During the 4th century BC, the Stoics, Epicurians, Praxagoras and Diocles all nominated the heart, while Strato placed the seat of the soul between the eyebrows.
7) Praxagoras (4th century BC) claimed that blood vessels terminated as nerves, so supporting the argument that the heart was the central controlling organ.
Although Praxagoras referred to 'psychic pneuma', this important concept was first formulated by Diogenes (4th century BC) who, as promoter of the heart as seat of the hegemonikon, claimed that 'psychic pneuma', formed in the heart, spread through the body's vessels to effect voluntary motion.
He was educated under Praxagoras, (12) a prominent physician of the Hippocratic school, in all likelihood at the school's centre on the island of Cos.
Pursuing the fields of interest of his teacher Praxagoras, he accurately distinguished, both anatomically and functionally, between veins, arteries and nerves.