ction of its ventricles.

Hence the very opposite of the opinions commonly received appears to be
true; inasmuch as it is generally believed that when the heart strikes
the breast and the pulse is felt without, the heart is dilated in its
ventricles and is filled with blood. But the contrary of this is the
fact; that is to say, the heart is in the act of contracting and being
emptied. Whence the motion, which is generally regarded as the diastole
of the heart, is in truth its systole. And in like manner the intrinsic
motion of the heart is not the diastole but the systole; neither is it
in the diastole that the heart grows firm and tense, but in the systole;
for then alone when tense is it moved and made vigorous. When it acts
and becomes tense the blood is expelled; when it relaxes and sinks
together it receives the blood in the manner and wise which will by and
by be explained.

From divers facts it is also manifest, in opposition to commonly
received opinions, that the diastole of the arteries corresponds with
the time of the heart's systole; and that the arteries are filled and
distended by the blood forced into them by the contraction of the
ventricles. It is in virtue of one and the same cause, therefore, that
all the arteries of the body pulsate, _viz._, the contraction of the
left ventricle in the same way as the pulmonary artery pulsates by the
contraction of the right ventricle.

I am persuaded it will be found that the motion of the heart is as
follows. First of all, the auricle contracts and throws the blood into
the ventricle, which, being filled, the heart raises itself straightway,
makes all its fibres tense, contracts the ventricles and performs a
beat, by which beat it immediately sends the blood supplied to it by the
auricle into the arteries; the right ventricle sending its charge into
the lungs by the vessel called _vena arteriosa_, but which, in structure
and function, and all things else, is an artery; the left ventricle
sending its charge into the aorta, and through this by the arteries to
the body at large.

The grand cause of hesitation and error in this subject appears to me to
have been the intimate connection between the heart and the lungs. When
men saw both the pulmonary artery and the pulmonary veins losing
themselves in the lungs, of course it became a puzzle to them to know
how the right ventricle should distribute the blood to the body, or the
left draw it from the _venae cavae_. Or