Editing Spontaneous generation (section)

== Experimental approach==

=== Early tests ===

The Brussels physician [[Jan Baptist van Helmont]] described a recipe for mice (a piece of dirty cloth plus wheat for 21 days) and scorpions ([[basil]], placed between two bricks and left in sunlight). His notes suggest he may have attempted to do these things.<ref>{{Cite web |last=Pasteur |first=Louis |author-link=Louis Pasteur |date=7 April 1864 |title=On Spontaneous Generation |type=Address delivered by Louis Pasteur at the "Sorbonne Scientific Soirée" |url=http://shell.cas.usf.edu/~alevine/pasteur.pdf |access-date=1 July 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090326183109/http://shell.cas.usf.edu/~alevine/pasteur.pdf |archive-date=26 March 2009 }}</ref>

Where Aristotle held that the [[embryo]] was formed by a [[coagulation]] in the [[uterus]], the English physician [[William Harvey]] showed by way of [[dissection]] of [[deer]] that there was no visible embryo during the first month.<!--Bayon 1947 esp pp 73–75--> Although his work predated the [[microscope]], this led him to suggest that life came from invisible eggs. In the [[Book frontispiece|frontispiece]] of his 1651 book ''Exercitationes de Generatione Animalium'' (''Essays on the Generation of Animals''), he denied spontaneous generation with the motto ''omnia ex ovo'' ("everything from eggs").<ref name="irisfry"/><ref name="Bayon 1947">{{cite journal |last=Bayon |first=H. P. |title=William Harvey (1578–1657): His Application of Biological Experiment, Clinical Observation, and Comparative Anatomy to the Problems of Generation |journal=Journal of the History of Medicine and Allied Sciences |date=1947 |volume=2 |issue=1 |pages=51–96 |doi=10.1093/jhmas/II.1.51 |jstor=24619518 |pmid=20242557 |url=https://www.jstor.org/stable/24619518 |access-date=4 January 2023 |archive-date=25 January 2023 |archive-url=https://web.archive.org/web/20230125230800/https://www.jstor.org/stable/24619518 |url-status=live }}</ref>

[[File:Illustration of Redi's 1668 experiment to refute spontaneous generation.svg|thumb|upright=1.5|Illustration of Redi's 1668 experiment to refute spontaneous generation]]

The ancient beliefs were subjected to testing. In 1668, the Italian physician and parasitologist [[Francesco Redi]] challenged the idea that maggots arose spontaneously from rotting meat. In the first major [[experiment]] to challenge spontaneous generation, he placed meat in a variety of sealed, open, and partially covered containers.<ref name="slowdeath">{{Cite web |last1=Levine |first1=Russell |last2=Evers |first2=Chris |url=http://webprojects.oit.ncsu.edu/project/bio183de/Black/cellintro/cellintro_reading/Spontaneous_Generation.html |title=The Slow Death of Spontaneous Generation (1668–1859) |access-date=December 19, 2008 |year=1999 |publisher=National Health Museum |location=Washington, D.C.|archive-url=https://web.archive.org/web/20160124023828/http://webprojects.oit.ncsu.edu/project/bio183de/Black/cellintro/cellintro_reading/Spontaneous_Generation.html |archive-date=24 January 2016 }}</ref> Realizing that the sealed containers were deprived of air, he used "fine Naples veil", and observed no worms on the meat, but they appeared on the cloth.<ref name="fredi">{{cite book |last=Redi |first=Francesco |author-link=Francesco Redi |translator=Mab Bigelow |title=Experiments on the Generation of Insects |url=https://archive.org/details/experimentsonge00bigegoog |orig-year=1669 |year=1909 |publisher=Open Court |location=Chicago }}</ref> Redi used his experiments to support the preexistence theory put forth by the Catholic Church at that time, which maintained that living things originated from parents.<ref name="Fry2000">{{cite book |last=Fry |first=Iris |title=Emergence of Life on Earth: A Historical and Scientific Overview |url=https://books.google.com/books?id=6KoRvUeUUuEC |date= 2000 |publisher=Rutgers University Press |isbn=978-0-8135-2740-6 |pages=27–}}</ref> In scientific circles Redi's work very soon had great influence, as evidenced in a letter from the English [[Natural theology|natural theologian]] [[John Ray]] in 1671 to members of the [[Royal Society]] of London, in which he calls the spontaneous generation of insects "unlikely".<ref>{{cite journal |title=Hutton, Charles, 1737–1823; Shaw, George, 1751–1813; Pearson, Richard, 1765–1836. The Extract of a Letter written by Mr. JOHN RAY, to the Editor, from Middleton, July 3, 1671, concerning Spontaneous Generation;... Number 73, p. 2219. |journal=The Philosophical Transactions of the Royal Society of London, from Their Commencement in 1665 |year=1800 |pages=617–618 |url=https://archive.org/details/philosophicaltra01royarich}}</ref>

