THE FOKEAKM AND HAND. 



1453 



At the dorsum of the forearm the intermuscular septum between the radial and 

 common extensors corresponds to the proximal part of a line extending from the 

 lateral epicondyle of the humerus to the tubercle on the dorsum of the distal end 

 of the radius. The dorsal interosseous nerve, at the point at which it emerges from 

 the substance of the supinator muscle, will be found at the bottom of this 

 septum, 2 in. distal to the head of the radius ; below that point the septum is the 

 best line along which to cut down upon the posterior surface of the radius. 

 Winding across the distal third of the dorsal surface is an oblique prominence, 

 caused by the abductor pollicis longus and extensor pollicis brevis muscles. 



Styloid process of third metacarpal 



Radial artery. 

 Extensor pollicis longus 

 Extensor carpi radialis longu 

 Extensor carpi radialis brevis 



Extensor pollicis brevis. 



Base of fifth metacarpal 



Styloid process of ulna 



Extensor digitorum communis 



Extensor digiti quinti communis 

 Extensor carpi ulnaris 



FIG. 1117. DORSAL ASPECT OF HAND. 



The flexor sheaths of the palm and of the digits are of surgical importance in 

 '.onsequence of their liability to suppurative inflammation. The common flexor sheath 

 )egins 1J in. proximal to the transverse carpal ligament, under which it extends to a 

 ittle beyond the middle of the palm. The digital flexor sheaths extend from the bases 

 >f the terminal phalanges to the level of the distal transverse crease of the palm, 

 >pposite the necks of the metacarpal bones, with the exception of the sheath of the 

 ittle finger, which is continuous with the common flexor sheath of the palm. The 

 heath of the flexor pollicis longus extends from the base of the terminal phalanx 

 >roximally to a point about 1 in. proximal to the transverse carpal ligament; it 

 requently communicates with the common flexor sheath. From this anatomical 

 rrangement it follows that suppuration in the sheaths of the little finger and 



