his ordinary dietetic habits, consumes more nitrogen than the body can possibly make use of. The excess is not stored up, “because the actual need of nitrogen is so small that an excess is always furnished with the food, except, of course, in carefully planned experiments” (Folin). We have seen at what low levels of proteid intake, nitrogen equilibrium can be established, and we may well have faith in the conception of an endogenous proteid katabolism which involves only minimal quantities of proteid. Further, we have observed the constant tendency of the body to maintain a condition of nitrogenous equilibrium, even with varying income, and how slow the body is to lay by nitrogen on a rich proteid diet, even when long deprived of proteid food; a fact difficult of explanation except on the assumption that the real need of the body for nitrogen is small, and that the tissues habitually carry a relatively large reserve of nitrogenous material. We may assume with Folin that “all the living protoplasm in the animal organism is suspended in a fluid very rich in proteid, and on account of the habitual use of more nitrogenous food than the tissues can use as proteid the organism is ordinarily in possession of approximately the maximum amount of reserved proteid in solution that it can advantageously retain. When the supply of food proteid is stopped, the excess of reserve proteid inside the organism is still sufficient to cause a rather large destruction of proteid during the first day or two of proteid starvation, and after that the proteid katabolism is very small, provided sufficient non-nitrogenous food is available. But even then, and for many days thereafter, the protoplasm of the tissues has still an abundant supply of dissolved proteid, and the normal activity of such tissues as the muscles is not at all impaired or diminished. When 30 grams or 40 grams of nitrogen have been lost by an average-sized man during a week or more of abstinence from nitrogenous food the living muscle tissues are still well supplied with all the proteid they can use. That this is so, is indicated on the one hand by the unchanged creatinin elimination, and on the other by the fact that one experiences no feeling of unusual fatigue or of inability to do one’s customary work. Because the organism at the end of such an experiment still has an abundance of available proteid in the nutritive fluids, it is at once seemingly wasteful with nitrogen when a return is made to nitrogenous food. This is why it only gradually, and only under the prolonged pressure of an excessive supply of food-proteid again acquires its original maximum store of this reserve material.”