^^^njBR?^^ This book is due on the date indicated below and is subject to an overdue fine as posted at the circulation desk. EXCEPTION: Date due will __ earlier if this item is RECALLED. 1 be I .ED. I THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS BY A. CHAUVEAU, M.D., LL.D. MEMBER OF THE INSTITUTE (ACADEMY OF SCIENCES); INSPECTOR-GENERAL OF VETERINARY SCHOOLS IN FRANCE; PROFESSOR AT THE MUSEUM OF NATURAL HISTORY, PARIS JElctiiseli antJ IBnlargeti, toftl) ti)e ©o^opcratfon ot S. ARLOING DIRECTOR OF THE LYONS VETERINARY SCHOOL PROFESSOR OF EXPERIMENTAL AND COMPARATIVE MEDICINE AT THE LYONS FACULTY OF MEDICINE SECOND ENGLISH EDITION TRANSLATED AND EDITED By GEORGE FLEMING, C.B., LL.D., F.R.C.V.S. LATE PRINCIPAL VETERINARY SURGEON OF THE BRITISH ARMY ; FOREIGN CORRESPONDING MEMBER or THE SOClETfe ROYALE DE MfeDKCINE, AND OF THE SOClfiTfi ROYALE DE mSdECINE PUBLIQUE, OF BELGIUM FOREIGN ASSOCIATE OF THE SOClllTfi CENTRALE DE MfeOECINE VfiT^RINAIRE OP FRANCE HONORARY LIFE MEMBER OF THE ROYAL AGRICULTURAL SOCIETY OF ENGLAND FOREIGN MEMBER OF THE SOClfiTfi NATIONALE D'AGRICULTURE OF FRANCE, ETC EXAMINER IN ANATOMY FOR THE ROYAL COLLEGE OF VETERINARY SURGEONS WITH 585 ILLUSTRATIONS NEW YORK D. APPLETON AND COMPANY 1905 IN COMMEMORATION OF THE CENTENARY OF THE ROYAL YETERINAEY COLLEGE, LONDON; THE PARENT OF VETERINARY SCHOOLS IN ENGLISH-SPEAKING COUNTRIES. AND IN MEMORY OF CHARLES VIAL DE SAINT-BEL, EQUERRY TO LOUIS XVI. OF FRANCE, PRINCIPAIi OF THE LYONS ACADEMY, PROFESSOR IN THE ROYAL VETERINARY SCHOOL OF THAT CITY, AND DEMONSTRATOR OF COMPARATIVE ANATOMY AT MONTPELLIER ; WHO, WHEN A REFUGEE FROM THE GREAT FRENCH REVOLUTION, WAS CHIEFLY INSTRUMENTAL IN ESTABLISHING THE FIRST ENGLISH VETERINARY SCHOOL, IN WHICH HE WAS THE FIRST TEACHER, 1791. PEEFACE TO THE SECOND ENGLISH EDITION. Since the translation of this work into English, seventeen years ago, it has been several times reprinted, the last occasion being in 1889. Cir- cumstances had, however, for some time indicated that there was need for a revision of the work in order to bring it up to the requirements of the present day, and the issue of a fourth French edition last year was considered a favourable opportunity for undertaking the task. In preparing this second edition, the necessities of advancing veteri- nary education in the English-speaking schools was kept in view, and this entailed considerable amendments, alterations, and additions, in order to adapt it more perfectly to the conditions it should fulfil as a text- book and standard work of reference on the subject. The high esteem in which the first edition has been held for so many years in this country, in our Colonies, and in the United States of America, amply testifies to the value of the work ; and in this new edition every- thing has been done to render it still more comprehensive, complete, and useful. The anatomy of the Ass, Mule, and Eabbit has been added, as well as that of the Camel — that animal being utilized not only in our army in different parts of the world, but also in some of our Colonies. The number of illustrations has been increased by more than one hundred and thirty, the pages have been enlarged, and the letterpress so modified as to make reading and reference much easier. A copious index — there is none in the French edition — has also been added, with the view of enhancing the usefulness of the book as a work of reference for students and practitioners. With these alterations, additions, and modifications, I trust the work may continue to be accepted as in every way worthy of the position accorded to it as the best on the subject. The editorial remarks — for which, as well as for the translation, I assume the entire responsibility — are included in brackets, as in the first edition. GEORGE FLEMING. London, April, 1891. TABLE OF CONTENTS. Dedication Preface to the Second Edition Table of Contents Table of Illustrations Vll ix xxvii GENERAL CONSIDERATIONS. Definition and Division of Anatomy ....... Enumeration and Classification of the Species of Domesticated Animals General Ideas of the Organization of Animals, and the order followed in studying the various apparatuses ........ BOOK I. IiOCOMOTORY APPARATUS. [RST SECTION.— THE BONES 7 Chapter I.— The Bones in General .... 7 Article I. — The Skeleton ...... 8 Article II.— General Principles applicable to the Study of all the Bones 11 Name, Situation, Direction, and Configuration of Bones 12 Internal Conformation of Bones. Structure of Bones 15 Development of Bones ...... 19 Chapter II.— The Bones of Mammalia in Particular 24 Article I.— Vertebral Column . . . . 24 Characters Common to all the Vertebrae .... 24 Characters Proper to the Vertebrae in each Region . 26 1. Cervical Vertebrae ...... 27 Differential Characters ...... 30 2. Dorsal Vertebrae ...... 32 Differential Ciiaracters ... , . 35 3. Lumbar Vertebrae ...... 36 Differential Characters ...... 37 4. Sacrum ....... 39 Differential Characters .... 40 5. Coccygeal Vertebrae ..... 41 Differential Characters ..... 41 The Spine in General ...... 42 Varieties in the Vertebral Column .... 43 Comparison of the Vertebral Column of Man with that of the 1 Domesticated Animals ...... 45 Article II.— The Head . . . c . . 46 The Bones of the Cranium ..... 46 1. Occipital ....... 46 Differential Characters ..... 48 2. Parietal ....... 49 Differential Characters ..... 49 3. Frontal 49 Differential Characters ..... 52 TABLE OF CONTENTS. 4. Ethmoid . DiflTerentiiil Characters 5. Sphenoid . Diflferentiiil Characters 6. Temporal . DiflFerential Characters The Bones of the B'ace . 1. Supermaxillii . Diflferential Characters 2. Premaxilla DiflFerential Characters 3. Palatine Differential Characters 4. Pterygoid Differential Characters 5. Malar . Differential Characters 6. Lachrymal Differential Characters 7. Nasal . Differential Characters 8. Turbinated Differential Characters 9. Vomer . Differential Charaeters 10. Inferior Maxilla Differential Characters 11. Hyoid Differential Characters 12. Wormian Bunes Of the Head in General . 1. General Configuration 2. Conformation of the Cranium in Particular 3. Relations between the Cranium and Face . 4. Modifications due to Age . Comparison of the Head of Man with that of Animals Article III. — The Tuobax The Bones of the Thorax in Particular Differential Characters Ribs ...... Differential Characters in the Ribs of other Animals The Thorax in General .... Comparison of the Thorax of Man with that of other Animals 1. Sternum 2. Ribs Article IV.— Anterior Limbs Shoulder Scapula . Differential Characters Arm Humerus Differential Ciiaracters Forearm 1. Radius 2. Ulna Differential Characters Anterior (or Fore) Foot, or Hand 1. Carpal Bones . Differential Characters 2. Metacarpal Bones Differential Characters TABLE OF CONTENTS. that of the Domesticated AND THEIR PARALLELISM 8. Bones of the Phalanges or Digital Region .... Differential Characters ...... Comparison of tJje Thoracic Limb of Man with that of the Domesticated Animal Article V. — The Hand in General ..... Article VI. — Posterior or Pelvic Limb Pelvis .... A. Coxa, or Os Innomatura B. The Pelvis in General Differential Characters Thigh .... Femur .... Differential Characters Leg ..... 1. Tibia 2 Fibula, or Peroneus . . 3. Patella Differential Characters Posterior Foot . 1. Bones of the Tarsus Differential Characters 2. Bones of the Metatarsus Differential Characters 3. Bones of the Digital Region Differential Characters Comparison of the Abdominal Limb of Man with Animals. Article VII. — The Foot in General Article VIII. — The Limbs in General, Chapter III.— The Bones in Birds Chapter IV.— Theory of the Vertebral Constitution of the Skeleton SECOND SECTION —THE ARTICULATIONS .... Chapter I.— The Articulations in General .... General Characters of the Diarthroses ..... General Characters of the Synarthroses ..... General Characters of the Amphiarthroses, or Symphyses . Chapter II. — The Articulations in Mammalia in Particular . Article I. — Articulations op the Spine ..... Intervertebral Articulations ...... Differential Characters ....... Article II.— Articulations of the Head 1. Atlo-axoid Articulation . . . . . . 2. Occipito-atloid Articulation ..... 3. Articulations between the Bones of tlie Head .... 4. Temporo-maxillary Articulation ..... 5. Hyoideal Articulations ....... Article III. — Articulations of the Thorax .... Extrinsic Articulations ....... Costo-vertebral, or Articulations of the Ribs with the Vertebral Column Intrinsic Articulations ....... A. Chondro-sternal or Costo-sternal Articulations B. Chondro-cdsta! Articulations, or Articulations between the Ribs and their Cartilages ... .... C. Articulations between the Costal Cartilages D. Sternal Articulation peculiar to the Ox and Pig The Articulations of the Thorax considered in a General Manner, with respect to their Movements .... A.RTICLE IV. — Articulations of the Anterior Limbs 1. Scapulo-humeral Articulation 2. Humero-radial Articulation 3. Radio- ulnar Articulation 4. Articulations of the Carpus . , xii TABLE OF CONTENTS. 5. Intermetacarpal Articulations .... 6. Metacarpo-plialangeal Articulations 7. Articulation of the First Phalanx with the Second, or First Articulation .... 8. Articulation of the Second Phalanx with tlie Third, Second Interphalangeal Articulation, or Articulation of the Foot , \bticle V. — Articulations of the Posterior Limbs 1. Articulations of tlie Pelvis 2. Coxo- femoral Articulation . 3. Femoro-tibial Articulation 4. Tibio- fibular Articulation . 5. Articulations of the Tarsus, or Hock . Chapter III.— The Articulations in Birds . THIRD SECTION. -THE MUSCLES Chapter I.— General Considerations on the Striped Muscles The Striped Muscles in General ..... Structure of the Striped Muscles .... Physico-chemical Properties of Striped Muscles Physiological Properties of Striped Muscles Appendages of the Muscles ...... Manner of Studying the Muscles Chapter II.— The Muscles of Mammalia in Particular Article I. — The Muscles of the Trunk Subcutaneous Region ...... Flesliy Pannicuius (Panniculus Carnosus) Cervical Region ....... A. Superior Cervical or Spinal Region of the Neck 1. Rhomboideus ...... 2. Angularis Muscle of the Scapula (Levator Anguli Scapulae) 3. Splenius ....... 4. Complexus (Complexus Major) .... 5. Trachelo-mastoideus (Complexus Minor) 6. Spinalis or Semispinalis Colli .... 7. Intertransversales Colli ..... 8. Great Oblique Muscle of the Head (Obliquus Capitis Auticus or Inferioris) 9. Small Oblique Muscle of the Head (Obliquus Capitis Posticus or Superioris) 10. Great Posterior Straight Muscle of the Head (Rectus Capitis Posticus Major) ........ 11. Small Posterior Straight Muscle (Rectus Capitis Posticus Minor) Differential Ciiaracters ....... B. Inferior Cervical or Trachelian Region 1. Subcutaneous Muscle of the Neck (Cervical Panniculus) . 2. Mastoido-humeralis (Levator Humeri) 3. Sterno-maxillaris ...... 4. Sterno-thyro-hyoideus ..... 5. Subscapulo-hyoideus ...... 6. Great Anterior Straight Muscle of the Head (Rectus Capitis Auticus Major) ........ 7. Small Anterior Straight Muscle of the Head (Rectus Capitis Auticus Minor) ....... 8 Small Lateral Straight Muscle (Rectus Capitis Lateralis) 9. Scalenus ....... 10. Long Muscle of the Neck (Longus Colli) Differential Characters ...... Spinal Region of the Back and Loins 1. Trapezius ....... 2. Great Dorsal (Latissimus Dorsi) 3. Small Anterior Serrated Muscle (Seiratus Anticue) 4. Small Posterior Serrated Muscle (Serratus Posticus) 5. Ilio-spiualis Muscle (Longissimus Dorsi) TABLE OF CONTENTS. 6. Common Intercostal Muscle (Transversalis Costarum) . 7. Transverse Spinous Muscle of the Back and Loins (Semispinalis of the Back and Loins) ...... Differential Characters ..... Comparison of the Muscles of the Back, Neck, and Cervix in Man with analogous Muscles in tbe Domesticated Animals 1. Muscles of the Back and Cervix .... 2. Muscles of the Neck ..... Sublumbar or Inferior Lumbar Region .... 1. Iliac Fascia or Lumbo-iliac Aponeurosis 2. Great Psoas Muscle (Psoas Magnus) .... 3 Iliac Psoas Muscle (Iliacns) .... 4. Small Psoas Muscle (Psoas Parvus) .... 5. Square Muscle of the Loins (Quadratus Lumborum) 6. Intertransversales of the Loins (Intertraiisversales Lumborum) Differential Characters ...... Comparison of the Sublumbar Muscles of Man with those of Animals Coccygeal Region ...... 1. Sacro-coccygeal Muscles .... 2. Ischio-coccygeus (Compressor Coccygeus) . Region of the Head ...... A. Facial Region ...... 1. Labialis or Orbicularis of the Lips (Orbicularis Oris) 2. Zygomatico-labialis (Zygomaticus) 3. Supermaxillo-labialis (Levator Labii Superioris Proprius, or Nasalis Longus) ...... 4. Maxillo-labialis (Depressor Labii Inferioris) 5. Mento-labialis, or Muscle of the Chin (Levator Menti) 6. Intermediate Posterior Muscle .... 7. Alveolo-labialis (Buccinator) .... 8. Supernaso -labialis (Levator Labii Superioris alaequi Nasi) 9. Great Supermaxillo-nasalis (Dilatator Naris Lateralis) 10. Small Supermaxillo-nasalis (Dilatator Naris Superioris) . 11. TransversalLs Nasi (Dilatator Naris Transversalis) . B. Palpebral Region ...... 1. Orbicularis of the Eyelids (Orbicularis Palpebrarum) 2. Frouto-Palpebral, or Corrugator Supercilii 3. Lachrymalis Muscle ..... C. Auricular or Conchal Region .... 1. Zygomaticus-auricularid (AttoUens Anticus) . 2. Temporo-auricularis Externus (Attollens Maximus) 3. Scuto-auricularis Externus .... 4. Cervico-auriculares (Retrahentes Aurem) 5. Parotido-auricularis (Abducens, or Deprimens Aurem) 6. Temporo auricularis Internus (Attollens Posticus) 7. Scuto-auricularis Internus .... 8. Mastoido-auricularis ..... D. Masseteric or Temporo-maxillary Region 1. Masseter. ...... 2. Temporalis ...... 3. Internal Pterygoid (Pterygoideus Internus) 4. External Pterygoid (Pterygoideus Externus) 5. Digastricus (Stylo-maxillaris) .... Z. Hyoideal Region ..... 1. Mylo-hyoideus . . . ... 2. Genio-hyoideus ..... 3. Stylo-hyoideus ...... >. Kerato-hyoideus (Hyoideus Parvus) . , , J. Occipito-styloideus ..... 6. Hyoideus Transversus .... Differential Characters ...... PAGE 265 jdT TABLE OF CONTENTS. 1. Facial Regrion . > . . 2. Palpebral Region . « . . . 3. Masseteric or Temporo-maxillary Region . 4. Hyoideal Region . . . . . Comparison of the Muscles of the Human Head with those of the Domesticated Animals . ...... 1. Epicranial Muscles ..... 2. Muscles of the Face ..... 3. Muscles of the Lower Jaw . „ . . 4. Hyoideal Muscles . . , . . Axillary Region ... , . 1. Superficial Pectoral (Pectoralis Anticus and Transversua) . 2. Deep Pectoral (Pectoralis Magnus and Parvus) , Differential Characters ...... Costal Region .... . 1. Serratus Magnus ...... 2. External Intercostala . . . 3. Internal Intercostuls o . . . . 4. Leva tores Costarum ..... 5. Triangularis Stemi ..... Differential Characters ..... Comparison of the Thoracic Muscles of Man with those of the Domesticated Animals ...... Inferior Abdominal Region ..... 1. Abdominal Tunic (Tunica Abdominalis, Tunica Elastica) 2. White Line (Linea Alba) ..... 3. Great or External Oblique of the Abdomen (Obliquus Abdominis Externus) .... ... 4. Small or Internal Oblique of the Abdomen (Obliquus Abdominis Internus) ....... 5. Great Straight Muscle of the Abdomen (Rectus Abdominis) 6. Transverse Muscle of the Abdomen (Transversalis Abdominis) Differential Characters ...... Comparison of the Abdominal Muscles of Man with those of Animals Diaphragmatic Region . . o . . Diaphragm . . . . . . = . . Differential Characters ....... Comparison of the Diaphragm of Man witli that of Animals Article II. — Muscles of the Anterior Limbs . « . o Muscles of the Shoulder . . .... A. External Scapular Region ..... 1. External Scapular Aponeurosis ...... 2. Long Abductor of the Arm, or Scapular Portion of the Deltoid (Teres Externus) ..... . . 3. Short Abductor of the Arm (Po.itea Spinatus Minor), or Teres Minor 4. Supra-spinatus (Antea Spinatus) . . . . 5. lufra-spinatus (Postea Spinatus) ..... B. Internal Scapular Region ....... 1. Subscapuliiris ..... 2. Adductor of the Arm (Teres Internus, or Teres Major) 3. Coraco-humeralis, Coraco-brachialis, or Omo-brachialis 4. Small Scapulo-humeralis (Scapulo-Humeralis Gracilis, Scapulo-Hume- ralis Posticus) ....... Differential Characters ........ Comparison of the Muscles of the Shoulder of Man with those of Animals . Muscles of the Arm . . , . . . A. Anterior Brachial Region ... . . 1. Long Flexor of the Forearm (Flexor Braehii), or Brachial Biceps 2. Short Flexor of the Forearm (Humeralis Obliquus, Brachialis Anticus, or Humeralis Externus) ...... B. Posterior Brachial Region , o ... PAGE 289 290 290 291 291 291 292 292 292 293 296 296 296 297 297 298 299 299 300 305 305 307 307 308 308 310 310 310 310 310 311 311 312 312 313 314 314 315 315 316 316 316 316 317 317 319 TABLE OF CONTENTS. 1. Large Extensor of the Forearm (Caput Magnum) 2. Short Extensor of the Forearm (Caput Medium) 3. Middle Extensor of the Forearm (Caput Parvum), luternal portion of the Triceps ....... 4. Small Extensor of the Forearm, or Anconeus Dififerential Characters ....... Comparison of the Muscles of the Arm of Man with those of Animals Muscles of the Forearm ....... Antibrachial Aponeurosis ...... A. Anterior Antibrachial Region ..... 1. Anterior Extensor of the Metacarpus (Extensor Metacarpi Magnus) 2. Oblique Extensor of the Metacarpus (Extensor Metacarpi Obliquus) 3. Anterior Extensor of the Plialanges (Extensor Pedis) 4. Lateral Extensor of the Phalanges (Extensor Suffragiuis) B. Posterior Antibrachial Region ..... 1. External Flexor of the Metacarpus (Flexor Metacarpi Externus, or Pos- terior Ulnaris) .... 2. Oblique Flexor of the Metacarpus (Flexor Metacarpi Medius, or Anterior Ulnaris) ........ 3. Internal Flexor of the Metacarpus (Flexor Metacarpi laternus, or Pal maris Magnus) ...... 4. Superficial Flexor, Sublimis of the Phalanges (Flexor Pedis Perforatus) 5. Deep Flexor of the Phalanges (Flexor Pedis Perforans) . Dififerential Characters .... Muscles proper to the Forearm in Carnivora . 1. Proper Extensor of the Tliumb and Index 2. Long Supinator .... 3. Short Supinator .... 4. Round Pronator .... 5. Square Pronator ...... Comparison of the Muscles of the Forearm of Man with those of Animals 1. Anterior Region ...... 2. External Region .... 3. Posterior Region .... Muscles of the Anterior Foot or Hand . A. Muscles of the Anterior Foot in Carnivora 1 Short Abductor of tlie Thumb 2. Opponens of the Thumb 3. Short Flexor of the Thumb 4. Adductor of the Index 5. Cutaneous Palmar (Palmaris Brevis) 6. Adductor of the Small Digit 7. Short Flexor of the Small Digit 8. Opponens of the Small Digit 9. Lumbrici ..... 10. Metacarpal Interosseous Muscles B. Muscles of the Anterior Foot in the Pig . C. Muscles of the Anterior Foot in Solipeds D. Muscles of the Anterior Foot in Ruminants Comparison of the Hand of Man with that of Animals A. Muscles of the Thenar Eminence . B. Muscles of the Hypothenar Eminence . C. Interosseous Muscles .... Article III.— Muscles of the Posterior Limbs Muscles of the Gluteal Region, or Croup 1. Superficial Gluteus (Gluteus Externus) 2. Middle Gleuteus (Gluteus Medius, Gluteus Maximus) 3. Deep Gluteus (Gluteus Internus) Dififerential Characters ..... Comparison of the Gluteal Muscles of Man with those of Animals Muscles of the Thigh .... PAGE 319 320 rvi TABLE OF CONTENTS. A. Anterior Crural, or Femoral Region .... 1. Muscle of the Fascia Lata (Tensor Fascia Latae, Tensor Vaginae Femoris) 2. Crural Triceps ....... 3. Crureus, Rectus Parvus, Anterior Gracilis B. Posterior Crural Region ...... 1. Biceps Femoris, Triceps Abductor Femoris 2. Semitendinosus Muscle (Biceps Rotator Tibialis) . 3. Semimembranosus (Adductor Magnus) .... C. Internal Crural Region ...... 1. Great Adductor of the Leg (Sartorius) .... 2. Short Adductor of the Leg (Gracilis) .... 3. Pectineus . ... 4. Small Adductor of the Thigh (Adductor Parvus, Adductor Brevis) . 5. Great Adductor of the Thigh (Adductor Maguus, Adductor Longus) 6. Quadrate Crural (Quadratus Femoris, Iscliio-Femoralis) 7. External Obturator (Obturator Externus) 8. Internal Obturator (Obturator Internus) .... 9. Gemelli ....... Differential Characters ....... 1. Anterior Crural Region ...... 2. Posterior Crural Region ...... 3. Internal Crural Region ...... Comparison of the Muscles of Man's Thigh with those of the Thigh of Animals 1. Anterior Muscles ....... 2. Muscles of the Posterior Region ..... 3. Muscles of the Internal Region ..... Muscles of the Leg .... . . Tibial Aponeurosis ........ A. Anterior Tibial Region ...... 1. Anterior Extensor of the Phalanges (Extensor Pedis) 2. Lateral Extensor of the Phalanges (Peroneus) . 3. Flexor of the Metatarsus (Flexor Metatarsi) B. Posterior Tibial Region ...... 1. Gastrocnemius, or Gemelli of the Tibia (Gastrocnemius Externus) . 2. Soleus (Plitntaris) ...... 3. Superficial Flexor of the Phalanges (Flexor Perforatus, Gastrocnemius Internus) . . ..... 4. Popliteus ....... 5. Deep Flexor of the Phalanges (Perforans, Flexor Pedis) 6. Oblique Flexor of the Phalanges (Flexor Accessorius) . Differential Characters ...... 1. Anterior Tibial Region ...... 2. Posterior Tibial Region ...... Comparison of the Muscles of the Leg of Man with those of Animals . 1. Anterior Region ....... 2. External Region ....... 3. Posterior Region ....... Muscles of the Posterior Foot Pedal Muscle (Extensor Pedis Brevis, Extensor Brevis Digitorum) . Differential Characters ....... Comparison of the Muscles of the Foot of Man with those of Animals \. Dorsal Region ....... 2. Plantar Region ....... 3. Interosseous Muscles .... Chapter IIL— The Muscles in Birds ..... Chapter IV.— General Table of the Attachment of the Muscles in Solipeds ....... ^^ TABLE OF CONTENTS. XTii BOOK 11. THE DIGESTIVE APPARATUS. Chapter I.— General Considerations on the Digestive Apparatus Chapter II.— The Digestive Apparatus in Mammalia Article I.— Preparatory Organs of the Digestive Apparatus . The Mouth ....... 1. Lips ........ 2. Cheeks ....... 3. Palate ....... 4. Tongue ....... 5. Soft Palate ....... 6. Teeth ....... 7. The Mouth in General ..... DifiFerential Characters in the Mouth of the other Animals Comparison of the Mouth of Man with that of Animals Table of Dentition ...... The Salivary Glands ...... 1. Parotid Gland ...... 2. Maxillary or Submaxillary Gland .... 3. Sublingual Gland ...... 4. Molar Glands ....... 5. Labial, Lingual, and Staphyline Glands DiflFereutial Characters in the Salivary Glands of the other Animals Comparison of the Salivary Glands of Man with those of Animals The Pharynx ....... DiflFereutial Characters in the Pharynx of the other Animals . Comparison of the Pharynx of Man with that of Animals The (Esophagus ...... DiflFereutial Characters in the (Esophagus of the other Animals . Comparison of the (Esophagus of Man with that of Animals Article II. — The Essential Organs of Digestion The Abdominal Cavity ..... DiflFereutial Characters in the Abdominal Cavity of the other Animals Comparison of the Abdominal Cavity of Man with that of Animals The Stomach ....... 1. The Stomach of Solipeds .... DiflFereutial Characters in the Stomach of the other Animals 1. The Stomach of the Rabbit . . . . 2. The Stomach of the Pig .... . 3. The Stomach of Carnivora ..... 4. The Stomach of Ruminants ..... Comparison of the Stomach of Man with that of Animals The Intestines ....... 1. The Small Intestine ..... 2. The Large Intestine ...... A. Csecum ....... B. Colon ....... 0. Rectum ....... Diflferential Characters in the Intestines of the other Animals 1. The Intestines of the Rabbit .... 2. The Intestines of Ruminants .... 3. The Intestines of the Pig .... 4. The Intestines of Carnivora . .... Comparison of the Intestines of Man with those of Animals General and Comparative Survey of the Abdominal or Essential Portion of the Digestive Canal ...... Organs Annexed to the Abdominal Portion of the Digestive Canal 1. Liver ....... 2. Pancreas ....... 8. Spleen ..... TABLE OF CONTENTS. Diflferential Characters in the Organ8 annexed to the Abdonainal Portion of the Digestive Canal in the other Animals ..... 508 Comparison of the Organs annexed to the Abdominal Portion of the Digestive Canal of Man with those of Animals ..... 510 Chapterlll.— The Digestive Apparatus of Birds . . . .511 BOOK III. RESPIRATORY APPARATUS. Chapter I.— Respiratory Apparatus in Mammalia ... 517 The Nasal Cavities ...... c . 517 1. The Nostrils ....... 518 2. The Nasal Fossae .... . . 519 3. The Sinuses ..... , . 524 DifTerential Characters in the Nasal Cavities of the other Animals . . 526 Comparison of the Nasal Cavities of Man with those of Animals . 527 The Air- tube succeeding the Nasal Cavities ..... 527 1. The Larynx ........ 527 2. The Trachea ....... 536 3. The Bronchi ........ 539 Differential Characters in the Air-tube succeeding the Nasal Cavities in the other Animals ........ 541 Comparison of the Larynx and Trachea of Man with these Organs in the Domesticated Animals ....... 542 The Thorax ......... 542 Differential Characters in the Thorax of the other Animals . . 545 The Lungs ......... 546 Differential Characters in the Lungs uf the other Animals . . 552 Comparison of the Larynx, Trachea, and Lungs of Man with those of Animals . 553 The Glandiform Bodies connected with the Respiratory Apparatus . 554 1. The Thyroid Body or Gland . . . . . .554 2. The Thymus Gland ....... 555 Differential Characters in the Glandiform Bodies annexed to the Respiratory Apparatus in the other Animals ...... 556 Comparison of the Glandiform Bodies annexed to the Respiratory Apparatus in Man with those of Animals ...... 557 Chapter II.— The Respiratory Apparatus of Birds . . .557 BOOK IV. URINARY APPARATUS. 1. The Kidneys 568 2. The Ureters ........ 574 3. The Bladder 575 4. The Urethra . . . . . . . . 578 5. The Supra-renal Capsules ...... 578 Differential Characters of the Urinary Apparatus in the other Animals . 579 Comparison of the Urinary Apparatus of Man with that of Animals . 581 BOOK V. CIRCULATORY APPARATUS. rlRST SECTION.— THE HEART . .... 583 1. The Heart as a Whole ...... 583 2. External Conformation of the Heart ..... 584 3. Internal Conformation of the Heart ..... 587 TABLE OF CONTENTS. 4. Structure of the Heart .... 5. The Pericardium ..•••• 6. The Action of the Heart Differential Characters in the Heart of the other Animals Comparison of the Heart of Man with that of Animals . SECOND SECTION.— THE ARTERIES Chapter I.— General Considerations . Chapter II.— Pulmonary Artery . Chapter III.— Aorta ..... Article I.— Common Aorta, or Aortic Trunk Cardiac, or Coronary Arteries, Article II. — Posterior Aorta .... Parietal Branches of the Posterior Aorta 1. Intercostal Arteries .... 2. Lumbar Arteries .... 3. Diphragmatic Arteries .... Middle Sacral Artery .... Visceral Branches of the Posterior Aorta . 1. Broncho-CEsophageal Trunk 2. Cceliac Artery ..... 3. Anterior or Great Mesenteric Artery 4. Posterior or Small Mesenteric Artery 5. Renal or Emulgent Arteries 6. Spermatic Arteries . . . ' • 7. Small Testicular Arteries (Male), Uterine Arteries (Female) Differential CLaracters in the Posterior Aorta and its Collateral Branches in the other Animals . . . . • 1. Posterior Aorta in Ruminants 2. Pesterior Aorta in the Pig .... 3. Posterior Aorta in Carnivora Comparison of the Aorta of Man with that of Animals Article III.— Internal Iliac Arteries, or Pelvic Trunks 1. Umbilical Artery . . • • • 2. Internal Pudic Artery, or Artery of the Bulb 3. Lateral Sacral or Subsacral Artery 4. Ilio-lumbar Artery, or Iliaco-muscular 5. Gluteal Artery . . . • • 6. Obturator Aitery . . • • • 7. Uiaco-femoral Artery . . • • • •. Differential Characters in the Internal Iliac Arteries of the other Animals 1. Internal Iliac Arteries of Ruminants 2. Internal Iliac Arteries of the Pig 3. Internal Iliac Arteries of Carnivora .... Comparison of the Internal Iliac Arteries of Man with those of Animals iiETicLE IV.— External Iliac Arteries, or Crural Trunks Femoral Artery ...••• 1. Prepubic Artery . • • * . " ^ x," 2. Profunda Femoris, Great Posterior Muscular Artery of the Deep Muscular Artery . . • • • 3. Superficialis Femoris, Superficial Muscular, or Great Anterior Artery ..-•••• 4. Innominate or Small Muscular Arteries . 5. Saphena Artery ..•••• Popliteal Artery ..•••• Terminal Branches of the Popliteal Artery 1. Posterior Tibial Artery . . • • • 2. Anterior Tibial Artery . . . • • 3. Pedal Artery . • • • ',/»., Differential Characters in the External Iliac Arteries of the other Animals 1. External Iliac Arteries of Ruminants 2. External Iliac Arteries of the Pig .... Thigh Muscular TABLE OF CONTENTS. 3. External Iliac Arteries of Carnivora. Comparison of the External Iliac Arteries of Man with those of Animals Article V. — Anterior Aorta ..... Article VI.— Brachial Trunks, or Axh.lary Arteries Collateral Branches of the Axillary Arteries 1. Dorsal, Dorso-muscular. or Transverse Cervical Aiteiy . 2. Superior Cervical, Cervico-muscuiar, or Deep Cervical Artery 3. Vertebral Artery ...... 4. Internal Tiioiacic Pectoral, or Internal Mammary Artery 5. External, Infi-rior Thoracic, or External Mammary Artery 6. Inferior Cervical Artery . ^ . . . 7. Supra-scapular Artery ...... 8. Infra-scapular or Subscapular Artery Humeral Artery, or Terminal Artery of the Brachial Trunk . 1. Anterior Radial (or Spiral) Artery .... 2. Posterior Radial Artery ...... (1) First Terminal Branch of the Posterior Radial (Radio-Palmar) Artery, ur Common Trunk of the Interosseous Metacarpals (2) Second Terminal Branch of the Posterior Radial Artery, or Collateral Artery of the Cannon .... Dififerential Characters in the Axillary Arteries of tht other Animals 1. Axillary Arteries of Ruminants .... 2. Axillary Arteries of the Pi^ .... 3. Axillary Arteries of Carnivora .... Comparison of the Axillary Arteries of Man with those of Animals Article VII.— Common Carotid Arteries .... Occipital Artery ...... Internal Carotid Artery ...... External Carotid Artery ...... Collateral Branches of the External Carotid Artery 1. Submaxillary, Facial, or Glosso-facial Artery 2. Maxillo-muscular Artery ..... 3. Posterior Auricular Artery . . . '. Terminal Branches of the External Carotid Artery 1. Superficial Temporal Artery, or Temporal Trunk 2. Internal Maxillary, or Gutturo-maxillary Artery Differential Chaiaftt-rs in the Carotid Arteries of the other Animals 1. Carotid Arteries of Carnivora .... 2. Carotid Arteries of the Pig .... 3. Carotid Arteries of Ruminants .... Comparison of the Carotid Arteries of Man with those of Animals THIRD SECTION. -THE VKINS ..... Chapter I.— General Considerations . Chapter II.— Veins of the Lesser Circulation, or Pulmonary Veins Chapter III.— Veins of the General Circulation Article I.— Cardiac or Coronary Veins Abticle II. — Anterior Vena Cava Jugular Veins ..... Roots of the Jugular .... 1. Superficial Temporal Vein 2. Internal Maxillary Vein . 3. The Sinuses of the Dura Mater Axillary Veins .... 1. Brachial or Subscapular Vein 2. Humeral Vein .... 3. Subcutaneous Thoracic or Spur Vein 4. Deep Veins of the Forearm 5. Superficial Veins of the Forearm 6. Metacarpal Veins 7. Digital Veins .... 8. Veins of the Ungual Region, or Foot TABLE OF CONTENTS. a External Venous Apparatus b. Internal or lutra-osseous Venous Apparatus Article III. — Posterior Vena Cava Plirenic or Diaphragmatic Veins Vena Portse 1. Roots of the Vena Portse 2. Collateral AflBnents of the Vena Portse Renal Veins . Spermatic Veins . Lumbar Veins Common Iliac Veins 1. Internal Iliac Vein 2. External Iliac Vein . 3. Femoral Vein 4. Popliteal Vein 5. Deep Veins of the Leg 6. Superficial Veins of the Leg 7. Metatarsal Veins 8. Veins of the Digital Region Diiferential Characters in the Veius of the other Animals Comparison of the Veins of Man with those of Animals FOURTH SECTION.— THE LYMPHATICS Chapter I. — General Considerations Lymphatic Vessels ..... Lymphatic Glands, or Ganglia Chapter II.— The Lymphatics in Particular Article I. — The Thoracic Duct . • • Article II.— The Lymphatics which constitute the Affluents of the Thoracic Duct . Lymphatics of the Abdominal Limb, Pelvis, inguinal Organs Abdominal Parietes, and Pelvi 1. Sublumbar Glands 2. Deep Inguinal Glands 3. Superficial Inguinal Glands 4 Popliteal Glands 5. Iliac Glands 6. Precrural Glands Lymphatics of the Abdominal Viscera 1. Glands and Lymphatic Vessels of the Rectum and Floating Colon 2. Glands and Lymphatic Vessels of the Double Colon 3. Glands and Lymphatic Vessels of the Csecum 4. Glitnds and Lymphatic Vessels of the Small Intestine 5 Glands and Lymphatic Vessels of the Stomach 6. Glands and Lymphatic Vessels of the Spleen and Liver . Glands and Lymphatic Vessels of the Organs contained in the Thoracic Cavity Glands and Lymphatic Vessels of the Thoracic Parietes Lyijiphatic Vessels of the Head, Neck, and Anterior Limb 1. Prepectoral Glands ..... 2. Pharyngeal Glands ..... 3. Submaxillary, or Subglossal Glands 4. Prescapular Glands ..... 5. Brachial Glands ...... Article III. — Great Lymphatic Vein Diflerential Characters in the Lymphatics of the other Animals Chapter III.— The Circulatory Apparatus in Birds . Article I.— The Heart ...... Article II. — The Arteries ..... Article III.— The Veins • . , , , Article IV. — The Lymphatics xm TABLE OF CONTENTS. BOOK VI. APPARATUS OF INNERVATION. FIRST SECTION.— THE NERVOUS SYSTEM IN GENERAL General Conformation of the Nervous System Structure of the Nervous System .... Properties and Functions of the Nervous Systems .... SECOND SECTION.— THE CENTRAL AXIS OF THE NERVOUS SYSTEM Chapter I.— Protective and Enveloping Parts of the Cerebro-spinal Axis The Bony Case containing the Central Cerebro-spinal Axis 1. The Spinal Canal 2. The Cranial Cavity . The Envelopes of the Cerebro-spinal Axis 1. The Dura Mater 2. The Arachnoid .... 3. The Pia Mater ....... Differential Characters in the Protecting and Enveloping Parts of the Cerebro- spinal Axis in the other Animals . Comparison of the Protective and Enveloping Parts of the Cerebro-spinal Axis of Man with those of Animals ...... Chapter II.— The Spinal Cord ...... External Conformation of the Spinal Cord Internal Conformation and Structure of the Spinal Cord Differential Characters in the Spinal Cord of the other Animals . Comparison of the Spinal Cord of Man with that of Animals Chapter III.— The Brain, or Eneephalon .... Article I.— The Brain as a Whole ..... Article II. — The Isthmus ...... External Conformation of the Isthmus .... 1. The Medulla Oblongata ..... 2. The Pons Varolii ...... 3. The Crura Cerebri ...... 4. The Crura Cerebelli ...... 5. The Valve of Vieusseus ..... 6. The Corpora Quadrigemina, or Bigemina 7. The Optic Tiialami ...... 8. The Pineal Gland ...... 9. The Pituitary Gland ..... Internal Conformation of the Isthmus ..... 1. The third or Middle Ventricle, or Ventricle of the Thalami Optici 2. The Aqueduct of Sylvius ..... 3. The Posterior, or Cerebellar Ventricle Structure of the Isthmus ...... Differential Characters in the Isthmus of the other Animals Comparison of the Isthmus of Man with that of Animals Article III. — The Cerebellum ..... 1. External Conformation of the Cerebellum .... 2. Internal Conformation of the Cerebellum Differential Characters of the Cerebellum in the other Animals Comparison of the Cerebellum of Man with that of Animals Article IV. — The Cerebrum ...... External Conformation of the Cerebrum . 1. The Longitudinal Fissure 2. The Cerebral Hemispheres . Internal Conformation of the Brain 1. The Corpus Callosum 2. The Lateral or Cerebral Ventricles 8. The Septum Lucidum 4. The Trigonum, or Fornix 5. The Hippocampi TABLE OF CONTENTS. xxiii 6. The Corpora Striata .... 7. The Choroid Plexus and Velum Interpositum Structure of the Brain .... DifFereutial Characters in the Brain of the other Animals Comparison of the Cerebrum of Man with that of Animals THIKD SECTION.— THE NERVES* . Chapter I.— The Cranial or Encephalic Nerves 1. First Pair, or Olfactory Nerves 2. Second Pair, or Optic Nerve* 3. Third Pair, or Common Oculo-:JIotor Nerves 4. Fourth Pair, or Pathetici Nerves . 5. Fifth Pair, or Trigeminal Nerves 6. Sixth Pair, or External Motor Ocular Nerves 7. Seventh Pair, or Facial Nerves 8. Eighth Pair, Auditory, or Acoustic Nerves 9. Ninth Pair, or Glosso-Pharyngeal Nerves 10. Tenth Pair, Vagus, or Pneumogastric Nerves 11. Eleventh Pair, Spinal, or Accessory Nerves of the Pneumogastrics 12. Twelfth Pair, or Great Hypoglossal Nerves Differential Characters in the Cranial Nerves of the other Animals Comparison of the Cranial Nerves of Man with those of Animals Chapter II.— Spinal Nerves ... Article I.— Cervical Nerves (Eight Pairs) Article II.— Dorsal Nerves (Seventeen Pairs) Article III. — Lumbar Nerves (Six Pairs) Article IV.— Sacral Nerves (Five Pairs) .... Article V. — Coccygeal Nerves (Six to Seven Pairs) Article VI. — Composite Nerves formed by the Inferior Branches of Spinal Branches ...... Diaphragmatic (or Phrenic) Nerve .... Brachial Plexus ....... 1. Diaphragmatie Branches ..... 2. Levator Anguli Scapulae and Rhomboideal Branch 3. Serratus Magnus, or Superior Thoracic Branch . 4. Pectoral or Inferior Thoracic Branches 5. Subcutaneous Thoracic Branch .... 6. Latissimus Dorsi Branch .... 7. Axillary or Circumflex Nerve .... 8. Nerve of the Teres Major .... 9. Subscapular Branches .... 10. Supra-scapular Nerve 11. Anterior Brachial or Musculo-Cutaneous Nerve . 12. Radial (or Mu^culo-spiral) Nerve 13. Ulnar or Culdto-cutaneous Nerve 14. Median or Cubito-plantar Nerve Differential Characters in the Brachial Plexus of the other Animals Compa4son of the Brachial Plexus of Man with that of Animals Lumbo-Sacral Plexus ...... A. Anterior Portion ..... 1. Iliaco-muscular Nerves .... 2. Crural or Anterior Femoral Nerve 3. Obturator Nerve ..... B. Posterior Portion ..... 4. Small Sciatic or Anterior and Posterior Gluteal Nerves 5. Great Sciatic or Great Femoro-popliteal Nerve Collateral Branches ...... Terminal Branches ...... Differential Characters in the Lumbo-sacral Plexus of the other Animals Comparison of the Lumbo-sacral Plexus in Man with that of Animals Chapter III.— The Great Sympathetic .... 1. Cranial Portion of the Sympathetic .... 887 TABLE OF CONTENTS. 2. Cervical Portion of the Sympathetic .... 3. Dorsal Portion of the Sympathetic .... 4. Lumbar Portion of the Sympathetic .... 5. Sacral Portion of the Sympathetic ... Differential Characters in the Great Sympathetic of the other Animals Ciimparison of the Great Sympathetic of Man with that of Animals . Chapter IV.— The Nervous System of Birds .... PAGE 887 891 892 893 894 894 BOOK VII. APPARATUSES OF SENSE. Chapter I.— Apparatus of Touch . . . . - Article I. — The Skin ...... Article II. — The Appendages of the Skin . . . Hairs ........ Horny Productions ...... 1. The Hoof of Solipeds ..... a. The Parts container! in the Huof .... b. Description of the Hoof .... 2. The Claws of Kuminants and Pachyderms 3. The Claws of Carnivora ..... 4. The Frontal Horns ...... 5. The Chestnuts ...... (6. The Ergots). ...... Chapter II.— Apparatus of Taste .... Differential Characters in the Apparatus of Taste in the other Animals Comparison of the Apparatus of Taste in Man with that of Animals Chapter III.— Apparatus of Smell ..... Chapter IV.— Apparatus of Vision .... Article I.— Essential Organ of Vision, or Ocdlar Globe Membranes of the Eye ..... A. Fibrous Membranes ...... 1 The Sclerotica ...... 2. The Cornea ...... B. Musculo-vascular . . c . . 1. The Choroid Membrane . , , . . 2. The Iris ...... C. Nerve Membrane ...... 3. The Betina ...... The Media of the Eye ...... 1. Crystalline Lens ...... 2. Vitreous Humour . . ... 3. Aqueous Humour ..... Article II.— Accessory Organs of the Visual Apparatus Orbital Cavity ...... Muscles of the Globe of the Eye ..... Protective Organs of the Eye ..... 1. Eyelids ....... 2. Membrana Nictitans ..... Lachrymal Apparatus ...... Differential Characters in the Visual Apparatus of the other Animals Comparison of the Visual Apparatus of Man with that of Animals . Chapter V.— Auditory Apparatus .... Article I. — Internal Ear, or Labyrinth .... The Osseous Labyrinth ..... 1. The Vestibule ...... 2. The Semicircular Canals .... 899 904 904 907 908 908 914 921 921 922 922 922 922 924 924 924 925 926 927 927 927 929 933 936 936 937 938 938 938 939 941 941 943 944 946 947 947 947 947 948 TABLE OF CONTENTS. 3. The Cochlea The Membranous Labyrinth 1. The Membranous Vestibule 2. The Membranous Semicircular Canals 3. The Membranous Cochlea Fluids of the Labyrinth . . . . , Distribution and Termination of the Auditory Nerve in the Membranous Labyrinth ••■•.. Article II.— Middle Ear, ob Case of the Tympanum 1. Membrane of the Tympanum .... 2. The Promontory, Fenestra Ovalis, and Fenestra, Rotunda 3. The Mastoid Cells .... 4. The Bones of the Middle Ear 5. The Mucous Membrane of the Tympanum 6. The Eustachian Tube 7. Tlie Guttural Pouches . Article III.— The External Ear . The External Auditory Canal. The Concha, or Pavilion . 1. Cartilages of the Concha. 2. Muscles of the External Ear . 3. Adipose Cushion of the External Ear 4. Integuments of the External Ear Differential Characters in the Auditory Apparatus of the other Animals Comparison of the Auditory Apparatus of Man with that of Animals PAGE 948 949 949 950 950 951 951 951 951 952 953 953 955 955 956 957 957 957 958 958 958 958 958 958 BOOK VIII. GENERATIVE APPARATUS. Chapter I.— Genital Organs of the Male Tiie Testicles, or Secretory Organs of the Semen . 1. The Tunica Vaginalis . . 2. The Testicles . . .'.*.*." Excretory Apparatus of the Semen . 1. The Epididymis and Deferent Canal. ..'.*. 2. The Vesiculse Seminales and Ejaculatory Ducts 3. The Urethra . . . •.".*." 4. The Glands annexed to the Urethra .'.'.'.* 5. The Corpus Cavernosum . . 6. The Penis Diiferential Characters in the Male Genital Organs of the otlier Animals . Comparison of the Genital Organs of Man with those of Animals Chapter II.— Genital Organs of the Female 1 The Ovaries .... 2. The Fallopian or Uterine Tubes, or Oviducts 3. The Uterus .... ... 4. The Vagina . • . . 5. The Vulva . . .'.'.*.' 6. The Mammae Differential Characters in tlie Female Genital Organs of the othpr Animals . Comparison of the Genital Organs of Woman with those of Domesticated Female Animals Chapter III.— Generative Apparatus of Birds ... * 1. Male Generative Organs ...... 2. Female Generative Organs ..... 960 960 963 967 967 968 970 973 973 975 976 984 993 995 997 999 1002 1003 1003 1004 UTi TABLE OF CONTENTS. BOOK IX. EMBRYOLOGY. Chapter I. -The Ovum and its Sarly Embryonic Developments Article I.— The Ovum ...... Article II. — First Embryonic Developments .... Article III. — General Direction of Development.— Vertebral Type Chapter II.— The Foetal Envelopes of Solipeds 1. The Chorion ...... 2. The Amniou ..... 3. The Allantois ....... 4. The Umbilical Vesicle . . ... 5. The Placenta ....... 6. The ITmbilical Cord ... . . Differential Cliaracters in the Annexes of the Foetus of the other Animals Comparison of the Annexes of the Human Foetus with those of Animals Chapter III.— Development of the Foetus Article I.— Formation of the Embryo ..... Development of the Chorda Dorsalis and Vertebral Laminae Article II. — Development of the Various Organs in the Animal Economy Development of the Nervous System. Development of the Organs of Sense Development of the Locomotory Apparatus . Development of the Circulatory Apparatus Development of the Respiratory Apparatus . Development of the Digestive Apparatus Development ot the Genito-urinary Apparatus PAGR 1005 1005 1005 1011 1016 1018 1019 1019 1023 1023 1025 1027 1032 1032 1033 1033 1035 1038 1040 1045 1046 1049 TABLE OF ILLUSTRATIONS. FIG. 1. 2. 3. 4. 5. Skeleton of the Dog . Skeleton of the Cat . . Skeleton of the Pig . Skeleton of the Rabbit . Skeleton of the Horse Skeleton of the Cow Skeleton of the Slieep Skeleton of the Camel . Vertical section of bone Minute structure of bone Lacunae, or osteoplasts of osseous substance Cartilage at the seat of ossification Elements of a vertebra A cervical vertebra Atlas (inferior surface) The axis or dentata (lateral view) Axis and sixth cervical of the Horse and Ass Type of a dorsal vertebra (the fourth) . Middle dorsal vertebra of the Horse, viewed from three typical lines Dorsal vertebra of the Horse and Ass (the eleventh) . Lumbar vertebra (front view) Upper surface of lumbar vertebrae . Lumbar vertebra of the Horse and Ass . , Lumbar vertebrae of the Cat and Rabbit . Lateral view of sacrum .... Horse's head (front view) .... Head of the Cat (posterior aspect) Head of the Pig (anterior face) . . , Head of tiie dog (anterior face) . Ox's head (anterior face) .... Head of a hornless Ox . . . , Ram's head (anterior face) .... Anterior bones of the head of a foetus at birth Posterior bones of the head of a foetus at birth Head of the Rabbit (posterior face) Head of the Rabbit (antero-lateral face) Ox's head (posterior lace) . . , , Posterior aspect of Horse's skull Head of the Pig (posterior face). Dog's head (posterior view) .... Longitudinal and transverse section of the Horse's head , Antero-posterior and vertical section of the Horse's head Median and vertical section of the Ox's head Inferior maxilla . . . , , Head of the Camel . , , Head of the Cat . Hyoid bone Wormian bones of the Ox Chauveau . PAGK 8 Chauveau . 8 Chauveau . 9 Chauveau . 9 Original 10 Original 10 Chauveau . 11 Chauveau . 12 Carpenter . 16 Carpenter . 17 Carpenter . 17 Carpenter . 20 After Owen . 25 Original 27 Original 28 (Jriginal 28 Chauveau . 29 Original 32 Chauveau . 33 Chauveau . 34 Original 36 Chauveau . 37 Chauveau . 38 ( 'hauveau . 39 Original . 40 Original . 46 Chauveau . 49 Chauveau . 50 Chauveau . 51 Chauveau . 52 Chauveau . 53 Chauveau . 53 Chauveau . 54 Chauveau . 57 Chauveau . 59 Chauveau ■ 62 Chauveau . 65 Original 66 Chauveau . 67 Chauveau . 68 Chauveau . 72 Chauveau . 72 Chauveau . 74 Chauveau . 76 Chauveau . 77 Chauveau . 78 Cliauveau . 78 Cornevin . 80 TABLE OF ILLUSTRATIONS. pro. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. G4. 65. 66 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. mb) Horse's head (anterior face) Horse's head (posterior face) Horse's head (lateral face Ass's head (lateral face) Crania of different breeds of Dogs Front view of the human cranium External or basilar surface of human skull . The sternum Typical ribs of the Horse Thorax of Man (anterior face) Scapula of the Horse (external face) Scapula of the Horse (internal face) Scapula of the Cat and Rabbit Antero-external view of right humerus Posterior view of right humerus . . Humerus of the Cat and Rabbit External face of the radius and ulna Forearm bones of the Ass Right fore foot of a Horse . Carpus of the Horse (anterior face) Carpus of the Horse (posterior face) Posterior view of right metacarpus Forearm and foot of the Ox (front view) Lateral view of the digital region (outside of right li Posterior view of anterior digital region Plantar surface of third phalanx Navicular bone .... Anterior limb of the Pig Forearm and foot of the Dog (anterior face) Human scapula (external aspect) Right human humerus (anterior surface) Human arm-bones (front view) . Palmar surface of left human hand . . Hand of Man and the domestic Mammalia, normal and The ossa innominata (seen from helow) . Pelvis (antero-lateral view) . Pelvis (lateral view) .... Pelvis of the Horse .... Pelvis of the Mare .... Pelvic bones of the Cat and Rabbit . Left femur (anterior view) Left femur (posterior view) . Section of left femur, showing its structure Femur of the cat and rabbit Posterior view of right tibia Leg-bone of the Mule Patella of the Horse (superior and posterior face) Patella of the Horse (anterior face) . Leg-bones of the Cat and Rabbit Left hind foot (external aspect) Tarsus of the Horse .... Left hock (front view) Left hock (internul aspect) Posterior aspect of left metatarsus . Human pelvis (female) .... Right human femur (anterior aspect) Human tibia and fibula of right leg (anterior aspect) Dorsal surface of left human foot Anterior limb of the Horse (antero-external view) Posterior limb of the Horse (antero-external view) Skeleton of a Fowl .... Original PAGE 81 . Original 81 Chauveau . 84 . . Chauveau . 85 . Chauveau . 89 Wilson 90 . Wilson 91 Chauveau . 93 , . Chauveau . 94 Wilmn 97 . Chauveau . 99 Chauveau . 99 . Chauveau . 100 , . Original 101 . . Original 102 Chauveau . 103 . Original 104 , Chauveau 106 . Original 108 Chauveau 109 , . Chauveau . 109 Original 111 e Chauveau 113 ) . Original 114 . Original 114 . . Original 116 G . Original 117 Chauveau 118 Chauveau 118 Wilson 119 . Wilson 120 Wilson 120 Wilson 121 teratological Chauveau 122 Chauveau 127 . Original 129 Original 129 . Chauveau 132 . . Chauveau 133 . Chauveau 136 Original 138 Original 138 m . Original 139 Chauveau 140 Original 141 . Chauveau 142 Chauveau 143 Chauveau 143 Chauveau 144 . Original 145 Chauveau 146 . Original 147 Original 147 . . Original 149 Wilson 151 . Wilson 152 Wilson 152 . Wilson 152 Chauveau 155 Chauveau 156 Chauveau 159 TABLE OF ILLUSTRATIONS. FIG. 110. Head of a Fowl (natural size : posterior view) 111. Sternum and bones of the wing . 112. Thoracic or pectoral vertebra of a Mammal • 113. Caudal vertebra of the Turbot . 114. Cephalic vertebrae of the Dog ..... 115. Plans of the different classes of articulations . . Beaunis 116. Section of branchial cartilage of Tadpole .... 117. Fibro-cartilage ..... 118. White or non-elastic fibrous tissue . 119. Yellow or elastic fibrous tissue . 120. Cervical ligament and deep muscles of the Horse's neck 121. Intervertebral articulations 122. Cervical ligament of the Ox ... 123. Cervical ligament of the young Camel . 124. Atlo-axoid and occipito-atloid articulations . 125. Temporo-maxillary articulation . 126. Articulations of the ribs with the vertebrae (upper plane) 127. Articulations of the ribs with the vertebrae (inferior plane) 128. Scapulo-liumeral and humeroradial articulations (external face) 129. Carpal articulations (front view) .... 130. Lateral view of the carpal articulations . . . . 131. Details of the metacarpo-phalangeal articulation of the Horse . 132. Carpal, metacarpal, and inter-phalangeal articulations of the Horse . 133. Section of inferior row of carpal bones, and metacarpal and suspensory ligament ........ 134. Posterior view of metacarpo-phalangeal and interphalangeal articu- lations ....... 135. Metatarso-phalangeal and interphalangeal articulations of the Horse 136. Articulation of the foot (inferior face) .... 137. Longitudinal and vertical section of the digital region of the Horse 138. Tendons and ligaments of the posterior face of the digital region of the Ox 139. Sacro-iliac and coxo-femoral articulations .... 140. Sacroiliac and coxo-femoral articulations 141. Femoro-tibial articulation ...... 142. Ligaments attaching the three bones of the leg . 143. Tarsal articulations (front view) ..... 144. Articulations of the tarsus (lateral view) 145. Ultimate fibril of muscle ...... 146. Striated muscular-tissue fibre ..... 147. Primitive fibre of red muscle ..... 148. Torn muscular fibre ...... 149. Primitive muscular fibre ...... 150. Relation of primitive muscular fibres with tendon 151. Transverse section of frozen muscle . . . * . 152. Arrangement of the fibres of a muscle . . . Beaunis 1 53. Distribution of capillaries in muscle ..... 154. Portion of elementary muscular fibre .... 155. Striated fibre of muscle during contraction .... 156. Horse fixed in first position ..... 157. Horse fixed in second position ..... 158. Lateral view of the neck (superficial muscles) . 159. Superficial muscles of the neck and spinal region of the back and loins 160. Lateral view of the neck (middle layer of muscles) . 161. Cervical ligament and deep muscles of the neck . 162. Muscles of the spinal region of the neck, back, and loins 163. Deep ditto ....... 164. Muscles of the back and cervix of Man .... 165. Muscles of the sublumbar, patellar, and internal crural regions . 166. Deep muscles of the sublumbar region .... 167. Sacro-iliac and coxo-femoral muscles .... Chauveau . PAGh 160 Chauveau . 164 Chauveau . 168 Chauveau . 168 Lavocat 168 and Bouchard 171 Carpenter . 172 Wilson 173 Carpenter . 174 Carpenter . 174 Chauveau . 181 Chauveau . 182 Chauveau . 184 Chauveau . 185 Chauveau . 187 Chauveau . 188 Chauveau . 191 Chauveau . 191 Chauveau . 196 Chauveau . 201 Chauveau . 202 Chauveau . 204 Chauveau . 205 Chauveau . 207 Original . 208 Chauveau . 210 Chauveau . 210 Chauveau . 211 Chauveau . 211 Chauveau . 213 Chauveau . 214 Chauveau . 217 Chauveau . 220 Chauveau . 222 Chauveau . 224 Bowman 232 Bowman 232 Renaut 233 Renaut 233 Renaut 234 Renaut 234 Kiihne 235 and Bouchard 236 Berres 236 Beale 237 Bowman 237 Chaiiveau . 240 Chauveau . 241 Original . 245 Chauveau . 247 Original . 248 Chauveau . 251 Chauveau , 261 Chauveau . 264 Wilson 267 Chauveau . 270 Chauveau . 271 Chauveau . 273 TABLE OF ILLUSTRATIONS. 168. Superficial muscles of the face and head .... 169. Muscles of external ear of Mule . 170. Muscles of the ear ....... 171. Hyoideal and pharyngeal regions .... 172. Superficial muscles of the Ox's head .... 173. Muscles of the human head . . . . 174. Muscles of the axillary and cervical regions .... 175. Axillary und thoracic muscles ..... 176. Muscles of the inferior abdominal region (Ass) 177. Muscles of the anterior aspect of the body of Man 178. Diaphragm (posterior face) ...... 179. External muscles of the anterior limb .... 180. Muscles of anterior aspect of Man's upper arm 181. Internal aspect of left anterior limb .... 182. Deep muscles on external aspect of right anterior limb , 183. Tendons and burtse of anterior limb of Horse 184. Flexor tendons of phalanges of Horse .... 185. Muscles of the forearm of the Ox ... . 186. Tendinous and ligamentous apparatus in the digital region of the Ox 187. Anterior antibrachial region of the Pig 188. Muscles of the forearm and paw of the Dog 189. Superficial muscles of human forearm .... 190. Deep layer of superficial muscles of human forearm 191. Muscles of human hand = . . . . 192. Dissecting- table ....... 193. Superficial muscles of the croup and thigh . . 194. Superficial muscles of the croup and thigh 195. Muscles of the sublumbar, patellar, and internal crural regions 196. Deep muscles of the coxo-femoral region 197. Coccygeal and deep muscles surrounding the coxo-femoral articu- lation ...... 198. Superficial muscles of the croup and thigh in the Cow 199. Muscles of the anterior femoral region in Man 200. Muscles of the posterior femoral and gluteal region in Man 201. External deep muscles of right posterior limb 202. Flexor muscle of metatarsus 203. Muscles on inner aspect of left posterior limb 204. Articular capsules and bursse in posterior limb . 205. External muscles of the leg of the Ox 206. Muscles of the human leg (anterior tibial region) 207. Superficial posterior muscles of the human leg 208. First layer of plantar muscles of human foot 209. Third and part of second layer of plantar muscles of human foot 210. Squamous epithelium from the mouth .... 211. Columnar epithelium . . ... 2 1 2. Columnar ciliated epithelium .... 213. Conical villi on mucous membrane of small intestine 214. Fusiform cells of smooth muscular fibre . . 215. Hard and soft palate ..... 216. Composite papilla from tongue of Dog . . . , 217. Simple filiform papillae ..... 218. Foramen of Morgagni ...... 219. Vertical section of a foramen csecum 220. Muscles of the tongue, soft palate, and pharynx . 221. Lobe of racemose gland from the floor of the mouth 222 Follicular gland ....... 223. Section of an amysdaloid follicle .... 224. Median longitudinal section of the head and upper part of neck 225. Magnified section of a canine tooth ..... 226. Section through the fang of a molar tooth . , 227. Transverse section of enamel . . . . c Original Cliauveau 275 280 Original Original Chauveau 282 287 290 Wilson 291 Chauveau 294 Original Chauveau 295 304 Wilson 306 Chauveau 309 Chauveau 311 Wilson 317 Original Original Chauveau 318 321 329 Chauveau 331 Chauveau 333 Chauveau 334 Chauveau . 335 Chauveau 337 Wilson 339 Wilson 339 Wilson 342 Chauveau 344 Chauveau 345 Original Chauveau 347 354 Chauveau 356 Chauveau 358 Chauveau 359 Wilson 361 Wilson 361 Original Chauveau 363 365 Original Chauveau 367 370 Chauveau 372 Wilson 375 Wilson 375 Wilson 377 Wilson 377 Wilson 393 Kolliker 393 Carpenter Wilson 393 394 Bowman 395 Chauveau 399 Chauveau 402 Chauveau 402 Chauveau 403 Chauveau 403 Chauveau 405 KSlliker 406 KdlUker 406 Chauveau 407 Original Wilson 4f)9 412 Carpenter Carpenter 413 414 TABLE OF ILLUSTRATIONS. zxxi FIG. ''■*<5E 228. Theoretical section of dental sac of permanent incisor . Chauveau . 415 229. Section of dentine and pulp of an incisor tooth . . . Carpenter , 416 230. Dentition of inferior jaw of Horse ..... Chauveau . 418 231 . Section of incisor tooth of Horse .... Chauveau . 418 232. Incisor teeth of Horse (details of structure) .... Chauveau . 419 233. Profile of upper teeth of the Horse .... Chauveau . 421 234. Transverse section of Horse's upper molar .... Chauveau . 422 235. The teeth of the Ox . . . . . Chauveau . 425 236. Ox's incisor tooth ....... Chauveau . 425 237. Incisor teeth of a Sheep two years old . . . . Chauveau . 427 238. Teeth of the Pig ... ... Chauveau . 428 239. General and lateral view of the Dog's teeth . . . Chauveau . 429 240. Anterior view of the incisors and canine teeth of Dog . . Chauveau . 429 241. Lateral and general view of the Cat's teeth . . . Chauveau . 429 242. Dentition of the Rabbit ..... Chauveau . 430 243. Section of the human face ..... Quain . 432 244. Lobule of parotid gland ... . . Wagner . 434 245. Capillary network of follicles of pirotiil gland . . . Berres . 434 246. Termination of the nerves in the salivary glands . . . Pfliiger . 435 247. Inferior aspect of head and neck .... Origincd . 436 248. Maxillary and sublingual glands ..... Chauveau . 437 249. Pharyngeal and laryngeal region .... Original . 441 250. Median lengitudinal section of head and upper part of neck . Original . 442 251. Pharynx of the Horse (posterior view) .... Chauveau . 443 252. Muscles of the pharyngeal and hyoideal regions . - . Original . 445 253. Human pharynx ...... Wilson . 447 254. Transverse vertical section of head and neck . . Original . 448 255. Pectoral cavity and mediastinum .... Chauveau . 449 256. Theoretical transverse section of abdominal cavity . . . Chauveau . 452 257. Theoretical, longitudinal, and median section of abdominal cavity Chauveau . 453 258. The abdominal cavity, with the stomach and other organs . . Origiiuil . 456 259. Stomach of the Horse ...... Chauveau . 457 260. Interior of the Horse's stomach ..... Chauveau . 458 261. Muscular fibres of stomach (external and middle layers) . Chauveau . 460 262. Deep and middle muscular fibres of stomach . . . Chauveau . 460 263. Peptic gastric gland ...... KoUiker . 461 264 Portion of a peptic caecum ...... Kolliher . 461 265. Mucous gastric gland ... . . KoUiker . 462 266. Capillaries of mucous membrane of stomach . . . Carpenter . 462 267. Stomach of the Dog ... . . Chauveau . 463 268. Stomach of the Ox . . . . . Chauveau . 464 269. Interior of the stomacli of Ruminants . . , Chauveau . 465 270. Section of the wall of the omasum of Sheep o . , , Chauveau . 467 271. Stomach of the Sheep ...... Chauveau . 468 272. Section of the omasum of the Sheep .... Chauveau . 469 273. Section of a leaf of the omasum ..... Chauveau , 470 274. Longitudinal section of a large papilla from the omasum . . Chauveau . 470 275. Villi of human and Sheep's intestine .... Teichmann . 474 276. Portion of Brunner's gland -...,. Thomson . 474 277. Section through Peyer's patch of Sheep . . . Teichmann . 475 278. Section through solitary follicle . . . . . Teichmann . 476 279. Injected villi of intestine ..... KoUiker . 476 280. Blood-vessels in Peyerian glandulse ..... KoUiker . 477 281. Diagram of origin of lacteals in villi .... Funke . 477 282. General view of the intestines of the Horse (right side) . . Chauveau . 479 283. General view of the Horse's intestines (inferior aspect) » . Chauveau . 480 284. The colon of the Horse ...... Original .. 481 285. Plan of the colon ...... Chauveau . 482 286. Intestines of the Rabbit (sreneral view) • c . . Cliauveau . 486 287. Stomach and intestines of the Sheep .... Chauveau . 487 288. General view of the intestines of the Ox . , . Chauveau . 488 TABLE OF ILLUSTRATIONS. FIG. 289. 290. 291. 292. 293. 294. 295. 296. 297. 298. 299. 300. 3(Jl. 302. 303. 304. 305. 306. 307. 308. 3ii9. 310. 311. 312 313. 314. 315. 316. 317. 318. 319. 320. 321. 322. 323. 324. 325. 326. 327. 331. 332. 334. 335. 339. 340. 341. 342. 343. 344. 345. 346. 347. 348. 349. General view of the intestines of the Pig . . . Chauveau . Intestines of the Dog ...... Chauveau . Digestive apparatus of the Cat ..... Chauveau . Human intestines ....... Wilson Abdominal cavity, with the liver and other organs . . Original Portion of a hepatic column, with secreting cells . . . Leidy Biliary capillaries and ducts ..... Irminrjer and Frey Blood-vessels in lobules of liver ..... Kiernan Section of lobules of liver, witli intra-lobular veins . . Kiernan Excretory apparatus of the Horse's liver .... Chauveau . Structure of the spleen (diagrammatic) . . . Beaunis and Bouchard Malpighian corpuscles attached to splenic artery . . . KSlliker Splenic corpuscle from the spleen of Ox . . . . Kdlliker Liver of the Ox ...... . Cliauveau . Liver of the Dog, with its excretory apparatus . . . Chauveau . Under surface of the human liver .... Wilson General view of the digestive apparatus of a Fowl . . Chauveau . Cartilages of the nostrils ...... Chauveau . Transverse section of the head of a Horse . . . Chauveau . Longitudinal section of the head and upper part of neck . . Original Cells of the olfactory mucous membrane . . Clarke and Schultze Fibres of olfactory nerve ...... Ecker Cartilages of the larynx disarticulated .... Chauveau . Superior face of larynx ...... Chauveau . Inferior face of larynx ...... Chauveau . Muscles of tlie Horse's larynx ..... Chauveau . Postero-lateral view of larynx ..... Original Entrance to the larynx of the Horse .... Chauveau . The respiratory organs (inferior aspect) .... Original Trachea, bronchi, and lungs of the Horse .... Chauveau . Ciliated epithelium from the trachea .... Kdlliker Bronchial tube, with its bronchules ..... Heale Mucous membrane of a broncliial tube .... Heale Theoretical section of thoracic cavity, behind the heart . . Chauveau . Theoretical section of thoracic cavity, at root of lungs . . Chauveau . Theoretical section of thoracic cavity, in front of right ventricle . Chauveau . Lungs of the Horse ...... Chauveau . Lungs of the Horse ....... Chauveau . Cast of bronchiole ...... Chauveau . Cast of bronchial divisions ...... Chauveau . Plan of a pulmonary lobule . . , . Waters Infundibula of lung ....... Kdlliker Capillaries around the infundibula of lung . . . Carpenter . Lung of the Sheep (inferior view) ..... Chauveau . Human lungs and heart ...... Wilson Gland-vesicles of thyroid ..... Kdlliker Portion of thymus of Calf ..... Kdlliker Course and termination of ducts in thymus gland of Calf . . Wilson General view of the air-sacs in the Duck . . , Chauveau . General view of the genito-uriuary apparatus in the Horse . . Chauveau . Horizontal longitudinal section of the Horse's kidney . Chauveau . Section of the cortical substance of the kidney . . . Ecker Course of the uriniferous tubuli ..... Hertz Diagram of the circulation in the kidney Transverse horizontal section of kidney . The kidneys and bladder in the foetus of Solipeds Right kidney of Ox (upper and external face) . Left kidney of Ox (internal and inferior face) The calices in left kidney of Ox Theoretical plan of the circulatory system . The heart and principal vessels (left face) Original Chauveau Chauveau Chauveau Chauveau Colin PAGE 489 490 491 492 496 498 498 499 499 500 504 505 505 508 509 510 513 519 520 521 523 524 .'i28 531 531 532 533 535 537 538 539 540 541 545 545 545 546 548 549 550 551 551 551 553 .')53 554 556 556 564 569 371 572 573 573 574 577 580 580 680 582 585 TABLE OF ILLUSTRATIONS. FIG. 350. 351. 352. 353. 354. 855. 356. 357. 358. 359. 360. 361. 362. 363. 364. 365. 366. 367. 370. 371. 372. 373. 374. 375. 376. 377. 378. 379. 380. 381. 385. 387. 391. 392. 395. 396. 397. 400. 401. 402. 403. 404. 405. 406. 407. 408. The heart and principal vessels (right face) . . . Chauveau Right side of the heart laid open ..... Wilson Section of the heart at the level of the valves . . . Sibson Left cavities of the heart laid open ..... Wilson Auriculo-ventricular fibro-cartilaginous rings . . . Parchappe Anastomosing muscular fibres of heart .... KoUiker Muscular whorl at point of heart .... Bourgery Posterior unitive fibres of auricles ..... Bourgery Epithelium of the endocardium ..... KoUiker Human lungs and heart (front view) .... WiUon Web of Frog's foot, showing blood-vessels and their anastomoses Wagner Epithelial cells of blood-vessels ..... KoUiker Fenestrated membrane from the carotid artery of the Horse . KoUiker Coarse elastic tissue from pulmonary artery of the Horse . KoUiker Transition of a minute artery of the brain into capillary vessels . KoUiker Abdominal or posterior aorta and cceliac axis in the Horse . Chauveau Distribution of the small mesenteric artery .... Chauveau Arteries of the stomach of Ruminants .... Chauveau Lateral view of ttie genito-urinary organs in the male . . Chauveau Abdominal aorta, with its branches, in Man . . . Wilson The external and internal iliac arteries in the Mare . . Chauveau Principal arteries of posterior foot of Horse . . . Cliauveau Anterior aspect of human leg and foot .... Wilson Posterior aspect of human leg . . . . . Wilson Arteries of sole of human foot ..... WiUmi Distributiou of the anterior aorta .... Chauveau Terminations of the axillary artery in the Horse , . . Chauveau Arteries of the anterior foot (seen from behind) . . Chauveau Arteries of the anterior foot of the Horse .... Chauveau Arteries of the human forearm and hand . . . Wilson Arteries of the brain ...... Chauveau Arteries of the head ...... Chauveau Rete mirabile of the Sheep (seen in profile) .... Chauveau Rete mirabile of the Ox (posterior face) .... Cliauveau Arteries of the face and head of Man .... Heath Radicles and collateral branches of the jugular vein in the Horse Chauveau Sinuses of the dura mater and radicles of the jugular vein of tiie Horse ........ Chauveau Subsphenoidal confluents in the Horse .... Cliauveau Veins of the foot ....... Bouley General view of the veins in the Horse .... Chauveau Vena portae and its roots ...... Chauveau A lymphatic vessel with its valves .... Chauveau Section of a lymphatic rete mirabile .... Teichmann Section of lymphatic gland ..... KoUiker Section of simple lymphatic gland ..... Teichmann Section of the medullary substance of lymphatic glaud of Ox . KoUiker Ordinary disposition of the thoracic duct .... Colin Double variety of the thoracic duct .... Colin Triple variety of the thoracic duct ..... Colin Lymphatic system of the Horse ..... Colin Great lymphatic vein and entrance of the thoracic duct . . Colin Great lymphatic duct (another variety) .... Colin Thoracic duct in the Ox . . . . . . Colin A variety of the thoracic duct in the Ox . . . Colin Another variety of the thoracic duct . . . . Colin A fourth variety of the thoracic duct .... Colin Thoracic duct of small Ruminants ..... Colin Diagram of structure of nerve-fibre .... Carpenter Nerve-tube ....... Ranvier Multipolar or stellate nerve-cell .... Ecker PAGE 586 587 589 591 592 594 594 595 597 599 603 604 604 604 605 614 619 622 627 628 630 637 642 642 643 647 651 653 655 678 680 681 695 700 704 707 714 717 718 718 719 723 723 723 725 731 731 732 733 733 733 7:-<4 740 740 741 TABLE OF ILLVSTBATIONS. 410. Several multipolar nerve-cells 411. Pyriimidal cell of the grey substance 412. Ganglion from heart of Frog 413. Bipolar ganglionic cells and nerve' 414. Stellate nerve-cell . « . . 415. Structure of ganglionic cells .... 416. General view of tlie spinal cord ... 417. Spinal cord at the cervical bulb or brachial plexus 418. Section of the spinal cord of the Horse at the lumbar region 419. Transverse section of spinal cord in the lumbar region . 420. Transverse section of spinal cord of Man in the middle of the lumbar region ...... 421. Ganglionic cell from the inferior cornu of spinal cord 422. Longitudinal secti>m through cervical bulb of spinal cord of the Cat 423. Brain of tlie Horse (upper surface) . 424. General view of the brain (lower surface) 425. Superior view of the encephalic isthmus 426. Lateral view of the isthmus .... 427. Transverse section of the brain . . • 428. Dissection of the medulla oblongata . . 429. Median and vertical section of the brain 430. Layers and cells of grey matter of cerebellum . . 431. Section of the cortical substance of the cerebellum . 432. Antero-posterior and vertical section of the brain . 433. Brain of the Horse (lateral face) 434. Corpus callosum . . . . , 435. Anterior portion of the lateral ventricles 436; Transverse section of human brain 437. Course of association nerve-fibres . . . 438. Course of association fibres in corpus callosum . • 439. Course of radiating fibres in the corona radlata 440. Layers and cells of a frontal convolution , . 441. Corticle substance; of the cerebral hemispheres 442. Brain of the Ox . 443. Brain of the Slieep ..... 444. Brain of the Pig ..... 445. Lateral face of the Dog's brain 446. Brain of the Dog (upper face) ... 447. Brain of the Cat ... . 448. Base of the human brain .... 449. Muscular fibres, with termination of motor nerve . 450. Nerves of the eye ..... 451. Section of the pons Varolii .... 452. Lateral view of the medulla oblongata . 453. General view of the superior and inferior maxillary nerves 454. Section of medulla oblongata and pons Varolii . 455. Section of middle portion of medulla oblongata 456. Origin of the nerves arising from the medulla oblongata 457. Origin and distribution of the eighth pair of nerves in Man 458. Distribution of the nerves in the larynx of the Horse 459. Deep nerves of the head .... 460. Nerves of the guttural region in the Ox. 461. Innervation of submaxillary and sublingual glands . 462. Nerves of the face and scalp of Man 463. Distribution of eighth pair of nerves on left side 464. Ganglion of a spinal nerve from the lumbar region 465. Nerves of the brachial plexus 466. External nerves of anterior limb . . . 467. Nerves of the digit of Horse 468. Nerves of tlie digital region of Ruminants 469. Nerves of the palmar face of Dog's foot PAOB , . Chauveau . 741 Chauveau . 741 . Ecker 742 Ecker 742 . Beale 742 . Beale and Arnold 742 . Colin 755 Colin 755 . Chauveau . 757 Deiters 758 e lumbar . I. L. Clarke 759 Kraus^e 760 the Cat I. L. Clarke 761 . CJiauveau . 764 Chauveau . 766 Chauveau . 770 Chauveau . 773 Cliauveau . 775 Solly and Carpenter 776 . Cliauveau . 780 Duval 781 . Kolliher . 782 Chauveau . 783 . Cliauveau . 787 Cliauveau . 789 . Chauveau . 789 Edinger 793 . Edinger 794 . Edinger 795 . Edinger 795 . Cliauveau . 796 . Kolliher . 796 , Chauveau . 797 , . Cliauveau . 798 . Chauveau . 799 Chauveau . 800 Chauveau . 801 . Chauveau . 801 Emchfeld and LeveilU 802 , . Cohnheim . 806 Chauveau . 812 . Duval 814 Erb 815 Chauveau . 818 Duval 825 . Duval 833 Toussaint . 836 . Wihon 837 Toussaint , 838 Chauveau . 843 Toussaint . 845 Bernard 848 Eirschfeld and LeveilU 850 Hirschfeld and LeveilU 851 KolUker . 854 . Chauveau . 863 Chauveau . 863 . Bouley 866 , Cliauveau . 868 . Chauveau . 870 TABLE OF ILLUSTRATIONS. FIG. 470. Nerves of the palmar face of Cat's foot . , , . Chauveau . 471. Nerves of the axilla of Man .... Hirschfeld ami LeveilU 472. Nerves of the front of forearm and hand of Man . Hirschfeld and Leveill€ 473. Lumbo-sacral plexus and internal nerves of posterior limb . . Cliauveau . 474. Posterior portion of the lumbo-sacral plexus . . . Chauveau . 475. External nerves of posterior limb ..... Chauveau . 476. Lumbar plexus of Man ..... Hirschfeld and Leveill^ 'ill. Nerves at the posterior aspect of human leg . . Hirschfeld and Leveill^ 478 Nerves at the front aspect of human leg . . Hirschfeld and Leveill€ 479. Sympathetic ganglion from a Puppy .... Kolliker 480. Sympathetic system of the Horse .... Cliauveau . 481. Brain of a Bird ....... Chauveau . 482. Section of Horse's skin ...... Chauveau . 483. Capillary loops in cutaneous papillae .... Berres 484. Tactile papillae from the skin ..... Ecker 485. Interungulate sinus of Sheep ..... Owen 486. Branches of cutaneous nerves in skin .... Ecker 487. Sudoriparous gland ....... Wagner 488 Oblique section of epidermis ..... Carpenter . 489. Hair-follicle ...... Morel and Villemin 490 Longitudinal median section of Horse's foot . . « Original 49L Horizontal section of Horse's foot ..... Original 492. Lower surface of the Horse's foot .... Original 493. Lateral view of the Horse's foot ..... Original 494. Horizontal section of hoof ..... Chauveau . 495. Horizontal section of the junction of the wall with the sole of hoof . Leisering . 496. Horizontal section of wall, and horny and vascular lamiuse . Leisering . 497. Hoof removed from the foot ...... Leisering . 498. Hoof with outer portion of wall removed . . . Leisering 499. Plantar surface of hoof ...... Leisering . 600. Horn-cells from the sole of hoof ..... Leisering . 501. Constituent elements of the wall ..... Leisering . 502. Theoretical section of the Horse's eye .... Chauveau . 503. Anterior segment of a transverse section of the globe of the eye (human) ........ Wilson 504. Cells from pigmentum nigrum ..... Carpenter . 505. The eye (human) with the sclerotic coat removed . . . Holden 506. Muscular structure of the iris ..... Kolliker 507. Vertical section of retina ...... MUller 508. Diagram of the structure of the retina .... Krause 509. Capillaries in the vascular layer of the retina . . . Berres 510. Muscles of the eyeball (viewed from above) , . . Original 511. Labyrinth in Fishes, Birds, and Mammals .... Gegenbaur . 512. Section of lamina spiralis of the cochlea . , , Carpenter 513. Section of the cochlea parallel to its axis .... Breschet 514. Cochlea opened ....... Chauveau . 515. Eight tympanic cavity of Horse's ear .... Chauveau 516. Bones of the middle ear of the Horse .... Lavocat 517. Diagram of the testicle ••.... Holden 518. Human testis, injected with mercury .... Lauth 519. Vertical section of the Horse's testis .... Chauveau 520. Internal genito-urinary organs of the foetus of a Mare , . Chauveau . 521. Spermatozoa of various animals ..... Carpenter 522. Superior view of the genito-uriuary organs . . . Chauveau 523. Transverse section of penis ...... Chauveau 524. Longitudinal section of the free extremity of the Horse's penis . Chauveau 525. Internal genital organs of a young Bull .... Chauveau 526. Sections of the urethra of the Ox at different points . . Chauveau 527. Penis and muscles of the sheath of the Bull .... Chauveau 528. Section of human pelvis ...... Gray 629. Section of the ovary ....... Schroen PAGE 870 871 872 876 877 879 884 895 900 900 901 901 902 902 903 905 908 909 910 912 912 914 914 915 916 916 919 919 927 931 931 932 933 935 936 936 940 948 949 949 950 953 954 963 963 964 965 967 969 974 976 977 978 979 982 TABLE OF ILLUSTRATIONS. FIG. 530. Ovaries, oviducts, and uterus of a foetus (equine) 531. Ovarium of the Rabbit .... 532. Constituent parts of Mammalian ovum, entire . 533. Constituent parts of Mammalian ovum, ruptured . 534. Formation of the corpus luteum 535. Generative organs of the Mare, isolated 536. Generative organs of the Mare, in situ . 537. Termination of milk-duct in cluster of follicles 538. Ultimate follicles of mammary gland, with secreting cells 539. Microscopic appearance of milk 540. Human uterus, witii its appendages 541. Ovary of the Bird ..... 542. Graafian vesicle ..... 543. Optical section of ovum of Eabbit . 544. Ovum of Rabbit ..... 545. Blastodermic vesicle of Rabbit 546. Section of a Fowl's unhatched egg 547. Area pellucida in early blastoderm 548. Transverse section of blastoderm 549. Area pellucida of blastoderm 550. Area pellucida in blastoderm .... 551. Transverse section of blastoderm 552. Transverse section of dorsal region 553. Manner in which embryo and envelopes are formed 554. Diagram of foetal membranes .... 555. Exterior of the chorial sac (Mare) . 556. Different parts of foetal Horse .... 557. Foetus of the Mare, with its envelopes 558. Portion of ultimate ramifications of umbilical vessels . 559. Vertical section of injected placenta 560. Portion of one of the foetal villi 561. Equine foetus, opened on left side to show umbilical vessels 562. Blood-vessels in liver of an equine foetus at mid-term . 563. Liver of a Lamb at birth .... 564. Foetus of the Slieep .... 565. Vertical section of a maternal cotyledon 566. Embryo of the Chick .... 567. Section of embryo Duck .... 568. Embryo of the Chick .... 569. Transverse section of embryo of Chick on third day 570. Plan of development of eye .... 571. Origin of encephalic centres in human embryo of fourth week 572. Plan of chorda dorsalis at period of formation of embryo 573. Plan of vertebra at an early period of development 574. Head of a foetal Lamb, showing Meckel's cartilage 575. Plan of first system of vessels (embryo) 576. Embryonic heart at an early period (anterior view) 577. Ditto, seen from behind 578. Heart of an equine foetus 579. Plan of the aorta and its arches at an early period 580. Plan of the circulation in the human embryo (side view) 581. Section of embryo of Rabbit 582. First appearance of the lungs . 583. Embryo of Dog at twenty-five days 584. Origin of liver from intestinal wall of embryo Chick 585. Urinary and genital apparatus in embryo Chick Chauveau . PAGE 986 Pouchet 987 Coste 988 Coste 988 Pouchet 989 Chauveau . 991 Chauveau . 994 Sir A. Cooper 998 Lehert 998 Funke 999 Wilson 1002 Chauveau 1004 BalUani 1006 VanBeneden 1006 Van Beneden 1007 Kdlliker 1008 Thomson 1010 Balfour 1010 Balfour 1011 Balfour 1012 Balfour 1012 Balfour 1013 Balfour 1014 Balfour 1015 Turner 1017 Chauveau 1018 Chauveau 1020 Chauveau 1022 Carpenter 1023 Turner 1024 Eclcer 1025 Cliauveau 1026 Colin 1026 Colin 1027 Cliauveau 1028 Turner 1029 Balfour 1032 Balfour 10.33 Balfour 1034 Kolliker 1035 Kdlliker 1035 Wagner 1037 Kdlliker 1039 Kolliker 1039 Huxley . 1039 Kolliker 1041 Kolliker . 1042 Kdlliker 1042 Chauveau . 1043 Kolliker . 1043 Coste . 1044 Balfour . 1045 Wagner . 1046 Bischoff . 1046 Muller . 1049 Muller . 1050 THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS. GENERAL CONSIDERATIONS. DEFINITION AND DIVISIONS OP ANATOMY. Anatomy is the science of organization ; it studies the structure of animals when these are dead. It comprises two grand divisions — physiological anatomy ^ which describes healthy organs, and pathological anatomy, the object of which is the description of diseased organs. Physiological anatomy, which alone is treated of in this book, in its turn embraces — 1. General anatomy, which is occupied with similar substances or tissues of the animal body, with regard to their texture, and their physical, chemical, and physiological properties, irrespective of the organs in which these tissues are found. The particular study of the anatomical elements entering into the composition of the tissues, is named histology. Histology necessarily requires the aid of the microscope. 2. Descriptive anatomy, which studies the situation, form, and relations of organs, as well as the relative arrangement of the various tissues composing them, with the exception of the structure and properties of these tissues. If this study be devoted to a single species, it is designated special anatomy. Example : human anatomy, or anthropotomy ; the anatomy of the Horse, or hippotomy. "When descriptive anatomy embraces the study of the organization of the entire animal kingdom, and examines the differences which characterize the same organ or the same series of organs in each class, family, genus, or species, it is named comparative anatomy. Restricted to the domesticated animals, this study constitutes veterinary anatomy. Philosophical or transcendental anatomy differs from comparative anatomy, in that it indicates the analogies of organs or apparatus, rather than their differences, in order to exhibit as clearly as possible the general laws of organization. Finally, if descriptive anatomy be limited to denoting the relations existing between the various organs of a region, particularly with a view to the perform- ance of operations and the diagnosis of external diseases, it takes the names of topographical, regional, or surgical anatomy. GENERAL CONSIDERATIONS. Enumeration and Classification of the Species of Domesticated Animals. The object of this book is the study of veterinary anatomy. The animals of which it treats belong to the Mammiferous class and to that of Birds. The domesticated Mammals of om- clunates have their representatives in a large number of orders. Thus, we find among them — 1. Of the Carnivora, the Dog and Cat; 2. A Rodent, the Rahhit ; 3. A Pachyderm, the Pig ; 4. Of Solipeds, the Horse and Ass ; the produce of the Male Ass with the mare, i.e. the 3fule, and that of the Horse with the Female Ass, known by the name of Hinny ; 5. Of Ruminants, the Ox, Sheep, and Goat. With regard to Poultry, they range themselves — 1. In the Gallinaceous or Columba order, the genera to which the Common Fowl, Guinea Foivl, Turkey, and Pigeon belong ; In the order of Palmipeds, the Goose and Duclc. Girard has proposed a special classification for the domesticated Mammals, based upon the number of digits terminating each of their limbs, and has defined four categories : the first comprises the Horse, Ass, Mule, and Hinny, which take the name of monodactyles, because their digital region is composed of a single digit ; in the second, under the denomination of didactyles or bisulcate animals, those with two digits, such as the Ox, Sheep, and Goat ; in the third, or regular tetradactyles, is found the Pig, each of whose limbs has four digits ; lastly, the Dog and Cat, which most frequently have four digits on the posterior members and five on the anterior ones, and form the class of irregular tetradactyles. This nomenclature will not be followed here, as it is opposed to the general laws of organization. Philosophical anatomy has, in fact, demonstrated that there are really no true monodactyles, didactyles, etc. ; all are materially or virtually pentadactyles. It is therefore considered better to keep to the classification established by zoologists, because it prevents confusion in scientific language. The regimen and habits of the domesticated animals bring about diiferences in their organization ; these appear very great at first sight, though in reality they are not so marked as they seem. In order to study the descriptive anatomy of all these annuals, we will not pass them in review, one after another, giving for each the description of every organ ; but shall take a type, which will most frequently be the Horse, implicitly compared with man, and briefly compare all the others with it. In this com- parison, the animals will be generally classed according to their domestic value ; though exceptions will be made to the rule which has been instituted by our predecessors, whenever any advantage m point of concision or perspicuity is likely to be obtained. General Ideas of the Organization of Animals. Order followed in studying the Various Apparatuses. The bodies of animals contain fluid and solid organic matters, as well as gases and some mineral substances. Organic Fluids. — The fluids are very abundant in the animal economy ; GENERAL CONSIDERATIONS. 