The inadequacy of "natural selection" / by Herbert Spencer ; reprinted from the Contemporary review.

  • Spencer, Herbert, 1820-1903.
Date:
[1893]
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Licence: Public Domain Mark

Credit: The inadequacy of "natural selection" / by Herbert Spencer ; reprinted from the Contemporary review. Source: Wellcome Collection.

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    - THE INADEQUACY OF “NATURAL SELECTION.'’ STUDENTS of psychology are familiar with the experiments of Weber on the sense of touch. He found that different parts of the surface differ widely in their ability to give information con- cerning the things touched. Some parts, which yielded vivid sensa- tions, yielded little or no knowledge of the size or form of the thing exciting it; whereas other parts, from which there came sensations much less acute, furnished clear impressions respecting tangible char- acters, even of relatively small objects. These unlikenesses of tactual discriminativeness he ingeniously expressed by actual measurements. Taking a pair of compasses, he found that if they were closed so nearly that the points were less than one-twelfth of an inch apart, the end of the forefinger could not perceive that there were two points :~ the two points seemed one. But when the compasses were opened so that the points were one-twelfth of an inch apart, then the end of the forefinger distinguished the two points. On the other hand, he found that the compasses must be opened to the extent of two and a half inches before the middle of the back could distinguish between two points and one. That is to say, as thus measured, the end of the forefinger has thirty times the tactual discriminativeness which the middle of the back has. Between these extremes he found gradations. The inner surfaces of the second joints of the fingers can distinguish separateness of positions only half as well as the tip of the forefinger. The inner- most joints are still less discriminating, but have a power of dis- crimation equal to that of the tip of the nose. The end of the great toe, the palm of the hand, and the cheek, have alike one-fifth of the perceptiveness which the tip of the forefinger has; and the lower part of the forehead has but one-half that possessed by the cheek. VOL, LXIII L