Fig. 93. Nerves and Veins on the Dorsum of the Right Hand. 



A fresh specimen, hi which only the skin has been removed. (The Veins and 

 Nerves on the jrd finger have been drawn after RtrD/NGERs Atlas of the Ner- 

 vous System.) 



Nerves: The Dorsum of the hand is supplied by Sensory Branches of 

 the Radial and of the Ulnar Nerve. Their areae of distribution are not constant; 

 moreover, there is, nearl}' always, at least one anastomosis, and thus an exchange 

 of fibres occurs between these 2 nerves: this explains wh}- in injury, paralysis etc., 

 the loss of sensation ma}' be very slight. In most cases they divide the Dorsum 

 of the hand equally between them; the axis of the middle finger being the boun- 

 dary between the 2 areae. 



The dorsal surfaces of the distal phalanges (2nd and 3rd) of the 4 inner 

 fingers (2 — 5), and of the terminal phalanx of the thumb are innervated by nerves 

 running on the palmar surface, thus the Median supplies the 2nd and 3rd phalanges 

 of 3rd fingers completely, and the outer half of those of the 4th finger. 



The dorsal surface of the terminal phalanx of the thumb may, however, 

 be innervated only by the Radial Nerve; there may also be Paccinian Corpuscles 

 here, although these bodies 'are usually found on the palmar surface along 

 the branches of Median and Ulnar Nerve (cf. Fig. 95 middle finger). 



There are no Motor Nerves on the Dorsum of the hand, because the 

 Dorsal Interossei are supplied, like the Palmar Interossei, b)- the Deep Ulnar Nerve. 



Veins: The blood flows from the fingers on the dorsum through several 

 (as many as to 4) Superficial Veins which begin at the first phalanges into larger 

 venous channels, the Radial and Posterior Ulnar Veins. The former crosses the 

 Tendons of the Extensor Primi Internodii, Extensor Secundi Internodii, and 

 Extensor Ossis Metacarpi Pollicis (cf. Fig. 92) and then runs upwards on the 

 anterior surface of the limb. 



The Veins and Nerves are quite superficial, i. e. they lie between the skin 

 and the Tendons of the Extensors. The Posterior Annular Ligament (cf. figure) 

 is formed by transverse and oblique fibres which strengthen the fascia of the 

 forearm. This fascia becomes very thin in the dorsum of the hand (cf. Fig. 92, 

 text). 



