end, and before and behind inferiorly. 2. The slightly salient malleoli. 3. The fibula, which is fused with tlie tibia in its lower third. LEG-BONES OF THE RABBIT AND CAT. A, Boues of the Rabbit. B, Bones of the Cat. 1, Diaphysis of the tibia ; 2, crest of the tibia ; 3, internal malleolus or tuberosity of the in- ferior extremity of the tibia ; 4, anteiior extremity of the median tenon on the inferior articular sur- face of the tibia ; 5, fibula ; 6, ex- ternal malleolus or tuberosity. Posterior Foot. This region, which bears the greatest resemblance to the same region in the anterior limb, comprises three subdivisions — the tarsus, the metatarsus, and the digital region. 1. Bones of the Tarsus (Figs. 98, 99). These are short, very compact bones, six or seven in number, and situated THE POSTERIOR LIMBS. 145 between the inferior extremity of the tibia and the superior extremity of the metatarsal bones ; they are arranged, like the bones of the carpus, in two tiers — a superior and an inferior. The superior row only comprises two bones, Fig. 98. the largest ; these are the astragalits and the calcnneum (or calcifi). The inferior row is formed, outwardly, of the cuboides alone ; inwardly and anteriorly, it is subdivided into two secondary rows, the superior of which is constituted by the scaphoidcs, and the inferior by the laruc and small cuneiform bones. The last is sometimes divided into two, in which case there are three cunei- forms ; then the total number of the bones is seven. Astragalus. — An irregular cubical bone, situ- ated in front of the calcis, between the tibia and the scaphoid, and divided into five faces : 1. A supfriur and anterior, formed as an articular pulley to correspond with the inferior extremity of the tibia. This pulley — oblique from above down- wards, forwards, and outwards — may be considered as the type of the most perfect trochlea in the body ; it forms with the median plane of the body an angle of from 12° to 1.')°. Its borders are slightly spiral, the inner being more prolonged backwards than the external ; its groove receives the median tenon of the tibia, and its two ridges or lips fit into the lateral furrows of that bone ; the two lips are deeply implanted in the lateral grooves, and their two fossa? are hollowed out of their lower extremity, to admit the end of the principal bone during flexion movements. 2. An infei-ior fare, occupied by a slightly convex articu- lar surface articulating with the scaphoid ; this surface is notched outwardly by an excavation for ligamentous insertion ; behind the internal ex- tremity of this furrow, the articular face is cut in such a manner as to present two facets inclined towards each other, and separated by a sharp ridge. ?>. A posterior face, irregular, cut into three or four diarthrodial facets adapted for similar facets on the calcis, and which are separated by a wide, rugged excavation ; the middle facet is elliptical, almost vertical, slightly convex, and is the largest. 4. An external face, covered with imprints for the tibo-tarsal ligaments. 5. An internal fare, provided below with a small tubercle for insertion, and, posteriorly, with a badly defined sinuous furrow for the tendon of the oblique flexor muscle of the phalanges (Fig. 99). lfft hind poot (external aspect). 1, Tibia ; 2, summit of calcis or cal- caneum ; 3, astragalus ; 4, cuboid; 5, scaphoid; 6, cuneiform mag- num ; 7, large metatarsal bone ; 8, small metatarsal bone ; 9, suf- fraginis, proximal, or first pha- lanx ; 10, sesamoid bones; 11, cor jnarv, second, or middle pha- lanx ; 12, pedal bone, or third or distal phalanx; 14, navicular bone ; 15, basilar process of pedal bone. 146 THE BONES. Calcaneum, or Calcis (Figs. 98, 99, 100, 101).— A bone vertically elongated, flattened on both sides, and presenting two faces, two borders, and two extremities. The extwnal face is smooth and nearly plane. The internal face is excavated into a ghding groove to form the tarsal groove, in which passes the tendon of the perforans. The anterior border is slightly concave. The posterior border is Fig. 99. TARSUS OF THE HORSE. INTERNAL ASPECT. 1, Calcis; 2, astragalus (first and second bones of the upper row) ; 3, cuboid ; 4, scaphoid ; 5, cuneiform magnum; 6, vascular canal bet>veen the cuboid, scaphoid, and cuneiform magnum ; 7, smooth sur- face for the tendon of the gastrocnemius; 8, surface for insertion of latter ; 9. smooth surface for the tendon of the perforans ; 10, anterior extremity of the tibia; 11, superior extremity of the large meta- tarsal bone. A, Bones of the upper row. B, Bones of the lower row. T, Tibia. M, Metatarsus. ANTERO-EXTERNAL ASPECT. Calcis ; 2, astragalus ; 3, cunei- form magnum ; 4, scaphoid ; 5, cuboid ; l3, cuneiform parvum ; 7, superior extremity of large meta- tarsal bone ; 8, superior extremity of inner small metatarsal bone. A, Bones of the upper row. B, Bones of the lower row. T, Tibia. M, Metatarsus. thicker, straight, and rugged. The superior extremity, shghtly enlarged, con- stitutes the summit of the calcaneum, and is divided into three parts : a middle, which gives attachment to the tendon of the gastrocnemius : the other, the anterior, is a smooth surface on which this tendon rests when the foot is much flexed ; the third, altogether posterior, also constitutes a gliding surface for the TEE POSTERIOIi LIMBS. 147 tendon of the perforatus. The inferior extremity, wide and voluminous, shows in front three or four articular facets which articulate with the astragalus, and are separated, like those of the last bone, by an irregular and slightly excavated sur- face for insertion. Below, it shows for articulation with the cuboid a fifth facet, continuous with one of the preceding. Development. — The calcaneum is developed from two nuclei of ossification, one of which is for the summit. Cuboid hone (Figs. 98, 99). — This little bone, situated at the external side of the scaphoid and the large cimeiform bone, between the calcis and two of the metatar- sals, does not resemble a cube, but a parellelopiped elongated from before to behind. It o^ers six faces .- a superior, an articular face, in contact with the calcaneum ; an inferim-, also articular, articulating with the principal and external rudimen- tary metatarsal bones ; an internal, furnished with three facets for contact with the scaphoid and great cuneiform, and crossed from before to behind by a fissure, Fig. 100. Fig. 101. LEFT HOCK (FRONT VIEW). LEFT HOCK (INTERNAL ASPECT). 1, Apex of calcaneum ; 2, astragalus, inner i, Apex of calcaneum ; 2. inner articular ridge; 3, cuneiform magnum ; cunei- ride of astragalus; 3, navicular, scaphoid, form medium ; 5, cuboid. or cuneiform medium ; 4, cuneiform mag- num ; 5, cuboid ; 6, cuneiform parvum. which forms with these two bones a vascular canal ; an external, an anterior, and 2k posterior, covered with imprints. Scaphoid hone (the large cuneiform of Percivall) (Figs. 98, 99). — Flattened above and below, it is described as having two faces and a circumference. The /aces, both articular, are furrowed by a channel of insertion, and are distinguished as superior and inferio'r. The first is concave, and articulates with the astragalus ; the second is convex, and in contact with the two cuneiform bones. The circumfefi'ence offers, outwardly, two small facets, which are adapted to similar facets on the cuboid bone. For the remainder of its extent, it is covered with imprints (Fig. 99). Greed Cuneiform hone (the middle cimeiform of Percivall) (Figs. 99, 100, 101). — Flattened above and below, and triangular in shape, this bone is much smaller than the scaphoid, though resembling it in a striking manner. Its superior face is in contact with the latter bone, and its inferior face articulates with the middle and internal lateral metatarsal bones. Its external horder is provided with one or two facets to correspond with the cuboid bone ; and its intei-nal horder ako shows one, 148 THE BONES. which is in contact with another on the small cuneiform. Its anterior border is roughened throughout its extent (Figs. 99, 100). Small Cuneiform bom (Figs. 99, 101). — Situated at the inner side of the tarsus, this bone — the smallest of any yet examined — is elongated from before to behind, flattened on both sides, and wedged in between the os scaphoides, the large cuneiform bone, and the large and internal small rudimentary metatarsal bones, with which it corresponds by four articular facets : a superior, two inferior, and one internal. When this bone is in two portions, there are then three cuneiforms, which may be distinguished, as in Man, by naming them first, second, and third (Fig. 99). It is not very rare to find the scaphoid {cuneiform magnum) fused with the great cuneiform {cuneiform medium), and sometimes even the cuboid is joined to the cunean bones. Development. — All the bones of the tarsus, with the exception of the calcis, are developed from a single nucleus of ossification. The astragalus in the Ass is distinguished from that of the Horse by the external lip of the trochlea, which is abruptly deviated outwards at its inferior extremity ; and by the disposition of the inferior articular surface, which is regularly convex from side to side, behind the groove for insertion ; in the Horse this part of the articular surface is formed by the union of two facets inclined towards each other. In the same animal, the scaphoid {cuneiform magnum) is recognized by the shape of the superior diarthrodial surface, which is a hollowed reproduction of the inferior face of the astragalus ; and the great cuneiform {cuneiform medium) by the larger concavity of its scaphoid face. Differential Characters in the Tarsal Bones of the other Animals. In the domestic animals, the tarsus difl'ers in the number and shape of the bones entering into its formation. A. Ox, Sheep, Groat. — The tarsus of these animals is slender, and has only five bones, the cuboid and scaphoid being fused into one. The astragalus is elongated from above to below, and is united to the scaphoid by an antero-posterior groove, and to the calcis by a vertical groove ; so that it has three trochleas. The principal trochlea has its external border thicker than the internal, and decreases from below to above. The posterior trochlea is not so deep as the others. The calcis is long and tljin ; tlie posterior gliding surface on the summit is excavated into a channel. The small cuneiform is pisiform, and but slightly developed. B. Camel. — In the Camel, there are six tarsal bones, two of which are cuneiform. The astragalus articulates, by means of a double groove, with the si-aphoid and cuboid. The calcis is relatively short, and about equally excavated on its two faces. The cuboid is voluminous. C. Pig. — The tarsus of this animal much resembles that of Ruminants in its general disposition, and in the astragalus ami calcis; but it has seven bones, because the cuboid aud scaphoid are separate, and there are constantly three cuneiform bones. D. Dog, Cat. — There are seven bones in the tarsus of these animals. The astragalus articulates with the scaphoid — almost as in Man — by means of a true ht ad, separated from the rest of the bone by a constriction named the neck of the astragalus. The cuboid and the three cuneiform bones articulate with the five metatarsal bones. 2. Bones of the Metatarsus (Figs. 98, 102). These bones are three in number — a median and two lateral — and offer the greatest analogy to the metacarpal bones. This enables us to dispense with a general description of them, and to confine ourselves only to indicating the differential characters which distinguish them from the corresponding bones in the anterior limb. TEE POSTERIOR LIMBS. 149 The principal, large, or median metatarsal bone, is longer than the same metacarpal, and its body, instead of being slightly compressed before and behind, is nearly a regular cylinder. It presents, outwardly, a fissure which is directed at first obliquely backwards and downwards (Fig. UD), and afterwards descends vertically along the lateral external metatarsal bone. The articular surface of the superior extremity is excavated in its centre by a large fossa for insertion (Fig. !)!)). This surface presents, behind and outwards, a thick tubercle which appears to spring from the body of the Fig. 102. bone, and which has a facet against which the external rudi- mentary metatarsal rests. The inferior extremity is at the same time wider and thicker than that of the metacarpus. Above and in front of the articular surface, it is hollowed by a small transverse fossa, which is deeper than in the corre- sponding bone in the anterior limb. Of the two rudimentary {digital, splint), or latei'al meta- tarsal hones, the external is always longest, if not thickest. The internal bears on the superior face of its head three articular facets, two of which articulate with the small cuneiform, and the third with the large bone of that name. The length of these rudimentary metatarsals is nearly equal to three-fourths that of the principal metatarsal. The metatarsus of the Ass is remarkable for the length of its rudimentary metatarsals, which are nearly five-sixths that of the principal bone. The latter is also notable, because of its length and fineness ; and if it is compared with that of the Horse, it is distinguished by : 1. The tri- angular shape of its upper extremity, due to the great development of the tubercle on which the external rudi- mentary metatarsal lies. 2. The flat diarthrodial facet which articulates with the antero-external part of the large cunei- form. ;}. The marked inequality of its condyles. Differential Characters in the Metatarsal Bones of the OTHER Animals. posterior aspect of left mktatarsus. 1, Head of printipal metatarsal bone ; 2, 3, external and in- ternal splint bones, or metatarsals of the rudimentar_v digits ; 4, rough surface for insertion of suspen- sory ligament ; 5, nutrient foramen ; 6, middle ridge or tenon of inferior arti- cular surface. The metatarsus is also a ngion in which the number of bones varies in the domesticated animals. Thus, in Ruminants there are two, and five in the Pig, Carnimra, and Rodents. The metatarsals of tlie latter are exactly like the same bones in the anterior limb. Those of Ruminants are slightly different. A. Ox, Sheep, Goat. — In the Ox, Sheep, and Goat are found a principal and a rudimentary metatarsal bone. The latter is a small lenticular bone, articulating, posteriorly, with the head of the large metatarsal bone. The latter differs from the principal metacarpul bone, in being longer, quadriliteral in form, and having a vascular canal traversing the posterior face of its upi)er extre'nity. B. Camel. — The metatarsus differs from the metacarpus by its greater width and less thickness ; the articular surface is divided by a depression into two parts, situated on the same horizontal plane. ^- Pig.— The Pig has four perfect metatarsals, and an internal rudimentary one. The latter is a small bone flattened on both sides, articulating by means of a diarthrodial facet, and Bometimes fused posteriorly with the upper end of the fourth metatarsal. D. Dog, Cat. — In the Dog and Cat are one rudimentary and four perfect metatarsals. The former is articulated with the internal cuneiform, and represents the vestige of the thumb. 150 THE BONES. 3. Bones of the Digital Region (Fig. 98). In Man, the digits of the foot — known as toes — are very different to those of the hand ; but it is otherwise with the domestic animals. The phalangeal region of the posterior, closely resembles that of the anterior limb. The analogy in the conformation of these bones is even pushed so far, that it becomes very difficult to distinguish them from one another. There are some differential characters, however. For instance, it is remarked : 1. That the first phalanx is not so long as in the anterior limb, and less wide and thick at its inferior extremity ; but it is, on the contrary, wider and thicker at its superior extremity. 2. That the lateral diameter of the second phalanx is shorter. 3. That the third phalanx, less expanded towards its inferior border, has more the shape of a V, and that its inferior face is more concave. 4. That the sesamoids are less voluminous. 5. That the navicular bone is shorter and narrower. In the Ass, the same differential features are observed between the posterior and anterior phalanges as in the Horse, and there are no very marked differences between the former in these two animals. The following may, however, serve to distinguish them. The^rs^ phalanx of the Ass is proportionately longer than that of the Horse, and the rugosities are larger ; the principal nutrient foramen is usually on the anterior face, and the external glenoid cavity is much smaller than the internal. The second phalanx is also proportionately longer than that of the Horse. Its inferior median furrow is deep, especially behind ; it has generally numerous nutrient foramina below the posterior gliding surface ; the median tenon of its upper face terminates before and behind by a salient tubercle, which prevents the bone from resting in equilibrium when it is placed vertically on that face. The third phalanx of the Ass is higher than that of the Horse, owing to the development of the pyramidal process ; it is constricted above the preplantar fissure ; the surface of the sole is proportionately more extensive, and the concavity of the semilunar crest is less marked ; the extremities of that crest are salient, and the plantar fissures very deep. The navicular bone shows very marked differences. In the Ass its thickness is very considerable, due to the median ridges on both faces. Its posterior border is very oblique downwards and backwards, and it is towards this border that it inclines when we attempt to make it lie horizontally on its upper face ; while its two extremities are more curved than in the Horse. In the Mule and Hinny, the two first phalanges much resemble those of the Ass, while the third shows the characters of that of their progenitors. Nevertheless, that of the Hinny is rather more like the third phalanx of the Horse than that of the Ass, while the contrary is observed in that of the Mule. Differential Characters in the Posterior Phalangeal Region of other Animals. In all the domesticated animals, the posteriir digits comport themselves exactly like the anterior. The Carnivora alone oflfer a notable difference ; in them, in reality, the' inner toe, the equivalent of the thumb, does not exist — or rather, it is only represented by the rudimentary metatarsal bone alluded to above. Nevertheless, it frequently occurs that a completely de- veloped thumb is found in this animal ; and in this case the rudimentary metatarsal is ordinarily followed by a ligamentous cord, to which is suspended a bony stylet that represents either the inferior extremity of the metiitarsal bone, or the first phalanx ; it is to this styht that are found articulated in succession the second and third phalanges. It is not rare to meet with a sixth floating toe in dogs of very large size. THE POSTERIOR LIMBS. 