THE RELATION BETWEEN THE THRESHOLD OF NERVE RESPONSE AND POLARIZATION BY GALVANIC CURRENT STIMULI

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Abstract
Assuming that electrical stimulation of nerve corresponds to electrochemical polarization of some critical interface, it is argued that polarization of other nonirritable structures in the nerve trunk as usually employed can account for the deviation of nerve from the simple behavior assumed in laws of stimulation. The curve of polarization of the nerve trunk is directly recorded on the cathode ray oscillograph, together with the nerve response. The curve of irritability preceding threshold response, as measured by an induction shock delivered during the passage of a galvanic current, is shown to correspond to it. The curve falls to 1/2 its value in about 0.0001 sec. Rhythmic repetitive responses to a galvanic current and change in irritability accompanying them are recorded, also the change of form and time relations of the action potential, with changes in intensity and duration of the galvanic stimulus. No evidence of depolarization during activity can be obtained from these records, but this might be masked by the persistent polarization of nonirritable structures. Two polarization effects of different order can be detected in nerve. The 1st corresponds to stimulation, and is a transient effect like a condenser charge, the irritability change in the nerve subsiding with it. The 2nd may be correlated with electrotonic effects due to currents of duration or intensity above threshold.

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