William Harvey
Harvey's ideas came from dissecting human bodies. Harvey found that the liver would have to make 540 pounds of blood every hour for Galen to be right. This showed him that the blood was not being used up. It was being reused by the body. He said blood flowed through the heart in two loops. One loop went to the lungs and got oxygen. The other loop went to the organs and body tissue giving them the oxygen. He said the heart was just a pump that pumped blood around the body.