I am well aware of the disproportion which exists between the magnitude of my task and the imperfections of my work. I have not been able to study as much as should be done the innumerable works which treat of the same subject. Others, better versed than myself in the literature of the subject, will be able later on to fill this regrettable lacuna. I have endeavored, above all things, to study the question from all points of view, in order to avoid the errors which result from any study which is made from one point of view only. This is a thing which has generally been neglected. I must express my thanks to my friend, _Professor Mahaim_, and especially to my publisher and cousin, _S. Steinheil_, for the help and excellent advice which they have given me in the revision of my work; also to _Professor Boveri_, who has been kind enough to revise the figures, 1 to 17. DR. A. FOREL. Chigny près Morges (Suisse). PREFACE TO THE SECOND EDITION The text of the first edition has been revised and corrected, but, apart from some points of detail, the subject matter has not been changed. The examples at the end of Chapter V (First Edition) no longer form a special appendix; they have been included in the parts of the book which specially concern them; some of them have been omitted as being superfluous. In the domain with which we are concerned the French public are too much afraid, I think, of crudities and of calling things by their proper name. By veiled words and by indirect locution one may say anything, but I have decided not to employ such subterfuges in treating of such a vital social question with the seriousness that it requires. It seems that there is a fear of young people hearing the sexual question spoken of freely and openly; but it is not taken into account that in hiding these things under half-understood words one only excites their curiosity, and, owing to their being blindfolded, they are delivered into the snares and surprises of debauchery. I cannot better illustrate the error that I have just pointed out than by quoting, among several others of the same kind, a letter which I have received from a young girl, aged 21 years, intelligent, virtuous, educated, and well brought up, but without restraint. Having read my book she put several questions to me to which I replied. On my part I requested her to tell me frankly: (1). If, in her opinion, I had been mistaken in my judgment of the sexual psychology of the normal young girl; (2). If my book had done her the least harm, moral or otherwise. I begged her to criticise me without pity, for I wished above all things to be clear on the effect produced by my book. This is her letter: