242 



THE ARM AND FORE- ARM. 



[chap. 



as great {f) and small (/') from their relative size in Man and 

 most Mammals ; the former is also called external^ and the 

 latter internal, from their relative situation in the most usual 

 position of the bone ; radial and ulnar are also terms 

 applied to them in relation to their situation, one on the 

 side of the humerus with which the radius, and the other on 

 the side with which the ulna, is connected below. 



Fig. 8i — Anterior surface of right humerus of Wombat [Phascolomys vombatus), \. 

 k head : bg bicipital groove ; t great or radial tuberosity ; t' small or ulnar 

 tuberosity; dr deltoid ridge; sr supinator ridge; cf supra-condylar foramen; 

 ec external condyle ; ic internal condyle; ar articular surface for radius ; aii arti- 

 cular surface for ulna. 



The lower or distal extremity of the humerus is some- 

 what flattened, and usually has a broad, semi-cylindrical 

 articular surface, which is received into a corresponding 

 concavity on the upper end of the bones of the fore- arm. 

 This is called the trochlea {ar and an). On each side, and 

 rather above this surface, is a prominence called the condyle, 

 one of which is external, or 7'adial (cc), the other internal, or 

 ulnar {ic). The latter is usually the most prominent. In 



