curtel, and not of two, as the arteries and wosen. For the arteries
receive spirits, and they keep and save them. And the veins coming out
of the liver, suck thereof, as it were of their own mother, feeding of
blood, and dealeth and departeth that feeding to every member as it
needeth. And so the veins spread into all the parts of the body, and
by a wonder wit of kind, they do service each to other.

Also among other veins open and privy, there is a vein, and it is
called Artery, which is needful in kind to bear and bring kindly heat
from the heart to all the other members. And these arteries are made
and composed of two small clothings or skins, called curtels, and they
be like in shape, and divers in substance. The inner have wrinkles and
folding overthwart, and their substance is hard, and more boystous
than the utter be. And without they have wrinkles and folding in
length: of whom the substance is hard for needfulness of moving,
opening, and closing. For by opening, itself doth receive from the
heart and that by the wrinklings and folding in length; by closing,
itself doth put out superfluous fumosity, which is done by wrinkling
and folding the curtels overthwart and in breadth, in the which the
spirit is drawn from the heart. Wherefore they be harder without than
all the other veins, and that is needful lest they break lightly and
soon. Also these veins spring out of the left hollowness of the heart.
And twain of that side are called Pulsative, of which one that is the
innermost hath a nesh skin, and this vein is needful to bring great
quantity of blood and spirits to the lungs, and to receive in air, and
to medley it with blood, to temper the ferventness of the blood. This
vein entereth into the lungs and is departed there in many manner
wises.

The other artery is more than the first, and Aristotle calleth it