OSTEOLOGY AND ARTHROLOGY 7 



surface of that of the quadruped. Of the cervical vertebrae, 

 the atlas and axis call for special notice. Apropos of the 

 atlas, we find that it, in the human being, is narrower than 

 the corresponding parts of the skull, and is therefore hidden 

 under the base of the cranium (Fig. 2) ; in quadrupeds its 

 width is equal to that of the skull, and sometimes exceeds, 

 because of the great development of its wing-shaped trans- 

 verse processes, that of the neighbouring parts of the head 



Fig. 2. — Size of the Atlas compared with the Transverse Dimen 



SIONS OF THE CORRESPONDING PARTS OF THE SkULL IN MaN. 



I, Atlas ; 2, mastoid process ; 3, external occipital protuberance ; 



4, inferior maxilla. 



(Fig. 3). On this account those transverse processes often 

 project under the skin of the lateral surfaces of the upper 

 part of the neck. 



The axis is furnished on its anterior surface with the odon- 

 toid process, which articulates with the anterior (or inferior) 

 arch of the atlas, according to the direction of the neck. 

 The spinous process, flattened from without inwards, is 

 more or less pointed ; it is elongated from before backwards, 

 so as partly to overlap the atlas and the third cervical 

 vertebra. 



We find that this process overlaps less and less the neigh- 

 bouring vertebrae when we examine in succession the bear, 

 the cat, the dog, the ox, and the horse. With regard to the 

 other vertebrae of this region, they diminish in width from 