3 not only do they fill certain vessels constructed for them, but they also impregnate all the solid parts of the body. Their importance is very great, for without them the organic solids would perish ; an element deprived of humidity is ipso facto deprived of life. These fluids vary in their nature and composition. Apart from those that the solids imbibe, there is not one which is completely amorphous. In the midst of a liquid holding organized matter in solution, there are always formed elements which will be referred to hereafter. Examples : the blood and lymph. Organic Solids. — In studying the organic solids, we will proceed from the simple to the complex. Solid organized matter is amorphous — as in the hyaline substance of cartilage and the fundamental substance of bone tissue, or it assumes the form of more or less voluminous particles in every instance invisible to the naked eye, and to which the name of anatomical elements has been given. They may be reduced to three principal : the granule, the cell, and the fibre. Granules. — These are the smallest known elements. They may be held in suspension in animal fluids, remain free among the other elements, or be enclosed in the interior of cells. Their nature is not always the same : they are proteic, fatty, or pigmentary. The pigmentary granules are of a brown colour. Cells. — The cell is pre-eminently the anatomical element. Theoretically, the cell is a microscopic mass of a nitrogenous substance, viscid {protoplasm or sarcode), uniformly transparent, or slightly granular. Frequently in the midst of this protoplasm there is perceived a nucleus provided with a nucleolus, and at its periphery an enveloping membrane. The cell lives like an entire organism : it feeds, grows, multiplies, absorbs, secretes, moves, etc. It behaves like a complete animal, though it be a micro- scopic one. The form of the cell, as well as its volume and nature, vary. It has therefore received various names. There are round, polyhedral, fusiform, conical, stellate, and other shaped cells. Some have a diameter of 1-1 2000th part of an inch, while others are l-2000th part. Cells multiply in various ways : 1st, by the division of the nucleus and segmentation of the protoplasm in the interior of the enveloping membrane {endogenous multiplication) ; 2nd, by constriction, then division of the nucleus, protoplasm, and enveloping membrane {flssiparous multiplication) ; 3rd, by a kind of bulging or swelling of the enveloping membrane, and constriction and separation of the enlargement thus formed {gemmation). A large number of cells only temporarily remain in this condition. In con- sequence of modifications that cannot be referred to here, they are converted into fibrillse or other elements, in which it is difiicult to recognize the primordial element. Others maintain the cellular form : then they develop, live, and die in several ways. Sometimes they are worn by the contact of foreign bodies, as on the sur- face of the skin ; sometimes they become liquefied, as in some glands ; and at other times they undergo fatty degeneration, which gradually brings about their complete destruction. The permanent cells are — 1. Hcematies or red corpuscles, which are found in a state of suspension in the blood ; they are round and discoid in Mammalia, with the exception of the Camel and Llama, in which they are elliptical, as well as in Birds, Reptiles, and 4 GENERAL CONSIDERATIONS. the majority of Fishes. These cells have an envelope, but they do not have a nucleus in JVIammalia ; 2. Leucocytes, white corpuscles, or lymph cells, which float in the blood, lymph, chyle, and the connective tissue interspaces. These cells are susceptible of amae- boid movements, and their fundamental form is spherical ; though they are often Irregular in shape, owing to the contractile prolongations they throw out, called pseupodes. They may have one or more irregular nuclei ; 3. Connective cells, which are flat, nucleated, and irregular ; they are applied to the fasciculi of connective fibres ; 4. Adipose cells, lying in the connective tissue and filled with fat, which has pushed the protoplasm and nucleus towards the envelope ; 5. Medullary cells, with a budding nucleus or multiple nuclei (myeloplaxes and medullo-cells), forming the principal elements of the marrow of bones ; 6. Cartilage cells, which have no envelope, and which, single or associated with a variable intermediate substance, form cartilages ; 7. Bone cells, lodged in a space remarkable for its elliptical shape and the numerous prolongations on its margin. The cells are nucleated, have no envelope, and secrete the fundamental solid substance of the bony tissue ; 8. Contractile cells, which constitute the basis of muscular tissue. They are fusiform and nucleated ; 9. Nerve cells, met with in the cerebro-spinal centres and the ganglia of the cerebro-spinal and sympathetic systems. They are provided with one, two, or more prolongations called poles ; hence they are uni-, bi-, or multipolar. 10. Epithelial cells, found on the surface of tegumentary membranes, or laid over the interior of more or less diverticulated cavities (glandular cavities or glands). The epithelial element is lamellar or polyhedric, cylindrical, calcif orm, vibratile, etc. 11. Endothelial cells, always lamellar, and hning serous cavities and vascular canals. Fibres. — A fibre is an elongated element of variable dimensions and com- position. Thus, it may be very fine {connective fibre), or thick and limited by two borders more or less apart (muscidar fibre) ; it is homogeneous throughout {elastic fibre), or has a contents and a distinct envelope {nerve fibre). The vitality of fibres is not comparable with that of cells. Once formed, they are only nourished, for it is not yet definitely ascertained whether they can multiply. In the animal economy there are four kinds of fibres — 1. Connective fibre, an extremely fine element, but in which, nevertheless, two borders can be distinguished if it be examined by a power of from 800 to 1000 diameters. The fibres form fasciculi in the connective tissue, or are distri- buted in the midst of a fundamental substance — as in the fibro-cartilages. The connective fibre constitutes the most solid organs of the animal economy — the ligaments, tendons, etc. 2. Elastic fibre, found closely packed in certain organs, such as the cervical ligament and abdominal tunic, or forming a network in the midst of connective tissue ; it is even found in the framework of bones. 3. Muscular fibre, smooth or striped (striated), which has the property of contracting under the influence of stimuli. Smooth (or unstriped), is found in a large number of viscera ; striped is more especially in the domain of the locomotory apparatus. 4. Nerve fibre, very remarkable for its continuous axis-cylinder. It is found in the nerve centres, cerebro-spinal nerves, and great sympathetic system. GENEBAL CONSIDERATIONS. 5 I Inorganic Substances. — These substances (gases and mineral matters) are usually found in solution in the animal fluids. Their presence is indispensable in the constitution of the living body. Sometimes the mineral matters are solid, amorphous, or crystallized. In this condition they are rarely met with in healthy organs (iriternal ear) ; but they are frequently found in diseased ones. Tissues. — The anatomical elements, by being grouped in different manners, form tissues. Some tissues are constituted by one kind of element ; these are simple tissues — for example, epithelial tissue. But the larger number are formed by a combination of several different elements ; these are composite tissues — for example, nerve tissue. The anatomical, physico-chemical, and physiological characters of the tissues, are repeated, it need scarcely be remarked, in the anatomical, physico-chemical, and physiological properties of the elements which enter into their composition. Only four simple types of fundamental tissue are described, and which are based on the morphological, chemical, and physiological characters of the constituent elements — 1. In the first place, there are to be noted the tissues of connective substance or framework, comprising the varieties of connective tissue, fibrous tissue, elastic tissue, cartilaginous tissue, and bone tissue. 2. Then there are the cellular tissues, formed entirely of persistent cells ; they are the epithelial tissue proper, and the glandular tissue. The cells of the epithehal tissue are differently arranged. If they are disposed in a single layer, they constitute a simple epithelium ; but if superposed so as to form two or more layers, then it is a stratified epithelium. According to the form of the superficial layer of cells, the epithelium is polyhedric, pavement., cylindrical, spherical, or calciform. In certain parts the superficial cells are furnished with vibratile cilia, and the epithehum is then called vibratile (or ciliated). 3. The third type is represented by the muscular tissue, the agent of move- ment, which is divided into striated and non-striated muscle. 4. Lastly, there is the nerve tissue, which is present under two aspects — white substance and grey substance. The first is formed entirely of nerve fibres and a supporting tissue or neuroglia ; the second by fibres and nerve cells united by neurogha. The grey substance belongs to the most important portions of the nervous system — the brain, spinal cord, and gangha, where it co-exists with the white substance. The latter entirely constitutes the peripheral ramifications of the nervous system. Organs. — The term " organ " is given to any portion of the body having a determinate form and a function to fulfil. A bone, a muscle, the stomach, the liver, and the brain, are organs. General Arrangement of the Organs and Apparatus. — All animal organs are enclosed between two membranes named limitary or tegumentary membranes, which are continuous with one another at the margin of the natural openings. These are the skin and the mucous membranes, in the composition of which are included a layer of connective tissue and an epithelium Organs protected by these membranes are solid or hollow. Among the first, a certain number act as supports : such are the organs formed by the connective tissue, and particularly the cartilages and bones. Others are destmed to produce movements : these are the muscles. The action of the muscles is communicated directly to the organs that are to be e GENERAL CONSIDERATIONS moved, or it is transmitted through the medimn of oth%r organs, such as the tendons and the aponeuroses. The central nervous organs — the nerves properly so called — belong to this group of solid organs. The activity of muscles and the sensibility of limitary membranes are due to them. With regard to the hollow organs, they are everywhere formed by an envelope of smooth (or unstriped) muscular tissue, lined by an internal tegumentary or mucous membrane. Examples : the bladder and stomach. There must also be included the vessels formed by elastic and contractile membranes arranged as canals, in which the blood and lymph circulate ; the glands, and, lastly, the serous membranes which line the interior of the splanchnic cavities, cover the surface of the organs contained in them, and the inner face of the articulations and synovial sheaths. It is remarkable that, in the trunk, the bones form two superposed cylinders, one of which lodges the organs of circulation, digestion, and respiration, and the other the central nervous system (neural and luemal ajUnder). Apparatus. — Organs are very numerous in the animal economy, and in order to study them profitably it is necessary to classify them in a methodical manner, according to their physiological affinities. Consequently, there have been col- lected into a single category all those organs which are destined to achieve the same physiological finality, and to such a group has been given the name of apparatus. Bichat has grouped the apparatuses according to the ultimate object of their functions, and has thus formed two great categories : one, comprising the apparatuses which maintain the individual {apparatuses of nutrition and relation) ; the other, the apparatus destined for the preservation of the species {apparatus of generation). We will describe these apparatuses in the following order : — 1. Locomotory Apparatus ; 2. Digestive Apparatus ; 3. Respiratory Apparatus ; 4. Urinary Depurative Apparatus ; 5. Circulatory Apparatus ; 6. Inner vatory Apparatus ; 7. Sensory Apparatus ; 8. Generative Apparatus. This description will be terminated by a brief notice of the evolution of ths /(Btus^ and its appendages. BOOK I. LocoMOTORY Apparatus. The locomotory apparatus is composed of all those organs which minister to the movements an animal may execute. It is certainly one of the most important in the economy, from the nmnber and size of the pieces which enter into its formation, and by the necessary co-operation it affords the majority of the other apparatuses in the performance of the physiological acts allotted to them. It is constituted of two kinds of organs— the bones and muscles. The hones, hard and resisting, stony in appearance, are really inert levers, joined by firm and movable articulatmis, which permit their playing upon each other with the greatest facility, at the same time maintaining them in their relative positions. The muscles, grouped around the bones and attached to them, are soft organs which possess the property of contraction, under certain determinate conditions, and of involving in that movement the bones to which they are fixed by their extremities. The bones are altogether passive in their motion, while the muscles are really the active organs of locomotion — the power intended to move the bony levers. We will study, successively — 1. The bones, a particular branch of descriptive anatomy which has received the name of Osteology ; 2. The articulations, or Arthrology ; 3. The muscles, or Myology. FIRST SECTION. The Bones. CHAPTER I. THE BONES IN GENERAL. Bones, properly speaking, are only to be found in vertebrate animals, and constitute their principal zoological character. In the animal body they form an internal framework which consolidates the entire edifice, and gives it its general form and dimensions. It is advantageous, before commencing a particular description of each bone, to survey them in a general manner. This study comprises: 1. The description of the skeleton; 2. A summary indication of 8 TEE BONES. ihQ general principles which should be known, in order to comprehend the details of the special descriptions. Aeticle I. — The Skeleton. The whole of the bones, considered in their natural relations to each other, constitute the skeleton. In order to prepare the skeleton of any animal, it is SKELETON OF THE DOG. sufficient to free it from the soft parts surrounding it. The skeleton should be designated natural, if in this operation the ligaments that naturally join the Fig. 2. SKELETON OF THE CAT. various pieces together are allowed to remain ; and artificial if, after these liga- ments have been destroyed, it is necessary to replace them by materials foreign to the organization, such as iron or brass wire. THE SKELETON. 9 The skeleton is divided into trunk and limbs. 1. The trunk offers for consideration, in the middle line, the spine or vertebral column — a flexible stalk measuring the entire length of the animal, and composed of a series of distinct pieces articulated one behind the other. An- teriorly, this stalk supports the head — a pyramidal mass which results from the assemblage of a large number of bones. On each side of the middle portion of Fig. 3. SKELETON OF THE PIG. I the spine, there are detached bony arches which have received the name of ribs, and which rest, directly or indirectly, by their inferior extremities, on a single bone called the sternum. These bony arches in this way circumscribe the thorax — a spacious cavity destined for the reception of the principal organs of respiration and circulation. 2. The limbs, four in number — two anterior and two posterior — are the ap- Fig. 4. SKELETON OF THE RABBIT. pendages which support the trunk of the domestic Mammals. They are usually distinguished as anterior and posterior (or fore and hind), but it will be more convenient to name them according to their relations, as thoracic (or pectoral) and abdominal limbs. Each represents a column divided into several rays resting upon one another, and generally forming more or less open angles. The anterior limbs 10 THE BONES. are each divisible into four principal regions : the shoulder, applied against the front part of the thorax ; the arm, which succeeds the shoulder ; and the fore- SKELETON OP THE HORSE. arm, and foot. The posterior limbs also comprise four regions : the haunch or pelvis, which articulates with the posterior part of the spine ; and the thigh, leg^ and posterior foot. Fig. 6. SKELETON OF THE COW. In Birds, the posterior limbs alone assume the function of columns of support. The thoracic limbs, formed for flight, constitute the wings. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 11 The number of bones entering into the composition of the skeleton of the principal domesticated animals, arrived at the adult period of life, varies accord- Fig. 7. SKELETON OF THE SHEEP. ing to the species. They are apportioned to the regions of the trunk and limbs just mentioned, in the manner indicated in the following table : — Designation. SOLIPEDS.' Ruminants. Pig. Dog.' Vertebral Column' Head^ 48 28 37 1- 2 1— 2 2— 2 16-32 1— 2 1- 2 3— 6 15-30 45 28 27 1— 2 1- 2 2- 4 20-40 1- 2 1— 2 3- 6 19—38 50 29 29 1— 2 1— 2 2— 4 36—72 1— 2 I— 2 3— 6 36-72 46 28 27 1— 2 1— 2 2— 4 36—72 1- 2 1— 2 3— 6 32—64 Thorax Shoulder Arm . Forearm Fore foot Pelvis Thigh Leg . Hind fool ^ Double regions - Tc tals 191 196 270 255 AeTICLE II. — GElfEEAL PkINCIPLES APPLICABLE TO THE StUDY OF ALL THE Bones, The description of a bone comprises its name, situation, shape, internal cori' formation, structure, and mode of development. ' One lumbar vertebra less is found in the Ass, and sometimes also in the Mule. * The 08 penis has not been included. ' The sacrum is reckoned as a single bone, and the number of coccygeal vertebrae at aa average of 16 for the Horse, 18 for the Ox, 22 for the Pig, and 18 for the Dog. * The OS hyoides is reckoned as a single bone. 12 THE BONES. Name. The nomenclature of osteology does not rest on any basis capable of confer- ring upon it a methodic form. Consequently, we find bones which derive their name from their shape (example : the fibula) ; others from their resemblance to known objects (the tibia and vomer). Some owe it to their position (the frontal bone), or their uses (the axis and parietal bones). Several attempts have been made to submit the nomenclature of the bones to more precise GENERAL PRINCIPLES APPLICABLE TO TEE STUDY OF ALL THE BONES. 13 and uniform rules, but the new designations proposed have not been sanctioned by custom. Situation. The situation of a bone should be viewed in two ways : 1st, Relative to the median plane of the body ; 2nd, Relative to the other portions of the skeleton. A. Situation relative to the median plane of the body. — The designation of median plane, improperly median line, is given to an imaginary vertical plane passing through the middle of the skeleton, which it divides from before to behind, into two equal portions. The bones may be situat|^ on the median plane, in which case there is only one of each kind, and they are called single ; they are also named symmetrical bones, because the median plane divides them into equal lateral halves exactly alike.^ The bones disposed in a double and regular manner on the sides of the median plane bear, for this reason, the name of pair bones ; they are also called asymmetrical bones, because their form does not admit of their being divided, in any sense, into two similar portions. On the contrary, a bone of this kind always offers the most perfect symmetry with its fellow on the opposite side.^ B. Relative situation to the other parts of the skeleton. — To indicate the situation of a bone, considered from this point of view, is to make known the place it occupies in the region to which it belongs, and the connections it may have with adjoining regions. Thus, the radius is situated in front of the ulna, between the arm-bone and the carpus. Direction. This is absolute or relative. A. The absolute direction is related to the axes of the bones themselves. Thus it is that a bone may be rectilinear, curvilinear, or twisted. B. The relative direction is determined by the relation to the fictitious planes established around or in the interior of the skeleton, or with regard to the neighbouring bones. For example, a bone is vertical, horizontal, or oblique. In the latter case it may be downwards and backwards, or in the reverse direction. Example : the scapula is placed obliquely downwards and forwards. Shape of the Bones. Form. — This is also absolute or relative. A. Absolute Form. — The absolute form of a bone is that which it owes to the relations existing between its three dimensions — length, width, and thickness. a. A bone in which one of its dimensions much exceeds those of the other two is a long bojie (example : the femur), provided it be hollowed out internally by an elongated space— the medullary canal. Long bones belong exclusively to the limbs. In the animal economy there are found bones which resemble them in their dimensions, but they have no medullary canal (example : the ribs). These differ essentially from the true long bones, and are also distinguished from them by the appellation of elongated bones, b. A bone that offers two dimensions much more developed than the third, is a flat or tvide bone (example : the parietal bone). The bones of this category, destitute of a medullary cavity, are • Instances have been recorded of asymmetry in single bones. Lesbre has seen the sixth cervical vertebra of the Horse tricuspid on one side and bicuspid on the other, and a last dorsal vertebra with one of its transverse processes having the characters of the lumbar vertebraj. * But there might be slight differences in weight, torsion, etc. In Man there is nearly always a difference between the right and the left side. 4 14 TEE BONES. met with in the head and the upper regions of the Umbs. c. A bone which offers nearly the same development in all its dimensions, is called a short bone (example : the astragalus). Destitute, like the preceding, of a medullary canal, the short bones are found in the spine and some regions of the limbs. B. Relative Form. — To make known the relative form of a bone, is to indicate the greater or less exact resemblance it may bear to geometrical figures, or to familiar objects. Thus, the scapula is a bone of a triangular shape. Regions of the Bones. — When describing the eminences and external cavities of bone^ it is essential not to allude to them casually by passing indifferently from one to another. To avoid the diificulties resulting from the application of such an irrational system, it is necessary to divide the bone to be studied into several regions, in which external peculiarities can be examined successively, as they present themselves. The general course to be followed in order to learn the regions of a long, a flat, and a short bone, is as follows : — a. A long bone is always divided into three parts — a body and two extremities. The bod// or middle portion, or diaphysis, is the narrowest part of the bone. In shape it is a geometrical solid, inclining somewhat to that of a very long prism. On the body of a bone, therefore, there are studied as many faces and planes, angles or borders, as on the prism it represents. The extremities, or epiphyses, are more or less considerable enlargements, formed primarily by a special bony nucleus, and offering articular surfaces, as well as surfaces for muscular or ligamentous insertion. b. A flat bone must necessarily have two faces, and borders and angles. c. A short bone has more or less faces, and plane or salient angles which are often ignored, because of their trifling ijnportance. External Peculiarities of Bones. — These markedly attract the attention, because they modify the general shape of bones, and singularly assist in distinguishing one bone from another. These peculiarities, which are real distinctive features that permit their description to be precisely established, are always either eminences or cavities, according to their different uses. A. Eminences. — The eminences that stand out in relief from the surfaces of bones, are divided into two different categories. One class concurs in the formation of the articulations which join the bones to each other ; they are named articular eminences, in which, again, are distinguished diarthrodial and synarthrodial eminences, according as they belong to movable or immovable articulations. The others, usually destined for the insertion of ligaments and muscles, are called non-art icidar eminences or eminences of insertion. (The term imp-int is also used in anatomy, and signifies a collection of small rugged eminences which make the surface of the bone uneven and rough. There are muscular, tendinous, ligamentous, and aponeurotic imprints, according as they give attachment to muscles, tendons, ligaments, or aponeuroses.) a. The synarthrodial eminences are always indentations more or less deep and finely cut, which stud the border of large bones. b. The diarthrodial eminences are volimiinous, smooth, and in a fresh state covered with cartilage. They are named heads and condyles : heads, when they describe the segment of a sphere (head of the femur, head of the humerus) ; condyles, when they represent an ovoid segment cut parallel to its larger axis (condyles of the femur). c. The non-articular eminences receive various names. If they are volumi- nous and much detached from the bone, they are called processes or apophyses. GENERAL PBINOIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 15 Apophyses receive qualificatives derived from the analogies perceived between them and known objects (examples : the styloid, clinoid, coronoid, and coracoid processes). The appellations of protuberances and hiherosities are given to non- articular eminences when they are large and round, and slightly detached. Lastly, they are named lines, crests, and ridges, when they are narrow and very long. The processes are sometimes epiphysary in early life, and formed by a special nucleus. B. Cavities. — The cavities of bones have also been divided into articular, diarthrodial or synarthrodia! , and non-articular cavities. a. The diarthrodial cavities correspond to the eminences of the same name in the bony joints. They take the designation of glenoid cavities when they are oval and shallow, and cotyloid cavities when they are deeply excavated, like a basin or the cup of an acorn (examples : the glenoid cavity of the scapula, and the cotyloid cavity of the coxa). The synarthrodial cavities fit into the dentations opposed to them. b. The non-articular cavities serve either for hgamentous or muscular insertion, or for the passage of vessels, nerves, tendons, etc. They are termed channels or furrows, when they are wide, deep, and smooth ; grooves, when they are long, narrow, and smooth at the bottom ; and fissures, when they are narrow and rugged. Digitcd impi'essions is the name given to those excavations in bones which look as if produced by the pressure of the finger. The fossce, sinuses, cells, and notches are also non-articular cavities of bones. The sinuses and cells are formed by open spaces in the interior of bones ; notches, by cavities excavated on their margins. When a cavity passes quite through a bone, it is termed a foramen. If this foramen has a certain length, it is designated a conduit or canal. Fissures are long, narrow openings ; hiatus is the term applied to a wide opening with an irregular outline. In order to aid the memory, the external peculiarities of bones are grouped in the following synoptical table : — i Non-Articulars ( Synarthrodials . Dentations. JDiarthrodials . ( gf^^^^s. I Styloids. Coracoids. Mastoids. 1 1 uoerosiiies. Lines. ^Crests. i Articulars. . .. aynarmroaiaiB -J Dentation ^Diarthrodials .{^^^^ Channels. ^, Furrows. •< ' Grooves. o Digital impressions. pa Fossae. Sinuses. Non-Articulars .< Cells. Notches. Foraminse. Canals. Ducts. Slits. , Hiatuses. Internal Conformation of Bones. Sections made in various directions through the substance of bones, show that their internal conformation varies, according as they belong to the category of long, flat, or short bones The diaphysis of long bones is hollowed out into a large fusiform cavity — the medullary canal. This' canal is absent in the flat and short bones, and is replaced by irregular cavities which communicate with each other, called medullary spaces. Its walls are formed by a very dense bony tissue, 16 TEE BONES. the pores of which are scarcely visible to the naked eye, and which is called the compact substance. The extremities of long bones are surrounded by a thin layer of compact substance, while the remainder of their mass is constituted by the spongy substance — bony tissue channeled into medullary spaces. { Reticulated bony tissue is but another form of spongy substance, the only difference between the two consisting in the cells or meshes of the first being formed of intercrossed osseous fibres, while those of the second are formed of lameUce.) The medullary canal, and areolae of the spongy tissue, are filled by the marrow (or medulla). The flat bones are constituted by a layer of spongy tissue placed between two plates of compact substance. (In the flat bones of the cranium, the two layers of compact tissue are termed the vitreous tables, while the cells of the spongy tissue are designated diploe.) In certain points of their extent, the spongy substance disappears, and then the bone is composed of a single lamina of compact tissue. The short bones have a nucleus of spongy substance, enveloped in a layer^ more or less thick, of compact tissue. The compact substance of the bones, being very resisting, is found in all those situations which have to sustain violent efforts. The spongy substance is very hght when compared with its volume, and is met with in the wider portions of the bones, to which it affords increased size without adding sensibly to their weight. Structure of Bones. Bones are formed of a proper tissue, covered externally by a particular membrane — the periosteum, and occupied internally by the medulla, vessels, and nerves. A. Proper tissue. — The elements of the proper tissue of bone are always and everywhere the same ; the texture alone is modified in the compact and spongy substance. Everywhere the bone tissue is composed of a funda- mental substance, which is amorphous or slightlj granular, white, and more or less opaque, according to the thickness it offers. This fundamental substance is penetrated by an infinite number of vascular canaliculi [bone cavities), with prolongations {hone canaliculi), which contain cells {bone cells). The cavities and their contents are named osseous corpuscles or osteoplasts. In a dried plate of bone, the corpuscles appear dark when viewed by reflected light, white and shining by direct light. In the spongy tissue, the bone corpuscles, anasto- mosing by the ends of their canahcuh, are distributed throughout the lamellte of fundamental substance, which is intercrossed in such a way as to circumscribe the numerous medullary spaces. In the compact tissue, the corpuscles are regularly distributed in the substance of the bony lamellae, which are arranged in concentric layers. In a transverse section of the diaphysis of a long bone, it is noticed that the fundamental substance is excavated by an infinite number of vascular canaliculi, named Haversian canals (Figs. 9, 10). These canals measure from l-2500th to l-200th of an inch in diameter, and are parallel to each other and to the larger Fig. 9. VERTICAL SECTION OF BONE, showing the network of Haversian canals. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 17 axis of the bone ; they communicate frequently by transverse branches. "While the most superficial open on the surface of the bone, beneath the periosteum, and the deepest into the medullary canal, a certain number terminate in the areolae of the spongy substance at the ends of the bones. '^" * The wails of these canals are con- stituted by several concentric lamellae of fundamental substance, in which are lodged the essential elements of the bony tissue. Each canal, with its vessels, its system of concentric lamellae, its osteoplasts, and its osseous canaliculi, forms a whole (the Haversian system) which represents the complete bone in miniature. All the Haversian systems preserve a certain independence ; the canalicuh of each, after reaching the minute structure of bone, as shown iu a thia . , 1 11 n , 1 , section cut transversely to the direction of the periphery, are nearly all reflected to- Haversian canals. wards the centre (the recurrent canaliculi l, A Haversian canal surrounded by its concentric lamellse ; the lacunae are seen between the lamella', but the radiating tubuli are omitted; 2, ibid., with its concentric laminae, lacunae, and radiating tuhuli; 3, the area of one of the canals ; 4, 4, intervening lamelljE, and between them, at the upper part, several very long lacunae with their tubuli. Fig. 11. of Ranvier) and rejoin the canaliculi of the same system, instead of anasto- mosing with those of the neighbouring system. Between the Haversian systems, there are the intermediate systems of lamellae which fill the spaces left through the imperfect contact of the former. In all the long bones there is a system of periphercd lamellae, enveloping, ex- ternally, all the Haversian systems ; while a system of perimediiUary lamellce, more or less perfect, also exists at the inner surface of the medullary canal. ^*«^^^^' ^^ '^'''^*?rf ™ °!- ''''f''' substance, ,,, , ^ , 1-11 magnified 500 diameters. Sharpey observed that the peripheral ^^ ^^^^,^1 ^^^-^^ . j^ j^s ramifications, bony lamellte were traversed by fibres {Sharpey's ov perforating fibres), and J. Renaut has remarked in the same lamellae the presence of elastic fibres. The proper tissue of bones is a framework of organic matter which has gelatine for its base, and in which are deposited the calcareous phosphates and carbonates which give to this tissue its characteristic hardness. This is easily rendered evident by immersing any bone in dilute nitric or hydro- chloric acid ; acid dissolve the calcareous salts, but do not act upon the organic framework. So it is, that after some days' maceration the bone becomes flexible, like cartilage, and loses part of its weight, although it preserves its volume and shape. The counterpart of this experiment may be made by submitting it to the action of fire. It is then rendered quite friable, because its organic skeleton has been destroyed, without the earthy salts it contained being affected. B. Periosteum. — This is a very vascular and nervous fibrous membrane which covers the entire bone, with the exception of the articular surfaces and the 18 THE BONES. insertions of tendons and ligaments. Its thickness and adherence are not the same everywhere ; it adheres most closely near the ends of bones. By its inner face it corresponds to the surface of the bone, into which it sends prolongations {arciform fibres) which ultimately become Sharpey's fibres ; by its external face, it is continuous with the surrounding connective tissue and that of the muscular aponeuroses. The periosteum may be resolved into two layers, though these are not always very distinct. The superficial layer is essentially fibrous, and is formed by a network of elastic fibres containing bundles of longitudinal fibres and cells. The deep layer is a closer elastic network, with finer connective tissue fibres, and a larger quantity of cells and vessels. This is called the osteogenous layer , because of its functions. C. Medulla. — The medulla, or marrow, is a pulpy, fatty substance, which fills the medullary canal and the areola of the spongy tissue of the bones, and partly the Haversian canals. Somewhat consistent, and of a rosy tint in the bones of young animals, the marrow becomes diffluent and yellow in the bones of those advanced in age, except in the vertebrae of the Horse, Ox, Dog, etc., and in the limbs of the Rabbit. In the first state, it is also mucous or fibrous in the cranial and facial bones undergoing development, and, rosy in colour, it only contains traces of fat ; while in the second, it has 96 per cent, of this substance. The medulla of bones is composed of : 1st, some trabecul^e of delicate connective tissue and a network of stellate cells, to support the vessels and nerves ; 2nd, fat cells ; 3rd, particular cells, named by M. Robin medullo- cells and myeloplaxes. The medullo-cells, abundant in the red or foetal marrow, are small cells with a spherical or budding nucleus {Bizzozero's cells), analogous to the lymph cells ; some are impregnated with hgemoglobine. With regard to the myeloplaxes, these are enormous flat cells, irregular in outline, and containing a large number of nuclei. Rare in the yellow marrow, they are more particularly found adhering to the walls of the medullary canal, or the alveoli of the spongy tissue. D. Blood-vessels. — The arteries of bones belong to three orders — a distinction based on their volume and the extent of their distribution. The arteries of the first order penetrate to the interior of the medullary canal of long bones, by a particular orifice — the nutrient foramen. They soon divide into two branches, which break up into a network that lines the walls of the canal and enters the tissue of the medulla. This network communicates with the arteries of the second order, which go to the spongy tissue of the extremities of the long bones, penetrating them by the numerous nutritive foramina that surround the epiphyses. Lastly, the arteries of the third order are branches of the periostic network that enters the superficial Haversian canals. These canals may be considered, strictly speaking, as a third category of nutrient conduits. In the flat and short bones there are no arteries of the first order. Veins accompany the arteries, and are always more voluminous than these ; they frequently make their exit by special and very large openings at those points where the spongy tissue is abundant. The veins of bones sometimes exhibit saccular dilatations on their course. Certain veins in the cranial bones have their walls partly or entirely channeled in the bony tissue ; they are lined by a simple endothelium. E. Lymphatic vessels. — The existence of these cannot be affirmed. GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 19 Nerves. — These belong to the eerebro-spinal and ganglionic system of nerves ; the latter are always vaso-motor nerves. Almost constantly, a somewhat volmninous nerve enters the medullary canal, by passing through the nutrient foramen, and is distributed to the medulla. The compact tissue receives few nerve filaments ; while, on the contrary, the spongy tissue at the extremities of the long bones, as well as the short bones, contains many. Certain short bones, such as the vertebrse, are remarkable for the numerous nerves they receive. DEVELOPMENT OP BONES. The bones, before arriving at the condition in which we see them in the adult animal, pass through several successive phases, the study of which consti- tutes Osteogemj. Nearly all the bones were originally cartilaginous, those of the roof of the cranium and the face being only represented by fibrous tissue. We will examine the development of these cartilaginous and fibrous bones. A. Development of the Cartilaginous Bones. — In the embryo at an early period, the bones are composed of a mucous material analogous to that which enters into the composition of all the other organs ; this matter is constituted by a mass of embryonic cells. Later, they become harder, white, and elastic — that is, cartila- ginous. Certain portions of the skeleton persist in this condition during the life of the animal. These permanent cartilages are found where the bony skeleton must have a certain amount of flexibility, and on the articular surfaces. The temporary cartilages, like the permanent, have a fundamental amorphous : 01 hyahne substance, in which are embedded round cells containing one or several nuclei. But they soon undergo modifications, which result in giving to the pieces they form the hardness and structure of perfect osseous tissue. These modifications gradually cause the cartilage to disappear, and to be replaced by bony tissue, without the skeleton ceasing for an instant to preserve its form and functions. The process commences by calcification of the peri- chondrium and of the middle part of the diaphysis, which ensures the stability of the organ. Then the blood-vessels, which are constantly present in temporary cartilages, pass through the diaphysary nucleus, ramify, and are directed in a parallel manner towards the extremities. Simultaneously, the chondroplasts are arranged in parallel series in front of the vessels (rivulation of the cartilage), and finish by merging into large, irregular, elongated cavities, incompletely separated by bands of fundamental substance of the calcified cartilage, designated the directing lines of ossification. The blood-vessels enter these cavities, carrying to their surface cells which proliferate, and are differentiated into osteoblasts or productive cells of bone. The osteoblasts are deposited, layer upon layer, against the walls of the spaces limited by the lines of ossification, and form, by a kind of secretion, concentric strata of the osseous fundamental system which surrounds them ; then the osteoblasts become osteoplasts. The cavities made in the cartilage finish by becoming filled up, except at the centre, where a central cylindrical space remains (Haversian canal), and a blood-vessel. In the extremities of the bones, where there are no Haversian canals, the preparatory modifications are the same as in the diaphysis, only the cartilaginous cells collect in small irregular masses, and not in parallel piles. Each of these 20 THE BONES. masses forms layers of bone substance, that finish by constituting the lamellaB of spongy tissue at the periphery and medullary tissue at the centre, to fill the areola of the latter. In this way is accomplished the transformation of cartilage into bone. As will have been observed, it is not a mere calcification of the cartilaginous tissue, «^A, but a real substitution of bone tissue, presentmg the following phases : 1. Peri- tijfe*^- , ( chondrial and endochondral calcification in places (nuclei or centres of ossifica- tion). 2. Invasion of the centres of ossification by vessels, rivulation of the cartilage. 3. MedulHzation of the cartilage, and formation of^ osteoblasts. 4. Development of the 'Jt^ <^^ .^^^ ■'• '■ " bone tissue, appearance of the osteoplasts. J"^ ^§ e^^ /^:r^ B. Development of the Fibrous Bones. — The bones originally fibrous are not merely charged with lime salts in order to acquire a bony appearance. They do not pass through a transitory cartilaginous state, but the phenomena of ossification take place in the fibrous tissue in the following manner : — The fasciculi of connective tissue become calcified, separate here and there from one another to form spaces, into which blood-vessels enter or osteoblasts appear. To this phase of medullization succeeds the phase of ossification, which is accomplished in the same manner as in the cartilaginous bones. Only the directing lines are represented by connective fasciculi, which later become Sharpey's fibres. 0. Progress of Ossification. — Ossification com- mences simultaneously in several parts of the skeleton, and in each of the bones in particular— though not throughout their entire extent at the same time. On CARTILAGE AT THE SEAT OF thc coutrary, lu certain determinate points of the carti- ossiFicATioN, showing at its lagiuous or fibrous mass, osseous tissue is developed ir^'lsCi:;...'": c:lr™: ^Wch, gradually extendmg, ends by completely in- each of which is enclosed in a vadiug it. These points are named nuclei (or centres) sheath of calcified intercellular ^f ossificatiou. The nuclei are primitive or comple- mentary. The latter, termed epiphyses, are in a fashion added to the bone, and wholly or partly form certain' apophyses, rtjlj* , '^' Although these centres of ossification increase from day to day, they never- theless remain for a long time independent of each other, and are united only by cartilage. When the skeleton is completely developed, the various centres of ossification become joined to each other, and the entire bone forms one piece ; there are no longer any apophyses. Up to the present time, attempts to discover the laws which govern the appearance of the centres of ossification have been futile ; the size of the bone counts for nothing ; and the influence of proximity to the centres of circulation, which has been sometimes brought forward (for the sternum, for example, which is never completely ossified), cannot be accepted. The law which presides over the union of the centres of ossification has also been sought for. A. Berard imagined he could formulate it in the following proposition .- Of the two extremities of along bone, it is always that towards ivhich the nutrient foramen is directed that is first united to the body of the bone. But to Berard's GENERAL PRINCIPLES APPLICABLE TO THE STUDY OF ALL THE BONES. 21 law there are nmnerous exceptions ; and in order to demonstrate that it is not absolute, it is sufficient to indicate that the direction of the nutrient foramen varies much, not only in similar bones of different species of animals, but also in similar bones of the same species^ ; and yet the progress of ossilication is alwajs the same. The period when fusion of the epiphyses terminates in the domestic animals is still little known ; fusion is evidently complete when growth is achieved, but this period is markedly modified by hygiene and the :'ood animals receive. Renault and some breeders have observed, that in the proocious breeds of cattle the evolution of the teeth is more rapid than in the common breeds. More recently, Sanson has affirmed that precocity, characterized by this prompt dental evolution, is marked by a more rapid fusion of the epiphyses, and he believes there is a direct relation between the evolution of the teeth and that of the bones. According to this principle, in the Horse the fusion of the epiphyses should commence and terminate between three and five years of age. Toussaint, however, did not share this opinion. In the Ox, Sheep, and Horse, he remarked that the first centres of ossification appeared in the body of the flat and the longbone^and in the centrum and arches of the vertebrae. When the first half of ^esrajtionnad not been passed, no other points of ossifica- tion were seen. It is necessary to add, however, those of the second and third phalanges and the calcis, which comport themselves as long bones. In the last half of gestation, ossification invades the complementary nuclei, as well as the short bones ; the exceptions are the pisiform bone and the inner condyle of the humerus in the Calf and Foal, and the large and small sesamoid bones in the Calf only. Ossification of these bones of the skeleton is slow. It must also be mentioned that at birth the complementary nuclei of the coxas^ are not yet visible, and they are net seen until ten months or a year afterwards. ^^ ^ ""' ^^^J With regard to fusion of the epiphyses, it occurs at the following periods in the principal bones of the Horse ; at the twelfth to the fifteenth month in the second phalanx at first, then in the first phalanx ; at the fifteenth to the eighteenth month in the middle metacarpal, afterwards in the metatarsal. At this age fusion also occurs at the upper end of the radius and inferior ex- tremity of the humerus : from twenty months to two years, at the lower end of the tibia ; from three to three and a half years, at the upper extremity of the humerus, at the two ends of the femur, and at the upper end of the tibia ; lastly, about five years, in the bodies of the vertebrae and in the coxae. In the Ox, ossification progresses at about the same rate as in the Horse, except that there is a little greater precocity in the fusion of the epiphyses of the humerus and radius, which are fused at the same time as those of the phalanges, and matacarpal and metatarsal bones. In this animal, the two lateral halves of the latter bones are united before union of the inferior epiphysis to the body of the bone. The Sheep offers an interesting peculiarity, in that the humero- radial epiphyses are consolidated before those of the phalanges, and towards the tenth month. If the results of these observations, made on our principal domestic animals, are compared with the evolution of the dental system, we are compelled to con- clude, with Toussaint, that fusion of the epiphyses does not commence at the same time as the eruption of the first permanent teeth. If a relationship exists between the evolution of the teeth and that of the bones, it has yet to be demonstrated in an exact manner. 22 THE BONES. Toussaint has also studied the course of ossification in the Bog, Pig, and Rabbit. In the Dog at birth, none of the complementary nuclei have been invaded by ossification. Consequently, bone tissue is only found in the dia- physis of the long and flat bones. In the thrge months after birth, the great majority of the epiphyses commence to ossify ; and after this period there only remain the pyramidal bone and the complementary nuclei of the coxffi, in the cartilaginous condition ; the ossification of these latter commence at from five to six months. The skeleton of the Rabbit is, at birth, in a condition almost identical with that of the Dog ; nearly all the epiphysary nuclei of the humerus and that of the lower end of the femur, however, show osseous points. In the Fig, at birth ossification is much more advanced than in the Dog ; but it is less so than in the larger Herbivora. The fusion of the epiphyses has been studied in the Dog. It commences at five months, in the phalanges and metacarpals, and continues in the humerus and radius, the corresponding epiphyses of which are consolidated at nine months ; at eighteen months there can be distinguished the nuclei at the upper border of the scapula, the upper end of the humerus, inferior extremity of the radius and uhia, the epiphyses of the femur, and the bodies of the vertebrae. The latter facts support the preceding ones, and likewise demonstrate that the conclusions of Sanson are probably too absolute. Growth of the Bones. Bones increase by the superposition of new elements, while the soft parts of the organism grow by the interposition of new elements in the mass of pre- existing elements. The manner in which this apposition of new elements is accomplished is not the same in the long, the flat, or the short bones. 1. Long Bones. As a general rule, the long bones elongate by the growth and ossification of the temporary cartilage situated between the diaphysis and the osseous nuclei at the extremities. Consequently, elongation ceases when the primitive or complementary nuclei are fused with one another. The increase in length in the bones of the Ihnbs does not take place everywhere in the same proportion. Duhamel, Flourens, and particularly Oilier and Humphry, have remarked that, in the thoracic limb, the extremity furthest removed from the humero-radial articulation grows fastest ; while in the abdominal limb, the extremity most distant from the femoro-tibial articulation grows the least. With regard to the increase in thickness of the bone, this occurs by ossifica- tion of the deeper layer of the periosteum — the osteogenous lager. The experiments of the authors just mentioned irrefutably demonstrate this, and those of Oilier have even proved that the periosteum may produce bone at a point where it has been transplanted. The periostic bone is developed according to the process of ossification in the fibrous tissue. In a transverse section of the diaphysis of a growing long bone, there is seen, as Laulaine has indicated, concentric circumferences united by radii of osseous substance. The diaphysary portion of the periostic bone is fused with the extremities, through the medium of the ossification notch of Ranvier — a prolongation of the periosteum into the articular enlargement around the cartilage of conjugation. The formation of bone tissue in the deeper layer of the periosteum is very active during the youth of animals, but it soon diminishes, and ceases completely in advanced age. GENERA L PRINCIPLES A PPLICABLE TO THE STUD Y OF ALL TEE BONES. 23 If the phenomena of growth were not counterbalanced by those of absorption, long bones would acquire an enormous thickness and weight. But in the first period of life, in proportion as new layers are applied to the surface of bones, the deeper parts — those occupying the axis of the diaphysis — disappear by absorption. In this way the medullary canal is formed, and a just proportion established between the volume and weight of the skeleton. When the bones are completely formed, during the entire adult period the process of destruction is equal to that of growth, so that their weight and com- position does not vary. At a later period, absorption is greater than the forma- tive force, which in old age is altogether in abeyance ; so that the organic matter of the bones is rarefied, and these lose their elasticity and gain in fragility. It has been remarked that the development of the bones is subordinate, in a certain measure, to the activity and resistance of the organs in their vicinity. Lesshoft and Popoff beheve that the development of a bone is in proportion to the activity of the neighbouring muscles, that the pressure of external organs- such as an aponeurosis — may produce torsion in a bone and retard its growth, so that its greatest thickness will correspond to the point where the surrounding Ijf^ resistances are at a minimum. Oilier, however, has noted that the long bones i^*^"^ become more elongated when they do not sustain pressure on their extremities. 2. Flat Bones. — These bones have sometimes only one primary nucleus of ossification, placed in the centre. They grow by the increase of this nucleus, which gradually invades the mass of the bone in radiating from the centre towards the periphery. When they have several nuclei, some of these are at the margin, and in such a case the bones increase by ossification of the marginal efpiphyses and growth of the central nucleus. Flat bones increase in thickness by the formation of sub-periosteal layers, and by the development of the spongy tissue between the two compact plates. 3. Short Bones. — These grow in thickness by the progressive ossification of the osteogenic layer of the periosteum ; and in length by ossification of the • epiphysary cartilages, when they possess complementary nuclei. Nutrition of Bones. The experiments which consisted in feeding young animals with madder, and afterwards examining their osseous system, have for a long period demonstrated the nutrition of bones. When bones cease to grow, nutrition becomes less active ; but it is evident that it does go on, in order to maintain the organic matter of the osseous tissue in a proper condition. The abundance of vessels carrying blood to all parts of the bone tissue, alone suffices to prove the existence of a nutritive movement in these apparently stony organs. THE BONES. CHAPTER 11. THE BONES OF MAMMALIA IN PARTICULAR. Article I. — Vertebral Column. The vertebral column, or spine, is a solid and flexible stalk situated in the middle and upper part of the trunk, of which it forms the essential portion. It protects the spinal cord and sustains the thorax, as well as the principal or2:ans of circu- lation, respiration, and digestion. Articulated anteriorly with the head, and terminating in a point at its posterior extremity, this stalk is formed by a some- what considerable assemblage of short, single, tuberous bones, to which has been given the name of vertehne. These bones, though all constructed on a uniform type, yet do not offer the same configuration throughout the whole spine. The differences they present in this respect have permitted their being divided into five principal groups ; whence the division of the vertebral column in five regions, which are, enumerating them from before to behind : 1. Cervical region. 2, Dorsal region. 3. Lumbar region. 4. Sacral region. 5. Coccygeal region. The first comprises seven vertebrse, which serve as a base for the animal's neck ; the second has eighteen, against which the ribs are placed ; the third has only six, which correspond to the loins ; in the fourth there are five, constantly fused into one mass in the adult, to constitute a single bone — the sacrum ; while the fifth possesses a variable number of small degenerate vertebrte, gradually decreasing in size to form the tail. The pieces constituting the first three regions are called true veiieircB ; those of the last two are designated /(v/se vertehrce. The subjoined table indicates the number of vertebrae in each of the regions of the spine, in the horse and other domestic Mammalia. Animals. Vertebra. Cervical. Dorsal. Lumbar. Sacral. COCCTGEAL. Horse Ox Sheep Goat Camel Pig Dog Cat Rabbit 7 7 7 7 7 7 7 7 7 18 13 13 13 12 14 13 13 12 6 or 5 6 6—7 6 7 6—7 7 7 7 5 5 4 4 4 4 3 3 4 15-18 16—20 16—24 11-12 15—18 21-23 16—21 21 16-18 The characters belonging to all these vertebrae will be first studied ; then a particular description of those of each region will be given ; and, finally, an examination will be made of the spine as a whole. Characters common to all the Vertebrae. Each of these small bones is pierced from before to behind by a wide opening — the spinal foramen., or vertebral canal ; whence results, for the entire spine, a long canal traversing its whole length, and which lodges a very important portion of the nervous centres— the spinal cord. This canal, which traverses the vertebrae VEBTEBB^. 25 from one end to the other, transforms it into a ring in which we recognize, for facility of description, two parts — the one inferior, the other superior. The first, or hotly, is very thick, and forms the base of the vertebras ; the second, which is thin, has been designated spinous or spinal — from one of the pecuUarities it presents, or annular — because it circumscribes the major portion of the spinal foramen. This division is not altogether an arbitrary one, for the body and the annular portion constitute, in the foetus, two distinct pieces, which do not become united for a long time after birth. Body {centrum). — The shape of the body of a vertebra is that of a prism Fig. 13. k B A. A i w. •{{ ELEMENTS OF A VERTEBRA. (AFTER OWEN.) A, Ideal typical vertebra ; B, Actual thoracic vertebra of a bird ; c, Centrum (or body), giving off, d, d, the diapophyses, and p,p, the parapophyses (transverse and articular processes) ; the neural arch, enclosing the spinal cord, is formed by n, n, the neurapophyses (lamince), saxd n, s, the neural spine {spinous process); the hamal arch, enclosing the great centres of the circulation, is formed by h, h, the haemapophyses (costal cartilages) ; and h, s, the haemal spine (sternum). From both the neurapophyses and haemapophyses may be given off the zygapo- physes, z, z. The lateral arches, which may enclose the vei'tebral arteries, o, o, are completed by the pleurapophyses (ribs), pi. ; these in B are bent downwai-ds, so as to form part of the hasmal arch, and give off the diverging appendages, a, a. with four faces, of which two only — the superior and inferior — are free, and can be studied in the adult ; the two lateral faces are united and confounded with the annular portion. This prism also presents two extremities — an anterior and posterior. Faces. — The superior face, limited in extent, forms part of the spinal foramen, constituting its floor. It exhibits : 1. On the middle line, two roughened, prominent surfaces, representing two triangles, whose summits are opposed. 2. On the sides, two depressed smooth surfaces, perforated by one or more openings that lead to the interior of the bone. The inferior face is divided into two lateral portions by a median crest (the htemal spine). Extremities. — The anterior has a prominent convex head, more or less detached. The posterior offers a cavity for the reception of the head of the next vertebra. These two planes — the one convex, the other concave — do not come into immediate contact ; an elastic, flexible fibro-cartila^e, firmly attached to each, is interposed between them. 26 THE BONES. Annulae Portion {neurcd arch or neuropophyses). — This is formed by an osseous plate that curves suddenly downwards, in the shape of an arch, the two extremities of which approach each other, enclose the body, and become united to it. It offers for study : 1. An internal and an external surface. 2. An anterior and &, posterior border. Surfaces. — The internal surface, concave and smooth, forms, with the superior face of the body, the spinal foramen. The external, convex and irregular, pre- sents : 1 . A single prominence, raised in the middle of the superior portion, and named the spinous process {neural spine). 2. The transverse processes (diapo- physes) are a double pair of eminences, one on each side, and projected trans- versely outwards. Borders. — The anterior border has two articular facets looking upwards : these are the anterior articular processes {prezygopophyses), right and left. In each is a notch which, when placed in opposition to a similar excavation in the preceding vertebra, forms the inter vertehrcd foramen. The posterior border pre- sents the same pecuUarities, with this difference, that the articular faces of the posterior articular processes {postzygopophyses) are inclined downwards, to corre- spond with the anterior facets of the succeeding vertebra.^ Structure of the vertebrce. —The compact substance, which is abundant in the spinous portion, forms in the body an extremely thin layer, inclosing a volumi- nous nucleus of spongy tissue. The latter is traversed by numerous venous canals, which open on the surface of the bone. Development. — It has been already shown that the body and spinous portion of a vertebra constitute, in yoimg animals, two distinct pieces. Each was primarily formed from two lateral centres, which met on the median line. In the body, the fusion of these centres is so prompt, that it is generally believed, perhaps justly, that the development of this part of the vertebra proceeds from a single centre of ossification. The union of the two centres in the annular portion, usually designated the vertebral lamince {parapophyses), is slower. It commences in the most anterior vertebrae, and is latest in the sacral and coccy- geal regions. To the three principal pieces of the vertebra in process of ossification, are added, at a subsequent period, complementary centres of ossifi- cation, variable in number according to the regions and species of animal ; there is always one for each of the anterior and posterior surfaces of the vertebral bodies ; while others, much less constant, concur to form the spinous and transverse processes. Characters proper to the Vertebrae of each Region. A casual inspection of a vertebra might suffice, strictly speaking, to dis- tinguish the region of the spine to which it belonged. For instance, a cervical vertebra is recognized by its volume, the absence of a spinous process, and the foramen which traverses the base of its transverse processes. The dorsal vertebra is conspicuous by its tubercular transverse processes, and by being furnished, outwardly, with an articular surface, as well as by the depressions on its body destined to receive the heads of the ribs. The lumbar vertebra has its long flattened transverse processes ; while the coccygeal vertebra offers rudi- (' Vertebrae which have centra concave at both ends, are designated amphicselous. Those distinguished by a concavity in front and a convexity behind, are known as procxlous ; but if the cavity is behind and tlie convexity before, they are then named opisthocxlous. A vertebra of the above description belongs therefore, to the opisthocaslous class.) VEBTEBRM 27 mentary laminae and processes. There is no necessity for noticing the sacrum, the five pieces of which form one bone— a feature that markedly distinguishes it from the other regions of the vertebral column. But these few distinctive characteristics do not satisfy the requirements of descriptive anatomy ; so that it is necessary to undertake a more extensive study of each of these regions. 1. Cekvical Vertebe^. General Characters. — These vertebrae, the longest and thickest in the spine, present generally a cubical form. They are usually distinguished from the vertebrae of the other regions by the following characters : The inferior spine of the body is strongly marked, especially behind, where it terminates in a small tubercle. The head is well detached from the remainder of the bone, and describes a very short curve. The posterior cavity, wide and deep, represents a veritable cotyloid de- pression, which is too large to fit the head exactly; the intermediate fibro-cartilage on these two sur- faces is also of a great thickness. The spinous process forms a simple roughened, and but slightly prominent, ridge. The transverse processes, very developed, are elongated in an antero-posterior direction, and inclined downwards. In this region they are designated the trachelian processes, be- ^ cervical vertebra. cause of their relations with the trachea ; a j^ Superior spinous process ; 2, an- f oramen that traverses them from before to terior articuiaj processes ; 3, pos- behind at their base has been, for the same f^tr ^^n^et fac^'^o^Tod^ f 'e!?; reason, named the trachelian foramen {^vertebral transverse processes, with their foramen). The articular processes, large and tubercles or rudimentary ribs ; 8, ' . , -TIT 1 J • J inferior crest, or spine : 9, concave promment, are mchned downwards and mwards. posterior face. The notches are wide and deep. Specific Characters. — The seven cervical vertebrae are reckoned from before to behind, and receive numerical names indicating their place in the region. First. — The first vertebra of the neck, which has been named the atlas,^ deserves a very careful description. At first sight there is recognized the great development of its transversal diameter, the considerable dimensions of the spinal foramen, and the thinness of its body. The intra-spinal face of the latter is divided into two portions by a transverse ridge : one anterior, furnished with hgamentous imprints, exhibits, laterally, two deep excavations, which lodge the venous sinuses ; the other, posterior, is smooth and concave from side to side, and forms an articular surface into which is received the odontoid process of the axis ; this surface takes the place of the cotyloid cavity. The inferior spine of the body appears as a large tubercle (Fig, 15, 6), The head is absent, and is replaced by two concave facets. The anterior articular processes have their gliding surfaces looking downwards ; they are joined to the two preceding facets to constitute two large diarthrodial cavities, which articulate with the occipital condyles (Fig, 15, 1), There is no spinous process, but a roughened surface instead. The transverse processes are large, flattened above and below, inclining forwards and downwards, and are provided with a thick rugged lip. Posteriorly, * Rudimentary ribs are sometimes attached by ligaments to the ends of the transverse processes (.Leshre). 28 THE BONES. Fig. 15. atlas; inferior sitrface. 1, Articular cavities for condyles of the occipital bone ; 2, articulai facet ; 3, vertebral or antero-internal fora- men ; 4, posterior, or cervical fora- men ; 5, transverse process or wing quite at their base, and on each side of the spinal foramen, they show two large vertical facets which represent the posterior articular processes ; these facets are uneven, are confounded with the articular cavity of the upper face of the body, and correspond to the two analogous facets of the axis. Each trans- verse process is pierced at its base by two foramina, which traverse it from below upwards. The posterior represents the vertebral foramen of the other vertebrae ; while the anterior is continued to the external surface of the process by a wide, deep, but very short channel, running from with- out to within, and joins a third foramen, which enters the spinal canal. These last two openings, with the demi-canal which unites them, replace the anterior notch ; the posterior is altogether absent. Lastly, an inflected venous canal, the position of which varies, and it is also sometimes tubercle representing the inferior absent, crosscs the lamiuffi of the atlas, and opens, spinous process; 7, superior arch, qjj Qjjg ^[^q^ j^to the Spinal caual, and on the forming the roof of the spinal fora- , , ^t ^^ ^ mi- ^i ^gn ^ other, beneath the transverse process, ihe atlas contains much compact tissue, and is generally developed from six centres of ossification : two for the body, which at an early period becomes a solid piece, and two for the annular part ; the other two are complementary centres, each of which forms one of the two posterior undulated facets and lip of the corresponding transverse process. Second. — This is named the axis, or dentata (Fig. 16). It is the longest of all the cervical vertebrae ; those which succeed it gradually diminish in length and in thickness. The body of the axis has no increase anteriorly, but a conical process termed the odontoid, which is flattened above and below, concave and rough from one side to the other on its superior face ; convex in the same direc- tion and perfectly smooth on its inferior face. The latter represents an articular half-hinge, around which glides the con- cave articular surface on the superior face of the body of the atlas. The anterior articular processes are carried to the base and to each side of the odontoidian pivot, in the shape of two undulated facets, which are confounded with the gliding surface of the latter, the destination of which has been already noted. The spinous process, very large and elongated antero-posteriorly, is divided behind into two roughened lips. The transverse processes are slightly developed, and terminate posteriorly in a single tubercle, directed backwards. The anterior notches are very deep, and are most frequently converted into foramina. This vertebra, although voluminous, is light, in consequence of its containing much spongy substance. In the young animal, the odontoid process and the articular surfaces on each side, constitute Fig. 16. THE AXIS, OR dentata; LATERAL VIEW. 1, Superior spinous process ; 2, odontoid pro- cess; 3, intervertebral foramen, or hole of conjugation; 4, body; 5, inferior spinous process ; 6, 7, inferior and superior articu- lating processes. VERTEBRM 29 two centres, distinct from each other and from the body of the vertebra. After the axis, the cervical vertebrae diminish in length and increase in thickness ; while the obliquity of their articular processes becomes more pronounced the more distant they are from that vertebra. Third, fourth, and fifth.— Each, of these has, at its transverse processes, two prolongations — one anterior, the other posterior. The inferior face of their bodies AXIS AND SIXTH CKRVICAL OF THE HORSE AND ASS. A. Axis of the Horse. 1, spinous process ; 2, transverse process ; 3, odontoid process ; 4, lateral articular facet. B. Axis of the Ass. Same numbers and same signification. a', Sixth cervical vertebra of the Horse. 1, Articular head ; 2, posterior articular process ; 3. articular cavitv ; 4, posterior prolongation of the transverse process : 5, anterior ditto. b', Sixth cervical vertebra of the Ass. Same numbers and same signification. exhibits a median spine terminated posteriorly by a tubercle, which gradually increases in volimie from the third to the fifth vertebra. The third presents, between its anterior and posterior articular processes, an almost complete gap ; if its anterior extremity be placed on a horizontal plane, it will touch that plane by its articular and transverse processes and its head. 30 TEE BONES. In the fourth, the articular processes are united by a thin, sharp osseous plate, notched only in front. Laid on a horizontal plane, the head remains some distance from that plane. The fifth is recognized by the continuous, thick, and rugged lamina which unites the articular processes, and by the tubercle of the inferior spine on the body, which is in shape like the heart on a playing-card. Sixth.— T\n& is distinguished by the slight prominence of the spinous process, but particularly by the almost total disappearance of the inferior spine, and the presence of a third prolongation, very strong and inchning downwards at its transverse process — a circumstance to which this vertebra owes its designation of tricuspid. Seventh. — This has received the name of prominens, because its spinous pro- cess, terminating in a point, is more distinct than in the preceding vertebrae, the axis excepted. It exhibits, besides : deep imprints, which replace the inferior spine ; a concave demi-facet on each side of the posterior cavity of the articulation, of the head of the first rib ; a particular disposition of its transverse processes, which are unituberculous ; the complete absence of the vertebral foramen ; and, lastly, the depth and width of its notches. The spinal foramen, which has already assumed a somewhat considerable diameter in the sixth cervical vertebra, is still larger in the seventh. Ass. — The cervical vertebra3 in this animal much resemble those in the Horse. Studying them more closely, however, it is possible to discover certain differences which distinguish them from those of the other Equidfe. Thus, the rugosities on the arch of the atlas are much less marked than in the Horse, and form a kind of thick depressed tubercle. The vertebral foramen is very large in proportion to the size of the vertebra, and the canal uniting the two portions of the anterior foramen of the transverse process is deep and protected by a well-defined rim. The axis has a less elevated spinous process than that of the Horse ; its upper border, nearly parallel with the transverse process, is more deeply divided into two lips, and the summit of its transverse process extends, backwards to the articular process, while in the Horse it does not go beyond the origin of the latter. In the third, the lamina uniting the two prolongations or points of the transverse processes, is notched behind the anterior prolongation, instead of being notchless as in the Horse. In the fourth Siud fifth this notch is still more marke4. In every instance the anterior prolongation of the transverse process is always more detached and better circumscribed in the Ass than in the Horse. The same remark applies to the tricuspid ; the posterior prolongation is also better detached, and the middle prolongation extends nearly to the articular cavity of the vertebra — a prolongation which, in the Horse, does not exceed one- half the length of the posterior one. The seventh differs little from that of the Horse ; nevertheless, the uni-tubercular transverse process has, in front, a small sharp projection which resembles somewhat the anterior prolongation of the bicuspid processes. In the Mule and Hinny, the cervical vertebrae hold the middle place between those of the Ass and the Horse. Differential Characters of the Cervical Vertebra in the other Domesticated Animals. A. Ox, Sheep, and Goat. — The cervical vertebrae of these animals differ from those of Solipeds by their shortness, and the greater development of their insertion eminences. In the Sheep and Goat they are relatively longer than in the Ox. The transverse processes of the VERTEBRA. 31 atlas are less inclined than in the Horse, and have no vertebral foramina ; the posterior facets for articulation with the axis, are nearly flat and join each other. The axis has a semi-cylindri- cal, not a conical, odontoid process, which is so concave on its upper t^urface that it looks like a groove. Its spinous process is not so thick as in the Horse, and is not bitid posteriorly. In the Jive succeeding vertebras, a rugged continuous lamina unites the anterior articular processes to the posterior. The spinous process inclines forward, and is flattened transversely at its summit, which is sometimes bifid ; it progressively increases in height from the third to the fifth vertebra. In the sixth, the transverse processes have only two prolongations — a superior and inferior; the latter, large and flattened on both sides, is bent abruptly downwards. The spinous process has already attained the height of 1| to 2 inches in this vertebra, and is flattened laterally. The seventh well deserves the name of prominens, its spinous process being no less than from 4 to 4f inches (see Figs. 6 and 7). B. Camel.— In the Camel, the cervical vertebrae are longer and thinner than in the other large domestic animals. Altogether, they form oue-third of the total length of the spine. Their vertebral lamiiise are deeply notched before and behind, which allows them to easily enter tlie spinal canal. Their articular processes are convex, and from the second to the sixth inclusively, the vertebral foramen is small and deeply placed in the laminae. The atlas is distinguished from that of the Horse and Ox by the absence of the tubercle on the inferior face of the body, and the shortness of the transverse processes, of which the border is thin and sharp. The vertebral foramen makes a somewhat long course in the transverse process of this vertebra, and opens at the bottom of the excavation in which the anterior inter- vertebral foramina meet — the latter being double. The axis is very long and constricted in its middle ; the inferior crest is only slightly salient ; there are ilouble invertebral foramina, the largest of which is divided by a bony septum ; the odontoid process is as in the Ox. The other cervical vertebrae gradually diminish in size and increase in thickness from before to behind. In the third, fourth, and fifth, the transverse processes are bi-tuberculated. In the sixth, the transverse process is a wide and thick plate, inclining downwards. The seventh is recognized by its long spinous process and the smallness of its transverse process, which has a larger and more obvious vertebral foramen than the other vertebras (see Fig. 8). C. Pig. — Of all the domesticated animals, this has the shortest, the widest, the most tuberous, and consequently tlie strongett cervical vertebrae. The body of these bones has no crest on the inferior face ; the head, but little detached, is scarcely round, and looks as if driven back on itself; consequently, tiie posterior cavity is not deep. The vertebral laminae are very narrow, and scarcely extend from one part of the vertebra to the other in the superior portion, so that the spinal canal appears at this point to be incomplete. In the atlas, the transverse processes are less inclined than in Ruminants ; the vertebral foramen is not constant, and when it exists, opens on one side, under the transverse process, and on the other, on its posterior margin, after pursuing a certain tiack in the substance of the bone. The odontoid process of the axis is constricted at its base. This verte*bra is distinguished by its high and thin spinous process inclining slightly back, by its transverse processes being but slightly prominent, and perforated by an enormous vertebral foramen. In the four succeeding vertebrae, the spinous process terminates in a blunt point, and inclines forward ; slightly salient in the first, it gradually rises in the others. The transverse processes form two prolongations : one, the superior, is tuberous, and is joined to the anterior articular process by a plate of bone, which is pierced by a foramen ; the other, the inferior, flattened on both sides, bent downwards, and large, as it belongs to a posterior vertebra, transforms the inferior face of these vertebral bodies into a large groove. The seventh has a spinous process as long as those of the dorsal region. A peiforated bony plate, as in the preceding vertebrae, unites the anterior articular process to the single tubercle composing the transverse process; the latter is continued back nearly to the posterior notch by a second plate, also perforated with a foramen (see Fig. 3). D. Dog and Cat. — In these animals, the cervical vertebrae are long and thick, and much resemble those of Solipeils. Nevertheless, besides their smaller volume, they are distinguished : 1. By the disposition of their corresponding articular surfaces ; the anteiior, or head, is nearly flat, and is even slightly excavated in its centre ; the posterior, or cavity, is l.ut little hollowed to receive the head of the next vertebra; 2. By the width of the vertebral laminae, which overlap one another; 3. By the height of their spinous processes, which increases as the vertebrae extend back ; 4. By the great extent of the anterior and posterior articular processes, 32 THE BONES. which are united by means of a continuous and very salient bony plate, that considerably augments the transversal diameter of each vertebra. In the atlas, the articular surface for the odontoid pivot is confounded in front with the cavities which correspond to the occipital condyles. The two facets which are annexed posteriorly to this articular surface, instead of being plane or gently undulated, as in the other domesticated animals, are transformed into real glenoid cavities. The triinsverse pro- cesses are carried directly outwards and a little backvvanl ; the lip wljicli borders eacli is slightly raised ; of the two foramina wiiich replace the anterior notch, one only exists, and this penetrates to the interior of the spinal canal ; the other is merely a simple notch. In the axis, the odontoid process is cylindrical, narrow at its base, and bent a little upwards ; the lateral facets of this eminence represents true condyles. The spinous process is very thin and undivided, and is curved forward above the laminae of the atlas. The anterior notches are never converted into foramina. The third cervical vertebra is the largest : and the succeeding ones gradually diminish in thickness to the last, contrary to what occurs in the other species. The seventh does not show the spinous process so developed as in Ruminants and Pachyderms (see Figs. 3, 4, 7). E. Rabbit. — The cervical vertebrae in this animal somewhat resemble those in the Cat, though they differ in certain general and particular characters. Thus, in the Rabbit they become larger as they proceed backward ; the atlas has its transverse processes horizontal, and they are narrow at their oriain ; the axis has a bifid tubercle at the posterior extremity of its spinous process, and a notch below it ; the succeeding vertebrae are thin ; the fourth, fifth, and sixth are trifid in their transverse processes ; and the seventh has a short spinous process. 2. DoESAL Vertebe^ (Fig. 18). Geneeal Chaeacters. — In the dorsal vertebrae the body is very short, and in front has a large slightly projecting head ; behind, it has a shallow cavity. Laterally, these vertebrae present, at the base of the transverse processes, four concave articular Jacets, the two anterior of which are situated near the head, while the posterior two are hollowed out of the border of the articular cavity of the body. Each of these facets is joined to an analogous facet on the neighbouring vertebra to form a small excavation, into which is received the head (or capitulum) of the corresponding rib. The spijious process is very high, is compressed on both sides, inclines backwards, and its summit is terminated by a tubercle. The transverse processes are unitubercular, and directed obliquely outwards and upwards ; on their external aspect they have a diarthrodial plane facet which corre- sponds to the tuberosity (or tuberculum) of the rib (and may therefore be named the tubercular transverse process). The articular processes are narrow, and constitute simple unrelieved facets cut on the base of the spinous process. The posterior notches are deep, and sometimes con- verted into foramina. Specific Charactees. — None of the eigh- teen dorsal vertebrae differ much from the type just described ; and it is difficult to establish special characters for each. It is, nevertheless possible to assign to a dorsal vertebra, approximately, the rank it should occupy, in accepting the following facts as a guide : 1. The vertical diameter of the ttpe op a dorsal vertebra (the fourth). 