spontaneous generation experiments

Microbe Notes

Experiments in support and against Spontaneous Generation

• Spontaneous generation is an obsolete theory which states that living organisms can originate from inanimate objects.
• The theory believed that dust created fleas, maggots arose from rotting meat, and bread or wheat left in a dark corner produced mice among others.
• Although the idea that living things originate from the non-living may seem ridiculous today, the theory of spontaneous generation was hotly debated for hundreds of years.
• During this time, many experiments were conducted to both prove and disprove the theory.

Table of Contents

Interesting Science Videos

Experiments in Support of Spontaneous Generation

The doctrine of spontaneous generation was coherently synthesized by Aristotle, who compiled and expanded the work of earlier natural philosophers and the various ancient explanations for the appearance of organisms, and was taken as scientific fact for two millennia.

• 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.

John Needham

• The English naturalist John Turberville Needham was in support of the theory.
• Needham found that large numbers of organisms subsequently developed in prepared infusions of many different substances that had been exposed to intense heat in sealed tubes for 30 minutes.
• Assuming that such heat treatment must have killed any previous organisms, Needham explained the presence of the new population on the grounds of spontaneous generation.
• 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 seventeenth century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks.

Experiments against Spontaneous Generation

Though challenged in the 17th and 18th centuries by the experiments of Francesco Redi and Lazzaro Spallanzani, spontaneous generation was not disproved until the work of Louis Pasteur and John Tyndall in the mid-19th century.

Francesco Redi

• The Italian physician and poet Francesco Redi was one of the first to question the spontaneous origin of living things.
• Having observed the development of maggots and flies on decaying meat, Redi in 1668 devised a number of experiments, all pointing to the same conclusion: if flies are excluded from rotten meat, maggots do not develop. On meat exposed to air, however, eggs laid by flies develop into maggots. 
• He tested the spontaneous creation of maggots by placing fresh meat in each of two different jars.
• One jar was left open; the other was covered with a cloth. Days later, the open jar contained maggots, whereas the covered jar contained no maggots.
• He did note that maggots were found on the exterior surface of the cloth that covered the jar. Redi successfully demonstrated that the maggots came from fly eggs.

Lazzaro Spallanzani

• The experiments of Needham appeared irrefutable until the Italian physiologist Lazzaro Spallanzani repeated them and obtained conflicting results.
• He published his findings around 1775, claiming that Needham had not heated his tubes long enough, nor had he sealed them in a satisfactory manner.
• Although Spallanzani’s results should have been convincing, Needham had the support of the influential French naturalist Buffon; hence, the matter of spontaneous generation remained unresolved.

Louis Pasteur

• Louis Pasteur ‘s 1859 experiment is widely seen as having settled the question of spontaneous generation.
• He boiled a meat broth in a flask that had a long neck that curved downward, like that of a goose or swan.
• The idea was that the bend in the neck prevented falling particles from reaching the broth, while still allowing the free flow of air.
• The flask remained free of growth for an extended period. When the flask was turned so that particles could fall down the bends, the broth quickly became clouded.
• This work was so conclusive; that biology codified the “Law of Biogenesis,” which states that life only comes from previously existing life.

John Tyndall

• Support for Pasteur’s findings came in 1876 from the English physicist John Tyndall, who devised an apparatus to demonstrate that air had the ability to carry particulate matter.
• Because such matter in air reflects light when the air is illuminated under special conditions, Tyndall’s apparatus could be used to indicate when air was pure.
• Tyndall found that no organisms were produced when pure air was introduced into media capable of supporting the growth of microorganisms.
• It was those results, together with Pasteur’s findings, that put an end to the doctrine of spontaneous generation.
• Parija S.C. (2012). Textbook of Microbiology & Immunology.(2 ed.). India: Elsevier India.
• Sastry A.S. & Bhat S.K. (2016). Essentials of Medical Microbiology. New Delhi : Jaypee Brothers Medical Publishers.
• https://study.com/academy/lesson/spontaneous-generation-definition-theory-examples.html
• https://www.britannica.com/science/biology#ref498783
• https://www.infoplease.com/science/biology/origin-life-spontaneous-generation
• https://www.allaboutscience.org/what-is-spontaneous-generation-faq.htm
• https://courses.lumenlearning.com/microbiology/chapter/spontaneous-generation/

About Author

Sagar Aryal

Leave a Comment Cancel reply

Save my name, email, and website in this browser for the next time I comment.

This site uses Akismet to reduce spam. Learn how your comment data is processed .

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.

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Access for free at https://openstax.org/books/microbiology/pages/1-introduction

• Authors: Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster
• Publisher/website: OpenStax
• Book title: Microbiology
• Publication date: Nov 1, 2016
• Location: Houston, Texas
• Book URL: https://openstax.org/books/microbiology/pages/1-introduction
• Section URL: https://openstax.org/books/microbiology/pages/3-1-spontaneous-generation

© Jul 18, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.

• COVID-19 Tracker
• Biochemistry
• Anatomy & Physiology
• Microbiology
• Neuroscience
• Animal Kingdom
• NGSS High School
• Latest News
• Editors’ Picks
• Weekly Digest
• Quotes about Biology

Spontaneous Generation

Reviewed by: BD Editors

Spontaneous Generation Definition

Spontaneous generation is an incorrect and obsolete hypothesis about the possibility of life forms being able to emerge from non-living things.

Spontaneous Generation Theory

The theory of spontaneous generation, first comprehensively posited by Aristotle in his book ”On the Generation of Animals” around 350 B.C., aims to explain the seemingly sudden emergence of organisms such as rats, flies and maggots within rotting meat and other decomposable items. The theory suggests that organisms do not descend from other organisms or from a parent, and only require that certain conditions in their environment be fulfilled in order for creation to occur.

Aristotle theorized that non-living matter contained a “vital heat” called pneuma —the concept of a “breath of life” and translated later as “anima” meaning “soul” in Latin—and a combination of the four elements believed to make up all life: earth, air, fire and water.

He suggested that animals and plants could arise from earth and liquid, because there was “vital heat” within all air, there is air in water, and there is water in earth, meaning there is “vital heat” or “soul” within everything.

His explanation of the spontaneous generation was as follows:

“… living things form quickly whenever this air and vital heat are enclosed in anything. When they are so enclosed, the corporeal liquids being heated, there arises as it were a frothy bubble. Whether what is forming is to be more or less honorable in kind depends on the embracing of the psychical principle; this again depends on the medium in which the generation takes place and the material which is included.”

Examples of Spontaneous Generation

One of the first accounts relating to spontaneous generation was by the Roman poet Virgil. He described, as a recipe, the process in which one could make synthetic bees.

The readers were instructed to beat a bovine calf to death, block up its mouth and nose, before leaving the carcass on a bed of cinnamon sticks and thyme.

He noted that creatures would magically appear “first voide of limbs, but soon awhir with wings”—presumably this is referring to maggots, which subsequently develop in to bees.

Virgil called the process described in the recipe “Bougonia”.

Spontaneous Generation of Mice

The “recipe” for making a mouse requires that sweaty underwear should be placed over an open-mouth jar containing husks of wheat inside for around 21 days.

A simple explanation: mice like to eat wheat and, with ease of entering a jar and finding a dark and safe space, would most likely to find themselves at home and have a few offspring in the new nest.

The European chemist Jean Baptiste van Helmont stated that scorpions could be manufactured by carving an indentation in to a brick, filling the hole with basil and covering the arrangement with another brick.

After leaving it in the sun for a couple of days, one could return to the brick formation and would be amazed to find that

“fumes from the basil, acting as a leavening agent, will have transformed the vegetable matter into veritable scorpions”!

Other Examples

• Wet soil after a flood was believed to create amphibians such as frogs and toads.
• Garbage in the streets was thought to create rats.
• Salamanders were thought to be borne within fire (they often hide inside logs and were probably trying to escape the blaze!).
• Oyster shells were believed to form as the earth solidified around them and the “vital heat” grew the creature within.
• Crocodiles in Egypt were thought to have emerged from the mud with the sunshine as a catalyst.

The Disproving of Spontaneous Generation Theory

Francesco redi, 1626-1697.

Francesco Redi was an Italian physician and the first scientist to suspect that the theory of spontaneous generation may be flawed, so he set up a simple experiment. He placed fresh meat into two different jars, one with a muslin cloth over the top, and the other left open. A few days later, the open jar contained maggots, while the covered container did not. He saw this as proof that maggots had to come from fly eggs and could not spontaneously generate.

John Needham, 1731-1781

Over 100 years later, John Needham, an English naturalist and an avid supporter of spontaneous generation theory, performed an experiment in which he boiled up a broth and poured it into a covered flask—at this time, people were aware that the process of boiling removed the microorganisms that they called “animacules”. After a short while, the broth was filled with microorganisms, a revelation to Needham who claimed these had arisen through spontaneous generation. His experiment was contested for the fact he did not heat the broth for long enough and his animacules were heat resistant.

Lazzaro Spallanzani, 1729-1799

Another Italian scientist, Lazzaro Spallanzani, performed a similar experiment to Needham and found that if the broth was heated after the flask was sealed rather than before, the organisms did not generate. He decided that Needham’s broths had been contaminated between the boiling pan and the flask.

Needham’s response claimed that air was necessary for spontaneous generation and that the “vital heat” in the air had been destroyed during Spallanzani’s experiment.

Louis Pasteur, 1822 – 1895

Finally in 1859, a French scientist named Louis Pasteur designed a series of flasks with the necks bent into an S shape. The necks were fashioned so that fresh air could reach the flasks, but were bent in such a way that any air-borne microbes would be trapped at the bottom of the curves.

He boiled the broth inside the flask and did not see any microbes in the broth for many months. When he eventually removed the top from the flask and left it off, he found the liquid to be teaming with microorganisms within a few days. Therefore, he had proved that the microbes from which life arises are present within the air and are not spontaneously generated!

Boundless. “Pasteur and Spontaneous Generation.” Boundless Microbiology Boundless. Retrieved from www.boundless.com/microbiology/textbooks/boundless-microbiology-textbook/introduction-to-microbiology-1/introduction-to-microbiology-18/pasteur-and-spontaneous-generation-205-5188/ Laura Moss (2014) How to make a mouse: The bizarre ‘recipes’ borne of spontaneous generation. Mother Nature Network. Retrieved from: http://www.mnn.com/green-tech/research-innovations/stories/how-to-make-a-mouse-the-bizarre-recipes-borne-of-spontaneous Matt Simon (2014) Fantastically Wrong: Why people once thought that mice grew out of wheat and sweaty shirts. WIRED. Retrieved from:https://www.wired.com/2014/06/fantastically-wrong-how-to-grow-a-mouse-out-of-wheat-and-sweaty-shirts/ Phillip Ball (2016) Man Made: A History of Synthetic Life. Distillations. Chemical Heritage Foundation. Retrieved from:https://www.chemheritage.org/distillations/magazine/man-made-a-history-of-synthetic-life Origin of Life: Spontaneous Generation (2017) Infoplease. Retrieved From: https://www.infoplease.com/science/biology/origin-life-spontaneous-generation Mark Kusinitz. (2017) Spontaneous Generation. JRank. Retrieved from: http://science.jrank.org/pages/6408/Spontaneous-Generation.html

Cite This Article

Subscribe to our newsletter, privacy policy, terms of service, scholarship, latest posts, white blood cell, t cell immunity, satellite cells, embryonic stem cells, popular topics, mitochondria, pituitary gland, cellular respiration.

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

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

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 (“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.

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 2 ).

• 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?

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. ↵

Microbiology: Canadian Edition Copyright © 2019 by Wendy Keenleyside is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

Share This Book

Lessons and Courses on Microbiology

SPONTANEOUS GENERATION (ABIOGENESIS)

Spontaneous generation (abiogenesis) is the mistaken hypothesis that living organisms are capable of being generated from non-living things. Mankind for many centuries (even till the time of Aristotle in 4 th century BC) previously believed that non-living things such as meat and even decaying organic matter can generate living things (e.g. maggot). The belief that life can emanate from non-life was widely accepted as at the time even by scientists who could have experimented on it to either disprove or accept the theory.

Nevertheless several scientists (including John Needham , Francesco Redi , John Tyndall and Louis Pasteur ) as at the time abiogenesis was accepted were curious on how the concept of abiogenesis was true and relevant. This led this notable scientist’s to conduct series of experiments which led to the final disapproval of the theory of spontaneous generation.

Spontaneous generation (though an obsolete biological theory) sparked a lot of controversies for many years in the world; and scientists, religious leaders and especially philosophers had different views as to how life originated. A wider part of the society as at the time believed that life could originate from nothing especially from non-living things or some kind of vital forces that were present in decomposing organic matter.

The concept of spontaneous generation was very appealing to some scientists and even philosophers as at the time who believed strongly that life originated from non-life, but religious leaders fought against it because they believed that life originated from a supernatural being. In the subsequent pages, we shall discover that spontaneous generation does not occur, and that life does not emanate from non-life but from pre-existing life as exemplified by the notable works of Louis Pasteur amongst others.

How did life originated? The increase in knowledge, human’s quest for understanding life and the development of the scientific method gave man a better perspective of his environment and how the organisms in it (inclusive of microorganisms) directly or indirectly affect him. Previously, people believed so many things even when they did not conduct experiment to know if what they observed in their immediate natural environment is true or not. The theory of spontaneous generation held-sway for a long period of time before it was challenged and disproven through the experimental works of some notable scientists like Louis Pasteur. It is noteworthy that the scientists who attempted to disprove abiogenesis carried out their experiments or testing based on the scientific method.

Scientific method is the general approach that involves series of systematic steps or modus operandi used by scientists (including microbiologists) to conduct research. This methodical approach enables scientists (anywhere in the world) to conduct make scientific inquiries and arrive at conclusive answers to their observations or questions; and scientific method is a universally accepted approach of conducting research by scientists. The basic steps involved in the scientific method (which may vary depending on the experimentation) are elaborated in Figure 1.

