70 



THE HORSE IN MOTION. 



the neck. From this it follows that the horse, in speeding, should be 

 allowed to follow its instinct in fixing the position of the head. The 

 ally of this muscle is the superficial pectoral, which has its insertion 

 on the anterior extremity and lower margin of the sternum, or breast- 

 bone. The course of its fibres is backward, downward, and outward ; 

 they divide into two branches : one is inserted into the anterior ridge 

 of the humerus, along with the mastoido humeralis ; the other is 

 spread out on the fascia of the inner face of the leg. The action of 

 this muscle is to carry the whole limb forward, in common with the 

 last described, and at the same time to adduct it to counteract the 

 abduction of that muscle. 



The action of these two sets of muscles is so unlike any other that 

 it is not readily understood. Let us suppose a man propelling a boat 

 through the water by means of an oar, and the handle end of the oar 

 made fast to the side of the boat opposite to that on which he is 

 seated, but free to move about a pin ; then let the man remove the 

 rowlock from its place and substitute for it his hands ; next make fast 

 the blade of the oar in the water, and the man shall then apply his 

 strength to the oar: the boat will move. Now, if this illustration be 

 modified so that the oar shall be vertical, and the blade of the oar be fixed 

 to the bottom, and the handle to a fixture above the man's head, the 

 similitude will be complete. Of course the nearer the power is applied 

 to the foot, or fulcrum, the faster the upper end will move, but the 

 greater must be the expenditure of power. There is another muscle, 

 acting from without upon the shoulder, whose office has been doubtful, 

 the small pectoral. It arises from the keel of the sternum, or breast- 

 bone, and passing between the shoulder and the neck, fills the angular 

 space in front of the scapula. It is thick below, where it is turned over 

 the breast, and becomes smaller as it is reflected on the scapula, tri- 

 angular in form, to fit the space it fills, and is the muscle against which 

 the collar rests ; this is a muscle of considerable power, being two and 

 a half pounds in weight. It is attached to the muscles of the scapula 

 by strong cellular tissue, and to the strong aponeurosis that covers it. 

 Besides being an element of beauty, by giving graceful contour to the 

 parts, it seems to have no other function than to pull forward the w hole 



