It must not be subjected to criticism, however, because it is sanctioned by custom, habit, and common usage. Still, I have ventured to experiment somewhat with a group of eight university athletes, all trained men, and with some surprising results. We have not space for details, but it may be mentioned that the men were young, from 22 to 27 years of age, and were experts in some field of athletic work. By a preliminary study of their ordinary dietetic habits, it was found that they were all large consumers of proteid food, with a corresponding high rate of proteid katabolism. One subject of 92 kilos body-weight, during ten days, showed an average daily excretion through the kidneys of 22.79 grams of nitrogen, implying a metabolism of 142 grams of proteid matter per day. On one of these days, the nitrogen excretion reached the high figure of 31.99 grams, corresponding to a metabolism of about 200 grams of proteid matter. Calculated per kilo of body-weight, this means a metabolism of 0.35 gram of nitrogen, or three and a half times the amount needed by the three professional men for the maintenance of nitrogen equilibrium. These subjects, with an intelligent comprehension of the point at issue, and with full freedom in the choice of food, gradually diminished their daily consumption of proteid material, at the same time cutting down very markedly the total consumption of food. The experiment extended through five months, and during the last two months, the average daily excretion of metabolized nitrogen of the eight men amounted to 8.81 grams per man. This corresponds to a metabolism of 55 grams of proteid matter. Further, the average daily output of nitrogen through the kidneys during the preceding two months was in many cases nearly, if not quite, as low as during the last two months of the experiment. If we contrast this average daily exchange of 8.81 grams of nitrogen with the average output prior to the change in diet, it is easy to see that the men were living on about one-half the amount of proteid food they were formerly accustomed to take. Moreover, if the metabolized nitrogen for each individual, with one exception, is calculated per kilo of body-weight, it is seen to vary from 0.108 gram to 0.134 gram; somewhat higher than was observed with the older professional men, but not conspicuously so. Again, it is to be emphasized that the lowered intake of proteid food with these men was quite adequate to maintain their bodies in nitrogen equilibrium. We may cite a single case by way of illustration: