■ 1 ™****^*^***mmmm . ■^■■■■■^^^^■■■■■■■i HHHhhhp* m Digitized by the Internet Archive in 2007 with funding from Microsoft Corporation http://www.archive.org/details/comparativeanatoOOchauricl THE COMPARATIVE ANATOMY OP THE DOMESTICATED ANIMALS. THE COMPARATIVE ANATOMY OF THE DOMESTICATED ANIMALS. By A. CHAUVEAU, PROFESSOR AT THE LYONS VETERINARY SCHOOL. Seomfr (Micro, $jUoiaeo ano dfelaroA foiijr % do-operation of S. ARLOING, LATE PRINCIPAL OF ANATOMY AT THE LYONS VETERINARY SCHOOL; PROFESSOR AT THE TOULOUSE VETERINARY SCHOOL. TRANSLATED AND EDITED GEORGE FLEMING, F. R. G. 8., M A. L, VETERINARY SURGEON, ROYAL ENGINEERS, AUTHOR OF "TRAVELS ON HORSEBACK IN MANTCHU TARTARY," "HORSE-SHOES AND HORSE-SHOEING,' "ANIMAL PLAGUES," "PRACTICAL HORSE-SHOEING," "RABIES AND HYDROPHOBIA," ETC. WITH 4SO ILLUSTRATIONS. NEW YORK: D. APPLETON AND COMPANY, 549 & 551 BROADWAY. 1873. y\ :" 873 TO THE MEMORY OF JOHN LAW SON, M. K.C.V.S., OF MANCHESTER, WHO FIRST URGED THE DESIRABILITY OF UNDERTAKING THIS TASK, AND WHOSE SINCERE AND INESTIMABLE FRIENDSHIP AND ENCOURAGEMENT FOR MANY YEARS THE EDITOR AND TRANSLATOR HEREBY ACKNOWLEDGES WITH SORROWFUL AFFECTION AND GRATITUDE. . . 'to PEEFACE BY THE TRANSLATOR AND EDITOR. In undertaking the arduous task of translating and editing the ' Traite olyhedral elements of an irregular outline, containing a great number of mclei. Rare in the yellow marrow, they are more particularly found .dhering to the walls of the medullary canal, or the alveoli of the spongy issue. Blood-vessels. — The arteries of bones belong to three orders ; a distinction ounded on their volume and the extent of their distribution. The arteries of the first order penetrate to the interior of the medullary anal of long bones by a particular orifice, the nutritious foramen. They oon divide into two branches, which break up into a network that lines the palls of the canal and enters the tissue of the medulla. This network ommunicates with the arteries of the second order, which are destined to he spongy tissue of the extremities of the long bones, penetrating them by he numerous nutritious foramina that surround the epiphyses. Lastly, the ■rteries of the third order are branches of the periostic network which enter he superficial Haversian canals. These canals which open in this manner n the surface of the bones may be considered, strictly speaking, as a third ategory of nutritious conduits. In the flat and short bonejs there are no .rteries of the first order. Veins accompany the arteries, and are always more voluminous than hese ; they frequently make their exit by special and very large openings those points where the spongy tissue is abundant. The veins of ►ones sometimes exhibit saccular dilatations on their course. Certain veins the cranial bones have their parietes entirely composed of osseous tissue. Lymphatic vessels. — The existence of these in the interior of bones annot be affirmed. Nerves. — These belong to the cerebro-spinal and ganglionic system of lerves ; the latter are always vaso-motory nerves. Almost constantly a somewhat voluminous nerve enters the medullary anal by passing through the nutritious foramen, and is distributed to the oedulla. The compact tissue receives few nervous filaments; while, on he contrary, the spongy tissue at the extremities of the long bones, as well & the short bones, obtains an abundant supply. Certain short bones, such s the vertebras, are especially remarkable for the numerous nerves they eceive. 16 GENERAL PRINCIPLES APPLICABLE TO DEVELOPMENT OF BONES. Bones, before arriving at the state in which they present themselves in the adult animal, pass through several successive phases, whose study consti- tutes what is termed osteogeny. In the embryo, at a very early period, the bones are composed of a mucous material analogous to that which enters into the composition of all the other organs ; this matter is constituted by a mass of what are called embryonic cells. At a later period they are impregnated with gelatine, and nearly all become harder, white, and elastic, passing into the cartilaginous state. Exception must be made, however, to the lateral and anterior parietes of the cranium and the face, the bones of which are at first fibrous but never cartilaginous. The cartilaginous bones show a fundamental amorphous substance, in which are disseminated spherical cells containing one or more nuclei. This condition is transitory ; the cartilaginous tissue soon submits to modifications which result in conferring on the pieces that it composes the hardness and structure of perfect osseous tissue. These modifications constitute the process of ossification. There are several portions of the skeleton which do not undergo this osseous transformation, and which most frequently remain in the cartilaginous condition during the entire life of the animal. These permanent cartilages are met with at those points where the bony skeleton must preserve a certain degree of flexibility, and on the articular surfaces. During the process of ossification, the cartilages become vascular, are impregnated with calcareous salts, and excavated with Haversian canaliculi and medullary cavities, The saline molecules are deposited in the amorphous substance, which grows more hard and opaque ; at the same time the cartilaginous cells become the point of departure of a new embryonic proliferation, from which results the neoplasts. Ossification begins at the same time in several parts of the skeleton, and in each of the bones in particular ; though it does not appear over the whole extent of the latter at once ; on the contrary, in certain determinate points of the cartilaginous mass, bony tissue can be perceived developing itself and extending gradually until it finishes by completely invading it. These points'are called centres of ossification. These centres are primary or complementary ; the latter are in some way added to the bone, and form, wholly or in part, certain processes. Although these centres of ossification enlarge from day to day, yet for a somewhat long period they remain completely independent of one another, and are only connected by cartilaginous tissue. The term epiphyses is given to the osseous centres which are placed at the extremities of the principal centre. When the skeleton is completely developed, the various centres of ossification are fused into each other, and then there are no longer epiphyses ; this fusion always takes place at an almost determinate epoch. It has been remarked that, of two epiphyses, it is con- stantly the one near which the nutritious foramen is directed that is first united to the body of the bone. Growth. — Bones grow in width and thickness by the apposition of new elements. In the long bones, the growth in length takes place by the ossification of the cartilage uniting the epiphyses to the body of the bone. Consequently, elongation should cease as soon as the epiphyses are incor- porated with the diaphysis. With regard to the long bones of the limbs, Duhamel, Flourens, and particularly MM. Oilier and Humphry, have remarked that, in the thoracic limb, the extremity furthest removed from THE STUDY OF THE BONES. 17 jthe humero-radial articulation grows fastest ; while in the abdominal limb, the extremity most distant from the femoro- tibial articulation grows the least. Concerning the growth of the bones in thickness, this occurs by the ossifi- cation of the deep layer of the periosteum called the osteogenetic layer. The sxperiments of the above-named authors have irrefutably demonstrated this ifact. The formation of bony tissue in the deep layer of the periosteum is very lactive during the youth of animals ; but it soon slackens, and in advanced age ceases completely. In the first period of life, in proportion as the new (layers are added to the surface of the bone, the old layers, those nearest the medullary canal, disappear by resorption. Later, the process of resorption exceeds that of formation, which is, in old age, completely annihilated. It has also been observed that the formation of a certain quantity of the osseous elements takes place on the inner face of the medullary canal, at the expense of the medullary tissue. In the flat bones, the primitive centre of ossification is developed nearly in the middle, and the calcareous salts are afterwards deposited in radiating lines from this spot towards the periphery. These bones are augmented in thickness by the formation of subperiostic layers, and by the development of the spongy tissue between their two compact laminaB ; they increase in width by the ossification of what are termed the marginal epiphyses. The short bones grow from the periosteum and the epiphysery cartilages, when they possess complementary centres. Nutrition. — The experiments which consisted in feeding young animals with madder, and afterwards examining their osseous system, have for a long period demonstrated the nutrition of bones. When bones cease to grow, their nutri- tion becomes less active ; but it is evident that it does go on, in order to maintain the organic matter of the osseous tissue in a proper con- I dition. (Professor Owen has explicitly and concisely stated the development of bone to occur as fol- lows : — "The primitive basis, or 'blastema* of I bone is a transparent glairy matter containing ^numerous minute corpuscles. It progressively acquires increased firmness ; sometimes assuming a membranous or ligamentous state, usually a gristly consistence, before its conversion into bone. The change into cartilage is noted by the appearance of minute nucleated cells, which I increase in number and size, and are aggregated I in rows, with intercellular tracts, where the ossification is about to begin, as in fig. 9. | These rows, in the cartilaginous basis of long bones, are vertical to its ends ; in that of flat bones they are vertical to the margin. The 1 cells furthest from the seat of ossification are [flattened and in close contact ; nearest that seat they become enlarged and separated. The first appearance of bone is that of minute granules in the inter- columnar and intercellular tissue. Canals are next formed in the bone by CARTILAGE AT THE SEAT OP ossification, showing at its lower portions the clusters of cells arranged in columns, each of which is inclosed in a sheath of calcified intercellular substance. 18 THE BONES absorption, which ultimately receive bloodvessels, and become the ' vascular canals.' The immediate nutrition of bone is provided for by the production of minute ' plasmatic canals ' from the vascular ones. When these canals become dilated, so as to offer definite forms, they are termed ' lacunae ' or * bone-cells,' and to some extent characterise, by their shape and size, the osseous tissue of the respective vertebrate classes. In the concentric laminae surrounding the vascular canal, the bone-cells or osteoplasts are arranged concentrically, between the laminae, with the long axis in the direction of the circular line of the plate. Most of the plasmatic tubes con- tinued from the bone-cells pierce the plates at right angles in their course to the vascular canal, with which they communicate ; and they form the essential vehicle of the material for future growth. Extension of parts, however, is not the sole process which takes place in the growth of bone ; to adapt it to its destined offices, changes are wrought in it by the removal of parts previously formed. In marine creatures, the bones usually remain solid ; but in the active land quadrupeds, the shaft of the long bones is hollow, the first-formed osseous substance being absorbed, as new bone is being deposited without. The strength and lightness of the limb-bones are thus increased after the well-known principle of the hollow column. The bones of birds present this quality in the highest degree, particularly those of powerful flight. In these the medullary cavity of beasts is transformed into a capacious cavity containing rarified air instead of marrow. In the mam- malian class, the air-cells of bone are confined to the head, and are filled from the cavities of the nose or ear, not from the lungs, as in birds. Such cells are called ' frontal sinuses,' ' antrum,' * sphenoidal,' and ' ethmoidal.' The frontal sinuses extend backward over the top of the skull in the rumi- nant and some other quadrupeds, and penetrate the cores of the horns in oxen, sheep, and certain antelopes. The most remarkable development of cranial air-cells is presented by the elephant, the intellectual physiognomy of this large quadruped being caused, as in the owl, not by the actual capacity of the brain-case, but by the vast extent of the pneumatic cellular structure between the outer and inner plates of the skull-wall. All these varied changes in the osseous tissue, from mere cancelli to large medullary or pneumatic cavities, are the result of secondary changes by absorption, and not of the primitive constitution of bones, which were at first solid.") CHAPTER II. THE BONES OF MAMMALIA IN PARTICULAR. Article I. — Vertebral Column. The vertebral column, or spine, is a solid and flexible stalk situated in the middle and upper part of the trunk, of which it forms the essential portion. It protects the spinal cord and sustains the thorax, as well as the principal organs of the circulation, respiration, and digestion. Articulated anteriorly with the head, and terminating in a point at its posterior extremity, this piece is formed by a somewhat considerable assemblage of short, single, tuberous bones, to which has been given the name of vertebrae. These THE VERTEBRAL COLUMN. 19 bones, though all constructed on an uniform type, yet do not offer the same configuration throughout the whole rachidean stalk. The differences they present into this respect, have allowed of their being formed into five prin- cipal groups ; whence the division of the vertebral column in five regions, which are, enumerating them from before to behind: 1, Cervical region; 2, Dorsal region ; 3, Lumbar region ; 4, Sacral region ; 5, Coccygeal region. The first comprises seven vertebrae, which serve as a base for the animal's neck : the second has eighteen, against which the ribs are placed ; the third has only six, which correspond to the loins ; in the fourth there are five, constantly solidified into one mass in the adult, to constitute a single bone — the sacrum ; while the fifth possesses a variable number of small degenerate vertebras, gradually decreasing in size to form the tail. The pieces consti- tuting the first three regions are called true vertebrae ; those of the last two are designated false vertebrae. The characters belonging to all these verteDrae will be first studied ; then a particular description of the vertebras of each region will be given ; and, finally, an examination will be made of the spine as a whole. CHARACTERS COMMON TO ALL THE VERTEBRiB. Each of these small bones is pierced from before to behind by a wide Fig. 10. i B nt jZ«EOJ§j|||oH»/)l F ELEMENTS OF A VERTEBRA: AFTER OWEN. A, Ideal typical vertebra ; b, Actual thoracic vertebra of a bird ; c, Centrum (or body), giving off, d, d, the diapophyses, and p, p, the parapophyses (transverse and articular processes); the neural arch, inclosing the spinal cord, is formed by n, n, the neurapophyses (lamina), and n, s, the neural spine (spinous process)} the haemal arch, inclosing the great centres of the circulation, is formed by h, hy the haemapophyses (costal cartilages) , and h, s, the haemal spine (sternum). From both the neurapophyses and haemapophyses maybe given off the zygapophyses, z, z. The lateral arches, which may inclose the vertebral arteries, o, o, are completed by the pleurapophyses (ribs), pi. ; these in B are bent downwards, so as to form part of the hasmal arch, and give off the diverging appendages, a, a. opening, the spinal foramen ; whence results, for the entire spine, a long canal traversing its whole length, and which lodges a very important 20 THE BONES. portion of the nervous centres — the spinal marrow. This canal, which traverses the vertebra from one end to the other, transforms it into a veritable ring in which we recognise, for facility of description, two parts — the one inferior, the other superior. The first, or body, is very thick, and forms the base of the vertebra ; the second, which is thin, has been de- signated spinous or spinal, from one of the peculiarities it presents, or annular, because it circumscribes the major portion of the spinal foramen. This division is not altogether an arbitrary one, for the body and the annular por- tion constitute, in the foetus, two distinct pieces, which do not become united for a long time after birth. Body. — The shape of the body of a vertebra is that of a prism with four faces, of which two only — the superior and inferior — are free, and can be studied in the adult ; the two lateral faces being united and confounded with the annular portion. This prism also presents two extremities — an anterior and posterior. Faces. — The superior face, limited in extent, forms part of the spinal foramen, constituting its floor. It exhibits: 1, On the median line, two roughened, prominent surfaces, representing two triangles, whose summits are opposed ; 2, On the sides, two depressed smooth surfaces, perforated by one or more openings that lead to the interior of the bone. The inferior face is divided into two lateral portions by a median crest. Extremities. — The anterior has a prominent convex head, more or less detached. The posterior offers a cavity for the reception of the head of the next vertebra. These two planes, the one convex, the other concave, do not come into immediate contact ; an elastic, flexible fibro-cartilage, firmly attached to each, being interposed between them. Annular Portion. — This is formed by an osseous plate that curves sud- denly downwards, in the shape of an arch, the two extremities of which approach each other, inclose the body, and become united to it. It offers for study : 1, An internal and an external surface ; 2, An anterior and a posterior border. Surfaces. — The internal surface, concave and smooth, forms, with the superior face of the body, the spinal foramen. The external, convex and irregular, presents : 1, A single prominence, raised in the middle of the superior portion, and named the spinous process ; 2, The transverse processes are a double pair of eminences, one on each side, and projected transversely outwards. Borders. — The anterior border has two articular facets looking upwards : these are the anterior articular processes, right and left. In each is a notch which, when placed in opposition to a similar excavation in the preceding vertebra, forms the intervertebral foramen. The posterior border presents the same peculiarities, with this difference, that the articular faces of the pos- terior articular processes are inclined downwards, to correspond with the anterior facets of the succeeding vertebra. Structure of the vertebral. — The compact substance, which is abundant in the spinous portion, forms, in the body, an extremely thin layer, inclosing a voluminous nucleus of spongy tissue. The latter is traversed by numerous venous canals, which open on the surface of the bone. Development. — It has been already shown that the body and spinous portion of a vertebra constitute, in young animals, two distinct pieces. Each was primarily formed from two lateral centres, which met on the median line. In the body, the fusion of these centres is so prompt, that it is generally believed, perhaps justly, that the development of this part of the vertebra THE VEBTEBRAL COLUMN. 21 proceeds from a single centre of ossification. The nnion of the two centres in the annular portion, usually designated the vertebral lamince, is slower. It commences in the most anterior vertebras, and is latest in the sacral and coccygeal regions. To the two principal pieces of the vertebra in process of ossification, is added, at a subsequent period, complementary points of ossifi- cation, five or six in number : one or two for the spinous process, one for the summit of each transverse process, another for the head, and the last for the posterior cavity of the body. CHARACTERS PROPER TO THE VERTEBRAE OF EACH REGION. A casual inspection of a vertebra might suffice, strictly speaking, to dis- tinguish the region of the spine to which it belonged. For instance, a cervical vertebra is recognised by its volume, the absence of a spinous process, and the foramen which traverses the base of its transverse processes. The dorsal vertebra is conspicuous by its tubercular transverse processes, and by being furnished, outwardly, with an articular surface, as well as by the depression on its body destined to receive the heads of the ribs. The lumbar vertebra has its long flattened transverse processes; while the coccygeal vertebra offers rudimentary laminae and processes. There is no necessity for noticing the sacrum, whose five pieces form one bone : a feature which markedly distinguishes it from the other regions of the vertebral column. But these few distinctive characteristics do not satisfy the require- ments of descriptive anatomy ; so that it is necessary to undertake a more extensive study of each of these regions. 1. Cervical Vertebral. General Characters. — These vertebrae, the longest and thickest in the spine, present generally a cubic form. They are usually distinguished from the vertebrae of the other regions by the following characters : — The inferior spine of the body is strongly marked, especially behind, where it terminates in a small tubercle. The head is well detached from the re- mainder of the bone, and describes a very short curve. The posterior cavity, wide and deep, represents a veritable cotyloid depression, which is too large to fit the head exactly ; the intermediate fibro-cartilage on these two surfaces is also of a great thickness. The spinous process forms a simple roughened, and but slightly prominent, ridge. The transverse processes, very developed, are elongated in an antero-posterior direction, and inclined down- wards. In this region they are designated the trachelian processes, because of their relations with the trachea; a foramen that traverses them from before to behind at their base has been, for the same reason, named the trachelian foramen {vertebral foramen). The articular processes, large and prominent, are inclined downwards and inwards. The notches are wide and deep. Specific Characters. — The seven cervical vertebrae are reckoned from before to behind, and receive numerical names indicating their place in the region. First. — The first vertebra of the neck, which has been named the atlas,1 deserves a very careful description. At first sight there is recognised the 1 So named from the mythological personage who was supposed to support the earth, as the first vertebra (human) supports the head. (For this bone in the domesticated animals the name is not appropriate.) 5 22 THE BONES. Fig. 11. great development of its transversal diameter, the considerable dimensions of the spinal foramen, and the thinness of its body. The intra-rachidian face of the latter is divided into two portions by a transverse ridge : one anterior, furnished with ligamentous imprints, exhibits, laterally, two deep excavations, which lodge the venous sinuses ; the other, posterior, is smooth and concave from side to side, and forms an articular surface into which is received the odontoid process of the axis; this surface resembles the cotyloid cavity. The inferior spine of the body appears as a large tubercle. The head is absent, and is replaced by two concave facets. The anterior articular processes have their gliding surfaces looking downwards; they are joined to the two preceding facets to constitute two large diarthrodial cavities, which correspond to the occipital condyles. There is no spinous process, but a rough- ened surface instead. The transverse pro- cesses are large, flattened above and below, incline forwards and downwards, and are provided with a thick rugged lip. Pos- 1, Articular processes for condyles of teriorly, quite at their base, and on each side the occipital bone ; 2, ibidem ; 3, of the spinal foramen, they show two large vertical facets which represent the posterior articular processes ; these facets are uneven, are confounded with the articular cavity of the upper face of the body, and correspond to the two analogous facets of the axis. Each transverse process is pierced at its base by two foramina, which traverse it from below upwards. The posterior repre- sents the vertebral foramen of the other ver- tebras ; while the anterior is continued to the external surface of the process by a wide, deep, but very short channel, running from without to within, and joins a third fora- men, which enters the spinal canal. These last two openings, with the demi-canal which unites them, replace the anterior notch; the posterior is altogether absent. 1, Superior spinous process ; 2, An- Lastly an inflected venous canal, whose fZv 2SE ESSSl 3,'PA°r Position varies, and whose presence is not tenor articular processes: 5, An- * > • . r ■ constant, crosses the lammee of the atlas, and opens, on one side, into the spinal canal, and on the other, beneath the trans- verse process. The atlas contains much compact tissue, and is generally developed from six centres of ossification : two for the body, which at an early period becomes a solid piece, and two for the annular part ; the other two are complementary centres, each of which forms one of the two posterior undulated facets, and the lip of the corresponding transverse process. Second. — This is named the axis (or dentata). It is the longest of all the cervical vertebras ; those which succeed it gradually diminish in length and augment in thickness. The body of the axis has not any head anteriorly, ATLAS: INFERIOR SURFACE. Vertebral or antero-internal fora- men ; 4, Posterior, or cervical fora- men; 5, Transverse process; 6, Tubercle representing the inferior spinous process; 7, Superior arch, forming the roof of the spinal fora- men. A CERVICAL VERTEBRA. terior convex face of body , 6, 7, Transverse processes, with their tubercles or rudimentary ribs; 8, Inferior crest, or spine ; 9, Concave posterior face. THE VERTEBRAL COLUMN. 23 but a conical process termed the odontoid, which is flattened above and below, concave and rough from one side to the other on its superior face ; convex in the same direction, and perfectly smooth on its inferior face. The latter represents an articular half-hinge, p. 13 around which glides the concave arti- cular surface on the superior face of the body of the atlas. The anterior articular processes are carried to the base and to each side of the odon- toidian pivot, in the shape of two un- dulated facets, which are confounded with the gliding surface of the latter, whose destination has been already noted. The spinous process, very powerful and elongated antero-pos- teriorly, is divided behind into two THE AXIS> 0R DENTATA. LATEral view. roughened lips. The transverse pro- 1? Superior spinous process ; 2, Odontoid pro- cesses are slightly developed, and ter- cess ; 3, Intervertebral foramen, or hole of minate posteriorly in a single tubercle, conjugation; 4, Body; 5, Inferior spinous directed backwards. The anterior process ; 6, 7, Inferior and superior articu- . . -l -i lating processes, notches are very deep, and are most r frequently converted into foramina. This vertebra, although voluminous, is light, in consequence of its containing much spongy substance. In the young animal, the odontoid process and the articular surfaces on each side, constitute two centres, distinct from each other and from the body of the vertebra. After the axis, the cervical vertebrae diminish in length and increase in thickness ; while the obliquity of their articular processes becomes the more pronounced the more distant they are from that vertebra. Third, fourth, and fifth. — Each of these has, at its transverse processes, two prolongations, one anterior, the other posterior. The inferior face of their bodies exhibits a median spine terminated posteriorly by a tubercle, which gradually increases in volume from the third to the fifth vertebra. The third presents, between its anterior and posterior articular processes an almost complete gap ; if its anterior extremity be placed on a horizontal plane, it will touch that plane by its articular and transverse processes and its head. In the fourth, the articular processes are united by a thin, sharp osseous plate, notched only in front. Laid on a horizontal plane, the head remains some distance from it. The fifth is known by the continuous, thick, and rugged lamina which unites the articular processes, and by the tubercle of the inferior spine on the body, which is in shape like the heart on a playing-card. Sixth. — This is distinguished by the slight prominence of the spinous process, but particularly by the almost total disappearance of the inferior spine, and the presence of a third prolongation, very strong and inclining downwards at its transverse process, a circumstance to which this vertebra owes its designation of tricuspid. Seventh. — This has received the name of prominens, because its spinous process, terminating in a point, is more distinct than in the preceding vertebrae, the axis excepted. It exhibits, besides: deep imprints, which replace the inferior spine, a concave demi-facet on each side of the posterior cavity for the articulation of the head of the first rib ; a particular disposition of its transverse processes, which are unituberculous ; the complete absence of the vertebral foramen; and, lastly, the depth and width of its notches. 24 THE BONES. The spinal foramen, which, has already assumed a somewhat considerable diameter in the sixth cervical vertebra, is still larger in the seventh.1 2. — Dorsal Vertebral. General Characters. — In the dorsal vertebrae the body is very short, and in front has a large slightly projecting head ; behind, it has a shallow cavity. Laterally, these vertebrae present, at the base of the transverse processes, four concave articular facets, the two anterior of which are situated near the head, while the posterior two are hollowed out of the border of the articular cavity of the body. Each of these facets is joined to Fig. 14. an analogous facet on the neighbouring ver- tebra to form a small excavation, into which is received the head of the corresponding rib. The spinous process is very high, is compressed on both sides, inclines backwards, and its summit is terminated by a tubercle. The transverse processes are unitubercular, and directed obliquely outwards and up- wards ; on their external aspect they have a diarthrodial plane facet which corresponds to the tuberosity of the rib. The articular processes are narrow, and constitute simple unrelieved facets cut on the base of the spinous process. The posterior notches are deep, and sometimes converted into foramina. Specific Characters. — None of the eighteen dorsal vertebrae differ much from the type just described ; and it is difficult to establish special characters for each. It is, nevertheless, possible to assign to a dorsal vertebra, approximately, the rank it should occupy, in accepting the following facts as a guide : — 1. The vertical diameter of the vertebral bodies augments progres- sively from before to behind. Their lateral diameter, which determines that of the spinal canal, becomes, on the contrary, less from the first to the tenth vertebra ; after which it assumes increasing proportions to the last one. The articular surfaces, which serve for the mutual contact of head and cavity, become larger and shallower in proportion as the vertebrae are more posterior. The inferior spine on the body is very salient and tuberculous in the two first vertebrae, very acute in the third and fourth ; it disappears in the sixth and ninth, to re-appear and become more marked from the tenth to the last. 2. The intervertebral cavities, intended for the reception of the heads of the ribs, diminish in depth and extent from the first to the last. 3. The longest spinous process belongs to the third, fourth, aud fifth vertebrae ; those which follow gradually decrease to the eighteenth. Their width diminishes from the second to the eighth ; it afterwards increases in a progressive manner in the succeeding vertebrae ; TVPE OF A DORSAL VERTEBRA; THE FOURTH. 1, Body ; 2, 2, Articular facets for the head of rib ; 3, Articular facet for tuberosity of the rib ; 4, Articular processes ; 5, Spinal foramen ; 6, Tuberous base of spinous process ; 7, Posterior articular face of body ; 8, 8, Transverse processes ; 9, Superior spinous process; 10, An- terior articulation of body. 1 M. Goubaux has sometimes met with asymmetrical cervical vertebrae ; certain vertebrae, tricuspid on one side, are only bicuspid or unicuspid on the opposite side. THE VERTEBRAL COLUMN. 25 from the second to the tenth vertebra, the summit of the spinous process is large and tuberculous; in the last seven it is flattened laterally. Their obliquity is less marked as they proceed backwards ; in the sixteenth and seventeenth vertebrae, the spinous process is nearly vertical; it inclines slightly forward in the eighteenth. Those of the tenth, eleventh, and twelfth vertebras are slightly curved like an S. 4. The articular processes, from the first to the tenth vertebra, gradually contract and approach the median line ; in the succeeding vertebras they, on the contrary, increase, and become concave and wider apart from those of the opposite side. 5. The volume of the transverse processes and the size of their diarthrodial facets diminish from before to behind. In the three first vertebras this facet is concave ; in the first nine the articular facet looks outwards and backwards, while the facet on the body looks forwards ; in the last the two facets are directed forwards. These two facets are generally confounded in the seventeenth and eighteenth vertebrae. The first dorsal vertebra much resembles the prominens; it is distinguished from it, however, by the presence of four diarthrodial facets on its extremities. It also differs from the other vertebras by the shortness of its spinous process, which terminates in a point ; by the size and prominence of its articular processes ; and by the depth of its notches. The last vertebra never has facets on the contour of its posterior cavity.1 3. Lumbar Vertebra?,. General Characters. — A little longer and wider than the dorsal vertebras, which they resemble in the arrangement of their bodies, these vertebras are characterised : 1, By their short, thin, and wide spinous processes, which are slightly inclined forwards, and are provided at their summits with a scabrous tubercle ; 2, By their largely developed transverse processes, flattened above and below, and directed horizontally outwards;2 3, By the salient anterior articular processes, hollowed out on each side, and provided externally with a tubercle for insertion ; 4, By their equally prominent posterior articular processes, rounded in the form of a half-hinge. Specific Characters. — The characteristics which may serve to distinguish these vertebras from one another are derived from the body, and the spinous and tranverse processes. 1. From the first to the last there is a progressive diminution in the vertical diameter of the bodies, and an increase in their transverse diameter. The inferior spine on the body becomes shorter and wider from the first to the last vertebra ; in the six vertebras it resembles an elongated triangle whose summit is directed forwards. 2. The spinous processes decrease in width from before to behind, and their anterior border becomes more and more concave ; their summits are thickened and tuberculous in the three first, and thin and sloping forward in the three last. 3. The transverse processes are longer in the middle vertebrae than in those placed before and behind. The processes in the first and 1 In well-formed horses, it is not uncommon to find nineteen dorsal vertebrae, with an equal number of ribs; though in these instances there are most frequently only five lumbar vertebrae. Husson and Goubaux have sometimes met with nineteen, and the normal number in the other regions. Sometimes there are only seventeen dorsal vertebrae. 2 It has been correctly stated that these processes are the representatives of rudi- mentary ribs which have become united to the vertebra. Therefore it is that they are frequently designated costiform processes. ;'6 THE BONES. second vertebra incline slightly backward ; in the third they are more up- right ; and in the succeeding ones are directed a little forward. In the last two they are remarkable for their thickness ; in the fifth an oval-shaped articular facet is observed on their posterior border; in the sixth, two are present — one in front, correspond- ing to the preceding, and one behind, slightly concave, meeting a similar facet on the sacrum. The fourth and fifth vertebrae very often correspond, at their transverse processes, by means of analogous facets.1 In the Ass, and sometimes in the Mule, only five lumbar vertebrae are found. According to M. Sanson, this is the natural number in the Arab Horse.2 4. Sacrum. The sacrum results, as already stated, from the consolidation of five vertebrae. This single bone articulates, in front, with the last lumbar vertebra ; behind, with the first coccygeal bone, and on the sides with the ossa innominata. It is triangular, flattened above and below, and from before to behind describes a slight curve up- wards. It offers for study a superior and an inferior face, two borders, a base, a summit, and a central canal, the exten sion of the spinal canal. Faces. — The superior face presents, on its middle, the spi- nous processes of the sacral vertebrae, which together con- stitute what is called the sacral or super sacral spine. These lumbar vertebra; front view. processes are united at their 1, Body; 2 Its articular face -3 Superior spinous bage j d {n isolated process, 4, Spinai foramen ; 5, Anterior articular _ ., J> . - „ .. . processes; 6, 6, Transverse, or costiform pro- for the remainder of their ex- cesses; 7, Posterior articular process. tent ; they all incline backwards 1 We possess the skeleton of a horse which has seven lumbar vertebrae, with the normal complement in the other regions. The seventh is no doubt the first sacral, as it has all its characters. The fifth sacral vertebra is evidently derived from the coccygeal region. 2 (This statement is scarcely correct. M. Sanson has established the fact that there is in reality no Arab horse ; and asserts that the specific type with five lumbar vertebra4, is very probably of African origin, and that these vertebrae, independently of their number, offer individual characteristics different from those observed in the vertebra) of the type which has six.) UPPER SURFACE OF LUMBAR VERTEBRAE. 1, Summit of spinous process, 2, 2, Anterior articular processes; 3, 3, Posterior articu- lar processes ; 4, 4, Transverse processes. . Fig. 16. THE VERTEBRAL COLUMN. 27 Fig. 17. and terminate, with the exception of the first, by a tuberous summit, which is often bifid ; their length diminishes from the second to the fifth bone. On each side of the sacral spine exists a groove, at the bottom of which are four openings — the super sacral foramina. These orifices open into the spinal canal, and communicate with four analogous, but wider aper- tures, pierced at the inferior face of the bone, and for this reason named the subsacral fo- ramina. The inferior face is smooth, and shows traces of the primitive separation of the ver- tebral bodies ; the subsacral fo- ramina, which represent, with the corresponding supersacral openings, the intervertebral fo- ramina of the other regions of the spine, are observed on this surface. Borders. — The two borders, thick and concave, form, posteriorly, a rugged lip ; in front, they present an irregular surface inclining obliquely from above to below, from within outwards, and from before to behind. This surface, which is intended for the articulation of the sacrum with the ossa innominata, is divided into two parts : one, the inferior, named in man the auricular facet, is slightly undulated and diarthrodial ; the other, the superior, serves for ligamentous insertions. Base. — This offers : 1, On the median line, the anterior orifice of the sacral canal, and the anterior articular surface of the body of the first sacral vertebra, which is oval and slightly convex ; 2, On the borders, the articular processes and anterior notches of this vertebra, as well as the elliptical and somewhat convex facets which bring it into contact with the transverse processes of the last lumbar vertebra. Summit. — The summit, thrown back, presents : 1, The posterior orifice of the sacral canal ; 2, The posterior articular surface of the body of the last sacral vertebra ; 3, The vestiges of the articular processes and posterior notches of that vertebra. Sacral canal. — This is the portion of the spinal canal which is channeled out of the sacrum ; it is triangular, and diminishes in width from before to behind. LATERAL VIEW OF SACRUM. 1, Articular surface of body : 2, 3, Articular surfaces corresponding to those on the transvei*se processes of last lumbar vertebra; 4, Spinal foramen; 5, Auricular facet ; 6, Anterior articular processes ; 7, Inferior or subsacral foramina; 8, Superior spinous processes ; 9, Summit or coccygeal ex- tremity. 5. Coccygeal Vertcbrce. The coccygeal region, or coccyx, comprises from fifteen to eighteen de- generate vertebrae, which gradually diminish from the first to the last. In the first three or four, nearly all the characteristics of true vertebrae are found; they show a spinal foramen, a body, a spinous process, and transverse processes, looking backwards ; the articular processes only are altogether absent. In the succeeding vertebras, these characters become effaced ; the vertebral laminae do not join completely, and the spinal canal is only a simple groove, which, gradually decreasing in depth, at last 28 THE BONES. entirely disappears. The insertion eminences also become less salient, and the coccygeal vertebrae are soon reduced to small bony cylinders, narrow in the middle and wider at both extremities, with a convex articular surface at each end (except the last, which has only one articular surface). These small cylinders, the last traces of the vertebral bodies, are each developed from three centres of ossification ; they are very spongy and light. The first coccygeal vertebra is frequently consolidated with the sacrum in aged animals. THE SPINE IN GENERAL. The vertebral column has now to be considered in its entirety, and examined successively in its superior face, its inferior face, its lateral faces, and its spinal canal. Afterwards its direction and mobility will be noticed. Superior face. — This presents, on its median line, the series of spinous processes. But little salient in the cervical region, these eminences are much developed in the dorsal and lumbar, where they constitute a long crest, the dorso-lumbar spine, as well as in the sacrum, where they form the sacral spine. They soon disappear in the coccygeal vertebraB. Outwards, and on each side of these processes, is seen a succession of tubercles of insertion, represented in the cervical and lumbar vertebrae by articular processes, and in the dorsal vertebrae by the superior or rugose portion of the transverse processes. These tubercles are disposed in line, and separated from the spinous processes by a channel designated the vertebral groove, which is more or less deep and wide. It is on these, and on the spinous processes, that the extensor muscular fasciculi of the spine receive the greater portion of their fixed or moveable insertions. Inferior surface. — Wide at the neck, this face becomes narrow in the dorsal region, to be again widened at the lumbo-sacral region, and once more contracted at the coccyx. Crests more or less developed, which divide the vertebral bodies into two lateral portions, right and left, are remarked. Lateral surfaces. — These offer for study the thirty-six intervertebral foramina, through which the spinal nerves pass. They exhibit besides, on the neck, the transverse processes; in the back, the external facets of these processes, and the intervertebral facets, all destined to sustain the heads of the ribs ; on the loins, the transverse or costiform processes. It may be remarked that the ribs and the transverse processes of the neck and loins furnish points of insertion to the powerful muscles which produce the lateral movements of the spine. In the sacrum, the lateral faces are formed for the articulation of the spine with the ossa innominata. Spinal canal. — This canal communicates, in front, with the cranial cavity. Very wide in the atlas, for the reception of the odontoid process and to permit the rotatory movements of the head without injury to the spinal cord, this canal suddenly diminishes in the axis. It again dilates at the termination of the cervical region and the commencement of the dorsal ; there the spinal cord presents a greater volume, and the movements of the spine are very extensive. Towards the middle of the back, the spinal canal offers its smallest diameter ; it widens from this part to the lumbo-sacral articula- tion ; after which it contracts rapidly, and disappears altogether near the fourth or fifth coccygeal vertebra. The lumbo-sacral dilatation coincides with the enlargement of the cord in this region, and with the enormous quantity of nerves lying beside it. THE VERTEBRAL COLUMN. 29 Direction of the vertebral column. — The spine does not extend in a straight line from the head to the posterior extremity of the body. If it is followed from the caudal termination, which is free and looks downwards, to the anterior extremity, it will be seen that it rises upwards and forwards, forming a convex inflexion corresponding to the roof of the pelvis. In the lumbar and the posterior half of the dorsal region it is nearly horizontal and rectilinear; from thence it descends to the cervical region, when it a^ain rises and forms two curves, the one posterior, bending upwards, the other anterior, turned down. This disposition of the cervical spine gives it the shape of a console. Mobility of the vertebral column. — In the cervical region, the almost total absence of spinous processes, the great development of the articular processes, and the very short curve described by the surfaces of contact of the vertebral bodies, allows the spine very extensive and very diverse movements. In the dorsal region, however, these movements are very limited, the spinous processes and the costal arches preventing the play of the vertebrte on each other. In the lumbar region, the spine can be flexed or extended more than in the dorsal ; but its lateral movements are quite as restricted, owing to the presence of the transverse processes and the reciprocal joining or dovetailing of the articular processes. Lateral motion is even rendered impossible in the posterior half of this region, from the manner in which the transverse processes are adapted to each other. It may be remarked, however, that this disposition singularly favours the integral transmission of the propulsive efforts thrown upon the trunk by the posterior extremities. The sacral vertebrae, having to afford the ossa innominafca a solid fixed point, could not preserve their independence and mobility, and are conse- quently consolidated into a single piece which fulfils all its requirements in this respect. In the coccyx the rachidean stalk again recovers its mobility, and to a degree more marked than elsewhere ; the coccygeal bones, articulated with each other by means of convex surfaces, and deprived of long processes at their extremities, are placed in the best possible conditions for variety and extent of movement. DIFFERENTIAL CHAEACTEES IN THE VERTEBEAL COLUMN OF OTHEE THAN SOLIPED ANIMALS. The Number of Pieces composing the Spine slightly varies in the Domesticated Animals, as will be seen in the following Table. VERTEBRAE. ANIMALS. Cervical. Dorsal. Lumbar. Sacral. Coccygeal. Ox . . 7 13 6 5 16 to 20 Sheep . 7 13 6 or 7 4 16 to 24 Goat . 7 13 6 4 11 to 12 Pig . . 