1. A son of Hippocrates, brother of Dracon I., and father of Gorgias, * So it is stated by Meibomius (Comment. in Hippocr. " Jusjur." p. 7) and other modern authors, but the Writer has hitherto been unable to find any ancient author who says that Thessalus had a son named Gorgias. Hippocrates III. (Jo. Tzetzes, Chil. vii., Hist. 155, in Fabric. Bibl. Gr. vol. xii. p. 682, ed. vet.; Suid. s. v. Ἱπποκπάτη ; Galen. Comment. in Hippocr. " De Humor." i. I. vol. xvi. p. 5), and Dracon II. (Suid. s. v. Δπάκων) He lived in the fifth and fourth centuries B. C., and passed some of his time at the court of Archelaus, king of Macedonia, who reigned B. C. 413-399. (Galen, Comment. in Hippocr. " De Nat. Hom." i. prooem. vol. xv. p. 12.) He was one of the founders of the sect of the Dogmatici (Dict. of Ant. s. v. Dogmatici), and is several times highly praised by Galen, who calls him the most eminent of the sous of Hippocrates (Comment. in Hippocr. " Epid. III." ii. prooem. vol. xvii. pt. i. p. 579), and says that he did not alter any of his father's doctrines (Comment. in Hippocr. " De Nat. Hom." i. prooem. vol. xv. p. 12). It is supposed, however, that in performing the difficult task of preparing some of the writings of Hippocrates for publication after his death he made some additions of his own (Galen, De Diffic. Respir. iii. l, vol. vii. p. 890, Comment. in Hippocr. " De Humor." i. prooem. vol. xvi. p. 4; Comment. in Hippocr. " Epid. VI." i. prooem. vol. xvii. pt. i. p. 796), which were sometimes not quite worthy of that honour. (Pallad. Schol. in Hippocr. " Epid. VI." p. 3, ed. Dietz.) He was also 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; viz. " De Humoribus " (Galen. Comment. in Hippocr. " De Humor." i. prooem. vol. xvi. p. 3), " De Officina Medici" (id. Comment. in Hippocr. " De Offic. Med." 1.5, vol. xviii. pt. ii. p. 666), the first book of the " Praedictiones " or " Prorrhetica " (id. Comment. in Hippocr. " Praedict. I." 2.54, vol. xvi. p. 625), and the second, fourth, fifth, sixth, and seventh books of the " Epidemia," or " De Morbis Popularibus " (id. De Diffic. Respir. 2.8, vol. vii. p. 855); but this point is considered by modern critics to be very uncertain. Among the Letters, &c. attributed to Hippocrates, there is one which professes to be addressed by him to Thessalus (vol. iii. p. 822), which contains no internal marks of a spurious origin, but which is perhaps hardly likely to be authentic if all the other pieces are apocryphal. There is also an oration, Πρεσβευτικός (vol. iii. p. 831), supposed to be spoken by Thessalus to the Athenians, in which he implores them not to continue the war against Cos, his native country; but this is undoubtedly spurious (see Littre's Oeuvres d'Hippocr. vol. i. p. 432). The epitaph of Thessalus is preserved in the Greek Anthology. (7.135, ed. Tauchn.) His name occurs in several other passages of Galen's writings, but chiefly in reference to the authorship of the different books " De Morbis Popularibus."