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作者: fizeau (.) 看板: EngTalk
標題: Re: On The Motion Of The Heart And Blood In Ani …
時間: Sun May 18 02:13:42 2008
Chapter I: The Author's Motives For Writing
When I first gave my mind to vivisections, as a means of discovering the
motions and uses of the heart, and sought to discover these from actual
inspection, and not from the writings of others, I found the task so truly
arduous, so full of difficulties, that I was almost tempted to think, with
Fracastorius, that the motion of the heart was only to be comprehended by
God. For I could neither rightly perceive at first when the systole and when
the diastole took place, nor when and where dilatation and contraction
occurred, by reason of the rapidity of the motion, which in many animals is
accomplished in the twinkling of an eye, coming and going like a flash of
lightning; so that the systole presented itself to me now from this point,
now from that; the diastole the same; and then everything was reversed, the
motions occurring, as it seemed, variously and confusedly together. My mind
was therefore greatly unsettled nor did I know what I should myself conclude,
nor what believe from others. I was not surprised that Andreas Laurentius
should have written that the motion of the heart was as perplexing as the
flux and reflux of Euripus had appeared to Aristotle.
At length, by using greater and daily diligence and investigation, making
frequent inspection of many and various animals, and collating numerous
observations, I thought that I had attained to the truth, that I should
extricate myself and escape from this labyrinth, and that I had discovered
what I so much desired, both the motion and the use of the heart and
arteries. From that time I have not hesitated to expose my views upon these
subjects, not only in private to my friends, but also in public, in my
anatomical lectures, after the manner of the Academy of old.
These views as usual, pleased some more, others less; some chid and
calumniated me, and laid it to me as a crime that I had dared to depart from
the precepts and opinions of all anatomists; others desired further
explanations of the novelties, which they said were both worthy of
consideration, and might perchance be found of signal use. At length,
yielding to the requests of my friends, that all might be made participators
in my labors, and partly moved by the envy of others, who, receiving my views
with uncandid minds and understanding them indifferently, have essayed to
traduce me publicly, I have moved to commit these things to the press, in
order that all may be enabled to form an opinion both of me and my labours.
This step I take all the more willingly, seeing that Hieronymus Fabricius of
Aquapendente, although he has accurately and learnedly delineated almost
every one of the several parts of animals in a special work, has left the
heart alone untouched. Finally, if any use or benefit to this department of
the republic of letters should accrue from my labours, it will, perhaps, be
allowed that I have not lived idly, and as the old man in the comedy says:
For never yet hath any one attained To such perfection, but that time, and
place, And use, have brought addition to his knowledge; Or made correction,
or admonished him, That he was ignorant of much which he Had thought he knew;
or led him to reject What he had once esteemed of highest price.
So will it, perchance, be found with reference to the heart at this time; or
others, at least, starting hence, with the way pointed out to them, advancing
under the guidance of a happier genius, may make occasion to proceed more
fortunately, and to inquire more accurately.
Chapter II: On The Motions Of The Heart
(As Seen In The Dissection Of Living Animals)
In the first place, then, when the chest of a living animal is laid open and
the capsule that immediately surrounds the heart is slit up or removed, the
organ is seen now to move, now to be at rest; there is a time when it moves,
and a time when it is motionless.
These things are more obvious in the colder animals, such as toads, frogs,
serpents, small fishes, crabs, shrimps, snails, and shellfish. They also
become more distinct in warm-blooded animals, such as the dog and hog, if
they be attentively noted when the heart begins to flag, to move more slowly,
and, as it were, to die: the movements then become slower and rarer, the
pauses longer, by which it is made much more easy to perceive and unravel
what the motions really are, and how they are performed. In the pause, as in
death, the heart is soft, flaccid, exhausted, lying, as it were, at rest.
In the motion, and interval in which this is accomplished, three principal
circumstances are to be noted:
1. That the heart is erected, and rises upwards to a point, so that at this
time it strikes against the breast and the pulse is felt externally.
2. That it is everywhere contracted, but more especially towards the sides so
that it looks narrower, relatively longer, more drawn together. The heart of
an eel taken out of the body of the animal and placed upon the table or the
hand, shows these particulars; but the same things are manifest in the hearts
of all small fishes and of those colder animals where the organ is more
conical or elongated.
3. The heart being grasped in the hand, is felt to become harder during its
action. Now this hardness proceeds from tension, precisely as when the
forearm is grasped, its tendons are perceived to become tense and resilient
when the fingers are moved.
4. It may further be observed in fishes, and the colder blooded animals, such
as frogs, serpents, etc., that the heart, when it moves, becomes of a paler
color, when quiescent of a deeper blood-red color.
From these particulars it appears evident to me that the motion of the heart
consists in a certain universal tension-both contraction in the line of its
fibres, and constriction in every sense. It becomes erect, hard, and of
diminished size during its action; the motion is plainly of the same nature
as that of the muscles when they contract in the line of their sinews and
fibres; for the muscles, when in action, acquire vigor and tenseness, and
from soft become hard, prominent, and thickened: and in the same manner the
heart.
We are therefore authorized to conclude that the heart, at the moment of its
action, is at once constricted on all sides, rendered thicker in its parietes
and smaller in its ventricles, and so made apt to project or expel its charge
of blood. This, indeed, is made sufficiently manifest by the preceding fourth
observation in which we have seen that the heart, by squeezing out the blood
that it contains, becomes paler, and then when it sinks into repose and the
ventricle is filled anew with blood, that the deeper crimson colour returns.
But no one need remain in doubt of the fact, for if the ventricle be pierced
the blood will be seen to be forcibly projected outwards upon each motion or
pulsation when the heart is tense.
These things, therefore, happen together or at the same instant: the tension
of the heart, the pulse of its apex, which is felt externally by its striking
against the chest, the thickening of its parietes, and the forcible expulsion
of the blood it contains by the constriction 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, and the heart, when
it contracts (and the impulse of the apex is conveyed through the chest
wall), is 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 only, when tense, is it moved and made vigorous.
Neither is it by any means to be allowed that the heart only moves in the
lines of its straight fibres, although the great Vesalius giving this notion
countenance, quotes a bundle of osiers bound in a pyramidal heap in
illustration; meaning, that as the apex is approached to the base, so are the
sides made to bulge out in the fashion of arches, the cavities to dilate, the
ventricles to acquire the form of a cupping-glass and so to suck in the
blood. But the true effect of every one of its fibres is to constringe the
heart at the same time they render it tense; and this rather with the effect
of thickening and amplifying the walls and substance of the organ than
enlarging its ventricles. And, again, as the fibres run from the apex to the
base, and draw the apex towards the base, they do not tend to make the walls
of the heart bulge out in circles, but rather the contrary; inasmuch as every
fibre that is circularly disposed, tends to become straight when it
contracts; and is distended laterally and thickened, as in the case of
muscular fibres in general, when they contract, that is, when they are
shortened longitudinally, as we see them in the bellies of the muscles of the
body at large. To all this let it be added, that not only are the ventricles
contracted in virtue of the direction and condensation of their walls, but
farther, that those fibres, or bands, styled nerves by Aristotle, which are
so conspicuous in the ventricles of the larger animals, and contain all the
straight fibres (the parietes of the heart containing only circular ones),
when they contract simultaneously by an admirable adjustment all the internal
surfaces are drawn together as if with cords, and so is the charge of blood
expelled with force.
Neither is it true, as vulgarly believed, that the heart by any dilatation or
motion of its own, has the power of drawing the blood into the ventricles;
for 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.
--
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作者: fizeau (.) 看板: EngTalk
標題: Re: On The Motion Of The Heart And Blood In Ani …
時間: Sun May 18 02:29:52 2008
Chapter III: 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, 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, "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.
Chapter IV: Of The Motion Of The Heart And Its Auricles
(As Seen In The Bodies Of Living Animals)
Besides the motions already spoken of, we have still to consider those that
appertain to the auricles.
Caspar Bauhin and John Riolan, most learned men and skillful anatomists,
inform us that from their observations, that if we carefully watch the
movements of the heart in the vivisection of an animal, we shall perceive
four motions distinct in time and in place, two of which are proper to the
auricles, two to the ventricles. With all deference to such authority I say
that there are four motions distinct in point of place, but not of time; for
the two auricles move together, and so also do the two ventricles, in such
wise that though the places be four, the times are only two. And this occurs
in the following manner:
There are, as it were, two motions going on together: one of the auricles,
another of the ventricles; these by no means taking place simultaneously, but
the motion of the auricles preceding, that of the heart following; the motion
appearing to begin from the auricles and to extend to the ventricles. When
all things are becoming languid, and the heart is dying, as also in fishes
and the colder blooded animals there is a short pause between these two
motions, so that the heart aroused, as it were, appears to respond to the
motion, now more quickly, now more tardily; and at length, when near to
death, it ceases to respond by its proper motion, but seems, as it were, to
nod the head, and is so slightly moved that it appears rather to give signs
of motion to the pulsating auricles than actually to move. The heart,
therefore, ceases to pulsate sooner than the auricles, so that the auricles
have been said to outlive it, the left ventricle ceasing to pulsate first of
all; then its auricle, next the right ventricle; and, finally, all the other
parts being at rest and dead, as Galen long since observed, the right auricle
still continues to beat; life, therefore, appears to linger longest in the
right auricle. Whilst the heart is gradually dying, it is sometimes seen to
reply, after two or three contractions of the auricles, roused as it were to
action, and making a single pulsation, slowly, unwillingly, and with an
effort.
But this especially is to be noted, that after the heart has ceased to beat,
the auricles however still contracting, a finger placed upon the ventricles
perceives the several pulsations of the auricles, precisely in the same way
and for the same reason, as we have said, that the pulses of the ventricles
are felt in the arteries, to wit, the distension produced by the jet of
blood. And if at this time, the auricles alone pulsating, the point of the
heart be cut off with a pair of scissors, you will perceive the blood flowing
out upon each contraction of the auricles. Whence it is manifest that the
blood enters the ventricles, not by any attraction or dilatation of the
heart, but by being thrown into them by the pulses of the auricles.
And here I would observe, that whenever I speak of pulsations as occurring in
the auricles or ventricles, I mean contractions: first the auricles contract,
and then and subsequently the heart itself contracts. When the auricles
contract they are seen to become whiter, especially where they contain but
little blood; but they are filled as magazines or reservoirs of the blood,
which is tending spontaneously and, by its motion in the veins, under
pressure towards the centre; the whiteness indicated is most conspicuous
towards the extremities or edges of the auricles at the time of their
contractions.
In fishes and frogs, and other animals which have hearts with but a single
ventricle, and for an auricle have a kind of bladder much distended with
blood, at the base of the organ, you may very plainly perceive this bladder
contracting first, and the contraction of the heart or ventricle following
afterwards.
