184 



THE SUPERIOR EXTREMITY 



" M. triceps brachii 



M. flex, 

 carp. uln. 



M. ext. 

 carp. uln. ' 



M. pronator 

 teres 



the tendons of the two radial extensors and the radial artery, 



it reaches the 

 thumb. It is 

 inserted into 

 the base of the 

 distal phalanx 

 of the thumb 

 and is supplied 

 by a branch of 

 the dorsal inter- 



M. biceps brachii osseous nerVe . 



M. supinator 1^-^^ y \ \ \\ It is an extensor 



of all the joints 

 of the thumb, 

 and it takes 

 part in the in- 

 itiation of sup- 

 ination of the 

 forearm (Figs. 

 78, 74, 75, 76, 

 79). 



When the 

 thumb is power- 

 fully extended, in 

 the living person, 

 the tendons of its 

 three last - men- 

 tioned muscles be- 

 come prominent 

 on the lateral 

 aspect of the wrist. 

 The oblique course 

 of the tendon of 

 the extensor pol- 

 licis longus is 

 rendered evident, 

 and a distinct de- 

 pression between 

 it and the other 

 two tendons is 

 seen. 



Ext. carp, 

 uln. 



Rad. extensors 

 Abd. poll. long, 

 and ext. poll, 

 brev. 



Ext. dig. comm. and ext. 

 indicis proprius 



Ext 



long> 



M. Extensor 

 Indicis Pro- 

 prius. The 



special extensor of the index finger arises, distal to the pre- 



FIG. 78. Dorsal aspect of the Bones of the Forearm, 

 with Attachments of Muscles mapped out. 



