Feeding experiments on tadpoles. II. A further contribution to the knowledge of organs with internal secretion

Abstract

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 a t 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 action of the latter, in part or entirely, may not be concerned with tho'se most important physiological processes in the embryo, namely, growth and differentiation.They might play their chief r61e, then, in the household of the postembryonic organism.Or, since taken from mammals, some of these internally secreting glands, if at all connected with embryonic development, may fail to reveal 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.