THE GROWTH-PROMOTING HORMONE 



flies, worms, amphibia, the fowl, and mammals. So far as the 

 promotion of growth is concerned, the only satisfactory re- 

 sults were obtained in amphibia. 



Feeding experiments in amphibia. — Smith (1918)^ fed the 

 fresh pars glandularis of the ox to normal and to hypophy- 

 sectomized tadpoles {R. boy lei). As a result, normal tadpoles 

 grew more rapidly in the last part of the larval cycle than did 

 normal tadpoles to which anterior pituitary was not fed. 

 Hypophysectomized tadpoles, if not fed anterior lobe, grew 

 about as rapidly as normal tadpoles until the mid-larval peri- 

 od, after which their growth-rate was clearly inferior to that 

 of normal animals. The feeding of pars glandularis caused an 

 acceleration of the growth-rate to the normal level during 

 this latter period. No metamorphosis occurred, and the tad- 

 poles frequently grew for a longer period and to a larger size 

 than normal tadpoles without pituitary feeding. The feeding 

 of the pars glandularis to hypophysectomized tadpoles, un- 

 like the injection of extracts, was not followed by any bene- 

 ficial effects on the pigmentary changes or on the atrophy of 

 the adrenal cortex, thyroid, and epithelial bodies. Uhlenhuth 

 (1920-23) fed the pars glandularis of the ox to salamanders 

 {Amblystoma tigrinum, A. opacum) after metamorphosis. His 

 experiments, conducted over many months, showed that the 

 feeding of liver or of pars glandularis was accompanied by an 

 increased growth-rate, so that salamanders larger than other 

 animals of the same variety fed on worms were produced. 

 The pituitary- fed animals were the largest — being about 20 

 per cent larger than the liver-fed animals.' 



Belkin (1934) concluded that the rate of regeneration of an 



^ Also see Smith and Smith (1922-23). 



^ Kfizenecky (1924) and Kfizenecky and Podhradsk}' (1926) believed that the 

 growth of tadpoles (R./usca and R. temporaria) might be increased by feeding either 

 the pars glandularis or the pars neuralis — the former increasing the weight, the 

 latter, the length. The later report (1926) did not confirm some of the other unusual 

 conclusions reached in the first report (1924). 



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