50 JUDGING FARM ANIMALS 



crum is the joint, and the weight is the foot which is being 

 lifted. 



The lever of the second class is commonly illustrated 

 by the wheelbarrow. The fulcrum is where the wheel rests 

 on the ground, the barrow is the weight, and the arms of 

 the person ■ lifting the handles provide the power. An 

 example of the lever of the second class in the horse, is to 

 be found in the hind leg, in moving the body forward. 

 Here the power is conveyed through the short leg bone, 

 the tibia ; the fulcrum is the point of the foot at the ground, 

 and the weight is at the hock joint. 



The lever of the third class is seen in the man fishing 

 with a rod. The fulcrum is the end of the handle next the 

 body, the power is where the hand holds the rod and the 

 weight is in the fish at the end of the line. The lower jaw 

 of the horse illustrates this leverage. The fulcrum is at 

 the point where the lower jaw is attached to the upper, the 

 power is at the center of the jaw bone, and the weight at 

 the front teeth. Referring to the relations between the 

 power and weight in levers, Hayes says : ^ " The farther 

 the power is from the fulcrum, the greater will be the 

 mechanical advantage at which it will act ; and vice versa. 

 Thus, if one arm of a see-saw is longer than the other, a 

 comparatively light weight at the end of the former will 

 counterbalance a heavy one at the extremity of the latter. 

 Also, the longer an oar is inboard, as in an outrigger, the 

 greater will be the power which a rower will have. If we 

 apply this principle to the horse, we shall see that the longer 

 is the OS calcis, the greater will be the mechanical ad- 

 vantage at which the muscles of the gaskin will act in kick- 

 ing or propelling the body forward." Hayes further calls 

 attention to the fact that the nearer a force is at right 

 angles with its lever, the greater will be the mechanical 

 advantage. Making a concrete application of this he says : 

 "Acting on the principle just enunciated, the cart horse, 

 with the view of obtaining the utmost mechanical ad- 



'The Points of the Horse. M. H. Hayes, London, 3d Am. ed., 1904, p. 57. 



