f 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 just now, Harvey, for a time, took
the royal side in the domestic quarrel of the Great Rebellion, as it
is called; and the Parliament, not unnaturally resenting that action of
his, sent soldiers to seize his papers. And while I imagine they found
nothing treasonable among those papers, yet, in the process of rummaging
through them, they destroyed all the materials which Harvey had spent a
laborious life in accumulating; and hence it is that the man's work and
labours are represented by so little in apparent bulk.

What I chiefly propose to do to-night is to lay before you an account of
the nature of the discovery which Harvey made, and which is termed the
Discovery of the Circulation of the Blood. And I desire also, with
some particularity, to draw your attention to the methods by which that
discovery was achieved; for, in both these respects, I think, there will
be much matter for profitable reflection.

Let me point out to you, in the first place, with respect to this
important matter of the movements of the heart and the course of the
blood in the body, that there is a certain amount of knowledge
which must have been obtained without men taking the trouble to seek
it--knowledge which must have been taken in, in the course of time,
by everybody who followed the trade of a butcher, and still more so by
those people who, in ancient times, professed to divine the course of
future events from the entrails of animals. It is quite obvious to
all, from ordinary accidents, that the bodies of all the higher animals
contain a hot red fluid--the blood. Everybody can see upon the surface
of some part of the skin, underneath that skin, pulsating tubes, which
we know as the arteries. Everybody can see under the surface o