During the centuries immediately preceding the Christian era, Greek medicine was represented by a collection of treatises which had been written by Hippocrates and his followers on anatomical, physiological, pathological, therapeutical and ethical subjects, and which constituted a fairly complete but not always easily intelligible system. As time went on, however, and especially as new and useful facts were constantly being added to the existing stock of medical knowledge, the more thoughtful physicians began to feel that the system, which up to that day had proved acceptable, needed to be perfected in a number of respects; and accordingly, as a result of this feeling of dissatisfaction, and also as an expression of the prevailing desire for a more perfect knowledge of the truth, there developed, as has been stated in the preceding chapters, a number of different medical sects. When Galen first appeared in the field as a physician of unusual promise, these various sects were all still in a thriving condition. The Methodists, in particular, were very popular. Galen did not favor any special sect, but in his writings he made it manifest that he attached more importance to the teachings of Hippocrates than to those of any other author. “It was Hippocrates,” he said, “who laid the real foundations of the science of medicine.” It is therefore not surprising that Galen should have devoted so much time to the writing of elaborate commentaries on the works of Hippocrates. The service which he thus rendered to medicine, says Daremberg, was of very great value. But Galen, notwithstanding his great admiration for Hippocrates, did not hesitate to criticise a number of his teachings, and especially those which, as he believed, were not stated with sufficient clearness. Valuable as was the service rendered to medicine by the writing of these commentaries, there still remained an urgent need for a service of a different and much more difficult kind, viz., that of welding together into a single clearly written and easily intelligible system of medicine, all that was good in the Hippocratic writings and in the disconnected and at times antagonistic teachings of the sects. To accomplish this successfully required the services of a man endowed with mental gifts of a most exceptional character--complete knowledge of medicine in all its departments, a mind thoroughly trained in philosophy, the power to express his thoughts in simple language, and an independence and fairness of judgment which would render him indifferent to the petty interests of the sects. Claudius Galen, as subsequent events showed, possessed these very gifts in a high degree, and he devoted the better part of his reasonably long lifetime to the accomplishment of this much-needed work. How greatly it was needed at that particular period of time, nobody then knew or could even suspect. It soon appeared, however, that all the vaunted civilization of the