1, Body, 2, 2, articular facets for the head of the rib; 3, articular facet for tuberosity of the rib; 4, articular processes ; 5, spinal foramen ; 6, tuberous base of spinous process; 7, posterior articular face of body ; 8, 8, transverse processes ; 9, superior spinous process ; 10, an- terior articulation of body. TEE VERTEBRA. vertebral bodies augments progressively from before to behind. Their lateral diameter, which determines that of the spinal canal, becomes, on the contrary, less from the first to the tenth vertebra ; after which it assumes increasing proportions to the last one. The articular surfaces, which serve for the mutual contact of head and cavity, become larger and shallower in proportion as the vertebrae are more posterior. The inferior spine on the body is very salient and tuberculated in the two first vertebrae, very acute in the third and fourth ; it disappears in the sixth and ninth, to reappear and become more marked from the tenth to the last. 2. The intervertehral cavities, intended for the reception "of the heads of the ribs, diminish in depth and extent from the first to the last. 3. The longest spi^ious pro- cess belongs to the third, fourth, and fifth vertebra ; those which follow gradually decrease to the eighteenth. Their width diminishes from the second to the eighth : it afterwards increases in a progressive manner in the succeeding vertebrfe ; from the second to the tenth vertebra, the summit of the spinous process is large and tuberculated ; in the last seven it is flattened laterally. Their obliquity is less marked as they pro- ceed backwards ; in the sixteenth and seventeenth vertebrae, the spinous process is nearly vertical ; it inclines slightly forward in the eighteenth. Those of the tenth, eleventh, and twelfth vertebrae are slightly curved like an S. 4. The articular processes, from the first to the tenth vertebra, gradually contract and approach the median line ; in the succeeding vertebrae they, on the contrary, increase, and become concave and wider apart from those of the oppo- site side. 5. The volume of the transverse processes and the size of their diarthrodial facets, diminish from before to behind. In the three first vertebrte this facet is concave ; in the first nine the articular facet looks outwards and backwards, while the facet on the body looks forwards ; in the last the two facets are directed forwards. These two facets are generally confounded in the seventeenth and eighteenth vertebrae. The first dorsal vertebra much resembles the prominens ; it is distinguished from it, however, by the presence of four MIDDLE DORSAL VERTEBRA OF THE HORSE, VIEWED FROM THREE TYPICAL LINES. The first line, A B, passes from before to behind by the most salient point of the transverse process, intersecting the middle of the lateral facet in- tended for the tuberosity of the rib, and of the cavity on the border of the posterior articular surface of the body. Below is the intervertebral foramen, the spinous process, and the articular facets on the base of the latter. The line c D is tangent to the summit of the transverse pro- cess and head of the vertebra ; it intersects the anterior articular processes. The line M N is horizontal, and tangent to the inferior face of the body. 9i TEE BONES. diarthrodial facets on its extremities. It also differs from the other vertebrae by the shortness of its spinous process, which terminates in a point ; by the size and prominence ,of its articular processes ; and by the depth of its notches. The last vertebra never has facets on the contour of its posterior cavity. Ass. — Besides the smaller volume of the vertebrse, the following differential characters will serve to distinguish these bones in this animal : 1. The spinous processes, as far as the tenth vertebra, are a little more inclined backwards than Fig. 20. A DORSAL VERTEBRA OF THE HORSE AND ASS (THE ELEVENTH). A, Vertebra of the Horse {anterior face). 1, Head ; 2, spinous process ; 3, 3, transverse processes. B, Vertebra of the Ass (anterior face). Same description as for the horse. a', Vertebra of the Horse (lateral face). 1, Head ; 2, spinous process ; 3, transverse process. b', Vertebra of the Ass (lateral face). Same description as for the horse. in the Horse, while the inclination forward of the latter is equally marked ; the anterior part of the summit of the spinous process is in contact with a horizontal plane, when the three last vertebrae of the Ass are laid on their anterior portion. 2. From the first to the tenth, the summit of the transverse processes lies behind the margin of the anterior articular facets in the Ass, while it is beyond them from the fourth in the Horse. From the eleventh to the thirteenth, the projection of the transverse processes is equal to that of the anterior articular facets in the THE VERTEBRA. 35 two species ; then the processes become predominant in the Ass (Fig. 20, A', B', 3, 3), and they preserve this character to the eighteenth. 3. All the transverse processes are" less oblique than those in the Horse ; also the line which intersects, in the middle, the summit of these processes and their lateral articular facet, passes always in front of the posterior facet on the body ; in the Horse, this line traverses the latter facet, except in the first and fifth vertebra (Fig. 20, A. B). 4. There are not seen on the nine last dorsal vertebrse of the Ass, the anterior articular facets ascending to the base of the spinous process, as usually occurs in the Horse. 5. Lastly, the notches of the intervertebral foramina are nearly always closed by a bony bridge in the Ass, and only rarely so in the Horse. The dorsal vertebrae in the Mule and Hinny off"er the same mixture of particular characters which are found in their parents ; though it is not doubtful that the vertebr^ of the Mule (Hinny) produced by the union of the female Ass -with the Stallion Horse, more resemble the former than the latter, especially in the transverse processes. Differential Characters in the Dorsal Vertebrae of other Animals. A. Ox.— In the Ox, these thirteen bones are longer and thicker than in the Horse. Their flpinous processes are larger and incline more backward ; their transverse processes are very- voluminous, and are provided with a convex facet from above to below ; while their posterior notclies are nearly always converted into foramina. Considered individually, they are more slender in the middle than at the extremities. Their spinous processes diminish in width, especially at their summits, from the first to the eleventh vertebra, and widen again in the two last ; they progressively increase in slope to the tenth, after which they become more and more upright; tlie first four are the longest, and are nearly the same in height ; the others gradually decrease. In the first four or five vertebrae, the articular facet of the transverse processes, while retaining its vertical convexity, is concave in an antero-posterior direction. This facet is always absent in the last vertebra, and sometimes even in the preceding one. The two bones terminating the dorsal region show, in addition, the articular processes disposed like those of "the lumbar vertebrae. B. Sheep and Goat.— The thirteen dorsal vertebrae of the Sheep and Goat are relatively less strong than those of the Ox; their spinous processes are not so wide, and their posterior notches are never converted into foramina. C. Camel.— The dorsal vertebrae of the Camel, twelve in number, are remarkable for the length of their bodies, and the height and width of their spinous processes. The transverse processes are a little less detached than in the Ox, but they are very tuberous. The posterior notclies are narrow, deep, and close to the base of the spinous processes; they do not form foramina. The convexity or concavity of the articular surfaces of the body diminishes from the first to the last bone; while the spinous processes increase in length and width from the first to the sixth, and diminish in the last six. These processes are much inclined from the third to the ninth ; then they gradually become erect in the last three. D. Pig.— The Pig has fourteen dorsal vertebrae, which, in their general disposition, are not unlike those of the Ox. As with that animal, the intervertebral foramina are double, each -vertebral lamina being perforated laterally by an opening situated in front of the posterior notch. In addition, the vertebrae of the Pig present this peculiarity, that their transverse processes are generally traversed at the base by a single or multiple foramen, which communicates with the preceding. With regard to the special characters proper to some of the vertebrae, these are, as with the other animals, very few, and may be described as follows: I. The transverse processes of the four vertebrae preceding the last project but slightly. 2. In the fourteenth this process resembles those of the lumbar vertebrae. 3. The articular facet of the transverse process in the four last vertebrae is confounded with the anterior lateral facet corresponding to the head of the rib. 4. The articular processes of the last five vertebrae are arranged like those of the lumbar vertebrae ; and the prominence formed by the tubercle on the outside of the anterior articular process replaces, to a certain degree, the transverse process of these vertebrae. E. Dog and Cat.— These animals have thirteen dorsal vertebrae formed on the same model 36 TEE BONES. as those of the Horse ; but their spinous processes are in general narrower and thicker. The tenth always has its spiuouss process vertical, triangular, and terminated in a sharp point. The last three liave no posterior facets tor tJie articulation of tlie heads of the ribs, and exhibit, in the conformation of their articular processes, the same disposition as the lumbar vertebrae. In the Cat, the transverse processes of the three last dorsal vertebrae are thin, sharp, and turned backwards ; they never possess facets for the tuberosity of the ribs. F. Rabbit. — The twelve dorsal vertebrae of this animal are similar to those of the Cat. But the spinous process of the first nine is thinner and more oblique, while that of the three last is higher and thinner than in the Cat. Besides, the transverse process is continued, in the Rabbit, by a triangular portion which increases the width of the vertebral lamina. The inferior face of the body is more hollowed in its middle portion, and the inferior crest is more salient than in the Cat. 3. Lumbar Vertebra (Figs. 21, 22). General Characters. — A little longer and wider than the dorsal vertebrae, which they resemble in the arrangement of their bodies, these vertebrae are characterized : 1. By their short, thin, and wide spinous processes, which are slightly inclined forwards, and are provided at their summits with a scabrous tubercle. 2. By their largely developed trans- ^'S- 21- verse processes, flattened above and below, and directed horizontally outwards.^ 3. By the salient an- terior articular pit'ocesses, hollowed out on each side, and provided ex- ternally with a tubercle for inser- tion. 4. By their equally prominent posterior articular processes, rounded in the form of a half -hinge. Specific Characters. — The LUMBAR VERTEBRA (FRONT VIEW). charactcristics which may serve to 1. Body ; 2, its articular face ; 3, superior spinous distinguish these Vertebrae from process ; 4, spinal foramen ; 5, anterior articular Qjjg another, are derived from the processes ; 6, 6, tran>verse, or costiform processes ; , t , , . -, , 7, posterior articular process. oody, and the spmous and trans- verse processes. 1. From the first to the last there is a progressive diminution in the vertical diameter of the bodies, and an increase in their transverse diameter. The inferior spine on the body becomes shorter and wider from the first to the last vertebra ; in the six vertebrae it resembles an elongated triangle, the summit of which is directed forwards. 2. The spinous processes decrease in width from before to behind, and their anterior border becomes more and more concave ; their summits are thickened and tuberculated in the three first, and thin and sloping forward in the three last. 3. The transverse processes are longer in the middle vertebrae than in those placed before and behind. The processes in the first and second vertebrae incline slightly backward ; in the third they are more upright ; and in the succeeding ones they are directed a little forward. In the last two they are remarkable for their thick- ness ; in the fifth an oval-shaped articular facet is observed on their posterior ])order ; in the sixth, two are present — one in front, corresponding to the pre- ceding, and one behind, slightly concave, meeting a similar facet on the sacrmn. The fourth and fifth vertebrae very often correspond, at their transverse processes, by means of analogous facets. ' Rudimentary ribs are sometimes found attached by ligaments to the extremities of the transverse processes (Lesbre). THE VERTEBR^\ 37 Fig. 22. According to Sanson, five is the natural number of lumbar vertebrae in the specific type of African Horses (see remarks on the Spine in General). The transverse processes in these animals also offer some peculiarities. Thus the increase in their length ceases at the second, and from this an almost insensible diminution occurs to the fifth. The transverse processes of the first lumbar ver- tebra are alone less inclined backward ; they are perpendicular to the direction of the body in the second and third, and inclined forward in the fourth and fifth. The thoroughbred English Horse has sometimes five, sometimes six lumbar vertebrae, but in every instance the lumbar region is comparatively short (Cornevin). Ass. — The lumbar vertebrae in the Ass, five in number, are easily distin- guished from those of the Horse by the characters special to their spinous and transverse processes, and articular tubercles. 1. The spinous processes are propor- tionately longer that those of the Horse, and they are also more inclined forward. If their bodies rest on a horizontal plane, and if a line be drawn tangent to the posterior border of the spinous process, an acute angle is always obtained at the point of junction of the line and plane ; but if this be done with the vertebras of the Horse, there is at least a right angle. 2. The transverse processes increase in length from the first to the second ; they are nearly equal in the second and third, and decrease suddenly in the ffth. They are usually inclined downwards ; their posterior border and superior face, near the body, are marked by a vasculo-nervous furrow, which is scarcely visible in the Horse. Finally, it is not rare to find no inter-transverse articulation between the two last. 3. The most important differential character is observed in the articular tubercules. The diarthrodial facets are surmounted by a flat tongue of bone, which is projected outwards in the direction of the summit (see Fig. 23, A, B, 4, 4). This piece gradually becomes lower from theirs;* to the fifth vertebra ; in the first, it projects beyond the articulation by more than one-fourth of an inch, and, up to a certain point, resembles the condition observed in the Rabbit or Dog. In the Mule there are sometimes six, sometimes only five, lumbar vertebras. These have the spinous and transverse processes somewhat as in the Horse ; their articular tubercles resemble those of the Ass. In the Hinny, of which opportunity has rarely been had for study, Goubaux and ourselves have found five lumbar vertebrae, which, in their shape, much resembled those of the Ass. UPPER SURFACE OF LUMBAR VERTEBRAE. , SuQimit of spinous process ; 2, 2, anterior articular jirocesses ; 3, 3, posterior articu- lar processes ; 4, 4, transverse processes. Differential Characters in the Lumbar VERTEBRiE of other Animals. A. Ox, Sheep, and Goat. — The six lumbar vertebrae of the Ox are longer and thicker than those of the Horse. The transverse processes are also generally more developed, are 38 THE BONES. coDcave on the anterior border, convex on the posterior, and incline slightly downward, with the exception of the two first, which remain nearly horizontal. They increase in length from the/r«< to the fourth vertebra ; in the latter and the fifth, they are nearly of the same dimensions ; in the last they suddenly become shorter. Their width gradually decreases from before to beliind. In the fifth and sixth vertebrae, these processes have no articular facets between them and the sacrum, these being only met with in Solipedd. The articular processes are prominent, and further removed from the median line as they belong to posterior vertebrae. « Fig. 23. A LUMBAR VERTEBRA OF THE HORSE AND ASS. A, Lumbar vertebra of the Horse {anterior face). 1, Head ; 2, 2, transverse processes ; 3. spinous process ; 4, 4, articular tubercles. B, Lumbar vertebra of the Ass {anterior face). Same description as for the horse. In the Goat the transverse processes are more inclined downwards. In the Sheep, on the contrary, the processes of the six or seven vertebrae ascend towards their extremities. B. Camel. — Apart from number, which is seven, the lumbar vertebrae of this animal offer nearly the same features as those of the Ox. C. Pig.— The lumbar vertebrae of the Pig greatly resemble those of ruminant animals. It commonly happ( ns that seven are met with ; but in this case the supplementary vertebra is generally a sacral one. It is not denied, however, that seven lumbar vertebrae may exist in the Pig, along with the normal number of sacral vertebrae. D. Dog and Cat.— In the Dog and Cat, the lumbar vertebrae, seven in number, are remarkable for their strength, due to their length, thickness, and the development of the eminences for insertion. The spinous process is low, and becomes acute in the last vertebra. TEE VERTEBRA. 39 The transverse processes incline very much forward and downward ; they become longer from the first to the second-last bone ; in the latter they become contracted, and in the seventh vertebra they are still more diminislied, and terminate in au obtuse point. The tubercle of the anterior articular process is extremely prominent, and the posterior notches are surmounted bv a small, very acute prolongation, directed backwards, which becomes more developed towards the anterior vertebrae. This small prolongation exactly represents the transverse process of the dorsal vertebrae. E. Rabbit.— They are stronger than those of the Cat, and the first three have on the lower surface of their bodies a very salient crest, which simulates a real inferior spine ; the others have a median crest which gradually decreases towards the last bone. The tubercle surmount- Fig. 24. LUMBAR VERTEBRA OF THE CAT AND RABBIT. A, Second, third, and fourth lumbar vertebrcB of the Cat (inferior face}. 1, 1, 1, TraDsverse processes ; 2, 2, 2, crest on the inferior face of the body; 3, articular tubercles of the first vertebra. B, Second, third, and fourth lumbar vertebra of the Babbit (inferior face}. 1, 2, Same signification as in preceding. C, Third lumbar vertebra of the Cat (lateral face}. prolongation; 2, ditto posterior prolongation; 3, 4, 4, posterior ditto; 5, spinous process. D, Third hcmbar vertebra of the Babbit (lateral face}. prolongation ; 2, ditto posterior prolongation ; 1, Transverse process, anterior I, anterior articular tubercles; 1, Transverse process, anterior , anterior articular tubercle : 4, 4, posterior articular tubercles : 5, spinous process. ing the posterior notches is more developed than in the Cat. The spinous process is prolonged backward by a translucent bony plate, wliich disappears in the last two. The anterior articular tubercles are more developed, more erect, and nearer the median line, than in the Caruivora. Lastly, the transverse processes are relatively longer, and those of the first are remarkable for the notched enlargement they offer at their free extremities. 4. Sacrum (Fig. 25). The sacrum results, as already stated, from the consolidation of five vertebrse. This single bone articulates, in front, with the last lumbar vertebra ; behind, with the first coccygeal bone, and on the sides with the ossa innominata. It is triangular, flattened above and below, and from before to behind describes a slight curve upwards. It offers for study a superior and an inferior face, two borders, a base, a summit, and a central canal — the extension of the spinal canal. Faces. — The superior face presents, on its middle, the spinous processes of the THE BONES. sacral vertebrae, which together constitute what is called the sacral or supersacral spine. These processes are united at their base only, and remain isolated for the remainder of their extent ; they all incline backwards and terminate, with the exception of the first, by a tuberous summit, which is often bifid ; their length diminishes from the second to the fifth bone. On each side of the sacral spine exists a groove, at the bottom of which are four openings — the super-sacral Jara- raina. These orifices open into the spinal canal, and communicate with four analogous, but wider apertures, pierced at the inferior face of the bone, and for this reason named the sub-sacral Fig- 25. foramina. The inferior face is smooth, and shows traces of the N^L ,m^''''. J^S&^fi^^^^ '''•■' primitive separation of the vertebral ^^■-^'"^^^P^^^^^^^i^mS^ V bodies ; the sub-sacral foramina, ~ ' ' ^ which represent, with the corre- sponding super-sacral openings, the intervertebral foramina of the other regions of the spine, are observed on this surface. Borders. — The hvo borders, thick and concave, form, posteriorly, a rugged lip ; in front, they present an irregular surface inclining ob- liquely from above to below, from within outwards, and from before to behind. This surface, which is intended for the articulation of the sacrum with the ossa innominata, is divided into two parts : one, the inferior — named in Man the auricular facet — is slightly undulated and diarthrodial ; the other, the superior, serves for ligamentous insertions. Base. — This offers : 1. On the median line, the anterior orifice of the sacral canal, and the anterior articular surface of the body of the first sacral vertebra, which is oval and slightly convex. 2. On the borders, the articular processes and anterior notches of this vertebra, as well as the elliptical and somewhat convex facets which bring it into contact with the transverse processes of the last lumbar vertebra. Siimmit. — The summit, thrown back, presents : 1. The posterior orifice of the sacral canal. 2. The posterior articular surface of the body of the last sacral vertebra. 3. The vestiges of the articular processes and posterior notches of that vertebra. Sacral canal. — This is the portion of the spinal canal which is channeled out of the sacrum ; it is triangular, and diminishes in width from before to behind. The sacrum of the Ass much resembles that of the Horse ; nevertheless, it is possible to distinguish it by the shape of the articular tubercles of the first sacral vertebrae, which resemble those of the articular tubercles of the lumbar region, and the traces those tubercles have left between the sacral vertebra3, especially between the first. LATERAL VIEW OF SACRUM. 1, Articular surface of body ; 2, 3, articular surfaces corresponding to those on the transverse processes of the last lumbar vertebra; 4, spinal foramen; 5, auricular facet; 6, anterior articular processes; 7, inferior or sub-sacral foramina ; 8, superior spinous processes ; 9, summit or coccygeal ex- tremity. Differential Characters in the Sacral Vertebra op other Animals. A. Ox. — The sacrum of the Ox is more voluminous and curved than that of the Horse The spinous processes are entirely consolidated, and are surmounted by a thick rugged lip ; THE VERTEBRAE. 41 they are bordered at their base and on each side by a ridge that represents the rudiments of the articular processes. The lateral borders are sharp and bent downwards. The surfaces that serve to unite the sacrum to the ossa innominata have a somewhat vertical direction. There are no lateral facets on the base of the bone, for the union of the sacrum with the transverse processes of the last lumbar vertebra. B. Sheep and Goat. — In the Sheep and Goat, the sacrum is shorter ; sometimes the con- solidation of the spinous processes is late, or never occurs. C. Camel. — Sacrum short ancl composed of four vertebrae; broad and curved on its inferior face. The spinous processes, rather low, are strong and free throughout their extent. The auricular facets are cut very obliquely. D. Pig. — This is formed by four vertebrae, which are a long time in becoming fused together ; and it is often difficult to discover where the sacrum ends and the coccyx begins.' The spinous processes are entirely absent. The vertebral laminae are not consolidated ; so that the spinal canal is half cut through in its upper portion, as in the cervical region ; this canal is also much compressed above and below. E. Dog and Cat. — The three vertebrae which form the sacrum of Carnivora are early con- solidated. The sacral spine constitutes a thin sharp ridge, while the lateral surfaces for articulation with the ossa innominata are turned quite outwards, and are nearly vertical. F. Rabbit. — Relatively longer than tliat of Carnivora, the sacrum of this animal is remark- able for the presence of four vertebrae, the spinous processes of which are isolated from each other. 5. Coccygeal Vertebe^. The coccygeal region, or coccyx, comprises from fifteen to eighteen degenerate vertebrae, which gradually diminish in thickness from the first to the last. In the first three or four, nearly all the characteristics of true vertebrae are found ; they show a vertebral foramen, a body, a spinous process, and transverse processes, directed backwards ; the articular processes only are altogether absent. In the succeeding vertebrae, these characters become effaced ; the vertebral laminte do not join completely, and the vertebral canal is only a simple groove, which, gradually decreasing in depth, at last entirely disappears. The insertion eminences also become less salient, and the coccygeal vertebrae are soon reduced to small bony cylinders, narrow in the middle and wider at both extremities, with a convex articular surface at each end (except the last, which has only one articular surface). These small cylinders — the last traces of the vertebral bodies — are each developed from three centres of ossification ; they are very spongy and light. The first coccygeal vertebra is frequently consolidated with the sacrum in aged animals. Differential Characters of the Coccygeal Bones in other Animals. A. Ox, Sheep, and Goat. — In proportion, the coccygeal vertebrae of ruminants are stronger and more tuberous than those of the Horse. The anterior articular processes exist in a rudi- mentary condition. B. Camel. — Fifteen to eighteen in number, they are not so strong and are less tuberous than in the Ox. The first six are channeled by a triangular canal. C. Pig. — These vertebrae in tlie Pig are more particularly distinguished by the presence of articular processes, by means of which the foremost bones correspond with each other. D. Dog and Cat. — In these animals, the vertebrae of the coccyx are very strong and tuberous. The first five or six are as perfect as the true vertebrae, and comport themselves in every respect like them. The last are small V-shaped bones, which M. Goubaux has described by the name of hypMoid bones. E. Rabbit. — The coccyx of the Rabbit is analogous to that of the Cat. ' This can always be made out, however, by consulting the disposition of the articular pro- cesses. Thus, in the sacral vertebrae these eminences — if we except the anterior ones of the first and the posterior of the last — never exist except in a rudimentary state ; while in the other five coccygeal vertebrae they reappear with all their characters. 12 THE BONES. The Spine in General. The vertebral column has now to be considered in its entirety, and examined successively in its superior face, its inferior face, its lateral faces, and its spinal canal. Afterwards its direction and mobility will be noticed. Superior surface. — This presents, on its median line, the series of spinous pro- cesses. But little salient in the cervical region, these eminences are much developed in the dorsal and lumbar, where they constitute a long crest — the dorso-Iumbar spine, as well as in the sacrum, where they form the sacral spine. They soon disappear in the coccygeal vertebrae. Outwards, and on each side of these processes, is seen a succession of tubercles for insertion, represented iu the cervical and lumbar vertebrae by articular processes, and in the dorsal vertebrae by the superior or rugose portion of the transverse processes. These tubercles are disposed in line, and separated from the spinous processes by a channel designated the vertebral groove, which is more or less deep and wide. It is on these, and on the spinous processes, that the extensor muscular fascicuU of the spine receive the greater portion of their fixed or movable insertions. Inferior surface. — Wide at the neck, this surface becomes narrow in the dorsal region, to be again widened at the lumbo-sacral region, and once more contracted at the coccyx. Crests more or less developed, which divide the vertebral bodies into two lateral portions, right and left, are remarked. Lateral surfaces. — These offer for study the thirty-six intervertebral foramina, through which the spinal nerves pass. They exhibit besides, in the neck, the transverse processes ; in the back, the external facets of these processes, and the intervertebral facets, all destined to sustain the heads of the ribs ; on the loins, the transverse or costiform processes. It may be remarked that the ribs and the transverse processes of the neck and loins furnish points of insertion to the powerful muscles which produce the lateral movements of the spine. In the sacrum, the lateral faces are formed for the articulation of the spine with the ossa innominata. Spinal canal. — This canal communicates, in front, with the cranial cavity. Very wide in the atlas, for the reception of the odontoid process and to permit the rotatory movements of the head without injury to the spinal cord, this canal suddenly diminishes in the axis. It again dilates at the termination of the cervical region and the commencement of the dorsal ; there the spinal cord presents a greater volume, and the movements of the spine are very extensive. Towards the middle of the back, the spinal canal offers its smallest diameter ; it widens from this part to the lumbo-sacral articulation ; after which it contracts rapidly, and disappears altogether near the fourth or fifth coccygeal vertebra. The lumbo-sacral dilatation coincides with the enlargement of the cord in this region, and with the enormous quantity of nerves lying beside it. Direction of the Spine.— The spine does not extend in a straight line from the head to the posterior extremity of the body. If it is followed from the caudal extremity — which is free and looks downwards — to the anterior extremity, it will be observed that it passes upwards and forwards, forming a convex inflexion corresponding to the roof of the pelvis. In the lumbar and posterior half of the dorsal region, it is nearly horizontal and rectilinear ; thence it descends to the cervical region, where it again rises and forms two curves — one, posterior, bend- ing upwards, the other anterior, passing downwards. This direction "of the spine gives it the form of a console. THE VERTEBRA. 43 MoMity of the Spine. — In the cervical region, the almost total absence of spinous processes, the great development of the articular processes, and the very short curve described by the surfaces of contact of the vertebral bodies, allow the spine very extensive and varied movements. In the dorsal region, however, these movements are very limited, the spinous processes and the costal arches preventing the play of the vertebrae on each other. In the lumbar region, the spine can be flexed and extended more than in the dorsal ; but its lateral move- ments are quite as restricted, owing to the presence of the transverse processes and the reciprocal union or dovetailing of the articular processes. Lateral motion is even rendered impossible in the posterior half of this region, from the manner in which the transverse processes are adapted to each other. It may be remarked, however, that this disposition singularly favours the integral transmission of the propulsive efforts communicated to the trunk by the posterior extremities. The sacral vertebrae, having to afford the ossa innominata a solid fixed point, could not preserve their independence and mobility if they were like the other vertebrae ; they are consequently consolidated into a single piece, which fulfils all that is required of it in this respect. In the coccyx the spine again recovers its mobility, and to an extent more marked than elsewhere ; the bones, articulating with each other by means of convex surfaces, and having no long processes at their extremities, are placed in the best possible conditions for effecting varied and extensive movements. Varieties in the Vertebral Column. To anatomists, the bones of the spine have frequently offered curious varieties in their shape and number. 1. Shape. — Goubaux has observed varieties of this kind in the last two cervical vertebrae of the Horse. In one instance, the sixth had the transverse process biscuspid on the left and tricuspid on the right. This anatomist has collected several similar examples. Husson has found the sixth cervical vertebra with a prolongation deficient in the transverse processes ; and the seventh, on the con- trary, with an additional prolongation. The dorsal vertebra have also exhibited varieties in shape. Daubenton has referred to the skeleton of an Ass, in which the last vertebra had on one side only a transverse process like that of the lumbar vertebrae. We have seen this variation in the Horse. In the lumbar region, Goubaux has noticed — as we have done — the fourth and fifth vertebrae sometimes articulating by their transverse processes ; the articula- tions may even be fused. Sometimes the transverse processes of the first lumbar vertebra articulate at their base with the body of the bone, and become floating ribs. Thomas has remarked an interesting variation in the sacrum. He found in the Sheep a long, costiform, transverse process on one of the sides of the first sacral vertebra. The last vertebra in this region sometimes shows, in the Dog — • either to the right or left, or on both sides at the same time— one or more articular facets on the transverse processes, uniting with similar facets on the first coccygeal bone (Goubaux). 2. Number. — For a long time, instances have been accumulating of variations in the number of bones in the spine ; but they do not form a very imposing array, probably because it is difficult to observe them without making a special and attentive study of the subject. 41 THE BONES. These variations have been noted in all the regions of the vertebral column, though they are rare in the cervical region. Sometimes they consist in a dimi- nution, sometimes in an increase, in the number of the vertebrse. a. So far as it is known, a decrease in the nimiber of the cervical vertebrae in the domestic animals has not been observed. Goubaux has sometimes met with eight cervical vertebrae, though, as the eighth offered relations with the first rib, he was disposed to place it in the dorsal region. In this case the anomaly was in the number of bones in the spine. b. The dorsal region is more frequently abnormal. Bourgelat and Rigot have dissected Horses which had only seventeen dorsal vertebra. Groubaux and ourselves have seen similar instances, though the length of the animals afforded no suspicion of modification in their spines. It is certainly more common to see the nimiber of dorsal vertebrae increased to nineteen, as is proved by the observa- tions of Bourgelat, Higot, Husson, Goubaux, and our own. This increase is observed also in the asinine species. We have the skeleton of an Ass in which there are twenty ribs on each side, and therefore twenty dorsal vertebrae. In the Ox, fourteen dorsal vertebrae have been found. c. The lumbar region is still more frequently modified. The Horse at times has only five lumbar vertebrae (Daubenton, Chauveau, Goubaux, Sanson, and several German anatomists) ; the Ass only four (Goubaux). In the other animals — the Dog, for example — an increase in nunlber has been remarked ; Girard has seen eight lumbar vertebrae, instead of seven. Goubaux and ourselves have on several occasions seen seven lumbar vertebrse in the Sheep. d. The sacrum has often one or two pieces more in old subjects, due to the fusion of the first or second of the coccygeal vertebrae with its posterior extremity. At other times, the supernumerary piece is situated at the base. Earely is the number of sacral vertebrae diminished ; Goubaux has only met with one instance in which there were four sacral vertebrae in the Horse. e. The number of coccygeal bones is extremely variable ; and in order to be convinced of this, one has only to look at the tables drawn up by anatomists. Nevertheless, it is certain that the normal number is never less than seven or eight, as Bourgelat stated in the first edition of his Anatomie. To resume, it is seen that all the regions of the spine may offer variations in the number of vertebrte, and that these variations — rare between the neck and the back — are, on the contrary, frequent at the two extremities of the lumbar region. When the bones are deficient, the diminution is only apparent — that is, the vertebra which is absent in one region is carried to the adjoining region. It frequently happens, for instance, when a lumbar vertebra is missing, that the sixth is united to the sacrum ; or when there are nineteen dorsal vertebrae, there is one less in the lumbar region. It is not always sufficient to examine the regions contiguous to the one which is modified, to gain an exact notion as to the modification. In fact, a change in the number of vertebrae in a region may be compensated for by an alteration in a distant region. In the museum of the Lyons school, there is the skeleton of an Ox in which there are fourteen dorsal vertebrae, with the normal number of cervical, but only four sacral. We also possess the skeleton of a Horse which has seven lumbar vertebra, with the normal number in the other regions, though the seventh bone is certainly the first sacral, as it has all its characteristics ; and with regard to the fifth sacral bone, this evidently comes from the coccygeal region. In the first skeleton, the increase in the dorsal region has therefore been com^imsated for by a decrease in the sacral THE VERTEBRA. 45 region ; and in the second, the augmentation in the lumbar region has been com- pensated for by a diminution in the coccygeal region. These transpositions occur more especially on the confines of the dorso-lumbar and lumbo-sacral regions. But the increase or decrease in the normal number of vertebrae is sometimes absolute. Goubaux and Husson have found, in the Horse, nineteen dorsal vertebrae with the normal number of the other vertebrae. The Ass with twenty ribs already mentioned, had the usual number of vertebras in the other regions. The first-named anatomist has counted, under the same conditions, seven lumbar vertebrae in the Sheep. Hering, Rueff, Leyh, Sanson, etc., have found five lumbar vertebrae in the Horse, without any modifications in any other parts of the vertebral column. Sanson has even remarked, that in several oriental Horses there are generally only five lumbar vertebrae. The presence of this anomaly is always allied to a particular shape of the cranium and face. In the estimation of Sanson, these characters are so important that they serve to distinguish specific types. The specific type with five lumbar vertebrae is pecuHar to north-east Africa, probably Nubia, It is not intended in this place to discuss the opinions of Sanson and the value of his specific types, but merely to remark that the number of vertebrae is very liable to variation in each region of the spine, and that these variations are even so frequent in animals of the same origin, that it would be perhaps premature to attribute to the number of vertebra in a given region the value of an absolutely specific character. It has been attempted to explain these variations by an ancestral influence, or by the influence of surroundings and exercise. But why might they not be the consequence of irregularities in the fusion of the nuclei which constitute the vertebral column of the foetus ? Fol has observed that at the fifth week the human embryo has thirty such pieces, and that at the sixth week the thirty- eighth, thirty-seventh, and thirty-sixth vertebrae have become one, while the thirty-fifth has no longer perfect limits — so that an embryo measuring nineteen millimetres has only thirty-four vertebrae. The spine of the embryo is com- posed, therefore, of a larger number of pieces than that of the adult. The reduction in number is due to fusions ; consequently, it is reasonable to admit the possibility of variations in the extent of these fusions and the places where they may occur. (For further details, see the Memoirs of Goubaux and Sanson, in Robin's Journal de VAnatomie de la Physiologie, 1867 and 1868.) Comparison of the Vertebral Column of Man with that of the Domesticated Animals. The vertebral column of Man is composed of twenty-nine bones : twenty -four vertebrae, the sacrum, and four pieces constituting the coccyx. The twenty-four vertebrae are thus distributed : Cervical vertebrae 7 Dorsal „ 12 Lumbar „ 5 In all these vertebrae, the bodies are slightly excavated at the two extremities, while in the domesticated animals, the superior or anterior is convex, and the inferior or posterior concave. 1. Cervical vertebrae. — These are wide and short. The spinous processes are moderately developed and bifid at their summits ; the transverse processes are also divided into two branches — a posterior and an anterior. 2. Dorsal vertebrx.—ln these vertebrae, the bodies increase in thickness from the first to the last. In the first as well as in the last dorsal vertebrae, the spinous process is almost 46 THE BONES. immediately directed backwards ; in the middle portion of this region these processes are very obliquely directed downwards and backwards. 3. Lumbar vertebras. — The lumbar vertebrae are the strongest bones in the spine, and their bodies are nearly as thick as those of the larger domesti- cated animals. This enormous development of the lumbar vertebrae in Man is related to his position as a biped. In the fifth, the lower face of the body is cut very obliquely backwards and upwards, and the transverse processes are more voluminous than those of the other lumbar vertebrae. 4. Sacrum. — The sacrum is formed by the union oi five pieces. It is very concave from above to below and before to behind. In becoming united to the lumbar region, it forms a salient angle in front, to which has been given the name of promontory or sacro-vertebral angle. The sacral spine is continuous or interrupted, according to the subject ; it is always bifid inferiorly. 5. Coccygeal vertebras. — These are little bones or flat- tened tubercles, four in number, rarely five, and usually consolidated. Tbe coccyx is conical in shape. Its base shows two processes directed upwards, which are called the cornua of the coccyx. Its summit is often deviated to the right or left. Article IL— The Head (Fig. 26). The head is a large, bony, quadrangular pyramid, elongated from above to below, sus- pended by its base to the anterior extremity of the spine. Its direction varies with the atti- tudes of the animal, but we will suppose it, for convenience of description, to be nearly verti- cal. It is formed of a great number of particular bones, which are only distinct from one another in very young animals ; for well before the adult period is reached, the majority of the bones are united and cannot be separated. The head is divided into two parts : the cranium and the face. horse's head (front view) I, Occipital tuberosity; 2, origin of the mastoid crest ; 3, parietal bone ; 4, saggital suture ; 5, junc- tion of the parietal and temporal bones ; 6, zygomatic arch ; 7, frontal bone ; 8, frontal suture ; 9, temporal fossa; 10, supra-orbital foramen ; 11, 12, lachrymal bone ; 13, malar bone ; 14, nasal border of frontal bone ; 15, nasal bone ; 16, suture of nasal bones; 17, super- maxillary bone ; 18, infra-orbital foramen ; 19, anterior, or pre- maxillary bone; 20, foramen in- cisivum ; 21, incisor teeth (young mouth). Bones of the Craniam. The cranium, or upper part of the head, is composed of seven flat bones, five of which are single : the occipital, parietal, frontal, sphenoid, and ethmoid; one only, the temporal, is double. These bones circumscribe a central cavity, the cranial, which communicates behind with the spinal canal, and lodges the principal portion of the nervous centres — the brain. 1. Occipital Bone (Fig. 26, 1). The occipital bone occupies the superior extremity of the head, which it supports from the anterior extremity of the spine. This bone is very irregular m its form, aud is bent at a right angle in front and behind. It has an external TEE HEAD. 47 and an internal face, and a circumference which brings it into contact with the adjoining cranial bones ; the latter is subdivided into two anterior lateral borders, two posterior lateral borders, an anterior and posterior salient angle, and two lateral re-entering angles. Faces. — The external face is divided into three portions by the double flexure of the bone : one looks forward, another upward, and the third backward. It exhibits : — 1. On the median line, and from before to behind : a, an antero- posterior ridge which constitutes the origin of the parietal ridges, to be mentioned hereafter ; b, a transverse, voluminous, and very prominent eminence, marked posteriorly by deep imprints, with a medium projection named the cervical tuberosity ; this is the external occipital tuberosity which, in the Horse, corre- sponds at the same time to the superior curved lines of the occipital bone of Man. This protuberance forms the culminating point of the head, and divides the anterior and superior parts of the external face of the bone ; c, the occipital foramen {foramen magnum), a large orifice that passes through the bone at the posterior flexure, and establishes a communication between the cranial cavity and spinal canal ; d, the external surface of the basilar process — a narrow and thick prolongation formed by the bone as it passes to meet the sphenoid : this surface is convex laterally. 2. On the sides : a, A sharp crest which prolongs, laterally, the superior curved lines, and descends on the middle of the lateral anterior border, to be continued with the superior root of the zygomatic process and the mastoid crest of the temporal bone ; b, Linear imprints, parallel to the latter, and prolonged on the base of the styloid process : they are destined for the insertion of the small oblique muscle of the head, and represent the inferior curved lines of the occipital bone of Man ; c, Within these imprints is a slightly roughened cavity for the insertion of the posterior recti muscles ; d, The two condyles — articular eminences with a double convexity, one superior, the other inferior : these eminences are situated on each side of the occipital foramen {foramen magnum), and correspond to the anterior cavities of the atlas ; e, More outwards are the two styloid {paroccipital) processes, or jugular eminences — long projections flattened on each side, terminated in blunt points, directed backwards, and separated from the condyles by a deep space, the stylo-condyloid notch ; f. Under the condyles is the condyloid fossa — a smooth depression, pierced at the bottom by the condyloid foramen, which penetrates the cranium. The internal face of the occipital bone is concave, and shows : behind, the foramen magnum ; above, an uneven surface, which forms the roof of the cerebral cavity ; below, the superior face of the basilar process, slightly hollowed into a groove ; on the sides, the internal orifice of the condyloid foramen. Circumference. — The anterior lateral borders are thick, and are united by suture with the parietal bone, and with the tuberous portion of the temporal bone by the harmonia suture. The posterior lateral borders are sharp, and constitute the sides of the basilar process ; each concurs in the formation of the occipito-spheno-temporal hiatus, also termed the foramen lacerum basis cranii — a vast irregular opening, extending from above downwards, penetrating the cranium, and divided by a ligament, in the fresh state, into two portions, one inferior, the anterior foramen lacerum, the other superior, the posterior foramen lacerum. The anterior angle, which is dentated, is dovetailed into the parietal bone. Theposterior angle is very thick, and forms the summit of the basilar process ; it is united by suture with the body of the sphenoid. The lateral re-entering angles, or jugular notches, correspond to the point where the bone is bent posteriorly ; they separate 48 THE BONES. the anterior lateral from the corresponding posterior lateral border, and are occupied by the petrous portion of the temporal bone. Structure. — The occipital bone contains much spongy substance. Development.— li is developed from four centres of ossification ; one, the anterior, is single, and forms the occipital tuberosity ; another, the posterior, also single, forms the basilar process ; the other two are pairs, and comprise each a condyle, with a styloid process and the corresponding condyloid foramen. The occipital bone in the Ass is distinguished by the prominence of the external occipital tuberosity (see the Head in General), by the depth of the groove (mastoid) which com^ses over the outer face of the styloid process, and by the articular surface prolonged to the origin of the basilar process, which constricts it in a circular manner. Differential Characters in the Occipital Bone op other Animals. A. Ox. — The occipital bone of this animal does not show any anterior elbow, neither does it form a portion of the iinierior part of the head. The external occipital tuberosity is obtuse, and givts rise on each side to the superior curved lines. The styloid processes are short and much bent inwards. Tlie basilar process, wide, short, and thick, has a groove in the middle of its external face ; this groove is sometimes absent in the Sheep and Goat. The condyloid foramina are double, sometimes triple ; the superior foramen does not pass directly into the cranium, but goes to a vast conduit that opens behind on the lateral margin of the occipital foramen, and wliich terminates in front by two orifices, one entering the parieto- temporal canal, the other opening on the external surface of the bone. The foramen lacerum is divided into an anterior aud posterior foramen, by the mastoid portion of the temporal bone. B. Sheep and Goat. — The inner tuberosity is only marked by a slight prominence of the internal plate of the bone. In the occipital bone of these animals are found the peculiarities noted in that of the Ox ; the groove on the basilar process is sometimes absent, and in the Sheep the superior curved lines are very salient and occupy the summit of the head. This feature is still more marked in the Goat, and also more in the Cervine species, in wliich this bone somewhat resembles that of the Horse. C. Camel. — The bone shows a double angle as in Solipeds. In its anterior and superior portions it resembles that of the Horse, and in its posterior portion that of the Ox. The crest, which constitutes the origin of the parietal crests, as well as the superior curved lines, are thin, sharp, and very high. The styloid processes are short, wide, thick, and articulated by harmonic suture with the tuberosity of the temporal bone. The superior curved lines are scarcely marked in young animals. D. Pig. — The occipital bone in this animal is not bent anteriorly; but the transverse protuberance representing the curved lines forms, nevertheless, as in the Horse, the summit of the Head. This eminence, which is excavated on both sides on the posterior face, unites in front with the parietal bone, which abuts on the occipital at an acute angle. There is no externa] occipital protuberance, properly speaking, and the styloid processes are very long and directed downwards. E. Camivora.— The external occipital tuberosity is very strong and high. The external occipital crest is absent or little marked ; the styloid processes are short. The foramen lacerum is divided into two portions by the mastoid process, and the basilar process is wide, long, and thick, and hollowed on the side by a channel that joins a similar one in the temporal bone to form a large venous canal. Tliis last communicates, behind, with the posterior foramen lacerum, and opens, in front, in the cranium, where it is continuous with the cavernous groove of the sphenoid. The anterior angle forms a very marked prominence, which is deeply fixed into the parietal bone, and partly constitutes the internal occipitnl process of that bone. The latter does not show the lateral excavations at its base; they are found lower, towards the summit of the petrous bone, on the sides of the occipital. The parieto-temporal canals are, nevertheless, continued to the base of the process, which they traverse to open into its interior. In the most intelligent breeds, the occipital foramen is deeply notched above (Faure). THE HEAD. 2. The Parietal Bone (Fig. 26). The parietal is a wide and thin bone, very much arched to form the roof of the cranial cavity. It is bounded above by the occipital bone, below by the frontal, and laterally by the two temporal bones. It offers for study an external and internal face, and a circumference divided into four regions or borders. Faces. — The external face is convex. It exhibits two curved ridges with concavity directed outwards ; these two crests, which are termed the parietal ridges, approach each other and unite superiorly, to be continued with the antero- posterior ridge of the occipital bone ; below they diverge and proceed, one on each side, to join ike supra-orbital process. They divide the surface of the bone into three portions : two lateral, which are rough and traversed by vascular channels, forming part of the temporal f ossa3 ; the third, or middle, is plane, smooth, and of a triangu- lar form, and covered by the skin. The interjial face is concave, covered by digital impressions, and grooved by small vascular canals ; it offers, on the middle line, and altogether above, the parietcd protuberance. This trifacial and very salient projection presents at its base, on each side, an excavation elongated transversely, into which opens the parieto-temporal canal, and which lodges a venous sinus. It is continued, in front, by a median crest, which is often replaced by a slight groove — ^the saggital furrow, bordered by linear imprints. Two other ridges, resulting from the abutment of the lateral border of the bone against the anterior face of the petrous bone, rise from the sides of this eminence and descend to the sphenoid bone ; they separate the cerebral from the cerebellar cavity. Borders. — The superior border is notched, thick, and slightly dentated ; it articulates with the occipital bone. The inferior border, slightly concave, and deeply dentated, offers an external bevel in its middle portion, and an internal bevel on its sides ; it corresponds with the frontal bone. The lettered borders are very thin, and are cut, at the expense of the external plate, into a wide, sloping edge, which shows a groove destined to form the parieto-temporal canal. A very prominent angle separates each into two portions — an inferior, that articulates by suture with the squamous portion of the temporal bone ; and a superior, curved inwards towards the centre of the cranial cavity. The latter portion of the lateral border is in contact with the anterior face of the petrous portion of the temporal bone, with which it concurs to form the lateral crest that descends to the parietal protuberance. Structure. — This bone contains much compact tissue, the spongy substance existing only in its middle. Development. — It is developed from two large lateral centres of ossification, to which is added a single centre to form the parietal protuberance. In early life the parietal ridges are absent. head of the cat (posterior aspect). 1, Occipital bone; 2, zygomatic process of the temporal bone; 3, tympanic bulb ; 4, condyle of the temporal bone ; 5, malar bone ; 6, orbital process of the malar ; 7, ditto of frontal bone ; 8, 8, palatine bones ; 9, 9, maxil- lary bone; 10, premaxillary bone; 11, pterygoid bone; 12, sphenoid bone ; 13, vomer. 50 THE BONES. Differential Characters of the Parietal Bone in other Animals. A. Ox. — The parietal bone in the Ox does not occupy the anterior aspect of the head, but concurs with the occipital to form the base of the neck. It represents a very narrow osseous plate, elongated transversely, and curved at its two extremities, which descends into the temporal fossae to rest upon the sphenoid bone. There are no parietal ridges. The internal protuberance is only marked by a slight elevation of the internal plate ; for the most part it belongs to the occipital bone. The parietal bone of the Ox is developed from three centres of ossification, and the middle nucleus is even primarily divided into lateral halves ; but these centres «re consolidated with each other at an early period, as well as with the anterior portion of the occipital. It does not aid in the formation of the parieto-teniporal canal, and is excavated internally by cavities which communicate with the frontal sinuses. B. Sheep, Goat.— The parietal bone of the Sheep and Goat is relatively much larger than that of the Ox. It participates in the formation of the parieto-temporal canal, and has no sinuses. C. Camel.— This bone occupies the anterior face of the cranium ; but it is long, narrow, and deeply lodged between the squamous portion of the temporal bone and the frontal bone, to rest on the sphenoid. The parietal crests, thin and elevated, lie against each other for nearly their entire lengtli, and are not pro- longed to the frontal bone (Fig. 45). These crests do not exist at an early age. D. Pig. — The parietal bone is very thick ; it has two very marked crests, which do not meet at their upper part (Fig. 28). E. Dog, Cat. — In the Dog, the parietal bone is distinguished by the great development of the temporal crests (Fig. 2li). In the Cat there are scarcely any parietal crests, and the in- ternal protuberance is replaced by two great transverse bony plates, which separate the cavity of the cerebrum from that of the cerebellum. F. Rabbit.— Almost quadrilateral, the parietal bone of the Rabbit has its temporal crests carried to near its lateral borders. 3. Frontal Bone (Fig. 26). The frontal is a flat quadrilateral bone, the sides of which are bent in the middle at an acute angle, and are carried back, and a little inwards, to meet the wings of the sphenoid bone. It assists in forming the cranial roof and part of the face. It is bordered : above, by the parietal bone ; below, by the nasal and lachrymal bones ; and on each side, by the temporal bones. It offers for study an external and an internal face, and four borders. Faces. — The external face is divided, by the double flexure of the bone, into three regions : a middle and two lateral. The first, nearly plane, is lozenge-shaped, is covered by the skin, and constitutes the base of the forehead. It gives rise on each side, at the point where it is inflected, to a long process, flattened above and below, which curves backward, forming the orbital arch. The superior or external face of this process is convex and slightly roughened ; the internal face is smooth and concave, and forms part of the orbital fossa. Its posterior border, thick and concave, is continued, inwardly, with the correspond- ing parietal ridge, and outwardly with the superior border of the zygomatic process. It limits, in front, the temporal fossa. The anterior border, also concave, but thin, concurs in the formation of the orbital margin ; the summit, head of the pig (anterior face). 1, Summit of occipital tuberosity. 2, parietal bone. 3, frontal bone : A, Supra-orbital fora- men ; a', channel de- scending from it. 4, zgomatic process. 5, malar bone. 6, lachry- mal bone : b, Lachrymal canals. 7, supermax- illary bone : C, Inferior orifice of the super- maxillo-dental canal. 8, nasal bone. 9, pre- maxillary bone. THE HEAD. thickened and denticulated, rests upon, and is united to, the zygomatic process of the temporal bone ; the base is wide, and is traversed by an opening termed the supra-orUtal, or superciUarij foramen. The two lateral regions of the external face of the frontal bone are slightly excavated, and assist, for the greater portion of their extent, to form the orbits. They often show, near the base of the orbital arch, a small depression corresponding to the flexure described by the great oblique muscle of the eye in passing through its pulley. The interned face of the frontal bone is concave, and divided into two unequal parts by a transverse ridge, corresponding to the anterior border of the cribriform plate of the ethmoid bone. The superior, the most extensive, is covered with digital impressions, and belongs to the cranial cavity. It exhibits : 1. On the median line, a slight furrow, or a crest which is continuous, above, with the median ridge of the parietal bone, and below, with the crista-gaJU process. 2. On the sides, and in the re-entering angle formed by the flexure of the bone, there is a narrow slit, or mortise, which receives the wing of the sphenoid bone. The inferior part is united, on the median line, to the perpendicular plate of the ethmoid. It assists in forming the bottom of the nasal cavities, and presents laterally two large openings which lead to the frontal sinuses — vast anfractuous spaces excavated between the two plates of the bone. Borders. — The superior border is denticulated and cut obliquely in its middle portion, at the expense of the internal plate, and on the lateral parts at the expense of the external table ; it is in contact with the parietal and squamous portion of the temporal bone. The inferior, prolonged to a point in the middle, is in apposition with the nasal bones through the medium of a wide external bevel ; laterally, it is very thin, faintly serrated, and articulates with the lachrymal bone. The lateral borders, thin and irregular, present two notches : one, the superior {incisura spJmioidaUs), is wide and deep, and occupied by the wing of the sphe- noid bone ; the other, inferior, is very narrow, and, uniting with a similar notch in the sphenoid bone, forms the orbital foramen, which opens into the cranium, very near, but external to, the ethmoid fossa. Each of these borders, also, is adapted, for a limited extent, to the corresponding palatine bone. Structure. — The two compact plates of the frontal bone are separated by spongy texture towards the middle and in the upper part ; they separate below to form the frontal sinuses. Laterally, they are very thin and consolidated with each other. Development. — The frontal bone is developed from two lateral centres of ossification, which only coalesce at a late period. In youth the cranial portion of the bone forms, in front of the head, a large rounded protuberance standing beyond the facial portion. This prominence disappears when the frontal sinuses begin to be developed. These cavities do not exist at an early period of foetal head of dog (anterior face). 1, Occipital tuberosity; 2, median spur of the occi- pital bone ; 3, parietal bone ; 4, origin of the pa- rietal crests; 5, zygomatic process ot the temporal bone ; 6, frontal bone ; 6', orbital process ; 7, malar bone ; 8, lachrymal bone ; 9, nasal bone ; 10, super- maxilla ; 11, inferior ori- fice of the supermaxillo- dental canal; 12, pre- maxillary bone. 52 THE BONES. life ; but commence to form about the fourth month of conception, by a process of resorption, which removes the spongy substance interposed between the two compact tables of bone, and may even cause the destruction of the internal table. The sinuses enlarge with age, and remain during life separated from one another by a vertical septum. Differential Characters in the Frontal Bone of other Animals. A. Ox, Sheep, Goat. — In Eumiaants, the frontal bone does not come in contact with the temporal or palatine bones (Figs. 30, 31, 32). In the Ox, this bone is extremely developed, occupying alone nearly one-half of the anterior surface of the head. It is particularly distinguished by: 1. Its great thickness. 2, The Fig. 30. ox's head (anterior face). 1, Mastoid process ; 2, superciliary, or supra-orbital foramen ; 3, malar bone ; 4, lachrymal bone ; 5, maxillary spine ; 6, inferior orifice of the supermaxillo-dental canal. osseous conical cores which support the horns. These eminences, more or less long and curved, very rugged, perforated by foramina, and grooved by small vascular channels, are detached outwards from each side of the bone, near the summit of the head. The proce.-^ses which form the orbital arches rest by their summits on the zygomatic bone. The supra-orbital foramen is transforraeil into a veritable and frequently multiple canal ; its anterior orifice opens into a vasculo-nervous groove, which ascends towards the base of the horns, and descends to near the lower border of the bone. Between this groove and the base of the orbital arch is the frontal boss. Thp orbital foramen entirely belongs to this bone. The inferior border is deeply notched in its middle to receive the nasal bones; the frontal sinuses are prolonged into the horn-cores, the parietal bone, and even into the occipital bone. , The frontal bones of the Angus breed of cattle (^polled cattle) have no horn-cores. The ablation in the calf of the periosteum, followed by cauterization, at the point where appear the osseous prolongations which serve as bases for the horns, prevents the development of these appendages. Cornevin mentions that a farmer of Haute Marne has in this way muti- lated the cattle bred on his farm for twenty-three years, and yet the mutilation has not become hereditary. Fig. 31, representing the head of an Ox so mutilated, shows that the removal of the THE BEAD. 53 periosteum in such animals has the effect of producing a considerable elongation and narrowing of the upper part of the frontal bone. In the Sheep and Goat, tlie frontal bone is relatively less extensive and strong than in the Ox; it does not ascend to the summit of the head, and the frontal sinuses are not prolonged beyond its superior border (Fig. 32). B. Camel. — The frontal bone of this animal much resembles that of Solipeds. The middle portion of its external face is triangular in shape, the base being wide, and the apex fixed in the deep notch formed on the inferior border of the parietal bone; it is slightly hollowed in the middle line, and convex on the lateral parts. The orbital arch rests on the Fig. 32. HEAD OF A HORNLESS OX. ram's head (anterior face). 1, Occipital bone ; 2, parietal bone ; 3, core of right frontal bone ; 4, the left core covered by its horn ; 5, supra-orbital foramen ; 5', channel descending from it ; 6, lachrymal bone ; 7, malar bone ; 8, nasal bone ; 9, supermaxillary bone ; 10, premaxillary bone; 10', its internal process; 11, incisive open- ing. zygomatic bone, as in the Ox (Fig. 37). The supra-orbital foramina are transformed into inflected canals, which open on the anterior face of the bone, near its middle. On the circumference of the bone are several notches, some of which concur with the other bones, to form foramina (orbital, nasal) ; two are seen to the right and left of the line of union of the bone with the supra-nasal, and two others are in the orbital cavity. These open- ings are partially closed by the Wormian bones ; they open into the upper compartments of the turbinated bones. In the young Camel, the middle portion is deeply excavated ; this excavation diminishes as the animal advances in age, and as the frontal sinuses enlarge. C. Pig.— The frontal bone of the Pig is very thick and short, and does not join the temporal or zygomatic bones ; the orbital arch is completed by a ligament. The supra-orbital foramen, disposed as in the Ox, abuts in a channel that descends on the nasal bones. The * In the Museum of the Lyons Veterinary School. 54 THE BONES. orbital foramen is formed by the frontal bone only. There is no mortise for the union of the frontal with the sphenoid bone ; and the frontal sinuses are prolonged into the parietal. The frontal bone articulates with the superior maxillarie.s (Fig. 28). D. Carnivora. — In the Carnivora, the external face of the frontal bone presents in its middle a more or less deep depression. The ori)ital arch is incomplete, and there is no supra- orbital foramen or mortise on the inner face. superior maxilLiry bones anterior bones of the head op a fcetus (horse) at birth, disarticulated, and viewed from behind. It unites with tht (Fi-. 29). E. Rabbit. — In this animal the frontal bone is long and narrow, and the orbital process is thin, elevated, and directed upwards and backwards, but it does not reach the zygomatic bone, and is deeply notched at its 4. Ethmoid Bone (Fig. 33). The ethmoid bone, deeply situated m the limit between the cranium and the face, is enclosed between the frontal, the sphenoid, the vomer, the palatine, and the supermaxillary bones. It is composed of three portions — a jjer- pendicular plate, and two lateral masses. The Perpendicular Lamina of THE Ethmoid Bone. — Situated in the mesian plane, and flattened on both sides, this bone presents tu'o faces, a left and right, and four borders. Faces. — The faces, covered by the ., Occipital bone : 1, condyle ; 2, condyloid foramen ; 3, styloid process ; 4, summit of basilar process. B, Parietal bone : 8, j)arie- tal protuberance; 9, channel which concurs to form the parieto-temporal canal. C, Fron- tal bone: 10, transverse crests separating the cranial from the facial portion of the bone; 11, frontal sinuses; 12, notch on the lateral border occupied by the wing of the sphenoid bone ; 13, notch for the formation of the orbital foramen ; 14, summit of the orbital process ; 15, supra-orbital foramen. D, Perpendicular lamina of the ethmoid bone. E, E, Lateral masses of the ethmoid bone : 16, the great ethmoid cell. F, Squamous portion of the temporal bone : 17, Supra- condyloid process ; 18, channel for the forma- tion of the parieto-temporal canal. G, Pet- rous portion of the temporal bone : 5, mastoid process ; 6, internal auditory hiatus ; 7, opening for the Eustachian tube into the tympanum, h, Lachrymal bone. I, Nasal bone. J, Superior turbinated bone. pituitary membrane, present, posteriorly, small sinuous crests ; elsewhere they are smooth. A very narrow interval, constituting the bottom of the nasal cavities, separates them from the lateral masses. Borders. — The superior border looks towards the centre of the cranial cavity, and constitutes what is called the ethmoidal ridge, or crista-galli ^wocess. It is THE HEAD. 55 free, concave, and sharp, prolonged in front and above by the median crest of the frontal bone, and confounded behind with the middle portion of the inferior sphenoid. The inferior border is continuous with the cartilaginous plate which separates the nasal cavities. When this plate becomes ossified, which is not unfrequent, it is impossible to discover the point where it begins or the ethmoid bone terminates. The middle Septum of the nose has been considered, and justly, as a prolongation of the perpendicular plate (or lamina) of this bone. The anterior border is consolidated with the vertical septum which separates the frontal sinuses. The posterior border is joined above to the median plate which divides the sphenoidal sinuses into two compartments. Below, it is fixed in the groove of the vomer, and soon becomes confounded with that bone, which is itself consolidated with the inferior sphenoid. Lateral Masses of the Ethmoid Bone. — These are two large pyriform tuberosities placed on each side of the perpendicular lamina, and offering for study a middle portion, a base, and a summit. Each of these is formed by an assemblage of numerous, extremely thin, osseous plates, curved into small and very fragile convolutions. These, elongated from above to below, become longer as they are more anterior ; they are attached by their superior extremities to the transverse plate which separates the cranium from the nasal cavities, and by one of their borders to a thin leaf of bone which envelops the lateral masses outwardly. They have received the name of the ethmoidal volutes (or cells). Middle portion. — This should be studied externally and internally The external surface of each ethmoidal mass is divided into two sections : an internal, making part of the nasal cavities ; the other, external, concurs in forming the walls of the frontal and maxillary sinuses. The first, the least extensive, is almost plane ; parallel to the perpendicular lamina, it is isolated from it by the narrow space which forms the bottom of the nasal cavities ; it presents several openings which separate the most superficial cells, and join the internal canals to be hereafter noticed. The second, very extensive and convex, looks outwards in front and behind, and is covered by an osseous plate traced with shallow furrows, which correspond internally with the small crests to which the cells are attached. This lamella is prolonged, inferiorly, a little beneath the inferior extremity of these latter, and turns outwards to articulate with the palate and superior maxillary bones ; superiorly, it coalesces with the sphenoid and the orbital portion of the frontal bone. Internally, the lateral masses are hollowed from above to below by extremely diverging canals, which open inferiorly into the nasal cavities, and separate the cells from one another. The latter are so incurvated that the internal cells communicate with each other. There are some, however, which are completely closed ; the anterior, or great cell, is frequently so.^ Base. — The base of each lateral mass looks upwards, and is formed by the transverse septum between the cranium and the nasal cavities. This septum is perforated by openings which give passage to the ethmoidal nerves ; it is named the cribriform plate of the ethmoid bone. It is concave on the superior surface, which constitutes the ethmoidal fossa, and convex on the opposite face, where attachment is given to the superior extremities of the cells. It is consolidated internally with the perpendicular plate ; the other points of its circumference are attached to the sphenoid bone, and to the transverse ridge on the internal face of the frontal bone. ' It is not rare to find it opening into the superior maxillary sinus. 96 THE BONES. Summit. — The summit of each lateral mass is formed by the inferioi extremity of the ethmoidal cells, which is directed downwards, towards the nasal cavities. One, more volmninous than the others, is carried much lower, and terminates by a rounded protuberance. It corresponds to the middle cornu {concha media) of Man. Structure of the ethmoid hone. — Very little* spongy tissue enters into the composition of this bone, and this is only found near the anterior border of the perpendicular plate. Development. — The ethmoid bone is late in attaining its development, and the adjoining bones are nearly completely ossified when it is yet entirely cartilaginous. The bony transformation commences in it at the inferior ex- tremity of the cells, and advances progressively from below upwards. The per- pendicular plate is only ossified in part when the cells have passed through the first half of the process ; at the same time it coalesces with the inferior sphenoid. The cribriform plate is the last to become ossified, this transforma- tion having scarcely been achieved when the animal is six or eight months old. Differential Characters in the Ethmoid Bone of other Animals. A. Ox, Sheep, Goat. — In Ruminants, the great ethmoidal cell is enormously developed, and looks like a third turbinated bone prolonged beyond tlie usual two ; it has been named the olfactory antrum. The bone is closely imprisoned between the adjacent bones, in con- sequence of the slight development of the sinuses around it. This character otherwise belongs to all the domesticated animals, except Solipeds (Fig. 36). B. Camel.— The crista-galli process is very thick, and the ethmoidal fossae are narrow and deep. C. Pig.— The superior turbinated bone is very long, and the papyraceous plate appears in the orbital cavity. D. Dog, Cat. — The ethmoidal fossa is very deep, and the cells very developed and diverticulated. The perpendicular lamina is at a late period consolidated with the sphenoid bone. 5. Sphenoid Bone (Fig. 34). The sphenoid bone is situated behind the cranium, between the occipital, ethmoidal, palatine, vomer, pterygoid, frontal, and temporal bones. It is formed by the union of two pieces, which have been sometimes described as distinct bones — the anterior or inferior sphenoid, and the posterior or superior sphenoid. It is now supposed, in the description, that this union has been completed. It is a bone flattened before and behind, curved from one side to the other, thick in its middle part, named the bodi/, and thin on the sides, which, in their inferior half, are prolonged in the form of aJce, or U'ings. It has two surfaces a,nd four borders. Surfaces. — The exfermd surface is convex, and presents : 1. On the median line, the external surface of the body, rounded from one side to the other, is continued with that of the basilar process, and has marked muscular imprints superiorly. 2. On the sides and from within outwards : (a) the Vidian (or pterygoid) fissure, directed from above downwards, and continued by the Vidian canal, a very smaU foramen which opens into the orbital hiatus ; (b) the sub- sphenoidal, or pterygoid process, a long eminence, flattened on both sides, inclining downwards, articulating with the palatine and pterygoid bones, and traversed at its base by the Vidian canal ; (f) a little behind and above this eminence, the superior orifice of the sub-sphenoidal (or pterygoid) foramen — a large canal which bifurcates inferiorly ; (d) more in front, the orbital hiatus, a kind of vestibule into THE HEAD. F Fig. 34. which open, in common, the principal branch of the subsphenoidal canal, the three supra-sphenoidal canals, the Vidian and optic canals, and the orbital opening : this hiatus is surmounted by a thin and sharp bony plate, above which opens the smallest branch of the subsphenoidal foramen ; (e) altogether without the hiatus is remarked a smooth surface belonging to the wing of the sphenoid, and which concurs to form the orbital cavity. The internal face is concave from side to side. It shows : 1. On the median line, and from before to behind, a small projection united to the crista-galli ; the optic fossa, elongated transversely in the form of a shuttle, and presenting at the bottom, and on each side, the superior orifice of the optic foramen, a cylindrical canal directed obliquely downwards, for- wards, and outwards, to reach the orbital hiatus ; the supra-sphenoidal or pituitary fossa, also named the sella Turcica, a slight depression, limited behind by a scarcely noticeable transverse projection separating it from the superior channel of the basilar process. 2. On the sides, and in front, the internal surface of the wings, depressed by very superficial digital impressions ; more behind and outwards, a fossa, elongated from before to behind, which lodges the mastoid lobule of the brain ; between this fossa and the sella Turcica, two vertical fissures — an internal, named the cavernous sinus, and an external, wider and deeper, for the passage of a large nervous branch. These two fissures open below, near the junction of the three supra-sphenoidal canals. Two of these, which are very wide, are placed one before the other, and separated only by a slight partition. The superior of these con- stitutes the great sphenoidal fissure {foramen lacerum orhitale) ; the other, the lower, is the foramen rotundum, and opens into the orbital hiatus. The third, very small {foramen pathe- ticiim), is situated outside the great anterior canal, opens above the optic foramen, within the bony mass surmounting the hiatus, and sometimes on the free margin of this lamina. Borders. — The superior is a little con- cave, and shows, in its middle, the superior extremity of the body, mammillated and articulated with the summit of the basilar process ; on each side, two notches which circumscribe below the occipito-spheno-temporal hiatus {foramen lacerum basis cranii). The internal notch is the narrowest, and from its affording a passage for the internal carotid artery, is called the carotid notch ; it is continued on the external face of the POSTERIOR BONES OF THE HEAD OF A FOETUS (horse) AT BIRTH, DISARTICU- LATED AND viewed in FRONT. A, Sphenoid bone : 1, ma.xillary notch ; 2, carotid notch ; 3, groove for the passage of the maxillary nerve ; 4, cavernous sinus ; 5, optic fossa ; 6, great wing ; 6', unossified portion of the great wing; 7, notch for the formation of the orbital foramen. B, Vomer. C, Palatine bone. D, Malar bone. E, Supermaxilla : 8, inferior orifice of the raaxillo-dental canal. F, Premaxillary bone. 5^ THE BONES. bone by a smooth excavation to which Rigot has given the name of carotid fossa. The external is also prolonged on the exterior surface of the sphenoid, by a short and wide fissure ; it lodges the inferior maxillary nerve. Outside this is another very narrow notch, intended for the passage of the middle meningeal artery. The fibro-cartilaginous substance that partly fills the occipito-spheno-temporal hiatus, transforms these notches into foramina, the first of which is named the carotid canal ; the second, the foramen ovale ; and the third, the foramen spinosum. The inferior' border, also concave, is likewise divided into three portions, a middle and two lateral. The first is thick, and formed by the inferior extremity of the body ; it is excavated by two large cavities belonging to the sphenoidal sinus. These cavities are separated from one another by a vertical osseous plate, often perforated, which, at an early period, is fused with the perpendicular lamina of the ethmoid bone. The very thin lateral portions form part of the circum- ference of the wings ; they are notched near their union with the middle piece to assist in the formation of the orbital foramen. The ttvo lateral borders are thin and convex in their anterior half, as is also the contour of the wings, which are mortised in the frontal bone. For the remainder of their extent they are thick, denticulated, and bevelled at the expense of the external plate, to articulate with the squamous portion of the temporal bone. Structure. — This bone is compact on its sides, and spongy in its middle part ; inferiorly, it is excavated by the sphenoidal sinuses. Development. — It is developed from two principal nuclei of ossification ; a superior forms the subsphenoidal process and the canal of the same name, the Vidian fissure, pituitary fossa, fissures of the internal face, and the most posterior of the great supra-sphenoidal canals ; the other, the inferior, forms that portion of the body hollowed by the sinuses, the lateral alas,^ and the optic fossa and canals. In meeting each other, these centres form the Vidian canal and the two anterior supra-sphenoidal canals. They are not consolidated with each other until a very late period ; for which reason they are sometimes described as two distinct bones. M. Tabourin has even proposed to attach the description of the inferior sphenoid to that of the ethmoid, because it is united with this bone a long time before it is joined to the superior portion.^ Differential Characters in the Sphenoid Bone op other Animals. A. Ox. — In the Ox, the subsphenoidal or pterygoid processes are large and thin The subsphenoidal canal is absent. The sella Turcica is deep, and the bony projection separating it from the basilar process is very high. The three supra-sphenoidal canals are converted into a single, but wide one. There are no notches in tlie superior border, for the passage of the internal carotid and spheno-spinous arteries. The oval foramen is entirely confined to this bone. B. Sheep. — In the Sheep, the osseous prominence that limits the pituitary fossa posteriorly forms a lamina curving forwards, and prolonged at its extremities into two points, which constitute' the posterior clinoid processes. C. Camel.— The sphenoid is longer and tliicker than in the Ox. The subsphenoidal or pterygoid processes are narrow and very thick. The oval foramen is relatively small. The optic canals are covered at their internal ojiening by a bony plate. The optic fossa is nearly on a level with the pituitary fossa. D. Pig. — The sphenoid of the Pig is very short, but the subsphenoidal processes are extraordinarily developed, and flattened before and behind. There is no subsphenoidal canal, and the sella Turcica is deep, and limited behind by a very salient crest. A single canal These wings are not analogous to those portions of the sphenoid bone in Man bearing the ( name. They are the processes of Ingrassias enormously developed. Tabourin, Journal de Med. Ve'tifrinaire, p. 229. Published at Lyons, 1845. THE READ. replaces the tbiameu rotimdum and the great sphenoidul fissure, as in the Ox. The wings, shghtly salient, are articulated by suture witli the frontal bone. E. Dog, Cat. — The superior sphenoid of the Dog is very short, and bears, laterally, two wide wings which ascend to the temporal fossa ; they correspond to those of the sphenoid bone in Man. The inferior sphenoid is, on the contrary, very narrow, and its lateral prolongations, or processes of Ingrassias, are reduced to very small proportions. The subsphenoidal or pterygoid process is very short, and the canal is single, and communicates witli the foramen rotundum. The pituitary fossa is shallow, limited behind and before by the posterior clinoid and anterior clinoid processes, so named because of their being compared to the four posts of an ancient bed. The supra- sphenoidal canals are only two in number: one represents the great sphenoidal fissure, the other the round foramen. The carotid notch, joining a similar one in the temporal bone, forms an opening which may be designated the carotid foramen, because it gives passage to an extremely remark- able loop the internal carotid artery describes after passing through the carotid canal. The oval foramen is the same as in the Ox. In the Cat there is the same disposition, with the excep- tion of no sphenoidal canal or carotid notch being present. F. Rabbit.