In the period following the increasingly evolutionary views on life,
there were two urgent problems that had to be resolved that touched on
spontaneous generation. Both were heterogenesis issues (life arising
from the degraded or putrified products of other life) and not
abiogenesis (a word coined much later in the century by T. H. Huxley, as
we shall see later). Heterogeny was a major problem in two ways not
related to evolution - one was the issue of the origin of diseases, and
in particular of parasitic worms and flukes; and the other was the cause
of fermentation. The former is a public health issue, exemplified by the
cholera pandemics of 1831, 1848, 1853 and 1861 in England, while the
latter was a matter of great concern in the viticulture and brewing
industry of France and elsewhere. Let us consider fermentation first.
There were two theories as to the origin of microorganisms in
fermentations, and the process of fermentation itself. One was put
forward in 1836 by a French engineer, Charles Cagniard-Latour
(1777-1859), that yeast, recognised as the active ingredient in
fermentation, was made up of minute organisms that caused the
fermentation directly through what we now call their metabolic processes
(a term that was coined only a few years later by Schwann, one of the
discoverers of the cell theory). {Nordenski.9ald 431, Singer 339} The
other, proposed by the famous chemist Antoine-Laurent Lavoisier in 1789,
and championed by Justus von Liebig (1802-1873), was that fermentation
was caused by a chemical process - of the action of air on grape juice
(Joseph-Louis Gay Lussac, 1778-1850, in 1810); or of a compound of
nitrogen in a state of putrefaction or decay that caused a similar
condition in other bodies (Liebig, 1840) {Farley 49}. Of course, the
chemical explanation, although bolstered by the work of Liebig's student
Friedrich W.9ahler (1800-1882) in the synthesis of the organic compund
urea, had a problem - in yeast during fermentation, microorganisms were
found to grow. Therefore, either they grew as a result of the chemistry,
that is, spontaneous generation, or they were infections that took
advantage of these products.
In 1837-8, three researchers independently found that yeast were living
organisms: Cagniard-Latour, Friedrich K.9ftzing, and Schwann. The first
two established that yeast causes the decomposition of sugar when alive,
and not when dead. Schwann, trying to prove that spontaneous generation
did not occur on meat, showed that the air in the flasks used to prove
that meat would not putrefy when boiled was still vital by using it to
grow yeast on boiled cane sugar. When they did not cause fermentation,
he examined the yeast and concluded it was an articulated fungi and
concluded, without real warrant, that alcoholic fermentation occurs when
yeast (or as he called it, the sugar fungus, or Zuckerpilz) uses sugar
and nitrogenous substances for its growth, incidentally converting these
elements to alcohol. He was right, but that was not known then. Liebig
rejected his evidence. So although there was a minority view that yeast
were living organisms causing fermentation, the majority view remained
that chemical fermentation occurred, and spontaneous generation was the
cause of yeast cells.
Contagion, on the other hand, was equally critical. It might be thought
that the success in antiseptic techniques introduced by Joseph Lister
(1827-1912) in 1865 proved that contagion was caused by pathogens, he
might be cell products, not cells. {Farley 83} In any case, this was
after Pasteur. More to the point was John Snow's () work on tracing the
source of cholera in London in 1849 and 1855 to certain wells. Although
it was thought that the epidemic was due to transmission, most British
contagionists thought that the contagion was due to nonorganismic
thought diseases were transmitted by miasmas. So it stood when Pasteur
undertook his research.
Theodor Schwann's work, in particular, had asserted that cells might
form out of cell products such as the extracellular material he called
the Cytoblastema, while his co-theorist Matthias Schleiden (1804-1881)
thought that all cells formed from structures within existing cells.
