Harvey, William
1587–1657
English physician

William Harvey is best known for his theory on the circulation of blood in the human body. Using only a magnifying glass, he overturned the most popular theory about blood flow at the time. He also discovered as much about the structure and function of the heart as one can see without a microscope.

Harvey received his medical degree from Italy's University of Padua in 1602. He returned to London to practice medicine and the following year married Elizabeth Browne, whose father was a court physician to James I. In the years following, Harvey was elected to the College of Physicians, which oversaw professional medicine in London. He also served the college as a lecturer in surgery and anatomy. In 1618 he reached the peak of his career as a royal physician to James I and later to James's son, Charles I. Harvey supported Charles I against Parliament during the English Civil War (1642–1649). As a result, supporters of Parliament attacked his house and destroyed most of his records. After the king's defeat, Harvey retired outside of London.

While working for the king, Harvey made his great discoveries on the circulation of the blood. His work contradicted the most popular theory of this time, which the ancient Roman physician Galen had proposed hundreds of years earlier. According to Galen, food and drink combined in the stomach to produce a substance called chyle. The chyle then passed to the liver, where it became blood that flowed into the veins. Some of the blood went to the hands and feet and some went to the right side of the heart to be purified. Most of the pure blood then flowed into the veins, while a small portion went to the left side of the heart. There it mixed with a life-giving "vital spirit" before leaving through the arteries for various parts of the body.

By dissecting* live animals and studying the movements of the heart, Harvey found several problems with Galen's theory. For example, too much blood left the heart at one time for the liver to absorb and replace with fresh blood made from chyle. Harvey also noted that in Galen's model, the amount of blood that the heart pumped in an hour exceeded the amount of blood in the entire animal. Therefore, Harvey stated that the body does not continually produce blood, but rather circulates the same blood around the body. He also proved that the veins carried blood to the heart, not away from it as Galen had taught.

In 1628 Harvey reported his findings in the book On the Movement of the Heart. In the Renaissance tradition, this work stressed the authority of personal observation over written sources that had no experiments to back them up. Although his theory met a mixed response at first, Harvey lived to see it accepted by the scientific world.

(See alsoAnatomy; Medicine; Science. )

* dissect

to cut open a body to examine its inner parts