Abstract
1. When adult male cockroaches are deprived of water for 3 days the subsequent overcompensation of water ingestion causes the release of a diuretic hormone into the blood. 2. Ligation experiments indicate that the hormone was released from the posterior part of the abdomen. 3. The testing of various tissues extirpated from within this region revealed that only extracts of the terminal abdominal ganglion could promote diuresis. 4. Homogenates of ganglia from normal animals fail to elicit the diuretic response; this and other evidence suggests the presence of an antidiuretic hormone.