Word: visional
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Dates: during 1930-1939
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...likely that the merely servient (left) eye will shrink away (as the pineal eye has already done) so that the right eye will become the cyclopean. Certain it is that the left eye, even today, is being used less and less continually. Man's binocular and stereoscopic visions are being destroyed-the price he pays for his speech center. The great cyclopean eye, however, will regain stereoscopic vision by developing two maculae [spots of sharpest vision] in the one eye, just in the fashion in which many birds have stereoscopic vision in each eye now. Although the field...
Frogs, toads and other amphibians have tears. Many amphibians "have fair color vision, but . . . their sight is in general poor...
...finest and most remarkable of all the eyes on earth, being often both telescopic and microscopic. . . . Visual acuity is almost incredible, being in some instances 100 times as great as that in men. . . . Birds do not see blues and violets at all. This helps in their distance vision because the haze which hangs about distant objects and which, for our eyes, renders them more or less invisible, for birds does not exist. Birds, on the other hand, see infra-red radiations which, for us, affect only the temperature sense of the skin and not the retinas...
...Nearly all birds have eyes on the sides of the head. Such birds, of course, can have no binocular vision. Many nevertheless possess stereoscopic vision which they get by virtue of the fact that they have two maculae ... in each eye. This gives in the one eye the two pictures from two different angles which constitutes the sine qua non for stereoscopic vision...
Primates (monkeys, apes, men) are the only creatures who have both binocular and stereoscopic vision. "Only in man, of all the mammals, does there seem to be continuous easily kept, binocular and stereoscopic vision. Even in the human child, however, the eyes do not as a rule move in perfect unison with each other till about three months after birth, because stereoscopic vision, in the history of life on this planet, is an extremely recent appearance. The same fact explains the ready loss-of-binocularity (cross-eyes) in many persons as the result of optical errors (eye-strain). ... I should...