OF THE MOTIONS OF 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 arterial vein [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 vena arteriosa [pulmonary artery] ceases also.
3. Further, when an artery is divided or punctured, the blood is seen to
be forcibly propelled from the wound at 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, finally, 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, 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, &c.) the stroke and the motion occur at both extremities at the
same time. Aristotle,[83] 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,[84] “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 this 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 wherever 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.