7 14 6 or 7 4 21 to 23 Dog . 7 13 7 3 16 to 21 Cat . . 7 13 7 3 21 A. Vertebrae of the Ox, Sheep, and Goat. — 1. Cervical Vertebrae. — The cervical vertebrae of the Ox differ from those of solipeds by their shortness and the greater deve- lopment of their insertion eminences. In the Sheep and Goat they are relatively longer, than in the Ox. The transverse processes of the atlas are less inclined than in the Horse, 30 THE BONES. and have no vertebral foramina ; the posterior facets for articulation with the axis are nearly flat and join each other. The axis has a semicylindrical, not a conical, odontoid process, which is so concave on its upper surface that it looks like a groove. Its spinous process is not so thick as in the Horse, and is not bifid posteriorly. In the five succeeding vertebra, a rugged continuous lamina unites the anterior articular processes to the posterior. The spinous process inclines forward and is flattened trans- versely at its summit, which is sometimes bifid ; it augments progressively in height from the third to the fifth vertebra. In the sixth, the transverse processes have only two prolongations— a superior and inferior ; the latter, large and flattened on both sides, is bent abruptly downwards. The spinous process has already attained the height of 1J to 2 inches in this vertebra, and is flattened laterally. The seventh well deserves the name of prominens' its spinous process being no less than from 4 to 4f inches. 2. Dorsal vertebrae.— in the Ox these bones are longer and thicker than in the Horse. Their spinous processes are larger and incline more backward ; their transverse processes are very volumiuous, and are provided with a convex facet from above to below ; while their posterior notches are nearly always converted into foramina. Considered individually, they are more slender in the middle than at the extremities. Their spinous processes diminish in width, especially at their summits, from the first to the eleventh vertebra, and widen again in the two last ; they progressively increase in slope to the tenth, after which they become more and more upright ; the first four are the longest, and are nearly the same in height ; the others gradually decrease. In the first four or five vertebrae, the articular facet of the transverse processes, while retaining its vertical convexity, is concave in an antero-posterior direction. This facet is always absent in the last vertebra, and sometimes even in the preceding one. The two bones terminating the dorsal region show, in addition, the articular processes disposed like those of the lumbar vertebrae. The dorsal vertebrae of the Sheep and Goat are relatively less strong than those of the Ox ; their spinous processes are not so wide, and their posterior notches are never con- verted into foramina. 3. Lumbar vertebrae. — The lumbar vertebrae of the Ox are longer and thicker than in the Horse. The transverse processes are also generally more developed, are concave on the anterior border, convex on the posterior, and incline slightly downward, with the exception of the two first, which remain nearly horizontal. They increase in length from the first to the fourth vertebra ; in the latter and the fifth, they are nearly of the same dimensions ; in the last they suddenly become shorter. Their width gradually decreases from before to behind. In the fifth and sixth vertebra, these processes have no articular facets between them and the sacrum, these being only met with in solipeds. The artic- ular processes are prominent, and further removed from the median line as they belong to posterior vertebrae. In the G )at the transverse processes are more inclined downwards. In the Sheep, on the contrary, the processes rise up towards their extremities. 4. Sacrum. — The tacrum of the Ox is more voluminous and curved than that of the Horse. The spinous processes are entirely consolidated, and are surmounted by a thick rugged lip ; they are lengthened at their base and on each side by a ridge that represents the rudiments of the articular processes. The lateral borders are sharp and bent down- wards. The surfaces that serve to unite the sacrum to the ossa innominata have a some- what vertical direction. There are no lateral facets on the base of the bone for the union of the sacrum with the transverse processes of the last lumbar vertebra. In the Sheep and Goat, the sacrum is shorter ; sometimes the consolidation of the spinous processes is late, or never occurs. 5. Coccygeal vertebrae. — In proportion, the coccygeal vertebrae of ruminants are stronger and more tuberous than those of the Horse. The anterior articular processes exist in a rudimentary condition. B. Vertebra of the Pig. — 1. Cervical vertebrae. — Of all the domesticated animals, this has the shortest, the widest, the most tuberous, and consequently the strongest cervi- cal vertebrae. The body of these bones is deprived of its crest on the inferior face ; its heid, but little detached, is scarcely round, and looks as if driven back on itself; con- sequently, its posterior cavity is not deep. The vertebral laminae are very narrow, and scarcely extend from one part of the vertebra to the other in the superior portion ; so that the spinal canal appears at this point to be incomplete. In the atlas, the transverse processes are yet less inclined than in ruminants ; the vertebral foramen is not constant, and when it exists, opens on one side, under the THE VEBTEBRAL COLUMN. 31 transverse process, and on the other, ou its posterior margin, after pursuing a certain track in the substance of the bone. The odontoid process of the axis is constricted at its base. This vertebra is distin- guished by its high and thin spinous process inclining slightly back, by its transverse processes being but slightly prominent and perforated by an enormous vertebral toramen. In the four succeeding vertebra;, the spinous process terminates in a blunt point, and inclines forward; slightly salient in the tirst, it gradually rises in the others. The irans- verse processes form two prolongations : one, the superior, is tuberculous, and is joined to the anterior articular process by a plate of bone, which is pierced by a foramen ; the other, tiie inferior, flattened on both sides, bent downwards, and large, as it belongs to the posterior vertebrae, transforms the inferior face of these vertebral bodies into a large groove. The seventh is provided with a spinous process as long as those of the dorsal region. A perforated bony plate, as in the preceding vertebra?, unites the anterior articular process to the single tubercle composing the transverse process ; the latter is continued back nearly to the posterior notch by a second plate, also perforated with a foramen (see Fig. 2). 2. Dorsal vertebrae. — The Pig has fourteen dorsal vertebra, which, in their general disposition, are not unlike those of the Ox. As with that animal, the intervertebral fora- mina are double, each vertebral lamina being perforated laterally by an opening situated in front of the posterior notch. In addition, the vertebrae of the Pig present this pecu- liarity, that their transverse processes are generally traversed at the base by a single or multiple foramen which communicates with the preceding. With regard to the special characters proper to some of the vertebrae, these are, as with the other animals, very few, and may be described as follows : 1. The transverse pro- cesses of the four vertebra? preceding the last project but slightly; 2. In the fourteenth this process resembles those of the lumbar vertebrae ; 3. The articular facet of the trans- verse process in the four last vertebras is confounded with the anterior lateral facet corresponding to the head of the rib , 4. The articular processes of the last five vertebrae are arranged like those of the lumbar vertebrae ; and the prominence formed by the tubercle on the outside of the anterior articular process replaces, to a certain degree, the transverse process of these vertebrae. 3. Lumbar vertebrae. — These bones in the Pig greatly resemble those of ruminant animals. It commonly happens that seven are met with ; but in this case the supple- mentary vertebra is generally a sacral one. It is not denied, however, that seven lumbar vertebrae may exist in the Pig, along with the normal number of sacral vertebrae. 4. Sacrum. — This is formed by four vertebrae, which are a long time in becoming fused together, and it is often difficult to discover where the sacrum ends and the coccyx begins.1 The spinous processes are entirely absent. The vertebral laminae are not consolidated , so that the spinal canal is half cut through in its upper portion, as in the cervical region ; this canal is also much compressed above and below. 5. Coccygeal vertebrae. — These vertebrae in the Pig are more particularly distin- guished by the presence of articular processes, by means of which the foremost bones correspond with each other. C. Veutebile of the Dog and Cat. — 1. Cervical Vertebrae. — In these animals, the cervical vertebrae are long and thick, and much resemble those of solipeds. Nevertheless, be.-ides their smaller volume, they are distinguished : 1, By the disposition of their corresponding articular surfaces ; the anterior, or head, is nearly flat, and is even slightly excavated in its centre ; the posterior, or cavity, is but little hollowc d to receive the head of the next vertebra ; 2, By the width of the vertebral laminae, which exactly cover one another ; 3, By the height of their spinous processes, which increases as the vertebrae extend back ; 4, By the great extent of the anterior and posterior articular processes, which are united by means of a continuous and very salient bony plate, that considerably augments the transversal diameter of each vertebra. In the atlas, the articular surface for the odontoid pivot is confounded in front with the cavities which correspond to the occipital condyles. The two facets which *are annexed posteriorly to this articular surface, instead of being plane or gently undulated, as in the * This can always be made out, however, by consulting the disposition of the articular processes. Thus, in the sacral vertebrae these eminences— if we except the anterior ones of the first and the posterior of the last — never exist except in a rudi- mentary state; while in the other five coccygeal vertebrae they re-appear with all their characters. 32 THE BONES. other domesticated animals, are transformed into real glenoid cavities.1 The transverse processes are carried directly outwards and a little backward; the lip which borders each is slightly raised ; of the two foramina which replace the anterior notch, one only exists, and this penetrates to the interior of the spinal canal ; the other is merely a simple notch. In the axis, the odontoid process is cylindrical, narrow at its base, and bent a little upwards ; the lateral facets* of this eminence represent true condyles.2 The spinous process is very thin and undivided, and is curved forward above the laminae of the atlas. The anterior notches are never converted into foramina. The third cervical vertebra is the largest, and the succeeding ones gradually diminish in thickness to the last, contrary to what occurs in the other species. The seventh does not show the spinous process so developed as in ruminants and pachyderms (see Fig. 1). 2. Dorsal vertebrae. — In the Dog the dorsal vertebrae are formed on the same model as those of the Horse ; but their spinous processes are in general narrower and thicker. The tenth always has its spinous process vertical, triangular, and terminated in a sharp point. The last three have no posterior facets for the articulation of the heads of the ribs, and exhibit, in the conformation of their articular processes, the same disposition as the lumbar vertebrae. In the Cat, the transverse processes of the three last dorsal vertebrae are thin, sharp, and turned backwards , they never possess facets for the tuberosity of the ribs. 3. Lumbar vertebras. — In the Dog and Cat, the lumbar vertebrae are remarkable for their strength, due to their length, thickness, and the development of the eminences of insertion. The spinous process is low, and becomes acute in the last vertebra. The transverse processes incline very much forward and downward ; they become longer from the first to the second-last bone , in the latter they become contracted, and in the seventh vertebra they are still more diminished, and terminate in an obtuse point. The tubercle of the anterior articular process is extremely prominent, and the posterior notches are surmounted by a small, very acute prolongation, directed backwards, which becomes more developed towards the anterior vertebrae. This small prolongation exactly represents the transverse process of the dorsal vertebrae. 4. Sacrum. — The three vertebrae which form the sacrum of carnivora are early con- solidated. The supersacral spine constitutes a thin sharp ridge, while the lateral surfaces for articulation with the ossa innominata are turned quite outwards and are nearly vertical. 5. Coeeygeal vertebras. — The vertebrae of the coccyx are very strong and tuberous. The first five or six are as perfect as the true vertebrae, and comport themselves in every respect like them. The last are small V-shaped bones, which M. Goubaux has described by the name of hypsiloid bones. COMPARISON OP THE VERTEBRAL COLUMN OF MAN WITH THAT OF THE DOMESTICATED ANIMALS. The vertebral column of Man is composed of twenty-nine bones . twenty-four vertebrae, the sacrum, and four pieces constituting the coccyx. The twenty-four vertebrae are thus distributed : Cervical vertebrae 1 Dorsal „ 12 Lumbar „ 5 In all these vertebra?, the bodies are slightly excavated at the two extremities, while in the domesticated animals, the superior or anterior is convex, and the inferior or posterior concave. 1. Cervical vertebrae.— Them are wide and short. The spinous processes are mode- rately developed and bifid at their summits ; the transverse processes are also divided into two branches — a posterior and an anterior. 2. Dorsal vertebras. — In these vertebrae, the bodies increase in thickness from the first to the last. In the first as well as in the last dorsal vertebrae, the spinous process is almost immediately directed backwards; in the middle portion of this region these processes are very obliquely directed downwards and backwards. 1 (A glenoid cavity is a shallow, oval, articular depression.) 2 (A condyle is an articular eminence representing an ovoid segment. Condyles always correspond to the glenoid cavities in the articulations.) 33 I™, . Lumbar vertebrae. — The lumbar vertebrae are the strongest bones in the spine, their bodies are nearly as thick as those of the larger domesticated animals. This enormous development of the lumbar vertebrae in Man is related to his position as a biped. In the fifth, the lower face of the body is cut very obliquely backwards and upwards, and the transverse processes are more voluminous than those of the other lumbar vertebrae. 4. Sacrum. — The sacrum is formed by the union of five pieces. It is very concave from above to Fi„ 18# below and before to behind. In becoming united to the lumbar region, it forms a salient angle in front, to which has been given the name of promon- tory or sacro-vertebral angle. The sacral spine is continuous or interrupted, according to the subject ; it is alway bifid inferiorly. 5. Coccygeal vertebrae. — These are little bones or flattened tubercles, four in number, rarely five, and usually consolidated. The coccyx is conical in shape. Its base shows two processes directed up- wards, which are called the cornua of the coccyx. Its summit is often deviated to the right or left. Article II. — The Head. The head is a large bony pyramid, elon- gated from above to below, and quadran- gular, suspended to the anterior extremity of the spine ; it is in a direction varying with the attitudes of the animal, but which we will suppose, for convenience of description, to be nearly vertical. It is formed of a great number of particular bones, which are only distinct from one another in very young animals ; for well before the adult period is reached the majority of the bones are united and cannot be separated. The head is divided into two parts : the cranium and the face. BONES OP THE CRANIUM. The cranium, or upper part of the head, is composed of seven flat bones, five of which are single : the occipital, parietal, frontal, sphenoid, and ethmoid ; one only, the temporal, is double. These bones circum- 1 scribe a central cavity, the cranial, which communicates behind with the spinal canal, and lodges the principal portion of the nervous centres — the encephalon. 1. Occipital Bone. The occipital bone occupies the superior extremity of the head, which it supports from the anterior extremity of the spine. This bone is very irregular in its form, and is bent at a right angle in front and behind. It has an external and an internal face, and a circumference which brings it into contact with the adjoining cranial bones ; the latter is horse's head; front view. Occipital protuberance ; 2, Origin of the mastoid crest ; 3, Parietal bone ; 4, Saggital suture ; 5, Junc- tion of the parietal and temporal bones ; 6, Zygomatic arch ; 17 Frontal bone ; 8, Frontal suture ; 9, Temporal fossa ; 10, Supraorbi- tal foramen; 11, 12, Lachrymal bone; 13, Malar bone; 14, Nasal border of frontal bone; 15, Nasal bone; 16, Suture of nasal bones ; 17, Superior maxillary bone; 18, Infraorbital foramen; 19, Ante- rior, or pre-maxillary bone ; 20, Foramen incisivum ; 21, Incisor teeth — young mouth. subdivided into two anterior 34 TEE BONES. lateral borders, two posterior lateral borders, an anterior and posterior salient angle, and two lateral re-entering angles. Faces. — The external face is divided into three portions by the double flexure of the bone: one looks forward, another upward, and the third backward. It exhibits : — 1. On the median line, and from before to behind : a, an antero-posterior ridge which constitutes the origin of the parietal ridges, to be mentioned hereafter; b, a transverse, voluminous, and very prominent eminence, marked posteriorly by deep imprints, with a medium projection named the cervical tuberosity ; this is the external occipital pro- tuberance which, in the Horse, corresponds at the same time to the superior curved lines of the occipital bone of Man. This protuberance forms the culminating point of the head, and divides the anterior and superior parts of the external face of the bone ; c, the occipital foramen {foramen magnum), a large orifice that passes through the bone at the posterior flexure, and esta- blishes a communication between the cranial cavity and spinal canal ; d, the external surface of the basilar process, a narrow and thick prolongation formed by the bone as it passes to meet the sphenoid : this surface is convex laterally. 2. On the sides : a, A sharp crest which prolongs, laterally, the superior curved lines, and descends on the middle of the lateral anterior border to be continued with the superior root of the zygomatic process and the mastoid crest of the temporal bone ; b, Linear imprints, parallel to the latter, and prolonged on the base of the styloid process : they are destined for the insertion of the small oblique muscle of the head, and represent the inferior curved lines of the occipital bone of Man ; c, Within these imprints is a slightly- roughened cavity for the insertion of the posterior recti muscles ; d, The two condyles, articular eminences with a double convexity, one superior, the other inferior : these eminences are situated on each side of the occipital foramen (foramen magnum), and correspond to the anterior cavities of the atlas; e, More outwards are the two styloid processes, or jugular eminences, long projections flattened on each side, terminated in blunt points, directed back- wards, and separated from the condyles by a deep space, the stylo-condyloid notch ; f Under the condyles is the condyloid fossa, a smooth depression, pierced at the bottom by the condyloid foramen, which penetrates the cranium. The internal face of the occipital bone is concave, and shows : behind, the foramen magnum ; above, an uneven surface, which forms the roof of the cerebral cavity; below, the superior face of the basilar process, slightly hollowed into a groove ; on the sides, the internal orifice of the condyloid foramen. Circumference. — The anterior lateral borders are thick, and are united by suture with the parietal bone, and with the tuberous portion of the temporal bone by the harmonia1 suture. The posterior lateral borders are sharp, and constitute the sides of the basilar process ; each concurs in the formation of the occipito-spheno-temporal hiatus, also termed the lacerated foramen, a vast irregular opening, extending from above downwards, penetrating the cranium, and divided by a ligament, in the fresh state, into two portions, one inferior, the anterior lacerated foramen, the other superior,2 the posterior lacerated foramen. The anterior angle, which is dentated, is dovetailed into the parietal bone. The posterior angle is very thick, and forms the summit of the basilar process ; it is united by suture with the body of the sphenoid. The lateral re-entering angles, or jugular notches, correspond to the 1 (The harmonia*8uture (&pc?v, to adapt) is the simple apposition of contiguous borders, which are roughened to facilitate retention.) 2 (The anterior and posterior lacerated foramen of Man.) THE HEAD. 35 point where the bone is bent posteriorly ; they separate the anterior lateral from the corresponding posterior lateral border, and are occupied by the tuberous portion of the temporal bone. Structure. — The occipital bone contains much spongy substance. Development. — It is developed from four centres of ossification : one, the anterior, is single, and forms the occipital protuberance; another, the posterior, also single, forms the basilar process ; the other two are pairs, and comprise each a condyle, with the styloid process and the corresponding condyloid foramen. 2. The Parietal Bone. The parietal is a wide and thin bone, very much arched to form the roof of the cranial cavity. It is bounded above by the occipital bone, below by the frontal, and laterally by the two temporal bones. It offers for study an external and internal face, and a circumference divided into four regions or borders. Faces. — The external face is convex. It exhibits two curved ridges whose concavity is directed outwards ; these two crests, which are termed the parietal ridges, approach each other and unite superiorly, to be continued with the antero-posterior ridge of the occipital bone ; below they diverge and proceed, one on each side, to join the supraorbital process. They divide the surface of the bone into three portions : two lateral, which are rough and traversed by vascular channels, forming part of the temporal fossae; the third, or middle, is plane, smooth, and of a triangular form, and covered by the skin. The internal face is concave, covered by digital impressions, and grooved by small vascular canals ; it offers, on the median line, and altogether above, the parietal eminence.1 This trifacial and very salient pro- jection presents at its base, on each side, an excavation elongated trans- versely, into which opens the parietotemporal canal, and which is destined to lodge a venous sinus. It is continued, in front, by a median crest, which is often replaced by a slight groove, the saggiial furrow, bordered by linear imprints. Two other ridges, resulting from the abutment of the lateral border of the bone against the anterior face of the petrous bone, rise from the sides of this eminence and descend to the sphenoid bone ; they separate the cerebral from the cerebellar cavity. Borders. — The superior border is notched, thick, and slightly dentated ; it articulates with the occipital bone. The inferior border, slightly concave, and deeply dentated, offers an external bevel in its middle portion, and an internal bevel on its sides; it corresponds with the frontal bone. The lateral borders are very thin, and are cut at the expense of the external plate into a wide, sloping edge, which shows a groove destined to form the parieto-temporal canal. A very prominent angle separates each into two portions, an inferior, that articulates by suture with the squamous portion of the temporal bone ; and a superior, curved inwards towards the centre of the cranial cavity ; the latter portion of the lateral border is in contact with the anterior face of the petrous portion of the temporal bone, with which it concurs to form the lateral crest that descends to the parietal eminence. Structure. — This bone contains much compact tissue, the spongy sub- stance existing only in its middle. Development. — It is developed from two large centres of ossification, to 1 The internal occipital eminence of Man. 36 THE BONES. which is added a single centre to form the parietal eminence.1 In early life the parietal ridges are absent. 3. Frontal Bone. The frontal is a flat quadrilateral bone, whose sides are bent in the middle at an acute angle, and are carried back, and a little inwards, to meet the wings of the sphenoid bone. It assists in forming the cranial roof and) part of the face. It is bordered : above, by the parietal bone ; below, by the nasal and lachrymal bones ; and on each side, by the temporal bones. It offers for study an external and an internal face, and four borders. Faces. — The external face is divided, by the double flexure of the bone, into three regions : a middle and two lateral. The first, nearly plane, is lozenge-shaped, is covered by the skin, and constitutes the base of the fore- head. It gives rise on each side, at the point where it is inflected, to a long process, flattened above and below, which curves backward, forming the orbital arch. The superior or external face of this process is convex and slightly roughened ; the internal face is smooth and concave, and forms part of the orbital fossa. Its posterior border, thick and concave, is continued, in- wardly, with the corresponding parietal ridge, and outwardly with the superior border of the zygomatic process. It limits, in front, the temporal fossa. The anterior border, also concave, but thin, concurs in the forma- tion of the orbital margin ; the summit, thickened and denticulated, rests upon, and is united to, the zygomatic process of the temporal bone ; the base is wide, and is traversed by an opening termed the supraorbital, or super- ciliary foramen. The two lateral regions of the external face of the frontal bone are slightly excavated, and assist, for the greater portion of their extent, to form the orbits. They often show, near the base of the orbital arch, a small depression corresponding to the flexure described by the great oblique muscle of the eye in passing 'through its pulley. The . internal face of the frontal bone is concave, and divided into two unequal parts by a transverse ridge, corresponding to the anterior border of the cribriform plate of the ethmoid bone. The superior, the most extensive, is covered with digital impressions, and belongs to the cranial cavity. It exhibits : 1, On the median line, a slight furrow, or a crest which is con- tinuous, above, with the median ridge of the parietal bone, and below, with the crista- galli process ; 2, On the sides, and in the re-entering angle formed by the flexure of the bone, there is a narrow slit, or mortice, which receives the wing of the sphenoid bone. The inferior part is united, on the median line, to the perpendicular plate of the ethmoid. It assists in forming the bottom of the nasal cavities, and presents laterally two large openings which lead to the frontal sinuses — vast anfractuous spaces excavated between the two plates of the bone. Borders. — The superior border is denticulated, and cut obliquely, in its middle portion, at the expense of the internal plate, and on the lateral parts at the expense of the external table; it is in contact with the parietal and 1 This centre is described as the interparietal bone by those anatomists who consider the two lateral centres as two distinct parietals. (Leyh is one of the veterinary anatomists who describe this nucleus as a separate bone, designating it the falciform or interparietal bone. He also describes the parietal as a pair or double bone ; whereas the majority of French anatomists include the interparietal bone as the median protuberance of the parietal, which they look upon as a single or impair bone. Percivall names it a pair bone, but follows the example of the French hippotomists with regard to the interparietal.) THE HEAD. 37 squamous portion of the temporal bone. The inferior, prolonged to a point in the middle, is in apposition with the nasal bones through the medium of a wide external bevel ; laterally, it is very thin, faintly serrated, and articulates with the lachrymal bone. The lateral borders, thin and irregular, present two notches : one, the superior, is wide and deep, and occupied by the wing of the sphenoid bone ; the other, inferior, is very narrow, and uniting with a similar notch in the sphenoid bone, forms the orbital foramen, which opens into the cranium, very near, but external to, the ethmoid fossa. Each of these borders, also, is adapted, for a limited extent, to the corresponding palate bone. Structure. — The two compact plates of the frontal bone are separated by spongy texture towards the middle and in the upper part ; they separate below to form the frontal sinuses. Laterally, they are very thin and consolidated with each other. Development. — The frontal bone is developed from two lateral centres of ossification, which only coalesce at a late period. In youth the cranial portion of the bone forms, in front of the head, a large rounded protuberance standing beyond the facial portion. This prominence disappears when the frontal sinuses begin to be developed. These cavities do not exist at an early period of foetal life ; but commence to form about the fourth month of conception, by a process of resorption, which removes the spongy substance interposed between the two compact tables of bone, and may even cause the destruction of the internal table. The sinuses enlarge with age, and remain during life separated from one another by a vertical septum. 4. Ethmoid Bone. The ethmoid bone, deeply situated in the limit between the cranium and the face, is inclosed between the frontal, the sphenoid, the vomer, the palate, and the supermaxillary bones. It is composed of three portions : a perpendicular 'plate, and two lateral masses. The Perpendicular Lamina of the Ethmoid Bone. — Situated in the median plane, and flattened on both sides, this bone presents two faces, a left and right, and four borders. Faces. — The faces, covered by the pituitary membrane, present, pos- teriorly, small sinuous crests ; elsewhere they are smooth. A very narrow interval, constituting the bottom of the nasal cavities, separates them from the lateral masses. Borders. — The superior border looks towards the centre of the cranial cavity, and constitutes what is called the ethmoidal ridge, or crista-galli process. It is free, concave, and sharp, prolonged in front and above by the median crest of the frontal bone, and confounded behind with the middle portion of the inferior sphenoid. The inferior border is continuous with the cartilaginous plate which separates the nasal cavities. When this plate becomes ossified, which is not unfrequent, it is impossible to discover the point where it begins or the ethmoid bone terminates. The middle septum of the nose has been considered, and justly, as a prolongation of the perpen- dicular plate (or lamina) of this bone. The anterior border is consolidated with the vertical septum which separates the frontal sinuses. The posterior border is joined, above, to the median plate which divides the sphenoidal sinuses into two compartments. Below, it is fixed in the groove of the vomer, and soon becomes confounded with that bone, which is itself conso- lidated with the inferior sphenoid. Lateral Masses of the Ethmoid Bone. — These are two large pyrifonn ?,s THE BONES. tuberosities placed on each side of the perpendicular lamina, and offering for study a middle portidh, a base, and a summit. Each of these is formed by an assemblage of numerous, extremely thin, osseous plates, curved into small and very fragile convolutions. These, elongated from above to below, become longer as they are more anterior ; they are attached by their superior extremities to the transverse plate which separates the cranium from the nasal cavities, and by one of their borders to a thin leaf of bone which envelops the lateral masses out- Fig. 19. wardly. They have received the name of the ethmoidal volutes (or cells). Middle portion. — This should be studied externally and inter- nally. The external surface of each ethmoidal mass is divided into two sections: an internal, making part of the nasal cavities ; the other, external, concurs in form- ing the walls of the f i-ontal and maxillary sinuses. The first, the least extensive, is almost plane; parallel to the perpendicular la- mina, it is isolated from it by the narrow space which forms the bottom of the nasal cavities ; it presents several openings which separate the most superficial cells, and join the internal canals to be hereafter noticed. The second, A, Occipital bone. — 1, Condyle ; 2, Con- dyloid foramen ; 3, Styloid process ; 4, Summit of basilar process. — B, Parie- tal bone. — 8, Parietal protuberance ; 9, Channel which concurs to form the parietotemporal canal. — C, Frontal bone. — 10, Transverse crests separating the cranial from the facial portion of the bone; 11, Frontal sinuses; 12, Notch on the lateral border occupied by the wing of the sphenoid bone ; 13, Notch for the formation of the orbital foramen ; 14, Summit of the orbital process ; 15, Supraorbital foramen. — D, Perpendicular lamina of the ethmoid bone. — E, E, Lateral masses of the eth- moid bone. — 16, The great ethmoid cell. — F, Squamous portion of the temporal bone. — 17, Supercondyloid process ; 18, Channel for the formation of the parieto-temporal canal. — G, Tuberous portion of the temporal bone. — 5, Mas- toid process; 6, Internal auditory hiatus ; 7, Opening for the eustachian ANTERIOR BONES OF THE HEAD OF A FCETUS tube into the tympanum. — H, Lach- (horse) at birth ; DISARTICULATED, and rymal bone. — I, Nasal bone. — J, Su- VIEWED FROM behind. perior turbinated bone. TEE HEAD. 39 very extensive and convex, looks outwards in front and behind, and is covered by an osseous plate traced with shallow furrows, which correspond internally with the small crests to which the cells are attached. This lamella is prolonged, inferiorly, a little beneath the inferior extremity of these latter, and turns outwards to articulate with the palate and superior maxillary bones ; superiorly, it coalesces with the sphenoid and the orbital portion of the frontal bone. Internally, the lateral masses are hollowed from above to below by extremely diverging canals, which open inferiorly into the nasal cavities, and separate the cells from one another. The latter are so incurvated that the internal cells communicate with each other. There are some, however, which are completely closed ; the anterior, or great cell, is frequently so.1 Base. — The base of each lateral mass looks upwards, and is formed by the transverse septum between the cranium and the nasal cavities. This septum is perforated by openings which give passage to the ethmoidal nerves ; it is named the cribriform plate of the ethmoid bone. It is concave on the superior surface, which constitutes the ethmoidal fossa, and convex on the opposite face, where attachment is given to the superior extremities of the cells. It is consolidated internally with the perpendicular plate ; the other points of its circumference are attached to the sphenoid bone, and to the transverse ridge on the internal face of the frontal bone. Summit. — The summit of each lateral mass is formed by the inferior extremity of the ethmoidal cells, which is directed downwards towards the nasal cavities. One, more voluminous than the others, is carried much lower, and terminates by a rounded protuberance. It corresponds to the middle cornu (concha media) of Man. Structure of the ethmoid bone. — Very little spongy tissue enters into the composition of this bone, and this is only found near the anterior border of the perpendicular plate. Development. — The ethmoid bone is late in attaining its development, and the adjoining bones are nearly completely ossified when it is yet entirely cartilaginous. The bony transformation commences in it at the inferior extremity of the cells, and advances progressively from below upwards. The perpendicular plate is only ossified in part when the cells have passed through the first half of the process; at the same time it coalesces with the inferior sphenoid. The cribriform plate is the last to become ossified; this transformation having scarcely been achieved when the animal is six or eight months old. 5. Sphenoid Bone. The sphenoid bone is situated behind the cranium, between the occipital, ethmoidal, palate, vomer, pterygoid, frontal, and temporal bones. It is flattened from before to behind, curved from one side to the other, thick in its middle part, named the body, and thin on the sides, which, in their inferior half, are prolonged in the form of alee or wings. It has two surfaces and four borders. Surfaces. — The external surface is convex, and presents: 1, On the median line, the external surface of the body, rounded from one side to the other, is continued with that of the basilar process, and has marked mus- cular imprints superiorly ; 2, On the sides and from within outwards : a, the vidian (or pterygoid) fissure, directed from above downwards, and con- tinued by the vidian canal, a very small foramen which opens into the 1 It is not rare to find it opening into the frontal sinus. 40 THE BONES. orbital hiatus ; b, the subsphenoidal, or pterygoid process, a long eminence, flattened on both sides, inclining downwards, articulating with the palate and pterygoid bones, and traversed at its base by the vidian canal ; c, a little behind and above this eminence, the superior orifice of the" sub" splienoidal foramen, a large canal which bifurcates inferiorly ; d, more in front, the orbital hiatus, a kind of vestibule into which oj>en in common the principal branch of the subsj>henoidal canal, the three supersphenoidal canals, the vidian and optic canals, and the orbital opening : this hiatus is surmounted by a thin and sharp bony plate, above which opens the smallest branch of the subsphenoidal foramen ; e, altogether without the hiatus is remarked a smooth surface belonging to the wing of the sphenoid, and which concurs to form the orbital cavity. The internal face is concave from side to side. It shows : 1, On the median line, and from before to behind, a small projection united to the crista-galli ; the optic fossa, elongated transversely in the form of a shuttle, and presenting at the bottom, and on each side, the superior orifice of the optic foramen, a cylindrical canal directed obliquely downwards, forwards, and outwards, to reach the orbital hiatus ; the supersphenoidal or pituitary fossa, also named the sella turcica, a slight depression, limited behind by a scarcely noticeable transverse projection separating it from the superior channel of the basilar process ; 2, On the sides, and in front, the internal surface of the wings, depressed by very superficial digital impressions ; more behind and outwards, a fossa, elongated from before to behind, which lodges the mastoid lobule of the brain; between this fossa and the sella turcica, two vertical fissures : an internal, named the cavernous sinus, and an external, wider and deeper, for the passage of a large nervous branch. These two fissures open below, near the junction of the three super- sphenoidal canals. Two of these,- which are very wide, are placed one before the other, and separated only by a slight partition. The superior of these constitutes the great sphenoidal fissure ; the other, the lower, is the foramen rotundum, and opens into the orbital hiatus. The third, very small, is situated outside the great anterior canal, opens above the optic foramen, within the bony mass surmounting the hiatus, and sometimes on the free margin of this lamina. Borders. — The superior is a little concave, and shows, in its middle, the superior extremity of the body, mammillated and articulated with the summit of the basilar process ; on each side, two notches which circumscribe below the occipito-spheno-temporal hiatus (foramina lacera basis cranii). The internal notch is the narrowest, and from its affording a passage for the internal carotid artery, is called the carotid notch ; it is continued on the external face of the bone by a smooth excavation to which Rigot has given the name of carotid fossa. The external is also prolonged on the exterior surface cf the sphenoid by a short and wide fissure ; it lodges the inferior maxillary nerve. Outside this is another very narrow notch, intended for the passage of the middle meningeal artery. The fibro-cartilaginous sub- stance that partly fills the occipito-spheno-temporal hiatus, transforms these notches into foramina, the first of which is named the carotid canal, the second, the foramen ovale, and the third, the foramen spinosum. The inferior border, also concave, is likewise divided into three portions, a middle and two lateral. The first is thick, and formed by the inferior extremity of the body; it is excavated by two large cavities belonging to the sphenoidal sinus. These cavities are separated from one another by a vertical osseous plate, often perforated, which, at an early period, is fused with the perpendicular THE HEAD. 41 Fig. 20. lamina of the ethmoid bone. The very thin lateral portions form part of the circumference of the wings; they are notched near their union with the middle piece to assist in the formation of the orbital foramen. The two lateral borders are thin and convex in their an- terior half, as is also the contour of the wings, which are mortised in the frontal bone. For the remainder of their extent they are thick, denticulated, and bevelled at the expense of the external plate, to articulate with the squamous portion of the temporal bone. Structure. — This bone is compact on its sides, and spongy in its middle part ; inferiorly, it is excavated by the sphe- noidal sinuses. Development. — It is developed from two principal nuclei of ossification ; a superior forms the subsphenoidal pro- cess and the canal of the same name, the vidian fissure, pituitary fossa, fissures of the internal face, and the most pos- terior of the great supersphenoidal canals ; the other, the inferior, forms that portion of the body hollowed by the sinuses, the lateral alas,1 and the optic fossa and canals. In meeting each other, these centres form the vidian canal and the two anterior supersphenoidal canals. They are not consolidated with each other until a very late period ; for which reason they are sometimes de- scribed as two distinct bones. M. Tabourin has even proposed to attach the description of the inferior sphenoid to that of the united with this bone a long time before it is joined to the superior portion. POSTERIOR BONES OP THE HEAD OP A FCETUS (HORSE) AT BIRTH; DISARTICU- LATED AND VIEWED IN FRONT. ethmoid, because it is A, Sphenoid bone, — 1, Maxillary notch ; 2, Carotid notch ; 3, Groove for the passage of the maxillary nerve ; 4, Cavernous sinus; 5, Optic fossa; 6, Great wing; 6', Unossified portion of the great wing ; 7, Notch for the formation of the orbital foramen. — B, Vomer. — C, Palate bone. — D, Zygoma. — E, Superior maxilla. — 8, In- ferior orifice of the maxillo-dental canal. — F, Premaxillary bone. 6. Temporal Bone, temporal bones inclose The temporal bones inclose the cranial cavity laterally, and articulate with the occipital, parietal, frontal, sphenoidal, and the zygomatic bones; also with the inferior maxilla and the hyoid bone. Each is divided into two pieces, which are never consolidated in the horse ; one forms the squamous portion of the temporal lone ; the other, the tuberous portion. They will be described separately. Squamous Portion. — This is flattened on both sides, oval, and slightly incurvated like a shell, a shape to which it owes its name. It offers for study an external and an internal face, and a circumference. 1 These wings are not analogous to those portions of the sphenoid bone in Man bear- ing the same name. They are the processes of Ingrassias enormously developed. 