208 ' Elementary Principles of Agriculture 



length and the relation of the bones to which they are 

 attached. The common idea among students of this 

 subject is expressed in these words, "Long muscles for 

 speed, short muscles for power." We have already seen 

 that a long muscle enables a horse to get over ground 

 rapidly. A short muscle, however, is not powerful 

 because it is short, but because in horses constructed 

 on that plan the muscles are thicker, containing more 

 fibers, all of which pulling together when contracted 

 exert a much greater pulling force than will a long, and 

 more slender muscle. It is because of this that in buying 

 horses to draw heavy loads we look for large and heavy 

 muscles, while in roadsters we must attach importance 

 to the length of the muscles. 



281. Muscles of - the Hind-quarters. The most of 

 a horse's muscle is in the hind-quarters. This may be 

 a surprise to you, but the next time you have an oppor- 

 tunity to see a horse pulling a very heavy load, study 

 him carefully. You will be impressed with the idea 

 that most of the work is being done with the hind legs. 

 When the hind foot is moved forward the toe rests 

 on the ground, and the leg is bent at the hock joint; 

 if the toe does not slip, and the horse is strong enough 

 for his load, the muscles above, pulling on the tendon 

 fastened to the back and upper point of the hock", will 

 close the joint, or, in other words, straighten the legs, 

 and cause the body to move forward. It is by the per- 

 formance of this act at every step that the horse moves, 

 although, of course, the strain on all the parts is much 

 greater when pulling very hard. This will also show the 

 necessity of having large, broad, straight joints, and 

 legs that give the horse the most secure footing. You 

 have probably also noticed when driving that many 