But I think it right to describe what I have observed of an opposite
character: the heart of an eel, of several fishes, and even of some (of the
higher) animals taken out of the body, pulsates without auricles; nay, if it
be cut in pieces the several parts may still be seen contracting and
relaxing; so that in these creatures the body of the heart may be seen
pulsating and palpitating, after the cessation of all motion in the auricle.
But is not this perchance peculiar to animals more tenacious of life, whose
radical moisture is more glutinous, or fat and sluggish, and less readily
soluble? The same faculty indeed appears in the flesh of eels, which even
when skinned and embowelled, and cut into pieces, are still seen to move.
Experimenting with a pigeon upon one occasion, after the heart had wholly
ceased to pulsate, and the auricles too had become motionless, I kept my
finger wetted with saliva and warm for a short time upon the heart, and
observed that under the influence of this fomentation it recovered new
strength and life, so that both ventricles and auricles pulsated, contracting
and relaxing alternately, recalled as it were from death to life.
Besides this, however, I have occasionally observed, after the heart and even
its right auricle had ceased pulsating, - when it was in articulo mortis in
short, - that an obscure motion, an undulation or palpitation, remained in
the blood itself, which was contained in the right auricle, this being
apparent so long as it was imbued with heat and spirit. And, indeed, a
circumstance of the same kind is extremely manifest in the course of the
generation of animals, as may be seen in the course of the first seven days
of the incubation of the chick: A drop of blood makes its appearance which
palpitates, as Aristotle had already observed; from this, when the growth is
further advanced and the chick is fashioned, the auricles of the heart are
formed, which pulsating henceforth give constant signs of life. When at
length, and after the lapse of a few days, the outline of the body begins to
be distinguished, then is the ventricular part of the heart also produced,
but it continues for a time white and apparently bloodless, like the rest of
the animal; neither does it pulsate or give signs of motion. I have seen a
similar condition of the heart in the human foetus about the beginning of the
third month, the heart then being whitish and bloodless, although its
auricles contained a considerable quantity of purple blood. In the same way
in the egg, when the chick was formed and had increased in size, the heart
too increased and acquired ventrieles, which then began to receive and to
transmit blood.
And this leads me to remark that he who inquires very particularly into this
matter will not conclude that the heart, as a whole, is the primum vivens,
ultimum moriens, - the first part to live, the last to die, - but rather its
auricles, or the part which corresponds to the auricles in serpents, fishes,
etc., which both lives before the heart and dies after it.
Nay, has not the blood itself or spirit an obscure palpitation inherent in
it, which it has even appeared to me to retain after death? and it seems very
questionable whether or not we are to say that life begins with the
palpitation or beating of the heart. The seminal fluid of all animals - the
prolific spirit, as Aristotle observed, leaves their body with a bound and
like a living thing; and nature in death, as Aristotle further remarks,
retracing her steps, reverts to where she had set out, and returns at the end
of her course to the goal whence she had started. As animal generation
proceeds from that which is not animal, entity from non-entity, so, by a
retrograde course, entity, by corruption, is resolved into non-entity, whence
that in animals, which was last created, fails first and that which was
first, fails last.
I have also observed that almost all animals have truly a heart, not the
larger creatures only, and those that have red blood, but the smaller, and
pale-blooded ones also, such as slugs, snails, scallops, shrimps, crabs,
crayfish, and many others; nay, even in wasps, hornets, and flies, I have,
with the aid of a magnifying glass, and at the upper part of what is called
the tail, both seen the heart pulsating myself, and shown it to many others.
But in the pale-blooded tribes the heart pulsates sluggishly and
deliberately, contracting slowly as in animals that are moribund, a fact that
may readily be seen in the snail, whose heart will be found at the bottom of
that orifice in the right side of the body which is seen to be opened and
shut in the course of respiration, and whence saliva is discharged, the
incision being made in the upper aspect of the body, near the part which
corresponds to the liver.
This, however, is to be observed: that in winter and the colder season,
exsanguine animals, such as the snail, show no pulsation; they seem rather to
live after the manner of vegetables, or of those other productions which are
therefore designated plant-animals.
It is also to be noted that all animals which have a heart have also
auricles, or something analogous to auricles; and further, that whenever the
heart has a double ventricle, there are always two auricles present, but not
otherwise. If you turn to the production of the chick in ovo, however, you
will find at first no more a vesicle or auricle, or pulsating drop of blood;
it is only by and by, when the development has made some progress, that the
heart is fashioned; even so in certain animals not destined to attain to the
highest perfection in their organization, such as bees, wasps, snails,
shrimps, crayfish, etc., we only find a certain pulsating vesicle, like a
sort of red or white palpitating point, as the beginning or principle of
their life.
We have a small shrimp in these countries, which is taken in the Thames and
in the sea, the whole of whose body is transparent; this creature, placed in
a little water, has frequently afforded myself and particular friends an
opportunity of observing the motions of the heart with the greatest
distinctness, the external parts of the body presenting no obstacle to our
view, but the heart being perceived as though it had been seen through a
window.
I have also observed the first rudiments of the chick in the course of the
fourth or fifth day of the incubation, in the guise of a little cloud, the
shell having been removed and the egg immersed in clear tepid water. In the
midst of the cloudlet in question there was a bloody point so small that it
disappeared during the contraction and escaped the sight, but in the
relaxation it reappeared again, red and like the point of a pin; so that
betwixt the visible and invisible, betwixt being and not being, as it were,
it gave by its pulses a kind of representation of the commencement of life.
--
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作者: fizeau (.) 看板: EngTalk
標題: Re: On The Motion Of The Heart And Blood In Ani …
時間: Sun May 18 02:47:15 2008
Chapter V: 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.1: "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 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.
Chapter VI: Of The Course By Which The Blood Is Carried
(From The Vena Cava Into The Arteries, Or From The Right Into The Left
Ventricle Of The Heart)
Since the intimate connexion of the heart with the lungs, which is apparent
in the human subject, has been the probable cause of the errors that have
been committed on this point, they plainly do amiss who, pretending to speak
of the parts of animals generally, as anatomists for the most part do,
confine their researches to the human body alone, and that when it is dead.
They obviously do not act otherwise than he who, having studied the forms of
a single commonwealth, should set about the composition of a general system
of polity; or who, having taken cognizance of the nature of a single field,
should imagine that he had mastered the science of agriculture; or who, upon
the ground of one particular proposition, should proceed to draw general
conclusions.
Had anatomists only been as conversant with the dissection of the lower
animals as they are with that of the human body, the matters that have
hitherto kept them in a perplexity of doubt would, in my opinion, have met
them freed from every kind of difficulty.
And first, in fishes, in which the heart consists of but a single ventricle,
being devoid of lungs, the thing is sufficiently manifest. Here the sac,
which is situated at the base of the heart, and is the part analogous to the
auricle in man, plainly forces the blood into the heart, and the heart, in
its turn, conspicuously transmits it by a pipe or artery, or vessel analogous
to an artery; these are facts which are confirmed by simple ocular
inspection, as well as by a division of the vessel, when the blood is seen to
be projected by each pulsation of the heart.
The same thing is also not difficult of demonstration in those animals that
have, as it were, no more than a single ventricle to the heart, such as
toads, frogs, serpents, and lizards, which have lungs in a certain sense, as
they have a voice. I have many observations by me on the admirable structure
of the lungs of these animals, and matters appertaining, which, however, I
cannot introduce in this place. Their anatomy plainly shows us that the blood
is transferred in them from the veins to the arteries in the same manner as
in higher animals, viz., by the action of the heart; the way, in fact, is
patent, open, manifest; there is no difficulty, no room for doubt about it;
for in them the matter stands precisely as it would in man were the septum of
his heart perforated or removed, or one ventricle made out of two; and this
being the case, I imagine that no one will doubt as to the way by which the
blood may pass from the veins into the arteries.
But as there are actually more animals which have no lungs than there are
furnished with them, and in like manner a greater number which have only one
ventricle than there are with two, it is open to us to conclude, judging from
the mass or multitude of living creatures, that for the major part, and
generally, there is an open way by which the blood is transmitted from the
veins through the sinuses or cavities of the heart into the arteries.
I have, however, cogitating with myself, seen further, that the same thing
obtained most obviously in the embryos of those animals that have lungs; for
in the foetus the four vessels belonging to the heart, viz., the vena cava,
the pulmonary artery, the pulmonary vein, and the great artery or aorta, are
all connected otherwise than in the adult, a fact sufficiently known to every
anatomist. The first contact and union of the vena cava with the pulmonary
veins, which occurs before the cava opens properly into the right ventricle
of the heart, or gives off the coronary vein, a little above its escape from
the liver, is by a lateral anastomosis; this is an ample foramen, of an oval
form, communicating between the cava and the pulmonary vein, so that the
blood is free to flow in the greatest abundance by that foramen from the vena
cava into the pulmonary vein, and left auricle, and from thence into the left
ventricle. Farther, in this foramen ovale, from that part which regards the
pulmonary vein, there is a thin tough membrane, larger than the opening,
extended like an operculum or cover; this membrane in the adult blocking up
the foramen, and adhering on all sides, finally closes it up, and almost
obliterates every trace of it. In the foetus, however, this membrane is so
contrived that falling loosely upon itself, it permits a ready access to the
lungs and heart, yielding a passage to the blood which is streaming from the
cava, and hindering the tide at the same time from flowing back into that
vein. All things, in short, permit us to believe that in the embryo the blood
must constantly pass by this foramen from the vena cava into the pulmonary
vein, and from thence into the left auricle of the heart; and having once
entered there, it can never regurgitate.
Another union is that by the pulmonary artery, and is effected when that
vessel divides into two branches after its escape from the right ventricle of
the heart. It is as if to the two trunks already mentioned a third were
superadded, a kind of arterial canal, carried obliquely from the pulmonary
artery, to perforate and terminate in the great artery or aorta. So that in
the dissection of the embryo, as it were, two aortas, or two roots of the
great artery, appear springing from the heart. This canal shrinks gradually
after birth, and after a time becomes withered, and finally almost removed,
like the umbilical vessels.
The arterial canal contains no membrane or valve to direct or impede the flow
of blood in this or in that direction: for at the root of the pulmonary
artery, of which the arterial canal is the continuation in the foetus, there
are three semilunar valves, which open from within outwards, and oppose no
obstacle to the blood flowing in this direction or from the right ventricle
into the pulmonary artery and aorta; but they prevent all regurgitation from
the aorta or pulmonic vessels back upon the right ventricle; closing with
perfect accuracy, they oppose an effectual obstacle to everything of the kind
in the embryo. So that there is also reason to believe that when the heart
contracts, the blood is regularly propelled by the canal or passage indicated
from the right ventricle into the aorta.
