Matthias Schleiden, Theodor Schwann, and Cell Theory
It was Robert Hooke in the 17th century who first observed cells and gave them that name, but the German botanist Matthias Schleiden (1804–81) was the first scientist to appreciate their importance. All living organisms either consist of a single cell or are made up of cells, and organisms grow and reproduce by the division of cells. This fundamental tenet of biology is called the cell theory. It was first stated in 1838 in a book by Schleiden entitled Beitrage zur Phytogenesis (Contributions of phytogenesis). Schleiden based his conclusion on observations of plant tissues.
Hooke had examined the dead tissues he found in cork, but Schleiden studied living cells and he saw that their contents moved within and between the cells and along fibers composed of elongated cells joined end to end. Schleiden called this process protoplasmic streaming; the protoplasm outside the cell nucleus that he saw is now known as cytoplasm. Schleiden also described the division of the cell nucleus during cell division, but mistakenly thought a daughter nucleus separated from the parent nucleus by budding. Nevertheless, his work gave biologists their first insight into the most basic structure of all living organisms.
In preparing his theory, Schleiden had consulted his friend the German physiologist Theodor Schwann (1810–82), and the following year, 1839, Schwann extended the cell theory to animals, in Mikroskopische Untersuchungen uber die Ubereinstimmung in der Struktur und dem Wachstum der Tiere und Pflanzen (Microscopical researches into the agreement between the structure and growth of animals and plants). Schleiden and Schwann are jointly credited with having originated the cell theory. Schwann was also the first scientist to observe that an egg begins as a single cell and develops into a complex organism by repeated cell division.
Matthias Jakob Schleiden was born in Hamburg on April 5, 1804. In 1824 he entered the University of Heidelburg to study law. He graduated in 1827, and for a time he practiced law in Hamburg, but then turned to botany and medicine, which he studied at the universities of Gottingen, Berlin, and Jena, finally graduating in 1831. After graduating Schleiden was appointed professor of botany at Jena, where he remained until 1862, when he became professor of botany at the University of Dorpat, Estonia. In 1864 he returned to Germany and began teaching privately in Frankfurt-am-Main, where he died on June 23, 1881.
Theodor Schwann was born on December 7, 1810, at Neuss, not far from Dusseldorf, Germany. He was educated at the Jesuit college in Cologne and studied medicine at the universities of Bonn, Wurzburg, and Berlin. He qualified in medicine at Berlin in 1834. After graduating he spent four years working as an assistant to the physiologist Johannes Muller (1801–58) at the Museum of Anatomy in Berlin. In 1836 and 1837 Schwann studied fermentation and was able to show that the fermentation of sugar to alcohol was the result of processes within living yeast cells. This work came in for heavy criticism, and in 1839 Schwann left Germany to become professor of anatomy at the Roman Catholic University of Louvain, Belgium. He remained there until 1848, when he became professor of anatomy at the University of Liege. He died in Cologne on January 11, 1882.
Schwann strongly refuted the idea of spontaneous generation—that living animals could emerge from putrefying matter. The cell theory supported this refutation, and the theory was encapsulated in an epigram omnis cellula e cellula (every cell from a cell) by the French naturalist and physiologist Francois-Vincent Raspail (1794–1878). The German physician and biologist Rudolf Virchow (1821–1902) popularized the epigram in 1858, and Virchow is sometimes included as one of the originators of the cell theory.
- Erasmus Darwin and The Botanic Garden
- Joseph Priestley and “Dephlogisticated Air”
- Stephen Hales, the Movement of Sap, and Transpiration
- Robert Hooke and the Cell
- Marcello Malpighi and the Microscopic Study of Plants
- Nehemiah Grew, Plant Reproduction, and Comparative Anatomy
- Nikolai Vavilov and the Origin of Cultivated Plants
- Gote Turesson and Plant Ecotypes