42 TRE BONES. Faces. — The external face is convex, and marked by some muscular imprints, vascular fissures, and openings which penetrate the parieto- temporal canal. It forms part of the temporal fossa, and gives origin near its middle to the zygomatic process, a long eminence which at first, runs outwards, and soon curves forwards and downwards to terminate in a thin summit. The base of this eminence forms, in front, a concave surface belonging to the temporal fossa ; behind, it offers the articular surface which corresponds with the maxillary bone. The latter is composed of : 1, A condyle transversely elongated, convex above and below, and slightly concave from side to side ; 2, A glenoid cavity, limited below by the condyle, above by a mammiform eminence, the super condyloid,1 against which rests the maxillary condyle when this bone is drawn backwards ; it is immediately above this eminence that the inferior orifice of the parieto-temporal canal opens. The external face of the zygomatic process is smooth and convex ; the internal, concave, is also smooth, and bordered outwards by the temporal fossa. Its anterior border is sharp and convex ; the posterior, very short, is thick and roughened. Its summit is flattened from before to behind, and marked by notches on its two faces; it somewhat resembles a wedge, fixed as it is between the orbital process of the frontal bone and the zygoma ; it comes in contact with the maxillary bone, and by a small portion of its anterior face, which is deprived of notches, it concurs in circumscribing the orbital cavity. In the domesticated animals, as in Man, the zygomatic process appears to arise from the surface of the bone by two roots : one, the inferior or transverse, is represented by the condyle ; the other, the superior, forms a sharp crest which is continuous with the anterior border of the process, and above, joins the lateral crest of the occipital protuberance. The internal or cerebral face of the squamous portion is divided into two parts by an almost vertical channel which terminates above the super- condyloid eminence, and which, meeting a similar furrow on the parietal bone, forms the parieto-temporal canal. The superior portion is but of small extent, and of a triangular form ; it articulates by a simple harmonia suture with the external face of the petrous portion. The inferior part, the widest, presents in its middle some cerebral impressions. For the re- mainder of its extent or circumference, it is cut into a wide, dentated, and lamellar bevel, which brings it in contact with the surrounding bones. Circumference. — This may be divided into two borders : one, anterior, is convex and united with the parietal and frontal bones ; the other, posterior, articulates with the sphenoid in its inferior moiety, and is provided, above the level of the supra-condyloid eminence, with a deep notch which receives the external auditory canal. Superiorly, the two borders unite at the summit in a thin point which rests on the occipital bone. Structure. — The squamous portion of the temporal bone is formed of two very thin compact plates which have but little spongy tissue between them ; the latter, however, is very abundant in the body of the zygomatic process. Development. — It is developed from a single nucleus of ossification. Tuberous Portion. — This is one of the most interesting parts of the skeleton for study, in consequence of its containing two systems of cavities which inclose the essential organs of hearing. One of these systems is named the cavity of the tympanum or middle ear ; the other forms the internal ear. These cavities will be studied when we come to speak of the auditory 1 In Man this is represented by the inferior or vertical ramus of the upper root of tho zygomatic process. THE HEAD. 43 apparatus. In the meantime, only the exterior surface and the structure and development of this portion of the temporal bone will be noticed. It is wedged between the antero-lateral border of the occipital bone, the lateral border of the parietal, and the superior part of the internal face of the temporal shell. It represents a quadrangular pyramid whose base is turned downwards and a little backwards. It will be studied successively in its four faces, a summit, and base. Faces. — The anterior face is united by harmonia suture to the parietal bone. The posterior face articulates in the same manner with the occipital bone. The external face lies against the squamous portion of the bone. The internal face, slightly concave and marked by very superficial digital impressions, forms a part of the lateral wall of the cerebellar cavity. It presents the canal or internal auditory hiatus (meatus auditorius internus), a small fossa, the bottom of which is pierced by several foramina for the transmission of nerves ; the largest of these is the internal orifice of the aquozductus Fallopii, a flexuous canal which passes through the bone and opens at the external surface of its base ; the other foramina penetrate the cavities of the internal ear. These faces are separated from each other by so many borders or plane angles, two of which more particularly merit attention ; one of these isolates the external from the posterior face, and the other separates the anterior from the internal face. The first is thick and rugged, and constitutes the mastoid crest ; it is continuous above with the lateral ridge of the occipital bone, after being united to the superior root of the zygomatic process, and terminates, near the base of the bone, by a tuberosity for muscular insertion, to which has been given the name of mastoid process. This border is traversed by a slit, the mastoid fissure,1 which passes under the squamous portion and enters the parietotemporal canal. The second is thin, and, with the superior part of the lateral border of the parietal bone, forms the crest which establishes the line of demarcation between the cerebral and cerebellar cavities of the cranium; it gives attachment to the tentorium cerebelli. Summit. — This is slightly denticulated, and articulates with the occipital bone. Base. — This is very irregular, and offers : outwardly, the external auditory canal which penetrates the middle ear, and the external orifice of which has been named in veterinary anatomy the external auditory hiatus ; inwardly, a sharp crest which circumscribes the external contour of the lacerated foramen ; above, and under the mastoid process, the stylo-mastoid or pre-mastoid foramen, the external orifice of the aqueduct of Fallopius ; below, the subuliform (or styloid) process for the attachment of the stylo-staphyleus (tensor palati) muscle and the Eustachian tube : this is a long, thin, and pointed process presenting, at its base and within, a canal which enters the cavity of the tympanum, and which is incompletely partitioned by a small bony plate into two parallel portions : in the centre, the hyoid prolongation or vaginal process,2 a little cylindrical eminence surrounded by a bony sheath, and the mastoid protuberance or process, a slightly salient, smooth, and round eminence hollowed internally by numerous cells, which form part of the middle ear. The several small and very remarkable canals which pass through the tuberous portion of the temporal bone, will be noticed when the nervous and arterial branches they lodge are described. 1 This is the analogue of the mastoid canal in Man. 2 This process is prolonged by a cartilage that unites it to the styloid bone. 44 THE BONES. Development. — The tuberous portion of the temporal bone is developed from two principal centres of ossification which are consolidated at birth, and which are often described as two distinct portions : the one as the petrous or stony portion, the other as the mastoid portion. The faces, borders, summit and inner side of the base of the bone are formed by the petrous part, which contains the cavities of the internal ear and furnishes the inner wall of the middle ear. The mastoid portion constitutes almost entirely the base of the temporal pyramid ; to it belongs the external auditory canal, the mastoid process, the sheath of the hyoid prolongation, and the styloid process; it forms the external wall and circumference of the case of the tympanum. For the tuberous portion of the temporal bone there are also two small complementary nuclei : one for the vaginal process, whose base is united to the petrous portion, and another forming the ring of the tympanum. Structure. — The petrous portion is the hardest mass of bone in the skeleton, and scarcely contains any spongy tissue, except at the centre of the mastoid process ; in the mastoid portion it may be said not to exist. In the other domesticated animals, the tuberous portion of the temporal bone is always consolidated with the squamous, and the summit of the zygomatic process only articulates with the malar bone. BONES OF THE FACE. The face is much more extensive than the cranium in the majority of the domesticated animals, and is composed of two jaws, a bony apparatus that serves as a support to the passive organs of mastication — the teeth. The superior or anterior jaw, traversed in its entire length by the nasal cavities, is formed by nineteen wide bones, only one of which, the vomer, is a single bone ; the pairs are : the superior and intermaxillaries (or premaxillaries), the palate, pterygoid, zygomatic, lachrymal, nasal, and superior and inferior turbinated bones. Of these only four, the maxillaries, are intended for the implant ition of the teeth ; the others form the union between the cranium and the superior maxilla, or concur in the formation of- the nasal cavities. The lower jaw has for its base a single bone, the inferior maxilla or maxillary bone. 1. Great Supermaxilla, or Superior Maxillary Bone. This bone, the most extensive in the upper jaw, is situated on the side of the face, and is bordered above by the frontal, palate, zygomatic, and lachrymal bones ; below, by the premaxillary bones ; in front, by the nasal bone ; behind and within, by that of the opposite side. It is elongated vertically, is irregularly triangular, and exhibits two faces, two borders, and two extremities. Faces. — The external face, which is more convex in the young than the old animal, presents : 1, On the level of the fourth and fifth molar teeth, a vertically elongated ridge which is continued above with the inferior border of the zygomatic bone ; this is the supermaxillary spine ; 2, The inferior orifice of the supermaxillo-dental canal, or infra-orbital foramen. The internal face concurs in forming the external parietes of the nasal cavities. We observe, above and in front, a deep, wide, and diverticu- lated excavation, forming part of the maxillary sinus ; above and behind, a surface roughened by fine lamellae and dentations to correspond with the palate bone, and traversed from above to below by a fissure which forms, in uniting with a similar fissure in the latter bone, the palatine canal. For the remainder of its extent it is unequally smooth, covered by the membrane THE HEAD. 45 of the nose, and divided into two surfaces by a slightly vertical and sinuous crest that affords attachment to the maxillary turbinated bone : the anterior surface, which responds to the middle meatus of the nasal fossa, shows the lower orifice of the osseous lachrymal canal continued by a fissure to the lower extremity of the bone ; the posterior surface belongs to the inferior meatus. This face presents, near its inferior border, a large vertical apophysis, the palatine process, which offers an anterior slightly concave face, forming the floor of the nasal fossae; a posterior face, furrowed by small fissures, perforated by fine openings, and traversed along its length by a somewhat wide groove, the 'palatine fissure, which commences above at the lower orifice of the palatine canal. The internal border of this process articulates with the analogue of the palatine process of the opposite side. Borders. — The anterior, thin and convex, is divided into two parts : an inferior, which is mortised to receive the external border of the nasal bone and the external process of the premaxillary ; and a superior, cut in a wide bevel at the expense of the external plate, to respond to the lachrymal and zygomatic bones. The external border is very thick and hollowed into six large quadrilateral cavities, named alveoli, in which are implanted the molar teeth. Above the last alveolus it forms a rugged eminence designated the alveolar tuberosity ; below the first it becomes thin and sharp, and constitutes part of the interdental space which separates the molar from the incisor teeth. Extremities. — The superior is the thickest, and represents a smooth rounded protuberance, into the interior of which the maxillary sinus is prolonged. Above and within this eminence, is a wide and deep excavation, in the formation of which the palate bones participate. This is the maxillary hiatus, situated directly opposite the orbital hiatus. At the bottom of this cavity is seen the nasal foramen, as well as the upper orifice of the supermaxillo-clental and the palatine canals. The nasal foramen belongs to the palate bone and enters the nasal cavity. The super- maxillo-dental or infra-orbital canal traverses the maxillary sinus in passing above the roots of the molar teeth, and terminates by two branches : one, short and wide, which opens on the external surface of the bone, on a level with the third molar ; the other, very narrow, continues the course of the canal in the thickness of the bone, and is prolonged by several small very fine branches into the premaxillary bone. The palatine canal, channeled between the supermaxillary and the palate bone, extends from the maxillary hiatus to the palatine fissure. The inferior extremity presents a cavity which forms the alveolus of the tusk by uniting with a similar space in the premaxillary bone. Structure and development. — This bone is developed from a single nucleus, and is the more spongy, particularly towards the alveolar border and the superior extremity, as the animal is young. 2. Premaxillary, Intermaxillary, Anterior Maxillary or Incisive Bone. This bone occupies the inferior extremity of the head, and is composed of a thick prismatic portion, lengthened superiorly by two long processes. Thick portion or base. — This presents a solid mass with three faces : an external or labial, smooth and convex ; an internal, denticulated for union with the opposite bone, and traversed from before to behind by an inflexed fissure, which forms, with an analogous one in the other premaxillary, the incisive canal or foramen ; the third or posterior, also called the buccal, is slighty concave, and shows the continuation of the palatine fissure, which •10 TEE BONES. Fig. 21. opens into the incisive foramen. These three faces are separated by as many borders : two internal, limiting before and behind the corresponding face ; and an external, separating the labial from the buccal face. The latter only merits notice ; it is very thick, and is divided into two parts : an inferior, which describes a curved line with the concavity upwards, and is hollowed by three alveoli to receive the incisor teeth ; another, the superior, is straight, vertical, and somewhat sharp, and forms a part of the dental interspace. It is limited above, near the base of the external process, by a cavity for the formation of the alveolus of the tusk. Processes. — These are distinguished as ex- ternal and internal. The first, the longest and strongest, is flattened on both sides ; its ex- ternal face is smooth and continued with that of the thick portion of the bone ; its internal face is covered by the mucous membrane of the nose ; the anterior border is smooth and rounded ; the posterior, denticulated to re- spond to the supermaxillary bone, is in con- tact with the external border of the base ; its summit is thin, and is insinuated between the latter and the nasal bone. The internal pro- cess, the smallest, is flattened from before to behind, and forms a very thin tongue of bone, separated from the other portions by a nar- row and very deep notch named the incisive opening or cleft. Its inferior face constitutes a small portion of the floor of the nasal fossas ; the posterior, continuous with the same face of the principal mass of the bone, forms part of the palatine roof; its external border cir- cumscribes, inwardly, the incisive opening ; the internal is united by dentated suture with the opposite bone. Structure and development. — It is a spongy bone, developed from a single nucleus. 3. Palate Bones. The palate bones are situated between the supermaxillaries, at the margin of the guttural opening of the nasal cavities, and are articu- lated with the sphenoid, ethmoid, vomer, frontal, and pterygoid bones. Elongated from above to below, flattened laterally, and curved POSTERIOR ASPECT OF HORSE S SKULL. 1, Occipital protuberance ; 2, Foramen magnum ; 3, 3, Oc- cipital condyles; 4, 4, Styloid processes; 5, 5, Petrous bone; 6, Basilar process; 7, Pterygoid fissure of the sphenoid bone ; 8, Foramen lacerum ; 9, 9, Supra-condyloid, or anterior mastoid process; 10, 10, Articular eminence, or temporal condyle; 11, Body ot sphenoid bone; 12, Pterygoid process; 13, Ethmoid bone; 14, Temporal bone and sphe- noidal suture; 15, Lachrymal bone; 16, Vomer; 17, Malar bone; 18, Maxillary tube- rosity, 19, Posterior, or guttural opening of the nose; 20, Palate bone; 21, Palatine styloid process ; 22, Palato-maxillary foramen ; 23, Palatine process of superior maxil- lary bone with suture ; 24-, Ditto of premaxillary bone ; 25, Premaxillary bone ; 26, Upper incisor teeth ; 27, Point of junction of the premaxillary with the superior maxil- lary bone ; 28, Upper molar teeth — young mouth. THE HEAD. 47 towards each other at their inferior extremity, which is flattened from before to behind, these bones, though irregular in shape, offer for study two faces, two borders, and two extremities. Faces. — The external face of the palate bone is divided into three frac- tions, a superior, or orbital, an inferior, or 'palatine, and a middle, or articular. The first is smooth and slightly excavated, and participates in the forma- tion of the maxillary hiatus ; it shows a small fissure, the staphyloid, which reaches the palatine fraction in passing between the posterior border of the bone and the alveolar tuberosity. The second is not extensive, and looks backwards in consequence of the antero-posterior flattening which the bone presents at its inferior extremity ; it forms part of the roof of the palate. The third presents a lamellar and denticulated surface which corresponds to a similar face on the supermaxillary bone, and is channeled from above to below by the internal fissure of the palatine canal. The internal face, smooth and concave, forms part of the external wall and the floor of the nasal fossa. Borders. — The anterior is indented, near its superior third, by a deep notch, which is often converted into a foramen, the nasal. Below this notch the bone is thin and denticulated for union with the supermaxillary bone ; above, its two plates separate widely from one another, giving rise to a very spacious cavity which forms part of the sphenoid sinus. The posterior border presents, above, a rugged crest called the palatine, flattened from side to side, bent outwards, and bordered at its base and inwards by a very narrow synarthrodial surface which responds to the pterygoid bone. It is smooth and concave in its inferior half, and forms, with that of the opposite side, a parabolic arch which circumscribes, below and at the side, the double guttural orifice of the nasal cavities. Extremities. — The superior, flattened on both sides, is bevelled on the external side to articulate with the subsphenoidal process. The inferior, flattened from before to behind, is curved inwards and united by simple suture with that of the opposite bone. Structure and development. — This is a very compact bone, developed from a single centre of ossification. 4. Pterygoid Bone.1 A small and very narrow bone, elongated from above to below, flattened on both sides, and situated on the inner aspect of the subsphenoidal process, but external to the vomer. Its external face is in contact with the palate and sphenoid bones ; the internal is smooth and covered by the pharyngeal mucous membrane. Its superior extremity is tapering, and concurs in forming the vidian canal ; the inferior is thickened into a small pointed process (the hamular process), whose apex, directed backwards, offers outwardly a groove which serves as a pulley to the tendon of the tensor palati. This bone is composed entirely of compact tissue, and is developed from a single centre of ossification. 5. Zygomatic Bone. This bone, also designated the malar and jugal bone, is elongated from above to below, flattened on both sides, and irregularly triangular in shape; it is situated on the side of the face, and articulates with the supermaxillary, 1 This bone is the representative of the internal wing of the pterygoid process in Man. 48 THE BONES. lachrymal, and temporal bones. It is described as having two faces, two borders, a base, and a summit. Faces. — The external face comprises two portions separated from each other by a semicircular ledge that extends from the summit to the middle of the anterior border of the bone, and concurs to form the outer margin of the orbit. The anterior portion, smooth and concave, belongs to the orbital cavity. The posterior, more extensive, is also smooth and slightly convex. The internal face is excavated in its central part, which corresponds to the maxillary sinus. On its margin it shows dentations and lamellae for articu- lation with the supermaxillary bone. Borders.- — The anterior, thin and denticulated, is joined to the lachrymal bone. The posterior, or masseteric border, is thicker, and constitutes a roughened crest, the zygomatic ridge, which is continued above with the posterior border of the process of the same name, and below with the maxillary spine.1 Base and summit. — The base, very thin, is united to the supermaxillary bone. The summit, flattened from before to behind and bevelled on its anterior face, joins the zygomatic process, and forms with it the jugal bridge or zygomatic arch. Structure and development. — This bone is rather spongy in its upper part, and is developed from a single nucleus of ossification. 6. Lachrymal Bone. A small, thin, and very light bone, bent on itself at a right angle, it is situ- ated beneath the orbit, which it aids in forming, and is wedged between the frontal, nasal, supermaxillary, and zygomatic bones. It is studied on its external and internal faces and circumference. Faces. — The external is divided into two regions, superior and inferior, by a curved crest which forms part of the orbital margin, and is provided with notches, which are variable in their form and number. The superior region, named the orbital, because of its situation in the orbit, is slightly concave and smooth. It presents, near the orbital margin, the orifice of the lachrymal duct, which traverses the maxillary sinus and opens on the internal face of the supermaxillary bone, where it is continued by a fissure ; behind this is the lachrymal fossa. The inferior or facial region is slightly bulging, and provided sometimes with a tubercle of insertion, the lachrymal tubercle. The internal face is employed, for the whole of its extent, in the formation of the walls of the maxillary and frontal sinuses ; it exhibits a cylindrical prominence produced by the bony tube of the lachrymal duct. Circumference. — This is very irregular and denticulated to respond to the neighbouring bones. Structure and development. — This bone is entirely compact, and is developed from a single nucleus of ossification. 7. Nasal Bones. Situated on the anterior aspect of the head, these bones articulate with each other in the median line, and are fixed between the frontal, lachrymal, and supermaxillary bones; they are triangular in shape, elongated from above to below, flattened from before to behind, and offer for study two faces, two borders, a base, and a summit. Faces. — The external or anterior face, larger above than below, is convex 1 The designation of zygomatic crest is often given to these three parts collectively. TEE EEAD. 49 from side to side and almost smooth. The posterior, internal, or nasal face exhibits a ver- tical crest passing along the external border of the bone, which gives attachment to the nated portion of the ethmoid; at its supe- rior extremity this crest bifurcates, and between its two branches shows a concave surface which forms part of the frontal sinus. For the remainder of its extent the internal face is smooth, and covered by the mucous membrane of the nasal fossa ; it is also excavated into a channel to form the superior meatus of this cavity. Borders. — The external border is very thin in its upper two-thirds, and articulates with the lachrymal bone, the anterior border of the supermaxillary, and the upper extremity of the premaxillary bones. In its lower third it becomes isolated from the latter bone, in forming with the anterior border of its large process a very acute re-entering angle whose opening looks downwards. The internal border is denticulated to correspond with the opposite bone. Base and Summit. — The base occupies the superior extremity of the bone; it describes a curved line with the convexity above, and in uniting on the median line with that of the opposite bone, forms a notch similar to that of the heart figured on playing cards; it is bevelled at the expense of the internal plate to articulate with the frontal bone. The summit of the two nasal bones, which is pointed, constitutes the nasal prolongation: the name given to a single triangular process which comprises all that portion of the nasal bones separated from the premaxillaries by the re- entering angle before mentioned. Structure and development. — Almost entirely compact in structure, it is developed from a single centre. 8. Turbinated Bones. The turbinated bones, two on each side, represent two irregular bony columns, wider above than below, compressed laterally, hol- lowed internally, and lying vertically side by side on the external wall of the nasal fossa, which they divide into three meatuses or pas- sages. They are distinguished into anterior and posterior turbinated bones. The anterior or superior, also named the Fte. 22. ANTERO-POSTERIOR AND VERTICAL SECTION OF THE HORSE'S HEAD. 1, Condyloid foramen ; 2, Parietal protuberance ; 3, Internal audi- tory hiatus ; 4, Cerebral cavity ; 5, Cerebellar cavity ; 6, Supe- rior border of the perpendicular plate of the ethmoid bone (crista- galli process) ; 7, Ethmoidal volutes— nasal face ; 8, Vestiges of the right frontal sinus •, 9, Ditto of the sphenoidal sinus ; 10, Pterygoid process; 11, Eth- moidal turbinated bone; 12, Maxillary turbinated bone; 13, Crest of the supermaxillary bone to which the latter is fixed ; 14, Vomer. — A, Orifice of com- munication between the nasal cavity and the sinus. 50 Fig. 23. THE BONES. ethmoidal, is formed by a very thin plate of compact tissue, fragile and like papyrus, fixed by its anterior border to the internal crest of the nasal bone, and rolled on itself, from before to behind, in the same manner as the cells of the ethmoid bone. Above, it is confounded with the last- named bone, of which it is only, properly speaking, the most anterior volute. At its inferior extremity, it is prolonged by a fibro-cartilaginous framework to the ex- ternal orifice of the nose. Its internal cavity is partitioned by a transverse plate into two portions: the superior compartment forms part of the frontal sinus ; the inferior is subdivided by other small lamellae into a variable number of cells which communicate with the nasal cavity. This bone, developed from a single nucleus, is ossified at the same time, and in the same manner, as the ethmoidal cells. Before birth, it is already intimately consolidated with the nasal bone. The posterior, inferior, or maxillary turbinated bone resembles the first, except in some particulars. Thus, its bony or proper portion is not so long or volu- minous, while its cartilaginous part is, on the contrary, more developed. It is at- tached, by its posterior border, to the ver- tical and sinuous crest of the super- maxillary bone, and is rolled from behind to before, or in an inverse direction to the other. It has no connection with the ethmoid, and its superior cavity forms part of the inferior maxillary sinus. It is late in becoming ossified, and is scarcely united in a definite manner to the max- illary bone until the horse is about a year old. The meatuses are distinguished into anterior or superior, middle, and posterior fissure; 5, Origin of the' supersphe- or inferior. The first passes along the front of the ethmoidal turbinated bone; the second separates the two turbinated bones, and presents, near its superior extremity, the opening communicating between the sinuses and the nasal cavi- LONGITUDINAL AND TRANSVERSE SEC- TION OF THE HORSE'S HEAD, SHOW- ING THE FLOOR OF THE CRANIAL AND NASAL CAVITIES, WITH THE MAXILLARY SINUSES. Condyloid foramen ; 2, Section of the parieto-temporal canal ; 3, Occipito- spheno-temporal hiatus; 4, Carotid notch ; 4', Maxillary notch. — a, Supermaxillary fissure ; o, Carernous noidal canals.— c, Sella turcica ; Q> Optic fossa; 7, Portion of the crista-galli process; 8, Cribriform plate of the ethmoid bone ; 9, Per- pendicular plate of the same bone; 10, 10, Its lateral masses; 11, Inte- rior of the great ethmoidal cell; 12, 12, Bottom of the maxillary sinuses communicating with the sphenoidal sinuses; 13, Supe> rior maxillary sinus ; 14, Inferior maxillary sinus ; 14', Superior compartment of the max- illary turbinated bone, forming part of the latter sinus; 15, Section of the supermaxillo dental canal; 16, Channel of the vomer; 17, Internal process, or point of the premax- illary bone. TEE HEAD. 51 ties.1 The third is situated behind the maxillary turbinated bone, and is confounded with the floor of the nasal fossa. The turbinated bones are essentially destined to furnish the membrane of the nose with a vast surface of development. This membrane, indeed, covers their entire superficies, and even penetrates the anfractuous cells of their lower compartment. 9. Vomer. This, a single bone, elongated from above to below, flattened on both sides, and extending on the median line from the body of the sphenoid to the premaxillary bone, offers for study two lateral faces, two borders, and two extremities. The faces are smooth, plane, and covered by the nasal membrane. The anterior border is channeled for the whole of its length by a deep groove which receives the posterior border of the cartilaginous septum of the nose. The posterior border is sharp and smooth in its upper half, which separates the two guttural openings of the nasal cavities: it is thick and slightly denticulated for the remainder of its extent, and rests on the median suture resulting from the union of the two supermaxillary bones. The superior extremity is provided, in its middle, with a notch which divides it into two lateral prolongations shaped like a cat's ears; it articulates with the inferior sphenoid, ethmoid, palate, and pterygoid bones. The inferior extremity rests on the prolongations of the incisive bones. This bone is entirely compact, and is developed from one centre of ossification. 10. Inferior Maxillary Bone. The maxillary bone is not consolidated with any of the preceding bones, and is only united to two of them, the temporals, by diarthrodial articula- tion. It is a considerable bone, situated behind the upper jaw, and composed of two symmetrical branches, which are flattened on both sides, wider above than below, curved forwards in their upper third, joined at their lower extremities, and separated superiorly so as to leave a wide gap between them, like the letter V in shape, called the intramaxillary space. Each offers for study two faces, two borders, and two extremities. Faces. — The external face of the maxillary branches is smooth and rounded in its inferior two-thirds, and transformed superiorly into a rugged surface, in which is implanted the fibres of the masseter muscle. The internal face presents, in the corresponding point, an excavated surface on which is remarked the superior orifice of the maxillo-dental canal, a long channel which descends between the two plates of the branch, passing under the roots of the molar teeth, and insensibly disappearing in the body of the bone after being widely opened externally by the mental (or anterior maxillary) foramen. In its inferior two-thirds, the internal face is smooth, nearly plane, and shows nothing very remarkable. Near the alveolar border there is a slightly-projecting line — the myloid ridge; and quite below, or rather at the very summit of the re-entering angle formed by the separation of the branches, there is a slight rugged excavation confounded with that of the opposite branch, and named the genial surface. Borders. — The anterior, also named the alveolar border, exhibits for study a straight or inferior, and a curved or superior portion. The first is hollowed by six alveoli to receive the inferior molar teeth. 1 The two turbinated bones, in being applied against the excavation on the inner face of the supermaxillary, almost entirely close it, only leaving between them a vertical filit which constitutes the opening mentioned above. 52 THE BONES. The second, thinner, concave, and rugged, serves for muscular insertion. The posterior border is also divided into straight and curved portions. The latter is convex, thick, rugged, and margined on each side by an uneven lij) ; the first is regularly rectilinear, so that all its points rest at the same time on a horizontal plane; it is thick and rounded in the young animal, but becomes sharp with age ; an oblique and transverse fissure — the maxillary — separates it from the curved part. The union of these two portions forms the angle of the jaw. Extremities. — The superior extremity has two eminences : a condyle, and a long non-articular process named the coronoid process. The condyle is elongated transversely, and convex in its two diameters ; it responds, through the medium of a fibrocartilaginous disc, to the articular surface of the zygo- matic process. The coronoid process is situated in front of the condyle, from which it is separated by a division called the sigmoid or corono-condyloid notch ; it is flattened on both sides, and curved backwards and slightly inwards. Fig. 24. INFERIOR MAXILLA. 1, Mental foramen ; 1', Superior orifice of the maxillo-dental canal ; 2, Surface ot implantation for the masseter muscle ; 3, Myloid ridge j 4, Coronoid process ; 5, Condyle. From the union of the branches of the maxillary bone at their inferior extremity results a single piece, flattened before and behind, and widened like a spatula, which has been designated the body of the bone. This merits a special description. Its form allows us to divide it into an anterior or buccal face, a posterior or labial face, and a circumference. The anterior face is smooth and concave, is lined by the buccal mucous membrane, and supports the free extremity of the tongue. The posterior face is convex, more extensive than the preceding, and continuous with the external face of the branches ; it presents : 1, On the median line, a slight crest or small groove, traces of its being originally separated into two pieces ; 2, On the sides and above, the mental foramen, the inferior orifice of the maxillo-dental canal. On a level with this foramen, the bone very markedly contracts to form the neck. The circumference describes a parabolic curve, the concavity being uppermost, and joins, by its extremities, the anterior border of each branch. It is excavated in its middle j)art by the six alveoli for the lodgment of the THE HEAD. 53 inferior incisors, and behind these, in male animals only, there is an additional alveolus for the tusk. The portion included on each side between the last incisor and first molar, forms a more or Jess sharp ridge, which constitutes the inferior interdental space or bars. Structure and development— formed, like all the flat bones, by two compact plates separated by spongy tissue, the inferior maxilla is developed from two centres of ossification, which correspond to each branch, and which coalesce some time after birth. 11. — The Ryoid Bone. The hjoid bone constitutes a small and special bony apparatus which serves to support the tongue, as well as the larynx and pharynx; its description is placed immediately after that of the bones of the head because of its connection with that region, it being situated between the two branches of the supermaxillary bone, and suspended to the base of the cra- nium in an oblique direction from above to below, and from before to behind. This apparatus is composed of seven distinct pieces, arranged in three series : a middle, constituted by a single bone, and named the body ; two lateral, forming two quasi-parallel branches, to the extremities of which the body is articulated. Body. — The body of the hyoid resembles a fork with two prongs. It presents : 1, A middle part flattened above and below, and consequently pro- vided with a superior and an inferior face : 2, A single and long prolongation flattened on both sides, which is de- tached from the middle part, and directed forward and downward to plunge into the muscular tissue of the tongue : this is the anterior appendix of the hyoideal body ; 3, Two lateral cornua, thyroid cornua, or great cornua, pro- jecting backwards and up- wards, articulating by their extremities with the thyroid Fig. 25. HYOID BONE. 1, Superior extremity of the styloid bones , 2, Angle described by their posterior border ; 3, 3, Styloid bones ; 4, 4, Extremities qf the thyroid cornua ; 5, Articular surface of the body corresponding with the small branches ; 6, Anterior appendix of the body ; 7, 7, Small branches, or styloid cornua. cartilage of the larynx, and offering, at their point of union with the middle part, two convex diarthrodial facets looking upwards, and corre- sponding with the styloid cornua. The body of the hyoid bone is developed by three centres of ossification, a middle, and two lateral for the cornua. Branches. — The three pieces composing these are articulated end to end, by means of a cartilaginous substance that joins them together ; they are of very unequal dimensions. The first, which is in relation with the body, is of medium size, and is named the styloid cornu, small cornu, or small branch. The second, termed the styloid nucleus, is the smallest. The third, the largest, constitutes the styloid process, or bone, or great branch. 1. The styloid cornu is a small cylindrical piece bearing a concave diarthrodial surface on its inferior extremity to unite it to the body ; it is very spongy, and is developed from two ossifying centres, one of which, the epiphysary, is for the inferior extremity. 2. The styloid nucleus, which is often absent, is imbedded in the uniting cartilaginous substance. V 51 THE BONES. 3. The styloid "bone, or great hyoideal branch, is long, thin, flattened on both sides, and directed obliquely from above to below, and before to behind ; it presents two faces, two borders, and two extremities. The faces — an external and internal — are marked by some few imprints. The anterior border is sharp and slightly concave in its upper third. The posterior border is thicker, and is divided into two portions : a superior or horizontal, which is very short, and an inferior or vertical, much more extensive. The angle they form at their point of junction presents a salient, and more or less roughened, tuberosity. The superior extremity is united to the hyoideal prolongation of the temporal bone by means of a cylindrical fibro-cartilage. By its inferior extremity, the styloid bone is united either to the styloid nucleus or the styloid cornu, forming a sharp elbow directed forwards. The styloid bone, developed from a single centre of ossification, is almost entirely formed of compact tissue. OF THE HEAD IN GENERAL. From the union of all the bones which constitute the cranium and face results a quadrangular pyramid, whose summit is inverted, which it is necessary to study as a whole. We will pass in review, successively, its four faces, its base, and its summit. Anterior Face. — The anterior aspect of the head has the parietal, frontal, and nasal bones for its base. Superiorly, it inclines backwards and offers, on each side of the parietal ridges, two bulging surfaces which form part of the temporal fossae. For the remainder of its extent, it presents a plane surface which forms the base of the forehead and the middle portion of the face. Wide above, this surface gradually tapers to the extremity of the nasal spine. In well-formed animals, it is as straight and wide as possible. Posterior Face. — This face, which is extremely irregular, presents : above, the basilar process, the lacerated foramina, and the base of the tuberous portion of the temporal bones ; then the intramaxillary space, and, at the bottom of this, the body of the sphenoid bone, vidian fissure, superior orifice of the subsphenoidal canal, sphenoidal process, palatine ridges, pterygoid bones, guttural openings of the nasal cavities separated from one another by the posterior border of the vomer, roof of the palate, incisive openings, and the incisive foramen. Lateral Faces. — These exhibit : behind, the external face of the maxillary branches ; before, a surface more or less convex, though sometimes hollow in old animals, presenting at its middle the inferior orifice of the maxillo- dental canal, and forming the base of the lateral parts of the face ; above, the zygomatic ridge and arch, the orbit, and the temporal fossa. These two cavities, in the formation of which many bones participate, have been hitherto merely indicated ; this is the place for giving them a more detailed description. The orbit or orbital cavity is irregularly circular in outline, and circumscribed by the orbital process of the frontal bone, the lachrymal and malar bones, and the summit of the zygomatic process. At the bottom, which shows the maxillary and orbital hiatus, it is confounded, in the skeleton, with the temporal fossa.1 It lodges the globe of the eye and the muscles which move it. Some organs, accessory to the visual apparatus, * A fibrous membrane, the ocular sheath, isolates it from the temporal fossa in the majority of mammiferous animals. Only in Man and the quadrumana has the orbital cavity complete bony walls. THE HEAD. 55 such as the lachrymal gland and the membrana nictitans, are also contained in this cavity. The temporal fossa surmounts the orbit, and is incompletely separated from it by the orbital arch (or process). Oval in shape, lying obliquely from above to below, and from within outwards, on the sides of the cranium the temporal fossa is limited, within, by the parietal ridge, and outwardly bv the anterior border of the longitudinal root of the zygomatic process. It lodges the temporal muscle. Base or superior extremity of the head.— This presents the occipital pro- tuberance, cervical tuberosity, occipital foramen, mastoidean ridge and fissures styloid processes of the occipital bone, stylo-condyloid notches, and the con- dyles. On a lower plane, and behind, the curved portion of the posterior border of the maxillary bone is remarked. Summit,— Formed by the premaxillary bones and the body of the super- Fig. 26. LATERAL VIEW OF THE HORSE S SKULL. 1, Premaxillary bone ; 2, Upper incisors ; 3, Upper canine teeth ; 4, Superior maxillary bone ; 5, Infraorbital foramen ; 6, Superior maxillary spine ; 7, Nasal bones; 8, Lachrymal bone; 9, Orbital cavity; 10, Lachrymal fossa; 11, Malar bone ; 12, Upper molar teeth ; 13, Frontal bone; 15, Zygomatic process, or arch; 16, Parietal bone; 17, Occipital protuberance; 18, Occipital crest; 19, Occipital condyles; 20, Styloid processes; 21, Petrous bone; 22, Basilar process; 23, Condyle of inferior maxilla ; 24, Parietal crest ; 25, Inferior maxilla ; 26, Inferior molars ; 27, Anterior maxillary foramen ; 28, Inferior canine teeth ; 29, Inferior incisor teeth. maxilla, the summit supports the incisor teeth, and presents a tuberosity more or less rounded, according to the age of the animal. In front, it is surmounted by the external opening of the nasal cavities; this opening, which is comprised between the external process of the premaxillary bones and the nasal spine, is divided in the fresh state into two orifices which constitute the nostrils. Internally, the head contains the nasal fossce and the cranial cavity. These will be described when the apparatus belonging to them is noticed. (See the respiratory and nervous apparatus). DIFFERENTIAL CHARACTERS OF THE HEAD IN OTHER THAN SOLIPED ANIMALS. A. Head of the Ox, Sheep, and Goat. — 1. Occipital bone. — The occipital bone in these animals docs not show any anterior elbow. The cervical tuberosity, or occipital 56 THE BONES. protuberance is obtuse, and gives rise on each side to the superior curved lines ; in the Sheep, these curved lines are very salient and occupy the summit of the head. The styloid processes are short and much bent inwards. The basilar process, wide, short, and thick, has a groove in the middle of its external face ; this groove is sometimes absent in the Sheep and Goat. The condyloid foramina are double, sometimes triple ; the superior foramen does not pass directly into the cranium, but goes to a vast conduit that opens behind on the lateral margin of the occipital foramen, and which terminates in front by two orifices, one entering the parieto-temporal canal, the other opening on the external surface of the bone. The foramen lacerum is divided into an anterior and posterior foramen by the mastoid portion of the temporal bone. Parietal bone.— The parietal bone in the Ox does not occupy the anterior aspect Fig. 27. ox's head; anterior face. 1, Mastoid process; 2, Superciliary, or supra-orbital foramen; 3, Zygoma; 4, Lachrymal bone ; 5, Maxillary spine ; 6, Inferior orifice of the supermaxillo-dental canal. of the head, but concurs with the occipital to form the base of the neck. It represents a very narrow osseous plate, elongated transversely, and curved at its two extremities, which descends into the temporal fosssp to rest upon the sphenoid bone. There are no parietal ridges. The internal protuberance is only marked by a slight elevation of the internal plate : for the most part it belongs to the occipital bone. The parietal bone of the Ox is developed from three centres of ossification, and the middle nucleus is even primarily divided into lateral halves ; but these centres are consolidated with each other at an early period, as well as with the anterior portion of the occipital. It does not aid in the formation of the parieto-temporal canal, and is excavated internally by cavities which communicate with the frontal sinuses. The parietal bone of the Sheep and Goat is relatively much larger than that of the Ox. It participates in the formation of the parieto-temporal canal, and has no sinuses. 3. Frontal bone. — In ruminants, the frontal bone does not respond to the temporal and palate bones. In the Ox, this bone is extremely developed, by itself occupying the anterior half of the THE HEAD. 57 face. It is particularly distinguished by : — 1, Its great thickness. 2, The osseous conical cores which support the horns. These eminences, more or less long and curved, very rugged, perforated by foramina, and grooved by small vascular channels, are detached outwards from each side of the bone, near the summit of the head. The processes which form the orbital arches rest by their summits on the zygomatic bone. The supra-orbital foramen is transformed into a veritable and frequently multiple canal; its anterior orifice opens into a vasculo-nervous groove, which ascends towards the base of the horns, and descends to near the lower border of the bone. Between this groove and the base of the orbital arch is the frontal boss. The orbital foramen entirely belongs to this bone. The inferior border is deeply notched in its middle to receive the nasal bones , the frontal sinuses are prolonged into the horn-cores, the parietal bone, and even into the occipital bone. In the Sheep and Goat, the frontal bone is relatively less extensive and strong than in the Ox ; it does not ascend to the summit of the head, and the frontal sinuses are not prolonged beyond its superior border. 4. Ethmoid bone. — In ruminants, the great ethmoidal cell is enor- mously developed, and looks like a third turbinated bone prolonged be- tween the usual two; it has been named the olfactory antrum. The ethmoid bone is closely im- prisoned between the adjacent bones, in consequence of the slight develop- ment of the siuuses around it. This character otherwise belongs to all the domesticated animals, except soli- peds. 5. Sphenoid bone. — In the Ox, the subsphenoidal or pterygoid pro- cesses are large and thin. The sub- sphenoidal canal is absent. The sella turcica is deep, and the bony projection separating it from the basilar process is very high. The three suprasphenoidal canals are converted into a single, but wide one. There are no notches in the superior border for the passage of the internal carotid and spheno- spinous arteries. That for the in- ferior maxillary nerve is converted into a canal — the oval foramen. In the Sheep, the osseous promi- nence that limits the pituitary fossa posteriorly forms a lamina curv- ing forwards and prolonged at its ex- tremities into two points, which constitute the posterior clinoid pro- cesses. 6. Temporal bone. — In the Ox, Sheep, and Goat, the tuberous portion of the temporal bone is always con ■ solidated with the squamous portion, and the summit of the zygomatic process only articulates with the malar bone. In the Ox, the condyle of the zygomatic process is very wide and convex in every sense. The parieto-temporal canal is very large and entirely excavated in the temporal bone ; its superior or internal extremity opens above the petrous portion in an excavation which represents the lateral cavity of the parietal protuberance in the Hor>e ; at its inferior extremity it always shows several orifices. The mastoid process is very salient, and belongs to the squamous portion. The mastoid crest is confounded with the upper root of the zygomatic process ; inferiorly, it ram's head; anterior face. 1, Occipital bone ; 2, Parietal bone; 3, Core of right frontal bone ; 4, The left core covered by its horn ; 5, Superciliary foramen ; 5', Channel descending from it ; 6, Lachrymal bone ; 7, Zygoma ; 8, Nasal bone; 9, Supermaxillary bone; 10, Premaxillary bone; 10', Its internal process; 11, Incisive open- ing. 58 THE BONES. surpasses the mastoid process, and is prolonged to the mastoid protuberance. The latter is very voluminous. The subuliform process is larger and stronger than in the Horse ; and there is no mastoid fissure. In the Sheep and Goat, the mastoid process is scarcely distinct from the crest ; and the mastoid portion of the bone is only at a late period consolidated with the petrous portion. Fia. 29. OX'S HEAD; POSTERIOR FACE. A, Parietal bone. — 1, Occipital foramen ; 2, Occipital condyle ; 3, Styloid process of that bone ; 4, Condyloid foramina ; 5, Mastoid process ; 6, Mastoid protuber- ance ; 7, Subuliform (temporal) process ; 8, Hyoideal sheath ; 9, Stylo-mastoid foramen; 10, External auditory hiatus; 11, Inferior orifice of the parietotem- poral canal; 12, Temporal condyle; 13, Posterior foramen lacerum ; 14, Oval foramen ; 17, Subsphenoidal process ; 18, Orbital hiatus ; 19, Optic foramen. — B, Frontal bone. — 20, Superciliary foramen; 21, Orbital foramen; 22, Lachrymal protuberance. — C, Zygoma. — 23, Pterygoid bone. — D, Palate bone. — 24, Nasal fora- men ; 25, Inferior orifice of the palatine canal. — E, Supermaxillary bone. — 26, Maxillary spine. — G, Premaxillary bone. — 27, Its internal process ; 28, External process ; 29, Incisive openings. 