OF THE MOTION, ACTION, AND OFFICE OF THE HEART.
From these and other observations of the like kind, 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 throws 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 sending its charge into
the lungs by the vessel which is 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.
These two motions, one of the ventricles, another 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, it
is ignited, upon which 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, the larynx is closed by its
own muscles, and the epiglottis, whilst the pharynx, raised and opened
by its muscles no otherwise than is a sac that is to be filled, is
lifted up, and its mouth dilated; upon which, the mouthful being
received, it is forced downwards by the transverse muscles, and then
carried farther by the longitudinal ones. Yet are all these motions,
though executed by different and distinct organs, 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 any one, 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, [the
organ] twisting itself slightly in performing its work. And indeed every
one may see, when a horse drinks, that the water is drawn in and
transmitted to the stomach at each movement of the throat, the motion
being accompanied with a sound, and yielding 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, that 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.
So much, indeed, is admitted by all [physiologists], 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; and
then they give utterance to diverse, contradictory, and incoherent
sentiments, delivering many things upon conjecture, as we have already
had occasion to remark.
The grand cause of hesitation 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 vena arteriosa [or pulmonary artery] and the arteriæ
venosæ [or 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
venæ cavæ. 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:[90] “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 any one 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 most important end;” if, I say, this father of
physic admits 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 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 sweating 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 any one 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.