抄録
The eye was illuminated by white light for 2 seconds, and then the electrical excitability of the eye was measured by applying electrical square pulses of varying frequencies to the eye for 0.5 seconds. Percentage increases in electrical excitability were denoted by ζ and plotted as ordinates against the time after the end of pre-illumination.
1. ζ-time curves thus obtained were compared with those deter-mined by a single pulse of 0.1 second, using colored lights for pre-illumina-tion. It was found that changes in frequency of stimulating currents have the same effect as color changes of pre-illuminating lights upon the shape of ζ-time curves.
2. When red light was used for pre-illumination ζ-time curves showed a maximum at 1 second, irrespective of frequencies of stimulating currents. ζ-frequency curves showed a maximum at 55 cps. Since red light of such extremely long wave-lengths as used in this experiment excites red receptors only and causes the supernormal electrical excitability of this kind of receptor, the ζ-frequency curve having a maximum at 55 cps. represents a resonance curve of the red receptors. Resonance curves for green and blue receptors determined in a similar way showed a maximum at 42 and 36 cps. respectively.
3. Rods were selectively excited by exposing the extreme periphery of the retina or by using very weak light below color-threshold for pre-illumination. The ζ-values thus obtained were plotted against the fre-quencies of stimulating currents. The curve so obtained represents a resonance curve of rods, and shows a definite maximum at 20 cps.
4. The relation between the minima of strength-frequency curves obtained by Motokawa and by Abe and the resonance frequencies deter. mined in the present experiments was discussed.
