pasteur beef broth experiment

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Pasteur's Experiment

The steps of Pasteur's experiment are outlined below:

First, Pasteur prepared a nutrient broth similar to the broth one would use in soup.

Next, he placed equal amounts of the broth into two long-necked flasks. He left one flask with a straight neck. The other he bent to form an "S" shape.

Then he boiled the broth in each flask to kill any living matter in the liquid. The sterile broths were then left to sit, at room temperature and exposed to the air, in their open-mouthed flasks.

After several weeks, Pasteur observed that the broth in the straight-neck flask was discolored and cloudy, while the broth in the curved-neck flask had not changed.

He concluded that germs in the air were able to fall unobstructed down the straight-necked flask and contaminate the broth. The other flask, however, trapped germs in its curved neck, preventing them from reaching the broth, which never changed color or became cloudy.

If spontaneous generation had been a real phenomenon, Pasteur argued, the broth in the curved-neck flask would have eventually become reinfected because the germs would have spontaneously generated. But the curved-neck flask never became infected, indicating that the germs could only come from other germs.

Pasteur's experiment has all of the hallmarks of modern scientific inquiry. It begins with a hypothesis and it tests that hypothesis using a carefully controlled experiment. This same process — based on the same logical sequence of steps — has been employed by scientists for nearly 150 years. Over time, these steps have evolved into an idealized methodology that we now know as the scientific method. After several weeks, Pasteur observed that the broth in the straight-neck flask was discolored and cloudy, while the broth in the curved-neck flask had not changed.

Let's look more closely at these steps.

Please copy/paste the following text to properly cite this HowStuffWorks.com article:

3.1 Spontaneous Generation

Learning objectives.

By the end of this section, you will be able to:

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

Clinical Focus

Barbara is a 19-year-old college student living in the dormitory. In January, she came down with a sore throat, headache, mild fever, chills, and a violent but unproductive (i.e., no mucus) cough. To treat these symptoms, Barbara began taking an over-the-counter cold medication, which did not seem to work. In fact, over the next few days, while some of Barbara’s symptoms began to resolve, her cough and fever persisted, and she felt very tired and weak.

What types of respiratory disease may be responsible?

Jump to the next Clinical Focus box

Humans have been asking for millennia: Where does new life come from? Religion, philosophy, and science have all wrestled with this question. One of the oldest explanations was the theory of spontaneous generation, which can be traced back to the ancient Greeks and was widely accepted through the Middle Ages.

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation , the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“spirit” or “breath”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. 1

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont , a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers ( Figure 3.2 ). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. 2 He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Lazzaro Spallanzani (1729–1799) did not agree with Needham’s conclusions, however, and performed hundreds of carefully executed experiments using heated broth. 3 As in Needham’s experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani’s results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani’s findings, Needham argued that life originates from a “life force” that was destroyed during Spallanzani’s extended boiling. Any subsequent sealing of the flasks then prevented new life force from entering and causing spontaneous generation ( Figure 3.3 ).

Check Your Understanding

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur , a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it ( Figure 3.4 ). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “ Omne vivum ex vivo ” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan-neck flask experiment, stating that “…life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” 4 To Pasteur’s credit, it never has.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?
1 K. Zwier. “Aristotle on Spontaneous Generation.” http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf
2 E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196.
3 R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206.
4 R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142.

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2.1 Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation , the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain molded, mice appeared. Jan Baptista van Helmont, a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

However, one of van Helmont’s contemporaries, Italian physician Francesco Redi (1626–1697), performed an experiment in 1668 that was one of the first to refute the idea that maggots (the larvae of flies) spontaneously generate on meat left out in the open air. He predicted that preventing flies from having direct contact with the meat would also prevent the appearance of maggots. Redi left meat in each of six containers ( Figure 2 .2 ). Two were open to the air, two were covered with gauze, and two were tightly sealed. His hypothesis was supported when maggots developed in the uncovered jars, but no maggots appeared in either the gauze-covered or the tightly sealed jars. He concluded that maggots could only form when flies were allowed to lay eggs in the meat, and that the maggots were the offspring of flies, not the product of spontaneous generation.

Francesco Redi’s experimental setup consisted of an open container, a container sealed with a cork top, and a container covered in mesh that let in air but not flies. Maggots only appeared on the meat in the open container. However, maggots were also found on the gauze of the gauze-covered container.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

Lazzaro Spallanzani (1729–1799) did not agree with Needham’s conclusions, however, and performed hundreds of carefully executed experiments using heated broth. [3] As in Needham’s experiment, broth in sealed jars and unsealed jars was infused with plant and animal matter. Spallanzani’s results contradicted the findings of Needham: Heated but sealed flasks remained clear, without any signs of spontaneous growth, unless the flasks were subsequently opened to the air. This suggested that microbes were introduced into these flasks from the air. In response to Spallanzani’s findings, Needham argued that life originates from a “life force” that was destroyed during Spallanzani’s extended boiling. Any subsequent sealing of the flasks then prevented new life force from entering and causing spontaneous generation ( Figure 2 .3 ).

(a) Francesco Redi, who demonstrated that maggots were the offspring of flies, not products of spontaneous generation. (b) John Needham, who argued that microbes arose spontaneously in broth from a “life force.” (c) Lazzaro Spallanzani, whose experiments with broth aimed to disprove those of Needham.

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

The debate over spontaneous generation continued well into the 19th century, with scientists serving as proponents of both sides. To settle the debate, the Paris Academy of Sciences offered a prize for resolution of the problem. Louis Pasteur, a prominent French chemist who had been studying microbial fermentation and the causes of wine spoilage, accepted the challenge. In 1858, Pasteur filtered air through a gun-cotton filter and, upon microscopic examination of the cotton, found it full of microorganisms, suggesting that the exposure of a broth to air was not introducing a “life force” to the broth but rather airborne microorganisms.

Later, Pasteur made a series of flasks with long, twisted necks (“swan-neck” flasks), in which he boiled broth to sterilize it ( Figure 2 .4 ). His design allowed air inside the flasks to be exchanged with air from the outside, but prevented the introduction of any airborne microorganisms, which would get caught in the twists and bends of the flasks’ necks. If a life force besides the airborne microorganisms were responsible for microbial growth within the sterilized flasks, it would have access to the broth, whereas the microorganisms would not. He correctly predicted that sterilized broth in his swan-neck flasks would remain sterile as long as the swan necks remained intact. However, should the necks be broken, microorganisms would be introduced, contaminating the flasks and allowing microbial growth within the broth.

Pasteur’s set of experiments irrefutably disproved the theory of spontaneous generation and earned him the prestigious Alhumbert Prize from the Paris Academy of Sciences in 1862. In a subsequent lecture in 1864, Pasteur articulated “ Omne vivum ex vivo ” (“Life only comes from life”). In this lecture, Pasteur recounted his famous swan- neck flask experiment, stating that “…life is a germ and a germ is life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment.” [4] To Pasteur’s credit, it never has.

(a) French scientist Louis Pasteur, who definitively refuted the long-disputed theory of spontaneous generation. (b) The unique swan-neck feature of the flasks used in Pasteur ’s experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur’s experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination. In the second part of the experiment, the flask was boiled and then the neck was broken off. The broth in this flask became contaminated.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?
K. Zwier. “Aristotle on Spontaneous Generation.” http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf ↵
E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur, trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵

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Spontaneous Generation

Spontaneous generation, also called abiogenesis, is the belief that some living things can arise suddenly, from inanimate matter , without the need for a living progenitor to give them life.

In the fourth century B . C ., the Greek philosopher and scientist Aristotle argued that abiogenesis is one of four means of reproduction, the others being budding (asexual), sexual reproduction without copulation, and sexual reproduction with copulation. Indeed, the Greek goddess Gea was said to be able to create life from stones. Even Albertus Magnus (Albert the Great), the great German naturalist of the thirteenth century Middle Ages, believed in spontaneous generation, despite his extensive studies of the biology of plants and animals.

Through the centuries, the notion of spontaneous generation gave rise to a wide variety of exotic beliefs, such as that snakes could arise from horse hairs standing in stagnant water , mice from decomposing fodder, maggots from dead meat, and even mice from cheese and bread wrapped in rags and left in a corner. The appearance of maggots on decaying meat was especially strong evidence, for many people, that spontaneous generation did occur.

Spontaneous generation found further support from the observations of the Dutch merchant Anton van Leewenhoek, the inventor of the first, primitive microscopes. From 1674 to 1723 Leewenhoek corresponded to the Royal Society in London, describing the tiny, rapidly moving, "animacules" he found in rain water, in liquid in which he had soaked peppercorn, and in the scrapings from his teeth (which, to Leeuwenhoek's surprise, had no such animacules after he had drunk hot coffee).

In the seventeenth century, however, some scientists set out to determine whether living organisms could indeed arise through spontaneous generation, or if they arose only from other living organisms (biogenesis).

In 1668, even before Anton van Leeuwenhoek began his study of microscopic organisms with the microscope , the Italian physician Francisco Redi began a series of experiments that showed that dead meat does not give rise spontaneously to maggots.

Redi filled six jars with decaying meat, leaving three open and sealing the other three. The unsealed jars attracted flies , which laid their eggs on the decaying meat, while the meat in the sealed jars was unavailable to flies. When maggots developed on the meat in the open jars, Redi believed he had demonstrated that spontaneous generation did not occur. However, supporters of the notion of spontaneous generation claimed that the lack of fresh air-not the absence of egg-laying flies-had prevented maggots from appearing on the meat.

Therefore, Redi undertook a second experiment, in which he covered the tops of three of the jars with a fine net instead of sealing them. Once again, maggots failed to appear on the meat in the covered jars, but did appear on the meat in the open jars, where flies were able to lay their eggs.

Nevertheless, the tiny "animacules," described by Leeuwenhoek in his observations on microscopic life in drops of water, still held the imagination of many scientists, who continued to believe that such creatures were small and simple enough to be generated from nonliving material.

John Needham, an eighteenth century English naturalist and Roman Catholic theologian, began his study of natural science after reading about Leewenhoek's animacules. Needham became a strong advocate of spontaneous generation, and performed an experiment that he felt supported his belief in biogenesis. In 1745, he heated chicken and corn broths, poured them into covered flasks. Soon after the broths cooled, they teemed with microorganisms , prompting Needham to claim that the organisms arose through spontaneous generation.

Needham's work was contradicted by another religious investigator, the Italian physiologist Lazzaro Spallanzani. Spallanzani, who was educated in the classics and philosophy at a Jesuit college, went on to teach logic, metaphysics, Greek, and physics . About 20 years after Needham announced the results of his own investigation of spontaneous generation, Spallanzani showed that when broth was heated after being sealed in a flask, it did not generate life forms. He suggested that Needham's broths had probably supported growth after being heated because they had been contaminated before being sealed in their containers.

Undeterred, Needham counterclaimed that heat destroyed the "vital force" needed for spontaneous generation, and that, by sealing the flasks, Spallanzani had kept out this vital force .

The argument continued into the nineteenth century, when the German scientist Rudolf Virchow in 1858, introduced the concept of biogenesis; living cells can arise only from preexisting living cells.

But the matter remained unresolved until two years later when the great French scientist Louis Pasteur, in a series of classic experiments demonstrated that (1) microorganisms are present in the air and can contaminate solutions; and (2) the air itself does not create microbes.

Pasteur filled short-necked flasks with beef broth and boiled them, leaving some opened to the air to cool and sealing others. While the sealed flasks remained free of microorganisms, the open flasks were contaminated within a few days.

In a second set of experiments, Pasteur placed broth in flasks that had open-ended, long necks. After bending the necks of the flasks into S-shaped curves that dipped downward, then swept sharply upward, he boiled the contents. The contents of these uncapped flasks remained uncontaminated even months later. Pasteur explained that the S-shaped curve allowed air to pass into the flask; however, the curved neck trapped airborne microorganisms at the bottom of the curve, preventing them from traveling into the broth.

Pasteur not only executed a brilliant set of experiments, he also used his zeal and skill as a promoter of his ideas to strike a decisive blow to spontaneous generation. For example, in a lecture at the Sorbonne in Paris in 1864, Pasteur said that he had water for his experimental liquids to generate life. But, he said, "....it is dumb, dumb since these experiments were begun several years ago; it is dumb because I have kept it sheltered from the only thing man does not know how to produce, from the germs which float in the air, from Life, for Life is a germ and a germ is Life. Never will the doctrine of spontaneous generation recover from the mortal blow of this simple experiment!" Pasteur's work not only disproved abiogenesis, but also offered support to other researchers attempting to show that some diseases were caused by microscopic life forms. Thus, in a simple, but elegant set of experiments, Pasteur not only struck the doctrine of spontaneous generation a "mortal blow," but also helped to establish the germ theory of disease .

Marc Kusinitz

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Louis Pasteur, Spontaneous Generation, and Germ Theory

“For I have kept from them, and am still keeping from them, that one thing which is above the power of man to make; I have kept from them the germs that float in the air, I have kept them from life.” - Louis Pasteur

“For I have kept from them, and am still keeping from them, that one thing which is above the power of man to make; I have kept from them the germs that float in the air, I have kept them from life.” – Louis Pasteur (1)

May 19, 1861 is a date that probably doesn’t ring a bell or cause any light bulbs to go off in terms of huge scientific events. In the United States, people weren’t thinking too much about science. The Civil War was only five weeks old, and Union and Confederate gunships were trying, to no avail, to capture the Chesapeake Bay (2) .

In England, Charles Darwin’s On the Origin of Species had already been in circulation for a year and a half, leaving scientific revolution and controversy in its wake. (3) Elsewhere in Europe, Gregor Mendel still tended the pea plants that became the basis of what we now know as “classical” genetics after he presented his work to the scientific world in 1865 (4) . And in Paris, a chemist named Louis Pasteur presented an experiment in front of his colleagues at the Paris Society for Chemistry that would turn the scientific world and much of what we believed on its head (5) .

Prior to Pasteur’s experiment, a belief called “spontaneous generation” was a prevalent scientific method to explain how life came to be. This belief outlined that life can essentially arise from anything, even out of thin air. So if a piece of meat spoiled, the cause of the spoilage simply materialized from the air!

What Pasteur did was put the belief of spontaneous generation to rest with a simple, yet brilliant experiment. Pasteur boiled some nutrient broth inside a flask with a long, twisted neck. The flask, while still open to the air, did not allow any microbes to enter the main area of the flask where the sterile broth was. Any bacteria in the air couldn’t pass through the long neck of the flask to get to the broth inside. No bacteria meant no contamination, and the broth stayed sterile for one whole year! Pasteur then broke the neck of the flask and exposed the broth to the microbe-filled air, which contaminated the broth in short order.

Life Comes From Life

What is the ultimate impact of Pasteur’s experiment? He didn’t win the Nobel Prize for it (the first Nobel Prizes were awarded in 1901, and Pasteur died in 1895) (1, 6) .

But there came a shift in attitude regarding how life came to be. The idea that “life comes from life” is now one of the major tenets of biology. Its significance is right up there with evolution and the cell theory (7) .

Even more significantly, Pasteur’s experiment had an even greater impact on medicine. In the years following Pasteur’s experiment, Pasteur and one of his contemporaries (and eventually, his bitter rival) Robert Koch began studying various diseases closely and concluded that specific microbes have the ability to cause specific diseases (1, 8, 9) .

This is the germ theory of disease. This theory led to the successful identification and treatment of many microbial diseases (1) , saving millions of lives and contributing to the development of what we know today as modern medicine.

