expression, and in his writings are no
half-truths struggling for utterance. But he was, though a staunch
transcendentalist, an eclectic of the older ideas current in his time;
for he picked out what was best in the older systems--Cuvier's
teleology, Geoffroy's principle of connections, Oken's idea of the
serial repetition of parts. In particular, he assimilated the teaching
of Cuvier, the great opponent of the transcendentalists, and reconciled
it in part with his own transcendentalism. His main theoretical views
are to be found in his volume _On the Archetype and Homologies of the
Vertebrate Skeleton_ (London, 1848). The master-idea of the book is that
the vertebrate skeleton consists of a series of comparable segments,
each of which Owen calls a vertebra. His definition of a vertebra is,
"one of those segments of the endo-skeleton which constitute the axis of
the body, and the protecting canals of the nervous and vascular trunks"
(p. 81). The parts of a typical vertebra are shown in Fig. 4, which is
copied from Owen's Fig. 14.

|||
zygapophysis ||| -- neural spine
\ |||
*//^\\*
diapophysis // \\ -- neurapohysis
\ // o \\
===== --- =====
/ \
===== |CENTRUM| O ===== -- peiurapophysis
\ /
===== --- =====
/ \\ //
parapophysis *\\v//*
/ |||
zygapophysis ||| -- haemal spine
|||

FIG. 4.--Ideal Typical Vertebra. (After Owen.)

In Fig. 5 (page 103) is shown an actual vertebra, as Owen conceives it,
the "vertebra" being that of a bird.

[Illustration: FIG. 5.--Natural Typical Vertebra; Thorax of a Bird.
(After Owen.)]

A segment of sternum is included as the "haemal spine" of the vertebra
(_hs_); the vertebral rib is the "pleurapophysis" (_pl_); the sternal
rib the "haemapophysis" (_h_); the uncinate process of the vertebral rib
is known as the "diverging appendage" (_a_). The whole vertebrate
skeleton is composed of a series of vertebrae which show these typical
parts. We arrive thus at the conception of an "Archetype" of the
vertebrate skeleton, such as is represented in Fig. 6.

The archetype is only a scheme of what is usually constant in the
vertebrate skeleton, and both the number and the arrangement of the
bones in any real Vertebrate are subject to variation. "It has been
abundantly proved," Owen writes, towards the end of his vo