THE UPPER EXTREMITIES. 183 



Of the flexors of the wrist the flexor carpi radialis is 

 inserted into the base of the index and usually of the 

 third metacarpal bone, the flexor carpi ulnaris into the 

 fifth metacarpal, the pisiform and the unciform bones, 

 while the palmaris longus goes to the anterior annular 

 ligament of the wrist and the palmar fascia of the hand. 

 The flexor sublimis digitorum is inserted by four tendons 

 into the second phalanges of the fingers, while the flexor 

 profundus digitorum arises from the upper part of the 

 ulna and is inserted into the last phalanges of the fingers. 

 The flexor of the thumb arises from the middle of the 

 radius and is inserted into the last phalanx of the thumb. 

 Which joint is flexed by a muscle depends upon the 

 origin and insertion of the muscle, all those included be- 

 tween being affected. Thus, the flexor sublimis digi- 

 torum, which has its origin in part at least from the 

 condyle and is inserted in the second phalanges of the 

 fingers, flexes the forearm, wrist, and all the finger-joints 

 but the last, while the flexor profundus digitorum, arising 

 from the ulna, though it flexes the wrist and fingers, has 

 no power of flexing the forearm. 



The pronator radii teres, besides arising from the supra- 

 condylar ridge, rises from the coronoid process of the 

 ulna. It is inserted into the middle of the outer sur- 

 face of the radius and serves to pronate the forearm. 

 The other pronator, the pronator quadratus, is a small 

 quadrilateral muscle extending transversely across 

 the radius and ulna just above their carpal extremities. 

 It rises from the anterior surface of the ulna and is 

 inserted into the anterior external border of the radius. 



On the back of the forearm the anconeus serves to 

 extend the forearm only, being inserted into the upper 

 part of the posterior surface of the ulna. The exten- 

 sors of the wrist are inserted into the bases of the various 

 metacarpal bones and have some power to extend the 

 forearm as well as the wrist. The extensors of the thumb, 

 as their names imply, go one to the metacarpal bone 

 and one to each of the phalanges, the longest one ex- 