— The body of the sphenoid is short, tri- angular, thick at its upper border, pierced in the middle by an orifice which opens into the pituitary fossa. Tlie wings are very developed ; the subsphenoidal processes, bifid, are closely embraced by the pterygoids and palatine bones ; and the optic fossa is replaced by a large foramen, which com- municates at the same time with the two orbital fossae. 6. Tempokal Bone (Figs. 26, 33). HEAD OF THE RABBIT (POS- TERIOR face). Occipital tuberosity; 2, sty- loid process of the occipital bone ; 3, condyle of ditto ; 4, tympanic bulb ; 5, basilar pro- cess of the occipital bone ; 6, body i)f the sphenoid ; 7, ptery- goid bone; 8, zygomatic bone ; 9, 9, condyles of the temporal bone; 10, palatine bone; 11, 11, superior maxillary bone; 12, 12, premaxilla; 13, orbital pro- cess of the fi-ontal bone ; 14, 14, superior double incisors. The temporal ■ bones enclose the cranial cavity laterally, and articulate with the occipital, parietal, frontal, sphenoidal, and malar bones ; also with the inferior maxilla and the hyoid bone. Each is divided into two pieces, which are never consoli- dated in the horse ; one forms the squamous portion of the temporal bone ; the other, the petrous portion. They will be described separately. Squamous -portion. — This is flattened on both sides, oval, and slightly incurvated like a shell, a shape to which it owes its name. It offers for study an external and an internal face., and a circum- ference. Faces. — The external face is convex, and marked by some muscular imprints, vascular fissures, and openings which penetrate the parieto-temporal canal. It forms part of the temporal fossa, and gives origin near its middle to the zygomatic process — a long eminence which at first runs outwards, and soon curves forwards and downwards to terminate in a thin summit. The base of this eminence forms, in front, a concave surface belonging to the temporal fossa ; behind, it offers the articular surface which corresponds with the maxillary bone. The latter is com- posed of : 1. A condyle transversely elongated, convex above and below, and slightly concave from side to side. 2. A glenoid cavity, limited below by the condyle, above by a mammilif orm eminence, the supra-condyloid (or anterior mastoid) process^ ' In Man this is represented by the inferior or vertical ramus of the upper root of the zygomatic process. 60 THE BONES. against %yhich rests the maxillary condyle when this bone is drawn backwards ; it is immediately above this eminence that the inferior orifice of the parieto-temporal canal (mastoid foramen) opens. The external face of the zygomatic process is smooth and convex ; the internal, concave, is also smooth, and bordered outwards by the temporal fossa. Its anterior border is sharp and convex ; the posterior, very short, is thick and roughened. Its summit is ilattened from before to behind, and marked by notches on its two faces ; it somewhat resembles a wedge, fixed as it is between the orbital process of the frontal bone and the zygoma ; it comes in contact with the maxillary bone, and by a small portion of its anterior face, which is deprived of notches, it concurs in circumscribing the orbital cavity. In the domesticated animals, as in Man, the zygomatic process appears to arise from the surface of the bone by two roots — one, the inferior or transverse, is represented by the condyle ; the other, the siqjerior, forms a sharp crest which is continuous with the anterior border of the process, and above, joins the lateral crest of the occipital protuberance. The internal or cerebral face of the squamous portion is divided into two parts by an almost vertical channel, which terminates above the supra-condyloid process, and which, meeting a similar furrow on the parietal bone, forms the parieto-temporcd canal. The superior portion is of small extent, and of a triangular form ; it articulates by a simple harmonia suture with the external face of the petrous portion. The inferior part, the widest, present in its middle some cerebral impressions. For the remainder of its extent or circumference, it is cut into a wide, dentated, and lamellar bevel, which brings it in contact with the surrounding bones. Circumference. — This may be divided into tivo borders .- one, anterior, is convex and united with the parietal and frontal bones ; the other, posterior, articu- lates with the sphenoid in its inferior moiety, and is provided, above the level of the supra-condyloid process, with a deep notch which receives the external auditory canal. Superiorly, the two borders unite at the summit in a thin point, which rests on the occipital bone. Structure. — The squamous portion of the temporal bone is formed of two very thin compact plates, which have but little spongy tissue between them ; the latter, however, is very abundant in the body of the zygomatic process. Development. — It is developed from a single nucleus of ossification. Petrous Portion. — This is one of the most interesting parts of the skeleton for study, in consequence of its containing two systems of cavities which enclose the essential organs of hearing. One of these systems is named the cavity of the tympanun or middle ear ; the other forms the interned ear. These cavities will be studied when we come to speak of the auditory apparatus. In the mean time, only the external surface, and the structure and development of this portion of the temporal bone, will be noticed. It is wedged between the antero-lateral border of the occipital bone, the lateral border of the parietal, and the superior part of the internal face of the temporal shell. It represents a quadrangular pyramid, the base of which is turned downwards and a little backwards. It will be studied successively in four faces, a summit, and base. Faces. — The anterior face is united by harmonia suture to the parietal bone. The posterior face articulates in the same manner with the occipital bone. The external face lies against the squamous portion of the bone. The internal face, slightly concave and marked by very superficial digital impressions, forms a part THE HEAD. 61 of the lateral wall of the cerebellar cavity. It presents the canal or internal audi- tory hiatus {rneatus auditorius internus), a small fossa, the bottom of which is pierced by several foramina for the transmission of nerves ; the largest of these is the internal orifice of the aqimdudus Fallopii — a flexuous canal which passes through the bone and opens at the external surface of its base ; the other foramina penetrate the cavities of the internal ear. These faces are separated from each other by so many borders or plane angles, two of which more particularly merit attention ; one of these isolates the external from the posterior face, and the other separates the anterior from the internal face. The first is thick and rugged, and constitutes the mastoid crest ; it is con- tinuous above with the lateral ridge of the occipital bone, after being united to the superior root of the zygomatic process, and terminates, near the base of the bone, by a tuberosity for muscular insertion, to which has been given the name of (poster io7-) mastoid process. This border is traversed by a slit, the mastoid fissure^ which passes under the squamous portion and enters the parieto-temporal canal. The second is thin, and, with the superior part of the lateral border of the parietal bone, forms the crest which establishes the line of demarcation between the cerebral and cerebellar cavities of the cranium ; it gives attachment to the tentorium cerebelli. Summit. — This is slightly denticulated, and articulates with the occipital bone. Base. — This is very irregular, and offers : outwardly, the external auditory canal which penetrates the middle ear, and the external orifice of which has been named in veterinary anatomy the external auditory hiatus ; inwardly, a sharp crest which circumscribes the external contour of the foramen lacerum basis cranii ; above, and under the mastoid process, the stylo-mastoid or pre-mastoid forammi, the external orifice of the aqueduct of Fallopius ; below, the subuliform (or styloid) process for the attachment of the tensor palati muscle and the Eustachian tube : this is a long, thin, and pointed process presenting, at its base and within, a canal (styloid foramen) which enters the cavity of the tympanum, and which is incom- pletely partitioned by a small bony plate into two parallel portions ; in the centre, the hyoid prolongation or vaginal process ^ — a little cylindrical eminence surrounded by a bony sheath, and the mastoid protuberance or auditory bulla — a slightly sahent, smooth, and round eminence hollowed internally by numerous cells, which form part of the middle ear. The several small and very remarkable canals which pass through the petrous portion of the temporal bone, will be noticed when the nervous and arterial branches they lodge are described. Development. — The petrous portion of the temporal bone is developed from two principal centres of ossification which are consolidated at birth, and which are often described as two distinct portions — the one as the petrous or stony portion, the other as the mastoid portion. The faces, borders, summit, and inner side of the base of the bone are formed by the petrous part, which contains the cavities of the internal ear and furnishes the inner wall of the middle ear. The mastoid portion constitutes almost entirely the base of the temporal pyramid ; to it belong the external auditory canal, the mastoid process, the sheath of the hyoid prolongation, and the styloid process ; it forms the external wall and circumference of the case of the tympanum. ' This is the analogue of the mastoid canal in Man. * This process is prolonged by a cartilage that unites it to the styloid hone. 7 62 TEE BONES. For the petrous portion of the temporal bone there are also two small com- plementary nuclei : one for the vaginal process — the base of which is united to the petrous portion, and another forming the ring of the tympanum. Structure. — The petrous portion is the hardest mass of bone in the skeleton, and scarcely contains any spongy tissue, except at the centre of the mastoid process ; in the mastoid portion it may be said not to exist. Differential Characters in the Temporal Bone of other Animals. In the other domestic animals, the petrous portion of the temporal bone becomes consolidated with the squamous portion, and the summit of the zygomatic process only articulates with the malar bone. A. Ox, Sheep, Goat.— The condyle of the zygomatic process is very wide and convex in every sense. The parieto-temporal canal is very large, and entirely excavated in the temporal bone; its superior or internal extremity opens above the petrous portion in an excavation which represents the lateral cavity of the parietal protuberance in the Horse ; at its inferior extremity it always shows several orifices. Tiie mastoid process is very salient, and belon<^s to the squamous portion. The mastoid cre.st is confounded with the upper root of the zygomatic process ; iiiferiorly, it surpasses the mastoid process, and is prolonged to the mastoid protuberance. Tlie latter is very voluminous. The subuliform process is larger and stronger than in the Horse ; there is no mastoid fissure. In the Sheep and Goat, the mastoid process is scarcely distinct from the crest ; and the mastoid portion of the bone is only at a late period consoli- dated with the petrous portion. B. Camel. — The squamous portion of the temporal is wider than that of the Horse ; it is excavated in tlie upper part of its external surface. The zygomatic process has a large and thin base; its articular surface is nearly level from before to behind, and is concave from one side to the other ; the supra-condyloid process is very developed (Fig. 45). The petrous portion is thin, and closely con- fined between the occipital and squamous bones. The mastoid crest and process are not markedly developed. The hyoid prolongation is placed at the bottom of a great bony sheath. C. Pig.— The articular surface of this bone resembles that of Rodents; it is not limited pos- teriorly by a subcondyloid eminence, and, in addition, offers a wider transverse surface. The zygomatic process articulates with the jugal bone by the wliole extent of its posterior border. A crest leading from the external auditory hiatus to the mastoid pro- The mastoid crest is, as in the Ox, confounded with head of the rabbit (antero-lateral face). 1, Occipital bone ; 2, parietal ; 3, tym- panic bulb ; 4, auditory canal ; 8, 8, nasal bones; 9, supermaxilla; 10, pre- maxilla; 11, inferior maxilla. tuberance replaces the mastoid process, the superior root of the zygomatic process. D. Carnivora. — In tlie Carnivora, the articular surface of the zygomatic process merely forms a glenoid cavity, into which the condyle of the msixillary bone exactly fits. Tlie temporal bone in these animals is alsodistinguisliedby the width of the externul auditorv canal, the absence of a liyoid prolongation, the small development of the mastoid and styloid pro- cesses, the enormous volume of the mastoid protuberance, and the presence of two particnlar canals which cannot be traced in the other animals. One of them— the carotid mmni-tra verses the mastoid portion, and joins, superiorly, the venous canal which passes between the basilar process and the temporal bone ; by its inferior extremity it joins the carotid foramen, which itself pern tiates the cranium, a little beyond the venous canal just mentioned. The other conduit is pierced in the petrous portion immediately above the carotid canal ; it affords a passage to tlie fifth pair of cranial nerves. E. Rabbit. --Tlie squamous portion is circular, and has a shoit process flattened from before to behind at its base, and from side to side at its extremity. The articular surface is TBI, HEAD. 63 concave transversely, and elongated from before tobeliind. The petrous portion has a consider- able tympanic bulb applied closely to the auditory canal, which is large and obliquo behind. The mastoid process is a simple crest situated above the auditory canal ; the hyoid prolongation is absent. Bones of the Pace. The face is much more extensive than the cranimn in the majority of the domesticated animals, and is composed of two jmvs — a bony apparatus that serves as a support to the passive organs of mastication — the teeth. The superior or anterior jaiv, traversed in its entire length by the nasal cavities, is formed by nineteen flat bones, only one of which, the vomer, is a single bone. The pairs are : the superior and intermaxilJaries (or premaxillaries), the palate, piterijgoid, malar, lachrymal, nasal, and superior and inferior turbinated hones. Of these only four — the maxillaries — are intended for the implantation of the teeth ; the others form the union between the cranium and the superior maxilla, or concur in the formation of the nasal cavities. The loiver jaw has for its base a single bone — the inferior maxilla, or maxillary hone. « 1. SuPEEioR Maxillary Bone (Fig. 26). This bone, also named the supermaxillary hone, the most extensive in the upper jaw, is situated on the side of the face, and is bordered above by the frontal, palate, zygomatic, and lachrymal bones ; below, by the premaxillary bones ; in front, 'by the nasal bone ; behind and within, by that of the opposite side. It is elongated vertically, is irregularly triangular, and exhibits two faces, two borders, and two extremities. Faces. — The external face, which is more convex in the young than the old animal, presents : 1. On the level of the fourth and fifth molar teeth, a vertically elongated ridge which is continued above with the inferior border of the zygomatic bone ; this is the maxillary spine. 2. The inferior orifice of the maxillo-dental canal, or infra-orbited foramen. The internal face concurs in forming the external parietes of the nasal cavities. We observe, above and in front, a deep, wide, and diverticulated excavation, forming part of the maxillary sinus ; above and behind, a surface roughened by fine lamellffi and denticulations to correspond with the palate bone, and traversed from above to below by a fissure which forms, in uniting with a similar fissure in the latter bone, the pcdatine canal. For the remainder of its extent it is unequally smooth, covered by the membrane of the nose, and divided into two surfaces by a slightly vertical and sinuous crest that affords attachment to the maxillary turbinated bone : the anterior surface, which responds to the middle meatus of the nasal fossa, shows the lower orifice of the osseous lachrymal canal continued by a fissure to the lower extremity of the bone ; the posterior surface belongs to the inferior meatus. From this face is detached, near its inferior border, a wide and long vertical plate, which forms, in Man and short-faced animals, a simple process — t\iQ palatine process. This plate, uniting in the middle line with that on the opposite side, concurs in forming the greater portion of the palatine arch. It shows : an anterior slightly concave face, forming the floor of the nasal fossae ; a posterior face, buccal, furrowed by small fissures, perforated by fine openings, and traversed along its length by a somewhat wide groove — the pcdatine fisstfre, which commences above at the lower orifice, of the palatine canal ; a denticulated border 61 THE BONES. which articulates with a similar border on the palatine process of the opposite side. Borders. — The anterior, thin and convex, is divided into two parts : an inferior, which is mortised to receive the external border of the nasal bone and the external process of the premaxilla ; and a superior, cut in a wide bevel, at the expense of the external plate, to respond to the lachrymal and zygomatic bones. The external border is very thick, and hollowed into six large quadrilateral cavities, named alveoli, in which are implanted the molar teeth. Above the last alveolus it forms a rugged eminence designated the alveolar tuberosity ; below the first alveolus it becomes thin and sharp, and constitutes part of the interdental space {diastema) which separates the molar from the incisor teeth. Extremities. — The superior is the thickest, and represents a smooth rounded protuberance, into the interior of which the maxillary sinus is prolonged. Above and within this eminence is a wide and deep excavation, in the formation of which the palate bones participate. This is the maxillary hiatus, situated directly opposite the orbital hiatus. At the bottom of this cavity is seen the nasal foramen, as well as the upper orifice of the infra-orbital and the palatine canals. The nasal foramen belongs to the palate bone, and enters the nasal cavity. The infra-orhital cayial traverses the maxillary sinus in passing above the roots of the molar teeth, and terminates by two branches — one, short and wide, which opens on the external surface of the bone, on a level with the third molar ; the other, very narrow, continues the course of the canal in the substance of the bone, and is prolonged by several small, very fine branches into the premaxillary bone. The palatine canal, channeled between the super- maxillary and the palate bone, extends from the maxillary hiatus to the palatine fissure. The inferior extremity presents a cavity which forms the alveolus of the tusk, by uniting with a similar space in the premaxillary bone. Structure and develojyment. — This bone is developed from a single nucleus, and is the more spongy- — particularly towards the alveolar border and the superior extremity — as the animal is young. Differential Characters in the Superior Maxillary Bone of the other Animals. A. Ox, Sheep, Goat. — In the Ox, Sheep, and Goat, the maxillary spine does not directly join the zygomatic crest ; a curved line, with concavity posterior, effects the union between these two parts. The inferior oriiice of the infra-orbital foramen is pierced above the first molar tooth. There is no fissure for the formation of the palatine canal. Tlie cavity of the sinus is more spacious than in the Horse, and is prolonged (in the Ox only) between the two laminae of the palatine roof. There is no alveolus for the tusk. B. Camel. — Not so long or wide as in the Horse and Ox, the supermaxilla of the Camel is deeply excavated iibove the forehead and the orbit. The maxillary spine is replaced by a round and i?mooth prominence, which disappears at the inferior opening of the superior dental canal, pierced above the interval separating the second from the third molar. The posterior face of the palatine process is narrow, has no palatine fissure, but shows the orifice of the palatine canal. C. Pig. — In the Pig, the external surface of this bone is hollowed in its middle, and presents in front a voluminous relief formed by the alveolus of the canine tooth. The cavity is entirely formed in the supermaxilla. There is no alveolar tuberosity, and the interdental spaoe is very short, while the cavity for the sinus is little developed. The lower orifice of the palatine canal is even pierced in the substance of the supermaxilla. D. — Dog, Cat. — In Carnivora, this bone is very short; its anterior border offers a long process analogous to the nasal spiiie of Man. It alone furnishes the alveolus of the tusk. The palatine canal, pierced entirely in the bone of that name, nevertheless opens, by its TBE HEAD. 65 inferior extremity, at tlie junction of the supermaxilla with the palatine bone. The maxillary sinus is not very spacious, and there is no maxillary spine (Fig. 29). E. Rabbit. — The superior maxilla in this animal is less extensive, proportionately, than that of the other animals. The external table is thin, and even cribriform. The malar tubercle is narrow and directed outwards. The palatine process is very narrow, and therefore only very slightly concurs in the formation of the arch of the palate ; it does not extend to the summit of the internal process of the incisive bone (Fig. 36). Fig. 37. ox's HEAD (POSTERIOR FACE), A, Parietal bone: 1. occiintal foramen; 2, occipital condyle; 3, styloid process of that bone; 4, condyloid foramina; 5, mastoid process; 6, mastoid protuberance; 7, subuliform (temporal) process; 8, hyoideal sheath ; 9, stylo-mastoid foramen ; 10, external auditory hiatus ; 11, inferior orifice of the" parieto-temporal canal; 12, temporal condyle; 13, posterior foramen lacerum ; 14, oval foramen ; 17, subsphenoidal process ; 18, orbital hiatus ; 19, optic foramen. B, Frontal bone : 20, supra-orbital foramen ; 21, orbital foramen ; 22, lachrymal protuberance. C, Malar bone : 23, pterygoid bone, d. Palatine bone : 24, nasal foramen ; 25, inferior orifice of the palatine canal. E, Supermaxillary bone : 26, maxillary spine. G, Premaxillary bone : 27, its internal process ; 28, external process ; 29, incisive openings. 2. Premaxillaey, Inteemaxillary, or Incisive Bone (Figs. 26, 38). This bone occupies the inferior extremity of the head, and is composed of a thick prismatic jwrtion, lengthened superiorly by two long processes. Thick portion or base. — This presents a solid mass with three faces : an external or labial, smooth and convex : an internal, denticulated for union with the opposite bone, and traversed from before to behind by an inflexed fissure, which forms, with an analogous one in the other premaxilla, the incisive canal or fora- men incisivum ; the third or posterior, also called the buccal, is slightly concave, and 66 THE BONES. shows the continuation of the foramen. These three faces Fig. 38. POSTERIOR ASPECT OF HORSE'S SKULL. , Occipital tuberosity ; 2, fora- men magnum ; 3, 3, occipital condyles ; 4, 4, styloid pro- cesses ; 5, 5, petrous bone ; 6, basilar process ; 7, pterygoid fissure of the sphenoid bone ; 8, foramen lacerum ; 9, 9, supra- condyloid, or anterior mastoid process ; 10, 10, articular emi- nence, or temporal condyle ; 11, body of sphenoid bone ; 12, ptery- goid process ; 13, ethmoid bone ; 14, temporal bone and sphenoidal sutuie; 15, lachrymal bone; 16, vomer; 17, malar bone; 18, maxillary tuberosity ; 19, pos- terior nares, or guttural opening of the nose ; 20, palatine bone ; 21, palatine styloid process ; 22, palato-maxillary foramen; 23, palatine process of superior maxillary bone, with suture ; 24, ditto of premaxillary bone; 25, premaxillary bone ; 26, upper incisor teeth ; 27, point of junc- tion of the premaxillary with the supermaxillary bone ; 28, up- per molar teeth (young mouth). palatine groove, which terminates in the incisive are separated by as many borders : two internah hmitiug the corresponding face before and be- hind ; and an external, separating the labial from the buccal face. The latter only merits notice. It is very thick, and is divided into two parts : an inferior, which describes a curved line, con- cavity upwards, and is excavated by three alveoli for the reception of the incisor teeth ; another, the superior, is straight, vertical, and somewhat sharp, and forms part of the dental interspace. It is limited above, near the base of the external process, by a cavity for the formation of the alveolus of the canine tooth. Processes. — These are distinguished as external and intei'iial. The first, the longest and strongest, is flattened on both sides ; its external face is smooth, and continued with that of the thick por- tion of the bone ; its internal face is covered by the mucous membrane of the nose ; the anterior border is smooth and rounded ; the posterior, denticulated to respond to the supermaxillary bone, is in contact with the external border of the base ; its summit is thin, and is insinuated between the latter and the nasal bone. The internal {ox palatine) process, the smallest, is flattened from before to behind, and forms a very thin tongue of bone, sepa- rated from the other portions by a narrow and very deep notch, named the incisive opening or cleft. Its inferior face constitutes a small portion of the floor of the nasal fossae ; the posterior, continuous with the same face of the principal mass of the bone, forms part of the palatine roof ; its external border circumscribes, inwardly, the incisive opening ; the internal is united by dentated suture with the opposite bone. Structure and development. — It is a spongy bone, developed from a single nucleus. Differential Characters in the Premaxillary Bone OF OTHER Animals. A. Ox, Sheep, Goat (Fig. 37).— Tlie iuferior or prin- cipal portion of this bone is flattened befure and behind, and deprived of alveoli in its external border; neither is there any incdsive foramen. It is rarely consolidated with the adjacent bones, and is never, in the smaller Ruminants (Sheep and Goat), articulated with the nasal bone by the summit of the external process. B. Camel. — By its form, tlie premaxillary bone much resembles that of the smaller Ruminants. Its base is not so wide, but it is thicker than in the Ox. This base is rugged in its lower surface, and excavated by an alveolar THE HEAD. 67 cavity. The incisive opening is very small, and the external process does not reacli the nasal bone. C. Pig. — In the Pig, the external process of tlie premaxillary bone is very long and wide at its base, and consolidated with the nasal bone fur about the upper two-thirds of its length. There is no incisive foramen or cavity for the tusk. The incisive openings are oval. D. Dog, Cat. — Of small size, the premaxilla of Carnivora has no incisive foramen or alveolar cavity for the canine tooth. The incisive open- ings are the same as in the Pig. Fig. 39. E. Rabbit.— Proportionately voluminous, the pre- r ^ maxilla of the Rabbit is remarkable for the great de- '^ ^ velopnient of its ascending processes, which reach the _ ^ {^mWI^^S^^ f frontal bone, and the width of the incisive slits, which are conlounded above the internal processes. It carries two incisors, placed one before the other. 3. Palatine Bones (Fig. 38). The folate or palatine hones are situated be- tween the supermaxillaries, at the margin of the guttural opening of the nasal cavities, and are articulated with the sphenoid, ethmoid, vomer, frontal, and pterygoid bones. Elongated from above to below, flattened laterally, and curved towards each other at their inferior extremity, which is flattened from before to behind, these bones, though irregular in shape, offer for study two faces, tivo herders, and two extremities. Faces. — The external face of the palate bone is divided into three fractions — a superior, or orbital, an inferior, or palatine, and a middle, or articular. The first is smooth and slightly ex- cavated, and participates in the formation of the maxillary hiatus ; it shows a small groove, the staphyloid, which reaches the palatine fraction in passing between the posterior border of the bone and the alveolar tuberosity. The second is not extensive, and looks backwards in conse- quence of the antero-posterior flattening which the bone presents at its inferior extremity ; it forms part of the roof of the palate. The third presents a lamellar and denticulated surface which corresponds to a similar face on the superm axillary bone, and is channeled from above to below by the internal groove of the palatine canal. The interned face, smooth and concave, forms part of the external wall and the floor of the nasal fossa. Borders. — The anterior is indented, near its superior third, by a deep notch, which is often converted into a foramen, the nasal. Below this notch the bone is thin and denticulated for union with the supermaxillary bone ; above, its two plates separate widely from one another, giving rise to a very spacious cavity HEAD OF THE PIG (POSTERIOR FACE). 1, Occipital tuberosity ; 2, occipi- tal foramen; 3, occipital con- dyle; 4, condyloiil foramen; 5, basilar process ; 6, 6, mastoid crest; 7, styloid process of the occipital bone ; 8, articular surface of the temporal bone ; 9, mastoid protu- berance ; 10. foramen lacerum ; 1 1, subsphenoidal process — external wing of pterygoid process ; 12, palatine crest ; 13, pterygoid bone (internal wing of the ])terygoid process) ; 14, inferior orifice of the palatine canal ; 15, 15, incisive openings. TEE BONES. which forms part of the sphenoid sinus. The posterior border presents, above, a rugged crest called the palatine, flattened from side to side, bent outwards, and bordered at its base and inwards by a very narrow synarthrodia! surface, which responds to the pterygoid bone. It is smooth and concave in its inferior half, and forms, with that of the opposite side, a parabohc arch (palatine arch) which circumscribes, below and at the side, the double guttural orifice of the nasal cavities. Extremities. — The superior, flattened on both sides, is bevelled on the external side to articulate with the subsphenoidal process. The inferior, flattened from before to behind, is curved inwards and united by simple suture with that of the opposite bone. Structure and deveJopment. — This is a very com- pact bone, developed from a single centre of ossifi- cation. Differential Characteks in the Palatine Bone in OTHER Animals. The principal distinctive feature of this bone in the different domestic animals is due to the part it takes in forming the arch of the palate. In this respect there are very great differ- ences in various species, but in none of them is tliis part so reduced as in Solipeds, in which the bone is scarcely equal to one-fifth of tlie palatine surface. A. Ox, Sheep, G-oat. — Tlie palatine bone in these animals is very developed, and noticeable for the considerable extent of the palatine portion of its external surface. The palatine canal is entirely channeled out in its substauce. The palatine crest, very thin and elevated, is formed altogether by the posterior border of the palate bone, the pterygoid, and the subsphenoidal process. There is no excavation for the sphenoidal sinuses ; but, instead, all that part of the bone which enters into the roof of the palate is hollowed, but in the Ox only, by irregular cavities which communicate with the maxillary sinus of the same side. The nasal foramen is very wide. B. Camel. — The staphyline fissure is wide and deep ; the palatine crest is very developed, and has two rugged depressions at its base. The palatine canal is not included in the palate bone ; it opens at the second molar. C. Pig. — The palatine portion is leas developed than in Ruminants, for it forms less tlian one-fourth of the palatine arch ; on the other hand, the orbital portion is very limited. The palatine crest is rt-placed by a tuberosity, against which rests, outwardly, the subsphenoidal process, and inwardly the pterygoid bone. The union of these three parts constitutes, on tlie posterior surface of the head, a thick and very remarkable trifid projection or mamelon. D. Dog, Cat.— It is in the Carnivora that the palatine bones are of greatest extent in their proper palatine portion, as they constitute nearly one-half of the palatine arch. They have no share in t)ie formation of the sphenoidal sinuses, but furnish a small excavation to the maxillary sinuses. E. Rabbit. — The palatine bones resemble those of the Horse, with regard to the part they play in forming the palatine arch. The palatine canal opens also between the palatine and superior maxillary bones, but the palatine crests are proportionately more developed than in Solipeds (Fig. 35). dog's head (posterior face). 1, Occipital tuberosity ; 2, occipital foramen ; 3, occi- pital condyle ; 4, condyloid foramen ; 5, styloid process of the occipital ; 6, mastoid protuberance ; 7, concave temporo-maxillary articular surface ; 8, supra-condy- loid eminence ; 9, inferior orifice of the parieto-tem- poral canal ; 10, posterior foramen lacerum ; 11, ditto, anterior. On the op- posite side at a is shown the orifice communicating with the Eustachian tube and the tympanum ; at h the passage for the carotid loop. 12, Body of the sphenoid ; 13, oval fora- men ; 14, inferior orifice of the subsphenoidal canal ; 15, pterygoid bone; 16, nasal surface of the palate bone; 17, palatine surface of the same; 18, vomer; 19, supermaxillary bone ; 20. incisive opening. THE HEAD. 69 4. Pteeygoid Bone (Figs. 34, 38).* A small and very short bone, elongated from above to below, flattened on both sides, and situated on the inner aspect of the subsphenoidal process, but external to the vomer. Its external face is in contact with the palate and sphenoid bones ; the internal is smooth, and covered by the pharyngeal mucous membrane. Its superior extremity is tapering, and concurs in forming the Vidian canal ; the inferior is thickened into a small pointed process (the hamular process), the apex of which, directed backwards, offers outwardly a groove which serves as a pulley to the tendon of the tensor palati muscle. This bone is composed entirely of compact tissue, and is developed from a single centre of ossification. Differential Characters in the Pterygoid Bone of other Animals. A. Ox, Sheep, Goat. — The pterygoid of the Ox, Sheep, and Goat is very wide, and closes an aperture left between the s|ihenoid and palatine bones. B. Camel. — In the Camel the pterygoid is short, broad, and applied to the internal face of the subsphenoidal process and palatine crest. It does not concur in the formation of the Vidian canal. Its inferior extremity has a narrow and deep fissure. C. Pig. — (See the description of the palatine bone.) D. Camivora. — This bone is very strong in Carnivora, and quadrilateral in shape. 5. Malar or Zygomatic Bone (Figs. 26, 34). This bone, also -designated the juf/al bone, is elongated from above to below, flattened on both sides, and irregularly triangular in shape ; it is situated on the side of the face, and articulates with the supermaxillary, lachrymal, and temporal bones. It is described as having tivo faces, two borders^ a base, and a summit. Faces. — The external face comprises two portions separated from each other by a semicircular ridge that extends from the summit to the middle of the anterior border of the bone, and concurs to form the outer margin of the orbit. The anterior portion, smooth and concave, belongs to the orbital cavity. The posterior, more extensive, is also smooth and slightly convex. The internal face is excavated in its central part, which corresponds to the maxillary sinus. On its margin it shows denticulations and lamellae for articulation with the super- maxillary bone. Borders. — The cmterior, thin and denticulated, is joined to the lachrymal bone. The posterior, or masseteric border, is thicker, and constitutes a roughened crest, the zygomatic ridge, which is continued above with the posterior border of the process of the same name, and below with the maxillary spine. Base and summit. — The base, very thin, is united to the supermaxillary bone. The summit, flattened from before to behind and bevelled on its anterior face, joins the zygomatic process, and forms with it the j'l/gal bridge, or zygomatic arch. SU-ucture and development. — This bone is rather spongy in its upper part, and is developed from a single nucleus of ossification. Differential Characters in the Malar Bone op other Animals. A. Ox, Sheep, Goat. — The malar bone of Kuminants is very developed. The zygomatic crest is no longer formed by the posterior border of the bone, but is carried to the posterior part of the external face, and runs parallel with the eyebrow. The summit is bifurcated, the ' This bone is the representative of the internal wing of the pterygoid process in Man. 70 THE BONES. anterior branch forming a buttress against tlie summit of tbe orbital process of the frontal bone, while the posterior articulates with the temporal. In these animals, the bone offers several centres of ossification. B. Camel. — This bone is very little developed, aud is compressed from before to behind^ Its anterior face is very concave, and circumscribes the orbit posteriorly. Its posterior face considerably overhangs the maxillary bone, and forms a very salient zygomatic crest. The summit is bifurcated, as in the Ox. C. Pig. — The summit of this bone in the Pig is flattened on each side, and divided inta two brandies, between which is wedged the summit of the zygomatic process ; the anterior branch is very sliort, and does not join the frontal bone. D. Camivora.— The malar of the Dog and Cat only articulates with the supermaxillary bone, and by its base alone. The crest describes a curve, the concavity backwards, and the summit comports itself as in the Pig. F. Rabbit. — The bone is flattened on both sides ; the summit, united with the zygomatic process of the temporal bune, is single ; while the base is confounded entirely with the malar tuberosity (Fig. 36). 6. Lachrymal Bone (Figs. 26, 51). A small, thin, and very light bone, bent on itself at a right angle, it is situated beneath the orbit, which it aids in forming, and is wedged between the frontal, nasal, snpermaxillary, and malar bones. It is studied on its external and internal faces and circumference. Faces. — The external is divided into two regions, superior and inferior, by a curved crest which forms part of the orbital margin, and is provided with notches, which are variable in their form and number. The superior region, named the orbital, because of its situation in the orbit, is slightly concave and smooth. It presents, near the orbital margin, the orifice of the laclirynud diict, which traverses the maxillary sinus and opens on the internal face of the super- maxillary bone, where it is continued by a fissure ; behind this is the lachrymal fossa. The inferior ov facial region is slightly bulging, and provided sometimes with a tubercle for insertion, — the lackrymal tubercle. The internal face is employed, for the whole of its extent, in the formation of the walls of the maxillary and frontal sinuses ; it exhibits a cylindrical prominence produced by the bony tube of the lachrymal duct. Circumference. — This is very irregular, and denticulated for articulation with the neighbouring bones. Structure and development. — This bone is entirely compact, and is developed from a single nucleus of ossification. In the Ass, the lachrymal tubercle is placed towards the anterior border of the bone ; usually, it partly belongs to the nasal bone, and is consequently found on the suture uniting the lachrymal bone to the proper bones of the nose. Differential Chakactebs in the Lachrymal Bone of other Animals. A. Ox, Sheep, Goat.— The lachrymal bone, much more extensive than that of tlie Horse, forms in tlie bottom of the orbit an enormous protuberance, hollowed internally by the maxillary sinus, and the walls of whicii are so thin and fragile that the slightest jar is sufficient to cause their fracture (in the skeleton). It would be convenient to designate it the lachrymal protuberance.^ In the smaller Kuminants, the inferior region of the internal face shows a depression — the lachrymal fossa. B. Camel.— This bone is much smaller than in the Horse ; its facial portion especially Is almost rndimi ntary. There is no lachrymal protuberance nor tubercle, the latter being carried to the superior maxilla. C. Pig.— In the Pig there are observed a lachrymal fossa and two lachrymal canals, which ' Girard, who named this eminence the orbital protuberance, wrongly described it as; belonging to the supermaxillary bone. THE HEAD. 71 are pierced outside the orbital cavity, and soon coalesce in the substance of the bone to constitute a single canal. The fossa is very deep. D. Camivora. — This bone in Carnivora is extremely small. Its external face entirely belongs to the orbit, and does not descend beneath the margin of tliat cavity; it has no lachrymal fossa. The reduced dimensions it presents in these animals well justifies the name, OS unguis, given to it in anthropotomy. 7. Nasal Bones (Fig. 26). Situated on the anterior aspect of the head, these bones articulate with each other in the median hne, and are fixed between the frontal, lachrymal, and super- maxillary bones ; they are triangular in shape, elongated from above to below, flattened from before to behind, and offer for study two faces, two borders, a base, and a summit. Faces. — The external or anterior face, wider above than below, is convex from side to side, and almost smooth. The posterior, internal, or nasal face exhibits a vertical crest passing along the external border of the bone, which gives attach- ment to the turbinated portion of the ethmoid ; at its superior extremity this crest bifurcates, and between its two branches shows a concave surface which forms part of the frontal sinus. For the remainder of its extent the internal face is smooth, and' covered by the mucous membrane of the nasal fossa ; it is also excavated into a channel to form the superior meatus of this cavity. Borders. — The extermd border is very thin in its upper two-thirds, and articu- lates with the lachrymal bone, the anterior border of the supermaxillary, and the extremity of the external process of the premaxilla. In its lower third it becomes isolated from the latter bone, in forming with the anterior border of its large pro- cess a very acute re-entering angle, the opening of which looks downwards. The interned border is denticulated for contact with the opposite bone. Base and Summit. — The base occupies the superior extremity of the bone ; it describes a curved line with the convexity above, and, in uniting on the median line with that of the opposite bone, forms a notch similar to that of the heart figured on playing-cards ; it is bevelled, at the expense of the internal plate, to articulate with the frontal bone. The summit of the two nasal bones, which is pointed, constitutes the nasal prolongation — the name given to a single triangular process which comprises all that portion of the nasal bones separated from the premaxillaries by the re-entering angle before mentioned. Structure and development. — Almost entirely compact in structure, it is developed from a single centre. Differential Characters in the Nasal Bones of other Animals. A. Ox, Sheep, Goat. — The nasal bones of the Ox are never consolidated with each other, nor yet with the neighbouring bones. The external border only comes in contact to a small extent with the supermaxillary bone ; the superior extremity is fixed in the notch of the inferior border of the frontal bone. At their inferior extremity, they each present a notch which divides them into two points. In the Sheep and Goat the nasal spine is unifid, as in the Horse (see Figs. 30, 32). B. Camel. — In the Camel, the proper bones of the nose are short and narrow; their external border is in contact only with the superior maxilla; the upper extremity is rounded. At the inferior extremity, they show a well-marked notch, which divides them into two points, but the inner point is very small. C. Pig. — Tliese bnnes are long and narrow, and traversed on their external face by the fissure that descends from the supra-orbital foramen. The nasal prolongation is short. D Carnivora.— The two bones of the nose are little developed, and are wider below than above ; they have no nasal prolongation, but offer, instead, a semicircular notch. THE BONES. E Rabbit.— Proportionately long and wide, the nasal bone of the Rabbit articulates, by the whole of its external border, with the ascending process of the preuiaxillary bone. The anterior extremity of the nasal bone is very slightly salient. Fig. 41. Fig. 42. LONGITUDINAL AND TRANSVERSE SECTION OP THE horse's head, SHOWING THE FLOOR OF THE CRANIAL AND NASAL CAVITIES, WITH THE MAXILLARY SINUSES. 1, Condvloid foramen. 2, Section of the parieto tem[ioval canal. 3, Foramen lacerum basis cranii. 4, Carotid notch. 4', Maxillary notch: o,supermaxillary fissure ; 6, cavern- ous fissure. 5, Origin of the supra-sphe- noidal canals : c, sella Turcica. 6, Optic fossa. 7, Portion of the crista-galli process. 8, Cribriform plate of the ethmoid bone. 9, Perpendicular plate of the s^ame bone. 10, 10, Its lateral masses. 11, Interior of the great ethmoidal cell. 12, 12, Bottom of the maxillary sinuses communicating with the sphenoidal sinuses. 13, Superior maxillary sinus. 14, Inferior maxillary sinus. 14', Superior compartment of the maxillary turbinated bone, forming part of the latter sinus. 15, Section of ttie supermaxillo- dental cannl. 16, Channel of the vomer. 17, Internal proc.'ss, or point of the pre- maxillary bone. ANTERO-POSTERIOR AND VERTICAL SECTION OF THE HORSE'S HEAD. 1, Condyloid foramen ; 2, parietal protuberance ; 3, internal audi- tory hiatus ; 4, cerebral cavity ; 5, cerebellar cavity; 6, supe- rior border of the perpendicular plate of theethmoidbone(crista- galli process) ; 7, ethmoidal volutes — nasal face; 8, vestiges of the right frontal sinus; 9, ditto of the sphenoidal sinus ; 10, pterygoid process; 11, eth- moidal turbinated bone; 12, maxillary turbinated bone ; 13, crest of the supermaxillary bone to which the latter is fixed ; 14, vomer. A, Orifice of communication between the nasal cavity and the sinus. THE BEAD. 73 TUEBINATED BONES (Fig. 42). The turlinated (or turUnal) hones, two on each side, represent two irregular bony columns, wider above than below, compressed laterally, hollowed internally, and lying vertically side by side on the external wall of the nasal fossa, which they divide into three meatuses or passages. They are distinguished into anterior and posterior turbinated hones. The anterior or superior, also named the ethmoidal, is formed by a very thin plate of compact tissue— fragile and like papyrus, fixed by its anterior border to the internal crest of the nasal bone, and rolled on itself, from before to behind, in the same manner as the cells of the ethmoid bone. Above, it is confounded with the last-named bone, of which it is only, properly speaking, the most anterior volute. At its inferior extremity, it is prolonged by a fibro-cartilaginous frame- work to the external orifice of the nose. Its internal cavity is partitioned by a transverse plate into two portions : the superior compartment forms part of the frontal sinus ; the inferior is subdivided by other small lamellEe into a variable number of cells which communicate with the nasal cavity. This bone, developed from a single nucleus, is ossified at the same time, and in the same manner, as the ethmoidal cells. Before birth, it is already intimately consolidated with the nasal bone. The posterior, inferior, or maxiUary turbinated hone resembles the first, except in some particulars. Thus, its bony or proper portion is not so long or volu- minous, while its cartilaginous part is, on the contrary, more developed. It is attached, by its posterior border, to the vertical and sinuous crest of the super- maxillary bone, and is rolled from behind to before, or in an inverse direction to the other. It has no connection with the ethmoid, and its superior cavity forms part of the inferior maxillary sinus. It is late in becoming ossified, and is scarcely united in a definite manner to the maxillary bone until the horse is about a year old. The meatuses are distinguished into anterior or superior, middle, and posterior or inferior. The first passes along the front of the ethmoidal turbinated bone ; the second separates the two turbinated bones, and presents, near its superior extremity, the opening communicating between the sinuses and the nasal cavities.^ The third is situated behind the maxillary turbinated bone, and is confounded with the floor of the nasal fossa. The turbinated bones are essentially disposed to furnish the membrane of the nose with a vast surface of development. This membrane, indeed, covers their entire superficies, and even penetrates the anfractuous cells of their lower compartment. Differential Characters in the Turbinated Bones of other Animals. A. Ox, Sheep, Goat. — In the Ox (Fig. 43), the ethmoitlal turbinated bone is very small, and is united to the nasal bone bv the two borders of its osseous plate ; its internal cavity entirely belongs to the frontal sinus. The maxillary turbinated bone is very developed, and is joined to the bone which sustains it at a later period than in the Horse. The bony lamina of which it is composed, is curved on itself in two different directions — from before to behind by its posterior border, and behind to before by its anterior border. It is fixed to the supermaxillary bone by its middle part, through the medium of a particular bony lamina, and it very incom- ' The two turbinated bones, in being applied against the excavation on the inner face of the supermaxillary, almost entirely close it, only leaving between them a vertical slit which con- stitutes the opening mentioned above. 74 THE BONES. pletely closes the excavatioh which coucurs to form the maxillary sinus. In the skeleton there is also found behind, and at the base of this turbinated bone, a vast opening which is totally closed in the fresh condition by the pituitary membrane. The maxillary sinus is not prolonged in its interior. In the smaller Euminants, tlie cavity of the sinus is closed by the maxillary turbinated bone in a more complete manner than in the Ox. B. Camel. — The ethmoidal turbinated bone is very small. Otherwise it is as in the other Ruminants. C. Pig. — The same arrangement as in tlie Sheep and Goat, except that the bones are mucli longer and less fragile. D. Carnivora.— These bones in tlie Dog and Cat are particularly distinguished for their numerous cou- volutions. Neither participate in the formation of the frontal or maxillary sinuses; the latter is not in any way closed by the maxillary turbinated bone, but opens into the nasal cavity by a large gaping aperture. E. Rabbit. — The bones are arranged as in the Dog, but the folds are less numerous. 9. VoMEE (Figs. 34, 38). This, a single bone, elongated from above to below, flattened on both sides, and extending on the median line from the body of the sphenoid to the premaxillary bone, offers for study two lateral faces, two borders, and two extremities. The faces are smooth, plane, and covered by the nasal membrane. The anterior border is channeled for the whole of its length by a deep groove, which receives the posterior border of the cartilaginous septum of the nose. The posterior border is sharp and smooth in its upper half, which separates the two guttural openings of the nasal cavities : it is thick and slightly denticulated for the remainder of its extent, and rests on the median suture resulting from the union of the two supermaxillary bones. The superior extremity is provided, in its middle, with a notch which divides it into two lateral prolongations shaped like a cat's ears {wings of the vomer) ; it articulates with the inferior sphenoid, ethmoid, palatine, and pterygoid bones. The inferior extremity rests on the prolongations of the premaxillae. This bone is entirely compact, and is developed from one centre of ossification. MEDIAN AND VERTICAL SECTION OF THE ox's HEAD. X, Condyloid foramen; 1', posterior ori- fice of the occipital lateral canal joining the parieto-temporal canal in front ; 2, internal auditory hiatus ; 3, anterior foramen lacerum ; 4, pos- terior ditto ; 5, iutra-cranial orifice of the parieto-temporal canal ; 6, 6, median bony plate separating the frontal sinuses ; 7, lamina which iso- lates the sphenoidal sinus; 8, lamina partitioning the palatine portion of the maxilliary sinuses ; 9, oval fora- men; 10, optic fossa; 11, vomer; 12, pterygoid bone ; 1.3, large open- ing leading into the maxillary sinus, and which, in the fresh state, is closed by the pituitary membrane ; 14, max- illary turbinated bone; 15, ethmoidal turbinated bone; 16, great ethmoidal cell. Differential Characteks in the Vomer of OTHER Animals. A. Ox, Sheep, Goat. — This is a very wide and thin bone, resting only on the lower half of the median suture of the premaxillaries (Fig. 43). B. Camel.— Wider in its upper part than in the Ox, the vomer reaches, outwardly, the THE HEAD. 75 orbital cavity. By its inferior border, it rests on the entire length of the median suture of the palatine and superraaxillary bones. C. Pig. — The vomer in this animal adheres to the bones of the palatine arch for a great extent. The free portion of the inferior border is short and but little prominent. D. Camivora.— In the Dog and Cat, the vomer is short, but its wings are very large. 10. Inferior Maxillary Bone (Fig. 44). The inferior maxillary hone is not consolidated with any of the preceding bones, and is only united to two of them — the temporals — by diarthrodial articulation. It is a considerable bone, situated behind the upper jaw, and composed of two symmetrical branches, which are flattened on both sides, wider above than below, curved forwards in their upper third, joined at their lower extremities, and separated superiorly so as to leave a wide gap between them, like the letter V in shape, called the intra-maxillary space. Each offers for study tivo faces, two borders, and two extremities. Faces. — The external face of the maxillary branches is smooth and rounded in its inferior two-thirds, and transformed superiorly into a rugged surface, in which is implanted the fibres of the masseter muscle. The internal face presents, in the corresponding point, an excavated surface on which is remarked the superior orifice of the maxillo-dental caned, a long channel which descends between the two plates of the branch, passing under the roots of the molar teeth, and insensibly disappearing in the body of the bone after being widely opened externally by the mental {ov anterior maxillary) foramen. In its inferior two-thirds, the internal face is smooth, nearly plane, and shows nothing very remarkable. Near the alveolar border there is a slightly projecting line — the myloid ridge ; and quite below, or rather at the very summit of the re-entering angle formed by the separation of the branches, there is a slight rugged excavation confounded with that of the opposite branch, and named the ye)iicd surface. Borders. — The anterior, also named the alveolar border, exhibits for study a straight or inferior, and a curved or superior portion. The first is hollowed by six alveoU to receive the inferior molar teeth. The second, thinner, concave, and rugged, serves for muscular insertion. The posterior border is also divided into straight and curved portions. The latter is convex, thick, rugged, and margined on each side by an uneven lip ; the first is regularly rectilinear, so that all its points rest at the same time on a horizontal plane ; it is thick and rounded in the young animal, but becomes sharp with age ; an oblique and transverse fissure — the maxillary — separates it from the curved part. The union of these two portions forms the angle of the jaw. Extremities. — The superior e.vtremity has two eminences : a condyle, and a long non-articular process named the coronoid process. The condyle is elongated transversely, and convex in its two diameters ; it responds, through the medium of a fibro-cartilaginous disc, to the articular surface of the zygomatic process. ■ The coronoid process is situated in front of the condyle, from which it is sepa- rated by a division called the sigmoid or corono-condyloid notch ; it is flattened on both sides, and curved backwards and slightly inwards. From the union of the branches of the maxillary bone at their inferior extremity, results a single piece, flattened before and behind, and widened like a spatula, which has been designated the body of the bone. This merits a special description. Its form allows us to divide it into an anterior or buccal face, a posterior or 76 THE BONES. labial face, and a circumference. The anterior face is smooth and concave, is lined by the buccal mucous membrane, and supports the free extremity of the tongue. The posterior face is convex, more extensive than the preceding, and continuous with the external face of the branches. It presents : 1. On the median line, a slight crest or small groove— traces of its being originally separated into two pieces. 2. On the sides and above, the mental foramen — the inferior orifice of the maxillo-dental canal. On a level with this foramen, the bone very markedly contracts to form the neck. The circumference describes a parabolic curve, the concavity being uppermost, and joins, by its extremities, the anterior border of each branch. It is excavated in its middle part by the six alveoli for the lodgment of the inferior incisors, and behind these— in male animals only— there is an additional alveolus for the tusk. The portion included on each side Fig. 44. INFERIOR MAXILLA. 1, Mental foramen; 1', superior orifice of the maxillo-dental canal ; 2, surface of implantation for the masseter muscle ; 3, myloid ridge ; 4, coronoid process ; 5, condyle. between the last incisor and first molar, forms a more or less sharp ridge, which constitutes the inferior interdental space or bar {diastema). Structure and development. — Formed, like all the flat bones, by two compact plates separated by spongy tissue, the inferior maxilla is developed from two centres of ossification, which correspond to each branch, and which coalesce some time after birth. But in the human foetus, there can oe seen five pieces developed around the dental canal — the coronary, articular, angular, opercular, and premaxillary — which proves that the maxilla of Mammalia is formed on the same type as that of oviparous Vertebrata (Lavocat). DiFFEKENTIAL CHARACTERS IN THE INFERIOR MaXILLA OP OTHER ANIMALS. A. Ox, Sheep, Goat.— In these animals, the part of the posterior border of the inferior maxilla below the molars is convex, and cannot rest on a horizontal plane by all its points at the same time. The condyle is convex in its small diameter, and slightly concave laterally The coronoid process is bent backwards and outwards. The body does not show any alveolus for the tusk, because this tooth is not present in these animals ; but it is hollowed by eight alveoli for the incisor teeth. The two branches of the bone are never consolidated, but remain movable on each other during life. THE HEAD. 77 B. Camel. — The branches are short and thick, the body very long, and the interdental space considerable. The straight border of tlie branches has a posterior rectilinear border, aa in the Horse ; the anterior margin of the curved portion is tliin and sharp. Oa its internal face is seen a plate in front of the superior opening of the inferior dental foramen, and a mylo- hyoid fissure. The condyle is convex in front, flat and oblique behind. The coronoid process is very strong. Below the condyle is a process separated from the latter by a deep notch. The circumference of the body is excavated by eight alveoli — six for the incisors, and two for the canines. C. Pig. — A straight line leading from the greater axis of the alveoli of the molar would Fig. 45. HEAD OF THE CAMEL. 1, Occipital bone ; 2', parietal crest ; 3, .squamous temporal ; 4, frontal bone ; 4', supra-orbital foramen; 5, malar bone; 6, nasal bones; 7, supermaxillary bone; 7', infra-orbital foramen; 8, premaxillary bone; 9, inferior maxilla; 10, 11, openings of the inferior dental foramen. not traverse the posterior border of the maxillary branches , the bottom of these alveoli corre- sponds to the relief on the iimer face. The condyle is compressed on both sides, and elongated from before to behind; while the coronoid process is short and wide. TIjere is no neck; the interdental spaces are very short ; and the maxillo-dental canal opens inferiorly by multiple orifices. D. Carnivora.— In Carnivore, this is hollowed at the point corresponding to the insertion of the masseter muscle into a somewhat deep fossa. The posterior border is disposed as in Ruminants, and below the condyle lias a very marked tuberosity. The condyle represents an ovoid segment, and fits exactly into the temporal cavity. The coronoid process is very strong, elevated, and wide. The mental foramina are double or treble. There are no interdental spaces, nor excavated surface on the inner face of tlie branches ; and the latter are never consolidated. E. Rabbit. — In the maxilla of the Rabbit, the coronoid process is very short, and the condyle narrow and elongated from before to behind. The posterior border is deeply notched 8 78 THE BONES. HEAD OF THE CAT. Parieto-occipital suture; 2, parietal bone; 3, frontal bone ; 4, orbital piocess of the frontal bone; 5, malar bone; 6, supermaxil- lary bone ; 7, 7, premaxilla ; 8, nasal bone ; 9, tympanic bulb ; 10, inferior maxilla. in its curved portion ; the interdental space is very long ; and the body has only two alveoli for the incisors. 11.— The Hyoid Bone (Fig. 47). The hi/oid bone constitutes a small and special bony apparatus which serves to support the tongue, as well as the Fig- -iS. larynx and pharynx ; its description is placed immediately after that of the bones of the head because of its con- nection with that region, it being situ- ated between the two branches of the supermaxillarybone, and suspended from the base of the cranium in an oblique direction from above to below, and from before to behind. This apparatus is composed of seven distinct pieces, arranged in three series : a middle, constituted by a single bone, and named the body ; two lateral, form- ing two quasi-parallel branches, to the extremities of which the body is articu- lated. Body or basihijal. — The body of the hyoid resembles a fork with two prongs. It presents : 1. A middle part flattened above and below, and consequently provided with a superior and an inferior face. 2. A single and long pro- p's- '*^' longation flattened on both sides, which is de- tached from the middle part, and directed forward and downward to plunge into the muscular tissue of the tongue : this is the anterior appendix of the hijoideaJ body, or Ungual prolongation. 3. Two late- ral cornua, thyroid cornua, great cornua, or urohyals, projecting backwards and upwards, articulating by their extremities with the thyroid cartilage of the larynx, and offering, at their point of union with the middle part, two con- vex diarthrodial facets looking upwards, and corresponding with the styloid cormia. The body of the hyoid bone is developed by three centres of ossification — a middle, and two lateral for the cornua. Branches. — The three pieces composing these are articulated end to end, by HYOID BONE OF THE HORSE. Body or ba^ihyal ; 2, lingual prolongation ; 3. 3, thyi'oid cornua, great cornua, or urohyals ; 4, 4, styloid cornua. small cornua. or apohyals ; 5, 5, styloid nuclei or ceratohyals ; 6, 6, styloids, great hyoideal branches, or stylohyais ; 7, 7, arthrohyals. or cartilaginous nuclei attaching the hyoid to the temporal bone. THE HEAD. 79 means of a cartilaginous substance that joins them together ; they are of very unequal dimensions. The first, which is in relation with the body, is of medium size, and is named the styloid cormi, small conm, or small branch. The second, termed the styloid nucleus, is the smallest. The third, the largest, constitutes the styloid process or bo7ie, or great branch. 1. The styloid cornua {cfpohyaV) is a small cylindrical piece bearing a concave diarthrodial surface on its inferior extremity to unite it to the body ; it is very spongy, and is developed from two ossifying centres, one of which, the epiphysary, is for the inferior extremity. 2. The styloid nucleus {ceratohyal), which is often absent, is embedded in the uniting cartilaginous substance. 3. The styloid bone, or great hyoideal branch {stylohyal), is long, thin, flattened on both sides, and directed obliquely from above to below, and before to behind ; it presents two faces, two borders, and two extremities. The faces — an external and internal — are marked by some few imprints. The anterior border is sharp and slightly concave in its upper third. The posterior border is thicker, and is divided into two portions — a superior or horizontal, which is very short, and an inferior or vertical, much more extensive. The angle they form at their point of junction presents a salient, and more or less roughened, tuberosity. The superior extremity is united to the hyoideal prolongation of the temporal bone by means of a cylindrical fibro-cartilage. By its inferior extremity, the styloid bone is united either to the styloid nucleus or the styloid cornu, forming a sharp elbow directed forwards. The styloid bone, developed from a single centre of ossification, is almost entirely formed of compact tissue. Differential Characters of the Htoid Bone in other Animals. A. Ox, Sheep, Goat. — The hyoid bone of Ruminants is always composed of seven piecea. the styloid nucleus, the presence of which is not constant in Solipeds, is never absent in these,' and has the proportions of the second small branch. The anterior appendix is very short, and only represents a large mamelon. B. Camel. — The liyoid is in this animal as in the Ox. C. Pig.— The body is voluminous and deprived of an appendix; the small branches are short and consolidated with the body ; while the large branches, curved like an S, are very thin, and are not united to the small branches and the temporal bone by libro-cartilage, but by veritable yellow elastic ligaments. D. Carnivora. — The three pieces composing the body of the hyoid in early life are never consolidated in the adult animal, but always remain isolated, as in Man. The middle piece has no anterior appendix; the fibro-cartilages uniting the styloid portions to each other and to the temporal bone are very long and flexible. 12. WoEMiAN Bones (Fig. 48). This name has been given to small irregular bones which Worms observed between some of the sutures of the cranial bones. They are developed after birth, in the cranial, cranio-facial, and facial sutures. Their number and position varies with the species of animals, and even the breeds of the same species. Vaguely described by Rigot, they have been recently studied by Cornevin, who observes that the cranial Wormian bones are rare. In more than sixty crania, they were found only once or twice in the Ox and Horse at the junction of the petrous with the occipital bone. The Wormian bones of the cranio-facial and the facial suture are more frequent ; nevertheless, they have been met with almost exclusively in the heads of common-bred animals, particularly in the bovine species. Cornevin has described a fontanelle lachrymo-nasal bone (Fig. 80 THE BONES. 48, 2), and Wormian fronto-nasal (Fig. 48, 1), as well as an interaasal, orbital, zygomato-maxillary, maxillo-nasal-incisive bone. (Sometimes two Wormian bones are found in the same head.) OP THE HEAD IN GENERAL. 1. Geneeal Configueation. From the union of all the bones which constitute the cranium and faoe, there results a quadrangular pyramid, with summit inverted, which it is necessary to study as a whole. We will pass in ^'S- *^" review, successively, its four faces, its base, and its summit. A. Anterior Face.— This is subdivided into four regions (Fig. 49) : 1. Parietal region. — This has for base the anterior portion of the occipital bone and the parietal bones. Limited, above, by the external occi- pital tuberosity, it presents on the middle line a spur which soon bifur- cates to form the parietal or temporal crests ; the latter join the posterior border of the zygomatic process. i 2. Frontal region. — Larger than^ the preceding, it is usually plane and lozenge-shaped. Boimded iuferiorly by the fronto-nasal suture, this region projects, laterally, the orbital pro- cesses, the base of which is pierced by the supra-orbital foramen, and the anterior border — somewhat sharp— is frequently made irregular by small notches, one of which is often converted into a foramen. 3. Nasal region. — This region has for its base the proper bones of the nose. It is narrow, convex on each side, and plane, concave, or convex in its length, according to the animals. It advances above the entrance to the nasal cavities, where it forms the nasal prolofigation, the summit of which, in the Horse, ceases at nearly two fingers' breadth from the intermaxillary symphysis. 4. Incisive region. — Principally formed by the incisive bones, this region presents : the inferior opening of the nasal cavities, divided in the fresh state by the median cartilaginous septum of the nose ; the incisive slits on the floor of the nasal fossfe ; the intermaxillary symphysis, channeled above by a more or less deep groove in nearly all Horses, but raised, on the contrary, into a conical tubercle in the Ass and Hinny, and perforated in the middle by the incisive canal. Right and left of the intermaxillary symphysis this region is convex, and elevated by the prominence which the roots of the incisor teeth form. B. Posterior Pace. — In this are recognized four distinct regions (Fig. 50) : 1. Sub-occipital region. — This presents : in the middle, the basilar process^ WORMIAN BONES OF THE OX. (AFTER CORNEVIN.) 1, Fronto-nasal Wormian bones; 2, 2, lachrymo- nasal fontanellar bones. THE HEAD. 81 a strong piece more or less deeply channeled, according to the animals, and provided at its inferior extremity with rugosities for the attachment of the anterior straight muscles of the head ; on the sides, the lacerated foramina — large irregular Fig. 49. horse's head (anterior face). 1, Occipital tuberosity ; 2, origin of the mastoid crest ; 3, parietal bone; 4, saggital suture ; 5, junc- tion of the parietal and temporal bones ; 6, zygomatic arch ; 7, frontal bone ; 8, frontal suture ; 9, temporal fossa ; 10, supra-orbital foramen ; 11, 12, lachrymal bone ; 13, malar bone ; 14, nasal border of frontal bone ; 15, nasal bone ; 16, suture of nasal bones; 17, super- maxillary bone ; 18, infra-orbital foramen; 19, anterior, or pre- maxillary bone ; 20, foramen in- cisivum ; 21, incisor teeth (young mouth). horse's head (posterior face). , Occipital tuberosity ; 2, foramen magnum ; 3, 3, occipital condyles; 4, 4, styloid processes; 5, 5, petrous bone ; 6, basilar process ; 7, ptery- goid fissure of the sphenoid bone ; 8, foramen lacerum ; 9, 9, supra-condyloid, or anterior mas- toid process; 10, lo, articular eminence, or temporal condyle; 11, body of sphenoid bone; 12, pterygoid process; 13, ethmoid bone; 14, temporal bone and sphenoidal suture; 15, lachrymal bone; 16, vomer; 17, malar Ijone ; 18, maxillary tuberosity; 19, posterior, or guttural opening of the nose ; 20, palate bone ; 21, palatine styloid process; 22, palato-maxil- lary foramen ; 23, palatine process of superior maxillary bone, with suture ; 24, ditto of pre- maxillary bone; 25, premaxillary bone; 26, upper incisor teeth ; 27, point of junction of the premaxillary with the superior maxillary bone ; 28, upper molar teeth (young mouth). openings divided, in the fresh state, into two portions {anterior and posterior lacerated foramina). To the outside of these openings is the base of the tuberous portion of the temporal bones, especially the tympanic bulb ov petrous bone ; above 82 THE BONES. are the condyloid fossae, with their condyloid foramen., and the styloid processes of the occipital hone or Jugular eminences. 2. Suhsphenoidal region. — This region is notably constricted in its middle part, where it has for base the body of the posterior sphenoid bone ; it is enlarged above by the temporal articular surfaces. It is limited by the inferior border of the foramen lacerum, on which are three notches transformed into foramina by the tissue that partitions the foramen lacerum basis cranii in the fresh state. These openings are, passing from within to without, the carotid or cavernous foramen, the foramen ovcde or foramen rotundum ; they are all preceded by a groove on the surface of the bone. On each side of the body of the sphenoid is the narrow Vidian fissure, prolonged by the Vidian canal, and margined outwardly by the origin of the suhsphenoidcd process. Laterally, is the suhsphenoidal canal for the passage of the internal maxillary artery, which is continued forward by two branches, one of which opens into the orbital hiatus, the other into the temporal fossa. 3. Spheno-pcdatine region. — This extends from the superior sphenoid to the palatine arch. In the median plane it shows a vast elliptical opening — the gutturcd opening of the nascd cavities, divided at the bottom into two portions by the vomer, and bordered laterally by two elevated crests (pterygo-pcdatines) resulting from the junction of the pterygoids with the palatine crests ; and limited in front by the posterior border of the palatine bones, which is raised in its middle by a blunt point directed backwards — the nasal spine. Beyond the pterygo-palatine orests is a slightly depressed surface, on which run the branches of the internal maxillary artery and the superior maxillary nerve. This surface extends, above, to the orhital or sphenoidctl hiatus, below to the maxillary hiatus. In the maxillary hiatus are : the upper opening of the superior dental canal, the palatine caned, and the nasal foramen. In passing from the maxillary hiatus on the margin of the guttural opening of the nasal cavities, we meet with the staphyline fissure, which is limited above by the alveolar tuberosity. 4. Pcdatine region. — .This is a wide elongated surface, limited laterally by the molar teeth and interdental spaces, and in front by the incisors. It shows : in the middle, the pcdcdine and superior maxillary suture, which terminates at the incisive canal ; on the sides and above, the inferior opening of the pcdatine grooves^ prolonged by the pcdatine fissures ; in front, the incisive slits. C. Lateral Face. — This is a pair face, and comprises three regions (Fig. 51) : 1. Maxillary region. — This is very extensive. Its shape is triangular, base superior — the supermaxilla being joined to the premaxilla. Proceeding backward, there are observed : a fossa, in which opens the infra^rhital foramen ; the lower orifice of the superior dental canal, pierced above the third molar tooth ; the malar or zygomatic spine — a long vertical crest for the insertion of the masseter muscle, commencing above the fourth molar teeth, and continuing upwards with the malar bone and zygomatic process. Lastly, the maxillary region is limited, above, by the orbit and the maxillary tuherosity. 2. Orhital region. — This includes the orbit or orbital cavity, for the reception of the essential and some of the accessory organs of vision. In Man and the Quadrumana this cavity has complete bony walls, but in the domestic animals it always largely communicates with the temporal fossa, and it is not always even circumscribed at its opening by a soHd ring. A fibrous lining {ocular sheath) converts it into a distinct cavity. In the Horse, the outline of the orbit is constituted : below, by the lachrymal THE HEAD. 83 bone ; above and in front, by the frontal bone and its process ; externally, by the malar bone. If its two largest diameters are measured, it is remarked that this opening is scarcely ever regularly circular, its width varying from above to below or from without to within. With nine Horses' heads of various ages and breeds, equal diameters were found in only one, the other eight being unequal ; of these, the vertical diameter of the orbit predominated in five, and was least in three. In the Ass, as a general rule the vertical diameter is smallest, the relation between the two diameters varying from ro9 to 1"15. Otherwise, the entrance to the orbit is irregularly square, and the orbital process which covers it is much wider and more salient than in the Horse — as Lecoq asserted, and as the observations of Goubaux and Sanson have confirmed. We have also noticed these differences, and they are not the only ones which permit the skeleton of the Ass to be recognized ; for there have been already cited those of the spine and bones of the head — such as the articular depression surrounding the basilar process, the vascular furrow on the styloid process, the position of the lachrymal tubercle, and the conical eminence surmounting the premaxillary symphysis, above the incisive foramen ; others will be noted hereafter (Figs. 51, 52). With regard to the cavity of the orbit, it is separated from the maxillary hiatus and the temporal fossa by two linear imprints, diverging forwards, to which the ocular sheath is attached. It presents, on its floor, the upper orifice of the lachrymal canal, the lachrymal fossa, where the small oblique muscle of the eye has its fixed insertion ; and within this, but higher, the little depression for the bend of the great oblique muscle of the eye. 3. Temporal region. — This region is more extensive than the preceding, and is composed of three principal parts — the temporal fossa, zygomatic arch, and petrous portion of the temporal bone. The temporal fossa surmoimts the orbit, from which it is incompletely separated in Solipeds and Ruminants by the orbital arch ; in the other domestic animals, this arch is incomplete in such a way, that in the skull the temporal fossa is confounded for the greater part with the orbit. Situated obliquely down- wards and outwards on the sides of the cranium, the temporal fossa is oval in shape, and bounded inwardly by the occipital or temporal crest, outwardly by the anterior border and longitudinal root of the zygomatic process. It lodges the temporalis muscle ; consequently, its width in our animals is proportionate to the power of that muscle. It is studded with muscular imprints, and has several vascular foramina which enter the parieto-temporal canal. The zygomcitic arch is formed as if by a loop thrown from the cranium on to the face, outside the temporal fossa and the orbit. It is constituted by the zygomatic process of the temporal bone and the malar bone, which latter prolongs it to the maxillary region. The tuberosity of the temporal bone shows, outwardly, the external auditory canal, usually larger in the Ass than the Horse. Between this orifice and the supra-condyloid eminence is the opening of the parieto-temporal canal ; and behind the latter are several irregular ridges, one of them being the hyoid process. The external face of the tympanic case is also studded with some styloid prolotiyations, one of which, more developed than the others, serves for the insertion of the peristaphyline muscles. Above the hyoid process is the mastoid process, and between these two parts is the external orifice of the aqueduct of Fallopius. From the mastoid process extends the mastoid crest, the summit of 84 THE BONES. which meets the external occipital protuberance ; it is crossed by the mastoid groove, which gives the mastoid artery passage to the parieto-temporal canal. All of the petrous portion is surrounded by deep clefts, resulting from the simple union of this bone with its neighbouring pieces. D. Base. — The base or superior extremity of the head, formed by the occipital bone, represents a trapezoid surface, incurvated from before to behind. It is separated from the anterior face by the external occipital tiiherosity, the projection of which is always greater in the Ass and Mule than in the Horse, with the exception of the English Horse, in which it has been found very developed (Figs. 51, 52). It is separated from the lateral faces by two crests — Fig. 51. _ 19 IS 12 17 22 horse's head (lateral face). 1, Occipital condyle; 2, styloid process of the occipital bone; 3, external occipital tuberosity, 4, parietal crest ; 5, external auditory hiatus ; 6, zygomatic process of the temporal bone ; 7, frontal bone; 8, orbit; 9, lachrymal bone and its tubercle; 10, zygomatic or malar bone ; 11, nasal bone; 12, supermaxillary bone; 13, zygomatic spine; 14, infia-orbital foramen; 15, pre- maxillary or intermaxillary bone; 16, incisor teeth; 17, molar teeth; 18, inferior maxilla; 19, maxillary fissure; 20, maxillary condyle; 21, coronoid process of the maxilla; 22, mental foramen; 23, supra-orbital foramen ; 24, basilar process of the occipital bone. the superior curved lines — which are prolonged backwards on the styloid processes of the occipital bone. In the middle plane is the occipital crest, behind the tuberosity ; it terminates, in becoming gradually effaced, at the orripital foramen, which is bordered on each side by the condyles of the occiput. The condyles are separated from the styloid processes by two deep notches — the stylo-condyloid notches. Between the middle line and the superior curved lines, are muscular imprints irregularly arranged in a half -circle — these are the inferior curved lines. The base of the skull joins the anterior and posterior faces in forming angles ; these possess some interest, as they may afford an important differential character between the Ass and Horse. THE HEAD. 85 If one of the branches of a goniometer be placed tangentiallj to the surface of the basilar process, and the other to the summit of the external occipital tuberosity, the basilo-occipital angle will be obtained. In the measurements we have taken of eight heads of Horses of diverse ages and breeds, this angle has varied from 70° to 91°. We except the head of a young English Stallion, the basilo-occipital angle of which was from 92° to 100°. Measurement of the heads of Asses showed the angle to be 103°. The average basilo-occipital angle was 85*36° for the Horse, and 95° for the Ass. If, instead of taking the basilo-occipital angle, the goniometer be applied to the origin of the temporal crests and the superior outline of the occipital Fig. 52. ass's head (lateral face). , Occipital condyle ; 2, styloid process of the occipital bone, with a very marked furrow on its external face; 3, external occipital tuberosity, more developed than in the horse; 4, parietal crest ; 5, external auditory hiatus ; 6, zygomatic process of the temporal bone ; 7, frontal bone ; 8, orbit, with its external outline more angular than in the horse; 9, lachrymal bone, with its tubercle partly implanted on the nasal bone; 10, zygomatic or malar bone; 11, nasal bone; 12, supermaxilla ; 13, zygomatic spine; 14, infra-orbital foramen; 15, premaxillary bone, with its inner border raised by a salient tubercle above the incisive canal ; 16, incisor teeth ; 17, molar teeth; 18, inferior maxilla; 19, maxillary fissure; 20, maxillary condyle; 21, coronoid process ; 22, mental foramen ; 23, supra-orbital foramen, carried more to the middle of the orbital process than in the horse ; 24, basilar process of the occipital bone. In the Horse, this angle is and S7° — the average being foramen, the parieio-occipifal angle is obtained between 81° and 104° ; in the Ass between 7' 91-12° for the Horse, and 84° for the Ass. It was foreseen that the value of these angles would be in inverse relation. In all cases when, on a head, the basilo-occipital angle was found very open and the parieto-occipital more closed, combined with a great development of the external occipital tuberosity and the differential characters already described, it was certain to be the head of an Ass. In the English Horse, the external Sa TEE BONES. occipital tuberosity of which is very developed, the two angles in question are nearly equal. In the JIule and Hinny, the value of the angles is intermediate between the Horse and Ass. In the Mule, the mean value has been 86-12° for the basilo-occipital angle, and 88° for the parieto-occipital angle. In the Hinny, it was 87° for the first, and 81° for the second. E. Summit. — This results from the union of the four faces ; but, instead of being acute, it is flattened from behind to before, curved from side to side, and furnished with the incisor teeth. ^ 2. CONFOEMATION OF THE CrANIUM IN PARTICULAR. Retzius was the first to start the idea of considering the cranium of Man independently of the fafce. He distinguished the races of mankind as hrachtj- cephalic (short-headed), and dolichocephalic (long-headed) — that is, crania long from before to behind, and crania relatively short. Broca more recently compared the transverse diameter of the cranium with the antero-posterior diameter taken as a unit, and has expressed this relation in hundredths by the term cephalic index. For some years, Sanson has endeavoured to introduce into the classifica- tion of animals the calculations of Retzius and Broca. Taking the dimensions of the cranium as a basis, he has divided Horses into two groups — the brachy- cephalic and the dolichocephalic kinds. If the cerebral cranial cavity — the only important one for this purpose — be enclosed in a parallelogram, two sides of which shall be at a tangent to the most salient points of the parietal bones, and the other two pass in front of the external auditory canals and across the supra-orbital foramina, the dimensions of the base and height of this parallelogram, measured in a straight line., will correspond to the longitudmal and transverse diameters of the cranium. In proceeding thus, Sanson has found that in certain crania the transverse diameter is greater than the longitudinal {brachycephalic crania), while in certain others the transverse is shorter than the longitudinal diameter {dolichocq)halic crcmia).