heart. It seemed unreasonable to suppose that a thick
fluid like the blood could find its way through pores so small that they
could not be demonstrated by any means devised by man. In evidence
that there could be no such openings he pointed out that, since the two
ventricles contract at the same time, this process would impede rather
than facilitate such an intra-ventricular passage of blood. But what
seemed the most conclusive proof of all was the fact that in the foetus
there existed a demonstrable opening between the two ventricles, and yet
this is closed in the fully developed heart. Why should Nature, if she
intended that blood should pass between the two cavities, choose to
close this opening and substitute microscopic openings in place of it?
It would surely seem more reasonable to have the small perforations in
the thin, easily permeable membrane of the foetus, and the opening in
the adult heart, rather than the reverse. From all this Harvey drew his
correct conclusions, declaring earnestly, "By Hercules, there ARE no
such porosities, and they cannot be demonstrated."

Having convinced himself that no intra-ventricular opening existed, he
proceeded to study the action of the heart itself, untrammelled by too
much faith in established theories, and, as yet, with no theory of his
own. He soon discovered that the commonly accepted theory of the heart
striking against the chest-wall during the period of relaxation was
entirely wrong, and that its action was exactly the reverse of this, the
heart striking the chest-wall during contraction. Having thus disproved
the accepted theory concerning the heart's action, he took up the
subject of the action of arteries, and soon was able to demonstrate by
vivisection that the contraction of the arteries was not simultaneous
with contractions of the heart. His experiments demonstrated that these
vessels were simply elastic tubes whose pulsations were "nothing else
than the impulse of the blood within them." The reason that the arterial
pulsation was not simultaneous with the heart-beat he found to be
because of the time required to carry the impulse along the tube.

By a series of further careful examinations and experiments, which are
too extended to be given here, he was soon able further to demonstrate
the action and course of the blood during the contractions of the heart.
His explanations were practically the same as those given to-day--first
the contraction of the auric