What is commonly said in regard to these two great communications, to wit,
that they exist for the nutrition of the lungs, is both improbable and
inconsistent; seeing that in the adult they are closed up, abolished, and
consolidated, although the lungs, by reason of their heat and motion, must
then be presumed to require a larger supply of nourishment. The same may be
said in regard to the assertion that the heart in the embryo does not
pulsate, that it neither acts nor moves, so that nature was forced to make
these communications for the nutrition of the lungs. This is plainly false;
for simple inspection of the incubated egg, and of embryos just taken out of
the uterus, shows that the heart moves in them precisely as in adults, and
that nature feels no such necessity. I have myself repeatedly seen these
motions, and Aristotle is likewise witness of their reality. "The pulse," he
observes, "inheres in the very constitution of the heart, and appears from
the beginning as is learned both from the dissection of living animals and
the formation of the chick in the egg." But we further observe that the
passages in question are not only pervious up to the period of birth in man,
as well as in other animals, as anatomists in general have described them,
but for several months subsequently, in some indeed for several years, not to
say for the whole course of life; as, for example, in the goose, snipe, and
various birds and many of the smaller animals. And this circumstance it was,
perhaps, that imposed upon Botallus, who thought he had discovered a new
passage for the blood from the vena cava into the left ventricle of the
heart; and I own that when I met with the same arrangement in one of the
larger members of the mouse family, in the adult state, I was myself at first
led to something of a like conclusion.
From this it will be understood that in the human embryo, and in the embryos
of animals in which the communications are not closed, the same thing
happens, namely, that the heart by its motion propels the blood by obvious
and open passages from the vena cava into the aorta through the cavities of
both the ventricles, the right one receiving the blood from the auricle, and
propelling it by the pulmonary artery and its continuation, named the ductus
arteriosus, into the aorta; the left, in like manner, charged by the
contraction of its auricle, which has received its supply through the foramen
ovale from the vena cava, contracting, and projecting the blood through the
root of the aorta into the trunk of that vessel.
In embryos, consequently, whilst the lungs are yet in a state of inaction,
performing no function, subject to no motion any more than if they had not
been present, nature uses the two ventricles of the heart as if they formed
but one, for the transmission of the blood. The condition of the embryos of
those animals which have lungs, whilst these organs are yet in abeyance and
not employed, is the same as that of those animals which have no lungs.
So it clearly appears in the case of the foetus that the heart by its action
transfers the blood from the vena cava into the aorta, and that by a route as
obvious and open, as if in the adult the two ventricles were made to
communicate by the removal of their septum. We therefore find that in the
greater number of animals - in all, indeed, at a certain period of their
existence - the channels for the transmission of the blood through the heart
are conspicuous. Bur we have to inquire why in some creatures - those,
namely, that have warm blood, and that have attained to the adult age, man
among the number - we should not conclude that the same thing is accomplished
through the substance of the lungs, which in the embryo, and at a time when
the function of these organs is in abeyance, nature effects by the direct
passage described, and which, indeed, she seems compelled to adopt through
want of a passage by the lungs; or why it should be better (for nature always
does that which is best) that she should close up the various open routes
which she had formerly made use of in the embryo and foetus, and still uses
in all other animals. Not only does she thereby open up no new apparent
channels for the passages of the blood, but she even shuts up those which
formerly existed.
And now the discussion is brought to this point, that they who inquire into
the ways by which the blood reaches the left ventricle of the heart and
pulmonary veins from the vena cava, will pursue the wisest course if they
seek by dissection to discover the causes why in the larger and more perfect
animals of mature age nature has rather chosen to make the blood percolate
the parenchyma of the lungs, than, as in other instances, chosen a direct and
obvious course - for I assume that no other path or mode of transit can be
entertained. It must be because the larger and more perfect animals are
warmer, and when adult their heat greater-ignited, as I might say, and
requiring to be damped or mitigated, that the blood is sent through the
lungs, in order that it may be tempered by the air that is inspired, and
prevented from boiling up, and so becoming extinguished, or something else of
the sort. But to determine these matters, and explain them satisfactorily,
were to enter on a speculation in regard to the office of the lungs and the
ends for which they exist. Upon such a subject, as well as upon what pertains
to respiration, to the necessity and use of the air, etc., as also to the
variety and diversity of organs that exist in the bodies of animals in
connexion with these matters, although I have made a vast number of
observations, I shall not speak till I can more conveniently set them forth
in a treatise apart, lest I should be held as wandering too wide of my
present purpose, which is the use and motion of the heart, and be charged
with speaking of things beside the question, and rather complicating and
quitting than illustrating it. And now returning to my immediate subject, I
go on with what yet remains for demonstration, viz., that in the more perfect
and warmer adult animals, and man, the blood passes from the right ventricle
of the heart by the pulmonary artery, into the lungs, and thence by the
pulmonary veins into the left auricle, and from there into the left ventricle
of the heart. And, first, I shall show that this may be so, and then I shall
prove that it is so in fact.
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Chapter VII: The Blood Passes Through The Substance Of The Lungs
(From The Right Ventricle Of The Heart Into The Pulmonary Veins And Left
Ventricle)
That this is possible, and that there is nothing to prevent it from being so,
appears when we reflect on the way in which water permeating the earth
produces springs and rivulets, or when we speculate on the means by which the
sweat passes through the skin, or the urine through the substance of the
kidneys. It is well known that persons who use the Spa waters or those of La
Madonna, in the territories of Padua, or others of an acidulous or
vitriolated nature, or who simply swallow drinks by the gallon, pass all off
again within an hour or two by the bladder. Such a quantity of liquid must
take some short time in the concoction: it must pass through the liver (it is
allowed by all that the juices of the food we consume pass twice through this
organ in the course of the day); it must flow through the veins, through the
tissues of the kidneys, and through the ureters into the bladder.
To those, therefore, whom I hear denying that the blood, aye, the whole mass
of the blood, may pass through the substance of the lungs, even as the
nutritive juices percolate the liver, asserting such a proposition to be
impossible, and by no means to be entertained as credible, I reply, with the
poet, that they are of that race of men who, when they will, assent full
readily, and when they will not, by no manner of means; who, when their
assent is wanted, fear, and when it is not, fear not to give it.
The substance of the liver is extremely dense, so is that of the kidney; the
lungs, however, are of a much looser texture, and if compared with the
kidneys are absolutely spongy. In the liver there is no forcing, no impelling
power in the lungs the blood is forced on by the pulse of the right
ventricle, the necessary effect of whose impulse is the distension of the
vessels and the pores of the lungs. And then the lungs, in respiration, are
perpetually rising and falling: motions, the effect of which must needs be to
open and shut the pores and vessels, precisely as in the case of a sponge,
and of parts having a spongy structure, when they are alternately compressed
and again are suffered to expand. The liver, on the contrary, remains at
rest, and is never seen to be dilated or constricted. Lastly, if no one
denies the possibility in man, oxen, and the larger animals generally, of the
whole of the ingested juices passing through the liver, in order to reach the
vena cava, for this reason, that if nourishment is to go on, these juices
must needs get into the veins, and there is no other way but the one
indicated, why should not the same arguments be held of avail for the passage
of the blood in adults through the lungs? Why not maintain, with Columbus,
that skilfull and learned anatomist, that it must be so from the capacity and
structure of the pulmonary vessels, and from the fact of the pulmonary veins
and ventricle corresponding with them, being always found to contain blood,
which must needs have come from the veins, and by no other passage save
through the lungs? Columbus, and we also, from what precedes, from
dissections, and other arguments, conceive the thing to be clear. But as
there are some who admit nothing unless upon authority, let them learn that
the truth I am contending for can be confirmed from Galen's own words,
namely, that not only may the blood be transmitted from the pulmonary artery
into the pulmonary veins, then into the left ventricle of the heart, and from
thence into the arteries of the body, but that this is effected by the
ceaseless pulsation of the heart and the motion of the lungs in breathing.
There are, as everyone knows, three sigmoid or semilunar valves situated at
the orifice of the pulmonary artery, which effectually prevent the blood sent
into the vessel from returning into the cavity of the heart. Now Galen,
explaining the use of these valves, and the necessity for them, employs the
following language: "There is everywhere a mutual anastomosis and
inosculation of the arteries with the veins, and they severally transmit both
blood and spirit, by certain invisible and undoubtedly very narrow passages.
Now if the mouth of the pulmonary artery had stood in like manner continually
open, and nature had found no contrivance for closing it when requisite, and
opening it again, it would have been impossible that the blood could ever
have passed by the invisible and delicate mouths, during the contractions of
the thorax, into the arteries; for all things are not alike readily attracted
or repelled; but that which is light is more readily drawn in, the instrument
being dilated, and forced out again when it is contracted, than that which is
heavy; and in like manner is anything drawn more rapidly along an ample
conduit, and again driven forth, than it is through a narrow tube. But when
the thorax is contracted the pulmonary veins, which are in the lungs, being
driven inwardly, and powerfully compressed on every side, immediately force
out some of the spirit they contain, and at the same time assume a certain
portion of blood by those subtle mouths, a thing that could never come to
pass were the blood at liberty to flow back into the heart through the great
orifice of the pulmonary artery. But its return through this great opening
being prevented, when it is compressed on every side, a certain portion of it
distils into the pulmonary veins by the minute orifices mentioned." And
shortly afterwards, in the next chapter, he says: "The more the thorax
contracts, the more it strives to force out the blood, the more exactly do
these membranes (viz., the semilunar valves) close up the mouth of the
vessel, and suffer nothing to regurgitate." The same fact he has also alluded
to in a preceding part of the tenth chapter: "Were there no valves, a
threefold inconvenience would result, so that the blood would then perform
this lengthened course in vain; it would flow inwards during the disastoles
of the lungs and fill all their arteries; but in the systoles, in the manner
of the tide, it would ever and anon, like the Euripus, flow backwards and
forwards by the same way, with a reciprocating motion, which would nowise
suit the blood. This, however, may seem a matter of little moment: but if it
meantime appear that the function of respiration suffer, then I think it
would be looked upon as no trifle, etc." Shortly afterwards he says: "And
then a third inconvenience, by no means to be thought lightly of, would
follow, were the blood moved backwards during the expirations, had not our
Maker instituted those supplementary membranes." In the eleventh chapter he
concludes: "That they (the valves) have all a common use, and that it is to
prevent regurgitation or backward motion; each, however, having a proper
function, the one set drawing matters from the heart, and preventing their
return, the other drawing matters into the heart, and preventing their escape
from it. For nature never intended to distress the heart with needless
labour, neither to bring aught into the organ which it had been better to
have kept away, nor to take from it again aught which it was requisite should
be brought. Since, then, there are four orifices in all, two in either
ventricle, one of these induces, the other educes." And again he says:
"Farther, since there is one vessel, which consists of a simple covering
implanted in the heart, and another which is double, extending from it (Galen
is here speaking of the right side of the heart, but I extend his
observations to the left side also), a kind of reservoir had to be provided,
to which both belonging, the blood should be drawn in by one, and sent out by
the other."
