axed, the arteries
meanwhile continuing unaffected, this is an obvious indication that the
blood passes from the arteries into the veins, and not from the veins
into the arteries, and that there is either an anastomosis of the two
orders of vessels, or pores in the flesh and solid parts generally that
are permeable to the blood.

And now we understand wherefore in phlebotomy we apply our fillet above
the part that is punctured, not below it. Did the flow come from above,
not from below, the bandage in this case would not only be of no
service, but would prove a positive hindrance. And further, if we
calculate how many ounces flow through one arm or how many pass in
twenty or thirty pulsations under the medium ligature, we shall perceive
that a circulation is absolutely necessary, seeing that the quantity
cannot be supplied immediately from the ingesta, and is vastly more than
can be requisite for the mere nutrition of the parts.

And the third point to be confirmed is this. That the veins return this
blood to the heart incessantly from all parts and members of the body.

This position will be made sufficiently clear from the valves which are
found in the cavities of the veins themselves, from the uses of these,
and from experiments cognisable by the senses. The celebrated Hieronymus
Fabricius, of Aquapendente, first gave representations of the valves in
the veins, which consist of raised or loose portions of the inner
membranes of these vessels of extreme delicacy and a sigmoid, or
semi-lunar shape. Their office is by no means explained when we are told
that it is to hinder the blood, by its weight, from flowing into
inferior parts; for the edges of the valves in the jugular veins hang
downwards, and are so contrived that they prevent the blood from rising
upwards.

The valves, in a word, do not invariably look upwards, but always
towards the trunks of the veins--towards the seat of the heart. They are
solely made and instituted lest, instead of advancing from the extreme
to the central parts of the body, the blood should rather proceed along
the veins from the centre to the extremities; but the delicate valves,
while they readily open in the right direction, entirely prevent all
such contrary motion, being so situated and arranged that if anything
escapes, or is less perfectly obstructed by the flaps of the one above,
the fluid passing, as it were, by the chinks between the flaps, it is
immediately received on the