The fables that bore his name seem not to have been committed by him to writing, but for a long time were handed down from generation to generation by oral tradition; so that the same fables are sometimes found quoted in slightly different forms, and we hear of men learning them in conversation rather than from books. They were, however, universally popular. Socrates while in prison amused himself by turning some of them into verse. Aristophanes cites them in his plays; and he tells how certain suitors once tried to win favor of a judge by repeating to him some of the amusing stories of Aesop. The Athenians even erected a statue in his honor. At a later period, the fables were gathered together and published by the Athenian statesman and orator, Demetrius Phalereus, in B.C. 320, and were versified by Babrius (of uncertain date), whose collection is the only one in Greek of which any substantial portion still survives. They were often translated by the Romans, and the Latin version by Phaedrus, the freedman of Augustus Caesar, is still preserved and still used as a school-book. Forty-two of them are likewise found in a Latin work by one Avianus, dating from the fifth century after Christ. During the Middle Ages, when much of the classical literature had been lost or forgotten, Aesop, who was called by the mediaevals "Isopet," was still read in various forms; and in modern times he has served as a model for a great number of imitations, of which the most successful are those in French by Lafontaine and those in English by John Gay. Whether or not such a person as Aesop ever lived, and whether or not he actually narrated the fables that are ascribed to him, it is certain that he did not himself invent them, but merely gave them currency in Greece; for they can be shown to have existed long before his time, and in fact to antedate even the beginnings of Hellenic civilization. With some changes of form they are found in the oldest literature of the Chinese; similar stories are preserved on the inscribed Babylonian bricks; and an Egyptian papyrus of about the year 1200 B.C. gives the fable of 'The Lion and the Mouse' in its finished form. Other Aesopic apologues are essentially identical with the Jatakas or Buddhist stories of India, and occur also in the great Sanskrit story-book, the 'Panchatantra,' which is the very oldest monument of Hindu literature.