In a previous communication,1 attention was directed to certain advantages in the use of creatinin as a test for renal function. This substance, which is apparently an end-product of metabolism, is excreted by the normal kidney with great ease; and its excretion, as emphasized by Schaffer,2 is remarkably constant for the same person.
In the series of cases reported, it was pointed out that while normal kidneys responded promptly to an excess of creatinin in the circulation by a greatly increased urinary output of creatinin, the kidneys in chronic nephritis showed no such marked increase, and at times even showed a decrease. As a convenient method of studying the creatinin excretion, the patient's urine was first collected for the period of one hour and the patient then given 0.5 gm. of creatinin intravenously. Subsequent collections of urine were made at the end of one hour and at the end of