William Harvey and the Discovery of the Circulation of the Blood | Page 5

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 of the skin more delicate

and softer looking tubes, which do not pulsate, which are of a bluish
colour, and are termed the veins. And every person who has seen a
recently killed animal opened knows that these two kinds of tubes to
which I have just referred, are connected with an apparatus which is
placed in the chest, which apparatus, in recently killed animals, is still
pulsating. And you know that in yourselves you can feel the pulsation
of this organ, the heart, between the fifth and sixth ribs. I take it that
this much of anatomy and physiology has been known from the oldest
times, not only as a matter of curiosity, but because one of the great
objects of men, from their earliest recorded existence, has been to kill
one another, and it was a matter of considerable importance to know
which was the best place for hitting an enemy. I can refer you to very
ancient records for most precise and clear information that one of the
best places is to smite him between the fifth and sixth ribs. Now that is
a very good piece of regional anatomy, for that is the place where the
heart strikes in its pulsations, and the use of smiting there is that you go
straight to the heart. Well, all that must have been known from time
immemorial--at least for 4,000 or 5,000 years before the
commencement of our era--because we know that for as great a period
as that the Egyptians, at any rate, whatever may have been the case
with other people, were in the enjoyment of a highly developed
civilisation. But of what knowledge they may have possessed beyond
this we know nothing; and in tracing back the springs of the origin of
everything that we call "modern science" (which is not merely knowing,
but knowing systematically, and with the intention and endeavour to
find out the causal connection of things)--I say that when we trace back
the different lines of all the modern sciences we come at length to one
epoch and to one country--the epoch being about the fourth and fifth
centuries before Christ, and the country being ancient Greece. It is there
that we find the commencement and the root of every branch of
physical science and of scientific method. If we go back to that time we
have in the works attributed to Aristotle, who flourished between 300
and 400 years before Christ, a sort of encyclopaedia of the scientific
knowledge of that day--and a very marvellous collection of, in many
respects, accurate and precise knowledge it is. But, so far as regards
this particular topic, Aristotle, it must be confessed, has not got very far
beyond common knowledge. He knows a little about the structure of

the heart. I do not think that his knowledge is so inaccurate as many
people fancy, but it does not amount to much. A very few years after
his time, however, there was a Greek philosopher, Erasistratus, who
lived about three hundred years before Christ, and who must have
pursued anatomy with much care, for he made the important discovery
that there are membranous flaps, which are now called "valves," at the
origins of the great vessels; and that there are certain other valves in the
interior of the heart itself.
Fig. 1.--The apparatus of the circulation, as at present known. The
capillary vessels, which connect the arteries and veins, are omitted, on
account of their small size. The shading of the "venous system" is given
to all the vessels which contain venous blood; that of the "arterial
system" to all the vessels which contain arterial blood.
I have here (Fig. 1) a purposely rough, but, so far as it goes, accurate,
diagram of the structure of the heart and the course of the blood. The
heart is supposed to be divided into two portions. It would be possible,
by very careful dissection, to split the heart down the middle of a
partition, or so-called 'septum', which exists in it, and to divide it into
the two portions which you see here represented; in which case we
should have a left heart and a right heart, quite distinct from one
another. You will observe that there is a portion of each heart which is
what is called the ventricle. Now the ancients applied the term 'heart'
simply and solely to the ventricles. They did not count the rest of the
heart--what we now speak