At the time when this historic period commenced all the known world was under the dominance of a single man. The power of Septimus Severus had more extent than that of Alexander the Great, and bid fair to be of a much longer existence. The Roman dominion, cemented by seven hundred years of bold and persevering government, seemed almost immovable. While the savages upon its frontiers occasionally troubled its peace, none were strong enough to penetrate its centres or place it in real peril. The great civil wars had ceased, or changed their object. Both the{048} people and the senate, those two eternal competitors, had gotten over the struggle for supreme power; monarchial government was accepted as a matter of fact, and the citizens contended only for choice of a master. Similar changes had taken place in the domain of the mind; philosophical discussions, which were so essentially a part of the schools of the ancient Greeks, had nearly lost their interest and were being discontinued. Such disputes as took place related less to principle than to interpretation of the language of the teacher. In morals, Plato, Epicurus, and Zeno were followed until the principles of Christianity gradually supplanted their teaching; in physics and metaphysics the authority of Aristotle, and in medicine that of Galen, were simply undisputed. Conditions being such as these, there was naturally but one sect in medicine, and one method of study and practice. Medical science retrograded rather than progressed, sad to say, and was undisturbed by any remarkable revolution. The scepter of medicine passed from the hands of one nation to those of another, and the language of Hippocrates and Galen was later replaced, as will duly be seen, by that of Avicenna and Albucassis. But this Greek Period, which is one of transition, offers little for our consideration more than the lives and writings of four of its most eminent physicians, who by their study in the school of Alexandria, and by their writings and teachings, left reputations which were sustained until the invasion of the Arabs. Of these it may be said that, while they did little or nothing original, and simply commented upon the writings of Hippocrates and Galen, they kept burning the torch of medical learning which else had been almost extinguished by their indolent contemporaries. Of these various commentators--for they were little more than that--the first of any importance after Galen was _Oribasius_, who was horn in Pergamos (328-403); he early attached himself to the fortunes of Julian the Apostate, and followed him into Gaul when he was{049} made its governor. Julian appreciated the good qualities of Oribasius, made him an intimate friend, and after he himself became emperor appointed his friend as quæstor at Constantinople. After the emperor's untimely death, Oribasius remained faithful to his memory, but his jealous colleagues so falsely and so