HYGIENIC ASPECTS OF NUTRITION 263 



We have such natural appetites as hunger and thirst, and such 

 pains as headache and stomach ache, which tell us superficially 

 about the needs of the human machine. But sometimes, when 

 these natural guides become intense enough to demand our 

 attention, the machine is already in trouble, and its efficiency 

 is impaired or threatened. If a locomotive engineer did not 

 supply his engine with water until the boiler was nearly 

 empty, it would then be dangerous to add the water. In the 

 human body severe pain is ordinarily an evidence that diffi- 

 culties have existed for some time. Pain is usually a distress 

 signal. The most efficient use of the body as a machine for 

 using energy is to be had by treating it in such a way that it 

 is neither overfed nor underfed, and that the food is in the 

 best condition for use by the human machine. 



289. Prolonged mastication. In the preceding chapter some 

 of the reasons for mastication were stated. Indigestion may be 

 caused by improper mastication, and some students of the 

 human machine believe that nearly all the intestinal troubles 

 are due directly or indirectly to this cause. Large pieces of 

 food are not readily digested in the stomach and intestine. 

 Therefore they should be broken into extremely small pieces 

 while in the mouth. 



While the food is being broken into small pieces in the 

 mouth the saliva is mixed with it and makes it partially or 

 wholly liquid, thus facilitating its digestion by other digestive 

 secretions. Furthermore, so much of our food is carbohydrate 

 (starch, sugar, etc.) and is digested by the saliva that the 

 importance of thorough mastication is easily seen. If fruits, 

 bread, pastries, candy, etc. were kept in the mouth and 

 thoroughly mixed with saliva before swallowing, there would 

 be fewer cases of indigestion. 



290. Heavy eating. Poor mastication of food is usually 

 associated with overeating. This may result partly from the 

 fact that poorly masticated food does not readily produce a 

 feeling of satisfaction. Since this is true, a rapid eater continues 



