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 between being affected. Thus, the flexor sublimis digitorum, 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 surface 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 extensors 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-
