but not least, the individual should cooperate in the great
movement against the social evil.

As soon as an individual becomes interested in caring for his own health
and for the health of his family, his interest will not cease at
individual hygiene; he will wish to improve the efficiency of the public
health service by increased appropriations, improved equipment and
personnel; and to cooperate with the health officer.

[Sidenote: Eugenics]

Race hygiene or eugenics, which has been mentioned as the third and most
important branch of hygiene, aims to conserve the health of _future_
generations, through the action of those now living. Hygiene (individual
and public) teaches us how to create for ourselves healthful conditions
of living, but on every side we see evidences of the fact that we cannot
entirely control conditions of health through hygiene only. Not all
maladies by any means can be attributed to unnatural or unhygienic
conditions of living. It is true that if followed out faithfully, the
rules of hygiene will enable a man to live out his maximum natural
life-span, with the maximum of well-being, and to run no risk of
allowing any inherent weakness to be brought out. But some persons, even
if they followed what is very nearly the normal code for the human
being, would scarcely be able to avoid dire physical and mental fates.
In short, we find that besides the hygienic factor in life which we may
call environment, there is something else on which the health of the
individual depends. This something else is heredity, or "the nature of
the breed." Back of all the individual can do by hygiene lies his
inheritance. To change this the individual can do nothing, but the
parents of the individual can affect his inheritance, and we as parents
can affect the inheritance of our offspring.

[Sidenote: Trustees of the Racial Germ-plasm]

First, we can carry through life uninjured the essential germ plasm
which has been entrusted to our care. We should never forget that this
germ plasm, which we receive and transmit, really belongs, not to us,
but to the race; and that we have no right, through alcoholic or other
unhygienic practises, to damage it; but that, on the contrary, we are
under the most solemn obligation to keep it up to the highest level
within our power. We are the trustees of the racial germ plasm that we
carry.

[Sidenote: Wise Combinations of Germinal Traits]

Second, we can affect the life of our off