Hugo von Mohl (1805-1872), though he thought that cells were in general
formed by direct division, still said in passing that free cell
formation might occur independently of life of the parent plant in the
creation of parasitic fungi, yeast cells, etc., both in the decomposing
fluid of cells and in the excreted or expressed juices. {Farley 53}
The famous pathologist and cytologist Rudolph Virchow (1821-1902) agreed
with Robert Remak (1815-1865) who said in 1852 that the occurrence of
free cell formation was as improbable as spontaneous generation. Virchow
considered spontaneous generation as heresy, or devil's work in 1855,
and much later asserted that Schwann had reinvigorated the old doctrine
of _generatio aequivoca_, as spontaneous generation was known. {Farley
199n} In its place, Virchow asserted that any kind of life required a
matrix, a prior organisation:
Life does not reside in the fluids as such, but only in their cellular
parts; it is necessary to exclude cell-free fluids from the realm of the
living and intercellular material of cell-containing fluids as well. ...
Life will always remain something apart, even if we should find out that
it is mechanically aroused and propagated down to the minutest detail.
{quoted in Farley 54} 
Virchow famously propounded the dictum _Omnis cellula e cellula_ (all
cells from cells), but he never was able to provide an absolute
demonstration of this established principle; for a very good reason -
you can neither prove a universal negative nor a universal positive with
a finite or limited set of observations. Even as Virchow was attacking
the non-ceullar origin of cells, cell theory itself was being modified
to accommodate the idea of a protoplasm, which will become important
in the period after Pasteur.
Other combatants over spontaneous generation at this time included
Christian Ehrenberg (1795-1876; opposed) and Felix Dujardin (1801-1862,
in favour), among others. {Farley 55-56}. One interesting side debate
was whether or not parasitic worm and liver flukes formed through
irritations in the tissues of the sufferers or due to infection. In
Britain, around 240 papers were published on this subject, which was
clouded by the fact that, as it turned out, many such parasites have
distinct forms in alternating generations, and so the infecting
parasites were not recognised as being the same species. The discovery
of the alternation of generations was made by Japetus Steenstrup
(1813-1897), a Danish zoologist, in 1842.
Pouchet and Pasteur
-------------------
The Director of the Natural History Museum in Rouen, F.8elix Archim.8fde
Pouchet (1800-1872), began presenting a series of papers in 1855 to the
Academy of Sciences in Paris, purporting to prove spontaneous
generation, and to show not only that it happened, but under what
circumstances. He named his subject _heterogenesis_, which was the title
of a massive volume he published in 1859. Like Buffon and Needham,
Pouchet thought that heterogenesis was not accidental, but due to the
vital force of the materials, which had to be pre-existing organic
matter. According to him, the causal factors involved were organic
matter, water, air, and the right temperature. {Magner 270} 
Pouchet's results showed, he claimed, that although in the animal
kingdom, all life arose from eggs, those eggs arose, at times, by
produce an adult being; it proceeds in the same manner as sexual
generation which, as we shall show, is initially a completely
spontaneous act by which the plastic force brings together in a special
organ the primitive elements of the organism. {quoted in Farley 97}
In other words, Pouchet thought that sexual generation was a spontaneous
act caused by a vital force as much as spontaneous generation. He held
that this occurred by divine providence rather than chance. Spontaneous
generation had been previously attacked for being irreligious, as the
event was due to the chance recombination of molecules. Pouchet's
version was divinely guided. He thought that both the original act of
creation was divinely guided, and so too were subsequent events. Hence,
Pouchet was trying to wrest spontaneous generation from the
the attributes of the Creator, can only augment Divine Majesty. {Farley
98} As Farley notes, Pasteur and subsequent accounts of the debate
overlooked Pouchet's orthodox theism and piety.
Moreover, Pouchet's account was based on the origination of new life
from the organic material of old life, not from non-living matter:
The succession of life on the surface of the globe links matter in a
narrow circle from which it cannot escape. It is successively attracted
sometimes intimately united to form organisms, and sometimes free in
space, are no less animated with a latent life, which seems to wait only
for their grouping to be visibly manifested. It seems that for organic
molecules, there is no death ... only a transition to a new life.
{quoted in Farley 98}
The obvious exception to this is, of course, the first divine creation.
