Thessălus in Harpers Dictionary of Classical Antiquities (1898)
A Greek physician, son of Hippocrates. He passed some of his time at the court of Archelaüs, king of Macedonia, who reigned B.C. 413-399. He was one of the founders of the sect of the Dogmatici, and is several times highly praised by Galen, who calls him the most eminent of the sons of Hippocrates. He was supposed by some of the ancient writers to be the author of several of the works that form part of the Hippocratic Collection, which he might have compiled from notes left by his father.
Also a Greek physician, a native of Tralles in Lydia, and one of the founders of the medical sect of the Methodici. He lived at Rome in the reign of the emperor Nero, A.D. 54-68, to whom he addressed one of his works; and he died and was buried, and his tomb was to be seen in Pliny 's time, on the Via Appia. He considered himself superior to all his predecessors. He is frequently mentioned by Galen, but always in terms of contempt and ridicule. None of his works are extant.