tuated that they can not even secure ventilation, granted
that they want it. But there is one important part of the twenty-four
hours when most people can completely control their own air supply. This
is at night. We spend a third of our time in bed. Most of us live such
confined lives during the day that we should all the more avail
ourselves of our opportunities to practise air hygiene at night.

[Sidenote: Tuberculosis]

[Sidenote: Well Persons]

It is the universal testimony of those who have slept out-of-doors that
the best ventilated sleeping-room is far inferior in healthfulness to an
outdoor sleeping-porch, open tent, or window tent (large enough to
include the whole bed). For generations, outdoor sleeping has
occasionally been used as a health measure in certain favorable climates
and seasons. But only in the last two decades has it been used in
ordinary climates and all the year round. Dr. Millet, a Brockton
physician, began some years ago to prescribe outdoor sleeping for some
shoe-factory workmen who were suffering from tuberculosis. As a
consequence, in spite of their insanitary working-places (where they
still continued to work while being treated for tuberculosis), they
often conquered the disease in a few months. It was largely this
experience which led to the general adoption, irrespective of climate,
of outdoor sleeping for the treatment of tuberculosis. The practise has
since been introduced for nervous troubles and for other diseases,
including pneumonia. Latterly the value of outdoor sleeping for _well_
persons of all classes, infants and children as well as adults, has come
to be widely recognized.

[Sidenote: Vital Resistance]

Outdoor sleeping increases the power to resist disease, and greatly
promotes physical vigor, endurance, and working power.

[Sidenote: Night Air]

Many people are still deterred from sleeping out by a mistaken fear of
night air and of the malaria which they imagine this dreaded night air
may bring. To-day we know that malaria is communicated by the bite of
the anopheles mosquito and never by the air. The moral of this is not to
shut out the night air, but, when necessary, to shut out the mosquito by
screens. The experiment has been made of sleeping out-of-doors _in
screened cages_ in the most malarial of places and no malarial infection
resulted, though those who were unprotected and were consequently bitten
by mosquitoes contracted malaria as usual. The truth is th