EFFECT OF ADRENIN ON PIGMENT IN FROG 395 



Another interesting question presents itself. How does this 

 drug act in causing the above results? Is it through the nerves 

 or directly upon the cells by being carried in the blood? To 

 answei: these questions, frogs in which the optic nerve of one 

 eye had been cut very close to the brain, the other optic nerve 

 not having been disturbed, were injected with adrenin under the 

 usual conditions. . In this experiment the retinal pigment was 

 found to be expanded in both eyes, thus showing that the optic 

 nerve is not concerned in this action, but that it is very probably 

 due to the drug carried in the blood. 



Another experiment was performed in which the eyes of several 

 frogs were removed and treated directly by injecting the adrenin 

 into the eyeball of one side and physiological salt solution into 

 the eyeball of the other side in each frog. Irregular results were 

 obtained, the pigment sometimes being retracted, but most gen- 

 erally expanded in all the eyes. These irregularities were evi- 

 dent in the control frogs as in the experimental set. This led to 

 the suspicion that the condition of the frogs was not satisfactory 

 owing to the season of the year. The earlier part of this work 

 was performed in the autumn and winter and the results were 

 strikingly uniform and consistent, but the later part of it was 

 done in the spring. It was, therefore, suspected that the advent 

 of the breeding season had something to do with the results. It 

 is not improbable that this irregular condition is dependent, as 

 Fuchs ('06) has .suggested, on an especially excited state of the 

 animals whereby adrenin is secreted naturally and in considerable 

 quantities by the frog itself. This suggestion, which seems 

 plausible, is nevertheless purely hypothetical. It is intended to 

 continue this part of the work with the view of a final determina- 

 tion as to the real cause of this irregularity. 



