CHAPTER VII. 



DIGESTION. 

 FOOD AND COOKING. 



THUS far we have been studying processes by which the 

 body's weight is reduced. We have studied the oxidation 

 in the tissues and the removal of the wastes. Unless the 

 tissues receive a corresponding supply, the heat and energy 

 of the body cannot long be maintained. 



All substances that go to make up the tissues or produce 

 energy are Foods. Certain substances that do not become 

 part of any tissues, nor in themselves produce energy, are 

 useful in aiding the processes going on in the body. These 

 may be called Accessory Foods, e.g., condiments ; some acces- 

 sory foods, such as coffee, seem to retard the waste of tissues. 



Poods and Foodstuffs. Most of our articles of food 

 consist of two or more different kinds of materials. For in- 

 stance, milk consists (1) chiefly of water ; in this are (2) the 

 substance that makes cheese (casein) ; (3) cream, from which 

 we get butter (fat) ; (4) sugar, which gives milk a sweet taste , 

 (5) salts, such as common salt, lime salts, etc. These differ- 

 ent materials are Foodstuffs. We have many kinds of foods 

 but few foodstuffs, which we find occurring over and over 

 again, in various forms, in the numerous things we eat. 



Foodstuffs are also called "alimentary principles," " nutri- 

 tive principles," "proximate principles," " food substances," etc. 



The foodstuffs are classified into : 



1. Proteids (example, casein). 



2. Fats. 



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