CHIEFLY CLINICAL 61 PART IV. CO-EDUCATION 118 PART V. THE EUROPEAN WAY 162 PREFACE. About a year ago the author was honored by an invitation to address the New-England Women's Club in Boston. He accepted the invitation, and selected for his subject the relation of sex to the education of women. The essay excited an unexpected amount of discussion. Brief reports of it found their way into the public journals. Teachers and others interested in the education of girls, in different parts of the country, who read these reports, or heard of them, made inquiry, by letter or otherwise, respecting it. Various and conflicting criticisms were passed upon it. This manifestation of interest in a brief and unstudied lecture to a small club appeared to the author to indicate a general appreciation of the importance of the theme he had chosen, compelled him to review carefully the statements he had made, and has emboldened him to think that their publication in a more comprehensive form, with added physiological details and clinical illustrations, might contribute something, however little, to the cause of sound education. Moreover, his own conviction, not only of the importance of the subject, but of the soundness of the conclusions he has reached, and of the necessity of bringing physiological facts and laws prominently to the notice of all who are interested in education, conspires with the interest excited by the theme of his lecture to justify him in presenting these pages to the public. The leisure of his last professional vacation has been devoted to their preparation. The original address, with the exception of a few verbal alterations, is incorporated into them. Great plainness of speech will be observed throughout this essay. The nature of the subject it discusses, the general misapprehension both of the strong and weak points in the physiology of the woman question, and the ignorance displayed by many, of what the co-education of the sexes really means, all forbid that ambiguity of language or euphemism of expression should be employed in the discussion. The subject is treated solely from the standpoint of physiology. Technical terms have been employed, only where their use is more exact or less offensive than common ones. If the publication of this brief memoir does nothing more than excite discussion and stimulate investigation with regard to a matter of such vital moment to the nation as the relation of sex to education, the author will be amply repaid for the time and labor of its preparation. No one can appreciate more than he its imperfections. Notwithstanding these, he hopes a little good may be extracted from it, and so commends it to the consideration of all who desire the _best_ education of the sexes. BOSTON, 18 ARLINGTON STREET, October, 1873. PREFACE TO SECOND EDITION.