POLL-EVIL 107 



none of the characteristics of vertebrae in gen- 

 eral. It articulates by means of diarthrodial 

 articulations with the occipital condyles an- 

 teriorly and with the odontoid process of the 

 axis posteriorly. Its wide expansive dorsal 

 surface gives attachment to the muscles to 

 which it is related. 



Its wings which extend downward and out- 

 ward become gradually thinner and thicken 

 again into a roughed heavy border. Each one 

 is perforated with a large foramen which gives 

 passage to the occipital artery, in its course 

 from the carotid to the region of the poll. 



The whole dorsal face is a smooth expanse 

 interrupted only by a slight median elevation 

 representing the superior spinous process. 



The dorsal surface of the atlas is important 

 in poll-evil because it sooner or later becomes 

 affected with periosteitis and osteitis on ac- 

 count of its close relations to the disease process 

 in and about the ligament um niich^. It 

 serves as a floor for the abscess cavity from 

 which it is often separated only by a carpet of 

 granulation tissue attached to the periosteum. 



The axis or second cervical vertebra may be 

 said to be the posterior boundary of the poll- 

 evil process. It is seldom itself involved in 

 disease. Its crest or superior spinous process 

 stands above the level of the axis where it serves 



