Theodor Schwann

German biologist

• Born: December 7, 1810; Neuss, Kingdom of Prussia (now Germany)
• Died: January 11, 1882; Cologne, Germany

Nineteenth-century biologist Theodor Schwann contributed to the development of cell theory through his observations of the notochord in animals. He also helped to uncover the role played by pepsin in digestions, and discovered the cell covering on nerves, now called Schwann cells.

Primary field: Biology

Specialty: Cellular biology

Early Life

Theodor Ambrose Hubert Schwann was born on December 7, 1810 in Neuss, a town in what was then the Kingdom of Prussia and is now simply part of Germany. He was the third of ten children. Both his father and grandfather were goldsmiths. Schwann’s father also operated a printing press. During his early life, Schwann was an introvert. He inherited his father’s mechanical abilities, and constructed crude microscopes and electrical devices to conduct rudimentary science work.

Schwann was raised in a strict Catholic family and culture. After graduating from the local Jesuit high school, where he excelled in physics and mathematics, Schwann enrolled at the Jesuit College of the Three Crowns in Cologne in 1826. Schwann’s family hoped he would follow in the footsteps of his elder brother, Peter, who joined the clergy and became a professor of theology at Frauenberg. However, after enrolling in a philosophy class in 1829 at the University of Bonn, Schwann decided he would pursue a career in medicine. It was at Bonn that Schwann also met the physiologist Johannes Müller, who played an influential role later in Schwann’s professional life. Müller introduced Schwann to scientific research and provided the opportunity for him to study spinal nerves and the process of blood coagulation.

In 1831, Schwann enrolled at the University of Würzburg and began studying medicine. At Würzburg, Schwann studied with bone surgeon Cajetan von Textor and pathologist Johann Lukas Schönlein.

In 1832, the July Revolution swept through much of Europe, including the German states, and many of the teachers at Würzburg, including Textor, were dismissed, or opted to relocate to safer environments. Schwann left Würzburg to enroll at the Friedrich Wilhelms University in Berlin. Coincidently, Müller was offered a position as Chair and Professor of Anatomy and Physiology at the university, providing Schwann with a mentor to direct his medical studies. In 1834 Schwann completed his doctoral thesis, “De necessitate æris atmosphærici ad evolutionem pulli in ovo incubato” (The requirement for atmospheric air for development of the chick embryo), and received his medical degree.

Life’s Work

Müller arranged for Schwann’s appointment as an aid at the university’s anatomical museum in 1834. Schwann replaced anatomist Jacob Henle as Müller’s assistant at the museum in 1840.

Schwann carried some of his most important scientific work during the first four years of his appointment as a museum aid, including his role in applying cell theory to animals. Schwann described these events late in his career, during a celebration of his professorship at Liege. He had a dinner discussion with the plant anatomist Matthias Schleiden, who described his observations of the nuclei found in plant cells. Schwann noted to Schleiden that he had observed similar structures in animal notochords and was curious whether they played a similar role in the gill cartilage of Rana esculenta (frogs). After showing the images to Schleiden back in the laboratory, Schwann decided to investigate the role played by nuclei in cell formation.

Schwann was interested in testing for the presence of a “life force.” In an era in which spontaneous generation had yet to be disproven, some scientists attributed the existence of all cell metabolic properties to such a force. Schwann attempted to address the question by demonstrating the role of specific physiological processes to account for events that take place within cells. Among his first discoveries was his identification of an enzyme involved in digestion. Schwann termed the enzyme pepsin, named for “pepsis,” an early term meaning digestion. He also demonstrated the role of microscopic agents in both putrefaction and fermentation, disproving any role of spontaneous generation.

Schwann’s application of what modern scientists would call the scientific method was particularly instructive in refuting the concept of a “life force” as a factor in spontaneous generation. In the 1760s, Italian biologist Lazzaro Spallanzani demonstrated that heated infusions did not decay. Schwann replicated Spallanzani’s work but also measured the oxygen content of the heated air, showing the level was identical to regular air, and that the heated air would still allow survival of a frog. Schwann’s idea was premature, however, and it was not until a generation later that French microbiologist Louis Pasteur proved his theory correct.

The foundation of cell theory as applied to plants and animals is attributed to the work of Schleiden and Schwann. However, their views regarding the role of the nucleus, or cytoblast as it was then known, were inaccurate. Schleiden and Schwann theorized that cells were generated from an amorphous material referred to as the “cytoblastem.” Further, their theory proposed that the nucleus formed within the cytoblastem, with the remainder of the cell crystallizing around the structure. Schwann’s first major publication, Microscopical Researches into the Accordancein the Structure and Growth of Animals and Plants (1839), was the outcome of this work. However, this view of the cell was later shown to be inaccurate through the work of Polish physiologist Robert Remak and German pathologist Rudolf Virchow in the 1840s and 1850s.

Schwann took a position as professor of anatomy at the Catholic University of Louvain in Belgium in 1838. He spent the next nine years in Louvain, working primarily as a lecturer. In his scientific work, he worked to further the idea that microscopic organisms are the basis for decay. Schwann also demonstrated the critical role of bile in digestion, concluding that interference with bile secretion by means of a biliary fistula can have lethal effects on the organism.

In 1848, Schwann’s colleague, physiologist Joseph Spring, persuaded him to accept an offer at the University of Liege. Schwann replaced Spring as chair of the anatomy department in 1853. His career in laboratory research was largely complete by the time he moved to Liege. Nevertheless, he remained interested in the development of mechanical devices, a skill he retained from his youth. Among his inventions in Liege was an industrial device used to remove water from mines.

In 1858, Schwann was appointed to professorships in physiology, general anatomy, and physiology. As he aged, he gradually retired, teaching only physiology by the 1870s as an emeritus professor. During Christmas 1881, he suffered a stroke while visiting his family in Cologne and died early in January 1882.

Impact

Schwann’s contribution to cell theory in animals mirrored the accomplishments of Schleiden in plant biology. While helping to refute the theory of spontaneous generation, Schwann also established the origins of cell and tissue structures in animals, demonstrating their development from preexisting cells. In Schwann’s view, the cell served a structural purpose but was also the source of metabolic processes for the organism.

Schwann’s use of microscopy for analysis of tissues and cells established the field of modern histology. His methods of investigation, including applications of the scientific method, served as a model for the scientific work of others. Virchow, considered the father of cellular pathology, was among those who built on Schwann’s work by demonstrating the role of the cell in the establishment of disease processes, while at the same time refuting Schwann’s views on the origin of cells from cytoblasts. In addition to his accomplishments in cell biology, Schwann’s investigation of digestive processes helped lay the foundation of metabolic research.

Bibliography

Alberts, Bruce, et al. Essential Cell Biology. New York: Garland Science, 2009. Print. College-level introduction to the cell. Highlighted with numerous photographs, the book provides a thorough description of cell structure and function in both plants and animals.

Pollard, Thomas, et al. Cell Biology. Philadelphia: Saunders, 2007. Print. Intermediate-level college textbook on cell structure and function. Emphasis is placed on cell processes.

Schwann, Theodor. Microscopical Researches into the Accordance in the Structure and Growth of Animals and Plants. Charleston: Nabu, 2010. Print. Reproduction of Schwann’s original paper on cell biology.