CHAPTER XVI
THE BLOOD AND HOW IT FLOWS THROUGH THE BODY
Fig. 68 —The cells in the blood. The two white ones were drawn while crawling. Much enlarged.
The Blood keeps the Body Clean within and gives it Food.—Every tiny particle of the body, whether in the legs, arms, or head, must have food to keep it alive and help it do its work. It must also have oxygen, and it must be washed clean of its waste matter. All this is done by the streams of blood, which bathe every cell to bring it food and oxygen and to wash away its waste.
Parts of the Blood.—Blood consists of a clear, watery part called plasma and many little bodies named cells. The liquid found in a blister is the clear part of the blood. The cells which float in the watery part are so little and so close together that more than a million are in each drop of blood.
A few of the cells are white, but most of them are red, and it is their color that makes the blood look red. Your body contains about one gallon of blood. It is carried through the body in branching tubes called blood vessels ([Fig. 70]).