[[Pier Antonio Micheli]], {{circa|1729}}, observed that when fungal [[spore]]s were placed on slices of melon, the same type of fungi were produced that the spores came from, and from this observation he noted that fungi did not arise from spontaneous generation.<ref name="Agrios2005">{{cite book |last=Agrios |first=George N. |title=Plant Pathology |url=https://books.google.com/books?id=CnzbgZgby60C&pg=PA17 |access-date=14 August 2012 |year=2005 |publisher=Academic Press |isbn=978-0-12-044565-3 |pages=17–}}</ref>

In 1745, [[John Needham]] performed a series of experiments on boiled [[broth]]s. Believing that boiling would kill all living things, he showed that when sealed right after boiling, the broths would cloud, allowing the belief in spontaneous generation to persist. His studies were rigorously scrutinized by his peers, and many of them agreed.<ref name="slowdeath"/>

[[Lazzaro Spallanzani]] did an extensive variety of observations and experiments that modified the experiments of Needham in 1768, where he attempted to exclude the possibility of introducing a contaminating factor between boiling and sealing. His technique involved boiling the broth in a sealed container with the air partially [[Vacuum|evacuated]] to prevent explosions. Although he did not see growth, the exclusion of air left the question of whether air was an essential factor in spontaneous generation.<ref name="slowdeath"/> But attitudes were changing; by the start of the 19th century, a scientist such as [[Joseph Priestley]] could write that "There is nothing in modern philosophy that appears to me so extraordinary, as the revival of what has long been considered as the exploded doctrine of equivocal, or, as Dr. [Erasmus] Darwin calls it, spontaneous generation."<ref>{{cite journal |last=Priestley |first=Joseph |author-link=Joseph Priestley |title=Observations and Experiments relating to equivocal, or spontaneous, Generation |journal=[[Transactions of the American Philosophical Society]] |year=1809 |volume=VI |pages=119–129 |url=https://archive.org/details/transactionsofam61809amer }}</ref>

In 1837, [[Charles Cagniard de la Tour]], a physicist, and [[Theodor Schwann]], one of the founders of cell theory, published their independent discovery of [[yeast]] in [[alcoholic fermentation]]. They used the microscope to examine foam left over from the process of [[brewing]] beer. Where the Dutch microscopist [[Antonie van Leeuwenhoek]] described "small spheroid globules", they observed yeast cells undergo [[cell division]]. Fermentation would not occur when sterile air or pure oxygen was introduced if yeast were not present. This suggested that airborne [[microorganism]]s, not spontaneous generation, was responsible.<ref>{{cite journal |last=Springer |first=Alfred |date=October 13, 1892 |title=The Micro-organisms of the Soil |journal=Nature |volume=46 |issue=1198 |pages=576–579 |url=https://books.google.com/books?id=LHkCAAAAIAAJ&pg=PT138 |doi=10.1038/046576b0 |bibcode=1892Natur..46R.576. |s2cid=4037475 }}</ref>

However, although the idea of spontaneous generation had been in decline for nearly a century, its supporters did not abandon it all at once. As [[James Rennie (naturalist)|James Rennie]] wrote in 1838, despite Redi's experiments, "distinguished naturalists, such as [[Johann Friedrich Blumenbach|Blumenbach]], [[Georges Cuvier|Cuvier]], [[Jean Baptiste Bory de Saint-Vincent|Bory de St. Vincent]], [[Robert Brown (botanist, born 1773)|R. Brown]], &c." continued to support the theory.<ref name=JRIT>{{cite book | url=https://archive.org/details/insecttransforma00renn |last=Rennie |first=James |title=Insect Transformations |publisher=Charles Knight |year=1838 |page=10}}</ref>

===Pasteur and Tyndall===

[[File:Experiment Pasteur English.jpg|thumb|upright=1.2|[[Louis Pasteur]]'s 1859 experiment showed that a boiled nutrient broth did not give rise spontaneously to new life, but that if direct access to air was permitted, the broth decomposed, implying that small organisms (in modern terms, [[Endospore|microbial spores]]) had fallen in and started to grow in the broth.<ref name="Ball"/><ref name="TyndallFragments2"/> ]]

