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No book shall be allowed to circulate until one month after its leceipt. 3 9090 013 413 774 Webster Family Library of Veterinary Medicine Cummings School cf Veterinary Medicine at Tufis University 200 Westboro Road THE ANATOMY THE HORSE, EMBRACING T^E Sttuctuvc of the dToot* WILLIAM PERCIVALL, M.R.C.S. VETERINARY SURGEON IN THE FIRST LIFE GUARDS; AUTHOR OK "LECTURES ON THE VETERINARY ART;" AND CO-EDITOR OK "THE VETERINARIAN." " Anatomy may be esteemed the very basis of medicine and surgery. Without a knowledge of anatomy, we feel ourselves incompetent to treat the most common surgical case. And in the majority of instances in which a member of our profession has disgraced himself, it may be traced to his Ignorance of this foundation of his art." Carmic/iael's Lectures. LONDON: LONGMAN, REES, ORME, BROWN, GREEN, AND LONGMAN, PATERNOSTER ROW. roY c 1 r ^:^ Coniptoii and Riteliie, Printers, Midille Strcft. Cloth Fair, Loncio PREFACE. Among the modern veterinary works published in our own country, that there should not be one exclusively devoted to the science of anatomy, will not appear alto- gether so surprising- when we come to consider the oppor- tunities of place and circumstance required to cultivate this study ; the unwearied assiduity and labour incumbent upon any chance of success ; and, after all, the probable unprofitableness of such a work in the book-mart : for (to echo the sentiments of Sir Charles Bell, our highly disting-uished physiologist) the public really do not com- prehend the importance of anatomy as a science. In the composition of the present work (parts of which have already made their appearance in "The Veterinarian"), the Veterinary Lectures, formerly published by the Author, have been freely drafted from : at the same time, the old matter has undergone much revision^ correction, and emendation, and has been altogether fresh cast — has been, in fact, arranged in a systematic form : a plan, the Author is induced to hope, that may tend much to facilitate the progress of the student. On points obscured by any doubt or mystery, the Author has consulted the most emi- nent continental veterinary authorities ; above all others. iv PllKFACE. the work of M. Giraid, Director of the Veterinary School at Paris. And in framing his nomencla- ture in accordance with that in use among- human anatomists, the Author has availed himself of the pro- ducts of the labours of his own countryman, the clever and indefatigable Stubbs. To Mr. Bean, also, who aided him in the dissection of the nerves ; and likewise to Mr. Smith, for an account of the ear, the Author begs to kindly acknowledge his obligations. That many, very many discoveries, and most import- ant and valuable ones too, yet remain to be made through anatomical research, no one conversant in the science will pretend to gainsay ; and that they, in the progress of time, will come to light, and redound amply to the credit of those who may elicit them, is no less the firm persuasion than the fervent hope of the Author of the work herewith offered to the profession. Ifcgfiit's Park Biinacks October, IH3-2. CONTENTS. Introduction Page xi Section I. — Osseous System . Of the skeleton . Tabular enumeration of the bones Terms used in descriptive anatomy Bones of the trunk Bones of the head Bones of the extremities Section II. — Muscular Si/ste/n. Of the muscles . Table of the muscles Cutaneous muscles Muscles of the head Muscles of the trunk Muscles of the extremities Section III. — Cii Of the blood . 163 Of the heart and pericardium . 172-173 Of the bloodvessels . 176 Of the arteries . ib. Table of the arteries . 177 Description of the arteries . 179 Of the veins . 207 Table of the veins . 208 Description of the veins . 210 Section IV . — Respiiafun/ Si/stem. Of the larynx . 221 Of the trachea . 223 ulatorij Sj/stem. 75 76 82 84 103 133 C(^NTKNTS. Of the tliyioul glands Of the lungs and pleura Pleura Lungs Pnfrp 226 227 229 Section V, — Digestive Sijstei Of the mouth . . 234 Of the tonf^ue . . 237 Of the salivary ^-lands . 23[) Of the pharynx . 240 Of the esophagus . 241 Of the abdomen . 242 Peritoneum . 243 Of the situation of the viscera of the abdomen . 245 Of the reflection of the peritoneum . 248 Of the stomach . . 249 Of the intestines . 263 Of the liver . 259 Of the spleen . . 262 Of the pancreas . . 263 Section VI. — Absorbent System. Of the absorbents . . . - . . . . 265 The thoracic duct ....... 267 Receptaculum chyli ..... . 268 Lymphatics discharging themselves into the abdominal (thoracic) duct ib. Lymphatics discharging themselves into the thoracic duct itself . 271 Section VII. — Uiinanj Si/stem. Of the kidneys The ureters Of the capsulse renales Of the bladder . 273 277 278 279 Section Y\\\.— Generative Si/slem. Male organs of generation Of the testicles and scrotum Of the vcsiculcc semint.les 282 ib. 291 CONTENTS Of the penis Of the prostate olands . Female organs of generation Of the vulva Of the clitoris . The meatus urinarius Of the uterus Of the Fallopian tubes . Of the fimbriae . Of the ovaries . Of the udders . Vll Page 292 298 299 ib. 300 302 303 305 306 ib. 307 Section IX. — Nervous Si^stem. Of the brain Dura mater Pia mater IMembrana arachnoide Brain Cerebrum Cerebellum Base of the brain Medulla oblongata Pituitary gland Of the spinal marrow Of the nerves . Table of the cerebral nerves First pair, or olfactory nerves Second pair, or optic nerves Third pair, or motores oculorum Fourth pair, or pathetic Fifth pair, or par trigeminum Sixth pair, or abducent Seventh pair, or auditory Eighth pair, or par vagum Accessory nerves to the eighth p Ninth pair, or lingual Tenth pair, or sub-occipital Spinal nerves Cervical nerves Dorsal nerves . Lumbar nerves Sacral nerves 310 311 313 314 ib. 316 322 324 325 ib. ib. 328 332 335 ib. 336 ib. ib. 339 340 341 344 ib. 345 ib. 346 348 350 351 VI 11 CONTENTS. Page Coccygeal nerves ....... 352 Nerves of the fore extremity . . . . ib. Nerves of tlie hind extremity ...... 355 Sympathetic nerve . . . .357 Section X.~ Sensitive Sj/stem. Of the nose ........ 362 Nasal fossae . ib. Nasal sinuses . 364 Nasal ducts . ib. Of the eye . . 364 Of the appendages . 365 Eyebrow . ib. Eyelids . ib. Eyelashes . 36/ Structure of the eyelids ib. Tarsal cartilages . 368 Ciliary or meibomian glands . ib. Tunica conjunctiva . 369 Membrana nictitans . 371 The lachrymal gland . 3/2 Caruncula lachrymalis . 373 Lachrymal puncta and conduits 374 Lachrymal sac ib. Ductus ad nasum 375 Muscles of the eyeball 376 Concluding observations ib. Of the eyeball . 377 The coats or membranes 379 Sclerotic coat . ib. Cornea 381 Iris 382 Corpora nigra 385 Choroid coat 386 Retina .... 389 Of the humours 390 Aqueous humour ib. Crystalline lens 391 Vitreous humour ..... 392 Of the ear 393 The external ear .... ib. Concha ... ib. CONTENTS. IV Meatus auditorius cxtenius .... . 3!>5 The internal ear ..... . 396 Tympanum ...... . ib. Labyrinth ...... . 399 Semicircular canals ..... . 400 Cochlea . 401 Section XI. — Tegumental Si/stem. Of the skin . 402 Cutis ....... . ib. Cuticle ...... . 406 Rete mucosum ..... . 409 Of the hair ...... . 410 Of cellular membrane .... . 414 Of fat . 416 Section XII. — Plantar System. Of the foot ...... . 418 External parts . 419 The hoof . ib. The wall . 422 The sole . 428 The frog . 429 Development of the hoof . 433 Structure of the hoof . 434 Production of the hoof . 435 Properties of horn . 436 Internal parts of the foot . 437 The coronary substance . ib. The cartilages . 439 The sensitive laminae or lamellae . 441 The sensitive sole . 442 The sensitive frog . 443 INTRODUCTION. IN all ages have medical philosophers regarded a knowledge of anatomy as requisite to the attainment of the science of medicine ; but in no age, we may venture to assert, has the truth of this opinion shone upon the mind with brighter light than at the present time. In this, our own day, we may look around and seem to trace the success of each one eminent in the healing art- to his anatomical acquirements : at least, we may safely affirm, that not one of our present medical distingues could have gained the same ground without a knowledge of anatomy ; and he would appear to have reached the highest station who has had the wisdom and foresight to make that science the foundation of his other professional pursuits. However much lack of knowledge and respectability on the part of its practitioners may have disparaged it, the Veterinary Art itself must claim kindred with human medicine, anatomy and physiology being their common parents. Both sciences spring from the same source, and must be attained by a like course of study. The surgeon has lived to the day to be convinced, that no so sure road to reputation and distinction lies open to him as the broad and accessible one through the dissecting room ; and the day ivill come (should it have not yet arrived) when the Veterinary Surgeon will discover that the same path is the only one which even he can rationally pursue. The age of grooms and farriers is on the decline ; and the day fast approaching, when Science must and will assert the same sway over the ve- terinary profession as she so triumphantly exercises at the present day over the medical world at large. After this encomium on anatomy, it comes very natural to inquire what we learn or profit by the science. A short and pithy answer (though it might be deemed an unsatisfactory one) may be given to this question, by repeating, that no really useful medical learning can be acquired without it. A professor of medicine with a mind unfurnished with anatomy and physiology, is precisely in the situation of a mechanic who undertakes to repair a deranged or broken machine without any acquaintance xii INTRODUCTION. whatever with its mechanism or operations : both such persons are empirics, and worse than empirics — impostors in their pro- fessions : either of them perchance may do good ; but there is ever much to be apprehended that they may be working some irreparable mischief. We hear of " wonderful cures" being performed by persons having no pretensions whatever — indeed possessing none — to medical science ; and in this hit-or-miss manner of proceeding, it cannot be denied that some valu- able discoveries have been made: could we, however, but set against these discoveries, brilliant as some of them may have turned out to be, a true catalogue of the failures attendant upon the experiments in which they had their origin, we are sorely afraid the picture would exhibit a complexion which even the discoverers themselves could not regard without mingled dissatis- faction and remorse. Plain and obvious as this necessity for fundamental know- ledge must appear to every reflecting mind, yet there are gentle- men — men of education — enough to be found who commit their horses, in disease as in health, entirely to the care of their grooms ! or, who call to their aid the blacksmith or bell-hanger, rather than put faith in a man who is, or ought to be, even under every disadvantage, alone qualified to comprehend the nature and cause of disease. It was once so with human medicine: science has, however, dispelled the gloom in that quarter ; and will as certainly, in the progress of time, in like manner enlighten our own clouded and sunless regions. Want of education among its members, literary as well as medical, has done more real injury to the cause of veterinary science than any one individual agent besides. Superiority in knowledge is the only eifective weapon we possess, with which we are able successfully to combat our opponents : without that, we may exhibit the shadow, but hold not the substance of pre- eminence over those who have for ages had possession of the practice of that art, of which we come before the public, not merely as practical but as scientific professors. By learning anatomy, we become acquainted with the situation, form, connexion, and structure of every part of the body. Its action or use is taught us by the science of physiology. From which we proceed to the third natural link in the chain of fun- INTRODUCTION. xiii damental medical knowledoe, — pathology, or the doctrine of dis- ease. Anatomy prepares the mind for, while it excites it to, the study of physiology ; a science no less admired for the sublimity of its dogmas, than ardently pursued for its fruitful and valuable products. To conclude, let us once more repeat, that anatomy forms the groundwork of physiology ; and that he who possesses a knowledge of both sciences combined, holds in his hand the key to all rational practice, as well in medicine as in surgery, be it human or be it veterinary. The science of anatomy admits of division into general, and particular or descriptive anatomy. General Anatomy treats of the several elementary parts or simple tissues into which the organs or complicated parts of the body are resolvable : developing their different properties — me- chanical, chemical, and vital ; and at the same time exposing their various modes of association, by which is constituted organization ; the phrase ''organization"" being used by anatomists to imply perfection or adaptation of structure to its end, design, or function. Particular or Descriptive Anatomy views parts and organs, entire — as we find them : taking cognizance of theybrm and structure oi each ; and noting its relations, such as situation, direction, position, dimensions, connexion, &c. In fact, it is the object of the work before us. Anatomy may also be said to be particular when its inquiries become confined to any one individual species of animals; in which sense many subdivisions may be made of it, though they all become conveniently reduced to three, viz., human, veterinary, and comparative anatomy/. Human Anatomy restricts its investigations to the human species. Veterinary Anatomy, though perhaps strictly applica- ble (in accordance with its derivation) to beasts of burthen, is, at the present day, understood to comprehend all domesticated animals ; or, at least, such of them as come more immediately into our domestic service. Comparative Anatomy extends its view over the whole animal creation, but derives its name from a reciprocal compari- son of them, or from a comparison of them individually with man xiv INTRODUCTION. as a standard ; and acquires importance from the mutual illus- trations it affords in structure and function. The study of anatomy, more, perhaps, than that of most other sciences, will be found to be facilitated by systematic arrange- ment ; and the nearer approach this makes to the end we have in view in such study (which is, primarily, physiology), the greater seem to turn out the advantages therefrom resulting. For this reason, in the work before us, a physiological systema- tization has been preferred ; by which, parts and organs co-ope- rating to one common end or purpose, will be found classed to- gether in the same system. Co-operation in function, however, so far from indicating identity of structure, is in many instances effected by organs of structures the most dissimilar ; while, on the other hand, similarity of texture pervades many parts be- longing to different physiological systems : two facts that may be adduced as forming some objection to the classification here adopted. But, we conceive, they are both overruled by the insight which the present plan gives us into physiology ; the ob- ject, let it never be forgotten, we have in view in prosecuting anatomy. The following table exhibits the PLAN OF THE WORK. SECTION. SYSTEM. CONTAiNED PARTS. J Osseous .... Bones; Ligaments; Joints. if. Muscular .... Muscles ; Tendons ; Bursa; Mucosa>. III. Circulatory . . . Blood ; Bloodvessels ; Heart. IV. Respiratory . . . Larynx; Trachea; Lunj^s. 1 Mouth; Tongue; Salivary Glands; Pharynx; V. Digestive . . . . -Esophagus; Stomach; Intestines; Liver; ( Spleen ; Pancreas. VI. Absorbent .... Absorbents; Absorbent Glands. VII. Urinary 4 Kidneys; Renal Capsules; Ureters; Blad- ( der. VIII. (Male . Generative J J Testicles; Vasa Defercntia; Vesicular Se- l minales. Penis. Vulva; Clitoris; Meatus Urinarius. /Female Vagina; Uterus; Fallopian Tubes; Fim- briae ; Ovaries. IX. Nervous .... Brain ; Spinal Marrow ; Nerves ; Ganglia. X. Sensitive .... Nose ; Eye; Ear. XI. Tegumental . . . Skin; Hair; Cellular Membrane ; Fat. XII. Plantar Feet. INTRODUCTION. xv Conformably to this plan, the bones come *first midcr consi- deration ; they it is that, being of a nature, hard, firm, and in- flexible in themselves, form the frame-work of the animal struc- ture ; — that constitute the walls of defence and pillars of support to the other parts of the body. The skeleton presents a beauti- ful illustration of this ; it exhibits almost a perfect outline of the living animal : — " How changed! and yet how like!" It forms altogether an inimitable piece of mechanism, serving the united purposes of protection, support, and locomotion. The cranium affords an asylum for the delicate organs of sensation ; the thorax, a place of security for the vitally important ones of respiration ; while the four legs, after the manner of the four columns of a building, support the body, resting upon the feet as their pedestals. Form and strength are likewise funda- mentally derived from the osseous fabric. The dimensions and proportions of parts must necessarily be regulated by the bony frame, and their powers also must be greatly dependent upon the nature of this foundation : a fact that has not escaped the observation even of those but little acquainted with the science of anatomy, as we may gather from the trite remark, that such a horse possesses "■ plenty of bone." Superadded to all this, the bones are the agents, though but jjassive ones, of locomotion ; the active or moving powers being the next order of parts— the muscles. And when we come to examine into the different forms and proportionate magnitude of the bones ; the curious and admirable methods by which they are fitted and adapted to each other ; and the singular advantages they, in their relative situations and positions, present to the moving- powers, the muscles ; we cannot fail to be struck less with the beauty of the structure of the skeleton, than persuaded of what paramount importance a knowledge of it must be to him who is setting out in the study of anatomy. Compared with other living substances, bone possesses so little animal or vital material in its composition, that hardly any differ- ence is perceptible in its aspect either in life or death : altogether, it is found to bear considerable analogy to inorganizcd matter ; xvi INTRODUCTION. not undergoing that rapid spontaneous decomposition, after the departure of hfe, to which other parts of the body are subject, but enduring for ages without losing even its original shape. During the earlier periods of fcetal existence, we find no bone whatever in the body — nothing but pieces of gristle or cartilage^ assuming the forms of the bones into which they become at various periods afterwards converted : cartilage being a firm, solid, flexible substance, intermediate in its degree of hardness between bone and flesh, and serving many useful purposes in the animal economy, for which bone would be too stiff, unyielding, and brittle, and other material too soft and unsubstantial. For this reason it is employed in the temporary place of bone, in the foetus ; and for the same reason, in some parts — in the ears, nose, windpipe, &c. — is continued as a substitute for it during life. No less than two hundred and thirty-eight bones are found to be required to complete the fabric of the skeleton ; which (in order for them to admit of elasticity and motion) are linked and joined one to another by curious, highly ingenious methods of connexion, that come, indiscriminately, under the general deno- mination of joints. Such, however, is the variety observable among the joints, that anatomists have found it necessary to make some sort of classification of them. The most natural and con- venient one seems to be that which arranges them in three classes : — Fii'st, into membranous joints, formed for elasticity only, such as those of the cranium and face. Secondii/, into cartilago-ligamentous joints, designed both for elasticity and motion ; such as the connexion existing between the splint and cannon bones ; between the bones of the pelvis ; and between the vertebree of the spine, and the ribs and the breast-bone. Lastly, into capsular joints, the most perfect but the most com- plicated description of articulation, and the one intended solely for the purpose of motion, simple or compound, according as the necessities of the parts themselves may require. In the con- struction of this kind of joint we find, first, the ends of the bones forming it to be nicely shaped and fitted to each other ; secondly, the adjusted extremities of the bones to be covered with cartilage, to render them smooth and polished like ivory ; thirdly, a capsule of a membranous nature attached around and irCTRODUCTION. xvii investing these cartilaginous ends; fourthly, lateral and other ligamentous chords, running from one bone to the other, to strengthen the connexion ; fifthly, a fluid resembling the white of egg, exuded from the internal surface of the capsule, for the purpose of lubricating the cartilaginous ends, and preserving them from friction. Although such is the general composition of this third kind of joint, we find it varied in every particular in- stance to suit the intentions of nature : exciting our admiration no less for its inimitable beauty or construction than for its won- derful power and effect. Ending our account of the passive mechanism of locomotion, we come to consider the active powers or means by which the machine is set in motion. Little, perhaps, would that person imagine, who contemplated simply the dead body, that muscle or flesh possessed such capability ; much less would he suppose its power to be of that wonderful nature which experience has taught us that it is. Even the anatomist himself discovers nothing in the structure of a muscle to account for such pro- perties ; but is compelled, after the most tedious and elaborate research, to ascribe them to something he cannot explain, de- pendent upon the presence and exercise of the vital energy. Only by calling in this mysterious power to his aid, can he pre- tend to offer any reason why a piece of flesh that would of itself be torn asunder by the weight of a few ounces, should, in a living state, be capable of lifting and sustaining a hundred or more pounds ! A muscle, anatomically examined, is found to consist simply of a congeries of longitudinal fibres, disposed in packets or bundles, severally encased in cellular membrane, and by the same material connected altogether into one solid body. These fibres have, superficially viewed, the appearance of being single and indivisible : through microscopic aid, however, we learn, that not only are the packets made up of bundles of fibres of smaller and finer mould, but that even their component fibres are themselves packets of similar composition ; in which way we become continually foiled and disappointed in our researches after the ultimate or original fibre, whereunto no investigator has hitherto arrived. c xviii INTRODUCTION. Though muscles ordinaiily are red, colour is not essential to them : it is entirely dependent on the blood contained in their vessels, some being- naturally white or colourless, like what we find them in almost all fish, and many birds. In general, mus- cles possess bulk correspondent to their power, and are so shaped and positioned as to have full effect in regard to the func- tion they have to perform; while in their situations they confer upon the body beauty of outline, combined with exquisite sym- metry of form. In number we compute them at about three hundred and twelve. And when we come to reflect that most of them are susceptible of varied action, and to calculate to what extent these actions niay be nniltiplied by different combinations, vve shall not feel so much surprise at the endless multiplicity and diversity manifested in the motions of the body. From what has been said, therefore, it appears that the muscles are the active or essential agents of locomotion; the bones, the passive part of the apparatus : the two chief ends of locomotion being, to enable the animal to obtain food, and avoid such objects as may seem anywise offensive or detrimental to him. With few exceptions, muscles are distributed over the body in pairs, or fellows, there being an equal number of correspondent magnitude and power ranged on either side. And their positions and attachments are such as to enable them to act as antagonists one to another, either direct or indirect, singly or in combination : the grand secret furnishing us with the explanation of the vast variety of motion, internal as well as external, of which the body is capable. The generality of muscles are furnished with what are called tendons or sinews ; which, being composed of a material me- chanically stronger than the flesh itself, but much less bulky, serve the useful purpose of connecting the muscles to the part to be moved, without at the same time proving an incumbrance from their volume. In texture, they are dense, tough, and fibrous ; and in aspect have a glistening blueish-white hue, form- ing a beautiful contrast with the florid red of the fleshy por- tion of the muscle. There is yet another part belonging to the muscular appara- tus ; one that answers the same purpose that the synovia or joint- INTRODUCTION. xix oil does in the interior of" a joint: in the same manner as that serves to prevent friction between bones, the bursa:, mitcoscc, which likewise contain synovia, obviate similar inconvenience arising between tendons, or between tendons and bones. From the organs of support and locomotion, we proceed to those concerned in the circulation of the blood over the animal machine. These consist of the heart, the arteries, and the veins. The heart in its situation in the middle of the cavity of the thorax, operates after the manner of a forcing pump, throwing blood into the trunks of the arteries, through whose manifold ramifi- cations it is conducted over every part of the body, to be after- wards conveyed back again by the veins. In this manner are executed the impoitant functions of //M^r?7?ow, groioth, and secre- tion. Blood is to the animal what sap is to the vegetable : it nourishes the body ; supplies new materials for its growth and repair; and, at the same time, becomes the vehicle for the re- moval of the old and worn-out matters; besides furnishing the various secretions, such as bile, urine, semen, perspiration, Stc, which, by a process alike wonderful and mysterious, are elabo- rated in organs constructed especially for the purpose, through the extreme ramifications of the arterial system. Above all, blood is the medium through which the spirit of life itself is elimi- nated and diffused over the body : every part owing it vitality and susceptibility of action to a contiimal fresh supply of this 'fluid. These important purposes served by the blood, necessarily tending to a consumption as well of its material quantity as of its vital principle, it became necessary that means should be provided in the animal economy for the replenishment of both these losses. Accordingly, we find one system of parts formed for the supply of fresh blood ; another for the purpose of the vivification of the fluid. This latter function is performed by the RESPrRATORv SYSTEM. The lungs, constituting that system, are two bulky bodies, in structure bearing much resemblance to a honeycomb, through whose cells a large proportion of the blood is conducted by the pulmonary vessels at every round of the circulation, in order that it may be exposed to atmospheric air, and from its in- fluence derive those vital properties that render it fit for the sup- XX INTRODUCTION. port of heat and life in every part through which it has subse- quently to circulate ; experience proving to us, that deprivation of blood to a part is followed first by the loss of heat, and ultimately of its vitality. In what this extraordinary influence of the air upon the blood consists, we are only vaguely informed : in truth, we know but very little more for certain concerning it than the palpable change of colour the blood undergoes, from a very dark to a bright scarlet red. To make up for the expenditure in the quantity of blood, we find a number of organs provided, comprehended under the head of the DIGESTIVE SYSTEM ; the ultimate object of whosc Combined operation is, the transmutation of the food into a fluid fit for becoming blood. The organs concerned in the process of digestion are — the mouth, in which the food is broken down and masti- cated by the teeth, and at the same time mixed with saliva; the 'pharynx, which receives the food from the mouth, and by the act of deglutition transmits it to the esophagus, the tube that conducts it into the stomach. Within the stomach, the food becomes converted into a uniform homogeneous mass, termed chyme ; and thus becomes prepared for its further passage into the intestines, in which, from the admixture of bile coming from the liver, and pancreatic juice from the pancreas, a further change takes place in the alimentary mass, attended by a spon- taneous separation of it into such parts as are veritably nutritious, and such as are excrementitious, or only fit for being ejected out of the body. The nutritious particles assume the appearance of a milky juice, to which anatomists have given the name o^ chyle ; and the process by which it is produced is denominated chylijicatiun. This brings us to the consideration of the ABSORBENT system : the absorbent vessels being the conductors of the chyle from the cavity of the intestines into the veins, in which it becomes mingled with the general mass of blood. Independently of this, however, the absorbents are employed in removing old, decayed, or worn-out parts of the body, at the time that the arteries are restoring the loss by the deposition of new material ; so that, in point of fact, the body is undergoing a continual repair, or rather renovation, and thus is maintained in perpetual vigour and aptitude for action. INTRODUCTION. jcxi The old wom-out material, together with other matters conveyed into the circulation, having now become useless and excrementi- tious, we find a channel for their expulsion in the urinary SYSTEM. This includes the kidneys and the bladder; the former being organs of secretion — by which is meant, organs having the power, by an action peculiar to themselves, of separating a sub- stance or fluid from the blood altogether different from the blood itself, and which either answers some important purpose in the animal economy, or becomes the medium for the ejection of useless or excrementitious matters ; the latter, simply a reservoir for the urine, containing it until convenience may suit for its discharge. In order for the animal machine, thus constituted, to be set in action, the nervous system becomes necessary ; that system which is the source of all sensation, as well as of all motion, and by which the animal is signally elevated beyond the vegetable creation. Sir Charles Bell, who has thrown such splendid new light upon this department of anatomy, arranges the nervous system in four classes: — First, comprising nerves of sensation; second, nerves of voluntary motion; third, nerves of respiratory motion ; fourth, nerves of the sympathetic system, by which are regulated the functions of nutrition, growth, and decay, and whatever is directly necessary to animal existence. The simplest form of nervous system is found to consist in a central ganglion, with a single nerve attached to it ; and is exhibited in animals whose organs of motion are found to be imperfect. But, should the creature possess organs of progression, and be endowed with organs of sense in addition, then nerves and ganglia are super- added, and a sensorium or brain is formed, which becomes at once the seat and source of all motion and sensation, the throne of reason, and grand focus of every intellectual faculty. In this manner, " Nature, in her productions slow, aspires By just degrees to reach perfection's height." Intimately in structure connected with, and in function entirely dependent upon, the nervous system, is the sensitive system ; comprehending the nose, the ei/e, and the ear. Were it not for the nerves interpassing between these organs and the brain, we could xxii INTRODUCTION. neither smell, nor see, nor hear ; and in proportion as these senses in different animals are acute, so we find the nervous structures of their individual organs to be more or less developed. The nerves belonging to the sensitive organs are not included in the foregoing classes: possessing the peculiar faculties of taking cognizance of odour, light, and sound, they differ as much from the nerves of common sensation as Sir Charles Bell has demon- strated the latter to do from those of motion. Exclusively of the nervous influence, the anatomical mechanism of the several organs included in the sensitive system, is no less wonderfully than admirably adapted to those ends which, in each of them, it is designed to answer ; and rises far more beyond all human art and contrivance than it is possible for the mind of man to conceive. That the hound should be able, with fatal fidelity to his prey, to pursue the evanescent odour of footsteps, is owing to a faculty possessed by the nose ; but one equally inexplicable to us, with the extraordinary telescopic and micro- scopic powers possessed by the eye, or the finer and more delicate sense inhabiting the ear. The term of life of every animal being limited to a more or less distant period, according to its kind, it became necessary, in order to guard against annihilation, to make provision for the procreation of the species. In the higher classes of animals, generation is effected by concurrence of the sexes, the organs for the purpose being different in them respectively, though recipro- cally adapted to the same end ; but in some animals of a lower grade, the sexes are found combined in the same individual, and generation takes place without any copulative act whatever. In the animals by which we are surrounded in common life, we find a male and female sex ; and these are distinguished, in an ana- tomical point of view, by the possession of organs of a totally dif- ferent character. In the male we have the testicles, which secrete the peculiar fluid from the blood, known by the name of semen ; and the penis, an organ formed for the conveyance and transmis- sion of the semen into the womb of the female ; besides seminal ducts and reservoirs to contain the fluid until it is wanted. In the female we find a vagina or canal leading into the uterus or womb ; attached to the horns of which by two serpentine tubes, called INTRODUCTION. xxiii the Ffil/opiait, are two oval bodies, smaller than the testicles in the male, named the ovaries, or female testicles, in which it is now ascertained the germ or first rudiments of the forthcoming foetus are generated. The organs of the female are set in action hy the stimulus of excitation they receive from the seminal fluid of the nmle ; and the result of a long, tedious, and mysterious jDrocess is, a foetus — a prototype of its parents. Covering all and clothing all, we have the skin with its coat of hair ; which two parts, along with the cellular membrane and fat, we have ranged in a system we have denominated the tegu- MENTAL. The cellular membrane itself may be regarded in the light of an inlenial covering to the body ; for it clothes or lines the inner surface of the skin, being the medium of connexion between the common integuments and the parts subjacent. The fat likewise is much intermingled with the cellular membrane, and answers the purpose of a covering ; as well as that of filling up vacuities and interstices, and giving a degree of rotundity and beauty to the form which the animal would much lack without it. Lastly, comes under our notice the system to which we have prefixed the epithet of plantar; meaning thereby to denote, that it embraces the four feet — the pedestals upon which repose and move the four limbs or columns of support. Though plain and unobtrusive in their outward aspect, the feet will be found to exhibit an internal mechanism worthy of the study and medita- tion of a medical philosopher of the highest pretensions : indeed, we are hardly going beyond our warranty in asserting, that in no part of any animal shall we find a structure exhibiting more beauty of design than is displayed in the anatomy of the horse's foot. In addition to this consideration, however, we, as veteri- narians, are enjoined, by an imperative duty consequent upon its importance in a pathological point of view, to examine this part with more than ordinary solicitude ; thereby, not only that we may obtain a more correct insight into the nature of its diseases, but be enabled to exercise a scientific controul over the mechani- cal operations of the farrier. ERRATA. Page 91 — For anterior read posterior maxillary region. P 142 1 14? (The French names of the muscles are, by mistake, placed \ before the English names. Page 202, line 3 — For peroneal read perineal artery. THE ANATOMY OF THE HORSE. SECTION I. OSSEOUS SYSTEM. OF THE SKELETON. THE SKELETON is the simple, jointed, bony frame, divested of the soft parts and dried. There are two kinds : — L The natural skeleton is that in which the bones remain attached to each other by their natural connections, denomi- nated ligaments. 2. The artificial skeleton is made by separating the bones from all their connections, by macerating or boiling, and after- wards joining them again in their natural order and relative po- sition, by wire or other means, so as to imitate as nearly as possible the natural one ; over which it possesses the advantages of cleanliness, distinctiveness, and more or less artificial mobi- lity of the joints. Construction. Leaving the head and neck out of considera- tion, the entire frame will be found to come with sufficient prox- imity within the limits of a square, formed by drawing perpen- diculars, touching the extreme parts before and behind, from a horizontal line level with the surface of the ground, to another parallel to it touching the summits of the back. A line extend- ed perpendicularly through the middle of this square, divides the frame into two nearly equal parts, and falls upon the ground (represented by the inferior horizontal line) equidistant from the four points of tread ; a line drawn in the horizontal direction through its middle, includes the trunk within the upper divi- sion of the square, the space formed by the limbs, as well as the limbs themselves, within the lower section. The limbs re- present four columns supporting the body, the bones composing which, though many of them are obliquely placed, are found, on taking the aggregate of their directions, to maintain their bearing in lines parallel to the common centre of gravity, which I ANATOMY OF THE HORSE. ' may be said to be represented by the perpendicular line extend- ed through the middle of the square : the angular position of these bones renders their motions more extensive and facile, at the same time that they, so placed, present convenient and powerful levers for the operation of the muscles. Furthermore, the bones forming the limbs are, superiorly, lengthy and fevv^ in number ; whereas, below the fetlock, they are small and consist of several pieces : the rationale of which is, that the long bones are well adapted for extent of motion; the short ones, for re- sistance and multiplicity of movements. The head and neck operate as a burden, in addition to half of the trunk, upon the fore limbs; although the hind limbs appear the greatest and most capable of resistance : this apparent incongruity is remov- ed when we come to learn that the latter constitute the power- ful engines of progression. Of the multiplicity and variety of pieces or distinct bones of which the skeleton is composed, most are found to be double, or to exist in pairs ; such are the ribs, most of the bones of the head, and all those of the limbs : there are however several single bones ; and these may be regarded as the key-stones of the fabric, iDeing in reality the media through which the two lateral halves of the skeleton (composed of the bones in pairs) are united together into one entire structure. In this arrangement, the symmetry of the whole is preserved most completely, even as completely as if every bone had had a fellow ; since both sides or longitudinal halves of the single bones exactly correspond. The bones so far influence and determine the form of the soft parts that in very many (perhaps the majority of) instances, the animal is recognised in the appearance of the skeleton ; in other examples however this is not so remarkable ; in all the re- semblance can be traced only in certain parts. In general, the head, chest, and legs — below the knees and hocks, present striking outlines of the same parts in the living animal ; where- as, the neck, loins, arms, and haunches, have few or no points of similitude. Division. THE SKELETON is composed of 238 bones, and is divided into trunk, head, and extremities. The Trunk is subdivided into spine, thorax, and pelvis. The Head comprises the cranium and thejace. The Extremities are four in number: two fore and two hind. ANATOMY OF THE HORSE. TABULAR ENUMERATION OF THE BONES. TRUNK. SPINE. Cervical Vertebrae Dorsal Vertebrae Lumbar Vertebrae Total 30 THORAX. Sternum Ribs, 18 on each side Total 37 PELVIS. Ossa Innominata Sacrum Coccygeal Bones, " varying from 13 to 18 16 Total 18 HEAD. CRANIUM. FACE. Frontal Bone. 1 "Nasal Bones . ^^ Parietal Bones — pair 2 Superior Maxillary Bones Occipital Bone Temporal Bones — tioopaim . 1 4 1 Inferior Maxillary Bones Malar Bones ■lis Ethmoidal Bone 1 S " Lachrymal Bones Sphenoidal Bone 1 P Palatine Bones . Superior Turbinated Bones Inferior Turbinated Bones . 10 r Malleus ) Vomer — sins'le . . 1 Bones of ) Incus ( 4 Lower Jaw " . . . 1 the Ear ] Stapes f ( Obiculare ) IS — Teeth . . . 40 Total 14 Os Hyoides ... 1 Total 59 EXTREl WITIES. "" FORE. HIND. Humerus} Shoulder Bones . 2 Femur — Haunch Bone . , 1 VsiitWv.— Stifle Bone . . 1 Itr ] ^^'^ Bones . 2 Kbl } TUgKBon^s . 2 Bones of the Knee. Astragalus . "J Os calcis . { IT I n Cuboid Bone . > I^ockBones 6 ^ Scaphoid '.\ ^\ Pisiform 1 ^ Lunar ;| | Trapezoid ( ^ Cuneiform .«• Os Magnum , - ! Trapezeum ' ^ ; Unciform J 8 3 Cuneiform Bones J The bones below the hock cor- Large Metacarpal Bone \'^l\ 2 Small Metacarpal Bones \^§,] 3 respond in name and number to those below the knee, viz. . 9 Sesamoid 'Ronts— Fetlock 2 — Pastern Bone 1 Total 19 Coronet Bone , 1 — Coffin ) L^ , n Navicular } ^'^'^ ^'"'^'^ 2 Total 21 4 ANATOMY OF THE HORSE. CERTAIN TERMS used in descriptive anatomi/ may re- quire some explanation. The anatomist views the body in the erect position ; the limbs preserving, in the direction of the tendency of the weight, per- pendicular lines in respect to the trunk, and parallel lines in re- gard to the correspondent fore and hind feet, and also, in the transverse direction, in relation to one foot to its fellow ; the head and neck maintaining theirnatural degrees of elevation and curvature; the tail erect. In this position, the anatomist as- sumes, to aid him in his descriptions, that an imaginary plane extends through the body, bisecting it into lateral halves ; this is continued through the neck and head, and descends between the legs. The correlative terms, superior- and inferior, anterior and posterior, require no elucidation, unless it be in regard to the head and neck : the line bounding the superior regions is considered to extend from the tip of the coccyx over the occiput to the upper lip ; that forming the inferior boundary, from the lower lip, along the under jaw, down the neck, and along the belly, with some interruption in the croup, to the extremity of the tail. The adoption of the compounds of these terms, leads to still further accuracy in description : such are antero-superior, antero-inferior, supero-anterior, infero-anterior, &c. Antero-supe- rior denotes the anterior compartment of the superior region : supero-anterior, the superior compartment of the anterior region ; and so on. Inner and outer express relation to the bisecting plane, running through the middle, median or mesian, region: but the compounds mesio-superior, rnesio-posterior, &c. have no reference whatever to the middle regions : they simply imply the middle compartments of the superior and posterior regions. According to this arrangement, every distinct part, the head, neck, shoulder, quarter, arm, thigh, &c. is divided, by imagi- nary lines, into five regions : — superior, inferior, anterior, poste- rior, and middle ; each of which is subdivisible into three minor compartments: e.g. the superior region is distinguishable, if lequired, into antero superior, mesio-superior, and postero- superior ; the anterior into supero-anterior, mesio-anterior, and infero-anterior; and so with the others. Without this explana- tion the anatomical detail, to follow, might prove perplexing or even unintelligible: by such preparation, the labour of the anatomist is abridged and facilitated ; the progress of the stu- dent smoothed and accelerated. OF THE TRUNK. The trunk coniprchcndb the vertebral chain, the thorax, and the pelvis. ANATOMY OF THE HORSE. I.— THE VERTEBRAL CHAIN. Also called the spine, vulgarly the back-bone, reaches from the occiput to the sacrum, constituting the bony structure of the neck, back, and loins, and consists of 30 separate pieces, denominated vevtebrce, which are classed, in accordance with the part they enter into the formation of, into cervical, dorsal, and lumbar. Co7i/iguration. It bears altogether a resemblance to an S, providing the letter be reversed, turned in the horizontal direc- tion, and an additional curve given to it; thus, ^--,_,'— . Pro- ceeding from the vertex with more or less crest-like curve, it sinks into a bend in the opposite direction at the posterior part of the neck; from this, in the back, it at first gradually rises, but shortly afterwards pursues the horizontal line, or even dips a little : in the loins, however, it rises very perceptibly, forming an arch of considerable extent, which, posteriorly, is completed by the declivity of the coccyx. OF THE VERTEBRAE IN GENERAL. Conformation. The vertebrae bear a common resemblance, one to another, manifested by the following general characters. Every vertebra is in form symmetrical, and presents middle and lateral divisions. \st. The middle consists of the body, a cylin- drical solid part, having a convex surface anteriorly, a concave one posteriorly, and both roughened by the implantation of the intervertebral substances ; the arch, extended transversely from the sides over the body, so as to include its superior surface ; and this surmounted by the spinous process ; lastly, the verte- bral, spinal, or medullary hole. 2nd. The sides present two transverse processes, jutting outward ; four articulatory pro- cesses, two anterior and two posterior, having smooth surfaces for articulation with those of the vertebrse next to them ; four notches, the excavations between the arch and the body, con- stituting, by apposition, with others in the contiguous vertebrae, the holes of conjugation. CERVICAL VERTEBRA. Larger than the others, and differ more remarkably in their individual conformation. — In nuniher, seven; and named ac- cording to their numerical order, beginning from the head : the first, however, has got the designation of atlas, and the second, b ANATOMY OF THE HORSE. of axis or vertebra dentata. — In Jigure, quadrangular. Body, oblong ; anterior surface of it, smooth, convex, heart-shaped, apex turned downwards ; posterior surface, correspondently concave. The vertebral hole is larger than in the other classes, and semi-oval in figure. Two spinous processes ; the crest or superior one is bifid, cleft and divergent posteriorly, united at a sharp angle anteriorly ; the inferior (the additional) spinous process is curved like an S reversed and inclined .^,^ ; being con- vex and prominent posteriorly, sharp-edged and curved upwards anteriorly. The transverse processes are very broad, but short, arise from the body as well as the arch, are bifid, presenting four projecting ends, two forwards, two backwards, and are each perforated by a foramen, which transmits the vertebral ar- tery and vein. The articular processes are large, directed hori- zontally forwards and backwards, and present broad surfaces for articulation ; those on the anterior looking upwards and inwards, those of the posterior downwards and outwards. The notches are found between the articular processes and the body. DORSAL VERTEBRAE. Volume, less than that of either of the other classes. — Num- ber, eighteen; (in some instances, nineteen;) distinguished by their numerical order, counting from the neck backwards. Body, small ; short, thick, and semi-circular ; flattened supe- riorly, prominent and edged inferiorly ; anteriorly, smooth, con- vex, and heart-shaped ; posteriorly, correspondently concave. At the junction of the arch with the body are situated four small cup-shaped articular surfaces, two presented forwards, two backwards, which in conjunction with those next to them form sockets for the reception of the heads of the ribs. The verte- bral foramen is of less diameter than in the neck, and is oval from side to side. Spinous process, long and flattened on its sides ; thick and triangular or prismatic at its root ; presenting a sharpened edge forwards, a flat or obtuse border backwards ; thick, irregular, and tuberous at its summit. Transverse pro- cesses, short and thick, incurvated upwards, and tuberous at their extremities; their sides presenting circular articulatory surfaces for the tubercles of the ribs. Articular processes, very short and proceeding from the roof of the arch : the anterior, face upwards ; the posterior, downwards and backwards. There are only two notches, and these are smaller than those of the cer- vical ; they are situated between the posterior articulatory pro- cesses and the costal surfaces upon the body. ANATOMY OF THE HORSE. LUMBAR VERTEBRA. Volume, between that of the cervical and dorsal, — Number, in some subjects five, in others six. Body, short and thick ; flattened superiorly, prominent inferiorly ; and bearing much re- semblance to that of a dorsal, only that it is something larger, is oval from side to side, and thicker anteriorly than posteriorly : its articulatory convexity in front and concavity behind assume also rather an oval than a heart shape. The vertebral hole is simi-circular, and of larger diameter than in the dorsal verte- brae. The spinous process is shorter than most of the dorsal ; has broad flat sides ; protuberates at the front of its summit ; and stands erect with a very slight inclination forwards. The trans- verse processes, stand out horizontally, at right angles from the body, slightly inclined in the form of arches ; are long and broad ; flattened above and below ; and gibbous at their extremi- ties. The articulatory processes, though small when compared with the cervical, are larger than the dorsal; they project from the roof of the arch in the horizontal direction : the anterior, protuberate at their extremities, are wide apart, and present concavities inwards ; the posterior, are nearer together, and pre- sent convexities outwards. The notches are similar to those in the dorsal vertebrae. PECULIARITIES OF THE VERTEBRiE. Of the cervical, four vertebrae are distinguished by peculiar characters. The First Vertebra, inappropriately named the atlas, (for the head is suspended from it instead of being supported by it,) is defective in the essential vertebral properties ; being sim- ply an irregular ring with broad projecting sides. It has no body; the place being in part supplied, in the articulated spine, by the odontoid process of the second vertebra, for the recep- tion of which, the infero-posterior part of the ring is made smooth and articulatory ; this somewhat reduces the dimensions of the vertebral hole, though it remains even then the most ca- pacious of any, and measures more from side to side than con- trariwise : its inferior surface is deeply impressed by the odon- toid ligaments. It has no superior spinous process, but there is a prominence in the situation of it; and the inferior spine is shorter, thicker, and more obtuse than the others. The trans- verse processes are broad undivided lateral plates, sloping downwards, perforated by three pairs of foramina : — one posteri- 8 ANATOMY OF THE HORSE. oily to their middles, through which run the vertebral arteries ; two through their anterior parts, one of which is directed out- wards and downwards, the other runs inward and opens into the vertebral canal : the latter give exit to the sub-occipital nerves. The anterior articular processes are represented by four horizontal projections, with semicircular borders, whose internal surfaces are smooth, look towards each other, and together form two lateral concavities for the reception of the condyles of the occipital bone. The posterior articular processes are formed into broad, triangular, convex, smooth surfaces, looking backwards, with an inclination inwards. The Second Vertebra, or axis, also denominated the den- tata (from a peculiar projection anteriorly, which in the human subject is resembled to a tooth) is the largest of the cervical class, exceeding the others however more in length than in breadth. The body is elongated, and (in place of a hemi-spherical termi- nation) anteriorly, presents the remarkable process named the odontoid, which is smooth and convex below, where it articu- lates with the infero-posterior part of the ring of the atlas ; ex- cavated and impressed above by the odontoid ligaments. The spinous process is very broad, and forms an elevated crest, bifid posteriorly. In front of the body are two oval foramina, corresponding to the holes of conjugation. The transverse pro- cesses are slender, and have only posterior extremities ; the holes through them are also small. The anterior articular pro- cess are represented by two broad ovoid smooth surfaces ; unit- ed with the sides of the odontoid projection; and sloped off backwards, both above and below, to admit of free motion be- tween them and the posterior articular surfaces of the atlas. The Third, Fourth, and Fifth possess the genuine cha- racters of cervical vertebrse, and closely resemble one another ; the third however has commonly a more elevated superior spine than either of the others, and is narrower across the mesio- superior part of the body, measuring from the roots of the arti- cular processes : which dimension increases in the fourth, but is greatest in the fifth. The Sixth has no inferior spine; and its transverse pro- cesses are trifid, consisting each of three eminences. The Seventh Cervical Vertebra is the shortest, and in its general conformation partakes of the character of the first dorsal. Its body posteriorly presents two semilunar arti- cular hollows for the formation of the sockets for the ribs. The superior spine is elevated and sharp. The transverse processes are short, obtuse, and not perforated. ANATOMY OF THF. HORSE. 9 Of the dorsal vertebrse, the distinctions arc less numerous and striking. The First Dorsal Vertebra has a cervico-dorsal confor- mation, manifested in the form of the body, the length and sharpness of the spinous process, the protuberance and single- ness of the transverse processes, the breadth and direction of the articular processes. The Second Dorsal Vertebra differs from the others in the curvation of its spine backwards, against that of the third ; and in the breadth and direction of its anterior articular processes. The other dorsal vertebrse are distinguishable principally from the comparative form and length of their spines. The first spine is short compared to the second, and terminates in a sharp apex; the second has a broader extremity, and in some instances is bifid ; the succeeding grow broader, and more ob- tuse at their ends until they assume a form similar to those of the lumbar vertebrm. The fifth spine is generally the longest; the 12th or 13th the first that assumes the lumbar character. M. Girard correctly observes, also, that the articular depres- sions upon their bodies for the heads of the ribs are less deeply marked as we proceed backwards. The Efghteenth Vertebra, and the seventeenth gene- rally, have no articular surfaces upon their transverse processes, but ivhole ones upon their bodies for the ribs. In the lumbar region, The First, Second, and Third have broader spines, and their articular processes are nearer together; The Fourth possesses a surface for articulation with the fifth on each trans- verse process; The Fifth assumes somewhat of the character of the first piece of the sacrum, and has four surfaces for arti- culation on its transverse processes; two anteriorly, opposed to those on the fourth ; two posteriorly, adapted to similar sur- faces on the sacrum. general remarks on the vertebral chain. The Spine exhibits for consideration four surfaces and two extremities. Surfaces — Extremely irregular, presenting various emi- nences and projections, hollows, grooves, and foramina. Superior Surface — In the neck, broad and (from the absence of spinous processes) preserving a general level ; the equality being interrupted only, anteriorly, by the spinal crest of the 10 ANATOMY OF THE HORSE. vertebra dentata ; posteriorly, by the spine of the seventh ver- tebra. In the back and loins, the surface offers a continued series of spinal projections; long, with broad tuberous ends, sloping backward, in the withers ; short, erect, with broad sides, and terminated by oblong ridges, posteriorly. On the sides, running close to the roots of the spinous processes, extending from the dentata to the last lumbar vertebra, are the vertebral grooves, filled by the spinal and semi-spinal muscles belonging to the neck, back, and loins. Inferior Surface — Presenting great uniformity from the gene- ral regularity of the inferior cervical spines and the angu- lar portions of the bodies of the dorsal and lumbar vertebrae ; excepting, that the sixth cervical spine is defective, and that the one or two last lumbar vertebras are flattened inferiorly. Lateral Surfaces — Very irregular. Presenting, in the neck, broad, bifid, transverse plates, with capacious vertebral channels or grooves between them and the articulatory processes above, which are occupied principally by the complexus major. Un- derneath these grooves run the foramina for the vertebral blood- vessels ; and through their sides pass the holes of conjugation. — In the back and loins the holes of conjugation are situated immediately behind the transverse processes; and the lumbar vertebrae alone possess lateral vertebral grooves, but which are very narrow compared with those along the neck. Extremities — Broad and articulatory. The anterior excavat- ed to receive the occipital condyles ; the posterior, transversely oblong, presents three smooth surfaces for articulation with the sacrum. Vertebral Canal — Capacious and semi-oval through the neck ; transversely oval and small through the back ; semi-circular through the loins, and of greater diameter than in the back, less than in the neck. United, anteriorly, with the cavity of the cranium ; continuous, posteriorly, with the sacral canal. Con- taining the spinal marrow and its membranes. H.— THE CHEST. (THORAX.) The thorax or chest is the ample conoid cavity constituting the anterior part of the trunk, formed by the ribs laterally and the sternum inferiorly, in which are contained the organs of re- spiration and circulation. THE RIBS. (COSTTR.) Number. Thirty-six ; ranged in pairs, eighteen on either ANATOiMY OF TtlE HORSE. 11 side : occasionally there exist ihirty-eigbt, and even forty ribs. They are distinguished by their numerical order, counting from before backwards. Co)iJ'ormation. In general similar : they are elongated, curv- ed or twisted, convex along their outer sides, concave along their inner, and taking a direction from within outwards and from above downwards; they vary however in their length, de- gree of curvature, and obliquity of direction. Division. Into true or sternal ribs, and false or asternal ; the former, nine in number, being those whose cartilages are actu- ally inserted into the sternum ; the latter, the remaining nine, being only connected therewith through the intervention of others. Each rib possesses two extremities, two surfaces, and two borders. Extremities. The superior or vertebral, comprehends — 1. The head, the protuberant or antero-superior portion, presenting two convex smooth surfaces, for articulation with the bodies of the vertebree between which it is received, and these divided by a rugged notch, into which is fixed the interarticular ligament of the head, 2. The neck, the contracted part, supporting the head. 3. The tubercle, the prominence behind the head, at the root of the meek, which has a flat smooth surface for articu- lation witii the transverse process of the hinder vertebra con- nected with the head. 4. In front of the tubercle, running across the back of the neck, is a groove, along which make their exit branches from the intercostal vessels and nerves. The in- ferior or sternal extremity swells a little in volume, and is of less compact or more porous texture than the bone above: it is terminated by an oval roughened depression ; from this takes root the cartilage of the nb, which thence proceeds at an angle more or less obtuse and rounded to the sternum. Surfaces. The external is convex and more or less uneven. The ribs do not form regular arches ; they project outwards from the spine, and then curve suddenly downwards, the poste- rior ones at the same time inclining backwards : the place where the rib commences its descent, the most curved or crooked part, is named its angle. In all the long ribs this surface, anteriorly, is more or less grooved for the attachment of the external inter- costal muscles. — The internal surface is uniformly concave, smooth, and polished. It is lined by the pleura. Borders. With the exception of the first and last ribs, the anterior borders are thin and sharp ; the posterior, obtuse and rounded : the former give attachment to the intercostal mus- cles ; the latter, along the upper half however only, present grooves in which run the intercostal vessels and nerves. 12 AiXATOiMY OF THE HORSE. Peculiarities. The ftrst is the shortest and tliickest of the ribs ; its upper part is rounder, and its lower broader and more expanded than any other : it is but httle and irregularly arch- ed, and the concavity of its arch is turned directly forwards. The second is a remarkably straight rib, being only curved in its neck. From the second the ribs progressively increase iix breadth to the seventh, in length to the ninth, and in curvature to the very last ; the eighteenth being in proportion to its length the most crooked rib : from the tenth, the ribs grow shorter, narrower, and more obtuse or rounder in their borders. The posterior differ also from the anterior ribs in being curved throughout their entire length ; whereas the former are only very perceptibly bent at their angles. In the eighteenth, and sometimes in the seventeenth rib, the articulatory surface of the tubercle is confounded with that of the head, and the neck is wanting. The Cartilages of the Ribs, properly so called in the young subject, receive depositions of osseous matter as the animal advances in life, until at length they acquire rather the charac- ter of spongy fragile bones than cartilage. They correspond in number to the ribs, and like them increase in length from the first to the ninth or tenth, after which they progressively de- crease ; but this is liable to variation: the first cartilage is re- markably short; those belonging to the true ribs are in general not very long, but broad, thick, and resisting; those proceeding from the false ribs are on the contrary mostly very long and comparatively slender, and incapable of offering much resistance — are in fact so formed and connected that they admit of considerable motion. lllE BREAST-BONE. (STERNUM.) Conjonnation. The sternum (being a single bone) is symme- trical in its form, shaped, altogether, like the keel of a ship ; posteriorly, flattened from above downwards; anteriorly, from side to side. It is composed of seven irregularly formed bones, and of the ensiform and cariniform cartilages. Division. Into four surfaces and two extremities. TAe Superior and Inferior Surfaces are pyramidal in figure, being broad posteriorly, contracted into borders anteriorly : the former, slightly concave, terminates between the cartilages of the two first ribs ; the latter, irregularly convex, ends in the ca- riniform cartilage. The Lateral 'Surfaces are broader anteriorly than posteriorly. The three foremost bones present broad, superficial, lateral con- ANATOiMV OF THE HORSE. 13 cavities; the four hiiidermost, projecting lateral borders, which incHne downwards and form the boundary lines between the in- ferior and lateral surfaces. The indentations upon the fore and hind parts of the separate bones, form, in the united state, lateral concavities for the reception of the cartilages of the ribs : the hindermost bone, itself, receiving two entire cartilages. The Extremities are constituted of projecting cartilages. — The Carinifoim Cartilage, arising in a curve from the inferior border, forms a prominent and remarkable convexity in front, flattened on either side, and affords attachment to the sterno-maxillares and sterno-thyro-hyoidei. — The Xiphoid or Ensiform Cartilage is fixed to the last bone, and assumes a form in some measure correspondent therewith, being broad and flattened above and below : it is terminated however by a thin border, to the figure of which it owes its name, though this is subject to much variation. GENERAL REMARKS ON THE THORAX. Form. That of a truncated cone slightly incurvated, the basis of which is cut obliquely, from above downward and from behind forward ; the point of the apex cut off perpendicularly ; the axis running in a direction from the front backward and downward. Dimensions. The antero-posterior diameter is the greatest. As we approach the apex the perpendicular more and more ex- ceeds the lateral measurement; towards the basis, in conse- quence of the sides diverging, these two diameters become about equal. Division. Into two surfaces and two circumferences. Exterior Surface — Presenting, anteriorly, the cariniform car- tilage projecting from the sternum, with its sharp edge turn- ed downwards, for affording attachment to the pectoral mus- cles; laterally, the convexities of the costal arches and their cartilages, and between them the intercostal spaces filled by the intercostal muscles ; superiorly, the dorsal spines, transverse processes, and vertebral grooves; inferiorly, the sharpened lower border of the sternum, terminated by the xiphoid cartilage. Interior Surface — Formed, below, by the incurvation of the sternum and xiphoid cartilage; on the sides, by the smooth concavities of the ribs together with their cartilages ; above and along the middle, by the angular, smooth, descending por- tions of the bodies of the dorsal vertebraB; above and along either side, by an oblong fossa formed by the angles of the libs, into which are received the superior thick borders of the lungs. 14 ANATOMY OF THE HORSE. AtUerioi' Circumference — Perpendiculaily semi-oval, the small end turned downward ; bounded by the first dorsal vertebra, the first pair of ribs, and the sternum ; making a passage for the trachea, esophagus, longus colli, carotid arteries, jugular veins, vertebral arteries and veins, axillary arteries and veins, par vagum, sympathetic and recurrent nerves, and thoracic duct. Posterior Circumference — Wide, but most extensive from above in the antero-inferior direction ; bounded by the last dorsal vertebra, the ensiform cartilage, the two last ribs, and the false cartilages; affording attachment to the abdominal muscles, but more particularly to the diaphragm, by which the intervening space is occupied. HI.— THE PELVIS, Forms the posterior boundary of the trunk ; is connected with the spine and supported by the femoral bones ; presents a large, irregular cavity, open before and behind, in which are con- tained part of the intestines and the urinary and genital or- gans; and is composed of four bones: — the sacrum and os coc- cygis, and the two ossa innominata. THE RUMP-BONE. (oS SACRUM.) Situation. At the superior part of the pelvis, continued from the vertebral chain between the ossa ilia. Figure. Resembling the lumbar portion of the spine, from which it declines with a slight bend, presenting a convexity externally, a concavity internally, thereby augmenting the area of the pelvic cavity. Division. Into two surfaces, two borders, a base, and an apex. Superior Surface. Very irregular. Presenting, \st. On the mesian line, five considerable eminences, corresponding to the lumbar spines, from which they differ in sloping in an opposite direction, in increasing in breadth, while they diminish in length, from first to last. 2ndlij. Laterally, two superficial grooves, pierced by the four superior sacral foramina, through which pass out the superior sacral nerves. Inferior Surface. Regular, smooth, and slightly concave. It presents — Four transverse lines of demarcation, denoting the original division of the bone into four separate pieces. These are bounded laterally by two superficial grooves, pierced by four pairs of inferior sacral foramina, through which make exit the corresponding sacral nerves. ANATOMY OF THE HORSE. 15 Lateral Surfaces. Thick anteriorly, growing thin posteriorly, and presenting slight protuberances, (corresponding to the ver- tebral transverse processes,) which serve for the attachment of the sacro-iliac ligaments. Base. Composed of a middle- and two lateral parts. The middle presents a convex articulatory surface, transversely oval, for adaptation to the last lumbar vetebra ; surmounted by two articulatory processes, between which are received the two last of that name of the loins ; and having on its sides two notches of conjugation for the last pair of lumbar nerves. The lateral or anterior transverse processes, broad, thick, and projecting, and triangular in figure, point forwards and upwards as well as outwards : superiorly, they have two surfaces of articulation for the ossa ilia; anteriorly, two others which unite with the last transverse processes of the loins. Apex. Presents* also an oval surface, which articulates with the foremost bone of the tail ; having on its sides two notches, for the fifth pair of sacral nerves ; and, farther removed out- ward, two little posterior transverse processes. The Sacral Canal for the spinal marrow is triangular in figure, and gradually contracts its diameter from before back- wards. Development. In the young subject this bone consists of five distinct and separable pieces, united, one to another, by a fibro- cartilaginous substance which in the adult is converted into bone. THE TAIL-BONES. (oSSA COCCYGIS.) Situation. Behind the sacrum, to which the coccyx forms an appendix. Fonn. (Of the coccyx entire.) Conical, elongated, and more or less curved. Co)for?nation. The coccyx or tail is constituted of several small bones resembling vertebrae, varying in size and develop- ment, and also in number from thirteen to eighteen. Division. As a whole, the coccyx presents for consideration two surfaces, two borders, a base, and an apex. Superior Surface — Convex. The two and sometimes three first bones possess complete bony arches, from which arise one or two spinous eminences giving attachment to the erectores coccy- gis, and consequently they possess an uninterrupted spinal canal ; in the following two or three pieces, the spinal arch becoming gradually more defective, the closed canal degenerates into a 16 ANATOMY OF THL; HORSE. channel, open superiorly, and that in the four or five subsequent pieces into a simple groove; until at length all traces of such formation disappear. Trtferior S^/r/ctce— Concave. The first bone possesses breadth and flatness inferiorly, the same as a lumbar vertebra : the others display less and less of the vertebral character back to the fifth or sixth, after which they present angular borders. Into these parts are inserted the depressores coccygis. Lateral Borders. The three or four anterior bones have trans- verse processes, increasing in length with their priority ; which give attachment to the sacro-sciatic ligaments, and also to the curvatorcs and compressores coccygis. The fifth and subse- quent bones are nothing more than cylindrical forms, and differ in little else than in a regular respective diminution in volume. Base — Presents an oval surface for articulation with the end of the sacrum ; and also two little articulatory processes, receiv- ing between them correspondent sacral eminences ; and below these processes two notches, for the transmission of the fifth pair of sacral nerves. Apex — Obtuse and rounded. THE HIP, HAUNCH, OR EDGE BONES. (OSSA 1 N N OM 1 N ATA *. ) Situation. Forming the lateral and inferior parts of the pelvis. Form. Very irregular : large and flat; broad at the extre- mities, which turn in different directions ; middle portion con- tracted. Division. Into two surfaces and four borders. J'he External or Dorsal Surface — Divided by the contracted portion in the middle into two parts. The anterior part, also distinguished as the dorsum ilei, is even and smooth, slightly concave, triangular in figure, and faces outwards and back- wards : it affords attachment to the glutei, maximus et in- ternus. — The posterior division presents, outwardly, the ace- tabulum or cotyloid cavity, hemispherical, nearly three inches in diameter, looking outwards and downwards, surrounded by a prominent lip of bone which is interrupted below by a notch, and having a roughened depression in its middle into which is implanted the round hgament confining the head of the os femoris within the cavity ; above and in front of the acetabulum the bone is depressed and roughened in two places from which takes root the bifurcated tendon of the rectus * Literally, unnamed bones ; but answering to the other English appella- tions. ANATOMY OF THE HORSE. 17 fenioris ; to the inner side of and below the cavity is the obtura- tor foramen, a large oval opening, closed by an expansion of ligament, through the anterior part of which is a perforation for the passage of the obturator vessels and nerves. Behind the foramen the surface is broad, even, and smooth, and gives origin to the abductor muscles of the thio-h ; above the foramen, it is smooth but rounded, over which part play the obturator inter- nus and gemelli. The Internal or Ventral Surface — Divided the same as the external. The anterior part faces inwards and forwards, is slightly and unevenly convex, has a superficial scabrous depres- sion posteriorly, marking the place where the bone rests upon, and has strong ligamentous attachment to the transverse pro- cesses of the sacrum : the remainder of the surface below is occupied by the iliacus, the part above being opposed to the sacrun). — The posterior part is subdivided by a prominent border (upon which is a rough mark showing the point of insertion of the psoas parvus) into a small triangular superficial concavity, look- ing forwards, which gives origin to the sartorius, and an exten- sive but irregular one directed upwards; this last is much con- sumed by the obturator foramen, posteriorly to which the surface is remarkably smooth and slightly excavated for sustaining the bladder. Anterior Border — Sigmoid in figure, slightly concave and thin in the middle; terminating, behind, in a sharp salient angle, the posterior iliac spine ; before, in a thick quadrangular part which gives rise to four eminences: the two larger ones are the antero- superior and antero-inferior iliac spines ; the two smaller, tubercles or appendices to them. The border itself is called the crista ilei. It affords attachment to the longissimus dorsi, obliqui abdominis, externus et internus, and transversalis abdominis. Posterior Border — Having its anterior third thick and scab- rous, where it is united through the intervention of fibrous car- tilage with its fellow, forming the symphysis pubis ; posteriorly to this, it grows thin, which part has also a ligamentous connec- tion with the opposite bone, and afterwards recedes from its fellow, terminating outwardly in a thick, oblong, waving, rough- ened prominence, called the tuberosity of the ischium, to which are attached the adductor magnus, biceps femoris, and abduc- tor tibialis, and also the sacro-sciatic ligaments. The Superior Border — Extending from the posterior iliac spine to the ischiatic tuberosity, is waving in its course, forming an ir- regular semi-circle, and presents along its anterior two-thirds a sharp edge, which opposite to the acetabulum is roughened by the implantation of the sacro-sciatic ligaments ; after this it is D 18 ANATOMY OF THE HORSE. rounded by the play over it of the obturator internus and ge- melli, and at length ends insensibly in the tuberosity. — There is a lesser superior border, running from the tuberosity to the acetabulum, whose posterior half is prominent, very sharp, and irregular, forming the ischiatic spine. The Inferior Border — Describes a sigmoid flexure : it extends from the anterior iliac spine to the symphysis pubis. Its ante- rior third is sharp ; about its middle is a medullary hole run- ning backward ; here it gives rise to two borders: one obtuse and smooth, ending at the edge of the acetabulum ; the other, more prominent and sharp, is the linea ilio-pectinea, or brim or boundary of the cavity of the pelvis, running onward to the symphysis. Upon its anterior part is a rough place, the ilio- pectineal eminence, marking the insertion of the psoas parvus ; posteriorly are two rough eminences, with a groove between them wherein run the united tendons of the psoas magnus and iliacus : to the outer one, the pubic spine, is fixed the external chord of the abdominal ring. Connection. Anteriorly and inferiorly with the sacrum ; pos- teriorly and inferiorly and in the middle with each other ; out- wardly with the femoral bones. Development. In the fcetus this bone is separable into three distinctly formed pieces : — the ileum, the largest division, the triangular plate in front ; the ischium, the part projecting back- wards ; and the pubes, the inferior and middle portion. They all contribute to the formation of the acetabulum ; the ischium and pubes together form the obturator foramen. These parts speedily complete their bony union after birth ; and the ischium and pubes the soonest. OF THE PELVIS IN GENERAL. Division. Into exterior and interior, inlet and outlet. The Exterior presents — in front, the crest and anterior and posterior spines of the ileum ; behind, the divergent tuberosities of the ischium ; on the sides, the triangular planes of the ilea which are clothed by the gluteal muscles, the acetabula, and, between them and the ischiatic tuberosities, the rounded smooth surfaces of the ischia, over which play the rotating muscles of the haunch ; above, the sacrum ; below, the symphyses of the pubes and ischia ; laterally and inferiorly, between the symphy- ses and the acetabula, the foramina obturatoria. The Interior is divided into two compartments by a prominent circumferent line forming the brim of the pelvis : the open irre- gular space before this line, is the inlet or entry ; behind it, com- ANATOMY OF THE HORSE. 19 raences the cavity of the pelvis, which again is bounded poste- riorly by the outlet. The lateral walls of the cavity are formed principally by the ilea; the ischia and pubes, united at their symphyses, including the obturator foramina, are mostly con- sumed in completing the cavity below ; while the sacrum alone constitutes the superior boundary. The supero-inferior diameter of the brim in the young subject exceeds the lateral ; in the adult mare these two diameters, and also the antero-posterior length of the cavity, measuring from the brim to the extreme points of the ischiatic tuberosities, are about equal — about ten inches. The Inlet displays — laterally, the ilea, with their thin project- ing anterior spinous processes; superiorly, the promontory of the sacrum and the sacro-iliac articulations ; inferiorly, the grooves for the psoas and iliacus, and the symphysis pubis. The Outlet presents three notches : two lateral, very exten- sive ; one middle, considerably smaller. The two former, named the great sciatic notches, constituted by the posterior borders of the ileum and ischium and the sides of the sacrum, are prin- cipally occupied by the sciatic ligaments, although they give transit to the pyramidal muscles, the gluteal and obturator ves- sels, and the sciatic nerves. The middle notch is the pubic arch, formed by the divergence of the ischiatic tuberosities : it is occupied in either sex by the urinary canal. OF THE HEAD. The head is an oblong quadrangular form, broad and flatten- ed on its sides, narrow and contracted anteriorly and superiorly, bulky at the opposite points, hollow interiorly. It is remarkable for the prolongation and capaciousness of the parts devoted to the formation of the nose and mouth, and for the diminished sphere of the cranium. It constitutes the anteriormost part of the skeleton, is articulated with the spine by which it is sus- pended, and is divided into cranium and face. I.— THE CRANIUM. The cranium or brain-case is but small when compared with the bulk of the body in general : it forms the supero-posterior part of the head ; is prominent and convex, superiorly and late- rally ; irregular and in places open, inferiorly ; hollow and vault- ed, within. It is composed of ten pieces — three pairs and four single bones; viz. superiorly and anteriorly, of the two frontals ; superiorly and in the middle, of the parietal ; superiorly and 20 ANATOMY OF THE HORSE. posteriorly, of the occipital ; laterally, of the four temporals ; inferiorly and anteriorly, of the ethmoid ; inferiorly and in the middle, of the sphenoid ; inferiorly and posteriorly, of the occipi- tal bone. FRONTAL BONES. (OSSA FRONTIS.) Situation. The frontal bones form the antero-superior part of the cranium, that broad flat part which we term the forehead, and which in the living horse is commonly marked with a patch of white hair, denominated a star. Figure — Irregular. Flat, superiorly; concave, underneath. Division — Into two surfaces and four borders. T/ie External Surface is flat and smooth, sometimes even slightly depressed in the situation of the frontal sinus. Pro- jecting from it outwardly is the external orbital process, forming the frontal arch and articulating with the temporal bone : un- derneath, the arch is excavated for the reception of the lachry- mal gland ; and through its inward end is a hole, (in some rare nistances, two,) the supra-orbital foramen, for the transmission of a small artery and nerve of the same name to the forehead ; below the foramen, internally, is a small depression, marking the place of attachment of the cartilaginous pulley belonging to the superior oblique muscle of the eye. From below and behind the arch proceeds downwards and backwards the internal orbi- tal process or plate, divided into two by a notch into which pro- jects the wing of the ethmoid bone, whose extremity is received into a mortise formed within the base of this plate ; this part also articulates, within the orbit, inferiorly, with the sphenoid, posteriorly, with the temporal, and, anteriorly, with the lachrymal and superior maxillary bones. The anterior portion of this pro- cess, behind, where it joins the sphenoid, is pierced by the in- ternal orbital foramen, which gives passage to the lateral nasal nerve ; the surface behind the posterior portion is smooth and depressed, making by union with it part of the temporal The Internal Surface is divided by a vaulted cranial septum into two unequal concavities: the posterior forms a cap for the anterior lobe of the cerebrum, which rests upon the septum, the indentations upon the surface answering to the cerebral emi- nences ; the anterior concavity constitutes the frontal sinus, whose interior is much enlarged by the slant taken by the septum, and the cavity continues to extend with age until it occupies the entire front of the bone. One frontal sinus is separated from the other by the nasal spine, composed of a lamina from each ANATOMY OF THE HORSE. 21 bone ; there are also several imperfect septa traversing the inte- rior of each sinus, partially dividing it into as many different chambers. Borders — Denticulated and squamous. The posterior or pa- rietal is arched, describing segments of two distinct circles, one running from within outwards, the other from above down- wards, and is overlaid by the parietal and temporal bones. The anterior or nasal border is waving, inclines backwards as well as outwards, is terminated internally by the nasal process, and is overlapped by the nasal and lachrymal bones. The frontal border is straight ; broad and triangular anteriorly, where it forms the septum between the sinuses : it unites with its fellow ; and has at the place of junction, internally, a slighly elevated longitudinal crest or spine, which with the opposite one forms a groove for the reception of the longitudinal process of the dura mater. The ethmoidal or outer border is irregular, forming a junction with the lachrymal and sphenoidal, and, by overlap- ping, with the ethmoidal bone. PARIETAL BOiNE. (OS PARIETALE.) Situation. Mesio-superior part of the cranium. Figure — Symmetrical; quadrilateral; vaulted: convex exter- nally, concave internally. Division — Into two surfaces and four borders. T/ie External or Convex S^r/ace is divided longitudinally by a mesian crest, which is bifurcated anteriorly and marks the course of the suture existing in early life, into two lateral convexities ; these are most elevated towards the supero-external angles, and their surfaces, though otherwise smooth, exhibit a few scattered small foramina, and are imprinted by the continual action of the muscles covering them, the prints growing deeper with age ; and, it appears, the general prominence less. The triangular space between the bifurcations of the crest generally rises above the level of the surrounding surface. The Diternctior Concave Surface is divided into two concavities by an internal crest which is commonly double, havino- a longi- tudinal groove in* the middle : it is terminated posteriorly by a three-sided process, the parietal protuberance, to which, as well as to the crest itself, is attached the falciform process of the dura mater. In front of this projection the longitudinal furrow ends in the two transverse grooves, which run along the poste- rior border, between it and the temporal bones : the former lodges the longitudinal, the latter the lateral sinuses of the dura mater. The cavities themselves are adapted to cover the mid- 22 ANATOMY OF THE HORSE. die lobes of the cerebrum, by which they are indented; they also show the traces of the ramifications of the arteries sup- plying the dura mater. Borders — Denticulated and squamous. The anterior is ser- pentine and unites with the frontal bones ; the posterior lies upon the occipital bone, and internally has two short bifid crests growing from it, forming sides of the transverse grooves, from which it extends down, on either side, to the wing of the sphenoid bone ; the lateral borders are irregular, and are over- laid by the temporal bone. Development. In the foal, indeed generally until the second or third year, a longitudinal suture is demonstrable, dividing this bone into two correspondent pieces. OCCIPITAL BONE. (OS OCCIPITIS.) Situation. Postero-superior and inferior parts of the cranium. Figure — Symmetrical ; irregular : presenting convexities and projections outwardly ; concavities, and a large circular aper- ture inwardly. Division — Into two surfaces, external and internal, and four borders. The External Surface is divided by a transverse mark into two portions, a super-occipital and a sub-occipital portion, which were once two separate bones, and presents, 1st. along its median line, and from above downwards, the occipital crest, bounding the cranium posteriorly, and giving attachment to the complexus ; below this, the occipital tuberosity, to which is fixed the cervical ligament, with broad, rugged, posterior occipi- tal depressions marked by the attachments of the recti capitis postici ; still lower, the occipital hole, transversely oval, and traversed by the spinal marrow and its membranes, the vertebral artery, and accessory and sub-occipital nerves; below and in front of this hole, the basilar process, articulating with the sphenoid bone, whose under surface shews the basilar fissure, triangular and widening in its course to the occipital hole, where it terminates : to this process are attached the recti capitis an- tici. 2clli/. On each side, the continuation of the crest, de- scending to the root of the styloid process of the same bone, into which is implanted the obliquus capitis superior ; below this, continued from it, the styloid process, whose length is regulated by that of the jaws, affording attachment to the ob- liquus capitis anticus ; inwardly to this, bordering on the occipital hole, the occipital condyles, extending backward for articulation with the atlas, and roughened upon their inner sides ANATOMY OF THE HORSE. '2.'> by the insertions of the long odontoid ligaments; between the condyle and the styloid process, the condyloid notch ; and in front of the condyles, the condyloid foramina, which are occa- sionally double, for transmitting the lingual nerves. The Internal or Cere6;flf/^?/r/<7cepresents, superiorly, the occipi- tal cupola, for covering the cerebellum, by which the surface is indented ; below, formed in the basilar process, the basilar fossa, which supports the medulla oblongata upon its broadest and posterior part, the pons varolii upon its anterior and deeper part. Borders. The superior is denticulated and unites with the parietal bone ; the inferior or anterior, with the sphenoid ; the lateral join the petrous portions of the temporal bones. Development. In the foal this bone consists of four pieces; in after age of two, the above described super-occipital and sub- occipital portions : in adult life it becomes one entire bone. TEMPORAL BONES. (OSSA TEMPOKUM.) Situation. Lateral parts of the cranium. Conformation. They consist of four separate pieces, in pairs, each irregular in its form. One pair presents vaulted ovoid plates, surmounted by curved or hooked projections ; the other are solid convex forms, remarkable for their hardness and white- ness. Division. In man these pieces are united and are considered as the squamous and petrous portions of one bone : in the horse, although the same names are preserved, iheportions are in reality distinct bones. THE SQUAMOUS PORTION. (PARS SQUAMOSA.) Presents two surfaces, an external and internal, and a cir- cumference. The Externalor Auricular Surfaceis convex, and has projecting forward from its middle in a curvilinear direction the zygomatic process ; this unites with a similar projection coming from the malar bone, the two forming the zygomatic arch, against which abuts the frontal arch : superiorly, this process presents a broad concave surface contributing to the temporal fossa, and has a nar- row sharpened convexity projecting upwards and backwards from it called the zygomatic crest ; inferiorly, running transversely to its root, is the glenoidal cavity, for the reception of the con- dyle of the inferior maxilla, bounded in front by a smooth trans- verse eminence denominated the articular from its being in- cluded within the temporary-maxillary articulation, and behind 24 ANATOMY OF THE HORSE. by the anterior mastoid process, which descends in the form of a cone, serves to strengthen and hmit the motion of the articula- tion, and gives attachment to part of the levator humeri. Be- hind the root of the posterior articular process is the mastoid foramen, for transmitting blood-vessels to and from the temporal fossa. Farther backward is the orifice of the temporal conduit, which gives passage to a vein. The Internal or Cerebral. Surface is concave, to contain and support the posterior lobes of the cerebrum by which it is imprinted, and displays several arborescent grooves, mark- ing the course of the posterior arterial ramifications of the dura mater. The Circumference, ovoid and elongated po&teriorly, is denti- culated and squamous, excepting at the posterior part, where it is joined to the petrous portion. The superior part lies upon the side of the parietal bone, and behind that upon a very small proportion of the occipital ; in front, it lies upon the frontal, and below upon the sphenoid. THE PETROUS PORTION. (PARS PETROSA.) Is important from lodging the internal organ of hearing. It presents two parts perfectly distinct from each other in structure, position, and use ; one is external or mastoideal, the other inter- nal or cerebral. From the former projects downwards the posterior mammiform or mastoid process, in which is distinguished a base inferiorly, and a crest superiorly : the latter joins the occipital crest. Below and rather towards the front of the process is the external orifice of the aqueduct of the vestibule ; directly in front of the process is the external auditory meatus and foramen, surrounded by a jutting oval rim, notched in the middle, which constitutes the auditory process ; to the inner side of the meatus is the hyoideal process, surrounded by a prominent circular edge, with which is connected the OS hyoides. Behind the meatus is a general protuberance, spheroid without, cavernous within, bottomed by a thin bony shell, within which are inclosed the mastoid cells ; proceeding from the inferior, anterior, and inner part of the bone is the styloid process; at whose root are two openings, one below for the Eustachian tube, the other above, the styloid foramen, for the chorda tympani. The Internal Part exhibits three surfaces for consideration. One superior and posterior, smooth though uneven, is excavated for adaptation to the side of the cerebellum, by which it is im- pressed in places ; it has a prominence running across its ANATOMY OF THE HORSE. 25 middle, and just beneatli this an irregular aperture, havino- interiorly two distinct passages, one terminated by a cul-de-sac, including a foramen, which leads to the cochlea and communi- cates through some small pores with the labyrinth ; the other, the internal auditory foramen, is for the conduit of the auditory nerves, and communicates with the aqueduct of the vestibule. Another surface, the anterior, contributes in a small degree to the formation of the concavity for the posterior lobe of the cere- brum. The inferior surface, parted from the superior by a fis- sure, is convex and prominent, but irregularly so : it constitutes the exterior wall of the labyrinth. The petrous portion is received between the squamous and the occipital bone, and though it is rarely found united with either of them by bony matter, yet, loose as it is, it is so locked in that it cannot be disjointed but with considerable difficulty and even fracture of some part. SPHENOID BONE. (OS SPHENOIDES.) Silualio?i. Inferior and middle parts of the cranium. Form. It bears a striking resemblance to a bird in flight, with its wings and legs extended : a comparison that has given rise to its Division — Into body, alae or wings, and pterygoid processes or legs : altogether presenting for consideration two surfaces and two borders. T/ie Infejnor Surface, irregularly convex, is distinguishable into three parts: — a middle and two lateral portions. The mid- dle, thick, prominent, cylindroid, and oblong from before back- wards, by its union with the basilar portion of the occipital bone and the body of the ethmoid, forms the base of the cranium : its porousness denotes muscular attachment. Between the middle and lateral parts, on either side, runs a narrow fissure denominated the pterygoid, which leads into two small canals, one entering the cavity of the nose, the other the orbital hiatus : this fissure affords a passage to the pterygoid branch of the por- tio dura. — The lateral divisions send forth by the sides of then fissures the pterygoid processes, which project downwards and forwards, form a union with the palate bones, and afford attach- ment to the internal pterygoid muscles. At the bases of these processes are the pterygoid foramina; above and internally to the base is the orbital hiatus, a considerable aperture, obliquely ovoid from above downwards, opening into the back of the orbit, and including the supero-posterior and infero-posterior or- bital foramina: the former transmitting the ophthalmic nerve 26 ANATOMY OF THE HORSE. and artery, and the third pair of nerves ; the latter, the superior maxillary nerve. Immediately over the hiatus is the opening of the canal which conducts the pathetic nerve into the orbit: it is in part formed by the ethmoid bone. The Superior or Cerebral Surface is unevenly concave, being impressed by the middle lobes of the cerebrum, which it sup- ports. It presents three general concavities : — a middle and two lateral. In the centre of the middle division is the pituit- ary fossa for lodging the gland from which it takes its name ; it is bounded on the sides by the optic fossae, which are occu- pied, inwardly, by the optic nerves, outwardly, by the cavernous sinuses. Farther removed outward and forward is the foramen lacerum orbitale ; and immediately over it the spinal foramfin, through which passes the pathetic nerve before it enters its canal. Borders. The Posterior or Occipital consists of an oval solid part in the middle, which is united with the basilar process of the occipital bone, and, laterally, of two wide irregular notches contributing to the formation of the foramina lacera basis cranii. — The Anterior or Palatine Border has a similar oval middle, joined to the ethmoid bone; and has a connection also with the vomer, — Each Lateral Border is distinguishable into two parts : — a posterior, which is scaly and denticulated for adaptation to the squamous temporal bone ; and an anterior or orbital por- tion, projected forward to unite with the anterior extremity of the same bone, and also with the ethmoid, while it forms the posteriormost part of the orbit. Connection — With the occipital, ethmoid, and squamous tem- poral bones; also with the palate bones and vomer. ETHMOID BONE. (oS ETHMOIDES.) Situation. Antero-inferior part of the cranium ; immediately before the sphenoid borie; where it constitutes the partition be- tween the cranial and nasal cavities. Form. One portion, the posterior, bears a resemblance to a bird with its wings extended, as in the act of flight, having no legs, but a long erected neck and a small round head : the an- terior part consists of a thin, brittle, porous, spongy structure, of considerable volume. Division — Into a middle and two lateral parts. The Middle Portion is large in bulk, consisting of a body be- hind, and of two voluminous spheroid spongy masses in front, parted by a septum. The body is oblong from before back- wards, concave superiorly, convex inferiorly, and interiorly ANATOMY OF THE HORSE. 27 formed into two concavities, tlie ethmoidal sinuses ; these are divided by a broad perpendicular plate, which extends upwards to unite with the nasal spine; (the partition between the fron- tal sinuses;) below, it is received into the groove of the vomer ; while in front it sustains the cartilaginous septum of the nose, the septum nasi ; altogether completing the division of the nasal cavity into two chambers : the ethmoidal plate itself is com- posed of two thin laminae which in old subjects become conso- lidated into one. Posteriorly, on either side, the body presents the optic hiatus, transversely oval, leading to the optic foramen : the posterior surface is oval to form a junction with the sphe- noid bone. Arising from the upper and fore part of the body is a pyramidal eminence somewhat curved, called the crista galli : it sustains in front the perpendicular plate, the falciform process of the dura mater behind, while from its sides extend the cribri- form plates — two ovoid, thin, brittle lamellae, which are received between the frontal orbital plates and the floors of the frontal sinuses, pierced by numerous small holes for the transmission of the filaments of the olfactory nerves, and whose concave cere- bral surfaces are denominated the ethmoidal fossae and are occupied by the olfactory sinuses. To the outer side of either fossa opens the internal orbital foramen ; from which a fissure runs upward to the part of the cribriform plate connected with the principal cornu of the ethmoidal cells. The Ethmoidal Cells, the voluminous structure protrud- ing from the front of the cribriform plates, consists of a great many thin, brittle, porous osseous plates, curved or rather con- voluted so as to form numerous narrow, elongated, cornuform sinuses, rendered separate and distinct from one another by in- tervening longitudinal grooves, with which from above they all in common have communication. These canals proceed, con- verging a little as they advance, to terminate underneath the superior turbinated bone, at the back of the nasal fossa, within a space communicating with the middle meatus. The anterior- most cornu or cell is conspicuously long and capacious : the rest increase in dimensions according to their proximity to this large one. Issuing from the front of the cells is a broad, thin, funnel-like process, which unites with the superior turbinated bone and forms a sharp prominent crest, serving as an imper- fect septum between the frontal and maxillary sinuses. The Lateral Portions, alse or wings, display more convexity than concavity superiorly, the reverse inferiorly : they originate from the supero-lateral parts of the body ; consist of thin, flex- ible plates; spread outward and upward, contributing to the posterior and inyvard parts of the orbits ; and terminate in semi- 28 ANATOMY OF THE HORSE. circular borders, sloped ofF behind, which, posteriorly, lie upon the wings of the sphenoid, laterally, are embraced by the bifid orbital plates of the frontal bone, and, in fine, received into the mortise of the same. Upon their internal surfaces the alae sup- port the anterior lobes of the cerebrum : their opposite surfaces constitute within the orbits the ossa plana. Connection — With the sphenoid and frontal, the vomer and superior turbinated bones ; and with the cartilaginous septum of the nose. H.— THE FACE. The face constitutes the antero-superior, anterior, and inferior parts of the head, making altogether (including the inferior maxilla) about four-fifths of the whole: it is the part to which the head owes its prolongation anteriorly, and principally its lateral breadth. It is bounded, behind, by the cranium ; at the sides, by the zygomatic and orbital arches ; infero-posteriorly, by the ethmoid and sphenoid bones, and the basilar process of the oc- cipital. It is composed of two perfectly distinct and separable parts ; viz. the superior maxilla or syncranium • and the inferior maxilla or diacranium : the latter consists of a single or indivi- sible piece, called the lower jaw ; the former or upper jaw is con- stituted of seventeen pieces, but which are closely and immove- ably united ; viz. the nasal bones, the superior and anterior maxillary, the malar, the lachrymal, the palatine, the superior and inferior turbinated, and the vomer : the teeth are equally distributed between the jaws. First, of the superior maxilla. NASAL BONES. (OSSA NASI.) Situation. Superior part of the face j where they constitute the roof of the cavity of the nose. Figure — Vaulted, thin, elongated ; mostly convex externally, concave internally ; broad posteriorly, tapering and terminating in a sharp point anteriorly : the single bone represents the sec- tion (about one-third) of a hollow cone, split longitudinally ; the two bones together form the outline of a heart as painted on cards. Division — Into two surfaces, two borders, a base and an apex. Surfaces. The External is not merely smooth ; it is polish- ed. It is not everywhere uniformly convex : indeed, the sides are towards their middle slightly concave ; and the outward side is most depressed. — The Internal Sutface is concave, that it may enlarge the area of the cavity of the nose : the channel it forms ANATOiMY OF THE HORSE. 29 is the nasal fossa, the posterior and inferior parts of which are occupied by the superior turbinated bone; the unoccupied part constituting the upper nasal meatus. Posteriorly, between the two bones a sinus is formed, which, though sometimes called the nasal, proves to be nothing more than the anterior chamber of the frontal, the two uniting into one cavity. Borders. The Superior is straight; but its edge is turned inward, forming a sort of internal crest, which along with its fellow is embraced by the superior border of the cartilaginous septum of the nose. Along their superior borders the two nasal bones are united — in the young subject by a sort of mortise- connection ; in the adult, by a suture half denticulated and half plain or smooth-edged. — The Inferior Border is waving, and is denticulated and mortised in its articulation with the superior and anterior maxillary bones ; it is united also by denticulation with the lachrymal. The Base has its border broadly sloped off and denticulated, and is united with the frontal bone, lying upon its anterior border. The Apices of the two bones form together the nasal peak ; a perfectly insulated or unconnected and remarkable projection, which gives support to the nostrils, and has attached to it the dilatator narium anterior. Connection — With the frontal, superior and anterior maxillary, and lachrymal bones : the two together maintain, superiorly, in its place, the septum nasi. SUPERIOR MAXILLARY BONES. (OSSA MAXILLARIA SUPERIORA.) Situation. Supero-lateral parts of the face. Figure — Trilateral : thick in the middle ; posterior part, gib- bous ; anterior, thin, tapering and laminous. Division — Into three surfaces, two extremities, and three bor- ders. 27ie External or Facial Surface is partially subdivided into antero-superior and postero-inferior portions by a protuberant ridge named the superior maxillary spine, which forms one continuous line with the zygomatic spine and ends abrubtly op- posite to the third molar tooth : the upper subdivision is much the larger, and affords attachment to the masseter. Rather above the middle of the upper surface opens the infra-orbital foramen, traversed by bloodvessels and nerves bearing the same name. The Inferior or Palatine Surface exhibits the concave side of 30 ANATOMY OF THE HORSE. a vaulted, demi-arched, oblong plate, called the palatine process or bony palate, which forms the partition between the cavities of the nose and mouth : posteriorly, this plate denticulates with the palate bone; anteriorly, with the anterior maxillary bone. The surface is bounded along the outer side by the alveolar pro- cesses, and between it and them runs a groove for the conduit of the palatine artery. The Superior or Nasal Surface forms the outer side and half of the floor of the nasal cavity. Like the inferior surface it is concave, but unevenly so, being more excavated towards the posterior than the anterior part : in fact, the broad channel formed by both bones constitutes three-fourths of the bony pari- etes of the nasal cavity. To a longitudinal spine running along either side of this channel is attached the inferior turbinated bone, dividing it laterally into two canals, named the inferior and middle meatus. At the supero-posterior part of the nasal chamber, behind the superior turbinated bone, the maxillary sinus opens through an oval aperture into the middle meatus : within the meatus itself, anteriorly to this, arched over by a little transverse eminence, is the orifice of the lachrymal con- duit, which is traversed by the lachrymal duct. Extremities. The Posterior swells into a large rounded protuberance, the maxillary tuberosity ; between which and the palate bone is a hiatus presenting three apertures : one is the posterior palatine foramen ; another, the anterior palatine fora- men and conduit leading to the palato-maxillary canal ; the third is that of the infra-orbital canal, leading to the foramen of the same name. To the outer side of the tuberosity is the malar process, articulating with the malar and lachrymal bones and the zygomatic process of the temporal. The Anterior or Dental Extremity is pyramidal and laminous, and contains an in- curvated, conoid, alveolar cavity for the lodgement of the tusk : it denticulates with the anterior maxillary bone. Borders. The Superior or Nasal is laminous to be united to the nasal bone ; and has a mortise in its fore part to receive the border of the anterior maxillary bone. The Inferior or Alveolar Border presents two parallel plates divided by transverse septa into six quadrangular cavities, the alveoli, for the implantation of the molar teeth. Behind the last molar tooth is the alveolar tuberosity, a rugged eminence giving attachment to the ptery- goideus internus. The Internal or Palatine Border denticulates with its fellow. Connection — With the squamous temporal and nasal bones ; and with the anterior maxillary, malar, lachrymal, palate and inferior turbinated bones. ANATOMY OF THE HORSE. 