Written by The Editors of Encyclopædia Britannica http://www.britannica.com/EBchecked/topic/527571/Mathias-Jacob-Schleiden
Mathias Jacob Schleiden, (born April 5, 1804, Hamburg—died June 23, 1881, Frankfurt am
Main), German botanist, cofounder (with Theodor Schwann) of the cell theory.
Schleiden was educated at Heidelberg (1824–27) and practiced law in Hamburg but soon developed his hobby of botany into a full-time pursuit. Repelled by contemporary botanists’ emphasis on classification,
Schleiden preferred to study plant structure under the microscope. While professor of botany at the
University of Jena, he wrote “Contributions to Phytogenesis” (1838), in which he stated that the different parts of the plant organism are composed of cells or derivatives of cells. Thus, Schleiden became the first to formulate what was then an informal belief as a principle of biology equal in importance to the atomic theory of chemistry. He also recognized the importance of the cell nucleus, discovered in 1831 by the Scottish botanist Robert Brown, and sensed its connection with cell division.
Schleiden was one of the first German biologists to accept Darwin’s theory of evolution. He became professor of botany at Dorpat, Russia, in 1863.
Written by The Editors of Encyclopædia Britannica http://www.britannica.com/EBchecked/topic/528563/Theodor-Schwann
, (born Dec. 7, 1810,
,
—died Jan. 11, 1882,
), German physiologist who founded modern
by defining the
as the basic unit of
structure.
After studying medicine in Berlin, Schwann assisted the physiologist
(1834–38).
In 1836, while investigating digestive processes, he isolated a substance responsible for
in the stomach and named it
, the first enzyme prepared from animal tissue. While professor of
at the Catholic University of Leuven (Louvain), Belg. (1839–48), he observed the formation of
spores and concluded that the
of sugar and starch was the result of
processes. He knew Mathias
well, and a year after the latter, working at University of
Jena, advanced the
for plants, Schwann extended it to animals in his Microscopical
Researches into the Accordance in the Structure and Growth of Animals and Plants (1839).
At the universities of Leuven and Liège, in Belgium (1849–79), he also investigated muscular contraction and nerve structure, discovering the striated muscle in the upper esophagus and the myelin sheath covering peripheral axons, now termed
. He coined the term
for the chemical changes that take place in living tissue, identified the role played by microorganisms in

putrefaction, and formulated the basic principles of embryology by observing that the egg is a single cell that eventually develops into a complete organism. His later years were marked by increasing concern with theological issues.
From: http://www.healio.com/endocrinology/news/print/endocrine-today/%7B74b8d2c3-073c-439d-bb6e-
4a1e5f4cf1b5%7D/rudolf-ludwig-karl-virchow-1821-1902
Rudolf Ludwig Karl Virchow’s career is notable for many achievements. He pioneered the theory of cellular pathology and helped develop the modern science of anthropology. Perhaps his greatest legacy, however, is his role as the champion of social medicine.
In 1848, the Prussian government sent Virchow to an area called Upper Silesia to investigate a typhus epidemic. Virchow spent three weeks there and was appalled by what he found: deplorable living conditions and rampant starvation and disease.
In his report on the epidemic, which was excerpted in the American Journal of Public Health,
Virchow noted that the region’s social and political conditions caused the problem. The only solution was to offer “full and unlimited democracy” to the ethnic Polish people living there. He made several recommendations: introduce Polish as the official language, establish democratic selfgovernment and separate the church and the state.
Virchow believed that preventing future epidemics was “very easy and simple.” According to him,
“education, with its daughters, liberty and prosperity,” would be the necessary tools for epidemic cessation.
He also believed that physicians were uniquely positioned to confront the greatest problems of their time and had a responsibility to solve them. He saw physicians as the greatest advocates for the poor. Virchow would remain a passionate advocate for social medicine and public health reform for the rest of his life.
Cellular pathology pioneer
Virchow is best known as a pioneer in cellular pathology. The theory he popularized, omnis cellula
ex cellula, or that cells are derived from cells, led to the realization that disease is created and reproduced at the cellular level. He presented this theory in a 20-lecture series that laid the foundation for his crucial text Cellular Pathology, which was published in 1858. His work on cellular medicine principles was a major development in modern medicine.