THE MUSCULAR SYSTEM 73 



process of the ulna. Insertion, fifth metacarpal bone, 

 annular ligament, and pisiform bone. Action, flexes the 

 wrist. Nerve, ulnar. (See Figs. 37 and 38.) 



Flexor Sublimis Digitorum. Origin, by three heads: 

 First, from the inner condyle; second, coronoid process of 

 ulna; third, oblique line of radius. Insertion, into the 

 second phalanges by four tendons. Action, flexes second 

 phalanges. Nerve, median. 



The flexor profundus digitorum arises from shaft of 

 ulna. Insertion, into last phalanges by four tendons. 

 Action, flexes the phalanges. Nerve, median. 



Flexor Longus Pollicis. Origin, shaft of radius and 

 coronoid process of ulna. Insertion, last phalanx of 

 thumb. Action, flexes the phalanx. Nerve, anterior 

 inter osseous. 



Pronator Quadratus. Origin, from lower fourth of 

 ulna. Inserted, in lower one-fourth of radius. Action, 

 pronates the hand. Nerve, anterior interosseous. 



Supinator Longus. Origin, upper two-thirds of external 

 condyloid ridge of humerus. Insertion, styloid process of 

 radius. Action, flexes forearm. Nerve, musculospiral. 



Extensor Carpi Radialis Longior. Origin, lower one- 

 third of external condyloid ridge of humerus. Insertion, 

 base of second metacarpal bone. Nerve, musculospiral. 

 Action, extends wrist. 



Extensor Carpi Radialis Brevior. Origin, external con- 

 dyle of humerus. Insertion, base of second and third 

 metacarpal bones. Action, extends wrist. Nerve, pos- 

 terior interosseous. 



Extensor Communis Digitorum. Origin, external con- 

 dyle of humerus. Insertion, the second and third pha- 

 langes. Action, extends the fingers. Nerve, posterior 

 interosseous. 



Extensor Minimi Digiti. Origin, external condyle of 

 humerus. Insertion, in the second and third phalanges of 



