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Antoni van Leeuwenhoek (1632-1723) |
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| Leeuwenhoek was born
in Delft on October 24, 1632. He was the son of a basketmaker, and
after apprenticing as a linen draper, Leeuwenhoek set up a linen shop in
1654. He was an amateur scientist, at some point becoming
interested in studying the microscopic world of life.
Although he was aware of Hooke's compound microscope, he favored the use of a single lens, probably because it gave smaller spherical and chromatic aberrations. Hooke's compound microscope, because of these aberrations, could only magnify 30-40X. Leeuwenhoek's simple microscope could magnify from 50-200X. His microscopes were made of brass plates (about 4.5 by 2.5 cm) riveted together. A lens was (somehow) fabricated and placed between them, with an effective diameter of about 0.5 millimeters. The object to be studied was fastened to the point of a needle, which was fixed to one of the plates. As crude as they looked, his microscopes allowed for horizontal and vertical adjustments of the specimen, as well as focus. In all, he made more than 400 of these microscopes in his lifetime! Perhaps not surprisingly, Leeuwenhoek was very secretive about his microscopes. Some said his success was in the way he ground his lenses. Others said that he didn't grind them at all, but melted glass in a fierce gas jet, collecting the little blobs of glass that flew off. Others said that it was his methods of illumination that were responsible. Whatever the case, he never revealed his secrets to anyone! In use, his microscopes could resolve details about 1.4 microns in width, close to the theoretical limit of 1 micron. (Until around 1800, compound microscopes could still resolve only around 5 microns.) With his microscopes, Leeuwenhoek studied the tissues in the human body--hair, skin, muscle, and bone. He studied the development of fleas from their eggs, even finding little parasites living on the flea. In pond water he found an incredible array of tiny critters, which he called "animalcules." Most importantly, in 1683 he became the first person to observe bacteria, scraped from his (and others) teeth! It would be over a hundred years before anyone would see bacteria again. His drawings were published by the Royal Society in 1673, and in 1680 he was elected a Fellow in the Society. |
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