Before it was disproved, people believed that life originated from non-living matter, a biological phenomenon known as spontaneous generation. Biogenesis is an alternative hypothesis to spontaneous generation; and it postulates that living organisms originated from pre-existing living things. Those who supported the claims of spontaneous generation (i.e. abiogenesis) believed that living organisms arise from non-living things or decomposing organic matter; and this hypothesis was invoke even till the late 19 th century before it was disproven by series of experiments conducted by notable scientists.

Francesco Redi (1626-1697) , an Italian Physicianwas the first to attack the theory of spontaneous generation, and this happened in 1668. At a time when it was widely believed that maggots arose from decaying meat, Redi carried out his experiment by filling a series of jars with decaying meat in order to disprove this belief. Some of the jars was left completely open to the air ( the test ); others were completely sealed while the remaining jars was covered with fine clothe or gauze (which prevented insects from entering). The flasks or jars that were completely sealed and covered with gauze served as the controls.

Francesco Redi believed that flies deposited eggs on the decaying meat, and this resulted to the development of maggots on the meat. After some days, it was discovered that maggots appeared only in the open jars in which the flies could easily reach and lay their eggs. Maggots did not appear in the jars that where completely sealed or covered with gauze. The laying of eggs on the decaying meat led to the development of maggots on the meat, and this was enough for Redi to disprove the theory of spontaneous generation. Francesco Redi challenged the theory of spontaneous generation by showing in his jar-decaying meat experiment that the maggot that appeared on the decaying meat (in the opened jar) came from the eggs of the fly deposited on the meat, and that the meat did not produce them. Despite Redi’s significant experiment (which gave impetus to the origin of life), the theory of spontaneous generation or abiogenesis remained strong and this continued for many centuries.

John Needham (1713-1781) used the boiling technique to determine whether or not boiling killed microorganisms. Needham supported the theory of spontaneous generation with his mutton or chicken broth boiling flask technique. He boiled mutton broth and put it in a flask which was tightly sealed after the broth was introduced in it. It was believed that boiling kills microorganisms. Needham allowed the flask for a long period of time, and discovered later that microorganisms developed in the broth even after boiling. Though his experiment supported abiogenesis; the fight to disprove spontaneous generation continued.

Lazzaro Spallanzani (1729-1799) , an Italian cleric boiled nutrient solutions in flask, and he showed in his experiment (which was a modification of Needham’s) that flask containing broth when sealed and boiled had no microbial growth. He drew out air from the flask before boiling in order to create a partial vacuum in the medium. Lazzaro was not convinced with Needham’s experiment because he contemplated that microorganisms could have entered the broth after it was boiled and before it was sealed. He showed in his significant work that air carried germs or microorganisms to the broth, and that air could support the growth of the organisms in the broth. However, Lazzaro’s experiment was still not accepted by supporters of spontaneous generation who believed that abiogenesis could not occur in the absence of air.

The theory of spontaneous generation was later put to rest and totally disproven by the significant experiments of Louis Pasteur (1822-1895) in 1859 and John Tyndall ( 1820-1893 ), an English physicist who extended Pasteur’s work by working on heat-resistant bacteria . A French chemist and microbiologist, Pasteur used the swan-necked flask experiment ( Figure 2 ) to disprove the theory of spontaneous generation. Louis Pasteur improved on the works of Needham and Spallanzani by boiling meat broth in bent-flasks which was opened to the air. Pasteur suggested that microorganisms in the air (which could contaminate the sterile broth) would be trapped on the sides of the bent flasks before they could finally reach the broth; and that if sterile broth had no prior contact with microorganisms, the broth would still remain sterile or free from microbes.

Louis Pasteur boiled meat broth in a flask and heated the neck of the flask in a flame until it became bent or curved (i.e. swan-necked). Though air could easily enter the flask, microorganisms in the air would be trapped in the neck of the bent flask. This was Pasteur’s idea of disproving the theory of spontaneous generation. The curved or bent flasks containing the broth were boiled to kill any form of microorganisms in it; and the flask was observed for a period of time for any possible microbial growth. But if the neck of the bent-flask was broken, dust particles or air-borne microbes would enter the flask and the broth will become polluted, and this will support the growth of germs.

Pasteur’s swan-necked experiment showed that the broth remained sterile for months because air-borne microbes were trapped in the bent-neck of the flask. Louis Pasteur then concluded that life only arises from life, and this is known as biogenesis. Though Louis Pasteur’s work laid the theory of spontaneous generation to rest; his notable experiment also showed that microbes are ubiquitous i.e. they are everywhere (even in the air).    

The theory of spontaneous generation was wildly acceptable to many as at the time it was invoke, but the experiments of Louis Pasteur and that of John Tyndall helped in laying it to rest once and for all. John Tyndall ( 1820-1893 ) gave impetus to the experiment of Louis Pasteur by showing in 1877 that dust particles indeed harboured microbes, and that the absence of it could cause the broth to remain sterile.

Tyndall went a step further to show the existence of heat-resistant forms of bacteria known as endospores , which are not easily killed by boiling. It is possible that the bacterial growth that was observed in Needham’s experiment after boiling was endopores (i.e. heat-resistant forms of bacteria). The observance of bacterial growth after boiling chicken broth made Needham to propose in 1745 that spontaneous generation did occur because microbes grew after the process. However, Pasteur and Tyndall’s experiment put a final stop to the theory of spontaneous generation and they convincingly showed that abiogenesis did not actually occur.   

Barrett   J.T (1998).  Microbiology and Immunology Concepts.  Philadelphia,   PA:  Lippincott-Raven Publishers. USA.

Beck R.W (2000). A chronology of microbiology in historical context. Washington, D.C.: ASM Press.

Brooks G.F., Butel J.S and Morse S.A (2004). Medical Microbiology, 23 rd edition. McGraw Hill Publishers. USA. Pp. 248-260.

Chung K.T, Stevens Jr., S.E and Ferris D.H (1995). A chronology of events and pioneers of microbiology. SIM News , 45(1):3–13.

Nester E.W, Anderson D.G, Roberts C.E and Nester M.T (2009). Microbiology: A Human Perspective. Sixth edition. McGraw-Hill Companies, Inc, New York, USA.

Salyers A.A and Whitt D.D (2001). Microbiology: diversity, disease, and the environment. Fitzgerald Science Press Inc. Maryland, USA.

Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.

Summers W.C (2000). History of microbiology. In Encyclopedia of microbiology, vol. 2, J. Lederberg, editor, 677–97. San Diego: Academic Press.

Talaro, Kathleen P (2005). Foundations in Microbiology. 5 th edition. McGraw-Hill Companies Inc., New York, USA.

Wainwright M (2003). An Alternative View of the Early History of Microbiology. Advances in applied microbiology. Advances in Applied Microbiology, 52:333–355.

Willey J.M, Sherwood L.M and Woolverton C.J (2008). Harley and Klein’s Microbiology. 7 th ed. McGraw-Hill Higher Education, USA.

Share this:

Discover more from #1 microbiology resource hub.

Subscribe to get the latest posts to your email.

Type your email…

Related Posts

Introduction to (Medical) Bacteriology

Leave a reply cancel reply.

Subscribe now to keep reading and get access to the full archive.

Continue reading

• History & Society
• Science & Tech
• Biographies
• Animals & Nature
• Geography & Travel
• Arts & Culture
• Games & Quizzes
• On This Day
• One Good Fact
• New Articles
• Lifestyles & Social Issues
• Philosophy & Religion
• Politics, Law & Government
• World History
• Health & Medicine
• Browse Biographies
• Birds, Reptiles & Other Vertebrates
• Bugs, Mollusks & Other Invertebrates
• Environment
• Fossils & Geologic Time
• Entertainment & Pop Culture
• Sports & Recreation
• Visual Arts
• Demystified
• Image Galleries
• Infographics
• Top Questions
• Britannica Kids
• Saving Earth
• Space Next 50
• Student Center
• Introduction & Top Questions
• Early education
• Molecular asymmetry
• Germ theory of fermentation
• Pasteur effect
• Pasteurization

Spontaneous generation

Work with silkworms.

• Vaccine development
• Implications of Pasteur’s work

• What did Louis Pasteur discover?
• What did Louis Pasteur invent?
• What was Louis Pasteur’s family like?
• How are vaccines made?
• Why is biology important?

Our editors will review what you’ve submitted and determine whether to revise the article.

• Science History Institute - Biography of Louis Pasteur
• Live Science - Louis Pasteur: Biography and Quotes
• Famous Scientists - Louis Pasteur
• Lemelson-MIT - Biography of Louis Pasteur
• National Center for Biotechnology Information - PubMed Central - Louis Pasteur, the Father of Immunology?
• Institut Pasteur - Our History
• Core - Louis Pasteur, from crystals of life to vaccination
• Louis Pasteur - Children's Encyclopedia (Ages 8-11)
• Louis Pasteur - Student Encyclopedia (Ages 11 and up)
• Table Of Contents

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 Turberville Needham and the French naturalist Georges-Louis Leclerc, count de Buffon . While both supported the idea of spontaneous generation , Italian abbot and physiologist Lazzaro Spallanzani maintained that life could never spontaneously generate from dead matter. In 1859, the year English naturalist Charles Darwin published his On the Origin of Species , Pasteur decided to settle this dispute. He was convinced that his germ theory could not be firmly substantiated as long as belief in spontaneous generation persisted. Pasteur attacked the problem by using a simple experimental procedure. He showed that beef broth could be sterilized by boiling it in a “swan-neck” flask, which has a long bending neck that traps dust particles and other contaminants before they reach the body of the flask. However, if the broth was boiled and the neck of the flask was broken off following boiling, the broth, being reexposed to air, eventually became cloudy, indicating microbial contamination. These experiments proved that there was no spontaneous generation, since the boiled broth, if never reexposed to air, remained sterile . This not only settled the philosophical problem of the origin of life at the time but also placed on solid ground the new science of bacteriology , which relied on proven techniques of sterilization and aseptic manipulation.

In 1862 Pasteur was elected to the Académie des Sciences , and the following year he was appointed professor of geology, physics , and chemistry at the École des Beaux-Arts (School of Fine Arts). Shortly after this, Pasteur turned his attention to France’s silkworm crisis. In the middle of the 19th century, a mysterious disease had attacked French silkworm nurseries. Silkworm eggs could no longer be produced in France, and they could not be imported from other countries, since the disease had spread all over Europe and had invaded the Caucasus region of Eurasia, as well as China and Japan. By 1865 the silkworm industry was almost completely ruined in France and, to a lesser extent, in the rest of western Europe. Pasteur knew virtually nothing about silkworms, but, upon the request of his former mentor Dumas, Pasteur took charge of the problem, accepting the challenge and seizing the opportunity to learn more about infectious diseases . He soon became an expert silkworm breeder and identified the organisms that caused the silkworm disease. After five years of research, he succeeded in saving the silk industry through a method that enabled the preservation of healthy silkworm eggs and prevented their contamination by the disease-causing organisms. Within a couple of years, this method was recognized throughout Europe; it is still used today in silk-producing countries.

In 1867 Pasteur resigned from his administrative duties at the École Normale Supérieure and was appointed professor of chemistry at the Sorbonne, a university in Paris . Although he was partially paralyzed (left hemiplegia ) in 1868, he continued his research. For Pasteur, the study of silkworms constituted an initiation into the problem of infectious diseases, and it was then that he first became aware of the complexities of infectious processes. Accustomed as he was to the constancy and accuracy of laboratory procedures, he was puzzled by the variability of animal life, which he had come to recognize through his observation that individual silkworms differed in their response to disease depending on physiological and environmental factors. By investigating these problems, Pasteur developed certain practices of epidemiology that served him well a few years later when he dealt with animal and human diseases.

Origin of Life: Spontaneous Generation

• Spontaneous Generation

Origin of Life

• Introduction
• Early Earth Environment

It was once believed that life could come from nonliving things, such as mice from corn, flies from bovine manure, maggots from rotting meat, and fish from the mud of previously dry lakes. Spontaneous generation is the incorrect hypothesis that nonliving things are capable of producing life. Several experiments have been conducted to disprove spontaneous generation; a few of them are covered in the sections that follow.

Redi's Experiment and Needham's Rebuttal

In 1668, Francesco Redi, an Italian scientist, designed a scientific experiment to test the spontaneous creation of maggots by placing fresh meat in each of two different jars. One jar was left open; the other was covered with a cloth. Days later, the open jar contained maggots, whereas the covered jar contained no maggots. He did note that maggots were found on the exterior surface of the cloth that covered the jar. Redi successfully demonstrated that the maggots came from fly eggs and thereby helped to disprove spontaneous generation. Or so he thought.

In England, John Needham challenged Redi's findings by conducting an experiment in which he placed a broth, or €œgravy,€ into a bottle, heated the bottle to kill anything inside, then sealed it. Days later, he reported the presence of life in the broth and announced that life had been created from nonlife. In actuality, he did not heat it long enough to kill all the microbes.

Spallanzani's Experiment

Lazzaro Spallanzani, also an Italian scientist, reviewed both Redi's and Needham's data and experimental design and concluded that perhaps Needham's heating of the bottle did not kill everything inside. He constructed his own experiment by placing broth in each of two separate bottles, boiling the broth in both bottles, then sealing one bottle and leaving the other open. Days later, the unsealed bottle was teeming with small living things that he could observe more clearly with the newly invented microscope. The sealed bottle showed no signs of life. This certainly excluded spontaneous generation as a viable theory. Except it was noted by scientists of the day that Spallanzani had deprived the closed bottle of air, and it was thought that air was necessary for spontaneous generation. So although his experiment was successful, a strong rebuttal blunted his claims.

Pasteurization originally was the process of heating foodstuffs to kill harmful microorganisms before human consumption; now ultraviolet light, steam, pressure, and other methods are available to purify foods€”in the name of Pasteur.

