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.