One group of subjects was composed of professional men, professors and instructors in the university, whose work was mainly mental rather than physical, though by no means excluding the latter. Of this group, two cases will be referred to with some regard for detail, since in no other way can so striking a picture be presented of the effects produced. The first subject weighed 65 kilos in the fall of 1902, and at that time was nearly 47 years of age. His dietetic habits were in accord with common practice, and his daily consumption of proteid food averaged close to 118 grams. With a clear recognition of the principle that the habits of a lifetime should not be too suddenly changed, a very gradual reduction in the total amount of food, and especially of proteid matter, was made. This finally resulted, with this particular subject, in the complete abolition of breakfast, with the exception of a small cup of coffee. A light lunch was taken at noontime, followed by a more substantial dinner at night. There was no change to a vegetable diet, but naturally any attempt to cut off largely the amount of proteid food necessarily results in a marked diminution in the quantity of animal food or meats. It is a somewhat singular though suggestive fact, that a change of this order gradually results in a stronger liking for simple foods, with their more delicate flavor, accompanied by a diminished desire for the heavier animal foods. As the day’s ration was gradually reduced in amount, the body-weight began to fall off, until after some months it became stationary at 57 kilos, at which point it has remained practically constant for over three years. The sixteen pounds of weight lost was composed, mainly at least, of superfluous fat. For a period of nine months, from October, 1903, to the end of June, 1904, the amount of proteid material broken down in the body was determined each day. The average daily metabolism of nitrogen for the entire period of nearly nine months amounted to 5.69 grams. For the last two months, it averaged 5.4 grams per day. Analyses made from time to time since these figures were obtained show that the subject is still living at the same low level of nitrogen metabolism. In fact, the data available afford satisfactory proof that for a period covering over three years this particular person has subsisted on an amount of proteid food equal to a metabolism of not more than 5.8 grams of nitrogen per day. It may be asked why the subject should have continued such a low proteid diet after the nine months’ period was completed? In reply, it may be said that the new habit has taken a firm hold, and entirely supplanted the dietetic desires and cravings of the preceding years. Further, the improved condition of health, freedom from minor ailments that formerly caused inconvenience and discomfort, and the greater ability to work without fatigue, have all combined to place the new habit on a firm basis, from which there is no desire to change.