Pasteur's Experiment

Louis Pasteur, the notable French scientist, accepted the challenge to re-create the experiment and leave the system open to air. He subsequently designed several bottles with S-curved necks that were oriented downward so gravity would prevent access by airborne foreign materials. He placed a nutrient-enriched broth in one of the goose-neck bottles, boiled the broth inside the bottle, and observed no life in the jar for one year. He then broke off the top of the bottle, exposing it more directly to the air, and noted life-forms in the broth within days. He noted that as long as dust and other airborne particles were trapped in the S-shaped neck of the bottle, no life was created until this obstacle was removed. He reasoned that the contamination came from life-forms in the air. Pasteur finally convinced the learned world that even if exposed to air, life did not arise from nonlife.

Excerpted from The Complete Idiot's Guide to Biology © 2004 by Glen E. Moulton, Ed.D.. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books , a member of Penguin Group (USA) Inc.

To order this book direct from the publisher, visit the Penguin USA website or call 1-800-253-6476. You can also purchase this book at Amazon.com and Barnes & Noble .

• Origin of Prokaryotes and Eukaryotes: Origin of Prokaryotes

Here are the facts and trivia that people are buzzing about.

An official website of the United States government

The .gov means it’s official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings

Preview improvements coming to the PMC website in October 2024. Learn More or Try it out now .

• Advanced Search
• Journal List
• 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. ”

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.

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.

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 ).

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).

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.

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 ].

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.

Is Spontaneous Generation Real?

• Cell Biology
• Weather & Climate
• B.A., Biology, Emory University
• A.S., Nursing, Chattahoochee Technical College

For several centuries it was believed that living organisms could spontaneously come from nonliving matter. This idea, known as spontaneous generation, is now known to be false. Proponents of at least some aspects of spontaneous generation included well-respected philosophers and scientists such as Aristotle, Rene Descartes, William Harvey, and Isaac Newton . Spontaneous generation was a popular notion due to the fact that it seemed to be consistent with observations that a number of animal organisms would apparently arise from nonliving sources. Spontaneous generation was disproved through the performance of several significant scientific experiments.

Key Takeaways

• Spontaneous generation is the idea that living organisms can spontaneously come from nonliving matter.
• Over the years great minds like Aristotle and Isaac Newton were proponents of some aspects of spontaneous generation which have all been shown to be false.
• Francesco Redi did an experiment with meat and maggots and concluded that maggots do not arise spontaneously from rotting meat.
• The Needham and the Spallanzani experiments were additional experiments that were conducted to help disprove spontaneous generation.
• The Pasteur experiment was the most famous experiment conducted that disproved spontaneous generation that was accepted by the majority of the scientific community. Pasteur demonstrated that bacteria appearing in broth are not the result of spontaneous generation.

Do Animals Spontaneously Generate?

Prior to the mid-19th century, it was commonly believed that the origin of certain animals was from nonliving sources. Lice were thought to come from dirt or sweat. Worms, salamanders, and frogs were thought to be birthed from the mud. Maggots were derived from rotting meat, aphids and beetles supposedly sprang from wheat, and mice were generated from soiled clothing mixed with wheat grains. While these theories seem quite ludicrous, at the time they were thought to be reasonable explanations for how certain bugs and other animals seemed to appear from no other living matter.

Spontaneous Generation Debate

While a popular theory throughout history, spontaneous generation was not without its critics. Several scientists set out to refute this theory through scientific experimentation. At the same time, other scientists tried to find evidence in support of spontaneous generation. This debate would last for centuries.

Redi Experiment

In 1668, the Italian scientist and physician Francesco Redi set out to disprove the hypothesis that maggots were spontaneously generated from rotting meat. He contended that the maggots were the result of flies laying eggs on exposed meat. In his experiment, Redi placed meat in several jars. Some jars were left uncovered, some were covered with gauze, and some were sealed with a lid. Over time, the meat in the uncovered jars and the jars covered with gauze became infested with maggots. However, the meat in the sealed jars did not have maggots. Since only the meat that was accessible to flies had maggots, Redi concluded that maggots do not spontaneously arise from meat.

Needham Experiment

In 1745, English biologist and priest John Needham set out to demonstrate that microbes, such as bacteria , were the result of spontaneous generation. Thanks to the invention of the microscope in the 1600s and increased improvements to its usage, scientists were able to view microscopic organisms such as fungi , bacteria, and protists. In his experiment, Needham heated chicken broth in a flask in order to kill any living organisms within the broth. He allowed the broth to cool and placed it in a sealed flask. Needham also placed unheated broth in another container. Over time, both the heated broth and unheated broth contained microbes. Needham was convinced that his experiment had proven spontaneous generation in microbes.

Spallanzani Experiment

In 1765, Italian biologist and priest Lazzaro Spallanzani, set out to demonstrate that microbes do not spontaneously generate. He contended that microbes are capable of moving through the air. Spallanzani believed that microbes appeared in Needham's experiment because the broth had been exposed to air after boiling but before the flask had been sealed. Spallanzani devised an experiment where he placed the broth in a flask, sealed the flask, and removed the air from the flask before boiling. The results of his experiment showed that no microbes appeared in the broth as long as it remained in its sealed condition. While it appeared that the results of this experiment had dealt a devastating blow to the idea of spontaneous generation in microbes, Needham argued that it was the removal of air from the flask that made spontaneous generation impossible.

Pasteur Experiment

In 1861, Louis Pasteur presented evidence that would virtually put an end to the debate. He designed an experiment similar to Spallanzani's, however, Pasteur's experiment implemented a way to filter out microorganisms. Pasteur used a flask with a long, curved tube called a swan-necked flask. This flask allowed air to have access to the heated broth while trapping dust containing bacterial spores in the curved neck of the tube. The results of this experiment were that no microbes grew in the broth. When Pasteur tilted the flask on its side allowing the broth access to the curved neck of the tube and then set the flask upright again, the broth became contaminated and ​ bacteria reproduced in the broth. Bacteria also appeared in the broth if the flask was broken near the neck allowing the broth to be exposed to non-filtered air. This experiment demonstrated that bacteria appearing in broth are not the result of spontaneous generation. The majority of the scientific community considered this conclusive evidence against spontaneous generation and proof that living organisms only arise from living organisms.

• Microscope, Through the. “Spontaneous Generation Was an Attractive Theory to Many People, but Was Ultimately Disproven.” Through the Microscope Main News , www.microbiologytext.com/5th_ed/book/displayarticle/aid/27.
• Life and Contributions of Robert Koch, Founder of Modern Bacteriology
• All About Photosynthetic Organisms
• Angiosperms
• Phases of the Bacterial Growth Curve
• Biology of Invertebrate Chordates
• What Is an Action Potential?
• Animal Viruses
• Slowest Animals on the Planet
• 5 Tricks Plants Use to Lure Pollinators
• Chromosome Structure and Function
• 7 Scary Diseases Caused by Bacteria
• The Photosynthesis Formula: Turning Sunlight into Energy
• Parts of a Flowering Plant
• What Is Phylogeny?
• 7 Fascinating Facts About Fungi
• What Is a Trophic Level?

• Site search
• Through the Microscope
• Why Microbes Matter
• Remember me
• Log in page
• Create new account
• Recover lost username
• Recover lost password
• Contact the Author
• Contact the Webmaster

Latest News

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

( 61926 Reads)

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

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.

• Earth and Environment
• Literature and the Arts
• Philosophy and Religion
• Plants and Animals
• Science and Technology
• Social Sciences and the Law
• Sports and Everyday Life
• Additional References

• Encyclopedias almanacs transcripts and maps

The Spontaneous-Generation Debate

According to the ancient theory of spontaneous generation, living organisms could originate from nonliving matter. During the seventeenth and eighteenth centuries, however, naturalists began to conduct experiments that challenged the doctrine of spontaneous generation. After Francesco Redi published his Experiments on the Generation of Insects, the spontaneous-generation debate was essentially limited to microscopic forms of life. During the eighteenth century, the French naturalist Georges Buffon and the English microscopist John Turbeville Needham carried out a series of experiments that seemed to support the doctrine of spontaneous generation, but their conclusions and experimental methods were challenged by the Italian physiologist Lazzaro Spallanzani . After conducting a series of rigorous experiments on the growth of microorganisms, Spallanzani vigorously challenged the belief in spontaneous generation. Spallanzani claimed that Needham had not heated his tubes enough and that he had not sealed them properly.

According to the theory of spontaneous generation, living organisms can originate from nonliving matter. Belief in the spontaneous generation of life was almost universal from the earliest times up to the seventeenth century. Small, lowly creatures and all sorts of vermin, which often appeared suddenly from no known parents, seemed to arise from lifeless materials. Insects, frogs, and even mice were thought to arise from slime, mud, and manure in conjunction with moisture and heat. In ancient times, this belief seemed to conform to common observations about the sudden appearance of insects, small animals, and parasites. Spontaneous generation also provided an answer to philosophical and religious questions about the origin of life.

During the seventeenth and eighteenth centuries, however, some naturalists began to conduct experiments that tested and challenged the doctrine of spontaneous generation. Italian physician and poet Francesco Redi (1626-1698) was one of the first to question the spontaneous origin of living things. In 1668 Redi initiated a now-famous experimental attack on the question of spontaneous generation. Redi discovered that when adult flies were excluded from rotting meat, maggots did not develop. If flies were not excluded, they laid eggs on the meat and the eggs developed into maggots. Thus, Redi demonstrated that maggots and flies were not spontaneously generated from rotting meats but instead developed from eggs that were deposited by adult flies. Although Redi's Experiments on the Generation of Insects (1668) did not totally discredit the doctrine of spontaneous generation, the eighteenth-century spontaneous-generation debate was essentially limited to microscopic forms of life.

Seventeenth-century microscopists were able to see a new world teeming with previously invisible entities, including protozoa, molds, yeasts, and bacteria. Many naturalists thought that the new world of microscopic "animalcules" discovered by the great microscopist Anton van Leeuwenhoek (1632-1723) provided proof that minute plants and animals were spontaneously generated in pond water or similar media. Some naturalists thought that these minute entities might even be the living molecules, or "monads," postulated by the mathematician and philosopher Gottfried Wilhelm Liebniz (1646-1716). While Leeuwenhoek was quite sure that he had discovered "little animals" that must have descended from parents like themselves, others took exception to this conclusion. Indeed, questions concerning the nature, origin, and activities of microorganisms were not clarified until the late nineteenth century.

Several interesting accounts of "infusoria" were, however, published in the eighteenth century. Louis Joblot (1645-1723), for example, confirmed the existence of some of Leeuwenhoek's animalcules. In 1718 Joblot published an illustrated treatise on the construction of microscopes that described his observations of the animalcules that could be found in various infusions. Joblot is now remembered primarily for his opposition to the doctrine of spontaneous generation. To prove that infusoria were not spontaneously generated, Joblot boiled his growth medium and divided it into two portions. A flask containing one portion was sealed off and the other sample was left uncovered. The open flask was soon teeming with microbial life, but the sealed vessel was free of infusoria. To prove that the medium was still susceptible to putrefaction, Joblot exposed it to the air and showed that infusoria were soon actively growing. Joblot concluded that something from the air had to enter the medium to produce microorganisms.

Joblot's experiments were repeated with many variations by other naturalists, but the results obtained were not consistent. Among the most notable eighteenth-century advocates of the doctrine of the spontaneous generation of microorganisms were the French naturalist Georges Buffon (1707-1788) and the English microscopist John Turbeville Needham (1713-1781). Together as well as separately, Needham and Buffon carried out a series of experiments to disprove the work of Joblot.

John Turberville Needham was a naturalist as well as a teacher and a clergyman. He was the first Roman Catholic to become a member of the Royal Society of London. In 1767 Needham retired to the English seminary in Paris. He devoted the rest of his life to his studies and experiments. Needham had decided to study natural history after reading accounts of "animalcules" and "infusoria" and philosophical speculations about microorganisms, spontaneous generation, and the origin of life. Having rejected mechanistic theories of physiology, Needham adopted vitalism (the idea that life processes cannot be explained by the laws of chemistry and physics) and the doctrine of spontaneous generation. In 1745 he published a book entitled An Account of Some New Microscopical Discoveries, in which he presented his experimental evidence for the theory of spontaneous generation.

According to Needham, many organisms developed in prepared infusions of various substances even if the infusions had been placed in sealed tubes and heated for 30 minutes. When Needham repeated Joblot's experiments, whether the flasks were open or closed and the medium boiled or not boiled, all vessels soon swarmed with microscopic life. Needham assumed that this heat treatment should have killed any living organisms that might have been in the original medium. According to Needham, a powerful vegetative force remained in every particle of matter that had previously been part of a living being. Therefore, when animals or plants died, they slowly decomposed and released the "common principle," which Needham thought of as a kind of universal semen from which new life arose. He concluded that the growth of microorganisms under his experimental conditions proved that spontaneous generation of microbial life had occurred. Published in the Philosophical Transactions of the Royal Society in 1748, Needham's views were well known. The claims of Needham and Buffon did not, however, stand unchallenged for very long.

When the Italian physiologist Lazzaro Spallanzani (1729-1799) repeated Needham's experiments, he obtained conflicting results. Spallanzani, who had studied philosophy, theology, law, and mathematics, was appointed professor of logic, metaphysics, and Greek at Reggio College in 1754. Six years later, he became professor of physics at the University of Modena. In 1769 he accepted a position at the University of Pavia and remained there until his death. (After attacking Needham and Buffon on the subject of spontaneous generation, Spallanzani investigated regeneration, transplantation, reproduction, generation, artificial insemination , the circulation of the blood, digestion, and the electric organ of the torpedo fish before returning to studies of microscopic plants and animals at the end of his career.) Like his friends Albrecht von Haller (1708-1777) and Charles Bonnet (1720-1793), Spallanzani supported an ovist preformationist view of generation and he attacked Buffon's mechanistic epigenetic theory.

