[Sidenote: Facts of heredity.] So far as we know, each coming generation will inherit only qualities that the parents inherited from their parents. It is a well-known principle of biology that changes in the bodies of human beings during their lifetime (dating from the fertilized egg that produces the individual) are never in any noticeable degree inherited by descendants. In short, acquired characteristics of the body tissues do not influence the germ plasm, the living matter concerned with heredity and reproduction, but the germ plasm that determines what the next generation will inherit is fixed at birth. Thus tuberculosis, alcoholism, gonorrhea, and syphilis may be acquired during the life of an individual, but do not become fixed in the germ plasm. If the infants show effects of any of these diseases, it is not because of true heredity but because they were infected or influenced before birth. Rarely does this happen to children of a tuberculous mother, but often to those of a syphilitic mother. In a gonorrheal ophthalmia neonatorum (specific inflammation of infants' eyes) it is a case of infection _during_ birth. [Sidenote: Sex-hygiene and eugenics parallel.] Thus, it appears that sex-hygiene either personal or social (concerned with venereal diseases) is not a part of eugenics. It is, however, a phase of euthenics, which deals with the environmental factors that affect the individual life. It is clear, then, that sex-hygiene (in the strict medical sense) and eugenics are parallel and not conflicting. Eugenics aims to select better parents who will transmit their own qualities genetically. Sex-hygiene in its personal and social aspects will make healthier parents able to give their offspring a healthier start in life, especially because the offspring is free from the prenatal effects of disease. The teaching of heredity and eugenics is intended to develop a sense of individual responsibility for the transmission of one's good or bad inherited qualities to offspring. The teaching of sex-hygiene, either personal or social, looks towards improving personal health and preventing infection and injurious influence on the unborn next generation. Obviously, we need both sex-hygiene and eugenics as part of the larger sex-instruction. Sec. 14. _Summary of Lectures on Sex Problems_ [Sidenote: Problems of health, attitude, and morals.]