If you
will follow the course of the arrows in Fig. 4 you will see at once
that--in accordance with the views of Columbus--the 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 vents--then from the roots of the veins it goes into the
trunk and veins--then to the right side of the heart--and 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.
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