After examining various forms of microscopic life, Spallanzani concluded that Leeuwenhoek had been correct in identifying these minute entities as living organisms. To prove that these entities were alive, he carried out a series of experiments in which he boiled rich growth media for fairly long periods of time. He found that, if he placed media that had been boiled for 30 minutes into phials and immediately sealed them by fusing the glass, no microorganisms were produced. He concluded, therefore, that the infusoria found in pond water and other preparations were actually living organisms.

In another series of experiments, Spallanzani exposed significant errors in the experiments conducted by Needham and Buffon. By heating a series of flasks for different lengths of time, Spallanzani determined that various sorts of microbes differed in their susceptibility to heat. Whereas some of the larger animalcules were destroyed by slight heating, other, very minute, entities seemed to survive in liquids that had been boiled for almost an hour. Further experiments convinced Spallanzani that all these little animals entered the media from the air. Convinced that a great variety of animalcular "eggs" must be disseminated through the air, Spallanzani concluded that the air could either convey the germs to the infusions or assist in the multiplication of those germs already in them.

In 1767 Spallanzani published an account of his research on the growth of microorganisms and his criticism of the theory proposed by Buffon and Needham. According to Buffon and Needham, living things contained special "vital atoms" that were responsible for all physiological activities. They suggested that after the death of an individual these living atoms were released into the soil and water and taken up by plants. They thought that the "infusoria" that could be found in pond water or infusions of plant and animal material were actually evidence of these vital atoms.

Despite Spallanzani's criticisms, Needham and Buffon continued to champion the doctrine of spontaneous generation. Indeed, the debate was not resolved until the nineteenth century, when the great French chemist Louis Pasteur and the English physicist John Tyndall declared war on spontaneous generation. Although Spallanzani's experiments answered many of the questions raised by advocates of spontaneous generation as well as proved the importance of sterilization, his critics claimed that he had tortured the all important "vital force" out of the organic matter by his cruel treatment of his media. The vital force was, by definition, capricious and unstable, rendering it impossible to expect reproducibility in experiments involving organic matter .

During the nineteenth century, the design of experiments for and against spontaneous generation became increasingly sophisticated as proponents of the doctrine challenged the universality of negative experiments. Because any apparent exception could allow proponents of the theory to maintain that spontaneous generation only occurred under special conditions, however, opponents were always on the defensive. The work of Louis Pasteur (1822-1895) and John Tyndall (1820-1893) effectively proved that the existence of germs in the air was the critical issue in establishing the experimental basis of the debate. Pasteur was convinced that microbiology and medicine could only progress when the idea of spontaneous generation was totally vanquished. Although both knew that it is logically impossible to prove a universal negative, they demonstrated that under present conditions living beings arise from "parents" like themselves. Pasteur and Tyndall proved that the microbes that Needham and Buffon thought arose from the media actually came from microbes carried by particulate matter in the air. Pasteur proved that microorganisms come from the multiplication of parent microorganisms of their own kind. The experiments conducted by Pasteur and Tyndall did not deal with the question of the ultimate origin of life, but they did demonstrate that microbes do not arise de novo in properly sterilized media under the conditions prevailing today. Advocates of the doctrine of spontaneous generation have argued that some form of the doctrine is necessarily true in the sense that if life did not always exist on earth it must have been spontaneously generated at some point.

LOIS N. MAGNER

Further Reading

Brock, T. D., ed. Milestones in Microbiology. Englewood Cliffs, NY: Prentice-Hall, 1961.

Conant, J. B., ed. Pasteur's and Tyndall's Study of Spontaneous Generation. Cambridge, MA: Harvard University Press, 1953.

Doetsch, R. N., ed. Microbiology: Historical Contributions from 1776-1908. New Brunswick , NJ: Rutgers University Press, 1960.

Epstein, Sam. Secret in a Sealed Bottle: Lazzaro Spallanzani's Work with Microbes. New York : Coward, McCann & Geoghegan, 1979.

Farley, J. The Spontaneous Generation Controversy from Descartes to Oparin. Baltimore, MD: Johns Hopkins Press, 1977.

Lechevalier, H. A., and M. Solotorovsky. Three Centuries of Microbiology. New York : Dover, 1974.

Nigrelli, Ross F., ed. Modern Ideas on Spontaneous Generation. New York: New York Academy of Sciences, 1957.

Vandervliet, G. Microbiology and the Spontaneous Generation Debate During the 1870s. Lawrence, KS: Coronado University Press, 1971.

Cite this article Pick a style below, and copy the text for your bibliography.

" The Spontaneous-Generation Debate . " Science and Its Times: Understanding the Social Significance of Scientific Discovery . . Encyclopedia.com. 15 Aug. 2024 < https://www.encyclopedia.com > .

"The Spontaneous-Generation Debate ." Science and Its Times: Understanding the Social Significance of Scientific Discovery . . Encyclopedia.com. (August 15, 2024). https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/spontaneous-generation-debate

"The Spontaneous-Generation Debate ." Science and Its Times: Understanding the Social Significance of Scientific Discovery . . Retrieved August 15, 2024 from Encyclopedia.com: https://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/spontaneous-generation-debate

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

• Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
• In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.

More From encyclopedia.com

About this article, you might also like, nearby terms.

Spontaneous Generation Theory

Table of Contents

Aristotle’s Work

Early experiments, franceso redi, pier antonio micheli, john needham, lazzaro spallanzani, disproving the theory, louis pasteur, john tyndall, frequently asked questions.

Spontaneous generation theory is an archaic scientific theory which stated that living organisms could arise from nonliving matter and that such a process was regular in nature. It also explained the origin of life from the nonliving subjects. According to that theory, a piece of bread and cheese wrapped and left in a corner could give rise to mice in a few weeks, or maggots could rise from dead flesh.

The hypothesis was designed by Aristotle on the basis of previous work of natural philosophers and the theory held its place for two millenniums. Francesco Redi and Lazzaro Spallanzani then challenged this theory in the 17th and 18th centuries, but it was still not discredited. It was not until the work of Louis Pasteur and John Tyndall in the 19th century that this theory was finally disproved.

The theory lines up with the theory of origin of life, which states the process of abiogenesis. Abiogenesis is the natural process of creation of simple organic compounds from nonliving matter. The term equivocal generation, also called heterogenesis, describes the theory of spontaneous generation. According to equivocal generation, one life arises from another unrelated life form.

According to Aristotle, every living being is made up of a compound of matter and form. In his sexual theory of reproduction, he stated that male’s semen was efficient cause that passed down characteristics to female matter (menstrual blood), and gave rise to its offspring. He believed that the male semen and female matter were refinements that were produced by bodies as a result of their proportions of heat, ingested food and were a byproduct of the elements earth and water. Yet, he believed that creatures arose from spontaneous generation and not sexual reproduction.

Analogous to his sexual reproduction theory, he said that non living matter just like seminal fluid had ‘pneuma’ or ‘vital heat’ that endowed the subtances with vital properties. He came to the conclusion that whether a life form arose from sexual reproduction or spontaneous generation, they were a result of interaction between vital heat and elemental matter.

Franceso Redi was an Italian naturalist who challenged the ancient belief of spontaneous generation of maggots on decaying meat in 1668. He believed that maggots could be prevented if flies were not allowed direct contact with the meat. He designed an experiment where he put pieces of meat in six different containers. He covered two of them with gauze, two tightly sealed with corks and left the remaining two open in the air. His hypothesis came true as it was observed that there were no maggots in the covered (with gauze and cork) containers but maggots were observed in the open container. He came to the conclusion that flies were able to lay their eggs on the open piece of meat and that the maggots were their offspring who grew on flesh.

Pier Antonio Micheli, an Italian botanist, performed another experiment in 1729 where he placed fungal spores on a slice of melon and observed that the same was produced on the melon slice. He concluded that the new spores definitely did not arise from spontaneous generation.

John Needham, an English biologist, did yet another experiment in 1745 with boiled broths. He infused a broth by mixing plant and animal matter and boiled it in the belief that it would kill all the microorganisms . He sealed the broth and left it for a few days. He observed that the broth had become cloudy and that it has microscopic organisms in it. He reiterated the spontaneous generation theory and many of his peers believed him. However, in reality, the broth was not boiled vigorously so as to kill all the microorganisms.

Lazzaro Spallanzani, an Italian biologist, reattempted Needham’s experiment in 1768. He took animal and plant matter-infused broths and boiled them vigorously. He kept one of the jars sealed and left the other one open to the air. According to his observations, the sealed jar was clear and did not have any growth. He then concluded that air was the force that was introducing microbes into the flask.

By this time, there was increased skepticism among scientists about the spontaneous generation theory.

In 1859, Louis Pasteur, a French microbiologist conducted another broth experiment that settled the question of spontaneous generation once and for all. He took swan flasks that had twisted necks for the experiment and boiled meat broth in it. The design of the flask was such that it allowed exchange or air from outside to inside but prevented the entry of microorganisms. If any microbes were to enter the flask they would get caught in the twisted neck of the flask. The broth remained clear for a long amount of time as long as the flask was kept intact. Once the flask was turned, which led to entry of microbes into the broth, it became cloudy.

John Tyndall, an Irish physicist, advanced the work of Louis Pasteur and finally the theory of spontaneous generation was disproved. Not much is known about Tyndall’s experiment on spontaneous generation.

In 1862, the French Academy of Sciences, announced a prize for the scientists who shed new light on the spontaneous generation controversy and appointed a jury to decide the winner. Louis pasteur was awarded the Alhumbert Prize from the Paris Academy of Sciences for his work that totally threw away the concept of spontaneous generation. 1n 1864, Pasteur was quoted saying in a lecture: “Omne vivum ex vivo” (“Life only comes from life”). Pasteur and other scientists started to use the word biogenesis for the origin of life which again meant that life comes only from another life.

This sums up the theory of spontaneous generation. Keep visiting BYJU’S Biology for more interesting topics.

• Conservation of Forest and Wildlife Overview
• Feedback Mechanism of Hormones
• Mendel Laws of Inheritance

Who proposed the spontaneous generation theory?

What is spontaneous generation and who disproved the theory, what is the difference between cell theory and spontaneous generation, what is another name for spontaneous generation.

Register with BYJU'S & Download Free PDFs

Register with byju's & watch live videos.

Revisiting The Debunked Theory Of Spontaneous Generation

16:54 minutes

• Read Transcript
• Listen on SoundCloud
• More from this episode

“Spontaneous generation” was the idea that living organisms can spring into existence from non-living matter. In the late 19th century, in a showdown between chemist Louis Pasteur and biologist Felix Pouchet put on by the French Academy of Sciences, Pasteur famously came up with an experiment that debunked the theory. He showed that when you boil an infusion to kill everything inside and don’t let any particles get into it, life will not spontaneously emerge inside. His experiments have been considered a win for science—but they weren’t without controversy.

In this interview,  Undiscovered’s Elah Feder, Ira Flatow, and historian James Strick talk about what scientists of Pasteur’s day really thought of his experiment, the role the Catholic church played in shutting down “spontaneous generation,” and why even Darwin did his best to dodge the topic.

Further Reading:

• Listen to more science history stories on our spinoff podcast,  Undiscovered.
• Learn about another once-great scientific idea: the luminiferous ether.

Segment Guests

James Strick is a professor of Science, Technology and Society at Franklin and Marshall College in Lancaster, Pennsylvania.

Segment Transcript

IRA FLATOW: This is Science Friday. I’m Ira Flatow. And for the rest of the hour, we’re diving into the vaults of science history, because the hosts of our podcast Undiscovered are working on a new series. It’s all, on one of my favorite subjects, all about science history. And co-host Elah Feder is here to tell us about it. Hey, Elah. 

ELAH FEDER: Hey, Ira. Yeah, me and my co-host Annie Minoff are really big science history buffs, like yourself. And recently, we got thinking about all of the scientific ideas that we used to think were true, that we’d had accepted as good, solid science until, one day, we didn’t believe them anymore. We’re thinking about old miracle cures or outdated beliefs about the universe, ideas that are often punchlines today. But we wanted to give them a closer look. Why did we believe in these ideas in the first place? What had us convinced? And then what did it take to change our minds? That’s what this upcoming series is all about. 

IRA FLATOW: And today, we’re talking about spontaneous generation. It’s really fascinating. 

ELAH FEDER: Yeah, so one of the basic ideas in biology is that every living thing comes from another living thing. A horse comes from horse parents. An oak tree comes from an oak tree’s acorn. An amoeba comes from another amoeba that has split in two. And if we work our way all the way back through evolution, all living things come from an original living thing. But for a long time, people believed that some living things didn’t have parents. They just spontaneously sprang into life. We called it spontaneous generation. You might have learned about this in high school. 

IRA FLATOW: Yeah. 

ELAH FEDER: So if you kept reading, you would have learned about how a scientist named Louis Pasteur disproved this idea. Science for the win. But it turns out that history is never that simple. Instead of a win for science, this might have been a win for religion. My guest is here to fill us in on the story behind the story. James Strick is a professor of science technology and society at Franklin and Marshall College in Lancaster, Pennsylvania. Welcome to the show, Jim. 

JAMES STRICK: Thanks, it’s nice to be here. 

ELAH FEDER: So you were a high school teacher for a while. So you know the textbook version of spontaneous generation pretty well. Can you give us the short version of it? 

JAMES STRICK: Well, spontaneous generation really has been used most of the time to mean living things coming into being from non-living starting materials. 

ELAH FEDER: But the upshot was that life was spontaneously coming into existence. It didn’t necessarily have living parents that brought it into being. 

JAMES STRICK: That’s right. 

ELAH FEDER: So today, we think of this as an idea that’s been thoroughly debunked. It’s very, very wrong, obviously wrong. But for over 2,000 years, a lot of very smart people believed in spontaneous generation, going all the way back to Aristotle. 

JAMES STRICK: Yeah, Aristotle certainly the best biologist of his day in ancient Greece and a real astute observer of nature. When he saw things like eels, and frogs, and tiny fish emerging from muddy river banks in the spring, it seemed pretty clear to him that you had a case of living things coming into being without parents and that it was the influence of the strengthening sun, an element from the sun that he called “pneuma” that interacted with the mud of the river bank to make it capable of producing new life when otherwise it wouldn’t be. 

