its beating heart. Placing it on his dissection table, the heart continued to
throb, and even when he cut it into smaller segments, each piece
contracted. Completely convinced that the heart was indeed a muscle
whose active phase was contraction, Harvey was well on his way to
solving one of life’s great mysteries.
Over the course of many years, William Harvey conducted countless
experiments on animals, often turning to dogs. By modern standards, it is
cruel and defenseless how hundreds of animals died without any
consideration for their sensations or consciousness. In fact, it is daunting
and troubling to review Harvey’s vivisection experiments, no matter how
important were the discoveries. In the 17th century, bearbaiting,
cockfighting, and public animal cruelty were commonplace, and it wasn’t
until 1835 that the English Cruelty to Animals Act was passed. Until that
point, most Englishmen viewed animals as incapable of feeling pain, and
they felt as emotionally conflicted about a dog dying a tortured death as
most of us feel about swatting a mosquito today.
Harvey’s many experiments were convincing him about the flow of
blood in and around the heart, but he was still confounded over the genesis
of blood and where it vanished. In a truly great moment for science,
Harvey realized that some sort of calculation was necessary to investigate
the function of the heart. With astronomy, physics, mathematics, and
biology in their infancy, Harvey pioneered an entirely new branch of
science.
Concluding that the active phase of the heart was systole (Greek,
“contraction”), Harvey realized he could estimate the amount of blood that
was pumping through the heart. In retrospect, his calculations were very
conservative, but his results led him to the proper conclusion. Harvey
guessed that the heart was not able to fully squeeze all the blood out of its
chambers with each contraction, so he calculated that only a fraction of the
full diastolic (or relaxed) volume was ejected with each contraction; he
estimated that amount to be no less than a dram weight of fluid (one-
eighth of an ounce), a vast, but safe, underestimate.
Estimating that the heart beats at least thirty times a minute, and
multiplying that times sixty minutes an hour and twenty-four hours a day,
a (very conservative) dram in weight of blood ejected with each
contraction would mean that a massive 50,000 drams of blood was
pulsated into the arteries each day. If that massive amount of blood was
marcin
(Marcin)
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