INTERACTION OF MEDULLATED FIBERS OF A NERVE TESTED WITH ELECTRIC SHOCKS

Abstract

Testing submaximal shocks are delivered to the sciatic of Rana pipiens while some of its fibers are volleying and the temporally distributed responses from the inactive fibers stimulated submaximally by electric shocks are recorded individually on a single film. When the tested locus is outside the effective range of a demarcation current the height of the responses to the testing shocks may increase slightly before the arrival of the conditioning spike; it then falls below normal but rises above normal during the transit of the spike. When the tested locus is within demarcation range spike height increases with the arrival of the conditioning spike, and then falls below the normal level. This sequence is occasionally preceded by a slight decrease in spike height. These results are referred to the interaction of 2 processes: an increase and a decrease in excitability determined by action on inactive fibers of eddy currents from active fibers; and an alteration in the testing stimulus due to change electrical conductivity of the active fibers. When excitability is normal the conductivity cycle masks the excitation cycle.