All because of a chemist and his funny-looking flask.

References:

Talaro, Kathleen Park, and Barry Chess. Foundations in Microbiology , ninth edition. New York: McGraw-Hill (2015).
Battle Summary: Sewell’s Point, VA . CWSCA Battle Summaries: The American Battlefield Preservation Program (ABPP) . Retrieved from https://www.nps.gov/abpp/Battles/va001.htm
Darwin, Charles. On the Origin of Species by Means of Natural Selection . London: John Murray (1859). Retrieved from https://www.gutenberg.org/files/1228/1228-h/1228-h.htm
Mendel, Gregor.Versuche über Pflanzen-Hybriden. Verh. Naturforsch. Ver. Brünn 4: 3–47 (1866) (Article in German). Retrieved from http://www.biodiversitylibrary.org/item/124139#page/133/mode/1up
Pasteur, Louis. Sur les corpuscles organisés qui existent dans l’atmosphère: Examen de la doctrine des générations spontanées. Leçon Professée a la Société Chimique de Paris, le 19 Mai 1861 (Article in French).
Nobel Prize Facts. Retrieved from http://www.nobelprize.org/nobel_prizes/facts/
Simon, Eric J., Dickey, Jean L., Hogan, Kelly A, and Jane B. Reece. Campbell Essential Biology, sixth edition. New York: Pearson Higher Education (2016).
Smith, Kendall. Louis Pasteur, the father of immunology? Frontiers in Immunology 3(68), 1-10 (April 2012).
Blevins, Steve M., and Bronze, Michael S. Robert Koch and the ‘golden age’ of bacteriology. International Journal of Infectious Diseases 14: e744–e751 (2010).

About the Author

Craig Fenn is in his fourth year of teaching for the American Public University in the School of Science, Technology, Engineering and Math, with a primary teaching assignment of SCIN 130 (Introduction to Biology with Lab). His primary employer is at Reading Area Community College, where he serves as the course lead for Principles of Biology and Microbiology as well as the chair of the Campus Life Committee. He is a native of Connecticut currently living outside of Lancaster, PA.

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The middle years 1862-1877

Louis Pasteur’s work raised a new set of research questions, such as " Where do fermentation agents come from ? " and " Do they originate from germs similar to themselves or do they appear spontaneously as explained by the spontaneous generation theory ? "

Spontaneous generation - the big debate

At the time the spontaneous generation theory was widely accepted in scientific circles. Louis Pasteur decided to approach the issue via his experimental method.

This required the use of swan-necked flasks. Water in the flask was brought to the boil for a few minutes until the steam escaped from the open end of the flask. It was then left to cool. While cooling, the air entering the flask deposited dust and germs on the first bend. Although in contact with outside air the liquid remained unaltered because germs could not get through.

Louis Pasteur showed that microbes were omnipresent - in water, in air, on objects, on the skin – and that some were responsible for diseases.

After some memorable struggles against his opponents, notably the famous biologist and fierce defender of the spontaneous generation theory, Félix Pouchet, in his 1862 paper Louis Pasteur was able to claim that :

airborne dust contained microorganisms which develop and multiply.
even the most putrescible liquids remained unadulterated if kept away from air (and hence these microorganisms) after heating.

He recommended ways of preventing and fighting these germs, and thus the habits essential for personal and social hygiene . This notably included the use of aseptic procedure s, i.e. the various measures to be taken to prevent invasion of live tissue or inert environments by exogenous microorganisms or viruses. He advocated the importance of sterilization of linen and dressings, passing instruments through a flame and clean hands . These recommendations led to the widespread advent of modern surgery.

So how does fermentation work ?

But Louis Pasteur still had ferments in mind. He pondered on fermentation and how ferments work. While studying butyric fermentation he discovered a new class of living organisms capable of living without air.

He used the term " anaerobic " to describe ferments able to live without air and " aerobic " for microorganisms requiring the presence of free oxygen to grow.

He came to the conclusion that fermentation is the consequence of life without air.

He applied his microbiological method to industry and agriculture to eradicate ancient diseases affecting crops and products.

To the rescue of industry and agriculture

He studied the formation of vinegar and the conversion of alcohol into acetic acid by Mycoderma aceti, which fixes oxygen from the air onto the alcohol. He showed vinegar makers how to produce vinegar of consistent quality by avoiding contamination by harmful mycoderma.

Wine diseases

Wine was France flagship industry and a difficult business in many respects. Winemakers had difficulty guaranteeing the quality of their production which was affected by diseases of no known cause or cure. The crisis was nothing new but risked damaging exports and above all trade agreements in place with England. Emperor Napoleon III called on Louis Pasteur to seek a solution. First he showed that each wine disease was due to a particular ferment. He developed a protocol to fight the diseases, heating the wine to between 55°C and 60°C, a temperature at which it does not deteriorate and its bouquet is preserved. This method is now known worldwide as pasteurization .

Just like wine, beer is infected by microorganisms transmitted by airborne dust. Louis Pasteur taught brewers to preserve the wort from the impurities and to heat the beer to 55° to prevent disease.

Silkworm diseases

In 1865, disease hit the silk industry. In France, this posed a threat to the economy of an entire region and the disease spread further afield to other silk-producing countries such as Italy, Austria and Asia Minor. Louis Pasteur discovered that silkworms were affected by two diseases - silkworm nosema disease and flacherie.

Under the microscope, Louis Pasteur noticed that the worms with nosema disease developed shiny corpuscles, and showed that the disease was both hereditary and contagious. He developed the cellular egg production method to enable the preservation of healthy silkworm eggs. He isolated the female moths to allow them to lay their eggs separately. After laying, he ground the female moths and examined them under the microscope. If the shiny corpuscles were observed he destroyed the eggs, otherwise he kept them for breeding. As for flacherie, he introduced the "specific terrain" concept, i.e. the physiological condition of the infected host favoring outbreak of the disease. A few hygiene rules, good ventilation and quarantine of the suspect batches sufficed to prevent contamination. These simple processes saved the silk industry from doom. But the research was of considerable value, paving the way for the study of contagious diseases. For the first time problems of heredity and contagion were scientifically proven and prophylaxis rules were established. The time had now come for Louis Pasteur to address human diseases.

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3. The Cell

3.1 Spontaneous Generation

Learning objectives.

Explain the theory of spontaneous generation and why people once accepted it as an explanation for the existence of certain types of organisms
Explain how certain individuals (van Helmont, Redi, Needham, Spallanzani, and Pasteur) tried to prove or disprove spontaneous generation

CLINICAL FOCUS: Part 1

What types of respiratory disease may be responsible?

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The Theory of Spontaneous Generation

The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter. Aristotle proposed that life arose from nonliving material if the material contained pneuma (“vital heat”). As evidence, he noted several instances of the appearance of animals from environments previously devoid of such animals, such as the seemingly sudden appearance of fish in a new puddle of water. [1]

This theory persisted into the 17th century, when scientists undertook additional experimentation to support or disprove it. By this time, the proponents of the theory cited how frogs simply seem to appear along the muddy banks of the Nile River in Egypt during the annual flooding. Others observed that mice simply appeared among grain stored in barns with thatched roofs. When the roof leaked and the grain moulded, mice appeared. Jan Baptista van Helmont , a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

An open container with meat has flies and the formation of maggots in meat. A cork-sealed container of meat has no flies and no formation of maggots in meat. A gauze covered container of meat has flies and maggots on the surface of the gauze but no maggots in the meat.

In 1745, John Needham (1713–1781) published a report of his own experiments, in which he briefly boiled broth infused with plant or animal matter, hoping to kill all preexisting microbes. [2] He then sealed the flasks. After a few days, Needham observed that the broth had become cloudy and a single drop contained numerous microscopic creatures. He argued that the new microbes must have arisen spontaneously. In reality, however, he likely did not boil the broth enough to kill all preexisting microbes.

a) drawing of Francesco Redi. B) drawing of John Needham c) drawing of Lazzaro Spallanzani.

Describe the theory of spontaneous generation and some of the arguments used to support it.
Explain how the experiments of Redi and Spallanzani challenged the theory of spontaneous generation.

Disproving Spontaneous Generation

a) Photo of Louis Pasteur b) Photo of Pasteur’s swan-necked flask, c) A drawing of Pasteur’s experiment that disproved the theory of spontaneous generation.

How did Pasteur’s experimental design allow air, but not microbes, to enter, and why was this important?
What was the control group in Pasteur’s experiment and what did it show?

Key Takeaways

The theory of spontaneous generation states that life arose from nonliving matter. It was a long-held belief dating back to Aristotle and the ancient Greeks.
Experimentation by Francesco Redi in the 17th century presented the first significant evidence refuting spontaneous generation by showing that flies must have access to meat for maggots to develop on the meat. Prominent scientists designed experiments and argued both in support of (John Needham) and against (Lazzaro Spallanzani) spontaneous generation.
Louis Pasteur is credited with conclusively disproving the theory of spontaneous generation with his famous swan-neck flask experiment. He subsequently proposed that “life only comes from life.”

Multiple Choice

Fill in the blank, short answer.

Explain in your own words Pasteur’s swan-neck flask experiment.
Explain why the experiments of Needham and Spallanzani yielded in different results even though they used similar methodologies.

Critical Thinking

What would the results of Pasteur’s swan-neck flask experiment have looked like if they supported the theory of spontaneous generation?

Media Attributions

OSC_Microbio_03_01_Rediexpt
https://link.springer.com/content/pdf/10.1007%2Fs10739-017-9494-7.pdf ↵
E. Capanna. “Lazzaro Spallanzani: At the Roots of Modern Biology.” Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
R. Mancini, M. Nigro, G. Ippolito. “Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation.” Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵

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Louis Pasteur’s Contributions to Science

Louis Pasteur in his laboratory, painting by Albert Edelfelt.

Many people know Louis Pasteur for the process that bears his name— pasteurization . However, Pasteur made several other very important contributions to science that you should know about.

Molecular asymmetry In studying crystals of sodium ammonium tartrate, Pasteur found that although they had the same chemical composition, they did not necessarily have the same structure. He noted that the molecules occurred in two mirror-image arrangements that could not be superimposed. This molecular asymmetry, or chirality, is the foundation of a branch of science known as stereochemistry . It had huge implications for how we now understand such things as DNA; the chirality of molecules can even affect how medication is absorbed in the body.
Fermentation In the mid-1850s, Pasteur undertook a series of studies on alcoholic fermentation at a local distillery. He learned about many aspects of fermentation, including the compounds that cause milk to sour. In 1857 he presented evidence that all fermentation is caused by microorganisms and that specific microorganisms cause specific kinds of fermentation.
Pasteurization Using his work with fermentation, Pasteur was able to devise a process, now known as pasteurization , to kill microbes and preserve certain products. Pasteurization prevents fermenting and spoilage in beer, milk, and other goods.
Spontaneous generation Before Pasteur, many prominent scientists believed that life could arise spontaneously . For instance, many people thought that maggots appeared from rotted flesh and that dust created fleas. Pasteur suspected that this was not the case. He disproved spontaneous generation by boiling beef broth in a special flask that deters contamination. When the broth was not exposed to air, it remained sterile and free of microorganisms. When the flask neck was broken and air was allowed to reach the broth, the fluid became cloudy with microbial contamination.
Germ theory Pasteur’s work with microorganisms in fermentation and pasteurization led to a much better understanding of germ theory —that certain diseases result from invasion of the body by microorganisms. Before Pasteur’s time, most people, including scientists, believed that all disease came from inside the body rather than from outside. Pasteur’s findings eventually led to improvements in sterilizing and cleaning in medical practices and antiseptic methods in surgery.
Infectious disease Pasteur successfully identified the organisms that had caused a mysterious disease in silkworms and endangered the French silk industry. He learned how to preserve healthy silkworm moth eggs and prevent contamination by disease-causing organisms. The methods he developed are still used in silk production today. Through his study of silkworms, Pasteur made advances in the field of epidemiology , the study of the distribution of disease as a result of the way host and parasite populations interact.
Vaccines Using his germ theory of disease, Pasteur also made important strides in the field of vaccination . He developed vaccines for chicken cholera and anthrax . Arguably his most important work with vaccines was his development of a rabies vaccine, a new “inactivated” type of vaccine, consisting of a neutralized agent rather than attenuated microorganisms. In 1885 he vaccinated a nine-year-old boy who had been bitten by a rabid dog and helped usher in the practice of preventive medicine.
Virulence Pasteur was the first scientist to recognize that virulence could be increased as well as decreased. This has become extremely important in the study of infectious diseases and their spread, especially epidemics of bovine spongiform encephalopathy ("mad cow" disease) and acquired immunodeficiency syndrome (AIDS), for example.

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Louis Pasteur: Biography, Inventions, Experiments & Facts

Louis Pasteur , the 19th-century French chemist and biologist, is known primarily as the "the father of germ theory," as he was the first scientist to offer formal support for the idea that microbes, or microscopic life forms, were responsible for the pathogenesis (the cause and progression) and transmission of certain diseases in humans, livestock and other animals.

As a consequence, his work in the realm of vaccines and food safety has led many science historians to observe that Pasteur's work has arguably saved more human lives than anyone else in the annals of history.

Pasteur, however, was the architect of a number of other groundbreaking ideas in the world of natural sciences, some of them unrelated or only tangentially related to his work in the area of infectious diseases.

In addition to introducing the concept of molecular asymmetry, Pasteur is credited with virtually saving both the wine and silk industries in his native France.

His ideas about how germs trigger the body to fight back against invaders have led to his being credited as "the father of immunology," making him, in effect, the "parent" of a pair of related yet distinct ideas in microbiology .

Louis Pasteur Biography

Born in Dole, France in 1822, Pasteur, like a lot of renowned figures in the comparative dawn of modern scientific exploration, did not limit himself to a single discipline.

The son of a sergeant major from whom he gained a strong sense of patriotism, Pasteur was reputedly only an average student as a child, though skilled in drawing and painting; some of his works are now displayed in the Pasteur Institute (Institut Pasteur).

The lad's creativity did not hearken to his brilliant future in science, which ultimately led him to receive the Legion of Honour, France's highest decoration.

After attending primary school in Arbois and secondary school (high school) as well as university in Besancon, Pasteur headed to the École Normale Supérieure in Paris – where he would later become director of scientific studies – in 1843, launching his science career in earnest.

Pasteur earned degrees in chemistry , physics and math, and, drawn initially to the first of these, became a professor of chemistry at the University of Strasbourg in 1848.

Three of his five children with his wife, Marie Laurent, whom Pasteur married in 1849, died from illness; many people believe that this was the main factor that prompted him to research diseases and illnesses, the real causes of virtually all of which were unknown at the time.

Molecular Asymmetry: Enantiomers

Perhaps like a future Academy Award-winning actor whose initial film role is obscure yet impressive, Pasteur's first major contribution to the body of scientific knowledge is not something he is widely remembered for. Pasteur produced the concept of molecular asymmetry , or the concept that molecules with the same chemical composition and bonding arrangement were not all actually the same shape.

Via meticulous experiments on the light-scattering properties of the tartaric acid found in wine (a hint of his work to follow), Pasteur's discovery demonstrated that chemically "identical" molecules can actually exist in mirror image – "left-handed" and "right-handed" – forms.

Further, he noted that all molecules in living things were left-handed. This was vitally important for understanding three-dimensional structures, especially in the science of crystallography .

Germs and Spontaneous Generation

Before Pasteur came along, most people believed in the notion of spontaneous generation , the idea that bacteria, microbes, germs and life in general appeared essentially out of nowhere, or from things like dust, dead flesh and even maggots.

