Ulljp i. B. ItU ffiibrarg Nnrtli (Earnlina ^tnU This book was presented by MILTON M. LEONARD, D.V.M. TO THE VETERINARY MEDICAL LIBRARY THIS BOOK MUST NOT BE TAKEN FROM THE LIBRARY BUILDING. 125M/07-94-941679 STRANGEWATS' VETERINARY ANATOMY, FOURTH EDITION. REVISED AND EDITED I. VAUGHAN. F.L.S., F.Z.S., KBLLOW OF, ASD BXAMINER ON COMPARATIVE ANATOMY TO, THE ROYAL COLLEGE OF VKTKRINARY SURGEONS, LATE LECTURER ON ANATOMY AND ZOOLOGY AT THE NEW VETgRINARY COLLEGE, EDINBURGH. EDINBURGH: BELL & BRADFUTE 12 BANK^^T>^fi^. TORONTO. CANAeA^.'" J. A. CARVETH & CO. MDCCCXCn. ^ ENGLISH-SPEAKING VETERINAEY STUDENTS, THIS, THE FOURTH EDITION OP 8TRANGEWAYS' ANATOMY, IS DEDICATED BY THE editor; -^. PREFACE TO THE FOURTH EDITION. The Third Edition of Strangeways' being exhausted, it is deemed advisable to issue a Fourth. The work has been very car%'ully read and considered, with the result that little or no material alteration has been made. The diction has occasionally been improved, and a few alterations and additions made in the nomenclature where such appeared necessary. Histology has become such a distinct branch of science, that the portions touching on that subject must, in a work like this, be somewhat brief and insufficient ; but they have been modified and allowed to remain, as they may not prove altogether useless. I trust that this Edition of the work will maintain the reputation acquired by its immediate predecessors.^ I. VAUGHAN. Edinburgh, 29th April, 1892. PREFACE TO THE FIRST EDITION. On the death of Professor Strangeways, there was a very general feeUng that his anatomical lectures should be given to the world. Working daily with him during my furlough, and being present at his death-bed, I was solicited to take the matter in hand. His friend, Dr. Call, and I accordingly undertook to re-write and arrange the lectures. The late Professor Goodsir's detached manuscript on the Myology of the Horse was, after an effectual search, discovered, and considerately placed in my hands by his brother, the Pev. Joseph Taylor Goodsir, F.R.S.E. It is believed this will enhance the value of the work, more especially as Strangeways was not only an ardent admirer of the great anatomist, but he informed me his principal lectures had been perused and approved of by Professor Goodsir. Strangeways' lectures, although generally very complete and excellent, demanded an entire recasting. In doing so, I adopted Leyh's arrangement, which, with due regard to French and English veterinary anatomy, I selected as the best. Dr. Call, notwithstanding his many professional engagements, has re-written the Osteology and the Anatomy of the Nervous System, the Eye, and the Ear. The Comparative Osteology, the Ligaments, Muscles, Digestive, Urinary, Sexual, and Respiratory Organs, and the Organs of Circulation, Lymphatics, Skin, and Hoof, have fallen to my lot. X PREFACE. It has been our object to produce what is greatly desiderated — a thorough-going Manual of Anatomy for the veterinary student. ■ The iDhoto-lithographs, with few exceptions, are selections from Leyh and Lecoq's classical works. To Dr. Morrison Watson, Assistant Demonstrator of Anatomy in Edinburgh University, my thanks are due for his assistance in arranging them during my absence on the Continent. The Editors cordially thank Mr. Thomas H. Douglas, Photo- grapher, Chamberlain Road, for his handsome gift of the Yignette of his friend, which will be appreciated by all the Professor's former students. Messrs. Maclachlan & Stewart, the Publishers, deserve every praise for the generous manner in which they have undertaken the publication ; and Messrs, Waterston, Hanover Street, for the style of the photo-lithographs. To Professor Turner of Edinburgh University, and Mr. Joseph Johnston of Montrose, I am indebted for many valuable sug- gestions. The work owes no small measure of its completeness to the kindly helping-hand of Dr. John Gray M'Kendrick, Assistant to the Professor of Physiology in the University of Edinburgh, who not only has been of immense service to me in the tedious work of proof correcting, but to whom the Editors are indebted for the complete Index and Glossary which accompanies the Avork. The Appendices speak for themselves. The work would have been incomplete without a "dissection manual," and a translation was accordingly made of Chauveau's directions, adopted because they are superior to any I am acquainted with. The Editors confidently commend the work to the veterinary student, farmer, stockbreeder, and to any and every one interested in domestic animals, inasmuch as the true pathological site of disease is incidentally pointed out au courant with the anatomical description. The Dentition Plates of the Horse, Cow, Sheep, and Dog aftord a coiip d'cml which will be a reminder to the PREFACE. . XI adept, and a useful guide to the veriest tyro in the difficult subject of dentition as an index of age. It has been our effort to produce the work at the lowest remunerative rate commensurate with the interests of the deceased's family, to whom all benefit directly passes. Assured that the student will find in these pages a good quid pro quo investment, we leave it with him, along with Seneca's advice and the sententious rule given by Sir William Hamilton in an autograph letter — " Non rnulta sed multum." " Be more anxious to read attentively a few than to read many works." J. WILSON JOHNSTON. KiNNABER House, 21f7i iSeiJtcmber, 1869. PREFACE TO THE SECOND EDITION. The proprietor of Strangeways' Anatomy having resolved on issuing a new and revised edition of the work, placed the matter in my hands, with a carte blanche to do what I thought most advisable. This I have striven to the best of my ability to do ; whether successfully or not, the dictum of future students alone will decide, since for them the work is designed. Books on Anatomy seem naturally to divide themselves into three classes — the exhaustive work for reference, the practical dissecting manual, and the current text-book. In the veterinary department of Anatomy, the first of these classes is represented by Mr. Fleming's well-known edition of " Chauveau," the second by Mr. Steel's " Outlines of Equine Anatomy," while the third is represented by the works of Percivall and Strangeways. In the present edition of Strangeways I have separated the matter into headed paragraphs and chapters ; the Comparative Anatomy being inserted in sections, each at the end of its proper chapter, and, to avoid error in rapid reference, printed in smaller type. The Introduction is my own. Dr. Strangeways' intro- ductory lecture being by some means omitted from the first edition. Other portions of the work which I have added I need not enumerate here, nor yet certain other portions which have been expunged. The photo-lithographic illustrations to the first edition, not being part of the copyright, were not forthcoming, but I have PREFACE. succeeded in procuring electrotype copies of all the original cuts, wkich were required, from the French edition of Leyh's Anatomy' and so venture to hope that the work has not suffered in that respect; my thanks are due to M. Asselin for this, and also to Messrs. Churchill, and Messrs. Routledge & Co., for the electros .'kindly supplied by them. An attempt has also been made by Messrs. Banks to reproduce, with certain modifications, the admirable anatomical plates of M. Megnin. A few minor illus- trations have been cut specially for the work. I have to thank Dr. F. E. Rice, of Springfield, Mass., U.S., for much valuable^assistance in indexing, and passing the work through the press : and Mr. J. J. Fraser, of the New Veterinary College, Edinburgh, for assistance in many ways. And I must also acknowledge with thanks some useful suggestions given to me by Mr. Robertson, F.R.C.Y.S., of Kelso, and by Principal Williams. Messrs. Bell & Bradfute, the publishers, and Messrs. Lorimer & Gillies, the printers of the work, deserve much thanks for the kind manner in which they have assisted me in a rather tedious undertaking. I venture to hope that the matter of the book is as correct as can reasonably be expected in a performance of the kind ; that the arranoemenT is such as to prevent confusion, and consequent loss of ti^ to those who may consult it ; that the book in its present form may, to some extent, meet the ordinary anatomical requirements of the veterinary curriculum of the present day ; and finally; that the student who wishes to go deeper into the' subject, mdj^by it be prepared for the consultation of more exhaustive tre|btises. ' :; J I. VAUGHAN. GatIeield House, PREFACE TO THE THIED EDITION. In the present edition, the general plan of the work has not been altered in any way ; and so far from attemj)ting to enlarge or elaborate the matter of the last edition, I have tried, when practicable, rather to reduce or condense it ; for I am of opinion that of all other books, the one designed as a text-book on a scientific subject should be as free as possible from that obtrusive prolixity or jjadding, which tends to influence in an unsatis- factory way both the patience and pocket of the student. The present edition is a trifle larger than the last, due to the addition of a few small sections which appeared necessary, and to the insertion of a number of extra cuts. The majority of the added illustrations are electrotypes from Franck's edition of Leyh's work, to the publishers of which, Messrs. Shickliardt & Ebner, my acknowledgments are due, as also to Mr. Renshaw, Messrs. Churchill & Co., and Messrs. Macmillan & Co., for various cliches from the works of Milne Edwards, Huxley, and Mivart. The plates will, I think, from an artistic point of view, be found greatly superior to those of the second edition, they having been engraved specially for the present one. I have received assistance, alike varied and valuable, from Professor Lewis, of Edinburgh, which I beg here to acknowledge, and especially his trouble in drawing up and arranging the article on foetal development — the last in the book. Professor XVi PREFACK. W. O. Williams has also given me very useful assistance, in reading the sheets, and rearranging the index. The favourable reception which the last edition received, might be said to promise well for the success of the present edition ; and knowing that no pains have been spared either in the revision, the correction, or in the printing of the work, I trust that Strangeways' Veterinary Anatomy as thus issued will not suffer in its reputation as a students' text-book. I. VAUGHAN. Edinburgh, I4th October, 1885. TABLE OF CONTENTS. INTKODUCTION. ANATOMY, Vertebrata, . Domesticated Mammals, Domesticated Aves, Descriptive Anatomy, PAGE 1 3 4 5 6 CHAPTER I. OSTEOLOGY, . Structure of bone, Osseous tissue. Classes of bones. The Skeleton,. Axial Skeleton, Vertebrte, . The Ribs, . The Sternum, General view of the Skull, Cranial bones, Facial bones, Appendicular Skeleton, Pectoral arch and limb, Pelvic arch. Pelvic limb, Comparative Osteology, Ruminantia, Omnivora, . Carnivora, . Rodentia, . ■Aves, 7 9 12 17 21 21 33 35 37 45 54 65 66 83 88 98 98 105 109 114 115 TABLE OF CONTENTS. CHAPTER II. P*GE ARTHROLOGY, 120 General Anatomy, . . ... 120 Classes of joints, ..... 126 Motion in joints, ..... 128 Articulations of the Axial Skeleton, 129 Vertebral articulations, .... 129 Articulations of tlie Skull, .... 134 .Articulations of the Appendicular Skeleton, . 136 Pectoral limb, ..... 136 Pelvis and pelvic limb, .... 143 Comparative Arthrology, .... 151 CHAPTER III. MYOLOGY, 155 Muscular tissue, 155 Tendons, . 158 Fascia, 159 Muscular nomenclature, . 160 Classification of muscles, . 160 Subcutaneous region. 161 The Head, . 162 The Trunk, 178 Pectoral limb, . 212 Pelvic limb, . 231 Arrangement of the fasciae, . 252 Table of muscular attachments, . 256 Comparative Myology, . 260 CHAPTER IV. SPLANCHNOLOGY, ....... 270 Epithelium, . 270 Mucous membrane^^, . 272 Serous membranes. . 273 Glands, . 274 Digestive System, . 275 Alimentary canal, . . 275 Mouth, . 276 Palate, . 277 Tongue, . 280 Salivary glands. . 285 Teetli, . . - 288 TABLE OF CONTENTS. digestion Digestive System — continued. PI larynx, Q^sophagup, Abdomen, . Stomach, Intestines, . Accessory organs of Liver, Pancreas, . Spleen, Peritoneum, Eespiratory System Nostrils, Nasal chambers. Larynx, Trachea, Thyroid and Tliymii; Bronchi, Thorax, Pleurfe, Lungs, Urinary System, Kidneys, Ureters, Bladder, Generative System, Male Organs, . Scrotum, Spei'matic cord. Testicle, . Vas deferens. Prostate gland, Cowper's glands, Urethra, Penis, Seminal fluid. Female Organs, Ovary, Fallopian tubes, Uterus, Vagina, Vulva, Mammary glands, Comparative Splanchnology, gland TABLE OF CONTENTS. ANGIOLOGY, . Blood- Vascular System- Heart, Pericardium, Course of circulatioi Arteries, Capillaries, . Pulmonary artery, Common aorta, Posterior aorta, Internal iliac. External iliac, Anterior aorta. Brachial artery, Cei^lialic and Carotid arteries, CHAPTER V. -Blood, Sysb Veins, . Pulmonary and Posterior cava. Portal vein. Iliac veins, . Anterior cava, Brachial vein, Jugular vein. Lymphatic System Glands, Lymph and Chyle. Thoracic duct. Lymphatics of posterior region, abdominal viscera, thoracic viscera, thoracic walls, anterior region. Lymphatic vein. Comparative Angiology, PAQK 387 387 397 398 400 400 401 402 409 411 418 418 424 433 435 436 437 438 442 444 446 449 450 451 451 452 454 455 456 456 458 458 CHAPTER VI. NEUROLOGY, . Nervous tissut Nerves, 465 466 467 TABLE OF CONTENTS. Cerebro-Spinal System — Meninges, . 468 Spinal cord, . 471 Brain, . 473 Encephalic circulation. . 485 Cranial nerves. . 490 Spinal nerves. . 502 Brachial plexus, .508 Lunibo-sacral plexus, .511 Sympathetic System— Cephalic portion, . . . .515 Cervical portion, . . 516 Thoracic portion, . . 519 Lumbar portion, . . 521 Sacral portion. . 521 Comparative Neurology, 522 CHAPTER VII. .ESTHESIOLOGY, ORGANS OF SPECIAL SENSE. ^^o The Ear— External ear, . . . . . . 525 Middle ear, ..... . 526 Internal ear, ..... . 529 The Eye— Tunics, . . . . . . 532 Humours, ..... . 536 Muscles, ....... . 537 Appendages, ..... . 538 ORGANS OF SENSATION. The Skin and its Appendages— Skin, . 541 Hair, . 543 Foot— Hoof, .... . 544 Soft parts of the foot, .... . 549 Comparative ^sthesiology, . . . . = . 552 CHAPTER VIII. EMBRYOLOGY, . 556 Ovum after Fecundation, . . 556 Placenta, ..... ■ . 557 Umbilical cord, .... . 558 Foetal circulation, .... . 559 Development of Fojtus, . 561 XX ii TABLE OF CONTENTS. APPENDIX. PAOB I. General directions for dissection, 565 II. On a snpernnmerary oblique muscle of the eyeball, . • 5*5 III. On a muscle connected with the orbital periosteum, • • 577 INDEX 583 TABLE OF ILLUSTEATIONS. -^ PAGE Plate I. Skeleton of Horse, .... opposite page 21 „ II. Muscles of Horse— superticial layer,. . 161 „ III. Muscles of Horse — deep layer. 193 „ IV. Digestive and Urinary Organs of Horse, 274 „ V. Heart and chief blood-vessels of Horse, 400 ,, VI. Nervous System of Horse, 503 FIG. 1. Transverse sections through the body of a vei tebrate and an inverte- brate animal — diagramatic. 3 2. Transverse section of bone, . 9 3. Longitudinal section of bone, 10 4. Lacunae of bone, 10 5. Section of ossifying cartilage, 16 6. Skeleton of Horse, . • 18 7. Transverse vertebral segment. 22 8. Cervical vertebras articulated. 24 9. Cervical vertebra. 25 10. Skull seen from above, 37 11. Inferior aspect of skull, 39 12. Lateral view of the skull. 41 13. Lo;igitudinal section of the skull. 43 14. Inferior maxilla, 62 15. Bones of the hyoid series. 64 16. Bones of the carpus, . 72 17. Bones of the carpus, metacarpus, and digit. 73 18. Development of foot, . 77 19. Phalanges disarticulated, 79 20. Lateral aspect of pelvis. 85 21. Posterior aspect of femur, 89 22. Bones of tarsus, 94 23. Bones of tarsus, metatarsus, and digi t, 96 TABLE OF ILLUSTRATIONS. 24. Posterior aspect of metatarsus, 25. Skeleton of Ox, . . . . 26. Skull of Ox, . . . . . 27. Cardiac bone of Ox, . . . . 28. Skull of Boar, . . . . 29. Skeleton of Hog, . . . . 30. Section of Hog's skull. ,31. Skeleton of Dog, . . . . 32. Bones of Digits compared, 33. Clavicle of Dog, . . . . 3-1. Clavicle of Cat, . . . . 35. Os penis of Dog, . . . . 36. Skeleton of Bird. . . . . 37. Sternum of Bird, . . . . .38. Skull of Fowl, . . . . 39. Pectoral arcli of Bird, 40. Pelvis of Bird, . . . . 41. Hyaline cartilage, 42. White fibrous tissue, . . ' . 43. Yellow elastic tissue, . 44. Adipose tissue. 45. Diarthrodial joint — diagram, . 46. Odontoid and superior common ligaments, 47. Costo- vertebral articulation— lateral aspect, 48. Costo-vertebral articulation— superior aspect 49. Temporo-maxillary articulation, 50. Hyoid articulations, . 51. Ligaments of elbow joint. 52. Ligaments of carpus— anterior, 53. Deep ligaments of carpus— external, . 54. Deep ligaments of carpus— postero-internal, 55. Superficial ligaments of carpus — posterior, .")6. Sesamoidean and digital ligaments, . 57. Deep sesamoidean ligaments, 58. Navicular ligaments, . 59. Sacral and pelvic ligaments, . 60. Sacral and pelvic ligaments— inferior view. 61. Ligaments of liip joint. 62. Ligaments of stifle joint, 63. Ligaments of stifle joint— posterior view. 64. Ligaments of tarsus— postero-internal view, 65. Ligaments of tarsus — antero-external view, 66. Striated musciilar fibres and tendon. 67. Muscular fibrillar, 68. Striated muscular fibres, 69. Non-striated muscular fibres, TABLE OF ILLUSTRATIONS. Fin. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 8L 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. Muscles of head — lateral view, Muscles of maxillaiy space, . Muscles of external ear, Lateral cervical muscles, Occipito-atlo-axoid muscles, . Pectoral muscles, SuLlumbar and internal femoral muscles, Diaphragm, .... External muscles of anterior limb, . Internal muscles of anterior limb, . Deep muscles of arm, Flexor muscles of fore-foot, . Section of digit, Deep muscles of hip, Muscles of thigh and haunch. Anterior tibial muscles, Posterior tibial muscles. Tendons and ligaments of Ox's extremity. Epithelial cells. Ciliated epithelium, Muscles of tongue, palate, and pharynx. Parotid and molar glands, . Mouth, and salivary glands, . Dentine, .... Enamel, .... Incisor and canine teeth, Structure of incisor tooth, . Structure of molar tooth. Stomach, .... Internal aspect of stomach, . The mesenteries. Section of mucous membrane of intestine. Chyle magnified, Caecum and great coh>ii, Liver and diaphragm. Hepatic lobules magnified, . Biliary and pancreatic ducts, Pancreas, .... Spleen, .... Kelations of abdominal viscera, Framework of nostril, Longitudinal section of head, Epiglottis, .... Ligaments of larynx — posterior view. Ligaments of larynx — anterior view, M-uscles of larynx — lateral view. TABLF. OF ITXr.STUATIOXS. FIG. 116. Deep muscles of larynx — Liteval vieu 117. Larynx laid open, 118. Eespiratory organs, . 119. Capillaries of lung, . 120. Section of kidney, 121. Structure of kidney, . 122. Distribution of renal arter}, 123. Male generative organs, 124. Testicle, 125. Diagram of structure of testicle, 126. Bladder and urethra, 127. Female iirino-genital organs, 128. Female generative organs, . 129. Stomach of Ox, 130. Stomach of Sheep, . 131. Ruminant stomach opened, . 132. Stomach of Musk Deer, 133. Mesentery and intestines of Ox, 134. Ctecum of Ox, 135. Liver of Ox, . 136. Kidney of Ox, 137. Section through vagina and bladde 138. Teeth of Hog, 139. Stomach of Hog, 140. Ca3cum and colon of Hog, . 141. Liver of Hog, 142. Kidney of Hog, 143. Teeth of Carnivora, . 144. Stomach of Dog, 145. Caecum and colon of Dog, . 146. Stomach, liver, &c., of Dog, . 147. Teeth of Rodent, 148. Alimentary canal of Bird, . 149. Urino-genital organs of Bird, 150. Right side of heart — opened, 151. Left side of heart — opened, . 152. Muscular fibres from heart, . 153. Diagram of circulation, 154. Heart and large vessels in situ, 155. Abdominal branches of posterior aor 156. Arteries of caecum and colon, 157. Breaking wp of posterior aorta, 158. Distribution of internal iliacs, 159. Arteries of thigh. 160. Arteries of leg, 161. Arteries of neck, if Cr TAHLK OF ILLT'STRATIONJ FIG. 162. Arteries of fore-limb, 163. Arteries of head, 164. Facial arteries, 165. Posterior vena cava, . 166. Portal system, 167. Heart and great veins, 1 68. Veins of face and neck, 169. Section of lymphatic gland, 170. Lymphatic trunks, . 171. Circulation in Reptile, 172. Circulation in Fish, . 173. Circulation in Crustacean, 174. Nerve tissue, . 175. Pacinian body, 1 76. Section of spinal cord, 177. Base of brain, 178. Brain viewed from above, 179. Lateral ventricles, 180. Cavities of brain — diagramatic, 181. Brain laid open, 182. Diagramatic section of brain, 183. Encephalic arteries, . 184. Arteries at base of brain, 185. Origins of cranial nerves, 186. Nerves of eye, 187. Fifth nerve, . 188. Facial nerves, 189. Posterior nerves of head, 190. Brachial plexus, 191. Carpal and metacarpal nervi 192. Lumbo-sacral plexus, 193. Tarsal and metatarsal nerves, 194. Sympathetic ganglion, 195. Nerves of thorax, 196. Abdominal nerves, . 197. Conchal and annular cartilages, 198. Scutiform cartilage, . 199. Malleus, 200. Incus, 201. Stapes, 202. Tympanum, . 203. Diagram of ear, 204. Membranous labyrinth, 205. Diagram of eye, 206. Globe of eye, . 207. Globe of eye — partly opened. TABLE OF ILLUSTrwVTIONS. 208. Pigment cells, 209. Iris, . 210. Globe of eve — opened, 211. Hoof,. " . 212. Solar aspect of hoof, . 213. Section of horn-tissne, 214. Sensitive foot — solar aspect, 215. Sensitive wall, 216. Foetus of Cow, 217. Foetus of Bitch, 218. Foetal circulation, PAOB 534 535 536 546 547 548 550 551 558 559 560 ERRATA. Page 278, line 24, for "duets" read "ducts." „ 362, „ 14, ,, " perineum " re«(? " perinseum.' INTRODUCTION. Biology, the comprehensive science which treats of living or organised bodies, is divisible into two parts, the one dealing with .the Vegetable, the other with the Animal Kingdom, Animal Anatomy, or Zootomy, has for its object the investigation of the animal frame, an investigation conducted by mechanically divid- ing it into its component parts, and studying their form, struc- ture, attachments, and relations. Anatomy may be Comparative, Special, or Transcendental, according to the scope and ultimate object in vieAv. Thus, if more than one sjaecies of animal be under consideration, the comparative anatomist takes note of their various deviations and similarities ; but, if the investiga- tions be confined to one variety of animal, as in Human Ana,tomy, the subject then becomes special. When Special Anatomy leads to the thorough investigation of one single variety, for the purpose of comparing other classes with it, the subject of such special study is termed a type. Comparative Anatomy, therefore, is not studied by the indis- criminate comparison of one class with another, but by referring them to certain types or standards. Embracing as it does the structural investigation of the whole animal kingdom, Compara- tive Anatomy is closely related to the science of Zoology, the latter science aiming especially at the attainment of a scientific method of classification. Transcendental or Philosophical Ana- tomy seeks for analogies and developmental facts, wliich may guide the investigator in his search after primary anatomical types. Since the prosecution of such a study must assume a more or less profound knowledge of Comparative Anatomy, this abstruse branch of the science is merely alluded to here in passing. If we consider a portion of the animal body with respect to its form, size, relative position, or structure, we are said to consider it anatomically ; but should we inquire into the use or B 2 INTRODUCTION. function of such portion, or seek to know the changes undergone by it while in a living condition, then we are investigating it lihysiologically. Such is a general distinction between the sciences of Anatomy and Physiology ; but it will readily be seen that they are to a great extent bound up in one another, since both the sciences must lend their aid to afford a complete description of any given organ or part. The branch treating solely of structure and form is termed Morphology. Histology, otherwise called General or Minute Anatomy, treats of the intimate structure of the tissues or materials of which the various parts of the body are composed. As the tissues present certain character- istics invisible to the naked eye, the microscope is largely employed by the histologist in his investigations. Embryology, from an anatomical point of view, is a science considering the various appearances presented by an animal after each of the many successive stages of its development, — from when it first appears as a mere speck of vitality until it has acquired the general characteristics of a perfect animal. Anatomy, in all the above-mentioned branches, deals only with normal or healthy material ; but should such material be in a diseased condition, the consideration of the changes it has conse- quently undergone is termed Morbid Anatomy. Surgical Anatomy embraces the description and investigation of such parts of the body as are most liable to be involved in surgical operations. The surgeon, by a competent knowledge of this branch of the subject, is enabled to operate svith the maximum of safety and expedition, together with the minimum of pain and inconvenience to the patient. Anatomy in either of its aspects may be descriptive or practical. In the former, the student relies on books, diagrams, lectures, &c., for his information ; in the latter, he verifies descrip- tions by actual dissection and demonstration of the various structures in question. Veterinary Anatomy, in the full sense of the vv^ord, includes the anatomy of all the domesticated animals, and is, therefore, a branch of the comparative science, and the animal usually referred to as its type is the Horse, the Anatomy of which animal, or Hippotomy, is primarily considered in this work, while the deviations from the type, which make up the compara- tive branch of the subject, will be noted in their more important features, as fully as the scope of the work will permit. INTRODUCTION. VERTEBRATA. As all the domesticated animals belong to the sub-kingdom Yertebrata, it is of importance to gain a clear idea of the lead- ing characteristics of a vertebrate animal ; and, except in one or two of the lowest orders, these are well marked. The animal kingdom is divided into the sub-kingdoms Invertebrata and Verte- BRATA. As the names would imply, the latter is distinguished from the former by its members possessing a vertebral column, or backbone, which forms, as it were, the axis of the bony framework, supports the head, and is placed dorsally, or in the region of the back, extending from one end . of the body to the other. It is pierced throughout the greater part of its extent by a canal called the neural canal, which is continuous with a cavity in the head called the craniuw,. These cavities are occupied by centres, from which the large series of nerves termed the cerebrospinal system. Underneath the backbone there is a second series of nerve- centres — those of the sympathetic system. Thus in a vertebrate animal there are system.-^/eiaal spine , 2, Aii- into two parts— one projecting an- ^^,^„^. ^i,,,,^^^ proce^^e,; s, Pctenoi tero-inferiorlv, and the other postero- obhque pioce^se, : 5, Onuex anteum end, . „ . , "ni • • • and 9, Concave posterior end of the cen- inierioriy. i hey increase m size as trum; 6, Anterior ends of transverse pro- they extend backwards, and all of cesses; and 7, Posterior end of right one ; J > S, Inferior process, or hypapoiihysi.s. them, except the seventh, are pierced by the vertebral foramen, through which pass the verte- bral artery and vein. These processes give attachment to the serratus magnus, splenius, longus colli, intransversalis colli, levator humeri, and other muscles acting upon the head and neck. The articular processes, larger than in any other region, have flattened oval articular surfaces ; the anterior two look upwards and inwards, while the posterior look downwards and outwards. The articular processes of the posterior five cervical vertebras give attachment to the comj^lexus major, trachelo mastoideus, and spinalis colli muscles. The arches, stronger than in any other region, enclose the spinal canal, which progressively increases in size in the direction of the dorsal vertebras, its vertical diameter being the greater. The notches of the three posterior cervical vertebra? are also larger than the rest. Viewed in situ, it is seen that the transverse jDrocesses of the three central cervical vertebrge are largest and strongest with the exception of that of the first, and they can be detected under the investing muscles in the living animal ; also that the bodies progressively diminish in length, and increase in breadth and depth from the second backwards. 26 OSTEOLOGV. The first, second, sixth, and seventh cervical vertebra? having features peculiar to themselves, require special notice. SPECIAL CERVICAL VERTEBRA. The Atlas. The First cervical vertebra is called the Atlas, because in human anatomy it supports the head ; in quadrupeds the head is suspended from it. It presents no well-defined body, but consists of a strong ring of bone, the superior surface of which is convex, with a slight longitudinal elevation in the median line, from which the alee or wings slope dowuAvards and backwards. The wings are large, flat transverse processes, wider than those of any other true vertebra, and they terminate in rough convex margins, which may be plainly felt through the skin in the living animal; they give insertion to portions of the levator humeri, splenius, trachelo mastoideus, and obliquus capitis posticus muscles, and are always largely developed in the carnivora. Superiorly, each ala exhibits three foramina ; the posterior is the largest, and corresponds to the vertebral foramen, giving passage to the anastomotic branch of the occipital artery. The two anterior foramina are joined by a short, deep depression, the alar gutter ; the external foramen gives passage to the occipital artery, vein, and nerve, while the internal passes through the ring into the neural canal, representing the intervertebral foramen, and through it pass the cerebro-spinal artery, and the first spinal nerve. The inferior surface of the atlas is convex centrally, and presents posteriorly a short, obtuse eminence, which represents the inferior spine, this is the tubercle of the atlas to which the tendon of the longus colli muscle is attached. On each side of the central convexity we find a large concave space limited exter- nally by the ala. The anterior surface presents two notches and two articular depressions. The notches are of great size, and contain the superior and inferior suspensory ligaments — one being above, and the other below, the spinal canal. The arti- cular glenoid cavities receive the condyles of the occipital bone, and are each constructed of a superior and an inferior continuous surface ; the inferior, representing the convex head of other vertebras, is concave ; while the superior, nearly flat, represents the oblique processes. A prominent bony ridge, to which is THE DENTATA. 