the place whence it started. But that is the circulation of the blood,
and it was exactly this which Harvey was the first man to suspect, to
discover, and to demonstrate.

But this was by no means the only thing Harvey did. He was the first
who discovered and who demonstrated the true mechanism of the heart's
action. No one, before his time, conceived that the movement of the
blood was entirely due to the mechanical action of the heart as a
pump. There were all sorts of speculations about the matter, but nobody
had formed this conception, and nobody understood that the so-called
systole of the heart is a state of active contraction, and the
so-called diastole is a mere passive dilatation. Even within our own
age that matter had been discussed. Harvey is as clear as possible
about it. He says the movement of the blood is entirely due to the
contractions of the walls of the heart--that it is the propelling
apparatus--and all recent investigation tends to show that he was
perfectly right. And from this followed the true theory of the pulse.
Galen said, as I pointed out just now, that the arteries dilate as
bellows, which have an active power of dilatation and contraction, and
not as bags which are blown out and collapse. Harvey said it was
exactly the contrary--the arteries dilate as bags simply because the
stroke of the heart propels the blood into them; and, when they relax
again, they relax as bags which are no longer stretched, simply because
the force of the blow of the heart is spent. Harvey has been
demonstrated to be absolutely right in this statement of his; and yet,
so slow is the progress of truth, that, within my time, the question of
the active dilatation of the arteries has been discussed.

Thus Harvey's contributions to physiology may be summed up as follows:
In the first place, he was the first person who ever imagined, and