7. Supermaxillary bone. — In the Ox, Sheep, and Goat, the maxillary spine does not directly join the zygomatic crest a curved line, whose concavity is posterior, effects the union between these two parts. The inferior orifice of the supermaxillo-dental canal or infraorbital foramen is pierced above the first molar tooth. There is no fissure for the formation of the palatine canal. The cavity of the sinus is more spacious than in the Horse, and is prolonged (in the Ox only) between the two laminae of the palatine roof. There is no alveolus for the tusk. 8. Premaxillary bone. — The inferior or principal portion of this bone is flattened before THE BEAD. ED and behind, and deprived of aveoliin its external border; neither. is there any incisive foramen. It is rarely consolidated with the adjacent bones, and is never, in the smaller ruminants, articu- lated with the nasal bone. 9. Palate bane. — This bone is very developed in the Ox, and noticeable for the considerable extent of the palatine portion of its external sur- face. The palatine canal is entirely channeled out in its substance. The palatine crest, very thin and elevated, is formed altogether by the posterior border of the palate bone, the ptery- goid, and the subsphenoidal process. There is no excavation for the sphenoidal sinuses; but, instead, all that part of the bone which enters into the roof of the palate is hollowed by irre- gular cavities which communicate with the max- illary sinus of the same side. The nasal foramen is very wide. In the Sheep and Goat, the maxil- lary sinuses do not extend to them. 10. Pterygoid bone. — The pterygoid of the Ox, Sheep, and Goat is very large, and closes an aper- ture left between tlie sphenoid and palate bones. 11. Zygoma. — The jugal bone of Ruminant* is very developed. The zygomatic crest is no longer formed by the posterior border of the bone, but is carried to the posterior part of the external face, and runs parallel with the eyebrow. The summit is bifurcated, the anterior branch form- ing a buttress against the summit of the orbital process of the frontal bone, while the posterior articulates with the temporal. 12. Lachrymal bone. — The lachrymal bone, much more extensive than that of the Horse, forms in the bottom of the orbit an enormous protube- rance, hollowed internally by the maxillary sinus, and whose walls are so thin and fragile that the slightest jar is sufficient to cause their fracture (in the skeleton). It would be convenient to designate it the lachrymal 'protuberance.1 In the smaller ruminants, the inferior region of the exter- nal face shows a depression, the lachrymal fossa. 13. Nasal bones. — The nasal bones of the Ox are never consolidated with each other, nor yet with the neighbouring bones. The external border only comes in contact to a small extent with the supermaxillary bone; the superior extremity is fixed in the notch of the inferior border of the frontal bone. At their inferior extremity, they each present a notch which divides them into two points. In the Sheep and Goat the nasal spine is unifid, as in the Horse. 14. Turbinated bones. — In the Ox, the eth- moidal turbinated bone is very small, and united to the nasal bone by the two borders of its osseous plate ; its internal cavity entirely belongs to the frontal sinus. The maxillary turbinated bone is very developed, and is joined to the bone which sustains it at a later period than in the Horse. The bony lamina of which it is composed is curved 1 Girard, who named this eminence the orbital protuberance, wrongly described it as belonging to the supermaxillary bone. Fisr- 30. MEDIAN AND VERTICAL SECTION OF THE OX'S HEAD. 1, Condyloid foramen; 1', Posterior ori- fice of the occipital lateral canal joining the parieto-temporal canal in front ; 2, Internal auditory hiatus ; 3, Anterior foramen lacerum ; 4, Pos- terior ditto; 5, Intra-cranial orifice of the parieto-temporal canal ; 6, «>, Median bony plate separating the frontal sinuses; 7, Lamina which iso- lates the sphenoidal sinus ; 8, Lamina partitioning the palatine portion of the maxillary sinuses ; 9, Oval fora- men; 10, Optic fossa; 11, Vomer;: 12, Pterygoid bone; 13, Large open- ing leading into the maxillary sinws, and which, in the fresh state, is closed by the pituitary membrane ; 14, Max- illary turbinated bone , 15, Ethmoidal turbinated bone; 16, Great ethmoidal cell. 60 THE BONES. Fie. 31. on itself in two different directions : from before to behind by its posterior border, and behind to before by its anterior border. It is fixed to the supermax ijlary bone by its middle part, through the medium of a particular bony lamina, and it very incompletely closes the excavation which concurs to form the maxillary sinus. In the skeleton there is also found behind, and at the base of this turbinated bone, a vast opening which is totally closed in the fresh condition by the pituitary membrane. The maxillary sinus is not prolonged in its interior. In the smaller ruminants, the cavity of the sinus is closed by the maxillary turbinated bone in a more complete manner than in the Ox. 15. Vomer. — This is a very large thin bone, resting only on the inferior half of the median suture of the premaxillaries. 16. Premaxillary bone. — In the Ox, the inferior part of the posterior border is convex, and cannot rest on a horizontal plane by all its points at the Siime time. The condyle is convex in its small diameter, and slightly concave laterally. The coronoid process is bent backwards and outwards. The body does not show any alveolus for the tusk, because this tooth is absent in these animals; but it is hollowed by eight alveoli for the incisor teeth. The two branches of the bone are never consolidated, but remain movable on each other during life. 17. Hyoid bone. — The hyoid bone of Ruminants is always composed of seven pieces; the styloid nucleus, whose presence is not constant in solipeds, is never absent in these, and assumes the proportions of a second small branch. The anterior appendix is very short and thick. B. Head of the Pig. — 1. Occipital bone. — The occipital bone in this animal is not bent anteriorly ; but the transverse protuberance representing the curved lines forms, nevertheless, as in the Horse, the summit of the head. This eminence, which is excavated on both sides on the posterior face, unites in front with the parietal bone, which abuts on the occipital at an acute angle. There is no external occipital protuberance, properly speaking, and the styloid processes are very long and directed downwards. 2. Parietal bone. — This bone is very thick, and deprived of an internal protuberance. The process concurring to cir- cumscribe the orbit is short, and joins neither the zygomatic or temporal bones; the orbital arch is completed by a liga- ment. The superciliary foramen, disposed as in the Ox, opens in front into a channel that descends to the nasal bones. The orbital foramen is formed by the frontal bone only. There is no mortice for the union of the frontal with the sphenoid bone, and the maxillary sinus is prolonged into the parietal bone. The frontal bone of the pig articulates with the super- maxillaries. 1 Summit of occipital pro- & Frontal bone. — The frontal bone of the Pig is very thick tuberance • 2 Parietal an& short, and does not join the t mporal or zygomatic bone ; bone; 3, Frontal bone. the orbital arch is completed by a ligament. The superciliary foramen, disposed as in the Ox. abuts in a channel that descends on the nasal bones. The orbital foramen is formed by the frontal bone only. There is no mortice for the union of the frontal with the sphenoid bone ; and the frontal sinuses are prolonged into the parietal. The frontal bone of the Pig articulates with the supermaxillaries. 4. Sphenoid bone. — The sphenoid of the Pis' is very short, but illary bone. — c. Inferior the subsphenoidal processes are extraordinarily developed and orifice of the supermax- flattened before and behind. There is no subsphenoidal canal, illo-dental canal ; 8, and the sella turcica is deep, and limited behind by a very salient Nasal bone ; 9, Pre- crest. A single canal replaces the foramen rotundum and the maxillary bone. great sphenoidal fissure, as in the Ox. The wings, slightly salient, are articulated by suture with the frontal bone. 5. Temporal bone. — The articular surface of this bone resembles that of rodents ; it is not limited posteriorly by a subcondyloid eminence, and, in addition, offers a wider transverse surface. The zygomatic process articulates with the jugal bone by the whole extent of its posterior border. A crest leading from the external auditorv hiatus to the HEAD OF THE PIG: ANTERIOR FACE. —A, Superciliary fora- men ; a' Channel des- cending from it. — 4, Zygomatic process ; 5, Zygoma; 6, Lachrymal bone. — B, Lachrymal canals. — 7, Supermax- THE HEAD. Gl Fig. 32. mastoid protuberance replaces the mastoid process. The mastoid crest is, as in the Ox confounded with the superior root of the zygomatic process. The proj( ction formed by the mastoid protuberance is enormous. The subuliform process is little marked, and there is no hyoideal prolongation or parieto-temporal canal. 6. Supermaxillary bone. — In the Pig, the ex- ternal surface of this bone is hollowed in its middle, and presents in front a voluminous relief formed by the alveolus of the canine tooth. The cavity is entirely formed in the supermaxilla. There is no alveolar tuberosity, and the interdental space is very short, while the cavity for the sinus is little developed. The lower orifice of the palatine canal is even pierced in the substance of the super- maxilla. 7. Premaxillary lone. — The external process of the premaxillary bone is very long and wide at its base, and consolidated with the nasal bone for about the upper two-thirds of its length. There is no incisive foramen or cavity for the tusk. The incisive openings are oval. 8. Palate bone. — The palatine portion of the ex- ternal face is more developed than in the Ox, but the orbital portion is very limited. The palatine crest is r( placed by a tuberosity, against which rests, outwardly, the subsphenoidal process, and inwardly, the pterygoid bone. The union of these three parts constitutes, on the posterior surface of the head, a thick and very remarkable trifid pro- jection or mamelon. 9. Pterygoid bone. — See the description of the palate bone. 10. Zygomatic bone. — The summit of this bone in the Pig is flattened on each side, and divided into two blanches, between which is wedged the summit of the zygomatic process; the anterior branch is very short, and does not join the frontal bone. 11. Lachrymal bone. — In the Pig there are ob- served a lachrymal fossa and two lachrymal canals, which are pierced outside the orbital cavity, and soon coalesce in the substance of the bone to consti- tute a single canal. The fossa is very deep. 12. Nasal bones. - These bones are long and nar- row, and traversed on their external face by the fissure that descends from the superciliary foramen. The nasal prolongation is short. 13. Turbinated bones. — The same arrangement as in the Sheep and Goat, except that they are much longer and less fragile. 14. Inferior Maxilla. — A straight line leading from the greater axis of the alveoli of the molar would not traverse the posterior border of the maxillary branches ; the bottom of these alveoli corresponds to the relief on the inner face. The condyle is compressed on both sides, and elongated from before to behind ; while the coronoid process is bhort and wide. There is no neck; the interdental spaces are very short ; and the maxiilo-dental canal opens interiorly by multiple orifices. 15. Hyoid bone.— The body is voluminous and deprived of an appendix ; the small branches are short and consolidated with the body ; while the large branches, curved like an S, are very thin, and are united to the small branches and the temporal bone no longer by fibro- cartilage, but by veritable yellow elastic ligaments. C. Head of Carnivora. — 1, Occipital bone. — The eminence which constitutes the HEAD OF THE PIG ; POSTERIOR FACE 1, Occipital protuberance; 2, Occi- pital foramen; 3, Occipital con- dyle ; 4, Condyloid foramen ; 5, Basilar process ; 6, 6, Mastoid crest ; 7, Styloid process of the occipital bone ; 8, Articular surface of the temporal bone ; 9, Mastoid protu- berance; 10, Foramen lacerum ; 11, Subsphenoidal process — external wing of pterygoid process; 12, Palatine crest ; 13, Pterygoid bone — internal wing of the pterygoid process; 14, Inferior orifice of the palatine canal ; 15, 15, Incisive openings. G2 THE BONES. origin of the superior curved lines is very elevated and strong. The cervical tuberosity of the external occipital protuberance is absent or little marked ; the styloid processes are short, and well deserve the name of jugular eminences. The foramen lacerum is divided into two portions by the mastoid protuberance, and the basilar process is wide, long, and thick, and hollowed on the side by a channel that joins a similar one in the temporal bone to form a large venous canal. This last communicates, behind, with the posterior foramen lacerum, and opens, in front, in the cranium, where it is continuous with the cavernous groove of the sphenoid. The anterior angle forms a very marked prominence, which is deeply fixed into the parietal bone, and partly constitutes the internal protuberance of that bone. 2. Parietal bone. — In the Dog the parietal bone, formed by two ossific centres only, is distinguished by the great development of the ridges and the parietal protuberance. This last, constituted in part by the occipital bone, does not show any lateral excavations at its base; they are carried lower, near the summit of the petrous process, on the sides of the occipital bone. The parieto-temporal canals are continued, notwithstanding, to the base of the protuberance, which they traverse, to open into each other in its interior. In the Cat there are scarcely any parietal crests, and the internal protuberance is replaced by two great trans- verse bony plates which (separate the cavity of the cerebrum from that of the cerebellum. 3. Frontal bone. — In carnivora, the external face of this bone presents in it3 middle a more or less marked de- pression. The orbital arch is incomplete, and there is no superciliary foramen, or mortice on the inner face. The bone is united with the supermaxillaries. 4. Ethmoid bone. — The ethmoidal fossa is very deep, and the cells very developed and diverticulated. The per- pendicular lamina is at a late period consolidated with the sphenoid bone. 5. Sphenoid bone. — The superior sphenoid of the Dog is very short, and bears, laterally, two wide wings which ascend to the temporal fossa ; they correspond to those of the sphenoid bone in Man. The inferior sphenoid is, on the contrary, very narrow, and its lateral prolongations, or pro- cesses of Ingrassias, are reduced to very small proportions. The sub-sphenoidal or pterygoid process is very short, and the canal is single, and communicates with the foramen rotundum. The pituitary fossa is shallow, limited behind and before by the 'posterior clinoid and anterior clinoid processes, so named because of their being compared to the four posts of an ancient bed. The supersphenoidal canals are only two in number : one represents the great sphenoidal fissure, the other the round foramen. The carotid notch, joining a similar one in the temporal bone, forms an open- ing which may be designated the carotid foramen, because rietel crests ^5" Zygomatic >* Rives passage to an extremely remarkable loop the in- process of the temporal te™}A™otul ^^^^^^^^^^3^^^ bone ; 6, Frontal bone ; 6', Orbital process; 7, Zy- goma ; 8, Lachrymal bone •, 9, Nasal bone; 10, Super- maxilla; 11, Inferior ori- fice of the supermaxillo- dental canal; 12, Pre- maxillary bone. HEAD OP DOG; ANTERIOR FACE. 1, Occipital protuberance; 2, Median spur of the occi- pital bone ; 3, Parietal bone ; 4, Origin of the pa carotid canal. The oval foramen is the same as in the Ox. In the Gat there is the same disposition, with the ex- ception of no sphenoidal canal or carotid notch beinj; present. 6. Temporal bone. — In the carnivora, the articular sur- face of the zygomatic process merely forms a glenoid cavity, into which the condyle of the maxillary bone exactly fits. The temporal bone in these animals is also distinguished by the width of the external auditory canal, the absence of a hyoid prolongment, the small development of the mastoid and styloid processes, the enormous volume of the mastoid protuberance, and the presence of two particular canals which cannot be traced in the other animals. One of them, the carotid canal, traverses the mastoid portion, and joins, superiorly, the venous canal which passes between ihe basilar process and the temporal bone ; by its inferior extremity it joins the carotid foramen which itself penetrates the cranium, a little beyond the venous canal just mentioned. The other conduit is pierced in the petrous portion immediately above the carotid canal ; it affords a passage to the fifth pair of encephalic nerves. THE HEAD. 7. Supermaxillary bone. — In carnivora, this bone is very short ; its anterior border offers a long process analogous to the nasal spine of Man. It alone furnishes the alveolus of the tusk. The palatine canal, pieiced entirely in the bone of that name, nevertheless opens, by its inferior extremity, at the junction of the supermaxillary with the palate bone. The maxillary sinus is not very spacious, and there is no maxillary spin " Premaxillary bone. — Of little size, the premaxillary of carnivora has no incisive foramen or alveolar cavity for the canine tooth. The incisive openings are the same as in the Pig. 9. Palate bone. — In the carnivora, the palate bones are of great extent in their proper palatine portion. They have no share in the formation of the sphenoidal sinuses, but furnish a small excavation to the maxillary sinuses. 10. Pterygoid bone. — This bone is very strong in car- nivora, and quadrilateral in shape. 11. Zygoma. — The zygoma of the Dog and Cat only articulates with the supermaxillary bone by its base. The crest describes a curve backwards, and the summit com- ports itself as in the Tig. 12. Lachrymal bone. — This bone in carnivora is ex- tremely small. Its external face entirely belongs to the orbit, and does not descend beneath the margin of that cavity ; it has no lachrymal fossa. 13. Nasal bone. — The two bones of the nose are little developed, and are wider below than above; they have no nasal prolongation, but offer instead a semicircular notch. 14. Turbinated bones.— These bones in the Dog and Cat are particularly distinguished for their numerous convo- lutions. Neither participate in the formation of the frontal or maxillary sinuses ; the latter is not in any way closed by the maxillary turbinated bone, but opens into the nasal cavity by a large gaping aperture. 15. Inferior maxillary bone. — In carnivora, this is hollowed at the point corresponding to the insertion of the masseter muscle into a somewhat deep fossa. The posterior border is disposed as in ruminants, and below the condyle has a very marked tuberosity. The condyle rt presents an ovoid segment, and fits exactly into the temporal cavity. The coronoid process is very strong, elevated, and wide. The mental foramina are double or treble. There are no interdental spaces, nor excavated surface on the inner face of the branches ; and the latter are never consolidated. 16. Hyoid bone. — The three pieces composing the body of the hyoid in early life are never consolidated in the adult animal, but always remain isolated, as in Man. The middle piece has no anterior appendix; the fibro- cartilages uniting the styloid portions to each other and to the temporal bone are very long and flexible. COMPARISON OP THE HEAD OF MAN WITH THAT OF THE DOMESTICATED ANIMALS. Fig. 34 1. Occipital bone. — The occipital of Man is large, flat, incurvated like a shell, and the external protuberance is slightly developed, and united by a ridge to the occipital foramen, which is relatively very wide. Two series of ridges arise from the external protuberance and pass towards the circumference of the bone; these are the superior and inferior curved or semicircular lines. There is an anterior and a posterior condyloid fossa pierced by a foramen at the bottom ; and the jugular eminences, wide and slightly prominent, re- place the styloid processes of the domesticated animals. The internal face of the occipital of Man corresponds with the cerebrum and DOG S HEAD ; POSTERIOR FACE. 1, Occipital protuberance ; 2, Occipital foramen ; 3, Occi- pital condyle ; 4, Condyloid foramen ; 5, Styloid process of the occipital ; 6, Mastoid protuberance ; 7, Concave temporo-maxillary articular surface ; 8, Supercondy- loid eminence ; 9, Inferior orifice of the parieto-tem- poral canal ; 10, Lacer- ated foramen, posterior ; II, Ditto, anterior. — On the op- posite side at a is shown the orifice communicating with the Eustachian tube and the tympanum; at 6 the passage for the carotid convolution. — 12, Body of the sphenoid ; 13, Oval fora- men; 14, Inferior orifice of the subsphenoidal canal ; 15, Pterygoid bone; 16, Nasal surface of the palate bone; 17, Palatine surface of the same; 18, Vomer; 19, Supermaxillary bone; 20, Incisive opening. G4 THE BONES. cerebellum ; and for this purpose it shows four fossse, distinguished into superior or cerebral, and inferior or cerebellar. These fossse are separated by a crucial projection whose most developed portion forms the internal occipital protuberance. The union of the occipital with the parietal bones constitutes the lambdoidal suture. At the point where this bone meets the parietal and the squamous portion of the temporal, is found, in the infant, the lateral posterior fontanella. 2. Parietal bones. — The parietals are always isolated in early life, and sometimes consolidated with each other at the adult age. They are very large, quadrilateral, and occupy the summit and sides of the cranium. The parietal crests are absent, but are replaced individuals, by Fig. 35. FRONT VIEW OF THE HUMAN CRANIUM. 1, Frontal bone ; 2, Nasal tuberosity ; 3, Supra-orbital ridge ; 4, Optic foramen ; 5, Sphenoidal fissure ; 6, Spheno-maxillary fissure ; 7, Lachrymal fossa ; 8, Opening of the nose divided by the vomer ; 9, Infra-orbital foramen; 10, Malar bone; 11, Symphysis of the lower jaw ; 12, Mental foramen ; 13, in certain individuals, by two faintly-marked curved lines situated a little above the inferior border of the bone. The middle portion of the external face is very convex. On the internal face there is no parietal pro- tuberance, but in its stead the internal occipital protuberance. It also exhibits ramous channels, which in disposition are analogous to the ribs of a fig-leaf ; as well as the parietal fossa which cor- responds to the parietal eminence. 3. Frontal bone.— The frontal bone of Man forms the upper part of the face and the anterior portion of the cranium. Convex from behind forward, then vertical in its upper three-fourths, the bone sud- denly bends at the orbits, so as to become hori- zontal in its lower fourth. The external face offers, above the forehead, two lateral frontal eminences, and above the nose, a middle frontal boss. To the right and left of the latter are two salient arches, the supraorbital ridges. The internal face entirely belongs to the cranial cavity. It offers on the median line, the saggital groove terminated by a frontal crest ; and on each side of this line the frontal fossse, corresponding to the eminences of that name, and orbital bosses to match the orbital roofs. There is no mortice for the articulation of the sphenoid bone. On the middle portion of the superior frontal border, in young persons, is the anterior angle of the anterior fontanella. The anterior border ex- hibits three superciliary foramina and the orbital arches. 4. Ethmoid bone. — In Man, the external face of the lateral masses, formed by a very thin lamina, Ramus of the lower jaw; 14, Parie- termed the os planum or lamina papyracx, belongs tal bone ; 15, Coronal suture ; 16, Temporal bone ; 17, Squamous suture ; 18, Upper part of the great ala of the sphenoid bone ; 19, Com- mencement of the temporal ridge ; 20, Zygoma of the temporal bone, concurring to form the temporal arch ; 21, Mastoid process. to the internal wall of the orbit. 5. Sphenoid bone. — This is distinguished, in Man, into a body and four wings, two large and two small. The inferior surface of the body offers nothing remarkable, except the presence of a conical pro- longation named the beak {rostrum) of the sphe- noid. The external face of the greater wings forms part of the temporal fossa, as also the external wall of the orbit At the union of the wings with the body are detached two bifid ptery- goid processes ; their internal branch represents the pterygoid bones of animals. There is no subsphenoidal canal. The two lesser wings are very thin and triangular, and visible only on the superior sur- face of the bone; they constitute the processes of Ingrassias. On the internal face of the bone are found : — 1, A deep pituitary fossa, limited by four clinoid processes ; 2, An optic fossa, shallow, showing very short optic canals trans- formed into foramina- 3, The sphenoidal fissure, which replaces the great super- ephenoidal canal in the Horse; 4, The great foramen rotundum : 5, The internal face of the wings, much excavated ; 6, The foramen ovale, which transmits the inferior maxillary nerve ; 7, The small foramen rotundum that lodges the spheno-spinous artery. THE HEAD. 65 6. Temporal bone. — In the squamous portion of the temporal bone of Man, the zygomatic process only rests on the malar bone, as in ruminants. The glenoid cavity is concave in every sense, and divided into two parts by an opening named the fissura Glaseri; the anterior portion only is articular, the posterior lying against the external auditory canal, does not belong to the articulation ; it corresponds to the supra condyloid eminence of the Horse. The tuberous portion is consolidated with the squamous. It is divided into a mastoid and a pyramidal portion ; the latter comprises, in its turn, the petrous and tympanic portions. The mastoid portion corresponds to the mastoid process, mastoid protuberance, and superior border of the petrous bone in the Horse. It presents; a rugged mastoid process ; above this is the mastoid canal ; and above and behind it, the digastric groove; the pyramid forming a con- siderable projection in the interior of the cra- nium. The styloid process or bone is altogether separate from the oti.er pieces of the hyoid. and in the adult is consolidated with the temporal bone. 7. Supermaxilla. — In Man the preiuaxilla is no longer found independent, the centre which forms it coalescing with thesupermaxillary bone. The supermaxilla of Man concurs, for the greater part of its extent, to form the floor of the orbit ; it is also divided into three faces : an external or facial, a superior or orbital, and an internal or naso-palatine. The external face presents, from before to behind: 1, A small fossa, into which is inserted the myrtiform muscle ; 2, The infraorbital, or canine fossa, showing the inferior orifice of the infraorbital canal; 3, A crest corresponding to the maxillary spine of solipeds ; 4, The alveolar tuberosity. This face carries, in front, a prolongation that forms the ascending process, also named, be- cause of its relation, the fronto-nasal process. The superior or orbital face offers a fissure which precedes the infraorbital canal, and, outwards, the malar process. The internal face is divided by the palatine process. It shows, in front, the half of the anterior nasal spine and a groove which participates in the formation of the in- cisive canal. 8. Palate bone. — The palate bone of Man is formed of two osseous laminae: one horizontal, the other vertical, which are joined at a right angle. The first part presents : one-half of the posterior nasal spine, which is altogether rudi- mentary, or even null in animals; the orifice of the posterior palatine canal, which belongs entirely to the palate bone ; the pterygopalatine foramen; lastly, the pterygoid process, which represents the pterygoid bone of animals. The vertical portion forms the external wall of the nasal cavities by its internal face, and by its ex- ternal face concurs in the formatiou of the zygomatic or temporal fossa. 9. Zygoma. — This offers three faces. The external, or cutaneous, serves as a base for the most salient part of the cheek. The superior, or orbital, forms part of the external wall and floor of the orbit; it belongs to a long apophysis, the orbital process, which rests on the sphenoid and frontal bones. The posterior face is smooth and concave behind, where it aids to form the temporal fossa; in front it is uneven, and articulates with the supermaxilla. The posterior, or masseteric border, unites with the zygomatic process of the temporal bone. 10. Lachrymal bone. — This bone is also called the os unguis in Man, because of its likeness to the nail in shape and tenuity. It is entirely lodged in the orbit, and its EXTERNAL OR BASILAR SURFACE OF THE BASE OF THE HUMAN SKULL. 1, 1, The bony palate ; 2, Incisive, or anterior palatine foramen ; 3, Palatine process of palate bone, with the pos- terior palatine foramen ; 4, Palate spine with transverse ridge ; 5, Vomer ; 6, Internal pterygoid palate ; 7, Sca- phoid fossa; 8, External pterygoid plate, with fossa ; 9, Zygomatic fossa ; 10, Basilar process of occipital bone ; 11, Foramen magnum; 14, Glenoid fossa, 15, Meatus auditorius exter~ nus; 16, Foramen lacerum anterius; 17, Carotid foramen of left side ; 18, Foramen lacerum posterius, or jugular foramen; 19, Styloid process; 20, Stylo-mastoid foramen, with jugular tubercle and digastric fossa-, 21, Mas- toid process; 22, Occipital bone; 23, Posterior condyloid fossa. m THE BONES. external face is divided into two portions by a vertical crest; the portion situated in front of this crest forms part of the lachrymal channel. By its internal face, the lachrymal bone limits, outwardly, the bottom of the nasal cavities, and covers the anterior cells of the ethmoid ; by its posterior border, within the orbit, it articulates with the os planum of the ethmoid. 11. Nasal bone. — The proper bones of the nose of Man exhibit a great analogy to those of the Dog. They do not possess a nasal prolongation, and they articulate with the lateral cartilage of tlie nose. 12. Vomer. — The same general form and relations as in solipeds. 13. Inferior maxillary bone. — This bone in Man is in shape somewhat like a horse- shoe. It is nearly of the same width throughout its whole extent. The symphysis is vertical — a character peculiar to Man. Below this symphysis is a triangular projection, the mental eminence The genial surface of the Horse is replaced by four little tubercles termed the genial processes. The alveoli of the molar teeth form a great projection on the inner face of the bone. The mylo-hyoid ridge is very developed. The superior orifice of the dental canal is covered by a little sharp lamina. From this orifice begins the mylo-hyoidean groove. The coronoid process is short ; the condyle is bent towards the median line, and the sigmoid notch is wide and shallow. The superior border contains fourteen or sixteen alveoli. Article III. — The Thorax. The thorax represents a conoid cage, elongated from before to behind, suspended under the vertebras of the dorsal region, and destined to contain the principal organs of respiration and circulation. It is composed of bony arches named ribs, thirty-six in number — eighteen on each side — and a single piece, the sternum, which serves for the direct or indirect support of the inferior extremities of the ribs. THE BONES OF THE THORAX IN PARTICULAR. 1. Sternum of the Horse. This is an osteo-cartilaginous body, elongated from before backwards, flattened on each side in two-thirds of its anterior extent, and from above to below in its posterior third, slightly curved on itself, and situated beneath the thorax in an oblique direction from above to below, and before to behind. It offers for study, a superior face, two lateral faces, three borders, and two extremities. Fig. 37, THE STERNUM. 1. The cervical prolongation (or cariniform cartilage); 2, The xiphoid appendage (or ensiform cartilage ; 3, 3, Cavities for the articulation of the sternal cartilages ; 4, Inferior border. Faces. — The superior face, slightly concave longitudinally, represents an isoscelated, lengthened triangle, the summit of which is directed forwards ; it constitutes the floor of the thoracic cavity. Each lateral face comprises two parts — a superior and an inferior. The first shows eight diarthrodial THE THORAX. 67 cavities, which receive the inferior extremity of the cartilages of the true ribs. These cavities are elongated vertically, and draw closer to each other as they extend backwards; The inferior part, which is more extensive before than behind, offers to the powerful pectoral muscles a large surface for insertion. Borders. — The two lateral borders separate the superior from the lateral faces ; they are situated above the diarthrodial cavities, are united anteriorly, and each gives attachment to a fibrous band. The inferior border is opposite the superior face ; convex, thin, and very prominent in its anterior two-thirds, it somewhat resembles the keel of a ship. Extremities. — The anterior flattened on each side and curved upwards, exceeds to some extent the first articular cavity of the lateral faces, and in this way constitutes the cervical prolongation of the sternum. The posterior extremity is flattened superiorly and inferiorly, and forms a large cartila- ginous plate, very thin, concave above, convex below, which has received the name of the abdominal prolongation (ensiform cartilage) or xiphoid appendage. Structure and development. — The sternum is one of the parts of the skeleton which do not submit to complete osseous transformation. It is developed, in solipeds, from six single centres of spongy substance, ranged one behind the other, like beads on a string. These centres never coalesce to form a solid piece, but remain separated, during the life of the animal, by the primitive cartilaginous mass. The latter constitutes the entire anterior pro- longation of the bone and its carina, as well as the xiphoid appendage. When these parts of the sternum become ossified, which is rare, it is only partially. 2. The Bibs. As has been already noticed, on each side of the thorax eignteen ribs are counted. These are nearly parallel to each other, and separated by the intervals termed the intercostal spaces. Attached by their superior extremity to the vertebras of the dorsal region, these bones terminate at their inferior extremity by an elastic and flexible prolongation, named the costal cartilage, by means of which they are brought into direct or indirect relations with the sternum. The characters common to all the ribs will be first noticed, then the special features which serve to distinguish them from each other, and, lastly, the differences they exhibit in other than soliped animals. A. Characters common to all the Eibs. — These will be studied from a typical point of view, first in the rib itself, and then in its cartilage. 1. Description of a typical rib. — A rib is an elongated symmetrical bone, oblique from above to below, and from before to behind, flattened on both sides, curved like a bow, and twisted on itself in such a fashion that its two extremities cannot rest on the same horizontal plane. It is divided into a middle portion and two extremities. Middle portion. — This offers two faces and two borders. The external face is convex, and hollowed by a wide groove in its anterior half; it shows superiorly, towards the point corresponding to the angle of the rib in Man, some tubercles and muscular imprints. The internal face is concave and smooth, and covered by the pleura, which separates it from the lungs. The anterior border is concave, thin, and sharp ; the posterior, convex, thick, and covered with rugged eminences, is channeled inwardly by a vasculo-nervous fissure, which disappears near the middle of the rib. Extremities. — The superior has two eminences, a head and a tuberosity, which serve for the support of the rib against the spine. The first is formed by two articular demi-facets, placed one before the other, and separated by a 08 THE BONES. groove for ligamentous insertion ; it is isolated from the tuberosity by a narrow part, named the neck, which exhibits a rugged fossa for the implanta- tion of a ligament. The second, situated behind the head, and smaller than it, is provided with imprints on its margin, and presents an almost flat diarthrodial facet at the summit. Each rib articulates by its head and tuberosity with two dorsal vertebrae ; the head is received into the inter- Fig. 33. TYPICAL RIBS OF THE HORSE. A, Inner face of the fifth sternal rib ; b, External face of the first asternal rib. — 1, Head of the rib ; 2, Its fissure ; 3, Neck ; 4, Tuberosity ; 5, Articular facet ; 6, Scabrous fossa for the insertion of the interosseous costo-transverse ligament 5 7, Groove on the external face ; 8, Vasculo-nervous groove of the posterior border ; 9, Prolonging cartilage ; 10, A, Articular tuberosity for union with the sternum. vertebral articular cavity ; the tuberosity corresponds, by its facet, to the transverse process of the posterior vertebra. The inferior extremity is tuberous and excavated by a shallow cavity, irregular at the bottom, for the reception of the upper end of the costal cartilage. Structure and development. — The ribs are very spongy bones, especially THE THORAX. 69 in their inferior moiety, and are developed at a very early period by three centres of ossification : a principal for the middle portion and inferior extremity, and two complementary for the head and tuberosity. 2. Description of a typical costal cartilage. — The costal cartilage very evidently represents the inferior rib in birds; it is a cylindrical piece, slightly compressed at the sides, and round and smooth on its faces and borders. By its superior extremity, it is united to the rib it serves to lengthen, and forms with it an angle more or less obtuse, opening in front. At its inferior extremity, it is terminated by an articular enlarge- ment, or by a blunt point. In youth, the costal prolongations are entirely composed of cartilaginous matter, but they are soon invaded by ossification ; so that in the adult animal they are already transformed into a spongy substance, with large areola? which remain during life surrounded by a thin layer of cartilage. B. Specific Characters of the Ribs. — The ribs, like the vertebras of each region of the spine, have received numerical designations of first, second, third, etc., computing them from before to behind. (See Fig. 1.) Owing to the pre- sence of an altogether essential characteristic, they are naturally divided into two great categories : the sternal or true ribs, and the asternal or false ribs. The sternal ribs, numbering eight (the first eight), have their cartilages terminating inferiorly by an articular enlargement, which corresponds to one of the lateral cavities of the sternum, and brings the true ribs into direct contact with this portion of the skeleton. The asternal ribs, ten in number, rest on each other — the last on the seventeenth, this on the sixteenth, and so on — by the inferior extremity of their cartilage, which ends in a blunt point. The cartilage of the first false rib is united somewhat closely to the last sternal rib, and it is through the medium of this that all the asternal ribs lie indirectly on the sternum. If, however, the ribs are considered altogether, with regard to the differen- tial characters presented by them in their length, width, and degree of incurvation, it will be noted: 1, That their length increases from the first to the ninth, and from this diminishes progressively to the last : 2, That the same progressive increase and decrease exists in the cartilages ; 3, That they become gradually wider from the first to the sixth inclusive, and then con- tract by degrees until the eighteenth is reached ; 4, That the curve described by each is shorter and more marked as the rib is si£uated more behind. It may be added that the channel on the external face is less conspicuous in proportion as the rib is narrow. The first rib, considered individually, is always distinguished by the absence of the groove on its outer surface, the vasculo-nervous fissure on its posterior border, and the groove or notch intermediate to the two facets of its articular head. It is also recognised by the deep muscular imprints on its external face, the shortness and thickness of its cartilage, and particularly by the articular facet which this cartilage exhibits inwardly, to correspond to that of the opposite rib. The last rib has no channel on its external surface ; the facet of its tuberosity is confounded with the posterior facet of the head. This last character is also nearly always remarked in the seventeenth rib, and sometimes even in the sixteenth. In the Ats and Mule, all the ribs in general, but particularly those most posterior, are less curved than in the Horse. (In the Horse, a nineteenth pair of ribs is sometimes found, and this even with five, and at other times with six lumbar vertebra? ; it happens that the nineteenth rib is formed by the transverse process of the first lumbar vertebra, and at times a ligament THE BONES. is given off from this process, which joins it to a pointed bone or a cartilage in its vicinity. If the hymn on the *' Sacrifice of the Horse," in the most ancient collection of Aryan poems, is to be credited, the horses of antiquity in Central Asia had only seventeen pairs of ribs. The mobility of the ribs is scarcely perceptible in the first, but increases until the ninth or tenth is reached, after which it gradually diminishes.) THE THORAX IN GENERAL. The description of the interior of the thoracic cavity will be referred to when treating of the respiratory apparatus. It is only necessary here to examine the external surface of this bony cage ; for this purpose it is divided into six regions : — a superior plane, an inferior plane, two lateral planes, a base, and a summit. Planes. — The superior plane is separated into two portions by the spinous processes of the dorsal vertebra} ; each forms, with these spinous processes, the costo-vertebral furrow, intended to lodge the majority of the muscles belong- ing to the spinal region of the back and loins. The inferior plane, less extensive than the preceding, offers: 1, On the median line, the cariniform and xiphoid cartilages of the sternum ; 2, On the sides, the chondro-sternal articulations, and the cartilages of prolongment of the true ribs. The lateral planes are convex and wider at their middle part than in front or behind, and exhibit the intercostal spaces. They serve to give support, anteriorly, to the superior rays of the two fore-limbs. Base. — This is circumscribed by the posterior border of the last rib, and by the cartilages of all the asternal ribs ; it is cut obliquely from above to below, and from before to behind. It gives attachment, by its internal circumference, to the diaphragm, a muscle which separates the thoracic from the abdominal cavity. Summit. — It occupies the anterior portion of the thorax, and presents an oval opening, elongated vertically,, situated between the two first ribs. This opening constitutes the entrance to the chest, and gives admission to the trachea, the oesophagus, and important vessels and nerves. DIFFERENTIAL CHARACTERS OF THE THORAX IN OTHER THAN SOLIPED ANIMALS. 1. Sternum. In all the domesticated animals except solipeds, the sternum is flattened above and below, instead of from side to side. Ruminants. — In ruminants, each piece is developed from two lateral centres of ossifica- tion. The bones which compose it are seven in number ; they are much more compact than those in the sternum of the horse, and at an early period are united to each other, with the exception of the first, which is joined to the second by a diarthrodial articula- tion that permits it to execute lateral movements. There is no cervical prolongation, and the xiphoid cartilage is feebly developed and well detached from the body of the bone. In the sternum of the Goat and Sheep, the two first pieces have no diarthrodial joint, but are simply united by a layer of cartilage which, in old animals, becomes completely ossified. Pig. — The sternum of this animal presents in its general conformation the essential features of that of large ruminants. It is provided with a well-defined cervical prolonga- tion, and is composed of six pieces which, at least in the four or five last, are each divided into two lateral centres. Carnivora. — The sternum of the Dog and Cat is formed of eight pieces elongated from before to behind, hollowed in their middle part, and thick at their ends— formed, indeed, like the last coccygeal vertebras of the Horse. They are never ossified to each other. THE THORAX. 