Imagine living in a time when most people believed that blood was created by the liver and used up by the muscles. That it flowed through two separate systems of vessels, one carrying red blood and the other carrying purple blood. That it moved back and forth like a tide, influenced by the planets and the stars.
This was the state of medical knowledge in the 16th century, based on the writings of Galen, an ancient Greek physician whose authority had been unquestioned for over a thousand years. But one man dared to challenge this dogma and to discover the truth about how blood circulates through the human body. His name was William Harvey, and he was an English physician who made a revolutionary contribution to science.
Harvey was born in Folkestone, Kent, in 1578. He received a good education at the King’s School in Canterbury and at Cambridge University. He then traveled to Italy to study medicine at the University of Padua, where he learned from the famous anatomist Hieronymus Fabricius. He obtained his doctorate in 1602 and returned to England to practice medicine. He married Elizabeth Browne, the daughter of a royal physician, in 1604. He became a fellow of the Royal College of Physicians in London in 1607 and was appointed physician to St. Bartholomew’s Hospital in 1609. He also served as a physician to King James I and King Charles I.
Harvey’s curiosity about the circulation of blood was sparked by his observation of the venous valves, small flaps inside the veins that allow blood to flow only in one direction. He realized that these valves were oriented toward the heart, not away from it as previously thought. He wondered how blood could flow from the heart to the extremities and back again without being consumed or overflowing. He conducted a series of experiments on animals and humans to measure the amount and speed of blood passing through the heart. He estimated that the heart pumped about half a liter of blood per minute, which was far more than could be produced by the liver or consumed by the body. He concluded that blood must circulate continuously through a single system of vessels, driven by the contraction and relaxation of the heart.
Harvey published his findings in 1628 in a book titled An Anatomical Exercise on the Motion of the Heart and Blood in Animals. The book was written in Latin and dedicated to King Charles I. It contained detailed descriptions of Harvey’s experiments and arguments, as well as illustrations of the heart and blood vessels. Harvey also explained how his theory was compatible with Aristotle’s philosophy, which was widely accepted at the time. In his book, he wrote:
“THE HEART IS SITUATED AT THAT POINT WHERE ALL PARTS MEET; IT IS NOT ONLY AN ORGAN BUT ALSO A GENERAL GATHERING PLACE FOR NATURE; IT IS NOT ONLY AN ORGAN BUT ALSO AN INSTRUMENT FOR LIFE.”
However, Harvey’s book was not well received by his peers, who were reluctant to abandon their traditional views based on Galen. Harvey faced criticism, mockery, and hostility from his colleagues, some of whom accused him of plagiarism or heresy. He also faced practical difficulties in proving his theory, such as the lack of a microscope to observe the capillaries, the tiny vessels that connect the arteries and veins.
Harvey continued to defend and refine his theory until his death in 1657. He also made other discoveries in anatomy and physiology, such as the role of the valves in the heart, the development of embryos, and the existence of pulmonary circulation. He donated his library and collection of specimens to the Royal College of Physicians, where they are still preserved today. His reputation gradually improved after his death, as more evidence and support for his theory emerged from other scientists and experiments. He is now regarded as one of the greatest physicians and anatomists of all time, and as a pioneer of modern medicine.