An Astonishing Circle

In 1628, physician William Harvey made a controversial claim: that blood circulated continuously through the body, pumping from the heart through the blood vessels into the tissues and returning to the heart. His research contradicted many anatomy “experts” who believed blood was produced in the liver and dissipated in the tissues. Some called Harvey’s work genius. Others called it a dangerous lie. This is the story of how humans came to understand the circulatory system – from Harvey to Ibn al-Nafis, an Arab Muslim scholar who discovered pulmonary circulation 300 years before Europeans did; to Marcello Malpighi, who studied capillaries; to Joseph Priestley and Antoine Lavoisier, who identified oxygen’s role; and beyond