CHAPTER IV 



FOODS AS BUILDING MATERIALS FOR JACK'S HOUSE 

 THE PROTEIDS 



OUR bodies are made up chiefly of bone, muscle, 

 fat, blood, and nerves, with an outside covering of 

 skin. These are constantly wearing away, and must 

 be daily supplied by the food we eat. Besides, during 

 the first twenty or more years of our lives, enough 

 more good building material must be furnished to 

 produce healthful development and growth of the 

 various tissues and organs of the body. 



If we could use food to make up bodily waste 

 and supply necessary additions in the same way that 

 a builder uses lumber to repair the wall of a house or 

 stone to strengthen a cellar wall, but a little knowl- 

 edge of foods would be necessary. The conditions 

 are very different, however. Only certain compo- 

 nents of foods are helpful building materials. These 

 must be extracted and carried to the parts where 

 each is needed. The rest is waste which must be cast 

 out, as the carpenter throws aside the shavings and 

 ends that are cut off to make the parts fit properly 

 together. 



The components of foods that are useful to the 



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