describe spallanzani experiment

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.

As an Amazon Associate we earn from qualifying purchases.

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

© Jan 10, 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.

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

2.1 Spontaneous Generation

Learning objectives.

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

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 molded, mice appeared. Jan Baptista van Helmont, a 17th century Flemish scientist, proposed that mice could arise from rags and wheat kernels left in an open container for 3 weeks. In reality, such habitats provided ideal food sources and shelter for mouse populations to flourish.

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

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

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

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

Disproving Spontaneous Generation

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

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

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

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

Allied Health Microbiology Copyright © 2019 by Open Stax and Linda Bruslind is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Share This Book

Unit 1: An Invisible World

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 generations.

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 seventeenth 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 seventeenth 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 1). 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.

Figure 1. Francesco Redi’s experimental setup consisted of an open container, a container sealed with a cork top, and a container covered in mesh that let in air but not flies. Maggots only appeared on the meat in the open container. However, maggots were also found on the gauze of the gauze-covered container.

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

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

Think about It

• 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 nineteenth 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). 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.

Figure 3. (a) French scientist Louis Pasteur, who definitively refuted the long-disputed theory of spontaneous generation. (b) The unique swan-neck feature of the flasks used in Pasteur’s experiment allowed air to enter the flask but prevented the entry of bacterial and fungal spores. (c) Pasteur’s experiment consisted of two parts. In the first part, the broth in the flask was boiled to sterilize it. When this broth was cooled, it remained free of contamination. In the second part of the experiment, the flask was boiled and then the neck was broken off. The broth in this flask became contaminated. (credit b: modification of work by “Wellcome Images”/Wikimedia Commons)

• 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 Concepts and Summary

• 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 seventeenth 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

Which of the following individuals argued in favor of the theory of spontaneous generation?

• Francesco Redi
• Louis Pasteur
• John Needham
• Lazzaro Spallanzani

Which of the following individuals is credited for definitively refuting the theory of spontaneous generation using broth in swan-neck flask?

• Jan Baptista van Helmont

Which of the following experimented with raw meat, maggots, and flies in an attempt to disprove the theory of spontaneous generation.

• Antonie van Leeuwenhoek

Fill in the Blank

The assertion that “life only comes from life” was stated by Louis Pasteur in regard to his experiments that definitively refuted the theory of ___________.

Exposure to air is necessary for microbial growth.

• 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.
• What would the results of Pasteur’s swan-neck flask experiment have looked like if they supported the theory of spontaneous generation?
• K. Zwier. "Aristotle on Spontaneous Generation." http://www.sju.edu/int/academics/cas/resources/gppc/pdf/Karen%20R.%20Zwier.pdf ↵
• E. Capanna. "Lazzaro Spallanzani: At the Roots of Modern Biology." Journal of Experimental Zoology 285 no. 3 (1999):178–196. ↵
• R. Mancini, M. Nigro, G. Ippolito. "Lazzaro Spallanzani and His Refutation of the Theory of Spontaneous Generation." Le Infezioni in Medicina 15 no. 3 (2007):199–206. ↵
• R. Vallery-Radot. The Life of Pasteur , trans. R.L. Devonshire. New York: McClure, Phillips and Co, 1902, 1:142. ↵
• OpenStax Microbiology. Provided by : OpenStax CNX. Located at : http://cnx.org/contents/[email protected] . License : CC BY: Attribution . License Terms : Download for free at http://cnx.org/contents/[email protected]

Lazzaro Spallanzani (1729-1799)

Lazzaro Spallanzani’s imaginative application of experimental methods, mastery of microscopy, and wide interests led him to significant contributions in natural history, experimental biology, and physiology. His detailed and thoughtful observations illuminated a broad spectrum of problems ranging from regeneration to the genesis of thunderclouds.

Born in the small town of Scandiano in northern Italy on 10 January 1729, Spallanzani grew up in a large, wealthy family and attended local schools until he was fifteen. He then studied at a Jesuit seminary in Reggio Emilia where his intellectual abilities earned him the nickname “the astrologer.” He matriculated in 1749 at the University of Bologna and began working toward a degree in jurisprudence. His love for the natural sciences and mathematics soon led him to change his focus to philosophy, in which he earned his doctorate in 1754. His philosophical studies encompassed metaphysics and theology, which prepared him to take minor orders and be ordained as a priest in the Roman Catholic Church. Spallanzani’s affiliation with the Church provided financial support, but more importantly offered protection from the Italian Inquisition, which often censored work deemed contrary to Catholic doctrine. He continued to officiate mass from time to time until later in life. In 1755 he was appointed to teach humanities at the College of Reggio Emilia and then went on to be professor of philosophy at Modena in the University and College of Nobles. He indicated, however, in a letter to Charles Bonnet, that his teaching responsibilities robbed him of his time, which he preferred to dedicate to scientific pursuits.

