lor into the cheek.

CHAPTER V.

BREATHING.

The first thing you did when you came into this world was to inspire,
that is, to breathe in. The last thing you will do will be to expire,
that is, to breathe out. And between your first inspiration and your
last expiration there will have been the process of respiration, that
is, breathing in and out at an average rate of twenty times a minute.
Twenty times a minute means twelve hundred times an hour, or nearly
thirty thousand times a day, or over ten million times a year. If you
should live to be fifty years old, you will have breathed in and out
over five hundred million times. We eat three times a day, twenty-one
times a week, over a thousand times a year, fifty thousand times in
fifty years, but we breathe over five hundred million times in fifty
years.

We realize the importance of eating, but we can live days without
food. On the other hand, we cannot live many seconds entirely without
air. We must infer from all this that breathing is more important than
eating. How can it be? From our food our body is rebuilt. What
life-process is accomplished by breathing?

To understand this, we must learn what processes are going on in the
body, by means of which food is converted into tissue, into heat and
energy. These processes we find are chemical, and may be likened to
the combustion of wood or coal in the furnace. We know that fire must
have air in order to burn. Burning is the process of oxidation or
combustion of oxygen with the atoms of fuel and the formation of a new
substance thereby. Coal, we are told, consists of carbon and nitrogen,
both of which readily combine with oxygen, and in the process of
uniting heat is liberated, and waste compounds thus formed pass off
through the smokestack or chimney. We may not understand this
scientifically, but we know that if we want the fire to burn well we
must give it draft or air.

Our bodies are living engines, and use food and air instead of coal
and air. Food in the body without air is like the coal in an engine
without air; and air is useful only because it brings oxygen to unite
chemically with the food. This process is going on all over the body.
Each little microscopical cell is a furnace in which oxidation is
taking place; and not only is energy liberated, but reconstructive
processes are going on, new tissues are being formed, and old tissues
removed.

But how can the oxygen get to the cells in all par