I am going to tell you of a wonderful stream that flows through our bodies. We may call it the stream of life. It is made of tiny rills, and of great branches, all of which join to form this wonderful stream.
This stream has a great, double force pump, which keeps pumping night and day. It always pumps the same way, its engine does not make much noise, but just a little sound that you may hear if you put your ear close to mother's breast. You can hear this busy little engine pumping away, forcing the stream on.
Many queer looking little boats float on its bosom. These boats carry freight to the far-away countries in all parts in the body. They are so small we cannot see them with the naked eye. They are of various shapes; some are round.
They have a very important freight to carry. There are more of these boats than there are of any other kind. They have a little cup-shaped centre, a kind of deck, and in this centre they carry the freight. They take on this freight at the Lung Station. They have something on deck which holds on to the goods they get at the station, to keep it from being lost on its long journey.
It never overflows its banks. Its color is not bright and blue as the waters of the Hudson or Potomac Rivers. It is yellow and red, like the Mississippi, the great "Father of Waters." If you would taste it you would find it to be salty like the ocean.
As soon as the little boats load up at the Lung Station, off they sail on this wonderful stream, carrying their freight to the Muscle Country, the Skin Country or the Gland Country. When the boats reach one of these countries, they unload and the little men of these countries (or cells) take the freight and put it just where it is needed. The freight is called oxygen. The Lung Station is filled with it every time a person takes a good breath of pure fresh air.
The little boats come to Lung Station and load up with oxygen about three times every minute, so you see how fast they travel. This freight is the thing that paints our cheeks a rosy color and gives us good health.
When each little boat has unloaded its cargo in the far countries, the little cell men load them with a return cargo, which is made up of waste matter (carbon dioxide). This cargo is carried back to the Lung Station, and unloaded there. It is breathed out into the air, through the air tubes.
If we breathe impure air, the little boats go back to the far countries with only a small cargo of oxygen. Then the cell men feel as if they are cheated and refuse to do good work for us. In fact, they grow weak and cannot do as good work as they could if the boats brought a full cargo of fresh air.