No. 638] INTERNAL SECRETIONS or AMl'lllll/AXS 217 



by feeding anterior lobe substance to tliyioidcctdini/i'd 

 tadpoles, but could not obtain complete ]iu't;iiii()i ])li(>sis ; 

 especially the atrophy of the tail and of the ,uills could not 

 be enforced. Similarly Allen (37) points out tli.it frcd- 

 ing anterior lobe of cattle does not result in mctiniior- 

 phosis of thyroidectomized tadpoles. 



If taken together, all these results seem to indicate that 

 although certain resemblances exist between the hor- 

 mones of the thyroid and the hypophysis glands, they are 

 nevertheless specific and can not replace each other as 

 regards at least certain functions. 



As pointed out above, the metamorphosed salaitiaiidcrs 

 react on anterior lobe feeding quite ditferi'iitly from the 

 larvae. Such differences in the reaction tlio same 



principle in different stages have Ix'cn oliscrxcd (juite 

 frequently and are apt to throw an important li^ht on the 

 nature of the chemical reactions involved in growth and 

 development of different stages. The salamander larvae 

 show no appreciable effect from an anterior lobe diet, 

 whether the anterior lobe be fed alone or in small quan- 

 tities added to normal food. If metamor])lios('(l sala- 

 manders of the species A. opaviiDi or A. tifirininn arc I'imI 

 anterior lobe, the rate of growth IxH-omcs ahno-t innnc- 

 diately accelerated and growth continues after the ani- 

 mals have reached the specific maximum size of the 

 species; they become giants. The latter result must be 

 attributed to the action of a specific growth promoting 

 hormone contained in the anterior lobe {'.V2). 



The thynnis -land a])r)arcntly has no effect on growth 

 and developnuMit, altlmngh it ha^ been believed that it 

 contains specilic growth-})romotin,u' and (lc\-elo])meiit- 



fed on thymus only, growth as well as metamorphosis 

 are inhibited. The inhibition of metamorphosis, how- 

 ever, is due to the fact that in the absence of uT.uvth the 

 releasing factor of the thyroid can not foi-m. as has lieeu 

 mentioned ab(»ve. Moreoxcr. the inhibition (»f urowth is 

 not caused by si)ecilic hormones of tiie thymus, hut is 

 merely a deficiency phenomenon. The more normal food 



