No. 038] iXTf-nxAL nav 7,'/;7 /o.v > or AMrin/iiAXs 215 



ment of normal larva', scciiis to he Iih-Hikm! to consider 

 these differences as boinu' of no siuniticaiicc ( 'crtainlv it 

 is of no small importaiieo that normal aial li\ jiophx scc- 

 tomized larvas react so differe]itl\- to a diet of anterior 

 lobe substance; apparently part of the actixc ])rincipk' 

 of the anterior lobe introduced, by the (bet, into the organ- 

 ism is made ineffective in the presence of a normal 

 hypophysis. Not yet completed experiments on sala- 

 mander larvae seem to suggest that the larval ,ui-o\vtli of 

 salamanders at least can not be affected by feeding an- 

 terior lobe of hypophysis; this may be due either to a 

 destruction of the active principle in the digestive tract 

 or to some peculiarity in the metabolism of the salaman- 

 der larva^, and is of particular interest witli regard to the 

 fact that the adult salamanders react very markedly to 

 an anterior lobe diet, as will be discussed i)resently. 



One of the most pertinent and yet most diftieult prob- 

 lems of endocrinology is presented by the existence of 

 interrelations and interactions between the vai ions endo- 

 crine glands. There can be no doubt that in tadp<des 

 such an interrelation exists between the hyi)ophy>i- and 

 thyroid glands. Thus IJouvrs CH) and later on iloskins 

 and Iloskins ( l'l' ) loun.l that upon thy n.i.lectomy j.er- 

 formed in early innbryonic stages of anurans the anterior 

 lobe of the hypo})liysis shows a tendency towards hyj)er- 

 trophy. (hi the other hand if the buccal anlage of the 

 hypophysis is removed, the thyroid soon ceases to grow 

 and to differentiate and finally presents a state of hypo- 

 plasia, as shown by Allen (30) and by Sndth CM'^). Since 

 the effects of the extirpation of either of these glands on 

 general body growth and on develo])ment ai'e (piitt' simi- 

 lar and since the behavior of each of these ulands after 

 the extirpation of the other one demonst rat^ s the exist- 

 ence of an interrelation between them, the .|uestion nduht 

 well be asked, if the function of each of these ulands ran 

 not be replaced by the h..rmone of the other om' of them. 

 Although this .piestion can not be satisfactorily answer.^) 

 thus far, it seems highly •prol)al)le that these hormones 