Galen adduces this argument for the transit of the blood by the right
ventricle from the vena cava into the lungs; but we can use it with still
greater propriety, merely changing the terms, for the passage of the blood
from the veins through the heart into the arteries. From Galen, however, that
great man, that father of physicians, it clearly appears that the blood
passes through the lungs from the pulmonary artery into the minute branches
of the pulmonary veins, urged to this both by the pulses of the heart and by
the motions of the lungs and thorax; that the heart, moreover, is incessantly
receiving and expelling the blood by and from its ventricles, as from a
magazine or cistern, and for this end it is furnished with four sets of
valves, two serving for the induction and two for the eduction of the blood,
lest, like the Euripus, it should be incommodiously sent hither and thither,
or flow back into the cavity which it should have quitted, or quit the part
where its presence was required, and so the heart might be oppressed with
labour in vain, and the office of the lungs be interfered with. Finally, our
position that the blood is continually permeating from the right to the left
ventricle, from the vena cava into the aorta, through the porosities of the
lungs, plainly appears from this, that since the blood is incessantly sent
from the right ventricle into the lungs by the pulmonary artery, and in like
manner is incessantly drawn from the lungs into the left ventricle, as
appears from what precedes and the position of the valves, it cannot do
otherwise than pass through continuously. And then, as the blood is
incessantly flowing into the right ventricle of the heart, and is continually
passed out from the left, as appears in like manner, and as is obvious, both
to sense and reason, it is impossible that the blood can do otherwise than
pass continually from the vena cava into the aorta.
Dissection consequently shows distinctly what takes place in the majority of
animals, and indeed in all, up to the period of their maturity; and that the
same thing occurs in adults is equally certain, both from Galen's words, and
what has already been said, only that in the former the transit is effected
by open and obvious passages, in the latter by the hidden porosities of the
lungs and the minute inosculations of vessels. It therefore appears that,
although one ventricle of the heart, the left to wit, would suffice for the
distribution of the blood over the body, and its eduction from the vena cava,
as indeed is done in those creatures that have no lungs, nature,
nevertheless, when she ordained that the same blood should also percolate the
lungs, saw herself obliged to add the right ventricle, the pulse of which
should force the blood from the vena cava through the lungs into the cavity
of the left ventricle. In this way, it may be said, that the right ventricle
is made for the sake of the lungs, and for the transmission of the blood
through them, not for their nutrition; for it were unreasonable to suppose
that the lungs should require so much more copious a supply of nutriment, and
that of so much purer and more spirituous a nature as coming immediately from
the ventricle of the heart, that either the brain, with its peculiarly pure
substance, or the eyes, with their lustrous and truly admirable structure, or
the flesh of the heart itself, which is more suitably nourished by the
coronary artery.
Chapter VIII: Of The Quantity Of Blood Passing Through The Heart
(From The Veins To The Arteries; And Of The Circular Motion Of The Blood)
Thus far I have spoken of the passage of the blood from the veins into the
arteries, and of the manner in which it is transmitted and distributed by the
action of the heart; points to which some, moved either by the authority of
Galen or Columbus, or the reasonings of others, will give in their adhesion.
But what remains to be said upon the quantity and source of the blood which
thus passes is of a character so novel and unheard-of that I not only fear
injury to myself from the envy of a few, but I tremble lest I have mankind at
large for my enemies, so much doth wont and custom become a second nature.
Doctrine once sown strikes deep its root, and respect for antiquity
influences all men. Still the die is cast, and my trust is in my love of
truth and the candour of cultivated minds. And sooth to say, when I surveyed
my mass of evidence, whether derived from vivisections, and my various
reflections on them, or from the study of the ventricles of the heart and the
vessels that enter into and issue from them, the symmetry and size of these
conduits, - for nature doing nothing in vain, would never have given them so
large a relative size without a purpose, - or from observing the arrangement
and intimate structure of the valves in particular, and of the other parts of
the heart in general, with many things besides, I frequently and seriously
bethought me, and long revolved in my mind, what might be the quantity of
blood which was transmitted, in how short a time its passage might be
effected, and the like. But not finding it possible that this could be
supplied by the juices of the ingested aliment without the veins on the one
hand becoming drained, and the arteries on the other getting ruptured through
the excessive charge of blood, unless the blood should somehow find its way
from the arteries into the veins, and so return to the right side of the
heart, I began to think whether there might not be a Motion, As It Were, In A
Circle. Now, this I afterwards found to be true; and I finally saw that the
blood, forced by the action of the left ventricle into the arteries, was
distributed to the body at large, and its several parts, in the same manner
as it is sent through the lungs, impelled by the right ventricle into the
pulmonary artery, and that it then passed through the veins and along the
vena cava, and so round to the left ventricle in the manner already
indicated. This motion we may be allowed to call circular, in the same way as
Aristotle says that the air and the rain emulate the circular motion of the
superior bodies; for the moist earth, warmed by the sun, evaporates; the
vapours drawn upwards are condensed, and descending in the form of rain,
moisten the earth again. By this arrangement are generations of living things
produced; and in like manner are tempests and meteors engendered by the
circular motion, and by the approach and recession of the sun.
And similarly does it come to pass in the body, through the motion of the
blood, that the various parts are nourished, cherished, quickened by the
warmer, more perfect, vaporous, spirituous, and, as I may say, alimentive
blood; which, on the other hand, owing to its contact with these parts,
becomes cooled, coagulated, and so to speak effete. It then returns to its
sovereign, the heart, as if to its source, or to the inmost home of the body,
there to recover its state of excellence or perfection. Here it renews its
fluidity, natural heat, and becomes powerful, fervid, a kind of treasury of
life, and impregnated with spirits, it might be said with balsam. Thence it
is again dispersed. All this depends on the motion and action of the heart.
The heart, consequently, is the beginning of life; the sun of the microcosm,
even as the sun in his turn might well be designated the heart of the world;
for it is the heart by whose virtue and pulse the blood is moved, perfected,
and made nutrient, and is preserved from corruption and coagulation; it is
the household divinity which, discharging its function, nourishes, cherishes,
quickens the whole body, and is indeed the foundation of life, the source of
all action. But of these things we shall speak more opportunely when we come
to speculate upon the final cause of this motion of the heart.
As the blood-vessels, therefore, are the canals and agents that transport the
blood, they are of two kinds, the cava and the aorta; and this not by reason
of there being two sides of the body, as Aristotle has it, but because of the
difference of office, not, as is commonly said, in consequence of any
diversity of structure, for in many animals, as I have said, the vein does
not differ from the artery in the thickness of its walls, but solely in
virtue of their distinct functions and uses. A vein and an artery, both
styled veins by the ancients, and that not without reason, as Galen has
remarked, for the artery is the vessel which carries the blood from the heart
to the body at large, the vein of the present day bringing it back from the
general system to the heart; the former is the conduit from, the latter the
channel to, the heart; the latter contains the cruder, effete blood, rendered
unfit for nutrition; the former transmits the digested, perfect, peculiarly
nutritive fluid.
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標題: Re: On The Motion Of The Heart And Blood In Ani …
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Chapter IX: That There Is A Circulation Of The Blood Is Confirmed
(From The First Proposition)
But lest anyone should say that we give them words only, and make mere
specious assertions without any foundation, and desire to innovate without
sufficient cause, three points present themselves for confirmation, which,
being stated, I conceive that the truth I contend for will follow
necessarily, and appear as a thing obvious to all. First, the blood is
incessantly transmitted by the action of the heart from the vena cava to the
arteries in such quantity that it cannot be supplied from the ingesta, and in
such a manner that the whole must very quickly pass through the organ;
second, the blood under the influence of the arterial pulse enters and is
impelled in a continuous, equable, and incessant stream through every part
and member of the body, in much larger quantity than were sufficient for
nutrition, or than the whole mass of fluids could supply; third, the veins in
like manner return this blood incessantly to the heart from parts and members
of the body. These points proved, I conceive it will be manifest that the
blood circulates, revolves, propelled and then returning, from the heart to
the extremities, from the extremities to the heart, and thus that it performs
a kind of circular motion.
Let us assume, either arbitrarily or from experiment, the quantity of blood
which the left ventricle of the heart will contain when distended, to be,
say, two ounces, three ounces, or one ounce and a half - in the dead body I
have found it to hold upwards of two ounces. Let us assume further how much
less the heart will hold in the contracted than in the dilated state; and how
much blood it will project into the aorta upon each contraction; and all the
world allows that with the systole something is always projected, a necessary
consequence demonstrated in the third chapter, and obvious from the structure
of the valves; and let us suppose as approaching the truth that the fourth,
or fifth, or sixth, or even but the eighth part of its charge is thrown into
the artery at each contraction; this would give either half an ounce, or
three drachms, or one drachm of blood as propelled by the heart at each pulse
into the aorta; which quantity, by reason of the valves at the root of the
vessel, can by no means return into the ventricle. Now, in the course of half
an hour, the heart will have made more than one thousand beats, in some as
many as two, three, and even four thousand. Multiplying the number of drachms
propelled by the number of pulses, we shall have either one thousand half
ounces, or one thousand times three drachms, or a like proportional quantity
of blood, according to the amount which we assume as propelled with each
stroke of the heart, sent from this organ into the artery - a larger quantity
in every case than is contained in the whole body! In the same way, in the
sheep or dog, say but a single scruple of blood passes with each stroke of
the heart, in one half-hour we should have one thousand scruples, or about
three pounds and a half, of blood injected into the aorta; but the body of
neither animal contains above four pounds of blood, a fact which I have
myself ascertained in the case of the sheep.
Upon this supposition, therefore, assumed merely as a ground for reasoning,
we see the whole mass of blood passing through the heart, from the veins to
the arteries, and in like manner through the lungs.
But let it be said that this does not take place in half an hour, but in an
hour, or even in a day; any way, it is still manifest that more blood passes
through the heart in consequence of its action, than can either be supplied
by the whole of the ingesta, or than can be contained in the veins at the
same moment.
Nor can it be allowed that the heart in contracting sometimes propels and
sometimes does not propel, or at most propels but very little, a mere
nothing, or an imaginary something: all this, indeed, has already been
refuted, and is, besides, contrary both to sense and reason. For if it be a
necessary effect of the dilatation of the heart that its ventricles become
filled with blood, it is equally so that, contracting, these cavities should
expel their contents; and this not in any trifling measure. For neither are
the conduits small, nor the contractions few in number, but frequent, and
always in some certain proportion, whether it be a third or a sixth, or an
eighth, to the total capacity of the ventricles, so that a like proportion of
blood must be expelled, and a like proportion received with each stroke of
the heart, the capacity of the ventricle contracted always bearing a certain
relation to the capacity of the ventricle when dilated. And since, in
dilating, the ventricles cannot be supposed to get filled with nothing, or
with an imaginary something, so in contracting they never expel nothing or
aught imaginary, but always a certain something, viz., blood, in proportion
to the amount of the contraction. Whence it is to be concluded that if at one
stroke the heart of man, the ox, or the sheep, ejects but a single drachm of
blood and there are one thousand strokes in half an hour, in this interval
there will have been ten pounds five ounces expelled; if with each stroke two
drachms are expelled, the quantity would, of course, amount to twenty pounds
and ten ounces; if half an ounce, the quantity would come to forty-one pounds
and eight ounces; and were there one ounce, it would be as much as
eighty-three pounds and four ounces; the whole of which, in the course of
one-half hour, would have been transfused from the veins to the arteries. The
actual quantity of blood expelled at each stroke of the heart, and the
circumstances under which it is either greater or less than ordinary, I leave
for particular determination afterwards, from numerous observations which I
have made on the subject.
