During the last few years the study of renal function has largely confined itself to the determination of kidney activity as measured by the quantitative excretion of various dyestuffs and chemicals, either those normally found in the urine or foreign substances which have been fed or injected. By observing the kidney in this manner, notable results have been obtained, especially with phenolsulphonephthalein, lactose, potassium iodid, urea, salt and kreatinin. In most instances, the outcome of intensive study has been the discovery that the elimination of nearly all of these substances may at times be increased quantitatively, in spite of marked renal lesions, or their complications, such as uremia. To supplement such tests, Hedinger and Schlayer1 have recently proposed a qualitative test of the mode of urinary function, as measured by the specific gravity, salt and water excretion in two-hourly periods. These authors show how the urinary response