xin PHYLUM CHORDATA 419 



size the fore limbs being much shorter than the hind limbs. 

 Both have the same general divisions as in the Lizard. The 

 upper arm is almost completely hidden by the skin, being applied 

 closely against the side of the body. The manus is provided with 

 five digits, each terminating in a horny claw. The thigh is also 

 almost hidden by the skin ; the pcs has four digits only, all pro- 

 vided with claws. 



Skeleton. The spinal column of the Rabbit is divisible, like 

 that of the Pigeon and the Lizard, into five regions the cervical, 

 the thoracic, the lumbar, the sacral, and the caudal. In the cervical 

 region there are seven vertebras ; in the thoracic twelve or some- 

 times thirteen, in the lumbar seven, or sometimes six, in the sacral 

 four, and in the caudal about fifteen. 



The centra of the vertebra? in a young Rabbit consist of three 

 parts a middle part which is the thickest, and two thin disks of 

 bone the epipliyses anterior and posterior, applied respectively 

 to the anterior and posterior faces of the middle part or centrum 

 proper. Between successive centra in an unmacerated skeleton 

 are thin disc-like plates of nbro-cartilage the inter-vertebral discs. 



cent 



FIG. 1018. Lepus cuniculus. A, atlas and axis, ventral aspect od. odontoid process of axis. 

 , lateral view of axis ; art. articular facet for occipital condyle ; od. odontoid process ; 

 pt.zy. post-zygapophysis ; up', neural spine. C, thoracic vertebrae, lateral view. cent, centrum ; 

 j'ac. facet for rib ; nut. rnetapophysis ; pr.zy. prezygapophysis ; pt.zy. post-zygapophysis ; 

 r&. rib ; sp. spinous process. I 



The first vertebra or atlas (Fig. 1018, A) resembles the cor- 

 responding vertebra of the Pigeon in being of the shape of a ring 

 without any solid centrum like that of the rest. On the anterior 

 face of its lateral portions are two concave articular surfaces 

 for the two condyles of the skull. The second vertebra or axis 

 (A and B) bears on the anterior face of its centrum a peg-like 

 process the odontoid process (od.) which fits into the ventral part 

 of the ring of the atlas : it has a compressed spine (sp.), produced in 

 the antero-posterior direction ; its transverse processes are short 

 and perforated by a canal for the vertebral artery. All the rest of 

 the cervical vertebras have their transverse processes bifurcated 

 and perforated at their bases by the canal vertebrarterial canal 

 for the vertebral artery. The seventh cervical differs from these 



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