On the relation of the strength-frequency curve in excitation by alternating current to the strength-duration and latent addition curves of the nerve fiber.

1. Determinations were done of the strength-duration, the strength-frequency, and the latent addition curves with single fiber preparations. 2. Calculation of the strength-duration and strength-frequency curves from the latent addition data by the Blair-Monnier-Hill-Rashevsky theory yielded results which showed a considerable divergence from the actual data. Calculation by the method of integrating the whole latent addition curve yielded satisfactory results. 3. The effects of electrotonus and the inactive tissues around the nerve fiber upon the strength-frequency relation were investigated. 4. It was suggested that, for alternating current stimuli and two-way condenser discharge stimuli of very high frequencies, threshold was lowered by the rectifying action of the plasma membrane.