The Sun.
London, England, 1824-01-13 00:00:00

THE HEART, GREAT VESSELS,
AND CIRCULATION OF THE BLOOD.

So important a subject as the circulation of the
blood cannot fail of being interestipg to our ge-
neral readers; roe shall therefore lay .before
them a brief account of it, divested of that corn-
plication which renders only intelligible to
anatomists. The heart, by the contraction of
which the blood is circulated, has arising Out of
it two great blood vessels, whose bran Ches extend
to all parts of the body, accompanying each,
other throughout : the one •is the great artery,
the aorta,- and the other the great vein, or. vena
caw:. The heart bas also two other great•vessels
arising from its other 'Side, one called the great
artery of the lung's, or pulmonary artery, tke
other, the great Vein of the lungs, or piamo-
\very-Vein. Lei 'us therefOre keep in- view that
-heartthas fOttr large trunks communicating-
‘v.ith' it, and that at the junction of each with the.
heort, thereare placed'Valves, most beautifully per-
feCt , which actin such a mannerastoadinit the tide
of blood through its own proper,channel, in passing
and '-'epassing the heart and lungs, and to home=
diatel y fly up and prevent its improper return,
like ft ood-gates. Arteries are always accom-
panied -by veins closely connected together—the
arteries carrying the blob(' from the heart—the
veins eai rying it back to it. An artery is elastic,
and can d:intract and dilate--a vein is an inactive
flaccid tub e. An artery has no valve in its whole
course to the extremities of the body—a vein
has valves placed at very short distances. These
valves are to support the upper column of blood
as it ascends from below hack to the heart, fly-
ing up and tithing as a floor to that portion of
blood which is above it and between the next
valve and itself, thus every motion of our limbs
rnoves the blood in their veins, and that motion
can be no other than upwards, on account of
those valves, while the motion of the blood in
the :arteries is directly from the contraction. of
the 'heart, and it has a free current to the extreme
parts of the body. With this,- general 'view in
mind, let us proceed to describe the circulation.
The blood is sent out at one gush, or pulsa-
tion, throughout the whole body into the most
minute branches of tire arteries; those arteries
make a turn, and, losing their elasticity, become
velios, which grow large in proportion as they
towards • the heart, and lie exactly in the
'course of *heir coPresponding arteries. Into
these veins the blood is therefore forced after
haling supplied the various secretions of the body.
This blood is thus brought hack by the great vein,
or vena cava, and at its junction with the left
..111P+ir and subciaviau vein it receives by a little'
tube the white chyle,
~or essence of the food
brought by that tube from the stomach. The
blood is then unfit.for the arteries, and therefore is
carried into one little cavity of the heart, and at
one Pulsation i< drivenby the pulmonary artery
into the hugs, where, coming in contact with the
air through their Membranes, it absorbs oxygen
from air breathed, which changes its colour from
dark to bright red. The blood thus prepared for
into t%ii
tother
the
supporting life is taken back hy the pulmonary
v
aorta
ao,f andi
bhyeaornt .vpv
pulsation
scaht
incootni:
niettl'nnsi
c :Les the
s r
e
sent to all parts of the body, returning again as
before through the
veins ;
and this course takes
place at every pulsation of that great and beau-
tiful machine of the heart.—(Medical ..Idviser.)