OPTICAL STIMULI AND WATER BALANCE IN FROGS

Abstract

Repeated blinding flashes of light caused frogs immersed in water to lose a % of their body water. The effect was analogous to that of very small doses of pituitrin. No loss of body water resulted if the eyes were removed, if the reflexes were lost under anesthesia or if the brain was destroyed by pithing. Pithing the spinal cord did not affect the reaction to optical stimuli. Optical stimuli had reflexly stimulated the output of a water balance hormone from the hypothalamico-hypophyseal region and that this hormone had lowered the level of water in the body. Evidence pertaining to the control of body water by the neurohypophysis is reviewed in an at- tempt to relate this control to the especial needs of the body at any given time. Further data are presented indicating that optical stimuli cause retention of body water when frogs are exposed to a drying environment.