1 The nature of evidence
William Harvey (1576-1657) was the rst, and one of the greatest, clinician-scientists. He studied medicine at Cambridge and Padua before establishing a ourishing medical practice in London, where his patients included two kings (James I and Charles I) and the Lord Chancellor of England (Francis Bacon). At the same time he pursued a parallel career as a clinical scientist. Among many discoveries, he showed that the blood circulated around the body, rather than ebbing and owing along the arteries and veins, and that the heart acted as a pump rather than a sucking device. In doing so he changed beliefs that had existed for more than 1000 years.