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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
veinFig。 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 veinFig。 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； 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 thisthat 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 heartwhat we call the 'systole'
or contraction of the heart； and the 'diastole' or dilatationGalen
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 careful to say that the nature of the pulse is comparable；
not to the movement of a bag； which we fill by blowing into it； and
which we empty by drawing the air out of it； but to the action of a
bellows； which is actively dilated and actively compressed。
Fig 3。The course of the blood from the right to the left side of the
heart （Realdus Columbus； 1559）。
After Galen's time came the collapse of the Roman Empire； the extinction
of physical knowledge； and the repression of every kind of scientific
inquiry； by its powerful and consistent enemy； the Church； and that
state of things lasted until the latter part of the Middle Ages saw the
revival of learning。 That revival of learning； so far as anatomy and
physiology are concerned； is due to the renewed influence of the
philosophers of ancient Greece； and indeed； of Galen。 Arabic
commentators had translated Galen； and portions of his works had got
into the language of the learned in the Middle Ages； in that way； but；
by the study of the classical languages； the original text became
accessible to the men who were then endeavouring to learn for
themselves something about the facts of nature。 It was a century or
more before these men； finding themselves in the presence of a
masterfinding that all their lives were occupied in attempting to
ascertain for themselves that which was familiar to himI say it took
the best part of a hundred years before they could fairly see that their
business was not to follow him； but to follow his examplenamely； to
look into the facts of nature for themselves； and to carry on； in his
spirit； the work he had begun。 That was first done by Vesalius； one of
the greatest anatomists who ever lived； but his work does not specially
bear upon the question we are now concerned with。 So far as regards
the motions of the heart and the course of the blood； the first man in
the Middle Ages； and indeed the only man who did anything which was of
real importance； was one Realdus Columbus； who was professor at Padua
in the year 1559； and published a great anatomical treatise。 What
Realdus Columbus did was this； once more resorting to the method of
Galen； turning to the living animal； experimenting； he came upon new
facts； and one of these new facts was that there was not merely a
subordinate communication between the blood of the right side of the
heart and that of the left side of the heart； through the lungs； but
that there was a constant steady current of blood； setting through the
pulmonary artery on the right side； through the lungs； and back by the
pulmonary veins to the left side of the heart （Fig。3）。 Such was the
capital discovery and demonstration of Realdus Columbus。 He is the man
who discovered what is loosely called the 'pulmonary circulation'； and
it really is quite absurd； in the face of the fact； that twenty years
afterwards we find Ambrose Pare； the great French sur