368 Ts^AYIX ON THE HOESE. 



ribs, and to the rump and haunch-bones. Other of these 

 muscles are the sj)uiaUs dorsi, beneath the longisshnus dor si, 

 in the region of the withers. It assists in forming the bulk 

 of the withers, and to raise the neck. The semi-s])inalis 

 dorsi lies back along the loins squarely. It assists the others. 



Another great muscle of the loins is the psoas magnus. It 

 forms the bulk of the inner part of the loins. It extends from 

 the last ribs backward, attaching to all the vertebra? it passes, 

 and is inserted into the upper and front part of the upper 

 thigh-bone, or femur. It acts to draw up the haunch. There 

 are several other muscles of this region, but they are only 

 helpers of the others, generally. 



The muscles of the chest are generally of considerable length, 

 and somewhat broad. They are attached to the back-bone, or 

 spine, above, and to the shoulder-blade, humerus, ribs, and 

 breast-bone below. Their office, as a class, is to complete the 

 walls of the chest, and to expand it in the act of breathing, 

 and, especially, to move the shoulder-blade and upper arm- 

 bone, or humerus. Some of them deserve particular mention. 



The trajyezius starts from some of the high projections, or 

 spines of the dorsal vertebra?, the third, fourth, fifth, and sixth 

 and descends down the side of the withers, and terminates in 

 a point which is fastened to the high ridge on the outside of the 

 shoulder-blade. It serves to draw this bone up and backward. 



The latlssimus dorsi arises from the bones along the withers, 

 and as far back as the small of the back, and passes downward 

 and forward, and is attached to the back part of the humerus, 

 or lower shoulder-bone. Its use is to draw this bone up, or 

 flex it. It is a very powerful muscle, and, in the well-formed 

 horse, acts with great mechanical advantage. 



The most important muscle of this part is the serratus mag- 

 nus, or great saw-muscle. It is found between the shoulder and 

 side of the chest. It arises from the side projections of the 

 last four bones of the neck, and from the lower portion of the 

 first ei'f'ht ribs, and i;asses up between the rib and shoulder- 



