Page:Popular Science Monthly Volume 55.djvu/529

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511
PRACTICAL PHASES OF MENTAL FATIGUE.

have wandered away from the Jewish race and have not affected the more conservative remnant.

The significance of this result for the science of anthropology can not be overrated. The great question of the science is that expressed by Dr. Galton as "the struggle between Nature and nurture"—the difference that social influences can produce on men of the same race. Jews afford the science almost the sole instance in which this problem can be studied in its least complex form. My own investigations have shown that social environment has a direct influence on such anthropometrical data as height and breathing capacity. The Jews of the West End of London, though of the same race as those of the East End, are superior in height and other external qualities, and this superiority can thus be shown to be due entirely to nurture. Similarly, if the argument I have previously adduced is correct, the brachycephalism of the Jew is a proof that intellectual development produces broad heads, and that, roughly speaking, the cephalic index is a key to intellectual capacity. I should rather reverse Professor Ripley's main contentions: breadth of skull is not a criterion of race, but of intellectual development; whereas features, which are not directly influenced by social or intellectual characteristics, are the true index to racial purity.

 

SOME PRACTICAL PHASES OF MENTAL FATIGUE.
By Prof. M. V. O'SHEA.
I.

MODERN studies in neurology have contributed much to our knowledge of the function of the nervous system as a whole and of its several parts, and also of the relation of psychical activity to cerebral conditions and processes. The architecture of the neural mechanism delineated by these investigations is not only interesting in itself on account of the marvelous unity of things apparently diverse, but it is at the same time suggestive respecting its office as the physical instrument through which mind must express itself in this world. Psychologists now quite generally conceive of a living being, human or otherwise, as a reacting organism, receiving impressions from its environment and responding to them in some characteristic manner. To be fitted for this office an individual must be provided with appliances alike for the reception of stimulations and for their transformation into incitements to muscular activity. In the human species Nature has ordained that action need not follow immediately and inevitably upon any sense stimulus; fortunately, it may be deferred, so that when it does finally occur it