The same theory was thus applied to illnesses: Weakness in an individual and the associated internal physical changes was presumed to allow these germs to appear, causing illnesses in an accordingly spontaneous way.

Pasteur, on the other hand, believed that these illnesses must arise from micro-organisms that themselves came from living things. That is, he theorized that "germs" didn't just appear out from scratch; they were living things in their own right. He achieved this through a series of elegant experiments that proved that food spoilage was a result of unseen elements in the air.

People were skeptical because Pasteur was not even a physician, but his work led to the development of antiseptics and revolutionized medicine.

Pasteur's Experiment: Fermentation

In his now-famous work involving fermentation , which is the oxygen-independent conversion of sugar by-products to alcohol and lactic acid, Pasteur showed that yeast is a living thing and an active part of the fermentation process . This was important in that it established fermentation as a biological process and not simply a chemical one.

Pasteur demonstrated that when air was pumped through the fermenting fluid, fermentation stopped. This showed that some kind of living organism that requires an oxygen-free environment has to be a part of the process. He was able to show that different microbes are responsible for different types of fermentation.

The Germ Theory of Disease

Pasteur was not the first to propose that unseen things in the environment could cause disease, but he was the first to offer evidence for the claim.

In experiments with beef broth, Pasteur showed that food would only spoil when exposed to microbes that were already present in the air. He applied these and similar findings to generate an elaborate germ theory of disease , which stated that bacteria and microbes cause disease, and that both diseases and their tiny causes exist in the world just like humans and other animals, rather than arising de novo ("from nothing").

This was no mere academic matter. By isolating a specific physical cause for diseases, Pasteur offered hope that these diseases could be prevented, thereby possibly staving off deaths like those that three of his children and countless others across Europe – for example, in the "Black Death" or bubonic plague of the 14th century, caused by the Yersinia pestis bacteria – had suffered.

Pasteur's Invention: Of Wine and Worms

Having come to understand that food and other things go bad not for mysterious or unpredictable reasons but because of bacteria, Pasteur was ready to address his home country's wine problem.

France had long been economically reliant on wine . Much of it was spoiling in transit because of bacterial contamination, but boiling the wine to kill the bacteria ruined the product. Using his signature methodical approach, Pasteur found that raising the wine to a certain intermediate temperature (55 C, or about 131 F) killed the bacteria without ruining the wine.

This process, now fittingly called pasteurization , has become universal in the food industry.

Pasteur's work with silkworms: Having rescued the wine industry, Pasteur used his knowledge of germ theory and disease to identify a parasite that was causing silkworm diseases. With the help of his wife, he was able to isolate the infected worms to get rid of the disease, thereby saving yet another vital sector of his country's economy.

Pasteur and Vaccines

In 1880, pushing the age of 60 but still as active as ever, Pasteur – who is sometimes erroneously credited with creating the first vaccine – developed the idea of vaccines with chickens. (Edward Jenner had developed a smallpox vaccine at the end of the 1700s, but with zero understanding of the underlying immunological mechanism.)

Pasteur showed that chickens, when inoculated (injected) with a non-virulent (non-disease-causing) form of the bacterial illness called chicken cholera, developed resistance to the virulent (disease-causing) types of cholera.

Pasteur's vaccine and others like it today, because they use living forms of the relevant organism, are called live attenuated vaccines, with "attenuated" meaning "thinned out."

Pasteur went on to use the same principles to produce an anthrax vaccine as well as a rabies vaccine, the latter demonstrating that the creation of vaccines for diseases caused by viruses rather than bacteria was possible, and also protecting against the bite of a rabid dog or other rabid animal.

On the basis of his contributions to both germ theory and immunology, Pasteur may be regarded as the father of microbiology and of preventive medicine in general.

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Frontiers in Immunology: Louis Pasteur, the Father of Immunology?
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Encyclopaedia Britannica: Louis Pasteur
Chemistry LibreTexts: Pasteur's Discovery of Enantiomers

About the Author

Kevin Beck holds a bachelor's degree in physics with minors in math and chemistry from the University of Vermont. Formerly with ScienceBlogs.com and the editor of "Run Strong," he has written for Runner's World, Men's Fitness, Competitor, and a variety of other publications. More about Kevin and links to his professional work can be found at www.kemibe.com.

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1-6 spontaneous generation was an attractive theory to many people, but was ultimately disproven..

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Learning Objectives

After reading this section, students will be able to...

Explain why people believed in the concept of spontaneous generation, the creation of life from organic matter.
Describe the experiment by Francesco Redi disproved spontaneous generation that disproved spontaneous generation for macroorganisms.
Explain how did John Needham's experiment re-ignited the debate about spontaneous generation for microorganisms.
Describe the swan-neck flask experiment of Louis Pasteur and why this ended the debate about spontaneous generation.

Spontaneous generation hypothesizes that some vital force contained in or given to organic matter can create living organisms from inanimate objects. Spontaneous generation was a widely held belief throughout the middle ages and into the latter half of the 19 th century. Some people still believe in it today. The idea was attractive because it meshed nicely with the prevailing religious views of how God created the universe. There was a strong bias to legitimize the idea because this vital force was considered a strong proof of God's presence in the world. Proponents offered many recipes and experiments in proof. To create mice, mix dirty underwear and wheat grain in a bucket and leave it open outside. In 21 days or less, you would have mice. The real cause may seem obvious from a modern perspective, but to the supporters of this idea, the mice spontaneously arose from the wheat kernels.

Another often-used example was the generation of maggots from meat left in the open. Francesco Redi revealed the failing here in 1668 with a classic experiment. Redi suspected that flies landing on the meat laid eggs that eventually grew into maggots . To test this idea, he devised the experiment shown in Figure 1.11. Here he used three pieces of meat. Redi placed one piece of meat under a piece of paper. The flies could not lay eggs onto the meat, and no maggots developed. The second piece was left in the open air, resulting in maggots. In the final test, Redi overlayed the third piece of meat with cheesecloth. The flies could lay the eggs into the cheesecloth, and when he removed this, no maggots developed. However, if Redi placed the cheesecloth containing the eggs on a fresh piece of meat, maggots developed, showing it was the eggs that "caused" maggots and not spontaneous generation. Redi ended the debate about spontaneous generation for large organisms. However, spontaneous generation was so seductive a concept that even Redi believed it was possible in other circumstances.

Figure 1.11. The Redi experiment. . Using several pieces of meat, paper and cheesecloth, Francesco Redi produced compelling evidence against the theory of spontaneous generation. One of the strong points of this experiment was its simplicity, which allowed others to easily reproduce it for themselves. See the text for details of the experiment.

The concept and the debate were revived in 1745 by the experiments of John Needham. It was known at the time that heat was lethal to living organisms. Needham theorized that if he took chicken broth and heated it, all living things in it would die. After heating some broth, he let a flask cool and sit at a constant temperature. The development of a thick turbid solution of microorganisms in the flask was strong proof to Needham of the existence of spontaneous generation. Lazzaro Spallanzani later repeated the experiments of Needham, but removed air from the flask, suspecting that the air was providing a source of contamination. No growth occurred in Spallanzani's flasks, and he took this as evidence that Needham was wrong. Proponents of spontaneous generation discounted the experiment by asserting that the vital force needed air to work properly.

It was not until almost 100 years later that the great French chemist Louis Pasteur, pictured in Figure 1.12, put the debate to rest. He first showed that the air is full of microorganisms by passing air through gun cotton filters. The filter trapped tiny particles floating in the air. By dissolving the cotton with an ether/alcohol mixture, the particles were released and then settled to the bottom of the liquid. Inspection of this material revealed numerous microbes that resembled the types of bacteria often found in putrefying media. Pasteur realized that if these bacteria were present in the air, they would likely land on and contaminate any exposed material.

Figure 1.12. Louis Pasteur . The French microbiologist Louis Pasteur. Drawing by Tammi Henke

Pasteur then entered a contest sponsored by The French Academy of Sciences to disprove the theory of spontaneous generation. Similar to Spallanzani's experiments, Pasteur's experiment, pictured in Figure 1.13, used heat to kill the microbes but left the end of the flask open to the air. In a simple but brilliant modification, he heated the neck of the flask to melting and drew it out into a long S-shaped curve, preventing the dust particles and their load of microbes from ever reaching the flask. After prolonged incubation, the flasks remained free of life and ended the debate for most scientists.

Figure 1.13. The swan neck flask experiment . Pasteur filled a flask with medium, heated it to kill all life, and then drew out the neck of the flask into a long S shape. This prevented microorganisms in the air from easily entering the flask, yet allowed some air interchange. If the swan neck was broken, microbes readily entered the flask and grew

A final footnote on the topic was added when John Tyndall show ed the existence of heat-resistant spores in many materials. Boiling does not kill these spores, and their presence in chicken broth, as well as many other materials, explains the results of Needham's experiments.

While this debate may seem silly from a modern perspective, remember that the scientists of the time had little knowledge of microorganisms. Koch would not isolate microbes until 1881. The proponents of spontaneous generation were neither sloppy experimenters nor stupid. They did careful experiments and interpreted them with their own biases. Detractors of the theory of spontaneous generation were just as guilty of bias but in the opposite direction. It is somewhat surprising that Pasteur and Spallanzoni did not get growth in their cultures since the sterilization conditions they used would often not kill endospores . Luck certainly played a role. It is important to keep in mind that the discipline of science is performed by humans with all the fallibility and bias inherent in the species. Only the self-correcting nature of the practice reduces the impact of these biases on generally held theories. Spontaneous generation was a severe test of scientific experimentation because it was such a seductive and widely held belief. Yet, even spontaneous generation was overthrown when the weight of careful experimentation argued against it. Table 1.3 lists important events in the spontaneous generation debate.

Table 1.3 Events in spontaneous generation

Year	Event
1668	Francesco Redi attacks spontaneous generation and disproves it for large organisms
1745	John Needham adds chick broth to a flask and boils it, lets it cool and waits. Microbes grow and he proposes it as an example of spontaneous generation.
1768	Lazzaro Spallanzani repeats Needham's experiment, but removes all the air from the flask. No growth occurs.
1859	Louis Pasteur's swan-neck flasks show that spontaneous generation does not occur.
1870	Thomas H. Huxley gives his "Biogenesis and Abiogenesis" lecture. The speech offered powerful support for Pasteur's claim to have experimentally disproved spontaneous generation.
1877	John Tyndall publishes his method for fractional sterilization, showing the existence of heat-resistant bacterial spores.

Key Takeaways

For many centuries many people believed in the concept of spontaneous generation, the creation of life from organic matter.
Francesco Redi disproved spontaneous generation for large organisms by showing that maggots arose from meat only when flies laid eggs in the meat.
Spontaneous generation for small organisms again gained favor when John Needham showed that if a broth was boiled (presumed to kill all life) and then allowed to sit in the open air, it became cloudy.
Louis Pasteur ended the debate with his famous swan-neck flask experiment, which allowed air to contact the broth. Microbes present in the dust were not able to navigate the tortuous bends in the neck of the flask.

The Theory of Biogenesis

What is Biogenesis?

An important theory in biology and molecular genetics, Biogenesis postulates the production of new living organisms from pre-existing life. Read ahead as we explore this seminal theory that changed age-old beliefs.

Biogenesis is based on the theory that life can only come from life, and it refers to any process by which a lifeform can give rise to other lifeforms. For instance, a chicken laying eggs, which hatch and become baby chicken.

Meaning of Biogenesis

The term ‘biogenesis’ comes from ‘bio’ meaning ‘life’, and ‘ genesis’, meaning ‘beginning’. Rudolf Virchow, in 1858, had come up with the hypothesis of biogenesis, but could not experimentally prove it. In 1859, Louis Pasteur set up his demonstrative experiments to prove biogenesis right down to a bacterial level. By 1861, he succeeded in establishing biogenesis as a solid theory rather than a controversial hypothesis.

What Was the Idea of Spontaneous Generation?

The belief in a spontaneous generation is age-old, quite literally. Aristotle in Ancient Greece first pronounces the idea. And consequently, the idea also came to be known as Aristotelian Abiogenesis.

The reason behind the resounding faith in this idea was perhaps the elusive and stealthy nature of the creatures attributed to it, i.e, mice, bacteria, flies, maggots, etc.

The 18th-century path-breaking invention of the microscope that allows most of these creatures, so we can observe them under the microscope and de-mystify their origin. By the time Pasteur set about to do his work in the field, macroscopic biogenesis was already accepted by the scientific community at large. He only had to confirm microscopic biogenesis to prove the hypothesis beyond doubt.

Macroscopic Biogenesis: Francesco Redi’s Experiment

Francesco Redi, as far back as 1668, had set out to refute the idea of macroscopic spontaneous generation, by publishing the results of his experimentation on the matter. Instead of his experiment , Redi had placed some rotting meat in two containers, one with a piece of gauze covering the opening, and the other without it.

He noticed that in the container without the gauze, maggots would grow on the meat itself. However, when he provided the gauze, the maggots would appear on the gauze instead of on the meat. He also observed that flies tend to lay eggs as close to a food source as possible. Thus, he surmised the possibility of macroscopic biogenesis.

Microscopic Biogenesis

Spallanzani’s experiment.

Source: Emaze

He solved this problem by drawing out all the air in the container after sealing it. After experimenting with this manner, he achieved his desired results of a broth that had not clouded with bacterial growth, in line with the theory of biogenesis.

However, his inference was countered by critics who asserted that air was indispensable to support life, therefore the lack of bacterial growth should be attributed to the lack of air, rather than the fact that bacteria spread through contamination. For almost a century since this criticism lay unchallenged.

Pasteur’s Experiment

The caveat of Pasteur’s 1859 experiment was to establish that microbes live suspended in air, and can contaminate food and water, however, the microbes do not simply appear out of thin air. As the primary step to his experiment, Pasteur boiled beef broth in a special flask that had its long neck bent downwards and then upwards.

This interesting contraption ensured the free diffusion of air, and at the same time prevent any bacterial contamination. As long as the apparatus remained upright, the flask remained free of any bacterial growth.

Once we slant the flask, it allows the broth to pass beyond the ‘goose-neck’ bend of the flask’s neck. The broth became clouded with bacterial growth in no time. This path-breaking experiment not only silenced all the criticism based on Spallanzani’s experiment but also cemented the Law of Biogenesis.

Law of Biogenesis Vs. Evolutionary Theory

Scientist fears that the law of biogenesis opposes the theory of evolution. It has surmised that all life stems from inorganic matter from billions of years ago. However, biogenesis simply refutes the theory of spontaneous generation and delves in a matter of generational time-span, and not of what may be achieved over thousands of generations.

While the evolutionary theories take into account the lack of predators, the difference in the chemical composition of the Earth’s atmosphere during the inception of life on Earth, as well as the trial-and-error that had taken place over millions of years to bring us to the stage of life on this planet we witness now, these do not concern the law of biogenesis at all.

Whereas the evolutionary theory demonstrates how life on earth took millions of years of trial-and-error and conducive but very different atmospheric conditions, the theory of spontaneous generation had asserted that complex life could simply appear fully formed in a matter of days. This is the belief that biogenesis had successfully challenged.

Solved Question for You

Q. Who Has Propounded the Theory of Spontaneous Generation?

Spallanzani

Ans. C. Aristotle. The idea was first propounded by Aristotle in Ancient Greece. Consequently, the idea came to be known as Aristotelian Abiogenesis.

