por Ian M. Davis (Programa Doutoral em História das Ciências e Educação Científica da UC)

 

Antoni van Leeuwenhoek is known primarily as an innovative late 17th and early 18th Century lens-maker for simple microscopes, which led to his revelation of the previously invisible world of “animalcules,” now known as protists and bacteria, more generally known as microbes. Van Leeuwenhoek was an innovator in lens-making and in the creation of single lens microscopes, but he was also part of a scientific explosion of interest in the structure of life. Starting in the last years of the 16th C., Hans and Zacharias Janssen, along with their competitor Hans Lipperhey, went from making spectacles to creating the first telescopes and compound microscopes. The early telescopes involved two lenses, one at the light collection end of a tube called an objective lens, which was a plano-convex lens, and one at the eyepiece end, which was a plano-concave lens. The earliest microscopes were “compound” microscopes that magnified objects at low power. These microscopes used two convex lenses. The intent was to examine objects held very close to the objective lens, an elaboration on magnifying glasses. Magnifying and burning glasses—used to start fires—had been in use since about 450 B.C.E. when Aristophanes mentioned them in a play.

When Antoni van Leeuwenhoek started making lenses and viewing objects, he is thought to have had several influences. He was a friend of Jan Swammerdam, an emerging Dutch physician from van Leeuwenhoek’s birthplace—Delft. Swammerdam was one of several individuals who had viewed and made crude drawings of red blood cells using a microscope. It is thought van Leeuwenhoek was aware of the publication of Robert Hooke’s Micrographia, an illustrated examination of objects with his low-power compound microscope. Van Leeuwenhoek had by the time of Hooke’s publication been a successful draper—a cloth and clothing merchant—for about a decade. His profession required use of a weaver’s glass to determine thread count and cloth quality.

Van Leeuwenhoek’s measurement methodology is less frequently discussed. Using a range of visible objects, including grains of sand, “vinegar eels,” millet seeds, as well as objects for which he helped define dimensions, allowed him to make estimates of microscopic objects, phenomena, and living things with prescient accuracy. His measurements in many instances have withstood scrutiny from contemporary microscopists and biologists using sophisticated microscopes and cell counters. His work demonstrated the extent of his curiosity; his work was labor-intensive and required extended periods of fastidious, repetitive observation to achieve the goals he set for himself. An examination of microscopy and van Leeuwenhoek’s methods as described in various letters to the Royal Society and as translated and reviewed by others will be presented.