SCHWANN, THEODOR (1810-1882), German physiologist, was born at Neus in Rhenish Prussia on the 7th of December 1810. His 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 Jesuits' college in Cologne and afterwards at Bonn, where he met Johannes Müller, 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 Müller, 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. Schwann in 1838 was called to the chair of anatomy at the Roman Catholic university of Louvain, where he remained nine years. In 1847 he went as professor to Liége, where he remained till his death on the 11th of January 1882. He was of a peculiarly gentle and amiable character, and remained a devout Catholic throughout his life. It was during the four years spent under the influence of Müller at Berlin that all Schwann's really valuable work was done. Müller 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-fibres which now bears his name, he initiated those researches in muscular contractibility since so elaborately worked out by Du Bois Raymond and others. He was thus the first of Müller's pupils who broke with the traditional vitalism and worked towards a physico-chemical explanation of life. Müller also directed his attention to the process of digestion, which Schwann showed 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 Müller) and instantly recognized the importance of connecting the two phenomena. The resemblance was confirmed without delay by both observers, and the results first appeared in his famous Microscopic Investigations on the Accordance in the Structure and Growth of Plants and Animals (Berlin, 1839: trans. Sydenham Society, 1837). 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 histology on a truly scientific basis.
An excellent account of Schwann's life and work is that by Léon Frédéricq (Liége, 1884).