The extent of social diseases is a fairly accurate measure of the minimum amount of immorality, for nothing is better established in medical science than that promiscuity in sexual relations is directly or indirectly responsible for spread of the microorganisms which cause the diseases. If for several generations all men and women limited their sexual relations to monogamic marriage, and the relatively rare cases of non-sexual and prenatal infection were treated so as to render them non-contagious, the social diseases would probably disappear from the human family. Such a statement is significant only in showing the relation of social diseases to sexual promiscuity, for of course, there is no reasonable hope that the venereal germs will ever be annihilated by universal monogamy. [Sidenote: Attack by education and sanitation.] Reduction of the amount of venereal disease must depend upon (1) hygienic and moral education which will lead people to avoid the sources of infection and (2) sanitary and medical science which works either by applying antiseptic or other prophylactic methods for preventing development of the causative microorganisms, or by using germicides for destroying those germs which have already produced disease. Thus the educational and the sanitary attack on the social diseases lie parallel. Both are needed, for, even with all the possible methods of attack, the progress against these diseases will be exceedingly slow. Those who are interested in the facts relating to social diseases which point to the need of sex-education as one method of prevention, are referred to the pamphlets published by the American Society of Sanitary and Moral Prophylaxis; Morrow's "Social Diseases and Marriage"; Creighton's "The Social Disease and How to Fight It"; Dock's "Hygiene and Morality"; Henderson's "Education with Reference to Sex"; and certain chapters in Warbasse's "Medical Sociology." [Sidenote: Estimated amount of disease.] With regard to the accuracy of the commonly quoted statements concerning the prevalence of social disease, and therefore of immorality, it must be said in all fairness that there has been much guesswork and some deliberate exaggeration. We learn from various books and lectures that fifty, sixty-five, seventy-five and even ninety per cent of the men in the United States over eighteen years of age are at some time infected with at least one of the social diseases. The fact is that there is no scientific way of getting accurate statistics, for unlike other contagious diseases, the venereal ones are kept more or less secret, and numerous cases cannot be discovered by health officers. All the published figures regarding the prevalence of such diseases are merely estimates based upon the experience of certain physicians with special groups of men, especially in hospitals. There is no reliable scientific evidence as to the prevalence of venereal disease in the whole mass of our American population.