Part 12

The =superior surface= is concave, and is crossed by a non-articular depression which divides it into two unequal facets; it articulates with the central tarsal. The =inferior surface= is slightly convex, and rests on the large metatarsal bone; it has an extensive central rough excavation. The =anterior= or =dorsal border= is convex and bears a rounded ridge on its inner part. The =internal border= is deeply notched and has a small facet for the second tarsal on its anterior part. The =external border= is also divided by a notch into two parts, and bears two diagonally opposite facets for articulation with the fourth tarsal. In some cases there is a facet for the inner small metatarsal bone.

[Illustration:

FIG. 85.—CROSS-SECTIONS OF METACARPAL AND METATARSAL BONES OF HORSE. (After Schmaltz, Atlas d. Anat. d. Pferdes.) ]

THE FOURTH TARSAL BONE

The =fourth tarsal= bone (Os tarsale quartum, cuboid) is the outer bone of the lower row, and is equal in height to the central and third together. It is cuboid in shape and presents six surfaces.

The =superior surface= is convex from side to side, and articulates chiefly with the fibular tarsal, but to a small extent with the tibial tarsal also. The =inferior surface= rests on the large and external small metatarsal bones. The =internal surface= bears four facets for articulation with the central and third tarsal bones. It is crossed from before backward by a smooth groove, which by apposition with the adjacent bones forms the =canal of the tarsus= (Canalis tarsi) for the passage of the perforating tarsal vessels. The =anterior= or =dorsal=, =external=, and =posterior= or =plantar surfaces= are continuous and rough. A tuberosity behind gives attachment to the plantar ligament.

=Development.=—The fibular tarsal bone has two centers of ossification, one for the main mass and the other for the tuber calcis; the latter fuses with the rest of the bone at about three years of age. The first and second tarsals have separate centers, but fusion usually occurs before birth. Each of the other bones ossifies from a single center.

[Illustration:

FIG. 86.—DIGITAL BONES OF FORE LIMB OF HORSE, VOLAR ASPECT. ]

[Illustration:

FIG. 87.—DIGITAL BONES OF HIND LIMB OF HORSE, VOLAR ASPECT. ]

THE METATARSUS

The =metatarsal= bones (Ossa metatarsalia), three in number, have the same general arrangement as the metacarpal bones, but present some important differences. Their direction is slightly oblique, downward and a little forward.

The =large= or =third metatarsal= bone is about one-sixth longer than the corresponding metacarpal; in an animal of medium size the difference is about two inches. The shaft is more cylindrical, and is almost circular on cross-section, except in its lower part. At the upper part of its external surface there is a groove, which is directed obliquely downward and backward, and is continued by the furrow formed by the apposition of the external metatarsal bone; it indicates the course of the great metatarsal artery. A faint impression in a similar place on the inner side marks the position of the corresponding vein. The nutrient foramen is relatively higher than on the metacarpal bone. The proximal extremity is much wider from before backward than that of the metacarpal bone. Its articular surface is slightly concave, and is marked by a large central non-articular depression, continued outward by a deep notch. The greater part of the surface articulates with the third tarsal, but there is an outer facet for the fourth, and usually a small facet posterointernally for the second tarsal bone. Posteriorly there are two pairs of facets for articulation with the small metatarsal bones. The front is crossed by a rough ridge for insertion, which becomes larger and turns downward on the outer side behind the vascular groove. The distal extremity closely resembles that of the corresponding metacarpal bone.

In some cases the lower part of the shaft is bent backward somewhat. The articular surface extends a little higher behind than in the case of the metacarpal bone. The large metatarsal bone is even more strongly constructed than the metacarpal. The shell of compact substance is very thick in the middle of the shaft, especially in front and internally.

The =small metatarsal= bones are a little longer than the corresponding metacarpals. The =external= (fourth) =metatarsal= is relatively massive, especially in its upper part. The head is large and outstanding, and bears two facets above for the fourth tarsal, and two in front and internally for articulation with the large metatarsal; elsewhere it is roughened for attachment. The =internal= (second) =metatarsal= is much more slender than the outer one, especially in its upper part. The head bears two facets above for the first and second tarsals, and sometimes one for the third tarsal.

