contrivance, whereby from the right ventricle the subtle blood
is agitated in a lengthened course through the lungs, wherein prepared,
it becomes of a crimson colour, and from the vena arterialis (pulmonary
artery) is transferred into the arteria venalis (pulmonary vein).
Mingled with the inspired air in the arteria venalis, freed by
respiration from fuliginous matter, and become a suitable home of the
vital spirit, it is attracted at length into the left ventricle of the
heart by the diastole of the organ." But when Servetus comes to speak of
the systemic circulation, what he has to say is as old as Galen.

The opinions, therefore, on the subject of the blood and its
distribution which were prevalent at the end of the sixteenth century
prove--

(1) That although the blood was not regarded as stagnant, yet its
circulation, such as is nowadays recognized, was unknown;

(2) That one kind of blood was thought to flow from the liver to the
right ventricle, and thence to the lungs and general system by
the veins, while another kind flowed from the left ventricle to
the lungs and general system by the arteries;

(3) That the septum of the heart was regarded as admitting of the
passage of blood directly from the right to the left side;

(4) That there was no conception of the functions of the heart as the
motor power of the movement of the blood, for biologists of that
day doubted whether the substance of the heart were really
muscular; they supposed the pulsations to be due to expansion of
the spirits it contained; they believed the only dynamic effect
which it had on the blood to be that of sucking it in during its
active diastole, and they supposed the chief use of its constant
movements to be the due mixture of blood and spirits.

This was the state of knowledge before Harvey's time. By his great work
he established--

(1) That the blood flows continuously in a circuit through the whole
body, the force propelling it in this unwearied round being the
rhythmical contractions of the muscular walls of the heart;

(2) That a portion only of the blood is expended in nutrition each time
that it circulates;

(3) That the blood conveyed in the systemic arteries communicates heat
as well as nourishment throughout the body, instead of exerting a
cooling influence, as was vulgarly supposed; and

(4)