DISSECTION OP THE ANTBBIOR LIMB. 31 



thereby allows these to approach each other. In the higher operation 

 of neurectomy the nerve is cut a little way above the fetlock, and before 

 it divides. About the middle of the metacarpus it gives off a consider- 

 able branch which winds obliquely downwards and outwards behind the 

 flexor tendons, to join the external plantar nerve an inch or more above 

 the button of the splint bone. At the level of the sesamoid bones the 

 trunk of the nerve divides into three digital branches, which are 

 distinguished as anterior, middle, and posterior. These are of very 

 unequal size, the posterior being much the largest, and also the most 

 important, as it is the nerve which is cut in the lower operation of 

 neurectomy when performed for navicular arthritis. The middle is 

 the smallest and most irregular, and all three branches are in close 

 relationship with the digital vessels. 



The Anterior branch descends in front of the vein, distributes 

 cutaneous branches to the front of the digit, and terminates in the 

 coronary cushion. 



The Middle branch, which is small and irregular, descends between 

 the artery and vein. It is generally, as in Plate 9, formed by the 

 union of several smaller branches which cross forwards over the 

 artery before uniting, and it terminates in the sensitive laminse and 

 coronary cushion. 



The Posterior branch lies close behind the artery, except at the 

 fetlock, where the nerve is almost superposed to the artery. It 

 accompanies the digital artery into the hoof, and passes with ■ the 

 preplanter branch of that vessel to be distributed to the os pedis and 

 the sensitive laminae. Within the hoof it gives off several branches, 

 which for the most part accompany the arteries. 



The External Plantar Nerve (Plate 9). This is formed by the 

 fusion of the termination of the ulnar nerve with one of the terminal 

 branches of the median. These two branches unite at the upper border 

 of the pisiform bone, beneath the middle flexor of the metacarpus. 

 Behind the carpus the nerve inclines downwards and outwards, in the 

 texture of the annular ligament that completes the carpal sheath. In 

 the metacarpal region it occupies, on the outside of the limb, a position ' 

 on the flexor tendons analogous to that of the internal plantar nerve 

 on the inside. Unlike the latter nerve, however, it is accompanied by 

 only a single vessel — the external metacarpal vein, which lies in front of 

 it. An inch or more above the button of the splint bone it is joined by 

 the oblique branch from the internal nerve. In the higher operation 

 of neurectomy it is cut at the same point as the inner nerve. At the 

 level of the sesamoid bones it divides into three digital branches, 

 exactly similar to those of the internal nerve already described. 



The plantar nerves give filaments to the lumbricales and interossei 

 muscles, and to the suspensory ligament. 



