562 THE SCIENTIFIC MONTHLY
shopping I buy tea and cakes in order to get a chance to sit down for half an hour.
It is eTident that many of these factors mentioned above have no conceivable relation to my bodily requirement for food, which is deter- mined chiefly by my age and stature, the amount of muscular work I do, my general nervous and muscular tone^ my exposure to cold. Di- gestibility of food materials and conditions which favor good digestion are essential. Yet it appears that the importance of the enjoyment of food to secure favorable psychic influences upon digestion has been considerably overestimated^ since men forcing themselves for experi- mental purposes to live upon a diet so monotonous as to be repugnant in the extreme, digest it in normal fashion; and similar results usually obtain with forced feeding of animals.
Any condition of food materials causing them to resist digestion will reduce their availability, and in proportion to the delicacy, sensi- tiveness or robustness of the individual digestive mechanism. The nutritive value of bran biscuits, or of rich pastry, may be zero for some persons, though both protein and fuel values of these two articles are very high when they are fairly well digested and assimilated.
An important factor in determining the nutritive value of the dietary is due to a tendency frequently observed toward large use of manufactured '^ or commercially manipulated food materials, and to elaborate blending of these materials by the cook into rich and sweet desserts and other made dishes, which, though high in fuel value^ may very likely be lacking in some of the essential body constituents. Modern processes of food manufacture frequently result in the prepara- tion of highly concentrated food materials — sugars, starches, fats and oils, various dried preparations — whose functions, when they are taken into the human organism, alone or in artificial combinations, are specialized and limited, and whose effects upon the instincts of hunger and appetite may easily be out of all proportion to their useful func- tions; e. g., starch is isolated from the potato, from maize, from a dozen other sources; fat is isolated from milk as butter, from pork as lard, from the olive as oil. Sugar, a carbohydrate taken from sugar cane, beet or maple, is consumed in enormous and ever-increasing quanti- ties; a recent estimate by a federal authority places its daily consump- tion at one fourth of a pound per capita, for the well-to-do claases, which would cover 450 calories, or almost 20 per cent, of the total food requirement of the adult sedentary worker, and a larger propor- tion of the child's requirement. The obvious reason for its popularity is not that it is a concentrated form of body fuel, but that it has a pleasing effect upon the palate (very similar, it happens, to that of saccharin, which has no food value whatever) ; therefore it is mixed with a large number of other foods. I add a teaspoonful or two'* of
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