Meantime this much I know, and would here proclaim to all, that the blood is
transfused at one time in larger, at another in smaller, quantity; and that
the circuit of the blood is accomplished now more rapidly, now more slowly,
according to the temperament, age, etc., of the individual, to external and
internal circumstances, to naturals and non-naturals - sleep, rest, food,
exercise, affections of the mind, and the like. But, supposing even the
smallest quantity of blood to be passed through the heart and the lungs with
each pulsation, a vastly greater amount would still be thrown into the
arteries and whole body than could by any possibility be supplied by the food
consumed. It could be furnished in no other way than by making a circuit and
returning.
This truth, indeed, presents itself obviously before us when we consider what
happens in the dissection of living animals; the great artery need not be
divided, but a very small branch only (as Galen even proves in regard to
man), to have the whole of the blood in the body, as well that of the veins
as of the arteries, drained away in the course of no long time - some
half-hour or less. Butchers are well aware of the fact and can bear witness
to it; for, cutting the throat of an ox and so dividing the vessels of the
neck, in less than a quarter of an hour they have all the vessels bloodless -
the whole mass of blood has escaped. The same thing also occasionally occurs
with great rapidity in performing amputations and removing tumors in the
human subject.
Nor would this argument lose of its force, did any one say that in killing
animals in the shambles, and performing amputations, the blood escaped in
equal, if not perchance in larger quantity by the veins than by the arteries.
The contrary of this statement, indeed, is certainly the truth; the veins, in
fact, collapsing, and being without any propelling power, and further,
because of the impediment of the valves, as I shall show immediately, pour
out but very little blood; whilst the arteries spout it forth with force
abundantly, impetuously, and as if it were propelled by a syringe. And then
the experiment is easily tried of leaving the vein untouched and only
dividing the artery in the neck of a sheep or dog, when it will be seen with
what force, in what abundance, and how quickly, the whole blood in the body,
of the veins as well as of the arteries, is emptied. But the arteries receive
blood from the veins in no other way than by transmission through the heart,
as we have already seen; so that if the aorta be tied at the base of the
heart, and the carotid or any other artery be opened, no one will now be
surprised to find it empty, and the veins only replete with blood.
And now the cause is manifest, why in our dissections we usually find so
large a quantity of blood in the veins, so little in the arteries; why there
is much in the right ventricle, little in the left, which probably led the
ancients to believe that the arteries (as their name implies) contained
nothing but spirits during the life of an animal. The true cause of the
difference is perhaps this, that as there is no passage to the arteries, save
through the lungs and heart, when an animal has ceased to breathe and the
lungs to move, the blood in the pulmonary artery is prevented from passing
into the pulmonary veins, and from thence into the left ventricle of the
heart; just as we have already seen the same transit prevented in the embryo,
by the want of movement in the lungs and the alternate opening and shutting
of their hidden and invisible porosities and apertures. But the heart not
ceasing to act at the same precise moment as the lungs, but surviving them
and continuing to pulsate for a time, the left ventricle and arteries go on
distributing their blood to the body at large and sending it into the veins;
receiving none from the lungs, however, they are soon exhausted, and left, as
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The reason is, that with a somewhat greater than usual resistance offered to
the transit of the blood by the bandage, coupled with the weaker action of
the heart, and its diminished impelling power, the stream cannot make its way
under the ligature; and farther, owing to the weak and languishing state of
the heart, the blood is not transferred in such quantity as wont from the
veins to the arteries through the sinuses of that organ. So also, and for the
same reasons, are the menstrual fluxes of women, and indeed hemorrhages of
every kind, controlled. And now, a contrary state of things occurring, the
patient getting rid of his fear and recovering his courage, the pulse
strength is increased, the arteries begin again to beat with greater force,
and to drive the blood even into the part that is bound; so that the blood
now springs from the puncture in the vein, and flows in a continuous stream.
Chapter XIII: The Third Position Is Confirmed
(And The Circulation Of The Blood Is Demonstrated From It)
Thus far we have spoken of the quantity of blood passing through the heart
and the lungs in the centre of the body, and in like manner from the arteries
into the veins in the peripheral parts and the body at large. We have yet to
explain, however, in what manner the blood finds its way back to the heart
from the extremities by the veins, and how and in what way these are the only
vessels that convey the blood from the external to the central parts; which
done, I conceive that the three fundamental propositions laid down for the
circulation of the blood will be so plain, so well established, so obviously
true, that they may claim general credence. Now the remaining position will
be made sufficiently clear from the valves which are found in the cavities of
the veins themselves, from the uses of these, and from experiments cognizable
by the senses.
The celebrated Hieronymus Fabricius of Aquapendente, a most skillful
anatomist, and venerable old man, or, as the learned Riolan will have it,
Jacobus Silvius, first gave representations of the valves in the veins, which
consist of raised or loose portions of the inner membranes of these vessels,
of extreme delicacy, and a sigmoid or semilunar shape. They are situated at
different distances from one another, and diversely in different individuals;
they are connate at the sides of the veins; they are directed upwards towards
the trunks of the veins; the two-for there are for the most part two together
-regard each other, mutually touch, and are so ready to come into contact by
their edges, that if anything attempts to pass from the trunks into the
branches of the veins, or from the greater vessels into the less, they
completely prevent it; they are farther so arranged, that the horns of those
that succeed are opposite the middle of the convexity of those that precede,
and so on alternately.
The discoverer of these valves did not rightly understand their use, nor have
succeeding anatomists added anything to our knowledge; for their office is by
no means explained when we are told that it is to hinder the blood, by its
weight, from all flowing into inferior parts; for the edges of the valves in
the jugular veins hang downwards, and are so contrived that they prevent the
blood from rising upwards; the valves, in a word, do not invariably look
upwards, but always toward the trunks of the veins, invariably towards the
seat of the heart. I, and indeed others, have sometimes found valves in the
emulgent veins, and in those of the mesentery, the edges of which were
directed towards the vena cava and vena portae. Let it be added that there
are no valves in the arteries, and that dogs, oxen, etc., have invariably
valves at the divisions of their crural veins, in the veins that meet towards
the top of the os sacrum, and in those branches which come from the haunches,
in which no such effect of gravity from the erect position was to be
apprehended. Neither are there valves in the jugular veins for the purpose of
guarding against apoplexy, as some have said; because in sleep the head is
more apt to be influenced by the contents of the carotid arteries. Neither
are the valves present, in order that the blood may be retained in the
divarications or smaller trunks and minuter branches, and not be suffered to
flow entirely into the more open and capacious channels; for they occur where
there are no divarications; although it must be owned that they are most
frequent at the points where branches join. Neither do they exist for the
purpose of rendering the current of blood more slow from the centre of the
body; for it seems likely that the blood would be disposed to flow with
sufficient slowness of its own accord, as it would have to pass from larger
into continually smaller vessels, being separated from the mass and fountain
head, and attaining from warmer into colder places.
But the valves are solely made and instituted lest the blood should pass from
the greater into the lesser veins, and either rupture them or cause them to
become varicose; lest, instead of advancing from the extreme to the central
parts of the body, the blood should rather proceed along the veins from the
centre to the extremities; but the delicate valves, while they readily open
in the right direction, entirely prevent all such contrary motion, being so
situated and arranged, that if anything escapes, or is less perfectly
obstructed by the cornua of the one above, the fluid passing, as it were, by
the chinks between the cornua, it is immediately received on the convexity of
the one beneath, which is placed transversely with reference to the former,
and so is effectually hindered from getting any farther.
And this I have frequently experienced in my dissections of the veins: if I
attempted to pass a probe from the trunk of the veins into one of the smaller
branches, whatever care I took I found it impossible to introduce it far any
way, by reason of the valves; whilst, on the contrary, it was most easy to
push it along in the opposite direction, from without inwards, or from the
branches towards the trunks and roots. In many places two valves are so
placed and fitted, that when raised they come exactly together in the middle
of the vein, and are there united by the contact of their margins; and so
accurate is the adaptation, that neither by the eye nor by any other means of
examination, can the slightest chink along the line of contact be perceived.
But if the probe be now introduced from the extreme towards the more central
parts, the valves, like the floodgates of a river, give way, and are most
readily pushed aside. The effect of this arrangement plainly is to prevent
all motion of the blood from the heart and vena cava, whether it be upwards
towards the head, or downwards towards the feet, or to either side towards
the arms, not a drop can pass; all motion of the blood, beginning in the
larger and tending towards the smaller veins, is opposed and resisted by
them; whilst the motion that proceeds from the lesser to end in the larger
branches is favoured, or, at all events, a free and open passage is left for
it.
But that this truth may be made the more apparent, let an arm be tied up
above the elbow as if for phlebotomy. At intervals in the course of the veins,
especially in labouring people and those whose veins are large, certain knots
or elevations will be perceived, and this not only at the places where a branch
is received, but also where none enters: these knots or risings are all formed
by valves, which thus show themselves externally. And now if you press the
blood from the space above one of the valves, from H to O, (fig. 2,) and keep
the point of a finger upon the vein inferiorly, you will see no influx of blood
from above; the portion of the vein between the point of the finger and the
valve O will be obliterated; yet will the vessel continue sufficiently
distended above the valve (O, G). The blood being thus pressed out and the vein
emptied, if you now apply a finger of the other hand upon the distended part of
the vein above the valve O, (fig. 3,) and press downwards, you will find that
you cannot force the blood through or beyond the valve; but the greater effort
you use, you will only see the portion of vein that is between the finger and
the valve become more distended, that portion of the vein which is below the
valve remaining all the while empty (H, O, fig. 3).
It would therefore appear that the function of the valves in the veins is the
same as that of the three sigmoid valves which we find at the commencement of
the aorta and pulmonary artery, viz., to prevent all reflux of the blood that
is passing over them.
