CARRY oxygen from the lungs to all the other parts of the body and BRING BACK the carbon-di-oxide from all such parts.Deficiency of RBC causes Anemia.RBC is formed in the BONE marrow and its destruction takes place in the liver and the spleen.White Blood Corpuscles:Monocytes are the largest white blood corpuscles. Their count is used to diagnose various kinds of diseases.Monocytes serve as a part of the defence against infection by "EATING" up foreign particles. When a monocyte is found in a tissue, it is called a macrophage.They are irregular in shape and larger in size than lymphocytes.They are present in very small quantities(1-6%).