31 ANTERIOR MAXILLARY BONES. (OSSA MAXILLARIA ANTERIORA.) Situntiou. Supero-anterior and antero-lateral parts of the face. Form— Irregular ; consisting of a broad, thick portion or base, turned forwards, from which is sent off a thin flexible plate ; and a narrow, elongated, tapering portion, turned backwards. Division — Into three surfaces and three borders. Surfaces. The superio?- or nasal surface is smooth, convex, and oblong; more extensive externally than internally; and free from all connection, it forming one side of the nasal space, in cor- respondence with its fellow. Outwardly, it affords attachment to the nasalis brevis labii superioris; inwardly, it is invested by the pituitary membrane. The inferior or palatine sinface is vaulted, it contributing to the formation of the palate : within it, of an oval form, is the interdental space, which is occupied by two thin flexible plates, the palatine processes, denticulating along the sides with each other. In the side of the bone is a deep hollow, for the reception of that portion of the superior maxillary bone which holds the tusk ; and the remainder of the surface, posteriorly, is arti- culated with the same. The anterior or labial surface is broad, smooth, and convex, and gives attachment to the depressor labii superioris, the gums, and the membranous and cellular tissue en- tering into the composition of the upper lip. Borders. The anterior border is broad and curved, and is composed of two laminee, formed apart and divided by five trans- verse septa into six conical alveolar cavities, for lodging the inci- sive teeth. The posterior border is narrow and sloped off, and denticulates with the nasal bone. The internal border is broad, quadrilateral, and curved, and denticulates with its fellow, forming thereby the superior maxillary symphysis, through which runs the foramen incisivum, for the transmission of the palatine arteries. Particularities. These bones are remarkable for smoothness of surface, and closeness and hardness of texture. They are united at the symphysis, in the young subject by a fibrous cartilage, in the adult by osseous matter; so that, by maceration, they are separable in the one instance, inseparable in the other. Their alveolar cavities increase in number and size with the age and growth of the animal. Connection — With the superior maxillary and nasal bones, and with each other. malar bones, (ossa malarum.) Situation. Antero-external part of the orbit. Figure— Irregularly triangular, presenting a broad basis for- wards. 32 ANATOMY OF THE HORSE. Division — Into three surfaces, three angles, a basiform and an apiform extremity. Surfaces. The internal or facial sui'face'i's. divided into two portions by the zygomatic angle or spine : the upper division is smooth and nearly flat, with the exception of a depression ante- riorly, which marks the attachment of the nasalis longus labii superioris ; the lower part is narrow, and roughened by the ad- herence of the masseter. From this surface, posteriorly, arises the zygomatic process, which is very obliquely sloped off, and laminated for adaptation to the process of the same name, meeting it from the temporal bone, the two together forming the zygomatic arch. The internal or maxillary suface is concave, to enlarge the capacity of the maxillary sinus, to which it contributes. The orbital surface presents a smooth concavity, which forms the infero-external part of the orbit, and is separated from the facial surface by the orbital angle. Angles. The inferior angle constitutes the principal part of the zygomatic spine : it is continuous with the temporal bone be- hind, and in front by the superior maxillary. Tlie superior angle is lunated, and constitutes the infero-external portion of the orbital circumference. The posterior angle, or rather border, is jagged and irregular, and unites with the superior maxillary bone. Extremities. The anterior extremity or base is broad, irre- gular, and denticulated, and articulates with the superior maxillary and lachrymal bones. The posterior or apiform end forms the zygomatic process. Particularities. These bones contribute to the formation of the orbits, maxillary sinuses, and zygomatic arches ; and their articu- lations exhibit a sort of dove-tail mechanism. Connection — With the temporal, superior maxillary, and lachry- mal bones. LACHRYMAL BONES. (OSSA LA CH RYM ALI A.) Situation. Antero-external part of the orbit. Form — Irregularly infundibuliform. Division — Into three surfaces and five borders. Surfaces. The external or facial surface, triangular, flattened, and smooth, is bounded, laterally, by the external and internal facial borders ; superiorly, by the orbital ridge. It exhibits, a little above its centre, a rounded eminence, the lachrymal tubercle, to which is fixed the orbicularis palpebrarum. — The internal sur- face is concave, but very irregularly so, being divided into two hollows by a cylindrical prominence, caused by the lachrymal conduit. It constitutes part of the roof of the maxillary sinus. ANATOMY ()F THE HORSE. 33 The orbital surface is triangular and smooth, deeply excavated in front, extended and flattened posteriorly, and makes the antero- external side of the orbit. In the excavated part are observable — a circular depression, marking the origin of the short oblique muscle of the eye, and, before the depression, the lachrymal fossa, a funnel- shaped hollow, forming the entrance into the lachrymal canal : within the hollow reposes the lachrymal sac; the canal is traversed by the lachrymal duct. Borders. — Denticulated, with the exception of the nasal, which is plain. The external facial border articulates with the malar bone ; the intenialfacial (including the nasal border), with the nasal and frontal bones : the external orbital border unites with the malar and maxillary bones ; the internal orbital border with the frontal bone. Particularities. — A semi-transparent bone, important from its connexion with the lachrymal apparatus. Connexion.— Vf'Ah the frontal, nasal, malar, and superior maxillary bones. PALATE BONES. (OSSA PALATI.) Situation. — Infero-posterior part of the face, adjoining the base of the cranium. Figure. — One portion is semi-circular; otherwise it is irregular. Surfaces. — The palatine surface is that which is turned downwards, and contributes to the formation of the palatine arch. The nasal surface, the broadest, confronts its fellow, the two forming the sides of the posterior opening of the nose : its supero- posterior part is pierced by the posterior palatine foramen. The orbital surface is in part smooth, where it enters into the compo- sition of the back of the orbit; and in part rough and laminated, where it articulates with the superior maxillary bone : the latter portion exhibits the palatine canal, which leads to the anterior pala- tine foramen. Between this and the superior maxillary bone, a hiatus or sort of vestibule is left vacant, in which is observable the posterior opening of the foramen above-mentioned, besides two others formally described. The ethmoidal surface is divided from the nasal by the palatine crest, to which the vomer is joined : it is oblong and concave, and constitutes the floor of the ethmoidal sinus, possessing several irregular ridges, which form so many im- perfect septa, projecting into the cavity. Borders. — The palatine, round, smooth and lunated, forms the circumferent boundary-line of the posterior opening of the nose, and afibrds attachment to the velum palati : from it, poste- 34 ANATOMY OF THE HORSE. riorly, descends the styloid process, whose extremity, in the recent subject, is provided with a cartilaginous pulley, in which runs the tensor palati ; the posterior side of the process is rough and lami- nated for articulation with the pterygoid process of the sphenoid bone. The supero-lateral and infero-lateral borders unite with the superior maxillary bone ; the former has also a connexion with the inferior turbinated bone : these borders are both denticu- lated. Extremities. — The posterior or orbital is expanded, and is received between the frontal and ethmoid bones : the anterior ex- tremity is narrow, incurvated upwards, and joins its fellow. Particularities. — The styloid processes, or rather epiphyses, are rarely preserved disunited and entire after maceration, owing to the late period at which they continue to be ligamentous at their roots, as also to the length, slenderness, and consequent fran- gibleness of them. Connexion. — With the frontal, ethmoid, and sphenoid ; and with the superior maxillary, inferior turbinated bones, and vomer. THE TURBINATED BONES, SUPERIOR AND INFERIOR. (OSSA TURBINATA, SUPERIORA ET INFERIORA.) Situation. — Within the chambers of the nose, attached to the outer walls ; the superior, above ; the inferior, below. Form. — Oblong, thin, foliated, convoluted, cavernous. Division. — Into external and internal surfaces ; superior and inferior extremities. Surfaces. — Porous. The external is convex; and presents series of longitudinal grooves, disposed in an arborescent manner, which mark the ramifications of very small blood-vessels. In consequence of the bone being rolled up or twisted round itself after the fashion of a turban, the outward superficies becomes extensive, although it diminishes in breadth beyond the exte- rior, from the internal convolution being, in course, smaller than the external. The internal surface, or opposite side, is con- cave, and, like the former, necessarily diminishes as it proceeds inward. The interior itself is, cavernous, or rather cellular, being unequally divided by transverse septa into several little sinuses or cells, communicating through small apertures one with another, and through the intervals between the convolutions, with the middle nasal meatus. Extremities. — The posterior or basiform, are broad; their interior is capacious, and open superiorly ; and they communicate with the sinuses immediately behind them. The anterior or api- ANATOMY OF THE HORSE. 35 form extremities are contracted and closed ; and give origin, in the recent subject, to two cartilaginous productions, which project into the chambers of the nose. Particularities. — These bones are four in number : two supe- rior, and two inferior. They are thin, and porous or spongy in their texture ; brittle, and yet possessing sufficient elasticity to enable them to resist considerable pressure, and withstand, without fracture, any ordinary injury. Difference. — The superior bone exceeds in volume the inferior, and makes its convolution from below, its upper border being attached ; whereas, the reverse is the case with the inferior one. Connexion. — The superior bone is connected, above, with the ethmoid; and laterally, with the nasal bone. It contributes to the formation of the anterior part or floor of the frontal sinus. The inferior turbinated is fixed to the superior maxillary bone. THE VOMER. Situation. — Along the floor of the nose, preserving the median longitudinal line dividing the chambers. ^i^w/e.— Elongated : posterior portion, broad, quadrilateral, and flattened ; anterior, narrow, grooved, and lengthened. Division. — Into two extremities and two borders. Extremities. — The Posterior or broad part exhibits a lower surface, somewhat convex, which is smooth and free ; an upper sujface, somewhat concave, which embraces and almost conceals the body of the ethmoid bone ; a superior crescenlic bor- der, between which and the ethmoid is a narrow hiatus, giving passage to some blood-vessels and nerves to the septum narium ; two lateral borders, united with the palate bones ; and four cornua or projecting acuminated ends, the two superior articulating with the sphenoid bone, the inferior with the palate bones. The an- terior extremity is broader than other parts of the grooved shaft, in consequence of being flattened above and below ; it reaches as far forward as the palatine processes of the anterior maxillary bone. Borders. — The superior presents a long narrow chasm or groove, deeper posteriorly than anteriorly, which receives the car- tilaginous partition called the septum narium. The inferior border is semi-cylindrical, and presents a posterior part, smooth and free from any connexion ; and an anterior, which denticulates with the palatine processes of the superior maxillary bone. Connexion. — With the ethmoid and sphenoid, and with the superior and anterior maxillary and palate bones. 36 ANATOMY OF THE HORSE. THE INFERIOR MAXILLARY BONE. (OS MAXILLARE INFERIUS.) Constituting, by itself, the inferior maxilla, or lower jaw. Situation. — Composing the inferior and posterior parts of the face. Form. — Symmetrical, bearing much resemblance to the letter <1 ; the angular or narrow part being presented forwards, the sides diverging and opening backwards. Division. — Into body, neck, sides, and limbs or branches, to- gether with their respective external and internal surfaces and borders. The body is the anterior undivided portion, reaching back so fiir as to include the tusks within their sockets. The neck is the contracted part springing from the body ; the two together form- ing a solid bond of union between the sides, sustaining them, together with the branches, in immovable relative position. I n the young subject, a longitudinal median suture, named the inferior maxillary symphysis, divides the bone at this part into separable synniietrical halves; bony union, however, solidifies the two early in life, after which they are no longer distinct pieces. The exter- nal surface of the body is convex and rounded, and in places rough and porous, from the attachment of the levator menti and gums. A groove across the neck marks the course of the former symphy- sis. At the place where the neck joins the side, near the supe- rior border, is the anterior maxillary foramen, which forms the outlet of a canal running between the laminai of the bone along the roots of the molar teeth : it is traversed by the third division of the fifth pair of nerves. The internal surface of the body is slightly concave, and is rough and porous from the attachments of the gums and membrane of the mouth; that of the neck forms a channel for the tongue, and receives the insertion of the frcenum linguis. 2'he border projects forward, forming a parabolic curve, and presenting, superiorly, conical alveolar cavities for the six lower incisive teeth and the two inferior tusks ; posteriorly, on the neck, the border rises into a sharp edge, which is rendered less prominent in old horses, in consequence, it would appear, of the repeated pressure and friction of the bit. The sides are the parts comprehended between the neck and the branches: they support all the inferior molar teeth. They in- crease in breadth from before backward, are flattened laterally, and present external and internal surfaces, superior and inferior borders. The surfaces, though, generally speaking, they may be jn'onounced to be flat, possess a degree of prominence in early and adult life which they lose in age : this may be ascribed in part to ANATOiMY 01- THE HORSE. 37 the teeth, and in part to the comparative porousness or incompact- ness of structure of the young bone. The external surface is occu- pied by the depressor labii superioris ; the internal by the muscles of the hyoidean region. The vacuity between the sides takes the name of inter-maxillary space. — Of the borders^ the superior exhi- bits twelve quadrangular alveolar cavities for the molar teeth, formed by the separation of the laminae composing the bone, and the addition of so many transverse thin partitions or septa. The inferior border is thick, round, and smooth in early life ; but, as age advances, grows thin, sharp, and irregular. The branches, the parts directed upwards, are broad, thin, and slightly curved ; and ofl'er for notice two surfaces, two borders, two processes, and a notch. The surfaces are generally smooth, though they exhibit marks of muscular attachment : the external one is clothed by the masseter ; the internal, by the pterygoideus internus ; the latter, also, is pierced a little behind the last molar tooth, by the posterior maxillary foramen, which forms the entrance to the dental canal, the anterior maxillary hole being its outlet. The borders : — The posterior is broad, and roughened by the attach- ment of the stylo-maxillaris and masseter : the part where it makes its curvature to join the side is called the angle of the jaw. The anterior border is thin, and presents a sharp edge, turned inwards : it gives attachment to the buccinator and depressor labii infcrioris. Processes : — The posterior border is surmounted by the condyle,^the transverse, cylindroid, smooth convexity which is received into the glenoid cavity in the temporal bone. The ante- rior border ends in the coronoid process, which is flattened on its sides, has sharpened edges, and is slightly curved backwards : into it is implanted the temporal muscle. Between the two pro- cesses is the corono-condi/Ioid notch, which affords space for the motion of the jaw, as also for the insertion of the temporal nmscle. HI.— THE HEAD IN GENERAL. We shall now take a review of the head in its entire or articu- lated state, making, to facilitate the description, a Division of it into External and Internal parts. The External Parts maybe conveniently distinguished into superior, posterior, inferior, and lateral surfaces ; and each of these surfaces admits of a fur- ther subdivision into cranial and facial regions. THE SUPERIOR EXTERNAL SURFACE comprehends— 1. The superior cranial region, in which we find several zigzag denticulated lines, denominated sutures, indicating the boundaries and articulations of the several individual bones. 38 ANATOMY OF THE HORSE. In this region, commencing from its anterior limits, we observe the frontal suture, formed by the articulation of the frontal bones ; surmounted by a transverse serpentine one, the coronal suture, showing the line of junction of these bones with the parietal; next, the parietal prominences, bounded posteriorly by the lamb- doidal suture, which joins the occipital with the parietal bones : lastly, forming the posterior boundary of the region, the occipital crest. 2. The superior facial region, continuous, behind, with the last-described region, presents to view, commencing from its posterior boundary, the transverse suture, the line of union between the bones of the cranium and those of the face, joining the frontal to the nasal and lachrymal bones : continued forwards, in a direct line with the frontal, the nasal suture, which unites the nasal bones : this suture runs within a sort of hollow from the bone, on its sides, rising into the nasal protninences : these are bounded laterally by the lateral nasal sutures, formed by the junction of the nasal with the maxillary bones, both superior and anterior. The nasal peak is the united apices of the nasal bones, projecting forward over the anterior nasal opening ; which aperture is bounded laterally by the superior convex surfaces of the anterior maxillary bones, and in front is oviform and conti- nued into the superior maxillary symphysis, through which runs the foramen incisivum : lastly, the superior alveolar processes, and the incisive teeth, ranged in a row and fixed within the alveolar cavities. The POSTERIOR SURFACE is entirely cranial: it is bounded, superiorly, by the occipital crest, and, inferiorly, by the occipital hole ; it presents the occipital tuberosity, and on its sides the broad posterior occipital depressions, deeply and rug- gedly pitted by muscular attachments ; also, projecting from the postero-lateral parts of the foramen magnum, the occipital con- dyles. THE INFERIOR SURFACE comprises— 1. The inferior cranial region, which is bounded, posteriorly, by the occipital hole and condyles ; anteriorly, by the vomer and palate bones; laterally, by the zygomatic arches. Proceeding from behind forwards, we observe — 1 st, along the me- dian line, the basilar process, impressed by the basilar fissure ; the condyloid foramina on its sides, near the roots of the condyles ; a semicircular prominence denoting its junction with the sphenoid bone ; the body of the sphenoid bone, its articulation with that of the ethmoid, and a small semilunar portion of the latter left visi- ble within the crescentic border of the vomer. 2d, On either side, the occipital sty loid process ; between it and the condyle, the ANATOMY OF THE HORSE. 39 occipital notch ; in front of the notch and root of the occipital sty- loid projection, THE PETROUS PORTION of the temporal bone — exhibiting, posteriorly, the posterior mastoid process^ having at its root the external orifice of the aqueduct of the vestibule: di- rectly in front, the auditory process and meatus, at the inner side- of which ig the hyoideal process ; behind the meatus are the mastoid cells; projecting from the inner and anterior part, is the slender temporal styloid process, having at its root the Eustachian opening and styloid foramen. In front of, and rather outwardly to the petrous portion, we observe, — the anterior mastoid process ; at its root, the mastoid foramen ; extending outwardly, in front of it, the glenoid cavity, bounded anteriorly by the temporal articu- lar process. The foramen lacerum is the large irregular opening formed by the occipital, temporal, and sphenoid bones, compre- hending the tempero-occipital and spheno- occipital hiatus, and traversed by the internal carotid artery, the jugular vein, the eighth pair of nerves, and the inferior maxillary nerve. This fora- men is bounded in front by the ala of the sphenoid bone, whose borders are joined to the temporal and ethmoid bones by the sphe- noidal suture. Curving forwards and downwards from the ala is the pterygoid process : it articulates along its front part with the palatine styloid process, which is comparatively slender and de- scends beyond it. At the root of the pterygoid process is seen the pterygoid for amen, forming one continued passage with the infero- posterior orbital hole. 2. The inferior facial region constitutes the remain- der of the inferior surface : it is bounded, posteriorly, by the sphenoid and ethmoid bones; and, anteriorly, by the incisive teeth. Beginning from behind, we perceive, — in the middle, the broad part of the vomer, embracing the body of the ethmoid ; and its superior cornua extending under that of the sphenoid bone, at whose points are found the spheno-palatine foramina, which open again under the infero-posterior orbital : anteriorly to this it arti- culates with the palate bones, both laterally and along their mid- dle — Laterally, the palatine styloid processes, and the nasal and palatine surfaces and borders of the palate bones, by which latter is formed the posterior opening of the nose : this aperture in its general figure is oval lengthwise, and is equally divided into two semilunar halves by the shaftofthe vomer, aboutone-third of whose length is seen through the orifice. Farther outward, on the sides of this opening, the maxillary tuberosities ; immediately above them, the maxillary hiatus or entrance io the posterior palatine foramen, the infra-orbital canal, and the anterior palatine cofi- duit : extending forward from the tuberosities in parallel lines, the alveolar processes and cavities for the twelve superior molar 40 ANATOMY OF THE HORSE. teeth; from which project inward Me ;jrt/a^z;/e processes belonging to the same bone, joined by the palate bones above, and the pa- latine processes of the anterior maxiUary hones below : these parts, altogether, constitute the bony palate. The anterior third of the palate takes the name of interdental space ; it is, in fact, a longitudinally oval interval, which is incompletely filled by the an- terior palatine processes. At the junction of the contributing por- tions of the palate and maxillary bones to the palatine arch, oppo- site and near to the last molar tooth, is the palato-maxillary fo- ramen : from which takes its rise the palato-maxillary canal, which courses the roots of the alveolar processes, and conducts an artery of the same name forwards. Along the middle of the arch runs the palatine suture, uniting the palate and superior and an- terior maxillary bones of one side to tlieir fellows on the other. At the external borders of the interdental space, formed by the superior and anterior maxillary bones, are the alveolar cavities for the tusks, commonly nearer by about one-third to the corner in- cisive than to the first molar teeth. The symphysis of the superior maxilla continued in a line from the palatine suture ; pierced by the lower opening of the foramen incisivum, which is situated at the roots of the anterior palatine processes, and gives passage to the palato-maxillary arteries. The anterior maxillary surface is vaulted in front, to extend the superficies of the palate. In conclusion, we have the inferior alveolar processes, alveolar cavities, and inferior surfaces and /aces of the incisive teeth. EACH LATERAL SURFACE INCLUDES— 1. The lateral cranial region, which is bounded, pos- teriorly, by the occipital crest and condyloid process ; anteriorly, by the orbit. It presents to observation — one side of the occipital crest, descending to the base of the styloid process, whence a sharp ridge extends from it to the zygomatic crest, which ridge forms the inferior boundary of the temporal fossa. The external side of the occipital styloid process, roughened from the attachment of the stylo-maxillaris. The petrous portion of the temporal bone, locked in between the squamous portion of the same and the occipital bone, comprising — the mastoid process, in apposition with the base of the occipital styloid process behind, and with the descending plate of the squamous portion in front. Within a circular space formed by this plate behind, and the anterior mas- toid process before, protrudes the auditory process, to which is attached the external ear: it is perforated by the meatus audito- rius externus, whose orifice is expanded or trumpet-shaped. 'The temporal zygomatic process is continuous, posteriorly and inferiorly, with the anterior mastoid ; at which part its surface is excavated to make room for the attachment of the external ear ; ANATOIMY OF THE HORSE. 41 from this the process curves upwards and outwards, and subse- quently forwards, in the form of an arch, meeting on the outer side of the orbit with the zygomatic process of the malar bone, and articulating with it through the zt/goinatic suture, the two com- pleting tlie zi/goniatic arch, against which abuts the frontal arch. The zygomatic crest and the articular process, the one rising, the other descending, from the temporal part of the arch, are also observable. 2. The lateral facial region extendsfrom the orbit to the incisive teeth. It is partially and very unequally divided into superior and inferior departments by the zi/gomatic spine; which arises from the infero-external and anterior part of the arch of the same name, reaches forward about one-third of the length of the face (measuring from the orbit), and ends abruptly : the inferior depart- ment is occupied by the masseter, to which the spine gives attach- ment; the superior, by much the most extensive surface, exhibits, a little higher than its middle, the infra-orbital J'oramen ; near the inner angle of the orbit, the lachrymal tubercle ; between the fora- men and the tubercle, a depression, marking the attachment of the nasalis longuslabii superioris; anteriorly, a superjicial hollow, de- noting the place of attachment of the caninus : besides these, various other muscular impressions are perceptible. The sutures displayed upon this surface, are — the lateral nasal, extending from the transverse suture to the lateral opening of the nose, and uniting the nasal to the lachrymal and superior and anterior maxillary bones ; the malar suture, running transversely down- ward and outward from the lateral nasal, and connecting the su- perior maxillary to the lachrymal and malar bones ; the lachrymal suture, extending perpendicularly backward from the malar, and continuing its course within the orbit, uniting the lachrymal and malar bones ; the maxillarij suture, extending obliquely, forward and downward, from the anterior part of the lateral nasal, and joining the superior and anterior maxillary bones. Supero- anteriorly (in relation to this surface^ we perceive oneof the lateral ope)iings of the nose, bounded in front by the nasal peak, behind by the superior or convex border of the anterior maxillary bone. In front of this border, the bone shows the surface for the attach- ment of the depressor labii superioris. From the inferior parts of this region project the molar, canine, and lateral incisive teeth. 42 OSTEOLOGY OF THE HORSE. INTERNAL PARTS: Comprehending the Cavities of the Cranium, Orbit, Nose, and Mouth. I. — CAVITY OF THE CRANIUM, Constructed for the lodgement of the brain with its appen- dages : is in form ovoid, flattened inferiorly, broader anteriorly than posteriorly ; its antero-posterior or long diameter measuring about seven inches ; its transverse or lateral diameter, about four inches ; its vertical or perpendicular diameter, about three and a half inches. At the same time it is to be observed, that, although the general form of the cavity is the same, its dimensions may and do vary in different heads. The eight bones composing the cranium all present internally surfaces more or less concave, which, united, form the cavity under consideration ; hence it is that the interior is not regular or uniform, but presents to view different hollows, which are adapted to distinct prominences of the cerebral mass. DIVISION of the interior surface into roof and base of the cranium : — The roof is formed by the frontal, parietal, and occipital bones : its superficies is larger than the extent of the base, and it is without any apparently defective places, observable in the latter. It presents — 1st, On the mesian line, from front to back, the sagittal groove, for the longitudinal sinus, formed by the frontal and parietal crests, crossed towards the front by the co- ronal suture, and bounded posteriorly by tlie parietal protuberance, to which is attached the tentorium, and behind which is the occi- pital cupula, for covering the cerebellum. — 2d, On either side, along the same line, the cerebral concavities of the frontal bone ; the coronal suture, the boundary line between them and the parietal concavities ; the transverse grooves, for the lateral sinuses j and, sunk within them, tlie lambdoidal suture. The base is formed by the temporal, sphenoid, ethmoid, and occipital bones. It presents — 1st, on the middle line, from before hdickwdivAs, the crista gain, and on its sides the ethmoidal fossa and cribriform plates, bounded laterally by the internal 07-bital plates of the frontal bones, and them pierced by the internal orbital foramina; the concave surf ace of the body of the ethmoid bone ; the optic hiatus leading to the optic foramina ; a transverse suture between the ethmoid and sphenoid bones. Upon the sphenoid bone, the pituitary fossa, bounded laterally by the two optic fossa; the latter leading to the foramina lacera orbitalia, over which are the spinal foramina : a transverse elevated line denotes the place of junction of the sphenoid with the occipital bone. Belonging to the occipital bone, are the basilar fossa and OSTEOLOGY OF THE HORSE. 43 the occipital hole. 2d, On either side, in the same direction, the internal surface of the tving of the ethmoid bone, rather more con- vex than concave, for the support of the anterior lobe of the cere- brum ; the concavity oj the wing of the sphenoid bone, for the re- ception of the middle lobe ; the concavity of the squamous part of the temporal bone, for lodging the posterior lobe : and the sutures bounding these three cerebral surfaces. The foramen lacerum basis cranii, formed between the wing of the sphenoid anteriorly, the basilar process of the occipital bone internally, and the petrous portion of the temporal bone externally and posteriorly : it is wide and irregular before, narrow behind, and is distinguished into the spheno-occipilal and temporo-occipital hiatus. — Th e petrous PORTION OF THE TEMPORAL BONE, presenting a narrow tri- angular surface forwards and upwards, which contributes to the posterior cerebral concavity ; a broad smooth but uneven surface inwards, against which inclines the cerebellum, and upon which we distinguish — a, the orifice of the meatus auditorius internus ; bf a transverse prominence, and several cerebral indentations ; c, an irregular convexity downwards, which forms the boundary wall of the labyrinth ; d, ?i fissure separating it from the former. Lastly, the sutures, uniting the petrous to the squamous portion and to the occipital bone. — Of the occipital bone, a part of the internal surface assisting in the formation of a concavity for the cerebellum, by the convolutions of which it is indented ; the surface even and smooth, and slightly excavated below this, for the support of the medulla oblongata ; still lower, the condyloid foramina, through which the ninth pair of nerves pass out. 11.— THE ORBITS, Two in number, are formed for the lodgement, attachment, and protection of the eyes and their appendages. Figure. — Symmetrical. The cavity, which is extended hori- zontally backward and inward, has, viewed in front, a pyramidal aspect : the base, represented by the front, has four sides and four angles ; one only of the sides, however, is sulEficient in extent to reach the apex, the others being all more or less imperfect. A line drawn in the horizontal direction through the axis of this figure, inclines more outwards than forwards, more forwards than downwards, intersecting another horizontal line projected directly forward at an angle of about 70", and one extended laterally, di- rectly outward, (at right angles with the former) at about 20°: Ihe inclination downward, liowever, will in course vary with the erect position of the head. Structure. — The orbit is composed of unequal portions coming 11 OSTEOLOGY OF THE HORSE. from four of the bones of the cranium, and from three of those of the face : viz. the frontal, ethmoid, sphenoid, and temporal bones; the malar, lachrymal, and palate bones. Division. — Into sides, angles, base, and apex. SIDES. — The superior side or roof of the cavity consists only of t/te frontal arch; which is concave and smooth internally, to make room for the lachrymal gland, and has anterior and pos- terior borders, sharp and slightly curvated. The inferior side or floor of the orbit is formed by the orbital surfaces of the lach- rymal and malar bones, is broader than the roof, though, like it, is deficient as a whole. It comprises the orbital portion of the lachrymal suture: it is terminated, in front, by a smooth, rounded, curvated border ; behind, nearly midway between the base and apex, by a shorter and straight er border. The inter- nal or NASAL SIDE, the broadest and only complete one, is formed principally by the internal orbital process of the frontal bone, into the notch of which is received the os planum : the ethmoid bone further contributes, and also the sphenoid and palate bones, the three constituting that irregular termination of the ca- vity behind which represents the apex. The frontal orbital plate is smooth and slightly concave, and is united below by a conti- nuation of tJie transverse suture with the lachrymal bone. Its border in front, though slightly curvated, is veri/ irregular, having several notches and one or tivo smallforamina in it; it also presents a little tubercle, to which the lachrymal caruncle is attached. The external or zygomatic side is formed principally by the zygomatic process of the malar bone, that of the temporal contributing but little : it is concave and smooth internally, somewhat broader below than upwards ; is intersected obliquely by the zygomatic suture, and has an anterior border, smooth and curvated ; a posterior one, sharp and straight. ANGLES. — The supero-internal angles, one before, the other behind, are formed by the beginning of the frontal arch, through which, midway between them, passes the supra-orbital foramen. The infero-internal angle includes the lachrymal fossa. The sijpero-externa l angles, one anterior, the other pos- terior, are intersected by the suture uniting the frontal and zy- gomatic arches. The infero-external angles, particularly the an- terior, are rounded and smooth. BASE. — Of the circumferent border, the superior and internal parts, about two-fifths of the entire circle, are formed by the OS frontis ; the inferior and internal parts, about one-fifth, by the. lachrymal bone ; and the remaining two-fifths by the malar and temporal bones, in the proportion of three parts of the former to one of the latter. OSTEOLOGY OF THE HORSE. 45 THE APEX or back of the orbit, formed by the ctlimoid, sphenoid, and palate bones, is pierced by five foramina: the two round are tlie internal orbital and optic, which are ranged in a row with two oval and larger in size, t/ie supero-posterior and infero- posterior orbital ; the one behind is t/ie spinal foramen. III. CAVITIES OF THE NOSE, Comprehending the nasal fossse or chambers, and the sinuses. These cavities occupy about two-thirds of the internal space of the superior maxilla, the remaining third belonging to the cranium ; from which they are partitioned by the cranial septum of the frontal bone, in union with the cribriform plates and crest of the ethmoid. THE NASAL FOSS^ may be said to include about two- thirds of the entire space devoted to the olfactory cavities. They constitute the interior of the proboscis; have four boundary walls, one above, one below, and two laterally ; are separated from each other by a septum ; but are open both before and behind. The SUPERIOR wall presents an irregular concave formed by the internal surfaces of the nasal bones, the cells and grooves of the ethmoid, and small portions of the nasal surfaces of the palate bones. The INFERIOR WALL is horizontal; it extends forwards be- yond the superior, but is considerably overreached by that wall posteriorly : it is formed by the palatine portions of the anterior and superior maxillary, and by the palate bones. The surface is transversely concave, and presents a slight eminence a little behind its middle. Each lateral wALLor side presents an irregular concavity, and is formed by the anterior and superior maxillary and the palate bones. To it are attached the superior and inferior turbinated bones, by which the fossa is divided into three separate passages or meatus. T/ie superior meatus, comprised between the nasal and superior turbinated bones, extends from the angle of the lateral nasal opening, passing over the ethmoidal cells, to the cribriform plate, following superiorly the declination of the wall. The mid- dle meatus, included between the turbinated bones, leads superi- orly into the ethmoidal grooves and cells, and into the sinuses of the head, and ends below beneath the termination of the superior. This passage, like the former one, is narrow ; but its greatest diameter is, obliquely, in the perpendicular direction ; whereas the other measures most from side to side. It receives the aper- tures of the ductus ad nasum, maxillary sinus, ethmoidal grooves, and turbinated cells. The inferior meatus is the most capacious 46 OSTEOLOGY OF THE HORSE. as well as most direct one: it extends along the inferior wall, from the anterior to the posterior opening of the nose. The septum nasi is the partition separating one fossa from the other. It is formed, posteriorly, by the ethmoidal plate ; in- feriorly and posteriorly, by the vomer ; superiorly and anteriorly, (and principally) by a broad perpendicular plate of cartilage. The openings of the nose are, — The anteinor, divided by the nasal peak and septum nasi into two, and formed by the superior borders of the anterior maxillary bones : the posterior, di- vided after the same manner by the vomer and septum, and formed by the nasal surfaces and crescentic borders of the palate bones. THE SINUSES OF THE HEAD communicate with, and may be said to constitute part of, the nasal cavities. They are the frontal, nasal, maxillary, sphenoidal, ethmoidal, and palatine. The frontal sinuses, formed within the frontal bones, are situated so that a straight line extended between the supero- internal angles of the orbits passes opposite to about the angular or deepest parts of their cavities. The sinus (on either side) has a triangular figure. The superior side or roof is flat, and (barring the septa) even upon its surface ; whereas the posterior side is irregular, being convex inwardly, where it is formed by the cranial septum ; concave outwardly, where it is opposed to the part composing the temporal fossa. The inferior side slants from behind forwards, and from below upwards, is irregular on its surface, and open or deficient outwardly, where the cavity communicates with the maxillary sinus. Of the angles, one is directed upwards; another downwards, terminating in the nasal sinus, with which it is conjoined, the two forming one continuous cavity ; the third points backwards, and is directly opposite to the imaginary transverse line above alluded to. The cavity is traversed and divided into several unequal open compartments and recesses by septa ; the principal of which is one extended be- tween the superior and inferior sides : it is partitioned from the opposite sinus by the nasal spine. The sinus is but small in the young compared to its proportionate dimensions in the adult sub- ject : it continues to increase afterwards with age, and ultimately extends throughout the whole of the frontal bone. The nasal sinuses, formed by the nasal bones above and the superior turbinated bones behind, are nothing more than the culs-de-sacs or blind terminations of the frontal sinuses. The maxillary sinuses, the largest of these cavities, arc spacious but very irregularly formed. They are situated below and in front of the frontal. Of this sinus, on either side, the posterior and external walls are formed by the malar and lach- OSTEOLOGY OF THE HORSE. 47 rymal bones, whose orbital processes constitute a thin partition be- tween it and the orbit ; the inferior parts consist of the excavations in the superior maxillary bone; superiorly, the sinus is open, being there continuous with the frontal : the boundary line between these cavities is marked by the suture uniting the lachrymal to the frontal and nasal bones on the outer side, and by the prominent crest formed by the junction of the superior turbinated with the ethmoid bone on the inner ; underneath which part, through a curved (and in the recent subject sort of valvular) fissure, the sinus opens into the middle meatus, between the bases of the turbinated bones. The cavity is but small, and still more irregular, in the young subject, in consequence of the intrusion of the yet uncut molar teeth. The frontal sinus, then, terminates in the nasal, but both dis- charge themselves into the maxillary ; the maxillary has also a blind termination, but empties itself into the posterior part of the middle nasal meatus. The sphenoidal sinus is situated within the palatine por- tion of the body of the sphenoid bone. It has no existence in the young subject, the bone being solid throughout; but in pro- cess of growth a cavernous hollow is formed, which, from the secession and attenuation of the laminae of the bone, continues to enlarge. It communicates, by two ovoid openings, with the ethmoidal sinuses. The ethmoidal sinuses are two cavities, separated by the perpendicular plate, situated beneath the ethmoidal cells. They have openings in front, communicating with the lowermost and largest grooves of the same bone, and with the palatine sinuses. The palatine sinuses are formed between the superior maxillary and palate bones; are situated below and in front of the former; are separated from each other by the vomer ; and open into the maxillary sinuses : they are irregular in form and cavernous interiorly. They are not to be found in the young sub- ject. Some might be inclined to treat them as parts of the max- illary sinuses; they are, however, as perfectly distinct from the latter as the frontal are. IV. — the mouth. The mouth is the cavity included between the superior and infe- rior maxillae, making (in the skeleton)onecommon vacuity with the inter-maxillary space. Its antero-posterior dimensions can be but little varied ; but its supero-inferior diameter will be increased in the ratio of the distance to which the inferior maxilla recedes from the superior; the cavity during the distraction of the jaws as- 48 OSTEOLOGY OF THE HORSE. Sliming the figure of a misplaced > , the angle of which is turned backwards. The mouth is formed — superiorly, by the palatine and supe- rior and anterior maxillary bones ; inferiorly, by the inferior max- illa; laterally, by the molar teeth; anteriorly, by the incisive teeth. Behind, through the posterior opening of the nose, it com- municates with the nasal fossae. OF THE EXTREMITIES. In number, four. — Disposed in pairs. — Divided into fore and hind extremities. I.— THE FORE EXTREMITIES. Situation. — Antero-lateral parts of the trunk, from which they proceed downward. Division. — Into shoulder, arm, knee, leg, pastern, coronet, and foot. OF THE SHOULDER. Constituted of the scapula, superiorly ; and of the humerus, inferiorly. BLADE BONE. (SCAPULA.) Situation. — Antero-lateral part of the thorax. Its position is oblique, the antero-superior angle being directed forwards and upwards ; the postero-superior, downwards and backwards. The former rises above the transverse process of the fourth dorsal ver- tebra ; the latter is opposed to the angle of the seventh rib. The coracoid process comes opposite to the sternal extremity of the first rib. Form. — ^Triangular: inferior angle irregular and detruncated. Broad and thin, superiorly ; narrowing, but growing thicker and more substantial, inferiorly. Division. — Into two surfaces, three borders or sides, and three angles. Surfaces. — External and Internal. The external, some- times called the dorsum scapulae, is divided unequally into two superficial concavities, named the fossae an tea et postea spinatte, by the spine, a longitudinal eminence arising gradually from the superior border, and terminating imperceptibly in the neck, the smooth contracted part above the lower extremity of the bone : the posterior is thrice as large as the anterior fossa ; the one giv- ing attachment to the antea spinatus, the other to the postea spinatus muscle ; and the spine to the trapezius. In the poste- rior fossa, near where it joins the cervix scapulae, is the medullary foramen, directed downward. — T/ie iutertmt surface, also called OSTEOLOr.V OF THE HORSE. 49 the venter scapulee, and sometimes the subscapular fossa, is smooth, though uneven, being excavated in the middle, flattened laterally and inferiorly, and is marked by the attachment of muscles : in the middle, and principally, by the subscapularis ; around the posterior angle, by the teres major ; superiorly, by the serratus magnus ; still higher, along the border, by the rhom- boidei. BouDKKs. — The superior, nearly straight and but little more than half the length of the lateral, is thick, and presents a grooved scabrous summit, into which is fixed the cartilage of the scapula, I'orming a flexible plate of considerable breadth, diminishing in thickness as it ascends from the bone, and terminating in a thin convex edge, which is inclined inward. — The anterior border describes the figure of an inverted S. It is thin, and presents a sharp edge superiorly ; below, it grows obtuse and rounded, and terminates in the coracoid process, a rough hemispherical pro- minence, presenting in front of the shoulder-joint, to which is affixed the coraco-brachialis and flexor brachii. — The posterior border is obtuse, rounded, and smooth, except that, infeiiorly, there are some few unimportant asperities : it affords attachment to the teres minor and large head of the triceps extensor brachii. Angles. — The two superior are rectangular and sharp : the postero-superior has, externally, a prominence just below it, mark- ing the origin of the teres major. — The inferior angle is repre- sented, or, rather, has its place supplied, by the glenoid cavity — the smooth ovoid shallow cup, notched inwardly, formed for arti- culation with the head of the os humeri : it is rendered deeper by a marginal cartilage ; and has around its border inequalities and porosities, to which is fixed the capsular ligament. Between the glenoid cavity and the coracoid process, internally, is an excava- tion, serving for a passage to the tendon of the subscapularis. Connexion. — The scapula is attached to the thorax by the several nmscles passing between them ; also by two ligamentous fasciae. Development. — In the very young subject, the coracoid pro- cess forms an epiphysis : in old age, the cartilage of the scapula takes on ossification. HUMERUS. Situation. — Between the scapula and the arm ; placed in an oblique but contrary direction to the scapula, viz. downwards and backwards ; whereby an angular space, of considerable extent, is left between the two bones. Form. -~Cy\\ndro\d ; presenting the appearance of having been twisted around itself. 50 OSTEOLOGY OF THE HORSE Division. — Into a body and two extremities. Body.— Angular, with expanded flattened sides, superiorly ; contracted and rounded, inferiorly. From its upper, fore, and outer part, projects the tuberosity; whose point is roughened by the insertion of the levator humeri. The outer side of the body is excavated and smooth ; it is occupied by the humeralis externus : the inner side is rather prominent and roughened, and exhibits a small scabrous eminence, which receives the tendons of the latis- simus dorsi and teres major ; also, lower down, we find the medullary foramen, pointing downwards. Superior extremity — Larger than the inferior, presents for consideration a head and four tubercles. — The head is the hemispherical smooth part projecting posteriorly ; it is designed for articulation with the glenoid cavity of the scapula, which it much exceeds in extent of superficies, and thereby obtains more freedom and variety of motion. Into the irregular and indented groove by which the head is surrounded, is fixed the capsular ligament. Anteriorly, the head is surmounted by the tubercles : the three directly in front are anti-articular, and have between them two smooth grooves, which, as well as themselves, are covered by cartilage, and altogether serve as a pulley for the ten- don of the flexor brachii to play over. The outer articular tubercle is joined by a protuberant ridge with the tuberosity. The fourth, or outer tubercle, serves to guard against dislocation. Inferior extremity — Displays a specimen of the diar- throdial or pulley-like articulation. It consists of two condyles, distinct from each other posteriorly, being there separated by a deep ovoid fossa, into which is received the olecranon of the ulna ; but united, inferiorly and anteriorly, into a broad semi- cylindrical articular surface, divided by a prominence encircling its middle into two depressed compartments, of which the inner has twice the breadth of the outer, and bounded by two lateral prominent edges : furthermore, the condyles, of which the inner is larger and more projecting behind as well as before, meet at an angle above the fossa, and there run into union with the body. There are also two scabrous pits above the articular sur- faces in front, which, like the cavity behind, occasionally receive processes of the bone below. Connexion. — The head of the humerus is adapted to the glenoid cavity of the scapula ; the condyles are fitted into concavities upon the upper extremity of the radius. Development. — In the young bone, the head, condyles, and tubercles are epiphyses. OSTKOLOGY OF THE HORSE. 51 OF THE ARM. The arm is composed of a single bone, the os brachii, which corresponds to the human radius and ulna united together. ARM-BONE (OS BRACHII.) Form. — Cylindroid ; flattened before and behind ; slightly curved forwards. Division. — Into radial and ulnar portions. The RADIAL PORTION consists of a body and superior and inferior extremities. The body is long; prominent and smooth anteriorly ; slightly excavated and roughened posteriorly, where it is pierced in a direction downward by the medullary foramen : the former is clothed by the extensor muscles of the leg and foot ; the latter by the flexors of those parts. The superior extremity, like the inferior, expanded into greater breadth than the body, presents an articulatory surface, divided, by a gentle eminence running across the middle, into two concavi- ties, of which the inner is broader and more circular than the outer; the latter, indeed, has a superficial rising, taking the direction which makes a similar but imperfect subdivision of it : those concavities receive the condyles of the humerus. The exter- nal lateral process is more prominent and sharper than the inter- nal, and is surmounted in front by a small tubercular eminence : to these processes the lateral ligaments are attached ; the eminence serves also to deepen the outer cup of articulation. The inferior extremity is remarkable for the number and variety of its articulatory surfaces, and for presenting a hiatus extero- posteriorly, as if a piece of the bone had been chiselled out. It possesses three articulatory surfaces. The largest, or inner one, is quadrilateral in outline, sigmoid in superficies; the middle is similar in form, but of smaller dimensions; the outer, or smallest, is an ovoid convexity. The internal lateral process is the most prominent; the external has a groove along it. The bone is also grooved in front by the passage of the extensor tendons. The Ulnar Portion consists of body, projection, and articu- latory surface. The body is the tapering triangular part which is firmly united above, but more intimately below, with the radial portion ; be- tween the two is an interval, admitting of the passage of a circulus of blood-vessels. — The surface composing part of the humero- brachial articulation, in form a semilunar concavity, is only in part articulatory, the lower half presenting roughened inequalities for ligamentous attachment : it is adapted to the smooth trochleal 52 OSTEOLOGY OF THE HORSE. surface between the humeral condyles behind. — The projeclion, named tJie olecranon, the part corresponding to the elbow in man, is one of considerable magnitude, standing out in a direction u|)- wards and backwards from the upper extremity of the radius; it is prominent and uneven on its outer side, excavated and smooth on its inner, and terminates in a broad, rough protuberance, into which is implanted the triceps extensor brachii. In addition to two sides, it possesses two borders, both sharp, and disposed in curvatures looking inwardly: the anterior terminates in a project- ing point, which forms the superior boundary of the articular sur- face ; the posterior extends down, and becomes continuous with that of the body. Connexion. — With the humerus, above; with the scaphoid, lunar, and cuneiform bones, below. Development. — In young life the ulnar portion forms a distinct bone from the radial, the two pieces corresponding to the ulnar and radius in man or the dog: indeed, the former in the colt ex- tends nearly to the knee; but as life advances, the two portions become so completely amalgamated and cemented together, in- feriorly, that no longer can any trace be found of their original separateness. OF THE KNEE. (CARPUS.) The knee of the horse corresponds to the wrist of man, and for this reason is technically considered as the carpus. It is com- posed of seven small bones: in some instances an eighth has been found. Six of these bones are ranged in rows, forming two tiers, consisting each of three pieces : the seventh is placed completely behind the others. The First, or Superior Row, is formed by the scaphoid, lunar, and cuneiform bones. The Second, or Inferior Row, by the trapezoid, great, and un- ciform bones. SCyVPHOIl) DONE. (oS SCAPHOIDES.) Form — Semi-ovoid : convex and curvated on one side; slightly but unevenly concave on the opposite. — Divided into four sur- faces : — 1st, Superior surface, sigmoid and smooth, articulating with the arm-bone. 2d, Inferior surface, semi-ovoid and smooth, resting upon the trapezoides and magnum. 3d, Interna/ surface, convex, and roughened l)y the attachment of the lateral ligaments. 4th, Interna/ surface, uniting in two distinct places with the lunar hone. OSTEOLOGY OF THE HORSE. 53 LUNAR liONE. (OS LUNARE.) Cuneiform. — Divided into four surfaces, base, and apex : — 1st, Superior surface, triangular, articulating with the arm-bone. 2d, Inferior surface, oblong, uniting with the magnum and un- ciform bones. 3d, Interualsuiface, excavated, joining above and below, with the scaphoid. 4th, luternal surface, excavated, ar- ticulating in two places with the cuneiform bone. — Base, broad and rough, presenting forwards. Apex, obtuse and rounded, turned backwards, CUNEIFORM BONE. (oS CUNEIFORME.) The smallest bone of the superior row. Figure — Pentan- gular. — Divided into five surfaces : — 1st, Superior sufface, small, oval, and cupped, articulating with the arm-bone. 2d, Lferior surface, smooth, resting upon the unciform bone. 3d, luternal suiface, convex and roughened, receives the attachment of the external lateral ligaments. 4th, Internal surface, ']o\w\n^ in two places with the lunar bone. 5th, Posterior surface, ovoid, smooth, and slanting, unites with the trapezium. TRAPEZOID BONE, (os TR A P EZO I D ES.) Situation — Inner side of the knee. Form — An irregular, curvated, flattened cone. Division — into four surfaces, a base, and an apex: — 1st, Superior snrj'ace, smooth and convex, arti- culating with the scaphoides. 2d, Inferior surface, flattened, articulatory, and divided, the larger part resting upon the inner splint bone. 3d, Internal surface, excavated, presenting three sniooth places for articulation with the os magnum. 4th, Internal surface, convex and roughened. Base, looking forwards and inwards. Apex, turned backwards and outwards. THE GREAT BONE. (oS MAGNUM.) The largest bone of the knee. Situated in the middle of the inferior row. Figure — Triangular. Divided into two surfaces, two sides, a base, and an apex. 1st, Superior suiface, presentino- two articulary compartments, one, sigmoid and oblono-, for the lunare ; the other, ovoid and flat, for the scaphoides. 2d, Inferior surface, broad and flat, resting upon the cannon bone. 3d, In- ternal side, excavated, presenting three little surfaces for articu- lation with the trapezoides. 4th, External side, having two smooth places, with a pit between them, for articulation with the next bone. UNCIFORM BONE. (OS UNCIFORME.) Situated outwardly. Form — irregularly conoid. Division into four surfaces, a base, and an apex. 1st, Su- perior sinfncr. convex, and oxtondcH outward -ind backward, 54 OSTEOLOGY OF THE IIOIISE. uniting with the cuneiform. 2d, Ltfeiiur surface, aiticiihitoiy, resting upon the outer splint, and also upon the cannon bone. 3d, Eitenial surface convex and rough, and ligamentous. 4th, Interiial surface presenting two places for articulation with the magnum. Base, presented forwards. Apex, backwards. TRAPEZrUM*. Situation — Behind the cuneiform bone. Figure — Flat, broad, quadrilateral. Division — Into two surfaces and four borders. Jst, External surface, convex, uneven; in places, elevated and roughened for ligamentous attachment. 2d, Internal surface, concave and porous. ^-Borders. Into i\\esuperior is fixed the tendons of the flexores metacarpi ; to the inferior, a ligament ; to the posterior, the posterior annular ligament of the knee : the an- terior possesses two smooth oval surfaces ; one for articulation with the cuneiform, the other with the arm-bone. PISIFORM BONE. (oS PISIFORME.) Not invariably present: in some instances two are found. Si- tuation — Behind the trapezoid bone. Form — Orbicular or pea- shaped, line — Not apparent. OF THE FORE LEG. (METACARPUS ) Frequently called the cannon : sometimes the shank. Although three bones enter into the composition of this part, viz., the large and the two small metacarpal bones, yet does the leg owe its form principally, and its support entirely, to the former one : — LARGE METACARPAL, CANNON, OR SHANK BONE. (OS METACARPI MAGNUM.) Form — Cylindrical ; flattened posteriorly. Division — Into body and two extremities. The Body presents anterior and posterior surfaces. The an- terior surface is rounded, prominent, and smooth, and extends round, laterally, so as to form about two-thirds of the entire su- * Stubbs has made this the Pisiform Bone; whilst the bone here called the Pisiform is his trapezium. Desirous as I am to observe an adherence to the nomenclature of human anatomy, in the present instance the incon- gruity appeared to be such as to warrant the hazard of a transposition of names. The bone which really is of the form and even magnitude of a pea, I have called pisiform ; whilst to Stubbs' pisiform, a broad, flat, ipiadrilateral bone, I have given the name of Trapezium. Girard, the French standard anatomist, calls the small round bone " pisiforme." OSTEOLOCJY OF THE HORSE. 55 perficies of the cylinder. — Tlie posterior surface is flattened, and, in places, depressed. About one-third of its length down, it is pierced by the medullary foramen, directed inward and downward. Its sides present two triangular slips of rough scabrous surface, extending about half way down, marking the places of attach- ment of the small metacarpal bones. The superior extremity presents an articulatory surface, the whole of which is flat, with the exception of a part bevelled off on its outer side, which articulates with the unciform bone ; and a small, depressed, bevelled spot on its inner and posterior side, which receives part of the trapezoid bone : the flat surface sup- ports the OS magnum, to which in figure it corresponds. It front, and rather inclined to its inner side, the extremity has a roughen- ed prominence, into which is implanted the extensor metacarpi : on either side, the bone is asperated by the insertion of lateral li- gaments ; and the rough part posteriorly gives origin to the sus- pensory ligament. The iuferior extremity exhibits an articulatory trochlea, consist- ing of two equal condyloid surfaces, parted by a semicircular emi- nence, which is fitted into a counterpart formation in the upper end of the large pastern bone. These condyles have uneven pits in their sides, into which are fixed the lateral ligaments. Connexion — Superiorly, with the magnum, unciform, and tra- pezoid bones ; laterally and posteriorly, with (he small metacarpal bones ; inferiorly, with the large pastern and sesamoid bones. SxMALl, METACARPAL OR SPLINT BONES. (OSSA METACARPI PARVA.) Number — Two :~ external and internal. Form. — Elongated; pyramidal. Situation — Attached to the lateral and posterior parts of the large metacarpal bone. Division — Into bases, middles, and apices. Extent — They vary somewhat in length : they commonly reach about two-thirds of the large bone, downwards. The base, or head, is turned upwards, and is surmounted by a flat articulatory surface, which enters into the formation of the knee-joint. Below this, the bone is tuberous and rough, for liga- mentous attachment: the external head also receives one of the tendons of the flexor metacarpi externus ; the internal receives the tendon of the flexor metacarpi internus. 2'he middle is trifacial. The anterior surface is asperous, for firm attachment to the large bone ; theinner surface is excavated, to make room for the suspensory ligament ; the outer surface is 56 OSTEOLOGY OF THE HORSE. smooth and rounded. This part is terminated by a sharp edge posteriorly. The apex is tapering and ends in a small bony tubercle, which inclines backwards, away from the large bone. Difference — The external is commonly rather larger than the internal bone ; they are, however, with more certainty distin- guished by their articulatory surfaces. Connexion — The external bone supports the unciform; the in- ternal, the trapezoid : both are attached to the large metacarpal bone. Development — In the growing animal the splint bones are maintained by cartilago-ligamentous connexions : in most adult, and in all old subjects, the ligamentous substance becomes con- verted into osseous matter. OF THE PASTERN. The pastern, corresponding to the first phalanx of the human foot, is supported by the pastern bone ; but it has also two ap- pendices, the sesamoid bones, which are necessary to the forma- tion of the fetlock -joint. PASTERN BONE. (OS S U FFR AGl N IS .) Situation — Below the cannon bone, with which, from taking an oblique direction, it forms an obtuse angle. Form — Cylindroid, flattened before and behind ; larger supe- riorly than inferiorly : about one-third the length of the cannon bone. Division — Into body, and superior and inferior extremities. The body presents two surfaces. The anterior is even and convex : the posterior is uneven, but flattened, and displays a slightly depressed triangular portion, into the asperous angle of which is implanted the short sesamoid ligament. The superior or larger extremity/ consists of two shallow ar- ticular cups, laterally, with a deeper transverse articular groove running between them, in which play the condyles and middle eminence of the lower extremity of the cannon bone. Behind, at the sides of the cups, are two tuberosities, to which are fixed the crucial ligaments. The inferior extremity is bi-convex or condyloid ; consisting of two equal, articular, semi-cylindroid convexities, parted by a transverse shallow depression, running from before backward, but more completely separated by a little pit behind. The asperous prominences on the sides are for ligamentous attachment. Connexion — With the cannon and coronet bones, and with the two sesamoids. OSTE0L0(iY OF THE HORSE. . O/ SESAMOID BONES, (OSSA S F.S A M Ol DE A.) Nitmbei- — Two. — Situated at the back of the articulation formed by the pastern and cannon bones. Fortn — Trapezoid ; three of the sides presenting triangular faces, whose apices unite in one point, which is directed upwards, and whose bases form the fourth side; turned downwards. Division — Into three sides, basis, and apex. The anterior surfaces are excavated, smooth, and articulatory, and along their inward borders, which are opposed to each other, are bevelled oft, by which, by the two together, a groove is formed for the reception of the middle eminence of the cannon bone ; while the concavities extend the articulatory surface for the con- dyles of that bone. — The posterior surfaces are convex and asperous, for the attachment of the suspensory ligament : the two together form a sort of channel between them, in which run the flexor tendons. — The lateral surfaces, which are grooved as well as roughened, receive the branches of the suspensory liga- ment. — The bases grow narrow as they approach each other: their surfaces are rendered uneven by the attachment of the long and sliort inferior and crucial ligaments. Connexion — These bones are articulated only with the large metacarpal ; they are connected both with that and the pastern bone. OF THE CORONET. This part answers to the second phalanx of the human foot. It has for its base, the CORONET BONE. (oS CORONiE.) Situation — Between the pastern and foot. Figure — Nearly square; its breadth exceeding its longitudinal diameter only by about one- fifth. It has four surfaces. The superior suiface is bi-concave — being divided by a simple transverse eminence into two ovoid concavities, into which are fitted the condyloid projections of the pastern bone : this eminence is bounded before and behind by small tubercular elevations ; the posterior receives part of a ligament : the anterior, a portion of the extensor tendon. Laterally and posteriorly, the surface is extended by two projections, to which are fixed the lateral ligaments. The anterior surface is convex, but irregular and asperous. Inferiorly, its sides present two remarkable depressions, into which are implanted the terminating branches of the tendo per- foratus : above and between them, the bone is roughened by the attachment of the extensor tendon. 58 OSTEOLOGY OF THE HORSE. The posterior surface is slightly excavated, and is free from asperities. Superiorly, it presents a smooth lip of bone, between which and the flexor tendon exists a bursal connexion. The inferior surface, like the superior, is entirely articulatory : it closely resembles that of the pastern bone, only it is rather broader. In outline, it has the figure of a painted heart, whose apex is curved forward aud upward : basis, backward and up- ward. It is bi-convex from before backward, consisting of two condyloid prominences, parted by a shallow transverse depression. It is adapted to a counterpart articulatory formation of the coffin bone. Connexion — With the pastern, coffin, and navicular b^ones. OF THE FOOT. The foot, or third phalanx, forms the resting, bearing, or ter- minating part of the limb. The coffin bone constitutes its osseous fabric ; to which the navicular may be regarded as an appendage. THE COFFIN BONE. (OS PEDIS.) Situated within the hoof, which it nearly resembles in /o/7w— Being in its outline semi-lunar: anteriorly and superi- orly, convex ; posteriorly and inferiorly, concave. Its shape, how- ever, varies with the natural make and morbid changes in the form of the hoof. Division — Into wall, sole, tendinous surface, articulatory sur- face, and wings. The wall is the semicircular prominent part in front, and corresponds to the wall or crust of the hoof. It is convex — most so, anteriorly ; it possesses a certain degree of declivity, which increases in degree, but decreases in extent, as we proceed from the front to the sides, the greatest elevation, as well as slant, of the wall presenting anteriorly ; and it exhibits everywhere a fur- rowed and porous surface; the furrows, which run from above downwards, being most distinct inferiorly and laterally ; and the holes or pores consisting of a large and small set, of which the large only are numerable or worthy of particular notice, the small ones being infinite, and numbers of them even imperceptible. The foramina (for the large are alone worthy of the name, the small being simply porosities) are regularly disposed in so far that we invariably find several of them ranged at nearly equal distances around the circumference of the wall, a little above its edge; and two others at or near the terminations of two grooves, which come from the wings, and run along the sides of the wall : five or six others also are commonly seen within the intermediate space, between the two latter. Through the foramina pass blood-vessels OSTEOLOGY OF THE HOR8E. 59 and nerves in and out of the interior of the bone. The porosities serve mostly for the fibrous attachment of the laminae. The inferior or circumj'erent edge of the wall is rather semi-oval than semicircular. It is notched or serrated, particularly towards the sides, where, in places, the notches opposite to the foramina widen into gaps, in order to give passage to blood-vessels to the sole. This edge, in its natural and healthy state, maintains at every point the level of a plane surface. — Superiorly, in the mid- dle, the wall is surmounted by the coronal process, from whose sides sharp waving edges run to the wings, forming the bounda- ries between it and the articulatory surface. The sole exhibits a broad, uniform, concave surface, of the figure of a horseshoe, free from asperities, excepting towards the wings. Still, however, it possesses porosities, or at least shows the marks of the fibrous implantation of the sensitive sole. It is bounded, anteriorly and laterally, by the circumferent edge of the wall ; posteriorly, by a sharp, uneven, semicircular edge, which divides it from the tendinous surface. The tendinous surface has a semicircular shape. It is placed immediately behind the sole, and exhibits — 1st. A rough depression in its fore and middle part, marking the insertion of the tendo perforans. 2dly. Two lateral grooves, passing obliquely inwards, and terminating each in a large foramen. 3dly. A porous space intermediate between the two former divisions, into which is fixed the inferior navicular ligament. The grooves lodge the trunks of the arteries and nerves of the foot, which pass through the foramina into the interior of the bone. The articulatory surface occupies the superior part. It is half-moon- shaped. It presents two lateral cups, extending angularly backwards as far as the wings, with a broad eminence running transversely between them, which rises so gently as to be more perceptible to the finger than the eye. This eminence is terminated in front by the coronal process, having an incurva- tion backwards : behind it, the surface is bevelled off, to which part is opposed the navicular bone. The articular cavities for the coronet bone are deepened by the sharp prominent edge running around their front and sides. The al(z or wings consist of two bifid protuberances, stretch- ing backwards from the body, beyond the limits of the articula- tory surface. The lower and larger division of the ala, projecting directly backwards, is irregular and asperous : to it is attached the cartilage of the foot. The upper portions are tubercular and smooth on their surface: to these are fixed the first pair of the coffin ligaments. Between these divisions of the ala is a notch : (which in the recent subject becomes a perfect foramen ;) ihiougli 60 OSTEOLOGY OF THE HORSE. it passes the lateral artery, to be conducted by the groove leading from it to a foramen (aforementioned) in the wall. Connexion — With the coronet and navicular -bones, and with the hoof. Particularities. — The coffin is a bone of a soft, i. e. of a spongy, fragile texture ; and its intrinsic stability is yet further reduced by the canals pervading its interior for the transmission of blood- vessels and nerves. The very reverse of this is the case with the pastern and coronet bones: they (particularly the latter) are re- markable for compactness and solidity of substance. THE NAVICULAR OR SHUTTLE BONE*. (OS NAVICULARE.) Situation — At the back of the coffin-joint, into whose compo- sition it enters. Form — Semi-lunar : its lunated border, however, will not make above one-third of a circle of such dimensions. D«t;is?o«— Into two surfaces ; two borders ; and two extremi- ties. Surfaces. Tlie superior bears a corresponding aspect to the articulatory surface of the coffin bone, having two superficial la- teral depressions, with an eminence imperceptibly rising between them. Dividing the entire articular surface, formed by the two bones, for the reception of the coronet bone, into five parts, the navicular forms about two divisions. — llie inferior surface is also articulatory ; and also exhibits lateral depressions, but still more superficial than the suj)erior, with an eminence across the middle, narrower and better marked than that above. Over this part plays the tendo perforans. Borders. — The lunated, broadest in the middle, narrowing towards the extremities, consists, superiorly, of a smooth narrow slip of surface along the middle, which is adapted to the bevelled portion of the articulatory surface of the coffin bone; and, below, of a fluted porous part, from which a broad ligament runs to the coffin. — T/ie straight border is thin, compared to the opposite one ; and is, superiorly, rough and porous, where the posterior ligament is attached; inferiorly, smooth and lipped, and continuous with the surface opposed to the tendon. 'The extremities, directed, one outward, the other inward, are obtusely pointed ; and are fixed by lateral ligaments to the coffin bone. n.— THE HIND EXTREMITIES. Situation — Connected with the posterior parts of the trunk, which they support. * Sainhel calls it " The Articular Bone."— Girard considers it as a sesa- moid bone. — (^ur old farriers, in their profound ignorance, have mistaken it for a production of disease, and described it as " the quUtor bone." ! OSTEOLOGY OF THE HORSE. 61 Divisiott— 'Into haunch, thigh, hock, leg, pastern, coronet, and foot. OF THE HAUNCH. The superior part of the haunch is formed by the ihac portion of the OS innominatum ; its middle has for base the os femoris ; below and in front, it is terminated by the patella. ROUND BONE. (OS FEMORIS.) Form — Long, cylindrical. Magnitude — The strongest and heaviest bone in the body; and oneof tJje longest. Direction — Oblique ; from above downward, and from behind forward. Division — Into body and extremities. Body. — Upper part, expanded ; flattened, posteriorly ; promi- nent, anteriorly ; and having, projecting from its outer border, a broad, flat, semicircular process, curved forwards, which is the small external trochanter : to it are fixed the faschia lata, tensor vaginai and gluteus externus. Nearly opposite to this, only somewhat higher, the inner border has an asperous oblong promi- nence, the internal trochanter, which receives the insertions of the psoae and pectineus muscles. The lower half of the body is con- tracted, round, and smooth: and on its postero-external part pre- sents a deep oval pit, with asperous surfaces, which give attach- ment to the gastrocnemii. About the middle of the body, be- hind, is the medullary foramen. The superior extremity consists of two parts : — a hemis- pherical, smooth, articulatory head, looking upwards and inwards, joined to the body by a thick flattened neck, and exhibiting on its inner side a wide deep fissure, into which is fixed the round liga- ment ; the head itself being adapted to the acetabulum in the OS innominatum. The other portion is a larger irregular projec- tion, rising posteriorly into a pyramidal eminence, at the root of which, behind, is a deep oval cavity : this process, the great external trochanter, presents a broad, uneven, asperous surface outwardly, which receives the implantation of the gluteal muscles ; a waving roughened crest, superiorly, to which are attached the obturator muscles ; and a concave smooth surface inwardly, to which is fixed the capsular ligament. The inferior extremity presents for consideration, a trochleal prominence and two condyles. The first, the pulley- like articulatory surface in front, consists of a broad semicircular groove, bounded on either side by a prominence, of which the in- ternal projects much more than the external : over this surface plays the patella. The condyles, most conspicuous posteriorly, much resemble each other, excepting that the external is the 62 OSTEOLOGY OF THE HORSE. thicker, the internal the more projecting, of the two. They ex- hibit bold, convex, rounded articulatory surfaces, presenting infe- riorly and posteriorly, which rest upon the tibia ; on their sides are rough eminences for the attachment of the lateral ligaments ; and between them is a deep asperous fossa, into which are implant- ed the inter-articular or crucial ligaments. At the base of the ex- ternal condyle, below and in front of it, is a pit from which springs the tendon of the extensor pedis. From the condyles, posteriorly, proceed epicondyloid ridges, uniting them with the body of the bone. Connexiou. — With the pelvis, above ; with the patella and tibia, below. Development — The extremities in the growing animal are epiphyses : prior to the adult period, however, they become con- solidated with the body ; and the inferior extremity earlier than the superior. STIFLE liONE. (PATELLA.) Situation — Upon the trocheal surface of the inferior extremity of the round bone. Outline — Quadrangular : convex externally ; irregularly con- cave internally. Division — Into three surfaces and four angles. The anterior surface is convex, most prominent towards the middle, and in places porous and roughened by tendinous and ligamentous attachments. The posterior surface is entirely articulatory, and un- equally divided by an eminence running across it into two shallow concavities, which are adapted to the condyles of the round bone, the inner being the larger one. The superior surface, the space bounded by the superior and lateral angles, is uneven and roughened by the implantation of the tendons of the rectus and vasti muscles. The angles are all blunt or rounded off. To the superior is fixed the tendon of the rectus ; to the inferior and lateral, the li- gamenta patellae : between the superior and external lateral one is an eminence looking like a fifth angle : it gives attachment to the vastus externus. Connexio)i—By muscles and its capsular ligament, with the round bone; by its own four proper ligaments, with the tibia. OF THE THIGH. The bone correspondent to the bone of the thigh— the veritable osfemoris of a man, in the horse enters into the formation of the part we call the haunch; while the tibia and fibula, the human OSTEOLOGY OF THE HORSE. 63 leg bones, become of this quadruped the basis of the part we are in the habit of calling the thigh. TIBIA. Situation — Between the stifle and the hock. Form — Long, straight, prismatic: larger superiorly than infe- riorly. Direction — Oblique; but contrariwise to the round bone. Division — Into body, superior and inferior extremities. The body exhibits three faces and three angles. Ttvo of the faces are smooth, and are seen anteriorly ; one looking outwards, the other inwards: the former covered by the extensor pedis, the latter by the skin. The posterior face is the broadest, and is strongly marked with several longitudinal muscular furrows. 'The anterior angle is rounded ofi", and below disappears altoge- ther : the sides are sharpened and roughened by muscular attach- ment. The superior extremity, more bulky and extensive than the inferior, exhibits — Superiorly, two irregularly ovoid flattened articulatory surfaces, which, by means of intervening cartilages, are accommodated to the condyles of the round bone : these are parted by a small sharp elevation and two asperous pits, into which latter are fixed the crucial ligan)ents. Anteriorly, a jutting pyramidal tuberosity, from which a rough ridge runs downward into the anterior angle of the body, while, above, it ends in a blunt asperous point, turned outwards. At the sides are the two lateral processes, the external the more projecting, for the lateral liga- ments. Between the external lateral process and the tuberosity, is a groove for the passage of the tendon of the extensor pedis ; and below this groove a broad excavated portion of surface, from which arises the flexor metatarsi. The external condyle has on its side a small transversely oval excavation, marking the place of junction of the fibula. The inferior extremity, flattened and spreading but little wider than the body itself, consists of two deep articular grooves, running obliquely from before backwards, and from with- out inwards, and of three sharpened projections : — one, extended obliquely, forms the partition between the grooves ; the others form the lateral processes, of which the internal is more promi- nent than the external, both being roughened exteriorly for the lateral ligaments. The external lateral process has a groove on its side, for the passage of the tendon of the peroneus. Connexion. — With the round bone, above ; the os calcis, below. Development. — The extremities, originally epiphyses, become apophoses prior to the adult period. 64 OSTEOLOGY OF THE HORSE. FIBULA. This small and seemingly unimjjortant bone can be regarded but as an appendix to the tibia. It is a long, slender, pyramidal bone, affixed to the external side of the tibia by a cartilago-liga- mentous substance, similar to that which binds the splint bones to the cannon. Its superior part or head \s bulky, flattened from side to side, and roughened — externally, by the attachment of the pe- roneus and the lateral ligament; internally, by its cartilago-liga- mentous connexion. The inferior part, slender and tapering, extends about half way down the tibia, whence a ligament is continued from its ter- mination to the lower extremity of that bone. Connexion — With the tibia. OF THE HOCK. (tARSUS.) As the knee of the horse answers to the wrist of man, and is therefore analogically regarded as the carpus ; so, in like man- ner, the hock becomes the correspondent part to the instep, and is consequently considered under the technical appellation of ta?-- sus. Six small bones enter into its composition : they are — the astragalus, os calcis, os cuboides, and the ossa cuneiforma : — ex- ternum, medium, and internum. THE KNUCKLE BONE. (ASTRAGALUS.) Situation — Uppermost bone of the hock : the one which alone supports the tibia. j.^0^^ — Distinguished by its pulley-like formation. Division — Into superior, inferior, and posterior surfaces. The superior or pulley-like surface is entirely articulatory, and consists of two bold semicircular prominences, with a deep capa- cious groove between them : the whole admirably adapted to the two o-rooves, parted by their middle projection, in the lower extremity of the tibia. — The posterior surface, extremely irregular, exhibits four polished places for articulation with the os calcis ; and, be- tween them, asperous porous interspaces for ligamentous attach- njent. — The inferior surface, smaller than either of the others, is irregularly flattened, and almost wholly articulatory : it is em- braced by the superior part of the large cuneiform bone. From a pit at the foot of the pulley-hke adaptation, takes its origin the extensor pedis accessorius. OS CALCIS. Situation— liiovms the posterior projecting part, called the point of the hock. OSTEOLOGY OF THE HORSE. 65 Figitre — Irregular. Division — Into body and tuberosity. Th k body is the broad or inferior |);irt. It is irregularly con- vex externally, where it is joined with the tuberosity : concave and expanded intCrniilly, where it presents four surfaces for articula- tion with the astragalus, with asperous interspaces for ligament. The inferior part of the body has a narrow articulatory surface, by which it articulates also with the cuboid bone. The tuberosity, the projecting part behind, is oblong, flat- tened on its sides, and exhibits a thick tuberous termination, into which is implanted the tendons of the gastrocneniii. The exter- nal side is flattened and roughened by ligamentous connexion ; the internal is smooth, and inclines to concavity, by which a space is left which gives passage to the tendon of the flexor pedis. CUBOID BONE (OS CUBOIDES.) Silucttion — Outer part of the hock. Form — Oblong, from back to front. Division — Into external, internal, superior, and inferior surfaces. 'J'he external surface, broad and irregularly curved, is roughen- ed by ligamentous adherence. — The internal surface, irregularly excavated and asperous, exhibits three places of articulation : one, posteriorly, for the great cuneiform ; the other two smaller, one anteriorly, one posteriorly, for the middle cuneiform bone. The superior surface has two articulations, with a little pit between them ; one for the astragalus, a larger one for theos calcis. — The inferior surface presents two articulatory places ; one for the ex- ternal splint bone, the other for the cannon bone. THE LARGE CUNEIFORM BONE. (OS CUNEIFORME MAGNUM ) Situation — Immediately underneath the nstragalus. Figure — Triangular: broadest side turned forwards; salient angle, backwards. Flat, above and below. Division— \nio superior and inferior surfaces, sides, and angles. —■The superior surface is entirely articulatory, with the exception of a little rough groove running to its middle from the outer side, which terminates in the medullary hole : it is adapted to the under part of the astragalus. — The inferior surface \s very similar in appearance to the superior, except that it is flat, or rather in- clines to convexity : it articulates with the middle cuneiform, and also, next the internal angle, with the small cuneiform. — I'he sa- lient or posterior angle, has on its external side a surface for arti- culation with the cuboid. Connexion With the astragalus, cuboid, middle and small cuneiforni bones. 66 OSTEOLOGY OF THE HORSE. THE MIDDLE CUNEIFORM BONE. (oS CUNEIFORME MEDIUM). Situation — Underneath the large cuneiform ; upon the hind cannon bone. — Figure and Division, the same as the large bone. • Superior Siiid inferior surfaces, also similar: the former articu- lates with the large bone ; the latter with the hind cannon bone. — The salient angle, behind, is sharper and more projecting: near its point, externally, is a small surface for articulation with the cuboid. THE SMALL CUNEIFORM BONE. (oS CUNEIFORME PARVUM.) Situation — Postero-internal part of the hock. Figure — small : irregular. Connexion — Superiorly, it articulates with the internal angle of the large cuneiform ; anteriorly, with the same angle of the middle cuneiform ; below, principally, with the internal hind splint bone ; partly, also, with the hind cannon bone. THE METATARSAL, HIND CANNON, OR SHANK BONE. (OS METATARSI MAGNUiM.) As the cannon bone of the fore leg is said to be a match for one of the longest metacarpal bones found in the human hand ; so this bone, in comparative anatomy, is regarded as a fellow of one of the metatarsal bones which compose the foot, although it is, in the horse, the bone of the hind leg. It so nearly resembles the fore cannon bone, that the two, at first sight, appear to be pre- cisely alike : there are differences, however, between them, and, in particular, three : — 1st, The bone of the hind leg is longer by about one-sixth part than the bone of the fore leg ; 2dly, the body of the former is rounder and more prominent anteriorly than that of the latter ; 3dly, the superior articulatory surfaces are different ; one being such as is adapted to the middle and small cuneiform and cuboid bones; the other accommodates the inferior row of the bones composing the knee. The PASTERN, SESAMOID, CORONET, COFFIN, and NAVICU- LAR BONES of the hind extremity, so closely resemble their fellows ill the fore, that the description already given of the latter, will be found to answer here. APPENDAGES TO THE HEAD ; To wit, the os hyoides and the teeth. THE OS HYOIDES Consists of a frame-work of small bones, connected together by ligament, situated between the larynx and the root of the tongue. Division — Into five pieces: body, and four horns. OSTEOLOGY OF THE HORSE. 67 The body has the precise shape of a spur; consisting of a semi-circular portion, from the middle of the convex side of which projects a straight part, corresponding to the neck of the spur : this (latter) part, also called the appendix, is surrounded by the root of the tongue, to the fleshy fibres of which both its sides and extremity afford original attachment. The branches, or sides of the spur, are directed backwards, embracing between them the superior border of the thyroid cartilage. The curved part, from which the branches and neck spring, is broader and thicker than elsewhere, and has, laterally, two small articulatory knots with which the short horns are connected. The horns are four in number — two long, and two short. 2Vie short, or inferior horns, ascend obliquely from their articu- latory connexions with the body, and terminate in two oblong smooth extremities, which form similar joint-like connexions with the long horns. They are flattened on the sides, and their ante- rior borders are sharper than their posterior. They give attach- ment to a pair of the muscles of the tongue. — The long, or superior horns, constitute two long, flattened, thin bones, extending back- wards, in a horizontal direction, from the summits of the inferior horns, with which they are articulated. Each horn presents — two smooth polished surfaces, viz. an internal and an external side ; two borders, an anterior and a posterior, the latter surmounted by a prominent crest; and two extremities : the supero-posterior has a cartilaginous junction with the hyoideal process of the petrous portion of the temporal bone; the infero-anterior, with the short horn. This bone gives attachment to the stylo-hyoideus and hyoideus magnus, and also to the pharynx. Connexion — With the temporal bone, larynx, pharynx, tongue, and some of the muscles of the neck. Development. — In the young animal the body itself is separa- ble into three pieces. THE TEETH : The instruments for the abscission and manducation of food. Number — Forty; disposed in pairs ; twenty in each jaw. Conformation — Conoid or oblong ; infixed within distinct alve- oles formed in the maxillae; whence we distinguish, in each tooth, a part without and a part within the socket: to the former portion we give the name of body, and that of face to the wearing surface of it ; the latter is called the root, and the pointed extremity of it, the fatig. Structure. — The tooth is composed of two hard substances, distinct from each other in aspect as well as nature; viz. a dense. 68 OSTEOLO(iY OF THE HORSE. hard, solid bone, which is organic ; and a still whiter and harder part, called enamel^ which is inorganic. It is only the body of the tooth which is coated with enamel; the root is quite destitute of it: the former owes its polished whiteness to it. Upon the face it is variously disposed, according to the form of the tooth, from which it sinks, more or less deeply, into the heart of all teeth excepting the tusks; forming thereby small funnel-shaped ena- mellated cavities, called the infundibula, whose mouths, named ihe pits, are indicated by the black marks upon the faces. The tooth is essentially formed of bone, the enamel being no more than a covering or defence to it. Within the bone is a cavity, corresponding in shape and dimensions to the tooth itself. This, the cavitjj of the tooth, contains the pulp, inclosed within the membrane of the tooth: these parts are amply furnished with blood-vessels and nerves, which gain admission through the points the fangs. Distribution. — Into three classes: 1st, the Incisors, or cutting teeth ; 2d, the Molares, or grinding teeth ; 3d, the Canini, or tusks. The incisors, twelve in number, are ranged in parabolic curves in the anteriormost parts of the jaws. — Form — A bent cone, of which the face is the basis; the fang, the apex. Face, elliptical. Pit of the same figure, and single. Fang, single, conical. The teeth in the upper jaw are somewhat larger than those in the lower. The forms, but more particularly the faces, of these teeth undergo alteration as age advances. Thk molars, twenty-four in number, are implanted, in four rows, into the sides of the jaws — twelve in the upper, and twelve in the lower maxilla, six on each side ; equal in magnitude to four or five incisors united together.' — Figure, oblong, quadrangu- lar, excepting the first and last, which are triangular. , Fucen, pre- senting two transverse ridges and two pits : those of the triangular teeth have an additional eminence. Infundibula, two in each tooth, which imperfectly divide the cavity, by extending through it down to the fangs, into chambers. — Fangs: an upper molar possesses three, excepting the first and last teeth, which have, occasionally, but two each. The lower molars have but two fangs. The canine teeth, or tusks, are four in number, two in each jaw, having isolated stations in the interspaces at the sides of the body of the maxilla, between the lateral incisors and the first molars. — Form, a double cone, slightly incurvated, whose bases are joined together in one body : during growth the inner side is slightly concave and fluted. — Cai'/Yj/ extends uninterrupt- edly through the whole length of the tooth. — Fang, single and perforated. No infundibulum. — Characteristic of the male : in the female, either imperfect or undeveloped. OSTEOLOGY OF THE HORSE. 69 Development of the Teeth. — The teeth with which the young- animal is provided, are, at certain intervals of age, cast off and replaced by others : hence the distinction of these two sets into temporary and permanent teeth. The temporary/ teeth are twenty- four in number — twelve incisors, and twelve molars. The tempo- rary incisors differ from the permanent — 1st, in being smaller and whiter; 2dly, in having necks or contractions where the root joins the body ; 3dly, in their fangs being slenderer and more pointed. The temporary molars differ from the permanent set — 1st, in number; 2dly, in being, individually, smaller and whiter; 3dly, in the eminences upon the faces being sharper. OF THE ARTICULATIONS OR JOINTS OF THE SKELETON. TRUNK. Akticulations between the occiput, atlas, and axis. —The condyles of the os occipitis are embraced by the smootii excavations forming the inner sides of the atlas: these articulary surfaces are covered with cartilage, and the two bones are fasten- ed together, by — 1st, Lateral ligaments, passing from the coro- noid processes of the occiput to the fore parts of the body of the atlas, to be fixed to the roots of its transverse processes ; 2d, The suspensory ligament of the head, fixed to the body of the atlas, between its anterior articular processes and the upper border of the occij)ital hole; 3d, The capsular ov synovial membrane, at- tached to the body of the occiput, around the roots of the condy- loid processes, and to the body and anterior articular processes of the atlas. It detaches a process to the membranous envelope of the odontoid projection, by which all communication is cut off between the joints formed by the first and second vertebrae. The axis articulates with the atlas, but is also connected with the occiput. It has — 1st, The superior ligament, passing from the spine of the axis to the inferior part of the bony ring of the atlas; 2d, The inferior ligament, broad, connecting their inferior spinous projections together ; 3d, The three odontoid ligaments : — two long, passing from the sides of the odontoid process to the inner sides of the occipital condyles ; the short and broad one, running from the point of the process, along a bony canal, to the antero-inferior part of the atlas ; 4th, Capsular membrane, in- cluding the articulatory surfaces, which are encrusted with carti- lage, of the first and second vertebrte, is attached around the pos- terior articular processes of the atlas and tlie anterior of the axis, around the odontoid process, and also to the odontoid ligaments. 70 OSTEOLOGY OF THE HORSE. In the ordinary movements of the head, all the cervical ver- tebrae, more or less, participate: it is only in the nodding motion, or sudden chuck of it, that the occipital joint is especially called into action. When the nose is carried to one side, the odontoid process revolves upon its own axis within the cavity of the atlas. Common articulations of the vertebra. — All the ver- tebrae, excepting the atlas and last lunsbar, articulate one with another, before and behind, through the apposition of their bodies, and the adaptation of their articulatory processes. They are bound together by — 1st, The inferior vertebral ligament, con- sisting of bands of ligamentous fibres running obliquely along the inferior surfaces of the bodies of the vetebrae, expanding as they approach, and taking root in each intervertebral substance ; 2d, The superior vertebral ligament, situated within the vertebral ca- nal*. It pursues the same course along the inner surfaces of the upper portions of the rings which the inferior ligament does be- low, maintaining the whole more firmly together; 3d, Inter- transverse ligaments, binding together the transverse processes ; 4th, Inter-spinous ligaments, between the spinous processes, but found only in the back and loins ; 5th, Capsular tnembranes, in- closing the smooth cartilaginous surfaces of the articulatory pro- cesses; 6th, The intervertebral Jibro-cartil ages, forming the prin- cipal bond of union between the vertebrae (so strong a one, that rather than this substance will part from its attachments, the bone itself will give way), consist of so many dense, concentric, fibrous substances, interposed between the bodies of the vertebrae, to the surfaces of which they are most firmly and inseparably in- herent. In form, they correspond to the bones, but in thickness and volume they differ in each vertebral region. The fibres are found to cross and intercross one another, and to be so disposed as to leave in the centre spaces, which are filled with a soft, pulpy, elastic tissue, which adds to facility of motion; 7th, Ligamentum Nucha vel Subjiavum, an elastic ligamentous substance, reaching from the occiput to ihe coccyx. It arises from the occipital tu- berosity, and there consists of a cylindrical chord. It is conti- nued backward along the superior border of the neck, and stretches broader and broader as it proceeds, in order to reach down to the spinous processes, to all of which (with the exception of the first) it is fixed. It is broadest at the dip made by the spine in front of the withers. As it approaches the tallest dorsal spine, it narrows, and, after having passed the sixth or seventh, again becomes a chord, or rather a band, whose greatest breadth is cross- * It cannot be demonstrated without sawing tlu-oiigh the bony arches. OSTEOLOGY OF THE HORSE. 71 wise. It passes onward, covering and connecting- the remaining superior spines of the back, and also those of the loins, sacrum, and coccyx, growing upon the last bone gradually smaller and smaller, and ultimately vanishing upon its extremity. Being highly elastic, it will admit of all the motions the spine is suscep- tible of; while it has a continual tendency to maintain or recover its original or natural form. Articulations of the thorax. — The vertebral extremity of the rib forms three distinct and separate joints with the spine, and is further maintained by two ligaments:— 1st, Capsular mem- brane of the head, in its attachment surrounds and includes the whole of the head ; but sends ofJ'a process, internally, by which the surface opposed to one vertebra is formed into a synovial ca- vity, distinct from that which is adapted to the other vertebra, next to it. This part of the union is strengthened by some liga- mentous fibres which spring from the summit of the head ; 2d, Capsular membrane of the tubercle, surrounds the process at its articulation with the transverse process of the vertebree; 3d, Ex- ternal ligament, fixing the neck of the rib to the spine, exter- nally ; 4th, Internal ligament, a similar one, internally. The cartilages of the true ribs, which are attached immediately to the sternum, are received into the cups in the lateral borders of that bone, and maintained there by — 1st, Ligamentous ex- pansions, radiating from the surfaces, both superior and inferior, of the sternum to their extremities; 2d, Capsular membranes, inclosing the extremities within their sockets. The several portions of the sternum are united, one to another, by fibro'Cartilaginous interpositions ; and their union is strength- ened by the ligamentary expansions upon the surface, internal as well as external. The anterior bone is surmounted by a cartilage of considerable breadth, which extends in a curvature upwards, not unlike the form of the keel of a ship ; hence it has got the name of the cariniform cartilage. Articulations of the pelvis. — The sacro-vertehral arti- culation, formed between the last lumbar vertebra and the base of the sacrum, consists — 1st, of an inter-vertebral substance in the middle, similar to what exists in the spine; 2dly, of two superior transverse ligaments, affixed to the transverse processes; and, 3dly, of two inferior transverse ligaments, which run from the fourth and fifth transverse processes of the loins to the crista of the ileum. — 'The sacro-iliac articulations are formed by the in- terposition of fibro-cartilaginous substances between the trans- verse processes of the sacrum and the venters of the ileum, resting upon them ; and is strengthened by ligamentary bands passing from the posterior spines and borders of the ileum to the trans- 72 OSTEOLOGY OF THE HORSE. verse processes of the sacrum. — The sacro-sciatic iigaments are broad expansions stretched across the sacro-sciatic notch. They are fixed to the transverse processes of the sacrum and those of the two or three anteriormost bones of the coccyx, and to the pos- terior parts of the ileum and ischium, and also to the tuberosity of the latter bone. Towards the anterior part of the notch, the liga- ment exhibits an oval opening, through which pass the sciatic blood-vessels and nerves. — The obturator ligament is the fibro- membranous expansion stretched like a drum-head across the ob- turator foramen: through its anterior part is a hole for the trans- mission of the obturator artery and vein. — The symphysis pubis is formed by the junction of the two ossa innominata, by means of a fibro-cartilaginous substance adherent to the opposing sur- faces. — The sacro-coccygeal articulation, formed between the sacrum and coccyx, is the same as a common vertebral joint. FORE EXTREMITY. The shoulder-joint* is formed betweien the head of the humerus and the glenoid cavity of the scapula: their adaptation (as dried bones) appears incomplete, in consequence of the com- paratively disproportionate magnitude of the ball to the socket: this is in some degree compensated for, however, by the project- ing border of the cartilage with which the glenoid cavity is lined. The bones are maintained in apposition by — The capsular mem- brane, which is found very loose when denuded of the surround- ing adherent muscles, bagging about the bones, in order that it may not, in the least, restrain their freedom of motion : it is in- serted around the rough margin of the glenoid cavity, and around the neck of the humerus. Its internal surface is synovial ; its exterior is clothed by firmly adherent muscles, to which the chief strength of the articulation is owing; viz. its outer and anterior parts by the antea and postea spinati ; its inner and posterior parts by the subscapularis and teres minor. The elbow-joint* is constituted of the condyles of the hu- merus moving in the concavities upon the superior extremity of the arm-bone, the surfaces of which are covered by cartilage. The joint is maintained by — 1st, The capsular membrane, which is thin, infixed around the condyles, including their cartilaginous surfaces and the hollow behind them, and around the edges of the articulatory parts of the arm-bone ; also to the olecranon pro- cess, to the lateral ligaments, and to the tendinous roots of the flexor muscles of the leg. 2d, The lateral ligaments. * These well-understood and familiar appellations are preserved in pre- ference to the adoption of those of a new nomenclature, viz., scapulo-hume- rat, humerO'brachial, &c. articulations. OSTEOLOGY OF THE HORSE. 