30 Bacteria
Van Leeuwenhoek started his microscopic studies with objects he could mount on the
point of a pin—a bee’s mouth parts, fleas, human hairs, etc. He described and drew what he
saw in precise detail. By 1674 he had developed the ability to focus on a flat dish and turned
his attention to liquids—water drops, blood cells, etc.
Those 1674 studies were where he made his great discovery. He discovered a host of
microscopic protozoa (bacteria) in every water drop. He had discovered microscopic life,
invisible to the human eye.
Van Leeuwenhoek expanded his search for these unseeably small creatures and found
them everywhere: on human eyelashes, on fleas, in dust, and on skin. He drew and described these tiny creatures with excellent, precise drawings.
Each drawing often took days to complete. As an amateur, Van Leeuwenhoek had to
work at his science in the evenings and early morning hours when not at work. Embarrassed
by his lack of language skills and by his poor spelling (even in Dutch), van Leeuwenhoek
felt hesitant to publish any articles about his wondrous findings.
Beginning in 1676, he agreed to send letters and drawings to the Royal Society of London. They had them translated into English. That extensive collection of letters (written and
collected over many decades) formed the first and best map of the microscopic world. What
van Leeuwenhoek ob served shat tered many scientific beliefs of the day and put him
decades—if not centuries—ahead of other researchers.
He was the first to claim that bacteria cause infection and disease. (No one else believed it until Pasteur proved it in 1856.) Van Leeuwenhoek saw that vinegar killed bacteria
and said that it would clean wounds. Again, it was two centuries before his belief became
standard medical practice.
It was also 200 years before anyone built a better microscope. But with his marvelous
microscope, van Leeuwenhoek discovered the critically important microscopic world.
Fun Facts: In 1999 scientists discovered the largest bacterium ever. The
organism can grow to as large as .75 mm across—about the size of the
period at the end of this sentence. The newfound bacterium is 100 times
larger than the previous record holder. For comparison, if the newly discovered bacterium was the size of a blue whale, the average bacterium
would be the size of a newborn mouse.
More to Explore
Dobell, Clifford. Anthony van Leeuwenhoek and His “Little Animals.” New York:
Dover, 1990.
Ralston, Alma. The Cleere Observer: A Biography of Antony van Leeuwenhoek. New
York: Macmillan, 1996.
Ruestow, E. The Microscope in the Dutch Republic: The Shaping of Discovery. New
York: Cambridge University Press, 1996.
Schierbeek, A. Measuring the Invisible World: The Life and Works of Anthony van
Leeuwenhoek. London: Abelard-Schuman, 1999.
Yount, Lisa. Antony van Leeuwenhoek: First to See Microscopic Life. Beecher, IL:
Sagebrush, 2001.