Circulatory system, 19th-century illustration. Blood is shown circulating (arrows) from the heart to the lungs and back again, and then around the body. The circulation is divided into deoxygenated blood (purple) and oxygenated blood (red). Blood is carried away from the heart in the arteries (arterial blood supply), and is brought back to the heart in the veins (venous blood supply). The organs shown here are the heart, the lungs (and trachea), the liver, the kidneys, the spleen, the intestines and the bladder. The blood vessels bringing blood to and from the head and arms are also shown. Published in 'La Vie Normale et la Sante' (Normal Life and Health, Paris, 1881) by Dr Jules Rengade.