Excitation in Nilella, Especially in Relation to Electric Stiumulation

抄録

Experiments and theory on electric stimulation were made in Nitella. The following two points were made clear by experiments.
1) The relation between threshold voltage strength and its duration can be represented by Weiss's experimental formula. Rheobase is about 50mV and chronaxie is about 0.5 sec. Condenser discharge current stimulation was also made. The relation between initial voltage and its time constant can be represented by Hoorweg's formula.
2) By application of a rectangular subthreshold stimulus, change in the threshold rises slowly and then decays gradually.
For comparison, experiments were made with an isolated single muscle fiber of toad. The results are the same in general as the results with Nitella, with the exception of the time scale.
The experimental results were explained by supposing that the accumulation of a certain quantity of ion is the necessary and sufficient condition for excitation. In order to known the aspect of accumulation of ion, differential equations which state the movement and reaction of ion in the protoplasm were made from a physical point of view. The solution of the equation made it possible to calculate change in the threshold on the assumption that it corresponds to a concentration difference of ions in a definite place in the protoplasm. Strength-duration relation was also deduced on the same ground. Good correspondences were seen between the calculated results and experimental ones.
We wish to thank Mr. T. Iijima for his assistance in the mathematical phases of thess problems.