Farther, the arm being bound as before, and the veins looking full and
distended, if you press at one part in the course of a vein with the point of
a finger (L, fig. 4), and then with another finger streak the blood upwards
beyond the next valve (N), you will perceive that this portion of the vein
continues empty (L. N), and that the blood cannot retrograde, precisely as we
have already seen the case to be in fig. 2; but the finger first applied (H,
fig. 2, L, fig. 4), being removed, immediately the vein is filled from below,
and the arm becomes as it appears at D C, fig. 1. That the blood in the veins
therefore proceeds from inferior or more remote parts, and towards the heart,
moving in these vessels in this and not in the contrary direction, appears
most obviously. And although in some places the valves, by not acting with
such perfect accuracy, or where there is but a single valve, do not seem
totally to prevent the passage of the blood from the centre, still the
greater number of them plainly do so; and then, where things appear contrived
more negligently, this is compensated either by the more frequent occurrence
or more perfect action of the succeeding valves, or in some other way: the
veins in short, as they are the free and open conduits of the blood returning
to the heart, so are they effectually prevented from serving as its channels
of distribution from the heart.
But this other circumstance has to be noted: The arm being bound, and the
veins made turgid, and the valves prominent, as before, apply the thumb or
finger over a vein in the situation of one of the valves in such a way as to
compress it, and prevent any blood from passing upwards from the hand; then,
with a finger of the other hand, streak the blood in the vein upwards till it
has passed the next valve above (N, fig. 4), the vessel now remains empty;
but the finger at L being removed for an instant, the vein is immediately
filled from below; apply the finger again, and having in the same manner
streaked the blood upwards, again remove the finger below, and again the
vessel becomes distended as before; and this repeat, say a thousand times, in
a short space of time. And now compute the quantity of blood which you have
thus pressed up beyond the valve, and then multiplying the assumed quantity
by one thousand, you will find that so much blood has passed through a
certain portion of the vessel; and I do now believe that you will find
yourself convinced of the circulation of the blood, and of its rapid motion.
But if in this experiment you say that a violence is done to nature, I do not
doubt but that, if you proceed in the same way, only taking as great a length
of vein as possible, and merely remark with what rapidity the blood flows
upwards, and fills the vessel from below, you will come to the same
conclusion.
--
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作者: fizeau (.) 看板: EngTalk
標題: Re: On The Motion Of The Heart And Blood In Ani …
時間: Sun May 18 03:53:16 2008
Chapter XIV: Conclusion Of The Demonstration Of The Circulation
And now I may be allowed to give in brief my view of the circulation of the
blood, and to propose it for general adoption.
Since all things, both argument and ocular demonstration, show that the blood
passes through the lungs, and heart by the force of the ventricles, and is
sent for distribution to all parts of the body, where it makes its way into
the veins and porosities of the flesh, and then flows by the veins from the
circumference on every side to the centre, from the lesser to the greater
veins, and is by them finally discharged into the vena cava and right auricle
of the heart, and this in such a quantity or in such a flux and reflux
thither by the arteries, hither by the veins, as cannot possibly be supplied
by the ingesta, and is much greater than can be required for mere purposes of
nutrition; it is absolutely necessary to conclude that the blood in the
animal body is impelled in a circle, and is in a state of ceaseless motion;
that this is the act or function which the heart performs by means of its
pulse; and that it is the sole and only end of the motion and contraction of
the heart.
Chapter XV: The Circulation Of The Blood Is Further Confirmed
(By Probable Reasons)
It will not be foreign to the subject if I here show further, from certain
familiar reasonings, that the circulation is matter both of convenience and
necessity. In the first place, since death is a corruption which takes place
through deficiency of heat, and since all living things are warm, all dying
things cold, there must be a particular seat and fountain, a kind of home and
hearth, where the cherisher of nature, the original of the native fire, is
stored and preserved; from which heat and life are dispensed to all parts as
from a fountain head; from which sustenance may be derived; and upon which
concoction and nutrition, and all vegetative energy may depend. Now, that the
heart is this place, that the heart is the principle of life, and that all
passes in the manner just mentioned, I trust no one will deny.
The blood, therefore, required to have motion, and indeed such a motion that
it should return again to the heart; for sent to the external parts of the
body far from its fountain, as Aristotle says, and without motion, it would
become congealed. For we see motion generating and keeping up heat and
spirits under all circumstances, and rest allowing them to escape and be
dissipated. The blood, therefore, becoming thick or congealed by the cold of
the extreme and outward parts, and robbed of its spirits, just as it is in
the dead, it was imperative that from its fount and origin, it should again
receive heat and spirits, and all else requisite to its preservation - that,
by returning, it should be renovated and restored.
We frequently see how the extremities are chilled by the external cold, how
the nose and cheeks and hands look blue, and how the blood, stagnating in
them as in the pendent or lower parts of a corpse, becomes of a dusky hue;
the limbs at the same time getting torpid, so that they can scarcely be
moved, and seem almost to have lost their vitality. Now they can by no means
be so effectually, and especially so speedily restored to heat and colour and
life, as by a new efflux and contact of heat from its source. But how can
parts attract in which the heat and life are almost extinct? Or how should
they whose passages are filled with condensed and frigid blood, admit fresh
aliment - renovated blood - unless they had first got rid of their contents?
Unless the heart were truly that fountain where life and heat are restored to
the refrigerated fluid, and whence new blood, warm, imbued with spirits,
being sent out by the arteries, that which has become cooled and effete is
forced on, and all the particles recover their heat which was failing, and
their vital stimulus wellnigh exhausted.
Hence it is that if the heart be unaffected, life and health may be restored
to almost all the other parts of the body; but if the heart be chilled, or
smitten with any serious disease, it seems matter of necessity that the whole
animal fabric should suffer and fall into decay. When the source is
corrupted, there is nothing, as Aristotle says, which can be of service
either to it or aught that depends on it. And hence, by the way, it may
perchance be why grief, and love, and envy, and anxiety, and all affections
of the mind of a similar kind are accompanied with emaciation and decay, or
with disordered fluids and crudity, which engender all manner of diseases and
consume the body of man. For every affection of the mind that is attended
with either pain or pleasure, hope or fear, is the cause of an agitation
whose influence extends to the heart, and there induces change from the
natural constitution, in the temperature, the pulse and the rest, which
impairing all nutrition in its source and abating the powers at large, it is
no wonder that various forms of incurable disease in the extremities and in
the trunk are the consequence, inasmuch as in such circumstances the whole
body labours under the effects of vitiated nutrition and a want of native
heat.
Moreover, when we see that all animals live through food digested in their
interior, it is imperative that the digestion and distribution be perfect,
and, as a consequence, that there be a place and receptacle where the aliment
is perfected and whence it is distributed to the several members. Now this
place is the heart, for it is the only organ in the body which contains blood
for the general use; all the others receive it merely for their peculiar or
private advantage, just as the heart also has a supply for its own especial
behoof in its coronary veins and arteries. But it is of the store which the
heart contains in its auricles and ventricles that I here speak. Then the
heart is the only organ which is so situated and constituted that it can
distribute the blood in due proportion to the several parts of the body, the
quantity sent to each being according to the dimensions of the artery which
supplies it, the heart serving as a magazine or fountain ready to meet its
demands.
Further, a certain impulse or force, as well as an impeller or forcer, such
as the heart, was required to effect this distribution and motion of the
blood; both because the blood is disposed from slight causes, such as cold,
alarm, horror, and the like, to collect in its source, to concentrate like
parts to a whole, or the drops of water spilt upon a table to the mass of
liquid; and because it is forced from the capillary veins into the smaller
ramifications, and from these into the larger trunks by the motion of the
extremities and the compression of the muscles generally. The blood is thus
more disposed to move from the circumference to the centre than in the
opposite direction, even were there no valves to oppose its motion;
wherefore, that it may leave its source and enter more confined and colder
channels, and flow against the direction to which it spontaneously inclines,
the blood requires both force and impelling power. Now such is the heart and
the heart alone, and that in the way and manner already explained.
--
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作者: fizeau (.) 看板: EngTalk
標題: Re: On The Motion Of The Heart And Blood In Ani …
時間: Sun May 18 04:20:15 2008
Chapter XVI: The Circulation Of The Blood Is Further Proved
(From Certain Consequences)
There are still certain problems, which, taken as consequences of this truth
assumed as proven, are not without their use in exciting belief, as it were,
a posteriore; and which, although they may seem to be involved in much doubt
and obscurity, nevertheless readily admit of having reasons and causes
assigned for them. Of such a nature are those that present themselves in
connexion with contagions, poisoned wounds, the bites of serpents and rabid
animals, lues venerea and the like. We sometimes see the whole system
contaminated, though the part first infected remains sound; the lues venerea
has occasionally made its attack with pains in the shoulders and head, and
other symptoms, the genital organs being all the while unaffected; and then
we know that the wound made by a rabid dog having healed, fever and a train
of disastrous symptoms may nevertheless supervene. Whence it appears that the
contagion impressed upon or deposited in a particular part, is by-and-by
carried by the returning current of blood to the heart, and by that organ is
sent to contaminate the whole body.
In tertian fever, the morbific cause seeking the heart in the first instance,
and hanging about the heart and lungs, renders the patient short-winded,
disposed to sighing, and indisposed to exertion, because the vital principle
is oppressed and the blood forced into the lungs and rendered thick. It does
not pass through them, (as I have myself seen in opening the bodies of those
who had died in the beginning of the attack,) when the pulse is always
frequent, small, and occasionally irregular; but the heat increasing, the
matter becoming attenuated, the passages forced, and the transit made, the
whole body begins to rise in temperature, and the pulse becomes fuller and
stronger. The febrile paroxysm is fully formed, whilst the preternatural heat
kindled in the heart is thence diffused by the arteries through the whole
body along with the morbific matter, which is in this way overcome and
dissolved by nature.
When we perceive, further, that medicines applied externally exert their
influence on the body just as if they had been taken internally, the truth we
are contending for is confirmed. Colocynth and aloes in this way move the
belly, cantharides excites the urine, garlic applied to the soles of the feet
assists expectoration, cordials strengthen, and an infinite number of
examples of the same kind might be cited. Perhaps it will not, therefore, be
found unreasonable, if we say that the veins, by means of their orifices,
absorb some of the things that are applied externally and carry this inwards
with the blood, not otherwise, it may be, than those of the mesentery imbibe
the chyle from the intestines and carry it mixed with the blood to the liver.
For the blood entering the mesentery by the coeliac artery, and the superior
and inferior mesenterics, proceeds to the intestines, from which, along with
the chyle that has been attracted into the veins, it returns by their
numerous ramifications into the vena portae of the liver, and from this into
the vena cava, and this in such wise that the blood in these veins has the
same colour and consistency as in other veins, in opposition to what many
believe to be the fact. Nor indeed can we imagine two contrary motions in any
capillary system - the chyle upwards, the blood downwards. This could
scarcely take place, and must be held as altogether improbable. But is not
the thing rather arranged as it is by the consummate providence of nature?
For were the chyle mingled with the blood, the crude with the digested, in
equal proportions, the result would not be concoction, transmutation, and
sanguification, but rather, and because they are severally active and
passive, a mixture or combination, or medium compound of the two, precisely
as happens when wine is mixed with water and syrup. But when a very minute
quantity of chyle is mingled with a very large quantity of circulating blood,
a quantity of chyle that bears no kind of proportion to the mass of blood,
the effect is the same, as Aristotle says, as when a drop of water is added
to a cask of wine, or the contrary; the mass does not then present itself as
a mixture, but is still sensibly either wine or water.
