Indirect Retinal Induction in Various Regions of the Human Retina

Abstract

By the method of electro-stimulation, the magnitude of indirect retinal induction was measured at various parts of the human retina.
1. The magnitude of the indirect retinal induction was found greatest at about 10° from the fovea. This fact might be correlated witn the psy-chological fact that color contrast can most easily be perceived in the parafoveal region of the retina.
2. The capacity to produce the indirect induction is great for red and green lights in the neighbourhood of the fovea, and for yellow and blue lights at the periphery of the retina.
3. The contrast effect increases in proportion to the logarithm of the intensity of colored light above a critical intensity, below which no induction takes place. The threshold of contrast effect is higher than the threshold of color effect.
4. Around the blind spot there is a zone in which no retinal induction takes place, but white sensations occur.