What _Eulenburg_ says regarding the prophylaxis of sexual neurasthenia in general is true regarding the sexual life of the girl at this period of life. “What is needed,” he writes, “is the control of educational influences with these ends in view, that, on the one hand, the sexual excitability of developing youth shall be diminished and kept within bounds, and that nevertheless, on the other, the urgently needed enlightenment shall be afforded to the young people at the proper time and in a suitable form. How these aims are to be effected cannot be explained in generally applicable propositions. It is a matter which must be left to the tact of the parents and of other members of the family, who will be guided by the insight they have acquired into the mental life of those concerned. * * *. Children inclined to onanism must be carefully supervised by day and by night; they must be protected from all stimulating things and from bad company; in boarding-schools it is the common dormitories that require the most strict, most careful, and most continuous control. In the case of auto-onanists, female as well as male, we must enquire into the possible existence of local stimulating influences, among which, in both sexes, oxyuris must be mentioned—but in truth it is rare for such local conditions to be the exciting cause of masturbation. A healthy mode of life in respect of clothing, sleep, and diet, and the systematic practice of bodily exercises to the point of considerable fatigue, are the most effectual means of counteracting the noxious propensity to onanism.” A high degree of freedom permitted to girls from a very early age is, as _Rousseau_ already maintained, by no means favorable to the preservation of virginity. A wise mother or a wise instructress can do much towards the preservation of physical and moral virginity, by enlightening her daughter or pupil at the right time and in a proper manner as to the nature of the sexual processes, and their significance for the whole life of woman. Ignorance in this respect, equally with pseudo-knowledge, entails many dangers. I regard it as indispensable that the adolescent girl should in good time learn from her mother the nature of menstruation, lest she should first receive enlightenment in an unfitting manner from some more experienced female friend. The mother should explain that the impending flow of blood is a natural process, unattended by danger, but indispensable to the sexual life, and a characteristic part of the process of “growing up.”