physiology; he had bad four temperaments, and
four humours. He had three spirits, and
three sources of those spirits. Moreover, the
brain was the origin of all the nerves; the
heart the origin of all the arteries; the liver
the origin of all the veins. The veins
proceeding from the liver carried the blood to
the members; a strange mistake, which the
most simple experiment, or even the most
simple attention to an every-day experiment,
would have sufficed to rectify. For, in fact,
bleeding was practised daily, and every-day
people could see the vein swell below and
not above the ligature. Consequently, in the
veins, the blood flowed from the members
towards the heart, and not from the heart to
the members. Césalpin is the first—the only
one before Harvey—who called attention to
this swelling of the veins which, as just
observed, always takes place below and never
above the ligature. But Césalpin had a
mind of a superior order; he was the first
among the moderns to avail himself of
method in natural science—that is, of
classification founded on organisation. He has
the double glory of giving us a method, and
of communicating the idea of the two
circulations.

Fabricius, of Acquapendente, also enjoys a
double glory. He was Harvey's master, and
in fifteen hundred and seventy-four he
discovered the valvules of the veins. He saw
clearly that they are directed towards the
heart. They prevent, therefore, the passage
of the blood in the veins in the direction
from the heart to the members; it flows,
therefore, from the members to the heart,
the reverse of what takes place in the
arteries, which have no valvules. The
valvules of the veins are the anatomical proof
of the circulation of the blood; the proof
that it makes a circuit, that it returns to
the point whence it started; but Fabricius
did not perceive that proof. He observed
the fact, but failed to draw from it the
important inference which Harvey alone was
able to deduce.

When Harvey appeared, every point
relative to the circulation had been already
indicated or suspected—nothing was established.
And so true is that assertion, that Fabricius,
who came after Césalpin, and who discovered
the valvules of the veins, was ignorant of the
circulation. Césalpin himself, who observed
so well the two circulations, mingled the
error of the passage through the partition of
the ventricles with the idea of the pulmonary
circulation. Colombo repeats, with Galen,
that the veins spring from the liver, and carry
the blood to the members.

Sprengel is right in saying that Harvey is
best explained by his education at Padua.
Doubtless, it was fortunate for Harvey to be
educated at Padua; but also it was fortunate
for the circulation to fall into the hands of
Harvey, the man most competent to study it,
to investigate its phenomena thoroughly, and
to explain their full import. Harvey's work
is a masterpiece. This little book of a hundred
pages is the finest literary effort physiology
has produced. Harvey begins by the
movements of the heart; and first he remarks that
the auricle and the ventricle of each heart
contract successively. After the heart, come the
arteries. Galen had said that the arteries
beat in consequence of a pulsative virtue,
which they derive from the heart through
their coats. Harvey, by opening an artery,
and watching the unequal jets in which the
blood issued from it, concluded that an
artery beats by impulsion,—by the blow of
the blood with which it is distended. If the
artery dilated of itself, it would not be at the
moment when it swells that it would drive
the blood with the greatest force. Harvey
took advantage of a case of ossification of
the crural artery which he had occasion to
observe. The artery beat below the ossification,
which, therefore, did not intercept the
effect of the pretended pulsative virtue; or,
rather, that virtue has no existence. The
pulsation of the arteries is due solely to the
movement of the blood, to the impulse of the
blood on the coats of the arteries.

From the arteries, Harvey proceeds to the
veins; and there he draws from the valvules
their full import—namely, that they allow
the blood to move only in one direction.
Lastly, Harvey comes to his experiments.
They are few, but decisive, indicative of his
genius. When a limb is slightly bound, the
blood is checked in the veins only, because
the veins alone are superficial. If the limb
be bound more tightly, the blood is stopped
in the arteries also, which are deep-seated.
When a vein is compressed, the swelling
takes place below the ligature; when an
artery is compressed, it swells above the
ligature. The blood, therefore, flows in
contrary directions in the veins and in the
arteries; in the veins, it goes from the
members to the heart; in the arteries, from the
heart to the members.

When any artery is opened and the blood
allowed to flow without check, the whole of
the blood contained in an animal's body will
issue by this orifice. Therefore, all the parts
of the circulating apparatus must
communicate with each other—the heart, the
arteries, and the veins. And if, in fact, you
think of the prodigious rapidity of the
current of the blood, you will see that it cannot
be otherwise; for as soon as the blood has
entered the heart, it leaves it to pass to the
arteries; as soon as it has entered the
arteries, it is driven forward to pass over to
the veins; as soon as it is in the veins, it is
sent on to the heart again. It flows, therefore,
continually from the heart to the
arteries, from the arteries to the veins, and
from the veins to the heart. This movement,
this continual return, is the circulation.

Modern physiology takes its date from the
discovery of the circulation of the blood,