73 The internal, implanted above, into a depression in the side of the internal condyle of the humerus, and below, where it becomes bifid, into the border of the inner articular cavity of the radial portion of the bone, and also into the body of the bone, about three inches below the first insertion. The external, shorter and stronger, runs from a similar depression on the external condyle to a tubercle on the upper and outer part of the radial bone. — In the young subject, the ulnar portion of the arm-bone is united to the radial by a fibro-cartilage ; but this gradually undergoes conversion into bone as the adult period approaches. Knee-joint. — This includes four distinct articulations : one between the arm-bone and the upper row of the carpal bones ; a second, between the upper and under rows of the carpal bones themselves ; a third, between the under row and the three meta- carpal bones ; a fourth, situated posteriorly, between the trape- zium and the cuneiform bone. They have ail their own proper capsular membranes, which are attached around the borders of their cartilaginous surfaces, and consequently have no communi- cation one with another. The knee-joint altogether is further maintained by — 1st, The lateral ligaments : the e.t7e;'»a/, passing on the outside from a tubercle on the arm-bone to the head of the external metacarpal bone ; the internal, divided into two portions proceeding together from a similar tubercle on the inner side of the arm-bone, the longer to be fixed to the head of the internal splint-bone, the shorter to the inner and fore part of the large metacarpal bone. Besides these, there are two annular liga- ments, one, the anterior, traversing the front of the knee, being- attached on the sides, and confining down the extensor tendons ; the other, the posterior, passing across, behind, from the scaphoid and cuneiform bones to the trapezium, inclosing the flexor tendons. The fetlock-joint is composed by the apposition of the in- ferior condyloid extremity of the cannon bone to the upper bi- concave surface of the pastern bone, and by the addition, poste- riorly, of the sesamoid bones, which are also fitted to the con- dyles of the cannon. Its binding parts are— 1st, The capsular membrane, which is infixed into the bone around the borders of the cartilaginous surfaces, and in front is inseparably united with the extensor tendon. 2d, The internal lateral ligaments : the long one passing from a little projection on the side of the large meta- carpal bone to the pastern ; the short one, passing underneath the former, from a depression immediately below the eminence to the pastern, behind the insertion of the long ligament. 3d, The se- ven SESAMOID ligaments: — a. The suspensory ligament^ (so * Bourgelat has regarded it as a tendon — " le tendon suspenseur dii boulet;" Girard as a muscle — " M. Tarso-phalangien." 74 OSTEOLOGY OF THE HORSE. called, I imagine, because the sesamoid bones seem to be sus- pended by it) is, perhaps, the strongest in the whole body, and is remarkable for jts high degree of elastic property. It takes root, superiorly, in a projection at the upper and back part of the cannon, whence it passes, inclosed within a cellular sheath, be- tween the splint bones, tilling up their interspace. Opposite to about the terminations of these small bones, it splits into two di- visions, which, diverging in their descent, become implanted into the lateral and posterior parts of the sesamoid bones, and into the fibro-cartilagiuous substance uniting them. From the places of implantation, two lateral slips are continued from it downward and forward to join the extensor tendon. Between the suspen- sory ligament and the joint, enveloped in adipose membrane, are some large bursa tnucosa. In composition and texture, this ligament possesses peculiarities : it has a sanguineous tinge inte- riorly, which is not perceptible in other ligaments or in tendons ; and its fibres, which are very coarse, are disposed in layers. But its chief peculiarity consists in its exhibiting an intertexture of de- licate, pinky, //esAy fibres, which appear to be the uniting me- dium of the ligamentous fasciculi, b, The long inferior ligament runs from the bases of the sesamoid bones, along the back of the pastern bone, to the upper extremity of the coronet bone, where it expands over the posterior part of the pastern joint, c, The short inferior ligament arises, by two portions, also from the bases of the sesamoid bones, where it is in part concealed from view by the former : it is implanted, a little lower down than the long one, into a well-marked angular asperity on the back of the pastern bone, c, Two external lateral ligaments are extended from the outer projecting angles of the sesamoid bones ; one to the cannon bone, the other to the pastern, d, Two crucial ligaments, si- tuated underneath the interior ligaments. They run, decussating- each other, from the bases of the sesamoid bones to the upper and posterior or projecting parts of the pastern bone. Pasteun-joint. — The condyloid eminences, terminating the inferior extremity of the pastern bone, fit into corresponding de- pressions upon the upper end of the coronet bone, the opposing surfaces being covered with cartilage. The articulation is fur- nished with — 1st, Capsular membrane infolding the smooth carti- laginous ends of the bones, and firmly inherent into their borders : it is also interwoven with the extensor tendon, which passes over it in front, and behind becomes inseparably united with the infe- rior sesamoid ligaments. 2d, Long lateral ligaments, rooted in rough surfaces on the sides of the pastern, whence they proceed to the coronet bone. 3d, Short lateral ligaments, broader and stronger than the former, are attached anteriorly to them, to the OSTEOLOGY OF THE HORSE. 75 same bones, above and below. — The long inferior sesamoid liga- ment protects this articulation behind, and the extensor tendon forms a broad defence to it in front: indeed, both these parts are so knitted in texture with the capsular membrane, that they ap- pear to form the principal strength of it. Coffin-joint. — The condyloid prominences constituting the inferior extremity of the coronet bone, are received into a bi-concave hollow formed by the upper surfaces of the coffin and navicular bones, although in an inconsiderable degree by the latter. The articulation is secured by — 1st, The capsular membrane, which inwraps the cartilaginous surfaces, and becomes inserted around their boundaries. In front, it is interwoven with the extensor tendon ; behind, it is greatly strengthened by connexion with the tendo perforans. 2d, Three pairs of ligaments of the coffin bone. a, First pair pass from the superior edges of the alae of the coffin bone upon the sides of the coronet bone, and are fixed about its middle. /», Second pair are stretched from the extremities of the aloe, also to the coronet bone, and are inserted below and behind the first. Third pair s\i\mg irova i\\Q sides of the coronal pro- cess, and run to be fixed to the cartilages. 3f/, Four liga- ments, two single and one pair, belonging to the navicular bone, a, Superior ligament, extending from the upper and posterior part of the bone to the tendo perforans. b. Inferior li- gament, a very broad one, occupying the entire lower edge of the bone, and thence passing into the coffin bone, just above the in- sertion of the long flexor tendon, c, The tivo lateral ligaments, fixing the lateral extremities of the shuttle to the sides of the co- ronet bone. The coffin ligaments are slight in comparison to those of the pas- tern and fetlock, because the coffin bone, from its situation within the hoof, is not liable to dislocation. Section II. MUSCULAR SYSTEM. OF THE MUSCLES. The fleshy parts of the body prove on dissection to be naturally divisible into numerous compact masses, assuming various forms and sizes, constituting so many distinct and separate muscles, whose number may be estimated at about 312. The majority of the muscles possess tendons or sinews, which are to be re- garded as component parts of (rather than appendages to) them. The symmetry of the entire body is preserved by each half pre- /b MUSCULAR SYSTEM. senting (as well as bones) muscles corresponding in every essen- tial particular ; hence they are described as pairs, of which we reckon 151 : the remaining ten being single muscles*. The fol- lowing Table exhibits the classification of the muscles into regions, indicative of their situation and relative connexion : it also dis- plays the respective nomenclatures of the English and French veterinary schools ; the former, met with in the works of Snape, Stubbs, and Blaine, will be found to have been borrowed from human anatomy ; the latter arose with Chaussier, and has been introduced very happily into veterinary anatomy by Girard. I.— MUSCLES COMMON TO THE HEAD AND TRUNK. No. 1. Cuticular Region. English names. French names. Membrana Carnosa, j Musculus Subcutaneus. vel Pannicuhis Carnosus S H.— MUSCLES OF THE HEAD. No. 92. 1st. — Auricular Region. No. of Muscles 9. .^. „ ^ ^ . rTeniporo-auricularis Externus Attollentes et .J Zygomatico-auricularis Adducentes Aurein i \ Temporo-auricularis Internus Anterior Conchae Scuto-'aiiricularis Externus Posterior Conchse Scuto-auricularis Internus iCervico-auricularis Externus Cervico-auricularis Medius Cervico-auricularis Internus Abducens t-^/Depriinens Aurem Parotido-auricularis Mastoido-auriciilaris, 2d.— Palpebral Region. No. 2. Levator Palpebrae Super. Externus, \ t^^ . ^,.„„,. •,• ..v ^./Corrusator Supercilii + / Fronto-supercihans [usculus Ciliaris, vel Orbicularis Palpebrarum 3d. — Ocular Region. No. 8. Levator Palpebra; Super. (Internus) Orbito-palpebralis AttoUens vel Levator Oculi Rectus Superior Oculi Deprimens vel Depressor Oculi Rectus Inferior Oculi Abducens vel Abductor Oculi Rectus Externus Oculi Adducens vel Adductor Oculi Rectus Internus Oculi Obliquus Superior vel Trochlearis Obliquus Magnus Oculi Obliquus Inferior Oculi Obliquus Parvus Oculi M. Septimus Oculi Suspensorius, | ^ p^^^^^j^^ q j; vel Retractor Oculi J * This computation does not include the Muscles of the Internal Ear. + Stubbs considers the tendinous expansion of this niusrle as distinct, under the name of " Epicianius." Musculus Ciliaris, | Orbicularis Palpebrarum . MUSCULAR SYSTEM. ' 77 4th.- Anterior Maxillary Region. No. 12. English names. French names. Zygomaticus Zy^omatico-labialis Levator Labii Superior. Alseq. Nasi Super-naso-labialis Dilatator Naris Lateralis Super-maxillo-nasalis Magnus Nasalis Longus Labii Super. Super-maxillo labialis Caninus, vel Levator Anguli Oris X oTtlie" \ Alveolo-labialis Buccinator Alveolo-labialis Depressor Labii Liferioris Maxillo-labialis Levator Menti Mento-labialis Dilatator Narium Anterior Naso-transversalis Nasalis Brevis Labii Superioris Super-niaxillo-nasalis Parvus Depressor Labii Superioris Orbicularis Oris Labialis, Anterior et Posterior. 5th. — Posterior Maxillary Re<>ion. No. 5, Temporalis Temporo-maxillaris Masseter Zyo-omatico-maxillaris Stylo-raaxillaris Stylo- maxillaris Pterygoideus Internus Spheno-maxillaris. Pterygoideus Externus The remaining- Regions of the Head are comprehended within THE Submaxillary Space. 6th. — Hyoideal Region. No. 6. Digastricus \ c .v J Stylo-maxillaris Mylo-hyoideus Mylo-hyoideus Genio-liyoideus Genio-hyoideus Hyoideus Magnus Kerato-hyoideus Magnu« Hyoideus Parvus Kerato-hyoideus Parvus Stylo-hyoideus Stylo-hyoideus 7th. — Glossal Region. No. 4. Hyo-glossus Longus Kerato-glossus Hyo-glossus Brevis Hyo-glossus Genio-hyo-glossus Genio-glossus Lingualis Lingualis 8th.— Pharyngeal Region. No. 5. Hyo-pharyngeus Kerato-pharyngeus Palato-pharyngeus Pterygo-pharyngeus Constrictor Pharyngis Anterior Hyo-pharyngeus Constrictor Pharyngis Medius Thyro-pharyngeus Constrictor Pharyngis Posterior Crico-pharyngeus Aryteno-pharyngeus 9th. — Laryngeal Region. No. 7. Hyo-thyroideus Hyo-thyroideus Crico-thyroideus Crico-thyroideus Crico-arytenoideus Posticus Crico-arytenoideus Posticus Crico-arytenoideus Lateralis Crico-arytenoideus Lateralis Thyro-arytenoideus Thyro-arytenoideus Aryteuoideus Arytenoideus Hyo-epigiottideus Hyo-epiglottideus. 78 MUSCULAR SYSTEM. 10th.— Pulatine Region. No. 2. English names. French names. Tensor Palati Stylo-staphyleus Circuniflexus Palati Staphyleus. III.— MUSCLES OF THE TRUNK, No. 1 13 «.— MUSCLES OF THE NECK. No. 40. 1st. — Hiimero-Cervical Region. No. 2. Rhomboideus Longus vel Minor Cervico-acroniialis Levator Humeri Cervico-subscapularis. 2d. — Lateral Cervical Region. No. 4. Splenius Cervieo-mastoideus Comple.xus Major Dorso-occipitalis Trachelo-niastoideus Dorso-mastoideus Spinalis Colli - Dorso-spinalis. 3d. — Superior Cervico-occipital Region. No. 5. Complexus Minor Axoido-occipitalis Longus Rectus Capitis Posticus Major Axoido-occipitalis Brevis Rectus Capitis Posticus Minor Atloido-occipitalis Parvus Obliquus Capitis Superior Atloido-mastoideus Obliquus Capitis Inferior Axoido-atloideus. 4th. — Inferior Cervical Region. No. 6. 1 Tfl^'^ I Levator Humeri Mastoido-humeralis Sterno-maxillaris Sterno-maxillaris Sternchyro-hyoideus | i::fr:Ko£s Subscapulo-hyoideus Subscapulo-hyoideus Scalenus Costo-cervicalis Longus Colli Subdorso-atloideus. 5th. — Inferior Cervico-occipital Region. No. 3. Rectus Capitis Anticus Major Trachelo-suboccipitalis Rectus Capitis Anticus Minor Atloido-suboccipitalis Obliquus Capitis Anticus Atloido-styloideus. i.— MUSCLES OF THE THORAX. No. 3/. 1st. — Dorso-scapular Region. No. 3. Trapezius Dorso-acroniialis Latissimus Dorsi Dorso-humeralis Rhomboideus Brevis vel Major Dorso-Subscapularis. 2d.— Pectoral Region. No. 3. p, . ,. rp ( Sterno-aponeuroticu!? Pectorahs Pransversu. | Sterno-humeralis Pectoralis Magnus Sterno-lrochincus Poctoralis Parvui: Sterno-scapularis. MUSCULAR SYSTEM . 79 3d.— Costal Region. No. 3. English names. French names. C Costo-subscapularis Serratiis INIairnus ' Dorso-costalis V Liimbo-costalis Intercostales Externi Intercostales Exteriii Intercostales Interni Intercostales Interni. 4th. —Sternal Region. No. 3. Lateralis Sterni Costo-sternalis Sterno-costales Externi Sterno-costales. Sterno-costales Interni 5th. — Dorso-costal Region. No. 3. Superficialis Costaruni Dorso-costalis Transversalis Costaruni Trachelu-costalis Levatores Costaruni Transverso-costales. ()lh.— Dorsal Region. No. 3. Longissinms Dorsi Ilio-spinalis Spinalis Dorsi Seini-spinalis Dorsi Transvcrso-spinalis Dorsi. 7th. — Diaphragmatic Region. No. 1. Diaphragma Diaphragma. c— MUSCLES OF THE ABDOMEN. No. \ J" ^}^ ^^^^^\ 'H' I in the Female, 33. 1st — Lumbar Region. No. 6. Semi-spinalis Lumboruni Intertransversales Lumboruni Sacro-lumbalis Sacro-costalis Psoas Magnus Sublunibo-trocliantineus Iliacus Iliaco-trochantineus Psoas Parvus Sublumbo-pubialis. 2cl. — Abdominal Region. No. 4. Obliquus Externus Abdominis Costo-abdoniinalis Obliquus Internus Abdominis Ilio-abdominalis Transversalis Abdominis Lumbo-abdominalis Rectus Abdominis Sterno-pubialis. 3d.— Anal Region. No. 2. Sphincter Ani Sphincter Retractor Ani Ischio-analis Ischio-perincalis. 4th. — Genital Region (in the Male). No. 4. Cremaster Ilio-testicularis Erector Penis Ischio-subpenialis Triangularis Penis Ischio-urethralis Accelerator Urinae Perineo-urethralis. 80 MUSCULAR SYSTEM. Genital Region (in the Female). No. 2. English names. French names. Tf ^ riiu -A- S Ischio-clitorideus Erector Clitondis j Sacro-clitorideus Sphincter Vaginae Perineo-clitorideus. 5th. — Coccygeal Region. No. 4. Erector Coccygis Sacro-coccygeus Superior Depressor Coccygis Sacro-coccygeus Inferior Gurvator Coccygis Sacro-coccygeus Lateralis Compressor Coccygis Ischio-coccygeus. IV.— MUSCLES OF THE EXTREMITIES. No. 106 Anterior Extremities. No. 48. «.— MUSCLES OF THE SHOULDER. No. 12. 1st. — External Scapular Region. No. 2. Antea-spinatus Super-acromio-trochitereua Postea-spinatus. Sub-acromio-trochitereus. 2d. — Internal Scapular Region. No. 1. Subscapularis. Subscapulo-trochineus. 3d, — Posterior Scapula Region. No. 2. Teres Major Subscapulo-humeralis Teres Minor. Superscapulo-troehiterius Minimus. 4th. — Anterior Humeral Region. No. 3. Coraco-humeralis Coraco-humeralis Flexor Brachii Coraco-radialis Humeralis Externus. Humero-radialis Obliquus. 5th. — Posterior Humeral Region. No. 4, S"ilS ) Gaput Magnum vel Primum Scapulo-olecranius s - I J CaputMedium ye/ Secundum Humero-olecranius Externus f- ca M ( Caput Parum nel Tertium Humero-olecranius Internus Anconeus. Epicondylo-olecranius. />.— MUSCLES OF THE ARM AND FORE-LEG. No. 12. 1st. — Anterior Brachio-crural Region. No. 4. Extensor Metacarpi Magnus Epitrochlo-premetaearpeus Extensor Pedis Epitrochlo-prephalangeus Extensor SufFraginis Radialis-prephalangeus Extensor Metacarpi |^'p'^j.""g"^^|Radialis-metacarpeus Obliquus MUSCULAR SYSTEM. 81 2cl. — Superficial Posterior Brachio-cruial Region. No. 4. English names. French names. Flexor Metaoarpi Externus Epitrochlo-carpeus Flexor Metacarpi Medius Epicondylo-carpeus Flexor Metacarpi Internus Epicondylo-metacarpeus Flexor Accessorius Sublimis Uliiaris (Accessorius) 3d. — Deep Posterior Brachio-crural Region. No. 4, Flexor Pedis Perforatus 7 t^ • j i v i Flexor Pedis Perforans } Epicondylo-phalangeus Flexor Accessorius Profundus Radialis (Accessorius) Lumbrici, Anterior et Posterior. Lumbricales. PosTEHioR Extremities. No. 58. ff.— MUSCLES OF THE HAUNCH. No. 20. 1st.— Gluteal Region. No. 3. Gluteus Externus Ilio-trochanterius Medius Gluteus Maximus Ilio-trochanterius Magnus Gluteus Minimus Ilio-trochanterius Parvus. 2d. — Pelvi-trochanterian Region. No. 5. Pyriforniis Sacro-trochantereus Obturator Externus Subpubio-trochantereus Externus Obturator Internus Subpubio-trochantereus Internus Gemini. Ischio-trochantereus. 3d. — Anterior Ilio-femoral Region. No. 4. Tensor Vaginae Ilio-aponeuroticus Rectus Ilio-rotuleus {Vastus Externus ^ Vastus Internus > Trifemoro-rotuleus Crureus J Rectus Parvus. Ilio-femoralis. 4th. — Internal llio-feinoral Region. No. 6. Sartorius Sublumbo-tibialis Gracilis Subpubio-tibialis Pectineus Superpubio-femoralis 0.2 (Addu .|| < Addu H^ (.Addu ........ctor Brevis ) Subpubio-femoralis Adductor Longfus S ^ ictor Magnus. Ischio -tibialis Externus. 5th. — Posterior Ilio-femoral Region. No. 2. Biceps Abductor Ischio-tibialis Medius vel Posterior Semitendiuosus ( Adductor ) r i • .-i • i- t ^ o • , i rr-u- 1- r Ischio-tibialis Internus. Semimembranosus! Tibialis ) ^.—MUSCLES OF THE THIGH AND HIND-LEG. No. 9. 1st. — Anterior Femoro-crural Region. No. 3. Extensor Pedis Femoro prephalangeus Peroneus Peroneo-prephalangeus Flexor Metatarsi. Tibio-prematarseus. M 82 MUSCULAR SYSTEM. 2d. — Superficial Posterior Fenioro-crnral Region. No. 3. English names. French tiames. Gastrocnemius Externus Bifeinoro-calcaneus Gastrocnemius Internus Femoro-phalanj^eus Plantaris. Peroneo-calcaneus. 3d. — Deep Posterior Femoro-crural Region. No. 3. Poplileus Femoro-tibialis Obliquus Flexor Pedis Tibio-plialangeus Flexor Pedis Accessorius. Peroneo-phalangeus. I.— CUTANEOUS MUSCLES. Panniculus Carnosus. — Musculiis Subcutaneus. A muscle peculiar to quadrupeds. Situation. — Subcutaneous ; and so uniformly and generally spread over the surface of the body, that it has been regarded as one of the common teguments. It not only clothes the broad sides of the trunk, but it extends forward upon the shoulder, neck, face; and, backwards, upon the haunch and stifle. Division. — On account of its extensiveness, into three por- tions : — cervical, thoracic, and abdominal. The Cervical Portion originates in some pale disgregated fasciculi, descending upon the side of the head; one parcel coming from the lateral parts of the mouth, another from the root of the ear and parotid gland, a third and larger one from the aponeurosis of the masseter ; all running to the angle of the jaw, and there collecting themselves into a fleshy band, which, after descending a little way lower down, again becomes resolved into separate fasciculi, and dispersed and spread over the side of the neck. The fleshy fibres, however, are principally confined to the infero-lateral regions : the superior portion consisting principally of an aponeurosis, partly cellular and partly tendinous, which is extended and fixed to the ligamentum nuchse. At the bottom of the neck some fasciculi are found running and attaching themselves to the spine of the scapula; others, paler and less distinct, take a downward course, passing over the shoulder- joint, where many become intermingled with and lost in the adipose membrane thereabouts; while others, again, continue still lower, and vanish upon the faschia of the arm. The Thoracic Portion consists of a broad layer of fleshy fibres, extending from a little above the middle of the scapula in a direct line down upon the arm, into the faschia of which it is (together with the cervical portion) inserted ; while, above, by means of an a[)oneurotic expansion, it is continued to be attach- ed to the spine. The Abdominal Portion forms a broad fleshy expansion; abstractedly viewed, ovoid in outline; clothing the false ribs and MUSCULAR SYSTEIM. 83 lateral parts of the abdomen ; whose fibres, generally, run in a longitudinal plane, from before backwards, from the shoulder to the flank : as they approach this latter part, they converge, and finally become collected into a broad, thick, muscular band, which is included within the fold of skin forming the border of the flank, and ends upon the front of the haunch, interwoven with the faschia covering that part, by which it is fixed to the patella. Anteriorly, the abdominal is connected with the tho- racic portion by an aponeurotic intervention ; along its superior border, the faschia covering the back and loins attaches the muscle to the spine ; inferiorly, it becomes gradually indistin- guishable from the faschia superficialis abdominis, with which it is blended, and through which it gets an attachment to the pubes. The spur-vein is seen ramifying, superficially, upon this portion of the muscle. Relations. — The strongest fibres of the panniculus are exhibit- ed by its abdominal portion : the palest and weakest are seen upon the face. Its cervical portion is in many places intimately blended with the levator humeri ; and also with the pectoral muscles. The thoracic part envelopes the trapezius, rhomboidei, latissimus dorsi, and spinati muscles ; the abdominal portion covers the external oblique muscle and its aponeurosis. Altachments. — Besides those already mentioned, it is loosely and partially connected, by cellular substance, with the several muscles and bones and ligaments which it immediately covers ; but everywhere intimately and generally with the skin. Direction. — Upon the head its fibres ramify in an arborescent form ; upon the neck they take an oblique course ; upon the shoulder they run in a perpendicular direction ; upon the abdomen, in a horizontal line. Action. — The contractions of the panniculus throw the skin into folds or corrugations, transversely in the direction of its fibres ; so that the one form right angles with the other. The chief points from which it acts, are the lower jaw, the scapula and head of the humerus, the patella, and the pubes. By sud- denly and repeatedly wrinkling his skin, the horse (unprovided with hands for the purpose) effects the dislodgement of insects which annoy him, and likewise of any irritating or noxious sub- stance, such as thorns or prickles, dirt, hayseeds, &,c. This power also enables him to resist, to a certain degree, the gripe or bite of an adversary. And so habitual does this cutaneous action become, that, although perfectly and fully at the command of the will, it often appears to take place involuntarily, or at least unheeded by the animal : this is particularly remarkable at the time that a horse is grazing or feeding, and is the while annoyed by Hies. 84 MUSCULAR SYSTEM. M. Girard conceives that it must give additional power of action to many muscles by operating as a brace or bandage to them : his words are — " 11 concoiirt a augmenter la force des muscles sur lesquelles il exerce une pression un peu forte." II.— MUSCLES OF THE HEAD. 1.— AURICULAR REGION. We shall consider these muscles in four classes — the Attol- lentes, the Musculi Proprii Conchse, the Retrahentes, and the Abducentes. 1. Attollentes et Adducentes Aurem. Attollens Maximus — Temporo-auricularis Externus. Situation. — Subcutaneous, upon the temple, at the inner side of the ear. Figure. — Broad, very thin, triangular. AttucJwieut. — By cellular membrane to the temporal faschia ; to a white tendinous (divisional or median) line extending in the direction of the sagittal suture ; and to the superior and posterior parts of the triangular cartilage, reaching from the vertex to the pit behind the orbit. Direction. — From within outward ; convergent in approaching the ear. Structure. — Fleshy and cellular ; fibres pale and slender ; and in their disposition aponeurotic. Atto LL E NS Anterio r — Zj/gomatico-fj u?'icularis. Situation. — Subcutaneous ; in front and to the outer side of the former. Attachment. — Anteriorly, to the posterior extremity of the zygoma ; along its middle, to the"^ temporal muscle ; posteriorly, to the front of the triangular cartilage. Relations. — Externally, the skin ; internally, the temporalis. Attollens Posterior— Temporo-aujicularis Internus. Siruation. — Vnderne^Lth the attollens maximus. For7n. — Thin, triangular; much smaller than the maximus. Attachments. — Inwardly, to the sagittal suture or ridge ; inter- nally, to the temporalis, by cellular tissue ; outwardly, to the pos- terior part of the concha. Relations. — Externally, the maximus ; internally, the tempo- ralis. Structure. — Principally fleshy ; in part aponeurotic, posteriorly. Action of the Attollentes. — These muscles all co-operate in the erection or cocking of the ears. Acting in pairs, the u)aximi will approximate ; the anteriores will depress them ; the posteriores elevate them. But, as the triangular cartilage is, more particu- MUSCULAR SYSTEM. 85 larly their seat of action, in order to produce the same effects on the concha, the aid of others will be required, next to be described. 2. — MuscuLi Proprii Concha. These muscles attach the triangular cartilage to the concha. Anterior Conchjs — Scuto-auricularis Eiteiuus. Situation. — Antero-internal side of the root of the ear- Form. — Two short, thin, narrow fleshy slips. Attachment. — To the outer side and posterior angle of the tri- angular cartilage, and to the antero-internal part of the concha. Relations. — Externally, skin ; internally, cartilage of the ear. Direction. — From behind, forwards; and from within, outwards. Posterior ConchjE — Scnto- auricular is Internus. Situation. — Deep-seated, at the inner side of the root of the ear. Form. — Two fleshy bands, thicker than the last described. Attachment. — To the inner side of the triangular cartilage; to the superior angle of the same ; and to the posterior part of the root of the concha. Direction. — Downwards, backwards, and outwards. Structure. — Fleshy ; the larger slip only possessing a few ten- dinous fibres at its conchal attachment. Action of the Musculi Concha:.— The anterior muscle will as- sist in the erection of the ear ; and present the aperture forwards, by drawing round the concha and maintaining it against the tri- angular cartilage. The posterior muscle will have directly the reverse operation : it will rotate the ear the contrary way ; so that the aperture may look backwards and collect sounds from the rear. 3. RETRAHENTES AUREM. Cervico-auriciilares, Externus et Internus. Situation. — Behind the ear, upon the side of the poll. Form. — Broad, thin, membraniform. Attachment. — Posteriorly, to the vertex, ligamentum nuchas, and obliquus capitis superior. Anteriorly, the external portion is attached to the dorsum conchae, about one-third of its extent, upwards : the internal portion, to the root of the concha, and to the annular cartilage. Action. — To retract the ear; to draw it down upon the poll ; also to rotate the car, turning the hollow part backwards. 86 MUSCULAR SYSTEM. 4. ABDUCENS Vel DEPRIMENS AUREM. Parotido-auricularis. Situation. — Below, and to the outer side of the root of the ear. Form. — Broad, thin, membraniform. Attachment. — To the surface of the parotid gland by dense cellular membrane ; and to the outer and fore part of the concha, just below its orifice. Relations. — Externally, with the panniculus and skin ; inter- nally, with the parotid gland. Direction. — From below upwards; inclining a little forwards. Structure. — Fleshy, and more substantial than the attoUentes. Action. — To abduct the ear, and assist in depressing it. 2.— PALPEBRAL REGION. LEV ATORPALPEBRilC SUPERIOR IS CO RRU GATOR SLPERClLll. Fronto-superciliaris. Situation. — Above the orbit. Figure. — Short, thin, narrow, pyramidal. Attachment. — Blended with the aponeurotic expansion upon the forehead, above the orbital arch; and inserted into the supe- rior part of the upper eyelid, nearer to its inner than outer angle. Relations. — Internally, with the skin ; externally, with the orbital arch ; inferiorly, blended with the next muscle. Direction. — Oblique : from above downwards, and from within outwards. Structure. — Superiorly, aponeurotic ; inferiorly, pale and de- licately fleshy. Action. — To draw up the upper eyelid, and particularly the inner part of it. ORBICULARIS PALPEBRARUM. MuSCuluS CiUaris. Situation. — Within the eyelids: in front of the base of the orbit. Figtir e.—OhVique\y oval ; slit in its long diameter. Attachment. — To the orbital portion of the ossa unguis et frontis ; to the palpebral ligament; and to the skin of both lids. Relations. — Externally, with the skin ; internally, with the membrana conjunctiva ; superiorly, with the former muscle ; in- feriorly with the levator labii; towards the margins of the lids, with the tarsi; at the inner canthus, with the lachrymal sac. Structure. — Fleshy : disposed in little packets or fasciculi. Action. — To approxinmtc or shut the eyelids. iMUSCULAR SYSTEM. 87 3._0CULAR REGION. LEVATOR PALPKBRiE SUPERIORIS INTERNUS. Orbitopalpebra/is. Si7//fl/ec?— Superiorly, between the eyeball and the orbit. Form. — Flat, tliin, fan-shaped : broad and expanded in front ; narrow and tapering, behind. Attachment. — To the inner and upper part of the parietes of the optic foramen ; and whole breadth of the border of the upper lid. Relations. — Superiorly, with the fibrous lining of the orbit, and the lachrymal gland : inferiorly, with the levator oculi and sclerotica. Direction. — Oblique : from behind, forwards ; from below, upwards ; and from within, outwards. Structure. — Posterior attachment, tendinous : anterior, apo- neurotic ; intermediate part, fleshy, pale and delicate. Action. — To raise the upper eyelid. i SUPERIOR OCULI. \ VS INFERIOR OCULI. f BDUCTOR OCULI. — RECTUS EXTERNUS OCULI. t DDUCTOR OCULI. — RECTUS INTERNUS OCULI. J LEVATOR OCULI. RECTUS SUPERIOR OCULI DEPRESSOR OCULI. RECT A A Situation. — Within the orbit, at respective and equal distances one from another, along the superior, inferior, and lateral parts of the eyeball. Form. — Elongated, curved, conoid : broad parts turned for- wards. Attachment. — To the circumferent parts of the optic foramen ; and to four opposite points, equidistant one from another, of the sclerotic, where it covers the front of the eyeball. Relations. — Externally, with the fibrous lining of the orbit ; internally, with the sclerotic coat; in the middle, with the re- tractor oculi. The levator oculi has also, above it, the levator palpebrse internus. Direction. — Oblique : from within outwards, in the direction of the visual axis; the levator, at the same time, winding up- wards ; the depressor, downwards ; the abductor, to the outer side; the adductor, to the inner side. Structure. — Posterior attachments tendinous and fleshy ; an- terior, aponeurotic ; intermediate parts, fleshv. Action. — The levator will turn the sight of the eyeball up- wards ; the depressor, downwards : the abductor, outwards ; the adductor, inwards. All four muscles acting simultaneously will draw the globe backwards, within the orbit. The combined 88 MUSCULAR SYSTEM. action of any two of them, will give the sight an oblique or inter- mediate direction. OBLIQUUS SUPERIOR Vtl MAGNUS OC U LI-T ROCH LE A R I S. Situation. — Inner and upper part of the cavity of the orbit. Form. — Elongated, cylindroid ; somewhat narrowed, posteri- orly ; anteriorly, curved at an acute angle towards the opposite side. Attachment. — To the border of the optic foramen, and to the upper and outer part of the sclerotic, near to the attachment of the abductor. Relations. — Superiorly, with the orbital parietes and pathetic nerve; inferiorly, with the adductor and supra-orbital branch of the ophthalmic nerve. Direction. — Horizontal, but somewhat curved : inchning from within outwards until it reaches the fore part of the cavity, where it becomes reflected outwards and downwards, with an inclina- tion backwards. Structure. — Posterior attachment tendinous and fleshy; ante- rior, aponeurotic ; middle part, fleshy. At the inner canthus, the fleshy part passes through a broad fibro-cartilaginous loop or pulley, which is fixed to the posterior part of the frontal orbital process. OBl-lQUUS INFERIOR Vel PARVUS OCULI. Situation. — Under the eyeball: antero-inferior part of the orbit. Figure. — Broad, thick, cylindroid : ocular attachment broadest. Attachment. — To a little depression in the os unguis, behind the lachrymal opening ; and to the inferior and outer side of the sclerotic, close to the junction of the white with the transparent part of the globe. Relations. — Inferiorly, with the floor of the orbit ; superiorly, with the aponeurotic tendon of the depressor ; internally, with the lachrymal sac. Structure. — Fleshy, included within a fibrous sheath. RETRACTOU Vcl RECTUS POSTERIOR OCULI. Situation. — ViQ\\\n6i the eyeball. Figure. — That of a hollow cone, with its base turned forwards. Attachment. — To the edge immediately surrounding the optic foramen ; and to the posterior third of the entire superficies of the globe of the eye. Relations. — Around its sides are the four straight muscles of the eye, and in the interspaces a quantity of adipose matter : through its middle runs the optic nerve. .lAlUSCULAR SYSTEM. 89 T)ireclion. — Radiated : the fibres diverging from tlie optic roramen as a centre, and spreading upon the surface of the globe. Stntcliire. — Posterior attachment, tendinous and fleshy : re- mainder, fleshy. 4.— ANTERIOR MAXILLARY REGION, z Y G o M A T I c u s . — Zi/gomatico-lahia lis. Situation. — Along the middle of the side of the face. Figure. — Very thin, flattened, elongated. Attachment. — Posteriorly, to the anterior part of the zygoma, and cellular tissue clothing the masseter; anteriorly, its fibres grow faint and vanish imperceptibly in approaching the angle of the mouth. Relations. — Externally, with the skin ; internally, with the caninus ; inferiorly, with the panniculus carnosus. Direction. — Horizontal, from behind forwards. Structure. — Fleshy, except at its posterior attachment. Action. — To assist in retracting the angle of the mouth. LEVATOR LABII SUPERIORIS AL^QUE NASI. Super-naso-labialis. Situation. — Upon the side of the face, above the preceding- muscle. Figure. — Broad, thin, elongated, bifurcated anteriorly. Attachments. — Posteriorly, to the subcutaneous surfaces of the nasal and frontal bones, reaching as far backward as the level be- tween the orbital arches; anteriorly, by one division to the lateral parts of the skin of the nose and the false nostrils ; by the other division, to the side of the upper lip and angle of the mouth. Relations. — Externally, with the skin ; the superior division, with the dilatator naris lateralis : internally, with the nasalis lon- gus labii superioris, pes anserinus, and the superior labial artery. Direction. — Rather oblique, from behind forwards, incliniiig downwards. Structure. — Posteriorly, a broad and extended aponeurosis ; anteriorly, fleshy. Action. — To assist in the retraction of the upper lip and angle of the mouth, and in the dilatation of both the true and false nostrils. jRe/?io>'A\— Stubbs describes the aponeurotic expansion of this muscle under the name of " epicranius." DILATATOR NARIS LATERALIS. — Super-maxUlo-nasalis magnus. Situation. — Upon the side of the face. Figure. — Flat, pyramidal, base presented forwards. N 90 AJUSCULAR SYSTEM. Altadiments. — Posteriorly, to the fore end of the zygoma, and to the superior umxilla for a short space in front of it ; anteriorly, it spreads upon the side of the nostril and the supero-lateral parts of the upper lip. Relations. — Externally, with the skin and the inferior division of the preceding muscle ; internally, with the superior division of the same muscle, the caninus, the superior maxillary bone, and the superior labial bloodvessels and nerves. Direcfiun. — Horizontal, diverging as it proceeds forwards. Sti'uctine. — A slender tendon attaches it to the bone, below which it is fleshy. Action. — To dilate the nostril and retract the upper lip. NASALis LONGUS LABii suPERiORis. — Super-mnxillo-lahialis. Situation. — Upon the upper part of the side of the face. Figure. — Elongated, pyramidal, base turned backwards : ex- ternal surface, convex; internal, flat. Attachments. — Posteriorly, to a slight bony depression at the junction of the superior maxillary and malar bones, a short dis- tance from the lower margin of the orbit; anteriorly, along the middle of the anterior part of the upper lip. jRe/aif?o;/s. — Externally, with the skin and the levator labii su- perioris alasque nasi, and the angular vein ; internally, with the superior maxilla, pes anserinus, and false nostrils : the united tendon crosses, in front, the dilatator naris anterior, and at the border of the lip enters the substance of the labial gland. Direction' — Horizontal, the fleshy flbres gradually converging from their origin to their termination in the tendon. Structure. — It has a few tendinous fibres at its origin ; other- wise, it is fleshy as far forward as the false nostrils, where it ends in a cylindroid tendon, and which here passes through a sort of cellular sheath, by which it is retained in its proper place. In turning over the front of the nose it grows flat, and at the peak formed by the apices of the nasal bones forms a junction with its fellow coming, from the opposite side. The two unite and form a single flat tendon, which expands a little in descending, and ulti- mately disa])pears in the fleshy substance of the lip. Action, — To raise and corrugate the upper lip, and in some de- gree assist in the dilatation of the false nostrils. CANINUS VHL LEVATOR ANGULl ORIS. Portion of the aheolo-maxillaris. Situation. — Fore part of the side of the face. Figure. — Broad, flat, triangular. MUSCULAR SVSTEiM. 91 Attachments. — Superiorly, to the broad depression upon the side of the fore angle of the superior maxillary bone; inferiorly, to the alveolar processes of the lower jaw, and the bone in front of them; internally, to the buccal membrane; anteriorly, to the side of the lip and angle of the mouth. Relations. — Externally, with the zygomaticus, inferior division of the levator labiisuperioris al^eque nasi, dilatatornaris lateralis, panniculus carnosus, and skin ; internally, with the raasseter, buccal membrane, and two anterior upper molar teeth. Direction. — Transverse and penniform : the superior fibres di- verge from their maxillary attachment; those below run obliquely, forwards and downwards. Structure. — Fleshy. Action. — To render the buccal membrane tense, and also to assist in elevating the angle of the mouth and side of the lip. BUCCINATOR. — Alveolo-labialis. Situation. — In the space between the jaws. Figure.— 'BroQ.d, flat, approaching the triangular. Attachments. — Posteriorly, to the border of the lower jaw in the space between the last molar tooth and the root of the coronoid process, and to the tuberosity of the superior maxilla; superiorly and inferiorly, to the outer walls of the alveolar cavities for the molar teeth ; anteriorly, to the angle of the mouth ; and inter- nally, to the buccal membrane. Relations. — Externally, with the masseter, caninus, pannicu- lus, and skin, and with the facial artery and vein and parotid duct ; internally, with the buccal membrane ; postero-inferiorly, with the buccal nerve, artery, and varicose vein ; antero-inferiorly, with the depressor labii inferioris and inferior labial bloodves- sels ; postero-superiorly, with the temporal vein. Direction. — Longitudinal, from behind forwards. Structure. — With the exception of its posterior or narrow ex- tremity, which contains some slips of tendon, and a few tendi- nous fibres which are visible about the angle of the mouth, it is entirely fleshy. Action. — To aid in tightening the buccal membrane, and retract the angle of the mouth. , DEPRESSOR LABII INFERIORIS. — MaxUlo-lahialis. Situation. — Along the side of the lower jaw. Figure. — Elongated, flattened, pyramidal, ba:5C turneil back- wards. 92 MUSCULAR SYSTEM. Attac/i/neiits. — Posteriorly, blended wi_th the buccinator, to the tuberosity of the superior maxilla, and the superior border of the inferior maxilla, behind its alveoli ; anteriorly, infero-lateral part of the interior of the lower lip. Relations. — Externally, with the panniculus and skin, crossed also by the facial artery and vein and parotid duct ; internally, with the inferior maxilla and buccinator; also with the inferior labial bloodvessels, which run between it and the buccinator. Direction. — Horizontal, the fibres very gradually converging. Structure. — Two slender tendons attach it to the jaws, and another connects it Vv'ith the lip, in the glandular substance of which the latter expands, splits, and disperses its fibres. LEVATOR M E N T i . — Meuto-labialis. Situation. — Under the chin. Figure. — Broad, and (though rather irregularly) quadrilateral. ^Attachments. — Superiorly, to the alveolar processes, and the antero-inferior and lateral parts of the inferior maxilla ; inferiorly, its fibres are lost sight of amid the adipose and glandular sub- stance forming the prominence of the chin. Relations. — Superiorly, with the bone ; inferiorly, with the membrane lining the lip ; anteriorly, with the teeth ; posteriorly, with the prominence of the chin. Direction. — Oblique, from before backwards, and from above downwards ; the lateral fibres making a curvature forwards. Structure. — Fleshy. Action.— To draw forward and raise the prominence of the chin, and with it the under lip. DILATATOR NARis ANTERIOR. — Naso-transversalis. Situation. — In front of and between the nostrils. Figure. — Transverse parallelogram . Attachments. — In the middle, to the bony peak formed by the apices of the ossa nasi ; on the side, to the anterior surface of the alas or broad cartilages of tlie nose. Relations. — Externally, with the skin and the united tendon belonging to the nasales longi labii superioris ; internally, to the broad and also to the narrow cartilages of tlie nose, and to the triangular space between them ; superiorly, with the ossa nasi ; inferiorly, with the glandular substance of the lip. Direction. — Transverse. Structure. — Fleshy, except at its attachment to the os nasi. MUSCULAR SYSTEM. 93 NASALIS 15REVIS LABII SUPERIORIS. Super-maxillo-iiasalis parvus. Situation. — Behind the external nares. Figure. — Narrow, thin, forming two sides of a triangle. Attachments. — Inferiorly, to the superior and anterior maxil- lary bones, and to the suture uniting them ; superiorly, to the os nasi ; in the middle to the horn or cornet of the nose and the skin of the false nostrils : it forms, in fact, a fleshy investment to the angular bony boundary of the false nostrils. Relations. — Externally, with the levator labii superioris alaque nasi, the tendon of the nasalis longus labii superioris, and the skin ; internally, with the membrane of the nose. Direction. — Transverse, inclining forwards. Structure. — Fleshy. DEPRESSOR LABII SUPERIORIS. Situation. — Side of the upper jaw. Figure. — Broad, thin, irregular. Attachment. — Inferiorly to the alveoli of the lateral and middle incisores, extending thence along the side of the jaw as far as the tusk ; superiorly, it is confounded with the glandular substance of the upper lip, and is also connected with the inferior nasal cartilages. Relations. — Anteriorly, with the labial gland, and, at the side, with the nerves descending from the pes anserinus ; posteriorly, with the front of the jaw; superiorly, with the cartilages of the nose; inferiorly, with the incisor teeth. Direction. — Oblique, from before backwards, and from below upwards. Structure. — Fleshy. Action. — To draw down the side of the lip, and with it the nasal cartilage, and thereby have some effect in dilating the nostril. ORBICULARIS ORIS. — LabiuHs. Situation. — Within the border of the lips, of which it consti- tutes the principal thickness. Figure. — It forms two semi ovals, directed backwards, united at the commissures of the lips. Attachments. — To the glandular substance and skin of the li])s, and more particularly at the commissures, where the fibres coming from both lips cross one another, and become confounded with those of other muscles inserted thereabouts. 94 MUSCULAR SYSTEI\i. Relations. — Externally, with the skin ; internally, with adi- pose tissue, the labial glands, and the membrane of the mouth. Direction. — Semicircular, in the horizontal line. Structure. — Consists of two bands of fleshy fibres, the upper one of which is broader, thicker, redder, and stronger than the lower. Action. — To approximate the lips and retain them in contact; also to assist in the dilatation of the nostrils. 6.— ANTERIOR MAXILLARY REGION, Comprising the muscles whose office it is to move the lower jaw. TEMPORALIS. — Temporo-maxiUaris. Situation. — Upon the parietal and temporal bones. Form. — Convex, externally ; concave, internally: broad, above; narrow and convergent, below. Attachment. — Superiorly, to the vertex and the anterior occipi- tal bone ; to the convex surface of the parietal ; to the squamous plate and zygomatic process of the temporal bone ; and to a small portion of the frontal : inferiorly, to the coronoid process of the inferior maxilla. Relations. — Externally, with the attollentes aurem and the zy- goma; internally, with the cranial bones ; postero-externally, with the ear ; anteriorly, with a volume of fatty substance lodged at the back of the orbit. Direction. — From behind, forwards ; and from above, down- wards : the fibres taking a curvilinear course. Structure. — Covered by a dense aponeurotic expansion, deno- minated the temporal faschia ; the broad part of the muscle is fleshy, but is intersected horizontally through its middle by a layer of tendon. Below, it is tendinous in its attachments to the sharp edges of the coronoid process; but fleshy around the sides of it. Action. — To raise the lower against the upper jaw ; and, thereby, when the mouth is opened, to shut it again. It is one of the principal agents in manducation. MAssETER. — Zygomatico-maxillaris. Situation. — It forms the prominence of the cheek. Form. — Broad, thick, semi-oval: superior and anterior sides, rectilinear ; postero-inferior border, curvilinear. Attachment. — Superiorly, to the whole of the zygomatic ridge, and lower border of the arch, reaching as far back as the mastoid, process ; inferiorly, to the roughened border surrounding the angle of the jaw, and to the contiguous parts of the external surface. MUSCULAR SYSTEM. 95 Relations. — Externally, with the panniculus carnosus, cellular tissue, and branches of the portio dura; internally, with parts of the superior and inferior maxillae, buccinator, mass of yellow fat filling the intermaxillary vacuity, posterior and anterior masseter arteries and veins; superiorly, with the temporal artery and vein; posteriorly, with the parotid gland ; anteriorly, with the parotid duct, anterior maxillary artery and vein. Diiectiun. — Oblique: from above, downwards; and from be- fore, backwards. Structure. — Of its exterior, the superior two-thirds is aponeuro- tic ; internally, it is composed of several distinct fleshy layers, separated by aponeurotic intersections. Action. — In co-operation with the former muscle, to elevate the lower jaw, and maintain it in approximation against the upper. STYLO-MAXILLARIS. Situation. — Behind the lower jaw. Figure. — Pyramidal : base turned downwards and forwards. Attaclnnent. — Superiorly and posteriorly, to the styloid process of the occipital bone : inferiorly and anteriorly, to the angle of the lower jaw. Relation. — Externally, with the parotid gland, temporal and occipital branches of the jugular vein, and the arteries piercing the gland ; internally, with the membrane bounding the guttural ca- vities; superiorly, with the stylo-hyoideus. Direction. — Oblique: from behind, forwards; and from above, downwards. Structure. — Tendinous, at its occipital attachment; remainder fleshy, intersected with layers of tendon, and having aponeurotic stripes along its surfaces. The posterior division of the digastri- cus is inseparably united with the inferior border. Action. — To draw the jaw backward, and at the same time depress it: it therefore assists in opening the mouth, and so far is an antagonist to the two former muscles. PTEKYGOiDEUS INTERN US. — SpImio-maxUlaris. Situation. — The same relative position upon the inner side of the jaw to what the masseter has upon the outer, filling up the excavation there in the bone. Form. — Broad and flat; terminating, inferiorly, in a semicircu- lar border, from which it narrows, upwards. Attachment. — Superiorly, to the pterygoid process, and crus of the sphenoid bone, to the palate bone, and to the tuberosity of the superior maxillary bone : inferiorly, to the fossa which it occu- pies, and around the angle of the jaw. 96 MUSCULAR SYSTEM. Re/a(lo)i. — Externally, with the branch of the jaw, and poste- rior maxillary nerve and blood-vessels ; internally, with the digas- tricus, hyoideus, stylo-pharyngeus, the os hyoides, the larynx, the anterior portion of the parotid gland, the submaxillary vessels, and the ninth and recurrent nerves : anteriorly, with the mylo- hyoideus and gustatory nerve; posteriorly, with the parotid gland, guttural cavities, and the next muscle : superiorly, with the base of the cranium; inferiorly, with the stylo-maxillaris and the skin. Direction. — Divergent, from above, downwards. Structure. — Fleshy, plenteously intersected with tendon. A ctioii. — To raise the jaw. If one act alone, the jaw, in being- closed, will be drawn to one side : the alternate action of the two produces the lateral movement of the jaw which is so effectual in comminuting the food. PTERYGOIDEUS EXTERNUS. Situation. — Above and behind the former. Form. — Short, thick, cylindrical. Attachment. — Anteriorly, to the ala and crus of the sphenoid; posteriorly, to the roughened depression upon the inner side of the jaw, at the root of the condyle. Relation. — Anteriorly, inferiorly, and internally, with the pre- ceding muscle, and the posterior maxillary nerve; superiorly, with the orbit; posteriorly, with the articulation of the jaws ; ex- ternally, with the neck of the jaw. Directio)i. — Oblique: from behind, forwards; and from with- out, inwards. Structure. — Fleshy, with slight tendinous intersections. Action. — To assist in the elevation of the jaw; and, at the same time, to draw it forwards : it is the antagonist in particular of the stylo-maxillaris. 6.— HYOIDEAL REGION. The muscles in this region, and those remaining to be described, belonging to the head, are comprehended within the inter-max- illary space — between the branches of the lower jaw. DiGASTRicus. — Portiou of the Sti/lo-maxillaris. Situation. — Along the inner side of the lower jaw. Form. — Broad and flattened at the extremities; cordiform in the middle. Attachment. — Posteriorly, to the styloid process of the occipi- tal bone ; anteriorly, to the side of the jaw, midway between the angle and the symphysis. Relation. — Externally, with the jaw and pterygoidei ; inter- MUSCULAR SYSTEM. 97 nally, with the larynx, os hyoides, and submaxillary gland : infe- riorly, with the submaxillary vessels and the skin. Direction. — Oblique : from behind, forwards and downwards ; from before, upwards and backwards. Structure. — It consists of two fleshy bellies united by an inter- mediate tendon, which passes and plays through a sort of pulley formed by the tendon of the hyoideus. Action. — Not very apparent; implicated, seemingly, with that of the hyoideus. MYLO-HYOIDEUS. Situation. — Spreading along the side of the jaw. Figure. — Broad, thin, half-penniform. Attachment . — Outwardly, to the roots of the alveolar processes and the side of the jaw, extending forwards to the symphysis: inwardly, to the body of the os hyoides. Relation. — Outwardly, with the jaw; inwardly, with the sub- lingual gland, genio-hyoideus, and gustatory and ninth pair of nerves. Direction. — Oblique: from above downwards, inclining out- wards. Structure. — Fleshy: united to its fellow (of the opposite side) through the medium of a tendinous line, which extends from the end of the spur process of the os hyoides to the symphysis of the jaw„ Action.— To draw the os hyoides forwards and upwards; and, thereby, raise the tongue within the mouth. GENIO-HYOIDEUS. Situation. — Above the preceding muscle. Figure. — Half-penniform: extremities, narrow; middle part, broad. Attachment. — Anteriorly, to the jaw, near the symphysis; pos- teriorly, to the spur process of the os hyoides. Relation. — Inferiorly and externally, with the mylo-hyoideus ; superiorly, with the genio-hyo-glossus ; internally, with its fellow. Direction. — Oblique : from before, backwards ; and from with- out, inwards. Structure. — Tendinous at the extremities : intermediate part, fleshy. HYOIDEUS MAGNUS. — Kerato-tiyoideus Magnus. Situation. — Antero-superior part of the neck. Form. — Fusiform : flattened upon its sides. Attachment. — Posteriorly, to the postero-inferior part or angle of the corner of the os hyoides ; anteriorly, to a little tubercle 98 MUSCULAR SYSTEM. arising from the middle and inferior part of the semicircular por- tion of the same bone. Direction. — Oblique : from behind, ft)rwards ; and from above, downwards. Relation. — Below, with the stylo-maxillaris, di^astricus, and parotid gland; above, with the corner of the os hyoides, ninth pair of nerves, and lingual vessels: externally, with the pterygoi- deus internus ; internally, with the larynx and recurrent nerve. Structure. — Tendinous and fleshy at its posterior attachment; ending in a slender tendon, anteriorly. Action. — To draw the body of the os hyoides still nearer to the sideof the jaw, and thereby assist in the dilatation of the glottis. HYoiDEUS PARVUS. — Kercito-hijoideus Parvus. Situation. — Above and rather before the preceding muscle. Form. — Small, flat, triangular. Attachment. — To the body and appendix of the os hyoides, filling up the triangular space between them. Action. — To approximate these parts. STYLO-HYOIDEUS. Situation. — I nfero -anterior part of the neck. Figure. — Quadrilateral. Attachment. — Posteriorly, to the front of the styloid process of the occipital bone; anteriorly, to the angle of the hyoideal cornu. Relation. — Externally, with the parotid gland ; internally, with the guttural membrane: inferiorly, with the stylo-maxillaris; pos- teriorly, with the obliquus capitis superior. Structure. — Fleshy, with tendinous intersections. Action. — To retract, and at the same time elevate, the cornu of the OS hyoides, 7.— GLOSSAL REGION. The muscles of this region form, collectively, the substance of the tongue : their number ^nd variety account for the well- known mobility of that organ. H Y o-G LO .s^ u s LONG US. — Kerato-'glossus. Situation. — Along the base and side of the tongue. Form. — Long, narrow : flattened upon its sides. Attachment. — Posteriorly, to the cornu of the os hyoides, a short distance from its junction with the appendix; anteriorly, infero-lateral parts of the tongue. Relations. — Externally, with the mylo-hyoideus ; internally, with the hyo-glossus brevis; inferiorly, with the gustatory nerves. MUSCULAR SYSTEM. 99 Slniclnre. — Thin, weak, aponeurotic, at its posterior attach- ment : remainder, fleshy. Action. — To draw the tongue within the mouth ; and at tiie same time, depress it. HYO-GLOSSUS B RE VIS. HyO-gloSSUS. Situation. — Similar to the preceding- muscle. Form. — Broad, flat, thin, quadrilateral, half-penniforni. Attachment. — Externally, to the side of the body of" the OS hyoides ; internally, to the base of the tongue. Relations. — Externally, with the mylo-hyoideus and hyo- glossus longus; internally, with the genio-hyo-glossus. Direction. — Obliquely transverse. Structure. — Entirely fleshy. Action. — To assist the former muscle in the retraction of the tongue ; and to depress, in particular, the base of it. GENIO-HYO-GLOSSUS. — Gcuio-gloSSUS. Situation. — Inferior part of the tongue. Form. — Broad, thin, half-penniform. Attachment. — Inferiorly, to the inner part of the jaw, near its symphysis: superiorly, to the under part of the tongue; and also to the appendix of the os hyoides. Relations. — Externally, with the genio-hyoideus, hyo glossus, sublingual gland, and branches of the gustatory nerve ; internally, with its fellow ; inferiorly, with the genio-hyoideus ; superiorly, with the tongue. Direction. — From below, upwards; and from before, back- wards. Structure. — Fleshy ; with the exception of the anterior half of its inferior border, where it is hemmed by a slender tendon which connects it more firmly to the jaw. Its surfaces are in part covered with adipose substance. Action. — To project the tongue within the mouth, and draw it down : if one muscle act alone, the organ will be drawn to one side. LINGUALIS. The internal substance of the tongue consists of masses of fleshy fibres, taking various directions, and having interwoven with them a considerable quantity of yellow adipose tissue : anatomists consider these as a distinct pair of muscles. They take their attachments at the root of the tongue, from the body and appendices of the os hyoides, where they are separable and dis- tinct portions ; and proceed downwards, between the hyo-glossi longi, and above the gcnio-hyo-glossi, to be buried and con- 100 MUSCULAR SYSTEiM. sumed in the substance of that organ. They receive the inaeitions of all the other glossal muscles. Action. — To contract the tongue lengthwise, and to draw it withni the mouth. 8.— PHARYNGEAL REGION. HYO-PHARYNGEUS. — Keiato-phai'ytigeus. Situation. — Infero-lateral and posterior part of the pharynx. Form. — Flat, thin, quadrilateral. Attachment. — Infero-posteriorly, to the superior border of the cornu of the os hyoides ; supero-anteriorly, to the side of the pharynx. Relations. — Externally, with the pterygoideus internus ; inter- nally, with the larynx. Action. — To dilate the bag to receive the food. p A L A To-p H A R Y N G E US. — Pteiygo-phatyngeus. Situation. — Upon the side of the pharynx. Form. — Broad and thin : irregular in figure. Attachment. — Superiorly, to the pterygoid process of the sphenoid, and to the palate bone : inferiorly, to the pharynx — its fibres intermixing and confounding themselves with those of the hyo-pharyngeus and stylo-pharyngeus. Direction. — The reverse of the former muscle : viz. from above, downwards ; and from before, backwards. Action. — To assist in the dilatation of the pharynx. STYLO-PHARYNGEUS. Situation. — Postero-lateral part of the pharynx. Attachment. — Posteriorly, to the styloid process of the tem- poral bone, and outer side of the cartilage of the Eustachian tube : anteriorly, to the side of the pharynx. Structure. — Tendinous at its origin : remainder, fleshy. Action. — To assist in dilatation, by drawing the side of the bag in a direction upwards and backwards. CONSTRICTOR PHARYNGis ANTERIOR. — Hyo-pharyngeus. Situation. — Antero-superior part of the pharynx. Attachment. — Inferiorly, antero-internal part of the cornu of the OS hyoides ; superiorly, to a tendinous line uniting it with its fellow along the mesio-anterior part of the pharynx. CONSTRICTOR PHARYNGIS MEDius. — Thi/ro-phari/ngcus. Situation. — Behind the former muscle. Attachment. — Inferiorly, lateral parts of the thyroid cartilage : MUSCULAR SYSTEM. 101 superiorly, to a tendinous line running along the superior part of the pharynx. CONSTRICTOR PHARYNGis POSTERIOR. — Crico-pharyngcus. Situation. — Postero-superior part of the pharynx. Atlachinent. — Inferiorly, its fibres are confounded with those of the muscular coat of the oesophagus : superiorly, to the lateral parts of the cricoid cartilage. llelatioiis of the three Constrictors. — ^u^pexxoxXy, with the guttural pouches; inferiorly, with the membranous parietes of the pharynx, with the os hyoides, and the thyroid and cricoid carti- lages ; laterally, with the anterior portions of the parotid gland. Structure of them. — Fleshy. Actio)!, of them. — To constrict or contract the cavity of tiie pharynx in the act of deglutition. 9.— LARYNGEAL REGION. Comprehending eight pairs and one single muscle. HYO-THYROIDEUS. Situation. — Upon the side of the larynx. Form. — Quadrilateral : flat and thin. Attachment. — To the inferior border of the semicircular por- tion of the OS hyoides ; and to a broad eminence upon the postero- inferior part of the side of the thyroid cartilage. Action. — To elevate the thyroid cartilage, and with it the larynx altogether ; or, to depress the os hyoides. CRICO-THYROIDEUS. Situation. — Upon the postero-lateral part of the larynx. Form. — Flat; triangular. Attachment. — To the borders and side of the cricoid cartilage; and to the posterior border of the thyroid, filling up the vacuity between the two cartilages. Action. — To approximate the two cartilages. CRICO-ARYTENOIDEUS POSTICUS. Situation. — Upon the upper part of the larynx. Attachment. — To the entire upper surface of the cricoid carti- lage, and to the posterior angle of the arytenoid cartilage. Structure. — Fleshy ; and furnished with two small tendons, which are fixed to the arytenoid. Action. — To draw the arytenoid cartilage backwards. CRICO-ARYTENOIDEUS L AT ERA LIS. Situation. — Postero-lateral and superior parts of the larynx, between the thyroid and cricoid cartilages. 102 MUSCULAR SYSTEM. Attachment. — To the anterior border of the cricoid cartilage ; and to the side of the posterior angle of the arytenoid. Action. — To draw the arytenoid cartilages asunder, and thus dilate the glottis. THYRO-ARYTENOIDEUS. Situation. — Upon the side of the larynx, between the thyroid cartilage and the lining membrane. Attachment. — To the inner surface of the thyroid, and the tri- angular ligament; and to the side of the arytenoid cartilage. Action. — To enlarge the glottis by separating the arytenoid cartilages. ARYTENOIDEUS. Situation. — Upon the superior part of the larynx. Attachment. — To the superior or excavated parts of the two arytenoid cartilages ; running across from one to the other. Action. — To contract the glottis, by approximating these carti- lages. HYO-EPIGLOTTIDEUS. Situation. — Between the epiglottis and semicircular part of the OS hyoides. Figure. — Fusiform. A single muscle. Attachment. — To the hollow part opposite to the neck of the OS hyoides ; and to the broadest part of the epiglottis : en- veloped within a doubling of the laryngeal membrane, and clothed in adipose matter. Structure. — Pale fleshy fibres, mingled with fatty matter at its hyoideal attachment, and fixed to the epiglottis by a very small tendon. Action. — To retract the epiglottis still further from the aper- ture, and thus increase the dimensions of the latter. 10.— PALATINE REGION. Including one pair, and a single muscle. TENSOR P ALATI . Stl/lo-stciphl/kus. Situation. — Upon the supero-lateral part of the pharynx. Form. — Slender, elongated ; tapering towards either extremity. Attachment. — Posteriorly, to the styloid process of the tem- poral bone, by means of a tendon common to it and the stylo- pharyngeus ; anteriorly, by means of a cartilaginous loop (acting as a pulley), through vvhicli its tendon passes, to the styloid process of the palate bone: and, making a sudden turn outward. MUSCULAR SYSTEM. 103 around this process, it becomes ultimately fixed to the postero- lateral part of the soft palate. Direction. — From behind, forwards. Jielatio7is. — \ uwardly , with the stylo-pharyngeus and palato- pharyngeus ; outwardly, with the pterygoideus internus. Stnictitre. — Fleshy, in the middle ; aponeurotic, externally : terminating, anteriorly, in a long, flat, slender tendon, which plays within a cartilaginous pulley. Action. — To stretch or dilate the palate. ciRcuMFLExus PALATi. — Staphyhus. Situation. — Infolded within the velum palati. Form, — Collected into fasciculi, posteriorly: broad, thin, and expanded, anteriorly. Attachment. — Anteriorly, to the semi-oval border formed by the union of the palate bones; posteriorly, to the palate; within the substance of which its fibres are intermingled with those of the stylo-pharyngeus and tensor palati. Structure. — Fleshy, posteriorly ; aponeurotic, anteriorly. A single muscle. III.— MUSCLES OF THE TRUNK. The trunk comprises the neck, the thorax, and the abdomen. a.— MUSCLES OF THE NECK. 1.— HUMERO-CERVICAL REGION. "RHOMBOiDEUS LONG US. — Cervico-ocromialis. Situation. — Supero-lateral part of the neck. Form. — That of an elongated flattened pyramid, having its apex turned forwards. Attachment. — Superiorly and anteriorly, to the entire length of the side of the ligamentum colli, reaching as far forward as the second cervical vertebra : posteriorly and inferiorly, to the supe- rior costa and cartilage of the scapula. Relations. — Externally, with the panniculus ; internally, with the ligamentum colli ; inferiorly, with the splenius ; posteriorly, it passes under the anterior angle of the scapula, uniting its fibres with those of the rhomboideus brevis. D/rec^iW.— Longitudinal ; following the curve of the neck. Structure. — Anterior end tendinous : remainder, fleshy. Action. — To assist in raising the scapula, and at the same time to draw the bone forwards. 104 MUSCULAR SYSTEM. LEVATOR HUMERI. — Cervico-subscapu/aris. Situatiou. — Antero-inferior and lateral parts of the neck. Form. — Flattened, elongated : broadest and thickest at its posterior and inferior parts. Attachment. — Superiorly and anteriorly, to the tubercle of the occiput, to the mastoid process of the temporal bone, to the trans- verse process of the atlas, and those of the second, third, and fourth cervical vertebrae; laterally, from the ligamentum nuchse and faschia covering the side of the neck ; inferiorly and poste- riorly, loosely to the head of the humerus, to the scapular faschia, to the muscles about the point of the shoulder, and ultimately to a ridge upon the body of the humerus, which arises from its greater tubercle. Relations. — The jugular vein runs along its antero-inferior border, and is covered by it for three-fourths of its length down- wards. The subcutaneous branches of the cervical nerves pierce its substance and ramify upon its surface. Superiorly and pos- teriorly, it is opposed to the splenius ; inferiorly and anteriorly, to the sterno-maxillaris; on its outer side, to the panniculus ; on its inner side, to the rectus capitis anticus major, and to the sca- lenus. Its antero-inferior margin is thin and expanded, and clips inward, forming a thin fleshy partition between the carotid artery and jugular vein. Direction. — Longitudinal : sloping with the neck. Structure. — Anteriorly it is split into two portions, both thin and aponeurotic at their extremities. Its middle part is thick and entirely fleshy, but upon the arm becomes aponeurotic. Action. — To raise the shoulder and arm, and at the same time draw them forwards : or, these parts being fixed, to turn the neck, and head also, to one side ; or, should both act, under such circumstances, the head will be depressed. Remark. — Professor Girard considers the fleshy expansion be- tween the artery and vein as a distinct muscle, and names it the subscapulo-hyoideus : and so it would seem most natural to regard it. 2, — LATERAL CERVICAL REGION. SPLENIUS. — Cervico-mastoideus. Situation. — Occupying the whole of the superior and lateral parts of the neck. Form. — Irregularly quadrangular; the supero-lateral portion being acute and extended : thick in substance and flattened upon the sides. AttacJunent. — Superiorly, to the ligamentum colli, reaching as MUSCULAR SYSTEM. 105 far forward as the occiput, and as far backward as the fourth or fifth dorsal spine: inferiorly, to the transverse processes of all the cervical vertebrae, and to the mastoid process of the temporal bone. Relations. — Internally, with the aponeurosis of the pannicu- lus upon the side of the neck, with part of the levator humeri near the head, and with part of the serratus magnus near the shoulder; along its inferior border runs the levator humeri ; and internally, with the complexus major, obliquus capitis inferior, and transversalis colli : which last-mentioned muscle is in places inseparably embodied with it. Structure. — Superior attachments, tendinous and fleshy; infe- rior ones, fleshy ; excepting that separate flattened tendons fix it to the atlas and head : the intermediate parts are thick and sub- stantial, and fleshy. Direction. — Oblique ; downwards and forwards : the anterior fibres incline more to a longitudinal course. Action. — Both muscles acting simultaneously, they will firmly erect the head and neck : one acting by itself, will incline these parts to one side. COMPLEXUS MAJOR. — Dor&o-occipilalis. Situation. — Deep-seated : underneath the former muscle. Form. — An extended triangle : broad, posteriorly ; narrow, anteriorly ; flattened ; thick in substance, in the middle. Attachments. — Posteriorly, to the spines of the four or five anterior dorsal vertebrae ; also to the transverse processes of the same : anteriorly, to the tubercle of the occiput. Relations. — On the outer side with the splenius; on the inner side, with the ligamentum colli, with the complexus minor, and also with the posterior cervical artery and vein, and the 3d, 4th, and 5th cervical nerves. Its posterior or aponeurotic part is in- cluded between the longissimus and spinalis dorsi ; its tendon, fixed to the occiput is subcutaneous. Direction. — Longitudinal : the fasciculi coming from the cer- vical vertebrae inclining upwards and forwards. Structure. — The dorsal portion is aponeurotic. Its fleshy belly is intersected by narrow slips of tendon ; and near the head ends in a flat tendon. Actio)!. — This muscle will forcibly erect the head, and have the eflect of protruding the nose; or, going beyond this, it will conduce to that appearance called i\\e ewe neck ; m which (latter) operation it co-acts with the splenius. 100 MUSCULAR SYSTEM. TR A c H E LO- M ASTo 1 D K u s . — Dorso-fnastuicleus. Situation. — Deep-seated : underneath the vertebral attach- ments of the splenitis. Figure. — Long; cyhndroid ; bifid. Attachments. — Posteriorly, to the transverse processes of the two foremost vertebrae of the back ; to the oblique processes of the six hindermost cervical : anteriorly, in union with the tendon of the splenius, into the mastoid process of the temporal bone. Relations. — Externally, with the splenius ; internally, with the spinalis colli ; posteriorly, it is included between the spinalis and longissinuis dorsi ; anteriorly, it is inseparably united with the splenius. Direction. — Along the neck. Structure. — Tendinous, where it is attached to the back ; fleshy from thence to its union with the splenius, where it ends in the tendon common to it and that muscle. Action. — To erect the head, or to draw it on one side. SPINALIS COLLI. — Dorso-spiualis. Situation. — Deepest seated upon the side of the neck, lying within the interval between the oblique and spinous pro- cesses. Figure. — A near approach to a parallelogram. Attachment. — Inferiorly, to the oblique processes of all the cervical vertebrte, except the first and second ; also to that of the first dorsal: superiorly, to the spines of all the cervical vertebrae, excepting that of the atlas. Relations. — On the outer side, with the complexus and tra- chelo mastoideus ; on the inner, with the ligamentum colli and the vertebr-cB of the neck. Structure. — More tendinous than fleshy at its attachments ; intersected with layers of tendon elsewhere. Action. — To aid in the erection of the head, but more par- ticularly in the constrained flexion of the neck backwards. 3.— SUPERIOR CERVICO-OCCIPITAL RE(;iON. COMPLEXUS MINOR. — Axoido-occipitoHs Longus. Situation. — Upon the poll. Figure. — Long, slender, fusiform. Attachment. — To the spinous process of the vertebra den- tata ; and at the other end inseparably united with the tendon of the complexus major. Relations. — Superiorly, with the complexus major; inferiorly, with the next muscle: on the inner side, with the ligamentum colli. MUSCULAR SVSTEM. 107 SliKclure. — The posterior part consists of pale delicate fasci- culi : the anterior is tendinous. Action. — To assist the complexus major in its operation. RECTUS CAPITIS POSTICUS MAJOR. — Axoido-occipUalis Brevis. Situation. — Underneath, and rather to the outer side of the former muscle. Attachment. — To the spine of the vertebra dentata ; and to a scabrous depression in the occiput, below its tubercle. Relations. — Superiorly, with the complexus minor; inferiorly, with the next muscle : to the outer side, with the obliquus capitis superior. Action. — To pull the head backwards; in doing which, it will assist in the protrusion of the nose. RECTUS CAPITIS POSTICUS MINOR. — Atloido-occipitalis Parvus. Situation. — Underneath the preceding muscle. Figure. — Quadrilateral. Attachment. — To the superior part of the atlas, and to the occiput. Relations. — Superiorly, with the preceding muscle ; inferiorly, with the capsular ligament of the occipital joint; on the outer side, with the obliquus superior; on the inner, with the ligamen- tum colli. Structure. — Entirely fleshy ; consisting of pale delicate fibres. Action. — To chuck up the head suddenly; and, at the same time, to save the capsular ligament from being pinched between the occiput and atlas. OBLIQUUS CAPITIS SUPERIOR. — Atluido-mustoideus. Situation. — Upon the side of the poll. Figure. — Nearly square. Attachment. — To the superior border of the transverse process of the atlas ; and to a ridge extending, laterally, from the tu- bercle of the occiput to the mastoid process of the temporal bone. Relations. — Externally, with the tendon of the splenius ; in- ternally, with the capsular ligament of the axoido-occipital ar- ticulation ; and on the inner side, with the rectus major and liga- mentum colli. Structure. — Fleshy, with one or two tendinous intersections. Direction. — Oblique; upwards and forwards. Action. — Both muscles operating, they will draw back the head, and at the same time elevate it: one alone acting, will turn the head to one side. 108 MUSCULAR SYSTEM. OBLIQUUS CAPITIS INFERIOR. — Axo'ulo-CUloideuS. Situation. — Deep-seated ; upon the supero-anterior and la- teral parts of the neck. Figure. — A near approach to a parallelogram. Attachment. — To the side of the spine of the vertebra den- tata; and to the supero-posterior part of the body of the atlas. Relations. — On the outer side, with the tendon of the sple- nius: on the irjner, with the ligamentum colli and complexus minor: superiorly, with the complexus major; inferiorly, with the capsular ligament of the articulation formed between the first and second vertebrse. Structure.— Th\ck, and almost entirely fleshy. Action. — When both muscles act, the atlas (and the head along with it) will be elevated. By their alternate action, a sort of rotatory motion is given to the head. 4.— INFERIOR CERVICAL REGION. STERN O-MAXILLARIS. Situation. — Inferior part of the neck. Form — Elongated ; cylindroid ; flattened above and below. Attachment. — Posteriorly, to the cariniform cartilage of the sternum ; anteriorly, to the angle of the lower jaw. Relations. — Externally, with the cellular faschia of the neck, panniculus and levator humeri; internally, with the next muscle, trachea, and carotid artery ; along its superior margin, with the jugular vein ; along its inferior border (the posterior half) with its fellow; from which it gradually diverges to the head, leaving the trachea and next muscle exposed in the interspace formed by the divergence. Its tendon passes between the parotid and sub- maxillary glands. Direction. — Longitudinal : curving with the neck. Structure. — Tendinous and fleshy at the sternal end, and in- timately united with its fellow. About three-fourths of the ex- tent of the neck upwards, it terminates in a flat tendon. Action. — To inflex the head towards the breast. If one muscle act alone, it will, at the time of this inflection, incline the head to one side. The pair will also assist in opening the mouth. , Sterno-huoideus. STERNO-TIIYRO-HYOIP'^'''^ <* '^ SSt i Sterno-thyroideus. Situation.— AhovQ the preceding muscle. Form. — Elongated, slender, cylindroid ; flattened above and below ; trigastric ; but unequal in its divisions. Attachment. — Postcnorly, to the cariniform curtilage of the MUSCULAR SYSTEM. 109 sternum, above the preceding muscle: anteriorly, to the spur process of the os hyoicles : also, by a detached slender tendon, to the lower border of the thyroid cartilage. llelations. — Inferiorly, with the sterno-maxillaris ; superiorly, with the trachea, and on the left side with the oesophagus like- wise : along its outer border, with the recurrent nerve; along its inner, or mesian line, with its fellow. Structure. — Sternal end, tendinous and fleshy, and united in one belly ; at the other end, there are two fleshy bellies ; and the three are connected contiguous to the trachea, about the middle of the neck, by an intermedinte, short, and slender tendon. Action. — To draw the os hyoides, and along with it, the larynx, downwards and backwards. SUBSCAPULO-IIYOIDEUS. Situation. — Continued from the levator humeri, and spread over the antero-superior parts of the neck. Form. — A broad, thin, elongated band; thicker and broader anteriorly than posteriorly. Attachment. — In connection with the levator humeri, to the inner surface of the scapula ; anteriorly, to the middle of the body of the OS hyoides. Relations. — Its course lies between the carotid artery and the jugular vein, between which it forms a fleshy partition ; having on its outer side, the sterno-maxillaris; on its inner, the sterno- thyro-hyoideus ; and at its anterior termination, becoming em- bedded between the submaxillary glands. Structure. — The scapular end consists of a thin flattened ten- don : the remaining part is fleshy. It forms altogether a sort of fleshy involucrum for the next muscle. Action. — It will draw the os hyoides downwards and back- wards. SCALENUS . — Costo-cervicalis. Situation. — Postero-infcrior part of the neck. Form. — Pyramidal : base cut slantwise and turned down- wards. Jttachment. — Posteriorly, to the middle of the first rib ; an- teriorly, to the bodies and transverse processes of the 5th and 6th cervical vertebrae. Relatiom. — Along its upper margin, with the transversalis colli; along its lower, with the sterno-maxillaris: on the outer side, with the levator humeri; on the inner, with the trachea; and on the left side, also with the oesophagus. In the interspace between one scalenus and the other, run the carotid artery, par no MUSCULAR SYS'I'EM. vagura, great sympathetic nerve, and, lower down, the jugular vein. The cervical nerves going to form the axillary plexus cross the scalenus in their descent ; and the axillary artery and vein turn round the first rib immediately beneath its postero- inferior extremity. Striictuie. — Constituted of two or three cylindroid divisions, lying one upon the other : its base is tendinous as well as fleshy : its cervical attachments are mostly fleshy. Actio)!. — It will aid in the depression of the neck ; and may also have some effect, the neck being fixed, in inspiration, by having a tendency to draw the rib forwards. LONGUS COLLI. — Subdorso-alloideus. Structure. — Deep-seated : extending along the inferior part of the neck, and thence for some distance along the back. Form. — Complicated : made up of many semi-cylindroid fas- ciculi running obliquely one into the other : altogether, broad in the middle and tapering at either extremity. Attachment . — Posteriorly, to the bodies of the six anterior- most dorsal vertebrae : anteriorly, to the bodies, transverse pro- cesses and inferior spines, of all the cervical vertebrae, excepting those of the first ; it being fixed by a strong tendon to the body oiili/ of the atlas. Relations. — On the outer side it has, posteriorly, the scalenus ; anteriorly, the rectus anticus major: below it, lies the trachea ; above it, the vertebrae. Structure. — The dorsal portion is pretty uniform, and is prin- cipally fleshy ; the cervical part is convoluted, and the fibres are intersected with alternate layers of tendon. The anterior end is entirely tendinous; the other part has also a tendon fixing it to the Gth cervical vertebra. The fasciculi run from one cervical transverse process to the other. Action. — Its many and extensive attachments, and the prox- imity of the points on which it acts, render it a muscle of con- siderable power and etl'ect in the flexion of the neck : the rainbow curve, and the constrained inflexion of the head towards the breast, are chiefly attiibutable to its full and forcible contrac- tions. 6.— INFERIOR CERVICO-OCCIPITAL REGION. RECTUS CAPITIS ANTICUS MAJOR. — Trachelo-suboccipitalis. Situation. — Deep-seated : antero-lateral part of the neck. Form. — Pyramidal : base turned forwards. Atlac/iment. — Posteriorly, to the transverse processes of the MUSCULAK SVSTEIVJ. HI 2(i, 3cl, 4th, 5tli, and Gtli cervical vertebrse : anteriorly, to the cuneiform process of the occipital bone. Relations. — Superiorly, with the vertebrni longus colli, and following muscle : inferiorly, with the oesophagus on the left side, and with the trachea and larynx on the right, and also with the membrane of the fauces. The carotid artery runs along its in- ferior border. Structure. — Posteriorly, consisting of slender fleshy fasciculi, including two or three long slips of tendon: anteriorly, it is fleshy, intersected by a broad flat tendon. Action. — To bend the head : one acting only, will incline it, at the time of depression, to one side. RECTUS CAPITIS ANTICUS MINOR. Atloido-iuhoCcipitaUs. Situation. — Deep-seated : at the back of the cavity of the fauces. Form. — Short, slender, cylindroid. Attachment. — Posteriorly, to the lower part of the body of the atlas : anteriorly, the same as the foregoing muscle. Relations. — Inferiorly, with the preceding muscle; superiorly, with the capsular ligament of the occipital joint. Structure. — Pale and entirely fleshy. Action. — To assist the major. OBLiQUus CAPITIS ANTICUS. — Atloido-stjjloideus. Situation. — To one side, at the back of the fauces. Attachment. — Posteriorly, close to the rectus minor, to the body of the atlas : anteriorly, to the postero-inferior part of the coronoid process of the occipital bone. Relations. — Above, with the occipital articulation ; below and to the inner side, with the rectus major anticus; to the outer side, with the parotid gland. Action. — The same as that of the former muscle. MUSCLES OF THE THORAX. 1 —DORSO-SCAPULAR REGION. The muscles included in this region form three of the princi- pal agents concerned in the motions of the scapula. TRAPEZIUS . — Dorso-acromia/is. Situation. — Upon the side of the withers. Figure. — A right-angled triangle ; with the base turned up- wards, and the right side forwards, in a parallel line with the spine of the scapula. Attachment. — Superiorly, to the spinous processes of the 3d, 4th, 5th and 6th dorsal vertebra?, and to the lioament and faschia 112 MUSCULAR SYSTEM. investing them ; infeiioiiy, to a small tubercle upon the spine of the scapula. Relations. — Superiorly, it covers the rhomboideus brevis ; in its course, downward, it passes over the posterior costa of the scapula; and also the postero-superior angle of the latissimus dorsi : inferiorly, it lies upon the aponeurosis enveloping the dorsum scapulae. Direction. — Perpendicular; excepting the posterior fasciculi, and they slant forward, in their course downward. Structure. — Superior attachments, aponeurotic; below, it ends in a flat triangular tendon ; the intermediate parts are entirely fleshy. Action. — To elevate the scapula : and, when the posterior fasciculi prevail, to incline the bone at the same time, backwards. LATISSIMUS DO RSI. — Dorso-humeralis. Situation. — Upon the supero- lateral part of the chest, behind the scapula. For^n. — Flat, thick : an extended triangle, presenting its base towards the spine. Attachment. — Superiorly, to the spinous processes of the dor- sal vertebrse, and to the ligamentum colli (vel potius, dorsi) investing them ; stretching as far forwards as the highest point in the withers, and as far backwards as the lumbar spines, to some of which it is also connected : inferiorly, to the inner and upper part of the body of the humerus. Relations. — Superiorly, with the trapezius, rhomboideus bre- vis, and posterior angle of the scapula ; inferiorly, with the triceps extensor brachii : externally, with the panniculus ; internally, with the ribs and serratus magnus. Direction. — Oblique: downwards and forwards; the fibres converging in their course. Structure. — Superior part, a broad and extended aponeurosis ; inferiorly, it ends in a long, flattened, thin tendon : the interme- diate parts are entirely flesliy. Action. — To flex the humerus, by drawing it backwards and elevating its inferior extremity. RHOMBOIDEUS BREv IS. — Dorsosubscopularis. Situation. — Upon the side of the withers: deeply seated. Form. — Flat and square. Thin, superiorly; thick, inferiorly. Attachment.— Superiorly, to the four or five anterior dorsal spinous processes, and to the ligament clothing their summits : inferiorly, to the inner part of the superior costa of the scapula, and of the cartilage surmounting it. MUSCULAR SYSTEM. 113 Relations. — Externally, with the trapezius and cartilage of the scapula; internally, with the vertebrae and ribs : anteriorly, it is connected with the rhoniboideus longus ; posteriorly, it is crossed by the latissimus dorsi. Structure. — Fleshy : enveloped in a cellular expansion. Action. — To elevate the scapula. 2.— PECTORAL REGION. These muscles form the breast, or what is vulgarly and ab- surdly called the bosom. FECTORALIS T R A N S V ERS U S.- ( "Jf ''""'f ^"^"7^^'^''^- t oterno-humeralis. Situation. — Lateral, anterior, and inferior parts of the breast. The pair form the fleshy prominences seen directly from the front. Form. — An approach to a triangle whose apex has been cut off: broad and thick, superiorly ; narrow, inferiorly. Attachment. — On the inner side, to a white tendinous line, and through the medium of that, to its fellow of the opposite side; also to the four first bones of the sternum: on the outer side, to the anterior part of the body of the humerus, and to the faschia covering the arm. Relations. — Superiorly, it is connected with the major and minor pectoral muscles ; externally, it is covered by the skin; in- ternally, opposed to the front of the elbow joint; anteriorly, to the levator humeri. Direction. — Transverse ; incurvating downwards. Structure. — Inner attachments, tendii;ous as well as fleshy ; outer, wholly aponeurotic : intermediate part, fleshy. Action. — To adduct the arm ; also to keep it close to the chest during its flexion and extension : this muscle has, probably, more to do in enabling the arm to support weight than to give it motion. PECTORALis MAGNUS. — Stcmo- troclijueus. Situation. — Infero-lateral part of the thorax. Figure. — Trapezoid ; flattened and thick in substance. Attachment. — Inwardly, to the 4th, 5th, and 6th pieces of the sternum, and to the cartilages connecting them ; also to the ensiform cartilage, where, through the intervention of a white tendinous line, it becomes united with its fellow ; still more pos- teriorly, to the aponeurosis of the external oblique muscle, and the cartilages of the false ribs : outwardly, it is attached to the lesser tubercle of the humerus and the inner part of the lower end of the scapula. 114 MUSCULAR SYSTEM. Relations. — Externally, with the panniculus and triceps mus- cles ; internally, with the aponeurosis of the external oblique, the serratus magnus, and the ribs : inferiorly, with its fellow, and in part concealed by the next muscle. Direction. — Longitudinal : inclining upwards. Structure. — Fleshy: only that its anterior end is in part apo- neurotic. Action. — To draw the head of the humerus, and along with it the lower end of the scapula, backwards, throwing the latter more into the upright position. PECTORALIS PARVUS. Situation. — Below the former muscle. Attachment. — Inwardly, to the side of the anterior half of the sternum, and to the cartilages of the first four ribs : outwardly, to the faschia covering the muscles in front of the scapula and shoulder-joint, extending nearly as high up as the place of origin of the antea-spinatus. Relations. — Superiorly and externally, with the preceding muscle ; inferiorly, with the pectoralis transversus ; internally, with the cartilages of the ribs ; anteriorly, with the levator humeri. Structure.— Fleshy ; excepting its inferior termination, which is aponeurotic. Its fleshy parts are formed into layers, one over- lapping another. Action. — To assist the pectoralis magnus. 3.— COSTAL REGION. Comprehending muscles which have, all of them, extensive attachments to the ribs. C Costo-subscapularis. SERRATUS MAGNU S. < DorSO-COStalis . (^ Lunibo-costalis. Situation. — Between the shoulder and the side of the chest. Figure. — In outline, semicircular: fibres radiating from a centre, and forming an indentated or serrated circumferent border. Attachment. — Anteriorly, to the bodies and transverse pro- cesses of the 4th, 5th, 6th and 7th cervical vertebrae ; posteri- orly, to the eight anterior ribs, as low down as their cartilages, by as many fleshy digitations : outwardly, to the upper and inner part of the scapula, occupying the space between the origin of the subscapularis and the insertion of the rhomboidei. Relations. — Externally, with the scapula ; internally, with the cervical portion of the longissimus dorsi, the cervical verte- MUSCULAR SYSTEM. 115 brse, and the ribs; inferiorly, with the pectoral, muscles; ante- riorly, with the splenius; and superiorly, with the latissimus dorsi. Dh-ectio)i. — The fibres converge from their various circum- ferent attachments, like the leaves of a fan, to one common focal point, which is its insertion into the scapula. Structure. — It is covered by a thin aponeurosis which is at- tached around, principally, to the ribs. The costal portion is fleshy and digitated ; the cervical portion is also fleshy ; but the part fixed to the scapula is mostly tendinous. The muscle is considerably thicker in the middle than around the circumference. Action. — It forms the principal agent of support to the trunk, maintaining it and the shoulder in close apposition. This pair of muscles are more or less concerned in all the motions of the sca- pula; and will become dilators of the chest whenever they are exerted while the limbs remain fixed points. INTERCOSTALES EXTERNI. Number. — Seventeen on each side. Sitttatio7i.—F\\\'mg up the intercostal spaces, outwardly: reaching from the articulations of the ribs with the transverse processes as far as the commencement of their cartilages. Attachment. — Anteriorly, to the external edge of the posterior border of one rib ; posteriorly, to the internal edge of the anterior border of the rib immediately behind the former. delations. — On the outer side, with the serratus, pectoral mus- cles, obliquus externus, and transversalis and superficialis costa- rum; on the inner side, with the intercostales interni ; supe- riorly, with the levatores costarum. Direction. — Oblique : from before, backward; and from above, downward. Structure. — Thick layers of united fleshy fibres included be- tween broad aponeurotic slips of tendon, and in places displaying tendinous intersections. INTERCOSTALES INTERNI. Number. — The same as the preceding. Situation. — Underneath the externi ; within the intercostal spaces, reaching from the angles of the ribs to the sternum. Attachment. — To the antero-internal edge of the border of one rib ; to the postero-internal edge of the rib immediately before it. Relations. — On the outer side, with the preceding muscles, and with the intercostal vessels and nerves; on the inner side, with the pleura. 116 MUSCULAR SYSTEM. Direction. — Oblique: but the reverse of that of the former nmscles ; viz. from behind, forwards; and from below, upwards : in fact, their fibres decussate each other, like the strokes of an X. Structure. — They are thinner than the external intercostals ; but are thicker in substance, themselves, near the sternum than in the vicinity of the spine: the reverse being the case with the external muscles. They are covered with very thin aponeuroses, which separate them from the externi. They are entirely fleshy in substance ; but paler and more delicate in their texture than the former. Action. — The intercostal muscles (both external and internal) act upon the ribs to which they are attached, posteriorly : they pull the costal arches forwards, which has a tendency to throw them at the same time outwards ; and thus becomes enlarged the caliber of the cavity of the chest. 4.— STERNAL REGION. Comprising some small muscular slips in the vicinity of and attached to the sternum. LATERALIS STERN I. — Costo-stenialis. Situation. — Upon the antero-inferior part of the outer surface of the thorax, bordering upon the sternum. Figure. — Long, flat, thin: trapezoid. Attachment. — Anteriorly, to the postero-inferior half of the first rib : posteriorly, to the superior three-fourths of the cartilage of the third rib; whence its aponeurosis is extended to the cartilages of the fourth and fifth, and also to the sternum. Relations. — Externally and inferiorly, with the pectoral muscles; superiorly, with the serratus ; internally, with the second rib and intercostal muscles. Direction. — Oblique ; from above downwards and from before backwards. Structure. — Its anterior attachment is by means of a short flat tendon ; its posterior is entirely aponeurotic. Both its surfaces are partially interspersed with tendinous expansions. Action. — To operate in the contraction of the chest by approxi- mating the cartilages of the anterior ribs, and elevating, in some measure, the sternum. sTERNo-cosTALEs. — {Extemi et Interni.) Several fleshy digitations, interspersed with slips of tendon, running from the cartilages of all the true ribs, excepting the first, to the sternum. Their fibres are taking the same course, and are continuous (in the intervals between the cartilages) with the \w- tercostales. MUSCULAR SVSTEiM. 117 Actiufi. — They seem to be for the purpose of contracting the dimensions of the thoracic cavity. 5— DORSO-COSTAL REGION. SUPERFICIALIS-COSTARUM. DorSO-COStailS. Situation. — Spread over the back. Figure. — Broad, thin, digitated, irregular. Attachmeut. — Superiorly, to the ligamenturn nuchee in its ex- tension through the back and loins : inferiorly, to the posterior borders, below their angles, of the 6th and all the ribs behind it. Relations. — Externally, with the panniculus; anteriorly, with the serratus ; internally, with the transversalis costaruiii, and longissimus et spinalis dorsi ; inferO-posteriorly, with theobliquus externus abdominis. Structure. — Consisting of a thin ajjoneurosis, superiorly ; from which originates eleven or twelve broad fleshy digitations : most of them (all the posterior ones) possessing thin tendinous cover- ings. The aponeurosis itself serves as a faschia to the muscles underneath it. Direction. — Downwards \ with a slight inclination forwards. TRANSVERSALIS cosTARUM. — Trachelo-costalis. Situation. — Upon the supero-laterai parts of the thorax. Form. — Elongated ; half penniform : broad in the middle; nar- rowing towards either extremity. Attachment. — Posteriorly, to the anterior borders of the ribs, near to the spine ; and to the posterior edges of their angles : an- teriorly, to the transverse process of the last cervical vertebra. Relations. — Externally and inferiorly, with the last muscle ; internally, with the costal arches ; superiorly, with the longissi- mus dorsi. Direction. — Longitudinal : inclining downwards. Structure. — Complicated. Consisting of two sets of tendons : one set embedded in fleshy fibres, and serving to strengthen its attachment superiorly ; the others are external, distinct from the fleshy parts, are flat and elongated, broad in the middle, grow- ing longer and more slender as they approach the extremities, and are fixed to the costal arches. A separate tendon extends to the cervical vertebra in front. Action. — To elevate the ribs, and thus produce some enlarge- ment of the cavity of the thorax. L E V A TO RE s c o s T A K I M . — Transverso-costales . Number. — About fifteen. 5'?V//rt/?o;?.— -Deep-seated ; upon the back. 118 MUSCULAR SYSTEM. Figure. — Flattened; conoid: bases turned downwards. Attachment. — Superiorly, to the transverse processes of the dorsal vertebrae : interiorly, to the anterior borders of the ribs, in the spaces between their tubercles and angles. i?e/a/20ws. — Externally, with the longissimus dorsi ; internally, with the ribs. Direction. — Oblique : from before backwards, and from above downwards. Structure. — Consisting of bundles of fleshy and tendinous fibres, having a similar arrangement to, and looking like the heads or beginnings of, the external intercostals. Their superior ends are interwoven with small compact tendons, whence proceed tendinous slips, which intersect their fleshy bellies. Their inferior parts are enveloped in aponeuroses, which become thin and va- nish upon their surfaces. The middle bundles are thickest and longest: the anterior ones are but scanty; and the three or four foremost ribs are entirely destitute of them. Action. — To assist in the elevation of the ribs. 6.— DORSAL REGION. Including muscles connected with the vertebrae of the back. Lo N GissiM u s DO RSI. — IHo-spinalis. Situation. — Upon the supero-lateral parts of the back and loins. Figure. — Broad, thick, and elongated. Attachment. — Posteriorly, to the crista of the ileum, to the side of the sacrum, to the spinous and transverse processes of all the lumbar vertebrae, and to the spinous processes of the six pos- terior dorsal : anteriorly, to the angles of the twelve posterior ribs, to the transverse processes of all the dorsal vertebrae, and to those of the three or four hindermost cervical. Relations. — 'Externo.Wy and inferiorly, with the superficialis cos- tarum ; internally, with the ribs and vertebrae ; superiorly, with the spinalis dorsi. Direction. — Longitudinal ; inclining downwards, as well as forwards. Structure. — This muscle (one of the longest and, at the same time, most bulky muscles in the body) is constituted of a dense and strong aponeurosis ; a thick, long, and uniform fleshy belly ; and several broad and flat tendons intimately connected with the fleshy parts. The aponeurosis completely invests the lum- bar portion of the fleshy belly ; with the fibres of which it is so intimately adherent, that the two are inseparable by the knife from one another. From this, the aponeurosis is continued up- wards, to be fixed to the spines of the vertebrae ; and forwards, to be spread over the dorsal division of the muscle, upon which MUSCULAR SYSTEM. 119 it grows thin and less expansive, and, aboutopposite to the withers, altogether vanishes. The fleshy part (which in its course adheres closely to the articulations of the vertebrae with the ribs) is pretty uniform in its breadth until it arrives at the withers, opposite to where it divides into three tails or portions, of a flattened pyra- midal form, and so disposed that one, more or less, overlaps another. Of these, the inferior division is the direct continuation of the common fleshy belly : from it proceed six or seven flat ten- dons, which goto be fixed to the ribs at their articulations with the transverse processes. The middle division sends oft" three broad thin tendons, to be fixed to the three last transverse processes of the neck. The superior division is a small conical slip, ending in a slender tendon, which is attached to the same process of the fourth cervical vertebra. These tendons are all embedded in, and intermediately connected by, continuous fleshy parts, which adhere to the costal articulations at the withers, and to the oblique pro- cesses and sides of the bodies of the three posteriormost vertebrae of the neck. Action. — It will incline to a state of flexion the fore quarters upon the hind; or the hind upon the fore ; according as the one or the other are made the fixed points. It is a principal agent in the acts of kicking, and rearing, and leaping. If one act by itself, the fore or hind parts of the body will be inclined to one side. The pair will also assist in the erection of the neck. SPINALIS DORSI. Situation. — Deep-seated upon the withers. Form. — Thick, elongated, pyramidal: base turned down- wards. Attachment. — Posteriorly, through the medium of the aponeuro- sis of the longissimus dorsi, to the spinous processes of several of the posterior dorsal vertebrae : anteriorly, to the spines of the six or seven anterior dorsal vertebrae, and to those of the three or four posterior cervical. Relations. — Externally and superiorly, with the trapezius, be- hind, andcomplexus major, in front ; internally,with the ligament- um nuchae ; and, inferiorly, it is inseparably united with the last muscle. Direction. — Longitudinal. Structure. — Thebroad and thick part is covered by a broad patch of inseparably adherent aponeurosis, which grows thin and less ap- parent posteriorly ; but, anteriorly, ends in a broad tendon, which pierces the fleshy termination of the belly, and becomes fixed to the spine of the last cervical vertebra. 1:20 MUSCULAR SYSTEM. Actioti. — To flex or writhe the back upon the withers; and to aid in the erection of the neck. SEMI-SPINALIS DORSI. Situation. — Deep-seated, upon the back. Fortn. — Half-penniform ; elongated ; curving with the spine. Attachment. — Posteriorly, to the sacrum, underneath the pos- terior spine of the ileum ; to the articular processesof the lumbar ver- tebrae, and the transverse of the dorsal : anteriorly, to the lumbar spines, and those of the back ; extending forwards to the withers. Relations. — Deeply buried underneath the longissimus et spi- nalis dorsi,and lying close upon the lateral parts of the spine of the back and loins. Direction. — Oblique, from below upwards, and from behind forwards : the obliquity of the packets increasing from behind to the front. Structure. — Consistingof a regular series of small fleshy packets, intersected with broad thin portions of tendon, which increase in length with the dorsal spines. The posterior packets are mostly fleshy in substance ; but the anterior present several long flat tendons, distinct from the other parts, which are fixed to the spines of the withers. Action. — To co-operate with the longissimus dorsi in pro- ducing a more complete flexion of the back. DIAPHRAGMATIC REGION. Containing only the single muscle from which it takes its name. DIAPHRAGMA. Situation. — It forms the fleshy and tendinous partition divid- ing the cavity of the chest from that of the abdomen. Form. — Broad, circular; flattened from before backwards; anterior surface, convex; posterior, concave: bifurcate, superiorly; having two elongations or appendices extended backwards, and terminating in pointed extremities. Division. — The broad circular portion is sometimes distin- guished as the greater muscle ; wiiile the appendices or crura are said to form the lesser. Attachment. — The greater muscle is attached by fleshy digita- tions to the cartilages of the eighth ptiir of ribs, and to those of all the posterior ribs, with the exception of the two last; also to the ensiform cartilage. Of the appendices, the right, the longer one, is attached to the bodies of all the lumbar vertebree ; the left, or shorter one, has separate tendinous attachments to the first MUSCULAR SYSTEM. 121 and second of these vertebrae. The two appendices form a union and decussation opposite to the seventeenth dorsal vertebra; and afterwards, again bifurcate. The greater and lesser muscles form a conjunction through the medium of the cordiform tendon. Relations. — The anterior or convex surface is covered by the pleura; is opposed to the bases of the lungs, and in part to the sides of the chest; and is connected, next to the spine, with the superior mediastinum and its important contents; next to the sternum, with the pericardium and inferior mediastinum. The posterior or concave surface is covered by peritoneum ; and is, together with the crura, connected, superiorly, with the psoas muscles and quadratus lumBorum ; infero-posteriorly, with the kidneys, renal capsules, pancreas and duodenum ; on the right side, with the liver; on the left, with the stomach and spleen. Direcfion. — The fibres of the larger muscle all converge in radii, and run to the cordiform tendon, as to a common centre: those of the appendices run longitudinally. Qnov attachment tendinous in part, but mostly fleshy. Inferior surface, aponeurotic. A little above the middle of the arm it sends off a tendon which passes under the posterior annular ligament of the knee, and there unites itself to the tendon of the perforans. DEEP POSTERIOR BRACHIO-CRURAL REGION. The following muscles constitute the deep-seated flexors : they lie anteriorly to and are concealed by the superficial. FLEXOR PEDIS PERFORATUs. — Epicoudj/lo-phalaiigeus. Situation. — Deep-seated in the posterior part of the arm. Form. — This and the flexor perforans form one thick, com- pact, cylindroid fleshy mass ; the tendons issuing from which are long and flattened, and adapted by convexity and concavity of surface to each other. Attuckmoit. — Superiorly, (and in common union with the fol- lowing muscle) to the lower side of the internal condyle : infe- riorly, to the upper and back part of the os coronse. Relations. — Posteriorly, to the three flexores raetacarpi and flexor sublimis ; anteriorly, to the radius and flexor profundus. Along the antero-internal border run the radial blood-vessels and nerves. 144 MUSCULAR SYSTEM. St7i(ctiire. — The superior attachments of the mass of muscle (common to this and the perforans) are in part fleshy, but prin- cipally tendinous : the tendinous part being underneath and applied to the trochlea of the condyle, which in the motions of the joint it plays over. The mass is divisible (more or less completely) into three or four or more distinct portions, whose surfaces are partly aponeurotic, and whose interiors (with the exception of the one next the radius, which is commonly the most completely separable) are intersected with layers of ten- don. Just above the knee it contracts its substance and be- comes tendinous, forming two flattened tendons which pass down under the posterior annular ligaments. The posterior of these tendons, the tendo perforatus, is neither so broad nor so flat as the other ; it presents a concave surface anteriorly, to embrace its companion in front. At the back of the fetlock joint, it ex- pands so as more completely to cover the perforans, and sends off a crescentic process which surrounds that tendon. At this part also a tendinous theca includes both tendons, having at- tachments on each side to the sesamoids. Opposite to the small pastern joint, the perforatus splits into two divisions, having the perforans passing between them : the triangular interval left is occupied by a portion of membrane which is so attached as to from a circumscribed synovial bag. Action. — To bend the fetlock and pastern joints ; and also to assist in the flexion of the knee. FLEXOR PEDIS PERFORANS. — Epico)idj/lo-phaIa)igeus. Situation, form, and superior attachment. — The same as the preceding. Inferior attachment, to the posterior concavity of the os pedis. Structure. — The fleshy origins and bellies of this muscle are confounded with those of the perforatus. As they approach the knee, however, they separate ; and then the perforans runs im- mediately behind the perforatus. At the knee, like its fellow, it is wholly tendinous, and here indeed partakes somewhat of the nature of cartilage, as it passes through the same synovial bag- as encloses its companion. Below the knee, these tendons as- sume different shapes; the perforans being cylindroid, the other flattened ; and this admits of the adaptation of their surfaces to each other. In their passage down the leg, they are connected together and invested by cellular tissue : a loose cellular sub- stance also connects them to the suspensory ligament and cannon bones. The perforans tendon at the back of the fetlock spreads again in breadth, and re-assumes a cartilaginous texture, and is likewise (the same as at the knee) surrounded by a syno- MUSCULAR SYSTEM. 