THE SKELETON 41 
in mammals by any part of the vertebra itself, but by certain 
distinct bones placed more or less in apposition to it, namely the 
ribs in the thoracic, and the “chevron bones” in the caudal region. 
In most cases the arch of one vertebra is articulated with that of 
the next by distinct surfaces with synovial joints, placed one on 
each side, called ‘“‘zygapophyses ” (u:, 2), but these are often entirely 
wanting when flexibility is more needed than strength, as in the 
greater part of the caudal region of long-tailed animals. In addition 
to the body and the arch, there are certain projecting parts called 
processes, chiefly serving for the attachment of the numerous 
muscles which move the vertebral column. Of these two are single 
and median, viz. the spinous process, neural spine, or neurapophysis 
(s), arising from the middle of the upper part of the arch, and the 
hypapophysis from the under surface of the body. The latter, how- 
ever, is as frequently absent as the former is constant. The other 
processes are paired and lateral. They are the transverse processes 
(t), of which there may be two, an upper and a lower, in which case 
the former ‘is called, in the language of Owen (to whom we are 
indebted for the terminology of the parts of vertebrae in common 
use), “ diapophysis,” and the latter “ parapophysis.” Other processes 
less constantly present are called respectively “ metapophyses ” (1) 
and “anapophyses ” (a). 
The vertebral column is divided for convenience of description 
into five regions—the cervical, thoracic or dorsal, lumbar, sacral, and 
caudal. This division is useful, especially as it is not entirely 
arbitrary, and in most cases is capable of ready definition ; but at 
the contiguous extremities of the regions the characters of the 
vertebrae of one are apt to blend into 
those of the next region, either normally 
or as peculiarities of individual skeletons. 
Cervical Vertebre.—The cervical region 
constitutes the most anterior portion of 
the column, or that which joins the 
cranium. The vertebrae which belong to 
it are either entirely destitute of movable 
ribs, or if they have any these are small, 
and do not join the sternum. As a general 
rule they have a considerable perforation 
through the base of the transverse process pitta ate 
(the vertebrarterial canal, Fig. 11, 7); or, Pera ae ser eine Dos, 
as it is sometimes described, they have 5, spinous process; az, anterior 
two transverse processes, superior and zysapophysis; «, vertebrarterial 
: + + : oye canal; t, transverse process ; ¢’, its 
inferior, which meet at their extremities j\pridr jamelia. 
to enclose a canal. This, however, rarely 
applies to the last vertebra of the region, in which only the upper 
transverse process is usually developed. The transverse process, 
