n't
it?--bright white around the edge and then a ring of color, brown or
blue or gray; and inside the color-ring, or _iris_, a little round
black hole that we call the _pupil_. Watch the little hole change as
you turn the face toward the window. It becomes ever so much smaller.
Now turn the face away from the window, back again into the shadow.
How did the pupil change this time?

[Illustration: EYES PROTECT THEMSELVES AGAINST THE LIGHT]

The iris, or color-ring, acts like a curtain, like the ring-shutter of
a camera, and closes up the hole, or pupil, when the light is too
bright and would dazzle or burn the inside of the eye; but when the
light is dim, the iris opens again, so as to let in light enough with
which to see. Look at the little window in your kitten's eyes. It is
not the same shape as yours; but when you carry her to the light, you
see how the iris closes in and leaves just a little black slit or
line.

You remember the blind children? Isn't it wonderful how they can play
games and study, too, even though they are blind! They have to make
their senses of touch and hearing tell them many things that you learn
through your sense of sight. Many of these children _need not have
been blind_, if the nurse who first took care of them when they were
born had known enough to wash their eyes properly, not with soap and
water, of course, but with just one or two drops of a kind of
medicine--an _antiseptic_, as we call it--that makes the eye perfectly
clean.

But you children who have good eyes that can see, do you really see
things when you look at them? You can train your eyes just as you can
train your ears. You can teach them to read quickly down a page, and
to find things in pictures, and, better still, to see things out of
doors, in the garden and the woods and on the seashore. We hear a
great deal about "sharp eyes," but most of us see very little of all
we might see. Our eyes are on the lookout, too, to protect us from
dangers that may come; with our skin and nose and ears, they are
constantly on the watch; so the better we see the safer we are.

Even if your eyes are perfect now, you will need to take good care of
them to keep them strong. Don't let any story, no matter how
interesting it is, tempt you to read in a dim light or a light that is
too strong. And if you can't see the blackboard easily, or can't read
big print, like the school calendar, across the room, tell your mother
or your teacher,