Page:Popular Science Monthly Volume 26.djvu/27

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17
MIND AND THE NERVOUS SYSTEM.

existing between the mind and the nervous system; but, having it in view, the connection is at once clear and well defined, there being no exception to the law that the mental development is in direct proportion to the amount of gray matter entering into the composition of the nervous system of any animal of any kind whatever.

A point which attracts a good deal of attention at the present day is that which relates to the differences in the brain and mind as exhibited in the sexes of the human species. A few words on this division of the subject may not, therefore, be out of place.

The skull of the male is of greater capacity than that of the female, and it is a singular fact that the difference in favor of the male increases with civilization. Thus, in savage nations, as the Australians and the negroes of Africa, the skulls of men and women are much more alike in size than they are in Europeans. It would appear from this fact either that women, from some cause or other, have not availed themselves of the advantages of civilization, as factors in brain development, to the same extent that man has; or that, among savages, there is not that dissimilarity in mental work that is found in civilized nations; and that, hence, there is not the same necessity for a difference in brain-development.

For it naturally follows that, in the normal skull, there is a correspondence between its size and that of the organ contained within it. Many observations have shown that the average male brain weighs a little over forty-nine ounces, while the average female brain is a little over forty-four ounces, or about five ounces less. The proportion existing between the two is, therefore, as 100 to 90.

This apparently makes a good showing for man, but, when we look at the matter in another and possibly a more correct light, the advantage is rather the other way, for, relatively to the weight of the body in the two sexes, the difference, what there is, is in favor of woman. The body of the female is shorter, and weighs less, than that of the male. Thus, in man the weight of the brain to that of the body has been found to be an average of 1 to 36·50, while in woman it was as 1 to 36·46. I have said that possibly this may be a more correct way of determining the size of the brain than by absolute measurements, without regard to the size of the body. The doubt arises from the fact that we do not know that very thin persons, in whom, of course, other things being equal, the brain would be relatively larger, are more remarkable for mental vigor than very stout ones, in whom the relative size of the brain would be less. Such being the case, it is difficult to believe that the proportionate size of the brain to that of the body has any important influence as a factor in the production of mind. It is the absolute, rather than the relative, amount of gray matter that is to be considered in determining the brain-power.

It must, however, be borne in mind that the quantity of gray matter can not be positively affirmed from a determination of the size