145 vial sheath, formed principally by the tendo perforatus ; from which it only emerges at the division of the latter. Opposite to the OS coronae it is destitute of any tendinous covering, and is invested by cellular membrane only. It next sinks into the substance of the frog, passing over the navicular bone, where it becomes cartilaginous, and adapted in shape to the posterior articular surface of that bone, a bursa or circumscribed syno- vial cavity existing between them. Finally, it ends in an ex- panded termination which is broadly implanted into the posterior concavity of the os pedis. Action, — To bend the foot. It will also assist in the flexion of the pastern, fetlock, and leg. RADiALis ACCESsoRius. — Flcxof uccessorius. Situation. — Deep-seated, along the infero-posterior side of the arm. Figure. — Irregular; short; flattened : upper part, bifurcate. Attachment. — Superiorly, mesio-posterior part of the radius : inferiorly, its tendon joins that of the perforans. Relations. — Anteriorly, with the radius ; posteriorly, with the bellies of the perforatus and perforans : internally, with the radial blood vessels and nerves. Direction. — From above downwards, inclining in a sort of curve from without inwards. Structure. — It has two beginnings. One is pyramidal, elon- gated, and tendinous, and extends high up the radius : the other is triangular and fleshy, and is attached lower down. They both unite to form one fleshy belly, which is intermixed with slips of tendon, and finally ends in a single narrow flattened tendon. Action. — To assist the perforans. LUMBRICI, ANTERIOR ET POSTERIOR. — I.Umbricalcs. Consist of two pairs of pale, delicate, small muscles, having long slender tendons. The lumbrici posteriores are to be found invested in adipose membrane, adhering to the inner side of the tendo perforans, about one-third of its lengtli upwards from the fetlock. Here- abouts they are broad ; but they grow narrow as they descend, assuming altogether a pyramidal figure; and they give off" at the fetlock slender flattened tendons, which aj)pear to unite to form the crescentic border of the cellular and tendinous sheath at that part inclosing the tendo perforans. The lumbrici anteriores lie within the spaces left between the small metacarpal bones and the suspensory ligament, under u 146 MUSCULAR SYSTEM. cover of the flexor tendons. They are longer but thinner than the former, and may be classed among the half-pen niform muscles. They adhere for some way down the leg to the small metacarpal bones, become tendinous about the middle of the cannon, turn round the tuberculous terminations of the small metacarpals, and vanish in the adipose substance in front of the limb connected with the extensor tendons. Action. — The use of these small muscles seems not to be known; at least, it is by no means well defined. MUSCLES OF THE HIND EXTREMITIES. The muscles of the hind extremity are invested and closely compacted together by a subcutaneous covering, in part ten- dinous and in part cellular in texture (according to the dif- ferent structures in the vicinity from which we find it to be derived), to which we may give the name (analogically) of faschia lata. In front of the haunch it is derived from the panniculus and crural arch, and is both fibrous and cellular in composition ; on the outer side of the haunch it is continued from the tensor vaginae, a muscle that may be said to belong or have an exclusive relation to it; on the inner side, it is con- tinuous with the faschia superficialis abdominis, faschia scroti et pubis, and is entirely cellular in structure; and posteriorly, it is connected with the faschia lumborum. The principal fixed points of attachment of this faschia are, the anterior spine of the ileum, the pubes, the coccyx, the trochanter minor ex- ternus, and the patella. Inferiorly, it spreads upon the muscles of the leg, giving them a compact investment, which portion of it maybe denominated the crural or tibial faschia : it derives various fibrous additions from the tendons of the gracilis, sar- torius, seniitendinosus, triceps, Sec, and finally vanishes in ex- pansion over the hock. The external surface of the faschia is adherent to the skin, through the intervention of a delicate cellular tissue; there being included between them, besides more or less adipose matter, the subcutaneous bloodvessels, nerves, and lymphatics. Its internal surface is applied to the muscles themselves, and between several of them it sends down processes which take root in the bone. From the faschia itself in some places the muscular fibres appear to aiise. The use of the faschia lata appears to be, to give both power and effect to the muscles during the time of their action, by retaining them in their respective places and relative positions, and keeping them closely and compactly braced together. MUSCULAR SYSTEM. 147 MUSCLES OF THE HAUNCH. 1— GLUTEAL REGION. Comprehending the three gluteal muscles, which compose the superior part of the haunch or quarter. GLUTEUS EXTERN us. — lUo-trochanterius Medius. Situation. — Mesio-external part of the haunch. Figure. — Triangular: base presented upwards. Attachment. — Superiorly, to the antero-superior and inferior spines of the ileum, to the spine of the sacrum, and to the faschia lumborum ; inferiorly, to the trochanter minor externus lie/atibns. — Externally, with the faschia and skin ; internally, with the gluteus maximus; anteriorly, with the tensor vaginae ; posteriorly, with the biceps adductor. Direction. — Convergent, from the several superior attach- ments to the trochanter. Structure. — It is constituted of two fleshy divisions, having a broad interval between them filled by aponeurosis. The an- terior or smaller division is tendinous superiorly, and internally its fibres are interlaced with those of the gluteus maximus. Inferiorly, both portions unite into one common, triangular, fleshy belly, which ends in an aponeurotic tendon ; and from this are sent down processes to the tibial faschia. Action. — The same as the other glutei. GLUTEUS MAXIMUS. — Uio-trochauterius Magnus. Situation.— Antev'iov, middle, and external parts of the haunch. Figure. — Pentagonal ; sides unequal ; angles rounded ; low- ermost angle extended. Attachment. — Superiorly, to the spinous and transverse pro- cesses of the two or three last lumbar vertebrse, to those of the two or three uppermost sacral, and to the faschia lumborum ; also to the crista of the ileum, its dorsum and posterior spine ; lastly, to the sacro-sciatic ligaments. Inferiorly, to the trochanter major. Relations. — Externally, with the gluteus externus and skin ; internally, with the dorsum ilei and gluteus internus ; anteriorly with the tensor vaginae ; posteriorly, with the lumbar and sacral spines and biceps adductor. Structure. — This is a bulky muscle, coarse and dark-coloured in its texture ; wholly fleshy, excepting some broad tendinous 148 MUSCULAR SYSTEM. intersections, which, at the trochanter, become formed into a broad flat tendon, surrounded by fleshy fibres. Action. — The same as that of the next muscle. GLUTEUS INTERN us. — lHo-troclianterius Parvus. Situation. — Deeply placed, underneath the preceding muscle. Figure. — Fan-shaped ; its fibres describing two contrary curves. Attachment. — Superiorly, to the dorsum ilei, as high up as where the gluteus maximus ceases to be attached, and as far back as the border to which the sacro-sciatic ligament is fixed ; inferiorly, to the (anterior protuberance upon the) trochanter major. Relations. — Externally, with the gluteus maximus ; internally, with the ilio-femoral articulation. Structure. — Principally fleshy : inferior portion intersected at regular distances by layers of tendon, which at the trochanter become united together into one broad flat tendon, curiously grooved (in radii) upon its external surface. Action of the Glutei. — These muscles are extensors either of the OS femoris upon the pelvis, or of the |)elvis and loins upon the hind quarter. When the limb has been carried in advance under the body by the muscles of the anterior femoral region, and the toe firmly set down upon the ground, the glutei, by extending the haunch, will carry the trunk forward ; thus, be- coming potent agents in progression ; and of them the maximus is by far the most powerful. In the acts both of rearing and kicking these muscles are thrown into violent and forcible contraction : in the former action, the limbs become the fixed points ; in the latter, the trunk. 2.— PELVI-TROCHANTERIAN REGION. These muscles are but small, and are all attached to the trochanter major. PYRiFORMis . — Sacro-trochanterius. Situation. — Supero-lateral parts of the pelvic cavity. Figure. — Conical : base turned forwards. Attachments. — Within the pelvis, to the transverse processes of the sacrum, and infero-internal part of the ileum : without the pelvis, to the hollow behind the trochanter major. Relations. — Superiorly and externally, with the pelvis; in- feriorly and internally, with the peritoneum: along its infeiior border run the obturator bloodvessels and nerves. MUSCULAR SYSTEM. 149 Structure. — Composed of a fleshy belly, having its superior border tendinous ; which border, after the muscTe has passed through the sciatic notch, gives origin to a slender tendon that insinuates itself between the geniini to gain the tro- chanter. Actio?i. — To assist in the extension of the haunch. OBTURATOR EXTERN US. — Subpubio-trocliauterius Externus. Situation. — Deep-seated, in the supero-internal part of the thigh. Form. — Quadrilateral, and putting on the appearance of a double muscle. Attachments. — Internally, to the external border of the obtu- rator foramen, and to the external surface of tlie obturator liga- ment : externally, to the cavity behind the trochanter major, and to the upper portion of the ridge extending from the larger to the lesser trochanter. Relations. — Posteriorly, with the biceps abductor; superiorly, with the gemini and obturator internus ; internally, with the adductor niagnus. Direction. — Outward. Structure. — Attachments, both tendinous and fleshy ; surfaces, striped with aponeurotic tendon. Action. — To assist in the extension of the haunch ; and at the same time to rotate it outwards. OBTURATOR INTERNUS. — Subpubio-trochanterius Internus. Situation. — Upon the lower side of the pelvic cavity. Form. — Circular border, having radiating fibres converging towards one common centre. Attachments. — Internally, to the internal border of the ob- turator foramen, and to the inner surface of the obturator liga- ment : externally, to the root of the trochanter major. Relations. — Superiorly, with the peritoneum ; inferiorly, with the obturator ligament. Structure. — From the foramen the fleshy fibres converge and form a belly which passes between the tuberosity and spine of the ischium, and then makes its appearance without the pelvis, in the vicinity of the hip joint. Action. — To approach the trochanter to the pelvis ; the eftbct of which will be to turn the haunch outwards. G E jM 1 N I . — Ischio-trochanterius . Situation. — Without the pelvis, at its postero-inferior part. Form. — Thin; flat; quadrilateral. 150 MUSCULAR SYSTEM. Attachments. — Internally, to the supero-posterior part of the ischium; externally, to the root of the trochanter major. Relations. — Posteriorly, with the biceps and obturator in- ternus ; superiorly, with the gluteus internus ; inferiorly, with the obturator externus ; anteriorly, with the hip jonit. The sciatic nerve crosses this and the other muscles entering the trochanterian hollow. Structure. — This is a pale delicate muscle, tendinous as well as fleshy at its attachments : in the middle, fleshy altogether. 3.— ANTERIOR ILIO-FEMORAL REGION. The muscles in this region form the fore and prominent part of the haunch. TENSOR VAGINA. — Ilio-aponeuroticns. Situation. — Antero-external part of the haunch. Figure. — Broad ; triangular ; flattened. Attachments. — Superiorly, to the anterior spine of the ileum : inferiorly, to the faschia lata. Relations. — Anteriorly and externally, with the skin ; inter- nally, with the posterior end of the panniculus, with the adipose matter enveloped in the flank, and with the iliacus, rectus and vastus externus ; posteriorly, with the glutei-maximus et ex- ternus. Structure. — Tendinous and fleshy at its superior attachment, from which it expands into a broad fleshy belly. About midway between the pelvis and stifle, it sends off" a thin expansion of tendon, which becomes continued into and confounded with the faschia lata, largely contributing to it. Action. — To draw up and render tense the faschia lata ; through whose interposition and connexion it will also aid in the advancement and elevation of the haunch, and seemingly in the extension of the thigh. RECTUS . — Ilio-rotuleus. Situation. — Forming the anterior prominence of the haunch. form. — Elongated ; cylindroid; fusiform; broader and thicker in the middle than at either extremity. Attachments. — Superiorly and anteriorly, to the dorsum of the ileum, above and rather in front of the acetabulum : inferiorly and posteriorly, to the supero-anterior part of the patella. Relations. — Its upper part lies between the iliacus and tensor vaginse. The body of the muscle is bounded laterally by the two vasti ; posteriorly, by the femoral bone ; and anteriorly, by the MUSCULAR SYSTEM. 151 faschia lata. It has also relations to the anterior crural nerve, and the femoral bloodvessels. Strnciiire. — The superior attachment consists of a broad, flat, bifurcated tendon. The chief bulk is fleshy. The antero-infe- rior and lateral parts are covered by aponeurosis, which ends in a thick flattened tendon running to the patella. Action. — Similar to that of the vasti and crureus. TRI-FEMORO-ROTULEUS. The three following muscles may either be considered under this name, as forming altogether a triceps muscle, or they may be viewed as three distinct muscles. The French anatomists prefer the former plan ; but our English schools, the latter; and in accordance with their rules, I shall here consider them separately. VASTUS EXTERN us. — {Outer Divisiu)! oj'the Tri-femoro-rotuleus.) Sittiatio7i. — Antero-external side of the haunch. Form. — Semi-oval : internal side, flattened ; external, convex ; thickest in the middle. Attachment. — Superiorly and anteriorly, to the root of the tro- chanter major, to the trochanter minor externus, and to the whole outward surface of the body of the femoral bone. Inferiorly and posteriorly, to the supero-external part of the patella. Relations. — On the inner side, with the preceding muscle ; on the outer side, with the tensor vaginge and faschia lata ; poste- riorly, with the femoral bone and biceps femoris. Structure. — Superior attachment, tendinous and fleshy : the other parts are fleshy, with the exception of a thin aponeurosis spread over its postero-external side. VASTUS INTERN us. — (Internal Division of the Tri-femoro- rotuleus.) Situation. — Antero-internal part of the haunch. Form. — Semi-ovoid : thicker in substance than the last muscle. Attachment. — Superiorly and anteriorly, to the neck of the femoral bone, to the root of the trochanter minor internus, and to the entire inner part of the body of the bone. Inferiorly and posteriorly, to the supero-internal part of the patella. Relations. — On one side with the rectus ; on the other with the sartorius : posteriorly, with the femoral bone ; anteriorly, with the faschia lata. Structure. — Covered by a thin aponeurosis ; otherwise, fleshy. The aponeuroses proceeding from the vasti extend downward over the patella to be fixed to the tubercle of the tibia. Infe- riorly, an aponeurotic tendon separates it from the crureus. 152 MUSCULAR SYSTEM. CRUREUS VEL CRURALIS. (Middle Division of Uie 'rri-J'emoro-roluleus.) Situation. — Deep-seated in the hollow formed by the rectus above, the vasti on either side, and the femoral bone below. Form. — Fusiform ; elongated. Attachment. — Antero-superiorly, to the ileum, just above the acetabulum ; postero-inferiorly, to the body of the femoral bone and to the patella. Relations.— yf'ith. the muscles and bone to which it lies con- tiguous. Structure. — Tendinous at its extremities; intermediate parts, fleshy ; under part, aponeurotic. Action of the two Vasti and the Crureus, considered as a Triceps or one entire Muscle. In consequence of their connexion, through the intervention of the patella and its ligaments, with the tibia, these muscles be- come direct extensors of the thigh ; and their power as such is considerably enhanced by the peculiar construction of the stifle- joint, which enables them to act with the combined mechanical advantages of pulley and lever. In progression, they raise the thigh and advance it forwards under the body ; and in that po- sition, as soon as the limb has become a fixed point, they will assist in progressing the haunch. INTERNAL ILIO-FEMORAL REGION, Comprehends the muscles forming the prominent rotundity of the inner part of the haunch. SARTORius. — Sub-lumho-tibialis. Situation. — Antero-internal part of the haunch. Form. — Long, slender, pyramidal ; anterior part broadest. Attachment. — Antero-superiorly, to the bodies of the posterior lumbar vertebrae, and to the brim of the pelvis midway between the symphysis pubis and the anterior spinous process of the ileum ; inferiorly, to the supero-internal part of the tibia, and to the in- ternal condyle of the femoral bone. Relations.— On the outer side, with the psoas magnus, vastus internus and gracilis ; on the inner, with the faschia lata and skin. Along its posterior and outer border run branches of the femoral bloodvessels. Structure.— Vleshy and rather pale ; except the extremities, which are aponeurotic. Its anterior aponeurotic end is so in- MUSCULAR SYSTEM. 153 timately united with the psoas parvus, as it runs forward side by side with it, that it is somewhat difficult to make out the kmibar attachments distinctly. The interior termination consists of a broad, flat, glistening tendon, which (in union with the tendon of the gracilis) expands into an aponeurosis, spread- ing over the entire inner side of the stifle joint. Action. — To assist in bending the leg ; and, in the flexed po- sition, to give the limb a rotatory motion inwards. G R A ci LIS. — Sub-pubio-tibialis. Situation. — Superficial, on the internal part of the thigh. Figure. — Quadrilateral, broad, thin, flattened. Attachment. — Superiorly, to the symphysis pubis, extending as low down as the ischium ; inferiorly, (along with the sar- torius) to the supero-internal part of the tibia, and the internal condyle of the femoral bone. Relations. — Along its antero-internal border, with the pec- tineus and sartorius ; on its inner side, with the adductors ; on its outer side, with the faschia lata and skin. Structure. — The pubal attachment is tendinous and fleshy : inferiorly, it ends in a broad aponeurosis, which, forming a union with the tendon of the sartorius, expands upon the inner side of the stifle, and is continued upon the leg into the tibial faschia. Action. — To bend the leg, and (when flexed) to rotate it inwards. PECTIN Eus. — Super-pubio-femoralis. Situation. — Inner, upper, and anterior part of the haunch. Form. — Fusiform; thickest in the middle; upper extremity flattened. Attachment. — Superiorly, to the brim and anterior surface of the pubes, near the symphysis ; and to the infero-anterior part of the same bone, near the acetabulum. Inferiorly, to a long ridge extending from the trochanter internus. Relations. — On the outer side, with the sartorius ; anteriorly and internally, with the gracilis ; posteriorly, with the ad- ductors. Structure. — The superior attachment consists of a bifurcated tendon ; the inferior is both tendinous and fleshy. Its fleshy belly is striped with aponeurosis. Actioyi. — To flex the haunch, and at the same time adduct it. X 154 MUSCULAR SYSTEM. ADDUCTORES FEMORIS. Different anatomists pursue different modes of treating of these muscles ; and all may be proved to be right or wrong, according to the light in which the dissector views the parts, and the artificial divisions which his knife may make of them. One considers the three adductors together, as a triceps muscle ; another describes them as three separate muscles ; while a third looks upon them as forming a single muscle and a biceps. The last mode of proceeding appears to me to be in the most strict accordance with nature, and therefore shall I adopt it here. ADDUCTOR BREVIS. ADDUCTOR LONGUS. > Suh-pubio-femoratis. Situation. — Deep-seated, on the inner part of the thigh. Attachment — Superiorly, (both having one common attach- ment) to that part of the pubes included between the symphysis and the acetabulum ; inferiorly, the short adductor is attached to the middle third of the body of the femoral bone ; the long adductor to the lower third of the body of the same bone, and to its internal condyle. Relations. — On the outer side with the gracilis ; and on the inner, with the trochanter minor internus. Along their anterior borders run the pectineus and sartorius. Posteriorly, lies the adductor magnus. Between these two adductors pass the femo- ral artery and vein. Sti'ucture. — One entire fleshy mass superiorly, split into two portions inferiorly, which at their insertions into the bone mani- fest tendinous fibres. Their surfaces exhibit aponeurotic patches and stripes. Action. — Will be considered with the next muscle. ADDUCTOR MAGNUS. — Ischio-tibialis. Situation. — Postero-internal part of the haunch and thigh ; forming the prominence behind termed ** the point of the quarter." Figure. — Irregular. Superior extremity, narrow, pointed, and curved ; from which it becomes broad, thick, and afterwards elongated. The posterior border is thick ; the anterior is thin. Attachment. — Superiorly, to the spine of the sacrum and tuberosity of the ischium ; inferiorly, to the lower third of the inner part of the body of the os femoris, to the internal condyle of that bone, and to the inner part of the head of the tibia. MUSCULAR SYSTEM. 155 Relations. — Posteriorly and externally, with the faschia and skin ; internally, with the biceps abductor and heads of the gastrocnemii ; anteriorly, with the gracilis. Direction. — Longitudinal ; inclining forwards in a curve. Structure. — Entirely fleshy, with the exception of the ex- tremities. The upper extremity is prolonged as high as the sacrum by means of aponeurosis, which forms part of the faschia lata. The inferior extremity is affixed to the condyle by a strong flattened tendon. Action. — That of the three adductors is to extend the os femoris upon the pelvis; so that they are opponents to the psoas magnus and iliac us, which flex the haunch : they are also pow- erful adductors of the whole limb. The great adductor will, moreover, assist in bending the thigh, and will rotate it inwards a little. 5— POSTERIOR ILIO-FEMORAL REGION. , The muscles of this region occupy the outer and posterior side of the haunch. BICEPS ABDUCTOR FEMORIS. — Ischio-tibialis Medius ve\ Posterior. Situation. — Postero-external side of the haunch and thigh ; where, being superficial, its course is well marked in the living- animal. Attachment. — Superiorly, to the lateral and posterior parts of the spine of the sacrum, and some of the upper pieces of the OS coccygis ; to the sacro-sciatic ligaments; to the tuberosity of the ischium, and to the faschia lata. Inferiorly, it is split into two portions, one of which is attached to the patella and its external ligament; the other (through the intervention of an aponeurotic expansion) to the ridge upon the upper part of the tibia, and to the faschia covering the leg. Relations. — Externally, with the faschia and skin ; internally and superiorly, with the gluteus maximus ; internally and inferi- orly, with the gastrocnemii; anteriorly, with the external tro- chanters, major and minor, and with the body of the femoral bone ; posteriorly, with the tuberosity of the ischium and serai- tendinosus. Structure. — Fleshy ; surfaces, aponeurotic. Attached by a broad flat tendon to the tuberosity of the ischium ; by a more slender one, to the trochanter minor externus ; by a broad, flat- tened, and thick tendon, invested by some few fleshy fibres, to the patella and its ligament ; and to the tibia and tibial faschia 156 MUSCULAR SYSTEM. by d broad expanded aponeurosis. The inferior division is, at its upper part, united with the next muscle by intermixture of fleshy fibres. Action. — The two divisions of this muscle will operate dif- ferently. The anterior or superior one will assist the rectus and vasti in extending the thigh ; but the posterior one will contri- bute towards its flexion. They will both co-operate in abducting the limb ; also in rotating it inwards — the hock at the time turning outwards. p;mitendinosus. 7 > adductor tibialis, emimembranosus. ) Ischio-tibialis Internus. Situation. — Posterior side of the haunch and thigh. Attachment. — Superiorly, to the postero-lateral part of the spine of the sacrum ; to the two or three uppermost bones of the coccyx ; and to the antero-inferior side of the tuberosity of the ischium. ]nferiorly, to the superior and antero-internal part of the tibia; directly opposite to the attachment of the lower head of the biceps abductor and tibial aponeurosis. Relations. — Posteriorly, with the faschia and skin ; anteriorly, with the tuberosity of the ischium, os femoris, and gastrocne- mii ; externally, with the biceps ; internally, with the adductor tibialis. Structure, — This is a long cyhndroid muscle, composed of two parts, one coming from the sacrum, the other from the ischium ; both of which are united below the tuberosity. The superior attachments are both fleshy and tendinous. From the inferior proceeds an aponeurotic expansion, contributing towards the tibial fasciiia. MUSCLES OF THE THIGH AND LEG. These muscles are invested and confined down in their places by the crural or tibial faschia, which is in part an extension from the faschia lata, and in part a production from those femoral muscles whose tendons or aponeuroses descend upon the leg ; such as the adductor magnus, biceps, and adductor tibialis. The muscles themselves (those now under consideration), being collected together into two packets or parcels, separate and dis- tinct from each other, the crural faschia admits of an anterior and a posterior portion ; one investing the muscles in the ante- rior crural region, the other in the correspondent posterior re- gion. The former has for its principal places of attachment the patella ; the upper and lower ends, tubercle, and spine of the tibia : and the anterior annular and lateral ligaments of the MUSCULAR SYSTEM. 157 hock; in front of which it is continuous with the tendinous va- ginae, formed for the passage of the extensor tendons : on the outer side this faschia sends a broad process inward, between the extensor pedis and peroneus, which is fixed to the body of the tibia, inclosing the latter muscle in a complete sheath. Be- yond this, the anterior faschia becomes continuous with the posterior. The chief attachments of the posterior division of the faschia are, the condyles, and postero-inferior part of the body of the femoral bone ; the postero-lateral parts of both extremities of the tibia, and the entire inner side of its body ; the lateral liga- ments of the hock ; and the tendinous point of the os calcis. 1.— ANTERIOR FEMORO-CRURAL REGION. Of the muscles situated in this region, two are extensors of the leg and foot, and at the same time aiders in the flexion of the hock : the other is a direct flexor of the hock. They are all three bound down to the tibia by a strong tendinous faschia. EXTENSOR PEDIS. — Femoro-prepha/dfigeus. Situation. — Superficial ; anterior part of the leg. Fonn. — Elongated ; fusiform : flattened from before back- wards. Attachment. — Superiorly, to a roughened depression upon the antero-inferior part of the external condyle of the femoral bone. Inferiorly, to the coronal process of the os pedis, and to the superior edge of the bone in the interval between the lateral cartilages. Relations. — Anteriorly, with the faschia and skin, and the aponeurotic tendon of the biceps ; postero-externally, with the peroneus; postero-internally, with the flexor metacarpi ; poste- ro-superiorly, with the capsular ligament of the stifle joint, the tendon passing through a groove upon the front of the tibia. Structure. — The muscle commences, superiorly, by a small flat tendon, which is common to it and the flexor metatarsi. Upon the tibia it becomes fleshy, exhibiting two or three thin tendi- nous intersections, together with aponeurotic surfaces. A little above the hock the fleshy belly ends in a flat tendon, which takes its course in front of the hock through a theca prepared for it, and upon the cannon (about one-third of its length downward) enters into union with the tendon of the peroneus, and so inti- mately that the two tendons appear but as one until they have descended as low as the fetlock joint, over which they disunite and again run separate. As it passes the front of this joint, the 158 MUSCULAR SYSTEM. extensor tendon expands itself, and continues to do so to its ter- mination. Action. — In consequence of this tendon being bound down upon the hock by the sheath through which it passes, it will have effect in flexing that joint, at the same time that it is performing its own special function, the extension of the foot, as well as the pastern and fetlock joints. **# Immediately beneatli the bend of the hock, from the antero-superior part of the metatarsal bone, issues a thin layer of fleshy fibres, enveloped in cellular substance, and concealed in part by the tendon of the above muscle, with which (about one-fourth of the length of the cannon downward) they form a union, and make some addition to its substance. In action, these supplementary fibres will brace the tendon ; and are probably furnished to prevent it from being compressed by the flexion of the hock. PERONEUS. — Pero?teo-prephalcuigeus. Situation. — Antero-external side of the limb. Form. — Cordiform; elongated; flattened from before back- wards. Attachment. — Superiorly, to the head of the fibula, continu- ing its attachment for the entire length of that bone. Inferiorly, the same as the foregoing muscle. Relations. — Externally, with the faschia and skin ; internally, with the fibula ; anteriorly, with the extensor pedis ; posteriorly, with the flexor pedis. Structure. — Superior attachment, fleshy and tendinous, from which a fleshy belly descends nearly the whole length of the tibia: a slender tendon, in form a flattened cord, then com- mences, which passes through a distinct tendinous sheath, across the front of the hock, and upon the cannon bone forms a con- nexion with the tendon of the flexor pedis. Action.— It will co-operate with the extensor pedis. FLEXOR METATA Hsi. — Tihio-prematarseus. Situation. — Antero-internal side of the limb. Figure. — Bifurcate at either extremity. Attachment. — Superiorly, in common with the extensor pedis, from the external condyle of the os femoris ; and from a broad triangular excavation marked upon the superior and antero- external part of the tibia. Inferiorly, to the head of the large metatarsal bone, and to that of the internal small metatarsal bone. Structure. — The tendon by which the flexor pedis is attached, superiorly, enters afterwards into the composition of the present muscle, whose fleshy belly, although in intimate connexion with the tendon, is ])laced behind it. In front of the hock, the fleshy part ends in a small cordiform tendon, which is enveloped by a MUSCULAR SYSTEM. 159 flattened one that runs in front of it, and indeed forms quite a sheath for it. Having emerged from its sheath, however, it spHts into two divisions, which are left with only cellular coverings. Action. — To flex the hock ; in doing which it will have a ten- dency to turn the joint inwards. 2.— SUPERFICIAL POSTERIOR FEINIORO-CRURAL REGION. The muscles contained in this region are all affixed to the OS calcis, and thereby become extensors of the hock : one of them is continued afterwards down the leg, to be fixed both to the fetlock and pastern, and hence operates as a flexor of those parts at the same time. GASTROCNEMIUS EXTERN US. — Bifemoro-calcancus . Situation. — Superficial ; along the posterior part of the leg. Figure. — Elongated : flattened from before backwards ; broad, thick, and bifurcated, superiorly; united and cordiform, inferiorly. Attachment. — Superiorly, to a roughened hollow just above the external condyle of the os femoris, to the inner condyle, and to a ridge extending from it : inferiorly, to the point of the OS calcis. Relations. — Posteriorly, with the faschia and skin; anteriorly, with the condyles of the femur, gastrocnemius and plantaris, muscles of the deep posterior crural region, and the popliteal bloodvessels and nerves; externally, with the biceps; internally, with the adductor magnus and adductor tibialis. Direction, — Downward and backward. Structure. — The superior and middle parts are bulky, and con- sist principally of a fleshy belly, bifurcate, whose surfaces are partially covered by aponeurosis, discovering inferiorly a few tendinous intersections. A little below the back of the stifle, the bifurcations unite and form one entire fleshy belly, glistening in many parts with tendinous fibres. Midway between the hock and stifle the belly ends in a flattened tendon, partially divisible into two or three portions, and decussates with the tendon of the gastrocnemius internus, by which at the hock it is completely enveloped. Action. — To extend the hock. GASTROCNEMIUS INTERNUS. — Fcmoro-phalangeus. Situation. — Postero-mesian part of the leg. Form. — Cordiform ; elongated ; thicker in the middle than at the extremities. Its tendon, below the hock, is flattened, and upon the anterior surface excavated. Attachnie)it. — Superiorly, to the upper part of the roughened hollow upon the back of the os femoris, above its external con- 160 MUSCULAR SYSTEM. dyle. Inferiorly. it is continued over the hock, down the posterior part of the leg, to be fixed to the os coronne. Relations. — Posteriorly, with the gastrocnemius externus and skin ; anteriorly, with the stifle joint, the muscles of the posterior deep crural region, tendons of the gastrocnemius externus, and flexor perforans. The first crural nerve runs also along the front side. Peculiarities. — Remarkable for the little difference in volume there exists between the fleshy belly and its tendon ; and in being entirely tendinous until it has descended to the stifle. Structure.— The belly of this muscle is of considerably less volume than that of the gastrocnemius externus, but it has more tendon in its composition. About half way down the thigh it becomes entirely tendinous ; and its tendon, which is flattened, turns round that of the gastrocnemius externus in approaching the hock : so that the relative position of the two muscles be- comes reversed in their tendons. In passing over the point of the hock the tendon expands into a sort of cap or theca, which is so fixed and closed in around its border, by cellular substance, to the bone, that a complete ball-and-socket joint is formed be- tween them, circumscribed within the space of about an inch from its centre all the way round, and lined by a thin delicate mem- brane secreting synovia into the interspace. It constitutes, in fact, altogether, what is denominated a bursa mucosa ; but is one that, from its size and disposition to take on disease, pecu- liarly merits the attention of the anatomist. From this bursal formation it proceeds down the posterior part of the leg; and from the place at which it leaves the hock takes the name of tendo perforatus. Its subsequent course and attachment, to- gether with its relations to the tendo perforans, answer to the descriptions given of the tendons of the same name in the fore extremity. Action. — To extend the hock ; but to flex the fetlock and pastern. PLANTARis. — Peroneo-calcaneus. Situation. — Postero-external part of the thigh. Form. — Elongated ; thin ; slender. Jttachment. — Superiorly, to the head of the fibula; inferiorly, (in union with the tendon of the gastrocnemius externus) to the OS calcis. Relations. — Externally, with the skin ; internally and poste- riorly, with the gastrocnemius externus; anteriorly, with the deep posterior crural muscles. The third popliteal nerve crosses its superior extremity. MUSCULAR SYSTEM. If) I Structure. — This is the most slender muscle, in proportion to its length, in the body. Its delicate belly, composed of pale fleshy fibres, and constituting two-thirds of its length, sends off an equally delicate cordiform tendon, vviiich unites inseparably, just above the hock, with the external gastrocnemius tendon. 3.— DEEP POSTERIOR FEMORO-CRURAL REGION. The muscles contained in this region lie deep-seated, in the interspace between the tibia and the gastrocnemii. They are covered and closely bound down by a dense firm tendinous faschia. poPLiTEus. — Femoro-tihialis Ohliquus, Situation. — At the back of the stifle-joint. Form. — Short; thick; triangular. Attachmoit. — Superiorly, to the postero-external side of the outer condyle of the femur, and to the capsular ligament of the stifle-joint. Inferiorly, to the upper half of the inner side of the body of the tibia. Relations. — Posteriorly, with the gastrocnemii internus et externus, the semilunar cartilages, the postero-internal side of the head and the superior part of the body of the tibia : also, with the popliteal artery and vein. Externally, with the internal lateral ligament ; internally, with the gastrocnemius externus. Superiorly, with the condyles of the femur; inferiorly, with the flexor pedis accessorius. Direction. — Of the superior fibres, nearly transverse ; of the inferior, obliquely inward and downward. Structure. — Its supero-external attachment consists of a flattened and partially cleft tendon, which plays over the back of the outer semilunar cartilage. This tendon is enclosed within a duplicature of the capsular ligament; but (notwithstanding that) is shut out by the internal fold of that duplicature from the cavity of the stifle joint. The tendon finally sinks into the fleshy part of the muscle, whose substance still in places discovers some scanty tendinous intersections. Action. — To bend the stifle ; and at the same time to turn the tibia inwards. It will also extricate the capsular ligament from being pinched between the bones. • FLEXOR PEDIS. — Tibio-pJialangcus. Situation. — Postero-external side of the limb. Figure. — Fusiform ; elongated : fleshy part, thick. Attachment. — Superiorly, to the postero-external side of the head of the tibia ; to the supero-posterior half of the body of the V 162 MUSCULAR SYSTEM. bone, and to the posterior side of the fibula. Inferiorly, the ten- don assumes the name of tendo peij'orans, and is disposed of in a manner so similar to the tendon of the same name in the fote extremity as to render any description of its lower attachments here quite unnecessary. Relations. — Posteriorly, with the plantaris and the gastrocne- mii, and also with the posterior tibial bloodvessels; anteriorly, with the tibia and fibula. Superiorly and internally, with the flexor accessorius ; externally, with the plantaris and the flexor metatarsi. Structure. — Superior attachment, both tendinous and fleshy, from which at the back of the hock proceeds a strong cordiform tendon, which passes within a groove upon the inner side of the OS calcis and runs down the posterior part of the leg, where it becomes connected with the tendons of the flexor accessorius and gastrocnemius interims. With the former of these it unites, and the two together form a single tendon ; but with the latter, the union is only one formed by cellular membrane. The tendon is denominated the tendo petforans, in contra-distinction to that derived from the gastrocnemius internus, which (as was before observed) is styled the tendo perforatus. Both tendons are inclosed within the same sheath ; and are, in fact, disposed of down the leg and foot in a similar manner to what the cor- responding tendons are in the fore extremity : on which account any further detail would prove but recapitulatory. Action. — That of the gastrocnemius internus corresponds to that of the externus : it extends the hock. But, as it continues down the leg through the medium of the tendo perforatus, it will also flex the fetlock and pastern joints. The flexor pedis will prove of some effect in the extension of the hock : although its principal operation is u])on the foot, which it alone flexes ; and at the same time it flexes the pastern and the fetlock. FLEXOR PEDIS ACCESSORIUS. — Peroieo-phdlangeus. Situation. — Deep seated : postero-internal part of the leg. Figure. — Elongated; fleshy portion pyramidal. Attachment. — Su\)ev\oY\y, to the postero-external part of the head of the tibia : inferiorly, it becomes inseparably united with the tendon of the flexor pedis, about one-third of the length of the cannon downwards. Relations. — Posteriorly, with the gastrocnemii ; anteriorly, with the body of the tibia, and the posterior tibial artery and vein. Superiorly and internally, with the popliteus ; inferiorly and externally, with the flexor pedis. Structure. — Superior attachment, fleshy and tendinous ; after- wards entirely fleshy, and so it continues until it ends in a tendon CIRCULATORY SYSTEM. U''3 which has its origin in its very centre. Its fleshy belly crosses ob- liquely over to the inner part of the leg, where it terminates, mid- way between the stifle and hock, in its cordiform tendon, which passes through a theca at the inner side of the hock. Opposite to the head of the gieat metatarsal bone it runs in the same sheath with the tendon of the flexor pedis, with which it ultimately forms one common tendon. Action. — It operates as a coadjutor to the flexor pedis. Section III. CIRCULATORY SYSTEM. THE CIRCULATORY SYSTEM COMPRISES THE BLOOD, THE BLOODVESSELS, AND THE HEART, OF THE BLOOD. BLOOD is the red fluid we see issuing from a fresh wound, and of which there is a considerable quantity continually circu- lating through the body of a living animal. So uniform is it, while circulating, in its appearance, that it looks like a simple, uncora- pounded, or homogeneous fluid ; a 'character it does not lose until some time after it has been drawn out of the body, and then it gradually assumes a change from a fluid into a solid mass, resem- bling jelly. In the fluid state it possesses a faint odour, a saline flavour, has an adhesive unctuous feel, and is some little (speci- fically) heavier than water : the latter being equal to 1000, blood may be estimated at 1090. Also, so long as it continues tepid, it is perceived to emit from its furface a halitus, or vapour • which is nothing more than ordinary steam, excepting that the evaporation may carry up with it minute particles of animal matter : a circum- stance that will accountfor the peculiar odour it is known to convey. It has been observed that blood, soon after its removal from the body, concretes into a solid gelatinous mass. This spontane- ous change, called the coagulation, proceeds very gradually to completion, until we discover the formation of two very different component parts : one solid, denominated the clot, ox crassamoi- liim ; the other fluid, named the serum. Simple concretion takes place in the blood of the horse in about twenty-five minutes : in that of a man it requires only seven. The relative proportions of the crassamentum and serum (when the coagulation is finally com- pleted) will be found to vary in the blood of difTerent animals, and that even of the same animal at difterent periods, depending on the state of health and condition of the subject from which it is drawn. In man, the crassamentum may be said to amount to about 164 CIRCULATORY SYSTEM. one-third of the weight of the serum; in the horse, the solid will bear nearly an equal ratio with the fluid portion. In the more perfect, or, as they have been denominated in contradistinction to the others, the warm-blooded animals, the blood is everywhere found, while circulating in the living body, to be of a certain degree of heat ; and this it steadily preserves in its circulation through the inward parts of the body, uninfluenced by the surrounding temperature. In all the interior or unexposed parts, the heat will exceed 100° of Fahrenheit's thermometer; it has been found, however, by experiment, that this degree is not equally maintained in the more superficial situations of the body : what these variations are we have but little to do with, though they may be ascertained by the aid of the thermometer, at any time, with precision. But in the lower orders of animals, or such as are called cold-blooded, the heat of the blood cor- responds with that of the medium in which they live. We are not, however, to suppose that the temperature of this fluid is never subject to variation, even in perfect animals, for it is found to be much influenced in them by disease : e. g. in the human subject, in whom the heat of the body is, in health, 98°, it has been known to rise to 110° during fever; and, in all superficial parts, increased heat is one of the essential symptoms of inflam- mation. The heat of the horse's blood, while flowing into a basin, is 100°. If the bulb of the thermometer be introduced into the wound, the quicksilver will rise to about lOP. The temperature of the more superficial parts of the body will, in course, vary with that of the surrounding atmosphere. Mr. Hunter found that the thermometer, introduced into a wound two inches deep, made into the gluteal muscles of an ass, indicated 100« ; and that the heat of the vagina was the same. The interior of the chest of the dog he ascertained to be lOP. The colour of the blood is red. Not in all animals, however; for in such as are called cold-blooded — in most fish, their gills ex- cepted, and in insects — it is colourless and transparent. So, like- wise, it is in parts even of such animals as are warm-blooded ; as, for example, in the common domestic fowl, in which the breast and wings are delicately white, while the legs and body partake of a dusky red hue. 1 believe the blood of the horse is not so high-coloured as that of a man, and that the latter yields in brightness to that of a dog. All this seems to argue that colour is not an indispensable property. The quant it 1/ of blood contained in an animal body may be made matter of speculation, but cannot, for many reasons, be ascertained with any degree of precision. If wc attempt to draw CIRCULATORY SYSTEM. 165 all the blood out of the body, the animal sinks and dies long- before its vessels are evacuated ; and as we possess no means of measuring what remains behind, any calculation we may make from the quantity that has flowed must necessarily turn out vague, if not allogether incorrect. The following experiment will serve to illustrate this; at the same time, that its result may serve as a datum to guide us in any future computation. The weight being ascertained to be 791b, a puncture was made with a lancet into the jugular vein, from which the blood, which flowed in a very free stream, was collected. The vein having ceased to bleed, the carotid artery of the same side was divided, but no blood came from it : in a few seconds after- wards the animal was dead. The weight of the carcass was now found to be 73^1fe; consequently, it had sustained a loss of 5ilb, precisely the measure of the blood drawn. It appears from this experiment that an animal will lose about l-15th part of its weight of blood before it dies ; though a less quantity may so far debilitate the vital powers as to be, though less suddenly, equally fatal. In the human subject the quantity of blood has been computed at about 1-Sth part of the weiglit of tiie body; and as such an opinion has been broached from the results of experiments on quadrupeds, we may fairly take that to be about the proportion of it in the horse : so that, if we estimate the weight of a common sized horse at about 12 cwt., the whole quantity of blood will amount to 84qrts., or 168 Ife, of which about 45 qrts., or 90 tfe, will commonly flow from thejugular vein prior to death ; though the loss of a much less quantity will sometimes de- prive the animal of life*. It is well known that young animals possess more blood than old, and that they will, perhaps, on this account sustain greater bodily injuries, and bear larger haemorrhages ; indeed, they are wisely provided with such an ex- cess, if we may so term it, in order that their growth may be promoted, and their several organs maintained in a state of vi- gour : but in old, in which the body is gradually decaying, and the powers of life declining, the quantity of this fluid becomes re- duced. Mr. Wilson, in his Lectures on the Blood, See, says, * Supposing a man to weigh 12 st., or 168 lb, the quantity of blood con- tained in his body may be rated at 21 lb, or 2 gall. 2 qrts. and 1 pint. Again, granting that a dog weighs 40 Iti, the amount of his blood will be 5 pints. These calculations are useful and worth our attention, inasmuch as they serve to guide us in practice, as to the probable extent to which we may, with safety, carry venesection in ditFerent animals. For instance, we may reckon the loss of a pint from a man to be equivalent to that of a gallon from a horse, or to four ounces from a dog, -AnA vice versa ; selecting in- i inch in diameter: and we may as well sit down contented with this, as spend our time in searching after other evidence, perhaps, after all, less conclusive. The colour of the globules is materially aflected by atmospheric CIRCULATORY SYSTEIVI. 109 air. If a clot of blood in a basin be examined, its upper sur- face, which has been exposed to the air, will be found to possess a bright scarlet colour, while the lower or unexposed part will appear of a dark Modena purplish hue : only invert the clot, however, and in a short time that part which is dark will turn to a bright red, while the other (now excluded from the air) will change to a dark purple aspect. This change of colour is wholly ascribable to the action of the oxygenous part of the air. Expe- riment has fully proved this fact; and also, that the other ingre- dient of the atmosphere, viz. azote (as well as the carbonic acid gas), has quite the contrary effect upon the blood, converting its scarlet hue into purple. Notwithstanding the fluctuating and contradictory accounts of chemical inquirers into the composition of the blood, there appears little reason to doubt the existence of iron in it, and in the red globules in particular the presence of the metal has been proved : through whose metallic agency, we may add, it is, that oxygen produces the remarkable change above alluded to. For the pre- sent, let this much suffice. I shall have occasion to amplify much on this part of my subject when I come to speak of respiration. SERUM Is the yellow or straw-coloured fluid which gradually exudes after coagulation from the crassamentum. It has a saline taste, and is adhesive in its nature, on which account it is found somewhat specifically heavier than water. Superficial observation and analogical inference have given rise to serious error in regard to the proportionate quantities of serum and crassamentum in the blood of the horse. For some hours after a horse's blood is coagulated, it' exhibits one uniform gela- tinous mass whose surface is scarcely moistened by serous exuda- tion ; whereas that of a man in the same interval of time would discover the clot actually swimming in serum. The truth of the matter however, is, that so far from there being a comparatively less quantity of serum in horses' blood, there is actually a taroer proportion ; the difference being that it requires a much lonoer time for its evolution in the graminivorous than in the carnivorous animal. Take a pint of blood from a man, and place it in a temperature of 50*, and in the course of three days it will not only have per- fectly resolved itself into its component parts, but will be o-rowino- putrid. But draw a pint from a horse, and place it in a medium of the same temperature, and serum will continue to ooze from it even for a week afterwards. In fact, the two most essential differences between human and 170 CIRCULATORY SYSTEM. horses' blood are,— 1st. That the latter much more slowly resolves itself into its component parts ; and, secondly, that it possesses greater preservative powers against putrescency. Serum itself exposed to the temperature of 160° is converted into a solid, white, opaque mass ; also the effect of coagulation. Mineral acids and alcohol will likewise produce this change. It now resembles boiled white of egg; and is found, in fact, to be the same in nature, viz. albumen. If this coagulum be cut or squeezed, a limpid fluid issues from it, that has been termed the serosity. "The most important chemical properties of albumen," ob- serves Dr. Bostock, "while in its liquid form, are its solubihty in water, and the precipitates which it forms with the mineral acids, tan, and a variety of metallic salts. Of the acids, the muriatic is supposed to combine with it the most readily, and is therefore employed as one of the most delicate tests^of its pre- sence in a substance where we expect it to exist. Tan forms with albumen a dense precipitate of tough consistence, and inso- luble in water. A variety of the metallic salts precipitate albumen, and, like the acids, serve as very delicate tests of its presence; of these probably the corrosive sublimate, or the bichloride of mer- cury, IS the most delicate, and at the same time the most dis- criminate, as it appears to have no action upon any other of the animal substances which enter into the composition of the albu- minous fluids," When coagulated, albumen becomes completely insoluble in water. The serosity exists in a comparatively very small quantity, and can only be obtained by slicing the albuminous coagulum and allowing it to drain, or else by expression, or by washing it in water. It has been particularly examined by Dr. Bostock, and found to contain an animal matter which is not albumen; and whose nature it is difficult to make out, in consequence of its being always found united with soda, and a variety of other salts, from which it cannot be separated, without being, at the same time, decomposed. To this substance Dr. Marcet has applied the name of muco-extractive matter; while Dr. Bostock prefers styling it the uncoagulable matter of the blood. BUFFY COAT — CUPPED BLOOD. I make the consideration of these points a distinct one, because I feel desirous to correct what I conceive to be an important error practitioners have fallen into. Let the crassamentura be examined at the side, and the upper layer of it will be found to be yellow or buff-coloured ; below this, it will appear of a light red hue ; lower still, darker and CIRCULATORY SYSTEM. 171 darker until it becomes a black or dark purple. This is the natural or healthy aspect of horses' blood : but, human blood is said never to put on such an appearance but as symptomatic of inflammatory, or, at all events, of increased vascular action. Whether it does or not, the simple explanation of this phenomenon is, that, in consequence of the blood taking an unusually long time to coagulate, the red particles, being specifically heavier than the fluid containing them, gradually subside to the bottom until they are arrested by the process of coagulation. And con- sequently, as the horse's blood takes so much longer to coagulate than the human, it cannot afford any matter Jor surprise that his blood should be always buffy. Still, obvious and easily account- able for as this fact is, buffy blood has been attributed to the horse as a mark of disease. And so, in like manner, has cupped blood ; — by which is meant, crassamentum, whose upper surface, instead of being flat or per- fectly plane, is concave or cupped, having its surrounding margin elevated and more or less inverted, in the form of a tea-saucer. But this is an appearance often to be met with in perfect health : one that no more certainly indicates any morbid condition with which I am acquainted than does buffy blood. I had a re- markable instance of this while engaged in some experiments connected with this subject. A horse, to every appearance in perfect health, was bled to one pound ; after which he was gal- loped (for the space of about twenty minutes) until he sweated profusely : while under extreme agitation from the exertions he had been put to, another pint of blood was drawn by un- pinning the same orifice. The coagulum of the first parcel of blood was sizy, tough, contracted, and deeply cupped ; that of the last exhibited no signs whatever of buff', was extremely loose and flabby in its texture ; so that, on being handled, it readily mingled with the serum, and in a much shorter time than the first went into the putrefactive state. This latter fact is intimately connected with what I have already advanced regarding the non-coagulation of the blood after an animal has been coursed to death ; since, had exertion been continued until the horse sunk under it, the blood would probably have remained wholly fluid ; whereas in this case, the animal being only in progress towards that state — being only urged to a point from which he could recover — the coagulating powers of the blood were merely diminished. I shall conclude this subject with a statement of the results of bleeding twelve horses in perfect health, under circumstances as nearly as possible similar and natural. From each horse the quantity drawn was one pint. The time it took in flowing in no 172 CIRCULATORY SYSTEM. case exceeded a minute. A film of coagulnm was generally per- ceptible on the surface at the expiration of ten minutes. Each parcel was firmly coagulated in twenty-five minutes. All the coagula shewed buff about half an inch in depth ; seven of them were very firm, of which five exhibited the surrounding edge elevated and turned in, the other two being still more decidedly cupped. In two out of the five not so firmly congealed, the coagula were soft and flabby. The serum amounted in every parcel to about o)te-haIJ' of the whole quantity. OF THE HEART AND PERICARDIUM. Situation. — The heart is inclosed within the pericardium ; and both together occupy the middle space of the cavity of the thorax. PERICARDIUM. The pericardium is a membrane formed into a conoid sac for the purpose of containing the heart. It has, exteriorly, an opaque white aspect; is dense in its consistence, and firm and tenacious in its texture. It is composed of two layers, intimately united by cellular tissue. The external one is dense and fibrous, is pos- sessed of the chief strength of the membrane, and is attached be- low by several ligamentary cords to the sternum and tendinous part of the diaphragm, and above to the roots of the large blood- vessels at the base of the heart, upon which we lose sight of it altogether: the sides of it are clothed and additionally strength- ened by the adhesions of the pleura;. The internal layer is fine and cellular, exhibits inwardly a smooth, polished surface, and appears to be similar to other serous membranes in its intimate texture and organization. It not only lines the external layer, and gives a covering to the roots of the large bloodvessels, but is re- flected from them upon the heart itself, to which it forms a close and complete tunic : so that the heart is absolutely out of (above) the cavity of the pericardium ; in fact, it is situated precisely the same in regard to this membrane as the human head is within a double nightcap. The liquor pericardii is the pale yellow serous fluid found within the cavity of the pericardium, secreted therein by the ex- halents of the membrane. It serves to lubricate the contiguous surfaces of the sac, and to preserve them against any ill conse- quences from friction. J'he use of the pericardium is to confine the heart in its situ- ation, to sustain it in its reciprocal action with the lungs, pre- venting any undue collision, and to serve as a protecting fence to the organ. CIRCULATORY SVSTEIM. 3 73 HEART. Form, Situatio)i, and Attachment. — It is of a conoid form. Its base, turned uppermost, is opposed to the bodies of the 4th, 5th, and Gth dorsal vertebree, from which it is suspended in its situation in the middle of the cavity of the thorax, by the at- tachments of the venous and arterial trunks immediately con- nected with it. Its apex hangs loose and unattached within the pericardiac cavity, pointing downwards and backwards, and is inclined to the left side. The tveight of the heart is about six or seven pounds. Division, external and internal. — For the convenience of de- scription, we distinguish in the heart a base, a bodif, and an apex. It is also said to have two sides, each of which contains two cavities : the two superior cavities (from having been likened to the ears of a dog) have been denominated auricles; the two infe- rior have been named ventricles. Their boundaries are marked externally by deep excavations, which are filled with fat; the limits of the ventricles are likewise pointed out by furrows upon the body of the heart, containing fat, continuous in substance with that which is deposited above. This fat is more abundant in old than in young horses. The heart owes its smooth glossy aspect externally to its thin duplicature of pericardium, which is everywhere in such intimate adhesion with its surface, and so transparent, that its parietes are too plainly demonstrable through it to require that this mem- brane be stripped off. The sides of this organ, commonly distinguished by the e\)\- ihei^right and left, would more properly be described, in allusion to the relative situation of then- cavities, as anterior and poste- rior ; for the right auricle forms the upper andyb/e pait, turning its apex to the left side ; and the greatest part of the left auricle is apparent behind, though its apex is also turned to the left side, and is inclined downward. The ventricles, being situated under their respective auricles, face consequently, like them, forwards and backwards. Though the auricles are essentially tiie same in structure as the ventricles, they differ from those parts in exte- rior appearance, in bulk, and in the substance of their parietes ; they are of a pale pink colour, are very uneven, when distended, upon their surfaces, and are indented along their inferior borders; whereas the ventricles are of a dnW red or deep flesh colour, are smooth and even upon their surfaces, and of themselves compose three-fourths of the organ. The right auricle, generally found full of blood after death, 174 CIRCULATORY SYSTEM. is lined by a fine, vascular membrane, and presents internally a polished surface, the regularity of which is interrupted in places by many fleshy prominences, named the musculi pectinati ; be- tween which are numerous little sinuses, or cul-de-sacs, that, as well as the fleshy pillars themselves, vary much in size, and are most numerous and remarkable within the appendix, or ear-like portion of the auricle, where they form together a reticulated structure. Three venous trunks terminate in this cavity : the vena cava anterior opens into the superior and posterior part of it ; the vena cava posterior opens into the inferior and posterior part ; and the coronary vein just below it. The vena azygos forms a junction with the anterior cava just as the latter pierces the auri- cular parietes. Between the openings made by the two venae cavse, there is a prominence that is usually called the tubercalum Loweri. There is a deep sac or sinus at the entrance of the pos- terior cava ; and between this and the mouth of the coronary vein, a crescentic valvular Jiap, which projects half way over the mouth of the latter vessel. The right auricle has a free commu- nication with the right ventricle by an aperture of large size, called the auriculo-ventricular opening. One auricle is divided from the other by a muscular partition, denominated the septum auricular um ; in which may be seen, when the part is held to the light, an elliptical inlet of semi- transparent membrane, crossed in places by fleshy fasciculi, which takes the name of fossa ovalis : in some subjects there is a small aperture through it, and this is all that remains of the foramen ovale. The right ventricle is redder and considerably thicker in substance than the right auricle: like it, it commonly contains, after death, a large coagulum of blood. It is likewise lined by a smooth, polished membrane, and has within it numerous^es//j/ pillars, which, instead of being reticulated as those are in the auricle, are disposed longitudinally. In addition to these, there are three conspicuous fleshy prominences, from their size named the carntfE columncB, from which several little tendinous cords, chorda ttndinea,, proceed to the edoes of three membranous and fibrous productions (sometimes distinguished by the name of cor- tina tendinea) that close the auriculo-ventricular opening : the ap- paratus altogether forms the valvula tricuspis. Other cords, similar to the cord'cB tendinea, but stronger than them, pass between the outer wall and the septum. The pulmonary artery emerges from the upper and back part of this cavity ; and its mouth is guarded by three semilunar valves, which present little pouches within the cavity of the vessel : these valves consist of doublings of the lining membrane of these parts, infolding, about the middle of their loose CIRCULATORV SYSTEM. 175 edges, three small granular substances, described as the corpus- cuia Arantii. Opposite to the valves, three depressions are ap- parent in the coats of the vessel, named the siuus Valsalvce. The left auricle is smaller than the right, and has thicker parietes. It contains, in general, but little blood, and in some subjects none. It presents nearly the same aspect internally as the right. It has not so much of the reticulated structure how- ever — (ewer muscu/i pectiuati ; what there are, are more strongly marked, and are principally confined to the appendix. The p?//- monary veins terminate by four openings in the superior and pos- terior part of this cavity. The auriculo-ventrkular opening is somewhat larger than that of the right side, and is rather square than round. Now that the auricles are both laid open, the septum auricularum, Jossa ovalis, and Jorame?i ovctle, may be distinctly viewed. The left ventricle, though smaller within, is longer, and more prominent and extensive without, than the right : it forms, of itself, i\\eapex cordis. Its outer wall far exceeds in thickness that of any other cavity of the heart, being thrice that of the right ven- tricle. Its musculi pectinati appear mostly upon the septum, within the apex, and under the valves. It has but two carnece columncE, but they are very bulky, and project much into the cavity. Its auriculo-ventricular opening is only furnished with ^?^o valvular productions ; in other respects the cortina tendinea and chordcc tendinea resemble those on the right side : this valve is called the valvnla biciispis vel mitralis. The aorta takes its rise from the upper and fore part of this ventricle, and, concealed at its origin by the pulmonary artery on one side and venae cavae on the other, makes its exit close to the spine. The mouth of the aorta is shut by three semilunar valves, similar in formation and disposition to those at the origin of the pulmonary artery : but the sinus Valsalva are much larger and deeper. Just above two of them are seen the mouths of the coronary arteries. The ventri- cles are divided by a thick fleshy partition, called the septum ven- triculorum. Organization. — Though the heart is composed mostly of fleshy fibres, a tendinous structure is demonstrable in its middle, which tendinous intertexture appears to be the common medium of at- tachment between its auricles, ventricles, vessels, and valves, one to another. The fleshy fibres composing the parietes of the auricles, stronger in the left than in the right, are disposed in every direction; those that form the walls of the ventricles, for the most part, appear to run longitudinally and obliquely, and many of them in a spiral manner. These fibres are more slender than those of other 176 CIRCULA'l'ORY SVSTEiM. muscles, and are more intimately and firmly compacted ; the cellular tissue also, uniting them, is finer, denser, and less in quantity. The heart is supplied with blood by the two coronary arteries; the first branches given off from the aorta. Its veins pour their blood into the coronary vein, by which it is returned into the right auricle. Its nerves are derived from the cardiac plexus. OF THE BLOODVESSELS. There are two orders of bloodvessels — arteries and veins: the former conduct the blood from the heart to all parts of the body ; the latter return it therefrom back to the heart. ARTERIES. These vessels, in all their manifold ramifications, spring origi- nally from two main trunks — the pulmonarj/ artery and the aqrta : the former sends its branches to the lungs ; the latter to all the other parts of the body. PULMONARY ARTERY. A vessel of larger caliber than the aorta. It takes its origin from the postero-superior part of the right ventricle of the heart, winds upwards to the root of the left lung, and there divides into right and left pulmonary arteries ; which divisions immediately enter the substance of their correspondent lungs, and therein ramify to capillary minuteness, the branches regulating their course and division by the ramification of the bronchial tubes. This trunk, together with its manifold branches, may be com- pared (viewing them altogether) to a short, but straggling and very branchy shrub or dwarf tree of luxuriant but extremely irre- gular growth ; and their number and ramification may be pic- tured to the mind, by remembering that no organized part of the body is without few or many of them. CIRCULATORY SYSTEM. 177 TABLE OF THE ARTERIES. 4.vprpi /Anterior Aorta AUKlA j Posterior Aorta ... A f / Ri?l»t Arteria Innoniinata Anterior Aorta I Left ditto LEFT ARTERIA INNOMINATA S^'rL. p..„;..i fPost. Cerebellal Posterior Cervical .„. r'„„^K^iioi Vertebral, /o;v«^W the Basilar^ p"\- '-erehellal- Internal Pectoral ] P?^^- ^'-^^'''^l. > External Pectoral *- C"*^"!^'" Arteriosus. Inferior Cervical -Axillary r External Thoracic \ Internal Thoracic Axillary s Dorsalis Scapulie , f Subscapular ^ Humeral {Ulnar Radial., f Small Metacarpal t Large ditto T ni . 1 f External Plantar Large Metacarpal I j^^^^j^^j ditto r Perpendicular \ Transverse Plantar \ Artery of the Frog / Lateral Laminal |" Ant. Laminal ^Circular Arteriosus.. -| Inf. Communicating' L Circumflex . . . ^ Solar The Right Arteria Innominata sends off branches correspondent to those on the left side ; and, in addition, the External Carotid Common Carotid r T E I Right Carotid I t> [Left ditto ];^ i i I I Ramus Anastomoticus nternal carotid /^ ^ Ascending Pharyngeal Pterygoid rRanine Lingual . . {sublingual Submaxillary...^ Inferior Labial {AnJulSoral r Masseter J Buccal I Sup. Labial L False Nasal Facial External Carotid /Parotideal Int. Pterygoid Post. Masseter Post. Auricular Temporal Ant. Auricular Int. Maxillary. . ^ Deep Temporal Palatine Inf. Maxillary Supra-Orbitar Ocular Infra-Orbitar .Palato Maxillary A a 178 CIRCULATORY SYSTEM. Ramus Anaslomot [nternal Carotid 1 _ rDurafl icus I Occipital \ Tempo J L Nucha Matral poral hal Arteria Communicans Anterior Dura Matral Anterior Cerebral . . . -( Ophthalmic Middle Cerebral Lateral Cerebral POSTERIOR AORTA / Thoracic Division 1 Abdominal ditto Thoracic Di Cseliac ; Esophageal {«2r;''i;!'.r' / Intercostals V- Phrenic Abdominal Division Splei Gastric Hepatic {Pancreati Splenic Left Cast eatic Branches ditto Gastric Ant. Mesenteric Renal Spermatic^ Right and Left f Post. Colic I Rectal /Superior Gastric I Inferior ditto Pancreatic Branches Duodenal Right Gastric Ri^ht and Left Hepatic r Duodenal Branches J Small Mesenteric I Coecal Branches lAnt. Colic ditto f Rio-ht Renal 1 External Branches t Left ditto J Capsular Renal Post. Mesenteric , Lumbars — Five or Six Pairs Bifurcation of the Posterior Aorta into External and Internal liac Arteries. Internal Iliac fLImbilical . . f a n u J Vesical Branches Artery of the Bulb ^p,.^^^^^i^ LAnal and Perineal Branches Arteria Innominata Foraminal Branches - Ischiatic Branches to the Crus Penis f 1^4. ^o A- \ Ditto Corpus Cavernosum ^I"t-^"^'0 Ditto Dorsum Penis J Ditto Glaus Penis v. Cutaneous Branches r Arl VFoi -^ Iscl CIRCULATORY SVSTEIM. 179 The Middle Sacral issues at the Bifurcation of the Trunk, r Circumflex of the Ileum Fv^Pl•n^^I IllnrJ Artery of the Chord f Branch to the Groin £-xteindi ijiac^ Arteria Profunda \ Epigastric <^ Branch to the Ring iFemoral L Ext. Pudic Inguinal Muscular Branches Stifle ditto Muscular ditto Popliteal -{ Recurrent r Recurrent Articular Anterior Tibial. . . . VV"scular Branches \ L-utaneous ditto / IMetatarsal Branches r Recurrent ^Metatarsal Artery . . \ Ext. Plantar rlMuscular Branches lint, ditto J Medullary ■ I Tarsal Lint. Metatarsal <{ Recurrent. Femoral ^Posterior Tibia THE AORTA, the main trunk of the general arterial system, takes its origin out of the base of the left ventricle of the heart, and mounts upward between the left auricle and the pulmonary- artery ; the latter vessel by inclining forward leaving visible, on a side view, a small angular portion of the aorta. The length of the single trunk measures about two inches. It is situated di- rectly underneath the fourth dorsal vertebra, where its bifurcation takes place into miterior and posterior aorta; vessels that are both of them curved in their course, but of unequal dimensions. The coronary arteries are the only branches given off from the single trunk : they arise close to its root, immediately above the semilunar valves. The right coronary artery emerges from the interspace between the pulmonary artery and the right auricle, winds round the fissure separating that cavity from the right ventricle, and turns down under the termination of the vena cava, within the furrow dividing the ventricles, upon the side of the heart, distributing lateral ramifications in its course which penetrate the substance of the parietes, and ending in small spiral branches near the apex cordis. The left coronary artery, in passing out between the pulmonary artery and left auricle, sends off a large branch which encircles the other auriculo-ven- tricular fissure ; it then takes its course downward within the ventricular furrow upon the left surface of the heart, distributing- lateral branches which supply the parieties forming this side, and ending in spiral ramifications which extend quite around the apex cordis, and anastomose with those \\\)0\\ the opposite side. 180 CIRCULATORY SYSTEiM. Anterior Aorta. The anterior, smaller, and shorter division of the main trunk, whose length falls somewhat short of an inch, in ascending, bends forward, and divides below the body of the third dorsal vertebra into the right and left avteriee innoniinatse vel com- munes. The course of this vessel is below the windpipe and rather to the left of it, within the space of the mediastinum. The trunk itself furnishes no branches; but its bifurcations give origin to those large arteries which are distributed over the breast, neck, head, brain, and anterior extremities. Arterice Linominata vcl Communes. The right artery is considerably longer than the left, and mea- sures nearly as much again in circumference, in consequence of its having to form the common carotid artery (the trunk from which the two carotids spring) after it has detached branches to the right side correspondent in size, number, and distribution to those into which the left division resolves itself. These vessels form a very acute angle as they leave the anterior aorta, and pursue their course horizontally forward, diverging very gradually as they advance: the right is placed lower than the left, and lies more immediately under the windpipe, having the vena cava an- terior upon the other side of it; the left describes a curve upward in passing forward, inclines outward, and gets under the esopha- gus : both branch out about the middle of the space between the two first ribs, where the right ends in the two carotid arteries, the left in the vessels now to be described, which, as was ob- served before, are nearly the same on one side as on the other. 1. The dorsal artery generally comes off' in one common root with the next vessel. From its origin, it curves upward and backward to arrive at the second intercostal space, which it per- forates very obliquely close to the posterior edge of the first rib, a little below its head. Out of the chest, it still pursues the same oblique course, crossing over the transverse process of the second dorsal vertebra, and then ascending upon the spines of the withers, among the muscles attached to which its ramifica- tions are expended. Its branches worthy of names are — a. Su- perior Mediastinal, a twig detached near its origin to the me- diastinum, fj. Anterior intercostal, a branch sometimes nearly equal in size to the dorsal itself, given off' just before the vessel penetrates the intercostal muscle, by which the second, third, fourth, and fifth intercostal arteries are furnished ; the reason for which is, that the posterior aorta (the vessel furnishing the majo- CIRCULATORY SYSTEM. 181 rity of the intercostals) is too far removed from these anterior ribs to send vessels to them ; their deficiency therefore becomes con- veniently supplied by the anterior intercostal. These intercostal branches follow the posterior margins of their correspondent ribs, each running within a shallow groove; midway, however, between the vertebra) and sternum, they leave the ribs for the middle of the intercostal spaces, and end in several slender ramifica- tions, some of which may be traced as low as the sternum, there anastomosing with similar ones coming from the internal pectoral artery. The intercostals in their course detach twigs to the pleura, but more especially supply the intercostal muscles. 2. The posterior cervical artery, arising in common with the dorsal on the right side, but by a separate root on the left, takes an opposite direction to that vessel, inclining forward and upward. It traverses the upper part of the first intercostal space, piercing the muscle filling it with considerable obliquity, and then ascends in a winding course between the transverse pro- cesses of the first dorsal and last cervical vertebrae, upon the body of the latter, where it turns forward, and runs as high as the vertebra dentata, close alongside of the roots of the ligamentum nuchae, concealed by the complexus major, to which its ramifica- tions are principally distributed. Besides some small and unim- portant branches within the chest, it gives off the Just intercostal arteri/, which descends behind the first rib, and anastomoses with twigs from the internal pectoral. 3. The vertebral artery is a vessel of considerable size, and is vastly important, from being one of the principal conduits of blood to the brain. It arises with a sort of bend from the upper part of the arteria innominata, directly opposite to the first rib, in such manner, that, if a knife were thrust into the chest behind the rib, the artery would just escape puncture. The right vertebral is at its origin placed lower than the left, and deviates somewhat less from a straight line in proceeding, which it does, close under the transverse process of the seventh cervical vertebra to enter the foramen through that of the sixth. They then both of them con- tinue their passage to the head, passing directly through the fo- ramina of the fourth, third, and second vertebrae, wherein they run securely barred from external injury : arriving at the atlas, they make a curve upward upon its transverse processes, proceed through the posterior pair of foramina, and enter the foramen magnum. In its course along the neck, the vertebral artery on either side detaches several short branches of considerable size, which turn round the transverse processes, and ramify among the deep-seated muscles. It also sends some smaller ones inward, which enter the intervertebral holes fur the supply of the medulla 182 CIRCULATORY SYSTEM. spinalis and its membranes. Under the utias, the vertebral trunk receives a large vessel of communication from the internal carotid : its further description, however, must be suspended until we come to trace the vessels of the brain. 4. The internal pectoral artery, less in volume than the vertebral, leaves the trunk below, opposite to the origin of that vessel above, protected by the first rib, along the posterior and inner margin of which it descends in a perpendicular direc- tion towards the sternum. Leaving the lower extremity of the rib, it makes a broad sweep downward and backward, and descends upon the internal surface of the second bone of the sternum : it afterwards diverges gradually from its fellow, tra- verses the ends of the cartilages of the posterior true ribs, and, having crossed that of the last, splits into two divisions. One of these ascends upon the internal part of the chest along the border of the seventh true cartilage ; thence it crosses the false cartilages, detaching slender ramifications to them which anastomose with some of the posterior intercostals, and makes its way towards the flank, and disperses its ultimate branches among the muscles there, souie of which reach far enough to communicate with the ramifications of the circumflex artery of the ileum. The other division (generally considered as the continuation of the trunk, being rather the larger one) pierces the sheath of the rectus, and makes it appearance upon the upper surface of that muscle, over which it ramifies extensively, sending branches out again to anas- tomose with the epigastric. Exclusively of these divisions, the trunk detaches muscular branches along the first rib, inwardly anterior mediastinal vessels, larger brandies to the muscles of the sternum, and inferior mediastinal ; and also thymic twigs. 5. The external pectoral artery, comparatively small and unimportant, comes off also from the under part of the trunk, makes a turn downward in front of the sternum, and dis- tributes its ramifications among the pectoral muscles. This ar- tery in some subjects is derived from the internal pectoral. 6. The inferior cervical artery, longer and larger than the afore-described vessel, arises from the common trunk opposite to or in company with it, and makes its exit from the chest below the vertebral artery, and then bends outward. At the bottom of the neck it divides into several branches : these run principally to the contiguous muscles, though some few ramify with the adipose substance in the neighbourhood, and others are destined to the absorbent glands hereabouts. 7. The seventh and last branch, and largest (if we except the carotids on the right side, and the continuation of the main trunk on the left), is the CIRCULATORY SYSTEM. 183 Axillary Artery, The source from which is derived all the arteries sup- plying THE rouE EXTREMITY. This vcsscl is SO buricd be- tween the scapula and the trunk, that not only is it out of the way of all injury, but is excluded from all possibility of being got at for the purpose of demonstration without detaching the limb from the side. It arises within the chest from the arteria inno- minata, and gains exit by making a sudden turn around the first rib, rather below its middle, crossing the lower border of the scalenus in the turn : it is first directed outward in this flexure, and then backward, and at length reaches the inner part of the head of the humerus, where it makes another turn backward, and subsequently takes the name of humeral artery. Its branches are — 1. The external thoracic extends backward across the arches of the ribs, taking the same course as the vessel called the " spur vein," and supplying the muscles thereabouts. 2. The humeral thoracic runs to the point of the shoulder, and gives its branches to the levator humeri and shoulder-joint. 3, The dorsal is sca- pula ascends in a flexuous manner obliquely upon the shoulder- joint, crossing the insertion of the subscapularis ; it next runs for a short way along the anterior costa, around which it subse- quently continues to reach the antea-spinatus. 4. The subscapu- laris, a large artery arising from the upper part of the trunk, but near to its termination, creeps upward along the posterior costa, screened from view by the edges of the subscapularis and teres major, to both of which muscles it detaches laterally several small branches, and ends near the posterior angle of the bone. It gives off a considerable branch at a short distance from its origin, which proceeds in a waving line across the inner surface of the triceps, and ends in the panniculus carnosus ; and another, a deep-seated one, about the middle of the costa, which is prin- cipally expended in the head of the triceps. The HUMERAL ARTERY desccuds from the inner and back part of the head of the os humeri in an oblique direction to the inferior and anterior part of the body of the bone, where it splits into the ulnar, spiral, and radial arteries. To its inner side run the spiral and ulnar nerves ; in front, the radial nerve ; and be- hind, the humeral veins : and it is covered internally by the pec- toralis magnus, to which it sends some small branches. But its principal branches are — 1. One near its origin which crosses the bone to get to the flexor brachii, and sends twigs to the shoulder- joint. 2. A posterior branch, arising a little lower down, which bifurcates and then enters the triceps, 3. Near its termination, another anterior branch passes to the flexor brachii. In the 184 CIRCULATORY SYSTEM. place where the artery divides, it is covered by the humeral plexus of veins, and by the absorbent glands of the arm. The ulnar artery consists of a common root from which spring three or four vessels of considerable size running in waving lines upon the inner surface of the lower end of the humerus. The upper one, commonly the largest, is directed to the ulna ; splitting, however, before it reaches the bone, and sending one branch upward upon the olecranon, and another downward to the heads of the flexors, to which muscles the other branches of this vessel are exclusively distributed. The spiral artery, the outermost division, turns round the OS humeri, and passes under the flexor brachii, sending a re- current branch to it, to arrive at the front of the head of the radius, where it splits into several branches, of which — I. Some run into the elbow-joint. 2. Others, larger and more in num- ber, penetrate the heads of the extensors. 3. Two long slender ones descend upon the radius, under the extensor muscles, to which they give branches in their course, as low as the front of the knee, and there end in ramifications about and into the joint, anastomosing with others coming from the radial. The radial artery, the principal division of the humeral, continues its descent along the radius, inclining as it descends from the inner to the back part of that bone; so that if it were purposed to cut down upon it about the middle of the arm, the incision should correspond in a line with the inner edge of the radius, from which, to expose the vessel, the faschia must be first detached, and afterwards the flexor metacarpi internus. The radial nerve, which in this place accompanies it, runs upon its outer side, but subsequently gets behind it. A short way above the knee, it splits into the metacarpal arteries. It gives off — 1. Small vessels to the elbow-joint. 2. Various branches to the flexor muscles during its course. 3. The medullary artery of the radius, at about one-fourth of the length of the bone downward. The small metacarpal artery descends, within a cel- lular sheath, along the inner and back part of the knee, more outwardly situated than the large one, from which it is separated by the posterior annular ligament. It continues its descent along with the metacarpal vein (which runs to its inner side) until it arrives below the knee, where it bifurcates and transmits its divi- sions down upon the front of the suspensory ligament — between it and the cannon-bone. It sends off"—]. Cutaneous branches over the front of the knee, which anastomose with the spiral. 2. Ramifications to the front of the cannon. 3. To the suspen- sory ligament. The large metacarpal artery, which may be regarded CIRCULATORY SYSTEINJ. 185 as the continuation of the radial trunk, continues its course down the leg by the side of the tendo perforatus, passing along with it at the knee under the posterior annular ligament, but inclosed within a cellular sheath of its own. As it proceeds, it inclines to the side of the tendo perforans, and, in approaching the fetlock, gets in advance of that tendon. Immediately above the joint, where it is situated between the tendo perforans and the suspen- sory ligament, it splits into three vessels. The middle division slides into the interval between the bifurcated terminations of the ligament, and between them and the bone forms a transverse arch, from which three recurrent arteries retrace in a flexuous line the suspensory ligament, and form communications with the small metacarpal artery : the lateral divisions become the plantar arteries. From the arch, below, come off two lateral branches which descend into the joint. The plantar arteries, one external, one internal, in the fore extremity result from the bifurcation of the metacarpal, in the hind from that of the metatarsal artery : I prefer this appel- lation for them, because it denotes their destination at once, and because it saves us the useless division of a trunk only six inches in length into three nominal arteries ; and because our descrip- tions and memories are not clogged by it as they are by the " large pastern," and the " small pastern," and the " coffin arteries." Their general distribution is the same both in the fore and hind feet. The plantar arteries, in emerging from their common origin be- hind the flexor tendons, describe two sides of the figure of a triangle, the base of which, turned downward, is represented by a line drawn across the backs of the sesamoid bones, the apex being the point of bifurcation. They descend the fetlock upon the outer sides of the sesamoids, in company with their corres- pondent veins which run in front of them, and with the plantar nerves which proceed behind them : in this part of their course, they describe correlative curves outward, to conform to the pro- minences of the fetlock, and henceforward continue to pursue pre- cisely the same uniformity both in course and distribution, so that we need only in the progress of our description make mention of one. In its passage over the sesamoid, the outer edge of that bone is found to rise between the vessel and the flexor tendon ; but in quit- ting the fetlock, the artery again approaches the tendo perforatus, and subsequently runs alongside of it to its implantation in the head of the os coronse, at which place the artery sinks down behind the cartilage into the substance of what is called the " fatty frog." Inclining forward in its subsequent descent, the artery next passes the inner and upper extremity of the ala of the os pedis, where it u 1) 186 CIRCULATORY SYSTEM. enters a groove scooped in that bone, and is conducted obliquely forward and inward, into the foramen in the posterior concavity of the bone. Here we lose sight of it altogether — the knife and forceps no longer avail us to discover its progress and destination : either the bone must be chiselled away, or (the vessels being pre- viously injected) be eroded by maceration in an acid. We shall then detect the artery in the interior of the coffin-bone, making a turn outward again, and subsequently another inward, in the course of which, meeting with its fellow, the two trunks coalesce, and in so doing form an arterial semicircle corresponding to the circumferent line of the edge of the os pedis, which has been very properly named by the Professor, the circulus arteriosus*. The plantar vessels and nerves are invested in the course of their descent to the foot by cellular substance, which binds them loosely to the parts contiguous, whereto they pass. This accounts for their canals being flexuous when distended with injection, or when the foot is flexed upon the fetlock ; a circumstance that seems to have escaped the notice of writers on the foot. The branches of the plantar artery are many and important. After detaching some small ramifications inwardly to the fetlock, posteriorly to the flexor tendons, which anastomose with their fellows, and anteriorly to the extensor tendon, which are also anastomotic, it sends off' — 1. The perpendicular artery, a little above the mid- dle of the OS suflfraginis : a slender branch that descends upon the side of the bone, inclining forward, and ends in the space above the coronary ligament in anastomosis with its fellow, form- ing an arch, presenting its convexity downward, called the super- Jicial coronary , from which emanate about eighteen small descend- ing arteries that run down over the coronary plexus of veins, whose principal function, it is said, is *' to secrete the crust." I would beg to remark here, however, that, although I believe what ] give to be the ordinary arrangement of these arteries, there is so much variation to be found in different subjects, that I cannot vouch for the unexceptionable correctness of this description, how- ever I may stand amenable for its general accuracy. The plantar trunk having detached various small unimportant branches back- ward, the great design of which appears to have been to preserve free and uninterrupted intercourse with the opposite trunk, it next sends off", below the pastern-joint, 2. The transverse artery, which proceeds directly across the front of the os coronse, underneath the extensor tendon, to join its fellow branch from the other side, the two together form- ing the superior coronary/ circle: this pours most of its blood through two short lateral conduits, the communicating arteries, * Professor Coleman, " On the Foot of the Horse" vol. ii. CIRCULATORY SYSTEM. 187 into the inferior coronary artery; though other short twigs are sent both upward and downward from it. The above two, just described, may be considered as the ante- rior branches of importance : we now proceed to those arising posteriorly : the first we need notice particularly is — 3. The artery of the frog. It comes off opposite to the pastern-joint, and descends obliquely inward through the sub- stance of the fatty frog, wherein it bifurcates: both divisions take nearly the same direction, one passing down upon the side of the cleft along which it continues, distributing branches in its course to the toe of the frog, and forming communications with the vessels of the sole ; the other ramifies over the heel of the frog, and sends branches outward to the cartilages. 4. The lateral laminal artery leaves the trunk just as the latter reaches the os pedis, passes through the foramen in the ala, and proceeds within a superficial groove to the front of the foot, distributing branches upward and downward to the lamince, and disappearing through a small foramen in the anterior and lateral part of the coffin, whose substance it enters in order to form a communication with the circulus arteriosus. From this vessel a branch descends upon the side of the bone to join the circumflex artery. 5. The circulus arteriosus, resulting from the coalition of the main trunks, preserves, to a certain extent around the toe of the coffin, the same curve interiorli/ that is made by the exterior edge of the bone itself, at the distance of about an inch above it. From the circulus arise two principal sets of vessels. 1. The anterior laminal arteries, numerous, small, short branches springing from the front of the circulus, and making their exit though the various foramina in the front and sides of the coffin, to ramify among the laminae, and anasto- mose with the descending and lateral coffin arteries. 2. The inferior communicating arteries, '* thirteen, and sometimes fourteen," in number, according to the Professor, arise from the convexity of the circulus arteriosus, and descend through the foramina in front of the coffin, a little above its boundary edge: having made their exit, they continue the same direction to gain the extreme edge, around which they are all received by the 3. Circumflex artery, which is commonly described as encircling "the toe" of the coffin-bone. Then again, from this vessel spring The solar arteries (which may be so named, as well from their radiated arrangement, as from their destination), thir- teen or fourteen in number, though they run from the same 188 CIRCULATORY SYSTEM. channel, do not " take their origin immediately opposite the ter- mination of the vessels into the circulus arteriosus," They are destined for the supply of the sole, upon which they run in radii, at pretty equal distances, whose coumion centre is the toe of the frog, where they end in communications with the arteries belong- ing to that body. The Carotid Arteries. The right arteria innominata (having detached seven branches which differ but unimportantly in their mode of origin, and not at all in their general course and distribution, from the seven arte- ries into which the left division resolves itself) becomes the com- mon carotid: a vessel of large caliber, about an inch in length, emerging through the upper part of the anterior opening of the chest, having the trachea between it and the spine, above ; the vena cava anterior, below it ; and dividing, as it quits the cavity, into the right and left carotids. These arteries bend upward from their origin, diverging as they ascend along the neck so as to leave a space between them for the windpipe, which they closely embrace and cling to for the first part of their course : towards the middle of the neck, however, we find them gradually inclining, as they ascend, to the posterior and lateral borders of that tube, a line of direction they preserve during the remainder of their course*. Having reached the top of the larynx, the carotid of either side splits into three divisions — the external and internal carotids, and the ramus anastomoticus : at which place, though the trunk itself is found deeply lodged in soft parts, yet its situ- ation is well indicated by the larynx (with which it is in contact) below; the transverse process of the atlas, above; the angle of the jaw a little in advance of it; and the coronoid process farther removed above and before it. A deep incision corresponding to the posterior border of the stylo-maxillaris, would sever the vessel at or very close to its division. The carotid detaches — I. Several unimportant muscular branches in its progress up the neck. 2. The th^roideal artery, coming off opposite to the top ring of the trachea : a branch of no mean size, which turns round the windpipe and enters the substance of the thyroid gland. In its way, the thyroideal furnishes the laryngeal, a small artery that perforates the ligament uniting the cricoid and thyroid cartilages, * The carotids lie more deeply the higher they proceed up the neck : each is covered by the steruo-maxillaris ; and the readiest way to find the vessel is to make a cut along the upper border of this muscle, and depress it with the finger or handle of the knife. The artery is separated, except at the bottom of the neck, from the jugular vein by a thin partition of muscu- lar fibres; the par vagum accompanies it outwardly, and the sympathetic n^rve runs between the two. CIRCULATORY SYSTEM. 189 and is dispersed upon the membrane lining the larynx : in some instances, however, this forms a branch of the main trunk. The common division of the carotid is into the three vessels just named ; but not infrequently we meet with a fourth coming from the point of ramification, the additional one being the facial artery; and, occasionally, we only find a simple bifurcation of the vessel into the external and internal carotids. The External Carotid Artery Is the large division, the one that looks like the continuation of the trunk of the common carotid itself. It takes a flexuous course : first it curves downward behind the angle of the jaw, where it crosses the insertion of the stylo-maxillaris, by which it seems defended from injury; next it makes a curve upward and forward, crosses the membranous sac of the fauces, and passes between the stylo-maxillaris and cornu of the os hyoides, deeply buried under the parotid gland ; lastly, it makes a third curve, directing it forward along the posterior border of the branch of the jaw, and to that it subsequently corresponds in its course until it bifurcates, which it does immediately behind the neck of the con- dyle. This vessel is so bedded in glandular substance, surround- ed by venous and nervous trunks, and protected by neighbouring bony prominences and muscles, that but a small, and that the upper, portion of it is safely accessible to the knife : rather more than an inch below and behind the condyle, it is com- paratively superficially lodged, being there only covered by the anterior thin border of the parotid and a thick aponeurosis, in addition to the common integuments. We reckon eight branches from it. 1. Submaxillary artery: it comes off behind the cornu of the OS hyoides, just as the vessel is going to make its second curve, and ranks next in size to the carotid itself. It takes an oblique course downward and forward within the submaxillary space, preserving at first the line of the cornu ; afterwards it crosses the lower portion of the pterygoideus, and reaches the posterior border of the branch of the jaw (about one-third of its length downward), round which it turns to mount upon the face: in making this turn it becomes subcutaneous, distinctly per- ceptible to the feel, and (from being in contact with the bone) very conveniently compressible, on which account, it is the vessel ordinarily selected to convey a knowledge of the state of the pulse. In ascending upon the face, it corresponds to the anterior border of the masseter; but before it reaches the alveolar processes it ends, by a pretty equal division, in the /ir/c/rt/ and inferior labial 11)0 CIRCULATORY SYSTEM. arteries. Its branches are — a. The ascending pharyngealy which mounts obliquely over the cornu of the os hyoides, and ramifies upon the side of the pharynx, giving off commonly a laryngeal twig or two in its way, and another to the velum, which in some instances is derived from the submaxillary itself, h. Various inconsiderable branches to the pterygoid muscle and parotid gland. c. The. lingual, nearly or quite equal in magnitude to the sub- maxillary itself. It first bends its course obliquely inward, de- taching a few twigs into the submaxillary space ; it then splits into two arteries, the ranine and the sublingual. The ranine, the larger one, the apparent continuation of the lingual, turns down- ward and proceeds in a flexuous manner along the under part of the tongue, serpentining between the muscles, and transmitting many branches into the interior: it continues of large size even to the tip of the organ, wherein its extreme ramifications are ex- pended. Its ramifications, I believe, have no anastomosis in ordinary cases with those of its fellow on the other side ; though I have a head now before me in which I find the two ranine arte- ries communicating by a large cross branch at the root of the tongue. The sublingual brunch winds along the under and outer border of the tongue, preserving a more superficial course than the former. It supplies the sublingual gland, and distributes its longer ramifications over the membrane and papillae of the tongue. d. The submental artery leaves the submaxillary contiguously to the internal side of the jaw, a little before the latter vessel begins to make its turn. It follows the course of the branch of the jaw, nearly preserving the line of its middle, detaching twigs princi- pally to the pterygoideusand mylo-hyoideus, and transmitting its furthest ramifications into the substance of the gums internally. e. Anterior masseter branches, one large, or two or three small vessels, coming off in the course of the ascent of the trunk upon the face. y. The inferior labial artery courses the side of the jaw, occupying nearly the same site externally to what the sub- mental does internally, invested in the cellular and fleshy sub- stance belonging to the retractor labii. It is principally destined for the supply of the glandular substance of the under lip, wherein it anastomoses with its fellow vessel. It gives off — a. Slender ramijications to the investing cellular substance, b. Buccinator arteries. c. A large branch to the angle of the mouth, which distributes buccal tioigs in its course, and then bifurcates, sending its divisions respectively to the upper and under lips, along their lateral borders: these form the superior and inferior coronary arteries of the lips. g. The facial artery ascends upon the side of the face^ CIRCULATORY SYSTEM. 191 with an inclination forward and downward, crossing the buccina- tor muscle a little in advance of the anterior border of the nias- seter. Having run as high as the level of the bony ridge from which the masseter arises, it detaches a large branch, and then winds upward and spreads into an arborescent expansion upon the upper and fore part of the face. a. It mostly sends one or two masseter branches backward, h. Buccal twigs from both sides, c. The superior labia/, the branch whose origin has just been shewn, takes its course below the false nostril, to which it sends ramifications, to the upper lip, wherein it anastomoses with the terminating branches of the palatine arteries and also with its fellow, d. Long slender branches, commonly two, to the false nostrils, e. Terminating ramifications to the cellular substance and skin covering the fore part of the face, which anastomose with others making their exit from the infra-orbitar foramen, and also with some straggling twigs escaping from the cavity of the orbit. 2. The parotideal branches are those we may consider next to the submaxillary branch of the external carotid. They are too variable in number, size, and mode of origin to admit of spe- cial description : they come off as the vessel continues its course under the gland. S. A large branch, internally, to the pterygoideus. 4. One much longer, externally, the posterior masseter artery. 5. The posterior auricular commonly comes off from the external carotid immediately opposite to the last -mentioned branch. It emerges from underneath the parotid gland, and as- cends in a direct line to the back of the concha of the ear, where it splits into three divisions, which thence proceed along its dor- sum to its tip, distributing branches right and left; and these anastomose freely with one another, and likewise with the other auricular arteries, and thereby form a beautiful vascular net-work. It also gives branches to the parotid gland, to the muscles of the concha, the meatus auditorius externus, and membrana tympani. 