71 2. Ribs. The number of ribs varies like that of the dorsal vertebrae. The following table indicates the number of these bones in the different domesticated animals. Pig 14 Ox 13 Sheep. c 13 Goat 13 Dog 13 Ruminants. — These animals have eight sternal and five asternal ribs. In the Ox, they are longer, wider, and less arched than in solipeds. The articular eminences of the superior extremity are voluminous and well detached; the neck especially is very long. The sternal ribs are joined to their cartilage of prolongment by a real diarthrodial articulation. In the last rib, and sometimes in the one before it, the tuberosity is scarcely perceptible, and has no articular facet. In the Sheep and Goat, the sternal ribs are consolidated with the cartilages (see fig. 5.) Pig. — In this animal there are fourteen pairs of ribs, seven of which are sternal and seven asternal. The first are provided with cartilages of prolongment flattened on both sides, extremely wide aud sharp, and convex on their superior border. In the four last asternal ribs, the facet of their tuberosity is confounded with the posterior facet of the head. (Otherwise, the ribs of the Pig resemble, in their general conformation, those of the Sheep or Goat ; though more incurvated and wider.) Carnivora. — They possess thirteen ribs Fig. 39. on each side — nine sternal and four asternal. , These are very much arched, narrow, and thick, and their cartilages rarely ossify. In the Dog, the articular facet of the tuberosity remains isolated from the posterior facet of A^*^| the head in all the ribs. It is absent in the J^^i^^1^^ three last ribs of the Cat. M&ZL. JF COMPARISON OF THE THORAX OF MAN WITH §b±^009Hu 1 THAT OF THE DOMESTICATED ANIMALS. il^^ 1 ^'^SHfe "rJPT 1. Sternum. MA. ^^gg^aj#y ^ The sternum of Man is flattened before ji\r^^^4^^^a|, liS and behind, and diminishes in width from Iw^^^^y^fffll above to below. The xiphoid appendage is V ^ ' | 'j^^Myfj narrow, and single or bifid. Besides the articular surfaces for the ribs, there are found " on the upper end two lateral notches for articulation with the clavicles. W; 5 2. Ribs. Of the twelve ribs in Man, seven are sternal s and five asternals. They are short, narrow, and much incurvated, especially thorax of man ; anterior face. the first ones. In each rib the curvature is %f Superior piece of the sternum; 2, more marked in the posterior fourth or fifth Middle piece, or body ; 3, Inferior piece, than in the anterior three-fourths or four- or ensiform cartilage; 4, First dorsal fifths; this sudden change of curvature is vertebra; 5, Last dorsal vertebra; 6, indicated in the external face by a kind of First rib; 7, Its head; 8, Its neck, rest- inflexion and thickening: called the angle of \ng against the transverse process of the the ribs. The prolonging cartilages of the first dorsal vertebra; 9, Its tubercle ; 10, eleventh and twelfth ribs are short, and are Seventh, or last true rib; 11, Costal car- lost in the texture of the abdominal parietes ; tilages of the true ribs ; 12, The last two for this reason they are termed the float ing (or faiSe or floating ribs; 13, The groove fahe) ribs (see fig. 39). along the lower border of the rib. Akticle IV. — Anterior Limbs. The anterior (or thoracic) limb is divided into four secondary regions : the shoulder, arm, fore-arm, and fore-foot or hand. 72 THE BONES. Fig. 40. SHOULDER. In solipeds, this region has for its base a single bone, the scapula or omoplat. % Scapula. This is a flat, triangular, and asymmetrical bone, prolonged at its superior border by a flexible cartilage, articulated inferiorly with the humerus only, and applied against the lateral plane of the thorax in an oblique direction downwards and forwards. It has two faces, three borders, and three angles. Faces. — The external face is divided by the scapular or acro- mian spine, into two cavities of unequal width — the supra and^ infraspinous (or antea and postea spinatus)fossse. The spine is a very salient crest which runs the whole length of the external scapular surface ; very elevated in its middle part, which shows an irregular enlargement — the tube-' rosity of the spine — it insensibly decreases towards its two ex- tremities. The supraspinous fossa, the narrowest, is situated above, or rather in front of the spine ; it is regularly concave from side to side, and perfectly smooth. The infraspinous fossa is twice the width of the pre- ceding, and occupies all the sur- face behind the spine. It ex- THE RIGHT SCAPULA; OUTER SURFACE. t«v«x 1 T> 1 l ±1 ,,..,, „ « . - - A. hibits : 1, Below, and near the 1, Antreior border ; 2, Superior margin for insertion • t. j i of cartilage; 3, Tuberosity of the spine; 4, Antea- posterior border, several rows spinatus fossa; 5, Postea-spinatus fossa; 6, Neck of roughened lines for muscular of the scapula ; 7, Coracoid process ; 8, Glenoid insertion ; 2, Near the neck, the cavitJr- nutritious foramen of the bone, and some vascular grooves. The internal face is excavated in its centre to form a hollow called the subscapular fossa, which is prolonged superiorly by three diverging points. The median point extends to the superior border of the bone, and separates two roughened triangular surfaces destined for muscular implantation. Borders. — The superior is indented by an irregular groove to receive the inferior margin of the cartilage of prolongment. The latter is convex on its superior border, extends beyond the posterior angle of the bone, and gradually diminishes in thickness as it leaves its point of attachment. In old horses it is nearly always found partially ossified. The anterior border, thin and sharp, is convex in its superior two-thirds, and slightly concave for the remainder of its extent. The posterior is thicker and a little concave. THE ANTEMOR LIMBS. 73 Angles. — The anterior or cervical angle is the thinnest of the three. The posterior or dorsal angle is thick and tuberous, The inferior or humeral angle is the most voluminous, and is separated from the remainder of the bone by a slight constriction, which constitutes the neck of the scapula. It exhibits : 1, The glenoid cavity, an oval diarthrodial surface, excavated to a slight extent to receive the head of the humerus, notched on the inner side, and bearing on the external margin of the ridge which surrounds it a small tubercle of insertion; 2, The coracoid process, situated in front, and at a certain distance from the glenoid cavity. This is a large eminence in which may be distinguished two parts : the base, a thick rugged process ; and the summit, a kind of beak curved inwards. Structure and development. — Like all the wide bones, the scapula is formed of two compact lamellae separated by spongy tissue. The latter is yery scanty towards the centres of the supra and infraspinous fossae, where it is often altogether wanting ; it is most abundant in the angles. The scapula is developed from two centres of ossification, one of which forms the coracoid pro- Fig. 41. cess. ARM. This region has only one bone, the humerus. Humerus. The humerus is a long single bone, situated between the scapula and the bone of the fore-arm, in an oblique direction downwards and backwards. Like all the long bones, it offers for study a body and two extremities. Bodyc — The body of the humerus looks as if it had been twisted on itself from within to without in its superior extremity, and from without to within at the opposite end. It is irregularly prismatic, and is divided into four faces. The anterior face, wider above than below, has in its middle and inferior por- tions some muscular imprints. The posterior, smooth and rounded from one side to the other, becomes insensibly confounded with the neighbouring faces. The external is excavated by a wide furrow, which entirely occupies it, and turns round the bone ob- liquely from above to below and behind to before , it is to the presence of this channel that the humerus owes its apparent twist, and it is in consequence designated the furrow of torsion of the body of the humerus. This furrow is separated from the anterior face by a salient border, the anterior crest of the furrow of torsion, which ends inferiorly above the coronoid fossa, and superiorly, towards the upper third of the bone, by the imprint, or deltoid tuberosity. This is a roughened, very prominent eminence, flattened before and behind, and inclining towards the furrow of torsion ; by its superior extremity it gives origin to a curved line which is carried backwards to join the of the articular head. Near the inferior extremity, backwards and ANTERO-EXTERNAL VIEW OF RIGHT HUMERUS. 1, Trochlear or bicipital ridges • 2, External or deltoid tuberosity ; 3, Head or articular sur- face ; 4, External tuber- cle; 5, Shaft or body with its twisted furrow; 6,7, Articular or trochlear condyles ; 8, Ulnar fossa with a sulcus ; 9, Fossa for the insertion of the external lateral liga- ment. 74 THE BONES. Fig. 42. outwards, is seen the posterior crest of the furrow of torsion, which separates the latter from the posterior face of the bone. The internal face of the body of the humerus, rounded from side to side, is not separated from the anterior and posterior faces by any marked line of demarcation. It offers, near its middle, a depressed scabrous process for the insertion of the adductor muscles — teres major and great dorsal — of the arm. Towards its inferior third it shows the nutritive foramen of the bone. Extremities. — These are distinguished into superior and inferior. Both are slightly curved, the first backwards, the second forwards, a disposition which tends to give to the humerus the form of an S. The superior extremity is the most voluminous, and has three thick eminences ; a posterior, external, and internal. The first constitutes the head of the humerus; it is a very slightly -detached articular eminence, rounded like the segment of a sphere, and corresponding to the glenoid cavity of the scapula, which is too small to receive it entirely. The external eminence, named the trochiter, large trochanter, and great tuberosity, com- prises three portions, named the summit, convexity, and crest of the great tuberosity. The internal eminence, the trochin, little trochanter, or small tuberosity, also presents three distinct portions, which, by their posi- tion, correspond exactly with the three regions of the large trochanter : these are so many muscular facets. The great and small trochanters are separated from one another in front by a channel called the bicipital groove, because the superior tendon of the biceps muscle glides over it; it consists of two vertical grooves with a median ridge between them. The inferior extremity of the humerus has an articular surface corresponding to the radius and ulna. This surface, elongated transversely, convex from before backwards, and of greater extent within than without, exhibits two trochlea separated by an antero- posterior relief. The median or internal trochlea, the deepest, is limited internally by a kind of voluminous condyle, Articular "head of the which corresponds to the inner lip of the humeral bone; 4, External tu- trochlea of Man. The external trochlea is bordered outwardly by a slightly salient lip, which corresponds to the condyle of the humerus of Man. Above and behind this articular surface is a wide deep fossa, the olecranian (or condyloid), so named because it lodges the rostrom of the olecranon in the extension movements of the fore-arm. It is bordered by two eminences, the external of which is less elevated than the internal. The first represents the epitrochlea, and the second the epi- condyle, of the humerus of Man. In front, and above the inner trochlea, there is another, but less spacious fossa, which receives the coronoid pro- cess during extreme flexion of the fore-arm, and which, for this reason, it would be convenient to designate as the coronoid fossa. Lastly, at the extremities of the transverse axis of the inferior articular surface is POSTERIOR VIEW OP THE RIGHT HUMERUS. 2, External tuberosity ; 3, bercle and ridge ; 5, Body or shaft of the bone ; 10, Condyloid THE ANTERIOR LIMBS. 75 remarked : outwardly, an excavation for ligamentous insertion ; inwardly, a small tuberosity intended for the same purpose.1 Structure and development. — The humerus, like all the long bones, is only spongy at its extremities. It is developed from six points of ossi- fication ; one of which alone forms the body, one the head and the small trochanter, another the large trochanter, a fourth the inferior articular surface, a fifth the epicondyle, and the last for the epitrochlea. The latter is sometimes absent. FORE -ARM. This region has for its base two bones, the radius and cubitus (or ulna') united into a single piece at an early period in most of the domesticated animals. 1. Badius. This is a long bone, placed in a vertical direction between the humerus and the first row of carpal bones, and divided into a body and two extremities. Body. — Slightly arched and depressed from before to behind, the body presents for study two faces and two borders. The anterior face is convex and perfectly smooth. The posterior, a little concave from one extremity to the other, offers : 1, Near the external border, a triangular surface, covered with asperities, elongated vertically, very narrow, commencing near the upper fourth of the bone and terminating in a fine point towards the lower fourth : this surface is brought into contact with the anterior face of the ulna by an interosseous ligament, which is completely ossified before the animal reaches adult age ; 2, Above, there is a wide, transverse, but shallow groove, which aids in forming the radio-ulnar arch and shows, near the point where it touches the preceding surface, the nutrient foramen of the bone ; 3, Near the internal border, and towards the inferior third, there is a ver- tically elongated and slightly salient eminence of insertion. The two borders, external and internal, are thick and rounded; they establish an insensible transition between the faces. Extremities. — The superior is larger than the inferior. It has : 1, An articular surface elongated from one side to the other, concave from before to behind, wider within than without, and moulded to the articular surface of the inferior extremity of the humerus ; there is also seen, outwardly, a double gorge which receives the two lips of the external trochlea ; in the middle, an anteroposterior ridge which is received into the internal trochlea ; within, an oval cavity corresponding to the internal border of the former ; 2, The external tuberosity, placed at the extremity of the great diameter of the articular surface ; it is prominent and well detached ; 3, The internal or bicipital tuberosity, a large, very rugged, and depressed process, situated within and in front of the glenoid cavity ; 4, A little lower, and on the same side, there is a strong muscular and ligamentous imprint, separated from the preceding tuberosity by a transverse groove intended for the passage of a tendinous branch ; 5, The coronoid process? a small conical eminence, at the summit of which terminates, anteriorly, the median ridge of the articular 1 The articular surfaces which, in veterinary anatomy, have received the names of trochlea and condyle, not being the same as in human anatomy, there results an annoying inversion of the situation of the epitrochlean and epicondyloid eminences, so named. It has therefore been our endeavour to remedy the improper employment of these denominations, which has been a cause of error in comparative anatomy. 8 In Man this belongs to the ulna. 73 THE BONES. Fis. 43. surface ; 6, Two diarthrodial facets elongated transversely, cut on tho posterior outline of the large articular surface, with which they are con- founded by their superior border ; they correspond to similar facets on the ulna ; 7, Below these, a roughened surface which extends to the radio- ulnar arch, and is in contact with an analogous surface of the same bone through the medium of an interosseous ligament ; in the Horse this liga- ment rarely ossifies. The inferior extremity, flattened from before to behind, presents: 1, Below, an articular sur- face elongated transversely and somewhat irregu- lar, responding to the four bones in the upper row of the carpus; 2, On the sides, two tube- rosities for ligamentous insertion, the internal salient and well circumscribed, the other external and excavated by a vertical fissure, in which passes a tendon ; 3, In front, three grooves for the gliding of tendons ; the external is the largest, and vertical like the median; the internal, the nar- rowest, is oblique downwards and inwards; 4, Posteriorly, a strong transverse ridge which sur- mounts the articular surface and serves for the insertion of ligaments. Structure and development. The radius is a very compact bone, and is developed from three centres of ossification : one for the body and two for the extremities. 2. Ulna, This is an elongated, asymmetrical bone, in the form of an inverted triangular pyramid, applied against the posterior face of the radius, to which it is united in adult solipeds. It offers for des- cription a middle portion and two extremities. Middle portion. — This has three faces wider above than below, and three borders which become joined at the inferior extremity of the bone. The external face is smooth and nearly plane. The internal is also smooth and slightly hollowed. The anterior is formed to correspond to the radius, and presents peculiarities analogous to those of the posterior face of that bone. Thus there is found in proceeding from above to below: 1, Two small diarthrodial facets ;x 2, A rough surface ; 3, A transverse groove for the formation of the radio-ulnar arch; 4, A triangular surface, studded with rugosities, which occupies the remainder of the bone to its lower extremity. The lateral borders, external and internal, are sharp, and, like the anterior face, are in contact with the radius. The posterior border is concave, rounded, and thicker than the other two. Extremities. — The superior extremity comprises all that portion which exceeds the articular surface of the radius. It constitutes an enormous 1 It is represented iu Man by the smaller sigmoid notch, EXTERNAL FACE OP THE RADIUS AND ULNA. , Ulna; 2, Point of the ole- cranon ; 3, Beak of the ole- cranon ; 4, Radio-ulnar arch ; Supero-external tuberosity ; 6, Radio-ulnar articular sur- faces for the humerus; 7, Bicipital tuberosity ; 8, Shaft or body of the radius ; 9, Grooves for tendons. THE ANTERIOR LIMBS. 77 process — the olecranon — flattened on both sides, external face, slightly convex; 2, An internal anterior border, thin and sharp superiorly, notched below to for mthe sigmoid cavity :x an articular surface concave from above down- wards, rounded from one side to the other, which corresponds with the humeral cavity, and is surmounted by a salient prolongation named the beak of the olecranon ; 4, A con- cave and smooth posterior border; 5, The summit, a kind of thick roughened tuberosity which terminates the olecranon above, and into which are inserted the extensor muscles of the fore-arm. At its inferior extremity, the ulna ends, towards the lower fourth of the principal por- tion of the fore-arm, in an acute point, and sometimes by a small knob (capitulum ulnai). It is not rare to see it prolonged, especially in the Ass and Mule, to the inferior external tuberosity of the radius. This tuberosity then appears to belong to it, at least in part ; and all that portion which is situated behind its vertical groove might be justly considered as belonging to the ulna. Structure and development. — The ulna con- tains much compact tissue, even in the region of the olecranon ; it is also very solid. It is an imperfect bone, developed from two centres of ossification only, one of these being for the apex of the olecranon. FORE-FOOT OR HAND. The anterior foot, or hand, is the region which presents the greatest differences when it is inspected in the various individuals of the animal series. Nevertheless, in all the mam- malia the constitution of the hand is funda- mentally the same, and may be divided into three sections: the carpus, metacarpus, and phalangeal region. The hand is formed by five parallel or quasi-parallel rays that constitute the digits, each of which is effectively or virtually com- posed of two superposed carpal, a metacarpal, and three phalangeal bones, forming altogether the digit, properly so called. But this typical and presenting: 1, An excavated face; 3, An Fig. 44. RIGHT FORE-FOOT OF A HORSE. 1, Radius; 2, Groove for the an- terior extensor of the phalan- ges; 3, Scaphoides; 4, Lunare; 5, Cuneiform ; ' 6, Trapezium ; 7, Magnum ; 8, Unciform ; 9, Metacarpal; 10, Small meta- carpal; 11, Sesamoid bone; 12, Suffraginis; 13, Coronary; 14, Navicular; 15, Pedal; 16, Its ala. composition, established through the labours of MM. Joly and Lavocat, is rarely found to be realised in a complete manner. The following is what is presented in the hand of Man, who is the most 1 The greater sigmoid cavity of Man. 78 THE BONES. perfect pentadactylous type. The carpus is composed of eight bones, the metacarpus of five small, parallel, bony columns ; the phalangeal region of five digits — thumb, index, medius, annularis, and auricularis, formed each of three phalanges, with the exception of the thumb, which has only two. In the domesticated animals, the constitution of the hand is more or less removed from this type, in consequence of abortive development, which diminishes either the number of rays, or the number of pieces composing these. Thus, in the Cat and Pig there are eight bones in the carpus ; but in the Dog and Horse there are no more than seven ; in the Ox and Sheep there are only six, for in them two or three bones are fused together. The metacarpus of the Dog and Cat has certainly five metacarpal bones, but the metacarpus of the Pig has no more than four, that of the Horse three, and that of Ruminants only two. In the metacarpus of the Pig the fifth bone is not developed. In the Horse it is entirely absent ; the fourth and first are independent, and the third and second are confounded to form a voluminous bone which has been named the principal (or large) metacarpal. In Ruminants, the fourth and fifth metacarpals are quite imperfect, the first being arrested in its development, and the second and third becoming consolidated as in the horse. Lastly, it is noted that the digital region of Carnivora has five digits, the Pig four, Ruminants two, and Solipeds only one. In the Pig, the thumb is undeveloped; in ruminants it is completely absent, and the first and fourth are represented by two small bones situated behind the metacarpo- phalangeal articulation ; while in solipeds the single digit already mentioned results from the fusion of the auricularis and medius. From this preliminary synthetical exposition, it will be easy to understand the description of the bones composing the hand in solipeds. 1. Carpal Bones. The carpus forms the base of the hand. Situated between the inferior extremity of the radius and the superior extremity of the metacarpal bones, it is composed of several small bones joined to each other in the fresh state by extremely solid articular bands. Collectively, they form an almost quadrilateral mass in which may be distinguished two faces and four borders. The anterior face is slightly convex from side to side and irregular ; it corresponds to the tendons of the extensor muscles of the metacarpus and phalanges. The posterior face is very unequal and converted, especially outwardly, into a groove in which the tendons of the flexor muscles of the phalanges glide. The superior border articulates with the radius ; the inferior border with the metacarpal bones. The lateral borders are nearly level ; above and behind the external border is remarked a considerable eminence, formed by the bone which will be hereafter studied as the supercarpal bone (or trapezium). In the carpus of the Horse are seven bones, which are disposed in two superposed rows. The superior row comprises four bones placed side by side, and designated by the numerical names of first, second, third, and fourth, viewing them from without to within. The inferior row has only three, which are named in the same manner. THE ANTERIOR LIMBS. 79 In applying to them the names proposed by Liser, we have, in the upper row: 1. The pisiform, or supercarpal bone (trapezium); 2. The pyramidal (or cuneiform) bone ; 3. The semilunar (or lunare) bone 4. The scaphoid bone ; In the inferior row : 1. The hook or unciform bone ; 2. The great bone or capitatum (magnum); 3. The trapezoid bone.1 The description of these bones is most simple, and may be made in a general manner for all. Thus, with the exception of the supercarpal bone, they are solids, nearly cubical in form, and exhibit on their periphery : 1, Articular surfaces ; 2, Surfaces of insertion. The articular surfaces represent small, flat, or slightly-undulating facets, distributed on the superior, inferior, and lateral surfaces ; none are found in front or behind. The superior and inferior faces are . entirely occupied by a single facet which responds either to the radius, the metacarpal, or to the bone of the other row. The lateral facets are always multiple and in contact with the bones of the same tier ; they do not exist, of course, on the eccentric side of the first and third bones of the superior or inferior rows. The surfaces of insertion are absent on the superior and inferior faces : they separate, in the form of roughened fossae, the lateral articular facets. Before and behind they are covered by more or less marked rugosities. Bones of the Upper or Antebrachial Row. — The first, or os pisiforme, is without the row ; it is situated above and behind the carpus, from whence its name of supercarpal bone, by which it is usually known in veterinary anatomy. This bone, which merits a special description, represents a disc flattened on both sides, offering for study two faces and a circumference. The external face is convex, roughened, and channeled anteriorly by a groove that traverses it from above to below, and in which glides the inferior tendon of the external flexor of the metacarpus. Its internal face, smooth and concave, concurs to form the external wall of the carpal sheath. The circumference presents, in front, two articular facets : the superior, concave, corresponds to the radius ; the inferior, convex, is in contact with the second bone of the upper row. The other three bones of this row increase in volume from without to within. The second, or os pyramidalis (or cuneiform), responds to the radius, the first bone of the lower row, the third of the upper, and the supercarpal bone ; it has in all five articular facets. The third, or os semilunare (lunare), has six facets, and is united below to the first and second bones of the second row. 1 The analogue of the trapezium of Man is not found in the Horse. According to M. Lavocat, we ought to regard as such a small supernumerary bone sometimes seen articu- lating behind the third bone. We are entirely of his opinion. (Leyh is also of this opinion, and states that this supernumerary bone is more frequently found in large common-bred horses. Stubbs, in his old, but fine « Anatomy of the Horse,' does not refer to it, but describes the seventh bone as the pisiform. Percivall says the supernumerary bone is not invariably present, and that sometimes two are found. He designates Stubbs' and Chauveau's pisiform bone as the trapezium. Girard names the supernumerary bone the " pisiform " or pea-shaped. When one or more of these osseous nodules are present, they represent the pollex and fifth digit of the human hand.) 80 THE BONES. The fourth, or os scaphoidcs, the most voluminous of the row, has only- four facets, and articulates by its inferior face with the os magnum and trapezoides. Collectively, the second, third, and fourth bones of the upper row form two articular surfaces. The superior, or radial articular surface, is very irregular ; but in ex- amining it from without to within there may be observed: 1, A glenoid cavity on the pyramidal bone ; 2, In front, a transversely-elongated condyle Fig. 45. Fig. 46, POSTERIOR VIEW OF THE RIGHT CARPUS. 1, Second cuneiform, or pyramidalis ; 2, Third, or lunare ; 3, Fourth, or sca- phoides; 4, First, supercarpal, pisiform, or trapezium ; 5, First of lower row, or unciform ; 6, Second, or magnum ; 7, Third, or trapezoides , *, *, Small metacarpal bones. FRONT VIEW OF RIGHT CARPUS. Second of upper row, or cuneiform ; 2, Third, or lunare ; 3, Fourth, or scaphoides; 4, First, supercarpal, or trapezium ; 5, First of second row, or unciform ; 6, Second, or magnum ; 7, Third, or trapezoides. on the semilunar and scaphoid bones ; 3, A groove placed behind the pre- ceding condyle. The inferior articulating surface, which corresponds to the second row, is constituted by several undulated facets ; it is convex outwardly and in front, concave posteriorly and inwardly. Bones of the Inferior or Metacarpal Row. — The thickness of these bones decreases from without to within. The first, unciform, or hookbone (os hamatum), has four diarthrodial facets, and responds, above, to the two first bones of the superior row ; below, to the first and second metacarpals. The second, os magnum, or os capitatum, the largest, has seven articular facets, three of which are on the interno-lateral face. It articulates, above, TUB ANTERIOB LIMBS. 81 with ther semilunar and scaphoides ; below, with the principal metacarpal and the internal rudimentary metacarpal. The third, or trapezoides, the smallest, is provided with five facets, and is in contact with the scaphoides above, and the middle and internal meta- carpals below. Collectively, these bones of the lower row form two Fig- 47. large diarthrodial surfaces. The upper surface responds to the bones of the upper row, and is constituted in front, and from without to within, by a small condyle and two glenoid cavities ; behind, by two isolated condyles, formed by the os magnum and the trapezoides. The inferior articular surface is only formed by more or less long and plane facets, which incline towards each other. It corresponds to the three portions of the metacarpus. Structure and development. — Each carpal bone is formed by a nucleus of close spongy substance enveloped in a layer of compact tissue. Each is developed from a single centre of ossification. 2. Metacarpal Bones. In Solipeds, the metacarpus is composed of three bones, named the " metacarpals/' standing parallel to each other. These are the principal metacarpal and the two rudimentary metacarpals, an external and internal. Principal Metacarpal. — This is a long cylindrical bone, situated vertically between the carpus and the digital region. Body. — The body is a little depressed before and behind, a disposition which permits it to be described as "having two faces and two borders. The anterior face is perfectly smooth and rounded from side to side. The posterior face is flat, and exhibits: 1, Towards the upper third, the nutritive foramen of the bone; 2, On the sides, two narrow, roughened surfaces, parallel and elon- gated vertically, commencing near the superior extremity to disappear a little below the middle of the bone ; these surfaces are held in apposition with the rudimentary metacarpals by means of an interosseous ligament which is often ossified in old horses. The borders, external and internal, are very thick, round, and smooth, like the an- terior face. Extremities. — The superior is flattened before and behind, and presents : 1, Above, an undulating articu- latory surface, formed by the union of several flat facets more or less inclined on one another : they respond to all the lower row of carpal bones; 2, An- teriorly and inwardly, a tuberosity for muscular inser- tion ; 3, Posteriorly, and directly above the roughened surfaces of the posterior face, four small diarthrodial facets in pairs, and running into the larger articular surface by their superior border: they are adapted to similar facets on the rudimentary metacarpals. The inferior extremity, elongated transversely, corresponds to the first phalanx and the large sesamoids by an articular surface, convex from before to behind, which POSTERIOR VIEW OF RIGHT METACARPUS. 1, Head of large meta- carpal bone for ar- ticulation with the trapezoides, mag- num, and unciform ; 2, Inner splint, or small metacarpal bone, for articula- tion with the trape- zoides; 4, Scabrous surface for the at- tachment of the sus- pensory ligament ; 5, Nutrient fora- men ; 6, Median ridge separating the two inferior con- dyles. 82 THE BONES. is composed of two lateral condyles separated by a median spine. The two condyles would be exactly alike, if the antero-posterior diameter of the external condyle was not less extensive than that of the opposite condyle. Both are hollowed on the sides by an excavation for the attachment of ligamentous fasciculi. Structure and development. — The principal metacarpal is one of the most compact bones in the body. It is developed from two centres of ossification, one of which is for the inferior extremity. Kudimentary Metacarpals. — The two rudimentary (small) metacarpal (or splint) bones are elongated, and placed against the posterior face of the principal bone, one without, the other within. Each is in the form of an inverted pyramid, and exhibits a middle part and two extremities. Middle portion. — Prismatic and triangular, this offers : 1, Three faces, — an external, smooth and rounded from one border to the other ; an interval, plane, and equally smooth ; an anterior, covered with asperities to give attachment to the interosseous ligament uniting the lateral metacarpal bone to the median ; 2, Three salient borders which markedly separate the faces from each other. Extremities. — The superior, the largest, is named the head, and shows: above, a diarthrodial facet which corresponds to one or two bones of the inferior row of the carpus ; in front, other two small facets continuous with the pre- ceding, and in contact with similar facets on the median metacarpal bone ; on the other points of its periphery are rugosities for the attachment of ligamentous and tendinous fibres. The inferior extremity only reaches to about the lower fourth of the large metacarpal bone, and terminates in a small enlargement or button, which is never consolidated with the latter. The two lateral metacarpals, although very much alike, may yet be easily distinguished from each other. For instance, the internal bone is always the thickest and often the longest ; besides, the superior articular surface of its head results from the union of the two facets corresponding to the two last carpal bones of the lower tier. Structure and development. — Of a somewhat compact texture, like all the long bones, these have no medullary canal, and are developed from only one ossific centre. Not unfrequently, however, the tubercle is formed from a special centre. 3. Bones of the Phalangeal Region or Digit. Solipeds have only one digit, supported by the principal metacarpal bone, and composed of three pieces placed end to end, one upon another. The first comprises three bones : a principal, the first phalanx, and two com- plementary ones, the sesamoids. The second is formed by the second phalanx, and the last, which terminates the limb, is constituted by the third phalanx and an accessory bone which has received the name of the small sesamoid (navicular bone). First (proximal) or Metacarpal Phalanx. — The first phalanx (or pastern bone), the smallest of all the long bones, is situated in an oblique direction from above downwards, and behind to before, between the principal metacarpal and the second phalanx. Body. — Depressed in front and behind, this bone exhibits : an anterior face, round from one side to the other, and slightly roughened above and below ; a posterior face, flat, covered with ligamentous imprints in the form of a triangle with the base reversed ; two lateral borders, thick, rounded, and provided with some imprints. THE ANTERIOR LIMBS. So Extremities. — The superior, the largest, presents: Above, an articular surface adapted to the inferior metacarpal surface, and consequently composed of two glenoid cavities separated by a groove running from front to back ; laterally, and a little posteriorly, a well-defined tubercle of insertion. The inferior extremity has a transversely elongated articular surface to cor- respond to the second phalanx; this surface is formed by two condyles separated by a middle groove, and surmounted laterally by a small tuberosity for ligamentous insertions. The external condyle is smaller Fiff. 48. Fig. 49. LATERAL VIEW OF THE DIGITAL REGION •, OUTSIDE OF RIGHT LIMB. 1, Large metacarpal bone; 2, 3, Outer and inner sesamoids ; 4, First, proximal, suffraginis or metacarpal phalanx, 5, Its posterior surface ; 6, Tuberosity for ligamentous insertion ; 7, Inner condyle of ditto ; 8, Eminences on second pha- lanx for attachment of lateral liga- ment; 9, Smooth surface for passage of deep flexor tendon on second pha- lanx ; 10, Imprint for the insertion of the terminal branch of the perforatus tendon ; 11, Navicular bone ; 12, Third phalanx, pedal, or coffin bone ; 13, Its basilar process. POSTERIOR VIEW OF FRONT DIGITAL REGION. 1, Large metacarpal bone ; 2, 3, Outer and inner splint bones ; 4, 5, Sesamoid bones; '6, Suffraginis; 7, 8, Tuberosi- ties for insertion of crucial ligaments ; 9, Triangular space for insertion of short sesamoid ligament ; 10, Anterior face of suffraginis ; 11, 12, Tuberosities for ligamentory insertion ; 13, Articu- lar depression separating condyles ; 14, 15, Second phalanx ; 16, Scabrous sur- face for ligamentous attachment; 17, Smooth surface for gliding of deep flexor tendon ; 18, Navicular bone ; 19, Pedal bone; 20, Basilar process; 21, Plantar foramen. than the internal, and when the bone is placed upon a horizontal plane, the anterior face turned upwards, it only touches by three points — the two tubercles of the upper extremity and the internal condyle ; by pressing on the external condyle, it is easy to make the bone rock. ^ The first phalanx is a very compact bone, and is developed from two points, one of which is for the superior extremity alone. 84 THE BONES'. Sesamoids. — These are two small short bones placed side by side behind the superior extremity of the first phalanx, whose articular surface it completes, as it has not extent enough to be exactly adapted to the metacarpal surface. Each of these bones represents a small, irregularly- shaped polyhedron, or rather, a short trifacial pyramid. It offers : an anterior face, which is articular, and corresponding to the inferior extremity of the principal metacarpal bone, moulded, as it were, on one of the condyles and one of the sides of the median ridge ; a posterior face, covered with cartilage in the fresh state, and forming, with that of the opposite bone, a gliding concave surface for the flexor tendons of the phalanges ; a lateral face, studded with ligamentous imprints ; a summit, directed upwards ; and a base, turned downwards, and serving for the attachment of several ligaments. Second (or Middle) Phalanx (Os Coronjs, Small Pastern Bone). — This is a short bone, situated in the same oblique direction as the first phalanx, and between it and the third. Its general form is that of a cube flattened before and behind, and offering the following features : an anterior face, covered with some slight imprints ; a posterior face, provided, above, with a transversely elongated gliding surface ; a superior face, channeled by two glenoid cavities, to match the inferior articulating surface of the first phalanx ; an inferior face, formed on the same plan as the last, being occupied by two unequal condyles which articulate with the third phalanx and the navicular bone ; two lateral faces exhibiting a very marked imprint. In the interior of this bone is found a nucleus of very condensed spongy substance, enveloped in a layer of compact tissue. It is usually developed from a single centre of ossification ; though in many subjects there is a complementary nucleus for the superior articular surface and the posterior gliding surface. Third (Distal) Phalanx, Os Pedis (or Pedal Bone). — This is a short bone which terminates the digit, and sustains the hoof' that incloses it and the navicular bone. When completed by a special fibro-cartilaginous apparatus, it represents the segment of a very short cone, obliquely truncated behind, from the summit to the base. It offers for study : three faces, three borders, and tivo lateral angles Faces. — The anterior, convex from side to side, and cribbled by porosities and vascular openings, shows on each side : 1, The preplantar fissure, a horizontal groove more or' less ramified, which commences behind, between the retrossal and basilar processes, ter- minating in front in one of the foramina which penetrate the bone ; 2, The patilobe eminence, a roughened projecting surface, situated between the preceding fissure and the inferior border of the bone. The superior face is occupied by an articu- lar surface formed by two glenoid cavities and a slight median ridge ; it comes in apposition with plantar surface of third ^ne inferior face of the second phalanx. The phalanx. inferior (or solar) face, hollowed out like an arch, 1, Lower face, or sole ; 2, 3, is divided into two regions by the semilunar crest, Wings, or retrossal pro- a Ralient line which describes a curve forwards, cesses; 4, Internal border; The anterior region ig perforated with very fine 5, Plantar foramina. . . , & * , ; ^ . porosities, and corresponds to that part of the hoof named the sole. The posterior region shows, immediately behind the semilunar crest, a median imprint, and two lateral channels designated the THE ANTERIOR LIMBS. 85 plantar fissures. These originate at the root of the basilar process, are directed obliquely downwards and inwards, and open into the plantar fora- mina, the external orifices of two large canals which enter the bone and unite in its interior to form the semilunar sinus. Borders. — The superior describes a curve, with the convexity forward, and presents : 1, In its middle, the pyramidal eminence of the os pedis, a single triangular process, flat before and behind, roughened on its anterior aspect, and concurring, by its posterior surface, to form the articular surface which responds to that of the second phalanx , 2, Laterally, two facets of insertion which encroach on the anterior surface, and even advance, posteriorly, nearly to the preplantar fissure. The inferior border is thin, dentated, convex, and semicircular; it is perforated by from five to ten large foramina which pass into the bone. The posterior border is slightly concave ; on it is observed a very narrow, transversely elongated, diarthrodial facet, which becomes confounded with the superior large articular surface, and is adapted to a similar facet on the navicular bone. Lateral angles. — These are two projections directed backwards, on whose summit the three borders of the bone unite, and which gives attachment to the lateiivl fibro-cartilages. A deep notch, the origin of the preplantar fissure, separates each into two particular eminences : one, the superior, named by M. Bouley the basilar process ; the other, the inferior, prolonged behind, and designated by Bracy Clark the retrossal process, from retro, behind, and os-m, bone. Structure. — The os pedis exhibits in its interior the semilunar sinus, a cylindrical, transversely elongated, and semicircular cavity resulting from the arching anastomoses of the two plantar canals. From this cavity pass off numerous channels, which anastomose frequently with each other, and open externally by the foramina on the anterior face of the bone, or by thos^ on its inferior border. The os pedis has for its base a nucleus of spongy substance, surrounded by a layer of compact tissue. The latter is thicker towards the pyramidal eminence than elsewhere, and sends into the interior numerous prolongations which form the walls of the semilunar sinus, as well as the bony channels which spring from it. Development. — The third phalanx, formed from a single nucleus of ossification, undergoes numerous changes in its configuration during life. Thus, in the young animal the lateral angles are thick, obtuse, and but little prolonged posteriorly ; but as it grows older, they increase in length and become salient. The development they then assume is due to the progressive ossification of the lateral cartilages implanted on their surface. It often happens, in very old horses, that this ossifying process is carried to an extreme degree, and nearly the whole substance of these complementary organs is invaded. From the commencement, its inevitable result is to convert the notch which separates the basilar from the retrossal process into a foramen. The complementary fibro- cartilaginous apparatus of the os pedis. — To understand properly the disposition of this portion of the foot, it is necessary that a previous knowledge of the ligaments and tendons attached to the os pedis should have been obtained ; therefore a detailed description will only be given when the Horse's foot is studied as a whole. It will be sufficient here to state that this apparatus consists of two lateral pieces, the fibro- cartilages of the os pedis, united behind and below by the plantar cushion, a fibrous and elastic mass on which rests the navicular bone through the medium of the perforans tendon. 9 g6 THE BONES. The Small Sesamoid (or Navicular) Bone. — This short bone is annexed to the third phalanx, behind which it is situated ; it is elongated transversely, flattened above and below, and narrowed at its extremities. It offers : 1, A superior face, on which are prolonged the glenoid cavities and the median ridge of the articular surface of the os pedis ; it responds to the second phalanx ; jr,g 51 2, An inferior face, divided by a e g e slight relief into two undulated / /^ facets, and covered with cartilage \ y ways by a groove of insertion, above navicular bone. which is remarked a diarthrodial a, Upper, or articular surface ;\ inferior border; ^cet that brings the small sesa- c, Superior border; d, Inferior, or posterior moid into contact With the pos-| surface ; e, The median transverse ridge ; /, terior border of the third phalanx ; Inferior margin ; g, Superior margin. ^ A p0Steri0r border and two ex- tremities, for ligamentous insertion. This bone, as well as the sesamoids, originates from a single centre of ossification. It is formed of a layer of compact tissue enveloping a nucleus of very condensed spongy substance. DIFFERENTIAL CHARACTERS OF THE ANTERIOR LIMB IN OTHER THAN SOLIPED ANIMALS. A. Shoulder.— In Carnivora the shoulder is composed of two bones, these creatures being furnished with a clavicle. This bone in the Dog is a little osseous shell imbedded among the muscles situated in front of the scapulo-humeral angle. That of the Cat constitutes a small styloid bone, which is joined to the acromion and sternum by two ligamentous cords. In all the domesticated animals except Solipeds, the coracoid process is immediately applied against the glenoid cavity. In all, al?o, with the exception of the Pig, the scapular spine gradually rises from above to below, and terminates in a sharp salient point, the acromion. The spine partitions the external face of the bone into two equal fossse in the Dog, and in Ruminants into two fossse, which", for extent, are as one to three to each other. The scapular spine of the Pig is much elevated towards the middle part, and bends more or less backwards, In the Carnivora the prolonging cartilage is entirely absent ; the anterior border of the scapula is very convex, as if the bone had been curved downwards. In the other domesticated mammals the scapula is somewhat regularly triangular. B. Aum. — Proportionately, the humerus is longer, and more inflected like an S, as the number of apparent digits is increased. Therefore it is that in the Carnivora the characters of length and inflexion are most marked. In the Ox, Sheep, Pig, and Dog, the furrow of torsion is not so deep as in the Horse, and the deltoid imprint is less salient. In the Dog this imprint is represented by a large roughened surface; in the Pig by some asperities only. The nutrient foramen is on the posterior face. It has been btated that the medullary canal in the Ox is traversed by an osseous band; but the presence of this is not constant. The summit of the trochiter is very elevated, particularly in Ruminants, and is thrown back on the bicipiial groove, which is single; in the Dog and Pig, this groove is carried inwards ubove the internal face of the humerus. The external trochlea in the Ox and Pig is well marked. In Carnivora, the inner lip of this trochlea is very high, and the external lip incomplete; a foramen establishes communication between the olecranian and coronoid fossse. In the Cat there is found, on the inner side of the lower extremity, a particular foramen that forms a vascular arch. C. Fore-arm. — The fore-arm is short in the Ox, Sheep, and Pig , very long in the Carnivora. The principal differential characters that it presents are connected with the relative dimensions of the two bones and their m/ones of the fore-arm are nearly equal in volume, and are slightly cro sed in an X fashion. The superior extremity of the ulna is thicker than its lower extremity ; it is nearly the opposite of this in the radius. Movable on one another, these bones only touch by their extremities, and to this effect offer : 1, Above, on the ulna, a concave articular surface, the small sig- moid cavity, and on the radius a rounded hinge-like facet; 2, Below, on the radius, a concave surface, and on the ulna a convex one. D. Fore-foot, or hand. — 1. Carpal bones. — The carpus of the Pig, like that of Man, contains eight bones — four in each of the rows. The second bone of the upper row corresponds with the ulna, and to a small extent with the radius. In the bones of the lower row, it is observed that the first corresponds with the two external met:icarpals, the second with ihe great internal metacarpal, the third with the preceding and the small internal metacarpal. The fourth, or trupezium. terminates inferiorly by a blunt point, and has no re'ations w th the metacarpal bones, because the thumb is entirely undeveloped in this animal. Fig, 52. 1, Olecranon ; 2, Body of the ulna ; 3, Body of the radius ; 4, 5, 6, First, second, and third bones of the upper row of the carpus ; 7, 8, First and second bones of the lower row ; 9, Rudimentary metacar- pals; 10x Principal metacarpals; 11, External digit; 12, Internal dieit. 