The Rate of Urea Excretion. Vii. the Effect of Various Other Factors than Blood Urea Concentration on the Rate of Urea Excretion.* by T. Addis

tions a constant (1). If now these conditions are all complied with, but in addition some new factor is introduced, the effect on the rate of urea excretion can be measured by the deviation of the ratio from its constant value. Most of the experiments given in this paper were carried out on the two subjects, Add. and Dru., whose ratios under standard conditions are given in Paper V of this series (1). For Add. the average ratio was 46.1 with a variability of f6.9 per cent, and for Dru. the average was 56.2 with a variability of f4.8 per cent. But some of our experiments on Dru. were carried out under conditions which differed from those we have called “standard” in that no urea was given. In these experiments the blood urea concentration was at a low level so that any error in the technique of the blood urea determinations would have a relatively greater effect on the ratio than in the experiments in which the blood urea concentration had been increased by urea administration. The method was, therefore, reexamined and a modification, used only in these experiments, was introduced which probably