Abstract
In decerebrate cats, the electrical excitability of the eye was measured at varying intervals after exposure to a light stimulus, taking spike discharges from the retina as an index. Increases in excitability were expressed in percentage of the resting level and denoted by ζ.
1.ζ-time curves or excitability curves showed a maximum at about 1, 1.5, 2.25 and 3seconds when the pre-illuminating light was red, yellow, green and blue respectively. The curve for white light seemed to represent an envelope of these curves. All these curves represented close copies of the corresponding ones obtained from human experiments.
2. The excitability curve for white light was greatly modified in such a manner that ζ-values at some part of the curve were depressed when the eye was exposed to another continuous colored light after illumination with white light. This phenomenon was termed “retinal inhibition” and interpreted in such a manner that the recovery of retinal processes was selectively opposed by inhibitory light.
3. When the eye was exposed to yellow and white lights in succession, an excitability curve was obtained of the same type as that for blue light alone. Similar measurements were carried out with blue and red lights combined with white light. In all these experiments, curves for successive stimuli, colored and white were always higher than that for white light alone. This phenomenon was designated “retinal induction.” Retinal induction is a retinal event underlying successive color contrast. It was pointed out that retinal induction cannot be accounted for in terms of the fatigue-theory by Helmholtz.
4. The crest time of the excitability curve was found to be prolonged enor mously after body temperature had fallen below a certain level. This finding seemed to give some clue to the understanding of the great difference observed between excitability curves of man and those of frogs or toads.