So in the mesenteric veins of an animal we do not find either chyme or chyle
and blood, blended together or distinct, but only blood, the same in colour,
consistency, and other sensible properties, as it appears in the veins
generally. Still as there is a certain though small and inappreciable portion
of chyle or incompletely digested matter mingled with the blood, nature has
interposed the liver, in whose meandering channels it suffers delay and
undergoes additional change, lest arriving prematurely and crude at the
heart, it should oppress the vital principle. Hence in the embryo, there is
almost no use for the liver, but the umbilical vein passes directly through,
a foramen or an anastomosis existing from the vena portae. The blood returns
from the intestines of the foetus, not through the liver, but into the
umbilical vein mentioned, and flows at once into the heart, mingled with the
natural blood which is returning from the placenta; whence also it is that in
the development of the foetus the liver is one of the organs that is last
formed. I have observed all the members perfectly marked out in the human
foetus, even the genital organs, whilst there was yet scarcely any trace of
the liver. And indeed at the period when all the parts, like the heart itself
in the beginning, are still white, and except in the veins there is no
appearance of redness, you shall see nothing in the seat of the liver but a
shapeless collection, as it were, of extravasated blood, which you might take
for the effects of a contusion or ruptured vein.
But in the incubated egg there are, as it were, two umbilical vessels, one
from the albumen passing entire through the liver, and going straight to the
heart; another from the yelk, ending in the vena portae; for it appears that
the chick, in the first instance, is entirely formed and nourished by the
white; but by the yelk after it has come to perfection and is excluded from
the shell; for this part may still be found in the abdomen of the chick many
days after its exclusion, and is a substitute for the milk to other animals.
But these matters will be better spoken of in my observations on the
formation of the foetus, where many propositions, the following among the
number, will be discussed: Wherefore is this part formed or perfected first,
that last, and of the several members, what part is the cause of another? And
there are many points having special reference to the heart, such as
wherefore does it first acquire consistency, and appear to possess life,
motion, sense, before any other part of the body is perfected, as Aristotle
says in his third book, "De partibus Animalium"? And so also of the blood,
wherefore does it precede all the rest? And in what way does it possess the
vital and animal principle, and show a tendency to motion, and to be impelled
hither and thither, the end for which the heart appears to be made? In the
same way, in considering the pulse, why should one kind of pulse indicate
death, another recovery? And so of all the other kinds of pulse, what may be
the cause and indication of each? Likewise we must consider the reason of
crises and natural critical discharges; of nutrition, and especially the
distribution of the nutriment; and of defluxions of every description.
Finally, reflecting on every part of medicine, physiology, pathology,
semeiotics and therapeutics, when I see how many questions can be answered,
how many doubts resolved, how much obscurity illustrated by the truth we have
declared, the light we have made to shine, I see a field of such vast extent
in which I might proceed so far, and expatiate so widely, that this my
tractate would not only swell out into a volume, which was beyond my purpose,
but my whole life, perchance, would not suffice for its completion.
In this place, therefore, and that indeed in a single chapter, I shall only
endeavour to refer the various particulars that present themselves in the
dissection of the heart and arteries to their several uses and causes; for so
I shall meet with many things which receive light from the truth I have been
contending for, and which, in their turn, render it more obvious. And indeed
I would have it confirmed and illustrated by anatomical arguments above all
others.
There is but a single point which indeed would be more correctly placed among
our observations on the use of the spleen, but which it will not be
altogether impertinent to notice in this place incidentally. From the splenic
branch which passes into the pancreas, and from the upper part, arise the
posterior coronary, gastric, and gastroepiploic veins, all of which are
distributed upon the stomach in numerous branches and twigs, just as the
mesenteric vessels are upon the intestines. In a similar way, from the
inferior part of the same splenic branch, and along the back of the colon and
rectum proceed the hemorrhoidal veins. The blood returning by these veins,
and bringing the cruder juices along with it, on the one hand from the
stomach, where they are thin, watery, and not yet perfectly chylified; on the
other thick and more earthy, as derived from the faeces, but all poured into
this splenic branch, are duly tempered by the admixture of contraries; and
nature mingling together these two kinds of juices, difficult of coction by
reason of most opposite defects, and then diluting them with a large quantity
of warm blood, (for we see that the quantity returned from the spleen must be
very large when we contemplate the size of its arteries,) they are brought to
the porta of the liver in a state of higher preparation. The defects of
either extreme are supplied and compensated by this arrangement of the veins.
--
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作者: fizeau (.) 看板: EngTalk
標題: Re: On The Motion Of The Heart And Blood In Ani …
時間: Sun May 18 05:02:35 2008
Chapter XVII: The Motion And Circulation Of The Blood Are Confirmed
(From The Particulars Apparent In The Structure Of The Heart, And From Those
Things Which Dissection Unfolds)
I do not find the heart as a distinct and separate part in all animals; some,
indeed, such as the zoophytes, have no heart; this is because these animals
are coldest, of one great bulk, of soft texture, or of a certain uniform
sameness or simplicity of structure; among the number I may instance grubs
and earth-worms, and those that are engendered of putrefaction and do not
preserve their species. These have no heart, as not requiring any impeller of
nourishment into the extreme parts; for they have bodies which are connate
and homogeneous and without limbs; so that by the contraction and relaxation
of the whole body they assume and expel, move and remove, the aliment.
Oysters, mussels, sponges, and the whole genus of zoophytes or plant-animals
have no heart, for the whole body is used as a heart, or the whole animal is
a heart. In a great number of animals, - almost the whole tribe of insects -
we cannot see distinctly by reason of the smallness of the body; still in
bees, flies, hornets, and the like we can perceive something pulsating with
the help of a magnifying glass; in pediculi, also, the same thing may be
seen, and as the body is transparent, the passage of the food through the
intestines, like a black spot or stain, may be perceived by the aid of the
same magnifying glass.
But in some of the pale-blooded and colder animals, as in snails, whelks,
shrimps, and shell-fish, there is a part which pulsates, - a kind of vesicle
or auricle without a heart, - slowly, indeed, and not to be perceived except
in the warmer season of the year. In these creatures this part is so
contrived that it shall pulsate, as there is here a necessity for some
impulse to distribute the nutritive fluid, by reason of the variety of
organic parts, or of the density of the substance; but the pulsations occur
unfrequently, and sometimes in consequence of the cold not at all, an
arrangement the best adapted to them as being of a doubtful nature, so that
sometimes they appear to live, sometimes to die; sometimes they show the
vitality of an animal, sometimes of a vegetable. This seems to be the case
with the insects which conceal themselves in winter, and lie, as it were,
defunct, or merely manifesting a kind of vegetative existence. But whether
the same thing happens in the case of certain animals that have red blood,
such as frogs, tortoises, serpents, swallows, may be very properly doubted.
In all the larger and warmer animals which have red blood, there was need of
an impeller of the nutritive fluid, and that, perchance, possessing a
considerable amount of power. In fishes, serpents, lizards, tortoises, frogs,
and others of the same kind there is a heart present, furnished with both an
auricle and a ventricle, whence it is perfectly true, as Aristotle has
observed, that no sanguineous animal is without a heart, by the impelling
power of which the nutritive fluid is forced, both with greater vigour and
rapidity, to a greater distance; and not merely agitated by an auricle, as it
is in lower forms. And then in regard to animals that are yet larger, warmer,
and more perfect, as they abound in blood, which is always hotter and more
spirituous, and which possess bodies of greater size and consistency, these
require a larger, stronger, and more fleshy heart, in order that the
nutritive fluid may be propelled with yet greater force and celerity. And
further, inasmuch as the more perfect animals require a still more perfect
nutrition, and a larger supply of native heat, in order that the aliment may
be thoroughly concocted and acquire the last degree of perfection, they
required both lungs and a second ventricle, which should force the nutritive
fluid through them.
Every animal that has lungs has, therefore, two ventricles to its heart-one
right, the other left; and wherever there is a right, there also is there a
left ventricle; but the contrary of this does not hold good: where there is a
left there is not always a right ventricle. The left ventricle I call that
which is distinct in office, not in place from the other, that one, namely,
which distributes the blood to the body at large, not to the lungs only.
Hence the left ventricle seems to form the principal part of the heart;
situated in the middle, more strongly marked, and constructed with greater
care, the heart seems formed for the sake of the left ventricle, and the
right but to minister to it. The right neither reaches to the apex of the
heart nor is it nearly of such strength, being three times thinner in its
walls, and in some sort jointed on to the left (as Aristotle says), though,
indeed, it is of greater capacity, inasmuch as it has not only to supply
material to the left ventricle, but likewise to furnish aliment to the lungs.
It is to be observed, however, that all this is otherwise in the embryo,
where there is not such a difference between the two ventricles. There, as in
a double nut, they are nearly equal in all respects, the apex of the right
reaching to the apex of the left, so that the heart presents itself as a sort
of double-pointed cone. And this is so, because in the foetus, as already
said, whilst the blood is not passing through the lungs from the right to the
left cavities of the heart, it flows by the foramen ovale and ductus
arteriosus directly from the vena cava into the aorta, whence it is
distributed to the whole body. Both ventricles have, therefore, the same
office to perform, whence their equality of constitution. It is only when the
lungs come to be used and it is requisite that the passages indicated should
be blocked up that the difference in point of strength and other things
between the two ventricles begins to be apparent. In the altered
circumstances the right has only to drive the blood through the lungs, whilst
the left has to propel it through the whole body.
There are, moreover, within the heart numerous braces, in the form of fleshy
columns and fibrous bands, which Aristotle, in his third book on
"Respiration," and the "Parts of Animals," entitles nerves. These are
variously extended, and are either distinct or contained in grooves in the
walls and partition, where they occasion numerous pits or depressions. They
constitute a kind of small muscles, which are superadded and supplementary to
the heart, assisting it to execute a more powerful and perfect contraction,
and so proving subservient to the complete expulsion of the blood. They are,
in some sort, like the elaborate and artful arrangement of ropes in a ship,
bracing the heart on every side as it contracts, and so enabling it more
effectually and forcibly to expel the charge of blood from its ventricles.
This much is plain, at all events, that in some animals they are less
strongly marked than in others; and, in all that have them, they are more
numerous and stronger in the left than in the right ventricle; and while some
have them present in the left, yet they are absent in the right ventricle. In
man they are more numerous in the left than in the right ventricle, more
abundant in the ventricles than in the auricles; and occasionally there
appear to be none present in the auricles. They are numerous in the large,
more muscular and hardier bodies of countrymen, but fewer in more slender
frames and in females.
