<Tr> <Th> Occupation </Th> <Td> Physician </Td> </Tr> <Tr> <Th> Era </Th> <Td> Hellenistic Greece </Td> </Tr> <P> Erasistratus (/ ˌɛrəˈsɪstrətəs /; Greek: Ἐρασίστρατος; c. 304--c. 250 BC) was a Greek anatomist and royal physician under Seleucus I Nicator of Syria . Along with fellow physician Herophilus, he founded a school of anatomy in Alexandria, where they carried out anatomical research . He is credited for his description of the valves of the heart, and he also concluded that the heart was not the center of sensations, but instead it functioned as a pump . Erasistratus was among the first to distinguish between veins and arteries . He believed that the arteries were full of air and that they carried the "animal spirit" (pneuma). He considered atoms to be the essential body element, and he believed they were vitalized by the pneuma that circulated through the nerves . He also thought that the nerves moved a nervous spirit from the brain . He then differentiated between the function of the sensory and motor nerves, and linked them to the brain . He is credited with one of the first in - depth descriptions of the cerebrum and cerebellum . </P> <P> Erasistratus is generally supposed to have been born at Ioulis on the island of Ceos, though Stephanus of Byzantium refers to him as a native of Cos; Galen, as a native of Chios; and the emperor Julian, as a native of Samos . Pliny says he was the grandson of Aristotle by his daughter Pythias, but this is not confirmed by any other ancient writer; and according to the Suda, he was the son of Cretoxena, the sister of the physician Medius, and Cleombrotus . From the latter it is not quite clear whether Cleombrotus was his father or his uncle . He was a pupil of Chrysippus of Cnidos, Metrodorus, and apparently Theophrastus . </P>

Who was the greek physician who distinguished the veins from the arteries