by germs. The germs are carried from one person to another on towels, on the hands, by flies, and in other ways. These diseases often leave the eyes weak and inflamed for life, and you should make every effort to avoid the germs that cause them.

Do not wash your eyes in a public wash basin or wipe them on a public towel. Do not rub them or pick at them with your fingers. Boracic acid dissolved in water (the solution is not too strong as long as it is all dissolved) and dropped into the eyes once or twice a day will often help to kill bacteria and relieve the smarting and burning that comes from red and inflamed eyes. Strong eye washes and eye salves should not be used without the advice of a physician.

FIG. 83. Germs often get into the eyes from the fingers.

Foreign bodies in the eye. When a particle of dust or other foreign body gets into the eye, the eye should not be rubbed. Sometimes the body can be washed out with clean water; or if the upper eyelashes are taken between the finger and the thumb and the eyelid drawn down and out, the position of the body may be changed until it can easily be removed. Some persons are skillful enough to turn the eyelids wrong side out and wipe the particle off with a cloth

or a tuft of cotton. When this is done, the fingers, the cloth, and everything that touches the eye should be absolutely clean, for it is an easy matter to get into the eye germs that will cause great trouble. Sharp pieces of metal ought to be removed by a physician or an oculist before they cut deep into the eye and start inflammation.

Questions: I. How does the light that enters our eyes cause us to see? 2. How are the eyes protected? 3. How are they cleansed? 4. Where do the tears come from? 5. Where do they go after they leave the eye? 6. How are the eyes moved? 7. Of what advantage is this to us? 8. What causes a person to be cross-eyed? 9. What is the trouble with the images in the eyes of a near-sighted person? 10. How may these difficulties be remedied? Why should this be done? symptoms of eye trouble? 13. Explain what kind of light is needed in reading and studying, and how the light should fall on the page. 14. How may the eyes be rested? 15. How do germs that cause diseases of the eye spread from one person to another? 16. Tell how to remove a foreign body from the eye.

II.

12. What are some of the

Suggestions and topics for development: The teacher should test the eyes of the pupils in the room. If no test card is provided by the school, one can be obtained by sending ten cents in stamps to World Book Company, Yonkers-on-Hudson, New York. Some children will be found who cannot read the writing on the blackboard from the back of the room. These children should be placed on the front benches, and the parents should be prevailed on to provide the needed glasses as soon as possible. The teacher should also look to the proper lighting of the schoolroom, paying special attention to whether parts of it are too dark and whether the children are seated facing the light.

THE EARS AND THEIR CARE

inner ear

tympanic membrane

middle ear

Eustachian tube

FIG. 84. The ear. The ear is composed of an outer, a middle, and an inner part.

WHEN you throw a stone into water, the stone causes waves to run out in the water. When you ring a bell, the bell causes waves to run out in the air. When you shout, when a whistle blows, or when a bird sings, waves are made to run through the air. When these waves strike the ear, you hear the bell, the shouting, the whistle, or the singing of the bird. If the air waves are large, the sound will be loud. If the air waves are small, the sound will be faint in your ears.

The function of the ear. The ear collects the sound waves and makes them strike on the ends of the nerves of hearing. This causes the nerves of

hearing to carry messages to the brain, and when these messages arrive in the brain we hear the sound. Certainly nothing in the world is more wonderful than the human ear, for it changes the air waves that come from the strings of a violin or piano into the sweetest music, and by collecting the waves that are caused by the voices of our friends, it brings to us the thoughts that they wish to express

to us.

The structure of the ear. The ear has three divisions: the outer, the middle, and the inner ear. The outer ear is made up of the part that we see and a canal that runs down into the head. At the bottom of this canal is a thin delicate membrane called the tympanic membrane. This separates the outer and the middle ear.

The middle ear is a little cavity in the bone of the skull. It is filled with air, and from it a little tube runs to the throat. In the middle ear are three small bones which stretch across from the tympanic membrane to the inner ear. The inner ear is filled with liquid, and in this liquid lie the endings of the nerve of hearing.

How we hear a sound. The outer ear collects the sound waves and turns them down the canal to strike against the tympanic membrane. This sets the tympanic membrane to swinging, and the membrane puts the chain of little bones in motion. The motion of the bones disturbs the liquid in the

inner ear and causes waves in it. These waves wash over the ends of the nerve of hearing and start messages to the brain, and when these messages reach the brain we hear the sound.

The care of the ear. Practically all the serious troubles of the ear come from germs that work up the tube from the throat into the middle ear. In Figure 26 you can see that the openings of these tubes are high up in the throat, where the matter that falls into the throat from the nose in cases of catarrh passes over them and where they may be pressed upon and closed by adenoid growths (compare Figure 37). Most children who are hard of hearing have nose or throat trouble, and most older persons who are deaf suffered from these troubles when they were young.

The danger from running ears. A running ear means that there are germs in the ear that are causing inflammation and forming the same kind of matter that comes from boils and sores. This trouble ought by all means to be attended to at once, for in a running ear there is already a hole in the tympanic membrane, and there is danger that this membrane will be destroyed or that the chain of bones will be broken down and incurable deafness caused. There is always the danger also that the germs will work through to the brain, which lies close above the ear, and cause the disease that is called meningitis.