The Japanese Journal of Physiology Volume 5 Supplement Issued in Memory of the 60th Birthday of Dr. Takashi Minoshima Professor of Physiology, Hokkaido University by His Pupils and Friends the Third Effect of Polarizing Electrodes on the Strength-duration-curve of Nerve

The third effect of electrodes of a polarizing current applied on a nerve denotes, as described by Suzuki (1) and Suzuki, Ando and Miyata (2), the effect of a longer or stronger polarization, which causes changes in the threshold of stimulation under both electrodes in direction opposite to those due to the electrotonus. The changes in the threshold by the electrotonus, which appear soon after the onset of polarization and are caused by the polarization potential itself, are replaced under both electrodes, if the polarization lasts longer, by the changes in reverse direction due to the third effect, and these changes result from such physicochemical changes in nerve membrane under the electrodes, as its ion-permeability becomes increased and the polarizability decreased under the cathode and vice versa under the and anode (Ebbecke (3, 4), Hecht (5), Suzuki (6) ). Although the third effect of polarizing electrodes was investigated on various functions of nerve and muscle in our laboratory (Suzuki (7, 8)), no one has yet observed its direct effect on the time-factor in electric excitation of nerve, since construction of a strength-duration-curve (i-t-curve) for a precise measurement of the time-factor postulates a certain duration of time, while the third effect increases in strength with passage of time. In the present research we have determined each i-value in a certain order in relation to t and constructed three i-t-curves during the polarization. By observing transition of changes in these