THE PHALANGES AND SESAMOIDS

The axis of the phalanges of the hind limb is about five degrees less oblique than that of the fore limb, and the chief differences in the form and size of the bones are as follows:

The =first phalanx= is a little shorter, wider above, and narrower below.

The =second phalanx= is narrower and slightly longer.

The =third phalanx= is narrower, the angle of inclination of the wall surface is a little (ca. 5 degrees) greater, the sole surface is more concave, and the wings are less prominent and closer together.

The =proximal sesamoids= are a little smaller, except in thickness. The =third sesamoid= or =navicular bone= is narrower and shorter.

SKELETON OF THE OX

VERTEBRAL COLUMN

The vertebral formula is C_{7}T_{13}L_{6}S_{5}Cy_{18–20}.

The =cervical vertebræ= are much shorter than those of the horse and are smaller in their other dimensions. The =articular processes= are smaller than in the horse, and a plate of bone connects each two of the same side. The transverse processes of the third, fourth, and fifth are double; the upper part projects backward, and is short and stout; the lower part is directed downward and forward, and is longer and more plate-like. The lower part of the sixth transverse process is a large, thick, quadrilateral and almost sagittal plate, directed downward. The seventh transverse process is single, short, and thick, and presents no foramen transversarium; it is in series with the upper part of the preceding processes. The =spinous processes= are well developed, and increase in height from before backward. They are directed upward and forward, with the exception of the last, which is nearly vertical and is about four or five inches (ca. 10 to 12 cm.) in height. The summit of that of the third bone is usually bifid. The =ventral spines= are prominent and thick in their posterior part; they are absent on the last two.

The =atlas= has a large rough =tuberosity= on its dorsal arch. The =ventral arch= is very thick. The =wings= are less curved than in the horse, and the foramen transversarium (posterior foramen) is absent. The cavities for the occipital condyles are divided into upper and lower parts by a non-articular area, and are separated by a narrow interval below. The =posterior articular surfaces= are flattened behind and are continued into the vertebral canal, forming an extensive area for the odontoid process of the axis.

The =axis= is short. The =spine= projects a little in front, and increases in height and thickness behind; its posterior border descends abruptly. The =odontoid process= (dens) is wide, and its upper surface is deeply concave from side to side. The =intervertebral foramen= is circular and not so close to the anterior border of the arch as in the horse. The =posterior notches= are not so deep. The =transverse processes= are stouter, but the =foramen transversarium= is small and sometimes absent.

The =thoracic vertebræ=, thirteen in number, are larger than those of the horse. The =bodies= are longer and are distinctly constricted in the middle. They bear a thin-edged ventral crest. The =arches=—in addition to the usual notches, which are shallow—are perforated in the posterior part by a foramen. The =transverse processes= are thick and strong, and bear rounded mammillary processes (except at the posterior end of the series); the last two, although prominent, do not always articulate with the ribs. The =spinous processes= are long. The first is much higher than in the horse, the next two are usually the most prominent, and behind this there is a very gradual diminution in height. The backward slope, slight at first, increases to the tenth; the last is vertical and lumbar in character. The summit is usually pointed on the first, and the thickening on those further back is less than in the horse. The width diminishes from the fifth to the eleventh usually. Both borders of the spines are in general thin and sharp, but the last three or four sometimes have thick posterior margins.

[Illustration:

FIG. 88.—SKELETON OF COW.

