t suck up nourishment from the soil in which it lives; that then it
was carried to the liver, there to be what was called "concocted," which
was their phrase for its conversion into substances more fitted for
nutrition than previously existed in it. They then supposed that the
next thing to be done was to distribute this fluid through the body; and
Galen like his predecessors, imagined that the "concocted" blood, having
entered the great 'vena cava', was distributed by its ramifications all
over the body. So that, in his view (Figure 2), the course of the blood
was from the intestine to the liver, and from the liver into the great
'vena cava', including what we now call the right auricle of the heart,
whence it was distributed by the branches of the veins. But the whole of
the blood was not thus disposed of. Part of the blood, it was supposed,
went through what we now call the pulmonary arteries (Figure 1), and,
branching out there, gave exit to certain "fuliginous" products, and
at the same time took in from the air a something which Galen calls the
'pneuma'. He does not know anything about what we call oxygen; but it
is astonishing how very easy it would be to turn his language into the
equivalent of modern chemical theory. The old philosopher had so just
a suspicion of the real state of affairs that you could make use of his
language in many cases, if you substituted the word "oxygen," which we
now-a-days use, 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 (Figure 2).

It is of great importance you should clearly understand these teachings
of Galen,