27 inserted tlie investing or capsular ligament, surrounds the anterior border of the bone. The posterior surface presents a somewhat triangular outline ; its inferior margin is excavated to. receive the odontoid process of the second vertebra, while the superior is thin, and roughened for ligamentous insertion, and, on each side, a broad slightly convex articular surface represents the posterior oblique processes. This surface is bounded externally by a ridge, which gives insertion to the capsular ligament ; and internally it is separated by a similar ridge from the spinal canal. The spinal foramen of the atlas is' very large, in order that the spinal cord may be preserved from injury during the extensive motions which take place between the head and neck. Its floor is divided by a transverse ridge into two portions, the anterior of which is roughened for the attachment of ligaments, the posterior being smooth for the articulation of the odontoid process. Its roof is smooth, and penetrated by two foranaina for the passage of an artery and nerves, and its sides have each an excavation in which a venous sinus is lodged ; a foramen from this excavation opens on the inferior surface of the ala, and transmits a vein from the sinus. The atlas has three articular processes, — two for the occipital condyles, and one for the axis, — all of which form true joints, the atlas being the only vertebra possessing none but true articulations. The Dentata. The Second vertebra is called also the axis, because the head rotates upon it, also vertebra dentata, from a process which, m the corresponding human bone, somewhat resembles a tooth in shape, and is called the odontoid process ; it is situated on the anterior end of the centrum, projecting forwards into the ring of the atlas, and around it the head and atlas rotate. In the horse the under surface of this process is smooth and rounded, and the upper roughened and excavated, for the attachment of the odontoid ligaments ; laterally, it terminates in a broad, oval, somewhat convex surface, which represents the oblique processes, and articulates with the posterior surface of the atlas ; these articular shoulders being bounded by a ridge, to which the capsular ligament is attached. The neural spine of the axis springs from a very strong arch, and is nearly as long as the body, which is longer than that of- 28 OSTEOLOGY. any other true vertebra ; this spine is convex, and consists of lateral halves, united anteriorly into a strong rough crest, but bifurcating posteriorly into ridges, which terminate in the oblique processes. The inferior spine arises from a notch in the inferior part of the odontoid process ; it is broad and rough anteriorly, but contracts into a sharp spine, which terminates in a roughened tubercle posteriorly. The transverse processes, the smallest in the cervical region, are single, and project outwards and backwards ; they are pierced by very small vertebral foramina. The spinal canal is somewhat narrow, and instead of notches, there are two oval foramina anteriorly for the passage of the spinal nerves. The posterior jDarts of the body and arch do not materially differ from those of the other cervical vertebrce. In the horse the atlas and axis do not approximate above the spinal canal, and there is a considerable space between them, the atlo-axoid space, which is covered by soft structures only ; and here the operation of " pithing " is easily performed. The Last Two Segments. The Sixth vertehra has a much shorter body than those anterior to it, and is destitute of an inferior spine. Its trans- verse processes consist of three lateral divisions, and its vertebral foramina, notches and spinal canal are of great size. The Seventh vertehra, or Vertebra prominens, the shortest of the series, is ver}^ strong and has an elevated neural spine, point- ing upwards and forwards, but scarcely the trace of an inferior one. Its oblique processes resemble the .four preceding ; its transverse processes are small, and have usually no vertebral fora- mina, while its notches and spinal canal are larger than in any other of the last six cervical vertebree. On each side of its body, posteriorly, it presents a depression which, with a corre- sponding depression on the first dorsal centrum, forms a cup for the articulation of the first rib. Altogether it closely resembles in character the first dorsal vertebra. DORSAL VERTEBRA. (PL. L F.) These vertebrae, of which there are eighteen or rarely nineteen, always correspond in number with the pairs of ribs, and in the horse form the weight-bearing portion of the column, extending DORSAL VERTEBRiE. 29 over the whole length of the chest. Their bodies, the smallest of the true vertebras, are short, thick, and somewhat semicircular in form, each presenting a middle ridge along its under surface, to which the inferior common ligament is attached. The superior surface of the body, which forms the floor of the spinal canal, is flattened and quadrilateral, presenting longitudinal furrows for the spinal vessels, and often a central tranverse one, partially covered by a bony plate. The anterior extremity presents a slightly convex head, on the superior and lateral aspect of which is a semicircular depression corresponding with another on the posterior extremity of the vertebra in front, so that together they form a cup-shaped cavity for the articulation of a rib, each articu- lating with one-half of the head of the rib. The posterior extremity is concave, to articulate with the contiguous bone, and has on each side an articular depression similar to those on the anterior extremit3\ The tranverse i^rocesses, rising from the sides of the arches, are small ; superiorly and anteriorly they are roughened for muscular attachment, and at its postero -inferior part, each presents a flat, smooth facet which articulates with the tubercle of the next anterior rib. The neural spines, larger than in any other region, vary much in size, shape, and direction, the first twelve being directed back- wards, the next three nearly upright, and the last three forwards ; their length gradually increases to the fifth, which is usually the longest, and then decreases to the fourteenth, which is generally somewhat shorter than those behind it ; the first is small and sharp, and the second, which is abruptly bent backwards, is very strong ; the summits of the next six or seven are flattened, roughened, and expanded laterally, assuming a bifid appearance, giving greater surface for the attachment of muscles and the great suspensory ligament of the head and neck, the ligamentum nuclice. The lateral surfaces are convex and slightly roughened, the anterior borders being thin and serrated, while the posterior, of the higher spines especially, are broad and concave, becoming cleft as they approach the oblique processes. The oblique processes are small, and their facets are more horizontal than in the cervical region, and close together. The pedicles are short and strong, and, with the exception of the anterior four or five, possess notches on their posterior edges only ; backwards, we find these notches become more and more closed in, until posteriorly there are foramina in lieu of notches. so OSTEOLOGY. The arch, and consequently the spinal canal, are small, the laminEe passing almost directly inwards from the pedicles. An ordinary dorsal vertebra has twelve articular surfaces — viz., three anterior and three posterior, as in the cervical, and three at each side ; of the latter, two are for the heads of two ribs, and the third for the tubercle of the anterior rib. The depressions for the heads of the ribs are deepest between the anterior vertebrae, and gradually grow shallower, in the two last becoming continuous with the facet on the transverse process. The eighteenth segment, being attached to but one rib on each side, has eight articulating surfaces only. Viewing the dorsal vertebrae in connection, it is seen that the spines diminish from the ififth backwards, and the vertebras them- selves o-row narrower. The first exhibits some of the characters of a cervical vertebra, and the second has a short body, with transverse and anterior oblique processes formed on the same bony projection, and a neural spine, short, convex anteriorly, and more bent than any other in the vertebral chain. The first thirteen form the skeleton of the withers, and, when well developed, the height of their spines increases the surface for muscular attach- meut, and also affords greater leverage. LUMBAR VERTEBRA. (Pl. I. G.) These form the skeleton of the loins, and are shorter in the horse in proportion to his size, than in other animals. Their number is six usually, sometimes five, in the horse, six in the mule, generally five in the ass, and also, it is said, in the Arab horse. Their bodies, intermediate in length between the cervical and the dorsal, are thick and strong, the three anterior being flattened superiorly and laterally, and possessing a strongly- developed median ridge ; the three posterior ones are convex laterally, and flattened above and below. More motion being required in the loins than in the back, the anterior extremities of the centra of the lumbar vertebrae are more convex, and the posterior extremities more concave than those in the dorsal region. The arches enclose a large semicircular spinal canal, and with one or two exceptions possess both anterior and posterior notches. The neural spines are strong, broad, and flattened laterally ; they incline slightly forwards, are about the same'length THE SACRUM. 31 as the posterior dorsal spine, and have sharp anterior and posterior edges, Avith rough expanded extremities ; they increase slightly in height, and diminish in strength backwards. The Transverse processes, longer than the corresponding pro- cesses in any other region, are broad and flat, with rounded extremities, and extend nearly horizontally fz'om the bodies ; the central are the largest, the first two inclining a little back- wards, and the last three slightly forwards. The last two of these processes articulate with each other by means of facets, and, in advanced age sometimes become united by ossification, the sixth articulating in a similar manner with the sacrum. The oblique processes project farther from the arch than those of the dorsal region ; the articular facets of the anterior ones are concave and directed inwards, while those of the jiosterior are convex and directed outwards. The first four lumbar vertebrce have six, the typical number of articular surfaces, the fifth having in addition one on each posterior border of its transverse processes, and the sixth one on each border, anterior and posterior, of these processes, or ten in all. False Yertebr^. the sacrum. (PL. I. H.) This, the bone of the croup, is a single, somewhat triangular- shaped bone, consisting of five false vertebrse united, in the young animal by articulation, and in the adult by ossification ; it con- tains the continuation of the spinal canal, forms the roof of the pelvis, and has articular surfaces by which the pelvic arches are attached, and in the horse these are the only articular connec- tions between the axial and appendicular skeletons. Its direction varies somewhat according to the breeding of the animal ; in lightly-made, highly-bred, and well-formed animals its long axis is usually placed in a nearly horizontal line, while in horses of coarser breed its coccygeal extremity is often considerably lower than the other, thus giving a drooping appearance to the contour of the croup. It presents for consideration superior and inferior surfaces, two lateral borders, and anterior and posterior extremities. The superior surface is irregularly convex, with the flat-topped spines of its vertebral segments running along its centre, decreas- ing in height, but increasing in breadth as they extend backwards. 32 OSTEOLOGY. In ai, groove at their base, opposite the interspinous spaces, are the four superior sacral foramina, which give exit to the superior branches of the sacral nerves. An irregularly-elevated ridge, external to the grooves, marks the division between the superior and inferior surface of the bone. The inferior oy pelvic surf axe is smooth and rather concave ; at its anterior end is a trans- verse elevation, the sacral promontory, not very pronounced in the horse, and crossing the bone transversely are four slightly-elevated lines, which show the connections between the original segments. Between these lines, and close to the borders on each side are the four large foramina through which pass the inferior branches of the sacral nerves, and at the anterior end two notches, which correspond with similar notches in the last lumbar vertebra, and form the foramina through which the first sacral nerves find their exit. The anterior extremity or base is almost entirely articular ; the central part, oval and convex, articulates with the last lumbar vertebra, and above it is the spinal canal surmounted by the articular processes. The lateral parts are the thick expanded transverse processes which terminate in sharpened extremities, and contain two broad facets for articulation with those on the last lumbar transverse processes. The posterior extremity or apex presents the diminished spinal canal in its centre, with the last spinous process above it, and below the flat surface which articulates with the first bone of the coccyx, while the notches and the sacral cornua are on its sides. The lateral borders, anteriorly, are roughened for attachment to the iliac bones under which they lie, and with which they form the sacro-iliac joint ; posteriorly, they are roughened for the attachment of the sacro-sciatic ligaments, and terminate in small tranverse processes — the sacral cornua. The sacrum has five articular surfaces on its base, one on each side, and one on its apex. Its spinal canal is somewhat triangular in shape, and decreases much in size posteriorly. THE COCCYX. (PL. I. I.) The coccygeal or caudal vertebrce are false vertebrae, varying in number from thirteen to twenty. In form, they are the most rudimentary of all the vertebral segments ; their centra are THE RIBS. S3 oblong, mostly constricted in the centre, and expanded where they articulate with one another : the four or five anterior ones are slightly flattened above, hollowed longitudinally below, and they possess generally incomplete arches and imperfectly-developed processes. The remaming segments consist merely of centra, which diminish in size jDosteriorly. There is, therefore, no complete neural canal in the caudal region, only the first two or three vertebrae being sometimes found with their neural arches complete. THE THORAX. The dorsal vertebrae superiorly, the ribs and their cartilages laterally, and the sternum or breast-bone inferiorly, form the skeleton of a large cavity called the Thorax. THE RIBS. (Pl. I. T. T.) In the horse the ribs usually number eighteen on each side. They extend in a series of arches of varying curvature from the dorsal vertebrae above, towards the sternum and sides of the abdomen below. Their shape, in a great measure, determines the conformation of the thorax ; they protect its contents, and materially aid in its contraction and expansion. To the distal end of each rib an elongated piece of cartilage is attached, and eight of these connect the eight anterior, termed sternal or true ribs, with the sternum ; the ten posterior ribs, having only an indirect sternal attachment, are known as asternal or false ribs. The ribs pass first outwards and backwards, and then in an arched direction downwards, their cartilages inclinino- inwards and forwards. They gradually lengthen from the first to the ninth, after which they progressively shorten ; their curvature increases from the first, which is nearly straight, to the last, which forms a large segment of a comparatively small circle. The greatest breadth is attained in the fifth, sixth, seventh, and eio-hth, which, in their middle portions, exhibit the more especial characters of flat bones. Each rib presents for consideration superior and inferior extremities, and a shaft or body having anterior and posterior borders and external and internal surfaces. D 34 OSTEOLOGY. The superior or 'proximal extremity consists of a head, a neck, and a tubercle. The head, which rests in a cavity in the verte- brae, is separated by a vertical furrow, in which the interarticular ligament is attached, into two convex articular surfaces — one of which is directed forwards and inwards, and the other backwards and inwards. The neck is the constricted iDortion supporting the head; it is strong and roughened for ligamentous attachment, and has a groove for the intercostal nerves and blood-vessels running across it in front. The tubercle is the prominent emi- nence at the posterior part of the neck ; it has a flat, smooth facet, which articulates posteriorly with the transverse j^rocess of a vertebra. External to the tubercle is another eminence, the angle, where the rib is suddenly bent downwards ; the distance between the angle and the head of the rib gradually increases from the third to the last, the first two scarcely possessing angles. In the third and fourth ribs the angles and the tuber- cles are from one to two inches apart, which distance increases, in a well-formed horse, to nearly five inches in the last. In horses possessing well-rounded chests the costal angles are plainly marked and separated from the vertebras, so as to form large costal grooves for the dorsal muscles ; in flat-sided animals they are indistinct and closer to the spinal column, the grooves being consequently narrower. The inferior or distal extremity is expanded and constructed of more elastic bone than the proximal extremity ; it is quite porous, and joined firmly to its cartilage. The anterior border is rough, and excavated along its upper third to give attachment to the intercostal muscles. The p)Osterior border is grooved along its upper third for the intercostal muscles, nerves, and blood- vessels ; in both borders the distal portion is thinner in the anterior than in the posterior ribs. The external surface is convex in every direction ; between the head and the angle it is roughened for muscular attachment, and below this point smooth, excepting in a few places the chief of which, a short distance below the angle, give attachment to muscles. The interned surface, concave from above downwards, and convex from side to side, is smooth, and for the greater part covered by the pleura, the membrane lining the thorax. With the exception of the last, and sometimes the last two on each side, each rib has its cartilage. These cartilages, which contain a large quantity of earthy or bony material, pass obliquely STERNUM. 8 5 forwards and inwards ; they diminish in thickness from before backwards, but increase in length to the eleventh or twelfth, after which they again grow shorter. Those attached to the true ribs are smallest at their proximal ends, becoming expanded before they articulate with the sternum ; those of the false ribs are largest at their proximal ends, and, gradually tapering to fine points below, they pass forwards and downwards, so that, having no inferior articulations, each is overlapped by the succeeding one. The special ribs are the two first and the last four or five. The first is shorter and straighter than the others, with rough surfaces, rounded borders, and no well-defined posterior groove ; its head is irregular in shape, and exceeded in size by the tubercle, and its distal end is flattened and expanded laterally, joining the short thick cartilage, which contains much ossific matter. The second possesses the above-named characters of the first in a less degree. The last four or five are slender ; the articular surfaces of their tubercles and the posterior divisions of their heads are usually continuous ; their curvature is great ; they are broadest immediately behind the tubercle, and their cartilages are remarkably slender and elongated. Each true rib has four articular surfaces, two on the head, one on the tubercle, and one at the distal end. STERNUM. The sternum or breast-bone, a comparatively small and short "bone in the horse, is single in the adult, and placed in the inferior longitudinal line of the body at the antero-inferior part of the thorax. The anterior portion somewhat resembles the keel and cut-water of a boat ; it is elongated and concave above, convex below, with its anterior part flattened laterally, and its posterior part flattened above and below. It is constructed of six, rarely seven, irregularly formed segments or sternehroe, united by cartilage in the young animal, and by partial ossifica- tion in the adult ; complete ossification seldom or never takes place in this bone. Its anterior end is surmounted by the carini- form cartilage, and its posterior extremity prolonged by the ensiform or xiphoid cartilage. Its superior surface is triangular in outline and concave, the superior sternal ligaments traversing its lateral borders. Its 86 OSTEOLOGY. inferior surface is narrow anteriorly and convex, the centre pre- senting a prominent ridge coated with cartilage, materiall}'' increasing the lateral surfaces, which give origin to the pectoral muscles ; the sides are flat and irregular, and present between the segments depressions, in which the cartilages of the true ribs articulate, another depression being entirely formed in the first, and an eighth in the last segment. These depressions are oval in shape, and are nearer to each other as they proceed backwards. The Gariniform or keel-shajjed cartilage presents a convex border looking forwards and upwards, and elevated so as to sur- mount the articular depressions for the first pair of costal cartilages, to which it is attached by ligaments ; laterally it is flattened to increase the surface for muscular attachment ; and its inferior border, prolonged over the first segments of the sternum, terminates in the cartilaginous ridge. The prominent convexity which this cartilage forms may often be plainly distinguished in the living animal. The Xiphoid or Fusiform cartilage is somewhat heart-shaped. The apex being directed downwards and backwards. Its superior surface, broad and cup-shaped, occupies a space bounded by the cartilages of the false ribs, and supports part of the abdominal viscera. Its inferior surface is convex, and roughened for muscular attachment, and its free borders are thin. It affords attachment for muscles, and for a fibrous cord called the linea alba. The bony framework of the thoracic cavity bears some resem- blance to a truncated cone, with its apex or anterior extremity compressed laterally. The anterior aperture is a triangular space, having its apex directed downwards and slightly forwards, formed by the sternum, the first pair of ribs, and the first dorsal vertebra; it gives passage to the oesophagus, trachea, and various important nerves and blood-vessels. The base or posterior aperture is oviil in outline, and slopes obliquely downwards and forwards from the vertebrae ; it is formed by the last dorsal vertebra, the last pair of ribs, the cartilages of the false ribs, and the Xiphoid cartilage, and its boundary gives attachment to the diaphragm, a large muscular curtain which separates the thorax from the abdomen. GENERAL VIEW OF THE- SKULL. 37 The Skull. GENERAL VIEW, The skull, or skeleton of the head, the most anterior part of the horse's skeleton, articulates with the first cervical vertebra, from which it is suspended by its posterior extremity, its anterior extremity being free. Its position varies with the attitude of the animal; but in our descriptions we shall allude to it as if it were placed in a horizontal position, as in Fig. 12. In the young animal the skull is comijosed of a number of bones, all of which, with the exception of the lower jaw, the teeth, the bones of the tongue, and ossicles of the ear, become united by ossification in the adult; excluding the teeth and the internal bones of the ear, there are thirty-eight bones in the skull — six single ones, and the rest pairs. The skull is divisible into two parts — viz., the cranium or calvoriwin, and the face. The former is a cavity situ- ated in the supero-posterior region of the skull, and continuous with the spinal canal ; it contains the brain and its appendages, and in the horse is comparatively a small cavity, occupying about one-fifth of the skull. The re- maining bones of the skull collectively form the face, hence the whole struc- ture is composed of cranial and facial bones. We shall first endeavour to give a general idea of the articulated skull, and afterwards describe separately the bones which com- jDose it. The bones of the head are in early life united to each other by means of sutures, or interposed layers of fibrous material, and after union by o.ssification, a well-marked line usually indicates Fig. 10. Skull of the Horse seen from above ; I. Occipital bone : II. Parietal bone ; III. Squamosal bone; IV. Frontal bone ; V. Nasal bone ; VI. Lachrymal bone ; VII. Malar bone ; VIII. Sup- erior Maxilla ; IX. Premaxilla. a, Occipital crest ; h, Parietal crest ; c, Orbital process ; 0. Supraorbital for- amen. .38 OSTEOLOGY. the position of the late suture. One of the principal sutures of the skull is the longitudinal, which extends in the median line from the poll to the nasal peak, and marks the division of the skull into two lateral halves. In shape the skull resembles a quadrangular pyramid, and contains various cavities or chambers. Supposing it to be placed in the horizontal position resting on the lower jaw, we can more easily give a general description of the most important external features if we divide it into the following regions : — Superior, Inferior, Lateral, Anterior, and Posterior. The Superior region is a surface formed by three pairs of bones, called the parietal, frontal, and nasal, each bone being joined to its fellow by a part of the longitudinal suture. The parietal bones are the hindermost of the three, and are convex, forming part of the roof of the cranium or brain cavity, while the frontal or middle pair are flatter, and very broad above the level of the orbits, the region of the forehead. The nasal bones together form a semi-cylinder, and gradually diminish in breadth anteriorly, finally forming the projecting nasal peak. The prominent trans- verse ridge bounding this region posteriorly is the occipital crest. The Inferior region presents a very irregular surface, bounded below by the inferior maxilla or lower jaw, a bone whose two segments are firmly united anteriorly, but diverge backwards somewhat in the form of a letter V, each terminating superiorly in a convex articular surface, the maxillary condyle, before which is the prominent coronoid process, the lever of the lower jaw. The diverging parts or rami of the jaw include a space, appro- priately called the maxillary space. We find in the united or anterior portion of this bone the inferior incisor and, in the male, the canine teeth, and in the rami the inferior molars or grinders; the space between the molar and front teeth is called the diastema or interdental space, and is always large in herbivorous animals. If we remove the inferior maxilla, we notice the following objects : — Anteriorly the premaxilla, bearing the upper incisor and partly the canine teeth, and just behind the incisors, in the median line, a small round aperture, the foramen incisivum, while the interdental space and molar teeth are similar to those in the lower jaw. The flattened surface extending from the incisors backwards between the molars is the bony palate, formed chiefly by the superior maxilla, and bounded posteriorly by the 'palatine GENERAL VIEW OF THE SKULL. 39 arch, which is semi-elliptical in form, and marks the entrance to a large cavity above called the nasal chamber ; this cavity is, in the fresh state, divided into right and left compartments or fossa' by a cartilaginous septum. Between the posterior molars and the palatine arch are the two palatine foramina. Behind, and bounded by the palatine arch, are the entrances to the nasal chamber, right and left, called the posterior nares, and the slender median bone stretch- ing from behind forwards in the cavity is the vomer ; it indicates the division of the chamber into right and left fosssd. Continuous with the vomer we find an irregular column of bono reaching to the back of the skull ; this column consists of three j^ieces, the pre-sphenoid anteriorly, then the basi-sphenoid, and lastly the basi- occipital bone. These bones arc respectively parts of the sphenoid and occipital bones, and they, together with the vomer, are regarded as the centra of the cranial vertehrcu ; and the ossified suture between the last two bones is usually marked by a roughened ridge. On the posterior edges of the pala- tine arch are two small sharp projec- tions, the ends of the pterygoid bones, and behind them the rough palatine ridges, the posterior edges of which are formed by the pterygoid processes of the sphenoid bone ; outside the base of each of these processes we have the posterior aperture of the siibsphenoidal or pterygoid foramen, which gives passage to an important artery. There are two large, rounded, and may be roughened promineiices, the alveolar tuberosities, immediately behind the last molar teeth, and between them and the palatine ridges and pterygoid bones are the smooth staphyline grooves. Inferior aspect of Horse's skull, the mandible being removed. Above the line A is the posterior regiou or liase, between A and B the middle, and below C the anterior or nasal region. a, Occipital condyle ; b, Foramen mag- num ; c, Styloid process ; d, Temporal articular surface ; e, Basi-occipital, and/, IJasi-splienoid bones ; cj. Petrosal bone ; 7), Ali-sphenoid boue ; i. Tem- poral bone ; h. Condyloid foi-amen ; k' Condyloid notch ; I, Foramen lacerum basis cranii ; vi , Pterygoid foramen ; n, Palatine suture ; o. Palatine fora- men ; p, Molar teeth ; ). Appendiculak Skeleton. pectoral limb. V, Scapula, 2 ; w, Humerus, 2 ; x, Radius, 2 ; y, Ulna, 2. Carpus : — s, Trapezium, 2 ; a', Cunei- form, 2 ; h', Lunar, 2 ; c', Scaphoid, 2 ; (/', Unciform, 2 ; c'. Magnum, 2 ; /', Trapezoid, 2 ; 3', Pisiform, 2. Metacarpus:—/)', Bones, 8 ; Large sesamoids, 16. Digit :— i', Proximal phalanges, S ; k', Median phalanges, S ; /', Distal phalanges, 8 ; I", Small sesamoids, S. PELVIC LIME. Pelvis. — Os Innominatuni : — s, Ilium, 2 ; t. Pubis, 2 ; it, Ischium, 2. The Limb.—)ii', Femur, 2 ; n', Patella, 2 ; 0', Tibia, 2 : p', Fibula, 2. Tarsus:— 7', Calcaneum, 3 ; r', Astragalus, 2 ; s', Cuboid, 2 ; t', Cuneiformo magnum, 2 ; «', Ecto-cuneiformo, 2; v' v:', Meso- and Endo-cuneiformes, 4. Metatarsus : — Large bones, 8 ; .)', Small bones, 2 ; 3/', Large sesamoids, 16. Digit : — Proximal phalanges, S ; Median phalanges, S ; Distal phalanges, S ; Small sesamoids, 8. YlSCEP.AL SKELETdX. None. The separate bones of the Skeleton of the Hog, as here considered, are 324. OMNIVORA VEllTEBE.E. 107 springs the tu.sk ; the alveoli for the molar teeth, usually seven in number, gradually increase in size, from the anterior one, which is very small, to the last, largely developed and strong. The maxillary sinus is small, projecting into the malar bone ; the palatine foramen opens on the palatine plate of the maxilla, before the palatine bone. The prcmaxiUa is large and strong ; it is not joined at the symphysis, and consequently forms no foramen incisivum ; its external process is very long, and articu- lates largely with the nasal bone ; there are three alveoli on each side for the incisor teeth. Part of the septum of the nose becomes ossified, forming the prenasal or snout bone (os rostri). The anterior nares are small arid round. The palatine bones form a large portion of the bony palate ;_ their orbital portion is very small. The palatine ridge is replaced by a tuberosity, •witli which the pterygoid process of the sphenoid bone articulates externally, and the pterygoid bone internally, and the union of these three parts results in a large trifid tubercle. The ttirbinals are longer and less fragile than in the horse. The inferior maxilla is very strong, having no Avell-defined heck, and small interdental spaces ; the coronoid process is short, but strong, and the condyles, somewhat nodular, are compressed laterally. The .dental canal terminates anteriorly by numerous small mental foramina ; and the alveoli for the molars are seven in nnmlier. Posteriorly this bone bears a certain resemblance to the corresponding human bone. The symphysis becomes early ossified in thi.