analyse the injesta or food consumed and compare it with the dejecta or excretions, until a quantity and kind of food is found which is just sufficient to keep the body in equilibrium.  This latter plan is the best, but to be quite satisfactory must be tried on a large number of suitable persons under varying conditions, both of quantity and kind of food.  Nearly all the experiments have been made on persons accustomed to a stimulating dietary:  their usual food has included a considerable quantity of flesh and alcoholic drinks.  Sufficient attention has not been paid to the dietaries of the more abstemious races who partake of little if any flesh food.  The standard daily dietary for a man of average weight, doing a moderate amount of work, is variously stated by the best authorities as proteids from 100 to 130 grammes, fat 35 to 125 grammes, and carbo-hydrates 450 to 550 grammes.  There is a surprising difference of opinion on the amount of fat, but those who give least fat give the largest quantity of carbo-hydrate and vice-versa.  Dr. R. Hutchison in “Food and Dietetics,” sums up the quantities given by the highest authorities as follows:—–­

Proteid 125 g. ( 4.4 oz.) x 4.1 = 512 cal. = 20 g.  N, 62 C
Carbo-hydrate 500 g. (17.6 oz.) 4.1 2050 200
Fat 50 g. ( 1.8 oz.) 9.3 465 38
              ----------------- ---- -------- -----
               675 g.(23.8 ) 3027 Total 20 g.  N, 300 C

The nutrient ratio is 1 :  4.9.  For scientific purposes, metrical weights and measures are used, instead of the inconvenient English grains, ounces, pounds, &c. (1 gramme = 15.43 grains; 1 ounce avoirdupois = 437.5 grains = 28.35 grammes).  A calorie is a measure of the power of a food in generating heat and muscular energy (these two being convertible).

The calories used in food tables are kilo-calories, representing the amount of heat which would raise a kilogramme (1000 grammes) of water 1 deg.  Centigrade.  This is the same as raising 1 pound weight 4 deg.  Fahrenheit.  According to the table given, 125 grammes of dry proteid are required per day; this contains 20 grammes of nitrogen and 62 of carbon.  When thoroughly consumed or utilised in the body, the heat or its equivalent in muscular work equals 512 kilo-calories.  Proteids have, of course, an additional value as tissue formers.  The factors used here, of 4.1 and 9.3, are those commonly employed; but the latest and most reliable research, taking account only of that part of the food which is actually available in the body, gives for proteid and carbo-hydrate 4 calories, and for fat 8.9 calories.