THE STIFLE. 263 



THE STIFLE. 



The upper bone of Uie thigh is united to the lower by a somewhat com- 

 plicated joint. It terminates by two round prominences behind, which are 

 received into slight depressions on the upper surface of the lower bone; 

 and in front is a curious groove, over which plays a small irregular bone, 

 the patella or stifle-bone. The whole is called by farriers tlie stifle-joint. 

 The patella (Q, p. 63) answers to the kneepan in the human subject. 

 Some of the tendons of the strongest muscles of the upper bone of the thigh 

 are inserted into it, and continued from it over the lower bone. This 

 important joint is hereby much strengthened ; for the proper ligament? 

 between the upper and lower bones, and these additional tendons and 

 ligaments from the patella, must form altogether a very powerful union 

 The patella likewise answers another and even more important purpose 

 The tendons of some of the strong muscles are inserted into it. When 

 these muscles are not in action, the patella lies in the groove which nature 

 has contrived for it; but when they begin to contract, it starts from its par- 

 tial hiding-place, becomes prominent from the joint, and alters the Ime of 

 direction in which the muscles act: it increases the angle, and thus very 

 materially increases the power of the muscles. 



The lower bone of the thigh is double: the larger portion, in front, 

 extending from the stifle to the hock, is called the tibia. The smaller bone, 

 or fibula, behind (see R, p. 63), reaches not more than a third of the way 

 down. It is united to the shank-bone, like the splint-bone, by a cartilagin- 

 ous substance, which is soon changed for bone. Of the use of these little 

 bones we caimot speak. 



The lower bone of the thigh forms an angle with the upper, the reverse 

 of that which exists between the upper bone and the pelvis. The objecl 

 of this is twofold ; to obviate concussion, and to give a direction to the 

 muscles favourable to their powerful action; and in proportion to the acute- 

 ness of the angle, or the degree ia which the stifle is brought under the 

 horse, will these purposes be accomplished. There is a great deal of differ- 

 ence in this in ditferent horses, and the construction of this part of the frame 

 is a matter worthy of more regard than is generally paid to it. 



This part of the thigh should likewise be long. In proportion to the 

 length of the muscle is the degree of contraction of which it is capable; 

 and 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 plenty of muscle, that the strength may be added to this extent or 

 compass of motion. We should not expect much endurance from a horse 

 with a thin arm: a horse with thin and lanky thighs cannot possibly be good 

 for any thing. In our cuts, 259 and 260, the principal muscles of this part 

 jf the thigh are delineated. They are usually somewhat prominent, and 

 may readtly be traced in the living animal : a very brief notice of them 

 may not be uninteresting. 



We will first take the external ones, beginning in front. The continua- 

 tion from g, p. 260, is the tendinous expansion given to bind and strengthen 

 these muscles. 



n is a very important muscle : it is the principal extensor mujcle of the 

 hind-leg {extensor pedis, extensor of the foot). It rises from the lower part 

 of the upper bone of the thigh, and from the upper part of the lower bone. 

 It is a strong, round, fleshy muscle: a little before it reaches the hock, it 

 will be seen to assume a tendinous form. It is covered and defended by a 

 sheath of its own ; and the cut will show the bands by which it is tied down 



