One night in 1677, a grizzled man in a wrinkled linen nightshirt rushed from his bemused wife's bed with a candle in hand to examine the “remains of conjugal coitus, immediately after ejaculation before six beats of the pulse.” Using the candle to cast a pool of light in his dark study, he put a drop of the liquid into a tiny glass vial he had blown himself, attaching it to the back of a strange-looking device he had also constructed. Two rectangular brass plates, about three inches tall and one inch wide, had been riveted together and held a tiny glass orb between them. He lifted this object up into the light of the candle, closed one eye, and watched, for hours, until finally: a shiver of movement at the edge of his vision. Was it merely a mirage? Were his eyes too tired? He blinked, looked away from the light to rest them, and then resumed his careful observation. He was soon rewarded with the sight of a swarm of tiny eellike creatures wriggling into view. Antoni van Leeuwenhoek—who died 300 years ago, on August 26, 1723—had just discovered spermatozoa.
It was not the first time that he had made the invisible visible, nor would it be the last. Leeuwenhoek was a pioneer, discovering a whole realm of living creatures that included bacteria and other “germs”—“little anianimals,” he affectionately called them. By doing so, he made us aware that the world contains more than meets the eye, and his crucial contributions to the field of microbiology remain as relevant as ever.
Laura J. Snyder is the author, most recently, of The Philosophical Breakfast Club: Four Remarkable Friends Who Transformed Science and Changed the World and Eye of the Beholder: Johannes Vermeer, Antoni van Leeuwenhoek, and the Reinvention of Seeing. She is at work on a biography of Oliver Sacks, for which she has been awarded a Public Scholars Grant from the National Endowment for the Humanities.
During these past three years of the Covid-19 pandemic, which has caused at least seven million deaths worldwide (more than one million in the United States alone) and which, according to the U.S. Centers for Disease Control and Prevention, has left one in 13 adults, or 19 million people in our country, with the disabling conditions caused by long Covid, my thoughts have returned often to Leeuwenhoek's discoveries and what came after. As we carry on through these interminable Covid days (and ready ourselves for epidemics and pandemics to come), we should understand and celebrate the person who made it possible to discover the invisible causes of—and possible cures for—so many of the illnesses that plague us.
If stronger lenses could be used to extend sight into the far reaches of the universe, could they not be used to enlarge the very small parts of it?
Baptized as Thonis—but always called Antonij or Antoni—he was born in Delft, Holland, in 1632, the same week as his neighbor Johannes Vermeer. His family took the surname “Leeuwenhoek” for the location of its home, “The Lion's Corner.” Only after he had achieved worldwide fame in the 1680s did he add the aristocratic-sounding “van” to his name.
Leeuwenhoek was not an obvious candidate for upending the received view of the universe. The son of a basket weaver, he had no schooling beyond reading, writing, and some arithmetic, and he was expected to follow in his father's profession— an important one in Delft, where a thriving export business required wellmade baskets for overseas transport. But when his widowed mother remarried, he was sent to Amsterdam and eventually became apprenticed to a cloth merchant. In those days, a clever haberdasher, needing to determine the fineness of the fabric being offered to him, would
