ady know; for you know how the
skin lets out the waste water in perspiration, or sweat, and how
important it is that we keep the little holes of the strainer open and
clean. And you know, too, that most of the water that passes out of
the body goes first to the kidneys.

The liver, however, is the largest cleaning machine of all and has to
work very hard. The blood comes to it full of foods and poisons. This
wonderful cleaner picks out the food it needs and takes up many of the
poisons, too. "What does it do with the poisons?" you ask. Some of
them it changes into good food, and others it makes harmless and sends
away down the food tube in a fluid called _bile_. If we are strong and
healthy, the liver has the power to kill many of the disease germs
that get into the body. That is why sometimes, when you have had a
chance to take mumps or grippe or some other "catching" disease, you
don't take it. Your liver kills the germs, or seeds. See how carefully
Mother Nature has planned that we may be clean inside as well as
outside.

[Illustration: THE POSITION OF THE LIVER

Compare this with the diagram on page 26, and see how the liver
partly overlaps the stomach.]

But you must not over-work your liver. If you do, it may become too
tired to do anything at all. Then all these poisons will spread
through the body; the skin and the whites of the eyes will grow
yellow, and you will be what is called "bilious." When this happens,
the poisons go to your brain, too, and make you feel sad; your tongue
looks white instead of pink, and you have a disagreeable taste in your
mouth. Your happiness depends very much on your liver.

"How shall I keep my liver rested and in good working order?" By
eating only sound, wholesome, pure food, and avoiding dirty milk; by
going to the toilet regularly every morning after breakfast; by
keeping your windows open and avoiding the poisons and disease germs
in foul air. Then, if you run and play and work out of doors, so that
the muscles move a great deal and you breathe in plenty of oxygen to
keep the body fires burning briskly, that will help a great deal.

Last summer up in the mountains I saw a big log close by the path. It
had been sawed across so that the end was smooth. It was brown and
weather-stained, so of course I knew that it had lain there a long
time. How surprised I was to see a pile of fine fresh sawdust on the
ground beside it. As I came nearer, I saw piece after piec