_1.H._, Atlas; _7.H._, seventh cervical vertebra; _1.R._, first thoracic vetrebra; _6.R._, sixth rib; _12.R._, twelfth thoracic vertebra; _13.R._, last rib; _1.L._, first, _6.L._, last lumbar vertebra; _K_, sacrum; _1.S._, first coccygeal vertebra; _6.K._, sixth costal cartilage; _x_, wing of atlas; _1_, scapula; _1′_, cartilage of scapula; _2_, spine of scapula; _3_, acromion; _4_, humerus; _4′_, external condyle of humerus; _5_, external tuberosity of humerus; _6_, deltoid tuberosity; _7_, ulna; _8_, olecranon; _9_, radius; _10_, carpus; _11_, accessory carpal bone; _12_, metacarpus; _13_, phalanges; _14_, sternum; _14′_, manubrium; _14″_, xiphoid cartilage; _15_, ilium; _16_, external angle of ilium; _16′_, internal angle of ilium; _17_, tuber ischii; _18_, femur; _19_, trochanter major; _20_, patella; _21_, tibia; _21′_, external condyle of tibia; _22_, tarsus; _23_, distal end of fibula; _24_, tuber calcis; _25_, metatarsus; _26_, phalanges. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =lumbar vertebræ=, six in number, are much longer than in the horse. The =bodies= are much constricted in the middle, expanded at either end, and bear rudimentary ventral crests. The fourth and fifth are usually the longest. The =intervertebral foramina= are often double in the anterior part of the series, and are very large further back. The =articular processes= are large, and their facets are more strongly curved than in the horse. The =transverse processes= all curve forward. They are separated by considerable intervals, and form no articulations with each other or with the sacrum. Their borders are thin and irregular, and often bear projections of variable size and form. The first is the shortest and the length increases to the fifth, the last being considerably shorter. The =spinous processes= are relatively low and wide, the last being the smallest; their summits are moderately thickened.

The =sacrum= is longer than that of the horse. It consists originally of five segments, but fusion is more complete and involves the spinous processes, which are united to form a =median sacral crest=, with a convex thick and rough margin. =A lateral crest= is formed by the fusion of the articular processes. The =pelvic surface= is concave in both directions, and is marked by a central =groove=, which indicates the course of the middle sacral artery. The =inferior sacral foramina= are large. The =wings= are quadrangular, short, compressed from before backward, and high dorso-ventrally. They have an extensive anterior surface, which is concave from side to side, and non-articular. The posterior surface is rough, and bears a triangular area below for articulation with the ilium. The body of the first segment is very wide, and the entrance to the sacral canal correspondingly wide and low. The =anterior articular processes= are large, and are concave and semicylindrical in curvature internally. The =lateral borders= are thin, sharp, and irregular. The =apex= is wider than in the horse, and the posterior end of the crest forms a pointed projection over the opening of the sacral canal.

The =coccygeal vertebræ= are longer and better developed than in the horse. The first five or six have complete arches and spinous processes. The transverse processes are relatively large in the anterior part of the series, in which there are also anterior articular processes (which do not articulate), and a pair of ventral spines which form a hæmal groove for the middle coccygeal artery.

Vertebral curves: The cervical curve is very slight and is concave dorsally. The thoracic and lumbar regions form a gentle curve, concave ventrally. The promontory is more pronounced than in the horse, especially in subjects in which the sacrum is inclined upward behind. Another promontory occurs at the junction of the sacrum and first coccygeal vertebræ.

Length: The following table gives the lengths of the regions of a shorthorn cow of medium size:

Cervical 47 cm. Thoracic 75 cm. Lumbar 40 cm. Sacral 24 cm. Coccygeal 75 cm. ——————— 261 cm.

Variations: Sometimes fourteen thoracic vertebræ and fourteen pairs of ribs are present; reduction to twelve with the normal number of lumbar vertebræ is very rare. According to Franck, there are sometimes seven lumbar vertebræ with the normal number in the thoracic region. The number of coccygeal vertebræ may vary from sixteen to twenty-one.

THE RIBS

Thirteen pairs of ribs are normally present, of which eight are sternal and five asternal. They are in general longer, wider, flatter, less curved, and less regular in form than in the horse. The eighth, ninth, and tenth are the longest and widest. The width of most of the ribs increases considerably in the middle, and the breadth of the intercostal spaces is correspondingly diminished. The neck is long, and forms (except in the posterior part of the series) a smaller angle with the shaft than in the horse. The articular surface of the tubercle is concave transversely, except on the last two or three, where the facet is small and flat or absent. The lower ends of the second to the tenth or eleventh inclusive form diarthrodial joints with the costal cartilages. The first costal cartilages are very short; they articulate by their internal surfaces with the sternum, but not with each other.

The presence of a fourteenth rib is not very rare. It is usually floating and may correspond to an additional thoracic vertebra or to the first lumbar. Reduction of the thirteenth is more common. The eighth cartilage often does not reach the sternum, but articulates with the seventh.

