RESPONSE OF SINGLE RANVIER NODES TO ELECTRICAL STIMULI

Abstract

By means of the method of "bridge-insulator" in combination with an amplifier and a chathode-ray oscillograph, the action current of a single motor nerve fiber (toad) was recorded under varying exptl. conditions. Direct observation showed that the fiber responds to an electric stimulus only at the node of Ranvier through which the stimulating current flows outwards. In excitation of a single node, which was made possible in consequence of narcosis of neighboring nodes, the latency of the action current is shortened as the strength of the rectangular current pulse in accordance with the so-called Weiss formula. A weakly narcotized node often develops action currents of variable size and form. Veratrine causes a node to produce a long-lasting current of a supra-rheobasic strength which corresponds to the negative after-potential in the ordinary recording. The difference in the forms of the electric responses obtained by the bridge-insulator method and by the ordinary method was discussed.