The operation devised by Archigenes proves, among other things, two important facts: first, that the anatomical constitution of the teeth had already been explored, seeing that Archigenes did not ignore the existence of the pulp cavity; and secondly, that Archigenes was greatly opposed to the extraction of a tooth unless absolutely necessary. It might be thought that such aversion depended upon an exaggerated idea of the dangers connected with the extraction of a tooth, an idea widely diffused at that period; but regarding such a daring surgeon as Archigenes was, it is more logical to suppose that in similar cases he had recourse to trephining and not to extraction, especially on account of the importance he attached to the preservation of the tooth. Surgery in ancient times was eminently conservative; later on—partly by effect of its own progress—it became too readily inclined to the removal of diseased parts; in modern times it has again become what it was originally, and what it must ever be, viz., conservative in the highest possible degree. CLAUDIUS GALEN, after Hippocrates the greatest physician of ancient times, was born at Pergamus, a city in Asia Minor, in the year 131 of our era. His father Nicon, a man of great abilities, who was at the same time a man of letters, a philosopher, a mathematician, and an architect, had put him, at a very early age, to the study of science and of the liberal arts. Galen began to study medicine at the age of seventeen, under the guidance of skilful doctors of his native country; he made several journeys in order to have the benefit of the instruction of celebrated masters, and finally frequented the renowned medical school at Alexandria. On going to Rome, in the thirty-fourth year of his life, he soon acquired in that city a very high renown. He died in the first decade of the third century, but we do not know exactly in what year. Galen was a most prolific writer, and his works, considering the period in which they were written, form a real medical encyclopedia. Anatomy through his researches made considerable progress, for he studied with the utmost care and attention (especially in apes) the bones, muscles, heart, bloodvessels, brain, nerves, and every other part of the organism. His anatomical researches enabled him to correct many errors, but as he had dissected almost exclusively animals and not human corpses, he himself fell into several errors, especially in attributing to man parts which he does not possess, for example, the intermaxillary bone. Galen justly observed that the inferior maxilla (resulting, according to him, from the union of two bones, which, indeed, is embryologically true) has in man, proportionally to the other bones of the skeleton, a lesser length than in animals.