151 Comparison of the Abdominal Limb of Man with that of Animals. A. Pelvis (Fig. 103). — The longitudinal axia of the pelvis of Man forma, with the horizon, an angle of about 40°. The bones which compose it are proportionately larger and stronger than in all the domesticated animals. The two faces of the ilium, and especially the inner face, are much hollowed; the iliac crest has the form of iin italic S. The pubis alone participates in the formation of the pelvic symphysis, and the concavity which, in the domesticated animals, is called the ischial arch, is desig- Fig. 103. nated in Man the pubic arch. In consequence of the excavation on the inner face of the ilium, the pelvic cavity may be divided into the great and lesser pelvis. In the latter are loe sharp crest of the tibia. DORSAL SURFACE OF LEFT HUMAN FOOT. 1, Astragalus ; 2, its anterior extremity articulating with the cuboid bone, 4 ; 3, 3, calcis ; 4, scaphoid ; 5, internal cuneiform bone; 6, middle cuneiform bone ; 7, external cuneiform bone ; 8, cuboid bone ; 9, metatarsal bones of first and second toes; 10, first phalanx of great toe ; 11, second ditto ; 12, 13, 14, phalanges of second toe. that the works of the anatomists already mentioned — and especially those of Joly and Lavocat — have demonstrated that the foot of animals is constructed on the same type as the hand. In it, as in the hand, three sections are remarked : the THE FOOT IN GENERAL. 153 tarsus, metatarsiis, and phalanges ; and, in the archetype, each section comprises five parallel rows, each of which has two tarsal bones, one metatarsal, and three phalangeal. In the present fauna there is not, perhaps, a Mammal which has a perfectly typical peutadactylous ahoriiinal limb ; for this ideal disposition is modified in the sense already indicated for the hand. In the following brief paragraphs, an attempt will be made to show the manner in which Man and the domestic animals may be allotted to the archetype. 1. Man. — In Man the archetype is realized in the metatarsal and phalangeal sections, and it will now suffice to examine the tarsal section. This contains seven separate bones — three in the upper and four in the lower row. It must not be forgotten that the scaphoid, although situated between the two rows, nevertheless belongs to the upper, as happens in the carpus of certain species. Apparently, it is deficient in two bones in the upper row and one in the inferior. This deficiency arises from fusion of the apex of the calcaneum {first sujjerior metatarsal bone) with the remainder of the bone {secmid bone), of the scaphoid with the fifth bone in the upper row, and of the first inferior tarsal bone with the cuboid in the second row. 2. Carnivora. — ^The foot of Carnivora only differs from that of Man in the arrangement of the thumb ; as this digit has usually no phalanges, and its meta- tarsal piece is only a small, very short styliform bone. Notwithstanding this difference, the peutadactylous archetype is as easily recognized in the foot of these animals as in that of Man. 8. Rodents. — The foot of the Rabbit and Hare is yet less complete than that of Carnivora, as the metatarsal of the thumb is absent ; but, by the constitution of the tarsus, Rodents resemble Carnivora and Man, and consequently they can be also classed in the peutadactylous type. 4. Pig. — In this animal, the tarsus presents the same number of pieces and the same fusions, as in Rodents, Carnivora, and Man. The metatarsus and phalangeal section have four complete toes — first, second, third, and fourth ; and with regard to the fifth digit, it is represented by a short, flat, and irregu- larly triangular metatarsal, articulating posteriorly with the third metatarsal, and attached to the third cuneiform by some ligamentous fibres. 5. Ruminants.- — The foot of the Ox, Sheep, and Goat present numerous fusions, and even some abortions. The tarsus has only five distinct bones ; for, besides the fusions which exist as in the preceding animals, the scaphoid is united to the cuboid, and the third n/neiform is completely aborted. The metatarsus of these animals includes a principal metatarsal, provided, inferiorly, with a double diarthrodial surface, and an internal rudimentary metatarsal. Must we consider the principal metatarsal as the result of the fusion of the third and fourth, and admit, in Ruminants, the abortion of the first two digits ? Several anatomists have professed this opinion. Lavocat did so at first, and then abandoned it. He considered the principal metatarsal as due to fusion of the metatarsals of the first four digits, and he expressed himself on this point as follows : " The first and the fourth metatarsals are visible, and fused above and behind the united large metatarsals. Each of them has the shape of a thick pyramid, with its base uppermost, large, and about five centimetres long in the Ox. Above, they join to form an arch, which is the contour of a wide and short vascular canal running between them and the two large metatarsals, and which does not exist in the Goaf and Shejp. Their widened superior extremity is in contact with the bones of the tarsus, to wit : the first metatarsal with a facet of 154 THE BONES. the prototarsus, or first portion of the cuboid ; the fourth metatarsal with all the inferior facet of the tetrofarsus, or second cuneiform. And each of them has, for this eminently normal connection, an articular facet well separated from the diarthrodial surface of the large metatarsals by a large fossa destitute of cartilage. In this way the first four metacarpals are gathered into a single bundle. . . . Lastly, the thumb, or fifth digit, is constantly represented in the foot by a distinct metatarsal bone — at least in the Ox, Goat, and Sheep.'' Notwithstanding the reasons on which Lavocat bases his last interpretation as to the metatarsals of the Ox, we prefer adopting the first. In fact, if some wild Ruminants are examined — Deer, for example — there will be found a tarsus identical with that of the Ox, and a principal metatarsal provided with a vascular canal, with two inverted pyramidal expansions ; and, in addition, two styliform bones lying to the outside and the inside of the principal bone of the shank. These bones evidently represent the metatarsals of the second and fifth digits ; as they exist at the same time as the lateral ridges on the principal metatarsal bone, it appears to be impossible to give to the latter the same signification. The posterior phalangeal region of the Ox is almost identical with the an- terior ; it is, therefore, needless to again demonstrate its constitution. That of the Sheq) and Goat has no rudimentary phalanges to serve as a base for the ergot, in the hand ; but the two ergots suffice to represent the first and fourth digits, and so to include these animals in the pentadactylous type. 6. SoUpeds. — The tarsus of these animals has six or seven bones. In the second case, it is identical with that of Carnivora and Man ; in the first, the second and third cuneiforms are fused. The metatarsus and posterior phalangeal section having the same constitution as those of the anterior, the reader is referred to the description of the Hand in General. Article VIII. — The Limbs in General and their Parallelism. A. The Limbs in General. — The bony sections which compose the limbs, are destined not only to support the trunk in a stationary attitude, but also to transport it during progression. This double use gives rise to a difference between the anterior and the posterior members. The front limbs, being nearer the centre of gravity than those behind, have to sustain the largest share of the weight. They ought, consequently, to be specially organized as organs of sup- port. Therefore it is, that the four principal bones composing each of them — shoulder, arm, forearm, foot — although flexed, or disposed to be flexed, in an inverse sense to one another, oppose to the pressure of the weight of the trunk — which tends incessantly to throw them down — obstacles purely mechanical, and of such energy that we may still understand how the body can be sustained on the anterior limbs, if we suppose all the muscular masses surrounding these bony columns to be removed, except one. Thus, the weight of the body is transmitted to the scapula through the muscles that attach that bone to the trunk. It then passes to the humerus, and thence to the radius, to be thrown, finally, on the different pieces composing the foot. Now, the humerus forming with the scapula an angle which is open behind, and with the bones of the forearm another angle open in front, the weight of the body pressing continually on these angles tends to close them, and thus cause the flexion of these bones. But this result is prevented by the combined action of two muscular powers — the biceps and the extensors of the THE LIMBS IN GENERAL AND THEIR PARALLELISM. 155 forearm. With regard to the radius, carpus, and metacarpus, owing to their vertical direction, thej themselves sup- port the pressure of the weight of the body without requiring any muscular aid. But the digital region, being di- rected obliquely forward and downward, forms, with the principal metacarpal, a third angle open in front, for the main- tenance of which nature has given solid, inert, or contractile mechanical bands. The anterior limbs are also agents of transport, for they can elevate the trunk by the spring of their bony rays, and fix themselves on the ground by their free extremities. The posterior limbs are less favour- ably disposed than those in front to as- sume the function of columns of support ; as their rays are, for the most part, in a state of permanent flexion, and joined in an angular manner to one another, as may be seen by glancing at the skeleton (Figs. 107, 108, 1, 2, 4, 5, 6). It is, therefore, necessary that muscular agency should prevent the breaking-down of these columns. Though defective as supports, they are nevertheless admirably designed to serve as agents of locomotion. The slightest erection of these inclined bones propels the mass of the body for- ward, and this impulsion is almost wholly transmitted to the trunk, in consequence of the very intimate union of the pelvis with the vertebral column. B. Parallel between the An- terior AND Posterior Limbs. — After what has just been said, it will be seen that the anterior limbs are more par- ticularly destined for the support of the body, while the posterior ones more especially play the part of propelling agents in the locomotory acts. Notwithstanding this difference in the functions assigned them, these two limits offer in their conformation such striking resemblances to each other, that some authors have been inclined to con- sider the posterior as an exact repetition of the anterior limb. The following is Fig. 107. ANTERIOR LIMB OF THE HORSE (AHTEBO- KXTERNAL VIEW). 0, Scapula ; n, liumerus ; A, radius ; C, carpus ; M, metacarpus ; p, phalanges ; 8, sesamoid bone. 1, Coracoid process ; 2, head of the humerus; 3, external trochanter ; 4, deltoid ridge ; 5, inferior articular surface of the humerus; 6. olecranon; 7, ulna; 9, pisi- form (trapezium), or supercarpal bone. 156 THE BONES. Fig. 108 POSTERIOR LTMB OF THE HORSE (ANTERO- EXTERNAL VIEW). C, Coxa ; F, femur ; J, tibia ; S, tarsus ; m, meta- tarsus; P, phalanges; S, sesamoid. 1, Ischium ; 1', pubis; 2, head of the femur; 3, troehanter major ; 4, trochanter minor ; 5, condyle of the femur ; 6, patella; 7, fibula ; tibial ridge; 9, calcis. a brief analysis of the analogies ex- isting between them. At the end of the last century, Winslow and Vicq-d'Azyr, and nearer our own time, Cuvier, Flourens, Paul Gervais, Martins, Gegenbauer, Lavocat, Foltz, and Sabatier, have occupied themselves with the homo- logy of the anterior and the posterior members. All these anatomists did not absolutely arrive at the same conclusion ; for several of them, for- getting that the question should be examined in the whole animal series, made Man alone the subject of their studies, Yicq-d'Azyr and Cuvier recom- mended that the anterior and pos- terior limbs of opposite sides should be compared. Martins and Gegen- bauer, allowing a torsion of the humerus of 180°, advised that the two members of the same side should be compared, care being taken to make allowance for the untwisting of the 180° contortion at the lower end of the humerus. Lastly, Flourens and Lavocat contrasted the two members of the same pair with each other, after placing the hand in a position of natural pronation by rotation of the radius on the ulna, and without turning either limb or bone, or even a portion of a bone, no matter what kind of animal may be under examination. We will adopt the latter proceeding, as it is the simplest and most natural. Parallel between the coxa and scapula. — The analogies existing be- tween these two bones are but little striking at first sight ; nevertheless, with attention there is no difficulty in finding in the coxa the three pieces that enter into the composition of the shoulder (Figs. 107, 108). The ilium represents the scapula. The external iliac fossa reminds one of the supra- and subspinous fossse. Occasionally, there is met with in the THE LIMBS IN GENERAL AND THEIR PARALLELISM. 157 Horse a rudiment of the crest dividing the ihac fossa into two parts, and in some animals — the Pig, Sheep, and Goat — this crest, which is the trace of the scapular spine, becomes constant and very evident. With regard to the cotyloid cavity, it repeats in the posterior limb the glenoid cavity of the scapula. There remains to determine, in the latter bone, the portions analogous to the ischium and pubis. If we rely upon the evidence afforded by the nmscular insertions, we come to the conclusion that the ischimn corresponds to the coracoid process, and the pubis to the clavicle of animals which are provided with one. It will also be remarked that the coxa is directed backwards, while the scapula inclines obliquely forwards ; this opposition in the direction of the bones in no way alters their analogies ; the functions of the members to which they correspond require this inverse position. Parallel between the femur and humerus. — The resemblance between these two bones is remarkable. Thus there is found in the first. 1. An articular head, better detached than that of the hmnerus, but shaped in the same manner. 2. A trochanter analogous to the great tuberosity, and also, like it, decomposable into three distinct parts — smnmit, crest, and convexity. 2. A lesser trochanter, representing the small tuberosity. 4. An eminence for the insertion of the superficial gluteus muscle, which takes the place of the deltoid imprint, 5. An inferior articular pulley continued between the two condyles by a non-articular groove ; this trochlea certainly corresponds to the median groove of the inferior humeral face. There are, no doubt, differences in the two bones, but they have no bearing upon the result just indicated. Thus, the linea aspera of the femur is situated behind ; that of the humerus in front. In the femur the two condyles of the inferior extremity are placed behind the trochlea ; the contrary holds in the humerus. These modifications are necessary, in order to give the movements of the limbs a convenient direction. The leg is flexed backward on the thigh, while the forear is flexed forward on the humerus. Parallel between the bones of the leg and those of the forearm. — It is more particularly in these two regions that the. question of analogies has been resolved in a contradictory manner by anatomists. It would have appeared less compli- cated had it been studied in a large number of species. If we examine the leg-bones of certain Marsupials., in which the tibia and fibula are apart as in the radius and ulna in Man, it will be found that : 1. These two bones articulate w ith the condyles of the femur. 2. The anterior face of the tibia has no ridge. 3. The patella is attached to the upper end of the fibula. From this it might be concluded that, in Man and the domestic animals, the tibia, with the exception of its anterior and external tuberosities, is the homologue of the radius, and the fibula and external and anterior tuberosities of the tibia are the homologues of the body and inferior extremity of the ulna. The patella corresponds to the olecranon ; the mobility of the first cannot be offered as an objection to this assimilation, for in Bactrians the olecranon forms, like the patella, an independent bony nucleus. Parallel between the bones of the posterior and those of the anterior foot. — The analogy becomes so marked when these tw'o regions are compared, that it is scarcely necessary to allude to them. The tarsal bones are to the posterior limb what the carpals are to the anterior one ; it is even possible to compare, one by one, the several pieces in these regions. The metatarsals are but a repetition of the metacarpals ; while the disrital bones are so much alike, that it is difficult to distinguish the anterior from the posterior phalanges. 