THE SENSES.
[Illustration: W]E have five ways of learning about all things around
us. We can see them, touch them, taste them, smell them, or hear them.
Sight, touch, taste, smell, and hearing, are called the five senses.
You already know something about them, for you are using them all the
time.
In this lesson, you will learn a little more about seeing and hearing.
THE EYES.
In the middle of your eye is a round, black spot, called the pupil. This
pupil is only a hole with a muscle around it. When you are in the light,
the muscle draws up, and makes the pupil small, because you can get all
the light you need through a small opening. When you are in the dark,
the muscle stretches, and opens the pupil wide to let in more light.
The pupils of the cat's eyes are very large in the dark. They want all
the light they can get, to see if there are any mice about.
[Illustration: _The eyelashes and the tear-glands._]
The pupil of the eye opens into a little, round room where the nerve of
sight is. This is a safe place for this delicate nerve, which can not
bear too much light. It carries to the brain an account of every thing
we see.
We might say the eye is taking pictures for us all day long, and that
the nerve of sight is describing these pictures to the brain.
CARE OF THE EYES.
The nerves of sight need great care, for they are very delicate.
Do not face a bright light when you are reading or studying. While
writing, you should sit so that the light will come from the left side;
then the shadow of your hand will not fall upon your work.
One or two true stories may help you to remember that you must take good
care of your eyes.
The nerve of sight can not bear too bright a light. It asks to have the
pupil made small, and even the eyelid curtains put down, when the light
is too strong.
Once, there was a boy who said boastfully to his playmates: "Let us see
which of us can look straight at the sun for the longest time."
Then they foolishly began to look at the sun. The delicate nerves of
sight felt a sharp pain, and begged to have the pupils made as small as
possible and the eyelid curtains put down.
But the foolish boys said "No." They were trying to see which would bear
it the longest. Great harm was done to the brains as well as eyes of
both these boys. The one who looked longest at the sun died in
consequence of his foolish act.
The second story is about a little boy who tried to turn his eyes to
imitate a schoolmate who was cross-eyed. He turned them; but he could
not turn them back again. Although he is now a gentleman more than fifty
years old and has had much painful work done upon his eyes, the doctors
have never been able to set them quite right.
You see from the first story, that you must be careful not to give your
eyes too much light. But you must also be sure to give them light
enough.
When one tries to read in the twilight, the little nerve of sight says:
"Give me more light; I am hurt, by trying to see in the dark."
If you should kill these delicate nerves, no others would ever grow in
place of them, and you would never be able to see again.
THE EARS.
What you call your ears are only pieces of gristle, so curved as to
catch the sounds and pass them along to the true ears. These are deeper
in the head, where the nerve of hearing is waiting to send an account
of each sound to the brain.
CARE OF THE EARS.
The ear nerve is in less danger than that of the eye. Careless children
sometimes put pins into their ears and so break the "drum." That is a
very bad thing to do. Use only a soft towel in washing your ears. You
should never put any thing hard or sharp into them.
I must tell you a short ear story, about my father, when he was a small
boy.
One day, when playing on the floor, he laid his ear to the crack of the
door, to feel the wind blow into it. He was so young that he did not
know it was wrong; but the next day he had the earache severely.
Although he lived to be an old man, he often had the earache. He thought
it began from the time when the wind blew into his ear from under that
door.
ALCOHOL AND THE SENSES.
All this fine work of touching, tasting, seeing, smelling, and hearing,
is nerve work.
The man who is in the habit of using alcoholic drinks can not touch,
taste, see, smell, or hear so well as he ought. His hands tremble, his
speech is sometimes thick, and often he can not walk straight.
Sometimes, he thinks he sees things when he does not, because his poor
nerves are so confused by alcohol that they can not do their work.
Answer now for your taste, smell, and touch, and also for your sight and
hearing; should their beautiful work be spoiled by alcohol?
REVIEW QUESTIONS.
1. Name the five senses.
2. What is the pupil of the eye?
3. How is it made larger or smaller?
4. Why does it change in size?
5. What can a cat's eyes do?
6. Where is the nerve of the eye?
7. What work does it do?
8. Why must one be careful of his eyes?
9. Where should the light be for reading or
studying?
10. Tell the story of the boys who looked at the
sun.
11. Tell the story of the boy who made himself
cross-eyed.
12. Why should you not read in the twilight?
13. What would be the result, if you should kill
the nerves of sight?
14. Where are the true ears?
15. How may the nerves of hearing be injured?
16. Tell the story of the boy who injured his ear.
17. How is the work of the senses affected by
drinking liquor?