192 SKELETON. 



cylindrical concavity, for receiving the lower end of the ulna. 

 The former or superficial cavity is divided into two by a slight 

 ridge in its short diameter ; the division next the styloid pro- 

 cess receives the scaphoid l?one, and the other the os lunare. 

 At this extremity also a ridge exists on the front of the bone 

 for forming the margin of the articular face, and giving origin 

 to the capsular ligament. The posterior and external faces of 

 the bone., here, are rendered irregular by several grooves and 

 ridges. The large groove next to the cylindrical concavity for 

 the ulna, transmits the tendons of the extensor communis digi- 

 torum and indicator, also the tendon of the extensor major pol- 

 licis, which forms a channel somewhat distinct, and on the sty- 

 loid side of the groove. Next to this is another large groove for 

 the tendons of the extensor carpi radialis brevior and loagior ; 

 and on the styloid side of the radius is the third groove for 

 transmitting the tendon of the extensor minor pollicis, and of 

 the extensor ossis metacarpi pollicis. The anterior margin of 

 this groove is formed by a small spine or ridge, into which is 

 inserted the tendon of the supinator radii longus. 



The body of the radius is somewhat triangular, and therefore 

 presents three ridges. One, on its ulnar side, extends from the 

 bicipital protuberance to the lower end, and gives origin to the 

 interosseous ligament: it is sharp and well marked. Another, 

 on the outer or styloid margin of the bone, also begins at the 

 bicipital protuberance, and terminates in the styloid process. 

 The upper part of this ridge is curved, has the supinator brevis 

 inserted into it, and a portion of the flexor digitorum sublimis 

 arising from it ; at its lower part the pronator quadratus is in- 

 serted. The third ridge is on the posterior- face of the radius, 

 and, arising insensibly from below its neck, is principally con- 

 spicuous in the middle third of the bone: it runs down, however, 

 to the carpal extremity, and, becoming more prominent there, 

 separates the two larger grooves from each other. This ridge 

 is shorter, and not so elevated as the other two. 



These three ridges form as many surfaces to the radius, of 

 which the anterior augmenting gradually in its descent, affords 

 attachment to the flexor longus pollicis above, and to the pro- 

 nator quadratus below; at its upper part is a canal, slanting up- 

 wards, for the nutritious artery. The posterior surface has the 



