NUTRITION. 475 



The proper diet must necessarily vary, at least as to 

 amount, with the work done; whether it should vary in kind 

 with the nature of the work is not so certain. Provided a 

 man gets enough proteids to balance those lost in the wear 

 and tear of his tissues, it probably matters little whether he 

 gets for oxidation and the liberation of energy either fats or 

 carbohydrates, or even excess of proteids themselves; any one 

 of the three will allow him to work either his brain or his 

 muscles, and to maintain his temperature. Proteids, how- 

 ever, are wasteful foods for mere energy-yielding purposes: 

 in the first place, they are more costly than the others; 

 secondly, they are incompletely oxidized in the Body; and, 

 thirdly, it is probably more laborious to the system to get rid 

 of urea than of the carbon dioxide $nd water, which alone 

 are yielded by the oxidation of fats and carbohydrates. Be- 

 tween fats and carbohydrates similar considerations lead to 

 a use of the latter when practicable: starch is more easily 

 utilized in the Body than fats, as shown by the manner in 

 which it protects the latter from oxidation; and a given 

 weight of starch fully oxidized in the Body will liberate 

 about one half as much energy as the same amount of butter, 

 while it costs considerably less than half the money. Also, 

 starch is more easily digested than fats by most persons: 

 children especially are apt to be fond of starchy or saccharine 

 foods and to loathe fats; and the appetite in ouch cases is 

 a good guide. As a rule the people of the United States 

 differ very markedly from the English in their love of sweet 

 foods of all kinds; whether this is correlated with their char- 

 acteristic activity, calling for some food that can be rapidly 

 used, is an interesting question. 



It is certain that no general rules for the best dietary 

 for all persons can be formulated, but on broad principles 

 the best diet is that which contains just the amount of pro- 

 teid necessary for tissue repair, and so much carbohydrates 

 as can be well digested; the balance needed, if any, being 

 made up by fats and platinoids. Such a food would be 

 the cheapest; that is, the supplying of it would call for less 

 of the time and energy of the nation using it, and leave more 

 work to spare for other pursuits than food production for 

 all the arts which make life agreeable and worth living, and 

 which elevate civilized man above the merely material life of 

 the savage whose time is devoted to catching and eating. 