< animal. ' The OS hyoides has a large body, but no appendix. The cornicula are short, while the cornua are thin, twisted somewhat like the letter S, and united to the temporal bones by elastic ligaments. ■ • KiG. 30. Longitudinal Section of a Hog's Skull. 1, Os rostri; 2, Maxillary Tur- binal; 3, Frontal Turbiual ; 4, Large Ethmoidal volute ; 5, Occipital Styloid process ; 6 C 6", Frontal Sinus ; 7, JS'asal chamber ; S 8', Cranial cavity ; 9, Auditory Imlla. VERTEBRA. The true vertebral column consists of 28 vertebra?. — 7 cervical, 14 dorsal, and ' 7 lumbar. The cervical vertebne are very short, convex below, and without inferior sj^ines ; the transverse processes are bifid, and, excepting the last, the posterior ones are large and overlapping. The articular processes are strong, the anterior being pierced liy a foramen entering the spinal canal. The transverse processes are small and generally pierced 1)V vertebral foramina. The atlas is strong, rough, and irregular, presenting a large tuberosity on its superior surface ; the wings are strong, particularly at their posterior borders ; 108 COMPAEATIVE OSTEOLOGY. the posterior foramen is inconstant, usually opening on tlie posterior edge. The axis is broad anteriorly, with a small odontoid process, and extended articular surfaces ; small transverse processes are pierced by large vertebral foramina ; the neural spine is tall and thin. The five posterior segments have large neural spines, the proviiimis especially so. There are usually 14 dorsal vertebrae, -vvith short centra, increasing in length from before backwards. The neural spines are broad, decreasing gradually from the first backwards ; the first is nearly upright, the rest slope backwards, excepting the last two or three, which are slightly inclined forwards. Two foramina enter the neural canal on each side from the base of the transverse process. Tiie lumbar vertebrte number 6, sometimes 7 ; their centra are longer than in any other region, resembling those of the ruminant. The neural spines are strong-pointed, and bifid at the posterior borders, the diverging laminte being continuous with the posterior oblique processes ; the transverse processes are long, nearly horizontal, and without articular surfaces ; the base of each is pierced by a small foramen leading into the neural canal. The sacrum is usually made up of 4 segments ; the neural spines are very rudimentary, in fact the laminse scarcely coalesce, leaving the neural canal partly open ; the articular processes are large and overlap those of the last lumbar vertebra. The coccygeal bones vary in number, being usually from 18 to 23, and the anterior ones have articular processes. Generally there are 14 pairs of ribs — 7 true and 7 false. They are thin and flat, the last three having their tubercles and the posterior part of their heads united. The second, third, fourth, and fifth have true articulations distally. The sternum is very long, and consists usually of 7 segments, the manubrium remaining separate as in the ox. The cariniform cartilage forms a long eminence terminating in a blunt point. Appendicular Skeleton. pectoral limb. The scapula is large, without an acromion process ; it has a prominent spine, bearing in its centre a large tubercle, wliich inclines backwards over the postea-spinatus fossa. The humerus is short, and compressed laterally, the head inclining backwards ; the bicipital groove is single, and the external trochanter is very large, with its summit curved over the bicipital groove, as in the ox ; the external tuberosity is small, the internal one being replaced by muscular imprints. The radius is small, and much curved ; while the ulna is a true long bone, having a medullary canal, and extending to the carpus, with which it articulates. The radius and ulna are united by ligaments, which rarely become ossified. The ulna is flattened from side to side, and lies on the posterior face of the radius, in close connection, except that there exists a radio-ulnar arch. The olecranon is prominent. The carpus consists of 8 bones, 4 in the upper and 4 in the lower row. The bones of the upper row are similar to those of the horse, the cuneiform articulating above with the ulna and a small portion of the radius, the lunar and scaphoid bones with the radius, but the trapezium with neither of the bones of the forearm. The bones of the lower row decrease from without inwards, and are the unciform, articulating with the two external, the os magnum with the large internal, and the trapezoid with the small internal metacarpal bones ; the pisiform, ter- CARNIVORA THE SKULL. 109 minating bluntly, does not articulate with the metacarpus, the pollex or thiimb being absent. The metacarpal bones are 4 in number. The middle pair are large, the side pair small ; the large ones articulate with each other, and with their relative small ones superiorly. Each terminates distally, as the single one of the horse, but the middle jDair are the sole weight-carriers, for the lateral ones do not rest upon the ground. In each of the four digits there are three jihalanges, with their accessory sesamoid and navicular bones. PELVIS AND PELVIC LIMB. The OS innominatum presents the same general characters as that of the ruminant ; it is, however, distinguished by the form of the ilium, which is very convex on its anterior border and crest, and by the absence of the protuberance on the inferior symphysis. The femur differs little from that of the ox, except in its more contracted neck, which is about on a level with the trochanter major ; the trochanter minor is wanting. The tibia resembles that of the ruminant ; its anterior tuberosity is notched, and the external malleolus is supplied by the distal end of the fibula. The Jibula extends the whole length of the tibia, articulating with it at both extremities, and distally with the astragalus and calcaneum. The tarsus presents no important deviation from the typical joint, except that the cuneiforme medium is divided, hence there are in the lower row the ecto, meso, and endo-cuneiform bones ; the distal articular surface of the astragalus articulates partly with the cuboid bone. The metatarsus and phalanges closely resemble those of the anterior limb. There is a very rudimentary fifth metatarsal bone on the inside, a vestige probably of the hallux or great toe. CAENIVORA. In this order our descriptions allude mostly to the Dog, that animal being an excellent type of the order, and one easily obtained. Axial Skeleton. the skull. The occipital bone of the Dog is very strong, and triangular behind, termina- ting in a sharp pointed crest. The tuberosity is not well marked ; tlie styloid processes are short, and the condyles large. Tlie foramen lacerum basis cranii is divided into two portions by the auditory bulla, which is large and rounded ; the basilar process is long and thick. The Wormian bone is united to the occipital ; the ossific tentorium is large. The parietal bones are very convex, in some breeds meeting in a sharp ridge, continuous with the occipital crest. The frontal bones are triangular, and present along their middle a hollow, more or less marked. The orbital process is simply a peak, the arch being completed by a ligament ; there is no supraorbital foramen ; the frontal bone articulates with the superior maxilla. The temporals are not divisible into distinct pieces, as in the horse ; the zygomatic processes are large, and project very much, forming capacious temporal fossaj, and having glenoid cavities which are elongated transversely, for the condyles of the inferior maxilla. 110 COMPARATIVE OSTEOLOGY. I'IG. 31. SKELETON OF THE DOG (CARNIVOKA). Axial Skeleton. the skull. Froutal, 2 ; 1:, Temporal, Sphenoid, 1 ; Malar, 2 ; h, Maxilla, 2 ; rj, Premaxilla, 2 ; A'omer, 1 ; Turbiuals, 4 ; Hyoid series, 9. Cranial Bones.— a, Occipital, 1 ; h, Parietal, 2 ; Etlimoid, 2 ; Auditory ossicles, 8. Facial Bones.— f, Nasal, 2 ; e, Lachrymal, 2 ; d, ■i, Inferior ]Ma.\ilia, 2 ; Palatine, 2 ; Pterygoid, 2 ; Teeth:— Incisors, 12; Canines, 4; Molars, 26. The Trunk.— I I, Cervical vertebrae, 7 ; in in, Dorsal vertebra;, 13 ; n n, Lumbar vertebrae, 7 : o. Sacrum (three segments), 1 ; p j). Coccygeal vertebrae (variable), 20 ; t t, Kibs, 26 ; " Sternum (eight steruebra^), 1 ; -jf Costal cartilages. Appendicular Skeleton, pectoral limb. u, Scapula, 2 ; v, Humerus, 2 ; w, Radius, 2 ; x, Ulna. Carpus -.—y. Trapezium, 2 ; :, Cunei- form, 2 ; a', Scaphoid, 2 ; h', Unciform, 2 ; c'. Magnum, 2 ; d', Trapezoid, 2 ; e', Pisiform, 2 ; Meta- carpal bones, 10; h', Anterior sesamoids, 10; (/', Posterior sesamoids, 20. Digit:— i', Proximal phalanges, 10 ; k', Median phalanges, 8 ; I', Distal phalanges, 10 ; Small sesamoids wanting. PELVIC LIMP.. Pelvis.— Os Innominatum :— g, Ilium, 2 ; r, Pubis, 2 ; s, Ischium, 2. Tlie Limb.—m', Femur, 2 ; o', Fabellse, 4 ; n', Patella, 2 ; q, Tibia, 2 ; p', Tibial sesamoid, 2 ; r'. Fibula, 2. Tarsus :— s', Calcaueum, 2 ; f. Astragalus, 2 ; u', Cuboid, 2 ; v', Superior cuneiform, 2 ; ■J, Ecto-c'uneiforme, 2 ; x', Meso-cuneiforme, 2 ; y', Eudo-cuueiforme, 2. Metatarsus :— Large bones, 8 ;' s' Small bones, 2 ; Anterior sesamoids, 8 ; Posterior sesamoids, 16. Digit :— Proximal phalanges, 8 '; Median phalanges, 8 ; Distal phalanges, 8 ; Small sesamoids wanting. Visceral Skeleton. Os Penis, 1 ; Rudimentary clavicle (inconstant), 2. The bones of the Carnivora Skeleton, thus considered, are 345. CARNIVORA VERTEBRAE. Ill The external auditory meatus and auditory bulla are large, the sense of hearing in carnivora being very acute ; there are only diminutive hyoid, and styloid processes. There are two canals, of which there exists no trace in other domestic animals — viz., the carotid, which traverses the mastoid portion to join the venous canal between the basilar process and temporal ; and another which pierces the petrous portion at the upper part of the carotid canal, and gives passage to the fifth pair of nerves. The sphenoid bone resembles that of man ; its posterior part is short, and presents two large wings, which mount to the temporal fossae, the anterior j^art being straight, and prolonged by small wings. The pterygoid processes are vei'v short, the pituitary fossa limited by the clinoid processes. The ethmoid bone presents, very deep fossae and well- developed volutes. The nasal bones are small, narrow, but w^ider in front, presenting a semi- circular concavity, instead of a peak. The suiKrior maxilla is short, but strong, differing, as all the facial bones do, with the breed; it articulates by a long process with the frontal, forms partly the socket for the canine tooth, and is spineless. The 2yi'emaxilla is short, and presents a small foramen incisivum, which is often wanting in the cat, alveoli for the incisors, and an oval incisive opening. The lachrymal is small, and in the cat confined to the orbital cavity. The malar bone articulates in the usual manner, while its zygomatic process is large, and curved outwards, and its summit bifid, the arclies being formed very similarly to those in the omnivora. The 'palatine bones form about a third of the palate ; they do not assist in the formation of the sphenoidal, but furnish a small portion of the maxillary sinuses. The pterygoids are strong and quadrilateral. Tlie turhinals extend to the anterior nares ; they are remark- able for the number of their convolutions, but do not assist in the formation of the frontal and maxillary sinuses. The inferior maxilla, is strong, its rami broad and large, presenting a deep depression on the postero-external aspect, in which is inserted the masseter muscle. The condyles are ovoid transversely, and the coronoid processes long and broad, the sigmoid notch very deep, the labial foramen double or triple, and there are no interdental spaces. There is a tubercle at the angle for the insertion of the stylo-maxillaris muscle. The symj^hysis rarely becomes ossified. The hyoid bone is triple — i.e., its three elements do not unite. It has two cornua and four cornicula, the cornua being united to the temporal bones by elastic ligaments. VERTEBRA. The true vertebral column consists of 27 segments — 7 cervical, 13 dorsal, and 7 lumbar. The cervical vertebrae in carnivora are proportionally as large as those of the horse. The atlas possesses large and expanded alpe ; a groove or notch takes the place of the anterior foramen, and the posterior foramen is present ; the posterior articulation, instead of being flat, lias glenoid cavities, the surface inside the ring, for the odontoid process, being continuous with them. The axis is long, its neural spine single and prominent, overlapping and sometimes articulating with the atlas, thereby completely occluding the atlo-axoid space ; the odontoid process is long, convex on all its surfaces, pointed anteriorly, and more nearly resembles that of man than does that of any other domestic animal ; it serves as a pivot, on which the head and atlas freely 112 COMPARATIVE OSTEOLOGY. rotate ; laterally are the condyles articulating witli the glenoid cavities of the atlas. The remaining cervical vertebrae diminish as they proceed backwards, and in most cases have large neural spines, \n hich gradually increase from the third backwards. The dorsal vertehrce, 13 in number, vary with the breed ; the pedicles contain large posterior notches in place of foramina. The spinous processes are strong ; the four or five anterior ones are equal in height, while the succeeding ones decrease, and incline backwards. There are 7, sometimes 6, strong lumbar vertebrcey the bodies are compressed from above downwards, the posterior notches are large, and the neural spines inclined forwards. The transverse processes slope downwards and forwards ; the anterior articular processes expand laterally, receiving between them the posterior ones of the contiguous vertebra. These vertebrce possess anapophyses diminishing backwards. The sacrum usually consists of 3 segments, and is frequently as broad behind as in front ; the first segment resembles the last lumbar. The sacral spine is thin, and serrated superiorly ; the transverse processes are bifid, consisting of upper and lower portions, the upper resembling those of the lumbar region. The coccygeal bones vary from 16 to 21, the anterior ones having the characters of true vertebrae. There are usually 13 pairs of ribs, 9 true and 4 false ; their size and curvature vary much, but they are iisually somewhat thick and straight. The sternum consists of 8 elongated cylindrical sternebr^, which resemble somewhat in form the terminal coccygeal bones of the horse. Appendicular Skeleton. pectoral limb. The scapula is very large, the spine being almost central, and terminating inferiorly in an acromion process, which descends close to the glenoid cavity, where it curves backwards. The cartilage of prolongation is wanting. The hibmcrus is long, slender, considerably curved, but not much twisted ; the external trochanter is well developed, tlie internal almost wanting ; the bicipital groove is single. The condyles are large, and the coronoid and intercondyloid fossre united, but not always, by a canal which penetrates the bone. In the Felidce there is a supracondyloid foramen, situated above the internal condyle, between the humeral shaft and an outer plate of bone. The radius and ulna are about equal in volume, the ulna, if anything, being the larger ; these bones articulate Avith each other solely by their extremities, above, by an articular concave facet on the ulna, and a convex one on the radius ; below, by a concaA-e facet on the radius and a convex one on the ulna ; the two, as it were, cross each other, the upper extremity of the ulna articulating behind and to the inner side, the lower extremity to the outer side. The bones of the carpus are 7.' The upper are the scaphoid and hmar tonitcd, the cuneiform, and trapezium ; the remainder correspond mostly with those of the hog. There are 5 metacarpal bones, 4 large and 1 small. The digits of the former, homologues of the four fingers of man, have three phalanges each, and two sesamoids, the third sesamoid bone being replaced by a ridge on the third phalanx. The fifth and most internal digit has only two phalanges, the median CAKNIYORA PELVIS AND PELVIC LIMB. 11 phalanx being wanting ; it corresponds to the human pollex or thumb. Between each metacarpal bone and its proximal plialanx we have anteriorly a very small sesamoid bone. PELVIS AND PELVIC LIMB. The pelvic cavity is generally long and narrow, but the ossa innominata are very strong ; the iliac spines and crest present a continuous thick rounded ridge. The ischium is also thick and strong, the ischiatic spine and tuberosity becoming one tubercle. The cotyloid cavity is surrounded by a prominent border, slightly notched within. The femur is straight and long, presenting a prominent neck, and a muscular line posteriorly, eqiiivalent to the linea as])era of man. The supracondyloid fossa is represented by a small tubercle. Above each condyle is a small facet, articulating with a sesamoid bone ; these two bones are called the fabeUce, or gastrocnemic sesamoids. The tibia and fibula are long, and united in the inferior half of their middle by ligaments, at either extremity by articulation ; the fibula also articulates Avith the astragalus, thus supplying the external malleolus to the tibia. There is a small sesamoid bone at the external part of the head of the tibia. HE IV" Fig. 32. A, Hand or Anterior Foot of the Dog ; B, That of the Hog ; C, That of the Elk ; D, That of the Ox. I. Pollex ; II. Index ; III. Medius ; I V, Annulus ; V. Minimus. The tarsals consists of 7 bones, as in the hog — viz., the calcaneum, astragalus, cuboid, and four cuneiforms, a superior one corresponding to tlie magnum of the horse, and three in a row below it, the ecto, meso, and endo-cuneiforms. The astralagus presents distally a distinct head, separated by a neck, which articulates with the cuneiforme magnum. The metatarsal bones are 4 large and 1 rudimentary, the large ones each teiminating in three phalanges, with their accessory sesamoids, as in the anterior limb ; the fifth, or small rudimentary metatarsal, homologous with the I 114 COMPARATIVE OSTEOLOGY. hallux of man, is very generally only a ligamentous cord, in wliicli is found a short bone, which represents a phalanx. Fig. 33. FiCx. 34. Clavicle of a Dog— enlarged one-h.alf. Clavicle of a Cat-natural size. VISCERAL SKELETON. In carnivora, generally speaking, there is a clavicle, but it is incomplete, tind is found embedded in the soft structures between the sternum and shoulder. In the dog it is often represented by a piece of ligamentous tissue, and when it does exist as a bone, it is very small and somewhat triangular in shape. The Felidee or cat tribe possess a clavicle Avhich, to a certain extent, resembles in shape that of the human subject, being elongated, rounded, and slightly curved. Occasionally this bone in the cat is continued by ligaments, which unite it both to the sternum and to the acromion process. Os Penis. This is a single bone very generally found in the penis of the carnivora, and always in the dog ; in the cat it is said to be less persistent, and when present much smaller, li is a thin piece of bone hollowed to form a longitudinal Fig. 35. Os Penis of a Dog, half the size of that of a large animal. a a, Inferior groove ; V, Anterior end ; c, Posterior end. groove, in which the iiretha lies ; the groove ceases anteriorly, and at this extremity the bone becomes flat and pointed. Both extremities are prolonged by cartilages. RODEXTIA. This large order we have already mentioned as being characterised by its peculiar dentition. One representative of the order is the common Rabbit, which belongs to the family Leporida). Axial Skeleton. There are 12 dorsal, 7 lumbar, and 4 sacral vertebrte. The wing of the atlas presents no foramina externally, but there is a very large notch in its anterior border, inside which is the cerebro-spinal foramen. As in the carnivora, there is no atlo-axoid space. The centra of the cervical vcrtebnc are short, broad, and strong ; while those of the dorsal region gradually increase in length backwards. The lumbar vertebra; are largely developed. AVES. 115 their transverse processes, long and slender, being directed downwards and forwards ; the articular processes are almost as prominent as the neural spines, the prominent portions being termed the mammillary processes (meta- pophyses), and they may be traced anteriorly into the dorsal region ; they give attachment to portions of the longissimus dorsi muscle. The anterior costal tubercles, prolonged and sharpened, likewise afford attachment to that muscle. The sternebrce are five in number, the presternum being very long and cariniform in shape. In the skull we note the unusual length of the zygomatic process of the malar bone, and absence of a frontal arch, which is represented by a short bifid process. The optic foramina unite to form a single passage leading from one orbital fossa to the other. The diastema and incisive openings are both very laro-e and laterally the superior maxilla is incompletely ossified, giving an irregular cribrated appearance to the bone ; the bony palate is exceedingly short. The auditory bulla and external meatus are well marked. The long axis of the maxillary condyle is placed longitudinally, and the coronoid 2^i'ocess is very small and far below the level of the condyle, whilfe at the angle of the jaw there is a prominent roughened ridge or spine. There are no canine teeth, and two chisel-shaped incisors exist in each jaw ; in the upper jaw of the rabbit and hare there are also two very small incisors placed immediately behind the large ones. Appendicular Skeleton. The scapula has a very large acromion process which projects backwards, arching over the postea-spinatus fossa. There is a small clavicle, but it is incomplete. The coronoid and condyloid foss£e of the humerus are connected by a foramen. The ulna is complete, reaching to the carpus, but there is no motion between it and the radius, and the extremitj^ is therefore prone. There are five digits, one of which represents the pollex or thumb. The velvis is broad and shallow, the ischial arch deep, and the obturator foramen larcfe. The femur has, like that of the horse, a third or minor trochanter ; also two well-marked fabellas. The tibia and fibula are anchylosed, the former bone being very long. The astragalus resembles that of the carnivora. There are five digits, including the hallux. AVES. The scope of the present work will allow only very brief treatment of this part of the subject. We shall, therefore, merely name a few of those features in which the skeleton of the bird diflers in a marlced manner from the mammalian type. The vertebrae vary greatly in number, the cervical in some classes number- ing over 20, and never less than 8. Small cervical ribs exist in the young animal, which in age may become anchylosed to the vertebrae, and in the dorsal region osseous splints unite the successive transverse processes. On the posterior edge of each rib, except the first and last,, is a process called the pro- cessus uncinatus, which overlaps the succeeding rib. The sternum is a single 116 COMPARATIVE OfeTEOLOGY. Fig. Skeleton of a Bird, a, Radius and Ulna ; b, Dorsal vertebrfE ; c, Sacrum and Pelvis ; g, Ploughshare bone ; h, Tibia; i, Metatarsus ; d, Furculum; e, Carina of the Sternum ; /, Distal phalanx of pectoral limb. Sternum of a Bird. A, Lateral aspect ; B, Inferior aspect ; r, Eostrum ; c.p. Costal process ; pl.o, Pleurosteon ; c, Carina ; m.x, Middle Xiphoid process. AVES. 117 Dorsal. Lumbo-Sacral. Coccygeal, bone presenting a very large central process posteriorly, tlie central xiphoid process (lophosteon), outside which is a large bifurcated process (metosteon), the two projections of which are called the median and external xiphoid processes, and antero-laterally is the ridge {plmrosteon), which gives attachment to the ribs. The inferior edge of the central ridge is called the carina; often a small median spine exists anteriorly, the rostrum or presternum. The following Table shows the number of vertebral segments usually foi;nd in domesticated birds : — Cervical. Pigeon, ... 12 Fowl, ... 14 Duck, ... 15 ' ( Goose, ... 18 The costal cartilages are ossified, and thus birds are said to possess sternal and vertebral ribs. Some of the lumbar and coccygeal vertebrae become anchylosed, and assist in forming the sacrum j it is not indeed easy to define the exact points of demarcation between the lumbar, sacral, and coccygeal regions. The coccygeal bones terminate in an expanded segment, termed the Rasores, . jSTatatores, Skull of px, Premaxilla ; Fig. 3S. fowl. A, Inferior aspect, the mandible being removed Superior maxilla ; p, , Lateral aspect ; Palatine bone ; v, Vomer ; j, Jugal bone ; qj, Quadrato-jugal bone ; I, Lachrymal ; me. Median ethmoid ; /, Frontal ; pf, Poat-froutal process ; p, Parietal ; x>t, Pterygoid ; q, Os quadratum ; sq, Squamosal ; eti, Process before the Eustachian aperture ; 6o, Basi-occipital, and so, Supra-occipital bones ; ar, Articular, a, Surangular, and d, Dentary portion of the Mandible. ploughshare bone. In the skull we have to note chiefly the absence of teeth, tlie existence of only one occipital condyle, and the articulation of the man- dible or lower jaw, which does not articulate directly with the skull above, but there is interposed the quadrate bone, which, when the lower jaw is depressed, acts on a process, the quadrato-jugal bone, connecting it with the maxilla, and so simultaneously raises the upper jaw, there being usually vslight vertical motion between the latter and the cranium. 118 COMPARATIVE OSTEOLOGY. The 2)Scto7ril arch consists of tliree parts — the scapula, clavicle, and coracoid bone. The scapula i? sword-shaped, and placed nearly horizontally ; the coracoid bone, the strongest of the three, is almost perpendicular, and firmly attached to the sternum below, affording a strong basis for the bones of the wing to move upon ; it helps to form the glenoid cavity for the humerus. The clavicles project downwards and slightly forwards, arching inwards, and generally becoming united below to form a flattened j)late, the hypodeidcum ; the united clavicles are termed i\\Q furcuhLm, familiarly known as the "merry- thought." The hypocleideum is usually joined by a ligament to the sternum below ; in some classes of birds it is absent ; in some the clavicles are not united ; in some again they are united by ossification to the sternum. The ^dna is larger and stronger than the radius; the carpus consists of two bones, the metacarpus of three, one of which is a rudimentary pollex. There are two digits, one of which has one, the other two or three phalanges. The pelvis is expanded and shield- like, and consists of the ilium, ischium, and pubis ; but there is no inferior symphysis, and, therefore, no tnte pelvic cavity. The pubis is styliform, and directed backwards and inwards ; in the ostrich alone it articu- lates with its fellow. The femur is short, the tibia long, and anchylosed with Fig. 39. Pectoral arch of a Bird, sc, Scapula ; co, cora- coid bone ; /, Clavicles, tenninating below in the hypocleideum ; gl. Glenoid cavity. Fig. 40. Pelvis of a Bird. A, Superior; B, Lateral aspect; sm, Sacrum; II, Ilium; /.<, Ischium; Ai Acetabulum. AVES. 119 the fibula, which is small. The tarsus is early fused with the metatarsus, the latter consisting generally of one long bone. The digits vary in number ; the domesticated birds usually have three anteriorly and the hallux postero-inter- nally ; the outermost has five phalanges, the next four, the next three, while the hallux has only two. The S20tir, a horny projection from the metatarsus, is sometimes counted as a digit. The bone tissue of birds is exceedingly compact and hard, and white in colour ; and some of the bones are pneumatic, or contain air instead of marrow ; notably these are the bones of the skull, the sternum^ and the proximal bones of the limbs. There is great variety in the amount of pneumaticity possessed by the skeleton in different species, but it is not necessarily guided by the flying power of the animal. CHAPTER II. ARTHROLOGY. The several bones which form the skeleton are united by means of certain soft structures, forming a series of artic illations or joints, the study of which is termed Arthrology or Syndesmology. Before considering the different forms of joints, it will be advis- able to describe briefly the various tissues, other than bone, which enter into and contribute towards their formation. These are chiefly cartilage, connective and elastic tissues, and fat. lu health, one bone never comes directly in contact with another, cartilage or fibrous tissue being always interposed ; an exception to this exists in the adult skull, most of the bones of which become firmly united by ossification of the interposed soft material. CARTILAGE. Cartilage, known also by the familiar name of gristle, is a firm, bluish-white, elastic animal substance, somewhat translucent, resilient, and flexible, possessing great cohesive power. That which forms the original basis of the bony framework is termed temporary, and that which persists in the adult, permanent cartilage ; the former disappears as it is replaced by bone, but the latter, of which alone we have to treat here, never under normal circumstances becomes ossified. Cartilage consists of corpuscles or cells, usually imbedded in an intercellular substance or matrix. The cells, which are contained in lacunae in the matrix, are oval, round, or fusiform, and nucleated, the nuclei, which aj^pear under the microscope as small spots, containing still smaller objects called nucleoli. Cartilage when boiled yields chondrine, a substance varying slightly from gelatine. There are three varieties of the permanent kind — hyaline, fihro, and cellular cartilage. In the first, the matrix is homogen- eous, or void of definite structure, appearing slightly granular under 120 CAIU'ILAGE. 121 the microscope. Fibro-cartilage is characterised by a matrix of librous tissue ; while the cellular variety consists of an aggrega- tion of cells without a matrix. Hyaline cartilage is distinguished by the following names, according to the purpose it serves : — Articular, when it encrusts the articular surfaces of bones, helping to form joints by supply- ing a smooth elastic cushion, which diminishes both concussion and friction ; Costal, when it supplies elastic prolongations (hgemapophyses) to the ribs, connecting them distally with the sternum; Memhraniform, when it appears as thin plates, form- ing permanently open tubes — the trachea or wind-pipe is com- posed of this kind of cartilage. In articular or encrusting cartilage the matrix is abundant, and the cells vary in form, those near the surface being flatter and more numerous. It is a ,-, always thickest in the young, .