THE RABBIT. 253 



The Skeleton. The axial part consists of the spinal 

 column (composed of vertebrce) and of the skull. The 

 bones of the whole axial series are perforated, and so 

 placed together, end to end, as to form a canal, which 

 lodges and protects the central parts of the nervous sys- 

 tem, brain and spinal cord. The vertebral series also 

 forms a very strong yet flexible support for all other 

 parts of the body. 



I. Vertebrae and Ribs. The vertebra may be con- 

 sidered as forming five groups : (1) cervical (or neck) 

 vertebrce; (2) thoracic (or chest) vertebrce, which bear 

 movably articulated ribs ; (3) lumbar (or back) vertebrce, 

 without ribs, the largest of the series ; (4) sacral verte- 

 brce, which are fused together, and support the bones of 

 the pelvis ; and (5) caudal (or tail) vertebrce. How many 

 vertebrae are there in each of these five groups ? 



Examine one of the middle lumbar vertebrae as a type, 

 and in it find the usual parts, centrum, neural arch, neural 

 spine, transverse processes, and articular processes. Find 

 also a median ventral process (hypapophysis) projecting 

 downward directly from the centrum. A pair of flat 

 plates of bone (epiphyses) may be found applied to the 

 ends of the centrum, if the vertebra be that of a young 

 animal. These become anchylosed with the centrum 

 with age. 



The transverse processes of the cervical vertebrae are 

 broad and flat and perforated, and the series of perfora- 

 tions forms an imperfect canal for the passage of a nerve 

 and an artery. The parts of the transverse processes out- 

 side the perforations are homologous with the ribs of the 

 vertebrae farther back. 



Note that each distinguishable rib has two articulations 

 with its vertebra, a head, which meets the centrum ; and 

 a tubercle, which meets the transverse process. The space 

 inclosed between these two articulations corresponds 



