Theory of Cells as Basic Units of Life
Better microscopes allowed observations and drawings that led to a Cell Theory for all of life, though the idea was not accepted immediately.
In the 1830s, the Germans Matthias Schleiden (with plants) and Theodor Schwann (with animals) declared that plants and animals are all made of cells. They argued that each cell begins with a nucleus, and the cell develops around that nucleus. Cells then join together to make up complex organisms like us.
They argued about whether cells arise by crystallization from surrounding material, through spontaneous generation, by cell division, or some other process.
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In the 1850s, the Polish-German Robert Remak showed that cells arise by division of other cells, then German pathologist Rudolf Virchow popularized the idea. Though science does not progress through instant agreement with new ideas, this assumption became part of what was accepted by 1900 as the cell theory. The ability to observe cell division and represent it in images eventually persuaded others.
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- Schwann, Theodor. Mikroskopische Untersuchungen. 1838–39. (Translated by Henry Smith as “Microscopical Researches,” in Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals. London: The Sydenham Society, 1847.) Plate 1.
- Schleiden, Mattias Jacob. 1838. "Beiträge über Phytogenesis." Müller's Archiv für Anatomie and Physiologie (1838): 137–176. (Translated by Henry Smith as "Contributions to Phytogenesis," in Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals. London: The Sydenham Society, 1847: 229-63.) Plate 1, Figures 1-8 and 22-24.
- Remak, Robert. Untersuchungen über die Entwicklung der Wirbelthiere. Berlin: Reimer, 1855. Table 3, Figure 35, A and B.
- Virchow, Rudolf. Die Cellularpathologie. 4th Edition. Berlin: Hirschwald, 1871. Page 18, Figure 2.