12 



and other incompletely oxidized nitrogenous bodies excreted in the 

 urine. There is this difference, however, the furnace would have 

 completed the combustion of the partly burned bits of coal if they had 

 not been shaken out with the ashes, while the body can not burn the 

 urea more completely. The body differs from a machine in a number 

 of important wa3^s; for instance, it is itself built up of the same mate- 

 rials which it utilizes as fuel, and further, if an excess of fuel, i. e., 

 food, is supplied, it may be stored as a reserve material for future use, 

 generally in the form of fat or gh'cogen. 



The amount of work performed by a horse, for convenience in meas- 

 urement, may be resolved into several factors, as follows: (1) The 

 energy expended in chewing, swallowing, and digesting food, keeping 

 up the beating of the heart, circulation of the blood, respirator}^ move- 

 ments, and other vital processes;" (2) the energy which is expended 

 in moving the body, walking, trotting, etc., which is usually spoken of 

 as energy required for forward progression; and (3) the energy which 

 is expended in carrying a rider, as in the case of a saddle horse, or 

 drawing a load, as in the case of a draft animal or carriage horse. 



The character of the road, whether level or up or dovn hill, is an 

 important factor in determining the amount of work. It is evident 

 that more energy is required to lift the body at each step and move it 

 forward when climbing an incline than when walking on a level. In 

 the same wa^^, when a load is drawn uphill it must be raised as well 

 as drawn forward. 



Work may be measured as foot-pounds or foot-tons, or bj^ an}- other 

 convenient unit. A foot-pound is the amount of energv expended in 

 raising 1 pound 1 foot; a foot-ton, that expended in raising 1 ton 1 

 foot; a commonly used unit of force is the "ton power," equivalent 

 to 650 foot-pounds per second. Work may also be measured in terms 

 of heat, i. e., calories. This is especially convenient in discussing 

 problems of nutrition, since the heat of combustion is one of the factors 

 usually determined or calculated when foods are analyzed; and further- 

 more, the feeding standards which have been proposed for horses and 

 other farm animals show the requirements per day in terms of nutri- 

 ents and energy. One calorie corresponds, as stated above, very 

 nearly to 1.54 foot-tons. 



COMPOSITION OF FEEDING STUFFS. 



The feeding stuffs of most importance for horses are cereal grains, 

 such as oats and corn, either ground or unground; leguminous seeds, 

 as beans and peas; cakes, and other commercial by-products, as oil- 



« The heat of the body is closely connected with this kind of work, and may be 

 derived either from the combustion of material directly for that purpose, or may be 

 the result of the energy liberated when internal muscular work is performed, or 

 may be due to both causes acting together. 