All else required a force plastique, a molding power.
But Louis Pasteur (1822-1895) objected to the idea of spontaneous
generation. The French Academy of Science offered the Alhumbert Prize of
2500 francs to whoever could shed new light on the question of
so-called spontaneous generation. Pasteur won it in 1862 for his famous
essay in 1861, M.8emoire sur les corpuscules organis.8es qui existent 
dans
l'atmosph.8fre, published in their Annales the next year. In this he
described a series of elegant experiments designed to disprove Pouchet's
major claim that there were no organisms introduced into his flasks.
Agreeing that neither the air used, nor the water contained germs in
Pouchet's experiment, and that he had sufficiently sterilised the flask
and materials with heat, he focused on another item in the experiment -
the mercury trough in which Pouchet cooled the flask. In this, Pasteur
claimed, dust, carrying germs, had settled and this introduced germs
into Pouchet's sealed flask.
Pasteur could not, of course, merely argue that Pouchet *might* have
made this mistake, he had to show that if properly carried out, no germs
would spontaneously develop. So he had flasks made with a series of
differing shapes designed to allow the movement of air, but not of dust
that would carry germs, into the flask containing sterilised broth. The
liquid remained clear for months. As one biographer notes, 
The observer had a choice between only two hypotheses: placing the
starches) that float in the atmosphere, or in spores of molds or the
eggs of infusoria. Pasteur said: I prefer to think that life comes from
life rather than from dust. {Debr.8e 161}
Subsequent debate and experiment involved sampling air from the ceilings
of cathedrals by Pouchet, and from a ballon by Pasteur, and mountaintops
by the two. A competition in June 1864 between the two overseen by a
Pasteur-inclined committee of the Academy was won by Pasteur when
Pouchet walked out claiming bias and misprocedure. Pasteur was held to
have shown that spontaneous generation did not exist, and became a hero
in French society. But had he shown this?
Strictly, Pouchet had shown that hay infusions would generate even when
boiled, because, as it was shown a while later, hay had heat resistant
spores. {Geison 131} Had he stayed in the competition, he may very well
have won (although not because he was right about spontaneous
generation). More worrying to us moderns is that it transpires, now that
Pasteur's notebooks have become available (they were made available only
in the 1970s, and an index published only in 1985), that Pasteur
repeatedly ignored positive results in experiments, claiming that they
were due to error rather than spontaneous generation; in fact only 10%
of his experiments gave his desired result. {Geison 130}
Even so, Pasteur was correct - modern life, including fungi and
infusorians, did not arise from non-living matter, whether or not that
matter was organic or elemental. The debate over his experimental
technique matters only to historians, although Geison's book caused an
enormous furore in France, where Pasteur is something of a secular saint.
In his later years, Pasteur was forced to modify some of his views (not
about spontaneous generation). He had thought that microorganisms
retained their virulence indefinitely. But in 1881, he was forced to
admit that virulence could attenuate spontaneously (and he made it the
foundation of his anti-rabies vaccine). Debr.8e says, And now, at the  age
of sixty, Pasteur was once again facing facts that did not fit in which
his concepts. Attenuated virulence conflicted with his biological
philosophy. He had to renounce his dogmas and enter the debate on the
evolution of species. He had to choose between Darwin's view that
selection was in operation, or Lamarck's that the environment directly
influenced the species of organism, and chose Lamarck. But he did accept
transmutation of species, as is demonstrated by his comment quoted in
Hilaire Cuny's biography, unfortunately not referenced, from Pasteur
{Cuny 122}:
Virulence appears in a new light which cannot but be alarming to
humanity; unless nature, in her evolution down the ages (an evolution
which, as we now know, has been going on for millions, nay, hundreds of
millions of years), has finally exhausted all the possibilities of
producing virulent or contagious diseases - which does not seem very
likely.
Although he shortly afterwards refers to the myriad species of
Creation, it is clear that he accepted the reality of evolution.
