No sooner has our food passed through the cells in the wall of the food-tube, than it goes straight into a set of tiny tubes--the blood-pipes, or _blood vessels_--which carry it to the heart; and the heart pumps it all over the body.
Veins and Arteries.

These blood-tubes running from the walls of the food-tube to the heart are called _veins_; and the other tubes through which the heart pumps the blood all over the body are called _arteries_.
If you will spell this last word "air-teries," it may help you to remember why the name was given to these tubes ages ago.

When the body was examined after death, they were found to be empty and hence were not unnaturally supposed to carry air throughout the body, and "air-teries" they have remained ever since.

While absurd in one way, the name is not so far amiss in another, for an important part of their work is to carry all over the body swarms of tiny baskets, or sponges, of oxygen taken from the air.
Why the Blood is Red.

The first and main purpose of the blood-pipes and the heart is to carry the dissolved food from the stomach and intestines to the cells all over the body.