Editing Cell theory (section)

== Cell theory ==

[[File:PSM V22 D156 Matthias Jacob Schleiden.jpg|thumb|[[Matthias Jakob Schleiden]] (1804–1881)]]

[[File:Schwann Theodore.jpg|thumb|upright|[[Theodor Schwann]] (1810–1882)]]

Credit for developing cell theory is usually given to two scientists: [[Theodor Schwann]] and [[Matthias Jakob Schleiden]].<ref>{{cite book |last=Sharp |first=L. W. |year=1921 |url=https://archive.org/details/introductiontocy032473mbp |title=Introduction To Cytology |location=New York |publisher=McGraw Hill Book Company Inc.}}</ref> While [[Rudolf Virchow]] contributed to the theory, he is not as credited for his attributions toward it. In 1839, Schleiden suggested that every structural part of a plant was made up of cells or the result of cells. He also suggested that cells were made by a crystallization process either within other cells or from the outside.<ref>{{cite journal|author=Schleiden, M. J. |year=1839|title= Beiträge zur Phytogenesis|journal=Archiv für Anatomie, Physiologie und wissenschaftliche Medicin|volume=1838|pages=137–176|url=https://www.biodiversitylibrary.org/item/49861#page/347/mode/1up}}</ref> However, this was not an original idea of Schleiden. He claimed this theory as his own, though [[Barthelemy Charles Joseph Dumortier|Barthelemy Dumortier]] had stated it years before him. This crystallization process is no longer accepted with [[#Modern interpretation|modern cell theory]]. In 1839, [[Theodor Schwann]] states that along with plants, animals are composed of cells or the product of cells in their structures.<ref>{{cite book |last=Schwann |first=T. |year=1839 |title=Mikroskopische Untersuchungen über die Uebereinstimmung in der Struktur und dem Wachsthum der Thiere und Pflanzen |publisher=Sander |place=Berlin |url=http://www.deutschestextarchiv.de/book/show/schwann_mikroskopische_1839}}</ref> This was a major advance in the field of biology since little was known about animal structure up to this point compared to plants. From these conclusions about plants and animals, two of the three tenets of cell theory were postulated.

:1. All living organisms are composed of one or more cells
:2. The cell is the most basic unit of life

Schleiden's theory of free cell formation through crystallization was refuted in the 1850s by [[Robert Remak]], [[Rudolf Virchow]], and [[Albert Kolliker]].<ref name="Unifying Concept">{{Cite journal| doi=10.1038/8964| pmid=10559875| year=1999| last1=Mazzarello| first1=P.| journal=Nature Cell Biology| volume=1| issue=1| url=http://newburyparkhighschool.net/barra/classes/bio_cp/handout_cell%20theory%20reading_students.doc| pages=E13–5| title=A unifying concept: the history of cell theory| s2cid=7338204| url-status=dead| archive-url=https://web.archive.org/web/20150603062810/http://newburyparkhighschool.net/barra/classes/bio_cp/handout_cell%20theory%20reading_students.doc| archive-date=2015-06-03}}</ref> In 1855, Rudolf Virchow added the third tenet to cell theory. In Latin, this tenet states ''Omnis cellula e cellula''. This translated to:

:3. All cells arise only from pre-existing cells

However, the idea that all cells come from pre-existing cells had already been proposed by Robert Remak; it has been suggested that Virchow plagiarized Remak.<ref>{{cite journal |last=Silver |first=G. A. |title=Virchow, the heroic model in medicine: health policy by accolade |journal=[[American Journal of Public Health]] |year=1987 |volume=77 |issue=1 |pmid=3538915 |pmc=1646803 |doi=10.2105/AJPH.77.1.82 |pages=82–88}}</ref> Remak published observations in 1852 on cell division, claiming Schleiden and Schawnn were incorrect about generation schemes. He instead said that [[binary fission]], which was first introduced by Dumortier, was how reproduction of new animal cells were made. Once this tenet was added, classical cell theory was complete.