us harm. These plants--the Colorless Plants, we may call them--are the
_molds_, the _fungi_, and the _bacteria_, or _germs_. You know how a
pair of boots put away in a dark, damp closet, or left down in the
cellar, will become covered all over with a coating of gray mold. Mold
grows rapidly in the dark. Just so, these other Colorless Plants,
which include most of our disease germs, grow and flourish in the
dark, and are killed by sunlight. That is why no house, or room, is
fit to live in, into which the sunlight does not pour freely sometime
during the day. The more sunlight you can bring into your bedrooms and
your playrooms and your schoolrooms, except during the heat of the day
in the summer time, the better they will be. The Italians have a very
shrewd and true old proverb about houses and light: "Where the
sunlight never comes, the doctor often does."

So you see that Nature is guiding you in the right direction when she
makes you love and delight in the bright, warm, golden sunlight; for
it is one of the very best friends that you have--indeed, you couldn't
possibly live without it.

In one sense, in fact, though this may be a little harder for you to
understand, you are sunlight yourselves; for the power in your muscles
and nerves that makes you able to jump and dance and sing and laugh
and breathe is the sunlight which you have eaten in bread and apples
and potatoes, and which the plants had drunk in through their leaves
in the long, sunny days of spring and summer.

So throw up your blinds and open your windows wide to the sunlight
every morning; and let the sunlight pour in all day long, except only
while you are reading or studying--when the dazzling light may hurt
your eyes--and for six or seven of the hottest hours of the day in