6. The temporal artery, the anterior auricular, and the internal maxillarij, may be considered as the terminating branches of the external carotid. The temporal leaves the trunk just as it is issuing from the depth of the parotid gland, and then curves upward and forward around the neck of the jaw, a little below the condyle, which serves as a guide to cut down upon it; from this, it runs in a straight line towards the outer circumference of the orbit, opposite to which margin it dips into the substance of the masseter, and so eludes further trace without the aid of dis- section. We find it henceforward corresponding in course to the line of the maxillary ridge, sending branches down into the 19^2 CIRCULATORY SYSTEM. muscle, and freely anastomosing with the anterior and internal masseter arteries. 7. The antehior auricular artery, arising in common with the former, inclines in an opposite direction, upward and backward, and is deeply seated at first under the parotid gland. It ascends to the fore part of the root of the ear, and ends in short ramifications to the anterior muscles of the concha, and in other superficial ones which anastomose with the anterior auri- cular arteries. It sends off — a. Branches to the temporal muscle. b. An internal auricular brancli, which enters the concha, c. A subcutaneous branch, Vvhich descends upon the forehead and anas- tomoses with the supra-orbitar arteries. 8. The intekmal maxillary artery originates deeply buried on the inner side of the articulation of the jaw, a little below the condyle, between the neck of the inferior maxilla and the upper portion of the cornu of the os hyoides. It pursues a winding course, first bending inward then downward, to the bottom of the orbit, where it splits into four arteries. In its way to the orbit, it gives off — a. Deep temporal branches : several small arteries, variable in number, some of which run into the pterygoid muscle, while others, longer ones, ascend in the space behind the orbit, ramifying within the adipose matter there, and penetrating the lower portion of the temporal muscle. b. Long slender twigs to the soft palate, to the ear, and to the articulation of the jaw. c The inferior maxillary, a small artery of considerable length, which creeps down the branch of the jaw, crossing the pterygoid muscle, to enter the foramen maxillare superius in company with the nerve of the same name; within which canal it distributes branches to the roots of the molar teeth and to the diploe, and afterwards makes its exit, greatly diminished in size, through the foramen maxillare inferius, upon the side of the mouth, where it becomes lost in anastomosis with the inferior labial artery : in some instances, the latter artery sends a twig into this hole in place of one coming out. The vessels in which the internal maxillary terminates are — d. The supra-orbitar artery, which traverses the upper and inner part of the roof of the orbit, and leaves the cavity through the foramen supra-orbitarium, and is lost in slender ramifications in the cellular membrane upon the forehead, anastomosing with the temporal branches of the anterior auricular and the ascending deep temporal arteries. e. The ocular, under which name are included a bunch of arteries arising from the bottom of the orbit, distributed to the fatty matter thereabouts, to the muscles of the globe, and to the ClRCLILATOllY SVSTIiM. 19.3 lachrymal gland, eyelids, and ductus ad uasuni. One in parti- cular, larger than the others, named the lateral nasal branch, enters the cavity of the cranium through the (bramen orbitale in- ternum, and after forming a communication there with the anterior cerebral artery, turns round and enters the nose through the eth- moidal cells to be dispersed upon the Schneiderian membrane. f. The injra-orbitar, a considerable branch entering the infra- orbitar canal, in order to supply the anterior molar teeth and medullary substance of the bone with blood : having served this purpose, it sends its remaining twigs out upon the cheek, through the maxillary hole there, whereupon they anastomose with tlie ramifications of the facial artery. g. Thepalato-maxillari/, the largest of the terminating divisions of the inferior maxillary artery, enters the foramen palatinum su- per! us, descends through the palatine canal, re-appears upon the roof of the palate, and follows the tract of the palatine groove, some short distance removed from the sides of the molar teeth, out of which, inferiorly, it makes a curve inward, just above the roots of the front teeth, to take its passage through the foramen incisivurn, to reach the front of the jaw, there to join its fellow. From this remarkable arterial union issue several branches, some of which run down to supply the glandular structure of the upper lip, while others are directed upward upon the external nares : the peeper-seated ones penetrate the dilatator narium and depressor labii superioris; and many of them anastomose with the termi- nating ramifications of the superior labial artery. This vessel gives off some few branches to parts at the back of the orbit, before it enters the foramen ; and other short twigs, as it courses the palate. — Sportsmen and farriers have a practice of cutting- through the bars and severing the palato-maxillary, in order to detract blood on any occasion of emergency : the artery however seldom bleeds much — it soon retracts into its cellular case, and forms a coagulum ; and this renders the operation, in a general way, both ineffectual and harmless. The second and smallest division of the carotid, is the Ramus Anastomoticus. It leaves the trunk of the carotid, commonly at the angle formed by the external and internal carotids, crossing the latter in proceeding to the spine. Deeply seated beneath the parotid gland, in its course it describes an arc backward, which, in the ordinary position of the head, nearly corresponds to the under border of the stylo-maxillaris. From below the coronoid process, it turns under the transverse process of the atlas, vvhi re it joins 194 CIRCULATORY SYSTEM. the vertebral artery, as soon as the latter has emerged from the foramen in that bone. From about the middle of the arch comes off The occipital artkry, a vessel nearly equal in magnitude to the trunk itself, which pursues a flexuous course to the occiput, first ascending upon the coronoid process, and then climbing the occipital ridge to reach the vertex. Its branches are — a. A long, slender, deep-seated one, that mounts upward and enters the cra- nium through the foramen lacerum to be dispersed upon the dura mater, though this is sometimes a branch from the anastomotic trunk itself, b. Twigs forwarded to the temporal muscle, c. Terminating I'amifications to the straight and oblique muscles of the occiput. The third division of the carotid is the Internal Carotid Artery. This vessel, whose caliber is not more than half that of the external carotid, is, originally, deeply lodged within the submax- illary space, whence it ascends to the base of the skull, crossing the upper extremity of the cornu of the os hyoides, inwardly, in its course, which is rendered remarkable by several tortuous turns : it first curves backward, next inward, then upward, and lastly forward, to reach the anterior part of the foramen lacerum, through which it enters the cavity of the cranium. It is accompanied in its way by one of the principal branches of the jugular vein, by the eighth pair of nerves, and by the sympathetic nerve. At its entrance into the skull, we find the artery lodged within the cavernous sinus, wherein it makes two more turns, one forward, the other inward, from which last flexure comes off a vessel named the 1. Arteria coMMUNiCANS. This runs in a direction up- ward and backward, passing under the crura cerebri, to join the basilar, with which it makes one continued vessel, thus forming one side of the circulus arteriosus — to be presently described. After having given off this branch, the internal carotid pierces the dura matter, and continues its course upward, alongside of the optic nerve, and immediately over the optic decussation splits into four principal divisions. At the point of division however, or prior to it, are sent off — 2. Two or three long branches of small size, which run forward and spread their ramifications upon the anterior and inferior portions of the dura mater. Its four divisions or remaining branches are — 3. The anterior cerebral; which advances by the side of the optic nerve, and in front of its decussation transmits a con- siderable branch across, which unites with a similar one coming CIRCULATORY SYSTERI. 195 from the opposite division, thereby forming a vessel nearly equal in size to the internal carotid itself, named the arteria corporis callosi : this is reflected upward and forward around the corpus callosum, and pursues through its entire length the tract of the raphe, detaching as it proceeds numerous lateral twigs for the supply of the corpus. The anterior cerebral artery now subdivides into several branches, which, with the exception of one, are dis- tributed over the anterior lobes of the brain. This one. The ophthalmic artery, leaves the cranium through the foramen lacerum orbitale, in company with the nerve of the same name, and at the bottom of the orbit, after forming some anastomoses with the orbital artery, furnishes a twig to the lachrymal gland, long ciliary arteries to the choroid coat and iris, and the central artery to the retina. 3 and 4. The middle arteries of the cerebrum. These vessels come off directly opposite to each other at right angles from the trunk, take a flexuous passage between the anterior and middle lobes, and ramify extensively within their substance. 5. The internal artery of the cerebrum; which arises a little higher than the former, pursues the course of the tractus opticus, and winds round to the tubercula quadrigemina. The remaining vessels of the brain are derived from the Vertebral Artery . This artery enters the cranial cavity through the foramen mag- num, and mounts upon the cuneiform process of the occipital bone, where, about opposite to the middle of the medulla oblongata, it unites with its fellow, the two forming a single trunk denominated the basilar artery. The vertebral itself gives off — 1. Posterior arteries to the dura mater. 2. Ramifications to the medulla oblongata. The BASILAR artery sends oflT — 1. The posterior arteries of the cerebellum ; which leave it as it passes under the medulla oblongata, wind up- ward around that body, and cross over to the cerebellum, to the posterior portions of which they are distributed. — The basilar artery then continues its course under the tuber annulare, detach- ing lateral branches as it advances, and from that passes between the crura cerebri, where it bifurcates. Its bifurcations proceed but a short way before each of them subdivide into two vessels : one (2.) runs forward to meet the communicating artery; the other is the 3. Anterior artery of the cerebellum; which winds outward, around the crura cerebri thence crosses to the cerebellum. 196 CIRCULATORY SYSTEM. and is principally expended within its lateral lobes. — Below the origin of this vessel, from the sides of the arterial circle come oft" three or four considerable branches, the principal of which is the Posterior artery of the cerebrum. This runs ob- liquely backward, across the crus cerebri and tractus opticus, and afterwards mounts upon the posterior lobe of the cerebrum to distribute its ramifications. The ciRCULUs arteriosus, then (as we have seen), is formed, anteriorly, by the transverse branch of the anterior cerebral divisions ; laterally, by the counnunicating arteries ; and pos- teriorly, by the bij'urcalions of the basilar artertj. The Posterior Aorta, Considerably longer and of greater volume than the anterior aorta, is the main trunk from which aie derived the arteries of the abdomen, pelvis, and posterior extremities, the posterior inter- costals, and some fo-w of the thoracic arteries. It commences opposite to the fourth dorsal vertebra, and is there some little distance removed from the spine. From its origin, it makes a curve, first upwaid and then backward — having the pulmonary artery on its left, the termination of the windpipe on its right : having reached the bodies of the dorsal vertebrae, it enters the superior mediastinum, and afterwards directs its course straight along the spine, inclined to the left side — having now the esopha- gus and vena azygos to its right, the thoracic duct to its left. The portion of the vessel within the cavity of the thorax, dis- tinguished as the thoracic aorta, gives rise to many branches, but they are but small. 1. The bronchial springs from the under part of the curva- ture of the trunk, bends its course downward and forward towards the root of the left bronchial tube, at which place it divides into two — the right and left bronchial arteries. These vessels pene- trate their respective lungs in company with the right and left bronchial tubes, to the branches of which they continue to cling in the course of their ramification within the substance of the parenchyma. 2. The esophageal likewise springs from the concavity of the arch, near to the former, in some instances before it; and proceeds backward and to the right, to reach the esophagus. Here it splits into a superior and an inferior division ; which both course the entire length of the esophageal tube, distributing branches right and left over its surface, and terminating at the cardiac orifice in anastomosis with the gastric artery. «i. The 1 ntercosta H.S, the remaining branches, come o(I" in CIRCULATORY SYSTEM. 197 pairs from the sides of the vessel, and are destined for the su])ply of those intercostal spaces posteriorly to the last which received a branch from the anterior intercostal artery. These arteries pre- serve the lines of the ribs, running close to their posterior borders, and expend themselves about the inferior parts of the thorax and abdomen in anastomosis with the internal pectoral and epigastric arteries. They furnish, near their origin, small branches which enter the vertebral canal through the spinal holes ; and also numerous muscular twigs during their course. Having detached these several small vessels, the posterior aorta continues its passage between the crura of the diaphragm into the cavity of the abdomen: in making its exit from the thorax, however, it gives rise to two other small arteries (or else to a single branch which afterwards forms two) named the Phrenic or diaphragmatic arteries, right and left. These vessels penetrate their respective crura, in whose substance they ramify, and ultimately expend themselves upon the chordi- form tendon. Within the abdomen, the aorta continues to be firmly attached to the spine through the medium of its several vessels and cellular covering, and thus proceeds, still inclined to the left side, as far as the last lumbar vertebra, underneath the body of which it splits into four large arterial trunks. Prior to this division, the abdominal aorta gives off" — I. The co^liac artery ; which is nothing more than an indemonstrable stump, or rather common root, from which spring the splenic, gastric, and hepatic — arteries that in some instances have separate roots — whose origin is from the under part of the trunk, a little posteriorly to the issue of the phrenic. a. The splenic artery, the middlemost of the divisions of the cceliac, takes a winding course to the left side of the cavity, turns forward along the greater curvature of the stomach, nmning between that and the concave part of the spleen, and at length ends in the left gastric artery. Soon after its origin, it gives two or three twigs to the pancreas as it passes that gland ; many considerable branches to the spleen from the convexity of its flexure; whilst from the concavity of it are passing smaller but longer branches upon the greater curvature of the stomach. It is prolonged beyond the tapering termination of the spleen, dis- tributing shorter branches to the stomach as it proceeds, and con- tinuing to encircle the organ towards its right extremity, from which is coming to inosculate with it the right gastric artery. b. The gastric artery, the smallest of the cceliac divisions, runs forward to the small curvature of the stomach, between the layers of the omentum, splitting before it reaches the organ into two branches that take the names of superior and inferior gastric : 198 CIRCULATORY SYSTEM. these spread their ramifications, in an arborescent form, upon the upper and under surfaces of the stomach, and anastomose with those of the right and left gastric. c. The hepatic artery, the largest of the coeliac divisions, pro- ceeds in front of the pancreas to the right side of the cavity, and winds forvrard over the pyloric end of the stomach. It gives off — a. Divers small branches to the pancreas, as it passes by the gland. /3. Near the pylorus, it sends a considerable branch to the beginning of the duodenum, which, as soon as it reaches the intestine, bifurcates: one division, the >. w £ § to-i a-oi ra-o lar w ■i^s-S hJ ? phh=c;5o v«^~v^ H hI; oi O ^^ Q a .rs -C .ri 3 ^ S ^• S? SOtf 2-3 " i § S 5PhO C^ I cS O 2 < 5g CIRCULATORY SYSTEM, 209 »-3 S Pi assage to nerves, of considerable importance, to the interior of the larynx. 222 RESPIRATORY SYSTEM. This cartilage not only constitutes by far the most extensive part of the larynx, but, as its name indicates, incloses and shields from external injury all the others. THE CRICOID or ring-like cartilage is placed below the thyroid. In front it appears like part of the trachea ; but it broadens so much behind, that it overlaps the first rnig of the windpipe, somewhat after the form of a helmet. Upon its broad or posterior part are four surfaces of articulation : the two upper receive the hinder extremities of the arytenoid cartilages, the two lower are adapted to the inferior cornua of the thyroid cartilage : they are all furnished with capsular ligaments and synovial mem- branes. Furthermore, it is attached by ligamentous expansions to those parts, and likewise to the first ring of the trachea. THE TWO ARYTENOID, or e?<;er-sA«perf cartilages, trian- gular in their figure, lie over the upper and back part of the tra- chea, leaving an aperture between them leading into that canal, denominated, from its proximity to the tongue, the glottis. Their inward parts are everted, and form a triangular prominent border, over which is spread the membrane of the glottis : their outward surfaces are marked by concavities in which are lodged the aryte- noid muscles. Posteriorly, they repose upon the cricoid cartilage, and are connected with them by capsular articulations : in front, they have a membranous connexion with the cartilage next to be noticed. THE EPIGLOTTIS, so named from being raised over the glottis, and occasionally covering it like the lid of a pot, is well adapted, from its heart-like shape, to the rz'wa g/o^^/f/?s ; whose margin is completed by two narrow slips of cartilage proceeding from the base of the lid to the arytenoid. By some, these slips of cartilage have been separately considered : but in my opinion im- properly so ; for they are, in reality, nothing more than prolonga- tions or appendices of the epiglottis. The surface of this carti- lage presented to the interior of the larynx is smooth and concave, and covered by an extension of membrane from the glottis ; that part opposed to the tongue is unevenly convex, and is tied to that organ, as well as to the os hyoides, by a doubling of membrane infolding some muscular fibres : to this musculo-membranous ligature, which assists in retaining the cartilage in its elevated position, the name offrccniim epiglottidis is properly given. The fracnum receives co-operation in this function from strong elastic ligaments connecting the base of the epiglottis to the thyroid and arytenoid cartilages. If we detach the epiglottis, or raise it forcibly, in order to ob- tain a more complete view of the rima glottidis, the latter will be found to be stretched inlu an oblong quadrilateral figure, whose RESPIRATORY SYSTEM. 223 width gradually diminishes from the middle towards either ex- tremity, and bears a ratio of about one to six when compared to its lengtli. The sides turned forwards, are formed by the aryte- noid cartilages ; those directed backwards, by two prominent folds of membrane (which envelope the thyro-arytenoid mus- cles), commonly described as the vocal ligaments, from their being concerned in the formation and intonation of the voice. Imme- diately over them are slit-like apertures, opening into membranous sacs, each large enough to contain a walnut ; these are the ven- tricles of the lon/iix, whose use is also connected with the pro- duction and modulation of the voice. The membrane lining the cavity of the larynx is one of great susceptibility ; on which account it is kept continually moist by a mucus, oozing from numerous lacuncz — the excretory orifices of small subjacent follicles whose situation is denoted by the little round eminences upon its surface. This is the common seat of that species of catarrh which is accompanied by cough. OF THE TRACHEA. The trachea, or windpipe, is a cartilaginous tube extending along the neck, from the larynx to the lungs, for the passage of air. In horses of ordinary size, it is from twenty-five to thirty inches in length. Course. — The trachea commences from the inferior border of the cricoid cartilage, opposite to the body and transverse processes of the atlas ; takes its course along the anterior and inferior part of the neck, inclining to the near side, between the sterno-myloidei mus- cles (which by their approximation conceal the lower portion of it), and enters the chest between the two first ribs ; wherein, under the curvature of the posterior aorta, it divides into two parts, the bronchial tubes. Structure. — From fifty to sixty annular pieces of cartilage enter into the composition of the windpipe; altogether constituting a structure so remarkable for the inequality or asperity of its exterior, that the ancients, in order to at oncedistinguish it from all other ves- sels, called it the asp ('/a arteria. No entire or undivided tubular substance could have partaken of the various motions of the head and neck, without having suffered more or less distortion, and con- sequent deformity and cHminution of caliber, of some part of its canal, which would have been attended with frequent interruptions to the free passage of the air, dangerous, and even fatal, to the re- spiratory functions; whereas, constructed as it is, with the aid of its muscular power, no attitude into which the animal may natu- rally put himself will impede the freedom of passage through it. The cartilages, or, as they are commonly described, the rings of 224 RESPIRATORY SYSTEM. tlie windpipe, have all a close resemblance to one another: if there beany disparity between them worthy of notice, it consists in those that form the superior part of the pipe being somewhat larger and broader than those nearest to the bronchial tubes*. A ling is not uniform in its breadth, in consequence of having waving or scolloped borders ; the advantage of which is, that a sort of dove-tailed connexion is effected which materially contri- butes to the compactness and strength of the entire structure. Its front and sides measure, in the broadest places, half an inch in breadth, and nearly a quarter of an inch in thickness — evidently made so substantial to resist external injury; whereas its poste- rior or unexposed parts grow suddenly thin and yielding, and taper to the extremities ; which instead of meeting and uniting, pass one over the other, and thus form a shield of defence behind, while they admit of a certain dilatation and contraction of the internal dimensions of the tube. These attenuated ends are joined toge- ther by a ligamentous expansion, mingled with a quantity of cel- lular membrane. The rings are likewise attached to one another by narrow ligamentary bands, strong and elastic ; which after they have been drawn apart in certain positions of the head and neck, have the power to approximate them : when the pipe is removed from the body, and suspended by the uppermost ring, these liga- ments counteract the tendency its weight has to separate the rings, and still maintain them in apposition. The lowermost ten or twelve pieces of cartilage appear on examination but ill to deserve the name of rings ; indeed they are little more than semi-annular, the deficiencies in them behind being made good by intermediate moveable pieces of cartilage. These pieces, whose breadth in- creases as we descend, are let into the vacuities in such manner as to overlap the terminations of the segments, and they are con- fined and concealed by the same sort of ligamentary and cellular investment as was before noticed. Muscle. — Where the outward extremity of the ring suddenly turns inward and degenerates into a thin flexible flap on either side, a band of muscular fibres is fixed and stretched across the canal, dividing it into two unequal semi-elliptical passages: — the ante- rior one is the proper air channel ; the posterior or smaller one is filled with a fine reticular membrane connecting the band to the posterior part of the ring, and preventing it, in action, from en- croaching upon the main conduit. This self-acting band appears to me to have been added to the tube to enable it to enlarge its * Now and then we find, at the upper part of the tube, two or three or more of these rings accreted together: it gives rise to some prominence thereabouts generally, and may often be detected by taction in the living animal. RESPIRATORY SYSTEM. 225 caliber — not to tliuiinish it, as a superficial view of these parts might lead one to imagine ; for, in consequence of the passage being naturally elliptical, and the muscle being extended across its long diameter, the contraction of its sides will give the tube a circular figure, by increasing the curvature of the ring anteriorly, and thereby, in effect, will expand and not contract the caliber of the canal. I would say, then, that the trachea was made muscular in order that it might have the power of increasing its capacity for the passage of air, whenever the lungs were called into extraordinary action : in addition to which, I think, that this band may, in some degree, counteract any tendency certain posi- tions of the head and neck have to alter its shape and diminish its circumference. This opinion is corroborated by the circum- stance, that the muscle grows slender and pale as we approach the lower end of the pipe, where the canal itself is nearly circular, and where it is placed in the least moveable part of the neck*. Membrane. — The trachea is lined by a soft, pale red membrane, which, anteriorly, has a close adhesion to the rings themselves, and presents a smooth polished internal surface; but which, poste- riorly, is loosely attached to the muscular band, and puckered into fourteen or fifteen longitudinal pliccB or folds, that extend with re- gularity from one end of the tube to the other. These folds were evidently made to allow of the contraction and elongation of this muscular band ; for I cannot myself assign any reason why they should exist in its relaxed state, unless this fulness of membrane be given to admit of enlargement of the caliber of the tube during the contractions of that muscle : if this be plausible, I may ad- duce the corrugation of the membrane as another proof that the caliber of the trachea is susceptible of augmentation. This mem- brane is continuous with that which clothes the rima glottidis ; but it is paler than it, and not near so sensitive. Its arterial rami- fications, also less abundant than upon the glottis, exhale a vapour from its surface; independently of which, it is kept continually lubricated by mucus, furnished from its numerous lacinia:, to de- fend it from any thing acrimonious that may be contained in the breath. BRONCHIAL TUBES.— The trachea having entered the thorax, bifurcates into the two bronchial tubes:— of them, the right is the more capacious canal, on account of having com- munication with the larger division of the lungs ; the left the * In this opinion I find I am at variance witliGiRARD. Tiie French pro- fessor ascribes to it the power of contracting the caliber of the trachea. "Cette couche, bien evidemment inusculeuse, pent retrecir le calibre de la trachee, en rapportant les extremites des segmens." Anat. Vet., p. 146 et 147, torn. ii. G g 22G RESPIRATORY SYSTEM. longer one, in consequence of having- to cross under the pos- terior aorta, in its course to the left division of the lungs. The last cartilage of the main pipe has a spear-like or angular pro- jection extending down between the bronchial tubes, filling up that space which would otherwise be left open from the diver- gent manner in which they branch oft': it is quite loosely at- tached, in order that the branches may accommodate themselves to the motions of the neighbouring parts. The bronchial tubes vary in structure from the trunk that gives origin to them : instead of their rings being formed of entire pieces of cartilage, they are constituted of several separate pieces, making up so many seg- ments of the circle, overlapping one another, and united together and invested by an elastic cellular substance : they also differ in having no muscular band, another fact connected with the physio- logy of that part. The bronchial tubes, in penetrating the sub- stance of the lungs, subdivide — the right into three principal branches, the left into two ; from which spring innumerable others that grow smaller and smaller, until the ramifications become so reduced that they are no longer traceable by the naked eye. In the larger branches we may dissect out five and even six segments of cartilage, held together by a thin, but dense and elastic cellular substance : in the smaller divisions, only two are found, and they are diminished in size ; and in the smallest visible ramifications of all, cartilage is altogether wanting, though, in many places, marks of the rings n)ay be traced upon the continuation of the lining membrane, which in these intimate parts composes the en- tire parietes of the tube. In the larger branches this membrane (whicli is continuous throughout the bronchial system) assumes a plicated disposition — apparently, to admit the more readily of ex- pansion. Thyroid Glands, Two egg-shaped, apparently glandular bodies, attached just below the larynx to the sides of the trachea, and united in front of that tube by an intervening poition of the same substance, which, by way of distinction, is by some called the isthmus. They are enveloped and attached in their situation by cellular membrane ; are larger and more vascular in the young than in the old subject ; and exhibit a spongy texture when cut into, which I am at pre- sent ignorant of the precise nature of. They are well supplied with bloodvessels, and have many small nerves going to them. Their physiology still remains obscure. OF THE LUNGS AND PLEURA. The lungs are the essential organs of respiration : tlie pleura is but the metnbrane by which they are invested. RI'SPIRATORV SYSTEM. 227 Pleura. The pleura is a fine semi-transparent membrane, lining the cavity of the chest, and giving a covering to the lungs. By that portion of it which is called the niediaslitmm, the cavity is divided into the right and left sides of the thorax. General Coiiformaiion. — If the lungs be exposed, by breaking off one or two of the ribs, we shall perceive that their surface, as well as that of the cavity itself, is everywhere smooth, polished, and humid : this is owing to the extensive investment of the pleura, the surface of which is now presented; so that, in reality, without breaking the surface, nothing but pleura can be touched ; although, from its extreme tenuity and pellucidity, the viscera appear, on a superficial view, to present their own bare exterior. Its other side, on the contrary, is rough, having numerous cellular flocculent appendages, by which it is united to the parts it in- vests : and so close and firm are these adhesions, that to cleanly detach it, in the recent subject, is a very ditficult and tedious dis- section. The pleura is a rejlected membralie ; by which is meant one that not only lines the cavity in which the viscera lie inclosed, but, by duplicature, or what in anatomical language is called re- flection, gives a partial or complete covering to the contained organs themselves. It is evident, therefore, that such a mem- brane admits of division into two portions : — a li/iing or parietal, and a rejlected portion ; and these, with regard to the pleura, have, for the sake of more definite description, received the names of pleura costalis and pleura pulmonalis : they are both, however, continuous at all points, are precisely similar in structure and function, and, in fact, are still but one and the same pleura. Mediastinum. — ^There is yet a third portion of this membrane to which a distinct appellation has been given, and that is the me- diastinum, the membranous partition between the cavities or sides of tlie thorax ; it differs from both the others in being com- posed of ^7^0 layers, which are derived from the two pleurseof the opposite sides. If we conceive the pleurae of the two sides of the thorax to be perfect sacs or bags, with flattened sides turned in- wardly, and closely applied and united together, in such a man- ner that the double membrane formed by their union extends through the middle of the chest, from the dorsal vertebra3 to the sternum, we shall at once have a tolerably correct idea of the for- mation as well as situation of the mediastinum. Structure. — The pleura, from the nature of its secretion, is one of those included in the list of st'yo^/-5 uiciubranes, to which it has been demonstrated also to be siunlariu its intimate organization. 228 RESPIRATORY SYSTEM. Like them, it presents a shining secreting surface, of a whitish aspect, and considerable transparency, and is composed of httle else than condensed cellular substance, whose texture is pene- trated by bloodvessels, absorbents, and nerves : by long mace- ration in water, indeed, it may be entirely resolved into cellular substance. In most parts it is extremely thin, and by no means tough : but it is not so in all ; for that portion which faces the diaphragm is much denser and stronger than the pulmonary or costal division of it. Organization. — The arteries of the pleura, which come from the adjacent parts, are in the natural state exceeding small, ad- mitting only the colourless parts of the blood — a circumstance that accounts for its pellucidity ; under inflammation, however, they contain red blood, and such is the explanation of that ar- borescent vascularity upon the sides of the thorax in horses that die of pneumonia ; than which state nothing can better de- monstrate the comparative number and distribution of these blood- vessels. The majority of them terminate in exhalent orifices, from which is continually poured, upon the contiguous surfaces ol the smooth interior of the membrane, a serous fluid, in the form of steam or vapour, which may at any time be rendered visible by opening the chest of an animal recently dead. The absorbenls of this membrane are very numerous ; and though their extreme exility prevents us from demonstrating them in a state of health, yet may they often be seen in considerable numbers in horses that die of dropsy of the chest; we have also abundant proofs of their existence from various phenomena that occur in the diseases of the part : we know, for instance, that these vessels take up the serous fluid effused in hydrothorax, for they have been found full of it after death ; and it is a fact that no longer admits of doubt, that blood, extravasated into the chest, is absorbed by the mouths of these minute vessels. The nerves of the pleura are too small to be traced by dissec- tion ; but, though it is not possessed of much sensibility in a healthy state, we know, at least we presume from analogy, that it is highly sensitive in the diseased ; for few diseases are more acutely painful in the human subject than pleurisy, and we have every reason to believe that horses suffer much from the same malady. Secretion. — It has been observed that the exhalents of the pleura secrete a serous fluid, which is emitted, in the form of an exhalation, or vapour, into the cavity of the thorax ; and that it may be rendered visible at any time, if an animal, recently dead, be opened while yet warm ; or, if an opening be made into the chest of a live animal : in either case, a whitish steam will be RESPIRATORY SYSTEM. 229 perceived to issue from the interior of" the cavity. This vapour, shortly after death, becomes condensed and converted into a hquid ; which accounts for the contiguous surfaces of the pleura being moist, and for a collection of more or less fluid, resembling- water, existing in the most depending parts of the cavity. In consequence of every part of the membrane being bedewed in this manner, the lung itself may be said to be in an insulated state ; for the pleura costalis does not, philosophically speaking, touch the pleura pulmonalis, nor is the latter in actual contact with the mediastinum : all friction therefore, in the motions of these parts, is by this interfluent secretion effectually prevented. In this, then, consists the chief use of the pleura, viz. to furnish a secretion for the purposes of lubrication and facility of motion, which it further promotes by its extreme glibness of surface. It is said also to answer the purpose of ligameiiis to the contained organs, thereby confining and strengthening them. The use of the mediastinum is to divide the chest into two compartments. Lungs. The lungs (by butchers called the lights) are two spongy bodies formed for the purpose of respiration. Situation and Relation. — They are contained in the lateral regions or sides of the thoracic cavity ; separated from each other by the mediastinum and heart, which occupy the middle region. Prior to any opening being made into the thorax, the lungs con- tinue to fill up every vacuity : no sooner, however, is a perforation made into the thoracic cavity than they shrink in volume, and be- come in appearance too small for the spaces they occupy. This arises from their being during life — or rather during the un- opened state of the thorax — in a constant state of inflation with atmospheric air, which preserves them expanded ; and they suffer collapse of substance the instant air is admitted, in consequence of the pressure of the atmosphere upon them, from which they were protected before by the parietes of the thorax. Division. — The lungs are two in number : the right and the left lung: partitioned from each other by the mediastinum. A further division of these organs has been made into lobes: — that on the right side, the larger of the two, consists of three lobes ; the left, only of two : these lobes, which are nothing more than partial divisions of the lung by fissures of variable extent through its substance, serve to adapt them more accurately to the thoracic cavities, and, at the same time, render them fitter for the pur- poses of expansion and contraction. 230 RESPIRATORY SYSTEM. Volume. — The lungs of the horse, when inflated, are of great bulk* ; and the right is the larger of the two : in consequence of the heart being inclined to the left side, less space is given for the left lung. Attachment. — The lungs are attached, superiorly, to the spine (which attachment is sometimes called their roots) by blood- vessels, the divisions of the trachea, and the mediastinal por- tions of the pleura : everywhere else, in a healthy subject, they are free and unconnected. Figure.— In form, the lungs of the horse are very like those of the human subject ; and the latter have been compared to the foot of an ox, to which the injected lung of the foetus bears in- deed much resemblance : for, though the two lungs are not sym- metrical, yet, both together, they put on this shape, which is the counterpart of that of the cavity they occupy. With regard to their general figure, however, the lungs may be said to be conical : being broad and concave posteriorly, where they are opposed to the convex surface of the diaphragm ; narrow and somewhat pointed anteriorly, where they are received into the blind pouches of the pleura, in the space between the two first ribs. Co/our. — In colour, these organs vary somewhat, depending upon the age of the animal, and upon the quantity and distribu- tion of the blood they contain. In the young subject, they are of a lighter and more uniform shade than in the adult. In per- fect health they assume a pink hue ; which, as age advances, becomes mottled with purple and greyish patches. Sometimes, in the dead subject, they are found of the colour of the darkest venous blood, which arises from an inordinate congestion of that fluid within the pulmonary veins. .Struct u}-e. — The lungs are composed of the branches of arteries and veins, and of the ramifications of the trachea ; all which vessels are connected together by an abundant, intervening cel- lular substance, known by the name of parenchyma. Beneath the curve made within the chest by the posterior aorta, the tra- chea divides into the two bronchial tubes, of which the right, is the larger, but the shorter : the left the longer, in consequence of having to pass under the aorta in order to reach the left lung. Having entered the substance of the lung, the right tube divides into four others ; the left only into three ; which difference arises from the right lung possessing an additional lobe : these branches may be traced for a considerable extent within the parenchyma, * 1 consider, in comparison with the boily, that they exceed in luai^iii- tiide those of the huuiuii subject. RESPIRATORY SYSTEM. 231 giving ofTin their passage numerous other smaller tubes of simi- lar structure ; but, as we prosecute our dissection of them, we shall find that, in growing smaller, they partake less and less of the nature of cartilage, and tliat the extreme ramifications are not only entirely membranous in their composition, but of so fine a texture as to be perfectly transparent. It will be remem- bered here, that, in speaking of the trachea, a membranous lin- ing to it was described of the mucous kind, which, it was ob- served, thence passed into the bronchial vessels : now, it is of the continuation of this membrane in an attenuated state that the minute air-tubes appear entirely to consist ; at the extremity of every one of which the membrane is prolonged into a kind of blind bag or cul-de-sac, to which the name of air-cell has been given. From the arborescent ramification and peculiar mode of ter- mination of the bronchial tubes, some anatomists have compared them, and the cells at their extremities, to a bunch of grapes — supposing the stalks to represent the ramifications of the former, and the grapes connected with them the air-cells ; others have described them as having a resemblance to a honeycomb : and so far as the knife, with the aid of glasses, can develope their intimate structure, the first is an apt comparison, insomuch as it relates to the disposition of their cells ; the last, insomuch as it conveys an idea of their ready inter-communication. For, though they do not communicate but through the ramifications of the bronchial tubes, this is a medium of intercourse at once so general and free, that numbers of them are inflated at the same time by impelling air into any one of the larger branches : with the parenchymatous substance, however, they have no communi- cation whatever*. The bloodvessels that enter into the composition of the lungs are denominated the pulmonary. The pulmonary artery, having taken its origin from the right ventricle of the heart, winds up- ward to the root of the left lung, and there divides into the right and left pulmonary arteries, which divisions enter their corres- pondent lungs. The ramifications of these vessels (which differ from other arteries in having no anastomotic communications one * If the substance of the luna^s be Ulcerated or rent asunder, the surface will be found to present a lohulated aspect. Introduce a blow-pipe into one of these lohuli, and all the other lobules — the entire lung- — may be in- flated from this one ; shewing- the free communication existing between them. The same may be effected by injecting quicksilver. You may do the same with the interstitial substance : but in this case you do not fill the lobules. In fine, the lungs with their cells resemble a sponge ; only that the connecting tissue has no communication with the sponge. ■ 232 RESPIRATORY SYSTEM. with another) accompany those of tlie bronchial tubes, and, like them, divide and subdivide, grow smaller and augment in num- ber as they approach the air-cells ; upon the internal* surfaces of which they become capillary, and assume a texture of corres- pondent thinness and pellucidity with the cells themselves. Through these minute vessels every particle of blood is impelled every time it is circulated over the system, as was stated when on the blood : a remarkable change of colour is thereby effected in it, and we have now an opportunity of seeing in what man- ner this fluid is exposed to the influence of atmospheric air for the purpose. It is evident that no immediate contact can hap- pen between the air and the blood, for the thin, transparent side of the vessel, if not that of the air-cell likewise, must ever be inter- posed ; so that whatever this influence be, it must take eftect through one or other or both of these membranes. We might conceive, indeed, that such minute vessels could not transmit through them such a body of fluid as the blood ; but when we look at the volume of the lungs, and consider the incalculable number of air-cells they must contain, the globular surface of every one of which is furnished with an expansion of pulmonary vessels, we shall feel more surprise and admiration at the extreme division and diff"usion of this fluid in order to receive the neces- sary change, than that such a prodigious number of capillaries should be equal, in their united caliber, to the pulmonary artery itself. From the extremities of the arteries, upon the surface of the air- cell, arise the pulmonary veins. These, by repeated union with one another, form themselves, first, into visible branches, which subsequently become branches of larger size, until at length they end in eight pulmonary venous trunks, which proceed to, and by four openings terminate in, the left auricle of the heart. The ramifications of these veins, unlike the generality of others, are not more numerous than those of their correspondent arteries : and the reason for this is obvious ; for, here, one set of vessels are not more subject to compression than the other, nor does the heart (which is so proximate to them) require any such aid as an additional number of veins affords to carry on the circulation. The pulmonary veins have only to convey the blood back to the heart, after it has received its due change within the capillaries upon the air-cells. Organization. — Besides the pulmonary bloodvessels, there are two others, named the bronchial arteries. They come off, by one trunk, from the posterior aorta, and each of them enters a division * Some say, " upon the external surfaces." RESPIRATORY SYSTEIVJ. 233 of the lungs, in the substance of which it branches forth, and takes the course of the bronchial tubes. These tubes they supply- as well as the coats of the pulmonary vessels, and the parenchyma of the lungs, with blood : in fact, they may be regarded as the nutrient vessels of these organs. It has been, however, and still remains, a subject of dispute, whether these vessels do exclusiveli/ nourish the substance of the lungs or not; some say that they do ; while others assert that they are assisted in this function by the pulmonary artery, with some of the branches of which they anastomose. The latter opinion certainly does not appear to be supported by facts of much weight; on the contrary, the blood which the pulmonary arteries contain is dark-coloured, and unfit for the nutriment of any organ; and as for anastomosis, we have no demonstrative proof of its existence. The bronchial veins end in one trunk, which returns the blood into the vena azygos. The nerves of the lungs are derived principally from a large plexus within the chest, constituted of the par vagum and sym- pathetic. They enter the pulmonary structure in company with the bronchial tubes and bloodvessels, and continue their course with them, to be dispersed upon the bronchial membrane and pa^ rietes of the air-cells. The absorbents of the lungs are large and numerous, particularly the deep-seated : and of the superficial, we may often succeed in injecting considerable numbers, by introducing a quicksilver-pioe under the pleura pulmonalis. They all pass through the absorbent glands situated around the roots of the bronchial tubes. Farenchynia. — The connecting medium of the various consti- tuent paits of these organs, or, as it is termed, their parenchyma, appears to consist of little else than cellular tissue, without any intermixture of adipose matter : it admits of the free diffusion of any fluid that may be extravasated into it — of air that may have escaped from the air-cells, or of serous fluid poured out when the lungs become anasarcous ; but, as was observed before, there is no intercommunication between it and the cells or vessels, as long as the organs preseive their integrity of structure. Specific Gravity. — The lungs, when healthy, are exceeding light in comparison to their volume; so that if they be immersed in water, unlike most other parts, they will float upon the surface, — a fact familiar to every one who has seen the liver and lights of an animal thrown into a pail of water to be washed : indeed, the name of lights itself seems to have been given to them from this very property. If the foetal lungs, however, be so treated, they will in- stantly sink to the bottom of the vessel: and this experimental result at once shews why those of an animal that has once breathed should swim; for, in the one instance they contain air, H h 234 DIGESTIVE SYSTEM. in the other they are wholly free from it. They are not to be re- garded as respiratory organs in the fcetus. It is evident therefore, that the lungs owe their property of hghtness to the air they con- tain ; and, as a further proof of it, if that fluid be by any means , absorbed or pressed from them, and their bulk diminished by col- lapse of the air-cells, like other viscera, they will prove heavier than an equal volume of water : hence it is that the lungs of a horse that has died of hydrothorax, even though they be sound, are of a greater specific gravity than those of one in health. It occasionally happens, however, that these viscera evince, in this particular, the properties of airless lung, while their natural vol ume and general appearance remain the same: there must be present interstitial deposition. Bronchial Glands. Small, oval-shaped, glandular-looking bodies, situated about the roots of the lungs, adhering more particularly to the bottom of the trachea and the bronchial tubes. They exhibit a dirty French grey hue, interspersed with dark blueish spots, and are about the volume (though this varies much) of a tick-bean. For a long time the nature of these bodies remained obscure : of late, skilful injections have clearly shewn them to be absorbent glands. They possess their capsules, and, when cut open, exhibit a cellular structure. They contain a dark fluid,' which will soil any thing it touches; whose principal ingredient chemists have found to be carbon. Section V. DIGESTIVE SYSTEM. IN THIS SYSTEM ARE COMPRISED THE MOUTH, TONGUE, SALIVARY GLANDS, PHARYNX, ESOPHAGUS, STOMACH, INTESTINES, LIVER, SPLEEN, PANCREAS. OF THE MOUTH. IT may be observed here (as prefatory to the description of this pait), that in quadrupeds in general, the facial angle* is one of very considerable obliquity, in consequence of the prolongation * The. facial angle is the point at which one line drawn parallel vvith the exterior of the frontal bone is intersected by another extended parallel with the lower border of the inferior maxilla. DIGESTIVE SYSTEM. 235 of that part of the head which corresponds to the face in the hu- man subject : and this development of feature is in none more striking than in the horse and dog. Consequently, in these ani- mals, the nose and mouth are cavities of large dimensions. And in the horse, the mouth appears to have been thus prolonged, not only to enable him to collect his food with more facility, but also that he might subject greater parcels of it at a time to the action of the grinding teeth, whereby the processes of mastication and deglutition are greatly accelerated. Conformation. — The mouth is constructed, in part, of bone, and in part of soft materials. The superior and anterior maxillary and the palate bones form the roof; the inferior maxilla, the lower part ; the incisive teeth, the front ; and the molar teeth, the sides. The lips, cheeks, soft palate, gums, and buccal membrane, consti- tute its soft parts. The tongue occupies its cavity, and the sali- vary glands are appendages to it. Lips. General Conformation. — The lips, two in number, superior and inferior, are attached to the alveolar projections of the supe- rior and inferior maxillae, by the muscles that move them ; by the cellular tissue entering into their composition ; and by the membrane that lines them. Their borders surround and bound the orifice of the mouth, and are united together on either side; which points of union are denominated their commissures, or the angles or corners of the mouth. Exteriorly, the lips are creased down the middle by perpendicular lines of division ; exhibit little papillary eminences upon their surface ; and present a softer and shorter coating of hair than what is found in ordinary places, out of which project several long straggling horse-hairs or whiskers. The inferior lip is altogether smaller, and is thinner in substance than the superior; and is distinguished by a remarkable promi- nence about its centre, from which grows a tuft of long coarse hairs, vulgarly designated as the beard. Structure. — The lips are both muscular and glandular in their composition. Several small muscles (which have already come under our observation*), arising from the maxillary bones, are inserted into them, and endow them with great self-mobility: one alone, consisting of circular fibres, is interwoven in their sub- stance without having any other connexion ; this is denominated the orbicularis oris, or sphincter labiorum, from its use, which is that of closing the mouth. This muscle is an antagonist to all the others ; they raise or depress the lips, or draw them to one * Vide " Anterior Maxillary Rej^ion," p. 8.9. 236 DIGESTIVE SYSTEM. side ; but this contracts them, and occasionally projects them in such a manner, that the horse can exert with them a prehensile power, which is most remarkably evinced at the time that he is picking up grain from a plain surface ; indeed, the act of nibbling our hands with his lips demonstrates this facidty, and also the force with which he can employ it. The lips are lined by the same membrane that lines other parts of the cavity of the mouth. Beneath it are seated numerous mucous follicles that elevate it everywhere into little papilla, which are perforated by the mouths of these follicular glands, as may be readily seen with the naked eye by everting either the superior or the inferior lip. The skin covering the lips is extremely thin, and possesses consider- able vascularity and sensibility. To the tenuity of it, and to the shortness and scantiness of their pilous covering, is to be ascribed the superior sensitive faculty of these parts. Cheeks. The cheeks are constituted substantially of the masseter and buccinator muscles, covered by the skin upon the outside, and the buccal membrane upon the inside. Their internal or membranous surface is studded with scattered mucous follicles, whose excretory orifices may be seen by everting the part. G urns. The gums consist of dense, compact, prominent, polished masses, of the nature of periosteum, adhering so closely and te- naciously to the teeth and the sides of their sockets, that it ren- ders the one inseparable from the other but by extraordinary mechanical force. Like other parts of the cavity of the mouth, they rec^iive a covering from the buccal membrane. Palate. Two distinct parts are included under this head ; the/?cr/'c?and the soft, palate. The hard palate is constituted of the palatine processes of the superior and anterior maxillary bones ; and of a firm, dense, periosteum -like substance, the vaulted, inward part of which is elevated into several semicircular ridges, vulgarly called the bars. The fibies of this substance, which possess great tenacity, are inserted into the pores of the bone in every part, but are most numerous and dense along the palatine suture : the interstices are filled up by a dense cellular tissue, through the substance of which are dispersed the ramifications of the j)alatine vessels and nerves. THB SOFT PALATE, sometimes called the velum palati, is DIGESTIVE SYSTEM. 237 attached to the superior or crescentic border of the hard palate, the border formed by the palatine bones ; from which the velum extends backward and downward as far as the larynx, and there terminates over the epiglottis, in close apposition with that part, in a loose semicircular edge. In consequence of the velum palati being long enough to meet the epiglottis, ihe cavity of the mouth has no communication with that of the nose — these two parts forming a perfect septum between them ; hence it is that a horse cannot respire and vomit by the mouth like a human being, in whom the velum is so short that there is an open space left be- tween it and the epiglottis, through which air or aliment can pass either upward or downward. The soft palate is coniposed of extensions of membrane from the nose and mouth, between which is interposed a pale, thin layer of muscular fibres (described at page 103, under the appellation oW-ircumJiexits palati). The velum performs the office of a valve : it prevents the food in the act of swallowing from passing into the nose, and it con- ducts the air from the windpipe into that cavity, without permit- ting any to escape into the mouth. OF THE TONGUE. The tongue, the principal organ concerned in taste and deglu- tition, is lodged in the mouth ; filling the interspace between the branches of the inferior maxilla. Dup/iciti/. — Like the other organs of sense, it is double; beincr composed of two parts, whose union is marked by a longitudinal crease along its middle, the divisions having no vascular nor nervous connexion, nor in fact any intercommunication whatever: so that an animal has to all intents and purposes two tongues, and apparently for the same reason that he has two eyes, two ears, and two nostrils. Anatomy, as far as we can carry our researches, demonstrates this ; perhaps we have no better proof of it, however, than what happens in hemiplegia, a disease in which only one half of the body is paralytic : under these cir- cumstances, in the human subject, the patient can only see with one eye, use one arm, and taste with but one (and that the cor- respondent) side of the tongue. Division. — The tongue, in description, is commonly divided into 7'oot, body, and apex : by the attachments of the two former it is held in its situation ; the latter is loose and unconnected. Attachment. — At its root, it is deeply and firmly inserted by several muscles which arise chiefly from the os hyoides and the inferior maxilla: it is also connected with the pharynx, and with the soft palate. From the sides of the lower jaw, separate layers 238 DIGESTIVE SYSTEM. of the membrane of the mouth are reflected upon its body, form- ing by their junction a sort of bridle, which is thence extended to the symjihysis : to this part, which serves to restrain the organ in its motions, the name offranum liiigucR has been given. PapillcR. — The dorsum or anterior surface of this organ has a peculiarcovering, which, though it appears to be continued from the buccal membrane, is a different structure altogether, and serves quite a different purpose. The surface of it is roughened, pos- sessing a villous texture, everywhere studded with numerous little conical eminences, called papil/ce, which are supposed to be formed out of the extremities of the nerves, and to be the especial seat of the sense of taste. These papillae vary in size and figure, and are more abundant and larger upon the base and along the sides of the organ. Interspersed with them are a number of mu- cous follicles, whose apertures may be seen with the naked eye, through which a mucus is discharged upon the papillary surface keeping it continually moist, and rendering its perception of taste more acute. Structure. — The tongue is said to possess a covering of com- mon integument; and certainly its strong compact tunic has all the appearances of skin, and presents the common tests of it : the external layer is laminated, is bloodless, is insensible ; the inter- nal or substantial part is tough, fibrous, vascular, and sensitive, in fact, is like cutis ; and the intermediate or connecting material is delicate, soft, and reticular, and forms a bed for the lodge- ment of the papillae. The substance of the tongue itself consists of an inter-union, or rather an incorporation of its muscles, the fibres of which intersect one another, and take a variety of direc- tions ; but intermixed with them is a fine adipose tissue to which is owing the flabby softness of the organ, and the peculiar aspect it exhibits when cut into. Use. — Though the tongue is emphatically denominated, from its essential character, the organ of taste, it is not the only part that possesses this faculty ; for the palate, the pharynx, and the esophagus, it is believed, participate in it. The tongue, in addi- tion to possessing this faculty, disposes of the food during man- ducation, and, when sufficiently masticated, collects and thrusts it, portion after portion, into the pharynx : and furthermore, at the time the animal is drinking, it is not only employed as an instrument of suction, but also as a canal along which the fluid ascends into the pharynx. Organization. — Every part of this organ is plentifully supplied with blood. Its arteries are the lingual, branches of large size from the external carotids. The bloodvessels of either side are generally found free from anastomosis with one another: if cither DIGESTIVE SYSTEM. 239 of the arterial trunks is filled with injection, it rarely happens that the opposite half of the organ receives any colouring from it. Its nerves are the ninth pair, which run to the muscles, and a con- siderable branch from the fifth pair, in whose extreme ramifica- tions, which are distributed to the papillae, the perception of taste is supposed to be inherent. OF THE SALIVARY GLANDS. Number and Names. — The salivary glands, properly so called, are six in number, three upon each side of the head ; — the parotid, the submaxillary, and the sublingual. THE PAROTID, the largest of these glands, so called from being placed near the ear, lies within a hollow space at the upper and back part of the head, bounded by the branch of the lower jaw before, and the petrous portion of the temporal bone behind: it extends as high up as the root of the ear, and as low down as the angle of the jaw, by which latter a small portion of it is con- cealed. This gland, like the others of the same class, is enveloped in a case of dense cellular membrane, and is constituted, in struc- ture, of many little lobes or lobuli, connected together by pro- cesses transmitted into the interior from this cellular covering. Every lobulus is composed of a distinct set of secretory vessels, from which numerous tubitli arise, conjoin, and at length form one main branch ; these branches, which correspond in number to the lobuli, unite and re-unite until they end in one common excretory duct. The duct emerges from the inferior part of the gland, runs along the inner part of the angle of the jaw, and crosses over the posterior edge of the bone immediately above or behind the submaxillary artery and vein : in the remainder of its course it corresponds to the border of the masseter, and, about opposite to the second anterior molar tooth, pierces obliquely the buccinator, and terminates by a tubercular eminence upon the internal surface of the buccal membrane*. THE SUBMAXILLARY GLAND, of smaller volume than the parotid, lies in the space between the angles of the jaw, to which, and to the muscles thereabouts, it is loosely attached by cellular membrane: a portion of it is also generally found pro- * To expose this duct, at or near its issue from the gland, an incision should be carried along the posterior border of the branch of the lower jaw : iirst, dividing the skin ; secondly, the panniculus ; thirdly, the cellular tissue immediately covering the duct, which is readily distinguished by its glistening pellucid aspect. By extending the incision around the angle of the jaw, directing it towards the inner edge of the bone, the duct will be found making its first turn : here, however, it is lodged in a huUow, deeply buried in cellular tissue. 240 DIGE>TIVE SYSTEINI. ceding backward as far as the trachea. It structure is similar to that of the parotid gland. The submaxillary duct issues near the centre of the gland, creeps along the under and inner border of the tongue, close to the lower edge of the sublingual <,land, and terminates by a little mammiform elongation of membiane, vul- garly called the barb (barbillon) or pap, upon the frsenum linguae, about half-an-inch above its attachment to the symphysis. Among the other ridiculous and mischievous practices of farriers is that of snipping off these processes. They were seemingly designed as valves, to prevent the insinuation of alimentary matters into the ducts. The coats of this vessel are extremely thin and translu- cent. THE SUBLINGUAL GLAND is still smaller in volume than the submaxillary, though, altogether, one much resembles the other in figure. It lies along the under part of the tongue, covered by the buccal membrane, where, from the lobular unevenness it gives to the surface, its situation is well marked. Its ducts penetrate the membrane by the side of the fraenum linguae. The use of the salivary glands is to secrete a saline limpid fluid, called saliva; which is conveyed and poured by their ducts into the mouth during manducation : here it is mixed with the food, mollifying it and rendering it more easy of digestion, and at the same time facilitating the passage of the alimentary bolus into the stomach. OF THE PHARYNX. The pharynx is a funnel-shaped sac, lodged in the throat for the reception of the food. Situation. — The pharynx is contiguous to the guttural pouches, superiorly ; the larynx, inferiorly ; and the anterior portions of the parotid glands and branches of the jaw, laterally. Posteriorly, it is continuous in substance with the esophagus: anterioily, it presents an opening to the mouth. Attachment. — In front, to the os hyoides and palate bones ; below, to the larynx ; behind, it grows narrow and ends in the esophagus. Structure. — The pharynx is in part muscular and in part mem- branous. Of the muscles belonging to it (described at page 100) the constrictors are those that more immediately enter into its composition. They are so disposed as to give the membrane forming the sac a complete fleshy covering, which is rendered the more uniform by their proximate fibres being indistinguish- ably blended : thus the muscles form the most substantial part of the pharynx. The lining membrane, which is of the mucous class, is soft and thick in substance, and palely tinged with red DIGESTIVE SYSTEM. 241 in colour, and is papillary and in places rugose upon its surface; being perforated by the ducts of numerous follicles which dis- charge a mucus that preserves glibness and moisture to its interior. The membrane itself is (where it meets them) con- tinuous both with the buccal membrane and that which lines the esophagus. Although the pharynx is designed for the reception of the food, it does not open directly into the mouth: the two cavities are separated from each other by the soft palate and epiglottis. Except in the act of swallowing and coughing, they have no com- munication : in the former case, the velum is pressed upward by the food against the posterior openings of the nose ; in the latter, the larynx is depressed by a convulsive action of the muscles in the vicinity. Into the cavity above the velum there are four openings — two of the chambers of the nose, one of the larynx, and one of the esophagus : the eustachian tubes do not open into the pharynx ; they end in two large membranous pouches at the upper part of the fauces. The opening leading into the esophagus is constantly closed, except when alimentary matters are passing to or from the stomach ; so that air received into the pharynx through the nose can pass nowhere else but into the windpipe ; but if food be returned from the stomach, it will be regurgitated into the nose; at least, only that portion of it which enlers the pharynx at the moment that the larynx is depressed in the act of vomiting, can be thrown into the mouth : in the same way that air is in the act of coughing. OF THE ESOPHAGUS. The esophagus, or gullet, is the tube through which the food is conducted from the pharynx into the stomach. Course. — It has its beginning from the pharynx, and is there placed at the upper and back part of the larynx, taking the first part of its course above and behind the trachea, between that tube and the cervical vertebrae. Having proceeded a short way down, it inclines to the left, and soon after makes its appearance altogether on the left side of the trachea, and continues so placed during the remainder of its passage down the neck : this explains why we look for the bolus during the act of swallowing on the left, and not on the right side of the animal. In company with the trachea, the esophagus enters the thorax between the first two ribs, at which place, running above that tube, it quits its com- panion for the superior mediastinum, which cavity it traverses below and a little to the right of the posterior aorta. Imme- diately beneath the decussation of the crura, the esophagus 1 i 242 DIGESTIVE SYSTEM. pierces the substance of the diaphragm, and enters the stomach, at a rio ht angle, about the centre of its upper and anterior part. Structure. — The esophagus presents, externally, a strong, red, muscular coat ; internally, one remarkable for its whiteness, which in its nature is cuticular. The muscular coat is com- posed of two orders of fibres — a longitudinal, forming an out- ward layer; and a circular, an inward layer: the former will shorten the tube, and perhaps dilate it for the reception of food ; the latter, by successive contractions of the canal, will transmit the food into the stomach. The second, or internal coat, is called the cuticular, from its analogy to the cuticle of the skin. Although it is continuous with the membrane of the pharynx, it is of a totally different composition : it is thinner, but it is much more compact and stronger in its texture, and, I believe, is both insensible and inorganic. It adheres to the muscular covering by a fine cellular tissue, the extensibility of which gives full play to the latter; and admits, during the empty or collapsed state of the tube, of the former being thrown into many longitudinal pUccs or folds ; as is demonstrated by making a transverse section of the tube : such appearances result from the contraction of the one coat, and the want of proportionate elasticity in the other. Between the two tunics, embedded amongst the connecting cel- lular tissue, are numerous follicular glands, whose office is to pour forth a mucous secretion upon the internal surface of tlie lining membrane to render the passage of food along it glib and free from any friction. OF THE ABDOMEN. In consequence of the organs next to be described being con- tained in the cavity of the abdomen, it will be necessary to ex- amine this cavity, in order to understand their relative situation and connexion. The abdomen, or belli/, is formed principally of soft parts; which parts consist, in the main, of the four pairs of abdominal muscles (described at page 124) : at least, they constitute its broad superficies below and laterally. Its anterior part (where the most important viscera are situated, viz. the stomach and liver) is bounded at the sides by the false ribs, and in front by the diaphragm; its posterior compartment (containing the organs of generation), by the pelvis ; its superior, by the dorsal and lumbar vertebrae, and muscles belonging to the loins. Seeing that the contained organs lie altogether in this cavity, which is one of capacious dimensions and without any natural division in it, anatomists have found it necessary (in order to DRiESTIVE SYSTEM. 243 render their descriptions definitive) to divide the cavity artificially ; and they have done this by drawing certain imaginary lines over its superficies^ which are supposed, by means of imaginary planes let down perpendicularly from them, to intersect or partition the cavity into so many compartments, to which the name of regions has been assigned. The primary and grand division of the abdomen is into three regions — the anterior, or epigastric; the middle, or umbilical; and the posterior, or hypogastric. TsiE EPIGASTRIC REGION is the space comprehended be- tween the ensiform cartilage and an imaginary line drawn across the abdomen, posteriorly to the cartilages of the false ribs: it is subdivided into three others — the scrobiculus cordis, the space included between the ribs; and the right and left hypochondria, the lateral cavities or boundaries of it. The umbilical region extends in breadth from the linejust mentioned to another drawn across from one anterior spinous pro- cess of the ileum to the other: it is equally subdivided into three others by tranverse lines, the middle of which retains the name of umbilical region, while the lateral are called the lumbar regions. The hypogastric region extends over the remainder of the belly- It is also subdivided into three: the part included between the spinous processes of the ilea and the pubes receives the name of regio pubis ; the lateral subdivisions, of iliac regions. The abdominal viscera of the horse differ from those of the human subject chiefly in the shape and comparative size of the stomach and the colon : their general relative situation and con- nexion we shall find to be much the same in both. Having opened the cavity of the abdomen, by making a crucial incision through its muscular parietes, we perceive that its inte- rior, and the viscera lying within it, present an uniform glisten- ing surface; are smooth, polished, humid, and slippery to the feel ; and are bedewed with a limpid exudation : all which arises from their possessing a general investing membrane of the same (serous) class as the pleura, and which appeaijs, in most respects, to perform similar uses. To this part the name of peritoneum has been given. Peritoneum. The peritoneum is the membrane, then, that lines the cavity of the abdomen, and is reflected upon the contained viscera. When I introduce my hand into the belly, cvciy surface I apply it to being covered by peritoneum, 1 am not, in truth, able to actually 2M DIGESTIVE SVSTExM. touch any of the viscera within it : this, we know, is precisely the same case in regard to the pleura. Texture.— Tho, texture of this membrane also is like that of the pleura. Strip it off from any part, and it will prove rough and shaggy, exteriorly, from the presence of numerous little floc- culent adhesions: and this shews tlie nature of its attachment to the several parts it invests; viz. by cellular tissue. But its inte- rior surface is everywhere smooth, glib, and humid ; and this is assignable to two causes — to the uniformity and compactness of its texture, and to the exhaktion of a serous vapour, which after death becomes condensed, and which we always find more or less of, in the liquid state, between the different viscera. The peritoneum appears to be composed of condensed cellular mem- brane, interwoven with numerous bloodvessels, some nerves, and many absorbents. It is extremely elastic, whereby it accommo- dates itself, without corrugation, to the perpetually varying ca- pacity of the cavity, as well as the frequent change of volume and relative situation of many of the viscera : indeed, at certain times, it must admit of very considerable extension ; e. g. in the mare during gestation, and in ascites. Ligaments. — What are called the ligaments of the peritoneum, are certain parts which in the foetus were vessels of importance, but which in the adult degenerate into impervious chords, and for this reason have their name altered. The anterior ligament or ligamentum rotundum (originally the umbilical vein) runs be- tween the peritoneum and abdominal muscles, from the umbilicus, or navel, to the liver. The two posterior ligaments (consisting of what once were the umbilical arteries and the urachus) pass in the same manner from the navel to the bladder ; the former tra- versing its sides to join the iliac arteries, the latter entering the substance of the bladder at the very apex of its fundus. In the young animal it generally happens that these vessels are per- vious for a considerable distance ; but then their caliber is ex- ceedingly reduced in size, their coats being proportionately thickened. Use. — The principal use of the peritoneum is to secrete a se- rous fluid — a fluid that exists in a vaporous state during life, for the lubrication of every part of the membrane ; in consequence of which those viscera that are continually moving within the belly glide over one another not only without friction, but with- out exciting the least consciousness of their motions on the part of the animal himself. In addition to this, the peritoneum fur- nishes most of the viscera with a complete external tunic, and tliereby adds strength and firmness to their several textures ; it attaches, and supports, and confines those viscera (within cer- DIGESTIVE SYSTEM. 245 tain limits) in their respective places; and it strengthens the abdominal cavity altogether by its uninterrupted extension every u'here through and around it. Of the Situation of the Viscera of the Abdomen. When the cavity of the belly is laid open, the large intestines present themselves first to view ; consequently they are placed undermost when the animal is standing, and are lying imme- diately in contact with the abdominal muscles. About the middle of the cavity, the apex of the coecum is seen protruding from the body of the intestine of that name, which is extended to the right side, encircled by the colon. Generally speaking, the small in- testines are not seen on first reflecting the muscular flaps : this, however, will depend on the state of the large ; for if they are flaccid some of the small guts will insinuate themselves between the coecum and colon : should we not see them, however, in the first instance, they may at once be brought into view by turning the coecum to the right side. The STOMACH is principally lodged in the left hypochondriac region, though a part of it extends into the epigastric, and there crosses the spine. Its anterior or convex part lies against the diaphragm and the false ribs of the left side ; its posterior or concave part is concealed by the intestines ; its lower surface is invested by omentum ; its left extremity has the spleen attached to it, which viscus also extends along its great curvature; and its right end is in contact with the left and middle lobes of the liver. Prior to proceeding to the situation and course of the intestines, it becomes necessary to anticipate a little in our descriptions, by observing here, that anatomists have divided these viscera into small and large ; and that the former, beginning from the sto- mach, comprehend three subdivisions — the duodenum, jejunum, and ileum; the latter, commencing from the termination of tlu; small, likewise three — the cacum, colon, and rectum. The duodenum takes its beginning from the right extre- mity of the stomach, and soon after forms a curvature around the head of the pancreas; having the liver above, and the great arch of the colon below it. Havmg reached the concave part of the liver, it makes a sudden turn backward and to the right, and be- comes attached to the right kidney ; lastly, it crosses the spine, between the roots of the mesentery and mesocolon, to the left side, where it takes the name of jejimum. This gut, during its course, is so closely bound down by peritoneum, that its motions must prove excccduig limited ; so that it will always bear pretty 246 DIGESTIVE SYSTEM. nearly the same relative situation in regard to those viscera whose motions, like its own, are confined — the stomach, the liver, and the kidney. The jejunum and ileum (two intestines that do not es- sentially differ from each other, except that the latter is one- fifth longer than the former) constitute together numerous con- volutions, which are lodged principally in the umbilical region, where they are encircled and in part concealed by the colon. They are but loosely connected to the spine by peritoneum ; so that (unlike the duodenum whose attachments are so short) they can move in various directions and to a considerable extent : a circumstance, of course, that will materially affect their rela- tive situation. The ileum, towards the right side of the cavity, terminates in a part of the large intestines, which, from its continuity with the colon, to which and to the ccecum it appears to give origin, has been denominated the ccecum caput coli, or blind head of the colon. From this part proceeds downward the body of the ca'',cuM, and this accounts for its apex protruding in the manner already described, amid the convolutions of the colon. The colon, taking its origin from the same part as the ccecum, at first passes downward, and encircles the body of the ccecum, running both before and behind that gut: next, it re- flects upon itself, and makes a second turn like the first; so that this part, which may be called its great arch, is double. That portion of the second flexure of the intestine which forms the upper and anterior part of the arch, and which fills up the bot- tom of the space between the cartilages of the false ribs, is of very considerable volume; in its course, however, to the left side of the spine, it becomes again contracted, and is there attached to the spleen, with which it now runs in contact. Under the left kidney it makes a sudden curve backward, and becomes reflected upon itself somewhat like the letter S : from which peculiarity of figure this part is called the sigmoid flexure of the colon, ft is worthy of remark here, that, although the colon and ccecum are intestines that possess considerable motion, they are so united that they cannot alter their places materially in regard to each other : it may be added also, that they will in- variably occupy the lowermost parts of the abdominal cavity. Rectum. — As soon as the colon has reached the basis of the sacrum, it ends, and the intestine assumes the name of rectum : the remaining portion of gut, however, though so called, is not perfectly straight, but follows the bend of that bone. It termi- nates by an enlarged extremity in the anus. The omentum (the intestines being drawn to one side) is DIGESTIVE SYSTEM. 247 now brought into view, investing the lower part of the stomach ; to the great curvature of which, and to that portion of colon which crosses the spine to form the sigmoid flexure (its last turn), it is attached. In the horse, the omentum is small, and seldom contains much adipose matter. It consists of four layers of peritoneum : two derived from the stomach, and two from the colon; which are disposed in a manner that will be pointed out when the reflection of that membrane is considered. Mesentery. — The small intestines are loosely connected to the spine by a duplicature of peritoneum, called the mesentery; the colon is attached in like manner to the bone by a production of the sajne membrane, named the mesocolon ; and the rectum is confined in its place by a similar reflection, by some described as the MESORECTUM. The LIVER is, in major part, situated in the right hypochon- driac region, though some part of it Ues in the epigastric, and a small portion extends between the stomach and diaphragm into .the left hypochondriac region. This viscus is confined in its situation by means of, what are named, its ligaments; which, with the exception of one, are nothing more than productions of peritoneum. The one attaching the right lobe to the diaphragm, is called the rig/it ligament ; a similar one connecting the left to it, the left ligament ; between the diaphragm and its middle lobe, we find the suspensory ligament; and immediately above that, surrounding the posterior vena cava, the coronary ligament : lastly, within the folds of the suspensory ligament are the re- mains of the umbilical vein, to which the name of round ligament has been given. The large lobe of this gland is concealed by the great arch of the colon ; its left and middle lobes are in con- tact with the stomach, and its right with the duodenum and upper margin of the right kidney : to all of which it has peritoneal attachments. The spleen is situated in the left hypochondriac region, lying there within the concavities of the false ribs, with the hindermost cartilages of which its margin lineally corresponds ; so that if the abdomen were pierced from the left side posteriorly to the last rib, this organ would escape injury. It is attached to the left half of the great curvature of the stomach ; but the chief bulk of it lies behind and rather above the stomach. Its an- terior end lies in contact with the left lobe of the liver : its posterior is connected to the left kidney, and concealed by the convolutions of the colon. Pancreas. — The most ready way to get a view of the pancreas is to tear through the omentum. It lies across the spine, within the epigastric region, underneath the crura of the 248 DIGESTIVE SYSTEiM. diaphragm, immediately behind and a little above the small cur- vature of the stomach. Its head is surrounded by the duodenum, with which, and with the stomach and colon, it is chiefly con- nected ; and its body, which is pierced by the vena portse, has one attachment to the spleen, another to the left kidney. Of the Hejiection of the Peritoneum. In order that the various connexions and relations of the peritoneum may be perfectly understood, it is usual, at this time, to trace (what the Schools call) its rejiectioiis ; by which is meant, to show the way in which it lines the cavity, and after- wards invests the different viscera contained in it. The peri- toneum, though a perfect sac, taken as a whole, is not, as far as regards the cavity of the belly, a circumscribed bag ; at least, it is not in the male, subsequent to the descent of the testicles ; for those organs in their passage carry down a portion of the mem- brane into the scrotum, whereby the cavity of the tunicae va- ginalis (in which the testicle is contained) becomes continuous with that of the abdomen ; and ever afterwards the two have free communication, so that water or air will readily pass from the one to the other : notwithstanding this, however, the integrity of the peritoneum itself remains still unimpaired. In consequence, therefore, of the membrane being continuous at all points, it possessing, the same as a bag without an opening, neither be- ginning nor ending, it imports but little from what part of it description is commenced. We may begin at the inferior part, where it gives a lining to the abdominal muscles, passing from them over the pubes upon the fundus of the bladder, from which it is extended on either side to the parietes of the pelvis, which extensions are called the vesical ligaments. From the fundus it continues round upon the superior surface of the bladder, as far backward as its cervix : at the same time ascending to inclose the rectum and attach it to the sacrum ; thus forming the meso- rectum. From the sacrum it advances upon the lumbar ver- tebrse, which it soon after quits to invest the colon, and after- wards returns to the spine, in this manner forming the meso- colon. It descends from the spine a second time, to invest the whole mass of small intestines (and also the arch of the colon) ; and having done so, returns again, and thus forms the mesentery ; at least one layer of it, the other coming up to meet this from off the surface of the pancreas. Having reached the spine, these two layers unite by adhesion, and become reflected together in a direction downward, and afterwards backward, spreading under the bowels for some short way posteriorly, and then doubling DIGESTIVE SYSTEM. 249 over upon themselves and turning back and advancing again, and running to the stomach, giving that a covering: in this manner the loose floating production of peritoneum denominated the ometitum, is formed; which consequently consists of four layers of peritoneum. From the stomach the membrane spreads right and left : the left invests the spleen ; the right passes to the liver, and having given the gland a complete coverino-, is continued upon the posterior surface of the diaphragm : the several portions of peritoneum connecting the one to the other, forming the ligaments of the liver. The part of the membrane which comes off" from the posterior parts of the liver extends from it to the duodenum, and from that to the pancreas, to go to form the anterior layer of the mesentery. The kidneys and the pancreas cannot be said to receive peritoneal coverings ; inas- much as the membrane simply passes over their unattached surfaces. OF THE STOMACH. The stomach is a pouch or bag, formed for the reception of the food as it passes through the esophagus. Importance. — It is an organ of singular importance in the body ; and the strongest proof, probably, we have of its being so, is the universality of its existence in animals, from the highest to the lowest amongst them : this is not the case with the brain, much less with the heart ; and it was this circumstance that led Mr. Hunter to regard the presence of a stomach as the chief characteristic between animals and vegetables. The stomach has been emphatically denominated the organ of digestion: be- cause within it, the aliment transmitted by the esophagus in a crude state, undergoes its primary and principal change in a process the object of which is to convert it into material for the support of the body. Situation, Position, and Plenitude. — The stomach is situated principally in the left hypochondrium, which it nearly fills, ex- tending more or less into the epigastrium, according to its state of plenitude. Its anterior part lies in contact with the liver ; its left extremity is opposed to the diaphragm and spleen, and it lies in part upon the small, but mainly upon the large intestines. It is evident that the full and empty conditions of the stomach must affect its position in relation to the neighbouring viscera, and that the motions of the diaphragm will alter its situation ; for during the recess of that muscle, it must be pushed more or less into the umbilical region. On the other hand, the action of the diaphragm will be impeded by distention of the abdominal viscera, and more particularly by fulness of the stomach : in- K k 250 DIGESTIVE SYSTEM. creased pressure must counteract its efforts to recede, and the thorax, under these circumstances, must have recourse to other inspiratory agents — the intercostal muscles, and those passing from the ribs to the fore extremities. This accounts for the in- aptitude of horses recently fed to undergo violent exertion, and the increased embarrassment in respiration that hard work then occasions — why they should be sooner blown, and why they will, if pressed, absolutely sink from premature exhaustion : hence the practice of keeping hunters short of water, and of feeding them unusually early, and on corn only, on the morning of hunting. Form. — The stomach has been not inaptly likened to the air- bag of a set of bag-pipes : I should probably fail in conveying so good an idea of its shape by any other resemblance. Division. — For the convenience of description, it has been divided into several parts : e. g. an upper and an under surf ace ; a left or large extremity, which is fornjed into a large blind pouch or cul-de-sac, called its fundus ; and a right or small end, which opens with a bend into the duodenum or first intestine ; a large curvature, to which the spleen is attached ; and a small one, extending between its two openings : the former of these curvatures, in the living animal, is turned upwards and back- wards ; the latter, downwards and forwards. Orijices. — The stomach has two orifces. One, in which the esophagus terminates, is situated about the centre of its anterior part, at the right extremity of the small curvature, and takes the name of cardia : it is constantly closed but when matters are passing into or out of the organ. The otlier is placed at the ter- mination of the right or small extremity, and opens into the duodenum : though it has the power of closing, this one is mostly open. Connexion. — The stomach is fastened in its place by its union with the esophagus and duodenum. It has other connexions, but they are of a peritoneal nature : viz. at its great curvature, it is attached to the spleen and colon by the omentum, at the cardia to the diaphragm by a fold of peritoneum, and near its pyloric end to the liver by an extension of the same membrane. The esophagus, previously to entering the stomach, makes a sudden incurvation downward, by which an angle of such a nature is formed between them at their junction as to have the effect of a valve in preventing any regurgitation of aliment. Volume. — Perhaps no animal, in proportion to its size, has so small a stomach as the horse. Let us only compare it with that of the human subject: the stomach of a middle-sized man (a man weighing twelve stone) will contain more than three quarts of water; whereas that of an ordinary-sized horse, whose body DIGESTIVE SYSTEM. 251 exceeds his in weight and bulk by eight times, will not hold more than three gallons, or four times the quantity of the man's. We are to bear in mind, however, that the stomach, like other hollow muscles, has the power of accommodating itself to the bulk of its contained matters ; so that we are not at liberty to draw conclusions of its comparative volume barely from the state of plentitude in which we may find it. At another time I shall endeavour to shew why Nature has given so small a stomach to the horse ; an animal whose consumption of food we know to be enormous. Structure. — The stomach is composed of four layers of sub- stance, termed coats. The first is that which it derives from the peritoneum, thence called the peritoneal coat : at the greater curvature the layers coming from the omentum disunite and separate, and spread uniformly over both surfaces of the organ. In texture, this coat is the same as the parietal portion of the membrane, and, like that, exhales a serous vapour from its sur- face, to obviate friction between the stomach and those viscera with which it lies in contact. Inwardly, the peritoneal adheres, by a fine dense cellular tissue, to the next tunic. The second or muscular coat, lies immediately underneath the peritoneal. It is composed of two orders of fibres, which may be most plainly seen when the stomach is distended with air, and its peritoneal covering stripped off. The exterior fibres run in a longitudinal direction, and are fewer in number and weaker than the interior, which take a circular course, and are strong and well-marked, particularly about the pyloric extremity, where they appear to be blended with those of the duodenum : from this arrangement of the fibres, the cavity can be diminished in every dimension*. If we slit open the pylorus, we shall find a valvular projection, forming the boundary line, internally, be- tween the stomach and the intestine : this is called the valve of the pylorus; it is made up of a circular production of muscular fibres enveloped within a fold of the internal coat. Though this valve certainly tends to prevent the return of alimentary matter from the intestines, yet do physiologists not regard this as its principal use. They believe that its operation is rather that of * In a case of oedema of the coats of the stomach, I found the muscular coat in a state particularly favourable for demonstration. I could not detect any longitudinal fibres but at the curmttures ; and they were most distinguishable around and in the vicinity of the great curvature. The circular fibres were everywhere very strong and demonstrable — their fasciculi were plainly shewn, in consequence of being separated and ele- vated from the internal tunic by the serous fluid with which the connecting cellular substance had become infiltrated. They were, many of them, nearly as large as crow-quills, and put on a very pale ash-coloured hue. 252 DIGESTIVE SYSTEM. preventing the escape or expulsion from the stomach of any crude or indigested aUment — of solid matters that have not been duly softened and dissolved — into the intestinal canal : I say solid matters, for fluids pass freely through it at all times into the intestines, without detention in the stomach. Actual experiment evinces that they do ; but we may also satisfy our- selves of this fact by contrasting the quantity of water a horse that is thirsty will lake at a single draught with the known capacity of his stomach. Cuticular. — The stomach of the horse-species differs remarkably from that, I believe, of all other quadrupeds, with the exception of the graminivorous moiiogastric, in having a partial cuticula?- lining, that maybe reckoned as a third coat: by turning the viscus inside out, or by slitting it open along its great curvature, this part, so conspicuous for its white and wrinkled surface, will be broadly exposed to view. And now we can trace its well- defined border, forming the boundary line between it and the other internal coat, the course of which is waving or serpentine, something like the figure of an S. This lining extends over the cul-de-sac or left extremity of the stomach, covering not quite one-half of its entire internal surface. We commonly find it thrown into wrinkles, technically termed rugce, which in some are so disposed as to form a sort of net-work ; a condition that is owing to its not being possessed of sufficient elasticity to ac- commodate itself to the varying capacity of the organ. This cuticular substance is of the same nature as the lining of the esophagus, with which, indeed, at the cardia it is continuous. Numerous small openings are visible upon its inner surface, through which issues a mucous fluid, the product of follicular glands underneath, which serves a use in the digestive process. The fourth^ mucous, villous, or other internal coat, extends over that part of the stomach left unoccupied by the cuticular. Its surface is of a yellowish cast, inclining in places to a red. It is soft, fine, and cellular in its texture, and possesses con- siderable vascularity. When closely and attentively examined, it is found to present inwardly numerous little ragged or shaggy processes, which, from their giving it the appearance of velvet, have received the name of villi : hence the epithet, villous. They appear to be composed principally of the minute ramifications of those bloodvessels which we believe to perform the office of the gastric secretion : by some the villi are supposed to have numer- ous minute glands in their composition ; but, in point of fact, we do not know precisely what is their intimate structure*. This * Some persons say that the follicles upon the internal coat are for the purpose of secreting mucus; others, that they prepare the gastric fluid. DIGESTIVE SYSTEM. 253 coat, as well as the cuticular, occasionally exhibits numerous rugse upon its internal surface, which disappear upon extension. 0/gatiization. — For no organ, with the exception of the brain, has Nature made more ample provision to insure a supply of blood than for this. Its arteries are — the superior gastric, which is derived from the posterior aorta, and is distributed to its small curvature, and upper and under surfaces ; the right and /ej't gastric, which branch from the hepatic and splenic arteries, and take their course along its great curvature ; besides numer- ous small ramifications from the trunk of the splenic, called the vasa brevia. Most of these vessels take a tortuous course, and by so doing accommodate themselves to the varying volume of the organ. Their ultimate distribution is to the villous lining, in which they ramify to great minuteness, and exist in such abundance as to render it uniformly red when injected with size and vermilion. The veins, which are somewhat larger in size than the arteries, and have no valves, terminate in the vena portae. The stomach possesses numerous absorbents, and is well supplied with nerves from the eighth pair and sympathetic. OF THE INTESTINES. The intestines are cylindrical tubes of extremely unequal volumes, forming one continued but convoluted canal from the pyloric orifice of the stomach to the anus ; in which, the process of digestion, begun in the stomach, is completed. Situation. — These viscera, taken collectively, cannot be said to be lodged in any particular regions : they are spread over principally the inferior parts of the cavity of the abdomen, im- mediately supported by the abdominal muscles, and are found, one or more of them, in every region of a cavity, of most of which they occupy the greater space. Length. — The intestines of the horse are ninety feet long, or between eight and nine times the length of his body : those of the human subject are about thirty-four feet long, or six times the length of the body*. Every one knows that the stomach does secrete mucus, and a peculiar liquor; but I do not, for my own part, see the sources of this. We see distinct sources in the intestines, but we do not in the stomach ; at least I cannot. — Ahernethi/'s Lectures in the Lancet. * I was at first undetermined in my mind how I should draw this com- parison. I put down the ordinary height of men at 5 feet 8 inches. I then extended a line from the forehead, above the orbital arch, of a middle- sized horse, to the point of the hip, and thence carried it to the ground : this I found to measure II feet. These, with the relative lengths of the 254 DIGESTIVE SYSTEM. Division. — These viscera are divided into the small and large intestines : the latter, as their name impUes, exceed in volume the former. Each of these divisions is subdivided into three parts ; and these have each of them a particular name. I shall take into consideration the general structure of these tubes, in which they all agree, before I proceed to a detail of their differences. General Structure. — An intestine is composed of three coats : the first or external is called the peritoneal ; the second or mid- dle, the muscular ; and the third or internal, the villous or mucous coat. The peritoneal coat is simply a covering continued from the peritoneum itself, which includes the mesenteric vessels and nerves in its way to the intestines, and connects them to the spine, to one another, and to other viscera. It intimately ad- heres by fine cellular membrane to the muscular coat under- neath. It serves to strengthen the tubes ; to furnish a lubri- cating serous perspiration ; and either to restrain their motions within certain limits, or to confine them altogether to their places. The muscular coat, like that of the stomach, is composed of two orders of fibres: — a longitudinal, running immediately un- derneath the peritoneum, and consisting of a few pale scattered fasciculi: and a circular, of which the fibres are placed more inwardly, are stronger, more numerous, and more distinct. By a combination of both their actions, the intestine may be con- tracted in every direction ; for while the former will have a ten- dency to shorten it, the latter order of fibres will operate forcibly in diminishing the caliber of its canal: it is the circular fibres, however, that are principally called on for action ; by their opera- tion the aliment is propelled gradually through them. The villous or mucous coat of the intestines, though in ge- neral appearance it resembles the one of the stomach, differs from it in many essential particulars. It is also of infinitely greater extent, presenting a surface for absorption and secretion, exceeding even that of the common integuments, lis villi {more especially in the small intestines), instead of consisting principally of minute bloodvessels, are crowded with lacteals, which are supposed to take their origin from them by open mouths. And besides the villi, its interior is studded with numerous glandules, intestinal canals, I have taken as the data of my calculation. Whatever objections they may be liable to, we may at least draw this conclusion from them, — that the intestines of a horse exceed in proportionate length those of a man. DIGESTIVE SYSTEM. 255 the size and seats of which vary somewhat in the different in- testines : these secrete a glairy, mucous fluid, which they pour forth upon the surface of the membrane, in order to sheath and defend it from the acrimony or mechanical irritation of the ali- ment (as well as from any supplementary mechanical or chemical irritant), and also to facilitate its passage through them. In the small intestines of the human subject, this coat is collected into numerous transverse folds, called valvule cotinivetites, from their being supposed to have the effect of so many imperfect valves : but in those of the horse no such structure exists, it not being requisite (for reasons I shall hereafter give) either to retard the passage of the aliment here, or to multiply the lacteal apparatus. Having described the appearance and structure of the intestines in general. I shall proceed to point out the peculiarities of them, beginning with the Small Intestines. The small intestines are much smaller and also more uniform in their caliber than the large, and exceed them greatly in length. They are constituted of three parts or subdivisions, named the duodenum, jejunum, and ileum. THE DUODENUM is more capacious than either of the others, especially at its beginning, but in length is much in- ferior to them : its name* is inapplicable in the horse, for it is nearly twice twelve inches long. I have already given its situa- tion, course, and connexions — I have no need therefore to enter again into their detail here ; all I wish to repeat is, that it be- gins at the pylorus of the stomach, and, having crossed the spine, terminates in the jejunum. It not only differs from the others in being larger and shorter, and in being straighter, but in being- redder — more vascular than either of them. It is however at once distinguished from all the other guts, both large and small, by receiving the ducts of two important glands, situated near it, viz. the liver and pancreas : these tubes terminate by one com- mon orifice upon its internal coat, about the distance of six inches from the pylorus. Unlike the jejunum or ileum, the duodenum receives only a partial covering from the peritoneum : the membrane is reflected only upon its inferior and lateral parts ; the superior surface being attached to the liver, kidney, and spine, by cellular tissue only. Its motions are exceeding hmited. * Duodenum. From duodenus, consisting of tweh'e ; so called, because it was not supposed to exceed the breadth of twelve fingers : but as the ancients dissected only animals, this does not hold good in the human sub- ject. — Hooper's Lexicon Medicum. 