inspection, to have no rib. The transverse processes differ from those
of thoracic series in having a perforation, the vertebrarterial canal,
through which the vertebral artery runs up the neck. A study of the
development of these bones shows that the part marked f.r. ossifies
separately from the rest of the transverse process; and the form of the
equivalent structures in certain peculiar lower mammals and in
reptiles leaves no doubt that f.r. is really an abbreviated rib; fused up
with the transverse process and body. The two anterior cervical
vertebrae are peculiar. The first (at.) is called the Atlas-- the figure
shows the anterior view-- and has great articular faces for the
condyles (Section 86) of the skull, and a deficient centrum. The next
is the axis, and it is distinguished by an odontoid peg (od.p.), which
fits into the space where the body of the atlas is deficient. In
development the centrum of the axis ossifies from one centre, and the
odontoid, peg from another, which at that time occupies the position
of centrum of the atlas. So that it would seem that the atlas is a
vertebra minus a centrum, and the axis is a vertebra plus a centrum,
added at the expense of the atlas.