CHAP. IV.] 



THE SKELETON OF THE LIMBS. 



95 



round by and witli the radius in that motion of the arm and hand 

 which is called pronation and supination — movements which will be 

 explained Avhen the articulations and ligaments of the pectoral limb 



I i!'i 



Fis- 50.— The Right Ulna. 



A. External aspect. 



B. Interual aspect. 



C. Surface of sigmoid fossa, 

 c. Coronoid process. 



<7*'. Greater sigmoid cavity. 



Is. Lesser sigmoid cavity. 

 c. Olecranon, 

 r. Surface for radius. 

 s. Styloid process. 



are described. The outer lower end of the radius also presents, in- 

 ternally, a small articular surface for the ulna {ii). 



§ 5.' The ■UL^'•A, or post-axial bone of the forearm, is longer than 

 the humerus, and considerably longer than the radius. While the 

 latter bone is broader below than above, the reverse condition obtains 

 in the ulna. The shaft is flattened both in front and behind, with a 



