284 THE HIND LBGS. 



muscle is the degree of contraction of which it is capable ; and also in proportion to 

 the contraction of the muscle is the extent of motion in the limb ; but it is still more 

 necessary that this part of the thigh should have considerable muscle, in order that 

 strength may be added to such extent or compass of motion. Much endurance would 

 not be expected from a horse witli a thin arm. A horse with thin and lanky thighs 

 will not possess the strength wliich considerable exertion would sometimes require. 

 In the cuts p. 281 and 282, the princijial muscles of this part of the thigh are deli- 

 neated. They are usually somewhat prominent, and may readily be traced in the 

 living animal : a very brief notice of them may not be uninteresting. 



The continuation from g, p. 282, is the tendinous expansion given to bind and 

 strengthen these muscles. 



n is a very important muscle. It is the principal extensor muscle of the hind leg 

 {extensor pedis, extensor of tlie 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 pursues its course in front of the hock 

 in union with the tendon of the peronaius. 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. 282, fig. /. 

 It helps to flex the hock joint, but is principally concerned in the extension of the 

 foot, and also the pastern and ietlock joints. 



At m, p. 282, is another of tlie extensor muscles, called the peronscvs, 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 

 coffin-bone. Its oflTice is to co-operate with the extensor pedis in raising the foot from 

 the ground, and bringing it forward under the body. 



At is i\\e, flexor 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. 



k is a very slender muscle, arising from the head of the fibula, and proceeding 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 evidently 

 most advantageously situated for powerful action ; for it acts almost at right angles, 

 and its eff"ect is increased in proportion to the projection of the point of the hock. 



We will now turn to the inner side. See cut, p. 281. 



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. 



1 is the peronaeus. 



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

 upper bcae of the thigh — becoming tendinous as it passes down the thigh — ex- 

 panding Jver 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 man- 

 ner so much resembling that of similar tendons in the fore leg, that it will be suffi- 

 cient to refer to a description of the perforated and perforating flexor tendons at page 

 280. 



At e is a continuation of the gracilis muscle, p. 281, over the stifle. 



At h is the extensor pedis, already described, p. 282, with its tendon. 



At i is a muscle used to bend the hock, the flexor rnefatarsi, or liender 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 ])ow('r, although disadvanta- 

 geous! y situated, both as to its direction and its being inserted so near to the joint 

 It flexes tlie hock, the joint turning somewhat inwards. 



At k is a short muscle extending from the upper to the lower thigh-bones (the V'lpd' 

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