158 TEE BONES. CHAPTER III. THE BONES IN BIRDS. These animals, destined for the most part to sustain themselves in the air,* should exhibit in the conformation of their skeleton all the conditions which may favour aerial locomotion ; from this arise the differences which distinguish their skeleton from that of the Mammaha — differences which will now be rapidly traced. Vertebeal Column. Cervical verUbrm. — The cervical spine represents in the Bird, as in the Mammal, a kind of balancing-pole curved like an S, which supports the head, and by its changes in form and direction varies the centre of gravity. When a Bird rises in the air and flies rapidly, it lengthens the neck and stretches out the head, to carry the centre of gravity forwards. But when it rests on the ground, it makes the balancing-pole assume the natural and more or less graceful inflection, by throwing the head backwards, and transferring the greater portion of the weight of its body to the columns of support formed by the posterior limbs. These displacements of the centre of gravity are executed in Birds on a more extensive scale than in Mammalia ; the vertebral limbs in the former are also longer, lighter, and enjoy an excessive mobility. The vertebrae composing it number fourteen in Foivls, twelve in the Pigeon^ fifteen in the Duck, and eighteen in the Goose ; in the Sivan twenty-three have been counted ; — a curious variety, which singularly contrasts with the numerical unity noticed as one of the most remarkable characters in Mammaha ! These vertebrae are generally longer than in the latter animals, and are particularly distinguished by the configuration of the articular surfaces of the inferior part or body. These are diarthrodial facets convex in one direction and concave in the other, articulating the vertebral bodies by a veritable and reciprocal clamping. In this manner, the anterior head of thje body of each vertebra is replaced by a facet concave on both sides, and convex vertically ; while the posterior extremity of the bone bears, instead of a concavity, a facet convex in the lateral sense, and concave from above to below. The inferior crest of the body (Fig. 109, 2, 2') only exists in the first and last vertebrae ; but it forms a veritable spine, analogous to that observed in the lumbar vertebrae of the Rabbit. The spinous process (Fig. 109, 1,1') only forms a simple crest in the middle part of the neck ; it becomes more salient in the vertebrae which occupy the two extremities of this region. The transverse process represents on the side of the vertebra a thick, obtuse, and irregular tubercle, situated under the anterior articular process, and pierced at its base by a large vertebral foramen (Fig. 109, 4, 4'). It is most frequently furnished with a small styloid prolongation (Fig. 109, 3, 3') directed backwards and downwards, forming an epiphysis at an early period, and representing a real imdeveloped rib. The atlas has no transverse processes. This vertebra is shaped like a thin ring, and is excavated on its anterior contour by a small cavity, into which is received the single condyle of the occipital bone. The axis shows a very marked odontoid process, with a single facet under that eminence. Dorsal vertehrce, (Fig. 109, b, c). — These are seven in the Foivl and Pi-geon, TBE BONES IN BIRDS. 159 and nine in the Goose and Duck; they are nearly always consohdated into a single piece to which the trunk is fixed, and which gives the wings a solid Fig. 109. SKELETON OF A FOWL. ^Tthe\°amV^Ti'!l^?'^''- \^^T r"""''' "^ '^' ^^''^ ^^'^^t*'*? 2, inferior ridge on body of the amp •' 1 ' ^*y'^!\P'°!«"g«t'«° ^^ ^^l^ transverse process of the same ; 4, vertebrfl forameJ 01 the same , 1,234 the same parts in the twelfth vertebra. From B to c, Dorsal Vertebra: • D t?F °°rT''"/ I' ^L^""'' ■' ''' "■^'* ^''"^'^ ^^ '^' ""'°" °f '^' «ther spinou^ processes. From betwee'n^Wwo Jh't Tn ^' ^' ^t^ ' f' ''''''^'}^'''^ ^^P*"™ = 9- foramen of communicafon between the two orbits ; 10, premaiillary bone ; 10', external openings of the nose; 11, masilla- 160 THE BONES. Fig. 110. support in the violent efforts that flight demands. The two or three last are often even covered by the wiag-bones, and joined to them. The inferior crest of the body forms a very long spine, especially in the first vertebrae. The spinous processes — flat, wide, short, and consolidated with each other by their opposite borders — constitute a long crest extending from the last cervical vertebra to the bones of the wings (Fig. 109, 7). The trans- verse processes widen to their summit ; in the Fowl they are nearly constantly fused with each other. Lumbar and sacral vertebrae. — All these vertebrae are formed exactly on the same type ; so that it be- comes ditficult, if not impossible, to fix the point where the lumbar region ends or the sacral begins. At first independent of each other, these vertebrtc, numbering fourteen, soon become consolidated with one another and with the ribs ; but their primitive separation is always indicated by the lateral septa, which form, on their inferior face, the vestiges of the transverse pro- cesses. The former are closely united to the latter in the dorsal region. Coccygeal vertebrae. — In the coccygeal region, the spine recovers its mobility. The tail of the Bird, indeed, fulfils the office of a rudder in directing it during flight ; and it is absolutely necessary that the vertebrae which serve as a base for the steering feathers should preserve their independence, so as to allow these to be carried to the right, left, downwards, or upwards. These vertebrae — seven in number — present spinous processes which are often bifurcated, transverse pro- cesses very developed, and sometimes even spines more or less long on the inferior surface of their bodies. The last vertebra is always the most voluminous ; it is flattened on both sides, and terminates in a curved-up point. Head (Fig. 110, f, g). — The head of the Bird is small, and of a conical form. The anterior extremity is elongated, and terminated by a pointed or flattened beak, which allows the animal to cut the air with more facility. Bones of the cranium. — The bones which compose the craniiun are, as in Mammalia, an occipital, paristal, frontal, ethmoid, sphenoid, and two temporals. These bones are not isolated from each other, excepting during early life in the shell ; and the ossifying process 12, OS quadratnm ; 13, malir bone. H, Sternum : 14, brisket or keel ; 15, episternal process ; 16, internal lateral process; 17, lateral e.xtcrnal process; 18, inembr.ine which cli.ses the internal notch; 19, membrane of the e.xte'-nal notch. I, etc., Sup<'rior Ribs: 20, posterior process of the fifth. J, Inferior ribs. K, Scapula. L. Coracoid bone. ^ M, Furculum : m, m, its two branches. N, Humerus. O, Ulna : o, radlua. p, p'. Bones of carpus. Q, q'. Bones of metacarpus. R, First phalanx of the large digit of the vnmj : r, second phalanx of the same, r'. Phalanx of thumb. S, Hium. s'. Ischium, fi". Pubis : 21 , sciatic foramen : 22, foramen ovale. T, Femur, v. Patella. V, Tibia. X, Fibula: y, single bone of tarsus. Y, Metatarsus: 2.3, stiperior process representing a united metatarsal bone; 24, process supporting the claw, z, etc.. Digits. HEAD OF AN OWL (NATURAL SIZE; POSTERIOR VIEW). 1, Occipital foramen ; 2, single occipital condyle; 3. ptery- goid ; 4, inferior articular surface of the os quadratuni ; 5, anterior process of ditto ; 6, 6, anterior face of the palatine bones, forming the guttural orifice of the nasal cavities; 7, posterior ex- tremity of ditto ; 8, zygo- matic ; 9, lachrymal; 10. premaxilla; 11, orbital pro- cess ; 12, right zygomatic process ; 12', zygom.^tic pro- cess on the opposite side, united to the orbital pro- cess. TEE BONES IN BIBD8. 181 which unites them is so rapid, that the cranium, shortly after hatching, is already a single piece. No detailed description of the separate bones will be given here, but only u few brief observations wliich may be of some utility. Thus, the occipital bone shows for articulation with the spine only a single condyle, situated mider the occipital foramen, and excavated by a slight groove. In Palmipedes, this bone is pierced, behind the crests which give attachment to the extensor muscles, by two foramina wliich penetrate the cranium, and represent permanent fontanella. The parietal bone is feebly developed, and formed from only two primary nuclei. The frontal is the largest bone of the cranium ; its orbital process (Fig. 110, 1), incomplete, is supported by a particular piece {posterior frontal) fixed between the principal frontal bone, parietal, and posterior sphenoid, with which it is sometimes confounded. The perpendicular lamina of the ethmoid is considerable, and forms between the two orbits a thin vertical septum (Fig. 109, 8). Its posterior border is notched opposite to the optic foramen, and thus constitutes an opening which communicates between the two orbital cavities (Fig. 109, 9). It is also channeled, near its upper border, by a fissiu-e which terminates by two openings at its extremities, one entering the craniimi, the other the nasal cavities. This fissure and these foramina permit the passage of the etlimoidal nerve, which in this way traverses the orbit before arriving at its destination. The ethmoidal cells are more membranous than bony : their base is attached to a very delicate transverse plate, which is often membranous and not cribbled, and forms part of the anterior orbital wall. These cells replace, at the same time, the lateral masses of the ethmoid and turbinated bones of Mammalia. The sphenoid appeal's to be formed of a single piece, and shows on its sides two diarthrodial facets coiTesponding to the pterygoids. It is pierced by one foramen for the passage of the optic nerves ; but this foramen opens on the outer and opposite side of the posterior notch of the interorbital septum, and thus allows each of the nerves passing through it to reach the eye for which it was intended. It is worthy of remark, that an analogous disposition is also noticed in the Rabbit.^ The temporal bones present at their base an articular surface coiTespond- ing to the square bone {os quadratum) (Fi^. 109, 12, 12'). In the Foivl species, the zygomatic process forms a small flattened tongue, directed forwards, sometimes free, and at other times united by its superior border to the summit of the orbital process. These two eminences are exceedingly short in Pigeons. In Palmipedes they are consolidated and confounded so intimately, that it becomes impossible to distinguish them from one another. From this union results a long and strong process, which inclines forward and meets a particular prolonga- tion of the OS unguis, forming with it a real bony arch. This arch limits, below and outwardly, the orbital cavity. Bones of the face. — The supermaxilla comprises : a premaxilla, two nasal, two lachrymal, two palatine, two pterygoid, two zygomatic, hones, and a vomer. The inferior jaw has for its base a maxillary hone, which articulates with the cranium by means of two supplementary pieces named the square hones. The premaxillary bom (Fig. 110, 10) is formed, before hatching is completed, of two lateral pieces, ' This analogy is really Btnking, and might, in our opinion, serve as a basis for a new determination of the interorbital septum. We are tempted, indeed, to consider this bony lamina as the inferior sphenoid and the miildle portion of the ethmoid in Birds. This manner of viewing it tends to confirm the ideas of M. Tabourin on the inferior sphenoid and the ethmoid of Mammals. 162 THE BONES. which represent the two small premaxillaries of Mammals. This bone is very considerable, and of itself forms the base of the upper beak, the form of which it determines ; it is pointed and conical in the Gallinacm, and wide and flattened above and below in Palmipedes. In front it circumscribes the external openings of the nose, and is prolonged superiorly into two lengthy processes which dovetail between the nasal bones. Two inferior processes belonging also to this bone concur in the formation of the palatine roof. The super maxillaries, analogues of the supermaxillaries of Mammals, are two rudimentary bones situated on the sides and at the base of the beak. They form a part of the palatine roof and the walls of the nasal cavities. The nasal hones circumscribe above, inwardly, and even outwardly, the external orifices of these cavities. The palatine hones encircle, as in Mammals, the guttural openings of the nose, and constitute in great part the roof of the palate ; their posterior extremity lies against the pterygoids ; the anterior joins the supermaxillaries and the inferior process of the premaxillary bone. The pterygoids extend obliquely from the sphenoid to the square bones, and are united to the sphenoid by diarthrodial articulation. The zygomatic holies have the form of two very thin stylets, and are united to the square bone by their posterior, and consolidated with the supermaxillary by their anterior, extremity. The vomer separates the guttural openings of the nose from one another. The bones of the upper jaw are not fused to each other so rapidly as the bones of the cranium. The ascending processes of the premaxillary and nasal bones even remain for a long time united to the frontal bone by a simple synarthrodial articulation. This arrangement allows the upper beak to execute a certain elevating movement, of which we will speak when describing the articulations. The inferior maxillary hone is originally formed of a great number of distinct segments, which are soon united into a solid piece. The square, petrous, or hone of the tympanum ought to be considered as detached from the temporal. It is prismatic in shape, and provided on its upper surface with a diarthrodial facet which unites it to the temporal, and on its lower face with another facet articu- lating with the branch of the maxilla. Outwards it joins the zygomatic bone, and inwards the pterygoid. Behind, it gives attachment to the membrane of the tympanum ; and in front it presents a small eminence of insertion, which Meckel considered a second zygomatic process. Thoeax. — Sternum (Fig. 109, H 1). — The sternum of Birds, serving as a basis of support to the muscles moving the wings, should offer, and does in fact show, a remarkable degree of strength, because of the extraordinary volume of these muscles. And these being more powerful and energetic as the Bird exhibits a greater degree of aptitude for flight, it results that the structure of the sternum is solid in proportion as -the creature is strong on the wing. For this reason, we may infallibly pronounce as to the extent and power of a bird's flight by an inspection of the sternum of individuals of its species. In this respect, however, we only announce what is well known to be a particular appli- cation of the rules established by the great law of concordance between the anatomical disposition of organs and their physiological finality. Studied in Palmipedes, which will serve as a type for description, the sternum presents itself in the form of a large rectangular cuirass, elongated from before to behind, of itself constituting the inferior wall of the thoracic cavity, and also largely protecting the abdominal cavity. Its superior face is concave, while the inferior is convex, and entirely occupied by the insertion of the pectoral muscles. THE BOOTES IN BIRDS. 163 It presents, ou the median line, a thin and very salient ridge, named the brisket {rariiia or keel) (Figs. 101), 14; 111, b. 2), which in a remarkable manner multiplies the points of atta(;hment of these muscles. The anterior border offers in its middle a small eminence of insertion, the episternal (Figs. 10!), 15 ; 111, A 2). Laterally, two articular grooves are seen which correspond to the coracoids. The posterior border is cut by two notches which are often converted into foramina (Fig. HI, b 3, :^). On the lateral borders are observed small double articular facets answering to the inferior ribs. The angles which separate these two borders from the anterior are both prolonged into a little eminence, named by some authors the costal process (Fig. Ill, a 33). In the Fowl, the sternum is not so strong as in the Goose or Duck. On each side of the brisket it shows two wide notches, which greatly reduce its substance. These notches (Figs. 109, 18, 19 ; HI, a 6, 7), closed in the fresh state by membranes, are distinguished as external and internal. The latter, of greater size than the former, extends nearly to the extremity of the bone. From this division of the lateral plates of the sternum, result two long and slender processes directed backwards (Figs. 109, 16, 17 ; 111, a 4, 5). The external terminates by becoming widened, and forming a kind of bony plate, which covers the last inferior ribs. The sternum of Pigeons is distinguished by the enormous development of the brisket. The two notches of the Fowl are also met with in these birds, but the internal is nearly always converted into a narrow foramen. This comparative study of the sternum in the chief domesticated birds, leads us to appreciate the correctness of the principles just enunciated, with regard to the form and extent this bone may exhibit. The Gallinaceous Birds, properly so called, which fly Uttle and badly, have the sterniiai singularly weakened by the deep notches cut in its lateral parts. With Palmipedes, the sternum is wide and but slightly notched, so that the Goose and Duck, which waddle along so awkwardly in our poultry yards, are capable of sustaining long and rapid flight, like that of the wild individuals of the same species. "With regard to Pigeons, which are well known to l)e swift and powerful flyers, may this advantage not be due to the extraordinary development of the keel which constitutes the brisket ? Ribs (Fig. 109, /, etc.). — In the Fowl and Pigeon there are seven pairs of ribs ; and in the Duck nine pairs. Articulated superiorly with the dorsal vertebrae, as in Mammals, these bones are provided, near their middle, with a flat eminence which commences at the posterior border, and is directed back- wards and upwards, to rest by its free extremity on the external face of the next rib. These eminences (Fig. 109, 20) form an epiphysis at an early period, and are usually absent in the first and last ribs. They concur in an efficacious manner to increase the solidity of the thorax. The costal cartilages of the Mammalia, are in Birds often transformed into veritable inferior ribs, joined to the superior ribs by a diarthrodial articulation (Fig. 109, j). These pieces are long and strong, and all terminate at their lower extremity by a double facet which articulates with the lateral border of the sternum ; they are nearly always absent in the two first ribs. It is not rare to see the last united to the one before it, instead of passing directly to the sternum ; in which case it comports itself like the asternal ribs of Mammals. Anterior Limbs. Shoulder-bone. — The shoulder comprises : a scapula ; a particular bone named the coracoid by Cuvier ; and a clavicle, which forms, in 164 TEE BONliti. coalescing with that of the opposite side, a single bone called the fork {furndum), or osfwculare. The scaptda (Figs. 10!), k ; 111, a S) is narrow, elongated, and falciform, and shows no trace of a spine. Its anterior extremity only forms a portion of the glenoid cavity, and is united by means of a fibro-cartilage with the fork of the coracoid bone. The latter (Figs. 109, l ; 111 a 9) is so named because it represents the coracoid process of Mammals, and is a long prismatic bone, directed obliquely from above downwards, and before to behind. Its superior extremity is often fused with the scapula, and united at an acute angle with that bone to form a portion of the articular cavity which receives the head of the humerus. Its inferior extremity is flattened from before to behind, and responds by a diarthrodial articulation to the anterior border of the sternum. The coracoid is long in Birds which fly slowly ; it is, on the contrary, short, thick, and therefore very solid, in quick flyers. T\iq fork (Figs. 109, m; 111, Fig. 111. STERNTTM AND BONES OF THE WING. A, Sternum and wing-hones of the Fowl (upper face). 