1. For the study of the character of nitrogen metabolism in nephritis the nitrogen intake of the patient needs to he regulated in such a manner that it should not exceed the nitrogen value which the diseased kidneys are capable of eliminating.
2. The eliminating capacity of the kidneys can he established in the following manner: the patient is placed on a diet containing a low proportion of protein (equivalent to about 5 grams of nitrogen) and a sufficient supply of calories. To this diet from day to day varying quantities of urea are added and the nitrogen output for every twenty-four hours is estimated. The highest nitrogen output under this condition is regarded as the maximum of the eliminating capacity of the kidneys for nitrogenous substances.
3. In the observations recorded in this communication the nitrogen output of the patient on the standard diet remained at 5.5 grams per day. The addition to the diet of 1.5 to 3 grams of nitrogen in form of urea caused a rise in the intake not exceeding 6.25 grams. On the basis of this, the diet was regulated so as not to exceed a nitrogen intake of 7 grams.
4. Comparing the rate of elimination of nitrogen after the administration of glycin, alanin, and asparagin with that after the administration of urea, there was noted a slower rate after the administration of the first two acids, and an equal rate after the administration of asparagin (probably owing to the presence of an acid amid group in the molecule).
5. After the administration of excessive protein in addition to the standard diet, there was noted a much lower rate of nitrogen elimination than was to be expected in a normal man, on the basis of the work of Falta.
6. Of the total nitrogen removed in excess over that on the standard diet in our patient, 80 per cent. was in the form of urea, while in normal man, as calculated from the tables of Folin, one finds the proportion of urea to vary between 90 and 100 per cent., while in a normal dog the proportion is always 100 per cent.
7. On the basis of these observations it was concluded that in our patient the rate of conversion of protein into simple nitrogenous substances and into urea is below the normal.
8. The patient remained for four months in a condition of nitrogenous equilibrium, and otherwise in good health, on a diet containing about 6.5 grams of nitrogen and 3,000 calories, which were reduced to 2,500 calories to prevent constant gain in weight.
9. From this it seems suggestive that also for dietetic-therapeutic purposes it may be of importance to establish the eliminating efficiency of the kidneys for nitrogenous substances.