Spallanzani read voraciously but was a persistent skeptic, hesitant to believe anything that he could not prove himself. Unconvinced by Needham and Buffon’s description of the genesis of animalcules in plant and animal infusions, Spallanzani carefully replicated their study and showed their techniques were inadequate and therefore that their conclusions about the existence of spontaneous generation were unwarranted. He published his results refuting spontaneous generation in 1765 and thereby initiated a lifelong correspondence with Bonnet. An avid and staunch preformationist, Bonnet seized upon Spallanzani’s results to support his theoretical inclinations and challenged him to carry on his own work investigating regeneration in flatworms. Spallanzani rose to the challenge and returned Bonnet’s letter with an explanation of his many sectioning experiments on a wide variety of animals.

Spallanzani performed hundreds of salamander tail amputations, believing exhaustive repetition was necessary to confirm results. Interested in the origin of regenerating tissue, he closely examined the interface between the stump and the regenerated tail. Observation alone offered no conclusions. He had trouble believing that an organized tail could result from a simple outgrowth, but continued to look for evidence in regenerating tadpole and salamander tails that could support his inclination toward the existence of preformed germs. He openly reported his observations, even those that questioned preformationism, once suggesting that tail regenerates in tadpoles appeared to be the result of an elongation, a comment which surely must have disturbed Bonnet but nevertheless failed to persuade him to consider epigenesis seriously.

Interested in questions about generation, Spallanzani performed the first artificial insemination of a viviparous animal, a spaniel dog, a feat he recognized as one of his greatest accomplishments. These results further convinced him of the ovist preformationist doctrine. He interpreted his many findings as evidence against epigenesis and the role of sperm, which he identified as “animalcules,” in generation.

In 1776 Spallanzani accepted a professorship at the University of Pavia where he remained for the next thirty years and published extensively. He was a member of the ten most distinguished Italian academies and a foreign associate to another dozen scientific societies across Europe. His work has been celebrated for its creative approach and rigorous use of scientific methodologies inspiring many scientists, including Thomas Hunt Morgan, to revisit his studies.

• Dinsmore, Charles E., ed. “Lazzaro Spallanzani: Concepts of Generation and Regeneration.” in A History of Regeneration Research: Milestones in the Evolution of a Science , 67–89. Cambridge: Cambridge University Press, 1991.
• Dolman, Claude E. “Spallanzani, Lazzaro.” Dictionary of Scientific Biography Volume 12: 553–67.

How to cite

Articles rights and graphics.

Copyright Arizona Board of Regents Licensed as Creative Commons Attribution-NonCommercial-Share Alike 3.0 Unported (CC BY-NC-SA 3.0)  

Last modified

Share this page.

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.

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

3 1.2 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 1.10 ). 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 1.11 ).

• 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 1.12 ). 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?
• 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. ↵

DeSales Microbiology Copyright © 2022 by DeSales University & Dr. Dia Beachboard is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License , except where otherwise noted.

Share This Book

• The Theory of Biogenesis

What is Biogenesis?

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

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

Meaning of Biogenesis

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

What Was the Idea of Spontaneous Generation?

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

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

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

Macroscopic Biogenesis: Francesco Redi’s Experiment

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

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

Microscopic Biogenesis

Spallanzani’s experiment.

Source: Emaze

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

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

Pasteur’s Experiment   

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

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

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

Law of Biogenesis Vs. Evolutionary Theory

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

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

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

Solved Question for You

Q. Who Has Propounded the Theory of Spontaneous Generation?

• Spallanzani

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

Customize your course in 30 seconds

Which class are you in.

Molecular Genetics

• What are Genotypes and Phenotypes? – Definition and Examples
• Chromatid – Definition, Parts, and Functions
• Chromosome – Definition, Structure, Function, Examples
• Homozygous – Definition, Characteristics, and Examples
• Chargaff’s Rule – What is Chargaff’s Rule of Base Pairing?
• Genetic Diversity – Definition, Importance, Examples
• Heterozygous – Definition and Characteristics
• Difference Between Homozygous & Heterozygous

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

Download the App

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.

