7. Circulatory System
The blood transfusion which is a common practice now is the result of the discovery of the circulatory system of the blood. Discoveries of the circulatory system are attributed to contributions by different scientists at various times. These discoveries were related to the process of pulmonary circulation, the identification of the capillary system, the discovery and classification of the four blood groups. With these discoveries in place, surgical procedures, transplants and blood transmission has become very convenient.