1 62 THE SURGICAL ANATOMY OF THE HORSE 



The following distribution of the digital divisions of the plantar 

 nerve is important : — 



The anterior digital nerve supplies the skin at the front of the 

 digit, and ends in the coronary cushion. 



The middle digital nerve supplies the sensory laminae and 

 coronary cushion. 



The posterior digital nerve, as already stated, follows closely the 

 course of the digital artery behind which it lies. The artery, it 

 will be remembered, divides into plantar and preplantar divisions, 

 the latter of which runs along the preplantar groove on the 

 laminal aspect of the pedal bone. With this division of the 

 digital artery the main portion of the posterior digital nerve 

 runs, and is distributed to the pedal bone itself and the sensitive 

 laminae. 

 The external plantar nerve is formed by the union of one of the 

 terminal branches of the median nerve with the ulnar. This union 

 occurs at the upper border of the pisiform bone, underneath the tendon 

 of the flexor metacarpi medius. The nerve runs at the back of the 

 carpus in the fibrous arch (Plate V.), taking an oblique direction 

 downwards and outwards. In the metacarpal region its position corre- 

 sponds to that of the internal plantar nerve, i.e., on the edge of the 

 perforans tendon. Near the button of the splint bone it receives the 

 communicating branch from the internal plantar nerve which has been 

 already referred to. Its terminal branches and their distribution are 

 similar to those described in dealing with the internal plantar nerve. 

 It differs from the latter in being accompanied only by the external 

 metacarpal vein, which lies in front of it. 



A small unnamed artery descends from the subcarpal arch in 

 front of the nerve, but this usually becomes lost above the seat of 

 operation. 



In addition to the distribution given, the plantar nerves supply the 

 suspensory ligament. 



