Vertebral Column

Skeleton of the Ox

The vertebral formula is C7T13L6S5Cy18–20.

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.

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.