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Page:Popular Science Monthly Volume 65.djvu/233

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cance of this loss can be better understood if we consider for a little such a sense as sight.

The eye is movable and is continually shifting its position. From this mobility two results follow which in the present connection it is important to notice. First, the eye can be readily turned so as to get the clearest vision of any object that is to be examined. We do not see equally well with all parts of the eye; we see most distinctly with the central part directly opposite the pupil, and when there is anything seen out of the corner of the eye which we wish to observe more closely, the eye is, in normal circumstances, turned upon it so as to catch the image in this central part. Spontaneously and accurately these changes in the eye's direction are made. It can readily be understood that great help to our perception is gained from them.

There is another result of this free movement which is of equal importance. To it is due the orderly spatial arrangement presented by the world of our vision. It may seem that our knowledge of the position of things in relation to each other is natural or instinctive, and we may be pointed to the behavior of many animals which are able to guide their movements correctly as soon as they enter the world. But such reflex activities do not seem to be strictly parallel to those of the human child. That the child has in its nervous system inherited a predisposition to its future adjustments, may be true. But it is also true that it does not respond to its surroundings as the chick, for instance, does; it gains its conscious appreciation of external relations by experience. What the child's first experience of sight is, it is difficult for the adult to guess; yet some of our perceptions approach to it. The German psychologist Volkmann von Volkmar calls attention to the fact that when we gaze into the blue depths of the sky our color perception has a character similar to that of a musical note. Probably our visual sensations are all, in their original intrinsic nature, of this sort; color feelings with no idea of position as yet developed. It is further to be noted that we might have a succession of color pictures, such as can be afforded by familiar mechanical devices, without any suggestion as to the spatial relations of these various pictures. And were the eye incapable of movement of any kind, its experiences would be a mere succession of vaguely voluminous color-feelings. But, on the other hand, let the eye be considered as capable of movement, and as free to play among these colors; it passes, say, from the image of the door to that of the wall, and then to that of the window. It is not less important to notice that it can by its power of movement reverse the series and pass from window to door. Such series may, to an indefinite extent, be increased, repeated, reversed. Thus the mind gets the idea of a series of images relatively permanent, always open to observation, and arranged in a perfectly