THE ANATOMY OF THE HORSE 5? 



is called the gamb of the leg, and are partly attached at the 

 point of the hock, the other part passing down to the fetlock 

 joint through a loop, or sheath, along the back part of the 

 pastern bones, and are attached to the os pedis, or foot bone. 

 This muscle, from the hock down, forms one of the back 

 tendons of the hind leg. Another important muscle is found 

 passing down underneath those already mentioned, through 

 a loop, or sheath, at the back part of the hock, where it is 

 supplied with a synovia sack. This is a point of importance, 

 because when it becomes strained it is the seat of what is 

 called thoroughpin. It then passes down the back part of 

 the shin bone beneath the other tendon already mentioned, 

 through the loop at the fetlock to the back part of the os 

 pedis or foot bone, where it is attached. The action of these 

 muscles are to flex or bend the fetlock and raise the hock 

 joint in traveling. 



8. Involuntary Muscles, or muscles not under the control 

 of the will. The first to notice are those of breathing or 

 respiration. They form a group situated around the chest 

 in such a way as to be the means of increasing or decreasing 

 the size of the chest cavity. When these muscles expand 

 the chest cavity is enlarged, causing the air to rush into the 

 lungs, known as inspiration. On the other hand, when these 

 muscles contract the air is expelled from the lungs, known 

 as expiration. 



The diaphragm is a muscular curtain which separates 

 the chest from the abdominal cavity. It also assists greatly 

 in drawing the air in, when it contracts. This muscle also 

 assists in passing manure, and in the mare foaling. It sepa- 

 rates the heart and lungs from the bowels, liver and stomach. 

 This muscle should be carefully examined. It can be seen 

 by opening any dead animal. 



There is one muscle which is both voluntary and invol- 

 untary. It is situated in the penis, surrounding the urethra, 

 or the tube, which carries the urine from the bladder to the 

 penis in the male animal. Its action is voluntary while the 

 animal is passing urine, or water. It acts involuntary during 

 sexual intercourse, forcing the semen down through the 

 penis. 



