THE GROWTH-PROMOTING HORMONE 



ed that the most striking changes were in the amounts of the 

 total nitrogen and of the dry tissue free from ash and fat. 

 The reduced amount of fat suggested that the injected ani- 

 mals oxidized more of the available fat than did the normal 

 animals (all the rats received the same amount and kind of 

 food). The chemical composition of the injected rats resem- 

 bled that of littermate rats analyzed when the injections were 

 begun (average weight, 190 g.) and was likewise similar to 

 that of an immature or growing mammal (Moulton, 1923). 



Percentage of 



It is not clear what is the significance of the increased 

 amount of water in the bodies of animals receiving growth- 

 promoting hormone. Targow (1934), who used castrated rats 

 which were still young (fifty-six days old) at the end of the 

 period of injection, concluded that the skin was the only tis- 

 sue which clearly contained more water. Downs and Gelling 

 (1929) and Downs (1930) observed a considerable increase in 

 the amount of water in the bodies of mice which had received 

 injections of the growth-promoting hormone. Wadehn (1932), 

 using a more refined extract, did not confirm this finding or 

 Downs's report that injected mice were composed of more ash 

 and fat; on the contrary, his results suggested that less fat 

 and less ash (in the skeleton but not in the rest of the body) 

 were present in the carcasses of injected mice. 



Metabolic studies in dogs before and after the administra- 

 tion of growth-promoting hormone have consistently re- 

 vealed changes in the metabolism of nitrogen-containing sub- 

 stances (Teel and Watkins, 1929; Teel and Gushing, 1930; 

 and Gaebler, 1933). The non-protein nitrogen of the blood 

 falls to the extent of 20-30 per cent; this is largely due to a re- 



[lOl] 



