pulmonary circulation flows from the heart to the lungs (rather than air in the lungs flowing to the heart as had been thought in Galen’s system). His discovery was based on the color of the blood, the size and location of the different ventricles, and the fact that the pulmonary vein was extremely large, which suggested that it performed intensive and transcendent exchange. • Servetus does not talk just about cardiology. he also talks of the brain, the cerebellum, the meninges, the nerves, the eye, the tympanum, etc.