^• becoming thinner as the sub- ,.-'^" jacent ossification proceeds. It (/ T ' > cJ is thickest in the centre of convexities, thinnest in the centre of cavities. In tlie adult it is non- vascular, being nour- ■'•' ished by a vascular zone in ' < ", ~~--'.:i3-- the synovial membrane, called : the circulus articulivasculosus, ^''''- '^^• n 1 • 1 xi j_ 'i' Sectiiiii of liviiliiie cartilage, o, Four separating from which the nutritive ma- ,,„, , ,,^ -^.^^ ,,i,s iu appostion ; c c, Nuclei ; terial is conveyed. The blood- ''■ ^"""'^y '° ^^^ "''"^'^j^ containing three ceii.s. vessels of the bone underneath the cartilKge also assist in supplying nourishment to the latter. All hyaline cartilage, except the articular kind, is covered by a menrbrane called the perichondrium. Fihro-cartilage consists of cartilage cells and librous tissue, which may be white or yellow, the former being tough and strong, the latter highly elastic. White fibro-cartilage is much the more plentiful, and presents the following varieties ; — It is called Inter- articular when it appears as a pad interposed between the two articular cartilages which form a joint ; such a j^ad is termed a meniscus, and the temporo-maxillary and femoro-tibial joints are furnished with such. Circumfereiitial, where it surrounds and deepens an articular cavity, as the acetabulum. Connecting, when it is interposed between bones and firmly connects them, as 122 AETHROLOGY. between the vertebral centra. Stratiform or Investing, when it clothes the part of bones over which the tendons of muscles play, sometimes existing in the tendons themselves. This tissue is dullish white, opaque, and, for the most part, devoid of jDerichondrium ; it is vascular, but its blood-vessels are few, and confined to the fibrous tissue, which exists as interwoven bundles of fibres, with cartilage cells interspersed amongst them. In the variety connecting vertebrse, it consists of concentric rings of fibrous tissue, enclosing a soft elastic centre, partly made up of cartilage cells, and often regarded as the remnant of the notochord. In fishes this portion is soft and pulpy, filling the opposing con- cavities of the vertebral centra. Fibro- cartilage has great power of cohesion, surpassing even that of bone. Yelloiv elastic fihro-cartilage is found in the epiglottis or valve which closes the principal air-tube ; it forms part of the frame- work of the ear, and of the Eustachian tubes which convey air to the tympanum. The fibres forming the matrix are similar to those of yellow elastic tissue. Cellular or reticular cartilage is found in the ear of some small rodents, and in the bat. It consists of cells densely packed, and apparently without a matrix ; the walls of the cells thus coming into contact, give it a net-like appeai-ance, hence the name reticular cartilage. CONNECTIVE TISSUE. In one form or other this tissue is found in all parts of the body. The chief varieties are the areolar and the fibrous ; the former serving as a connecting medium and support to the various organs, and to the structures of which they are formed. It appears as a loose translucent mesh, its interwoven bundles form- ing spaces termed the areola3 or cells, hence its name Cellular or Areolar Tissue. It consists of minute laminae and filaments mixed with small fibres of elastic tissue, while cells, or their remains, nuclei and walls, are also present, the whole embedded in a perfectly transparent basis. Other slightly varying forms are termed Betiform, Gelatinous, &c., while the connective tissue of the brain and retina has received the name of Neuroglia. White fibrous tissue has a similar structure to the above, but is dense, strong, and practically non-elastic. The filaments which form it are mostly parallel and wavy in their arrangement. It YELLOW ELASTIC TISSUE. 12J appears iu two forms — the sheeted or aponeurotic, which is found in investing ligaments, membranes, periosteum, &c.; and the cordi- form, in Avhich the fibres are col- lected in strong bundles ; this is the chief constituent of the binding ligaments, which hold articulating bones together and limit their mo- tion. The tendons of muscles are also made up mostly of this kind of tissue, but both in them and in ligaments yellow elastic fibres are also found. Connective tissue contains nerves and blood-vessels, for the supply of neighbouring structures as well as ^^ di'™'s- for its own nourishment, and also tendon cells, the latter lying in the spaces between the smaller bundles. When healthy this tissue is little sensitive to pain. Flo. 42. White filirous tissue from a ligament. Jl YELLOW ELASTIC TISSUE. This dilfers from the white tissue in being yellow, elastic, and not so tough or strong. Its fibres are sometimes as large in dia- meter as ^oVo' '^^^' ' ^^^ when mixed with white tissue in tendons the diameter may not be more than one-sixth of this. The fibres branch and join each other, and their ends curl up when cut or broken. Acetic acid has no effect on the yellow tissue, while it causes fibres of the white to swell greatly and become quite transparent ; again, when white tissue is boiled, gelatine is obtained, which is not the result of boil- ing the yellow fibres Yellow elastic tissue is found nearly pure in the ligamentum nuchie, the tunica abdominis, the coats of the largest arteries, and elsewhere. The lungs contain a large quantity of this tissue. Fig. 43. Vellow elastic tissue, magnified, from the liga- mentum nuclipe of a calf. 65 diamrs. 12-i AilTHROLOGY. ADIPOSE TISSUE. JVS'^F' Fat or adipose tissue consists of cells containing an oily material and arranged in isolated groups, or slightly separated by meshes of areolar tissue and capillary blood-vessels. It is found in many parts of the body, and varies greatly in quantity ; in joints it occurs between the ligaments, and serves the purpose of a packing material, while in the form of medulla or marrow it occupies the cavities of bones. In fat cells a nucleus is rarely visible, without special preparation. LIGAMENTS. Ligaments are dense, fibrous, connecting structures. They exist in most articula- tions, and are made up princiiDally of white inaguifleii. fibrous tissuc. There are two kinds — Fig. 44. Adipose tissue a a, Fat cells— tiiose ou tiie cccpsulcii' ov buTsal, and fuiiiciilav or right in mass; those on the ,.,.,. left spread amongst the con- binding llgameutS. Bective tissue fibres/. 6. Ccq^sulciv ligaments are membranous structures, generally, but not always, enclosing true joints. They consist of a dense interlacement of fibres attached to bones, round the edges of the articular cartilages, partially or wholly surround- ing the joint ; some regard them as a continuation of the perios- teum. They are never closely applied, their use being to foi'm cavities round the joints, enclosing and protecting the synovial or lubricating apparatus inside. Funicuhir or binding ligaments consist of rounded or flattened cords, or bands of fibrous tissue, passing from one bone to another, firmly attached to roughened portions of their surfaces. They hold the bones in their places, at the same time allowing the requisite amount of motion in the joints. Ligaments which are situated between bones are often termed interosseous. Annular ligaments are those which bind down and protect the tendons of muscles in certain joints, converting grooves in Ihe bones into channels or tubes which are lined with synovial membrane, and through which the tendons play. Some ligaments are composed almost entirely of yelloiv elasiic tissue, such as the ligamentum nuchce and the ligaments connect- ia^ the vertebral arches. SYNOVIAL MEMBRANES. 125 SYNOVIAL MEMBRANES. These are thin membranes lining the capsular or binding liga- ments of true joints, or they are interposed elsewhere between structures which move one upon another, and which would otherwise be injured by the friction. They resemble what are termed serous membranes, in lining closed cavities, and in containing a layer of endothelial cells which secrete a lubricating fluid, called synovia or joint-oil ; the foundation of these mem- branes is a layer of connective tissue, which varies considerably both in density and thickness. The synovial membrane terminates at the border of the articu- lar cartilage, which in the adult it never covers ; in the foetus it is said by some authorities that it covers the cartilage also. Near the borders of articular cartilages the membrane is generally found as a projecting fold, the projection being due to a small pad of fat, interposed between the membrane and the capsular ligament. These projections were once erroneously termed synovial glands, but their use is probably to assist in forcing the synovia between the opposing surfaces of cartilage. Under the cellular layer blood-vessels are found, and near the articular cartilage there is formed a vascular zone, the circulus articuli vasculosiis, in which the capillaries terminate by dilated loops ; articular cartilage derives its nourishment partly from this source (see page 121). There are three forms of these membranes : — the capsulm% which line the capsular or other ligaments of true joints ; bursal membranes, found where one structure moves upon another, as when a tendon plays over a bone, and known as synovial bursce ; or, when they exist in the subcutaneous tissue, between the skin and certain prominent parts of the skeleton, they are known as bursal mucosa?. The third form, vaginal membranes or sheaths, exist where one tendon forms a sheath for another, or in other canals through which tendons glide. Synovia or joint oil, is a viscid, transparent fluid, colourless, or pale yellow, physically resembling oil, but it contains very little fatty material consisting chiefly of albumen, salts, and water ; it is secreted by the cells on the inner surface of the membrane. When an animal is in active exertion, there is a greater demand for joint oil than when at rest, consequently there is an increased secretion of it. 126 ARTHROLOGY. CLASSES OF JOINTS. Joints may be divided into three classes — Immovable or Synartbi'odial, Movahle or Diarthrodial, and Mixed or Amphi- arthrodial. SYNARTHROSIS. In an immovable joint there is only a thin layer of fibrous or cartilaginous material interposed between the bones, the fibrous layer of the periosteum of both bones uniting to cover and become attached to the connecting material, thus serving as a ligament. If the connection is fibrous, the joint is generally called a suture ; if cartilaginous, a synchondrosis. These joints are found chiefly, but by no means solely, in the skull ; and they tend to become obliterated, in the adult, by ossification of the connecting material. The varieties of synarthrosis are the sutura, synchondrosis, schindylesis, and gomphosis. Sutures are true or false. In the sutura vera or true suture, the contiguous margins are united by a series of interlocking jDrocesses and indentations, a thin fibrous layer being interposed, connected externally with the periosteum. Variety of shape has led to the following nomenclature : — sutura dentcda, where the processes are large and tooth-like, as in the interparietal ; sutura serrata, where they are small and fine like the teeth of a saw, as in the interfrontal ; and sutura limhosa, where the contiguous ]3arts are dentated and also bevelled, as in the parieto-occipital — the sutura lamhdoidcdis of the human subject. In the false sutures, or sutura notha, the bones are joined by plain rough surfaces, of which there are two forms — sutura squamosa, where the adjacent borders are bevelled, the edge of one bone resting on and overlapping the other, as in the parieto- temporal ; and sutura harmonia, where the articulating surfaces of two bones present no marked irregularity, as the nasal and premaxilla. Synchondrosis, as already stated, resembles a suture, but the connecting medium is cartilage instead of fibrous tissue ; examples are found in the joints between the basi-occipital and basi-sphenoid bones, and between the latter and the pre-sphenoid. Schindylesis is that form of immovable articulation, where a ridge or plate of one bone is received into a slit or fissure in another, as the orbito-sphenoid into the incisura sphenoidalis of the frontal bone. AMPHIARTHROSIS. 12^ Gompliosls is the form where one bone is inserted in a cavity or socket in another, as the teeth in the alveoli. DIARTHROSIS. In movable or true joints the articular surface of each bone is covered by cartilage of encrustation ; the bones are held together by ligaments, the capsular one often surrounding the joint, and enclosing the synovial membrane. In some joints there is a pad of fibro-cartilage interposed between the two articular cartilages. Such a pad is called a oneniscus, and it adds to the elasticity and freedom of the joint. Movable joints form the most numerous class ; they are found in the limbs and else- where. The chief varieties are the arthrodia, enarthrosis, and the ginglymus. In Arthrodia the motion is slight and gliding, the bony surfaces being flat or slightly undulating, and the motion limited by ligaments or processes of bone, as in the small bones of the carpus and tarsus. Enarthrosis, the ball-and-socket joint, is capable of moving in any direction ; the ex- tremity of one bone is globular, and fits into a cup-shaped concavity in another bone ; the hip and shoulder joints are examples. The Gingly- mus, or hinge joint, although it may allow extensive motion, limits it to one plane, back- wards and forwards, as in the elbow. A Rotatory joint (diarthrosis rotatorius), where the motion is limited to rotation, is formed by a pivot on one bone fitting into a ring on another, as the atlo-axoid joint. FiC. 45. Diagram of a diar- throdial joint, a a, Articulating bones ; c c c, Synovial mem- brane. The shaded poitions represent the articular cartilages, which are said by some to be covered in •early fatal life by the inflected continuations {h li) of the synovial membrane. AMPHIARTHROSIS. There is but one kind of ar)iphiarthrosis or mixed joint ; the variations are too slight to warrant separation into classes. The term mixed is used with reference, not to the motion in such joints, but to their structure, which partakes of the nature of both the movable and immovable, the bones being firmly joined together by a strong interposed pad of fibro- cartilage, which is likewise adherent to the ligaments of the joint. There are no capsular ligaments ; the cartilaginous jDad 12« ARTHROLOGY. or disc is softer towards the centre, ^vhere occasionally there may be one, or even two, narrow cavities, and authorities differ as to whether sach cavities are lined by synovial membrane or not. Since there are really no frictional surfaces in such a joint, motion depends upon the flexibility of the disc. The joints between the vertebral centra afford the best illustration of the mixed class. The classification of the joints is here tabulated for reference. Synarthrosis (Immovable). Sutui-a. ( Dentata. Vera. J Serrata. ' Limbosa. Notha. Synchondrosis. Schindylesis. ' Gomphosis. SqiTamosa. Harmonia. ( Artlirodia. Diarthrosis ' Enarthrosis. (Movable). 1 Ginglymus. Diarthrosis rotatorius. Amphiarthrosis (Mixed). MOTION IN JOINTS. The following terms express the various movements allowed by joints : — extension tends to bring two bones as nearly into a straight line as the structure of the joint will permit ; flexion is the reverse of this, and diminishes the angle that extension increases ; abduction expresses the outward movement of a limb or bone from the central plane of the body ; adduction is the reverse action ; rotation signifies the jDartial revolution of a bone or number of bones, as it were, on their own axis ; circumduc- tion implies the movement of the distal end of a bone or limb, when it describes a curve, as the arc of a circle, ellipse, &c. The term gliding explains itself, and is peculiar to diarthroses, other joints having no frictional surfaces. common ligaments. 129 Articulations of the Axial Skeleton. common vertebral articulations. With the exception of the atlas and dentata, which form special joints, the true Vertebrse present great uniformity in their mode of union, articulating with each other by an amphi- arthrosis, which unites their centra, and by a pair of true joints formed by the oblique processes. These connections are com- pleted or strengthened by ligaments, some of which are co'inmon, others special, the former are continuous, passing over and uniting many vertebras, while the latter exist sej)arately between the contiguous segments. The bodies are united by intervertebral discs of fibro-cartilage, convex in front, and concave behind, firmly fixed to the articular surfaces of the centra. The discs consist of laminae arranged concentrically, with fibres crossing among themselves, and passing from one articular surface to the other. The central portion is yellowish, presenting more the character of true cartilage, and towards the circumference the laminae become denser. The discs do not exist between the first and second cervical joints ; they are thick in the neck and loins, but thinner in the dorsal region, where they assist in forming sockets for the heads of the ribs. The lumbo-sacral disc is very thick. Common Ligaments. These are the Superior and Inferior Common, and the Supra- spinous ligaments, the latter in the cervical region being termed the Ligamentura Nuchse. The superior common ligament is ribbon-like in form, extend- ing in the spinal canal from the sacrum to the axis, placed upon the superior part of the bodies of the vertebrse, to which, as well as to the intervertebral substances, it is attached, becoming broader at each of the latter attachments. The inferior common ligament, situated below the vertebral bodies, stretches from the sacrum only to the sixth dorsal vertebra, anterior to which its place is taken by a muscle called the longus colli. It is strongest in the posterior part of the dorsal and in the lumbar regions, and broadest on the interverte- bral substances. K ISO ARTHROLOGY. Posteriorly the siiprasijinous ligament is a white fibrous cord, extending from the spine of the sacrum, along the ujDper margin of the neural spines, to the first dorsal vertebrae, where its character becomes so greatly changed that the cervical portion may be, and often is, described as a separate structure — the ligamentum nuchcB or ligamentum colli (PI. l.ff); it is formed of yellow elastic tissue, and remarkable for its strength, elasticity, and insensibility to pain. It consists of a funicular and a lamellar portion ; the former, called also the cord of the ligament, is double, and extends from the first, second, and third dorsal spines to the occipital tuberosity, continuous posteriorly with the white supraspinous ligament, in which elastic tissue may be traced to some distance. The right and left ligaments meet in the median line, and from the postero-inferior aspect springs the lamellar portion, which is flat and triangular, separating the muscles of tlie neck into right and left. It consists of two plates, joined by cellular tissue ; the lamellae or bands descending from the cord and spinous processes usually of the first three dorsal vertebrae, run obliquely forwards, to be inserted to the superior spines of the six posterior cervical vertebrae, blending v/ith the interspinous ligaments. The lamella, although widely separate, are connected by smaller branches, and also by connective tissue. This ligament being highly elastic, is not a binding ligament, but acts as a passive support to the head and neck, diminishing the muscular tension in the superior cervical region. Special Ligaments. The special ligaments of a common vertebral articulation are the interspinous, the ligamenta subfiava, the intertransverse, and the capsular. The interspinous ligaments connect the neural spines, and are continuous with the supraspinous ligament above ; they are composed of yellow elastic tissue in the cervical region, elsewhere of white fibrous tissue. The ligamenta suhflava, or ligaments of the arches, connect the laminae of the articulating vertebra; they may be regarded as bifurcations of the inter- spinous ligaments, and their regional structure varies like that of the latter. The intertransverse ligaments are found between the transverse processes, and are strongest in the lumbar region ; these ligaments are well marked only in the solipede (Fig. 60. a). The capsular ligaments invest the articulations of the oblique processes, forming true synovial joints. SPECIAL VERTEBRAL ARTICULATIONS. 131 SPECIAL VERTEBRAL ARTICULATIONS. Occipito-atloid Articulation. — This joint is formed by the occipital condyles and the glenoid cavities of the atlas, and possesses five ligaments — one capsular, tivo lateral or styloid, superior suspensory, inferior suspensory. This joint is a true one, having tivo synovial membranes — one for each condyle. The styloid ligaments pass from the base of the occipital styloid processes to the sides of the atlas. The superior suspensory or occiinto-atloid is very broad, and consists of fibres, which cross each other, extending from the superior margin of the foramen magnum to the notch on the anterior border of the atlas. The inferior suspensory or occipito-atloid stretches from a notch on Fig. 46. Neural canal of first three cervical vertebrEe, opened from above to show the internal ligameuts. The occiput and foramen magnum are seen to the right, h, The odontoid ligament ; a, The occipito- atloid portion (long odontoid) ; c, Superior common ligament ; d. Posterior articular cavity of a vertebral centrum. the antero-inferior part of the atlas to the inferior margin of the foramen magnum ; it is thin and membranous. The capsular ligament passing completely round the joint, becomes blended with the other ligaments. The latter are sometimes considered as mere enlargements or strengthenings of the capsular ligament, which, this view being taken, would then become the only liga- ment of the joint. This joint allows of flexion, extension, circumduction, and lateral motion. Atlo-axoid Articidation. — This joint is formed by the oppo- sing articular surfaces of the atlas and axis, and is also a true joint. The atlo-axoid ligaments are the capsular, the superior, the inferior, and the odontoid. The capsular is very broad superiorly, where it closes the atlo-axoid space. The sujyerior ligament passes from the supero-posterior part of the ring of the atlas to the neural spine of the dentata. The inferior joins the inferior spines of the two bones. The odontoid springs 132 ARTHROLOGY. from the superior part of the odontoid process, inside the ring of the atlas, and may be regarded as a continuation of the superior common ligament ; it divides into two strong bands, which become attached on either side to roughened surfaces inside the neural canal of the atlas. This portion is sometimes called the short odontoid, while the long odontoid consists of smaller bands which pass forwards and are attached inside the foramen magnum of the occipital bone ; the latter ligament is also called the occipito- axoid. The motion of this joint is purely rotatory, being in fact the rotatory joint of the head ; or, in other words, when the head rotates the atlas moves with it. Sacro-lwmhar Articulation. — This is formed by the last lumbar and first sacral vertebrae. There are the usual typical articulations between the centra and zygapophyses, and in addition a pair of diarthroses formed by the facets on the trans- verse processes, which exist and form joints also between the fifth and sixth lumbar vertebrse (Fig. 60). The usual vertebral ligaments are found, with the addition of a pair of capsular ones for the transverse joints. t Coccygeal Articulations. — These are of the typical form, but become more and more rudimentary as the bones lose more and more the true vertebral character, the discs are formed, but the ligaments become gradually blended, finally enveloping the bones in a fibrous sheath. Thoracic Articulations. The thoracic skeleton contains the articulations which unite the dorsal vertebrse to one another and to the ribs, those which connect the ribs and costal cartilages, those joining the latter to the sternum, and finally, those which connect the sternal segments. We have already described the vertebral joints. Costo-vertebral Articulation. — A diarthrodial connection is here formed by the head and tubercle of a rib, the juxtaposed facets on the bodies df two dorsal vertebrse, and the transverse process of the posterior one. The ligaments are as follows : — The stellate or radiating ligament is situated inferiorly, and consists of strong fibres, divided into three fasciculi, uniting the head of the rib, one to the vertebra in front, a second to the intervertebral disc, while the third passes to the posterior vertebra ; the interarticular or round ligament passes from the THORACIC ARTICULATIONS. 133 ridge on the head of one rib through the articulation, giving a sHp to the intervertebral disc, and is attached to the fellow rib on the opposite side ; the head of the rib is thus divided into two distinct articulations, with cai^sidar liga- ments and synovial sacs. Super- iorly the anterior costo-transverse unites the neck of the rib to the infero-anterior part of the vertebral transverse process, while the jws- terior costo-transverse passes from the supero-posterior part of the tubercle to the lateral part of the transverse process. One capsular ligament unites the tubercle and transverse process, enclosing a syno- vial sac. Fin. 47. C'osto-vertebral articulation, right lateral aspect, a, Anterior, and b, Posterior costo-transverse ligaments ; c, Ligamen- tum subflavum ; d, Interspinous, and t', Supra-spisioiis ligaments Fig. 4S. Costo-vertebral articulation. Neural canal opened from above, and superior common ligament removed, a. Inter- articular ligament ; b b, Branches joining the disc. CJiondro-costal Articulation. — This is a fixed joint between the rib and its cartilage ; each rib is cupped on its lower extremity, the convexity of the cartilage resting in it, and the joint, a gomphosis, is clothed around with strong fibrous tissue. Costo-sternal Articulation. — This joint is formed by two sternal segments and a true costal cartilage. The first cartilage, however, articulates with the presternum only, and the last only with the last sternal segment. The ligaments are the capsular and the superior and inferior costo-sternal, which stretch from the costal cartilages to the sternum aBbve and below, blending with the capsular ligament. The asternal or false cartilages are united, each free extremity becoming attached to the cartilage in front by a small elastic ligament. The first asternal cartilage is very firmly attached to the last sternal one ; a small ligament, the chondro-xiphoicl, is also described, which connects the xiphoid and first asternal cartilages. 134 ARTHROLOGY. The first pair of costo-sternal joints which are close together usually have a common capsular ligament. Sternal Articulations. — These bind together the sternal seg- ments. The ligaments in the horse are the superior sternal, extending along the upper surface of the bones, and the intervening fibro-cartilages which eventually ossif}'. The cartilaginous appendages of the sternum are the cariniform and xiphoid cartilages. In the horse the former appears as a sharp ridge running from above and before the presternum, down the lower median line of the anterior sternal segments. Its shape bears a marked resemblance to the keel and cut-water of a boat, hence its name. The xiphoid is a flat ovoid plate of cartilage attached to the posterior segment of the meso-sternum ; unlike the cariniform, its sharp edge is placed transversely. It is also called the ensiform cartilage. Articulations of the Skull. These are all synarthrodial, excepting the temporo-maxillary joints and those between the hyoid bone and its appendages. Collectively, the remaining joints are called the sutures of the skull, and some of these have received special names. sutures. The straight median suture, extending from the occipital crest to the nasal peak, is the longitudinal one, subdivided into the nasal portion, which is open at the apex, the frontal, and the sagittal, the latter situated between the parietal bones, while joining the nasal and lachrymal bones to the frontal is the trans- verse suture. The coronal suture extends obliquely upwards and backwards from the temporal fossa, between the frontal and parietal bones, while the sutura lirnhosa runs upwards between the parietal and occipital bones, reaching from the temporal bone to the sagittal suture. For structure of sutures see page 126. TEMPORO-MAXILLARY JOINT. This articulation is a diarthrosis, and it is furnished with cajpsular, external lateral, and posterior ligaments, and also with a meniscus or interarticular disc of cartilage. The joint ARTICULATIONS OF THE HYOID SERIES. 135 is formed by the condyle of the inferior maxilla, and the condyle and glenoid cavity of the temporal bone. The meniscus is irregular and flattened from above downwards, the superior surface being concavo-convex to correspond with the condyle and glenoid cavity above; its _ inferior surface being con- cave for the reception of the maxillary condyle. The capsular ligament is at- tached to the circumference of the meniscus, so forming two synovial cavities. The posterior ligament runs from the mastoid process, and the external lateral one from the zygomatic arch of the temporal bone, both going to the neck of the maxilla ; both are mere thickenings of the capsular ligament. This joint admits of lateral motion, extension, flexion, and in the herbivora elevation and depression. Kight temporo-maxillary articulation — external view. «, The meniscus; 6, external lateral, and c, Posterior ligaments. ARTICULATIONS OF THE HYOID SERIES. The Hyoid articulations are as follows. The temporo- hyoicl articulation is amphiarthrodial, the superior angle of Hyoid articulations, a, Point going to form the tem- poro-hyoid articulation ; b, Rudimentary second corni- culum ; c. Proximal, and d, Distal interhyoid articulations. the cornu articulating with the hyoid process of the petrosal 136 ARTHROLOGY. bone by a piece of fibro-cartilage. The i^roxhnal inierhyoid articulation is also amphiarthrodial, a similar cartilage joining the cornu and corniculum ; the latter articulates with the hyoid bone by a true synovial joint, the distal interhyoid. In the proximal interhyoid cartilage a small ossicle may be found, which in ruminants appears as a second corniculum. The motion in the two first-named joints is considerable. We may mention here that the heel processes are attached at their ends to the thyroid cartilage of the larynx by the lateral hyo-thyroid ligaments, between which is found the middle ligament {see " Laryngeal Ligaments "). Articulations of the Appendicular Skeleton, pectoral ldib. the shoulder JOINT. The Scajndo-humeral articulation is formed by the glenoid cavity of the scapula, and the articular head of the humerus. It is a ball-and-socket joint, with one strong capsular ligament. The bones are held in position by the follow- ing muscles which pass from the shoulder- blade to the arm, and play the part of active ligaments : — The antea spinatus, postea spinatus, postea spinatus minor, sub- scapularis, and flexor brachii. The motion of the joint is angular, lateral, and circum- ductive. THE ELBOW JOINT. The Humero-radio-ulnar is a ginglymus formed by the radius, ulna, and humerus. It has capsular and lateral ligaments. The capsular is strongest in front, where it stretches from the distal end of the humerus to the head of the radius ; posteriorly it encloses the articulation of the ulna with the humerus, and it also surrounds the double articulation between the head of the ulna and the radius. Anteriorly it is attached to the brachii, posteriorly to that of the anconeus Fig. 51. Ligaments of the elbow joint — posterior view. a. External lateral ligament ; h, Internal lateral ligament ; c, External, and d, Internal arciform ligaments. tendon of the fl exor SPECIAL CARPAL LIGAMENTS. 