DISSECTION OF THE POSTERIOR LIMB. 81 



2. The External Metatarsal Vein (Plate 19)) ascends on the inner edge 

 of the deep flexor, having the same, relationship to nerve and artery as 

 the internal vein. After communicating with the deep vein, it is con- 

 tinued through the tarsal sheath to become the posterior root of the 

 internal saphena. 



3. The Deep Metatarsal Vein ascends between the suspensory liga- 

 ment and the large metatarsal bone ; and, passing from the back to the 

 front of the hock, by the vascular canal for the perforating metatarsal 

 artery, it is continued as the anterior tibial vein. 



The Plantar Nerves. These nerves result from the bifurcation of 

 the posterior tibial nerve when it gains the back of the tarsus. They 

 accompany the perforans tendon in the tarsal sheath ; and, diverging 

 from one another, they descend in the metatarsal region, one at each 

 side of the deep flexor tendon. Each is accompanied in the metatarsus 

 by the metatarsal vein of that side, and by a slender artery from the 

 vascular arch at the back of the tarsus. A little below the middle of 

 the metatarsus the inner nerve detaches a considerable branch that 

 winds obliquely downwards and outwards behind the flexor tendons to 

 join the outer nerve above the level of the button of the splint bone. 

 At the fetlock each nerve, coming into relation with the digital vessels, 

 resolves itself into three branches for the supply of the digit. These 

 are identical in their arrangement with the like branches of the plantar 

 nerves in the fore limb, for the description of which turn to page 30. 



The student must now pursue the dissection of the following muscles 

 which have already been dissected in the leg, viz., the extensor pedis 

 and peroneus on the front of the limb, and the superficial and deep 

 flexors behind. In addition to these, there are the short extensor of 

 the foot, the lumbricales, and the interossei, which entirely belong to 

 this region ; and since they are of small size, and might easily be over- 

 looked or injured, their dissection must be first undertaken. 



The Lumbricales (Plate 19) and Interossei Muscles. These exactly 

 resemble the muscles of the same name in the anterior member. Turn, 

 therefore, to the description of the latter given at page 31, substituting 

 the word foot for hand, toes for fingers, and metatarsal for metacarpal. 



The Short Extensor of the foot (extensor brevis digitorum of man) 

 {Plate 19). Look for this small muscle at the front of the tarsus, in the 

 angle of union of the extensor pedis and peroneus tendons. It arises 

 from the os calcis and astragalus, and is inserted into the united tendon 

 of the above-mentioned muscles, to whose action it is auxiliary. 



The Extensor Pedis tendon (Plate 19) descends along the middle 

 line of the limb in front, to be inserted into the pyramidal eminence of 

 the os pedis. Above the middle of the metatarsus it receives on its 

 outer side the tendon of the peroneus, and at the same point it is joined 

 by the short extensor. A small synovial bursa is interposed between 