1, Body of the sternum ; 2, its episternal process; 3, 3, its costal processes; 4,4, its lateral external processes; 5, 5, its lateral internal processes; 6, 6, internal notches; 7, 7, external notches; 8, scapula; 9, coracoid; 10, fork; 11, opening for the passage of the elevator of the wing; 13, humerus; 14, air-opening in that bone; 15, ulna; 16, radius; 17, ulna-carpal bone; 18, radio-carpal bone; 19, large metacarpal; 20, small metacarpal ; 21, first phalanx of the large digit ; 21', second phalanx of ditto ; 22, small phalanx lying beside the first bone of the large digit, and representing the remains of a third digit ; 23, thumb. B, Sternum and shoulder-bone of a young Duck (inferior surface). 1, 1, Sternum; 2, keel; 3, 3, lateral notches ; 4, 4, coracoid ; 5, 5, fork ; 6, opening for the passage of the elevator of the wing. B 5, 5) is a single bone, shaped like a V or U, situated at the base of the two wings, in front of the trunk, and in an oblique direction downwards and back- wards. The two branches which form it represent the clavicles : they meet and are united at their inferior extremities, where they describe a curvilinear angle more or less open, attached to the brisket by means of a membranous ligament THE BONES IN BIRDS. 165 Their superior extremity rests within and opposite to the j^lenoid cavity, against the scapula and coracoid, forming with these hones a remarkal)ie foramen, through which passes the tendon of the elevator muscle of the wing (Fig. HI, A 4, B 6). The forks play the part of an elastic spring, whose office it is to prevent the wings coming towards each other during contraction of the depressor muscles. The conformation of this bone is, therefore, like the sternum, related to the extent and power of flight ; and for this reason it is that, in swift flyers, the two branches of the furculum are thick, solid, widely separated, and curved like a U ; while in those which fly heavily and with difficulty, these branches are thin and weak, and joined at an acute angle. The latter formation greatly diminishes its strength, and lessens, in a singular manner, the reactionary power of the bony arch it represents. Bone of the arm. — The humerus (Figs. 109, n ; 111, a 13) offers an articular oval-shaped head, and an air-opening placed beneath this eminence. It is long in Palmipedes, ordinarily so in the GalUnacm projyer, and very short in Pigeons. Bones of the forearm (Figs. 109, o, o ; 111, a 15, 16).— The radius is much less voluminous than the ulna. The latter has an extremely short olecranon ; and the two bones are separated from one another in their middle part to meet again at their extremities, where they are united by ligamentous bands in such a way as to render the movements of pronation and supination impossible. This mode of union, which nevertheless does not prevent the two bones from gliding slightly on each other in the direction of their length, has been wisely adopted by nature in order that the wing might strike the air, like an oar, by its inferior face ; otherwise, the resistance of the aerial medium would make these two bones pivot, and cause the wing to present itself to the air in a wrong direction. Bones uf the carpus (Figs. 109, p, p' ; 111, a 17, 17).— These are only two, and are distinguished by the names of radius and ulna, in consequence of their corresponding more particularly to these bones in other animals. Bones of the metacarpus (Figs. 109, Q, q' ; HI, a, 19, 20). — These also number only two, and are separated at their middle portion, to be consolidated at their extremities. Bones of the digital region. — The wing of a bird is composed of three digits One of them, which resembles the thumb and forms the basis of the false wing is composed of a single styloid-shaped phalanx, articulated at the base of a small particular process belonging to the superior extremity of the largest metacai-pal bone (Figs. 109, r' ; 111, a 23). The largest digit comprises two phalanges, which succeed the last bone (Figs. 109, R, r ; 111, a 21, 21'). The third digit is represented by a small rudimentary phalanx (Fig. 109, A 22), which corre- sponds to the inferior extremity of the small metacarpal bone, and lies beside the first phalanx of the large digit in the closest manner. It is well to remark that the hand and forearm are longer in proportion to the quality of flight ; those two regions of the wing, for example, are very short in Gallinaceous Birds. Posterior Limbs. Coxa, or os iliac. — This is a voluminous and very solid piece, particularly in walking birds, and composed, as in the Mammalia, of an ilium, ischium, and pubis. The ilium (Fig. 109, s), very long, is con- solidated with the last two dorsal, the lumbar, and the sacral vertebrae ; it is excavated on its internal face. The ischium partly incloses the side of the pelvic cavity ; between its internal border and the external border of the ilium is an orifice which replaces the great ischiatic notch. Its inferior border is united to 166 THE BONES. the pubis. The latter (Fig. 109, s") is thin and elongated, and follows the direction of the inferior border of the ischium, with it circumscribing an oval opening more or less spacious (Fig. 109, 22). Its inferior extremity extends beyond the ischium, to curve inwards towards that of the opposite side, but without uniting with it. We do not, therefore, find the pelvic symphysis in Birds, and the pelvis is slightly open below, a circumstance which favours the passage of the egg through the cavity and out of the cloaca. The cotyloid cavity is perforated by an opening at the bottom, which passes through the bone. Thigh-bone. — The femur (Fig. 109, t) is articulated inferiorly with the patella, tibia, and fibula. In all walking Birds, Uke the Gallinacae, it is long and strong, as well as the bones below it. Leg-bones. — The patella (Fig. 109, u) is wide and thin. The tibia (Fig. 109, v) terminates, below, by two condyles separated by a groove, which becomes articular behind. The fibida (Fig. 109, x) articulates by its head with the external condyle of the femur, and is consolidated with the tibia ; it never descends to the inferior extremity of that bone. Tarsal bones. — The tarsus appears to be altogether absent in Birds. Never- theless, we may venture to consider, as a vestige of the bones of this region, a small bony nucleus buried in a fibro-cartilaginous mass which gUdes on the posterior pulley of the tibia. This nucleus (Fig. 109, y) represents the calcaneum of Mammals. Metatarsal bone. — A single metatarsal bone is found in Birds, articulating superiorly with the inferior extremity of the tibia, and terminating inferiorly by three pulleys which support the three principal digits. This bone (Fig. 109, y) shows in the Fowl, near its inferior third, a conical process turned backwards, which serves as a base for the spur. Behind its superior extremity, it exhibits another which may be considered as a consolidated metatarsal bone (Fig. 109, 23). Bones of the digital region (Fig. 109, z, etc.). — All the domesticated Birds have four digits on the inferior members : three principal, directed forwards, and one rudimentary, carried backwards. The first, designated as internal, median, and external, articulate with the inferior pulleys of the metatarsal bones. The in- ternal is formed by three phalanges, the second has four, and the third five. These phalanges are formed something like those of the Carnivora ; the last is pointed, conical, and enveloped in a horny sheath. The fourth digit, or thumb, is composed of three pieces ; one of these, the first, is generally considered as a rudimentary metatarsal bone. It is attached by fibro-cartilaginous tissue to the inner and posterior aspect of the inferior extremity of the principal metatarsal bone. THEORY OF THE VERTEBRAL CONSTITUTION OF TEE SKELETON. 167 CHAPTER IV. THEORY OF THE VERTEBRAL CONSTITUTION OF THE SKELETON. In the series of vertebrated animals, the bony pieces of the trunk bearing the name of vertebrae are those which offer the highest degree of fixity, and to which the existence or the arrangement of the others appears to be subordinate. This feature in organization, recognized by E. Geoffroy Saint-Hilaire and Professor Owen, has caused these authorities to assert that the type of construction of vertebrated animals is the vertebra. After E. Geoifroy Saint-Hilaire and Professor Owen, several German, English, and French anatomists have studied the vertebral composition of the skeleton ; and among the works published in France on this subject, must be specially noticed those of Lavocat. In principle, all the writers have arrived at the same conclusions, and only differ in some few details. It is certain that the base of the vertebral column is formed by a series of bony segments. Each of these segments is called an osteodesm, and each osteo- desm represents the bodi/ or centrum of a vertebra. In examining the dorsal region, it is evident that to the body or centrum of a vertebra are added two complete osseous arches — a superior and an inferior. The superior arch is formed by the vertebral laminae ; the inferior by the ribs, their cartilages, and a portion of the sternum. The first is designated the neural arrh, as it furnishes a protective case for the nervous centres ; and the second, which more particularly protects the vascular system, is called the hmmal arch (see Figs. 112, 113). The haemal arch may have prolongations or appendices more or less developed, and comparable to the apophysary prolongations of the ribs in Birds and some Fishes. Such is the general composition of a typical vertebra ; but there are also to be distinguished in the neural and haemal arches the following parts : — H^MAL ARCH. 1. Haemal parapophysis = the tuberosity of the rib. 2. Haemal metapophysis = the head of the rib. 3. Haemal diapophysis = the rib proper. 4. Haemapnphysis = the coetal cartilage. 5. Haemal spine = the corresponding stem*! portion. NETIBAL ABCH. 1. Neural parapophysis = the posterior costiil cupola. 2. Neural metapophysis = the anterior costal cupola. 3. Neural diapophysis = the summit of the transverse process. 4. Neurapopliysis = the vertebral lamina. 5. Neural spine = the summit of the spinous process. , ' The vertebrae sometimes depart more or less from the model just described. They may vary not only from one species to another, but also in the same animal, and even in the same region. Thus, the neural arch may be absent, aa has been observed in certain coccygeal vertebrae ; or the hiemal arch is incom- plete or null, as in the cervical or lumbar vertebrae ; or, lastly, the arches are often unequal ; though this inequality is of no importance, since their size is in relation to the volume of the parts they should protect. Notwithstanding these differences and variations, or the transformationa 168 THE BONES. experienced by certain parts, there is not a bone in the skeleton which cannot be included in the vertebral type. Fig. 112. THORACIC OR PECTORAL VERTEBRA OF A MAMMAL. C, Centrum ; n, neural arch ; h, haemal arch. Fig. 113. CAUDAL VERTEBRA OF THE TURBOT. c, Centrum , n, neural arch ; A, haemal arch. The vertebra being admitted as the type of construction of the skeleton, it is easy to find it in all the regions of the bony framework. In the thoraco- Fig. 114. CRANIAL VERTtBRiE OF THE DOG. (AFTER LAVOCAT.) 1, Occipito-hyoideal vertebra; 2, parieto-maxillary vertebra; 3, fronto-mandibular rertebn; 4, naso-turbinal vertebra. THEORY OF TEE VERTEBRAL CONSTITUTION OF THE SKELETON. 169 abdominal region, the centrum, neural arch, and haemal arch are readily per- ceived ; for in the lumbar vertebrae, the enormously developed transverse process indicates the existence of an intra- vertebral arch. In the sacral region, the bony girdle of the pelvis represents the haemal arch. The posterior limbs, articulating with the bones of the pelvis, also belong to the httmal arch, and should be considered as appendices of this arch, analogous to the costal appendices of birds. The cervical region may be compared to the sacral region ; as in it the inferior haemal arch is represented by the osseous ring supporting the anterior limbs — the scapulo-clavicular girdle. The limbs themselves are appendices of the cervical haemal arch. Difficulties begin to appear when the extremities of the trunk — the head and coccyx — come to be examined. Nevertheless, the composition of the coccyx is revealed when the caudal vertebrae of certain Fishes, especially those of the Pleuronectidte, in which the neural and haemal arches are complete, are examined (Fig. I I'd). But the vertebral constitution of the head remained for a long time an insoluble question, or it was solved in a contradictory manner by the naturalists who attempted it. Some admitted a single cranial vertebra ; others included three or four ; while others, again, found six or seven.' These difficulties and contradictory results may be understood, when it is borne in mind what profound modifications the vertebrae must have undergone to constitute the bones of the head. At present the problem appears solved. The head is composed of four vertebrae, in which are found the various parts enumerated in the description of the typical vertebra. In the four classes of vertebrata, the head is constantly formed of four vertebrae, which are determined as follows, according to Lavocat : — 1 Vertebra. Centhum. Neural arch. H.SMAL ARCH. Occipito-hyoideal. Basilar process of the occipi- tal. Occipital (3 pieces). Mastoid walls of the tympanum. Hyoideal apparatus (JBve pieces). Parieto-maxillary. Body of the posterior sphe- noid. Wing and pterygoid process of the pos- terior sphenoid. Squamous portion and zygomatic process of the temporal. Parietal. Inferior maxilla (five pieces). Frouto-mandibular. Body of the anterior sphe- noid. Wing and pterygoid pn icess of the anterior spiienoid. Posterior Frontal and its orbital process. Frontal. Malar. Lachrymal. Palatine. Supcrmaxillary. Premaxillary. Naso-turbinal. 1 Vomer, Etlimoid. Nasal. Turbinated. Sub-ethmoidal. 170 THE ARTICULATIONS. The number of cranial vertebrae is invariable, as each is destined to lodge the organs of one of the four senses. The occipito-hyoideal receives the principal organs of hearing ; the parieto-maxillary osteodesm protects the sense of taste ; finally, the organs of vision are sustained by the fronto-mandibular vertebra, while the naso-turbinal contains the sense of smell. Several anatomists, at the head of whom are Huxley and Gegenbauer, do not entirely share these views. They certainly admit the existence of the occipital vertebra, but it appears to them to be impossible to recognize the others. They remark that all the bones which constitute the spine are found in the primary cartilaginous skeleton ; so that, in order to establish the vertebral constitution of the head, it would be necessary to allot to the same cranial vertebra : 1. The pieces that are found in the cartilaginous cranium. 2. The other pieces which are developed in the fibrous tissue — those skeletal tegumentary pieces (temporals, parietals, etc.). It must also be observed that the division into vertebral bodies of the parts which form the base of the cranium, far from being easy in the lowest animals, is, on the contrary, only possible, with some trouble, in the highest classes. So that if the vertebral constitution of the head were a fact, it must be admitted that the differentiation of the bones at the base of the cranium is less advanced in Mammals than in the lower vertebrates. The vertebral type is not, therefore, universally accepted by all anatomists. SECOND SECTION. The Articulations. THE ARTICULATIONS IN GENERAL. The different pieces constituting the solid framework of the animal body are, as has been said, united in such a manner that they can move one upon the other. From this union results the articulations, or articular Joints, the construction of which will now be referred to in a general manner, before commencing a particular description of each. Arthrology, or Syndesmology, is the name given to that division of anatomy which treats of the articulations. To form articulations, the bones correspond with each other by certain determined points of their periphery, which are named articular surfaces. Every articulation is, therefore, essentially constituted by two opposite osseous surfaces, simple or complex, which are moulded to each other. These are either contiguous, independent, and very movable — continuous with each other by means of a cartilaginous substance which confines them, if not to total immobility, at least to very limited movements ; or united by a fibro- cartilage, the elasticity of which permits a certain degree of displacement between the bones in contact. In the first case, the articulations are classed as diarthroses^ or movable articulations. In the second, they are designated synarthroses, sutures, or immovable articulations. THE ARTICULATIONS IN GENERAL. 