V. FOODS AND NUTRITION. 



One of the earliest sensations that a child experiences 

 is hunger or the desire for food. A child comes early to 

 recognize that this hunger is merely a way the body has 

 of telling us that it must have food at certain intervals. 

 Further experience teaches that this food must be of a 

 certain kind to enable the body to grow and maintain 

 itself in a state of health and activity. An examination 

 of other animals and of plants teaches that they too re- 

 quire food and that without food they die. 



The foods of the different plants and animals differ 

 greatly, however, and what supports life in one does not 

 necessarily answer the same purpose in another. For 

 example, the hay on which a horse feeds would be useless 

 to us, and the fertilizer and water on which a plant flour- 

 ishes would prove valueless to both the horse and our- 

 selves. How then shall we define food as a general term 

 which shall include all classes? Broadly, we may define 

 it as follows: Anything which an animal or plant takes 

 into its body as nourishment is food. Applying this defi- 

 nition to ourselves, food is anything which we eat or 

 drink that nourishes our body. The number of such 

 substances is very great. Chemists have analyzed all the 

 various forms of food, however, and have found that they 

 are composed of one or more of some six classes of com- 

 pounds. These compounds then are the structural units 

 of which all the varied forms of foods are built up. These 



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