Theodor Schwann (December 7, 1810 - January 11, 1882) was a German physiologist, histologist and cytologist. Among his many contributions to biology there were the cell theory, the discovery of Schwann cells in the nervous system, the discovery and study of pepsin, the discovery of the organic nature of yeast and the invention of the term metabolism.
Life
Schwann's father was a man of great mechanical talent; at first a goldsmith, he afterwards founded an important printing establishment. Schwann inherited his father's tastes, and the leisure of his boyhood was largely spent in constructing little machines of all kinds. He studied at the Jesuit's college in Cologne and afterwards at Bonn, where he met Johannes Muller, in whose physiological experiments he soon came to assist. He next went to Würzburg to continue his medical studies, and thence to Berlin to graduate in 1834. Here he again met Muller, who had been meanwhile translated to Berlin, and who finally persuaded him to enter on a scientific career and appointed him assistant at the anatomical museum. In 1828 Schwann was called to the chair of anatomy at the Roman Catholic University of Louvain, in Louvain, Belgium, where he remained nine years. In 1847 he went as professor to Liège, where he remained till his death in 1882. He was of a peculiarly gentle and amiable character, and remained a devout Catholic throughout his life.
In 1836, while at the University of Berlin, he discovered pepsin, an enzyme responsible for digestion, in extracts from the stomach lining. Pepsin was the first enzyme prepared from animal tissue. In 1837, Schwann showed conclusively that something in the air that was destroyed by heat caused putrefaction, but the air itself did not.
Schwann became professor at the Belgium University of Louvain]], in 1838, and Liège, in 1848. While there, he found that sugar and starch fermentation were the result of life processes, investigated muscular contraction and nerve structure, and discovered the striated muscle of the upper esophagus and the myelin sheath of peripheral axons, called Schwann cells. Schwann coined the term "metabolism" to describe the chemical changes that take place in living tissue and formulated the basic principles of embryology by observing that an egg is a single cell that will eventually develop into a complete organism.
Schwann, together with Matthias Schleiden, developed the cell theory in 1839, which identified cells as the fundamental particles of plants and animals. Schwann and Schleiden recognized that some organisms are unicellular while others are multicellular. They also recognized cell membranes, nuclei and cell bodies to be common cell features and described them by comparison of various animal and plant tissues. These observations and the cell theory were included in Schwann’s Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants, published in 1839.
Schwann’s animal cell theory stimulated a great deal of research. He is now recognized as the founder of modern histology. Theodor Schwann died in January, 1882, at the age of 71.
Works
It was during the four years spent under the influence of Muller at Berlin that all Schwann's really valuable work was done. Muller was at this time preparing his great book on physiology, and Schwann assisted him in the experimental work required. His attention being thus directed to the nervous and muscular tissues, besides making such histological discoveries as that of the envelope of the nerve fibers which now bears his name, he initiated those researches in muscular contractility since so elaborately worked out by Du Bois-Reymond and others. He was thus the first of Muller's pupils who broke with the traditional vitalism and worked towards a physico-chemical explanation of life.
Muller also directed his attention to the process of digestion, which Schwann showed in 1836 to depend essentially on the presence of a ferment called by him pepsin. Schwann also examined the question of spontaneous generation, which he greatly aided to disprove, and in the course of his experiments discovered the organic nature of yeast. In fact the whole germ theory of Pasteur, as well as its antiseptic applications by Lister, is traceable to his influence.
Once when he was dining with Schleiden in 1837, the conversation turned on the nuclei of vegetable cells. Schwann remembered having seen similar structures in the cells of the notochord (as had been shown by Muller) 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 (Berlin, 1839; trans. Sydenham Society , 1847). The cell theory was thus definitely constituted. In the course of his verifications of the cell theory, in which he traversed the whole field of histology, he proved the cellular origin and development of the most highly differentiated tissues, nails, feathers, enamels, &c. His generalization became the foundation of modern histology, and in the hands of Rudolf Virchow (whose cellular pathology was an inevitable deduction from Schwann) afforded the means of placing modern pathology on a truly scientific basis.
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