pasteur's experiments supported the idea that

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Pasteur's Experiment

The steps of Pasteur's experiment are outlined below:

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

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

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

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

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

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

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

Let's look more closely at these steps.

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pasteur's experiments supported the idea that

3.1 Spontaneous Generation

Learning objectives.

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

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

Clinical Focus

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

What types of respiratory disease may be responsible?

Jump to the next Clinical Focus box

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

The Theory of Spontaneous Generation

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

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

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

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

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

Check Your Understanding

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

Disproving Spontaneous Generation

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

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

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

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

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Scientific Biographies

Louis Pasteur

During the mid- to late 19th century, Pasteur demonstrated that microorganisms cause disease and discovered how to make vaccines from weakened, or attenuated, microbes. He developed the earliest vaccines against fowl cholera, anthrax, and rabies.

Louis Pasteur (1822–1895) is revered by his successors in the life sciences as well as by the general public. In fact, his name provided the basis for a household word— pasteurized .

His research, which showed that microorganisms cause both fermentation and disease, supported the germ theory of disease at a time when its validity was still being questioned. In his ongoing quest for disease treatments he created the first vaccines for fowl cholera; anthrax, a major livestock disease that in recent times has been used against humans in germ warfare; and the dreaded rabies.

Early Life and Education

Pasteur was born in Dole, France, the middle child of five in a family that had for generations been leather tanners. Young Pasteur’s gifts seemed to be more artistic than academic until near the end of his years in secondary school. Spurred by his mentors’ encouragement, he undertook rigorous studies to compensate for his academic shortcomings in order to prepare for the École Normale Supérieure, the famous teachers’ college in Paris. He earned his master’s degree there in 1845 and his doctorate in 1847.

Study of Optical Activity

While waiting for an appropriate appointment, Pasteur continued to work as a laboratory assistant at the École Normale. There he made further progress on the research he had begun for his doctoral dissertation—investigating the ability of certain crystals or solutions to rotate plane-polarized light clockwise or counterclockwise, that is, to exhibit “optical activity.” He was able to show that in many cases this activity related to the shape of the crystals of a compound.

He also reasoned that there was some special internal arrangement to the molecules of such a compound that twisted the light—an “asymmetric” arrangement. This hypothesis holds an important place in the early history of structural chemistry—the field of chemistry that studies the three-dimensional characteristics of molecules.

Fermentation and Pasteurization

Louis Pasteur in his laboratory, holding a jar containing the spinal cord of a rabbit infected with rabies, which he used to develop a vaccine against the disease.

Pasteur secured his academic credentials with scientific papers on this and related research and was then appointed in 1848 to the faculty of sciences in Strasbourg and in 1854 to the faculty in Lille. There he launched his studies on fermentation. Pasteur sided with the minority view among his contemporaries that each type of fermentation is carried out by a living microorganism.

At the time the majority believed that fermentation was spontaneously generated by a series of chemical reactions in which enzymes—themselves not yet securely identified with life—played a critical role.

In 1857 Pasteur returned to the École Normale as director of scientific studies. In the modest laboratory that he was permitted to establish there, he continued his study of fermentation and fought long, hard battles against the theory of spontaneous generation. Figuring prominently in early rounds of these debates were various applications of his pasteurization process, which he originally invented and patented (in 1865) to fight the “diseases” of wine.

He realized that these were caused by unwanted microorganisms that could be destroyed by heating wine to a temperature between 60° and 100°C. The process was later extended to all sorts of other spoilable substances, such as milk.

Germ Theory

At the same time Pasteur began his fermentation studies, he adopted a related view on the cause of diseases. He and a minority of other scientists believed that diseases arose from the activities of microorganisms—germ theory. Opponents believed that diseases, particularly major killer diseases, arose in the first instance from a weakness or imbalance in the internal state and quality of the afflicted individual.

In an early foray into the causes of particular diseases, in the 1860s, Pasteur was able to determine the cause of the devastating blight that had befallen the silkworms that were the basis for France’s then-important silk industry. Surprisingly, he found that the guilty parties were two microorganisms rather than one.

A New Laboratory

Pasteur did not, however, fully engage in studies of disease until the late 1870s, after several cataclysmic changes had rocked his life and that of the French nation. In 1868, in the middle of his silkworm studies, he suffered a stroke that partially paralyzed his left side. Soon thereafter, in 1870, France suffered a humiliating defeat at the hands of the Prussians, and Emperor Louis-Napoléon was overthrown. Nevertheless, Pasteur successfully concluded with the new government negotiations he had begun with the emperor.

The government agreed to build a new laboratory for him, to relieve him of administrative and teaching duties, and to grant him a pension and a special recompense in order to free his energies for studies of diseases.

Attenuating Microbes for Vaccines: Fowl Cholera and Anthrax

In his research campaign against disease Pasteur first worked on expanding what was known about anthrax, but his attention was quickly drawn to fowl cholera. This investigation led to his discovery of how to make vaccines by attenuating, or weakening, the microbe involved. Pasteur usually “refreshed” the laboratory cultures he was studying—in this case, fowl cholera—every few days; that is, he returned them to virulence by reintroducing them into laboratory chickens with the resulting onslaught of disease and the birds’ death.

Glassware of the same type Louis Pasteur would have used to culture microorganisms.

Months into the experiments, Pasteur let cultures of fowl cholera stand idle while he went on vacation. When he returned and the same procedure was attempted, the chickens did not become diseased as before. Pasteur could easily have deduced that the culture was dead and could not be revived, but instead he was inspired to inoculate the experimental chickens with a virulent culture. Amazingly, the chickens survived and did not become diseased; they were protected by a microbe attenuated over time.

Realizing he had discovered a technique that could be extended to other diseases, Pasteur returned to his study of anthrax. Pasteur produced vaccines from weakened anthrax bacilli that could indeed protect sheep and other animals. In public demonstrations at Pouilly-le-Fort before crowds of observers, twenty-four sheep, one goat, and six cows were subjected to a two-part course of inoculations with the new vaccine, on May 5, 1881, and again on May 17. Meanwhile a control group of twenty-four sheep, one goat, and four cows remained unvaccinated.

On May 31 all the animals were inoculated with virulent anthrax bacilli, and two days later, on June 2, the crowd reassembled. Pasteur and his collaborators arrived to great applause. The effects of the vaccine were undeniable: the vaccinated animals were all alive. Of the control animals all the sheep were dead except three wobbly individuals who died by the end of the day, and the four unprotected cows were swollen and feverish. The single goat had expired too.

Rabies and the Beginnings of the Institut Pasteur

Pasteur then wanted to move into the more difficult area of human disease, in which ethical concerns weighed more heavily. He looked for a disease that afflicts both animals and humans so that most of his experiments could be done on animals, although here too he had strong reservations. Rabies, the disease he chose, had long terrified the populace, even though it was in fact quite rare in humans. Up to the time of Pasteur’s vaccine, a common treatment for a bite by a rabid animal had been cauterization with a red-hot iron in hopes of destroying the unknown cause of the disease, which almost always developed anyway after a typically long incubation period.