256 DIGESTIVE SYSTEM. THE JEJUNUM, paler, less in caliber, and much longer than the duodenum, is extremely tortuous in its course, floating about loosely within the cavity together with the convolutions of the ileum : there is, in fact, little or no distinction between these guts, except that the latter, by an arbitrary division, is longer by one-fifth than the former. THE ILEUM is the longest of the small (and indeed of all the) intestines : it forms the greater part of that convoluted tube which lies principally in the umbilical region. Probably it is still less vascular (being somewhat paler) than the jejunum. It is certainly less in caliber towards its posterior extremity ; which ends, rather abruptly, in the beginning of the large intestines. The jejunum and ileum being attached to the spine by that loose doubling of peritoneum, the mesentery, can move about within the cavity, regulating their movements and relative posi- tion according to the volume of the stomach and stage of the digestive process. Organization. — The small intestines are supplied with blood by the aiderior mesenteric artery ', a vessel of large size, that, after having divided and subdivided many times, sends off nu- merous small branches, which ramify to great minuteness between their muscular and villous coats. Their veins, which have no valves, return the blood into the vena portae. The nerves come from the mesenteric plexus. Capacity. — The small intestines altogether will contain about eleven gallons of fluid. Large Intestines. The large intestines are shorter in length, but considerably more bulky in volume, than the small. They also differ re- markably from the latter in their general appearance — in being puckered into numerous plaits or folds. This peculiarity is oc- casioned by some longitudinal muscular bands, which, not being so long as the rest of the intestine, pucker its coats, and contract them into folds : to these bands are appended numberless little, fatty processes, to which anatomrsts have given the name of appendiculcE pingnedinosce. Interiorly, the large intestine is di- vided into many little elliptical pouches, denominated ce//s, with partitions between them ; which, though they appear to answer similar purposes as the valvulae conniventes of the human intes- tine, viz. the retardation of the passage of the contents and the augmentation of the surface for absorption, differ essentially from them in being constituted of all the coats of the gut. In other respects, the structure of the large and small guts is not materially diff'erent. DIGESTIVE SYSTEM. 257 Subdivision. — The large intestines, like the small, are three in number, viz. the cotcum, colou^ and rectum: they do not, how- ever, bear the same degree of resemblance, one to another, as the divisions of the small. THE CGECUM or blind gut, the first subdivision of the laige intestines, originates in a bulky capacious head or receptacle, called the cacarn caput coli, or blind head of the colon, from which it extends downward, and terminates in a blind extremity or cul-de-sac : from this part, in the human subject, proceeds a slender elongation of gut, about the size of a quill, denominated the appendix vermiformis. Before we proceed further in the description of the coecum, it is proper to notice the manner in which the small are united to the large intestines. The termi- nation of the ileum projects for some way into the caput coli, and does so at right angles both with it and with the coecum, so that the contents, having once passed the ileum, are not likely to return : independently of this preventive contrivance, however, there is a valve at this part very like that at the pylorus. This valve, the valvu/a coli, is formed of a doubling of the internal coat, within which is folded a circular band of muscular fibres; and in its shape resembles a half-moon, so that it is not equally prominent at every part : its office is that of permitting certain alimentary matters and all fluids to pass from the ileum, but to oppose their return. Peculiarities. — The coecum differs from all the other guts, in liaving but one opening into it; consequently all matters that have once entered it, must re-ascend into the caput coli in order to continue their route. The exterior parts are braced by three longitudinal bands, and puckered by them into three sets of cells internally ; these cells, which are abundantly supplied with bloodvessels and absorbents, extend the surfaces for absorption and secretion, at the same time that they prolong the stay of the contained matters. The contents of this gut after death are generally found to be fluid : it would appear, indeed, to be the proper receptacle for fluids ; for if we give a horse water to drink, the greater part of it will flow at once through the sto- mach and small guts, and collect within the coecum. Capacity. — It will hold about four gallons of fluid. THE COLON in the horse is a gut of enormous size, being the most capacious and longest of the large intestines. Capacity. — It will contain about tvvelve gallons of water, a greater quantity than the small intestines will hold, put them all together. Form and Course. — This is an intestine possessing a pecu- liarity of figure as well as course. It begins at the ccecum caput l1 258 DIGESTIVE SYSTEM. coli — that voluminous dilatation of gut between the termination of the ileum and mouth of the coecum — and soon expands into a cavity of greater dimensions than even that of the stomach it- self; having attained which prodigious bulk, it begins to con- tract, and continues to do so gradually during its course around the ccecum, until it has completed its second flexure, where it grows so small, that it scarcely exceeds in caliber one of the small intestines ; and though from about the middle of this turn it again swells out by degrees, it never afterwards acquires its for- mer capaciousness : indeed, previously to its junction with the rectum, it once more diminishes, and finally assumes the caliber and general appearance of that gut. Its first flexure has three longitudinal bands, which give it a plicated appearance exter- nally, like the coecum, and form it into very many deep and ca- pacious cells within : its last turn, however, has but two, and the cells in it are not only less numerous, but are much shallower as we approach the rectum. This fact tends much to strengthen our opinion of the uses of these cells : for in this part of the ali- mentary canal the matters being feculent, no farther absorption is required to be made from them ; therefore, of course, they need not be longer detained. Not only, however, are the cells fewer and less distinct at this part, but their supply of blood is diminished ; so that the intestinal secretion (which it is believed contributes to the completion of the digestive process) is here probably wanting altogether, or but very sparingly produced. RECTUM. — At the upper part of the circumferent margin of the pelvis, the colon terminates in the rectum. In the iiorse, this is a comparatively short gut, being continued in nearly a straight line to the anus. Capacity. — It will hold about three gallons of fluid. Peculiarities. — The rectum, independently of its general figure and dimensions, differs from the coecum and colon in possessing but a partial peritoneal covering, and in having no muscular bands, nor cells. Its posterior extremity, more capacious than the ante- rior part of it, is furnished with a circular muscle — the sphincter ani : which, with the adipose matter in which it is cushioned, forms and gives that prominence to the anus so remarkable in the living animal. The use of the sphincter is, by keeping the anus closed, to retain the feculent matter until so much of it be accu- mulated in the rectum as to excite a desire to discharge it. So that the sphincter is a muscle that is in constant action, other- wise the faeces would be continually escaping, and so far it acts in- voluntarily ; but in order to expel them, the animal has recourse to a voluntary power — to abdominal compression, exerted prin- cipally by the internal oblique and transverse muscles ; whose DIGESTIVE SYSTEM. 259 operation is aided by the muscular coat of the intestine itself, which, for that purpose, is possessed of stronger fibres than the others. Organization. — The large intestines receive their supply of biood from a vessel of less size than the one going to the small ; viz. i\\Q posterior mesenteric artery. It is a branch from the pos- terior aorta ; and its distribution is similar to that of the anterior mesenteric. The veins end in the vena portae, and possess no valves. The nerves belonging to these intestines issue from the mesenteric plexus. OF THE LIVER. The liver is the largest gland in the body : it performs the function of secreting bile. Situation and Connexion. — Already given at page 247. Figure. — Its figure varies somewhat, but not a vast deal, in different domestic animals: it is convex upon its anterior sur- face ; concave upon its posterior; is thick in substance about its middle parts ; but in general declines to attenuated edges around its circumference. It is cleft in various places. These clefts are deeper, and the edges are thinner, in general, in quadrupeds than in the human body. Colour. — A reddish brown : its hue will vary according to the quantity of blood there may be in the gland. Division. — By its clefts or Jissures, the liver is divided into what are called its lobes ; of which division there is a great va- riety in the different species of quadrupeds. In the horse the gland is constituted of two principal lobes, right and left, united by a middle or intervening portion, and two lobuli, or small or accessory lobes. Lobes. — The right, the larger of the two principal lobes, is situated entirely within the right hypochondrium. Proceeding from Its obtuse border, along its concave part, is seen one of the lobules — the lobulus caudatus — which is nothing more than a sort of triangular portion of liver included within the fold of the right ligament. The other lobule possessing a circular border with several clefts or fissures through it, whence it may be de- nominated the lobulus scissatus, issues from the anterior and under part of the middle portion. The left lobe, nearly equal in size to the right, has the general outline of an oval: indeed this figure would be perfect, were it not interrupted by the union of the lobe with the middle portion. Peritoneal Covering. — Every part of the liver (with the excep- tion of the spaces occupied by the coronary ligament and pos- terior vena cava) is so closely invested by peritoneum, that the 260 DIGESTIVE SYSTEM. membrane lias the effect of being a distinct capsule : and (though some have described a covering underneath, as separable from it, which they have named the tunica cellulosa hepatis) anatomists in general do not admit of any other tunic. Arteries. — The liver, like other true glands, is composed of arteries, veins, excretory ducts, nerves, and absorbents, united together by a particular tissue, to express which we have the term, 'parenchijrna. Its artery, the hepatic, a branch of the ab- dominal aorta, is but of small size in proportion to its bulk, and in comparison with others which supply the viscera in the vicinity : e. g. if we contrast the splenic artery with the spleen, or the emulgent with the kidney, and then compare them with the hepatic, and contrast the hepatic with the liver, we shall find that the latter are remarkably disproportionately small. Vena Porta. — In the venous system of the liver we discover a peculiarity, of which no parallel instance is to be found in the animal structure : not only is it furnished with veins that per- form the office of returning blood, but it has others for the pur- pose of conveying blood to it, which are to be regarded in the light of secerning arteries. The trunk they spring from is called the vena porta, a vessel formed out of the union of the splenic and mesenteric veins, which takes place immediately above the pancreas. Its course lies over the duodenum, on the right of the hepatic artery and duct, to the concave part of the liver: about opposite to the middle of the right lobe, it bifurcates; the right division directly enters the gland ; the left continues its course forward, in company with the hepatic artery, and subdivides into two others, which penetrate the middle portion and left lobe of the organ. Their branches spread out in an arborescent man- ner within the substance of the liver, ramify to great minuteness, and at length radiate into a system of capillary tubes, which, from some peculiarities they exhibit in their arrangement, have been named penicilli. The hepatic veins, the vessels that return the blood conveyed hither by the vena porlae and hepatic artery, are in the horse remarkably small, but exceeding numerous : their orifices may be seen, appearing like so many pin-holes, by slitting open the pos- terior vena cava. The hepatic duct, remarkable for the whiteness of its coats, will be found running along the upper and inner edge of the right lobe, and receiving in its course many small ductiform tubes from the interior of the gland : its trunk afterwards accompanies the hepatic artery, to the right of which, and below the vena portae, it continues its passage to the duodenum. This duct is a muscular tube, having a membranous lining ; is large enough to i DIGESTIVE SYSTEM, 2(5 1 admit of the introduction of the little finger; and is about three inches in length. It pierces the coats of the duodenum, six inches distant from the stomach, in conjunction with the pan- creatic duct, but opening by an orifice distinct from the one of that duct : the terminations of both, however, are guarded by the same circular flap, one composed of doublings of the inner and muscular coats of the gut, which performs a valvular function in preventing the intrusion of alimentary matters into these tubes. The nerves of the liver, neither large nor numerous (for it does not appear to possess much sensibility either in health or disease), come principally from the sympathetic; it receives also a few filaments from the par vagum. Its lymphatic vessels, on the other hand, are extremely plentiful and are readily demonstrated : we have nothing more to do than to insert a small injecting pipe under its peritoneal capsule, and allow quicksilver to diffuse itself, and we shall instantly fill very many of them, making a beautiful, vascular, arborescent display upon the surface. Structure. — The hepatic artery having entered the substance of the organ, disperses its ramifications through every part; and they terminate not only in open nutrient points, but in vessels of communication with all the others: at least, if fine injection be thrown in, it will not only pass into the hepatic veins, but also find its way into the branches of the vena portae, and those of the hepatic duct as well. In fact, the researches of anatomy appear to prove, that there is free intercommunication between all these different sets of vessels ; for if either of the others are injected (except the hepatic veins which have valves), the same result is aflbrded. If a piece be torn or broken off the liver, we shall perceive, on close inspection of the lacerated surface, nu- merous little granulary eminences, to which anatomists have given the name of aci/i?: these small bodies, which adhere to- gether by means of a fine cellular web, are composed of the ramifications of some or all of the vessels that have been men- tioned ; but what their intimate structure is, or how or in what manner they are constituted, remains yet to be explained. Again, if we nicely examine the surface of a clean cut into its substance, we shall perceive numerous minute pores, from which a yellowish fluid may be expressed : these are the pori biliarii, the radicles of the hepatic duct, which run in company with the arterial and venous ramifications, repeatedly unite and re-unite, until, at length, they all end in a single tube — the liepatic duct. BILE is a sort of soapy viscid fluid. Its viscidity it derives from gelatine, which a solution of tannin or alcohol will precipi- tate. By the agency of the latter, the gelatinous matter may be 262 DIGESTIVE SYSTEM. separated, leaving what is called a tincture of bile. Gall-stones are found to consist principally of a sort of spermaceti, that has been used for soap to clean cloth with. The colour and notorious bitterness of bile do not seem to be owing to the presence of any thing peculiar ; but rather ascribable to some peculiarity of arrangement of its component parts, which is not understood. For if the tincture of bile is exposed to the air, it becomes white ; or if nitric acid be dropped into it, that will likewise render it white*. OF THE SPLEEN. The spleen or milt is a spongy viscus, of a pyramidal figure, situated in the left hypochondrium, between the stomach and false ribs. Colour. — Its colour is principally owing to the stagnant blood in it. The surface possesses a blue mottled or marble hue, which becomes reddened by exposure to air. It is much darker interiorly — when its contained blood becomes exposed. Volume and Weight. — Though it vacies continually in its volume, depending on the condition of the circulation through it, it seldom or never exceeds three pounds in weight. Form. — The spleen is adapted in shape to the space in which it is lodged ; being concave next the stomach, convex where it is opposed to the ribs. It differs remarkably from the spleen of the human subject in form ; for, instead of being oval in its cir- cumference, and having an obtuse margin, it is elongated after the form of a tapering pyramid, and at length terminates in a point. Capsule. — It receives a complete capsular envelope from the peritoneum, to the close fitting and intimate adhesion of which it chiefly owes its feel of solidity and firmness : for, when strip- ped of this tunic, its texture is discovered to be soft, lacerable, and spongy, and to present all the appearances of glandular arrangement ; and as such any one could not fail to regard it who had not made himself previously acquainted with its intimate structure. Structure. — It differs remarkably, however, from a gland, in not having any excretory duct ; an appendage for which it has no occasion, as it is not believed to perform any secretory function. It is now generally supposed, that the arteries of the spleen, after having spread their branches within its substance into innume- rable ramifications, terminate in cells of a membranous composi- tion, from which veins, about equivalent in number, take their * Aberncthv's Lectures in tlie Lnncct. DIGESTIVE SYSTEM. 263 origin. To elucidate this structure, it has been likened to a piece of sponge, or a honeycomb ; to which, if bloodvessels were superadded, probably the general fabric bears some resemblance. By regarding it as a spongy or porous body, we can account very satisfactorily for the extreme variableness in ti)e magnitude and weight of this organ ; for it is obvious that it will admit of great latitude in its state of distention, and that its volume must greatly depend upon the quantity of blood it may contain. It also pos- sesses nerves, though they are but small; as well as absorbents, which vessels are very numerous, and readily demonstrable by injecting quicksilver under its peritoneal tunic. Oiganizalion. — This viscus receives its blood from the splenic artery, a larae branch of the posterior aorta, which, in running along the great curvature of the stomach, detaches numerous short ramifications both to it and to the spleen. The splenic veins, much larger than the arteries, unite with those of the sto- mach, and form a vessel that largely contributes to the produc- tion of the vena portse. Its nerves come from the coeliac plexus. Importance. — The magnitude and organization of the spleen in the higher order of animals, together with the constancy of its presence, are of themselves forcible arguments to establish its im- portance in the animal constitution, though it would appear, from some facts, not to be equally useful with other abdominal viscera; for, if it be carefully extirpated, the animal will not only survive, but thrive and do well : indeed, in the human subject, it has been found after death so disorganized from disease, as to have been apparently incapable of performing its function during life ; and one case is related in which it was cut out without the indivi- dual experiencing any great inconvenience from its loss. From the resemblance in general appearance and structure be- tween this organ and those that are known to be glandular, very diligent search has been made after an excretory duct: no ves- sel of the kind, however, has yet been demonstrated, though, more than once, have anatomists been led away with the idea that they had discovered traces of one. Seeing, then, that the spleen was without a duct (and, as was observed before, there is no want of one, there being no secretion carried on), physiolo- gists, compelled to relinquish the notion of its being a gland, have attempted to explain its use from what appears to be a faithful description of its structure, connexions, and relative situation. OF THE PANCREAS. The pancreas or sweetbread is a glandular body lying across the spine in the epigastric region. 264 DIGESTIVE SYSTEM. Situation and Connexion — explained at page 247. It possesses no peritoneal covering — that membrane simply passes over its inferior surface. Division. — The pancreas has been divided into Iiead, bodi/, and tail ; it has also a fourth part, attached to the right side of the spine, a prolongation from its head, to which the name of pancreas minoi- has been given. Structure. — Anatomists all agree, that there exists a similarity of structure between this organ and the salivary glands; and what tends to confirm this opinion, is, the resemblance that the pancreatic fluid bears to common saliva. The pancreas is of a pale red speckled colour, and is composed of manv small lobes or rather lobules, which, though they intimately adhere together by a fine cellular tissue, are perfectly distinct from one another in regard to their ultimate organization. For every one of these lobules, or (as some call them) acini, appears to be constituted of a set of arteries, veins, and ducts, which vessels have no com- munication, except through the medium of their trunks, with those of any other ; so that a certain quantity of secretion is prepared within, and discharged from, every one of them singly : in fact, every lobule may be said to be a distinct gland of itself, and this is precisely the case in respect to the salivary glands. In the dissection of an injected pancreas, we may trace many arterial twigs into these acini, which are detached at right angles from the principal pancreatic artery as it pervades the interior of the gland. The veins also may be seen accompanying the ar- teries. The duct, which is the result of two main branches, has a similar mode of ramification. Formed at the extreme end of the gland, by the union of several smaller tubes, it takes its course through the middle of the viscus, receiving in its way other little ductiform vessels which come from the neighbouring lobules, and contribute to augment its size. Thus formed, the long branch issues from the body of the gland, the short and larger one from the head and pancreas minor : the tw^o then form a single trunk, about an inch in length, which extends directly from the spleen to the duodenum, and pierces the latter alongside of the hepatic duct. The tube is composed of a thin, pellucid membrane of considerable strength, and is large enough in its caliber to admit of the introduction of the finger. Organization. — The pancreatic arteries are derived mostly from the hepatic : several, however, come from the splenic, in its course to the left side of the abdomen ; and one or two from the gastric. The veins are tributary to the vena portse. The small nerves dis- covered in it are furnished by the coeliac plexus. 265 Section VI. ABSORBENT SYSTEM. COMPRISING THE ABSORBENTS AND ABSORBENT GLANDS. THE absorbents constitute that system of vessels which are employed in absorbing alimentary and other matters, and convey- ing- them into the general circulation. Division. — These vessels were, when they were first discovered, supposed to exist of different kinds in the body : hence the appel- lations lacleals and lymphatics. It is now, however, ascertained that they exhibit no difference whatever in their anatomy ; and also that, although the lacteals are ordinarily employed in ab- sorbing chyle from the intestinal canal, they are, equally with the lymphatics, capable of taking up other matters. The only natural division they appear susceptible of, is, into sitperjicial and deep-seated absorbents : the former are distributed in great numbers immediately beneath the skin, and perforate it through almost every point ; the latter are commonly found rami- fying in company with the trunks of the bloodvessels, more especially with the veins. Peculiarities. — The absorbents are so minute as to bear no sort of comparison with the bloodvessels, in point of magnitude. To make up for this, however, they are in general vastly more numerous, and have much more frequent anastomosis. They also exhibit peculiar tortuosities in their course, and are every- where beset with valves. Glands. — The absorbent glands are small oval-shaped bodies, varying in magnitude from a pea to a walnut, found in many un- exposed parts of the body along the course of the absorbent ves- sels. Generally speaking, they exhibit a reddish hue : but there are some that assume a dark blue, and even a black complexion. They exist mostly in groups or clusters — rarely solitary. Communication. — The superficial and deep-seated vessels com- municate very frequently with each other, and never fail to send off, in addition, other anastomotic branches to whatever solitary absorbents there may be in the vicinity. The glands, likewise, are linked together by absorbent tubes of inter-communication running from one to the other. Demonstratio)i. — The following different methods of proceeding with a view to demonstrate these minute and ordinarily hardly visible vessels, are extracted from the laborious and accurate re- searches of the late celebrated anatomist, Mr. Cruikshank: — 266 ABSORBENT SYSTEM. In an animal opened alive, some hours after it has been fed, the lacteals are seen turgid with chyle : they may also be made visible by throwing coloured thin fluids into the intestines ; or, by making ligatures on the trunk of the anterior mesenteric artery, which will include the trunk of the absorbents. An eye accus- tomed, readily distinguishes lacteals upon the intestines from arteries and veins, even when they are collapsed and empty : punctures may be made with a lancet, and the vessels injected with quicksilver by means of a tube formed expressly for that purpose. I have sometimes injected lacteals from punctures mades by the sides of veins, where I knew they must be, though they were then invisible to the naked eye. Upon the liver and lungs lymphatics are frequently visible, and maybe injected by puncturing one of the small branches; but the valves almost always make the injecting of them froui the trunk to the branches impracticable. Pressure in the course of the absorbent circulation will commonly force from the extreme branches into the trunks some little reddish or brownish fluid, making the latter visible, which may then be punctured and in- jected. — Watery fluids thrown into the arteries, veins, or ducts of glands, very commonly get into the absorbents, and render them visible. — One of the best methods is to previously inject the arte- ries and veins of the part, and afterwards macerate it for some days : putrefaction then takes place, air is generated in the cel- lular membrane, whence it gets into the orifices of the lymphatics, and uniformly fills their branches. — The best subject for these injections is one whose limbs are without fat and are dropsical, but not too much so. In parts where glands are to be found, it is only necessary to puncture the gland, and introduce a tube filled with quicksilver, or push the pipe into its substance without any previous punc- ture. The mercury thus fills the cells of the gland, and from these the lymphatics. The thoracic duct itself is most suc- cessfully injected in the same way, that is, either from glands upon the mesentery, upon the bodies of the lumbar vertebrse, or those upon the inside of Poupart's ligament. — When vessels are injected, and very much resemble lymphatics, the best me- thod of determining whether they are or are not lymphatics, is to trace them to the nearest lymphatic glands : if they terminate in them in the usual manner, they are lymphatics. No English veterinarian, to my knowledge, has, up to the pre- sent day, been at the pains to demonstrate practically the particular distribution of the absorbing vessels of the horse : we have hi- therto travelled onward analogical/i/, and so, I have a notion, should we continue to do, had not our French professional con- ABSORBENT SYSTEM. 267 temporaries furnished us, as well as themselves, by their praise- worthy exertions in the cause of science, with materials to fill up this lamentable hiatus in veterinary anatomy. Professor Girard, whose " Traitt d'Anatomie Vtterhiaire " does no less credit to the talent and industry of its author than honour to the veteri- nary school over which he presides, has presented us with an article on the ramification of the lymphatics, which I shall trans- late, and take the liberty to transcribe into this place. The Thoracic Duct, The largest, longest, and most remarkable of the lymphatic vessels, in which terminate the majority of the lymphatics of the body, is situated within the thorax, on the right side of the dorsal vertebrae, between the aorta and the vena azygos : it receives the lymphatics from the posterior extremities, pelvis, parietes, and viscera of the abdomen, head, neck, withers, and left anterior extremity. It takes its origin under the loins in a dilatation or sinus, very variable in its form and dimensions, situated at the root of the great mesenteric artery, named the receptaculum chj/li ; it directs its course forward, enters the thoracic cavity by the aortic per- foration through the diaphragm, extends along the bodies of the dorsal vertebrae until it arrives opposite to the base of the heart, where it curves downward to cross over to the left side, in its way to the anterior opening of the thorax, and, as it leaves the spine for this purpose, runs obliquely over the trachea and esophagus ; having reached the left side, it stretches forward to the beginning of the anterior vena cava, and terminates, against the middle of the anterior border of the left first rib, in the base of the left axil- lary vein : not infrequently, it ends in the right axillary ; in some instances, even in the beginning of the anterior cava. At its termination it dilates and forms a sinus, whose mouth, open- ing into the vein, is guarded by a broad valve so disposed as to prevent any reflux of blood into the duct* : it has also a ligament- ous band around it at this part, which confines it to the vein re- ceiving its contents. This canal shews but little uniformity in its cahber : in some places it is strait, in others varicose. And it is not uncommon to find it detaching one and even several branches in its course, large or small, which either remain separate, or else, after running a certain distance, rejoin the main channel. * Notwithstanding this valve, blood often gains admittance into the canal : this is observable in all cases of violent death, or in which struggles and convulsions attend expiration. 268 ABSORBENT SYSTEAl. The Receptaculum Chj/li. This reservoir forms the point of general confluence of all the lymphatics of the posterior limbs and abdomen, and that from which originates the thoracic duct : it is maintained by the aorta on one side, and the vena cava posterior on the other ; and is formed by the union of five or six large lymphatics, of which two or three come from the entrance of the pelvis, two or three others from the mesentery, a single one from the environs of the stomach and liver. The Professor here makes a classification of all the lymphatics of the body into those that proceed to the abdominal and those that run to the thoracic portion of the duct. I. Lymphatics discharging their Contents into the ABDOMINAL PoRTION OF THE ThORACIC DuCT. 1. Lijmphatks of the Posterior Extremities. These are distinguishable into the superficial and deep-seated. The first originate particularly from the skin and subcutaneous cellular tissue. They form divers ramifications which accom- pany the superficial veins ; of which the most remarkable attend the vena saphena major, frequently anastomosing with one ano- tiier, and forming altogether an anastomotic network. All these lymphatics run to the subcutaneous inguinal glands, which are lodged upon the superior and anterior part of the thigh. The deep-seated lymphatics take their rise from the foot, as- cend along with the plantar veins, continue upward among the muscles in company with the deep-seated veins, corresponding in their principal divisions to those vessels, and proceed to the in- guinal glands. All the lymphatics of the posterior limbs assemble at these glands, and here form a plexus, from which several large branches depart and traverse the iliac glands, clinging to the sides of the iliac vessels, and discharge their contents into the pelvic branch, contributing to the receptaculum chyli. 2. Lymphatics of the Pelvis. The vessels coming from this cavity run in part to the inguinal glands and in part to the internal pelvic glands. The superficial Tymphatics about the pubes and the outlet of the pelvis run and join those of the extremity ; those of the perineum and anus enter the cavity, and are accompanied by those coming from the croup and tail, both proceeding to the glands within the interior ABSORBENT SYSTEM. 269 of the pelvis. All the deep-seated lymphatics accompany the veins, make for the pelvic glands, form unions with the others, and run and empty themselves into the main pelvic branch, wherein their lymph mixes with that coming from the inguinal glands. The lymphatics of the urinary and genital organs, included in the pelvic cavity, also traverse the glands lodged therein, and unite with those of the parietes of the pelvis. Those of the scrotum enter the inguinal glands, as also do those belonging to the sheath and penis. The ramifications derived from the tes- ticle and spermatic chord take the course of the veins, and pene- trate one or two of the lumbar glands lodged at the entrance of the pelvis. The lymphatics of the mammae, which are also di- visible into superficial and deep-seated, run to the inguinal glands, and anastomose with the superficial set belonging to the inferior parietes of the abdomen ; but, before they reach these last glands, they pervade those of the mammae. 3. Lymphatics of the Pmietes of the Abdomen. These vessels, in general but little developed, for the most part run to the inguinal glands. The superficial set of the lower parietes accompany the cutaneous (inguinal) vein, anastomose with the lymphatics of the scrotum and mammae, and traverse the glands in the groin : some of them direct their course for- ward along with the cutaneous (external thoracic) vein of the thorax, unite with the superficial lymphatics of that part, and proceed to the axillary glands. The deep-seated vessels of the belly run in company with the epigastric vein, and go to the in- guinal glands, or else they accompany the pectoral vein, and per- vade the glands in front of the thorax. The superficial or subcutaneous lymphatics of the loins join either those of the croup or those of the flanks : the deep-seated, which spring from the peritoneum, muscles, and spinal canal, perforate one of the internal lumbar glands, and pass onward to terminate in the main pelvic branch. Among the lymphatics of the abdominal surface of the dia- phragm, those issuing from the peritoneum and muscular texture make almost all for the main hepatic branch ; some others take the course of the phrenic veins, and form a union with those of the thoracic side of the muscle. 4. Absorbents of the Mesentery. The mesenteric trunks, ordinarily two or three in number, tlie most considerable of which is constantly united to the great me- 270 ABSORBENT SYSTEM. senteric artery, receive all the vessels continued from the mesen- teric glands, as well as those coming from the mesentery and in- testines. The mesenteric absorbents, extremely numerous, are sustained between the layers of the mesentery, where they form a vascular network : many of them issue from the exhalent surface of the mesentery and intestinal tube ; others take their rise from the interior of the intestine, from which they imbibe chyle. All these vessels converge towards the lymphatic reservoir, clinging in their passage around the mesenteric veins ; some, however, taking a solitary course at a greater or less distance from any bloodvessel : having arrived at the root of the mesentery, they pass through one or two, sometimes three, of the mesenteric glands, and after- wards join the principal lumbar lymphatics. The absorbents of the ccecum and ccscum caput coli run to the glands set at inter- vals along the intestinal tube, whence they proceed to the recep- taculum chyli. 5. Lymphatics of the Liver, Stomach, Spleen, and Omentum. The hepatic trunk comprises the lymphatics issuing from the liver, stomach, spleen, and omentum : the branch of the recepta- culum chyli not uncommonly consists of two divisions, and re- ceives, in addition to the above-mentioned vessels, many ramifi- cations from the crura of the diaphragm. The lymphatics of the liver, extremely numerous, are distin- guishable into a superficial and a deep-seated set. The first arise more particularly from the exhalent surface of the organ, creep along upon its peritoneal capsule, and there form a plexus of close and intricate network. Those from the anterior surface make one or two large branches which perforate the diaphragm, enter the thoracic cavity, unite with the lymphatics from the chordi- form tendon, and proceed to the fore part of the thoracic duct ; whilst those of the posterior surface enter the glands placed around the great fissure, where they unite with the deep-seated set. The deep-seated hepatic spring from the parenchyma of the gland, cling around the divisions of the hepatic artery and he- patic veins, issue from the interior of the viscus by the great fissure, run to the glands there, and afterwards proceed along with the superficial to the main hepatic trunk. The lymphatics of the stomach, of which the superficial come from the external surface, the deep-seated from its cavity, follow the veins, and are distinguishable into a superior and an inferior set. The former take the direction of the lesser curvature, per- forate the glands thereabouts, and go to join the absorbents of ABSORBENT SYSTEM. 271 the liver : the latter run over the greater curvature, enter the glands arranged along the fissure of the spleen, form communications with the lymphatics of that viscus and those of the omentum, and depart to contribute to the hepatic trunk. As to the Lynifhatics of the spleen, the superficial, like those of the liver, come from the periphery of the organ and enter into a thick and complicated network : the deep-seated issue from the interior, and contract with the former numerous anastomoses. Along the fissure of the spleen these vessels become united, form large branches which follow the course of the splenic veins, and anastomose with the lymphatics of the great curvature of the stomach : both sets then run to the great fissure of the liver, and there terminate in the hepatic trunk. The lymphatics of the omentum accompany the venous ramifi- cations, and either join those of the great curvature of the sto- mach, or the superficial absorbents coming from the ccecum caput coli. Those around the pylorus anastomose with the pancreatic, and accompany them to the hepatic trunk. The lymphatics of the pancreas also run with the divisions of its veins, and join either those of the liver or those of the spleen : some proceed directly to the common hepatic trunk. Besides these three portions or lymphatic trunks which con- stitute the receptaculum chyli, the abdominal portion of the thoracic duct also receives the lymphatics of the kidneys, and renal capsules. These vessels, distinguished into superficial and deep-seated, perforate the glands placed internally, next to the parts from which they spring, and empty themselves into the superior side of the thoracic duct. II. Ramifications terminating in the Thoracic Portion of the main common Duct. This, the terminating portion of the thoracic duct, receives the lymphatics transmitted from the internal dorsal, bronchial, and cardiac glands, and those either from the left axillary glands, or from the sublingual and guttural glands. In this numerous series we find the lymphatics of the parietes and viscera of the thorax, of the head, neck, and left anterior extremity. I. Lymphatics of the Parietes of the Thorax. The superficial absorbents of the thorax take their rise either from the surface of the skin or else from the subcutaneous mus- cles ; they form several large branches which accompany the thoracic cutaneous vein, unite with the superficial lymphatics 272 ABSORBENT SYSTEM. coming from the anterior parietes of the abdomen, and proceed to the axillary glands. The deep-seated set take divers directions and pass through different sets of glands. The pectoral, which anastomose with ramifications from the abdomen, follow the pectoral vein, and reach one or two glands at the entrance of the chest. The inter- costal spring from the pleura and intercostal muscles, accompany the intercostal veins, pervade the internal dorsal glands, and ter- minate by several branches in the thoracic duct. The lymphatics of the Jieshy part of the diaphragm unite, some with the poste- rior intercostal, others with the pectoral : those coming from the crura run to the dorsal glands, where they anastomose with the intercostal ; those from the chordiform tendon anastomose with .the deep hepatic, run forward between the layers of mediastinum, nearly to the heart, and enter the cardiac glands. 2. Lymphatics of the Thoracic Viscera. The absorbents of the different organs contained within the thorax, traverse one or several of the bronchial or cardiac glands, and afterwards form divers branches which end in the thoracic duct. The pulmonary lymphatics, very numerous, are distin- guished into superficial and deep-seated. The first take their rise from the surface of the lungs, creep along under their enve- loping membrane, and make for one or more of the bronchial glands. The deep set, which originate from the air-cells and from the areolae of the parenchymatous tissue, follow the divisions of the pulmonary veins, run to the root of the bronchial tubes, there unite with the superficial, and perforate one or two of the broncliial glands. The cardiac lymphatics derive their origin, either from the surfaces (both exterior and interior) of the heart, or from the mus- cular substance of the organ : they mount upon the curvature of the posterior aorta, and disappear in the cardiac glands. The lymphatics of the superior part of the mediastinum and of the esophagus join, some the intercostal, others the bronchial : those coming from the anterior part of this membranous parti- tion, from the thymus, trachea, and esophagus, unite either with the pectoral, or else with the cardiac and anterior intercostal. 3. Lymphatics of the Head. The lymphatics of the head form two planes, a superficial and a deep one. The superficial pursue the course of the cutaneous veins, and run in part into the sublingual, in part into the gut- tural glands. The deep vessels, which come from the nostrils, URINARY SYSTEM. '273 fauces, palate, &c., also run to the sublingual and guttural glands, in which they unite with the superficial. From these two groups of glands, through which pass the lytnphatics of the head, depart several large branches, two or three of which descend upon the anterior surface of the trachea ; others follow the passage of the deep and subcutaneous veins, unite with those of the neck, and descend to the front of the thorax. Almost all these vessels ter- mitiate in the thoracic duct ; some lew alone on the right side ending in the riglit axillary trunk. 4. Lymphatics of the Left Fore Extremity. The lymphatics of this member present the same disposition as those of the posterior limbs, and are divided into superficial and deep-seated. The former, consisting of divers ramifications, accompany the superficial veins; the more considerable of them forming a plexus which accompanies the cutaneous (superficial brachial) vein of the limb. The deep vessels originate from the foot, muscles, and bones, pursue the divisions of the deep veins, and plunge into the axillary glands, wherein they unite with the superficial, and whence they all proceed to the thoracic duct. The right terminating Trunk of the Lymphatics. This very short lymphatic canal is obliquely situated at the entrance of the thorax, upon the transverse process of the last vertebra of the neck, extending in a direction from above down- ward and from without inward, and terminating most commonly in the right axillary vein ; though in some instances it joins the thoracic duct, or else ends close by the side of it. — This lesser trunk is formed by the lymphatics coming from the right axil- lary glands, and by some from the right lung, and right side of the neck and trachea. Section VII. URINARY SYSTEM. COMPRISING THR KlDiNEVS, RRNAL CAPSULES, UKETEKS, AND BLADDER. OF THE KIDNEYS. THE kidneys are two ovoid reddish bodies, occupying the lumbar regions of the abdomen, performing the function of the secretion of urine. 274 . URINARY SYSTEM. Relative Situation and Attachment. — In consequence of the kidneys not receiving the same complete covering from the peri- toneum as the abdominal viscera in general*, they have been regarded as extra abdominal organs ; custom, however, appears to be somewhat capricious in this particular, for they are cer- tainly as much within the cavity as the pancreas* (which, no more' than the kidneys, gets but a covering on one side from the peritoneum), and may, anatomically considered, with equal pro- priety, be included among the viscera of the abdomen. Indeed, they cannot be properly examined in situ but from within the abdominal cavity. Herein they are found a little further back- ward than the pancreas, immediately above (or concealed by, as the horse lies upon his back) the small intestines. They repose, one upon either side of the spine, close to the bodies of the lumbar vertebrae, or rather underneath the psose muscles, to which they are firmly attached by a surrounding and enveloping mass of adipose and cellular substance, as well as to the vertebrse themselves. Their anterior ends reach under the last ribs ; posteriorly they come in contact with the cristse of the ilea ; and to both these parts they are tied by cellular tissue. They receive some support from the peritoneum as it passes under them, and are attached by it to the contiguous viscera ; but their strongest connexion is to the spine through the me- dium of their bloodvessels. The right kidney has peritoneal attachments to the right lobe of the liver, and to the head of the pancreas : the left has a similar connexion with the blind pouch of the stomach, from the pressure of which in a state of dis- tention it is pushed a little further backward than the right; the left is also connected with the pancreas and the spleen. Figure. — The figure of the kidney varies remarkably in dif- ferent subjects; nay, the right is commonly unlike the left, is less elongated and broader : in fact, it is a gland that does not appear to possess any very determinate form. Generally speak- ing, it may be said to represent an irregular flattened oval : but it is an imperfect oval ; one side is interrupted by an inlet or deficiency of substance, technically called the notch, into which the bloodvessels are received. Magnitude. — The magnitude of the gland, not less unde- terminable than its form, estimated by its weight, may be stated in round numbers to average about forty ounces. Division. — The kidney may be divided into its upper and under surfaces, its border, and its notch. The under surface, the part covered by peritoneum (underneath which is interposed * Vide " Reflection of Peritoneum," page 249. URINARY SYSTEM. 275 a layer of soft yellow fat), is partially divided into two un- equal lobes by a fissure running directly across from the notch towards the circumference: in many subjects the upper division is in part subdivided by a smaller fissure, which also proceeds transversely from the notch, into two portions : still it is one continuous or conglobate body, which is not the case in bears and in the cat tribe, where these lobes, being perfectly distinct, constitute it a conglomerate gland. The under surface has like- wise a middle transverse fissure, but it is less in extent ; some- times we find two or three others, but small and unworthy of notice. This is the part bedded in adipose matter : the quan- tity of adeps, however, though considerable in very fat subjects, is inferior to what is found in the herbivorous ruminant, in whom it concretes after death into a remarkably white, firm mass, well known by the name of suet. Now, that the gland is inverted, the notch is brought more into view : in some subjects this forms a considerable breach in the body of the gland, in others it makes only a part of the transverse fissure aforementioned : it is designed, like the porta of the liver, to give ingress to the bloodvessels and egress to the duct belonging to the gland. — The border, thick and rounded, narrows and describes the seg- ment of a circle anteriorly ; broadens and extends into a larger arc posteriorly : by adverting to this circumstance, and attending to the distinguishing characters of the surfaces, the kidney of one side may be known from that of the other, although both should have been removed from the body. Capsule. — The kidney has a capsule of its own, every where adherent to its surfaces through the intervention of a very deli- cate cellular tissue, which tissue may be traced in places into the glandular substance itself: at the notch also processes leave the capsule to accompany the renal vessels and nerves throughout their ramification, and serve at once as an additional tunic to them, and a suitable connecting medium between them and other parts. Structure. — The interior substance of the kidney is most broadly exposed to view by carrying a horizontal section through its middle in the line of its long axis. The surface exposed by this section exhibits two distinct shades of colour, united by a broad intervening circle of dark red : the outer part has a brownish red tint, and is denominated the cortical substance, because it surrounds the medullary or tubular substance, as it is called, which has a carnation hue, growing lighter as it extends inward. These substances not only differ in hue ; they differ in consistence, in disposition, and in structure. The cortical part possesses a uniformity of aspect something like that of the liver, 276 URINARY SYSTEM. and a texture comparatively soft and easily lacerable : the me- dullary is much closer and tougher in its composition, and evi- dently exhibits a fibrous texture. The two substances are not conjoined in any regular line ; but dark-red denticular prolonga- tions of cortical, shoot in between the lobulated portions of me- dullary substance. Though the ultimate or intimate structure of the kidney may not be demonstrable with absolute certainty, it would appear, from the results of researches of anatomists in general, that there is less speculation interwoven with the accounts commonly ren- dered of it, than is but too often found blended with those of other complicated glandidar organs. Injections sent into the emulgent arteries colour the cortical substance, but are not to be detected in the medullary ; a simple fact that has led to the con- clusion, that the former is principally composed of bloodvessels ; at least this is the common result of the experiment. To pass over the detail of the means, however, whereby we have attained our knowledge, the minute structine of the kidney appears to be this: — The several divisions into which the emulgent artery splits in penetrating the substance of the gland, end in a multi- plied number of smaller arteries ; and these form arches within the cortical substance from whose convexities a still smaller set come off; which miimt.e vessels proceed inward, few (if any) of them reaching into the medullary part, and end in little globular bodies that have been resembled to the acini of the liver, and named i\\e corpora glohosa ; a sort of arterial arrangement alto- gether that has been compared to grapes as they grow upon their slender stalks. The corpora globosa were at first supposed to be cellular: but later researches afford us reason for believing that they are constituted of the vessels runnitig into them : instead of terminating within them, they are continued and coiled into these globular forms. From the corpora globosa pro- ceed inward, in convergent radii, fasciculi of minute vessels, named, from their office, the tuhuiiiainijeri ; which fasciculi are so disposed in sets (commonly six or seven in number) as to admit of a resemblance to so many paps or dugs, and hence have been denominated the processus manunillares. These coni- cal fasciculi, which take then- rise in the cortical part, constitute the medullary substance of the kidney. The papillcc, the apices of the mammillary processes, are received into little membranous sacs, varying in form and size, denominated the inj'undibula, into which the secreted fluid is distilled through the orifices of the tubuli uriniferi perforating the papillae : the number of infundir bula, however, is not regulated by that of the processus mammil- lares, for one sac may embrace two or even three papillaj. The in- URINARY SYSTEM. "Hi fundibula (each one contractino; in its course) converge towards a common centre, and open commonly by three canals into the pelvis, whose orifices are large enough to admit the small end of a common blowpipe. The pelvis, then, is the common recep- tacle of the fluids transmitted through the infundibula : it is a cavity in the centre of the gland, almost surrounded by medul- lary matter, and consists of a dense, firm, membranous sub- stance, forming an extended sac, which is continuous towards the interior with the infundibula, but towards the notch contracted into a small funnel-shaped outlet, having one continued passage with the ureter. This continuity of component parts has led some to consider the infundibula, pelvis, and ureter, as one and the same extended structure : whether this be the case or not, they pos- sess a common mucous lining that puts on the same aspect, ex- amine it in which of these parts we may. THE URETER (the tube conveying the urine from the kidney into the bladder), emerging from the posterior end of the pelvis, makes its exit through the notch, and then suddenly turns backward under the posterior extremity of the gland, pass- ing between it and the capsula renalis; it then takes its course directly backward, a little distance laterally removed from the bodies of the lumbar vertebrae, crossing obliquely the psoas parvus and afterwards the great iliac vessels; here it enters the pelvis by a sweep upward and outward (embracing within its concavity the vas deferens and ligamentum rotundum), and be- comes included within the fold of the ligamentum latum, by which it is conducted to the lateral and superior part of the bladder: latterly, it runs in close connexion, from the middle of the bladder half-way to its neck, where it imperceptibly vanishes between its tunics. Though we insensibly lose sight of the tube, however, it does not end here ; for after having obliquely pene- trated the muscular coat, it travels onward for the space of an inch between that and the internal coat, and at length terminates by piercing the latter in the same oblique line of dn-ection. The diameter of the ureter near its origin is equal to that of a large- sized black-lead-pencil ; from which it so insensibly diminishes in caliber throughout its course, that we are only assured of the fact by comparing the anterior with the posterior portion. That part of the tube not included within the broad ligament, is in- vested with cellular and adipose tissue binding it down in its course. The ureter is composed of tiuo tunics. The external one is thick, resisting, and longitudinally fibrous, and is believed to be muscular: the inlenial is soft and fine in its texture; is commonly rugose lengthwise; is loosely adherent to the other; 278 URINARY SYSTEM. and is constantly besmeared within with a mucous secretion, to shield it from the acrimony of the urine. Organization. — T/ie emu/gent arteries, right and left, arise immediately in front of their respective glands from the sides of the posterior aorta: each enters the notch, and there divides into three, or four, or even five principal branches, which, unlike the trunk, become flexuous in their course and then penetrate the glandular substance : the outer branches turning in contrary directions, one forward the other backward, to enter the cortical part at once ; those in the middle traversing the tubular to ar- rive at it ; in which they all subdivide and ramify to terminate as afoie described. T/ie emu/gent veins, which exceed in volume, though not or- dinarily in number, the arteries, correspond in their ramification to those vessels : their terminating branches, three, four, five, or upwards in number, converging within the notch, there unite into one trunk, which accompanies its artery and ends in the posterior vena cava. The nerves supplying the kidney are derived principally from the renal plexus, and very numerous they are : notwithstanding their numbers, however, and notwithstanding the acute pain which accompanies active inflammation in it, the organ in the liealthy condition is by no means remarkable for its sensibility. OF THE CAPSULyE RENALES. These are two small, elongated, irregularly-formed, brownish bodies, a right and a left, placed opposite to the kidneys, be- tween those glands and the spine. The right, the longer one, lies in contact with the posterior vena cava, and reaches forward to the liver ; the left, the broader one, and rather obliquely placed, is opposed to the aorta ; and, anteriorly, is contiguous to the pancreas : they are respectively connected to these several parts by loose enveloping cellular substance, and are furthermore retained in their places by the peritoneum, which covers their under surfaces. Their magnitude varies with age : in early fce- tality they are equal in volume to the kidneys themselves; their subsequent growth, however, being less rapid than that of the kidneys, this equality in the course of time becomes destroyed. Their outward borders are partially cleft by several little notches, giving them a lobulated appearance. They possess tunics of their own of condensed cellular tissue, processes from which penetrate their substance and enter into their composition. Structure. — Divided by a perpendicular section, the renal capsule shews a palish brown substance above and below, in- URINARY SYSTEM. 279 terspersed with vessels and nerves, soft and uniform in its tex- ture, and constituting full two-thirds of its whole ; and, in the middle, a longitudinal whitish part, which, though of a very loose texture, is evidently not a vacuity ; for, after some yellowish fluid it commonly contains is expressed, there still remains some internal cellular structure. The fluid expressible from this part is said to vary in its appearance and quantity with the time of life: in the foetus it is said to be red and abundant; yellowish and sparing in the adult ; yellower still and more scanty as age advances. This body receives two or three small vessels, either from the emulgent artery or the aorta, or from both ; and these have their full proportion of veins. It has also an adequate supply of nerves coming principally from the renal plexus. What the disposition or arrangement of these several component parts may be, remains yet to be developed. M. Girard says, concerning them, that, although these bodies are plentifully furnished with bloodvessels and nerves, " ils n'offrent dans leur organisation aucune disposition qui puisse faire presumer une secretion particuliere." The physiology of the capsulae renales remains to this day an unsolved problem. Not one fact has been broached to lead to any rational hypothesis. All that Mailer's indefatigable research and penetrating mind could discover for certain about them, was, that they secrete a fluid more required in foetal than adult life, and that their functions are probably important since they are found in so many animals. OF THE BLADDER. The musculo-membranous bag that receives the urine from the ureters. Situation. — The bladder occupies the middle and inferior regions of the pelvis, taking the oblique axis of that cavity, and resting upon the symphysis pubis, with the rectum above it in the male, the vagina in the female. In the undistended state, this viscus is wholly confined to the pelvic cavity ; but when full, its fundus advances before the pubes into the abdomen, the advancement being in ratio with the degree of distention : in the foetus it rises still more into the abdominal cavity, as a ne- cessaiy consequence of its proportionally greater development, as well as of the narrowness and shallowness of the pelvis at that period. Figure. — In a state of distention the bladder is pretty regu- larly pyriform, and its parietes are thin and semi-transparent; but when completely empty, it assumes the spheroid figure, be- •280 URINARY SYSTEM. comes thick in substance, and exhibits no vacuity internally : in fact, it is (in that state) a httle, white, round, firm, and, I may add, sohd body. Volume. — Its capacity will vary much in different subjects ; and this we have some reason to ascribe (from a correlative fact in human anatomy) to the habit the animal had of retaining the urine : for it is found that women (whom we know from mo- tives of delicacy are oftentimes compelled to restrain their in- clinations to void their urine) have generally larger bladders than men; and now and then in such subjects, bladders are found of extraordinary volume. Coiiiiexioiis. — The bladder is connected by loose cellular adhe- sions to the pubes, the walls of the pelvis, the rectum in the male, the vagina in the female ; and is kept and balanced in its proper place and position by two broad productions of perito- neum expanded across the cavity from its sides to the walls of the pelvis, called its broad /igameuts. These ligaments are formed thus : — the peritoneum being reflected upward from the recti muscles upon the body of the bladder, about its middle, proceeds forward upon the fundus, then turns back again and covers still more extensively the upper surface ; at the sides, these (under and upper) layers of the membrane, meeting to- gether, unite, and afterwards proceed in union to the walls of the pelvis, where they once more split and take opposite direc- tions. The middle portion of the upper layer of peritoneum is reflected upward from the hind part of the body of the bladder upon the rectum in the male, the vagina in the female, and thus a peritoneal pouch is formed between the two. In addi- tion to these connexions, the neck of the bladder is attached to the pubes by a thin fibrous expansion, denominated the tri- angular ligameut ; and the fundus receives the insertion of two round chords which run within the folds of the broad ligaments, named the round ligaments. Division. — The bladder may be distinguished into \i& fundus, body, and cervix or iteck. The fundus is the round prominent part presented forward, completely covered by peritoneum, occa- sionally protruding into the abdomen, receiving the attachments of the round ligaments, and the insertion of the degenerated urachus (which is in the foetus a urinary conduit continued along the umbilical chord to the membranes of the womb). The body is the bulky or capacious part of the bag. Only one-third of its under surface is covered by peritoneum; nearly the whole of its upper. It is supported by the broad ligaments ; has along its sides in the male the vesiculae seminales and vasa deferentia ; and behind, grows suddenly contracted, and ends in the neck. - URINAL' SYSTEiAl. 281 The cervix is the small, circular, posterior part of the bladder. It has a light-pinkish hue, and is comparatively thick and sub- stantial to the feel. The triangular ligament attaches it to the pubes, and it is continuous at the posterior end with the urethra. Structure. — The bladder has three coats : an external one, which is derived from the peritoneum ; a mucous membrane, to which it mainly owes its integrity and consistence ; and a dif- fuse fibrous texture interposed between the two, which is of a muscular nature. The peritoneal coat, which forms but a |)ar- tial covering, is smooth, polished, and moistened with serous exudation externally ; but found rough and pilous internally, when torn from its adhesions with the muscular: in a word, it in nowise differs in its properties from the peritoneal tunics of the abdominal viscera in general. It serves to hold the bladder in its proper place and position, and to a certain degree to counter- act preternatural distention. 'J'he muscnlar coat, though it may be demonstrated through the pellucid peritoneum, is brought more distinctly into view by stripping off that membrane, to which it is closely and firmly attached by fine cellular tissue. Pale fasciculi are then seen running irregularly in a longitudinal manner; and, underneath them, others which are smaller, taking an equally iiregular course in the circular direction: in the empty or half-distended state of the organ, however, both these orders of fibres assume spiral courses ; which enables them to bear considerable exten- sion without the risk of rupture, while their cellular connexions, being loose, admit of their being drawn apart with equal facility. The longitudinal fasciculi are thickest about the fundus, where they all converge to its central point ; the circular are strongest around the cervix : the former exert a special contraction in forcing the urine towards the neck, constituting what has been called the detrusor uriuce; the latter, which are mingled with cellular tissue and some small veins, giving them the feel of greater substance than they really possess, form the sphincter vesiccE of those who (with no more reason in my opinion) make a separate muscle of this part. By the simultaneous contraction of both orders of fibres the parietes of the bladder may be drawn towards one common centre, so as to diminish its capacity gradually in every part, until the cavity is even altogether annihilated. The mucous coat shews itself exteriorly in the interspaces be- tween the fasciculi of the muscular, covered only by the inter- posed cellular tissue which serves as the conmion uniting me- dium of all three tunics. While the bladder remains empty, the contractions of the muscular coat throw this one into riigce, and o o 282 GENERATIVE SYSTEM. in cases of extreme contraction these folds assume rather a re- markable appearance ; the cellular tissue interposed between this and the middle tunic being loose enough to admit of this. It is this same cellular intertexture which, from its being pressed into a pretty regular layer wherein the vessels and nerves ramify, has been described by some as the nervous coat. The internal mem- brane is white, soft in its texture, and highly organized. It possesses numerous follicles from whose excretory pores issue a plentiful mucous secretion to defend it from the acrimony of the saline matters contained in the urine : this mucous matter being perpetually washed off the surface by the urine, is kept con- tinually renewed ; and it is occasionally voided in considerable quantities, especially when any calculi or other irritants are within the bladder. About an inch anterior to the cervix, in the sides of the bag, are seen the orifices of the ureters, whose oblique insinuations in perforating the parietes operate in pre- venting any reflux of the urine at the time that the bladder is contracting, and thereby possess all the effect of valves. Section VIIL GENERATIVE SYSTEM. COMPRISING THE MALE AND FEMALE ORGANS OF GENERATION. MALE ORGANS OF GENERATION. THE male animal, although the part he appears to contribute towards the work of procreation appears but insignificant, when contrasted with the lengthened, tedious, critical process per- formed by the female, is, nevertheless, provided with an assem- blage of organs whose individual structures and functions may be ranked among the most complicated in the system. These organs consist of the testicles — whose office it is to prepare the fluid necessary for impregnation; of the vasa deferentia and vesicu/cE seminales — canals and receptacles for this fluid ; and of the penis — the instrument by which this same fluid is transmitted into the parts destined for its reception in the female body. OF THE TESTICLES AND SCROTUM. The testes or testicles (the truly essential organs of procreation in the male species) are the two oval glandular bodies suspended genjlRative system. 283 from the hollow between the thighs, within a case or bag, de- nominated the scrotum. THE SCROTUM, or purse, as it is sometimes called, is mainly constituted of a loose production of the common integu- ments, which is, on either side, continuous with the skin cover- ing the flanks and thighs ; in front, with the sheath of the penis ; and behind, with the perineum : a term under which may be comprehended the space included between the scrotum and anus. The skin forming the scrotum is thin and soft in its texture, generally black, and is clothed with fine downy hair, long and bushy around its sides, short, scanty, and hardly per- ceptible about its inferior parts. The testicles, by their promi- nences, produce a longitudinal crease along the middle of the scrotum, named the raphe, of which a faint trace extends into the perineum : this crease denotes the line of attachment of the septum scroti. Prior to the appearance of the testicles, the purse is comparatively small and insignificant, consisting merely of some loose folds of skin : during their descent from the belly it is that the scrotum becomes gradually developed, and the wrinkles, in consequence of its extension, as gradually effaced. Dartos. — On cutting through the integuments of the scrotum, we expose a pale, yellowish, fibrous layer of substance, which by some is regarded and described as a muscle, and named the dartos ; while others view it but as a continuation of the faschia superficialis abdominis. Its fibres, which run longitudinally, are strongest where they cover the testes. Anteriorly they are continued into the cellular substance of the sheath, wherein they are lost: posteriorly they are spread upon the root of the penis. This substance loosely adheres to the skin by cellular membrane, and is still more loosely connected by the same tisssue to the parts within. It is certainly distinctly fibrous in composi- tion, but its fibres possess a density and toughness and a yellow cast which, to my eye, accord more with the properties of liga- ment than muscle: to which I may add, I am acquainted with no physiological fact that warrants such an inference. The scrotum of the horse does not corrugate from the application of cold or other stimuli, as that of a man is known to do; we can- not, therefore, avail ourselves of the contractile power of the scrotum — at least not to the same extent as some human ana- tomists have done — to strengthen suppositions of the presence of a dartos. The fibrous substance is most loose and abundant along the middle of the bag, where its expansions from either side unite and become reflected upward in inseparable union with each other, tlirough the inicrspacc between the testes, forming in this manner a partition through the nuddle of the 284 GENERATIVE SYSTEM. purse, denominated the septum scroti ; which consequently ex- tends from the raphe to the under and posterior part of the penis, and serves to prevent one testscle from encroaching upon or in- terfering with the other. Cellular Structure. — The celhilar membrane of the scrotum (vvliich may be considered as the third l|yer of substance enter- ing into its composition) is interposed in the greatest abundance between the fibrous expansion and the peritoneaLcoverings of the testicles. Being very long and loose in its texture, and desti- tute of any adipose matter, the parts it connects are extremely moveable upon each other, at the same time that it admits itself of considerable extension. Testicles. Coverings. — The first or external covering of the testicle, one common both to it and the chord, is a borrowed one from the pe- ritoneum, known as the tunica vaginalis. The acquisition and reflection of this covering will not be clearly understood until the descent of the testicle has been explained ; though it may be ob- served here, that it is a production of peritoneum formed into a loose vagina or sheath, which originates at the internal ring, pro- ceeds with and loosely envelopes the chord, and, lastly, covers in the same lax manner the testicle and epididymis ; so that if the bag (it forms) be punctured, and air or liquid be impelled into the cavity, the fluid will not only distend it, but mount into the abdomen, since both cavities have a free communication at the internal ring. The elongated membrane, however, does not end in single investment of the testicle. Along the superior and an- terior border of the eididymis, we find it firmly attached, but not terminated ; for here it becomes reflected, first upon the epididy- mis itself, next over the testicle, and lastly upon the chord, so as to give them all a second covering, which only differs from the first in being every where in close adhesion with the parts it in- vests : this last production is called, by way of distinction, the tunica reflexa or tunica vaginalis testis : it must not be forgot- ten, however, that they arc ho\\\ peritoneal productions — one and the satne continuous membrane. The vaginal cavity possesses a smooth polished surface, and this is constantly bedewed with a limpid, colourless, serous fluid, which in the operation for castra- tion spirts out the instant the knife or cautery has penetrated the tunica vaginalis. It is an accumulation of this fluid that con- stitutes hydrocele; a disease that has no existence, I believe, in the horse, abstractedly from abdominal dropsy. THE TESTICLES, with their appendages, the epididymes, GENliRATlVE SYSTEIVl. 285 constitute the glandular apparatus for the secretion of the male sperm or semen ; the penis, as was stated before, being simply the instrument of transmission. We have already seen that these bodies, although loose and pendulous, are not wiattnclied within the cavity of the scrotum : we have found them enclosed within peritoneal tunics; confined by cellular and fibrous envelopes; and fenced in their respective apartments by the septum scroti. Figure, Magnitude, Division. — The general figure of the tes- ticle IS that of an oval flattened at the sides ; the magnitude, that of the egg of a hen : M. Girard says, that the left is gene- rally a little larger and more pendent than the right. The tes- ticle is suspended within the scrotum by the spermatic chord ; and in such a position, that its long axis corresponds to that of the body. It possesses, therefore, anterior and posterior ends: to the latter is joined the termination of the chord, while the vas deferens departs -from the globus major of the epididymis, which is attached by a ligamentous band to the former^ It has also an i)iferior or convex border, along which are seen the tortuous windings of the spermatic artery ; a superior or straight border, to which is attached the epididymis ; and two convex sides, free and unconnected. The Spermatic Chord, the substance by means of which Ihc testicle is connected with the abdomen, and by which it is sus- pended within its scrotal cavity, is composed in the following manner: — 1st. It has four coverings: — there is, immediately underneath the skin, the faschia superficialis ; next, the cremas- ter; thirdly, the tunica vaginalis; and, lastly, the tunica vagi- nalis reflexa. Within the cavity formed by the vaginal tunics it is that the intestine is protruded in inguinal and scrotal herniae : the hernial coverings, consequently, exclusive of the sac, will be the faschia and the cremaster muscle. 2dli/, The constituent parts of the chord itself are — a. The arteries, which are two in number: — the artery of the chord, a small branch of the ex- ternal iliac, which ramifies and expends itself upon the chord ; and the spermatic artery, which, as soon as it reaches the inter- nal ring, enters the inguinal canal, runs down the posterior part of the chord, growing tortuous as it descends, serpentines along the superior border of the testis, between it and the epididymis, winds round the anterior end of the gland, and lastly reaches the convex border, where it becomes extremely convoluted, and whereto its branches are principally distributed. In its descent it detaches small unimportant twigs to the adjacent parts ; and as it approaches the testicle becomes surrounded by an assem- blage of venous vessels, b. The veins accompany their corres- pondent arteries ; and they indeed uuiy be said to make up the 286 GENERATIVE SYSTEM. principal bulk of the chord, for they are not only numerous, but large and flexuous, and, as they approach the testicle, form a sort of plexus which has got the name of corpus pampiniforme : they return their blood into the posterior vena cava. c. The NERVES, which are derived from the hypogastric plexus, also accompany the spermatic artery; they are small, but sufficiently numerous. Though the testicle does not possess any very great sensibility in health, we may vouch for its being acutely sensitive in a state of disease, d Absorbents exist, both large and numerous, in the chord. They are readily found alongside of the venous trunks ; and not infrequently may be filled by introducing mercury into the spermatic artery, e. The vas deferens, though a constituent of the chord, takes at first a solitary course, remote from the bloodvessels. The duct issues from the sum- mit of the head of the epididymis, beginning in a series of con- volutions gradually unwinding as it proceeds ; it takes an oblique course nearly as high as the external ring, where it joins the bloodvessels, and continues to accompany them posteriorly through the inguinal canal : at the internal ring it leaves them, turns inward and ascends into the pelvis, where we find it creep- ing along the side of the bladder infolded in peritoneum to get to the cervix, crossing under its course first the umbilical artery and then the ureter ; at length it terminates by rather a con- tracted orifice within the mouth of the duct of the vesicula semi- nalis, just behind a little eminence in the urethra — the caput galinaginis, about an inch posteriorly to the cervix of the blad- der. Within the inguinal passage the duct is accompanied by the artery of the vas deferens, a long slender branch of the epi- gastric. Its canal, flexuous until the duct has joined the chord, but straight in its subsequent course, is not uniform throughout in caliber; the area of its tortuous part is large, but as it becomes straight it grows contracted : having entered the pelvis, it gra- dually enlarges again, and acquires unusual volume in running along the side of the bladder ; and the canal of the enlarged por- tion presents a reticulated structure, which gives its exterior an irregular, tuberculated appearance ; the most contracted part is that in union with the duct of the vesicula seminalis, which is a comparatively small cylindrical conduit. The parietes of the duct are so remarkably thick and firm to the feel, that we distin- guish it at once by the fingers from the other parts of the chord : they consist of two tunics ; the external one (in which its main thickness consists) is white, fibrous, and approaches in appear- ance to cartilage ; the internal one is thin and fine in texture, muco-membranous in its nature, and here and there incloses a reticulated structure. The different constituent parts of the chord GENRRATIVI' SYSTEM. 287 are connected altogether by cellular substance, destitute of any fat ; and from the circumstance of the parts in general being more bulky below the ring, the chord increases in breadth and thickness as it approaches the testicle. Close Coverings. — The close or intimate tunic of the testicle is perfectly distinct from its vaginal coats, and from its conspicuous whiteness is called the tunica albuginea. Though it may be stripped off in places by the forceps, and the separation may be also effected by diffusing quicksilver into the cellular texture uniting them, the tunica reflexa so intimately and uniformly ad- heres to this tunic, that, the former being transparent, they appear to constitute but one and the same covering. The albuginea, however, is much denser and firmer in its nature, and much re- sembles other fibrous membranes, particularly the dura mater, both in appearance and texture : like that membrane, it is exten-r sile and contractile, but neither suddenly nor greatly so, and im- parts a compactness and firmness of feel to the inclosed structure which the latter, deprived of it, is not found to possess. Over the convex part of the gland this tunic is perforated by nume- rous holes for the transmission of the spermatic blood-vessels. Internally, it is connected to the substance of the testicle, by these vessels, by a fine cellular web, and by numerous little processes that traverse the gland perpendicularly, serving to hold the in- ternal parts together, as well as aiding to preserve the form of the whole, and which are generally described as the sej)ta or sep- tula tetis. Structure. — On cutting into the testicle, we find that it con- sists of a soft pulpy substance of a pale brown colour, and that this, by being nipped and drawn out by the forceps, is extensible into numerous whitish threads of extreme exility, which may oc- casionally be elongated to a considerable degree : it is believed that these are the seminiferous tubes. Like other secreting or- gans, the testicle receives into its composition congeries of arte- ries, veins, nerves, and absorbents, the peculiarity of structure chiefly residing in the arrangement of the secretory and excretory parts of the apparatus. It is imagined, in the instance before us, that this consists in many vascular coils or complexures which are only separated from one another by the septulae, and that these, independently one of the other, possess the power of secre- tion. After the spermatic trunk has dispersed its ramifications over the albuginea, numerous twigs are transmitted through that tunic into the interior of the gland : from these, capillary ar- teries spring, which, it is presumed, communicate with the tubuli seminiferi, but in what manner anatomists have not been able to detect; for in the old subject these tubes are constantly 288 GENERATIVE SYSTEM. plugged with secretion, and so foil all our attempts to inject them ; and in the young subject, before they begin to se- crete, they are not sufficiently developed to admit of the exami- nation. If quicksilver be suliered to pervade the arteries by its own weight, it is found to return by the veins ; and in a prepara- tion of the testicle of a dog at present before me, the absorbents have been filled from the same source. Towards the posterior end of the testicle, the seminiferous tubes assemble from the dif- ferent parts of the interior, and unite into a set of larger tubes of the same description, disposed after the manner of network, and hence have got the name of the rete ; then, from the rete proceed another set of similar tubes, still larger (about a dozen, I believe, in number), from the testis to the epididymis, constituting the sole medium of communication, and the principal one of connex- ion, between the two : these are the vasa efferentia. In addi- tion to these minutiee, we may notice that the superior border of the testicle is marked by a broad wliite line : this denotes the si- tuation of a supposed canal, and is generally mentioned as the corpus Higlwiorianum. The epididymis is extended along the superior border of the testicle, upon which it rests, and to which it is connected by the tunica vaginalis reflexa. Its ends are bulky in comparison to its middle : that receiving the vasa efferentia, the smaller one, is the caput or globus minor ; the other, giving rise to the vas deferens, is the globus major — the part farriers call the uut. The interior of this appendage to the testicle exhibits a structure en- tirely vascular. The vasa efferentia unite and re- unite until they form a single duct, of whose numberless and very remarkable con- volutions the globus major is entirely constituted : these tortuo- sities (which, when squeezed, freely emit semen) will admit of being unwound for a considerable extent, so as to have the length of the duct calculated with very tolerable exactness from begin- ning to end, which has been found to amount to several yards. It is small at its formation, but grows imperceptibly larger in making its manifold windings and turnings, until at length it as- sumes the size of the vas deferens, in which it ends. Its various convolutions are connected together by cellular membrane, and are interspersed with a sparing supply of bloodvessels. The course of the semen is this: — It is secreted by the ca- pillary coils of the spermatic artery, from which it is received by the tubuli seminiferi : these tubes carry it into the rete, and the rete discharges it through the vasa efferentia into the epidi- dymis, from which it is conducted by the vas deferens into the urethra. Formation and Descent. — It is a singular fact, that the organs GENERATIVE SYSTEM. 289 whose structure we have been investigating, are originally formed in a situation remote from that in which they are destined to carry on their functions: " the colt has no testicles," is the com- mon observation of the uninformed on these matters ; and we know ourselves that the purse is without them, but we know, in addition, that they exist ready-formed within the abdomen, and that they will descend at a certain period of age into their proper receptacle, the scrotum. During the fcetal state, we find them more or less developed, tinged with a blush of red, lodged under- neath the psooe muscles, in contact with the inferior borders of the kidneys, covered and retained in their situations by peri- toneum, and concealed by the intestines around them. Here they receive their arteries from the contiguous trunk — the pos- terior aorta ; the vasa deferentia run forward to them ; and the cremasters likewise turn forv\ard instead of backward: there being at this time no such thing as a spermatic chord. Thus placed, the testicle may be regarded as one of the glands of the abdomen : indeed, it has considerable similarity to the kidney — receiving its vessels from the same contiguous source, and send- ing a long duct backward into the cavity of the pelvis : nor does there appear any conclusive reason why it should not perform the same office in that situation that it does in the scrotum, and par- ticularly since it is known that in birds they remain within the belly during life. From the part where the bloodvessels enter, we find growing a whitish substance, extended backward, di- minishing in breadth as it recedes, passing through the ring, wJiere the fibres of the cremaster may be traced upon it, and whence it is prolonged into the scrotum, growing nanower and narrower until it vanishes : this substance, regarded by some simply as a ligament, -was considered by Mr. Hunter as the giibernaculum or pilot, by means of which the testicle is directed in its passage from the abdomen into the scrotum. Quitting the spot where it has been formed and matured, the testicle gradually retrocedes, guided by the gubernaculutn, until it arrives at the internal ring, which, at this time (like every other part of the parietes) is closed by peritoneum : this temporary obstruction it overcomes by drawing the membrane down along with it through the ring, and carrying the pouch made thereby down into the scrotum ; the gubernaculum at the time undergoing a complete inversion. This accounts for the production of the tunica vaginalis, and explains how that membrane comes to be doubled or reflected : the testicle, receiving originally (as an ab- dominal viscus) one close and adherent peritoneal tunic, and acquiring another, which forms a loose covering, as it passes pp 290 GENERATIVE SYSTEM. through the ring, must necessarily have tivo ; and since both are derived from one and the same membrane, it follows that one must be a continuation of the other. These elongations of mem- brane, though every where in contact, are prevented from ad- hering together by a continual exhalation of the natural serous secretion. Any interval that might subsist between them, in course, communicates with the cavity of the abdomen, through the ring, a part that remains open through life: this, however, is not the case with man — in his body the communication is cut off, after the testicles have descended, by a natural contraction and obliteration both of the ring and the inguinal passage. In many instances, one, in some few, both of the testicles, are known to have remained within the belly through life. As we are unac- quainted with the immediate cause of their descent, so we are unable to give any rational explanation of this phenomenon. I have understood, that in many of these cases the glands have been found to be but imperfectly developed : this, however, is not without exception. Period of Descent. — Most animals have their testicles within the scrotum at the period of birth. In the human foetus they begin to move about the seventh month ; about the eighth they reach the groins; and before birth arrive in the scrotum. In the horse, they pass through the ring about the sixth or seventh month before birth, and are found within the scrotum at the period of parturition. In some cases, one testicle will not make its appearance for some time after the other ; and as the opera- tion for castration is seldom long delayed, this will account for the rigs (as horses having but one testicle are called) with which we meet every now and then. Again, instances are not wanting in which one testicle has descended to the ring and there remained through life*. * In a communication I have been favoured with from Mr. Brettargh (which I have inserted in the second volume of The Veterinarian), is contained the following information on this subject : — " Colts are foaled with their testicles in the scrotum, which remain' there (in ordinary cases) until the fifth or sixth month, \vhen they are taken up between the internal and external abdominal rings, and there remain until the eleventh, twelfth, or thirteenth month, all depending upon the degree of keep, as in some that are well fed the testicles can at all times be found in the scrotum. Were the testicles drawn up into the abdomen, they would be too large to pass through the internal abdominal ring at the time they are wanted to prepare for secretion ; which is occasionally the case, and at once accounts for our meeting with horses that are said to have but one stone. I have seen one instance where both were wanting in the scrotum at four years old." GENERATIVE SYSTEM. 291 The Vesicii/ce Seminales Are two oblong, membranous sacs, placed contiguously to the terminations of the vasa deferentia, which have been so denomi- nated from a supposition that they were receptacles for the semen. They occupy the lateral intervals left between the bladder and the rectum, with their internal prominences, while their external are opposed to the sides of the pelvis. They are principally sustained in their places by the bladder. In relation to each other, they represent ift situ the two sides of a triangle : for their posterior extremities are nearly in contact, while their bases diverge as they advance, and leave a considerable breadth of interspace. The longitudinal channel between the bladder and vesicula is occupied by the vas deferens. The vesiculse are confined in their situation by cellular connexions with the bladder and rectum, the walls of the pelvis, and the vasa deferentia. Form aud Strticture. — These bodies have a near approach to the pyriform. Anteriorly they present broad round bases, which are elongated posteriorly into contracted circular necks, and the necks end in ducts of some length, which may (to carry the re- semblance on) be said to represent the stalks of the pears : they incline, however, to convexity superiorly and to flatness inferiorly, and their surfaces are rendered uneven by some tubercular emi- nences. The parietes of the vesicula are distinguishable into two textures. The external one, when cleared of the enveloping cellular substance, is white, and, though soft to the feel and not so thick as the outer tunic of the vas deferens, possesses con- siderable density and toughness, and in some parts, particularly around the base, assumes a fibrous texture : these fibres are described as muscular, and certainly the functions attributed to the vesiculse appear to warrant such a supposition, even were we unconvinced of its truth from anatomical inspection — which, I should say, we certainly are. This tunic is lined with a mem- brane, whose surface is of the papillary description — every where presenting to view (through a magnifying glass more plainly) numerous pinhole-like perforations, the orifices of subjacent fol- licles furnishing the whitish, viscous, jelly-like secretion peculiar to these bodies. Their ducts are of considerable volume, not greatly inferior even to the urethra itself: both proceed back- ward in a convergent direction in union with the vasa deferentia, alongside of the membranous part of the urethra, and terminate behind the verumontanum. 292 GENERATIVE SYSTEM. OF THE PENIS. The penis ox yard is an organ of large dimensions in the horse species, capable of projection and retraction, but ordinarily con- cealed within a loose and pendulous doubling of skin, at the in- ferior and posterior part of the belly, known by the name of the sheath. It is not only destined for the important office of im- pregnation, and made the seat of that enjoyment experienced by the male during the copulative act, but it serves the subordinate purpose of a convenient conduit for the discharge of urine. THE SHEATH (in which the penis is inclosed, and by whicii, unless it be in a state towards erection, it is concealed from view) is nothing more than a prolongation of the common integuments, with one part drawn within the other, and puckered so as to form a sort of corrugated bag — corresponding to the prepuce in man — whose dimensions vary with the degree of retraction of the penis. Posteriorly, the sheath is continuous with the scrotum ; anteriorly, it is cleft, and has two large pendent folds of skin, proceeding from the sides of the vagina propria penis, with a broad deep furrow between them, which extends along the belly as far forward as the navel. In most horses, these parts are either dark-coloured or black : in some they are clothed with fine, long, downy hair ; in others they are inferiorly almost bare, having but a few scatte'red short hairs which are only perceptible on close inspection. But there is so much variety in these unim- portant particulars, that any single description, accurately and minutely drawn, will not apply with jirecision to another indi- vidual. Near the borders of retiection of the sides of the sheath — in the ordinary state of the parts — grow two small papillae or teats, resembling the dugs of the mare, presenting, in a less per feet degree, the same internal structure, and being perforate at their apices: they are not to be found, however, I believe, in all horses, and it is the practice of some cutters to take them off at the time of castration ; Girard observes, with truth, that they are largest in the ass species. Tlie internal sheath — the vagina propria penis, exhibits two large, circular, tegumental plications: the outer and larger one is formed by an involution of the ex- ternal vagina, and exhibits internally numerous corrugations, which, though by no means regularly ranged, for the most part run in circles around the inner phcation, the veritable preputinm glandis penis, whose internal surface is also puckered into cir- cular corrugations, but smaller, and still more numerous, and GENERATIVE SYSTEM. 293 more irregularly disposed than those of the former. These pli- cations are nothing but a continuation of the common integu- ments disposed after this manner to admit of the projection and erection of the penis — a state in which they, together with their corrugations, are extended and annihilated ; though the skin composing them is of a kind remarkable for its fineness and soft- ness of texture, for its black or marbled complexion, and for the excretory pores of myriads of little subjacent glands, which are so closely packed that it is hardly possible to introduce the point of the scalpel through it without penetrating one or more of them. These involutions of skin are supported in their corrugated form and connected to the body of the penis by an interposed stratum of cellular substance, which is so loose and abundant as to readily admit of their sliding over each other, and of the penis being protracted and retracted with the greatest facility. Rejiection. — From the inner plication the skin is reflected upon the penis, extending forward and giving a complete covering to the part named the glans penis. This part exhibits a very re- markable corrugated aspect, which I cannot resemble to' any thing so nearly as to the leaf of a curled cabbage : its cellular substratum is shorter and more condensed than that of tlie sheath, it not being designed to be protracted beyond the penis ; and, like the inner plication, it is destitute of those glands with which the outer is so thickly studded. The glandu/te odorij'erce are numberless little brown follicular bodies set in the internal part of the outer vaginal fold, for the purpose of discharging a white caseous matter through their ex- cretory pores upon the surface. This secretion, which has a peculiar odour, preserves the sensibility of the parts, and facilitates their slipping backward and forward. It is occasionally found collected in considerable masses between the outer and inner pli- cations, even, it has been said, so as to plug the orifice of the urethra, and cause retention of urine : knowing this, will put us upon our guard, and lead us to inspect the part in cases where the cause of retention is not very apparent. The surfaces covered by the inner plication are lubricated by a mucous se- cretion. Cul-de-sac. — There is yet another involution of the skin. This takes place at the extremity of the organ, where a little cul-de- sac is formed, in the centre of which protrudes the end of the urethra, a part also covered by a reflection of this thin, hairless, corrugated integument. Around the end of the urethra is a little recess, partially divided into two chambers, commonly contain- ing concreted masses of a peculiar unctuous secretion ; the use of which excavation is not very apparent. 294 GENERATIVE SYSTEM. Faschial Covering. — The penis, inferiorly, receives a covering from the J'aschia supej-Jicialis abdominis, lateral portions of which descend from the flanks, and unite along its middle : as we approach its root the faschia grows stronger, and exhibits a fibrous texture. The organ derives considerable support from this covering. THE PENIS is constituted of five distinct parts, which appear to view without the aid of any dissection or disarrange- ment of the organ : viz. the two corpora cavernosa, which form the middle and sides, the largest proportion of the body ; the glans penis or head, forming the anterior protuberance ; the co?'- pus rnusculosum urethra:,, making up the inferior portion ; and the plexus venosus, surmounting the corpora cavernosa. The muscles belonging to the organ having been described (at page 128), we proceed to the CORPORA CAVERNOSA PENIS, the principal parts in respect to bulk in the constitution of the organ ; parts whose erectile capacity fits it as the instru- ment of copulation, extending from the ischial arch to the glans penis, and insinuating their extremities for some little way under the flattened portion of the latter. They are attached by means of two branches, the crura penis, to the posterior ends of the tube- rosities of the ischia, and to the sides of the ischial arch, where they are clothed by the erectores penis ; from which attach- ments they converge along the branches of the ischium, and under the summit of the ischial arch form a union. The attach- ment of the penis to the pelvis is considerably strengthened, just below this union of the crura, by two suspensory/ ligaments, which fasten the sides of the cavernous bodies to the pubes. These cylindrical bodies, joined together in one common tunic, continue their passage forward to the glans penis, within the substance of which they terminate by two rounded protuberances. Structure. — The corpora cavernosa are composed of a liga- mentous case, of unusual thickness and toughness, common to them both, whose fibres, running in every direction, are so inter- laced and matted together, that it not only defies our industry to unravel it, but is even impenetrable ; unless when sharp instru- ments, and they with no ordinary force, are made use of. It is not every where uniform in thickness, however : it is compara- tively thin over the crura and where it is opposed to the urethra, those parts being sufficiently supported and protected by their muscular coverings. The internal structure of these bodies, spongy, reticular, or honeycomb-like in its arrangement, is found to involve three difl^erent textures. First, numberless little ten- dinous chords, which arc processes detached from the ligamentous case, unetiuul in size, run irregularly from one side to the other : (iENERATIVE SYSTEM. 295 these are crossed in the middle by a perpendicular set, broader and stronger, and so arranged as to resemble the teeth of a comb ; on which account, these last, forming the partition between the two corpora, have been collectively named the pecten. Thus, preternatural distention of the organ, and consequent liability to rupture, are guarded against both laterally and perpendicularly. Seco)idlj/ , the interspaces are filled with a pale-red spongy sub- stance, in which may be distinguished cylindrical processes taking a longitudinal course: these JM. Girard pronounces to be " evidemment musculaires ;" and I see reason for so con- sidering them ; though I think it is a point which demands con- firmation from physiological or experimental inquiry, and not entirely to be decided upon anatomical evidence. Thirdly, these cylindrical bands are surrounded and connected together by a cel- kdar structure, that would appear to be the result or product of some peculiar venous arrangement : at least, the small veins, which are here far more numerous than the arteries, have every where the freest communication with these apparent cells. Organization. — The cavernous structure is especially supplied with blood by a large vessel, the internal pudic artery, a branch of the obturator artery, which enters the crus, giving off several small branches to the other parts of the organ. The pudic nerves, two in number, springing from under the ischial arch, are seen entering the corpus at the same place, one before, the other be- hind the artery. The internal pudic veins, which are large and numerous, divide here into two sets, one accompanying the arteries, the other the nerves, after they have quitted the penis. THE GLANS PENIS is the large, irregular, fungus-iike protuberance, forming the fore part of the organ, vulgarly called its head. This part puts on a very different appearance when distended from the state in which we find it in the dead animal: it then presents a broad surface anteriorly, surrounded by a pro- minent inflected border, which is turned back for some distance above, but altogether deficient below, where there is a notch or division of the glans. The lateral portions are prominent, incor- porated in one superiorly, separate and divergent inferiorly : posteriorly, they are terminated by a contracted circular part, whose prominent border forms the corona glandis. From the corona extends along the dorsum penis, a flattened substance of an oblong oval figure : this is the posterior or terminating portion of the glans. In the middle of the glans is a prominence, in front, marking the termination of the corpora cavernosa ; and below this is a circular fossa having in its centre the projecting orifice of the urethra. Altogether, the glans may be regarded as a part l>y which the penis is surmounted in order to enable the 296 GENERATIVE SYSTEM. animal to direct the semen witli more certainty into the womb of the female ; the mouth of that organ being precisely its counter- part in form. Structure. — The internal corrugated production of sheath, as well as the reflected portion by which the glans is immediately covered, have already been described : underneath this last we find a fibrous case, of a ligamentary and cellular texture, holding- together the internal structure. The interior exhibits a honey- comb appearance, being throughout composed of a soft spongy tissue, in a high degree distensible and elastic, which some are of opinion is nothing more than a congeries of veins : whether this be wholly or in part true, venous vessels are found running among the cells, becoming large and more conspicuous towards the posterior parts, from whicli spring those veins that afterwards so suddenly enlarge and multiply upon the dorsum penis, forming thereon that remarkable venous conglomeration, the PLEXUS VENOSUS PENIS, a structure that may, to all appearances, be regarded as a development of the glans ; and one that, when distended with blood, in the erect state of the organ, constitutes no inconsiderable part of its volume. Though the veins composing it have free and frequent communication, yet, being furnished with valves, this communication is not such as will permit us to fill them with common injection contrary to the course of the blood ; so that, when we mean to distend them with wax, we introduce the pipe into the substance of the glans. Towards the root of the penis these venous convolutions dimi- nish in number and volume, and at length coalesce in front of the symphysis pubis in three or four veins of ordinary size, which are here joined by the epigastric and superficial femoral veins, and then proceed into the pelvis to end in the trunk of the internal iliac vein. THE URETHRA is a membranous canal extended from the bladder to the extremity of the penis, to afford a passage for the urine and seminal fluid. Arising from the neck of the bladder, the urethra, in its way to the outlet of the pelvis, runs at first horizontally backward, with a slight curve downward, between the lobes of the great prostate, embraced superiorly by the portio media of that body, and arrives at the small prostates, which are situated upon its sides : this intermediate portion is called the membranous part ; incorrectly, however, for we find that it is en- circled by some of the fibres of the triangularis penis. Behind the small prostates the urethra suddenly bulges or swells in volume, which part is named t/ie bulb : it is here that the acce- lerator urinse begins — the muscle that incloses the canal during the remainder of its course, and is, in fact, a part itself of the GENERATIVE SYSTEM. 