THE STRENGTH-DURATION RELATION OF THE NORMAL, POLARIZED AND NARCOTIZED NERVE FIBER

Abstract

A method is described for stimulating an isolated myelinated fiber by insulating the intemode on a "ridge-insulator." The strength-duration relations were detd. by the new method on the normal, narcotized and polarized nerve fiber of the toad. All the results were found to be in best accord with Weiss''s empirical formula. In the normal nerve fiber (at 10-15[degree]C), the chronaxie was found to be 0.3-0.5 msec., and the rheobasic voltage was 25-50 mvolts. Sometimes with ascending current pulses and more frequently in the narcotized nerve fiber the threshold cannot be detd., due probably to block of the descending nerve impulse by the anodal depression. The chronaxie in the nerve devoid of the sheath was found to be about a half as long as that in the intact nerve.