^ Toussaint took direct measurements of the interior of the cranium, and, no matter what the breeds of horses were which he examined, he always observed that the longitudinal diameter exceeded the transverse. We have made cranio- metrical investigations on a number of Horses, and are able to confirm Toussaint's statements. In eight skulls from different sources, the longitudinal diameter varied between 118 and 1S6 millimetres, the transverse between 88 and 104 millimetres. Consequently, in none of these animals was the transverse diameter equal to the longitudinal. In the number examined were the skulls of a Syrian and an English stallion — types which Sanson would have selected as the most brachycephalic ; the relations between the length and width were 1'17 for the first, and VSl for the second. The average for the eight heads was 1*24. We are of opinion that there are no brachycephalic Horses, in the rigorous sense of the word, such as Sanson admits ; so that, if it is attempted to establish brachycephalic and dolichocephalic types, it will be necessary to previously fix what shall be the limit between these two types, and this has not yet been done. The crania of Asses from the south of France are longer than that of the ' For the regions of the head, see Lavocat's Nouvelle Osteologie compar€e de la tete des Animaux Domestiques. ^ Sanson, " Me'moire sur la Nouvelle determination d'un type specific de race Chevaline," Journal de VAnatomie et de la Physiologie, de Ch. Robin, 1867; also the later works of M, Sanson. THE READ. 87 Horse ; for in eight the average relation between the length and width was 1-25, instead of 1'24 — a difference not very great, certainly. The difference becomes more marked, however, between the Ass and Horse, if the length of the cerebral be compared with that of the cerebellar cavity. This comparison has yielded an average of 1-962 in the Horse, and 1-927 in the Ass — which proves that the cerebellar cranium is longer in the Ass than the Horse. The cranium is, as it were, strangled behind the orbital processes of the frontal bones. In glancing at the cranium of the Horse and Ass, it would at first appear that that of the Ass is relatively narrower than the cranium of the Horse. We have measured six heads of each species for the width of the cranium at its greatest diameter, behind the orbital processes, and, in comparing these two diameters, have obtained the following results : in the H^orse, the relation varied between 1-18 and 1-27 ; in the Ass, between 1-20 and 1-47. The average has been, for the Horse, 1-226, and 1-335 for the Ass. From these figures, it might be concluded that the cranium of the Ass is relatively more constricted at its inferior extremity than that of the Horse. In the hybrids of the Horse and Ass, the cranial cavity is more elongated, and in this respect the Hinny more resembles the Ass than the Horse. With regard to narrowness of the crauium behind the orbital processes, the Mide holds the middle place between its parents, while the Hinny comes nearest to the Ass — the reverse of what is noticed in the development of the cerebellar cranium. In Ruminants, the shape of the cranium is more or less masked by the frontal or parietal sinuses ; consequently, it is difficult to study satisfactorily this part of the head, particularly in the bovine species. The cranium of the domestic Dog offers great varieties ; for the creation of numerous breeds has brought about important differences in the form and dimensions of this part, which it is impossible to deal with here. 3. Relations between the Cranium and Face. Instead of studying the cranium alone, we may compare it with the face in regard to width, length, and the area that each of these two regions occupies in a vertical and median section. We may also, in measuring the facial angle, form an idea of the manner in which these two regions unite to form the head. 1. The forehead, properly speaking, measured from the union of the parietal crests to the fronto-nasal suture, is always, in the Horse, longer than the cerebral cranium, the second to the first being as 1 : 1"425. The forehead of the Ass is proportionately less developed, for we have found that the cranium is to the forehead as 1 : 1-265. 2. This shortness of the Ass's forehead, which renders the head heavy, is corrected by its narrowness ; the head enlarges at the orbital processes. In com- paring the distance between the supra-orbital foramina and the transverse diameter of the cerebral cavity, it has been noted that the width of the cranium is to the space between these foramina as 1 : 1-454 in the Horse, and 1 : 1-265 in the Ass. The forehead of the Ass is, therefore, in proportion to the cranium, shorter and narrower than in the horse. From this point of view, the heads of the 3I'uIe and Hinny are intermediate to those of their parents ; but the first of these hybrids is nearer the Horse, and the second approaches the Ass. 3. Cuvier imagined that one of the means of judging of the intelligence ot animals, would be to compare the area of the cranium with that of the face, measured on a median section of the head, deprived of the lower jaw. This TEE BOXEd. great naturalist remarked that the area of the cranium diminishes as the animals are further removed from the hmuau type, while the area of the face increases in the same sense. Colin has studied the heads of the domesticated animals from this point of view. Putting to one side the surface occupied by the sinuses, he found that the area of the cranium to the face was as — 1 : 2-69 in the Horse. 1 : 2 09 in the Ass. 1 : 3-43 in the Ox. 1 : 2-20 in the Ram. 1 : 1-95 in the Goat. 1 : 3 24 in the Pig. 1 : 117 in the Dog. 1 : 0-68 in the Cat. 1 : 1-47 in the Rabbit. 1 : 054 in the Lamb. From this table it will be seen that, if the domesticated animals are classified according to the area of the cranium, they will stand in the following order : Cat, Dog, Rabbit, Goat, Ass, Ram, Horse, Pig, and Ox. 4. Camper measured the facial aiigU by drawing two lines, starting from the entrance to the nasal cavities, and passing towards the middle of the external auditory canal and towards the most prominent part of the forehead. The facial angle gives an idea as to the relative volume of the face and cranium, and the dimensions of the latter ; but with animals it furnishes very imperfect information, because of the form of the face and the development of the sinuses around the cranial cavity. Colin has measured the facial angle of the domestic animals, by drawing two lines from the upper incisors towards the external auditory canal and the fore- head, in the point corresponding to the lower end of the brain ; and he obtained the following average values : from 12° to 15° for the Horse ; 16° for the Ass ; 20° for the Bull ; from 20° to 25° for the Ram ; from 3-4° to 41° for Dogs ; and 41° for the Cat. On the other hand, we have measured this angle in Equines, and find that it varies : in the Horse, between 11° and 13° ; in the Ass, between 12° and 16° ; and in the Mule, between 13° and 15°. In the Hinny, it measures 14°. It is somewhat remarkable that, in the Equidae, the Ass should have a greater facial angle than the Horse. 4. Modifications due to Age. Age brings modifications bearing upon the form of some regions of the head, the development of external peculiarities of the bones, the shape of the cranium, and its relations with the surface. 1. It has been remarked that the development of the occipital tuberosity, the temporal crests, and the lachrymal tubercle, increases with age in the Equine species ; the infra-orbital foramen, which is frequently only a notch in youth, becomes a true foramen when the animal is advanced in age. In the Foal, the forehead is convex ; that bone and the nasal bones become flat as the creature grows, and sometimes even the line of the nasal bones is concave in old age. The maxillary region, which is at first convex, becomes gradually hollow as the molar teeth are pushed out of the alveoli ; while the straight part of the posterior border of the inferior maxilla becomes thin and sharp in very old Horses. The entrance to the orbit is also notably modified, though its shape is not identical in all the animals. In every instance, it has been remarked that the direction of the larger axis of the orbital cavity, comprised at first in the plane which passes by the auditory canal and the implantation of the upper incisors, is depressed in THE HEAD. front, and at an advanced age is found in a plane passing by the inferior extremity of the zygomatic crest and the summit of the external occipital tuberosity. 2. If the cranium be examined by itself, it will be noted that, in proportion, it is less narrowed behind the orbital processes in the young animal than in the adult. With regard to the cerebellar cranium, it is elongated when the animal is aged — a consequence of the natural development of the external occipital tuberosity. 3. The relation of the areas of the cranium and face change with age. If the measurements obtained by Colin on the Lamb and Ram are compared, it will be perceived that the face grows as the creature ages. This change is very evident if the development of the young Hare is watched. At birth the face is very short — like that of a common dog, it is said ; but when development is completed, we know how much the face has become lengthened. 4. Finally, in consulting the table of angles drawn up by Colin, we might believe that the facial angle widens as the animal advances in age. Thus, in the young Hinny, Colin estunated the facial angle at 15° ; this angle was 16° on an Fig. 53. A, B, C, D. 1, Fronto-parietal crests; 2, external occipital tuberosity; 3, 3, superior root of the zygomatic process of the temporal bone. old Hinny, and 17° on another very old one. In every instance, however, according to the same table, this angle will be equal in a four-years-old Horse and in an adult Horse ; and even in the Calf it diminishes one degree when it becomes an adult animal. The measurements we have taken in domestic Solipeds, have demonstrated that the facial angle diminishes in a constant manner as the animal grows old. Thus, this angle is 16° in an Ass three years old ; it is 15° in the adult, and 12° in the very old Ass. We have found it 13° in a Foal of two years, and 11° in an old Horse ; 15° in a Mule of eighteen months, and 12*30° in a very aged Mule. This question has, therefore, to be again examined ; and, however it may be decided, it will be seen, by what has been stated, that age induces very interesting changes in the form and proportions of various parts of the head. If the crania of different breeds of Dogs are compared, there will be found very marked diversities in the prominence of the parietal convexity, and the development and distance apart of the fronto-parietal crests. A mere glance at the ligures above (Fig. 53), will afford evidence of this. 90 THE BONES. On the cranium of the Mastiff (a), the parietal bulgings are httle marked ; the parietal crests are very elevated, and join each other early, so that the temporal muscles are in contact throughout the greater part of their inner margin. In the little Lap-dog (d), the parietal crests are widely separated from one another, and the cranium is so very convex as to resemble that of a Monkey. Between these extremes are many intermediates (b, c) ; and it would appear that the development of inteUigence in the Dog results in rendering the parietal bones more convex, and the temporal fosssB narrower. Comparison of the Head of Man with that of the Domesticated Animals. 1. Occipital hone. — The occipital of Man is large, flat, incurvated like a shell, and the ex- ternal tuberosity is slightly developed, and united by a ridge to the occipital foramen, which is relatively very wide. Two series of ridges arise from the external tuberosity and pass towards the circum- ference of tlie bone ; these are the superior and inferior curved or semicircular lines. There is an anterior and a posterior condyloid fossa pierced by a foramen at the bottom; and the jugular eminences, wide and slightly prominent, replace the styloid processes of the domesti- cated animals. The internal face of the occipital of Man corresponds with the cer( brum and cerebellum ; and for this purpose it shows four fossae, distinguished into superior or cerebral, and inferior or cerebellar. These fossse are separated by a crucial projection whose most developed portion forms the internal occipital protuberance. The union of the occipital with the parietal bones, con- stitutes the liimlidoidal suture. At the point where this bone meets the parietal and the squamous portion of the temporal, is found, in the infant, the lateral posterior fontanel. 2. Parietal hones. — The parietals are always isolated in early life, and sometimes consolidated with each other at the adult age. They are very large, quadrilateral, and occupy the summit and sides of the cranium. The parietal crests are absent, but are replaced, in certain individuals, by two faintly marked curved lines situated a little above the inferior border of the bone. The middle portion of the external face is very convex. On the internal face there is no parietal protuberance, but in its stead the internal occipital tuberosity. It also exhibits ramous channels, which in disposition are analogous to the ribs of a tig-leaf ; as well as the parietal fossa, which corresponds to the parietal eminence. 3. Frontal hone. — The frontal bone of Man forms the upper part of the face and the anterior portion of the cranium. Convex from behind forward, then vertical in its upper three-fourths, the bone suddenly bends at tlie orbits, so as to become horizontal in its lower fourth. The external face offers, above the forehead, two Literal frontal eminences, and above the nose, a middle frontal boss. To the right and left of the latter are two salient arches— the supra-orbital ridges. The internal face entirely belongs to the cranial cavity. It offers, on the median line, the saggital groove terminated by a frontal crest; and on each side of this line the frontal fosste, corresponding to the eminences of that name, and orbital bo.sses to match the orbital roofs. There is no mortise for the articulation of the sphenoid bone. On the middle poition of the superior frontal border, in young persons, is the anterior angle of the anterior fontanel. The anterior border exhibits three supra-orbital foramina and the orbital arches. front view of the human cranium. , Frontal bone ; 2, nasal tuberosity ; 3, supra-orbital ridfijp ; 4. optic foramen ; 5, sphenoidal fissure ; 6, spheno-maxillary fissure ; 7. lachrymal fossa ; 8, opening of the nose divided by the vomer; 9, infra-orbital foramen; 10, malar bone ; 11, symphysis of the lower jaw; 12, mental foramen; 13, ramus of the lower jaw ; 14, parie- tal bone ; 15, coronal suture ; 16, temporal bone ; 17, squamous suture ; 18, upper part of the great ala of the sphenoid bone; 19, com- mencement of the temporal ridge ; 20, zygoma of the temporal bone concurring to form tlie temporal arch ; 21, mastoid process. THE HEAD. 91 Fig. 55. 4. Ethmoid hone.— In Man, the external fa^e of the lateral masses— formed by a very thin lamina, termed the os planum or lamina pap2/r«e«— belongs to the internal wall of the orbit. 5. Sphenoid bone.— TLiis is distinguished, in Man, into a body and four wings- two large and twfi small. Tlie inferior surface of the body oflfers nothing remarkable, except the presence of a conical prolongation named the beak (rostrum) of the .sphenoid. The external face of the greater wings forms part of the temporal fowsa, as also the external wall of the orbit. At the union of the wing.s with the body, are detached two bifid pterygoid proce.-^ses ; their internal branch represents the pterygoid bones of animals. There is no sub- sphenoidal canal. Tlie two lesser wings are very thin and triangular, and visible only on the superior surface of the bone ; they constitute the processes of Ingrassias. On the internal face of the bone are found : (1) a deep pituitary fossa, limited by four cUnoid pro- cesses; (2) an optic fossa, shallow, showing very short optic canals transformed into foramina ; (3) the sphenoidal fissure, which replaces the great super- spheiioidal canal in the Horse; (4) the great foramen rotundum; (5) the internal face of the wings, much excavated ; (6) the foramen ovale, which transmits the inferior maxillary nerve ; (7) the small foramen rotundum that lodges the spheno-spinous artery. 6. Temporal hone. — In the squamous portion of the temporal bone of Man, the zygomatic process only rests on the malar bone, as in Ruminants. The glenoid cavity is concave in every sense, ami divided into two parts by an opening named t\\e fi'<° to 130° for the external ribs, and from 100° to 132° for the asternal ribs, of the first ; from 60° to 125° for the sternal, and from 140° to 150° for the asternals, of the second. The upper extremity of the sternal ribs in the Ass is less twisted outwards than the same part in the Horse ; and in the latter, the plane which passes by the head of the rib is more distant than the plane which, in the Ass, passes across the tubercle. The ribs of the Mule are intermediate between those of the Ass and Horse, with regard to the value of the angle just indicated ; they approach those of the Ass by the twist in their superior extremity. Differential Characters in the Ribs of other Animals. The number of rib:^ varies like that of tlie dorsal vertebrae. The following table'* indicate the number uf these bones in the different domesticated animals : — Pig 14 Ox l.S Sheep 13 Goat 13 Dog 13 Camel ... 12 Rabbit 12 A. Ruminants. — These animals, with the exception of the Camel, have eight sternal and five asternal ribs. In the Ox, they are longer, wider, and less arched than in Solipeds. The articular eminences of the superior t-xtremity are voluminous and well thorax op man (anterior face). 1, Superior piece of the sternum ; 2, middle piece, or body ; 3, inferior piece, or ensiform cartilage; 4, first dorsal vertebra ; 5, hist dor.^al vertebra ; 6, first rib ; 7, its head ; 8, its neck, rest- ing against the transverse process of the first dorsal vertebra ; 9, its tubercle ; 10, seventh, or last true rib ; 11, costal cartilages of the true ribs ; 12, the last two false or floating ribs ; 13, the groove along the lower border of the rib. abdominal parietes ; for this reason they Article IV. — Anterior Limbs. The anterior ( pectoral or thoracic) limb is divided into four secondary regions — the shoulder, arm, forearm, and fore foot or hand. 98 THE BONES. SHOULDER. In Solipeds, this region has for its base a single bone — the scapula or omoplat. ^^ Scapula (Figs. 59, 60). This islW»^ triangular, and asymmetrical bone, prolonged at its superior border by a flexible cartilage, articulated interiorly with the humerus only, and applied against the lateral plane of the thorax in an oblique direction downwards and forwards. It has two faces, three borders, and three angles. Faces. — The external face (or dorsum) is divided by the scapidar or acroynian spine, into two cavities of unequal width — the supra- and infra-spinous (or antea and 2)ostea spinatus) fosscB. The spine is a very salient crest which runs the whole length of the external scapular surface ; very elevated in its middle part, which shows an irregular enlargement — the tuberosity of the spine — it insensibly decreases towards its two extremities. The supraspinous fossa — the narrowest — is situated above, or rather in front of the spine ; it is regularly concave from side to side, and perfectly smooth. The infra-spinous fossa is twice the width of the preceding, and occupies all the surface behind the spine. It exhibits : 1. Below, and near the posterior border, several rows of roughened lines for muscular insertion. 2. Near the neck, the nutritient foramen of the bone, and some vascular grooves. The interned face is excavated in its centre to form a hollow, called the subsca- pular fossa, which is prolonged superiorly by three diverging points. The median point extends to the superior border of the bone, and separates two roughened triangular surfaces. Borders. — The superior is indented by an irregular groove, to receive the inferior margin of the cartilage of prolongation. The latter is convex on its superior border, extends beyond the posterior angle of the bone, and gradually diminishes in thickness as it leaves its point of attachment. In old horses it is nearly always found partially ossified. The anterior border, thin and sharp, is convex in its superior two-thirds, and slightly concave for the remainder of its extent. The posterior is thicker and a little concave. Angles. — The anterior, or cerviccd angle, is the thinnest of the three. The posterior or dorsal angle is thick and tuberous. The inferior, or humeral angle, is the most voluminous, and is separated from the remainder of the bone by a slight constriction, which constitutes the neck of the scapula. It exhibits : 1. The glenoid cavity — an oval diarthrodial surface, excavated to a slight extent to receive the head of the humerus, nbtched on the inner side, and bearing on the external margin of the ridge which surrounds it a small tubercle of insertion. 2. The coracoid process, situated in front, and at a certain distance from the glenoid cavity. This is a large eminence in which may be distinguished two parts : the base, a thick rugged process ; and the summit, a kind of beak curved inwards. Structure and development. — Like all the flat bones, the scapula is formed of two compact layers separated by spongy tissue. The latter is very scanty towards the middle of the supra- and infra-spinous fossfe, where it is often alto- gether wanting ; it is most abundant in the angles. In Solipeds and Ruminants, the scapula is developed from two principal centres of ossification, one of which forms the coracoid process. In the Carnivora, the cartilage of prolongation is replaced by an epiphysary lip. It may be added that in Mammaha, Meckel, Cuvier, and Strauss-Durckheim have noted a supplementary nucleus in the glenoid cavity ; and that Lavocat and Goubaux have observed it in Horses especially. Lavocat has described it as THE ANTERIOR LIMBS. 99 a pyramidal nucleus, base inferior, and flattened before and behind. In the Horse, it appears at the centre of the cavity towards the seventh or eighth month ; it increases and pushes forward the coracoid process beyond the articular sur- face. In about nine or ten months it is fused with the principal part of the bone, and in about a year with the coracoid nucleus. In the Ass and Mule, the glenoid Fig. 59. Fig. 60. SCAPULA OF THE HORSE (EXTERNAL FACE). 1, Subscapular fossa ; 2, anterior triangular 1, Tuberosity of the spine ; 2, supra-spinous f ^face ; 3 posterior triangular surface ; fossa ; 3, infra-spinous fossa ; 4, nutrient *' *' vascular furrow ; 5, glenoid cavity ; foramen; 5, 5, 5, linear imprints for the ^ base of the coracoid process (insertion insertion of the coraco-humeralis ; 6, of the coraco-humeralis). tubercle for the same ; 7, border of the glenoid cavity ; 8, coracoid process ; 9, cervical angle; 10, dorsal angle; 11, cartilage of prolongation. nucleus appears about the fourth month, and its evolution is completed at the seventh or eighth month. In the Ass, the scapula is usually more curved than in the Horse, while the greater development of its superior border, and the more considerable constric- tion of its neck, give it a peculiar appearance. It represents a wider and shorter ]00 TEE BOXES. triangle than in the Horse, and the spine gradually decreases from the tuberosity until it is nearly lost on the surface of the bone, towards the nutrient foramen. In the Horse, this subsidence of the spine occurs at the neck, where it takes, place quite suddenly ; so that it forms a more or less marked prominence. The scapula of the Hinny has the general form of that of the Ass ; in the Mule, on the contrary, it is elongated Kke that of the Horse. Differential Characters in the Scapula of other Animals. The shoulder is composed of one or two bones, according as the limb is intended exclu- sivelj' to support the body, or is required for other purposes. A. Ox, Sheep, Goat.— In these animals the shoulder comprises only one bone— the scapula— which is more regularly triangular than in the Horse. The spine does not diminish in passing to the neck, but, on the contrary, terminates at a certain distance above the glenoid Fig. 61. R A scapula of the cat and rabbit. A, Scapula of the Cat. B, Scapula of the Rabbit. 1, Inferior extremity of the acromian spine v 2, supra-spinous fossa; 3, infra-spinous process; 4, superior border. cavity by an abrupt ridge prolonged to a point, which represents a rudimentary acromion pro- cess. It divides the external surfnce of the bone into two fossse, which in extent are as 1 :3. The neck is more constricted, and the humeral angle better detached, than in Solipeds. B. Camel. — The scapula of this animal resembles that of the Ox in its general form, but the spine divides the face into two equal fossae. The acromion process descends to the glenoid cavity. C. Pig. — The .spine, depressed at its two extremities, rises considerably at its middle por- tion, and bends over towards the infra-spinous process. D. Camivora.— Their shoulder has two bones — the scapula and clavicle. In the Dog , the latter is little more than a shell embedded in the muscles in front of the scapulo-humerul angle ; in the Cat, it constitutes a small styloid bone which is united to the acromion process and the sternum through the medium of two ligaments. The scapula has no cartilay;e of pro- longation ; its anterior border is very convex, as if it had been curved over on itself. The fos.'ife of the external face are equal, and the spine terminates in an acromion process that reaches the glenoid cavity. E Rabbit. — Two bones form the shoulder of this animal. The clavicle, although longer than that of the Cat. nevertheless does not rest directly on the sternum and scapula. The latter is in shape regularly triangular; the neck is slender; the fos^sse on the external face are very unequal ; the spine is prolonged by a thin acromion pedicle to the vicinity of the glenoid cavity ; and the superior border of the bone is [irovided with a cartilage of prolongation. TEE ANTERIOR LIMBS. 101 Arm. Fig. 62. This region has only one bone, the humerus. Humerus (Figs. 62, 63). The humerus is a long single bone, situated between the scapula and the bone of the forearm, in an oblique direction downwards and backwards. Like all the long bones, it offers for study a bodt/ and two extremities. Body. — The body of the humerus looks as if it had been twisted on itself from within to without in its superior extremity, and from without to within at the opposite end. It is irregularly prismatic, and is divided into four faces. The anterior face (Fig. 62), wider above than below, has in its middle and inferior portions some muscular imprints. The pos- terior, smooth and rounded from one side to the other, "becomes insensibly confounded with the neighbouring faces. The external is excavated by a wide furrow, which entirely occupies it, and turns round the bone obliquely from above to below and behind to before ; it is to the presence of this channel that the humerus owes its ap- parent twist, and it is in consequence designated the /?/rrow of torsion (or inusculo-spiral groove) of the body of the humerus. This furrow is separated from the anterior face by a salient border — the deltoid ridge, which ends inferiorly above the coronoid fossa, and superiorly, towards the upper third of the bone, by the imprint, or deltoid (or external) tuberosity. This is a roughened, very prominent eminence, flattened before and behind, and inclining to- wards the furrow of torsion ; by its superior extremity, it gives origin to a curved line which is carried backwards to join the base of the articular head. Near the inferior extremity, backwards and outwards, is seen the posterior deltoid ridge, which separates the latter from the posterior face of the bone. The internal face of the body of the humerus, rounded from side to side, is not separated from the anterior and posterior faces by any marked line of demarcation. It offers, near its middle, a depressed scabrous process (the internal tuberosity) for the insertion of the teres major and latissimus dorsi muscles. Towards its inferior third it shows the nutrient foramen of the bone. Extremities. — These are distinguished into superior and inferior. Both are slightly curved — the first backwards, the second forwards— a disposition which tends to give to the humerus the form of an S. The superior extremity is the most voluminous, and has three thick eminences — a posterior, external, and internal. The first constitutes the head of the humerus. It is a very slightly detached articular eminence, rounded like the segment of a sphere, and corresponding with the glenoid cavity of the scapula, which is too «mall to receive it entirely. The external eminence — named the trochiter, large ANTERO-EXTERNAL VIEW OF RIGHT HUMERUS. 1, Trochlear or bicipital ridges ; 2, external or deltoid tuberosity ; 3, head or articular sur- face ; 4, external tuber- cle ; 5, shaft or body with its twisted fur- row; 6, 7, articular or trochlear condyles; 8, uluar fossa with a sul- cus; 9, fossa for the insertion of the exter- nal lateral ligament. 102 THE BONES. Fig. 63. (or external) trochanter, and great fuberositi/—corm[>Y[ses three portions, named the summit, convexitij, and crest of the great tuberosity. The internal eminence — the trochin, little (or interned) trochanter, or small tuherosity — also presents three distinct portions, which, by their position, correspond exactly with the three regions of the external trochanter ; these are so many muscular facets. The external and internal trochanters are separated from each other in front by a channel called the bicipital groove, because the superior tendon of the biceps muscle glides over it. It consists of two vertical grooves, with a median ridge between them. The inferior extremity of the humerus has an articular surface corresponding with the radius and ulna. This sur- face— elongated transversely, convex from before backwards, and of greater extent within than without — exhibits two- trochlea separated by an antero-posterior relief. The median or interned trochlea, the deepest, is limited internally by a kind of voluminous condyle, which corre- sponds to the inner lip of the humeral trochlea of Man. The external trochlea is bordered outwardly by a slightly salient lip, which corresponds to the condyle of the humerus of Man. Above and behind this articular surface is a wide deep fossa — the olecranian (or condyloid), so named because it lodges the rostrom of the olecranon in the extension move- ments of the forearm. It is bordered by two eminences, the external of which is less elevated than the internal. The first represents the epitrochlea, and the second the epicondyle, of the humerus of Man. In front, and above the inner trochlea, there is another, but less spacious fossa, which receives the coronoid process during extreme flexion of the forearm, and which, for this reason, it would be convenient to designate as the coronoid fossa. Always in front, but above the external trochlea, are imprints for the attach- ment of the capsular ligament of the elbow- joint and the- extensor metacarpi magnus. Lastly, at the extremities of the transverse axis of the inferior articular surface is remarked, outwardly, an excavation for ligamentous insertion; inwardly, a small tuberosity for the same purpose. Structure and development. — The humerus, like all the long bones, is only spongy at its extremities. It is developed from six points of ossification, one of which alone forms the body, one the head and the internal trochanter, another the- external trochanter, a fourth the inferior articular surface, a fifth the epicondyle, and the last for the epitrochlea. The latter is sometimes absent. In the young animal the humerus is less twisted, and the eminences for muscular insertion less developed, than in the adult. In the Ass, the humerus is more twisted and curved in S form than in that of the Horse, and these modifications replace the eminences on this bone in the latter. Consequently, the equilibrium of the humerus is altered when it lies on a horizontal plane by any one of its faces and its lower extremity. Thus, while the humerus of the Ass may rest in equilibrium on a plane — its trochlea and two other points of its anterior face touching it — the Horse's humerus can only do so when the condyle, trochlea, and one or two points of its superior extremity touch it.. POSTERIOR VIEW OF THE RIGHT HUMERUS. 2, External trochanter; 3, articular head of the bone; 4, external tubercle and ridge ; 5, body or shaft of the bone ; 10, condy- loid fossa. THE ANTERIOR LIMBS. 103 Fig. 64. Laid on its posterior face, the humerus of the Ass is in unstable equiUbrium, if it has to touch the plane by the epicondyle and epitrochlea ; this is not so with the humerus of the Horse. If it is placed on its external side, the deltoid imprint remains above the horizontal plane with the Ass, and touches it with the Horse. Lastly, the epitrochlea descends nearly to the articular surface in the Ass, so that the bone is almost in equilibrium when it is placed on its inferior extremity. The humerus of the Mule and Hinny resembles that of their parents, but that of the Hinny is more like the Ass's, and that of the Mule the Horse's. Differential Characters in the Humerus of other Animals. Proportiot)ately, the Immeius is longer, ami more inflected like an S, as the number of apparent digits is increased. Therefore it is that, in the C.irnivora, the characters of length and inflection are most marked. A. Ox, Sheep, Goat.— In these animals, the furrow of torsion is less marked, and the deltoid imprint less salient than in the Horse, while the extremities are larger and more curved. The bicipital groove is divided into two depressions by a median ridge ; the external trochanter is enormous, and its very elevated summit is bent over the bicipital groove. Tlie head is better detitched and the trochlea deeper than in the Horse. The medul- lary eanal of the humerus of the Ox is sometimes crossed by an osseous band. B. Camel. — Humerus cylindrical and nearly straight. Torsion furrow shallow ; nutrient foramen on its anterior face. Bicipital groove double, the inner cavity being larger than the external. The inferior articular surface is relatively very narrow, and the external trochlea deep. C. Pig. — The humerus of this animal is com- pressed on both sides; the head is much bent back- wards, which increases its S inflection. A single bicipital groove placed within the superior extremity ; the external trochanter voluminous, and the summit turned over the bicipital groove. Deltoid imprint and internal tuberosity of the body replaced by simple muscular imprints. D. Dog and Cat. — The humerus is very elon- gated and more S-curved than in all the other animals, and the internal tuberosity is leplaced by some imprints ; while the bicipital groove is single, and the nutrient foramen, on the posterior face, is as in the Ox, Sheep, and Pig. The coronoid fossa com- municates with that of the olecranon by a foramen. E. Rabbit. — The humerus of this animal greatly resembles that of the Dog, except that it is much more flattened on each side, and the deltoid imprint is on the anterior face and nutrient foramen on the inner lace of the bone. Forearm. This region has for its base two bones — ^the radius and mtitus (or vino), united into a single piece {os aniihrachii) at an early period in most of the domesticated animals. HUMERUS OF THE CAT AND RABBIT. , Humerus of the Rabbit. B, Humerus of the Cat. 1, Condyle; 2, trochlea; 3, diaphysis ; 4, external trochanter ; 5, internal trochanter ; 6, bicipital groove. 1. Radius (Figs. 65, 66). This is a long bone, placed in a vertical direction between the humerus and the first row of carpal bones, and divided into a body and two extremities. 104 THE BONES. Body. — Slightly arched and flattened before and behind, it presents for study two faces and two borders. The anterior face is convex and perfectly smooth. The posterior, a little concave from one extremity to the other, offers : 1. Near the external border, a triangular surface, covered with asperities, elongated vertically, very narrow, commencing near the upper fourth of the bone, and terminating in a fine point towards the lower fourth ; this surface is brought into contact with the anterior face of the ulna by an interosseous liga- ^^S- 65. ment, which is completely ossilied before the animal -^''' reaches adult age. 2. Above, there is a wide, trans- verse, but shallow groove, which aids in forming the radio-ulnar arch, and shows, near the point where it touches the preceding surface, the nutrient foramen of the bone. 3. Near the internal border, and towards the inferior third, there is a vertically elongated and slightly salient eminence for insertion. The two borders — external and internal — are thick and rounded ; they establish an insensible transition between the faces. Extremities. — The superior is larger than the inferior. It has : 1. An articular surface elongated from one side to the other, concave from before to behind, wider within than without, and moulded to the articular sur- face of the inferior extremity of the humerus ; there is also seen, outwardly, a double depression (glenoid cavities), which receives the two lips of the external trochlea ; in the middle, an antero-posterior ridge, which is received into the internal trochlea ; within, an oval cavity corresponding to the internal border of the former. 2. The external tuberosity, placed at the extremity of the great diameter of the articular surface ; it is prominent and well detached. 3. The interned or bicipital tuberosity — a large, very rugged, and depressed process, situated within and in front of the glenoid cavity. 4. A little lower, and on the same side, there is a strong muscular and ligamentous imprint, separated from the preceding tuberosity by a transverse 1, Ulna; 2, point of the groove intended for the passage of a tendon. .5. The coronoid process,^ a small conical eminence, at the summit of which terminates, anteriorly, the median ridge of the articular surface. (3. Two diathrodial facets elongated transversely, cut on the posterior outline of the large articular surface, with which they are con- founded by their superior border ; they correspond with similar facets on the ulna. 7. Below these, a roughened surface which extends to the radio-ulnar arch, and is in contact with an analogous surface of the same bone through the medium of an interosseous ligament. In the Horse, this hgament rarely becomes ossified. The inferior extremity, flattened before and behind, presents : 1. Inferiorly, an articular surface elongated transversely and somewhat irregular, responding to the four bones in the upper row of the carpus. 2. On the sides, two tuberosities * In Man this belongs to the ulna. EXTERNAL FACE OF THE RADIUS AND ULNA. Ulna; 2, point of the ulna; 3, beak of ulna or olecranon ; 4, radio-ulnar arch ; 5, supero-external tuberosity; 6, radio-ulnar articular surfaces for the humerus; 7, bicipital tu- b rosity ; 8, shaft or body of the radius ; 9, grooves for tendons. THE ANTERIOR LIMBS. 105 for ligamentous insertion — the internal salient and well circumscribed, the other external, and excavated by a vertical fissure — in which passes a tendon. 3. In front, three grooves for the gliding of tendons ; the external is the largest, and vertical like the median ; the internal, the narrowest, is oblique downwards and inwards. 4. Posteriorly, a strong transverse ridge which surmounts the articular surface, and serves for the insertion of ligaments. Structure and development.— The radius is a very compact bone, and is developed from three centres of ossification — one for the body, and two for the extremities. 2. Ulna (Figs. 65, 66). This is an elongated, asymmetrical bone, in the form of an inverted triangular pyramid, applied against the posterior face of the radius, to which it is united in adult Solipeds. It offers for description a middle portion and two extremities. Middle portion. — This has three faces wider above than below, and three borders which become joined at the inferior extremity of the bone. The external face is smooth and nearly plane. The internal is also smooth and shghtly hollowed. The anterior is formed to correspond with the radius, and presents pecuharities analogous to those of the posterior face of that bone. Thus, there is found, in proceeding from above to below : 1. Two small diarthrodial facets.^ 2. A roughened surface. 3. A transverse groove for the formation of the radio- ulnar arch. 4. A triangular surface, studded with rugosities, which occupie^the remainder of the bone to its lower extremity. The lateral borders — externatand internal — are sharp, and, like the anterior face, are in contact with the radius. The posterior border is concave, rounded, and thicker than the other two. Extremities. — The superior extremity comprises all that portion which exceeds the articular surface of the radius. It constitutes an enormous process — the olecranon — flattened on both sides, and presenting : 1. An external face, slightly convex. 2. An internal excavated face. 3. An anterior border, thin and sharp superiorly, notched below to form the sigmoid cavity^ — an articular surface concave from above downwards, rounded from one side to the other, which corresponds with the humeral cavity, and is surmounted by a salient prolongation named the bectk of the olecranon. 4. A concave and smooth posterior border. 5. The summit — a kind of thick roughened tuberosity which terminates the uhia above, and into which are inserted the extensor muscles of the forearm. At its inferior extremity, the ulna ends, towards the lower fourth of the principal portion of the forearm, in an acute point, and sometimes by a small knob (capitulum ulnce). It is not rare to see it prolonged, especially in the Ass and Mule, to the inferior external tuberosity of the radius. This tuberosity then appears to belong to it, at least in part ; and all that portion which is situated behind its vertical groove might be justly considered as a dependency of the uhia. Structure and development. — The ulna contains much compact tissue, even in the region of the olecranon ; it is also very solid. It is an imperfect bone, developed from two centres of ossification only, one of these being for the apex of the olecranon. In the Ass (Fig. 66), the radius is more curved than in the Horse, and when its anterior face is placed on a horizontal plane, the bone only rests on its upper ' Tlv smaller siqmmrl cavity of Man. * 'The qreater f^iijinoid en vity of Man. 106 THE BONES. end and the middle of the body. It is also distinguished from that of the Horse by the depth of a narrow groove, which passes through the rough lip above and behind the inferior surface, superior to the small fossa F'g- 66. that receives the third bone of the upper row of the carpus during flexion and extension movements. The ulna of this animal is more developed than that of the Horse, and its olecranon is proportionately shorter, broader, and more hollowed on its internal face. The inferior extremity (Fig. 66, 9) is nearly always formed by a particular nucleus, which is also sometimes the case in the Horse. In the Hinny, the bone of the forearm resembles that of the Ass, with the exception of the smallness of the lower end of the ulna. Differential Characters in the Forearm Bones of OTHER Animals. The principal ditferential characters that they present are con- nected with the relative dimensions of the two bones and their mode of union. Regarding these, and as generally applicable, tlie follow- ing principles may be laid down : — 1 . The development of the ulna is in direct relation to the division of the foot. — Mouodactylous animals — such as the Horse, Ass, and Mule — have, in fact, only a rudimentary ulna. In the pentadacty- lous animals, on the contrary — as Man, the Cat, Elephant, etc., — this is a veritable long bone which equals, or even exceeds, the radius in volume. 2. The closeness of union between the radius and ulna is in increased proportion as the animal exchmvely employs its inferior extremity for standing and walking. — Thus, in Solipeds and Rumi- nants, and Pachyderms in general, the two bones are consolidated, or at least united by an interosseous ligament, and in so firm a manner that they can only execute very obscure movements on each other. The anterior limb of these animals is, indeed, only used to support the body on the ground. In those, on the contrary, which may employ it to dig up the soil, climb on trees, etc., or as an organ of preliension, the radius and ulna are merely joined at their extremities by an articulation, which permits them to move upon one another with the greatest facility. Rodents, the majority of the Caniivora, and the Quadrumana, are so provided ; but it is in Man that the relative independence of the two bones is carried to the highest degree. No animal can so easily execute the movements of pronation and supination of tiie hand, which are determined by the play of tlie two bones of the forearm on each other. To the indication of these fundamental characters, may be added some details on a few particular and important points. A. Ox, Sheep, Goat. — The forearm of the Ox is short; that of the Sheep and Goat is longer ; but in the three species, the ulna— thicker than in the Horse— is a long bone developed from three primary nuclei. It extends the whole length of tlie radius, and concurs in forming the articular surface corresponding with the carpal liones. The inferior articular surface is cut obliquely downwards and inwards. There are two radio-ulnar arches — a superior and in- ferior— united externally by a deep fissure. The union of tlie two bones is more intimate than in the Horse; for ossification always ends by invading that portion uf the interosseous ligament placed above the superior vascular arcli (Fig. 71). forearm bones OF THE 1, Diaphysis of the radius; 2, bicipital tuberosity ; 3, external and superior tuberosity of the radius ; 4, groove for the passage ot the anterior extensor of the phalanges ; 5, surface for insertion of branch of the perforans tendon ; 6, body of the ulna interrupted at its lower third, but more complete than usual ; 7, summit of the olecranon ; 8, beak of ditto ; 9, in- ferior extremity of ditto ; 10, radio-ulnar arch ; 11, crest above the inferior articular surface of the radius, behind. THE ANTERIOR LIMBS. 107 B. Camel. — The radius of this animal has a narrow, superior, articulating surface of two glenoid cavities, separated by a median salient crest terminating in front by a very marked coronoid process ; the bicipital tuberosity is large, and on the anterior face. The ulna is very -concave in its middle part, and tlie olecranon is broad and low. C. Pig. — The radius is short, its inferior surface cut rather obliquely as in Ruminants, and partly formed by the inferior extremity of the ulna, which is a voluminous bone provided with a medullary canal, and solidly united to the radius by an interosseous ligament, the complete ossification of wliich is rare. It is flattened before and behind, and is spread over the posterior face of the radius, so as nearly to completely cover it. The olecranon is very prominent (Fig. 7G). D. Dog, Cat. — The two bones of the forearm are nearly equal in volume, and are in contact only by their extremities, where they show for this purpose : 1. Above, on the ulna, a concave articular surface — the small sigmoid cavity ; and on the radius, a rounded hinge-like facet. 2. Below, two facets analogous to the preceding, but much smaller; that on the radius is concave, and that on the ulna convex. Tliese two bones slightly cross each other, so that the upper end of the ulna touches the radius behind and inwards, wliile the inferior terminates altogether outwards. In the Pig and Ruminants, the lower end is in contact with the upper row of carpal bones (Fig. 77). E. Kabblt. — The ulna is still more developed than in the Cat, and more curved length- ways. The posterior border of the olecranon is almost vertical, instead of being oblique from before to behind, and the sigmoid notch is deeper and shorter curved than in the Carnivora. ANTERIOR (OR FORE) FOOT, OR HAND. The anterior foot, or hand, is the region which presents the greatest 0flfe- rences when it is examined in the various individuals of the animal series. Nevertheless, notwithstanding these varieties, its constitution is fundamentally the same, and may be divided into three sections — ^the carpus, metacarpus, and phalangeal region. In vertebrate animals, the hand is composed of a certain number of parallel or quasi-parallel segments, which constitute the digits. Each complete digit is subdivided into three sections, placed one above the other ; these are, reckoned from above to below — carpus, metacarpus, and phalanges. The number of apparent digits varies from one to five ; and, however it may otherwise appear, philosophical anatomy has shown that the hand of all the domesticated animals may be considered as belonging to the pentadactylous type. When it does not appear to be so, this is due to more or less numerous or extensive atrophies or abortions always occurring according to fixed laws. (See remarks hereafter on the Hand in General.) 1. Caepal Bones (Figs. 67, 68, 69). The carpus (or 'knee') forms the base of the hand. Situated between the inferior extremity of the radius and the superior extremity of the metacarpal bones, it is composed of several small bones joined to each other, in the fresh state, by extremely solid articular bands. Collectively, they form an almost quadrilateral mass, in which may be distinguished two faces and four borders. The anterior face is slightly convex from side to side, and irregular ; it is in contact with the tendons of the extensor muscles of the metacarpus and phalanges. 1h.Q posterior face is very unequal, and converted — especially outwardly — into a groove, in which the tendons of the flexor muscles of the phalanges glide. 108 THE BONES. Fig. 67. The superior border articulates with the radius ; the inferior border with the metacarpal bones. The lateral borders are nearly flat ; above and behind the external border is remarked a considerable eminence, formed by the bone which will be hereafter studied as the super- carpal bene (pisiform or trapezium). In the carpus of the Horse are seven or eight bones, which are disposed in two superposed rows. The superior row comprises four bones placed side by side, and designated by the numerical names of Jirst, second, third, and fourth, viewing them from without to within. The inferior row has only three, which are named in the same manner. In applying to them the names proposed by Liser, we have, in the upper row — 1. The pisiform, or supercarpal bone. 2. The cuneiform bone. 3. The lunar bone. 4. The scaphoid bone. In the inferior row — 1. The unciform bone. 2. The magnum bone. 3. The trapezoid bone. 4. The trapeziimi (not constant). The description of these bones is most simple, and may be made in a general manner for all. Thus, with the exception of the supercarpal bone, they are solid, nearly cubical in form, and exhibit on their periphery : 1. Articular surfaces. 2. /Surfaces for insertion. The articular surfaces are small, flat, or slightly undulating facets, distributed on the superior, in- ferior, and lateral faces ; none are found in front or behind. The superior and inferior faces are entirely occupied by a single facet, which responds either to the radius, the metacarpals, or to the bones of the other row. The lateral facets are always RIGHT ANTERIOR FOOT OR HAND multiplc, aud iu coutact with the bones of the same OF A tier ; they do not exist, of course, on the outside of the bones at the ends of each row. The surfaces for insertion are absent on the superior and inferior faces ; they separate, in the form of roughened depressions, the lateral articular facets. Before and behind, they are covered by more or less marked rugosities. Bones of the Upper or Antibrachial Row (Figs. 68, 69). — The first, or os pisiforme, is outside the row ; it is situated above and behind the carpus, whence its name of super- carpal bone, by which it is usually known in veterinary anatomy. This bone, which merits a special description, represents a disc flattened on both sides. HORSE. 1, Radius; 2, grooves for the ex- tensor of the phalanges; 3, scaphoid; 4, lunar; 5, cunei- form ; 6, pisiform ; 7, mag- num; 8, unciform ; 9, great metacarpal; 10, small meta- carpal ; 11, sesamoid bone ; 12, suffraginis ; 13, coronary; 14, navicular; 15, pedal ; 16, basi- lar process. THE ANTERIOR LIMBS. 109 oflFering for study two faces and a circumference. The external face is convex, roughened, and channeled anteriorly by a groove that traverses it from above to below, in which glides the inferior tendon of the external flexor of the CARPUS OF THE HORSE (ANTERIOR FACE). 1, Pisiform or supercarpal bone (first of the upper row); 2. cuneiform (second ditto) ; 3, lunar (third ditto); 4, scaphoid (fourth ditto) ; 5, unciform (first of lower row) ; 6, OS magnum (second ditto) ; 7, trape- zoid (third ditto) ; 9, inferior articular face of the radius; 10, groove for the oblique extensor tendon of the meta- carpus; 11, groove for the anterior ex- tensor of the metacarpus; 12, groove for the anterior extensor of the phalanges ; 13, superior extremity of the large meta- carpal bone ; 14, tubercle for the inser- tion of the anterior extensor of the meta- carpus ; 15, superior extremity of the external small metacarpal bone. CARPUS OF THE HORSE (POSTERIOR FACE> 1, 2, 3, 4, 5, 6, 7, Same bones as in preced- ing figure ; 8, trapezium (fourth bone of the lower row); 9, 9, inferior articular surface of the radius ; 10, transverse crest for insertion of common posterior liga- ment of the carpus; 11, superior extremity of large metacarpal bone; 12, rugosities in which are fixed the deep layer of the suspense) y ligament of the fetlock or superior sesamoid ligament; 13, external small metacarpal ; 14, internal ditto. metacarpus. Its internal face — smooth and concave — concurs in forming the external wall of the carpal sheath. The circumference presents, in front, two 10 110 THE BONES. articular facets : the superior, concave, corresponds to the radius ; the inferior, convex, is in contact with the second bone of the upper row. The other three bones of this row increase in volume from without to within. The second bone, os pyramidalis, or cuneiform, articulates with the radius, the first bone of the lower row, the third of the upper, and the supercarpal bone ; it has, in all, five articular facets. The third, or os lunctre, has six facets, and is united below to the first and second bones of the second row. The fourth, or os scajjhoides — the most voluminous of the row— has only four facets, and articulates by its inferior face with the os magnum and trctpezoides. Collectively, the second, third, and fourth bones of the upper row form two articular surfaces. The superior, or radial articular surface, is very irregular ; but in examining it from without to within, there may be observed : 1. A glenoid cavity on the cuneiform bone. 2. In front, a transversely elongated condyle on the lunar and scaphoid bones. 3. A groove placed behind the preceding condyle. The inferior articulating surface, which corresponds to the second row, is constituted by several undulated facets ; it is convex outwardly and in front, concave posteriorly and inwardly. Bones of the Infekior or Metacarpal Row (Figs. 68, 69). — The thick- ness of these bones decreases from without to within. The first, unciform, or hookbone {os hainatum), has four diarthrodial facets, and responds, above, to the two first bones of the superior row ; below, to the first and second metacarpals. The second, os magnum, or os capitatum — ^the largest — has seven articular facets, three of which are on the interno-lateral face. It articulates, above, with the lunar and scaphoides ; below, with the principal metacarpal and the internal rudimentary metacarpal. The third, or trapezoides — the smallest — is provided with five facets, and is in contact with the scaphoides above, and the middle and internal metacarpals below. Collectively, these bones of the lower row form two large diarthrodial surfaces. The upper surface responds to the bones of the upper row, and is constituted in front, and from without to within, by a small condyle and two glenoid cavities ; behind, by two isolated condyles, formed by the os magnum and the trapezoides. The inferior articular surface is only formed by more or less long and plane facets, which incline towards each other. It articulates with the three portions of the metacarpus. Structure and deveJopm£nt. — Each carpal bone is formed by a nucleus of close spongy substance, enveloped in a very thick layer of compact tissue. Each is developed from a single centre of ossification. The carpal bones of the Ass much resemble those of the Horse, but the upper face of the Junar is more concave ; the facet of the cuneiform, for the pisiform, is less concave, but larger and triangular, and is always separated from the superior articular surface by a rough, wide, and deep groove. The pisifot m is more circular than that of the Horse, and is modified in shape to correspond with the cuneiform ; while the inferior surface of the os magnum is almost plane in the Ass, but in the Horse it is cut into a condyle in front and a glenoid cavity behind. Lesbre states that the trapezium is more frequent in the carpus of the Ass than the Horse. THE ANTERIOR LIMBS. Ill The carpal bones of the Hinny are hke those of the Ass, but those of the Mule resemble the Horse. Fi^. 70. Differential Characters in the Carpal Bones of other Animals. A. Ox, Sheep, Goat. — In these animals the carpus is composed of only six bones — four in the upper and two in the lower row, where the os magnum and trapezoid are fused together. The pisiform bone is in shape as its name implies, has no groove, and has no relation with the radius. The cuneiform bone articulates with the radius and ulna. The bones of the lower row only articulate with the large metacarpal bone (Fig. 71). B. Camel. — Among tlie seven carpal bones of the Camel are seen : a pisiform bone, having on its external face a large smooth groove ; a lunar, flattened on each side, and deeply notched laterally ; an unciform having a pyramidal prolongation behind ; an os magnum, smaller than the latter ; and a trapezoid, little developed, and entirely removed to the posterior part of the carpus. C. Pig. — The carpus of the Pig, like that of Man, contains eight bones — four in each of the rows. The second bone of the upper row articulates with the ulna, and to a very small extent with the radius. In the bones of the lower row, it is observed that the first articulates witli the two external metacarpals, the second with the great internal metacarpal, the third with the preceding and the small internal meta- carpal. The fourth, or trapezium, terminates inferiorly by a blunt point, and has no relations with the metacarpal bones, because the thumb is entirely undeveloped in this animal (Fig. 76). D. Dog, Cat. — In the Cat and Dog there are also eight bones. Lesbre says, however, that the scaphoid and lunar are sometimes one bone, and that often a lenticular bone is found in the upper row. The cuneiform bone is very developed, and occupies all the external border of the carpus, articulating with the ulna, first bone of the second row, and the first metacarpal. 'J'he pisiform bone is elongated, prismatic, thick at both ends, and has in front two contiguous articular facets— one for articulation with tlie ulna, the other for union with the cuneiform bone. The bones of the lower row diminish in size from the first to the fourth, and articulate — the first, with the first and second metacarpals; the second, with the metacarpal of the third digit; the third, with the fourth digit ; and the fourth with the metacarpus of the thumb. E. Rabbit. — This animal possesses nine carpal bones; for it is stated that between the two rows there is a piece which Blainville has named the intermediate bone It really belongs to the upper row, and represents the scaphoid. There are, therefore, five bones in the first carpal row of the Rabbit, and in this respect the hand of this species more nearly approaches the typical hand than that of the other domestic animals (see the Hand in General). 2. Metacarpal Bones (Figs. 67, 70). In Solipeds, the metacarpus is composed of three bones, named the " metacarpals," standing parallel to each other. These are the principal metacarpal and the two rudimentary metacarpals — an external and internal. Principal Metacarpal Bone {psmetacarpi magnum').— This is a long cylindrical bone, situated vertically between the carpus and the digital region. Bodij. — The body is a little depressed before and behind, which permits it to be described as having two faces and two borders. The anterior face is perfectly smooth and rounded from side to side. The posterior face is flat, and exhibits : 1. Towards the upper third, the nutrient foramen of the bone. 2. On the sides, posterior view of right metacarpus. 1, Head of large meta- carpal bone for ar- ticulation with the trapezoi'i, magnum, and unciform ; 2, inner splint, rudi- mentary, or small metacarpal bone,for articulation with the trapezoid ; 4, scabrous surface for the attachment of the suspensory liga- ment ; 5, nutrinnt foramen ; 6, median ridge separating tne two inferior con- dyles. 112 THE BONES. two narrow, rousrhened surfaces, parallel and elongated vertically, commencing near the superior extremity, to disappear a little below the middle of the bone ; these surfaces are held in apposition to the rudimentary metacarpals, by an interosseous ligament which is often ossified in old Horses. The borders — external and internal — are very thick, round, and smooth, like the anterior face. Extremities. — The superior is flattened before and behind, and presents. 1. Above, an undulating articular surface, formed by the union of several flat facets more or less inclined towards each other ; they articulate with all the lower row of carpal bones. 2. Anteriorly and inwardly, a tuberosity for muscular insertion. 3. Posteriorly — and directly above the roughened surfaces of the posterior face — four small diarthrodial facets in pairs, and running into the larger articular surface by their superior border ; they are adapted to similar facets on the rudimentary metacarpals. The inferior extremity, elongated transversely, articulates with the first phalanx and the sesamoid bones by an articular sm-face — convex from before to behind — which is composed of tivo lateral condyles separated by a median spine. The two condyles would be exactly alike, if the antero-posterior diameter of the external condyle were not less extensive than that of the opposite condyle. Both are hollowed on the sides by an excavation for the attachment of ligamentous fasciculi. Structure and development. — The principal metacarpal is one of the most compact bones in the body. It is developed from two centres of ossification, one of which is for the inferior extremity. RuDiMENTAEY METACARPALS (ossa metacctrpi pavva). — The two rudimentary (sm.aU) metacarpal (or splint) bones are elongated, and placed against the posterior face of the principal bone, one without, the other within. Each is in the form of an inverted pyramid, and exhibits a middle part and two extremities. Middle portion. — Prismatic and triangular, this ofl^ers : 1. Three faces — an external, smooth and rounded from one border to the other ; an internal, plane, and equally smooth ; an anterior, covered with asperities to give attachment to the interosseous ligament uniting the lateral metacarpal bone to the median. 2. Three salient borders which markedly separate the faces from each other. Extremities. — The superior, the largest, is named the head, and shows : above, a diarthrodial facet which articulates with one or two bones of the inferior row of the carpus ; in front, other two small facets continuous with the preceding, and in contact with similar facets on the large metacarpal bone ; on the other points of its periphery are rugosities for the attachment of ligamentous and tendinous fibres. The inferior extremity only reaches to about the lower fourth of the large metacarpal bone, and terminates in a small button-shaped enlarge- ment, which is never fused with the latter. The two small metacarpals, although very much alike, may yet be easily distinguished from each other. For instance, the internal bone is always the thickest, and often the longest ; besides, the superior articular surface of its head results from the union of the two facets articulating with the two last carpal bones of the lower tier. Structure and development. — Of a somewhat compact texture, like all the long bones, these have no medullary canal, and are developed from only one ossifying centre. Not unfrequently, however, the tubercle is formed from a special centre. The metacarpus of the Ass is recognized by : 1. The great inequality of the small metacarpals. 2. The thickness of the large metacarpal (the width is to the thickness as 1-35 : 1 in the A&s, and as 1*53 : 1 in the Horse). 3. The depth of THE ANTERIOR LIMBS. 113 the depressions above the inferior articular surface, poste- riorly. 4. The level form of the facet articulating with the OS magnum of the second row. 5. The presence of a small, flat, vertical facet on the posterior contour of the upper articular surface of the large metacarpal. In the Mule and Hinny, the small metacarpals are nearly- alike, as in the Horse ; the large metacarpal is flattened, as in that animal, with marked depressions posteriorly. Differential Characters in the Metacarpus of other Animals. The number of metacarpal bones naturally varies with tliat of the digits : — In the Carnivora there are 5 In the Pig there are 4 In Ruminants there are 2 or 3 With regard to their shape and form, they offer interesting differences, which will now be studied. A. Ox, Sheep, Goat. — In these animals the metacarpal bones are two in number — a principal, which itself results from the consolidation of the second and third metacarpals ; another, altogether rudimentary, situated outwardly; and a third— not constant — embedded in a fibrous cord passing along the inner border of tlie principal metacarpal. The principal metacarpal is channeled on its anterior face, and for its whole length, by a deep vascular fissure — a trace of the primitive separation of the bone into two pieces. Tliis fissure presents, inferiorly, the anterior orifice of a canal that completely traverses the bone. The posterior face is nlso marked by a very slight longitudinnl groove. The superior extremity exhibits, externally and posteriorly, a single diar- throdial facet for articulation with the rudimentary metacarpal. The inferior extremity is divided by a deep notch into two articular surfaces, which together resemble the single surface in the Horse ; each articulates with one of the digits ; the external is always smaller than the internal. In the foetus, the two long bones that form the great metacarpal are simply laid together, and their medullary canals are separated from each other by the double partition which results from this apposition ; after their coalescence, however, the partitions are completely destroyed by absorption, and in a short time there is only a single medullary canal for the entire bone. Tiie rudimentary metacarpal is only a small osseous stylet, articu- lating, by a diarthrodial facet, beiiind and to the outside of the superior extremity of the principal metacarpal; it is sometimes absent in the Sheep and Goat. B. Camel.— The metacarpus of the Camel is very long, quadran- gular in its upper two-thirds, and flattened behind and before in its inferior third. Its posterior face is converted into a kind of concave furrow, by the considerably raised borders of the bone. The superior articular surface is divided into two parts by a large roughened depres- sion ; the inner part is on a higher level than the outer. The inferior extn mity is also divided into two articular surfaces by a very deep notch ; each surface is condyloid in its anterior moiety, and is like that of the Horse in its posterior moiety. C. Dog, Cat, Rabbit.— The five metacarpals of the Dog and Cat articulate with each other, at their superior extremities, by lateral facets; they offer, at their inferior extremity, a condyle prolonged back- wards by an articular surface resembling that of the Horse. The forearm and foot OF THE ox (front view). 1, Olecranon ; 2, body of the ulna ; 3, body of the radius; first and second bones rudimentary metacarpals; 10, principal inetacarpals ; 11, external digit; 4, 5, 6, first, second, and third bones of the upper row of the carpus; 7, of the lower row ; " " ' ' 12, internal digit. 114 THE BONES. middle two are always longer than the two lateral. The smallest belongs to the fifth digit, or thumb, and is terminated inferiorly by a trochlea. D. Pig. — The four metacarpals of the Pig articulate with each other, as in the Carnivora. The second and third are larger than the first and fourth. The fifth metacarpal is not developed (Fig. 76). 3. Bones of the Phalangeal or Digital Region (Figs. 72, 73). Solipeds have apparently only one digit, supported by the principal metacarpal bone, and composed of three pieces placed end to end, one upon another. The first comprises three bones — a principal, the first phalanx — and two complemen- Fig. 72. Fig. 73. LATERAL VIEW OF THE DIGITAL REGION (OUTSIDE OF RIGHT LIMB). 1, Large metacarpal bone ; 2, 3, outer and inner sesamoids ; 4, first, jiroximal, os suf- fraginis, or metacarpal phalanx ; 5, its posterior surface ; 6, tuberosity for liga- mentous insertion ; 7, inner condyle of ditto ; 8, eminences on second phalanx for attachment of lateral ligament; 9, smooth surface for passage of deep flexor tendon on second phalanx ; 10, median or second phalanx, os coronae, or small pastern bone ; 11, navicular bone; 12, third phalanx, pedal, or coffin bone ; 13, its basilar process. POSTERIOR VIEW OF THE DIGITAL REGION. 1, Large metacarpal bone ; 2, 3, outer and inner splint bones ; 4, 5, sesamoid bones ; 6, suffraginis ; 7, 8, tuberosities for inser- tion of crucial ligaments ; 9, triangular space for insertion of short sesamoid liga- ment ; 10, anterior face of suffraginis ; 11, 12, tuberosities for ligamentous inser- tion ; 13, articular depression separating condyles ; 14, 15, second phalanx ; 16, scabrous surface for ligamentous attach- ment; 17, smooth surface for gliding of deep flexor tendon ; 1 8, navicular bone ; 19, pedal bone ; 20, basilar process ; 21, plantar foramen. tary ones, the sesamoids. The second is formed by the second phalanx, and the last, which terminates the limb, is constituted by the third phalanx, and an accessory bone which has received the name of the small sesamoid {navicular First (proximal) or Metacarpal Phalanx (Large Pastern Bone, or Os Suffraginis).— The first phalanx (Figs. 72, 73), the smallest of all the long bones, is situated in an oblique direction from above downwards, and behind to before, between the principal metacarpal and the second phalanx. THE ANTERIOR LIMBS. 115 Body. — Flattened before and behind, this bone exhibits : an anterior face^ round from one side to the other, and slightly roughened above and below ; a posterior face, flat, covered with ligamentous imprints in the form of a triangle with the base reversed ; two lateral borders, thick, rounded, and provided with some imprints. Extremities. — The superior, the largest, presents : Above, an articular surface adapted to the inferior metacarpal surface, and consequently composed of two glenoid cavities separated by a groove running from front to back ; laterally, and a little posteriorly, a well-defined tubercle of iiisertion. The inferior extremity has a transversely elongated articular surface, to articulate with the second phalanx ; this surface is formed by tivo condyles separated by a middle groove, and surmounted laterally by a small tuberosity for ligamentous insertions. The external condyle is smaller than the internal, and when the bone is placed upon a horizontal plane, the anterior face turned upwards, it only touches by three points— the two tubercles of the upper extremity and the internal condyle ; by pressing on the external condyle, it is easy to make the bone oscillate. The first phalanx is a very compact bone, and is developed from two points of ossification, one of which is for the superior extremity alone. Professors Yachetta and Fogliata, of Pisa, assert that this bone, as well as the second phalanx, has three centres of ossification during uterine life. Sesamoids (Figs. 72, 7^). — These are two small, short bones placed side by side behind the superior extremity of the first phalanx, the articular sur- face of which it completes, as it has not extent enough to be exactly adapted to the metacarpal surface. Each of these bones represents a small, irregularly shaped polyhedron, or, rather, a short trifacial pyramid. It offers : an anterior face, which is articular, and corresponding to the inferior extremity of the principal metacarpal bone, moulded, as it were, on one of the condyles and one of the sides of the median ridge ; a posterior face, covered with cartilage in the fresh state, and forming, with that of the opposite bone, a gliding concave surface for the flexor tendons of the phalanges ; a latercd face, studded with ligamentous imprints ; a summit, directed upwards ; and a base, turned downwards, and serving for the attachment of several ligaments. Second (or Median) Phalanx (Os Coron.^, Small Pastern Bone (Figs. 72, 73). — This is a short bone, situated in the same oblique direction as the first phalanx, and between it and the third. Its general form is that of a cube flattened before and behind, and offering the following features : an anterior face, covered with some slight imprints ; a posterior face, provided, above, with a transversely elongated gliding surface ; a superior face, channeled by two glenoid cavities, to match the inferior articulating surface of the first phalanx ; an inferior face, formed on the same plan as the last — being occupied by two unequal condyles, which articulate with the third phalanx and the navicular bone ; two lateral faces exhibiting a very marked imprint. In the interior of this bone is found a nucleus of very condensed spongy substance, enveloped in a layer of compact tissue. It is usually developed from a single centre of ossification, though in many subjects there is a complementary nucleus for the superior articular and the posterior ghding surface. Third (Distal or Ungual) Phalanx, Os Pedis (Pedal or Coffin Bone) (Figs. 72, 73, 74). — This is a short bone which terminates the digit, and sustains the hoof that incloses it and the navicular bone. When completed by a special tibro-cartilaginous apparidus, it represents the segment of a very short cone. 116 THE BONES. obliquely truncated behind, from the summit to the base. It offers for study : three faces, three borders, and two lateral angles. Faces. — The anterior, convex from side to side, and cribbled by porosities and vascular openings, shows on each side: 1. The preplantar fissure — a horizontal groove more or less ramified, which commences behind, between the retrossal and basilar processes, terminating in front in one of the foramina that penetrate the bone. 2. The patilohe eminence — a roughened projecting surface, situated between the preceding fissure and the inferior border of the bone. The superior face is occupied by an articular surface formed by two glenoid cavities and a slight median ridge ; it comes in apposition with the inferior face of the second phalanx. The inferior (or solar) face, hollowed out like an arch, is divided into two regions by the semilunar crest, a salient line which describes ^'-- '^^- a curve forwards. The anterior region is perforated with very fine porosities, and corresponds to that part of the hoof named the sole. The posterior region shows, immediately behind the semilunar crest, a median imprint, and two lateral channels designated the plantar fissures. These originate at the root of tlie basilar process, are directed obliquely downwards and inwards, and open into the plantar foramina, the external orifices of two large canals which enter PLANTAR SURFACE OF THIRD ^j^g jjQ^g ^ud uultc lu Its luterlor to form the semilunar PHALANX. « o sinus. 1, Lower face, or sole \ 2, i, r, i n^^ • ^ ■^ -ii, wings, or retrossal pro- Borders.— ThQ Superior describes a curve, with cesses; 4. internal border; the convexity forward, and presents : 1. In its middle, 5, plantar foramina. ^.j^^ pyramidal eminence of the OS pedis — a single tri- angular process, flat before and behind, roughened on its anterior aspect, and concurring, by its posterior surface, to form the articular surface which responds to that of the second phalanx. 2. Laterally, two facets of insertion which encroach on the anterior surface, and even advance, posteriorly, nearly to the preplantar fissure. The inferior border is thin, dentated, convex, and semicir- cular ; it is perforated by from five to ten large foramina, which pass into the bone. The posterior border is slightly concave ; on it is observed a very narrow, transversely elongated, diarthrodial facet, which becomes confounded with the superior large articular surface, and is adapted to a similar facet on the navicular bone. Lateral angles. — These are two projections directed backwards, on the summit of which the three borders of the bone unite, and which gives attachment to the lateral fibro-cartilages. A deep notch — the origin of the preplantar fissures — separates. each into two particular eminences: one, the superior, named by Bouley the basilar process ; the other, the inferior, prolonged behind, and desig- nated by Bracy Clark the retrossal process (from retro, behind, and ossa, bone). Sfructvre. — The os pedis exhibits in its interior the semilunar sinus — a cylin- drical, transversely elongated, and semicircular cavity resulting from the arching anastomoses of the two plantar canals. From this cavity pass off numerous channels, which anastomose frequently with each other, and open externally by the foramina on the anterior face of the bone, or by those on its inferior border. The OS pedis has for its base a nucleus of spongy substance, surrounded by a layer of compact tissue. The latter is thicker towards the pyramidal eminence than elsewhere, and sends into the interior numerous prolongations which form THE ANTERIOR LIMBS. 11? the walls of the semilunar sinus, as well as the bony channels which spring from it. Development. — The third phalanx, formed from a single nucleus of ossifica- tion, undergoes numerous changes in its configuration during life. Thus, in the young animal the lateral angles are thick, obtuse,^ and but little prolonged posteriorly ; but as it grows older, they increase in length and become salient. The development they then assume, is due to the progressive ossification of the lateral cartilages implanted on their surface. It often happens, in very old horses that this ossifying process is carried to an extreme degree, and nearly the whole substance of these complementary organs is invaded. From the commencement, its inevitable result is to convert the notch which separates the basilar from the retrossal process into a foramen. The comple me atari/ Jihro-cartilaiiinous apparatus of the as pedis. — To under- stand properly the disposition of this portion of the .foot, it is necessary that a previous knowledge of the ligaments and tendons attached to the os pedis should have been acquired ; therefore a detailed description will be given when the Horse's foot is studied as a whole, in the article on the Sense of Touch. It will be sufficient here to state that this apparatus consists of two lateral pieces — the fibro-cartilages of the OS pedis, united behind and below by iheplantar cushion — a fibrous and elastic mass on which rests the navicular bone, through the medium of the perforans tendon. The Small Sesamoid or Navicular Bone (Figs. 72, 75). — This short bone is annexed to the third phalanx, behind which it is situated ; it is elongated transversely, flattened above and below, and narrow at its extremities. It offers : 1. A superior face, on which are pro- longed the glenoid cavities and the median ridge of the articular surface of the OS pedis ; it articulates with the second phalanx. 2. An inferior face, dixided by a slight ridge into two undulated facets, and covered with cartilage to form a gliding surface. An anterior border, channeled lengthways by a groove of insertion, above which is remarked a diar- throdial facet that brings the small sesamoid into contact with the posterior border of the third phalanx. 4. A posterior border and two extremities, for ligamentous insertion. This bone, as well as the sesamoids, originates from a single centre of ossification. It is formed of a layer of compact tissue enveloping a nucleus of very condensed spongy substance. (For differences in the Ass, see Posterior Limb.) NAVICULAR BONE OF THE HORSE. Anterior Border and Inferior Face. 1, articu- lar facet for the facet on the po.stenor border of the OS pedis; 2, roughened groove on the anterior border ; 3, inferior face, smooth and undulated. B, Posterior Border and Superior Face. 1, Articular face for the lower end of the second phalanx; 2, posterior border, with many foramina. 118 THE BONES. • Differential Characters in the Digital Region of other Animals. In the other domesticated animals, the number of complete digits is as follows : — Carnivora 5 Pig 4 Ruminants • .... 