The only[513] person among us, at least so far as I have been able to ascertain, who had treated of this subject before the time of Valgius, was Pompeius Lenæus,[514] the freedman of Pompeius Magnus; and it was in his day, I find, that this branch of knowledge first began to be cultivated among us. Mithridates, the most powerful monarch of that period, and who was finally conquered by Pompeius, is generally thought to have been a more zealous promoter of discoveries for the benefit of mankind, than any of his predecessors—a fact evinced not only by many positive proofs, but by universal report as well. It was he who first thought, the proper precautions being duly taken, of drinking poison every day; it being his object, by becoming habituated to it, to neutralize its dangerous effects. This prince was the first discoverer too of the various kinds of antidotes, one[515] of which, indeed, still retains his name; and it is generally supposed that he was the first to employ the blood of the ducks of Pontus as an ingredient in antidotes, from the circumstance that they derive their nutriment from poisons.[516] It was to Mithridates that Asclepiades,[517] that celebrated physician, dedicated his works, still extant, and sent them, as a substitute for his own personal attendance, when requested by that monarch to leave Rome and reside at his court. It is a well-known fact, that this prince was the only person that was ever able to converse in so many as two-and-twenty languages, and that, during the whole fifty-six years of his reign, he never required the services of an interpreter when conversing with any individuals of the numerous nations that were subject to his sway. Among the other gifts of extraordinary genius with which he was endowed, Mithridates displayed a peculiar fondness for enquiries into the medical art; and gathering items of information from all his subjects, extended, as they were, over a large proportion of the world, it was his habit to make copies of their communications, and to take notes of the results which upon experiment had been produced. These memoranda, which he kept in his private cabinet,[518] fell into the hands of Pompeius, when he took possession of the royal treasures; who at once commissioned his freedman, Lenæus the grammarian, to translate them into the Latin language: the result of which was, that his victory was equally conducive to the benefit of the republic and of mankind at large. CHAP. 4.—GREEK AUTHORS WHO HAVE DELINEATED THE PLANTS IN COLOURS.