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The Theory of Biogenesis & Louis Pasteur: Definition & Development

Categories : Genetics , Science
Tags : Science genetics topics molecular biology

The Spontaneous generation hypothesis proposed by scientists to explain the origin of the “animalcules” observed by Antoni van Leeuwenhoek in his magnifying lenses had received wide acceptance all over Europe from Antoni’s time until the time of Louis Pasteur. Erroneous experimental set up, results, and conclusions of some scientists had supported and strengthened the hypothesis.

For example, the Englishman John Needham claimed that vital life is needed for the spontaneous generation of microbes. He added that the reason why no living organisms emerged from heated and sealed solutions in containers is that the “vital life” was destroyed by the heat and new “vital life” was not supplied to the solutions because they cannot enter the sealed containers.

Fortunately, there were scientists skeptical about the hypothesis, so they designed their own experimental set up and from the results they gathered, they drew the most feasible explanation on the origin of the “animalcules”.Among the scientists was the Italian Lazzaro Spallanzani who opposed Needham’s idea of the “vital life” (Go back to part 1 of this series to read on Spallanzani’s argument).

Proponents and opponents of spontaneous generation hypothesis debated a lot starting from the time Leeuwenhoek presented his discoveries (1670s) to the public until the time of Rudolf Virchow, who in 1858 challenged the spontaneous generation with his concept and definition of biogenesis .

This concept claims that living cells can arise only from preexisting living cells. Virchow defended this concept to the scientific community but he did not come up with a convincing experiment to back up his idea. In 1861, the French scientist Louis Pasteur resolved the issue on the origin of microbes (“animalcules”) through a series of ingenious and persuasive experiments.

Pasteur showed that microorganisms exist in the air and can contaminate sterile solutions, but he emphasized that air itself does not produce microbes. He filled a number of short-necked flasks with beef broth and then boiled their contents. He immediately sealed the mouths of some of the flasks while he left the others open and allowed to cool.

After few days, the contents of the unsealed flasks were found to be contaminated with microorganisms. No evidences of growing microorganisms were found on the sealed flasks. Pasteur concluded that the microorganisms in the air were responsible for contaminating non-living matter like the broths in John Needham’s flask.

Pasteur performed another experiment but this time he put beef broth in open-ended long-necked flasks. He bent the necks of the flasks into S-shaped curves and boiled the contents of the flasks. Amazingly, the contents of the flasks were not contaminated even after several months.

The unique S-shaped design of Pasteur’s flasks allowed air to pass but trap microorganisms that may contaminate the broths.Do you know that some of the original vessels used by Pasteur in his experiments are still displayed in the Pasteur Institute, Paris today? A few of the flasks contain broths that remain uncontaminated for more than 100 years!

Pasteur demonstrated the presence of microbes in non-living materials whether they are solid, liquid, or air. In addition, he laid the foundation of aseptic techniques, techniques that prevent contamination by unwanted microbes.

These techniques are based on Pasteur’s idea that microbes can be killed by heat and that procedures can be designed to inhibit the access of airborne microbes to nutrient environment. Application of aseptic techniques is now the standard practice in medical and laboratory procedures.

Disproving the idea that microorganisms spontaneously generated from non-living matter through mystical forces is one of the greatest contributions of Pasteur in science. He provided the evidence that any appearance of “spontaneous” life in nonliving solutions can be attributed to microbes that already exist in the air or in the fluids themselves.

Serafini, Anthony. 1993. The Epic History of Biology. Plenum Press.

Madigan, Michael. 2006. Brock Biology of Microorganisms . Upper Saddle River, N.J. : Prentice Hall/Pearson Education.

Photo credit

Louis Pasteur Image https://en.wikipedia.org/wiki/File:Tableau _Louis_Pasteur.jpg

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Biomolecules

Louis Pasteur: Between Myth and Reality

Jean-marc cavaillon.

1 National Research Agency (ANR), 75012 Paris, France

Sandra Legout

2 Centre de Ressources en Information Scientifique, Institut Pasteur, 75015 Paris, France; [email protected]

Associated Data

Not applicable.

Louis Pasteur is the most internationally known French scientist. He discovered molecular chirality, and he contributed to the understanding of the process of fermentation, helping brewers and winemakers to improve their beverages. He proposed a process, known as pasteurization, for the sterilization of wines. He established the germ theory of infectious diseases that allowed Joseph Lister to develop his antiseptic practice in surgery. He solved the problem of silkworm disease, although he had refuted the idea of Antoine Béchamp, who first considered it was a microbial infection. He created four vaccines (fowl cholera, anthrax, pig erysipelas, and rabies) in the paths of his precursors, Henri Toussaint (anthrax vaccine) and Pierre Victor Galtier (rabies vaccine). He generalized the word “vaccination” coined by Richard Dunning, Edward Jenner’s friend. Robert Koch, his most famous opponent, pointed out the great ambiguity of Pasteur’s approach to preparing his vaccines. Analysis of his laboratory notebooks has allowed historians to discern the differences between the legend built by his hagiographers and reality. In this review, we revisit his career, his undeniable achievements, and tell the truth about a hero who made every effort to build his own fame.

1. Introduction

In 2022, we are recognizing the 200-year anniversary of Louis Pasteur’s birth. Pasteur belongs to the pantheon of the most prestigious scientists, whose contributions allowed major improvements in the war against pathogens ( Table 1 ). The ongoing COVID-19 pandemic reminds humanity that this war remains contemporary. However, behind the great scientist there was a man with a huge ego who made every effort to build his fame, helped by the lay press and his hagiographers ( Figure 1 ). Among those, René Vallery-Radot [ 1 ], his son-in-law, and Émile Duclaux [ 2 ], his successor at the head of the Institut Pasteur, contributed to his legend, even if they had to tell fairy tales. Analysis of his correspondence and laboratory notebooks has allowed historians to decipher between myth and reality [ 3 , 4 , 5 , 6 ]. As such, a more realistic description of this character has emerged, such as that offered by Patrice Debré [ 7 ], qualifying him as unfair, arrogant, haughty, contemptuous, dogmatic, taciturn, individualist, authoritarian, careerist, flatterer, greedy, and ruthless with his opponents. This was illustrated when he was administrator and director of scientific studies at the prestigious “École Normale Supérieure” (ENS), which educates teachers and professors. His authoritarianism, his inflexible temperament, and his conflicting relationships with the students ended in the resignation of 73 students. This required the intervention of the Minister of Education and led to his resignation. Regarding his scientific contributions, Debré added: “ sometimes he gives the impression of merely checking the results described by others, then making them his own ”. One could add he was a misogynist. When Pasteur became professor and dean at the University of Lille (1854), he wrote to his rector: “ I have the honor of proposing to you that ladies no longer be admitted to the science courses of the faculty [...] I do not need to insist at length, Mr. Rector, on the inconveniences which may result from the presence of ladies at these lessons. I do not see any reason to admit them. If their number were to become large, they could cause an appreciable lowering of the level of teaching. Their presence is always a nuisance in the natural history class. ”

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Left: Pasteur in the French Press seen as a lay saint ( Le Courrier Français , 4 April 1886); center: as an angel fighting rabies ( Le Don Quichotte , 13 March 1886); right: as a revered icon after his death ( Le Petit Journal , 13 October 1895). (© Institut Pasteur, Musée Pasteur).

Main contributions of Louis Pasteur.

1848–1858	Studies on molecular chirality: crystallography of tartaric and paratartaric acid
1857–1879	Studies on fermentation; First patent on alcoholic fermentation (1857)
1861	Discovery of anaerobic bacteria
1861–1879	Refutation of the theory of spontaneous generations. Discovery of germs
1863–1873	Studies on diseases of wine, vinegar, and beer
1865	Pasteurization of wine; Patent on wine preservation
1865–1870	Study on the diseases of silkworms
1871	Patent on beer preparation and preservation
1877	First observation of antibiosis
1877–1881	Studies on infectious diseases (anthrax, puerperal sepsis, boils)
1878	Demonstration in a vineyard that isolation of grapes from environmental air prevents fermentation in the further wine-making process
1880	Co-discovery with Alexander Ogston (UK) of
1881	Co-discovery with George M. Sternberg (USA) of
1880–1885	Preparation of vaccines (fowl cholera, anthrax, pig erysipelas, rabies)
1887	First bacteriological war: elimination of rabbits by over the cellar of Champagne of Mrs. Pommery (Reims)

The acquisition of knowledge is built on the shoulders of giants; however, many of these giants owe their notoriety to more obscure scientists who opened the furrows of knowledge and sowed the seeds which would hatch in other minds. Because Pasteur’s work was disruptive with nineteenth century knowledge, he faced many opponents, and history has forgotten those scientists whose only fault was to be right ahead of him.

2. From Molecular Chirality to Fermentation

Born in a family of tanners, Louis was the only boy with three sisters ( Table 2 ). He was a mediocre student who failed to pass his baccalaureate the first time, but he was an excellent pastellist. When he finally passed, he joined the ENS. Pasteur was invited by Antoine-Jérôme Balard (1802–1876), a prestigious chemist who had discovered bromine in 1826, to join his laboratory at ENS. Two other mentors supported Pasteur’s young career: Jean Baptiste Dumas (1800–1884), a professor of chemistry and member of the French Academy of Sciences, and Jean-Baptiste Biot (1774–1862), a professor of astronomy and physics and also a member of the French Academy of Sciences, who invented the polarimeter used by Pasteur for his first studies on the divergent diffraction of the light by tartaric and paratartaric acids. His studies on the optical activity and crystallography of these molecules allowed Pasteur to identify their molecular dissymmetry and their mirror-image nature. Pasteur was well ahead of his time and his discovery on molecular chirality catapulted the young Pasteur to the forefront of French research, recognizing what his eminent predecessors (J.-B. Biot, Frédéric-Hervé de la Provostaye (1812–1863), Wilhelm Gottlieb Hankel (1814–1899), and Eilhard Mitscherlich (1794–1863)) had missed [ 8 ]. For ten years, he pursued his research in chemistry and crystallography, founding stereochemistry.

Main steps of Louis Pasteur’s life and career.

27 December 1822	Birth in Dôle (Jura) (third child of Jean-Joseph Pasteur (1791–1865) and Jeanne-Étiennette Roqui (1793–1848)
1827	The family moved to Arbois
1831–1843	Studied in Arbois, Besançon, Dijon, and Paris
1844–1847	Studied at Ecole Normale Supérieure (ENS, Paris)
1846	“Agrégé préparateur” at ENS
1847	Thesis for his Doctorat ès-Sciences (physics and chemistry)
1848–1853	Taught physics in high school in Dijon and chemistry at the University of Strasbourg
29 May 1849	Married Marie Laurent, daughter of the Strasbourg university’s rector
1850	Birth of Jeanne, first child (deceased in 1859, 9 ½ years)
1851	Birth of Jean-Baptiste, second child (deceased in 1908)
1853	Birth of Cécile, third child (deceased in 1866, 12 ½ years)
	Knight of the Légion d’Honneur
1854	Professor of chemistry and dean of the faculty of sciences of Lille
1857	Failure of his application to the Academy of Sciences
1857–1867	Administrator and director of scientific studies at ENS
1858	Birth of Marie-Louise, fourth child (deceased in 1934)
	Set up his research laboratory in the attics of ENS
1862	Election at the French Academy of Sciences
1863	Birth of Camille, fifth child (deceased in 1865, 2 years)
	Professor of geology, physics, and applied chemistry at the School of Fine Arts
1867–1888	Director of a laboratory at ENS
1867–1872	Professor, chair of organic chemistry at the Sorbonne
1868	First severe brain stroke that paralyzed his left side
1873	Election at the French Academy of Medicine
1875	Failure to be elected Senator for Jura
1879	His daughter Marie-Louise married René Valéry-Radot (1853–1933)
1881	Election at the French Academy; Great Cross of the Légion d’honneur
1888–1895	Director of Institut Pasteur
28 September 1895	Death in Institut Pasteur annex (Marnes la Coquette)
26 December 1896	The coffin of Louis Pasteur was transferred in the crypt of Institut Pasteur

While in Lille, Pasteur was contacted by beet alcohol producers who were facing difficulties in their process of fermentation. Studying this process would be the second main field of investigation of Pasteur. However, in contrast to the study of molecular chirality, Pasteur had many precursors. The fact that fermentation is part of the action of a living entity had been hypothesized since Antonie van Leeuwenhoek (1632–1723) observed yeast under his microscope in 1680. The link between these cells and the fermentation process was described in 1787 by Adamo Fabroni (1748–1816), in 1803 by Baron Louis Jacques Thénard (1777–1857), in 1836 by Theodor A.H. Schwann (1810–1882) ( Figure 2 ), in 1837 by Friedrich T. Kützing (1807–1893), in 1838 by Pierre Jean François Turpin (1775–1840) and Charles Cagniard de Latour (1777–1859), and finally in 1854 by Antoine Béchamp (1816–1908), who understood the process a few years before Pasteur, establishing the complementarity between yeast and a soluble substance he named “zymase” ( Figure 3 ).

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The main predecessors recognized by Louis Pasteur (Spallanzani, Davaine, and Schwann) and his main supporters (Tyndall and Lister) (© Institut Pasteur, Musée Pasteur; © Wikipedia; © Collection of Pauls Stradiņš, Museum of History of Medicine, Riga, Latvia).

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Louis Pasteur faced numerous precursors, opponents, and competitors. Some were wrong, but a few, particularly Hameau, Béchamp, Toussaint, Galtier, and Duboué, were right despite being unknown or poorly recognized by Louis Pasteur (© Wikipedia/© https://gw.geneanet.org accessed on 19 March 2022).

With regard to the first work of Pasteur on fermentation, his text published in 1858 [ 9 ] is at the very least ambiguous concerning his position on the concept of spontaneous generation: “ It is not necessary to already have lactic yeast to prepare it: it takes birth spontaneously, with as much ease as brewer’s yeast, whenever the conditions are favorable “ […] I use this word (spontaneous) as an expression of the fact, completely reserving the question of spontaneous generation. In contact with the common air, lactic yeast is born if the natural conditions of the environment and temperature are suitable .” In this text, he evaded the issue, hence this convoluted style. In 1856–1857, when he began to write this memoir, he had already been at work on fermentation for over a year. He was about to leave his position as dean of the faculty of Lille for the ENS. He apparently discussed this subject with his mentor Jean-Baptiste Biot, who dissuaded him from openly engaging in such a controversial subject. He knew he would need funding for his research and that he would apply for it through an Academy of Sciences Prize (Prix Montyon, 1859). He did not waver. This is what explains its lack of clarity; it does not engage yet. In addition, it was in 1860, when the Academy of Sciences proposed a competition (Alhumbert prize) to: “Try by well-made experiments to throw a new light on the question of spontaneous generations”, that he really launched into the battle and supported the role of living cells in the process of fermentation against the idea previously defended by Antoine Lavoisier (1743–1794) and arguing with his contemporary detractors, Justus Freiherr von Liebig (1803–1873), Friedrich Wöhler (1800–1882), and Claude Bernard (1813–1878). In a fight from beyond the grave, after Claude Bernard’s death, Pasteur, addressing his late opponent, published a book “ Critical examination of a posthumous writing by Claude Bernard on fermentation ” (1879), affirming urbi et orbi the importance of yeast and germs to obtain alcoholic fermentation.

Invited by beer and wine producers, bringing a microscope into a biochemistry laboratory, Pasteur identified pathogens that were responsible for different wine diseases. Thanks to pasteurization developed to allow the export of wines to England and his work on beer and wine, Pasteur became a recognized authority on industrial fermentation. The Whitebread breweries in Britain and Carlsberg in Denmark attribute their success to Pasteur’s visit after identifying that a microorganism was contaminating the fermentations required to make beer.

