This letter confirms the statement of Dr. Hagen, and shows that the educational and social regimen of a German school-girl is widely different from that of her American sister. Perhaps, as is intimated above, the German way, which is probably the European way also, may err on the side of too great confinement and caution; and that a medium between that and the recklessness of the American way would yield a better result than either one of them. German peasant girls and women work in the field and shop with and like men. None who have seen their stout and brawny arms can doubt the force with which they wield the hoe and axe. I once saw, in the streets of Coblentz, a woman and a donkey yoked to the same cart, while a man, with a whip in his hand, drove the team. The bystanders did not seem to look upon the moving group as if it were an unusual spectacle. The donkey appeared to be the most intelligent and refined of the three. The sight symbolized the physical force and infamous degradation of the lower classes of women in Europe. The urgent problem of modern civilization is how to retain this force, and get rid of the degradation. Physiology declares that the solution of it will only be possible when the education of girls is made appropriate to their organization. A German girl, yoked with a donkey and dragging a cart, is an exhibition of monstrous muscular and aborted brain development. An American girl, yoked with a dictionary, and laboring with the catamenia, is an exhibition of monstrous brain and aborted ovarian development. The investigations incident to the preparation of this monograph have suggested a number of subjects kindred to the one of which it treats, that ought to be discussed from the physiological standpoint in the interest of sound education. Some, and perhaps the most important, of them are the relation of the male organization, so far as it is different from the female, to the labor of education and of life; the comparative influence of crowding studies, that is of excessive brain activity, upon the cerebral metamorphosis of the two sexes; the influence of study, or brain activity, upon sleep, and through sleep, or the want of it, upon nutrition and development; and, most important of all, the true relation of education to the just and harmonious development of every part, both of the male and female organization, in which the rightful control of the cerebral ganglia over the whole system and all its functions shall be assured in each sex, and thus each be enabled to obtain the largest possible amount of intellectual and spiritual power. The discussion of these subjects at the present time would largely exceed the natural limits of this essay. They can only be suggested now, with the hope that other and abler observers may be induced to examine and discuss them.