FOREARM AND HAND 



137 



Closely accom- 



. triceps 



*""- M. biceps brachii 



M. supinator. 



munis and the extensor carpi radialis brevis. 

 panied by the ex- 

 tensor pollicis 

 brevis it crosses 

 the two radial 

 extensors. The 

 tendon which 

 issues from it at 

 this point is con- 

 tinued distally 

 over the lateral 

 side of the ex- 

 panded lower end 

 of the radius, 

 and under cover 

 of the dorsal 

 carpal ligament. 

 It is inserted into 

 the lateral side of 

 the base of the 

 metacarpal bone 

 of the thumb. 

 This muscle is 

 supplied by the 

 dorsal interosseous 

 nerve. 



M. Extensor 

 Pollicis Brevis 

 (O.T. Extensor 

 Primi Internodii 

 Pollicis). This 

 muscle is placed 

 along the distal 

 border of the pre- 

 ceding muscle. 

 It arises from a 

 small portion of 

 the dorsal surface 

 of the radius, and 

 also from the in- 

 terosseous mem- 

 brane. Its tendon is closely applied to that of the abductor 



Ext. carp, 

 uln. 



Ext. dig. comm. and ext. indici 



id. exts. 

 \bd. poll. long, 

 ind ext. poll, 

 jrev. 



Ext. poll. long. 



FIG. 53. Dorsal aspect of Bones of Forearm with 

 Attachments of Muscles mapped out. 