2 A. Ox, Sheep, Goat. — These animals certainly possess four digits, but only two are perw feet— the mMius and annularis — and these articulate with the inferior extremity of the principal metacarpal (Fig. 71). The two others — the index and auricularis — are in a rudimentary con- dition, and are represented by two small bones situated above and behind the metacarpo- phalangeal articulation. In the Ox, Sheep, and Goat, each of the perfect digits comprises (like the single digit of the Horse) three phalanges and three sesamoids. The first phalanx fairly represents the moiety of this phalanx in the Horse. It has no Fig. 77. Fig. 76. y^ ^- if' '' *~ ANTERIOR LIMB OF THE PIGi. FOREARM AND FOOT OF THE DOG (AN- TERIOR face). 1, First digit ; 2, second digit ; 3, third digit ; 4, fourth digit ; 5, thumb ; 6, 7, 8, 9, first, second, third, and fourth bones of the lower row of carpnl bones ; 10, 11, first and second bones of the upper row; 12, supercarpal bone; 13, body of the ulna ; 14, apex of the olecranon; 15, beak of the olecranon; 16, body of the radius. posterior imprints, but shows them on its inner surface for the attachment of several ligaments. This internal face is plane, and the external convex ; these characters are repeated in the other two phalanges. It is also remarked in all the phalangeal bones, that the external articular facet of the extremities is always larger than the iuterual. Of the two sesamoids, the external THE ANTERIOR LIMBS. 119 Fig. 78. is wider and less elongated than tlie internal. They articulate with each other and with the first phalanx, by small diarthrodial facets. The second phalanx is hollowed internally by a small medullary cavity. The ungual phalanx, as a whole, resembles one of the lateral moieties of the os pedis of Solipeds. Tills phalanx has no complementary fibro-cartilage, basilar process, or retrossal eminence, nor yet a cavity for insertion on the sides of the pyramidal eminence. The semilunar crest is replaced by an obtuse, thick, and rugged ridge, which occupies quite the posterior limit of tlie inferior face of the bone. Three large canals penetrate the third phalanx— two to the base of the [lyramidal eminence, and one towards the origin of the preplantar fissure. They form, in the interior of the bone, a vast sinus, giving rise to several vascular canals which open on the surface. There is only one foramen at the base of the pyramidal eminence in the smaller Ruminants. B. Camel. — In this animal, there are in each digit only three phalanges and two large sesamoids. The direction and form of these phalanges differ notably from what is seen iu Ruminants. The first phalanx is long, very oblique, constricted in the middle, and very thick at both ends. On the superior articulating surface is a single glenoid cavity, dirided posteriorly by a median groove. The inferior surface is prolonged on the posterior face of the bone, which is converted into a kind of pulley. The second phalanx is nearly horizontal, and much flattened above and below. The ungual phalanx is somewhat like an irregular trifacial pyramid with a blunt summit ; near its base, on its upper face, it has a roughened tubercle. C. Pig. — The Pig has four complete digits articu- lating from the metacarpals ; the thumb is absent. The index and auricularis— or fourth and fifth digits — are short, and do not usually rest on the ground (Fig. 76). D. Dog, Cat, Rabbit.— The five digits of the log and Cat are exactly analogous to those of Man. Thus, the external corresponds to the auricularis, the second to the annularis, the third to the medius, the fourth to the index, and the internal to the thumb. The latter, very small, has only two phalanges, and does not come into contact with the ground. Each of the first four is composed : 1. Of a first phalanx, to which are annexed two sesamoids. 2. A second phalanx, which represents a veritable long bone. 3. A conical phalan- gette, pointed, curved downwards, and hollowed at its base by a circular groove, in which is lodged the matrix of the claw. The small sesamoid (or navicular bone) la absent, but is replaced by a prominence of the ungual phalanx. The auricularis and index are alike, and not 80 long as the annularis and medius, which are the same in length. HUMAN SCAPULA (EXTERNAL ASPECT). 1, Supra-spinous fossa; 2, infra-spinous fossa ; 3, superior border ; 4, supra- sca|)ular notch; 5, anterior or axil- lary boi-der ; 6, head of the scapu- lar and glenoid cavity ; 7, inferior angle ; 8, neck of the scapula ; 9, posterior border; 10, spine; 11, triangular smooth surface, over which the tendon of the trapezius glides, with the tuberculum spinse scapulae between it and 10 ; 12, acromion process ; 13, nutrient fora- men ; 14, coracoid process. Comparison of the Thoracic Limb of Man with that of the Domesticated Animals. A. Shoulder. — The shoulder of man has for its base two well-developed bones — the scapula and clavicle. The scapula (Fig. 78) is more distinctly triangular than that of all the domesti- cated animals ; its vertebral border is also more extensive. The scapular spine, very elevated is continued by an acromion whose extremity reaches to above the scai)ulo-humeral articulation. The latter is separated from the remainder of the spine by a constriction called the pedicle of the acromion. The coracoid process is voluminous, and resembles a semi-flexed finger. The clavicle extends from the acromion to the sternum ; it is flattened above and below, and flexed like an italic S. This inflection of the clavicle is more pronounced in the male than the female. B. Arm. — The humerus (Fig. 79) of Man is much longer than that of animals. Its dia- physis is prismatic, and divisible into three faces ; the deltoid imprint has the form of a V with its point directed downwards. The voluminous articular head is turned inwards ; the bicipital 120 THE BONES. groove is single, and looks outwards. The inferior articular surface resembles that of animals, except that the condyle is more distinct. C. Forearm (Fig. 80). — The two bones of the forearm, as we have already seen, only articu- late by their extremities; they are separated from one another in their middle part. The superior extremity of the radius corresponds with the condyle of the humerus ; that of the ulna articulates with the humeral trochlea. The coroiioid process belongs to the ulna. At the lower extremity of the forearm, it is reiniirked : 1. That the radius corresponds with tlie greater portion of the cnrpus, while the ulna only articulates with the pyramidalis. 2. Tliat the radio- carpal articulation is protected outwardly and inwanlly by two small osseous prolongations — the styloid processes of thu ulna and radius. D. Hand. — 1. Carpus (Fig. 81). — The carpus of Man is composed of eight bones — four in each row. The three tirst of the upper row articulate with the radius ; the fourth responds to F.2. Fig. 8U. RIGHT HUMAN HUMERUS (ANTERIOR SURFACE). 1, Shaft ; 2, head ; 3, neck ; 4, greater tu- berosity ; 5, lesser tuberosity ; 6, bici- pital groove ; 7, interior bicipital groove ; 8, posterior bicipital ridge ; 9, rough sur- face for insertion of deltoid; 10, nutrient foramen; 11, eminentia capitata ; 12, trochlea; 13, external condyle; 14, in- ternal condyle ; 15, external condyloid ridge; 16, internal condyloid ridge; 17, fossa for the coronoid process of ulna. HUMAN ARM-BONES (FRONT VIEW). 1, Shaft of ulna ; 2, greater sigmoid notch j 3, lesser sigmoid notch ; 4, olecranon process ; 5, coronoid process ; 6, nutrient foramen ; 7, ridges for insertion of in- terosseous membrane ; 8, capitalum ulnae ; 9, styloid process; 10, shaft of radius; 11, its head ; 12, its neck ; 13, its tube- rosity ; 14, oblique line ; 15, lower end of bone ; 16, styloid process. the ulna. In the bones of the lower row, the trapezium responds to the metacarpal of the thumb and that of the index; the trapezoides to the latter only, the os magnum am unciform to the metacarpals of the medius, annularis, and little finger. The pisiform bone and the cuneiform process of the unciform convert the posterior face of the carpus into a channel. 2. Metacarpus (Fig. 81).— The five metacarpals of Man are parallel to each other; they articulate by their superior extremities witli the bones of the carpus, and by their inferior ex- tremities witii the phalange-s. They are all concave in their middle portion, and tiiickened at their ends. Tlie metacarpal of the thumb is the shortest and strongest. The others diminish in volume from the fourth to the first. THE ANTERIOR LIMBS. 121 Fig. 81. 3. Digital Region (Fig. 81). — Here we fiurl five digits, each compcsed of three bony colum- nettes, with tlie exception of the thumb, in which only the second and third phalanges are present. They decrease in length from the third to the first, and the third to the fifth. The first and second phalanges are small semi-cylindrical bones, slightly thickened at their ex- tremities. The ungual phalanges are constricted in their middle, and widened like a horse- slioe at their inferior extremity ; the palmar face is roughened, the dorsal face smooth. Article V. — The Hand in General. 1. The limits of this region, as already mentioned, extend from the lower end of the forearm to the third phalanx, inclusive. If it is examined super- ficially, the diiferences it presents in the number and arrangement of the parts composing it are very striking. The digits that terminate the hand are pieces which, from the earliest times, have most occupied the attention of observers. Thus, when we do not go beyond simple appearances, it might be believed that, with regard to the number of digits, there were great diiferences in animals. From this point of view, the domestic animals form a nearly decreasing series, commencing with the Gar- ni vora and terminating with Solipeds. And in relying upon these appearances, some anatomists have dis- tinguished these animals as monodacti/les, didad ij.es, and. regular and irregular tetradadijUs ; but in the generalizations in this work, we have ignored these designations, as they are in complete disaccord with the teachings of philosophical anatomy. In fact, although the Horse appears to have only one digit, the Ox two, the Pig four, the Dog and Cat five, yet the hand in all these creatures may be referred to the pentadactylous type. To demonstrate this unity in composition, the laws promulgated by Grethe with regard to the vege- table kingdom, and developed and applied to animals by Geoff"roy Saint-Hilaire, are accepted ; and we have indicated in these few words the laws of analogy and harmony, the principle of relations, the elective affini- ties, the organic adjustments. These laws and these principles have been more particularly applied to the study of the 'hand of animals by Joly and Lavocat, Paul Gervais, Richard Owen, Delplanque, and Arloing. Comparisons, and the attentive study of normal conditions and anomalies, have served as a basis for the conclusions arrived at by these authorities. The anomalies that certain zoologists were tempted to regard as proper facts likely to mislead philosophical anatomists, have, on the contrary, been of assistance to the latter ; because, according to the expression of Geoffroy Saint-Hilaire, " an anomaly restores that which \ye term, in zoology, -normal conditions." 2. The Archetypal Hand. The chief type is composed of five digits, and a complete digit in three sections — the carpus, -which has two bones ; the metacarpus, which has only one : and the phalangeal section, which has three. This constitution of the hand has been conceived by Joly and Lavocat, and reasoning would sanction its acceptance, if it were not presented in some animals PALMAR SURFACE OF LEFT HUMAN HAND. 1, Scaphoid bone; 2, semilu- nare; 3, cuneiform ; 4, pisi- form ; 5, trapezium ; 6, groove in trapezium for ten- don of flexor car))i radialis; 7, trapezoides ; iS, magnum ; 9, unciform ; 10, 10, the five metacarpal bones; 11, 11, first row of phalanges; 12, 12, second row; 13, 13, third row; 14, first phalanx of the thumb; 15, second and last phalanx. 122 THE BONES. DESCRIPTION ON OPPOSITB PAGE. THE ANTERIOR LIMBS. 123 —such as the 3Ioh, Marmot, and Guinea-pig— each, of which have five digits arising from the two carpal bones. In order to study the hand, these authorities place it in its natural position — pronation ; and the different pieces are reckoned from without to within by the numbers 1, 2, 3, 4, 5. 3. Modifications in the Archetype. But the archetypal hand is not constantly realized, even when five digits— such as they are usually understood to be — are present. The hmnan hand, for instance, is formed by five digits and five metacarpal bones, with only eight bones in the carpus. When we go from Man, the number of bones in the three sections is more or less diminished ; and in the carpus of the domestic animals, as in that of Man, if the archetypal number does not exist in all the sections, it is because certain pieces have been fused with adjoining ones, or they are not developed. In several instances, certain bones become so atrophied that at the first glance they are not recog- nizable. Joly and Lavocat at first imagined that these atrophies took place according to some fixed law ; they believed that the atrophy operated on the middle part of the bones, extending downwards, and that the last piece to dis- appear, in an atrophied digit, was that of the carpus. But since the publication of their first memoires, Lavocat has had occasion to state that this law is not absolute. After these preliminary remarks, we will study the modifications in the archetypal hand in Man and the domestic animals, and demonstrate that in these it may easily be referred to the pentadacty- lous type. 1. Man. — The human hand having five digits and five metacarpal bones, it is rational to admit the virtual existence of five pieces to each of the carpal rows. Materially, there are only four bones in each of these two rows ; but the com- parative study of the relations of each of these bones in the human carpus, and in that of animals which are in possession of the archetypal hand, leads to the belief that the scaphoid is the result of fusion of the fourth and fifth bones of the upper row, and the unciform the fusion of the first and second bones of the HAND OF MAN AND THE DOMESTIC MAMMALIA, NORMAL AND TERATOLOGICAL (Fig. 82). A, Human hand (dorsal face). B, Dog's hand (same position). C, Pig's hand (normal condition). 1, Trapezium. c', Pig's hand : the thumb (1) is completely developed from the trapezium (2). D, Sheep's hand (normal condition). 1, Principal metacarpal ; 2, rudimentary metacarpal, external ; 3, ditto, mternal (not constant). E, Hand of the aquatic Chevrotain. 1, Double principal metacarpal; 2, 3, lateral metacarpals followed by phalanges. F, Lamb's hand, a. Carpus and superior extremity of metacarpus (seen in profile), on which the metacarpus of the thumb (1) was shown. 6, Ditto (face) : 1, internal rudimentary metacarpal completely developed ; 2, horny plate representing the thumb on the surface of the skin ; 3, horny plate representing the first digit on the surface of the skin. G, Lamb's hand on which are four complete digits. 1, Principal metacarpal ; 2, 3, lateral meta- carpals completely developed. H, Horse's hand (normal condition). 1, Principal metacarpal ; 2, 3, rudimentary metacarpals. I, Horse's hand, adult (teratological specimen, showing the division of the phalangeal section, 1, 1, of the single digit of Solipeds). K, Foal's hand (teratological specimen described by Delplanque). 1, Principal metacarpal bifid in its lower third ; 2, e.\ternal rudimentary metacarpal ; 3, 4, phalangeal sections resulting from the division of the great digit. L, Horse's hand, adult (teratological piece), a. Carpus (inner aspect) : 1, trapezium ; 2, trapezoid ; 3, principal metacarpal ; 4, internal rudimentary metacarpal transformed into a complete meta- carpal ; 5, styliform piece representing the metacarpal of the thumb. 6, Inferior extremity of the digital region (inner aspect): 1, principal metacarpal, followed by normal phalanges; 2, in- ternal rudimentary metacarpal transformed into a complete metacarpal, followed by normal phalanges. 124 THE BONES. inferior row (Fio;. 82, a). It is easy, therefore, to refer Man to the most perfect pentadactylous type. 2. Carnii'ora. — The hand of the Dog and Cat has five distinct digits, the internal of which — the thumb — smaller than the others, does not reach the ground (Fig. 82, b). By the metacarpus and the phalangeal section, these animals belong, then, to the pentadactylous type. They appear to be removed from it by the constitution of the carpus, for it has only seven (Dog) or eight bones (Cat) ; there has been fusion of the lunar and scaphoid, but the fifth bone of the upper row is free. The number of bones being thus raised to eight, we know how they may be referred to the archetype — by proceeding in the same manner as for the human carpus. 3. Rodents. — The Rabbit has five digits, like the Cat, and nine carpal bones. Five of the latter are in the upper row, in consequence of the duplication of the fourth bone, which comports itself as in Carnivora. The scaphoid is between the two rows, as in the tarsus. The Rabbit, therefore, only differs from the archetype by the fusion of the first to the second inferior carpal bone, which sometimes is incomplete. We have thus demonstrated the pentadactylous composition of the hand in the domestic Carnivora and Rodents — an easy task, as these animals have five apparent digits. We will now pass to the Pig. 4. Pig. — This animal has eight carpal bones and four complete digits, with metacarpals and phalanges — two large and two small (Fig. 82, c). There is no difficulty in referring the carpus of the Pig to that of Man or the Carnivora, and from these to the archetype. It suffices to find in this creature a trace of the fifth digit, in order to place it in the pentadactylous type. Normally, the fifth bone of the lower row — the trapezium — has no relation with the bones of the metacarpus ; which proves that the remainder of the thumb is absent. But this thumb has been found entirely developed, and having the appearance of the other digits. In Fig. M (c'), this has been shown in the teratological cases observed by Joly and Lavocat, and Goubaux and ourselves. Consequently, although the Pig has been classed among bisculcate animals by certain zoologists, yet it has in the anterior limb five digits, more or less completely developed. 5. Ruminants. — Intended as an organ of support, the hand of Ruminants offers several fusions or abortions, which increase its solidity at the expense of its suppleness and flexibility. Thus, in the first place, it appears more difficult than in other animals to find, materially or virtually, the elements of the five digits. Only six bones are found in the carpus of the 0-r, Sheep, and Goat ; but the study of relations demonstrates that there are : abortion of the fifth bone of the upper row ; fusion between . the first and second, and between the third and fourth, and abortion of the fifth bone, of the lower row. So that, in reality, there are met with, in the carpus of the domestic Ruminants, the elements of ten bones, with the exception of two not developed (Fig. 82, d). The metacarpus comprises a principal metacarpal — the inferior articular face of which is double — and a stylif orm bone placed alongside its external and internal borders. For a long time, GeofFroy Saiut-Hilaire had demonstrated that the principal metacarpal is formed by two metacarpals brought together during foetal life, and separated by a more or less incomplete medullary septum during extra- uterine existence. Besides, the isolation of the two metacarpals — temporary in the Ox — is permanent in some other Ruminants, such as the Chevrotain of Guinea and THE ANTERIOR LIMBS. 125 the Aquatic Chevrotain (Fig. 82, e). With regard to the external stylet, it is an atrophied metacarpal ; for in some teratological instances it becomes elongated, and supports a more or less perfect digit. In addition, in the Chevrotain it is replaced by the metacarpal and a complete digit (Fig. 82, e). It is the same with the internal stylet, which is usually smaller, and embedded in a fibrous cord running along the large metacarpal ; it may, like the external stylet, be converted into a perfect metacarpal (Fig. 82, P and g). It remains to demonstrate the virtual existence of a fifth metacarpal. Nor- mally, no traces of it are found in the domestic Ruminants, but it appears in some anomalies. The museum of the Toulouse Veterinary School possesses the hand of a Lamb, in which it can be seen, inside the internal stylet, which has been transformed into a long metacarpal — a small styliform bone which is assuredly nothing else than the metacarpus of the thumb (Fig, 82, f, i,). Here is the metacarpus brought to the pentadactylous type ; now for the phalangeal region. The digital region of Ruminants presents two perfect digits (the second and third. Fig. 82, d), and two rudimentary digits reduced to one or two small phalanges covered by a horny plate (ergot), situated behind the metacarpo- phalangeal articulation. The two rudimentary digits may, in certain cases, be reproduced— to the right and left of the normal ones — complete and suspended from real metacarpals. This was seen in a specimen from a young sheep (Fig. 82, g) ; and this condition is normal in the Chevrotain (Fig. 82, e), only the lateral digits are less voluminous than those appertaining to the principal metacarpal. The presence of the fifth digit is normally indicated, according to Joly and Lavocat, by a tuft or spike of hair inside the carpus, rather above than below it. Sometimes it is better marked ; for in the specimen sho^Ti in Fig. 82, f' a, where the metacarpal of the thumb had appeared, this digit was represented on the surface of the skin by a plate of horn in the form of an ergot (f, a and b, 2). Otherwise, in order to dispel all doubts, it may be mentioned that Geoff roy Saint-Hilaire studied a new-born Lamb which had five digits in the anterior limb. 6. SoUpeds. — In Solipeds, there is apparently only one digit enclosed in one hoof. Nevertheless, by the aid of analogous facts to those which have already assisted us in proving pentadactylism in Ruminants, we shall be able to demon- strate that the hand of the Horse, Ass, etc., is no exception to the general law. Many anatomists only describe seven bones in the carpus of the Horse — four in the upper row, three in the lower. But it is not rare to see a pisiform bone on the inner side of the trapezoid, which raises the number of carpal bones to eight. And Bourgelat, Girard, Rigot, and Goubaux have observed in the carpus of the Horse, in addition to the bones mentioned, a similar piece alongside the external bone of the second row. Lavocat considered this second piece as the first of the inferior carpal bones — the base of the external digit, and that the bone found beside the trapezoid was the trapezium or base of the internal digit or thumb, the trapezoid being the base of the fourth finger. The trapezium and trapezoid are shown, with the significance attributed to them by Lavocat, on the carpus represented in Fig. 82 (l a, 1, 2). The carpus of Solipeds does not differ, then, from the archetype, except in the frequent abortion of the fifth superior carpal bone, and the first and fifth of the lower tier. The metacarpus of Solipeds comprises a large bone articulating with the 11 126 THE BONES. digital section, and two rudimentary pieces on each side of it, and which are really atrophied metacarpals ; for in some teratological specimens they are as long as the principal bone, and terminate in a diarthrodial surface which articulates with a perfect digit (Fig. 82, l b). At first sight, there are, then, three meta- carpals in Solipeds. With several authorities, and particularly Joly and Lavocat, we have admitted the duplicity of the large median metacarpal bone, basing our admis- sion on several considerations with regard to form and relations, and especially on certain anomalies similar to those represented in Fig. 82, i, in which is seen the single digit of Solipeds divided like that of the Ox — the division extending to the lower end of that bone. But an attentive study of the metacarpal region in the Mammalia, and notably in Pachyderms, and of the arrangement it offers in the various fossil Equidfe, has caused us to abandon this opinion. "We consider the principal metacarpal of Sohpeds to be the analogue of the metacarpus of the medius of pentadactylous Mammals. With regard to the anomaly shown at i and k. Fig. 82, it should be interpreted as an example of division of an organ normally single. The Horse, then, has always three metacarpals — one for the medius, the index, and the annularis ; and it remains to prove the existence of two other metacarpals. Usually, the metacarpal of the thumb is completely aborted ; but yet the existence of these bones is indicated by the frequent presence of the trapezium at the inner side of the carpus. Lastly, as a continuation from the trapezium there may be found a conical prolongation (Fig. 82, L a, 5), parallel with the metacarpal bone of the index — a prolongation which, because of its connections, should be regarded as the metacarpal of the thumb. With respect to the metacarpal of the auricularis, or little digit, we do not know of one teratological example in which it can be distinctly seen. But its existence is virtually indicated by the presence of the small external carpal bone we have sometimes observed, and which was noted by Bourgelat, Eigot, and Goubaux. The phalangeal section only possesses the elements of a single digit. But besides the hoof, Soliped animals have a horny plate divided by a slight median groove, and resting on an elastic cushion behind the metacarpo-phalangeal articula- tion. This plate occupies the same position as the ergots in the Ox ; it has vessels and nerves from the same source as those of the principal digit ; it lies upon an elastic bed similar to that belonging to that organ ; and Joly and Lavocat regard it as the representative of the phalanges, which should be continued with the rudimentary metacarpals. Otherwise, when one of these metacarpals is developed into a perfect digit, the horny plate or ergot diminishes in volume, because a portion of its substance is carried to the extremity of the supplementary digit. It -is, therefore, easy to find three digits in these animals, but the thumb is more difficult to render evident. However, the presence of a trapezius, and, much more rarely, of an atrophied metacarpal succeeding it, would warrant the admis- sion that this digit exists, if it were not represented on the surface of the skin by the chestnut — the horny plate situated on the internal aspect of the forearm. The position of this small mass of horn above the carpus has been invoked against this signification ; but it is easy to overcome this objection in showing, by the ascending vessels and nerves of the chestnut, that this is a displaced organ ; the vessels and nerves arise from the same trunks that supply the other digits. The fifth digit is not absolutely represented except by its carpal base, which is TEE POSTERIOR LIMBS. 127 often absent ; however, its presence in a certain number of instances allows it to be affirmed that Solipeds materially and virtually belong to the pentadactylous type. This conclusion applies a fortiori to all the domestic animals. According to statistics drawn up by Cornevin, the return to the pentadacty- lous type is much more frequently manifested, in Solipeds, in the anterior than the posterior limbs. Article YI. — Posterior or Pelvic Limbs. Each of these is divided, as already noted, into four secondary regions : the pelvis, thigh, leg, and foot. Pelvis (Figs. 83, 84, 85). The pelvis is a kind of bony cavity formed by the union of the sacrum with two lateral pieces — the ossa innominata, or coxae — which are consolidated with each Fig. 83. THE OSSA INNOMINATA (SEEN FROM BELOW). 1, Iliac surface ; 2, auncular facet ; 3, angle or crest of the ilium ; 4, angle of the haunch ; 5, ?eSs. r;^' V^"'\T '^'^'V*"' '\ °°^ ""^ '^' '"P'-'°'^ f""- tl^e insertion of the rec'tu rator) foramen ; 11, sciatic spine ; 12, 12, ischiatic arch, r ) , ^, Other in the inferior median line. The description of the sacrum having been ah:eady given, it now remains to speak of the os inn^ominatum of each side. A. Coxa, or Os Innominatum. The OS innominatum—2X^o designated os coxa, os iliacum, os innominatum-is a very irregularly shaped flat bone, double (with its fellow on the opposite side), and directed obhquely downwards and backwards. It is contracted in its middle part, which presents externally a deep cavity-the cotgloid ; anteriorly, where 128 THE BONES. it rests on the sacrum, it becomes widened, as it also does in its posterior portion, which is inflected inwards to be united, on the median Hne, with the OS innominatum of the opposite side. It is divided, in the foetus, into three distinct pieces, joined by cartilage in the centre of the cotyloid cavity, which they concur in forming. Although they soon become consolidated into a single piece, it is customary to describe them as so many separate bones by the names of ilium, pubis, and ischium. Ilium (Figs. 83, 84). — The ilium — a flat and triangular bone, curved on itself, directed obliquely downwards, backwards, and outwards — forms the anterior portion of the coxa which corresponds with the sacrum. It is the most consider- able of the three divisions, and has two faces, three borders, and three angles or processes. Faces. — The external or superior face (Fig. 83), studded Avith some muscular imprints, is excavated on both sides, and is named the external iliac fossa. The internal or inferior face offers for study : 1. An external portion, smooth, and crossed by some vascular grooves ; this is the iliac surface, which is replaced in Man by an excavation called the internal iliac fossa. 2. An internal portion, roughened and uneven, presents, posteriorly, the auricular facet — an irregular diarthrodial surface, elongated from side to side, a little oblique in front and inwards, and responding to an analogous surface on the sacrum. Borders. — The anterior border, or crest of the ilium, is slightly concave, and bears a roughened lip for muscular insertion. The external border is thick, concave, and furrowed by vascular fissures ; it presents, inferiorly, the nutrient foramen. The internal border is thin and concave, particularly in its posterior part, which constitutes the great sciatic notch. Angles. — The externcd angle, or anterior and superior spinous 2)rocess, is thick, wide, and flat, and bears four tuberosities : two superior and two inferior. The internal angle, or posterior and siqjerior sp)inous j^rocess, represents a rugged tube- rosity curved backwards and upwards. The posterior — or cotyloid angle — is pris- matic and very volimiinous. It exhibits : 1. Behind, a wide concave articular facet, which forms part of the cotyloid cavity. 2. Above this cavity, the supra-cotyloid crest, represented in Man by the ischiatic spine. This is an eminence elongated from before to behind, sharp on its summit, smooth inwardly, roughened out- wardly, and continuous by its anterior extremity with the internal border of the bone. 3. Outwardly, two deep imprints for the insertion of the rectus femoris muscle. 4. In'front and inwards, the ilio-2^ectineal spine, a small elongated pro- minence forming the most salient point of a kind of ridge {linea ilio-pectinea) that insensibly subsides above on the inner face of the ilium, and is continued below by the anterior border of the pubis. Of the three angles of the ilium, the first is also termed the angle of the haunch, and the second the angle of the croup. Pubis (Fig. 83). — Situated between the ilium and ischium, elongated from side to side, flattened above and below, and irregularly triangular, the pubis — the smallest of the three divisions — is divided, for convenience of description, into two faces, three borders, and three angles. Faces. — The superior, smooth and concave, concurs in forming the floor of the pelvis. It shows one or two nutrient foramina. The inferior is roughened, and marked throughout its length by a wide channel which reaches the bottom of the cotyloid cavity. This fissure lodges the pubio-femoral ligament and a very large vein. THE POSTERIOR LIMBS. 129 Borders. — The anterior is constituted by a thin rugged lip, which is curved upwards. The posterior, thick and concave, circumscribes anteriorly a wide opening, the oval, suhpiiUc, or obturator foramen ; it is channeled near the coty- Fig. 84. PELVIS (ANTERO-LATERAL VIEW). 1, Anterior iliac spine ; 2, posterior iliac spine ; 3, shaft of the ilium, with the ilio-pectineal crest ; 4, cotyloid cavity ; 5, symphysis pubis ; 6, inferior ischiatic spine and tuberosity. loid angle by a fissure which runs obliquely inwards and downwards. The internal is united with that of the opposite bone, to form the pubic portion of the pelvic symphysis. Ayigles. — The ex- Fig- 85. ternal, also named the cotyloid angle, is the thickest of the three. To it chiefly belongs the rugged depressed surface that constitutes the bottom of the coty- loid cavity. The in- ternal unites with the analogous angle of the opposite bone. The •posterior is consolidated at an early period with the antero - internal angle of the ischium, to enclose, inwardly, the oval foramen. Ischium (Figs. 84, 85). — This is the mean, in volume, of the three pieces of the coxa. Situated behind the pubis and ilium, it is flattened above PELVIS (LATERAL VIEW). 1, External angle of the ilium, or anterior iliac spine ; 2, internal angle, or posterior iliac spine ; 3, shaft of the ilium and ilio- pectineal line ; 4, cotyloid cavity, or acetabulum ; 6, inferior ischiatic spine, with tuberosity behind. 130 THE BONES. and below, and of a quadrilateral form. It offers for study : two faces, four borders, and four angles. Faces. — The superior is smooth and nearly plane, and forms part of the floor of the pelvic cavity. It has a small nutrient foramen directed outwards. The inferior presents some rugosities, clustered particularly about the symphysis. Borders. — The anterior, thick and concave, circumscribes the oval foramen posteriorly. The posterior, straight and directed obliquely forwards and inwards, forms, with the analogous border of the opposite bone, a large notch named tjie ischial arch. It exhibits, throughout its extent, a rugged depressed lip (the spine), arising from the side of the inferior face. The external, thick and concave, constitutes the lesser ischiatic notch. The internal is joined to the ischium of the other side, to constitute a portion of the pelvic symphysis. Angles. — The antero-externcd, or cotyloidean, is the most voluminous of the four, and affords for study : 1. An excavated diarthrodial facet, making part of the cotyloid cavity. 2. The posterior extremity of the supra-cotyloidean crest, limited by a small transverse fissure which separates from the external border of the bone. The antero-internal angle is consolidated with the posterior angle of the pubis. The poster o-external angle forms the ischial tuberosity. This is a large prismatic process which looks upwards, and is prolonged by a salient ridge, elongated from before to behind, with its sharp border turned outwards and downwards. The postero-internal angle forms, with that of the other ischium, the summit of the triangular space which constitutes the ischial arch, or pubic arch of some species. The Coxa in General. — This bone, the three constituent parts of which we have just been studying, presents for consideration, as a whole, a middle portion and two extremities. The middle, very much contracted, offers, outwards and downwards, the cotyloid cavity (or acetabulum), which has not yet been described, because its study does not properly pertain to either of the three regions of the coxa. This cavity is intended to receive the articulating head of the femur, and represents the segment of a hollow sphere ; it is circumscribed by a very salient rim, which is thin at its free margin, and widely notched on the inner side. The deeper portion is occupied by the roughened and depressed surface already designated as the bottom of the cotyloid cavity {fundus acetabuli), which communicates, by the internal notch of the rim, with the inferior groove of the pubis. The anterior extremity, flattened on both sides, and formed by the ilium, rests, as has been shown, on the sacrum. The posterior extremity, flattened in an inverse sense to the preceding, is constituted by the pubis and the ischium, and is traversed, from above to below, by the sub-pubic (or obturator) foramen — the large oval aperture which separates these two bones from one another, and perforates the floor of the pelvis ; this opening is closed in the fresh staie by muscles. The two coxae, by uniting in their posterior part, form the articulation to which has been given the name of ischio-pubic or pelric symphysis ; thus united, the two bones represent something like a V with the opening in front — a circumstance which makes the lateral diameter of the pelvis greater in front than behind. Structure and Development of the Coxa. — To the three centres of ossification which constitute the coxa, are added two complementary centres : one for the anterior spinous process and spine of the ihum, another for the ischial tuberosity. THE POSTEBIOB LIMBS. 131 It must be added that there is, within and in front of the cotyloid cavity, a cotyloid nucleus analogous to the glenoid nucleus of the scapula. This nucleus, comprised between the three bones of the coxa, has been named by Serres the Y-shaped bone. In youth, the different parts of the coxa are very thick, and the spongy tissue is abundant, while the compact is rare. The pubis is always convex on its two faces, and the middle part of the coxa — that adjoining the cotyloid cavity — is of considerable thickness, a feature which much diminishes the extent of the pelvic cavity. As the animal advances in age, however, the layers of compact tissue increase in thickness, approaching each other as the spongy substance is lessened. The pubis becomes thinnest, and at an advanced period of life is sometimes even translucid. The compact tissue is always abundant in the neighbourhood of the cotyloid cavity, as this is the centre on which converge all the impulsive efforts com- municated to the trunk by the posterior limbs. It is also in this cavity that ossification commences. B. The Pelvis in Genekal. 1. External and Internal Conformation of the Pelvis. — The pelvis is a kind of rear cavity in the form of a cone, which prolongs the abdominal cavity between the sacrum and coccygeal vertebrae. It occupies the posterior part of the trunk, and, with regard to its conforma- tion, presents for study an external and internal surface. External surface. — This may be resolved into four planes or faces. The superior plane is slightly oblique from above to below, and before to behind ; its degree of obliquity, varies. It is contracted from before to behind, and shows : 1. On the median line, the spinous processes of the sacral and the first coccygeal vertebrae. 2. On each side the sacral grooves, at the bottom of which open the supra-sacral canals. The inferior pla?ie is nearly horizontal. Formed by the pubes and ischial I)ones, it presents from before to behind : 1. In the middle, the ischio-pubic symphysis. 2. On each side the subpubic groove, the oval foramina, and the inferior face of the ischial bones. 3. Quite externally, the cotyloid cavities, by which the pelvis rests upon the posterior limbs. , The lateral faces are oblique downwards and outwards, and are wider in front than behind. They exhibit : 1. The spine of the ilium and the two anterior ■spinous processes. 2. The external iliac fossa. 3. The ischial arch. 4. The supra-cotyloid crest or ischiatic spine, which presents, outwardly, the surface of insertion for the internal or deep gluteus muscles. 5. The lesser ischiatic notch. 6. The ischial tuberosity. Internal surface. — The internal surface of the Horse's pelvis cannot be divided into two portions as in Man, because the inner surface of the iliac bones is not hollowed out to form an anterior cavity. The pelvis of Solipeds is, therefore, a simple conoid cavity, in which are distinguished four planes or faces, and two apertures called the inlet and outlet. The anterior openinq, or inlet, is nearly circular, especially in the Mare, and a little oblique downwards and backwards. It is limited above by the inferior face ^f the first vertebra of the sacrum ; inferiorly, by the anterior border of the 182 TEE BONES. pubis ; and on the sides by a part of the inner face of the iliac bones, and also the internal aspect of the pectineal crests. The inlet presents four diameters, a knowledge of which is important in obstetrics — a vertical, horizontal, and two oblique. The first, the sacro-pubir, extends from the inferior face of the sacriun to the anterior border of the pubic symphysis ; its mean length is 8:^ inches. The second, the bis-iliac, is measured from one pectineal crest or eminence to another ; the mean of this is H^jj inches. The two last diameters, the ileo-sacral, are estimated from the inferior face of the sacro-iliac articulation of one side to the ilio-pectineal eminence of the other ; this is, on an average, SyV inches. These measurements irrefutably Fig. 86. PELVIS OF THE HORSE. demonstrate that the inlet is not elliptical in the vertical direction ; but it may happen that the transverse diameter is the greatest. The posterior aperture or outlet, situated at the posterior end of the pelvic cavity, gives exit to the rectum and genital organs. It is limited by the inferior face of the summit of the sacrum, the superior face of the ischial bones, the supra-cotyloid crest or ischiatic spine, and the internal face of the sacro-sciatic ligaments. At the outlet only two diameters are recognized — a vertical and a horizontal. The vertical, extending from the inferior face of the sacrum to the superior face of the ischial symphysis, measures on an average 6yV inches. The horizontal diameter, comprised between the two supra-cotyloid crests, is 7-j^ inches. The superior face of the pelvic cavity is a little concave from before to THE POSTERIOR LIMBS. 133 behind ; it has for base the sacrum, which presents on each side of the median line the subsacral foramina. This part is also called the sacral plane, or roof of the pelvis. The inferior region, or ischio-pubic plane, is formed by the pubes and the ischial bones. It is concave from side to side ; its anterior border is nearly straight, and its posterior border is scooped out by a wide notch to form the arch of the ischium. It has been remarked by Goubaux, that the portion of this plane correspond- ing to the pubis presents numerous varieties. The superior face of the pubis may be convex in its anterior moiety, and concave in its posterior ; or it may be Fifr. 87. PKLVIS OF Tllli MARE. ooncave before and convex behind, the concavity being separated from the convexity by a transverse ridge. This ridge is sometimes represented by a series of small conical eminences ; at other times this upper face is disposed as a smooth inclined plate, directed backwards and upwards, and a kind of rim surmounts the anterior contour of the oval foramen.^ With regard to the lateral faces, they are formed by a small portion of the inner face of the iliac bones, and in great part by the sacro-sciatic ligaments. The foetus must pass through the pelvic canal during parturition ; it is, therefore, important to know at any time if the female pelvis is of sufficient dimensions to allow the foetus to leave it. Pelvimetry is the name given to ' It is necessary to be aware of the frequency of these asperities on the floor of the pelvic cavity, in order not to arrive at false inductions when exploring the bladder per re,etum. 134 THE BONES. that section of obstetrics dealing with the diameters of the pelvis. These may be determined in several ways, which, in veterinary surgery, daily receive the sanction of experience. Some years ago we indicated one,^ which consists in measuring the horizontal distances between the two haimches and the two ischiatic tuberosities, and the vertical distance extending from the coxo-femoral articulation to the most salient part of the croup ; then to take a fourth of the total of the two first measurements, in order to obtain the transverse diameter of the inlet, and three-fourths of the third, to have the vertical diameter of this opening. Saint-Cyr and Violet have investigated the relation existing between the height of the Mare and the vertical diameter of the pelvis, then that of the width of the croup to the bis-iliac diameter ; and they have found that the first was equal to 0"1515 centimetres ; the second to 0'4654, in a well-bred Mare, to 0*3945 in common-bred Mares. Consequently, according to the pelvimetric procedure of these authorities, it is sufficient to multiply the height of the Mare by 0-1515 to have the vertical diameter of the inlet, and the width of the croup by 0*4654 or 0"3945, according to circumstances, to find the transverse diameter. But this question rather appertains to obstetrics.^ 2. Differences in the Pelvis of the Sexes. — The pelvis of the Mare exceeds that of the Horse in all its dimensions, but the difference is most, marked in the transverse diameters (Figs. 86, 87). The inlet forms a vast circumference, when compared with that of the male ; the pectineal crests are wide apart, and the distance separating the anterior border of the pubis from the lower face of the sacrum is considerable. If the pelvis be viewed in its superior plane, it is found that in the Mare the ischiatic notches are very deep ; that the internal border of the ilium forms a regularly curved and very concave line ; and that the supra-cotyloid crests, or ischiatic spines, are widely separated from each other. It is also noticed that the floor of the pelvis is wide, and that the bones composing it tend towards the same horizontal Hne. In the male, the ischiatic border is only represented by a very curved line ; this line is composed of two almost straight portions, which join at an obtuse angle at the origin of the neck of the ilium ; the supra-cotyloid crests are relatively near each other, and bent towards the longitudinal axis ; while the two moieties of the pelvic floor are directed very obliquely downwards and inwards. In the Mare, the ischial arch is larger than in the male, and forms a regular curve uniting the two tuberosities of the same name. In the Horse, the two ischial tuberosities are but little apart, and the ischial arch forms a somewhat acute angle, with its borders nearly straight. Lastly, when the pelvis is examined in its inferior plane, in addition to the features already indicated in the ischial arch, it is found that in the Mare the obturator foramina are large and nearly circular, while in the Horse they are elliptical ; the cotyloid cavities are also further removed from the ischio-pubic symphysis in the female than in the male. The sacrum of the Mare has appeared to us, in some individuals to be a little more arched from before to behind than that of the Horse ; but this character is not constant. ' Arloing;, Journal Vet^rinaire de Lyon. 1868. = Saint Cyr and Violet, Trait€ cV Ohstetrique VitMnaire, Paris: 1888. Tn:E POSTERIOR LIMBS. 135 The following figures, relating to the capacity of the pelvis of the Mare and Horse, confirm what has just been enunciated : — Mare. Horizontal Diameters. Horse. Horizontal Diameters. Between the Pectineal Crests. Between the Supra-cotyloid Crest,. Between the Pectineal Cre^t8. Between the Supra-cotyloid Crests. Inches. 9| Inches. 7^ Inches. 8t', Inches. Mare. Vertical Diameters. Horse. Vertical Diameters. Between the Sacrum and Pubis. Between the Sacrum and Ischium. Between the Sacrum and Pubis. Between the Sacrum and Ischium. Inches. 8^ Inches. Inches. 8 Inches. 6^ To recapitulate, there is observed in the pelvis of the Mare : — 1. A great increase in the transverse diameters. 2. A deep and regularly concave ischiatic notch. 3. A wide and concave ischial arch. 4. Circular obturator foramina. 5. The cotyloid cavities distant from the pubic symphysis. In the Ass, the inlet of the pelvis is a longer oval than in the Horse. The coxse are distinguished by : 1. The less curvature of the anterior border of the ilium. 2. A slightly excavated external iliac fossa. 3. The triangular shape of the obturator foramina. 4. A short and deep notch separating the external border of the ilium from the angle of the haunch. 5. The direction of the tuberosities of this angle ; they approach more nearly the parallelism with the median plane of the trunk than in the Horse. 6. The disposition of the rugo- sities in tubercles for the insertion of the suspensory ligaments of the corpus cavernosum on the inferior face of the ischium. In the Ass, also, a line which would unite the inferior contour of the auricular facet to the most salient point of the angle of the haunch, would be parallel to the anterior border of the ihum, while it would be oblique on this border in the Horse. The inlet of the pelvis in the Hinny resembles that of the Ass ; in that of the Mule, it holds a middle place between the Ass and Horse. The pelvis of the Hinny resembles that of the Ass, also, by the form of the obturator foramina, the direction of the anterior border of the ilium, and the position of the auricu- lar facet ; while that of the Mule, on the contrary, resembles the pelvis of the Horse in these features. The reverse is noted with regard to the disposition of the angle of the haunch. Differential Characters in the Pelvis op other Animals. It is remarked : 1. That in all the domesticated animals, with the exception of Solipeds and the Camel, the direction of the coxse is nearly horizontal. 2. That in all, the ilium is more oblique than in Solipeds. 3. That in all, the transverse diameters of the pelvis are relatively less extensive. A. Ruminants. — In the Ox, the space between the two coxae is scarcely so great in front THE BONES. as behind ; the ilium is not voluminous, and has only three processes on the anterior and superior iliac spines. There is no furrow on the lower face of the pubes, and its upper face, like that of the ischium, is very concave. Thrt-e eminences are seen on the posteio-external angle of the ischium. In early life, the ischio-pubic symphysis shows an epiphysary nucleus in the middle of its inferior face. (The epiphysis on the inner border of the ischium has been considered by some anatomists as an independent bone, and described by them as the inter-ischial bone). Tiie ischio-pubic symphysis has, in the middle of its inferior face, a thick protuberance, flattened on each side and very pointed; in early life this is an epiphysis, and the epipliysary nucleus, bifurcated posteriorly, is continued along the posterior border of tlie ischial bones as far as the ischial tuberosity, in the form of two marginal bands. The rim of the cotyloid cavity has also three notches, and the supra-coryloid crest, or ischiatic spine, is very ele- vated and shiirp, and but little rou; posterior, covered with imprints. Scaphoid hone (the large cuneiform of Percivall) (Figs. 98, 99). — Flattened above and below, it is described as having two faces and a circumference. The faces, both articular, are furrowed by a channel of insertion, and are distinguished as superior and inferior. The first is concave, and articulates with the astragalus ; the second is convex, and in contact with the two cuneiform bones. The circumference offers, outwardly, two small facets, which are adapted to similar facets on the cuboid bone. For the remainder of its extent, it is covered with imprints (Fig. 99). Oreat Cuneiform hone (the middle cuneiform of Percivall) (Figs. 99, 100, 101). — Flattened above and below, and triangular in shape, this bone is much smaller than the scaphoid, though resembling it in a striking manner. Its superior face is in contact with the latter bone, and its inferior face articulates with the middle and internal lateral metatarsal bones. Its external harder is provided with one or two facets to correspond with the cuboid bone ; and its internal herder also shows one. 148 THE BONES. which is in contact with another on the small cuneiform. Its anterior border is roughened throughout its extent (Figs. 99, 100). Small Cuneiform hone (Figs. 99, 101). — Situated at the inner side of the tarsus, this bone — the smallest of any yet examined — is elongated from before to behind, flattened on both sides, and wedged in between the os scaphoides, the large cuneiform bone, and the large and internal small rudimentary metatarsal bones, with which it corresponds by four articular facets : a superior, two inferior, and one internal. When this bone is in two portions, there are then three cuneiforms, which may be distinguished, as in Man, by naming them //•«/, second, and third (Fig. 99). It is not very rare to find the scaphoid {cuneiform mafjnum) fused with the great cuneiform {cuneiform medium), and sometimes even the cuboid is joined to the cunean bones. Development. — All the bones of the tarsus, with the exception of the calcis, are developed from a single nucleus of ossification. The astragalus in the Ass is distinguished from that of the Horse by the external Hp of the trochlea, which is abruptly deviated outwards at its inferior extremity ; and by the disposition of the inferior articular surface, which is regularly convex from side to side, behind the groove for insertion ; in the Horse this part of the articular surface is formed by the union of two facets inclined towards each other. In the same animal, the scaphoid {cuneiform maffnum) is recognized by the shape of the superior diarthrodial surface, which is a hollowed reproduction of the inferior face of the astragalus ; and the g7-eat cuneiform {cuneiform medium) by the larger concavity of its scaphoid face. Differential Characters in the Tarsal Bones of the other Animals. In the domestic animals, the tarsus differs in the number and shape of the bones enteriug into its formation. A. Ox, Sheep, Goat. — The tarsus of these animals is slender, and has only five bones, the cuboid and scaphoid being fused into one. The astragalus i.s tlongated from above to below, and is united to the scaphoid by an antero-posterior groove, and to the calcis by a vertical groove ; so that it has tiiree trochleas. The principal trochlea has its external border thicker than the internal, and decreases from below to above. The posterior trochlea is not 80 deep as the others. The calcis is lon^' and thin; the posterior gliding surface on the summit is excavated into a channel. The small cuneiform is pisiform, and but slightly developed. B. Camel. — In the Camel, there are six tarsal bones, two of which :ire cuneiform. The astragalus articulates, by means of a double groove, with the scaphoid and cuboid. The calcis is relatively short, and about equally excavated on its two faces. The cuboid ia voluminous. C. Pig. — The tarsus of this animal much resembles that of Ruminants in its general disposition, and in the astragalus ami calcis; but it lias seven bones, because the cuboid and scaphoid are separate, and there are constantly three cunfi/nrm bones. D. Dog, Cat. — There are seven bones in the tarsus of these animals. The astragalus articulates witli the scaphoid— almost as in Man— by means of a tiue In ad, separated from the rest of the bone by a constriction named the neck of the astragalus. The cuboid and the three cuneiform bones articulate with the five metatarsal bones. 2. Bones of the Metatarsus (Figs. 98, 102). These bones are three in number — a median and two lateral — and offer the greatest analogy to the metacarpal bones. This enables us to dispense with a general description of them, and to confine ourselves only to indicating the differential characters which distinguish them from the corresponding bones in the anterior limb. THE POSTERIOR LIMBS. 149 The principal, large, or median metatarsal bone, is longer than the same metacarpal, and its body, instead of being slightly compressed before and behind, is nearly a regular cylinder. It presents, outwardly, a fissure which is directed at first obliquely backwards and downwards (Fig. 99), and afterwards descends vertically along the lateral external metatarsal bone. The articular surface of the superior extremity is excavated in its centre by a large fossa for insertion (Fig. 99). This surface presents, behind and outwards, a thick tubercle which appears to spring from the body of the Fig. 102. bone, and which has a facet against which the external rudi- mentary metatarsal rests. The inferior extremity is at the same time wider and thicker than that of the metacarpus. Above and in front of the articular surface, it is hollowed by a small transverse fossa, which is deeper than in the corre- sponding bone in the anterior limb. Of the tivo rudimentary {digital, splint), or lateral meta- tarsal bones, the external is always longest, if not thickest. The internal bears on the superior face of its head three articular facets, two of which articulate with the small cuneiform, and the third with the large bone of that name. The length of these rudimentary metatarsals is nearly equal to three-fourths that of the principal metatarsal. The metatarsus of the Ass is remarkable for the length of its rudimentary metatarsals, which are nearly five-sixths that of the principal bone. The latter is also notable, because of its length and fineness ; and if it is compared with that of the Horse, it is distinguished by : 1. The tri- angular shape of its upper extremity, due to the great development of the tubercle on which the external rudi- mentary metatarsal lies. 2. The flat diarthrodial facet which articulates with the antero-external part of the large cunei- form, 3. The marked inequality of its condyles. Differential Characters in the Metatarsal Bones of the OTHER Animals. posterior aspect op left metatarsus. 1, Head of principal metatarsal bone ; 2, 3, external and in- ternal splint bones, or metatarsals of the rudimentary digits ; 4, rough surface for insertion of suspen- sory ligament ; 5, nutrient foramen ; 6, middle ridge or tenon of inferior arti- cular surface. The metatarsus is also a region in which the number of bones varies in the domesticated animals. Tlius, in Ruminants there are two, and five in the Pig, Camivora, and Rodents. The metatarsals of the latter are exactly like the same bones in the anterior limb. Those of Ruminants are slightly different. A. Ox, Sheep, Goat.— In the Ox, Sheep, and Goat are found a principal and a rudimentary metatarsal bone. The latter is a small lenticular bone, articulating, posteriorly, with the head of the large metatarsal bone. The latter differs from the principal metacarpal bone, in being longer, quadrilateral in form, and having a vascular canal traversing the posterior face of its upper extremity. B. Camel. — The metatarsus differs from the metacarpus by its greater width and less thickness; the articular surface is divided by a depression into two parts, situated on the same horizontal plane. C. Pig.— The Pig has four perfect metatarsals, and an internal rudimentary one. The latter is a small bone flattened on both sides, articulating by means of a diarthrodial facet, and sometimes fused posteriorly with the upper end of the fourth metatarsal. D. Dog, Cat.— Ill the Dog and Cat are one rudimentarv and four perfect metatarsals. The former is articulated with the internal cuneiform, and represents the vestige of the thumb. 150 THE BONES. 3. Bones of the Digital REOrioN (Fig. 98). Id Man, the digits of the foot — known as toes — are very different to those of the hand ; but it is otherwise with the domestic animals. The phalangeal region of the posterior, closely resembles that of the anterior Hmb. The analogy in the conformation of these bones is even pushed so far, that it becomes very difficult to distinguish them from one another. There are some differential characters, however. For instance, it is remarked : 1. That the first phalanx is not so long as in the anterior limb, and less wide and thick at its inferior extremity ; but it is, on the contrary, wider and thicker at its superior extremity. 2. That the lateral diameter of the second phalanx is shorter. 8. That the third phalanx, less expanded towards its inferior border, has more the shape of a V, and that its inferior face is more concave. 4. That the sesamoids are less voluminous. 5. That the navicular bone is shorter and narrower. In the Ass, the same differential features are observed between the posterior and anterior phalanges as in the Horse, and there are no very marked differences between the former in these two animals. The following may, however, serve to distinguish them. The ^rs^ phalanx of the Ass is proportionately longer than that of the Horse, and the rugosities are larger ; the principal nutrient foramen is usually on the anterior face, and the external glenoid cavity is much smaller than the internal. The second phalanx is also proportionately longer than that of the Horse. Its inferior median furrow is deep, especially behind ; it has generally numerous nutrient foramina below the posterior gliding surface ; the median tenon of its upper face terminates before and behind by a salient tubercle, which prevents the bone from resting in equilibrium when it is placed vertically on that face. The third phalanx of the Ass is higher than that of the Horse, owing to the development of the pyramidal process ; it is constricted above the preplantar fissure ; the surface of the sole is proportionately more extensive, and the concavity of the semilunar crest is less marked ; the extremities of that crest are saUent, and the plantar fissures very deep. The navicular bone shows very marked differences. In the Ass its thickness is very considerable, due to the median ridges on both faces. Its posterior border is very oblique downwards and backwards, and it is towards this border that it inclines when Ave attempt to make it lie horizontally on its upper face ; while its two extremities are more curved than in the Horse. In the Mule and Hinny, the two first phalanges much resemble those of the Ass, while the third shows the characters of that of their progenitors. Nevertheless, that of the Hinny is rather more like the third phalanx of the Horse than that of the Ass, while the contrary is observed in that of the Mule. Differential Characters in the Posterior Phalangeal Region of other Animals. In all the domesticated animals, the posterior digits comport themselves exactly like the anterior. The Carnivora alone offer a notable difference ; in them, in reality, the inner toe, the equivalent of the thumb, does not exist — or rather, it is only represented by tiie rudimentary metatarsal bone alluded to above. Nevertheless, it frequently occurs that a completely de- veloped thumb is found in this animal ; and in this case the rudimentary metatarsal is ordinarily followed by a ligamentous cord, to which is suspended a bony stylet that represents either the inferior extremity of the metatarsal bone, or the first phalanx ; it is to this stylet that are found articulated in succession the second and third phalanges. It is not rare to meet with a sixth floating toe in dogs of very large size. THE POSTEBIOR LIMBS. 151 Comparison of the Abdominal Limb of Man with that of Animals. A. Pelvis (Fig. 103). — The longitudinal axis of the pelvis of Man forms, with the horizon, an angle of about 40°. The bones which compose it are proportionately larger and stronger than in all the domesticated animals. The two faces of the ilium, and especially the inner face, are much hollowed ; the iliac crest has the form of an italic S. The pubis alone participates in the formation of the pelvic sympliysis, and the concavity which, in the domesticated animals, is called the ischial arch, is desig- Fig. 103. nated in Man the pubic arch. In consequence of the excavation on the inner face of the ilium, the pelvic cavity may be divided into the great and lesser pelvis. In the latter are lodged the genital and urinary organs, as well as the ex- tremity of the digestive tube. B. Thigh (Fig. 104).— The femur of Man is nearly vertical, and situ- ated in a direction sligiitly oblique downwards and inwards ; it presents a curvature forwards. The body of the bone is prismatic and triangular in its middle part; the posterior border of this prism forms a some- what salient cresf, which takes the place of all the insertion eminences on the posterior aspect of the femur in animals, and is designated the linea aspera. This line bifurcates above and below ; below, the branches margin a triangular or popliteal space. The head is supported by a long neck, inserted obliquely into the superior extremity. The two con- dyles are joined together in front by the trochlea, which is wide and* shallow. a Leg (Fig. 105) —Three bones : human pelvis (female). 1, Last lumbar vertebra ; 2, 2, intervertebral substance ; 3, promontory of the sacrum ; 4, anterior surface of the sacrum ; 5, coccyx ; 6, iliac fossae ; 7, antero-superior spinous process ; 8, antero-inferior spinous process ; 9, acetabulum, a. Its notch ; 6, body of ischium; c, its tuberosity ; d, its spine ; e, pubis ; /, symphysis pubis ; g, arch of the pubes ; h, angle of os pubis; i, spine of pubes, with crest between it and h; k, k, pectineal line ; I, I, ilio-pectineal line, with its prolongation, m, m ; n, ilio-pectineal eminence ; o, smooth surface for femoral vessels ; p, p, great sacro-ischiatic notch. the tibia, fibula, and patella. The tibia is very long ; its crest (or spinous process) is much more developed than in any of the domesticated animals, and describes a kind of curve like an italic S. On the inner aspect of the inferior extremity is seen a voluminous process which occupies, inwardly, a portion of the tibio-tarsal articulation : this is the internal malleolus. The articular surface ia not exactly formed to correspond with the whole articular surface of the astragalus. The fibula is as long as the tibia. It is prismatic, and slightly twisted on itself. It articu- lates above and below with the tibia. The lower extremity responds to the astragalus, and forms a prominence named the external malleolus. There is nothing particular to note in the patella. D. Foot (Fig. 106). — The foot of Man is pLaced in a horizontal direction. Its upper aspect is convex; its inferior face is excavated, and it rests on the ground by its two extremities. 1. Tarsus. — In the tarsus there are seven bones, three of which are cuneiform. The astra- galus articulates with the tibia and fibula ; it responds to the scaphoid by a well-detached convex articular surface, named the head. In the bones of the lower row, it is remarked that the cuboid responds to the fifth and fourth metatarsals; the first cuneiform to the third; the second cuneiform to the second metatarsal : and the third to the first. 2. Metatarsus. — The metatarsus is composed of five bony columns, nearly parallel to each 152 TEE BONES. other. They are enumerated from without to within, and increase in length from the first to the fourth ; the fifth is the shortest and most voluminous. 3. Digital region-— This comprises five digits or toes. The phalanges of these toes are analogous to those of the fiiigersi, from which they are distinguished by their small size. They increase in volume from tlie first to the fifth digit. Article VIL — The Foot in General. It would be useless to reproduce here the general considerations discussed when treating of the hand (p. 121), and it may therefore be sufficient to state Fig. 104. Fig. 105. Fig. 106. RIGHT HUMAN FEMUR (ANTERIOR ASPECT). 1, Shaft ; 2, head ; 3, neck ; 4, great trochanter ; 5, anterior intertrochanteric line; 6, lesser trochanter; 7, external condyle ; 8, internal condyle ; 9, tu- berosity for attachment of external lateral liga- ment; 10, fossa for ten- don of origin of popliteus muscle ; 11, tuberosity for attachment of inter- nal lateral ligament. HUMAN TIBIA AND FIBULA OF RIGHT LEG (ANTERIOR ASPECT). 1, Shaft of tibia; 2, inner tuberosity; 3, outer tu- berosity ; 4, spinous pro- cess ; 5, tubercle ; 6, in- ternal surface of shaft ; 7, lower extremity of tibia; 8, internal malleo- lus; 9, shaft of fibula; 10, its upper extremity; 11, its lower extremity; between 1 and 6 is the sharp crest of the tibia. DORSAL SURFACE OF LEFT HUMAN FOOT. 1, Astragalus ; 2, its anterior extremity articulating with the cuboid bone, 4 3, 3, calcis ; 4, scaphoid 5, internal cuneiform bone 6, middle cuneiform bone 7, external cuneiform bone ; 8, cuboid bone ; 9, metatarsal bones of first and second toes; 10, first phalanx of great toe ; 11, second ditto ; 12, 13, 14, phalanges of second toe. that the works of the anatomists already mentioned — and especially those of Joly and Lavocat — have demonstrated that the foot of animals is constructed on the same type as the hand. In it, as in the hand, three sections are remarked : the THE FOOT IN GENERAL. 153 tarsus, metatarsus, and phalanges ,- and, in the archetype, each section comprises five parallel rows, each of which has two tarsal bones, one metatarsal, and three phalangeal. In the present fauna there is not, perhaps, a Mammal which has a perfectly typical pentadactylous abominal limb ; for this ideal disposition is modified in the sense already indicated for the hand. In the following- brief paragraphs, an attempt will be made to show the manner in which Man and the domestic animals may be allotted to the archetype. 1. 31 an. — In Man the archetype is realized in the metatarsal and phalangeal sections, and it will now suttice to examine the tarsal section. This contains seven separate bones — three in the upper and four in the lower row. It must not be forgotten that the scaphoid, although situated between the two rows, nevertheless belongs to the upper, as happens in the carpus of certain species. Apparently, it is deficient in two bones in the upper row and one in the inferior. This deficiency arises from fusion of the apex of the calcaneum {first superior metatarsal hone) with the remainder of the bone {second hone), of the scaphoid with the fifth hone in the upper row, and of the first inferior tarsal bone with the cuboid in the second row. 2. Carnivora. — The foot of Carnivora only differs from that of Man in the arrangement of the thumb ; as this digit has usually no phalanges, and its meta- tarsal piece is only a small, very short styliform bone. Notwithstanding this difference, the pentadactylous archetype is as easily recognized in the foot of these animals as in that of Man. 3. Rodents. — The foot of the Rahhit and Hare is yet less complete than that of Carnivora, as the metatarsal of the thumb is absent ; but, by the constitution of the tarsus, Rodents resemble Carnivora and Man, and consequently they can be also classed in the pentadactylous type. 4. Pig. — In this animal, the tarsus presents the same number of pieces and the same fusions, as in Rodents, Carnivora, and Man. The metatarsus and phalangeal section have four complete toes — first, second, third, and fourth ; and with regard to the fifth digit, it is represented by a short, flat, and irregu- larly triangular metatarsal, articulating posteriorly with the third metatarsal, and attached to the third cuneiform by some ligamentous fibres. 5. Ruminants. — The foot of the Ox, Sheep, and Goat present numerous fusions, and even some abortions. The tarsus has only five distinct bones ; for, besides the fusions which exist as in the preceding animals, the scaphoid is united to the cuboid, and the third cuneiform is completely aborted. The metatarsus of these animals includes a principal metatarsal, provided, inferiorly, with a double diarthrodial surface, and an internal rudimentary metatarsal. Must we consider the principal metatarsal as the result of the fusion of the third and fourth, and admit, in Ruminants, the abortion of the first two digits ? Several anatomists have professed this opinion. Lavocat did so at first, and then abandoned it. He considered the principal metatarsal as due to fusion of the metatarsals of the first four digits, and he expressed himself on this point as follows : " The first and the fourth metatarsals are visible, and fused above and behind the united large metatarsals. Each of them has the shape of a thick pyramid, with its base uppermost, large, and about five centimetres long in the Ox. Above, they join to form an arch, which is the contour of a wide and short vascular canal running between them and the two large metatarsals, and which does not exist in the Goat and SheejJ. Their widened superior extremity is in contact with the bones of the tarsus, to wit : the first metatarsal with a facet of 154 TEE BONES. the p-ototarsiis, or first portion of the cuboid ; the fourth metatarsal with all the inferior facet of the tetrofarsus, or second cuneiform. And each of them has, for this eminently normal connection, an articular facet well separated from the diarthrodial surface of the large metatarsals by a large fossa destitute of cartilage. In this way the first four metacarpals are gathered into a single bundle. . . . Lastly, the thumb, or fifth digit, is constantly represented in the foot by a distinct metatarsal bone — at least in the Ox, Goat, and Sheep.''' Notwithstanding the reasons on which Lavocat bases his last interpretation as to the metatarsals of the Ox, we prefer adopting the first. In fact, if some wild Rimiinants are examined — Deer, for example — there will be found a tarsus identical with that of the Ox, and a principal metatarsal provided with a vascular canal, with two inverted pyramidal expansions ; and, in addition, two styliform bones lying to the outside and the inside of the principal bone of the shank. These bones evidently represent the metatarsals of the second and fifth digits ; as they exist at the same time as the lateral ridges on the principal metatarsal bone, it appears to be impossible to give to the latter the same signification. The posterior phalangeal region of the Ox is almost identical with the an- terior ; it is, therefore, needless to again demonstrate its constitution. That of the Sheep and Goat has no rudimentary phalanges to serve as a base for the ergot, in the hand ; but the two ergots suffice to represent the first and fourth digits, and so to include these animals in the pentadactylous type. 6. SoUpeds. — The tarsus of these animals has six or seven bones. In the second case, it is identical with that of Carnivora and Man ; in the first, the second and third cuneiforms are fused. The metatarsus and posterior phalangeal section having the same constitution as those of the anterior, the reader is referred to the description of the Hand in General. Article VIII. — The Limbs in General and their Parallelism. A. The Limbs in General. — The bony sections which compose the limbs, are destined not only to support the trunk in a stationary attitude, but also to transport it during progression. This double use gives rise to a difference between the anterior and the posterior members. The front limbs, being nearer the centre of gravity than those behind, have to sustain the largest share of the weight. They ought, consequently, to be specially organized as organs of sup- port. Therefore it is, that the four principal bones composing each of them — shoulder, arm, forearm, foot — although flexed, or disposed to be flexed, in an inverse sense to one another, oppose to the pressure of the weight of the trunk — which tends incessantly to throw them down — obstacles purely mechanical, and of such energy that we may still understand how the body can be sustained on the anterior limbs, if we suppose all the muscular masses surrounding these bony columns to be removed, except one. Thus, the weight of the body is transmitted to the scapula through the muscles that attach that bone to the trunk. It then passes to the humerus, and thence to the radius, to be thrown, finally, on the diflferent pieces composing the foot. Now, the humerus forming with the scapula an angle which is open behind, and with the bones of the forearm another angle open in front, the weight of the body pressing continually on these angles tends to close them, and thus cause the flexion of these bones. But this result is prevented by the combined action of two muscular powers — the biceps and the extensors of the THE LIMBS IN GENERAL AND THEIR PARALLELISM. 155 forearm. With regard to the radius, carpus, and metacarpus, owing to their vertical direction, they themselves sup- port the pressure of the weight of the body without requiring any muscular aid. But the digital region, being di- rected obliquely forward and downward, forms, with the principal metacarpal, a third angle open in front, for the main- tenance of which nature has given solid, inert, or contractile mechanical bands. The anterior limbs are also agents of transport, for they can elevate the trunk by the spring of their bony rays, and fix themselves on the ground by their free extremities. The posterior limbs are less favour- ably disposed than those in front to as- sume the function of columns of support ; as their rays are, for the most part, in a state of permanent flexion, and joined in an angular manner to one another, as may be seen by glancing at the skeleton (Figs. 107, 108, 1, 2, 4, 5, 6). It is, therefore, necessary that muscular agency should prevent the breaking-down of these columns. Though defective as supports, they are nevertheless admirably designed to serve as agents of locomotion. The slightest erection of these inclined bones propels the mass of the body for- ward, and this impulsion is almost wholly transmitted to the trunk, in consequence of the very intimate union of the pelvis with the vertebral column. B. Parallel between the An- terior AND Posterior Limbs. — After what has just been said, it will be seen that the anterior limbs are more par- ticularly destined for the support of the body, while the posterior ones more especially play the part of propelling agents in the locomotory acts. Notwithstanding this difference in the functions assigned them, these two limits offer in their conformation such striking resemblances to each other, that some authors have been inclined to con- sider the posterior as an exact repetition of the anterior limb. The followina: is ANTERIOR LIMB OF THE HORSE (ANTERO- EXTERNAL VIEW). 0, Scapula ; H, humerus ; a, radius ; C, carpus ; M, metacarpus ; p, phalanges ; s, sesamoid bone. 1, Coracoid process; 2, head of the humerus; 3, external trochanter ; 4, deltoid ridge; 5, inferior articular surface of the humerus; 6, olecranon; 7, ulna; 9, pisi- form (trapezium), or supercarpal bone. 156 THE BONES. Fig. 108. POSTERIOR LIMB OF THE HORSE (ANTERO- EXTERNAL VIEW). C, Coxa ; F, femur ; J, tibia ; 8, tarsus ; M, meta- tarsus; p, phalanges; S, sesamoid. 1, Ischium ; 1', pubis; 2, head of the femur; 3, trochanter major; 4, trochanter minor ; 5, condyle of the femur ; 6, patella ; 7, fibula ; tibial ridge ; 9, calcis. a brief analysis of the analogies ex- isting between them. At the end of the last century, Winslow and Vicq-d'Azyr, and nearer our own time, Cuvier, Flourens, Paul Gervais, Martins, Gegenbauer, Lavocat, Foltz, and Sabatier, have occupied themselves with the homo- logy of the anterior and the posterior members. All these anatomists did not absolutely arrive at the same conclusion ; for several of them, for- getting that the question should be examined in the whole animal series, made Man alone the subject of their studies. Vicq-d'Azyr and Cuvier recom- mended that the anterior and pos- terior limbs of opposite sides should be compared. Martins and Gegen- bauer, allowing a torsion of the humerus of 180°, advised that the two members of the same side should be compared, care being taken to make allowance for the untwisting of the 180° contortion at the lower end of the humerus. Lastly, Flourens and Lavocat contrasted the two members of the same pair with each other, after placing the hand in a position of natural pronation by rotation of the radius on the ulna, and without turning either limb or bone, or even a portion of a bone, no matter what kind of animal may be under examination. We will adopt the latter proceeding, as it is the simplest and most natural. Parallel between the coxa and scapula. — The analogies existing be- tween these two bones are but little striking at first sight ; nevertheless, with attention there is no ditficulty in finding in the coxa the three pieces that enter into the composition of the shoulder (Figs. 107, 108). The ilium represents the scapula. The external iliac fossa reminds one of the supra- and subspinous fossae. Occasionally, there is met with in the THE LIMBS IN GENERAL AND THEIR PARALLELISM. 157 Horse a rudiment of the crest dividing the ihac fossa into two parts, and in some animals — the Pig, Sheep, and Goat— this crest, which is the trace of the scapular spine, becomes constant and very evident. With regard to the cotyloid cavity, it repeats in the posterior limb the glenoid cavity of the scapula. There remains to determine, in the latter bone, the portions analogous to the ischium and pubis. If we rely upon the evidence afforded by the muscular insertions, we come to the conclusion that the ischium corresponds to the coracoid process, and the pubis to the clavicle of animals which are provided with one. It will also be remarked that the coxa is directed backwards, while the scapula inclines obliquely forwards ; this opposition in the direction of the bones in no way alters their analogies ; the functions of the members to which they correspond require this inverse position. Parallel hehveen the femur and hwiwus. — The resemblance between these two bones is remarkable. Thus there is found in the first. 1. An articular head, better detached than that of the humerus, but shaped in the same manner. 2. A trochanter analogous to the great tuberosity, and also, like it, decomposable into three distinct parts — summit, crest, and convexity. 2. A lesser trochanter, representing the small tuberosity. 4. An eminence for the insertion of the superficial gluteus muscle, which takes the place of the deltoid imprint. 5. An inferior articular pulley continued between the two condyles by a non-articular groove ; this trochlea certainly corresponds to the median groove of the inferior humeral face. There are, no doubt, differences in the two bones, but they have no bearing upon the result just indicated. Thus, the linea aspera of the femur is situated behind ; that of the humerus in front. In the femui' the two condyles of the inferior extremity are placed behind the trochlea ; the contrary holds in the humerus. These modifications are necessary, in order to give the movements of the limbs a convenient direction. The leg is flexed backward on the thigh, while the fprear is flexed forward on the humerus. Parallel hetween the bones of the leg and those of the forearm. — It is more particularly in these two regions that the question of analogies has been resolved in a contradictory manner by anatomists. It would have appeared less compli- cated had it been studied in a large number of species. If we examine the leg-bones of certain Marsupials^ in which the tibia and fibula are apart as in the radius and ulna in Man, it will be found that : 1. These two bones articulate with the condyles of the femur. 2. The anterior face of the tibia has no ridge. 3. The patella is attached to the upper end of the fibula. From this it might be concluded that, in Man and the domestic animals, the tibia, with the exception of its anterior and external tuberosities, is the homologue of the radius, and the fibula and external and anterior tuberosities of the tibia are the homologues of the body and inferior extremity of the ulna. The patella corresponds to the olecranon ; the mobility of the first cannot be offered as an objection to this assimilation, for in Bactrians the olecranon forms, like the patella, an independent bony nucleus. Parallel between the bones of the posterior and those of the anterior foot. — The analogy becomes so marked when these two regions are compared, that it is scarcely necessary to allude to them. The tarsal bones are to the posterior limb what the carpals are to the anterior one ; it is even possible to compare, one by one, the several pieces in these regions. The metatarsals are but a repetition of the metacarpals ; while the digital bones are so much alike, that it is difficult to distinguish the anterior from the posterior phalanges. 