FEEDING EXPERIMENTS ON TADPOLES 



II. A FURTHER CONTRIBUTION TO THE KNOWLEDGE OF ORGANS 

 WITH INTERNAL SECRETION 



J. F. GUDERNATSCH 



Dcparlmenl of Anatomy, Cornell Universily Medical College, New York 



{Fro)}i the Department of Histology and Embryology, University 



of Munich. Director: Prof. S. Mollier) 



TWO DOUBLE PLATES 



Certain mammalian glands with a so-called internal secretion, 

 when given as food, can enact a decided influence on the growth 

 and differentiation of amphibian embryos. This was shown by 

 experiments that were carried out during the summer of 1911 on 

 tadpoles of Rana temporaria and Rana esculenta. 



During the spring of 1912 these experiments were repeated 

 and at the same time varied to such an extent that no doubt as 

 to their results remained. Although the experiments of the two 

 seasons revealed many precise data, there is still a great number 

 of obscure features regarding the definite action of internally 

 secreting glands when fed to the tadpoles. While the influence 

 on growth and differentiation resulting from feeding some of the 

 glands was striking, others exerted no marked effects. The ac- 

 tion of the latter, in part or entirely, may not be concerned with 

 those most important physiological processes in the embryo, name- 

 ly, growth and differentiation. They might play their chief role, 

 then, in the household of the postembryonic organism. Or, since 

 taken from mammals, some of thfese internally secreting glands, 

 if at all connected with embryonic development, may fail to re- 

 veal this influence, when fed to amphibian embryos. Their ac- 

 tion must finally be studied in experiments on higher vertebrates. 



The experiments in 1912 were performed on tadpoles of Rana 

 temporaria, Rana esculenta, Bufo vulgaris and Triton alpestris. 



431 



THE AMERICAN' JOURNAL OF ANATOMY, VOL. 15, NO. 4 



