evices of civilization. The inventions of
civilization have done so much for man that he is apt to unduly glorify
them and to overlook the injurious by-products. These by-products are
often of prodigious significance to the race. The invention of houses
introduced the problem of house hygiene; the invention of clothing, the
problem of clothing hygiene; that of cooking, the problem of food
hygiene; that of division of labor, the problem of industrial hygiene;
and so on. To make these statements more concrete, we may consider some
of them in more detail.

[Sidenote: Houses Artificial]

The invention of houses has made it possible for men to live in all
climates, yet this indoor living is responsible for much disease. The
houses give comfortable shelter and warmth and protect us from the
elements and from wild animals. But the protection has been overdone.
Like his cousin, the anthropoid ape, man is biologically an outdoor
animal. His attempt at indoor living has worked him woe, but so
gradually and subtly has it done so that only recently have we come to
realize the fact. At first, dwellings were really outdoor affairs,
caves, lean-tos, tents, huts with holes in the roof and the walls.
These holes served to ventilate, though they were not intended for that
purpose. The hole in the roof was to let out the smoke and the holes in
the walls to let in the light. Gradually the roof-hole developed into a
chimney with an open fireplace, which, in turn, gradually changed into a
small flue for stoves whereupon it almost ceased to serve any
ventilating function. The stove in turn has largely gone and is replaced
in many cases by the hot-water or steam radiator, without any attempt at
ventilation. The holes in the wall gave way, after the invention of
glass, to windows which let in the light without letting in the air.
Weather-strips, double windows, vestibule-doors, interior rooms,
completed the process of depriving man of his outdoor air, shutting him
into a cell in which he now lives--a sickened but complaisant
prisoner--often twenty hours of the twenty-four. Tuberculosis, one of
the worst scourges of mankind, is primarily a house disease. It is
prevalent as indoor living is prevalent, and reaches its maximum in the
tenement quarter of a great city.

[Sidenote: Effects on Different Races]

Only by generations of natural selection could we expect to make man
immune to the evils of bad air. The robust Indian and the Negro, whose