What did Vesalius do?
He boiled peoples bodies to play with the human skeleton. Doing this, he was the first man to discover how all the bones and muscles in the body fit together.
What did William Harvey do?
He worked out that the heart was used to pump blood around the body, he discovered veins and arteries.
What did Thomas Sydenham do?
He was the first person to theorize that a disease was something that attacked the body, and that the 4 humors was wrong.