(See diagram.)
Each vein of the other pair stretches from the region of the ear
to the brain, and branches off in a number of fine and delicate
veins into the so-called meninx, or membrane, which surrounds the
brain. The brain itself in all animals is destitute of blood, and no
vein, great or small, holds its course therein. But of the remaining
veins that branch off from the last mentioned vein some envelop the
head, others close their courses in the organs of sense and at the
roots of the teeth in veins exceedingly fine and minute.
4
And in like manner the parts of the lesser one of the two chief
blood-vessels, designated the aorta, branch off, accompanying the
branches from the big vein; only that, in regard to the aorta, the
passages are less in size, and the branches very considerably less
than are those of the great vein. So much for the veins as observed in
the regions above the heart.
The part of the great vein that lies underneath the heart
extends, freely suspended, right through the midriff, and is united
both to the aorta and the backbone by slack membranous communications.
From it one vein, short and wide, extends through the liver, and
from it a number of minute veins branch off into the liver and
disappear.
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