Abstract
The reduction of membrane potential of frog sartorius muscle fibers which was produced by the removal of Ca ions has been compared with the depolarization due to high K. The change of membrane potential and the passive fluxes of K ions have primarily been investigated. At the same level of depolarization, K rich or Ca free condition has each pattern of the movements of K ions. This discrepancy can probably be explained by the difference in the membrane structure resulting from the high K or Ca free condition. Although it is said that K ions act on the membrane as ionic activity and Ca ions as the regulator of the normal structure of the cell membrane, both are the constituents which maintain the membrane structure in the respective ways. However, the valency of each ion may be the most important factor for the membrane structure by which the resting or action potential can be produced.
