FOODS 



53 



Foods. Another resource of our environment is food. 

 We know that when we are hungry we eat, but we cannot 

 tell why, nor can we tell what the foods do for us. This 

 will be the subject of a later lesson. All we need to know 

 now is that these foods which are taken into our bodies 

 may be used for two purposes, to build more body material, 

 and to release energy or work power in the body. We grow 



up to about the age of twenty, and may increase in weight 

 after that, but it is not easy for us to realize that the 

 food we take into our bodies must actually be oxidized or 

 burned in order to release energy or work. But if we think 

 back to one of our former experiments, this is not so diffi- 

 cult to understand. You remember that when limewater 

 turned milky, it was a test that carbon dioxide had been 

 released, or that something containing the element carbon 

 had been oxidized. If we expel air from our lungs into a 

 jar of limewater we notice that in a very short time the 



