~22.~ There is a little muscle in the eye which makes the change needed
to enable us to see objects close by as well as those which are farther
away. When people grow old the little muscles cannot do this so well,
and hence old people have to put on glasses to see objects near by, as
in reading. Children should not try to wear old persons' glasses, as
this is likely to injure their eyes.

~23. How to Keep the Eyes Healthy.~--(1.) Never continue the use of the
eyes at fine work, such as reading or fancy-work, after they have become
very tired.

(2.) Do not try to read or to use the eyes with a poor light--in the
twilight, for instance, before the gas or lamps are lighted.

(3.) In reading or studying, do not sit with the light from either a
lamp or a window shining directly upon the face. Have the light come
from behind and shine over the left shoulder if possible.

(4.) Never expose the eyes to a sudden, bright light by looking at the
sun or at a lamp on first awaking in the morning, or by passing quickly
from a dark room into a lighted one.

(5.) Do not read when lying down, or when riding on a street car or
railway train.

(6.) If any object gets into the eye have it removed as soon as
possible.

(7.) A great many persons hurt their eyes by using various kinds of