Abstract
(1) Isolated single nerve fibers of the toad were excited with exponentially rising voltages. It was shown that the relation between the final voltage Vi and the time-constant of voltage-rise RC is expressed by a good straight line. This experimental fact indicates that the rate of increase of the stimulating voltage dV (t)/dt shows a constant value at the moment when the voltage V (t) crosses the rheobasic voltage.
(2) The utilization-time and the latent period of action current were also determined. It was found that the action current of the nerve fiber is set up a few milliseconds after V (t) has crossed the rheobasic voltage at a rate greater than the minimal voltage gradient of the fiber. The utilization-time ended near the moment at which the action current of the fiber was set up.
(3) The effect of CaCl2-excess and CaCl2-deficiency and of electrotonus upon the Vi-RC relation was also investigated. Change in the content of CaCl2 in Ringer changed the rheobase but not at once influenced the minimal gradient of the fiber. Catelectrotonus decreased and anelectrotonus increased the minimal gradient.