297 urethra. Leaving the bulb, the urethra suddenly curves down- ward, and shortly after turns sharply forward, passing under the ischial arch — the tuberosities bounding it laterally — at which place it is joined by the crura and subsequently surmounted bv the corpora cavernosa. At the extremity of the penis the canal is enveloped in the ghms, terminating in the centre of the front of that body — within a prolapsus of membrane covered with a reflection of fine skin — by an open orifice, which is insulated from the glans by the fossa running around it. In turning round the ischial arch, the urethra has extensive cellular attachments to the bone ; but it is principally retained at its curvature by the suspensory ligaments of the penis. The length of the urethra is nearly two feet. It is a canal also of considerable caliber, so that I can with facility introduce the handle of the scaljjel into the orifice, though that is the smallest part ; for, after it has passed the bulb, it pretty regularly diminishes in caliber all the way to the orifice : the canal at the curvature measuring, when distended with wax, four inches in circumference ; near the oiifice, not more than txvo. The interior of the canal exhibits a smooth, polished, lubri- cated surface, having a pale blush upon it. In structure it does not materially differ fiom other mucous membranes, unless it be that its follicles are larger and more numerous, and that their orifices are called lacunce. It is continuous, and appears to be one and the same texture with the mucous membrane of the bladder. About an inch and a half from the neck of that viscus, within the membranous part of the canal, is a little eminence named the venonontanum or caput galinagiuis, at whose root open the ejaculatory ducts : the use of this tubercle (which I believe has not been noticed) appears to me to be. to perform the office of a valve to the orifices of these ducts, preventing any influx of the urethral fluids. Upon either side of it are many small perforations through the membrane : these are the excretory openings of the ducts of the great prostate. A little in the rear of the verumontanum are several small papillary emi- nences, perforated through their centres, and longitudinally ranged in two distinct sets: these are the openings throu^'ii which the ducts of the lesser prostates discharge their secretion. The bulb of the uretlna is a longitudinal prominence, begin- ning immediately behind the lesser prostates, and proceed- ing with the canal around its curvature; not indeed ending- there, for it may be traced on, though considerably shrunk in volume, even to the glans penis : the continuation of it being the part corresponding to the corpus spongiosum in human ana- Q rj 298 GENERATIVE SYSTEM. tomy, a name it hardly merits in this instance. It has a celhilar arrangement internally, which we may regard in the same light as the spongy structure of the glans itself: indeed, if I might be allowed here to draw a comparison between these parts in a man and in a horse (the spongy body being more developed in the penis of the former, the glans in that of the latter), I should say, that the glans was an expansion of the corpus spongiosum, and that the glans in the horse and the corpus spongiosum in man bore strong evidence of some peculiar venous arrangement. OF THE PROSTATE GLANDS. These bodies are three in number: a single large one situated around the neck of the bladder, corresponding to the gland of the same name in the human subject ; and two small ones, which answer in situation to two little glandular bodies occasionally met with in man, named, from their discoverer, Coivper's glands. THE GREAT PROSTATE embraces the neck of the bladder and incipient portion of the urethra, both superiorly and laterally, being placed between those parts (by which it is supported) and the rectum. It is firmly attached to the parts it surrounds by cellular tissue; and has also a cellular connexion in front with the vesiculae seminales, and above with the rectum. We distinguish in this gland two lateral lobes, and a uniting middle portion ; which, in man, Sir E. Home has described as the third lobe, in consequence of its assuming frequently the lobular form when in a state of disease. The lobes are envelojied in incompact cellular cases, have exteriorly a con- glomerate disposition, and are of a palish brown colour. Internally, they possess a spongy or cellular structure, diffused through which are sets of thin membranous tubes, very large for the size of the gland, which are readily inflated, and then are seen to open, through orifices before described, around the base of the verumontanum. The gland secretes a whitish liquor resembling- thin mucus, and this mingles with the sperm at the time of its ejection ; but for what particular purpose has not been satisfac- torily determined. THE LESSER PROSTATES are situated against the sides of the urethra, contiguously to the posterior part of the bulb, where they lie upon the branches of the ischium. Each of them is about equal in bulk to one of the lateral lobes of the large prostate. They are included in loose cellular sheaths, that are continuous with the substance of the triangular mus- cle. In figure, they are flattened ovals. In colour, they are likewise a pale brown; but it is a lighter shade still than GENERATIVE SYSTEM. 299 that of the large one. Their exterior is even, and such as in- dicates their structure to be of the conglobate kind. The inte- rior exhibits a more uniform appearance : a longitudinal section through the middle displays an arborescent membranous struc- ture, wliich is demonstrated (by the use of the blowpipe) to be the system of excretory ducts, whose papillary terminations in the urethra have been already pointed out. These glands likewise secrete a peculiar fluid, and that is also ejected in commixture with the sperm. FEMALE ORGANS OF GENERATION; CONSISTING OF EXTERNAL AND INTERNAL PARTS, AND APPENDIX. EXTERNAIi PARTS, Such as can be examined without the aid of dissection; comprehending the Vulva, the Clitoris, and the Meatus Uri- narius. OF THE VULVA. THE VULVA, or pudeiidam, is the broad slit included between two prominences of the common integuments, extending from a little belov^' the anus down in a perpendicular direction between the supero-posterior parts of the hind quarters. It is constituted of the Jissuie, in the middle, denominated the Jissura mag/ia : of the two lateral prominences, or labia pudendi ; and of two angles, superior and inferior, called the commissures. THE FISSURA MAGNA, or sinus pudor is.— T\vq external orifice of the vagina, several inches in extent, is largest in mares that have borne foals, in consequence of the extension it under- goes in parturition. The short interspace between the fissure and the anus is termed the perineum. THE LABIA PUDENDI are composed exteriorly of dou- blings of the common skin, which here exhibits a particularly fine and soft texture, is hairless, and in most mares black, and is pre- served moist and supple by a sebaceous secretion continually ex- uding from minute pores in their opposed surfaces. But the labia owe their bulk principally to adipose substance ; which accounts for the variations in regard to prominence they undergo in con- formity with the age, as well as the embonpoint of the animal. With the fatty substance is blended a fibrous texture, and so intricately, that the one cannot be demonstrated separately from the other, nor can their mutual connexion and arraniiemcnt be 300 GENERATIVE SYSTEINI. at all accurately made out; which fibrous texture it is that gives the labia their firmness, resistance, and elasticity. Interposed between this mixed substance and the skin, we find scattered iasciculi of pale fleshy fibres : these come from the perineum, grow larger and more conspicuous as they descend, and form a union below the inferior commissure, with similar fasciculi com- ing from the opposite labium. Some consider these fasciculi, collectively, as forming a distinct muscle, and give it the name of sphincter vagina. They will, unquestionably, perform such an office ; but I know of no occasion on which they appear to be so manifestly called into action, as when a mare, just after staling, is ejecting the stagnating drops of urine from the vagina by re- ])eated eversions of the labia and os vaginee. The labia are lined l)y a mucous membrane (the same as that which lines the vagina), which is continuous with the skin covering them externally, has a smooth humid surface, a pinkish hue (unless it be at the season of the venereal oestrum, when it is deeply reddened), and is perforated by the discharging mouths of numberless mucous follicles. THE COMMISSURES are the angles uniting the labia, above and below. The superior cotnmissure is extended into a sharp angle, and joins the perineum ; (he inferior is obtuse or rounded off, and is bounded by a hollow, named ihej'ossa navicu- laris, at the bottom of which is lodged the CLITORIS. — This miniature resemblance of the male organ is brought into view by simply dilating the vulva. Not only in its appearance is it strikingly like the penis, but it is found to bear the same close analogy in structure. Its extremity is in- vested in a doubling of thin and delicate skin, which is hairless, and commonly marbled ; or, if not, black, or entirely white : a part that corresponds to the prepuce of the penis. It is firmly at- tached to the pubes by two short ligamentous prolongations, forming its roots. These unite into a cylindrical body, from two to three inches in length in a state of distention, and this consists of two spongy canals, separated by a pectinated fibrous parti- tion, and inclosed within a dense, firm, white tunie : in fact, it is a structin-e altogether the counterpart of the corpora cavernosa penis. To this is added a bulbous termination similar in form and composition to the glans penis ; and through it is a per- foration out of which may be squeezed a sebaceous matter that serves to anoint the part, and preserve its aptitude for that sen- sual enjoyment of which it (as well as the glans penis) is known to be peculiarly susceptible. To the clitoris belong a pair of muscles, named the ereclores cliloricUs ; they will be found de- scribed at page 130. GENERATIVE SYSTEM. 301 The Meatus Urinaiuus is also a part that can be shewn without the aid of dissection, and this is a stage of inquiry in which we ought to make ourselves well acquainted with its si- tuation : but, as it is blended in composition with the vagina, I shall postpone the consideration of its structure until that canal has been described. INTERNAL PARTS. THE VAGINA, UTERUS, FALLOPIAN TUBES, TIMBRI/E, AND OVARIES. OF THE VAGINA. The Vagina is a musculo-uiembranous canal of large dimen- sions, extending from the vulva to the uterus. Situation and Connexion. — It is situated within the cavity of the pelvis, having the bladder below and the rectum above it; to both of which it has broad cellular attachments, in addition to the reciprocal connexion of all three parts through the reflections of peritoneum. To the rectum it is closely and firmly attached, by cellular membrane, along its upper side; to the cervix, and to the upper half of the body of the bladder (which is not covered by peritoneum), its inferior and anterior part is connected by a broader and looser cellular band ; and the extreme parts of the canal in front, both superiorly and inferiorly, are applied against the peritoneal pouches formed between the uterus and rectum above, and the uterus and bladder below. Figure and Volume. — The figure of the vagina (when dis- tended) is that of an oblong cylinder; but in the collapsed state its sides fall into contact, and it will then vary its form according to the full or empty condition of the bladder and rectum : when they, especially the latter, are distended, the long axis of the canal will prove from side to side, with the exception of its ori- fice, which will have the long vertical diameter still preserved by its union with the vulva. The most capacious part of the canal is the posterior ; there it even exceeds the dimensions either of the bladder or rectum : the part joined to the meatus urinarius is considerably contracted, but from thence it gradually widens to the outlet. Length and Course. — The length of the canal is about eighteen inches. Its course is horizontal : its axis, however, does not exactly preserve the straight line; it rather shews an inclination to a curve the same as the rectum does. Corjwra Cavernosa Vagiiuc. — The vagina at its commence- ment I'loui the vulva is much thicker in its parictes than clbc- 302 GENERATIVE SYSTEM. where ; a circumstance partly owing to a coating of strong mus- cular fibres, and partly to two cellular or cavernous membranous bodies, one upon either side, which have some resemblance in structure to the interior of the glans penis. They are inclosed in membranous coverings, enveloped in adipose substance, and shew signs internally of having, in life, contained blood. I know of no appellation in use for these bodies : M. Girard calls them " bulbes vaginals." I see no impropriety in naming them the corpora cavernosa vagincc. Structure. — The vagina in composition is partly muscular and partly membranous. The orifice of it is bound by the strong, red, circular, fleshy band forming the sphincter vaginae ; and the adjoining part of the canal is also encircled by some considerable fleshy fasciculi : but the part most compacted, and most thickly and regularly coated with muscular fibres, is that which is con- tracted — which receives the urine as it flows from the meatus urinarius; though the fasciculi hereabouts are not so red, nor so strong, as those blended with the sphincter. Farther forward than this, the vagina is substantially composed of membrane. There are, indeed, to be found colourless fibres taking various di- rections scattered over its surface ; but they present no very un- equivocal marks of muscularity, though they are commonly con- sidered to be of that nature : fibres apparently similar to these are likewise discoverable underneath the red fasciculi posteriorly; but there they take a logitudinal course. The membrane of the vagina, the part of which it is integrally constituted, is one of the mucous class, and one that possesses considerable density, extensibility, and resistance. Its exterior surface is rough and flocculent, from the adhesion of muscle and other parts. Its interior is smooth and polished, humid from se- cretion, and has a very pale pinkish cast ; unless the mare be under the influence of the venereal oestrum, and then its redness is considerably heightened and its secretion abundantly aug- mented. In the ordinary state this membrane is thrown into folds, larger in breeding mares than in others, technically called ruga, which continue without much regularity from its outlet to its uterine end. Follicles furnishing the mucous secretion are scattered about underneath the membrane ; and their orifices are generally most conspicuous within the more capacious part of the canal. MEATUS URINARIUS.— Considerably in advance of the cli~ toris, altogether about four inches in the collapsed state from the entrance of the vulva, is an opening leading from the lower part of the vaginal canal, large enough to admit with ease any one of the fingers: this is the orifice oj' the meatus urinarius, and it is a GENERATIVE SYSTEM. 303 part with the situation of vvliich we cannot be too famiUar, as upon such knowledge will principally depend our skill in passing the catheter. The conduit — the meatus — into which it leads is about two inches in length; and its course is downward and for- ward : it is surrounded below by the muscular fasciculi of the vagina, and covered above by its lining membrane. The instru- ment therefore (which should have more curve than is commonly given to it) must be introduced so as to follow this oblique direc- tion, which will be accomplished by elevating the handle of it as soon as the point is pushed into the meatus. The orifice of the meatus is guarded by a doubling of the vaginal membrane, hang- ing over it like a curtain, and serving the purpose of a valve. Care must be taken to elevate this by means of the instrument ; or, should there be any difficulty experienced in doing this, the left hand may be carried per vaginam to the part itself as an assistant. The large and conspicuous cauliflower protuberance at the bottom of the vagina, is the cervix uteri: it will be described with the uterus. OF THE UTERUS. The uterus or womb is a hollow, musculo-membranous organ, imited to the anterior part of the vagina, destined for the recep- tion of the fruits of impregnation. Figure and Volume. — The uterus of the mare is one of striking and peculiar figure. Its bodij (which is the bulky, oblong part) bifurcates anterioily into two coruua or horns. I hardly know what the whole is like in figure, unless the vagina be taken with it, and then (m a mare that has never been fecundated) the tout ensemble very much resembles an insect of the beetle tribe : the vagina representing the bottle or body ; the uterus, the head and neck ; and the cornua, the horns. But, during the period of gestation, the womb undergoes an almost incredible augmentation in volume ; and it never afterwards recovers either its identical original form or virgin state of contraction. Division. — We distinguish in the uterus, bodi/, harm, neck, and mouth. The body is the oblong or cylindrical part, growing out of the anterior portion of the vagina, into the centre of whose cavity it is presenting its posterior termination, the os uteri, while it is giving origin in front to the horns. Its upper and under surfaces are convex, and most prominent towards the middle ; its corners or angles are round, it being evidently formed altogether for the purpose of giving capaciousness within. This part of the uterus 304 GENERATIVE SYSTEM. lies wholly within the pelvis, between the bladder and rectum, and is entirely covered by peritoneum. The cornua or Iwrns, rising from the body at an acute angle with each other, take a progressively divergent course to the loins, under the broad plates of the ilea ; they are consequently not entirely confined to the pelvic bason. Their length and vo- lume will be much greater in breeding mares than in others, though their increase will be less than that of the capacity of the uterus : indeed, in virgin mares, the diameter of a single horn is little exceeded by that of the womb itself In figure they are cylindrical ; they bend upward in their course, and they termi- nate in round extremities ; to which is loosely appended the ovaries, through the medium of the Fallopian tubes. The cervix or neck of the uterus is the rugose portion pro- truded backward into the cavity of the vagina. From its flower- like appearance, the French have fantastically named it " la fleur epanouie :" it is a part, however, that can only be said to be de- monstrable in a virgin uterus in the undistended state : inflate the womb, and the cervix will disappear ; also one that during gestation undergoes very remarkable changes. The vertical slit or oval-shaped aperture in its middle is the os uteri or mouth of the uterus. The peculiar florulent aspect of the cervix is owing to its being enveloped in a prolongation from the lining membrane of the uterus, which is uniformly puckered into many rugcc as it passes through the os uteri : around the sides of the cervix these rugae become continuous with those of the vaginal membrane. This is a part that receives an especial abundant supply of mu- cous secretion. Ligaments. — Independently of its connexion with the vagina, the uterus is confined in its place by two broad productions of peritoneum which attach it to the sides of the pelvis, named its broad ligaments. They are formed in this manner — one portion of peritoneum reflected from the bladder covers the under parts of the body and horns of the uterus, their upper parts receiving a similar covering from another portion of the same membrane de- rived from the rectum ; the two portions subsequently unite at the sides of the uterus, and continue in union to the opposite parts of the pelvic parietes : by which arrangement the membrane really divides the pelvis into two cavities, or rather blind pouches, one existing between the uterus and bladder, the other between the uterus and rectum ; at the same time that it serves to connect these parts mutually to one another. The cervix consequently receives no peritoneal covering. These ligaments serve to sus- tain between their layers the vessels and nerves belonging to the GENERATIVE SYSTEM. 305 organ ; to preserve its equilibrium during gestation; and to aid in retaining it in its proper centrical situation. Structure. — Underneath the peritoneal tunic of the uterus, intimately united with it by a short cellular tissue, is a dense fibrous structure, possessing a considerable degree of sfrengtii and extensibility, and generally considered to be muscular : and the fibres certainly assume that appearance, though their direc- tion is very various, some running circularly, others deeper- seated longitudinally, and others again decussating these. But, about the cervix in particular, where the fibres ai'e strongest, most collected, and often have a pale bloody tinge, the muscular structure is palpable. Still, however, were this disputed, proofs of its muscularity might be drawn from a physiological as well as an anatomical source. During the period of gestation, this tunic not only experiences considerable extension, but may be proved to undergo veritable accretion. Inwardly, the muscular is opposed and adherent to the internal tunic; but their connex- ion, which is also cellular, is looser than that existing between it and the peritoneal covering. Caviti/. — The cavity of the uterus, having the same irregular form as the exterior, has three outlets — one of considerable magnitude communicating with the vagina, through the os uteri ; two others of very small size, through the extremities of the cornua, leading into the Fallopian tubes ; the situations of which are denoted by two little whitish eminences visible upon the in- ternal surface. The membrane lining the cavity is one of the mucous description. It assumes a more vascular and villous as- pect than that coating the vagina, but, like it, is thrown in the collapsed state of the organ into numerous rugee, which pervade the cornua as well as the body, and bear some comparison to an irregular network : these rugae are larger and looser in mares who have bred foals. The surface is every where copiously furnished with mucous secretion by subjacent follicles, whose orifices are here visible to the naked eye. OF THE FALLOPIAN TUBES. The Fallopian tubes are two trumpet-shaped or conical canals, running with a remarkably serpentine course, within the folds of the ligamenta lata, from the extremities of the cornua uteri to the ovaries. Course. — The tube on either side commences by an aperture in the cornu, encircled by an elevated whitish margin, which is scarcely large enough to admit a small silver probe : froui this it proceeds forward, folded in peritoneum, extremely convoluted in its course, until it reaches the ovary, to which it becomes R r 30G GENERATIVE SYSTEM. attached ; it then begins to enlarge in its diameter, grows less convoluted, and serpentines along the posterior side of the ovary, in order to reach the fissure of that body ; at which part it ends in a fringed doubling of membrane, named the corpus Jimbriutwn, by a funnel-shaped irregular opening, turned back- wards, and large enough to admit an ordinary-sized black-lead pencil. Structure. — These tubes, when stripped of their peritoneal envelopes, shew a fibrous texture ; and when opened, exhibit a rugose, villous, mucous surface, very similar to that of the in- ternal membrane of the uterus. They are amply supplied with bloodvessels, which make their way to them between the layers of the broad ligaments. OF THE FIMBRIA. The fimbria, or corpora Jimbriata, are, then, nothing more than the fringed terminations of the Fallopian tubes, formed by doublings of the enveloping membrane around their open ori- fices. They spread over the ovaries, concealing the posterior or cleft parts of those bodies from our view ; but are perfectly unattached and loose, and consequently can follow the ovaries in any movements of place or position occasioned by visceral commotion within the abdominal cavity. OF THE OVARIES. The ovaries, or female testicles, are two egg-shaped bodies, situated farther forward than the Fallopian tubes, within the cavity of the abdomen, at the distance of an inch and a half from the cornua uteri. They receive close coverings from the anterior portions of the bi'oad ligaments, by which they are loosely attached to the spine, in their situation beneath the ilea, and a little behind the kidneys : indeed, the left ovary has a peritoneal attachment to the left kidney. So that if it were our intention to extract them, the incision should be carried along the crista of the ileum, and the hand introduced in a direction backward and inward. Magnitude and Form. — These bodies are about the size of walnuts. They are not regularly oviform : they have deep fis- sures in their posterior sides, which are occupied by the corpora fimbriata. Taking them and the Fallopian tubes together, they bear a striking resemblance, at fii'st view, to the testicles and their ducts in the male. Structure. — Underneath their peritoneal coverings, the ova- ries have whitish fibrous tunics, dense and inelastic in their texture, and which warrant the comparison generally made of GENERATIVE JiYSTEM. 307 them to the albugiueous tunics of the testicles. Internally, the ovaries are composed of a whitish spongy substance, in which are, in some instances, found little vesicles containing a yellowish glairy fluid, in others one or more dark yellow or brownish sub- stances, named corpora lutea: the vesicles are the ova, which from impregnation take on further development ; the corpora lutea denote the parts from which vesicles have already burst, and consequently only exist in the ovaries of mares whose organs have been engaged in the generative process. Prior to the age ripe for sexual intercourse these bodies are small and white ; but as soon as the time for copulation arrives, they grow large, redden externally, and present many yellow spots or streaks through their substance within. Organizatiou. — The arteries supplying all these parts are — 1. The vaginal artery, a branch from the internal iliac, which accompanies the obturator artery, and afterwards dips down by the side of the vagina, upon which it branches out in various directions, sending some ramifications in its way to the rectum, and transmitting others to the uterus and bladder. 2. The uterine artery, a branch from the external iliac, coming otT after the ilio-lumbar, and distributing its branches principally upon the cornu uteri. 3. The spermatic artery, coming from the aorta, is convoluted in its course, and supplies the ovary, fimbriated body, and Fallopian tube. The nerves are derived from the hypogastric plexus. Both the vessels and nerves take their passage between the layers of the broad ligaments, insinuate themselves underneath the peri- toneal covering, obliquely pierce the substance of the muscular tunic, and ramify extensively between it and the internal mem- brane. APPENDIX TO THE GENERATIVE ORGANS. THE UDDERS. Although not immediately concerned in the process of genera- tion, these organs co-operate towards the same important end — the continuation of the species. The mamm^, or udders, are two flattened oval-shaped bodies, formed for the purpose of secreting milk. Situation. — They depend between the thighs from the postero- inferior part of the belly, in quadrupeds in general ; but in the human species, and in the ape tribe, they are attached to the breast. The advantages resulting to the quadruped (who has no power of erecting himself or handling his young) from this si- 308 GENERATIVE SYSTEM. tuation of the mammaB, are — that they are well protected, by the trunk above and the thigh on either side, from external injury, that they are conveniently placed for the foal, and that they do not in the least interfere with progression. Volume. — In fillies and virgin mares the udders are so small that there hardly appears to be any ; and in mares who have not hud more than one or two foals, they likewise regain nearly their original flatness ; butin this last instance the teats are commonly left larger, looser, and more pendulous than before, in conse- quence of the reiterated extension of them by the foal : a circum- stance on which we may rely with tolerable certainty for a knowledge of this fact. In mares who have had several foals, the udders continue prominent and pendulous, and possess a flabby feel ; and this is a state we cannot well mistake. To- wards the latter end of gestation this part undergoes further evolution, swells and grows firm to the feel, and becomes dis- tinctly visible as we stand behind the mare. Within a few days of parturition secretion begins, and the udders grow turgid with milk : they do not, however, acquire their full distention until the foal has drawn them for a few days, from which time they main- tain their volume with little variation during the period of lacta- tion. Soon after the foal begins to forsake the teat, the secretion of milk diminishes ; and this is followed by a contraction of the bag, which goes on gradually until it has resumed nearly or quite its former flatness. In a state of full evolution, the udders assume a hemispherical form, and acquire a firm plump feel; at other times they are soft, flabby, more or less pendulous, and possess neither definite figure nor volume. Coverings. — The outer covering of the udders is an extension from the common integuments of the belly. This is thin and fine in its texture, is commonly black, and is cloathed with a few long downy hairs, growing thinner as they approach the teat, immediately around which the skin is without any hair. Under- neath the skin, adhering to it by intervening cellular membrane, is spread over the gland a white, elastic, ligamentous covering, interspersed with several fibrous bands, which is derived from the faschia superficialis abdominis : this serves to give support and compactness to the glandular structure, and, in consequence of detaching processes into the interior among the lobules, to strengthen their inter-union one with another. Structure. — The interior of the udder exhibits a light yellowish aspect, and evidently possesses a lobulated structure, held to- gether by a fine cellular tissue, here and there interspersed with granules of fat. It is constituted of glandular masses, irregular in magnitude and form, and loosely connected one with another, GENERATIVE SYSTEM. 309 each of vvliich masses is composed of a number of lobules closely compacted and united together : a composition altogether that accounts for the loose or knotty feel which the gland is well known to possess. These insulated lobulous portions receive small arteries in numbers from the parent arterial trunk, from whose terminations arise (we do not precisely know in what manner) the tuhuli lactij'eri. These numberless little tubules, by repeatedly conjoining one with another, become at length several demonstrable canals, radiating from every part to as- semble in the teat : still uniting one with another in their course, and occasionally dilating into considerable reservoirs for holding the secretion. The lactiferous conduits are continued through the substance of the teat, wherein during its relaxation they are so serpentined or coiled, that milk cannot spontaneously flow from them ; but in the distended state of that body, or when it is drawn out in the act of suction or milking, these ducts are ren- dered straight, and the milk, either in consequence of internal or external pressure, readily runs out. THE PAPILLA, teat, or dug, depending from the most prominent part of either udder, near its middle, is conical, black, and hairless. Its tegumental sheath is of the same description as that covering the bag from which it is derived, only it is per- forated at the apex by three holes, to give issue to the milk ; and underneath this is a second tunic, which comes from the elastic ligamentous covering, also of the gland. Through these open- ings (one of which is commonly conspicuous for its size) the milk is discharged from the conduits of the lactiferous tubes. When the udder becomes charged with milk, it flows into the teat, and distends it ; and as the secretion is probably influenced in animals (as it is in the human subject) by anxiety for the young, the animal evinces this feeling by a state of distention of these parts. The papilla, as has been remarked before, en- larges during the season of lactation, and it does not afterwards recover its original volume so nearly as the udder itself does: a fact, I repeat, that may lead, when the first sign is wanting, to the discovery of mares that have bred. Sucking is apparently an opeiation purely mechanical. The teat is seized, and so closely compressed by the lips of the foal, that the imbibing effort which follows has a tendency to pro- duce a vacuum in the lactiferous tubes, now rendered straight from extension : this is counteracted by the pressure of the at- mosphere upon the surface of the udder, and the consequence is, that the milk is forced from its reservoirs into the mouth, on the same principle that water is impelled into the barrel of a syringe by raising the piston. 310 Section IX. NERVOUS SYSTEM. comprising the brain ; the spinal marrow nerves; and the ganglia. OF THE BRAIN. THE brain is the soft white mass filling the cavity of the cranium. Magnitude. — In no animal is the cranium so large, in relation to the face, as in man ; consequently, in none other is the brain (whose volume is always in uniformity with that of the cranium) of such magnitude. In horses the brain is but small, compared with the general bulk of the animal ; and though there exists some difference in the dimensions, as well as form, of the heads of horses of different breeds, they are too trifling, in an anatomi- cal point of view, to merit notice here*. Division. — In the brain are distinguished three divisions, though all three are continuous in one and the same substance : t/ie cerebrum, so large that it occupies at least three-fourths of the interior of the skull ; the cerebellum, or little brain ; and the medulla oblongata. That portion of medullary substance which extends from the brain through the whole length of the spinal canal is called the medulla spinalis, or spinal marrow. Situation. — No viscus in the body is so well defended from external injury as the brain : on every side it is enclosed by bony walls, well constructed to make great resistance, and more espe- cially so at those parts where external violence is likely to be received. The interior of the skull is variously furrowed and indented by the more projecting parts of the organ, to which, in every particular, its figure is nicely adapted ; for it is by the shape of the brain that that of the cranium is moulded, inasmuch as the formation of the one precedes that of the other. The re- lative situation of the divisions of the brain differs in the horse from that of the corresponding parts of the brain of the human * " The brain of the shark does not weigh 3 ounces, although the animal itself is generally 300 lbs. in weight. The brain of the sheep, with respect to the whole weight of the body, bears the proportion of 1 to 150. In a dog the proportion is less : it is as 1 to 100. As we ascend in the general scale of rational beings, the magnitude of the brain bears an increased and strongly marked proportion to the size of the system in general. In the African, it is as 1 to 54. In an European, as 1 to the 50th part of the sys- tern altogether." — Saumarbz'* System of Plii/siology. NERVOUS SYSTEM. 311 subject ; though both organs, in regard to the bones of the cranium, are similarly lodged : e. g. the cerebrum, which forms the upper and anterior portion in the human subject, constitutes the lower and anterior in the horse ; while the cerebellum, which in the former is placed below and behind the cerebrum, in the horse is placed above and behind it. This difference, however, is but imaginary, being entirely referable to the position of the head ; for if we place the horse's head upon a table, so that it rest upon the branches of the lower jaw, we shall find no difference whatever in the relative situation of these parts. Coverings. — The brain has three coverings, called its mem- hranes or meninges ; the dura mater, the pia mater, and the tunica arachnoides. Of these, the exterior is the DURA MATER. — Though called a membrane, this outer covering is a substance, dense, tough, and inelastic in its texture, its component material being chiefly tendinous fibre. It is firmly adherent to the interior of the cranium, offering consider- able resistance to the elevation of the skull-cap, even after the bone has been completely divided ; which union is the result of many little processes shooting from the membrane in between the teeth of the sutures of the cranium, as well as of numerous small bloodvessels passing from it into the pores of the inner table of the bone, to which it supplies the place of internal periosteum. Surfaces. — The external exhibits a smooth, dry, opaque, red- dish aspect, rendered uneven by the subjacent prominences of the brain. The internal is lighter in shade, shiny and slippery, and moist from the exudation of a serous secretion. It has no connexion with the membrane underneath ; at least, no other than it has with the brain itself — by means of the vessels passing between them. Organization. — The bloodvessels of the dura mater are not numerous, but of sufficient magnitude to admit of coarse injec- tion. The membrane itself aflbrds a good example of the truth of the observation, " that the capillaries are not abundant in fibrous texture." By some, nerves are denied to exist in the dura mater: others conceive that they have discovered nervous filaments in its texture. In a sound state, the membrane ap- pears to possess very little if any sensibility ; for it may be cut or irritated in various ways without seeming to cause the animal any pain whatever. Processes. — The dura mater sends off detached portions or processes, which are extended across the cavity of the cranium, for the purpose (it would seem) of more steadily and effectually supporting the brain, and guarding against the pressure of one part or division upon another. These processes are two in num- 312 NERVOUS SYSTEM. her, and each consists of a duplication (or two layers) of the membrane. They are named the J'alx and the tentorium. The falx or longitudinal process, so called from its being resembled to the blade of a scythe (and indeed the comparison is a striking one), is that expansion of the membrane which de- scends for a short distance between the lobes of the cerebrum. It takes its rise from the crista galli, including the projection between its laminae, from which it curves forward and upward, adhering in its way, first to the frontal, then to the entire length of the sagittal suture, growing broader as it proceeds : at length it terminates upon a thin transverse plate of bone, a process of the OS occipitis anterior, where its laminae split, diverge, and end in continuity with the tentorium. Whatever may be the ?/se of the falx, it seems to be a part whose presence can be dispensed with, for I have a cranium now before me in which it may be said to be deficient ; at least, all such appearance consists in a small tri- angular piece of membrane which does not project more than an inch from the tentorium : and this cranium belonged to a young horse who was perfectly free from any phrenetic disorder. The falx is commonly said, however, to stay one lobe of the cerebrum from falling or pressing upon the other when the head is inclined to one side. The tentorium, or transverse process, is extended, after the manner of an arch, from the cerebral plate of theos occipitis, along the sides of the cranium, to its base ; whence, greatly di- minished in breadth, it may be traced onward to the body of the OS sphenoides, where it vanishes in the common covering of the dura mater. It is composed of two laminae : one is continuous with the falx ; the other joins that portion of the membrane which covers the cerebellum. The tentorium is equally divided by the falx into two lateral portions. There is some variation to be seen in different subjects in the figure and extent of this pro- cess, but I have not remarked that it is ever deficient. It forms a transverse intersection within the cavity of the cranium, or partial septum between the cerebrum and cerebellum, and ap- pears to be of service in fencing these important parts in their proper places, and keeping them, during the various motions and positions of the head, from pressing upon each other. Sinuses. — These are triangular spaces, or cavities, found to exist between the two layers of membrane forming the processes. There are several of them. Those most worthy of notice are the following : — first. The superior or longitudinal sinus, which runs within the duplicature of the falx, along its superior border. It begins in a narrow channel, gradually widening and assuming a NERVOUS SYSTEM. 313 triangular figure as it extends backward, and terminates with the falx, at the cerebral process, where the lateral sinuses and it conjoin their canals. Internally, this sinus presents to view an uneven surface, upon which the veins are seen terminating by large open orifices discharging their blood in the same direc- tion that the stream takes within the sinus itself. Here and there are seen slender chords, crossing the canal from side to side ; which serve to strengthen its parietes and prevent over- distention. The two lateral sinuses are formed within the duplica- ture of that part of the tentorium which is attached to the tem- poral and occipital bones; one extending to the right side, the other to the left side. They begin at the cerebral process, where the longitudinal sinus ends ; and they terminate at the foramina lacera basis cranii in the jugular veins. Their canals are also tri- angular, and are intersected by fibrous filaments. They receive veins both from the cerebrum and cerebellum. The cavernous sinuses, so named from the cavernous appearance of their interior, which includes a structure having some resemblance to the corpus cavernosum penis, are formed out of the dura mater upon the body of the os sphenoides. These cavities are remarkable from receiving some important nervous trunks in their passage from the brain, and from lodo-- ing the terminations of the internal carotid arteries. They com- monly communicate with the Sub-occipital sinuses. — These are likewise of the same formation, and are found upon the cuneiform process of the os occipitis, running longitudinally to the foramen magnum. They receive veins from the cerebellum and posterior parts of the cerebrum. THE PIA MATER is the membrane immediately investing the brain, sending processes into its substance which separate the cortical portions of its convolutions, and having a further connexion with the organ through the medium of the numerous interpassing bloodvessels. The reticular arterial ramification we descry upon it, is for the purpose of transmitting vessels of mi- nute dimensions into the interior of the brain; which, thouoh they can be traced by us no deeper than the cortical, are ulti- mately destined for the cerebral substance. The pia mater not only clothes the convoluted part of the cerebral mass, passing from one hemisphere to the other, but it gains admission into the ventricles, and gives them a lining. It differs altogether in its aspect and structure from the dura mater; presenting a smooth surface exteriorly, but a rough and villous one next to the brain, and being composed of a beautiful network of bloodvessels, 314 NERVOUS SYSTEM. united together by a delicate cellular tissue : it is, in fact, the immediate source from which the brain derives its blood, and, at the same time, the medium through which the unexpended blood is returned to the sinuses of the dura mater. THE ARACHNOID MEMBRANE (so called from being resembled to the spider's web) is of a texture so fine, and of a nature so perfectly transparent, that, under ordinary circum- stances, it is hardly demonstrable from the pia mater underneath it, to which it is everywhere closely and intimately applied, ex- cepting that it does not (like that membrane) dip down between the convolutions. With pains, it is occasionally demonstrable in places about the base of the brain. Physiologically con- sidered, we have no right to doubt of its being organized ; al- though, hitherto, the most successful injections have not demon- strated the existence of bloodvessels in it. In the human subject (in whom these parts are more developed) it has been said to have shewn vascularity in cases where the membranes have recently undergone the effects of inflammation. Concerning its use, no writer has been bold enough to speak ; physiologists are unable to say for what purpose so delicate and transparent a structure is here interposed. Vascula?- communication. — From the vascular connexion which subsists between the scalp, upon the exterior of the skull, and the dura mater, upon its interior, we have at once an explanation of that apparent anomaly in pathology, viz. that external injuries of the skull frequently induce symptoms of inflammation of the brain, or its membranes : in the human subject, such wounds are always considered, on this account, as dangerous, and, in- deed, it not very unfrequently happens that they prove mortal. Though we have never seen a case of this description in the horse, there does not appear to be any good reason why we should not be cautious how we make or treat wounds of such a nature. Effusion. — A fluid, differing from serum in its properties, though like it in appearance, is occasionally effused between the dura mater and tunica arachnoides, or, more commonly, under- neath the latter membrane (as well as within the substance of the brain itself), constituting a disease, termed hydrocephalus : it rarely happens in horses ; but in the human subject, and more especially in children, it is by no means an unfrequent cause of dissolution. BRAIN. — Having already given an outline of the situation and division of this organ, I shall now make some general ob- servations in regard to its structure. Structure. — If a vertical section is made of any part of the NERVOUS SYSTEM. 315 brain, we perceive that its interior presents two substances of different colours: the outer of these, of a dirty greyish hue, is called the cineritious or cortical part ; the inner, which is white, and of which the chief bulk of the organ is composed, the me- dullary. The cortical part (which is, proportionately to the medullary, more prevalent in the brain of the horse than in that of the human subject) is not always the outer — in some places, the relative disposition of the medullary and it being reversed — it is that, however, in which the bloodvessels of the organ are most conspicuous : for, in consequence of being closely invested by the vascular pia mater, it receives the numerous ramifications of arteries transmitted by that membrane for the nourishment of the interior parts of the brain . On the other hand, in the medul- lary portion, the bloodvessels, which in health only convey the colourless parts of the blood, are so minute that they escape no- tice ; unless, occasionally, here and there, when it has been in- flamed, the bloody specks upon its divided surface denote the division of those that have become of sufficient magnitude to admit the red globules. According to the investigations of the most accurate anato- mists, the brains of animals appear to be of a fibrous nature; and in many parts of the human brain (which is larger than that of any other animal) the disposition and course of its fibres have been traced : such inquiries, however, have, unfortunately, not led to any elucidation of the sensorial functions, nor are we aware that they have been attended with any advantageous result in regard to its pathology. After all, the truth is, that the inti- mate structure of this organ is still unknown to us. With regard to the cineritious or cortical part, there is much reason to be- lieve, that it is almost wholly constituted of the ramifications of bloodvessels of extreme exility ; from which others, still more minute, are distributed to the substance of the medulla. It is here worthy of remark, that in no instance does Nature so invariably present us with the same structure and arrangement of parts as in this viscus : in almost every other in the body, we can discover some little variation, in this respect, in different subjects ; but in the brain, the same uniform appearances ever present themselves on dissection : so intimately united do struc- ture and function seem to be in this organ. Duplicity. — The cerebrum is divided into two halves, called hemispheres, each of which is formed of parts precisely sin)ilar, in every particular, to each other; so that, in fact, every part of the organ may be said to be double, i. e. its two halves arc con- stituted of several small portions, which are not only perfectly 316 NERVOUS SYSTEiM. alike in structure, but are of corresponding symmetrical forms and dimensions : a remark that not only applies to the brain it- self, but one that holds good, likewise, with regard to the spinal marrow. An animal, therefore, has, to all intents and purposes, tivo brains : and, probably, for the same reason that he has two eyes, two ears, and a double tongue. Arteries. — The arteries which supply the brain, are the two vertebrals, besides two other considerable branches from the carotids, called the internal carotids : its blood is returned from the sinuses of the dura mater by the vertebral and jugular veins. It is on the supply from the vertebral arteries, however, that this organ mainly depends for the preservation of that energy essen- tial to the support of life ; for if ligatures be put on these ves- sels, the animal speedily dies ; whereas both the carotids may be tied without occasioning any apparent ill effects. We shall now examine the divisions of the brain Cviz. the cerebrum, cerebellum, and medulla oblongata) separately; com- mencing with the Cerebrum. The largest portion of the brain, and that which presents itself to our view immediately on raising the skull-cap, is the cere- brum. It is lodged in that capacious elliptical chamber which is formed, in front, by the parietal bones; behind, by the ethmoid, sphenoid, and posterior occipital bones ; laterally, by the tem- poral bones ; inferiorly, by the roofs of the frontal sinuses, and by the ethmoidal plates ; and, superiorly, by the tentorium. The visible surface of it (as the cranium is ordinarily sawn open) may be said to represent a convex semi-oval, of which the broader end is turned upward. It is equally divided by a longitudinal fissure along its middle, into which the falx cerebri descends ; and its divisions, which are perfectly symmetrical, both internally and externally, are denominated hemispheres. Corpus CaHosum. — In parting the hemispheres, so as to admit light between them (by which a iesw small interpassing vessels and some weak celullar connexions become lacerated), we per- ceive a white longitudinal body, covered by pia mater, uniting the hemispheres at the bottom of this fissure : this is the corpus callosum. Each hemisphere, separately regarded, has an outer surface, waved or convoluted, which is adapted to the undulated concavity of the skull-cap ; an inner perpendicular plane, which is opposed to the one of the opposite hemisphere ; and a base, di- vided into lobes, the description of which I shall postpone until the interior parts have been examined. NKRVOUS SYSTEM. 317 Centrum Ovale. — In the dissection of the brain I shall pursue the customary method of the schools of anatomy; and in de- scribing its several parts, preserve the names used in human phre- nology so long as I find them applicable to correspondent ap- pearances. The first step consists in making a clean horizontal section of the brain, parallel to its present convexity, by laying the knife flat upon the surface of the corpus callosum, and making a sweeping cut (With its edge first inclined a little upward, after- wards a little downward) through one hemisphere at a time. There being no distinguishable parts in the abscised portions, they may be cast away ; but the surface which their removal has exposed being one that presents the greatest superficial extent of medullary substance that can be shewn at one view, the appear- ance altogether has been described as the centrum ovale* . The form and disposition of the corpus callosum become now de- monstrable. It is placed in the centre of this medullary con- vexity, with which it is continuous in substance. It is narrower below than above. It unites the medulla of the two hemispheres in the middle. Inferiorly, it passes between the hemispheres, turns backward and terminates at the base of the brain, in the crura cerebri ; superiorly, it joins the fornix, and spreads upon the hippocampi ; and anteriorly, it may be said to form the roof of the lateral ventricles. Running along its surface are seen two prominent lines of medullary matter, between which exists a lon- gitudinal linear depression, named the raphe. Lateral Ventricles. — By making a longitudinal incision through the corpus callosum, on either side of the raphe, we penetrate a cavity occupying the innermost part of the brain, which, with its fellow within the opposite hemisphere, constitute the two lateral ventricles. Having freely opened it, we find a watery fluid within, which serves to keep its parietal surfaces constantly wet, and to prevent (it is said) adhesion of them. The figure of the ventricle, both from its construction and from the inequalities of its contents, to which it is adapted, is extremely irregular. Its cavity extends as far forward as the front incurvation of the corpus callosum, from whence a winding canal is continued for- ward and downward to the base of the anterior lobe of the cere- brum, where it ends in a small circular conduit that leads into the ethmoidal ventricle : this canal, from its being represented to * The cortical matter, however, cannot be all pared away — it will intrude in places, and interrupt the uniformity of the surface : indeed, the horse's brain will less admit of being carved into such an aspect, in consequence of the proportionably greater quantity of cortical substance in its com- position. 318 NERVOUS SYSTEM. wind in its course like a horn, has got the name of the inferior cornu. From the superior part of the cavity, another flexuous passage, smaller than the former one, taking a direction at first outward, then downward, and lastly forward, leads to the base of the brain, through the substance of the middle lobe, and there ends in a blind termination : from which circumstance, and from its cylindroid figure, some call it the digital cavity, others the superior cornu. The two ventricles are lined (and the parts within them covered) by an extension of pia mater, which finds its way into them along with the vessels forming the choroid plexus. By this membrane, whose vascularity appears to be lower than that of the pia mater elsewhere, the watery fluid, it is supposed, is secreted : unlike serous cavities in general, however, the ventricles appear to hold water during life; for, if an animal is put to death suddenly, and these cavities are opened with all possible expedition, water, and not vapour, is uniformly found contained. Contents. — We now come to what are considered as the con- tents of the lateral ventricles. They are — the corpora striata, the hippocampi, the plexus choroides, the fornix, and the thalami nervorum opticorum. But a view of all these parts cannot be obtained until we have reflected the corpus callosum ; prior to which being done, that body should be cautiously raised, in order to shew the Septum Lucidum, the translucent medullary partition between the ventricles, which extends perpendicularly along the corpus callosum in front, and is attached to the fornix behind. It is broad inferiorly, grows gradually narrow superiorly, where it ends in a point, at the angular junction of the corpus callosum with the fornix. It consists of two thin laminse of medullary matter, included between and supported by the membranous linings of the ventricles, in the middle of which is a fissure or small cavity, by some described as the ffth ventricle, but more generally known as the fossa Sylvii. Sometimes this fissure is very de- monstrable, glistening interiorly with moisture ; at other times it is hardly perceptible. Corpora Striata. — When the corpus callosum is turned back, four large and remarkable eminences present themselves, two upon each side of the septum lucidum. The two inferior, and most bulky, are the corpora striata. They rise out of the lower and back parts of the ventricles, projecting into the middle of the cavities, where they become broad and approach the septum ; growing narrow and receding from each other, above ; below, extending along the anterior cornua. Externally, they have a NERVOUS SYSTEM. 319 thin lamina of medullary matter ; but this is partly obscured by the cortical substance of which their interior is exclusively composed. Hippocampi. — The two superior eminences, smaller and whiter than the last, whose anterior extremities lie between the pos- teiior of the corpora striata, are the hippocampi. These bodies, remarkable for their prominence and whiteness, occupy the su- perior spaces of the ventricles, where they lie in contact with the septum ; but, in proceeding backward, they diverge, stretch first outward, then downward, and lastly forward ; in fact, they de- scend into the superior cornua, and there end in bulbous ex- tremities, called the pedes hippocampi. This descent or elonga- tion, which may be denominated the cms hippocampi, is continu- ous above with the crus fornicis, but below it gets to the outward part of the crus fornicis, and gives off a thin, plaited, medullary border, which may be said to be an extension of the corpus fimbriatum. Their medullary covering appears to be continued from the corpus callosum ; their internal cortical substance, which is interspersed with medullary strite, originates from the very middle of the hemispheres. If sliced, they will be found to consist of alternate laminae of medullary and cortical matter. Plexus Choroides. — Deeply lodged in the channel between the corpus striatum and hippocampus, lies a red, soft, vascular sub- stance, consisting of a plexus or collection of minute bloodvessels, invested in an extension of pia mater, called the plexus choroides. This plexus first makes its appearance from behind the fornix : inferiorly, it ends abruptly in a round bulbous mass; superiorly, it sends down a process into the superior cornu. The arteries composing it come from the posterior arteries of the cerebrum : they enter the interior of the brain along a fissure, which in one place is a complete canal, existing between the posterior lobes of the cerebrum, and gain admission into the ventricles around the sides of the fornix. Its veins assemble and form a large branch, the vena Galeni, which branch unites with a similar one coming from the opposite plexus : the two conjoined make a single trunk, and that proceeds upward, along the above-mentioned fissure. The fornix is that part which receives the posterior border of the septum lucidum. It is extended, after the manner of an arch, between the corpora striata, below, and the heads of the hippocampi, above; where it forms a junction with the corpus callosum, which it meets at an acute angle. It has four pro- cesses or crura. The two inferior crura spring from the corpus albicantium, at the base of the brain; in their course forward from which, they approximate and unite into one main crus or 320 NERVOUS SYSTEM. pillar: thus united, they wind upward, describing an arc, and, as soon as they make their appearance within the ventricles, con- stitute the body of the fornix. The superior crura, which are comparatively slender, proceed from the upper end of the fornix, wind upward, and then descend into the superior cornua of the lateral ventricles, where they grow tapering, and at length end in sharp-pointed extremities. Their anterior or concave edges, which are thin, unattached, and somewhat uneven, have been named the corpora Jimhriat a; their posterior borders are continu- ous with the crura hippocampi : along their fimbriated edges run the lateral processes of the plexus choroides. The middle part or arch of the fornix is unattached ; but its superior or broad part is contiguously applied behind to the thalami, and adheres to them through the intervention of a fine membrane, investing the vessels of the choroid plexus which are ramifying hereabouts, named the velum hiterpositum : from the circumstance of the back of the fornix being imprinted by these vessels with many minute linear grooves, mostly running obliquely, this surface of it is commonly described as the lyra,psalterium, or harp. Thalami. — Having divided and reflected the fornix, and turned back the heads of the hippocampi, we bring into view the thalami nervorum opticorum. These bodies are also said to be in the lateral ventricles : more properly speaking, they form the upper and back parts of those cavities. They are white and conoid in form ; narrow and approximated, inferiorly, where they lie between, and rather behind, the corpora striata ; broad and directed opposite ways, superiorly; in front, they are opposed to the fornix, which they in a measure support; and behind, they contract into medullary bands — the tracfus optici, which turn round the crura cerebri to the base of the brain. Upon these bodies the separate portions of the plexus choroides unite into a single vascular chord, which takes its course along the canal between them, and makes its exit from the brain through the fissure left between the posterior lobes of the cerebrum. The thalami are firmer in their composition than the corpora striata : like those bodies, however, they are cortical within, thinly striated with medullary matter. Taenia. — In the groove between the thalamus and corpus stri- atum, partly covered by the plexus choroides, runs a conspicuously white, medullary band, designated the centrum semicirculare ge- minum, vel feeuia semicircularis. Commissures. — The contiguous parts of the thalami, flattened and closely applied, are united in one broad circular place by pulpy cortical matter, which union is called their commissura mollis. Immediately behind the fore part of the fornix, runs iNERVOUS SYSTEM. 321 transversely a firm medullary chord, which is extended in a curved direction, on either side, into the substance of the corpus striatum : this forms a band of connexion between the hemi- spheres, and takes the name of commissura inferior cerebri. Superiorly, above the commissura mollis, is another medullary chord, similar to the one last mentioned, but shorter and smaller, which is the commissura superior cerebri. Foramen. — Just over the commissura inferior, between it and the commissura mollis, between and in front of the optic thalami, under the arch of the fornix, is a triangular hole, called ihe fora- men commune inferius. Now, since the lateral ventricles com- municate underneath the arch of the fornix, it is evident that both of them must open into this foramen ; and since this fora- men leads into the third ventricle, it follows that this cavity and the lateral sinuses must reciprocally communicate through its medium. Between the commissura mollis and the commissura superior is another foramen, which would also be one of like communica- tion were it not covered and closed by the velum interpositum, which is here spread over the surfaces of the thalami, and tra- versed by the vessels of the choroid plexuses The third ventricle, as it is called, is nothing more than the fissure existing between the thalami, in consequence of their partial divergence, below and behind the commissura mollis, in the medium line of the brain. The floor or back part of this narrow oblong cavity is constituted of the crura cerebri. [nfundibu/uni. — Leading from the inferior part of this ven- tricle, is the infundibulum, a passage small at its commence- ment, but gradually enlarging to its termination, which takes place in a blind extremity, in front of the corpus albicantium, at the pituitary gland. Superiorly, under the superior commissure, is a passage leading from this cavity into the fourth ventricle (situated within the cerebellum), the 4ter a tertio ad quartuni ventriculum. Pineal Gland. — Over the third ventricle, deeply lodged be- tween the summits of the thalami, above and rather before the superior commissure, we find the pineal gland — a little, conoid, greyish body, marked by a slight depression along its middle ; enveloped in pia mater, derived from the vessels of the choroid plexus; and attached by that membrane to the thalami, and to the tubercula quadrigemina, which are placed behind it. From its base or inferior part proceed two \\i\\Q peduncles or foot-stalks, which run along the top of the superior commissure, and are implanted into the crura cerebri. The structure of this little organ remains unknown. It is possessed of considerable firmness, T t 322 NERVOUS SYSTEM. and is deeply reddened and higlily vascular within; but I have not remarked that it contains earthy matter, as is the case so frequently with that of the human brain. Nates and Testes. — Above the third ventricle, behind the pi- neal gland, and immediately over the iter a tertio ad quartuin ventriculum, are four considerable eminences, the tubercula qua- drigemina — or rather bigemina, since they are divided into the TWO nates and two testes. The 7iates, the foremost and by much the largest of these bodies, separated by a groove from the testes, and by a deep perpendicular fissure from each other, pre- sent semi-oval exteriors, of a mixed composition, cineritious and medullary, and are in intimate union with each other and with the testes. The testes, much smaller than the nates, are also ovoid in figure, but their long diameters are placed contrariwise — transversely. In their composition they are alike also, as well as in their connexions, both being jonied to the crura cerebri, by which they are supported. Cerebellum. In order to guard against a common misconception of the rela- tive position of this part, I shall repeat here what I took occasion to lay some stress upon in a former place — that the three divisions of the horse's brain are similarly lodged, in regard to their cra^ nial case, to what the correspondent parts in man are; but that when we view them as the animals naturally stand, their relative situation is altogether altered. The cerebellum (as in man) occu- pies that compartment in the basis of the cranium which is formed, above and behind, by the anterior occipital bones ; late- rally, by the petrous portions of the temporal bones ; and supe- riorly and anteriorly, by the tentorium : that septum being defi- cient inferiorly and anteriorly, to give passage to the crura cerebri to form a junction with the cerebellum; while the vacuity admits also of the projection of the anterior vermiform process, which is the only portion of the latter that does not rest upon the ten- torium. Peculiarities. — In volume, figure, and aspect, the cerebellum is at once distinguishable from the cerebrum. It is only one- sixth of the volume of the cerebrum. Its figure is irregular — it has two oval ends, placed transversely, united in the middle by a broad and prominent vermiform belt, its lateral dimension ex- ceeding its longitudinal. Its aspect is lobular or convoluted : but, in addition, it is everywhere so striated with deej) transverse fissures, that its appearance is altogether different from any other part of the brain. NERVOUS SYSTEM. 323 Lobes. — The cerebellum is superficially divided into three ob- long /obes — a middle lobe, and two lateral lobes. The lateral lobes, which are opposed to the posterior lobes of the cerebrum, are small and ovoid. The middle lobe is prominent, arched, and subdivided into lobuli by several sulci, conspicuous for their depth, crossing its upper and under surfaces. The anterior and more prominent part of this lobe, which is received into the great fissure of the cerebrum, is denominated the aiiterioi- vermiform process J the continuation of it, along the summit of the head, forming the posterior vermiform process. Arrangement of component Substances. — In the cerebellum, the disposition and pro|)ortioiiate quantities of medullary and cortical matters are reversed, with regard to the cerebrum. Herein the cortical substance exceeds the medullary in quantity, and, in- stead of forming the outward parts, pervades the innermost. Slice the cerebellum horizontally, and these substances present a laminated appearance : on the other hand, make a vertical sec- tion of it, and they are found so disposed as to give the surface an arborescent representation, usually denominated the arbor vita. Fourth Ventricle. — Within the cerebellum, or rather between it and the tuber annulare and medulla oblongata (which two last form its back part), is situated the fourth ventricle. Beginning above the testes, where it is perforated by the iter a tertio, it ex- tends upward and backward to the extremity of the medulla ob- longata, where it ends in a sharp angular point, which, with a groove issuing from it and continued along the floor of the ven- tricle, anatomists have resembled to a pen, and thence called the calamus scriptorius. Valvula Vieussenii. — Extended across the inferior and anterior part of the ventricle, closing the cavity between the testes and lower extremity of the anterior vermiform process, is a membrano- medullary curtain, the velum vel valvula Vieussenii. It is supported at the sides by two medullary productions, remarkable for their whiteness, the processus a cerebello ad testes, which some regard as the colunuis of the valve. The choroid plexus of the cerebellum is found, lying crosswise, within the posterior part of the fourth ventricle, between the cere- bellum and medulla oblongata. Jt nowise differs in its composi- tion from the plexuses of the lateral ventricles. It is distributed into three principal divisions: one lies in the middle of the cala- mus ; the other two (lateral) are lodged within fissures in the cerebellum, occupying the spaces between it and the tuber an- nulare. 324 NERVOUS SYSTEM. Base of the Brain. The base or posterior part of the cerebrum is divided into six lobes : two injerior or anterior, reposing upon the alte of the ethmoid bone ; two nuddle, upon those of the sphenoid ; and two superior or posterior, lodged in the fossse of tiie squamous por- tions of the temporal bones. Over the middle lobes are two broad prominences whose sur- faces are remarkably even and smooth : these are the bases of the corpora striata, the parts from which the olfactory nerves are seen taking their origin. Crura Cerebri. — Above these bodies again, in the middle of the brain, are two oblong medullary eminences, intimately united together: these are the crura cerebri. They rest upon the alas of the sphenoid bone. They take their rise from the inferior and middle lobes of the cerebrum, and are continued into an ovoid protuberance above them, named the tuber annulare. Though medullary without, the crus, when cut deeply into, exhibits a ci- neritious hue, and the part of the interior the most darkly shaded has been designated the locus uiger. Corpus Atbicantium. — Seated between the crura, is a small, hemispherical, medullary eminence, distinguished as the corpus alhicantiuui. In the human subject this body is double ; and there is some appearance of a depression along its middle in the horse. It is medullary without, but has a tinge of cortical matter within. Tractus Optici. — Winding obliquely tlownward, around the crura, proceeding from the terminations of the thalami, are the tractus uptici: they are to be regarded as the roots of the optic nerves, with which they are continuous. They are entirely me- dullary. Crura Cerebelli. — Higher up and more outward than the crura cerebri, are the crura cerebel/i— two stout, cylindroid, medullary chords joining the lateral lobes of the cerebellum to the tuber annulare. These parts consist of a prolongation of that portion of medullary substance which forms the trunks of the arbor vitae. The tuber annulare vel pons Varolii (whose situation now need not be pointed out) may be said to be constituted of the united substances of the crura cerebri and crura cerebelli : it is, in fact, the common termination or medium of junction of the cerebrum with the cerebellum. It is supported by the cuneiform process of the posterior occipital bone. Its surface is marked by a shallow depression along its middle, which gives it the appear- ance of having lateral eminences. Internally, the tuber exhibits a mixture of cortical and medullary matter. NERVOUS SYSTEM. 325 Foramina Cccca. — Above and below the tuber, centiically si- tuated, are little round depressions or blind holes, which are ge- nerally described as the foramina cceca, superior et inferior. They serve as places of lodgment for small plexuses of bloodvessels. Still higher than the tuber is placed the Medulla Oblongata"^ , The smallest division of the cerebral mass : more properly speaking, it is the commencement of the spinal marrow^ It rests upon the cuneiform process of the occipital bone, and is continued upward and backward to the foramen magnum. Regarded in an excised or separate state, it is of an oblong, quadrilateral figure. It has a deep fissure along its middle (in which runs the basilar artery) that divides it into lateral portions. Contiguous to this fissure, rising from the sides of it, are two longitudinal emi- nences, called the Eminenticc pyramidales. From the lateral parts project two other eminences, named the Uminentia Olivares. The upper surface of the medulla oblongata forms, with the tuber annulare, the floor of the fourth ventricle. Though, like the tuber, it is composed internally of a mixture of cortical and medullary substances, its shade is lighter than that body. Lastly, remains to be considered the Pituitary Gland, A reddish body, of an ovoid form, seated upon the sella tursica, within a fold of the dura mater. It has a membranous capsule, surrounded by cellular adhesions, by which it is firmly retained in its place ; whence it is not dislodged, even though the cerebral mass be taken out. It has the appearance of being highly vas- cular; it is, however, of a lighter colour internally than exter- nally, and assumes, in places, a mottled aspect. The ancients entertained a notion that it imbibed some fluid from the brain, vvhich they called pituita, through the infundibulum, and trans- mitted it to the nose; but we find that these parts have no communication whatever : in short, its real use is unknown. OF THE SPINAL MARROWf. The medulla spinalis, or spinal marrow, is that extended cylinder of brain-like substance which is continued from the * " The seat of power which controls the respiratory motions is the me- dulla oblongata." — " He who holds the medulla oblongata in his hand, has the key to the nervous system." — C. Bell, F.R.S. f " In animals which do not breathe by an uniform and general motion of their bodies, there is no spinal marrow, but only a long compound and ganglionic nerve, extending through the body for the purpose of sensation and motion. This chord in those creatures does not actuate the animal machine with alternate dilatation and contraction." — The Nercous Systein. By Charles Bell, F.R.S. 326 NERVOUS SYSTEM. posterior part of the medulla oblongata through the entire length of the spinal canal. Lodged within a cavity whose form is con- tinually undergoing more or less variation, it neither fills nor fits that cavity : in some places it swells in volume, in others it grows contracted ; everywhere it has the appearance of having shrunk from, or of being disproportionably small for, the canal ill which it is contained. Coverings. — It is inclosed in the same membranes that envelop the brain ; but, in addition to them, the fiiiperior ligament of the spine serves as a covering and defence to it below. To this, and to the periosteum lining the canal, its proper theca is loosely at- tached by cellular, adipose, and gelatinous matter. Its dura mater is derived from that which covers the brain : in being con- tinued through the foramen magnum, the membrane is contracted into a cylindrical sheath which loosely incases the marrow, and is generally described under the denomination of theca vertebra/is. About the beginning of the sacrum, the theca narrows; it re- cedes from the sides of the canal, and, having inclosed the ter- mination of the marrow, is extended into a point and lost upon the Cauda equina. The dura mater is connected to the mem- branes underneath — the membrana arachnoides and pia mater, by a fine cellular tissue ; and these coverings have the same re- lation to the marrow that the same membranes have to the brain — of which, indeed, they may be considered prolongations. Structure. — The spinal marrow, stripped of its membranes, is cylindroid in form, but flattened along its upper and under surfaces, each of which is marked by a longitudinal linear fissure : these fissures, of which the inferior is the more conspicuous one, are con- tinuations of those that traverse the medulla oblongata — dividing the marrow into two lateral portions, and serving as convenient tracts for the spinal bloodvessels. In places, also, some trans- verse fissures or little wrinkles are apparent, which are evidently for the purpose of admitting of certain degrees of elongation and contraction, in order to guard against extension or laceration of the marrow under any motion or altered position of the spine. The marrow varies in its dimensions at different parts ; and, also, somewhat in its form. At its continuation from the medulla ob- longata, it is large, from which to the fifth cervical vertebra it gradually grows less in circumference ; here it swells again, but again diminishes in entering the first dorsal vertebra. Along the back it is small, and nearer approaches the form of a perfect cylinder ; but in the loins it grows flatter than ever, and, a third time, increases in size, until it reaches the last lumbar vertebra ; from which it begins to taper, and continues so to do until it at length ends in a pyramidal point, within the second piece of the NERVOUS SYSTEM. 327 sacrum. Around its termination come off several large nervous chords, which are continued along the canal, and extend, some of them, into the coccyx : altogether, they have been resembled to a horse's tail, and thence denominated cauda equina. In the year 1808, Mr. Sewell conveyed, in a letter to Sir E. Home (which was afterwards read to the Royal Society), the par- ticulars of what he conceived to be a canal running from the fourth ventricle through the whole length of the spinal marrow, containing a limpid colourless fluid, and lined by the membrana arachnoides, or a membrane very like it; but, since this, M. Bellen- geri, of the College of Medicine of Turin, has proved that this supposed canal is, in truth, a median furrow, dividing the spinal marrow into six columns : he has likewise shewn, that the roots of the spinal nerves, both anterior and posterior, are triple. More recently, Sir Charles Bell has discovered, that of the three tracts or columns contained in each lateral portion, the inferior column is for motion, the superior for sensation, and the middle one for respiration. The two former extend up into the brain, and are dispersed or lost in it; but the latter stops short in the medulla oblongata. Origin of Nerves. — The nerves given off by the spinal marrow are twenty-nine pairs. They originate from the superior and in- ferior columns, by superior and inferiory'oscgs, or bundles of fila- ments, piercing the theca vertebralis in several places, from which they derive sheaths in their egress. The cervical and dorsal nerves, for the most part, arise from the marrow opposite to the foramina, through which they make their exit from the spine ; but the pos- terior lumbar and sacral nerves proceed obliquely backward be- fore they turn out ; and some of the latter, and all the coccygeal nerves, run longitudinally down the canal before they quit it. The filaments composing the fasces are themselves small ; they bear a proportion in size and number to the nerves of which they are the roots. Threads of communication may be seen, oftenest in the neck, running from one fascis to another. The supe- rior fasces are separated from the inferior ones by a strong, white, fibrous band, which runs along the side of the marrow, and has a puckered attachment in one particular place to the theca, between every pair of nerves, on either side ; inwardly, it being intimately joined to the pia mater. This band, which is denominated, from its several pointed connexions, the ligatnentum denticulatum, prevents any such injurious extension of the nerves, when the spine is forcibly flexed, as might occasion laceration of their medulla. In the space between the vertebr-ae, the superior set of filaments converge and form a ganglion, from the opposite side of which many filaments arise, and proceed with the inferior and join them, and thus form the trunk of the nerve. 328 NERVOUS SYSTEM. OF THE NERVES. The nerves are dense, white, fibrous chords, proceeding from the brain and spinal marrow to all parts of the body. Number. — From the brain issue ten pairs, denominated cere- bral nerves ; from the spinal marrow, thirty-six, termed spinal : making, altogether,yor(y-su' pairs*. Magnitude. — In some animals (among which may be num- bered the horse) the nerves, taking them generally, are of larger size than they are in the human body, although the brain of the latter far preponderates in volume. According to Richerand, " the spinal marrow and the nerves, in the different animals furnished with them, are larger in proportion to the brain, ac- cording as the animal is more distant from man in the scale of animation." Coverings. — The nerves are covered by the same membranes as cover the brain : the one may be traced from the other. The pia mater, indeed, enters into the composition of the nerve, form- ing minute sheaths in which the nervous matter is contained. These external coverings, however, seem to proceed only to a short distance ; for if we examine the outer cases in which they are subsequently inclosed, we shall find them to be nothing more than condensed celkdar membrane. It is to the external covering that the compactness and density of a nerve are entirely owing; when deprived of it, but a slight degree of pressure will destroy its texture : indeed, there are some nerves whose exposed situation would subject them to perpetual contusion and lacera- tion, were it not for the protection afforded them by this compact cellular envelope. Structure. — The substance of the nerves is pulpy ; and their pulpy matter is contained within minute membranous sheaths or tubes (composed either of simple cellular membrane or of pia mater), constituting in this manner so many filaments or funiculi, which form one continuous tract from their exit from the brain to their ending in the skin or muscle. Every one of these filaments * " In the view which I have taken of the nerves of the (human) body, there are, besides the nerves of vision, smell, and hearinaf, four systems combined into a whole. Nerves entirely different in function extend through the frame : 1 st, those of sensation ; 2dly, those of voluntary motion ; 3dly, those of respirator!/ motion ; and, lastly, nerves constituting the st/mpa- thetic si/stem, which froin their being- deficient in qualities that distinguish the three others, seem to unite the body into a whole, in the performance of the functions of nutrition, growth, and decay, and whatever is directly ne- cessary to animal existence. Of these, the two first are bound together through their whole course ; the third are partially joined to the two former; and the last are the most irregular of all." — Such is a coup d'crit of the new arrangement of the nervous system introduced by Sir Charles Bell. NERVOUS SYSTEM. 329 or tracts of nervous matter (as we learn from the celebrated labours of Sir Charles Bell) " has its peculiar endowment, inde- pendently of the others which are bound up along with it; and this same endowment it continues to have throughout its whole length." Elasticity. — It has been generally supposed, that nerves are inelastic in themselves, and that any extension or contraction they admitted of, arose from the elasticity of their component cellular membrane. Sir E. Home, however, has proved, by some ingenious experiments, that they possess a power of retraction when divided in the living body : a circumstance which, of late, cannot altogether have escaped the observations of those who have performed the operation of neurotumj/. This retraction does not seem entirely to depend on any inherent contractility of tissue, otherwise extension of the nerve would be a necessary preparative ; on the contrary, it happens under the most com- plete state of relaxation : an effect that will not place in the dead subject under similar circumstances. Mode of Origin. — A nerve is said to have two extremities — a cerebral, and a sentient : the former is that part by which it is connected with the brain, or spinal marrow ; the latter, that by which it terminates in the vifleous structures of the body. It has been usual to say, that the* nerves arise, or have their be- ginning, from the brain, though it would appear, from some recent investigations into their composition and functions, that we might, with equal propriety, regard them as deriving their origin from the organs to which they are said to be distributed, and as ending in the sensorium. Supposing, however, that they do issue from the brain, there still remains unsolvable mystery respecting their beginning or roots. Some nerves may be fol- lowed through a tract or streak of pulpy matter, distinguishable from the surrounding medullary substance, until at length we lose the tract, from its vanishing in the cineritious substance. So that, although we continue, for the sake of anatomical definition, to assign certain parts of the brain as the beds or origins of certain nerves, we are still, in truth, ignorant of the veritable sources of their original or radical fibres. It would appear, from many familiar facts (the result of experiments and patholo- gical observations) that the nerves distributed to one side of the body arise from or are connected with the opposite side of the brain ; and if this be true, there m.ust be somewhere a decussa- tion of them : if an injury be received on the left side of the skull, the right side of the body will become paralytic ; an effect that could not happen unless there was a ready communication be- tween one side of the brain and the nerves of the opposite side of u u 330 NERVOUS SYSTEM. the body, by means, in all probability, of direct continuity of fibre. If one of the lateral halves of the spinal marrow be cut through, the animal will become paralytic, not on the opposite, but on the same side ; a fact which, although it at first view appears con- tradictory to what we have just stated, in truth tends to confirm this opinion : for the medulla spinalis being composed of lateral portions, the fibres decussate each other in the same manner as those of the nerves are supposed to do. Ramljication. — The nerves of motion, before entering the mus- cles, form various communications with others in the vicinity ; in many parts, by such frequent intercourse, that a kind of ner- vous network is formed, to which the term plexus is applied. And the plexus is intricate in proportion to the number of mus- cles to be supplied, and the variety of combinations into which the muscles enter*. In their course, the nerves generally proceed in straight lines to the parts to which they are dis- tributed ; deviating only (like the arteries) for their own safety, or for some wise and evident purposef . Sometimes they run with the bloodvessels, sometimes alone : we commonly find a nervous trunk, and in some places two, accompanying the principal arteries and veins of the extremities. The Joranches of the nerves, for the most part, come off at acute angles : those springing immediately from the trunk send off others of smaller size, until filaments of such minuteness are formed, as to be invisible to the naked eye. Termination. — The twig-like ramifications of nerves end in two different ways : either by inter-communication — which is similar to the anastomosis of arteries, or by sentient extremities within the substance of those organs to which they are distributed. In the retina (a part of the eye entirely composed of the expanded termination of the optic nerve) an extremely delicate tissue, of a pulpy consistence, and semipellucid yellowish appearance, is observable ; from which it has been conjectured, that the extre- mities of other nerves may be somewhat similar: but, to confess the truth, we do not know what form they actually assume — we think it very probable, that their mode of termination may vary according to the nature and texture of the part in which they arc * The Nervous System. By C. Bell, F.R.S. f There is no such thing as irregularity in the nervous system. The term may be applicable to arteries or veins, because it si;^nifies not whether a part be supplied with this or with that branch, so that arterial I)loofl is furnished. But one nerve cannot supply the office of another. (The pro- perty dispended resulting from the source from which the nerve is derived). There is no such thing as a nerve deviating or being found wanting (an occurrence frequent in the vascular system) without the loss of some essen- tial i^cuMy.— C.Bell, F.R.S. NERVOUS SYSTEM. 331 expended*. The nerves are very unequally distributed to different parts : the organs of sense, the skin, muscles, and mucous mem- branes are plentifully supplied with them : the serous, fibrous, and medullary membranes receive but few ; and none have yet been detected in either cartilage or tendonf. Ganglion. — A ganglion is a little knot or swelling upon a nerve, perfectly natural to it. We find them in various parts of the body ; more especially about the neck, chest, and abdomen. They will be pointed out in tracing the distribution of those nerves to which they appertain. Bichat discovered that neither the sympathetic nerve nor the ganglia it forms, possess sensibility. Origin and Distribution of the Nerves. It has been observed, that the ten pairs of nerves connected with the brain are denominated cerebral; while the thirty-six pairs connected with the spinal marrow, are contra-distinguished as the spinal. All the nerves being symmetrical in number and dis- tribution, on either side of the body, take their origins by pairs, and these pairs are numbered, and so distinguished from one another, according to the order in which they arise — proceeding from below upward within the head, from before backward within the spine. In addition to this distinction of ordinal number, how- ever, every pair of cerebral nerves has obtained a particular epithet significant of the specific purpose they serve, the part they supply, or else some peculiarity in their division or distribution. * Wherever we trace nerves of motion, we find that before entering- the muscles, they interchange branches, and form an intricate mass of nerves, or what is termed a plexus. The filaments of nerves which go to the skin regularly diverge to their destination. — Nervous System. By C. Bell, F.R.S. t And yet the granulations of these parts possess sensibility, of which I have had very marked evidence, in the case of broken-knee. The horse has never failed to snatch up the leg, every time the granulating edges of the extensor tendon were touched with the probe. 332 NERVOUS JSV-STEiy, V? 5^ 5 ,C c :s ^ o ■-=: ^ '^j ^ iJH s gpfe FS c\£ Si f :! CD W a; '^ J • ~ 'C ;-'^ -s • -S "i^ -S >. O :« C 2 els =^ W H t-H r- x H fe C c ^ Q *^ « 5. -2 o. b) ^ ^ •^ ■i g % 1 t 1 1 1 .1 1 NERVOUS SYSTEIM. 333 SI 3^ §Hw 3:34 NERVOUS SYSTEAJ. - i2 ■or. -s i £. Hi -S H^S If 1^ O O O u c3 CIS O O P-. hi:>.?bi:-b£bc^ < fS & 2 fS le several pliccc, of which two are more elevated and conspicuous than the rest : the inner of these two plicae forms the boundary line of the belts, and casts a shade upon the inner belt, imparting to it the effect of distance when viewed in the living eye. — The posterior surface of the iris is covered with a thick stratum of black mucous matter derived from the pigment, which, from impregnating it with the colour of a grape, has be- got for it the name of uvea ; and it would appear that the colour of the iris (the nature and production of which yet remain a mys- tery) is essentially dependent upon the uvea: for if the pigment be washed off, the iris will be rendered colourless. In wall-eyes, in which the uvea is wanting, the iris is white; so it is in AIbi- 384 SENSITIVE SYSTEM. nos, in whose eyes there is the same deficiency. This surface has hkewise a division into two parts by a prominent elliptical fold in the middle: the larger one exhibits numerous convergent strise which run in radii from the outer margin, where they look almost like continuations of the ciliary processes, and terminate in this prominent fold ; the inner and lesser division is a phme oval surface, apparently without striaB, perforated in the centre by the pupil. Margins. — J'he greater or ciliary margin of the iris is em- braced by the ciliary circle, and has a broad attachment to the choroid coat besides, through the continuation of the pigmentum nigrum. The lesser or pupillary margin, rendered black and prominent by an edging from the uvea, and hanging loose and floating in the aqueous humour, constitutes the boundary line of the pupil, and gives attachment to the corpora nigra. The pupil, then, is nothing more than a hole in the iiis, oblong or elliptical in the same direction as the cornea is, whose diame- ter varies with the intensity of the light to which the eye is ex- posed. There are animals, however, in which the pupil does not ordinarily correspond in shape with the cornea, in consequence of its altering its figure as well as its magnitude under sucli circum- stances : e.g. in the cat, the cornea is circular, but the pupil dur- ing the daylight is elliptical in the vertical direction, though at night it becomes circular ; and, indeed, the pupil of the horse, widely dilated from the effects of amaurosis or the influence of belladonna, likewise assumes the circular figure. Structure. — All that we know about the structure of the iris, is, that it is apparently a fibrous membrane, divisible into two layers, provided abundantly with bloodvessels and nerves, and thickly coated behind with uvea : the division of it cannot be carried through the pupillary margin, there its layers becoming inseparable. Its fibres are believed by some to be muscular, the quick and free motions of the part forming the principal grounds of their argument; for the fibres (even by their own admission) are too minute to admit of anatomical demonstration. Professor Coleman found them well marked in the eye of a greyhound that had been long inured to cunning coursing in a rabbit warren. Not only do these fibres elude all anatomical test of their nature, they are insensible to the common mechanical and chemical excitants of other muscles, and even to galvanism. — The arteries of the iris come from the long ciliary, and are arranged so as to form two circuli arterosi upon its anterior smface, corresponding to the two prominent pliccB thereon : from these, minute branches are detached, which are so numerous, that they of themselves appear to constitute the basis or essential part of its texture. SENSITIVE SYSTEM. 385 The ciliary nerves lavish their branches upon the iris ; but, owing to their minuteness, defy all attempts to make out their distri- bution. Motion. — The motions of the iris consist in contraction and dilatation, and the dimensions of the pupil are conversely regu- lated thereby : when the iris becomes contracted the pupil be- comes dilated, and vice versa; the pupil, however, is never shut so completely as to exclude light altogether. These motions are involuntary — excited by the presence of light — and, ceteris pat i- bus, are regulated by the quantity admitted, or the suddenness with which it is admitted, into the eye. This action, however, is not the effect of direct stimulus, but proves to be a secondary or sympathetic result, since light has no visible influence upon the iris itself — the impression is made upon the retina: in gutta serena (paralysis of the optic nerve), for example, the pupil be- comes dilated and the iris remains motionless ; and when the pupil is closed so that light cannot get to the bottom of the eye, the iris becomes fixed. Furthermore, the motions of the iris are influenced by the magnitude and distance of the object of vision : when the eye is intently viewing a near object, or one very small, the pupil becomes contracted j but if the object be removed to a distance, or it have a wide surface, the pupil will become di- lated. During sleep the pupil is contracted. After death it re- mains in that state (either contracted or dilated) in which it hap- pened to be at the instant of the last expiration, and cannot by any means we may employ be re-excited to action. The efficient cause of these movements remains undeveloped. Corpora Nigra. I have given this name to the little globular, black bodies found attached around the pupillary margin of the iris ; and I have taken the liberty to do so, because I am not aware that any appellation has been assigned them by the veterinarians of this country. Girard, speaking of them, says, " que I'ouverture pu- pillaire ofFre commumtneiit quelques tubercles noirs, sortes de prolongemens franges, replies en dehors, et nommes fungus ;^^ but the termjungus sounds to our ears so much like disease, that I consider this a sufficient reason for not adopting it. By this laconic description of Girard's (for this is all he says about them) it would appear that they are not uuexceptionably present: I have not myself remarked their deficiency unless where the pig- ment was wanting. There are commonly three of them, about the magnitude of peppercorns, ranged en masse along the upper margin of the pupil, something nearer to the outer than the inner corner; and the largest is placed outvvardmost — unless 3 D 386 SENSITIVE SYSTEM. we reckon a very small one indeed, which is generally found be- side it. Along the lower edge there are likewise three, sometimes four of them : but these are comparatively inconsiderable, not being larger than pins' heads. The corpora nigra superiora hang more or less over the pupillary opening in front: the cor- pora inferiora project just enough to interrupt the regularity of the pupillary line. I am inclined to regard these bodies as pro- ductions of the black pigment: they have similar fringed or velvety surfaces, and appear to be resolvable into the same mu- cous substance, and to be continued from the uvea — to be, in fact, uveal excrescences. Professor Coleman has seen them as large as the largest garden peas, without their seeming to interfere at all with vision. Choroid Coat. The tunica choroides is the black, soft, delicate texture immediately covered by the scleiotica. It extends from around the termination of the optic nerve, by which it is perforated, in intimate contact with the internal surface of the sclerotica, as far forward as the edge of the cornea, where it ends in the ciliary circle : it being connected to the sclerotica by a very fine cellular web, by intercurrent bloodvessels, and by the ciliary nerves. Ciliary Circle. — If that part of the sclerotica in union with the cornea be removed, we shall expose, immediately behind the vanishing edge of the latter, a whitish cellular belt about two lines in breadth : this is named the orbicularis ciliaris, ciliary circle, or ciliary ligamoit. It forms the medium of union or line of demarcation between the choroides and iris ; it is also the place where the sclerotica has the firmest connexion with the choroides, and through that connexion likewise an intermediate one with the iris. The basis of the ciliary circle is nothing but condensed cellular membrane ; but the ciliary vessels and nerves in their course pervade it, forming a sort of vascular and nervous plexus : a circumstance that has given rise to other names for it. This part may be stripped off altogether with the forceps; and in doing so it will be found to adhere with most tenacity to the choroides. Fontana has described in the human eye a triangular canal in the cellular tissue between the sclerotica and this circle; but, for my own part, I cannot find any such cavity in the eye of the horse. Structure. —The inner surface of the choroides is accurately applied in every point to the internal tunic — the retina ; though so closely applied, however, they nowhere adhere, either by vas- cular or cellular connexion. Externally, the choroides presents SENSITIVE SYSTEM. 387 everywhere a black surface ; internally, only the anterior parts are black : the posterior concave part, about one half of the entire internal superficies, being of a brilliant variegated green tint. The black part is called the nig/Km pigmeittum : the green, the tapetiim luctdum. The basis of the structure of the choroides consists in vascularity : arteries and veins in count- less numbers enter into its composition, dispersed through an intertexture of fine cellular web. Though this fact has been ascertained, however, the arrangement of the vessels is a question that does not seem to this day to have been satisfactorily de- termined. It appears certain that there are two strata or sets of vessels ; but, some say an external one of veins, which they call the vena vorticosa, and an internal one of arteries, to which has been given the name of tunica Rui/schiana ; while others place the veins upon the inside. — " Les arteres," says Girard, " dis- tribuees a la surface externe forment une couche premiere, unie a une lame interieure, dans laquelle se rendent les veines." It is, perhaps, sufficient for us to know, that this tunic is (with least difficulty in the situation of the tapetum) separable into two layers ; that these layers consist almost entirely of bloodvessels, wliich cross and intercross one another so as to form a vascular network very difficult if not impossible to unravel ; and that its arteries come from the ciliary, and its veins pour their blood into the ophtliahnic vein. In order to examine the structure of the choroides it should be freed from the colouring matter ad- hering to it ; and this cannot be done without suftering it to remain some days in water, which is very apt to impair its texture. Pigment. — This adventitious substance is spread over both of the choroid surfaces ,• but the inner layer is thicker and more consistent and determinable in its limits and disposition than the outer. The outer, the entirely black one— the veritable nigrum pigmentum — begins just behind the ciliary circle, and appears to be uniformly continued over the whole of the posterior hemi- sphere ; the inner one, partly black and partly green, lines the dark chamber, fills up the interstices between the ciliary pro- cesses, and coats the posterior surface of the iris. The coloured part, called the tapetum or carpet, or from its brightness the tapetum lucidum, is not found in the eyes either of men, birds, or fishes, and in quadrupeds it is seen of different colours : in tlie horse, it is pea-green ; in the cat, it is yellow ; in the stag, blue. In all, however, its relative situation is the same : it makes a circular sweep to a certain extent around the entrance of the optic nerve ; in the horse, it spreads wider superiorly than in- feriorly, occupying the posterior half of the dark chamber — that 388 SENSITIVE SYSTEM. part which is within the axis of vision. In a perfectly fresh eye, the tapetum is bright, and its hmits are distinctly marked ; in- deed, with pains, it may be stripped cleanly off the sclerotica, and even without staining the fingers in so doing ; but putrefac- tion destroys its verdure and consistency, and converts the entire pigment into a thin, sooty, semi-fluid matter, readily diffusible in water, and which leaves a dusky stain upon the sclerotica and other parts in contact with it. The pigmentum and tapetum (apparently the same substance, differing only in colour) are supposed to be a peculiar secretion from the vessels of the cho- roides — a secretion of a mucous nature — only that it is con- tained within a very fine, soft, and delicate cellular tissue by which it is held together. Mr. Hunter compared it to the rete mucosum : and there would appear not only to be a similarity in composition, but also some mysterious relationship existing be- tween them in regard to their formation ; for, in Albinos, in purely white and cream-coloured horses, in white rabbits, ferrets, &c. in whose eyes the pigment is deficient, the rete mucosum is also wanting : this accounts for the delicate whiteness of their skins, and for the redness of their eyes, in which the blood (cir- culating in the vessels of the choroid) is seen through the pupil, unobscured by colouring matter. Ciliary Processes. — Leaving the ciliary circle, the choroides makes a sudden inflection inward behind the iris, and then turns intensely black. This inflection considerably contracting the space the tunic was formerly spread over, there results a super- abundance of substance, which we find to be disposed of in puckers or plaits, arranged in parallel lines, like-radii, around the circumference of the crystalline lens : regarding the doubling and plaits together as a whole, the part is named the corpus ciliare ; but the plaits by themselves are called the processus ciliares. These processes repose, posteriorly, upon the soft bed of the vitreous humour, whereupon they make counter-impres- sions, the membramda corona ciliaris being alone interposed. The corpus ciliare is coated with pigment of the deepest dye — the interstices of the processes in particular are thickly bespread with it : this explains the remarkable blackness of this part, and accounts for the radiated circle of black stria marked upon the surface of the membranula ciliaris, after the processes have been stripped off. In order to examine the structure and connexions of the corpus ciliare, the pigment should be washed oft. It will then be found to be continuous at the ciliary circle with the choroid, to possess the same vascular basis as that tunic, and, in fact, in nowise to differ from the choroid but in its disposition and arrangement. The internal part of the choroides near the SENSITIVE SYSTEM. 