chap, xv.] THE WRIST AND HAND. 247 



28). Thus, after the division of the sheath, as in 

 amputation, an open channel is left leading into the 

 palm of the hand, and offering the greatest facility for 

 the spread of pus into that part. It 

 is this rigidly open fibrous sheath that 

 probably may explain the frequency of 

 suppuration in the palm after amputa- 

 tion of a part of a finger, and I am 

 decidedly of opinion that some steps 

 should be taken to protect or shut off 

 this channel in any case where the 

 sheath has been accidentally or inten- 



tioiially divided. 



Synovial sacs and sheaths. 



There are two synovial sacs beneath a, Flexor profun- 



.-, IT i p j_i n dus tendon: 6. 



the annular ligament for the flexor fibrous sheath of 



-, . -. n i tendon ; c, exten- 



tendons, one for the flexor longus sor tendon; d, 



n. Xl ,1 r ,i YI i digital artery and 



pollicis, the other tor the flexor sub- nerve. 

 limis and profundus tendons. The 

 former extends up into the fore-arm for about 1|- 

 inches above the annular ligament, and follows its 

 tendon to its insertion in the last phalanx of the 

 thumb. The latter rises about 1-J- inches above the 

 annular band, and ends in diverticula for the four 

 fingers. The process for the little finger usually 

 extends to the insertion of the flexor profundus tendon 

 in the last phalanx. The remaining three diverticula 

 end about the middle of the corresponding metacarpal 

 bones. The synovial sheaths for the digital part of the 

 tendons to the index, middle, and ring-fingers, end 

 above about the neck of the metacarpal bones, and are 

 thus separated by about a quarter to half an inch from 

 the great synovial sac beneath the annular ligament. 

 Thus there is an open channel from the ends of the 

 thumb and little finger to a point in the fore-arm 

 some inch and a half above the annular ligament. 

 The arrangement explains the well-known surgical 



