In works dealing with the history of civilisation, we also encounter occasional references to our subject. Take, for instance, the knightly _Code of Love_ (_Liebeskodex_), a work highly esteemed in the days of chivalry, and legendarily supposed to have originated in King Arthur's Court. Paragraph 6 of this _Code_ runs: "A man shall not practise love until he is fully grown." According to Rudeck,[5] from whom I quote this instance, the aim of the admonition was to protect the youth of the nobility from unwholesome consequences. Obviously, the love affairs of immature persons must have been the determining cause of any allusion to the matter. We may also draw attention in this connexion to many marriage laws, which show that the subject has come under consideration, either because they expressly sanction the marriages of children, or, conversely, because they forbid such unions. At the present day, among many peoples (as, for instance, the Hindus), child-marriages are frequent; and in many countries in which such marriages are now illegal, they were sanctioned in former ages. Many works on prostitution also touch on our chosen subject. Parent-Duchatelet, in his great book, refers to girls who had become prostitutes at the ages of twelve or even ten years. I shall show later that in individual instances such early prostitution is directly dependent upon the sexuality of the children concerned. Many ethnological works also contribute to our knowledge of the sexual life of the child, describing, as they do, in certain races, the early awakening of sexual activity. Remarkably little material do we find, however, in many works in which we might have expected to find a great deal. I refer to works on education and on the psychology of the child. In exceptional instances, indeed, as I have already indicated, the educationalists have taken part in the movement in favour of sexual enlightenment. But when we consider the enormous importance and great frequency of the sexual processes of the child, we are positively astounded at the manner in which this department of knowledge has been ignored by those who have written on the science and art of education, and by those psychologists who have occupied themselves in the study of the mind of the child. Has it been a false notion of morality by which these investigators have been withheld from the elucidation of the sexual life of the child? Or has the reason merely been their defective powers of observation? As a matter of fact, I suppose that both these causes have operated in producing this remarkable gap in our knowledge.