The =sternum= consists of seven sternebræ, most of which are developed from two lateral centers. It is wider, flatter, and relatively longer than in the horse, and the ventral crest or “keel” is absent. The manubrium is somewhat wedge-shaped and laterally compressed. Its base forms a diarthrodial joint with the body of the bone, and laterally it bears extensive facets for articulation with the first pair of costal cartilages. The body widens from before backward, but behind the last pair of costal facets it becomes much narrower. The ventral surface is prominent on the second and third segments, concave further back. The lateral borders are notched for the passage of vessels. The cariniform cartilage is absent. The xiphoid cartilage is like that of the horse but is smaller.

THE THORAX

The bony thorax is shorter than in the horse. The inlet is higher. The roof is short, and the floor wider and relatively longer. The transverse diameter is wider in the posterior part. The summits of the spinous processes are almost in a straight line from the second thoracic to the middle of the lumbar region.

BONES OF THE SKULL

BONES OF THE CRANIUM

The =occipital bone= is situated in the lower part only of the posterior surface of the skull, and is separated from the highest part (the frontal eminence) by the parietal and interparietal bones. The supraoccipital, interparietals, and parietals fuse before birth or soon after, and the mass so formed is separated from the lateral parts of the occipital bone by a transverse suture in the skull of the calf. Above this suture is a central tuberosity, to which the ligamentum nuchæ is attached, and the surface on either side is depressed and rough for muscular attachment. Below the suture the bone is much wider than that of the horse. The foramen magnum is wide, so that the condyles are further apart except below. The paramastoid processes are short and wide and are bent inward. Two constant foramina are found in the condyloid fossa; the anterior one is the hypoglossal, the other (sometimes double) conducts a vein from the =condyloid canal=. The latter passes upward from a foramen on the inner side of the condyle and opens into the parieto-temporal canal. The cranial surface of the supraoccipital presents a central depression, and above this is a variable but never very pronounced eminence, which corresponds to the tentorium osseum of the horse. On either side is a groove leading to the parieto-temporal canal. The basilar process is short and wide; its cranial surface is deeply concave, and the internal spheno-occipital crest is prominent. Two large tubercles below mark the junction with the sphenoid. The foramen lacerum is short and very narrow. In the adult animal the bone is excavated to contain an air-cavity which is regarded as a part of the frontal sinus.

The =sphenoid bone= is short. The cranial surface of the body presents a deep sella turcica, in front of which it rises abruptly. The high anterior part bears a central ridge (Rostrum sphenoidale), which joins the crista galli of the ethmoid. Two foramina occur on either side. Of these, the large anterior one is equivalent to the foramen rotundum, lacerum orbitale, and patheticum of the horse. The posterior one is the =foramen ovale=, which transmits the inferior maxillary nerve. The orbital wing is thick and is overlapped by the frontal in such manner as to appear externally to divide into two branches; the anterior part joins the ethmoid close to the sphenopalatine foramen, and contains a small sinus which communicates with an ethmoidal meatus. The temporal wing is small, but forms a prominent thick pterygoid crest. The pterygoid process is wide, and the pterygoid or alar foramen is absent. The sphenoidal sinus is absent in the calf and small in the adult; it communicates by one or two small openings with an ethmoidal meatus, and so with the nasal cavity.

[Illustration:

FIG. 89.—SKULL AND ATLAS OF OX, LATERAL VIEW.

_9_, Zygomatic arch; _11_, coronoid process; _12_, supraorbital process; _13″_, paramastoid or styloid process; _13‴_, occipital condyle; _14_, parietal bone; _15_, frontal bone; _16_, squamous temporal bone; _17_, external auditory meatus; _18_, temporal condyle; _19_, orbital surface of lacrimal bone; _20_, malar bone; _21_, facial surface of lacrimal bone; _22_, nasal bone; _23_, nasal process of premaxilla; _24′_, incisor teeth; _26_, maxilla; _27_, facial tuberosity; infraorbital foramen in front of _27_; _28′_, molar part of ramus of mandible; _30_, broad vertical part of ramus; _30′_, angle of jaw; _31_, condyle of mandible; _32_, atlas; _x_, wing of atlas. (After Ellenberger-Baum, Anat. für Künstler.) ]

The =ethmoid bone= has an extensive perpendicular plate. The lateral mass consists of five endoturbinals and eighteen ectoturbinals (Paulli). The largest ethmoturbinal is so extensive as to be termed a third or middle turbinal bone; it projects forward between the upper and lower turbinals. The lamina papyracea appears to a small extent externally in the pterygo-palatine fossa, forming part of the upper margin of the sphenopalatine foramen.

