FLUIDS OF HUMAN BODY: BLOOD

Blood is the most important fluid in the human body. The normal blood contains from about five million red blood cells to six million, in each cubic millimeter. The blood of women contains slightly less than that of men. The body of a woman is smaller and needs fewer red blood cells. Red blood cells grow in the bone marrow. The blood contains fluid matter called plasma which contains some solid substances that settle out, leaving the serum. An examination of the blood is a vital part of any complete physical examination. The doctor may obtain the blood from a puncture of the ear or finger or by putting a needle into a vein. He counts the red blood cells, the white blood cells and the blood platelets; he may determine the amount of sugar or protein in the blood as a whole; he detects the amount of hemoglobin, or red coloring matter. The blood carries the anti-substances against infections, it provides the tissues with oxygen and nutrients and it carries waste matter to the kidneys, where such waste matter is eliminated. It is also responsible for carrying the hormones, or substances of the glands of internal secretion, to various parts of the body. The total amount of blood is equal to about one-thirteenth of the body weight. Of this 78 per cent is water and 22 per cent solid.*12/318/5*