Editing Spontaneous generation (section)

=== 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>