i6 4 



ANIMAL BIOLOGY. 



[Part I. 



the peduncles of the neural arches. It is the intervertebral fora- 

 men, by means of which the spinal nerves make their exit. And 

 when the centra are in contact a capitular facet for the articula- 

 tion of the head of the rib is formed by the juxtaposition of 

 two demi-facets (c. s.), one on each centrum. 



FIG. 53. FOURTH THORACIC VERTEBRARABBIT. 



A. From the side. B. From the anterior end. 



c. Centrum, c. s. Capitular semi-facet, n. Neurapophysis of neural arch. 

 n. s. Neural spine, pr. z. Prezygapophysis. pt. z. Postzygapophysis. t. f. 

 Tubercular facet, tr. Transverse process. 



The following points may be noted in other parts of the 

 column: The transverse processes of the cervical vertebras are 

 pierced by a vertebrarterial canal. The second cervical (axis) has 

 a peg-like odontoid process; the first (atlas) is a mere ring of 

 bone with facets for the condyles of the skull, and flattened 

 transverse processes. In the eleventh thoracic vertebra the 

 neural spine becomes vertical, sloping forward in the twelth. 

 In the vertebrae of this region there is a large process .(the meta 

 popliysis) just behind the prezygapophysis. In the first three 

 lumbar vertebrae there is a flattened process (hypapopliysis] 

 beneath the centrum, and in the first five lumbar small pointed 

 processes (anapophyses) looking backwards, beneath the postzy- 

 gapophyses. The four sacral vertebrae are fused into one mass ; 

 but only the first, or at most, the first two, come into relation 

 with the ilia by means of their expanded transverse processes or 

 ankylosed ribs. The metapophyses are here smaller, and there 

 are no ana- nor hypapophyses. The caudal vertebras gradually 

 diminish in size and in complexity until they are reduced to 

 mere centra. 



