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Anton van Leeuwenhoek Anton van Leeuwenhoek

Born: October 24, 1632 in Delft, Netherlands
Died: August 26, 1723
Nationality: Dutch
Occupation: naturalist, microscopist

The Dutch naturalist and microscopist Anton van Leeuwenhoek (1632-1723), using simple microscopes of his own making, discovered bacteria, protozoa, spermatozoa, rotifers, Hydra and Volvox, and also parthenogenesis in aphids.

Anton van Leeuwenhoek was born on Oct. 24, 1632, at Delft. His schooling was informal, probably including some mathematics and physical sciences but no languages. At the age of 16 he was sent to Amsterdam to become an apprentice at a linen draper's shop where he remained for about 6 years. In 1654 van Leeuwenhoek returned to Delft and married Barbara de Mey, who was to bear him five children. He bought a house and shop and set up in business as a draper. He remained there for the rest of his life. His wife died in 1666 and in 1671 he remarried; his second wife bore him one child.

In 1660 van Leeuwenhoek was appointed chamberlain to the sheriffs of Delft, an office which he held for 39 years. Little is known of his activities for the next 13 years; however, in his spare time he must have begun to grind lenses to make simple microscopes. As early as 1668 he took one of his microscopes on a visit to England and used it to examine chalk from the cliffs in Kent.

In 1673 Regnier de Graaf, a brilliant young physician of Delft, wrote a letter about Van Leeuwenhoek's work to Henry Oldenburg, Secretary of the Royal Society in London. This letter was published in PHILOSOPHICAL TRANSACTIONS, and Oldenburg wrote to the author requesting further communications. Thus began a correspondence with the Royal Society which was to continue until van Leeuwenhoek's death. All his observations were described in letters (at least 200), either to the Royal Society or to his friends, that were written in his own language, Nether-Dutch. He never wrote a scientific paper or a book. His letters are full of random observations, with little coherence, and were written in a conversational style. Despite the casual way in which he described his observations, he never confused the facts with his speculations, and so it is possible to identify easily many of the organisms he studied from his detailed descriptions.

The Royal Society elected him a fellow in 1680, an honor which pleased him although he never found time to visit London to sign the register. His discoveries soon made him famous, and many came to visit him in Delft. His enthusiasm for the study of nature never waned even in old age, and despite his infirmities he still continued to make observations and send letters to the Royal Society. After his death on Aug. 26, 1723, his daughter Maria sent a cabinet to the Royal Society which her father had prepared 22 years previously, containing 26 of his microscopes made from silver.

Van Leeuwenhoek's Microscopes

Apart from those microscopes sent to the Royal Society, van Leeuwenhoek left 247 completely finished microscopes, most of which had an object mounted in front of the lens, and also 172 lenses mounted between metal plates. Properly speaking, the instruments were not microscopes at all but simple magnifying glasses. Each consisted of a single biconvex lens of remarkable clarity which was mounted between two metal plates. The lens was fixed, and the object to be examined was raised or lowered and rotated upon its axis by a coarse-threaded-screw. The lenses were of exceptional optical quality and had magnifying powers ranging from 50 to 200. The short (about 1 millimeter) focal lengths of the lenses would have necessitated placing the eye almost in contact with the lens, and it is not clear how van Leeuwenhoek obtained the necessary illumination to achieve his remarkable results. He was always very secretive about his methods. Clifford Dobell suggested that he might have discovered some simple method of dark-ground illumination, whereas Barnett Cohen pointed out that the optical properties of spherical drops of fluid containing the objects under observation may have been used by van Leeuwenhoek.

Photo: Courtesy of the National Library of Medicine.

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Source: From ENCYCLOPEDIA OF WORLD BIOGRAPHY, 2nd ed. 17 vols. Gale Research, 1998. Reprinted by permission of The Gale Group.


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