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Louis Pasteur; his life and legacy


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-Pasteur’s microscope

Gentlemen, it is the microbes who will have the last word.

The French chemist and biologist Louis Pasteur is generally acknowledged to be the most important single figure in the history of medicine. Pasteur revolutionized chemistry and biology with his discovery of mirror-image organic molecules then founded microbiology with his work on fermentation. The process he invented to stop foodstuffs going bad, Pasteurization, is still in use worldwide. He made many other contributions to science, but he is most renowned for his advocacy of the germ theory of disease and his development of the technique of preventive inoculation. 

However, the publication of Pasteur’s private journals, one hundred years after his death, clouds his legacy. 


Louis Pasteur was born in Dole, France in 1822.  His ancestors had been serfs. Louis and his three sisters were the children of a tanner and former sergeant major in Napoleon’s army. The father, a hard-working upright man who idolized the Emperor, stressed the value of education to his son. He dreamed of Louis becoming a respected high school teacher.  Little did he know… 

In his teenage years, Louis received free tutoring from his father’s friend, a scholar. With this extra help, Louis began to show academic ability – he started winning prizes at school – and it increasingly looked like a college education would be suitable for him. In addition to his growing academic prowess, young Louis also showed considerable artistic talent. 


Pastel portrait of his father, by Louis Pasteur, aged 15.

As a college student in Paris, Pasteur studied science. His genius was not evident; one of his professors graded him as ‘mediocre’ in chemistry. However, after receiving his doctorate in 1847, he showed that judgment to be in error. His research on the mirror-images of tartaric acid made Pasteur a renowned chemist at the age of 26. In 1852 Pasteur became chairman of the chemistry department at the University of Strasbourg, in Strasbourg, France. Here he began studying fermentation, a type of chemical process in which sugars are turned into alcohol. His work resulted in tremendous improvements in the brewing of beer and the making of wine. He married at this time.


Life comes only from life.


Devoting himself to the study of microbes, the world of the unseen, Pasteur benefited by advances in microscopy. It was his experiments which demonstrated that microorganisms do not arise from spontaneous generation (biogenesis), a dogma current in his day and which formed the cornerstone of the recent theory of evolution. Pasteur incurred the wrath of the Darwinists but, in the end, he prevailed. 

Though not the first person to suggest the germ theory of disease, Pasteur’s numerous and well-publicized demonstrations were the principal factors in convincing the scientific community that the theory was correct. He therefore stressed the importance of antiseptic methods for physicians, a major influence on Joseph Lister who introduced his methods in surgery. 

Pasteur became so obsessive over microbes that he refused to shake the hand of Napoleon III during an awards ceremony in his honour. 


A painting of Pasteur in his laboratory, circa 1880 

In mid-life Pasteur turned his attention to the study of anthrax, a serious infectious disease that attacks cattle and many other animals, including humans. Showing that a bacterium was responsible for the disease he developed a technique for producing a weakened strain of the anthrax bacillus. Injected into cattle it produced a mild form of the disease-producing immunity. It was soon realized that this method could be applied to countless other communicable diseases. Using Pasteur’s basic ideas other scientists have developed vaccines against many other diseases, including polio, tuberculosis, cholera, smallpox and typhus. Pasteur also discovered the phenomenon of anaerobiosis that is certain microorganisms can live in the absence of any air or oxygen. 

Pasteur, in his most celebrated achievement, developed a technique for inoculating people against the frightful disease of rabies. On July 6, 1885, in front of a crowd, he administered his vaccine to Joseph Meister*, a 9-year-old boy who had been attacked by a rabid dog. The boy survived and avoided contracting rabies, which one assumes, would have almost certainly proved fatal. Good thing it worked: Pasteur was not a licensed physician and could have been prosecuted had the vaccine failed. The legalities were forgotten and Pasteur instead became a national hero. 

Pasteur, the ultimate drudge, committed himself to a twelve hour day, seven-day work week. Absorbed in his experiments, he had to be summoned to church on his wedding day; apparently, he forgot. Three of his five children died prematurely, tragedies that darkened his life.

World famous and showered with honours Pasteur died in 1895. The extent of his religious beliefs has been debated but his lifeless hand was found gripping rosary beads. 


Pasteur had a rather difficult personality: he could be aloof, gruff, authoritarian, secretive, and, above all, intensely competitive. He and the German Robert Koch, the second most influential figure of the era in medical microbiology, engaged in a long-running feud over pre-eminence fueled by nationalism and duelling egos. Most modern biologists have declared Pasteur the winner.  

In 1995, the centenary of his death, Pasteur’s name was posthumously disgraced on an international stage.  He had ordered his family members to hold on to his private journals and never disclose them to anyone but his last surviving descendant donated the papers to the French National Library. It appears that Pasteur not only oversold some if his findings; he had unabashedly lied about the results of his several of his experiments and even stole credit from rival scientists. 

Concerning his rabies trials, it was revealed that only a fraction of the diseased mutts had been examined and half of them died from their illnesses. Even more distressing was the ‘foolproof’ vaccine which he had injected into the dogs was used on Joseph Meister. He had exposed the boy to an untested treatment. 


Jean-Joseph Toussaint 

Jean-Joseph Toussaint, a local veterinarian, was conducting similar research at the same time, but using a personally designed chemical formula. Thrilled by the progress he was making, Toussaint visited Pasteur and made the mistake of confiding in him the recipe for his proprietary cocktail. Before he knew it, the Great Man appropriated his formula and began using it- without attribution- in his public experiments.

Toussaint never found his happy ending; the rage and the inability to change his fate supposedly drove him to such a deep depression that he suffered nervous breakdowns for what was left of his abruptly short life.


Since the 19th-century life expectancies have roughly doubled, In effect modern science has gifted us with virtually a second lifetime.  Louis Pasteur’s uncountable contributions are so fundamental that there is little question that he deserves the largest share of the credit for the decline in death rates that began a century and a half ago. 

Despite the controversies, many- or most- scientists and historians rank Pasteur among the most significant individuals who ever lived. 

Can we agree? 

*- Joseph Meister




As an adult, Meister served as a caretaker at the Pasteur Institute until his death in 1940 at age 64. On 24 June 1940, ten days after the German army invaded Paris during World War II, Meister committed suicide with his gas furnace.








Edited by Childress
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