Science.
The discoveries of Leeuwenhoek
Bernard Dixon
This week sees the 250th anniversary of the death of Antony van Leeuwenhoek, one of the remarkable and talented (yet curiously unsung) figures in the entire history of biological science. Born in Delft on October 24, 1632, he was apprenticed at the age of sixteen to a linen-draper in Amsterdam and continued in that trade for the rest of his life. By all accounts he was a modest man. Yet it was Leeuwenhoek who, in hie spare moments, constructed microscopes of exceptional clarity and used them to reveal for the first time the world of what he termed " animalcules " — protozoa and other microbes. His work thus ended centuries of specula
tion about unseen forms of life, and set the stage for the later achievements of Louis Pasteur and the other pioneer microbiologists.
Has it not been for the efforts of his friend Reinier de Graaf, the physiologist, who introduced Leeuwenhoek to the Secretary of the Royal Society in London, the Dutchman's researches may well have remained in obscurity. "I have oft-times been besought, by divers gentlemen, to set down on paper what I have beheld through my newly invented Microscopia," he wrote to the Royal Society in 1673," but I have generally declined; first because I have no style, or pen, wherewith to express my thoughts properly; secondly, because I have not been brought up to languages or arts, but only to business; and in the third place, because I do not gladly suffer contradiction or censure from others." Seeing, however, that his "observations did not displease the Royal Society," Leeuwenhoek was persuaded to begin sending a series of detailed reports of his work to the Secretary. Some 120 extracts from these were published between then and his death in 1723, providing a vivid record of a lifetime of scrupulous and at times obsessional research.
Leeuwenhoek became a compulsive scrutiniser and recorder, putting all manner of materials under his microscopes. He examined blood from various animals, plant cells, dung, and infusions of hay and other substances. He took scrapings from his friends' teeth and sketched the microorganisms he found in them. He discovered spermatoza in dogs and other animals, and peered too at specimens of his own semen (an investigation ommitted, on grounds of decency, from one nineteenth century account of Leeuwenhoek's work). As a result of this wholesale microscopy — undertaken while running his draper's business and serving as Chamberlain to the Sheriffs of Delft — Leeuwenhoek described numerous previously unknown forms of life, which he recorded with both accuracy and affection in his long series of letters.
To the modern mind, many of his investigations seem crazy and some of them positively dangerous. His discovery of bacteria, for example, came when he was peering at macerated peppercorns in an attempt to learn why pepper was hot. And Leeuwenhoek must still be the only man who has watched the explosion of gunpowder under the microscope — almost blinding himself in the process. Yet it was this insatiable curiosity that led him into pioneering studies in half a dozen different branches of science. In most of these fields he was, to an absurd degree, ahead of his time — certainly in microbiology, which had to wait over a century for its further development.
To this day, one great mystery surrounds Leeuwenhoek's work — how he actually used his microscopes to achieve such excellent results. When he died, Leeuwenhoek left 247 finished microscopes and 172 lenses, from which it was
possible to learn that his fine skill in lens grinding was an important factor in his success. But there must have been more to it than that. Did Leeuwenhoek, who always kept secret his "method for seeing the smallest animalcules," discover the modern technique known as dark ground illumination? Or did he devise some other sophisticated method? Microscopists still argue and speculate about this — which is probably exactly what the quiet Dutchman hoped for.
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