3^0 NAVIN ON THE HOESE. 



The postea spinatus fills the space behind the ridge of the 

 outer side of the shoulder-blade, to which it is fastened, and 

 extends downward, to be attached to the upper and outer part 

 of the humerus and to the capsular ligament of the shoulder- 

 joint. Its action is to assist in drawing the humerus, or upper 

 arm-bone, upward and backward. ^ . . .i i n .f 



These two muscles make up the prmcipal part of the bulk ot 

 the side of the shoulder, at the upper part. They are the seat 

 of the disease called siveemj. It is a wasting away, or atrophy, 

 of these muscles, or either of them. t^ • + 



The teres major lies behind the last-named muscle. It is at- 

 tached to the back part of the shoulder-blade and ribs, and ex- 

 tends downward, and is attached to the upper arm-bone, or 

 humerus. Its action is to flex this bone and turn it inward 

 Other muscles of this region, concerned in the backward and 

 forward motion of the upper arm-bone, or humerus, might be 

 studied with interest; but it does not suit our purpose to take 

 space to explain them. But every horseman should l^^^e their 

 proper shape, size, and locality well fixed in his mmd. Much 

 •of the animal's usefulness depends on these muscles. _ 



The next important group of muscles to be noticed are 

 :those chiefly concerned in the motions of that part of the 

 limb commonly called the arm, and the parts of the leg below 

 it These muscles consist of three groups. The first group 

 consists of four muscles, lying in front of the arm, and their 

 use is to extend, or straighten, the diflln-cnt parts of the limb 

 to which their long tendons are attached. They are cal ed 

 ■extensor muscles, and their tendons extensor tendons, bc- 

 •cause they act to extend, or straighten, the limb. 



The next o-roup lie at the outer side of the arm, and are also 

 •four in nunrber. Their office is to eff"ect the drawing up and 

 backward motion of the diflercnt parts to which they are at- 

 tached by their long tendons. They are called flexor mus- 

 -cles, and their tendons ftexor tendons, because they act to 

 :flex, or draw up, the leg. 



