PALM OP THE HAND. 153 



deep arch about the middle of the hand. The terminal 

 part of the superficial artery unites with the superficialis 

 volse, and with the branch of the radial artery which sup- 

 plies the radial side of the forefinger. 



The median nerve, after emerging from beneath the annu- 

 lar ligament, divides into two trunks ; the external of these, 

 besides giving off a muscular branch to the muscles of the 

 thumb (p. 143), divides into three digital branches, which 

 go to the two sides of the thumb and the radial side of the 

 forefinger; the internal trunk divides into two branches 

 which bifurcate to supply the contiguous sides of the fore and 

 middle, and middle and ring fingers. The digital nerves pass 

 down the sides of the fingers, superficially to the arteries, 

 and terminate by filaments in the pulp at their extremities. 



The ANTERIOR ANNULAR LIGAMENT is a firm ligamentous 

 band, beneath which pass the tendons of the flexor muscles; 

 it is attached to the trapezium and scaphoid bones on one 

 side, and to the unciform and the pisiform bones on the 

 other. The canal formed by this ligament is lubricated 

 by a synovial membrane, which surrounds each tendon 

 separately, and is prolonged both above and below the 

 ligament, sometimes even as far as the fingers, where it 

 communicates with the synovial membrane of the sheaths 

 of some of the tendons; this communication has been de- 

 monstrated to be nearly constant in the tendons of the 

 thumb and little finger; with the others it is only of occa- 

 sional occurrence. This continuity in their synovial mem- 

 branes explains the terrible consequences which sometimes 

 follow phlegmonous inflammation of the fingers. The 

 synovial sac of the wrist and fingers may be demonstrated 

 by insufflation. 



The annular ligament is now to be divided ; the median and ulnar 

 nerves are also to be cut through, and turned over toward the fingers. 



The tendons of the flexor sublimis digitorum muscle are 

 superficial to those of the deep; these enter the sheaths of 

 the fingers, and are inserted by two processes into the mar- 

 gins of the second phalanges at about their middle, being- 

 split opposite the first phalanges for the passage of the 

 deep flexor tendons. The sheath of the tendons consists 

 of transverse tendinous fibres attached to the sides of the 

 first and second phalanges; in front of the articulations the 

 sheaths are either wanting or imperfectly developed ; they 

 firti lined by a synovial membrane. 



