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it really is quite absurd； in the face of the fact； that twenty years
afterwards we find Ambrose Pare； the great French surgeon； ascribing
this discovery to him as a matter of common notoriety； to find that
attempts are made to give the credit of it to other people。 So far as
I know； this discovery of the course of the blood through the lungs；
which is called the pulmonary circulation； is the one step in real
advance that was made between the time of Galen and the time of
Harvey。 And I would beg you to note that the word 〃circulation〃 is
improperly employed when it is applied to the course of the blood
through the lungs。 The blood from the right side of the heart； in
getting to the left side of the heart； only performs a half…circleit
does not perform a whole circleit does not return to the place from
whence it started； and hence the discovery of the so…called 〃pulmonary
circulation〃 has nothing whatever to do with that greater discovery
which I shall point out to you by…and…by was made by Harvey； and which
is alone really entitled to the name of the circulation of the blood。
If anybody wants to understand what Harvey's great desert really was； I
would suggest to him that he devote himself to a course of reading；
which I cannot promise shall be very entertaining； but which； in this
respect at any rate； will be highly instructivenamely； the works of
the anatomists of the latter part of the 16th century and the beginning
of the 17th century。 If anybody will take the trouble to do that which
I have thought it my business to do； he will find that the doctrines
respecting the action of the heart and the motion of the blood which
were taught in every university in Europe； whether in Padua or in Paris；
were essentially those put forward by Galen； 'plus' the discovery of
the pulmonary course of the blood which had been made by Realdus
Columbus。 In every chair of anatomy and physiology （which studies were
not then separated） in Europe； it was taught that the blood brought to
the liver by the portal vein； and carried out of the liver to the 'vena
cava' by the hepatic vein； is distributed from the right side of the
heart； through the other veins； to all parts of the body； that the
blood of the arteries takes a like course from the heart towards the
periphery； and that it is there； by means of the 'anastomoses'； more or
less mixed up with the venous blood。 It so happens； by a curious
chance； that up to the year 1625 there was at Padua； which was Harvey's
own university； a very distinguished professor； Spigelius； whose work
is extant； and who teaches exactly what I am now telling you。 It is
perfectly true that； some time before； Harvey's master； Fabricius； had
not only re…discovered； but had drawn much attention to certain
pouch…like structures； which are called the valves of the veins； found
in the muscular parts of the body； all of which are directed towards
the heart； and consequently impede the flow of the blood in the
opposite direction。 And you will find it stated by people who have not
thought much about the matter； that it was this discovery of the valves
of the veins which led Harvey to imagine the course of the circulation
of the blood。 Now it did not lead Harvey to imagine anything of the
kind。 He had heard all about it from his master； Fabricius； who made a
great point of these valves in the veins； and he had heard the theories
which Fabricius entertained upon the subject； whose impression as to
the use of the valves was simply thisthat they tended to take off any
excess of pressure of the blood in passing from the heart to the
extremities； for Fabricius believed； with the rest of the world； that
the blood in the veins flowed from the heart towards the extremities。
This； under the circumstances； was as good a theory as any other；
because the action of the valves depends altogether upon the form and
nature of the walls of the structures in which they are attached； and
without accurate experiment； it was impossible to say whether the
theory of Fabricius was right or wrong。 But we not only have the
evidence of the facts themselves that these could tell Harvey nothing
about the circulation； but we have his own distinct declaration as to
the considerations which led him to the true theory of the circulation
of the blood； and amongst these the valves of the veins are not
mentioned。
Fig。 4。The circulation of the blood as demonstrated by Harvey （A。D。
1628）。
Now then we may come to Harvey himself。 When you read Harvey's
treatise； which is one of the most remarkable scientific monographs
with which I am acquaintedit occupies between 50 and 60 pages of a
small quarto in Latin； and is as terse and concise as it possibly can
bewhen you come to look at Harvey's work； you will find that he had
long struggled with the difficulties of the accepted doctrine of the
circulation。 He had received from Fabricius； and from all the great
authorities of the day； the current view of the circulation of the
blood。 But he was a man with that rarest of all
qualitiesintellectual honesty； and by dint of cultivating that great
faculty； which is more moral than intellectual； it had become impossible
for him to say he believed anything which he did not clearly believe。
This is a most uncomfortable peculiarityfor it gets you into all
sorts of difficulties with all sorts of peoplebut； for scientific
purposes； it is absolutely invaluable。 Harvey possessed this
peculiarity in the highest degree； and so it was impossible for him to
accept what all the authorities told him； and he looked into the matter
for himself。 But he was not hasty。 He worked at his new views； and he
lectured about them at the College of Physicians for nine years； he did
not print them until he was a man of fifty years of age； and when he
did print them he accompanied them with a demonstration which has never
been shaken； and which will stand till the end of time。 What Harvey
proved； in short； was this （see Fig。 4）that everybody had made a
mistake； for want of sufficiently accurate experimentation as to the
actual existence of the fact which everybody assumed。 To anybody who
looks at the blood…vessels with an unprejudiced eye it seems so natural
that the blood should all come out of the liver； and be distributed by
the veins to the different parts of the body； that nothing can seem
simpler or more plain； and consequently no one could make up his mind
to dispute this apparently obvious assumption。 But Harvey did dispute
it； and when he came to investigate the matter he discovered that it was
a profound mistake； and that； all this time； the blood had been moving
in just the opposite direction； namely； from the small ramifications of
the veins towards the right side of the heart。 Harvey further found
that； in the arteries； the blood； as had previously been known； was
travelling from the greater trunks towards the ramifications。 Moreover；
referring to the ideas of Columbus and of Galen （for he was a great
student of literature； and did justice to all his predecessors）； Harvey
accepts and strengthens their view of the course of the blood through
the lungs； and he shows how it fitted into his general scheme。 If you
will follow the course of the arrows in Fig。 4 you will see at once
thatin accordance with the views of Columbusthe blood passes from
the right side of the heart； through the lungs； to the left side。 Then；
adds Harvey； with abundant proof； it passes through the arteries to all
parts of the body； and then； at the extremities of their branches in
the different parts of the body； it passes （in what way he could not
tell； for his means of investigation did not allow him to say） into the
roots of the ventsthen from the roots of the veins it goes into the
trunk and veinsthen to the right side of the heartand then to the
lungs； and so on。
That； you will observe； makes a complete circuit； and it was precisely
here that the originality of Harvey lay。 There never yet has been
produced； and I do not believe there can be produced； a tittle of
evidence to show that； before his time； any one had the slightest
suspicion that a single drop of blood； starting in the l