Capacity of Muscle Fiber Membrane

Using two or three microelectrodes inserted into single muscle fibers of the toad sartorius, the electric impedance of the muscle fiber membrane was measured with a.c. between 25 and 1500 cps. It was found that the capacity of the muscle fiber membrane is practically independent of the frequency of the measuring a.c. The membrane capacity determined from the time constant of potential rise in the foot of a propagated muscle action potential agrees with the value determined by a.c. impedance measurement. It was emphasized that the a.c. method of determining the cable constants of the muscle fiber (based on eq. 1 under methods) is simple and gives satisfactory results.