Rabies presented new obstacles to the development of a successful vaccine, primarily because the microorganism causing the disease could not be specifically identified; nor could it be cultured in vitro (in the laboratory and not in an animal). As with other infectious diseases, rabies could be injected into other species and attenuated. Attenuation of rabies was first achieved in monkeys and later in rabbits.

Meeting with success in protecting dogs, even those already bitten by a rabid animal, on July 6, 1885, Pasteur agreed with some reluctance to treat his first human patient, Joseph Meister, a nine-year-old who was otherwise doomed to a near-certain death. Success in this case and thousands of others convinced a grateful public throughout the world to make contributions to the Institut Pasteur.

Historian Bert Hansen discusses his book, Picturing Medical Progress from Pasteur to Polio.

It was officially opened in 1888 and continues as one of the premier institutions of biomedical research in the world. Its tradition of discovering and producing vaccines is carried on today by the pharmaceutical company Sanofi Pasteur.

A Great Experimenter and Innovative Theorist

Pasteur’s career shows him to have been a great experimenter, far less concerned with the theory of disease and immune response than with dealing directly with diseases by creating new vaccines. Still it is possible to discern his notions on the more abstract topics. Early on he linked the immune response to the biological, especially nutritional, requirements of the microorganisms involved; that is, the microbe or the attenuated microbe in the vaccine depleted its food source during its first invasion, making the next onslaught difficult for the microbe.

Later he speculated that microbes could produce chemical substances toxic to themselves that circulated throughout the body, thus pointing to the use of toxins and antitoxins in vaccines. He lent support to another view by welcoming to the Institut Pasteur Élie Metchnikoff and his theory that “phagocytes” in the blood—white corpuscles—clear the body of foreign matter and are the prime agents of immunity.

Featured image: Portrait of Louis Pasteur , photograph of Louis Pasteur taken in 1886, reproduced in the 1911 biography The Life of Louis Pasteur . Science History Institute

Does Louis Pasteur Still Matter?

Or will the scientist’s 200th birthday be his last hurrah?

Biting Back

The story of Louis Pasteur and the development of the rabies vaccine.

Stories of the Great Chemists

In the 1950s comic books took Mexico’s youth by storm. But alongside familiar superhuman avengers were other kinds of heroes: real-life chemists.

Browse more biographies

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Science News

Louis pasteur’s devotion to truth transformed what we know about health and disease.

A photo of Louis Pasteur's head surrounded by illustrations of scientific equipment, leaves, and swirls

Louis Pasteur demonstrated, more dramatically than any other scientist, the benefit of science for humankind.

Sam Falconer

How Pasteur developed pasteurization

In his youth, Pasteur did not especially excel as a student. His interests inclined toward art rather than science, and he did display exceptional skill at drawing and painting. But in light of career considerations (his father wanted him to be a scholar), Pasteur abandoned art for science and so applied to the prestigious École Normale Supérieure in Paris for advanced education. He finished 15th in the competitive entrance examination, good enough to secure admission. But not good enough for Pasteur. He spent another year on further studies emphasizing physical sciences and then took the École Normale exam again, finishing fourth. That was good enough, and he entered the school in 1843. There he earned his doctoral degree, in physics and chemistry, in 1847.

Among his special interests at the École Normale was crystallography. In particular he was drawn to investigate tartaric acid. It’s a chemical found in grapes responsible for tartar, a potassium compound that collects on the surfaces of wine vats. Scientists had recently discovered that tartaric acid possesses the intriguing power of twisting light — that is, rotating the orientation of light waves’ vibrations. In light that has been polarized (by passing it through certain crystals, filters or some sunglasses), the waves are all aligned in a single plane. Light passing through a tartaric acid solution along one plane emerges in a different plane.

Even more mysteriously, another acid (paratartaric acid, or racemic acid), with the exact same chemical composition as tartaric acid, did not twist light at all. Pasteur found that suspicious. He began a laborious study of the crystals of salts derived from the two acids. He discovered that racemic acid crystals could be sorted into two asymmetric mirror-image shapes, like pairs of right-handed and left-handed gloves. All the tartaric acid crystals, on the other hand, had shapes with identical asymmetry, analogous to gloves that were all right-handed.

An illustration of two crystal forms of racemic acid

Pasteur deduced that the asymmetry in the crystals reflected the asymmetric arrangement of atoms in their constituent molecules. Tartaric acid twisted light because of the asymmetry of its molecules, while in racemic acid, the two opposite shapes canceled out each other’s twisting effects.

Pasteur built the rest of his career on this discovery. His research on tartaric acid and wine led eventually to profound realizations about the relationship between microbes and human disease. Before Pasteur, most experts asserted that fermentation was a natural nonbiological chemical process. Yeast, a necessary ingredient in the fermenting fluid, was supposedly a lifeless chemical acting as a catalyst. Pasteur’s experiments showed yeast to be alive, a peculiar kind of “small plant” (now known to be a fungus) that caused fermentation by biological activity.

Pasteur demonstrated that, in the absence of air, yeast acquired oxygen from sugar, converting the sugar to alcohol in the process. “Fermentation by yeast,” he wrote, is “the direct consequence of the processes of nutrition,” a property of a “minute cellular plant … performing its respiratory functions.” Or more succinctly, he proclaimed that “fermentation … is life without air.” (Later scientists found that yeast accomplished fermentation by emitting enzymes that catalyzed the reaction.)

Pasteur also noticed that additional microorganisms present during fermentation could be responsible for the process going awry, a problem threatening the viability of French winemaking and beer brewing. He solved that problem by developing a method of heating that eliminated the bad microorganisms while preserving the quality of the beverages. This method, called “pasteurization,” was later applied to milk, eliminating the threat of illness from drinking milk contaminated by virulent microorganisms. Pasteurization became standard public health practice in the 20th century.

Incorporating additional insights from studies of other forms of fermentation, Pasteur summarized his work on microbial life in a famous paper published in 1857. “This paper can truly be regarded as the beginning of scientific microbiology,” wrote the distinguished microbiologist René Dubos, who called it “one of the most important landmarks of biochemical and biological sciences.”

The germ theory of disease is born

Pasteur’s investigations of the growth of microorganisms in fermentation collided with another prominent scientific issue: the possibility of spontaneous generation of life. Popular opinion even among many scientists held that microbial life self-generated under the proper conditions (spoiled meat, for example). Demonstrations by the 17th century Italian scientist Francesco Redi challenged that belief , but the case against spontaneous generation was not airtight.

A photo of a double flask in the foreground and another flask in the background, both used by Louis Pasteur

In the early 1860s Pasteur undertook a series of experiments that should have left no doubt that spontaneous generation, under conditions encountered on Earth today, was an illusion. Yet he was nevertheless accosted by critics, such as the French biologist Charles-Philippe Robin, to whom he returned verbal fire. “We trust that the day will come when M. Robin will … acknowledge that he has been in error on the subject of the doctrine of spontaneous generation, which he continues to affirm, without adducing any direct proofs in support of it,” Pasteur remarked.