137 muscle. The internal lateral ligament is crucial, longer but less strong than the external; it stretches from a small tuberos- ity on the inner side of the internal condyle of the humerus to the head of the radius. The external lateral ligament, crucial, short and thick, passes from a ridge on the epitrochlea, and a cavity on its outside, to a tuberosity outside the head of the radius. The joint possesses flexion and extension only. KADIO-ULXAE, JOINT. This articulation, small and very firm, is formed by the articular surfaces of the radius and ulna, and consists of two true and two mixed joints. The arciform or superior radiating ligaments are attached on both sides to the superior part of the ulna and radius. They are curved, and blend with the lateral ligaments of the elbow. Below the radio-ulnar arch are a few fibres, which constitute the inferior radiating ligament. The surfaces above and beneath the radio-ulnar arch are joined by the interosseous ligaments, which ossify early in life. The motion is practically nil. THE CARPUS. The ligaments of this joint, or rather group of joints, are special and common. The articulations between the bones of the upper row may be termed the superior carpal ; those between the bones of the lower row the inferior carpal ; between the radius and the upper row we have the radio-carpal ; between the upper and lower rows the inter-carpal ; and between the lower row and the metacarpus the carpo-nietacarpal. I'lG. 52. Ligaments of the car- pus— anterior aspect, a, Internal lateral ligament. h. External lateral liga- ment ; c c, Anterior car- pal ligaments ; a d. Anterior carpo-metacar- pal ligaments. Spec ial Ligaments. Superior Carpal Ligaments. — The four bones of the upper roiu are held together by three anterior and three interosseous ligaments. The anterior are flat bands placed one between each pair of bones ; and the two inner ones are covered by and attached to the capsular ligament ; the third, the median 138 ARTHROLOGY. trapezial, is covered by the external lateral ligament. The interossei are attached to the roughened grooves between the articular facets on the lateral surfaces of the scaphoid, lunar, and cuneiform bones. The tAvo inner are blended with the anterior, while the external one is covered by the posterior common ligament. Inferior Carpal. — The bones of the loivei' roiv are held together by four liga^ients, tiuo anterior and two interos- seous. The anterior are covered, the internal one by the internal lateral, the other by the capsular ligament. The _„ interossei are two ; the one joining the mag- num to the trapezoid is blended with the anterior ligament, but the other is separated from the corresponding anterior one by an articular facet, Radio-Carpal. — The special ligaments join- ing the radius to the upper row are three in number. The oblique one stretching obliquely from the lower extremity of the radius, under the posterior common ligament, to tlie scaphoid bone. A second small one, the superior tra- pezial, stretches from the external side of the inferior extremity of the radius to the superior border of the trapezium, partly covered by the external lateral ligament. A third, the smallest of all, is buried under the former, and stretches from the inferior part of the radius to the os lunare. Intercarpal. — There are three special liga- ments ; two are short, and situated under the posterior common ligament. The first runs vertically from the scaphoid to the magnum and trapezoid, the second passes obliquely from the cuneiform to the magnum ; while the third, the inferior trapezial, by far the strongest, stretches from the trapezium to the unciform and head of the external splint bone, blending externally with the lateral, internally with the posterior common ligaments. Garpo-nietacarpal. — This joint has the following special ligaments : — tiuo anterior, tivo p)osterior, and two interosseous. The first anterior consists of two bundles uniting the os magnum to the large metacarpal bone. The second anterior Pig. 53. Deep ligameuts of the carpus — external view. a and 6, Deep portions of the external lateral ligament ; c, Superior, d. Median, and e, Inferior trapezial ligaments. COMMON CARPAL LIGAMENTS. ISd binds the unciform to the external splint bone. The hvo posterior bind the magnum and trapezoid to the large and inner metacarpal bones. The interossei unite the heads of the .splint bones to the large metacarpal and bones of the lower row. Common Ligaments. The Common Ligaments are the external and internal lateral, and the anterior and posterior common, or capsular. The internal lateral ligament, stronger than the external one, is slightly crucial, consisting of two bundles of fibres which cross each other ; both spring from the internal side of the inferior extremity of the radius ; the superficial bundle goes to the OS magnum and large metacarpal, and the dee-p set to the scaphoid, trape- zoid and inner splint bones. A part of this ligament, deep-seated also, joins the scaphoid and small metacarpal bones. The external lateral ligament also con- sists of two fasciculi, springing from the external side of the distal end of the radius ; the superficial fibres are attached to the external splint, the deep to the same, and also to the cuneiform and unciform bones. The anterior common or capsular ligament is membranous, covering the anterior portion of the carpus. This ligament is attached to the radius, the head of the large metacarpal bone, the lateral ligaments, and to the carpal bones and their anterior ligaments. The annular ligaments are thickenings of this structure, which bind down the extensor tendons. The inner surface is smooth, and lined by synovial membrane. The posterior common ligament is one of the strongest in the body, and covers the posterior surface of the carpus, filling up the depressions. It passes from the distal end of the radius to the head of the large metacarpal bone, adhering to the internal lateral, median. Fig. hi. Ligaments of the carpus — postero-internal view, a h, Deep portions of internal lateral liga- ment ; c, Oblique ligament ; d. Interosseous metacarpal ligament; c, External interosseous ligament of the upper row. 140 ARTHROLOGY. and inferior trapezial ligaments. Its anterior surface is attached to the two rows of bones, while its posterior is smooth, for the passage of the great flexor tendons ; the inferior carpal or cliech ligament is continuous with it. A ligamen- tous structure passes obliquely downwards from the posterior border of the trapezium to the large and inner metacarpal bones, completing the carpal groove or sheath for the flexor tendons ; this is the posterior or investing annular ligament. The carpal or check ligaments, superior and inferior, will be alluded to in describing the muscles of this region. The synovial capsules are four, perhaps five — tioo small and three large. Of the latter, one is for the radius and the upper row, extending between the bones as far as the interossei ; another is situated between the upper and lower rows, and a third between the lower row and metacarpus, dipping be- tween its large and small bones. There is usually a separate synovial capsule between the trapezium and cuneiform bone, and perhaps one for the pisiform, when present. Motion in the carpus takes place chiefly in the radio-carpal portion, to a far less degree in the intercarpal, and very slightly in the carpo-metacarpal ; the movements are flexion and extension ; very slight lateral and circumductive movements are possible. Fig. 55. Superficial ligaments of the carpus — posterior view, a, Posterior annu- lar ligament ; 6 6, Pos- terior common ligament. METACARPAL ARTICULz^TIOX. This consists of diarthrodial and synarthrodia! joints. The latter are furnished with interosseous ligaments which very generally become ossified ; the articular surfaces of the former are held together, partly by those carjxd ligaments which sur- round them, and partly by the interosseous ligaments just named. METACARPO-PHALANGEAL ARTICULATION. This, which is popularly termed the fetlock joint, is formed by the large metacarpal bone, the jDroximal phalanx, and a pair METACARPO-PHALAXGEAL ARTICULATIOX. 141 of sesamoids. The ligaments may be divided into those proper to the joint and the accessory. The former consist of a capsular and two lateral ones. The capsular ligament passes anteriorly from the lower end of the large metacarpal bone to the head of the OS suftraginis, and is attached to the lateral ligaments, which stretch from the in- fero-lateral aspect of the metacarpus to the supero-lateral surface of the os suffraginis. The accessory ligaments are those imme- diately connected with the sesamoid bones. The superior sesamoidean or susjyensory ligament is a long, strong band, arising posteriorly from the lower bones of the carpus and the head of the metacarpus, occupying the space between the splints. It bifurcates, and becomes attached to the summits and external sides of the sesamoids, whence the parts pass downwards and for- wards, reuniting as the broad ligament, and joining the exten- sor pedis tendon at the antero- inferior part of the os suffraginis. The infer iorsesamoideanliga,- ments are named the external or long, the oniddle or short, -and the internal or crucial.V The external one is Y-shaped, and runs from the base of the sesamoids to the supero-posterior part of the os corona3. The middle one is V-shaped, arising from the base of the sesamoids, and it passes down to a ridge on the back of the os suffraginis. The interned one, crucial or X-shaped, likewise passes from the base of the sesamoids to the supero-posterior part of the os suffraginis, its fibres intei'crossing. The lateral sesamoidean ligaments, external and internal, are two thin layers, passing from the external surfaces of the sesa- moids to the tubercles on the head of the os suffraginis. Pos- teriorly, the sesamoid bones are connected by the interosseous Fig. 56. Sesamoidean and digi- tal ligaments — posterior aspect. a, Suspensory ligament ; 6 6 6, External and middle inferior sesa- moidean ligaments. The central bundle is the Y, the two lateral ones forming the V ligament ; c, Annular sesamoidean ligament ; d d, Posterior ligaments of the pastern joint ; e e, Lateral, and /, Inferior, navicular ligaments. Fig. 57. Deep sesamoid- ean ligaments, a. Inter - sesamoid- ean ligament ; 6, Crucial or X liga- ment. 142 ARTHROLOGY. or intersesamoidean ligament, and covered by a pad of fibro- cartilage, which forms a smooth groove for the passage of the flexor tendons, and is converted into a canal by the annular ligament, a strong fibrous band which forms an arch posteriorly from one sesamoid bone to the other. The joint is capable of flexion and extension, with very slight lateral motion. The synovial membrane of this joint is continued upwards posteriorly, in the bifurcation of the suspensory ligament, where it forms a large cul-de-sac. " Wind-galls " are projections of this sac when it is abnormally full. PASTERN JOINT. The Proximal inter plicdangeal articulation, or pastern joint, is formed by the proximal and median phalanges, joined by the capsular, lateral, and two posterior ligaments. The cajisular ligament extends anteriorly from the articular margin of one bone to that of the other, and is adherent in front to the extensor tendon. The lateral ligaments are large and very strong, springing from the distal end of the os suffraginis and passing obliquely down- wards to the postero-lateral aspect of the os coronse. The tivo posterior ligaments run each from three points on the sides of the OS suffraginis to a piece of fibro-cartilage, described as the glenoid cartilage, and attached to the postero-superior edge of the OS corona3 ; between them is the insertion of the external inferior sesamoidean or Y-shaped ligament. The synovial membrane of this joint lines the glenoid cartilage and a portion of the extensor tendon, and sends upwards a sac which lies between the jDostero -inferior part of the first phalanx and the cartilage. The movements are flexion and extension, ^nd, during flexion, some slight lateral motion. COFFIN JOINT. The Distal interpJicdangecd articidation, or coffin joint, is formed by the median and distal phalanges and the navicular bone. Its ligaments are the capsidar, antero and postero- lateral, and the broad, lateral, and inferior navicular. The capsular ligament includes the articulation formed by the three bones, and is attached to the extensor tendon in front and the flexor behind. The antero-lateral, which are strong and thick. THE PELVIS. 143 spring from the imprints on the lateral aspect of the os coronas, and are inserted into two depressions at the superior border of the OS pedis, j)artly covered by the lateral cartilages. The postero-lateral are continuations of the lateral ligaments of the pastern joint, which, after reaching the os coronas, form an elastic fibrous cord, attached to the upper border of the navicular bone, the two uniting to form the siqyerior or hroacl ligament. They give off short lateral bundles to the retrossal pro- cesses and inner surfaces of the lateral carti- lages. The lateral navicular ligaments con- sist of strong white fibres, which join the angles of the navicular bone to the inner aspect of the lateral cartilages, and the wings of the os pedis. The inferior ligament is an inter- osseous one, which is attached to a roughened groove on the anterior border of the navicular bone and to the semilunar ridge of the os pedis. The synovial niemhrane lines the cavity of the joint, and sends upwards a very large sac along the posterior surface of the median phalanx. Smaller projections are found between the anterior and posterior lateral ligaments. The motion of the joint is that of flexion and extension. i-IG. 5S Navicular ligaments. a a, Superior, or broad ; h, Inferior ; and c c, Late- ral ligaments. Articulatioxs of the Pelvic Limb. THE PELVIS. Sacro-iliac Articulation. — This is the articular connection between the axial skeleton and the pelvic limb ; it is described both as a diarthrosis and an amphiarthrosis ; it is capable of little motion, and the synovia is small in quantity, if present at all; the joint is formed by the venter of the ilium, and the supero- lateral surface of the sacrum, which articular surfaces are clothed with cartilage, and the union completed by the three sacro-iliac ligaments, inferior, lateral, and superior. The inferior consists of strong bundles of fibres, which envelop the articulation like a strong and irregular capsular ligament, and are attached below to the transverse process of the sacrum, and above to the venter ilii. The swperior sacro-iliac, short and strong, stretches from 144 ARTHEOLOGY. the spines of the sacrum to the posterior spine of the ilium. The lateral sacro-iliac is triangular, the fibres running obliquely Sacral and pelvic ligaments— left lateral aspect, o, Superior sacro-iliac ligament ; ?), Sacral ligament ; c, Lateral sacro-iliac ligament ; d, Sacro-sciatic ligament. backwards, and it is attached above to the posterior spine and border of the ilium, below to the lateral border of the sacrum. Sacro-sciatic Ligament. — This is a broad membranous expan- FiG. CO. Sacral and pelvic ligaments— inferior aspect, a, Intertransverse lumbar ligament ; b and c, Capsular ligaments of lumbar and sacro- lumbar transverse articulations ; d, Inferior sacro-iliac ligament ; e. Obturator ligament ; //, Ligament of the ischio-pubic symphysis. sion situated at the side of the pelvis, helping to form the pelvic cavity. It is attached superiorly to the lateral borders of the transverse processes of the sacrum and first two or three coccygeal HIP JOINT. 145 vertebrae ; inferiorly, to the superior ischiatic spine and tuberosity of the ischium. Between this ligament and the iliac shaft is a space, the great sciatic notch ; and a second, the lesser sciatic notch, exists between the ligament and the ischial shaft. The former gives passage to the great sciatic nerve and gluteal blood- vessels, the latter to the tendons of the obturator internus and pyriformis muscles. Some lateral bands are found joining the sacral spines to the transverse processes ; these are termed the sacral ligaments. Pelvic or Ischio-puhic Symphysis. — This articulation is formed by the respective surfaces of the ischium and pubis, and joins the right and left ossa innominata ; in the young it consists of fibro- cartilage and white fibrous tissue, which ossify Mnth age. The Obturator ligaments are thin membranes, almost closing u p the obturator foramina, a small passage being left for the transit of blood-vessels. HIP JOINT. The Femoro-pelvic is a ball-and-socket or enarthrodial joint, and is formed by the acetabulum of the os innominatum and the articular head of the femur. It has the following lisfaments :— i Fig. 61. Ligaments of the Hp joint — infero-internal view. a. Cotyloid ligament ; 6, Round ligament ; c, Pubio- femoral, crossed by the transverse ligament. The capsular, which grasps the brim of the acetabulum and roughened edge of the head of the femur ; the cotyloid, which surrounds and deepens the acetabulum; and the transverse, which stretches over the cotyloid notch, completing the circum- L 14G ARTHEOLOGY. ference of the cavity, but leaving a sj)ace for the passage of the pubio-femoral ligament. The binding ligaments of the joint are two — the round or ligamentum teres, very short and strong, which arises from the notch in the head of the femur, and is inserted in the fundus acetabuli ; the second is the inihio-femoral ligament, which arises from the head of the femur, close by the round ligament ; bound down by the transverse ligament, it passes through the cotyloid notch and along the groove on the under side of the pubis, meeting and crossing its fellow at the symphysis, and becoming con- tinuous with the abdominal fascia of the opposite side ; thus the head of the right femur is partially supported in position by the muscles of the left side, and vice versa. As it passes over the pubis, a synovial bursa is inter- posed. This ligament is jDeculiar to the Equidas. The motion of the joint is flexion, extension, abduction, adduc- tion, rotation, and circumduction. STIFLE JOINT. The Fcmoro-tihial articulation, a compound ginglymus, is formed by the trochlea and condyles of the femur, the tibia, and patella. The ligaments con- sist of two groujDS, the fernoro-tihial and the ixdellar. Patellar Group. — The capsular ligament, which is attached round the trochlea of the femur, and the articular surface of the patella, is capacious, allowing considerable motion in the joint. The lateral ligaments, internal and external, arise from the lateral aspects of the femur, j ust above the condyles, and are inserted to the corresponding surfaces of the patella, the ex- ternal being the larger; they may be regarded as thickened portions of the capsular ligament. The three straight ligaments, external, middle, and internal, arise from the antero-inferior surface of the patella, and are inserted to the anterior aspect of the tuberosity of the tibia, the middle one occupying the small Fig. G2. Ligameuts of the stifle joint — antero-iuterDal aspect, a. Internal lateral femoro-tibial ligament • h. In- ternal lateral patellar ligament ; c, Internal, d, Middle, and e. External straight patellar ligaments. STIFLE JOINT. 147 At its patellar attachment, the internal straight ligament becomes enlarged, and fibro-cartilaginous in structure, projecting over the edge of the femoral trochlea, and thus enlarging the articular surface of the patella, Femoro-tihial Group. — There are two crescentic fibro-carti- laginous discs, the semilunar cartilages or menisci, interposed between the condyles of the femur, and the head of the tibia, the internal one being the larger and thinner. Their internal borders are sharp and con- cave, embracing the tibial spine, while the external are thick and convex. Their super- ior surfaces are hollowed for the reception of the femoral condyles, while the inferior are smooth and flat, resting on the tibia. Their extremities terminate in the coronanj ligaments, which attach them to the bones ; these are five in number, two for the i^iter- nal disc, an anterior one attaching it to an excavation in front of, while the posterior one is fixed to a furrow behind, the tibial spine. The external disc has three, one fixed in front of the tibial spine, and tivo behind it, of which the superior one is longer and stronger, being inserted in the intercondyloid notch of the femur, while the inferior is thin and flat, and fixed to the head of the tibia. Crucial or Interosseous Ligaments. — These, anterior and posterior, are very strong, and are situated between the con- dyles of the femur. The anterior or exter- nal stretches obliquely forwards, and is attached in the intercondyloid notch inside the external condyle of the femur, and to a depression on the summit of the tibial spine. The iwsterior or internal, the longer, arising anteriorly inside the internal condyle, crosses the anterior ligament, and is attached posteriorly to a small eminence behind the inner articu- lar surface of the head of the tibia. Lateral Ligaments. — The external one, the shorter and stronger. Fig. 63. ligaments of the stifle joint — posterior aspect, o, Exter- nal lateral patellar ligament ; h, External lateral femoro- tibial ligament ; c, Posterior crucial ligament ; d, External meniscus ; e, Internal menis- cus ;/, Femoral coronary liga- ment ; (J, Posterior external coronary ligament ; h, Fibulo- tibial ligament. 148 ARTHROLOGY. arises from the external condyle of the femur, and passes over the head of the tibia to the fibula ; a synovial bursa lies between it and the tibia. It is separated from the capsular ligament by the tendon of origin of the popliteus. The internal lateral arises from the internal condyle of the femur, and is attached to the intero-lateral aspect of the head of the tibia. Ca'psular Ligament. — This name is usually applied to a mem- branous ligament enclosing the joint posteriorly, and attached to the femur, tibia, lateral ligaments, and menisci. It is by some called the posterior ligament. Anterior to this there is a pair of membranes enclosing the joint antero-laterally. These are generally described as the synovial membranes ; but as they are considerably strengthened, and help to play the part of a capsular ligament, it may be convenient to describe them as such. There- fore if there is a complete capsular ligament investing the joint, it is thickened posteriorly. The synovial apparatus is double, each side having its own membrane, and between the two are the crucial ligaments of the joint. Anteriorly, the synovial membranes contact that of the femoro-patellar joint, and it is found that sometimes the synovial cavities are continuous with that of the latter. A large quantity of fat fills up the space between the capsules and the straight ligaments of the patella. The motions of this joint are flexion and extension, and a certain amount of rotation, permitted by the presence of the discs. TIBIO-FIBULAR ARTICULATION. This small articulation is formed by the facets on the adjacent surfaces of the tibia and fibula, and is a diarthrodial joint. The ligaments are a strong caiosular one and the interossei, which divide into superior and inferior ; the former being a small bundle at the upper third of the fibula ; the latter consists of a membranous expansion, extending from the middle to the distal extremity of the fibula. Between the two interosseous parts pass the chief artery and vein of the region, the anterior tibial. A ligamentous cord extends downwards from the fibula to the external malleolus of the tibia, " where this cord bifurcates and unites with the two external lateral ligaments of the tarsal joint '* {Rigot). Motion in this joint can hardly be said to exist. COMMON LIGAMENTS. 149 THE TAESUS. Similar to the carpus, this, the hoch joint, consists of a true or tibio-tarscd jDortion, together Avith the upper and lower tarsal, the intertarsal, and the tarso-metatavsal accessory articulations. The ligaments are common and special. Common Ligaments. These are the external and internal lateral ^nd. the capsular. The internal lateral is formed of three fasciculi of fibres, superficial, middle, and deep. The superficial, the longest and strongest, connects the internal malleolus of the tibia Avith the astragalus, two cuneiform, and the large and inner meta- tarsal bones. The middle fasciculus, con- sisting of two cords, likewise arises from the internal malleolus of the tibia, one division being attached to the astragalus, the other to the calcaneum. The deep fasciculus is very small ; it passes from the internal malleolus to the astragalus. The external lateral ligament consists of two crucial fasciculi, superficial and deep. The superficial is strong and flat, joining the external malleolus of the tibia to the astragalus, calcaneum, cuboid, large and external metatarsal bones. The deep fasciculus is short ; it passes obliquely backwards, arising from the external malleolus of the tibia, to the astragalus and calcaneum. The capsular ligament is very strong, and attached superiorly round the distal articular surface of the tibia, to the inferior border of the astragalus, to the cuneiforme mag- num and medium, and to the lateral aud oblique ligaments ; posteriorly it is attached to the calcaneum and astragalus, and there is a fibro-cartilaginous disc in its centre, over which glides the flexor tendon, furnished with a synovial membrane. The capsular ligament is often described as double, and named the anterior and posterior, the lateral ligaments with which it blends being the lines of division. Fig. Ci. Ligaments of the tarsus— pos- tero-iutenial view, lateral ligament ; cuboid ligameut. Internal Calcaneo- 150 ARTHROLOGY. special Ligaments. Suj^erior Tarsal. — These ligaments occur between the astra- galus and calcaneum, and consist of one superior-', tiuo lateral, and one interosseous. The sujjerior stretches from the upper border of the pulley of the astragalus to the calcaneum ; the lateral are very thin, and covered by the lateral common liga- ments ; the interosseous one is strong, occupying the greater part of the rough excavation between the articular facets of the bones. Inferior Tarsal. — The ligaments of the lower roiu are five, two anterior, which con- nect the cuboid to the great and middle cuneiform bones, and three interosseous ones, two of which correspond to the anterior ligaments ; the third interosseous ligament unites the three cuneiform bones. Some of these ligaments bound the tarsal foramen, which gives passage to the perforating pedal artery, Intertarsal. — The four ligaments in this group are of greater importance than those of the two last groups. The calcaneo- cuboid or calcaneo-metatarsal ligament stretches from the posterior border of the calcaneum to the posterior part of the cuboid, termina- ting on the head of the external metatarsal bone ; externally it reaches the lateral, in- ternally the tarso-metatarsal ligament. This ligament becomes implicated in the lesion known as curb. The Oblique, or Astragalo-metatarsal ligament, arising from the antero-internal side of the astragalus, becomes attached to the cuneiforme magnum and medium, the large metatarsal bone, and the capsular ligament, the fibres radiating from above, and running downwards and outwards. This ligament covers the seat of bone-spavin. The Tarso-metatarsal is a single strong ligament, which covers the tarsal groove and unites posteriorly all the bones of the joint to the three metatarsal bones. It is smooth, for the passage of the fiexor tendon, and is the analogue of the posterior Fig. 65. Ligaments of the tarsus aiitero external yiew. External lateral, and Oblique ligament. EUMINANTTA. 151 carpal ligament. It is pierced by the perforating pedal artery and vein, and inferiorly is continuous with the check ligament. The great interosseous ligament unites the calcaneum and astragalus to the cuboid and cuneiforme magnum, occupying the internal space formed by these bones. Annular Ligaments. — The posterior of these closes in the tarsal groove, completing the sheath for the deep flexor tendon ; hence it passes from the tuberosity and posterior border of the calcaneum to the internal ridge of the same bone, and is reflected as far down as the inner metatarsal bone. It is strengthened by a strong band which arises almost with the calcaneo-cuboid ligament. The anterior annular ligament presents three well- marked portions ; they are strong and more or less flattened bands, an inferior one passing across from the proximal end of the outer to that of the inner metatarsal bone, a middle one attached to the cuboid bone and flexor metatarsi tendon, and a superior crossing the distal end of the tibia obliquely outwards and down- wards. The three portions of this ligament bind down the tendons playing over the tarsus anteriorly. There are at least three synovial membranes, one between the astragalus and tibia, another between the rows of bones, and one also between the lower row and the metatarsus, which sends a branch upwards between the calcaneum and astragalus. The motion in the tarsal joint is in effect limited to flexion and extension, and the joint may therefore be regarded as a gingly- mus. The tarsal check ligament will be described with the muscles. The metatarsal, metatarso-phalangeal, smd interphalangeal joints are like those of the anterior limb. COMPARATIVE ARTHROLOGY. RUMINANTIA. AXIAL SKELETOX. In the ox, the dorso-lumbar siipras'pinous ligament is composed of yellow elastic tissue, and anteriorly is expanded, and attached to the sides rather than to the summits of the neural spines. The inferior common ligament is very strong, and the intervertebral discs thicker than those of the horse ; the ligamen- tum mtchce is also stronger, as the weight it has to bear is greater. The sternal 152 COMPARATIVE ARTHROLOGY. ribs articulate with their cartilages by means of true diarthroses, and are supplied with synovial membranes. The sternum is furnished with an inferior common ligament, and the presternum or manubrium articulates with the meso- sternum by a diarthrosis of limited motion. The transverse lumbo-sacral and interlumbar articulations, being peculiar to the horse, are entirely wanting here. PECTORAL LIMB. In the elboru joint the internal lateral ligament is shorter than the external. The carpus, being articulated on the same general plan as that of the horse, calls for no special description. The metacarpo-phalangeal joint is double, each digit articulating in a manner very like the single one of a horse, and each having two lateral ligaments. The sxispensory ligament divides into several parts inferiorly, four of which go to the sesamoid bones, one to each, either of the two external ones giving off a band which winds round to the front, and joins the tendon of the extensor proprius of the digit, while two other bands pass directly from the ligament through the interarticular notch of the metacarpus, separate and likewise join the above-named extensor tendons from the inside ; two slips pass down, unite, and become attached to the small rudimentary digits or claws, afterwards separating to become united postero-superiorly to the distal phalanges ; finally, two deep branches go to the tendon of the flexor perforatus and form two rings through which passes the divided tendon of the flexor perforans. The inferior sesamoid ligaments are small, and consist of two lateral bands, which attach the sesamoid bones to the head of the proximal phalanx, and between them a very small X ligament. The inter sesamoidean ligaments are three in number ; there is one between each pair of bones, and one joining the two internal ones. A common annular ligament is found about the region of the fetlocks, and two smaller special annular ligaments lower down. (Fig. 81,fgg'.) The superior interdigital ligament is crucial, and situated between the two proximal phalanges; in small ruminants it is very rudimentarj'. There are only two fibrous bands wdiich attach the glenoid cartilage to the first phalanx. The inferior interdigital ligament joins the distal phalanges and navicular bones together, and in the ox is connected with the tendon of the flexor perforans. The superior navicidar ligament, coming from the median phalanx, is formed of elastic tissue. Pelvic Limb. The pubio-fernoral ligament is wanting in all the domesticated animals other than the horse ; the absence of this ligament enables the larger ruminants to deliver those sweeping circular blows with the foot, which are known by the familiar name of " cow-kicks." There is only one straight ligament of the patella in the smaller ruminants. With respect to the tarsus, we may remark that there is more motion in that joint in the ruminant, due to the greater mobility of the astragalus, which possesses gliding motion upon the calcaneum, the cubo-cuneiform bone, the tibia, and the malleolar bone, all of which assist in forming the mobile portion of the joint. In the elephant there is no round ligament ; and the femur instead of being, when at rest, inclined downwards and forwards, maintains an almost perpen- dicular position ; this accounts for the peculiar contour of the haunch in that animal. CARNIVORA. 