The Nature of the Frog Skin Potential

Summary. 1. The outside of the isolated frog skin in the absence of penetrating anions behaves over a wide range of concentrations as a sodium electrode, while the inward‐facing surface behaves like a potassium electrode. 2. A theory concerning the origin of the frog skin potential is put forward based on these observations and the assumption that the active transport of sodium is located at the inward‐facing membrane of the epithelial cells. 3. Reasons are given for the hypothesis that the active transport of sodium in reality is a forced exchange of sodium against potassium.