es of the heart, but he denies to them the office of valves.
To him the motion of the blood was of a to-and-fro kind, and valves in
the veins acting as such would have interfered with anything of the
sort. He expresses clearly the idea, that was entertained in the old
physiology, of the attractions exerted by the various parts of the body
for the blood; and especially that of the veins and heart for the blood
itself. "The right sinus of the heart," he says, "attracts blood from
the vena cava, and the left attracts air from the lungs through the
_arteria venalis_ (pulmonary vein), the blood itself being attracted by
the veins in general, the vital spirit by the arteries." Again, he
speaks of the blood filtering through the septum between the ventricles
as if through a sieve, although he knows perfectly well from his
dissection that the septum is quite impervious.

It will thus be seen that the physiological teaching of Galen was left
undisturbed by Vesalius.

FOOTNOTES:

[19] See Professor Morley's article on "Anatomy in Long Clothes," in
_Fraser's Magazine_, 1853, from which most of the facts in this sketch
have been taken.

HARVEY.

_HARVEY._

The importance of Harvey's discovery of the circulation of the blood can
only be properly estimated by bearing in mind what was done by his
predecessors in the same field of inquiry. Aristotle had taught that in
man and in the higher brutes the blood was elaborated from the food in
the liver, conveyed to the heart, and thence distributed by it through
the veins to the whole body. Erasistratus and Herophilus held that,
while the veins carried blood from the heart to the members, the
arteries carried a subtle kind of air or spirit. Galen discovered that
the arteries were not merely air-pipes, but that they contained blood as
well as vital air or spirit. Sylvius, the teacher of Vesalius, was aware
of the presence of valves in the veins; and Fabricius, Harvey's teacher
at Padua, described them much more accurately than Sylvius had done; but
neither of these men had a true idea of the significance of the
structures of which they wrote. Servetus, the friend and contemporary of
Vesalius, writing in 1533, correctly described the course of the lesser
circulation in the following words: "This communication (_i.e._ between
the right and left sides of the heart) does not take place through the
partition of the heart, as is generally believed; but by another
admirable