Erasistratus (c. 304–c. 250 BC)

Greek physician and anatomist. Regarded as the founder of physiology, he came close to discovering the true function of several important systems of the body, which were not fully understood until nearly 1,000 years later. For example, the principle of blood circulation, though he had it circulating in the wrong direction. Tracing the network of veins, arteries, and nerves, he postulated that the nerves carry the ‘animal’ spirit, the arteries the ‘vital’ spirit, and the veins blood. He did, however, grasp a rudimentary principle of oxygen exchange and condemned bloodletting as a form of treatment.

Erasistratus dissected and examined the human brain, noting the convolutions of the outer surface, and observed that the organ is divided into larger and smaller portions (the cerebrum and cerebellum). He compared the human brain with those of other animals and made the correct hypothesis that the surface area/volume complexity is directly related to the intelligence of the animal.

Erasistratus was born on the Aegean island of Ceos (now Khios). He learned his skills in Athens and became court physician to Seleucus I, who governed western Asia. He then moved on to Alexandria, where he taught.