78 THE ANATOMY OF THE HORSE. 



At the upper purt of the inner face of the metatarsus is a flattened 

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

 form of a spur, or err/ot, is concealed in the tuft of hair behind the 

 fetlock. By manipulation in the neighlwurhood of the heels, the lateral 

 cartilages may be felt. 



Directions. — Remove the entire remaining portion of skin from the 

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

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

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

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

 following description ; and while the vessels and nerves are being 

 cleaned, care umst l)e taken of the small lumbricales muscles, which lie 

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



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

 metatarsus arc twigs of the internal saphenous and posterior tibial 

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

 external saphenous and musculo-cutaneous nerves. 



The Large INIetatarsal Artery {Dorsalis 2)edis of man) (Plate 19) 

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

 artery at the front of the tarsus. It inclines outwai-ds and down- 

 wai-ds under the extensor brevis and the peroneus, and places itself in 

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

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

 descends in company with the slender continuation of the anterior 

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

 passes to the back of the metatarsus by penetrating between the two 

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

 divisions of the suspensory ligament, to form the digital arteries. It 

 gives ofl" 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 side 

 of the flexor tendons, in com2)any with the vein and nerve, and another 

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

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

 the origin of the suspensory ligament from the back of the tarsus. The 

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

 formed as follows : — 



The Perforating Metatarsal Artery, the smaller branch resulting 

 from the division of the anterior tibial artery, passes from the front to 

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

 cuneiform bones. Here it unites with the outer and inner plantar 

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

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

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



