Nearly about the same time, Fabricius ab Aquapen dente, a professor at Padua, struck with some appear ances which the arm presented after being bound with the ligature in venesection, laid open the whole course of a vein, and, in 1574, observed certain membranes within it, which he called ostiola, or little doors. Ena bled, as he thought, to account, by these membranes, for time appearances which he observed in the arm, lie next proceeded to lay open the other veins of the body, when he perceived similar membranes in all the veins of the extremities, but none in the veins which run through the trunk. At last, after much examination and mature reflection, he published his discovery, describing the form, situation, and structure of these membranes, and the distance at which they are generally placed from each other in the course of the veins. In this publica tion, he expresses his wonder, that these membranes should have escaped the observation of all preceding anatomists; yet it was found that, nearly a century be fore, they had been traced through all the veins of the extremities by Jacobus Sylvius, mentioned by Charles Stcphans as apophyses venarum, to prevent the reflux of the venous blood ; and in the same year in which Fa bricius made the discovery, had been seen by Cannanus, who afterwards pointed them out to Vesalius.
Fabricius, probably ignorant of these circumstances, was continuing to demonstrate these membranes to his students with all the enthusiasm of a discoverer, when a young Englishman, named Harvey, came to prosecute his medical studies at Padua. The singular novelty of these membranes strongly attracted his attention, and excited in his mind the highest respect for the discoverer. Dissatisfied, however, with the uses which Fabricius had assigned to them, he could not help suspecting that they performed a different, and probably a more impor tant, office in the system. On his return to England, therefore, lie became anxious to resume the subject. He procured a number of animals, and, opening them alive, completely ascertained the function of the venous membranes, to which he gave the name of valves; and thence was led, as he informed Mr Boyle, to the noblest discovery which has ever been made in anatomy, the circulation of the blood. It was made public in the year 1628; and the changes which it necessarily introduced into all our reasonings on the animal economy are uni versally known.
Never was prejudice more strongly exemplified than in the opposition which was made to this illustrious dis covery. Physicians and anatomists were equally alarmed by a circumstance which seemed to sweep from the very foundation many of the systems which they had reared. So inveterate, indeed, was the prejudice against the new w doctrine, that it considerably diminished the practice of its immortal discoverer. Not one physician above forty years of age became a convert to it ; and so rancorous was the envy of its opponents, that they first attempted to prove it erroneous; when they found that impossible, they next searched the writings of Hippocrates for something which might seem to resemble it ; but in this attempt they were equally unsuccessful : from Hippo crates they went to Plato ; from Plato to Nemesius, bi shop of Emessa; from Nemesius to one Rueff, a Swiss; and from Rue1r to Andrew Cesalpinus ;—but all in vain.
Chagrined with disappoimment, they next began to de tract from its merit ; alleging, that the loundation of it was laid by Fabricius ab Aquapcndente, and that Har vey had little more to do than to dress it up into a sys tem. They have brought him into comparison with Columbus aod Copernicus, to show that his rank as a discoverer is comparatively low. None of his writings, they have said, spew him to have been a man of uncom mon abilities; they have even charged hint with obsti nacy and envy; since, though he lived almost thirty years alter the lacteals were made known by AseBins, he seemed to persist, to the last, in doubting their exist ence. Of these invidious and unmanly charges, his own works, De motu cordi., et Gencratione annnalium, afford the most complete confutation ; works which will perpetuate his memory in the annals of fame ; vindicate his claim to the distinguished character of genius; and elevate him to a height tar beyond the reach of the envenomed, but impotent, darts of envy and de traction.
Harvey's discovery was soon followed by another, in many respects even more extraordinary : the discovery of a great and important system of vessels, which had seldom been even partially seen, and which the greater number of anatomists did not suppose even to exist. The food had been traced Irom the mouth to the sto mach, and front the stomach through the different wind ings of the intestines ; but no person had ever observed a single passage by which the nutritious part of the ali ment might be conveyed into the system. There had been seen, indeed, a number of veins on the tube, par ticularly on the part which is called intestine; but as none else were observed except the concomitant branches of arteries, it was naturally concluded, that the veins were the vessels which convey the chyle ; and as those arising from the stomach and intestines end in the liver, anatomists assigned to that viscus the office of changing the chyle into blood, and called it the organ of sanguifi cation. This explanation was considered as completely satisfactory, till, in the year 1622, Asellius, a doctor of Pavia, happening to open a live dog, observed vessels of a different nature, all commencing from the intestines, and containing a fluid of a white colour. The white appearance led him at first to suppose that they were nerves; but, upon farther and stricter inquiry, he con cluded, that they were the vessels destined by nature to convey the chyle; traced them as far as a large gland, or cluster of glands, which he calls pancreas ; and, from the white colour of their fluid, gave to the vessels them selves the name of tacteals. He perceived likewise a few on the liver ; and, as he entertained the general notion of its function, he naturally supposed that they all went to that gland, and calls them its arms, by which, as by leeches, it sucks up the chyle. This comparison has given rise to a hypothesis, which, without any just title, lays claim to originality, and which, like too many of our modern theories, is altogether nugatory. Asel lius modestly disclaims all merit from his discovery ; ascribes it wholly to chance ; confesses that Erasistratus had observed similar vessels in a kid, but had mistaken them for arteries, and supposed that at times they con tained air.