Theodor Schwann

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Theodor Schwann

Library of Congress

[b. Neuss (Germany), December 7, 1810, d. Cologne, Germany, January 11, 1882]

In 1839 Schwann proposed that all organisms are composed of cells. Together with Matthias Schleiden he formulated the cell theory of life. Schwann also discovered the cells, now known as Schwann cells, that form a sheath surrounding nerve axons and conducted experiments that helped disprove the theory of spontaneous generation. He coined the word metabolism to define the chemical changes that take place in cells and he demonstrated that yeast organisms cause fermentation of sugar solutions.

The German biologist Theodor Schwann (1810-1882) is considered a founder of the cell theory. He also discovered pepsin, the first digestive enzyme prepared from animal tissue, and experimented to disprove spontaneous generation.

Theodor Schwann was born at Neuss near Düsseldorf on Dec. 7, 1810. At the University of Bonn, which he entered in 1829, he met Johannes Müller, the physiologist, whom he assisted in his experiments. Schwann continued his medical studies at the University of Würzburg and later at the University of Berlin, from which he graduated in 1834. His doctoral dissertation dealt with the respiration of the chick embryo.

Contributions to Physiology and Anatomy

At the University of Berlin, Schwann again came into contact with Müller, who convinced him that he should follow a scientific career. Very soon after he began to work under Müller, he had his first success. From extracts which he made of stomach lining, Schwann demonstrated that a factor other than hydrochloric acid was operating in digestion. Two years later, in 1836, he succeeded in isolating the active principle, which he named pepsin.

Between 1834 and 1838 Schwann undertook a series of experiments designed to settle the question of the truth or falsity of the concept of spontaneous generation. His method was to expose sterilized (boiled) broth only to heated air in a glass tube, the result being that no micro-organisms were detectable and no chemical change (putre-faction) occurred in the broth. He was convinced that the idea of spontaneous generation was false. His sugar fermentation studies of 1836 also led to his discovery that yeast originated the chemical process of fermentation.

At Müller's suggestion, Schwann also began research on muscle contraction and discovered striated muscles in the upper portion of the esophagus. He also identified the delicate sheath of cells surrounding peripheral nerve fibers, which is now named the sheath of Schwann.

Cell Theory

In 1838 Schwann became familiar with Matthias Schleiden's microscopic research on plants. Schleiden described plant cells and proposed a cell theory which he was certain was the key to plant anatomy and growth. Pursuing this line of research on animal tissues, Schwann not only verified the existence of cells, but he traced the development of many adult tissues from early embryo stages. This research and the cell theory which followed were summarized in Mikroskopische Untersuchungen ueber die Uebereinstimmung in der Struktur und dem Wachstum der Thiere und Pflanzen (1839; Microscopical Researches on the Similarity in the Structure and the Growth of Animals and Plants, 1847). This work, which in Schwann's own words demonstrated that "the great barrier between the animal and vegetable kingdoms, viz. the diversity of ultimate structure, thus vanishes," established the cell theory to the satisfaction of his contemporaries.

Schwann proposed three generalizations concerning the nature of cells: First, animals and plants consist of cells plus the secretions of cells. Second, these cells have independent lives, which, third, are subject to the organism's life. Furthermore, he realized that the phenomena of individual cells can be placed into two classes: "those which relate to the combination of the molecules to form a cell. These may be called plastic phenomena," and "those which result from chemical changes either in the component particles of the cell itself, or in the surrounding cytoblastema [the modern cytoplasm]. These may be called metabolic phenomena." Thus Schwann coined the term "metabolism," which became generally adopted for the sum total of chemical processes by which energy changes occur in living things.

Contributions to Histology

Schwann also contributed to the understanding and classification of adult animal tissues. He classified tissues into five groups: separate independent cells, such as blood; compacted independent cells, such as skin; cells whose walls have coalesced, such as cartilage, bones, and teeth; elongated cells which have formed fibers, such as tendons and ligaments; and finally, cells formed by the fusion of walls and cavities, such as muscles and tendons. His conclusions were also basic to the modern concept of embryology, for he described embryonic development as a succession of cell divisions.

This generalization of the essential structural kinship of all living things had been denied for centuries by the old Aristotelian doctrine of vegetable and animal souls. Perhaps Schwann's findings were more disturbing than he liked to admit, since he realized that they supported an ultimate physical rather than a theological explanation. Schwann saw the implications of his discovery, and the idea of the world of life being nothing more than a machine appalled him. He found refuge in the Roman Catholic faith, choosing, as he said, a God "more sensitive to the heart than to reason."

In 1839 Schwann was appointed professor of anatomy at the University of Louvain, Belgium, where he remained until 1848, when he accepted a professorship at the University of Liège. He remained there until his retirement in 1880. After leaving the influence of Müller, Schwann's productivity practically ceased; in Belgium he published only one paper, on the use of bile. He was an excellent, conscientious teacher, loved and appreciated by his students.

Schwann's work was ultimately recognized by scientists in other countries, and in 1879 he was made a member of the Royal Society and also of the French Academy of Science. In 1845 he had received the Copley Medal. Death came to Schwann on Jan. 11, 1882, 2 years after his retirement, in Cologne.

