OF THE MOTIONS OF THE ARTERIES, AS SEEN IN THE DISSECTION OF
LIVING ANIMALS
In connexion with the motions of the heart these things are
further to be observed having reference to the motions and pulses
of the arteries.
1. At the moment the heart contracts, and when the breast is
struck, when in short the organ is in its state of systole, the
arteries are dilated, yield a pulse, and are in the state of
diastole. In like manner, when the right ventricle contracts and
propels its charge of blood, the pulmonary artery is distended at
the same time with the other arteries of the body.
2. When the left ventricle ceases to act, to contract, to
pulsate, the pulse in the arteries also ceases; further, when
this ventricle contracts languidly, the pulse in the arteries is
scarcely perceptible. In like manner, the pulse in the right
ventricle failing, the pulse in the pulmonary artery ceases also.
3. Further, when an artery is divided or punctured, the blood is
seen to be forcibly propelled from the wound the moment the left
ventricle contracts; and, again, when the pulmonary artery is
wounded, the blood will be seen spouting forth with violence at
the instant when the right ventricle contracts.
So also in fishes, if the vessel which leads from the heart to
the gills be divided, at the moment when the heart becomes tense
and contracted, at the same moment does the blood flow with force
from the divided vessel.
In the same way, when we see the blood in arteriotomy projected
now to a greater, now to a less distance, and that the greater
jet corresponds to the diastole of the artery and to the time
when the heart contracts and strikes the ribs, and is in its
state of systole, we understand that the blood is expelled by the
same movement.
From these facts it is 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; the arteries, therefore, are
distended, because they are filled like sacs or bladders, and are
not filled because they expand like bellows. 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.
Finally, that the pulses of the arteries are due to the impulses
of the blood from the left ventricle, may be illustrated by
blowing into a glove, when the whole of the fingers will be found
to become distended at one and the same time, and in their
tension to bear some resemblance to the pulse. For in the ratio
of the tension is the pulse of the heart, fuller, stronger, and
more frequent as that acts more vigorously, still preserving the
rhythm and volume, and order of the heart's contractions. Nor is
it to be expected that because of the motion of the blood, the
time at which the contraction of the heart takes place, and that
at which the pulse in an artery (especially a distant one) is
felt, shall be otherwise than simultaneous: it is here the same
as in blowing up a glove or bladder; for in a plenum (as in a
drum, a long piece of timber, etc.) the stroke and the motion
occur at both extremities at the same time. Aristotle, [Footnote:
De Anim., iii, cap. 9.] too, has said, "the blood of all animals
palpitates within their veins (meaning the arteries), and by the
pulse is sent everywhere simultaneously." And further, [Footnote:
De Respir., cap. 20] "thus do all the veins pulsate together and
by successive strokes, because they all depend upon the heart;
and, as it is always in motion, so are they likewise always
moving together, but by successive movements." It is well to
observe with Galen, in this place, that the old philosophers
called the arteries veins. I happened upon one occasion to have a
particular case under my care, which plainly satisfied me of the
truth: A certain person was affected with a large pulsating
tumour on the right side of the neck, called an aneurism, just at
that part where the artery descends into the axilla, produced by
an erosion of the artery itself, and daily increasing in size;
this tumour was visibly distended as it received the charge of
blood brought to it by the artery, with each stroke of the heart;
the connexion of parts was obvious when the body of the patient
came to be opened after his death. The pulse in the corresponding
arm was small, in consequence of the greater portion of the blood
being diverted into the tumour and so intercepted.
Whence it appears that whenever the motion of the blood through
the arteries is impeded, whether it be by compression or
infarction, or interception, there do the remote divisions of the
arteries beat less forcibly, seeing that the pulse of the
arteries is nothing more than the impulse or shock of the blood
in these vessels.