Total nitrogen content of the day’s food = 4.941 grams.

June 27.

Breakfast.—Coffee 112 grams, cream 22 grams, sugar 10 grams.

Lunch.—Roast lamb 9 grams, baked potato 90 grams, wheat gems 47 grams, butter 12 grams, iced tea 250 grams, sugar 25 grams, vanilla éclair 47 grams.

Dinner.—Lamb chop 32 grams, creamed potato 107 grams, asparagus 49 grams, bread 35 grams, butter 17 grams, lettuce-orange salad with mayonnaise dressing 150 grams, crackers 21 grams, cream cheese 12 grams, coffee 63 grams, sugar 9 grams.

Total nitrogen content of the day’s food = 5.486 grams.

It can be seen that there was nothing especially peculiar in these dietaries, aside from their simplicity, except that the quantities were small. Meat was not excluded; there was no approach to a cereal diet; there were no fads involved, nothing but simple moderation in the amounts of nitrogen-containing foods. Further, there was perfect freedom of choice; full latitude to consider personal likes and dislikes in the selection of foods; anything that appealed to the appetite could be eaten, with the simple restriction that the amount taken must be small. During the balance days, naturally, every article of food had to be carefully weighed and analyzed, which fact undoubtedly tended to limit in some degree the variety of foods chosen, since increase in the number of articles meant increased labor in analysis. Quite noticeable, however, was the extreme constancy in the nitrogen-content of the daily diet, even on those days when the food was not weighed. In other words, there had been gradually acquired a new habit of food consumption, and the individual, unconsciously perhaps, rarely overstepped the limits fixed by the new level of proteid metabolism. This is a fact that has been conspicuous in nearly all of our experiments, where freedom of choice in the taking of food has been followed; and is in harmony with the view that after a lower level of proteid metabolism has once been established, and the body has become accustomed to the new conditions, there is little tendency for any marked deviation from the new standards of food consumption.

With maintenance of body-weight, together with nitrogen equilibrium through all these months; and with health, strength, and mental and physical vigor unimpaired, there is certainly ground for the belief that the real needs of the body were as fully met by the lowered consumption of proteid food as by the quantities called for by the customary standards. Finally, it should be noted that this particular subject was small in weight, and hence did not need so much proteid as a man of heavier body-weight would require. In recognizing this principle, we may for future comparison calculate the nitrogen requirement of the body, on the basis of the present results, per kilo of body-weight. With the weight of the subject placed at 57 kilos, and with an average daily excretion of nitrogen amounting to practically 5.7 grams, it is plain that this individual was quite able to maintain a condition of equilibrium with a metabolism of 0.1 gram of nitrogen per kilo of body-weight. Translated into terms of proteid matter, this would mean a utilization by the body of 0.625 gram of proteid daily per kilo of body-weight. Regarding the fuel value of the daily food, we need not be more precise than to emphasize the fact that so far as could be determined, on the basis of chemical composition, the heat value of the food rarely exceeded 1900 calories per day. If we make a liberal allowance, for the sake of precaution, it would seem quite safe to say that this particular individual, under the conditions of life and bodily activity prevailing, did not apparently need of fuel value more than 2000 calories per day, which would correspond to 35 calories per kilo of body-weight.

Let us turn now to the second subject in this group, a man of 76 kilos body-weight, 32 years of age, and of strong physique. His active life in the laboratory called for greater physical exertion than the former subject, and consequently there was need for greater consumption of non-nitrogenous food, with the accompanying increase in fuel value of the day’s ration. As in the preceding case, there was no prescribing of food, but a gradual and voluntary diminution of proteid material. During the last seven months and a half of the experiment, the average daily excretion of nitrogen through the kidneys amounted to 6.53 grams, equivalent to a metabolism of 40.8 grams of proteid matter daily; a little more than one-third the minimal quantity called for by common usage. At first, the body-weight of the subject gradually fell until it reached 70 kilos, at which point it remained fairly constant during the last five months. That the quantity of food taken was quite sufficient to maintain the body in a condition of nitrogen equilibrium is apparent from the results of a comparison of income and outgo of nitrogen, as shown in the following table:

Output.

Nitrogen in
Food.

Nitrogen through
Kidneys.

Weight of Excre-
 ment (dry).

May 18

 8.668 grams. 6.06 grams.14 grams.

19

 6.474 7.1739

20

 6.691 6.3330
──

21

 8.345 6.7883 contain 6.06% N. = 5.03 grm. N.

22

 7.015 5.70. .

23

 9.726 5.7538

24

10.424 6.3957
──── ─────
95 contain 5.76% N. = 5.47 grm. N.
    ───
10.50 grm. N.
57.34344.18  +  10.50 grams nitrogen.
────────────────
57.343 grams N.    54.68 grams nitrogen.

Nitrogen balance for five days  =  +2.663 grams.

Nitrogen balance per day     =  +0.380 gram.