Abstract
It was shown in previous papers that spreading induction was reflected and refracted at the boundary between dark-adapted and lightadpated retinal parts. In the present experiments evidence has been provided that spreading induction shows diffraction. A pair of patches, an inducer and a detector, was used together with a patch whose retinal image served as a diffraction grating. The inducer was a patch to initiate spreading induction, and the detector a devide to detect the arrival of the spreading induction from the inducer. The grating patch consisting of light and dark stripes was presented half-way between the inducer and the detector so that the spreading induction from the inducer had to traverse the retinal image of the grating to reach the detector. Under these conditions the arrival of spreading induction was found only at several discrete parts of the detector in a manner similar to light bands of a diffraction spectrum. An arrangement of patches imitating Rowland's concave grating was found most suitable for this experiment. The wavelength of spreading induction was measured by this method, and values about 30 μ and 50 μ were obtained for yellow and blue spreading inductions respectively.
The wave-length was longer in the order:
red<yellow<green<blue. It is reverse to the order of spectral lights concerning wave-lengths.
