254 



Agricultural Chemistry. 



culated that the power exerted daily by the heart of a man 150 Ibs. 

 in weight, would raise 1 ton to a height of 242 feet. Then in ad- 

 dition, there is always some work done in moving the body from 

 place to place. A horse of 1100 pounds weight, walking 20 miles 

 on level ground, and without a load, will do work equivalent to 

 raising 2328 tons 1 foot. The internal work finally appears 

 largely as heat, while in the external movements of the body, 

 probably 70 per cent of the total energy developed in the muscles 

 appears as heat. 



The smaller the animal the greater the loss of heat per unit of 

 weight, and consequently the more liberal must be the supply of 

 food. This is because small bodies have in proportion to their 

 weight, a much greater surface. Thus, heat is lost by radiation 

 from the surface of the body and in evaporating the water ex- 

 haled through the lungs and skin. 



In the following table the heat production in resting animals 

 is given: 



Heat Production in Resting Animals. 



This shows that animals will produce heat in proportion to 

 their surface ; it is interesting to note that in the standard rations 

 for animals, the quantity of food increases at nearly the same 

 ratio as the surface increases. For example, while the oxen in 

 growing from a weight of 165 to 935 pounds increases in weight 

 5.7 times, the surface of the animal increases but 3.2 times and 

 the food required, 3.5 times. 



