The Story -Book of the Fields 



the animal will die. In this respect the 

 animal may be compared to a very perfect 

 machine set in motion by heat. It feeds 

 and breathes in order to produce heat and 

 motion ; it eats the fuel in the form of food 

 and burns it in its body by means of the air 

 supplied by respiration. 



That is why the need of food is felt more 

 keenly in winter. The body becomes colder 

 by contact with the cold air outside, so we 

 must burn more fuel to keep the natural 

 heat at the same level. A cold temperature 

 excites the need of eating, and a high tempera- 

 ture reduces it. The hungry stomachs of 

 the northern nations need strong meat, fat 

 or lard ; the tribes of the Sahara are satisfied 

 with three or four dates in the day, with a 

 pinch of flour kneaded in the palm of the 

 hand. Everything which diminishes the 

 waste of heat also diminishes the need of food. 

 Sleep, rest, warm garments all assist our 

 food to keep up the natural heat, and to a 

 certain extent they take its place. Popular 

 common-sense repeats this in the saying, 

 " He who sleeps, dines." 



The materials which the air burns within 

 us are provided by the very substance of our 

 body, that is to say, by the blood into which 



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