VERTEBRAL COLUMN 



4S1 



natural position, an iiiiervertebral foramen is /ormerl for the passage 

 of a spinal nerve. The roof of the arch is continued into a long 

 neural spine (it. sp) projecting upwards and backwards, and just 

 above the intervertebral notches are a pair of anterior and posterior 

 articular processes or r^ygapophyses (pr. :, pi. ;), which articulate 

 synovially with the vertebrse next in front and behind respectively. 

 The articular surface of each pre-zygapophysis looks upv\ards and out- 

 wards, that of the post-zygapophysis downwards and inwards. Arising 

 laterally from each side of the 

 arch is an outstanding Iraiis- 

 vcrse process (t. pr), on the 

 under surface of which is 

 an articular tubercular facet, 

 [t. f) with which the upper 

 fork of the rib (p. 483) arti- 

 culates. The lower fork or 

 head of the rib articulates 

 with a facet (i. / ) formed 

 partly by the anterior edge of 

 the corresponding centrum 

 just at the base of the neural 

 arch, and partly by the pos- 

 terior edge of the centrum 

 next in front, so that each 

 centrum bears half a capitu- 

 lar facet, as it is called, on 

 either side, both anteriorly 

 and posteriorly (c. f, c. f" ). 



There arc no free ribs in the vcrtebr;e of other regions, in which, 

 however, they are represented in the embryo, but early fuse with the 

 corresponding transverse processes. 



The first cervical vertebra, or atlas, is ring-shaped, and its lo^tr 

 portion is narrow and unlike the other centra. The neural spine is 

 small, and the transverse processes are broad horizontal ):)lates, each 

 |ierforated at its base by a vertehrarterial canal, through which the 

 vertebral artery runs. On the anterior face of the lateral parts of the 

 atlas are two concave articular facets for articulation with the occipital 

 condyles of the skull, and on its posterior face are two smaller acets fur 

 articulation with the second vertebra. The second cervical vertebra, cjr 



Pral r. ZooL. 1 I 



V\ 



n.a c 



124. — Fifth thoracic \citcbi\-i nf tlic 

 rabbit, from the left side ( >: ij). 

 centrum ; c.f . capitular half-facet for fifth, 

 and c.f" . lor si.xth rib ; cp. epiphysis ; 

 /. r'. n. intervertebral notch ; ;;. a. ireural 

 arch ; 11. sp. Tieural spine ; fir. z. pre-zyga- 

 pophysis : fil.z. post-zygapophysis; t.f. 

 tnbercular facet for fifth rib; t.fir. tians- 

 \erse fjrocess. 



