THE THIGH. 261 , 



right or perpendicular line ; in that line in which we have seen that the 

 greatest power is gained. A reference to the ])late of the skeleton will 

 place this in a striking yjoint of view ; and this advantage is the more 

 necessary, because, as is almost miiformly the case, there is a corresponding 

 disadvantage to be overcome. These muscles are inserted into the great 

 trochanter or protuberance of the upper bone of the thigh, and that is but 

 a very little way removed from the joint or centre of motion. The power 

 is close to the centre of motion ; the weight supposed to be concentrated 

 in the middle of the limb, is far off. It is more than 30 times as far as 

 the power, and this muscle must act with a disadvantage of more than 

 30 to ] : or, if the hinder extremity, and the weight of the trunk 

 above amount to six hundred pounds, the force applied, or the power of 

 the muscle, must be equal to 30 times 600, or 18,000 pounds. The nu- 

 merous origins of these muscles, and the extensive surfaces whence they 

 arise, and their immense bulk, render them ecpial to this ; and then, as we 

 have demonstrated with regard to the flexor muscles of the arm, what is 

 lost in power is gained in velocity ; for while this portion of the upper 

 thigh bone moves rapidly through a certain space, by the powerful con- 

 traction of the glutaei and other muscles, the extremity of that bone moves 

 through thirty times the space, and the extremity of the whole limb or the 

 foot moves through more than 100 times that space, and hence results, 

 and hence only could result the speed of the horse. 



Now comes another consideration ; — in proportion as this protuberance 

 behind and above the joint is lengthened, so is the shorter arm of the 

 lever lengthened, and so is power or muscular exertion spared. This 

 protuberance is lengthened in proportion to the length of the croup, and 

 the depth of the quarters, and hence the importance of this conformation* 

 We have explained this as it regards the depth of the elbow. It holds 

 more especially good here, because these are the parts with which the 

 speed and power of the horse are most concerned. The quarters com- 

 mence, by the common consent of sporting men, from about the middle 

 of the back, and extend to the hock downward, and to the tail behind ; 

 and although little regarded by those who are unaccustomed to horses, and 

 the just proportions of those parts uriderstood but by few who pretend to 

 know the horse, the quarters are by far the most important points in his 

 frame. Their muscularity will indicate power, and the depth of the 

 quarters the proper direction and the advantageous action of that power. 



These is another and smaller ghda^vs muscle under that we have last 

 described, arising likewise from the back of the ilium, and inserted into 

 the same protuberance of the thigh bone, and assisting in the same office. 

 It is not visible in our cut. There are also several other muscles pro- 

 ceeding from different parts of the haunch bones, and inserted about the 

 heads of the upper thigh bone, and performing the same work ; but there 

 are two muscles to which we must particularly refer. The first occupies 

 the outer part of the quarter behind, and is beautifully developed in the 

 blood horse ; it is found at e, p. 260. It arises high up from the bones of 

 the spine, from others at the root of the tail, from the protuberances ot 

 the ischium (vide cut, p. 63), and from other bones of the pelvis. It in fact 

 consists of three muscles, but is usually described as one muscle with three 

 heads. Triceps femoris (the three-headed muscle of the thigh). It is inserted 

 into the upper part of the lower bone of the thigh, and its office is the 

 same as the last, to draw back the thigh when placed under the trunk, 

 and by so doing urge forward the body. Being inserted nearly in a per- 

 pendicular direction, it has great power, but that power is employed 