3. Fighting against Spontaneous Generation and Germ Theory

When he started his studies to refute spontaneous generation and initiated his germ theory, many demonstrations were already published by a large number of scientists ( Table 3 ). Indeed, Louis Pasteur was a great admirer of Lazzaro Spallanzani (1729–1799), recognizing his immense contribution when he first demonstrated the non-existence of spontaneous generation ( Figure 2 ). Pasteur was offered by Raphaël Bischoffsheim (1823–1906), banker, philanthropist, and deputy, a painting by Jules Édouard (1827–1878) representing Spallanzani, which hung in his large dining room. There is another scholar to whom Pasteur paid tribute by writing him in 1878: “ For twenty years now, I have been following some of the paths you have opened. As such, I claim the right and the duty to associate myself wholeheartedly with all those who will soon proclaim that you have well deserved science and to sign these few lines. One of your numerous and sympathetic disciples and admirers ” [ 10 ]. This is Theodor Schwann (1810–1882), a Berliner doctor who, in 1836, refined Spallanzani’s experiment by passing the air through a flame which enters in a flask containing an infusion sterilized by boiling. The same year, Franz Schulze (1815–1921), a German chemist and professor of anatomy in Rostock, Graz, and Berlin, enriched the experimental approach to demonstrate that air is a vector of germs. However, there were some awesome scientists who were fully ignored by Pasteur. Joseph Grancher (1843–1907), the physician who injected the first Pasteur rabies vaccine into humans, quoted some of them [ 11 ]: Jean Hameau (1779–1851) ( Figure 3 ) was a country doctor in the southwest of France who studied glanders, malaria, dysentery, yellow fever, smallpox, and cholera. In a prophetic book, entitled “ Studies on viruses ” (1847), he explained how germs are responsible for infectious diseases. Grancher wrote: “ if M Pasteur had known his work, he would have cited him as one of his precursors ”; Dr J. Hameau, in his study on viruses, talks about these viruses, their incubation and their multiplication, as a student of Pasteur would do nowadays. It is certainly a great accomplishment that this one! To have foreseen, divined, affirmed, with all the proofs which science of his time could offer him, a doctrine which, only fifty years later, and thanks to the genius of Pasteur, was to reign as absolute; it is, in my opinion, showing a penetrating sagacity. ” Jean Hameau died of a devastating sepsis in the arms of his son, himself a doctor. The epigraph to his book was: “ Everywhere life is in life and everywhere life devours life! ” It could not be a more appropriate definition of a microbe that carries away the human being that hosts it. Grancher also quoted Girolamo Fracastoro (1483–1553). This XVIth century doctor, who coined the word syphilis, anticipated the contagiousness of tuberculosis and considered that rabies was consecutive to the entrance of “seminaria” (germs) into the body: “ he was also an instinctive and brilliant precursor, also unknown to M. Pasteur, I am sure .

Some of the precursors who, before Louis Pasteur, proposed the germ theory and/or refuted the concept of spontaneous generation.

Before JC	Marcus Terentius Varro (Varron) (116 BC–27 BC) (Roman)
1st century	Galen of Pergamon (129–216) (Greece)
1546	Girolamo Fracastoro (1483–1553) (Italy)
1658	Athanasius Kircher (1601 or 1602–1680) (Germany)
1663	Robert Boyle (1627–1691) (Ireland)
1668	Francesco Redi (1626–1697) (Italy)
1714	Nicolas Andry de Bois-Regard (1658–1742) (France)
1718	Louis Joblot (1645–1723) (France)
1720	Benjamin Marten (1690–1752) (UK)
1721	Jean-Baptiste Goiffon (1658–1730) (France)
1762	Marcus Antonius von Plenčič (1705–1786) (Austria)
1765	Lazzaro Spallanzani (1729–1799) (Italy)
1836	Theodor Schwann (1810–1882) (Germany)
1836	Franz Schulze (1815–1921) (Germany)
1837	Jean Hameau (1779–1851) (France)
1839	Sir Henry Holland (1788–1873) (UK)
1840	Jakob Henle (1809–1885) (Germany)
1844	Agostino Bassi (1773–1856) (Italy)
1846	Gideon Algernon Mantell (1790–1852) (UK)
1866	Auguste Chauveau (1827–1917) (France)

In his fight against the concept of spontaneous generation, Pasteur was helped by Balard, who conceived the experiments with the swan neck flasks, which were decisive in demonstrating that there are germs in the air [ 12 ]. Pasteur had to fight against some strong opponents of his germ theory who continued to defend spontaneous generation. Among those were, in France, Félix Archimède Pouchet (1800–1872) and his theory of heterogenesis [ 13 ] and Hermann Pidoux (1808–1882) and his theory of organic vitalism [ 14 ] and, in the UK, Lionel Beale (1828–1906) [ 15 ]. By contrast, John Tyndall (1820–1893), a famous Irish physicist ( Figure 2 ), was a great supporter of Pasteur’s theory of germs and published his own experiments on the presence of germs in the air [ 16 , 17 ]. A French catholic priest, Abbé Moigno (1804–1884), a great popularizer of science, gathered texts from Tyndall and Pasteur in a book on “ Organized microbes, their role in fermentation, putrefaction and contagion ”, [ 18 ]. The word “microbe” had been coined in 1878 by a French surgeon, Charles Sédillot (1804–1883), as a tribute of the works of Pasteur: “ Mr. Pasteur has demonstrated that microscopic organisms, widespread in the atmosphere, are the cause of the fermentations attributed to the air, which is only the vehicle and has none of their properties […] The names of these organizations are very numerous and will have to be described and, in part, reformed. The word microbe having the advantage of being shorter and of a more general meaning, and my illustrious friend M. Littré, the most competent linguist in France, having approved it, we adopt it […] ” [ 19 ]. However, Pasteur preferred to use the word microorganism. The word bacterium was coined in 1828 by Christian Gottfried Ehrenberg (1795–1876), a German naturalist, from the Greek βακτηριον, meaning “little stick”. The same six species of Vibrio described by Ehrenberg were recognized 35 years later by Pasteur as being the germs of putrefaction [ 20 ].

4. Fighting against the Silkworm Disease

Alexander von Humboldt (1769–1859), the great explorer, stated: “ The frequent sequence of reactions to an important discovery is first a denial of its veracity, then a denigration of its importance, and finally usurpation of credit for it ”. Such a statement fully fits with the contribution of Pasteur in the fight against silkworm disease. J.B. Dumas was minister of agriculture and trade and a senator in 1865 when he invited his former student to address the major threat that was facing the silkworm industry. Pasteur received subsidies from the government and spent five stays in Alès in the Cévennes. Pasteur initially admitted that he knew nothing about this topic. The famous entomologist Henri Fabre said: “ Ignoring caterpillar, cocoon, chrysalis, metamorphosis, Pasteur came to regenerate the silkworm. The ancient gymnasts presented themselves naked to the fight. Genius fighter against the scourge of the magnaneries, he also came to the battle naked, that is to say, without the simplest notions about the insect to get out of the peril. I was stunned; better than that I was amazed ” [ 21 ].

For two years, Pasteur denied that the disease (pebrin) could be due to a pathogen. However, Agostino Bassi (1773–1856), an Italian entomologist, had demonstrated as early as 1835 that another disease (muscardin) was caused by a fungus ( Beauveria bassiana ). In 1844, Bassi asserted the idea that not only animal (insect) but also human diseases are caused by other living microorganisms. On his side, A. Béchamp ( Figure 3 ), without official support, suggested as early as 6 June 1865 in front of the Central Agricultural Society of Hérault that the disease was due to a parasitic pathogen. On 25 September 1865, Pasteur communicated to the Academy of Sciences, opting for a spontaneous intrinsic blood disease [ 22 ]. The following year, Béchamp published: “ The pebrin, in my opinion, attacks the worm from the outside first, and the germs of the parasite come from the air. Sickness, in short, is not originally constitutional ” [ 23 , 24 ]. Béchamp’s diagnosis was supported by Édouard-Gérard Balbiani (1823–1899), an entomologist and embryologist who declared in 1866: “ The corpuscles that we observe in the disease described under the name of pebrin in silkworms are not anatomical elements […] but indeed psorospermia, that is to say parasitic plant species ” [ 25 ]. It was Désiré Gernez (1834–1910), working alongside Pasteur, and Franz von Leydig (1821–1908), a German zoologist, who had been contacted by Pasteur, who both convinced Pasteur of the real nature of disease. Gernez had worked as a physics associate/preparer in Pasteur’s laboratory at ENS from 1860 to 1864, and he joined Pasteur in Alès. The same as Béchamp and Balbiani, he concluded that the disease was parasitic. It was only in April–May 1867 that Pasteur sent a letter to Dumas finally acknowledging the parasitic origin of the disease [ 26 ]. Pasteur sent a letter in 1867 to the secretary of the agricultural committee, which overwhelmed Béchamp with discourteous contempt: “ Poor Mr. Béchamp is at this moment one of the most curious examples of the influence of preconceived ideas gradually turning into fixed ideas. All his statements are so biased that I wonder if he has ever observed more than ten silkworms in his life ” [ 27 ]. In his book written in 1870 on his studies of the diseases of silkworms, dedicated to the Empress Eugénie, to better capture all the glory and build his legend, Pasteur neither admitted his wanderings nor acknowledged the visionary works of Béchamp. The latter said: “ I am Pasteur’s forerunner, just as the stolen is the forerunner of the fortune of the happy and insolent thief who taunts and slanders him ” [ 28 ]. Unfortunately for Béchamp, his approach to treat the disease with fumigations of creosote was not fully appropriate while Pasteur’s technique of segregating the cocoons, an approach already proposed by Emilio Cornalia (1824–1882), an Italian naturalist, was successful. Thus, it was Pasteur who put an end to the epidemic and reaped all the praise. In fact, the success was very partial, as the production of cocoons, which reached 25,000 tons per year in 1850 and had collapsed to 5000 tons in 1865, never exceeded more than 8000 tons by the end of the 19th century.

Sadly for Béchamp, his concept of “microzyma”, which he subsequently developed, did not contribute to letting him enter the pantheon of heroes of microbiology. According to him, any animal or plant cell would be made up of small particles capable, under certain conditions, of evolving to form “microzymas”, small autonomous elements which would continue to live after the death of the cell from which they would come. After Pasteur’s death, Béchamp published a booklet entitled: “Louis Pasteur—His chemicophysiological and medical plagiarism—His statues” (1903). In this work, Béchamp published his various letters written in vain to restore the truth to the directors of the “ Petit Journal ” and “ La Liberté ”. He denounced “ The most brazen plagiarist of the nineteenth century and of all centuries: it is Pasteur ” and criticized the press “ for propagating the false legend which makes a famous plagiarist a great man ”. Reading Béchamp, one sympathizes with so much suffering illustrated by such harsh words: “ Pasteur, great man, the purest glory of the nineteenth century and undisputed scholar, not only he was not, but the pure truth is that he was the less genius, the most simplistic and the most superficial scientist of our time, at the same time the most plagiarist, the most false, and the biggest noise-maker of the nineteenth century ” and having shamelessly attributed the success to himself, Pasteur was able to further promote himself to Dr. Paul Bert (1833–1886), student of Claude Bernard and member of the National Assembly, where he obtained for Pasteur by a vote on 28 March 1874 a life pension of 12,000 gold francs per year, transformed on 13 July 1883 into a pension of 25,000 francs.

5. Identifying the Germs of the Infectious Diseases (1877–1881)

One of the main handicaps of Pasteur was having been educated as a physicist and a chemist and thus having ignored some key contributors in the field of medicine, infectious diseases, and physiology of inflammation. Furthermore, because he only spoke the French language, he missed many breakthrough publications from German scientists, leading him to make incorrect statements. For example, in 1878, he claimed [ 29 ]: “ For us currently, it would be the red blood cells that would be the pus cells from a simple transformation from the first into the second ”, ignoring the work of two of Rudolf Virchow’s (1821–1902) students, Julius Friedrich Cohnheim (1839–1884), who, eleven years earlier, had demonstrated that white blood cells cross blood vessels to become pus cells [ 30 ], and that of Julius Arnold (1835–1915), who in 1875 had illustrated the diapedesis of blood cells [ 31 ].

The competition between the German school led by Robert Koch (1843–1919) ( Figure 2 ) and that of Pasteur [ 32 ] was based on the identification of the germs responsible for some infectious diseases. Of course, the name of Koch is associated with discovery of the bacillus of tuberculosis and improperly to that of cholera, which was first identified by Filippo Pacini (1812–1883) in Florence (Italy) in 1854. The name “ Pasteurella ” was inappropriately coined by an Italian bacteriologist in 1887, Vittore Trevisan (1818–1897), while the germ responsible for the fowl cholera was first identified by two Italian scientists, Sebastiano Rivolta (1832–1893) in 1877 and Edoardo Perroncito (1847–1936) in 1878! In France, the first isolation of this bacterium was made by Henri Toussaint (1847–1890) in 1879 ( Figure 3 ), a medical doctor, a veterinarian, and a docteur ès-Sciences who provided Pasteur with this germ.

Let us speak of Joseph Grancher [ 11 ], the first French medical doctor with Isidore Strauss (1845–1896) who, thanks to Émile Roux (1853–1933), studied bacteriology with Pasteur under the supervision of Charles Chamberland (1851–1908): “ But already Germany had surpassed us in microbial techniques and Mr. Pasteur’s laboratory, faithful to cultures in liquid media, neglected the art of staining microbes and that of cultivating them on solid media. It was M. Babès (Victor Babeș (1854 in Vienna–1926 in Bucharest)) who, coming from Germany, introduced in France, in M. Cornil’s laboratory (Victor André Cornil (1837–1908)), the methods of staining microbes then used in M. Koch’s laboratory. And I believe I brought from Berlin, after a trip made with M. Brouardel (Paul Brouardel (1837–1906)) for Emersleben trichinosis (in November 1883), the first tubes of gelatinized blood serum. ” Indeed, thanks to the work of Angelina (Fanny) Hesse (1850–1934), her husband Walther Hesse (1846–1911), and Julius Richard Petri (1852–1921), Koch’s team had developed the agar–agar containing culture medium and the device known as the Petri dish. Grancher, with great objectivity rare in the close entourage of Pasteur, recognized the superiority of the experimental approach of the German school of bacteriology. The consequences were expressed in terms of discoveries: “ And while the studies on rabies and the search for its microbe continued on rue d’Ulm, while a few French doctors were beginning or better resuming their studies, Germany gave us almost in quick succession the important discoveries of the microbe of erysipelas, diphtheria, glanders, tetanus, pneumonia, this one recognized at the same time in France by Talamon (Charles Talamon (1850–1929) ” [ 33 ].

However, studying the boils of his colleague É. Duclaux and samples from a 12-year-old girl suffering from osteomyelitis, Pasteur identified Staphylococcus in 1880 [ 34 ] concomitantly with Alexander Ogston (1844–1929), a British surgeon who was studying the germs present in abscesses [ 35 ]. Ogston indicated that 917,775 cells/mm 3 were present in pus, which contained 2,121,070 micrococci/mm 3 . In 1882, Ogston coined the word Staphylococcus from ancient Greek staphyle, which means a bunch of grapes. Furthermore, concomitantly with the American George M. Steinberg (1838–1915) in 1881, Pasteur identified the bacteria first known as pneumococcus , then diplococcus pneumonia , and finally named Streptococcus pneumoniae [ 36 , 37 ].

