As a teacher of anatomy, especially in its relations to physiology, Fabricius was held in the highest esteem. Albert von Haller speaks of him as being one of the glories of the Italian school of medicine. Pupils came in flocks from all parts of Europe to attend his lectures, and among them were some who, like William Harvey of England, afterward attained great celebrity for the effective work which they did in advancing the science of medicine. One of the attractive features of Fabricius’ teaching was to be found in his practice--something quite new at that period--of showing to the students, not only the particular organ (human) upon which he happened then to be lecturing, but also the corresponding organ in one or several of the animals; thus enabling them to learn what were the features possessed in common by all the species, and what were those in respect of which the species differed. As time went on, the number of those who came to witness his anatomical demonstrations increased so greatly that he felt impelled to build, at his own expense, a new and larger amphitheatre. But even this, in a short time, proved to be too small, and then the Senate at Venice, which exercised a governing control over the University of Padua, erected (in 1593) a much larger and more complete amphitheatre, upon the walls of which there was placed an inscription stating that it had been built in honor of Fabricius. Among the other distinctions which were conferred upon him at this time he was raised to the rank of Knight of the Order of Saint Mark and made an honorary citizen of Padua. Fabricius ab Acquapendente added to our stock of anatomical knowledge by his researches on the structure of the oesophagus, stomach and intestines, the eye, ear, larynx and foetus. One of his chief claims to distinction, however, rests upon the fact that he wrote an elaborate monograph on the valves of the veins. Although these structures had been seen and described at an earlier date by Charles Estienne, Berengarius, Vesalius, Cannani and others (Fra Paolo Sarpi, for example), nobody had yet offered a satisfactory explanation of their probable use or had traced them through the venous system at large. In 1574 Fabricius demonstrated their presence in all the veins of the extremities.