72 Jf FORE-ARM AND FOOT OF THE OX ; FRONT VIEW. THE BONES. In the Cat there are also eight bones. The second, or pyramidalis, of the upper row is very developed ; it occupies all the external border of the carpus, and articulates with the ulna, the first bone of the second ruw, and the first metacarpal. The supercarpal bone, elongated, prismatic, and thickened at its extremities, offers in front two coalescing articular facets, one to correspond with the ulna, the other to join the 'pyramidalis. The bones of the inferior row decrease in thickness from the first to the fourth, and correspond : the first, to the first and second metacarpals ; the second, to the metacarpal of the third digit ; the third, to that of the fourth digit ; the Fig. 53. fourth, to the metacarpal of the thumb. j In the Bog there are only seven bones, as the scaphoid and semilunar bones are united, but the general disposition is the same as that in the Cat. Lastly, in the Ox and Sheep the carpus is only composed of six bones: four in the upper row, and only two in the lower, where the os magnum and trapezoides are consolidated. The supercarpal bone has no groove for gliding, and tfce pyramidalis articulates with the radius and cubitus. The bones of the lower row only articulate with the principal metacarpal bone. (Professor Gobaux, in 1865, exhibited specimens which go to prove that of the two bones of the lower row in the carpus of Ruminants, the internal really represents two; so that these animals actually have seven carpal bones like the Horse.) 2. Metacarpal bones. — The number of metacarpal bones varies much in the domesticated animals : — In the Carnivora there are 5 In the Pig there are 4 In Kuminants there are 2 The five metacarpals of the Bog and Cat articulate with each other, at their superior extremities, by lateral facets; they offer, at their inferior extremity, a condyle prolonged backwards by an articular surface resembling that of the Horse. The middle two are always longer than the two lateral. The smallest belongs to the fifth digit, or thumb, and is terminated inferiorly by a trochlea. The four metacarpals of the Pig articulate with each other, as in the Carnivora. The second and third are larger than the first and fourth. The fifth metacarpal is not developed. In Ruminants the metacarpal bones are two in number : a principal, which itself results from the consolidation of the second and third metacarpals, and another altogether rudi- mentary. The principal metacarpal is channeled on its anterior face, and for its whole length, by a deep vascular fissure— a trace of the primitive separation of the bone in two pieces. This fissure presents, inferiorly, the anterior orifice of a canal that completely traverses the bone. The posterior face is also marked by a very slight longitudinal groove. The superior extremity exhibits, externally and posteriorly, a single diar- throdial facet for the articulation of the rudimentary meta- carpal. The inferior extremity is divided by a deep notch FORE-ARM AND FOOT OF THE DOG ; ANTERIOR FACE. 1, First digit ; 2, Second digit; 3, Third digit; 4, Fourth digit ; 5, Thumb ; 6, 7, 8, 9, First second, third, and fourth into two articular surfaces, which together resemble the single surface in the Horse; each corresponds to one of the digits; the external is always smaller than the internal. In the foetus, the two long bones that form the great metacarpal are simply laid together, and their medullary canals are sepa- rated from each other by the double partition which results from this apposition ; after their coalescence, however, the par- titions are completely destroyed by resorption, and in a short time there is only a single medullary canal for the entire bone. The rudimentary metacarpal is only a small osseous stylet, articulating, by a diarthrodial facet, behind and to the outside of the superior extremity of the principal metacarpal ; it is sometimes absent in the Sheep and Goat. bones of the lower row of carpal bones ; 10, 11, First and second bones of the upper row; 12, Supercarpal bone ; 13, Body of the ulna ; 14, Apex of the olecranon ; 15, Beak of the olecra- non; 16, Body of the radius. THE ANTERIOR LIMBS. 8. Digital Region. — In the domesticated animals the number of complete digits is as follows : — Carnivora 5 Pig 4 Ruminants 2 The five digits of the Dog and Cat are exactly analogous to those of Man. Thus, the external corresponds to the auricularis, the second to the annularis, the third to the medius, the fourth to the index, and the internal to the thumb. — The latter, very small, has only two phalanges and does not come into contact with the ground. Each of the first four is composed: 1, Of a first phalanx, to which are annexed two sesamoids; 2, A second phalanx, which yet represents a veritable long bone ; 3, A conical phalan- gette, pointed, bent downwards, and hollowed at its base by a circular groove, in which is lodged the matrix of the claw. The small sesamoid (or navicular bone) is absent, but is replaced by a prominence of the ungual phalanx. The auricularis and index are alike, and not so long as the annularis and medius, which are the same in length. The Pig has four complete digits articulating from the metacarpals ; the thumb is absent. The index and auricularis, or fourth and fifth digits, are short, and do not usually rest on the ground. Ruminants certainly possess four digits, but only two are perfect— the medius and annularis — and these articulate with the inferior extremity of the principal metacarpal. The two others — the index and auricularis - are in a rudimentary condition, and are represented by two small bones situated above and behind the metacarpophalangeal articulation. In the Ox, Sheep, and Goat, each of the perfect digits comprises three phalanges and three sesamoids. The first phalanx fairly represents the moiety pj 54. of the phalanx in the Horse. It has no posterior imprints, but shows them on its inner surface for the attachment of several ligaments. This internal face is plane, and the external convex ; fPS^^®^"11!!^ ^i^fff these characters are repeated in the other two ■JIlP^i'^-^ ''* r^-^wi,n '% ' ' one of the lateral moieties of the os pedis of ■&'/ //•';.■'/.//, $.,.. solipeds. This phalanx has no complementary K&V'v $'''■',• H'r fibro-cartilage, basilar process, or retrossal emi- mm'.'''J"il'sity. Infernal surface. — The internal surface of the Horse's pelvis cannot be divided into two portions as in Man, because the inner aspect of the iliac bones is not hollowed out to form an anterior cavity. The pelvis of Solipeds is, therefore, a simple conoid cavity, in which are dis- tinguished four regions or faces, and two apertures called the inlet and outlet. The anterior opening or inlet is nearly circular, especially in the Mare, and a little oblique downwards and backwards. It is limited above by the inferior face of the base of the sacrum ; inferiorly, by the anterior border of the pubis ; and on the sides by a portion of the inner face of the iliac bones, and also the internal aspect of the pectineal crests. The inlet presents four diameters : a vertical, horizontal, and two oblique. The first extends from the inferior face of the sacrum to the anterior border of the pubic symphysis; its mean length is 8k inches. The second is measured from one pectineal crest or eminence to another ; the mean of this is 8T6^ inches. The two last diameters are estimated from the inferior face of the sacro-iliac articulation of one side to the ilio-pectineal eminence of the other ; this is on an average 8t7q- inches. These measurements irrefutably demonstrate that the inlet is not elliptical in the vertical direction. The posterior aperture or outlet, situated at the posterior end of the pelvic cavity, gives exit to the rectum and genital organs. As the pelvis of the horse is horizontal, the outlet should be considered as limited^ we think, by the inferior face of the summit of the sacrum, the superior face of the ischia, the supercotyloid crest or ischiatic spine, and the internal face of the sacro-ischiatic ligaments. At the outlet only two diameters are recognised : a vertical and a horizontal. The vertical measures on an average 6t7q inches ; it extends from the inferior face of the sacrum to the superior face of the ischial symphysis. The horizontal diameter, comprised between the two supercotyloid crests, is 7^ inches. The superior region of the pelvic cavity is a little concave from before to behind ; it has for base the sacrum, which presents on each side of the median line the subsacral foramina. This part is also called the sacral plane or roof of the pelvis. The inferior region, or ischio-pubic plane, is formed by the pubis and the ischia. It is concave from side to side ; its anterior border is nearly straight, and its posterior border is scooped out by a wide notch to form the arch of the ischium. It has been remarked by M. Gobaux, that the portion of this plane corre- sponding to the pubis presents numerous varieties. The superior face of the pubis may be convex in its anterior moiety and concave in its posterior ; or it may be concave before and convex behind, the concavity being separated from the convexity by a transverse ridge. This ridge is sometimes represented by a series of small conical eminences ; at other times this upper face is THE POSTERIOR LIMBS. 97 disposed as a smooth inclined plane, directed backwards and upwards, and a kind of rim surmounts the anterior contour of the oval foramen. With regard to the lateral regions, they are formed by a small portion of the inner face of the ilia, and in great part by the sacro- sciatic ligaments. 2. Differences in the Pelvis of the Sexes. — The pelvis of the Mare exceeds that of the Horse in all its dimensions, but the difference is most marked in the transverse diameters. The anterior inlet forms a vast circumference when compared with that of the male ; the pectineal crests are widely apart, and the distance separating the anterior border of the pubis from the lower face of the sacrum is considerable. If the pelvis be viewed in its superior plane, it is found that in the Mare the ischiatic notches are very deep ; that the internal border of the ilium forms a regularly curved and very concave line ; and that the supracoty- loid crests, or ischiatic spines, are widely separated from each other. It is also noticed that the floor of the pelvis is wide, and that the bones com- posing it tend towards the same horizontal plane. In the male, the ischiatic border is only represented by a very curved line ; this line is composed of two almost straight portions, which join at an obtuse angle at the origin of the neck of the ilium ; the supracotyloid crests are relatively near each other, and bent towards the longitudinal axis ; while the two moieties of the pelvic floor are directed very obliquely down- wards and inwards. In the Mare, the ischial arch is larger than in the male, and forms a regular curve uniting the two tuberosities of the same name. In the Horse, the two ischiatic tuberosities are but little apart from each other, and the ischial arch forms a somewhat acute angle whose borders are nearly straight. Lastly, when the pelvis is examined in its inferior plane, in addition to the features already indicated in the ischiatic arch, it is found that in the Mare the obturator foramina are large and nearly circular, while in the Horse they are elliptical ; the cotyloid cavities are also further removed from the ischio-pubic symphysis in the female than the male. The sacrum of the Mare has appeared to us, in some individuals, to be a little more arched from before to behind than that of the Horse ; but this character is not constant. The following figures relating to the capacity of the pelvis in the Mare and Horse confirm what has just been enunciated. MARE. Horizontal Diameters. HORSE. Horizontal Diameters. Between the Pectineal Crests. Between the Supercoty- loid Crests. Between the Pectineal Between the Supercoty- C rests. loid Crests. Inches. Inches. ?3 Inches. Inches. 04 MARE. Vertical Diameters. HORSE. Vertical Diameters. Between the Sacrum and Between the Sacrum and Between the Sacrum and Pubis. Ischium. Pubis. Between the Sacrum and Ischium. Inches. 89 TS Inches. Ota Inches. 8 Inches. 6ft 98 THE BONES. To recapitulate, there is observed in the pelvis of the Mare: 1. A great increase in the transverse diameters; 2. A deep and regularly concave ischiatic notch; 3. A wide and concave ischial arch ; 4. Circular obturator foramina; 5. The cotyloid cavities distant from the pubic symphysis. THIGH. This has for its base one bone, the femur Femur. The femur is a long, pair bone, situated in an oblique direction down- wards and forwards, between the coxa and the principal bone of the leg ; it is divided into a body and two extremities. Body. — It is irregularly cylindrical, and presents for study four faces. The external, internal, and anterior, confounded with one another, are regularly rounded and almost smooth, showing only some slight imprints and vascular grooves. The posterior, nearly plane, and wider above than below, offers : 1, Outwardly and towards the superior third, an uneven circular surface ; 2, On the same level, and inwardly, a slight crest, oblique downwards and outwards; 3, In the middle, a very extensive roughened surface, having the form of an obliquely angular parallelogram, for the attachment of the great adductor muscle of the thigh ; 4, Below this surface, a large vascular groove running obliquely outwards and downwards. On the limit of the posterior and external faces are found, towards the upper third, a large rugged, flattened eminence, curved in front, and termed the suhtrochanterian crest,1 because of its position under the trochanter ; below, a deep fossa, named the subcondyloid, garnished at its bottom with asperities and bordered in front by an uneven lip. On the limit of the posterior and internal face, there is observed from above to below : 1, The small trochanter, a large scabrous tuberosity, elongated in conformity with the bone, and situated near its upper fourth; 2, A marked longitudinal imprint for the attachment of the pectineus ; behind, it is confounded with the surface for the insertion of the great adductor muscle of the thigh, and presents, in front, the nutrient foramen of the bone; 3, The origin of the great posterior fissure ; 4, Quite below, a collection of large tubercles which form the supracondyloid crest. Extremities. — The superior extremity is sensibly flattened before and behind, and shows : 1, Inwardly, an articular head which is received into the cavity of the acetabulum. This head is separated from the other portion of the body by a neck, which is, however, not well .marked in the Horse, and forms two-thirds of a sphere, excavated in its internal part by a very deep cavity for ligamentous insertion , 2, Outwardly, a very large eminence, the trochanter, or great (external) trochanter, in which is recognised, as in the trochlea of the humerus : a summit, much more elevated than the articular head and slightly bent inwards ; a convexity, incrusted with cartilage and anterior to the summit, from which it is separated by a narrow and deep notch ; a crest situated under the convexity, and formed by a tuberculous surface on which one of the tendons of the middle gluteus muscle becomes 1 This is the third trochanter of Cuvier, and takes the place of the external and superior branch of the linea aspsra of Man. (It is the external small trochanter of Percivall and the middle trochanter of Leyh.) THE POSTERIOR LIMBS. 99 inserted, after gliding over the convexity ; 3, Posteriorly, the fossa of the trochanter, or digital fossa, a deep cavity studded with imprints and circumscribed, outwardly, by a salient lip which descends vertically from the summit of the trochanter to the posterior face of the bone, where it gradually subsides. The inferior extremity is flattened on both sides ; consequently, its larger axis crosses at a right angle that of the upper extremity. It is distinguished Fig. 61. Fig. 62. LEFT FEMUR ; ANTERIOR VIEW. 1, Head; 2, 2, Trochanter major, with its crest ; 3, Trochanter minor externus, sub- trochanterian crest, or third trochanter; 4, Lesser, or internal trochanter; 5, Notch for insertion of ligamentum teres ; 7, 8, Tuberosities for tendinous and ligamentous insertion ; 9, Trochlea. LEFT FEMUR; POSTERIOR VIEW. 1, Head ; 2, Great trochanter ; 3, Third, or trochanter minor externus ; 4, Lesser, or internal trochanter ; 5, Fossa for insertion of ligamentum teres; 6, Trochanterian fossa ; 7, 8, Tuberosities ; 9, Fossa for the insertion of the external meniscus; 10, Supracondyloid fossa, 11, Condyles. "by the presence of two condyles and a trochlea. The two condyles, placed, pno beside, the other behind, correspond to the superior extremity of tha tibia; They are separated by a deep depression designated the iniercondylcid'fvssa, which lodges the spine of the tibia and the interosseous ligaments of the femoro-tibial articulation. The external condyle bearu, outwardly ^wo.fossre; one superior, for ligamentous insertion; the other, inferior,-, ibr, muscular 100 THE BONES. Ficr. 63. attachment. The internal condyle presents, posteriorly and inwardly, near the posterior extremity of the intercondyloid notch, a roughened depression for the insertion of the fibro-cartilaginous meniscus interposed between the external condyle and the corresponding articular plane of the tibia. It is surmounted outwardly, i.e., on the side opposite to the intercondyloid notch, by a large tubercle of insertion. The trochlea, a wide pulley on which the patella glides, is situated in front of the condyles. It is slightly oblique downwards and inwards, and appears to continue in front the inter- condyloid notch. Of the two lips which border its cavity laterally, the internal is the thickest and the most prominent. Between the external and the corresponding con- dyle is seen a digital fossa for muscular insertion. Structure and development. — The femur, very spongy at its extremities, is developed from four principal centres of ossification : one for the body, another for the articular head, the third for the trochanter, and the last for the inferior extremity alone. LEG. This has for its base three bones : the tibia, peroneus (or fibula), and the rotula (or patella),, 1. Tibia. The tibia is a long, prismatic bone, thicker at the superior than the opposite extremity, and situated between the femur and the astragalus, in an oblique direction downwards and backwards, constituting the principal portion of the leg. Body. — This offers for study three faces and three borders. The faces are wider above than below. The external is almost smooth, and is concave in its superior part and convex below, where it deviates to become the anterior. The internal, slightly convex on both sides, presents, superiorly, deep imprints lor the attachment of the adductor muscles of the thigh and the semi- tendinosus. The posterior, nearly plane, is divided into two triangular surfaces : one, superior, slightly roughened, serves for the attachment of the popliteus muscle ■; the other, inferior, much more extensive, is furrowed into numerous longitudinal crests which give attachment to the perforans muscle. On the limit of these two surfaces is remarked the nutrient foramen of the bone. The borders are distinguished as anterior, external, and internal. The first is rounded, and not very salient in its inferior two-thirds ; it forms in its superior third, a curved crest, with the concavity external, which joins the anterior and superior tuberosity of the bone ; this has received the name of the tibial crest. The external border is very thick and concave above, where it constitutes, in common with the fibula, the tibial arch. The 'internal is also very thick, straight, and provided superiorly with some tfalieflt ctubercles to which the popliteus is attached. fi$tr£mi\ie$'.-;-%he superior extremity, the most voluminous, is formed by . three iuberfrsitJep/;ari interior and two lateral, which are external and interna^ [The ' first r the smallest, is a rugged process continuous with fac^ibwtl crest, an4r separated from the external tuberosity by a wide and SECTION OF LEFT FEMUR, SHOWING ITS STRUCTURE. THE POSTERIOR LIMBS. 101 Fisr. 64. deep groove in which passes a tendinous cord ; it is excavated, in front, by a vertically elongated fossa which lodges the middle ligament of the patella. The external tuberosity, medium in size and the most detached, has outwardly an articular facet for the head of the fibula. The internal tuberosity, the largest and least detached, presents : on the sides, ligamentous imprints ; behind, a small tubercle which gives attachment to the pos- terior crucial ligament of the femoro- tibial articu- lation. The superior face of the two lateral tube- rosities is occupied by two Jarge irregular and undulated articular surfaces, which respond to the condyles of the femur through the medium of the two meniscus- shaped fibro -cartilages interposed be- tween the two bones. Of these two surfaces the external is always the widest, because it serves, by its posterior part, for the gliding movements of the popliteal tendon. They are separated from each • other by the tibial spine, a conical articular eminence divided into two lateral parts by a groove of inser- tion excavated at its base, and in front by two lateral facets for the insertion, anteriorly, of the two inter- articular cartilages ; it is bordered behind by another fossa which receives the posterior insertion of the internal meniscus. The inferior extremity, flattened behind and before, exhibits an articular surface moulded on the pulley of the astragalus, and two lateral tuberosities. The articular surface is formed by two deep cavities oblique from behind to before and within outwards, and separated by a median tenon which terminates pos- teriorly by a very prominent projection on which the. bone rests when it is made to stand vertically on a horizontal plane. The external tuberosity l projects but little, and is traversed in its middle by a vertical fissure. The internal tuberosity,2 better defined, is margined posteriorly by an oblique channel. Structure and development.— The tibia is very compact in its inferior portion, and is developed from four chief centres of ossification. The body is formed by one and the superior extremity by two, the anterior tuberosity taking one of these ; the last develops the whole of the inferior extremity. It is rare to see the external tuberosity of this extremity formed from a separate nucleus. 2. Fibula (or Peroneus). ^ A small, undeveloped bone, elongated and sty- loid in shape, situated outside the tibia, and extend- ing from the superior extremity of that bone to the middle or lower third of its body. ^ The middle portion of the fibula is thin and cylin- drical, and forms above, in common with the external border of the larger 1 The external malleolus of Man. 2 The internal malleolus. 10 POSTERIOR VIEW OF RIGHT TIBIA. 1, Tibial spine; 2, for the insertion of the internal meniscus ; 3, External tuberosity with articulation for the fib- ula; 4, Fossa for the insertion of external meniscus ; 5, Fibula, forming with the tibia the tibial arch ; 6, Shaft, or body of the tibia; 7, 8, External and in- ternal malleoli, inferior tuberosities, or lateral processes of the tibia ; 9, Articular trochlea? with a median ridge, for articulation with the astragalus. 102 THE BONES. bone, the tibial arch. Its superior extremity, wide and flattened on both sides, has received the name of head; it offers, on its internal face, a diarthrodial facet to articulate with the external and superior tuberosity of the tibia; on its external face it shows ligamentous imprints. The inferior extremity of the fibula terminates in a blunt point, and gives attachment to the ligamentous fibres that unite it to the tibia. The fibula is sometimes continued to the external inferior tuberosity of the latter bone, with which it is confounded ; and as it is particularly under such circumstances that this tuberosity has Been noticed to be deve- loped from a special nucleus, it seems quite natural, having regard to the disposition observed in pachyderms and carnivores, to consiHer it as the inferior extremity of the fibula joined to the tibia. With these animals, indeed, the tuberosity or external malleolus is formed by the inferior ex- tremity of the fibula. Structure and development. — This bone is very compact, and developed from a single nucleus of ossification. 3. Patella. A small, short, and very compact bone, situated in front of the femoral trochlea, and annexed to the tibia, to which it is attached by three extremely solid ligamentous bands. The small polyhedron which it represents only offers for observation three faces : the superior, roughened, and serving for the insertion of the triceps cruralis and rectus muscles ; the anterior, convex and irregular ; and the third, the posterior, moulded on the femoral trochlea, to which it is but imperfectly adapted. In the fresh state, however, the articular surface formed by the latter face is completed by a fibro-cartilaginous apparatus, which will be noticed when describing the femoro-tibial articulation. This articular surface is composed : 1, Of a median ridge, which occupies the bottom of the trochlear cavity ; 2, Of two depressed, gliding, lateral facets on the sides of this cavity ; the internal facet is always larger than the external, a disposition which permits the patella of one limb to be distin- guished from that of the other. POSTERIOR FOOT. This region, which bears the greatest resemblance to the same region in the anterior limb, comprises three subdivisions: the tarsus, metatarsus, and the digital region. 1. Bones of the Tarsus. These are short, very compact bones, six or seven in number, and situated between the inferior extremity of the tibia and the superior extremity of the metatarsal bones ; they are arranged, like the bones of the carpus, in two tiers— a superior and an inferior. The superior row only comprises two bones, the largest ; these are the astragalus and the calcaneus (or calcis). The inferior row is formed, out- wardly, by the cuboides alone ; inwardly and anteriorly, it is subdivided int> two secondary rows, the superior of which is constituted by the scaphoides, and the inferior by the large and small cuneiform bones. The last is sometimes divided into two, in which case there are three cuneiforms ; then the total number of the bones is seven. Astragalus. — An irregular cubical bone, situated in front of the THE POSTERIOR LIMBS. 103 calcaneus, between the tibia and the scaphoid, and divided into five faces : — 1, A superior and anterior $ formed as an articular pulley to correspond to the in- ferior extremity of the tibia; this pulley, oblique from above downwards, forwards, and outwards, may be considered as the type of the most perfect trochlea in the organism; its groove receives the median tenon of the tibia, and its two ridges or lips fit into the lateral furrows of that bone. 2, An inferior face, occupied by a slightly convex articular surface responding to the scaphoid ; this surface is notched outwardly by an excavation for ligamentous insertion. 3, A posterior face, irregular, cut into three or four diarthrodial facets adapted for similar facets on the calcaneus, and which are separated by a wide, rugged excavation. 4, An external face, covered with imprints. 5, An internal face, provided below with a small tubercle of insertion. Calcaneus. —A bone vertically elongated, flattened on both sides, and presenting two faces, two borders, and two extremities. The external face is smooth and nearly plane. The internal face is excavated into a gliding groove to form the tarsal arch, in which passes the tendon of the perforans. The anterior border is slightly concave. The posterior border is thicker, straight, and rugged. The superior extremity, slightly tuberous, constitutes the summit of the calcaneus, and is divided into three parts : a middle, which gives attachment to the tendon of the gastrocnemius ; the other, the anterior, is a smooth surface on which this tendon rests when the foot is much flexed ; the third, altogether posterior, also constitutes a gliding surface for the tendon of the perforatus. The inferior extremity, wide and voluminous, shows in front three or four articular facets which correspond to the astragalus, and are separated, like those of the last bone, by an irregular and slightly excavated surface of insertion. Below, it shows for articulation with the cuboid a fifth facet, continuous with one of the preceding. Development. — The calcaneus is deve- loped from two nuclei of ossification, one of which is for the summit. Cuboid bone. — This little bone, situated at the external side of the scaphoid and the LEFT HIND FOOT; EXTERNAL ASPECT. 1, Tibia; 2, Summit of calcis or cal- caneus ; 3, Astragalus ; 4, Cuboid ; 5, Scaphoid; 6, Cuneiform mag- num ; 7, Large metatarsal bone ; 8, Small metatarsal bone; 9, Suf- fraginis, proximal, or first phalanx ; 10, Sesamoid bones ; 11, Coronary, second, or middle phalanx : 12, Pedal bone, or third or distal phalanx ; 14, Navicular bone ; 15, Basilar process of pedal bone. 104 TEE BONES. large cuneiform bone, between the calcaneus and two of the metatarsals, does not resemble a cube, but a parellelopiped elongated from before to behind. It offers six faces : a superior, an articular face, and in contact with the calcaneus ; an inferior, also articular, responding to the principal and external rudimentary metatarsal bones ; an internal, furnished with three facets for contact with the scaphoid and great cuneiform, and crossed from before to behind by a fissure, which forms with these two bones a vascular canal ; an external, an anterior, and a posterior, covered with imprints. Scaphoid bone (the large cuneiform of Percivall). — Flattened above and below, it is described as having two faces and a circumference. TMfe faces, both articular, are furrowed by a channel of insertion, and are distinguished as superior and inferior. The first is concave, and responds to the astra- galus ; the second is convex and in contact with the two cuneiform bones. The circumference offers, outwardly, two small facets which are adapted* to similar facets on the cuboid bone. For the remainder of its extent, it is covered with imprints. Great Cuneiform bone (the middle cuneiform of Percivall). — Flattened above and below, and triangular in shape, this bone is much smaller than the scaphoid, though resembling it in a striking manner. Its superior face is in contact with the latter bone, and its inferior face articulates with the middle and internal lateral metatarsal bones. Its external border is provided with one or two facets to correspond with the cuboid bone ; and its internal border also offers one, which is in contact with another on the small cuneiform. Its anterior border is roughened throughout its extent. Fig. 66. Fig, 67. LEFT HOCK; FRONT VIEW. LEFT HOCK; INTERNAL ASPECT. 1, Apex of calcaneus ; 2, Astragalus, inner 1, Apex of calcaneus ; 2, Inner articular ridge ; 3, Scaphoid ; 4, Cuneiform mag- ridge of astragalus ; 3, Navicular, scaphoid, num ; 5, Cuboides. or cuneiform medium ; 4, Cuneiform mag- num ; 5, Cuboides ; 6, Cuneiform parvum. Small Cuneiform bone. — Situated at the inner side of the tarsus, this bone, the smallest of any yet examined, is elongated from before to behind, flattened on both sides, and wedged in between the os scaphoides, the large cuneiform bone, and the large and internal small rudimentary metatarsal bones, with which it corresponds by four articular facets : a superior, two inferior, and one internal. When this bone is in two portions, there are then three cuneiforms, which may be distinguished, as in Man, by naming them first, second, and third. THE POSTERIOR LIMBS. 105 Fig. 2. Bones of the Metatarsus. These bones are three in number, a median and two lateral, and offer the greatest analogy to the metacarpal bones. This enables us to dispense with a general description of them, and to confine ourselves only to indicating the differential characters which distinguish them from the corresponding bones in the anterior limb. The principal, or median metatarsal bone, is longer than the same metacarpal, and its body, instead of being slightly compressed before and behind, is nearly a regular cylinder. It presents out- wardly a fissure which is directed at first obliquely backwards and downwards, and afterwards descends vertically along the lateral external metatarsal bone. The articular surface of the superior extremity is ex- cavated in its centre by a large fossa of insertion. The inferior extremity is at the same time wider and thicker than that of the metacarpus. Of the two rudimentary (digital) or lateral metatarsal bones, the external is always longest and thickest. The internal bears on the superior face of its head three articular facets, two of which respond to the small cuneiform, and the third to the large bone of that name. 3. Bones of the Digital Megion. The digital region of the posterior closely resembles that of the anterior limb. The analogy in the con- formation of these bones is even pushed so far, that it becomes very difficult to distinguish them from one another. It is remarked, nevertheless : 1, That the first pha- lanx is not so long as in the anterior limb, and less wide and thick at its inferior extremity, but is, on the contrary, wider and thicker at its superior extremity ; 2, That the lateral diameter of the second phalanx is shorter ; 3, That the third phalanx, less spread out"] towards its inferior border, has more the shape of a V, * and that its inferior face is more concave ; 4, That the sesamoids are less voluminous; 5, That the navicular bone is shorter and narrower. KO DIFFERENTIAL CHARACTERS OF THE POSTERIOR LIMB IN OTHER THAN SOLIPED ANIMALS. A. Pelvis. — It is remarked: 1, That in all the domesticated animals, with the exception of Solipeds, the direction of the coxae is nearly horizontal ; 2, That in all, except Solipeds, the ilium tends to assume a vertical direction ; 3, That in all the trans- verse diameter of the pelvis is relatively less extensive. In the Ox, Sheep, and Goat, the space between the two coxae is scarcely so great in front as behind ; the ilium is not volumi- nous, and has only three processes on the superexternal iliac spine. There is no furrow on the lower face of the pubis, and its upper face, like that of the ischium, is very concave. Three eminences are seen on the postero-external angle of the ischium. In early life, the ischio-pubic symphysis shows an epiphysary nucleus in the middle of its inferior face. (The epiphysis on the inner border of the ischium has been considered by some anatomists as an inde- pendent bone, and described by them as the interischial bone.) POSTERIOR ASPECT OF LEFT METATARSUS. 1, Head of principal metatarsal bone $ 2, 3, External and in- ternal splint bones, or metatarsals of the rudimentary digits; 4, Rough surface for insertion of suspen- sory ligament ; 5, Nutrient foramen ; 6, Middle ridge of inferior articular surface. 106 THE BONES. The rim of the cotyloid cavity has also three notches, and the supracotyloid crest, or ischiatic spine, is very elevated and sharp, and but little roughened outwardly. The external iliac fossa of the Sheep and Goat is separated into two portions by a small longitudinal crest. The pelvis of the Pig closely resembles that of the smaller ruminants; though the crest of the ilium is convex, and there is no protuberance outside the ischio-pubic symphysis. In Carnivora the lateral diameter of the pelvis is greater behind than in front. The ilium is nearly vertical, and its external face is much depressed. The notch forming the ischial arch occupies no more than the internal moiety of the posterior border of the ischium ; between this arch and the ischiatic tuberosity is a rugged lip directed down- wards. There is no furrow on the lower face of the pubis. m B. Thigh. — In all the domesticated animals except Solipeds, the femur tends to become curved, prismatic, and triangular ; the posterior lace contracts, and the surfaces of insertion that it presents gradually approach each other until they become confounded and form the linea aspera in certain species. The head is more distinct , the small trochanter is a rough tubercle, and is joined to the large trochanter by an oblique osseous lip ; the latter trochanter subsides and forms a single mass whose summit and convexity are con- founded; the third trochanter, the fossa, and the supracondyloid crest are more or less effaced. In the Ox, there is no subtrochanterian crest ; the supracondyloid fossa is shallow, and the crest little noticeable. The head is well detached and 1 as its centre ex- cavated by a shallow fossa of insertion. The trochlea is narrow, and its inner border ascends much higher on the anterior face of the bone than the external. In the Sheep and Goat, the general form of the femur resembles that of the Ox. It is observed, however, that the body is slightly curved backwards; that the supracondyloid fossa is nearly obliterated ; that the trochanter has subsided nearly to a level with the articular head, and that the trochlea is circumscribed by two equal-sized lips. In the femur of the Pig there is also noticed a supracondyloid fossa, but it is wide and shallow ; the rugosities of the posterior face are replaced by some salient lines ; the trochanter is on a level with the head ; the latter is supported by a somewhat constricted neck, and is situated within and in front of the great trochanter. This latter disposition changes the direction of the great axis of the superior extremity, which obliquely crosses that of the inferior extremity. In the Dog and Cat, the femur is long and curved like a bow. The rugged surfaces of the posterior face are confounded, and form two crests representing the linea aspera of the human femur. These crests do not lie against each other in the middle portion of the bone; they are merely parallel, then, they diverge above and below, to terminate beneath the great and small trochanters, and above the two condyles. The great tro- chanter is not so high as the articular head. The femur of Carnivora is also distin- guished : 1, By the complete absence of the third trochanter and the supracondyloid fossa — this last being replaced by a small tubercle which terminates below the external branch of the linea aspera; 2, By the marked constriction and length of the neck sup- porting the articular head ; 3, By the depth of the digital fossa, which is bordered by an oblique lip extending from the great to the small trochanter. C. Leg. — In the leg-bone there is observed, in the various domesticated animals, differ- ences analogous to those mentioned as existing in the fore-arm of the thoracic limb. More particularly is this the case with regard to the development of the fibula ; in Kuminants this bone is reduced to its inferior nucleus. In these animals the patella is also very narrow; and in all the domesticated species except Solipeds, the articular grooves in the lower end of the tibia are directed immediately from before to behind. In the Ox, the tibia is short ; it is longer in the Goat and the Sheep. The tibia of these animals is remarkable for: 1, The absence of the lateral facet on the supero- external tuberosity ; 2, The absence of a vertical fossa on the anterior tuberosity ; 3, The absence of roughened lines on the posterior face ; the obliquity downwards and inwards of the inferior articular surface. The most salient point of this surface is the anterior extremity of the middle tenon. The body of the fibula and its upper extremity are replaced by a fibrous cord which is sometimes ossified wholly or in part. In the Pig, the fibula is flattened on both sides, extends the whole length of the leg, and is united to the tibia by its two extremities : above, by a diarthrodial facet below, by an interosseous ligament. It is developed from three ossific centres: the inferior articulates with the calcaneus and astragalus, and forms a prominence resembling the external malleolus. In Carnivora, the tibia is long and slender, and presents a salient anterior crest. The THE POSTERIOR LIMBS. 107 fibula is also as long as the tibia, and is united to that bone at three points : at the two extremities by articular surfaces, in the inferior third and middle by an interosseous ligament. D. Posterior Foot. — 1. Bones of the tarsus. — The number of tarsal bones varies a little in the domesticated animals, as the following list will show : Carnivora and Pig 7 Ox, Sheep, and Goat ■. 5 In the Dog, Cat, and Pig, there are three cuneiform bones, and in the Ox and Sheep, in addition to there being only two cuneiforms, the scaphoid and cuboid bones are < on- solidated into one piece. The astragalus of the carnivora articulates with the scaphoid by means of a veritable head, separated from the rest of the bone by a constriction termed the n( ck of the astra- galus. The cuboid and the cuneiform bones respond to all the metatarsals. In the Pig, the astragalus and calcaneus are very long. The cuneiforms and cuboid respond to the four perfect digits. The tarsus of the domesticated Ruminants is slender above. The astragalus is elongated from above to below, and is united to the scaphoid by an antero-posterior groove, and to the calcaneus by a more superficial vertical groove. The calcaneus is long and ti.in; the posterior gliding surface on the summit is excavated into a channel; the small cuneiform is pisiform and but slightly developed. 2. Bones of the metatarsus. — The metatarsus is also a region in which the number of bones varies in the domesticated animals. Thus in the Carnivora and Pig there are five, and only two in Ruminants. The metatarsals of the Carnivora and Pig are exactly like the same bones in the anterior limb. Those of Ruminants are slightly different. In the Dog and Cat are one rudimentary and four perfect metatarsals. The former is articulated with the internal cuneiform, and represents the vestige of the thumb. The Pig has four perfect metatarsals, and an internal rudimentary one. The latter is a small bone flattened on both sides, articulating by means of a diarthrodial facet, and sometimes consolidated behind the upper end of the fourth metatarsal. In the Ox, Sheep, and Goat, is found a principal and a rudimentary metatarsal bone. The latter is like the rudimentary metacarpal bone, but the former differs from the principal metacarpal bone in being longer, quadrilateral in form, and having a vascular canal traversing the posterior face of its upper extremity. 3. Bones of the digital region. — In all the domesticated animals, the posterior digits comport themselves exactly like the anterior. The Carnivora alone offer a notable differ- ence; in them, in reality, the thumb does not exist, or rather, it is only represented by the rudimentary metatarsal bone alluded to above. Nevertheless, it frequently occurs that a completely developed thumb is found in this animal ; and in this case the rudi- mentary metatarsal is ordinarily followed by a ligamentous cord, to which is suspend< d a bony stylet that represents either the inferior extremity of the metatarsal, or the first phalanx ; it is to this stylet that are found articulated in succession the second and third phalanges. (Professor Fuchs, of Carlsruhe, found, in a Newfoundland dog, four true claws and two false : the internal of the latter corresponded to a well-developed, small metatarsal bone, while the external was only rudimentary, terminating in a point, and bound to the tarsus by a simple ligament.) COMPARISON OF THE ABDOMINAL LIMB OF MAN WITH THAT OF ANIMALS. A. Pelvis. — The longitudinal axis of the pelvis of Man forms, with the horizon, an angle of about 40°. The bones which compose it are proportionately larger and stronger t' an in all the domesticated animals. The two faces of the ilium, and especially the inner face, are much hollowed ; the iliac crest has the form of an italic S. The pubis alone participates in the formation of the pelvic symphysis, and (he con- cavity which, in the domesticated animals, is called the ischial arch, id designated in Man the pubic arch. In consequence of the excavation on the inner face of the ilium, the pelvic cavity may be divided into the great and lesser pelvis In the latter are lodged the genital and urinary organs, as well as the extremity cf the d'g^tive tube. B. Thigh. — The femur of Man is nearly vertical, and situated in a direction slightly 108 THE BONES. oblique downwards and inwards ; it presents a curvature forwards. The body of the bone is prismatic and triangular in its middle part ; the posterior border of this prism forms a somewhat salient crest, which takes the place of all the insertion eminences on the pos- terior aspect of the femur in animals, and is designated the linea asptra. This line bifurcates above and below ; below, the branches margin a triangular or popliteal space. HUMAN PELVIS; FEMALE. 1, Last lumbar vertebra; 2, 2, Intervertebral substance j 3, Promontory of the sacrum ; 4, Anterior surface of the sacrum ; 5, Coccyx ; 6, Iliac fossae ; 7, Antero- superior spinous process; 8, Anteroinferior spinous process; 9, Acetabulum. — a, Its notch ; 6, Body of ischium ; c, Its tuberosity ; d, Its spine ; e, Pubis ; /, Symphysis pubis ; g, Arch of the pubes ; h, Angle of os pubis ; i, Spine of pubes, with crest between it and h ; k, kf Pectineal line ; I, I, Ilio-pectineal line, with its prolongation, m, m ; n, Ilio-pectineal eminence ; o, Smooth surface for femoral vessels ; p, p, Great sacro-ischiatic notch. The head is supported by a long neck, inserted obliquely into the superior extremity. The two condyles are joined together in front by the trochlea, which is wide and shallow. C. Leg. — Three bones : the tibia, fibula, and patella. The tibia is very long ; its crest (or spinous process) is much more developed than in any of the domesticated animals, and describes u kind of curve like an italic S. On the inner aspect of the inferior extremity is seen a voluminous process which occupies, inwardly, a portion of the tibio tarsal articulation : this is the internal malleolus. The articular surface is not exactly formed to correspond with the whole articular surface of the astragalus. The fibula is as long as the tibia. It is prismatic, and slightly twisted on itself. It articulates above and below with the tibia. The lower extremity responds to the astra- galus, and forms a prominence named the external malleolus. There is nothing particular to note in the patella. D. Foot. — The foot of Man is situated in a horizontal direction. Its upper aspect is convex ; its inferior face is excavated, and it rests on the ground by its two extremities. 1. Tarsus. — In the tarsus there are seven bones, three of which are cuneiform The astragalus articulates with the tibia and fibula ; it responds to the scaphoid by a well detached convex articular surface, named the head. In the bones of the lower row, it is remarked that the cuboid responds to the fifth and fourth metatarsals : the first cuneiform to the third ; the second cuneiform to the second metatarsal, and the third to the first. 2. Metatarsus. — The metatarsus is composed of five bony columns, nearly parallel to each other. They are enumerated from without to within, and increase in length from the first to the fourth ; the fifth is the shortest and most voluminous. TEE LIMBS IN GENERAL. 109 3. Digital region. — This comprises five digits or toes. The phalanges of these toes are analogous to those of the fingers, from which they are distinguished by their small size. They increase in volume from the first to the fifth digit* Fig. 70. Fig. 71, Fig. 72. tfffi RIGHT HUMAN FEMUR*, ANTERIOR ASPECT. 1, Shcaft; 2, Head; 3, Neck ; 4, Great tro- chanter ; 5, Anterior intertrochanteric line; 6, Lesser trochanter ; 7, External condyle ; 8, In- ternal condyle ; 9, Tu- berosity for attachment of external lateral liga- ment; 10, Fossa for ten- don of origin of popliteus muscle; 11, Tuberosity for attachment of in- ternal lateral ligament. HUMAN TIBIA AND FIB- ULA OF RIGHT LEG; ANTERIOR ASPECT. 