MYOLOGY 107 



Relations. Inferiorly, the anconeus and superiorly, the extensor 



gitorum communis. 



Action. A powerful flexor of the hand. 



Pronator Brevis (Fig. 13, No. 18). Location. Supero-Iaterar- 

 side of the forearm. 



Origin. From just above the internal condyle of the humerus: 



Insertion. The tendon passing obliquely across the interosseous 

 space and is inserted to the ulnar side of the shaft of the radius, 

 just beyond the juncture of the proximal and the middle thirds. 



Shape. Fusiform. 



Relations. Superior to the pronator longus. 



Action. Pronates the forearm, and flexes the forearm upon the 

 arm. 



Pronator Longus (Fig. 14, No. 6). Location. Lateral side of the 

 ^/ radio-ulnar region. 



Origin. From the middle of the internal condyle of the humerus. 



Insertion. To the shaft of the radius just beneath the pronator 

 brevis. 



Shape. Massive, ellipsoidal. 



Relations. Between the pronator brevis and flexor digitorum 

 profundus. 



Action. A pronator. 



/ Extensor Ossis Metacarpi Pollicis (Fig. 13, No. 23). Location. 

 Slightly interposed between the ulna and. radius. 



Origin. Immediately in front of the greater sigmoid cavity of the 

 ulna. 



Insertion. To the palmar side of the base of the first metacarpal 

 in common with the extensor metacarpi radialis longior. 



Shape. Delicate, straight. 



Relations. Superiorly, the extensor indicis longus, and inferiorly, 

 the anconeus and the flexor digitorum profundus. 



Action. Extends the hand upon the forearm. 



Anconeus (Fig. 15, No. 4). Location. Between the ulna and the 

 radius. 



Origin. By a short, strong, subcylindrical tendon from the lower 

 posterior of the external condyle of the humerus. 



Insertion. To the latero-radial side of the ulna somewhat beyond 

 its middle. 



Shape. Fusiform. 



