30 THE ANATOMY OF THE HORSE. 



the grooves between these bones and the large metacarpal. They 

 supply the skin and subjacent structures on the front of the meta- 

 carpus, and anastomose above the fetlock with divisions of the artery 

 springing from the large metacarpal at its point of bifurcation. 



2. The Posterior or Palmar Interosseous Metacarpal Arteries. — These 

 descend on the edge of the suspensory ligament, each being internally 

 placed to the small metacarpal bone of its own side. They anastomose 

 like the preceding, and supply small branches to the suspensory liga- 

 ments and flexor tendons. One of them gives off the nutrient artery of 

 the large metacarpal bone. They are of unequal size, the outer being 

 the larger. 



The Digital Veins (Plate 9). These are the satellites of the digital 

 arteries, in front of which they ascend. They drain away the blood 

 from the venous plexuses within the hoof, and, uniting with one another 

 above the fetlock, they form an arch between the deep flexor and the 

 suspensory ligament. From this arch spring the metacarpal veins. 



The Metacarpal Veins are three in number : — 



1. The Internal Metacarpal Vein (Plate 9) which is the largest of 

 the three, ascends in front of the large metacarpal artery, on the inner 

 edge of the flexor tendons. At the inner side of the back of the carpus 

 it is continued as the median vein. 



2. The External Metacarpal Vein is similarly disposed on the outside 

 of the flexor tendons, in company with the external plantar nerve. At 

 the carpus it divides into several anastomosing branches, which are 

 continued as the ulnar and posterior radial veins. 



3. The Interosseous or Deep Metacarpal Vein is an irregular vessel 

 ascending between the suspensory ligament and the inner splint bone. 

 At the back of the carpus it breaks up into branches that anastomose 

 with the external and internal metacarpal veins. 



The Plantar Nerves (metacarpal nerves of Percivall). — These are the 

 nerves which confer sensibility on the digit, and which, in their main 

 trunks or in one of their terminal branches, are cut in the operation of 

 plantar neurectomy. They must therefore be dissected with great care, 

 and the student must make himself thoroughly acquainted with their 

 situation and relations. 



The Internal Plantar Nerve (Plate 7). This is one of the terminal 

 branches of the median nerve. Beginning at a variable point above 

 the carpus, it passes within the carpal arch, in close company with the 

 large metacarpal artery, both resting on the side of the deep flexor 

 tendon. Here the nerve crosses beneath the artery, to place itself 

 behind it. Throughout the metacarpal region the same relationship 

 is preserved, the nerve lying immediately behind the artery, in front 

 of which is the internal metacarpal vein. Just above the fetlock the 

 artery sinks in somewhat more deeply than the vein and nerve, and 