153 OMNIVORA. AXIAL SKELETON. In the hog the ligamentum nuchce can scarcely be said to exist ; a fibrous cord from the dorsal spines to the occiput represents it. There is only one synovial capsule in the occipito-atloid joint, and there is a transverse odontoid ligament which passes over the odontoid process, and keeps it down on the floor of the atloid ring. The sternal ribs articulate distally like those of the ox, and the remarks on the sternal articulations of that animal also apply to the hog. The temporo-inaxillary joint possesses great motion anteriorly and posteriorly, resembling in its structure that of the rabbit, the anterior mastoid process being small, and the temporal articular surface large. The ligaments between the hyoid cornua and cornicula are elastic. APPENDICULAR SKELETON. The synovial membrane of the shoulder joint is continued into the bicipital groove. In the elbow joint the internal lateral ligament is shorter than the external one. The radius and ulna have been described as anchylosed and also as closely connected by fibrous tissue. Whichever be the more common mode of union, there is no motion between these bones. The foiu' bones of the metacarpus are joined by prolongations of the great carpal ligaments above, and below by interarticular ligaments. Each metacarpo-phalangeal joint is supplied with an intersesamoid, two lateral, a crucial inferior sesamoid, and an anterior capsular ligament, also with a synovial membrane, and lateral liga- ments for the joint itself. The suspensory ligament is replaced by the inter- osseous palmar muscles, and there are small superior interdigital ligaments between the proximal phalanges. A very small osseous nodule is usually found on each of the anterior capsular ligaments of these joints. The external lateral navicular ligaments resemble those of the horse ; the internal ones are wanting. An elastic navicular ligament like that of the ox is found in the large digits. There is no pubio-femoral, and only one straight patellar ligament. The tibio- fibular articulation consists of an amphiarthrosis superiorlj^, a diarthrosis inferiorly, and between these an interosseous ligament, stronger below than above. The tarsal articulation resembles in the main that of the ruminant. ' CARNIVORA. AXIAL SKELETON. The ligamentum nuchas is represented by a fibrous band which is larger in the dog than in the cat ; in the cervical vertebrae of the former, and in the vertebrae generally of the latter, there are interspinous muscles instead of liga- ments. The occipito-atloid and odontoid ligaments are similar to those of the hog. In the temporo-7naxillary ^oint there is merely ginglymoid motion, and the meniscus is very thin. APPENDICULAR SKELETON. In the carnivora the synovial membrane of the shoulder joint is similar to that of the hog in its arrangement. The lateral ligaments of the elbow joint, 1^4 COMPARATIVE ARTHROLOGY. together with the annular ligament, form a kind of ring in which the head of the radius slightly revolves, as there is a certain amount of motion between it and the ulna. The racUo-ubiar articulation consists of a superior and an inferior rotatory diarthrosis, and an interosseous ligament ; the rotatory movements between these bones are termed 2>ronation and supination, the prone being the normal position of the extremity. The metacarpus is formed similarly to that of the hog, but it is more mobile, and the rest of the articu.la- tions of the limb resemble those of that animal, with the exception of the distal interphalangeal, where we find anteriorly an elastic ligament which acts as the retractor of the claw, and is stronger and much more active in the cat than in the dog, the claw of the former being much more retractile. Posteri- orly a piece of fibro-cartilage is the analogue of the navicular bone, which is wanting. The patella has one straight ligament, and the menisci are united. In the tibio-fibular articulation, there is superiorly a diarthrosis, otherwise it is formed on the same plan as that of the hog, as is the tarsal joint, excepting that the astralagus has an inferior head instead of a trochlea. CHAPTER III. MYOLOGY. The branch of anatomy which treats of the muscular system is called Myology. The muscles are the active organs of motion, or of locomotion, the bones and ligaments being passive organs of the same. Before studying the muscles individually it is necessary to take a brief view of their anatomical and histological structure. They contain the specific contractile substance termed m,uscular tissue, together with areolar and fibrous tissue, and a certain amount of fatty material ; they are also furnished with nerves, blood-vessels, and absorbents. MUSCULAR TISSUE. Muscular tissue is the name applied to contractile fibres, which are either collected into bundles connected at their extremities, and forming distinct organs termed muscles, to which the familiar name flesh is apj^lied ; or they are found helping to form the walls of the hollow viscera, as the bladder, stomach, &c. In the first variety the fibre presents, when magnified, a striped appearance, the stripes being placed transversely ; it is therefore known as striped or striated fibre, and as with little exception its contraction and relaxation are controlled by the will of the animal, it is also termed voluntary fibre or muscle. The second variety differs from the first in not being striped, and also in its action being beyond the control pf the will ; hence it is named non-striated or involuntary fibre. The chief exceptions to this general distinction occur in the heart and in the upper part of the oesophagus, which contain Mivoluntary striated tissue. Both varieties are red in colour, but the hue of the striated kind is far deeper. We therefore describe two kinds of muscular tissue, the striated and the non-striated. 155 156 MYOLOGY. STRIATED MUSCULAR TISSUE. '':m Voluntary or striated muscular tissue forms the mass of the so-called muscles, which terminate at either extremity in fibrous structures termed the tendons, by means of which they are attached to the bones ; the intermediate fleshy portion is often called the belly of the muscle. A muscle is composed of bundles, or fasciculi of fibres, which are the integral parts of the structure. The microscope shows these fibres to consist of fine filaments tei-med jihrillce, which run 2)arallel to each other, maintaining an undivided course throughout. Each fibre is enclosed in a delicate tubular sheath called the sarcolemma or mijulemvia, composed of a transparent and ap- parently homogeneous membrane, tough and elastic, which isolates each fibre, and frequently remains intact after rupture of its contents. The fibres, about -g^ytli of an inch in diameter, are gathered into prismatic or polyhedral fasciculi, and invested with a sheath of connective tissue, which is inflected between the fibres, and called the 'pervniysium internwni ; the entire muscle has likewise an investing sheath of connective tissue, the 'peri- mysium externum, continuous with the above. This connective ii ill of Fig. 66, Fasciculus striated muscu- lar fibres. Trans- verse striae seen at a ; b, Union of fibres ^^ith the teudon. Fifi. 67. A single striated muscular fibre, showing its com- ponent tibrillas. tissue is membranous in structure, its use being to connect the bundles and fibres, and to serve as a matrix for the ramification of blood-vessels, nerves, and absorbents. A muscular fibre, examined under a power of 300 diameters or less, will display the transverse waving strice or lines, from which the name " striated " is derived. Longitudinal markings NOX-STRIATED MUSCULAR TISSUE. 157 or lines are also often apparent, but are less I'egular than the strise.' The component fibrilljie of a muscular iibre may be demon- strated by macerating the tissue in strong alcohol, and pressing the prepared object, when each fibrilla will be seen to consist of a row of alternately light and dark spots. By other means, such as treatment with hydrochloric acid, or by a smart blow, a muscular fibre may be separated into transverse discs correspond- ing to its striated appearance. These two separations of a fibre have been termed the longitudinal and transverse cleavages. Could both these operations be performed on the same fibre, the result would be a crucial cleav- age of it into a number of objects which would appear under a high power as dark spots, with light spaces round them, both being rectang- ular in form ; they are known as the sarcous elements of BoiumcLii, and in them was believed to rest the inherent power of con- tractility. Thus a transverse row of sarcous elements forms a disc ; a longitudinal row a fibrilla. "When seen through the medium of the sarcolemma the dark spots apjDear trans- versely as a continuous line, hence the striated appearance of the fibre. The fibres cleave more readily into fibrillar than into discs. Modern observation modifies the above, the fibre being gener- ally regarded as a series of alternate light and dark discs, the latter having on each transverse surface a number of darker granules, connected by fine longitudinal and transverse lines. The former with their nodular extremities are termed muscle-rods. A number of oval objects, related with the sarcolemma, appear on treating a fibre with acetic acid ; these are the onuscle corpuscles, and they are nucleated. Striated fibres are for the most part isolated, but those of the heart, which, as already stated, are involuntary, divide into branches, and the branches of different fibres frequently join, or, as it is termed, anastomose. (Fig. 152.) NON-STRIATED MUSCULAR TISSUE. Involuntary or non-striated muscular tissue is pale in colour, and consists of fibres, bound into fasciculi by a fine perimysium of areolar tissue. striated muscular fibres from the Horse. 158 MYOLOGY. The fibres never terminate in tendons, and are not invested in a sarcolemma ; they are cylindrical in shape, and composed of fusiform or elongated cells, which become apparent after macera- tion of the tissue in dilute hydrochloric acid or other reagents, or it may be without any such preparation. These cells are the contractile cells of Kolliker, and in them an elongated nucleus may be visible. The fasciculi vary very greatly in size in dift'erent situations, and often crossing each other, they give the tissue in some parts a mesh-like appearance. The non-striped tissue is very abundant, being found in the walls of the alimen- tary canal and hollow viscera, in gland ducts, in the coats of ^ T, c blood-vessels, in the skin, and elsewhere. Both varieties of muscular tissue are plentifully supplied with blood, and in stri- ated tissue the capillaries or minute blood- vessels are arranged longitudinall}'' with transverse connecting branches, but they do not penetrate the sarcolemma, they and the larger vessels alike being found in the perimysium or interstitial connective tissue. The striated tissue is supplied with nerves from the cerebro-spinal system, but the non- striated tissue receives its supply from the sympathetic system, and the vital stimulus conveyed by either of these causes the con- traction of the fibres. The description of the arrangement of involuntary^ tissue forms no part of the present section of our subject; the tissue is described here chiefly in order that its structure may be com- pared with that of the voluntary kind Fig. 69. A, Non-striated muscular fibres ; a a, The component fusiform cells ; b i, The nuclei. B and C, Single cells more highly magnified ; C having been treated with acetic acid. TENDONS. The tendons in which voluntary muscles terminate at either end are structures resembling ligaments in their composition, being formed of white fibrous tissue mixed with yellow fibres. Like ligaments, they are practically non- elastic, and while they attach the muscles to the bones, they merely transmit the action of the former to the latter, and are therefore jDassive instruments of motion. The extremity of a muscle which has the most fixed attachment FASCIA. 159 is called its origin ; the other extremity attached to the more movable structure, its insertion. The tendon of insertion is often longer than that of origin, which is frequently rudimentary. In some cases both extremities are equally movable. The strongest part of a muscle is its point of union with the tendon, but the manner in which that union is effected is not satisfactorily explained. According to some authorities, the muscular fibres are prolonged into the connective tissue of the tendon ; or, " the contractile fibre terminat-es in a rounded ex- tremity which is buried in a corresponding depression in the tendon " (Ghauveau). The sarcolemma and the areolar tissue, both of the fibre and tendon, are no doubt instrumental in effecting the union. Tendons often send processes into the substance of the muscle, which may extend throughout its length ; such processes are described as tendinous intersections ; they also appear to send small fibres into the substance of the bones to which they are attached. Tendons vary in form, size, and density, but all are either rounded or flattened. The former are funicular, the latter aponeurotic tendons ; in either form their use is the same. They become attached to bones through the medium of the periosteum, sometimes expanding to strengthen its outer layer. Each group of muscles is invested and bound down by a strong membranous expansion of white fibrous tissue, called fascia, which is firmly connected with the bone. This term is, however, applied to other membranous expansions, differing very materially in strength, texture, and relations. For example, below the skin and panniculus there is a membranous expansion, which forms a continuous covering over the whole body, composed of connective tissue more or less condensed. Hence fasciae have been divided into superficial, and deep or aponeurotic. Superficial fascia, consists of cellular and elastic tissue, varying in thickness in different regions of the body. Where the skin is loose it is most distinct ; and sometimes it is inseparable from the muscles and skin, as in the eyelids and lips. Its meshes may be filled with adipose cells, or condensed so as to form a fibro-cellular membrane destitute of fat. Its use is to connect and protect the various structures it contacts, and to furnish a matrix for 160 MYOLOGY. blood-vessels; the fat in the subcutaneous fascia helps to conserve the animal heat, fat being a bad conductor. Aponeurotic fascia not only covers, supports, and binds down the groups of muscles, but affords processes between them, and becomes united to, and blended with, the periosteum. Some of these fasciae have distinct muscles for rendering them tense, as the tensor fasciae latse. Fasciae are also found in connection with the walls of cavities, as in the pelvis. In the limbs, where the muscular bellies form lengthy masses, with long tendons attached at considerable distances, there would be considerable displacement during motion, were it not that in these parts the fascia is very strong, enclosing the body of each muscle in a sheath, as also each group of muscles. MUSCULAR NOMENCLATURE. Muscular nomenclature is unsatisfactory and confused, some muscles being named from their form, as Trapezium, E-homboideus, Scalenus ; others from their use, as Flexor, Extensor, Adductor, Abductor, &c. ; some from their direction, as Rectus, Transversus, Obliquus ; others from their situation, as Temporalis, Peroneus, Subscapularis ; some again from their attachments, as Sterno- maxillaris, Coraco-radialis, and Stylo-hyoideus ; and some from their homologues in the human subject. A muscle may have a physiological name expressing its use, and an anatomical one alluding to some feature in its morphology ; but perhaps the most satisfactory system of nomenclature is that which names muscles from their attachments. Muscles vary so much in shape that no classification of them can be based on that feature. Some of them, however, present such marked features that certain terms are used to describe their form. Thus, hiceps and triceps express a two or three-headed muscle ; a diagastric muscle has two bellies, joined by a median tendon ; a radiating muscle consists of bundles diverging from a point of attachment ; a penniform muscle resembles a feather in shape, and a semipenniforni one the lateral half of the same, the tendon corresponding to the axis or scapus of the feather. In the descriptions of muscles which follow, the names printed in small capitals are those most commonly in use in Great Britain, whereas the names below, and in italics, are almost uniformly anatomatical, expressing in most cases the places of EXPLANATION OF PLATE IL Muscles of the Horse. Superficial Layer. The jMnnicul'US and tunica ahdomhialis are removed. 1. Alxlncens. 33. Extensor metacarpi magnus. 2. Eetrahentes muscles. 34. Humeralis obliquus. 2'. Attolleiis maximus. 35. Extensor pedis. 2".Attolleni? anticus. 36. Flexor metacarpi externus and 3. Temporalis. medius. 4. Nasalis longus. 5. Orbicularis palpebrarum. 37. Flexor metacarpi internus. 6. Levator labii superioris alaeque nasi. 46. Cervical ) ^ , > serratus magnus. Dorsal J 7. Dilatator naris lateralis. 47. 8. Orbicularis oris. 48. Rhomboideus longus. 9. Zygomaticus. 49. Superficialis costarum. 9'. Buccinator. 50. Splenius. 10. Depressor labii inferioris. 52. Intercostales. 11. Masseter. 54. Tensor fasciae latse. 12. Levator humeri. 55. Triceps abductor femoris. 13. Trapezius cervicalis. 56. Gluteus externus. 14. Trapezius dorsalis. 61. Biceps rotator tibialis. 15. Latissimus dorsi. 62. Rectus femoris. 18. Pectoralis parvus. 19. Pectoralis magnus. 63. Vastus externus. 20. Sterno-maxillaris. 65. Gastrocnemius. 23. Subscapulo-hyoideus. 68. Flexor pedis perforans. 24. Antea-spinatus. 69. Peroneus. 25. Teres externus. 70. Extensor pedis. 26. Postea-spinatus. 71. Flexor metatarsi. 30. Caput medium 1 of the triceps 31. Caput magnum J extensor brachii. 72. Flexor pedis accessorius. 74. Obliquus abdominis externua PANNICULUS CARNOSUS. 161 attachment of the muscles — a nomenclature more valuable though less current than the one in use. CLASSIB^ICATION OF MUSCLES. Either an Anatomatical or Physiological mode of classification can be applied to the muscular system, but the former is of cojrse the one adopted here. Again, muscles may be classed anatomatically either according to their attachments or to the regions their fleshy portions chiefly cover. Although a nortien- clatiire based upon the attachments of muscles is most valuable, a descriptive classification so constructed would lead to confusion, hence we group the muscles according to the regions they mainly occupy, and divide them primarily into those covering each of the following regions : — Subcutaneous region. Head. Trunk. Pectoral limb. Pelvic limb. We shall describe them in the above order, subdividing each region as may be necessary. Muscles. subcutaneous region. panniculus carnosus. {Musculus Suhcutaneus.) After carefully removing the skin and subcutaneous cellular tissue, the first muscle which presents itself is one peculiar to quadrupeds, the Pannicuhis carnosus. This muscle is spread over the greater part of the body, and may be divided into facial, cervical, thoracic, and abdominal portions, but as these are con- tinuous with each other, we can conveniently describe the whole as a single structure. The panniculus, as a whole, is aponeurotic superiorl}^ becoming more and more fleshy as it descends. It is firmly attached to the skin by connective tissue. The facial portion consists of an aponeurotic expansion, which becomes muscular over the muscles situated below and before the zygoma. Its fibres are arranged in a divergent manner, radiating M 162 ',* MYOLOGY. from the arlgle of the iliaxilla, and a portion is inserted to the orbicular muscle of the mouth, forming the Retractor anguli oris '(Risorius Santorini). Posteriorly it unites with the cervical por- tion, which is likewise chiefly aponeurotic, comm^cing in^ "front of the neck by' a thin muscular band, it joins itp fellow in the median line by a. fibrous raphe, and covers the ^^muscles of the inferior cervical region. Above it becomes aponeurotic, and is \attached to the ligamentum nuchse, while iiifero-laterally it becomes more fle^iy, and is inserted to the mteHor pq|tion of the cariniform cartilage ; some describe thJs= |i^rtion as ^^krt of the Levator humeri, the panniculus being firml^f blended with that muscle inferiorly. The thoracic portion is colitinuoUs with the cervjcal,. at the sternum, and passes over thfe front of the ♦shoulder superiorly, covering its external side; it is attached to the dorsal spines together with the trapezius. The abdominal - portion forriis' a -broad oval-shaped lleshy expansion, its fibres rtinnihg from" tlie flank to the shoulder; it is thick and flesh}^ behind the arm, where it has a well-rnarked, flat tendinous attach- ment to 4he skin, and below which a tendinous expansion pene- trates between the chest and the 'limb, and is. attaelred to the Pectoralis i^agnus and internal trochanter of the humerus. Posteriorly, by.a strong band, fleshy and ^apojie orotic, it reaches the stifle joint and fascia of th^ thi^h ; above, it ^reaches the lumbar and dorsal spines; and below it betomes "blended with the abdominal fascia: - ,' '^ ' \» ^' ■'■' Relation^ — It is i:elated externally with thq skin ; intefnally with the sup#ficial layer of muscles. - --- "'T.- Action., — .Jt corrugates the skin, and' thus enables tlie animal to expel insects and irritating bodies, its use being thus protec- tive ; to some extent it also supports and binds down the subja- cent muscles. The Head. * The muscles of this region may be divided into the following groups : Anterior maxillary. Posterior maxillary. . Hyoidean. Palpebral. . -- ^ \ Auricular. ' . .- ; In addition to these we h^ve tlie Glogs^l,"lP'haryngeal, ^nd Laryngeal groups also associated with the head> the two first>of ANTERIOR MAXILLARY GROUP. - / . ''n 163 _ -^ ^■: these will be more ajDiJropriately described hereafter >#Ken treat- ing of the Tongue and Pharynx, and the las|i alaiigv with the Larynx. ANTERIOR MAXILLARY GROI*. In the broad sense this group occupies the anterior half of the skirH, -certain of the muscles extending further backwards ; it consists of the following muscles : — Zygomaticus. Buccinator. Orbicularis oris. Levator labii superioris alteque Nasalis longus. [nasi. Dilatator naris lateralis. Dilatator naris transvei'sus. Dilatator naris inferioris. Dilatator naris superioris. Depressor labii superioris. Levator labii inferioris. Depressor labii infeiioris. ZYGOMATICUS. ,< (Zi/ffomatico-lahicdis.) ... (PL. XL 9.) A ribbon-shaped muscle, very pale and small, situated on the side of the face, its fibres extending forwards. Attachments. — It arises from the fascia of the masseter, near the anterior aspect of the maxillary spine, being blended with, the panriiculus, and is inserted near the angle of the mouth, its fibres blending Avith the buccinator. AcHon. — It retracts the angle of the mouth. BUCCINATOR. [Alveolo-labialis.) (Pl. n. 9'. Fig. 7Q. l) Situated on the side oT the face, covering the diastema and molar teeth, this muscle is flat and-itfcin, and con&ists of two layers, sometimes described as separate muscles. Attachments. — The internal layer arises, under the masseter, from the alveolar tuberosity, and alveoli of the molar teeth of • both jaws, and blends with the orbicularis oris. The external layer exists- only antefiojly, and is penniform,, its fibres being inserted along the rnferdental spaces. Relations'. — ^This/muscle is related superiorly with the molar glands, postero- externally with the masseter, and internally with the buccal membrane. 164 MYOLOGY. Action. — It retracts the angle of the mouth, but specially serves to force the food between the molars, and to prevent the buccal membrane from being injured by the latter. ORBICULARIS ORIS. {Labialis.) (PL. IL 8.) This is a sphincter or annular constrictor muscle, and as such has virtually neither origin nor insertion ; surrounding the mouth and forming the substance of the lips, it is separable into two layers, and is related internally with the mucous membrane of the mouth and the labial glands, and externally with the skin, to which it is firmly adherent. It is the intrinsic muscle of the lips, and receives for the most part the insertions of the extrinsic muscles. Action. — It is the constrictor of the anterior aperture of the mouth, and also assists in mastication, suction, and prehension of food. LEVATOR LABII SUPERIORIS AL^QUE NASL (Sitpernaso-lahialis.) (Pl. IL 6.) Situated superiorly, on the side of the cheek, running forwards and downwards, this muscle is long, flat, and aponeurotic supe- riorly, dividing into two unequal bands, between which passes the dilatator naris lateralis. Origin. — It arises from the frontal and nasal bones, the anterior division, the larger and thicker, passing under the dila- tator above named. Insertion. — To the nostril and upper lip, the posterior division reaching the angle of the mouth. Action. — It raises the upper lip and angle of the mouth, and dilates the nostril. NASALIS LONGUS. {SupermaxiUo-Iahialis.) (Pl. II. 4. Fig. 70. cj.) Situated below the preceding muscle, this muscle runs hori- zontally forwards. In shape it is pyramidal, with a fleshy belly and a long tendon of insertion. NASAL MUSCLES. 165 Origin. — It arises from the surface of tlie superior maxilla, at its junction with the malar and lachrymal bones. Insertion. — The tendon passes to the extremity of the nose, where, joining its fellow, it forms a radiating expansion, becoming lost in the upper lip. Action. — It elevates and corrugates the uj)per lip, if acting with its fellow ; if acting alone, it pulls the lip to one side. Fig. 70. Muscles of the head — left lateral view, a, Abducens ; h c d, Scuto-auriculaiis externus, luferior, middle, aud superior i)ortions ; e, Levator palpebraj superioris exteriius ; / /, Orbicularis palpebrarum ; , Trachelo-aiastoideus ; r c c c, lutertrausversalis colli. flat, and triangular ; aponeurotic only at its periphery, its belly is made up of large fleshy bundles, which are directed obliquely forwards and upwards to the head and first cervical vertebra. Attachments. — To the funicular portion of the ligamentum nuchse, the transverse processes of the third, fourth, and fifth cervical, and the spines of the first four or five dorsal vertebras ; to the crest and mastoid ridge, in union with the tendon of the trachelo-mastoideus, and to the wing of the atlas, along with the common tendon of the trachelo-mastoideus and the levator humeri. 186 MYOLOGY. Relation. — Externally with the levator humeri, cervical trape- zius, serratus magnus, and rhomboideus muscles ; internally with the complexus major, trachelo-mastoideus, and obliquus capitis muscles. Action. — With its fellow it elevates the head ; alone it draws the head to one side. (Dorso-mastoicleits.) (Fig. 73. h.) Situated under and along the inferior border of the splenius, it is elongated and fleshy, its fibres passing forwards and upwards ; the belly is divided into two portions, which run parallel, each terminating by a tendon anteriorly. Origin. — From the transverse processes of the first two dorsal and the oblique processes of the last five cervical vertebrae. Insertion. — By two tendons; one to the wing of the atlas, common also to the splenius and levator humeri ; the other, continuous with that of the splenius, to the mastoid ridge. Relation. — Externally with the splenius ; internally with the spinalis colli ; posteriorly with the longissimus and spinahs dorsi. Action. — "With its fellow to erect the head ; acting alone, it draws it to one side. COMPLEXUS MAJOR. ( Borso-occipitcdis. ) (Fig. 73. a.) Situated on the inside of the splenius, this muscle resembles an elongated triangle, with the base backwards ; it is fleshy, with tendinous intersections. The posterior part is aponeurotic at its origin, the anterior terminating in a single tendon. Origin. — From the transverse and spinous processes of the first five dorsal, and the oblique processes of all the cervical vertebrae. Insertion. — To the side of the occipital tuberosity. Relation. — Externally with the splenius and trachelo- mastoideus ; internally with the complexus minor, ligamentum nuchae, and oblique muscles ; posteriorly with the longissimus * This is the complexus minor of M. Chauveai;. LATERAL CERVICAL GROUP. 