William Harvey and the Discovery of the Circulation of the Blood | Page 7

us. Well then, the first thing that Galen
did was to make out experimentally that, during life, the arteries are not
full of air, but that they are full of blood. And he describes a great
variety of experiments which he made upon living animals with the
view of proving this point, which he did prove effectually and for all
time; and that you will observe was the only way of settling the matter.
Furthermore, he demonstrated that the cavities of the left side of the
heart--what we now call the left auricle and the left ventricle--are, like
the arteries, full of blood during life, and that that blood was of the
scarlet kind--arterialised, or as he called it "pneumatised," blood. It was
known before, that the pulmonary artery, the right ventricle, and the
veins, contain the darker kind of blood, which was thence called venous.
Having proved that the whole of the left side of the heart, during life, is
full of scarlet arterial blood, Galen's next point was to inquire into the
mode of communication between the arteries and veins. It was known
before his time that both arteries and veins branched out. Galen
maintained, though he could not prove the fact, that the ultimate
branches of the arteries and veins communicated together somehow or
other, by what he called 'anastomoses', and that these 'anastomoses'
existed not only in the body in general but also in the lungs. In the next
place, Galen maintained that all the veins of the body arise from the
liver; that they draw the blood thence and distribute it over the body.
People laugh at that notion now-a-days; but if anybody will look at the
facts he will see that it is a very probable supposition. There is a great

vein (hepatic vein--Fig. 1) which rises out of the liver, and that vein
goes straight into the 'vena cava' (Fig. 1) which passes to the heart,
being there joined by the other veins of the body. The liver itself is fed
by a very large vein (portal vein--Fig. 1), which comes from the
alimentary canal. The way the ancients looked at this matter was, that
the food, after being received into the alimentary canal, was then taken
up by the branches of this great vein, which are called the 'vena portae',
just as the roots of a plant 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 (Fig. 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 (Fig. 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,