171 In the third, they are amphiarthroses, or mixed articulations; so termed because they participate in the movements of the other two classes : synarthroses, by the continuity established between the articular surfaces ; and diarthroses. by the extensive motion they permit. The general characters that distinguish each of these three great classes ol articulations will be successively studied. Fia 115. PLANS OF THE DIFFERENT CLASSES OF ARTICULATIONS. ♦, Suture: 1, periosteum ; 2, sutural ligament. B, Amphiarthrosis : a, first degree — 1, periosteum ; 2, articular cartilage ; 3, iQterarticular ligament : h, second degree — 4, single cavity in the interarticular ligament : c, third degree — 5, double cavity in the interarticular ligament. C, Diarthrosis : 6, simple diarthrosis — 1, periosteum; 2, articular cartilage,* 3, epithelial layer of the synovial membrane (dotted line) ; 4, fibrous capsule ; 5, cul-de-sac of the synovial membrane ; 6, fibrous layer of the synovial membrane : c, double diarthrosis — 7, interarticular meniscus ; 8, 9, cavities of the two synovial membranes. General Characters of Diarthroses. We ought to consider, in the diarthrodial articulations (Fig. 115, c, J and c) : 1. The contiguous hony surfaces which form them. 2. The cartilaginous layers {cartUages of incrustatioyi) which cover these. 3. The fibrous or fibro-cartilagi- nous tissue {articular fibro-cartilages) which complete them, when they are not shaped so as to be reciprocally adapted to each other. 4. The ligaments which 172 THE ARTICULATIONS. maintain them in contact. 5. The scrotis membranes (synovial capsules) that cover the internal face of the latter, and which secrete the synovia, a kind of animal oil that facilitates the gliding of the articular surfaces. 6. The movements of which these articulations may be the seat. 7. Their methodical classification. 8. Their nomenclature. Aeticular Surfaces. — These surfaces have the common character of being destitute of asperities, so that they can glide with the greatest facility on each other. They are designated, according to their form, by the names of facets, heads, condyles, cotyles, ylenes, pulleys, etc. There is no need to revert to their general description, as they have already been sufficiently studied in the osteo- logy ; so we will confine ourselves to repeating that they are found at the extremities of long bones, on the faces of short bones, and on the angles of wide bones. We may mention, also, that they are often excavated by one or several depressions named synovial fossiB, or hollows for the insertion of ligaments. The first are a sort of natural reservoirs which receive the unctuous fluid secreted by the interarticular serous membranes ; the second give attachment to interosseous ligaments. Cartilages op Incrustation. — This designation is given to the layers of cartilaginous matter which, as it were, varnish the articular surfaces they adhere to by their inner face ; their free surface is distinguished by a remarkable polish and brilliancy. Thicker towards the centre than at the circumference when they cover bony eminences, these carti- lages show an inverse disposition when they line cavities. They are elastic, of a pearly whiteness, and resisting — though they are soft enough to be cut by a sharp instrument ; in a word, they possess all the physical characteristics of the primary cartilage of bones. They appear to be formed of parallel fibres placed perpen- dicular to the bony surfaces, and im- planted in these by one of their ex- tremities ; the opposite extremity corre- sponding to the free surface of the cartilage. Viewed by the microscope, they are found to present the characters of true or hyaline cartilage. The fundamental matter is amorphous and homogeneous ; but under the influence of slight dessication, there appears in the hyaline substance a partition- ing formation, which may be regarded as an agent in the distribution of the nutritive juices in the substance of the cartilaginous tissue (Renaut). The cavities (cartilage capsules) are irregular, and more or less wide. They contain from one to five cells without walls, and their contents — slightly granular — have in the centre of each cell one or two nuclei with nucleoli (Fig. 116). These cavities are elongated, and are directed almost perpendicularly towards the osseous articular surface in the deep layer ; in the middle layer they are round ; and they are lenticular, and parallel to the surface of friction, in the superficial layer. (It has been stated that a membrane lines these spaces. In addition to the SECTION OF BRANCHIAL CARTILAGE OF TADPOLE. «, Group of four cells separating from each other ; 6, pair of cells in apposition ; c, c, nuclei of cartilage-cells ; d, cavity contain- ing three cells. These cells are embedded in the finely granular matrix, or funda- mental substance. THE ARTICULATIONS IN GENERAL. 173 granular matter observed in the cells, it is not rare to find fat globules. The nuclei of the cells vary from ;|i5inT to -o^jts of an inch in diameter. The cells multiply endogenously.) The cartilage cells are insoluble in boiling water ; consequently, so far as their chemical composition is concerned, they are distinct from the fundamental sulistance. The diartlirodial cartilages have no vessels or nerves. The presence of cartilages of incrustation in the articulations is of the greatest importance. When they are worn, absorbed, or transformed into bone in con- sequence of certain articular ujaladies, the movements become painful and very difficult. With regard to the part they play in the economy, it may be said that : 1. They favour, by their smoothness, the gliding and displacement of the bones. 2. They attenuate, by their suppleness and elasticity, the violent shocks to which the articulations are exposed. 8. They resist the wear and deformation of the articular surfaces. Complementary Fibro-cartilages. — There are two kinds of complementary fibro-cartilages. Some {interosseous) represent circular cushions which pad the margins of certain cavi- ties,finingupthe notches * Fig. 1 17. that might render these imperfect. They in- crease the depth of these cavities, and protect their borders from injury — for example, the coxo-femo- ral articulation. Others {inter-articular) are in- terposed between arti- cular surfaces when these do not exactly fit each other — as when two opposing extremities are convex. It may be remembered that the lateral tuberosities of each tibial surface present, for articulation with the condyles of the femur, two convex diarthrodial faces, the coaptation of which is rendered perfect by the interposition between each condyle and corresponding tibial surface, of a crescent-shaped fibro-cartilage, which for this reason has been named a meniscus. In other joints, these interarticular fibro-cartilages are shaped like discs or biconcave lenses. There then result double diarthroses (Fig. 115, c, e) : example, the temporo-maxillary articulation. (Fibro-cartilage also covers bony surfaces over which the tendons play, as on the trochlear surface of the humerus, postero-inferior face of the navicular bone, and elsewhere. In these situations it is named stratiform fibro-cartilaf/e.) These organs are formed sometimes by fibrous, at other times by cartilaginous tissue ; their mode of association need not be referred to here, though it may be observed that the cartilage is more particularly found in all those points where there is most articular friction. They receive very few vessels, and it is questionable if they have nerves. Ligaments. — These are bands which unite contiguous diarthrodial surfaces. They are sometimes formed of white fibrous tissue, and sometimes of yellow ; hence their division into two great classes of tchite and i/eUow ligaments. a. The white ligaments are distinguished by the pearly whiteness of their 14 FIBRO-CARTILAGE, MAGNIFIED 155 TIMES. Showing interlacement of Hbroii.s t'asciculi, with scattered groups of cartilage-cells. 174 THE ARTICULATIONS. tissue and want of elasticity. Those which are found around the margin of articulations are termed peripheral, and those in their interior are designated mterosseoi/s or interarticular ligaments. The peripheral ligaments are generally composed of parallel fibres collected in fasciculi, or spread out as membranes. In the first they are called funicular, or ribbon-shaped ; in the second, they are termed membraniform, or capsular. The funicular ligaments are short, round, or flattened bands, attached by their extremities to the two bones they unite ; they are lined on their inner aspect by the synovial capsule, and are covered externally by tendons, aponeuroses, muscles, vessels, or nerves. The capsular ligaments are often complete — that is Fig. 11^ Fi?. 119. WHITE OR NON-ELASTIC FIBROUS TISSUE. TELLOVV OR ELASTIC FIIIROUS TISSUE, FROM THE LIGAMENTUM NUCHiE. to say, they envelop the whole articulation like a sack. At other times they are incomplete, and then they are simple membranes, binding together the different funicular ligaments of a joint. The interosseous ligaments — less numerous than the preceding — are often formed of interlacing fibres ; they are always funicular, and fixed by their extremities into excavations in the centre of articular surfaces. b. The yelloiv ligaments are all pei'ipheral, funicular, or membranous, and enjoy a marked degree of elasticity, which permits them mechanically to bring back to their usual position the bony levers that have been momentarily displaced. These ligaments, which are powerful auxiliaries to the muscular forces, give permanent equilibrium to the weight in certain parts of the body, which incessantly tend to fall to the ground ; for instance, the cervical ligament of Solipeds and large Ruminants. The ligaments are always assisted in their action by atmospheric pressure, which is exerted over all the surface of the body ; and also frequently by the tendons and aponeurosis of muscles, and even by the muscles themselves, when they pass over an articulation or are inserted in its vicinity. In several regions the ligaments are more or less confounded with tendons or aponeuroses — as in the anterior extensor tendon of the phalanges and superior sesamoid liga- ment, the ligaments of the femoro-tibial articulation, and the aponeuroses of the posterior portion of the superficial gluteal muscle. Synovial Capsules. — These are very thin membranes of a serous character, intended to secrete the sj/novia. They are composed of two layers : a deep, formed by fasciculi of connective tissue ; the other, superficial, formed by an THE ARTICULATIONS IN GENERAL. 175 endothelium. The first sometimes adheres intimately to the inner face of the funicular or membranous lit^aments of the articulation ; at other times it is loosely attached to them by an abundance of connective tissue. The second layer is con- stituted by a single row of flattened polygonal cells, except at the bottom of certain grooves, where they are more or less crowded. Though belonging to the serous membranes, the synovial membranes do not form complete sacs, as, after lining the internal surface of the ligaments, they cease at the articular margins. Direct observation demonstrates that the cartilages have no covering, and that there is no synovial membrane on their surface. The anatomists who imagined that the thin pellicle, which can be rendered evident in cutting the surface of cartilage obliquely and separating it by teazing, was a membrane, were deceived, as this pellicle has not the texture of a serous membrane ; and it is not vascular, for it has never been possible to inject vessels on the surface of such cartilages, nor yet in their substance. Neither is it covered with epithelium, and, if submitted to microscopical examination, it has all the characters of cartilage. Pathological facts prove nothing in favour of the existence of a synovial membrane on cartilages. It may be accepted, then, that the synovial membrane never extends to the surface of articular cartilage ; but, after being fixed around the margin of a diarthrodial surface, it is reflected in every direction to hne the internal surface of the ligaments, and become attached to the periphery of the diarthrodial surface in contact wrth the other, so that it entirely isolates the interior of the joint from the peri-articular connective tissue. There are generally found within articulations, little masses of fat which push the synovial membrane enveloping them inwards. Erroneously considered by Clopton Havers as glands for the secretion of synovia, these accumulations of fat have been named synovial fringps, or viUi. They are more particularly numerous in the neighbourhood of the articular margins — that is, on the border of diarthro- dial surfaces. They are formed by a prolongation of the synovial membrane, which covers some connective tissue fibres associated with adipose cells, or an amorphous substance provided with nuclei. The synovial membrane, after lining the inner surface of ligaments, sometimes escapes between these, forming a hernia. The term sijnovinl culs-de-sac has been given to these external prolongations of the articular serous membrane. This membrane often covers the inner surface of a tendon or ligament, in order to facilitate their gliding over a bony eminence. The synovia is a viscid, colourless, or slightly yellow fluid, in its physical characters somewhat resembling oil ; it does not possess them, however, so far as its composition is concerned, for chemical analysis has not demonstrated the presence of fatty principles. It is the albumen it contains which gives to it its viscidity, and which fits it for lubricating the articular surfaces over which it is spread. Its use in the anima] economy is absolutely identical with that of the greasy substances employed to lubricate the axles of carriages. To the means of union described under the names of ligaments and synovial membranes, may be added atmospheric pressure, the influence of which is relatively considerable, as the experiments of Weber have demonstrated. Movements. — The movements peculiar to diarthrodial articulations are divided into seven principal classes : 1. Simple yJidiny, the only movement possible between two plane or undu- lating facets. 176 TEE ARTICULATIONS. 2. Flexion, which brings two bony pieces nearer each other, by closing more or less their angle of union. 3. Extension, the inverse movement, during which the bones are straightened on each other. 4. Adduction, which brings the inferior extremity of the movable bone towards the median line. 5. Abduction, the contrary movement to the preceding. 6. Circumduction, or the sling movement, during which the bone passes successively through the last four positions. 7. Rotation, in which one bone pivots on another. Classification of the Diarthroses. — The basis of this classification is founded on the configuration of the articular surfaces and the nature of the movements they permit. This double base serves to establish five kinds of diathrodial articulation : 1. Enarthrosis, characterized by the reception of an articular head within a cavity of appropriate form. This articulation, the surfaces of which are derived from a sphere, may be the seat of the most extensive and varied movements — flexion, extension, abduction, adduction, circumduction, and rotation. Example : the coxo-femoral articulation. 2. The trochlean, angular ginghjmoid, or perfect hinge articulcdion, when the articular surfaces are formed into trochlea, reciprocally fitting into each other, and the movements of which — flexion and extension only — are executed, from before to behind, with the precision of a hinge. Example : the tibio-tarsal articulation. 3. The pivot, trochoid, or lateral ginglymoid artindation, is a diarthrosis formed by a pivot which turns in a semi-cylindrical cavity. Rotation is the only move- ment. Example : the atlo-axoid articulation. 4. The condyloid, or imperfect hinge artindation, which permits, like the preceding, the two principal movements of extension and flexion, and the acces- sory movements of rotation or lateral inclination. The articular surfaces, though very diversely shaped, nevertheless exhibit in all the articulations one or moi3 condyles opposed to an equal number of oval excavations. Example : the femoro- tibial articulation. 5. Arthrodia, or planiform diarthrosis, is constituted by plane or nearly plane facets. Gliding is the only possible movement. Example : the carpo-metacarpal articulation. NoMENCLATUEE. — The names of the articulations are usually those of the bones which form them. For instance, the scapulo-humeral articulation is the joint between the scapula and himierus ; the intervertebral articulations join to each other the various bones constituting the spine. When the qualifying name of an articulation is composed of two elements, as in the first instance, it is well to place first the word which indicates the bone usually most fixed. General Characters of the Synarthroses. Sutures (Fig. 1 1 5, a) are the temporary articulations which exist only at an early period of life. They nearly all disappear in the adult animal, in consequence of the bones forming them becoming consolidated. They belong almost exclusively to the bones of the head. Articular Surfaces. — The bones forming these come in contact by theii \ THE ARTICULATIONS IN GENERAL. 177 borders or ano^lea, which, for this purpose, generally present very uneven surfaces. Sometimes they arc cut perpendicularly and simply roughened ; at other times they are bevelled, and joined by means of fine laminae or triflinor inequalities ; agaiui vhey are notched into deep and sinuous dentations ; and lastly, one bone is fix hI into a groov it in tb other. It will be under.stood that such formations of the articular su s wil -nit their movements, and assure the solidity of their union. Modes of V i ;. — A fib. is tissue interposed between these synarthrodial .^ "ices, unites th ^n. losely to each other. It has absolutely the same texture as the primary cartilage of the bones, and, like it, possesses the property of becoming ossified after having been vascularized. This ossification, which causes the disapppearance of the sutures, occurs earlier inwards than outwards. The periosteum, in passing from one bone to another, also concurs in bringing about a more complete synarthrosis. It should, therefore, be included in their means of union. Movements. — These are very obscure, and only noticeable in young animaLs, by the elasticity they communicate to the bony walls of the cranium or face. In the adult, they may be said to be null. Classification. — There are four principal descriptions of Hufures .