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 .

• 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.

Lazzaro spallanzani: A blow against spontaneous generation

• Historical Biographies
• Published: December 1993
• Volume 9 , pages 101–107, ( 1993 )

Cite this article

• Annalisa Ariatti 1 &
• Paolo Mandrioli 1  

251 Accesses

4 Citations

4 Altmetric

Explore all metrics

Spallanzani might be considered the founder of modern biology. His great success is mainly due to his incomparable ability in observing things and to the methods he utilised. His investigations into the development of microscopic life in nutrient culture solutions may be considered as decisive steps to counteract the leading theory of spontaneous generation and paved the way for the research work of Louis Pasteur.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Subscribe and save.

• Get 10 units per month
• Download Article/Chapter or eBook
• 1 Unit = 1 Article or 1 Chapter
• Cancel anytime

Price includes VAT (Russian Federation)

Instant access to the full article PDF.

Rent this article via DeepDyve

Institutional subscriptions

Similar content being viewed by others

Synthetic Biology and Darwinism

Leibniz, Organic Matter and Astrobiology

Synthetic Life and the Bruteness of Immanent Causation

Caldani L.M.A. , (1982) — Lazzaro Spallanzani. Carteggio (1768–1798) . Milano. Istituto Ed. Cisalpino — La Goliardica.

Google Scholar  

Capparoni P. , (1941) — I grandi Italiani. Spallanzani . Torino. Unione Tipografico-Editrice Torinese. XIX, pp. 243.

Encyclopaedia Britannica , (1982) — Macropaedia . Knowledge in Depth. XV ed., H. Hemingway Benton Publ., 17 444–445.

Encyclopaedia Britannica , (1982) — Micropaedia. Ready Reference and Index . XV ed., H. Heming-way Benton Publ., 7 240.

Pancaldi G. , (1972) — La generazione spontanea nelle prime ricerche dello Spallanzani . Pisa. Domus Galilaeana. pp. 79.

Rostand J. , (1963) — Lazzaro Spallanzani e le origini della biologia sperimentale . Torino. G. Einaudi pp. 206.

Spallanzani L. , (1760) — Riflessioni intorno alla traduzione dell'Iliade del Salvini al co. Francesco Algarotti . Parma. Fratelli Borzi.

Spallanzani L. , (1765) — Dissertazioni due. la. Saggio di Osservazioni microscopiche concernenti il sistema della generazione de' signori di Needham e Buffon. 2a. De lapidibus ab aqua resilientibus dissertatio . Modena, Eredi di Bart. Soliani.

Spallanzani L. , (1768) — Dell'azione del cuore ne' vasi sanguigni, nuove osservazioni dell'Abate Spallanzani . Modena. G. Montanari.

Spallanzani L. , (1780) — Dissertazioni di fisica animale e vegetabile cui sono aggiunte due lettere di Bonnet . Modena. Società Tipografica.

Spallanzani L. , (1803) — Memorie su la respirazione. Opera postuma . Milano. Agnello Nobile.

Spallanzani L. , (1825) — Opere. Saggio di osservazioni concernenti il sistema della generazione di Needham e Buffon . Milano, Tip. De' Classici Italiani, vol. V.

Spallanzani L. , (1825) — Opere. Osservazioni e sperienze intorno agli animalucci delle infusioni in occasione che si esaminano alcuni articoli della nuova opera di Needham . Milano, Tip. De' Classici Italiani, vol. VI.

Download references

Author information

Authors and affiliations.

Institute FISBAT-CNR, Via De' Castagnoli 1, I-40126, Bologna, Italy

Annalisa Ariatti & Paolo Mandrioli

You can also search for this author in PubMed   Google Scholar

Rights and permissions

Reprints and permissions

About this article

Ariatti, A., Mandrioli, P. Lazzaro spallanzani: A blow against spontaneous generation. Aerobiologia 9 , 101–107 (1993). https://doi.org/10.1007/BF02066251

Download citation

Issue Date : December 1993

DOI : https://doi.org/10.1007/BF02066251

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

• Plant Pathology
• Research Work
• Great Success
• Culture Solution
• Environmental Biotechnology
• Find a journal
• Publish with us
• Track your research