again it sends it self
back towards the heart: so that its course is no other thing but a
perpetuall circulation. Which he very wel proves by the ordinary
experience of Chirurgians, who having bound the arm indifferently hard
above the the place where they open the vein, which causeth the bloud to
issue more abundantly, then if it had not been bound. And the contrary
would happen, were it bound underneath, between the hand and the
incision, or bound very hard above. For its manifest, that the band
indifferently tyed, being able to hinder the bloud which is already in
the arm to return towards the heart by the veins; yet it therefore
hinders not the new from coming always by the arteries, by reason they
are placed under the veins, and that their skin being thicker, are less
easie to be press'd, as also that the bloud which comes from the heart,
seeks more forcibly to passe by them towards the hand, then it doth to
return from thence towards the heart by the veins. And since this bloud
which issues from the arm by the incision made in one of the veins, must
necessarily have some passage under the bond, to wit, towards the
extremities of the arm, whereby it may come thither by the arteries, he
also proves very well what he sayes of the course of the bloud through
certain little skins, which are so disposed in divers places along the
veins, which permit it not to pass from the middle towards the
extremities, but onely to return from the extremities towards the heart.
And besides this, experience shews, That all the bloud which is in the
body may in a very little time run out by one onely artery's being cut,
although it were even bound very neer the heart, and cut betwixt it and
the ligature: So that we could have no reason to imagine that the bloud
which issued thence could come from any other part.

But there are divers other things which witness, that the true cause of
this motion of the bloud is that which I have related. As first, The
difference observed between that which issues out of the veins, and that
which comes out of the arteries, cannot proceed but from its being
rarified and (as it were) distilled by passing thorow the heart: its
more subtil, more lively, and more hot presently after it comes out;
that is to say, being in the arteries, then it is a little before it
enters them, that is to say, in the veins. And if you observe, you will
finde, that this difference appears not well but about the heart; and
not