Diagram of the circulation of blood as understood after William Harvey's work, showing blood leaving the left ventricle of the heart by the aorta and returning to the heart via the vena cava at the right auricle: it has now completed the Greater Circulation. It next passes to the right ventricle and out into the Pulmonary Artery and undertakes the Lesser Circulation (Pulmonary Circulation) and returns to the heart at the left auricle. William Harvey (1578-1657) an English physician who made seminal contributions in anatomy and physiology. Dated 20th century