398 



THE MUSCLES AND FASCIAE. 



The Supinator brevis (Fig. 236) is a broad muscle, of hollow cylindrical form, 

 curved round the upper third of the radius. It consists of two distinct planes of 

 muscular fibres, between which lies 

 the posterior interosseous nerve, 

 two planes arise in common : 



The 

 the 



superficial one by tendinous, and the 

 deeper by muscular, fibres from the 

 external condyle of the humerus ; 

 from the external lateral ligament 

 of the elbow-joint and the orbicular 

 ligament of the radius ; from the 

 ridge on the ulna, which runs ob- 

 liquely downward from the posterior 

 extremity of the lesser sigmoid cav- 

 ity ; from the triangular depression 

 in front of it ; and from a tendinous 

 expansion which covers the sur- 

 face of the muscle. The superficial 

 fibres surround the upper part of 



Int. 



Cmidyle. 



Olecranon. 



C'oronoid 

 proc. 



Head of 

 radius.' 



TENDON OF 

 BICEPS. 



^SFl~--"5 . 



FIG. 237. Posterior surface of the forearm. Deep muscles. 



Pronator radiTteres^TlTe iT" "m^ 8 ' & f ] W d Wn the insertion of the 

 fasciculus, which encircles &Z* oTthl %Sti? ?g$ft 



