THE GENERAL .NATURE OF DIET 145 



ciently, and that if he chewed it more he would get from it much nutriment 

 which is now wasted. These more recent researches would tend to cut 

 down the average requirements of proteid 40 per cent., or even more. 

 It is believed by many physiologists, however, that to do this would so 

 decrease the working surplus, so to say, of the individual's food-income 

 that emergencies, such as illness, would be much more dangerous to a 

 person who had lived on this quantity of food . It remains to be seen, then, 

 by further research on a much larger scale and lasting a much longer 

 time how much food an average adult actually needs. Here as elsewhere 

 the relations are more widespread and more complicated than the experi- 

 mental conditions take account of. 



The Right Proportion of the Diet's Components is Important. The third 

 general requirement of diet is that its proximate principles should be in 

 nearly the proportion best suited to the organism's needs. In the average 

 published heretofore by these seven authorities recently mentioned, the 

 proteid was about 17 percent., the fat about 8.5 percent., and the carbo- 

 hydrate about 74 per cent., if we neglect the inorganic salts and the water. 

 The whole principle underlying the right proportion of proximate prin- 

 ciples in food is that an excess of one of them in the diet necessitates the 

 useless expense of energy to digest and absorb this excess. In general 

 terms, only milk and eggs contain the proximate principles in just the 

 right proportion. White bread perhaps approaches this condition next 

 best. Rice, for example, contains about one-third the ideal proportion of 

 nitrogen. The person who is compelled to live upon it continually, there- 

 fore, has to burden his digestive apparatus with a large excess of carbohy- 

 drate (almost wholly starch). In some South American tribes the diet 

 was formerly, at least, almost wholly meat. These people w^ould have to 

 eat a large excess of the flesh to get a sufficient amount of carbohydrate. 

 In the Arctic regions the diet, on the other hand, is largely fat, and 

 carbohydrate might often be lacking in a diet in this region. In order to 

 obtain these deficient proximate principles, an excess of the others must 

 be digested and absorbed, only to be excreted again unused. All of these 

 processes (mastication, deglutition, digestion, absorption, excretion, etc.) 

 use up many varied forms of energy which might be better employed. 



Variety in the Diet is Necessary. A fourth requirement of a proper 

 diet is that it should consist of a considerable variety of foods. This 

 exaction of Nature in its effects on the world's diet is not unlike the 

 preceding demand that the proportions of the alimentary components 

 should not depart too far from the composition of the consumer's body. 

 The ingestion of a large variety of foods in practice assures this right 

 proportion. But several other things involved in the matter of variety 

 are as yet unconsidered, and especially the preparation of food-materials 

 for being eaten by man. 



It is not enough that an animal's diet should contain both energizers 



and sources of tissue-replacement, or that it should consist of a sufficient 



quantity of the proximate principles of the animal tissues, even if nearly 



or quite in their proper proportions. Most of the brutes, to be sure, 



10 



