Chapter II: Physiological Determination of the Standard Ration, I.—: Physiology of Nourishment.

I. Physiology of nourishment; Atwater’s standard—II. French soldier’s diet falls below this. Assimilation of animal and vegetable food—III. Necessary standard for the French nation. Lagrange’s formula. Reduction of the population by one-fifth. Correctness of the formula. Reduction to a quarter. Thirty millions of daily rations in France.

Ten years ago the Office of Experiment Stations of the United States Department of Agriculture began, under the direction of Mr. A. E. True, a series of inquiries into the nutritive value of certain foods and their cost. These inquiries were superintended by Mr. W. O. Atwater, Professor of Chemistry at the Wesleyan University of Middletown, assisted by first-rate collaborators. His books on “The Principles of Nutrition and the Nutritive Value of Food” give the conditions of human nourishment which I briefly summarise.

The human body is composed of fifteen to twenty elements, among which the most important are water and mineral elements, e.g., phosphates of lime, the bone-forming substance. Then in the proportion of 18 per cent. to the weight of the average man come proteids, in two groups: (1) albuminous, e.g., such substances as white of egg, lean meat, casein of milk, gluten in wheat; (2) gelatinous, such as form the connecting tissues, the tendons, the skin, the periosteum of the bones. These constitute the human body; they are also fuel, for they are burned to create energy and transformed again into fat. Sugar and starch can both be stored up as fat in the body; fat forms 15 per cent. of the weight of an average man. Carbohydrates comprise sugar, starch, and cellulose, and are found most in milk, cereals, and potatoes, but they only form 1 per cent. of the tissues of the human body. Sugar and starch form a chief constituent of energy; they are readily transformed into fat. There are certain waste products, bones, fish-bones, eggshells, and fruit skins, which are not eatable. Food should (1) form new tissue and repair waste; (2) maintain bodily heat and supply energy for action. Thanks to the calorimeter, it is possible to measure in calories the amount of energy a man gives out. A calorie is the quantity of heat needed to raise the temperature of 2·2 lbs. of water 2·04° F.; transformed into mechanical power it is equivalent to about 930 foot-pounds. An adult man gives out about 2,400 calories in twenty-four hours; that is, 100 per hour. Moreover, he loses in various ways more than 147 cubic inches of water; and he exhales a quantity of carbonic acid containing 61-69 per cent. of oxygen and 23-26 per cent. of carbon: in all he gives off some 3,450 grains of the latter. In urine and fæces he loses some 330 grains of mineral salt, more than half being sea-salt. His food must, then, furnish the equivalent of this loss and, moreover, energy.

The following is Atwater’s table:—

Dr. Dunlop, from experiments made in Scotland, on prisoners employed eight hours a day at stone-breaking, found 3,700 calories to be necessary for an adult in moderately active work, and thus Atwater’s figures, far from being exaggerated, are probably rather below the mark.