Franciscus dele Boë Sylvius, born in Hanau in 1614, studied medicine at Sedan, Jena, Wittenberg and Leiden, where Otto Heurnius was one of his teachers. After successfully defending his thesis at the University of Basel he went back to Hanau, where he practiced medicine for a time before becoming a lecturer in Leiden, where he was later to become professor of medicine and vice-chancellor. Sylvius is considered the founder of the 17th-century iatrochemical school of medicine, which held that all phenomena of life and disease are based on chemical action. He was also one of the earliest defenders of the theory of the circulation of the blood in the Netherlands. Rather than Boerhaave, it was Sylvius who was the champion of Leiden bedside teaching, involving his students in his rounds in the hospital.