Antonie van Leeuwenhoek

By Lin Yue

He never went to university, never wrote in Latin, never left Delft — and he discovered an entire universe. Antonie van Leeuwenhoek, born in 1632, was a draper: a cloth merchant who used magnifying glasses to inspect the weave of fabric. Dissatisfied with the lenses he could buy, he taught himself to grind them, and then to make them — tiny spheres of glass, some barely a millimeter across, mounted in brass plates that he held to his eye. His single-lens microscopes magnified up to 270 times, better than anything the great compound microscopes of the Royal Society could manage, and he guarded his lens-making secrets to the grave.

What he did with them, beginning in the 1670s, no human had ever done: he looked at the small. In 1674 he found single-celled organisms in lake water — the infusoria. In 1676 he wrote to the Royal Society of London describing animalcules in pepper water, creatures smaller than anything known to live; the fellows were incredulous until Robert Hooke confirmed them. He discovered bacteria — the first human being to see them — in 1676, and found them swarming in his own dental plaque in 1683, making the first drawings of microbes from the human body. He observed red blood cells, spermatozoa (though he misread their role), the structure of muscle fiber, the circulation in a fish's tail fin.

The Royal Society made him a fellow in 1680 — the Delft draper among the gentlemen of science — and for fifty years he sent them letters in Dutch, patiently describing the invisible world. He worked alone, without students, without a theory to prove; his only doctrine was to look again. He died in 1723 at ninety, still grinding lenses. Two centuries would pass before Pasteur and Koch understood what his animalcules meant — that the invisible world rules the visible one, for good and ill. Leeuwenhoek saw it first, through a bead of glass held to a draper's eye.

Impact on civilization

Leeuwenhoek founded microbiology by revealing that living things exist at scales invisible to the naked eye — bacteria, protozoa, blood cells, spermatozoa — a discovery that doubled the known living world overnight. His single-lens microscopes, superior to anything of their age, set the standard for observational technique, and his fifty years of letters to the Royal Society created the model of the patient, theory-free observer. Without his animalcules there is no germ theory, no Pasteur, no modern medicine: he mapped the continent that bacteriology would later conquer.