170) Galen prepared the famous medicine _theriaca_ for Marcus Aurelius, who took a small quantity daily. The Emperor Septimius Severus employed the same physician and the same medicine about thirty years afterwards. It is recorded that the philosopher Eudemius was successfully treated by Galen for a severe illness caused by an overdose of theriaca, and that the treatment employed was the same drug in small doses. Galen stayed several years in Rome, and wrote and practised as on his former visit. He again returned to Pergamos, and probably was in Rome again at the end of the second century. It is certain he was still alive in the year 199, and probably lived in the reign of the Emperor Caracalla. He was not only a great physician, but a man of wide culture in every way. In matters of religion he was a Monotheist. There was persecution of the Christians in his day, and it is likely that he came little into contact with the disciples of the new religion, and heard distorted accounts of it, but in one of his lost books, quoted by his Arabian biographers, Galen praises highly the love of virtue of the Christians. He no doubt found the practice of medicine lucrative when he had gained pre-eminence, and it is recorded that he received £350 for curing the wife of Boetius, the Consul. Galen wrote no less than five hundred treatises, large and small, mostly on medical subjects, but also on ethics, logic, and grammar. His style is good but rather diffuse, and he delights in quoting the ancient Greek philosophers. Before his time, as we have seen, there were disputes between the various medical sects. The disciples of Dogmatism and of Empiricism had been opposed to each other for several centuries, and the Eclectics, Pneumatists, and Episynthetics had arisen shortly before his time. Galen wrote against slavish attachment to any sect, but "in his general principles he may be considered as belonging to the Dogmatic sect, for his method was to reduce all his knowledge, as acquired by the observation of facts, to general theoretical principles. These principles he, indeed, professed to deduce from experience and observation, and we have abundant proofs of his diligence in collecting experience, and his accuracy in making observations; but still in a certain sense at least, he regards individual facts and the details of experience as of little value, unconnected with the principles which he had laid down as the basis of all medical reasoning. In this fundamental point, therefore, the method pursued by Galen appears to have been directly the reverse of that which we now consider as the correct method of scientific investigation; and yet, such is the force of natural genius, that in most instances he attained the ultimate object in view, although by an indirect path. He was an admirer of Hippocrates, and always speaks of him with the most profound respect, professing to act upon his principles, and to do little more than expound his doctrines,