Meet Leeuwenhoek, the 1st Man Ever To See Microbes
Travel back 4 centuries, to Delft and the unexpected first step of microbiology
If you are well-bathed in the probiotics world, read the stories of microbiology, or visited the Micropia museum in Amsterdam, of course, you’ve heard of Antoni Van Leeuwenhoek. But what do you really know about the man and his discoveries?
Meet the simple merchant who made history. Get acquainted with his utterly honest and naive look upon the Newfoundland of a microscopic world, and with his peculiar jealousy for his instruments.
Holland in the early 17th century, and Leeuwenhoek’s humble beginnings
Leeuwenhoek was born in Delft, Holland, in 1632. In these days, Europe had little respect for science and much respect for God. If you recovered from mumps as a child and asked your father about the cause of the disease, he would tell you “a mumpish evil spirit had got into you”. And you’d better not question Authority.
“It was a world where Servetus was burned to death for daring to cut up and examine the body of a dead man, where Galileo was shut up for life for daring to prove that the Earth moved around the sun.”
Antoni Van Leeuwenhoek was born to a respectable family of basket-makers and brewers. As a child, his mother sent him to school, so he could become a government official. But the boy gave up at 16 and started as an apprentice in a dry-goods store in Amsterdam. His education was in serving Dutch housewives and presenting the receipt. At age 21, he returned to Delft, got married, and opened his own dry-goods store. Soon after, he also became appointed janitor of the City Hall of Delft.
Leeuwenhoek was a simple man, speaking merely Dutch, and his only reading, as was the case of honest men like him, was his Dutch Bible.
“You will see that his ignorance was a great help to him, for, cut off from all the learned nonsense of his time, he had to trust to his own eyes, his own thoughts, his own judgment.”
The tipping point to greatness
Leeuwenhoek heard that looking through carefully ground lenses from clear glass makes things appear much bigger. These magnifying lenses, however “would hardly make a ten-cent piece look as large as a quarter”. And the man started cultivating a peculiar love for lenses. Curiosity led him to spectacle-makers, from whom he learned this art of lens-grinding. With alchemists and apothecaries, he learned to work silver and gold, and with patient perfectionism, with the “fanatical persistence of a lunatic” as De Kruif describes, he was soon crafting the best lens-mounting silversmithing of his time.
His neighbors and his children thought the fellow was a little crazy, but he didn’t think much of his neighbors.
Once his lenses were mounted, Leeuwenhoek set out to observe any and every minuscule object he could get a hold of. The scales of his skin, ox eyes from the butcher, hairs of sheep and beavers, wood, plants, seeds…
“He delicately dissected the head of a fly, he stuck its brain on the fine needle of his microscope” and revealed that the complex perfection of the human body was reproduced at the scale of much smaller beings.
Once he’d stuck a specimen at the right focal length, he would come back to observe it again and again. Objects of attention could stay up for months — and he crafted many more of his incredible microscopes — hundreds of them — to continue observing the rest of the world that was at its mercy. Every one of these was, according to Molyneux, a thousand times better than the best available in the whole UK and Holland together.
Leeuwenhoek looked, from all possible angles, at countless objects of nature. Insects, crystals, grains of sand, and all matter inspired his awe at the beauty and perfection of the microscopic universe. For innumerable hours he squinted and squinched, solitary, and “worked for 20 years that way, without an audience”.
In parallel, a scientific revolution was rumbling in the undergrounds of England. Educated, independent rebels rejected the established authority from ancient Greece and from the Pope. They started to test the fads no one had ever contested. From a secret society, they now formed the official Royal Society of England and included no less than Robert Boyle and Isaac Newton. And this group was Leeuwenhoek’s first audience. Regnier de Graaf, a member of this society, peeked through Leeuwenhoek’s lenses, and urged the noblemen of science: “Get Antoni Leeuwenhoek to write you telling of his discoveries.” This is how Leeuwenhoek’s detailed letters, containing as much gossip about his ignorant neighbors and his own health, as detailed descriptions of his visions, under titles such as “A Specimen of some Observations made by a Microscope contrived by Mr. Leeuwenhoek, concerning Mould upon the Skin, Flesh, etc.; the Sting of a Bee, etc.” Over the next 50 years, this was followed by a correspondence of hundreds of such letters — immortalizing the janitor and merchant’s magic discoveries.