Moreover, he characterised the interaction between microbes and hosts as
a struggle for existence (a phrase, it must be remembered, invented by
the Swiss botanist Alphonse de Candolle, and borrowed by Darwin).
However, I doubt he accepted that evolution occurred by natural
selection, as the French rarely did until the 1950s and Jacques Monod's
writings. However, he was not a creationist, at least at this point in
his life.
Moreover, much has been made about Pasteur's faith. It is often claimed
that he was a devout Catholic, but it seems he was very lax in his
religious devotion, reading through church services as a student, and
not attending church much during his life. He was, it must be said,
opposed to the philosophical vogue of radical materialism in France,
from which the spontaneous generation debate sprang, but he was hardly a
model believer. Even so, despite claims made by Farley and Geison that
Pasteur allowed his research to be guided by his a priori philosophy, he
*did* turn out to be correct that the growths of germs were caused by
pre-existing germs, and that fermentation was due to yeast.
So we must ask - what did Pasteur prove? Did he prove that no life can
ever come from non-living things? No, he didn't, and this is because you
cannot disprove something like that experimentally, only theoretically,
and he had no theory of molecular biology to establish this claim. What
he showed was that it was highly unlikely that *modern* living organisms
arose from non-living organic material. This is a much more restricted
claim than that primitive life once arose from non-living non-organic
material.
Summary
-------
So far we have seen that neither Redi, Spallanzani nor Pasteur disproved
the origination of life in all cases, only in particular cases.
Moreover, we have seen that the claims all life from eggs, all cells
from cells and all life from life are generalisations not fully
supported by the experimental evidence available at the time they were
made.
References (not previously cited)
----------
Cuny, Hilaire. 1965. Louis Pasteur: the man and his theories. Translated
by P. Evans. London: The Scientific Book Club.
Debr.8e, P. 1998. Louis Pasteur. Baltimore: Johns Hopkins University
Press.
Farley, John. 1977. The spontaneous generation controversy from
Descartes to Oparin. Baltimore: Johns Hopkins University Press.
Geison, Gerald L. 1995. The private science of Louis Pasteur. Princeton,
N.J.: Princeton University Press.
--
The theory of spontaneous generation was finally laid to rest in 1859 
by the young French chemist, Louis Pasteur. The French Academy of 
Sciences sponsored a contest for the best experiment either proving 
or disproving spontaneous generation. Pasteur's winning experiment 
was a variation of the methods of Needham and Spallanzani. He boiled 
meat broth in a flask, heated the neck of the flask in a flame until 
it became pliable, and bent it into the shape of an S. Air could 
enter the flask, but airborne microorganisms could not - they would 
settle by gravity in the neck. As Pasteur had expected, no 
microorganisms grew. When Pasteur tilted the flask so that the broth 
reached the lowest point in the neck, where any airborne particles 
would have settled, the broth rapidly became cloudy with life. 
Pasteur had both refuted the theory of spontaneous generation and 
convincingly demonstrated that microorganisms are everywhere - even 
in the air.
-- us
generation, and to show not only that it happened, but under what
circumstances. He named his subject _heterogenesis_, which was the title
of a massive volume he published in 1859. Like Buffon and Needham,
Pouchet thought that heterogenesis was not accidental, but due to the
vital force of the materials, which had to be pre-existing organic
matter. According to him, the causal factors involved were organic
matter, water, air, and the right temperature. {Magner 270} 
Pouchet's results showed, he claimed, that although in the animal
kingdom, all life arose from eggs, those eggs arose, at times, by
produce an adult being; it proceeds in the same manner as sexual
generation which, as we shall show, is initially a completely
spontaneous act by which the plastic force brings together in a special
organ the primitive elements of the organism. {quoted in Farley 97}
In other words, Pouchet thought that sexual generation was a spontaneous
act caused by a vital force as much as spontaneous generation. He held
that this occurred by divine providence rather than chance. Spontaneous
generation had been previously attacked for being irreligious, as the
event was due to the chance recombination of molecules. Pouchet's
version was divinely guided. He thought that both the original act of
creation was divinely guided, and so too were subsequent events. Hence,
Pouchet was trying to wrest spontaneous generation from the
the attributes of the Creator, can only augment Divine Majesty. {Farley
98} As Farley notes, Pasteur and subsequent accounts of the debate
overlooked Pouchet's orthodox theism and piety.
