THE FRAMEWORK OF THE BODY 43 



Two shallow depressions in the forward portion of the 

 centrum of each of the dorsal vertebrae, with correspond- 

 ing depressions in the adjoining vertebra, form pits which 

 receive the heads of the ribs. Similar depressions at the 

 ends of the transverse processes of the dorsal vertebrae 

 assist in securing the ribs to the spine (Fig. 31). 



Fig. 31. Articulation of a pair of ribs to a vertebra. 



ce centrum of the vertebra. r rib. 



tr transverse process. co costal cartilage. 



st sternum. 



Between each two adjoining vertebras are elastic cush- 

 ions of fibrocartilage, which assist in providing for motion 

 and flexibility in the spinal column and in preventing 

 injurious jarring of the brain and spinal cord. 



42. The Atlas and Axis. The first two cervical vertebras 

 have certain modifications of structure for the sake of 

 the freer motion needful in the neck. The atlas or first 



