Abstract
At various pH values of the environmental medium, excised single nerve fibre was stimulated with the long lasting direct current of vaious strengths. The response time of the action current was thereby determined to investigate the fluctuation of the genuin latent period of the action current. Even if the current of the same strength was employed as the stinulus, the response time, consequently the genuin latent period of the action current, fluctuated. Further, as the stimulating current became stronger, the response time became shorter. The amplitude of the fluctuation of the response time became smaller as the stimulating current became stronger. When the relation between the voltage and the shortest response time at each strength of the stimulating current, i. e., the voltage-response time relationship, was sought, it was found to be a hyperbola, satisfying the Weiss' experimental formula. In the voltage-response time relationship, the rheobase became lower and the chronoxie was prolonged as the pH value became larger. When the largest amplitude of the fluctuation of the response time by each pH value was investigated, it was found that the smallest amplitude of the fluctuation is at the normal pH value (pH 7.2), and that the amplitude of the fluctuation became largerat a higher pH value than pH 7.2. Since the smallest amplitude of the fluctuation of the response time indicates the steadiest progress of the excitation it can be utilized for the quantitative indication of the excitability.
