6 PIGMENTARY GROWTH AFTER ABLATION OF 



to be necessary in studies upon hypophysial extirpation if the 

 prolonged survival of the animals is desired, since the complete 

 extirpation of the epithelial hypophysis 2 in the adult invariably 

 proves fatal within a brief period. And it would appear that 

 only by the prolonged survival of the animal can the maximal 

 alterations in the other members of this correlative system fully 

 express themselves, as is shown by the structural picture pre- 

 sented by the endocrine organs of the 'hypophysectomized' 

 tadpole. These organs exhibit structural changes exceeding in 

 magnitude those obtaining in the hypophysectomized mammal. 

 Indeed, it is possible to look upon these structural alterations 

 as the expression of a restored functional balance in the endo- 

 crine system which has permitted the survival of the animal. 

 One further advantage is bestowed by the use of embryonic 

 material, for we may discover a more general influence of the 

 endocrine organ in question on the manner or rate of develop- 

 ment of all of the tissues and organs of the body namely, on 

 growth and, as we shall see further on, growth effects are 

 among the most prominent ones manifested by these disturb- 

 ances. 



In 1912 Gudernatsch reported that frog larvae could be meta- 

 morphosed by thyroid feeding. This remarkable result stimu- 

 lated Adler in the same year to utilize the tadpole for the abla- 

 tion of members of the endocrine system. By what now appears 

 to be a crude method, Adler, in 1912, burned out the pituitary 

 from half-grown frog larvae. Although the failures were numer- 

 ous, the death rate high, and in the surviving successful cases 

 the injury to the neighboring structures severe, nevertheless, 

 Adler was able to show that the destruction of the pituitary 

 impaired the thyroid gland and prevented metamorphosis. 

 Subsequent and far more successful ablations of the hypophysis 

 have amply confirmed Adler's findings. 



In 1914 the author attempted to remove the epithelial anlage 

 of the hypophysis in the early larvae of the newt D. torosus. 

 As had been the experience of other investigators, this urodele 

 material proved unfavorable for early operation. The follow- 



2 That portion of the hypophysis arising from the oral ectoderm. 



