dangerous rate of speed, and in this way shorten its life by abuse
just as the careless boy may by neglect.

It is just so with the human body which, after all, is a machine too,
and, more than that, it is the most wonderful and perfect machine in
the world. With care it should last many years. With abuse or neglect
it may very soon wear out. The boy who neglects his health is like the
boy who allows the bearings on his wheel to become dry or the metal
parts rusty. The chief difference is that when the bicycle wears out
or breaks down we may replace the parts or even buy another machine,
but when our health is injured, money will not restore it.

In order to keep well we must observe certain rules of health. By
exercise we keep the working parts in good order. If we are lazy or
indolent we are like the bicycle that is allowed to go to pieces from
lack of use. If we are reckless and foolhardy we may injure some part
of the delicate machinery from excessive exercise or strain.

Play is the most natural thing in the world but we must use judgment
in our play. A boy or girl who is not allowed to play or who is
restrained by too anxious parents is unhappy indeed. Nearly all
animals play. We know, for instance, that puppies, kittens, and lambs
are playful. It is a perfectly natural instinct. By proper play we
build up our bodies and train our minds. The healthy man never gets
too old to play. He may not care to play marbles or roll hoops, but he
will find his pleasure in some game or sport like tennis, golf,
horseback riding, camping, fishing or hunting.

In this book we shall talk about some forms of play and recreation
that are not strictly confined to children, but which we may still