In those animals in which the ventricles of the heart are smooth within and
entirely without fibres of muscular bands, or anything like hollow pits, as
in almost all the smaller birds, the partridge and the common fowl, serpents,
frogs, tortoises, and most fishes, there are no chordae tendineae, nor
bundles of fibres, neither are there any tricuspid valves in the ventricles.
Some animals have the right ventricle smooth internally, but the left
provided with fibrous bands, such as the to be blown and to require a large
quantity of air. But of these things, more in our "Treatise on Respiration."
It is in like manner evident that the auricles pulsate, contract, as I have
said before, and throw the blood into the ventricles; so that wherever there
is a ventricle, an auricle is necessary, not merely that it may serve,
according to the general belief, as a source and magazine for the blood: for
what were the use of its pulsations had it only to contain?
The auricles are prime movers of the blood, especially the right auricle,
which, as already said, is "the first to live, the last to die"; whence they
are subservient to sending the blood into the ventricles, which, contracting
continuously, more readily and forcibly expel the blood already in motion;
just as the ball-player can strike the ball more forcibly and further if he
takes it on the rebound than if he simply threw it. Moreover, and contrary to
the general opinion, neither the heart nor anything else can dilate or
distend itself so as to draw anything into its cavity during the diastole,
unless, like a sponge, it has been first compressed and is returning to its
primary condition. But in animals all local motion proceeds from, and has its
origin in, the contraction of some part; consequently it is by the
contraction of the auricles that the blood is thrown into the ventricles, as
I have already shown, and from there, by the contraction of the ventricles,
it is propelled and distributed. Concerning local motions, it is true that
the immediate moving organ in every motion of an animal primarily endowed
with a motive spirit (as Aristotle has it) is contractile; in which way the
word veuPou is derived from veuw, nuto, contraho; and if I am permitted to
proceed in my purpose of making a particular demonstration of the organs of
motion in animals from observations in my possession, I trust I shall be able
to make sufficiently plain how Aristotle was acquainted with the muscles, and
advisedly referred all motion in animals to the nerves, or to the contractile
element, and, therefore, called those little bands in the heart nerves.
But that we may proceed with the subject which we have in hand, viz., the use
of the auricles in filling the ventricles, we should expect that the more
dense and compact the heart, the thicker its parietes, the stronger and more
muscular must be the auricle to force and fill it, and vice versa. Now this
is actually so: in some the auricle presents itself as a sanguinolent
vesicle, as a thin membrane containing blood, as in fishes, in which the sac
that stands in lieu of the auricles is of such delicacy and ample capacity
that it seems to be suspended or to float above the heart. In those fishes in
which the sac is somewhat more fleshy, as in the carp, barbel, tench, and
others, it bears a wonderful and strong resemblance to the lungs.
In some men of sturdier frame and stouter make the right auricle is so
strong, and so curiously constructed on its inner surface of bands and
variously interlacing fibres, that it seems to equal in strength the
ventricle of the heart in other subjects; and I must say that I am astonished
to find such diversity in this particular in different individuals. It is to
be observed, however, that in the foetus the auricles are out of all
proportion large, which is because they are present before the heart makes
its appearance or suffices for its office even when it has appeared, and
they, therefore, have, as it were, the duty of the whole heart committed to
them, as has already been demonstrated. But what I have observed in the
formation of the foetus, as before remarked (and Aristotle had already
confirmed all in studying the incubated egg), throws the greatest light and
likelihood upon the point. Whilst the foetus is yet in the form of a soft
worm, or, as is commonly said, in the milk, there is a mere bloody point or
pulsating vesicle, a portion apparently of the umbilical vein, dilated at its
commencement or base. Afterwards, when the outline of the foetus is
distinctly indicated and it begins to have greater bodily consistence, the
vesicle in question becomes more fleshy and stronger, changes its position,
and passes into the auricles, above which the body of the heart begins to
sprout, though as yet it apparently performs no office. When the foetus is
farther advanced, when the bones can be distinguished from the fleshy parts
and movements take place, then it also has a heart which pulsates, and, as I
have said, throws blood by either ventricle from the vena cava into the
arteries.
Thus nature, ever perfect and divine, doing nothing in vain, has neither
given a heart where it was not required, nor produced it before its office
had become necessary; but by the same stages in the development of every
animal, passing through the forms of all, as I may say (ovum, worm, foetus),
it acquires perfection in each. These points will be found elsewhere
confirmed by numerous observations on the formation of the foetus.
Finally, it is not without good grounds that Hippocrates in his book, "De
Corde," entitles it a muscle; its action is the same; so is its functions,
viz., to contract and move something else - in this case the charge of the
blood.
Farther, we can infer the action and use of the heart from the arrangement of
its fibres and its general structures, as in muscles generally. All
anatomists admit with Galen that the body of the heart is made up of various
courses of fibres running straight, obliquely, and transversely, with
reference to one another; but in a heart which has been boiled, the
arrangement of the fibres is seen to be different. All the fibres in the
parietes and septum are circular, as in the sphincters; those, again, which
are in the columns extend lengthwise, and are oblique longitudinally; and so
it comes to pass that when all the fibres contract simultaneously, the apex
of the cone is pulled towards its base by the columns, the walls are drawn
circularly together into a globe - the whole heart, in short, is contracted
and the ventricles narrowed. It is, therefore, impossible not to perceive
that, as the action of the organ is so plainly contraction, its function is
to propel the blood into the arteries.
Nor are we the less to agree with Aristotle in regard to the importance of
the heart, or to question if it receives sense and motion from the brain,
blood from the liver, or whether it be the origin of the veins and of the
blood, and such like. They who affirm these propositions overlook, or do not
rightly understand, the principal argument, to the effect that the heart is
the first part which exists, and that it contains within itself blood, life,
sensation, and motion, before either the brain or the liver were created or
had appeared distinctly, or, at all events, before they could perform any
function. The heart, ready furnished with its proper organs of motion, like a
kind of internal creature, existed before the body. The first to be formed,
nature willed that it should afterwards fashion, nourish, preserve, complete
the entire animal, as its work and dwelling-place: and as the prince in a
kingdom, in whose hands lie the chief and highest authority, rules over all,
the heart is the source and foundation from which all power is derived, on
which all power depends in the animal body.
Many things having reference to the arteries farther illustrate and confirm
this truth. Why does not the pulmonary vein pulsate, seeing that it is
numbered among the arteries? Or wherefore is there a pulse in the pulmonary
artery? Because the pulse of the arteries is derived from the impulse of the
blood. Why does an artery differ so much from a vein in the thickness and
strength of its coats? Because it sustains the shock of the impelling heart
and streaming blood. Hence, as perfect nature does nothing in vain, and
suffices under all circumstances, we find that the nearer the arteries are to
the heart, the more do they differ from the veins in structure; here they are
both stronger and more ligamentous, whilst in extreme parts of the body, such
as the feet and hands, the brain, the mesentery, and the testicles, the two
orders of vessels are so much alike that it is impossible to distinguish
between them with the eye. Now this is for the following very sufficient
reasons: the more remote the vessels are from the heart, with so much the
less force are they distended by the stroke of the heart, which is broken by
the great distance at which it is given. Add to this that the impulse of the
heart exerted upon the mass of blood, which must needs fill the trunks and
branches of the arteries, is diverted, divided, as it were, and diminished at
every subdivision, so that the ultimate capillary divisions of the arteries
look like veins, and this not merely in constitution, but in function. They
have either no perceptible pulse, or they rarely exhibit one, and never
except where the heart beats more violently than usual, or at a part where
the minute vessel is more dilated or open than elsewhere. It, therefore,
happens that at times we are aware of a pulse in the teeth, in inflammatory
tumours, and in the fingers; at another time we feel nothing of the sort. By
this single symptom I have ascertained for certain that young persons whose
pulses are naturally rapid were labouring under fever; and in like manner, on
compressing the fingers in youthful and delicate subjects during a febrile
paroxysm, I have readily perceived the pulse there. On the other hand, when
the heart pulsates more languidly, it is often impossible to feel the pulse
not merely in the fingers, but the wrist, and even at the temple, as in
persons afflicted with lipothymiae asphyxia, or hysterical symptoms, and in
the debilitated and moribund.
Here surgeons are to be advised that, when the blood escapes with force in
the amputation of limbs, in the removal of tumours, and in wounds, it
constantly comes from an artery; not always indeed per saltum, because the
smaller arteries do not pulsate, especially if a tourniquet has been applied.
For the same reason the pulmonary artery not only has the structure of an
artery, but it does not differ so widely from the veins in the thickness of
its walls as does the aorta. The aorta sustains a more powerful shock from
the left than the pulmonary artery does from the right ventricle, and the
walls of this last vessel are thinner and softer than those of the aorta in
the same proportion as the walls of the right ventricle of the heart are
weaker and thinner than those of the left ventricle. In like manner the lungs
are softer and laxer in structure than the flesh and other constituents of
the body, and in a similar way the walls of the branches of the pulmonary
artery differ from those of the vessels derived from the aorta. And the same
proportion in these particulars is universally preserved. The more muscular
and powerful men are, the firmer their flesh; the stronger, thicker, denser,
and more fibrous their hearts, the thicker, closer, and stronger are the
auricles and arteries. Again, in those animals the ventricles of whose hearts
are smooth on their inner surface, without villi or valves, and the walls of
which are thin, as in fishes, serpents, birds, and very many genera of
animals, the arteries differ little or nothing in the thickness of their
coats from the veins.
Moreover, the reason why the lungs have such ample vessels, both arteries and
veins (for the capacity of the pulmonary veins exceeds that of both crural
and jugular vessels), and why they contain so large a quantity of blood, as
by experience and ocular inspection we know they do, admonished of the fact
indeed by Aristotle, and not led into error by the appearances found in
animals which have been bled to death, is, because the blood has its
fountain, and storehouse, and the workshop of its last perfection, in the
heart and lungs. Why, in the same way, we find in the course of our
anatomical dissections the pulmonary vein and left ventricle so full of
blood, of the same black colour and clotted character as that with which the
right ventricle and pulmonary artery are filled, is because the blood is
incessantly passing from one side of the heart to the other through the
lungs. Wherefore, in fine, the pulmonary artery has the structure of an
artery, and the pulmonary veins have the structure of veins. In function and
constitution and everything else the first is an artery, the others are
veins, contrary to what is commonly believed; and the reason why the
pulmonary artery has so large an orifice is because it transports much more
blood than is requisite for the nutrition of the lungs.
All these appearances, and many others, to be noted in the course of
dissection, if rightly weighed, seem clearly to illustrate and fully to
confirm the truth contended for throughout these pages, and at the same time
to oppose the vulgar opinion; for it would be very difficult to explain in
any other way to what purpose all is constructed and arranged as we have seen
it to be.
--
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→ fizeau:Do not very understand English translations 05/18 05:10
→ fizeau:may be due to first time reading 05/18 05:10
→ fizeau:have to read the French translation or Latin original 05/18 05:11