Abstract
Marked antidiuretic activity was present in the urine of rats after oral loading with 5% NaCl solution. The antidiuretic material was in part retained by an ultrafilter and was destroyed by thioglycolate. In its reaction to pepsin, trypsin, chymo-trypsin and pancreatic carboxypeptidase the material snowed a "pattern" similar to that of vasopressin.