187 and spinalis dorsi. The superior cervical aitery passes through its divisions posteriorly. Action. — It extends the head. COMPLEXUS MINOR. {A xoido-occipitalis Longus. ) (Fig. 74. c.) Situated on the poll, it is fusiform, slender, and fleshy, being tendinous at its insertion. Origin. — From the neural spine of the dentata. Insertion. — With the tendon of the complexus major. Relation. — Externally with the complexus major ; inferiorly with the rectus capitis posticus major ; internally with the liga- mentum nuchse. Action. — To assist the complexus major. RECTUS CAPITIS POSTICUS MAJOR. (^Axoido-occvpitalis Brevis.) (Fig. 74. d.) Situated below the complexus minor, it is long, slender, and fusiform. Origin. — From the neural spine of the dentata. Insertion. — To a roughened depression on the occiput below its tubercle. Relation. — Externally Avith the complexus major ; inferiorly with the rectus capitis posticus minor. Action. — To extend the head. RECTUS CAPITIS POSTICUS MINOR. [A tloido-occipitcdis Brevis. ) (Fig. 74. e.) Situated below the preceding, this muscle is small, flat, and somewhat triangular. Origin. — From the supero-anterior part of the atlas. Insertion. — Below that of the preceding muscle. Relation. — Superiorly with the major ; inferiorly with the capsular ligament ; externally with the obliquus capitis anticus ; internally with the ligamentum nuchte. Action. — It assists the preceding muscle. 188 MYOLOGY. OBLTQUUS CAPITIS ANTICUS. (AtJoido-)nastoideus.) (Fig 74 I.) Situated on the side of the poll, it is flat, nearly square, and fleshy, with tendinous intersections. Origin. — From the supero-anterior portion of the roughened edge of the wing of the atlas. Insertion. — To the mastoid crest and styloid process of the occiput. fiG. 74. Occipito-atlo-axoid muscles— lateral view, a, 0b]i(iuus capitis posticus ; I, Obliquus capitis anticus ; c, Complexus minor ; d, Rectus capitis posticus major ; e, Rectus capitis posticus minor. Relation. — Externally with the tendon of the splenius; internally with the capsular ligament and rectus capitis posticus muscles. Action. — Together, to extend the head slightly ; singly, to bend it laterally on the atlas. OBLIQUUS CAPITIS POSTICUS. (Axoido-afloideus. ) (Fig. 74. a.) Situated between and upon the atlas and axis, it is broad, flat, thick, and fleshy. LATERAL CERVICAL GROUP. 189 Origin. — From the lateral surface and superior spine of the dentata, and the capsular ligament. Insertion. — To the upper surface of the wing and body of the atlas. Relation. — Externally with the splenius, trachelo-mastoideus, and complexus major ; internally with the atlas, axis, and the atlo-axoid capsular ligament ; superiorly with the rectus posticus, and inferiorly with the rectus anticus major muscles. Action. — It is the rotator muscle of the head. SPINALIS COLLI. (Do^'so-sjnnalis. ) Deep-seated on the side of the neck, it consists of six short fleshy bundles, intersected by tendons, whose fibres extend obliquely upwards and inwards. Origin. — Posteriorly, from the oblique processes of the first dorsal and the last five cervical vertebrae. Insertion. — To the neural spines of all the cervical vertebra but the first. Relation. — Externally with the complexus major and trachelo- mastoideus ; internally with the ligamentum nuchas and the vertebrae. Action. — To extend and curve the neck. INTERTRANSVERSALIS COLLI. [Iniercervicalis.) (Fig. 73. c c c c.) Placed along the lateral part of the cervical vertebra, it consists of six distinct bundles with strong tendinous intersections, the fibres passing obliquely outwards and upwards. Origin. — The oblique process of one vertebra. Insertion. — The transverse process of the vertebra in front, filling up the interspaces of all, excepting those of the first and second. Relation. — With several deep-seated muscles of the neck, the vertebrae, the vertebral artery, and vein. Action. — To assist in flexing the neck laterally. 190 MYOLOGY. Costal Region. The muscles of this region are those which cover the lateral aspect of the thoracic cavity ; some of them are attached to the anterior limb, three of which we describe the first, as it is necessary in dissection to cut through them, and remove or deflect the limb in order to expose fully the deeper-seated muscles. The following are the muscles of the region : — Superficialis costarum. Trans versalis costarum. Levatores costarum. Trapezius dorsalis. Rhomboideus brevis. Latissimus dorsi. Serratus magnus. Intercostales. TRAPEZIUS DOESALIS. {Dorso-acromicdis. ) (Pl. IL 14.) Situated on the side of the withers, this muscle is flat and triangular, being almost the reversed counterpart of the cervical trapezius. The two form the trapezius onuscle. It is aponeu- rotic at its superior border, while its belly is fleshy, terminating in a flat tendon. Origin. — Superiorly, from the supraspinous ligament, and from the third dorsal spine back to the tenth or eleventh. The fibres converge downwards and forwards, over the superior costa of the scapula, and join the cervical portion. Insertion. — The tubercle on the spine of the scapula. Relation. — Externally with the skin and panniculus ; internally with the rhomboideus brevis, postea-spinatus, and latissimus dorsi. Action. — To draw upwards and retract the scapula. rhomboideus brevis. (^Dorso-suhscapularis. ) (Pl. IIL 12.) Deep-seated, on the side of the withers above the scapula, it is flat and square ; the fibres extend downwards, and are entirely fleshy. COSTAL REGION. 191 Origin. — From the neural spines of the first four or five dorsal vertebrse, and from their supraspinous ligament. Insertion. — To the inner surface of the superior costa of the scapula, and to its cartilage of prolongation. Relation. — Externally with the cartilage of the scapula, and the dorsal trapezius, and separated from the anterior portion of the superficialis costarum by a thin layer of elastic tissue ; anteriorly with the rhomboideus longus; posteriorly with the latissimus dorsi ; internally with the splenius. Action, — To draw the scapula upwards. LATISSIMUS DORSI. {Dorso-humercdis. ) (Pl. XL 15.) This muscle is situated on the supero-lateral part of the chest and the loins ; it is very large, flat, thick, and triangular, its fibres extending obliquely downwards and forwards ; it is aponeu- rotic above, fleshy below, with a tendinous and aponeurotic insertion. Origin. — By a broad aponeurosis, from the supraspinous liga- ment and spinous processes of the vertebrae, commencing about the highest point of the withers, and stretching as far as the last lumbar. The fleshy portion becomes thick just behind the scapula, then it contracts, terminating in a flat tendon, which passes under the latter. It fits in a notch at the dorsal scapular angle, formed by the projection of the cartilage of prolongation, which it overlaps. Insertion. — The internal tuberosity of the humerus, along with the teres internus, and between the two insertions of the coraco-humeralis. Before passing under the scapula, it gives off a strong aponeurosis, which passes over the supero-posterior part of the scapula, and becomes continuous with its fascia. Relation. — Externally with the panniculus carnosus, skin, triceps extensor brachii, and dorsal trapezius ; superiorly with the rhomboideus brevis and dorsal angle of the scapula ; inter- nally with the ribs, serratus magnus, superficialis costarum, and gluteus maximus. Action. — To elevate the humerus, and thus flex the shoulder- joint ; it is likewise an expiratory muscle, when the limb is fixed. 192 MYOLOGY. SERRATUS MAGNUS. (Costo-subsca2mlaris. ) (Pl. III. 10. 15.) Situated between the shoulder and chest, and on the side of the neck, this is a large fan-shaped muscle ; it may be divided into a cervical and a costal portion, and consists of several bundles with many tendinous intersections, converging upwards to the common point of insertion. Origin. — Anteriorly, from the transverse processes of the five posterior cervical vertebrae ; postero-inferiorly, from the external surfaces of the eight true ribs, from about their middles to their cartilages. Insertion. — Superiorly to the venter surface of the scapula, between the origin of the subscaj)ularis and the insertion of the rhomboidei. Relation. — Anteriorly with the splenius ; superiorly with the rhomboidei ; supero-posteriorly with the longissimus dorsi ; poste- riorly with the great oblique muscle of the abdomen, with which it interdigitates ; inferiorly with the pectorals ; internally with the ribs, longissimus dorsi, splenius, cervical vertebrae, and iuter- costals ; externally with the subscapular and triceps extensor muscles. Action. — It depresses the scapula ; when the limbs are fixed, it elevates the neck, and is^so a subservient muscle of inspira- tion; but it chiefly serves with its fellow as a muscular sling, in which the body is suspended between the anterior limbs. SUPERFICIALIS COSTARUM. [Dorso-costalis.) Pl. II. 49. Placed on the supero-lateral part of the back, this muscle is broad, thin, and digitated, and consists of an anterior and a posterior portion. Origin. — Anteriorly, from the supraspinous ligament, and dorsal spines from the second to the thirteenth inclusive ; poste- riorly from the spines of the last eight dorsal and anterior lumbar vertebrae. Insertion. — The anterior part to the nine ribs behind the fourth, just below their angles, and to their anterior borders; the posterior part to the posterior borders of the last nine ribs. 1^ EXPLANATION OF PLATE IIL Muscles of the Horse. Layer. 1. Temporalis. r. Stylo-maxillaris 2. Rectus capitis anticus major. 3. Sterno-thyro-liyoideus. 4. Sterno-maxillaris. 5. The Trachea. 6. Scalenus. 7. Splenius. 8. Funicular part of ligamentum nuchse. 9. Rhomboideus longus. K). Cervical J f serratus magnus. 15. Costal J ^ 11. Cartilage of prolongation. 12. Rhomboideus brevis. 13. Transversalis costarum. 14. Longissimus dorsi. ] 5. Serratus Magnus. 16. External intercostals. 17. Internal intercostals. 18. Rectus abdominis. 19 19. Pectoralis magnus. 20. Postea-spinatus minor. 21. Flexor brachii. 22. Humeralis obliquus. 22'. Caput parvum (of triceps extensor brachii). 23. Extensor suffraginis, 24. Extensor metacarpi magnus divided. 25. Extensor metacarpi obliquus. ' 25'. Its tendon. 26. 28. Flexor pedis perforans and perforatus.. 29. Obliquus abdominis internus. 30. Gluteus maximus. 31. Erector coccygis. 32. Curvator coccygis. 33. Depressor coccygis. 34. Rectus femoris. 35. Vastus externiTs.' 36. Part covered by triceps abductor. 37. Biceps rotator tibialis. 38. Gastrocnemius. 39. Plantaris. 40. Flexor pedis perforans. -41. Peroneus. 42. Flexor metatarsi. 43. Extensor pedis (cut across) COSTAL EEGION. 193 Relation. — Internally with the ribs, transversalis costarum, and longissimus dorsi ; externally with the rhomboideus, serratus magnus, and latissimus dorsi. Action. — Respiratory ; the anterior portion drawing the ribs outwards and forwards, acts as an inspiratory, the posterior, by drawing them backwards and upwards as an expiratory muscle. TEANSVERSALIS COSTAEUM. ( Trachelo-costalis. ) (Pl. III. 13.) Situated on the supero-lateral part of the thorax, it is long, thin, and semipenniform, the fibres passing downwards, outwards, and forwards, its numerous muscular bundles each terminating in a flat tendon. Origin. — From the transverse processes of the first lumbar vertebrae, and the ribs near their tubercles. Insertion. — To the external surface of all the ribs, a tendon to each, and one to the last cervical vertebra. Relation. — Externally with the preceding muscle ; internally with the ribs ; superiorly with the longissimus dorsi. Action. — It compresses the ribs, assisting in expiration. LEVATORES COSTARUM. ( Transverso-costales. ) Situated deeply on the back, these muscles are small, flat, and triangular, extending obliquely dowuAvards and backwards. They are fleshy and tendinous. Origin. — Superiorly, from the transverse processes of the dorsal vertebrae, just above the tubercles of the ribs. Insertion. — Inferiorly to the external faces of the ribs, just above their angles. Relation. — Externally with the longissimus dorsi ; internally with the external intercostals, with which posteriorly they are much blended. Action. — To raise and draw the ribs forwards, thus acting as inspiratory muscles. o 194 MYOLOGY. INTERCOSTALES. {Externi and interni.) (PL. III. 16, 17.) These fill up the spaces between the ribs, are external and internal, and usually seventeen in number, consisting of flat bands, included in, and intersected by, many broad aponeurotic slips. The external ones are thickest above, the internal below, the former terminating at the costal cartilages, between which the latter extend. Origin. — From the posterior border of each rib. Insertion. — The anterior border of each succeeding rib, the fibres of the external ones extending downwards and backwards, those of the internal ones downwards and forwards. The external terminate at the costal cartilages, while the internal do not extend above the angles. Relation. — Externally with the serratus magnus, superficialis and transversalis costarum, and latissimus dorsi ; internally with the pleura. Action. — They are inspiratory muscles, drawing the ribs for- ward, the first rib being rendered a fixed point by the contraction of the scalenus. They thus aid the diaphragm in its action. Pectoral Region. In this region we describe two groups of muscles, the 'pectoral and the sternal, the latter being deep-seated. Pectoral Group. This group consists of four pairs of muscles, which are largely developed in the horse, and all of which arise from the external surface of the sternum and its appendages, and become attached to the pectoral limb, upon which they, as a group, assist in sus- pending the body, also in moving the limb, and in respiration. They are differently described by different authorities ; Percival and Leyh describe three pairs, Chauveau two, but as the latter divides each of them into two parts, his consideration ultimately agrees with the one adopted here. We describe four pairs of pectoral muscles : — Pectoralis transversus. I Pectoralis anticus. PectoralLs magnus. | Pectoralis parvus. PECTORAL GROUP. 195 PECTOEALIS TRANSVERSUS. {Sterno-cq^oneuroticus.) (Fig. 75. d.) Situated on the latero-inferior part of the thorax, this muscle is quadrilateral, the fibres extending outwards and downwards. Fig. 75. Pectoral muscles, .and inferior deep muscles of the neck, a, Longus colli ; h, Eectus capitis lateralis ; c, Rectus capitis anticus minor ; d, Pectoralis transversus ; e, Pectoralis anticus ; //, Pectoralis luaguus ; (/, Pectoralis parvus. Ou the left side the pectoralis transversus and anticus have been removed. Near its origin it is fleshy, mixed with tendon, but afterwards becomes aponeurotic. Origin. — By fleshy fibres usually from the first four bones of the sternum, meeting its fellow at a white central line. Insertion. — To the olecranon, by fascia covering the inner side of the arm, and to the anterior part of the humerus. Relation. — Externally with the skin; anteriorly with the pectoralis anticus ; superiorly with the pectoralis magnus. Action. — To adduct the arm, and especially to tense the brachial fascia. 196 PECTORALIS MAGNUS. (Sterno-trochineus. ) (Pl. III. 19, 19. Fig. 75. //.) This muscle is situated on the infero-lateral part of the thorax, and is large, irregularly four-sided, flat, and thick, the fibres extending forwards and outwards. Slightly aponeurotic ante- riorly, elsewhere it is fleshy. Origin. — From the inferior liorder of the last three or four bones of the sternum, the ensiform cartilage, and its fellow of the opposite side ; externally from the cartilages of the false ribs, fascia of the external oblique muscle of the abdomen, and the abdominal tunic. Insertion. — To the fascia on the inside of the arm, and to the inner trochanter of the humerus, under the tendon of the coraco- humeralis, and by fascia over the bicipital groove, to the external trochanter. Relation. — Externally with the panniculus, skin, and pectoralis transversus ; internally with the fascia of the external oblique, and the ribs ; anteriorly with the pectoralis parvus. Action. — To draw the shoulder back and adduct the arm ; in difficult respiration it acts as an inspiratory muscle. PECTORALIS ANTICUS. (Stemo-humercdis.) (¥iG. 75. e.) Situated on the anterior part of the breast, it forms the fleshy prominence seen in front. Short, thick, and fusiform, its fibres extend outwards ; it is tendinous at its attachments, with a fleshy belly. Origin. — From the cariniform cartilage and first bone of the sternum. It is directed somewhat backwards, outwards, and downwards. Insertion. — To a ridge on the anterior part of the shaft of the humerus by fleshy fibres, and an aponeurotic tendon common also to the levator humeri, and pectoralis transversus. Relation. — Externally with the skin ; anteriorly with the levator humeri and panniculus ; posteriorly with the pectoralis magnus and transversus ; internally with the parvus. Action. — Its chief action is to adduct the arm. STERNAL GROUP. 197 PECTORALIS PARVUS. (Sterno-prescapularis. ) (Fig. 75. g.) In front of the magnus, on tbe ant ero -inferior part of the thorax, elongated and prismatic in form, its fibres extend out- wards, forwards, and upwards ; it is lendinous at its origin, fleshy elsewhere. Origin. — From the three or four anterior sternal segments, cartilages, ribs, and cariniform cartilage. Insertion. — To the fascia in front of the shoulder-joint, and the anterior costa of the scapula, nearly as high up as the origin of the antea-spinatus. Relation. — Externally with the magnus and transversus; inferiorly with the transversus and anticus ; internally with the first costal cartilages, intercostales, and transversalis costarum ; anteriorly with the levator humeri. Action. — To draw the shoulder-joint backwards and down- wards, assist the magnus, and tense the scapular fascia. Sternal Group. The muscles of this unimportant group are two in number — Lateralis sterni. Triangularis sterni. LATERALIS STERNI. {C osto-sternalis.) Placed along the inferior border of the serratus magnus, its fibres extend downwards and backwards. It is flat, thin, and aponeurotic at its extremities. Origin. — From the outer surface of the first rib, passing over the next two or three ribs, and becoming attached to the ster- num at about the fourth segment. Relation. — Externally with the pectorals ; superiorly with the serratus magnus ; posteriorly with the rectus abdominis ; inter- nally with the ribs and intercostals. Action. — An auxiliary muscle of expiration. 108 TRIANGULARIS STERNI. (Sterno-costalis. ) Situated in the thorax and upon the sternum, it is triangular, tendinous, and dentated on its outer border. Origin. — From the superior sternal ligament and segments. Insertion. — To the cartilages, and inner surfaces of the distal ends of the true ribs, excepting the first. Action. — To assist in expiration. DORSO-LUMBAR REGION. The muscles of this region, a single group, are closely related with the superior aspect of the vertebral column, and we describe them as consisting of four — Longissimus dorsi. I Semispinalis dorsi et lumborum. Spinalis dorsi. | Intertransversales lumborum. LONGISSIMUS DORSL (Tlio-s2nnalis.) (Pl. in. 14.) Situated on the superior part of the back and loins, this, the longest and most powerful muscle in the body, occupies the space between the costal angles and the dorso-lumbar spines ; broad and fleshy at its origin in the loins, it becomes deeper and narrower as it proceeds forwards. Towards the withers it diverges, presenting three distinct portions, two of which proceed in an oblique direction to the neck, and terminate by several tendons (the deeper portion is described as the spinalis dorsi) ; the third portion is adherent to the sides of the anterior dorsal spines. The belly of this muscle is intersected by several tendons, and is invested posteriorly by a very strong, tendinous aponeurosis. Attachments. — The crest, inner surface, and supero-anterior spine of the ilium ; the spinous and transverse processes of the first two bones of the sacrum ; the spinous, transverse, and oblique processes of all the lumbar vertebrse ; the spinous and transverse processes of all the dorsal vertebrse ; the external surface of the last fifteen or sixteen ribs just above the trans- versalis costarum, and the spinous and transverse processes of the last three or four cervical vertebrse. DORSO- LUMBAR REGION. 199 Relation. — Externally with the superficialis costarum, and gluteus maximus which overlaps it in the lumbar region ; in- feriorly with the transversalis costarum ; internally with the ribs, vertebrse, and semispinalis dorsi et lumborum ; anteriorly Avith the spinalis dorsi. Action. — It is brought powerfully into play in kicking and rearing, by elevating the fore or hind quarters, according to whether the fore or hind limbs are fixed. Acting singly, the result is lateral flexion of the back and loins. It may assist also in expiration. SPINALIS DORSI. "^ Situated deeply on the withers, it is pyramidal in form, aponeurotic at its origin, with a fleshy belly ; it is with difficulty separated from the longissimus dorsi. Origin. — By aponeurosis from the supraspinous ligament, as far back as the twelfth, and from the posterior borders of the spinous processes of the six anterior dorsal vertebrae. Insertion. — To the superior spinous processes of the last three .or four cervical vertebrse. Relation. — Externally with the trapezius and rhomboideus brevis ; anteriorly with the complexus major and splenius ; infe- riorly with the longissimus dorsi ; internally with its fellow, the ligamentum nuchas, the anterior dorsal vertebrse, and semispinalis dorsi. Action. — To assist in elevatins the neck. SEMISPINALIS DORSI ET LUMBORUM. (Sjnnalis Transversus. ) In contact with the dorsal and lumbar spines, this muscle con- sists of a number of fasciculi, whose fibres are directed upwards and forwards. Origin. — From the sacrum, the oblique processes of all the lumbal', and transverse processes of all the dorsal vertebrse. Insertion. — The spinous processes of the vertebrse, the fasciculi each passing over two or three spines before being inserted ; it becomes continuous with the spinalis colli at the seventh cervical. * [This muscle may be regarded as part of the longissimus dorsi.— Ed.] 200 MYOLOGY. Relation. — Externally with the longissimus dorsi ; internally with the vertebrae. Action. — To assist in extending the spine. INTERTRANSVERSALES LUMBORUM. These are small muscular slips, invested by strong tendinous fasciae, running from the transverse process of one lumbar vertebra to the one adjacent. Relation. — With the longissimus dorsi and intertransverse ligaments. Action. — To assist in flexing the spine laterally, by bringing these processes nearer to each other. Abdominal Region. The infero-lateral walls of the abdomen are formed by a large musculo-aponeurotic envelope, consisting of four pairs of muscles, covered externally by the abdominal tunic, the muscles on the right being separated from those on the left by the linea alba, a white fibrous cord extending from the sternum to the pubis. These muscles, the rectus excepted, consist each of a fleshy and an aponeurotic portion, and the general line of demarcation between the aponeurotic and the fleshy region is known as the linea semiluiutris. We have to describe the following structures : — Tunica abdominalis. Linea alba. Ihcsdes. Obliquus abdominis externus. I Rectus abdominis. Obliquus abdominis internus. | Transversalis abdominis, TUNICA ABDOMINALIS. ( Tunica Blast ica. ) The abdominal tunic is an immense expansion, composed of yellow elastic tissue, which covers the external oblique muscles. It is thickest at the pubis, and on each side of the linea alba, thinning as it approaches the sternum, and disappearing at the posterior attachment of the pectoralis magnus muscle. It blends with the external oblique, anteriorly reaching the digitations of ABDOMINAL REGION. 201 the serratus magniis ; posteriorly it furnishes a few fibres, which, detached from the surface of the common abdominal tendon (prepubian), pass between the thighs, and become lost in the muscles of that region. Relation. — Externally by cellular tissue to the panniculus and skin. It is continuous with the suspensory ligament of the sheath and dartos in the male, and the elastic envelope of the mamma in the female, in whom it is always thickest. Use. — To afford a mechanical support to the abdominal viscera, and conserve muscular action by substituting elasticity for it. On the application of distensile force it yields con- siderably. LINEA ALBA. The linea alba is a white fibrous cord situated between the inner borders of the two recti-abdominales, to which it gives attachment, as to the other abdominal muscles. Anteriorly it is attached to the inferior surface of the xiphoid cartilage, and posteriorly it becomes confounded with a large tendon, common to the abdominal muscles, the prepubian tendon, which is attached to the anterior border of the pubis, and assists in the formation of the internal commissures of the inguinal canals. Between its posterior and middle third the linea alba is enlarged, and forms a lozenge-shaped space, in the centre of which is the remnant of the umbilicus. The fact of this structure joining the sternum to the pubic symphysis, together with certain co-related features, has induced anatomists to regard the linea alba as representing a rudimentary abdominal sternum. OBLIQUUS ABDOMINIS EXTERNUS. ( Costo-abdominalis. ) (Pl. IL 74.) The largest and most external muscle of the group, situated on the infero-lateral aspect of the abdomen, and consisting of a fleshy and an aponeurotic portion. It is quadrilateral, its fibres run- ning downwards and backwards. Its aponeurosis commences at a line called the linea semilunaris, and is continued to the linea alba, where it bends with that of the internal oblique. Attachments. — By fleshy fibres, anteriorly to the outer surface of the last thirteen or fourteen ribs, just below their middle ; the 202 MYOLOGY. four anterior digitations are received between the corresponding ones of the serratus magnus ; to the fascia of the latissimus dorsi, and superiorly to the lumber fascia ; to the anterior iliac spine and crest ; to the pubis and prepubian tendon, and inferiorly to the linea alba throughout its whole extent. Relation. — Externally with the abdominal tunic ; antero- externally with the pectoralis magnus ; internally with the ribs, cartilages, and intercostals, the internal oblique and the rectus; anteriorly with the serratus magnus. Action. — To support and compress the abdominal viscera, and assist in defecation, urination, and parturition. It is also a flexor of the vertebral column, and a muscle of expiration. APONEUROSIS OF THE OBLIQUUS EXTERNUS. The distribution of this aponeurosis being very singular and important, it merits separate consideration. It stretches from the anterior spine of the ilium to the pubis, answers to the fold of the groin, and marks the division between the trunk and hind extremity. Posteriorly it splits into two layers ; one descends internally over the thigh, forming the crural a^poneurosis; the other is reflected upwards, and enters the abdominal cavity, this fold receiving the name of the crural arch or Powpart's ligament. Near the prepubian tendon, and immediately in front of its division, the aponeurosis is pierced by a large oval aperture, the external abdominal ring, which is the external opening of the inguinal canal. Crural AjJoneurosis. This descends over the fold of the groin to the patella, and internal surface of the thigh, blending outwardly with the fascia lata, and internally becoming less dense in structure ; it covers the sartorius, part of the gracilis, vastus internus, and the crural vessels as they leave the abdomen. Poupart's Ligament. The Crural Arch or Poupart's Ligament is a ribbon-shaped reflected portion of the aponeurosis of the external oblique, and is attached by its extremities to the anterior spine of the ilium, and anterior border of the pubis. Anteriorly it forms the posterior ABDOMINAL REGION. 203 pillar of the inguinal canal, and externally gives attachment to the posterior fibres of the internal oblique. Posteriorly it contacts the sartorius and pectineus muscles, and the crural vessels, embracing those parts in a sort of arch, hence its name. Its superior border at its external half is attached to the lumbo-iliac aponeurosis ; while its middle is confounded with the external surface of the sartorius and iliacus. Inside the attachments of the pectineus and psoas parvus, it forms, with the anterior border of the pubis, the iliacus and sartorius, a triangular open- ing called the crural ring, through which the crural vessels pass out of the abdomen. The inferior border is continuous with the femoral and great oblique aponeuroses. IiTf/uinal Canal. The Inguinal Canal is infundibuliform and compressed laterally ; through it pass the spermatic cord and external pudic artery of the male, and mammary vessels of the female. It is situated obliquely between the crural arch, which is its posterior, and the internal oblique muscle, which forms its anterior wall. The external orifice is called the external abdominal ring, and is larger than the internal, being oval in form and directed backwards and inwards. It presents two pillars and two extremities or commissures. The pillars, anterior and posterior, are merely the edges or lips of the aperture, and are formed by the arciform fibres of the aponeurosis of the external oblique muscle, the posterior one being assisted by Poupart's ligament. The commissures, external and internal, are formed by the union of the pillars, the latter being limited by the prepubian tendon. The peritoneal or internal abdominal ring, the internal orifice of the canal, is situated in front of the crural ring. It is a mere dilatable cleft betAveen the crural arch and the internal oblique, and but indifferently marked at its extremities. OBLIQUUS ABDOMINIS INTERNUS. {Ilio-abdominalis. ) (PL. III. 29.) Situated under the externus, on the postero-lateral and inferior aspects of the abdomen, its fibres expanding downwards, it is, like the externus, fleshy and aponeurotic ; the fleshy portion is 204 MYOLOGY. thick, and occupies the flank ; the aponeurosis commences at the linea semilunaris, its fibres blending with those of the external oblique. Attachments. — Supero-posteriorly, to the anterior spine of the ilium, whence its fleshy fibres radiate ; a portion is attached to the transverse processes of two or three of the first lumbar vertebra, and passes to the posterior border of the last rib (this portion is described by the German anatomists as a retractor costce) ; and to the fascia of the latissimus dorsi ; to the cartil- ages of the false ribs ; postero-inferiorly to the symphysis pubis, by the prepubian tendon, aiding in the formation of the internal abdominal ring; inferiorly to the linea alba throughout its whole extent. Relation. — Externally with the external oblique ; internally with the transversalis and rectus abdominis. Action. — It assists the externus in compressing the abdomen in the act of respiration, and in flexing the spine. It also draws the last rib backwards. RECTUS ABDOMINIS. (Stertio-jntbialis. ) (Pl. III. 18.) Situated along the inferior and middle part of the abdomen, it is long, flat, polygastric, and broadest in the middle. Tendinous at its attachments, its belly consists of numerous flat muscular fasciculi, with' transverse tendinous intersections, to which the aponeuroses of the oblique muscles are adherent ; these intersec- tions are called the linece transversa^ {inscriptiones tendinece), and may be regarded as the abdominal representatives of the ribs. The posterior part of the muscle assists in the formation of the internal abdominal ring. Attachments. — Anteriorly to the inferior surface of the xiphoid cartilage and sternum ; to the cartilages of the last four true and first two false ribs ; posteriorly to the crest of the pubis, through the medium of the prepubian tendon, which is directly continuous with it ; internally to the linea alba. Relations. — Inferiorly with the aponeurosis of the internal oblique muscle ; anteriorly with the pectoralis magnus ; superiorly with the transversalis, and the cartilages of nearly all the ribs ; internally with its fellow at the linea alba. SUBLUMBAR EEGION. 