The Response of the Water-regulating Mechanism of Developmental Stages of the Common Toad, Bufo Bufo Bufo (l.), to Treatment with Extracts of the Posterior Lobe of the Pituitary Body

INVESTIGATIONS made in recent years have demonstrated a connexion between the posterior lobe of the pituitary gland and water regulation in Amphibia. Injection of extracts causes a retention of water in the body of frogs (Brunn, 1921; Heller, 1930; Steggerda, 1931; Collin & Drouet, 1932; Steggerda & Essex, 1934; Oldham, 1936; Boyd & Brown, 1938; Boyd & Whyte, 1939), toads (Steggerda, 1931; Novelli, 1933), Amblystoma (Belehradek & Huxley, 1927), Necturus maculatus (Steggerda, 1937), and some reptiles (Boyd & Dingwall, 1939). In mammals the antidiuretic effect of the posterior lobe is now well established. On the other hand, freshwater fish show no such effect even when given doses of pituitrin up to 2-0 i.u. per 10 g. body weight. Nevertheless, the fish pituitary contains a substance causing a typical water retention in frogs (Boyd & Dingwall, 1939). It appears therefore that while the principle concerned is elaborated in the fish pituitary, either the appropriate effector is not developed or an alternative system which deals with the greater part of water regulation, is present. Thus, on the basis of the data available, it may be said that the regulation of the body water by agents of the posterior pituitary is characteristic of terrestrial but not of primarily aquatic vertebrates.