5.1. Puerperal Fever

Pasteur investigated puerperal fever ten years after Victor Feltz (1835–1893) and Léon Coze (1819–1896), two physicians working in Strasbourg, demonstrated in 1869 the presence of a deadly bacterium ( Streptococcus ) in the blood of a patient who died of puerperal fever [ 38 ]. Starting in 1865 and for four years, the two Alsatian doctors established the presence of contaminating germs able to transmit death to rabbits injected with the blood of patients with typhoid fever, smallpox, pneumonia, erysipelas, and scarlet fever [ 39 ]. On 17 March 1879, Feltz, then in Nancy after the loss of Alsace in the 1870 war, republished a similar observation in the Comptes Rendus de l’Académie des Sciences, although this time he transmitted the death to a guinea pig [ 40 ]. Feltz called his observed bacteria Leptothrix puerperalis. The following day, Pasteur reported in the Bulletin de l’Académie de Médecine the presence of germs in the lochia, blood, and uterus from a patient who died of puerperal fever [ 41 ]. Pasteur did not perform experiments to transmit the disease to an animal but suggested washing the genital tract with diluted boric acid. Pasteur came into contact with Feltz and denied Feltz’ observation. He obtained some blood of Feltz’ patient, which he injected into one guinea pig while two others were injected with anthrax. He sent the animals by train to Nancy, where Feltz received the dying guinea pigs. Then, amazingly, Feltz, the medical doctor, accepted the diagnosis given by the scientist and he conceded that his patient after delivery had died of anthrax despite there being no case of anthrax in the area [ 42 ]! Most probably, both had observed Streptococci , a name coined by Theodor Billroth (1829–1894), as a combination of the ancient Greek streptos meaning twisted and kokkos meaning berry.

In the movie “ The story of Louis Pasteur ” (1936), directed by William Dieterle with Paul Muni playing Pasteur (a role for which he received the Oscar for best actor), following one death after puerperal fever, a document was created stating “ Wash your hands. Boil your instruments. Microbes cause disease and death to your patients ”, signed Louis Pasteur. In fact, Pasteur never mentioned that the hands of the obstetricians could transmit the disease, although Pasteur was very reluctant to shake hands and was himself regularly washing his hands. However, Pasteur and the scriptwriter ignored the statements of Alexander Gordon (1752–1799), who admitted in 1795 that he had transmitted diseases to women after delivery [ 43 ], and the major achievement of Ignaz Semmelweis (1818–1865), who demonstrated in 1847 that the hands of medical students, after performing autopsies, contaminated the parturients they visited [ 44 ]. In his Vienna hospital, Semmelweis advocated hand and nail washing with calcium hypochlorite, reducing the mortality from 16% to 0.85% [ 45 ].

5.2. Anthrax

The Bacillus anthracis was first observed in Germany by Aloys Pollender (1799–1879) in 1855 and Friedrich A. Brauell (1807–1882) in 1857. In France, in 1850, Pierre Rayer (1793–1867) was the first to demonstrate the contagiousness of the disease. However, the main achievement was accomplished by a precursor of Pasteur, Casimir J. Davaine (1812–1882) ( Figure 2 ). Jean Rostand (1894–1977), a famous writer and biologist, wrote: “ It is commonly believed in the public that it was Pasteur who discovered the role of microbes in the production of infectious diseases. In fact, this considerable discovery does not belong to him; it belongs to another French scientist: Davaine […] Who, the first, dared to affirm and knew how to demonstrate by the experimental method that a microscopic organism is the agent responsible for a disease ” [ 46 ]. Similarly, Jean Theodoridès (1926–1999), one of the most prestigious French historians of biological science wrote: “ The credit of demonstrating for the first time the pathogenic role of a bacterium in the human being and in domestic animals goes to the little-known French physician Casimir Davaine ” [ 47 ]. In 1863, Davaine observed the presence of bacteria in the blood of animals with anthrax and showed that the disease was communicable by infected blood [ 48 ]. Later, he reported that only live bacteria can transmit the disease [ 49 ]. Davaine was the first scientist to make a direct link between the presence of certain bacteria and an infection. He was well aware of the importance of his contribution: “ It has been a long time since doctors or naturalists theoretically admitted that contagious diseases, serious epidemic fevers, plague, etc., are determined by invisible animalcules or by ferments, but I am not aware of any clear demonstration to confirm this view ”. Indeed, Davaine was recognized by Pasteur to have been a major predecessor of his own work. In 1876, Koch was the first to publish photos of anthrax [ 50 ].

In 1877, Pasteur and Jules Joubert (1834–1910) reported [ 51 ] that the bacterium of anthrax could not develop when associated with other microorganisms: “ life prevents life ”. This was the very first report of a phenomenon named “antibiosis” by Jean Paul Vuillemin (1861–1932), mycologist and professor at the faculty of medicine in Nancy in 1889. The phenomenon would give rise years later to the discovery of the antibiotics. Finally, in 1880, Pasteur offered up an explanation for the natural contamination of cattle. He demonstrated that earthworms brought germs emanating from the carcasses of the dead sick animals to the surface, which had been buried in fields [ 52 ].

5.3. Cholera

In August 1883, a cholera epidemic broke out in Alexandria (Egypt). On August 15th, Pasteur sent his collaborators, Émile Roux, Isidore Strauss, Edmond Nocard (1850–1903), and Louis Thuillier (1856–1883), to isolate the germs and to reproduce the disease in animals. Not only did the mission fail, but Thuillier contracted cholera and died. Koch, on 24 August, also traveled to Alexandria to isolate the bacillus from the intestinal mucosa of dead people. He pursued his travel to Calcutta, India where another epidemic had broken out. On 7 January 1884, he sent a telegram informing Berlin that he finally isolated and cultured the bacillus. In 1893, Pasteur entrusted André Chantemesse (1851–1919) with a mission in Constantinople for another cholera epidemic. There, Chantemesse organized the fight against the epidemic with the construction of three disinfection stations. Later, Institut Pasteur sent Waldemar Haffkine (1860–1930), who trained in Metchnikoff’s laboratory, to fight against cholera epidemics in India thanks to a vaccine he had developed [ 53 ].

5.4. Plague

At the request of Institut Pasteur, Alexandre Yersin was sent to Hong Kong in 1894 to study the nature of the plague epidemic that was raging there. He was in competition with Shibasaburō Kitasato (1853–1931), a former trainee of Koch. When Kitasato was looking in blood samples, Yersin was luckier in studying buboes. On 20 June 1894, Yersin isolated the bacillus responsible for the disease, later named Yersinia pestis [ 54 ]. Back in France, he developed with Emile Roux, André Borrel, and Albert Calmette an anti-plague horse serum. While a large plague epidemic occurred in Guǎngzhōu (China) in 1896, Yersin went there to successfully offer his anti-plague serum. In the following years, Haffkine developed an anti-plague vaccine used in India to fight plague epidemics [ 53 ].

6. Pasteurization, Filtration and Sterilization

As previously mentioned, in his fight against the diseases of wines, Pasteur obtained a patent on 11 April 1865 that offered a means to get rid of the contaminating bacteria by heating the wines at 64 °C for 30 min. This process was later adapted to other products and named pasteurization. However, this approach had been previously proposed by Alfred de Vergnette de Lamotte (1806–1886), a gentleman winemaker (1846) of whom Pasteur denied the anteriority of his work. However, in fact, the very first approach had been reported in 1831 by Nicolas Appert (1749–1841), inventor of preserves who proposed the heating of wine in the 4th edition of his book [ 55 ] Then, Pasteur offered a scientific explanation to the empirical findings of his predecessors. Of note, it was Franz von Soxhlet (1848–1926) who first applied the process to milk.

In Pasteur’s laboratory, his close collaborator Charles Chamberland defended his doctoral thesis in 1879 on the origin and development of microorganisms. This was the starting point for his work on the sterilization of culture media that led him to design a disinfection oven that bears his name: the Chamberland autoclave. In 1884, to fight against the spread of typhoid fever raging in Paris, he developed a filter, designed from a porous porcelain of his invention, to eliminate microbes from drinking water. The instrument was named the Chamberland filter–Pasteur system and became very popular to provide safe drinking water. A Pasteur–Chamberland filter company was created in Dayton, Ohio, USA. They sold germ-proof filters to private homes, hotels, bars, and restaurants, offering many different designs. They advertised: “ This filter was invented in my laboratory, where its great usefulness is put to test every day. Knowing its full scientific and hygienic value, I wish it bears my name. Louis Pasteur ” [ 56 ].

Pasteur’s discoveries on germs allowed great advances in the practice of surgery. In 1865, Joseph Lister (1827–1912), a Scottish surgeon in Glasgow ( Figure 2 ), learned Louis Pasteur’s theory that microorganisms cause infection. Using phenol as an antiseptic, he reduced the mortality of amputee patients to 15% in four years, compared to 45–50% who died of sepsis previously. He is considered to be the founder of antiseptic medicine [ 57 , 58 ]. In 1870, Alphonse Guérin (1816–1895), a French surgeon, invented the wadded bandage and declared: “ I firmly believed that miasmas emanating from the pus of the wounded were the real cause of that dreadful disease to which I had had the pain of seeing the wounded succumb [...]. I then had the thought that the miasmas whose existence I had admitted because I could not otherwise explain the production of the purulent infection, and which were known to me only by their deleterious influence, might well be animated corpuscles that Pasteur had seen in the air [...] If the miasmas were ferments, I could protect the wounded against their fatal influence by filtering the air as Pasteur had done [...] I imagined then the wadded bandage and I had the satisfaction to see my forecasts being carried out ” [ 59 ].

On 27 December 1892, for Pasteur’s 70th birthday, the international scientific community celebrated Pasteur’s “jubilee”. The reception took place in the large amphitheater of the Sorbonne. In a painting painted ten years later, the artist Jean-André Rixens recalled this celebration displaying Lister precisely in the middle of the painting, shown going up a few steps to congratulate Pasteur ( Figure 4 ). In 1874, Just Lucas-Champonnière (1843–1913), after travelling to Scotland, introduced Lister’s antiseptic approach in France [ 60 ]. Similarly, Lewis Atterbury Stimson (1844–1917) attended a presentation of Pasteur in 1875 at the Academy of Medicine on spontaneous generation and the capacity of lime hyposulphite to instantly destroys all germs. Back in New York, in January 1876, he successfully completed the first amputation in the USA under completely aseptic conditions [ 61 ].

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On 27 December 1892, for his 70th birthday, the international scientific community celebrated Pasteur’s “jubilé”. The reception took place in the great amphitheater of “la Sorbonne”. On the picture, one sees the president of France, Sadi Carnot, helping Pasteur to walk and Lister climbing a few steps to congratulate Pasteur. Oil on canvas by Jean-André Rixens (1902). © Institut Pasteur/Musée Pasteur.

7. Elaboration of Four Vaccines

7.1. fowl cholera.

Toussaint sent the heart of a guinea pig inoculated with the germ of chicken cholera to Pasteur in December 1878. After Pasteur had obtained the Pasteurella from Toussaint, he prepared a bacterial culture and developed his first vaccine against fowl cholera, which he reported in 1880 [ 62 ]. The legend told by Duclaux [ 2 ] is the following: a virulent culture of Pasteurella that was killing injected hens was left on the bench during Pasteur’s vacation. Back from vacation, Pasteur used this bacterial culture, which failed to kill the hens. He prepared a newly fresh virulent culture, injected it in the same hens, and these hens survived the lethal injection. From that observation, Pasteur elaborated that bacteria exposed to air or oxygen lose their virulence and can be used as a vaccine. Then, it could be claimed: “ In the fields of observation, chance favors only prepared minds ”. However, this event never happened. In 1878, Pasteur asked his son-in-law to never show his laboratory notebooks to anyone. However, in 1964, his grandson, Professor Louis Pasteur Vallery-Radot (1886–1970), donated the 152 notebooks to the French National Library, allowing the historians to explore legend and reality. The most accomplished investigation was carried out by Gerald L. Geison (1943–2001), who was awarded [ 3 ] with the William H. Welch Medal by the American Association for the History of Medicine for his book. The demystification of the great hero by Geison led to numerous laudatory comments [ 63 , 64 ]. The book was judged to be judicious, meticulous, and carefully argued [ 65 ]. Only the chapter on molecular chirality was severely criticized [ 66 ]. Jean Théodoridès wrote: “ This critical but objective work demystifies Pasteur, who became, partly on his own initiative, a hero of his time and a concentrate of all human virtues ” [ 67 ]. In addition, he recalled Auguste Lutaud (1847–1925), one of the most virulent Pasteur opponents: “ In France, one can be anarchist, communist, or nihilist, but not anti-Pasteurian. A simple scientific question has become a matter of patriotism ”. Théodoridès regretted that Geison did not address the story of silkworms nor the “Rouyer affair”.

Similar critical analyses have been previously proposed by Antonio Cadeddu [ 4 , 5 , 6 ] and Philippe Decourt (1902–1990) [ 27 ]. Considering the publications of Pasteur, his correspondence, the book of Pasteur’s nephew, Adrien Loir (1862–1941) [ 68 ], and the laboratory notebooks, they showed how much Pasteur sought for glory above all, to the detriment of his predecessors and his collaborators, rigging his experiments if necessary or distorting his results.

The analysis of notebook #88 reveals no text between July 1879 and November 1879: Pasteur was on vacation in Arbois, where he celebrated the wedding of his daughter Marie-Louise to René Valéry-Radot and afterward suffered from a gastroenteric disease. Texts from mid-November deal with anthrax, boils, and puerperal fever but not with the fowl cholera vaccine. On 14 January 1880, Pasteur wrote in his lab book: “ Hen’s germs: when should we take the microbe, so it could vaccinate?”, illustrating that there was not yet a clear understanding of the protective vaccine.

7.2. Anthrax (1881)

While the story of the fowl cholera vaccine was romanticized, Pasteur and his team were among the first after Edward Jenner to propose a new vaccine. However, the glory of developing the first vaccine against anthrax should not be attributed to Pasteur. In August 1880, Toussaint published his efforts to attenuate germs to obtain a protective vaccine in dogs and sheep [ 69 ]. He tried heating the bacteria, which was not successful; however, treating the germs with phenol led to a protective vaccine. In Vincennes, in August 1880, Toussaint organized a vaccination session on a total of 26 sheep on the farm of the Alfort Veterinary School in Vincennes. Twenty-two animals successfully resisted to the anthrax challenge [ 70 ].