205 Action. — To support and compress the abdominal viscera and assist in respiration. It is the chief flexor of the spinal column. TRANSVERSALIS ABDOMINIS. (Lumbo-abdoniinalis. ) Placed on the infero-lateral aspect of the abdomen, imme- diately outside the peritoneum, this muscle is broad, flat, and quadrilateral, its fibres extending downwards. It is fleshy from its origin to the linea semilunaris, where it becomes aponeurotic. Attachments. — To the transverse processes of the lumbar vertebrae, and the inner surface of the cartilages of the false ribs, interdigitating with the attachments of the diaphragm, and by its aponeurosis to the xiphoid cartilage and linea alba, becoming- rudimentary posteriorly. Relations. — Anteriorly with the diaphragm ; externally with the cartilages of the false ribs, the obliquus internus and rectus ; internally with a thin layer of fascia (the fascia transversalis) which connects it with the peritoneum. Action. — To assist the oblique muscles, and raise the viscera. SUBLUMBAR REGION. The muscles of this region, a single group, connect the lumbar and last dorsal vertebrae with the pelvis or the posterior limb. They are covered by the iliac fascia, and this by the peritoneum, a serous membrane lining the abdominal cavity. In this group we place four muscles : — Psoas magnus. 1 Iliacus. Psoas parvus. | Quadratus lumborum. PSOAS MAGNUS. [Suhlumbo-trochantineus,) (Fig. 76. c.) Situated below the transverse processes of the lumbar vertebrae, it is elongated and fusiform, flattened anteriorly, conical posteriorly, its fibres extending downwards and backwards; it is almost entirely fleshy, except at its insertion. Origin. — From the inferior surfaces of the last two ribs, the 206 MYOLOGY, bodies of the last two dorsal, and all the lumbar vertebras except the last, and to the lumbar transverse processes, jDassing between the two parts of the iliacus. Insertion. — By a tendon, common to it and the iliacus, to the internal trochanter of the femur. Relation. — Posteriorly with the iliacus; internally with the psoas parvus and the bodies of the vertebrae ; above with the Muscles of the sublumbar and internal deep femoral regions— seen from below, a, a. Qiiadratus lumborum ; h, Psoas parvus ; c, Psoas magnus ; d, c, Iliacus ; /, Pectineus ;■ (j. Adductor brevis ; h. Adductor longus ; i, Adductor iiiagnus ; k, Vastus internus ; I, Rectus femoris. quadratus lumborum, and below with the kidney and iliac fascia, the diaphragm, and, in the thoracic cavity, with the pleura. Action. — To flex and rotate the thigh, or, the latter being fixed, to flex the loins ; the latter action tends to " roach " the back. PSOAS PARVUS. (Sublumbo-pubialis. ) (Fig. 76. h.) Situated on the inner side of the psoas magnus, it is long, thin, and semipenniform, the fibres extending backwards and o^twards. SUBLUMBAR KEGION. 207 Fleshy above, it has posteriorly a strong flat tendon passing along the lower surface to its insertion. Origin. — From the bodies of the last three or four dorsal and all the lumbar vertebrae. Insertion. — To the ilio-pectineal eminence on the brim of the pubis, midway between the symphysis and the acetabulum, and to the iliac fascia. Relation. — Inferiorly with the diaphragm, pleura, posterior aorta and vena cava ; externally with the psoas magnus. Action. — To flex the pelvis on the spine, when the loins are fixed ; when the pelvis is flxed, to arch the back. It is also the tensor of the iliac fascia. ILIACUS. (^Ilio-trochantineus.') (Fig. 76. d, e.) Situated under the false pelvis, this muscle is strong, thick, and pyramidal, the base being forwards, and the fibres extending downwards, backwards, and inwards. The belly is incompletely divided by a fissure into two unequal portions, the external being the larger ; through this fissure passes the tendon of the psoas magnus, which its own tendon joins. Origin. — From the ilio-pectineal ridge, nearly all the venter surface of the ilium, and the inferior sacro-iliac ligament. Insertion. — To the internal trochanter of the femur, along with the psoas magnus. Relation. — Superiorly with the ilium ; inferiorly with the iliac fascia and sartorius ; externally with the tensor fascise latse and rectus femoris, from which it is separated by a layer of fat ; internally with the crural vessels. It passes between the vastus internus and the pectineus. Action. — To flex the femur, and rotate it outwards. QUADRATUS LUMBORUM. {Sacro-lumhalis.) (Fig. 76. a.) Placed below and between the lumbar transverse processes, this is a flat, thin muscle, consisting of several bundles, with strong tendinous intersections. The principal bundle is situated exter- 208 MYOLOGY. nally and longitudinally, the lesser ones diverging from it inwards and forwards. Origin. — The chief bundle arises from the inferior sacro-iliac ligament at the angle of the sacrum, passing directly forwards. Insertion. — To the posterior border of the last rib, becoming attached in its course to the free extremities of the transverse processes of the lumbar vertebrae. The other bundles leave the internal border of the first, and are attached to most of the transverse processes of the lumbar vertebra?, and inner surfaces of the last two or three ribs. Relation. — Superiorly with the vertebrte, and intertransversales lumborum ; inferiorly with the j^soas magnus. Action. — To assist in lateral flection of the lumbar vertebree, and to draw the last ribs backwards. Diaphragmatic Region. This region contains only one muscle, from which it takes its name. DIAPHRAGM. {Diaphragma.) (Fig. 77. A.) The diaphragm, or midrif, is the muscular partition which separates the thorax from the abdomen ; it slopes obliquely down- wards and forwards, and is in form elliptical, or somewhat heart- shaped, being widest superiorly. The thoracic surface is convex and covered with pleura, the abdominal concave and covered with peritoneum. It is divided into a body or septum, and two crura or appendices ; the body, or greater muscle, is made up of a fleshy periphery and tendinous 'phrenic centre {Speciilu'm Helmontii). Attachments. — The fleshy portion is attached to the inner surface of the distal ends of the last twelve ribs, or to their cartilages, and to the superior surface of the ensiform cartilage, the fibres converging towards the tendinous centre. The crurcc or pillars, two in number, lie below the vertebrae in the sublumbar region. The right is the longer and larger, and arises from the inferior surface of the bodies of all the lumbar vertebrge but the last, by strong tendinous fibres which blend with the inferior common ligament. The left differs from the right in arising from only one or two anterior lumbar vertebrae. The crura pass DIAPHKAGMATIC KEGIOX. 209 down the central line of the tendinous portion, and gradually blend with its fibres. Near the centre of the diaphragm, and a little to the right, is a large opening, the foramen dextrum, through which passes the posterior vena cava. Between the pillars superiorly is a second opening, the hiatus aorticus, through which pass the posterior aorta, vena azygos, and thoracic duct. Below this, the right crus forms towards the left a third opening, the foramen sini strum, for the passage of the oesophagus and pneumogastric nerves, accompanied by the j^leural artery. There Fig. 77. The diaphragm, and superficial muscles of the internal femoral region— viewed from below. A, The diaphragm; a a. The tendinous centre; a' a', The fleshy periphery; a" a". The crura: a'". The hiatus aorticus; a"", The foramen sinistrum ; a'"", The foramen dextrum; b. The sar- torius ; c, The giacilis. are thus three openings — the hiatus aorticus above, the foramen sinistrum in the middle, and the foramen dextrum below. Certain of the sublumbar muscles originate partly in the thorax, and the diaphragm forms arches which allow their passage, and that of the sympathetic and splanchnic nerves ; these arches are bounded by ligaments, the ligamenta arcuata ; outside the arches the diaphragm is attached to the last rib by a broad fold of elastic tissue. Helation. — Anteriorly with the pleura, which covers both it 210 MYOLOGY. and the lungs ; posteriorly, covered by peritoneum, it contacts the liver, stomach, spleen, and the large colon. Action. — Essentially a muscle of inspiration. When it con- tracts it becomes flattened, forces the abdominal viscera back- wards, and so enlarges the thoracic cavity. This action is antagonistic to one of the actions of the abdominal muscles. It also assists in the expulsive efforts of defecation and parturition. Coccygeal Region. The muscles of this region, that of the tail, are enclosed in strong fascia, which may be said to be continuous with the approximate pelvic ligaments. We find one group containing four muscles : — Erector coccygis. } Curvator coccygis. Depressor coccygis. \ Compressor coccygis. ERECTOR COCCYGIS. (Sacro-coccygeus Superior.) (PL. IIL 3L) Situated on the supero-lateral part of the tail, it consists of bundles of fibresj intersected by tendons, which gradually diminish in size from before backwards, each terminating in a short tendon. Origin. — The tuberous summits and lateral aspect of the posterior sacral spines, and superior surface of the coccyx. Insertion. — To the coccygeal bones. Relation. — Internally with its fellow, and the coccygeal verte- brae ; externally with the skin and fascia. Action. — When acting together to elevate the tail ; singly, to draw it upwards and outwards. DEPRESSOR COCCYGIS. (Sacro-coccygeus Inferior.) (Pl. IIL 33.) Situated on the infero-lateral aspect of the tail, and similar to the erector, but thicker. Origin. — Within the pelvis, from the inferior surface of the sacrum, the inner surface of the sacro-sciatic ligament, and the coccygeal vertebrse. MUSCLES OF THE LIMBS. 211 Insertion. — By tendons to the inferior surface of all the coccygeal vertebrae successively. Relation. — Superiorly with the sacrum, coccyx, and curvator ; inferiorly with the rectum; externally with the curvator and sacro-sciatic ligament ; internally with its fellow. Action.— To bend the tail downwards; singly, to draw it downwards and to one side. CURVATOR COCCYGIS. [Sacro-coccygeus Lateralis.) (PL. III. 32.) Situated on the side of the tail, and similar in structure to the preceding, it is merely a continuation of the semispinalis lumborum. Origin. — From the spines of the last lumbar, and lateral aspect of the sacral and coccygeal vertebrae. Insertion. — The side of the coccyx, between the erector and depressor. Relation. — Superiorly with the erector and sacral ligament ; inferiorly with the dejDressor ; externally with the compressor. Action. — To curve the tail, drawing it sideways over the quarter. COMPRESSOR COCCYGIS. ( Ischio-coccygeus. ) Situated at the side of the pelvis, it is a large, thin, and tri- angular muscle. Origin. — By aponeurosis, from the superior ischiatic spine and the inner surface of the sacro-sciatic ligament, running upwards and backwards. Insertion. — By jBeshy fibres, to the side of the terminal sacral and first two coccygeal vertebras. Relation. — Externally with the sacro-sciatic ligament ; inter- nally with the curvator and rectum. Action. — To depress the entire tail. Muscles of the Limbs. The muscles of this class are those which are specially related to the limbs, for the most part acting upon them alone ; they are intrinsic and extrinsic, according to their origin. These muscles 212 MYOLOGY. are either flexors, extensors, abductors, adductors, or rotators, but in the horse the lastj are comparatively few, limited in their action, and nearly all extrinsic, the joints of the horse's limbs below the shoulder and hip allowing very slight rotatory motion. Muscles of the Pectoeal Limb. These may be conveniently divided into the following regions: — Scapular .... The shoulder. Brachial .... The arm. Antibrachial .... The fore-arm. Metacarpal .... The foot (hand). Scapular Region. Externally the region is covered by the strong scapular fascia, and comprises an external group of four and an internal of three muscles. External Scapular Group. Teres externus. I Postea-spinatus. Antea-spinatus. | Postea-spinatus minor. TERES EXTERNUS. {Scaiiulo-humeralis Magnus. ) (Fig. 78. c.) This is the long abductor of the arm, which corresponds to the deltoid of man. Situated on the outer and posterior part of the shoulder, it consists of two portions, anterior and posterior. The posterior or larger portion is triangular in form and very fleshy, the fibres extending obliquely downwards and forwards \ it is lodged in a depression in the caput magnum. The anterior or superior portion is thin, and aponeurotic above, extending over the postea-spinatus muscle, to which it is adherent. Attachments. — The posterior section arises from the dorsal angle and posterior costa of the scapula ; the anterior by strong- fascia from a tubercle on the spine of the scapula, and the scapular fascia. They unite inferiorly, and by tendinous and fleshy fibres are inserted to the deltoid ridge of the humerus below the inser- tion of the postea-spinatus minor. EXTEKNAL SCAPULAR GROUP. 213 Relation. — Anteriorly with the caput magnum, caputmedium^andpostea- spinatus ; externally with the scapular fascia. Action. — To abduct the humerus, and rotate it outwards; when acting with the teres internus to flex the shoulder joint. ith the postea-spinatus ; internally ANTEA-SPIXATUS. {Superacromio-trochiterius.^ (Fig. 78. a.) Occupying the antea- spinatus fossa of the scapula, this muscle is jiyramidal in shape, with ||' \\ ji f the base downwards. Its fleshy fibres extend ob- liquely forwards ; then becoming tendinous in- feriorly, it is bifurcated for the passage of the flexor brachii tendon, the divisions being connected by aponeurosis. Origin. — From the anterior fossa, anterior costa, and cervical angle of the scapula, and the anterior surface of its spine. Insertion. — By two parts, one external, to the summit of the exter- , ^^''' '^' Muscles of the anterior limb— external view, a, Antea- nal trochanter, and one splnatus -, 6, Postea-spinatus ; c. Teres externus ; d, caput intprnnl to thp tJlimiTlit magnum; e, Caput medium;/. Flexor brachii; g, Ex- mieiuai, W LUe bumunu tensor metacarpi magnus ; 7t, Extensor metacarpi obliquus; of the internal trochanter, i, Flexor metacarpl externus ; k, Extensor pedis; k', Its f, , , tendon ; k", Fibrous baud from the suspensory ligament; 01 the humerus. i^ Extensor suffraginis ; I', Its tendon. 214 MYOLOGY. Relation. — Externally with the scapular fascia; anteriorly with the pectoralis parvus ; posteriorly with the scapular spine and the anterior border of the postea-spinatus ; internally with the bone ; antero-inferiorly with the levator humeri and the tendon of the flexor brachii. Action. — To extend the humerus on the scapula, and tense the fascia covering the flexor brachii. It serves, like the other scapular muscles, as an active ligament of the shoulder joint. POSTEA-SPINATUS. (Sitbacromio-trochiterius.) (Fig, 78. 6.) Lodged in the postea-spinatus fossa, it is broad, flat, and triangular, with the apex below, to which its fibres converge ; it is fleshy, with strong tendinous intersections. Origin. — From the posterior costa and fossa of the scapula, the posterior border of its spine, and the cartilage of prolongation. Insertion. — By two divisions, one of which goes to the inner side of the convexity of the external humeral trochanter ; the other, a strong tendon, passes over the trochanter, and is inserted to a roughened ridge below. Between the tendon and convexity is a synovial bursa. Relation. — Externally with the aponeurosis of the teres ex- ternus and with the scapular fascia; anteriorly with the antea- spinatus and the scapular spine ; posteriorly with the teres externus ; internally with the scapula, its cartilage, and the postea-spinatus minor ; inferiorly it contacts the capsular ligament of the shoulder joint. Action. — To abduct the humerus, and rotate it outwards. POSTEA-SPINATUS MINOR. (Scapulo-hiovieralis Parvus. ) (Fig. 80. a a.) Situated on the inside of the teres externus, below the postea- spinatus, and along the posterior border of the scapula, it is long and prismatic inferiorly, fleshy, and intersected by tendon, and is easily divided into a large and small portion. Origin. — From the posterior border of the scapula, and by INTERNAL SCAPULAR GROUP. 215 tendinous slips from the posterior fossa, and a small tubercle on the external side of the rim of the glenoid cavity. Insertion. — To the deltoid ridge. Relation. — Externally with the teres externus and postea- spinatus ; internally with the caput magnum, caput medium, and •capsular ligament. Action. — Like the last, to abduct, and rotate the humerus outwards. Internal Scapular Group. Subscapularis. Teres internus. Scapulo-humeralis posticus. SUBSCAPULARIS. {Suhscapulo-trochineus. ) (Fig. 79. a.) Situated on the inner side of the shoulder blade, occupying the subscapular fossa, it is fan-shaped, forming three points superiorly, its fibres converging downwards. It is covered by strong fascia, from which arises the subscapulo-hyoideus. Origin. — From the whole of the subscapular fossa. Insertion. — To the internal humeral trochanter, by a strong ten- don passing over its summit, where there is a small synovial bursa. Relation. — Externally with the scapula ; internally with the serratus magnus ; anteriorly with the antea-spinatus, with which it blends, the two forming a space through which passes the pre- scapular artery ; posteriorly with the teres internus. Action. — To adduct the arm, and perhaps to rotate it slightly inwards. TERES INTERNUS. {Teres Major — Suhscapulo-humeralis.) (Fig. 79. h.) This, an adductor of the arm, is situated just behind the sub- scapularis, at the posterior border of the scapula ; it runs obliqely downwards, corresponding to the teres externus. It is elongated, wide in the middle, tapering at the extremities, its posterior edge being thin. Origin. — From the dorsal angle and posterior costa of the scapula. 21G Insertion. — By a flat tendon, which joins that of the latissi- mus dorsi, to the internal tuberosity of the humerus, between the tendons of in- sertion of the coraco-humeralis. Relation. ■ — Postero-externally with the fascia of the latissimus dorsi and* scapulo-ulnaris ; anteriorly with the sub- scapularis ; internally with the serratus magnus ; inferiorly with the coraco- liunieralis and humeralis obliq.uus. Action. — To adduct, and rotate the humerus inwards ; acting with the teres externus the result is flexion. SCAPULO- HUMERALIS POSTICUS. (Scapulo-hiuneralis Gracilis — G'rele. ) Situated behind the shoulder joint, between the caput magnum and the cap- sular ligament, it is very small, slender, and fusiform, with a pale, delicate, fleshy belly, and tendinous extremities. Origin. — From the postero-inferior part of the scapula, just above the glenoid cavity, and the capsular ligament of the shoulder joint. Insertion. — Between the flbres of the humeralis obilquus, to the posterior part of the humerus, just below its head. Action. — To render tense the capsular ligament of the joint, and thus prevent its being crushed during flexion ; this action was ascribed to it by Rigot, who was the first to describe it. It is believed to be peculiar to the solidun- gula. I'k;. 7'.). Muscles of the anterior limb — internal view, a, Subscapulari.s ; h, Teres iiiteruus ; c, Coraco- humeralis ; d, Scapulo-ulnaris ; c, Flexor metacarpi iuternus ; /, Fle.xor metacarpi medius ; g. Caput parvum. Brachial Region. This region, clothed by the brachial fascia, includes the muscles which cover the humerus and its vicinity ; they consist of an ANTERIOR BRACHIAL GROUP. 217 anterior and a posterior group, the former being mostly anterior or lateral to the bone, the latter situated behind it. In either group we find three muscles. Anterior Brachial Group. Flexor brachii. Coraco-humeralis. Humeralis obliquus. FLEXOR BRACHII. {C oraco-radialis. ) (Fig. 78. /.) The analogue of the biceps in man, this muscle is situated in front of the humerus : it is long and cylindrical, passing down- wards and backwards. The tendon of origin contains fibro-car- tilage, and the belly is intersected by tendinous fibres. Origin. — From the base of the coracoid process of the scapula, by a strong tendon, which passes over the bicipital groove where there is a synovial bursa. Insertion. — By a short tendon to the bicipital tuberosity on the antero-internal part of the head of the radius, and to the capsular ligament of the elbow joint ; a part of it passes under the internal-lateral ligament of the elbow joint. A strong fibrous band is given off interiorly which joins and expands over the extensor metacarpi magnus, and becomes blended with the anti- brachial fascia. Relation. — Anteriorly with fascia, covered by the levator humeri ; internally with the coraco-humeralis ; posteriorly with the humerus ; superiorly its tendon passes between the two insertions of the antea-spinatus, where a strong fascia envelopes it and is tensed by the last-named muscle. Action. — To flex the radius on the humerus, extend the latter on the scapula, and to tense the antibriichial fascia. A band of unyielding tendinous material runs through this muscle, enabling it to act as a ligament, and passively support the shoulder joint, when the animal is at rest ; the band joining the extensor meta- carpi also relieves muscular tension. 218 MYOLOGY. CORACO-HUMERALIS. , ( Omo-brachiaUs. ) (Fig. 79. c.) Situated on the inner side of the humerus, this muscle is ten- dinous, long, and fusiform, its fibres passing obliquely downwards. Attachments. — From the beak of the coracoid process of the scapula. Passing between the subscapularis and the antea- spinatus, the tendon is succeeded by two fleshy bellies, a super- ficial and a deep one. The latter, thin and short, is inserted to the shaft of the humerus just above its internal tuberosity ; the former, by far the larger, is inserted to a rough surface on the same bone, lower down, and more anteriorly. Relation. — Anteriorly with the flexor brachii ; superiorly with the antea-spinatus and subscapularis ; internally with the pector- alis magnus ; posteriorly with the latissimus dorsi and teres internus, whose tendons pass between its two bellies. Action. — To extend, adduct, and rotate the arm inwards. HUMERALIS OBLIQUUS. [Humero-radialis — Brachialis Anticus.) (Fig. 80. d.) Occupying the musculo-spiral groove, it is flat, oblong, wide superiorly, and almost entirely fleshy ; it covers successively portions of the posterior, external, and anterior surfaces of the humerus, terminating on the inner aspect of the radius. Origin. — From the postero-superior part of the shaft of the humerus, just below the articular head, winding round the bone under the external tuberosity. Insertion. — To a ridge on the inner part of the head of the radius, after passing through a transverse groove just below, and within the insertion of the flexor brachii ; also to the ulna, passing under the internal-lateral ligament of the joint, and blending with the arciform ligament. Relation. — Externally with the caput magnum and caput medium ; internally with the humerus ; anteriorly with the flexor brachii. Action. — Solely to flex the elboAv joint. POSTERIOR BRACHIAL GROUP. 219 Posterior Brachial Group. Scapulo-ulnaris. Triceps extensor brachii. Anconeus. SCAPULO-ULNARIS. {Scapido-olecranius Longus.) (Fig. 79. d.) Situated on the postero-internal aspect of the region, adhering- to the caput magnum, this is a broad and flat muscle, aponeurotic at its origin, with a fleshy belly, and divisible into an anterior and posterior portion. Origin. — Aponeurotic, from the dorsal angle and posterior costa of the scapula. Insertion: — To the inner part of the apex of the olecranon, and to the antibrachial fascia. Relation. — Externally with the caput magnum ; anteriorly with the caput medium ; internally with the pectoralis magnus ; superiorly with the latissimus dorsi. Action. — To flex the shoulder joint, extend the elbow joint, and tense the antibrachial fascia. TRICEPS EXTENSOR BRACHII. {Triceps Brachii.) (Fig. 78. d, e.) A very large and powerful muscle, occupying the space between the posterior border of the scapula, the humerus, and the olecranon. It consists of three parts, which have different origins, but a common insertion to the olecranon process. We describe them as if they were separate muscles, under their respective names : — Caput magnum. Caput medium. Caput parvum. 220 MYOLOGY. CAPUT MAGNUM. (Scapulo-olecraniics Magnus. ) (Fig. 78. d.) This, the great extensor of the fore-arm, is situated on the posterior aspect of the shoulder. It is thick and triangular, extending obliquely downwards and backwards, and consists of several bundles, with tendinous intersections. Origin. — From the dorsal angle and posterior costa of the scapula. Insertion. — By a strong tendon to the inner and upper part of the olecranon, a synovial bursa being interposed between it and the apex. It receives many fibres from the caput medium. Relation. — Externally with the fascia, the panniculus carnosus, and the teres extern us, which occupies a depression in it ; inter- nally with the latissimus dorsi, scapulo-ulnaris, and teres internus ; inferiorly with the caput medium and caput parvum. Action. — To flex the shoulder joint, and extend the fore-arm. CAPUT MEDIUM. {Humero-olecranius Externus.) (Fig. 78. c.) Placed between the preceding muscle and the humerus, it is thick, short, and fleshy, extending obliquely backwards and down- wards. Origin. — Aponeurotic, from a ridge on the supero-posterior part of the shaft of the humerus, running from the deltoid ridge to the neck. Insertion. — The supero-posterior part of the olecranon ; or it may join the tendon of the caput magnum. Relation. — Superiorly with the caput magnum ; externally with the teres externus ; inferiorly with the humeralis obliquus and extensor metacarpi magnus ; internally with the caput parvum. Action. — To extend the fore-arm. ANTIBKACHIAL REGION. 221 CAPUT PARVUM. {Humero-olecranius Internus. ) (Fig. 81. a.) Placed on the inner and median portion of the shaft of the humerus, along the inferior border of the caput magnum, this muscle is slender and triangular, with a fleshy origin. The fibres pass obliquely backwards and downwards, terminating in two flat tendons. Origin. — From the postero-internal part of the middle third of the humerus, extending from the inner tubercle. Insertion. — To the inner part of the apex of the olecranon, one tendon passing over a small groove before its insertion, which is situated below the other one. Relation. — Superiorly with the caput magnum ; externally with the humerus, humeralis obliquus, and caput medium ; in- ternally with the insertion of the coraco-humeralis, with the teres internus, latissimus dorsi, and scapulo-ulnaris. Action. — To extend the fore-arm. ANCONEUS. (Humero-olecranius Parvus. ) (Fig. 80. e.) Situated at the back of -the elbow joint, it is small, thick, and almost entirely fleshy, filling up the space between the condyles of the humerus, or the olecranon fossa. Origin. — From the borders of the fossa, chiefly the epitrochlea, and the capsular ligament of the elbow joint. Insertion. — The antero-external part of the olecranon. Relation. — Posteriorly with the caput medium muscle ; ante- riorly with the elbow joint and humerus. Action. — To tense the capsular ligament, and prevent it from being crushed during extreme extension. Antibrachial Region, The muscles of this region, the fore-arm, cover the ulna and radius, except on the inner aspect of the latter, where there is little interposed between the skin and the bone ; they are 222 MYOLOGY. divided into two distinct groups, the anterior and posterior, the first of which are all extensors, the second all flexors. All these muscles are inserted below the radius, and therefore act upon the carpus or on the joints below. The region is enclosed in the antibrachial fascia, an exceedingly strong covering, which is firmly attached to the radius and ulna. Anterior Antibrachial Group. extensors. The extensor group includes four muscles : — Extensor metacarpi magnus. I Extensor pedis. Extensor metacarpi obliquus. ] Extensor suffraginis. EXTENSOR METACARPI MAGNUS. {Epicondylo-irremetacmyeus. ) (Fig. 78. g.) Situated in front of the radius, and in figure pyramidal, extending downwards, it consists of a fleshy belly, and a long flat tendon, which commences at about the lower third of the radius, and passes over the carpus, terminating at the head of the metacarpus. Origin. — From the epitrochlea, or ridge above the external condyle of the humerus, from the capsular ligament of the elbow joint anteriorly, and the surface just above. It receives a strong tendinous band from the flexor brachii. The tendon passes through a groove or theca in the anterior part of the distal end of the radius, where there is a synovial sheath or bursa, then over the knee through a second synovial apparatus. Two synovial sheaths are thus interposed between the bones and the tendon, the latter being bound down by the anterior annular ligaments, and by the tendon of the extensor metacarpi obliquus, which crosses it in an oblique manner just above the carpus. Insertion. — To a tuberosity on the anterior part of the head of the great metacarpal bone, towards its inner side. Relation. — Anteriorly with the fascia ; posteriori}'' with the radius ; externally with the extensor pedis ; supero-internally with the humeralis obliquus and flexor brachii ; inferiorly with the extensor obliquus. Action. — To extend the carpus. ANTERI(31l ANTIBRACHIAL GllOUP. 223 EXTENSOR METACARPI OBLIQUUS. {Radio-premetacarpp.us.) (Fig. 78. A.) This muscle is situated on the in- fero-anterior part of the radius, and is triangular and penniform ; aponeurotic above, it terminates in a small tendon, which crosses obliquely the inferior extremity of the anterior surface of the radius, under the extensor pedis, and over the extensor metacarpi magnus tendon. Origin. — From the external border of the radius. Its tendon passes through the oblique groove on the antero-internal part of the distal end of the radius, where there is a synovial sheath. Insertion. — The head of the inner metacarpal bone. Relation. — Anteriorly with the ex- tensor pedis and the fascia ; posteriorly with the extensor metacarpi magnus and the bone. Action. — To extend the metacarpus and rotate it slightly, carrying the inner aspect forwards. EXTENSOR PEDIS. ( Epitrocldeo-prephalangeus. ) (Fig. 78. i; Fig. SO./.) Placed on the antero-external part of the fore-arm, it is long and pyra- midal, extending downwards ; fleshy above, its belly is bifid inferiorly, and terminates in a long tendon, which is double, and commences about the inferior third of the radius. Fig. 80. External view of the muscles of the anterior limb— showing the deeper ones of the upper region, a a, Postea- spinatus minor ; h, Deep portion of postea-spiuatus ; c. Flexor brachii divided, and the upper part raised; c', Its tendon, which fits the bicipital groove ; d, Humeralis obliquus ; e. An- coneus ; /, Extensor pedis ;