IRA FLATOW: So he was only talking about small living creatures, not elephants and things like that? 

JAMES STRICK: Nothing larger than frogs or eels, but to many people that already seems stunning enough in today’s context. 

ELAH FEDER: So you see these creatures coming up out of nowhere, it seems like they are just spontaneously emerging. But the Catholic church was very against this idea. Why were they so against it? 

JAMES STRICK: For most of the history of the Catholic church, it was not opposed to spontaneous generation. Saint Augustine, for example, in the early fifth century, one of the most important and influential church fathers who left a lot of writings, had no problem at all reconciling spontaneous generation with Catholic doctrine. He thought that God had put seed principles into certain kinds of matter at the beginning of creation and that meant that, over time, they would unfold and develop into living things. But it’s only in the late 17th century when there really comes to be a sharp conflict between the dominant Catholic doctrine and the doctrine of spontaneous generation. 

Church is moving away from Aristotelian physics because of all the new discoveries of the scientific revolution. But there’s also new doctrines of preformation and pre-existence to explain where living things come from. They work with Genesis in a way, but not in a way that is compatible with spontaneous generation. 

It conflicts with this doctrine that all generations of organisms were created at the beginning, serially in case, that Russian dolls within the eggs or the sperm of the very first member of that species. But also, as you get into the early 18th century, spontaneous generation is seen to potentially be an underpinning for philosophical materialism, the idea that matter alone contains everything necessary to generate life, mind, and that things like the soul and the afterlife are an illusion. 

ELAH FEDER: So it kind of seems to cut God out of the equation. You can have life coming up from non-life. I could see why they would object to that. So in the 1800s, you get a showdown between two scientists. You have Louis Pasteur and, somewhat less famous today, Felix Pouchet, over this idea of spontaneous generation. What happened? 

JAMES STRICK: Pouchet, in the same year that Darwin’s Origin of Species came out, 1859, Pouchet published a book-length report of many, many experiments that he had done that seemed to validate the possibility of spontaneous generation, at least for microorganisms, even if not for anything larger or more complex than that. 

The French Academy of Sciences, the most prestigious body of scientific opinion in France at the time, responded to this by posing a competition. There was a prize of 500 francs for the winner. They said, we challenge every scientist in France to present experiments that can clarify the subject of spontaneous generation. 

And, essentially, Pouchet’s book, he entered as his entrance into this competition, and the French Academy, I guess, was waiting to see whether somebody would come in on the other side of the story and claim to have experiments that disproved spontaneous generation, that torch was taken up by a young, at the time, relatively little-known chemist named Louis Pasteur. 

ELAH FEDER: So Pouchet had claimed to demonstrate that spontaneous generation was real. What was Pasteur’s problem with Pouchet’s demonstration? 

JAMES STRICK: Pouchet’s pushes main line of evidence was what are called “infusion experiments,” meaning you infuse or soak something in water, you boil it extensively to try to make sure that nothing that might have been previously alive could possibly still be alive in there. You boil it in a sealed container for an extended period of time. And then you let the infusion cool down in the sealed container. 

And if, over time, the results in there become turbid, cloudy, then you judge that there’s a growth of microorganisms occurring. And in Pouchet’s case, you claim that that proves those microorganisms must have been produced by spontaneous generation. Pasteur did not think that Pouchet’s experiments were sufficiently precise, as he put it. He thought that Pouchet had not adequately sealed his containers to prevent the ability of microbes getting in from the outside. 

And Pasteur believed that microbes are widely distributed through nature, riding around, for one thing, on dust particles everywhere. So Pasteur thought that if he could somehow duplicate Pouchet’s infusion experiments but find a way to make sure that dust was kept out, that he could show that in those infusions, you’d never see the result turned turbid. There’d never be the growth of microorganisms in there. 

And he came up with a really bright idea. He created what were later called “swan-necked flasks.” He heated up the neck of the glass, flask that the infusion was in in a Bunsen burner flame while the infusion was boiling and drew the neck out into a long, curved shape, where it had a dip in the curve before finally opening with a small opening to the outside air. 

And in those flasks, when Pasteur boiled them, never in any of his publicly reported experiments did he ever see any growth of microorganisms. So the French Academy of Sciences pronounced Pasteur’s experiments decisive and judged that Pasteur was right, that Pouchet had not prevented the admitting of dust particles carrying microorganisms because he hadn’t adequately sealed his flasks. And, therefore, Pasteur’s experiments proved that spontaneous generation was impossible. 

IRA FLATOW: So it was a slam dunk, then? 

JAMES STRICK: That is how it is described in most textbooks, and that is how it was described by the French Academy of Sciences at the time. The interesting thing is that scientists, at the time, split maybe close to 50/50 on whether they found this persuasive or not. An awful lot of scientists, not just Pouchet and his allies, but, for example, Richard Owen in Britain, one of the premier comparative anatomists of the day and, in some ways, an opponent of Darwin in many parts of the evolution debate. Owen said pointedly that, it’s really interesting. 

Pasteur doesn’t seem to have proven anything other than that dust is a necessary ingredient for spontaneous generation, just as Pouchet claimed. And the French Academy is premature in declaring Pasteur’s experiments decisive. And Owen was not the only scientist in other countries who had that point of view. 

ELAH FEDER: If it wasn’t a slam dunk and a lot of scientists objected, why did the Academy of Sciences declare this a case closed? 

JAMES STRICK: This is a time of a politically very conservative government in France that came to power in 1850. And Louis Napoleon, the nephew of the famous Napoleon, declared himself emperor and was supported by most of the Conservative political forces in France, including the Catholic church. So the Pasteur-Pouchet controversy is taking place at a time of politically a very conservative government in France. The French Academy of Science is a government-appointed body and, therefore, under considerable government influence in terms of its point of view, had appointed a jury to judge the Pasteur-Pouchet competition. 

And a couple of the people on the jury had publicly before stated that spontaneous generation is absolutely impossible and would be an outrage against all morality and Christian society if it were proven to be true. And yet, they were considered to be able to be objective judges on this commission. And they wanted to declare this case closed and settled, even when many scientists considered the experimental evidence, as we say, underdetermined. 

ELAH FEDER: And it sounds like, at the time, a lot of people were capitulating to the church. You mentioned Darwin when we spoke. 

JAMES STRICK: You know, his book had just come out two years earlier in 1859. And if you read Darwin’s book and are half awake, you have to realize by the time you get near the end of the book, you know what this guy is saying is the further back in time you go, the fewer and fewer common ancestors there are. And if you go back far enough, all living things must be descended from someone single, common ancestor or, at most, a tiny handful of original ones. 

And so the book is kind of begging the question, where did that one come from? Many people perceive Darwin’s book to be a project about getting the supernatural out of the life sciences. This question is so loaded, and Darwin avoids it for almost the entire length of the book. 

And then on page 484, almost to the very end, there’s one throwaway sentence on this subject. And what Darwin says, and I’m quoting is, “Therefore I should infer that probably all the organic beings which have ever lived on this earth have descended from some one primordial form into which life was first breathed.” 

IRA FLATOW: I’m Ira Flatow. This is Science Friday from WNYC Studios. And that’s where scientists are now, right? Talking about that mystery chemical soup, that primordial soup on earth that could have led to life? 

JAMES STRICK: That’s where modern origin of life research is right now. But imagine what an 1859 audience thought when it read that last expression. “Some one primordial form into which life was first breathed.” I mean, it’s clearly biblical language, and it was clearly not selected unintentionally by Darwin. 

He’s trying to dodge the question. He knows he’s going to have quite enough difficulty already convincing a Christian audience to accept species change over time. He really doesn’t want to tie his doctrine inseparably, this is my argument in my first book, to the argument that you have to believe if Darwin is right, there is no creator god. 

IRA FLATOW: I guess, in a sense, this is, as science history being just a subset of all history, usually, the historians who are the victors write the history. 

JAMES STRICK: They sure do. And Pasteur was conclusively declared the victor in France. And a number of people in other countries took up the French Academy of Science’s pronouncement. Textbook writers don’t always follow the primary source literature that closely. They just listened to what the authoritative bodies of opinion say are the outcome of these debates. And so, for generations of biology textbooks written since the 1860s, it has been copied practically word for word from the French academies pronouncement that these experiments of Pasteur prove once and for all that life can never possibly come into being from non-life. 

If you’re a modern origin of life researcher, obviously, that’s not right. You obviously believe that, under some circumstances and under the conditions that existed on the primitive earth, it must have been possible. Origin of life research in the 1870s, early 1880s, kind of went in the tank for an extended period of time as a result of the French Academy of Science’s pronouncements about the Pasteur-Pouchet debate. 

IRA FLATOW: That’s about all time we have. I want to thank James Strick, professor of science technology and society at Franklin and Marshall College in Lancaster, Pennsylvania for joining us. And also, Ellah Feder, co-host of our Undiscovered podcast, who’s hard at work on a new series all about the failed ideas of science history, right? Thanks, Ellah. 

ELAH FEDER: Thanks for having us. 

IRA FLATOW: And we’ll be hitting the road again in August, this August coming to San Antonio. Yeah, join us Saturday, August 10 for Science Friday Live from the Lone Star State. We’re going to talk about science stories in the San Antonio area. And believe me, there are lots of them. Plus, can’t go to San Antonio without having live music, more, all kinds of fun. That’s Saturday, August 10th, not Friday night, Saturday night, August 10, info and tickets at sciencefriday.com/sanantonio. 

And if you’re saying, hey, what about an event near me, you can visit the Events page. Want to know where we’re going to be near you? It’s on our Events page on our website. Sign up for our events there at the same time. 

We have a special announcement. We have a new app you can use to add your voice to our shows. It’s a way for us to interact with you, to get you involved in our coverage. It’s available for iPhone and Android, so search for “sci-fri vox pop–” sci-fri vox pop. Wherever you get your apps, sci-fi vox pop, V-O-X P-O-P, and share your voice comments for our upcoming shows. 

And we’re active all week on Facebook, Twitter, Instagram, all social media. Of course, if you have a smart speaker, ask it to play Science Friday whenever you want to, sitting around, listening, lounging around– play it. And you can email us, yes– [email protected]. Have a great weekend. I’m Ira Flatow in New York.

Copyright © 2019 Science Friday Initiative. All rights reserved. Science Friday transcripts are produced on a tight deadline by 3Play Media. Fidelity to the original aired/published audio or video file might vary, and text might be updated or amended in the future. For the authoritative record of Science Friday’s programming, please visit the original aired/published recording. For terms of use and more information, visit our policies pages at http://www.sciencefriday.com/about/policies/

Meet the Producers and Host

About alexa lim.

Alexa Lim was a senior producer for Science Friday. Her favorite stories involve space, sound, and strange animal discoveries.

About Elah Feder

Elah Feder is the former senior producer for podcasts at Science Friday. She produced the Science Diction podcast, and co-hosted and produced the Undiscovered podcast.

About Ira Flatow

Ira Flatow is the host and executive producer of Science Friday .  His green thumb has revived many an office plant at death’s door.

Explore More

Revisiting a once-great scientific idea.

Mainstream physicists once believed light was simply a disturbance of the "luminiferous ether"—before the idea fell from grace.

The Origin Of The Word ‘Vaccine’

This world-changing tool of immunization got its name from a cow virus.

Privacy Overview

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• Open access
• Published: 20 August 2024

Isolated attosecond pulse generation in a semi-infinite gas cell driven by time-gated phase matching

• Federico Vismarra   ORCID: orcid.org/0000-0002-2348-2749 1 , 2   na1 ,
• Marina Fernández-Galán   ORCID: orcid.org/0000-0003-3047-1244 3 , 4   na1 ,
• Daniele Mocci 1   na1 ,
• Lorenzo Colaizzi 1 ,
• Víctor Wilfried Segundo 3 , 4 ,
• Roberto Boyero-García 3 ,
• Javier Serrano   ORCID: orcid.org/0000-0003-2093-2000 3 , 4 ,
• Enrique Conejero-Jarque   ORCID: orcid.org/0000-0002-5328-6714 3 , 4 ,
• Marta Pini   ORCID: orcid.org/0000-0002-3772-4542 1 , 2 ,
• Lorenzo Mai 1 ,
• Yingxuan Wu 1 ,
• Hans Jakob Wörner 5 ,
• Elisa Appi 6 ,
• Cord L. Arnold   ORCID: orcid.org/0000-0003-4249-411X 6 ,
• Maurizio Reduzzi 1 ,
• Matteo Lucchini   ORCID: orcid.org/0000-0001-6476-100X 1 , 2 ,
• Julio San Román   ORCID: orcid.org/0000-0002-2645-7039 3 , 4 ,
• Mauro Nisoli   ORCID: orcid.org/0000-0003-2309-732X 1 , 2 ,
• Carlos Hernández-García   ORCID: orcid.org/0000-0002-6153-2647 3 , 4 &
• Rocío Borrego-Varillas   ORCID: orcid.org/0000-0002-4499-0558 2  

Light: Science & Applications volume  13 , Article number:  197 ( 2024 ) Cite this article

406 Accesses

Metrics details

• High-harmonic generation
• Nonlinear optics
• Ultrafast lasers

Isolated attosecond pulse (IAP) generation usually involves the use of short-medium gas cells operated at high pressures. In contrast, long-medium schemes at low pressures are commonly perceived as inherently unsuitable for IAP generation due to the nonlinear phenomena that challenge favourable phase-matching conditions. Here we provide clear experimental evidence on the generation of isolated extreme-ultraviolet attosecond pulses in a semi-infinite gas cell, demonstrating the use of extended-medium geometries for effective production of IAPs. To gain a deeper understanding we develop a simulation method for high-order harmonic generation (HHG), which combines nonlinear propagation with macroscopic HHG solving the 3D time-dependent Schrödinger equation at the single-atom level. Our simulations reveal that the nonlinear spatio-temporal reshaping of the driving field, observed in the experiment as a bright plasma channel, acts as a self-regulating mechanism boosting the phase-matching conditions for the generation of IAPs.

