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In the year 1675, I discovered very small living creatures in rain water,
which had stood but few days in a new earthen pot glazed blue within.
Those are the famous words that Antony Van Leeuwenhoek used
to describe microbes. Though he didn’t use the word “microbe”--he called them animalcules--and
the letter itself is not exactly the one he wrote. Leeuwenhoek’s version was written,
of course, in Dutch and then sent off to Henry Oldenburg, the secretary of the Royal
Society in London who founded the publication Philosophical Transactions. Oldenberg translated
Leeuwenhoek’s work into English and published it in 1677. The rest, as they say, is microbiology.
In 1932, the scientist Clifford Dobell published a biography of Leeuwenhoek
called “Antony van Leeuwenhoek and his “Little animals,”. Dobell introduces his
subject with some self-consciousness for taking on the story of someone who--if
you’ve been interested in microscopy--you have almost certainly heard of. And he wrote:
Dear reader: I know full well that you and everyone else must have met Mr van
Leeuwenhoek many a time before; but please let me reintroduce him to you, for he is a man
worth knowing more intimately. Though he was born exactly 300 years ago he is still very much alive,
and would be glad to make your better acquaintance—provided only that you are
a “true lover of learning” (as of course you are). The fascination with Leeunwenhoek’s
work for Dobell and so many of us lies in the scope of Leeuwenhoek’s curiosity,
and in the writing that documented his many journeys into the microcosmos.
Born in the Netherlands in 1632, Leeuwenhoek was a draper by trade, meaning that he sold cloth. He
took up microscopy as a hobby, learning to grind lenses and turn them into a tool to see into
tiny worlds. The simple microscopes he built were better than many of those of his contemporaries,
producing images that were both more magnified and more clear. Those of course compared to what the
average high school biology class has today, they were very bad at both of those things.
The creatures Leeuwenhoek described in his 1677 publication were not his
first description of tiny animals in water though. In 1674, he wrote of “green streaks,
spirally wound,” a description that later observers have taken to refer to
the filamentous green algae spirogyra. He also wrote of little creatures he’d found that were,
as he described them, “a thousand times smaller than the smallest ones I have ever yet seen
upon the rind of cheese.” Those little cheese rind creatures he was describing were likely mites.
Reading Leeuwenhoek’s work is kind of like following an old treasure map. His words
lay out pathways and clues that help us navigate through a drop of 17th century water. And if you
follow that map, at the end you find a wealth of information, the knowledge of microbes and their
identities that was still unknown in his time, but that in the centuries since has been accumulated.
For Dobell, Leeuwenhoek’s 20th century scientist biographer, this treasure hunt was a long one,
borne out of his own enchantment with these original discoveries and a desire
to better understand them. He learned Dutch, only to find that the 17th century Dutch of
Leeuwenhoek’s letters was impenetrable to him And with World War I raging around him,
he had to set aside his attempts to translate Leeuwenhoek’s work for some time.
But eventually, through what seems to be largely a lot of determination, Dobell was able to work his
way through Leeuwenhoek’s letters. And that labor of love led, naturally, to translating things like
Leeuwenhoek’s descriptions of his own poop. Per Dobell, Leeuwenhoek wrote the following:
I have usually of a morning a well-formed stool;
but hitherto I have had sometimes a looseness of the bowels. […] My excrement being so thin,
I was at divers times constrained to examine it. But Leeuwenhoek wasn’t documenting his stool just
for the sake of it. In that sample, he saw an opportunity to observe the animals within.
I have at times seen very prettily moving animalcules […] Their bodies were somewhat
longer than broad, and their belly, which was flattened, provided with several feet, with
which they made such a movement through the clear medium and the globules that we might fancy we saw
a pissabed running up against a wall. That description sounds promising,
but Dobell had a problem. Leeuwenhoek had compared his microbes to a “pissabed,” and like us,
Dobell had no idea what a “pissabed” is. Even the original English translation he’d
read shrugged it off as a Dutch term with no obvious English equivalent. Dobell had
to find a 17th century Dutch-English dictionary to figure out that a “pissabed” is a woodlouse.
With that reference point, Dobell had enough to diagnose Leeuwenhoek—very belatedly,
of course—with Giardia, the product of a flagellate known as Giardia intestinalis.
At the time that Leeuwenhoek was identifying the microbial residents of his stool,
he almost certainly didn’t know their role in his poor digestion. Nor did he of course have
any name for them, or any of the other microbes that we now know he saw. And yet we can identify
rotifers from his characterization of their wheeled heads, and vorticella
from his description of their belled bodies. The irony of our centuries-later fascination
with reconstructing and replicating Leeuwenhoek’s work is that his contemporaries had a much harder
time of it. Leeuwenhoek didn’t help his cause much, refusing to provide extensive
details of his methods and even keeping his microscope-building techniques to himself.
He did, however, provide eight signed testimonies from various men, including a minister,
to verify that he had made these observations. Of course, signed testimony is one thing.
Reproducibility is another. Several of Leeuwenhoek’s contemporaries tried and failed
to replicate his observations until finally Robert Hooke—the famed microscopist and
writer-slash-illustrator of Micrographia—was able to see the tiny animalcules Leeuwenhoek had seen.
Hooke however was willing to outline his specific methods and demonstrate them, validating the
observations Leeuwenhoek had made and providing others with the means to make their own microbial
ventures. And like Dobell centuries later, Hooke was reportedly so taken with Leeuwenhoek’s
work that he learned Dutch to read his letters. The legacy of Leeuwenhoek is in the microbes he
uncovered, but of course it was more than that. It was also the curiosity that he passed on,
and the acts of interpretation that they inspired—both literally with all of these
scientists taking up Dutch to just learn from his letters, and then scientifically as we decipher
what microbes he must have seen. And so it seems fitting to close
with how Leeuwenhoek viewed his own little animalcules. He said,
“Among all the marvels that I have discovered in nature, these are the most marvelous of all.”
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
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