158 THE BONES, CHAPTER III. THE BONES IN BIRDS. These animals, destined for the most part to sustain themselves in the air, should exhibit in the conformation of their skeleton all the conditions which may favour aerial locomotion ; from this arise the differences which distinguish their skeleton from that of the Mammalia — differences which will now be rapidly traced. Veetebeal Column. Cervical vertebne. — The cervical spine represents in the Bird, as in the Mammal, a kind of balancing-pole curved like an S, which supports the head, and by its changes in form and direction varies the centre of gravity. When a Bird rises in the air and flies rapidly, it lengthens the neck and stretches out the head, to carry the centre of gravity forwards. But when it rests on the ground, it makes the balancing-pole assume the natural and more or less graceful inflection, by throwing the head backwards, and transferring the greater portion of the weight of its body to the columns of support formed by the posterior Hmbs. These displacements of the centre of gravity are executed in Birds on a more extensive scale than in Mammalia ; the vertebral limbs in the former are also longer, hghter, and enjoy an excessive mobility. The vertebrae composing it number fourteen in Fotvls, twelve in the Fir/eon, fifteen in the DmJc, aijd eighteen in the Goose ; in the Swan twenty-three have been counted ; — a curious variety, which singularly contrasts with the numerical unity noticed as one of the most remarkable characters in Mammalia ! These vertebras are generally longer than in the latter animals, and are particularly distinguished by the configuration of the articular surfaces of the inferior part or body. These are diarthrodial facets convex in one direction and concave in the other, articulating the vertebral bodies by a veritable and reciprocal clamping. In this manner, the anterior head of the body of each vertebra is replaced by a facet concave on both sides, and convex vertically ; while the posterior extremity of the bone bears, instead of a concavity, a facet convex in the lateral sense, and concave from above to below. The inferior crest of the body (Fig. 109, 2, 2') only exists in the first and last vertebrae ; but it forms a veritable spine, analogous to that observed in the lumbar vertebrae of the Rabbit. The spinous process (Fig. 109, 1, 1') only forms a simple crest in the middle part of the neck ; it becomes more salient in the vertebras which occupy the two extremities of this region. The transverse process represents on the side of the vertebra a thick, obtuse, and irregular tubercle, situated under the anterior articular process, and pierced at its base by a large vertebral foramen (Fig. 109, 4, 4'). It is most frequently furnished with a small styloid prolongation (Fig. 109, 3, 3') directed backwards and downwards, forming an epiphysis at an early period, and representing a real undeveloped rib. The atlas has no transverse processes. This vertebra is shaped like a thin ring, and is excavated on its anterior contour by a small cavity, into which is received the single condyle of the occipital bone. The axis shows a very marked odontoid process, with a single facet under that eminence. Dorsal vertebrce (Fig. 109, b, c). — These are seven in the Fotvl and Figeon, TEE BONES IN BIRDS. 159 and nine in the Goose and Duck; they are nearly always consolidated into a single piece to which the trunk is fixed, and which gives the wings a sohd Fig. 109, SKELETON OF A FOWL. From A to B, Cervical VertebrcE . 1, spiDous process of the third vertebra; 2, inferior ridge on body of the same ; 3, styloid prolongation of the transverse process of the same; 4, vertebral foramen of the same ; 1', 2', 3', 4', the same parts in the twelfth vertebra. From B to C, Dorsal Vertebrae: 6, spinous process of the first ; 7, crest formed by the union of the other spinous processes. From D to E, Coccygeal Vertebrce. F, G, Head: 8, interorbital septum; 9, foramen of communication between the two orbits ; 10, premaxillary bone ; 10', external openings of the nose; 11, maxilla; 160 THE BONES. Fig. 110. support in the violent efforts that flight demands. The two or three last are often even covered by the wing-bones, and joined to them. The inferior crest of the body forms a very long spine, especially in the first vertebras. The spinous processes — flat, wide, short, and consolidated with each other by their opposite borders — constitute a long crest extending from the last cer\ical vertebra to the bones of the wings (Fig. lOD, 7). The trans- verse processes widen to their summit ; in the FovjI they are nearly constantly fused with each other. Lumbar and sacral vertebne. — All these vertebrae are formed exactly on the same type ; so that it be- comes difficult, if not impossible, to fix the point where the lumbar region ends or the sacral begins. At first independent of each other, these vertebra?, numbering fourteen, soon become consolidated with one another and with the ribs ; but their primitive separation is always indicated by the lateral septa, which form, on their inferior face, the vestiges of the transverse pro- cesses. The former are closely united to the latter in the dorsal region. Coccygeal vertebrce. — In the coccygeal region, the spine recovers its mobility. The tail of the Bird, indeed, fulfils the office of a rudder in directing it during flight ; and it is absolutely necessary that the vertebr* which serve as a base for the steering feathers should preserve their independence, so as to allow these to be carried to the right, left, downwards, or upwards. These vertebrje — seven in number — present spinous processes which are often bifurcated, transverse pro- cesses very developed, and sometimes even spines more or less long on the inferior surface of their bodies. The last vertebra is always the most voluminous ; it is flattened on both sides, and terminates in a curved-up point. Head (Fig. 110, f, g).— The head of the Bird is small, and of a conical form. The anterior extremity is elongated, and terminated by a pointed or flattened beak, which allows the animal to cut the air with more facility. Bones of the cranium. — The bones which compose the cranium are, as in Mammalia, an occipital, parietal, frontal, ethmoid, sphenoid, and two temporcds. These bones are not isolated from each other, excepting during early life in the shell ; and the ossifying process 12. OS quadratum ; 13, malar bone. H, Sternum : 14, brisket or keel ; 15, episternal process ; 16, internal lateral process; 17, lateral external process; 18, membrnne which closes the internal notch ; 19, membrane of the exte^-nal notch, i. etc., Superior Ribs : 20, posterior process of the fifth. J, Inferior ribs. K, Scapula. L, Coracoid hone. M, Furculum : m, m, its two branches. N, Humerus. 0, Ulna : o. radius, p. p', Bones of carpus. Q, q'. Bones of metacarpus. R. First phalanx of th° large digit of the loinq : r. second phalanx of the same, r'. Phalanx of thumb. S, Hium. s'. Ischium, s". Pubis : 21. sciatic foramen : 22, foramen ovale. T, Femur, v. Patella. V, Tibia. X, Fibula : y, single bone of tarsus, y. Metatarsus : 23, superior process representing a united metatarsal bone ; 24, process supporting the claw. Z, etc.. Digits. HEAD OF AN OWL (NATURAL SIZE ; POSTERIOR VIEW). 1, Occipital foramen ; 2, single occipital condyle ; 3, ptery- goid ; 4, inferior articular surface of the os quadratum ; 5, anterior process of ditto ; 6, 6, anterior face of the palatine bones, forming: the guttural orifice of the nasal cavities; 7, posterior ex- tremity of ditto; 8, zygo- matic ; 9. lachrymal ; 10. premaxilla ; 11, orbital pro- cess ; 12, right zygomatic process ; 12', zygomatic pro- cess on the opposite side, united to the orbital pro- cess. TEE BONES IN BIRDS. 161 which unites them is so rapid, that the cranium, shortly after hatching, is already a single piece. No detailed description of the separate bones will be given here, but only a few brief observations which may be of some utility. Thus, the occipital bone shows for articulation with the spine only a single condyle, situated under the occipital foramen, and excavated by a slight gi'oove. In Palmipedes, this bone is pierced, behind the crests which give attachment to the extensor muscles, by two foramina which penetrate the cranium, and represent permanent fontanella. The parietal bone is feebly developed, and formed from only two primary nuclei. The frontal is the largest bone of the cranium ; its orbital process (Fig. 110, 1), incomplete, is supported by a particular piece (posterior frontal) fixed between the principal frontal bone, parietal, and posterior sphenoid, with which it is sometimes confounded. The perpendicular lamina of the ethmoid is considerable, and forms between the two orbits a thin vertical septum (Fig. 109, 8). Its posterior border is notched opposite to the optic foramen, and thus constitutes an opening which communicates between the two orbital cavities (Fig. 109, 9). It is also channeled, near its upper. border, by a fissm-e which terminates by two openings at its extremities, one entering the cranium, the other the nasal cavities. Tliis fissure and these foramina pennit the passage of the ethmoidal nerve, which in this way traverses the orbit before arriving at its destination. The ethmoidal cells are more membranous than bony : their base is attached to a very delicate transverse plate, which is often membranous and not cribbled, and forms part of the anterior orbital wall. These cells replace, at the same time, the lateral masses of the ethmoid and turbinated bones of MammaUa. The sphenoid appeal's to be formed of a single piece, and shows on its sides two diarthrodial facets corresponding to the pterygoids. It is pierced by one foramen for the passage of the optic nerves ; but this foramen opens on the outer and opposite side of the posterior notch of the interoi-bital septum, and thus allows each of the nerves passing through it to reach the eye for which it was intended. It is worthy of remark, that an analogous disposition is also noticed in the Rabbit.^ The temporal bones present at their base an articular surface correspond- ing to the square bone (os qimdratum) (Fig. 109, 12, 12'). In the Foivl species, the zygomatic process forms a small flattened tongue, directed forwards, sometimes free, and at other times united by its superior border to the summit of the orbital process. These two eminences are exceedingly short in Pigeons. In Palmipedes they are consolidated and confounded so intimately, that it becomes impossible to distinguish them from one another. From this union results a long and strong process, which inclines forward and meets a particular prolonga- tion of the OS unguis, forming with it a real bony arch. This arch limits, below and outwardly, the orbital cavity. Bones of the face. — The supermaxilla comprises : a premaxilla, two nasal, two lachrymal, two palatine, two pterygoid, two zygomatic hones, and a vomer. The inferior jaw has for its base a maxillary hone, which articulates with the cranium by means of two supplementary pieces named the square hones. The premaxillary hone (Fig. 110, 10) is formed, before hatching is completed, of two lateral pieces, ' This analogy is really striking, and might, in our opinion, serve as a basis for a new ietermiuation of the interorbital septum. We are tempted, indeed, to consider this bony lamina as the inferior sphenoid and the middle portion of the ethmoid in Birds. This manner of viewing it tends to confirm the ideas of M. Tabourin on the inferior sphenoid and the ethmoid of Mammals. 162 THE BONES. which represent the two small premaxillaries of Mammals. This bone is very considerable, and of itself forms the base of the upper beak, the form of which it determines ; it is pointed and conical in the GalUnacea, and wide and flattened above and below in Palmipedes. In front it circumscribes the external openings of the nose, and is prolonged superiorly into two lengthy processes which dovetail between the nasal bones. Two inferior processes belonging also to this bone concur in the formation of the palatine roof. The supennaxillaries, analogues of the supermaxillaries of Mammals, are two rudimentary bones situated on the sides and at the base of the beak. They form a part of the palatine roof and the walls of the nasal cavities. The nasal bones circumscribe above, inwardly, and even outwardly, the external orifices of these cavities. The palatine hones encircle, as in Mammals, the guttural openings of the nose, and constitute in great part the roof of the palate ; their posterior extremity lies against the pterygoids ; the anterior joins the supermaxillaries and the inferior process of the premaxillary bone. The pterygoids extend obliquely from the sphenoid to the square bones, and are united to the sphenoid by diarthrodial articulation. The zygomatic hones have the form of two very thin stylets, and are united to the square bone by their posterior, and consolidated with the supermaxillary by their anterior, extremity. The vomer separates the guttural openings of the nose from one another. The bones of the upper jaw are not fused to each other so rapidly as the bones of the cranium. The ascending processes of the premaxillary and nasal bones even remain for a long time tmited to the frontal bone by a simple synarthrodial articulation. This arrangement allows the upper beak to execute a certain elevating movement, of which we will speak when describing the articulations. The inferior maxillary hone is originally formed of a great number of distinct segments, which are soon united into a solid piece. The square, petrous., or hone of the tympanum ought to be considered as detached from the temporal. It is prismatic in shape, and provided on its upper surface with a diarthrodial facet which unites it to the temporal, and on its lower face with another facet articu- lating with the branch of the maxilla. Outwards it joins the zygomatic bone, and inwards the pterygoid. Behind, it gives attachment to the membrane of the tympanmn ; and in front it presents a small eminence of insertion, which Meckel considered a second zygomatic process. Thokax. — Sternum (Fig. 109, H 1). — The sternum of Birds, serving as a basis of support to the muscles moving the wings, should offer, and does in fact show, a remarkable degree of strength, because of the extraordinary volume of these muscles. And these being more powerful and energetic as the Bird exhibits a greater degree of aptitude for flight, it results that the structure of the sternum is solid in proportion as the creature is strong on the wing. For this reason, we may infallibly pronounce as to the extent and power of a bird's flight by an inspection of the sternum of individuals of its species. In this respect, however, we only announce what is well known to be a particular appli- cation of the rules established by the great law of concordance between the anatomical disposition of organs and their physiological finality. Studied in Palmipedes., which will serve as a type for description, the sternum presents itself in the form of a large rectangular cuirass, elongated from before to behind, of itself constituting the inferior wall of the thoracic cavity, and also largely protecting the abdominal cavity. Its superior face is concave, while the inferior is convex, and entirely occupied by the insertion of the pectoral muscles. THE BONES IN BIRDS. 1G3 It presents, on the median line, a thin and very salient ridge, named the brisket {carina or keel) (Figs. 109, 14 ; 111, B. 2), which in a remarkable manner multiplies the points of attachment of these muscles. The anterior border offers in its middle a small eminence of insertion, the episternal (Figs. 109, 15 ; 111, A 2). Laterally, two articular grooves are seen which correspond to the coracoids. The posterior border is cut by two notches which are often converted into foramina (Fig. Ill, b 3, 3). On the lateral borders are observed small double articular facets answering to the inferior ribs. The angles which separate these two borders from the anterior are both prolonged into a httle eminence, named by some authors the costal process (Fig. Ill, a 33). In the Fowl, the sternum is not so strong as in the Goose or Duck. On each side of the brisket it shows two wide notches, which greatly reduce its substance. These notches (Figs. 109, 18, 19 ; 111, a 6, 7), closed in the fresh state by membranes, are distinguished as external and internal. The latter, of greater size than the former, extends nearly to the extremity of the bone. From this division of the lateral plates of the sternum, result two long and slender processes directed backwards (Figs. 109, 16, 17 ; 111, a 4, 5). The external terminates by becoming widened, and forming a kind of bony plate, which covers the last inferior ribs. The sternum of Pigeons is distinguished by the enormous development of the brisket. The two notches of the Fowl are also met with in these birds, but the internal is nearly always converted into a narrow foramen. This comparative study of the sternum in the chief domesticated birds, leads us to appreciate the correctness of the principles just enunciated, with regard to the form and extent this bone may exhibit. The Gallmaceous Birds, properly so called, which fly little and badly, have the sterur.-n singularly weakened by the deep notches cut in its lateral parts. With Palmipedes, the sternum is wide and but slightly notched, so that the Goose and Duck, which waddle along so awkwardly in our poultry yards, are capable of sustaining long and rapid flight, like that of the wild individuals of the same species. With regard to Pigeons, which are well known to be swift and powerful flyers, may this advantage not be due to the extraordinary development of the keel which constitutes the brisket ? Ribs (Fig. 109, I, etc.).— In the Fowl and Pigeon there are seven pairs of ribs ; and in the Duck nine pairs. Articulated superiorly with the dorsal vertebrte, as in Mammals, these bones are provided, near their middle, with a flat eminence which commences at the posterior border, and is directed back- wards and upwards, to rest by its free extremity on the external face of the next rib. These eminences (Fig. 109, 20) form an epiphysis at an early period, and are usually absent in the first and last ribs. They concur in an efficacious manner to increase the solidity of the thorax. The costal cartilages of the Mammalia, are in Birds often transformed into veritable inferior ribs, joined to the superior ribs by a diarthrodial articulation (Fig. 109, J). These pieces are long and strong, and all terminate at their lower extremity by a double facet which articulates with the lateral border of the sternum ; they are nearly always absent in the two first ribs. It is not rare to see the last united to the one before it, instead of passing directly to the sternum ; in which case it comports itself like the asternal ribs of Mammals. Anterior Limbs. Shoulder-bone. — The shoulder comprises : a scapula ; a particular bone named the coracoid by Cuvier : and a clavicle, which forms, in 164 THE BONES. coalescing with that of the opposite side, a single bone called the /or A' (furcidum)^ or osfuradare. The scapula (Figs. 109, k ; 111, a 8) is narrow, elongated, and falciform, and shows no trace of a spine. Its anterior extremity only forms a portion of the glenoid cavity, and is united by means of a fibro-cartilage with the fork of the coracoid bone. The latter (Figs. 109, L ; 111 a 9) is so named because it represents the coracoid process of Mammals, and is a long prismatic bone, directed obliquely from above downwards, and before to behind. Its superior extremity is often fused with the scapula, and united at an acute angle with that bone to form a portion of the articular cavity which receives the head of the humerus. Its inferior extremity is flattened from before to behind, and responds by a diarthrodial articulation to the anterior border of the sternum. The coracoid is long in Birds which fly slowly ; it is, on the contrary, short, thick, and therefore very solid, in quick flyers. Th.^ fork (Figs. 109, M; 111,. Fig. 111. STERNUM AND BONES OF THE WING. A, Sternum and mng-bones of the Fowl {upper face). 1, Body of the sternum; 2, its episternal process; 3, 3, its costal proces>es ; 4, 4, its lateral external processes; 5, 5, its lateral internal processes; 6, 6, internal notches; 7. 7, external notches; 8, scapula; 9, coracoid; 10, fork; 11, opening for the passage of the elevator of the wing; 13, humerus; 14, air-opening in that bone; 15, ulna; 16, radius; 17, ulna-cavpal bone; 18, radio-carpal bone; 19, large metacarpal ; 20, small metacarpal ; 21, first phalnnx of the large digit ; 21', second phalanx of ditto ; 22, small phalanx lying beside the first bone of the large digit, and representing the remains of a third digit ; 23, thumb. B, Sternum and shoulder-hone of a young Duck (inferior surface). 1, 1, Sternum ; 2, keel ; 3, 3, lateral notches ; 4, 4, coracoid •, 5, 5, fork ; 6, opening for the passage of the elevator of the wing. B 5, 5) is a single bone, shaped like a V or U, situated at the base of the two wings, in front of the trunk, and in an oblique direction downwards and back- wards. The two branches which form it represent the clavicles ; they meet and are united at their inferior extremities, where they describe a curvilinear angle more or less open, attached to the brisket by means of a membranous ligament. THE BONES IN BIRDS. 165 Their superior extremity rests within and opposite to the glenoid cavity, against the scapula and coracoid, forming with these bones a remarkable foramen, through which passes the tendon of the elevator muscle of the wing (Fig. Ill, A 4, B 6). The forks play the part of an elastic spring, whose office it is to prevent the wings coming towards each other during contraction of the depressor muscles. The conformation of this bone is, therefore, like the sternum, related to the extent and power of flight ; and for this reason it is that, in swift flyers, the two branches of the furculum are thick, solid, widely separated, and curved like a U ; while in those which fly heavily and with difficulty, these branches are thin and weak, and joined at an acute angle. The latter formation greatly diminishes its strength, and lessens, in a singular manner, the reactionary power of the bony arch it represents. Bone of the arm. — The humerus (Figs. 109, n ; 111, a 13) offers an articular oval-shaped head, and an air-opening placed beneath this eminence. It is long in Palmipedes, ordinarily so in the Gallinaca, proper, and very short in Pigeons. Bones of the forearm (Figs. 109, o, o ; 111, A 15, 16).— The radius is much less voluminous than the ulna. The latter has an extremely short olecranon ; and the two bones are separated from one another in their middle part to meet again at their extremities, where they are united by ligamentous bands in such a way as to render the movements of pronation and supination impossible. This mode of union, which nevertheless does not prevent the two bones from gliding slightly on each other in the direction of their length, has been wisely adopted by nature in order that the wing might strike the air, like an oar, by its inferior face ; otherwise, the resistance of the aerial medium would make these two bones pivot, and cause the wing to present itself to the air in a wrong direction. Bones of the carpus (Figs. 109, p, p' ; 111, a 17, 17).— These are only two, and are distinguished by the names of radius and ulna, in consequence of their corresponding more particularly to these bones in other animals. Bones of the metacarpus (Figs. 109, q, q' ; 111, a, 19, 20).— These also number only two, and are separated at their middle portion, to be consolidated at their extremities. Bones of the digital region. — The wing of a bird is composed of three digits. One of them, which resembles the thumb and forms the basis of the false wing is composed of a single styloid-sliaped phalanx, articulated at the base of a small particular process belonging to the superior extremity of the largest metacarpal bone (Figs. 109, r' ; 111, A 23). The largest digit comprises two phalanges, which succeed the last bone (Figs. 109, R, r ; 111, a 21, 21'), The third digit is represented by a small rudimentary phalanx (Fig. 109, a 22), which corre- sponds to the inferior extremity of the small metacarpal bone, and lies beside the first phalanx of the large digit in the closest manner. It is well to remark that the hand and forearm are longer in proportion to the quality of flight ; those two regions of the Aving, for example, are very short in Gallinaceous Birds. Posterior Limbs, Coxa, or os iliac. — This is a voluminous and very solid piece, particularly in walking birds, and composed, as in the Mammalia, of an ilium, ischium, and pubis. The ilium (Fig. 109, s), very long, is con- solidated with the last two dorsal, the lumbar, and the sacral vertebrae ; it is excavated on its internal face. The ischium partly incloses the side of the pelvic cavity ; between its internal border and the external border of the ilium is an •orifice which replaces the great ischiatic notch. Its inferior border is united to 166 THE BONES. the pubis. The latter (Fig. 109, s") is thin and elongated, and follows the direction of the inferior border of the ischium, with it circumscribing an oval opening more or less spacious (Fig. 109, 22). Its inferior extremity extends beyond the ischium, to curve inwards towards that of the opposite side, but without uniting with it. We do not, therefore, find the pelvic symphysis in Birds, and the pelvis is slightly open below, a circumstance which favours the passage of the egg through the cavity and out of the cloaca. The cotyloid cavity is perforated by an opening at the bottom, which passes through the bone. Thigh-bone. — The femur (Fig. 109, t) is articulated inferiorly with the patella, tibia, and fibula. In all walking Birds, Uke the Gallinacge, it is long and strong, as well as the bones below it. Leg-bones. — The patella (Fig. 109, u) is wide and thin. The tiUa (Fig. 109, v) terminates, below, by two condyles separated by a groove, which becomes articular behind. The fibula (Fig. 109, x) articulates by its head with the external condyle of the femur, and is consolidated with the tibia ; it never descends to the inferior extremity of that bone. Tarsal bones. — The tarsus appears to be altogether absent in Birds. Never- theless, we may venture to consider, as a vestige of the bones of this region, a small bony nucleus buried in a fibro-cartilaginous mass which ghdes on the- posterior pulley of the tibia. This nucleus (Fig. 109, y) represents the calcaneum of Mammals. Metatarsal bone. — A single metatarsal bone Ls found in Birds, articulating superiorly with the inferior extremity of the tibia, and terminating inferiorly by three pulleys which support the three principal digits. This bone (Fig. 109, y) shows in the Fowl, near its inferior third, a conical process turned backwards, which serves as a base for the spur. Behind its superior extremity, it exhibits another which may be considered as a consolidated metatarsal bone (Fig. 109, 23). Bones of the (ligital region (Fig. 109, z, etc.). — All the domesticated Birds have four digits on the inferior members : three principal, directed forwards, and one rudimentary, carried backwards. The first, designated as internal, median, and external, articulate with the inferior pulleys of the metatarsal bones. The in- ternal is formed by three phalanges, the second has four, and the third five. These phalanges are formed something like those of the Carnivora ; the last is pointed, conical, and enveloped in a horny sheath. The fourth digit, or thumb, is composed of three pieces ; one of these, the first, is generally considered as a rudimentary metatarsal bone. It is attached by fibro-cartilaginous tissue to the inner and posterior aspect of the inferior extremity of the principal metatarsal bone. THEORY OF THE VERTEBRAL CONSTITUTION OF THE SKELETON. 167 CHAPTER IV. THEORY OF THE VERTEBRAL CONSTITUTION OF THE SKELETON. In the series of vertebrated animals, the bony pieces of the trunk bearing the name of vertebrse are those which offer the highest degree of fixity, and to which the existence or the arrangement of the others appears to be subordinate. This feature in organization, recognized by E. Geoffroy Saint-Hilaire and Professor Owen, has caused these authorities to assert that the type of construction of vertebrated animals is the vertebra. After E. Geoffroy Saint-Hilaire and Professor Owen, several German, English, and French anatomists have studied the vertebral composition of the skeleton ; and among the works published in France on this subject, must be specially noticed those of Lavocat. In principle, all the writers have arrived at the same conclusions, and only differ in some few details. It is certain that the base of the vertebral column is formed by a series of bony segments. Each of these segments is called an osteodesm, and each osteo- desm represents the bodi/ or centrum of a vertebra. In examining the dorsal region, it is evident that to the body or centrum of a vertebra are added two complete osseous arches — a superior and an inferior. The superior arch is formed by the vertebral laminae ; the inferior by the ribs, their cartilages, and a portion of the sternum. The first is designated the neural arch, as it furnishes a protective case for the nervous centres ; and the second, which more particularly protects the vascular system, is called the hcemal arch (see Figs. 112, 113). The hfemal arch may have prolongations or appendices more or less developed, and comparable to the apophysary prolongations of the ribs in Birds and some Fishes. Such is the general composition of a typical vertebra ; but there are also to be distinguished in the neural and htemal arches the following parts : — H^MAL ARCH. 1. Haemal parapophysis = the tuberosity of the rib. 2. Haemal metapophysis = the head of the rib. 3. Haemal diapophysis = the rib proper. 4. Hsemapophysis = the costal cartilage. 5. Haemal spine = the corresponding sternal portion. NEURAL ARCH. 1. Neural parapophysis = the posterior costal cupola. 2. Neural metapophysis = the anterior costal cupola. 3. Neural diapophysis = the summit of the transverse process. 4. Neurapophysis = the vertebral lamina. 5. Neural spine = the summit of the spinous process. The vertebrae sometimes depart more or less from the model just described. They may vary not only from one species to another, but also in the same animal, and even in the same region. Thus, the neural arch may be absent, as has been observed in certain coccygeal vertebrae ; or the hsmal arch is incom- plete or null, as in the cervical or lumbar vertebrae ; or, lastly, the arches are often unequal ; though this inequality is of no importance, since their size is in relation to the volume of the parts they should protect. Notwithstanding these differences and variations, or the transformations 168 THE BONES. experienced by certain parts, there is not a bone in the skeleton which cannot be included in the vertebral type. Fig. 112. THORACIC OR PECTORAL VERTEBRA OF A MAMMAL. C, Centrum ; n, neural arch ; h, hsemal arch. Fig. 113. CAUDAL VERTEBRA OF THE TURBOT. c, Centrum , n, neural arch ; h, hsemai arch. The vertebra being admitted as the type of construction of the skeleton, it is easy to find it in all the regions of the bony framework. In the thoraco- Fig. 114. CRANIAL VERTEBRiE OF THE DOG. (AFTER LAVOCAT.) 1, Occipito-hyoideal vertebra; 2, parieto-maxillary vertebra; 3, fronto-mandibular vertebra; 4, naso-turbinal vertebra. THEORY OF TEE YERTEBRAL CONSTITUTION OF THE SKELETON. 169 abdominal region, the centrum, neural arch, and hsemal arch are readily per- ceived ; for in the lumbar vertebrae, the enormously developed transverse process indicates the existence of an intra-vertebral arch. In the sacral region, the bony girdle of the pelvis represents the hsemal arch. The posterior limbs, articulating with the bones of the pelvis, also belong to the hsemal arch, and should be considered as appendices of this arch, analogous to the costal appendices of birds. The cervical region may be compared to the sacral region ; as in it the inferior haemal arch is represented by the osseous ring supporting the anterior hmbs — the scapulo-clavicular girdle. The limbs themselves are appendices of the cervical haemal arch. Difficulties begin to appear when the extremities of the trunk — the head and coccyx — come to be examined. Nevertheless, the composition of the coccyx is revealed when the caudal vertebrae of certain Fishes, especially those of the Pleuronectidae, in which the neural and hsemal arches are complete, are examined (Fig. 113). But the vertebral constitution of the head remained for a long time an insoluble question, or it was solved in a contradictory manner by the naturalists who attempted it. Some admitted a single cranial vertebra ; others included three or four ; while others, again, found six or seven. These difficulties and contradictory results may be understood, when it is borne in mind what profound modifications the vertebra must have undergone to constitute the bones of the head. At present the problem appears solved. The head is composed of four vertebrae, in which are found the various parts enumerated in the description of the typical vertebra. In the four classes of vertebrata, the head is constantly formed of four vertebrse, which are determined as follows, according to Lavocat : — Vertebra. Centrum. Neural arch. Hjemal arch. Occipito-hyoideal. Basilar process of the occipi- tal. Occipital (3 pieces). Mastoid walls of the tympanum. Hvoideal apparatus ('five pieces). Parieto-maxillary. Body of the posterior sphe- noid. Wing and pterygoid process of the pos- terior sphenoid. S(iiiamnus portion and zygomatic process of the temporal. Parietal. Inferior maxilla (five pieces). Froiito-manflibular. Body of the anterior sphe- noid. Wing and pterygoid pr<'cess of the anterior splienoid. Posterior Frontal and its (irhital process. Frontal. Malar. Laclirvnial. Palatine. Supermaxillary. Preriiaxillary. Naso ttnbinal. Vomer. Ftlimoid. Nasal. Turbinated. Sub-ethmoidal. 170 THE ARTICULATIONS. The number of cranial vertebrae is invariable, as each is destined to lodge the organs of one of the four senses. The occipito-hyoideal receives the principal organs of hearing ; the parieto-maxillary osteodesm protects the sense of taste ; finally, the organs of vision are sustained by the fronto-mandibular vertebra, while the naso-turbinal contains the sense of smell. Several anatomists, at the head of whom are Huxley and Gegenbauer, do not entirely share these views. They certainly admit the existence of the occipital vertebra, but it appears to them to be impossible to recognize the others. They remark that all the bones which constitute the spine are found in the primary cartilaginous skeleton ; so that, in order to establish the vertebral constitution of the head, it would be necessary to allot to the same cranial vertebra : 1. The pieces that are found in the cartilaginous cranium. 2. The other pieces which are developed in the fibrous tissue — those skeletal tegumentary pieces (temporals, parietals, etc.). It must also be observed that the division into vertebral bodies of the parts which form the base of the cranium, far from being easy in the lowest animals, is, on the contrary, only possible, with some trouble, in the highest classes. So that if the vertebral constitution of the head were a fact, it must be admitted that the differentiation of the bones at the base of the cranium is less advanced in Mammals than in the lower vertebrates. The vertebral type is not, therefore, universally accepted by all anatomists. SECOND SECTION. The Articulations. THE ARTICULATIONS IN GENERAL. The different pieces constituting the solid framework of the animal body are, a-s has been said, united in such a manner that they can move one upon the other. From this union results the articulations, or articular joints, the construction of which will now be referred to in a general manner, before commencing a particular description of each. Arthrology, or Syndesmology , is the name given to that division of anatomy which treats of the articulations. To form articulations, the bones correspond with each other by certain determined points of their periphery, which are named articular surfaces. Every articulation is, therefore, essentially constituted by two opposite osseous surfaces, simple or complex, which are moulded to each other. These are either contiguous, independent, and very movable — continuous with each other by means of a cartilaginous substance which confines them, if not to total immobility, at least to very limited movements ; or united by a fibro- cartilage, the elasticity of which permits a certain degree of displacement between the bones in contact. In the first case, the articulations are classed as diarthroses, or movable articulations. In the second, they are designated synarthroses, sutures, or immovable articulations. THE ARTICULATIONS IN GENERAL. 171 In the third, they are amphiarthroses, or mixed articulations; so termed because they participate in the movements of the other two classes : synarthroses, by the continuity established between the articular surfaces ; and diarthroses. by the extensive motion they permit. The general characters that distinguish each of these three great classes of articulations will be successively studied. Fig. 115. u rammiQ 1^ a/ / e V pn 4 — fefjfjft PLANS OF THK DIFFERENT CLASSES OP ARTICULATIONS. A, Suture: 1, periosteum ; 2,sutural ligament. B, Amphiarthrosis : a, first degree— 1, periosteum; 2, articular cartilage ; 3, interarticular ligament : b, second degree — 4, single cavity in the interarticular ligament : c, third degree — 5, double cavity in the interarticular ligament. C, Diarthrosis: b, simple diarthrosis — 1, periosteum; 2, articular cartilage; 3, epithelial layer of the synovial membrane (dotted line) ; 4, fibrous capsule ; 5, cul-de-sac of the synovial membrane ; 6, fibrous layer of the synovial membrane : c, double diarthrosis— 7, interarticular meniscus ; 8, 9, cavities of the two synovial membranes. General Characters of Diarthroses. "We ought to consider, in the diarthrodial articulations (Fig. 115, c, 6 and c) : 1. The contiguous boni/ surfaces which form them. 2. The cartilaginous layers (cartilages of incrustation) which cover these. 3. The fibrous or fibro-cartilagi- nous tissue {articular fihro-cartilages) which complete them, when they are not shaped so as to be reciprocally adapted to each other. 4. The ligaments which 172 THE ARTICVLATIONS. maintain them in contact. 5. The serous membranes {synovial capsules) that cover the internal face of the latter, and which secrete the synovia, a kind of animal oil that facilitates the gliding of the articular surfaces. 6. The movements of which these articulations may be the seat. 7. Their methodical classification. 8, Their nomenclature. Articular Surfaces. — These surfaces have the common character of being destitute of asperities, so that they can glide with the greatest facility on each other. They are designated, according to their form, by the names of facets, heads, condijles, cotyles, glenes, pulleys, etc. There is no need to revert to their general description, as they have already been suihciently studied in the osteo- logy ; so we will confine ourselves to repeating that they are found at the extremities of long bones, on the faces of short bones, and on the angles of wide bones. We may mention, also, that they are often excavated by one or several depressions named synovial fossce, or hollows for the insertion of ligaments. The first are a sort of natural reservoirs which receive the unctuous fluid secreted by the interarticular serous membranes ; the second give attachment to interosseous ligaments. Cartilages of Incrustation. — This designation is given to the layers of cartilaginous matter which, as it were, varnish the articular surfaces they adhere to by their inner face ; their free surface is distinguished by a remarkable polish and brilliancy. Thicker towards the centre than at the circumference when they cover bony eminences, these carti- lages show an inverse disposition when they line cavities. They are elastic, of a pearly whiteness, and resisting — though they are soft enough to be cut by a sharp instrument ; in a word, they possess all the physical characteristics of the primary cartilage of bones. They appear to be formed of parallel fibres placed perpen- dicular to the bony surfaces, and im- planted in these by one of their ex- tremities ; the opposite extremity corre- sponding to the free surface of the cartilage. Viewed by the microscope, they are found to present the characters of true or hyaline cartilage. The fundamental matter is amorphous and homogeneous ; but under the influence of slight dessication, there appears in the hyaline substance a partition- ing formation, which may be regarded as an agent in the distribution of the nutritive juices in the substance of the cartilaginous tissue (Renaut). The cavities (cartilage capsules) are irregular, and more or less wide. They contain from one to five cells without walls, and their contents — slightly granular — have in the centre of each cell one or two nuclei with nucleoH (Fig. 1 IG). These cavities are elongated, and are directed almost perpendicularly towards the osseous articular surface in the deep layer ; in the middle layer they are round ; and they are lenticular, and parallel to the surface of friction, in the superficial layer. (It has been stated that a membrane lines these spaces. In addition to the SECTION OF BRANCHIAL CARTILAGE OF TADPOLE. , Group of four cells separating from each other ; b. pair of cells in apposition ; c, c, nuclei of cartilage-cells ; d, cavity contain- ing tiiree cells. These cells are embedded in the finely granular matrix, or funda- mental substance. THE ARTICULATIONS IN GENERAL. 173 granular matter observed in the cells, it is not rare to find fat globules. The nuclei of the cells vary from ^^V? *o Wmj o^ 8,n inch in diameter. The cells multiply eudogenously.) The cartilage cells are insoluble in boiling water ; consequently, so far as their chemical composition is concerned, they are distinct from the fundamental substance. The diarthrodial cartilages have no vessels or nerves. The presence of cartilages of incrustation in the articulations is of the greatest importance. When they are worn, absorbed, or transformed into bone in con- sequence of certain articular maladies, the movements become painful and very difficult. With regard to the part they play in the economy, it may be said that : 1. They favour, by their smoothness, the gliding and displacement of the bones. 2. They attenuate, by their suppleness and elasticity, the violent shocks to which the articulations are exposed. S. They resist the wear and deformation of the articular surfaces. Complementary Fibro-caetilages. — There are two kinds of complementary fibro-cartilages. Some (interosseous) represent circular cushions which pad the margins of certain cavi- ties, filling up the notches ^' S- ^ ^ '^• that might render these imperfect. They in- crease the depth of these cavities, and protect their borders from in j ury — for example, the coxo-femo- ral articulation. Others (infer-articular) are in- terposed between arti- cular surfaces when these do not exactly fit each other — as when two opposing extremities are convex. It may be remembered that the lateral tuberosities of each tibial surface present, for articulation with the condyles of the femur, two convex diarthrodial faces, the coaptation of which is rendered perfect by the interposition between each condyle and corresponding tibial surface, of a crescent-shaped fibro-cartilage, which for this reason has been named a meniscus. In other joints, these interarticular fibro-cartilages are shaped like discs or biconcave lenses. There then result double diarthroses (Fig. 115, C, e) : example, the temporo-maxillary articulation. (Fibro-cartilage also covers bony surfaces over which the tendons play, as on the trochlear surface of the humerus, postero-inferior face of the navicular bone, and elsewhere. In these situations it is named stratiform fibro-cartilage.) These organs are formed sometimes by fibrous, at other times by cartilaginous tissue ; their mode of association need not be referred to here, though it may be observed that the cartilage is more particularly found in all those points where there is most articular friction. They receive very few vessels, and it is questionable if they have nerves. Ligaments. — These are bands which unite contiguous diarthrodial surfaces. They are sometimes formed of white fibrous tissue, and sometimes of yellow ; hence their division into two great classes of white and yeUoiv ligaments. a. The white ligaments are distinguished by the pearly whiteness of their 14 FIBRO-CARTILAGE, MAGNIFIED 155 TIMES. Showing interlacement of fibrous fasciculi, with scattered groups of cartilage-cells. 174 THE ARTICULATIONS. tissue and want of elasticity. Those which are found around the margin of articulations are termed peripheral, and those in their interior are designated interosseous or interarticular ligaments. The peripheral ligaments are g^erallj composed of parallel fibres collected in fasciculi, or spread out as membranes. In the first they are called funicular, or riMon-shaped ; in the second, they are termed membraniform, or capsidar. The funicular ligaments are short, round, or flattened bands, attached by their extremities to the two bones they unite ; they are lined on their inner aspect by the synovial capsule, and are covered .externally by tendons, aponeuroses, muscles, vessels, or nerves. The capsular ligaments are often complete — that is Fig. 118. Fig. 119. ^^S Wl^m^^UJSlfmije'^^M^KplMwMl'' WHITE OR NON-ELASTIC FIBBOUS TISSUE. YELLOW OR ELASTIC FIBROUS TISSUE, THE LIGAMENTUM NUCH^E. to say, they envelop the whole articulation like a sack. At other times they are incomplete, and then they are simple membranes, binding together the different funicular ligaments of a joint. The interosseous ligaments — less numerous than the preceding — are often formed of interlacing fibres ; they are always funicular, and fixed by their extremities into excavations in the centre of articular surfaces. J. Hhe yellow ligaments are 2k[[ perijyheral, funicular, or 7nembranous, and enjoy a marked degree of elasticity, which permits them mechanically to bring back to their usual position the bony levers that have been momentarily displaced. These ligaments, which are powerful auxiliaries to the muscular forces, give permanent equilibrium to the weight in certain parts of the body, which incessantly tend to fall to the ground ; for instance, the cervical ligament of Solipeds and large Ruminants. The ligaments are always assisted in their action by atmospheric pressure, which is exerted over all the surface of the body ; and also frequently by the tendons and aponeurosis of muscles, and even by the muscles themselves, when they pass over an articulation or are inserted in its vicinity. In several regions the ligaments are more or less confounded w^ith tendons or aponeiu-oses — as in the anterior extensor tendon of the phalanges and superior sesamoid liga- ment, the ligaments of the femoro-tibial articulation, and the aponeuroses of the posterior portion of the superficial gluteal muscle. Synovial Capsules. — These are very thin membranes of a serous character, intended to secrete the synovia. They are composed of two layers : a deep, formed by fasciculi of connective tissue ; the other, superficial, formed by an THE ABTIGULATIONS IN GENERAL. 175 endothelium. The first sometimes adheres intimately to the inner face of the funicular or membranous ligaments of the articulation ; at other times it is loosely- attached to them by an abundance of connective tissue. The second layer is con- stituted by a single row of flattened polygonal cells, except at the bottom of certain grooves, where they are more or less crowded. Though belonging to the serous membranes, the synovial membranes do not form complete sacs, as, after lining the internal surface of the ligaments, they cease at the articular margins. Direct observation demonstrates that the cartilages have no covering, and that there is no synovial membrane on their surface. The anatomists who imagined that the thin pellicle, which can be rendered evident in cutting the surface of cartilage obliquely and separating it by teazing, was a membrane, were deceived, as this pellicle has not the texture of a serous membrane ; and it is not vascular, for it has never been possible to inject vessels on the surface of such cartilages, nor yet in their substance. Neither is it covered with epithelium, and, if submitted to microscopical examination, it has all the characters of cartilage. Pathological facts prove nothing in favour of the existence of a synovial membrane on cartilages. It may be accepted, then, that the synovial membrane never extends to the surface of articular cartilage ; but, after being fixed around the margin of a diarthrodial surface, it is reflected in every direction to line the internal surface of the ligaments, and become attached to the periphery of the diarthrodial surface in contact with the other, so that it entirely isolates the interior of the joint from the peri-articular connective tissue. There are generally found within articulations, little masses of fat which push the synovial membrane enveloping them inwards. Erroneously considered by Clopton Havers as glands for the secretion of synovia, these accumulations of fat have been named synovial fringes,- ot villi. They are more particularly numerous in the neighbourhood of the articular margins — that is, on the border of diarthro- dial surfaces. They are formed by a prolongation of the synovial membrane, which covers some connective tissue fibres associated with adipose cells, or an amorphous substance provided with nuclei. The synovial membrane, after lining the inner surface of ligaments, sometimes escapes between these, forming a hernia. The term synovial culs-de-sac has been given to these external prolongations of the articular serous membrane. This membrane often covers the inner surface of a tendon or ligament, in order to facilitate their gliding over a bony eminence. The synovia is a viscid, colourless, or slightly yellow fluid, in its physical characters somewhat resembling oil ; it does not possess them, however, so far as its composition is concerned, for chemical analysis has not demonstrated the presence of fatty principles. It is the albumen it contains which gives to it its viscidity, and which fits it for lubricating the articular surfaces over which it is spread. Its use in the animal economy is absolutely identical with that of the greasy substances employed to luliricate the axles of carriages. To the means of union described under the names of ligaments and synovial membranes, may be added atmospheric pressure, the influence of which is relatively considerable, as the experiments of Weber have demonstrated. Movements. — The movements peculiar to diarthrodial articulations are divided into seven principal classes : 1. Simple gliding, the only movement possible between two plane or undu- lating facets. 176 THE ARTICULATIONS. 2. Flexion, which brings two bony pieces nearer each other, by closing more or less their angle of union. 3. Extension, the inverse movement, during which the bones are straightened on each other. 4. Adduction, which brings the inferior extremity of the movable bone towards the median line. 5. Abduction, the contrary movement to the preceding. 6. Circumduction, or the sling movement, during which the bone passes successively through the last four positions. 7. Rotation, in which one bone pivots on another. Classification of the Diarthroses. — The basis of this classification is founded on the configuration of the articular surfaces and the nature of the movements they permit. This double base serves to establish five kinds of diathrodial articulation : 1. Enr/rfhrosis, characterized by the reception of an articular head within a cavity of appropriate form. This articulation, the surfaces of which are derived from a sphere, may be the seat of the most extensive and varied movements — flexion, extension, abduction, adduction, circumduction, and rotation. Example : the coxo-femoral articulation. 2. The trochlea?!, angular ginglymoid, or perfect hinge articulation, when the articular surfaces are formed into trochlea, reciprocally fitting into each other, and the movements of which — flexion and extension only — are executed, from before to behind, with the precision of a hinge. Example : the tibio-tarsal articulation. 3. The piiwt, trochoid, or lateral ginglymoid articulation, is a diarthrosis formed by a pivot which turns in a semi-cylindrical cavity. Rotation is the only move- ment. Example : the atlo-axoid articulation. • 4. The condyloid, or imperfect hinge articulation, which permits, like the preceding, the two principal movements of extension and flexion, and the acces- sory movements of rotation or lateral inclination. The articular surfaces, though very diversely shaped, nevertheless exhibit in all the articulations one or more condyles opposed to an equal number of oval excavations. Example : the femoro- tibial articulation. 5. Arthrodia, or 'plamform diarthrosis, is constituted by plane or nearly plane iacets. Gliding is the only possible movement. Example : the carpo-metacarpal articulation. Nomenclature. — The names of the articulations are usually those of the bones which form them. For instance, the scapulo-humeral articulation is the joint between the scapula and humerus ; the intervertehrnl articulations join to each other the various bones constituting the spine. When the qualifying name of an articulation is composed of two elements, as in the first instance, it is well to place first the word which indicates the bone usually most fixed. General Characters of the Synarthroses. Sutures (Fig. 1 1 5, a) are the temporary articulations which exist only at an early period of life. They nearly all disappear in the adult animal, in consequence of the bones forming them becoming consolidated. They belong almost exclusively to the bones of the head. Articular Surfaces. — The bones forming these come in contact by their THE ARTICULATIONS IN GENERAL. 177 borders or angles, which, for this purpose, generally present very uneven surfaces. Sometimes they arc cut perpendicularly and simply roughened ; at other times they are bevelled, and joined by means of fine laminse or trifling inequalities ; again, they are notched into deep and sinuous dentations ; and lastly, one bone is fixed into a groove cut in the other. It will be understood that such formations of the articular surfaces will limit their movements, and assure the solidity of their union. Modes of Union, — A fibrous tissue interposed between these synarthrodia! surfaces, unites them closely to each other. It has absolutely the same texture as the primary cartilage of the bones, and, like it, possesses the property of becoming ossified after having been vascularized. This ossification, which causes the disapppearance of the sutures, occurs earlier inwards than outwards. The periosteum, in passing from one bone to another, also concurs in bringing about a more complete synarthrosis. It should, therefore, be included in their means of union. Movements. — These are very obscure, and only noticeable in young animals, by the elasticity they communicate to the bony walls of the cranium or face. In the adult, they may be said to be null. Classification. — Tliere are four principal descriptions of sutures .- 1. When two wide bones correspond by means of denticulations fitting into each other, the suture is named frup, Umhosa, serrated, or dentated. Example : the articulations unitmg the three portions of the parietal bone. 2. If the opposite borders of two bones in contact are widely bevelled, one inwards, the other out- wards, it forms a scaly or squamous suture {squamosa). Example : the parieto- temporal articulations. 3. When the union of bones takes place by plane or roughened surfaces, cut perpendicularly on their borders or angles ; this constitutes the harmoaia suture, or suture hij juxtaposition (or apposition). Example : the occipito-temporal articulations. 4. The schiruii/Iesis, mortised suture, synchron- drosis, or gomphosis, results from the reception of a bony plate into a groove more or less deep in another bone. Examples : the spheno-frontal and supermaxillo-nasal articulations ; the teeth in the alveolar cavities. General Characters of the Amphiarthroses or Symphyses. Articulae Surfaces. — They are frequently smooth, and formed almost on the same model as the diarthrodial surfaces. They are covered by a thin layer of cartilage ; but, instead of being smooth and polished, they are more or less rugged, without, however, presenting the anfractuous disposition of the majority of synar- throdia! surfaces. Modes of Union. — The organs which perform this office are : 1. Fibro- cartilage, which establishes continuity between the articular surfaces. 2. Ribbon- shaped and peripheral ligaments (Fig. 115, b a). These latter do not differ from the analogous bands attaching the diarthrodial articulations. With regard to the fibro-cartilage, it is distinguished from the complementary discs of these same articulations, by a less intimate mixture of the cartilaginous and fibrous elements entering into its composition. The last may be sometimes absent, as well as the peripheral bands ; and then the articulation only differs from the synarthroses by the extent of motion it permits. Occasionally, the interarticular fibro-cartilages are excavated by one or two little narrow cavities (Fig. 115, b b, c) ; but these are never lined by a synovial membrane, like the diarthrodial cavities. 178 THE ARTICULATIONS. Movements. — The amphiarthroses only permit of a see-saw or swinging movement, the extent of which depends on the thickness of the intermediate fibro-cartilage. Classification. — Only one kind of amphiarthrosis is recognized in the Horse, the most, remarkable of which is found in the articulations between the bodies of the vertebrae. CHAPTER II. ARTICULATIONS OF MAMMALIA IN PARTICULAR. In the special study of the articulations, the same order will be followed as for the bones ; the articulations of the spine will be first noticed, then those of the head, thorax, and anterior and posterior limbs. Preparation. — The preparation of the bones which have been described, has not been made the subject of any particular recommendation, because it suffices, in order to study them, to remove the soft parts by which they are surrounded, either by boiling, maceration, or scraping. But when we come to examine the soft textures, in order to do so profitably it is necessary to learn beforehand the rules whicli should be followed in their preparation. The following directions are given with regard to the study of the articulations : — 1. To prepare the articulations, young subjects are cliosen in preference to those advanced in years, because the density of tlie connective tissue in them is not so great, and this tissue is easily removed from around the ligaments. As tiiese are prepared with difficulty when the external surface is in a dry state, care should be taken, before dissecting them, to have them excluded from the air by covering them with damp cloths, or with the skin of the animal. 2. It is convenient to separate the articulation we wish to dissect, by sawing through the bones at a certain distance from the articular surfaces. The manipulation of the part is then rendered easier, and its dissection can be made under the most favourable conditions. 3. It is necessary to preserve, as carefully as possible, the muscles surrounding the articula- tions, in order to be able to study their relations with the ligaments which bind these. If it be absolutely requisite to remove them, their insertions corresponding to the articulation should always be retained. 4. The capsular ligaments should be first studied, as they have soon to be removed, the better to show the funicular ligaments. Tliese, in their turn, must be sacrificed in order to display, by different sections, the interosseous ligaments, when they are present. Lastly, the two articular surfaces should be completely separated, so as to examine their conformation. 5. The synovial membranes, with their different cuU-de-sac, being a very important study — with reference to the diagnosis and treatment of articular tumours — it is convenient to devote a special piece to the examination of these serous membranes. It is very useful to inject their interior with plaster or tallow coloured black, in order to distend their cavities, and thus aid the study of their relations with ligaments, tendons, or muscles. 6. When an articulation is completely dissected, it may be left exposed to the air for some time. When the ligaments begin to dry, they are more visible and easier studied. For the preparation of each articulation it is not necessary to give any directions ; a glance at the figures accompanying the description will suffice to dispel any embarrassment the student may experience, while he always requires particular indications. Article I. — Articulations of the Spine. These articulations comprise all those of the vertebrse with each other. Preparation. — In order to properly study the vertebral joints, the spine of one subject should be freed from all tlie muscles surrounding it; this being done, portions consisting of at least two vertebrse from the cervical, dorsal, and lumbar regions, should be detached trum it. In the portions from the cervical regions, the interlamellar ligaments and the capsules of the ARTICULATIONS OF TEE SPINE. 179 articular processes are easily dissected ; and on the dorsal region portions, the interspinous, Bupra-spinous, interlamellar, and common inferior ligaments, can be examined. On those portions from the lumbar region, in a horizontal section through the spinal canal, the inferior face of the interlamellar ligaments and the common superior vertebral ligament will be seen ; while in those from the dorsal region, a good idea will be derived of the common inferior vertebral ligament. The intervertebral ligaments can be studied in vertical and horizontal eections of the bodies of the vertebrae from any region. A second subject, which should be fixed in the third position (see Preparation of the Muscles), is necessary for the dissection of the supra-spinous, dorso-lumbar, and cervical ligament. This may be eflPected by removing the muscles which occupy the vertical channels above the cervical vertebrse (see Preparation of the Cervical Kegions). Intervertebral Articulations. The vertebrae articulate : 1. By their bodies. 2. By their spinal or annular portion. There results from this union two kinds of articulation, which must be studied separately, as they do not belong to the same class. It is well to mention, however, that the general details into which this study leads us, apply only to the articulations uniting the last six cervical vertebrae, all the dorsal and lumbar vertebrae, and the first sacral vertebra. Union op the Vertebra by their Bodies. — The articulations forming this union are so many amphiarthroses. Articular surfaces. — The vertebral bodies come into contact by the surfaces which terminate them before and behind. In the cervical region these surfaces represent, anteriorly, a real head ; posteriorly, a cotyloid cavity which receives the head of the next vertebra. Beginning from the first dorsal vertebra and passing on to the sacrum, these surfaces tend to become effaced and more and more plane, though they still preserve their convexity and concavity. Means of union. — 1. By fibro-cartilages interposed between the articular surfaces. 2. By a common superior vertebral ligament. 3. By a common inferior vertebral ligament, a. Intervertebral fihro-cartilages (Fig. 121, 1, 1). — These are circular or elliptical discs, convex in front, concave behind, and soUdly fixed by their faces to the articular planes which they separate. The fibro-cartilaginous substance composing them consists of concentric layers, which become denser and closer to each other as they near the circumference ; they even disappear towards the centre of the disc, where this substance becomes pulpy, and assumes the histo- logical characters of pure cartilage. It may be remarked, that each of these layers is made up of a collection of thick parallel filaments, which cross with those of other layers Hke an X, and are attached by their extremities to the articular surfaces. From this aiTangement results so intimate an adherence between the vertebral bodies and their intermediate fibro-cartilages, that an attempt to disunite them is more likely to cause a fracture of the former. The fibro-cartilages, thicker in the cervical and lumber regions than in the dorsal, respond by their circumference to the two common ligaments. Those which separate the vertebrte of the back concur to form the intervertebral cavities, intended for the reception of the heads of the ribs, and give attachment to the interosseous costo-vertebral ligaments. h. Common superior vertebral ligament (Fig. 126, 1). — This ligament extends from the axis to the sacrum, and is lodged in the spinal canal. It is a long fibrous band cut on its borders into wide festoons. By its inferior face, it is attached to the intervertebral discs, and the triangular imprints on the upper faces of the bodies of the vertebrte. Its superior face is in contact with the dura 180 THE ARTICULATIONS. mater, tlirough the medium of an abundant cellulo-adipose tissue. Its borders are margined by the intra-vertebral venous sinuses (venm basium vertehrarium). c. Common inferior vertebral ligament (Fig. 127, 5). — Situated under the spine, this ligament is absent in the cervical, and the anterior third of the dorsal region. It only really begins about the sixth or eighth vertebra of the latter region, and is prolonged in the form of a cord — at first narrow, then gradually widening until it reaches the sacrum, on the inferior surface of which it terminates by a decreasing expansion. From its commencement, it is attached to the inferior crests of the bodies of the vertebrae and the intervertebral discs. By its inferior face, it is in contact with the posterior aorta. (Leyh commences this ligament at the seventh cervical vertebra, and says that it adheres to the crests on the bodies of the dorsal and lumbar vertebrae, as well as to the lower face of the sacrum and coccyx. At the fifth dorsal vertebra it widens and thickens, and in the lumbar region is bound up with the pillars of the diaphragm, and confounded on each side with the large ligaments of the pelvis.) Union of the Vertebra by their Spinal Portions. — Each vertebra, in uniting by its annular portion with that which follows or precedes it, forms a double arthrodial joint. Articular surfaces. — These are the facets cut on the anterior or posterior articular processes, and which have been described when speaking of the vertebrse themselves. They are covered by a thin layer of cartilage. Means of union. — 1. A common supra-spinous ligament. 2. Interspinous ligaments. 3. Interlamellar ligaments. 4. Ligamentous capsules, proper to the articular processes. a. Capsules proper to the articular processes (Fig. 124, 5). — Each anterior articular process is maintained against the corresponding posterior process, by a direct band. This is a peripheric capsule attached around the diarthrodial facets, lined by a synovial membrane which facilitates their gliding, and covered, outwardly, by the insertions of some spinal muscles. These capsules, yellow and elastic in the cervical region, are composed of white fibrous tissue in the dorso- lumbar region. Very developed at the neck, in consequence of the thickness of the articular tubercles they envelop, they become reduced, near the middle of the back, to some fibres which cover, outwardly, the diarthrodial facets in contact. b. Common supraspinous ligament. — This ligament, the name of which suffi- ciently indicates its situation, extends from the sacrum to the occipital bone, and is divided into two portions — one posterior, or supraspinous dor so-lumbar ligament ; the other anterior, or supraspinous cervical ligament. These two ligaments, although continuous with one another, yet differ so strikins^ly in form and structure that they are best described separately. 1. Supra-dorso-lumbar ligament (Fig. 127, 2). — This is a cord of white fibrous tissue, which commences behind on the sacral spine, and ceases in front, about the inferior third of the dorsal region, by insensibly assuming the texture and elasticity of the cervical ligament, with which it is continuous. It is attached in its course to the summits of all the lumbar spinous processes, and to the ten or twelve last dorsal. On the sacral spine, it is confounded with the superior ilio-sacral ligaments. In the lumbar region, it is united on each side to the aponeuroses of the longissimus dorsi muscles. 2. Supraspinous cervical, or simply cervical ligament {ligamentum nucha, liga- ARTICULATIONS OF THE SPINE. 181 mmtum colli) (Fig. 120, 1, 2). — This ligament is entirely formed of yellow fibrous tissue, and constitutes, in the median plane of the body, a very remarkable elastic apparatus, which separates the superior cervical muscles of the right side from those of the left, and plays the part not entirely of an articular band, but rather of a permanent stay, charged to balance the weight of the head. In the cervical ligament there is distinguished a fumriiJar and a lamellar portion. The first, usually called the cord {funicular or cordiform portion) of the ligament, is a wide funiculus which extends directly from the first dorsal spinous Fig. 120. CERVICAL LIGAMENT AND DEEP MUSCLES OF THE HORSE S NECK. 1, Lamellar portion of the cervical ligament ; 2, funicular portion of the same. processes to the summit of the head. Divided into two lateral lips by a median groove, this cord is continued posteriorly by the dorso-lumbar ligament, and is inserted, anteriorly, into the tuberosity of the occipital bone. It is covered above by a mass of fibro-adipose tissue, which, in certain common-bred horses, is very abundant. Below, it gives rise, in its posterior two-thirds, to the majority of the fibres belonging to the lamellar portion. On the sides, it receives the insertions of several cervical muscles. The lamellar portion — comprised between the funicular portion, the spinous processes of the second dorsal vertebra, and the cervical 182 THE ARTICULATIONS. vertebrae, constitutes a vast triangular and vertical septum, which itself results from the apposition of the two laminae that lie back to back, and are united by connective tissue ; they are bordered above by the two lateral lips of the cord. The elastic fibres which enter into their composition are given off either from the latter, or from the spinous processes of the second and third dorsal vertebrae ; they are directed downwards or forwards, and reach the spinous processes of the last six cervical vertebrae, into which they are inserted by so many digitations, becoming confounded with the interspinous ligaments of the neck. The fibres of the two last digitations are few in number, widely separated from one another, and united by many anastomosing branches, which make them appear as a kind of wide network. The lamina of the cervical ligament are in relation, outwardly, with the superior branch of the ilio-spinal ligament, the intertransversalis colli muscles, and the complexus muscle. (This important structure, which is, in reality, the mechanical stay and support of the heavy head and neck of quadrupeds, and is usually temied the ligamentvm nucJm, is all but absent in Man, being represented in him by a tliin narrow band — or rather two thin planes of fibres, the ligamenta suhflava. It is described by Leyh as if there were not two portions, and that excellent anatomist does not appear to insist suificiently on the difference between the dorso-nuchal and the dorso-lumbar divisions. Percivall, who almost entirely neglects the ligaments, also makes no distinc- tion. The difference in structure, elasticity, and situation, wairants the distinction made by Chauveau. As already indicated, the function of this ligament — and more particularly of its nuchal division — is to maintain the head and neck in their natural position during repose, and to allow the most extensive move- ments at other times.) c. Interspinous Ugaments (Fig. 121, 3). — Fibrous laminae fill the interspinous spaces, and are attached, before and behind, to the opposite borders of the spinous processes, which they unite. They are confounded superiorly with the supra-spinous hgament, and are continued inferiorly by the interlamellar ligaments — forming two lateral planes which are applied against each other, hke the laminae of the cervical ligament, and covered outwardly by the inter- transversalis colli muscles. In the region of the neck, the interspinous ligaments are yellow and elastic. In the dorso-lumbar region, they are formed by fasciculi of white fibrous tissue, loosely united to each other at their extremities, and directed very obliquely backwards and downwards. In consequence of this disposition, and notwith- standing their inextensibility, they permit the separation of the spinous processes. Their lateral surfaces are divided by a layer of grey elastic fibres, which cross hke an X the direction of the preceding fasciculi. Very abundant in the anterior moiety of the dorsal region, these fibres operate, by their proper elasticity, in bringing the spinous processes towards each other. d. Interlamellar, or interannular ligaments. — Situated, as their name indicates, between the vertebral laminae, and divided into two lateral moieties, these INTERVERTEBRAL ARTICULA- TIONS. A, B, C, Bodies of three dorsal ■vertebrse divided longitudi- nally ami vertically to show (1, i) a section of the inter- vertebral discs ; 2, supra- spinous dorso-lumbar liga- ment ; 3, interspinous liga- ment ; 4, fibrous fascia, con- stituting the proper capsule of the articular processes in the dorsal region. ARTICULATIONS OF THE SFINE. 183 ligaments appear to be produced by the two fibrous planes of the preceding ligaments, which, on arriving at the base of the spinous processes, separate from one another to be carried outwards. Their anterior border is inserted into the posterior margin of the vertebral lamina in front. Their posterior border is fixed to the anterior border and inferior face of the lamina behind. Their superior face is in relation with some spinal muscles, and their inferior face is in contact with the dura mater. Outwardly, they are confounded with the capsules proper to the articular processes. Yellow and elastic in the cervical region, these ligaments are Avhite and inelastic in the dorso-lumbar region. Ohaeactees proper to some Intervertebral Articulations. 1. Inter- coccygeal ana sacro-coccijgeal articulations. — These articulations are adapted to the rudimentary type of the vertebrae they unite. The coccygeal bones only come in contact by their bodies — their spinal laminse being reduced to the merest traces, or are altogether absent. The anterior and posterior articular surfaces of each vertebra are convex, and the interarticular fibro-cartilages, hollow on both faces, resemble a biconcave lens. With regard to the peripheral bands, they are repre- sented by a bundle of longitudinal fibres spread over the surface of the bones, which they envelop in a common sheath. 2. Intersacral articulations. — The sacral vertebras being fused into one piece — the OS sacrum — there is no occasion to study the true articulations in this region. It may be remarked, however, that the supra-spinous dorso-lumbar liga- ment is continued on the sacral spine, and that there exist between the processes formed by this spine, true interspinous ligaments. 3. Sacro-lumhar articulation. — In this articulation, the great thickness of the fibro-cartilage is to be remarked ; and, in addition, that the last lumbar vertebra corresponds with the sacrum not only by its body and articular processes, but also by the oval and slightly concave facets shown on the posterior border of its transverse processes, which are adapted to analogous slightly convex facets on the sides of the base of the sacrum. The bundles of fibres thrown from one bone to another from around these sacro-transversals (real planiform diarthroses) maintain the articular surfaces in contact, and cover, outwardly, the synovial membrane which facilitates their gUding. 4. Articulation of the tivo last lumbar vertebrce. — This is distinguished by the presence, between the transverse processes, of a planiform diarthrosis, like that of the sacro-transversal just noticed. These two articulations are only found in Solipeds. 5. Atlo-axoid articulation. — This is so far removed by its conformation and special uses from the other intervertebral articulations, that it will be described as an extrinsic articulation of the head and spine. (See Articulations of the Head.) The Movements of the Spine in general. — Each intervertebral articula- tion is the seat of very obscure movements, the separate study of which offers little interest. But these movements, when conjoined with those of the other articulations, result in bending the whole spine in a somewhat marked manner, and producing either the flexion, extension, or lateral inclination of this flexuous column. When flexion takes place, the spine is arched upwards, the common inferior ligament is relaxed, the spinous processes separate from one another, and the supra-spinous ligament, becoming very tense, soon imposes limits to this movement. Extension is effected by an inverse mechanism, and is checked by the tension of the common inferior ligament and the meeting of the spinous processes. 181 THE ARTICULATIONS. Lateral inclination takes place when the spine bends to one side. This movement is very easily executed in the cervical and coccygeal regions, but is arrested by the ribs and the costiform processes in the dorso-lumbar region. A circumflex movement is possible at the two extremities of the vertebral column— neck and tail ; for they pass easily from extension to lateral inclination, and from tliis to flexion, etc. Owing to the elasticity of the intervertebral fibro-cartilages, the spine is endowed with a very limited amount of rotation, or rather of torsion. For the special study of the movements of each spinal region, reference must be made to what has been already said (,p. U) regarding tlie mobility of this part. Fig. 122. CERVICAL LIGAMENT OF THE OX. L, l', The two laminse which form the cord of the cervical ligament : 1, 2, 3, 4, the four anterior digitations of the cordiform portion. R, Its accessory portion : 5, first dorsal vertebrae ; 6, 6, 6, interspinous ligament of the dorsal region. Differential Characters in the Vertebral Articulations and Ligaments in the OTHER Animals. A. In the Ox the intervertebral discs are much thicker than in the Horse. The common inferior vertebral ligament is very strong in the lumbar region. The supraspinous dorso-lumhar ligamsnt is composed of yellow elastic tissue. The cervical ligament is much more developed than in Solipeds,in consequence of the greater weight of the head ; and it presents a conforma- tion altogether special, which M. Lecoq has made known in the following terms : " On lenving the withers, the stipra- spinous ligament ceases to cover the head of the spinous processes, and extends from each side in a wide and strong band, taking points of attachment on the sides of the processes, and becoming separated, on leaving that of the first dorsal vertebra, into two parts — a superior and inferior. The first reaches the cervical tuberosity in the form of a thick cord united to the cord of the opposite; the other thins off into a band, which is attached to the posterior half of the spinous process of the axis, and to that of the third and fourth vertebrae. A production of the same kind — an auxiliary to the principal portion — leaves the anterior border of the spinous process of the first dorsal vertebra, and is attached to that of the fourth, fifth, ARTICULATIONS OF THE SPINE. 185 sixth, and seventh vertebrae. The superior border of this auxiliary ligamentous production, is concealed between the two lamiua of the principal ligament." ' B. Camel. — In this animal, the common supraspinous ligament is entirely composed of yellow elastic tissue ; it is therefore impossible to distinguish, physically, a dorso-lumbar and a cervical portion. It is remarkable for its thickness and width ; and its dimensions increase from behind to before, especially from the second lumbar vertebra. At the fifth, sixth, seventh, eighth, ninth, and tenth dorsal vertebrae an elastic band is given off fi om its borders ; as this descends, it gradually becomes thinner until it reaches the external intercostal muscles. From the ninth dorsal vertebra, the supraspinous ligament divides into two layers, which are placed against the lateral faces of the spinous processes. In the cervical region, the layers Fig. 123, kt^i^l^^-^ ^i x\\\-^ CERVICAL LIGAMENT OF A YOUNG CAMEL. become rounded, are joined to each other by means of connective tissue, and describing an S- shaped curve, become inserted into the occipital bone. They give oflf, from their inferior border, six digitations, which are attached to the spinous processes of tlie last six cervical vertebrae. An accessory leaf is situated between the two portions just described : it is detached from the anterior border of the spinous process of the first dorsal vertebra, and is fixed anteriorly into the two last cervical vertebrae. C. Pig. — The Pig, remarkable for the shortness of its neck and the limited movements of this region, does not show any cervical ligament, properly so called. It is replaced by a super- ficial fibrous raphe', extending from the occipital bone to tlie spinous process of the first dorsal vertebra. ^Journal de MMecine VeW-inaire, p. 122. Lyons, 1848. 186 TEE ARTICULATIONS. D. Camivora. — The Cat has no cervical ligament, and shows, instead, a raphe like the Pig. In the Dog, the ligament is reduced to a simple cord, continued from the dorso-lumbar ligament, and goes no further than behind the spinous process of the axis. In the Cat, the interspinous ligaments are replaced by small muscular fasciculi ; in the Dog, this substitution only takes place in the xiervical region. The laminae of the first coccygeal vertebrae possess the principal characters which distinguish perfect vertebrae, and are united by vestiges of the articular bands which exist in the other regions of the spine. Aeticle IL — Articulations of the Head. We will first study the two extrinsic articulations which are the centre of the movements of the head on the spine — the atlo-axoid and occipito-athid articula- tions. Afterwards, we will pass to the examination of the joints which unite the different bones of the head. 1. Atlo-axoid Articulation (Fig. 124). Preparation. — It suffices to remove the soft parts from around the articulation, to expose the interannular, the interspinous, and the inferior odontoid ligament. To examine the superior odontoid ligament and the synovial membrane, one half the atlas and axis must be separated by sawing longitudinally through them from oue side to the other. This may be considered as the type of the trochoid articulation. Articular surfaces. — To form this articulation, the axis offers its odontoid pivot and the undulated diarthrodial facets at its base. The atlas opposes to the pivot the concave semi-cylindrical surface hollowed on the superior face of its body ; and for the lateral undulated facets it has analogous facets cut on the transverse processes, on each side of the vertebral canal. Mode of union. — 1. An odontoid, or odonto-atloid ligament. 2. An inferior atlo-axoid ligament. 3. A superior ditto. 