METABOLISM, NUTRITION AND DIETETICS 479 



plainest food which will suffice to maintain the prisoners in health 

 A 'hard work' prison diet in Munich was found to contain 104 

 grammes proteids, 38 grammes fat, and 521 grammes carbo-hydrates ; 

 a 'no work' diet, only 87 grammes proteids, 22 grammes fat, and 

 305 grammes carbo-hydrates. Here we recognise the influence of 

 price; carbon can be much more cheaply obtained in vegetable 

 carbo-hydrates than in animal fats ; the cheapest possible diet contains 

 a minimum of fat and proteids. 



Many poor persons live on a diet which would not maintain a 

 strong man, for an emaciated body has a smaller mass of flesh to 

 keep up, and therefore needs less proteid ; it can do little work, and 

 therefore needs less food of all kinds. A London needlewoman, 

 according to Playfair, subsists, or did subsist, thirty years ago, on 

 54 grammes proteid, 29 grammes fat, and 292 grammes carbo- 

 hydrates. But this is the irreducible minimum of the deepest 

 poverty ; and a woman, with a smaller mass of flesh and leading 

 a less active life than a man, requires less food of all sorts. Even 

 the Trappist monk, who has reduced asceticism to a science, and, 

 instead of eating in order to live, lives in order not to eat, consumes, 

 according to Voit, 68 grammes proteid, n grammes fat, and 469 

 grammes carbo-hydrates; but manual labour is a part of the dis- 

 cipline of the brotherhood, and this must be still above the lowest 

 subsistence diet. 



A growing child needs far more food than its weight alone would 

 indicate ; for, in the first place, its income must exceed its expendi- 

 ture so that it may grow ; and, in the second place, the expenditure 

 of an organism is pretty nearly proportional, not to its mass, but to 

 its surface. Now, speaking roughly, the cube of the surface of an 

 animal varies as the square of the mass ; when the weight is doubled, 

 the surface only becomes 3 v / " r > or one and a half times as great. 

 The surface of a boy of six to nine years, with a body-weight of 

 1 8 to 24 kilos, is two-fifths to one-half that of a man of 70 kilos; 

 and he should have about half as much food as the man say, 70 

 grammes proteids, 40 grammes fat, and 200 grammes carbo-hydrates. 

 A child of four months, weighing 5 -3 kilos, consumed per diem food 

 containing '6 gramme nitrogen per kilo of body-weight, or 3*18 

 grammes nitrogen altogether, as against a daily consumption of only 

 275 gramme nitrogen per kilo in a man of 71 kilos (Voit) (p. 512). 



An infant for the first seven months should have nothing except 

 milk. Up to this age vegetable food is unsuited to it ; it is a purely 

 carnivorous animal. By careful observations on the amount of 

 carbon dioxide and nitrogen excreted by a child nine weeks old, fed 

 exclusively on its mother's milk, it has been shown that the absorp- 

 tion and assimilation of milk in the infant is very complete, over 91 

 per cent, of the total energy being utilized ; while an adult, taking 

 as much milk as is necessary for the maintenance of nitrogenous 

 equilibrium, does not utilize at most more than 84 per cent. Human 

 milk contains about 2 per cent, of proteid (mainly caseinogen), 

 3 per cent, of fat, 5 or 6 per cent, of carbo-hydrate (lactose or milk- 

 sugar), and from '2 to -3 per cent, of salts. Cow's milk contains 



