An English physician principally remembered for his demonstration of the circulation of the blood and the action of the heart as a pump. He was educated at the universities of Cambridge and Padua, where he was greatly influenced by Fabricius. The conjoined problem of blood circulation and heart action puzzled him, as it had many others. In the fourth century B.C.E., Empedocles had put forward the idea of the ebb and flow of the blood. Galen in the second century C.E. supported this theory, which was accepted by the medical profession for the ensuing 1400 years.
By Harvey’s time Galileo’s experiments and the problems of the mining industry and of land drainage had led to an interest in the way pumps functioned. There was also a growing reliance on experiment rather than on blind acceptance of hallowed texts. Anatomical dissection had established that there are one-way valves in the main veins, casting doubt on the ebb-and-flow theory. By 1616, Harvey, backed by careful dissection and experimentation both on animals and humans, showed that the heart pumped blood through the lungs, back to the other side of the heart, and then out through the arteries, returning via the veins. He published his findings in De Moto Cordis et Sanguinis in Animalibus (On the motion of the heart and blood in animals; 1628). As Pledge writes: ‘“De Moto Cordis’ is a classic of science. Negatively, it was unencumbered by metaphysics, a virtue then exceedingly rare. Positively, it stands for the entry at once of the quantitative and of the comparative methods into biology.”