_a_, Odontoid process (dens); _b_, spinous process; _c_, anterior
articular process; _d_, posterior articular processes; _e_,
transverse process; _f_, foramen transversarium; _g_, bar of bone
which bounds _h_, intervertebral foramen; _i_, vertebral foramen.
(Ellenberger-Baum, Anat. d. Haustiere.)
]
The =thoracic vertebræ= are often fifteen in number. Their bodies are
relatively long, constricted in the middle, and without ventral crests.
Their extremities are elliptical, depressed in the middle and prominent
at the periphery. The arch is perforated by a foramen on either side,
and in most of the series there is also a foramen in the posterior part
of the root of the transverse process which communicates with the former
or with the posterior intervertebral foramen. Sometimes there is a
foramen in the anterior part of the process also. There are mammillary
processes except on the first two; in the posterior five or six vertebræ
they project from the anterior articular processes. The facet for the
tubercle of the rib is absent or fused with that for the head in the
last five or six. The last transverse process is lumbar in character,
plate-like, and about an inch (2 cm.) long. Small accessory processes
occur in the posterior part of the region. The first spinous process is
broad, very high, and inclined a little forward. The others diminish
very gradually in length to the tenth, beyond which they are about
equal. The second to the ninth are inclined backward, the tenth is
vertical (anticlinal), and the rest incline forward. The width decreases
decidedly from the fourth to the tenth, beyond which there is a gradual
increase. The summits are slightly enlarged and lie almost in a straight
line.
The occurrence of fifteen thoracic vertebræ appears to be quite
common, and some observers have recorded the existence of sixteen and
even seventeen; a reduction to thirteen is rare.
The =lumbar vertebræ= are six or seven in number. The bodies are longer
than in the thoracic region and bear a ventral crest. They become wider
and flatter in the posterior part of the series. The arches are deeply
notched, and are separated by an increasing space dorsally. The
mammillary processes project outward and backward. The transverse
processes are bent downward and incline a little forward. Their length
increases to the fifth and is much diminished in the last. They form no
articulation with each other or with the sacrum. The posterior edge of
the root of the process is marked by a notch in the anterior part of the
series, a foramen in the posterior part. The spines are broad and
incline forward, with the exception of the last, which is narrow and
vertical.
Lesbre states that six and seven lumbar vertebræ occur with almost
equal frequency. The number may be reduced to five, and the number of
presacral vertebræ varies from twenty-six to twenty-nine.
The =sacrum= consists usually of four vertebræ, which fuse later and
less completely than in the other domesticated animals. It is less
curved than in the ox. The spines are absent, excepting small rudiments
on the last two segments. The middle of the dorsal surface is flattened
and smooth, and presents openings into the sacral canal between adjacent
arches (Spatia interarcualia). On either side are the superior sacral
foramina, and tubercles which indicate the fused articular processes.
The wings resemble those of the ox. The anterior articular processes are
very large. The pelvic surface resembles that of the ox, but is not so
strongly curved, and the transverse lines are very distinct.
[Illustration: