ed.

The following is a simple but effective device to increase humidity:
Roll an ordinary desk blotter into a cone about 8 inches in diameter at
the base, and keep it constantly submerged for about one inch in a dish
of water. The water rises to the top of the blotter and a large surface
for evaporation is thus afforded.

[Illustration: FIG. 7.]

Stagnant air is harmful. Air should be in constant though not
necessarily perceptible motion. Air about the body, if motionless, acts
like a warm moist blanket, preventing the passage of heat from the body.

The three factors, heating, humidity, and air motion, must be considered
together. Every person requires each hour about 3000 cubic feet of air,
and the problem of heating and ventilating is that of providing this
amount in gentle motion, at a temperature of about 65 deg. F., and of
humidity from 50-55%. Higher temperatures and stagnant air cause
disinclination to work, headache, nausea, restlessness, or sleepiness,
and if continued are likely to result in loss of appetite, and anemia.
The tuberculosis movement has clearly shown the benefits both for the
sick and the well of living in the open air, and has caused great and
beneficial changes within a generation. The more time spent in the open
air the better; since however most persons who work must spend the
greater part of the day indoors, ventilation is a matter of great
importance.

Although fresh air enthusiasts are still too few, yet some go to the
extreme and think that because cool air in motion is good, the colder
the air and more violent the motion the better. On the contrary,
chilling the whole body or a part of the body lowers resistance.
Draughts of air have no bad effects upon persons in good health,
particularly those accustomed to changes in temperature. But draughts
are likely to be injurious to aged or sick persons and babies, by
diminishing their resistance to such infections as common colds and
pneumonia. It should be remembered that draughts or cold alone cannot
cause colds; the specific germs must be present.

LIGHTING.--Amount and direction of light are physiologically important.
Defects of the eyes, too prolonged use, and insufficient light are the
commonest causes of eye strain. Most eye defects can be relieved by
glasses. Children's eyes should be examined upon entering school, and as
often afterward as the oculist advises. Prolonged use causes fatigue of
the eyes, especially when the illum