, the
hollow vein (vena cava), which is the principal receptacle of the blood,
and the trunk of the tree, as it were, of which all the other veins in the
body are branches; and the arterial vein (vena arteriosa), inappropriately
so denominated, since it is in truth only an artery, which, taking its
rise in the heart, is divided, after passing out from it, into many
branches which presently disperse themselves all over the lungs; in the
second place, the cavity in the left side, with which correspond in the
same manner two canals in size equal to or larger than the preceding,
viz., the venous artery (arteria venosa), likewise inappropriately thus
designated, because it is simply a vein which comes from the lungs, where
it is divided into many branches, interlaced with those of the arterial
vein, and those of the tube called the windpipe, through which the air we
breathe enters; and the great artery which, issuing from the heart, sends
its branches all over the body. I should wish also that such persons were
carefully shown the eleven pellicles which, like so many small valves,
open and shut the four orifices that are in these two cavities, viz.,
three at the entrance of the hollow veins where they are disposed in such
a manner as by no means to prevent the blood which it contains from
flowing into the right ventricle of the heart, and yet exactly to prevent
its flowing out; three at the entrance to the arterial vein, which,
arranged in a manner exactly the opposite of the former, readily permit
the blood contained in this cavity to pass into the lungs, but hinder that
contained in the lungs from returning to this cavity; and, in like manner,
two others at the mouth of the venous artery, which allow the blood from
the lungs to flow into the left cavity of the heart, but preclude its
return; and three at the mouth of the great artery, which suffer the blood
to flow from the heart, but prevent its reflux.
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