William Harvey was born in 1578 and studied medicine
. He worked in London as a doctor
at the Royal College of Surgeons
, before coming Royal Physician
to James I and Charles I.
He did comparitive studies on humans and animals. He performed vivisection on animals with a very slow metabolism to observe hearts in action. He disproved Galen, who thought that blood was constantly been created and then used up. Harvey worked out mathematically that this was an impossibility.
Harvey also identified the difference between arteries and veins. He also worked out that capillaries must exist, but lacked the technology to see them. He also noticed that blood changes colour as it passes through the lungs.
Harvey, along with Vesalius and Ambroise Pare, was a Renaissance man who added to the theory of medicine and anatomy, but did not change medical practice at the time. Their discoveries allowed the age of medical enlightenment to happen, but didn't have much effect on the health of people living at the time.
Despite Harvey's discoveries, the practice of bleeding continued.