FROM the death of Hippocrates about the year 375 B.C. till the founding of the Alexandrian School, the physicians were engrossed largely in speculative views, and not much real progress was made, except in the matter of elaborating the humoral pathology. Only three or four men of the first rank stand out in this period: Diocles the Carystian, "both in time and reputation next and second to Hippocrates" (Pliny), a keen anatomist and an encyclopaedic writer; but only scanty fragments of his work remain. In some ways the most important member of this group was Praxagoras, a native of Cos, about 340 B.C. Aristotle, you remember, made no essential distinction between arteries and veins, both of which he held to contain blood: Praxagoras recognized that the pulsation was only in the arteries, and maintained that only the veins contained blood, and the arteries air. As a rule the arteries are empty after death, and Praxagoras believed that they were filled with an aeriform fluid, a sort of pneuma, which was responsible for their pulsation. The word arteria, which had already been applied to the trachea, as an air-containing tube, was then attached to the arteries; on account of the rough and uneven character of its walls the trachea was then called the arteria tracheia, or the rough air-tube.(31a) We call it simply the trachea, but in French the word trachee-artere is still used. (31a) Galen: De usu partium, VII, Chaps. 8-9. Praxagoras was one of the first to make an exhaustive study of the pulse, and he must have been a man of considerable clinical acumen, as well as boldness, to recommend in obstruction of the bowels the opening of the abdomen, removal of the obstructed portion and uniting the ends of the intestine by sutures. After the death of Alexander, Egypt fell into the hands of his famous general, Ptolemy, under whose care the city became one of the most important on the Mediterranean. He founded and maintained a museum, an establishment that corresponded very much to a modern university, for the study of literature, science and the arts. Under his successors, particularly the third Ptolemy, the museum developed, more especially the library, which contained more than half a million volumes. The teachers were drawn from all centres, and the names of the great Alexandrians are among the most famous in the history of human knowledge, including such men as Archimedes, Euclid, Strabo and Ptolemy. In mechanics and physics, astronomy, mathematics and optics, the work of the Alexandrians constitutes the basis of a large part of our modern knowledge. The school-boy of today--or at any rate of my day--studies the identical problems that were set by Euclid 300 B.C., and the student of physics still turns to Archimedes and Heron, and the astronomer to Eratosthenes and Hipparchus. To those of you who wish to get a brief review of the state of science in the Alexandrian School I would recommend the chapter in Vol. I of Dannemann's history.(31)