y you have more than once met with an accident of this
sort. All parts of the body contain blood. If the skin is broken in any
place the blood flows out.

~2.~ How many of you know what a microscope is? It is an instrument
which magnifies objects, or makes them look a great deal larger than
they really are. Some microscopes are so powerful that they will make a
little speck of dust look as large as a great rock.

~3. The Blood Corpuscles.~--If you should look at a tiny drop of blood
through such a microscope, you would find it to be full of very small,
round objects called _blood corpuscles_.

~4.~ You would notice also that these corpuscles are of two kinds. Most
of them are slightly reddish, and give to the blood its red color. A
very few are white.

~5. Use of the Corpuscles.~--Do you wonder what these peculiar little
corpuscles do in the body? They are very necessary. We could not live a
moment without them. We need to take into our bodies oxygen from the
air. It is the business of the red corpuscles to take up the oxygen in
the lungs and carry it round through the body in a wonderful way, of
which we shall learn more in a future lesson.

~6.~ The white corpuscles have something to do with keeping the body in
good repair. They are carried by the blood into all parts of the body
and stop where they are needed to do any kind of work. They may be
compared to the men who go around to mend old umbrellas, and to do other
kinds of tinkering. It is thought that the white corpuscles turn into
red ones when they become old.

~7.~ The corpuscles float in a clear, almost colorless fluid which
contains the digested food and other elements by which the body is
nourished.

SUMMARY.

1. The blood contains very small objects called blood corpuscles.

2. There are two kinds of corpuscles, red and white.

3. The red corpuscles carry oxygen.

4. The white corpuscles repair parts that are worn.

5. The corpuscles float in a clear, almost colorless fluid, which
nourishes the body.

CHAPTER XI.

WHY THE HEART BEATS.

~1.~ If you place your hand on the left side of your chest, you will
feel something beating. If you cannot feel the beats easily, you may run
up and down stairs two or three times, and then you can feel them very
distinctly. How many of you know the name of this curious machine inside
the chest, that beats so steadily? You say at once that it is the heart.

[Illustration: THE HEART.]

~2.~ The