7 December 1810|
Neuss, First French Empire (now in Germany)
|Died||11 January 1882
|Known for||Cell theory
|Influences||Johannes Peter Müller|
Theodor Schwann (7 December 1810 – 11 January 1882) was a German physiologist. His many contributions to biology include the development of cell theory, the discovery of Schwann cells in the peripheral nervous system, the discovery and study of pepsin, the discovery of the organic nature of yeast, and the invention of the term metabolism.
Early life 
Theodor Schwann's breakthrough investigations occurred primarily in his four years working under the influence of physiologist Müller at Berlin. Assisting Müller, who was preparing his treatise on physiology, Schwann microscopically viewed animal tissues, and found particular interest in nervous and muscular tissues. Schwann observed cells associating with the sheath of nerve fibers, cells now called Schwann cells.
Schwann's identification of the upper esophagus's striated muscle initiated research into muscle contraction, research elaborated greatly by Emil du Bois-Reymond and others. Müller directed Schwann's attention to digestion, and in 1837 Schwann isolated an enzyme, apparently essential to digestion, that Schwann named pepsin.
Schwann's later years found growing interest in theological issues. Schwann died in Cologne on 11 January 1882.
Cell theory 
In 1837, Matthias Jakob Schleiden found that all plants are composed of cells, and communicated the finding to Schwann, who had found similar structures in the cells of the notochord, as shown earlier by Müller. Other researchers confirmed the similarity, as explained in Schwann's Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals, where he concluded, "All living things are composed of cells and cell products".
This became cell theory or cell doctrine, compatible with Schwann's observations across all other tissues he investigated, concluding a cellular origin even of nails, feathers, and tooth enamel. Schleiden's contribution extended cell doctrine to plants. In 1857, pathologist Rudolf Virchow posed the maxim Omnis cellula e cellula—that every cell arises from another cell—widely accepted. By the 1860s, cell doctrine became the conventional view of the elementary anatomical composition of plants and animals.
Schwann was the first of Johannes Peter Müller's pupils to break with vitalism and work towards a physico-chemical explanation of life. Schwann also examined the question of spontaneous generation, which led to its eventual disconfirmation. In the early 1840s, Schwann went beyond others who had noted simply the multiplication of yeast during alcoholic fermentation, as Schwann assigned the yeast the role of primary causal factor, and then went further and claimed it was alive. Embattled controversy ensued as eminent chemists alleged that Schwann was undoing scientific progress by reverting to vitalism.
After publishing anonymous mockery in a journal of their own editorship, they published a purely physicochemical if also hypothetical explanation of the interaction resulting in fermentation. As both the rival perspectives were hypothetical, and there was not even an empirical definition of 'life' to hold as a reference frame, the controversy—as well as interest itself—fell into obscurity unresolved. Pasteur began fermentation researches in 1857 by approximately just repeating and confirming Schwann's, yet Pasteur accepted that yeast were alive, thus dissolving the controversy over their living status, and then Pasteur took fermentation researches further.
Germ theory 
In the early 1860s, upon Pasteur's publication on fermentation to butyric acid, a putrefaction product, fellow Frenchman Casimir Davaine sought a microorganism as causal in anthrax, but Davaine's identified bacterides would vanish from the blood, a finding whereby rival explanations assigned to Davaine's bacterides the role merely of incidental byproduct.
In Germany, Robert Koch, influenced by Ferdinand Cohn's report of a nearly invisible spore stage of a particular bacterial species, isolated in pure culture a spore stage of Davaine's bacterides, inoculated it into animals, and reproduced anthrax, concluding fulfillment of his onetime teacher Jakob Henle's postulates to establish the causal and not merely incidental role of a microorganism in the process of a disease.
- Chisholm 1911.
- Schwann, Theodor (1839). Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals. Berlin. (English translation by the Sydenham Society, 1847)
Further reading 
- Aszmann, O. C. (2000). "The life and work of Theodore Schwann". Journal of reconstructive microsurgery 16 (4): 291–5. doi:10.1055/s-2000-7336. PMID 10871087.
- Florkin, M. (1958). "Episodes in medicine of the people from Liège: Schwann & the stigmatized". Revue médicale de Liège 13 (18): 627–38. PMID 13591909.
- Florkin, M. (1957). "1838; Year of crisis in the life of Théodore Schwann". Revue médicale de Liège 12 (18): 503–10. PMID 13466730.
- Florkin, M. (1957). "Discovery of pepsin by Theodor Schwann". Revue médicale de Liège 12 (5): 139–44. PMID 13432398.
- Florkin, M. (1951). "Schwann as medical student". Revue médicale de Liège 6 (22): 771–7.
- Florkin, M. (October 1951). "Schwann at the Tricoronatum". Revue médicale de Liège 6 (20): 696–703. PMID 14883601.
- Florkin, M. (1951). "The family and childhood of Schwann". Revue médicale de Liège 6 (9). PMID 14845235.
- Haas, L. F. (1999). "Neurological stamp. Theodore Schwann (1810–82)". J. Neurol. Neurosurg. Psychiatr. 66 (1): 103. PMC 1736145. PMID 9886465.
- Hayashi, M. (1992). "Theodor Schwann and reductionism". Kagakushi kenkyu. Journal of the history of science, Japan 31 (184): 209–14. PMID 11639601.
- Kiszely, G. (1983). "Theodor Schwann". Orvosi hetilap (Hungary) 124 (16): 959–62. PMID 6343953.
- Kosinski, C. M. (2004). "Theodor Schwann". Der Nervenarzt (Germany) 75 (12): 1248–1248. doi:10.1007/s00115-004-1805-5. PMID 15368056.
- Kruta, V. (1987). "The idea of the primary unity of elements in the microscopic structure of animals and plants. J. E. Purkynĕ and Th. Schwann". Folia mendeliana (Czech Republic) 22: 35–50. PMID 11621603.
- Lukács, D. (April 1982). "Centenary of the death of Theodor Schwann". Orvosi hetilap 123 (14): 864–6. PMID 7043357.
- Watermann, R. (1973). "Theodor Schwann accepted the honorable appointment abroad". Medizinische Monatsschrift (Germany, West) 27 (1): 28–31. PMID 4576700.
- Watermann, R. (1960). "Theodor Schwann as a maker of lifesaving apparatus". Die Medizinische Welt 50: 2682–7. PMID 13783359.
|Wikimedia Commons has media related to: Theodor Schwann|
- Short biography and bibliography in the Virtual Laboratory of the Max Planck Institute for the History of Science
- Schwann, Theodor and Schleyden, M. J. 1847. Microscopical researches into the accordance in the structure and growth of animals and plants. London: Printed for the Sydenham Society
- "Theodor Schwann". Catholic Encyclopedia. New York: Robert Appleton Company. 1913.