There are about five and half quarts of blood circulating through the veins, arteries, and organs of your body. This rich red stream is kept in constant circulation by your heart. When things are going well you hardly need to think about this. But there are times when the blood volume may be altered so that the number of red cells in your  circulation may drop down a long way below the normal 5,000,000 per cubic millimeter of blood.

This is a serious conditions known as anemia.  There are several ways in which this may happen. For instance, there is a question of hemorrhage. A person whose blood level has normal may suddenly lose a lot of blood  because of a serious accident or illness. The body seeks to replace this sudden loss by pouring in more fluid or plasma. But the  red cells are not so easily replaced. The victim may have enough fluid in circulation,  but the red cell count may be so low that he feels weak and worn out from the slightest effort. This is the typical picture of anemia  following a rapid loss of blood.

However, slow bleeding from an ulcer in the stomach or intestine may also produce varying degrees of anemia. If the red blood cells are lost more rapidly than the body can replace them, the patient will naturally begin to feel the effects of anemia. A slow, steady loss of red blood cells through the urinary  tract will do the same thing. Anemia also occurs from heavy menstrual bleeding, and the woman will feel tired and weak from lack of blood.

In some cases, such as in hemolytic anemia, the blood cells are to fragile. They seem to be synthesized in some way, so that large numbers of them are destroyed in the spleen. The same is true of malaria in which the parasite enters the red blood cell, feed on the substance of the cell, and later divides into eight or sixteen new organism that in turn attack other red cells. Certain metals, such as lead, arsenic, silver, may also destroy red cells. The same is true of quinine and drugs in some patients.

In other types of anemia the red cells are not properly formed. Instead of being round and flat like a plate, they may be roughly spherical or irregular. They may then cause trouble in the spleen, and ulcers may develop in the legs, along with changes in the bones. There are even some rare types of anemia in which the hemoglobin itself may not be properly formed so that it cannot carry out its normal functions. Such cases are very difficult to treat.