Paul Severing - "Marvels of Modern Science"

Leacock, Stephen, 1869 1944 - "Arcadian Adventures With the Idle Rich"

John Lothrop Motley - "The Rise of the Dutch Republic, 1580 82"

Charles James Fox - "A History of the Early Part of the Reign of James the Second"

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Books: The Harvard Classics Volume 38

V >> Various >> The Harvard Classics Volume 38




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 (A, A, fig. 1). At
intervals in the course of the veins, especially in labouring
people and those whose veins are large, certain knots or
elevations (B, C, D, E, F) will be perceived, and this not only
at the places where a branch is received (E, F), but also where
none enters (C, D): 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.

[NOTE.--Woodcuts of the veins of the arm to which these letters
and figures refer appear here in the original.--C. N. B. C]

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.




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, [Footnote: Aristoteles De Respirations, lib. ii et iii: De
Part. Animal. et alibi.] 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 ail
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 old 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, [Footnote: De Part. Animal., iii.]
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.




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 mesenteries, 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.




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.