It was his work on spontaneous generation that led Pasteur directly to the development of the germ theory of disease.

For centuries people had suspected that some diseases must be transmitted from person to person by close contact. But determining exactly how that happened seemed beyond the scope of scientific capabilities. Pasteur, having discerned the role of germs in fermentation, saw instantly that something similar to what made wine go bad might also harm human health.

After disproving spontaneous generation, he realized that there must exist “transmissible, contagious, infectious diseases of which the cause lies essentially and solely in the presence of microscopic organisms.” For some diseases, at least, it was necessary to abandon “the idea of … an infectious element suddenly originating in the bodies of men or animals.” Opinions to the contrary, he wrote, gave rise “to the gratuitous hypothesis of spontaneous generation” and were “fatal to medical progress.”

His first foray into applying the germ theory of disease came during the late 1860s in response to a decline in French silk production because of diseases afflicting silkworms. After success in tackling the silkworms’ maladies, he turned to anthrax, a terrible illness for cattle and humans alike. Many medical experts had long suspected that some form of bacteria caused anthrax, but it was Pasteur’s series of experiments that isolated the responsible microorganism, verifying the germ theory beyond doubt. (Similar work by Robert Koch in Germany around the same time provided further confirmation.)

Understanding anthrax’s cause led to the search for a way to prevent it. In this case, a fortuitous delay in Pasteur’s experiments with cholera in chickens produced a fortunate surprise. In the spring of 1879 he had planned to inject chickens with cholera bacteria he had cultured, but he didn’t get around to it until after his summer vacation. When he injected his chickens in the fall, they unexpectedly failed to get sick. So Pasteur prepared a fresh bacterial culture and brought in a new batch of chickens.

When both the new chickens and the previous batch were given the fresh bacteria, the new ones all died, while nearly all of the original chickens still remained healthy. And so, Pasteur realized, the original culture had weakened in potency over the summer and was unable to cause disease, while the new, obviously potent culture did not harm the chickens previously exposed to the weaker culture. “These animals have been vaccinated,” he declared.

Vaccination, of course, had been invented eight decades earlier, when British physician Edward Jenner protected people from smallpox by first exposing them to cowpox, a similar disease acquired from cows. (Vaccination comes from cowpox’s medical name, vaccinia, from vacca , Latin for cow.) Pasteur realized that the chickens surprisingly displayed a similar instance of vaccination because he was aware of Jenner’s discovery. “Chance favors the prepared mind,” Pasteur was famous for saying.

Because of his work on the germ theory of disease, Pasteur’s mind was prepared to grasp the key role of microbes in the prevention of smallpox, something Jenner could not have known. And Pasteur instantly saw that the specific idea of vaccination for smallpox could be generalized to other diseases. “Instead of depending on the chance finding of naturally occurring immunizing agents, as cowpox was for smallpox,” Dubos observed, “it should be possible to produce vaccines at will in the laboratory.”

Pasteur cultured the anthrax microbe and weakened it for tests in farm animals. Success in such tests not only affirmed the correctness of the germ theory of disease, but also allowed it to gain a foothold in devising new medical practices.

Later Pasteur confronted an even more difficult microscopic foe, the virus that causes rabies. He had begun intense experiments on rabies, a horrifying disease that’s almost always fatal, caused usually by the bites of rabid dogs or other animals. His experiments failed to find any bacterial cause for rabies, leading him to realize that it must be the result of some agent too small to see with his microscope. He could not grow cultures in lab dishes of what he could not see. So instead he decided to grow the disease-causing agent in living tissue — the spinal cords of rabbits. He used dried-out strips of spinal cord from infected rabbits to vaccinate other animals that then survived rabies injections.

Pasteur hesitated to test his rabies treatment on humans. Still, in 1885 when a mother brought to his lab a 9-year-old boy who had been badly bitten by a rabid dog, Pasteur agreed to administer the new vaccine. After a series of injections, the boy recovered fully. Soon more requests came for the rabies vaccine, and by early the next year over 300 rabies patients had received the vaccine and survived, with only one death among them.

Popularly hailed as a hero, Pasteur was also vilified by some hostile doctors, who considered him an uneducated interloper in medicine. Vaccine opponents complained that his vaccine was an untested method that might itself cause death. But of course, critics had also rejected Pasteur’s view of fermentation, the germ theory of disease and his disproof of spontaneous generation.

A cartoon from the magazine Puck in 1885 showing people in a line for Louis Pasteur's rabies vaccine

Pasteur stood his ground and eventually prevailed (although he did not turn out to be right about everything). His attitude and legacy of accomplishments inspired 20th century scientists to develop vaccines for more than a dozen deadly diseases. Still more diseases succumbed to antibiotics, following the discovery of penicillin by Alexander Fleming — who declared, “Without Pasteur I would have been nothing.”

Even in Pasteur’s own lifetime, thanks to his defeat of rabies, his public reputation was that of a genius.

Pasteur’s scientific legacy

As geniuses go, Pasteur was the opposite of Einstein. To get inspiration for his theories, Einstein imagined riding aside a light beam or daydreamed about falling off a ladder. Pasteur stuck to experiments. He typically initiated his experiments with a suspected result in mind, but he was scrupulous in verifying the conclusions he drew from them. Preconceived ideas, he said, can guide the experimenter’s interrogation of nature but must be abandoned in light of contrary evidence. “The greatest derangement of the mind,” he declared, “is to believe in something because one wishes it to be so.”

So even when Pasteur was sure his view was correct, he insisted on absolute proof, conducting many experiments over and over with variations designed to rule out all but the true interpretation.

“If Pasteur was a genius, it was not through ethereal subtlety of mind,” wrote Pasteur scholar Gerald Geison. Rather, he exhibited “clear-headedness, extraordinary experimental skill and tenacity — almost obstinacy — of purpose.”

This painting depicts French President Sadi Carnot helping Louis Pasteur walk across the stage during a ceremony held at the Sorbonne in Paris in honor of Pasteur’s 70th birthday

His tenacity, or obstinacy, helped him persevere through several personal tragedies, such as the deaths of three of his daughters, in 1859, 1865 and 1866. And then in 1868 he suffered a cerebral hemorrhage that left him paralyzed on his left side. But that did not slow his pace or impair continuing his investigations.

“Whatever the circumstances in which he had to work, he never submitted to them, but instead molded them to the demands of his imagination and his will,” Dubos wrote. “He was probably the most dedicated servant that science ever had.”

To the end of his life, Pasteur remained dedicated to science and the scientific method, stressing the importance of experimental science for the benefit of society. Laboratories are “sacred institutions,” he asserted. “Demand that they be multiplied and adorned; they are the temples of wealth and of the future.”

