ENERGY IN FEEDINGSTUFFS AND ITS USES 103 



as in case of the engine), which may be recovered in the form 

 of work. In experiments with men, it was found that 28 to 

 37 per cent of the net energy was recovered as work. Dogs 

 recovered 29 to 31 per cent, and horses 29 to 38 per cent. 

 In general, about one-third of the net energy may be re- 

 covered in the form of voluntary work, i.e. the coefficient 

 of utilization is about 33 per cent. Computed on the basis 

 of the gross energy of the ration, it is about 20 per cent. The 

 best steam engines have about the same coefficient of utili- 

 zation, while the average steam engine usually falls below 10 

 per cent. Good internal combustion engines range from 18 

 to 25 per cent. 



Heat Production. — All warm blooded animals, such as 

 man, the horse, cow, hog, etc., must maintain their body 

 temperature at a practically constant level. If there is 

 any considerable increase or decrease in the body tempera- 

 ture, the result is usually fatal to the animal. There is 

 always a certain amount of heat generated in the living 

 animal coming from the energy hberated in the work of the 

 vital processes, the so-called work of digestion, and any 

 voluntary muscular work done by the animal. Consequently 

 a certain amount of heat is always being given off by the 

 animal body by radiation and conduction. In mild weather 

 the heat generated in the ordinary functions of the body is 

 sufficient to maintain the body temperature. In fact, in 

 warm weather, or when the amount of heat hberated is 

 increased by excessive muscular work, the heat is generated 

 by the body more rapidly than it can be disposed of by con- 

 duction and radiation. In such instances the body reHeves 

 itself of the surplus heat by the evaporation of water or 

 perspiration from the surface of the body. In other words, 



