field of operations, to the region of brain activity. The result is a most brilliant show of cerebral pyrotechnics, and degenerations that we have described. That undue and disproportionate brain activity exerts a sterilizing influence upon both sexes is alike a doctrine of physiology, and an induction from experience. And both physiology and experience also teach that this influence is more potent upon the female than upon the male. The explanation of the latter fact--of the greater aptitude of the female organization to become thus modified by excessive brain activity--is probably to be found in the larger size, more complicated relations, and more important functions, of the female reproductive apparatus. This delicate and complex mechanism is liable to be aborted or deranged by the withdrawal of force that is needed for its construction and maintenance. It is, perhaps, idle to speculate upon the prospective evil that would accrue to the human race, should such an organic modification, introduced by abnormal education, be pushed to its ultimate limit. But inasmuch as the subject is not only germain to our inquiry, but has attracted the attention of a recent writer, whose bold and philosophic speculations, clothed in forcible language, have startled the best thought of the age, it may be well to quote him briefly on this point. Referring to the fact, that, in our modern civilization, the cultivated classes have smaller families than the uncultivated ones, he says, "If the superior sections and specimens of humanity are to lose, relatively, their procreative power in virtue of, and in proportion to, that superiority, how is culture or progress to be propagated so as to benefit the species as a whole, and how are those gradually amended organizations from which we hope so much to be secured? If, indeed, it were ignorance, stupidity, and destitution, instead of mental and moral development, that were the _sterilizing_ influences, then the improvement of the race would go on swimmingly, and in an ever-accelerating ratio. But since the conditions are exactly reversed, how should not an exactly opposite direction be pursued? How should the race _not_ deteriorate, when those who morally and physically are fitted to perpetuate it are (relatively), by a law of physiology, those least likely to do so?"[27] The answer to Mr. Greg's inquiry is obvious. If the culture of the race moves on into the future in the same rut and by the same methods that limit and direct it now; if the education of the sexes remains identical, instead of being appropriate and special; and especially if the intense and passionate stimulus of the identical co-education of the sexes is added to their identical education,--then the sterilizing influence of such a training, acting with tenfold more force upon the female than upon the male, will go on, and the race will be propagated from its inferior classes.[28] The stream of life