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| b. Chemistry, Biology, and Geology |
| 1848 |
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| Louis Pasteur (1822–95), in a series of brilliantly conceived and executed experiments, demonstrated the connection between the optical activity of organic molecules and crystalline structure, thus founding stereochemistry. | 1 |
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| 1848 |
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| Claude Bernard (1813–78) demonstrated the ability of the liver to store sugar in the form of glycogen. His widely read Introduction à l'étude de la médecine expérimentale (1865) influenced the literary world as well as scientists. | 2 |
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| 1852 |
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| Edward Frankland (1825–99) announced his theory of valency, that is, each atom has a certain “valency,” or capacity for combining with a definite number of other atoms. | 3 |
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| 1856–64 |
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| Bernard evolved the concept of the milieu intérieur, envisioning that cells were autonomous physiological units, yet were dependent upon and protected by the internal environment of the whole organism. | 4 |
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| 1856–66 |
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| Hermann Helmholtz (1821–94) extended the doctrine of specific nerve energies developed by Johannes Müller to vision and hearing, indicating the penetration of physics and physiology into psychology. | 5 |
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| 1857–60 |
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| Louis Pasteur demonstrated that fermentation was a product of yeast cell activity. This challenged the view of Liebig that the ferment was merely an unstable chemical substance. | 6 |
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| 1858 |
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| Rudolph Virchow (1821–1902) in Die Cellularpathologie declared that disease reflects an impairment of cellular organization. Here, too, he stated his famous generalization “omnis cellula e cellula” (all cells arise from cells) and described the cell as the basic element of the life process. | 7 |
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| 1858 |
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| Friedrich A. Kekulé (1829–96) published Über die Konstitution und die Metamorphosen der chemischen Verbindungen und über die chemische Natur des Kohlenstoffs, in which he recognized that carbon is quadrivalent, and that carbon atoms link together to form long chains that serve as skeletons for organic molecules. | 8 |
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| 1858 |
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| Stanislao Cannizzaro (1826–1910) showed that one could unambiguously determine atomic weights. He was thus able to provide a table giving the correct molecular formulas of many compounds. | 9 |
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| 1859 |
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| Gustav R. Kirchhoff (1824–87) and Robert W. Bunsen (1811–99) began researches that made spectrum analysis a powerful method for the investigation of matter. They showed that a chemical element was clearly characterized by its spectrum, and by spectrum analysis they were able to discover previously unknown elements. | 10 |
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| 1859 |
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| Darwin amassed 25 years of careful research in Origin of Species. Inspired by the evidence in geology, paleontology, zoogeography, and domestic animal breeding, he declared that species evolved through variation and the natural selection of those individuals best suited to survive in given environmental conditions. A similar theory was developed independently by Alfred R. Wallace (1823–1913). | 11 |
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