EFFECT OF ADRENIN ON PIGMENT IN FROG 393 



jected into the lymph spaces of a number of frogs kept in the 

 hght and they were killed at varying intervals from seven min- 

 utes to five hours. Complete retraction was found to last for 

 about two hours; at three hours, moderate contraction was noted, 

 while in four to five hours retraction was replaced by full expan- 

 sion, thus showing that the influence of the adrenin had com- 

 pletely passed off. 



The migration of the retinal pigment under the influence of 

 light and darkness is well known to be outward from the cell in 

 light and into the cell in the dark. To test the influence of adre- 

 nin on these pigment cells, eight frogs that had been kept in the 

 light for five hours were injected each with 0.06 cc. of adrenin 

 solution one in a thousand and were killed in pairs, the first pair 

 after fifteen minutes' exposure to the drug, the second after 

 thirty minutes, the third after forty-five minutes, and the fourth 

 at the end of an hour. The eyes after removal were fixed in 

 Perenyi's fluid, cut into sections, and mounted unstained. In 

 all instances the retinal pigment was found to be fully expanded. 



The experiment was then reversed, the frogs being kept in the 

 dark five hours and subjected to the adrenin while still in the 

 dark. They were also killed in pairs at quarter-hour intervals. 

 To my surprise, the retinal pigment in every case was fully 

 expanded. To avoid possible error, I repeated the experiment, 

 with exactly the same results. Control frogs injected with phys- 

 iological salt solution, instead of adrenin, were made to accom- 

 pany the others. The retinal pigment in all of these remained 

 retracted as in the regular dark condition. It is therefore cer- 

 tain that the adrenin acts upon the retinal pigment in the same 

 way as light, as maintained by Fujita ('11). It thus appears 

 that the action of adrenin on the retinal pigment cells is the op- 

 posite of what it is on the melanophores of the skin. My results, 

 therefore, are opposed to those of Klett ('08), who maintained 

 that adrenin caused a retraction of the retinal pigment. His re- 

 sults were obtained by an intra-ocular application and not by 

 injecting it into the blood stream. He could get no results by 

 the latter method. In all his experiments the frogs were in 

 direct, strong light or in diffused light, but never in the dark, 



