for the word 'pneuma'. Then he imagined that the blood, further
concocted or altered by contact with the '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.