Three years before his death in 1895, Pasteur further extolled the value of science and asserted his optimism that the scientific spirit would prevail. In an address, delivered for him by his son, at a ceremony at the Sorbonne in Paris, he expressed his “invincible belief … that science and peace will triumph over ignorance and war, that nations will unite, not to destroy, but to build, and that the future will belong to those who will have done most for suffering humanity.”

A painted portrait of Louis Pasteur on the cover of a french newspaper from 1895

Two hundred years after his birth , ignorance and war remain perniciously prominent, as ineradicable as the microbes that continue to threaten public health, with the virus causing COVID-19 the latest conspicuous example. Vaccines, though, have substantially reduced the risks from COVID-19, extending the record of successful vaccines that have already tamed not only smallpox and rabies, but also polio, measles and a host of other once deadly maladies .

Yet even though vaccines have saved countless millions of lives, some politicians and so-called scientists who deny or ignore overwhelming evidence continue to condemn vaccines as more dangerous than the diseases they prevent. True, some vaccines can induce bad reactions, even fatal in a few cases out of millions of vaccinations. But shunning vaccines today, as advocated in artificially amplified social media outrage, is like refusing to eat because some people choke to death on sandwiches.

Today, Pasteur would be vilified just as he was in his own time, probably by some people who don’t even realize that they can safely drink milk because of him. Nobody knows exactly what Pasteur would say to these people now. But it’s certain that he would stand up for truth and science, and would be damn sure to tell everybody to get vaccinated.

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2.1 Spontaneous Generation

Learning objectives.

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

The Theory of Spontaneous Generation

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

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

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

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

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

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

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

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

Disproving Spontaneous Generation

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

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

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

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

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

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.

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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/

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Sagar Aryal

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

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The Theory of Spontaneous Generation

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

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

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

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

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

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

Disproving Spontaneous Generation

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

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

Key Takeaways

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

Multiple Choice

Fill in the blank, short answer.

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

Critical Thinking

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

Media Attributions

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

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Origins of Life I: Early ideas and experiments

by David Warmflash, MD, Nathan H Lents, Ph.D.

Listen to this reading

Did you know that it is much easier to determine when life appeared on Earth than how life came to exist? Evidence points to life on Earth as early as 3.8 billion years ago, but the question of how life came to be has puzzled scientists and philosophers since prehistoric times. In the 1950s, scientists successfully created biological molecules by recreating the atmosphere of primordial Earth in a bottle and shocking it with lightning. This and other experiments give clues to the origins of life.

Theories about the origins of life are as ancient as human culture. Greek thinkers like Anaximander thought life originated with spontaneous generation, the idea that small organisms are spontaneously generated from nonliving matter.

The theory of spontaneous generation was challenged in the 18th and 19th centuries by scientists conducting experiments on the growth of microorganisms. Louis Pasteur, by conducting experiments that showed exposure to fresh air was the cause of microorganism growth, effectively disproved the spontaneous generation theory.

Abiogenesis, the theory that life evolved from nonliving chemical systems, replaced spontaneous generation as the leading theory for the origin of life.

Haldane and Oparin theorized that a "soup" of organic molecules on ancient Earth was the source of life's building blocks. Experiments by Miller and Urey showed that likely conditions on early Earth could create the needed organic molecules for life to appear.

RNA, and through evolutionary processes, DNA and the diversity of life as we know it, likely formed due to chemical reactions among the organic compounds in the "soup" of early Earth.

The work of Darwin and Wallace went a long way in answering the question of how species evolved over time. The theory of natural selection provided a mechanism by which complex life forms, including humans, could arise from simpler organisms . But that still left open a more difficult question, namely, what is the origin of life itself? It’s one of the most challenging questions in science, even today when we can say confidently when life appeared on Earth.

Microscopic fossils called stromatolites and remains of communities of microorganisms called microbial mats suggest that Earth harbored microorganisms 3.5 billion years ago (Figure 1). Also, the presence of particular carbon isotopes in certain metamorphic rocks in Greenland tell scientists that some kind of life may have been present as much as 3.8 billion years ago. This means that 700 million to one billion years after Earth had formed, life was here. It makes sense, because it corresponds to the time when the planet had reached a cool enough temperature for any life to survive. But honing in on the time when life appeared on this planet still does not tell us how life came to exist.

Stromatolites in the Soeginina Beds of Estonia

Since prehistoric times, people sought mostly spiritual answers to this question. Around campfires during the Stone Age, each budding culture told and retold tales of how the gods created life from some kind of nonliving material, be it mud, clay, rock, or straw. The details of the ancient creation stories changed noticeably over time, but religion was still the mode of thinking by Darwin’s era when it came to the initiation of life itself. Darwin did consider the origin of life and speculated that it had occurred in a warm pond. He suggested that phosphoric salts and ammonia in the pre-biotic pond somehow had been changed chemically by heat , light , and electricity, leading to the synthesis of the organic compounds needed to produce the first living cells . Darwin was not a chemist and this was a very cursory speculation about Earth’s pre-biotic chemistry. It contrasted sharply with the detail and systematic approach of Darwin’s own theory of natural selection .

Even so, the pond idea was a start. Despite living in a society that almost universally assumed Earth had an intelligent creator, scientists in Darwin’s time were already comfortable with and accustomed to considering the possibility of life getting started without intervention from the gods. The idea was called spontaneous generation and, while it was already very well established by Darwin’s time, it dates all the way back to the time of the ancient Greeks.

Early thinkers

About 2,600 years ago, in the Ionian city of Miletus (Figure 2), the natural philosopher Anaximander (c. 610–546 BCE) pondered how human babies were born utterly helpless. Without their parents , young humans had no chance to survive and the state of helplessness continued for years. That reality made for a dilemma when considering the first generation of humans, which, Anaximander assumed, must have begun as infants. To grow up and have their own babies, human ancestors in the very distant past must have been more independent as newborns, Anaximander reasoned. They must have been more like certain other animals whose young are born ready to survive on their own.

Location of Miletus on the western coast of Anatolia

Considering the various animals, Anaximander decided the ancestors of humans had to be fish. Unlike mammals, which needed their mothers to get started in life, fish simply emerge from their eggs and either die or survive. This means that distant human ancestors could survive as infants if they were more like fish than like humans.

Even in Anaximander’s time, people saw skeletons from long-dead creatures. Fossils of extinct life were found long before paleontologists went looking for them. Ancient Greeks lived by the sea, and often the sea washed up skeletons or eroded the ground to expose buried bones. Living in this environment , Anaximander had a general idea of skeletal anatomy and how it was similar and different between humans and other animals. Because of this, he decided that the transition from fish to humans must have been gradual. In other words, humans descended from fish through an evolutionary process .

Since Anaximander proposed no idea of how the apparent evolution from fish to human had taken place, it was not an early form of Darwin’s theory of natural selection . But it was the beginning of thinking that life on Earth began with small organisms . Anaximander’s idea quickly led to the idea that small organisms were generated through a natural process from nonliving matter , such as the mud at the bottom of the sea.

