Word: retinas
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Professor Chaffee's experiments have led him into a variety of fields ranging from the optical research in which he claimed to have heard the eye see by attaching wires to the retina, to implanting electric coils in animals to study nervous responses by remote control. In 1938 Professor Chaffee broke into the news with the development of a new power saving radio broadcasting tube which the New York "Times" heralded as a "triumph of laboratory and mathematical skill over one of the most complex engineering problems of the generation...
...color vision (bony fishes, reptiles and birds, monkeys, apes and man) are those with the greatest visual acuity-and those most active in the daytime. "It is no accident," says he, that diurnality and hue-discrimination are associated, for they have a common basis in the structure of the retina...
Cones & Rods. The retina (the screen upon which the lens of the eye casts the image) has two kinds of visual cells: cones, each with its direct line to the brain; rods connected in multiple to the optic nerve fibers. The cones give sharp, color vision, work in bright light only. The rods "gang up" faint and dim impressions in weak light, catch no color. Some animals have cones but apparently no color vision; no known color-seeing animals have rod cells alone...
Sharp vision and color vision have two other common denominators. One is a highly sensitive dimplelike spot on the retina (the fovea centralis-literally, "central pit"), which acts as a magnifying device to spread the image over a greater number of visual cells. In this dimple, common to the vertebrates with the highest acuity (some birds have two in each eye), there are no rod cells. The cones are slim and tight-packed. The other common denominator is the mechanism for accommodation-ability to focus the eye, maintain a sharp image of a moving object...
...front of the eye; the six muscles around each eye have no function except to turn the eyeball. In myopia (nearsightedness) the eyeball is usually long from front to back; in far-sighted people it is often short. In a nearsighted eye, the image falls in front of the retina; in a farsighted eye, behind the retina. Astigmatism is usually laid to slight eye distortions. As orthodox doctors agree that a patient's efforts can not alter the shape of an eyeball, they accept distortions as final, prescribe glasses...