Moreover, Pouchet's account was based on the origination of new life
from the organic material of old life, not from non-living matter:
The succession of life on the surface of the globe links matter in a
narrow circle from which it cannot escape. It is successively attracted
sometimes intimately united to form organisms, and sometimes free in
space, are no less animated with a latent life, which seems to wait only
for their grouping to be visibly manifested. It seems that for organic
molecules, there is no death ... only a transition to a new life.
{quoted in Farley 98}
The obvious exception to this is, of course, the first divine creation.
All else required a force plastique, a molding power.
But Louis Pasteur (1822-1895) objected to the idea of spontaneous
generation. The French Academy of Science offered the Alhumbert Prize of
2500 francs to whoever could shed new light on the question of
so-called spontaneous generation. Pasteur won it in 1862 for his famous
essay in 1861, M.8emoire sur les corpuscules organis.8es qui existent 
dans
l'atmosph.8fre, published in their Annales the next year. In this he
described a series of elegant experiments designed to disprove Pouchet's
major claim that there were no organisms introduced into his flasks.
Agreeing that neither the air used, nor the water contained germs in
Pouchet's experiment, and that he had sufficiently sterilised the flask
and materials with heat, he focused on another item in the experiment -
the mercury trough in which Pouchet cooled the flask. In this, Pasteur
claimed, dust, carrying germs, had settled and this introduced germs
into Pouchet's sealed flask.
Pasteur could not, of course, merely argue that Pouchet *might* have
made this mistake, he had to show that if properly carried out, no germs
would spontaneously develop. So he had flasks made with a series of
differing shapes designed to allow the movement of air, but not of dust
that would carry germs, into the flask containing sterilised broth. The
liquid remained clear for months. As one biographer notes, 
The observer had a choice between only two hypotheses: placing the
starches) that float in the atmosphere, or in spores of molds or the
eggs of infusoria. Pasteur said: I prefer to think that life comes from
life rather than from dust. {Debr.8e 161}
Subsequent debate and experiment involved sampling air from the ceilings
of cathedrals by Pouchet, and from a ballon by Pasteur, and mountaintops
by the two. A competition in June 1864 between the two overseen by a
Pasteur-inclined committee of the Academy was won by Pasteur when
Pouchet walked out claiming bias and misprocedure. Pasteur was held to
have shown that spontaneous generation did not exist, and became a hero
in French society. But had he shown this?
Strictly, Pouchet had shown that hay infusions would generate even when
boiled, because, as it was shown a while later, hay had heat resistant
spores. {Geison 131} Had he stayed in the competition, he may very well
have won (although not because he was right about spontaneous
generation). More worrying to us moderns is that it transpires, now that
Pasteur's notebooks have become available (they were made available only
in the 1970s, and an index published only in 1985), that Pasteur
repeatedly ignored positive results in experiments, claiming that they
were due to error rather than spontaneous generation; in fact only 10%
of his experiments gave his desired result. {Geison 130}
Even so, Pasteur was correct - modern life, including fungi and
infusorians, did not arise from non-living matter, whether or not that
matter was organic or elemental. The debate over his experimental
technique matters only to historians, although Geison's book caused an
enormous furore in France, where Pasteur is something of a secular saint.
