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,[94] 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; whence heat and life are dispensed to all parts as from a
fountain head; whence 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, become 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 afflux and appulsion
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 well-nigh 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 the heart being
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,[95] which can be of service either to it or aught that depends on
it. And hence, by the way, it may perchance be wherefore 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 cacochemy 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 concocted 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; and 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 then 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, were there
even no valves to oppose its motion; whence 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 an impelling power. Now such is the heart and the heart alone,
and that in the way and manner already explained.