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a convex lense with a magnification greater than x5 became available
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first compound microscopes used in Europe ( used 2 convex lenses to make object look larger). Suffered badly from colour distortion - an effect called 'spherical aberration'
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Antoni van Leeuwenhoek of Leyden , Holland, produced over 500 single lens microscope. Discovered bacteria, human blood cells, spermatozoa, and protozoa. Friend of Robert Hooke of England
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Marcello Malpighi used lenses to study insects. Discovered capillaries and may have described cells in writing of 'globules' and 'saccules',
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Robert Hooke introduced the term 'cell' in describing the microscopic structure of cork. He believed that the cells walls were the most important part of otherwise empty structure. Published Micrographia in 1665
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Botanist Matthias Schleiden and zoologist Theodor Schwann proposed the Cell Theory for plants and animals; plants and animals are composed of groups of cells and that the cell is the basic unit of living organisms.
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Rudolph Virchow extended the cell theory by stating that: new cells are formed only by the division of previously existing cells.
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August Weismann added to Virchow's idea by pointing out that: all the cells living today can trace their ancestry back to ancient times ( the link between cell theory and evolution).