HYGIENIC ASPECTS OF NUTRITION 357 



machine. But sometimes when these natural guides become 

 intense enough to demand our attention the machine is 

 already in trouble and its efficiency impaired or threatened. 

 If a locomotive engineer did not supply his machine 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 difficulties have existed for 

 some time. Pain is usually a distress signal. The body as 

 ' a machine for using energy will give most efficient service 

 if it is treated 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. 



363. Thorough 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 many intestinal troubles are due 

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

 not readily digested in the stomach and intestine. 



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 carbohy- 

 drate (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. 



364. Heavy eating. Poor mastication of food is usually 

 associated with overeating. This may result partly from the 

 fact that pooriy masticated food does not readily produce a 

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

 tinues to eat until he has swallowed an amount of food 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 