The =interparietals= are primitively paired, but unite before birth. As already mentioned, fusion occurs before or shortly after birth with the parietals and supraoccipital. No distinct tentorium osseum is present.

[Illustration:

FIG. 90.—SKULL OF OX, BASAL VIEW, WITHOUT MANDIBLE.

_F_, Pterygoid bone; _G_, horizontal and _G′_, perpendicular part of palate bone; _H_, occipital bone; _J_, malar bone; _K_, sphenoid bone; _O_, maxilla; _P_, vomer; _Sch._, squamous temporal; _St._, frontal bone; _Z_, premaxilla; _1_, for. magnum; _2_, occipital condyle; _3_, paramastoid (styloid) process of occipital; _4_, hypoglossal and condyloid foramina; _5_, for. lacerum; _6_, pharyngeal tubercles; _7_, bulla ossea; _8_, muscular process (left one is removed to expose for. ovale); _9_, hyoid process; _10_, ext. auditory meatus; _11_, zygomatic process; _12_, external opening of parieto-temporal canal; _13_, postglenoid process; _14_, temporal condyle; _15_, for. ovale; _16_, for. lac. orbitale + for. rotundum; _17_, optic foramen; _18_, ethmoidal foramen; _19_, orbital opening of supraorbital canal; _20_, pterygoid crest; _21_, hamulus of pterygoid bone; _22_, lacrimal bulla; _23_, temporal process of malar; _24_, pterygoid process of maxilla; _25_, sphenopalatine foramen; _26_, maxillary foramen; _27_, posterior palatine foramen; _28_, anterior palatine foramen; _29_, accessory palatine foramina; _30_, palate process of maxilla; _31_, interalveolar border; _32_, palatine cleft; _33_, palate process of premaxilla; _34_, fissura incisiva; _35_, facial tuberosity; _36_, posterior nares. (Ellenberger-Baum, Anat. d. Haustiere.) ]

The =parietal bones= do not enter into the formation of the roof of the cranium. They constitute the upper part of the posterior wall, and bend sharply forward along the lateral wall, forming part of the wall of the temporal fossa. The line of inflection is marked by the prominent =parietal crest=, which is continuous with the temporal crest below. The parietals are excavated to form part of the frontal sinuses in the adult animal.

The condition in the young subject is as follows: The two parietals are united with each other and also with the interparietal and supraoccipital. The resulting mass is somewhat horseshoe-shaped. Its occipital part (Planum occipitale) forms the greater part of the posterior wall of the cranium and bears about its center the tuberosity for the attachment of the ligamentum nuchæ. From either side of this a line curves outward, and divides the surface into an upper smooth area and a lower area which is rough for muscular attachment. The upper border joins the frontal bone and concurs in the formation of the frontal eminence. The temporal parts (Plana temporalia) are much smaller and are concave externally; they join the frontal above and the squamous temporal below.

[Illustration:

FIG. 91.—SKULL OF OX, DORSAL VIEW (WITH MANDIBLE).

_12_, Supraorbital process; _14_, parietal bone; _15_, frontal bone; _16_, squamous temporal bone; _19_, orbit; _20_, malar bone; _21_, lacrimal bone; _22_, nasal bone; _23_, premaxilla; _26_, maxilla; _27_, facial tuberosity; _24_, incisor teeth. (After Ellenberger-Baum, Anat. f. Künstler.) ]

[Illustration:

FIG. 92.—SKULL AND ATLAS OF OX, VENTRAL VIEW.

_13_, Basi-occipital; _13″_, paramastoid or styloid process; _13‴_, occipital condyle; _24′_, incisor teeth; _28_, body of mandible; _31_, condyle of mandible; _32_, ventral tubercle of atlas. (After Ellenberger-Baum, Anat. für Künstler.) ]