Claudius, commonly called Galen, the most celebrated of the ancient medical writers, and a man who has exercised a greater influence on medical science than any other individual author of ancient or modern times. Of his personal history little is known except what is gathered from his own works; but these are so full of personal detail as to furnish sufficient material for a life. He was born at Pergamus in Mysia towards the close of the year 130 A.D. His father, whose name was Nicon, was an architect and geometrician of that city, and is highly praised by Galen for his many good qualities both of heart and head. His mother, on the other hand, is described as a second Xanthippe, differing only from her prototype by being worse than she. No expense was spared in educating the young Galen, whose teachers were the most celebrated scientific men of his native town. Stratonicus, a disciple of the Hippocratic school; Satyrus, an eminent anatomist; and Echirion, an empiric. After the death of his father, whom he lost in his twentieth year, Galen went to study successively at Smyrna, Corinth, and Alexandria, which last was the most famous medical school of the ancient world. He likewise seized the opportunity of travelling in various other foreign countries. In A.D. 158 he was publicly invited by his fellow-citizens to return home, and was appointed physician to the gladiatorial school. Five years later he was compelled, by civil dissensions, to quit his native city, and he then betook himself to Rome, where his unparalleled success drew down upon him the jealousy and hatred of the Roman practitioners. For some time he bore up against the ill-treatment which he met with at their hands, and wrote and lectured for a number of years with ever-growing success, but in daily dread of being poisoned by his rivals. In A.D. 167, Galen at length left, partly to avoid an introduction to the emperor M. Aurelius, partly to revisit his native city. His departure was probably hastened by the breaking out of the pestilence at Rome. He had hardly settled down at Pergamus when he received orders to join M. Aurelius in the north of Italy. Soon after he joined the emperor the plague broke out with great violence in the Roman camp, and M. Aurelius instantly returned to Rome, taking Galen in his train. It was probably about this time that he prepared for the emperor the famous medicine called "theriaca" of which the royal patient took a little every day. During his stay at Rome Galen composed two of his best known works in the leisure moments of his extensive practice. These were his treatises De Usu Partium Corporis Humani, and De Hippocratis et Platonis Decretis. After this time his history is not very clearly ascertained. He seems to have left Rome and returned to Pergamus, visiting on his way the island of Lemnos, where he learned the method of preparing the "terra lemmia" or sigillata, a medicine then much in vogue. It is not fully known whether he ever returned to Rome; but it seems probable that he did. Neither the year nor the place of his death is thoroughly ascertained. Suidas, whose testimony is generally followed, says that he died when he was seventy years of age, which would place his death in the year 201. One of his Arabian biographers, however, makes him survive till his eightieth year; and another, Abul-faraj, states that he died in Sicily at the age of eighty-eight.

Galen is, on the whole, one of the most remarkable writers of antiquity. As is frequently the case, his worth was ill appreciated during his lifetime, but after his death his native city caused medals to be struck in his honour; and he became generally known by the title of "the wonderful." During his early residence at Rome, indeed, his skill had earned for him the titles of "Paradoxologus," the wonder-speaker, and "Paradoxopoeus," the wonder-worker. But Galen it was not on his skill as a physician alone or chiefly that his fame depended. He was one of the most extensively and variously learned men of his age, and is known to have written nearly five hundred distinct treatises on different subjects, including logic, ethics, and grammar. He seems to have entertained a very justifiable respect for himself and his influence and position, and to have looked down with perhaps too great contempt on his rivals and detractors. But the bitter disgust which he felt towards them is excusable, if we remember that he lived among them in daily terror of his life. It is remarkable that though Christianity was in Galen's time spreading apace, he seems to have known no more about it than might have been picked up in ordinary conversation. At least he only alludes to the Christians in one of his works as remarkable for their self-denial, temperance, chastity, and other virtues, never indicating, however, any personal sympathy for them in the persecutions to which they were exposed. For a detailed account of Galen's influence and position in medical science, see Anatomy, vol. ii., pp. 752-754.

The works now extant, attributed to Galen, amount to 128 separate treatises. Of these only eighty-three are undoubtedly genuine; nineteen are doubtful; forty-five confessedly spurious; nineteen are mere fragments; fifteen are comments upon portions of Hippocrates; while fifty are enumerated as still lying unpublished in various European libraries. There have been numerous editions of Galen's complete works, and also of some of the individual treatises. A list of those who have edited or illustrated Galen is given by Conrad Gesner in the Basle edition of 1561. The most important of these, as well as of others who have since followed in the same track, are named in the following list:—Jo. Bapt. Opizo, A. Lacuna, Ant. Musa Brassavolus, Aug. Gadaldinus, Conrad Gesner, Sylvius, Cornarius, Joannes Montanus, Joannes Caius, Thomas Linacre, Theodore Goulston, Caspar Hoffmann, Rene Chartier, Haller, and Kuhn. There have been numerous Latin translations of Galen. Altogether, according to Choulant, there was one version in the fifteenth century; twenty-two versions in the following century; and none since. There have been also four editions of the Greek text; the first by the Aldi at Venice, in 5 vols. fol., 1525; the next, also in 5 vols. fol., Basle, 1538; the third, by Rene Chartier, bears date Paris, 1679, and amounts to 13 vols. fol.; the last and best is that by C. G. Kuhn, Leipzig, 1821-1833.