Further Reading

Excerpts in English translation from Mikroskopische Untersuchungen are found in the following works: Forest Ray Moulton and Justus J. Schifferes, eds., The Autobiography of Science (1945; rev. ed. 1960); Augusto Pi Suñer, Classics of Biology (1955); Friedrich S. Bodenheimer, The History of Biology: An Introduction (1958); and George Schwartz and Philip W. Bishop, eds., Moments of Discovery (2 vols., 1958). There is no biography of Schwann. Gilbert Causey in The Cell of Schwann (1960) devotes the first chapter to a sparse recital of the essential details of Schwann's life. Erik Nordenskiöld, The History of Biology (1928; new ed. 1935), gives a brief biographic account, as does Gordon R. Taylor, The Science of Life (1963). A good treatment of the cell theory and Schwann's part in it is in William A. Locy, Biology and Its Makers (1908; rev. ed. 1915).

Not to be confused with army general Theodore Schwan.

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Theodor Schwann
Theodor Schwann
Born	7 December 1810
Died	11 January 1882
Known for	Cell Theory Schwann Cells
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. He died on Jan. 11, 1882, 2 years after his retirement, in Cologne.

Contents 1 Vitalism and germ theory 2 Theory 3 Honors 4 References 5 Further reading 6 External links

Vitalism and germ theory

Schwann was the first of Müller's pupils to break with vitalism and work towards a physico-chemical explanation of life. Schwann's rediscovery of the cell came when he was paying particular attention to the cytoplasm of a plant cell, and noticed its jelly-like consistency. He went on to view animal cells, and noted that they had different properties. Müller also directed Schwann's attention to the process of digestion, which Schwann showed in 1837 to depend essentially on the presence of a ferment he called pepsin. Schwann also examined the question of spontaneous generation, which led to its eventual disproof. In the course of hieriments, he discovered the organic nature of yeast. In fact, the whole germ theory of Pasteur, as well as its antiseptic applications by Lister, can be traced to Schwann's influence.

Theory

Once, when Schwann was dining with Matthias Jakob Schleiden (who in 1837 had viewed and stated that new plant cells formed from the nuclei of old plant cells) in 1837, the conversation turned on the nuclei of plants and animal cells. Schwann remembered seeing similar structures in the cells of the notochord (as had been shown by Müller) and instantly realized the importance of connecting the two phenomena. The resemblance was confirmed without delay by both observers, and the results soon appeared in his famous Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals, in which he declared that "All living things are composed of cells and cell products."^[1] Thus cell theory was definitely constituted. In the course of his verification of cell theory, in which Schwann traversed the whole field of histology, he proved the cellular origin and development of the most highly differentiated tissues including nails, feathers, and tooth enamel.

His generalization became the foundation of modern histology, and in the hands of Rudolf Virchow (whose cellular pathology was an inevitable deduction from Schwann) placed modern pathology on a truly scientific basis.

Honors

He was elected a member of the Royal Swedish Academy of Sciences in 1874.

References

1. ^ Schwann, Theodor (1839). Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals. Berlin. http://vlp.mpiwg-berlin.mpg.de/library/data/lit28715/index_html?pn=7.  (English translation by the Sydenham Society, 1847)

Further reading

• Aszmann, O. C. (May 2000). "The life and work of Theodore Schwann". Journal of reconstructive microsurgery (United States) 16 (4): 291–5. ISSN 0743-684X. PMID 10871087. 
• Florkin, M. (September 1958). "Episodes in medicine of the people from Liège: Schwann & the stigmatized". Revue médicale de Liège 13 (18): 627–38. ISSN 0370-629X. PMID 13591909. 
• Florkin, M. (September 1957). "1838; Year of crisis in the life of Théodore Schwann". Revue médicale de Liège 12 (18): 503–10. ISSN 0370-629X. PMID 13466730. 
• Florkin, M. (March 1957). "Discovery of pepsin by Theodor Schwann". Revue médicale de Liège 12 (5): 139–44. ISSN 0370-629X. PMID 13432398. 
• Florkin, M. (November 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. ISSN 0370-629X. PMID 14883601. 
• Florkin, M. (May 1951). "The family and childhood of Schwann". Revue médicale de Liège 6 (9): 231–8. ISSN 0370-629X. PMID 14845235. 

• Haas, L. F. (January 1999). "Neurological stamp. Theodore Schwann (1810-82)". J. Neurol. Neurosurg. Psychiatr. (England) 66 (1): 103. ISSN 0022-3050. PMID 9886465. 
• Hayashi, M. (1992). "Theodor Schwann and reductionism". Kagakushi kenkyu. Journal of the history of science, Japan (Japan) 31 (184): 209–14. ISSN 0022-7692. PMID 11639601. 
• Kiszely, G. (April 1983). "Theodor Schwann". Orvosi hetilap (Hungary) 124 (16): 959–62. ISSN 0030-6002. PMID 6343953. 
• Kosinski, C. M. (December 2004). "Theodor Schwann". Der Nervenarzt (Germany) 75 (12): 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. ISSN 0085-0748. PMID 11621603. 

• Lukács, D. (April 1982). "Centenary of the death of Theodor Schwann". Orvosi hetilap (Hungary) 123 (14): 864–6. ISSN 0030-6002. PMID 7043357. 

• Watermann, R. (January 1973). "Theodor Schwann accepted the honorable appointment abroad". Medizinische Monatsschrift (Germany, West) 27 (1): 28–31. ISSN 0025-8474. PMID 4576700. 

• Watermann, R. (December 1960). "Theodor Schwann as a maker of lifesaving apparatus". Die Medizinische Welt 50: 2682–7. ISSN 0025-8512. PMID 13783359. 

External links

 "Schwann, Theodor". Encyclopædia Britannica (11th ed.). 1911. 

• 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. http://en.wikisource.org/wiki/Catholic_Encyclopedia_(1913)/Theodor_Schwann. 

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