34 



CERVICAL VERTEBRA. 



[CHAP. 



flattened, or slightly-concave. The transverse processes are 

 short, stout, and perforated ; the arch presents scarcely a 

 rudiment of a spinous process. On its anterior edge im- 

 mediately above the articular surface is a deep notch or 

 groove (g) of some importance, as it corresponds with the 

 slight notch in front of the pedicle in other vertebrae, which 

 contributes with the deeper notch in the hinder border of 

 the pedicle of the preceding vertebra to form the "inter- 

 vertebral " foramen for the exit of a spinal nerve, and because, 

 occasionally in man, and constantly in many animals, it is 

 converted by a bridge of bone into a canal, through which 



to, 



FIG. 9. Human atlas, young, showing development, \. ia inferior arch ; as articular 

 surface for occiput ; t transverse process ; g groove for first spinal nerve and 

 vertebral artery. 



the first cervical (or suboccipitat) nerve passes out. The 

 inferior arch of the atlas (ia) differs entirely from the bodies 

 of the other vertebrae, being a simple, depressed, slightly 

 curved bar of bone, with a smooth facet on its neural or 

 upper surface, for articulation with the odontoid process of 

 the axis. 



The second cervical vertebra, axis, epistrophens, or vertebra 

 dsntata (Fig. 10), has a body terminating anteriorly in a 

 large subconical median projection, the odontoid process 

 (0), which is received into, and articulates with, the con- 

 cavity of the inferior arch of the atlas. It is retained in 



