Abstract
The effects of different concentrations of methyl, ethyl, n-propyl, n-butyl, i-amyl, and phenyl carbamate in Ringer's solution on the electric potential of frog skin have been quantitatively and comparatively studied.
The skin of each frog used was divided into 11 pieces which were fastened over the mouths of tubes by means of rubber bands, and were bathed in Ringer's solution maintained at a temperature of 25° ± 0.5° C. Determinations of E.M.F. were made potentiometrically. After a preliminary period of approximately 2 hours in Ringer's solution, the skins were transferred to one containing a certain percentage of carbamate and were finally again placed in Ringer's.
Inasmuch as the magnitude of the electric potential of different pieces of skin, from the same or from different frogs, varied widely, but since the electromotive behavior of different skins was qualitatively similar, the E.M.F. in millivolts was transposed to per cent in order to permit of quantitative evaluation of the effect of carbamate. The potential at the time of application of carbamate (at which time electromotive equilibrium had been established) was arbitrarily designated as 100%. In terms of per cent, the skins from the same or from different frogs behaved quantitatively alike.
The normal E.M.F. of frog skin gradually decreases with time. The application of carbamate to skin causes a reversible diminution of E.M.F. which is a function of the duration of application and of concentration. The activity of the members of the homologous series conforms to the rule of Traube which states that the activity of the individuals of a series accords with the ratio 1-3- 32 - 33 etc.
The relative depression of E.M.F. by a carbamate parallels its action in lowering the surface tension of water.
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