590 



MAMMALIAN ANATOMY 



the interosseous membrane which divides the flexor muscles from the 

 extensors and gives origin to fibres of each. To the tubercle is 

 fastened the tendon of the biceps, the principal flexor of the fore- 

 arm upon the arm. 



Blood Supply. The radius is supplied with blood from the 

 brachial artery through a small nutrient branch, arising from the 

 anterior interosseous, sometimes in common with the nutrient artery 

 of the ulna. 



Ossification. The radius develops from three principal centres 

 (Fig. 451), one for each extremity and one for the shaft, to which 

 a small centre for the tubercle is said to be added after birth. 



FIG. 451. 



Head.- 



Shaft.- 



Lower Extremity - 



PLAN OF THE DEVELOPMENT OF THE RADIUS BY THREE CENTRES. 



VARIATIONS IN THE EADIUS. 

 VARIATIONS IN SIZE. 



The measurements of the radius were taken as follows : 



The maximum length is the distance from the top of the head to 

 the tip of the styloid process. 



The diameter at the head is the greatest diameter of the proximal 

 surface. 



The width at the lower end is the greatest transverse diameter. 



