Schwann

Schwann Theodor (Theodor Schwann; 1810-1882), one of the greatest histologists and physiologists of the first half of the 19th century. He studied natural sciences and medicine in Bonn, Würzburg, and Berlin. He was a student and one of the closest colleagues of the famous physiologist Johannes Müller. From 1839 to 1848, he was a professor of anatomy in Leuven (Belgium). From 1848 to 1878, he was a professor of physiology and comparative anatomy in Liège. Schwann rejected the hypothesis of the digestive role of gastric mucus and established for the first time the importance of pepsin as a digestive enzyme; he also found the fundamental analogy between the processes of digestion, fermentation, and decay. As a histologist, Schwann is known for his work on the fine structure of blood vessels, smooth muscles, and nerves (establishing the sheath surrounding nerve fibers, composed of a series of cells, the so-called Schwann sheath, or neurilemma). Schwann is best known as one of the creators of the so-called cell theory (see). In 1837, under the influence of Schleiden's report on the structure of plant organisms, Schwann began to study the animal organism from a new perspective, and in 1839 he published his famous work "Mikroskopische Untersuchungen über die Übereinstimmung in der Struktur und dem Wachstum der Tiere und Pflanzen" (Berlin; reissued, Leipzig, 1910), in which he formulated his view of the animal organism as being built from individual cells, the most important part of which Schwann considered the cell wall, and the most characteristic constant element the nucleus. Cells arise, in Schwann's opinion, through a special process that closely resembles crystallization from a homogeneous maternal substance (cytoblast). Despite a number of completely erroneous views, which were subjected to review and correction in the following years, the scheme of the structure of the animal organism created by Schwann formed the basis of cell theory and proved to be one of the most important and fruitful ideas in biology. A special merit of Schwann should be recognized as his use of the evolutionary method in his research, that is, the study of cells, starting from the early stages of development.