The study of a variety of experimental renal lesions in the dog demonstrates that the phenolsulphonephthalein test of Rowntree and Geraghty is one of the most satisfactory and at the same time most delicate methods of estimating the functional activity of the kidney. The elimination of the test dye is decreased in so-called spontaneous nephritis and in experimental nephritis due to potassium chromate, uranium nitrate, cantharidin, diphtheria toxin, and arsenic, and in those lesions caused by snake venom, hemolytic serum, prolonged renal anemia, and extensive reduction of the kidney substance. Its elimination is not' diminished, but is increased, in the presence of the renal lesion caused by nephrotoxic immune serum, and for this discrepancy no explanation is at hand. The test is a reliable method of demonstrating improvement in the functional activity of the kidney, as is shown in our study of spontaneous nephritis. The increased elimination of the dye occurring after small doses of various irritants, which is frequently characteristic of the early stages of a severe nephritis, and which is seen also several days after unilateral nephrectomy, would appear to have an important relation to the problem of kidney function; and although probably not of clinical importance, it is worthy of further study as a phase of renal activity.
