大众英语80篇背诵阅读带翻译(二十三)
"46 Vision
Human vision like that of other primates has evolved in an arboreal environment. In the dense complex world of a tropical forest, it is more important to see well than to develop an acute sense of smell. In the course of evolution members of the primate line have acquired large eyes while the snout has shrunk to give the eye an unimpeded view. Of mammals only humans and some primates enjoy color vision. The red flag is black to the bull. Horses live in a monochrome world. Light visible to human eyes however occupies only a very narrow band in the whole electromagnetic spectrum. Ultraviolet rays are invisible to humans though ants and honeybees are sensitive to them. Humans have no direct perception of infrared rays unlike the rattlesnake which has receptors tuned into wavelengths longer than 0.7 micron. The world would look eerily different if human eyes were sensitive to infrared radiation. Then instead of the darkness of night, we would be able to move easily in a strange shadowless world where objects glowed with varying degrees of intensity. But human eyes excel in other ways. They are in fact remarkably discerning in color gradation. The color sensitivity of normal human vision is rarely surpassed even by sophisticated technical devices.视觉人类的视觉，和别的灵长目动物的一样，是在丛林情况中退化出来的。在浓密、庞大的热带丛林里，好的视觉比灵敏的嗅觉更减轻要。在退化历程中，灵长目动物的眼睛变年夜，同时鼻子变小以使视野不受阻碍。在哺乳类动物中，只要人和一些灵长目动物可以分辨颜色。红旗在公牛看来是黑色的，马则糊口在一个单色的世界里。但是，人眼可见的光在整个光谱中只占一个极度狭隘的频段。人是看不到紫外线的，虽然蚂蚁和蜜蜂可以感受到。与响尾蛇不合，人也不能直接感遭到红外线。响尾蛇的感受器可以感触熏染波长跨越 0.7微米的光芒。如果人能感遭到红外线的话，此日下看上往将非常不合，并且可怕。到那时，将与夜的漆黑相反，我们能随便地在一个奇特的没有暗影的世界里走动。任何物体都强弱不等地闪着光。但是，人眼在别的方面有精良之处。毕竟上，人眼对颜色梯度具有特殊的分辨本领。通俗人类的视觉感触熏染颜色的灵敏程度，乃至连细密的技能配备都很难逾越。
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