4. =An Examination of Actual Dietaries= under various conditions has strikingly confirmed the results obtained by other methods. It has been found that (_a_) the _potential energy_ required by a healthy man weighing 11 stones, and doing a moderate amount of muscular work is 3,000 to 3,500 Calories (=310 grains); and that (_b_) about 20 grammes of nitrogen and 320 grammes (=4,960 grains) of carbon are excreted by such a man. (_c_) Expressing the 3,000 Calories required in terms of grammes of food, it is found that 125 grammes of proteid, 500 of carbohydrate and 50 of fat are necessary. These facts are expressed in the following table (Hutchison):— ┌──────────────┬──────────────────┬───────────────────┬───────────────┐ │ │STANDARD AMOUNT OF│ SAME AMOUNT OF │ │ │ │FOOD CONSTITUENTS │ FOOD IN TERMS OF │YIELDING ENERGY│ │ │REQUIRED ├─────────┬─────────┤ IN CALORIES. │ │ │(IN GRAMMES). │ CARBON. │NITROGEN.│ │ │ ├──────────────────┼─────────┼─────────┼───────────────┤ │_Proteid_ │ 125 │ 62 │ 20 │ 512·5 │ │_Fat_ │ 500 │ 200 │ ── │ 2050· │ │_Carbohydrate_│ 50 │ 38 │ ── │ 465· │ │ ├──────────────────┼─────────┼─────────┼───────────────┤ │ │ 675 │ 300 │ 20 │ 3027·5 │ └──────────────┴──────────────────┴─────────┴─────────┴───────────────┘ Three of the best known standard dietaries give the amounts in grammes of each food constituent as follows:── ┌──────────────┬─────────────┬─────────────┬─────────────┬────────────┐ │ │ PLAYFAIR. │ MOLESCHOTT. │ ATWATER. │ AVERAGE. │ │ ├─────────────┼─────────────┼─────────────┼────────────┤ │_Proteid_ │ 119 │ 130 │ 125 │ 125 │ │_Fat_ │ 51 │ 40 │ 125 │ 72 │ │_Carbohydrate_│ 531 │ 550 │ 450 │ 510 │ ├──────────────├─────────────┼─────────────┼─────────────┼────────────┤ │Calories │ 3140 │ 3160 │ 3520 │ 3273 │ └──────────────┴─────────────┴─────────────┴─────────────┴────────────┘ Expressing the same facts in English ounces instead of grammes, 4-2∕5 oz. of proteid, 2½ oz. of fat, and 18 oz. of carbohydrate, would represent the ounces of each constituent required according to