Finally, as affording additional evidence, we may refer to a third subject in this group, a man of 65 kilos body-weight, 26 years of age, who for a period of six consecutive months maintained body-weight, nitrogen equilibrium, and a general condition of good health, with a proteid metabolism equal to 7.81 grams of nitrogen per day. During the last two months of the experiment, the average excrejion of nitrogen per day amounted to 6.68 grams, corresponding to a metabolism of 0.102 gram of nitrogen per kilo of body-weight. This figure, it will be noted, is practically identical with the values obtained with the preceding subjects, calculated to the same unit of weight. Further, this third subject did not reduce his nitrogen intake by an exclusion of meat, but made use of his ordinary diet gradually reduced in amount. His daily consumption of proteid food averaged 55grams or8.83grams, of nitrogen, and on this amount of proteid, without increasing the intake of fats and carbohydrates, he was quite able to do his work with preservation of physiological equilibrium.

Views so radically different from those commonly accepted can be made to carry weight, only by the accumulation of supporting evidence obtained under widely different conditions of life, and by methods which will defy criticism. It might be argued, and with perhaps some justification, that while professional men, with freedom from muscular work, may be able to live without detriment on a relatively small amount of proteid food, such a conclusion would not be warranted for the great majority of mankind with their necessarily greater muscular activity. We are confronted at once with the oft-heard statement that the laboring man requires more proteid food; he has a more vigorous appetite, and he must take an abundance of meat and other foods rich in proteid, if he is to maintain his ability as a worker. Note the statements already made in other connections regarding the food consumption of Maine lumbermen, of men on the football team, of trained athletes in general. These men consume large amounts of proteid daily, because their work de-mauds it. If the demand did not really exist, they would not so agree in the use of high proteid standards, so runs the argument. The custom certainly does exist and is almost universally followed; men in training for athletic events deem it necessary to consume large amounts of proteid food. Custom and long experience sanction a high proteid diet, rich in nitrogen, for the development and maintenance of that strength and vigor that help to make the accomplished athlete. It is common knowledge to-day, however, that the energy of muscle work does not have its origin in the breaking down of proteid material, certainly not when there is an adequate amount of fat and carbohydrate in the diet. A high proteid intake must therefore be called for because of some subtle quality, not at present fully understood. 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 2*2.79 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 bo. 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: