302 St - J- Brooks, 



border of the thumb and shared with the ulnar in the supply of the 

 ulnar border of that digit, the radial nerve being absent x ). 



I have never succeeded in following the internal cutaneous as far 

 as the back of the wrist; it stops immediately above the lower end 

 of the ulna. 



It appears from the above facts that certain areas of the skin on 

 the back of the hand may be supplied by no less than three nerves; 

 viz. part of the ring finger by the radial, ulnar, and median nerves; 

 a small area below the ulnar side of the wrist by the radial, ulnar 

 and musculo -spiral nerves, and, more rarely, a very limited area, si- 

 tuated more towards the radial side, by the radial, ulnar and musculo- 

 cutaneous nerves. It also appears that the amount of intercrossing 

 varies very greatly in different hands. 



I have not been able to find any description of a double inner- 

 vation of the skin of the hand in the literature of the subject. Most 

 anatomists do not even hint at such a thing. Henle 2 ) however figures 

 a twig of the ulnar crossing the radial for a very short distance but 

 he does not describe it in the text. Ranney 3 ) referring to a figure 

 representing the areas of distribution of the median, ulnar and radial 

 nerves on the back of the hand, says: „This diagram limits the distri- 

 bution of each nerve with more positiveness than can well be verified, 

 since the cutaneous filaments of two nerves may supply the borders of 

 any of these regions, as the nerves tend to overlap each other". 



With regard to the cutaneous supply of the fingers, some text- 

 books have represented the dorsal digital nerves extending uniformly 

 as far as the ungual phalanges of the fingers ; — these statements do 

 not require to be seriously criticised. In Quain's Anatomy and in the 

 German text- books the dorsal nerves are represented as extending to 

 the nail only in the case of the thumb; the dorsal branches to the 

 four inner digits are described as reaching no further than the first 

 inter-phalangeal joint, the palmar digital nerves curving round beyond 

 that point to supply the fingers on their dorsal aspect. Henle 4 ) has 



*) Journ. of Anat. and Phys. Vol. XXI. p. 511. 



3 ) Op. cit. Fig. 291. p. 545. 



s ) Applied Anatoiney of theJSTrvous System; by A. L. Ranney. Londou. 1881. p. 411. 



*) Op, cit. p. 550. „Der Daumen ist der einzige Finger, an welchem die dorsalen 



