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 excretion 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 55 grams, or 8.83 grams 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 demands 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.