How it began
Antony van Leeuwenhoek was born in Delft on October 24, 1632. He was a draper who also worked as a surveyor, wine assayer and minor city official, with no university education and no language but Dutch. Some time before 1668 he learned to grind lenses and began observing with simple microscopes, apparently inspired by Robert Hooke's illustrated book Micrographia. In 1673 he began writing letters to the Royal Society of London, and in a letter of September 7, 1674, he described living things in lake water.
Before it existed
Compound microscopes, with more than one lens, had been invented around 1595, and Robert Hooke in England and Jan Swammerdam in the Netherlands were making discoveries with them. Because of technical difficulties in building them, however, these early instruments were not practical for magnifying more than about twenty or thirty times. The existence of single-celled organisms was entirely unknown.
How it works
Leeuwenhoek's instruments were in effect very powerful magnifying glasses. Each had one small lens mounted in a tiny hole in a brass plate. The specimen sat on a sharp point in front of the lens and was positioned and focused with two screws. The whole device was only three to four inches long and had to be held close to the eye in good light. His skill at grinding lenses gave magnifications of over 200 times, with clearer and brighter images than his contemporaries achieved.
How it spread
For fifty years his letters, written in Dutch, were translated into English or Latin and printed in the Philosophical Transactions of the Royal Society. On September 17, 1683, he described living animalcules in the plaque from his own teeth, among the first recorded observations of living bacteria. He was elected a full member of the Royal Society in 1680, and in 1698 he showed the circulation in the capillaries of an eel to Tsar Peter the Great.
Who pushed back
He was an outsider to the learned world, and his reports were not accepted at once. When he sent the Royal Society his first observations of microscopic single-celled organisms, in a letter dated October 9, 1676, his credibility was questioned. He kept his lens-making methods to himself and worked alone, so others could not easily repeat what he described, though he hired an illustrator to draw what he saw.
What lasted
Leeuwenhoek discovered bacteria, free-living and parasitic protists, sperm cells, blood cells, and microscopic nematodes and rotifers, which opened a whole world of microscopic life to science. He made over 500 microscopes, of which fewer than ten survive. He continued observing until his death on August 30, 1723. Specimens that he sent to London were later found again in the archives of the Royal Society by Brian J. Ford.
