The eyelashes and the tear-glands.
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.
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.