=How the Eyeball is Moved.=--Six muscles fixed to the bones of the socket holding the eye have their other ends fastened to the tough coat of the eyeball. One muscle turns the ball upward, another turns it downward, one turns it inward and another turns it outward. If an inner or an outer muscle is too strong, a person may have cross eyes. =Keeping the Eye Strong.=--Nearly all young children have perfect eyes. After a year or two in school the eyes of some children become weak. Many children get weak eyes after they are ten or twelve years old. This is because they have not taken care of the eyes. The eyes are often hurt by reading a book with fine print, reading in a dim light, or by leaning over the book so that the eyes look downward instead of straight forward. As the eyes are very weak after measles and most other diseases, they should not be used much until a week or more after recovery. In reading the book should be held a little over a foot in front of the chest and you should sit nearly straight and let the light fall on the page from one side. Never read while lying down because it strains the eyes. Stop reading as soon as the eyes smart. =Helping the Eyes to See.=--Very few old people can see to read without the help of glasses, because the lens of the eye hardens in old age. To see things near by, the shape of the lens must be changed. In some children, the shape of the eyes has become so changed by straining them to read fine print or see things in a dim light that the eyes hurt after being used for any kind of work, and the head may often ache and make the whole body feel bad. Such eyes need help. You should have them examined by an eye doctor who can fit you with glasses which will help you see clearly without headache. =Keeping the Eyes Well.=--Bits of dirt often get beneath the eyelids and cause much pain. By taking hold of the eyelashes the lid may be pulled out from the eye and any dirt removed with the corner of a clean handkerchief passed gently along the lid. The eyes sometimes become sore because they are rubbed with soiled fingers on which are germs. These germs get inside the lids and grow, and in this way poison the eyes. Unless care is used sore eyes are likely to spread from one child to another in the school. The sick child rubs its eyes and then handles a book or pencil on which the germs are smeared by the fingers which touched the eyes. The next child picks up the same book later, gets the germs on the fingers, and then rubs the eyes. For this reason you should never rub the eyes. If you have sore eyes, _be careful that no one else catches the sickness from you_.