Another extremely interesting invention made by Heron is the famous fountain called by his name, and which still is used to illustrate principles in pneumatics in our classrooms and laboratories. By means of condensed air water is made to spring from a jet in a continuous stream and seems paradoxically to rise higher than its source. Probably his best work in the domain of physics is that on pneumatics in which are given not only a series of discussions, but of experiments and demonstrations on the elasticity of air and of steam. These experiments could only have been conducted in what we now call a physical laboratory. Indeed these inventions of his are still used in laboratories for demonstration purposes. While we may think, then, that the foundation of laboratories was reserved to our day, there is abundant evidence for their existence at the University of Alexandria. We shall return to this subject a little later, when the evidence from other departments has been presented, and then it will be clear, I think, that the laboratory methods were favorite modes of teaching at the University of Alexandria and were in use in nearly all departments of science both for research and for demonstration purposes.
The work of the other great teacher at Alexandria which was to influence mankind next to that of Euclid, was not destined to withstand the critical study of succeeding generations, though it served for some 1,500 years as the basis of their thinking in astronomy. This was the work of Ptolemy, the great professor of astronomy at Alexandria of the first century after Christ. It is easy for us now to see the absurdity of Ptolemy's system. It is even hard for us to understand how men could have accepted it. It must not be forgotten, however, that it solved all the astronomical problems of fifteen centuries and that it even enabled men, by its application, to foretell events in the heavens, and scientific prophecy is sometimes claimed to be the highest test of the truth of a system of scientific thought. Even so late as 1620 Francis Bacon refused to accept Copernicanism, already before the world for more than a century, because it did not, as it seemed to him, solve all the difficulties, while Ptolemy's system did. As great an astronomer as Tycho Brahe living in the century after Copernicus still clung to Ptolemy's teaching. It must not be forgotten that when Galileo restated Copernicanism, the reason for the rejection of his teaching by all the astronomers of Europe almost without exception, was that his reasons were not conclusive. They preferred to hold on to the old which had been so satisfying than to accept the new which seemed dubious. Their wisdom in this will be best appreciated from the fact that none of Galileo's reasons maintained themselves.
Though his system has been rejected, still Ptolemy must be looked up to as one of the great teachers of mankind and his work the "Almagest" as one of the great contributions to human knowledge. The fact that he represented a climax of astronomical development at Alexandria some four centuries after the foundation of that university, serves to show how much that first modern university occupied itself for all the centuries of its highest prestige, with physical science as well as with mathematics. Astronomy, physics, especially hydrostatics and mechanics, were all wonderfully developed. Generations of professors had given themselves to research and to the publication of important works quite as in the modern time, and Alexandria may well claim the right to be placed beside any university for what it accomplished in physical science, and rank high if not highest in the list of great research institutions adding new knowledge to old, leading men across the borderland of the unknown in science and furnishing that precious incentive to growing youth to occupy itself with the scientific problems of the world around it.
The most important part of the scientific work of the University of Alexandria to my mind remains to be spoken of, and that is the medical department. It is a well-known law in the history of medicine that, whenever medical schools are attached to universities in such a way that students who come to the medical department have been thoroughly trained by preliminary studies and have such standards of scholarship as obtain in genuine university work, then great progress in medicine and in medical education is accomplished. This was eminently the case at Alexandria. The departments of the arts, of linguistics and of philosophy were gathered around the great building known in Greek as the Mouseion, a word that has come to us through the Latin under the guise of Museum. This temple of the Muses contained collections of various kinds and near it was situated the great library. Not far away was the Serapeum, or Temple of Serapis, the Goddess of Life, around which were centred the biological sciences, and close by was the medical school. As teachers for this medical school some of the greatest physicians of the time were secured by the first Ptolemy and a great period in medical history began.
The practical wisdom guiding the Ptolemys in the organization of this medical school will be best appreciated from the fact that they took the first step by inviting two distinguished physicians, the products of the two greatest medical schools of the time, to lay the foundations at Alexandria. They were probably the best investigators of their time and they had behind them fine traditions of research, thorough observation and conservative reasoning and theorizing on scientific subjects. Erasistratos was a disciple of Metrodoros, the son-in-law of Aristotle. He had studied for a time under another great teacher, Chrysippos of Cnidos. We are likely to know much more of Cos than of Cnidos because of the reputation in the after time of Hippocrates, whose name is so closely connected with Cos that the two are almost invariably associated, but Cnidos was one of the great university towns of the later Greek civilization. Eudoxus the astronomer, Ctesias the writer on Persian history, and Sostratos the builder of the great lighthouse, one of the seven wonders of the world, the Pharos at Alexandria, were products of this university. Its medical school was famous when Cos had somewhat declined, and Chrysippos was one of the leading physicians of the world and one of the acknowledged great teachers of medicine when Erasistratos studied under him at Cnidos, and obtained that scientific training and incentive to original research which was to prove so valuable to Alexandria.
His colleague, Herophilos, was quite as distinguished as Erasistratos and owed his training to the rival school of Cos. Whether it was intentional or not to secure these two products of rival schools for the healthy spirit of competition that would come from it, and because they wanted to have at Alexandria the emulation that would naturally be aroused by such a condition, is not known, but there can be no doubt of the wisdom of the choice and of the foresight which dictated it. Herophilos had studied medicine under Praxagoras, one of the best-known successors of Hippocrates. While distinguished as a surgeon he had more influence on medicine than almost any man of his time, except possibly Erasistratos. He was, however, a great anatomist and, above all, a zoologist who, according to tradition, had obtained his knowledge of animals from the most careful zootomy of literally thousands of specimens. His fair fame is blackened by the other tradition that he practised vivisection on human beings–criminals being turned over to him for that purpose by the Ptolemys, who were deeply interested in his researches. The traditions in this matter, however, serve to confirm the idea of his zeal as an investigator and his ardent labors in medical science. Tertullian declares that he dissected at least 600 living persons. We know that he did much dissection of human cadavers and there is question whether Tertullian's statement was not gross exaggeration due to confusion between dissection and vivisection.
Both of these men did some magnificent work upon the brain. This being the first period in the history of humanity when human beings could be dissected freely, it is not surprising that they should take up brain anatomy with ardent devotion, in the hope to solve some of the many human problems that seemed to centre in this complex organ. Before this anatomy had been learned mainly from animals, and as human beings differ most widely from animals by their brain, naturally, as soon as the opportunity presented itself, anatomists gave themselves to thorough work on this structure where so many discoveries were waiting to be made. After the brain and nervous system the heart was studied, and Erasistratos' description of its valves, of its general structure and even of its physiology, show how much he knew. To know something of the work of these two anatomists is to see at once what is accomplished