Over the next centuries, Greek thinkers such as Anaximenes (588–524 BCE), Xenophanes (576–480), Empedocles (495–435), Democritus (460–370), and finally Aristotle (384–322) developed and modified the spontaneous generation idea so that it corresponded to what people often observed on land. Farmers leaving grain in an open container noticed that pretty soon mice appeared, as if the grain generated the mice. People leaving meat untended returned to find maggots infesting the meat, as if the meat generated the maggots.

Comprehension Checkpoint

Testing spontaneous generation

By the 18 th and 19 th century, the older Greek idea of spontaneous generation was well ingrained in the minds of everyone who ventured to think that the origin of life might not have required the gods. And living at a time when science was coming to age, some early modern thinkers started treating spontaneous generation less like a philosophy and more like a scientific hypothesis . Gradually, they began subjecting the idea to scientific experimentation.

An early attempt at testing spontaneous generation occurred in the 17 th century, when the Italian scientist Francesco Redi (c. 1626–1697) looked carefully at the meat-maggot phenomenon. After leaving meat in an open jar, he observed that maggots did indeed appear, and that the maggots then developed into flies, which then flew away. However, when he left meat in a sealed jar, the maggots did not appear. Nor did maggots appear when he left the meat in a jar covered with a mesh screen, a precaution he took just in case spontaneous generation required fresh air for some reason. In the terminology of today’s science, we say that the mesh-covered jar “controlled for” the possibility that spontaneous generation required fresh air (Figure 3).

Francesco Redi's spontaneous generation experiment

Since the mesh cover prevented the appearance of maggots, it meant that the maggots were not coming from spontaneous generation , but simply from eggs of adult flies. By the standards of experimental methods in contemporary science, it was a rudimentary experiment , but it was as good as it could be given the equipment available in Redi’s time.

Despite the result of his maggot experiment , Redi still believed that smaller creatures, called “gall insects” came from spontaneous generation . At the same time, a developing invention, the microscope, allowed scientists to focus on creatures even smaller: microorganisms. Using his microscope, an English experimenter, John Needham, noticed that broths made from meat were teeming with microorganisms, so he put spontaneous generation to his own test (see our module Experimentation in Scientific Research ). Needham heated a bottle of broth to kill any microorganisms, and left the bottle for a few days. Then, he looked at the broth under the microscope and found that, despite the earlier heating, the broth contained microorganisms again (Figure 4a).

Needham's spontaneous generation experiment

In Needham’s mind, this finding suggested that the lifeless broth had given rise to life. But another scientist, an Italian named Lazzaro Spallanzani , thought that Needham must have done something wrong. Perhaps, he hadn’t heated the broth to a high enough temperature or for a long enough time. To find out, Spallanzani performed his own experiment . He boiled broth in two bottles, left one bottle open and one closed, and found that new microorganisms appeared only in the open bottle. His conclusion: the microorganisms entered the bottle through the air; they were not generated spontaneously in the broth (Figure 4b).

Experiments seeming to prove or disprove spontaneous generation of life went on for another century. Because of the difference between closed and open vessels, arguments focused on the possibility that spontaneous generation of life might require fresh air. Thus, lack of air in Spallanzani’s closed bottle could have been a factor confusing the results. This possibility attracted the attention of the 19 th century’s most famous microbiologist: Darwin’s contemporary, Louis Pasteur .

Pasteur was drawn to the issue, but once involved he knew he that needed to control for the possibility that air was needed to generate life from nonliving matter . To do this, he designed flasks with long, specially curved, swanlike necks. This allowed sterilized broth to be exposed to fresh air from the outside, but any microorganisms from the air would be trapped in a pool of water in the neck. (See our module Experimentation in Scientific Research for more information on designing experiments .)

The sterilized broths in Pasteur’s special flasks did not become infested with microorganisms despite being exposed to fresh air (Figure 5). And so, after a run of more than 24 centuries, the hypothesis of spontaneous generation was finally laid to rest.

Pasteur's flask with long, swan-like necks

This meant that scientists no longer thought that microorganisms, or small animals, could suddenly emerge with no parents , but it didn’t stop people from thinking about life coming from nonliving matter . Pasteur’s publication of his experimental results disproving spontaneous generation of microorganisms came in the very same year as Darwin’s Origin of Species . This made for paradox. Around the world, scientists were fairly certain that evolution really happened, that all modern species came ultimately from pre-existing, living forms. However, as for the question of how life started in the first place, scientists had just disproved the only explanation they had.

Darwin’s pond idea was completely speculative. There was no way to test it the way he tested natural selection through years of observation of numerous species . And so, when it came to the initiation of life itself, scientists of Darwin’s era were stumped. All they could do was to throw up their hands, or chalk it up to the creation stories of their religions.

Old and new ideas

In addition to spontaneous generation , the ancient Greeks produced another idea for the origin of life on Earth: panspermia . An Ionian Greek named Anaxagoras (510–428 BCE) thought that life arrived on Earth as seedlings that came through space from other worlds. Often people think of panspermia as an alternative to the idea of life emerging from nonliving matter , but it’s actually not. Instead, panspermia only moves the origin of life off the Earth to another planet or moon, and further back in time. Thus, after Pasteur’s disproval of spontaneous generation , the motivation was stronger than ever to determine how life got started.

By the late 19th century, English biologist Thomas Henry Huxley (1825–1895) coined the term abiogenesis to describe life forms emerging from non-living chemical systems . On first hearing the term, it may sound as if abiogenesis is merely a more modern take on spontaneous generation , but there is a major difference. With spontaneous generation , the idea was that certain materials, be it meat, grain, or mud, were capable of constantly producing some kind of creature. What Huxley had in mind was the chemical reactions of life slowly emerging on the early Earth over a long period of time. Huxley knew that the mixture would have to be more complex than Darwin’s ammonia and phosphoric salts , but he did not attempt to work out the details. Somehow, though, he thought an optimal mixture of simple chemicals generated the complex chemicals needed for life, such as enzymes , and the earliest living cells .

Abiogenesis

As for how abiogenesis could occur on the primordial Earth, serious thinking about this began in the 1920s with two scientists working entirely independently of one another.

In 1922, Aleksandr Oparin, a Russian biochemist, gave a lecture on the origins of life, which was published as a booklet in 1924. For several years, the booklet was not translated from Oparin’s native Russian, so his ideas were unknown outside of the USSR. Meanwhile, British biochemist John Burdon Sanderson Haldane (usually known by his initials JBS Haldane) was working on similar ideas. Unlike his Russian counterpart, Haldane and his work were extremely visible. He was a great popularizer of science, doing for the early 20th century what astronomer Carl Sagan did later, making science understandable and fascinating for the masses. Haldane’s hands were in numerous areas of life science. He was the author of dozens of scientific papers and spent a great deal of time explaining his work and its importance to people outside the scientific world.

