The spleen is the largest of the lymphoid tissues. It is just about the size of the heart and is a spongy material which will hold up to .3 gallons of blood. It is located on the left side of the body, just behind the stomach. The spleen is a valuable organ which produces some of the white blood cells, filters the blood, destroys old, worn-out red blood cells and returns needed iron to the blood, disposing of the rest as waste. The spleen also stores excess blood for emergencies; for example, when oxygen in the circulatory system is short. We often hear that the victim of an auto accident has had a ruptured spleen which has been removed surgically. Because the spleen is so soft and spongy, it cannot be repaired by surgery, so it is removed to stop the loss of blood.