Harvey had no appreciation of how the arteries and veins communicated with each other.

Galen, you may remember, recognized that there were anastomoses, but Harvey preferred the idea of filtration.
The "De Motu Cordis" constitutes a unique piece of work in the history of medicine.

Nothing of the same type had appeared before.

It is a thoroughly sensible, scientific study of a definite problem, the solution of which was arrived at through the combination of accurate observation and ingenious experiment.

Much misunderstanding has arisen in connection with Harvey's discovery of the circulation of the blood.
He did not discover that the blood moved,--that was known to Aristotle and to Galen, from both of whom I have given quotations which indicate clearly that they knew of its movement,--but at the time of Harvey not a single anatomist had escaped from the domination of Galen's views.
Both Servetus and Colombo knew of the pulmonary circulation, which was described by the former in very accurate terms.