hers,
however, such as Eustachius and Fabricius (1537-1619), were more
successful, and found and described these structures. But the purpose
served by these valves was entirely misinterpreted. That they act in
preventing the backward flow of the blood in the veins on its way to the
heart, just as the valves of the heart itself prevent regurgitation, has
been known since the time of Harvey; but the best interpretation that
could be given at that time, even by such a man as Fabricius, was that
they acted in retarding the flow of the blood as it comes from the
heart, and thus prevent its too rapid distribution throughout the body.
The fact that the blood might have been going towards the heart, instead
of coming from it, seems never to have been considered seriously until
demonstrated so conclusively by Harvey.

Of this important and remarkable controversy over the valves in veins,
Withington has this to say: "This is truly a marvellous story. A great
Galenic anatomist is first to give a full and correct description of the
valves and their function, but fails to see that any modification of the
old view as to the motion of the blood is required. Two able dissectors
carefully test their action by experiment, and come to a result, the
exact reverse of the truth. Urged by them, the two foremost anatomists
of the age make a special search for valves and fail to find them.
Finally, passing over lesser peculiarities, an aged and honorable
professor, who has lived through all this, calmly asserts that no
anatomist, ancient or modern, has ever mentioned valves in veins till he
discovered them in 1574!"(2)

Among the anatomists who probably discovered these valves was Michael
Servetus (1511-1553); but if this is somewhat in doubt, it is certain
that he discovered and described the pulmonary circulation, and had
a very clear idea of the process of respiration as carried on in the
lungs. The description was contained in a famous document sent to Calvin
in 1545--a document which the reformer carefully kept for seven years
in order that he might make use of some of the heretical statements it
contained to accomplish his desire of bringing its writer to the stake.
The awful fate of Servetus, the interesting character of the man, and
the fact that he came so near to anticipating the discoveries of Harvey
make him one of the most interesting figures in medical history.

In this document which was sent to Calvin, Servetus rejected the
d