362 TYPES AND MARKET CLASSES OF LIVE STOCK 



to the trunk but are connected by intervening muscles which 

 form a sort of sling which suspends the body between the two 

 fore legs. The muscle attaching the fore limb to the trunk is 

 called the serratus magnus. It is an enormous triangular muscle 

 which originates on the upper part of the internal surface of the 

 shoulder blade and spreads out like a fan on the sides of the 

 chest and neck and ends on the cervical vertebrae and first eight 

 or nine ribs. The drawing presented herewith shows a front 

 view of the muscular attachment of the scapula to the neck 

 and trunk. 



When the horse is standing, the base of support is rep- 

 resented by a rectangle the corners of which are the horse's 

 feet. In the walk, the base of support is triangular, for then 

 only three feet touch the ground. In the trot or pace, only 

 two feet touch the ground, and the base of support will be rep- 

 resented by a line. In the run or gallop, the base of support 

 is a point. Thus as speed increases there is a corresponding 

 decrease in stability. 



The horse in motion. We have seen that the horse iu 

 rather unstable because the center of weight lies almost over 

 the fore legs. Hence the fore legs answer the purpose simply 

 of a support to the horse's weight when he is in motion. If we 

 could replace the fore legs with a wheel, we would have an equally 

 efficient motor. 



When a man walks, he leans forward in order to throw 

 the center of his weight ahead of his base of support. This 

 causes him to begin to fall forward, and indeed he would fall 

 if he did not advance his foot and so bring his base of support 

 once more under, or nearly under, the center of weight. Walk- 

 ing is simply a succession of interrupted falls. The same is 

 true of the horse. In walking he pushes backward against the 

 ground with his hind feet and causes his center of weight to 

 tip forward. The result is that he begins to fall, and if he did 

 not advance a fore foot he would land on his head. By step- 

 ping forward he again assumes his equilibrium and immediately 

 tips his weight forward again by propelling with his hind legs. 

 Walking is simply the repetition of this performance over and 

 over again. 



In the trot and the gallop or run, there is the same backward 

 thrust with the hind feet and the same recovery with the fore feet, 

 but the thrust is much greater, the stride is longer, and the 

 shock and effort in the recovery are increased in proportion. 



