CERVICAL VERTEBRA 261 



transverse processes, through which the vertebral 

 arteries run. 



a, The first or atlas vertebra, differs very markedly 

 from all the others : its more important characters 

 are as follows. 



i. The neural canal is very large, and is divided into 

 two parts by a transverse ligament, which is 

 usually preserved in the dried skeleton : of 

 these, the upper and larger is the true neural 

 canal, giving passage to the spinal cord ; while 

 the lower and smaller one lodges the odontoid 

 process of the second vertebra. 



ii. The centrum is probably represented by the 

 odontoid process, which has become detached 

 from the atlas, and fused with the centrum 

 of the second vertebra. The mid-ventral 

 portion of the atlas is very narrow, and is pro- 

 duced backwards into a short process. 



iii. The neurapophysis is a very insignificant ridge, 

 most prominent in front. 



iv. The transverse processes are broad horizontal 

 lamellae, perforated at their bases by longi- 

 tudinal vertebr arterial canals. In front of 

 each transverse process the canal is continued 

 upwards as a groove to a foramen in the 

 neural arch, through which the vertebral artery 

 enters the neural canal and the first spinal 

 nerve leaves it. 



Along the inner and hinder border of each 

 transverse process is a deep groove, corre- 

 sponding to an intervertebral notch, for the 

 passage of the second spinal nerve. 



v. The articular surfaces. The anterior end of the 

 atlas has two very large, deeply concave sur- 

 faces, for articulation with the condyles of the 

 skull : the posterior end has two much smaller 

 facets for the second vertebra. 



