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William Harvey
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Class
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William Harvey was an English doctor who lived from 1578 to
1657. He made the real breakthrough in our understanding of
the circulatory system. Harvey made careful observations of the
heart and blood vessels and came up with theories as to how
they worked. He made predictions and carried out experiments
to test the predictions. He would only say something was a fact
if he could prove it in his experiments and he was not put off
by superstitions, as previous scientists had been. He discovered
that blood was pumped from the heart around the body, then
returned to the heart to be re-circulated. He also carried out
experiments to prove that there are valves in veins that allow
blood to flow in one direction only.
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B
b
At the time, microscopes were not generally available so Harvey
never discovered how the arteries and veins were connected –
the capillaries were too small to be seen. However, he predicted
that capillaries must exist and they were later found by Marcello
Malpighi (1628–1694).
1 Underline the sentence that best explains why Harvey’s theories were more likely to be
correct than those of previous scientists.
2 Put a wavy line underneath two of Harvey’s discoveries about the circulation.
3 Complete these sentences.
Harvey found valves inside
. He proved that they allowed
direction only.
to flow in
4 a What other prediction did Harvey use his theory to make? Circle it in the text.
b Why didn’t Harvey discover how arteries and veins are connected? Draw a box around
the answer in the text.
5 What are the tiny blood vessels that connect arteries and veins called?
I CAN...
• explain that scientific theories are based on observations
• recall that theories make predictions
• describe what the circulatory system is and what it does.
Exploring Science
M02_EXSC_CM_Y8GBR_2506_UB.indd 69
edition
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© Pearson Education Limited 2008
21/8/08 12:12:30