VERTEBRAL COLUMN 129 
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 (Crista sacralis media), with a convex 
thick and rough margin. A lateral sacral crest is formed by the fusion of the ar- 
ticular processes. The pelvic surface is concave in both directions, and is marked 
by a central groove (Sulcus vasculosus), which indicates the course of the middle 
sacral artery. The ventral sacral foramina are large. The wings curve downward 
and forward; they are quad- 
rangular, 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 sur- 
face is rough, and at its lower 
part there is a triangular area 
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 
widely separated; they are 
coneave and semicylindrical 
in curvature medially. The 
lateral borders are thin, 
sharp, and irregular. The 
bone does not become nar- 
rower posteriorly, so that the 
apex is usually a little wider 
than the part just behind the 
wings; the posterior end of 
the median crest forms a 
: . : Fie. 126.—Sacrum or Ox; Ventrat VIEW. 
pointed pro) ection over the I-V, Segments; 1—4, ventral sacral foramina; 5, anterior end of body 
opening of the sacral eanal. of first sacral vertebra; 6, vascular groove; 7, posterior end of body of 
last sacral vertebra. 
The coccygeal vertebrae 
are longer and better devel- 
oped 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 articu- 
late), and a pair of ventral spines which form a groove (Sulcus vasculosus) 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 prominence occurs at the junction 
of the sacrum and first coceygeal vertebre. 
pen the following table gives the lengths (inclusive of the inter- 
