See Lucian (in Eunuch. tom. ii. p. 350 - 359, edit. Reitz,) Philostratus (in Vit. Sophist. l. ii. c. 2,) and Dion Cassius, or Xiphilin, (lxxi. p. 1195,) with their editors Du Soul, Olearius, and Reimar, and, above all, Salmasius, (ad Hist. August. p. 72.) A judicious philosopher (Smith's Wealth of Nations, vol. ii. p. 340 - 374) prefers the free contributions of the students to a fixed stipend for the professor.