392 ANDREW JOHNSON BIGNEY 



In testing the effects of this drug on the melanophores of the 

 skin, preUminary experiments were made on the effect of hght 

 and darkness on these cells. This was merely to confirm the 

 work of previous investigators that in the light the pigment 

 expands and in the dark it contracts. This action takes place 

 in an hour or so ; but to be sure that there was a complete migra- 

 tion, the frogs were kept either in the light or in the dark for 

 six hours. 



To determine the influence of adrenin on this pigment, two 

 frogs were placed in strong, diffused daylight for six hours, 

 after which 0.06 cc. of a solution of adrenin one part in a thousand 

 was injected into the dorsal lymph spaces of each animal. The 

 frogs were then kept a quarter of an hour in the light and killed 

 and a small portion of the skin from the hip was removed and 

 prepared for microscopic examination by fixing it in Perenyi's 

 fluid and mounting it, unstained, by the usual method. In both 

 instances the melanophores were found to be strongly retracted, 

 which was opposite to the state induced by light. 



Two more frogs were next treated in the same manner, but 

 they were kept in the dark, and upon examining their skin the 

 melanophores were found retracted, thus showing that the adre- 

 nin prodiices no other effect in the dark. These results harmo- 

 nize with the investigations of previous workers. 



To determine the strength of the adrenin necessary to produce 

 these reactions, a number of frogs were kept in the light the 

 usual time, then injected with the adrenin in concentrations, 

 one part in ten thousand, one in fifty thousand, and one in five 

 hundred thousand. The frogs were killed at the end of an 

 hour. Those with one part in ten thousand had the pigment al- 

 most completely retracted, while those with one in fifty thousand 

 had slight retraction, and those with one in five hundred 

 thousand showed no effect. 



The same concentrations were used on frogs kept in the dark 

 and in all instances the melanophores remained retracted, as 

 was to have been expected. 



To determine how long the influence of the adrenin lasted, the 

 usual amount, 0.06 cc. of a solution one in a thousand was in- 



