498 



THE RABBIT 



CHAP. 



interuertebral 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), 

 which articulate synovially with the vertebrae next in front 

 and behind respectively. The articular surface of each 

 pre-zygapophysis looks upwards and outwards, that of the 



post-zygapo physis 

 downwards and inwards. 

 Arising laterally from 

 either side of the arch is 

 an outstanding trans- 

 verse 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. 500) 

 articulates. The lower 

 fork or head of the rib 

 articulates with a facet 

 (c. f) formed partly by 

 the anterior edge of the 

 corresponding centrum 

 just at the base of the 

 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. /', c. f"). 

 There are no free ribs in relation with the vertebrae of otlier 

 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 vertc- 

 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 



n.a c 



FIG. 134. Fifth thoracic vertebra of the 



Rabbit, from the left side. ( x ii.) 

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

 and c. /" 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 ; /. /. 

 tubercular facet for fifth rib ; /. pr. trans- 

 verse process. 



