2t>4 ELEMENTS OF GENERAL SCIENCE 



to eat until he has swallowed an amount of food much in 

 excess of what he would have desired if he had masticated 

 thoroughly and satisfied his hunger in a proper way. Not only 

 is this extra quantity of food present in the digestive system, 

 but the starchy foods which should have been digested, in part 

 at least, in the mouth add an extra burden to the work of the 

 starch-digesting element of the pancreatic secretion ; even here 

 they may not be thoroughly digested and so may not all be 

 used in the nutrition of the body. One is in no danger of 

 being too thorough in the mastication of his food. 



291. Variety of food. If one were to eat nothing but carbo- 

 hydrate food, he would throw the work of digestion upon the 

 saliva and the starch-digesting element of the pancreatic secre- 

 tion. Similarly, if he were to eat mostly protein food, as meats 

 and eggs, an overburden of work would be thrown upon other 

 elements of the pancreatic secretion. There are more important 

 reasons for a mixed diet, and these reasons lie in the needs of 

 the body. It is generally supposed that the protein foods are 

 the ones that are used in building up tissues, and that fats and 

 carbohydrates are used chiefly as more direct sources of energy. 

 All three kinds of food are needed, and something like a proper 

 balance between them should be maintained. The appetite may 

 serve as a partial guide to the kind of food needed, but it is 

 not fully to be trusted, partly because we are often uncertain 

 concerning the exact kind of food we are hungry for, and 

 partly because our habits of eating often cultivate appetites 

 that may not call for exactly what we need. 



It is generally stated that from 100 to 125 grams (about 

 4 ounces) of protein food per day is needed for a man who is 

 engaged in active work, but it has been proved that people 

 may work well and without discomfort upon less protein. 

 Professor Chittenden of Yale University performed a series 

 of carefully planned tests upon people engaged in various 

 kinds of work soldiers, teachers, and athletes and found 

 that they worked well for five months (the period of the 



