~6. The Body is Like a Machine.~--In some ways the body is more like a
machine than like a house. It has many different parts which are made
to do a great many different kinds of work. We see with our eyes, hear
with our ears, walk with our legs and feet, and do a great many things
with our hands. If you have ever seen the inside of a watch or a clock
you know how many curious little wheels it has. And yet a watch or a
clock can do but one thing, and that is to tell us the time of day. The
body has a great many more parts than a watch has, and for this reason
the body can do many more things than a watch can do. It is more
difficult, too, to learn about the body than about a watch.

~7.~ If we want to know all about a machine and how it works, we must
study all its different parts and learn how they are put together, and
what each part does. Then, if we want the machine to work well and to
last a long time, we must know how to use it and how to take proper care
of it. Do you think your watch would keep the time well if you should
neglect to wind it, or if you should break any of its wheels?

~8.~ It is just the same with the human machine which we call the body.
We must learn its parts, and what they are for, how they are made, how
they are put together, and how they work. Then we must learn how to take
proper care of the body, so that its parts will be able to work well
and last a long time.

~9.~ Each part of the body which is made to do some special kind of work
is called an _organ_. The eye, the ear, the nose, a hand, an arm, any
part of the body that does something, is an organ.

~10.~ The study of the various parts of the body and how they are put
together is _anatomy_ (a-nat´-o-my). The study of what each part of the