EXTENSOR CARPI RADIALIS BREVIS 



389 



the fingers. It is a flexor of the forearm; a supinator when the forearm is extended, a pronator 

 when it is flexed. 



Relatio7is. — It is covered by the brachio-radiahs near the elbow. Below it becomes super- 

 ficial except where crossed by the tendons of the muscles of the thumb. (For the relations to 

 the short radial carpal extensor see below.) 



Fig. 367. — Muscles of the Radial Side and the Back of the Forearm. 



Biceps — l4!lli!Mi(lli \A'' 

 Brachialis - 



Brachio-radialis 



Extensor carpi radialis longus 



Extensor digitorum communis 



Extensor carpi radialis brevis 



Abductor pollicis longus 

 Extensor pollicis brevis 



Extensor pollicis longus 



Triceps 



Anconeus 



Flexor carpi ulnaris 



Extensor carpi ulnaris 



Extensor digiti quinti proprius 



Variations. — The humeral attachment may be more extensive than that indicated above. 

 The tendon of insertion may send a band to the third or to the fourth metacarpal or to the mul- 

 tangulum majus (trapezium). The muscle may be fused, partly or completely, with the short 

 radial extensor. It may send a shp to the abductor pollicis longus or to some "of the interossei. 



The extensor carpi radialis brevis (figs. 367, 368). — Origiri. — From a band which descends 

 on its deep surface from the common extensor tendon attached to the lateral epicondyle, from 

 the intermuscular septa surrounding its head, and from the radial collateral hgament of the 

 elbow-joint. 



