. 58.--Face cut through the middle to show how the
adenoids stop the air from passing through the nose. Arrows show the
course which the air should take.]

The air should pass only through the nose because it is lined with
hairs and tiny waving threads which catch the dust. In this way germs
and dirt are prevented from getting into the throat and lungs, and in
winter the cold air is warmed.

=Why Some Children cannot breathe through the Nose.=--When one has a
cold, the lining of the nose becomes swollen and gives out a white
substance called _mucus_. The swelling of the lining and the mucus fill
up the passages. The nose should be kept clean by using a handkerchief
and blowing out the mucus into it. _Never put the finger into the nose._
Disease germs often get on the fingers from things touched.

Children who have the habit of breathing through the mouth should be
examined by a physician. He will, in most cases, find soft spongy
growths called _adenoids_ in the back part of the nose. They should
always be removed as soon as possible. They may cause disease or
deafness and may even injure the mind.

[Illustration: FIG. 59.--A view of the voice box from the top.]

=The Voice.=--In the upper part of the voice box at the top of the
windpipe is a fold of tissue stretched on either side. These two folds
of tissue form the _vocal cords_. The air rushing past them causes
sound. The different sounds are made by stretching the cords tight or
loosely. By means of the tongue, teeth, and lips the sound is formed
into words.

=How to use the Voice.=--A cold or much shouting makes the vocal cords
swell and we become hoarse. Rest is the best cure. It is not polite to
shout or whistle in the house and you should never use an angry tone
of voice. When talking to a person, always speak distinctly but
pleasantly and turn your face toward his and look directly into his
eyes. Never use a harsh, loud tone of voice.

=Why you should not spit on Floors or Sidewalks.=--We used to think
that any one well had no germs of sickness in his mouth, but we now
know that many well persons have germs in their mouths which can cause
long sickness when they get into other persons. If you are sick with
diphtheria, scarlet fever, or sore throat, the germs of the disease
are likely to remain in your mouth two or three months. Persons with
tuberculosis throw out millions of these germs in their spit every day.

Spitting is not only an unclean habit but