389 angle of inflection presents to minute inspection (or through a magnifying glass) numerous delicate and faintly-marked stripes, arranged in parallel radii, which are the cilianj strice ; and every two or more of these striee unite afterwards to form a single plait or ciliary process, that runs direct to the crystalline lens, growing broader as it proceeds, adhering in its way to the raem- branula ciliaris (which is behind it), and terminating with an angular point at the capsule of the lens, with which, though in contact, it has no connexion whatever. The best view we can have of these processes is obtained by making a perpendicular section of the eye and looking at them through the remaining portion of vitreous humour: a broad, black, well-defined line will then be seen, shewing their union with the choroides; and in consequence of their posterior edges having a greyish cast, we are enabled to distinguish their interstices filled with black pigment. We can also distinguish that they vary in length, but not perceptibly in breadth. The retina (so called from its supposed reticulated texture) is the third or innermost tunic. The optic nerve, having reached the inner and inferior part of the globe, pierces the sclerotic and choroid coats, and in its passage through them grows somewhat contracted in its diameter : having arrived at the internal part, the nerve swells into a little, white, eminent papilla (appearing as a white spot in the living eye), from whose circumference issues, in white radiating lines, a medullary pulp which spreads over the entire surface of the dark chamber. It is sustained in this state of globular expansion by the vitreous humour, and thus becomes accurately applied to the choroides externally, but without contracting any adhesions whatever until it has reached the corpus ciliare. In an eye perfectly recent, and unpre- pared in any way for the examination, the retina appears to terminate on a sudden, by a defined edge, at the black circle upon the ciliary body, by adhesion there to the tunica vitrea : it is asserted, however, by some anatomists, that it does not end but only grows much thinner here, afterwards extending almost imperceptibly between the ciliary processes and tunica vitrea, and proceeding to the capsule of the lens ; and this part, they say, in consequence of being much compressed, puts on the appearance of nervous striae ; whereby, they add, its con- nexion with the iris becomes established. During life, the re- tina is transparent — the choroides shines through it and gives colour to the pupil ; but speedily after death, it loses its pellu- cidity, and exhibits a dead or opaque whiteness : immersion in spirits of wine produces the opacity at once, at the same time giving to the membrane a degree of firmness". — lit composition, 390 SENSITIVE SYSTEM. it appears at first view merely to be an expanded mass of ner- vous pidp ; but, by scra])ing the surface of it as it floats in water, it becomes resolvable into a pulpy or medullary part (which is seen dispersed in the fluid) and an extremely delicate membrane, whose texture has been found to be almost entirely vascular; the latter forming the basis or vascular network upon which the former is spread, and by which it is nourished and supported. This membrane is intimately united with the border of the open- ing that gives passage to the optic nerve. It receives its vessels from the central artery of the retina — a vessel that takes its course through the axis of the nerve. OF THE HUMOURS. These are three in number, viz. the aqneous, crystalline, and vi- treous ; and they occupy in succession the spaces in the anterior, middle, and posterior parts of the globe. Aqueous Humour. The aqueous humour escapes as soon as the cornea is punc- tured, and the cornea itself falls afterwards into wrinkles, shewing that the convexity and tension of the one is owing to the presence and pressure of the other. It fills the interval between the cornea and crystalline lens, insulating the iris by which the whole space is divided into two cavities, named the anterior and posterior chambers: these chambers consequently communicate through the pupil; but they are very unequal in their dimensions, the posterior being nothing more than a very narrow chasm between the uvea and the lens, surrounded by the ciliary pro- cesses, whose points may be said to project into it. The aqueous humour is a bright limpid fluid, and in its properties bears a great resemblance to the vitreous, in the condition in which the latter drops from its cellular case : they are both compounded of albu- men, gelatine, and muriate of soda, suspended in a watery men- struum. This humour (as well as the others) has a capsule of its own; at least, we infer so from analogy, or rather from the separa- bility of a thin transparent lamina from the concavity of the cornea not possessing the fibrous character of the other corneal laminae, and which some have been able, they say, to trace upon the iris; though no one, I believe, has seen it enter the pupil : this mem- brane is supposed to secrete the humour; and, if we may judge from the rapidity with which the fluid is reproduced after it has been let out, its secretion is by no means either a difficult or an expensive process. SENSITIVE SYSTEM. 391 Crystalline Lens. The crystalline lens, though a solid body, is always considered as one of the humours. It is named crystalline from its resemblance to crystal, and lens from its shape. It is lodged between the aqueous and vitreous humours, the latter pre- senting in front a hollow bed for its reception ; and it is surrounded by the ciliary processes, and parted from the iris by the posterior chamber. The lens is inclosed within a capsule of its own, by whose attachment to the tunica vitrea it is retained in its place, with the assistance of the membranula corona ciliaris. This cap- sule, the tunica crystallina of some, is denser, firmer, and more resisting than the tunica vitrea : it cannot be shewn to have any adhesion to the lens itself, there being between them an aqueous moisture, which some regard merely as a post-mortem exudation, while others consider it as necessary during life to prevent adhesion of the contiguous surfaces, and call it the aqua vel liquor Mor- gagni, from its discoverer. The anterior part of the capsule is thicker, stronger, and more elastic than the posterior part ; though the latter is something strengthened by the membranula ciliaris, and is closely, but not inseparably, united by a fine cellular web to (and consequently cannot, as some have supposed, be continuous in substance with) the tunica vitrea. Successful injections shew the vascularity of the capsule ; and the liquor Morgagni is supposed to be a secretion from its vessels, which themselves are derived from the central artery of the retina. The lens in figure approaches more or less to a sphere : it is not uniformly spherical, but is composed of the segments of two un- equal spheies, the posterior of which has more convexity than the anterior. Though perfectly transparent, it has this peculia- rity in its composition — that it is soft externally, but gradually increases in firmness and density of substance from the super- ficial to the central parts, which latter becomes its nucleus. It appears to be placed, as it were, in a state of insulation within the capsule ; for we cannot detect any cellular, vascular, or other direct connexion between one and the other; and we constantly find both their surfaces moist with the liquor Morgagni, rendering them so slippery that whenever the capsule is wounded the lens readily makes its escape. — The nature and composition of the lens is a subject still open to inquiry. As in other doubtfid and obscure cases, where anatomical tests forsake us, hypothesis is ready to supply their place, and, as in the present instance, now and then furnishes us with some ingenious and plausible con- jectures. Dr. Young* thought that at one time he saw in the * 'S'ounj" " Oh Nataiul Pliilosopliif." 392 SENSITIVE SYSTEM. lens of a bullock's eye muscular fibres with intersecting tendons, to which he ascribed the power of augmenting its sphericity : indeed, Mr. Hunter had a notion that it possessed a power of varying its figure, and had made some allusions to a fibrous structure. These suppositions, however, have arisen from exa- minations of the lens in an opaque and altered condition : so long as it remains pellucid, though its substance does come away in spherical laminae, there appear no grounds for ascribing a fibrous composition to it. Notwithstanding the physiological ingenuity, therefore, of these hypotheses, all that we are absolutely warranted in offering upon the subject of its composition is rather the result of chemical inquiry than any anatomical knowledge we possess of its organization. In the living animal, it is as transparent as the clearest crystal : after death it gradually loses its pellucidity, and more rapidly when immersed in water, by which it becomes converted into an opaque pulpy mass. Even if it is simply squeezed between the fingers, it turns opaque : a change rationally explained by saying, that we have destroyed its organization and extravasated its fluids. Acids and alcohol take the same effect that boiling water does upon it : they convert it into an opaque, white, and more solidified body, such as we see it in the head of a boiled fish. It is found to be chemi- cally composed of albumen, gelatine, and water ; and this seems to be the sum and substance of our present knowledge of its conformation. Neither bloodvessels nor nerves have ever been traced into it ; nor are we certain that it is organized at all, unless we receive as proofs the ordinarily assigned tests of organ- ization — the phenomena of growth and morbid changes. Vitreous Humour. The vitreous humour fills the posteiior concavity of the globe — the dark chamber — occupyingnearly four-fifths of its whole interior. It is of the consistence of thin jelly, and from its pellu- cidity and glassy appearance has got its name. It is moulded to the form of the cavity containing it, and lies in contact every- where with the retina, though there is no connexion whatever between them. Beyond the boundary line of the retina it is covered by the corpus ciliare ; and in front is shaped into the form of a hollow bed for the reception of the lens. Let this tremulous mass be pricked or otherwise wounded, and a limpid fluid drops from it, very like water, leaving behind a thick and gelatinous part which at length becomes resolved into a mem- branous substance : this membranous residue is said to be dis- posed in small cells, varying in figure and size, and is called the tunica vitrea vol hj/aluidea. Oj^posite to the corpus ciliare, this SENSITIVE SYSTEM. 393 membrane is double : one part of it lines the hollow containing the lens ; the other advances under the ciliary processes, for whose reception it is arranged into an equal number of radiated longitudinal folds, with depressions between them, which proceed to the border of the lens and adhere to the anterior circum- ference of its capsule. The portion of black pigment between the ciliary processes and these plicae adheres to both : so that when the processes are stripped off, the plicae are seen marked with a regular series of black striae forming a radiated circle around the lens, which appearance has obtained the name for this folded portion of membrane of memhramda corona ciliaris. This being the arrangement of the divisions of the hyaloid mem- brane, it follows that there must necessarily exist a triangular interval or canal around the capsule of the lens, which forms the base of it, having indentations in its front side: this is the canal of Petit — canalis Pelitianus. This canal possesses the breadth of the corpus ciliare, behind which it is readily inflatible. It has no communication with any other part. The Ji aid that escapes from the punctured vitreous mass, though of greater specific gravity, is much the same in appear- ance as the aqueous humour, from which, I believe, it only differs in the proportion, not in the number or nature, of its ingre- dients— ?;/z. albumen, gelatine, common salt, and water. The arteiia centralis retina takes its course through the middle of the vitreous humour to the capsule of the lens : but for all this, anatomists have not succeeded in detecting any signs of vascularity or organization in this extremely delicate tremulous mass. OF THE EAR. The organ of hearing is constituted of divers parts, which have been arranged in two classes — the external and the internal ear. The External Ear, Comprises the Concha and the Meatus Auditor ius Ext emus. Concha*. The concha, or conch, is the term we use to denote the whole of that part of the organ which is exposed to external view. This consists of a flexible, trumpet-shaped, moveable structure, * In g'eneral form and external appearance the horse's ear bears no sort of comparison with the ear of a man. The external ear of the latter, alto- gether, has got the appellation of pinna; and on examining the surface of a well-formed human ear, we perceive five eminences, the heiia;, antihelix, 3 E 394 SENSITIVE SYSTEM. erected on either side of the summit of the liead, for the purpose of collecting the vibrations of sound. Superiorly, the concha, (which is ordinarily about six inches in length) grows contracted, and terminates in a point : inferiorly, it presents abroad, firm, circular base or root, so connected with the. cranium upon which it rests, as to admit of some considerable extent of sliding mo- tion. Antero-externally, appears the aperture or external orifice of the concha, ovoid in its outline, and of large dimensions, ex- tending from the point down to within an inch of the base : it is broader above than below, and is terminated inferiorly by a rounded angle. Internally, the concha exhibits a capacious cavity, broadly exposed by the external orifice ; but ending below, at the back part, in a sort of chamber or cul-de-sac, in front of which is the funnel-like entrance to the meatus auditorius. The sides of the conchal cavity are marked by several longitudinal grooves or furrows, separated by irregular salient ridges ; and the whole is so thickly clothed with long downy hair that the cavity in some horses seems to be almost choked up by them. Compoaition. — The concha is composed of three cartilages, connected and attached by ligaments and muscles, and enveloped within an external and an internal covering of common integu- ment. THE CARTILAGES OF THE EAR, fibrous in their struc- ture, are the conchal, the annular, and the scutiform. The conchal cartilage (so denominated from its giving shape to the concha) is the largest of the three, constituting the entire upper or trumpet shaped part of the ear. In its detached state it represents a hollow cylinder very obliquely detruncated along its outer side, in which defective part is formed the external orifice. Its superior end or apex runs into a point: the base or inferior part bulges posteriorly, forming the chamber aforemen- tioned ; while anteriorly it is elongated into a bifurcated process of a semicircular form, which assists in the formation of the meatus auditorius. All the muscles but two, moving the ex- ternal ear, are connected with this cartilage*. By them it is at- tached to the cranium, and also, as well as by ligamentous ex- pansion, to the cartilage next to be considered. tragus, anlitragus, and lobulu ,• and three cavities, that of the heliv, fossa navicularis, and concha. On the present occasion I have (after the manner of the French Anato- mists) adopted the term concha as an appellation for the whole external ear : its literal signification (a shell) bearing out very well this extended appli- cation of it. The general cavity, or interior of the external ear, I call the conchal cavity ; and the cartilage, which more particularly gives this shell- like or trumpet-form to the external ear, the conchal cartilage. * Vide page 84, " Auricular Region." SENSITIVE SYSTEM. 395 The annular cartilage, ring-like in its shape, surrounds the auditory process of the temporal bone, in which situation it is embraced by the lower end of the conchal cartilage, the two being connected bv ligamentous substance. It forms the en- trance or beginning of the meatus auditorius externus. — Its use appears to be, to admit of the motions of the external ear, and, at the same time, preserve the meatus from sustaining obstruc- tion or interruption in its canal in consequence of such move- ments, whereby sound might be checked or arrested in its way to the interior. The scutiform, or triangular cartilage (wrongly called triaiigidar, however, since its form bears a nearer approach to an oval, flattened), is situated at the inner and fore part of the base of the conchal cartilage, reposing upon the temporal muscle. It gives attachment to several of the muscles moving the ear. THE SKIN covering the ear, although continuous with the other common integument of the body, exhibits within the cavity of the concha a comparatively thin and delicate texture. It becomes very thin and dry; and adheres to the cartilage by a cellular tissue, dense and compact, and destitute of adipose substance. After having lined the conchal cavity, it ends in a sort of blind pouch over the membrane of the tympanum, to which it contributes an outward layer. Underneath the skin we find numerous follicles, from which oozes a peculiar greasy mat- ter, for the purpose of keeping the parts soft and pliant. Below these follicles there is a second set of glands — the glandula. ceruminos(£ ; whose ducts open between the roots of the hairs, and issue a sticky bitter matter, which, acquiring consistence from evaporation, constitutes the cerumen or wax of the ear. This secretion protects the bottom of the ear from the insinuation of insects, dust, &c. Sometimes it collects and forms concre- tions, obstructing the passage into the interior. Organization, — The arteries supplying the external ear are derived from the anterior and posterior auricular branches of the external carotid. Its veins return their blood into the jugular. Its nerves come from the portio dura of the seventh pair. Meatus Auditorius Externus. The external auditory passage \H the tubular canal leading from the cavity of the concha to the membrane of the tympanum. Its commencement is dilated after the form of a funnel, from which the canal grows contracted, and at the farther end is elongated m the direction of the membrane of the tympanum. In composi- tion, it is partly osseous and partly cartilaginous : the auditory process of the petrous portion of the temporal bone constituting 396 SENSITIVE SYSTEM. the inner, the annular cartiliio;e, the outer part. It is lined by an extension of the skin from the concha, and is plentifully fur- nished with sebaceous glands*. The Inlernal Ear. This comprehends two parts— the Tj/mpanum and the Labj/- rinth. Tympanum. The tympanum consists of an irregular cavity, situated within the petrous portion of the temporal bone, having the meatus au- ditorius externus on its outer side, the labyrinth on its inner. The cavity is lined by a very delicate mucous membrane, though it contains no fluid; and exhibits several foramina or apertures. At one part it has a communication, through the Eustachian tube, with the external air ; but the entrance into it through the meatus auditorius is closed by the membrana tympani. This semi-transparent membrane is stretched tightly across the termi- nation of the meatus ; not, however, after the manner of the parchment of a drum, but funnel-like, a shape into which it is drawn from the attachment to its centre of a lengthened process belonging to one of the little bones contained within the cavity. Two layers enter into its composition — an outer of skin, an inner of lining membrane ; which last exhibits so high a state of vas- cularity as to have been assimilated to the irisf. FetiestrcB. — The side of the cavity facing the meatus externus exhibits a very irregular aspect, and is perforated by two aper- tures — the fenestra ova/is and the fenestra rotunda. Between these two perforations is an osseous eminence called the tubercle. The fenestra ovalis (also known ^?, i\\Q foramen ovale) is an aperture bearing an approach to the fissure of an oval, looking from the cavity of the tympanum into the labyrinth. The fenestra rotunda (also called the foramen rotun- dnm) is likewise an ovoid opening, situated by the side of the tubercle, and communicating (not with the labyrinth, as in the case of the former opening, but) with the scalce of the cochlea. Bones. — Arranged along the interval between, and connected * In the foetus a thick whitish substance is secreted by these glands, which answers the purpose of defending- the parts against any acrimony in the liquor amnii. After birth, this secretion is discharged along with the subsequent issue of waxy matter. t In the foetus, the membrana tympani (and, indeed, the tympanum alto- gether) is very superficially placed ; for that which forms the osseous part of the meatus externus in the adult is a mere bony ring at this period, across which the membrane is extended. This is beautifully illustrated in the cranium of a foetal puppy now bcfich Mr. C. points out as an attribute of health) being wholly oiving to the spread, will, of course, dis- appear with the annihilation of the spread*." Although Mr. Goodwin has not here explained what he con- ceives to be the origin or cause of the spread, it is evident we both concur in viewing it rather as a deviation from health or nature than a circumstance worthy of the consideration it has been accounted of by Mr. Clark. Colour. — Hoofs are black or white, or some intermediate shade, or they may exhibit a black and white strijicd or marbly * Goodwill's New System of Shoeing, edit, second, pajre o3. \ PLANTAR SYSTEM. 421 aspect. It is an old observation, and one that passes current among us at the present day, that black or dark-shaded hoofs possess greater strength and durability, and indicate less prone- ness in the feet to disease, than such as are composed of white or striped horn. The rationale of which appears to be, that white horn (the same as white hair) is the product of parts weaker by nature than such as produce dark or black horn, and, being weaker, consequently are more liable to disease, less able to resist those impressions that tend to disorder. White hoofs are m^e porous than black ones, and consequently absorb moisture and lose it again by evaporation with more facility : a fact that may probably aid us in accounting for the failures attributed to them. Magnitude. — It requires no veterinary skill to discover any very material disproportion in the magnitude of the foot : it will strike lis at once as being large or small, in comparison to the limb or the size of the animal. A foot of any description that is out of proportion is to the horse possessing it more or less objectionable : but for all that, these out-of-proportion feet, abstractedly con- sidered, have their advantages as well as their disadvantages. Sainbel tells us, that a large wide hoof, by extending the surface of tread, " will increase the stability and firmness of the fabric;" but then, he adds, " this partial advantage grows into an evil when it becomes applied to a body capable of translation, and considered in a state of actual motion ; because, then, the n)ass and weight of the foot overburthen the muscles of the extremity." And because, I would add, the surfaces of contact being greater, the attraction of cohesion becomes greater, and so much the more muscular force is required to raise the foot (particularly in moist ground) from the earth. Besides which, a large foot is apt to become objectionable from its striking, during action, the oppo- site leg. On the other hand, it is contended, that a large foot will not sink so deep into soft ground as a small one, and conse- quently vvill not demand so great an effort of strength to draw it out. This is an argument, however, that can only hold good under the supposition, that in both cases the muscular strength is equal, which we know but rarely to happen ; in general, broad or flat- footed horses possessing superior strength; small narrow-footed ones, superior speed. There cannot be a doubt about a large foot being unfavourable for speed ; a small one for stability : neither one nor the other can be indiscriminately found fault with ; both within certain limits possess their respective advantages; though to turn out as such, they each of them require to be com- bined with suitable conformation and action. Large bulky hoofs are found to be mechanically weaker than others, in consequence of being composed of a thin, soft, porous 422 PLANTAR SYSTEM. description of horn. Sainbel ascribes all this to " a relaxation of the fibres composing the hoof: in which case, the diameters of the vessels are increased, the porosities are multiplied, and the fluids abound in them in too great quantities; consequently this kind of foot is soft, tender, and sensible." Small feet, on the con- trary, in general possess a close woven horn, thick in substance, and consequently prove strong : they are rather oval than circular in figure, with great depth of substance, and are found to be of a durable nature. ** In feet of this description," says Sainbel, " from the too close union and too close tension of their fibres, the vessels destined to conduct the nutritious fluid are contracted and obliterated ; whence proceeds that dryness of the part which renders the horn brittle and liable to spUt*." Division. — To the common observer the hoof appears to con- sist of one entire or indivisible case; but the anatomist finds, by subjecting it to maceration, or coction, or even to putrefaction, that it resolves itself into three separate pieces : still, so long as the hoof maintains its integrity, such is the force of cohesion existing between these three parts, that we as easily rend it in any other place as dissever one of its jointures. These consti- tuent parts are the iva/l, the sole, and the frog. The Wall. The wall or crust is the part of the hoof which is visible while the foot stands upon the ground. It forms a circular boundary wall or fence inclosing the internal structures. On taking up the foot, we find the wall prominent all round beyond the other parts, making the first impression upon the ground, and evidently taking the largest share of bearing. It is the part to which the shoe is nailed. It is, in fact, the most important division of the hoof; appearing to form (in the words of Mr. Clark) " the basis or first principle in the mechanism of the hoof, the other parts being all subordinate to this." Situation and Relations. — The wall takes its beginning at the coronet, from the terminating circular border of the skin, with which it is intimately united ; their line of union being concealed by a row of overhanging hairs. From the coronet the wall descends in an oblique direction to the bottom of the foot, where it embraces the sole, and terminates in a circular projecting border. The anterior and lateral parts of the hoof are Ibrmed entirely by the wall ; but at the posterior part, instead of the heels of the wall being continued one into the other so as to com- plete the circle, they become inflected, first downward, afterwards forward and inward, and are elongated in the latter direction * Saiiibcl's Lcctutes on the Elements ol Farrierv. PLANTAR SYSTFilM. 423 until they reach the centre of tlie bottom of the foot, where they terminate : these inflections or processes of the wall constitute the bars. Altogether, the wall may be said to form about two thirds of the entire hoof. Connexion. — Superiorly, around the coronet, the wall is united with the skin ; inferiorly, within its circumferent border, with the sole ; posteriorly, between its heels, with the heels of the frog ; in- feriorly, between the bars, with the sides of the frog ; and internally, with the sensitive laminse. Let us now consider the wall in its detached or separate state. Figure. — That of a hollow cylinder, having the side presented to the ground cut much aslant, and whose circle exhibits a hiatus or deficiency behind, from the lateral boundaries of which issue two narrow processes or appendages. Taking a lateral view, the wall assumes a conical shape, being broad and deep in front, and gradually narrowing as it stretches backward. Division. — For facility of reference, and in aid of our descrip- tions, we distinguish in the wall, First, the toe ; secondly, the quarters ; thirdly, the heels ; fourthly, the superior or coronary border ; fifthly, the inferior or solar border; sixthly, the lamina or lamella ; lastly, the bars or appendages. THE TOE forms the bow or front of the hoof, and compre- hends about two-thirds of the superficies of the wall. It is the deepest, broadest, and thickest part of the wall ; for reasons that will appear hereafter. It exhibits a degree of slant about equal, naturally, to an angle of forty-five degrees ; though there are varia- tions from this which (as was explained before) will he found, in a measure, to be dependent upon the oblique truncation of the cylinder. When we come to understand the physiology of this part, however, a more operative and efiicient cause for this varia- tion will be found in the weight the wall has to sustain, and in its own mechanical strength or force of resistance : on which principle it is that light horses, thorough-breds, and poneys, as well as mules and asses, have upright or strong feet (i. e.) walls but moderately sloped ; whereas heavy horses, cart-horses, and coach-horses, have commonly /fa^ or weak feet (i. e.), walls that slant immoderately. And (as was before observed) upon the degree of obliquity of the wall must very much depend that of the pasterns. In estimating the slant or slope of the wall, it is proper to distinguish between that which is consequent on the detruncation of the hoof, and such as is the effect of a burthen under which the wall succumbs. The depth of horn in front of the toe, measuring from the termination of the skin to the most prominent point below (and supposing the hoof to be cut and ready to receive the shoe), may be rated at about three and 424 PLANTAR SYSTEM. a half inches. The bow or degree of convexity of the toe in front must depend upon its obhquity as well as upon the circularity of the foot. The thickness of the horn composing the toe may be estimated at three eighths of an inch, or from that to half an inch, and this substance is the same from immediately beneath the coronary circle to the junction of the wall with the sole ; at which .part there is an accession of horny matter to block up the inter- stices between the laminas, and also to fill the angular vacuity that would otherwise exist here between the wall and sole. In the forefeet, the toe is thicker in substance than either the quar- ters or heels : but (we have it from Sainbel) " in the hind, on the contrary, the heels and quarters are generally thicker than the toe." THE QUARTERS are the portions of the wall intermediate between the toe and the heels. They are commonly described as standing upright, and, according to a carpenter's square set against the wall, so they appear to do ; this is not, however, the view the anatomist ought to take of their position : to him the oblique course of their component fibres, together with the slant of their lammas, demonstrate that they slope in the same manner and degree as the toe does. The quarters do not run in straight lines from before backward, but by their prominence describe gentle curves, the outer making a wider sweep than the inner. This gives the hoof altogether a sort o^ Hoisted appearance, and makes the inner part of the toe look more projecting than the outer: a deviation that seems principally to have originated in the spiead, and one, methinks, that has had more attention given it than any consequences attachable to it render it deserving of. The quarters range in depth from two to three inches ; and measure in thick- ness from one-fourth to three-eighths of an inch. THE HEELS are the two protuberant portions of the wall by which it is terminated posteriorly. They are the shallowest, and thinnest, and {in connexion) only flexible parts of the wall. Though their surfaces recede from the perpendicular, they maintain the same slope as the toe and quarters. At their angles of inflection, from which are continued the bars, they form (in conjunction with the heels of the sole) pouches or sockets into which are received the heels of the sensitive foot. In depth they range from one and a-half to two inches. In substance they do not exceed a quarter of an inch, the outer heel being rather thicker than the inner. THE SUPERIOR or CORONARY BORDER, is the cir- cular, attenuated, concavo-convex part entering into the compo- sition of the coronet. Its extent is marked exteriorly by the whitish aspect it exhibits, and also by some partial separation PLANTAR SYSTEM. 425 and eversion ot the outer flakes of horn around its junction with the wall below. Externally, it assumes the same character as the wall below it; but its internal surface is altogether different. Instead of possessing laminae, the surface is smooth and uni- formly excavated, being moulded to the form of the sensitive co- ronet, and everywhere presenting numerous pores for the purpose of receiving the secreting villi. Superiorly, the coronary bonier presents two edges, having a groove between them for the recep- tion of the terminating border of the cutis. It is this groove that marks the reception of the coronary border into two parts : the internal edge belonging to the inner part, which is the beginning of the wall itself; the external edge to the white band by which the other is embraced, and to which Mr. Clark has in particular drawn our attention, under the appellation of Coro- nary Frog- band. This covers the proper or veritable coro- nary border of the hoof; having, through its fibres, which are very fine, a sort of dove-tailed connexion with it. As it recedes backward, it grows broader to that degree, that its breadth at length becomes doubled ; being about half an inch broad in front, and one inch behind. It is thickest around its middle parts ; its inferior edge, like the superior, becoming attenuated, until it grows so fine as to end in imperceptible union with the substance of the wall, giving it its beautifully polished surface : from the heat, however, to which the hoof is artificially exposed, the thin part below the coronet often grows arid, splits from the crust, and becomes everted ; turning at the same time, in consequence of dryness, of a whitish complexion. Posteriorly, we find it continued round the heels of the wall and frog, and from thence across the back of the cleft, forming altogether a complete cir- cle, and everywhere shewing itself to be the medium of connexion between the skin and the hoof. It has been already stated that the cutis terminates in a circular border, let into a groove around the summit of the wall : the cuticle, however, does not end here — it is continued down ; in fact, we trace it to the horny band we have been describing, the one being continuous in substance with the other. Indeed, the only detectible differences in them are, that one is thicker than the other, and grows hard, and dry, and white, from the effects of heat upon it from without, and the want of moisture from within. This cuticular origin and assimilation may be demonstrated in the putrefied foot ; or, better still, in the foot of the foetus. The band is broader at the heels than else- where, in consequence of the greater breadth of exposed cutis at those parts. In its texture it is fibrous, and its fibres pursue the same direction as those of the wall, from which they differ only in being of a finer texture. Mr. Bracy Clark appears to enter- 3 1 426 PLANTAR SYSTEM. tain some singular notions m regard to the structure, but more particularly the uses of this part ; which in the respect I bear for their author, I shall consider when the time may arrive for me to treat of the physiology of the foot. THE INFERIOR or SOLAR BORDER offers but httle worthy of observation. It constitutes the ground or wearing sur- face of the wall, and is the part to which we nail the shoe. It grows thicker and more exuberant around the toe than in other places, and from its projecting beyond the sole, presents a conve- nient and suitable hold for the nails of the shoe. Around the anterior and lateral parts, it embraces the sole; behind, it joins the bars, which two points of union form two principal bearing places for the shoe. The inferior border possesses a larger cir- cumference than the superior, in consequence of the oblique de- truncation of the hoof. This is a part that requires paring down every time the horse is shod. Such is its exuberating nature, that (like the human nail), were it not continually kept worn down, or broken or cut off, it would elongate very considerably, and gradually turn up, exhibiting forms not only of the most unsightly but even gro- tesque description, and proving incommodious to a degree to be almost entirely destructive of progression. THE LAMINjE (better named lamella,) consist of numerous narrow thin plates or processes, arranged with the nicest order and mathematical precision upon the internal surface of the wall. They extend, in uniform parallels, in a perpendicular direction from the lower edge of the superior border down to the line of junction of the wall with the sole; and are so thickly set, that no part of the superficies remains unoccupied by them. They are likewise continued upon the surfaces of the bars. In the recent subject they are found soft, yielding, and elastic ; but from exposure they become dry and rigid. Every lamella exhibits two edges and two surfaces. By one edge it grows to the wall ; the other, which is somewhat attenu- ated, hangs loose and floating within the cavity of the hoof. The surfaces, which are two lateral, are smooth, and, considering the magnitude of the lamella itself, of enormous extent ; so much so that it might be said almost to be constituted entirely of super- ficies. And this leads us to the contemplation of the great and magnificent design which Nature evidently had in view in their formation, viz., the production of ample surface within a small space, an end that has been obtained through the means of multiplication. Mr. Bracy Clark procured from the late Thos. Evans, LL.D , mathematical teacher of Christ's Hospital, a cal- culation of what their united superficies amounted to ; and it PLANTAR SYSTEM. 427 appeared to afford an increase of actual surface more than the simple internal area of the hoof would give of about twelve times, or about 212 square inches, or nearly one square foot and a half. The lamellae exhibit no differences but in their dimensions. In length they correspond to the respective depths of the wall; being longest, and likewise broadest, around the toe, and gra- dually decreasing towards the hinder parts. In composition, they are horny. Viewed through a microscope, Mr. Clark discovered in their substance two planes of fibres, " the one running in parallel lines to the axis of the hoof, the other obliquely intersecting these." When stretched, they ex- hibit signs of elasticity; but this appears greater in the trans- verse than in the perpendicular direction. By means of its lamellae, the wall presents a superficies of ex- traordinary amplitude for the attachment of the coffin-bone. A structure consisting of similarly formed lamellae envelops the bone, and these are dovetailed in such a manner with the horny lamellae, as to complete a union wliich for concentrated strength, combining elasticity, may vie with any piece of animal mecha- nism at present known to us. THE BARS are processes of the wall, inflected from its heels obliquely across the bottom of the foot. For a long time, by far- riers, they were confounded with the substance of the sole, an error that owed its origin and perpetuation to the malpractice they exercised in paring the foot — in cutting both bars and sole down, without any distinction, to a common level. In the na- tural healthy foot the bars appear, externally, as elongated sharpened prominences, extending from the bases of the heels into the centre of the foot, between the sole and the frog : pos- teriorly, they are continuous in substance with the wall, with which they form acute angles ; anteriorly, they stretch as far as the point of the frog, constituting two inner walls or lateral fences between that body and the sole. Sainbel conceives, from their position, that they offer resistance to the contraction of the heels. Their internal surfaces exhibit rows of lamellae, continued from those lining the wall, but which are here short, and in their direction transverse, two circumstances referrible to the narrowness and inflection of the bar: towards the extremity of the bar they gradually grow shorter, and less distinctly marked, until we at length lose all vestige of any more of them. While the prominence of the bars is such as to give them a secondary bearing upon the gi'ouiid, their sharpened forms will sink them more or less deeply into every impressible surface. 428 PLANTAR SYSTEM. The Sole. The sole is the arched plate entering into the formation (as its name implies) of the bottom of the hoof: or, to adopt Sainbel's definition, "it is that part which covers the whole inferior sur- face of the foot, excepting the frog." It is a very just practical observation of Mr. Coleman's, that although a knowledge of every part of the foot is indispensably necessary to render us scientific overseers of the farrier's art, no individual part re- quires such undivided attention, as regards shoeing, as the sole, since the success of this mechanical operation mainly depends on the paring and defence of this arched horny plate. Situation and Connexion. — It fills up the interspaces between the outer and inner walls (or bars) of the crust. I differ in opinion from those who describe it to surround the toe of the frog. I hold its circumferent support and connexion to be the wall of the hoof, to which it is firmly cemented by an inter- stitial horny matter, filling the crevices between the laminae. Figure. — The circumferent outline of the sole measures about two-thirds of a circle, the remaining third being omitted to form a triangular-shaped hiatus or opening for the reception of the frog and bars. This circular form, however, is by no means true, or even invariably the same, in its dimensions. Ge- nerally, the longitudinal exceeds the transverse diameter. Its greatest diameter is shewn by a line extended from either heel across its middle to the opposite point of the toe. Aich. — Commonly, the sole presents an arch of more or less concavity inferiorly, and convexity superiorly. But it is not a regular or uniform arch, being one that rather waves or undu- lates, so as to bear a comparison, made of it by Mr. Clark, '* to the mouth of a bell extremely extended or flattened." Like that of the bell, the arch is highest in the middle, from which it slopes, laterally, down to a flat, subsequently to rise again around its border, in order to present a dilated surface for attach- ment towards the wall. There is, however, vast variety in the degree of arc of the sole: in some feet it is of surprising depth; in others, the arch is converted into a flattened surface ; and yet both seem to perform equally well. In the hind feet the sole is generally more arched than in the fore, and approaches in figure nearer to the oval than the circle. Division. — In the sole we distinguish an anterio?' part or toe; a middle or central part ; two points or heels ; and two suffaces. These divisions are not very well defined : but they prove ser- viceable in aid of our descriptions. — The toe of the sole is the part encircled by the toe of the wall, against which it abuts, and PLANTAR SYSTEM. 429 to which it is intimately united by horny matter, the two toge- ther forming a stout bulwark of defence to those parts of the internal foot included between them. — The points or heels are the two posterior salient angles received into the angular inter- vals between the outer and inner walls or bars. Although, naturally, the least exposed, these are the parts most subject to injury or pressure from the shoe, being the seat of that disease mistakenly called corn. — The middle or centre of the sole is the portion more immediately surrounding the fore parts of the frog, and would (were the sole a regular arch) be the most ele- vated part ; but, in general, we find the sole flattened hereabouts : the highest parts of the arch being the angles alongside of the bars ; the lowermost, those around the toe. Surfaces. — Of the surfaces, the superior (as was mentioned before) is unevenly convex ; the inferior, correspondently con- cave. The former is everywhere pitted, particularly about the heels, with numerous circular pores, running in an oblique direc- tion, the marks of which remain evident upon the inferior surface hkewise. These pores are the impressions made in the soft horn by the villi of the sensitive sole, from whose orifices the horny Hjatter is produced. They also form the bond of union between the horny and the sensitive soles : which is of a nature so strong and resisting, that it requires the whole strength of a man's arm to effect their separation — an operation of a cruel description that was wont to be practised in times past, under the fallacious notion that " drawing the sole" was extirpating the malady. Thickness. — The natural thickness of the sole may be estimated at about one-sixth of an inch. There will be found, however, variations from this standard in different horses ; and it will also very much depend on the part selected for measurement. The portion of the sole most elevated from the ground — that which forms a union with the bars — is nearly double the thick- ness of the central or circumferent parts ; and next to this, in substance, comes the heel. I do not find that the sole " grows thinner from the circumference to the centre," as has been stated by an author of celebrity. The Ff og. The frog is the prominent, triangular, spongy body, occupying the chasm l^ft by the inflection of the bars. Situation and Connexion. — The frog is fitted into the interval between the bars ; the three, altogether, filling up the vacuity in the sole, and thereby completing the circle, and establishing the solidungulous character of the foot. The frog extends for- ward, towards the toe, about two-thirds of the longitudinal 430 PLANTAR SYSTEM. diameter of the ground-surface of the hoof, terminating a Uttle beyond the central point (or what would be the central point) of the sole — or rather shooting directly through it, so as to anni- liilatethe spot. Posteriorly, it is embraced by the heels of the wall ; laterally, it possesses firm and solid junctions with the bars, and through their medium with the sole: and these unions are etFected not by simple apposition and cohesion of surface, but by a lameUated structure, apparent on the sides both of the frog and bars, by which the parts are reciprocally dovetailed into each oiher. Lamella) are discoverable upon its sides, even all round the toe of the frog ; and this is a circumstance that con- firms me in my belief that the bars reach thus far. Figure. — The frog may be called pyramidal, or cuneiform, or triangular in figure ; its outline forming the geometrical figure denominated an isosceles triangle. I know of no comparison so familiarly apt as that of resembling it to a ploughshare : not only do they both correspond, as near as such comparisons can be expected to do, in outline and make, but they likewise exhibit a singular coincidence in function ; the frog, like the plough- share, being intended by its point to plough or divide the surface of the earth, and in that manner serve as a stay or stop to the foot. Division. —We distinguish in the frog two surfaces, an inferior and a superior ; two sides ; a point or toe ; and two bulbs or heels. SURFACES. — Both surfaces of the fro^ manifest striking- irregularities, and these are respectively reversed, making one surface the exact counterpart of the other. In other respects, the only difference they exhibit, is, that the superior exceeds the inferior both in length and breadth. The Inferior Surface presents to our view a remarkable cavity, broad, deep, and triangular in its shape, bounded on the sides by two sloping prominences, which divaricate from the convexity forming the toe of the frog, and terminate, after a short divergent course, at the heels. This cavity or hollow is denominated The Cleft of the Frog : with seeming reference to the re- lationship existing, through its presence, between the horse's foot and the cloven one of the ox, deer, sheep, &c. In conse- quence of its sides sloping inward, the cleft at bottom gapes wide open ; but along the top is roofed by a simple linear mark running from before backward. The horn is kept continually soft and pliant within the cleft by a peculiar secretion from the sensitive parts its covers, the odour of which is notorious. The solid wedge-like portion of horn in front of the cleft, ex- tending from it to the point of the toe, has been observed by PLANTAR SYSTEM. 431 Mr. Clark to exhibit, in the natural foot at its full growth, "a considerable bulbous enlargement," which, by way of distinction, he calls the cnshion of the frog. On making a perpendicular section of the foot, Mr, C. finds this part is situated " nearly opposite or under the navicular bone." And it would appear (ac- cording to this author) that this "rotundity, or swell of the frog," is never reproduced after it has once been annihilated by the knife of the smith. The superior Surface of the Frog, every where con- tinuous, uniform, and porous, being the counterpart in form of the inferior, presents us with nothing but reverses: where the one is hollow or depressed the other rises into swells and emi- nences, and vice versa. This accounts for our finding the part opposite to the cleft elevated into a conspicuous eminence, bounded on its sides by two deep channels, and a hollow of broader but shallower dimensions in the front. To this central conical elevation Mr. Clark has given the name of frog-stai/, from some novel notions he entertains of its physiology. Such a bold promontory of horn rising in the middle of iDroad and deep channels is well calculated to form that dovetailed sort of connexion with the sensitive foot, which greatly augments their surfaces of apposition, and establishes their union beyond all risk or possibility of dislocation. It is a part which (as far as my observations on it have extended) grows and becomes developed together with other parts of the foot ; and one that is apt to vary in its relative volume in different feet. In front of the frog-stay, the lateral borders, bounding the hollow in the middle, describe a waving line, which, near half-way to the point of the toe, exhibits a dip or depression: this marks the impression of the navicular bone, and is the part immediately opposite to the " cushion of the frog," — a coincidence important to be borne in mind, as tending to throw some light on the nature of this new-christened structure*. THE SIDES are the parts by which the frog establishes its union with the borders of the triangular vacuity in the hoof into which it is admitted. Along their superior borders they are transversely lamellated, or rather indentated, in order that they may be fitted to the internal surfaces of the bars, which exhibit a similar structure. The Commissures are the two deep triangular-shaped hollows between the bars and the sides of the frog. In being only the superior borders of these parts that are engaged in their union ; their broad unattached parts, below, form the boundary wails * In fact, the cushion of the frog appears to be nothing more than a bulge of the part produced by the superincumbent pressure of the navicular bone. 432 PLANTAR SYSTEM. of the commissures. Looking into the interior of the hoof, we discover that the commissures, internally, are converted into rounded promontories, similar in appearance and texture to the one in the middle— the frog-stay— on the sides of which they are rising. In the natural state, the commissures must unavoidably get plugged with dirt, or whatever the animal may happen to tread upon ; a circumstance from which some far-fetched notions have been extracted concerning their use. THE TOE or Point of the Frog, is the anterior, undi- vided, elongated portion ; that which forms the apex of the pyramid or wedge — the acute or extended angle of the triangle — the only part displaying that prominent or rounded form that would warrant us in using the epithet " conical" to the frog. It possesses solidity of substance, firmness of texture, and lux- uriance of growth in an eminent degree ; facts well known to the farrier, who, in paring the foot, seldom fails to make more free with this than any other part of the frog. THE HEELS or bulbs of the frog are the posterior protube- rant parts embraced by the heels of the wall, and separated from each other by the cleft, forming, together, the base of the wedge or triangle. They present greater depth of substance than the toe, but are of a softer, more spongy texture, and are less resist- ing and stable, in consequence of being deprived of mutual sup- port by the division of the cleft. Anteriorly, the heels unite with the lateral prominences bounding the cleft; inferiorly, they present two surfaces of tread to the ground, evidently designed to take a share in the bearing of the foot; posteriorly and supe- riorly, they exhibit a bulbous fulness, in consequence of receiving at this part a supplementary covering from a production which has been (in the description of the wall) adverted to, under the appellation given it by Mr. Clark, of Coronary Frog-band. — It was there stated, that the coronary groove (the groove or canal in the coronary border of the cutis) broadened considerably as it descended to and turned round upon the heels ; in like manner does the horny band produced by it broaden, and not only grow broader but thicker in substance, and consequently in the same degree augments the substance of the heels, occasioning that swell of them which has suggested the appellation of "bulb." The horny band itself is every where lamellated upon its internal surface ; but these broadened parts of it display lamellse of a much bolder character, and conse- quently render their union with the heels so much the more intimate and enduring. The inferior edge of the band is denti- culated, and the denticulations become so interlaced with the lamellated fibres of the wall, that their union is rendered, in the PLANTAR SYSTEM. 433 ordinary state of the hoof altogether imperceptible. For drawing our attention to this part we are indebted to Mr. Clark ; and insomuch as he considers it to be a production of the cutis (not having any connexion with the glandular circle that secretes the wall), and to serve the purpose of " uniting the sensible parts with the insensible," I agree with him. I find something very similar to this growing upon the human nail, issuing fron^ the superior edge of the terminating border of the cutis, and continued from the cuticle, which proceeds for some way upon the nail, uniting it more closely and firmly with the cutis, and protecting the latter from external injury. This production is no more the beginning of the nail itself than is the so-called y/oo- band the commencement of the wall : they are both distinct parts, though but supplementary ones, and seem to be of a nature j^artaking both of horn and cuticle. It has no more im- portant relation to the frog, in my opinion, than it has to the wall : it serves the same purpose to both, — that of strapping up the heels of the frog and binding them in closer and more intimate connexion with the neighbouring parts. Were I asked what other use it appeared to have, I should say, that it was formed to cover and protect fro)a hijury the new-formed horn of the hoof, guarding it in its passage downward, until it has acquired substance and hardness sufficient to resist external impressions of itself. Development of the Hoof. During the early months of fcetality, no horn or hoof is to be found. The foot is covered with a substance, white, firm, and elastic, resembling cartilage in its appearance, but proving more of the nature of cuticle on examination, which supplies the place of hoof. At the coronet this substance takes its origin from the cutis, being found to be continuous with the cuticle ; but that which covers the bottom of the foot is a production from tlie sen- sitive sole and frog. Altogether, it possesses the general form and appearance of the hoof, differing however in these particu- lars — that the substitute for the wall is comparatively thin in its substance ; while that which grows from the bottom of the foot is enormously thick, and, instead of being shaped into sole and frog, exuberates to a degree to constitute club-footedness. About the same period at which the pastern and coffin-bones take on ossification, horn makes its appearance underneath this cuticular wall, in the form of plates descending from the coronet, exhibiting with peculiar distinctness the lamellated structure. The horny wall becomes considerably advanced before we per- ceive any change in the bottom of the foot. At length, horn is detected forming underneath the cuticular substance, vvhich, 3 K 434 PLANTAR SYSTEM. increasing in thickness, gradually rejDresents sole and frog. Not, however, in an undeveloped state ; for even at birth, these parts are yet concealed by the exuberant cuticular covering, now become loose in its texture, and shaggy and ragged, in conse- quence of not receiving any further supply from the parts that produced it, and of being near its decadence ; for it not long after falls off, disclosing sole and frog, both ready formed. Structure ojthe Hoof. Horn is found to differ in its texture or quality, not only in the many animals in which it is met with, but in different parts, and even in the same part of the body of the same animal. That which composes the hoof of the horse is a remarkable example of this. How different is the horn of the frog from the horn of the wall ; and yet neither of them agree in texture with the sole. The horny substance of the wall is resolvable into fibres, bearing a resemblance to thick or coarse hairs, which in the entire hoof are so intimately matted and glued together, as to have the appearance and strength of solidity. By close and accurate inspection these fibres may be seen, descending in paral- lel lines, taking the obliquity of the wall, from the coronet to the inferior or solar border : they do not run promiscuously, but are arranged in rows, forming sorts of beds or strata, lying one upon another — a disposition made manifest in the foot of the foetus. A clean-cut transverse section of the wall exhibits upon its surface numerous minute, circular, whitish spots, which grow larger and more distinct towards the internal part, and through a glass appear to be hollow or tubular. These spots I take to be produced by section of the horny tubes, apparently containing a whitish matter, a sort of pith, or pulp, or gelatinous instillation which pervades them from their origin from the villi of the coro- nary circle ; the same as hairs derive their unctuous matter from the bulbs producing them, and (as this matter does the hair) renders the horny fibre tough and elastic — in fact, embues it with the peculiar attributes so well known to smiths by the appellation of living horn ; the epithet "living " being here used to denote the obvious differences the hoof of a living animal evinces from one that has been long detached from the body, or that is dead. We are too apt to believe that the various agents known to act upon the dead hoof or horn must take similar effect on the living ; and upon this erroneous belief we employ hot and cold water, &c. &c. in treating disease of the feet, forgetting that we have opposed to our remedies the resisting or self-preserving properties of living horn. PLANTAR SYSTEM. 435 The Sole, as well as the wall, is fibrous in its structure; but its fibres appear to be of a finer quality, and, in course, are very much shorter: they, however, take an oblique direction, from behind forwards, following the same degree of slope as those of the wall. They issue from the villi penetratiug the superior surface. To the fineness of its fibres, combined with the relative magnitude of the tubular canals, and consequent relative pro- portions of horny and gelatinous substances, may be ascribed the comparative softness and elasticity of the sole. The Frog, however, displays these qualities in such a remark- able degree as to appear, in fact, to be composed of quite another kind of horn; though, on examination, we find it to evince the same fibrous structure, the only perceivable differences being the comparative fineness of the fibres and their proportion- ably greater tubularity : their direction is oblique, correspondent with those of the wall. Production of the Hoof. The wall is produced by the coronary substance, a sensitive and glandular part we shall have occasion soon to examine. Its villi, by some peculiar, mysterious, secretory process, convert the blood circulating through them into a soft pulpy gelatinous matter, which by exposure becomes hard horn, descending from the villous point that produced it, in the form of a tubular fibre, down to the sole. The fibres are united together at their very origin, but their tubes or canals diminish, the lower they descend ; which accounts for the porous or honeycomb-like structure of the interior of the coronary border and the comparative solidity of the parts below. The outer layers or strata of fibres are found to be more compact and of closer texture than the inner; which arises, in part, from the villi producing them being removed to a greater distance, and to the comparative smallness of their canals, and which, con- sequently, the sooner become obliterated. The use of Mr. Clark's coronary frog-band becomes now more apparent, serving, as it evidently does, to cover and protect these external fibres until they grow sufficiently firm and solid of themselves to bear exposure and resist casualties. The sensitive laminae make no additiop to the substance or thickness of the wall: they simply produce the horny lamellae arranged along its interior; as one proof of which, the wall measures as much in thickness at the place where it quits the coronet as it does at any point lower down. Other demon- strations of this fact come every day before such practitioners as have to treat canker, quittor, sandcrack, and other diseases of the feet. The Hokny Sole is a pioductiou from the villi of the sen- 436 PLANTAR SYSTEM. sitive sole ; after the same process as that by which the horny FROG is secreted from the vilh of the sensitive frog. In a state of health of the foot, the secretion of horn is un- ceasingly going on. Disease or injury of the glandular parts may diminish, or altgether suspend the process ; disease, under certain other forms, appears also to have the effect of increasing it ; but whether we have any artificial means of effecting this, seems questionable. The wall grows from above downwards. If a mark be made in any part of the wall, it will remain until it grows down and becomes cut off below, at the inferior border ; and by observations made on the gradual descent and disappear- ance of these marks, calculations may be formed of the period of tiuie required for the renewal or restoration of the wall. Properties of Hor?i. Horn is a tough, flexible, elastic substance, consisting of tubu- lar fibres, more or less intimately connected together, taking the direction from the surface of the body on which it grows. Its property of toughness or resistance much depends on its con- dition in regard to moisture; for if it is exposed to a degree of heat sufficient to abstract much of its natural juice or imbibed moisture, it loses its flexibility and toughness, and becomes brittle. On the other hand, saturated with moisture, it is converted into a soft and highly flexible substance, but at the same time becomes weak and unresisting. This known effect aids us to account for the flat-footedness of horses reared in low, fenny, or marshy situ- ations ; the hoof being constantly in a state of saturation with moisture, the wall and sole yield to the superincumbent burthen of the body, and the latter grows flat (instead of remaining con- cave or arched), and even in some instances bulges. If oily or unctuous applications have any effect in softening the hoof, they appear to do so by filling the crevices and interstices be- tween the fibres on the surface, and in this manner checking or suppressing evaporation. Horn takes a high and beautiful polish. Although much inferior in transparency to tortoise-shell, it may be worked up to bear so near a resemblance to it as to be often, in manufactures, substituted for it, as in combs, &c. The hoof admits of an elegant polish ; and in that altered and improved state has been manufactured into articles no less useful than valuable and ornamental* : even the hoofs of the living animal may, by being- kept clean, and when dry rubbed with linseed oil, be numbered among the ornamental beauties Nature has bestowed upon quadrupeds. * The Eclipse hoof, presented by his IVlajctily at Ascot Races, as the reward uf the best horse on the turf, forms a notable illustration of this. PLANTAR SYSTEM. 437 By chemical analysis horn has been found to consist of mem- branous substance, having the properties of coagulated albumen, and of some gelatine. The horns of some animals, the deer species, from containing bone, become exceptions to this. Mr. Hatchett burnt five hundred grains of ox's horn, and the resi- duum proved only one and a half grain, not half of which was pliosphate of lime. Shavings of hoof thrown into nitric acid become soft, and speedily melt into a yellow mass, which in about eight hours disappear in complete solution. The same thrown into sulphuric acid, turn black, in becoming soft, and require thrice the time for their solution. Muriatic acid also turns horn black, and corrodes it, but has so little effect towards its solution, that after ten days a piece of hoof soaked in it was found to have become only more brittle or rotten. Common vinegar will turn horn dark-coloured, but does not appear to have any power in impairing its texture, or, at least, in dissolving it. Liquor potassai will not only turn it black, but will corrode the horn of the hoof. Ammonia does not change its colour, but slowly destroys its texture, rendering it brittle and rotten. INTERNAL PARTS OF THE FOOT. THE internal, sensitive, organic parts of the foot, comprise the hones, ligaments, tendons, coronaty substance, cartilages, sen- sitive lamina, sensitive sole, and sensitive fi'og. THE BONES entering into the composition of the foot are the coffin and navicular bones : to which may be added (as form- ing part of the coffin-joint, and consequently having intimate re- lation to them), the coronet bone. Their descriptions will be found given at pages 57, 58, 59, and 60. THE LIGAMENTS have likewise been already described at page 75, in giving the particulars of the coffin-joint. THE TENDONS immediately connected with the foot are those of the extensor pedis and the Jiexor pedis perj'oraiis : the former being inserted into the posterior concavity of the coffin- bone ; the latter into its coronal process, as described at pages 140 and 144. The Coronary Substance, A less inappropriate name for the part commonly called the coronan/ ligament*. * Averse as I am to changing- or altering names, nothing less than a palpable contradiction, in regard both to slrncdtre and fttnction, would have induced me to do so in the present instance. 438 PLANTAR SYSTEM. To revert, for the sake of elucidation here, to former descrip- tion — after the hoof has been detached by a process of maceration or putrefaction, in a perfectly entire, uninjured condition, it pre- sents around its summit a circular groove, bounded in front by a soft whitish substance, having a thin edge, and being of a na- ture between horn and cuticle ; and behind, by an attenuated margin, more horny in its character, whose thin edging is denti- culated or serrated. Into this circular groove or canal is received the terminating margin of the cutis; the cuticulo-horny layer of the hoof, in front of it, having every appearance of being a con- tinuation of the cuticle. Situation — Dimension. — The coronary substance occupies the concavity formed upon the inside of the superior or coronary bor- der of the wall of the hoof: it is the part constituting the basis of the circular prominence commonly distinguished in the living animal as the coronet. It is broadest around the toe of the wall, diminishing in breadth towards the quarters and heels, and being somewhat broader around the outer than the inner side. It is thickest in substance around its middle and most promi- nent parts, growing gradually thinner both above and below. Connexion. — Externally, the coronary substance is connected with the hoof; and the connexion appears to be principally, if not entirely, of a vascular nature: the surface of the wall pre- senting a porous honeycomb- like texture, and the villi or ves- sels issuing from the coronary substance entering the pores, and thus establishing an intimate and extensive vascular union be- tween these organic and inorganic parts. Internally, the coro- nary substance is connected with the coffin-bone, the extensor tendon, and the cartilages, by a fine, dense, copious cellular tis- sue, which at the same time forms a bed for the assemblage and ramification of the bloodvessels concerned in the secretion of the wall of the hoof. Superiorly, its union with the skin is so in- timate and complete, that one has been thought to be a conti- rmation of the other; and, so far as meets the eye of a common observer, they might be taken as such : but, when we come to examine them by anatomical tests, we not only find a line of external demarcation between them, but discover such difference of internal structure as forbids the adoption of this delusive no- tion. As it descends upon the coffin-bone, the coronary substance not only grows thinner, but in growing attenuated becomes im- perceptibly gathered or puckered into numerous pomts from which issue a like number of plaits or folds, which afterwards form the sensitive laminae. It is worthy of remark, that the part of the bone upon which this transformation takes place is smaller in circumference than the coronet; consequently the same mea- PLANTAR SYSTEM. 439 sure of coronary substance which but tensely and smoothly covered the latter, admitted of being disposed in gathers or folds so soon as it reached the former. Posteriorly, the coronary sub- stance forms a junction, indeed becomes continuous in substance, with the heels of the sensitive frog. Structure. — The coronary substance discloses three different parts in its composition : — 1. A Jibro-cartilaginous circling band, forming the substratum and basis of the entire structure. 2. A cuticular covering, so called from its resemblance in texture to the cutis. 3. A network of bloodvessels, reposing upon the for- mer, and covered by the latter. The cartilaginous structure, freed from its vascular connexions, is found to be wrought in the form of a coarse, open, irregular network, and appears designed mainly for the purpose of affording a bed for the lodgment and ramification of the bloodvessels destined to produce the wall. The looseness of its connexion, added to its own elasticity, ren- ders this substance peculiarly adapted to accommodate itself to the motions of the coffin-joint, and thus preventing those movements from operating prejudicially to the superimposed glandular struc- ture. Organization. — The coronary substance may be ranked among the most vascular parts of the body : no gland even possesses, for its magnitude, a greater abundance of bloodvessels, or of bloodvessels (taking them generally) of larger size ; nor does there exist any part in which greater care appears to have been taken to arrange its vessels so as to insure an uninterrupted supply of blood. These vessels it is that produce the wall : and there is every reason to believe that they perform this office without any assistance from the vessels of the laminae. The Cartilages Are two broad, scabrous, concavo-convex, cartilaginous plates, erected upon the sides and wings of the coffin-bone. Professor Coleman calls them " the lateral cartilages," in contradistinc- tion to two others he has named " the inferior cartilages." Situation. — The cartilages form the postero-lateral parts of the sensitive foot, extending the surface considerably in both these directions. Attachment. — The cartilages are fixed into fossae excavated in the supero-lateral borders of the coffin-bone. Their anterior parts become united, on each side, with descending lateral ex- pansions from the extensor tendon, and are also attached to the coronet bone by cellular membrane. Their posterior parts sur- mount the al(e or wings of the bone, to which they are firmly fixed, and from which they project backwards, beyond the bone. 440 PLANTAR SYSTEM. giving form and substance to the heel. Supposing one of the car tilages to be divided into two equal parts by a line drawn horizon- tally across its middle, the superior half, which extends as high as the pastern-joint, is covered by skin only ; and on that account is quite perceptible to the feel, and (in form) to the sight, as the animal stands with his side towards us. The lower half is covered, superiorly, by the encircling coronary substance ; inferiorly, by sensitive laminae : consequently, over all by the hoof, wiiich envelopes both the coronary substance and the laminae. The extreme posterior ends of the cartilages incurvate downward and backward ; but, being overreached by the heels of the sensitive frog, any abrupt or exposed termination of them is prevented. Around these points also the coronary substance makes its in- flections upon the sensitive frog, thereby giving them additional substance and support. Form. — Considered in the detached state, the cartilage in its general figure describes an irregular quadrangle, of which the supero-anterior and infero-posterior angles are the most project- ing ; the latter at the same time being incurvated inwards. Ex- ternally, the cartilage is pretty regularly convex ; internally, it is unevenly concave, the surrounding border turning inwards into the substance of the sensitive frog. The posterior part of the cartilage is somewhat thinner than the anterior, and has several foramina through it — three or four of large size — which transmit vessels to the frog. THE FALSE CARTILAGES.— From the inferior and pos- terior sides of the true cartilages, proceed in a direction forward — towards the heels of the coffin-bone — two fibro-cartilaginous productions, to which Mr. Coleman has given the name of" in- Jerior cartilages." If they are to be considered as t«////oofsatall, I prefer denominating themy"a/se ; they being, as well in structure as in use, different from the true or lateral cartilages. They spread inwards upon the surface of the tendo perforans ; become united at their inner sides with the superior margin of the sensi- tive frog ; are covered inferiorly by the sensitive sole; and at the same time assist in the support of the sensitive frog. They are triangular in their figure, and are arched in the same manner as the sole. Use. — Their use appears to me to be, to fill up the triangular vacant spaces left between the tendo perforans and heels of the coffin-bone, thereby completing the surface of support for the sensitive frog, and extending that for the expansion of the sensi- tive sole. Bone in these places must have proved inconvenient by more or less impeding the impression upon — and consequent reaction of — the sensitive frog. PLANTAR SYSTEM. 441 l^he Sensitive LumintB or Lamellce. So is denominated the laminated, membranous, vascular struc- ture clothing the wall of the coffin-bone. Production. — The sensitive laminae appear to be derived from the coronary substance— the one, in fact, seems to be a continua- tion from the other; for if, in a foot in a putrid condition, we attempt to part them by force, we may make an artificial rent somewhere, but can find no natural separation between them. The cuticular covering of the coronary substance having descend- ed upon the coffin-bone, the circumference of which is less than that of the coronet, because thereupon gathered into numerous little plaits or folds, which proceed in parallel slanting lines down the wall of the bone : a transformation it may be difficult to ex- plain, since the laminae unfolded would occupy a much larger surface than the coronet ; at the same time, it is one that has its parallels in the animal constitution, and a remarkable one in the instance of the ciliary processes. Division. — According to this mode of derivation, every lamina consists of one entire plait or duplication of substance, having its inward sides intimately and inseparably united ; its outward sides being the surfaces of attachment for the horny laminae. It has also two borders; one opposed to the coffin-bone, the other to the hoof: and two ends or extremities, one issuing out of the coronary substance, the other vanishing in the sensitive sole. Structure. — The substance of the laminae when held to the light evinces a degree of transparency ; although its nature is ex- tremely dense, and it possesses extraordinary toughness and tena- city. Veterinary writers and lecturers have endowed the laminae with a high degree of elasticity : but it appears to me that the property is referrible to their cotinexions, and not one that is in- herent in their own substance. Elastic Structure. — This is a substratum of a fibrous perios- teum-like texture, attaching the laminae to the coffin-bone, in which it is that the property of elasticity resides to that remark- able extent usually ascribed to the laminae themselves : indeed, so elastic is it found to be, that it can be made to stretch and recede the same as a piece of Indian rubber. Its fibres take a direction downward and backward. At the same time, it affords a commodious bed for the ramification of bloodvessels issuing from the substance of the bone, in which they are (particularly in the stretched condition of the substance) protected from in- jurious compression and consequent interruption to their circula- tion. Number. — In round numbers we may estimate the laminae at 3 L 442 PLANTAR SYSTEM. about 500 ; not including tliose of the bars. They vary, how- ever, in number : I have reckoned upwards of 600. Dimensions. — In length they decrease from around the toe towards the sides and heels in a corresponding ratio with the wall : those in front, the longest, being rather more than two inches in extent; the shortest, those at the heels, being rather less than one inch. In breadth there is no variation : all measure alike— one-tenth of an inch. Organization. — The laminae are highly organized, though they are not equally so with either the sensitive sole or sensitive frog ; nor are they so red as those parts : and the obvious explanation of this is, that (over and above what is requisite for their own nutrition) all the blood they have occasion for is only that which is sufficient for the secretion of the horny laminse. The Sensitive Sole. The sensitive sole, or (as Sainbel calls it) the fleshy sole, is the fibro-vascular substance covering the arched concave, or ground surface, of the coffin-bone : in fact, is the part corresponding to the horny sole. Strncivre. — The same kind of elastic fibrous structure that sustains the laminae is found constituting the groundwork of the sensitive sole ; only that in the latter case it is closer, denser, and firmer in its texture. Upon this is spread a remarkably beautiful venous net-work. And the whole is enveloped in an outer cuticular covering, derived from the heels and frog, from which are sent villous processes, loaded -with the points of arteries into the porosities of the horny sole : not, however, perpendicularly downward, but in an oblique direction — downward and forward — the same in which the horny fibres grow. Connexion. — Around the circumference of the coffin-bone, the sensitive sole is connected with the fibrous substance descending from the wall, together with the tapering, vanishing points of the laminae. In the centre, it is united with the bars and frog. But its principal attachment consists in its being firmly rooted into the sole of the coffin-bone ; a connexion that receives con- siderable addition from the bloodvessels issuing out of the sub- stance of the bone. Thickness. — The sensitive sole varies in thickness at different places. On an average, it may be said to measure one-eighth of an inch in thickness. In the vicinity of the frog, it is something less than this. At the heels, it possesses double that thick- ness. Organization. — This is one of the most vascular and sensitive pails in the body. Independently of the much adiuiicd venous PLANTAR SYSTKM. 4^3 net-vvovk expanded over the fibrous substance of the sole, arteries enter it issuing froui the substance of the bone, and penetrate its villi, which, by taking this course, elude all compression and ob- struction : there are also others — the nutrient arteries ; but these have an external origin, from the inferior coronary artery. The chief assemblage of arteries takes place within the villi, upon the cuticular surface — those issuing out of the interior of the bone simply passing through (without ramifying within) the fibrous substance : so that, if the substance of the sole is laid open by transverse section, the incised edge, near the surface, exhibits a deep red tint ; while the interior, nearer the bone, has a pinkish or pale red aspect. The Sensitive Frog. Under this head is included the cleft cuneiform body, pro- jecting from the bottom of the foot, together with the substance continued from it and filling the interval between the cartilages. Sainbel call it " the fleshy frog." Division. — We distinguish, in the sensitive as in the horny frog, an opex or toe ; two heels, separated by the cleft ; and a portion intermediate between these, which is the bodi/. Situation and Connexion. — The sensitive frog occupies the posterior and central parts of the bottom of the foot, forming in the tread a firm and secure point d'appui. Being in the hoofless foot equally prominent with the projecting edge of the coffin- bone, one might be led to infer that the horny frog should take the same line of bearing with the crust. The frog, altogether, is lodged in a capacious irregular space, bounded superiorly by the tendo-perforans and common skin, laterally by the cartilages, and inferiorly by the horny frog: with all which parts it has con- nexions ; besides being continuous with the sensitive bars and sole, and at the heels with the coronary substance. On its sides are two shallow ill-defined hollows, corresponding to the com- missures of the horny frog, into which are received the horny prominences opposed to them. Structure. — Entering into the composition of this body we distinguish four parts: — An exterior or cuticular covering; a congeries, or network of bloodvessels ; a fibro-cartilaginous texture ; and an elastic interstitial matter. The exterior or cuticular covering invests the prominent bul- bous portion of the frog, and also gives a lining to the cleft. Superiorly, it is continuous with the skin descending upon the heels; anteriorly, with the cuticular covering of the coronet; in- teriorly, with that of the sole. Numerous villous processes sprout from its surface, and enter the porosities in the interior of the 444 PLANTAR SYSTEM. horny frog, taking a direction downward and forward, the same as that in which the fibres of the horn grow. The vascular covering succeeds the cuticular, lying immediately underneath it. It consists of a network of bloodvessels, princi- pally veins, but which are not so thickly set as upon the sole. The JibrO'Cartilaginous case comes next. We find it spread over those parts most subjected to pressure, and to be, in many places, one-fourth of an inch in thickness. From its interior are sent off numerous processes, pervading the elastic matter of the frog, forming so many septa intercrossing one another, and di- viding it without any notable regularity into many unequal com- partments. In the posterior and bulbous parts, the septa exist in greater numbers, and are closer arranged than in the middle parts. The fibres of this vaginal substance run obliquely downward and forward, and become intermixed around the borders with those of the bars and sole. The elastic interstitial matter, however, composes the bulk of the sensitive frog. It consists of a pale yellowish soft substance, which has been mistaken for fat or oil, and hence has been named *' the fatty frog." When cut deeply into, it exhibits a granulated appearance, and the fibrous intersecting chords become apparent, putting on the ramous arrangement of a shrub or tree. Altogether, the sensitive frog forms a peculiar, spongy, elastic body, for which we lack some more appropriate name. *»* The Bloodvessels and Nerves of the Foot will be found described in their places, in the circulatory and nervous systems. INDEX. A. ABDOMEN 242 muscles of 122 Abdominal parietes, lymphatics of ... 269 Abdominal region 124 Abduceus auiem 86 Abducent nerves 339 Abductor Oculi 87 Absorbent system 265 Accelerator urinae 130 Accessory nerves 344 Adductor femoris 154 oculi 87 tibialis 156 Anal arteries 201 Anal region 128 Anconeus 139 Antea-spinatus 133 Anterior artery of the cerebellum 195 cerebrum 194 Anterior auricular artery 192 brachio-crural region l39 Anterior (musculus) conchas 85 Anterior femoro-crural region 157 humeral region 1.% ilio-femoral region 150 — laminal arteries 187 masseter arteries 190 maxillary region 89 Aorta 176 anterior 180 posterior 196 origin and course of 179 Aortic plexus 360 Aqueous humour 390 Arachnoid membrane 314 Arm, bone of 51 Arm and fore-leg, muscles of 139 Arteria communicans 194 profunda femoris 203 Arteriae Innominatae (corporis) 180 (Ilii) 201 Arteries 176 table of.. 177 Articulations or joints 69 Arytenoid cartilages 222 Arytenoidcus 102 Ascending pharyngeal artery 190 Astragalus 64 Atlas and axis, joints between 69 Attollentes aurem 84 Attollens maximus jb. anterior jb. posterior ib. Auditory nerves 340 Auricle, right 173 left 175 Auricular arteries 191 & 192 veins 210 nerves 340 Auricular region 84 Axillary artery 183 vein 212 & 215 Bars of the hoof Basilar artery Biceps abductor femoris Blade- bone Bladder situation and figure of.. volume of division of connexions of =. structure of Blood odour and flavour of halitus of spontaneous concretion of heat of colour of quantity of Bloodvessels Brachial vein Brachii os Brain 310 & magnitude of - division of. situation of , coverings of structure of duplicity of ... arteries of. base of Breast-bone Bronchial artery tubes glands Buccal arteries 190 & Buccal nerve Buccinator Bufty coal of the blood Bulb of the penis, artery of. 427 279 ib. 280 ib. ib. 281 163 ib. ib. ib. 164 ib. ib. 176 214 51 314 310 ib. ib. 311 .314 315 316 324 12 196 225 234 191 339 91 170 200 Canine teeth 68 Caninus 90 Calcis OS 64 Capsulae renales 278 Cardiac Plexus 359 Carpus 52 446 IXDKX. tity of.. Cartilages of the foot 439 ■ situation of ... ib. attacliineiu of ib. form of ib. false 440 Cartilages of the ribs 12 Carotid arteries 188 Caruncula lachrynialis 373 Cellular luembrane 414 ■■ kinds of ib. comparative q uan- ib. texture of ib. exhalation into... 415 modification of... ib. i elasticity of ib. | organization of... ib. i Central artery of the retina 195 Centrum ovale 4... 317 Cerebellum 322 j peculiarities of ib. lobes of 323 ventricle of ib. I Cerebrum 316 ventricles of 317-321 commissures of 320 Cervical ganglia 358 & 359 nerves 346 1st and 2d ib. 3d, 4th, and 5th 347 6th and 7th 348 Cervical vein, inferior 216 Cervico-auricularis 85 Cheeks 236 Chest 10 Chord spermatic 285 artery of 203 Choroid coat 386 Choroid plexus of the cerebrum 319 ofthecerebellum 323 Ciliary arteries 195 circle 386 glands 368 processes 388 Circulatory system 163 Circulus Arteriosus of the braiii 196 of the foot 187 Circumflex arterv of the ilium 202 of the foot 187 Circumflex vein of the ilium , 218 Circumflexus palati 103 Cleft of the frog 430 Clitoris 300 Coccygeal arteries 202 nerves 352 -region 130 Coccvgis ossa 15 Cochlea 401 Ccecum 257 Cceliac artery 197 Coffin bone 58 joint 75 Colon, course of „. 246 description of 257 Commissures of the brain 320 i of the foot 431 Commissures of the pudendum 300 Complexus major 105 minor 106 132 Compressor coccygis Concha Conjunctive tunic Constrictor pharyngis anterior. — medius... posterior 101 Coraco-huraeralis 136 Cornea 381 Cornua Uteri 304 Corona glandis penis 295 Coronary arteries 179 frog-band 432 substance 437 Coronet bone 57 Corpora cavernosa penis structure of 296 vaginas 301 Corpora nigra 385 striata 318 Corpus albicantium 324 Corpus callosum 316 Costal region 114 Costre 10 Covvper's glands 298 Cranium 19 cavity of 42 Cremaster 128 Crico-arytenoideus lateralis.. 101 posticus ib. Cricoid cartilage 222 Crico-thyroideus 101 Crura cerebri 324 cerebelli ib. Crural nerve 355 Crureusvel cruralis 152 Crystalline lens 391 Cuboid bone 65 Cuneiform bone of the knee 59 hock, large ... 65 — ■ middle.. 66 small ... ih. 170 ;ygis. Cupped blood. Curvator coc Cuticle, composition of 406 colour of 407 extent of ib. pores of ib. — production of ib. sensibility of 408 density of ib. Cutis 402 density of.., 403 colour of il>. structure of ib. organization of 404 poresof 405 resreneration of 406 Dartos 283 Deep posterior brachio-crural region 143 Deep posterior femoro-crural region 161 INDKX. 447 Deep temporal arteries 192 Dental nerve 339 Depressor coccygis 131 • labii suuerioris 93 iinerioris 91 oculi 87 Diaphragina 120 Diaphragmatic arteries 197 nprves 3i8 veins 217 ■ region 120 Digastricus 96 Digestive system 234 Dilatator naris anierior 92 lateralis 89 Dorsal artery ISO ganglia 359 — nerves 3!S Dorsalis scapulae, arttria 183 ■ ■ vena 215 Dorsal region 118 Dorso-ccrvical vein 216 Dorso-costal region 117 Dorso-scapular region Ill Ductus ad iiasum 375 Duodenum, course of. 245 Dura mater description of 255 surfaces of. , organization of., processes of. E. Ear, external 393 internal 396 cartilages of 394 skin covering , 395 Elbow joint 72 Emulgent arteries 199 vein 217 Epididymis 288 Epigastric artery 203 region 243 Epiglottis 222 Erector clitoridis 130 coccygeus 131 penis 129 Esophageal artery 196 Esophagus 241 Ethmoid bone 26 cells 27 Eustachian tube 399 Extensor metacarpi magnus 139 parvus 141 obliquus ib. Extensor pedis, anterior 140 ■ posterior 157 Extensor suffraginis 141 External carotid artery 189 pectoral artery 182 thoracic artery 183 nerves 352 External scapular region 133 Externus mallei 398 Extremities, bones of 48 Extrsmities, muscles of Eye appendages of Eyeball muscles of defence and position of situation and connexion of magnitude,tigure,and diameter of constituent parts of coats of humours of Eyebrow Eyelashes Eyelids structure of organization of use of Pace, bones of... 23 Facial artery 190 vein 211 • nerves 338 Fallopian tubes 305 course of ib. structure of. False cartilages (of the foot) 440 use of ib. Falx, dursematris 312 Fat 410 production of 417 deposition of ib. absorption of ib. Femoral artery 204 vein 219 Fetlock-joint 73 Fibrin 166 Fibula 64 Fimbriae 306 Fissura magna 299 Flexor brachii 138 metacarpi externus 142 -internus 143 medius 142 metatarsi 158 pedis (posterior) 161 perforans 144 perforatus. accessorius. 143 Foot, bones of 58 number of 418 toes or claws of ib. division of ib. external parts of 419 internal parts of 437 Foramen commune inferius 321 Foraminacoeca 325 Fore extremities, bones of 54 joints of. muscles of. nerves of. 72 352 Fore extremity, left, lymphatics of ... 273 leg, bones of Fornix 54 319 448 INDEX. Frog, artery of 187 veins of 213 Frog, horny, situation and connexion of 429 tigureof 430 division of. ib. surfaces of ib. -cleft of ib. sides of 431 commissures of ib. toe of. 4:32 heels of ib. coronary band of ib. production of 436 sensitive 443 division of ib. — situation and connexion of. structure of ib. -cuticular covering of ib. vascular covering of... 444 ti bro-cartilaginous case ib. - elastic matter of ib. Gastric artery 197 Gastrocnemius externus 159 ■ internus ib. Gemini 149 Generative system 282 Genio-hyo-glossus 99 Genio-hyo-ideus 97 Genital region, male 128 female 130 Glandulae odoriferae 293 Glans penis 295 Glossal region 98 Glosso-pharyngeal nerve 341 Gluteal artery 201 nerve 356 region 147 Gluteus externus ib. — maximus ib. internus 148 Gracilis 153 Great bone of the knee 53 Gums 236 Gustatory nerve 339 H, Hair, quality of 410 thickness of ib. . direction of 411 structureof ib. identity of 412 colour of , ib. shedding of 413 reproduction of ib. Haunch, bones of 61 muscles of 117 Head, appendages to bones general description of., Head, lymphaticsof 272 muscles of 84 Heart 173 Heel, skin of 405 Hepatic artery 198 veins 217 plexus . Hind extremities, bones of..., muscles of .. 144 nerves of 355 Hip or haunch bones 16 Hippocampi 319 Hock, bones of 64 Hoof, form of 419 spread of 420 colour of ib. magnitude of 421 development of .. 433 structureof 434 reduction of 435 Horn, properties of. 436 Humeral artery 183 vein 215 Humeral thoracic artery 183 veins 215 Humeralis externus 137 Humero-cervical region 103 Humerus 49 Humours of the eye 390 Hyo-epiglottideus 102 Hyo-glossus longus 98 brevis 99 Hyoideal region Hyoides, os 66 Hyoideus magnus 97 parvus , 98 Hyo-pharyngeus 100 Hyo-thyroideus 101 Hypo-gastric plexus 361 region 243 Ileum, course of. 246 description of 256 Iliac arteries, external 202 internal 200 Iliac veins, common 217 external 218 internal ib. Uiacus 123 Incisor teeth 68 Incus 397 Inferior cervical artery 182 region 108 Inferior cervico-occipital region 110 Inferior communicating arteries 187 Inferior labial artery 190 Inferior maxillary artery 192 nerve. Infra-orbitar artery 193 Infundibulum 321 Inguinal artery 204 vein 218 Insensitive laminae 426 Intcrcostalcs cxierni 115 INDEX. 449 Intercostales iuterni 115 Intercostal arterios 196 veins !il6 nerves 349 Internal carotid artery 194 Internal ilio-fenioral region. Internal maxillary artery. Internal pectoral artery. 152 192 132 Internal scapular region 134 Inter-transversales luniboruni. Intestines large. small. surfaces of... margins of... structure of.. motion of..... Ischium Ischiatic arteries. veins .... 18 201 218 Jejunum 250 ■ course of 246 Jugular vein 210 K. Kidneys 273 situation and attachment of... 274 figure of il). magnitude of ib. division of. ib. capsules of 275 structure of ib. organization of 278 Knee, bones of 52 Knee-joint 73 Knuckle bone 64 Labial artery, inferior., superior. vein nerves Labia pudendi ... Labyrinth Lachrymal artery vein nerve caruncle puncta and conduits. sac Lacteals Lamina spiralis Laminaeof the hoof internal foot. veins of. 399 !-195 32 211 337 372 373 374 ib. 269 401 426 441 213 Large metacarpal artery. Laryngeal region , artery veins Larynx membrane lining. Lateral cervical region.. Lateralis sterni .. ... Lateral laniinal artery ... Lateral nasal artery nerve Lateral sacral artery Latissimus dorsi Laxator tympani Levator anguli oris Levatores costarum Levator humeri Levator labii superioris alaeq. nasi.... Levator nienti oculi • palpebraa superioris ■ internus. Lingualis Lingual artery ' vein nerves Lips Liver, situation of.... description of. lymphatics of . Longissimus dorsi.... Longus colli Lumbar region arteries , veins nerves Linnbrici Lunar bone i^ungs . Lymphatics, Magnum os , Malar bones Malleus Masseter , Masscter arteries • veins Maxillary bone, superior. anterior . ' — inferior . Maxillary artery, internal. inferior Maxillary vein, internal inferior Meatus auditorius externus. internus... Meatus urinarius Medulla oblongata Menibrana nictitans Mesenteric artery, anterior.. posterior , Mesenteric plexus, anterior.. 184 101 188 211 342 218 223 104 116 187 193 337 2(tl 112 .S98 90 117 104 89 92 87 86 87 99 190 211 344 236 247 259 5^70 118 110 122 199 217 350 145 53 229 53 31 397 94 191 200 29 31 36 192 ib. 210 ib. 395 401 -302 325 371 450 INDEX. Mesenteric plexus, posterior 361 Mesenteric veins 220 Mesentery 247 absorbents of 269 Metacarpal arteries 184 Metacarpal bone (large) 54 (small) 55 Metacarpal nerves 354 veins 213 Metacarpus 54 Metatarsal artery 206 bone 60 356 219 195 401 nerves, vein. Middle arteries of the cerebrum. Modiolus Molar teeth 68 Motorcs oculorum 336 Mouth 234 Muscles, cutaneous 82 table of 76 Muscular system 75 Musculi proprii conchse 85 Mylo-hyoideus 97 N. Nasal fossas 362 Nasalis brevis labii superioris 93 longus labii superioris 90 Nates and Testes 322 Navicular bone 60 Neck, bones of 5 muscles of 103 Nerves, number of 328 magnitude of ib. coverings of ib. structure of ib. — elasticity of 329 mode of origin of ib. ramification of 330 termination of ib. distribution of 331 table of 332 placesof origin of 335 Nervoussystem 310 Nose 362 cartilages of ib. cavities of 45 ducts of 364 sinuses of ib. Nostrils 363 Obliquus capitis anticus Ill inferior 108 ■ superior 107 Obliquus externus abdominis 124 internus 126 Obliquus inferior oculi superior. Obturator internus , Obturator nerve ... Occipital artery bone 194 22 vein 210 Ocular artery 192 region 87 Olfactory nerves 335 Omentum 246 lymphatics of 270 Ophthalmic artery 195 nerve. Optic nerves 335 Orbicularis oris palpebrarum 93 Orbits. Organs of generation, male female external parts internal parts. ib. 301 1 Osseous system. Osorbiculare ^ «*97 Ovaries 306 magnitude of ib. form of ib. structure of ib. ^ organization of 307 Palate 236 soft ib. Palate bones 33 Palatine region 102 Palato-maxillary artery 193 ■ nerve 338 Palato-pharyngeus 100 Palpebral region... 86 Pancreas 263 situationof 247 division of 263 structure of ib. organization of ib. lymphatics of 271 Obturator artery 201 Obturator externus 149 Pancreas minor ib. Papilla 309 Parietal bones 21 Parotideal arteries 191 nerves 340 veins 210 Parotid gland 239 duct ib. Par trigeminum 336 vagum 341 Pastern bone 56 joint 'i^ Pathetic nerves 336 Pectineus 153 Pectoral arteries 182 veins 216 region. Pectoralis inagnus ib. parvus 114 transversus 113 Pedis OS 58 INDEX. ^51 Pelvis, bones of general description of ■ — articulations of lymphatics of Pelvi-trochanterian region Penis sheath of cul-de-sac of faschial covering of structure of organization of plexus venosus of Pericardium Perineal arteries veins Peritoneum reflection of Peroneus Perpendicular artery Petrous portion of the temporal bone Pharyngeal artery, ascending vein nerves region Pharynx Phrenic arteries ■ veins nerve Pia mater Pineal gland Pigment of the eye Pisiform bone Pituitary gland Plantar arteries nerves 355- veins Plantar system Plantaris Plat vein 212- Pleura Plexus choroides Pons varolii Popliteal arteries nerves Popliteus Portio dura mollis Postea-spinatus Posterior aorta arteries of the cerebellum... cerebrum.... auricular artery cervical artery conchae musculus extremities, bones of lymphatics of.. — muscles of nerves of ■ humeral region ilio-fenioral region masseter artery maxillary region — scapular region Prostate glands Prostatic artery Psoas magnus Psoas parvus Pterygoid arteries . veins.... 210 Pterygoideus externus., internus . Pubic arteries 201 Pudendum 299 Pudic artery, external 203 "internal 201 Pulmonary artery 176 plexuses 343 veins 207 Pupil 384 Pyriformis 148 R. Radial artery 184 nerve 353 —veins 214 Radialis accessorius 145 Ramus anastomoticus 193 Ranine artery 190 Receptaculum chyli 268 Rectum, course of 246 description of 258 Retractor oculi 88 ani.... 128 Rectus abdominis 127 Rectus capitis anticus major 110 minor Ill Rectus capitis posticus major 107 minor.... ib. Rectus femoris 150 Recurrent nerve. Red particles .. Renal arteries plexus .. veins 348 167 217 Respiratory system 221 Rete mucosum 409 composition of ib. colour of ib. regeneration of ib. Retina 389 Retrahentes aurem 85 Rhomboideus brevis 112 longus 103 Ribs 10 Round bone 61 Rump bone 14 Sacral artery, middle 202 nerves 351 vein, lateral 218 ■ — middle ib. Sacro-lumbalis 132 Sacro-spinal arteries 202 Sacrun), os 14 Salivarv glands 239 use of 240 452 Saphena major minor Sartorius Scalenus Scaphoid bone , Scapula Scapular nerves Schneiderian membrane Sciatic nerve Sclerotic coat of the eye Scrotum cellular structure of. Semen, course of Semicircular canals Semilunar ganglion valves INDEX. Semimembranosus Semispinalis dorsi lumbornm Semitendinosus Sensitive laminae production oF , division of structure of — elastic structure of... • number of dimensions of organization of Sensitive system Septum lucidum nasi Serratus magnus Scrum Sesamoid bones Shoulder, bones of Shoulder-joint Shoulder, muscles of Shuttle bone ..., Sinuses of the dura mater of the head Skeleton Small metacarpal artery Sole, horny situation and connexion of figure of — arch of division of surfaces of 219 220 152 109 52 48 353 363 356 379 283 281 288 400 3G0 175 156 120 122 156 441 ib. ib. ib. ib. ib. 44'^ ib. 362 318 362 141 ju'oduction of.. Sole, sensitive .•.. structure of • connexion of.... thickness of. organization of.. arteries of veins of ... . nerves of Spermatic arteries chord nerves, vein ... Sphenoid bone Sphincter ani vagina? Sphaeno-palaline nerve, bpinalis colli Spinalis dorsi Spinal marrow coverings of. structure of . Spinal nerves Spiral artery nerve Splanchnic nerves Spleen —lymphatics of.. situation of .... Splenic artery plexus . Splenius Spur vein Squamous portion of temporal bone. Stapedius Stapes Sternal region Sterno-costalis Stefuo-maxillaris Sterno-thyro-hyoideus Sternum Stifle, arteries of Stifle bone Stomach lymphatics of situation of Stylo-hyoideus Stylo-maxillaris... Stylo-])haryngeus , Sublingual artery. sland . Submaxillary artery gland . vein.... Submental artery.... Suboccipital nerves. Subscapular artery. Subscapularis Subscapulo-hyoideus SufFraginis, os Superticialis costarum Superficial post, brachio-crural region post, femoro-crural region Stiperior cervico-occipital region ■ labial arteries maxillary nerve iupra-orbitar artery, nerve. Sympathetic nerve 357 119 325 326 ib. 345 184 353 359 262 270 247 197 360 220 104 215 23 398 397 116 ib. 108 109 12 2[»5 62 219 270 245 98 95 100 190 240 211 189 239 211 190 211 345 183 215 134 109 56 117 1J2 159 106 191 337 192 337 -361 Tabular enumeration of the l)ones 3 Tail, bones of... 15 muscles of 130 arteries of 201-202 nerves of 352 veins of 218 Tarsal cartilages 368 INDEX, 453 Tarsus, bones of 64 Tears, course of 375 Teeth 67 development 69 Temporal artery 191 bones 23 vein , 210 Tensor palati 102 tynipani , — vaginas femoris 150 Tentorium 312 Teres, major 135 minor ib Terms, anatomical 4 Testes cerebri 322 Testicles 284 coverings of ib. figure and magnitude of. 285 close coverings of 287 structure of ib. formation and descent of.... 288 period of descent of 290 female 306 Thalanii nervorum opticorum 320 Thigh, bones of 62 — : muscles of. 156 Thoracic aorta 196 arteries 183 ducts 267 lymphatics of 271-2 veins 215 Thorax, articulations of.... 71 bones of 10 general remarks on 13 muscles of. Ill Thyrb-arytenoideus 102 Thyroideal artery 188 veins 212 Thyroid cartilage 221 gland 226 Tibia 63 Tibial arteries 205 veins 219 Taenia semicircularis 320 Tongue 237 Trachea 223 muscles of 224 membrane of 225 Tracheal plexus 359 veins,. 212 Trachelo-mastoideus 106 Tractus optioi 324 Transversalis abdominis 126 costarum 117 Tranverse artery 186 Trapezium 54 Trapezius Ill Trapezoides : 53 Triangularis penis 129 Triceps extensor bracliii 137 Trifemoro rotuleus , 151 Trunk, bones of 4 joints of 69 muscles of 103 Tuber annulare ;i24 Tunica conjunctiva 369 Tusks Tympanum. U. Udders 307 volume of. 308 coverings of ib. Udders, structure of 308 Ulnar artery 184 nerve 354 veins 214 Ulnaris accessorius 143 Umbilical artery 200 243 Unciform bone . .. 53 277 296 bulb of. 297 273 Uterus .. 303 figure and volume of ib. ib. ligaments of structure of cavity of 304 305 ib. V. Vagina situation and connexion of. figure and volume of length and course of structure of membrane of Valvula Vieussenii Varicose vein Vastus externus — internus Veins table of Vena Azygos Vena cava anterior posterior Venaportas Ventricle (of the heart) right. —left.. Ventricles (of the brain) lateral • — contents of.. cervical dorsal lumbar peculiarities of. articulations of. Vertebral artery vein chain Vesical arteries Vesiculae seminalcs. ■formation of. -structure of.. Vestibule Viscera of the abdomen, situation of... 301 , ib. . ib. , ib. 302 , ib. 323 211 151 151 207 208 216 210 216 220 174 175 317 318 5 ib. 6 7 ib. 70 -195 212 5 200 291 ib. ib. 400 245 454 INDEX. Vitreous humour 392 Vomer 35 Vulva 299 Wall of the hoof 422 situation and relations of ib. Wall ofthe hoof, connexion of 4^3 figure of ib. division of ib. toe of ib. quartersof 424 ■ heels of ib. • superior border of ... ib. inferior border of 42G laminae of ib. VETERINAWV LECTURES. A FEW Copies of the Third Part of "A Series of Lectures on tlie Veterinary Art," by the Autlior of the present Work, remain on Sale, and may be iiad by appli- cation to Messrs. Longman and Co., Paternoster Row. Published monlhli/^ price \.i.6d. THE VETERINARIAN, A JOURNAL & REPOSITORY OF VETERINARY TRANSACTIONS lV SCIENCE; EDITED BY VV. PERCIVALL, M.R.C.S. & V.S. and Author of the "Anatomy of the Horse," AND VV. VOUATT, Lecturer on Veterinary Medicine and Surgery at the University of London, and Author of "The Horse" and "Cattle," published by the Society for the Diffusion of Useful Knowledge. Each Number contains a Leading Article, in which the most interesting veterinary topics of the day are impartially discussed; Original Communicationft on every branch of veterinary practice; Lectures on Veterinary subjects; a Review or Analysis of some veterinary work ; Extracts from all Foreign Veterinary Journals ; a record of the most interesting Sporting Transactions ; and, in fact, combining every subject that can interest the sportsman or the veterinary practitioner, and extending to every domesticated animal. Four volumes are already completed, and may be had of the publishers, Messrs. Longman, Rees, Orme, Brown, and Green, Paternoster Row; and of all other Book- sellers in the United Kingdom. PATENT HORSE SANDAL. The present invention consists in a novel sort of Horseshoe, so constructed as to be attached to the foot by straps (instead of nails), and to be put on and taken off in any situation by and at the pleasure of the rider himself, and within the short ^pace of a minute ; the intention of which is, to supply the place of a lost shoe in the hunting field : whereby thehimter will be enabled to proceed in his chace, while his horse is spared the sad injury likely to accrue from travelling barefoot. Its lightness (its weight being only one-half that of a common horseshoe) and its portability, will enable the hunter to carry it either in his pocket, or (inclosed in a little bag) under the flap of his saddle, without the slightest inconvenience. It will likewise be found useful for race-horses, during the time they are travelling from one race- course to another : whereby their feet will be saved so much nailing and unnailing ; and will be freed from all constraint while standing in the stable. It is also recommended to veterinarians for cases of diseased feet, or such as re- quire frequent removal of the shoes, liberty of foot, and exercise. The Sandal is sold by Messrs. Tate and Johnson, Saddlers, 92, Park-street, Grosvenor-Square; and by Messrs. Townes and Sons, Saddlers, 14L Cheapside, and No. 14, Princes-street, Hanover-square, London. Price 10s. 6d. (fl^f* It is not absolutely necessary for the horse to attend to have a Sandal fitted. The Saddler will be enabled to send a proper size by being furnished with one of the animal's old fore shoes; or even the outline of his hoof (without the shoe) taken upon paper, and sent in a letter. Coniplon 1' Ritchie, Pi inters, Middle Street, Cloth Fail , I-oiidon. i Webster Family Library of Veterinary Medicine Cummings School of Veterinary' Medicine at Tufts University 200 Westboro Road North Grafton, IVIA 01536 .^Si...