OSTEOLOGY AND ARTHROLOGY 



41 



limits the movement of extension of the forearm. It is for 

 this reason that, even in those quadrupeds in which the ulna 



Fig. 28. — Inferior Extremity of the Bones of the Forearm of a 

 Man : Left Side, Posterior Surface, Position of Supination. 



I, Radius ; 2, ulna ; A, groove for the long abductor and short extensor 

 muscles of the thumb ; B, groove for the radial muscles ; C, groove for the 

 long extensor of the thumb ; D, groove for the special extensor of the index 

 finger and of the common extensor of the fingers ; E, groove for the proper 

 extensor of the little finger ; F, groove for the posterior ulna. 



is atrophied, the olecranon process presents a relatively 

 considerable degree of development. 



We know that on the posterior surface of the inferior 



Ei^C 



Fig. 29. — Inferior Extremity of the Bones of the Forearm of the 

 Dog : Left Side, Anterior Surface, Normal Position — that 

 is, the Position of Pronation. 



I, Radius; 2, ulna; A, groove for the long abductor and for the short 

 extensor of the thumb ; B, groove for the radials ; D, groove for the long 

 extensor of the thumb, the special extensor of the index-finger, and the 

 common extensor of the fingers ; E, groove for the special extensor of the 

 little finger. 



extremity of the bones of the human forearm are grooves 

 in which pass the tendons of the posterior and external 



