Two types of luminosity horizontal cells in the retina of the turtle

Abstract

1. Two classes of luminosity horizontal cells have been identified in the retina of the turtle by intracellular recording. These cells differ in the area of retinal surface over which they are sensitive to light. For moderate light intensities the maximum response amplitude of `type I' cells increases progressively as the radius of a circle of light is enlarged to over 750 μm. Responses of `type II' cells instead reach maximum amplitude with circular illumination of about 300 μm radius.