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| 1809 |
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| Jean-Baptiste Lamarck (1744–1829), in Philosophie zoologique, gave the most complete explanation of his theory of evolution. He argued that through a combination of unconscious striving, the physiological effects of use and disuse, and the influence of the environment, anatomical parts became modified. Furthermore, he believed that by the “inheritance of acquired characteristics,” living forms evolved in an ever-ascending scale of perfection. | 1 |
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| 1809 |
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| Lorenz Oken (1779–1815), one of the leaders of the German Naturphilosophie movement, published an antimechanist treatise that taught the superiority of intuitively derived concepts, expressed a belief in the archetypal polarities of nature, and championed a search for ideal types and a teleological unity in nature. | 2 |
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| 1809 |
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| Ephraim McDowell (1771–1830) performed a successful ovariotomy, thus showing that surgery of the abdominal cavity was not necessarily fatal. | 3 |
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| 1811 |
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| Amedeo Avogadro (1776–1856) concluded that equal volumes of all gases at the same temperature and pressure contain equal numbers of molecules; in effect, he distinguished between atoms and molecules, but his ideas were neglected until 1858. | 4 |
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| 1811 |
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| Georges Cuvier (1769–1832), the founder of modern vertebrate paleontology, and Alexandre Brongnïart (1770–1847) brought out their Essai sur la géographie minéralogique des environs de Paris with a map, ordering important tertiary strata. | 5 |
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| 1812 |
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| Jöns Berzelius (1779–1848) developed a dualistic electrochemical theory to account for electrolysis and chemical combination. | 6 |
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| 1815 |
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| William Prout (1785–1850) published an anonymous paper in which he advanced the hypothesis that the atoms of all other elements were really aggregates of hydrogen atoms. | 7 |
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| 1815 |
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| William Smith (1769–1839) published his famous geological map of England and Wales and established that specific strata can be identified by their fossil content, the principle upon which historical geology is founded. He also worked out the main divisions of the Secondary, or Mesozoic, strata. | 8 |
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| 1819 |
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| Pierre Dulong (1785–1838) and Alexis Petit (1791–1820) formulated the rule that the product of the relative atomic weight and the specific heat of an element is a constant. This made possible the experimental determination of relative atomic weights. | 9 |
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| 1819 |
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| René Laënnec (1781–1826) invented the stethoscope. | 10 |
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| 1822 |
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| François Magendie (1783–1855) showed that the sensory and motor functions arise from different spinal roots. He was anticipated in 1811 by the more discursive work of Charles Bell (1774–1842). | 11 |
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| 1824 |
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| Justus von Liebig (1803–73) obtained the chair of chemistry at Giessen, where he established the first truly effective laboratory for the teaching of chemistry. He greatly improved methods of organic analysis and, with his students, accurately analyzed a great number of organic compounds. | 12 |
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