• 1. When two wide bones correspond by means of denticulations fitting into each other, the suture is named true, Umbosa, serrated, or dentated. Example : the articulations uniting the three portions of the parietal bone. 2. If the opposite borders of two bones in contact are widely bevelled, one inwards, the other out- wards, it forms a scaly or squamous suture (squamosa). Example : the parieto- temporal articulations. 3. When the union of bones takes place by plane or roughened surfaces, cut perpendicularly on their bordera or angles ; this constitutes the harmonia suture, or suture by juxtaposition (or airposition). Example: the occipito-temporal articulations. 4. The schindylesis, mortised suture, synchron- drosis, or gomphosis, results from the reception of a bony plate into a gi-oove more or less deep in another bone. Examples : the spheuo-frontal and supermaxillo-nasal articulations ; the teeth in the alveolar cavities. General Characters of the Amphiarthroses or Symphyses. Articular Surfaces. — They are frequently smooth, and formed almost on the same model as the diarthrodial surfaces. They are covered by a thin layer of cartilage ; but, instead of being smooth and polished, they are more or less rugged, without, however, presenting the anfractuous disposition of the majority of spiar- throdial surfaces. ]MoDES OF Union. — The organs which perform this office are : 1. Fibro- cartilage, which establishes continuity between the articular surfaces. 2. Ribbon- shaped and peripheral ligaments (Fig. 115, b a). These latter do not differ from the analogous bands attaching the diarthrodial articulations. With regard to the fibro-cartilage, it is distinguished from the complementary discs of these same articulations, by a less intimate mixture of the cartilaginous and fibrous elements entering into its composition. The last may be sometimes absent, as well as the peripheral bands ; and then the articulation only differs from the synarthroses by the extent of motion it permits. Occasionally, the interarticular fibro-cartilages are excavated by one or two little narrow cavities (Fig. lib, h b, c) \ but these are never lined by a synovial membrane, like the diarthrodial cavities. 178 THE ABTICULATI0N8. Movements. — The amphiarthroses only permit of a see-saw or swinging movement, the extent of which depends on the thickness of the intermediate fibro-cartilage. Classification. — Only one kind of amphiarthrosis is recognized in the Horse, the most remarkable of which is found in the articulations between the bodies of the vertebrae. CHAPTER 11. ARTICULATIONS OF MAMMALIA IN PARTICULAR. In the special study of the articulations, the same order will be followed as for the bones ; the articulations of the spine will be first noticed, then those of the head, thorax, and anterior and posterior limbs. Preparation. — The preparation of the bones which have been dusciibed, has not been made the subject of any particular recoranieiidation, because it suffices, in order to study them, to remove the soft parts by wliich tliey are surrounded, either by boiling, maceration, or scraping. But when we come to examine the soft textures, in order to d) so profitably it is necessary to learn beforehand tlie rules which should be followed iu their preparation. The following directions are given with regard to the study of the articulations : — 1. To prepare the articulations, young subjects are cliosen in preference to those advanced in years, because the density of the connective tissue in them is not so great, and this tissue is easily removed fiom around the ligaments. As tliese are prepared with difficulty when the external surface is in a dry state, care should be taken, before dissecting them, to have them excluded from the air by covering them w'ith damp cloths, or witli the skin of the animal. 2. It is convenient to separate the articulation we wish to dissect, by sawing through tiie bones at a certain distance from the articular surfaces. The manipulation of tiie part is theu rendered casior, and its dissection can be made under the most favourable conditions. 3. It is necessary to preserve, as carefidly as possible, the muscles surrounding the articula- tions, in order to be able to study their relations with the ligaments which bind these. If it be absolutely requisite to remove them, their insertions corresponding to the articulation should always be retained. 4. The capsular ligaments should be first studied, as they have soon to be removed, the better to show tlie funicular ligaments. Tliese, in their turn, must be sacrificed in order to display, by different sections, the interosseous ligaments, when they are present. Lastly, the two articular surfaces should be completely separated, so as to examine their conformation. 5. Tiie synovial membranes, with their different cuh-de-snc, being a very important study — with reference to the diagnosis and treatment of articular tumours — it is convenient to devote a special piece to the examination of these serous membranes. It is very useful to inject their interior with plaster or tallow colouieEKP MUSCLES OF THE HORSE'S NECK. 1, Lamellar portion of the cervical ligament; 2, funicular portion of the same. processes to the summit of the head. Divided into two lateral lips by a median groove, this cord is continued posteriorly by the dorso-lumbar ligament, and is inserted, anteriorly, into the tuberosity of the occipital bone. It is covered above by a mass of fibro-adipose tissue, which, in certain common-bred horses, is very abundant. Below, it gives rise, in its posterior two-thirds, to the majority of the fibres belonging to the lamellar portion. On the sides, it receives the insertions of several cervical muscles. The lamdlar portion — comprised between the funicular portion, the spinous processes of the second dorsal vertebra, and the cervical 182 THE ARTICULATIONS. 121. vertebrse, constitutes a vast triangular and vertical septum, which itself results from the apposition of the two laminae that lie back to back, and are united by connective tissue ; they are bordered above by the two lateral lips of the cord. The elastic fibres which enter into their composition are given off either from the latter, or from the spinous processes of the second and third dorsal vertebras ; they are directed downwards or forwards, and reach the spinous processes of the last six cervical vertebra?, into which they are inserted by so many digitations, becoming confounded with the interspinous ligaments of the neck. The fibres of the two last digitations are few in number, widely separated from one another, and united by many anastomosing branches, which make them appear as a kind of wide network. The laminfe of the cervical ligament are in relation, outwardly, with the superior branch of the ilio-spinal ligament, the intertransversaUs colli muscles, and the complexus muscle. (This important structure, which is, in reality, the mechanical stay and support of the heavy head and neck of quadrupeds, and is usually tenned the ligiimentvyn nvrhcp, is all but absent in Man, being represented in him by a thin narrow band — or rather two thin planes of fibres, the ligammta subflava. It is described by Leyh as if there were not two portions, and that excellent anatomist does not appear to insist sufficiently on the diff"erence between the dorso-nuchal and the dorso-lumbar divisions. Percivall, who almost entirely neglects the ligaments, also makes no distinc- tion. The difference in structure, elasticity, and situation, waiTants the distinction made by Chauveau. As already indicated, the function of this ligament — and more particularly of its nuchal division — is to maintain the head and neck in their natural position during repose, and to allow the most extensive move- ments at other times.) c. Interspinous Ugaments (Fig. 121, 3). — Fibrous laminae fill the interspinous spaces, and are attached, before and behind, to the opposite borders of the spinous processes, which they unite. They are confounded superiorly with the supra-spinous ligament, and are continued inferiorly by the interlamellar ligaments — forming two lateral planes which are applied against each other, like the laminae of the cervical ligament, and covered outwardly by the inter- transversalis colli muscles. In the region of the neck, the interspinous ligaments are yellow and elastic. In the dorso-lumbar region, they are formed by fasciculi of white fibrous tissue, loosely united to each other at their extremities, and directed veiy obliquely backwards and downwards. In consequence of this disposition, and notwith- standing their inextensibility, they permit the separation of the spinous processes. Their lateral surfaces are divided by a layer of grey elastic fibres, which cross like an X the direction of the preceding fasciculi. Very abundant in the anterior moiety of the dorsal region, these fibres operate, by their proper elasticity, in bringing the spinous processes towards each other. d. Interlamellar, or inter annular ligaments.— 9,itimted, as their name indicates, between the vertebral laminae, and divided into two lateral moieties, these INTERVERTEBRAL ARTICULA- TIONS. A, B, C, Bodies of three dorsal vertebrae divided longitudi- nally and vertically to show (1, 1) a section of the inter- vertebral discs ; 2, supra- spinous dor^o-lumba^ liga- ment ; 3, interspinous liga- ment ; 4, fibrous fascia, con- stituting the proper capsule of the articular processes in the dorsal region. ARTICULATIONS OF THE SPTNE. 188 ligaments appear to be produced by the two fil)rous planes of the preceding ligaments, which, on arriving at the base of the spinous processes, separate from one another to be carried outwards. Their anterior border is inserted into the posterior margin of the \'ertebral lamina in front, Their jwsterior border is fixed to the anterior border and inferior face of the lamina behind. Their suj erior face is in relation with some spinal muscles, and their inferior face is in contact with the dura mater. Outwardly, they are confounded with the capsules proper to the articular processes. Yellow and elastic in the cervical region, these ligaments are white and inelastic in the dorso-lunibar region. Characters proper to some Intervertebral Articulations. 1. Infer- eorri/geul and sacro-corri/ijpaJ artirulations. — These articulations are adapted to the rudimentary type of the vertebrae they unite. The coccygeal bones only come iu contact by their bodies — their spinal laminge being reduced to the merest traces, or are altogether absent. The anterior and posterior articular surfaces of each vertebra are convex, and the interarticular fibro-cartilages, hollow on both faces, resemble a biconcave lens. "With regard to the peripheral bands, they are repre- sented by a bundle of longitudinal fibres spread over the surface of the bones, which they envelop in a common sheath. 2. Intersarral artm/lations. — The sacral vertebrae being fused into one piece — the OS sacrum — there is no occasion to study the true articulations in this region. It may be remarked, however, that the supra-spinous dorso-lumbar liga- ment is continued on the sacral spine, and that there exist between the processes formed by this spine, true interspinous ligaments. 3. Sdcro-Jumbar artirvlation. — In this articulation, the great thickness of the fibro-cartilage is to be remarked ; and, in addition, that the last lumbar vertebra corresponds with the sacrum not only by its body and articular processes, but also by the oval and slightly concave facets shown on the posterior border of its transverse processes, Avhich are adapted to analogous slightly convex facets on the sides of the base of the sacrum. The bundles of fibres thrown from one bone to another from around these sacro-tra7is?'ersals (real planiform diarthroses) maintain the articular surfaces in contact, and cover, outwardly, the synovial membrane which facilitates their gliding. 4. Artirulation of the two last lumbar vertphnc. — This is distinguished by the presence, between the transverse processes, of a planiform diarthrosis, like that of the sacro-transversal just noticed. These two articulations are only found in Sohpeds. f). Atlo-axoid articulation. — This is so far removed by its conformation and special uses from the other intervertebral articulations, that it will be described as an extrinsic articulation of the head and spine. (See Articulations of the Head.) The Movements of the Spine in general. — Each intervertebral articula- tion is the seat of very obscure movements, the separate study of which offers little interest. But these movements, when conjoined with those of the other articulations, result in bending the whole spine in a somewhat marked manner, and producing either the ^flexion, extmsion, or lateral inclination of thLs flexuous column. When flexion takes place, the spine is arched upwards, the common inferior ligament is relaxed, the spinous processes separate from one another, and the supra-spinous ligament, becoming very tense, soon imposes limits to this movement. Extension is effected Ijy an inverse mechanism, and is checked by the tension of the common inferior ligament and the meeting of the spinous processes. 184 THE ARTICULATIOJ^B. Lateral inclination takes plaxje when the spine bends to one side. This movement is very easily executed in the cervical and coccygeal regions, but is arrested by the ribs and the costiform processes in the doreo-iumbar region, A circumflex movement is possible at the two extremities of the vertebral column— neck and tail ; for they pass easily from extension to lateral inclination, and from this to flexion, etc. Owing to the elasticity of the intervertebral fibro-cartilages, the spine is endowed with a very limited amount of rotation, or rather of torsion. For the special study of the movements of each spinal region, reference must be made to what has been abeady said (p. 4:3) regarding the mobility of this part. Fig. 122. CERVICAL LIGAMENT OF THE OX. L, l', The two laminje which form the cord of the cervical li^aTnent : 1, 2, 3. 4, the four anterior diijitations of the cordiform (lortion. R, Its accessory portion : 5, tirst dorsal vertebrae ; 6, 6, 6, interspinous ligament of the dorsal region. Differential Characters in the Vertebral Articulations and Ligaments in the OTHER Animals. A. In the Ox the intervertebral discs are much thicker than in the Horse. Tho common inferior vertebral ligament is veiy strong in the lumbar region. The supraspinous dorso-lumbar ligament is composed of yellow elastic tissue Tiie cervical ligament is mucli riinre developed than in Solipt-ds, in consequence of the gronter weight of tlw^ head ; and it prest-nts a conforma- tion iiltogetiier special^ which ^I. I.ecoq has made known in the following terms: "On leiving the withers, the fuprn- spinous ligament ceases to cover t\w head of the s|iinous prncessf-s. and extends from each side in a wide and strong band, takiny; points of attachment on the sides of tiie processes. ann, does not siiow any cervical ligament, properly so called. It is replaced by a super- ficial fil)rou;j raphe', extending from the occipital bone to the spinous process of the first dorsal vertebra ^Journal de Me'deHue Velerinaire, p. 122. Lyons, 1848. 186 TEE ARTICULATIONS. T). Camivora. — The Cat has no rervical ligament, and shows, instead, a raphe like the Tig. In the Dog, the ligament is reduced to a simple cord, continued from the dorso-lumliar ligament, and goes no further than behind the spinous process of the axis. In the Cat, the interspinous ligaments are replaced by small muscular fasc-iculi ; in the Dog, this suljfctitution only takes place in the cervical region The laminae of the first coccygeal vertebrae possess the principal characters whieJi distinguish perfect vertebrae, and are united by vestiges of the articular bands which exist in the other regions of the spine. Article II.— Aeticulations of the Head. We will first study the two extrinsic articulations which are the centre of the movements of the head on the spine — the atlo-axoid and occipito-atloid articula- tions. Afterwards, we will pass to the examination of the joints which unite the different bones of the head. 1. Atlo-axoid Articulation (Fig, 124). Preparation. — It suffices to remove the soft j>arts from around the articulation, to expose the interannular, tiie interspinous, and the inferior odontoid ligament. To examine the superior odontoid ligament and the synovial membrane, one half the atlas and axis must be separated by sawing longitudinally through them from oue side to the other. This may be considered as the type of the trochoid articulation. Articular surfaces. — To form this articulation, the axis offers its odontoid pivot and the undulated diarthrodial facets at its base. The atlas opposes to the pivot the concave semi-cylindrical surface hollowed on the superior face of its body ; and for the lateral undulated facets it has analogous facets cut on the transverse processes, on each side of the vertebral canal. Mode of union. — 1. An odontoid, or odonto-atloid ligament. 2. An inferior atlo-axoid ligament. 3. A superior ditto. 