It is plain from the foregoing results, that all the men of this group, like the members of the professional group, experienced no difficulty in reducing in large measure their rate of proteid metabolism. The intake of proteid food was steadily diminished, with a corresponding diminution in the extent of nitrogen metabolism. Take as an illustration the average daily output of nitrogen from April 13 to June 15, a period of sixty-three consecutive days:
AVERAGE DAILY EXCRETION OF METABOLIZED NITROGEN FOR THE LAST TWO MONTHS OF THE EXPERIMENT.
| grams | ||||
|---|---|---|---|---|
| G. W. Anderson | 8.81 | ⎫ | Grand average for this period = 8.81 grams of nitrogen per day. | |
| W. L. Anderson | 10.07 | ⎪ | ||
| H. S. Bellis | 8.45 | [42] | ⎪ | |
| W. H. Callahan | 9.52 | ⎬ | ||
| M. Donahue | 7.39 | ⎪ | ||
| C. S. Jacobus | 7.43 | ⎪ | ||
| H. R. Schenker | 9.82 | ⎪ | ||
| John Stapleton | 9.00 | ⎭ |
An excretion of 8.81 grams of nitrogen through the kidneys corresponds to the metabolism of 55 grams of proteid matter. Compare this average amount of proteid matter metabolized each day with the figures obtained during the preliminary period of ten days, when the men were living on their ordinary diet. Then, many of the men were excreting nitrogen at the rate of 17 to 22 grams per day. In a general way, we may safely say that all these men during the last two months of the experiment were living on about one-half the proteid food they were formerly accustomed to take.
Further, the average daily excretion of nitrogen for the preceding seventy-three days, i. e., from February 1 to April 13, was in most instances nearly, if not quite, as low as during the last two months of the experiment, so that we are certainly justified in the statement that these men—trained athletes, doing athletic work more or less strenuous—were able to practise during this long period marked physiological economy in the use of proteid food, equal approximately at least to a saving of full fifty per cent in proteid matter.
The individual tables must be carefully studied, however, in order to trace out the changes in detail in the rate of nitrogen metabolism, and in so doing much information will be obtained regarding modification in the excretion of uric acid, a matter to be discussed in another connection, later on. Further, it is interesting to note in the tables the changes in body-weight of the men. Some of the men, like Dr. Callahan, who were abundantly supplied with adipose tissue, lost very considerably in body-weight, but eventually came to a standstill, with establishment of body equilibrium, under the changed dietary habits. Some of the men reached this condition of equilibrium much more quickly than others. Dr. Callahan who suffered a large loss in body-weight—to his great gain, as he expressed it—dropped from 92.2 kilos to 83 kilos in two months, but from March 22 to June 15 his body-weight, while naturally showing fluctuation, did not fall again permanently.
What now was the amount of metabolized nitrogen per kilo of body-weight in these men toward the close of the experiment? Taking the average daily nitrogen excretion for the period from April 13 to June 15, and the body-weights of the men at this same period, as indicated in the accompanying table, we have the following figures:
| Body- weight. | Average daily Nitrogen excreted. | Metabolized Nitrogen per kilo of body-weight. | |
|---|---|---|---|
| kilos | grams | gram | |
| Bellis | 78 | 8.45 | 0.108 |
| Callahan | 83 | 9.52 | 0.114 |
| Donahue | 62 | 7.39 | 0.119 |
| Stapleton | 75 | 9.00 | 0.120 |
| Anderson, G. W. | 71 | 8.81 | 0.124 |
| Jacobus | 56 | 7.43 | 0.132 |
| Schenker | 73 | 9.82 | 0.134 |
| Anderson, W. L. | 61 | 10.07 | 0.165 |
These figures, with one exception, show as low a proteid metabolism per kilo of body-weight as was obtained with the soldiers on a prescribed diet, yet these men were athletes accustomed to vigorous muscular exercise, and likewise accustomed to the eating of relatively large amounts of proteid food. Theoretically, it might not be expected that these men would drop to as low a level as men who were not addicted to the consumption of excessive amounts of proteid foods, yet for two months, and practically for a period of four months, these University students easily maintained themselves at this lower level of nitrogen metabolism.