In connection with other questions of biology, Haldane was working with enzymes , which he thought were on the border between living and nonliving chemistry. Consequently, he hypothesized that abiogenesis took place through a complex mechanism involving enzymes and viruses. By Haldane’s time, scientists figured out that the atmosphere of the primordial Earth had been a reduced atmosphere. This means that it contained reduced carbon chemical compounds , such as methane, in contrast to oxidized chemical compounds, such as carbon dioxide (which could be present, but in much lower quantities compared with methane). It also contained hydrogen, ammonia, some water vapor, and, importantly, no oxygen.

Oxygen can come only from organisms that carry out photosynthesis to make their own food. Such organisms are called autotrophs. Haldane reasoned that the first cells must have been heterotrophs, organisms that take their food from the surrounding environment . Methane is a gas , but other simple, organic compounds made from it are liquid and would have rained down on the early Earth. They accumulated as pools of liquid on the surface , forming a kind of organic broth that became known as “Haldane’s soup” (Figure 6).

Grand Prismatic Spring in Yellowstone National Park

Because there was no oxygen in the atmosphere , the early Earth lacked a layer of ozone to block out powerful ultraviolet radiation from space. Haldane hypothesized that the ultraviolet radiation from space, along with lightning constantly hitting the primordial organic soup, delivered energy to the various simple organic compounds . This caused chemical bonds between the atoms of the molecules to break and reform, creating new and different molecules, leading to extremely large, complex organic molecules . Haldane speculated that this happened over millions of years, until finally a molecule arose that could copy itself crudely using other molecules in the “soup” as building blocks.

Molecules that could copy better than their neighbors multiplied and gradually dominated the soup. Some of these self-copying molecules became surrounded by a kind of barrier, the precursor to what we call a membrane . This happened by accident, so it was very rare, but when it did happen, Haldane explained, the enclosed, self-copying molecules had an enormous survival advantage. So they came to dominate, ate up the soup, and life had begun.

Haldane’s idea was purely hypothetical. No one tested it yet, but it was far more elaborate than Darwin’s phosphoric salt idea. Moreover, it was perfectly consistent with the state of science in the 1920s and 30s regarding the chemistry of the early Earth. Then, in 1936, Oparin’s work was finally translated from Russian. It turned out that he was proposing almost the same thing as Haldane, so the idea became known as the Oparin-Haldane hypothesis .

Putting ancient Earth into the lab

As for testing the Oparin-Haldane hypothesis , that role fell into the hands of a graduate student, Stanley Miller. In the early 1950s, Miller was looking for a thesis project in the Department of Chemistry at the University of Chicago. In 1952, his academic mentor, Professor and Nobel laureate Harold Urey, suggested that he try putting the origins of living molecules to a test. That meant recreating the kind of atmosphere that scientists thought had existed on primordial Earth: hydrogen, methane, ammonia, and water. It also meant providing what Haldane thought set the stage for creating more complicated molecules needed for life: lightning and ultraviolet light .

Once the ancient atmosphere was created and contained in a flask, Miller and Urey exposed the mixture to powerful ultraviolet light . They also put electrodes inside the flask and sent an electric current through the apparatus, creating sparks to simulate lightning, which interacted with the gases in the flask. After several days, they checked the contents of the liquid that accumulated at the bottom of the apparatus (Figure 7). They found that different molecules had been created, including various important biological molecules, such as the amino acids glycine, alanine, and valine. They ran the experiment over and over and, depending on how they changed around the gas mixture, different varieties of amino acids and other biological molecules were created. This showed that it was possible for biologically important molecules to form on a planet under abiotic conditions.

Over the years, as Miller progressed through his career, scientists studying planetary atmospheres and the ancient Earth had second thoughts about Earth’s primordial atmosphere. Perhaps it had not been dominated by methane, hydrogen, and ammonia, and possibly it could have been more oxidized as opposed to reduced. But as theories about the ancient atmosphere were refined, Miller tried variations of his original experiment with the adjusted gas mixtures . Although chemical products changed with each new mixture, in each case they included compounds that were vital to life, such as amino acids , or nitrogenous bases , the building blocks needed to make DNA and RNA . The emerging answer seemed to be that, almost regardless what the precise mixture and conditions were, complex organic molecules would result.

After the Miller-Urey experiment: Exploring proteins and membranes

While ideas about Earth’s primordial atmosphere were in flux from the 1970s onward, NASA’s exploration of the outer Solar System revealed some amazing things about the moons orbiting Jupiter and Saturn. In particular, the space probes Voyager 1 , Voyager 2 , and Cassini and an atmospheric entry probe to Saturn’s moon Titan called the Huygens probe revealed the exact makeup of Titan’s atmosphere. This inspired other scientists, such as Carl Sagan , to redo Miller’s 1952 experiment with a Titan atmospheric mixture. This too produced important biological compounds . Thus, today, the moon Titan is a prime focus for astrobiology studies in the Solar System. It may have exotic life forms, or it may be a model of how Earth was prior to life.

Several years after the original Miller-Urey experiment , another investigator, Sidney Fox, ran experiments showing that some of the Miller-Urey compounds – the amino acids – could join together to form polymers , bigger molecules known as peptides , or small proteins . This happened when amino acids made through a Miller-Urey mechanism were splashed onto surfaces of clays and other materials, under hot, dry conditions. On the ancient Earth, such conditions would have occurred at the boundary between ancient ponds or seas and ancient land. Given enough time, complex proteins could arise.

Other researchers later found that spheres of lipids (the class of organic molecules that includes fats) also could form under conditions thought to exist on the ancient Earth. This would create a water environment inside the sphere that was separated from the outside. In other words, crude membranes can form spontaneously under the same conditions in which biological compounds like amino acids and small proteins can form. The fact that membranes can form spontaneously is key to origins of life research . This is because to move from non-living chemistry to biology, very complex networks of chemical reactions need to emerge. Like a car being made on an assembly line, biological molecules are put together section by section. They also are converted into different molecules section by section, so there is a series of intermediate chemicals in addition to a starting molecule (called a substrate) and final product of each reaction .

In an open environment like Haldane’s primordial soup, or in an ocean, the various intermediates would simply diffuse away before the chemical pathway had a chance to evolve. But a membrane would enclose all of the chemicals within a compartment. That compartment would then act as a chemical laboratory, holding inside any reactions that happened to emerge. Since we know that membrane spheres can spontaneously form, the primordial soup of early Earth must have had billions of these little chemical laboratories in which the chemistry of life was sputtering along.

Moving to a DNA world

Demonstration that biological molecules and membranes can arise in an abiotic environment is not a demonstration of the emergence of life. It shows only what might have happened in the transition from non-living chemistry to the eventual formation of life. It does, however, show that a necessary step in abiogenesis – the spontaneous emergence of complex organic molecules – is not only possible, but likely under the right conditions.

Theoretically, continuous rearrangement and construction of larger and larger organic molecules from chemical building blocks that would form on the early Earth should eventually lead to molecules that can copy themselves. That’s because the bigger an organic molecule gets, the more functional chemical groups it has. Functional groups are sections of molecules with atoms other than carbon, such as oxygen, nitrogen, and phosphorus, which like to hold onto electrons . This allows for electrons to be moved around between parts of the molecule and between the molecule and other molecules. Also, the bigger a molecule gets, the more it’s able to bend and twist around. This capability, together with the capability to move around a lot of electrons, &^means it’s possible, simply by luck, for any random, very large organic molecule with a lot of nitrogen, oxygen, and phosphorus atoms to have some enzymatic capability –that is, to be able to catalyze chemical reactions .