4. A fibrous capsule. a. Odontoid ligament (Fig. 124, 3). — Continuous with the common superior vertebral ligament, very short and strong, flattened above and below, and triangu- lar in shape, the odontoid ligament is composed of glistening white fibres, fixed behind in the superior channel of the odontoid process, and inserted in front on the transverse ridge which separates the superior face from the inferior arch of the atlas, as well as on the imprints situated in front of this ridge. It is covered, on its lower face, by the synovial membrane of the articulation ; and its upper surface is in contact with the spinal dura mater. It sends some bands within the condyles of the occipital bone. h. Inferior atlo-axoid ligament. — This is a wide, thin, and nacrous-looking band, extending from the inferior face of the axis to the inferior tubercle of the atlas, and is covered by the longus colli muscle ; it is united to the synovial mem- brane by its deep face, and confounded on its bordere with the fibrous capsule to be immediately described. It represents the common inferior vertebral ligament. c. Superior atlo-axoid ligament. — This exactly represents the interepinous liga- ments of the other cervical articulations. Yellow, elastic, and formed hke the two lateral bands, it is contijuious, laterally, with the capsular hgament. It represents the interspinous and interlamellar ligaments. d. Capsidar ligament. — This, it may be said, is only the interlamellar Ugament proper to the atlo-axoid articulation. It commences from the sides of the pre- ceding ligament, and becomes united to the inferior atlo-axoid, after contracthig adhesions with the borders of the odontoid ligament. In this way it encloses the articulation and the spinal canal. Before aiid behind, it is attached to the anterior or posterior margin of tlie bones it unites. Its external face is in contact with ARTICULATIONS OF THE HEA'D. 187 the great oblique muscle of the head ; its internal responds, in its inferior half, to the articular synovial membrane, and its superior moiety to the spinal dura mater. It is analogous to the ca|)sules in other regions. (Leyh describes this ligament as tlie interannular). Fig. 124. Sijnovial membrane. — Tliis lines the odontoid ligament and atlo-axoid hgaments, and the articular portion of the peripheral capsule. Movements. — Rotation, the only movement possible in the atlo-axoid articulation, is effected in the following manner : the axis remains tixed, and the first vertebra, drawn to one side chiefly by the great oblique muscle, rotates on the odontoid pivot, carrying the head with it. The rotation movements of the head have, therefore, this diarthrosis for a centre, and not the atloido-occipital articulation. lu the Dog and Cat, the odontoid ligament is replaced by three particuhir ligaments : 1. Two lateral cords, rising in common from the summit of the odontoid process, and inserted, each on its own side, within the condyles of tlie occipital bone. 2 A transverse ligament, passing (iver the odontoid process, which it maintains in its place against the inferior arch of the atla:?, and is attached by its extremities to the superior face of the latter. A small synovial capsule facili- tates the gliding of the odontoid process beneath this ligament. The articular synovial membrane always communicates with that of the occipitn-atloid articulation. In the Pig, the disposition is nearly the same as in the Caruivora. 2. OCCIPITO-ATLOID ARTICULATION (Fig. 124). (Preparation. — Dissect away all the soft parts that pass from the neck to the head and cover the articulation, and more particularly the flexor, the recti, and the small oblique muscles of the head. To expose tlie synovial membranes, open the sides of the capsular ligament.) This is a condyloid articulation. Articular surfaces. — In the atlas, the two cavities which replace the anterior articular processes and the heads of the other vertebrfe ; in the occipital bone, the two condyles flanking the sides of the occipital foramen. Mode of union. — A single capsular ligament envelops the entire articulation ; it is attached by its anterior border to the margin of the occipital condyles, and by its posterior to the anterior contour of the atlas. Thin and slightly elastic in its inferior half, this ligament presents, supe- riorly, four reinforcing fasciculi : two middle, which inter- cross in X — whence the name "cruciform," sometimes given to this ligament (Fig. 124, 1, 1) ; and two lateral, which pass from the sides of the atlas to the base of the styloid processes (Fig. 124, 2, 2). It is lined by the synovial membranes, and is enveloped externally by a large number of muscles, which protect the articulation and greatly strengthen it everywhere. Among these may be particularly noticed the recti muscles of ATLO-OXOID AND OCCIPI- TO-ATLOID ARTICULA- TION'S (the upper arch of the atlas has been removed to show the odontoid ligament). 1, 1, Middle accessory fas- ciculi ; 2, 2, lateral fasciculi of the capsular ligament of the occipi- to-alloid articulation; 3, odnntoid ligament ; 4, interspinous liga- ment uniting the second and third vertebrae of the neck ; 5, fibrous capsule uniting the articular processes of these vertebrae. A, Anterior internal fora- men of the atlas con- verted into a groove by the section of the bone ; B, B, vertebral foramina of the atlas ; C, C, fora- mina replacing the an- terior notches of the axis. 188 THE ARTICULATIONS. the head, the small oblique, and the complexus. There is also the cord of the cervical ligament. Synovial nfmbrams. — These membranes are two in number — one for each condyle and coiTCsponding atloid cavity. Sustained above, below, and outwardly by the capsular ligament, they are related inwardly to the dura mater and the fibrous tractus which, from the odontoid ligament, is carried to the internal face of the occipital condyles. Movempnts. — Extension, flexion, lateral inclination, and circumduction, are the possible movements of the occipito-atloid articulation. In the Pig, Dog, and Cat, this articulation — strengthened, as it is, by the capsular and odontoido-occipital ligaments already mentioned — has only one synovial capsule. 3. Aeticulation of the Bones of the Head with each other. If we except the articulation which unites the inferior jaw to the cranium — the temporo-maxillary — and the hyo ideal articulations, it will be found that all the bones of the cranium and face are united to each other by synarthrosis, forming the different kinds of sutures already generally described (p. 170). Nothing is to be gained by entering into more detail with regard to these articu- lations, as it will be found sufficient to call to mind the topographical description of each bone entering into their formation. 4. Temporo-maxillary Articulation (Fig. 125). (Preparation. — Remove the masseter muscle and the parotid gland. Saw through the head about the middle line. Open the articulation externally, to exhibit the interarticular meniscus.) The lower jaw, in its union with the cranium, constitutes a double condyloid articulation. Articular surfaces. — "With the temporal bone, these are the condyle, the glenoid cavity, and the supra-condyloid process at the base of the zygomatic process. The glenoid cavity is not lined by cartilage, and appears to be merely covered by synovial mem- brane. On the maxillaiy bone is the oblong condyle situated in front of the coronoid process. Interarticular fibro-cartil age. — The articular sur- faces just named are far from fitting each other accurately ; this is only accomplislied by the inter- position of a fibro-cartilaginous disc between the temporal and maxillary bones. This disc is a kind of irregular plate, flattened above and below, thicker before than behind, and moulded on each of the diarthrodial surfaces it separates. Its superior face, therefore, presents : in front, a cavity to receive the condyle of the temporal bone ; behind, a boss which is lodged in the glenoid cavity. The inferior face is hollowed by an oblong fossa, in which the maxillary condyle is lodged (Fig. 125, 1). Mode of union. — A fibrous envelope — a true capsular Ucjament — suiTounds the articulation, and is attached by its borders to the margin of the articular surfaces it unites. Formed, outwardly, by a thick fasciculus of white vertical fibres (Fig. TEMPORO-MAXILLARY ARTICU- LATION . 1, Interarticular fibro-cartilase ; 2, external fasciculus of the capsular ligament. A, Base of the coronoid proce.ss ; B, neck of the maxillary condyle; c, mastoid process ; D, external auditory hiatus. ARTICULAIIONS OF THE HEAD. 189 125, 2), this ligament becomes greyish-coloured and elastic for the remainder of its extent, and greatly diminishes in thickness, especially in front. Its inner face IS covered by the synovial capsules, and adheres to the circumference of the interarticnlar tibro-cartilage. Its external face is related, in front, to the temporal and masseter muscles ; behind, to the parotid gland ; inwardly, to the external pterygoid muscle ; and outwardly, to a fibrous expansion which separates it from the skin. (Leyh mentions a lateral external and a posterior ligament for this articulation, but Chauveau and Rigot evidently look upon these as portions of the capsular.) Si/noiual membranes. — This articulation has two synovial sacs — one above the other — which are separated by the fibro-cartilaginous disc. Movemmts. — The temporo-maxillary articulation is the centre of all the movements performed by the lower jaw. Tliese are : depression, elei'ation, lateral motion, and horizontal gliding. The lower jaw is dqnessed when it separates from the superior one, and is elevated when it approaches this. These two opposite movements are executed by a mechanism of such great simplicity, that it need not be described here. Lateral movements take place when the inferior extremity of the jaw is carried alternately to the right and left. It then happens that one of the maxillary condyles, taking with it the fibro-cartilage, is brought into contact with the temporal condyle, while the other is embedded in the glenoid cavity of the opposite side. The horizontal gliding is effected from behind to before, or vice veisd. In the first case, the two maxillary condyles are carried at the same time under the temporal condyles, bearing with them the fibro-cartilages. In the second case, they are drawn into the glenoid cavities, and rest against the supra-condyloid eminence, which prevents their going further. It will be undei-stood, after this brief description, that the presence of the fibro-cartilages singularly favoure the lateral movements and horizontal gliding of the lower jaw. In the Pig, the teraporo-maxillary articulation is formed after the same type as that of Rodents, and allows very extensive movements from before to behind — a circumstance due to the complete absence of the supra-eondyloid eminence. In the Dog and Cat, the maxillary condyle is exactly fitted to the temporal cavity. This disposition, in giving great precision to the movements of depression and elevation, restrains in a singular manner the lateral and horizontal gliding motions. The interarticular fibro-cartilage is extremely thin in these animals. In the Rabbit, tlie narrow condyle of the maxilla moves from before to behind and to each side, on tlie temporal bone, the articular surface of which is very elongated and destitute of a subglenoid eminence. 5. Hyoideal Articulations. (^Preparation. — Disarticulate the lower jaw, and dissect away from the right of each articulation the muscles that may conceal the view.) These are of two kinds — &xtrinsic and intrinsir. The first comprise the two temporo-hgo ideal articulations ; to the second belong the joints which unite the different pieces of the hyoid bone — the i?iterh go ideal articulations. Temporo-hyoideal Articulations. — These are two amphiarthrodial joints, in the formation of which each great cornu of the hyoid bone opposes its upper extremity to the hyoideal prolongation lodged in the vaginal sheath of the temporal bone. An elastic cartilage, from -j-*, to ^j^ of an inch in length, unites the two bones in a solid manner ; and it is owing to the flexibility of this cartilage that the hyoid bone can move entirely on the temporal bones. 15 190 TEE ARTICULATIONS. Inter-hyoideal Articulations. — A. The great cornu articulates with the small one, by an amphiarthrosis analogous to the preceding. To form this articu- lation, these two pieces of bone are joined at an acute angle, through the medium of a more or less thick cartilaginous band, in the centre of which there is often a little bony nucleus — the styloid nucleus, or kerato-hyal bone. This cartilage is elastic and flexible, and permits the opening and closing of the articular angle at the summit of which it is placed. B. Each styloid cornu is united to the body of the hyoid bone, or basihyal, by an arthrodial articulation. The articular surfaces are : for the hyoideal branch, the small cavity terminating its inferior extremity ; for the body, the convex lateral facet situated at the origin of the thyroid cornua. These surfaces are covered by cartilage, and enveloped by a small synovial sac and a peripheral fibrous capsule. They can gUde on each other in nearly every direction. (Median and superior hyoideal capsular hgaments are described by Leyh as sometimes present. The latter unites the upper and middle branches, and the former the middle with the inferior branches. They are absent when these branches are confounded with the superior ones.) Article III. —Articulations of the Thorax. These are also divided into extrinsic and intrinsic. The first — named costo- vertebral— unite the ribs to the spine. The second join the different bones of the thorax together ; they comprise : 1. The chondro-sternal articulations. 2. Chondro-costal articulations. 3. The articulations of the costal cartilages with each other, 4. The sternal articulation perculiar to the larger Ruminants and the Fig. All these joints will be first studied in a special manner, then examined in a general way as to their movements. • Extrinsic Articulations. Articulations of the Ribs with the Vertebral Column, or Costo- vertebral Articulations. (Preparation. — This is simple. No difficulty need be experienced except in exposing the interarticular ligament, and tliis is effected by sawing tluough cue of the dorsal vertebra transversely, close to the posterior intervertebral joint formed by that bone. A few cuts of the bone forceps will then show the whole extent of the ligament.) Each rib articulates with the vertebral column by two points — its head and its tuberosity. The first is received into one of the intervertebral cavities hollowed out on the sides of the spine, and is therefore in contact with two doi-sal vertebrae ; the second rests against the transverse process of the posterior vertebra. From this arrangement arises two particular articulations belonging to the arthrodial class, which are named costo-vertebral and costo-trcmsverse. Costo-vertebral Articulations. — Articular surfaces. — Pertaining to the rib, we have the two convex facets of the head, separated from each other by a groove of insertion, and covered by a thin layer of cartilage. On the vertebrae, the concave facets which, by their union, form the intervertebral cavity ; these facets are also covered with cartilage, and separated, at the bottom of the cavity, by the corresponding intervertebral disc. Mode of union. — 1. An interarticular ligament (Figs. 126, 2 ; 127, 1), fixed in the groove in the head of the rib, and attached to the superior border of ths ARTICULATIONS OF THE THORAX. 191 intervertebral disc, which it encircles upwards and inwards, to unite on the median line with tlie ligament of the opposite side. 2. An inferior peripheral ligament (Vv^. 127, 2, 3, 4), fiat above and below, thin and radiating (whence it is oftt-ii named the stellate ligament), formed of thr-ie fasciculi, which are fixed in common on the inferior face of the head of the rib, and in diverging are carried over the bodies of the two vertebrae and the mtervertebral disc. Lined above by the synovial membranes, this ligament is covered below by the pleura. (Leyh includes a capsular ligament for the head of the rib, and another for the costal tuberosity. He probably considered the synovial membrane of these articulations as such.) Synovial membranes. — These are two in number — an anterior and posterior,; lying against each other, and separated in part by the interarticular ligament they cover. Supported below by the stellate ligament, above they are directly in contact with the levatores costarum muscles, and with vessels and nerves. COSTO-TRANSVERSE ARTICULATIONS. Articular surfaces. — In the rib, the Pig. 126. articulations of the ribs with the ver- tebryb, and of these with each other (upper plane). 1, Spinal canal, upper face, showing the common superior ligament; 2, interarticular costo- vertebral ligament ; 3, interosseous costo- transverse ligament ; 4, posterior costo-ti-ans- verse ligament. •ARTICULATIONS OF THE KIBS WITH THE VERTEBRA. AND OF THESE WITH EACH OTHER (INFERIOR PLANE). 1, Interarticular cnsto-vertebral liga- ment; 2, 3, 4, fasciculi of the stellate, or inferior costo-vertebral ligament; 5, common inferior vertebral ligament. diarthrodial facet cut on the tuberosity. In the vertebra, the analogous facet on the outside of the transveree process. Mode of union. Two ligaments bind this articulation : 1. The posterior cosfo- transverse ligament (Fig. 126, 4), a white fibrous band attached by its extremities behind the transverse process and the costal tuberosity, lined by synovial mem- brane, and covered by the transverse insertions of several spinal muscles. 2. The anteri&r costo-transverse, or interosseous ligament (Fig. 126, 3), a fasciculus of short, thick, white fibres, fixed on the anterior surface of the transveree process near its base, and in the rugged excavation on the neck of the rib. This liga- ment is invested, posteriorly, by the synovial membrane, and covered in front by pads of adipose tissue which separate it from the costo-vertebral articulation. Synovial membrane. — This is a small particular capsule, kept apart from the posterior synovial membrane of the costo-vertebral articulation by the costo-trans- verse interosseous ligament. Characters peculiar to some Costo-vertebral Articulations. — 1. The first, and sometimes the second, costo-vertebral articulation has no inter- osseous ligament, and only exhibits one synovial membrane. The intervertebral 192 THE ARTICULATIONS. cavity which concurs in forming the first is often excavated between the last cervical and first dorsal vertebrae. 2. The two or three last costo-trans verse articulations are confounded with the corresponding costo-vertebral joints. They have no proper serous membrane, but the posterior synovial membrane of the latter is prolonged around their articular surfaces. Intrinsic Articulations. A. The Chondko-sternal or Costo-sternal Articulations. (Preparation. — To show the articulatioii of the rib.