octrine of natural, vital, and animal spirits, as contained in the
veins, arteries, and nerves respectively, and made the all-important
statement that the fluids contained in veins and arteries are the same.
He showed also that the blood is "purged from fume" and purified by
respiration in the lungs, and declared that there is a new vessel in the
lungs, "formed out of vein and artery." Even at the present day there is
little to add to or change in this description of Servetus's.

By keeping this document, pregnant with advanced scientific views, from
the world, and in the end only using it as a means of destroying
its author, the great reformer showed the same jealousy in retarding
scientific progress as had his arch-enemies of the Inquisition, at whose
dictates Vesalius became a martyr to science, and in whose dungeons
etienne perished.

THE COMING OF HARVEY

The time was ripe for the culminating discovery of the circulation of
the blood; but as yet no one had determined the all-important fact that
there are two currents of blood in the body, one going to the heart, one
coming from it. The valves in the veins would seem to show conclusively
that the venous current did not come from the heart, and surgeons must
have observed thousands of times the every-day phenomenon of congested
veins at the distal extremity of a limb around which a ligature or
constriction of any kind had been placed, and the simultaneous depletion
of the vessels at the proximal points above the ligature. But it should
be remembered that inductive science was in its infancy. This was the
sixteenth, not the nineteenth century, and few men had learned to put
implicit confidence in their observations and convictions when opposed
to existing doctrines. The time was at hand, however, when such a man
was to make his appearance, and, as in the case of so many revolutionary
doctrines in science, this man was an Englishman. It remained for
William Harvey (1578-1657) to solve the great mystery which had puzzled
the medical world since the beginning of history; not only to solve it,
but to prove his case so conclusively and so simply that for all time
his little booklet must he handed down as one of the great masterpieces
of lucid and almost faultless demonstration.

Harvey, the son of a prosperous Kentish yeoman, was born at Folkestone.
His education was begun at the grammar-school of Canterbury, and later
he became a pensioner of Caius College, Cambridge