at you do not eat too
much of any one kind of food, but remember to eat a little of many
kinds. Your engine can use only a little of each at one time.

Wood is chopped into short pieces, and coal is broken up before it will
do good work in the engine, so the fuel must be prepared before it will
suit your engine. It must be well cooked and then chewed thoroughly
before it will do its best work in your body-engine. You should be
careful not to swallow any food until it has been chewed as fine as it
can be.

If you put into your engine the right amount of food, and the right kind
of well-prepared food, you will have an engine more wonderful than any
steam engine that ever pulled a train, or carried a big ship across the
wide ocean.

The engineer sees that his engine is kept clean and bright, in order
that it may run smoothly. Since you are the engineer of your
body-engine, you must keep it neat and clean that it may work well.

[Illustration]

QUESTIONS

1. What is it that causes the big steam engine to
do its work, draw long trains, or big ships, or
turn great factory wheels?

2. What must happen to this fuel--wood, coal, or
gasoline--before it can make the engine do its
work?

3. Did you ever wonder why it is that your body is
always warm? It is very much like the engine.

4. What do you call this fuel that your
body-engine uses? Just as the fuel for the steam
engine must be burned if it is to make heat, even
so must the food be burned in your body if it is
to keep it warm and able to work. Of course the
food in your body does not burn exactly as the
wood and coal burn in the steam engine. It burns
much more slowly--so slowly that you would not
know that it burns at all if it were not that it
always keeps your body warm.

Just as the steam engine needs the fuel if it is
to do its work well, your body needs the best of
food if it is to be healthy and do the best work.
You have learned that all foods do not serve the
same purpose equally well. For instance, some
foods such as lean meat, eggs, and milk build up
more muscle than other foods do; while others,
such as fats, syrup, sugar and potatoes, give more
heat than other foods.