The Pasteur team was groping for the development of an anti-anthrax vaccine. The main problem was Pasteur’s belief that it was exposure to air that produced attenuated germs that should be used for vaccinations. Chamberland and Roux tried various approaches with heated blood exposed or not to oxygen or attenuated by an antiseptic. About this last approach, Pasteur said to them: “ Me alive, you will not publish this, until you find the attenuation of the bacterium by oxygen. Look for it! ” [ 68 ]. However, Pasteur surprised his two acolytes when he announced in April 1881 that he had accepted the proposal of Charles-Paul-Marie Moreau, baron de La Rochette (1820–1889), president of the Society of Agriculture of Melun: “ We put at your disposal 60 sheeps. Ten will not undergo any treatment, 25 will be vaccinated, 25 will not be. After 12 new days, we will inoculate the virulent strain of the disease to the 25 sheeps and 25 others who did not receive a vaccine. Then we will see the results .” Taken aback, Chamberland and Roux were preoccupied and very busy actively pursuing the tests. The experiment was carried out on the farm of the veterinarian Joseph Hippolyte Rossignol (1837–1919) in Pouilly-Le-Fort in the presence of many personalities, including Eugène Tisserand (1816–1888), veterinarian and director at the Ministry of Agriculture, and a few journalists including one from The Times , who came from London specially to attend this unprecedented event. The vaccine was administered on 5 May 1881, as announced according to the protocol; however, two goats replaced two sheep, and eight cows, an ox, and a bull were added to the experiment, although the Pasteur team did not have any expertise with cattle. A boost was performed twelve days later. On 31 May, the very virulent strain was injected into all vaccinated and control animals. On June 2nd, all these people were back in Pouilly-Le-Fort. It was a huge success; the vaccinated sheep were in great shape, except for one ewe that died. It was identified that she was pregnant and had a stillborn fetus in her womb. The control animals were all dead or dying when the public rushed to the experiment site. All vaccinated and naïve cattle survived the inoculation. Baron de la Rochette and Dr. Rossignol hailed Pasteur’s great victory over anthrax. The phrase “ Fortune favors the daring ” has never been applied so well. Pasteur made an incredible bet, while his vaccine was still in its infancy, that no previous experiment had been conducted on this scale, and he descended into the arena, inviting the public to witness his experiments live. On 13 June 1881, Pasteur communicated his brilliant results to the Academy, failing to specify the nature of his vaccine [ 71 ], and for a good reason. In their race to produce an effective vaccine on time, Pasteur, Roux, and Chamberland ended up adopting Toussaint’s approach, namely, to attenuate the virulent germ, not by exposure to air as Pasteur will continue to imply but by exposing it to an antiseptic agent, in this case potassium dichromate.

Of course, the Pouilly-Le-Fort event caused a great sensation, and a statue was commissioned from the sculptor André d’Houdain and erected in 1897 in Melun. The bronze statue would eventually be melted down in 1943, the Vichy regime offering the occupier something to make cannons. However, a controversy arose between the professors of the Turin Veterinary School and their director, Domenico Vallada (1822–1888), to whom Pasteur had sent his vaccine against anthrax. Unfortunately, this vaccine was unable to protect Italian sheep. Pasteur estimated that the Italian veterinarians had made the mistake of inoculating for the test the blood of a corpse that had been dead of anthrax for more than twenty-four hours and that consequently germs other than those specific to anthrax had been injected. Vallada and his colleagues in Turin responded by publishing a text entitled “ On the scientific dogmatism of the illustrious Prof. Pasteur and the use that can be made of it ” (10 June 1883) [ 72 ]. They concluded their text to charge: “ We do not want to take away from our illustrious opponent the illusion of complete success which may have smiled upon him in this discussion, we likewise refrain from disturbing the sweet pleasure he experienced, when he provided new proof of the fault committed by the Turin Commission, however we believe that we are not straying from the truth, and not disrespecting him either, by expressing the opinion, that his complete success may in some way be compared to the historic victory of Pyrrhus ”. This was not the only failure of the vaccine. Nikolaï Gamaleïa (1859–1949), a medical doctor from Odessa who had come to Paris to be trained by the Pasteurians, studied the parameters that influenced the preparation of the anthrax vaccine and reported his own experiments carried out on more than 300 sheep and some dogs, rabbits, and rats [ 73 ]. He reported that certain preparations could kill sheep and established that the fever induced by the vaccine was a prerequisite for its effectiveness. Despite his efforts to master a vaccine that was complicated to prepare, during the summer of 1887, an anthrax vaccination organized by the Odessa bacteriological station resulted in the death of 80% of the vaccinated animals, i.e., 3549 sheep, at a cost of more of 40,000 rubles. The owner asked Elie Metchnikoff (then director of the bacteriological station) and Gamaleïa to reimburse him half the price and started a lawsuit. Of course, the popular press echoed this disaster. No doubt a major mistake had been made, in particular the large-scale use of a vaccine not previously tested. By contrast, Adrien Loir organized a successful anthrax vaccination of 400,000 sheep in Australia.

Pasteur reported his discoveries on the vaccine against fowl cholera and anthrax at the International Medical Congress in London (1881), where he stated: “ I have given the term vaccination a broad meaning. I hope science will dedicate it as a tribute to the merit and immense service rendered by one of England’s greatest men, your Jenner. What a joy for me to glorify that immortal name on the very soil of the noble and hospitable city of London ”. In fact, the word vaccination was coined in 1800 by Dr. Richard Dunning (1761–1851) [ 74 ], a founding member of the Plymouth Medical Society and friend and great supporter of Jenner, who had endorsed the word. As testimony of his admiration, Dunning named one of his sons Edward Jenner Dunning. Unfortunately, the child died at the age of ten months. Pasteur’s talk on the attenuation of viruses at the Fourth International Congress on Hygiene and Demography in Geneva (1882) ended with a vehement reply from Koch [ 75 ]: “ Pasteur is not a physician, and he cannot be expected to be able to comment accurately on pathological processes and symptoms of the disease.” […] ” The tactic followed by Mr. Pasteur is to communicate only what speaks in his favor about an experiment, and to ignore the facts which are unfavorable to him even when those are decisive for the purpose of the experiment. Such methods may be appropriate when it comes to advertising in business, but science must vigorously reject them. “ […] “It i s not only by the flawed methods, but also by the means of publishing his research, that Pasteur has provoked criticism. In industrial enterprises, it is permissible, and often even in commercial interests, to keep the process that led to the discovery a secret. But in science, it is another habit which is applied. Whoever appeals to faith and confidence of the scientific world has the duty to publish the methods that it follows, in such a way that everyone is able to verify the accuracy of the published results. M. Pasteur does not comply with this duty. Already in his publications on chicken cholera, Mr. Pasteur has long hidden his method of attenuating the virus and finally it was only at Colin’s (Gabriel-Constant Colin (1825–1896), Professor at the Maison Alfort veterinary school, Member of the Academy of Medicine) insistence that he decided to publicize his method. The same was repeated about the mitigation of the anthrax virus, because the communications that Mr. Pasteur has made so far on the preparation of the two vaccines are so imperfect that it is impossible without further information to repeat and examine its process ”. About Colin, Pasteur said: “ Only one path leads to the truth, a thousand lead to error, but it is always one of the latter that Mr. Colin chooses ” [ 76 ]. On his turn, Pasteur argued against Koch.

7.3. Pig Erysipelas

The development of Pasteur’s third vaccine was undoubtedly the least controversial. The originality of this work, however, is that Pasteur discreetly abandoned his approach attenuating germs by exposure to oxygen in the air [ 77 ]. In the summer of 1877, Achille Maucuer (1845–1923), a veterinarian based in Bollène (Vaucluse), wrote to Pasteur to challenge him on a pathology that was rampant in pig farms, swine erysipelas. Pasteur admitted he had never heard about that disease and asked Maucuer to provide him with some documents. In his letter (23 September 1877), Pasteur wrote a diatribe on the organization of research in his country that has a very particular resonance, as in recent years (2010–2020) France has dropped from fifth to ninth place in terms of scientific production in biology and medical sciences: “ If I could master my material resources for the research projects which impassion me, I would train young scientists who, under my direction, would undertake studies on all the contagious diseases of animals and men; but our poor France, always grappling with politics, remains ignorant of the great destinies of science. I would like to see the public authorities ceaselessly preoccupied with scientific interests; most often it is for immediate utility that they consider them. Witness, in the subject which occupies us, the standing committee of epizootics decreed in 1876 and which until now limited its work to the laws of sanitary police; without trying anything for the knowledge of the epizootics ” [ 78 ].

Pasteur wished to have access to the bacillus responsible for the disease. Maucuer sent a sick pig who died at Lyon Perrrache railway station. Nevertheless, it allowed the first inoculations. The germ, Erysipelothrix , was first isolated by Robert Koch in 1876–78 from septic mice that had been inoculated subcutaneously with the blood of rotten meat. In 1882, Friedrich Loeffler (1852–1915) observed a similar organism in the skin blood vessels of a pig that died of porcine erysipelas and published the description of the organism a few years later. Pasteur entrusted his assistant Louis Thuillier with the task of isolating the germ. The success of the young assistant was made possible by the development of a culture medium based on sterilized calf broth. Pasteur, Thuillier, and Loir went to Bollène in November 1882. The Maucuer couple hosted the Pasteurian delegation and—greatly honored by their presence—did their best to make their stay as pleasant as possible, even gastronomic. Pasteur reported that the quality of the dishes, in particular the truffled guinea fowl, was particularly appreciated. Pasteur quickly wrote to François de Mahy, Minister of Agriculture, to report on the progress of his work, emphasizing the economic impact of the problem. In the Rhône valley, around 20,000 animals had died. In Bollène and in the neighboring villages and castles, the Pasteurians had access to many animals for experimentation. After three weeks on site, Pasteur returned to Paris. The vaccine developed by Pasteur’s team consisted of erysipelas germs attenuated by passing them from rabbits to rabbits. Conversely, Pasteur found that successive passage through guinea pigs or pigeons increased their virulence. The details of the procedure, however, remained vague enough that no one could copy the preparation of the vaccine. Pasteur advised Maucuer: “ The vaccine would be considered of little value if we gave it for free. It will be delivered to you by Mr. Boutroux, 28 rue Vauquelin, at 0 fr 20 centimes per pig. You will charge your work as it fits you . However, I believe you would be wrong to charge a high price ” [ 78 ]. While some disappointments were reported with some animals that died after vaccination, overall, it was a huge success both in Vaucluse and in various regions of France. In 1892, Loir and Chamberland reported that the death rate was 1.07% for 57,900 vaccinated animals. Pasteur obtained from the Minister of Agriculture that Maucuer would be awarded the Legion of Honor. Since then, an Achille Maucuer Avenue has existed in Bollène, and of course in this same town, a bronze bust of Pasteur was inaugurated in 1924. As in Melun, in 1943 the bust was melted down under the Vichy regime. Rebuilt in 1945, the base and the bust regained their place in the city center of Bollène in 2017.

7.4. Rabies

Pasteur’s fourth vaccine was undoubtedly the one that contributed the most to his fame, but it was also a hot topic of contradictory debate. What was the motivation that led Pasteur to work on rabies? Pasteur was a hero among breeders and veterinarians, but tackling a human disease would have much more prestige, more repercussions in the medical world, and in the general population. The choice of rabies may be intriguing because it was an epiphenomenon compared to the mortality resulting from the other infectious diseases that were rife at the time. No doubt he wanted to avoid German competition, which was on many fronts but not that of rabies. What characterizes rabies is the long delay between the bite (assumed to have been given by a rabid animal) and the onset of the disease, at least if the bite was on the extremities of a limb. This delay allowed Pasteur to carry out his inoculations and hope for the establishment of immune protection before the onset of the disease.

Once again, there are forgotten precursors. Pierre Victor Galtier (1846–1908) was a professor at the veterinarian school of Lyon holding the chair of pathology of infectious diseases ( Figure 3 ). In 1879, he demonstrated the transmissibility of rabies from dogs to rabbits [ 79 ]. This key information was then used by Pasteur: rabbits could be a source of rabies virus, and the rabbits used for tests developed the disease very quickly. Roux improved the model by proposing an intracerebral inoculation. On 1 August 1881, Galtier reported to the Academy of Sciences the success of his rabies vaccination [ 80 ]: “ I injected rabies saliva into the chinstrap of the sheep seven times, without ever getting rabies; one of my test subjects has since been inoculated with rabid dog slime, and for over four months after this inoculation, the animal has always been well; it seems to have acquired immunity. I inoculated it again two weeks ago by injecting it eight cubic centimeters of rabies saliva into the peritoneum, it is still doing well ”. In total, he injected the rabies virus into the blood stream of nine sheep and one goat. He then injected the deadly virus into these animals and ten control animals. The ten vaccinated animals survived, and the ten control animals perished. In 1886, Galtier published a work entitled: “ Rabies considered in animals and in humans from the point of view of its characteristics and its prophylaxis ”. Even though a bust of Pierre Victor Galtier by Louis Prost can be seen at the veterinary school in Lyon, very few remember his original work.

In addition to Galtier, we should also mention among the precursors Pierre-Henri Duboué (1834–1889), a doctor trained in Paris and member of the Academy of Medicine, who practiced in Pau ( Figure 3 ). On 12 January 1881, he sent his book to Pasteur [ 81 ] in which he reported his discovery that the progression of the rabies virus takes place through the peripheral nerve fibers to the central nervous system and not through the blood, at a time when Pasteur was still looking for the viruses in the bloodstream. In 1887, Duboué wrote a new book in which he stated [ 82 ]: “ I come with this work, to defend my unjustly unrecognized rights, on the subject of the progresses made in recent years on the great question of rabies, progresses which I can strongly affirm to have been prepared by my own research ”. Decidedly, it was not good to be in the shadow of Pasteur’s work. Later, he added: “ To make it clear the full extent of the denial of justice to me contained in Pasteur’s communication, I must indicate here the reason which gave a whole new direction to the researches of M. Pasteur.” […] “No civet without hare […] Similarly, no preventive treatment possible with attenuated viruses, without the prior culture of the rabies virus, and no culture of the latter, without knowledge of the tissues or organs where this virus resides ” wrote appropriately Duboué.

Pasteur experimented with his rabies vaccine in humans before he had accumulated sufficient evidence of the efficacy and safety of his vaccine. Ethics in Pasteur’s time were obviously not as scrupulous as that of the twenty-first century, as illustrated by his request in 1884 to the Emperor of Brazil to be allowed to test his vaccine on prisoners in exchange for their freedom [ 83 ]. In his book and after examining Pasteur’s notebooks, Geison makes a damning observation [ 3 ]. Before the first attempts on humans, between August 1884 and May 1885, experiments involved 26 dogs bitten by rabid dogs with three different vaccine approaches. The overall success rate was 62%. However, none of them correspond to the one used on Joseph Meister. This is undoubtedly one of the reasons why his most loyal collaborator, Dr Roux, refused to test the vaccine in humans on which he himself had been working, and it was Joseph Grancher who performed the injections. As a source of attenuated viruses, it was Roux’s idea to dry out the spinal cords of rabbits that had succumbed to rabies, hung in vials, while Pasteur had the idea to add potash to accelerate the drying. Pasteur’s laboratory notebooks reveal that Joseph Meister was not the first human to be treated with Pasteur’s rabies vaccine. The very first rabies vaccination was carried out on 2 May 1885 on a patient of Dr. Georges Dujardin-Beaumetz (1833–1895), member of the Academy of Medicine, at Necker hospital, named Mr. Girard (61 years old), who had been bitten on the knee by a rabid animal. The treatment was initiated with two injections twelve hours apart. However, the treatment was stopped by the hospital authorities who had consulted the Ministry of Public Health. On May 3rd, Girard’s conditions deteriorated with tremors that lasted three days. On May 7th, the patient was much better, and a fortnight later, the patient was discharged from the hospital. Doubt persisted as to the nature of this first patient’s illness. The second injection took place on 22 June 1885 at the Saint-Denis hospital, where an eleven-year-old girl, Julie-Antoinette Poughon, was vaccinated. Unfortunately, she died the next day, suggesting that the administration of the vaccine was too late. The best-known inoculation took place on 6 July 1885 on young Joseph Meister (1876–1940), aged 9, who came with his mother from Alsace. Administration of the vaccine, as defined by Pasteur, consisted of a succession of inoculations with the desiccated spinal cords of rabid rabbits by injecting increasingly virulent virus preparations until the fully active virus was injected. The experimental approach with parched spinal cord was initially started on 28 May and 3 June in 20 dogs and repeated on 25 and 27 June in 20 new dogs. This is to say whether on July 6th Pasteur had little data to ensure the efficacy and safety of his protocol. Pasteur notes in his notebook: production of the refractory state on a child very dangerously bitten by a rabid dog. Pasteur is aware of the dangerousness of his treatment: “ Joseph Meister therefore escaped not only the rage caused by the bites, but also the one I injected into him to control immunity ” [ 84 ].

