THE THIGH. 26} 



almost in a right or perpendicular line ; in that l\ne in which we have seen 

 that the greatest power is gained. A reference to the plate of the skeleton 

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

 necessary, because, as is almost uniformly 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 powei 

 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 a* 

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

 30 to 1 : or, if the hinder extremity, and the weight of the trunk above 

 amount to 600 pounds, the force applied, or the power of the muscle, must 

 be equal to 30 times 600, or 18,000 pounds. The numerous origins of 

 these muscles, and the extensive surfaces whence they arise, and their 

 immense bulk, render them equal to this ; and then, as we have demon- 

 strated 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 contraction of the glutse; 

 and other muscles, the extremity of that bone moves through 30 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, 

 ♦he 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 unnaccustomed to horses, and the 

 just proportions of those parts understood 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. Therefore, it 

 behooves those who are about making a selection, to have a careful eye, in 

 regard to these parts, in order to determine whether the animal is naturally 

 formed for the purposes required. «s^ 



There is another and smaller glulaus muscle under that we have last 

 described, rising 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 rises high up from the bones of 

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

 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, 