Similar content being viewed by others

Enhanced coherent transition radiation from midinfrared-laser-driven microplasmas

Intense multicycle THz pulse generation from laser-produced nanoplasmas

Intense isolated attosecond pulses from two-color few-cycle laser driven relativistic surface plasma

Introduction.

Since its initial demonstration 1 , the generation and manipulation of isolated attosecond pulses (IAPs) have provided groundbreaking tools for tracking electronic motion in atoms, molecules, and solids 2 . As a result, several fundamental processes, such as photoionization time delays 3 , charge migration 4 , electronic decoherences 5 , or carrier motion in solids 6 , have been observed and measured with unparalleled time resolution, opening new and exciting fields of research.

In conventional high-order harmonics generation (HHG) table-top setups, an intense (~10 14 –10 15  W·cm −2 ) femtosecond driving laser field, centred in the near-infrared (IR) spectral region, is focused on a noble gas target. When macroscopic phase matching in the gas is ensured, the highly non-linear response of the medium leads to the coherent production of extreme-ultraviolet (XUV) radiation 7 , 8 . The natural form of this radiation is a train of attosecond pulses separated by half an optical cycle of the driving field 9 . The isolation of a single attosecond pulse from this train relies either on the use of extremely short driving pulses 10 or on specific techniques, known as gating techniques 11 . For instance, polarization gating 12 , 13 relies on a time-dependent polarization shaping of the driving radiation. Colour gating 14 , instead, introduces a second colour to break the electric field symmetry. A combined scheme that integrates both polarization and colour gating, the double optical gating approach 15 , can also be followed. Another widespread technique is ionization gating 16 , 17 , which utilizes a time-gated window for HHG phase matching 18 .

HHG efficiency is largely affected by the phase-matching of the harmonic radiation from all emitters in the generating medium 19 , 20 , 21 . Recent theoretical efforts 22 , later confirmed experimentally for trains of attosecond pulses 23 , have demonstrated two equivalent regimes of harmonic phase matching for efficient HHG, namely high-pressure in short-medium, with length L smaller than the laser Rayleigh range, z R ( L   <<   z R ), and low gas pressure in long medium with L  ≈  z R . It is important to note that the term “long medium” refers to the ratio of the medium length with respect to the Rayleigh length and it is not necessarily related to extended geometries (i.e., an HHG scheme for which the focusing length is typically >1 m and the energy of the driving pulse is greater than a few mJ). This latter scheme is prevailing in high-flux setups, such as the beamlines at NEXUS, SYLOS GHHG long beamline in ELI-ALPS 23 , Lund 23 and MBI 24 . Currently, most laboratories utilize short-medium gas cells operated at high gas pressures for IAP generation. However, when scaling up the driving pulse energy becomes necessary, a long-medium scheme is generally more feasible than a short-medium one 23 . At the same time, long medium schemes operating at low pressure can lead to similar, if not higher, conversion efficiencies than static cells and pulsed valves 25 and generally provide better spatiotemporal properties of the generated XUV radiation 22 , 23 . Moreover, prior research 26 has emphasized the beneficial impact of terminating any generation process with a sharp pressure gradient. This approach generally promotes phase matching and restricts re-absorption, enhancing HHG efficiency. Despite these potential advantages, the possibility of generating IAPs in a long medium, such as semi-infinite gas cells (SIGCs) 27 , 28 , 29 , has not been fully established yet. On the contrary, due to the nonlinear phenomena that take place in a long medium and challenge favourable phase-matching conditions, these sources are commonly perceived to be inherently unsuited for IAP generation. Additionally, to model this regime, more advanced simulation tools are needed to support the interpretation of experimental results. These tools should be capable of simultaneously addressing the intricate nonlinear spatiotemporal dynamics of the driving radiation as it traverses the gas medium and the subsequent generation, propagation, and phase matching of harmonics. Consequently, due to the intrinsic complexity of modelling these processes, the mechanisms that could lead to IAPs generation in extended gas media have not been thoroughly investigated.

In this work, we present clear experimental evidence of efficient generation of IAPs in a SIGC geometry, unveiling the phase-matching mechanism in this regime (i.e., L   »   z R and peak powers well below the critical power for filamentation). Our theoretical simulations show that the nonlinear spatiotemporal reshaping of the driving field in the SIGC acts as a self-regulating mechanism boosting the IAP generation, thanks to favourable phase-matching conditions. By reporting their adoption in an attosecond streaking measurement we not only demonstrate their suitability for real attosecond pump-probe experiments but also provide a reliable temporal characterization, revealing a duration of 180 as in the 20–45 eV spectral region. To understand the relevant role of harmonic phase-matching, we develop a novel 3D simulation method for macroscopic HHG, which combines nonlinear spatiotemporal reshaping of an intense driving few-cycle pulse with the solution of the three dimensional time-dependent Schrödinger equation (3D-TDSE) to account for the quantum dynamics of microscopic HHG. This approach allows us to unravel the role of the spatiotemporal nonlinear reshaping of the driving field as it propagates through the SIGC, as well as to identify a pressure-dependent phase-matching window that enables efficient generation of IAPs.

The SIGC consists of three main regions 30 , as shown in Fig. 1a . In the first region, the IR pulse interacts with a noble gas (Argon) and generates high-order harmonics in the XUV (20–45 eV). In this section, the pressure is homogeneously distributed and can be tuned within a range of up to 10 mbar. The gas region extends into the second chamber, through a mechanically adjustable element that allows for tuning the length of the gas-filled region from 370 mm to 400 mm. As shown in Fig. 1b , following this component, a plate with a drilled hole of 200  µ m diameter and 7 mm length connects the first chamber to the second one, where a roughing pump stabilizes the pressure at 0.01 mbar. In our geometry, the SIGC length is set at 380 mm and the IR focus lies 5 mm before the exit hole. A second plate with a 500  µ m diameter hole separates the second chamber from the last one, where the pressure is kept at 10 −6  mbar using a turbo pump with an effective speed of 80 l·s −1 . At increasing values of pressure in the first chamber, we observed the gradual development of a bright plasma channel extending over a few centimetres. Consequently, as depicted in Fig. 1c , we conducted a comprehensive characterization of the IR spectrum after generation at different operating pressures using a standard spectrometer (AvaSpecULS4096).

a Scheme of the SIGC: the IR driving field, characterized by a streaking measurement, focuses after 375 mm, 5 mm before the cell-exit channel (at 380 mm). The first region (1) is filled with Argon gas (constant pressure tuneable from <1 mbar up to 10 mbar). A second chamber (2), which is maintained at 0.01 mbar vacuum using a roughing pump, separates (1) from a high vacuum region (3) (10 −6  mbar) achieved by a turbo-pump, allowing easy interfacing of the SIGC with the rest of the beamline. Output XUV pulses with a duration of 180 as are characterized by a streaking measurement. b Detail of the region around chamber (1) and (2). A 7 mm channel connects the first chamber with the intermediate one (2). In the region around the geometrical focus z  = 375 mm, as highlighted in the figure, a bright plasma channel appears for pressure >2 mbar. c Spectra of the IR driving field measured at the output of the SICG for various pressure configurations, as indicated in the legend

As presented in Fig. 2a , we have measured the evolution of the HHG spectra upon varying the gas pressure in the SIGC. For each value of the pressure, the CEP of the driving IR pulses was optimized for the generation of continuous XUV spectra at high photon energy (above ≈ 35 eV). The results indicate that the high-order harmonics are phase-matched within a narrow pressure range between 3 and 7 mbar. Notably, we have observed that the recorded harmonic spectrum remains relatively stable against slight variations in the 200  µ m exit pinhole longitudinal position (±5 mm from the reported configuration).

a Evolution of the spectrum of the XUV pulses as a function of the gas pressure. Around 5.5 mbar the spectrum becomes more continuous. b Spectra for two values of pressures in ( a ), 4.2 mbar (green curve) and 5.8 mbar (purple curve), respectively. c Experimental streaking trace in the case of 5.8 mbar. d Reconstructed streaking spectrogram with the ePIE algorithm. e Reconstructed XUV intensity profile, showing a clean IAP with a duration of 180 as. In the insert, <1% IAP satellites are shown; these structures are compatible with the modulation observed in both the trace reported in ( c ) and the violet XUV spectrum in ( b )

As the pressure is increased, a transition of the XUV spectrum from modulated (green curve in Fig. 2b , at 4.2 mbar) to a quasi-continuum (violet curve in Fig. 2b , at 5.8 mbar) can be observed. In addition, the latter is accompanied by a noticeable reduction of the lower-order harmonics, as well as by an enhancement of the higher-order ones, close to the cutoff frequency. This continuum spectrum is sensitive to CEP variations (see Supplementary Material ), differently from what has been observed for short media at similar intensities of the driving field 1 , 31 . Importantly, this shift from discrete to a quasi-continuum spectrum when increasing the pressure occurs without observing significant change in the overall harmonic flux. The conversion efficiency is estimated to be ~10 −6 , higher than what reported for the polarization gating technique 12 , 13 and similar to what was obtained with the ionization gating 16 in a 3 mm static cell using the same beamline. This aspect presents a distinct advantage compared to other gating methods (e.g. polarization gating) where a continuum spectrum is achieved at the expense of XUV flux.

We have then measured the temporal characteristics of the XUV pulses generated at 5.8 mbar, using the Frequency-Resolved Optical Gating for Complete Reconstruction of Attosecond Bursts (FROG CRAB), or simply streaking technique 32 . A portion of the residual IR radiation, not involved in the generation process, is delayed relative to the XUV pulse, and focused (I peak  = 5 × 10 12 W·cm −2 ) in the TOF spectrometer where an Argon target is present. The resulting interaction leads to a streaking spectrogram, as demonstrated in Fig. 2c . To confirm the presence of an IAP, we performed a numerical reconstruction of the trace using the extended ptychographic iterative engine (ePIE) 33 . The reconstructed trace, illustrated in Fig. 2d , allowed us to retrieve both the IR field and the XUV pulse intensity. As shown in Fig. 2e , the ≈6 mbar configuration indeed supports an IAP with an intensity full-width at half maximum (FWHM) duration of 180 as. Furthermore, we can observe the presence of <  1% satellites (in intensity) of the IAP. These features are responsible for the residual modulations observed in both the photoelectron and XUV spectra. However, for most spectroscopic applications requiring IAPs, these temporal structures can be considered irrelevant. To gain a deeper insight into the physical mechanism behind the IAP generation in the SIGC, we have developed a novel theoretical approach that combines nonlinear IR propagation with macroscopic HHG, as described in the Methods section.

In Fig. 3 , we show the simulation results for the generation of IAPs in the SIGC. The propagated IR electric field in the cell is used as an input for macroscopic HHG calculations through 3D-TDSE and propagation of the harmonics. This allows us to compute the spatially averaged HHG emission spectrum at the far field detector by integrating along the azimuthal coordinate and the divergence angle up to 1.5 mrad, where most of the XUV radiation is emitted. The radiation was also propagated through a 150 nm thick Al filter (including both material absorption and dispersion), and a response function was assumed for the XUV camera to mimic the experimental measurements (high-pass filter from ≈23 eV). As depicted in Fig. 3a , the computed harmonic spectra align with the trends found in the experiment, despite a slight deviation between the experimental and theoretical pressure range of phase matching and the cleanness of the IAP. As the pressure is increased, the HHG spectrum is shifted towards higher energies, and becomes less modulated, thus favouring the generation of IAPs. This becomes evident also when comparing the time evolution of the radiation on axis in Fig. 3b . As we increase the pressure, the temporal profile of the XUV radiation becomes less modulated, with the cleanest temporal structure achieved at 6 mbar. Furthermore, the simulation is in general agreement with the experimental trend, which demonstrates a gradual decrease in generation efficiency as the pressure increases.

a Simulation results of the XUV spectrum as a function of the gas pressure. b On-axis IAP obtained at pressure values of 2 mbar (blue), 6 mbar (green), 10 mbar (orange), and 14 mbar (dark red) after performing the Fourier transform of a sub-set of the HHG spectra indicated by dotted lines in ( a )

As illustrated experimentally and theoretically in Figs. 2 and 3 , two crucial features in our HHG spectrum support the generation of an IAP: the formation of a continuous cut-off and the re-absorption of low-order harmonic components. In the following, we aim to address the origin of these features.

In order to understand the physics behind the IAP mechanism, we investigate the effects of the nonlinear propagation of the driving pulse. Several works in literature have reported that nonlinear effects can lead to the generation of an IAP. In ref. 34 Steingrube and co-workers investigated the formation of continuous XUV spectra emerging from a filament by employing a loose focusing geometry ( L/z R  ~14.2) at moderate intensities ( I 0  = 8 × 10 13   W·cm −2 in vacuum) and high pressures (1 bar) 34 . A theoretical work by Gaarde and Schafer 31 (related to the experiments presented in 1 ) and the experiments by Haworth and co-workers 35 discussed instead nonlinear propagation in short media ( L/z R  < 0.15) at moderate pressures (few hundreds of mbar) and high intensities (between 6 and 9 × 10 14  W·cm −2 ), showing that defocusing of the driving field leads to on-axis IAP generation. All these studies have thus addressed the effect of nonlinearities in IAP generation either in long media ( L»z R ) at peak powers above the critical power for self-focusing 34 ( P c ) or short media ( L  <  z R ) at low peak powers 1 , 16 , 17 , 35 ( P  «  P c ). Here we deal with a different scenario: long medium geometries ( L/z R  ~15.1) at low pressures (6 mbar) and high intensities ( I 0  = 1.2 × 10 15  W·cm −2 in vacuum), exploring therefore long media ( L   »   z R ) at peak powers well below the threshold for self-focusing.

