Polybus was one of the pupils of Hippocrates, and also his son-in-law. He lived on the island of Cos in the 4th century BC. With his brothers-in-law, Thessalus and Draco, he was one of the founders of the Dogmatic school of medicine. He was sent by Hippocrates, with his fellow-pupils, during the time of the plague, to assist different cities with his medical skill. Afterwards, he remained in his native country. According to Galen, he followed implicitly the opinions and practices of Hippocrates, but the strict accuracy of this assertion has been doubted.