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THE MADAM C. J. WALKER SCHOOLS

body. The color of the blood changes from the bright red of the arteries called arterial blood, to the dark red or crimson tint in the veins, called venous blood.

COMPOSITION OF BLOOD

The blood is composed of PLASMA, a clear yellowish fluid, and three types of CELLS known as the RED CORPUSCLES, the WHITE CORPUSCLES, and the BLOOD PLATELETS.

PLASMA is a straw colored fluid composed of about nine-tenth water to one-tenth solids, absorbs foods from the intestines and waste materials from the body. It is the liquid portion of the blood in which the cells float.

RED CORPUSCLES (Erythrocytes)—These are minute albuminous circular discs so small that five million are required to cover the area of one tiny drop of water. They are produced in the red marrow of bones and have no Nuclei, that is cannot divide or sub-divide: They are soft, flexible, and elastic so that they readily squeeze through openings smaller than their own size. They are much more numerous in the blood stream than the white cells and platelets. The red corpuscles contain a solid called HEMOGLOBIN which combines with oxygen taken from the lungs and gives the blood its bright red hue. The chief function of the Red Corpuscles then, is to carry oxygen throughout the body. When there is a deficiency of red corpuscles in the blood or a deficiency of hemoglobin in the cells there is a deficiency of oxygen reaching the body tissue and the term applied to such conditions is ANEMIA. Persons so afflicted are referred to as ANEMIC. Lack of nutritious food, diseases of the marrow in the bones and various infections bring about this condition. The healthy human being should have between 4 or 5 million red corpuscles to one cubic millimeter of blood.

WHITE CORPUSCLES (Leucocytes)

These are transparent bluish masses of protoplasm which vary in size, some being smaller than the red corpuscles, but the majority are larger. They are known as the "scavengers" of the body, because of the work they perform. In one tiny drop of healthy blood there are approximatelly six thousand white corpuscles or roughly, one to each 750 red corpuscles. They move by their own effort and are able to penetrate the walls of the capillaries into the lymph spaces and channels of the surrounding tissue. Because of

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this power of migration these cells are also called "the wandering cells." They do not carry oxygen but perform other important functions such as:

1. Help protect the body from bacteria and foreign organisms.
2. Cooperate in repairing injured tissue.
3. Aid in absorbing intestinal waste.
4. Aid in the clotting of blood.
5. Help to maintain normal blood content.

White cells originate in the Lymph-Nodes of the body and in bone marrow.

INFLAMMATION

When body tissue becomes injured or attacked by foreign bacteria (infection) the blood rushes to the injured part and the white corpuscles escape through the walls of the blood vessels and become very active in attempting to combat the bacteria. Such a condition is known as INFLAMMATION, and is recognized by pain, heat, swelling, discoloration and loss of function of the affected part. If the white corpuscles are victorious they kill the bacteria, clean up the area and return to the blood. If the bacteria are victorious large numbers of the white corpuscles and tissue will be destroyed and SUPPURATION (the formation of pus) will follow. PUS is an accumulation of dead and living bacteria, ineffective white corpuscles, dead tissue cells and material escaped from the blood vessels.

BLOOD-PLATELETS (Thrombocytes)

These are minute disc-shaped bodies much smaller than the red corpuscles. They number about three hundred thousand to a small drop of blood. They are numerous in unshed blood but rapidly diminish in number after bloodshed. It is thought that blood-platelets aid in clotting the blood, by supplying two substances essential to clotting known as TISSUE EXTRACT (THROMBOPLASTIN) and PROTHROMBIN.

FUNCTIONS OF THE BLOOD—The blood is known as the nutritive fluid of the body. It is more than merely that, as may be seen from the following functions which it performs:
1. It carries oxygen from the lungs to the tissue.
2. It carries food material absorbed from the intestines to the tissues.
3. It carries products called Hormones and internal secretions formed in one tissue to other tissues.