Source of the Pigmentary Hormone of Amphibian Hypophysis

Abstract

There has been some confusion as to the rôle of the different lobes of the hypophysis in the secretion of the hormone that causes the well known pigmentary effects in tadpoles consisting of a darkening in the presence of an excess of the hormone and the assumption of a very pale color in its absence. The various methods of experimentation have been largely responsible for this diversity of view. P. E. and I. B. Smith caused these pigment changes by making repeated intraperitoneal injections of saline extracts of crushed beef glands, securing positive results with pars anterior, pars nervosa and pars intermedia, the last named being the most pronounced. This method would not preclude the possibility of the fainter color changes caused by pars anterior and pars nervosa material being due to the presence of secretion diffused from the pars intermedia. In the work of the writer for several years the method of transplantation has been used. Care is taken to use only unmixed material of the pars intermedia sliced off at some distance from its surface of intimate union with the pars nervosa. Transplants of the latter never cause pigmentary effects when taken with similar precautions against contamination with pars intermedia substance. In all cases the region of junction between these two portions is discarded. While there is a slight transitory pigmentary effect produced by pars anterior or pars nervosa transplantation, they do not persist, while on the other hand pars intermedia of an adult frog transplanted into normal or hypophysectomized tadpoles becomes functional and causes most intense expansion of the superficial melanophores with deposition of pigment granules in the epidermal cells. This forms a dense mass closely applied to the side of the nucleus directed toward the surface of the body.