Source: Getty Images
All we know is still infinitely less than all that remains unknown.
William Harvey was an English physician who was the first to describe accurately the circulation of blood. He was a doctor to two kings of England, James I and then his son Charles I.
He was inspired by Aristotle. Same as Aristotle, Harvey also believed several things: First, the different organs in each organism adopt a specific shape for functions; Second, every piece of structure found in organisms has a specific function. Apart from these two, Aristotle was very into the research of the heart (he cracked the eggs and observed the tiny speck of blood pulsating), and this convinced William Harvey.
Harvey was fascinated by blood and the heart. He wanted to understand the ‘motions’ of the heart, that is, what exactly happens in each heartbeat. By dissection, he discovered the fact that the presence of valves prevent back flow of the blood. One of his experiments was to place a tight bandage around an arm. If he tightened it, no blood can get into the arm at all, so the hand became very pale; if he loosened it a bit, the hand became very red, because the blood can enter the arm but can not return back into the heart.
Illustrations of Harvey’s experiments from De Motu Cordis, 1628
Source: Royal College of Physicians
Moreover, he studied so many hearts and realised there would not be enough blood in the entire body if new blood is pumped at each heartbeat. Therefore, he found out the blood goes from the heart to the body and return back to the heart to begin a new cycle of ‘circulation’. “I began privately to consider that the blood had a movement, as it were, in a circle.” He wrote these words in a book called De motu cordis.
William Harvey discusses his theory of blood circulation with King Charles I
Source: famousscientists.org
He was also the first one to suggest that human beings and other mammals reproduce via fertilisation of the egg by sperm. It was two centuries later when mammalian egg cells was first observed.
“I have often wondered and even laughed at those who fancied that everything had been so consummately and absolutely investigated by an Aristotle or a Galen or some other mighty name, that nothing could by any possibility be added to their knowledge.”
Acknowledgements:
- William Bynum, A Little History of Science, New York: Yale University Press, 2013. pp.69-73
- William Harvey, BBC. http://www.bbc.co.uk/history/historic_figures/harvey_william.shtml
- William Harvey, Famous Scientists. https://www.famousscientists.org/william-harvey/
- Ceaseless motion: William Harvey’s experimentations in circulation, Royal College of Physicians. https://history.rcplondon.ac.uk/exhibitions/past-exhibitions/ceaseless-motion-experimentations-circulation
