William Harvey was an English physician who lived in the 17th century. He was the first person to correctly describe blood’s circulation in the body. He showed that arteries and veins form a complete circuit and that this circuit starts at the heart, and leads back to the heart. He also established that the heart’s regular contractions drive the flow of blood around the whole body. Before his discoveries, blood was thought to ebb and flow through the body by the contraction of arteries. Harvey’s knowledge came from observations he made of blood flowing through the veins and arteries of living animals that he cut open. This may seem crule, as there were no anaesthetics in Harvey’s time. Nevertheless, it how we arrived at an understanding of blood and its circulation in the body. William Harvey’s work also laid down the foundations of physiology, which is the study of body functions.