To validate our numerical methodology, we start by examining the experimental IR spectra measured at the output of the SIGC when driven at varying pressures. As shown in Fig. 1c , the experimental data reveals a distinct ionization-induced self-phase modulation effect, which manifests as a clear blue shift of the spectrum. This process has been noted in recent works to enhance generation efficiency 36 , 37 . Figure 4a shows the simulated IR spectra after nonlinear propagation in the SIGC for different Ar pressures, accurately reproducing the experimental blue shift (Fig. 1c ). Figure 4b depicts the corresponding reshaping of the IR driving pulse at the output of the SIGC.

a IR spectra and ( b ) corresponding on-axis electric field obtained at the SIGC output with the nonlinear propagation code (utilizing the experimental parameters as input) as a function of the gas pressure in the first chamber. c – f Simulated nonlinear reshaping of the driving field as it propagates along the z -direction in the final portion of the cell around the geometrical focus: ( c ) on-axis peak intensity, ( d ) beam radius, ( e ) on-axis ionized electron density and ( f ) pulse energy during propagation under different pressure conditions

With this empirical validation, we proceed to numerically monitor the nonlinear modification of the driving field as it propagates along the z -direction in the cell. This allows for a deeper understanding of the spatiotemporal reshaping of the IR driving radiation along the cell for different pressures. To this end, we analyse the evolution of the on-axis peak intensity (Fig. 4c ), the beam radius (Fig. 4d ), the ionized population (Fig. 4e ), and the pulse energy (Fig. 4f ) under different pressure conditions. Noticeably, as the gas pressure within the SIGC increases, we note a progressive beam size stagnation (Fig. 4d ) and a reduction in the pulse energy (Fig. 4f ), attributed, respectively, to plasma defocusing and losses due to ionization and plasma absorption. These phenomena collectively lead to an overall reduction in the peak intensity (Fig. 4c ) of the driving field, as compared to linear propagation in vacuum. The observed reduction in peak intensity due to plasma defocusing and absorption appears to act as a self-regulating mechanism, which has been recently shown to contribute to efficient harmonic generation 36 , 38 . We should note that the measured HHG cutoff energy corresponding to the decreased intensity is in good agreement with the classical cutoff law, deviating from the much higher value that would be expected from the peak intensity of the beam focused in vacuum. This regulating mechanism also leads to a region of space where the driving field intensity and phase remain nearly constant along the propagation direction in the final part of the SIGC, which is the most relevant one for HHG as it is less affected by harmonic reabsorption. This peculiar condition, mostly induced by plasma de-focusing and pulse reshaping, can be observed experimentally as an extended channel of plasma.

In addition, the self-regulating mechanism plays a key role in harmonic phase-matching. Despite the long generation medium, nonlinear propagation of the driving pulse reduces the influence of intensity and phase variations to the harmonic phase mismatch, thus geometric and intrinsic contributions can be neglected. Therefore, in our SIGC geometry, the phase mismatch, ∆ k q , is mainly due to free electrons and neutral atoms near the laser focus, a situation that resembles that encountered in capillaries 39 , 40 , or in the high-pressure and short-medium regime 25 , 26 . Since these two contributions to ∆ k q have opposite signs and vary with the degree of ionization along the driving pulse, perfect phase matching (∆ k q  = 0) is only achieved during a finite temporal window 20 , 21 . If this window is reduced to a single laser half-cycle, a single attosecond pulse can be isolated and, consequently, the XUV spectrum manifests continuous features. Under these circumstances, the phase mismatch of the q -th-order harmonic along the propagation direction ( z ) can be approximated by ref. 19 :

where P is the gas pressure, η ( z,t ) is the instantaneous ionization fraction, δn q  =  n ( λ L ) −  n ( λ q ) ~  n ( λ L ) − 1 is the difference between the index of refraction at the fundamental and harmonic wavelengths at a pressure of 1 atm, N atm is the total number density of atoms at 1 atm, r e represents the classical electron radius, and λ L is the central wavelength of the driving laser (here assumed λ L  = 700 nm, which is roughly the center of the spectra shown in Fig. 4a ).

Finally, the width ∆ t of the temporal phase-matching window can then be estimated from the inverse of the time derivative of the phase mismatch 1 / ∆ t ∝ ( ∂ ∆ k q /∂t )· L , where L is the medium length 20 . Note that, under these assumptions, the nonlinear propagation of the driving pulse modifies the role of pressure in harmonic phase-matching. Indeed, while the perfect phase-matching condition (∆ k q  = 0, see Eq. ( 1 )) does not depend on pressure, the temporal phase matching window, instead, is inversely proportional to it, ∆ t   ∝  1 /P . Therefore, as the pressure increases, the temporal-phase matching window narrows. Note that the increase in harmonic efficiency with pressure is not only limited by the temporal phase-matching window, but also by reabsorption 24 .

To illustrate the role of the phase-matching window in the SIGC configuration, in Fig. 5 we show the analytical estimation of its time derivative for the harmonic of order q  = 25 ( ≈ 44 eV) at the cell output, for the different pressures used in this work. For simplicity, we have just considered the on-axis temporal dependence of the ionization rate η ( z,t ) obtained from the 3D nonlinear propagation simulations. This model confirms that the temporal phase matching window shrinks as the gas pressure increases, perfectly aligning with the formation of a continuous cut-off and the isolation of an IAP. For high pressures (>6 mbar) the phase-matching window continues to narrow, eventually becoming too short to allow for the HHG recombination step to occur within the phase-matched interval. This results in a drastic decrease in the XUV signal at higher pressures, as shown in Fig. 2a .

a Time-derivative of the numerical phase mismatch calculated using Eq.( 1 ) for harmonic 25th at the cell output ( z  = 380 mm). b 2D-representation of the phase mismatch time-derivative for harmonic 25th at 6 mbar as a function of the propagation axis, showing that the isolation of an attosecond pulse takes place in the last 30 mm

An equally important insight from the numerical analysis concerns the actual phase-matching length within the SIGC geometry. Figure 5b demonstrates that efficient HHG occurs predominantly in the last 3 cm of the cell (350 mm  <   z  < 380 mm), roughly corresponding to the driving field Rayleigh range in vacuum. Nonetheless, as shown in Fig. 4d , the nonlinear spatial reshaping leads to a progressive increase in the effective Rayleigh range within the medium, reaching up to 10 cm at high gas pressures. As a result, by varying the pressure in our SIGC geometry, we can investigate different ratios between the Rayleigh range and the length of the generating medium. This approach enables the exploration of various phase-matching regimes as outlined in ref. 24 . Moreover, we note that the shortest phase-matching window (phase matching peak) occurs at z  = 368 mm ~13 mm before the cell output (8 mm before the geometrical laser focus), in excellent agreement with earlier reports on optimal phase matching in SIGC geometries 30 .

IAP generation is further enhanced by the reabsorption of low-order harmonics (see Figs. 2 and 3 ) favoured by the 7 mm channel connecting the region at a few-mbar pressure to the evacuated region at 10 −2  mbar in our SIGC. A COMSOL simulation of the gas distribution (see Supplementary Information ) revealed a linear pressure gradient developing within the channel with concomitant re-absorption of lower-order harmonics (under 35 eV) as the pressure is increased; conversely, the higher energy spectrum is mostly unaffected due to the Argon cross-section. As a result, the contrast of the IAP is significantly enhanced, effectively functioning as a high-pass spectral filter. It is important to note that in short gas cells operating at high pressures, sharp gradients are instead suggested as the optimal configuration to avoid significant re-absorption effects and poor phase matching 28 . This imposes a sub-optimal compromise between sharp gradient and high-pass filtering for geometries based on short cells (see Supplementary Information ).

In conclusion, we demonstrated, both experimentally and theoretically, the feasibility of a SIGC to efficiently generate isolated attosecond pulses in the extreme ultraviolet spectral window. We proved that nonlinear propagation effects of the driving field have a key role in achieving favourable phase-matching conditions. We showed how IAPs can be obtained by only increasing the generation pressure, keeping at the same time a good level of flux. This is attributed to an interplay between an efficient time-gated phase matching and a controlled reabsorption of low-order harmonics.

In order to identify the physics beyond the efficient IAP generation in a SIGC configuration, we have introduced and tested a novel simulation method that combines, for the first time to the best of our knowledge, the nonlinear spatiotemporal reshaping of an intense few-cycle driving field due to propagation through the generation medium with macroscopic HHG comprising full-quantum 3D-TDSE calculations and propagation of the harmonics to a far-field detector. Our simulations and models emphasize that the progressive stagnation of beam size, induced by the spatiotemporal reshaping of the driving field and by plasma defocusing, seen in the experiment as a bright plasma channel, causes the phase-matching in our SIGC geometry to resemble the one encountered in capillaries or in short medium. Consequently, with increasing pressures, the phase matching for isolated attosecond pulses exhibits a straightforward pattern. Due to the balancing of phase mismatch between free electrons and neutral atoms, as the gas pressure increases, the temporal window for phase-matching becomes narrower, thereby enabling the efficient creation of IAPs.

Unlike standard gas cell geometries or capillaries, where scaling up the energy implies modification of the cell length or capillary size 41 , any construction limits do not constrain the coherence length of generation in a SIGC. Consequently, when changing the laser pulse parameters together with the focusing optics, the SIGC region of phase-matching will automatically adapt, requiring only fine adjustment on the gas pressure. This might make the SIGC a very versatile option when scaling up the driving pulse energy, an important issue in view of the growth of high-flux, long geometries beamlines 23 , 24 . These facts, in addition to its intrinsic simplicity and pressure/generation position tunability, makes the SIGC an attractive candidate for expanding the practical usability of IAP technology in various research fields, e.g., XUV-XUV pump-probe or NIR/VIS/UV pump-XUV probe experiments.

Materials and methods

Experimental setup.

Our experimental setup uses a 25 fs, 800 nm, 1 kHz, CEP-stabilized ( < 300 mrad) Ti:Sa laser system (Legend DUO HE + , Coherent). These pulses are focused into a 3 m-long stretchable hollow core fiber with a 450  µ m inner diameter (Polymicro TSP450670), which is filled with 1.8 bar of helium in a differential gradient configuration. At the output of the fiber, the spectrally broadened IR pulse undergoes post-compression using chirped mirrors (Ultrafast Innovations PC1332), resulting in a sub-4-fs pulse with an energy of 2 mJ.

The laser is then directed into a delay-stabilized interferometer designed for pump-probe experiments, and after a 80/20 beamsplitter and several reflections, 420  µ J of pulse energy are focused ( f  = 75 cm) for HHG in the SIGC apparatus. We characterize the IR driving pulse for HHG both in the temporal and spatial domain. The former is performed is by employing the D-scan technique 41 , revealing a temporal duration of 4 fs. The spatial characterization is done by measuring in air the caustic of a small portion of the beam after the focusing element, obtaining a beam waist w 0  = 77  µ m and a Rayleigh length z R  = 2.5 cm.

The generated XUV radiation passes through a 150 nm Al filter to remove the remaining portion of the driving IR field and filter out the harmonics below 20 eV. The XUV radiation is then first focused by a gold toroidal mirror into a time-of-flight spectrometer (TOF, Kaesdorf ETF15), and recombined with sub-4-fs IR pulses to perform streaking (FROG-CRAB) measurements 42 . The pump-probe delay is actively stabilized with an rms below 50 mrad. The XUV radiation is collected by a gold-coated grating (Hitachi 600 lines/mm), where it is spectrally dispersed and directed towards a microchannel plate (MCP) for measuring the radiation spectrum using a phosphor screen and a camera.

Theoretical simulations

The complete theoretical description of HHG requires to couple the propagation of the driving field with the generation of the high-order harmonics at the single-atom level and their subsequent propagation. However, such calculation is tremendously expensive computationally. First, at the microscopic level, the exact laser-driven dynamics of the quantum electronic wavepacket in the HHG process is described by the 3D-TDSE. The full 3D-TDSE calculation could include the dynamics of all electrons in the atom but, as the main physics of HHG is accurately described by the electron occupying the outermost valence orbital, we work under the commonly used single-active electron approximation. Second, at the macroscopic level, the emission from all atoms in the gas cell—typically trillions—must be considered to account for harmonic phase-matching, together with the propagation of the driving field. Several methods have been successfully developed to account for macroscopic HHG, using the 3D-TDSE 20 , 36 , 43 , 44 , 45 , the strong field approximation 46 , 47 , which cannot be used when dealing with few-cycle drivers 48 , or even artificial intelligence 49 . Although separate simulations of nonlinear propagation of the driving field and HHG have already been performed, for example, to successfully account for soft X-ray generation in a waveguide through HHG 39 , to the best of our knowledge there is no previous method that couples nonlinear few-cycle IR propagation with macroscopic HHG that makes use of the 3D-TDSE at the single-atom level.

In our simulations we employ the 3D-TDSE in Argon under the single-active electron approximation. The resulting harmonics are then propagated to a far-field detector through the electromagnetic field propagator, and phase-matching is considered by coherently adding the elementary contributions along the gas cell, following the method described in ref. 47 . For each emitter location, the associated IR driving field was computed with a 3D nonlinear pulse propagation code 50 , which takes the experimental parameters as an input and solves the IR propagation in the complete SIGC volume. These propagation simulations for the IR driver included the complete dispersion of the gas, the Kerr effect, self-steepening and shock terms, and photoionization and plasma absorption. To further strengthen our investigation, we used a realistic gas profile distribution, calculated using computational fluid dynamics tools (COMSOL). This gas profile was included in the propagation of the harmonic radiation through the 200  µ m-diameter and 7-mm-long channel connecting the first two chambers of the SIGC (here, further generation was neglected), while the gas pressure in the HHG generation volume was assumed to be constant.

In order to realistically simulate the nonlinear propagation in the SIGC and the HHG process, the results of the experimental temporal and spatial characterizations (4 fs pulses, beam waist w 0  = 77  µ m and Rayleigh length z R  = 2.5 cm) were used as the input for the nonlinear propagation simulations.

Data availability

The data that support the findings of this study are available from the corresponding authors upon reasonable request.

Hentschel, M. et al. Attosecond metrology. Nature 414 , 509–513 (2001).

