'pneuma', passed to
a certain extent to the left side of the heart. So that Galen believed
that there was such a thing as what is now called the pulmonary
circulation. He believed, as much as we do, that the blood passed
through the right side of the heart, through the artery which goes to
the lungs, through the lungs themselves, and back by what we call the
pulmonary veins to the left side of the heart. But he thought it was
only a very small portion of the blood which passes to the right side of
the heart in this way; the rest of the blood, he thought, passed through
the partition which separates the two ventricles of the heart. He
describes a number of small pits, which really exist there, as holes,
and he supposed that the greater part of the blood passed through these
holes from the right to the left ventricle (Fig 2).

It is of great importance you should clearly understand these teachings
of Galen, because, as I said just now, they sum up all that anybody knew
until the revival of learning; and they come to this--that the blood
having passed from the stomach and intestines through the liver, and
having entered the great veins, was by them distributed to every part of
the body; that part of the blood, thus distributed, entered the arterial
system by the 'anastomoses', as Galen called them, in the lungs; that
a very small portion of it entered the arteries by the 'anastomoses' in
the body generally; but that the greater part of it passed through the
septum of the heart, and so entered the left side and mingled with the
pneumatised blood, which had been subjected to the air in the lungs,
and was then distributed by the arteries, and eventually mixed with the
currents of blood, coming the other way, through the veins.

Yet one other point about the views of Galen. He thought that both the
contractions and dilatations of the heart--what we call the 'systole'
or contraction of the heart, and the 'diastole' or dilatation--Galen
thought that these were both active movements; that the heart actively
dilated, so that it had a sort of sucking power upon the fluids which
had access to it. And again, with respect to the movements of the pulse,
which anybody can feel at the wrist and elsewhere, Galen was of opinion
that the walls of the arteries partook of that which he supposed to be
the nature of the walls of the heart, and that they had the power of
alternately actively contracting and actively dilating, so that he is
car