Antony van Leeuwenhoek (1632-1723)
http://www.ucmp.berkeley.edu/history/leeuwenhoek.html
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. . . my
work, which I've done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a
craving after knowledge, which I
notice resides in me more than in
most other men. And therewithal, whenever I found out anything remarkable, I
have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed
thereof.
Antony van
Leeuwenhoek. Letter of June 12, 1716
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Antony van
Leeuwenhoek was an unlikely scientist.
A tradesman of Delft, Holland, he
came from a family of tradesmen, had no fortune,
received no higher education or university
degrees, and knew no languages other than his native Dutch. This would have
been enough to exclude him from the scientific community of his time
completely. Yet with skill, diligence,
an endless curiosity, and an open mind, Leeuwenhoek succeeded in making some of
the most important discoveries in the history of biology. It was he who
discovered bacteria, free-living and parasitic microscopic protists, sperm cells,
blood cells, and much more. His researches,
which were widely circulated, opened up an entire
world of microscopic life to the awareness
of scientists.
Leeuwenhoek
was born in Delft on October 24, 1632. His father was a basket-maker, while his
mother's family were brewers. Antony
was educated as a child in a school in the town of Warmond, then lived with his
uncle at Benthuizen; in 1648 he was an apprentice
in a linen-draper's shop. Around 1654 he returned to Delft, where he spent the
rest of his life. He set himself up in business as a draper (a fabric merchant). And at some time before 1668, Antony van Leeuwenhoek
learned to grind lenses, made simple microscopes, and began observing with them. He seems to have
been inspired to take up microscopy by having seen a copy of Robert Hooke's
illustrated book Micrographia, which depicted Hooke's own observations with the microscope and
was very popular.
Leeuwenhoek
is known to have made over 500 "microscopes," of which fewer than ten
have survived to the present day. In basic design, probably all of
Leeuwenhoek's instruments -- certainly all the ones that are known -- were
simply powerful magnifying glasses,
not compound microscopes of the type
used today. Compared to modern microscopes, it is an extremely simple device, using only one lens, mounted in a tiny hole in the brass plate that makes up the body of
the instrument. The specimen was
mounted on the sharp point that sticks up in front of the lens, and its
position and focus could be adjusted by
turning the two screws. The entire
instrument was only 3-4 inches long,
and had to be held up close to the eye; it required
good lighting and great patience to
use.
Compound
microscopes (that is, microscopes using more than one lens) had been invented
around 1595, nearly forty years before Leeuwenhoek was born. Several of
Leeuwenhoek's predecessors and contemporaries, notably Robert Hooke in
England and Jan Swammerdam in the Netherlands, had built compound microscopes
and were making important discoveries with them. These were much more similar
to the microscopes in use today. Thus, although Leeuwenhoek is sometimes called
"the inventor of the microscope," he was no such thing.
However,
because of various technical difficulties in building them, early compound
microscopes were not practical for magnifying
objects more than about twenty or thirty times natural size. Leeuwenhoek's
skill at grinding lenses, together with his naturally acute eyesight and great care in adjusting the lighting where he
worked, enabled him to build microscopes that magnified over 200 times, with
clearer and brighter images than any of his colleagues could achieve. What further distinguished him was his curiosity to
observe almost anything that could be placed under his lenses, and his care in
describing what he saw. Although he himself could not draw well, he hired an illustrator to prepare drawings of the things he saw, to accompany his written descriptions. Most of his descriptions of
microorganisms are instantly recognizable.
In 1673,
Leeuwenhoek began writing letters to the newly-formed Royal Society of London,
describing what he had seen with his microscopes. For the next fifty years he
corresponded with the Royal Society; his letters, written in Dutch, were
translated into English or Latin.
On
September 17, 1683, for example, Leeuwenhoek wrote to the Royal Society about
his observations on the plaque
between his own teeth. He repeated these observations on two ladies (probably
his own wife and daughter), and on two old men who had never cleaned their
teeth in their lives. Looking at these
samples with his microscope, Leeuwenhoek reported how in his own mouth:
"I then most always saw, with great wonder, that in the said matter there were many very little
living animalcules, very prettily
a-moving. The biggest sort. . . had a very strong and swift motion, and shot through the water (or spittle) like a pike does through the water. The second sort. . . oft-times spun round like a top. . . and these were far more in number." In the mouth of
one of the old men, Leeuwenhoek found "an unbelievably great company of
living animalcules, a-swimming more nimbly
than any I had ever seen up to this time. . . Moreover, the other animalcules
were in such enormous numbers, that all the water. . . seemed to be
alive." These were among the first observations on living bacteria ever recorded.
Leeuwenhoek
looked at animal and plant tissues,
at mineral crystals and at fossils. He discovered blood cells, and was the
first to see living sperm cells of animals. The list of his discoveries goes on
and on. Leeuwenhoek soon became famous as his letters were published and
translated. In 1680 he was elected a
full member of the Royal Society. In 1698 he demonstrated circulation in the capillaries
of an eel to Tsar Peter the Great of
Russia, and he continued to receive visitors curious to see the strange things
he was describing. He continued his observations until the last days of his
life. He died on August 30, 1723.
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To Make a Van Leeuwenhoek Microscope Replica
http://www.mindspring.com/%7Ealshinn/Leeuwenhoekplans.html
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