4. A fibrous capsule. a. Odontoid ligament (Fig. 124, 3). — Continuous with the common superior vertebral ligament, very short and strong, flattened above and below, and triangu- lar in shape, the odontoid ligament is composed of glistening white fibres, fixed behind in the superior channel of the odontoid process, and inserted in front on the transverse ridge which separates the superior face from the inferior arch of the atlas, as well as on the imprints situated in front of this ridge. It is covered, on its lower face, by the synovial membrane of the articulation ; and its upper surface is in contact with the spinal dura mater. It sends some bands within the condyles of the occipital bone. b. Inferior atlo-axoid ligament. — This is a wide, thin, and nacrous-looking band, extending from the inferior face of the axis to the inferior tubercle of the atlas, and is covered by the longus colli muscle ; it is united to the synovial mem- brane by its deep face, and confounded on its bordei-s with the fibrous capsule to be immediately described. It represents the common inferior vertebral ligament. c. Superior atlo-axoid ligament. — This exactly represents the interspinous liga- ments of the other cervical articulations. Yellow, elastic, and formed like the two lateral bands, it is continuous, laterally, with the capsular Ugament. It represents the interspinous and interlamellar ligaments. d. Capsular ligament. — This, it may be said, is only the interlamellar ligament proper to the atlo-axoid articulation. It commences from the sides of the pre- ceding ligament, and becomes united to the inferior atlo-axoid, after contracting adhesions with the borders of the odontoid Ugament. In this way it encloses the articulation and the spinal canal. Before and beliind, it is attached to the anterior or posterior margin of the bones it unites. Its external face is in contact wiih ARTICULATIONS OF THE HEAD. 187 the great oblique muscle of the head ; its internal responds, in its inferior half, to the articular synovial membrane, and its superior moiety to the spinal dura mater. It is analogous to the capsules in other regions. (Leyh describes this Ugament as the interannular). Fig. 124. Synovial membrane. — This lines the odontoid ligament and atlo-axoid ligaments, and the articular portion of the peripheral capsule. Movements. — Rotation, the only movement possible in the atlo-axoid articulation, is effected in the following manner : the axis remains fixed, and the first vertebra, drawn to one side chiefly by the great oblique muscle, rotates on the odontoid pivot, carrying the head with it. The rotation movements of the head have, therefore, this diarthrosis for a centre, and not the atloido-occipital articulation. In the Dog and Cat, the odontoid ligament is replaced by three particular ligaments : 1. Two lateral cords, rising in common from the summit of the odontoid process, and inserted, each on its own side, within the condyles of tlie occipital bone. 2 A transverse ligament, passing over the odontoid process, which it maintains in its place against the itiferior arch of the atlas, and is attached by its extremities to the superior face of the latter. A small synovial capsule facili- tates the gliding of the odontoid process beneath this ligament. The articular synovial membrane always communicates with that of the occipito-atloid articulation. In the Pig, the disposition is nearly the same as in the Caruivora. 2. Occipito-atloid Articulation (Fig. 124). (^Preparation. — Dissect away all the soft parts that pass from the neck to the head and cover the articulation, and more particularly the flexor, the recti, and the small oblique muscles of the head. To expose the synovial membranes, open the sides of the capsular ligament.) This is a condyloid articulation. Articular surfaces. — In the atlas, the two cavities which replace the anterior articular processes and the heads of the other vertebrfe ; in the occipital bone, the two condyles flanking the sides of the occipital foramen. Mode of union. — A single capsular ligament envelops the entire articulation ; it is attached by its anterior border to the margin of the occipital condyles, and by its posterior to the anterior contour of the atlas. Thin and slightly elastic in its inferior half, this ligament presents, supe- riorly, four reinforcing fasciculi : two middle, which inter- cross in X — whence the name "cruciform," sometimes given to this ligament (Fig. 124, 1, 1) ; and two lateral, which pass from the sides of the atlas to the base of the styloid processes (Fig. 124, 2, 2). It is lined by the synovial membranes, and is enveloped externally by a large number of muscles, which protect the articulation and greatly strengthen it everywhere. Among these may be particularly noticed the recti muscles of ATLO-OXOID AND OCCIPI- TO-ATLOID ARTICULA- TIONS (the upper arch of the atlas has been removed to show the odontoid ligament). 1, 1, Middle accessory fas- ciculi ; 2, 2, lateral fasciculi of the capsular ligament of the occipi- to-atloid articulation ; 3, odontoid ligament ; 4, interspinous liga- ment uniting the second and third vertebrae of the neck ; 5, fibrous capsule uniting the articular processes of these vertebrae. A, Anterior internal fora- men of the atlas con- verted into a groove by the section of the bone; B, B, vertebral foramina of the atlas ; C, C, fora- mina replacing the an- terior notches of the axis. 188 THE ARTICULATIONS. the head, the small oblique, and the complexus. There is also the cord of the cervical ligament, Sijiiovial membranes. — These membranes are two in number — one for each condyle and coiTesponding atloid cavity. Sustained above, below, and outwardly by the capsular ligament, they are related inwardly to the dura mater and the fibrous tractus which, from the odontoid ligament, is carried to the internal face of the occipital condyles. Movements. — Extension, flexion, lateral inclination, and circumduction, are the movements of the occipito-atloid articulation. In the Pig, Dog, and Cat, this articulation— strengthened, as it is, by the capsular and odontoido-occipital ligaments already mentioned — has only one synovial capsule. 3. Aeticulation of the Bones of the Head with each other. If we except the articulation which unites the inferior jaw to the cranium — the temporo-maxillary — and the hyoideal articulations, it will be found that all the bones of the cranium and face are united to each other by synarthrosis, forming the different kinds of sutures already generally described (p. 170). Nothing is to be gained by entering into more detail with regard to these articu- lations, as it will be found sufficient to call to mind the topographical description of each bone entering into their formation. 4. Temporo-maxillary Articulation (Fig. 125). {Preparation. — Remove the masseter muscle and the parotid gland. Saw through the head about the middle liue. Open the articulation externally, to exhibit the interarticular meniscus.) The lower jaw, in its union with the cranium, constitutes a double condyloid articulation. F'g 125. Articular surfaces. — With the temporal bone, these are the condyle, the glenoid cavity, and the supra-condyloid process at the base of the zygomatic process. The glenoid cavity is not lined by cartilage, and appears to be merely covered by synovial mem- brane. On the maxillary bone is the oljlong condyle situated in front of the coronoid process. Interarticular fihro-cartilage. — The articular sur- faces just named are far from fitting each other accurately ; this is only accompUshed by the inter- position of a fibro-cartilaginous disc between the temporal and maxillary bones. This disc is a kind of irregular plate, flattened above and below, thicker before than behind, and moulded on each of the diarthrodial surfaces it separates. Its superior face, therefore, presents : in front, a cavity to receive the condyle of the temporal bone ; behind, a boss which is lodged in the glenoid cavity. The inferior face is hollowed by an oblong fossa, in which the maxillary condyle is lodged (Fig. 125, 1). Mode of union. — A fibrous envelope — a true capsular ligament — surrounds the articulation, aiid is attached by its borders to the margin of the articular surfaces it unites. Formed, outwardly, by a thick fasciculus of white vertical fibres (Fig, TEMPORO-MAXILLARY ARTICU- LATION . 1, Interarticular fibro-cartilag;e ; 2, external fasciculus of the capsular ligament. A, Base of the coronoid process ; B, neck of the maxillary condyle; C, mastoid process ; D, external auditory hiatus. ARTICULATIONS OF THE HEAD. 189 125, 2), this ligament becomes greyish-coloured and elastic for the remainder of its extent, and greatly diminishes in thickness, especially in front. Its inner face IS covered by the synovial capsules, and adheres to the circumference of the interarticular fibro-cartilage. Its external face is related, in front, to the temporal and masseter muscles ; behind, to the parotid gland ; inwardly, to the external pterygoid muscle ; and outwardly, to a fibrous expansion which separates it from the skin. (Leyh mentions a lateral external and a posterior ligament for this articulation, but Chauveau and Bigot evidently look upon these as portions of the capsular.) Synovial membranes. — This articulation has two synovial sacs — one above the other — which are separated by the fibro-cartiiaginous disc. Movements. — The temporo-maxillary articulation is the centre of all the movements performed by the lower jaw. These are : depression, elevation, lateral motion, and horizontal gliding. The lower jaw is depressed when it separates from the superior one, and is elevated when it approaches this. These two opposite movements are executed by a mechanism of such great simplicity, that it need not be described here. Lateral movements take place when the inferior extremity of the jaw is carried alternately to the right and left. It then happens that one of the maxillary condyles, taking with it the fibro-cartilage, is brought into contact with the temporal condyle, while the other is embedded in tiie glenoid cavity of the opposite side. The horizontal gliding is effected from behind to before, or vice veisd. In the first case, the two maxillary condyles are carried at the same time under the temporal condyles, bearing with them the fibro-cartilages. In the second case, they are drawn into the glenoid cavities, and rest against the supra-condyloid eminence, which prevents their going further. It will be understood, after this brief description, that the presence of the fibro-cartilages singularly favours the lateral movements and horizontal gliding of the lower jaw. In the Pig, the temporo-maxillary articulation is formed after the same type as that of Rodents, and allows very extensive movements from before to behind — a circumstance due to the complete absence of the supra-condyloid eminence. In the Dog and Cat, the maxillary condyle is exactly fitted to the temporal cavity. This disposition, in giving great precision to the movements of depression and elevation, restrains in a singular manner the lateral and horizontal gliding motions. The interarticular fibro-cartilage is extremely thin in these animals. In the Rabbit, the narrow condyle of the maxilla moves from before to behind and to each side, on the temporal bone, the articular surface of which is very elongated and destitute of a subglenoid eminence. 5. Hyoideal Aeticulations. (Preparation. — Disarticulate the lower jaw, and dissect away from the right of each articulation the muscles that may conceal the view.) These are of two kinds — extrinsic and intrinsic. The first comprise the two tempo ro-hyoideal articulations ; to the second belong the joints which unite the different pieces of the hyoid bone — the interhyoideal articulations. Temporo-hyoideal Articulations. — These are two amphiarthrodial joints, in the formation of which each great cornu of the hyoid bone opposes its upper extremity to the hyoideal prolongation lodged in the vaginal sheath of the temporal bone. An elastic cartilage, from -^q to i%- of an inch in length, unites the two bones in a solid manner ; and it is owing to the flexibility of this cartilage that the hyoid bone can move entirely on the temporal bones. 15 190 THE ARTICULATIONS. Inter-hyoideal Articulations. — A. The great cornu articulates with the small one, by an amphiarthrosis analogous to the preceding. To form this articu- lation, these two pieces of bone are joined at an acute angle, through the medium of a more or less thick cartilaginous band, in the centre of which there is often a little bony nucleus— the styloid nucleus, or kerato-hyal bone. This cartilage is elastic and flexible, and permits the opening and closing of the articular angle at the summit of which it is placed. B. Each styloid cornu is united to the body of the hyoid bone, or basihyal, by an arthrodial articulation. The articular surfaces are : for the hyoideal branch, the small cavity terminating its inferior extremity ; for the body, the convex lateral facet situated at the origin of the thyroid cornua. These surfaces are covered by cartilage, and enveloped by a small synovial sac and a peripheral fibrous capsule. They can ghde on each other in nearly every direction. (Median and superior hyoideal capsular ligaments are described by Leyh as sometimes present. The latter unites the upper and middle branches, and the former the middle with the inferior branches. They are absent when these branches are confounded with the superior ones.) Article III. —Articulations of the Thorax. These are also divided into extrinsic and intrinsic. The first — named costo- vertebral—unite the ribs to the spine. The second join the different bones of the thorax together ; they comprise : 1. The chondro-sternal articulations, 2. Chondro-costal articulations. 3. The articulations of the costal cartilages with each other. 4. The sternal articulation perculiar to the larger Ruminants and the Pig. All these joints will be first studied in a special manner, then examined in a general way as to their movements. Extrinsic Articulations. Articulations of the Ribs with the Vertebral Column, or Costo- vertebral Articulations. (Preparation.— This is simple. No difficulty need be experienced except in exposing the interartieular ligament, and this is efifected by sawing tlirough one of the dorsal vertebra transversely, close to the posterior intervertebral joint formed by that bone. A few cuts of the bone forceps will then show the whole extent of the ligament.) Each rib articulates with the vertebral column by two points — its head and its tuberosity. The first is received into one of the intervertebral cavities hollowed out on the sides of the spine, and is therefore in contact with two doi-sal vertebrfe ; the second rests against the transverse process of the posterior vertebra. From this an'angement arises two particular articulations belonging to the arthrodial class, which are named costo-vertehral and costo-transverse. Costo-vertebral Articulations. — Articular surfaces. — Pertaining to the rib, we have the two convex facets of the head, separated from each other by a groove of insertion, and covered by a thin layer of cartilage. On the vertebras, the concave facets which, by their union, form the intervertebral cavity ; these facets are also covered with cartilage, and separated, at the bottom of the cavity, by the con'esponding intervertebral disc. Mode of union. — 1. An interartieular ligament (Figs. 126, 2 ; 127, 1), fixed in the groove in the head of the rib, and attached to the superior border of the ARTICULATIONS OF THE THORAX. 191 intervertebral disc, Avhich it encii-cles upwards and inwards, to unite on the median line with the ligament of the opposite side. 2. An inferior peripheral ligament (Fig. 127, 2, 3, 4), flat above and below, thin and radiating (whence it is often named the stellate ligament), formed of three fasciculi, wliich are fixed in common on the inferior face of the head of the rib, and in diverging are carried over the bodies of the two vertebrte and the intervertebral disc. Lmed above by the synovial membranes, this ligament is covered below by the pleura. (Leyh includes a capsular ligament for the head of the rib, and another for the costal tuberosity. He probably considered the synovial membrane of these articulations as such.) Synovial membranes. — These are two in number — an anterior and posterior, lying against each other, and separated in part by the interarticular ligament they cover. Supported below by the stellate ligament, above they are directly in contact with the levatores costarum muscles, and with vessels and nerves. CosTO-TRANSVERSE ARTICULATIONS. Avticular surfttces. — In the rib, the Fig. 127. Fig. 126. articulations of the ribs with the ver- tebra, and of these with each other (upper plane). 1, Spinal canal, upper face, showing the common superior ligament; 2, interarticular costo- vertebral ligament ; 3, interosseous costo- transverse ligament ; 4, posterior costo-trans- verse ligament. ARTICULATIONS OF THE RIBS WITH THE VERTEBRA, AND OF THESE WITH EACH OTHER (INFERIOR PLANE). 1, Interarticular costo-vertebral liga- ment ; 2, 3, 4, fasciculi of the stellate, or inferior costo-vertebral ligament; 5, common inferior vertebral ligament. diarthrodial facet cut on the tuberosity. In the vertebra, the analogous facet on the outside of the transveree process. Mode of union. Two ligaments bind this articulation : 1. The posterior costo- transverse ligament (Fig. 126, 4), a white fibrous band attached by its extremities behind the transverse process and the costal tuberosity, lined by synovial mem- brane, and covered by the transverse insertions of several spinal muscles. 2. The anterior costo-transverse., or interosseous ligament (Fig. 126, 3), a fasciculus of short, thick, white fibres, fixed on the anterior surface of the transverse process near its base, and in the rugged excavation on the neck of the rib. This liga- ment is invested, posteriorly, by the synovial membrane, and covered in front by pads of adipose tissue which separate it from the costo-vertebral articulation. Synovial membrane. — This is a small particular capsule, kept apart from the posterior synovial membrane of the costo-vertebral articulation by the costo-trans- verse interosseous ligament. Characters peculiar to some Costo-vertebral Articulations. — 1. The first, and sometimes the second, costo-vertebral articulation has no inter- osseous ligament, and only exhibits one synovial membrane. The intervertebral 192 THE ARTICULATIONS. cavity which concurs in forming the first is often excavated between the last cervical and first dorsal vertebras. 2. The two or three last costo-transverse articulations are confounded with the corresponding costo-vertebral joints. They have no proper serous membrane, but the posterior synovial membrane of the latter is prolonged around their articular surfaces. Intrinsic Articulations. A. The Chondro-sternal or Costo-sternal Articulations. {Preparation. — To show the articulation of the ribs with the cartilages, these with the sternum, and the cartilages with each other, carefully remove the pleura, the triangularis sterui muscle, the diaphragm, tlie transverse muscle of the abdomen, then the pectorals, the great oblique, the transversalis of the ribs, and the intercostal muscles.) The first eight ribs, in resting upon the sternum by the inferior extremity of their cartilages, form eight similar arthrodial articulations. Articular surfaces. — Each sternal cartilage opposes to one of the lateral cavities of the sternum, the convex and oblong facet at its lower extremity. Mode of union. — The diarthrosis resulting from the union of these two surfaces is enveloped everywhere by bundles of white, radiating, fibrous tissue, which con- stitute a veritable ligamentous capsule. The superior part of this capsule — known as the stellate or superior costo-sternal ligament, is covered by the triangularis sterui muscle ; it is joined to a fibrous cord lying on the superior face of the sternum, and which is confounded in front with that of the opposite side. The inferior portion — the irtferior stellate or costo-sternal ligament — is in relation with the pectoral muscles. Synovial ccqysule. — There is one for each articulation. Characters proper to the first costo-sternal articulation. — The first costo-sternal articulation is not separated from its fellow of the opposite side ; so that these two joints are, in reality, only one, and the two cartilages lying close to each other correspond by a small diarthrodial facet, continuous with that for the sternum. The two sternal facets are inclined upwards, and confounded with one another. Only one synovial cavity exists for this complex articulation, which unites the two first ribs to each other and to the sternum. B. Chrondo-costal Articulations uniting the Ribs to their Cartilages. These are synarthrodial articulations, the movements of which are very obscure. They are formed by the implantation of the cartilages in the nigged cavities the ribs present at their inferior extremities. The solidity of these articu- lations is assured by the adherence of the fibro-cartilages to the proper substance of the ribs, and by the periosteum which, in passing from the bone to the cartilage, plays the part of a powerful peripheral band. In the Ox, the sternal ribs, in uniting with their oartilages, form a true ginglymoid diar- throsis, the movement of whicli is facilitated by a small synovial capsule. C. Articulations of the Costal Cartilages with each other. The ribs, attached to each other by means of the intercostal muscles, are not united by real articulations ; neither are their cartilages of prolongation. But ARTICULATIONS OF THE THORAX. ■ 193 the asternal cartilages are bound together by a small yellow elastic ligament, which is carried from the free extremity of each to the posterior border of the preceding cartilage ; the anterior border of the first asternal cartilage is directly united to the posterior border of the last sternal cartilage, through the medium of the perichondrium and very short Kgamentous bands. This same asternal cartilage is also bound to the inferior face of the xiphoid appendage by a small white ligament (the chondro-xiphoicl), under which passes the anterior abdominal artery. D. Sternal Articulation peculiar to the Ox and Pig. It has been already shown that in these animals the anterior piece of the sternum is not consolidated with the second portion. Tlie two are united by a diurthrodial articulation ; and for this purpose the anterior presents a concave surface, the posterior a convex one. Bundles of peripheral fibres firmly bind tliem to each other, and a special small synovial capsule facili- tates their movements, which are very limited. The Articulations of the Thorax considered in a General Manner, with Regard to Movements. The thorax can increase or diminish in diameter, in an antero-posterior and a transverse direction ; whence arise the dilatation and contraction of this cavity — the inspiratory movements accompanying the entrance of the external air into the lungs, and the expiratory movements expelling the air contained in these organs. The variations in the antero-posterior diameter of the chest being due to changes in the figure of the diaphragm, need not be noticed here. But the transverse variations being the result of the play of the costal arches on tjie spine and sternum, it is advantageous to study the mechanism which presides in the execution of theii' movements. The costal arches, being inclined backwards on the middle plane, the space they enclose in their concavity is not nearly so extensive as if they were perpen- dicular to this plane. Owing to their double arthrodial joints, the ribs are movable on the spine ; and their inferior extremity, also movable, rests either directly or indirectly on the sternum. Therefore it is that, when they are drawn forward by their middle portions, they pivot on theii' extremities, and tend to assume a perpendicular direction, which is the most favourable for the largest increase of the space they limit ; then there is enlargement of the lateral diameter of the thorax, which signifies dilatation of its cavity. The inverse movement, by an opposite mechanism, causes contraction of the chest. The ribs are said to be elevated during the forward movement, and depressed when they fall backwards. These expressions, though perfectly applicable to Man, who stands in a vertical position, are not correct when employed in veterinary anatomy. Besides the enlargement of the thorax in the transverse and the antero-posterior directions, it is necessary to remark on an increase in a vertical direction, caused by the displacement of the sternum forward, due to elevation of the ribs. In this movement, the costal arches are erected not only on the median plane, but also on the spine. The inferior extremity, carried forward, also takes the sternum with it ; and this movement cannot take place without that piece being farther removed from the vertebrae above. In Man, the displacement of the sternum is very marked. 194 THE ARTICULATIONS. AeTICLE IV.---AETICULATIONS OF TRE ANTERIOR LiMBS. 1. SCAPULO-HUMERAL ARTICULATION (Fig. 128). (Preparation. — Detach the limb from the trunk. Remove from the upper extremity those muscles which are inserted in the vicinity of the glenoid cavity of the scapula ; turn down from its lower extremity those which are inserted into the superior end of the humerus or a little below, preserving the attachments of their tendons with the capsular ligament. The seapulo- humeralis gracilis muscle may be allowed to remain, in order to show its relations.) To constitute this enarthrodial articulation, the scapula is united to the humerus, and forms an obtuse angle which is open behind. Articular surfaces. — In the scapula there is the glenoid cavity — the shallow, oval fossa, elongated in an antero-posterior direction, notched inwardly, and excavated at its centre, or near the internal notch, by a small synovial f ossette. A ligamentous band, attached to the brim of the cavity, fills up this notch, and is the vestige of the glenoid ligament of Man. In the humerus, the articular head, fixed between the large and small tuberosities, is often excavated by a shallow synovial f ossette. Mode of union. — One capsular ligament (Fig. 128, 1), a kind of sac having two openings — one inferior, embracing the head of the humerus ; and a superior, inserted into the margin of the glenoid cavity. This capsule presents, in front, two sup- porting fasciculi, which diverge as they descend from the coracoid process to the great and small tuberosities. The aponeurotic expansion thus formed is very thin and loose, so as to allow the two bones to separate to the extent of from -f*Q to y^o of an inch ; but it is far from being sufficiently strong to bind them firmly together. The articulation is, therefore, strengthened by the powerful muscles which surround it, among which maybe noticed : 1. In front, the coraco- radialis (flexor brachii), separated from the fibrous capsule by an adipose cushion. 2. Behind, the large extensor of the forearm and scapulo-humeralis gracilis (or teres minor) muscles, the use of which appears to be to pull up this capsule during the movements of flexion, so as to prevent its being pinched between the articular surfaces. 3. Outwards, the short abductor of the arm and the infra-spinatus (postea spinatus) tendon. 4. Inwards, the wide and strong tendon of the subscapularis muscle. In addition to this powerful retaining apparatus, there is the atmospheric pressure, the influence of which is of a certain importance. This may be proved by removing all the surrounding muscles, when it will be found that the capsule is not relaxed, nor are the articular surfaces separated ; to effect this, it is neces- sary to make an opening in the capsule, so as to allow the air to enter its cavity, when the surfaces immediately fall apart. Synovial capsule. — This is very loose, and entirely enveloped by the peripheral capsule, the internal surface of which it lines. Movements. — Like all the enarthrodial articulations, the scapulo-humeral permits extension, flexion, abduction, adduction, circumduction, and rotation. These various movements, however, are far from being so extensive as in Man, the arm in the domesticated animals not being detached from the trunk, but, on the contrary, is fixed with the shoulder against the lateral parietes of the thorax. Flexion and extension are the least limited, and the most frequently repeated movements ; their execution always demands a displacement of the two bones, wliich are almost equally movable. In flexion, the scapulo-humeral angle is closed, not only because the inferior extremity of the humerus is carried back- wards and upwards, but also because the scapula pivots on its superior attach- ARTICULATIONS OF TEE ANTERIOR LIMBS. 1S5 merits in such a manner as to throw its glenoid angle forward and upward. Extension is produced by an inverse mechanism. During the execution of the other movements, the scapula remains fixed, and the humerus alone is displaced, bringing with it the inferior bones of the limb. If it is carried outwards, we have abduction, or inwards, adduction ; if the leg passes successively from flexion to abduction, and from that to extension, etc., in describing a circle by its lower extremity, then there is circumduction ; if it pivots from left to right, or right to left, we have rotation. In the Pig, Dog, and Cat, the synDvial membrane is not exactly enclosed by the fibrous capsule, but forms in front a cul-de-sac, which descends in the bicipital groove to favour the gliding of the coraco-radialis tendon. In Man, the scapulo-humeral articulation is disposed as in animals, but it is also protected above by the coraco-acromion arch. For the reasons noted above, this articulation allows of more extensive motion than in animals. As remarked by Cruveilhier, of all the joints in the human body, tlie scapulo-humeral is that which has the most extensive motion; in movements forward and outward, the humerus can become horizontal; in those of circumduction it describes a complete cone, which is more extensive in front and laterally than behind and inwardly. 2. HuMERO-RADiAL, OE Elbow Aeticulation (Fig. 128). (^Preparation. — Turn down the inferior extremity of the flexors of the forearm, remove the •olecranian, epicondyloid, and epitrochlean muscles, taking care not to damage the ligaments to which they somewhat closely adhere.) Three bones concur to form this articulation, which presents a remarkable •example of an angular ginglymus : the humerus, by its inferior extremity, and the two bones of the arm by their upper extremities. Artkidar surfaces. — The humeral surface, already described at page 102, is transversely elongated, and convex from before to behind. It presents : 1. A median groove excavated by a synovial fossette. 2. An external groove (humeral trochlea) not so deep as the preceding. 3. A kind of voluminous condyle wliich borders, inwardly, the internal pulley, and whose antero-posterior diameter is much greater than that of the external lip of the trochlea of the opposite side. The antibrachial surface, divided into two portions, is moulded to the humeral surface ; it is, therefore, concave before and behind, and is composed : 1. Of a double external groove. 2. Of an internal glenoid cavity, both excavated, on the superior extremity of the radius. 3. A middle ridge for the middle groove of the humerus, separating the two preceding surfaces, and prolonged on the ulnar beak, where it forms the sigmoid notch. This ridge shows a small synovial fossette hollowed out on the radius and ulna. Mode of union. — Three ligaments : two lateral and an anterior. a. The external lateral ligament (Figs. 128, 8) is a thick, short, and strong funicle, attached above to the crest limiting outwardly and posteriorly the musculo- .spiral groove, and in the small cavity placed at the external side of the humeral articular surface. Below, it is inserted into the supero-external tuberosity of the radius. Its anterior border is confounded with the capsular ligament, and is margined by the principal extensor of the phalanges, which derives from it numerous points of attachment. By its posterior border it is in contact with the external flexor of the metacarpus. Its internal face is lined by synovial membrane, and its external face is only separated from the skin by the anti- brachial aponeurosis, and some of the fasciculi from the origin of the lateral extensor muscle of the phalanges. Its superficial fibres are vertical, and are 196 THE ARTICULATIONS. continuous, behind, with the arcif orm ligamentous bands which stretch from the ubia to the radius. Its deep fibres are shghtly obUque downwards and forwards. b. The lateral internal ligament — also funicular — is longer, but not so strong as the preceding. It arises from Fig. 128. the small tuberosity on the inner side of the superior articular face of the humerus, and, widening as it descends, reaches the radius. Its median fibres, which are the longest, are directed vertically downwards to reach the imprints situated below the bicipital tuberosity ; its anterior fibres, curved forwards, are united to the tendon of the coraco-radialis muscle, or are confounded ^^■ith the anterior ligament ; the posterior are turned backwards, near their in- ferior extremities, to join the arci- form fibrous fascicuU, which in- wardly unite the ulna to the radius. The middle fibres of this Ugament cover the inferior insertion of the short flexor of the forearm, and — in part only — that of the long flexor. It is covered by the ulna-plantar nerve and the posterior radial artery and vein. c. The anteiior or capsular liga- ment (Figs. 128, 9) is a membrani- form band, attached by its superior border above the humeral articular surface, and by its inferior to the anterior margin of the radial sur- face. By its lateral borders, it is confounded with the funicular Uga- ments. Its internal half is formed of vertical fibres which descend from the humerus and expand over the radius, where they become united with the inferior tendon of the coraco-radialis muscle. In its exter- nal moiety it is extremely thin, and composed of fibres crossed in various directions. Lined internally by synovial membrane, this ligament is in contact, by its external surface, with the anterior radial vessels and nerves, the two flexor muscles of the forearm, the anterior extensor of the metacarpus, and the anterior extensor of the phalanges. The two latter muscles 6capul0-humeral and humero-radial articula- tions, with the muscles surrounding them (external face). 1, Scapulo-humeral capsular ligament ; 2, short ab- ductor muscle of the arm ; 3, its insertion in the humerus; 4, insertion of the infra-spinatus muscle on the crest of the great tuberosity; 5, coraco-radialis muscle; tj, its tendon of origin ;ittached to the coracoid process; 7, its radial insertion confounded with the anterior ligament of the ulnar articula- tion ; 8, 8, external lateral ligament of that articu- lation ; 9, anterior ligament ; 10. aconeus, or small extensor of the forearm ; 11, origin of the external flexor muscle of the metacarpus; 12, short flexor muscle of the forearm. A, Tuberosity of the scapii- lar spine; B, supra-spinous fossa; C, infra-spinous fossa : D, convexity of the small trochanter ; E, summit of the ti-ochanter. ABTICDLATIONS OF THE ANTERIOR LIMBS. 197 are even attached to it in a very evident manner. The elbow articulation, closed in front and on the sides by the tliree ligaments just described, has no particular ligaments posteriorly ; but it is powerfully strengthened there by the olecranian insertion of the extensor muscles of the forearm, and by the tendons of origin of the five flexor muscles of the metacarpus or phalanges. Synovial membrane. — This membrane is very extensive, and, stretched out on the internal face of the before-mentioned hgaments, forms, behind, three great culs-de-sac of prolongment : a superior, occupying the olecranian fossa, and covered by a fatty cushion, as well as by the small extensor muscle of the fore- arm ; ^ two lateral, which descend from each side of the ulnar beak, and are ■distinguished as internal and external — the first lines the tendon of the external flexor of the metacarpus, the second facilitates the play on the upper radial extremity of the four flexor muscles of the foot or digits, and which are attached in common to the epitrochlea. This synovial sac also furnishes the radio-ulnar articulation with a diverticulum, which descends between the bones of the fore- arm to below the adjacent diarthrodial facets. Movements. — Flexion and extension. In flexion, the two bones do not approach each other directly, the inferior extremity of the radius deviating a little outwards. This is due more to the .sHght obliquity of the articular grooves, than to the difference in thickness between the external and internal extremities of the humeral surface. Extension is limited by the reception of the beak of the olecranon in its fossa, and by the tension of the lateral ligaments ; so that the two bones cannot be straightened on one another in a complete manner, or placed on the same line. In the Dog and Cat, tlie external lateral ligament is very thick, and forms in its inferior moiety a fibro-cartilaginous cap wliich is fixed on the ulna and radius, and united in front to the annular ligament of the superior radio-ulnar joint. This cap, with the last-named liga- ment, completes the osteo-fibrous ring in wliich the superior extremity of the radius turns. The internal lateral ligament is inserted, by two very short fasciculi, into the ulna and inner side of the head of tlie radius. A third fasciculus, deeper and median, much more developed than the first, and covered by the inferior insertion of the flexors of tlie forearm, descends between the radius and ulna to the posterior face of the former, and is there inserted near the inferior attachment of the external ligament, which it appears as if about to join. In Man, the elbow articulation is formed nearly on the same plan as that of the Dog and Cat. The radius and ulna move together when the forearm is flexed and extended on the humerus. • 3. Radio-ulnar Articulation. Jirticular surfaces. — The two bones of the forearm articulate by diarthrodial 'and synarthrodial surfaces. a. The diarthrodial surfaces consist of four undulated, transversely elongated facets, two of which are radial and two idnar. The first border, posteriorly, the great articular surface forming the elbow- joint ; the second are situated beneath the sigmoid notch. h. The synarthrodial surfaces are plane and roughened, and are also two on each bone : one, superior, extends below the diarthrodial facets to the radio-ulnar arch ; the other, inferior, more extensive, occupies all the anterior face of the ulna from this arch ; on the radius it forms a very elongated triangular imprint, which descends to the lower fourth of the bone (see pp. 104, 105). ' Some grey elastic fibres which cover this cul-de-sac externally, have been wrongly described as a posterior membraniform ligament. 198 THE ABTICV LATIONS. Mode of union. — Two interosseous and two peripheral ligaments. a. The interosseous ligaments, interposed between the synarthrodia! surfaces,, are composed of extremely short white fibres passing from one to the other surface, and which are endowed with a very remarkable power of resistance. The inferior always ossifies a long time before the animal is full grown — a circum- stance which caused the older veterinary anatomists to describe — and with some show of reason — the radius and ulna as a single bone. Ossification of the superior ligament is very rare. b. The peripheral bands are bundles of arciform fibres which, from the beak of the olecranon to the radio-ulnar arch, leave the lateral faces of the ulna to pass — some inwards, others outwards — to the posterior face of the radius. The fibres of the external ligament are confounded with the external humero-radial ligament. The internal fibres are united to the internal humero-radial ligament,. and to the small ulnar tendon belonging to the short flexor of the forearm. Analogous fibres are found beneath the radio-ulnar arch ; but they are much shorter and less apparent. (This is the external transverse radio-idnar ligament of Leyh.) Movements. — Very obscure in youth ; nearly null when the two bones are fused together. In the Ox, ossification of the superior interosseous ligament is constant at adult age. In the Dog anti Cat, we have already seen (p. 107) that the radius and uhia are not fused to each other, but remain independent during life. They are united in their middle portion by an interosseous ligament, and join by diarthrosis at their two extremities. These animals therefore exhibit; 1. An interosseous ligament. 2. A superior radio-ulnar articulation. 3. An inferior radio-ulnar articulation. Interosseous ligament. — It is composed of very resisting white fibres, attached by their extremities to the bodies of the bones. Notwithstanding their sliortneas, they are loose enough to allow movements taking place between the radio-ulnar articulations. Superior radio-ulnar articulation. — This is a trochoid articulation, which only allows movements of rotation or pivoting. The articular swr/'aees which form this articulation are: in the ulna, the small sigmoid cavity — a surface excavated in the lateral sense, and semicircular; in the radius, a cylindrical half-liinge received into the preceding cavity. To unite these there is an annular ligament — a kind of fibrous web thrown around the superior extremity of the radius, fixed inwardly on the ulna near the inner extremity of the small sigmoid cavity, attached outwardly to the external lateral ligament of the elbow^ articulation, and confounded superiorly with the anterior ligament of the same articulation. This fibrous web, in uniting with the fibro-cartilaginous cap of the external humero-radial ligament, and joining the small sigmoid cavity by its iiiternal extremity, transforms this last into a complete ring, covered with cartilage in its bony portion. The head or superior extremity of the radius is also encrusted, over its entire contour, with a layer of cartilage — a con- dition which pt-rmits it to glide not only in the concave face of the small sigmoid cavity, but also on the internal face of the two ligaments which complete this cavity. Inferior radio-ulnar articulation. — This is also a trochoid articulation analogous to the pre- ceding, but inversely disposed. Thus, the concave articular surface is hollosved on the radius, outside tlie inferior extremity; the convex surface lies within the ulna. These two facets are very small, and are maintained in ctmtact by a diminutive peripheral fibrous capsule. A strong interosseous ligament, situated beneath the articular facets, also consolidates this diatlirosis, and concurs by its inferior border to form the antibrachial surface of the radio-carpal articulation. A small synovial capsule is specially devoted to this articulation. Mechanism of the radio-ulnar joints. — The play of these two articulations is simultaneous,, and tends to the same end— that is, to the execution of the double rotatory movement which constitutes supination and pronation. Supination is when the ulna remains fixed, and the radius pivots on it in such a manner as to carry its anterior face outwards. Its superior extremity then turns from within forwards — and even from before outwartls if the movement is exaggerated, in the articular girdle formed ARTICULATIONS OF THE ANTERIOR LIMBS. 199 by the small sigmoid cavity of the ulna and the ligaments which complete it. The inferior extremity also rolls on the ulnar facet in describing a similar movement, and the internal tuberosity of this extremity is carried forwards. In the movement of pronation, this tuberosity is brought inwards, and the anterior face of the radius comes forward by an opposite mechanism. The inferior bone of the anterior limb being articulated in a hinge-like manner with the radius, it follows this bone in its rotatory movements, the anterior face of the metacarpus looking outwards during supination and forwards in pronation. The radio-ulnar articulation in Man resembles that of the Dog and Cat, the articular surfaces only being larger and the movements more extensive. In supination, the palmar face is turned forward, and the radius, situated on the outer side of the ulna, is in the same direction as the latter. In pronation, on the contrary, the palmar face of the hand looks backwards, and the radius — remaining outwards in its upper part — crosses the ulna in front in such a manner that its lower extremity is placed witliiu the ulna. 4. Articulations of the Carpus (Figs. 129, 130) Preparation. — After removing the tendons surrounding the carpus, the ligaments cbmmon to all the carpal articulations can be studied. The anterior and posterior membraniform ligament can tben be removed, and the ligaments proper to each row, as well as those uniting the two rows, and these to adjoining bones, can be dissected. Some time is required for this dissection, which is not difficult. These comprise : 1. The articulations uniting the carpal bones of the first row to each other. 2. The analogous articulations of the second row. 3. The radio-carpal articulation. 4. The articulation of the two rows with each other. 5. The carpo-metacarpal articulation. Articulations which unite the Bones of the First Row to each other. — These bones, four in number, are joined by the diarthrodial facets on their lateral faces, and form small arthrodial articulations.^ They are maintained in contact by six ligaments, three anterior, and three interosseous. The anterior ligaments are small flattened bauds carried from the fourth bone to the first, from the first to the second, and from that to the third. The first, placed outside rather than in front of the carpus, is covered by the external lateral ligament and the inferior tendon of the external flexor of the metacarpus ; the others adhere to the capsular ligament. The interosseous ligaments are implanted in the grooves of insertion which separate the diarthrodial facets. One of them, derived from the common superior ligament, unites the first to the second bone. The two others, situated between the three last carpal bones, are confounded with the corresponding anterior ligaments. Articulations uniting the Carpal Bones of the Second Row. — These are arthrodial articulations, like the preceding, but numbering only two. They are fixed by two anterior and two interosseous ligaments. One of the anterior ligaments joins the first bone to the second, and strongly adheres to the capsular ligament ; the other is entirely covered by the lateral internal ligament, and attaches the two last bones to each other. Of the two interosseous ligaments, the second alone is confounded with the corresponding anterior ligament. That which is situated between the two first bones is separated from the anterior hgament by one of the diarthrodial facets between these bones. Radio-carpal Articulation. — The inferior extremity of the radius, in becoming united to the upper row of carpal bones, constitutes a diarthrosis which, from the nature of the movements it permits, may be considered as an imperfect hinge- joint. ' The facet uniting the supercarpal to the first bone is not situated on one of its faces, but rather on the anterior part of its circumference. 200 THE ARTICULATIONS. Articular surfaces. — The radial surface, elongated transversely and very irregular, presents : 1, Outwardly, a wide groove, limited in front by a small glenoid cavity, and bounded, posteriorly, by a non-articular excavation which receives a prolongation of the second bone in the movement of flexion ; 2, Inwardly, a condyle with a more extensive curvature than that of the pre- ceding groove, and, like it, completed by a small anterior glenoid cavity. The carpal surface, moulded exactly on the radial, offers depressions corresponding to the projections on it, and rice verm. Mode of union. — The radio-carpal articulation is bound by three ligaments which entirely belong to it ; and by four stronsf ligaments that are common to it and articulations which will be studied hereafter. Of the three ligaments proper belonging to the radio-carpal articulation, one forms a thick, rounded funicle, extending from the radius to the fourth bone in an oblique direction downwards and inwards, and concealed by the common posterior ligament. The second (Fig. 130, 5), much smaller, is carried from the supercarpal bone to the external side of the inferior extremity of the radius, and is partly covered by the common external ligament. When the synovial capsule is distended by dropsy, it may form a hernia at the outer side of the carpus, by passing between this small ligament and the common posterior ligament. The third, very delicate, but always present, is deeply situated beneath the last ; it is inserted, for one part, into the radius near the first proper ligament, and for the other, into the second bone and the interosseous ligament which unites the supercarpal to that bone. tSi/norial membrane. — After lining these three ligaments, and the four great ligaments yet to be described, this membrane is prolonged between the three first carpal bones, to cover the superior face of the interosseous ligaments which unite them. It even more frequently descends into the articulation which joins the supercarpal to the first bone ; though it also sometimes happens that this has a particular synovial capsule of its own. Akticulation of the Two Rows between each other. — Like the pre- ceding, this is an imperfect hinge articulation. Articnlar surfaces. — These are two, and are both transversely elongated, very irregular in their configuration, and divided into three portions. The inferior shows : behind, three small condyles placed side by side ; in front, two slightly concave facets. The superior corresponds to the first by three glenoid cavities and two convex facets. 3Io(le of anion. — For this articulation, besides the common great ligaments, there are three particular ligaments. Two of these are very short, and are situated behind the carpus, underneath the great common posterior ligament. They are readily perceived by removing the capsular ligament, and strongly flexing the carpus. " The strongest extends vertically from the internal bone of the superior row to the second and third bones of the metacarpal row ; the other descends obliquely from the first bone of the antibrachial row to the second of the inferior row " (Rigot). The third ligament proper, much stronger than the other two, reaches from the supercarpal to the first bone of the inferior row and the head of the external metacarpal bone. It is confounded, outwardly, with the great external lateral ligament ; inwardly, with the common posterior ligament. Its posterior border gives attachment to the fibrous arch which completes the carpal sheath. This ligament has also a branch which is fixed on the second bone of the upper row (Fig. 130, 4). ARTICULATIONS OF THE ANTERIOR LIMBS. 201 Fig. 129. Synovial membrane. — This lines all the ligaments, and is prolonged above and below, between the carpal bones, to facilitate the gliding of their articular facets. Two upper prolongations ascend between the three first bones of the antibrachial row, to cover the inferior face of the interosseous ligaments uniting them. Two other prolongations descend between the carpal bones of the second row ; the external, after covering the first interosseous ligament, passes between it and the corresponding anterior ligament, and communicates with the synovial capsule of the carpo-metacarpal articulation. The internal forms a cul-de-sac which rests on the interosseous ligament. Carpo-Metacarpal Articulation. — The carpal bones of the second row articulate with the superior extremity of the metacarpal bones, constituting a planiform diarthrosis. Articular surfaces. — These are, on each side, plane facets more or less inclined one on the other, and continued between each other. The largest is in the middle, and is generally hollowed by a small, shallow, synovial fossette. Mode of union. — There are the four great common liga- ments, and also six specicd ligaments .- two anterior, two posterior, and two interosseous. Of the two anterior ligaments (Fig. 129, 2, 2), one is divided into two distinct bands, and unites the second bone to the principal metacarpal ; the other, concealed by the external lateral ligament, attaches the first bone to the head of the ex- ternal metacarpal bone. The two posterior Hgaments described by Rigot do not appear to us to be suificiently distinct from the great ligament to merit a special description. The two interosseous ligaments, completely overlooked by that able anatomist, start from the interstices which separate the median metacarpal bone from the lateral metacarpals, and join the interosseous ligaments of the second row ; they are thick and short. We have sometimes noted one or other of them to be absent. Synovial membrane. — This communicates, as indicated above, with the synovial capsule of the preceding articulation. It furnishes a superior cul-de-sac, which rests on the interosseous ligament interposed between the two last cai-pal bones of the second row. Two inferior culs-de-sac descend into the inter- metacarpal arthrodial articulations. Ligaments common to the three preceding Articulations. — As before mentioned, these are four in number : two lateral, one anterior, and one posterior. a. The externcd lateral ligament (Figs. 129, 3 ; 130, 3) is a thick funicular cord composed of two orders of fibres — a deep-seated and a superficial order, slightly crossed. It leaves the external and inferior tuberosity of the radius, descends vertically to the side of the carpus, transmits a fasciculus to the first bone of the upper row, gives off another fasciculus which stops at the external bone of the second row, and terminates on the head of the corresponding metacarpal bone. Traversed obliquely by the lateral extensor of the phalanges, this ligament covers the external carpal bones. In front, it is united to the capsular ligament ; near its inferior extremity, it is confounded with the strong ligament which joins the carpal articula- tions (front view). 1, 1, Anterior liga- ments uniting the carpal bones of each row ; 2, 2, an- terior ligaments proper to the carpo -metacarpal articulation ; 3. common external ligament ; 4, com- mon internal liga- ment. ao2 THE ARTICULATIONS. Fig. 130. supercarpal bone to the first bone of the inferior row and to the head of the external metacarpal bone. b. The internal lateral ligament (Fig. 129, 4), analogous to the preceding and situated on the opposite side, is wider and thicker than it. It commences on the internal tuberosity of the radius, and terminates on the upper extremity of the middle and internal metacarpal bones, after being attached, by two distinct fasciculi, to the third carpal bone of the upper row, and the two last of the metacarpal row. In contact by its external face with the tendon of the oblique extensor muscle of the metacarpus, this ligament responds, by its deep face, to the synovial membranes of the carpus and to the bones to which it is attached. By its anterior border it is united to the capsular ligament ; the opposite border is intimately confounded with the posterior ligament, from wliich it is impossible to distinguish it. c. The anterior, or capsular ligament, is a membranous band covering the anterior face of the carpal articulations. Its superior border is attached to the radius ; the inferior is inserted into the superior extremity of the principal metacarpal bone. The two right and left borders are united with the lateral ligaments. Its external face is in contact with the tendons of the anterior extensor muscles of the metacarpus and phalanges. The internal face is lined at certain points by synovial membrane, and adheres in others to the carpal bones and the anterior ligaments binding these to one another. This ligament is composed of transverse fibres more or less oblique, and arranged cross- wise ; by its amplitude it can adapt itself to the movements of flexion of the knee. d. The posterior ligament, one of the strongest in the animal economy, covers the posterior face of the carpus, filling up the asperities which roughen it. It is inserted : above, on the transverse crest surmounting the articular surface of the radius ; by its middle portion into all the carpal bones ; below, into the head of the principal meta- carpal bone. Confounded inwardly with the internal lateral ligament, united outwardly to the band which at- taches the supercarpal to the external metacarpal and the second carpal bone of the upper row, this ligament is continued, by its inferior extremity, with the carpal stay (or check ligament) which sustains the perforans tendon. Its posterior face is perfectly smooth, and is covered by the synovial membrane of the carpal sheath. Movements of thf Carpal Articulations. — The carpus is the seat of two very extensive and opposite movements— flexion and extension; to wliich are added three very limited accessory movements — adduction, abduction, and circumduction. All the carpal articulations do not take an equal part in the execution of these movements ; for it is easy to discover that they are chiefly performed in the radio-carpal diarthrosis, and in the imperfect hinge articulation uniting the two rows of carpal bones. Each of these articulations participates in the movements LATERAL VIEW OF THE CARPAL ARTICOLATIONS. 1, 1, Anterior ligaments uniting the two rows of carpal bones; 2, 2, anterior ligaments pro- per to the carpo-meta- carpal articulation ; 3, common external liga- ment; 4, one of the ligaments proper to the articulation of the two rows (metacarpo-supra- carpal) ; 5, one of the ligaments proper to the radio-carpal articu- lation (radio-supercar- pal). A, Groove on the external surface of the supercarpal bone, for the passage of the ex- ternal flexor of the metacarpus. ARTICULATIONS OF THE ANTERIOR LIMBS. 203 of the carpus in nearly the same proportions, and both act in an identical manner. Their mechanism is most simple. In flexmi, the first tier of bones rolls backwards on the radius, the inferior row moves in the same sense on the upper, the metacarpus is carried backwards and upwards, the common posterior ligament is relaxed, the capsular ligament becomes tense, and the articular surfaces, particularly those of the second joint, separate from each other in front. In extensmi, the metacarpus is carried down- wards and forwards by an inverse mechanism. This movement stops when the ray of the forearm and that of the metacarpus are in the same vertical line. In flexion, these bones never directly approach each other, the inferior extremity of the metacarpus being always carried outwards. It may also be remarked, that the slight movements of abduction, adduction, and circumduction of the carpus are only possible at the moment when the foot is flexed on the forearm. With regard to the planiform diarthroses articulating the carpal bones of the same row, they only allow a simple gliding between the surfaces in contact ; and with the carpo-metacarpal arthrodia it is absolutely the same. The restricted mobility of these various articulations has but a very secondary influence on the general movements of the carpus ; but it nevertheless favours them by permitting the carpal bones to change their reciprocal relations, and adapt themselves, during the play of the radio-carpal and intercarpal hinges, to a more exact coaptation of the articular planes which they form. In the other animals, the carpal articulations have the same essential characteristics we have noticed in Solipeds. The four principal peripheral bands differ but little in them; though in the Dog and Cat they are lax enough to allow somewhat extensive lateral movements. 5. Intermetacarpal Articulations. Each lateral metacarpal bone articulates with the middle one, by means of diarthrodial and synarthrodial surfaces, for the description of which refer to page 112. An interosseous ligament, composed of very short and strong fasciculi, is interposed between the synarthrodial surfaces, and binds them firmly together. Its ossification is not rare. The diarthrodial facets are maintained in contact by the preceding ligament, and by the carpal ligaments inserted into the head of the lateral metacarpal bones. The intermetacarpal articulations only allow a very obscure, vertical, gliding movement. In the Ox, there is only one intermetacarpal articulation, which is much simpler than those in the Horse. In the Pig, the four metacarpal bones correspond, at tlieir upper extremity, by means of small diarthrodial facets on their sides. Fibrous fasciculi, derived from the great anterior and posterior ligaments of the carpus, protect these intermetacarpal articulations before and behind. Other fibres, situated between the adjacent faces of the metacarpal bones, are real interosseous ligaments. In the Dog and Cat, the four great metacarpal bones articulate with each other in almost the same manner as in the Pig, but their mobility is greater 6. Metacarpo-phalangeal Articulation (Figs. 131, 132). Preparation.— In order to study the whole of this articulation, it is well to have an anterior limb from the lower fourth of the forearm. From this the tendons of the flexors and extensors of the phalanges are to be removed, and then the suspensory ligament of the fetlock, anterior capsular ligament, lateral ligaments, and the superficial inferior sesamoid ligament, can be dissected. To study the ligaments which bind the bones forming the inferior articular surface, the first phalanx and sesamoid bones should be removed, which allows of the dissection 2M THE ARTICULATIONS. of the inter-, lateral, and inferior sesamoid middle and deep ligaments. An injection of the eynovinl capsule brings into relief some features which are interesting, from a surgical point of view. This is a perfect hinge-joint, formed by the inferior extremity of the median metacarpal bone on the one part, and the superior extremity of the upper phalanx and sesamoids on the other. Articular surfaces. — For the metacarpal bone, there are two lateral condyles and a median antero-posterior eminence ; for the first phalanx, two glenoid cavities and an intermediate groove prolonged posteriorly on the anterior face of the two sesamoids. Divided in this manner into three portions, the digital surface is well constituted for solidity, because the pressure transmitted to this region is diminished and. Fig. 131. diffused by the natural -*- ^ elasticity of the bands which unite these three pieces to each other. 3Iode of union. — The means of union may be divided into two cate- gories : 1. Those which join together the several bones of the inferior sur- face. 2. Those which maintain in contact the two opposed articular surfaces. A. The firet have re- ceived the generic name of sesamoid ligaments, and are six in number : an intersesamoid ligament y which holds together the two complementary bones of the digital surface ; three inferior and two lateral sesamoid ligaments, which unite these bones to the first phalanx. a. The intersesamoid ligament is composed of fibro-cartilaginous substance, that appears to be the matrix in which the two sesamoids were developed ; as it is spread around these bones, after being solidly fixed on their internal face. Behind, this ligament, in common with the posterior face of the sesamoids, forms the channel (Fig. 131, 5) in which the flexor tendons glide. In front, it occupies the bottom of the intersesamoid articular groove. h. The inferior sesamoid ligaments, situated at the posterior face of the first phalanx, are distinguished as superficial, middle, and deep. The superficial ligament (Figs. 131, 14 ; 134, 8), the longest of the three, is a narrow band flattened before and behind. It arises from the middle of the fibro-cartilaginous mass which completes, posteriorly, the superior articular surface of the second phalanx, and, shghtly widening, ascends to the base of the sesamoids. DETAILS OF THE METACARPO-PHAI.ANGEAL ARTICULATION OF THE HORSE. A. Middle inferior sesamoidean ligaments. P. First phalanx (posterior face). 1, Inter sesamoidean ligament (pos- terior fnce); 2, 2, lateral sesamoidean ligaments ; 3, middle inferior sesamoidean ligament. B. Deep inferior sesamoidean ligaments. P. First phalanx : 1, Inter-sesamoidean liga- ment ; 2, 2, lateral sesa- moidean ligaments; 3, in- ferior deep sesamoidean liga- ment. ARTICULATIONS OF THE ANTERIOR LIMBS. Fie;. 1 into which it is inserted by becoming confounded with the intersesamoid liga- ments. Its posterior face, lined by the synovial membrane of the so-called sesa- moid sheath, is covered by the flexor tendons ; it partly covers the middle ligament. The middle ligament, triangular and radiating, is composed of three particular fasciculi : two lateral (seen on each side of the superficial ligament in Fig. 131, A 8), and a median which has been generally confounded with the superficial ligament, although it is clearly distin- guished from it by its inferior insertion. Fixed in common to the posterior imprints of the first phalanx, these three fasciculi diverge in ascending to the base of the sesamoids, where they have their upper insertion. The deep ligament is constituted by two small bands concealed beneath the middle ligament. Thin, short, flattened before and behind, and intercrossed (Fig. 131, B 3), these bands are fixed to the base of the sesamoids in one direction, and in the other to the superior extremity of the first phalanx, near the margin of its articular surface. This ligament is covered on its anterior face by the synovial membrane of the articulation. CARPAL, METACARPAL, AND INTER-PHALANGEAL ARTICULATIONS OF THE HORSE (POSTERO- LATERAL view). R, Radius ; c, carpus ; M, metacarpus ; s, navicular bone ; P, third phalanx. 1, Supercarpal bone ; 2, its proper ligament ; 3, external lateral liga- ment of the carpal articulations (superficial layei'); 3, ditto (deep layer); 4, groove for the tendon of the external Hexor of the metacarpus; 5, common posterior ligament of the carpal articulations; 6, superior sesamoidean, or sus- pensory ligament of the fetlock ; 7, an originating branch of ditto ; 8, 8, terminal branches of ditto ; 9, band given off by ditto to the anterior extensor of the phalanges ; 10, tendon of the anterior extensor of the phalanges ; 11, groove formed by the posterior face of the intersesamoidean liga- ment; 12, lateral metacarpo-phalangeal ligament (superticial layer); 12', ditto (deep layer) ; 14, inferior superficial sesamoidean ligament ; 15, ditto (deep layer); 16. elenoidal fibro-cartilage of the second phalanx ; 17. 18, 19, superior, middle, and inferior bands of that fibro-cartilage ; 20, lateral ligament of the first inter-phalangeal articulation; 21. lateral posterior ligament of the second inter-phalanceal ai'ticulation ; 22, anterior lateral ligament of ditto. 16 20» 206 THE ARTICULATIONS. e. The lateral sesamoid ligaments are two thin layers, extending from the external face of each sesamoid to the tubercle of insertion on the side of the superior extremity of the first phalanx (Fig. 131, a 2). They are covered by the digital vessels and nerves, by the fibrous stay detached from the suspensory liga- ment to the anterior extensor tendon of the phalanges, and by the supei-ficial fasciculus of the lateral metacarpo- phalangeal ligament ; they are covered by synovial membrane on their internal face. B. The ligaments destined to unite the two articular surfaces of the meta- cai-po-phalangeal joint are four : tivo lateral, one anterior, and one posterior . a. Each lateral ligament comprises two fasciculi — a supei-ficial and a deep — firmly united by their adjacent faces. The superficial fasciculus (Fig. 132, 12) commences on the button of the lateral metacarpal bone, attaches itself to the median metacai-pal, and descends vertically to terminate at the superior extremity of the first phalanx. It covers the phalangeal insertion of the lateral sesamoid ligament and the deep fasciculus. The latter, attached superiorly in the lateral excavation of the inferior extremity of the principal metacarpal, radiates as it reaches the sesamoid and the superior extremity of the first phalanx, where it is fixed by mixing its fibres with those of the lateral sesamoid ligament. The inner face of this fasciculus is lined by the articular synovial membrane (Fig. 132, 12'). I. The anterior ligament (Fig. 132) belongs to the class of capsular ligaments. It is a veiy resisting membraniform expansion, which envelops the anterior face of the articulation. Attached by its upper border to the anterior margin of the metacarpal surface, and by its inferior border to the first phalanx, this expansion is confounded at its sides with the lateral ligaments. It is covered by the extensor tendons of the phalanges, which glide on its surface by means of small serous sacs. Its internal face adheres throughout its whole extent to the synovial capsule. c. The posterior ligament,^ very appropriately named the suspensory ligament of the fetloch (Figs. 132, 6 ; 133, 134, 4), is a long and powerful brace, composed of white fibrous tissue, and often containing fasciculi of fleshy fibres in its textm-e. Lodged behind the median metacai-pal, and between the two lateral metacarpal bones, this brace is quite thin at its origin, but it soon becomes enlarged, and pre- serves its great thickness to the extent of its upper fourth. Examined in section, it appears to be formed of two superposed portions which are closely adherent to each other. The superficial portion, the thinnest, commences by three small branches, which are fixed to the first and second bones of the lower carpal row (Figs. 132, 133, 5) ; the deep portion, much thicker, is attached to the posterior face of the principal metacai"pal for about ^ of an inch. It has been wrongly asserted that the suspensoiy ligament of the fetlock is continuous with the common posterior ligament of the cai-pus ; it is, on the contrary, quite distinct from it. The carpal stay {deep palmar aponeurosis of Man) is alone in direct continuity mth the common posterior ligament of the cai'pus (133, 3). The suspensory ligament of the fetlock is bifid at its inferior extremity ; its two branches, after being fixed into the summits of the sesamoid bones, give origin to two fibrous bands which pass downwards and forwards to become united on each side to the anterior extensor tendon of the phalanges (Fig. 132, 9). It is in relation, by its posterior face, Avith the perforans tendon and its carpal stay ; by its anterior face, with the median metacarpal bone, and arteries and veins ; by its borders, ' It coiresponds to the two muscles which, in Mun, lie alongside the interosseous meta- carpal muscles. (See Muscles of the Foot.) ARTICULATIONS OF THE ANTERIOR LIMBS. 207 with two small interosseous muscles, the lateral metacarpal bones, and the digital vessels and nerves. Synovial membrane. — Tliis membrane is prolonged as a cul-de-sac between the terminal branches of the preceding ligament. It is the distension of this sac which causes the articular swellings vulgarly designated " windgalls." Fig. 133. Movements. — The metacarpo-phalangeal articulation permits the extension and flexion of the digit, and some slight lateral motion when the movable osseous segment is carried to the limits of flexion. In the Ox, Sheep, and G-oat, this articulation constitutes a dotible hinge, which resembles the simple ginglymus of Solipeds. They have three intersesamoid ligaments : two lateral, to unite the large sesamoids of each digit ; and a median, which unites the interual sesamoids. The inferior sesamoidean ligamentous apparatus is far from showing the same degree of development as in the Horse. It is reduced for each digit to four small bands, which remind one very much of the deep ligament of the latter animal, as it has been described by Rigot : two lateral bands pass directly from the sesamoids to the upper extremity of the first phalanx ; the other two, situated between the first, intercross and are confounded with the latter by their extremities. A lateral tesamoid ligament unites the first phalanx to the exterual sesamoid. For each digit there are two lateral metacarpo-phalangeal ligaments— a,n external, analogous to that of the Horse, but less complicated, is attached by its inferior extremity to the first phalanx only ; the other, internal, fixed superiorly in the bottom of the inter-articular notch of the metacarpal bone, is inserted into the inner face of the first phalanx in mixing its fibres with those of the superior interdigital ligament. This latter is situated between the two first phalanges, and is composed of short, inter- crossed fibres, attached to the imprints which in part cover the internal face of the two first phalangeal bones. In the Sheep there are only traces of this interdigital ligament, and each internal metacarpal-phalangeal gives rise, near its phalangeal insertion, to a fibrous branch which is directed backwards from the interdigital Bpace, and is terminated in the bone of the ergot (or posterior rudimentary digit), which it sustains. The anterior or capsular ligament, single as in Solipeds, unites the two external lateralliga- ments. The suspensory ligament, single superiorly, is divided inferiorly into eight branches, two of which are joined to the periuratus tendon, to form with it the double ring through which the two branches of the perforans pass. Four other branches, in pairs, extend to the summits of the sesamoids. That which is sent to each external sesamoid gives off, on the side of the first phalanx, a reinforcing band to the proper extensor of the digit. The two last, profound and median, descend into the inter-articular notch of the metacarpal bone, after becoming a single fasciculus ; afterwards, they pass between two internal metacarpo-phalangt-al ligaments, and separate from each other in passing downwards and forwards on the inner side of the first phalanx, to join the proper extensor tendon of each digit. In the Pig, Dog, and Cat, for each metacarpo-phalangeal there is: a proper synovial membrane; an intersesamoid ligament; an inferior sesamoid ligament composed of two cross- bands; two small lateral sesamoid ligaments; two lateral metacarpo-phalangeal ligaments, attached inferiorly to the first phalanx and the sesamoids ; an anterior capsular ligament, in the centre of which is found a small bony nucleus — a kind of anterior sesamoid— over which glides one of the branches of the common extensor of the digits. The suspensory ligament is replaced by real palmar interosseous muscles (see the Muscles of the Anterior Foot). Some fibres situated between the first phalanges in the great digits of the Pig, resemble the superior interdigital ligament of the Ox. In Man, the cavity in the upper extremity of the first phalanx is completed by a glenoid SECTION OF THE INFERIOR ROW OF CARPAL BONES, THE METACARPAL, AND THE SUSPENSORY LIGA- MENT OF THE FETLOCK. 1, Os magnum ; 2, common posterior ligament of the carpus ; 3, stay, or band for tlie perforans tendon , 4, suspensory ligament of the fetlock ; 5, its super- ficial layer ; 6, its deep fasciculus ; 7, principal metacarpal bone. TEE ARTICULATIONS. ligament. The prenoid ligaments of the four first digits are united to each other by a trans- verse ligament of the metacarpus. The articulations are cousolidated by two lateral ligaments. The metaciirpo-plialaiigeal articulations allow flexion and ex- Fig. 134. tension movements, as well as those of abduction and adduction; but the latter are limited by the lateral ligaments. M rosterior view of the metacarpo-phalangeal and inter-phalangeal articulations (right limb). 1, 3, Outer and inner rudimentary metatarsal bones ; 2, perforans tea- don and its check liga- ment ; 4, suspensory liga- ment ; 5, gliding surface or sheath for the flexor tendons, f'rmed by the posterior face of the sesa- moid bones, and interse- samoid. transverse, and annular ligaments; 6, section of lateral sesamoid ligament ; 7, lateral fasci- culus of the middle infer lateral ligament of the fir of the perforatus tendon; surface of navicular bone; 14, perforatus tendon, 15, 7. Abticulation of the Fibst with the Second Phalanx, or First Interphalangeal Articulation. (Preparation. — Kemove the extensor tendon ; throw open the metaearpo-pnalangeal sheath, and turn down the flexor tendons.) This is an imperfect hinge-joint. Articular surfaces. — On the inferior extremity of the first phalanx are two lateral condyles, separated by a groove. On the superior surface of the second phalanx are two glenoid cavities, and an antero-posterior ridge. The latter surface is completed behind by a glenoidal fihro-cartilage, very dense and thick (Fig. 132, 16), which also acts as a ligament. It is attached, in one direction, to the second phalanx, between the superior articular surface and the kind of fixed sesamoid which margins it behind ; in the other, it is inserted into the first phalanx by means of six fibrous bands (Fig. 135, 4, 5, 6) : two superior, which embrace the inferior, middle, and super- ficial sesamoid ligaments ; two middle, and two inferior, which extend to the sides of the inferior extremity of the first phalanx. This fibro-cartilage is moulded, in front, to the articular surface of the latter bone, and forms, by its posterior face, a gliding surface for the perforans tendon (Figs. 132, 16 ; 134, 5). It is con- founded, laterally, with the two branches of the per- foratus, and receives, in the middle of its superior border, the insertion of the inferior superficial sesamoid liga- ment. Mode of union. — Two lateral ligaments (Fig. 135, 7), to which are added, behind, the fibro-cartilage just described, and in front the tendon of the anterior extensor of the phalanges. These ligaments are large and thick, and, passing obliquely downwards and backwards, are inserted, superiorly, into the lateral tubercles of the inferior extremity of the first phalanx. They are at- tached, beneath, to the sides of the second phalanx. Their most inferior fibres are even prolonged below that point to reach the extremities of the navicular bone, and constitute the posterior lateral ligaments of the pedal articulation. Synovicd membrane. — This covers the tendon of the •ior sesamoid ligament; 8, inferior superficial sesamoid ligament ; 9, st interphalangeal articulation ; 10, section of the terminal branch 11, section of the lateral cartilage of the foot; 12, postero-inferior 13, section of lateral cartilage, plantar cushion, and wing of pedal bone; perforans tendon. ARTICULATIONS OF THE ANTERIOR LIMBS. 209 anterior extensor of the phalanges, the lateral ligaments, and the glenoid fibro- cartilage. Behind, it forms a cul-de-sac, which extends between the latter and the posterior face of the first phalanx (Fig. 137). Movements. — This imperfect hinge is the seat of two principal movements : extension and flexion. It also allows the second phalanx to pivot on the first, and permits some lateral movements. In the Ox, Sheep, and Goat, the glenoid fibro-cartilage is confounded with the perforatus tendon, and is only attached to the first pliahmx by two lateral bands. The internal lateral ligament comprises two fasciculi : one, very short, which terminates in the st-coml phalanx ; and another, very long, descending to the internal face of the third phalanx. The external is very thin, and is also prolonged to the terminal phalanx ; so that the two last inteiphalangeal articuhitions of each digit are fixed by two common lateral li'j;aments which correspond exactly, by their position and inferior attachments, to the anterior lateral ligaments of the pedal joint of Solipeds. In the Dog and Cat, the glenoid cartilage, also confounded by its posterior face with the perforatus tendon, only adheres to the first phalanx by some cellular bands. The two lateral ligaments pass from the inferior extremity of the first phalanx to the superior extremity of the second. In the Pig, there is somewhat the same arrangement as in Carnivora. The external lateral ligament is, nevertheless, more like that of the Horse, in its most anterior fasciculi being prolonged lo the external extremity of the navicular bone. 8. Aeticulation of the Second Phalanx with the Third, Second Interphalangeal Articulation, or Articulation op the Foot. Preparation. — Eemove the hoof according to the directions given hereafter, when treating of the muscles of the forearm ; then the plantar cushion, the flexor tendons, and one of the lateral cartilages. A section like that shown in Fig. 137 is useful to show the relations between the % synovial capsule of this joint and the bursae, behind the second phalanx. To form this imperfect hinge-joint, the second phalanx is opposed to the tliird, and to the navicular bone. Articular surfaces. — On the inferior face of the second phalanx there are two lateral condyles and a median groove. On the superior face of the third phalanx and the navicular bone, are two glenoid cavities separated by an antero-posterior ridge. The two bones which form tliis last surface, articulate with each other by arthrodia ; the navicular bone presents for tliis purpose an elongated facet on its anterior border ; the os pedis also offers an analogous facet on the posterior contour of the principal articular surface. Mode of union. — Five ligaments : a single interosseous one, which joins the navicular to the pedal bone ; and four lateral bones, distinguished as anterior and posterior. a. Interosseous ligament (Fig. 136, 2). — This is formed of very short fibres, which are inserted, behind, into the anterior groove of the navicular bone ; and in front, into the posterior border and inferior face of the third phalanx. This ligament is lined, on its superior surface, by the synovial membrane, and on its inferior face is covered by the navicular sheath. h. Anterior lateral ligaments (Figs. 132, 22 ; 135, 9).— These are two thick, short, and wide fasciculi, attached by their superior extremities to the lateral imprints of the second phalanx, and by their inferior extremities into the two cavities at the base of the pyramidal eminence of the os pedis. Each ligament is partly covered by the complementary fibro-cartilage of that bone, and appears to form a portion of it. Its anterior border is continuous with the common extensor 210 TEE ARTICULATIONS. tendon of the phalanges ; its internal face is covered by the synovial membrane, which adheres closely to it. c. Posterior lateral ligaments (Figs. 132, 21 ; 135, 8). — These have been already noticed. Each is composed of the lowermost fibres of the lateral ligament of the first interphalangeal articulation ; these fibres, after being attached to the ?econd phalanx, unite into a sensibly elastic fibrous cord, which is chiefly fixed Fig. 1^5. M E r ATARSO - PHALANGEAL AND INTER-PHALANGEAL ARTICULATIONS OF THE HORSE. These are almost the same as in the anterior limb. 1, Superficial layer of the external lateral ligament of the metatarso-phalan- geal articulation ; 2, sesa- moid branch of the deep layer; 3, phalangeal branch of the same ; 4, superior branch of the glenoidal fibro-cartilage; 5, middle branch of ditto; 6, inferior branch of ditto ; 7, lateral ligament of the first inter- phalangeal articulation ; 8, posterior lateral ligament of the pedal articulation ; 9, anteiior lateral ligament of ditto. ARTICULATION OF THE FOOT (INFERIOR FACE). P, Inferior face of the third phalanx. S, Infe- rior face of the navicular bone. 1, Semilu- nar crest ; 2, interosseous ligament. into the extremity and superior border of the navicular bone, where the Ugaments join each other, and in this way form a kind of complementary cushion that in- creases the navicular articular surface. It also sends off a short fasciculus to the retrossal process, and a small band to the internal face of the lateral fibro- cartilage. Partly concealed by the latter and the plantar cushion, this ligament is covered inwardly by the articu- lar synovial membrane. Synovial memlrane. — This descends below the facets which unite the navicular to the pedal bone. It offers, posteriorly, a vast cul-de-sac which reaches the posterior face of the second phalanx, and hes against the two sesamoidean bursse (Fig. 137, 13). It also forms another much smaller, by being prolonged between the two lateral ligaments of the same side. This is very often distended, and it is liable to be opened in the operation for diseased lateral cartilages. Movements. — The same as those of the first interphalangeal articulation. In the Sheep are found : 1. An interosseous ligament to unite the navicular bone to the third phalanx. 2. Two anterior lateral ligaments commencing:, as already stated, at the first phalanx. 3. Two lateral posterior ligaments, passina: to the posterior face of the second phalanx and the navicular bone (the internal is yellow and elastic). 4. A single, anterior, elastic liga- ment, attached above to the superior extremity of the second phalanx, and fixed below into the third, between the insertion of the common extensor of the digits and that of the internal anterior lateral ligament; an inferior interdigital ligament, situated between the ungueal phalanges, whose separation from each other it limits This ligament is compose