eeps the stomach from digesting food.

7. Alcohol soaks into the blood tubes and goes to the liver.

8. The liver destroys the alcohol, but is hurt in doing it.

CHAPTER IX

THE BLOOD

=81. Blood.=--After food becomes blood, it goes to every part of the
body to feed the cells. Even a pin prick anywhere in the body draws
blood. The blood makes the skin pink. There are five or six quarts of
blood in a man's body. This is about 1/13 of his body.

[Illustration: =Blood corpuscles (x400).=

_a_ a pile of red blood cells.
_b_ red blood cells seen flatwise.
_c_ red blood cells seen edgewise.
_d_ white blood cells.]

Blood looks like a red liquid. But if you look at it through a strong
microscope, it looks like water, and millions of little red cells.
These cells carry air through the body. They make the blood look red.
There are also a smaller number of white cells. Blood is made of red
cells, white cells, and a liquid.

=82. The liquid in blood.=--The liquid part of the blood is albumin,
and water, with a little fat, sugar, and minerals. It is food and
drink for the cells of the body. When blood is drawn from the body it
soon becomes like jelly. We call the jelly a _clot_. When you cut your
finger, a clot forms in the cut and plugs up the bleeding place. If
it did not, the blood would all run out of the body and we should die.

[Illustration: =Diagram of the heart while it is beating.=

_a_ vein entering the auricle.
_b_ auricle.
_c_ closed valve to keep blood from flowing back into the auricle.
_d_ ventricle.
_e_ artery.
_f_ valve to keep blood from returning to the ventricle.]

=83. The heart.=--The blood is held in tubes. A pump inside the body
keeps it always moving. This pump is called the _heart_. The heart is
a bag of muscle with thick sides. It is about as large as your fist.
When it is full, it has the power to make itself smaller, and so it
squeezes the blood out through a tube. We can feel each squeeze as a
heart-beat. You can find the heart-beat just to the left of the middle
of the body about two hand-breadths below the neck.

=84. The heart-beat.=--A man's heart beats about seventy times each
minute. Boys' and girls' hearts beat much faster. Running or hard work
of any kind makes the heart beat faster yet. Your heart will keep on
beating until you die. It does not seem to rest at all, yet it works
only while you feel it beat. Between each beat it rests whi