The experiments reported in this paper were planned to determine whether there might not be certain special conditions under which the specific gravity of the urine could be used as a means for estimating the amount of secreting tissue in the kidney.
In 1914 Hedinger and Schlayer1 described a method in which renal function was studied by observations of the specific gravity, volume, and chlorid content of collections of urine made at short intervals over a period of twenty-four hours. The modification of this test introduced by Mosenthal2 has been used widely in this country. The interpretation of the results has given rise to much discussion but it has never been maintained that the test can be taken as a measure of the amount of renal tissue; in fact, Schlayer3 has taken pains to point out that such an interpretation would be quite unwarranted. It would seem, then, that altogether