1, Shaft of tibia ; 2, Inner tuberosity ; 3, Outer tuberosity ; 4, Spinous process ; 5, Tubercle ; 6, Internal surface of shaft; 7, Lower extremity of tibia ; 8, Internal mal- leolus; 9, Shaft of fib- ula ; 10, Its upper ex- tremity; 11, Its lower extremity ; between 1 and 6 is the sharp crest of the tibia. DORSAL SURFACE OF LEFT HUMAN FOOT. 1, Astragalus; 2, Its An- terior extremity articu- lating with the cuboid bone, 4 ; 3, 3, Calcis ; 4, Scaphoid;/ 5, Inter- nal ■cuneiform bone ; 6, Middle cuneiform bone ; 7, External cuneiform bone ; 8, Cuboid bone ; 9, Metatarsal bones of first and second toes; 10, First phalanx of great toe; 11, Second ditto; 12, 13, 14, Pha- langes of second toe. Article VI. — The Limbs in General and their Parallelism. A. The Limbs in General. — The interrupted columns which compose the limbs are destined not only to support the trunk in a stationary attitude, but also to transport it during progression. This double destination gives rise to a difference between the anterior and posterior members. The front limbs, 110 TEE BONES. being nearer the centre of gravity than those behind, have to sustain the largest share of the weight. They ought, consequently, to be specially organised as organs of support. Therefore it is that the four principal rays composing each of them — shoulder, aim, fore-arm, and foot — although flexed, or disposed to be flexed, in an inverse sense to one another, oppose to the pressure of the weight of the trunk, which tends incessantly to throw them down, obstacles purely mechanical, and of such energy that we may still understand how the body can be sustained on the anterior limbs, if we suppose all the muscular masses surrounding these bony rays removed except one. ^ Thus, the weight of the body is at first transmitted to the scapula through the muscles that attach that bone to the trunk. It then passes to the humerus, and from thence to the radius, to be thrown, finally, on the different pieces composing the foot. Now the humerus forming with the scapula an angle which is open behind, and with the bones of the fore-arm another angle open in front, the weight of the body pressing continually on these angles tend3 to close them, and thus cause the flexion of the bony rays. But this result is prevented by the combined action of two muscular powers — the biceps and the extensors of the fore-arm. With regard to the radius, carpus, and metacarpus, owing to. their vertical direction they themselves support the pressure of the weight of the body without requiring any muscular aid. But the digital region, being directed obliquely forward and downward, forms, with the principal metacarpal, a third angle open in front, for the sustenance of which nature has given solid, inert, or contractile mechanical bands. The anterior limbs are also agents of transport, for they can elevate the trunk by the spring of their bony rays, and fix themselves on the ground by their free extremity. The posterior limbs are less favourably disposed than those in front to assume the function of columns of support, as their rays are for the most part in a state of permanent flexion, and joined in an angular manner to one another, as may be seen by glancing at the skeleton (See Figs. 1, 2, 3, 4, 5). It is therefore necessary that muscular agency should prevent the breaking-down of these rays. Though defective as supporting columns, they are nevertheless admirably designed to serve as agents of locomotion. The slightest erection of these inclined rays propels the mass of the body forward, and this impulsion is almost wholly transmitted to the trunk in consequence of the very intimate union of the pelvis with the vertebral column. B. Parallel between the Anterior and Posterior Limbs. — After what has just been said, it will be seen that the anterior limbs are more par- ticularly destined for the support of the body, while the posterior ones more especially play the part of impulsive agents in the locomotory acts. Notwithstanding this difference in the functions assigned them, these two columns offer in their conformation such striking resemblances to each other, that some authors have been inclined to consider the posterior as an exact repetition of the anterior limb. The following is a brief analysis of the analogies existing between them. At the end of the last century, Winslow and Vicq-d'Azyr, and nearer our own time, Cuvier, Flourens, Paul Gervais. Martins, Gegenbaur, and Lavocat, have occupied themselves with the parallelism existing between the anterior and the posterior members. All these anatomists did not absolutely arrive at the same conclusion ; for several of them, forgetting that the question should be examined in the whole animal series, made Man alone the subject of their THE LIMBS IN GENERAL. Ill meditations. In such a matter, it must not be forgotten that the limbs are constructed with a view to their physiological functions, and that the differences remarked in examining them in several species are dictated by the kind of life the animals are intended to lead. Vicq-d'Azyr and Cuvier recommend that the anterior and posterior limbs of opposite sides should be compared. Martins and Gegenbaur, allowing a torsion of the humerus of 180°, advise that the two members of the same side should be collated, care being taken to make allowance for the untwisting of the 180° contortion at the lower end of the humerus. Lastly, Flourens and Lavocat contrast the two members of the same pair with each other, after placing the hand in a position of natural pronation by rotation of the radius on the ulna, and without turning either limb or ray, or even a portion of a ray, no matter what kind of animal may be under examination. We will adopt the latter proceeding, as it is the simplest and most natural. Parallel between the coxa and scapula. — The analogies existing between these two bones are but little striking at first sight ; nevertheless, with atten- tion there is no difficulty in finding in the coxa the three pieces that enter into the composition of the shoulder. The ilium represents the scapula. The external iliac fossa reminds one of the supra- and subspinous fossae. Occasionally, there is met with in the Horse a rudiment of the crest dividing the iliac fossa into two parts, and, in some animals — the Pig, Sheep, and Goat — this crest, which is the trace of the scapular spine, becomes constant and very evident. With regard to the cotyloid cavity, it repeats in the posterior limb the glenoid cavity of the scapula. There remains to determine in the latter bone the portions analogous to the ischium and pubis. If we rely upon the evidence afforded by the muscular insertions, we come to the conclusion that the ischium corresponds to the coracoid process, and the pubis to the clavicle of animals which are provided with one. It will also be remarked that the coxa is directed backwards, while the scapula inclines obliquely forwards ; this opposition in the direction of the bones in no way alters their analogies ; the functions of the members to which they correspond require this inverse position. Parallel between the femur and humerus. — The resemblance between these two bones is remarkable. Thus there is found in the first : 1, An articular head, better detached than that of the humerus, but shaped in the same manner ; 2, A trochanter analogous to the great tuberosity, and also like it decomposable into three distinct parts — summit, crest, and convexity ; 3, A lesser trochanter, representing the smaller tuberosity ; 4, An eminence for the insertion of the superficial gluteus muscle, which takes the place of the deltoid imprint ; 5, An inferior articular pulley continued between tbe two condyles by a non-articular groove ; this trochlea certainly corresponds to the median groove of the inferior humeral face. There are, no doubt, differences between the two bones, but they have no bearing upon the result just indicated. Thus the linea aspera of the femur is situated behind ; that of the humerus in front. In the femur the two condyles of the inferior extremity are placed behind the trochlea ; the contrary holds in the humerus. These modifications are necessary in order to give the movements of the limbs a convenient direction. The leg is flexed backward on the thigh, while the fore-arm is flexed in front on the humerus. Parallel between the bones of the leg and those of the fore-arm. — It is 112 TEE BONES. more particularly in these two regions that the question of analogies has been resolved in a contradictory manner by anatomists. It would have appeared less complicated had it been studied in a large number of species. It has been pretended that the patella and the upper part of the tibia represent the superior extremity of the ulna and radius; and that the inferior portion of the ulna is represented by the fibula, and the lower part of the radius by that of the tibia. This opinion is erroneous. It is true that in Man the tibia and patella articulate with the femur, as the superior extremity of the ulna and radius responds to the humerus. But in quad- rupeds, whose thoracic members are destined to sustain the weight of the body, this disposition is no longer observed ; the radius is seen to give support to all the humeral surface, just as the tibia receives the femoral surface ; and, besides, the ulna becomes only a simple complement to the elbow articulation, as the fibula does to the femoro-tibial articulation. The tibia, therefore, corresponds to the radius, and the fibula to the ulna. The olecranon is represented by the superior nucleus of the fibula, and not by the patella. The latter bone is nothing more than a kind of sesamoid, intended to facilitate the action of the extensor muscles of the leg. It might be objected to this comparison that, in the anterior limb, the extensor muscles are attached to the olecranon. But we reply that it matters little where the muscles which move the leg or arm are fixed on one or other of the two bones of these regions, because these bones act conjointly in the movements of flexion and extension. Parallel between the bones of the posterior and those of the anterior foot. — The analogy becomes so marked when these two regions are compared, that it is scarcely necessary to allude to it. The tarsal bones are to the posterior limb what the carpals are to the anterior one ; it is even possible to compare, one by one, the several pieces in these regions. The metatarsals are but a repetition of the metacarpals ; while the digital bones are so much alike that it is difficult to distinguish the anterior from the posterior phalanges. CHAPTEE III. THE BONES IN BIRDS. These animals, destined for the most part to sustain themselves in the air, should exhibit in the conformation of their skeleton all the conditions which may favour serial locomotion ; from this arise the differences which distinguish their skeleton from that of mammalia, — differences which will now be rapidly traced. Vertebral Column. — Cervical vertebrae. — The cervical stalk represents in the bird, as in the mammal, a kind of balancing pole curved like an S, which supports the head, and by its changes of form and direction varies the centre of gravity. When a bird rises in the air and flies rapidly, it lengthens the neck and stretches out the head to carry the centre of gravity forwards. But when it rests on the ground, it makes the balancing-pole assume the natural and more or less graceful inflection, by throwing the head backwards, and transferring the greater portion of the weight of its body to the columns of support formed by the posterior members. These displacements of the centre of gravity are executed in birds on a more extensive scale than in mammalia; the vertebral stalk in the former is also longer, lighter, and enjoys an excessive mobility. The vertebrae composing it number fourteen in foivls, twelve in the pigeon, fifteen in the duck, and eighteen in the goose ,- in the swan twenty-three have been counted :— a curious variety which singularly contrasts with the numerical unity noticed as one of the most remarkable characters in mammalia ! These vertebrae are generally longer than in the latter class, and are particularly distinguished by the configuration of the TEE BONES IN BIRDS. 113 articular surfaces of the inferior part or body, These are diarthrodial facets convex in and concave in the other, articulating the vertebral bodies by a veritable and SKELETON OF A FOWL. From A to B, Cervical Vertebra. — 1, Spinous process of the third vertebra ; 2, Inferior ridge on body of the same ; 3, Styloid prolongation of the transverse process of 114 THE BONES. reciprocal clamping. In this manner, the anterior head of the body of each vertebra is replaced by a facet concave from one side to the other, and convex vertically ; while the posterior extremity of the bone bears, instead of a concavity, a facet convex in the lateral se;ise, and concave from above to below. The interior crest of the body (fig. 73, 2, 2 ) only exists in the first and last vertebrae , but it forms a veritable spine, analogous to that observed in the lumbar vertebrae of the rabbit. The spinous process (fig. 73, 1, 1') only forms a simple crest in the middle part of the neck, it becomes more salient in the vertebras which occupy the two extremities of this region. The transverse process represents on the side of the vertebra a thick, obtuse, and irregular tubercle, situated under the anterior articular process, and pierced at its base by a large vertebral foramen (tig. 73, 4, 4'). It is most frequently furnished with a small styloid prolongation (fig. 73, 3, 3') directed backwards and downwards, forming an epiphysis at%m early period, and representing a real undeveloped rib. The atlas has no transverse processes. This vertebra is shaped like a thin ring, and is excavated on its anterior contour by a small cavity into which is received the single condyle of the occipital bone. The axis shows a very marked odontoid process with a single facet under that eminence. Dorsal vertebrae (Fig. 73. b, a). — These are seven in the Fowl and Pigeon, and nine in the Goose and Duck , they are marly always consolidated into a single piece to which the trunk is fixed, and which gives the wings a solid support in the violent efforts that flight demands. The two or three last are often even covered by the wing-bones, and joined to them. The inferior crest of the body forms a very long spine, especially in the first vertebrae. Tne spinous processes, flat, wide, short, and consolidated with each other by their opposite borders, constitute a long crest extending fiom the last cervical vertebra to the bones of the wings (fig. 73, 7). Tne transverse processes widen to their summit; in the fowl they are nearly constantly fused with each other. Lumbar and sacral vertebral. — All these vertebrae are formed exactly on the same type; so that it becomes difficult, if not impossible, to fix the point where the lumbar region ends or the sacral begins. At first independent of each other, these vertebrae, numbering fourteen, soon become consolidated with one another and with the ribs ; but their primitive separation is always indicated by the lateral septa which form, on their inferior face, the vestiges of the transverse processes. The former are closely united to the latter in the dorsal region. Coccygeal vert&hrse. — In the coccygeal region, the spine recovers its mobility. The tail of the bird, indeed, fulfils the office of a rudder to direct it during flight; and it is absolutely necessary that the vertebrae which serve as a base for the steering feathers should preserve their independence, so as to allow these to be carried to the right, left, downwards, or upwards. These vertebrae, seven in number, present spinous processes which are often bifurcated, transverse processes very developed, and .sometimes even spines more or less long on the inferior surface of their bodies. The last vertebra is always the most voluminous; it is flattened on both sides, and terminates in a curved-up point. Head (Fig. 73, f. g.). — The head of the bird is small, and of a conical form. The anterior extremity is elongated, and terminated by a pointed or flattened beak, which allows the animal to cut the air with more facility. the same ; 4, Vertebral foramen of the same ; 1', 2', 3', 4', The same parts in the twelfth vertebra. — From B to c, Dorsal Vertebras. — 6, Spinous process of the first ; 7, Crest formed by the union of the other spinous processes. — From D to E, Coccy- geal Vertebra;. — F, G, Head. — 8, Interorbital septum ; 9, Foramen of communica- tion between the two orbits; 10, Premaxillary bone ; 10', External openings of the nose; 11, Maxilla; 12, Square bone; 13, Jugal bone. — H, Sternum. — 14, Brisket or keel; 15, Episternal process; 16, Internal lateral process; 17, Lateral external process; 18, Membrane which closes the internal notch; 19, Membrane of the external notch. — 1, etc., Superior ribs. — 20, Posterior process of the fifth. — J, Inferior ribs; K, Scapula; L, Coracoid bone; M, Furculum. — m, m, Its two branches. — N, Humerus ; O, Ulna. — 0, Radius. — P, p', Bones of carpus ; Q, q', Bones of metacarpus; R, First phalanx of the large digit of the wing. — r, Second phalanx of the same. — r', Phalanx of thumb; s, Ilium; s', Ischium; s", Pubis. — 21, Sciatic foramen; 22, Foramen ovale.— T, Femur; u, Patella; V, Tibia ; x, Fibula. — y, Single bone of tarsus. — Y, Metatarsus. — 23, Superior process representing a united metatarsal bone ; 24, Process supporting the claw. — z, etc.. Digits. THE BONES IN BIRDS. 115 Bones of the cranium. — The bones which compose the cranium are, as in mammalia, an occipital, parietal, frontal, ethmoid, sphenoid, and two temporals. These bones are net isolated from each other, excepting during early life in the shell, and the ossifying process which unites them is so rapid, that the cranium, shortly after hatching, is already a single piece. No detailed description of the separate bones will be given here, but oniy a few brief observations which may be of some utility. Thus, the occipital bone shows fur articulation with the spine only a single condyle, situated under the occipital foramen, and excavated by a slight groove. In palmipedes, this bone is pierced, behind the crests which give attachment to the extensor muscles, by two foramina which penetrate the cranium, and represent permanent fontanella. The parietal bone is feebly developed, and formed from only two primary nuclei. The frontal is the largest bone of the cranium; its orbital process is supported by a particular piece which is generally considered as belonging to the large wing of the sphenoid. The perpendicular lamina of the ethmoid is considerable, and forms between the two orbits a thin vertical septum (fig. 73, 8). Its posterior border is notched opposite to the optic foramen, and thus constitutes an opening which com- municates between the two orbital cavities (fig. 73, 9). It is also channeled, near its upper border, by a fissure which terminates by two openings at its extremities, one entering the cranium, the other the nasal cavities. This fissure and these foramina permit the passage of the ethmoidal nerve, which in this way traverses the orbit before arriving at its destination. The ethmoidal cells are more membranous than bony ; their base is attached to a very delicate transverse plate, which is often membranous and not cribbled, and forms part of the anterior orbital wall. These cells replace, at 1he same time, the lateral masses of the ethmoid and turbinated bones of mammalia. The sphenoid appears to be formed of a single piece, and shows on its sides two diarthrodial facets corresponding to the pterygoids. It is pierced by one foramen for the passage of the optic nerves ; but this foramen opens on the outer and opposite side of the posterior notch of the interorbital septum, and thus allows each of the nerves passing through it to reach the eye for which it was intended. It is worthy of remark, that an analogous disposition is also noticed in the rabbit.1 The temporal bones present at their base an articular surface corresponding to the square bone. In the fowl species, the zygomatic process forms a small flattened tongue, directed forwards, sometimes free, and at other times united by its superior border to the summit of the orbital process. These two eminences are exceedingly short in pigeons. In palmipedes they are consolidate;! and confounded so intimately, that it becomes impossible to distinguish them from one another. From this union results a long and strong process, which inclines forward and meets a particular prolongation of the os unguis, forming with it areal bony arch. This arch limits, below and outwardly, the orbital cavity. Bones of the face. — The supermaxilla c mprises ! a premaxilla, two nasal, two lachrymal, two palate, two pterygoid, two zygomatic bones, and a vomer. The inferior jaw has for its base a maxillary bone, which articulates with the cranium by means of two supplementary pieces named the square bones. The premaxiliary bone is found, before hatching is completed, of two lateral pieces, which represent the two small premaxillaiies of mammals. This bone is very considerable, and of itself forms the base of the upper beak, whose form it determines , it is pointed and conical in the gallinacea, and wide and flattened above and below in palmipedes. In front it circumscribes the external openings of the nose, and is prolonged superiorly into two lengthy processes which dovetail between the nasal bones. Two inferior processes belonging also to this bone concur in the formation of the palatine roof. The supermaxillaries, analogues of the supermaxillaiies of mammals, are two rudimentary bones situated on the sides and at the base of the beak. They form a part of the palatine roof and the walls of the nasal cavities. The nasal bones circumscribe above, inwardly, and even outwardly, the external orifices of these cavities. The palate bones encircle, as in mammals, the guttural openings of the nose, and constitute in great part the roof of the palate ; their posterior extremity lies against the pterygoids ; the anterior joins the supermaxillaries and the inferior process of the premaxiliary bone. The pterygoids extend obliquely from the sphenoid to the square bones, and are united to the sphenoid by diarthrodial articulation. 1 This analogy is really striking, and might, in our opinion, serve as a basis for a new determination of the interorbital septum. We are tempted, indeed, to consider this bony lamina as the inferior sphenoid and the middle portion of the ethmoid of birds. This manner of viewing it tends to confirm the ideas of M. Tabourin on the inferior sphenoid and the ethmoid of mammals. 116 THE BONES. The zygomatic bones have the form of two very thin stylets, and are united to the square bone by their posterior, and consolidated with the supermaxillary by their anterior extremity. The vomer separates the guttural openings of the nose from one another. The bones of the upper jaw are not fused with each other so rapidly as the bones of the cranium. The ascending processes of the premaxillary and nasal bones even remain for a long time united to the frontal bone by a simple synarthrodial articulation. This arrangement allows the upper beak to execute a certain elevating movement, of wThich we will speak when describing the articulations. The inferior maxillary bone is originally formed of a great number of distinct seg- ments which are soon united into a solid piece. The square, petrous, or bone of the tympanum ought to be considered as detached from the temporal. It is prismatic in shape, and provided on its upper surface with a diarthrodial facet which unites U to the temporal, and on its lower face with another facet articulating with the branch of the maxilla. Outwards it joins the zygomatic bone, and inwards with the pterygoid. Behind, it gives attachment to the membrane of the tympanum; and in front it presents a small eminence of insertion which Meckel considered a second zygomatic process. Thorax. — Sternum (fig. 73, h). — The sternum of birds, serving as a basis of support to the muscles moving the wings, should offer, and does in fact show, a remarkable degree of strength, because of the extraordinary volume of these muscles. And these being more powerful and energetic as the bird exhibits a greater degree of aptitude for flight, it results that the structure of the sternum is solid in proportion as the bird is strong on the wing. For this reason we may infallibly pronounce as to the extent and power of a bird's flight by an inspection of the sternum of individuals of its species. In this respect, however, we only announce what is well known to be a particular application of the rules established by the great law of concordance between the anatomical disposition of organs and their physiological finality. Studied in Palmipedes, which will serve as a type for description, the sternum presents itself in the form of a large rectangular cuirass, elongate! from before to behind, of itself constituting the inferior wall of the thoracic cavity, and also largely protecting the abdominal cavity. Its superior face is concave, while the inferior is convex, and entirely occupied by the insertion of the pectoral muscles. It presents, on the median line, a thin and very salient ridge, named the brisket (or heel), which in a remarkable manner multiplies the points of attachment of these muscles. The anterior border offers in its middle a small eminence of insertion, the episternal. Laterally, two articular grooves are seen which correspond to the coracoids. The posterior border is cut by two notches which are often converted into foramina. On the lateral borders are observed small double articular facets answering to the inferior rib3. The angles whicli separate these two borders from the anterior are both prolonged into a little eminence, named by some authors the costal process. In the Fowl, the sternum is not so strong as in the Goose or Duck. On each side of the brisket it shows two wide notches, which greatly reduce its substance. These notches, closed in the fresh state by membranes, are distinguished as external and internal. The latter, of greater size than the former, extends nearly to the extremity of the bone. From this division of the lateral plates of the sternum result two long and slender processes directed backwards. The external terminates by becoming widened, and forming a kind of bony plate, which covers the last inferior ribs. The sternum of Pigeons is distinguished by the enormous development of the brisket. The two notches of the fowl are also met with in these birds, but the internal is nearly always converted into a narrow foramen. This comparative study of the sternum in the chief domesticated birds leads us to appreciate the correctness of the principles just enunciated, with regard to the form and extent this bone may exhibit. The Gallinaceous Birds, properly so called, which fly little and badly, have the sternum singularly weakened by the deep notches cut in its lateral parts. With Palmipedes, the sternum is wide and but slightly notched, so that the goose and duck, which waddle along so awkwardly in our poultry yards, are capable of sustaining long and rapid flight, like that of the wild individuals of the same species. With regard to Pigeons, which are well known to be swift and powerful flyers, may this advantage not be due to the extraordinary development of the keel which constitutes the brisket ? Bibs. — In the Fowl and Pigeon there are seven pairs of ribs ; and in the Buck nine pairs. Articulated superiorly with the dorsal vertebrae, as in mammals, these bones are provided near their middle with a flat eminence which commences at the posterior border, and is directed backwards and upwards to rest by its free extremity on the external face of the next rib. These eminences (Fig. 73, 20) form an epiphysis at an THE BONES IN B1BDS. 117 early period, and are usually absent in the first and last ribs. They concur in an efficacious manner to increase the solidity of the thorax. The costal cartilages in mammalia are in birds often transformed into veritable inferior ribs, joined to the superior ribs by a diarthrodial articulation (Fig. 73, i). These pieces are long and strong, and all terminate at their lower extremity by a double facet which articulates with the lateral border of the sternum ; they are nearly always absent in the two first ribs. It is not rare to see the last united to the one before it, instead of passing directly to the sternum; in which case it comports itself like the asternal ribs of the mammalia. Anterior Members.— Shoulder-bone. — The shoulder comprises: a scapula, a par- ticular bone named the coracoid by Cuvier ; and a clavicle, which forms, in coalescing with that of the opposite side, a single bone called the fork (furculum), or os furculare. The scapula is narrow, elongated, and falciform, and shows no trace of a spine. Its anterior extremity only forms a portion of the glenoid cavity, and is united by means of a fibro-cartilage with the fork of the coraeoid bone. The latter is so named because it represents the coracoid process of mammals, and is a long piismatic bone, directed obliquely from above downwards, and before to behind. Its superior extremity is often fused with the scapula, and united at an acute angle with that bone to form a portion of the articular cavity which receives the head of the humerus. Its inferior extremity is flattened from before to behind, and responds by a diarthrodial articulation to the anterior border of the sternum. The coracoid is long in birds which fly slowly ; it is, on the contrary, short, thick, and therefore very solid in quick flyers. The fork is a single bone, shaped like a V or U, situated at the base of the two wings, in front of the trunk, and in an oblique direction downwards and backwards. The two branches which form it represent the clavicles ; they meet and are united at their inferior extremities, where they describe a curvilinear angle more or less open, attached to the brisket by means of a membranous ligament. Their superior extremity rests within, and opposite to the glenoid cavity, against the scapula and coracoid, forming with these bones a remarkable foramen, through which passes the tendon of the elevator muscle of the wing (Fig. 73, a, 4, b, 6). The fork plays the part of an elastic spring, whose office it is to prevent the wings coming towards each other during contraction of the depressor muscles. The conformation of this bone is, therefore, like the sternum, related to the extent and power of flight ; and for this reason it is that, in swift flyers, the two branches of the furculum are thick, solid, widely separated, and curved like a U ; while in those which fly heavily and with difficulty, these branches are thin and weak, and joined at an acute angle. The latter formation greatly diminishes its strength, and lessens, in a singular manner, the reactionary power of the bony arch it represents. Bone of the arm. — The humerus offers an articular oval-shaped head, and an air- opening placed beneath this eminence. It is long in Palmipedes, ordinarily so in the GaUinacx proper, and very short in Pigeons. Bones of the fore-arm. — The radius is much less voluminous than the ulna. The latter lias an extremely short olecranon ; and the two bones are separated from one another in their middle part to meet again at their extremities, where they are united by ligamentous bands in such a way as to render the movements of pronation and supination impossible. This mode of fastening, which nevertheless does not prevent the two bones from gliding slightly on each other in the direction of their length, has been wisely adopted by nature in order that the wing might strike the air, like an oar, by its inferior face ; otherwise, the resistance of the aerial medium would make these two bones pivot, and cause the wing to present itself to the air in a wrong direction. Bones of the carpus. — These are only two, and are distinguished by the names of radius and ulna, in consequence of their corresponding more particularly to these bones in other animals. Bones of the metacarpus. — These also number only two, and are separated at their middle portion, to be consolidated at their extremities. Bones of the digital region. — The wing of a bird is composed of three digits. One of them, which resembles the thumb and forms the basis of the false wing, is composed of a single styloid-shaped phalanx, articulated at the base of a small particular process belonging to the superior extremity of the largest metacarpal bone. The largest digit comprises two phalanges which succeed the last bone. The third digit is represented by a small rudimentary phalanx, which corresponds to the inferior extremity of the small metacarpal bone, and lies beside the first phalanx of the large digit in the closest manner. It is well to remark that the hand and the fore-arm are longer in proportion to the o o gi I is « -a 5 5 rO « 3 Pi S borne in mind what profound modifications the vertebrae must have ex- perienced to constitute the bones of the head At present the problem appears solved. The head is composed of four vertebra?, in which are found the various parts enumerated in the description of the typical vertebra. THE VERTEBRAL CONSTITUTION OF THE SKELETON. 121 In the four classes of vertebrata, the head is constantly formed of four vertebra?, which are determined as follows :" l VERTEBRA. CENTRUM. i NEURAL ARCH. ] H/EMAL ARCH. ! Occipito-hyoideal. j Basilar process j Occipital (3 pieces). \ Hyoideal appa- | of the Occipi- j Mastoid walls of the j ratus (5 pieces), i tal. Tympanum. ! Parieto-in axillary. i Body of the pos- i Wing and pterygoid teiior Sphe- i process of the pos noid. i terior Sphenoid. | Squamous portion and j zygomatic process of j the Temporal. Parietal. Inferior Maxilla 5 pieces). Fronto-mandibular. • Body of the ! Wing and pterygoid \ Jugal. Anterior Sphe- \ process of the anterior j Lachrymal, noid. j Sphenoid. ' Palatine. j Posterior Frontal and j Superm axillary. its orbital process. i Premaxillary. I Frontal. Naso-turbinal. Vomer. Ethmoid. Nasal. Turbinated Subetlimoidal. The number of cephalic vertebra? is invariable, as each is destined to lodge the organs of one of the four senses. The occipito-hyoideal lodges the principal organs of hearing; the pari eto-m axillary osteodesm protects the sense of taste ; finally, the organs of vision are sustained by the fronto-man- dibular vertebra, while the naso-turbinal contains the sense of smell. It was therefore with reason that Geoffroy Saiut-Hilaire and Professor Owen proclaimed that the type of construction of the vertebrated animals is the vertebra. SECOND SECTION. The Articulations. CHAPTER I. THE ARTICULATIONS IN GENERAL. The different pieces constituting the solid framework of the animal body are, as has been said, united in such a manner that they can move one upon the other From this union results the articulations or articular joints, whose construction will now be referred to in a general manner, before commencing a particular description of each To form articulations, the bones correspond to each other by certain points of their periphery, which are named articular surfaces. Every articu- 1 Lavocat, ' Nouvelles etudes sur le systeme vertebral,' 1860. 122 THE ARTICULATIONS. lation is, therefore, essentially constituted by two opposite osseous surfaces, which are moulded to each other. These are either contiguous, independent, and very movable — continuous with each other by means of a cartilaginous substance which condemns them, if not to total immobility, at least to very PLANS OF THE DIFFERENT CLASSES OF ARTICULATIONS. A, Suture. — 1, Periosteum ; 2, Sutural ligament. — B, Amphiarthrosis ; a, First degree. — 1, Periosteum ; 2, Articular cartilage ; 3, Interarticular ligament. — 6, Second degree ; 4, Single cavity in the interarticular ligament. — c, Third degree ; 5, Double cavity in the interarticular ligament. — c, Diarthrosis ; 6, Simple diarthrosis. — 1, Periosteum ; 2, Articular cartilage; 3, Epithelial layer of the synovial membrane — dotted line ; 4, Fibrous capsule ; 5, Cul-de-sac of the syno- vial membrane ; 6, Fibrous layer of the synovial membrane. — c, Double diarthrosis ; 7, Interarticular meniscus ; 8, 9, Cavities of the two synovial membranes. limited movements : or united by a fibro-cartilage whose elasticity permits a certain degree of displacement between the bones which are in contact. In the first case, the articulations are classed as diarthroses, or movable articulations. In the second, they are designated synarthroses, sutures, or immovable articulations. THE ARTICULATIONS IN GENERAL. 123 In the third, they are amphiarthroses, or mixed articulations ; so termed because they participate in the movements of the other two classes ; synar- throses, by the continuity established between the articular surfaces ; and diarthroses, by the extensive motion they permit. The general characters that distinguish each of these three great classes of articulations will be successively studied. (The study of the articulations, or rather of the ligaments, is termed syndesmology — from avv, together, and Seoyxos, bond; or arihrology — from ap6pov, a joint, and Aoyos, a description.^ GENERAL CHARACTERS OP DIARTHROSES. We ought to consider in the diarthrodial articulations : 1, The con- tiguous bony surfaces which form them ; 2, The cartilaginous layer (cartilages of incrustation) which cover these ; 3, The fibrocartilaginous tissue (articular fibro-cartilages) which complete them, when they are not shaped so as to be reciprocally adapted to each other ; 4, The ligaments which maintain tbem in contact; 5, The- serous membranes (synovial capsules) that cover the internal face of the latter, and which secrete the synovia, a kind of animal oil that facilitates the gliding of the articular surfaces ; 6, The movements of which these articulations may be the seat ; 7, Their methodical classifica- tion ; 8, Their nomenclature. Articular Surfaces. — These surfaces have the common character of being destitute of asperities, so that they can glide with the greatest facility on each other. They are designated, according to their form, by the names of facets, heads, condyles, cotyles, glenes, pulleys, etc. There is no need to revert to their general description, as they have already been sufficiently studied in the osteology; so we will confine ourselves to repeating that they are found at the extremities of long bones, on the faces of short bones, and on the angles of wide bones. We may mention also that they are often excavated by one or several hollows named synovial fossce, a sort of natural reservoirs which receive the unctuous fluid secreted by the interarticular serous membranes , Cartilages of Incrustation. — This designation is given to the layers of cartilaginous matter which, as it were, varnish the articular surfaces they adhere to by their inner face; their free surface is distinguished by a remarkable polish and brilliancy Thicker towards the centre than at the circumference when they cover bony eminences, these cartilages show an inverse disposition when they line cavities. They are elastic, of a pearly whiteness, and resisting, though they are soft enough to be cut by a sharp instrument ; in a word, they possess all the physical characteristics of the primary cartilage of bones They appear to be formed of parallel fibres placed perpendicular to the bony surfaces, and implanted iu these by one of their extremities : the opposite extremity corresponding to the free surface of the cartilage. Viewed by the microscope, they are found to consist of a fundamental substance excavated by small cavities The cartilage of incrustation therefore belongs to the group of true or hyaline cartilages. The fundamental matter is amorphous and homogeneous, and more or less transparent, according to its thickness. It is transformed into chondrine by boiling in water. The cavities are irregular, and more or less wide. They contain from one to five cells whose walls are very thin, and their contents slightly gran^ ular; in the centre of each cell is a nucleus with a nucleolus. These 124 TEE ARTICULATIONS. cavities are elongated and directed almost perpendicularly towards the articular surface in the deep layer ; iu the middle layer they arj oblique, and are parallel to the surface of friction in the superficial layer. (Under a high magnifying power the fundamental substance, or matrix, loses its homogeneous and amorphous character, and appears to be granular or faintly striated. In the midst of this granular matrix, the lacunae or cavities are observed to contain from one to six different-sized cells. It has been stated that a membrane lines these spaces. In addition to the granular matter observed in the cells, it is not rare to find fat globules. The nuclei of the cells vary from ¥W(T to 24V0- °f an ^ncn *n diameter. The cells multiply endogenously.) The cartilage cells are insoluble in boiling water ; consequently, so far as their chemical composition is con- cerned, they are distinct from the fundamental substance. The diarthrodial cartilages receive neither vessels nor nerves. The presence of cartilages of incrustation in the articulations is of the greatest importance. When they are worn, absorbed, or transformed into bone in consequence of certain articular maladies, the movements become painful and very difficult. "With regard to the part they play in the economy, it may be said that* 1, They favour, by their smoothness, the gliding and displace- ment of the bones , 2, They attenuate, by their suppleness and elasticity, the violent shocks to which the articulations are exposed ; 3, They resist the wear and deformation of the articular surfaces. Complementary Fibro-carttlages. — There are several kinds of com- plementary fibro cartilages : — Some (interosseous) represent circular cushions which bolster the margins of certain cavities, filling up the notches which might render them imperfect. They increase the depth of these cavities Fig. 77. SECTION OF BRANCHIAL CARTILAGE OF TADPOLE. Group of four cells separating from each other ; b, Pair of cells in apposition ; c, c, Nuclei of cartilage-cells ; d, Cavity con- taining three cells. These cells are im- bedded in the finely-granular matrix, or fundamental substance. fibro-Cartilage ; magnified 155 times. Showing interlacement of fibrous fasciculi, with scattered groups of cartilage-cells. and protect their borders from injury. Others (interarticular) are inter- posed between articular surfaces when these do not exactly fit each other, as THE ARTICULATIONS IN GENERAL 125 when two opposing extremities are convex. It may be remembered that the lateral tuberosities of each tibial surface present, for articulation with the condyles of the femur, two convex diarthrodial faces whose coaptation is rendered perfect by the interposition between each condyle and correspond- ing tibial surface of a crescent-shaped fibro-cartilage, which for this reason has been named a meniscus. In other joints these interarticular fibro- cartilages are shaped like discs or biconcave lenses. There then result double diarthroses : — example, the temporo-maxillary articulation. (Fibro- cartilage also covers bony surfaces over which tendons play, as on the trochlear surface of the humerus, postero-inferior face of the navicular bone, and elsewhere. In these situations it is named stratiform fibro-cartilage.) These organs are formed, as their name indicates, by fibrous and car- tilaginous tissue ; their mode of association need not be referred to here, though it may be observed that the cartilage is more particularly found in all those points where there is most articular friction. They receive vessels, and sometimes nerves. Ligaments. — These are bands which unite contiguous diarthrodial surfaces. They are sometimes formed of white fibrous tissue, and some- times of yellow ; from whence their division into two great classes of white and yelloio ligaments. a. The white ligaments are distinguished by the pearly whiteness of their tissue and want of elasticity. Those which are found on the outer Fig 78 Fig 79, WHITE OR NON-ELASTIC FIBROUS TISSUE. YELLOW OR ELASTIC FIBROUS TISSUE, FROM THE LIGAMENTUM NUCH.E. aspect of the articulations are termed peripheral, and those in their interior are designated interosseous or interarticular ligaments. The peripheral ligaments are generally composed of parallel fibres collected in fasciculi, or spread out as membranes. In the first they are called funicular, or ribbon-shaped; in the second, they are termed mem- braniform, or capsular. The funicular ligaments constitute short, round, or flattened bands, attached by their extremities to the two bones they unite ; they are lined on their inner aspect by the synovial capsule, and covered externally by tendons, aponeuroses, muscles, vessels, or nerves. The capsular ligaments are often complete — that is to say, they envelope the whole articulation like a sack. At other times they are incomplete, and 126 THE ARTICULATIONS. then they are simple membranes, binding together the different Yunicular bands of a joint. The interosseous ligaments, less numerous than the preceding, are often formed of interlacing fibres ; they are always funicular, and fixed by their extremities into excavations in the centre of articular surfaces. b. The yellow ligaments are all peripheral, funicular, or membranous, and enjoy a marked degree of elasticity, which permits them mechanically to bring back to their usual position the bony levers which have been momen- tarily displaced. These ligaments, which are powerful auxiliaries to the muscular forces, are destined to give equilibrium in a permanent manner to the weight of certain parts of the body which incessantly tend to fall to the ground. Synovial. Capsules. — These are very thin membranes of a serous nature, intended to secrete the synovia. They are composed of two layers : a deep, formed by fasciculi of the connective tissue; the other, superficial, is of an epithelial character. The first sometimes adheres intimately to the inner face of the funicular or membranous ligaments of the articulation ; at other times it is loosely attached to them by an abundance of connective tissue. The second layer is constituted by a single row of flattened polygonal cells. It is generally admitted that the synovial membranes comport themselves like the other serous membranes, by forming sacs which are everywhere closed. According to this admission, a synovial membrane, after covering the internal face of the peripheral ligaments of a diarthrodial articulation, ought to be prolonged on the free surface of the cartilages of incrustation, and should give them their brilliancy and polish. But it is necessary to state that this is a pure hypothesis, against which rises a multitude of care- fully-observed facts. The discussion of these belongs to general anatomy, but they will be referred to here as briefly as possible. 1. If direct observation be consulted, it gives on this debated subject the most precise information ; the cartilages are uncovered, and there is no synovial membrane on their face. The anatomists who have mistaken for this membrane the thin pellicle which it is possible to render evident on the cartilages in obliquely cutting their substance and separating morsels by tearing it off, were evidently deceived. This pellicle has nothing of a serous nature in its texture ; it is not vascular, for it has never been possible to inject vessels on the surface of cartilages, nor yet in their thickness ; it is not covered by epithelium ; and submitted to microscopical examination, it exhibits nil the characters of the amorphous matter of cartilage. It ought, then, to be considered as a cartilaginous pellicle, detached from the super- ficial layers of the articular surface — a pellicle which it has always been impossible to find on cartilages which are quite fresh ; and it has never been possible to observe it without giving, by a preliminary desiccation, a certain degree of tenacity to the cartilaginous substance about to be examined. 