In his later years, Pasteur was forced to modify some of his views (not
about spontaneous generation). He had thought that microorganisms
retained their virulence indefinitely. But in 1881, he was forced to
admit that virulence could attenuate spontaneously (and he made it the
foundation of his anti-rabies vaccine). Debr.8e says, And now, at the  age
of sixty, Pasteur was once again facing facts that did not fit in which
his concepts. Attenuated virulence conflicted with his biological
philosophy. He had to renounce his dogmas and enter the debate on the
evolution of species. He had to choose between Darwin's view that
selection was in operation, or Lamarck's that the environment directly
influenced the species of organism, and chose Lamarck. But he did accept
transmutation of species, as is demonstrated by his comment quoted in
Hilaire Cuny's biography, unfortunately not referenced, from Pasteur
{Cuny 122}:
Virulence appears in a new light which cannot but be alarming to
humanity; unless nature, in her evolution down the ages (an evolution
which, as we now know, has been going on for millions, nay, hundreds of
millions of years), has finally exhausted all the possibilities of
producing virulent or contagious diseases - which does not seem very
likely.
Although he shortly afterwards refers to the myriad species of
Creation, it is clear that he accepted the reality of evolution.
Moreover, he characterised the interaction between microbes and hosts as
a struggle for existence (a phrase, it must be remembered, invented by
the Swiss botanist Alphonse de Candolle, and borrowed by Darwin).
However, I doubt he accepted that evolution occurred by natural
selection, as the French rarely did until the 1950s and Jacques Monod's
writings. However, he was not a creationist, at least at this point in
his life.
Moreover, much has been made about Pasteur's faith. It is often claimed
that he was a devout Catholic, but it seems he was very lax in his
religious devotion, reading through church services as a student, and
not attending church much during his life. He was, it must be said,
opposed to the philosophical vogue of radical materialism in France,
from which the spontaneous generation debate sprang, but he was hardly a
model believer. Even so, despite claims made by Farley and Geison that
Pasteur allowed his research to be guided by his a priori philosophy, he
*did* turn out to be correct that the growths of germs were caused by
pre-existing germs, and that fermentation was due to yeast.
So we must ask - what did Pasteur prove? Did he prove that no life can
ever come from non-living things? No, he didn't, and this is because you
cannot disprove something like that experimentally, only theoretically,
and he had no theory of molecular biology to establish this claim. What
he showed was that it was highly unlikely that *modern* living organisms
arose from non-living organic material. This is a much more restricted
claim than that primitive life once arose from non-living non-organic
material.
Summary
-------
So far we have seen that neither Redi, Spallanzani nor Pasteur disproved
the origination of life in all cases, only in particular cases.
Moreover, we have seen that the claims all life from eggs, all cells
from cells and all life from life are generalisations not fully
supported by the experimental evidence available at the time they were
made.
References (not previously cited)
----------
Cuny, Hilaire. 1965. Louis Pasteur: the man and his theories. Translated
by P. Evans. London: The Scientific Book Club.
Debr.8e, P. 1998. Louis Pasteur. Baltimore: Johns Hopkins University
Press.
Farley, John. 1977. The spontaneous generation controversy from
Descartes to Oparin. Baltimore: Johns Hopkins University Press.
Geison, Gerald L. 1995. The private science of Louis Pasteur. Princeton,
N.J.: Princeton University Press.
--
The theory of spontaneous generation was finally laid to rest in 1859 
by the young French chemist, Louis Pasteur. The French Academy of 
Sciences sponsored a contest for the best experiment either proving 
or disproving spontaneous generation. Pasteur's winning experiment 
was a variation of the methods of Needham and Spallanzani. He boiled 
meat broth in a flask, heated the neck of the flask in a flame until 
it became pliable, and bent it into the shape of an S. Air could 
enter the flask, but airborne microorganisms could not - they would 
settle by gravity in the neck. As Pasteur had expected, no 
microorganisms grew. When Pasteur tilted the flask so that the broth 
reached the lowest point in the neck, where any airborne particles 
would have settled, the broth rapidly became cloudy with life. 
Pasteur had both refuted the theory of spontaneous generation and 
convincingly demonstrated that microorganisms are everywhere - even 
in the air.
--