THE STIFLE. 359 



hind leg {extensor pedis, extensor of the foot). It commences by a small flat 

 tendon, common to it, and the flexor metatarsi. Passing over the tibia it 

 becomes fleshy : but a little above the hock it changes to a flat tendon, and pur- 

 sues its course in front of the hock in union with the tendon of the peronaeus. 

 On the fetlock joint they disunite. It now begins to expand, and is finally 

 inserted into the upper part of the coffin-bone, or bone of the foot, after having 

 given various fibres to both the pasterns. The course of the corresponding 

 tendon in the hind leg is given in the cut, p. 366, fig. I. It helps to flex the 

 hock-joint, but is principally concerned in the extension of the foot, and also 

 the pastern and fetlock joints. 



At m, p. 356, is another of the extensor muscles, called the peronceus, from a 

 name given to the fibula. It arises from the whole course of the fibula, and 

 also becomes tendinous before it reaches the hock. About half way down the 

 shank it is found in the same sheath with the principal extensor muscle, and is 

 inserted with it into the coflin-bone. Its office is to co-operate with the extensor 

 pedis in raising the foot from the ground, and bringing it forward under the 

 body. 



At o is the flavor pedis, one of the principal flexor muscles of the foot, arising 

 from the upper part of the tibia. As it approaches the hock it is distinguished 

 by its large round tendon, which is seen to enter into a groove at the back of the 

 hock. Its tendon passes down the back of the leg like that of a similar muscle 

 in the fore leg. It is the perforating flexor muscle of the hind leg, and assists in 

 flexing the pastern and fetlock. 



A is a very slender muscle, arising from the head of the fibula, and proceed- 

 ing over the external part of the thigh, and, just above the hock, its tendon 

 unites with that of the perforating muscle. 



j is a very powerful muscle, springing from the head of the upper bone of the 

 thigh, and, midway down the lower bone of it, ending in a flat tendon, which is 

 inserted into the point of the hock. Its use is to extend the hock. It is evi- 

 dently most advantageously situated for powerful action ; for it acts almost at 

 right angles, and its effect is increased in proportion to the projection of the 

 point of the hock. 



We will now turn to the inner side. See cut, p. 355. 



m gives a portion of the muscle which has been just described. 



n is an inside view of the perforating flexor muscle of the foot. 



I is the peronasus. 



o is the flexor perforatus muscle, having its origin from near the lower head 

 of the upper boneof the thigh — becoming tendinous as it passes down the thigh — 

 expanding over and surrounding the point of the hock, and assisting in extending 

 it. After this the tendon pursues its course down the posterior part of the leg, in a 

 manner so much resembling that of similar tendons in the fore leg, that it will 

 be sufficient to refer to a description of the perforated and perforating flexor 

 tendons at page 351. 



At e is a continuation of the gracilis muscle, p. 355, over the stifle. 



At h is the extensor pedis already described, p. 366, with its tendon. 



At i is a muscle used to bend the hock, the flexor metatarsi, or bender of the 

 leg; arising from the external condyle of the os femoris, and inserted into the 

 large and small metatarsal bones. It is a muscle of considerable power, although 

 disadvantageous^ situated, both as to its direction and its being inserted so near 

 to the joint. It flexes the hock, the joint turning somewhat inwards. 



At k is a short muscle extending from the upper to the lower thigh-bones 

 (the popliteus), bending the stifle and turning the limb inward. 



These cuts represent the situation of some of the principal blood-vessels and 

 nerves of the hind extremities. 



