On the photosensitive substance in the retina of the grasshopper eye

The so-called "cone substance" was isolated by Studnitz, and has been confirmed by Hosoya and Wald. In my previous communication it was reported that the retinal action current of the grasshopper's eye was greatly decreased by the application of digitonine solution. The author tried, therefore, to extract the photosensitive substance from the grasshopper's eye with digitonine solution. Method: Dark-adapted eyes from 50 grasshoppers were grounded in 2 p.c. digitonine solution immediately after the excision, centrifugalized after about 18 hours. Absorptions of the extract for various wave lengths were determined with Pulfrich's step-photometer. Results: The absorption maximum lies in red (650mμ), yellow (563mμ) and blue-violet (480-460mμ) regions. Prolonged irradiation with the light from electric lamp caused a decrease in absorption. But the difference in extinction coefficient between the unbleached and the bleached preparations was slightly. Similar experiments were performed on the eye of snail, chicken and dove, which showed the same results as in the case of the grasshopper's eye. Since the eyes of these animals were constructed mainly from cones, it is concluded that the extracted photosensitive substance through digitonine solution must be "cone substance" after Studnitz, because it differs from rhodopsin in its absorption maximum.