When a 17th-century Dutch draper told London’s finest minds he had seen “animalcules” through his home-made microscope, they took some convincing
EARLY in the autumn of 1674, Henry Oldenburg, secretary of the Royal Society in London, received an extraordinary letter. Sent by (pictured, left), a draper from Delft in the Netherlands, it contained an unlikely-sounding claim.
Using a microscope of his own invention, van Leeuwenhoek had seen tiny creatures, invisible to the naked eye, living in lake water. Some of these “animalcules” were so small, he later estimated, that 30 million of them would still be smaller than a grain of sand.
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Royal Society fellows were sceptical. Even with his most powerful instruments, the celebrated English microscopist Robert Hooke had never observed anything like the little creatures.
In fact, the Dutchman had developed far superior lenses to Hooke’s, and had discovered bacteria and protozoans. By producing ever smaller and more curved lenses – using a technique that he kept secret – van Leeuwenhoek was able to magnify objects up to 500 times. As well as discovering micro-organisms, he was the first to see red blood cells.
In 1677, van Leeuwenhoek sent the Society further animalcule observations. Hooke eventually improved his own microscopes to the point where he, too, could see the tiny creatures. Three years later van Leeuwenhoek was made a fellow.
It was not until 1890, more than 160 years after van Leeuwenhoek’s death, that bacteria were linked with disease. “Reading van Leeuwenhoek’s letters, you very much get the impression of somebody dazzled by what he was finding,” says Lesley Robertson, curator of the archives at Delft University’s school of microbiology. “He thought he’d found a whole new world – but he certainly never picked up on the connection with illness.”
Read more: Zeros to heroes: 10 unlikely ideas that changed the world
In the version of this article printed in New Scientist magazine, Lesley Robertson’s name is spelled incorrectly
