236 



METABOLIC HORMONES 



though the action of an antidiuretic hormone might also be 

 expected. Ahhough extracts of the fish neurohypophysis have a 

 potent antidiuretic effect on frogs, there is no direct evidence of 

 the hormone having the same action on the fish themselves. The 

 best indirect evidence for the relation of hormones to an anti- 



FiG. 5-24. Effects of injection of neurohypophysial extract 

 (Frog ADH), at the time marked by the arrow, on the water content 

 of the frog, Rana pipiens. O : values calculated from changes in 

 body weight ; % : values for direct measurement of bladder contents. 

 The cloaca was ligatured and injected with phenol red to show if 

 any leakage occurred; the frogs then sat in water, which was 

 imbibed through the skin and excreted into the bladder, for 

 3 hr; then the controls (dotted line) continued to excrete for the 

 next 2 hr while the specimens, which received the injection at hour 

 3 (full line), showed a marked decrease in bladder water. This was 

 taken to mean that water had been reabsorbed into the tissues 

 from either the bladder or the cloaca (from Sawyer, 1956). 



diuretic function in Callionymus and Animodytes (Arvy, 1957; 

 Arvy, Fontaine and Gabe, 1954) is the observation that on transfer 

 from normal sea water to hypertonic sea water, the increased 

 dehydrating action of the environment is accompanied by depletion 

 of the neurosecretory store in the hypothalamus and neuro- 

 hypophysis. The secretion is re-formed when the fish are restored 

 to normal sea water and increased if they are placed for a short 



