78 THE ANATOMY OF THE HORSE. 



At the upper part of the inner face of the metatarsus is a flattenei 

 horny callosity, or chestnut; and another horny excrescence, in th 

 form of a spur, or ergot, is concealed in the tuft of hair behind th 

 fetlock. By manipulation in the neighbourhood of the heels, the latere 

 cartilages may be felt. 



Birectiom. — Remove the entire remaining portion of skin from thi 

 limb ; and if it is intended to study on the same preparation the part 

 contained within the hoof, this must, before the removal of the skin, b 

 detached by force in the manner described at page 35. The variou 

 structures are now to be defined by dissection, in the order of th 

 following description; and while the vessels and nerves are beinj 

 cleaned, care must be taken of the small lumbricales muscles, which lii 

 on the tendon of the deep flexor, above the fetlock. 



Cutaneous Nerves. — Descending over the inner side of the hock anc 

 metatarsus are twigs of the internal saphenous and posterior tibia 

 nerves, and on the outer side of the same regions are branches of thi 

 external saphenous and musculo-cutaneous nerves. 



The Large Metatarsal Artery (Dorsalis pedis of man) (Plate 19 

 is the larger branch resulting from the division of the anterior tibia 

 artery at the front of the tarsus. It inclines outwards and down 

 wards under the extensor brevis and the peroneus, and places itself ii 

 the groove formed on the outer side of the metatarsus by the junction o 

 the large and outer small metatarsal bones. Along this groove i 

 descends in company with the slender continuation of the anterioi 

 tibial nerve, until, a little above the button of the smaller bone, i 

 passes to the back of the metatarsus by penetrating between the tw( 

 bones. Finally, it bifurcates above the fetlock, between the twc 

 divisions of the suspensory ligament, to form the digital arteries. I' 

 gives off numerous un -named twigs to the skin, tendons, etc. 



Descending in the metatarsal region, there are other four arteries 

 besides the vessel just described. They will be found, one at each sid( 

 of the flexor tendons, in company with the vein and nerve, and anothej 

 at each edge of the suspensory ligament, within the splint bone of th( 

 same side. All of these are. branches of an arterial arch formed aorosi 

 the origin of the suspensory ligament from the back of the tarsus. Th( 

 arch corresponds to the subcarpal arch of the anterior limb, and ii 

 formed as follows : — 



The Perforating Metatarsal Aetbry, the smaller branch resulting 

 from the division of the anterior tibial artery, passes from the front t( 

 the back of the tarsus by the canal between the cuboid, scaphoid, anc 

 cuneiform bones. Here it unites with the outer and inner planta: 

 divisions of the posterior tibial, which descend in the tarsal sheath, on 

 on each side of the perforans tendon. Of the four vessels that spring 

 from the arch thus formed, the two that descend with the planta 



