DISSECTION OF THE ANTERIOR LIMB. 31 



important, as it is the nei've which is cut in the lower operation of 

 neurotomy when performed for navicular arthritis. The middle is the 

 smallest and most irregular, and all three branches are in close relation- 

 ship with the digital vessels. 



The Anterior branch descends in front of the vein, distributes cutane- 

 ous branches to the front of the digit, and terminates in the coronary 

 cushion. 



The Middle branch, Avhich 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 preplantar branch of 

 that vessel to be distributed to the os pedis and the sensitive laminfe. 

 "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 analagous 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 neurotomy 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. 



Directions. — The student must now pursue the dissection of the 

 following muscles which have already been dissected in the fore -arm, 

 viz., the extensor pedis and extensor suffraginis on the front of the 

 limb, and the superficial and deep flexors behind. In addition to these, 

 there are the lumbricales and interossei muscles, which entirely belong- 

 to this region ; and, as they are of small size, and might easily be 

 overlooked, their dissection must be first undertaken. 



The Lumbricales Muscles (Plate 9) receive their name in the 

 human hand from their resemblance to a common earthworm. In the 



