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Gerard Peter Kuiper
Gerard Peter Kuiper was a Netherlands-born American astronomer.
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Theodor Schwann7.12.1810

Wikipedia (28 Jan 2014, 07:43)

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

Schwann was born in Neuss. His father was a goldsmith, later a printer. Schwann studied at the Jesuits College in Cologne, and then at Bonn, where he met physiologist Johannes Peter Müller.


It was during the four years spent under the influence of Müller at Berlin that Schwann's most valuable work was done. Müller was at this time preparing his great book on physiology, and Schwann assisted him in the experimental work required. Schwann observed animal cells under the microscope, noting their different properties. Schwann found particular interest in the nervous and muscular tissues. He discovered the cells which envelope the nerve fibers, now called Schwann cells in his honour.

Schwann discovered the striated muscle in the upper esophagus and initiated research into muscle contraction, since expanded upon greatly by Emil du Bois-Reymond and others. Müller directed Schwann's attention to the process of digestion, and in 1837 Schwann isolated an enzyme essential to digestion, which he called pepsin.

In his later years, Schwann found growing interest in theological issues. Schwann died in Cologne on 11 January 1882.

Cell theory

In 1838, 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.

Vitalism and germ theory

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.

In retrospect, the germ theory of Pasteur, as well as its antiseptic applications by Lister, can be traced to Schwann's influence.

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