Published in 1628, On the Motion of the Heart and Blood was written by English physician William Harvey. In the treatise, Harvey introduces the doctrine of the circulatory system. He asserts that blood is pumped from the heart to the extremities, and then the blood returns from the extremities to the heart in a circular fashion.
His theory can be outlined as follows:
1) Blood enters the right ventricle of the heart from the right atrium.
2) Blood is pumped through the pulmonary artery to the lungs, where it is oxygenated.
3) Oxygenated blood travels through the pulmonary veins to the left atrium.
4) Oxygenated blood enters the left ventricle of the heart from the left atrium.
5) Oxygenated blood is pumped through the aorta and then through the arteries to the extremities of the body.
6) Deoxygenated blood travels through veins to the right atrium, where the cycle is repeated.
Arteries carry oxygenated blood away from the heart. Veins carry deoxygenated blood toward the heart.
Harvey’s methodology is just as important as his conclusion. He relies on countless observations, dissections, and vivisections to form his conclusion. In that sense, he would have made Francis Bacon proud.
“THE HEART of animals is the foundation of their life, the sovereign of everything within them, the sun of their microcosm, that upon which all growth depends, from which all power proceeds.”
“True philosophers, who are only eager for truth and knowledge, never regard themselves as already so thoroughly informed, but that they welcome further information from whomsoever and from wheresoever it may come.”
“All we know is still infinitely less than all that still remains unknown.”
“I found the task so truly arduous, so full of difficulties, that I was almost tempted to think, with Fracastorius, that the motion of the heart was only to be comprehended by God.”
“Experimenting with a pigeon upon one occasion, after the heart had wholly ceased to pulsate, and the auricles too had become motionless, I kept my finger wetted with saliva and warm for a short time upon the heart, and observed that under the influence of this fomentation it recovered new strength and life, so that both ventricles and auricles pulsated, contracting and relaxing alternately, recalled as it were from death to life.”
“Doctrine once sown strikes deep its root, and respect for antiquity influences all men.”
“It is absolutely necessary to conclude that the blood in the animal body is impelled in a circle, and is in a state of ceaseless motion; that this is the act or function which the heart performs by means of its pulse; and that it is the sole and only end of the motion and contraction of the heart.”