DISSECTION OF THE POSTERIOR LIMB. / 9 



Surface-marking. — Extending down the middle line in front is the 

 tendon of the extensor pedis, which, a little below the tarsus, is joined 

 obliquely by the tendon of the peroneus. Behind the metatarsus, and 

 resting on the bone, is the suspensory ligament ; and behind that a^ain 

 are the deep and superficial flexors of the foot. The edges of these 

 structures can be distinctly seen or felt in the living animal, and in 

 the dead subject they may be identified by a reference to Plate 19. 

 At the upper part 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 ergot, is concealed in the tuft of hair behind the fetlock. 

 By manipulation in the neighbourhood of the heels, the lateral carti- 

 lages 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 must be 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 are 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 musculocutaneous nerves. 



The Large Metatarsal Artery (Dorsalis pedis 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 outwards and downwards 

 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 off 

 numerous unnamed 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 company 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 : — 



