[21] Body and Mind. By Henry Maudsley, M.D. Lond. p. 31 [22] Op. cit., p. 87. [23] Op. cit., p. 32. PART IV. CO-EDUCATION. "_Pistoc._ Where, then, should I take my place? _1st Bacch._ Near myself, that, with a she wit, a he wit may be reclining at our repast."--BACCHIDES OF PLAUTUS. "The woman's-rights movement, with its conventions, its speech-makings, its crudities, and eccentricities, is nevertheless a part of a healthful and necessary movement of the human race towards progress."--HARRIET BEECHER STOWE. Guided by the laws of development which we have found physiology to teach, and warned by the punishments, in the shape of weakness and disease, which we have shown their infringement to bring about, and of which our present methods of female education furnish innumerable examples, it is not difficult to discern certain physiological principles that limit and control the education, and, consequently, the co-education of our youth. These principles we have learned to be, three for the two sexes in common, and one for the peculiarities of the female sex. The three common to both, the three to which both are subjected, and for which wise methods of education will provide in the case of both, are, 1st, a sufficient supply of appropriate nutriment. This of course includes good air and good water and sufficient warmth, as much as bread and butter; oxygen and sunlight, as much as meat. 2d, Mental and physical work and regimen so apportioned, that repair shall exceed waste, and a margin be left for development. This includes out-of-door exercise and appropriate ways of dressing, as much as the hours of study, and the number and sort of studies. 3d, Sufficient sleep. This includes the best time for sleeping, as well as the proper number of hours for sleep. It excludes the "murdering of sleep," by late hours of study and the crowding of studies, as much as by wine or tea or dissipation. All these guide and limit the education of the two sexes very much alike. The principle or condition peculiar to the female sex is the management of the catamenial function, which, from the age of fourteen to nineteen, includes the building of the reproductive apparatus. This imposes upon women, and especially upon the young woman, a great care, a corresponding duty, and compensating privileges. There is only a feeble counterpart to it in the male organization; and, in his moral constitution, there cannot be found the fine instincts and quick perceptions that have their root in this mechanism, and correlate its functions. This lends to her development and to all her work a rhythmical or periodical order, which must be recognized and obeyed. "In this recognition of the chronometry of organic process, there is unquestionably great promise for the future; for it is plain that the observance of time in the motions of organic molecules is as certain and universal, if not as exact, as that of the heavenly bodies."[24]