The Greek physician and anatomist Erasistratus (304-250 B.C.E.) is considered the father of physiology. Based on his numerous dissections of human cadavers, he accurately described the brain, including its cavities and membranes, stomach muscles, and the differences between motor and sensory nerves. He understood correctly that the heart served as a pump to circulate blood. Anatomical research ended with Erasistratus until the thirteenth century, in a large part because of public opinion against the dissection of human cadavers.