races, until the last generation or two, roamed in the open, fell easy
prey to tuberculosis as soon as they adopted the white man's houses and
clothes. The Anglo-Saxons who have withstood the influence of indoor
living for several generations have, probably by the survival of the
fittest, become a little better able to endure it, while the Jews, a
race which has lived indoors longer than any other existing race, are
now, probably by the same law of survival, the least liable to
tuberculosis, except when exposed to especially unfavorable conditions
of life.

[Sidenote: Compensation for Civilization]

But we, of this generation, can not afford to wait for natural selection
to fit the race to an indoor environment; hence the supreme importance
to us of air hygiene. We must compensate for the construction of our
houses by insisting on open windows, or forced drafts, or electric fans,
or open-air outings, or sleeping porches, or the practise of deep
breathing, or all of these things.

[Sidenote: Clothing Artificial]

In the same way, clothing has protected our bodies from the cold but
enervated or constricted them as well. The aboriginal tribes, even in
cold climates, seldom used clothing. The Eskimo is an exception. The
tribes toward the South Pole in similarly cold climates often have
little more clothing than a blanket which they hang over their shoulders
toward the wind. The weak, pale skin--to whose lack of adaptability we
owe the chilling preceding a cold--the bald head, the distorted foot,
the corns upon it, the cramped waist, are among the results of clothing
ourselves wrongly. Hence we are discovering the need of restoring, as
far as we can, the original conditions by making our clothes more light,
more loose, and more porous, and, when possible, by taking the "barefoot
cure," or the air bath.

[Sidenote: Cooking Artificial]

We come next to foods, and note that civilization has invented cooking
and artificial foods. These inventions have greatly widened the variety
of man's diet, but the foods of civilization are largely responsible for
the decay of our teeth and the abuse of our digestive and eliminating
organs.

[Sidenote: Soft Foods Artificial]

Judging from man's teeth and digestive apparatus as well as his general
kinship to the anthropoid ape, it is reasonable to believe that, before
fire was discovered, man was primarily a frugivorous animal, whose
ordinary diet consisted of fruits, nuts, and ten