Certain sets of reactions catalyzed by a molecule can result in the molecule making a copy of itself. Thus, with plenty of building materials in a Haldane soup, as time goes on, it is likely that self-replicating molecules would emerge. The first self-replicating molecule would have only crude copying ability. But, since it would not copy itself exactly, each new “copy” would be a little different than the “parent” molecule. Randomly, a newly copied molecule might have the ability to copy slightly better than the molecule that made it. Natural selection would then work for non-living chemical molecules similar to how Darwin described it working for living organisms . Those molecules copying better would make more copies using building blocks taken from the breakdown of other molecules that could not copy themselves so well.

Self-copying molecules enclosed in membranes would fare even better because they would be held close together with other chemicals. But for life to really begin, there has to have been a molecule whose copying ability was extremely good. Today, there is such a molecule: DNA . However, DNA is incredibly complex and this makes for a chicken and egg kind of dilemma.

In the 1980s, scientists began to realize that not all enzymes are proteins . Scientists dissected some cell components called ribosomes and found that they are made of protein and RNA . What was strange was that some of the RNA molecules actually work as enzymes. They can catalyze chemical changes in themselves and in other RNA molecules.

Like DNA , RNA can hold genetic information, but RNA is less complex than DNA (Figure 8). Consequently, a hypothesis called the “RNA world” was proposed independently by three different researchers: Leslie Orgel, Francis Crick , and Carl Woese. It’s a keystone in origins of life research today. The idea is that RNA emerged on Earth prior to DNA and was the genetic material in the first cells (or in the first cells on a different world, if life began somewhere else).

Today, no known bacterial cell or other fully-fledged life form uses RNA the way that we use DNA , as the storage molecule for genetic information. But there are RNA viruses. Not all viruses are RNA viruses; some use DNA to hold genetic instructions, just as our cells do. But if RNA is adequate as the only genetic material in some viruses, it’s easy to imagine RNA also being the only genetic material in an early bacterium, or other singled-celled creature that could have existed on the early Earth.

It’s not hard to image how the transition from RNA to DNA might have occurred. As with the evolution of everything else, there would have been mistakes. In living organisms today, DNA stores genetic information over the long term and DNA sequences are transcribed into RNA sequences, which then are used to put together sequences of amino acids into proteins (see our Gene Expression: An overview module). Essentially, DNA is an additional layer beyond RNA and the proteins that RNA makes. RNA sequences could have been the genes before a mistake created DNA. Being more stable chemically than RNA, DNA took over the job of storing genetic information. This gave RNA a chance to get better at translating genetic information into proteins.

That would have been an enormous step in life’s evolution . It also would mean that life was not here all at once. Rather, abiogenesis occurred in increments or steps during prebiotic, chemical evolution. Thus, entities must have existed along a spectrum from nonliving to living, just as viruses today have characteristics of both living and nonliving entities. We don’t know the precise abiogenesis pathway, but scientists have worked out each of the major steps necessary to go from nonliving chemistry to self-sustaining cells . Importantly, scientists also have conducted laboratory experiments demonstrating that each step is possible. Unlike the days of Anaximander , Darwin, or even Haldane, there are no big holes or theoretical barriers to abiogenesis. Scientists have a good idea of how it probably happened. Still, in terms of the details within each major step, that is where science is now focused on getting some answers.

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Is Spontaneous Generation Real?

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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.
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The Theory of Biogenesis

What is Biogenesis?

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

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

Meaning of Biogenesis

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

What Was the Idea of Spontaneous Generation?

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

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

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

Macroscopic Biogenesis: Francesco Redi’s Experiment

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

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

Microscopic Biogenesis

Spallanzani’s experiment.

Source: Emaze

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

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

Pasteur’s Experiment

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

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

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

Law of Biogenesis Vs. Evolutionary Theory

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

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

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

Solved Question for You

Q. Who Has Propounded the Theory of Spontaneous Generation?

Spallanzani

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

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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. ”

An external file that holds a picture, illustration, etc.
Object name is biomolecules-12-00596-g001.jpg

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

Main contributions of Louis Pasteur.

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

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

2. From Molecular Chirality to Fermentation

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

Main steps of Louis Pasteur’s life and career.

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

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

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

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

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

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

3. Fighting against Spontaneous Generation and Germ Theory

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

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

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

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

4. Fighting against the Silkworm Disease

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

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

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

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

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

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

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

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

5.1. Puerperal Fever

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

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

5.2. Anthrax

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

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

5.3. Cholera

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

5.4. Plague

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

6. Pasteurization, Filtration and Sterilization

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

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

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

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

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

7. Elaboration of Four Vaccines

7.1. fowl cholera.

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

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

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

7.2. Anthrax (1881)

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

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

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

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

7.3. Pig Erysipelas

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

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

7.4. Rabies

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

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

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

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

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

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

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

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

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

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

8. Concluding Remarks

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

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

Author Contributions

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

This research received no external funding.

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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

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Louis Pasteur

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Science History Institute - Biography of Louis Pasteur
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Institut Pasteur - Our History
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Louis Pasteur - Children's Encyclopedia (Ages 8-11)
Louis Pasteur - Student Encyclopedia (Ages 11 and up)
Table Of Contents

Among Louis Pasteur’s discoveries were molecular asymmetry, the fact that molecules can have the same chemical composition with different structures; that fermentation is caused by microorganisms; and that virulence can be increased as well as decreased. He also disproved the theory of spontaneous generation and contributed to germ theory and the study of infectious disease.

Louis Pasteur is best known for inventing the process that bears his name, pasteurization . Pasteurization kills microbes and prevents spoilage in beer, milk, and other goods. In his work with silkworms, Pasteur developed practices that are still used today for preventing disease in silkworm eggs. Using his germ theory of disease, he also developed vaccines for chicken cholera, anthrax, and rabies.

What is pasteurization?

Pasteurization is a heat-treatment process that destroys pathogenic microorganisms in certain foods and beverages. It is used for preserving goods such as beer, milk, and cream.

Louis Pasteur grew up in a relatively poor family. He was one of four children, and his father was a tanner. In 1849 he married Marie Laurent, the daughter of the rector of the University of Strasbourg , where Pasteur was a professor of chemistry. They had five children together, only two of whom survived to adulthood.

Louis Pasteur (born December 27, 1822, Dole , France—died September 28, 1895, Saint-Cloud) was a French chemist and microbiologist who was one of the most important founders of medical microbiology . Pasteur’s contributions to science , technology , and medicine are nearly without precedent. He pioneered the study of molecular asymmetry; discovered that microorganisms cause fermentation and disease; originated the process of pasteurization ; saved the beer , wine , and silk industries in France ; and developed vaccines against anthrax and rabies .

