Electrotonus in Colour Vision

Abstract

DURING the past year, we have studied the influence of a weak constant electrical current upon the foveal (colour) sensitivity of the human eye. The foveal sensitivity was measured in respect of monochromatic lights of different wave-lengths. Two silver electrodes were used. The indifferent one was put on the observer's hand, the second—the different one—being applied to the contralateral eyeball of the observer or (in some control series) on his temple near the lateral angle of the eyelids. The current used always had a strength of 0·2 mA. Our experiments, in which we determined the threshold values for foveal sensitivity, were carried out during 50–60 minutes of dark adaptation. At about the thirtieth minute of dark adaptation, when the foveal sensitivity reached its maximal stationary level, we switched on the current and allowed it to remain on for 4–5 minutes. During that period of electrical stimulation we determined the thresholds of the foveal sensitivity two or three times.