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 saying--I speak in the presence of
distinguished physiologists, but I am perfectly certain that they will
endorse what I say--that 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 know--I hope it is now a matter of popular knowledge--it 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