VISUAL a.
l purple (Physiol.), a photochemical substance, of a purplish red color, contained in the retina of human eyes and in the eyes of most animals. It is quickly bleached by light, passing through the colors, red, orange, and yellow, and then disappearing. Also called rhodopsin, and vision purple. See Optography. -- Visua…
YELLOW a.
at.) A small yellowish spot with a central pit, the fovea centralis, in the center of the retina where vision is most accurate. See Eye. (b) (Zoöl.) A small American butterfly (Polites Peckius) of the Skipper family. Its wings are brownish, with a large, irregular, bright yellow spot on each of the hind wings, most con…