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FOODS 



elaborated organs within him to do that careful and. complicated select- 

 ing which he could not do otherwise than through them if he would. 

 The day has long gone by, for example, when physiology could say to a 

 brain worker, "Eat more fish than muscle-workers eat, for fish contains 

 phosphorus, which your brain, consuming phosphorus, needs." Science 

 today would say, rather, "If the brain needs phosphorus, you may be 

 sure that the brain-bioplasm knows how to absorb it from the general 

 store of food circulating so rapidly and constantly through it." And this 

 is the principle all through the average conditions of average animals. 

 Voluntary selection of foods extends only to the right quantity of a mix- 

 ture of proteids, fats, carbohydrates, salts, and water suitably prepared 

 for being eaten. Trained protoplasm automatically does the rest. 



There are, however, at least five conditions common to animals which 

 do require more or less qualitative adaptation of diet to their respective 

 needs. These conditions are infancy, pregnancy and lactation, senility, 

 idiosyncrasy, and a few special forms of disease. Three of these, the 

 first three, are physiological, one, the last, pathological, and the other is 

 as yet undetermined, whether normal or abnormal. Let us consider these 

 in turn, so far as their discussion properly forms a part of a general 

 treatise on physiology. The last condition, disease, however, is largely 

 outside our present province. 



INFANCY. The feeding of infants is a matter which only in very recent 

 years is beginning to receive the careful attention it deserves. Few sub- 

 jects are more vital to society. In America and Europe, on the average, 

 nearly one-third of all children born die before before they are five years 

 old, and largely from disease more or less dependent on improper or 

 inadequate food. The infant during the first seven or eight months of 

 its extra-uterine life needs nothing but milk. The comparative compo- 

 sitions of ten kinds of milk are given in this table : 



PERCENTAL COMPOSITIONS OF VARIOUS SORTS OF MILK (Konig). 



Human milk contains 2.3 per cent, of proteid, 3.8 per cent, of fat, and 

 6.2 per cent, of carbohydrate, almost wholly lactose or milk-sugar, while 

 cows' milk has about 3.5 per cent, proteid 3.7 per cent, fat, and only 4.9 

 per cent, sugar. The inorganic salts and water are practically the same 

 in both. When necessity compels an infant to be "brought up on the 



