e and eugenics. Many people who ought to know better use the
two terms synonymously, perhaps because they are afraid of that
comparatively novel but frank prefix in "sex-hygiene." The fact is that
eugenics and sex-hygiene have little in common. Eugenics is the
science of reproducing better humans by applying the established laws
of genetics or heredity. In brief, it means, on the positive side,
selecting desirable people as parents; and, negatively, preventing
propagation by the undesirables. This is the sum total of the task of
eugenics in the accurate sense of the term.

[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