[Illustration: THE INSIDE OF THE EAR.]

~6. How we Hear.~--Scratch with a pin upon one end of a long wooden
pole. Have some one listen with the ear placed close against the other
end of the pole. He will tell you that he hears the scratching of the
pin very plainly. This is because the scratching jars the ear and
especially the drum-head, which vibrates just as the head of a drum does
when it is beaten with a drum-stick. When the drum-head vibrates it
moves the bones of the ear, and these carry the vibration to the nerves
of hearing in the inner chamber. We hear all sounds in the same way,
only most sounds come to the ear through the air.

The snail-shell of the inner part of the ear hears musical sounds. The
rest of the inner ear hears ordinary sounds or noises.

~7. How to Keep the Ears Healthy.~--The ears are very delicate organs
and must be carefully treated. The following things about the care of
the ears should never be forgotten:

(1.) Never use a pin, toothpick, or any other sharp instrument to clean
out the ear. There is great danger that the drum-head will be torn, and
thus the hearing will be injured. Neither is it ever necessary to use an
ear-spoon to remove the wax. Working at the ear causes more wax to form.

(2.) Do not allow cold water to enter the ear or a cold wind to blow
directly into it.

(3.) If anything accidentally gets into the ear, do not work at it, but
hold the head over to one side while water is made to run in from a
syringe. If an insect has gone into the ear, pour in a little oil. This
will kill the insect or make it come out.

(4.) Never shout into another person's ear. The ear may be greatly
injured in this way.

(5.) Boxing or pulling the ears is likely to produce deafness, and ought
never to be done.

~8. The Eye.~--The eye is one of the most wonderful organs in the whole
body. It enables us to know what is going on at some distance from us,
and to enjoy many beautiful things which our sense of hearing and other
senses can tell us nothing about. It also enables us to read. Let us
learn how this wonderful organ is made.

~9. The Eyeball.~--Looking at the eye, we see first a round part which
rolls in different directions. This is the _eyeball_. We see only the
front side of the eyeball as it fits into a hollow in the skull. Being
thus in a safe place, it is not likely to get hurt.

[Illustration: THE EYE.]

The eyeball is mostly filled with a clear substance very much