498 



THE RABBIT 



CHAP. 



intervertebral foramen is formed for the passage of a spinal 

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

 spine (n. sp) projecting upwards and backwards, and just 

 above the intervertebral notches are a pair of anterior and 

 posterior articular processes or zygapophyses (pr. z, pt. z), I 

 which articulate synovially with the vertebrae next in front 

 and behind respectively. The articular surface of each I 

 pre-zygapophysis looks upwards and outwards, that of the I 



post- zy g apo physis 

 down wards and inwards, j 

 Arising laterally from 

 either side of the arch is 1 

 an outstanding trans- \ 

 verse process (t. pr}, on 

 the under surface of 

 which is. an articular 

 tubercular facet (t. f), 

 with which the upper j 

 fork of the rib (p. 500) 

 articulates. The lower j 

 fork or head of the rib i 

 articulates with a facet 1 

 (c. f) formed partly by ' 

 the anterior edge of the I 

 corresponding centrum j 

 just at the base of the I 

 neural arch, and partly 

 by the posterior edge of 

 the centrum next in 

 front, so that each cen- ] 

 trum bears half a capi- 

 tular facet, as it is called, 

 on either side, both anteriorly and posteriorly (c. f, c. f"). 

 There are no free ribs in relation with the vertebra} 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 

 lower portion is narrow and unlike the other centra. The 

 neural spine is small, and the transverse processes are broad 

 horizontal plates, each perforated at its base by a verte- 

 brarterial 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 small 

 facets for articulation with the second vertebra. The 

 second cervical vertebra, or axis, has its centrum produced 



FIG. 



72 a c 



134. Fifth thoracic vertebra of the 



Rabbit, from the left side. ( x . 

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

 and c. f" for sixth rib ; ep. epiphysis : 

 t. v. n. intervertebral notch ; n. a. neural 

 arch ; n. sp. neural spine ; pr. z. pre-zyga- 

 pophysis ; pt. z. post-zygapophysis ; t. /. 

 tubercular facet for nfth"rib ; t. pr. trans- 

 verse process. 



