158 THE SUPERIOR EXTREMITY 



to the pulp of the finger and to the bed upon which the 

 nail rests. 



At the cleft of the finger immediately before it divides, 

 each digital artery is joined by the corresponding volar 

 metacarpal artery from the deep volar arch; and, as the 

 branches run along the sides of the fingers, they give off 

 numerous twigs to supply the skin, the flexor tendons and 

 the joints of the fingers. 



The superficial volar arch is not uncommonly absent in whole or in 

 part. In such cases the digital arteries are replaced by the volar meta- 

 carpal branches of the deep volar arch. 



Nervus Medianus. The median nerve was traced to the 

 proximal border of the transverse carpal ligament when the 

 front of the forearm was dissected. As it passes from the 

 forearm to the palm of the hand it lies behind the transverse 

 carpal ligament at the lateral margin of the tendons of the 

 flexor digitorum sublimis (Fig. 60) and in close relation 

 with the mucous sheath which surrounds those tendons. 

 Near the distal border of the transverse carpal ligament it is 

 first flattened antero-posteriorly and then it divides into a 

 smaller lateral, and a larger medial division. The lateral 

 division gives off a branch which supplies the short abductor, the 

 opponens and the short flexor of the thumb ; then it divides 

 into three digital branches, of which two go to the sides of 

 the thumb and the third to the radial side of the index 

 finger. The digital branches supply the skin, tendons, 

 ligaments and joints of the regions to which they are dis- 

 tributed. In addition the branches to the medial side of 

 the thumb and the radial side of the index digit give branches 

 to the fold of integument which stretches between the roots 

 of those digits, and the nerve to the index finger also gives 

 a branch to the first lumbrical muscle. 



The larger medial division divides into two branches. One 

 runs towards the cleft between the index and middle fingers 

 and divides to supply the adjacent sides of those fingers ; before 

 it divides it gives a muscular branch to the second lumbrical 

 muscle. The second branch of the medial division divides, 

 in a similar manner, to supply the adjacent sides of the 

 middle and ring digits, but before it divides i gives a 

 communicating twig to the lateral branch of the superficial 

 division of the ulnar nerve. It sometimes gives a muscular 



