OF THE MOTION, ACTION AND OFFICE OF THE HEART
From these and other observations of a similar nature, I am
persuaded it will be found that the motion of the heart is as
follows:
First of all, the auricle contracts, and in the course of its
contraction forces the blood (which it contains in ample quantity
as the head of the veins, the store--house and cistern of 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 sends its charge into the lungs by the vessel
which is called vena arteriosa, but which in structure and
function, and all other respects, is an artery. The left
ventricle sends its charge into the aorta, and through this by
the arteries to the body at large.
These two motions, one of the ventricles, the other of the
auricles, take place consecutively, but in such a manner that
there is a kind of harmony or rhythm preserved between them, the
two concurring in such wise that but one motion is apparent,
especially in the warmer blooded animals, in which the movements
in question are rapid. Nor is this for any other reason than it
is in a piece of machinery, in which, though one wheel gives
motion to another, yet all the wheels seem to move
simultaneously; or in that mechanical contrivance which is
adapted to firearms, where, the trigger being touched, down comes
the flint, strikes against the steel, elicits a spark, which
falling among the powder, ignites it, when the flame extends,
enters the barrel, causes the explosion, propels the ball, and
the mark is attained--all of which incidents, by reason of the
celerity with which they happen, seem to take place in the
twinkling of an eye. So also in deglutition: by the elevation of
the root of the tongue, and the compression of the mouth, the
food or drink is pushed into the fauces, when the larynx is
closed by its muscles and by the epiglottis. The pharynx is then
raised and opened by its muscles in the same way as a sac that is
to be filled is lifted up and its mouth dilated. Upon the
mouthful being received, it is forced downwards by the transverse
muscles, and then carried farther by the longitudinal ones. Yet
all these motions, though executed by different and distinct
organs, are performed harmoniously, and in such order that they
seem to constitute but a single motion and act, which we call
deglutition.
Even so does it come to pass with the motions and action of the
heart, which constitute a kind of deglutition, a transfusion of
the blood from the veins to the arteries. And if anyone, bearing
these things in mind, will carefully watch the motions of the
heart in the body of a living animal, he will perceive not only
all the particulars I have mentioned, viz., the heart becoming
erect, and making one continuous motion with its auricles; but
farther, a certain obscure undulation and lateral inclination in
the direction of the axis of the right ventricle, as if twisting
itself slightly in performing its work. And indeed everyone may
see, when a horse drinks, that the water is drawn in and
transmitted to the stomach at each movement of the throat, which
movement produces a sound and yields a pulse both to the ear and
the touch; in the same way it is with each motion of the heart,
when there is the delivery of a quantity of blood from the veins
to the arteries a pulse takes place, and can be heard within the
chest.
The motion of the heart, then, is entirely of this description,
and the one action of the heart is the transmission of the blood
and its distribution, by means of the arteries, to the very
extremities of the body; so that the pulse which we feel in the
arteries is nothing more than the impulse of the blood derived
from the heart.
Whether or not the heart, besides propelling the blood, giving it
motion locally, and distributing it to the body, adds anything
else to it--heat, spirit, perfection,--must be inquired into by--
and--by, and decided upon other grounds. So much may suffice at
this time, when it is shown that by the action of the heart the
blood is transfused through the ventricles from the veins to the
arteries, and distributed by them to all parts of the body.
The above, indeed, is admitted by all, both from the structure of
the heart and the arrangement and action of its valves. But still
they are like persons purblind or groping about in the dark, for
they give utterance to various, contradictory, and incoherent
sentiments, delivering many things upon conjecture, as we have
already shown.
The grand cause of doubt and error in this subject appears to me
to have been the intimate connexion 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 or by what means the right ventricle
should distribute the blood to the body, or the left draw it from
the venae cavae. This fact is borne witness to by Galen, whose
words, when writing against Erasistratus in regard to the origin
and use of the veins and the coction of the blood, are the
following [Footnote: De Placitis Hippocratis et Platonis, vi.]:
"You will reply," he says, "that the effect is so; that the blood
is prepared in the liver, and is thence transferred to the heart
to receive its proper form and last perfection; a statement which
does not appear devoid of reason; for no great and perfect work
is ever accomplished at a single effort, or receives its final
polish from one instrument. But if this be actually so, then show
us another vessel which draws the absolutely perfect blood from
the heart, and distributes it as the arteries do the spirits over
the whole body." Here then is a reasonable opinion not allowed,
because, forsooth, besides not seeing the true means of transit,
he could not discover the vessel which should transmit the blood
from the heart to the body at large!
But had anyone been there in behalf of Erasistratus, and of that
opinion which we now espouse, and which Galen himself
acknowledges in other respects consonant with reason, to have
pointed to the aorta as the vessel which distributes the blood
from the heart to the rest of the body, I wonder what would have
been the answer of that most ingenious and learned man? Had he
said that the artery transmits spirits and not blood, he would
indeed sufficiently have answered Erasistratus, who imagined that
the arteries contained nothing but spirits; but then he would
have contradicted himself, and given a foul denial to that for
which he had keenly contended in his writings against this very
Erasistratus, to wit, that blood in substance is contained in the
arteries, and not spirits; a fact which he demonstrated not only
by many powerful arguments, but by experiments.
But if the divine Galen will here allow, as in other places he
does, "that all the arteries of the body arise from the great
artery, and that this takes its origin from the heart; that all
these vessels naturally contain and carry blood; that the three
semilunar valves situated at the orifice of the aorta prevent the
return of the blood into the heart, and that nature never
connected them with this, the most noble viscus of the body,
unless for some important end"; if, I say, this father of
physicians concedes all these things,--and I quote his own
words,--I do not see how he can deny that the great artery is the
very vessel to carry the blood, when it has attained its highest
term for term of perfection, from the heart for distribution to
all parts of the body. Or would he perchance still hesitate, like
all who have come after him, even to the present hour, because he
did not perceive the route by which the blood was transferred
from the veins to the arteries, in consequence, as I have already
said, of the intimate connexion between the heart and the lungs?
And that this difficulty puzzled anatomists not a little, when in
their dissections they found the pulmonary artery and left
ventricle full of thick, black, and clotted blood, plainly
appears, when they felt themselves compelled to affirm that the
blood made its way from the right to the left ventricle by
transuding through the septum of the heart. But this fancy I
have already refuted. A new pathway for the blood must therefore
be prepared and thrown open, and being once exposed, no further
difficulty will, I believe, be experienced by anyone in admitting
what I have already proposed in regard to the pulse of the heart
and arteries, viz., the passage of the blood from the veins to
the arteries, and its distribution to the whole of the body by
means of these vessels.