Article   ADS   Google Scholar  

Borrego-Varillas, R., Lucchini, M. & Nisoli, M. Attosecond spectroscopy for the investigation of ultrafast dynamics in atomic, molecular and solid-state physics. Rep. Prog. Phys. 85 , 066401 (2022).

Schultze, M. et al. Delay in photoemission. Science 328 , 1658–1662 (2010).

Calegari, F. et al. Ultrafast electron dynamics in phenylalanine initiated by attosecond pulses. Science 346 , 336–339 (2014).

Matselyukh, D. T. et al. Decoherence and revival in attosecond charge migration driven by non-adiabatic dynamics. Nat. Phys. 18 , 1206–1213 (2022).

Article   Google Scholar  

Lucchini, M. et al. Attosecond dynamical Franz-Keldysh effect in polycrystalline diamond. Science 353 , 916–919 (2016).

McPherson, A. et al. Studies of multiphoton production of vacuum-ultraviolet radiation in the rare gases. J. Opt. Soc. Am. B 4 , 595–601 (1987).

Li, X. F. et al. Multiple-harmonic generation in rare gases at high laser intensity. Phys. Rev. A 39 , 5751–5761 (1989).

Paul, P. M. et al. Observation of a train of attosecond pulses from high harmonic generation. Science 292 , 1689–1692 (2001).

Christov, I. P., Murnane, M. M. & Kapteyn, H. C. High-harmonic generation of attosecond pulses in the “single-cycle” regime. Phys. Rev. Lett. 78 , 1251–1254 (1997).

Midorikawa, K. Progress on table-top isolated attosecond light sources. Nat. Photonics 16 , 267–278 (2022).

Sola, I. J. et al. Controlling attosecond electron dynamics by phase-stabilized polarization gating. Nat. Phys. 2 , 319–322 (2006).

Sansone, G. et al. Isolated single-cycle attosecond pulses. Science 314 , 443–446 (2006).

Oishi, Y. et al. Generation of extreme ultraviolet continuum radiation driven by a sub-10-fs two-color field. Opt. Express 14 , 7230–7237 (2006).

Mashiko, H. et al. Double optical gating of high-order harmonic generation with carrier-envelope phase stabilized lasers. Phys. Rev. Lett. 100 , 103906 (2008).

Ferrari, F. et al. High-energy isolated attosecond pulses generated by above-saturation few-cycle fields. Nat. Photonics 4 , 875–879 (2010).

Chen, M. C. et al. Generation of bright isolated attosecond soft X-ray pulses driven by multicycle midinfrared lasers. Proc. Natl Acad. Sci. USA 111 , E2361–E2367 (2014).

Google Scholar  

Hernández-García, C. et al. Isolated broadband attosecond pulse generation with near- and mid-infrared driver pulses via time-gated phase matching. Opt. Express 25 , 11855–11866 (2017).

Salières, P., L’Huillier, A. & Lewenstein, M. Coherence control of high-order harmonics. Phys. Rev. Lett. 74 , 3776–3779 (1995).

Gaarde, M. B., Tate, J. L. & Schafer, K. J. Macroscopic aspects of attosecond pulse generation. J. Phys. B At. Mol. Opt. Phys. 41 , 132001 (2008).

Constant, E. et al. Optimizing high harmonic generation in absorbing gases: model and experiment. Phys. Rev. Lett. 82 , 1668–1671 (1999).

Weissenbilder, R. et al. How to optimize high-order harmonic generation in gases. Nat. Rev. Phys. 4 , 713–722 (2022).

Appi, E. et al. Two phase-matching regimes in high-order harmonic generation. Opt. Express 31 , 31687–31697 (2023).

Sobolev, E. et al. Terawatt-level three-stage pulse compression for all-attosecond pump-probe spectroscopy. arXiv https://doi.org/10.48550/arXiv.2404.18266 (2024).

Brichta, J. P. et al. Comparison and real-time monitoring of high-order harmonic generation in different sources. Phys. Rev. A 79 , 033404 (2009).

Major, B. & Varjú, K. Extended model for optimizing high-order harmonic generation in absorbing gases. J. Phys. B: At. Mol. Opt. Phys. 54 , 224002 (2021).

Sutherland, J. R. et al. High harmonic generation in a semi-infinite gas cell. Opt. Express 12 , 4430–4436 (2004).

Steingrube, D. S. et al. Phase matching of high-order harmonics in a semi-infinite gas cell. Phys. Rev. A 80 , 043819 (2009).

Tsai, M. S. et al. Nonlinear compression toward high-energy single-cycle pulses by cascaded focus and compression. Sci. Adv. 8 , eabo1945 (2022).

Von Conta, A., Huppert, M. & Wörner, H. J. A table-top monochromator for tunable femtosecond XUV pulses generated in a semi-infinite gas cell: experiment and simulations. Rev. Sci. Instrum. 87 , 073102 (2016).

Gaarde, M. B. & Schafer, K. J. Generating single attosecond pulses via spatial filtering. Opt. Lett. 31 , 3188–3190 (2006).

Pazourek, R., Nagele, S. & Burgdörfer, J. Attosecond chronoscopy of photoemission. Rev. Mod. Phys. 87 , 765–802 (2015).

Article   ADS   MathSciNet   Google Scholar  

Lucchini, M. et al. Ptychographic reconstruction of attosecond pulses. Opt. Express 23 , 29502–29513 (2015).

Steingrube, D. S. et al. High-order harmonic generation directly from a filament. N. J. Phys. 13 , 043022 (2011).

Haworth, C. A. et al. Half-cycle cutoffs in harmonic spectra and robust carrier-envelope phase retrieval. Nat. Phys. 3 , 52–57 (2007).

Major, B. et al. High-order harmonic generation in a strongly overdriven regime. Phys. Rev. A 107 , 023514 (2023).

Kretschmar, M. et al. Compact realization of all-attosecond pump-probe spectroscopy. Sci. Adv. 10 , eadk9605 (2024).

Shim, B. et al. Generation of high-order harmonics and attosecond pulses in the water window via nonlinear propagation of a few-cycle laser pulse. Opt. Express 31 , 32488–32503 (2023).

Rundquist, A. et al. Phase-matched generation of coherent soft X-rays. Science 280 , 1412–1415 (1998).

Popmintchev, T. et al. Bright coherent ultrahigh harmonics in the keV X-ray regime from mid-infrared femtosecond lasers. Science 336 , 1287–1291 (2012).

Heyl, C. M. et al. Introduction to macroscopic power scaling principles for high-order harmonic generation. J. Phys. B At. Mol. Opt. Phys. 50 , 013001 (2017).

Miranda, M. et al. Simultaneous compression and characterization of ultrashort laser pulses using chirped mirrors and glass wedges. Opt. Express 20 , 688–697 (2012).

Itatani, J. et al. Attosecond streak camera. Phys. Rev. Lett. 88 , 173903 (2002).

L’Huillier, A., Li, X. F. & Lompré, L. A. Propagation effects in high-order harmonic generation in rare gases. J. Opt. Soc. Am. B 7 , 527–536 (1990).

Catoire, F. et al. Complex structure of spatially resolved high-order-harmonic spectra. Phys. Rev. A 94 , 063401 (2016).

Priori, E. et al. Nonadiabatic three-dimensional model of high-order harmonic generation in the few-optical-cycle regime. Phys. Rev. A 61 , 063801 (2000).

Hernández-García, C. et al. High-order harmonic propagation in gases within the discrete dipole approximation. Phys. Rev. A 82 , 033432 (2010).

Becker, A. et al. Total ionization rates and ion yields of atoms at nonperturbative laser intensities. Phys. Rev. A 64 , 023408 (2001).

Pablos-Marín, J. M., Serrano, J. & Hernández-García, C. Simulating macroscopic high-order harmonic generation driven by structured laser beams using artificial intelligence. Comput. Phys. Commun. 291 , 108823 (2023).

Couairon, A. et al. Practitioner’s guide to laser pulse propagation models and simulation: Numerical implementation and practical usage of modern pulse propagation models. Eur. Phys. J. Spec. Top. 199 , 5–76 (2011).

Download references

This project has received funding from the European Union’s Horizon 2020 research and innovation programme (grant agreement No 871161, IMPULSE) and European Research Council (ERC): ERC Synergy grant agreement no. 951224, TOMATTO; ERC StG grant no. 851201, ATTOSTRUCTURA and ERC StG grant no. 848411, AUDACE. We also thank financial support from Fondazione Cariplo (grant n. 2020-4380, DINAMO), Ministero dell’Università edella Ricerca (202239HFZN) and Ministerio de Ciencia e Innovación (MCIN/AEI/ 10.13 039/501100011033, I + D + i PID2022-142340NB-I00). M.F.G. acknowledges support from Ministerio de Universidades under grant FPU21/02916.

Author information

These authors contributed equally: Federico Vismarra, Marina Fernández-Galán, Daniele Mocci.

Authors and Affiliations

Department of Physics, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133, Milano, Italy

Federico Vismarra, Daniele Mocci, Lorenzo Colaizzi, Marta Pini, Lorenzo Mai, Yingxuan Wu, Maurizio Reduzzi, Matteo Lucchini & Mauro Nisoli

IFN-CNR, Piazza Leonardo da Vinci 32, 20133, Milano, Italy

Federico Vismarra, Marta Pini, Matteo Lucchini, Mauro Nisoli & Rocío Borrego-Varillas

Grupo de Investigación en Aplicaciones del Láser y Fotónica, Departamento de Física Aplicada, Universidad de Salamanca, E-37008, Salamanca, Spain

Marina Fernández-Galán, Víctor Wilfried Segundo, Roberto Boyero-García, Javier Serrano, Enrique Conejero-Jarque, Julio San Román & Carlos Hernández-García

Unidad de Excelencia en Luz y Materia Estructuradas (LUMES), Universidad de Salamanca, Salamanca, Spain

Marina Fernández-Galán, Víctor Wilfried Segundo, Javier Serrano, Enrique Conejero-Jarque, Julio San Román & Carlos Hernández-García

Laboratorium für Physikalische Chemie, ETH Zürich, 8093, Zürich, Switzerland

Hans Jakob Wörner

Department of Physics, Lund University, Lund, Sweden

Elisa Appi & Cord L. Arnold

You can also search for this author in PubMed   Google Scholar

Corresponding authors

Correspondence to Mauro Nisoli , Carlos Hernández-García or Rocío Borrego-Varillas .

Ethics declarations

Conflict of interest.

The authors declare no competing interests.

Supplementary information

Supplementary material, rights and permissions.

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/ .

Reprints and permissions

About this article

Cite this article.

Vismarra, F., Fernández-Galán, M., Mocci, D. et al. Isolated attosecond pulse generation in a semi-infinite gas cell driven by time-gated phase matching. Light Sci Appl 13 , 197 (2024). https://doi.org/10.1038/s41377-024-01564-5

Download citation

Received : 14 March 2024

Revised : 31 July 2024

Accepted : 04 August 2024

Published : 20 August 2024

DOI : https://doi.org/10.1038/s41377-024-01564-5

Share this article

Anyone you share the following link with will be able to read this content:

Sorry, a shareable link is not currently available for this article.

Provided by the Springer Nature SharedIt content-sharing initiative

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies

Maintenance work is planned from 21:00 BST on Tuesday 20th August 2024 to 21:00 BST on Wednesday 21st August 2024, and on Thursday 29th August 2024 from 11:00 to 12:00 BST.

During this time the performance of our website may be affected - searches may run slowly, some pages may be temporarily unavailable, and you may be unable to log in or to access content. If this happens, please try refreshing your web browser or try waiting two to three minutes before trying again.

We apologise for any inconvenience this might cause and thank you for your patience.

Journal of Materials Chemistry C

Chiral cadmium–amine complexes for stimulating non-linear optical activity and photoluminescence in solids based on aurophilic stacks †.

* Corresponding authors

a Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Poland E-mail: [email protected]

b Doctoral School of Exact and Natural Sciences, Jagiellonian University, Łojasiewicza 11, 30-348 Kraków, Poland

c Department of Materials Science, Institute of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan

d Department of Chemistry, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan

The design of high-performance optical materials can be realized using coordination polymers (CPs) often supported by non-covalent interactions, such as metallophilicity. The challenge is to control two or more optical effects, e.g. , non-linear optics (NLO) and photoluminescence (PL). We present a new strategy for the combination of the NLO effect of second-harmonic generation (SHG) and the visible PL achieved by linking dicyanidoaurate( I ) ions, which form luminescent metallophilic stacks, with cadmium( II ) complexes bearing chiral amine ligands, used to break the crystal's symmetry. We report a family of NLO- and PL-active materials based on heterometallic Cd( II )–Au( I ) coordination systems incorporating enantiopure propane-1,2-diamine (pda) ligands ( 1 - S , 1 - R ), their racemate ( 2 ), and enantiopure trans -cyclopentane-1,2-diamine (cpda) ligands ( 3 - S , 3 - R ). Due to acentric space groups, they exhibit the SHG signal, tunable within the range of 11–24% of the KDP reference, which was correlated with the dipole moments of Cd( II ) units. They show efficient blue PL whose energy and quantum yield, the latter ranging from 0.40 to 0.83, are controlled by Cd( II ) complexes affecting the Au–Au distances and vibrational modes. We prove that chiral Cd( II )–amine complexes play the role of molecular agents for the stimulation of both the NLO and PL of the materials based on aurophilic stacks.

Supplementary files

• Supplementary information PDF (9004K)
• Crystal structure data CIF (4821K)

Article information

Download Citation

Permissions.

Chiral cadmium–amine complexes for stimulating non-linear optical activity and photoluminescence in solids based on aurophilic stacks

K. Boidachenko, M. Liberka, J. Wang, H. Tokoro, S. Ohkoshi and S. Chorazy, J. Mater. Chem. C , 2024, Advance Article , DOI: 10.1039/D4TC01042F

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence . You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

Read more about how to correctly acknowledge RSC content .

Social activity

Search articles by author.

This article has not yet been cited.

Advertisements