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.