(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 like jelly. It is so clear that the light can shine through it just as easily as it can shine through water. ~10. The Pupil.~--If you look sharply at the eyeball you will see a small black hole just in the centre. This is a little window which lets the light into the inside of the eyeball. We call this the _pupil_. Just around the pupil is a colored ring which gives the eye its color. We say a person has blue or brown or gray eyes according as this ring is blue or brown or gray. This colored ring is a kind of curtain for the window of the eye. ~11.~ If you observe the pupil closely, you will see that it is sometimes larger and sometimes smaller. If you look at the light the pupil is small; if you turn away from the light the pupil grows larger at once. This is because the curtain closes when in a bright light and opens in the darkness. It does this of itself without our thinking about it. In this way the eye is protected from too strong a light, which would do it great harm. ~12.~ If you look a little sidewise at the eyeball, you will see that the curtain has something in front of it which is clear as glass. It is about the shape of a watch crystal, only very much smaller. This is to the eye what the glass is to the windows of a house. It closes the opening in the front of the eyeball and yet lets the light shine in. ~13. The White of the Eye.~--The white of the eye is a tough, firm membrane which encloses the eyeball and keeps it in a round shape. ~14. The Lens.~--Do you know what a lens is? Perhaps you do not know it by this name, but you are familiar with the spectacles which people sometimes wear to help their eyes. The glasses in the spectacle frames are called lenses. Well, there is something in the eye almost exactly like one of these lenses, only smaller. It is also called a _lens_. If some one will get the eye of an ox for you, you can cut it open and find this part. The lens is placed in the eyeball just behind the pupil. (See picture.) [Illustration: THE INSIDE OF THE EYE.]