Pasteur’s academic positions were numerous, and his scientific accomplishments earned him France’s highest decoration, the Legion of Honour , as well as election to the Académie des Sciences and many other distinctions. Today there are some 30 institutes and an impressive number of hospitals, schools, buildings, and streets that bear his name—a set of honours bestowed on few scientists.

Pasteur’s father, Jean-Joseph Pasteur, was a tanner and a sergeant major decorated with the Legion of Honour during the Napoleonic Wars . This fact probably instilled in the younger Pasteur the strong patriotism that later was a defining element of his character. Louis Pasteur was an average student in his early years, but he was gifted in drawing and painting. His pastels and portraits of his parents and friends, made when he was 15, were later kept in the museum of the Pasteur Institute in Paris . After attending primary school in Arbois, where his family had moved, and secondary school in nearby Besançon, he earned his bachelor of arts degree (1840) and bachelor of science degree (1842) at the Royal College of Besançon.

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Louis Pasteur
Louis Pasteur - Microbiology, Germ Theory, Pasteurization: Fermentation and putrefaction were often perceived as being spontaneous phenomena, a perception stemming from the ancient belief that life could generate spontaneously. During the 18th century the debate was pursued by the English naturalist and Roman Catholic divine John Turberville Needham and the French naturalist Georges-Louis ...
Pasteur's Experiment
The steps of Pasteur's experiment are outlined below: First, Pasteur prepared a nutrient broth similar to the broth one would use in soup. Next, he placed equal amounts of the broth into two long-necked flasks. He left one flask with a straight neck. The other he bent to form an "S" shape. Then he boiled the broth in each flask to kill any ...
3.1 Spontaneous Generation
Figure 3.4 (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.
Louis Pasteur
Louis Pasteur (1822-1895) is revered by his successors in the life sciences as well as by the general public. In fact, his name provided the basis for a household word—pasteurized. His research, which showed that microorganisms cause both fermentation and disease, supported the germ theory of disease at a time when its validity was still being questioned.
Louis Pasteur invented microbiology and transformed public health
He invented microbiology and established the foundations for immunology. Louis Pasteur (seated) poses with, among others, children treated with his rabies vaccine. By early 1886, more than 300 ...
2.1 Spontaneous Generation
Figure 2.4 (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.
Spontaneous generation
spontaneous generation, the hypothetical process by which living organisms develop from nonliving matter; also, the archaic theory that utilized this process to explain the origin of life.According to that theory, pieces of cheese and bread wrapped in rags and left in a dark corner, for example, were thus thought to produce mice, because after several weeks there were mice in the rags.
Experiments in support and against Spontaneous Generation
Experiments in support and against Spontaneous Generation. January 30, 2022 by Sagar Aryal. Edited By: Sagar Aryal. 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 ...
3.1 Spontaneous Generation
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 3.4.
Spontaneous generation
However, although the idea of spontaneous generation had been in decline for nearly a century, its supporters did not abandon it all at once. As James Rennie wrote in 1838, despite Redi's experiments, "distinguished naturalists, such as Blumenbach, Cuvier, Bory de St. Vincent, R. Brown, &c." continued to support the theory. [45]
Louis Pasteur's Contributions to Science
However, Pasteur made several other very important contributions to science that you should know about. Molecular asymmetry. In studying crystals of sodium ammonium tartrate, Pasteur found that although they had the same chemical composition, they did not necessarily have the same structure. He noted that the molecules occurred in two mirror ...
Louis Pasteur's Battle with Microbes and the Founding of Microbiology
The main figure in this achievement was Louis Pasteur (1822-1895), a French scientist who first demonstrated the crucial role microbes (microscopic organisms) play in the life process. He established the germ theory of disease and was the first to show that vaccines against infectious diseases can be manufactured.
Origins of Life I
Since prehistoric times, people have pondered how life came to exist. This module describes investigations into the origins of life through history, including Louis Pasteur's experiments that disproved the long-held idea of spontaneous generation and and later research showing that the emergence of biological molecules from a nonliving environment - or abiogenesis - is not only possible ...
Louis Pasteur, a child of the Jura, a man for the world
With great ardor Pasteur began his investigation, making a city of Arbois, in his native Jura department, a theater of the experiments. In a country laboratory, with a group of his best students from the École Normale, in full view of onlookers and amazed winegrowers, Pasteur pursued to fathom the mystery of wine «disease».
Is Spontaneous Generation Real?
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 ...
The Theory of 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 ...
Louis Pasteur: Between Myth and Reality
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.
Louis Pasteur
Louis Pasteur (born December 27, 1822, Dole, France—died September 28, 1895, Saint-Cloud) was a French chemist and microbiologist who was one of the most important founders of medical microbiology. Pasteur's contributions to science, technology, and medicine are nearly without precedent. He pioneered the study of molecular asymmetry ...
7 Best Stocks Under $5 to Buy Now
It owns interests in the Palangana mine, Goliad, Burke Hollow, Longhorn, and Salvo projects located in Texas; Anderson, Workman Creek, and Los Cuatros projects situated in Arizona; Dalton Pass and ...

How the Scientific Method Works

Pasteur's Experiment

3.1 Spontaneous Generation

Clinical Focus

The Theory of Spontaneous Generation

Check Your Understanding

Disproving Spontaneous Generation

Louis Pasteur

Early Life and Education

Study of Optical Activity

Fermentation and Pasteurization

Germ Theory

A New Laboratory

Attenuating Microbes for Vaccines: Fowl Cholera and Anthrax

Rabies and the Beginnings of the Institut Pasteur

A Great Experimenter and Innovative Theorist

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Does Louis Pasteur Still Matter?

Biting Back

Stories of the Great Chemists

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How Pasteur developed pasteurization

The germ theory of disease is born

Pasteur’s scientific legacy

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2.1 Spontaneous Generation

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

Share This Book

Experiments in support and against Spontaneous Generation

Experiments in Support of Spontaneous Generation

John Needham

Experiments against Spontaneous Generation

Francesco Redi

Lazzaro Spallanzani

Louis Pasteur

John Tyndall

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3.1 Spontaneous Generation

CLINICAL FOCUS: Part 1

The Theory of Spontaneous Generation

Disproving Spontaneous Generation

Multiple Choice

Critical Thinking

Media Attributions

Share This Book

Origins of Life I: Early ideas and experiments

Comprehension Checkpoint

Is Spontaneous Generation Real?

Key Takeaways

Do Animals Spontaneously Generate?

Spontaneous Generation Debate

Redi Experiment

Needham Experiment

Spallanzani Experiment

Pasteur Experiment

What is Biogenesis?

Meaning of Biogenesis

What Was the Idea of Spontaneous Generation?

Macroscopic Biogenesis: Francesco Redi’s Experiment

Microscopic Biogenesis

Pasteur’s Experiment

Law of Biogenesis Vs. Evolutionary Theory

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Customize your course in 30 seconds

Molecular Genetics

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