[[Louis Pasteur]]'s  experiment's in the late 1850's are widely seen as having settled the question of spontaneous generation.<ref>{{Cite web |url=https://www.immunology.org/pasteurs-col-de-cygnet-1859 |title=Pasteur's "col de cygnet" (1859) |website=www.immunology.org |publisher=[[British Society for Immunology]] |archive-url=https://web.archive.org/web/20190811175656/https://www.immunology.org/pasteurs-col-de-cygnet-1859 |access-date=August 11, 2019 |archive-date=11 August 2019 }}</ref> He boiled a meat broth in a [[swan neck flask]]; the bend in the neck of the flask prevented falling particles from reaching the broth, while still allowing the free flow of air. The flask remained free of growth for an extended period. When the flask was turned so that particles could fall down the bends, the broth quickly became clouded.<ref name="slowdeath" /> However, minority objections were persistent and not always unreasonable, given that the experimental difficulties were far more challenging than the popular accounts suggest. The investigations of the Irish physician [[John Tyndall]], a correspondent of Pasteur and an admirer of his work, were decisive in disproving spontaneous generation. All the same, Tyndall encountered difficulties in dealing with [[Endospore|microbial spores]], which were not well understood in his day. Like Pasteur, he boiled his [[microbiological culture|cultures]] to sterilize them, and some types of bacterial spores can survive boiling. The [[autoclave]], which eventually came into universal application in medical practice and microbiology to sterilise equipment, was introduced after these experiments.<ref name= "TyndallFragments2">{{cite book |last=Tyndall |first=John |author-link=John Tyndall |title=Fragments of Science |volume=2 |chapter=IV, XII, XIII |orig-year=1876–1878 |publisher=P. F. Collier |location=New York |date=1905 |url=https://archive.org/details/fragmenoscien02tyndrich }}</ref>

In 1862, the [[French Academy of Sciences]] paid special attention to the issue, establishing a prize "to him who by well-conducted experiments throws new light on the question of the so-called spontaneous generation" and appointed a commission to judge the winner.<ref>{{cite book |last1=Engelhardt |first1=Hugo Tristram |last2=Caplan |first2=Arthur L. |title=Scientific Controversies: Case Studies in the Resolution and Closure of Disputes in Science and Technology |url=https://books.google.com/books?id=6nkSX63VsLkC&pg=PA107 |year=1987 |publisher=Cambridge University Press |isbn=978-0-521-27560-6 |page=107}}</ref> Pasteur and others used the term ''biogenesis'' as the opposite of spontaneous generation, to mean that life was generated only from other life. Pasteur's claim followed the German physician [[Rudolf Virchow]]'s doctrine ''Omnis cellula e cellula'' ("all cells from cells"),<ref>{{cite book |last=Virchow |first=Rudolf |author-link=Rudolf Virchow |title=Die Cellularpathologie |language=de |trans-title=Cell Pathology |publisher=August Hirschwald |year=1859 |location=Berlin |url =https://archive.org/details/diecellularpatho00virc/ }}</ref> itself derived from the work of [[Robert Remak]].<ref>{{cite journal |last=Remak |first=Robert |date=1852 |title=Über extracellulare Entstehung thierischer Zellen und über Vermehrung derselben durch Theilung |language=de |trans-title=On the extracellular origin of animal cells, and their multiplication by division |journal=Archiv für Anatomie, Physiologie und Wissenschaftliche Medicin |volume=19 |pages=47–57}}</ref><ref name="slowdeath"/> After Pasteur's 1859 experiment, the term "spontaneous generation" fell out of favor. Experimentalists used a variety of terms for the study of the origin of life from nonliving materials. ''Heterogenesis'' was applied to the generation of living things from once-living organic matter (such as boiled broths), and the English physiologist [[Henry Charlton Bastian]] proposed the term ''archebiosis'' for life originating from non-living materials. Disliking the randomness and unpredictability implied by the term ''spontaneous generation'', in 1870 Bastian coined the term ''biogenesis'' for the formation of life from nonliving matter. Soon thereafter, however, the English biologist [[Thomas Henry Huxley]] proposed the term ''abiogenesis'' for this same process, and adopted ''biogenesis'' for the process by which life arises from existing life.<ref>{{cite book |last=Strick |first=James |title=Evolution & The Spontaneous Generation |chapter-url=https://books.google.com/books?id=yjKplNQv9zoC&pg=PR11 |access-date=August 27, 2012 |date= 2001 |publisher=Continuum International Publishing Group |isbn=978-1-85506-872-8 |pages=xi–xxiv |chapter=Introduction}}</ref>