Abstract
The electrical excitability of the human retina was measured by means of a constant current pulse 100 msec. in duration in the dark and after an illumination of definite duration and varying intensities. The increase in excitability due to illumination was expressed in percentage of the excitabi-lity in the dark before illumination, and plotted against the time interval, between the end of illumination and the electrical stimulation.
1. The time course of so obtained curves varies with wave-lengths of light in such a manner that the crest time or time to the maximum in-creases as the wave-length decreases. The values of crest time for various colors are as follows: I sec. for red (650mμ), 1.25 sec. for yellow (585mμ), 2.25 sec. for green (530mμ) and 2.75 sec. for blue (470mμ).
2. The crest time is entirely independent of intensities of illumination.
3. Curves for varying intensities of one and the same colord light vary only in their teight and run completely parallel to one another, indicating that the intensity- and time factors of this phenomenon are independent of each other.
