Before proceeding with a detailed account of the experimental work, it may be well again to emphasize that what is especially desired is to ascertain how far, if any, the intake of proteid food can be diminished without detriment to the body, _i. e._, with maintenance of nitrogen and body equilibrium and without impairment of bodily and mental vigor. Further, if a lower proteid standard than that generally adopted can be established, it is desirable to ascertain whether it can be maintained indefinitely, or for a long period of time, without loss of strength and vigor. Obviously, it is of primary importance that we should know quite definitely what the minimal proteid requirement of the healthy man per kilo of body-weight really is, and the experimental work about to be detailed has aimed especially to determine whether it is possible to materially lower the amount of daily proteid food, without detriment to the bodily health and with maintenance of physical and mental vigor. The writer, fully impressed with his responsibility in the conduct of an experiment of this kind, began with himself in November, 1902. At that time he weighed 65 kilos, was nearly 47 years of age, and accustomed to eating daily an amount of food approximately equal to the so-called dietary standards. Recognizing that the habits of a lifetime should not be too suddenly changed, a gradual reduction was made in the amount of proteid or albuminous food taken each day. In the writer’s case, this resulted in the course of a month or two in the complete abolition of breakfast, except for a small cup of coffee. A light lunch was taken at 1.30 P. M., followed by a heavier dinner at 6.30 P. M. Occasionally, however, the heartier meal was taken at noontime, as the appetite suggested. It should be added that the total intake of food was gradually diminished, as well as the proteid constituents. There was no change, however, to a vegetable diet, but a simple introduction of physiological economy. Still, there was and is now a distinct tendency toward the exclusion of meat in some measure, the appetite not calling for this form of food in the same degree as formerly. At first, this change to a smaller amount of food daily was attended with some discomfort, but this soon passed away, and the writer’s interest in the subject was augmented by the discovery that he was unquestionably in improved physical condition. A rheumatic trouble in the knee joint, which had persisted for a year and a half and which only partially responded to treatment, entirely disappeared (and has never recurred since). Minor troubles, such as “sick headaches” and bilious attacks, no longer appeared periodically as before. There was greater appreciation of such food as was eaten; a keener appetite and a more acute taste seemed to be developed, with a more thorough liking for simple foods. By June, 1903, the body-weight had fallen to 58 kilos.