CHAPTER XX 

 HEALTH AND FOOD STANDARDS 



125. Conditions of health. The normal, healthy digestion and 

 absorption of food depend upon 



(1) the secretion of digestive juices by the glands ; 



(2) the fermentative action of the substances in these juices ; 



(3) the muscular contractions of the gullet, the stomach, and 

 the intestines. 



We can do nothing to control these processes directly, either 

 to hasten them or to stop them. But indirectly we can do a 

 great deal to control them. 



First of all, we can decide what to eat, Jioiv to eat, and 

 ^vheji to eat. 



Then we can decide for ourselves what kind of habits we 

 will have with regard to the behavior of the large intestine. 



And, finally, we can do a number of things that are not 

 directly connected with feeding, but that have important 

 bearings on the healthy behavior of the digestive system. 



All these controls come to us from a better understanding 

 of the biology of nutrition and digestion. 



126. What to eat. Since all living beings consist essentially 

 of proteins, fats, and carbohydrates, it would seem that almost 

 any plant or animal stuff would be suitable for food. But we 

 know from experience that some of these things are not 

 pleasant to the taste, or are even disagreeable, and that others 

 are poisonous. Some substances, while neither unpleasant nor 

 mjurious, contain so little usable or digestible material that they 

 are not worth eating. In the course of ages human customs 

 have selected the plant and animal materials in any given 

 region that are most valuable for food. We are all the time 



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