Fabricius was more than a teacher to Harvey, for a fast friendship seems to have sprung up between master and pupil. Fabricius--then a man of sixty-one he lived to be eighty-two--was engaged during Harvey's residence in Padua in perfecting his knowledge of the valves of the veins. The valves had been known and described by Sylvius of Louvilly (1478-1555), that old miser, but prince of lecturers, who warmed himself in the depth of a Parisian winter by playing ball against the wall of his room rather than be at the expense of a fire, and who threatened to close the doors of his class-room until two defaulting students either paid their fees or were expelled by their fellows. But the work of Sylvius had fallen into oblivion and Fabricius rediscovered the valves in 1574. His observations were not published until 1603, when they appeared as a small treatise "de venarum ostiolis." There is no doubt that he demonstrated their existence to his class, and Harvey knew of the treatise, though it was published a year after he had returned to England. Indeed, when we look at Harvey's work, much of it appears to be a continuation and an amplification of that done by Fabricius. Both were intensely interested in the phenomena of development; both wrote upon the structure and functions of the skin; both studied the anatomy of the heart, lungs, and blood vessels; both wrote a treatise "de motu locali." Harvey's youth, his comparative freedom from the trammels of authority, and his more logical mind, enabled him to outstrip his master and to avoid the errors into which he had fallen. This advance is particularly well seen in connection with the valves of the veins. Fabricius taught that their purpose was to prevent over-distension of the vessels when the blood passed from the larger into the smaller veins (a double error) whilst they were not needed in the arteries because the blood was always in a state of ebb and flow. It was left for Harvey to point out their true use and to indicate their importance as an anatomical proof of the circulation of the blood.