Roman medicine was Greek medicine operating in Latin. The systematic approach to understanding the body that the Romans inherited and developed had been established by Greek physicians — Hippocrates in the fifth century BC, whose school produced the first sustained attempt to explain disease through natural causes rather than divine intervention; Herophilus and Erasistratus in the third century BC, who performed human dissection at Alexandria and advanced anatomical knowledge beyond anything previously achieved. By the time Rome had absorbed the Greek world, Greek physicians were practicing in Roman cities, Greek medical texts were being translated and adapted, and the leading medical authority of the imperial period — Galen of Pergamon — wrote in Greek while practicing in Rome as physician to the emperors Marcus Aurelius, Commodus, and Septimius Severus.