A certain manuscript of the great Cornelius Celsus, the De
Medicine, which had been lost for many centuries, was found in
the church of St. Ambrose, at Milan, in 1443, and was at once put
into print. The effect of the publication of this book, which had
lain in hiding for so many centuries, was a revelation, showing
the medical profession how far most of their supposed true copies
of Celsus had drifted away from the original. The indisputable
authenticity of this manuscript, discovered and vouched for by
the man who shortly after became Pope Nicholas V., made its
publication the more impressive. The output in book form of other
authorities followed rapidly, and the manifest discrepancies
between such teachers as Celsus, Hippocrates, Galen, and Pliny
heightened still more the growing spirit of criticism.

These doubts resulted in great controversies as to the proper
treatment of certain diseases, some physicians following
Hippocrates, others Galen or Celsus, still others the Arabian
masters. One of the most bitter of these contests was over the
question of "revulsion," and "derivation"--that is, whether in
cases of pleurisy treated by bleeding, the venesection should be
made at a point distant from the seat of the disease, as held by
the "revulsionists," or at a point nearer and on the same side of
the body, as practised by the "derivationists." That any great
point for discussion could be raised in the fifteenth or
sixteenth centuries on so simple a matter as it seems to-day
shows how necessary to the progress of medicine was the discovery
of the circulation of the blood made by Harvey two centuries
later. After Harvey's discovery no such discussion could have
been possible, because this discovery made it evident that as far