Part 29

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.

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.