Probably some of you have seen a fire-engine throwing a stream of water through a hose upon a burning building.
As the engine forces the water through the hose, so the heart, by the working of its strong muscles, pumps the blood through tubes, shaped like hose, which lead by thousands of little branches all through the body. These tubes are called arteries (är´tĕr iz).
Those tubes which bring the blood back again to the heart, are called veins (vānz). You can see some of the smaller veins in your wrist.
If you press your finger upon an artery in your wrist, you can feel the steady beating of the pulse. This tells just how fast the heart is pumping and the blood flowing.
The doctor feels your pulse when you are sick, to find out whether the heart is working too fast, or too slowly, or just right.
Some way is needed to send the gray fluid that is made from the food we eat and drink, to every part of the body.
To send the food with the blood is a sure way of making it reach every part.
So, when the stomach has prepared the food, the blood takes it up and carries it to every part of the body. It then leaves with each part, just what it needs.
THE BLOOD AND THE BRAIN.
As the brain has so much work to attend to, it must have very pure, good blood sent to it, to keep it strong. Good blood is made from good food. It can not be good if it has been poisoned with alcohol or tobacco.