292 



HUMAN ANATOMY. 



inner side of the styloid. A faint ridge from before backward, beginning at a slight 

 notch, marks oil an inner square surface for the semilunar and an outer triangular 

 ■one for the scaphoid. The surface looks slightly forward, thus causing the forward 

 rising of the hand from the forearm. 



In man the ulna is evidently the more important bone at the elbow and the 

 radius at the wrist. In mammals below primates they are often more or less fused 

 and the upper end of the radius relatively larger than in man. It often occupies 

 the front of the elbow-joint, being anterior instead of external to the upper end of 

 the ulna. 



Structure. — The radius, like the ulna, is thick-walled through the greater 

 part of the shaft. The tuberosity is composed internally chiefly of longitudinal 



Scaphoid surface 



Styloid process' 



Fig. 305. 



Ext. OSS. met. poll. } 

 Ext. brev. poll. j" 



Ext. carp. rod. long. 

 Ext. carp. rad. brev 



Semilunar surface 



Sigmoid cavity 



Ext. communis dig. 

 Ext. long, poinds and ext. indicis 

 Tubercle 



Lower end of right radius. 



Fig. 306 B. 



Fig. 306 A. 



m 



MM 



m 



m 



m 



mMm. 



■^'«/ 



Longitudinal sections of radius ; B in frontal plane, showing arrangement of trabeculae in lower end of bone. 



plates. A frontal section of the lower end of the radius shows the walls splitting 

 up into longitudinal plates, which run to the lower end, connected by a system of 

 lighter transverse ones. 