2. Pathological facts prove nothing in favour of the existence of a synovial membrane on the cartilages. Hypertrophy of this pretended membrane has never been witnessed ; the fungosities looked upon as a result of this hypertrophy are derived from another source. It has been demonstrated that they extend, in certain cases, from the articular margins of the cartila- ginous surface, whence their successive invasions may often be followed. In other cases, the vegetating membrane which constitutes them appears in the centre of the articular surfaces, at points deprived of cartilage ; they after- wards extend to a certain distance on the remaining cartilage. TEE AMTICULATIONS IN GENEBAL. 127 3. It may be asked of the partisans of the opinion now combated, how they can believe in the existence of a serous membrane between two articular surfaces, without its being exposed to bruises and destruction a thousand times in the day? Do they take into account the amount of pressure sustained by certain articulations, and the intense friction to which their surfaces are submitted ? Have they compared the intensity of these destructive influences, with the delicate texture of the serous membranes, and their great inflammatory susceptibility ? It is sufficient to lightly touch in this way the weak side of our adversaries' argument, and to conclude the third portion of this discussion: There is friction between the cartilages of the two opposed articular surfaces, therefore there must be wear , this is a physical law which no body escapes, let it be as hard as the diamond, or as soft as caoutchouc. And if there is wear between these rubbing surfaces, there cannot be an irritable and sensitive membrane lying on the inert and insensible strata which constitute them. In fine, a synovial membrane, after being fixed to the margin of the articular cartilage of a diarthrodial joint, is reflected in every direction to cover the inner aspect of the liga- ments, and becomes attached to the periphery of the diarthrodial surface corresponding to the first. There are generally found within articulations little masses of fat which push the synovial membrane enveloping them inwards. Erroneously con- sidered by Clopton Havers as glands for the secretion of synovia, these accumulations of fat have been named synovial fringes. They are more par- ticularly numerous in the neighbourhood of the articular margins : that is, on the edges of diarthrodial surfaces. The synovia is a viscid, colourless, or slightly yellow fluid, in its physical characters somewhat resembling oil; it does not possess them, however, so far as its composition is concerned, for chemical analysis has not demonstrated the presence of fatty principles. It is the albumen it contains which gives it its viscidity, and which fits it for lubricating the articular surfaces over which it is spread. Its use in the animal economy is absolutely identical with that of the greasy substances employed to lubricate the axles of carriages. Movements. — The movements peculiar to diarthrodial articulations are divided into seven principal classes : 1. Simple gliding, the only movement possible between two plane or undulating facets. 2. Flexion, which brings two bony pieces nearer each other by closing more or less their angle of union. 3. Extension, the inverse movement, during which the bones are straightened on each other. 4. Adduction, which brings the inferior extremity of the movable bone towards the median line. 5 Abduction, the contrary movement to the preceding 6 Circumduction, or the sling movement, during which the bone passes successively through the last four positions, 7. Motation, in which one bone pivots on another Classification op the Diarthroses. — The basis of this classification is founded on the configuration of the articular surfaces and the nature of the movements they permit. This double base serves to establish five kinds of diarthrodial articulation . 1. Enarthrosis, characterised by the reception of an articular head within 128 THE ARTICULATIONS. a cavity of appropriate form. This articulation may be the seat of the most extensive and varied movements : flexion, extension, abduction, adduction, circumduction, and rotation. Example : the coxo-femoral articulation. 2. The trochlean, angular ginglymoid, or perfect hinge articulation, when the articular surfaces are formed into trochlea, recij>rocally fitting into each other, and whose movements — flexion and extension only — are executed with the precision of a hinge. Example : the tibio-tarsal ar- ticulation. 3. The condyloid, or imperfect hinge articulation, which permits, like the preceding, the two principal movements of extension and flexion, and. the accessory movements of rotation or lateral inclination. The articular surfaces, {hough very diversely shaped, nevertheless exhibit in all the articulations one or more condyles opposed to an equal number of oval excavations. Example : the femoro-tibial articulation. 4. The pivot, trochoid, or lateral ginglymoid articulation, is a diarthrosis formed by a pivot which turns in a semi-cylindrical cavity. Rotation is the only movement. Example : the atlo-axoid articulation. 5. Arthrodia, or planiform diarthrosis, is constituted by plane, or nearly plane facets. Gliding is the only possible movement. Example : the carpo- metacarpal articulation. Nomenclature. — The names of the articulations are usually those of the bones which form them. For instance, the scapulo-humcral articulation is the joint between the scapula and humerus ; the intervertebral articulations join to each other the various pieces constituting the spine. When the qualifying name of an articulation is composed of two elements, as in the first instance, it is well to place first the word which indicates the bone usually most fixed. GENERAL CHARACTERS OF THE SYNARTHROSES. Sutures are the temporary articulations which exist only at an early period of life. They nearly all disappear in the adult animal, in con- sequence of the bones forming them becoming consolidated. They belong almost exclusively to the bones of the head. Articular Surfaces. — The bones forming these come in contact by their borders or angles, which, for this purpose, generally present very anfractuous surfaces. Sometimes they are cut perpendicularly and simply roughened,* at other times they are bevelled and joined by means of fine laminae or trifling inequalities; again, they are notched into deep and sinuous dentations; and lastly, one bone is fixed into a groove cut in the other. It will be understood that such conformations of the articular surfaces ought to limit their movements and assure the solidity of their union. Modes of Union. — Cartilage interposed between these synarthrodial surfaces directly unites them to each other. It absolutely possesses the same texture as the primary cartilage of the bones, and like it, has the property of becoming ossified after having been vascularised. This ossi- fication, which causes the disappearance of the sutures, occurs earlier inwards than outwards. The periosteum, in passing from one bone to another, adheres intimately to the sutural cartilage, and also aids in bringing about a more complete synarthroses. It should, therefore, be included in their means of union. Movements. — These are very obscure, and only noticeable in young ARTICULATIONS OF MAMMALIA IN PARTICULAR. 129 animals by the elasticity they communicate to the bony walls of the cranium or face. In tbe adult, they may be said to be null. Classification. — There are four principal descriptions of sutures : 1. When two wide bones correspond by means of denticulations fitting into each other, the suture is named true or dentated. Example: the articulations uniting the three portions of the parietal bone. 2. If the opposed borders of two bones in contact are widely bevelled, one inwards, the other outwards, it forms a scaly or squamous suture. Example : the parieto-temporal articulations. 3. When the union of bones takes place by plane or roughened surfaces, cut perpendicularly on their borders or angles, this constitutes the harmonia suture, or suture by juxtaposition (or appo- sition). Example : the occipito-temporal articulations. 4. The schindylesis, or mortised suture, results from the reception of a bony plate into a groove more or less deep in another bone. Example : the spheno-frontal and supermaxillo-nasal articulations. GENERAL CHARACTERS OF THE AMPHIARTHROSES OR SYMPHYSES. Articular Surfaces. — They are frequently smooth, and formed almost on the same model as the diarthrodial surfaces. They are covered by a thin layer of cartilage, but instead of being smooth and polished, they are more or less rugged, without, however, presenting the anfractuous disposition of the majority of synarthrodial surfaces. Modes of Union. — The organs which perform this office are : 1, The fibro-cartilage which establishes continuity between the articular surfaces ; 2, Kibbon-shaped or peripheral ligaments. These latter do not differ from the analogous bands attaching the diarthrodial articulations. . With regard to the fibro-cartilage, it is distinguished from the complementary discs of these same articulations by a less intimate mixture of the cartilaginous and fibrous elements entering into its composition. The last may be sometimes absent, as well as the peripheral bands ; and then the articulation only differs from the synarthroses by the extent of motion it permits Occasionally the interarticular fibro-cartilages are excavated by one or two little narrow cavities ; but these are never lined by a synovial membrane like the diarthrodial cavities. Movements. — The amphiarthroses only permit of a see-saw or swinging movement, the extent of which depends on the thickness of the intermediate fibro-cartilage. Classification. — Only one kind of amphiarthrosis is recognised, the most remarkable example of which is found in the articulations between the bodies of the vertebrae. CHAPTEK II. ARTICULATIONS OF MAMMALIA IN PARTICULAR. In the special study of the articulations, the same order will be followed as for the bones ; the articulations of the spine will be first noticed, then those of the head, thorax, and anterior and posterior limbs. Preparation. — The preparation of the bones which have been described has not been made the subject of any particular recommendation, because it suffices, in order to study them, to remove the soft parts by which they 130 THE ARTICULATIONS. are surrounded either by boiling, maceration, or scraping. But when we come to examine the soft textures, in order to do so profitably it is necessary to learn beforehand the rules which should be followed in their preparation, m The following are laid down with regard to the study of the articulations : 1. To prepare the articulations, young subjects are chosen in preference to those ad- vanced in years, because the density of the cellular tissue in them is not so great, and this tissue is easily removed from around the ligaments. As these are prepared with difficulty when the external surface is in a dry state, care should be taken before dissecting them to have them excluded from the air by covering them with damp cloths, or with the skin of the animal. 2. It is convenient to separate the articulation we wish to dissect by sawing through the bones at a certain distance from the articular surfaces. The manipulation of the part is then rendered easier, and its dissection can be made under the most favourable conditions. 3. It is necessary to preserve as carefully as possible the muscles surrounding the articulations, in order to be able to study their relations with the ligaments whicli bind these. If it be absolutely necessary to remove them, their insertions corresponding to the articulation should always be retained. 4. The capsular ligaments should be the first studied, as these have soon to be removed the better to show the funicular ligaments. These, in their turn, must be sacrificed in order to display, by different sections, the interosseous cords, when these exist. Lastly, the two articular surfaces should be completely separated, so as to examine their conformation. 5. The synovial membranes, with their different culs-de-sac, being a very important study, with reference to the diagnosis and treatment of articular tumours, it is convenient to devote a special piece to the examination of these serous membranes. It is very useful to inject their interior with plaster or tallow coloured black, in order to distend, their cavities, and thus aid the study of their relations with ligaments, tendons, or muscles. For the preparation of each articulation it is not necessary to give any directions; a glance at the figures accompanying the description will suffice to dispel any embarass- ment the student may experience, while he always requires particular indications. (Notwithstanding the above remarks with regard to the preparation of the ligaments, I have thought it advisable to follow the example given in the last edition of ' Leyh's Anatomy ' by Zundel, and briefly indicate the readiest method of demonstrating these organs, for the special benefit of the student.) Article I. — Articulations of the Spine. (Preparation. — Kemove all the soft parts surrounding the vertebral column, taking care not to injure the inferior longitudinal ligament in cutting away the pillars of the diaphragm and the psoas muscles ; nor the ligaments uniting the articular processes to each other and the transverse processes of the dorsal vertebrae to the ribs, in removing the supercostal and transverse spinal muscles. To expose the common superior longitudinal ligament, separate the bodies of the vertebra from their annular portions by the saw or chisel, and remove the spinal cord and dura mater ; in doing this the inferior face of the interannular ligaments will be also removed. Examine an intervertebral fibro-cartilage by two sections — a transverse at an equal distance from the two vertebrae, and a longi- tudinal through the middle line of the bodies.) These articulations are intrinsic and extrinsic. The first comprises all the articulations of the vertebrae with each other ; the second those of the spine with the head, the ribs, and the coxae. Intervertebral Articulations. The vertebrae correspond : 1, By their bodies ; 2, By their spinal or annular portion. There results from this union two kinds of articulation, which must be studied separately, as they do not belong to the same class. It is well to mention, however, that the general details into which this study leads us apply only to the articulations uniting the last six ARTICULATIONS OF TEE SFINE. 131 cervical vertebrae, all the dorsal and lumbar vertebrae, and the first sacral vertebra. Union of the Vertebra by their Bodies. — The articulations forming this union are so many amphiarthroses. Articular surfaces. — The vertebral bodies come into contact by the surfaces which terminate them before and behind. In the cervical region these surfaces represent, anteriorly, a veritable head, posteriorly, a cotyloid cavity which receives the head of the next vertebra. Beginning from the first dorsal vertebra and passing on to the sacrum, these tend to become effaced and more and more plane, though they still preserve their convexity and concavity. Modes of union.— 1, By fibro-cartilages interposed between the articular surfaces ; 2, By a common superior vertebral ligament ; 3, By a common inferior vertebral ligament. a. Intervertebral fibro-cartilages (Fig. 80, 1, 1). — These are circular or elliptical discs, convex in front, concave behind, and solidly fixed by their faces to the articular planes which they separate. The fibrocartilaginous substance composing them consists of concentric layers, which become denser and closer to each other as they near the circumference ; they even disappear towards the centre of the disc, where this substance becomes pulpy and assumes the histological characters of pure cartilage. It may be remarked, that each of these layers is made up of a collection of thick parallel filaments, which cross with those of other layers like an X, and are attached by their extremities to the articular surfaces. From this arrangement results so inti- mate an adherence between the vertebral bodies and their intermediate fibro- cartilages, that an attempt to disunite them is more likely to determine a fracture of the former. The fibro-cartilages, thicker in the cervical and lumbar regions than in the dorsal, respond by their circumference to the two common ligaments. Those which separate the vertebrae of the back concur to form the intervertebral cavities, which are destined for the reception of the heads of the ribs, and give attachment to the interosseous costo- vertebral ligaments. (Leyh designates the superficial fibres of the excentric layer of these fibro-cartilages as intervertebral ligaments. Luschka has shown that the cartilages are in reality articular capsules.) b. Common superior vertebral ligament (Fig 83, 1). — This ligament extends from the axis to the sacrum, and is lodged in the spinal canal ; it represents a long fibrous band cut on its borders into wide festoons. (The wide portions correspond to the discs.) By its inferior face, it is attached to the intervertebral discs and the triangular imprints on the upper faces of the bodies of the vertebrae. Its superior face is in contact with the dura mater through the medium of an abundant cellulo-adipose tissue. Its borders are margined by the intra- vertebral venous sinuses (venm basium vertebrarium). c. Common inferior vertebral Mgament(Fig. 84, 5). — Situated under the spine, this ligament is absent in the cervical and the anterior third of the dorsal region. It only really begins about the sixth or eighth vertebra of the latter region, and is prolonged in the form of a cord, at first narrow, then gradually widening until it reaches the sacrum, on the inferior surface of which it terminates by a decreasing expansion. From its commencement, it is attached to the inferior crest of the bodies of the vertebrae and the interver- tebral discs. By its inferior face, it responds to the posterior aorta. (Leyh commences this ligament at the seventh cervical vertebra, and says 132 THE ABTICULATIONS. that it adheres to the crests on the bodies of the dorsal and lumbar vertebrae, as well as to the lower face of the sacrum and coccyx. At the fifth dorsal vertebra it widens and thickens, and in the lumbar region is bound up with % the pillars of the diaphragm and confounded on each side with the large ligaments of the pelvis.) Union of the Vertebra by their Spinal Portions — Each vertebra, in uniting by its annular portion with that which follows or precedes it, forms a double arthrodial joint. Articular surfaces. — These are the facets cut on the anterior or posterior articular processes, and which have been described when speaking of the vertebrae themselves. They are covered by a thin layer of cartilage. Modes of union. — 1, A common superspinous ligament ; 2, Interspinous ligaments ; 3, Interlamellar ligaments ; 4, Ligamentous capsules, proper to the articular processes. a. Common superspinous ligament. — This ligament, whose name suf- ficiently indicates its situation, extends from the sacrum to the occipital bone and is divided into two portions : one posterior, or superspinous dorso-lumbar ligament; the other anterior, or superspinous cervical ligament. These two ligaments, although continuous with one another, yet differ so strikingly in form and structure that they are best described separately. 1. Superdorso-lumbar ligament (Fig. 80, 2). — This is a cord of white fibrous tissue, which commences behind on the sacral spine and ceases in front about the inferior third of the dorsal region by insensibly assuming the texture and elasticity of the cervical ligament, with which it is continuous. It is attached in its course to the summits of all the lumbar spinous processes and to the ten or twelve last dorsal. On the sacral spine, it is confounded with the superior ilio-sacral ligaments. In the lumbar region, it is united on each side to the aponeuroses of the common mass of muscles. 2. Superspinous cervical, or simply cervical ligament (Fig. 104, 1, 2). — This ligament is entirely formed of yellow fibrous tissue, and constitutes, in the median plane of the body, a very remarkable elastic apparatus which separates the superior cervical muscles of the right side from those of the left, and plays the part not entirely of an articular band, but rather of a permanent stay charged to balance the weight of the head. In the cervical ligament there is distinguished a funicular and a lamellar portion. The first, usually called the cord of the cervical ligament, is a wide funiculus which extends directly from the first dorsal spinous processes to the summit of the head. Divided into two lateral lips by a median groove, this cord is continued posteriorly with the dorso-lumbar ligament, and is inserted forwards into the cervical tuberosity of the occipital bone. It is covered above by a mass of fibro -adipose tissue which, in certain common- bred horses, is very abundant. Below, it gives rise, in its posterior two- thirds, to the majority of the fibres belonging to the lamellar portion. On the sides, it receives the insertions of several cervical muscles. The lamellar portion, comprised between the funicular portion, the spinous processes of the second dorsal vertebra, and the cervical stalk, constitutes a vast triangular and vertical septum, which itself results from the apposition of the two laminae which lie back to back, and are united by cellular tissue ; they are bordered above by the two lateral lips of the cord. The elastic fibres which enter into their composition are given off either from the latter, or from the spinous processes of the second and third dorsal vertebrae ; they are directed downwards or forwards, and reach the spinous processes of the last six cervical vertebrae, into which they are inserted by so many digitations, ABTICULATIONS OF THE SPINE. 133 Fig. 80. becoming confounded with the interspinous ligaments of the neck. The fibres of the two last digitations are few in number, widely separated from one another, and united by many anastomosing branches, which make them appear as a kind of wide network. The laminae of the cervical ligament are in relation, outwardly, with the superior branch of the ilio-spinal ligament, the transverse spinous muscle of the neck, and the great complexus. (This important structure, which is in reality the mechanical stay and support of the heavy head and neck of quadrupeds, and is usually termed the ligamentum nuchce, is all but absent in Man, being represented in him by a thin narrow band, or rather two thin planes of fibres, the ligamenta subflava. It is described by Leyh as if there were not two portions, and that excellent anatomist does not appear to insist sufficiently on the difference between the dorso-nuchal and the dorso-lumbar divisions. Percivall, who almost entirely neglects the ligaments, also makes no distinction. The difference in structure, elasticity, and situation, warrants the distinction made by Chauveau. As already indicated, the function of this ligament, and more particularly of its nuchal division, is to maintain the head and neck in their natural position during repose, and to allow the most extensive movements at other times. ) b. Interspinous ligaments (Fig. 80, 3). — Fibrous laminae fill the inter- spinous spaces, and are attached, before and behind, to the opposite borders of the spinous processes which they unite ; they are continued below by the interlamellar liga- ments, forming two lateral planes which are applied against each other, like the laminae of the cervical ligament, and covered outwardly by the transverse spinous (dorsalis colli) muscle. In the region of the neck, the interspinous ligaments are yellow and elastic. In the dorso- lumbar region, they are formed by fasciculi of white fibrous tissue, loosely united to each other at their extremities, and directed very obliquely backwards and downwards. In consequence of this disposition, and notwithstanding their in- extensibility, they permit the separation of the spinous processes. Their lateral surfaces are divided by a layer of grey elastic fibres, which cross like an X the direction of the preceding fasciculi. Very abundant in the anterior moiety of the dorsal region, these fibres operate, by their proper elasticity, in bringing the spinous pro- cesses towards each other. c. Interlamellar, or interannular ligaments. — Situated, as their name indicates, between the vertebral laminae, and divided into two lateral moieties, these ligaments appear to be produced by the two fibrous planes of the preceding ligaments, which, on arriving at the base of the spinous processes, separate from one another to be carried outwards. Their anterior border is inserted into the posterior margin of the vertebral lamina in front. Their posterior border is fixed to the anterior border and inferior face of the lamina behind. Their superior face is in relation with some spinal muscles, and their inferior face is in contact with the dura mater. Outwardly, they are confounded with the capsules proper 12 INTERVERTEBRAL ARTICULA- TIONS. A, B, C, Bodies of three dorsal vertebrae divided longitudi- nally and vertically to show (1, 1) a section of the in- tervertebral discs ; 2, Super- spinous dorso-lumbar liga- ment ; 3, Interspinous liga- ment ; 4, Fibrous fascia, con- stituting the proper capsule to the articular processes in the dorsal region. 134 THE ABTICULATIONS. to the articular processes. Yellow and elastic in the cervical region, these ligaments are white and inelastic in the dorso-lumbar region. d. Capsules proper to the articular processes (Fig. 81, 5). — Each anteriol articular process is maintained against the corresponding posterior process by a direct band : this is a peripheric capsule attached around the diarthrodial facets, doubled internally by a synovial membrane which facilitates their gliding, and covered, outwardly, by the insertions of some spinal muscles. These capsules, yellow and elastic in the cervical, are composed of white fibrous tissue in the dorso-lumbar region. Very developed at the neck, in consequence of the thickness of the articular tubercles they envelope, they become reduced, near the middle of the back, to some fibres which cover, outwardly, the diarthrodial facets in contact. Characters proper to some Intervertebral Articulations. — 1. Inter- coccygeal and sacro-coccygeal articulations. — These are constructed after the same type as the other spinal articulations, except that they are appropriate to the rudimentary state of the vertebrae they unite. The coccygeal bones only come in contact by their bodies, their spinal laminae being reduced to the merest traces, or are altogether absent. The anterior and posterior articular surfaces of each vertebra are convex, and the interarticular fibro-cartilages, hollow on both faces, resemble a biconcave lense. With regard to the peripheral bands, they are represented by a bundle of longitudinal fibres spread over the surface of the bones, which they envelope in a common sheath. 2. Intersacral articulations. — The sacral vertebrae being fused into one piece — the os sacrum — there is no occasion to study the true articulations in this region. It may be remarked, however, that the superspinous dorso- lumbar ligament is continued on the sacral spine, and that there exist be- tween the processes formed by this spine veritable interspinous ligaments. 3. Sacro-lumbar articulation. — In this articulation, the great thickness of the fibro- cartilage is to be remarked ; and, in addition, that the last lumbar vertebra corresponds with the sacrum not only by its body and articular processes,, but also by the oval and slightly concave facets shown on the posterior border of its transverse processes, which are adapted to analogous slightly-convex facets on the sides of the base of the sacrum. The bundles of fibres thrown from one bone to another from around these sacro- transversals (real planiform diarthroses) maintain the articular surfaces in contact, and cover, outwardly, the synovial membrane which facilitates their gliding. 4. Articulation of the two last lumbar vertebrae. — This is distinguished by the presence, between the transverse processes, of a planiform diarthrosis like that of the sacro-transversal just noticed. These two articulations are only found in Solipeds. 5. Atlo-axoid articulation. — This is so far removed by its conformation and special uses from the other intervertebral articulations, that it will be described as an extrinsic articulation of the head and spine. (See the Articulations of the Head.) The Movements of the Spine in general. — Each intervertebral articula- tion is the seat of very obscure movements, whose separate study offers little interest. But these movements, when conjoined with those of the other articulations, result in bending the whole spinal stalk in a somewhat marked manner, and producing either the flexion, extension, or lateral inclination of this flexuous column. When flexion takes place, the spine is arched upwards, the common inferior ligament is relaxed, the spinous processes separate from one ARTICULATIONS OF THE HEAD. 135 another, and the superspinous ligament, becoming very tense, soon imposes limits to this movement. Extension is effected by an inverse mechanism, and is checked by the tension of the common inferior ligament and the meeting of the spinous processes. Lateral inclination takes place when the spine bends to one side. This movement is very easily executed in the cervical and coccygeal regions, but is arrested by the ribs and the costiform processes in the dorso-lumbar region. A circumflex movement is possible at the two extremities of the vertebral column — neck and tail; for they pass easily from extension to lateral inclination, and from this to flexion, etc. Owing to the elasticity of the intervertebral fibro-cartilages, the spine is endowed with a very limited amount of rotation, or rather of torsion. For the special study of the movements of each spinal region, reference must be made to what has been already said (page 29) regarding the mobility of this column. Tn the Ox the intervertebral discs are much thicker than, in the Horse. The common inferior vertebral ligament is very strong in the lumbar region. The superspinous dorso-lumbar ligament is composed of yellow elastic tissue. The cervical ligament is much more developed than in Solipeds, in consequence of the greater weight of the head ; and it presents a conformation altogether special, which M. Lecoq^ has made known in the following terms : " On leaving the withers, the superspinous ligament ceases to cover the head of the spinous processes, and extends from each side in a wide and strong band, taking points of attachment on the sides of the processes, and becoming separated, on leaving that of the first dorsal vertebra, into two parts — a superior and inferior. The first reaches the cervical tuberosity in the form of a thick cord united to the cord of the opposite ; the other thins off into a band which is attached to the posterior half of the spinous process of the axis and to that of the third and fourth vertebrae. A production of the same nature, an auxiliary to the principal portion, leaves the anterior border of the spinous process of the first dorsal vertebra, and is attached to that of the fourth, fifth, sixth, and seventh vertebras. The superior border of this auxiliary liga- mentous production is concealed between the two lamina of the principal ligament." 1 The Pig, remarkable for the shortness of its neck and the limited movements of this region, does not show any cervical ligament, properly so called. It is replaced by a superficial fibrous raphe extending from the occipital bone to the spinous process of the first dorsal vertebra. The Cat has no cervical ligament, and shows, instead, a raphe like the Pig. In the Dog the ligament is reduced to a simple cord, continued from the dorso-lumbar ligament, and which goes no further than behind the spinous process of the axis. In the Cat the interspinous ligaments are replaced by small muscular fasciculi ; with the Dog this substitution only takes place in the cervical region. The laminae of the first coccygeal vertebrae possess the principal characters which distinguish perfect vertebrae, and are united by vestiges of the articular bands which exist in the other regions of the spine. Article II. — Articulations of the Head. We will first study the two extrinsic articulations which, are the centre of the movements of the head on the spine — the atlo-axoid and occipito-atloid articulations. Afterwards, we will pass to the examination of the joints which unite the different bones of the head. 1. Atlo-axoid Articulation. (Preparation. — It suffices to remove the soft parts from around the articulation to expose the interannular, the interspinous, and the inferior odontoid ligament. To examine ' Journal de Medecine Ve'terinaire ' (Lyons, 1848), p. 122. 136 THE ARTICULATIONS. the superior odontoid ligament and the synovial membrane, one half the atlas and axis must be separated by sawing longitudinally through them from one side to the other.) This may be considered as the type of the trochoides. Articular surfaces. — To form this articulation, the axis offers its odontoid pivot and the undulated diarthrodial facets at its base. The atlas opposes to the pivot the concave semicylindrical surface hollowed on the superior face of its body ; and for the lateral undulated facets it has analogous facets which are cut on the transverse processes, on each side of the vertebral canal. Mode of union. — 1. An odontoid, or odonto-atloid ligament; 2. An inferior atlo-axoid ligament ; 3. A superior ditto ; 4. A fibrous capsule. a. Odontoid ligament (Fig. 81, 3). — Continued to the common superior vertebral ligament, very short and strong, flattened from above to below, and triangular in shape, the odontoid ligament is composed of glistening white fibres, fixed behind in the superior channel of the odontoid process, . and inserted in front on the transverse ridge which separates the superior face from the inferior arch of the atlas, as well as on the imprints situated in front of this ridge. This ligament is covered, on its lower face, by the synovial membrane of the articulation; and by its upper surface is in contact with the spinal dura mater. It sends some bands within the condyles of the occipital bone. b. Inferior atlo-axoid ligament. — This is a wide, thin, and nacrous- looking band, extending from the inferior face of the axis to the inferior tubercle of the atlas, and covered by the long muscle of the neck ; it is united to the synovial membrane by its deep face, and confounded on its borders with the fibrous capsule to be immediately described. c. Superior atlo-axoid ligament. — This exactly represents the inter- spinous ligaments of the other cervical articulations. Yellow, elastic, and formed like the two lateral bands, it is continuous, laterally, with the capsular ligament. d. Capsular ligament. — This, it may be said, is only the interlamellar ligament proper to the atlo-axoid articulation. It commences from the sides of the preceding ligament, and becomes united to the inferior atlo- axoid one, after contracting adhesions with the borders of the odontoid ligament. In this way it encloses the articulation and the spinal canal. Before and behind, it is attached to the anterior or posterior margin of the bones it unites. Its external face is in contact with the great oblique muscle of the head ; its internal responds, in its inferior half, to the articular synovial membrane, and its superior moiety to the spinal dura mater. (Leyh describes this ligament as the interannular.) Synovial membrane. — This lines the odontoid ligament, the atlo-axoid ligament, and the articular portion of the peripheral capsule. Movements. — Botation, the only movement possible in the atlo-axoid articulation, is effected in the following manner: the axis remains fixed, and the first vertebra, drawn to one side chiefly by the great oblique muscle, rotates on the odontoid pivot, carrying the head with it. In the Dog and Cat the odontoid ligament is replaced by three particular ligaments : 1, Two lateral cords, rising in common from the summit of the odontoid process, and inserted, each on its own side, within the condyles of the occipital bone ; 2, A transverse ligament, passing over the odontoid process, which it maintains in its place against the inferior arch of the atlas, and is attached by its extremities to the superior face of the latter. A small synovial capsule facilitates the gliding of the odontoid process beneath this ligament. The articular synovial membrane always communicates with that of the occipito-atloid articulation. In the Pig the disposition is nearly the same as in the Camivora ABTICVLATIONS OF THE HEAD. 13? 2. Occipito-atloid Articulation. (Preparation. — Dissect away all the soft parts that pass from the neck to the head and cover the articulation, and more particularly the flexor, the recti, and the small oblique muscles of the head. To Yig. 81. expose the synovial membranes, open the sides of the capsular ligament.) This is a condyloid articulation. Articular surfaces. — In the atlas, the two cavities which replace the anterior articular processes and the heads of the other vertebras; in the occipital bone, the two condyles flanking the sides of the occi- pital foramen. Mode of union. — A single capsular ligament en- velopes the entire articulation ; it is attached by its anterior border to the margin of the occipital con- dyles, and by its posterior to the anterior contour of the atlas. Thin and slightly elastic in its inferior half, this ligament presents, superiorly, four reinforcing fasciculi : two middle, which intercross in X — from whence the name " cruciform," sometimes given to this ligament (Fig. 81, 1, 1) ; and two lateral, which pass from the sides of the atlas to the base of the styloid processes (Fig. 81, 2, 2). It is lined within by the synovial membranes, and is enveloped externally by a large number of muscles, which protect the articu- lation and greatly strengthen it everywhere. Among these may be particularly noticed the straight muscles of the head, the small oblique, and the great com- plexus. There is also the cord of the cervical liga- ment. Synovial membranes. — These membranes are two in number, one for each condyle and corresponding rtloid cavity. Sustained above, below, and outwardly by the capsular ligament, they are related inwardly to the dura mater and to the fibrous tractus which, from the odontoid ligament, is carried to the in- ternal face of the occipital condyles. Movements. — Extension, flexion, lateral inclination, and circumduction, are the possible movements of the occipito-atloid articulation. In the Pig, Dog, and Cat this articulation, strengthened as it is by the capsular and odontoido-occipital ligaments already mentioned, has only one synovial capsule. 3. Articulations of the Bones of the Head. If we except the articulation which unites the inferior jaw to the cranium — the temporo-maxillary — and the hyoideal articulations, it will be found that all the bones of the cranium and face are united to each other by synarthrosis, forming the different kinds of sutures already generally described (page 128). Nothing is to be gained by entering into more detail ATLO-OXOID AND OCCIPI- TO-ATLOID ARTICULA- TIONS. The upper arch of the atlas has been removed to show the odontoid ligament. 1, 1, Middle accessory fas- ciculi ; 2. 2, Lateral fasciculi of the capsular ligament of the occipito- atloid articulation ; 3, Odontoid ligament ,- 4, Interspinous ligament uniting the second and third vertebras of the neck ; 5, Fibrous capsule uniting the articular processes of these verte- brae.— A, Anterior in- ternal foramen of the atlas converted into a groove by the section of the bone • B, B, Verte- bral foramina of the atlas • c, C, Foramina replacing the anterior notches of the axis. 138 THE ARTICULATIONS. Fig. 82. with regard to these articulations, as it will be found sufficient to call to mind the topographical description of each piece entering into their formation. 4. Temporo-maxillary Articulation. (Preparation. — Remove the masseter muscle and the parotid gland. Saw through the head about the middle line. Open the articulation externally to exhibit the inter- articular meniscus.) The lower jaw, in its union with the cranium, constitutes a double condyloid articulation. Articular surfaces. — With the temporal bone, these are the condyle, the glenoid cavity, and the supracondyloid process which exists at the base of the zygomatic process. The glenoid cavity is not lined by cartilage, and appears to be merely covered by synovial membrane. With the maxillary bone there is the oblong condyle situated in front of the coronoid process. Interarticular fibro-cartilage. — The articular surfaces just named are far from fitting each other accurately ; this is only accomplished by the interposition of a fibro-cartilaginous disc between the temporal and maxillary bones. This disc is a kind of irregular plate, flattened above and below, thicker before than behind, and moulded on each of the diarthrodial surfaces it separates. Its superior face, therefore, presents : in front, a cavity to receive the condyle of the temporal bone; behind, a boss which is lodged in the glenoid cavity. The inferior face is hollowed by an oblong fossa in which the maxillary con- dyle is lodged. Mode of union. — A fibrous envelope — a true capsular ligament — surrounds the articulation, and is attached by its borders to the margin of the articular surfaces it unites. Formed, out- 2, External fasciculus of the wardly, by a thick fasciculus of white vertical capsular ligament.— a, Base of fibres (Fig. 82, 2), this ligament becomes grey- ly coixmoid process ; b Neck ^.coloured and eiastic for the remainder of ot the maxillary condyle; C, ., . , ., ,. . . , ., . , Mastoid process; d, External its extent, and greatly diminishes in thickness, auditory hiatus. especially in front. Its inner face is lined by the synovial capsules, and adheres to the cir- cumference of the interarticular fibro-cartilage. Its external face responds, in front, to the temporal and masseter muscles; behind, to the parotid gland; inwardly, to the external pterygoid muscle; and outwardly, to a fibrous expansion which separates it from the skin. (Leyh mentions a lateral external and a posterior ligament for this articulation, but Chauveau and Eigot evidently look upon these as portions of the capsular.) Synovial membranes. — This articulation has two synovial sacs, one above the other, which are separated by the fibro-cartilaginous disc. Movements. — The temporo-maxillary articulation is the centre of all the movements performed by the lower jaw. These are : depression, elevation, lateral motion, and horizontal gliding. The lower jaw is depressed when it separates from the superior one, and is elevated when it approaches this. These two opposite movements are executed by a mechanism of such great simplicity that it need not be TEMPORO-MAXILLARY ARTICTJ LATION. 1, Interarticular fibro-cartilage; ARTICULATIONS OF THE HEAD. 139 described here. Lateral movements take place when the inferior extremity of the jaw is carried alternately to the right and left. It then happens that one of the maxillary condyles, taking with it the tibro-cartilage, is brought into contact with the temporal condyle, while the other is imbedded in the glenoid cavity of the opposite side. The horizontal gliding is effected from behind to before, or vice versa. In the first case, the two maxillary condyles are carried at the same time under the temporal condyles, bearing with them the fibro-cartilages. In the second case, they are drawn into the glenoid cavities, and rest against the supracondyloid eminence, which prevents their going further. It will be understood, after this brief description, that the presence of the fibro-cartilages singularly favours the lateral movements and horizontal gliding of the lower jaw. In the Pig the temporo-maxillary articulation is formed after the same type as that of rodents, and allows very extensive movements from before to behind; a circumstance due to the complete absence of the supracondyloid eminence. In the Dog and Cat the maxillary condyle is exactly fitted into the temporal cavity. This disposition, in giving great precision to the movements of depression and elevation, restrains in a singular manner the lateral and horizontal gliding motions. The inter- articular fibro-cartilage is extremely thin in these animals. 5. Hyoideal Articulations. (Preparation. — Disarticulate the lower jaw, and dissect away from the right of each articulation the muscles that may conceal the view.) These are of two kinds : extrinsic and intrinsic. The first comprise the two temporohyoideal articulations ; to the second belong the joints which unite the different pieces of the hyoid bone — the interhyoideal articulations. Tempoko-hyo ideal Articulations. — These are two amphiarthrodial joints, in the formation of which each great branch of the hyoid bone opposes its upper extremity to the hyoideal prolongation lodged in the vaginal sheath of the temporal bone. An elastic cartilage, from 4-10ths to 6-10ths of an inch in length, unites the two bones in a solid manner ; and it is owing to the flexibility of this cartilage that the hyoid bone can move entirely on the temporal bones. Interhyoideal Articulations. — A. The great branch articulates with the small one by an amphiarthrosis analogous to the preceding. To form this articulation, these two pieces of bone are joined at an acute angle through the medium of a more or less thick cartilaginous band, in the centre of which there is often a little bony nucleus. This cartilage is elastic and flexible, and permits the opening and closing of the articular angle at the summit of which it is placed. B. Each small branch is united to the body of the hyoid bone by an arthrodial articulation. The articular surfaces are : for the hyoideal branch, the small cavity terminating its inferior extremity ; for the body, the rounded lateral facet situated at the origin of the cornu. These surfaces are covered by cartilage, and enveloped by a small synovial sac and a peripheral fibrous capsule. They can glide on each other in nearly every direction. (Median and superior hyoideal capsular ligaments are described by Leyh as sometimes present. The latter unites the upper and middle branches, and the former the middle with the inferior branches. They are absent when these branches are confounded with the superior ones.) 140 THE ARTICULATIONS. Article III. — Articulations of the Thorax. These are also divided into extrinsic and intrinsic. The first, named costo- vertebral, unite the ribs to the spine. The second join the different* pieces of the thorax together; they comprise: 1, The chondro-sternal articulations ; 2, Chondro-costal articulations ; 3, The articulations of the costal cartilages with each other ; 4, The sternal articulation peculiar to the larger Ruminants and the Pig. All these joints will be first studied in a particular manner, then examined in a general way as to their movements. 1. Articulations of the Bibs with the Vertebral Column, or Costo-vertebral Articulations. Each rib responds to the vertebral column by two points— its head and its tuberosity. The first is received into one of the intervertebral cavities hollowed out on the sides of the spine, and is therefore in contact with two dorsal vertebrae ; the second rests against the transverse process of the posterior vertebra. From this arrangement arises two particular articulations belonging to the arthrodial class, which are named costo-vertebral and costo- transverse. Costo-vertebral Articulations. — Articular surfaces. — Pertaining to the rib, we have the two convex facets of the head, separated from each other by a groove of insertion and covered by a thin layer of cartilage. On the vertebrae, the concave facets which by their union form the inter- vertebral cavity ; these facets are also covered with cartilage, and separated, at the bottom of the cavity by the corresponding intervertebral disc. Mode of union. — 1. An interarticular ligament (Figs. 83, 2 ; 84, 1), im- planted in the groove of insertion of the head of the rib, and attached to Fig. 83. Fi