Scientific knowledge of the heart dates back almost as far as the beginnings of recorded history. The Egyptian physician Imhotep made observations on the pulse during the 2600s bc. During the 300s bc the Greek physician Hippocrates studied and wrote about various signs and symptoms of heart disease, and the Greek philosopher Aristotle described the beating heart of a chick embryo. Among the first people to investigate and write about the anatomy of the heart was another Greek physician, Erasistratus, around 250 bc. Erasistratus described the appearance of the heart and the four valves inside it. Although he correctly deduced that the valves prevent blood from flowing backward in the heart, he did not understand that the heart was a pump.
Galen, a Greek-born Roman physician, also wrote about the heart during the second century ad. He recognized that the heart was made of muscle, but he believed that the liver was responsible for the movement of blood through the body. Heart research did not greatly expand until the Renaissance in Europe (14th to 16th centuries). During that era, scientists began to connect the heart's structure with its function. During the early 16th century the Spanish physician and theologian Michael Servetus described how blood passes through the four chambers of the heart and picks up oxygen in the lungs. Perhaps the most significant contributions were made by English physician William Harvey, who discovered the circulation of blood in 1628. Harvey was the first to realize that the heart is a pump responsible for the movement of blood through the body. His work revealed how the heart works with the blood and blood vessels to nourish the body, establishing the concept of the circulatory system.