The Greek physician and anatomist Galenos of Pergamon (129-216) was one of the most famous physicians of antiquity. He studied near Smyrna. At the age of 19, he travelled to Alexandria, which was a centre of the healing arts at the time and where anatomical dissections and examinations of human cadavers were allowed. In 158 he returned to Pergamon, where he worked as a sports and wound doctor for the gladiators and maintained a medical practice. From 161, Galen was active in Rome and fought a plague epidemic that had broken out in Aqulileia on behalf of the Roman Emperor Marcus Aurelius (121-180). He became personal physician to the emperor's son Commodus (161-192) and to the emperor Septimius Severus (146-211). Galen summarised all the knowledge of his time into a system of teaching that was generally valid until the Middle Ages. In doing so, he took up the theory of the four humours (blood, phlegm, yellow and black bile) developed in Hippocratic medicine. This was later questioned by Paracelsus (1493-1541). Galen's main medical work is the "Methodus medendi" (The Therapeutic Method), which was written from around 175 and consists of 14 books.