ations of the Life Extension Institute--25 West 45th Street, New
York City.

CHAPTER II

HEALTH AND THE HOME

Of all the considerations that determine health, heredity is the one
unalterable factor. Although certain characteristics are obviously
hereditary,--complexion, height, and mental and physical traits in great
variety,--yet in the past heredity has been little understood. In
consequence it has served too often as a scape goat for faults and
failings not beyond an individual's control. Our first clear
understanding of the principles underlying heredity resulted from
experiments made by Mendel, an Austrian monk, during the last century,
and it is now possible to predict with a high degree of accuracy the
inheritance of certain characteristics.

Many diseases, formerly considered hereditary because their actual
causes were unknown, are now known to be communicable. Thus, it is now
understood that tuberculosis is not hereditary, although little children
may be infected by tuberculous parents. No germ diseases are inherited
in the strict sense of the word; but a baby may be infected with
syphilis before birth if his father or his mother has the disease.

It is true, however, that certain tissue weaknesses of the body seem to
be hereditary, and in consequence one family is more susceptible to
digestive disorders, another to diseases of the lungs, a third to
deafness, and so on. Moreover, general low vitality may be inherited. It
should be emphasized, however, that hereditary weakness does not
inevitably lead to disease. Many persons have succeeded in preventing
the development of active disease by guarding against strain in
directions where they are weak by inheritance.

Of all tissue weaknesses that may be inherited, defects of the nervous
system are the most serious. Nervous disorders of every degree of
severity, from slight nervous instability even to insanity, may result
when these tissues are defective; but it is now a recognized fact that
nervous disorders in many cases can be prevented from developing.
Feeblemindedness, another condition due to defective tissue, is known to
be inherited in the majority of cases, and in all cases it is incurable.

HYGIENE OF ENVIRONMENT AND PERSON

By environment is meant everything outside the body that affects it;
taken in its complete meaning the word might include everything that is
or ever was in the whole universe. It is possible to consider here a few
o