DISSECTION OF SUPERFICIAL STRUCTURES 71 



brevis muscle and is accompanied by a digital artery. The five 

 most lateral digital nerves are branches of the median nerve, the 

 two most medial are branches of the ulnar nerve, therefore the 

 median nerve supplies three and a half digits, the thumb, the 

 index, the middle and half the ring digit, and the ulnar supplies 

 the remaining one and a half, viz., the little finger and half the 

 ring finger. 



As the branches of the median nerve to the fingers are followed 

 along the fingers they will be found to send branches not only to 

 the volar surfaces but also to the dorsal surfaces in the regions 

 of the second and terminal phalanges. 



The careful dissector will note that some of the finer branches of the 

 digital nerves terminate in minute ovoid bodies embedded in the fat. 

 They are the Pacinian touch corpuscles and are associated with the sense 

 of touch. 



Two other cutaneous nerves have still to be dissected ; they are 

 the dorsal branch of the ulnar nerve and the superficial division 

 of the radial nerve. Both are distributed to the dorsum of the 

 hand and to the dorsal aspects of the digits. 



The dorsal branch of the ulnar nerve must be sought for as 

 it turns round the ulnar border of the wrist immediately distal 

 to the styloid process of the ulna. It gives a branch to the ulnar 

 side of the little finger and a branch to supply the adjacent sides 

 of the ring and little fingers ; the latter communicates with the 

 most medial branch of the superficial division of the radial nerve. 



The superficial branch of the radial nerve will be found at 

 the radial border of the forearm. It appears from under cover 

 of the tendon of the brachio-radialis about 8 cm. (3^ inches) 

 above the wrist, and, as it descends to the hand, it breaks up 

 into five branches ; one to each side of the thumb, one to the 

 radial side of the index-finger, one to the adjacent sides of the 

 index and middle fingers, and one to the adjacent sides of the 

 middle and ring fingers. The last branch is connected with the 

 adjacent ramus of the dorsal branch of the ulnar nerve by a 

 communicating twig. A palmar cutaneous branch is distributed 

 to the ball of the thumb either from the trunk of the superficial 

 part of the radial nerve or from the branch to the radial side 

 of the thumb. The dorsal digital nerves of the thumb can be 

 traced to the end of the thumb, those of the index digit to the 

 proximal end of the second phalanx, those of the middle finger 

 to the middle of the second phalanx and those of the ring and 

 little fingers to the proximal end of the terminal phalanx. The 

 remaining parts of the dorsal aspects of the fingers are supplied 

 by the volar digital nerves. The important practical point is 

 that parts of the dorsal surface of the index, middle, and ring 

 digits are supplied not by the radial but by the median nerve. 



The arrangement of the nerves on the dorsum of the hand is very 

 variable. That described above is usually met with, but not uncommonly 

 the ulnar nerve supplies a larger and the radial nerve a smaller area. 

 The reverse arrangement is also found. 



When the dissection of the cutaneous nerves of the superior 

 extremity is completed remove the remains of the fatty superficial 

 fascia and proceed to the study of the deep fascia, 

 i 5c 



