484 



THE MUSCLES AND FASCIAE 



It occasionally gives off two slips near its insertion one to the trapezium, and the 

 other to blend with the origin of the Abductor pollicis. 



Int. 

 Condyle. 



Coronoid 



proc. 

 Head of 

 radius. 



Olecranon, 



FIG. 361. Supinator [brevis]. (From a prepa- 

 ration in the Museum of the Royal College of 

 Surgeons of England.) 



Relations. By its superficial surface, 

 with the Extensor communis digitorum, Ex- 

 tensor minimi digiti, and fascia of the fore- 

 arm, and with the branches of the posterior 

 interosseous artery and nerve which cross 

 it; by its deep surface, with the ulna, the 

 interosseous membrane, the radius, the ten- 

 dons of the Extensor carpi radialis longior 

 and brevior, which it crosses obliquely, and 

 at the outer side of the wrist, with the 

 radial vessels; by its upper border, with the 

 Supinator [brevis]; by its lower border, with 

 the Extensor brevis pollicis. 



The Extensor brevis pollicis (m. 

 extensor pollicis brevis), the smallest 

 muscle of this group, lies on the inner 



3 .. r T . . FIG. 362. Posterior surface of the left forearm. 



side or the preceding. It arises rrom muscles. 



the posterior surface of the shaft of 



the radius, below the Extensor ossis metacarpi pollicis, and from the interosseous 



membrane. Its direction is similar to that of the Extensor ossis metacarpi 



