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Monika S. Sanchez
Math 1332
Instructor Simpson
30 June 2003
Simple Arithmetic Proves Convincing: William Harvey’s Great Discovery
William Harvey (1578-1657) was a famous English physician whose greatest discovery
was the circulation of blood. Human physiology fascinated Harvey, especially how blood
flowed through the human body. He based his theory of blood circulation on first-hand
observations utilizing the dissection of humans and animals. His work became the basis for
modern research of the heart and blood vessels.
Harvey described the blood flow through the body as single directional. He concluded
that the heart acts as a pump sending blood through the body in a closed circuit of vessels. The
heart pumps blood through an artery to the lungs where the blood picks up oxygen then flows
through a vein back to the heart. Then, the heart pumps oxygenated blood from the left side (of
the heart) to the arteries through the body, flowing to the veins, then up to the right side of the
heart.
Harvey made his discovery using simple arithmetic. Using dissections, Harvey noted that
the left ventricle held more than two ounces of blood. He counted the heartbeats in a living
specimen, and estimated the pulse rate to be 33 to 34 beats per minute (a low estimate), which
means the heart beats about 2,000 times per hour ( 33.5  60  2,010 ). He argued that even if the
left ventricle ejects only one-fourth of its contents with each beat, then in one hour the heart will
have pumped 1,000 ounces of blood ( 14  2  2,000  1,000 ), which is about 60 pounds (Marcus
70). This means the heart pumps a person’s weight in blood every few hours, so Harvey reasoned
that the blood must be circulating; otherwise, there is no way to account for the large quantities
of blood pumped by the heart.
Today it is common knowledge that the average pulse rate is sixty to eighty beats per
minute. We also know that the ejection factor is three ounces from the left ventricle, rather than
the a quarter of two ounces quoted by Harvey. However, even with his grossly underestimated
numbers, Harvey’s theory proved valid. “Each half hour the heart pumps far more blood than
the total weight of blood in the entire body” (Marcus 70).
Harvey’s greatest discovery regarding the circulation of blood has brought better
understanding of the workings of the body. Through his meticulous research, he was able to
reach a conclusion that continues to be valid three and a half centuries later. His theory
regarding the flow of blood from the heart through the vessels and back again is accurate to this
day. Even though his exact calculations were inaccurate, the total amount of blood pumped
through the heart greatly exceeds the total weight of the blood in the body. His published theory
is essentially the theory used by medical students today.
Works Consulted
Ward, Joseph J. Mysteries of the Human Body. Virginia: Time-Life Books Inc., 1990.
“Harvey, William” The World Book Encyclopedia. Vol. 9. Chicago: Scott Fetzer Company,
2001. 143-144.
Marcus, Rebecca B. William Harvey: Trailblazer of Scientific Medicine. New York: Franklin
Watts Inc., 1962.