THE CIRCULATION OF THE BLOOD IS FURTHER PROVED FROM CERTAIN CONSEQUENCES
There are still certain phenomena, 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. The phenomena alluded
to 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 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, indisposed to exertion; because
the vital principle is oppressed and the blood forced into the lungs
and rendered thick, does not pass through their substance, (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, 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
[applied externally] 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. It will not, therefore, be found unreasonable perchance, 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 cœliac 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 portæ 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 concocted, 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 proportion of chyle
or unconcocted matter mingled with this 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 anastomosis existing from the vena portæ, so
that the blood returns from the intestines of the fœtus, 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 fœtus
the liver is one of the organs that is last formed; I have observed
all the members perfectly marked out in the human fœtus, 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 save 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 portæ;
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 fœtus, 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 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: Wherefore one kind of pulse should indicate
death, another recovery? And so of all the other kinds of pulse, what
may be the cause and indication of each. So also in the consideration
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, 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 like
manner, 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 fæces, 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.