446 THE HUMAN BODY. 



Persons who fatten cattle for the butcher find that the 

 foods useful for the purpose all contain proteids, carbohy- 

 drates, and fats, and that rapid fattening is only obtained 

 with foods containing a good deal of fat; as oilcake, milk,, 

 or Indian corn. Taking all the facts into account we shall 

 probably not be wrong in concluding that nearly all the 

 bodily fat is manufactured either from fats or proteids; 

 from fats easier than from anything else, but when much 

 proteid is eaten some is made from it also. * Carbohydrates 

 alone do not fatten; the animal body cannot make its pal- 

 matin, etc. , out of them. Nevertheless they are, indirectly, 

 important fattening foods when given with others, since, 

 being oxidized instead of it, they protect the fat formed. 



Dietetics. That " one man's meat may be another 

 man's poison" is a familiar saying, and one that, no doubt, 

 expresses a certain amount of truth; but the difference 

 probably depends on the varying digestive powers of indi- 

 viduals rather than on peculiarities in their laws of cell 

 nutrition: we all need about the same amount of proteids,. 

 fats, and carbohydrates for each kilogram of body weight; 

 but all of us cannot digest the same varieties of them equally 

 well : it is also a matter of common experience that some 

 foods have peculiar, almost poisonous, effects on certain 

 persons. Many people are made ill by mutton, which the 

 majority digest better than beef. 



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 car- 

 bohydrates, 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, however, are 

 wasteful foods for mere energy-yield ing 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 and water, which alone are yielded by 



