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 left ventricle
of the heart； passes through the whole arterial system； comes back
through the venous system； goes through the lungs； and comes back to
the place whence it started。 But that is the circulation of the blood；
and it was exactly this which Harvey was the first man to suspect； to
discover； and to demonstrate。
But this was by no means the only thing Harvey did。 He was the first
who discovered and who demonstrated the true mechanism of the heart's
action。 No one； before his time； conceived that the movement of the
blood was entirely due to the mechanical action of the heart as a
pump。 There were all sorts of speculations about the matter； but nobody
had formed this conception； and nobody understood that the so…called
systole of the heart is a state of active contraction； and the
so…called diastole is a mere passive dilatation。 Even within our own
age that matter had been discussed。 Harvey is as clear as possible
about it。 He says the movement of the blood is entirely due to the
contractions of the walls of the heartthat it is the propelling
apparatusand all recent investigation tends to show that he was
perfectly right。 And from this followed the true theory of the pulse。
Galen said； as I pointed out just now； that the arteries dilate as
bellows； which have an active power of dilatation and contraction； and
not as bags which are blown out and collapse。 Harvey said it was
exactly the contrarythe arteries dilate as bags simply because the
stroke of the heart propels the blood into them； and； when they relax
again； they relax as bags which are no longer stretched； simply because
the force of the blow of the heart is spent。 Harvey has been
demonstrated to be absolutely right in this statement of his； and yet；
so slow is the progress of truth； that； within my time； the question of
the active dilatation of the arteries has been discussed。
Thus Harvey's contributions to physiology may be summed up as follows：
In the first place； he was the first person who ever imagined； and
still more who demonstrated； the true course of the circulation of the
blood in the body； in the second place； he was the first person who
ever understood the mechanism of the heart； and comprehended that its
contraction was the cause of the motion of the blood； and thirdly； he
was the first person who took a just view of the nature of the pulse。
These are the three great contributions which he made to the science of
physiology； and I shall not err in sayingI speak in the presence of
distinguished physiologists； but I am perfectly certain that they will
endorse what I saythat upon that foundation the whole of our
knowledge of the human body； with the exception of the motor apparatus
and the sense organs； has been gradually built up； and that upon that
foundation the whole rests。 And not only does scientific physiology
rest upon it； but everything like scientific medicine also rests upon
it。 As you knowI hope it is now a matter of popular knowledgeit is
the foundation of all rational speculation about morbid processes； it
is the only key to the rational interpretation of that commonest of all
indications of disease； the state of the pulse； so that； both
theoretically and practically； this discovery； this demonstration of
Harvey's； has had an effect which is absolutely incalculable； and the
consequences of which will accumulate from age to age until they result
in a complete body of physiological science。
Fig。5。The junction of the arteries and veins by capillary tubes；
discovered by Malpighi （A。D。 1664）。
I regret that I am unable to pursue this subject much further； but there
is one point I should mention。 In Harvey's time； the microscope was
hardly invented。 It is quite true that in some of his embryological
researches he speaks of having made use of a hand glass； but that was
the most that he seems to have known anything about； or that was
accessible to him at that day。 And so it came about； that； although he
examined the course of the blood in many of the lower animalswatched
the pulsation of the heart in shrimps； and animals of that kindhe
never could put the final coping…stone on his edifice。 He did not know
to the day of his death； although quite clear about the fact that the
arteries and the veins do communicate； how it is that they
communicatehow it was that the blood of the arteries passed into the
veins。 One is grieved to think that the grand old man should have gone
down to his tomb without the vast satisfaction it would have given to
him to see what the Italian naturalist Malpighi showed only seven years
later； in 1664； when he demonstrated； in a living frog； the actual
passage of the blood from the ultimate ramifications of the arteries
into the veins。 But that absolute ocular demonstration of the truth of
the views he had maintained throughout his life it was not granted to
Harvey to see。 What he did experience was this： that on the
publication of his doctrines； they were met with the greatest possible
opposition； and I have no doubt savage things were uttered in those old
controversies； and that a great many people said that these new…fangled
doctrines； reducing living processes to mere mechanism； would sap the
foundations of religion and morality。 I do not know for certain that
they did； but they said things very like it。 The first point was to
show that Harvey's views were absolutely untrue； and not being able to
succeed in that； opponents said they were not new； and not being able
to succeed in that； that they didn't matter。 That is the usual course
with all new discoveries。 But Harvey troubled himself very little
about these things。 He remained perfectly quiet； for although reputed
a hot…tempered man； he never would have anything to do with controversy
if he could help it； and he only replied to one of his antagonists
after twenty years' interval； and then in the most charming spirit of
candour and moderation。 But he had the great satisfaction of living to
see his doctrine accepted upon all sides。 At the time of his death；
there was not an anatomical school in Europe in which the doctrine of
the circulation of the blood was not taught in the way in which Harvey
had laid it down。 In that respect he had a happiness which is granted
to very few men。
I have said that the other great investigation of Harvey is not one
which can be dealt with to a general audience。 It is very complex； and
therefore I must ask you to take my word for it that； although not so
fortunate an investigation； not so entirely accordant with later results
as the doctrine of the circulation； yet that still； this little
treatise of Harvey's has in many directions exerted an influence hardly
less remarkable than that exerted by the Essay upon the Circulation of
the Blood。
And now let me ask your attention to two or three closing remarks。
If you look back upon that period of about 100 years which commences
with Harvey's birthI mean from the year 1578 to 1680 or
thereaboutsI think you will agree with me； that it constitutes one of
the most remarkable epochs in the whole of that thousand years which we
may roughly reckon as constituting the history of Britain。 In the
commencement of that period； we may see； if not the setting； at any
rate the declension of that system of personal rule which had existed
under previous sovereigns； and which； after a brief and spasmodic
revival in the time of George the Third； has now sunk； let us hope；
into the limbo of forgotten things。 The latter part of that 100 years
saw the dawn of that system of free government which has grown and
flourished； and which； if the men of the present day be the worthy
descendants of Eliott and Pym； and Hampden and Milton； will go on
growing as long as this realm lasts。 Within that time； one of the
strangest phenomena which I think I may say any nation has ever
manifested arose to its height and fellI mean that strange and
altogether marvellous phenomenon； English Puritanism。 Within that
time； England had to show statesmen like Burleigh； Strafford； and
CromwellI mean men who were