-; with the cartilnges. these with the ' sternum, and the cartilages with each oher, carefully remove the pleura, the triangularis sterui muscle, the diajihragm, tl e trau.svt rse museU- of the abdomen, then the pectorals, the great oblique, the transversalis of the ribs, and the intt rcN>!. continuous, behind, with the arcif orm ligamentous bands which stretch from the ulna to the radius. Its deep fibres are slightly oblique downwards and forwards. b. Tfie Mend internal Uyament — also funicular — is longer, but not so strong as the preceding. It arises from Fig. 128. the small tuberosity on the inner Bide of the superior articular face of the humerus, and, widening as it descends, reaches the radius. Its median fibres, which are the longest, are directed vertically downwards to reach the imprints situated below the bicipital tuberosity ; its anterior fibres, curved forwards, are united to the tendon of the coraco-radialis muscle, or are confounded \\ith the anterior ligament ; the posterior are turned backwards, near their in- ferior extremities, to join the arci- form fibrous fasciculi, which in- wardly unite the ulna to the radius. The middle fibres of this Ugament cover the inferior insertion of the short flexor of the forearm, and — in part only — that of the long flexor. It is covered by the ulna-plantar nerve and the posterior radial artery and vein. c. The anterior or capsular liga- ment (Figs. 128, 9) is a membrani- f orm band, attached by its superior border above the humeral articular surface, and by its inferior to the anterior margin of the radial sur- face. By its lateral borders, it is confounded with the funicular liga- ments. Its internal half is formed of vertical fibres which descend from the humerus and expand over the radius, where they become united with the inferior tendon of the coraco-radialis muscle. In its exter- nal moiety it is extremely thin, and composed of fibres crossed in various directions. Lined internally by synovial membrane, this ligament is in contact, by its external surface, with the anterior radial vessels and nerves, the two flexor muscles of the forearm, the anterior extensor of the metacarpus, and the anterior extensor of the phalanges. The two latter muscles I SCAPULO-HUMERAL AND HUMERO-RADIAL ARTICULA- TIONS, WITH THE MUSCLES SURROUNDING THEM (EXTERNAL FACE). 1, Scapulo-humeral capsular ligament; 2, short ab- ductor muscle of the arm ; 3, its insertion in the humerus; 4, insertion of the infra-spinatus muscle on the crest of the great tuberosity; 5, coraco-radialis muscle; b, its tendon of origin attached to the coracoid process; 7, its radial insertion confounded ■with the anterior ligament of the ulnar articula- tion ; 8, 8, external lateral ligament of that articu- lation; 9, anterior ligament; 10, aconeus, or small extensor of the forearm ; 1 1, origin of the external flexor muscle of the metararpus ; 12, short flexor muscle of the forearm, a, Tuberosity of the scapu- lar spine ; B, supra-spinous fossa; C, infra-spinous fossa; D, convexity of the small trochanter; E, summit of the trochanter. ARTICULATIONS OF lUE ANTERIOR LIMBS. 197 are even attached to it in a very evident manner. The elhow articulation, closed in front and on the sides by the three ligaments just described, has no particular ligaments posteriorly ; but it is powerfully strengthened there by the olecranian insenioa of the extensor muscles of the forearm, and by the tendons of origin of the five flexor muicles of the metiicarpus or phalanges. 8i/ii0i'ial membrane. — -This membrane is very extensive, and, stretched out on the internal face of the before-mentioned ligaments, forms, behind, three great culs-de-sac of prolongraent : a superior, occupying the olecranian fossa, and covered by a fatty cushion, as well as by the small extensor muscle of the fore- 'irm ; ' two lateral, which descend from eacli side of the ulnar beak, and are distinguished as internal and external — the first lines the tendon of the external flexor of tlie metacarpus, the second facilitates the play on the upper radial extremity of the four flexor muscles of the foot or digits, and which are attached in common to tht. «pitrochlea. This synovial sac also furnishes the radio-ulnar articulation with a diverticulum, which descends between the bones of the fore- arm to below the adjacent diarthrodial facets. Movements. — Flexion and extension. In fleximi, the two bones do not approach each other directly, the inferior extremity of the radius deviating a little outwards. This is due more to the slight obliquity of the articular grooves, than to the difference in thickness between the external and internal extremities of the humeral surface. Extension is limited by the reception of the beak of the olecranon in its fossa, and by the tension of the lateral ligaments ; so that the two bones cannot be straightened on one another in a complete manner, or placed on the same line. In the Dog and Cat, the external lateral ligiment is very thick, and forms in its inferior moiety a titiro-cartilaginoiis cap which is fixed o'l the ulii:i and radius, and united in fronc ♦<) the annular ligament of the superior radio-ulnar joint. This cap), with the last-named liga- ment, complttcs the Osteo-fibroiis ring in which tlie superior extremity of the radius turns. The internal lateral lig^iment is inserted, by two very sliort fasciculi, into the ulna ane inter-articular notch of the metacarpal bone, is inserted into the inner face of the first phalanx in mixing it.s fibres with those of the superior interdigital ligament. This latter is situated between the two first phalanges, and is composed of short, inter- crosted fibres, attached to the imprints which in part cover the internal face of the two first phalangral bones. In the Sheep there are only traces of this interdigital ligament, and each internal metacarpal-phalangeal gives rise, near its phalangeal insertion, to a fibrous branch which is directed backwards from the interdigital space, and is terminated in the bune of the ergot (or posterior ru'limentary digit), which it sustains. The anterior or capsular ligament, single as in Solipeds, unites the two external lateral liga- ments. The suspensory ligamsnt, single superiorly, is divided inferiorly into eight branches, two of which are joined to tlie perloratns tendon, to form with it the double ring through which the two branches of the perforans pass. Four other branches, in pairs, extend to the summits of the sesamoids. That which is sent to each external sesamoid gives off, on the side of the first phalanx, a reinforcing band to the proper extensor of the digit. The two last, profound and median, descend into the inter-articular notch of the metacarpal bone, after becoming a single fasciculus ; afterwards, they pass between two internal metacarpo-phalang> al ligaments, and separate from each other in passing downwards and forwards on the inner side of the first phalanx, to join the proper extensor tendon of each digit. In the Pig, Dog, and Cat, for each metacarpo-phalangeal there is : a proper synovial nienjbrane ; an intersesamoid ligament; an inferior sesamoid ligament composed of two cross- bands; two small lateral sesamoid ligaments; two lateral metacarpo-phalangeal ligaments, attached inferiorly to the first phalanx and the sesamoids ; an anterior capsular ligament, in the centre of which is found a small bony nucleus — a kind of anterior sesamoid— over which glides one ot the brandies of the common exten.^or of the digits. The suspensory ligament is replaced by real palmar interosseous muscles (see the Muscles of the Anterior Foot). Some fibres situated between the first phalanges in the great digits of the Pig, resemble the superior interdigital ligament of the Ox. In Man, the cavity in the upper extremity of the first phalanx is completed by a glenoid SECTION OF TlllC INFEaiOR ROW OF CARPAL BONES, THE METACARPAL, AND THE SUSPENSORY' LIGA- MENT OF THE FETLOCK. 1, Os magnum ; 2, common posterior ligament of the carpus ; 3, stay, or band for the perforans tendon , 4, suspensory ligament of the fetlock ; 5, its super- ficial layer ; 6, its deep fasciculus ; 7, principal metacarpal bone. 208 TEE ARTICULATIONS. ligament. The gfenni.l lip^aments of the four firet dip:it8 are united to each otlier by a tfans- ver«e ligament of tlie metacarpus. Ti.e articulations are consolidated by two lateral ligaments. The metacarpo-phalangeal articulations allow flexion and ex- Yis. 134- tension movements, as well -as those of abduction and adduction; but the latter are limited by the lateral ligaments. 7. Articulation of the First with the Second Phalanx, or First Interphalangeal Articulation. {Preparation. — Remove the extensor tendon ; throw open the metacaipo-pi.alangeal sheath, and turn down the flexor tendons.) This is an imperfect hinge-joint. Articular surfaces. — On the inferior extremity of the first phalanx are two lateral condyles, separated by a groove. On the superior surface of the second phalanx are two glenoid cavities, and an antero-posterior ridge. The latter surface is completed behind by a glenoidal fihro-cartilage, very dense and thick (Fig. 132, 16), which also acts as a ligament. It is attached, in one direction, to the second phalanx, between the superior articular surface and the kind of fixed sesamoid which margins it behind ; in the other, it is inserted into the first phalanx by means of six fibrous bands (Fig. 135, 4, 5, 6) : two superior, which embrace the inferior, middle, and super- ficial sesamoid ligaments ; two middle, and two inferior, which extend to the sides of the inferior extremity of the first phalanx. This fibro-cartilage is moulded, in front, to the articular surface of the latter bone, and forms, by its posterior face, a gliding surface for the perforans tendon (Figs. 132, 16 ; 134, 5). It is con- founded, laterally, with the two branches of the per- foratus, and receives, in the middle of its superior border, the insertion of the inferior superficial sesamoid liga- ment. Mode of union. — Ttvo lateral ligaments (Fig. 135, 7), to which are added, behind, the fibro-cartilage just described, and in front the tendon of the anterior extensor of the phalanges. These ligaments are large and thick, and, passing obliquely downwards and backwards, are inserted, superiorly, into the lateral tubercles of the inferior extremity of the first phalanx. They are at- tached, beneath, to the sides of the second phalanx. Their most inferior fibres are even prolonged below that point to reach the extremities of the navicular bone, and constitute the posterior lateral ligaments of the pedal articulation. Synovial membrane. — This covers the tendon of the ligament ; 7, lateral fasci- culus of the middle inferior sesamoiil ligament; 8, inferior superficial sesamoid ligament ; 9, lateral ligament of the first interphalangeal articulation; 10, section of the terminal branch of the perforafus tendon; 11, section of the lateral cartilage of the foot; 12, postero-inferior surface of navicular bone; 13, section of lateral cartilage, plantar cushion, and wing of pedal hone," 14, peiforatus tendon, 15, perforans tendon. 'osterior view of the metacarpo-phalangeal and inter-phalangeal articulations (right limb). 1, 3, Outer and inner rudimentary metatarsal bones ; 2, jierforans ten- don and its check liga- ment; 4, suspensory liga- ment ; 5, gliding surface or sVieath for the flexor tendons, f'rmed by the posterior face of the sesa- moid bones, and interse- samoid, transverse, .ind annular ligaments ; 6, section of lateral sesamoid ARTICULATI0S8 OF THE ANTERIOR LIMBS. 209 anterior extensor of the phalanges, tlie lateral ligaments, and the glenoid fibro- cartilage. Behind, it forms a cul-de-sac, which extends between the latter and the posterior face of the first phalanx (Fig. 187). Movements. — This imperfect hinge is the seat of two principal movements : extension a.udfiexion. It also allows the second phalanx to pivot on the tirat, and permits some lateral movements. In the Ox, Sheep, and Goat, the glenoid fibro-ciirtilago is confounded with tlie perforatua tendon, and is only attachi d to the first piialanx by two lateral bands. Tlie internal lateral ligament comprist-a two fasciculi : one, very atiort, which terminates in the second phalanx ; and another, vt- ry lon;r, descending to the internal face of the third phalanx. The external is very thin, and is also prolonged to the terminal phalanx ; so that the two last interphalangeal articnltions of eich digit are fixed by two common lati-ral ligaments which correspond exactly, by their position and inferior attachments, to the anterior lateral ligaments of the pedal joint of Solipeds. In ti e Dog and Cat, the glenoid cartilage, also confounded by its posterior face with the perforatus tendon, only adheres to the first phalanx by some cellular bands. The two lateral ligaments pass from the inferior extremity of the first phalanx to the superior extremity of the second. In the Pig, jthere is somewhat the same arrangement as in Carnivora. The external latenil ligament is, nevertheless, more like that of the Horse, in its most anterior fascici li being proloiigtd 10 the external extremity of the navicular bone. 8. Articulation of the Second Phalanx with the Third, Second Interphalangeal Articulation, or Articulation of the Foot. Preparation. — Remove the hoof according to the directions given hereafter, wlieu treating of the Tnnscles of the forearm; then tlie plantar cushion, the flexor tendons, and one uf the lateral cartilages. A section like that shown in Fig. 137 is useful to show the relations between the synovial capsule of this joint and the bursas, beldnd the second phalanx. To form this imperfect hinge-joint, the second phalanx is opposed to the tliird, and to the navicular bone. Articular surfaces.- — On the inferior face of the second phalanx there are two lateral condyles and a median groove. On the superior face of the third phalanx and the navicular bone, are two glenoid cavities separated by an antero-posterior ridge. The two bones which form this last surface, articulate with each other by arthrodia ; the navicular bone presents for this purpose an elongated facet on its anterior border ; the os pedis also offers an analogous facet on the posterior contour of the principal articular surface. Jfod^' of union. — Five ligaments : a single interosseous one, which joins the navicular to the pedal bone ; and four lateral bones, distinguished as anterior and posterior. a. Interosseous ligament {Yig. 136, 2). — This is formed of very short fibres, which are inserted, behind, into the anterior groove of the navicular bone ; and in front, into the posterior border and inferior face of the third phalanx. This ligament is lined, on its superior surface, by the synovial membrane, and on its inferior face is covered by the navicular sheath. h. Anterior lateral ligaments (Figs. 132, 2i ; 135, 9).— These are two thick, short, and wide fasciculi, attached by theii* superior extremities to the lateral imprints of the second phalanx, and by their inferior extremities into the two cavities at the base of the pyramidal eminence of the os pedis. Each ligament is partly covered by the complementary fibro-cartilage of that bone, and appears to form a portion of it. Its anterior border is continuous with the common extensor 21U TEE ABTICVLATIONS. tendon of the phalanges ; its internal face is covered by the synovial membrane, which adheres closely to it. c. Posterior lateral ligaments (Figs, 132, 21 ; 135, 8).— These have been abeady noticed. Each is composed of the lowermost fibres of the lateral ligament of the first interphalangeal articulation ; these fibres, after being attached to the iiecond phalanx, unite into a sensibly elastic fibrous cord, which is chiefly fixed Fig. 135. Fig. 136. MliTATARSO - PHALANGEAL AND INTER-PHALANGEAL ARTICULATIONS OF THE HORSE. Tliese are almost the same as in the anterior limb. ], Superficial layer of the external lateral ligament of the metatarso-phalan- geal articulation ; 2, sesa- moid branch of the deep layer; 3, phalangeal branch of the same ; 4, superior branch of the glenoidal fibro-cartilage; b, middle branch of ditto; 6, inferior branch of ditto; 7, lateral ligament of the first inter- phalangeal articulation ; 8, posterior lateral ligament of the pedal articulation ; 9, anterior lateral ligament of ditto. ARTICULATION OF THE FOOT (INFEBIOE FACE). P, Inferior face of the third phalanx. S, Infe- rior face of the navicular bone. 1, Semilu- nar crest ; 2, interosseous ligament. into the extremity and superior border of the navicular bone, where the Ugaments join each other, and in this way form a kind of complementary cushion that iti- creases the navicular articular surface. It also sends off a short fasciculus to the retrossal process, and a small band to the internal face of the lateral fibro- cartilage. Partly concealed by the latter and the plantar cushion, this ligament is covered inwardly by the articu- lar synovial membrane. Synovial membrane. — This descends below the facets which unite the navicular to the pedal bone. It offers, posteriorly, a vast cul-de-sac wliich reaches the posterior face of the second phalanx, and lies against the two sesamoidean bursa (Fig. 137, 13). It also forms another much smaller, by being prolonged between the two lateral ligaments of the same side. This is very often distended, and it is liable to be opened in the operation for diseased lateral cartilages. Movements. — The same as those of the first interphalangeal articulation. In the Sheep are found : 1. An interosseous ligament to unite the navicular bone to the third phalanx. 2. Two anterior lateral ligaments commencing, as already stated, at the first phalanx. 3. Two lateral posterior lif^aments, passincr to the posterior face of the second phalanx and the navicular bone (the internal is yellow and elastic). 4. A single, anterior, elastic liga- ment, attaciied above to the superior extremity of the second phalanx, and fixed below into the third, between the insertion of the common extensnr of the digits and that of the internal anterior lateral ligament; an inferior interdigital ligament, situated between the ungiieal phalanges, whose separation from each other it limits This ligiiment is composed of parallel fibres, whicli extend transversely from the one navicular bone to the other, and is covered on ARTICULATIONS OF TEE ANTERIOR LIMBS. 211 its inferior faee by the skiu of the interdigital epace. Ite upper face is in coDtact with aa adipoee cushion. In the Ox, the external anterior lateral ligament, wide and expanding, \% almost eatireiy covered by the long branch of the proper extensor of the digit, to which it is intimately adherent. The iuterdigit.il ligament has a much more complicated character than that of the Sheep. It is formed of fibres intercrossed on the median line, and divided at its extremities into two fasciculi : a superior passes over the perforans tendon, to which it serves as a restrain- ing band, and is fixed to the outside of the inferior extremity of tin; first phalanx, after con- tracting very close adhesions with a strong fibrous web which descends from the posterior metac