William Harvey and the Circulation of the Blood HTML version

investigations, was enabled to give an entirely new direction to at
least two branches—and two of the most important branches—of
what now-a-days we call Biological Science. On the one hand, he
founded all our modern physiology by the discovery of the exact
nature of the motions of the heart, and of the course in which the
blood is propelled through the body; and, on the other, he laid the
foundation of that study of development which has been so much
advanced of late years, and which constitutes one of the great
pillars of the doctrine of evolution. This doctrine, I need hardly tell
you, is now tending to revolutionise our conceptions of the origin
of living things, exactly in the same way as Harvey's discovery of
the circulation in the seventeeth century revolutionised the
conceptions which men had previously entertained with regard to
physiological processes.
It would, I regret, be quite impossible for me to attempt, in the
course of the time I can presume to hold you here, to unfold the
history of more than one of these great investigations of Harvey. I
call them "great investigations," as distinguished from "large
publications." I have in my hand a little book, which those of you
who are at a great distance may have some difficulty in seeing, and
which I value very much. It is, I am afraid, sadly thumbed and
scratched with annotations by a very humble successor and
follower of Harvey. This little book is the edition of 1651 of the
'Exercitationes de Generatione'; and if you were to add another
little book, printed in the same small type, and about one-seventh
of the thickness, you would have the sum total of the printed
matter which Harvey contributed to our literature. And yet in that
sum total was contained, I may say, the materials of two
revolutions in as many of the main branches of biological science.
If Harvey's published labours can be condensed into so small a
compass, you must recollect that it is not because he did not do a
great deal more. We know very well that he did accumulate a very
considerable number of observations on the most varied topics of
medicine, surgery, and natural history. But, as I mentioned to you