[History of blood circulation].

Until the beginning of the 17th century it was assumed that the arteries carried a subtle kind of air or spirit to the organs, and the veins the nutrient blood. No one seems to have seriously considered that a backflow was necessary. The circulation of the blood was discovered in 1628 by William Harvey. Blood pressure was first measured in animals by Hales (1733). Reliable blood pressure measurements in humans were rendered possible at the beginning of the 20th century through the efforts of Mahomed, von Basch, Potain, Riva-Rocci and Korotkoff. In 1903 electrocardiography was introduced by Einthoven. In 1941 the use of venous catheterization by Cournand initiated the giant forward strides of modern cardiovascular research, diagnosis and therapy.