(4) And there is one other line of facts concerning prostitution that the developing young man should know well, namely, that every prostitute is likely at any time to be infected with the social diseases, and that no ordinary medical examination can prove that she will not transmit these awful diseases to men who consort with her. In fact, within an hour after most careful medical examination she may become infected by some diseased man, and then she is capable of inoculating other men. Such facts, for which the greatest of special physicians vouch, will eradicate from the young man's mind the widespread notions that prostitutes are safe if they carry a physician's certificate, or one of the official cards given in some European cities. Many a young man of sixteen to twenty has not heard that prostitutes as a class are universally dangerous as distributors of the most terrible diseases, and his education is incomplete until he knows the exact truth from reliable sources. [Sidenote: Limited reading.] (5) It is not desirable that the young man should be set to read the numerous books packed with more or less sensational reports on the social evil, for these may sometimes tend toward morbidity. Any young man who is not effectively appealed to by the above facts will not be influenced by the most voluminous reports on prostitution ever published. Such reports are not useful for young men. They serve a good purpose by informing mature men and women and awakening them to the necessity of legislation, education, and other weapons with which we may fight the great black plague of social vice. For the average young man the books recommended in Sec. 8 will give sufficient information and viewpoint. [Sidenote: Liaisons.] (6) Finally, the young man of adolescent years should be made to understand his responsibility for immorality that is not prostitution, that is, extra-marital relations with his girl friends and without pecuniary considerations. He should know the probability that he will ruin a girl's life, either because illegitimacy occurs or because her reputation suffers. Even if such immoral liaisons are kept private, both persons concerned are likely in after years to regret their illicit intimacy, especially if either marries another person. Sec. 34. _Need of More Refinement in Men_