The second vaccination was carried out on 20 October 1885 in a young 15-year-old shepherd, Jean-Baptiste Jupille (1869–1923). Meister, like Jupille, was infinitely grateful and became a guardian of the Institut Pasteur. Meister committed suicide when the Nazi army entered Paris. Another thing the two young people had in common was that there was a lack of evidence that they were actually bitten by rabid dogs. The dog that bit Meister was killed and autopsied; finding wood debris in his stomach was the only evidence that he would have had rabies. Yet, Michel Peter (1824–1893), member of the Academy of Medicine, reminded his colleagues: “ In the past, you remember, any dog in whose stomach one found foreign bodies: wood, straw, etc., was famous enraged; this proof is abandoned ” [ 85 ]. As for Jupille, it was not the dog who attacked the child but the child who attacked the dog by rushing towards him with his whip (which Pasteur knew). The animal defended itself and bit young Jupille’s hand. The latter tied the dog’s mouth with the rope of his whip and threw it into the river. The statue which stands in the grounds of the Institut Pasteur, where one sees the young Jupille fighting with a dog to protect his little comrades from the attack of a mad dog, helped to propagate the legend.

During the course of Jupille’s vaccination, Grancher pricked himself in the thigh with the needle of a syringe filled up with four-day-old spinal cord, that is to say containing virulent virus. A full vaccination process was then necessary for Grancher. Pasteur asked to be inoculated as well. Grancher refused, as did Loir, and in doing so disobeyed Pasteur for the first time. Then, Adrien Loir and Eugène Viala (1858–1926), a laboratory technician, got vaccinated as well [ 68 ].

On 26 October 1885, Pasteur presented his successes to the Academy of Sciences and its president, Henri Bouley (1814–1885), which was hailed a memorable moment in the history of medicine and forever glorious in French science. The next day, Pasteur presented the same results to the Academy of Medicine, hailed once again as a most memorable moment in the history of the conquests of science and in the annals of the Academy. The international impact was arguably as high as Pasteur had hoped. As early as the fall/winter of 1885, people came from far away to receive the life-saving treatment: from Russia, the nineteen muzhiks of Smolensk (fifteen of whom were rescued), who had been welcomed at the railway station by the Baron Arthur Pavlovitch de Mohrenheim, ambassador of Russia in Paris, or from America, the four boys from New Jersey. Robert M. McLane (1815–1898), ambassador of USA, offered a banquet to glorify Pasteur. These successes played an essential role in the creation of the Institut Pasteur, inaugurated on 14 November 1888 [ 86 ].

Léon Perdrix (1859–1917), a former student at ENS and associate preparer in Pasteur’s laboratory, published the results of the first years of vaccination [ 87 ]: from 1886 to 1889, 7893 people (including 15.9% foreigners) were treated, and the mortality was only 0.67%. Admittedly, the mortality from rabies was greater than 98%, but how many of the people treated had actually had rabies? Decourt says he has verified and estimated the number of cases of rabies in France during the years 1850 to 1876 at 28.5 cases per year. It emerged that a number of people were treated even though they had not been bitten by rabid dogs [ 27 ].

Despite the aura of Louis Pasteur’s vaccination against rabies, a few clouds gathered in the sky of the glorious hero. There is first the “Jules Rouyer affair”, when a ten-year-old boy was bitten on the arm by an unknown dog through his overcoat on 8 October 1886. Pasteur was on vacation in Bordighera on the Italian Riviera, and it was Andrien Loir who took over the vaccination. Rabies inoculations began on 20 October, carried out daily for twelve days. Sadly, the child died on 26 November. Due to the father, Édouard Rouyer, having lodged a complaint, an autopsy was performed in Loir’s presence by Brouardel and Grancher, who took the child’s medulla oblongata and sent it to Roux so that he could inoculate two rabbits. The result was not long to come, and both rabbits quickly died of paralytic rabies. Roux and Brouardel perjured themselves in court, claiming that the rabbit tests had been negative and that the child had not died of rabies but of a uremic attack [ 7 ]. By doing so, they felt they were acting for the benefit of mankind by saving vaccination. The risk/benefit ratio of such a revelation was recognized by Roux himself. However, not all were convinced, in particular Michel Peter, who considered that the child had indeed died of rabies. He regularly opposed Pasteur, especially since he also witnessed another case of death despite (or because?) of the vaccine, that of a young man of twenty, called Réveillac, who died of rabies after receiving treatment. Peter declared: “ To amplify the benefits of his method and to mask its failures, Mr. Pasteur has an interest in making the annual mortality rate from rabies in France believed to be higher. But these are not the interests of the truth. Do we want to know, for example, how many individuals in 25 years have died of rabies in Dunkerque? He died of it: one… And do we want to know how many died in this city in a year, since the application of the Pasteurian method? He died: one ”. However, Pasteur considered Peter’s words null and void. Among the failures, let us also note the case of Hayes St Leger, fourth Viscount Doneraile (1818–1887). In Ireland at the time of the last outbreak of rabies, Lord Doneraile and his coachman Robert Barrer were both bitten by a rabid fox on 13 January 1887. Lord Doneraile suffered severe, multiple, and deep bites on both hands. They went to Paris to receive the full treatments between 24 January and 21 February. Unfortunately, Lord Doneraile finally died of rabies on 26 August 1887 as a result of fox rabies or the inoculation during the treatment. Pasteur dealt with another opponent, Anton von Frisch (1849–1917), an Austrian urologist who had nevertheless come to train with him. In 1887, he published a work entitled “ The treatment of rabies disease: an experimental critique of Pasteur’s method ”, in which he questioned the reliability and relevance of Pasteur’s vaccine approach.

The discovery that rabies was due to a virus was made in 1903 by Paul Remlinger (1871–1964), director of the Imperial Bacteriology Institute of Constantinople [ 88 ]. At the beginning of the 20th century, in Italy, Claudio Fermi (1862–1952), a doctor who worked at the Institute of Hygiene in Rome, questioned the preparation of the vaccine. He applied the Toussaint’s method, exposure to phenol, developing a vaccine that was simpler, more effective, and above all safer, without risk of transmission since the virulence was essentially eliminated. The poor value of the vaccine as it had been defined by Pasteur from dehydrated spinal cord was demonstrated by one of his heirs within the institution he had created: Pierre Lépine (1901–1989), a physician who had joined Professor Constantin Levaditi (1874–1953) in 1927. Lépine was director of the Institut Pasteur in Athens from 1930 to 1935, then head of the virology department at the Institut Pasteur in Paris from 1940 to 1971. In 1937, Lépine undertook a comparative study of the rabies vaccines of Pasteur and Fermi. He demonstrated by injecting 40 rabbits that the protective power of the Pasteur vaccine was 35%, while tested on 52 rabbits, Fermi’s vaccine reached a protection rate of 77.7% [ 89 ].

8. Concluding Remarks

After Jenner, Béchamp, Toussaint, and Galtier, Pasteur allowed vaccination to acquire its credentials. However, it was not until the experiments of Emil von Behring (1854–1917), Shibasaburo Kitasato (1853–1931), and Paul Ehrlich (1854–1915) that science could fully understand the exact nature of the immune host response [ 90 , 91 ]. Pasteur, as a microbiologist, conceived of the protection acquired by vaccination by attenuated bacteria as a consumption of the nutritional requirements needed for the growth and survival of the microbe, just as a culture media contained only trace amounts of vital nutrients. Thus, the host would not support the growth of a subsequent infection by the same microbe [ 92 ]. Pasteur admitted that the use of dead germs for vaccines did not fit with his own explanation.

In his obituary published in Science in 1895, the American bacteriologist H.W. Conn, director of the Cold Spring Biological laboratory, wrote: “ Pasteur is regarded as the father of modern bacteriology, but we must remember that he was not a pioneer in these lines of work. There was hardly a problem that he studied which had not been already recognized, and even studied to a greater or less extent by his predecessors ”, but nicely adding “ Others discovered facts, Pasteur determined laws ” [ 93 ]. Fifty years later, when a special exhibition devoted to Louis Pasteur was organized in London (1947), Alexander Fleming paid tribute to the great scientist. He cited many of those who, with Pasteur, contributed to the fight against microbes, but he failed to mention Béchamp, Toussaint, Feltz, Duboué, or Galtier, illustrating that Pasteur’s efforts to minimize the role played by his precursors had been successful. The legend was written and even a leading figure would not dare to flout it [ 94 ].

Author Contributions

J.-M.C. and S.L. contributed to gather the historical information and to write of the manuscript. All authors have read and agreed to the published version of the manuscript.

This research received no external funding.

Institutional Review Board Statement

Informed consent statement, data availability statement, conflicts of interest.

The authors declare no conflict of interest.

Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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Pasteur's Experiment
The steps of Pasteur's experiment are outlined below: First, Pasteur prepared a nutrient broth similar to the broth one would use in soup. Next, he placed equal amounts of the broth into two long-necked flasks. He left one flask with a straight neck. The other he bent to form an "S" shape. Then he boiled the broth in each flask to kill any ...
Louis Pasteur
Agnes Ullmann. Louis Pasteur - Microbiology, Germ Theory, Pasteurization: Fermentation and putrefaction were often perceived as being spontaneous phenomena, a perception stemming from the ancient belief that life could generate spontaneously. During the 18th century the debate was pursued by the English naturalist and Roman Catholic divine John ...
3.1 Spontaneous Generation
(b) The unique swan-neck feature of the flasks used in Pasteur's experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur's experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination.
2.1 Spontaneous Generation
(b) The unique swan-neck feature of the flasks used in Pasteur 's experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur's experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination.
Spontaneous Generation
Pasteur filled short-necked flasks with beef broth and boiled them, leaving some opened to the air to cool and sealing others. While the sealed flasks remained free of microorganisms, the open flasks were contaminated within a few days. In a second set of experiments, Pasteur placed broth in flasks that had open-ended, long necks.
Louis Pasteur, Spontaneous Generation, and Germ Theory
Pasteur then broke the neck of the flask and exposed the broth to the microbe-filled air, which contaminated the broth in short order. ... In the years following Pasteur's experiment, Pasteur ...
The middle years 1862-1877
Spontaneous generation - the big debateAt the time the spontaneous generation theory was widely accepted in scientific circles. Louis Pasteur decided to approach the issue via his experimental method.This required the use of swan-necked flasks. Water in the flask was brought to the boil for a few minutes until the steam escaped from the open end of the flask. It was then left to cool. While ...
3.1 Spontaneous Generation
(b) The unique swan-neck feature of the flasks used in Pasteur's experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur's experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination.
Louis Pasteur's Contributions to Science
Before Pasteur, many prominent scientists believed that life could arise spontaneously. For instance, many people thought that maggots appeared from rotted flesh and that dust created fleas. Pasteur suspected that this was not the case. He disproved spontaneous generation by boiling beef broth in a special flask that deters contamination.
Pasteur's Experiment
1 Louis Pasteur designed a procedure to test whether sterile nutrient broth could spontaneously generate microbial life. To do this, he set up two experiments. In both, Pasteur added nutrient broth to flasks, bent the necks of the flasks into S shapes, and then boiled the broth to kill any existing microbes. If left undisturbed, will the broth ...
Louis Pasteur: Biography, Inventions, Experiments & Facts
In experiments with beef broth, Pasteur showed that food would only spoil when exposed to microbes that were already present in the air. He applied these and similar findings to generate an elaborate germ theory of disease, which stated that bacteria and microbes cause disease, and that both diseases and their tiny causes exist in the world just like humans and other animals, rather than ...
Spontaneous generation was an attractive theory to many people, but was
Pasteur then entered a contest sponsored by The French Academy of Sciences to disprove the theory of spontaneous generation. Similar to Spallanzani's experiments, Pasteur's experiment, pictured in Figure 1.13, used heat to kill the microbes but left the end of the flask open to the air. In a simple but brilliant modification, he heated the neck of the flask to melting and drew it out into a ...
Q: How did Louis Pasteur disprove spontaneous generation?
Flexi Says: Louis Pasteur provided evidence to disprove spontaneous generation through his famous experiment using swan-necked flasks. He filled these flasks with a nutrient-rich broth and heated them to kill any existing microorganisms. The swan-necked design allowed air to enter the flask but prevented dust and other particles, which could ...
The Theory of Biogenesis
Pasteur's Experiment The caveat of Pasteur's 1859 experiment was to establish that microbes live suspended in air, and can contaminate food and water, however, the microbes do not simply appear out of thin air. As the primary step to his experiment, Pasteur boiled beef broth in a special flask that had its long neck bent downwards and then ...
The Theory of Biogenesis & Louis Pasteur: Definition ...
No evidences of growing microorganisms were found on the sealed flasks. Pasteur concluded that the microorganisms in the air were responsible for contaminating non-living matter like the broths in John Needham's flask. Pasteur performed another experiment but this time he put beef broth in open-ended long-necked flasks.
Chapter 1 Introduction, Historical Microbiology Flashcards
In this activity, you will view Foundation Figure 1.3 and determine the purpose of key aspects of this experiment: beef broth, a Bunsen burner, a flask with an S-shaped neck, and air. Louis Pasteur conducted an experiment to disprove the theory of spontaneous generation. An overview of this experiment is summarized in this figure.
Louis Pasteur: Between Myth and Reality
Pasteur did not perform experiments to transmit the disease to an animal but suggested washing the genital tract with diluted boric acid. Pasteur came into contact with Feltz and denied Feltz' observation. ... The success of the young assistant was made possible by the development of a culture medium based on sterilized calf broth. Pasteur ...

How the Scientific Method Works

Pasteur's Experiment

3.1 Spontaneous Generation

Clinical Focus

The Theory of Spontaneous Generation

Check Your Understanding

Disproving Spontaneous Generation

2.1 Spontaneous Generation

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

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Spontaneous Generation

Additional topics

Louis Pasteur, Spontaneous Generation, and Germ Theory

Life Comes From Life

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Learning Objectives

Table 1.3 Events in spontaneous generation

Key Takeaways

What is Biogenesis?

Meaning of Biogenesis

What Was the Idea of Spontaneous Generation?

Macroscopic Biogenesis: Francesco Redi’s Experiment

Microscopic Biogenesis

Pasteur’s Experiment

Law of Biogenesis Vs. Evolutionary Theory

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Molecular Genetics

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The Theory of Biogenesis & Louis Pasteur: Definition & Development

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Louis Pasteur: Between Myth and Reality

Sandra Legout

Associated Data

1. Introduction

2. From Molecular Chirality to Fermentation

3. Fighting against Spontaneous Generation and Germ Theory

4. Fighting against the Silkworm Disease

5. Identifying the Germs of the Infectious Diseases (1877–1881)

5.1. Puerperal Fever

5.2. Anthrax

5.3. Cholera

5.4. Plague

6. Pasteurization, Filtration and Sterilization

7. Elaboration of Four Vaccines

7.2. Anthrax (1881)

7.3. Pig Erysipelas