Abstract
The change in electrical excitability of excised frog eyes was investigated with action potentials of optic nerves as the index of excitation.
1. The excitability-time curve or excitability curve after an illumination by white light shows three humps at about 1.5, 3, and, 5 minutes after, the end of the illumination at room temperature of 15-20°C. These humps are called R, G and B elevations.
2. When colored light is used instead of white light for pre-illumination the three elevations appear in different proportions according to the wave-length of the light. Predominant elevations of curves obtained by pre-illumination with red, green and blue lights are R, G and B respectively.
3. Percentage increases of electrical excitability above its resting level are denoted by ζ. Between the maximum ζ and the logarithm of the intensity of pre-illuminating light a linear relation holds in a wide range of intensities.
4. The excitability curve for white light is markedly deformed when the eye is continuously exposed to weak colored light after removal of the pre-illuminating white light. This phenomenon is due to an inhibitory effect exerted by the continuous light upon color processes. Red, green and blue lights have a selective inhibitory action upon the R, G and B processes respectively.
5. When pre-illuminating white light is preceded by any colored light, an excitability curve is obtained which is similar to that obtained when the eye is illuminated by the complementary color alone. For example, in this respect white light preceded by blue light is equivalent to yellow light. This is evidently a physiological phenomenon underlying successive color contrast.