The major discovery
Until one day, his open-minded curiosity turned his lens on a fraction of a drop of clear rainwater. Who could have expected to see anything more in water than water? His daughter Maria, who was devoted to her father, must have thought he was losing his mind… And all of a sudden came his exclamation:
“Come here! Hurry! There are little animals in this rainwater… They swim! They play around! They are a thousand times smaller than any creatures we can see with our eyes alone… Look! See what I have discovered!” — Leeuwenhoek.
It was at this moment that the janitor of Delft opened the door to “a fantastic sub-visible world of little things, creatures that had lived, had bred, had battled, had died, completely hidden from and unknown to all men from the beginning of time.” His excitement was infinite. But he needed to be sure. He looked, and looked again, he found several kinds — some bigger, some smaller, some swimming around like fish. He wrote:
“They stop, they stand still as ‘twere upon a point, and then turn themselves round with that swiftness, as we see a top turn round, the circumference they make being no bigger than that of a fine grain of sand.”
And he calculated, with fiendish precision, the size of these little creatures — taking reference from the previous wee beasts he’d studied.
“This last kind of animal is a thousand times smaller than the eye of a large louse”
and he couldn’t have been more accurate.
He checked water from different sources and found them, again and again. He set to write to the Royal Society, his astonishment displayed neatly on long pages of fine handwriting.
“You could put a million of these little animals into a coarse grain of sand and that one drop of pepper-water, where they grew and multiplied so well, held more than two-million seven-hundred-thousand of them…”
He explained his calculations, and when the dumbfounded and dubious men wanted proof, he showed them the real deal through his lenses — but never would he tell them how he made his microscopes. “This was a suspicious man! He held his little machines up for people to look through, but let them so much as touch the microscope to help themselves to see better and he might order them out of his house… He was like a child anxious and proud to show a large red apple to his playmates but loth to let them touch it for fear they might take a bite out of it.”
Doctor Molyneux, who was asked to make a report on these findings, offered a generous price for one of the microscopes — and was sure he could spare one of the few hundreds lined in his study. But the Dutchman would not consider it.
The Royal Society made Leeuwenhoek a Fellow, sending him a beautiful Diploma of Membership in a precious silver case. Leeuwenhoek promised to serve the companionship for the rest of his life — and he did, continuing to report on his observations until his death, at the age of 91.
More discoveries for posterity
In the subsequent years, with undying curiosity, Leeuwenhoek redoubled his imagination to come across new subjects. He scrubbed the white stuff between his teeth and found a world of moving animalcules. He found them in the intestines of frogs and horses, and even in his own excretions — they were especially numerous when “he was troubled with a looseness”. In the tail of a little fish, he discovered capillaries. He observed mussels being gobbled up by microbes. He even discovered the human sperm through these lenses.
One day as he looked again at the white stuff between his teeth, he was shocked to find no living creatures — but numerous apparently dead ones, immobile in the liquid. Startled, he hoped the great Lords of the Royal Society would not contradict his findings with similar experiences. He realized that he’d been drinking coffee — so hot that it almost caused his lips to blister. The back teeth still had living creatures, but the front ones, that touched the liquid, presented dead or dying ones. Wondering if the heat had killed the animalcules, he tested heating water in tiny tubes — and observed the animals stopped their running to and fro. As the water cooled down, they didn’t restart moving. It’d been the hot coffee that had killed the wee beasts!
In 1723 when he was on his deathbed, he sent for his friend to translate his last observations to Latin and send them to the Royal Society — but he never accepted to transmit the exceptional know-how of his lenses.
This was the story of the first Microbe Hunter, and an inspiring lesson of curiosity, common sense, accuracy, and an uninhibited sense of honesty that allowed him to observe and report beyond any complex or disgust — in search of nothing more than the truthful fact. His life radiates gorgeous, unconditional awe and love for all creation.
The details and quotes are from the 1926 book Microbe Hunters, by Paul De Kruif, who retraces the discoveries and characters that made the beginnings of Microbiology. De Kruif is a fantastic storyteller who learned the intimacy of those early scientists — if you like this chronicle, I recommend you read the whole book! Or follow me to see more stories about the great names of Microbiology.
