William Harvey (continued)
Harvey came along during the Renaissance, the "age of enlightenment" when thoughtful people began to challenge old myths and to explore new ways of looking at things. This fresh approach applied to medicine as well as to art and literature. The ancient belief about what the heart did was challenged by Harvey and he devised clever ways to determine what the heart really did and how blood circulates.
In those days, medical professionals recognized that there was arterial and venous blood, but they had some primitive ideas otherwise. For example, they thought that blood originated from three places. The liver provided blood for nourishment and growth, the heart provided blood for life itself, and the brain provided blood for sensation and reason. Arterial blood was thought to be "used up," never returning to its source. These medicine men had the bizarre notion that the heart did not pump blood, but rather sucked it in like a vacuum when the heart relaxed in between contractions. Movement along the vessels was thought to result from contractions of the arteries! They did know that it took air (actually oxygen) to make arterial blood, but they thought the air was transported by the pulmonary veins into the heart. So, you can see how hard it would be to convince such people of our modern notions of blood circulation. That was the challenge that Harvey faced when he finally figured out the truth and published it in 1628.
Some anatomists in that era helped lay the groundwork for acceptance of Harvey's ideas. Most notable was Vesalius, who showed that the two sides of the heart were separated. Realdo Colombo worked out the connections with the lung and performed experiments showing that pumping of blood occurred when the heart contracted.
Harvey performed actual experiments on animals, first on frogs because their hearts were simpler. He noticed that so much blood left the heart in one minute that there was no way it could continually be absorbed by the body and re-made. His calculations proved that the amount of blood pumped out of the body far exceeded the total amount of blood in the body. Thus, blood HAD to circulate!
Of course, Harvey could not prove by direct observation how circulation continued through the organs in capillaries. But his experiments proved that there had to be very small connections between the arterial side and the venous side of an organ. One of his most famous experiments was in the human, where he put a tourniquet around the forearm. At first, the arm was tied so tight that arterial blood could not enter. The veins looked normal. When the tie was loosened enough to let arterial blood in toward the hand, yet the surface veins were still closed, the veins became swollen, showing that blood had poured into the hand and then moved back up in veins. Harvey also showed that the valves inside of veins were oriented so that they always directed blood back toward the heart.
Harvey published his findings in Latin in a book entitled "An Anatomical Exercise Concerning the Motion of the Heart and Blood in Animals." All learned books in that day were published in Latin. This one, interestingly, was published in Germany, not England (where he was from). In his own words, here is what Harvey gave as the reason for writing the book, "These views as usual, pleased some more, others less; some chide and calumniated me, and laid it to me as a crime that I had dared to depart from the precepts and opinions of all anatomists; others desired further explanations of the novelties, which they said were both worthy of consideration, and might perchance be found of signal use."
The book was an immediate sensation, because it so effectively challenged views that had dated back to the days of Aristotle.
Many people do not realize that Harvey was also a pioneer in reproductive science. He argued that humans and other mammals develop from the eggs of females that have been fertilized by sperm from males. Mammalian eggs had never been seen and it was 200 years later that they were. Harvey's line of thinking was so persuasive that this idea was immediately accepted, although no proof could be demonstrated at that time.
Harvey became a very wealthy man. Not only was his medical practice enormously successful, but he profited from the advice he got from his brothers, who were successful merchants. He gave a building and library to the College of Physicians. But his original manuscripts were destroyed when the building burned down in the Great Fire of London in 1666. Toward the end of his life, Harvey became a political outcast, because the King he served so loyally, Charles I, had been executed in a civil war.
Harvey was also troubled by his enemies in the medical community. Some physicians in that day had difficulty accepting that they had been wrong. Harvey's discoveries would require them to abandon long-held views and practices or require them to construct new justification for practices that they could not give up, such as blood-letting. These people considered Harvey to be a "crack pot," and they tried to ruin his reputation. His medical practice did suffer.
Harvey did not bother to argue the matter, although he did write one rebuttal to a particularly obnoxious critic. Harvey let his observations and clear thinking stand on their own merit. Harvey prevailed, even in his own time.