A Delft cloth merchant found microbes and hid how he did it
Antonie van Leeuwenhoek sold linen and ribbon in Delft and wanted a better look at his thread. His homemade lenses revealed bacteria, sperm cells and red blood cells, yet he guarded his lens-making secret so closely that it took a 2021 neutron scan of his microscopes to confirm how they were made.
Born in Delft on 24 October 1632, Van Leeuwenhoek lost his father, a basket maker, at five and his stepfather around ten. At 16 he apprenticed as a bookkeeper to a linen draper in Amsterdam, and in 1654 he married Barbara de Mey and opened his own draper's shop in Delft. He held municipal posts for decades, including nearly 40 years as chamberlain to the city hall sheriffs and a spell as the town's wine-gauger, overseeing wine imports and taxes. The painter Johannes Vermeer, baptized just four days before him, lived nearby, and Van Leeuwenhoek served as executor of his will in 1675.
His tiny microscopes, the largest about 5 centimetres long, held a single bead of glass in a silver or copper frame, with screws to move the specimen into focus. Held right up to the eye, surviving examples magnify up to 275 times, and he may have had some reaching 500. He made more than 500 lenses and at least 25 microscopes, of which nine survive. Most powerful lenses were apparently formed by melting the tip of a drawn-out glass whisker, a technique first devised by Robert Hooke, though he let visitors believe he ground them.
The physician Reinier de Graaf introduced him to the Royal Society, which printed his first letter in 1673, on mould, bees and lice. In 1674 he concluded that the moving specks in his samples were living creatures, and his October 1676 report of single-celled organisms met real scepticism, since nobody had imagined such life existed. The Society sent ministers and other witnesses to Delft, and in 1677 accepted his observations. He went on to describe muscle fibres, bacteria and blood flowing through capillaries.
He wrote only in colloquial Dutch, never a Latin paper, sending about 190 letters to London that Henry Oldenburg, who learned Dutch to read them, translated; Oldenburg also coined the word animalcules. Elected a fellow in 1680, Van Leeuwenhoek never attended a meeting. Visitors included Leibniz and John Locke, and in 1697 he gave Tsar Peter the Great an eel-viewer for watching blood circulate, but he showed guests only his ordinary lenses. He died on 26 August 1723.
Source: Antonie van Leeuwenhoek
